Vol 58 Issue 1 January 2014 - Johnson Matthey Technology ... · By Yurii V. Kudriavtsev and Elena...

Published by Johnson Matthey Plc

Vol 58 Issue 1

January 2014

www.platinummetalsreview.com

E-ISSN 1471-0676

A quarterly journal of research on the

science and technology of the platinum

group metals and developments in their

application in industry

© Copyright 2014 Johnson Matthey

http://www.platinummetalsreview.com/

Platinum Metals Review is published by Johnson Matthey Plc.

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1 © 2014 Johnson Matthey

E-ISSN 1471-0676 •Platinum Metals Rev., 2014, 58, (1), 1•

Editorial Team: Sara Coles (Assistant Editor); Ming Chung (Editorial Assistant);Scott Turnbull (Scientifi c Information Assistant)

Platinum Metals Review, Johnson Matthey Plc, Orchard Road, Royston, Hertfordshire SG8 5HE, UKEmail: [email protected]

Platinum Metals ReviewA quarterly journal of research on the platinum group metals

and developments in their application in industryhttp://www.platinummetalsreview.com/

JANUARY 2014 VOL. 58 NO. 1

Contents

Platinum Metals Review is Changing in 2014 2 An editorial by Sara Coles

Focused Ion Beam and Nanomechanical Tests for High Resolution 3 Surface Characterisation: New Resources for Platinum Group Metals Testing By Marco Sebastiani, Marco Renzelli, Paolo Battaini and Edoardo Bemporad

High Temperature Thermomechanical Properties of 20 Titanium-Rhodium-based Alloys Containing Scandium By Yurii V. Kudriavtsev and Elena L. Semenova

EuropaCat XI 31 A conference review by Silvia Alcove Clave, Francesco Dolci, Peter R. Ellis and Cristina Estruch Bosch

The Discoverers of the Isotopes of the Platinum Group of Elements: 38 Update 2014 By John W. Arblaster

PGMs in the Lab: Platinum Group Metals in Polyoxometalates 40 Featuring Ulrich Kortz

Publications in Brief 43

Abstracts 46

Patents 50

Final Analysis: Effects of Platinum Group Metals Doping 54 on Stainless Steels By Andrew Fones and Gareth D. Hatton

http://dx.doi.org/10.1595/147106714X677955 •Platinum Metals Rev., 2014, 58, (1), 2•


Platinum Metals Review, Johnson Matthey’s journal

of research on the science and technology of the

platinum group metals (pgms) and developments

in their application in industry, has a long and

proud history having been published by Johnson

Matthey since 1957 – continuous publication for 58

years.

From mid-2014, regular readers will see changes, not

least of which will be to the name of the journal:

Platinum Metals Review will become the Johnson

Matthey Technology Review.

This change refl ects our intention to cover a

much wider range of technologies than at present.

Today, Johnson Matthey is more than just a precious

metals company, with interests which extend to

base metal catalysis, products for pharmaceutical

and medical applications and battery materials,

among others. These technologies will also begin

to feature in future issues of the journal alongside

pgms, which remain indispensable for so many

applications and processes.

The format of a peer-reviewed scientifi c journal,

which has worked well for us in the past, will

remain as it is important to maintain a high quality

publication that our readers will want to read and

cite.

We welcome and encourage submissions from all

who are working in fi elds of interest to the journal,

which is provided as a service to the community

who work with pgm and now, non-pgm science and

technology in a range of relevant fi elds. The journal

will still be free to access and free to publish; all of

the costs are absorbed by Johnson Matthey as part

of its service to the community.

On behalf of Johnson Matthey I would like to

thank all of Platinum Metals Review’s readers,

authors, reviewers, Editorial Board members and

other stakeholders for your input over the years

and I hope that you will be interested in continuing

your contribution to the success of the journal in

future.

Please look out for further announcements,

including the wider range of topics which we will

begin to cover, via our website, Twitter, email and in

the next issue of the journal. We hope you are as

excited as we are about this opportunity to greatly

expand the range of subjects that will fi nd a home,

and an interested audience, in the Johnson Matthey

Technology Review.

SARA COLES, Assistant Editor

Platinum Metals Review

Contact InformationJohnson Matthey PlcOrchard RoadRoystonHertfordshire SG8 5HEUKEmail: [email protected]

Editorial

Platinum Metals Review is Changing in 2014

� •Platinum Metals Rev., 2014, 58,�(1),�3–19•


Focused Ion Beam and Nanomechanical Tests for High Resolution Surface Characterisation: New Resources for Platinum Group Metals TestingUse of two high resolution techniques allows process optimisation and prediction of in-service behaviour

http://dx.doi.org/10.1595/147106714X675768 http://www.platinummetalsreview.com/

By Marco Sebastiani and Marco Renzelli

University of Rome “Roma Tre” Engineering Department, Via della Vasca Navale 79, 00146 Rome, Italy

Paolo Battaini

8853 SpA Via Pitagora 11, I-20016 Pero, Milano, Italy

Edoardo Bemporad*

University of Rome “Roma Tre” Engineering Department, Via della Vasca Navale 79, 00146 Rome, Italy

*Email: [email protected]

Recently, the increasing importance and scope of nanotechnology has extended the need for high resolution characterisation tools beyond their traditional domains. As a consequence, advanced high-resolution tools at the nanoscale are now increasingly used in research and development (R&D) activities, offering the chance for a better understanding of submicron feature size dependence. This paper gives an overview of the synergic application of two high resolution techniques on the platinum group metals (pgms): focused ion beam (FIB) coupled with electron beam imaging, milling and deposition techniques; and nanoindentation testing. After a brief description of both techniques (architecture, probe-sample interaction basics and operation modes), the effectiveness of this combined approach is demonstrated for microstructural and nanomechanical investigations on very small samples. The advantages are low cost, fast and site-specific sample preparation for transition electron microscopy (TEM) analysis; study of the mechanical hardening effect on microstructure and hardness profile at the micron scale; failure analysis; and understanding of plasticity and elasticity behaviour. Two specific case studies related to a platinum-copper alloy for jewellery use and a platinum-rhodium alloy for sensor manufacturing are presented and discussed.

1. IntroductionThe structural characterisation of engineered surfaces is of increasing importance due to the growing application of surface modification processes and coating techniques, which are usually applied to improve either mechanical or functional surface performance. Some examples include surface hardness, load bearing capacity, impact bearing capacity, wear resistance, specific surface area (related to surface free energy and chemical reactivity),

http://dx.doi.org/10.1595/147106714X675768� •Platinum Metals Rev., 2014, 58,�(1)•


electrical resistivity, thermal conductivity and ‘smart’ optical properties (1).

The development of nanostructured materials and the increasing use of nanosystems and nanostructures make the use of advanced procedures for nanoscale mechanical characterisation necessary to understand chemical and physical phenomena at this scale (2). The in-service macroscale mechanical behaviour of micro- and nanocrystalline metals (for example, their fracture and plastic deformation behaviour) is strictly related to the complex interactions between the different micro- and nanostructural features (for example dislocation sources, grain boundaries and nanoscale porosity). These latter aspects are particularly critical in the advanced metallurgy of pgms alloys, where the actual role of phase transitions, the microstructural evolution of interfaces during processing and the correlation with their mechanical properties are not yet completely understood.

The in-service performance of such materials is dependent on the evolution of nano- and microstructural features during processing, including development of nanodispersed phases, grain growth, evolution and composition of grain boundaries, dislocation density and distribution. Therefore an understanding of the correlation between the micro- or nanostructure and the mechanical properties of a material is critical for the development of new and improved materials. High resolution microscopy analysis together with nanomechanical characterisation are powerful tools that can allow such understanding.

The present paper gives an overview of the synergic use of two high resolution techniques, which are expected to be established as enabling technologies for improving the current understanding of the correlations between process, microstructure, properties and performance for precious metal alloys. These are: y FIB coupled with electron beam for imaging,

milling and deposition (referred to as ‘dualbeam’ (3–5))

y Nanoindentation (6–12) for hardness measurement with a very low load.

1.1 Advantages of the TechniquesA key advantage of these two techniques (FIB/SEM and nanoindentation) for high-technology manufacturing is that both are very site-specific and virtually artefact free in measuring as well as in imaging or shaping samples in order to expose the region of interest.

Moreover, some analysis on cross-sections and even TEM lamellae extraction are virtually nondestructive, as the sample size required is just a few cubic microns.

In this paper, two examples are outlined to show how the combined use of nanomechanical testing and high resolution microscopy can help gain understanding of the processing mechanisms and in-service behaviour of components. In particular: y Cross-section cut-and-view for rapid

microstructural investigation (grain size and inclusions) on very small samples without any sample preparation or preprocessing (dualbeam)

y Low cost, fast and site-specific sample preparation for TEM analysis (dualbeam)

y Deformation mechanisms at the nanoscale (dualbeam and nanoindentation)

y Mechanical hardening effect on microstructure and hardness profile at the micron scale (dualbeam and nanoindentation)

y Separate measurement of elastic modulus, apparent hardness, true hardness, plasticity and hardening behaviour (nanoindentation).

The article will focus on two case studies, explaining the importance of the combined use of dualbeam and nanomechanical testing for the correct evaluation of mechanical and functional performances of nanostructured systems in the pgms: y Order hardening of platinum-5 wt% copper

alloys: microstructural and nanomechanical characterisation for this alloy used in jewellery;

y Influence of process history on microstructure and mechanical properties of platinum-rhodium alloys, used in thermocouples.

In both cases, it will be demonstrated that nanoindentation testing can give valuable information on the microstructural changes due to phase transition and intragrain microstructure. In addition, the combined use of FIB/scanning electron microscope (SEM) and TEM techniques could help to understand how and why microstructural changes due to heat and/or mechanical treatments affect the mechanical behaviour of samples.

1.2 Brief Introduction to Focused Ion Beam (FIB) Techniques FIB technology was first introduced in the 1980s in the semiconductor industry. FIB instruments derive their design from the SEM. However while SEM instruments use electrons that are accelerated and focused on a surface, FIB uses ions (usually gallium). The image is derived from secondary electrons resulting from



the particle irradiation. The use of ions means that it is not only possible to image the surface but also to mill it, using sputtering phenomena to remove material. From an engineering point of view, the two instruments, albeit similar in concept, are different in construction: the high mass of the ions requires electrostatic lenses, instead of electromagnetic lenses as used in SEM (3–5).

The new generation of FIB equipment is equipped with both an ion beam column and an electron beam column (SEM), providing imaging of the ion beam milling process. In this case the instrument is called a dualbeam microscope (Figure 1(a)). It can be seen from Figure 1(a) that the instrument can use the electron and ion columns at the same time; considering that the resolution of the FIB is 5 nm, it is possible to mill the surface in real time with nanometre resolution, working it with ions and observing it with electrons, as in Figure 1(b). In dualbeam with in situ SEM three dimensional tomography can be obtained by the slice-and-view process (3–5). An additional feature of FIB is the capability to deposit thin films (for example, made from Pt or carbon) by ion- or electron-assisted chemical vapour deposition (CVD), as shown in Figure 1(b).

FIB milling can be performed on hard, soft and biological materials with minimal artefacts (3–5). Some Ga atom implantation and amorphous layers will typically be observed but these artefacts can be limited to a thickness of a few nanometres by careful selection of the milling parameters (mainly current and voltage). FIB systems use a focused beam of Ga+ ions at low beam currents (of the order of pA) for

imaging and at high beam currents (of the order of nA) for site-specific milling.

FIB techniques can be also used for TEM lamella preparation: a finished electron transparent portion of the sample (usually 5 μm × 20 μm) is obtained by FIB milling (performed at 30 kV by using a decreasing sequence of ion milling currents, from 9 nA down to 0.28 nA for the final polishing) and then carried by a micromanipulator on a sample holder to be inserted into the TEM microscope: this procedure at present represents the best site-specific and artefact-free TEM sample preparation methodology. Figure 2 illustrates how a dualbeam can be used to prepare site specific thin sections for high resolution TEM imaging and analysis.

1.3 Brief Introduction to Nanoindentation Testing Nanoindentation testing (6) has been widely adopted in the last two decades for the surface mechanical characterisation of bulk materials and coatings. The method involves the controlled penetration of a diamond indenter of known shape into the material. Usually, a three-sided pyramidal indenter (Berkovich) is used in conventional nanoindentation. By measuring the load and displacement during the loading and unloading parts of the test, hardness (i.e. resistance to plastic deformation) and elastic modulus can be calculated (6, 7). In this way, a very accurate characterisation of the elastic and plastic properties at a material’s surface can be achieved, with a depth resolution and a lateral spatial resolution of the order of a few nanometres.

SEM

FIB52º

~4.1mm

(a)

10 µm

(b)

Fig. 1. (a) Schematic of dualbeam FIB/SEM equipment; (b) an example of a cross-section by FIB. A thin layer of Pt is deposited before ion milling



During a basic indentation test an ideally rigid indenter of known geometry is pressed against the sample surface up to a controlled maximum load, following a controlled loading (or displacement) rate. When the indenter is driven into the material, both elastic and plastic deformation processes occur, producing a hardness impression that conforms to the shape of the indenter to a certain contact depth, hc (Figure 3(a)).

The hardness H is easily obtained as a function of load (or penetration depth) by the following equation:

H PAc

= (i)

where P is the maximum load and Ac is the indenter projected contact area, which is given as a polynomial function of the contact depth, hc, for a Berkovich indenter:

A a h a h a h a hc c c c c= + + + +02

1 21 4

31 8/ / ... (ii)

The contact depth is defined as follows (see also Figure 3(a)):

h h PSc = − ⋅ε

(iii)

The coefficient ε can range between 0.72 and 1; a value of 0.75 is usually adopted for the Berkovich indenter.

The contact area expressed in Equation (ii) is evaluated by calibration on a certified fused silica reference sample, performed before and after each series of tests. As the indenter is removed from the surface, a purely elastic recovery phenomenon occurs, thus giving a measurable unloading elastic contact

10 µm

(a)

20 µm

(b)

5 µm

(c)

Fig. 2. Sequence for TEM lamella preparation by FIB techniques for a Pt-Cu alloy: (a) FIB milling of a thick lamella and cutting section (~300 nm, milled at 0.92 nA); (b) lift-out of the lamella by the micromanipulator; (c) welding of the lamella on the TEM sample holder and final thinning to electron transparency (~80 nm, at a current of 0.28 nA)

Load (P)

Ac=f(hc)

ht Yhc

(a)500450400350300250200150100500

Displacement into surface, nm

0 1000 2000

Unloading curve

Loading curve

Load

on

sam

ple,

mN

(b)

Fig. 3. (a) Contact geometry usually adopted in modelling sharp indentation testing. The equivalent cone angle ψ is equal to 70.3º for the Berkovich and Vickers indenters; (b) an example of a load-displacement curve for an amorphous fused silica reference sample



stiffness, which can be analytically correlated to both the material’s and the indenter’s elastic properties by the use of the Sneddon solution for the contact on an axisymmetric elastic body on a flat surface (6):

E SAr = ⋅

πβ2

(iv)

S = dP/dh is the elastic contact stiffness which is evaluated, after fitting the upper portion (usually 50%) of the unloading curve to a power-law relation (Oliver-Pharr method (6)), as the slope of the unloading curve at maximum load Pmax.

Er is the reduced modulus (which takes into account both the elastic deformation of sample and indenter), given by:

1 1 12 2

Es

sEiiE*

=−( )

+−( )ν ν

(v)

where Ei and νi are, respectively, the Young’s modulus and the Poisson ratio of the indenter. β is a numerical correcting factor equal to 1.034 for a Berkovich indenter, which is introduced to correct for the lack of symmetry of the indenter with respect to the ideal conical shape. As recently reviewed by Oliver and Pharr (6), values in the range of 1.0226 ≤ β ≤ 1.085 can be found in the literature; in the present work the value of 1.000 is adopted, as suggested by the ISO 14577-1-2 standard.

Equations (i)–(v) give a short synthesis of the Oliver-Pharr method (see also Figure 4), which is conventionally adopted for the analysis of hardness and elastic modulus from a generic nanoindentation test.

An interesting modification of the conventional nanoindentation is the so called ‘continuous stiffness measurement’ (CSM) method. In the CSM method (7), the contact stiffness S is dynamically measured during indentation and continuous hardness/depth and modulus/depth curves are obtained using Equations (i)–(v).

Apart from the most conventional analysis, nanoindentation testing has been used for the evaluation of several other surface mechanical properties, such as yield strength and strain hardening behaviour of metals (7, 8), damping and internal friction in polymers (i.e. storage and loss modulus), activation energy and stress exponent for creep (8), fracture toughness of bulk ceramics and coatings (9), adhesion of thin films and work of adhesion (11),

scale effects in mechanical behaviour of small scale specimens (11) and residual stress (12, 13).

In the case of metals, significant dependence of the measured hardness on the applied load is usually observed, even if a self-similar indenter is used for testing (for example, a pyramidal indenter). This experimental evidence, which is usually referred to as ‘indentation size effect’ (ISE), is not only due to the effects of surface preparation (i.e. surface hardening) and/or indenter tip blunting (i.e. not perfectly sharp indenters), but also to a real ‘material scale-dependent plasticity’, that has been related to subsurface modifications of the dislocation density across the plastically deformed volume which is created during indentation.

The most diffused model to understand ISE was proposed by Nix and Gao (10). The model is based on a simple concept, that ‘geometrically necessary dislocations’ (GNDs) must be created in the plastically deformed volume (beneath the indenter) to accommodate the deformed material from the surface. The GNDs exist in addition to the other statistically stored dislocations (SSDs), which are usually present in any polycrystalline metal. The additional amount of GNDs gives rise to an additional hardening effect, which is higher as the size of indentation decreases, thus explaining the observation of increasing hardness with decreasing applied load.

Starting from this idea and assuming a conical rigid indenter, Nix and Gao came out with a simple equation describing the variation of hardness as a function of the penetration depth during indentation:

H H hh

= +0 1*

(vi)

where H0 is the macroscale hardness and h* is a characteristic length scale, which depends both on the material’s properties and the indenter geometry.

2. Case Study 1: Microstructural and Nanomechanical Characterisation of Pt-5%Cu Order Hardened AlloysPt-5 wt% Cu alloys are used in jewellery mainly because the addition of Cu significantly improves the mechanical properties compared to pure Pt, particularly its resistance to plastic deformation (i.e. yield strength and hardness); it is also known that heat treatment of Pt-5 wt% Cu alloys can result in a further increase of indentation hardness (often



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measured by Vickers microhardness testing) (14). This phenomenon is related to the fact that the Pt-Cu binary system forms an ordered structure (described by the CuPt7 model) from the disordered face-centred cubic (fcc) solid solution, in the composition range 12–25 at% Cu (14).

It has also been previously reported that the order-disorder transition can be strongly enhanced by inducing a certain quantity of microstructural defects in the structure, for example, by quenching or by plastic deformation (14).

A recent paper (15) reports a study of the order-disorder transition in Pt-5 wt% Cu alloys using TEM-selected area electron diffraction (SAED) probing, showing that initially quenched specimens were characterised by relatively larger ordered domains after heat treatment and by a lower increase of Vickers hardness in comparison with cold plastically deformed samples. Nevertheless, a deeper analysis of the influence of the mechanical hardening process on the microstructural and structural characteristics of order-disorder transition is still required, in order to discover the optimal cold working process in terms of induced plastic strain and induced modification of hardness and of hardening coefficient, which can guarantee the maximum increase of hardness after heat treatment. Furthermore, there is still a strong necessity for the development of more reliable and accurate procedures for the technological assessment of phase transitions after heat treatment.

In this section, an innovative procedure for the mechanical and microstructural characterisation of Pt-Cu order hardened alloys is presented, essentially based on the combined use of micro- and nanoindentation testing and ISE modelling, dualbeam and TEM techniques. It is shown that the correct modelling of micro- and nanoindentation hardness results coupled with high resolution dualbeam and TEM observations can give deeper information on the actual influence of the preliminary cold working process on the order hardening transition.

2.1 Experimental DetailsOne as cast Pt-5 wt% Cu ingot was subjected to homogenisation at 1000ºC for 15 h and then plastically deformed by uniaxial compression (milled) with a thickness reduction of 75%. From the milled plate two samples were cut. One of these two samples was heat treated at 290ºC for 3 h and finally cooled in air. The hardness of both samples was studied by nanoindentation testing by means of a Berkovich

diamond indenter, using an Agilent G200 Nano Indenter, in a CSM mode under a constant strain rate of 0.05 s–1 and a maximum penetration depth of 2000 nm (other test and fitting parameters were chosen according to ISO 14577-1-2 standards) (18). Cross-section SEM-field emission guns (SEM-FEG) microstructural observation and TEM-SAED analyses were performed after FIB sample preparation in a dualbeam (FEI Helios Nanolab 600).

Cross-sections were obtained by FIB milling after a preliminary in situ Pt deposition to protect the surface layers during ion milling; the sectioning process consisted of a preliminary high ion current milling (9 nA) followed by cleaning the section (0.9 nA) until the desired section was obtained. Microstructural observation was performed using both the ion probe (maximum microstructural contrast) and the electron probe (maximum morphological contrast), secondary electrons were detected in both cases. The dualbeam technique was also used to extract electron transparent foils for TEM (Philips CM 120, LaB6 analytical). TEM analyses consisted of bright field high magnification observation followed by SAED, performed both at the surface of the TEM foil and at its centre.

2.2 Results and DiscussionThe results of the nanoindentation testing are reported in Figure 5 and summarised in Table I. The nanohardness profiles presented in Figure 5 clearly confirm that the hardness is significantly increased after heat treatment. Furthermore, in this case, the presence of a surface hardened layer is observed for penetration depths lower than 500 nm. Nanoindentation testing allows a more detailed analysis of this effect to be performed: it is very important to note that the hardness profiles for both samples have a very similar shape, i.e. a very similar skin effect is observed in both cases.

This observation suggests that the microstructure derived from the cold working process (which likely involves the formation of a surface hardened layer) is completely maintained after heat treatment, because the same hardness gradient is observed in both cases. This also means that neither recrystallisation nor changes of grain size occurred during the heat treatment at 290ºC, suggesting that the order-disorder phase transition is realised at a subgrain level with no significant modification of dislocation density.

Another relevant observation comes from SEM-FEG imaging of the nanoindentation marks. Figure 6 shows the rounded shape of the indent lateral profile.



Fig. 5. (a) Nanoindentation hardness depth for both Pt-Cu samples under investigation; (b) analysis of hardness data through the Nix-Gao ISE model. Hardness is confirmed to be higher for the heat treated sample

From Figure 6(b) it can be clearly seen that for the heat treated sample there was a higher amount of piling up at the edge of indentation. This suggests that the heat treatment may have influenced not only

hardness, but also the hardening coefficient of the sample. As reported earlier (8), a different hardening coefficient usually involves a different amount of piling-up during indentation.

H0 = 3.72 GPah* = 0.077 µm{Cold worked and heat treated at 290ºC

Only cold workedH0 = 2.76 GPa h* = 0.186 µm{

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

00 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

1/h, µm–1

(H/H

0)2

H 2 h*

H0 h –– = 1 + –– ( )

(b)

6.5

6

5.5

5

4.5

4

3.5

3

2.5

2

1.5

1

0.5

00 200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Nan

ohar

dnes

s, G

Pa


Cold worked and heat treated at 290ºC

Only cold worked

(a)



This observation is confirmed by an analysis of the hardness data using the Nix-Gao ISE model (10), where a significantly different value of the h* parameter is found (see Table I and Figure 5(b)), thus suggesting that the two samples may have a different hardening coefficient. This leads to a very important conclusion: the hardening behaviour (not only hardness) of the heat treated sample is modified, which can have a significant effect on workability and on service performance of materials heat treated in such a way.

The results of the indentation modulus profile are reported in Figure 7, where elastic modulus is shown to be constant with penetration depth and does not depend on sample microstructure (as expected). The elastic modulus seems to be ~5% higher for the heat treated sample, however this is not considered statistically significant. This difference is likely due to

the observed pile-up during indentation. As widely reported in the literature, piling up always involves an over-estimation of the measured elastic modulus, due to incorrect evaluation of the real contact area by the Oliver-Pharr method (7). The observed difference in the elastic modulus is therefore likely not to be a real effect, thus suggesting that modulus does not change significantly after the heat treatment (as expected).

In both Figures 8 and 9, the left column refers to the cold worked sample, while the right column refers to the cold worked and heat treated sample. Dualbeam characterisation analysis clearly shows that the microstructure and microscale morphology of both samples are very similar. In both cases, a strongly oriented (biaxial) grain structure is observed, which is likely to be a consequence of the cold forming process. These results confirm that the microstructure of the sample is not modified by the

Table I

Summary of Results for the Micro- and Nanomechanical Characterisation of Platinum-5 wt%

Copper Samples

Hardnessa, GPa Modulusa, GPaNix-Gao parameters (Equation

(vi)) (H0; h*), GPa; µm

Cold worked sample 3.08 ± 0.11 205.1 ± 4.7 2.76; 0.186

Cold worked and heat treated sample 3.88 ± 0.21 215.2 ± 7.1 3.72; 0.077

a Average in the penetration depth range of 300–900 nm

5 µm

(a)

5 µm

(b)

Fig. 6. Dualbeam (SEM column) micrographs on Berkovich nanoindentation marks for: (a) cold worked sample; (b) cold worked and heat treated sample. A higher amount of piling up is observed in case of the heat treated sample, thus suggesting that order hardening also involves a modification of the hardening coefficient



heat treatment and that the order-disorder transition is likely to happen at a subgrain level. A similar result can be achieved by a careful analysis of the nanoindentation hardness profile.

The results of TEM-SAED analysis on dualbeam prepared thin foils are reported in Figure 9. Figures 9(a) and 9(e) show detail of the grain structure at the sample surfaces. It is clear that the grain structure has been maintained almost identically after heat treatment and that the dislocation density is similar in both cases, confirming the results obtained by nanoindentation and dualbeam cross-section observation. In addition, a very thin surface hardened layer (characterised by a finer grain size) is clearly shown in Figures 9(b) and 9(f). Figures 9(c)–(g) show details of the intragrain morphology, which are significantly different for the two samples. In the case of the heat treated sample the ordered domains are clearly visible confirming that the phase transition happens at a subgrain level.

In addition, a complete change of dislocation distribution is evident in the ordered domain, suggesting that dislocations (or generally speaking, all defects coming from plastic deformation) can be considered the main nucleation sites for the phase transition. This explains why the order-disorder

transition is usually observed only for seriously plastically deformed samples and not for quenched or as-cast samples.

3. Case Study 2: Influence of Process History on Microstructure and Mechanical Properties of Platinum-Rhodium AlloysAlloys of Pt and Rh (19, 20) are widely used in many industrial sectors, due to their high strength compared to pure Pt, good workability and very good corrosion resistance even at high temperature. Examples from industry include thermocouples for high-temperature measurement, clean and inert heating elements in experimental high-temperature furnaces, components in the manufacture of glasses, catalyst gauzes and laboratory equipment (21–24). The use of Pt-Rh alloys has been increasing due to the fact that Rh dissolves in all proportions in Pt, thus forming a substitutional solid solution which usually involves an increase of hardness with no significant loss of workability.

However, there are still controversial results in the literature on the actual phase evolution of Pt-Rh systems at temperature below 1033 K. Some authors have proposed the presence of a miscibility gap below 1033 K (19), which was not confirmed

Fig. 7. Elastic modulus as measured by nanoindentation testing for both samples

Cold worked and heat treated at 290ºC

240

220

200

180

160

140

120

100


0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Elas

tic m

odul

us, G

Pa

Only cold worked



(a)

20 µm 10 µm

(c)

1 µm

(b)

1 µm

(d)

160.8 nm (cs)

Fig. 8. Dualbeam (FIB and SEM column) analysis of samples: (a) and (b) the cold worked sample; (c) and (d) the cold worked and heat treated sample. It is worth noting that the microstructure obtained after cold working is maintained after heat treatment, including the surface hardened layer

by other similar studies, thus suggesting that further investigations should take place to achieve a better and deeper understanding of the actual microstructural and phase evolution of Pt-Rh systems after heat treatment and cooling to room temperature (20).

Another issue of interest is represented by the observed tendency to oxidation of Rh after heat treatment of Pt-Rh systems, which usually involves a decrease in the indentation hardness of the samples; in the case of industrially produced components (for example, wires) the mechanisms of oxidation behaviour as a function of process parameters have not been completely investigated. These examples suggest that innovative characterisation procedures

are strongly needed, with the main objective of finding out the existing correlations between the observed microstructures and the technological performance (for example, hardness) of the components. This data can then be used to optimise the process parameters.

In this work, the usefulness of the above described procedure for the microstructural and nanomechanical characterisation is demonstrated for Pt-10 wt% Rh wires. Two different industrially produced samples (which were expected to be identical) were investigated by high resolution microscopy techniques (dualbeam-TEM) and nanoindentation testing. A correlation between the observed differences in terms of indentation hardness and the actual microstructure is finally presented.



(d) (h)

(e)

200 nm

(f)

200 nm

(g)

20 nm

(b)

200 nm

(a)

200 nm

(c)

20 nm

Fig. 9. TEM-SAED analysis on dualbeam prepared thin foils: (a), (b), (c) and (d) cold worked samples; (e), (f), (g) and (h) cold worked and heat treated samples. High dislocation density is observed in both cases. Order hardening is observed at a subgrain level; (d) and (h) SAED patterns clearly show the change of crystal structure after heat treatment



3.1 Experimental DetailsTwo sets of Pt-10 wt% Rh wires from two different producers, referred to as Sample 1 and Sample 2, were investigated. The samples were nominally produced by the same process, consisting of various stages of drawing and annealing from the initial ingot down to the final section of about 350 µm. Vickers hardness (applied load 100 gf) was preliminarily performed on both samples and a significant difference was observed (as briefly reported in Figures 11(a) and 11(b)). In particular the Vickers hardness was about 15% higher for Sample 2.

Starting from this preliminary result, characterisation activities consisted of dualbeam-TEM microstructural observations and nanoindentation testing. The ion beam was used at a current of 48 pA in the dualbeam microscope to produce physical etching of the microstructure: in this way, the cross-section grain structure of the wires could be investigated by using the ion source and detecting secondary electrons.

A TEM lamella was realised at the external edge of each sample: one grain boundary was included at the centre of each lamella, as reported in Figure 10. In this way, all microstructural features influencing the mechanical properties of the wires were able to be investigated (for example, subgrain microstructure, grain boundary oxidation, presence of precipitates at grain boundary or in the matrix and oxygen diffusion from the sample edge).

Nanoindentation testing was used to evaluate the subgrain hardness profile: one line of Berkovich indentation (maximum penetration depth 1 µm, CSM mode, 0.05 s–1 constant strain rate) was realised across the section of each wire. The measured hardness profile was then compared to the observed grain structure.

3.2 Results and DiscussionConventional metallographic observations are shown in Figure 11. Dualbeam observation with ion source

5 µm

(a)

5 µm

(b)

100 mm

(b)

100 mm

(a)

Fig. 10. TEM lamella for: (a) Sample 1; and (b) Sample 2. A grain boundary is clearly visible in both cases

Fig. 11. (a) Cross-section of Pt-10 wt% Rh wire Sample 1: Vickers hardness HV00.1 = 92 ± 4 (optical microscope after polishing, ×50, applied force: 0.1 N); (b) cross-section of Pt-10 wt% Rh wire Sample 2: Vickers hardness HV00.1 = 105 ± 4 (optical microscope after polishing, ×50, applied force: 0.1 N)



of the cross-sections of both wires are reported in Figure 12. In Figure 11(b) a coarser grain size is clearly observed for Sample 2. It is important to note that twins and low-angle grain boundaries can also be revealed by using the FIB source for surface etching, thus explaining why a larger number of grains are revealed by this method compared to the conventional chemical etching and optical microscopy. The difference in observed grains was resolved with the FIB, which showed that the large grains of Sample 2 are composed of smaller subgrains.

Nanohardness section profiles (Figure 13) confirmed a higher hardness for Sample 2. Nevertheless, the observed differences are reduced

in comparison with data from microhardness testing (performed at 100 gf): this suggests that some artefacts are present during microhardness testing, likely due to bending (or buckling) of the wires during indentation. For nanoindentation testing, the results reported in Figure 13 correspond to a penetration depth of 300 nm (applied load of about 1 gf), to avoid any artefact due to buckling or bending of the wire. It is also worth noting that some variation of nanohardness is observed from one grain to another.

A grain boundary is clearly visible for both samples. In the case of Sample 2 the TEM lamella was likely created at a twin boundary, as clearly identifiable in Figure 14. Looking at Figures 14(b) and 14(d),

100 mm200 mm

(a) (b)

Fig. 12. Example of dualbeam analysis for: (a) Sample 1; and (b) Sample 2. Grain structure is clearly visible by using the ion source. The nanoindentation section profile is also clear in both cases. The TEM lamella was obtained at the sample edge corresponding to a grain boundary for each sample

0 50 100 150 200 250 300 350

Radial position over the wire section, mm

Nan

ohar

dnes

s, G

Pa

2.5

2

1.5

1

0.5

0

Pt-10 wt% Rh Sample 2Pt-10 wt% Rh Sample 1

Fig. 13. Nanohardness cross-section profiles for both Pt-Rh wires under investigation (error bars have been removed for clarity)



significant microstructural differences can be identified between the two samples. In particular, Sample 1 is characterised by the presence of precipitates in the matrix (average diameter ~15 nm). In Sample 2, a different intragranular microstructure can be observed, mainly characterised by very fine precipitates dispersed in the matrix. The observed difference in micro- and nanoindentation hardness may therefore be due to differences of the intragrain phase distribution, which are likely strongly influenced by cooling rates during processing.

It is also worth noting that no differences in terms of crystal structure (SAED) and composition (EDS) were detected between the two samples, thus meaning that observed differences are essentially due to different (or not completely controlled) cooling rates during some of the processing steps.

To verify this latter hypothesis, both samples were subjected to a heat treatment at temperature of 450ºC for 1 h, followed by cooling in air. Results of the TEM analysis are reported in Figure 15, where a similar

microstructure is observed in both cases. In this case, precipitates in the matrix of average diameter ~15 nm are also observed for Sample 2, thus confirming that the much finer subgrain microstructure that had been observed in the as-received Sample 2 was likely due to higher cooling rates during processing.

This example clearly explains how critical it is to properly control all parameters during the processing of these components. The use of high-resolution microscopy was in this case absolutely necessary to examine the actual correlations between the measured technological performance (for example, indentation hardness), the actual microstructural features of samples and the main process parameters.

4. ConclusionsThis paper presents the application of high resolution, multitechnique and multiscale procedures to the nanomechanical characterisation of materials.

It was observed that a comprehensive characterisation of complex alloys can be achieved

(a) (c)

100 nm 100 nm

(b) (d)

20 nm 20 nm

Fig. 14. TEM-SAED analysis on Sample 1: (a) TEM, 120 kV, ×140.000; (b) (TEM, 120 kV, ×660.000) – (TEM-SAED, 120 kV, Z = [100]); and Sample 2: (c) TEM, 120 kV, ×230.000; (d) (TEM, 120 kV, ×660.000) – (TEM-SAED, 120 kV, Z = [114])



by the combination and synergic use of micro- and nanohardness testing and dualbeam-TEM techniques. Two case studies were reported relating to the nanomechanical and microstructural characterisation of an order hardened Pt-Cu alloy and a Pt-Rh wire alloy. In particular, the analysed case studies showed that nanoindentation testing can give valuable information on the level of microstructural changes as a consequence of phase transition and intragrain microstructure. The use of dualbeam-TEM combination technique may finally help to understand how and why microstructural changes due to heat treatment affect the mechanical properties of materials.

In the first case it was shown how the order-disorder transition in Pt-Cu alloys can be evaluated by indentation testing and that the analysis of hardness depth profiles can be extremely useful in suggesting the mechanisms of phase transition, which were later proved using high resolution microscopy, demonstrating that the order-disorder transition happens at a subgrain level only in previously cold worked alloy.

In the second case the use of FIB showed that the results from optical imaging of the grains were misleading, as were those from the microhardness test, because they did not give correct information of the real grain structure and the actual nanomechanical properties of the Pt-Rh wires. High resolution TEM imaging pointed to a likely mechanism (differences in nanoprecipitates) explaining the differences in hardness of the grains. With this work the existence of a miscibility gap and the absence of oxidation have been clearly shown, clarifying a point of contention between researchers in the field.

Such results clearly show how nanomechanical testing in combination with high resolution microscopy can be usefully applied to the characterisation of nanostructured systems for functional (or non-mechanical) application and how they can be a powerful tool for process optimisation and/or prediction of in-service behaviour.

AcknowledgmentsThis paper is dedicated to the memory of our wonderful friend and colleague, Dr Paolo Battaini, who recently passed away. The authors acknowledge the assistance of Daniele De Felicis during dualbeam characterisation activities, carried out at the “Interdepartmental Laboratory of Electron Microscopy” (LIME), University ROMA TRE, Rome, Italy, http://www.lime.uniroma3.it.

References 1 P. H. Mayrhofer, C. Mitterer, L. Hultman and H. Clemens,

Progr. Mater. Sci., 2006, 51, (8), 1032

2 S. Zhang, D. Sun, Y. Fu and H. Du, Surf. Coat. Technol., 2003, 167, (2–3), 113

3 M.W. Phaneuf, Micron, 1999, 30, (3), 277

4 “Introduction to Focused Ion Beams – Instrumentation, Theory, Techniques and Practice”, 2nd Edn, eds. L. A. Giannuzzi and F. A. Stevie, Springer Science+Business Media, New York, USA, 2005

5 L. A. Giannuzzi and F. A. Stevie, Micron, 1999, 30, (3), 197

6 W. C. Oliver and G. M. Pharr, J. Mater. Res., 1992, 7, (6), 1564

7 W. C. Oliver and G. M. Pharr, J. Mater. Res., 2004, 19, (1), 3

8 A. Bolshakov and G. M. Pharr, J. Mater. Res., 1998, 13, (4), 1049

9 S. J. Bull, J. Phys. D: Appl. Phys., 2005, 38, (24), R393

100 nm 50 nm

(a) (b)

Fig. 15. (a) Sample 1 after heat treatment at 450ºC for 1 h (TEM, 120 kV, ×230.000); (b) Sample 2 after heat treatment at 450ºC for 1 h (TEM, 120 kV, ×380.000) – (Z = [100])



10 W. D. Nix and H. Gao, J. Mech. Phys. Solids, 1998, 46, (3), 411

11 M. D. Uchic, D. M. Dimiduk, J. N. Florando and W. D. Nix, Science, 2004, 305, (5686), 986

12 H. Bei, S. Shim, M. K. Miller, G. M. Pharr and E. P. George, Appl. Phys. Lett., 2007, 91, (11), 111915

13 A. M. Korsunsky, M. Sebastiani and E. Bemporad, Mater. Lett., 2009, 63, (22), 1961

14 C. Mshumi and C. Lang, Platinum Metals Rev., 2007, 51, (2), 78

15 M. Carelse and C. I. Lang, Scripta Mater., 2006, 54, (7), 1311

16 ASTM Standard E384, ‘Standard Test Method for Knoop and Vickers Hardness of Materials’, ASTM International, West Conshohocken, PA, 2011

17 D. Tabor, “The Hardness of Metals”, Oxford University Press, New York, USA, 1951

18 ISO 14577-1/2:2002 ‘Metallic materials – Instrumented indentation test for hardness and materials parameters –� Part� 1:� Test� method’� and� ‘Part� 2:� Verification� and�calibration of testing machines’

19 K. T. Jacob, S. Priya and Y. Waseda, Metall. Mater. Trans. A, 1998, 29, (6), 1545

20 Z. M. Rdzawski and J. P. Stobrawa, J. Mater. Process. Technol., 2004, 153–154, 681

21 R. Wilkinson, Platinum Metals Rev., 2004, 48, (2), 88




The Authors

Marco Sebastiani, PhD, is an Assistant Professor of Materials Science at the University of Rome “Roma Tre”. His research is focused on surface engineering, micron-scale residual stress analysis and nanomechanical testing of thin films and nanostructured materials. He is the author of more than 40 papers in peer reviewed international journals.

Marco Renzelli received his Msc in Physics in 2010 at La Sapienza University of Rome. In January 2012 he started his PhD in Engineering at the University of Rome “Roma Tre”. His interests lie in advanced materials production and characterisation, surface engineering, PVD technologies, focused ion beam microscopy and nanomechanical characterisation.

Paolo Battaini held a degree in nuclear engineering, had been a consulting engineer with 8853 SpA, and was a Professor of Precious Metal Working Technologies at Milano Bicocca University, Italy, from 2003 to 2011. He has been a recipient of the Santa Fe Symposium Research and Ambassador Award. He died on 27th September 2013.

Edoardo Bemporad is a nuclear engineer and holds a PhD in Materials Engineering. He is a full Professor of Materials Science and Technology at the University of Rome “Roma Tre”. He is the author of more than 300 papers published in international and national journals, and his interests lie in structured and nanostructured coatings, especially for wear resistance, corrosion resistance and high temperature oxidation.

� •Platinum Metals Rev., 2014, 58,�(1),�20–30•


High Temperature Thermomechanical Properties of Titanium-Rhodium-based Alloys Containing ScandiumUnusual shape memory effects observed in scandium-substituted alloy system


By Yurii V. Kudriavtsev*

G. V. Kurdyumov Institute of Metals Physics of the National Academy of Sciences of Ukraine (NASU) Vernadskiy Str. 36, 03142, Kiev, Ukraine


Elena L. Semenova**

I. N. Frantsevich Institute for Problems of Materials Science of NASU Krzhyzhanovsky Str. 3, 03680, Kiev, Ukraine

**Email: [email protected]

At high temperatures, the equiatomic binary compounds formed by Groups 4 and 8 transition metals are known to undergo martensitic transformation, which may be accompanied by a shape memory effect. Among these compounds, titanium-rhodium (TiRh) is of special interest not only because it undergoes two martensitic transformations at high temperature, for one of which the shape memory effect has been observed, but also because it demonstrates unusual shape recovery behaviour at temperatures higher than 400ºC. The present work focuses upon the thermomechanical and mechanical properties of 50 at% rhodium-scandium-titanium ternary alloys where Ti is substituted by Sc. These alloys were investigated for the first time using electrical resistance, dilatometry and three-point bending techniques in the temperature range 20ºC to 850ºC. It was found that the sample with 0.1 at% Sc exhibited full shape restoration in the ranges of both martensitic transformations at ~340ºC and ~750ºC. Two-way shape recovery was also observed. A small temperature hysteresis, desirable for alloys used in actuator applications, is present in TiRh and Rh-Sc-Ti alloys. Both TiRh and Sc-containing alloys exhibit continuity of the deformation process on cooling and shape restoration on heating in a wide range of temperatures. This feature of both TiRh and Rh-Sc-Ti alloys implies the possibility of their application in different heat-regulating elements at temperature ranges from room temperature to 850ºC.

IntroductionAn important field for the application of commercial alloys with shape memory effect is heat regulation. The alloys considered in this paper are being investigated for use in this application at high temperatures. Thermomechanical regulators have a number of advantages over electromechanical and electronic regulators, which are prone to failure under certain conditions. Regulators made from shape memory alloy, such as locking devices for control rods in



nuclear power stations, could provide more robust safety systems as they do not require any external power source for their activation, for example.

One of the challenges in high-temperature materials science is to discover alloys that exhibit a high-temperature shape memory effect and to investigate the conditions, including temperature range, under which these properties are observed. The Rh-Ti system is considered promising taking into account information on the alloys based on equiatomic phase (1–5) and data on the thermoelastic properties of the equiatomic TiRh alloy at high temperatures (6).

There is limited literature data on the character and temperatures of transformation in near-equiatomic Rh-Ti binary alloys. Such data are to a certain extent conflicting, and concern mainly the crystal structure of the phases formed (1–5). An X-ray study of TiRh in the temperature range from room temperature to 1000ºС showed that a high-temperature phase with a caesium chloride (CsCl) type cubic crystal structure transformed to a phase with tetragonal structure at 845 ± 20ºС when cooled from 1000ºС, then transformed to a monoclinic phase at 83 ± 5ºС (3). Both transitions were considered as second order transitions. It was noted that no domain of coexistence of cubic and tetragonal phases was observed, while the tetragonal character of the phase structure increased on cooling gradually from 845ºC to 83ºС. At temperatures lower than 83ºС further distortion of the crystal lattice toward monoclinic symmetry took place.

Observed temperature intervals of three modifications of TiRh (3) confirmed previously published data (2) that the TiRh phase crystal structure at 700ºС is tetragonal and of the AuCu type, while at room temperature the phase is monoclinic with lattice parameters different from those previously given (3). In alloys with compositions deviating from stoichiometry towards 10 at% Rh content, according to the Rh-Ti phase diagram, a phase with orthorhombic crystal structure was observed at room temperature (2) within the homogeneity range of the equiatomic phase (4, 5).

Two transformations in TiRh were revealed by an electrical resistance method with temperatures that differ from those previously obtained (3, 6) (Figure 1(a)). Both transformations occurred almost without hysteresis. The fact that they are clearly separated by temperature (6) puts in doubt the interpretation of the transformation as a second order transformation (3).

The shape memory effect accompanies the formation of a phase with a monoclinic crystal

structure in TiRh at temperatures close to those obtained by the electrical resistance method, Ms

2

~340ºC. Anomalous behaviour of the sample when heated to 400ºC has been observed (6).

The aim of the present paper is to study the influence of the third component, Sc, on the properties of TiRh-based alloys and particularly the thermomechanical behaviour of these alloys in the temperature range from ambient to 850ºC. Sc was chosen to substitute Ti because it is similar to Ti by chemical properties and also forms an equiatomic compound with Rh. However the crystal structure of ScRh, which is of the CsCl type (the same as the TiRh parent phase), is stable from subsolidus temperature to room temperature (7). This makes it easy to follow changes that occur in the Rh-Sc-Ti ternary alloys with increasing scandium content.

Information on the effect of scandium on the martensitic transformation (MT) in TiRh is almost unknown. It was noted earlier that substitution of Ti by Sc would lead to a decrease of the martensitic transformation temperature (8). The phase relations in the ScRh-TiRh system have been studied elsewhere (9).

ExperimentalThe starting metals used for alloying were iodised Ti, Rh powder (99.97 wt%), distilled Sc to prepare the alloys with 0.1 at% and 1 at% Sc, and Sc metallic powder (chemical analysis: 1.3 wt% O and less than 0.15 wt% of metal admixture) to prepare the remaining alloys. Before melting the alloys, the rhodium powder was sintered in vacuum at 1200ºC and melted in an arc furnace in order to avoid sputtering during alloying. The alloys with 0.1 at% and 1 at% Sc were melted directly from the components and those with 2.2 at%, 3.5 at%, 16.7 at% and 21 at% Sc were melted from the ligature (the Sc-Rh binary alloys) with additions of titanium in an arc furnace with a non-consumable tungsten electrode on a water-cooled copper hearth under an atmosphere of purified argon gas. The ingots were melted four times to ensure a complete melt. The weight losses on melting were small (below 0.5 wt%) so nominal compositions are reported.

Samples of the six alloys were prepared along the ScRh-TiRh section. The as-cast alloys were investigated by electrical resistance and dilatometry tests. The electrical resistance was measured by the four-probe method with continuous heating of the sample at a rate of 20ºC min–1. The change in sample length (l20ºC = 14.7 mm) on heating and cooling in the dilatometry test was measured by an induction micrometer ‘Micron-02’



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1

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2 Mf1 As

1Ms

1 Af1

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Temperature, ºC

r/r 0

Fig. 1. Dependence of electrical resistance on temperature in ScRh-TiRh alloys: (a) TiRh; (b) Rh-0.1 at% Sc-Ti; and (c) Rh-1 at% Sc-Ti

supplied by All-Union company ‘Stankoimport’, Moscow, Russia, with accuracy ±0.1 micron. The temperature of each sample was measured with a chromel-alumel thermocouple welded to the sample

that was placed in a quartz holder. Thermomechanical properties of the alloys were examined using the three point bending technique by thermocycling through the transformation range during cooling under load and



heating after unloading (10). Thermomechanical curves were taken several times for each sample at different loads. The sample sizes were 0.4 × 0.4 × 10 mm (alloys with 0.1 at% and 1 at% Sc) and 0.4 × 1.5 × 8 mm (alloys with 2.2 at% and 3.5 at% Sc). The loads varied between 50 g and 375 g. The sample of the alloy with 0.1 at% Sc underwent more detailed investigation in the temperature range which covered both transformations according to data on electrical resistance. The sizes of the sample and the load applied in this experiment are presented and discussed together with the results. The alloys were characterised by X-ray diffraction (XRD) and microstructure analyses and the results are presented elsewhere (9).

Results and Discussion Electrical ResistanceThe TiRh resistance curve shows two transformations in the solid (Figure 1(a)). The transformation at ~750ºC (Ms

1 ), of small intensity and without hysteresis, is indicated by a point of inflection on the curve of resistance. The transformation at ~340ºC (Ms

2 ), of greater intensity, occured with a small hysteresis: the change in electrical resistance reached ~10%.

Investigation of MT in the ScRh–TiRh ternary alloys by the electrical resistance method was carried out on the samples with 0.1 at%, 1 at%, 2.2 at%, 3.5 at%, 16.7 at% and 21 at% Sc (Figures 1(b), 1(c) and 2(a)–2(d)). The resistance curves for the first four alloys exhibit two transformations as was observed in the TiRh alloy. The heating and cooling curves of the alloys with 0.1 at% and 1 at% Sc almost superimpose in a wide temperature range (Figures 1(b) and 1(c)). The effect that corresponds to the second transformation is more pronounced in these alloys, although unlike that in TiRh the transformation became almost without hysteresis. Given that the temperature of both transformations slowly decreased with increasing content of scandium in the alloys, the resistance curves were observed to behave similarly to TiRh.

In contrast to the curves of TiRh and the alloys with 0.1 at% and 1 at% Sc, a larger change in resistance with decreasing temperature was observed in the curves for the alloys with 2.2 at% and 3.5 at% Sc (Figure 2). The first martensitic transformation (Ms

1 ) for these alloys was clearer and more intense (Figures 2(a) and 2(b)). Its temperature varied little with increasing scandium content. At the initial transformation stage (740ºC–705ºC) a sharp change in electrical resistance took place which is a characteristic of the transformation and gives reason to believe that in the

process of structural transformation an intermediate phase with a crystal structure similar to the R-phase in TiNi might form first (premartensitic transformation) (11). The second MT was identified by a change in the slope of the resistance curve. The critical temperatures of the martensitic points in the forward and reverse transformations coincide.

With increasing scandium content in the alloys to 16.7 at% Sc only one transformation was observed in the resistance curve at approximately 400ºC, a temperature significantly lower than the first transformation in alloys with lower scandium content (Figure 2(c)). The shape of the alloy curve on cooling repeated that for alloys with 2.2 at% and 3.5 at% Sc (Figures 2(a) and 2(b)). Tests on the alloy with 16.7 at% Sc at temperatures below room temperature (down to –196ºC) showed the absence of any effect. This confirms the assumption that with increasing content of scandium in the alloys the second transformation disappeared instead of lowering its temperature. According to X-ray analysis this alloy has a tetragonal crystal structure of AuCu type at room temperature (9). Thus, it may be concluded that the effect observed on the resistance curve of the alloy with 16.7 at% Sc corresponds to the structural transformation CsCl → AuCu. Given the above as well as data on the electrical resistance of TiRh and the alloys with lower scandium content, even without direct studies of the structure by high-temperature X-ray analysis, it seems clear that the product of the first MT in all alloys of the ScRh-TiRh system is a phase with a tetragonal crystal structure of the AuCu type.

Only a little variation in the slope of the resistance curve of the alloy with 21 at% Sc was observed at about 200ºC, indicating that the intensity of the transformation decreases with increasing content of scandium in the alloys (Figure 2(d)). This alloy is two-phased at room temperature: CsCl + AuCu (9).

Thus, according to electrical resistance studies, substitution of Sc for Ti in TiRh resulted in inhibition of the second MT, the product of which would be a phase with monoclinic crystal structure, and in lowering the characteristic points of the first transformation, which disappeared with increasing content of scandium in the alloys.

The electrical resistance data concerning the two stage transformations in the solid Rh-Sc-Ti ternary alloys and similar data on TiRh point to the existence of a two phase region in these alloys and are at variance with earlier conclusions (3) on the attribution of the transformation in TiRh to second order transformation.



Fig. 2. Dependence of electrical resistance on temperature in ScRh-TiRh alloys: (a) 2.2 at% Sc; (b) 3.5 at% Sc; (c) 16.7 at% Sc; and (d) 21 at% Sc

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X-ray analysis of the ScRh-TiRh alloys with 0.1 at%–16.7 at% Sc showed regions of coexistence of phases of TiNi and AuCu types as well as those of AuCu and CsCl types (9). The electrical resistance data on TiRh-TiCo alloys in which rhodium atoms were replaced with cobalt atoms also demonstrated two stages of transformation that were distinctly separated (6). In addition, some effects related to both transformations have been observed on the thermal analysis curve of TiRh (9). All these data strongly suggest that the transformations in TiRh and alloys based on it are first order.

Thermomechanical TestsThermomechanical tests were carried out for the alloys with 0.1 at%, 1 at%, 2.2 at% and 3.5 at% Sc (Figures 3–5). There was a continuous bend for the sample with 0.1 at% Sc cooled under a load of 50 g from ~900ºC–50ºC, and this was more intense in the range 750ºC–650ºC. On heating (after unloading) the

sample recovered its shape completely. In the range 400ºC–200ºC the degree of deformation on cooling increased almost linearly. At a load of 100 g a bend occurred in the same temperature range (Figure 3(a), dashed lines) and the deformation of the sample proved to be twice as large in comparison with that at a load of 50 g; however the sample recovered fully on subsequent heating. Some residual plastic deformation that occurred after loading and unloading of the sample at ~850ºC indicated the inconsistency of the applied load with the elastic parameters of the sample at this temperature. Note the basic similarity of the thermomechanical curves of the alloy at different loads (Figure 3(a)).

The first transformation in the alloy containing 1 at% Sc occurred in the same temperature range, 750ºC–650ºC (Figure 3(b)). In the temperature range from 650ºC to room temperature the thermomechanical curve was almost linear. After unloading at 20ºC and subsequent

100 200 300 400 500 600 700 800 900

Temperature, ºC

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ght,

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ght,

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–P

Ms1≤Af

1

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+P

Fig. 3. Dependence of bending on temperature in ScRh–TiRh alloys: (a) 0.1 at% Sc; and (b) 1 at% Sc



Fig. 5. Dependence of bending on temperature in TiRh alloy

Fig. 4. Dependence of bending on temperature in ScRh–TiRh alloys: (a) 2.2 at% Sc; and (b) 3.5 at% Sc

100 200 300 400 500 600 700 800 900Temperature, ºC

0.2

0Hei

ght,

mm

+P

(b)–P

Ms1

≤+P2

(b)

Af1

100 200 300 400 500 600 700 800 900Temperature, ºC

0.2

0

Hei

ght,

mm

Ms1

+P

–P

(a)

100 200 300 400 500Temperature, ºC

+0.2

0

–0.2

Hei

ght,

mm

B+P

–P

Ms2

heating to 850ºC, the sample’s shape restored fully. Cooling under load to the temperature of liquid nitrogen (–196ºC) showed that the Mf temperature of the alloy was about 20ºC. Below this temperature cooling did not lead to additional deflection of the sample. The thermomechanical curves of both alloys were without hysteresis except in the MT temperature range for the transition CsCl → AuCu, where a small hysteresis occurred (Figures 3(a) and 3(b)).

The thermomechanical curves of the alloys with 2.2 at% and 3.5 at% Sc are similar to those of the alloys with 0.1 at% and 1 at% Sc (Figures 4(a) and 4(b)). The curves in Figures 3–5 show the results of the thermomechanical experiments. They show the presence or absence of the shape memory effect and the unusual feature of the expansion of shape recovery at temperatures between 20ºC–700ºC. Such a feature has not been observed in other alloys exhibiting a shape memory effect.



The unusual performance of TiRh alloy observed during a study of its thermomechanical properties has already been mentioned (6). No further experiments had been carried out to study the sample’s behaviour when heated above the temperature of 400ºC and it was only noticed that on reducing the elastic constants of the alloy with temperature, the bend of the sample would remain constant or increase with increasing temperature. Instead, during experiments further straightening of the sample was observed.

In order to study this anomalous behaviour, further tests were carried out during the present study on a sample of the ternary alloy with 0.1 at% Sc composition, chosen for being closest to TiRh. The similarity of the resistance curves of the two alloys (Figures 1(a) and 1(b)) together with the proximity of their compositions is believed to justify treating the test results obtained for the 0.1 at% Sc alloy as being comparable to those expected for the TiRh binary alloy. Figure 6 presents thermomechanical test curves of the 50 at% Rh–0.1 at% Sc-Ti alloy in different temperature ranges. The full bending curve taken in the range 20ºC–900ºC for the sample with parameters 0.5 × 1.3 × 8 mm repeated the curves that were obtained in previous experiments (Figures 3(a) and 6(a)): under constant load (P1 = 250 g) in the temperature range 750ºC–20ºC continuous bend on cooling and subsequent full shape restoration on heating of the sample were observed. More intense bending took place in the temperature range of the first MT compared to that in the range of the second MT. While approaching the Ms

1 point on the cooling curve, a distinct bend was observed. This might be caused by the appearance of deformation martensite overtaking the tetragonal thermal martensite at the temperature Ms

1 (Figure 6(a), A).The fact that the contribution of the second MT

to the overall bending is smaller than the first might be due to insufficient loading. With decreasing temperature, the coefficients of elastic deformation of all metals and alloys increase. Therefore for more accurate detection of bending in the temperature range of the second MT a bigger load of 600 g was used for the same sample. A partial bending curve for the interval of the second transformation is shown in Figure 6(b). A partial bending curve for the first transformation for another sample with parameters 0.9 × 1.4 × 8 mm and a load of 250 g is shown in Figure 6(c). Applying a load greater than 250 g was not possible, due to expected plastic deformation at 850ºC when the alloy is in a high temperature phase with a cubic crystal structure.

These partial curves demonstrate full shape restoration and almost no hysteresis between the forward and reverse transformations. Alloys exhibiting transformation with a very small temperature hysteresis are known to be very useful for actuator applications (12). Another quality of thermomechanical behaviour of the alloy with 0.1 at% Sc was observed earlier for the TiRh binary alloy in the range of the second MT, which at the time was not explained (6). Upon heating of the sample free of load gradual spontaneous bending took place, followed by outward bending on subsequent cooling throughout the temperature range corresponding to the second transformation without a load (Figure 5, B). A bend on cooling and heating curves of the unloaded sample of the ternary alloy with 0.1 at% Sc was also observed in the temperature range of both transformations. (Figures 6(a), B, and 6(b)). In the case of the first transformation the effect was quite pronounced. This is thought to be evidence of a two-way shape memory effect in these alloys. This performance can be amplified by mechanical work hardening of the samples at 20ºC. During abrading of the 0.9 mm sample to the 0.5 mm sample it spontaneously began to bend at room temperature.

One possible explanation for the simple shape of the bending and recovery shape curves in the 20ºC–750ºC temperature range, while the resistance curves demonstrate two separate effects at 750ºC–650ºC and 350ºC–250ºC corresponding to two martensitic transformations, is that the electrical resistance measurement technique registers the occurrence of only thermal martensite whereas bending of the sample may be caused by the formation of both thermal and deformation martensites. The latter may appear above the Ms point as a result of bending load, as was observed in the case of alloys based on TiNi (13).

Thus despite the high temperature (~750ºC) the first martensitic transformation in Rh-0.1Sc-Ti alloy is accompanied by a shape memory effect when heated at a rate of about 20ºC min–1. It has recently been reported that the ZrIr equiatomic compound with a temperature of martensitic transformation about 740ºC reveals a partial shape recovery, ~75%, only on a rapid heating of the sample (~100ºC sec–1) (14).

Dilatometry The results of dilatometric analysis of alloy with 0.1 at% Sc agree with those of the electrical resistance and thermomechanical tests. There are two inflections in



Fig. 6. Thermomechanical curve of the 50Rh-0.1Sc–Ti alloy: (a) full bending curve; (b) partial bending curve in the region of the second MT; (c) partial bending curve in the region of the first MT; A – area of deformation martensite prior to the first transformation; and B – a two-way shape memory effect

Ms1

Ms1

Ms2

0.5

0.4

0.3

0.2

0.1

0

(a)

–P1

A

B

(b)

–P2

+P2

+P1

100 200 300 400 500 600 700 800 900Temperature, ºC

(c)

+P1

–P1

0.1

0

Hei

ght,

mm

Hei

ght,

mm

Ms1

Ms1

Ms2



the dilatometric curve, corresponding to the beginning of the first (A) and second (B) MTs (Figure 7). A sharp change in the length of the sample in a narrow temperature range related to the first MT was observed as an abnormal effect on the electrical resistance curve at the same temperature for the alloys containing more scandium (Figures 2(a) and 2(b)).

Ductility It was noticed that the Rh-Sc-Ti alloys are only slightly oxidised at 20ºC–950ºC and are quite ductile at 900ºC. A sample of the alloy with 0.1 at% Sc having a section of 0.5 × 1.3 mm was bent at an angle of 90º, then was straightened and bent again in the opposite direction by 90º at 900ºC. It remained undestroyed and without any sign of cracks. In order to elucidate the degree of plasticity of the alloy, hot rolling of a 0.4 × 6 × 2 mm sample cut from ingot was performed. The sample

was packed in an envelope made of stainless steel. Initial package thickness was 2.3 mm. As a result of 15 cycles of rolling and heating to 950ºC the thickness of the package decreased to 0.8 mm. The obtained sample was 0.18 mm thick and 17 mm long. From the experiment it follows that at 950ºC this alloy is ductile whereas at 20ºC it is not. Therefore, parts of heat sensitive items can be manufactured by hot rolling and extrusion. Not all alloys with a shape memory effect can be used for high-temperature materials; from observations on the mechanical properties of 50 at% Rh-0.1 at% Sc-Ti alloy, it can be assumed that material based on it would not meet difficulties in processing.

ConclusionThe transformation characteristics and recovery behaviour of ScRh-TiRh alloys have been studied. The results show that ScRh-TiRh alloys containing

100 200 300 400 500 600 700 800 900Temperature, ºC

A

B

0.15

0.10

0.05

0

Sam

ple

leng

th, m

m

Fig. 7. Dilatometric curve of the 50Rh-0.1Sc-Ti alloy: A, B – effects related to transformation in the alloy (see text for explanation)



0–3.5 at% Sc undergo two high-temperature martensitic transformations: Ms

1 ≤ 750ºC and Ms2 ≤ 340ºC; while

alloys with 16.7 at% and 21 at% Sc reveal only one MT. Both transformations are responsible for the shape memory effect in these alloys. The temperature of martensitic transformations in ScRh-TiRh alloys depends on the scandium content and decreases on substitution of scandium for titanium. The martensitic transformation temperatures of ScRh-TiRh alloys demonstrate low hysteresis. Transformations occurring in TiRh and ScRh-TiRh alloys are first order. TiRh binary and 50 at% Rh-Sc-Ti ternary alloys can display 100% shape memory effect in two temperature ranges up to 850ºC; TiRh and ScRh-TiRh alloys also exhibit a two-way shape memory effect.

All characteristics of ScRh-TiRh alloys observed in the study make them good candidate materials for high-temperature shape memory alloys. Both TiRh and 50 at% Rh-Sc-Ti alloys display the unusual features of continuity of the deformation process on cooling and continuity of shape recovery process when heated in a temperature range from 20ºC to 750ºC, which might be due to two stages of transformation. The large range of shape memory effect observed in this work suggests that these alloys may be useful in different temperature-regulating elements that are designed to work in a wide temperature range.

This article presents the results of a preliminary investigation of the unusual properties of Rh-Sc-Ti alloys, in particular with respect to their thermomechanical behaviour. Further experimental work is required in order to confirm the effects observed. It is hoped that the article will be of interest to other scientists and will stimulate cooperation.

References 1 A. Raman and K. Schubert, Z. Metallkd., 1964, 55,

(11), 704

2 P. Rogl, Atomic Energy Rev., 1983, Special Issue 9, 201

3 S. S. Yi, B. H. Chen and H. F. Franzen, J. Less Common Met., 1988, 143, (1–2), 243

4 T. D. Shtepa, “Interaction of Titanium with Platinum Group Metals”. It was placed in collected articles (compendium) titled “Physical chemistry of condense phases, superhard materials and their interface”, Naukova Dumka, Kiev, 1975, pp. 175–191

5 J. Balun and G. Inden, Intermetallics, 2006, 14, (3), 260

6 E. L. Semenova, V. M. Petyukh and Yu. V. Kudryavtsev, J. Alloys Compd., 1995, 230, (2), 115

7 H. Okamoto, J. Phase Equilib., 2000, 21, (4), 413

8 E. L. Semenova and Yu. V. Kudriavtsev, “The Effect of Scandium on Martensitic Transformation in TiNi and TiRh” in the Programme and Abstracts of the 13th International Conference on Solid Compounds of Transition Elements (SCTE 2000), Stresa, Italy, 4th–7th April, 2000, P-C42

9 O. L. Semenova, Yu. V. Kudriavtsev, V. M. Petyuch and O. S. Fomichov, Powder Metall. Metal Ceramics, in press

10 V. V. Martynov and L. G. Khandros, Phys. Met. Metallog., 1975, 39, (5), 1037

11 V. G. Pushin, V. V. Kondrat'ev and V. N. Khachin, Izv. Vyssh. Fiz., 1985, 28, (5), 5

12 K. Otsuka and X. Ren, Mater. Sci. Eng. A, 1999, 273–275, (12), 89

13 V. N. Khachin, Izv. Vyssh. Fiz., 1985, 28, (5), 88

14 Yu.V. Kudryavtsev and O. L. Semenova, Powder Metall. Metal Ceramics, 2011, 50, (7–8), 471

The AuthorsYurii Kudriavtsev is a scientific researcher at the Kurdyumov Institute of Metals Physics of NASU. His interests are in the field of physics metals and martensitic transformation. He is involved in the investigation of shape memory effect at high temperatures of platinum-based alloys.

Elena Semenova is a senior researcher at the I. N. Frantsevich Institute for Problems of Materials Science of NASU . She has been working there since graduating from Kiev State University. Her key field of research has been focused on the interaction in binary and multicomponent systems formed by transition metals (including platinum group metals) and the equiatomic phases of which undergo martensitic transformation. Physical and chemical properties of the alloys have been investigated for characterisation.

•Platinum Metals Rev., 2014, 58, (1), 31–37•


EuropaCat XIHighlights of catalysis by pgms and base metals from the biennial congress


Reviewed by Silvia Alcove Clave, Francesco Dolci, Peter R. Ellis* and Cristina Estruch Bosch

Johnson Matthey Technology Centre, Blount’s Court, Sonning Common, Reading RG4 9NH, UK


1. IntroductionThe 11th EuropaCat meeting was hosted in Lyon,

France, on the 20th anniversary of the fi rst meeting held

in 1993 in Montpelier – bringing it back to its origin in

France. The event was a large gathering of delegates

in many disciplines of catalysis from across Europe

and further afi eld. The schedule was busy, with plenary

lectures and keynote talks from invited speakers, oral

and poster presentations and a full programme of

discussion sessions where the presentations were brief

and discussion amongst the delegates was promoted.

Of particular note was the high quality of the six

plenary lectures. These are discussed in more detail

below, followed by selected highlights on the themes

of emissions control, biomass conversion, process

chemistry and catalyst synthesis.

Further information on the EuropaCat XI conference,

including details of the scientifi c programme and

biographies of the invited speakers, can be found on

the conference website (1).

2. Plenary LecturesEach session began with a plenary lecture given by a

notable professor in the fi eld of catalysis.

The fi rst presenter was Bert Weckhuysen (Utrecht

University, The Netherlands) who provided an overview

of in situ characterisation to understand issues such

as catalyst coking and catalyst poisoning in fl uid

catalytic cracking and methanol-to-olefi n processes.

Combinations of techniques such as ultraviolet-

visible (UV-Vis) microscopy, fl uorescence, hard micro-

X-ray diffraction, time-of-fl ight-secondary ion mass

spectrometry (ToF-SIMS) and X-ray absorption near

edge structure (XANES) spectroscopy using different

energies managed to evidence three-dimensional

(3D) dis-homogeneities in the elemental distribution

of samples (zeolites in particular) and correlate them

with the specifi c reactivity of different regions on the

catalyst surface.

Ferdi Schüth (Max-Planck-Institut f. Kohlenforschung,

Germany) was invited to present different preparation

routes for controlled nanoparticle systems. He

proposed the introduction of a size-controlled gold

nanoparticle in a zirconium dioxide (ZrO2) system

http://dx.doi.org/10.1595/147106714X676244 •Platinum Metals Rev., 2014, 58, (1)•


starting from a colloidal suspension with the aim of

preventing the sintering of catalytically active particles.

This has been extended to the formation of alloys

(platinum, ruthenium) coated onto carbon shells for

fuel cell catalysts and CoPt for biomass conversion.

A second interesting idea was the use of ball milling

to promote catalytic reactions. For example, carbon

monoxide could be oxidised over cobalt(II,III) oxide

(Co3O4) in a ball mill, but the reaction stopped when

the mill was switched off. The milling was thought

to generate transient sites on the Co3O4 which were

highly active.

Marc Fontecave (Collège de France, France) gave

a talk on recently developed Co and nickel-based

catalysts for the (photo)catalytic production and

oxidation of hydrogen. The insertion of Co into

iron(III) oxide/tungsten oxide (Fe2O3/WO3) catalysts

for the (photo)anode was suggested. Co3O4 has been

shown to have good storage properties but has no

effect on H2 production. Fe-Ni compounds and some

Co complexes are currently used for the production

of H2. More recently, Ni complexes have been grafted

onto carbon nanotubes (CNTs) and deposited on

an electrode. They have also been modifi ed to be

resistant to CO; however, it has been suggested that a

diimine-dioxime Co complex binding system may be

more robust under acidic conditions. At the moment,

other metals such as Ru and iridium are under

investigation in the photosynthesis fi eld.

During the Michel Boudart Award lecture, Jens

Norskov (Stanford University, USA) gave an interesting

overview on the possibilities offered by computational

modelling applied to catalysis. The speaker showed

how linking catalytic activity to the electronic

structure and chemical composition of a material

is feasible if the problem is approached correctly.

The main message of the presentation lay in the

importance of fi nding the appropriate descriptors for

catalytic activity and selectivity. Once this information

is available, the design and optimisation of a process

becomes possible, and catalyst and process selections

can be carried out on a more rational and effective

basis. Examples such as ammonia synthesis were

provided and illustrated these concepts well.

Enrique Iglesia (University of California, USA) gave

the François Gault lecture in which he discussed the

challenges presented by the conversion of molecules

without a C–C bond, such as methane, methanol

and dimethyl ether. Overcoming thermodynamics,

the use of inexpensive oxidants, protecting species

with weaker C–H bonds, inhibition of carbon and

CO2 formation are some of the issues faced when

working with these reactions. The speaker presented

several examples during his talk. When considering

CH4 pyrolysis the C2–C10 yield is limited by both

thermodynamics and polynuclear aromatic chain

growth. The C11+ formation can be controlled by using

catalytic materials, such as Mo/H-ZSM5, that can stop

chain growth. The thermodynamics and kinetics for this

reaction can be improved by removing the hydrogen.

Indirect paths can be used to reduce the conversion

of CH4 to the undesired CO2 or C. The process will

include chemically protected intermediates which are

less reactive than methane. For example, synthesis gas

is a thermodynamically protected form of activated

methane. This is quite reactive and can be converted

to a broad range of hydrocarbons.

The fi nal plenary lecture, given by Dmitry Murzin

(Åbo Akademi University, Finland) was a fascinating

insight into the synthesis of pharmaceutical materials

from naturally-occurring biomolecules. On the face

of it, this may seem like an unpromising avenue,

but as both classes of molecule contain high levels

of functionality, signifi cant progress can be made

by appropriate selection of the starting material

and effi cient use of catalytic functional group

transformations. A good example of material selection

was the lignan 7-hydroxymatairesinol (Figure 1(a)).

The knots found in wood are particularly rich in

such lignans and since they cannot be processed

into paper due to their hardness they are essentially

a low value waste material. 7-hydroxymatairesinol

can be converted into a number of useful products,

including 7-oxomatairesinol (Figure 1(b)) which

is has potential anticarcinogenic and antioxidative

properties. This conversion was achieved using an

Au-catalysed selective oxidation reaction. In these

reactions, achieving excellent selectivity to the desired

product is critical to applications in pharmaceutical

materials.

3. Emission Control TechnologiesThe catalytic conversion of environmentally hazardous

pollutants in automobile exhausts was a thoroughly

debated topic in the conference and a wide range of

research studies were presented, including theoretical

modelling of materials or processes, optimisation

of the current state of the art and new ideas and

concepts. Those presentations presenting original

ideas and newly achieved insight can have a more

general appeal and have been selectively covered in

this report.



3.1 Selective Catalytic Reduction Many advances have been achieved in selective

catalytic reduction (SCR) technology over the years.

Fe- and copper-zeolite and vanadium-based catalyst

technology is still the most studied for the NH3-SCR

reaction. A keynote speaker in this area was Isabella

Nova (LCCP Politecnico di Milano, Italy), who

proposed a detailed and universal SCR mechanism

over the standard commercial catalysts (Figure 2)

(2). Several speakers provided information on the

reaction mechanism and metal active sites in Cu-

zeolites. Florian Göltl (Université de Lyon, France)

suggested a new type of active site for Cu in chabazite

structures (SSZ-13) by modelling the adsorption of

CO to a Cu(I) site. Janos Szanyi (Pacifi c Northwest

National Laboratory, USA) also focused his studies on

Cu-SSZ13 and proposed that the formation of Cu-nitrosyl

adsorbed onto SSZ-13 could be the key intermediate

for the NH3-SCR reaction. Regarding V-based catalysts,

a ceria loaded Sb-V/TiO2 catalyst was mentioned by

Heon Phil Ha (KIST, South Korea). The addition of

CeO2 to the Sb-V/TiO2 catalyst resulted in superior

catalytic activity over a wide range of temperatures,

higher thermal stability and improved sulfur dioxide

tolerance.

The addition of H2 to the gas feed containing nitric oxide

and NH3 has also been considered over silver/alumina

catalysts. Stefanie Tamm (Haldor Topsoe) provided a

global kinetic model for this reaction. Another type of

SCR system uses hydrocarbons (HC) instead of NH3

as a reductant, although at the moment these systems

cannot offer the performance of NH3-SCR systems.

Asima Sultana (Advanced Industrial Science and

Technology (AIST), Japan) showed that by adding NH3

into a HC SCR over Ag/Al2O3 catalyst nitrogen oxides

conversion could be improved.

3.2 NOx Storage-Reduction TechnologyNOx can be removed from a lean gas stream by

chemical adsorption onto a catalyst and subsequently

reduced to N2. Several materials were proposed for

NOx storage during the conference. The commercial

Pt-Ba/Al2O3 catalyst was mentioned by two speakers.

Laura Righini (Politecnico di Milano) proposed a

mechanism for the reduction by NH3 of NOx stored

on this catalyst, suggesting that the release of stored

OMe

OH

O

O

HO

MeO

(b)O

OMe

OH

O

HO

MeO

(a)O

HO

Fig. 1. The structure of: (a) 7-hydroxymatairesinol; and (b) 7-oxo-matairesinol

Fig. 2. A proposed mechanistic model for standard and fast NH3-SCR reaction (2, 3)

NH4+

NO

NH4+

NH4NO3

NH3 + HNO3

N2O + 2H2O

NO3–

2NO2

NO2–

NO2

NH4+

O2

NO

NH4NO2

N2 + 2H2O



NOx is the rate determining step for the reduction of

nitrates. Beñat Pereda-Ayo (University of the Basque

Country, Spain) provided evidence that the addition

of Ce improves the NOx storage capabilities of

Pt-Ba/Al2O3. The optimum Ce loading was found to be

5%. Manganese and Co-based lanthanum perovskite

doped with Pd were also presented as optimum

catalysts with high NOx storage capacity and good

S-uptake/release properties. Merve Dogaç and

Emrah Özensoy (Bilkent University, Turkey) proposed

lanthanum manganite (LaMnO3) perovskite as the

best example, with a higher surface area compared to

a Co-based equivalent.

3.3 Soot OxidationMarzia Casanova (University of Udine, Italy)

introduced Fe/V catalysts supported on ceria-zirconia

(Ce0.75Zr0.25O2) for simultaneous activity for both

SCR and soot oxidation. Obtaining a good activity for

both processes remains challenging and further work

seems to be needed before this concept can acquire

commercial viability. Michela Klots (Centre National

de la Recherche Scientifi que (CNRS), Saint-Gobain,

France) and Emil Obeid (Institut de Recherches sur

la Catalyse et L’Environnement de Lyon (IRCELYON),

France) showed how the design of a soot oxidation

catalyst can be improved by exploiting knowledge of

oxygen and electronic diffusion processes commonly

used in designing solid state fuel cells.

By using a theoretical modelling approach,

Andrzej Kotarba (Jagiellonian University, Poland)

explored the key parameters of the soot oxidation

process for a platinum group metal (pgm)-free soot

oxidation catalyst. The interaction between the soot

grains and the oxide catalyst, topology of the soot

molecular framework and infl uence of potassium

doping on the work function were investigated. For

K-Fe-O systems a strong correlation was observed

between the catalytic activity and the work function.

The infl uence of potassium on the nanostructure of

iron oxide, leading to tunnelled and layered forms,

together with surface decoration by CeO2 helped to

lower the work function, resulting in a substantial

increase in catalytic activity. It was proposed that

enhanced electron availability is benefi cial for the

generation of surface reactive oxygen species that

initialise the combustion process.

3.4 Methane OxidationZbigniew Sojka (Jagiellonian University) presented

a model for rationalising the activity of deposited

oxo-clusters for methane oxidation. The crucial

parameters of the proposed model are the C–H bond

activation energy, the highest occupied molecular

orbital-lowest unoccupied molecular orbital (HOMO-

LUMO) gap of the surface transition metal oxo-

clusters and the properties of the Lewis basic support

(gauged by the optical basicity, ), accommodating

the detached proton. By optimising different

parameters at the same time the authors managed

to show how catalytic activity can be improved. A

very interesting concept for obtaining an active and

ageing-resistant CH4 oxidation catalyst was presented

by Paolo Fornasiero (University of Trieste, Italy). Core-

shell structures of Pd encapsulated in CeO2 appear

to stabilise the active phase of the catalyst, not only

preventing agglomeration of palladium(II) oxide

(PdO) particles during the catalytic reaction, but also

preventing PdO from being transformed to Pd at its

usual transition temperature. The authors speculated

also on the role played by hydroxyl groups on the

loss of catalytic performance and how regeneration

strategies impact the recovery of catalytic activity.

4. Biomass ProcessingIn recent years interest in the conversion of biomass

into biofuels and biochemicals has increased due

to growing demand for energy and more stringent

environmental requirements. This interest was refl ected

throughout the conference. In the area of biofuels, the

conversion of glycerol to form hydrogen by aqueous

phase reforming (APR) was discussed by Pedro Arias

(University of Basque Country). His group compared

the activity of Pt/ɣ-Al2O3, Ni/ɣ-Al2O3 and PtNi/ɣ-Al2O3

catalysts prepared by two different methods: sol-gel

and impregnation. The catalyst prepared by the sol-gel

method initially showed a higher H2 production but

subsequent deactivation reduced the levels to the

same as those of the impregnated catalysts. For these

catalysts the ɣ-Al2O3 was converted into boehmite

(ɣ-AlOOH) during APR, resulting in Ni sintering. The

stability of the catalyst is a well-known problem in APR

and the use of other supports such as carbon may be

a solution. Another example of hydrogen production

was delivered by Dimitri Bulushev (University of

Limerick, Ireland). He explained that the production

of hydrogen from biomass-derived formic acid at low

temperatures (60ºC) could be improved by doping the

Pd/C catalyst with K ions.

Several talks focused on the production

of biochemicals. The production of 1,2- and

1,3-propanediol from glycerol using a Pt/WO3/Al2O3



catalyst was examined by Sara Garcia Fernandez

(University of Basque Country). The catalyst was

prepared by sequential impregnation of Al2O3. The

Lewis/Bronsted acidity could be tuned by the amount

of WO3. An increase of Lewis sites decreased the

selectivity towards 1,2-propanediol. The effect of Pt

was also studied, showing an increase in activity with

increasing metal content.

The hydrodeoxygenation of biomass derived ketones

was presented by several groups. Ivan Kozhevnikov

(University of Liverpool, UK) showed high conversion

of methyl isobutyl ketone (MIBK) to 2-methylpentane

over Pt/H-ZSM-5 at 200ºC. At lower temperatures the use

of Pt loaded on acidic heteropoly salt Cs2.5H0.5PW12O40

catalyst for the hydrogenation of MIBK and diisobutyl

ketone to the corresponding alkanes gave yields of

97%–99%. This catalyst was stable for over 16 h and

little coke formation was observed. A bifunctional

metal-acid catalysed pathway was identifi ed for these

catalysts. The effect of Pd and Pt particle sizes on the

hydrodeoxygenation of 5-nonanone to form n-nonane

and 5-nonanol was investigated by Irina Simakova

(Boreskov Institute of Catalysis, Russia). The catalysts

studied were Pd/ZrO2 and Pt/ZrO2. An increase in

selectivity to n-nonane was observed with decreasing

particle size.

5. Process Chemistry5.1 Syngas Processing Freek Kapteijn (Delft University of Technology, The

Netherlands) took an engineering approach to the

Fischer-Tropsch (FT) reaction, describing the effects

of diffusion and H2:CO ratio. CO diffuses more slowly

than hydrogen and so the ‘real’ H2:CO ratio in catalyst

pores could be much higher than that supplied to the

reaction. He also reported a Co/ZSM-5 catalyst which

maximised the yield of the petroleum fraction made

and decreased C21+ to almost zero. The CH4 selectivity,

however, increased from 6% to 15% when compared

with a similar Co/SiO2 catalyst, although the Co/ZSM-5

catalyst was more active. Ye Wang (Xiamen University,

China) used Ru/zeolite catalysts for the same reaction.

Ru nanoparticles gave lower selectivity to CH4 and C2–4

than Co and using a wide pore zeolite support gave

less secondary cracking to low Cn products due to a

reduced residence time. A Co/TiO2-SiC catalyst was

described by Y. Liu (University of Strasbourg, France).

This performed well, with C5+ selectivity at 90% and

50% conversion at a gas hourly space velocity (GHSV)

of 2850 h−1.

Processing syngas to higher olefi ns was also

discussed by James Spivey (Louisiana State University,

USA). He used a CuCo catalyst and found through

modelling that a bimetallic active site gave the best

performance. Ard Koeken (Utrecht University) used an

Fe catalyst for the same reaction; typically for Fe-based

FT, iron carbide was thought to be the active site.

The formation of iron carbide was measured using

a tapered element oscillating microbalance. The

formation of carbon phases was also observed when

the catalyst was exposed to 20 bar syngas at 350ºC,

although this could be supressed by increasing the

H2/CO ratio from 1 to 2.

Conversion of syngas to alcohols using Pd and Rh

catalysts was presented by Shuichi Naito (Kanagawa

University, Japan). A Pd/CeO2 catalyst gave methanol

and HCs, whilst Rh/CeO2 gave mostly hydrocarbons.

Increasing Rh particle size increased hydrocarbon

selectivity. Addition of lithium to either system

decreased hydrocarbon formation and increased

selectivity to oxygenates.

5.2 Selective Hydrogenation Selective hydrogenation was a major theme at the

conference. One of the main feedstocks investigated

was alkynes which can be selectively hydrogenated

to alkenes. One talk of particular interest by Daniel

Lamey (Ecole Polytechnique Fédérale de Lausanne

(EPFL), Switzerland) described the use of supported

Pd nanoparticles in the hydrogenation of acetylene

to ethane in the presence of excess ethane. The

nanoparticles were made by reduction of Pd salts in the

presence of polymer stabilisers. Catalyst testing showed

that the larger particles (10 nm) were the most active,

whilst the smallest particles (2 nm) were the most

selective to ethane and gave the lowest amounts of the

by-product green oil. The best catalyst described was a

4 nm nanoparticle stabilised with polyvinylpyrrolidone

(PVP) and using a polyethyleneimine polymer to block

unselective sites on the catalyst.

Gianvito Vilé (Eidgenössische Technische

Hochschule (ETH) Zürich, Switzerland) reported silver-

based catalysts for propyne hydrogenation, supported

on titania or silica. Catalytic measurements suggested

that splitting H2 was the rate limiting step on these

catalysts – as the hydrogen concentration increased,

the rate increased. However density functional theory

(DFT) calculations suggested a lower energy route

which reacted molecular hydrogen directly with the

alkyne (Equation (i)).



(i)

The selective hydrogenation of dimethyl oxalate to

ethylene glycol was reported using Cu/SiO2 catalysts

by Y. Yuan (Xiamen University, China). The catalyst was

reduced at 350ºC prior to reaction, leading to Cu(0)

and Cu(I) active sites. Decoration of the catalyst with

low levels of Au increased the conversion and the

selectivity to ethylene glycol. Meanwhile P. Chen (Ruhr

University, Germany) investigated CNTs doped with

oxygen or nitrogen as supports for the hydrogenation

of olefi ns. Addition of Pt or Pd gave an active catalyst;

X-ray photoelectron spectroscopy (XPS) showed that

the N- or O-dopant had an electronic impact on the

precious metal.

5.3 Oxidation Catalysis Again, a wide range of substrates, processing methods

and catalysts were described for selective oxidation.

Selective oxidation attracted much more attention

than total oxidation, despite the relevance of the latter

to pollution control. As is often the case in oxidation,

a wide range of materials were reported, including

pgms, Au, base metals and combinations of two or

more of the above. Au catalysts were inevitably well

represented. This was especially true of Au/TiO2

which has taken the role of a benchmark oxidation

catalyst, amongst the academic community if not the

industrial one. Bimetallic catalysts containing Au were

also popular choices, especially PdAu and CuAu on a

range of supports.

One notable feature of the oxidation work presented

was the range of substrates being investigated.

Whilst the oxidation of CO and of benzyl alcohol

could be considered as standard gas-phase and

liquid-phase reactions, respectively, more complex

substrates were also investigated. For example,

Stefania Albonetti (Università di Bologna, Italy) and

Florentina Neatu (University of Bucharest, Romania)

both reported the oxidation of hydroxymethylfurfural

to furandicarboxylic acid. Hydroxymethylfurfural

is of interest as it can be readily synthesised from

cellulose (Figure 3). Albonetti used Au and CuAu

catalysts whilst Neatu used CuMn and FeMn,

illustrating the range of materials which are active

oxidation catalysts.

6. Catalyst SynthesisA number of talks were focussed on materials synthesis

rather than understanding of reactions. The main

catalyst preparation technologies – impregnation,

deposition and so on – were well-represented. The

synthesis of catalysts using pre-formed nanoparticles

is growing in popularity, as parameters such as particle

size and shape and the addition of second metals can

be controlled.

One talk which stood out was by Gonzalo Prieto

(Utrecht University). He described a Cu/SBA-15

material which was prepared by impregnation

and calcined in two ways. When calcined under

N2, the CuO particles were well dispersed through

the support, whilst calcination using a 2% NO/N2

atmosphere led to only some of the support’s channels

containing the particles. The catalyst calcined under

nitrogen resisted sintering as the particles were

further apart (Figure 4). The work has been reported

in full elsewhere (4).

Sintering control was also discussed by Ferdi

Schüth in his plenary lecture. He reported a multistep

synthesis of Au nanoparticles captured in zirconia

shells (Figure 5). The shells were porous enough to

oxidation

Hydroxymethylfurfural

HO O

Furandicarboxylic acid

HO2C CO2HFig. 3. The oxidation of hydroxymethylfurfural to furandicarboxylic acid

H2C CH2

hydrogenationHC CH

Fig. 4. A Cu/SBA-15 material was calcined in two ways: (a) NO/N2 calcined which sintered easily; and (b) N2 calcined which resisted sintering

(a) (b)



allow reagents and product to diffuse in and out, but

the particles were trapped and therefore could not

sinter. A similar approach was described by Paolo

Fornasiero, as discussed in Section 3.4.

7. SummaryOverall this EuropaCat conference was very well

attended and managed in a very effi cient way, despite

the volume of participants. The different parallel

sessions and discussion symposia (up to seven

parallel sessions in the same time slot) covered almost

all possible topics, established and new, relevant

for the catalysis community. As a general feeling

heterogeneous catalysis received more attention

than homogeneous catalysis, but both were covered.

The next EuropaCat conference (EuropaCat XII)

will take place in Kazan, Russia, in 2015, reaching

the geographical boundaries between Europe

and Asia and hopefully again bringing together a

comprehensive and stimulating programme.

References1 XIth European Congress on Catalysis:

www europacatlyon2013.fr (Accessed on 6th December 2013)

2 A. Grossale, I. Nova, E. Tronconi, D. Chatterjee and M. Weibel, J. Catal., 2008, 256, (2), 312

3 I. Nova, C. Ciardelli, E. Tronconi, D. Chatterjee and M. Weibel, AIChE J., 2009, 55, (6), 1514

4 G. Prieto, J. Zecevic, H. Friedrich, K. P. de Jong and P. E. de Jongh, Nature Materials, 2013, 12, (1), 34

Au nanoparticle SiO2 coated ZrO2 Shell Au in ZrO2 Shell

Si Source Zr Source HF etching

Fig. 5. The multistep synthesis of Au nanoparticles captured in ZrO2 shells

The Reviewers

Silvia Alcove obtained her BSc from Rovira i Virgily University, Spain. She joined the Emission Control Technologies department at Johnson Matthey Technology Centre, Sonning Common, UK, in 2009. , She is currently undertaking an Engineering Doctorate (EngD) in collaboration with Nottingham University. Her research project mainly consists of improving the NH3-SCR catalysis technology for high NOx reduction and better mercury oxidation in power plant industries.

Francesco Dolci obtained a BSc and a PhD from the University of Turin, Italy. He then moved to The Institute of Nanotechnology in Karlsruhe, Germany, and to the Joint Research Centre of the European Commission in Petten, The Netherlands for working on solid state hydrogen storage materials. In August 2012 he joined the Emission Control Research department in Johnson Matthey, working mainly on three-way catalysis development.

Peter R. Ellis gained his BSc and PhD from Durham University, UK. Following post-doctoral placements in Reading University, UK, and Queens University Belfast, UK, he joined Johnson Matthey in 2001. His current research interests are heterogeneous catalysts for a range of processes including Fischer-Tropsch, direct hydrogen peroxide synthesis and selective oxidation and also the utilisation of pre-formed nanoparticles in heterogeneous catalysis.

Cristina Estruch Bosch studied Chemistry followed by a Masters in Catalysis at the Rovira i Virgili University . She carried out her master’s fi nal project during an internship at Johnson Matthey Technology Centre, studying liquid phase methane oxidation. After that, she became a Johnson Matthey employee and continued to work in heterogeneous catalysis. She then started a PhD in collaboration with Ghent University, Belgium, within a European project in which Johnson Matthey is a project partner. She is now working on new projects involving biomass conversion and hydrogenation whilst writing up her thesis.

•Platinum Metals Rev., 2014, 58, (1), 38–39•


The Discoverers of the Isotopes of the Platinum Group of Elements: Update 2014A resolution of the discovery circumstances of 195Os plus new isotopes found for Ru


Further to a previous update (1), a new investigation of

the discovery circumstances of 195Os by Juan Flegen

(2) has shown that Baró and Rey almost certainly

discovered this isotope in 1957 (3, 4). A previous

suggestion that they had only observed the isotope 81Rb was due to a misunderstanding which was only

resolved by a critical assessment of the papers of Rey

and Baró by Birch et al. (5). In addition Reed et al.

(6) have identifi ed an isomer of 195Os by determining

the half-life on the bare nucleus, Os76+. They obtained

32+154–16 m for the half-life which NUBASE 2012

(7) normalised to a value of 2 ± 1.7 h. The details

surrounding the discoveries of 195Os isotopes are

summarised in Table I. In addition the new isotopes 85Ru and 86Ru have been discovered at the RIKEN Nishina

Center in Japan (8) with the discovery circumstances

summarised in Table II. Table III shows the total number

of isotopes to date for each platinum group element.

JOHN W. ARBLASTER

Wombourne, West Midlands, UK

Email: [email protected]

Table I

The Discoverers of the 195Os Isotopes

Mass number Half-life Decay modes Year of discovery Discoverers References

195 6.5 min –? 1957 Baró and Rey 3, 4

195m 2 h –?, IT? 2012 Reed et al. 6

Table II

New Isotopes of Ruthenium

Mass number Half-life Decay modes Year of discovery Discoverers References

85 ps EC + +? 2013 Suzuki et al. 8

86 ps EC + +? 2013 Suzuki et al. 8

ps: Particle stable (resistant to proton and neutron decay)

EC: Orbital electron capture in which the nucleus captures an extranuclear (orbital) electron which reacts with a proton to

form a neutron and a neutrino, so that the mass number of the daughter nucleus remains the same but the atomic number

decreases by one

+: Beta or proton decay for nuclear defi cient nuclides is the emission of a positron (and a neutrino) as a proton in the

nucleus decays to a neutron. As with EC the mass number of the daughter nuclide remains the same but the atomic number

decreases by one. However this decay mode cannot occur unless the decay energy exceeds 1.022 MeV (twice the electron

mass in energy units)



Table III

Total Number of Isotopes and Mass Ranges Known for Each Platinum Group Element to 2014

Element Number of known isotopes Known mass number ranges

Ru 40 85–124

Rh 38 89–126

Pd 38 91–128

Os 43 161–203

Ir 42 164–205

Pt 44 166–209

References

1 J. W. Arblaster, Platinum Metals Rev., 2012, 56, (4), 271

2 J. Flegen private communication to J. W. Arblaster, June 2013

3 G. Baró and P. Rey, Z. Naturforsch., 1957, 129, (6), 520

4 P. Rey and G. Baró, Publs. Com. Nucl. Energia Atòmica (Buenos Aires) Ser. Quim., 1957, 1, (10), 115

5 M. Birch, J. Flegenheimer, Z. Schaedig, B. Singh and M. Thoennessen, Preprint arXiv: 1312.3985v1 [nucl-ex], 14th December, 2013

6 M. W. Reed, P. M. Walker, I. J. Cullen, Yu. A. Litvinov, S. Shubina, G. D. Dracoulis, K. Blaum, F. Bosch, C. Brandau, J. J. Carroll, D. M. Cullen, A. Y. Deo, B. Detwiler, C. Dimopoulou, G. X. Dong, F. Farinon, H. Geissel, E. Haettner, M. Heil, R. S. Kempley, R. Knöbel, C. Kozhuharov, J. Kurcewicz, N. Kuzminchuk, S. Litvinov, Z. Liu, R. Mao, C. Nociforo, F. Nolden, W. R. Pla, Zs. Podolyak, A. Prochazka, C. Scheidenberger, M. Steck, Th. Stöhlker, B. Sun, T. P. D. Swan, G. Trees, H. Weick, N. Winckler, M. Winkler, P. J. Woods, F. R. Xu and T. Yamaguchi, Phys. Rev. C, 2012, 86, (5), 054321

7 G. Audi, F. G. Kondev, M. Wang, B. Pfeiffer, X. Sun, J.

Blachot and M. MacCormick, Chinese Phys. C, 2012, 36, (12), 1157

8 H. Suzuki, T. Kubo, N. Fukuda, N. Inabe, D. Kameda, H. Takeda, K. Yoshida, K. Kusaka, Y. Yanagisawa, M. Ohtake, H. Sato, Y. Shimizu, H. Baba, M. Kurokawa, T. Ohnishi, K. Tanaka, O. B. Tarasov, D. Bazin, D. J. Morrissey, B. M. Sherrill, K. Ieki, D. Murai, N. Iwasa, A. Chiba, Y. Ohkoda, E. Ideguchi, S. Go, R. Yokoyama, T. Fujii, D. Nishimura, H. Nishibata, S. Momota, M. Lewitowicz, G. DeFrance, I. Celikovic and K. Steiger, Preprint arXiv:1310.5945v1 [nucl-ex], 22nd October, 2013

The AuthorJohn W. Arblaster is interested in the history of science and the evaluation of the thermodynamic and crystallographic properties of the elements. Now retired, he previously worked as a metallurgical chemist in a number of commercial laboratories and was involved in the analysis of a wide range of ferrous and non-ferrous alloys.


http://dx.doi.org/10.1595/147106713X675787 •Platinum Metals Rev., 2014, 58, (1), 40–41•

PGMs IN THE LAB

Platinum Group Metals in Polyoxometalates

Here another researcher whose work has benefited

from the support of Johnson Matthey and Alfa

Aesar, A Johnson Matthey Company, is profiled.

Ulrich Kortz is a Professor of Chemistry at Jacobs

University in Bremen, Germany, and he is interested

in the synthesis and characterisation of noble metal-

containing polyoxometalates.

About the ResearchPolyoxometalates (POMs) are a large class of discrete,

soluble metal-oxo anions of early transition metals

in high oxidation states, such as tungsten(VI) or

molybdenum(VI). Due to a unique combination of

properties, such as thermal and oxidative stability,

tunability of acidity and redox activity, solubility

in various media, and ability to undergo multistep

multi-electron transfers without structural changes,

POMs keep attracting more and more attention in

different areas of fundamental and industrial science,

in particular in homogeneous and heterogeneous

catalysis.

Kortz’s group are world leaders in the synthesis and

characterisation of noble metal-containing polyanions.

They prepared the fi rst example of a Pt(IV)-containing

polyoxovanadate, [H2PtIVV9O28]5– by a facile synthetic

procedure, using the Pt(IV) precursor H2Pt(OH)6. The

polyanion [H2PtIVV9O28]5– was characterised in the

solid state by X-ray diffraction (XRD) and in solution

by 195Pt and 51V NMR spectroscopy.

Their research also includes the fi rst example

of a Pd(II)-containing heteropolyoxometalate,

[Cs2Na(H2O)10Pd3(-SbIIIW9O33)2]9– which consists

of two (-SbW9O33) moieties linked by three square

planar-coordinate Pd2+ ions resulting in a sandwich

type structure (Figure 1(a)). The central belt is

completed by two Cs+ and a Na+ ion which occupy the

vacancies between the adjacent Pd centres, resulting

in a polyanion with idealised C2v symmetry (Figure 1(b)).

Kortz’s group have pioneered the class

of polyoxopalladates with the discovery of

[PdII13AsV

8O34(OH)6]8–, which has the shape and

dimensions of a molecular nanocube (Figure 2).

Meanwhile the same group has isolated several other

polypalladate derivatives of various shapes, sizes

and compositions. Kortz’s group has also pioneered

the class of polyoxoaurates with the discovery

of [AuIII4AsV

4O20]8–. The Se(IV) derivative of this

polyanion has also been reported very recently.

Polyoxo-noble-metalates can be used in a wide

range of applications such as catalysis, analysis,

medicine, biochemistry and materials science.

Johnson Matthey and Alfa Aesar support new platinum group metals research

About the Researcher

* Name: Ulrich Kortz

* Position: Professor of Chemistry

* Department: School of Engineering and Science

* University: Jacobs University

* Street: Campus Ring 1

* City: Bremen

* Post or Zip Code: 28759

* Country: Germany

* Email Address: [email protected]

* Website: http://www.jacobs-university.de/ses/ukortz

Professor Ulrich Kortz



Selected PublicationsY. Xiang, N. V. Izarova, F. Schinle, O. Hampe, B. Keita and U.

Kortz, Chem. Commun., 2012, 48, (79), 9849

M. Barsukova-Stuckart, N. V. Izarova, R. A. Barrett, Z. Wang, J. van Tol, H. W. Kroto, N. S. Dalal, P. Jiménez-Lozano, J.

J. Carbó, J. M. Poblet, M. S. von Gernler, T. Drewello, P. de Oliveira, B. Keita and U. Kortz, Inorg. Chem., 2012, 51, (24), 13214

N. V. Izarova, M. T. Pope and U. Kortz, Angew. Chem. Int. Ed., 2012, 51, (38), 9492

N. V. Izarova, A. Banerjee and U. Kortz, Inorg. Chem., 2011, 50, (20), 10379

N. V. Izarova, N. Vankova, T. Heine, R. N. Biboum, B. Keita, L. Nadjo and U. Kortz, Angew. Chem. Int. Ed., 2010, 49, (10), 1886

N. V. Izarova, N. Vankova, A. Banerjee, G. B. Jameson, T. Heine, F. Schinle, O. Hampe, U. Kortz, Angew. Chem. Int. Ed., 2010, 49, 7807

E. V. Chubarova and U. Kortz, Exxonmobil Chemical Company, ‘Novel Heteropolyanions with Late Transition Metal Addenda Atoms and Process for their Preparation’, US Patent Appl. 2009/0,216,052

U. Lee, H.-C. Joo, K.-M. Park, S. S. Mal, U. Kortz, B. Keita and L. Nadjo, Angew. Chem. Int. Ed., 2008, 47, (4), 793

E. V. Chubarova, M. H. Dickman, B. Keita, L. Nadjo, F. Miserque, M. Mifsud, I. W. C. E. Arends and U. Kortz, Angew. Chem. Int. Ed., 2008, 47, (49), 9542

L.-H. Bi, M. Reicke, U. Kortz, B. Keita, L. Nadjo and R. J. Clark, Inorg. Chem., 2004, 43, (13), 3915

Cs3

Na1

Pd2

Cs3’Pd1

Pd2’

(a) (b)

Fig. 1. (a) Combined polyhedral/ball-and-stick representation of [Cs2Na(H2O)10Pd3(-SbIIIW9O33)2]9–.

The WO6 octahedra are shown in red and the balls represent palladium (blue), antimony (green), caesium (yellow), sodium (purple) and water molecules (red); (b) ball-and-stick representation of the central belt of [Cs2Na(H2O)10Pd3(-SbIIIW9O33)2]

9– (Reprinted with permission from L.-H. Bi, M. Reicke, U. Kortz, B. Keita, L. Nadjo and R. J. Clark, Inorg. Chem., 2004, 43, (13), 3915. Copyright 2004 American Chemical Society)

Fig. 2. Ball-and-stick representation of [PdII

13AsV8O34(OH)6]

8–. The colour code of the balls is as follows: Pd (green), As (blue), O (red). Hydrogens not shown (Copyright 2013 Professor Ulrich Kortz)

http://dx.doi.org/10.1595/147106714X676172 •Platinum Metals Rev., 2014, 58, (1), 42•




BOOKS“A Theoretical Study of Pd-Catalyzed C-C Cross-Coupling Reactions”

By M. G. Melchor (Autonomous University of Barcelona, Spain), Springer Theses, Springer International Publishing Switzerland, 2013, 136 pages, ISBN: 978-3-319-01490-6, £90.00, US$129.00

The Springer Theses series

recognises outstanding PhD

research. This thesis describes how

theoretical calculations are used

to determine, elucidate and propose mechanisms

for Pd-catalysed C--C cross-coupling reactions. Due

to its versatility, broad scope and selectivity under

mild conditions, the Pd-cross-coupling reaction can

be applied in fi elds as diverse as the agrochemical

and pharmaceutical industries. The thesis also

covers reaction intermediates and transition states

involved in the Negishi, the copper-free Sonogashira

and the asymmetric version of Suzuki-Miyaura

coupling. A detailed picture of the associated reaction

mechanisms is included.

“Calorimetry and Thermal Methods in Catalysis”Edited by A. Auroux (Institut de Recherches sur la Catalyse et I’Environnement de Lyon, France), Series: Materials Science, Vol. 154, Springer-Verlag, Berlin, Heidelberg, Germany, 2013, 561 pages, ISBN: 978-3-642-11953-8, £117.00, €139.09, US$179.00

This book discusses calorimetry

and thermal analysis methods,

alone or linked to other techniques and applied to the

characterisation of catalysts, supports and adsorbents,

and to the study of catalytic reactions in various

domains: air and wastewater treatment, clean and

renewable energies, refi ning of hydrocarbons, green

chemistry, hydrogen production and storage. This book

aims to fi ll the gap between the basic thermodynamic

and kinetics concepts and the use of experimental

techniques such as thermal analysis and calorimetry

to answer practical questions. The book is suitable as a

reference for researchers and engineers, and useful as a

tutorial for graduate students.

“Computational Catalysis”Edited by A. Asthagiri (Ohio State University, USA) and M. J. Janik (Pennsylvania State University, USA), RSC Catalysis Series No. 14, The Royal Society of Chemistry, Cambridge, UK, 276 pages, ISBN: 978-1-84973-451-6, £139.99

The ultimate goal of computational

catalysis is the design of a novel

catalyst entirely from the computer.

This book gives a comprehensive review of the

methods and approaches being adopted to push

the boundaries of computational catalysis. There are

applied examples to support each method and the

editors share over two decades’ experience in this fi eld.

This book is an essential reference to postgraduates

and professionals working in the fi eld.

“Green Diesel Engines: Biodiesel Usage in Diesel Engines”

By B. Kegl, M. Kegl and S. Pehan (University of Maribor, Slovenia), Series: Lecture Notes in Energy, Vol. 12, Springer-Verlag, London, UK, 2013, 263 pages, ISBN: 978-1-4471-5324-5, £90.00, €106.99, US$129.00

Diesel engines are explored in

relation to current research and

developments, with a focus on

ecology, economy and engine performance. The

most frequently used alternative fuels in diesel

engines, the properties of various types of biodiesel

and the concurrent improvement of diesel engine

characteristics are examined in this book. “Green

Diesel Engines” provides a solid foundation in current

research.

“Hydrometallurgy: Fundamentals and Applications”

By M. L. Free (University of Utah, USA), John Wiley & Sons, Inc, Hoboken, New Jersey, USA, 2013, 444 pages, ISBN: 978-1-118-23077-0, £90.50, €108.60, US$135.00

This book provides a condensed

collection of information that can

be used to improve the effi ciency

and effectiveness with which metals

Publications in Brief



are extracted, recovered, manufactured and utilised

in aqueous media in technically viable and reliable,

environmentally responsible and economically

feasible ways. The book is suitable for students and

researchers.

“MWW-Type Titanosilicate: Synthesis, Structural Modifi cation and Catalytic Applications to Green Oxidations”

By P. Wu, H. Xu, L. Xu, Y. Liu and M. He (East China Normal University, China), Series: SpringerBriefs in Molecular Science, Springer, Heidelberg, Germany, 125 pages, ISBN: 978-3-642-39114-9, £44.99, €53.49, US$49.99

A comprehensive review of a new

generation of selective oxidation

titanosilicate catalysts with the

MWW topology is provided in this book which gives

an overview of the synthesis, structure modifi cation

and catalytic properties of Ti-MWW. Ti-MWW can

be prepared by direct hydrothermal synthesis with

crystallisation-supporting agents, using dual structure

directing agents and a dry gel conversion technique.

It can also be post-synthesised through unique

reversible structure transformation and liquid phase

isomorphous substitution. A summary of the structural

conversion of Ti-MWW into materials for processing

large molecules is provided.

“New Trends in Emission Control in the European Union”

By J. Merkisz, J. Pielecha (Poznan University of Technology, Poland) and S. Radzimirski (Motor Transport Institute, Poland), Series: Springer Tracts on Transportation and Traffi c, Vol. 4, Springer International Publishing, Switzerland, 2014, 170 pages, ISBN: 978-3-319-02704-3, £90.00, €106.99, US$139.00

Recent changes in the European

legislation for exhaust emissions from vehicles are

discussed in this book. The structure and range of

applicability of new regulations such as Euro 5 and

Euro 6 for light-duty vehicles and Euro VI for heavy-

duty vehicles are analysed. This comprehensive book

also covers:

The latest procedures for performing exhaust

emissions tests under both bench and operating

conditions

Reports on portable emission measurement

systems and their application for assessing

gaseous and particulate matter emissions under

actual operating conditions and in all transport

modes

Selected fi ndings from exhaust emissions

research on engines for various vehicles such as

light-duty, heavy-duty and non-road vehicles.

“Transition Metal-Catalyzed Couplings in Process Chemistry: Case Studies from the Pharmaceutical Industry”

Edited by J. Magano and J. R. Dunetz (Pfi zer Inc, USA), Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, Germany, 2013, 401 pages, ISBN: 978-3-527-33279-3, £115.00, €138.00, US$190.00

The focus of this book is on case

studies of large scale industrial

applications, presenting the

information and facts that are otherwise hard to fi nd

in the current literature. There are contributions by

authors from Pfi zer, Merck, DSM, Novartis, Amgen and

Astra Zeneca and they use case studies to showcase

project evolution from inception to early and late

development, including commercial routes where

applicable. At least one transition metal-catalysed

cross-coupling step is included with each case study.

Metal removal from the reaction mixtures is also

discussed. There is a small section which covers novel

technologies for cross-coupling with high future

potential for applications on a large scale such as metal

removal on a large scale, microwave, fl ow chemistry

and green chemistry. This book is aimed at chemists

working in the pharmaceutical, agrochemical and fi ne

chemical industries and also for synthetic chemists

working in academia.

JOURNALSSpecial Issue: Fuels and Chemicals from Synthesis Gas: State of the Art

Catal. Today, 2013, 214, 1–152

This special issue is dedicated to

a selection of papers presented at

the Syngas Convention “Fuels and

Chemicals from Synthesis Gas: State

of the Art” which was organised

by the national DST-NRF Centre of

•



•

Excellence in Catalysis (c*change) at the University of

Cape Town, South Africa, and run under the auspices

of the Catalysis Society of South Africa (CATSA).

This convention focused on the generation and

uses of synthesis gas for the production of fuels and

chemicals. The technologies used for the conversion

of synthesis gas into liquid fuels and chemicals

are well established but these processes need to be

improved to meet the requirements on current and

future generations of these technologies. The papers

presented at the Syngas Convention were aimed at all

areas of synthesis gas conversion.

ChemElectroChemEditor: G. Heydenrych; Wiley-VCH; e-ISSN: 2196-0216

ChemElectroChem is a sister

journal to Angewandte Chemie,

ChemPhysChem and nine more

journals of the ChemPubSoc Europe

journal family. Electrochemistry

in terms of basic and applied

chemistry is one of the fastest-

growing fi elds in chemistry today. Moreover, it has

developed a strong interdisciplinary fl avour due

to the emergence of bioelectrochemistry and the

development of alternative energy sources. A sample

of articles includes: ‘Composition-Dependent Oxygen

Reduction Activity and Stability of Pt-Cu Thin Films’,

‘Promotion Effects of Sn on the Electrocatalytic

Reduction of Nitrate at Rh Nanoparticles’ and

‘Topologically Sensitive Surface Segregations of Au-Pd

Alloys in Electrocatalytic Hydrogen Evolution’.



CATALYSIS – APPLIED AND PHYSICAL ASPECTSMild Synthesis of Mesoporous Silica Supported Ruthenium Nanoparticles as Heterogeneous Catalysts in Oxidative Wittig Coupling ReactionsA. L. Carrillo, L. C. Schmidt, M. L. Marín and J. C. Scaiano, Catal. Sci. Technol., 2014, Advance Article

A new effi cient approach for in situ synthesis of anchored

ruthenium nanoparticles (RuNPs) in three different kinds

of mesoporous silica materials (MCM-41, SBA-15 and

HMS) has been developed. The solids were synthesised

under very mild conditions from RuCL3•H2O salt reduced

in 1 h at room temperature in the mesoporous silicas

grafted with aminopropyltriethoxysilane (APTES). The Ru

nanoparticles were well dispersed with an average size

of 3 nm. These materials have a molar ratio of Si:Ru = 40.

Porous MOFs Supported Palladium Catalysts for Phenol Hydrogenation: A Comparative Study on MIL-101 and MIL-53D. Zhang, Y. Guan, E. J. M. Hensen, L. Chen and Y. Wang, Catal. Commun., 2013, 41, 47–51

Two metal organic frameworks, chromium

benzenedicarboxylates MIL-101 and MIL-53 were

synthesised and used as supports for Pd catalysts.

MIL-101 is highly hydrophilic and benefi cial as

support for fi ne Pd nanoparticles, of average size

2.3 nm. Microporous MIL-53 is relatively hydrophobic

and larger Pd particles of 4.3 nm formed on the

external surface. The phenol adsorption behaviours

on the MILs were studied with different initial phenol

concentrations (0.05 M, 0.1 M, 0.15 M, 0.2 M and

0.25 M) at 20°C to compare surface hydrophobicity.

Pd/MIL-101 showed better phenol selective hydrogenation

activity to cyclohexanone (>98%) under mild reaction

conditions. The results show that MIL-101 is superior to

the MIL-53 as a support when aqueous PdCl2 is used as

a precursor.

CATALYSIS – INDUSTRIAL PROCESSCharacterization and Performance of the Bifunctional Platinum-Loaded Calcium-Hydroxyapatite in the One-Step Synthesis of Methyl Isobutyl KetoneN. Takarroumt, M. Kacimi, F. Bozon-Verduraz, L. F. Liotta and M. Ziyad, J. Mol. Catal. A: Chem., 2013, 377, 42–50

Ca-hydroxyapatite catalysts loaded with different

amounts of Pt(Pt(x)/CaHAp) were synthesised and

characterised by N2-adsorption, XRD, TEM, FT-IR,

UV-VIS-NIR spectroscopy and TPR. The loaded

Pt exchanged and dispersed on the apatite

surface, forming particles of average size 2 nm.

The specifi c surface area of CaHAp decreased as

Pt loading increased. The catalysts were tested for

dehydrogenation of butan-2-ol into MEK. The important

activity at low temperatures was attributed to Pt and Pt2+

species associated with the basic Ca2+-O2– groups of the

apatite. Optimal performance for acetone conversion

to MIBK was achieved with sample loaded with

0.5 wt% Pt. At 150°C and stationary state a MIBK yield

of 23% was obtained with a selectivity of 74%. All the

Pt(x)/CaHAp catalysts showed acceptable stability

over time on stream with no production of heavy

compounds.

CATALYSIS – REACTIONSPoly (Styrene-co-Divinylbenzene) Amine Functionalized Polymer Supported Ruthenium Nanoparticles Catalyst Active in Hydrogenation of XyloseD. K. Mishra, A. A. Dabbawala and J. Hwang, Catal. Commun., 2013, 41, 52–55

The title catalyst has been evaluated for the fi rst

time in hydrogenation of xylose to xylitol. The

Ru/PSN catalyst was characterised by XRD, TEM

and CO chemisorption. Experiments were carried

out using the catalyst with different Ru loading of

1.0–3.0%, at different temperatures of 100–400°C

under different H2 pressures of 30–55 bar and with

varying stirring speeds from 400–1200 rpm. The

catalyst could be reused up to four times.

An Effective Strategy for Immobilizing a Homogeneous Palladium Complex onto Silica: Effi cient and Reusable Catalyst for Suzuki-Miyaura ReactionsC. Sarmah, D. Sahu and P. Das, Catal. Commun., 2013, 41, 75–78

A strategy to immobilise a homogeneous Pd complex

onto silica gel by introducing 4-pyridinecarbaldehyde

into the coordination sphere of Pd has been

investigated. The material was characterised by FTIR,

Abstracts



BET measurements, XRD, SEM-EDX and ICP-AES.

The supported material is an efficient catalyst for

the Suzuki-Miyaura reactions of aryl halides with

low Pd loading, 0.04 mol%, in an environmentally

friendly reaction. The reaction proceeded smoothly

and 96% 4-methoxybiphenyl was isolated after 6 h

reaction time.

Ruthenium-Catalyzed ortho-C-H Halogenations of BenzamidesL. Wang and L. Ackermann, Chem. Commun., 2014, 50, (9), 1083–1085

The first Ru-catalysed ortho-selective C–H

halogenations on arenes through C–H activation

are reported. A catalytic system of Ru3(CO)12 and

AgO2C(1-Ad) allowed site-selective brominations

and iodinations on amides with ample scope and

excellent functional group tolerance. Preliminary

mechanistic studies provided evidence for a

reversible C–H metallation event.

EMISSIONS CONTROLSelf-Regeneration of Three-Way Catalyst Rhodium Supported on La-Containing ZrO2 in an Oxidative AtmosphereH. Kawabata, Y. Koda, H. Sumida, M. Shigetsu, A. Takami and K. Inumaru, Catal. Sci. Technol., 2013, Accepted Manuscript

Rh supported on lanthanoid (La, Ce, Pr or Nd)-

containing ZrO2 was investigated as a TWC, following

an ageing treatment by oxidation at 1273 K to

simulate 80,000 km in real vehicles. The properties

of Rh were assessed by TEM, CO chemisorption and

TPR using CO. The aged catalyst exhibited superior

activity for the steam reforming reaction. The

hydrogen produced reduced the previously oxidised

Rh in Rh/Zr-La-O, regenerating the catalyst. The

results highlight the potential of the present strategy

for developing active TWC with high tolerance to

oxidative conditions. The Rh particles supported on

Zr-La-O maintained their low oxidation state during

the reaction.

FUEL CELLSThe Electrooxidation Mechanism of Formic Acid on Platinum and on Lead ad-Atoms Modified Platinum Studied with the Kinetic Isotope EffectM. Bełtowska-Brzezinska, T. Łuczak, J. Stelmach and R. Holze, J. Power Sources, 2014, 251, 30–37

Poisoning of the electrode surface by CO-like species

was prevented by suppression of dissociative

chemisorption of FA due to a fast competitive

underpotential deposition of lead ad-atoms on

the Pt surface from an acidic solution containing

Pb2+ cations. HCOOH was oxidised 8.5 times faster

on a Pt/Pb electrode than DCOOD. C–H and O–H

bonds were shown to be simultaneously cleaved in

the rate determining step. C–H bond cleavage was

found to be accomplished by C–OH and not O–H

bond split during FA decomposition.

PHOTOCONVERSIONA Simple Synthetic Route to Obtain Pure Trans-Ruthenium(II) Complexes for Dye-Sensitized Solar Cell ApplicationsC. Barolo, J. H. Yum, E. Artuso, N. Barbero, D. Di Censo, M. G. Lobello, S. Fantacci, F. De Angelis, M. Grätzel, M. K. Nazeeruddin and G. Viscardi, ChemSusChem., 2013, 6, (11), 2170–2180

A synthetic route to obtain a functionalised

quaterpyridine ligand and its trans-dithiocyanato Ru

complex based on a microwave-assisted procedure

is presented. This Ru and quaterpyridine ligand

complex is used as a sensitiser in dye-sensitised solar

cells yielding a short circuit photocurrent density of

>19 mA cm–2 with broad incident photon to current

•

OH

OH

OH

SiO2 SiO2 SiO2APTES @APTES @APTES-Pd

EtO

EtO

EtO

O

O

OSi Si

N2

NH2

Toluene

Refl ux,Refl ux

[Pd]

Ethanol,NH2

OOO

O

OO

Si

Si

CH

CHN

N N

Pd

P

(CIO4)2

N

N

C. Sarmah, D. Sahu and P. Das, Catal. Commun., 2013, 41, 75–78

+

=

=



•

conversion effi ciency spectra ranging from 400–900

nm, exceeding 80% at 700 nm.

CHEMISTRYGrowth of Concave Polyhedral Pd Nanocrystals with 32 Facets through in situ Facet-Selective EtchingZ-c. Zhang, F. Nosheen, J-c. Zhang, Y. Yang, P-p. Wang, J. Zhuang and X. Wang, ChemSusChem, 2013, 6, (10), 1893–1897

Concave Pd polyhedra have been successfully

prepared by selectively etching the {100} facets

in situ by I– ions. Due to the presence of a high density

of atomic steps and surface relaxation, the concave

Pd polyhedra exhibit an enhanced electrocatalytic

activity towards ethanol oxidation.

ELECTRONICSEffi cient Electronic Communication of Two Ruthenium Centers through a Rigid Ditopic N-Heterocyclic Carbene LinkerM. Nussbaum, O. Schuster and M. Albrecht, Chem. Eur. J., 2013, 19, (51), 17517–17527

A ditopic benzobis(carbene) ligand precursor

containing a chelating pyridyl moiety was prepared

and used to obtain bimetallic Ru complexes by

transmetalation. The two metal centres were found

to be electronically decoupled when the Ru is in a

pseudotetrahedral geometry imparted by a cymene

spectator ligand. Ligand exchange of the Cl−/cymene

ligands for two bipyridine or four MeCN ligands induced

a change of the coordination geometry to octahedral.

As a consequence, the Ru centres, separated through

space by more than 10 Å, became electronically

coupled, evidenced by two different metal-centred

oxidation processes. These results demonstrate the

effi ciency of carbenes and, in particular, of the bbi

ligand scaffold for mediating electron transfer and for

the fabrication of molecular redox switches.

ELECTROCHEMISTRYActivation of Nickel for Hydrogen Evolution by Spontaneous Deposition of IridiumM. Duca, E. Guerrini, A. Colombo and S. Trasatti, Electrocatalysis, 2013, 4, (4), 338–345

Activation of Ni electrodes was performed by

deposition of Ir from HCI solutions of IrCl2. Effi ciency

of deposition was dependent on precursor and

aqueous solution ageing. Cyclic voltammetry

showed hydrogen de/adsorption peaks with

magnitude proportional to the amount of Ir

deposited. Tafel plots showed slope decrease from

120 mV, typical of bare Ni, down to 40 mV typical of

pure Ir.

MEDICALCyclic RGD-Linked Polymeric Micelles for Targeted Delivery of Platinum Anticancer Drugs to Glioblastoma through the Blood-Brain Tumor BarrierY. Miura, T. Takenaka, K. Toh, S. Wu, H. Nishihara, M. R. Kano, Y. Ino, T. Nomoto, Y. Matsumoto, H. Koyama, H. Cabral, N. Nishiyama and K. Kataoka, ACS Nano, 2013, 7, (10), 8583–8592

A highly effi cient drug delivery to intractable human

glioblastoma (U87MG) tumours has been achieved by

using a Pt anticancer drug incorporating polymeric

micelle with cyclic Arg-Gly-Asp (cRGD) ligand

molecules. A rapid accumulation and high permeability

from vessels into the tumour parenchyma was revealed.

The selective and accelerated accumulation of cRGD/m

into tumours occurred via an active internalisation

pathway (possibly transcytosis), thereby producing

signifi cant antitumour effects in an orthotopic mouse

model of U87MG human glioblastoma.

NANOTECHNOLOGYPure Platinum Nanostructures Grown by Electron Beam Induced DepositionC. Elbadawi, M. Toth and C. J. Lobo, ACS Appl. Mater. Interfaces., 2013, 5, (19), 9372–9376

A method for localised, mask free deposition of high-

purity Pt employs room-temperature, direct-write EBID

using the precursor Pt(PF3)4, and a low temperature

(400°C) postgrowth annealing in H2O. This annealing

removes phosphorus contaminants. The resulting Pt is

indistinguishable from pure Pt fi lms by WDS.

PHYSICAL METHODSOsmium Isotope Evidence for a Large Late Triassic Impact EventH. Sato, T. Onoue, T. Nozaki and K. Suzuki, Nature Commun., 2013, 4, 2455

A report on the Os isotope fi ngerprint of an



•

extraterrestrial impact from Upper Triassic chert

successions in Japan is presented. Os isotope data

exhibit a marked negative excursion from an initial Os

isotope ratio (187Os:188Osi) of ~0.477 to unradiogenic

values of ~0.126 in a PGE-enriched claystone layer.

The timing of the Os isotope excursion coincides

with both elevated Os concentrations and low Re:Os

ratios. The magnitude of this negative Os isotope

excursion is comparable to those found at Cretaceous-

Paleogene boundary sites. The geochemical lines

of evidence demonstrate that a large impactor of

3.3–7.8 km in diameter, produced a global decrease

in seawater 187Os:188Os ratios in the late Triassic.



CATALYSIS – APPLIED AND PHYSICAL ASPECTSProducing a Ruthenium CatalystKyoto University, Japanese Appl. 2013-115,378

A method for producing a Ru catalyst is claimed.

Ru supported by a metal oxide is pretreated with

an aldehyde compound, a phosphorus compound

and a lower alcohol compound. This Ru catalyst

can be used for producing an alkyl group- or

alkenyl group-substituted compound. Treating this

tris(acetylacetonato) Ru catalyst supported on

cerium oxide with formaldehyde, triphenylphosphine

and methoxyethanol gave a catalyst useful for adding

styrene on -tetralone.

Manufacture of Supported Ruthenium OxideSumitomo Chemical Co, Ltd, Japanese Appl. 2013-169,517

A supported Ru oxide is manufactured by contact

treatment of a support with a solution containing a

Ru compound, drying in a gas stream while stirring,

and fi ring in an oxidising gas atmosphere. Preferably,

the support contains TiO2, Al2O3 and/or SiO2. The

supported Ru oxide is used in preparation of Cl2 by

oxidation of HCl.

Magnetic Nanoparticle Supported Osmium Oxide CatalystNational Institute of Advanced Industrial Science & Technology, Japanese Appl. 2013-181,025

Magnetic nanoparticle (Fe3O4) supported Os oxide

catalysts for dihydroxylation of an olefi n are prepared.

During dihydroxylation the title catalysts exhibit little

leaching of Os. As an example, a Fe3O4 nanoparticle

supported compound was synthesised by reaction

of Fe3O4, K2OsO4 and a precursor. The compound

is used as a catalyst for dihydroxylation of trans--

methylstyrene.

CATALYSIS – INDUSTRIAL PROCESSElectrically Insulating Material using Platinum CatalystOAO KZSK, Russian Patent, 2,490,739; 2013

Insulating material is claimed based on addition

curing a silicone rubber containing both vinyl and

hydride-containing silicones and fi llers, crosslinked

under the infl uence of a Pt catalyst. The

silicone rubber contains 40--70 wt% of a cyano-

organophosphorus compound and/or 10--150 wt%

of a modifi ed aluminium hydroxide with

respect to the amount of polyorganosiloxane.

CATALYSIS – REACTIONSProducing Ethanol Using Rhodium CatalystsCelanese International Corporation, US Appl. 2013/8,536,383

A process for producing ethanol involves hydrogenating

acetic acid in the presence of a hydrogenation catalyst

containing Rh and Sn. The molar ratio of Rh to Sn is

from 20:80 to 80:20. The Rh and Sn are present in

0.1 wt% to 25 wt% based on total weight of the catalyst;

the metal loading of rhodium is from 0.5 wt% to

2 wt%. The catalyst may further contain an active metal

selected from Co, Zn, Cr, Cu, Pt, Pd, Ni, Fe, W, Mo, V and

combinations thereof. The hydrogenation is performed

in the vapour phase at a temperature from 250--375ºC;

with a pressure of 10 kPa to 3000 kPa, and a hydrogen

to acetic acid mole ratio greater than 4:1. The support

is selected from silica, silica/alumina, pyrogenic silica,

high purity silica, carbon, alumina, and mixtures

thereof. This support is present in 25 wt% to 99 wt%,

based on total weight of the catalyst. The acetic acid

conversion is greater than 30%.

EMISSIONS CONTROLPalladium and Gold CatalystsWGCH Technology Ltd, US Appl. 2013/0,217,566

An emission control catalyst for treating an engine

exhaust includes an oxide carrier, and Pd particles

and Au particles supported on the oxide carrier. The

catalyst has a Pd to Au weight ratio in a range of about

0.5:1 to about 1:0.5. The emission control catalyst

further comprises a substrate having a honeycomb

structure with gas fl ow channels, wherein the oxide

carrier and the Pd and Au particles are coated on the

walls of the gas fl ow channels. A second oxide carrier

may have Pt and Pd particles. An example is given

of a supported catalyst containing 1% Pd and 2% Au

prepared by adding 1% Pd, 2% Au colloid solution to

a fl ask while stirring; adding MI-386 alumina powder

to the fl ask, and then stirring the mixture for 18 h. The

Patents



•

mixture is then fi ltered and dried at 130ºC for 3 h, and

then ground to a fi ne powder. The powder is calcined

in air at 500ºC for 2 h using a heating ramp rate of

8ºC min--1.

FUEL CELLSGas Diffusion Electrode Applying Platinum NanowiresThe University of Birmingham, World Appl. 2013/128,163

A gas diffusion electrode comprising a gas diffusion

layer with a surface to which Pt nanowires have

been applied and the surface is at least partially

weakly hydrophobic or hydrophilic is claimed. The

Pt nanowires are applied substantially or on regions

of the surface. The surface area may be 50--100%

weakly hydrophobic or hydrophilic. The gas diffusion

layer has a water contact angle less than 130º. The Pt

nanowires cover 75--99% of the total surface. These are

uniformly distributed. The Pt nanowires are of length

50--500 nm, with a diameter 1--10 nm. The nanowires

form a catalyst layer of thickness 50 nm--1 μm. The gas

diffusion layer is selected from carbon cloth or carbon

paper.

Polymer Electrolyte Fuel CellsToshiba Corp, Japanese Appl. 2013-178,963

The title fuel cells have a MEA with a Ru-containing

anode catalyst layer and a Pt-containing cathode

catalyst layer. Either (i) a means for application of

voltage above its open circuit voltage is provided or

(ii) the anode catalyst layer, the electrolyte layer or

their interface contains a catalyst to oxidise Ru(III)

to Ru(IV) or Ru(III) adsorbent. The PEFC is operated

with application of voltage higher than its open circuit

voltage under open circuit conditions and the output

can be recovered by reactivating the cathode catalyst.

CHEMISTRYManufacture of Aqueous Ruthenium Nitrate SolutionsTanaka Noble Metal Industrial Co Ltd, Japanese Appl. 2013-180,936

Aqueous Ru nitrate solution of <1000 ppm Cl is

prepared by neutralisation of a starting aqueous Ru

nitrate solution with alkali hydroxide (e.g. KOH, to pH 8--13),

rinsing the formed Ru hydroxide with dilute nitric

acid ≥1 time(s) to remove the hydroxide-derived alkali

metals, then dissolving the rinsed Ru hydroxide in

nitric acid.

ELECTRICAL AND ELECTRONICSStructure Comprising Ruthenium MetalMicron Technologies Inc, US Appl. 2013/0,221,420

A semiconductor device includes a smooth Ru metal

layer which may form a capacitor bottom plate or a

transistor gate such as a control gate. The smooth Ru

may be on an oxide such as a gate oxide. The thickness

of the Ru layer may be 150--800 Å and there may

optionally be a capping material of thickness 100--500 Å.

Ruthenium Seed Layer in a Magnetic Recording MediumHitachi Global Storage Technologies, US Appl. 2013/0,235,490

An apparatus is claimed with a perpendicular magnetic

recording medium including a substrate, a soft

underlayer above the substrate, a seed layer structure

which contains Ru and a magnetic recording layer

above the Ru seed layer. The seed layer structure is 10

nm or less in thickness. This structure has composition

of NiW (2--10 at%) Ru (3--9 at%). The concentration of

Ru is 3--9 at%.

ELECTROCHEMISTRYMesostructured Thin-Films as ElectrocatalystsV. Stamenkovic and N. Markovic, US Appl. 2013/0,209,898

The manufacturing of thin fi lm catalysts comprises of

(i) providing a substrate; (ii) providing a source of Pt

group metal and alloying metal; (iii) using physical

vapour deposition to deposit both metals; and (iv)

annealing the thin fi lm at a temperature of 300--400ºC,

forming a morphology of (111) hexagonal faceted

surface grain structure in the thin fi lm having a

catalytic activity approaching Pt3Ni(111). The Pt group

metal is selected from Pt, Pd and Rh. The transition

metal is selected from Fe, Co, Ni, V and Ti. The thin fi lm

electrocatalyst thickness is about 5--20 nm.

MEDICALPlatinum Based Antitumour AgentYamaguchi University, Japanese Appl. 2013-155,159

A polymeric antitumour agent characterised

by containing an ionic complex of a Pt-based



•

antitumour agent and a styrene-maleic acid based

copolymer is disclosed. The agent containing

the ionic complex is accumulated in a tumour

site due to enhanced permeability and retention

effect. In an example, cisplatin and styrene-maeic

acid copolymer were reacted, and the obtained

ionic complex was freeze-dried to give stable

nanoparticles, which inhibited proliferation of HeLa

cells with an IC50 value of 104.1 μm.

NANOTECHNOLOGYImaging Mass Analysis Using Platinum NanoparticlesNissan Chemical Industries Ltd, World Appl. 2013/122,225

A method for imaging mass analysis is characterised

by preparing a sample by physical vapour deposition

of Pt nanoparticles. This provides an improved method

for imaging mass analysis using a matrix to assist in

ionising a sample with high ionisation effi ciency,

reduction in visible information and migration,

absence of interference peaks originating from the

matrix and high spatial resolution.

PHOTOCONVERSIONIridium Complexes Contained in Luminescent MaterialsMitsubishi Chemical Corp, World Appl. 2013/105,615

The title complexes show good organic solvent solubility,

and can be stored without precipitation. The title organic

electroluminescent devices, preferably having emitter layers

containing charge-transporting N-containing aromatic

heterocyclic compounds as hosts and the complexes as

dopants, have a low operating voltage and long service life. The

title complexes are represented by 1 (A = 5- or 6-membered

aromatic hydrocarbon ring or aromatic heterocycle including

carbon atoms C1 and C2; B = 5- or 6-membered aromatic

heterocycle including carbon atom C3 and nitrogen atom

N1; L = organic ligand; p, q= 1--4; n = 1--3; R1, R2 = substituent;

>1 of R1 and R2 = (Ar1Z)mXm1; X = C6--20 (hetero)arylene;

Ar1 = C3--20 (hetero)aryl; Z = [C(R)2; R = H, F, Cl, Br,

C1--20 alkyl, etc.; m = 1--3; m1 = 0--3; m2 = 1--20).

Platinum Phosphine Diphenyl Ether Derivative ComplexesUbe Industries, Ltd, Japanese Appl. 2013-155,131

The title complexes are represented by [L 1L2Pt(o-C6(R1–4)4-X-

o-C6(R5–8)4]where X = O, S, NR9, silylene; R9 = H, halo, (cyclo)

alkyl, alkenyl, aryl, aralkyl, alkoxyl, arylalkoxyl; R1--R8 = H,

halo, (cyclo)alkyl, alkenyl, aryl, aralkyl, alkoxyl, aryloxyl,

dialkylamino, alkylsily; L1, L2 = electronically neutral

monodentate phosphine ligand; L1L2 may form a bidentate

phosphine ligand. The title complexes can be used in

electroluminescent devices that emit light from blue to green.

REFINING & RECOVERYSeparating Platinum Sulfi desOAO Krastsvetmet, Russian Patent, 2,490,349; 2013

The invention involves pulping a concentrate of Pt

and Re sulfi des in an aqueous ammonia solution.

The pulp is treated with hydrogen peroxide solution

at a temperature of 25--45ºC. This reaction mixture

is acidifi ed with sulfuric acid until a pH 0.2--2.0 is

achieved. This is heated and aged. The precipitate of Pt

compounds is separated from the solution by fi ltering.

The effect is to enable separation of Pt at the step for

extracting Re from a sulfi de concentrate.

SURFACE COATINGSFilms with Absorbent Palladium CoatingMorgan Adhesives Company, European Appl. 2,626,379; 2013

A multilayer fi lm has a polymeric fi lm layer and

an absorbent layer containing a Pd complex. The

absorbent layer also contains at least one of a

cyclodextrin, a hydrophobin protein, or a derivative

thereof and is effective to absorb an odour, a volatile

organic compound or both. The absorbent layer

comprises between 0.1--0.75 wt% Pd complex, 2--7 wt% of

cyclodextrin and 0.1--0.5 wt% of hydrophobin protein.

The polymeric fi lm layer comprises at least one of

polyethylene, polypropylene, polyvinyl chloride and

polyethylene terephthalate. The absorbent layer has a

(R1)a A

C1

C2

C3

(R2)b Bn

N1

lr L3-n

World Appl. 2013/105,615

1



•

surface area between 280--320 cm2 and when placed

in a chamber having a volume of 400 cm3 with 2 ml of

an n-butanol saturated atmosphere injected into the

chamber it absorbs greater than 80% of the n-butanol

in 1 h.

Sulfonation of Plastic and Composite Materials M. Wotjtaszek et al., US Appl. 2013/0,209,689

A method of preparing a plastic article to accept

plating is claimed. A portion of the plastic article is

rendered plateable by sulfonation by: (i) exposing

the plastic article to an atmosphere containing a

sulfonating agent to sulfonate at least a portion of

the plastic article; (ii) contacting the sulfonated

plastic article with a conditioner; (iii) contacting the

plastic article with a Pd metal activator so that the

noble metal is adsorbed on at least a portion of the

surface of the plastic article; and (iv) contacting the

plastic article with an accelerator to react with the

adsorbed Pd to increase the catalytic activity of the

adsorbed noble metal towards plating. The plastic

may be selected from poly(ether-ether-ketone) resins,

polyamide, polyethylene, polypropylene, etc., or a

combination. The sulfonating agent comprises fuming

sulfuric acid or vapour phase sulfur trioxide. Timing of

contact between the sulfonating agent and the plastic

article is between 1 sec and 60 min.

Obtaining Platinum Group Metal CoatingsFGUP Radievyl Institut im. V. G. Khlopina, Russian Appl. 2,489,516; 2013

An invention to help obtain pore-free microcrystalline

coatings with high adhesion to substrate materials

is claimed. Coatings are obtained from Ir or Rh by a

thermal decomposition process at a temperature

between 250--450ºC and pressure 0.01--0.05 mm Hg.

The precursors are Ir tetratrifl uorophosphine hydride

of formula Hlr(PF3)4 or Rh tetratrifl uorophosphine

hydride of formula HRh(PF3)4.



FINAL ANALYSIS

Effects of Platinum Group Metals Doping on Stainless Steels

The positive effects of palladium and ruthenium on

the corrosion properties of titanium alloys are well

known and led to the development of new grades

to extend the operating window for titanium alloys

(1). The same mechanism, cathodic modifi cation,

should also function in any alloy that is protected by

a corrosion resistant oxide fi lm. This is the case for

stainless steels, which typically rely on a chromium

oxide fi lm to protect the alloy.

Passivation Behaviour Cathodic modifi cation refers to the increase in

cathodic activity caused by the presence of platinum

group metal (pgm) at the surface of the metal. This

causes an increase in the cathodic current at any

given potential, which will increase the open circuit

potential (OCP) to higher voltages. Classical Tafel

behaviour would show that the increased OCP would

also lead to a higher anodic current (increasing

corrosion) (2, 3). However, passivating alloys do not

follow Tafel behaviour at all potentials, due to the

formation of a passive region (where the passive fi lm

dominates the behaviour). The increase in cathodic

potential can push the OCP into this passive region,

preventing corrosion. If the increase in OCP is not high

enough to reach the passive region, some dissolution

will occur. However, during this dissolution the pgm

will not dissolve into solution and more pgm will be

revealed as the other metals do dissolve. This leads

to an enrichment of the surface in pgm, which will

increase the cathodic modifi cation, pushing the

OCP further towards the passive region and often

passivating the alloy (4).

Stainless steels are more complicated than titanium

alloys, due to both design (more elements are added

to provide specifi c functions) and the use of recycled

scrap steel in their production. The location of the pgm

within the microstructure, which has a controlling

effect on the benefi ts gained, is much harder to predict

in stainless steels. Further, the OCP of a stainless steel

in an oxidising solution is close to the transpassive

region. Adding pgms will increase the OCP further,

potentially out of the passive region and into the

transpassive region, which allows attack to occur.

Corrosion in Doped SteelsCorrosion in pgm doped stainless steels is therefore

dependent on the alloy composition and the

environment that the steel is exposed to. Corrosion in

stainless steels occurs at breaches in the oxide fi lm.

These are discrete and the initial breaches cause

metastable pits to form, which will only stabilise if the

diffusion distance out of the pit is suffi ciently long to

present a barrier to loss of the solution within the pit.

Pitting is a therefore a localised phenomenon and

as such the location of the pgm relative to the pit is

important to the corrosion resistance. One technique

for investigating this is electron probe micro analysis

(EPMA), which produces high resolution elemental

maps of the surface. EPMA on polished sections

through pits in ruthenium-doped 304 stainless steel

showed that the ruthenium was enriched by the pit

edge compared to the bulk (Figures 1(a) and 1(b)),

as predicted by the theory outlined above. This implies

that some regions within the pit will become cathodic

with respect to the bulk, potentially allowing cathodic

processes to operate within the pit. The results of

this are likely to be system specifi c and could be

investigated by artifi cial pit studies.

Platinum Group Metal Doping and Chloride IonsPits are more common in chloride containing

solutions, though the exact mechanism by which

chloride causes fi lm breakdown is not agreed



(5–7). Chloride containing environments have also

presented a situation where the choice of doping

pgm is important. Electrochemical studies coupled

with examination of the surfaces following the

electrochemical testing on samples of 304 doped with

either palladium, ruthenium or undoped, in solutions

containing 0.05 M sulfuric acid and 0.1 M sodium

chloride clearly showed the possible outcomes

(Figures 2(a)–(c)).

Undoped 304 rapidly initiated pits at the exposed

surface (Figure 2(a)). As expected these pits initiated

under lacy covers of oxide fi lm which provide the

increased diffusion distance required to maintain the

aggressive solution within the pit.

Palladium doped 304 showed a much lower current

than the undoped steel during potentiodynamic

testing (Figure 2(b)). However, after the experiment

was completed, it was discovered that the surface of

the alloy had disintegrated into powder. It is believed

that this powder had acted as an insulating layer on

the surface, reducing the current passed. Analysis of

the powder showed a much higher palladium content

than the doping level, which can be explained by

remembering that the other elements are dissolving

into the solution.

Ruthenium doped 304 showed virtually no sign

of attack (Figure 2(c)) and the measured current

density was orders of magnitude lower than had

200 μm

Level159213931194

995796597398199

0

326

200 μmRu

Ru Level508444381317254190127

630

108Average Average

Fig. 1. (a) Secondary electron image of a section through a pit in ruthenium-doped 304 stainless steel showing the topography of the surface; (b) ruthenium concentration map of the section through the pit showing the increased level of ruthenium at the pit edge

100 μm100 μm100 μm

(a) (b) (c)

Fig. 2. Corrosion damage on: (a) undoped 304 stainless steel; (b) palladium doped 304; and (c) ruthenium doped 304 following electrochemical testing



been measured on the undoped steel. This shows

that the steel was well protected by the addition of

ruthenium.

For a further practical example of how pgm

doping can protect a steel, the effect of ruthenium on

sensitisation in 304 stainless steel can be considered.

Sensitisation is a degradation mechanism operating

in stainless steels that are heated to between

500ºC and 800ºC. At these temperatures, chromium

diffuses to the grain boundaries to form chromium

carbides, resulting in the formation of chromium

depleted regions by the grain boundary. These

allow intergranular attack to develop in corrosive

media. In ruthenium doped steels, the formation of

carbides was observed, however the alloy resisted

corrosive attack beyond a slight etching of the grain

boundaries.

This observation can be explained by considering

the local electrochemical potentials and the effect of

ruthenium on these. Initially, the reduced chromium

content at the grain boundary prevents the formation

of the protective oxide fi lm and the boundary will be

anodic with respect to the rest of the steel, which

will galvanically drive the corrosion of the grain

boundary. However, during corrosion, ruthenium will

become enriched at the grain boundary, increasing

the OCP. As corrosion continues, the enrichment

continues, further increasing the OCP of the grain

boundary. Once this OCP rises suffi ciently for the

grain boundary to be cathodic with respect to the rest

of the steel, the corrosion at the grain boundary will

cease. EPMA mapping of a corroded grain boundary

in such a steel clearly showed both the formation

of chromium carbides at the grain boundary and

increased ruthenium content along that same grain

boundary (Figures 3 and 4).

ConclusionsWhile not as consistently benefi cial as additions of

palladium have been seen to be in titanium grade 7,

C Elemental Percents

140

135

130

125

120

115

110

90 95 100 105 110 115

X, mm

3

2.8

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

Y, m

m

Fig. 3. Carbon EPMA map showing concentration increases at a grain boundary in a sensitised 304 doped steel sample



additions of the correct pgm to stainless steels can

increase the corrosion resistance of the steel. To

successfully protect steels in this manner, the corrosive

environment and the pgm additions must be carefully

considered. The location of the pgm within the steel

can greatly affect its local protectivity.

ANDREW FONES* and GARETH D. HATTON

Johnson Matthey Technology Centre, Blounts Court,Sonning Common, Reading RG4 9NH, UK


References1 R. W. Schutz, Corrosion, 2003, 59, (12), 1043

2 Platinum Metals Rev., 1958, 2, (4), 117

3 J. H. Potgieter and H. C. Brookes, Corrosion, 1995, 51, (4), 312

4 M. A. Streicher, Platinum Metals Rev., 1977, 21, (2), 51

5 E.-S. M. Sherif, J. H. Potgieter, J. D. Comins, L. Cornish, P. A. Olubambi and C. N. Machio, Corros. Sci., 2009, 51, (6), 1364

6 V. S. Agarwala and G. J. Biefer, Corrosion, 1972, 28, (2), 64

7 T. Itagaki, H. Kutsumi, H. Haruyama, M. Igarashi and F. Abe, Corrosion, 2005, 61, (4), 307

The AuthorsAndrew Fones is a Research Scientist at the Johnson Matthey Technology Centre, Sonning Common, UK, working in the Platinum Group Metals Applications group. He is a corrosion scientist with a materials background, interested in the effects of platinum group metals doping on alloys.

Gareth Hatton received his BSc in Archaeological Sciences at the University of Bradford in 2000. Subsequently he undertook a DPhil at the University of Oxford working on the analysis and replication of ancient vitreous materials. He joined the electron microscopy group at Johnson Matthey in 2005 where he specialises in the application of EPMA.

Ru Elemental Percents

140

135

130

125

120

115

110

90 95 100 105 110 115X, mm

Y, m

m

1.451.41.351.31.251.21.151.11.0510.950.90.850.80.750.70.650.6

Fig. 4. Ruthenium EPMA map showing concentration increases at a grain boundary in a sensitised 304 doped steel sample

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Sara ColesAssistant Editor

Ming ChungEditorial Assistant

Scott TurnbullScientifi c Information Assistant

Email: [email protected]

Platinum Metals Review is Johnson Matthey’s quarterly journal of research on the science and technologyof the platinum group metals and developments in their application in industry

http://www.platinummetalsreview.com/

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Platinum Metals ReviewJohnson Matthey PlcOrchard Road RoystonSG8 5HE UK

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Editorial Team

Sara Coles Assistant Editor

Ming Chung Editorial Assistant

Scott Turnbull Scientifi c Information Assistant

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