Michigan Ion Beam LaboratoryFOR SURFACE MODIFICATION AND ANALYSIS

.............

.............

... ...................

....

...

...........

ANNUAL RESEARCH REPORT

2011

Gary S. Was, Director Ovidiu Toader, Operations Manager

Fabian Naab, Engineer

2600 Draper Road Department of Nuclear Engineering and Radiological Sciences

University of Michigan Ann Arbor, Michigan 48109-2145

http://www.ners.engin.umich.edu/research/mibl/

Telephone: (734) 936-0166 Fax: (734) 763-4540

2

The Annual Research Report

This report summarizes the principal research activities in the Michigan Ion Beam Laboratory during the past calendar year. Eighty-two researchers conducted thirty-eight projects at MIBL that accounted for over 3900 hours of equipment usage. The programs included participation from researchers at the University, corporate research laboratories, private companies, government laboratories, and other universities across the United States. The extent of participation of the laboratory in these programs ranged from routine surface analysis to ion assisted film formation. Experiments included Rutherford backscattering spectrometry, elastic recoil spectroscopy, nuclear reaction analysis, direct ion implantation, ion beam mixing, ion beam assisted deposition, and radiation damage by proton bombardment. The following pages contain a synopsis of the research conducted in the Michigan Ion Beam Laboratory during the 2010 calendar year.

About the Laboratory

The Michigan Ion Beam Laboratory for Surface Modification and Analysis was completed in October of 1986. The laboratory was established for the purpose of advancing our understanding of ion-solid interactions by providing up-to-date equipment with unique and extensive facilities to support research at the cutting edge of science. Researchers from the University of Michigan as well as industry and other universities are encouraged to participate in this effort.

The lab houses a 1.7 MV tandem ion accelerator, a 400 kV ion implanter, and an ion beam assisted deposition (IBAD) system. Additional facilities include a vacuum annealing furnace, a surface profilometry system, and a scanning laser surface curvature measurement system. The control of the parameters and the operation of these systems are mostly done by computers and are interconnected through a local area network, allowing off-site monitoring and control.

In 2010, MIBL became a Partner Facility of the Advanced Test Reactor, National Scientific User Facility (ATR-NSUF), at Idaho National Laboratory, providing additional opportunities for researchers across the US to access the capabilities of the laboratory. In its first year as a Partner Facility, MIBL hosted projects from Idaho National Laboratory, Oak Ridge National Laboratory and University of Wisconsin.

Respectfully submitted,

Gary S. Was, Director

3

RESEARCH PROJECTS

4

EFFECT OF HIGH DOSE PROTON IRRADIATION ON THE NUCLEATION AND GROWTH OF <C> COMPONENT DISLOCATION

LOOPS IN ZR ALLOYS

L. Tournadre1, F. Onimus1, J.-L. Béchade1, O. Toader2 1CEA-Saclay, France

2 Department of Nuclear Engineering and Radiological Sciences, University of Michigan

Zirconium alloys used as cladding and structure material of the nuclear fuel assembly undergo growth strain under irradiation without applied stress. The growth behavior has been related to the crystal defects created under irradiation. It has been shown that breakaway growth occurring at high fluence (>10 dpa) is related to the appearance of <c> component dislocation loops.

In order to improve our knowledge on Zr alloys behavior under irradiation, especially in PWR conditions, the CEA (Commissariat à l’Energie Atomique) has undertaken a research program using charged particle irradiations. The objective of this program is to provide insight into the evolution of the microstructure under irradiation to high doses using charged particles, such as ions and protons.

A first irradiation was performed at 350°C on recrystallized Zy-4 samples using 2 MeV protons. The beam current measured on the sample holder was 40 µA leading to a damage creation rate (using 40 eV as displacement energy) of 1.95×10-5 dpa.s-1. The irradiation ran during 201 hours, leading to a damage of 12,5 dpa at 60% of the damage peak depth. After irradiation the rear side of the samples has been mechanically polished and Transmission Electron Microscopy (TEM) foils have been extracted from the samples. The irradiated side has been electro polished up to 10 µm depth under the surface and the electro polishing has been completed from the rear side of the sample. The TEM observations have been done at CEA on a Philips EM430 TEM operating at 300 keV. The TEM observations have proved that for proton irradiation performed at 350°C up to an irradiation dose of 12.5 dpa, <c> component dislocation loops are observed.

A second irradiation has been done in the same experimental conditions up to a dose of 19 dpa (250 hours). The main objective of this experiment is to have a better understanding of the dose dependence of the <c> loops population. TEM observations will give us new data regarding defects density and mean size at upper dose.

<c> component dislocation loops observed head-on using g=0002 diffraction vector in recrystallized Zy-4 irradiated with 2 MeV protons at 350°C up to 12.5 dpa.

5

ACCELERATOR BASED STUDY OF IRRADIATION CREEP IN PYROLYTIC CARBON USED IN TRISO FUEL PARTICLES FOR THE

VHTR

A. A. Campbell and G. S. Was,

Department of Nuclear Engineering and Radiological Sciences, University of Michigan

This work has focused on performing proton irradiation induced creep experiments on pyrolytic carbon (PyC). Pyrolytic carbon is the primary coating material for the TRISO fuel particles for the Gen-IV Very High Temperature Reactor (VHTR). Current research is being performed with graphite strips until pyrolytic carbon samples become available.

The most recent irradiation induced creep experiment was performed to observe initial effects of temperature and dose rate on the primary regime creep behavior of graphite. The figure below shows the creep results for the experiment, which was performed with 3MeV protons with an initial applied stress of 20MPa and variable temperature and dose rate conditions. Initial results show a linear dependence of the true graphite creep rate on dose rate, but temperature effects are inconclusive.

This work is supported by the Department of Energy under NERI grant DE-FC07-06ID14732.

Creep strain on graphite irradiated with 3MeV protons with a 25.48MPa stress. The figure is a plot of measured stressed sample elongation (LSE measurement red line, LVDT green line), reference sample strain (blue line),

irradiated region temperature (black line), and measured beam current (pink line).

6

FABRICATION OF GaAs:In NANOCOMPOSITES USING ION IMPLANTATION

M. V. Warren1, A. W. Wood2, J. C. Canniff1, C. Uher2, R. S. Goldman1

1Department of Materials Science and Engineering, University of Michigan 2Department of Physics, University of Michigan

Nanocomposites consisting of InAs nanostructures embedded in GaAs have been proposed for high efficiency photovoltaics and high figure-of-merit thermoelectrics. A promising approach to nanocomposite synthesis is matrix-seeded growth, which involves ion-beam-amorphization of a semiconductor film, followed by nanoscale re-crystallization via annealing. In limited earlier studies of In+ implantation into GaAs, Rutherford backscattering studies (RBS) have shown that In aggregates upon annealing, suggesting the possibility of selective formation of InAs-rich nanocrystals in a GaAs matrix. To date, the nanostructure and properties of In+ implanted plus annealed GaAs structures have not been reported.

In this work, we are endeavoring to fabricate InAs-rich nanocrystals within a GaAs matrix, using blanket ion beams. To maximize the implanted In concentration by preventing In sputtering, we used a “sputter mask” consisting of a 50 nm epitaxial AlAs layer deposited on top of the GaAs. For these investigations the AlAs/GaAs bi-layer was broad area implanted using 100 keV In+ ions with fluences ranging from 2.6x1011 to 3.8x1016 cm-2. During implantation, the substrate temperature was maintained at 77 K. A portion of these films were then subjected to rapid thermal annealing (RTA) at 600°C for 60 s in an Ar atmosphere.

Following implantation, we examined the temperature (T) dependence of the resistivity and Seebeck coefficient, S. The figure shows the T-dependence of S of the GaAs:In films before and after RTA, compared to a similarly-doped GaAs reference film. For all but the lowest In+ dose, |S| of GaAs:In is higher than that of GaAs. In the low T range (T<10 K), all films exhibit a T-dependent increase in |S| with a maximum at ~10 K, followed by a decrease up to ~100 K. The significant enhancement of |S| in the low-T regime is attributed to increased electron-phonon coupling, often termed the “phonon drag” component of S. In this phonon drag regime, |S| increases (remains the same) for the lowest (higher) In+ doses after RTA. For T>100 K, |S| increases monotonically with T, due to electron diffusion driven by the T gradient. RTA causes |S| to increase (decrease) for the lowest (highest) dose. To examine the chemistry and microstructure of the GaAs:In films, cross-sectional transmission electron microscopy and RBS measurements are underway.

Temperature dependence of the Seebeck coefficient of

GaAs:In films for varying ion fluences.

This work is supported in part by the GAANN Fellowship and the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center.

7

MICROSTRUCTURAL AND IRRADIATION EFFECTS ON AG AND CS DIFFUSION IN CVD-SIC

T. J. Gerczak1, T. R. Allen1, Z. Zhu2

1Department of Engineering Physics, University of Wisconsin-Madison 2Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory

This work is focused on directly measuring diffusion of Ag and Cs in SiC to support the development of TRIstrutural ISOtropic nuclear fuel which is the proposed fuel for the Very High Temperature Gas-cooled Nuclear Reactor. Ion implantations conducted by the Michigan Ion Beam Laboratory will serve as constant source approximations for diffusion experiments. The implantations were conducted on 6H single crystal SiC wafers from Cree, Inc. and polycrystalline CVD-SiC from Rohm and Hass. A comparison of the diffusion profiles from single crystal and polycrystalline samples will illuminate the contributions of grain boundaries to diffusion of Ag and Cs in SiC. The implanted samples have been exposed to temperatures ranging from 1300-1500oC. Future work will focus on measuring the irradiation enhanced diffusion using a specially designed hot stage at the Ion Beam Laboratory at the UW, Madison.

Analysis of the implanted and exposed samples is currently underway. The analysis techniques are Rutherford Backscattering Spectroscopy (RBS), Time of Flight Secondary Ion Mass Spectroscopy (ToF SIMS), and Scanning Transmission Electron Microscopy with Energy Dispersive Spectroscopy (STEM/EDS). RBS has been conducted on the as implanted samples and the exposed samples to determine the maximum peak concentration and depth of implantation peak which is necessary for determination of relative sensitivity factors to correlate SIMS intensity to concentration. The figure shows the Ag distribution from RBS for the Ag/6H as implanted and exposed samples. Depth profiling will be conducted via ToF SIMS at the Pacific Northwest National Laboratory’s Environmental and Molecular Sciences Laboratory, a national user facility. The ToF SIMS possesses nm depth resolution and ppm level sensitivity making it an ideal technique for measuring diffusion in SiC. STEM/EDS is being employed to measure segregation of the implanted species to microstructural features.

This work is supported by DoE NERI Grant Award No. DE-FC07-07ID14823 and NRC Grant Award NRC-04-07-120 and this research utilized NSF-supported shared facilities at the University of Wisconsin. Part of this research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at Pacific Northwest National Laboratory (PNNL).

Ag concentration in 6H SiC profiles from RBS.

8

AGING AND EMBRITTLEMENT OF HIGH FLUENCE STAINLESS STEELS

Z. Jiao, J. Michalicka and G.S. Was,

Department of Nuclear Engineering and Radiological Sciences, University of Michigan

Self-ion irradiations are capable of producing samples at high fluences over a short time frame. However, microstructure and microchemistry by heavy ion irradiations need to be validated against those from neutron irradiations. Microstructure/radiation-induced segregation (RIS) of 304L SS irradiated in BOR60 to 46 dpa at 320ºC were used as the reference state against which effects of self-ion irradiation were compared. Three self-ion irradiations (46 dpa at 500ºC; 30 dpa at 600ºC and 260 dpa at 380ºC) were chosen and conduced. The first irradiation was conducted at 500°C to 46 dpa to capture both microstructure and RIS, while 260 dpa at 380ºC and 30 dpa at 600ºC irradiations were used to separately emulate microstructure and RIS, respectively. Self-ion irradiation to 260 dpa at 380ºC produced similar dislocation loop size, and density and precipitate size as neutron irradiation to 46 dpa at 320ºC. Self-ion irradiation to 30 dpa at 600ºC produced the highest level of segregation at the grain boundary, although it is still not as high, nor are the profiles as narrow as that by neutron irradiation to 46 dpa at 320ºC. The data suggests it may not be possible to create a similar microstructure and RIS as in neutron irradiation with a single temperature/dose combination, and that the best way to study a neutron irradiated microstructure in austenitic stainless steel using self-ion irradiation may be to study microstructure evolution and RIS separately.

Support for this research was provided by the U.S. DOE NEUP under award # 91752.

A comparison of RIS profiles in 304L SS following neutron and various heavy ion irradiation conditions.

9

IRRADIATION DAMAGE AND LOCALIZED DEFORMATION OF AUSTENITIC STAINLESS STEELS IN PWR ENVIRONMENT

M. Le Millier1, J. Crépin1, C. Duhamel1, A. Pineau1, L. Fournier2, O. Calonne3, Y. Vidalenc3,

E. Heripre4 1Centre des Matériaux, CNRS, France, 2AREVA NP, Tour AREVA, France, 3AREVA NP,

Centre Technique, France, 4Laboratoire de Mécanique des Solides, CNRS, France The purpose of this work is to improve the understanding of irradiation effects on the mechanical behaviour of internal stainless steel structures in PWR environments. We are particularly interested in the deformation mechanisms of irradiated samples and a protocol is developed to study the coupling between microstructure, deformation, irradiation and environment.

Therefore, 304L specimens were irradiated with 2 MeV protons at 360°C to 5 dpa. Those specimens are then strained to various macroscopic strains in PWR primary water. To correlate crack initiation and propagation to crystallographic orientations and strain field measurements, full field analysis are performed, at a microscale, by SEM digital imaging correlation technique coupled with EBSD cartography. Cracking features are characterized using SEM and TEM. The approach developed in this work is summarized by the schematic below.

This research is supported by the chair AREVA of Mines ParisTech graduate school.

10

PHASE STABILITY IN PROTON AND HEAVY ION IRRADIATED FERRITIC-MARTENSITIC ALLOYS

Z. Jiao, V. Shankar and G. S. Was, Department of Nuclear Engineering and Radiological Sciences, University of Michigan

Phase stability of both pre-existing and radiation-induced precipitates was examined in four ferritic-martensitic alloys; T91, HCM12A, HT-9 and a 9Cr model alloy. Alloys were irradiated to between 1 and 10 dpa at 400 and 500ºC using 2 MeV protons, and to 100 dpa using 5 MeV Fe++ ions. Pre-existing precipitates were characterized using a TEM replica extraction technique and radiation-induced precipitates were analyzed using atom probe tomography. The grain boundary coverage by carbides and the mean carbide size in T91 increased with dose up to 3-7 dpa at 400°C, after which both size and coverage decreased slightly. The Cr/Fe ratio in the grain boundary carbides in T91 and the 9Cr model alloy increased following irradiation to 7 dpa at 400°C. With increasing temperature, both precipitate size and percentage coverage at the prior austenite grain boundaries increased. Ni/Si/Mn-rich, Cu-rich and Cr-rich precipitates formed in alloys T91, HCM12A and HT-9 under certain irradiation conditions. No radiation-induced precipitates were observed in T91 following irradiation to 1 dpa at 400ºC, indicating that higher doses are required for precipitate nucleation. Following irradiation at 500°C, the average sizes of Ni/Si/Mn-rich and Cu-rich precipitates in T91 and HCM12A are significantly larger and the densities are much lower than for irradiation at 400ºC. Cr-rich precipitates were only observed in HCM12A and HT-9 with Cr content greater than 11 at% and the number density in HT-9 (higher bulk Cr content) is about 3 times as high as that in HCM12A. The formation of Cr-rich precipitates is temperature dependent and no Cr-precipitates were observed in HCM12A irradiated at 500ºC. Heavy ion irradiation produced precipitates of similar size and composition to those induced by proton irradiation at the same temperature but at a lower number density. Support for this research was provided by the U.S. DOE under contract DE-FG07-07ID14894.

Distribution of Cu-rich, Ni/Si/Mn-rich and Cr-rich precipitates in T91, HCM121A and HT9 following irradiation to 7 dpa at 400ºC. The concentrations of Cr, Cu, Ni and Si are also listed.

11

Er-IMPLANTATION OF GaN FOR THE DEVELOPMENT OF SCALABLE SOLID STATE HIGH ENERGY LASERS

J. D. Demaree, G. A. Gilde and A. C. Sutorik Weapons & Materials Research Directorate

U. S. Army Research Laboratory Aberdeen Proving Ground, Maryland 21005-5069

The viability of compact high-energy lasers for future Army systems depends on the development of laser host materials capable of withstanding extremely high pump power densities. Current diode-pumped rare-earth-doped lasers commonly use host materials like yttrium aluminum garnet (YAG), with poor thermal conductivity, limiting the ability to remove heat from the system. The development of a light-emitting host based on a wide bandgap material like GaN, with a thermal conductivity with 10-15 times higher than that of YAG, could reduce thermal distortions and enable the development of a compact, scalable high-power laser for a variety of Army applications. The development of an Er-doped GaN host material is being pursued by a number of techniques at the Army Research Laboratory, including the investigation of erbium ion implantation into GaN thin films. In our first experiments, performed at the Michigan Ion Beam Laboratory using the 400 kV ion implanter, GaN films on sapphire substrates were subjected to three different ion beam doses (3 x 1014, 1 x 1015 and 3 x 1015 ions/cm2) of 390 keV Er+ ions while either being heated on a hot stage to 75°C or left “unheated” (save for the energy from the ion beam). The figure shows the 2 MeV He+ Rutherford backscattering spectrometry (RBS) spectrum obtained using a tandem accelerator at the Army Research Laboratory from the sample receiving the highest dose. The total amount of erbium found in the sample closely matched the expected ion dose (with less than 5% error), and the depth distribution of the erbium was almost identical to that predicted by ion implantation theory, and Monte Carlo simulation programs like SRIM. No migration of the implanted Er was noted as a result of the higher substrate temperature during implantation, though the heated sample appeared to be lighter in color than the unheated sample, perhaps indicating a reduction in ion beam damage due to dynamic annealing. RBS results (not shown) also indicate that the surface of the high-temperature samples underwent some GaN dissociation, which was not expected at 750°C; it’s possible that the actual surface temperature was somewhat higher (>800°C) or that there is synergistic effect between temperature and implantation damage that encouraged this dissociation.

Rutherford backscattering spectrometry of Er-implanted GaN at the highest dose (3 x 1015

ions/cm2) for both heated & unheated samples.

12

ION IMPLANTATION OF BULK FERROELECTRIC MATERIALS

R. M. Reano Department of Electrical and Computer Engineering, Ohio State University, Columbus, Ohio

Ion implantation on a bulk ferroelectric material, using a small atomic mass ion, is conducted to produce a deeply buried damage layer. The majority of the ions are deposited in a relatively narrow spatial region of the sample where lattice defects are introduced by the transfer of energy to sample nuclei. The energy of the ions determines the depth of the damage layer. Our ion implantation run consisted of He+ ions with 195 keV energy, fluence equal to 4 x 1016 ions/cm2, and beam current equal to 0.25 microamperes/cm2. After implantation, the sample was found to be cracked along the left edge (Fig. at left). The crack may be due to the pressure produced by the mechanical clip holding it in the chamber. Optical inspection also revealed microcracks in the sample (Fig. at right). Methods to remove the microcracks are currently under investigation.

Optical micrograph of implanted ferroelectric material (left). The crack in the wafer may be due to the pressure produced by the mechanical clip holding it in the chamber. Optical micrograph on a 10

micrometer scale shows the presence of microcracks in the sample (right).

13

FABRICATION OF GAAS:IN NANOCOMPOSITES USING ION IMPLANTATION

M. V. Warren1, J. Schrauwen2, R. S. Goldman1 1Department of Materials Science and Engineering, University of Michigan

2Photonics Research Group, Department of Information Technology, Ghent University - IMEC

The controlled formation of semiconductor nanocomposites offers a unique opportunity to tailor functional materials with a variety of novel properties. In particular, nanocomposites consisting of InAs nanostructures embedded in GaAs have been proposed for high efficiency photovoltaics and high figure-of-merit thermoelectrics. A promising approach to nanocomposite synthesis is matrix-seeded growth, which involves ion-beam-amorphization of a semiconductor film, followed by nanoscale re-crystallization via annealing. In limited earlier studies of In+ implantation into GaAs, Rutherford backscattering studies have shown that In aggregates upon annealing, suggesting the possibility of selective formation InAs-rich nanocrystals in a GaAs matrix [1-3]. To date, the nanostructure and properties of In+ implanted plus annealed GaAs structures has not been reported. In this work, we are endeavoring to fabricate InAs-rich nanocrystals within a GaAs matrix, using a combination of blanket and focused ion beams. To maximize the implanted In concentration, we used a “sputter mask” to prevent sputtering of In out of the GaAs layer. Thus, prior to In implantation, a 50nm epitaxial AlAs layer, with In sputter yield lower than that of GaAs, was deposited on top of the GaAs. Subsequent broad-area implantation of 100 keV In+ ions, with doses ranging from 1 to 5 x 1011 cm-2, was accomplished using an indium tin oxide source in the NEC ion implanter at MIBL. During implantation, the AlAs/GaAs bi-layer samples were maintained at room temperature via water cooling.

Following implantation, we examined the electrical properties of the GaAs:In films using resistivity and Hall measurements, both in the Van der Pauw configuration. For all implanted samples, the free carrier concentration was 2.1 ± 0.1 x 1017, independent of In+ dose. Interestingly, the resistivity increases with In+ dose, as shown in the figure [4]. Thus, In+ implantation primarily increases electron scattering with minimal influence on electron trapping. To examine the chemistry, microstructure, and thermal properties of the GaAs:In films before and after annealing, Rutherford backscattering spectroscopy, cross-sectional transmission electron microscopy and Seebeck measurements are underway.

This work was supported in part by the AFOSR through the MURI program under Contract No. FA9550-08-1-0340.

Resistivity versus In+ implantation dose for ion-beam synthesized

AlAs/GaAs:In films.

14

RADIATION-INDUCED SEGREGATION AND MICROSTRUCRE EVOLUTION AT VARYING DOSE RATES IN T91

J. P. Wharry1, Z. Jiao1, G. S. Was1, J. Bentley2 and C. Parish2

1Department of Nuclear Engineering and Radiological Sciences University of Michigan 2Oak Ridge National Laboratory

T91 is a Fe-9Cr ferritic-martensitic (F-M) alloy, and is a candidate for structural materials in the advanced burner reactor. Both T91 and a high-purity counterpart 9Cr model alloy, have been irradiated with 2.0 MeV protons (~1x10-5 dpa/sec) to 7 dpa at 400ºC. The same alloys were irradiated with 5.0 MeV Fe++ ions (~1x10-3 dpa/sec), with the intention of replicating the effects of the reference proton irradiation, in order to later use Fe++ ions to achieve higher doses. Because of the difference in proton vs. heavy ion dose rates, the irradiation temperature and dose were adjusted based upon the inverse Kirkendall model. Two ion irradiation conditions emerged: 440ºC to 30 dpa, where the difference in flow of defect type is expected to capture processes such as loop growth; and 600ºC to 14 dpa, a sink-dominant regime in which microchemical (i.e. radiation-induced segregation (RIS)) changes are dominant. TEM specimens were prepared by focused ion beam (FIB) milling. RIS measurements across prior austenite grain boundaries were performed by scanning transmission electron microscopy with energy dispersive x-ray spectroscopy (STEM/EDS). No pre-existing segregation of any element was observed in T91 or the 9Cr model alloy. Following proton irradiation to 7 dpa at 400ºC, both T91 and 9Cr model alloy exhibit Cr enrichment of ~1 wt%, and Fe depletion of ~1 wt%. In addition, minor elements Si, Ni, and Cu all enrich by <0.5 wt% in proton-irradiated T91. Both Fe++ ion irradiation conditions yield Cr, Si, Ni, and Cu enrichment, and Fe depletion in T91. However, the RIS magnitudes from the 440ºC ion irradiation are closer to the reference proton irradiation RIS magnitudes than are those from the 600ºC ion irradiation. Dislocation loops in T91 are studied as a gauge of microstructure evolution. The 600ºC Fe++ ion irradiation produces the largest loops at the lowest volume density; the reference proton irradiation produces the smallest loops at the highest density. For both RIS and microstructure, the 440ºC Fe++ ion irradiation is a closer match to the reference proton irradiation than is the 600ºC Fe++ irradiation. This work is supported by the U.S. Department of Energy under grant DE-FG07-07ID14828.

Left: Comparison of Si, Cr, Fe, Ni, and Cu RIS in T91 and 9Cr model alloy under various conditions. Right: Comparison of dislocation loop size and density in T91 under various irradiation conditions.

15

BROAD-BAND, HIGH-EFFICIENCY OPTOACOUSTIC GENERATION USING A NOVEL PHOTONIC CRYSTAL-METALLIC STRUCTURE

Y. Guo1,2, H. W. Baac2, S-L. Chen2, T. B. Norrisa1,2, and L. J. Guo2

1Center for Ultrafast Optical Science, 2Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA

Currently, the unavailability of two-dimensional (2-D) high-frequency transducer arrays (> 50 MHz) is a major bottleneck preventing further development of high-frequency ultrasound, especially in real-time 3-D high-resolution applications. We proposed an innovative photonic crystal-metallic (PCM) structure which provides many unique advantages for high frequency ultrasound generation and detection. It can act as an ideal ultrasound transmitter which absorbs 100% of the energy of the laser pulse to generate a strong broad-band ultrasound signal; at the same time, it can also be used as a high-sensitivity optoacoustic receiver to the reflected ultrasound. Therefore, an all-optical ultrasound transducer can be achieved by the PCM structure. Part of the process to manufacture this transducer, involves the use of the IBAD system at the Michigan Ion Beam Laboratory (MIBL) to deposit alternate layers of SiO2, TiO2 and Si. Part (a) of the figure shows the schematic of the photonic crystal-metallic structure. It consists of a one-dimensional photonic crystal structure (i.e. alternating multiple dielectric layers including a defect layer) with an adjacent metallic structure (like gold film) on the top, which is operated in a total-internal-reflection geometry. If we put sensitive polymer materials (like Poly(methyl methacrylate) (PMMA) on top of the metallic structure, the incident light (a laser pulse) will be absorbed and transformed into heat, which can be used to generate an ultrasound signal in the polymer material via a thermo-elastic effect. As shown in Part (b) of the figure, the experimentally generated ultrasound has a broad-band frequency spectrum as the laser pulse (6-ns width) up to 78 MHz at -6 dB. Obviously, much broader bandwidth could be achieved in the PCM structure with a narrower laser pulse (like 2 ns for 250 MHz bandwidth at -6 dB).

This project has been supported by Rackham Graduate Student Research Grant from the University of Michigan.

(a) Schematic of PCM structure

0 30 60 90 120

-16

-12

-8

-4

0

Magnit

ude (

dB)

Frequency (MHz)

Laser pulse PCM+PMMA

(b) Spectrum of laser pulse and generated ultrasound

16

IRRADIATION CREEP STUDY ON BETA SILICON CARBIDE

V. Shankar, G. S. Was,

Department of Nuclear Engineering and Radiological Sciences, University of Michigan

The silicon carbide (SiC) layer integrity in the TRISO-coated gas-reactor fuel particle is critical to the performance of high temperature gas cooled reactors. Since irradiation creep can be a major cause of dimensional instability of structural material at high temperatures where thermal creep is negligible, information on irradiation creep behavior of structural material such as SiC is valuable. In view of this, experiments were conducted at 910°C and at stresses of 18.5 MPa and 97.9 MPa between dose rates of 1.5 and 2.45 × 10-6 dpa/s on a 50 µm thick β-SiC using 3.2 MeV proton beam at the Michigan Ion Beam Laboratory. Strain was measured using a laser speckle extensometer (LSE) and a linear variable differential transformer (LVDT), and temperature was measured using a 2-dimensional infrared pyrometer. Results showed that the total strain rate increased with increasing stress and dose rate (Fig. a). The creep rate was found to exhibit a linear dependence on the applied tensile stress, and on dose rate to the power of 3. Shifts of XRD peaks following proton irradiation of SiC at 910°C indicated that swelling had occurred and that it increased with dose (Fig. b). The swelling obtained in proton irradiations were in good agreement with the swelling data reported in the literature for neutron irradiations (Fig. b). Detailed X-ray profile analysis of the spectra obtained from specimens under various experimental conditions of the present investigation indicated a uniform expansion of the lattice without any X-ray line broadening and that swelling was due to single point defects. This work was supported by the U.S. Department of Energy under grant DE-FG07-071ID14894

(a) (b)

Creep strain accumulated during the irradiation creep experiment performed at 97.8 MPa at two dose rates 1.49x10-6 dpa/s followed by 2.45x10-6 dpa/s (a), and comparison of the average volumetric swelling occurring during proton

irradiation with the neutron irradiation data (b).

17

DEVELOPING A MECHANISTIC UNDERSTANDING OF RADIATION TOLERANT MATERIALS

D.T. Hoelzer1, M.K. Miller1 and J. Bentley1, G.S. Was2, E. Marquis3

1Oak Ridge National Laboratory 2Department of Nuclear Engineering and Radiological Sciences, University of Michigan

3Department of Materials Science and Engineering, University of Michigan In this work, high dose ion irradiation and He ion implantation experiments will be conducted at MIBL to explore the tolerance of the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy to radiation damage, including the accumulation of He. The concept for achieving this goal was to develop the 14YWT ferritic alloy with a high sink strength for attracting radiation produced point defects, resulting in their recombination, and transmutation products, such as He, to form nano-size bubbles or cavities that prevents He from accumulating on grain boundaries to form large bubbles that cause embrittlement of alloys. The 14YWT ferritic alloy contains a high concentration of dispersed nano-size Ti-, Y- and O-enriched clusters (NC) and an ultra-fine size grain structure as shown in the figure below. The very high internal interfacial area associated with these microstructural features forms the basis of the high sink strength concept. The unique structure and remarkable stability of the NC and ultra-fine grain structure at high temperatures plus the attractive mechanical properties they impart on the 14YWT ferritic alloy make it desirable for components of advanced nuclear energy systems.

Several ion irradiation and He implantation experiments have been planned to provide a more quantitative description of the stability and point defect trapping behavior of the Ti-, Y- and O-enriched NC and ultra-fine grains present in the 14YWT ferritic alloy. The first experiments consisted of irradiating polished rectangular-shaped specimens of 14YWT with 5 MV Fe2+ ions to 10, 100 and 200 dpa doses at 200ºC. Another set of ion irradiation experiments using similar parameters will be performed in the future at ~600ºC. These experiments will focus on studying the stability of the NC at relatively low and high temperatures where it is expected that the role of point defect formation and diffusion through the bcc Fe lattice will vary. To study the trapping behavior of He by the NC, a series of implantation experiments will be conducted using the 400 kV Ion Implanter that will consist of implanting 500 appm He in the 14YWT specimens at 25ºC and 300ºC. The results obtained from these experiments will help guide further alloy development to achieve the radiation tolerance required for future nuclear reactor concepts.

TEM bright-field micrograph (left) showing the nano-size grains and Ti, Y and O atom maps obtained by LEAP (right) showing the size, distribution and composition of the NC present in the advanced ODS 14YWT ferritic alloy.

18

IRRADIATION ACCELERATED CORROSION OF REACTOR CORE MATERIALS

S. S. Raiman1, G. S. Was1, O. Toader1, F. U. Naab1, A. Flick1, Z. Jiao1, D. Bartels2, A. Plugatyr2

1Department of Nuclear Engineering and Radiological Sciences, University of Michigan 2Radiation Laboratory, University of Notre Dame

The goal of this project is to understand the mechanisms behind irradiation accelerated corrosion (IAC). It has been shown that irradiation causes order-of-magnitude increases in corrosion growth rate, which is a serious problem in reactor cores. We have identified three possible mechanisms by which IAC may occur. By properly understanding their roles, better models can be developed, and accurate predictions can be made when considering license extensions for existing light-water reactors.

The first effect, radiolysis, affects corrosion by creating more oxidizing species in coolant water, thus raising the corrosion potential. Secondly, radiation induces exciton production in the materials which affect corrosion kinetics. Lastly, displacement damage produces defects can accelerate corrosion.

The experiment at the Michigan Ion Beam Lab will include all three effects, while our collaborators at The University of Notre Dame will perform experiments that isolate one or two of the effects. We will utilize a new beamline, built especially for this project. A corrosion cell containing water around 300ᵒC at ~2000 psi will be fixed at its end. Samples will serve as the barrier between the high vacuum beamline and the corrosion cell. Carefully designed safety systems will protect beamline and accelerator components in the event of sample failure. We plan to make use of varied diagnostics, such as in-situ Raman spectroscopy to study the oxide layer structure, and careful monitoring of water chemistry to record corrosion potential.

This research is supported by the U.S. Department of Energy and the Electric Power Research Institute.

Plot of radiation damage due to proton irradiation in 316 stainless steel as a function of depth. The vertical orange line shows the thickness of the sample that will be used for irradiation accelerated corrosion experiments.

19

ION IMPLANTATION OF NIOBIUM WIRE WITH PALLADIUM

D. Li and A. Shah Greatbatch Medical, Clarence, New York

The objective of this project was to modify the surface properties of niobium wires surface (Figure) in a way that they can be widely used as implantable medical device feedthroughs. Niobium wires exhibit favorable mechanical properties and biocompatibility and they are cheaper than noble metal wires. However, after processing, the surface oxide on niobium wires needs to be removed, which is labor intensive, expensive and hazardous. In addition, the surface properties of the wires are sensitive to the native surface oxide. For example, the wetting of gold on the wires largely depends on the oxide. Also, niobium wires are difficult to solder using traditional solders, which hinders the application of the wires as feedthroughs.

Initial evaluation of palladium modified wires with different dosage is being performed in Greatbatch Medical. It appears that the selection of alloy element to be ion implanted is a key factor, and exploratory study on other elements is needed.

Photograph of tool holding niobium wire.

20

HEAVY ION IRRADIATION OF CLADDING COATING FOR ADVANCED FAST REACTOR FUEL DEVELOPMENT

J. Gan1, J. I. Cole1, F. Khatkhatay2, I. Kim2, L. Jiao2 and H. Wan2

1Idaho National Laboratory 2Department of Electrical Engineering, Texas A & M University

In this work, two ferritic/martensitic steels (MA957 and HT-9) that are selected as model alloys for the advanced fast reactor fuel cladding development program are coated with ceramic thin films under three different deposition conditions at Texas A$M University. The coupon specimens were irradiated with 5 MeV Fe++ ions at Michigan Ion Beam Laboratory at the University of Michigan. The irradiations were conducted at 500°C to three doses of 10, 50 and 200 displacement per atoms (dpa) at a dose rate of approximately 3 dpa/hour. This is an ATR-NSUF rapid turn-around project to investigate the radiation effect on microstructure of the ceramic coatings and the bonding strength at the coating interface.

Post irradiation examination will include the microstructural characterization using scanning electron microscopy, transmission electron microscopy, nano-indentation hardness test, thermal cycle test and scratch test. This work coupled with the planned neutron irradiation in ATR will provide insight on the role of a thin ceramic coating as a diffusion barrier on reducing or suppressing the fuel/cladding chemical interaction. The radiation tolerance of the ceramic coating and the interface bonding strength is critical to the effectiveness of this diffusion barrier.

The figure the three deposition conditions for each material. The picture on the right shows the as-deposited coupon specimens to be used for heavy ion irradiation. For each irradiation batch, there are two substrate materials with three coating conditions. The cross-section TEM samples will be prepared using the focused ion beam (FIB) technique and microstructural characterization will be carried out at INL. The post-irradiation thermal cycle, nano-hardness and scratch test will be performed at Texas A&M University.

500 nm thick TiN/AlN multilayer film, 1 µm thick TiN film deposited at 500°C, and 1 µm TiN film deposited at RT on MA957 and HT-9.

21

CALIBRATION FOR IR MEASUREMENT OF WATER IN APATITE BY ELASTIC RECOIL DETECTION

K. L. Wang1, Y. Zhang2, F. U. Naab2

1Department of Geological Science, University of Michigan 2Department of Nuclear Engineering and Radiological Sciences, University of Michigan

Fourier transform infrared spectroscopy (FTIR) can detect water in apatite by the OH fundamental stretching peaks at ~3540 cm-1, with high potential spatial resolution (routinely 50 µm x 50 µm) and high sensitivity. However, IR can only indicate the presence or absence of OH. In order to determine absolute OH concentrations from IR absorption data, a calibration of the IR method using an independent method for determining absolute concentration is needed. For this, we chose to use elastic recoil detection (ERD), carried out at the Michigan Ion Beam Laboratory at the University of Michigan.

We have calibrated the IR method for measuring OH concentration in apatite using IR absorption data from five oriented single-crystal apatite samples analyzed with polarized transmission infrared spectroscopy, and absolute concentrations obtained through elastic recoil detection (ERD) analysis (Figure). The weight percent (c) of H2O is 0.0134±0.0006 (2σ) times A/d, where A is the linear absorbance peak height measured when the light vector E is parallel to the c-axis of the apatite crystal, and d is the sample thickness in mm. This corresponds to a linear molar absorptivity, ε = 422±20 L mol-1 cm-1. Based on this calibration, the detection limit of H2O concentration in apatite by IR approaches ppm level for apatite wafers of 0.1 mm thickness.

IR calibration line for apatite.

22

THE EFFECT OF ION IMPLANTATION ON ADHESIVE WEAR BETWEEN AL-BASED AND FE-BASED SLIDING INTERFACES

L. Autry. Materials Engineering, University of Connecticut

In many engineering applications, aluminum alloys are in sliding contact with steels. The range of operating conditions in which this sliding-couple is used is limited by adhesive wear. Control of surface loads, speeds, and lubrication must be maintained to keep the tribo-surface in the mild-wear-regime.

Ion implantation may be a way to modify the surface in order to control adhesive wear. In this study, interstitial free (ISF) iron will be implanted with S+, C+, Ar+, and N+ ions at various doses and energies. These implants were performed at the Michigan Ion Beam Laboratory, at the University of Michigan in Ann Arbor MI with the 400 KeV NEC ion implanter.

Low temperature, post-implantation heat treatments will be performed to diffuse the implanted species towards the surface in order to raise the implanted element surface composition. In order to evaluate the effectiveness of implants against adhesive wear dry-sliding, single-pass sliding experiments will be performed using Al-1100 as the counter-material. The amount of transferred material will be evaluated via a combination of AES /EDS-mapping and weighing the sheet-metal /pin on a micro-gram scale. In order to evaluate the transferability of the implant for an engineering application, low-carbon steel will be implanted, and dry-sliding/lubricated multi-pass wear tests will be performed using Al-6061 as the counter-material. It is hoped that the hardening and alloying effects provided by ion implantation will offer some benefit for this particular tribo-system.

23

INFLUENCE OF HYDROGEN CONTENT ON THE TRIBOLOGICAL PERFORMANCE OF DLC COATINGS

A. A. Gharam and A. T. Alpas

Mechanical, Automotive and Materials Engineering, University of Windsor, Canada

The adhesion of aluminum to the mould or tools during the forming and machining of aluminum parts can be prevented by coating the tool surfaces by diamond-like carbon (DLC) coatings. The physical, chemical and tribological properties of DLC films can be improved by incorporating doping elements into the DLC structure. The addition of H was found to improve the tribological properties of the DLC coatings under inert atmospheres (vacuum, argon, nitrogen). Literature has shown that the amount of hydrogen is crucial to achieve low friction; therefore in all our studies it is critical to determine the hydrogen content. Consequently, we have used the facilities in Michigan Ion Beam Laboratory (MIBL) to measure the hydrogen content using elastic recoil detection (ERD). Dry sliding experiments were carried out under vacuum and elevated temperatures in air using a pin-on-disc system with hydrogen free DLC (NH-DLC) with less than 2 at% of hydrogen and hydrogenated DLC, with 30-40 at% of hydrogen sliding against 319 Al pins. In Figure on the left, a very low (<0.1) coefficients of friction (COF) was observed between Al and H-DLC in vacuum compared to what was observed for the NH-DLC. At elevated temperatures in air, the H-DLC in (Figure on the right) was shown to withstand temperatures up to 200 °C, compared to 100 °C reported in literature for NH-DLC. This research was financially supported by National Science and Engineering Research Council of Canada (NSERC) and General Motors of Canada.

(a) (b)

319 Al sliding against H-DLC and NH-DLC at 5 N load and 0.1 m/s linear speed in vacuum (0.04 Pa)

for 5000 sliding cycles.

319 Al sliding against H-DLC and NH-DLC at 5 N load and 0.1 m/s linear speed in air at

temperatures ranging from 25 °C to 400 °C and each point represent steady state average COF

after sliding for 1000 sliding cycles.

24

ESTABLISHING A CAUSE-AND-EFFECT RELATIONSHIP BETWEEN LOCALIZED DEFORMATION AND IASCC

G. S. Was1, Z. Jiao1 and W.-J. Lai2 1Department of Nuclear Engineering and Radiological Sciences, University of Michigan

2Department of Materials Science and Engineering, University of Michigan

The objective of the project consists of three parts: 1) to find the direct evidence of a cause-and-effect relationship between localized deformation and IASCC, 2) to understand how localized deformation leads to IASCC, and 3) to develop theoretical models and mitigation strategies of IASCC based on the outcomes of the first two objectives. Approaches were developed in order to achieve these objectives. Five alloys were selected for this study; CP304, 16Cr12Ni, 15Cr12Ni, 13Cr15Ni and 21Cr32Ni. Three of the five grades of austenitic stainless steels selected for this study were first irradiated with 2 MeV protons to a damage level of 5 dpa at 360˚C using a specially designed stage connected to the tandem accelerator at the Michigan Ion Beam Laboratory. These samples were analyzed using OIM prior to irradiation to record the grain orientation for measuring localized deformation. After the irradiation, the samples were then strained up to 2% in argon to initiate localized deformation. The degree of localized deformation of the samples will be measured and used as a reference to see if the crack forms around the place where the degree of localized deformation is higher. The degree of localized deformation was measured in terms of channel height by AFM. The picture below shows the channels on the irradiated sample after straining. The localized deformation is believed to be responsible for IASCC and the channel height information was recorded for investigating the cause-and-effect relationship between them.

This research has been supported by the Electric Power Research Institute under Agreement EP-P35203/C15971.

2D and 3D Channel feature measured by AFM.

25

LOCALIZED DEFORMATION AND INTERGRANULAR FRACTURE OF IRRADIATED ALLOYS UNDER EXTREME ENVIRONMENTAL

CONDITIONS

M. D. McMurtrey1, G. S. Was1, I. M. Robertson2, D. Farkas3. 1Department of Nuclear Engineering and Radiological Sciences, University of Michigan,

2Department of Materials Science and Engineering, University of Illinois, Urbana Champaign, 3Material Science and Engineering, Virginia Tech University

The goal of this project is to determine the role of localized deformation in austenitic stainless steel during irradiation assisted stress corrosion cracking (IASCC). The project is a collaboration between three universities, with the purpose of working together to better understand the mechanisms involved in IASCC. Atomistic models of the experiments are being developed at Virginia Tech University, and irradiated samples will be strained in-situ in a TEM at the University of Illinois. Samples are being irradiated at the University of Michigan to study the cracking behavior and also to prepare samples for the in-situ TEM work to be performed at UI. This year, a third set of samples were irradiated using 2 MeV protons in the Tandetron accelerator located in the Michigan Ion Beam Laboratory. The latest irradiation included two high purity alloys, a Fe-13Cr-15Ni and a Fe-21Cr-32Ni. These samples will be strained in argon to initiate dislocation channels and then sent to Illinois to study the dislocation interactions with grain boundaries. The samples from the previous two irradiations were strained up to 6% in 288 °C water and the relation between strain accommodation and cracking was studied. Grain boundaries that accommodated the strain had continuous slip where dislocation channels transmitted slip across the boundary. Where stress was accommodated, cracking susceptibility was decreased. This is depicted in the attached figures. This research has been supported by the Basic Energy Science office of the U.S. Department of Energy under grant DE-FG02-08ER46525.

Cracked grain boundary of 13Cr-15Ni irradiated to 5 dpa and strained to 6% in 288°C BWR, NWC water, showing that (a) the majority of the cracks occur at boundaries with discontinuous slip, (b) decreasing slip continuity with

increasing trace angle, and (c) increasing cracking probability with increasing trace angle, suggesting a connection between slip continuity and cracking resistance.

ac

26

STABILIZING A DENSE TWIN STRUCTURE OF NI-MN-GA SAMPLES BY ION IMPLANTATION

M. Chmielus1,2,3, K. Ullakko1, and P. Müllner1 1College of Engineering, Boise State University, Boise, Idaho 83725, USA, 2Helmholtz Center Berlin for Materials and Energy, Hahn-Meitner-Platz 1,

14109 Berlin, Germany 3now at Department of Materials Science and Engineering, Cornell University,

214 Bard Hall, Ithaca, New York 14853, USA.

The mechanical properties of magnetic shape-memory alloys depend strongly on details of the twin microstructure. The twin microstructure varies in the course of dynamical experiments, with a corresponding change in mechanical properties. In an effort to stabilize the twin microstructure, a Ni-Mn-Ga single crystal was implanted with Nb ions. The mechanical properties were measured in compression tests (figure) indicating an increase of the twinning stress. After deformation, the surface revealed a dense pattern of twins. Ion implanted surfaces effectively stabilize a dense twin microstructure and possibly extend the fatigue lifetime of magnetic shape-memory alloys. The results of this study will be presented at and published in the proceedings of the International Conference of Ferromagnetic Shape Memory Alloys (ICFSMA), Dresden, Germany, July 18-22, 2011.

We thank Phil Boysen for machining the sample holder, and acknowledge financial support of DOE BES Contract No. DEFG-02-07ER46396. MC thanks the Deutsche Forschungs-gemeinschaft (Grant No. SPP1239 Schn 1106/1) for financial support. P.M. is grateful to ETH Zürich for donating magneto-mechanical testing devices.

Stress-strain curves of four subsequent compressive deformation tests of the ion-implanted sample. Between each deformation test, the sample was manually stretched parallel to D - its longest dimension.

27

IMPLANTATION STUDY OF SILVER DIFFUSION IN SILICON CARBIDE

S. Dwaraknath, G. S. Was Department of Nuclear Engineering and Radiological Sciences, University of Michigan

This work is focused on creating ion implanted diffusion couples for a first round test of the silver diffusion in silicon carbide (SiC). SiC is the primary fission product barrier in the TRISO fuel design for the Gen-IV Very High Temperature Reactor (VHTR). Silver is one of the fission products that is known to diffuse through the SiC layer. Understanding the mechanisms by which silver diffuses will provide methodologies on impeding its release.

Preliminary diffusion couples have been made by direct implantation of silver into SiC samples to a fluence of 1 x 1016 atoms / cm2 Rutherford Backscattering (RBS) analysis was used to verify the implantation profile using a 2MeV

He++

ion beam and a backscatter angle of 160 degrees. The results are shown in the figure along with a simulated implantation profile for a peak concentration of 1.2% with a Gaussian profile at a depth of 120nm below the surface of the sample.

This work is supported by the Department of Energy under NEUP Contract #00103195.

Rutherford backscattering spectrum, for a silicon carbide sample implanted with silver atoms, using 2 MeV helium ions at a backscattering angle of 160°. The figure is a plot of the data (red) and a simulated spectrum (blue) for a Gaussian implant profile with a peak concentration of 1.2% at a depth of 120nm.

28

TRISO-COATED FUEL DURABILITY UNDER EXTREME CONDITIONS

I. Reimanis1, D. Butt2

Collaborators: John Youngsman2, Brian Gorman1 1Metallurgical and Materials Engineering, Colorado School of Mines

2College of Engineering, Boise State University The current study will examine the effect of CO-CO2 environments on the oxidation behavior of the SiC layer of a TRISO particle and the resulting change in mechanical performance. Corrosion of the carbide layer can occur in the presence of a number of species produced during reactor fission events. Some of these products are seen to diffuse through the carbide layer. Diffusion studies are used to aid in a thorough understanding of the kinetic behavior of the system.

Presently, the diffusion work consists of ion implanted substrates (accomplished at the Michigan Ion Beam Laboratory) of cesium and palladium that are subjected to various heat treatments that vary dwell time, temperature and atmosphere. Analysis is accomplished with SIMS at the Micron Surface Analysis Lab. Additional analyses of structure is conducted with the TEM, SEM, and XPS instruments that are part of the Boise State Center for Materials Characterization. Mechanical testing is completed at the Colorado School of Mines facility. Preliminary results show the rapid diffusion of Cs through the SiC as temperatures climb through 1250°C. Research is supported under NEUP Award Number: DE-AC07-05ID14517 Project Number: 09-257.

Diffusion profile of Cs in SiC at various temperatures for a 48 hour isotherm.

29

IN-SITU PROTON IRRADIATION AND THERMAL CREEP OF FERRITIC-MARTENSITIC STEEL T91

C. Xu, G. S. Was Department of Nuclear Engineering and Radiological Sciences, University of Michigan

In this work, an irradiation creep apparatus was developed for in-situ straining of T91 strip samples while exposed to 2-3MeV proton irradiation at 300-600°C. Thermal creep experiments were conducted at 500°C and 160MPa to benchmark the experimental setup. Linear fits of the thermal creep strain rates between 40 to 80 hours yielded values of 1.28x10-8s-1 (LSE) and 1.15x10-8s-1 (LVDT) for sample #1, and 8.05x10-9s-1 (LSE) and 3.92x10-9s-1 (LVDT) for sample #2. The measured strain rates between the two experiments are within a factor of 2 of each other, which demonstrates acceptable repeatability of data for creep experiments conducted under the same conditions. Comparison of 500°C:200MPa thermal creep experiments with existing thermal creep data by Gupta et al [1] showed that the strain rates in the thin samples are higher than those in the standard creep samples, but still within the maximum error bounds of the data. The thermal creep strains were in reasonable agreement with literature data on bulk samples of T91. An irradiation creep experiment previously conducted at 500°C, and 160MPa with a damage rate ranging from 1.58x10-6 dpa/s to 2.44x10-6 dpa/s, exhibited a linear dose rate dependence with a ration of strain rate to dose rate of 0.0037dpa-1[2]; demonstrating the utility of in-situ irradiation creep experiment to capture accurate creep rates at varying doses, temperatures, and stresses.

Support for this research was provided by the Department of Energy under awards #NERI 08-055 DE-FG07-07ID14894.

Thermal creep experiments conducted at 180MPa and irradiation creep experiment conducted at 160MPa at 500°C.

30

SELF-ION IRRADIATION OF PWR AND VVER REACTOR CORE INTERNALS STAINLESS STEELS TO A HIGH DOSE

J. Michalička1, Z. Jiao2, G. S. Was2

1Nuclear Research Institute Řež plc., Czech Republic 2Nuclear Engineering and Radiological Science, University of Michigan, USA

Lifetime extension of existing nuclear power plants will become important to preserve the power source. However, behavior of microstructure and microchemistry of reactor materials at high dose is unknown. Therefore, high dose rate, self-ion irradiations have been used to gain insight into neutron damage in a short period of time. This study is aimed at self-ion irradiation of material extracted from non-active reactor internals of PWR – 316SS used for a baffle bolt, and VVER – 08Ch18N10T (equivalent to 321SS) used for a core shroud basket. The main goal was to obtain radiation induced microstructure and microchemistry and compare to that from neutron irradiation. For benchmarks the same heat of 316SS, irradiated by neutrons to 46 dpa at 320°C in the fast reactor BOR-60 was used as referential material to determine proper conditions of self-ion irradiations. Self-ion irradiations were accomplished using Ni++ ions accelerated to 5MeV. Conditions of the first irradiation were 30dpa and 500°C. It was found from evaluations of 316SS, that the adequate microstructure and microchemistry cannot be preserved in one irradiation. Because Ni++ ions have a dose rate several orders of magnitude higher than neutrons, the behavior of point defects differs significantly. Two limiting cases exist: domination of recombination when processes such as RIS are preserved, and partitioning of defects at cluster, which is relevant to processes such as loop or void growth. That is why the microstructure (Frank loops) evolution was very different in the first irradiation in comparison with the neutron irradiated 316SS, even though the radiation induced segregation of Cr and Ni at a grain boundary occurred similarly. The second Ni++ irradiation of both alloys was set up to 260dpa at 380°C to simulate the microstructure evolution. The results were much closer to the neutron irradiated 316SS, then the first Ni++ irradiation. Evaluation of both materials is still in progress.

Comparison of dislocation loop microstructure and RIS of 316SS irradiated by neutrons and Ni++ ions.

31

ULTRAFAST LASER INTERACTIONS WITH INTERFACES

R. Murphy and S. Yalisove Department of Materials Science and Engineering, University of Michigan

We have found that interfaces play an important role in the removal thresholds of materials after irradiation by ultrafast light. Nickel films were sputtered onto silicon substrates with a DC magnetron sputtering system and irradiated with a single 150 fs laser pulse at normal incidence to the film. Atomic force microscopy in tapping mode was used to characterize the irradiated region and the thickness of the film was shown to play a crucial role in the removal process. Therefore it was important to accurately measure the thickness of the nickel films that were sputtered. RBS spectra were taken of Ni films on Si substrates. From the spectrum below the thickness of the film was calculated to be 70 nm.

RBS spectrum produced with He++ ions at 2 MeV and scattering angle of 160°. The Ni peak and the Si substrate are clearly visible.

32

PHYSICAL VAPOR DEPOSITION FOR COATING MICROCHANNEL PLATES IN X-RAY RADIOGRAPHY

S.L. Perry, R.P. Drake, A.D. Swain, N.C. Cornwall, M.A. Forsyth, E.C. Harding, C.M. Huntington

Atmospheric, Oceanic and Space Sciences, University of Michigan

Photocathodes are for x-ray imaging of targets used in astrophysical experiments. In-house custom coatings of metals and phosphors like cesium iodide (CsI) on microchannel plates (MCPs) can improve metrology of targets and allow the development of our own photocathodes. A physical vapor deposition chamber has been designed and constructed to coat a desired substrate with a thin, even layer of atoms via physical thin-film deposition. MCPs are used to amplify the amount of electrons they are hit with using the photoelectric effect. Coating the MCP enhances quantum efficiency, a percentage of how many photons from a source are successfully converted to electrons, which are used to produce an image or signal. The thin films deposited by the coater are only dozens of nanometers thick. We are pursuing several methods to characterize and confirm our coating thicknesses, from scanning electron microscopes to Rutherford backscattering. Phosphors like cesium iodide are difficult to measure with these tests, leading us to pursue metals like aluminum to confirm our coating thicknesses and quality. This research is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Lab. Plasmas, under grant number DE-FG52-09NA29548.

This modified mount allows a top down

view of a clean edge. The glass serves as an MCP analogue.

SEM image of a glass disk’s surface with typical grain structure of fluffy CsI.

33

RADIATION-INDUCED MICROSTRUCTURE EVOLUTION IN ODS AUSTENITIC STAINLESS STEELS

J. Sun, H. Xing, X. Wang

School of Materials Science and Engineering, Shanghai Jiaotong University, China

Oxide-dispersion strengthened (ODS) stainless steels have been extensively investigated as candidate structural materials in advanced nuclear reactors. The nanosized oxide particles of yttria can stabilize grain boundaries and enhance the creep resistance, which allows for an increase of using temperature of the ODS steels. Furthermore, the nanosized oxide particles could act as sinks for trapping of point defects and helium atoms, retarding radiation-induced steel degradation. In this work, radiation-induced microstructure evolution in the ODS 304 austenitic stainless steel prepared by powder metallurgy method will be investigated by transmission electron microscopy. Irradiations have been performed using 2 MeV protons for doses of 2 dpa at temperatures of 300 and 550°C, respectively. Additionally, the effect of radiation on the mechanical properties of the ODS steel will be characterized by nano-indentation.

34

HELIUM IMPLANTATION EFFECTS ON MICROSTRUCTURE OF SODIUM BOROSILICATE GLASSES

L. Chen and L. M. Wang

Nuclear Engineering and Radiological Science, University of Michigan

Understanding the structural evolution of nuclear waste glasses after irradiation is crucial for evaluating and predicting its performance after long-term storage. In this work, X-ray photoelectron spectroscopy and infrared reflection spectroscopy were used to investigate the modification on microstructure of sodium borosilicate glasses after 400 keV He ion-irradiation at different doses from 1014 to 1016 ions/cm2. The observed broad bands in infrared reflection spectra are the results of the overlapping of individual band with each other. The intense band around 1050 cm-1 is shifted to lower wavenumber after He-ions irradiation, indicates that a decrease in the average Si-O-Si angle, i.e. densification processes. The intensity of broad weak band around 1360 cm-1, which is assigned to B-O stretching vibrations of BO3 units, increases with irradiation dose. More non-bridging oxygen (NBO) will form by the transformation from BO4 to BO3 (BO4→BO3+NBO). It is consistent with our result in XPS spectra (b), indicates a depolymerization caused by helium implantation. The more NBOs formed in depolymerization process can also lead to the densification of silicate networks, since the Si–NBO bond lengths are normally shorter than those of Si–BO. This research is funded by US DOE DE-FG02-02ER46005

Infrared reflection spectra of irradiated sodium borosilicate glasses (left) and the XPS spectra of sodium borosilicate glass showing an increase in the fraction of non-bridging oxygen with irradiation dose (right).

35

STUDYING CARRIER DYNAMICS SILICON NW pn JUNCTIONS

S. B. Cronin Department of Electrical Engineering, University of Southern California

In this study, we grow silicon nanowires by chemical vapor deposition (CVD). pn junctions are created in the nanowires using ion implantation at the Michigan Ion Beam Laboratory at the University of Michigan. Using a focused laser spot to irradiate the nanowire, we measure the spatially mapped photocurrent to reveal various characteristics about the carrier dynamics, such as minority carrier diffusion lengths. The figure shows a schematic diagram of the experimental setup for this measurement. A fundamental understanding of these characteristics will be important for utilizing these nanowires for solar energy conversion. By applying a bias voltage to the same devices, we measure the photoconductivity spectra in the 450nm - 2000nm wavelength range. In addition to the spectral information, we will measure the quantum efficiency of the device as a function of doping concentration element, voltage, and post-annealing.

This work is supported as part of the Center for Energy Nanoscience, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001013.

Schematic diagram of nanowire pn junction for photodetection (left), and photoemission (right).

36

INVESTIGATION OF LOCAL PLASTIC DEFORMATION IN PROTON-IRRADIATED 304 STAINLESS STEEL

4C. Andrzejewski and G. S. Was

Nuclear Engineering and Radiological Science, University of Michigan

Irradiation assisted stress corrosion cracking (IASCC) is a primary degradation mode for core components of nuclear power reactors. Recent studies with austenitic alloys suggest that localized deformation is a potential contributor to IASCC. In many studies, tensile bars with thin irradiated layers can be strained just a few percent in high temperature water, initiating cracking in the irradiated region. The yield strength in this thin irradiated layer is much higher than that found in the unirradiated counterpart. As a consequence, a stress concentration will be developed in this thin hardened irradiated when uniaxial tensile test is performed on the sample (strains in this region are significantly smaller than the ones found in the unirradiated counterpart). This research combined computational (Finite Elements analysis-FE) and experimental techniques (surface strain displacement measurements-SSDM) to obtain the local stresses and strains inside a thin 304 SS proton-irradiated layer when the sample is submitted to uniaxial tensile test. For the plastic regime, the stress-strain data were fit to a power-law hardening curve. Such data were used to feed the constitutive modules of the FE Code. Silver markers were deposited on the top of the irradiated samples using physical vapor deposition technique (MIBL). Those markers were used in the SSDM enabling the evaluation of the local deformations occurred during the CERT tests and to benchmark the results generated by the FE analyses. The differences in the local strains obtained by FE and by the SSDM can be attributed to different factors such as the sudden changes in the grain orientations occurred in real polycrystalline materials but not accounted for in the FE analysis. At SSDM closer to the middle of the sample, the changes brought by the different grain orientations are averaged out over more grains (plot below). A direct comparison between the theoretical predictions and the averaged strains obtained by the SSDM shows an acceptable agreement. The local SSDM performed in the centerline and in the middle of the tensile bar deviated about 5.5% from the FE predictions for a 1% macroscopic strain, and about 7.9% and 3.8% from the FE predictions for a 2 and 3.5% macroscopic strain respectively.

Local strains in ¼ of the irradiated tensile bar (1.0% macroscopic strain).

Local strains by the FE analysis and SSDM for 1% macroscopic strain

(center line and in the middle of the irradiated sample).

Marker deposition using physical vapor deposition (silver) at different magnifications.

37

ION IRRADIATION-INDUCED DEGRADATION OF REACTOR STRUCTURAL MATERIALS

Z. Jiao1, G. S. Was1, T. Miura2 and K. Fukuya2

1Nuclear Engineering and Radiological Science, University of Michigan 2Institute of Nuclear Safety System, Japan

The Institute for Nuclear Safety Systems (INSS) and the University of Michigan are jointly conducting a three-year program on ion irradiation-induced degradation of reactor structural materials, aimed at exploring the processes and mechanisms that contribute to materials degradation in light water reactors arising from irradiation, such as irradiation assisted stress corrosion cracking, embrittlement, deformation modes and mechanisms. The objective of the program is to develop an understanding of these irradiation-induced degradation processes using ion irradiation as an emulation for neutron irradiation. The program is experimentally based, and focuses on irradiation with light ions (e.g., 2-3 MeV protons) and heavy ions (e.g., 5 MeV Ni and Fe ions). Proton irradiations were conducted on SUS316 and SUS316 to 5 dpa at 300ºC using 1.2 and 3 MeV protons at MIBL. Constant extension rate tensile tests were conducted on the irradiated samples at 300ºC to 2% strain in argon using a strain rate of ~1×10-7/s. The height of dislocation channels formed on the sample surface was characterized using atomic force microscopy. The average channel height of proton-irradiated samples was compared to that of the unirradiated samples and the Fe++ -irradiated samples (5 dpa at peak) that were conducted at INSS in the figure. Both heavy ion and proton irradiations promote the average channel height. However, the effect of proton irradiations on dislocation channel height is much more appreciable than that of heavy ion irradiations. 1.2 MeV protons (~20 µm irradiation depth) produce comparable average channel height with 3 MeV protons (~40 µm irradiation depth). Support for this research was provided The Institute for Nuclear Safety Systems, Japan.

0

20

40

60

80

100

120

SUS316 SUS304

Unirradiated

5 dpa at peak, 2.8 MeV Fe++

5 dpa at plateau, 1.2 MeV proton5 dpa at plateau, 2 MeV proton

A comparison of the average dislocation channel height in unirradiated SUS316 and SUS 304 and following proton and heavy ion irradiations to 5 dpa at 300ºC. The samples were strained to 2% in argon at 300ºC.

38

SPATIALLY DIRECTED FORMATION OF EMBEDDED PHASE-SELECTED GALLIUM NITRIDE NANOCRYSTALS

A.W. Wood,1 R.R. Collino,2 F. Naab,3 and R.S. Goldman1

1Department of Physics, University of Michigan 2Department of Mechanical Engineering, University of Michigan

3Department of Nuclear Engineering and Radiological Sciences, University of Michigan Ion beams have been used to form nanocomposite materials consisting of nanocrystals embedded in a variety of host matrices. For example, it has been reported that broad-area N implantation into GaAs followed by RTA stimulates the growth of both ZB and WZ nitride nanocrystals. However, the mechanisms for selective nucleation of ZB over WZ nanocrystals remain unclear. It has been proposed that the interfacial energy of GaN nanocrystals with remnant GaAs crystals plays a significant role in the nucleation of the ZB phase, but this has not been examined experimentally. In this work, we are endeavoring to determine the influence of lattice damage and crystalline remnants on the phase selection of nitride nanocrystals embedded in GaAs following RTA. To compare the influence of broad-area N irradiation on damage depth profiles, (001) channeling-RBS measurements were performed on implanted samples. The figure shows the normalized yield versus energy and depth following N implantation (75 and 100 keV) in comparison with random and (001) channeling yields from GaAs. For 100-keV (75-keV) as-implanted, the normalized yield has a broad peak which spans depths from ~150 to 350 nm (~100-300 nm). The presence of this peak indicates an increase in lattice disorder which encompasses both the depths of highest vacancy concentration and highest nitrogen concentration. For depths to 300nm, the normalized yield is an average of 32% higher for 100-keVimplantation of GaAs in comparison with that of 75-keV implantation of GaAs. The higher normalized yield indicates a higher vacancy concentration following 100-keV implantation. This work was supported by in part by the U.S. Department of Defense through the Intelligence Community Postdoctoral Research Fellowship under grant HM1582-05-1-2027, by the AFOSR through the MURI program under Contract No. FA9950-08-1-0340, and by NSF through Grant No. CMMI 0700301.

0

200

400

600

1000 1100 1200 1300 1400 1500 1600

Energy(keV)

as‐grown(random)

as‐grown

100‐keVas‐imp.

75keVas‐imp.

1000

800 600 400 200 0

600

400

200

0

1000 1200 1400 1600

Depth(nm) Normalized

Yield(a

.u.)

Channeling RBS spectra as a function of backscattered energy of GaAs layers of as-

grown GaAs comparing 100-keV as-implanted, and 75-keV as-implanted samples with GaAs in the random and (001) aligned

configurations.

39

ION IMPLANTATION FOR THE GROWTH AND DOPING OF SEMICONDUCTOR NANOWIRES

W. Fung and W. Lu Electrical Engineering and Computer Science, University of Michigan

In this work we will explore the possibilities of using ion implantation for the growth and doping of semiconductor nanowires (NW). First, the metal catalysts for vapor-liquid-solid (VLS) NW growth can be implanted into the substrate. The advantages of ion implantation compared with other deposition techniques include prevention of oxidation prior to NW growth, the possibility of templated deposition using a mask, and the possibility of using a focused ion beam for localized deposition at the nanoscale. Currently, we have successfully grown Si NWs using this technique. Using the facilities at MIBL, we have implanted Au into a Si substrate at an ion fluence of 1 x 1016 cm-2 and an energy of 30 keV, annealed the substrate at 580°C for 10min., and have grown Si NWs using VLS (see figures). Future work will include achieving epitaxial growth, exploring the use of metal catalysts other than Au, and the growth of germanium NWs. Second, ion implantation can be used to dope semiconductor NWs. This is a standard doping technique in top-down semiconductor manufacturing and its advantages include the ability to create abrupt junctions and the ability to dope at high levels on the order of 1 x 1020 - 1 x 1021 cm-3. Both of these features would be useful for, e.g., fabricating NW-based high performance tunneling field-effect transistors.

Si substrate implanted with Au and annealed at 600°C, showing the formation of Au droplets at the surface.

Si nanowires grown from an Au-implanted sample.

40

TEACHING ACTIVITY

41

MSE 465 CLASS DEMONSTRATION AT MIBL

S. Yalisove Materials Science and Engineering, University of Michigan

MIBL hosted the MSE 465 class (Structural and Chemical Characterization of Materials) for an hour and a half session to collect RBS spectra from a known sample and an unknown sample. The students were given a tour of the lab and the equipment. A short tutorial was given on the accelerator, electronics, detectors, software, and vacuum components. The students were required to write up a lab report, prior to visiting the lab, in which they generated an RBS random spectrum using material provided in class and in the library. Plotted below are the data collected during the tour of MIBL.

Deuterium beam at 1.4 MeV. Scattering angle: 150 degrees. Channel position for 1.4 MeV is channel 732 Channel position of peak edges: 498 for the leading edge of the low E feature and 587 for the leading edge of the peak. Energy per channel: 1.404 keV/Channel

The students were able to identify the components and calculate a stoichiometry without using any software simulation. They were given the scattering geometry, the ion type and energy, and the energy calibration.

42

NERS 425 LABORTORY ON NUCLEAR REACTION ANALYSIS

O. Toader, F. Naab, and G. S. Was Nuclear Engineering and Radiological Science, University of Michigan

For one laboratory in the NERS 425 course, students conducted an experiment to determine the stoichiometry of a TixNy sample using the reaction between a deuterium particle and a nitrogen nucleus: N14(d,α)C12. Nuclear reaction analysis (NRA) is a well established surface analysis technique. In this method, an energetic particle (deuterium – produced by the Tandem accelerator at MIBL) interacts with the nucleus of an N atom (from the target) to give a reaction product (α particle) that can be measured. The students also use the backscattered yield from an RBS experiment to determine the amount of Ti in the sample by implementing simulation codes like RUMP or SIMNRA with the given experimental spectrum.

In the first class, and prior to the experiment, a short tutorial was given to the students on the accelerator, electronics, detectors, software, and vacuum components. After that, they worked independently in a few groups with just the basic support from the MIBL staff (required in the setup of the ion beam and the collection of the spectra). The students decided on a few parameters of the experiment (beam energy, time for spectrum acquisition, etc.) and after that each group obtains spectra similar to the ones in the figure.

Typical NRA spectrum for the TiN film obtained during class. Conditions: beam energy: 1.4 MeV D+, solid angle 5 msr., detector angle 1500.

α0

α1

43

REFERENCES

44

PUBLICATIONS AND PRESENTATIONS

Z. Jiao and G.S. Was, “The Role of Irradiation Microstructure in Localized Deformation in Austenitic Alloys,” Journal of Nuclear Materials, 407 (2010) 34-43.

A. Abou Gharam, M.J. Lukitsch, M.P. Balogh, and A.T. Alpas, “High Temperature Tribological Behaviour of Carbon Based (B4C and DLC) Coatings in Sliding Contact with Aluminum” Thin Solid Films. 519, 1611-1617 (2010).

Z. Jiao and G.S. Was, “Impact of Localized Deformation on Irradiation-Assisted Stress Corrosion Cracking”, Journal of Nuclear Materials, doi:10.1016/j.jnucmat.2010.10.087

Z. Jiao and G.S. Was, “Novel Features of Radiation-Induced Segregation and Radiation-Induced Precipitation in Austenitic Stainless Steels” Acta Materialia, doi:10.1016/j.actamat.2010.10.055.

G. S. Was, R. Zhou, E. A. West and Z. Jiao “Intergranular Cracking Behavior of Irradiated Austenitic Alloys in Supercritical Water,” Proc. 14th Int. Conf. on Environmental Degradation of Materials in Nuclear Power Systems, American Nuclear Society, Lagrange Park, IL, 2010, 1679-1689.

E. A. West, Z. Jiao and G. S. Was “Influence of Taylor Factor on IASCC in SCW and Simulated BWR Environments,” Proc. 14th Int. Conf. on Environmental Degradation of Materials in Nuclear Power Systems, American Nuclear Society, Lagrange Park, IL, 2010, 1690-1701.

Z. Jiao and G. S. Was, “An Atom Probe Tomography Study of Proton-Irradiated Austenitic Stainless Steels,” Proc. 14th Int. Conf. on Environmental Degradation of Materials in Nuclear Power Systems, American Nuclear Society, Lagrange Park, IL, 2010, 1240-1247.

Anne A. Campbell, Gary S. Was, “Proton Beam Irradiation Creep Behavior of POCO Graphite”, American Nuclear Society Student Conference, Ann Arbor, MI, April 8-10 2010.

Anne A. Campbell, Gary S. Was, “Proton Irradiation-Induced Creep Studies for the VHTR Reactor”, VHTR R&D FY-10 Technical Review Meeting, Denver, CO, April 27-29, 2010.

G. S. Was, “Influence of Local Stresses and Deformation on Intergranular Cracking of Irradiated 316L in SCW,” ICG-EAC 2010, Jeju, S. Korea, April, 2010. Z. Jiao and G.S. Was, “Atom Probe Tomography of Radiation-induced Precipitation in Reactor Cladding and Structural Steels.” Microscopy and Microanalysis, Volume 16, Supplement S2, 16 (2010) 1598-1599.

G. S. Was, “Radiation-Induced Segregation in Austenitic and Ferritic-Martensitic Alloys,” 5th Forum on New Materials, CIMTEC, Montecatini Terme, Italy, June, 2010

Z. Jiao, V. Shankar, J. Wharry and G.S. Was, “Phase Stability in Proton and Heavy Ion Irradiated Ferritic-Martensitic Alloys,” Transactions of the American Nuclear Society. Vol. 102, pp. 824-825. 0-17 June 2010.

45

E. A. West and G. S. Was, “Influence of Microstructural Parameters on the Intergranular Cracking of Irradiated 316 Stainless Steel in Supercritical Water,” American Nuclear Society, 2010 Annual Meeting, San Diego, CA, June, 2010. C. Xu and G. S. Was, “In-situ Proton Irradiation Creep of Ferritic-Martensitic Steel, T91C. Xu and G. S. Was, American Nuclear Society, 2010 Annual Meeting, San Diego, CA, June, 2010. X. Choudhury, L. Barnard, D. Morgan, K. Field, T. Allen, J. Wharry, Z. Jiao, G. S. Was, B. Wirth, “Radiation-induced Segregation in Ferritic/Martensitic Steels,” American Nuclear Society, 2010 Annual Meeting, San Diego, CA, June, 2010. Anne A. Campbell, Kent B. Campbell, and Gary S. Was, “A Methodology for Quantitative Determination of Anisotropy of Pyrolytic Carbon”, Transactions of the American Nuclear Society and Embedded Topical Meeting Nuclear Fuels and Structural Materials for the Next Generation Nuclear Reactors (NFSM), Vol. 102, June 13-17, 2010, San Diego, CA, p 843-844.

Z. Jiao and G.S. Was, “Atom Probe Tomography of Radiation-induced Precipitation in Reactor Cladding and Structural Steels.” Microscopy and Microanalysis 2010, Portland, OR, August 1-5 2010.

G. S. Was, “Applications of Ion Beams to Study Radiation Effects in Extreme Environments,” Conference on Accelerator Applications in Research and Industry, Fort Worth, TX, August, 2010.

G. S. Was, Z. Jiao, M. McMurtrey, E. West, “Key Factors Affecting Stress Corrosion Cracking in Irradiated Stainless Steels,” Fontevraud 7, Contribution of Materials Investigations to Improve the Safety and Performance of LWRs, SFCEN, Avignon, France, September, 2010. Anne A. Campbell, Gary S. Was, Yutai Katoh, “In-situ Study of Proton Irradiation-Induced Creep in Graphite”, 11th International Nuclear Graphite Specialists’ Meeting, Eastbourne, United Kingdom, September 12-15, 2010.

Z. Jiao, J. Wharry, J. Michalicka, G.S. Was, “Microstructure of Austenitic Steels Irradiated to High Fluences.” Materials Solutions for the Nuclear Renaissance, MS&T 2010, Houston, TX.

M. Briceno, J. Fenske, M. Dadfamia, P. Sofronis, I. M. Robinson, G. Was and M. McMurtrey, “Real-time studies of Dislocation Interactions with Grain Boundaries in Irradiated Steels,” MS&T 2010, Houston, TX, October, 2010. Z. Jiao, J. Wharry, J. Michalicka and G. S. Was, “Microstructure of Austenitic Steels Irradiated to High Fluences,” MS&T 2010, Houston, TX, October, 2010. G. S. Was, M. McMurtrey, D. Farkis, L. Patrick, N. Floyd, “Localized Deformation and Intergranular Fracture of Irradiated Austenitic Steel,” MS&T 2010, Houston, TX, October, 2010.

J. Youngsman R. Revis, G. Gorman,J. Reimanis, D. Butt, TRISO-coated Fuel Durability under Extreme Conditions: Oxidation and Diffusion in the Carbide Layer. MS&T10, Houston, TX October 2010.

Z. Jiao and G.S. Was, “Radiation-Induced Ni/Si-rich Precipitates in Austenitic and F-M steels.” 2010 MRS Fall meeting, Nov. 29-Dec. 3, Boston, MA.

46

Z. Jiao, J, Wharry, G.S. Was, C. Ling, A. Van der Ven, “Ni-Si Phases in Irradiated Austenitic Steels.” 2010 MRS Fall meeting, Nov. 29-Dec. 3, Boston, MA.

Anne A. Campbell, Kent B. Campbell, and Gary S. Was, “A Methodology for Quantitative Determination of Anisotropy of Pyrolytic Carbon”, Transactions of the American Nuclear Society and Embedded Topical Meeting Nuclear Fuels and Structural Materials for the Next Generation Nuclear Reactors (NFSM), Vol. 102, June 13-17, 2010, San Diego, CA, p 843-844.

K.L. Wang, Z. Xu, and Y. Zhang, Calibration for infrared measurements of water in apatite. In: 41st Lunar and Planetary Science Conference; 2010 Mar 1-5; The Woodlands, TX; Abstract 1121.

K.L. Wang, F. Naab, Y. Zhang, Calibration for Infrared Measurements of OH in Apatite. In: AGU Fall Meeting; 2010 Dec 13-17; San Francisco, CA; Abstract V53C-2277.

S. L. Perry, R. P. Drake, et. al, “Physical Vapor Deposition Chamber for Coating Microchannel Plates in X-Ray Radiography,” 52nd Annual Meeting of the APS Division of Plasma Physics, American Physical Society, Chicago (2010).