Post on 10-Mar-2018
AMPERE Newsletter Issue 88 March 31, 2016
1
Issue 88 March 31, 2016
In this Issue:
Prospects in RF and microwave application on medical diagnosis and treatment Yoshio Nikawa 2
Looking while cooking in a microwave oven Raymond L. Boxman, Edi Ya’ari, Sergei Shchelkunov 5
The microwave materials processing group at KIT Guido Link 8
Microwave technology in manufacturing and research at Corning Incorporated Rebecca L. Schulz 12
Field assisted processing of advanced ceramics: A research perspective Bala Vaidhyanathan 14
Microwave discharges Yuri A. Lebedev 18
The International Scientific Committee (ISC) on Microwave Discharges Yuri A. Lebedev 20
Ricky's afterthought: A “corrugated” conundrum A. C. (Ricky) Metaxas 22
Recently published journal papers 24
Upcoming Events 25
Call for Papers:
- Special Issue on Solid-State Microwave Heating
- Regular issues 25
Previous issues of AMPERE Newsletter are available at http://www.ampereeurope.org/index-3.html
AMPERE Newsletter Trends in RF and Microwave Heating ISSN 1361-8598
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AMPERE Newsletter Trends in RF and Microwave Heating
www.AmpereEurope.org
ISSN 1361-8598
AMPERE Newsletter Issue 88 March 31, 2016
2
Prospects in RF and Microwave Applications on Medical Diagnosis and Treatment
Yoshio Nikawa
Department of Health and Medical Engineering, School of Science and Engineering, Kokushikan University, 4-28-1 Setagaya, Setagaya-ku, Tokyo 154-8515, Japan
Email: nikawa@kokushikan.ac.jp
RF and microwave are non-ionizing radiation
energies. They are safe in application to the
human body hence applicable in medicine,
especially in noninvasive diagnosis and
treatment. For this reason, RF and microwave
energies contribution in the field of medicine
and healthcare is significantly expected.
One of the current technologies most
contributing in diagnosis is the magnetic
resonance imaging (MRI). Magnetic resonance
(MR) equipment applying an RF pulse is used
for obtaining a cross-sectional image of human
body for detecting hidden disease by measuring
longitudinal relaxation time of proton T1, as
well as the horizontal relaxation time T2.
Technology advancement makes it possible to
measure the phase shift of the longitudinal
relaxation signal. Thus, the cross-sectional
distribution of temperature elevation can be
obtained1. This new technique for obtaining
noninvasive temperature elevation inside the
human body is very useful not only for
treatment using RF and microwave energies,
such as hyperthermia treatment of cancer, but
also for treatment in the field of oriental
medicine such as moxibustion therapy which is
a heat treatment. Temperature distribution in
the anatomical transverse plane of leg at
acupuncture point ST 36 is shown in Fig. 1.
The results show that this kind of temperature
stimulation on skin will increase the
subcutaneous temperature, and can discover the
heat effects against human body2.
Furthermore, the MR equipment can also be
applied for RF heating device for application of
treatment inside the medium such as
hyperthermia application treatment of cancerous
tissues. To localize the RF energy at the treat-
ment area, the applicator design is essential in
the field of medical heating3-5.
In developing and applying these effects,
knowing the electromagnetic (EM) properties of
the human tissue is essential6. To measure
detailed complex permittivity, especially in the
millimeter wave region, EM transmission and
reflection data can be utilized for obtaining
detailed biological information such as blood
glucose level noninvasively7. Figure 2 shows
experimental results of the return loss versus
frequency for various blood glucose concent-
rations. The change of reflection coefficient was
measured in vivo as a parameter of blood
glucose level. The result shows that by measur-
ing the change of reflection coefficient, the
change of blood glucose level might be
estimated non-invasively8.
Not only for research but also for education,
an EM field sensor will be one of the most
important devices in this area. The tri-axial field
sensor is shown in Fig. 3. This sensor array is
useful to know the microwave field distribution.
The sensor can be used to show the spatial
distribution of the magnetic field not only in the
free space but also in the medium9. The LED
visualization of the microwave field especially
in the heating medium is very useful in order to
establish the SAR distribution and will be
applicable beforehand for medical usage of
microwaves especially for safety checking.
Application of RF and microwaves energies
on medical diagnosis and treatment will be more
and more significant and it is expected more
researchers will join the field of medicine and
healthcare.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
3
Figure 2. Experimental results of return loss vs. frequency as a parameter of blood glucose concentration.
Figure 3. LED visualized microwave field distribution from a microwave surgical knife.
Microwave surgical knife
Figure 1. Temperature distribution of a human leg at acupuncture point ST36: (a) T1 enhanced MRI; (b) temperature elevation mapping by phase change of T1 enhanced MRI; (c) initial temperature distribution; and (d) temperature elevation at 12 minutes after moxa ignition.
Research brief
(a) (b)
(c) (d)
1.0⁰C
0
10cm
AMPERE Newsletter Issue 88 March 31, 2016
4
For further reading:
[1] Y. Nikawa and A. Ishikawa, “Microwave and RF
heating for medical application under noninvasive
temperature measurement using magnetic
resonance,” Jour. Korean Inst. Electromagnetic Eng.
Sci. 10 (2010) 244.
[2] S. Nakamura, M. Nakamura, E. Maeda, Y. Nikawa,
“Study on temperature measurement using MRI
during acupuncture and moxibustion,” IEEJ Trans.
Electronics, Information & Systems 135 (2015)
1205.
[3] Y. Nikawa, M. Kikuchi, T. Terakawa, T. Matsuda,
“Heating system with a lens applicator for 430 MHz
microwave hyperthermia,” Int’l Jour. Hyperthermia
6 (1990) 671.
[4] T. Matsuda, S. Takatsuka, Y. Nikawa, M. Kikuchi,
“Heating characteristics of a 430 MHz microwave
heating system with a lens applicator in phantoms
and miniature pigs,” Int’l Jour. Hyperthermia 6
(1990) 685.
[5] T. Michiyama and Y. Nikawa, “Simulation of SAR
in the human body to determine effects of RF
heating,” IEICE Trans. Communication E92-B
(2009) 440.
[6] S. Gabriel, R.W. Lau, C. Gabriel, “The dielectric
properties of biological tissues: III. Parametric
models for the dielectric spectrum of tissues," Phys.
Med. Biol. 41 (1996) 2271.
[7] Y. Guan, Y. Nikawa, E. Tanabe, “Study of simulat-
ion for high sensitivity non-invasive measurement of
blood sugar level in millimeter waves,” IEICE
Trans. Communication E86-C (2003) 2488.
[8] Y. Nikawa and T. Michiyma, “Blood-sugar
monitoring by reflection of millimeter wave,” Proc.
Asia-Pacific Microwave Conf. Proc. III (2007) 1581.
[9] Y. Nikawa, Y. Kudo, S. Nakamura, “Development
of miniature diode sensor to visualize EM field
distribution”, Proc. 14th Int'l Conf. Microwave &
High Freq. Heating (2013) 296.
About the Author:
Yoshio Nikawa received the B.E., M.E. and Ph.D. degrees in electrical engineering from Keio University, Japan, in 1981, 1983, and 1986, respectively. He joined The National Defense Academy in 1986 as a Research Associate. From 1987 to 1988, he was a Visiting Scholar at the University
of Texas at Austin. He became an Associate Professor at The National Defense Academy in 1991. In April 1999, he joined Kokushikan University, Tokyo as a Professor in the Department of Electrical and Electronics Engineering. From 2007, he is a Head in the Department of Health
and Medical Engineering, Kokushikan University. From 2014, he is a Dean in the School of Science and Engineering, Kokushikan University.
Prof. Nikawa is awarded in recognition of distinguish-ed service as Associate Editor, IEEE Transactions on Microwave Theory and Techniques in 2008. He was the recipient of Electronics Society Award from the Electronics Society of the Institute of Electronics, Information and Communication Engineers (IEICE) in 2008. His research activities include microwave and millimeter-wave measurements and applications, microwave and millimeter-wave heating and processing for medical and industrial applications.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
5
Looking while Cooking in a Microwave Oven
Raymond L. Boxman1, 2, *, Edi Ya'ari2, and Sergey Shchelkunov3
(1) Clear Wave Ltd., Herzliya, Israel, (2) Tel Aviv University, Tel Aviv, Israel, (3) Yale University, New Haven CT, U.S.A.
* E-mail: boxman@eng.tau.ac.il
Cooks like to look while cooking. Visual
observation, together with sound, smell and
taste, give them essential feedback on the
cooking progress: e.g. the need to adjust the
heat flow, to stir, and in particular, an indication
that the cooking is complete. Recently,
transparent lids have become popular on pots
and pans for this purpose. Visual observation
during microwave cooking is particularly
critical, since even 10 or 20 seconds of
overcooking can convert a tasty meal into a
platter of “dog food”.
Today, conventional domestic microwave
oven doors are equipped with a window, which
employs a metallic grid. Apertures in the grid
allow some degree of visibility of the oven
contents, while sufficiently blocking microwave
leakage to meet current safety standards.
However, the visibility is very poor. The eye
focuses on the grid, and the easily discernable
details of the state of the oven contents is
insufficient to provide good cooking feedback.
This article describes a transparent window,
which provides excellent food visibility, while
attenuating microwave leakage even better than
conventional grid windows1. The window is
based on a pair of transparent conductive oxide
coatings, applied to glass substrates, and spaced
a quarter-wavelength apart. The basic idea has
been around for over 50 years2. However,
presently transparent microwave oven windows
are not commercially available.
Transparent conductive oxides are wide
band-gap semiconductors. Their band gaps are
typically a bit above 3 eV, which allows
transmission of visible light but causes
absorption of ultra-violet light. Electrical
conduction is provided by n-doping the oxide,
but only to an extent that their plasma frequency
is in the infra-red region of the spectrum.
Frequencies below the plasma frequency,
including microwave frequencies, are generally
reflected, while frequencies above the plasma
frequency are transmitted.
Quantitatively, the reflectance r iS S , trans-
mission t iS S and absorption a iS S of a single
conductive coating is determined by its sheet
resistivity R d , where is the resistivity of
the transparent oxide coating material and d is
the coating thickness (Fig. 1).
0.0
0.2
0.4
0.6
0.8
1.0
0 100 200 300 400
R [Ω]
Sa /Si
Sr /Si
St /Si
Figure 1. Reflectance
r iS S , transmission t iS S
and absorption a iS S of a conductive coating as a
function of the sheet resistivity R.
While in principle the microwave trans-
mission can approach 0 if R is sufficiently
small, in practice R cannot economically be
made small enough to satisfy safety require-
ments: the resistivity is limited by the doping of
the film, while very thick coatings tend to
absorb light and delaminate. To overcome this
difficulty, two coatings are employed, spaced a
quarter-of-wavelength apart. Figure 2 shows the
transmission as a function of the spacing
between 10- coatings for normal incidence. At
the optimal 4 spacing (or at odd integer
multiples thereof), attenuation of –57 dB is
obtained. However, if the wave is obliquely
incident, the attenuation depends on the angle of
incidence and the polarization, as shown in
Fig. 3. For increasing angle of incidence, the
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
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transmission of TE waves is decreased, while
the transmission of TM waves is increased.
Figure 2. Transmission of a pair of 10 coatings spaced a distance L apart in air (normal incidence).
Figure 3. Transmission (dB) of TE and TM waves for pair of coatings at oblique incidence as a function of
incidence angle (with R between 2 to 12 ).
In a microwave oven, typically multiple
cavity modes are excited, each with its own
polarization and angle of incidence at the
window. The amplitude of each mode depends
on the excitation strength, geometry and
frequency, and on the load, whose properties
change during heating. Furthermore, the
properties of the load affect the magnetron
frequency and power. Thus for real food loads,
the transmission cannot be accurately predicted.
Figure 4 shows measurements of the band-
pass power leaking from a 20-litre microwave
oven with various loads, equipped with its
standard grid window, and with a ClearWaveTM
etalon window using 5 coatings separated by
12.6 mm of glass. It may be seen that under all
conditions, the leakage via the etalon window is
considerably less than the standard window.
Figure 4. Band power under the following conditions: (1) empty oven, after 20 s operation, (2) 300 ml water load, after 20 s operation, and (3) 300 ml water load, after 55 s operation
Figure 5 is a photograph of a lentil and
tomato mini-casserole being cooked in a 20-litre
microwave oven equipped with an etalon
window. Video clips of various foods cooking
in microwave ovens and photographed through
the ClearWaveTM etalon window may be
viewed at YouTube3. It may be seen that the
transparent etalon window provides except-
ional food visibility.
Figure 5. Lentil-tomato mini-casseroles during cooking in a 20-litre microwave oven, photo-graphed via a ClearWaveTM etalon window (see www.youtube.com/channel/UCiZLxQCzAqdYXUFuDUhWkdA).
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
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The main challenge in developing this
window was finding an appropriate combination
of techniques and materials that would allow
safe operation under exceptional conditions
(e.g. empty oven operation), while having an
affordable price. The cost of the coated glass
used in the present implementation is about $2.5
for the 20-litre oven, in large quantities, and
thus should be affordable in mid-range and
luxury domestic ovens.
For further reading:
[1] R. Boxman, V. Dikhtyar, E. Gidalevich, V.
Zhitomirsky, "Microwave oven window," US Patent
8772687, July 2014.
[2] D. B. Haagensen, Microwave Ovens, U.S. patent
2,920,174, 5 Jan. 1960.
[3] www.youtube.com/channel/UCiZLxQCzAqdYXUFuDUhWkdA
About the Authors:
Raymond L. Boxman received his S.B. and S.M. degrees in Electrical Engineering in 1969, and his Ph.D. from M.I.T. in 1973. He worked as a Senior Research Engineer at GE from 1973 to 1975, at which time he took up a position on the Faculty of Engineering at Tel Aviv
University. Prof. Boxman is the co-founder of the Electrical Discharge and Plasma Laboratory at TAU, which he currently directs. His teaching included electro-magnetic fields, plasma, and thin film courses. He served as Head of the Department of Interdisciplinary Studies,
Coordinator of the Materials Engineering Program, Associate Dean for Research in the Faculty of Engineering, and Incumbent of the Kranzberg Chair for Plasma Engineering. He received the Joffee Foundation Award and the Walter Dyke Award, and is a Fellow of the IEEE. Prof. Boxman is the Founder and CEO of Clear Wave Ltd. He served as Chairman of the Technical Program Committee for the International Microwave Power Institute Conference in 2014 and 2015. He has presented over 480 scientific papers at conferences and in technical journals, as well as eleven patents. He also teaches short courses in scientific writing and is now completing a textbook on this subject.
Sergey V. Shchelkunov received his B.S. in Physics from Novosibirsk State University in 1994. He received subsequently his two M.S. degrees from Novosibirsk State University in 1996, and Columbia University, New York, in 2004. He received his Ph.D. (in Applied Physics and Math) from Columbia University in 2005. He worked from
1996 to 1999 as a teaching assistant in Novosibirsk State University, and also as a Junior Research Scientists in Budker Institute of Nuclear Physics (Novosibirsk, Russia). After having received his Ph.D., he pursued a career of accelerator scientists working first at Columbia University, and later at Yale University (from 2008). He
presently works as a Research Scientists at Yale University, and as a Senior Research Scientists at Omega-P, R&D, Inc. in New Haven. He has over 50 publications in journals and conference proceedings in the areas of RF engineering and high-gradient acceleration research. His latest synergetic activities include reviewing the articles submitted to Physics Review, Special Topics (PR-STAB) and Nuclear Instruments and Methods in Physics Research, Section A (NIM-A); participating as an invited speaker/presenter in meetings organized to assess the state of, and advise on possible direction of development in the fields of structure-based dielectric-wakefield accelerators and high-gradient acceleration research; and supervising and mentoring summer students at Yale University.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
8
The Microwave Materials Processing Group at KIT
Guido Link
Institute for Pulsed Power and Microwave Technology Karlsruhe Institute of Technology, Karlsruhe, Germany
E-mail: Guido.Link@kit.edu
As "The research university in the Helmholtz
Association", the Karlsruhe Institute of
Technology (KIT) is a pioneer in the German
science system, and it maximizes its synergies.
In the coming years, the tasks of national large-
scale research and a state university will be
merged step by step. In future, KIT will bring
the topics of energy, mobility and information
even more into focus. This aligns the KIT
traditional and major research fields at long-
term challenges of the society with the aim to
develop sustainable solutions to urgent
questions of the future. The perfect match in
basic and applied research is essential, for
example for the success of the energy
transition.
Within this political frame, the KIT
Institute for Pulsed Power and Microwave
Technology is - since more than 20 years now -
active in the field of microwave materials
processing. Besides program oriented funding
by the Helmholtz Association, further funds
have been raised in numerous cooperative
research and development activities with
partners from research and industry.
As well known in the microwave
community, heating by microwave may offer
advantages with respect to energy and time
saving, as compared to conventional heating.
This is based on microwave specific features,
including volumetric heating, selective heating,
and the potential of heating in a cold applicator
without temperature limit. During the last
decades, there have been motivating
investigations and developments all over the
globe in numerous applications. Similar
changes occurred at KIT, resulting in
substantial experience in fields like
debindering, sintering and calcination of
ceramics, metal powder sintering, melting,
welding and annealing of glasses, as well as
processing of glass and carbon fibre reinforced
composites, microwave assisted foaming of
polymers, microwave assisted gluing, and
microwave assisted chemistry, beside others.
When those activities have been started in
1993, as a spin off from nuclear fusion
research, a compact 30 GHz, 15 kW gyrotron
system was installed in close collaboration with
the Institute of Applied Physic, RAS Nizhny
Novgorod. While systematic investigation on
high temperature processes, like sintering of
functional and structural ceramics1-3 as well as
metal powder compacts4, 5, were performed, the
system was continuously improved and
extended. Meanwhile, it is a versatile system
that allows in-situ dilatometry and/or in-situ
resistivity measurement during mm-wave
sintering. Furthermore, those diagnostic tools
can be combined with a hybrid heating
module6.
Although high-frequency microwave
processing at 30 GHz using gyrotrons may have
significant benefits to processes with respect to
heating efficiency and heating uniformity, in
particular in applicators with hexagonal
geometry7, a real technology transfer into
industrial applications so far has not been
possible. Therefore, more than 10 years ago,
additional activities have been started at the
standard ISM Band frequencies (915 MHz,
2.45 GHz and 5.8 GHz) with a major focus on
2.45 GHz for applications in the field of
processing of fibre reinforced plastics. Initiated
by the former colleague Lambert Feher, a
modular large scale applicator technology has
been developed and successfully licensed to a
major industrial partner Vötsch Industrie-
technik GmbH, Germany. In collaboration with
automotive and avionic industries, significant
energy and time saving have been demonstrated
as comparted to regular heating technologies.8, 9
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
9
Meanwhile, this so called HEPHAITOS
technology has been further improved and
upgraded. Now, this unique system technology
can be offered with features like hybrid heating
for temperatures up to 200°C, to improve
temperature uniformity in processes such as
curing of thick wall composites or foaming of
polymers. Furthermore, a conveyor belt can be
mounted that allows demonstrating continuous
processing, and a rotary feedthrough can be
installed for curing of filament winding part
(see Fig. 1).
Beside this, various process specific
microwave systems have been developed for
applications such as pultrusion of carbon fibre
reinforced composite10, microwave assisted
heterogeneous11, and homogeneous catalysis or
hydrothermal synthesis. Further investigation
has been successfully started in the field of
microwave assisted ablation of concrete that
could be used for the decommissioning of
nuclear power plants, what will be an exigent
problem in coming years, in particular in
Germany where nuclear technology has been
abandoned12 (see Fig. 2).
Figure 1. Modular hybrid HEPHAISTOS system with conveyor belt for continuous processing (left); with filament winding tool (middle), and microwave cured high precision filament winding parts (right).
Figure 2. Carbon-fiber reinforced polymer (CFRP) profiles successfully produced by microwave assisted pultrusion (left), pilot reactor for high temperature dry reforming and RWGS (middle), and concrete surface after microwave ablation (right).
In parallel to those system and process
developments, the implementation of in-situ
diagnostics was always of special interest in
terms of more fundamental investigations on
how microwave can influence processes. So
applicators have been developed that can be
combined with IR, RAMAN and X-ray absorp-
tion spectroscopy13,14, as well as thermogravi-
metry.
For a successful system and process design,
the detailed knowledge of the dielectric proper-
ties of materials is imperative. This information
is the essential input in any electromagnetic and
multi-physics simulation that allows design
studies and process optimization. Dielectric
materials of interest typically cover a wide
range of permittivity and all states of
aggregation. Furthermore, such permittivity
may change significantly with frequency and
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
10
temperature as well as with phase transitions or
chemical reactions. To cover all those aspects, a
large variety of dielectric test-sets is needed.
Meanwhile, various test-sets based on resonant
and non-resonant methods are available in our
Institute, that cover a frequency range from 50
MHz to 24 GHz, and a temperature range from
room temperature up to 1000°C14-16. For
investigations of chemical reactions, test sets
for in-situ dielectric measurements at 2.45 GHz
have been developed based on the transmission-
reflection method18 (see Fig. 3) as well as the
cavity perturbation method. The latter allows
collecting calorimetric data to get qualitative
information about reaction enthalpy19.
In-house equipment and expertise can be
offered to interested partners from industry and
research for feasibility studies or more long-
term collaboration in research and development
of novel microwave applications.
0 50 100 150 200 250 3000.0
0.3
0.6
0.9
1.2
1.5
r"
Time in minutes
meas @80°C
meas @70°C
model
0
20
40
60
80
100
Te
mp
era
ture
in
°C
Figure 3. Dielectric loss factor of DGEBA based epoxy resin at 2.45 GHz during curing at differ-ent temperatures.
For further reading:
[1] Link, G.; Feher, L.; Thumm, M.; Ritzhaupt-Kleissl,
H. J.; Böhme, R.; Weisenburger, A.; Sintering of
advanced ceramics using a 30-GHz, 10-kW, CW
industrial gyrotron. Research Workshop of the Israel
Science Foundation on Cyclotron Resonance Masers
and Gyrotrons, Kibbuz Ma'ale Hachamisha, IL, May
18-21, 1998 IEEE Transactions on Plasma Science,
27(1999) S.547-54.
[2] Rybakov, K. I.; Semenov, V. E.; Link, G.; Thumm,
M.; Preferred orientation of pores in ceramics under
heating by a linearly polarized microwave field.
Journal of Applied Physics, 101(2007) S.84915/1-5. http://dx.doi.org/10.1063/1.2723187
[3] Paul, F.; Menesklou, W.; Link, G.; Zhou, X.; Haußelt,
J.; Binder, J. R.; Impact of microwave sintering on
dielectric properties of screen printed Ba₀ ̣₆Sr₀ ̣₄TiO₃ thick films. Journal of the European Ceramic Society,
34(2014) pp.687-694. . http://dx.doi.org/10.1016/j.jeurceramsoc.2013.09.009
[4] Takayama, S.; Link, G.; Miksch, S.; Sato, M.;
Ichikawa, J.; Thumm, M.; Millimetre wave effects on
sintering behaviour of metal powder compacts.
Powder Metallurgy, 49(2006) S.274-80. http://dx.doi.org/10.1179/174329006X110835
[5] Mahmoud, M. M.; Link, G.; Thumm, M.; The role of
the native oxide shell on the microwave sintering of
copper etal powder compacts. Journal of Alloys and
Compounds, 627(2015) pp.231-237. . http://dx.doi.org/10.1016/j.jallcom.2014.11.180
[6] Link, G.; Ichikawa, J.; Thumm, M.; Millimeter wave
sintering of metal powder compacts utilizing a
modified dilatometer for resistivity measurements. 1st
Global Congress on Microwave Energy Applications,
Otsu, J, August 4-8, 2008 Proc.S.561-64 Tokyo:
Japan Society of Electromagnetic Wave Energy
Applications, 2008 ISBN 978-4-904068-04-5.
[7] Feher L.; Link G.; Microwave resonator for the high
temperature treatment of materials; DE19633245;
US6072168
[8] Link, G.; Kayser, T.; Köster, F.; Weiß, R.; Betz, S.;
Wiesehöfer, R.; Sames, T.; Boulkertous, N.; Teufl,
D.; Zaremba, S.; Heidbrink, F.; Maus, M.; Ghomeshi,
R.; Küppers, S.; Milwich, M. (2015). Faserverbund-
Leichtbau mit Automatisierter Mikrowellenprozess-
technik hoher Energieeffizienz (FLAME):
Schlussbericht des BMBF-Verbundprojektes (KIT
Scientific Reports ; 7701). http://dx.doi.org/10.5445/KSP/1000047509
[9] Link, G. et al.; Innovative, modulare Mikrowellen-
technologie zur Herstellung von Faserver-
bundstrukturen. Schlussbericht für das BMBF-
Verbundprojekt Förderkennzeichen: 01RI05133,-135-
140, -282 Laufzeit: 01.09.2006 - 31.05.2011
Eggenstein-Leopoldshafen, 2011.
[10] Kayser, T., Link, G., Seitz, T., Nuss, V., Dittrich, J.,
Jelonnek, J., Heidbrink, F., Ghomeshi, R.; An
applicator for microwave assisted pultrusion of
carbon fiber reinforced plastic; (2014) IEEE MTT-
S Int'l Microwave Symp. Digest, art. no. 6848325
[11] Kayser T., Soldatov S., Melcher A.; Link G.;
Jelonnek J.; A microwave applicator for high
homogeneous high temperature heating of catalysts;
(2013) IEEE MTT-S Int'l Microwave Symp. Digest,
art. no. 6697418.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
11
[12] Lepers B., Seitz T., Link G., Jelonnek J., Zink M.;
Development of a 10 kW microwave applicator for
thermal cracking of lignite briquettes; Frontiers in
Heat and Mass Transfer (FHMT), 6, 20 (2015) http://dx.doi.org/10.5098/hmt.6.20
[13] Link, G.; Heissler, S.; Faubel, W.; Weidler, P.;
Miksch, S.; Thumm, M.; Novel methods to
investigate microwave specific effects. 1st Global
Congress on Microwave Energy Applications, Otsu,
J, August 4-8, 2008 Proc.S.275-78 Tokyo : Japan
Society of Electromagnetic Wave Energy
Applications, 2008 ISBN 978-4-904068-04-5.
[14] Link, G.; Thumm, M.; Faubel, W.; Heissler, S.;
Weidler, P. G.; Raman spectroscopy for
experimental investigation of microscale selective
microwave heating. Materials Science and
Technology Conf. and Exhibition (MS&T 2010),
Houston, Tex., October 17-21, (2010), p.2936.
[15] Akhtar, M. J.; Tiwari, N. K.; Devi, J.; Mahmoud,
M. M.; Link, G.; Thumm, M.; Determination of
effective constitutive properties of metal powders at
2.45 GHz for microwave processing applications.
Frequenz, 68(2014) pp.69-81. http://dx.doi.org/10.1515/freq-2013-0083
[16] Soldatov, S.; Kayser, T.; Link, G.; Seitz, T.; Layer,
S.; Jelonnek, J.; Microwave cavity perturbation
technique for high-temperature dielectric
measurements. IEEE MTT-S International
Microwave Symposium Digest (IMS'13), Seattle,
Washington/USA, June 2-7, (2013), pp. 1-4. http://dx.doi.org/10.1109/MWSYM.2013.6697793
[17] Link, G.; Measurement and modelling of intrinsic
dielectric properties of ionic crystals at microwave
frequencies. Tao, J. [Hrsg.] Microwave and RF
Power Applications : Proc.of the 13th
Internat.Conf.on Microwave and High Frequency
Heating (AMPERE 2011), Toulouse, F, September
5-8, (2011) pp.115-118 ISBN 978-2-85428-978-7.
[18] Prastiyanto, D.; Link, G.; Arnold, U.; Thumm, M.;
Jelonnek, J.; Time- and temperature-dependent
dielectric measurements of thermosetting resins.
Multiphysics Models and Material Properties; 16th
Seminar Computer Modeling in Microwave Power
Engineering, Karlsruhe, May 12-13, (2014)
Proceedings pp.47-51.
[19] Ramopoulos, V.; Soldatov, S.; Link, G.; Kayser, T.;
Jelonnek, J.; System for in-situ dielectric and
calorimetric measurements during microwave
curing of resins. German Microwave Conference
(GeMic 2015), Nürnberg, March 16-18, (2015)
pp.29-32 ISBN 978-3-9812668-6-3.
About the Author:
Guido Link received the Dipl.-Phys. and Dr. rer. nat. degree in physics from the Technical University Karlsruhe, Germany in 1990 and 1993, respectively. His diploma thesis and graduate research was devoted to the frequency and temperature dependent dielectric
characterization of low loss ceramics and ionic crystals. Since 1993, he has been working at the Karlsruhe Institute of Technology, Germany (former Forschungszentrum Karlsruhe) in the field of high power microwave and millimeter-wave processing of materials as a team leader at the Institute for Pulsed Power and Microwave Technology.
The microwave materials processing group in 2015
Research brief
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AMPERE Newsletter Issue 88 March 31, 2016
12
Microwave Technology in Manufacturing and Research at Corning Incorporated
Rebecca L. Schulz
Corning Incorporated, Corning, NY 14830 E-mail: SchulzRL@Corning.com
The interest in microwave technology at
Corning Incorporated (Corning) has spanned
the last six decades. In the late 1950’s,
Corning Glass Works (CGW) became involved
in material selection, design and fabrication of
guided missile radomes as well as radomes for
aircraft. Starting in the late 1960’s, CGW was
developing materials for the manufacture of
microwave integrated circuits, highly stable
resonator cavities (silver-coated glass
ceramics) and high temperature/high intensity
Luneburg lenses (borosilicate and high silica
content foamed glass (Vycor)) and other
dielectric devices and antennae. In addition to
material development and forming, Corning
scientists were advancing the theoretical
understanding of dielectric properties in
conjunction with material properties.
In the 1970’s, Corning pioneered some of
the first susceptors for home microwave use.
These browning devices were comprised of tin-
antimony slurries that were applied to either to
the exterior under-surface or interior bottom
surface of Corning Ware casseroles, pizza
plates, skillets and other devices. Some of this
cookware was designed expressly for
microwave manufacturers and often came with
a small cookbook with microwave-specific
recipes. The main drawback of these early
browning devices was that they had to be pre-
heated in the microwave prior to use in order to
fully optimize the browning effects. Likely due
to the added time element, the products were
not readily accepted by consumers. Today,
even with advent of many consumer
susceptors, browning and the appearance of
microwave-cooked foods remains a challenge
for the frozen/processed food industries.
Microwave generated plasma chemical-
vapor deposition method was investigated for
the production of optical fiber preforms. This
method used a 2.45 GHz microwave to
generate non-isothermal plasma. One of the
key features of this methodology was the
ability to laydown fully consolidated layers, as
opposed to laying down soot layers and then
consolidating. Research into this process resul-
ted in improved understanding of applicator
heads, plasma stability and methods for charac-
terizing the plasma, the uniformity and density
of the glass layers and what parameters
affected the quality of the preform, as well as
numerical modeling of the processes.
Figure 1. Vintage cookware produced by Corning with tin-antimony susceptor coatings.
Also in the mid-1970’s, Corning began a
new venture to produce air pollution abatement
equipment in the form of catalytic converters,
and expanded into the production of auto-
motive and diesel filters (light and heavy duty
vehicles). Initially, these products were hot-air
dried, but, as this was very time-consuming,
research was carried out to determine if an
alternate drying method could improve process
time and product quality.
During this work, the cement and part
compositions were systematically altered to
produce a material that would adhere to the
walls of the unfired filter channels, dry with
minimal shrinkage, survive the subsequent
firing process, and meet customer
requirements. At the same time, the various
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AMPERE Newsletter Issue 88 March 31, 2016
13
compositions were subjected to several
different drying methods to determine what
method would provide a high quality part and
maintain production rates. Initially, most work
was carried out at a lab scale with small parts
and batch curing. As microwave drying was
much more rapid than other methods, it quickly
rose to the forefront. However, to successfully
implement microwave processing on an
industrial level, it was key that composition
work and process development be undertaken
simultaneously. This was necessary as very
minor adjustments in either path could result in
failures down the line.
An example of a successful collaboration
can be found in a study undertaken to eliminate
post-firing cracks in plugged diesel filters.
Different drying methods were tested in
conjunction with varying the depth of the plug
material, the geometry and part size. No
method was completely successful in
eliminating cracked parts. However, micro-
wave drying did result in fewer cracks when
compared to the other methods.
Large scale experiments were carried out
on the production lines. In one experiment, two
different compositions (A and B) were plugged
under identical conditions with the same batch
cement and the same plug depth. The samples
were dried at three different microwave drying
schedules. The results showed that slow drying
at low powers resulted in the greatest number
of cracks in both compositions. However,
Composition A had significantly more cracks
than B regardless of power level. Thermal
images show a very different heating profile for
the two compositions, as shown in Fig. 2.
Composition A absorbed the microwave
energy primarily at the ends, while B was
warm throughout the piece. This shows that
for Composition A, water in the wet cement
was the primary absorber and for B, the entire
composition absorbed the microwave energy.
Figure 3. Thermal profiles for compositions A (Left) and B (Right) after microwave drying at similar power levels and times.
As industry continues to push the envelope
of innovation with advanced materials and
processes, in order to meet the demands of an
ever-changing electronic society, microwave
technology will remain a processing tool to be
used when appropriate. While this option may
not always be applicable, it is anticipated that
with continued research, advances in process
control systems, and applicator design,
microwave energy may be able to replace many
fossil-fuel dependent processes and will no
longer be viewed as a novel technique.
About the Author:
Rebecca Schulz received her PhD in Materials Science and Engineer-ing from the University of Florida under the supervision of David C. Clark in 1998. During her doctoral studies, she developed and demonstrated the use of micro-wave energy as a remediation
technique in the destruction of electronic circuitry from weapons components. As part of this work she design-ed, constructed, and successfully demonstrated a micro-wave off-gas system for waste circuitry work. Rebecca was awarded an Oak Ridge Institute of Science and Education (ORISE) Fellowship to complete her studies at Westinghouse Savannah River Company (WSRC). Following graduation, she was employed by WSRC
where she continued research on microwave remed-iation of transuranic wastes, tires, and medical waste. In 2001, Dr. Schulz was recruited by Corning Incor-porated where she worked on various projects related to microwave technology. In 2002, she was promoted to Senior Scientist III and in 2007 to Development Associate. Rebecca was the conference chair for the 2012, 2nd Global Congress on Microwave Energy Applications (2GCMEA) and is on the technical comm-ittee for 3GCMEA (2016). Rebecca has over 40 technical publications, served as co-editor for conference proceedings, co-authored several invited book chapters, authored 30 internal technical reports, and holds 9 pat-ents with 5 applications in prosecution. She is currently serving as President of the Microwave Working Group.
Research brief
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AMPERE Newsletter Issue 88 March 31, 2016
14
Field Assisted Processing of Advanced Ceramics:
A Research Perspective
Bala Vaidhyanathan
Department of Materials, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom
E-mail: B.Vaidhyanathan@lboro.ac.uk
Advanced ceramic materials are being increase-
ingly used in a wide range of applications,
including aerospace, defence, electronics,
transport and energy. The global market for
advanced ceramics is projected to exceed $75B
by 2020, driven by resurgence in global
manufacturing activity, legislation of strict
environmental regulations, technology innova-
tions and expanding application areas1.
Both electronics and structural ceramics
markets are predicted to grow at >7% annually
for the foreseeable future2. For existing
applications, growth will come predominantly
from performance enhancement, whilst for new
applications advanced ceramics are delivering
performances previously not feasible1. All these
products however require densification/sintering,
a high temperature process (e.g. 1000 – 2000oC)
that in industry can take days. The amount of
energy needed, and CO2 emitted, is therefore
very significant; energy can account for 30% of
costs (one factory spent £1.9M pa on energy and
released 353.5 t of CO2 equivalent3). Thus energy
efficient, eco-friendly sintering methods such as
Spark Plasma Sintering (SPS)4, Microwave
Assisted Sintering (MAS)5,6, Flash Sintering
(FS)7,8 and Hybrid methods like Flash-SPS
(FSPS), Microwave-FS (MFS) are continuously
being developed. These approaches are together
referred as Field Assisted Sintering Techniques
(FAST), and in all these cases application of
electric, magnetic and/or electro-magnetic field
were demonstrated to have a positive effect on
ceramic densification.
For example, the recently invented DC
(direct current) flash sintering method, for
reasons that are far from fully understood, has
yielded full densification in very short periods at
very low temperatures, e.g. 5 s at 850oC for
zirconia7, and at a surprisingly low temperature
of 325oC for Co2MnO4 spinel8 ceramics. Thus
the associated time and energy advantage is
estimated to be staggering, as well as the ability
to tailor the required micro/nano structure and in
turn the performance9,10. Figure 1 shows the
comparative energy needs of the FAST and
conventional sintering methods for the
processing of advanced ceramics.
Though electric sparks and plasmas at
particle-particle contacts, joule heating,
additional driving force provided by the E/H
fields, and temperature-gradient-driven diffusion,
have been proposed as explanations for field-
enhanced sintering of materials. However, a clear
understanding of the underlying atomistic
mechanisms still remains clouded.
In this research brief, let us have a closer look at
two of the FAST methods, namely Microwave
Assisted Sintering and Flash Sintering – one a
well established and other a newly emerging
densification method. Whilst MAS received
significant research attention due to its ability to
reduce processing times from days to
hours/minutes11, the FS method was
demonstrated to achieve full densification within
seconds7! The MAS method can be suitable for
the processing of various simple and complex
shaped engineering components12, the early use
of FS method was restricted to dog-bone shaped7
ceramic specimens – that are both difficult to
make and do not have much industrial
applicability. However, the recent developments
at Loughborough University (LU) and elsewhere
have demonstrated that FS can be used to sinter
different sample shapes. LU recently constructed
the unique controlled gradient flash sintering
(GFS) facility with atmospheric capability and
the ability to be used in a hybrid flash sintering /
conventional mode. The latter allows the strength
of the electric field to be varied whilst the
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
15
conditions remain otherwise identical. This is
particularly helpful for determining the
operational mechanism(s). Results have
demonstrated that the flash sintering effect is
genuine and a perspective is now starting to be
gained into how the process works and,
importantly, how it can be manipulated
desirably13.
Figure 1. Schematic showing the time and energy savings associated with the FAST methods
The use of MAS and FS at LU have been
demonstrated to produce genuinely
nanostructured, fully dense zirconia based
ceramics (see Fig. 2) for a number of applications
including ceramic armour, Solid Oxide Fuel cells
(SOFCs), petro-chemical valve and pump seats
etc. However, in particular, significant
performance advantage was gained when the
nanostructured zirconia based ceramics was
found to exhibit more than 500 times
improvement on the hydro-thermal ageing
(HTA) resistance14. Whilst the conventional
zirconia ceramic render itself into a pile of damp
powder (due to a tetragonal to monoclinic phase
transformation that is accelerated in the presence
of moisture, temperature and pressure) at 2450C
and 4 bar pressure, the longevity of these LU
made nanostructured ceramics against HTA is
extended up to the extreme conditions of >300oC
and in excess of 65 bar pressure – an accelerated
ageing time equivalent to >1800 years in ambient
conditions - essentially showing complete
immunity against HTA whilst retaining excellent
mechanical properties. HTA degradation is the
Achilles-heel for the use of zirconia based
ceramics in the biomedical sector. This was the
reason behind the well-publicised failure of
zirconia hip replacements around year 2000.
Thus, when HTA is countered, numerous
opportunities opened up. Interestingly we also
demonstrated that the HTA immunity can be
achieved even with 90% density nano zirconia
specimens, a trait that can be further exploited in
implant situations. For example if the fabrication
of completely HTA immune, all-ceramic, graded,
acetabular cups with a porous outer nanostructure
for direct bonding with natural bone and a dense
core to align with the femoral head can be
achieved - this could pave the way for a
functionally gradient, hierarchically structured
implants. Indeed this could be achieved by using
nanoceramic suspensions, granulation, compact-
ion and FAST firing methods. Based on this, a
new research project funded by the Engineering
and Physical Sciences Research Council, UK
(EPSRC Grant reference: EP/L024780/1) is
looking at the manufacture of functionally
graded, all-ceramic implants (see Fig. 3) using
GFS and MAS methods for ever-lasting hip and
knee prosthesis.
Figure 2. Microstructure of the fully dense nano-structured (a) and commercial (b) zirconia ceramics, fabricated at LU using the FAST methods
Figure 3. Schematic of the novel functionally gradient all-ceramic implant (a) and the functionally graded microstructure (b) fabricated using FAST methods
The FS process was further adapted for the
use of AC as well as Pulsed electric fields at LU
(b)
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
16
that led to the achievement of homogeneous
temperature distribution inside ceramic
specimens and hence uniform microstructure
both are vital for consistency and large scale
production needs. The MAS and FS methods
have been successfully extended to the
processing of a number of technologically
important advanced ceramic materials such as
Zinc Oxide for varistors, Barium Titanate (BT)
and Calcium Copper Titanate for capacitors,
Lead Zirconium Titanate (PZT) for transducers,
Silicon Carbide and Zirconia based ceramics for
armour, Silicide’s and Chalcogenides for thermo-
electrics, Li/Na phosphates for batteries, Ultra
High Temperature (UHT) Carbides and Borides
for hypersonic aviation applications to name a
few. There were also some interesting similarities
noted and comparisons derived between the two
field assisted sintering methods described here,
namely MAS and FS (see Table 1), suggesting
that similar underpinning mechanisms may be
operative in these processing scenarios. Further
detailed investigations are underway.
Table 1: Similarities between MAS and FS methods for the processing of advanced ceramics
Materials Microwave Assisted Processing Flash Processing Yttria stabilised zirconia (YSZ) 8YSZ is a better microwave absorber
and easy to sinter compared to 3 YSZ. 8 YSZ easy to flash than 3 YSZ.
Zirconia toughened alumina (ZTA) Sintering temperature decreases with increasing Z content.
FS field and on-set temperature decreases with increasing Z content
Barium Calcium Zirconium Titanate, Barium Zirconium Titanate, Barium Titanate etc.
The ease of sintering follows BCZT < BZT <BT in that order
Very similar behaviour in terms of FS field and on-set temperature
Chalcogenides During processing photo-emission noticed in some cases
During FS process also photo-emission noticed in some cases
Dielectrics High loss materials are easier to process compared to low loss materials
High loss dielectrics (zirconia) are easier to flash than low loss dielectrics (e.g. alumina)
However in terms of the use of field assisted
sintering techniques for advanced ceramics, the
optimisation of process parameters (e.g. heating
rate, sintering time, sintering temperature,
applied field, applied power etc) is often
achieved mainly by a laborious and expensive
trial and error approach rather than through
informed judgement. This is where FAST
process modelling could be of vital significance
towards developing predictive capabilities that
are validated through in-situ field and
temperature mapping for a wide variety of
advanced ceramic materials. This can not only
help to enhance the understanding of the
operative mechanisms that are common to field
assisted sintering methods in general and also to
improve the ability to achieve the required
properties through microstructural tailoring.
Ability to predict whether a ceramic will be
amenable to FAST processes or not and if so at
what conditions would be a great advantage to
catapult industrial take-up of these advanced
manufacturing processes for the rapid fabrication
of these materials. LU is also developing a hybrid
microwave-FS capability that could lead to
contactless flash sintering of complex ceramic
parts where 3D-printing and FS/MAS methods
are innovatively combined to gain significant
advantages. This opens up new horizons for
advanced ceramics manufacturing where some of
the demanding needs of ceramics production
such as complex shape fabrication, near-net
shape manufacturing, reducing raw-material
usage, co-sintering of dissimilar materials etc.
can be looked at holistically to develop
sustainable engineering solutions.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
17
For further reading:
[1] Advanced Ceramics: A global strategic business
report, MCP1001, Global Industrial Analysts Inc,
(2014).
[2] Advanced Ceramics - Demand and Sales Forecasts,
Report 3091, The Freedonia Group Ltd, (2011).
[3] http://www.ceram.com/industries/ceramics/energy-
reducing-firing-technology
[4] Ning H, Mastrorillo GD, Grasso S, Du B, Mori T, Hu
C, Xu Y, Simpson K, Maizza G and Reece MJ, Jour.
Materials Chemistry A Vol. 3, (33) 17426-32 (2015).
[5] Vaidhyanathan B, Annapoorani K, Binner JGP,
Raghavendra R, Jour. Am. Ceram. Soc. 93(8),
pp.2274-2280 (2010).
[6] Binner JGP, Ketharam A, Paul A, Santacruz I,
Vaidhyanathan B, Jour. Euro. Ceram. Soc, 28 (5), pp.
973-977, (2008).
[7] Cologna M, Rashkova B, Raj R, Jour Am. Ceram.
Soc., 93 (11) 3556-9 (2010).
[8] Prette ALG, Cologna M, Sglavov V, Raj R, Jour.
Power Sources 196, 2061-2065 (2011).
[9] Binner, JGP and Vaidhyanathan, B, J. Euro. Ceram.
Soc, 28 (7), pp.1329-1339, (2008).
[10] Binner, JGP, Vaidhyanathan, B, Paul, A,
Annapoorani, K, Raghupathy, B, Int. J. Appl. Ceram.
Technol, 8(4), pp.766-782, (2011).
[11] Vaidhyanathan, B, Agrawal, DK, Roy, R, J. Am.
Ceram. Soc, 87(5), pp.834-839, (2004).
[12] Gadevanishvili, S, Vaidhyanathan, B, Agrawal, DK,
Roy, R, US Patent 6,512,216, (2003).
[13] Vaidhyanathan, B, Invited Paper, AMPERE 2015
Meeting, Krakow, Poland, (2015).
[14] Paul, A, Vaidhyanathan, B, Binner, JGP, J. Am.
Ceram. Soc, 94(7), pp.2146-2152, (2011).
About the Author:
Bala Vaidhyanathan (Vaidhy) is a Professor of Advanced Materials and Processing and the Associate Dean for Enterprise at Loughborough University, UK. Prior to this, he was a Lead Scientist at GE, Global Research Corporation and a member of
Research Faculty at The Pennsylvania State University, USA. He was born in Salem, India and obtained his PhD from Indian Institute of Science, Bangalore. He specializes in nanostructured functional materials and non-conventional field assisted processing with an emphasis to Energy, Electronic and Healthcare applications. He has published over 150 peer-reviewed articles (h-index: 29), 6 book chapters, holder of 14 patents and has delivered >50 key note and invited presentations across the globe. He has held/holds >40 Government/Industry sponsored projects worth >£8.2M. With 20 years of experience, Vaidhy is one of the leading exponents in the field of microwave-
assisted materials processing, pioneered the development of hybrid two stage sintering methods and was the first to set up an atmosphere controlled, gradient flash sintering facility for the processing of advanced functional oxide/non-oxide nanomaterials and devices. He is a member of ACerS, ECerS, ICS (life member), MRS, AMPERE (management team), DCERN, IOM3and is a Fellow of the IoN. He is also the fellow of Higher Education Academy, UK. He is an invited ‘Visiting Professor’ at two international institutions, Editor of Advances in Applied ceramics, Editorial Board member for 4 international materials’ journals, Session Chair and Organizing Committee Member for >10 International Materials Conferences and Symposia. He won numerous awards and prizes including the prestigious ‘Glory of India’ Award for his contribution to Science, Technology and Education in 2010 and Verulam Medal and Prize for his significant contributions to the field of ceramics by the Institute of Materials, Minerals and Mining (IOM3), UK in 2015.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
18
Microwave Discharges
Yuri A. Lebedev
Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences, Moscow, Russia E-mail: lebedev@ips.ac.ru
Microwave discharges (MD) are electrical
discharges generated by electromagnetic waves
with frequencies exceeding 300 MHz (the wave
length in free space [cm] = 30/f [GHz], where f
is the microwave frequency)1-29. The used
wavelengths of microwaves lie in the range from
millimeters up to several tens of centimeters and
should correspond to the permitted microwave
bands for industrial, medical and scientific (ISM)
applications16.
The starting point in the development of MD
and microwave induced plasma (MIP) was
related with successes in radar technologies. For
example, the antenna switches are microwave
plasma devices which use high-power micro-
wave pulse for plasma generation, in order to
prevent the damage of high sensitivity micro-
wave receiver as this pulse passes through the
microwave circuit.
Further development of microwave tech-
niques created the necessary prerequisites for
application of microwave devices in different
areas of science and technology, and in particular
for generation of microwave-induced plasma
(MIP). Quasi-equilibrium and non-equilibrium
microwave plasma is applied in many areas. The
low-temperature plasma is used for instance in
light and ion sources, in processes of plasma
chemical deposition of organic and inorganic
films, for coating (amorphous and nanocristalline
silicon, nitrides, oxides, diamond film), diamond
growth, formation of fullerenes, nanotubes,
graphene, for surface cleaning, polymer surface
functionalization for biomaterial applications,
etching organic and inorganic materials, planar-
ization, microwave plasma sterilization, in analy-
tical chemistry, for generation of the active
medium in gas discharge lasers, creation of
artificial ionized areas in the Earth’s atmosphere,
recovering of the Earth’s ozone layer, etc.
One could pose the question: “Why does
MIP attract the attention of scientists and
engineers?” There are several reasons for this
attention:
• MD's are interesting topics for fundamental
studies as they unite phenomena of electro-
dynamics, plasma kinetics and plasma
chemistry, in non-equilibrium and non-
homogeneous conditions;
• Wide range of operating pressures (from 10-2
Pa up to pressures exceeded the atmospheric
pressure);
• Wide range of plasma absorbed powers (0.1 –
10 W/cm3);
• Possibility of control of the internal structure
of plasma by means of changing the
electrodynamic characteristics of the
microwave-to-plasma applicator;
• Possibility for plasma generation both in
small and large volumes, including free space;
• Providing joint action of plasma and electro-
magnetic field on the treated substances (e.g.,
powders) to increase the energy efficiency of
plasma chemical processes;
• Possibility of plasma generation in the
electrode discharge systems without
contamination of the gas phase or treated
samples by products from electrode erosion;
• Possibility to treat large gas chambers or
processing of large area surfaces (e.g.,
cleaning) by scanning the small plasma region
over the chamber by means of electro-
magnetic optics;
• MIP produces little electrical interference;
• MD present no dangerous high voltage, hence
could be safer than other types of plasma;
• Numerous designs of developed high efficacy
microwave plasma devices permit to choose a
required construction for any application.
New designs of MD appear every year.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
19
MD can be generated in the pulse and
continuum wave regimes, at incident microwave
powers ranging between several watts and
hundreds of kW. The power absorbed by the
plasma can be high enough, and it may run up to
90% of the incident power. The electron density
in microwave-induced plasma usually exceeds
the critical density,
2-3 10cm 1 24 10 GHzecn . f ,
which corresponds to the electron density when
the electron plasma frequency e is equal to the
microwave frequency 2 f .
It is worth to note some general
dependences of plasma parameters on the gas
pressure. The decrease of the gas pressure from
1 atmosphere leads to the decrease of the
electron collision frequency with heavy particles.
This in turn decreases the efficiency of energy
exchange between electrons and heavy particles,
and leads to the decrease of the gas temperature
and increases the mean electron energy. As a
consequence, the degree of plasma non-
equilibrium is increased. The role of resonance
phenomena in plasma is increased with
decreasing the collision damping of the electron
energy (as the pressure decreases).
Typical experimental arrangement for
microwave plasma generation includes several
elements: the microwave power source (usually
the magnetron generator), elements for
protecting the magnetron from the reflected
power (a nonreciprocal device, e.g., isolator), a
standing-wave-ratio meter (such as a directional
coupler), a matching circuit, a microwave-to-
plasma applicator, and the plasma chamber.
The main element of the microwave plasma
generator is the microwave-to-plasma applicator
because it provides the input of microwave
energy to the plasma, and defines the type of
microwave discharge. It determines the energy
efficiency of the plasma generator (the portion of
the incident power absorbed by the plasma), the
levels of minimal and maximal plasma powers,
the system bandwidth, the electromagnetic field
structure in the plasma, its uniformity or non-
uniformity, and the size of the plasma. It is
difficult though to classify the microwave-to-
plasma applicators uniquely since the researchers
design their plasma devices to meet the
conditions of their own tasks.
Following16 all microwave discharges were
separated into two broad groups. The first group
unites discharges sustained inside the microwave
applicator (with a localized discharge zone). For
description of such applicators, the quasi-static
approach can be used as the phase incursion of
microwave field between two points in the
plasma is negligible. The second group unites the
microwave discharges with dimensions larger
compared to the wavelength. These discharges
were denoted as the travelling-wave discharges.
Microwave-to-plasma applicator can enclose a
short part of the discharge tube or covers all
length of the discharge.
At low pressures, when the effects resulting
from the field intensification in the plasma-
resonance region appear to have a dominant
effect on the dynamics of the discharge, these
were called plasma-resonance discharges. The
numerous microwave plasma devices can be
illustrated in the form of a tree of microwave
discharges, as shown below.
Information about the physics, chemistry
and applications of MD's are presented in
numerous books, papers, and in the Proceedings
of many plasma conferences. The Proceedings of
the specialized International Workshops on
Microwave Discharges: Fundamentals and App-
lications (1992, 1994, 1997, 2000, 2003, 2006,
2009, 2012, and 2015) contain comprehensive
data on microwave discharges.
Research brief
AMPERE Newsletter Issue 88 March 31, 2016
20
For further reading:
[1] Golant B E 1959 Soviet Physics-Uspekhi 23 958
[2] The Applications of Plasmas to Chemical Processing
1967 ed R. F. Baddour and R. S. Timmins, Cambridge,
Mass.: MIT Press
[3] MacDonald A D 1966 Microwave Breakdown in Gases
John Willey&Sons, NY, London, Sydney
[4] Ginzburg V L 1967 Propagation of electromagnetic
waves in plasma Moscow, Nauka (in Russian)
[5] Microwave Power Engineering 1968 ed E. Okress,
New York: Acad. Press
[6] Techniques and Applications of Plasma Chemistry
1974 J.R. Hollahan, A.T. Bell Eds. John Willey&Sons,
NY, London, Sydney, Toronto
[7] Wightman J P 1974 Proc IEEE 62 4
[8] Ginzburg V L, Rukhadze A.A. 1975 Waves in
Magnitoactive Plasma Moscow: Nauka (in Russian)
[9] Gekker I R 1978 Interaction of Strong
Electromagnetic Fields with Plasma Moscow:
Atomizdat (in Russian)
[10] Lebedev Yu A, Polak L S 1980 High Energy Chem.
13 331
[11] Zander A T and Hieftje G M 1981 Applied
Spectroscopy, 35 357
[12] Rusanov V D, Fridman A A 1984 Physics Chem.
Active Plasmas. Moscow: Nauka, (in Russian)
[13] Musil J 1986 Vacuum 36 161
[14] Batenin V M, Klimovskii I I, Lusov G V, Troitskii V
N 1988 Generators of Microwave Plasma, Moscow:
Energoatomizdat (in Russian)
[15] Moisan M and Zakrzewski Z 1991 J. Phys. D:
Appl.Phys. 24 1025
[16] Microwave Excited Plasmas 1992 ed M Moisan and J
Pelletier, Amsterdam: Elsevier.
[17] Physics and chemistry of gas discharges in
microwave beams. 1994 L.M. Kovrizhnykh, Ed.
Proceedings of IOFAN, 47 140 p (Nauka, Moscow)
[18] Wertheimer M R and Moisan M 1994 Pure &Appl.
Chern., 66 1343
[19] Zakrzewski Z and Moisan M 1995 Plasma sourses
Sci Technol. 4 379
[20] Lebedev Yu A Chemistry of Nonequilibrium
Microwave Plasma /Plasma Chemistry ed L S Polak,
Yu A Lebedev (1998): Cambridge Interscience
[21] Ohl A 1998 J. Phys. IV France 08 Pr7-83
[22] Sugai H, Ghanashev I, Nagatsu M 1998 Soursec
Sci.Technol. 7 192
[23] Marec J, Leprince P 1998 J. Phys. IV France 8 Pr7-1
[24] Moisan M and Zakrzewski Z 1986 Radiative
Processes in Discharge Plasmas eds. Proud J M,
Luessen L H, Plenum Publ. (p. 381)
[25] Lebedev Yu A 2010 J. of Phys.: Conf. Series, 257
012016.
[26] Conrads H and Schmidt M 2000 Plasma Sources Sci.
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[27] Asmussen J, Grotjohn T A, Mak P, Perrin M A, 1997
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[28] Moisan M, Pelletier J 2012 Phys. Collisional Plasma.
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[29] Lebedev Yu A, Plasma Sources Sci. Technol., 2015
24, 053001
The International Scientific Committee on Microwave Discharges
The International Scientific Committee (ISC)
was organized and first elected in 1994 during
the International Workshop on Microwave Dis-
charges: Fundamentals and Applications in
Zvenigorod, Russia. The Constitution of the
Workshop was also accepted in 1994. It was
decided to organize meetings every three years
alternatively in Russia and elsewhere. It was
decided also to begin the numbering of the
Workshop from the NATO ARW Workshop
“Microwave Discharges: Fundamentals and
Applications” held in Portugal in 1992.
The ISC defines the next Workshop place,
and its main topics and plenary speakers. The
ISC staff are appointed and renewed on ISC
meetings during the Workshops. Several
rotations have already been done for different
countries. The tradition is that the representative
of the country of the next Workshop is also the
Chairman of ISC for the next period. The ISC
elected in 2015 contains representatives from 11
countries, including Profs. Asmusen (USA),
Awakowicz (Germany), Benova (Bulgaria),
Dias (Portugal), Gamero (Spain), Jerby (Israel),
Lebedev (the ISC Chairman, Russia), Lacoste
(France), Moisan (Canada), van der Mullen
(The Netherlands), and Nagatsu (Japan).
The principal aim of the Workshop is the
generalization of results of researches obtained
in the previous three years and identification of
promising directions of investigations. Very
important task is intensification of collaboration
MD presentation
AMPERE Newsletter Issue 88 March 31, 2016
21
of scientists from different countries in the
various fields of basic studies and applications
of microwave discharges. The latter promotes
the development of this perspective area of
science and technology. To increase the
effectiveness of mutual contacts of participants,
no parallel sections are conducted. Thus, all
participants could attend and discuss all reports.
The scientific program covers all modern
aspects of microwave discharges connecting
fundamental research and applications. The
main topics of the MD Workshops are:
Methods of microwave plasma generation.
High and low pressure MD's.
CW and pulsed microwave discharges.
Interaction of microwaves with plasma.
Discharge modeling and diagnosis.
Applications of microwave plasmas (surface
treatment, etching, film deposition, growth of
structures, ecology, improvement of burning
processes, light sources, plasma medicine,
analytical chemistry, etc).
Selected topics of closely related gas dis-
charge problems can also be discussed. The Int'l
Workshop on “Microwave Discharges:
Fundamentals and Applications” is usually
attended by 70-100 participants. The previous
meetings include the following:
1992, May 11-15: NATO ARW Workshop,
Vimeiro, Portugal. Director C.M. Ferreira.
1994, September 5-8: Zvenigorod, Russia.
Chairman A.A. Rukhadze.
1997, April 20-25: Fontenvraud, France.
Chairman J. Marec
2000, September 18-22: Zvenigorod, Russia.
Chairman Yu.A. Lebedev
2003, July 08-12: Greifswald, Germany.
Chairman A. Ohl
2006, September 11-15: Zvenigorod, Russia.
Chairman Yu. A. Lebedev
2009, September 23-27: Hamana-Like, Japan,
Chairman M. Kando
2012, September 10-14: Zvenigorod, Russia.
Chairman Yu. A. Lebedev
2015, September 7-11: Cordoba, Spain,
Chairman A. Gamero
The next MD Workshop will be held in 2018 in
Russia.
About the Author:
Yuri A. Lebedev was born in USSR. His education includes engineer in electronics (1968) and physicist (1974). He obtained his PhD degree in 1977 and degree of Doctor of Sciences in plasma physics in 1993. He has over 45 years of research experience in low temperature
plasma, electric gas discharges, microwave plasma, plasma chemistry, plasma diagnostics and modeling. He is a member of editorial boards of several journals and published over 350 papers, editor and co-author of 9 books. He is a member and one of the founders of the International Scientific Committee on Microwave
Discharges: Fundamentals and Applications (Chairman 1997-2000, 2003-2006, 2009-2012, 2015-2018), Deputy Chairman of the Scientific Council of the Russian Academy of Sciences on Physics of Low Temperature Plasma, Member of the Executive Boards of the United Physical Society of the Russian Federation and of the Moscow Physical Society, the Chairman/Member of Advisory and Program Committees of various conferences and schools on Low temperature Plasma Physics and Plasma Chemistry. His affiliation since 1971 is the Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences, Moscow, Russia. Since 1996 he is a head of the Laboratory of Plasma Chemistry and Physical Chemistry of Pulse Processes.
MD presentation
AMPERE Newsletter Issue 88 March 31, 2016
22
Ricky's Afterthought:
A “Corrugated” Conundrum A. C. (Ricky) Metaxas
AC Metaxas and Associates, Cambridge, UK E-mail: acm33@cam.ac.uk
A recent report stated that the corrugated
packaging industry is booming. For example, if
the predicted annual rises of about 4% do
materialize the digital print industry packaging,
which relies heavily on corrugated paper, will in
2019 amount to some 115 million tonnes of
converted material worth an estimated $176
million. These are staggering amounts and
focus the mind to efficient ways of producing
the parts of corrugated paper in the first place
before any printing is applied.
The essential part of the corrugated paper is
the flute, which is a thin planar material which
is ultimately sandwiched between two heavier
papers (or indeed board). This flute starts as a
slurry and then is dried in various stages to
produce a thin paper of around 8% moisture, its
equilibrium value. The final stages of drying
often entails pressing the flute over steam
heated cylinders or drums, these being a few
metres in diameter and up to several metres in
length, as the product travels at around 400
m/min. These drums are cascaded over the
length of the entire dryer, which could be some
100 metres long.
There are drawbacks with such an
operation, for example, the moisture content
across the broadloom flute is not even when it
emerges from the last drum but could vary by at
least 2% from its mean. To remedy this, one
way is to over-dry down to say 5% and let the
flute idle for a few days to regain its equilibrium
moisture of 8%. This is wasting energy, as
every 1% of over-drying requires 3% additional
energy. Further, under-drying and then letting
the flute attain its equilibrium moisture is not
viable, as the wetness of the flute will damage
its structure.
Given the staggering amounts of flute
currently required for the production of
corrugated paper, we can assume that
manufacturers of the flute medium would
welcome novel ways of increasing production
rates from current machines without having to
install another conventional dryer. So one
solution would be to use a compact RF system
at the end of the existing drying line, where
conventional energy is inefficient, and increase
the throughput by say 20%.
The slide above shows the main parts of
such an application for a broadloom flute of
around 3-4 m in width. The addition of the RF
at the dry end of the gas fired drum dryer allows
one to increase the speed of operation and using
900 kW of RF could increase the speed from
334 to 400 m/min (that is a 20% increase). As
can be observed, essentially the RF will dry the
last 5% of moisture (dry basis), from say 13±2%
(red line on the diagram shown on the right)
down to the equilibrium at 8±0.5% (blue line).
Further, wet planar materials, such as the flute
for example, exhibit excellent moisture levelling
characteristics at around 27 MHz. Therefore, the
additional benefit of using RF would be that the
flute exiting at the dry end would be “moisture
levelled” down to the required equilibrium
value requiring no over-drying.
A cost benefit analysis of such an
application, taking into account both capital and
running costs as well as the interest on any
Ricky's afterthought
5 10 15
M
Dry basis
%
Distance in the dryer
RF drying
Speed = 400 m/min
Steam heated cylinder drying
13%
8%
13
8
%
M
Web width
.
Existing steam cylinder bank
Moving web
Wet end
RF dryer
Dry end
10 m 120 m
AMPERE Newsletter Issue 88 March 31, 2016
23
borrowed capital to purchase the RF source,
resulted in a payback period of just under 2
years.
An experimental system, which tested the
essential elements of such an industrial
application, is shown in the photo above where
an RF dryer was connected at the end of a
cascade of drum dryers the latter of which
removed the bulk of the moisture from the flute.
There is, however, a distinct lack of industrial
systems worldwide being applied to such an
operation contrary to the several thousands of
RF textile dryers and paper converters (drying
the glue, for example) operating very
successfully in the past 40 years.
One has to probe the scarcity of such
applications for the flute particularly given the
appropriateness of using a self-excited Class C
RF source coupled to a strayfield type of
applicator. The higher the moisture of the flute
entering the wet end of the RF dryer, the better
the coupling of RF energy into it, and
conversely, the lower the moisture content, the
less the power coupled to it. Indeed, it is
fascinating to observe what happens when the
last bit of material, say the flute in this case,
enters the dryer. Progressively as less and less
load fills the applicator the power lowers down
to its standby conditions. I cannot think of a
more suitable application than drying a wet
material through an RF system operating under
Class C conditions.
The following questions are bound to be
asked: are conventional paper, board or flute
dryers that efficient requiring no assistance from
an RF source. How is moisture levelling
effected with present equipment or could it be
that the latter is no big deal given the low gas
energy costs involved in their operations?
Indeed, a new gas plant came on stream in
February 2016 in the Shetland Islands north
west of Scotland run by the giant energy
company Total. The plant pumps gas from two
fields 125 km to the north west of the Shetlands
islands. It is also well known that gas costs for
large industrial users are four times cheaper than
electricity costs (2.5p/kWh as compared to
10p/kWh with reference to 2015 energy data).
But no one is advocating using electricity to dry
the flute when it is very wet! RF will be inserted
near the dry end when conventional energy
becomes very inefficient. One has to preserve
gas, an exhaustible energy resource, and use it
where it is very efficient, in this case from a
very wet flute down to moistures of around
15%.
Drum dryers
RF end dryer
Ricky's afterthought
AMPERE Newsletter Issue 88 March 31, 2016
24
Recently Published Journal Papers Microwave heating of heavy oil reservoirs: A critical analysis D. Oloumi and K. Rambabu Microwave and Optical Technology Letters Vol. 58, pp. 809-813, April 2016
Abstract: In this article, microwave heating of the heavy oil reservoir, oil-sand, is critically studied. The study is carried out based on full wave and multiphysics simulations that are performed at 2.45 GHz using both CST Microwave studio and COMSOL. It is demonstrated that most of the microwave power is deposited in bitumen rather in sand due to the dielectric properties of bitumen. Thermal analysis showed that most of the heat is generated in bitumen and is conducted to sand. Although microwave power is selectively deposited into bitumen of the oil-sand, the temperature gradient between the bitumen and sand is not able to maintain due to high thermal conductivity of the oil-sand medium. Microwave heating can play very important role to reduce the tailing ponds and protect the environment by minimizing water usage in the recovery process.
Microwave heat treatment of natural ruby and its characterization S. Swain, S. K. Pradhan, M. Jeevitha, P. Acharya, M. Debata, T. Dash, B. B. Nayak, B. K. Mishra Applied Physics A: Materials Science and Processing Vol. 122, Art. No. 224, pp. 1-7, March 2016
Abstract: Natural ruby (in the form of gemstone) collected from Odisha has been heat-treated by microwave (MW). A 3-kW industrial MW furnace with SiC susceptors was used for the heat treatment. The ruby samples showed noticeable improvements (qualitative), may be attributed to account for the improvement in clarity and lustre. Optical absorption in 200–800 nm range and photoluminescence peak at 693 nm (with 400 nm λex) clearly show that subtle changes do take place in the ruby after the heat treatment. Further, inorganic compound phases and valence states of elements (impurities) in the ruby were studied by X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The valence states of the main impurities such as Cr, Fe, and Ti, in the untreated and MW heat-treated ruby, as revealed from XPS, have been discussed in depth. The overall results demonstrate for the first time the effect of fast heating like MW on the microstructural properties of the gemstone and various oxidation states of impurity elements in the natural ruby.
Thermodynamics model based temperature tracking control in microwave heating Y. Yuan, S. Liang, Q. Xiong, J. Zhong, Z. Wang Journal of Thermal Science and Technology Vol. 11, Paper No.15-00102, January 2016
Abstract: Microwave heating technology has been widely used in both domestic and industrial applications. Temperature control technique is significant in improving the performance of microwave heating. A generalized numerical thermodynamics model associating with the temperature-dependent thermal and physical properties of material for the microwave heating process is proposed in this paper. Experimental data is applied to estimate the microwave power coefficients. Two controllers, sliding mode controller (SMC) and proportional-integral-differential (PID) controller, are presented as the easily implementable and efficient on-line controllers to track the desired temperature profile while acting on the microwave power and the heated material’s temperature. The effectiveness of the proposed thermodynamics numerical model is verified by simulations and experiments, which shows that SMC controller has better dynamic control performance than PID controller.
Enhanced reduction of copper oxides via internal heating, selective heating, and cleavage of Cu-O bond by microwave magnetic-field irradiation J. Fukushima and H. Takizawa Materials Chemistry and Physics Vol. 172, pp. 47-53, April 2016
Abstract: The reduction behavior of copper (II) oxide (CuO) covered with boron nitride (BN) powder under microwave H-field irradiation was investigated to understand the mechanism of enhanced reduction of CuO in microwave processing. Internal heating using microwave irradiation resulted in a unidirectional diffusion of oxygen from inside the CuO pellet to its outside, and selective heating prevented the oxidization of the BN powder near the CuO pellet. A quantum chemical interpretation of this phenomenon revealed that the microwave H-field couples to the Fermi level electrons of CuO, and the copper-oxygen bond may be cleaved by both microwave energy and thermal energy. As a result, microwave H-field irradiation resulted in a more effective reduction of CuO to copper metal compared to conventional heating.
Recently published
AMPERE Newsletter Issue 88 March 31, 2016
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Upcoming Events 3rd Global Congress on Microwave Energy Applications (GCMEA) July 25-29, 2016, Cartagena, Spain
http://cpcd.upct.es/3gcmea
50th IMPI’s Annual Microwave Power Symposium
June 21-23, 2015, Florida, USA
http://impi.org/symposium-short-courses
Call for Papers Special Issue on Solid-State Microwave Heating
AMPERE Newsletter is planning a Special Issue on the various aspects of solid-state technologies of RF and microwave heating, to be published on June 30, 2016. Authors who wish to contribute to this issue are kindly requested to contact the Editor before April 30, 2016 in order to coordinate the contents of their articles.
Regular issues
AMPERE Newsletter welcomes submissions of articles, briefs and news on topics of interest for the RF-and-microwave heating community. These may include: • Research briefs and discovery reports. • Review articles on R&D trends and thematic issues. • New inventions and patents. • Technology-transfer and commercialization. • Safety, RFI, and regulatory aspects. • Technological and market forecasts. • Comments, views, and visions. • Interviews with leading innovators and experts. • New projects, openings and hiring opportunities. • Tutorials and technical notes. • Social, cultural and historical aspects.
• Economical and practical considerations. • New products and services. • Upcoming events, new books and papers.
AMPERE Newsletter is an ISSN registered
periodical publication hence its articles are citable as references. However, the Newsletter's publication criteria may differ from that of common scientific Journals by its acceptance (and even encouragement) of news in more premature stages of on-going efforts. We believe that this seemingly less-rigorous editorial approach may accelerate the circulation of new ideas and discoveries among the AMPERE community; and consequently enrich our common knowledge, and excite new ideas, findings, and developments.
Please send your submission to the Newsletter
or any question, comment or suggestion in this regard directly to the AMPERE-Newsletter Editor:
Eli Jerby Faculty of Engineering Tel Aviv University, Israel E-mail: jerby@eng.tau.ac.il
AMPERE Disclaimer
The information contained in this Newsletter is given for the benefit of AMPERE members. All contributions are believed to be correct at the time of printing and AMPERE accepts no responsibility for any damage or liability that may result from information contained in this publication. Readers are therefore advised to consult experts before acting on any information contained in this Newsletter. AMPERE is a European non-profit association devoted to the promotion of microwave and RF heating techniques for research and industrial applications.
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