Ampere Newsletter

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AMPERE Newsletter Issue 88 March 31, 2016 AMPERE Newsletter Trends in RF and Microwave Heating www.AmpereEurope.org Issue 88 March 31, 2016 Page 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 ISSN 1361-8598 1 AMPERE Newsletter Issue 88 March 31, 2016 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: [email protected] 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 treatment area, the applicator design is essential in the field of medical heating3-5. Research brief 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 concentrations. The change of reflection coefficient was measured in vivo as a parameter of blood glucose level. The result shows that by measuring 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. 2 AMPERE Newsletter Issue 88 (a) March 31, 2016 (b) 1.0⁰C 10cm (c) (d) 0 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. Microwave surgical knife Figure 2. Experimental results of return loss vs. frequency as a parameter of blood glucose concentration. Research brief Figure 3. LED visualized microwave field distribution from a microwave surgical knife. 3 AMPERE Newsletter Issue 88 March 31, 2016 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. 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 simulation for high sensitivity non-invasive measurement of blood sugar level in millimeter waves,” IEICE Trans. Communication E86-C (2003) 2488. Nikawa and T. Michiyma, “Blood-sugar monitoring by reflection of millimeter wave,” Proc. Asia-Pacific Microwave Conf. Proc. III (2007) 1581. [8] Y. [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. [5] T. Michiyama and Y. Nikawa, “Simulation of SAR in the human body to determine effects of RF 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 Research brief 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 distinguished 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. 4 AMPERE Newsletter Issue 88 March 31, 2016 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: [email protected] 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 Research brief reflected, while frequencies above the plasma frequency are transmitted. Quantitatively, the reflectance Sr Si , transmission St Si and absorption Sa Si 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). 1.0 0.8 Sr /Si 0.6 Sa /Si 0.4 0.2 St /Si 0.0 0 100 200 R [Ω] 300 400 Figure 1. Reflectance Sr Si , transmission St Si and absorption Sa Si of a conductive coating as a function of the sheet resistivity R. While in principle the microwave transmission can approach 0 if R is sufficiently small, in practice R cannot economically be made small enough to satisfy safety requirements: 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 5 AMPERE Newsletter Issue 88 transmission of TE waves is decreased, while the transmission of TM waves is increased. March 31, 2016 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 2. Transmission of a pair of 10  coatings spaced a distance L apart in air (normal incidence). 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 exceptional food visibility. 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 bandpass power leaking from a 20-litre microwave oven with various loads, equipped with its Research brief Figure 5. Lentil-tomato mini-casseroles during cooking in a 20-litre microwave oven, photographed via a ClearWaveTM etalon window (see www.youtube.com/channel/UCiZLxQCzAqdYXUFuDUhWkdA). 6 AMPERE Newsletter Issue 88 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. March 31, 2016 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 electromagnetic 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 OmegaP, 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 7 AMPERE Newsletter Issue 88 March 31, 2016 The Microwave Materials Processing Group at KIT Guido Link Institute for Pulsed Power and Microwave Technology Karlsruhe Institute of Technology, Karlsruhe, Germany E-mail: [email protected] 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 largescale 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 longterm 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 Research brief 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 Industrietechnik 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 8 AMPERE Newsletter Issue 88 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). March 31, 2016 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 absorption spectroscopy13,14, as well as thermogravimetry. Research brief For a successful system and process design, the detailed knowledge of the dielectric properties 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 9 Issue 88 term collaboration in research and development of novel microwave applications. 1.5 100 1.2 80 0.9 60 meas @80°C meas @70°C model 0.6 0.3 40 20 0.0 0 50 100 150 200 250 Temperature in °C 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 transmissionreflection 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- March 31, 2016  r" AMPERE Newsletter 0 300 Time in minutes Figure 3. Dielectric loss factor of DGEBA based epoxy resin at 2.45 GHz during curing at different 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 Ba₀₆̣ Sr₀₄̣ TiO₃ 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, Research brief 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). FaserverbundLeichtbau mit Automatisierter Mikrowellenprozesstechnik 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 Mikrowellentechnologie zur Herstellung von Faserverbundstrukturen. Schlussbericht für das BMBFVerbundprojekt Förderkennzeichen: 01RI05133,-135140, -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 MTTS 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. 10 AMPERE Newsletter Issue 88 [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 March 31, 2016 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. [16] Soldatov, S.; Kayser, T.; Link, G.; Seitz, T.; Layer, S.; Jelonnek, J.; Microwave cavity perturbation technique for high-temperature dielectric 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. Research brief The microwave materials processing group in 2015 11 AMPERE Newsletter Issue 88 March 31, 2016 Microwave Technology in Manufacturing and Research at Corning Incorporated Rebecca L. Schulz Corning Incorporated, Corning, NY 14830 E-mail: [email protected] 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 tinantimony 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 preheated 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 chemicalvapor deposition method was investigated for the production of optical fiber preforms. This method used a 2.45 GHz microwave to Research brief 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 resulted in improved understanding of applicator heads, plasma stability and methods for characterizing 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 automotive 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 12 AMPERE Newsletter Issue 88 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, microwave 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 March 31, 2016 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. A B 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 Engineering 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 microwave energy as a remediation technique in the destruction of electronic circuitry from weapons components. As part of this work she designed, constructed, and successfully demonstrated a microwave 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 Research brief where she continued research on microwave remediation of transuranic wastes, tires, and medical waste. In 2001, Dr. Schulz was recruited by Corning Incorporated 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 committee 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 patents with 5 applications in prosecution. She is currently serving as President of the Microwave Working Group. 13 AMPERE Newsletter Issue 88 March 31, 2016 Field Assisted Processing of Advanced Ceramics: A Research Perspective Bala Vaidhyanathan Department of Materials, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom E-mail: [email protected] Advanced ceramic materials are being increaseingly 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 innovations 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 Research brief 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 fieldenhanced 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 14 AMPERE Newsletter Issue 88 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 Research brief March 31, 2016 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, compaction 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 nanostructured (a) and commercial (b) zirconia ceramics, fabricated at LU using the FAST methods (b) 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 15 AMPERE Newsletter Issue 88 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 March 31, 2016 armour, Silicide’s and Chalcogenides for thermoelectrics, 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. Sintering temperature decreases with increasing Z content. The ease of sintering follows BCZT < BZT 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- Research brief 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. 17 AMPERE Newsletter Issue 88 March 31, 2016 Microwave Discharges Yuri A. Lebedev Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences, Moscow, Russia E-mail: [email protected] 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 microwave pulse for plasma generation, in order to prevent the damage of high sensitivity microwave receiver as this pulse passes through the microwave circuit. Further development of microwave techniques 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, planarization, microwave plasma sterilization, in analytical 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 Research brief engineers?” There are several reasons for this attention: • MD's are interesting topics for fundamental studies as they unite phenomena of electrodynamics, plasma kinetics and plasma chemistry, in non-equilibrium and nonhomogeneous 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 electromagnetic 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 electromagnetic 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. 18 AMPERE Newsletter Issue 88 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, nec cm-3   1.24 1010   f GHz  , 2 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 nonequilibrium 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-toplasma 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 nonuniformity, and the size of the plasma. It is difficult though to classify the microwave-toplasma applicators uniquely since the researchers design their plasma devices to meet the conditions of their own tasks. Research brief March 31, 2016 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 plasmaresonance 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 Applications (1992, 1994, 1997, 2000, 2003, 2006, 2009, 2012, and 2015) contain comprehensive data on microwave discharges. 19 AMPERE Newsletter Issue 88 March 31, 2016 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. Technol. 9 441 [27] Asmussen J, Grotjohn T A, Mak P, Perrin M A, 1997 IEEE Trans on Plasma Science, 25 1196 [28] Moisan M, Pelletier J 2012 Phys. Collisional Plasma. Intro. to High-Frequency Discharges, Springer [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 Discharges: 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. MD presentation 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 20 AMPERE Newsletter Issue 88 March 31, 2016 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). attended by 70-100 participants. The previous meetings include the following: Selected topics of closely related gas discharge problems can also be discussed. The Int'l Workshop on “Microwave Discharges: Fundamentals and Applications” is usually The next MD Workshop will be held in 2018 in Russia. 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 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 MD presentation 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. 21 AMPERE Newsletter Issue 88 March 31, 2016 Ricky's Afterthought: A “Corrugated” Conundrum A. C. (Ricky) Metaxas AC Metaxas and Associates, Cambridge, UK E-mail: [email protected] 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 Ricky's afterthought 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%. % Speed = 400 m/min M Dry basis % M Steam heated cylinder drying RF drying 15 10 5 8% Wet end 13 13% 8 . Distance in the dryer Existing cylinder steam bank RF dryer Web width Dry end Moving web 120 m 10 m 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 22 AMPERE Newsletter Issue 88 borrowed capital to purchase the RF source, resulted in a payback period of just under 2 years. RF end dryer Drum dryers 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 Ricky's afterthought March 31, 2016 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%. 23 AMPERE Newsletter Issue 88 March 31, 2016 Recently Published Journal Papers Microwave heating of heavy oil reservoirs: A critical analysis Thermodynamics model based temperature tracking control in microwave heating D. Oloumi and K. Rambabu Microwave and Optical Technology Letters Vol. 58, pp. 809-813, April 2016 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: 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. 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. 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. Recently published 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. 24 AMPERE Newsletter Issue 88 March 31, 2016 Upcoming Events 3rd Global Congress on Microwave Energy Applications (GCMEA) 50th IMPI’s Annual Microwave Power Symposium July 25-29, 2016, Cartagena, Spain June 21-23, 2015, Florida, USA http://cpcd.upct.es/3gcmea 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-andmicrowave 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: [email protected] 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. AMPERE Newsletter ISSN 1361-8598 Call for papers 25