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In this article, ZnO thin-film deposition on a glass substrate was done using microwave induced oxygen plasma based CVD system. The prepared thin-films were tested in terms of crystallinity and optical properties by varying the microwave power. The effect of power variation on the morphology and size of final products was carefully investigated. The crystal structure, chemical composition and morphology of the final products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and photoluminescence (PL). This technique confirmed the presence of hexagonal ZnO nanocrystals in all the thin-films. The minimum crystallite grain size as obtained from the XRD measurements was ~9.7 nm and the average diameter was ~18 nm.

A novel, low temperature process for the formation of Si-BC8 phase is obtained while growing Silicon nanowires. The nanowires growth is performed in a CVD reactor under exposure of the substrate to microwaves, employing Sn nanospheres as catalyst and a flux of SiH4 as precursor, respectively. Microwaves allow for selective heating of the metal catalyst while keeping the substrate at low temperature. At the end of the process, silicon nanowires with the metal sphere on top are obtained, together with the (unexpected) transition of a portion of silicon substrate from the diamond to the Si-BC8 crystallographic phase. Silicon atoms in Si-BC8 phase are arranged in body-centered-cubic unit cells resulting into a different energy-wavevector diagram compared to the silicon diamond cubic phase. Indeed, Si-BC8 possesses a direct band gap as low as 30 meV at room temperature. These features may be employed in a large variety of applications, requiring CMOS-compatible manufacturing. Systematic structural analysis and a phenomenological model for Si-BC8 phase formation are discussed.

The pursuit of sustainable relationship between the production and consumption of energy has accelerated the research into new fuels alternatives, and mainly focused on new technologies for biomass based fuels. Microwave pyrolysis of biomass is a relatively new process which has been long recognized to provide better quality bio-products in shorter reaction time due to the direct sample heating and the particular heating profile resulting from the interaction of biomass with the electric field component of an electromagnetic wave [1,2]. During the course of this research, flax shives were pyrolysed using a rotatory kiln reactor inside a microwave single mode cavity using a range of power between 100 and 200 watts, to reach a temperature range between 450 °C and 650°C. The liquid bio-oil samples recovered in each case were analyzed though gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID) to identify and quantify the different molecules presents and paying a particular attention to the BTX’s concentration. More than two hundred compounds were identified and grouped into families such as carboxylic acids, alcools, sugars for a deep analysis of the results. The effect of the operating conditions on the proportion of gas, liquid and char produced were studied as well as some properties of the pyrolysis products. In most cases, carboxylic acids were the dominating chemical group present. It was also noticed that the increase of temperature enhanced the carboxylic acids production and diminished the production of other groups, as sugars. Finally, pyrolysis oils were produced in higher quantities by microwaves than in a classical oven and showed a different composition. The examination of the pyrolytic liquid products from different biomass components helped to determine the provenance of each molecule family. On the operational side, the rotatory kiln reactor provided a fast and homogeneous heating profile inside the reactor, desired for fast pyrolysis. The high temperature was maintained without making hot spots during the reaction time. The microwave irradiation setup consisted in a single-mode cavity, a system of plungers, incident and reflected power monitors, an isolator and a 2.45 GHz continuous microwave generator with a power upper limit of 2000 watts. The plunger system was calibrated to maintain a range of reflective wave between 5 and 15%, taking advantage of a minimum of 85 percent of the applied power. In conclusion, the developed microwave pyrolysis process gives a clear way to produce an exploitable bio-oil with enhanced properties. References Beneroso, D., Monti, T., Kostas, E., Robinson, J., CEJ, 2017.,316, 481- 498. Autunes E., Jacob M., Brodie, G., Schneider, A., JAAP, 2018,129, 93-100.

The German chemist Theodor Grotthuss was the first to formulate the first law of photochemistry in 1817; he postulated that a reaction could be driven by light when the energy of light is absorbed by molecules [1]. After that, photochemistry has greatly contributed to the development of photography. In addition, second laws of photochemistry (Stark-Einstein law) was enacted, and these two laws have elevated photochemistry as an academic (science) discipline over the last one hundred years. In addition, because of advances in light sources and various devices (engineering), such materials and processes as photocatalysts, organic solar cells, photopolymerization, quantum dots, and photochromism (among others) are currently being applied in various other fields. The next significant surge in chemistry is microwave chemistry wherein microwaves, which represent electromagnetic waves other than light, were introduced as a driving force in the chemical reaction domain in the late 1980s. There are three characteristics in this chemistry when using microwaves. The first is the high heating efficiency caused by the energy of the microwaves that directly reach and are absorbed by the substance. The second is the selectivity with which a specific substrate is heated, while the third characteristic is the enhancement of chemical syntheses by the microwaves’ electromagnetic wave energy, often referred to as the microwave effect (or non-thermal effect). The phenomenon of the microwave effect (third characteristic) impacting chemical reactions has been summarized in much of the relevant literature, however, the reason why the microwave effect has not been clarified to anyone’s satisfaction is that the term microwave effect in microwave chemistry includes numerous factors. In order to fix microwaves in the chemical field, it is urgent to develop laws of “microwavechemistry”, and to do it is necessary to systematization against the phenomenas of electromagnetic waves for materials and reactions. One of the reasons for the dramatic growth in photochemistry is the development of high power laser technology. In recent years, coherent semiconductor generator with the generating high power microwaves have become easy to get, so “microwavechemistry” can proceed to the next stage. We examined that the phenomena as microwave electromagnetic waves in chemical reactions by using a semiconductor generator and a power sensor. And, it clarified that the reaction rate and yield of a very small part of the chemical reaction change with the unique phenomenon to electromagnetic waves [2]. On the other hand, generally, as plants, enzymes, biological substances temperature rises, it inhibits growth and reaction. This phenomenon was used to overcome the electromagnetic wave effect. We have succeeded in improving these activities by irradiating weak microwaves which do not increase these temperatures [3]. If microwave heating is given to them, it will work negatively. In this invited presentation, it introduces the possibility of electromagnetic wave effect(s) in these and explain its industrial application.

[EN] In this work the microwave effect of enhancing chemical reactions was applied to maleic anhydride esterification with 2-ethylhexanol-1 catalyzed by p-toluene sulfonic acid. The analysis of this reaction was simplified considering the industrial practice of withdrawn the reaction water, which makes the whole reaction act as a pseudo irreversible one. A statistical design of experiments was applied to determine an empirical chemical kinetics equation with three levels of catalyst concentration and two levels related to the kind of heating (microwave and conventional); six chemical kinetics equations (three for microwave heating and three for conventional heating) were determined. A batch/plug flow simulation was done and a spreadsheet developed for the reactor’s behavior. The most interesting result was the confirmation of a synergic effect between microwaves and acid catalysis that accelerated this esterification reaction, transforming it in a fast reaction., The authors would like to thank C. Tognela. Support from Instituto Mauá de Tecnologia – IMT – and from Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP – (Grant 2017/24238-7) are gratefully acknowledged.

[EN] Preconditioning of hard rocks by microwave energy has recently been considered a potentially effective technology in mechanical rock breakage for civil and mining engineering. To obtain the amount of mechanical damage that a single-mode microwave treatment produces in rocks, it is necessary to analyze and evaluate the thermal cracking process by microwave heating at different power levels, exposure times, and distances from the antenna. The current study employs the scanning electron microscopy imaging technique to capture images from surfaces of irradiated rock specimens and to compare them with a nontreated specimen. To evaluate and quantify the amount of cracking (i.e. crack density, crack size, etc.) in a rock specimen after microwave irradiation with different microwave input operating parameters, the following steps were evaluated. First, several experiments of single-mode microwave treatments with different operating parameters were performed on rectangular specimens of basalt. Then, cylindrical core samples with a dimension of r = 0.5 cm, h = 2cm, were drilled from the center of the irradiated specimens and prepared for image processing. The results of the present study show that there are significant differences between the number of microcracks present in samples irradiated at different power levels and distances from the antenna. Also, longer exposure times result in more severe cracks., Financial support for this work from the Natural Sciences and Engineering Research Council of Canada (NSERC), De Beers Group, Argex, Metso and the McGill Engineering Doctoral Award (MEDA) Award is gratefully acknowledged.

Liquid Crystal (LC) is an anisotropic liquid material which flows like a liquid, but at the same time its molecules have an orientational order like in the solid state [1]. Thus, LC is a promising dielectric material for designing reconfigurable devices at microwave frequencies. In order to optimize the design of reconfigurable microwave devices, accurate values of the dielectric permittivity and the loss tangent of LCs are needed. However, new LCs are not well characterized at these frequencies because of its recent use for microwave applications. Therefore, the characterization in this frequency range is required for its practical use within microwave components and devices [2]. In this work, the split-cylinder resonator method has been used for the characterization of LCs at two frequency points, i.e. 5 and 11 GHz. The method is based on the measurement of the resonance frequency and quality factor of the two states of the LC molecules for extracting the complex dielectric permittivity [3]. For achieving these two states, no electric or magnetic fields are needed, just the cell must be turned 90º inside the cavity. The dielectric properties (permittivity and loss tangent) of four different LC samples, GT3-23002 from Merck and QYPD193, QYPD142, and QYPD036 from Qingdao QY Liquid Crystal Co, have been obtained. The highest values of the dielectric anisotropy are presented for the samples QYPD036 and QYPD193, together with the highest values of the corresponding loss tangent parameters. Furthermore, it is observed for all the LCs that the loss tangent decreases and the dielectric anisotropy increases at higher frequencies, which must be taken into account in the development of reconfigurable microwave devices.

[EN] Both high temperature phases and microstructure transformations of stoneware products microwave and conventionally (gas and electric) fired are investigated aiming at a better understanding of factors affecting their mechanical and aesthetic properties. The microstructure of microwave fired stoneware has similar characteristics to those of conventionally fired samples, microwave firing requiring lower temperatures to achieve a similar structure. X-Ray diffraction and scanning electron micrographs show that the most relevant transformations are complete for lower temperatures when using microwave heating. Microwave radiation is presented as an alternative heating technology for stoneware firing, leading to similar, or even better, mechanical properties and similar microstructural characteristics, requiring lower firing temperatures and shorter processing times., This work was funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the project UID/CTM/50025/2019. The authors express their sincere thanks to Grestel, Produtos Cerâmicos S.A. (Portugal) and to its staff member Eng. Carlos Pinto for his help and for providing the samples required for this study. The authors also express their sincere thanks to Doctor Manuel Graça from Department of Physics and I3N of University of Aveiro for its help in SEM measurements, to Doctor Maria Rosário from Central Laboratory of Analysis/CICECO of University of Aveiro for its help in the XRD analysis. Author V. A. F. Costa acknowledges the Portuguese Foundation for Science and Technology for the financial support provided through project UID/EMS/00481/2013-FCT, and CENTRO-01- 0145-FEDER-022083.

[EN] Low laminar burning velocity’s and slow reactions propagation are among a key problem in combustion processes with low calorific gas mixtures. The mixtures have a laminar burning velocity of 10 cm/s to 15 cm/s or even below which is 37% of natural gas. Thermal use of these gases could save considerable amounts of fossil fuel and reduce CO2 emissions. Due to low burning velocities and low enthalpy of combustion, ignition and stable combustion is complex, often preventing utilization of these gases. Microwave-assisted combustion can help to solve these problems. With microwave assistance, these gas mixtures could be burned with a higher burning velocity without preheating or co-firing. Therefore, this effect could be used for flame stabilization processes in industry applications. Microwaves could also change the combustion properties, for example radical formation and flame thickness. In this paper, we explore a possibility of using microwaves to increase the burning velocity of propane as one component in low calorific gas mixtures and also show higher productions of OH* and CH* radicals with an increase of the input microwave power. Different compositions of low calorific fuels were tested within a range of equivalence ratios from φ= 0.8 to φ= 1.3 for initial temperatures of 298 K and atmospheric conditions and microwave powers from 120 W to 600 W. For the experiments, a standard WR340 waveguide was modified with a port for burner installation and filter elements allowing for flue gas exhaust and optical access from the side. A 2.45 GHz CW magnetron was used as microwave source, microwave measurements were carried out with a 6-port- reflectometer with integrated three stub tuner. An axisymmetric premixed burner was designed to generate a steady conical laminar premixed flame stabilized on the outlet of a contoured nozzle under atmospheric pressure. The burner was operated with a propane mass flow of 0.2-0.4 nl/min at an equivalence ratio of φ= 0.8 to φ= 1.3. The optical techniques used in the current study are based on the flame contours detection by using the OH* chemiluminescence image technique. For every experimental case, 150 pictures were taken and averaged. Additionally, spectroscopic analysis of the flames was undertaken. The results suggest that production of OH* radicals in the flame front increases with microwave power. For evaluation, a picture based OH* chemiluminescence and a spectrographic method was used. In addition, a 9.9% increase of the burning velocity was observed in the premixed propane-air mixture for a 66 Watt absorbed microwave power. This effect is attributed to the increased OH* (~310nm) and CH* (~420nm) radical formation, which also reduces the flame thickness. It was found that absorption of microwaves in flames is generally low, but could be improved by a customized applicator design., The authors gratefully acknowledge the financial support by the European Union and the state of Saxony in the ESF project (project number 040606100).

[EN] Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 20011. Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation2. Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process3. In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed. References 1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635. 2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014. 3. Presenda, Á., Salvador, M. D., Moreno, R., Borrell, A. J. Am. Ceram. Soc., 2015, 98, 3680–3689., The authors thank the Generalitat Valenciana for the financial support provided to the PROMETEU/2016/040 project. A. Borrell is grateful to the Spanish Ministry of Economy and Competitiveness for her RyC contract (RYC-2016-20915).

Since the first serendipity of carbon quantum dots (CQDs)1, it is expected to be used for imaging materials for reusable living bodies (e.g. Hela cells). However, the reported CQDs synthetic methods have yet to be at the practical levels; the quantum yields is low, and synthetic condition is over 5 hrs under more than 30 atms. In this research, we ameliorated the problems of CQDs synthesis and luminescence (quantum yields) by the novel synthesis protocol using microwave chemistry. Specifically, we synthesized high quantum yields CQDs (61%) by utilizing a microwave chemical synthesis, synthesizing at low pressure condition (lower than 5 atom) and short reaction time (3 hrs). The achievement of this high quantum yields made it clear that the contribution of polyethylene glycol (PEG) shell to CQDs is large. It was confirmed from the DLS and TEM image that the particle size of the synthesized particles was 8 to 13 nm (Fig. 1). On the other hand, the relationship between the polymerization degree of added PEG and the quantum yields to the addition amount is summarized in Table 1. The quantum yields of CQDs without addition of PEG was 16.7 %, while it was improved at 61.1 % when 0.6 g of PEG6000 (Molecular weight: 6000) was added.We succeeded in remarkably improving the quantum yields by using PEG, which is usually used as a protective agent, as a shell. By using this method, we succeeded in improving the quantum yields of the existing report by approximately 3 times. From the surface modified structure of PEG, the mechanism of improvement of quantum yields will be considered.[1] X. Xu et al., J. Am. Chem. Soc., 2004, 126, 12736–12737.

[EN] This paper presents an efficiency study for scalable microwave waste management. When waste with carbon content is subjected to volume power densities on the order of 0.25W/cm3 at GHz frequencies, it converts to solid coke fuel with oil and gas bi-products that can further be processed for fuel, leaving no trace. For an efficient process, a well-controlled uniform RF field should be maintained in a non-uniform and time-variable material. We are developing a 2.45-GHz active microwave cavity with solid-state (GaN) spatially power combined sources for lower volumes, Fig.1. In the energy balance calculations, the input energy into the system consists of the waste chemical energy and the DC electrical energy used to obtain the RF power with an efficiency that can reach 70% for kW power levels. The efficiency of RF power conversion to heat in the waste mass is calculated from full-wave simulations for typical waste mixtures and ranges from 10 to 90% depending on the material and cavity filling. The output energy estimates are collected from various pyrolysis process descriptions, e.g. [1], with the total energy being that of the solid fuel (35MJ/kg) and oil caloric values, e.g. 40MJ/kg for plastics and about 10-15MJ/kg for nonplastics [2]. A byproduct is flue gas which can be converted to Syngas [3]. The total worse-case carbon footprint balance (0.3-3) calculations will be presented. Fig. 1. Block diagram of active microwave cavity for waste to fuel conversion. References D. Czajczyńska, “Potential of pyrolysis processes in the waste management sector,” Thermal Science and Engineering Progress, vol. 3, p. 171. Sept., 2017. J.A. Onwudili, “Composition of products from the pyrolysis of polyethylene and polystyrene in a closed batch reactor: effects of temperature and residence time,” Journal of Analytical and Applied Pyrolysis, vol. 86 p. 293–303. Nov., 2009. S. Chunshan, "Tri-reforming of methane: a novel concept for synthesis of industrially useful synthesis gas with desired H2/CO ratios using CO2 in flue gas of power plants without CO2 separation." Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem 49, no. 1 (2004): 128., This work was funded by DARPA under contract W911NF-18-1-0073.

Ryszard Parosa PROMIS-TECH, Poland Subcritical Hydrothermal Conversion (SHC) process can be used for utilization of wet biomass with recovery of energetic gases and diesel-like fluids. Process is carried out in high pressure (over 200 Barr) and wet biomass is heated up to 350°C. In our research we have apply microwave system to heat wet biomass in high pressure vessel – with control of the most important process parameters like temperature, pressure, microwave power and reflection coefficient. In the first stage process was tested with use of small metallic vessel connected to microwave line (rectangular waveguide) by special ceramic window. Microwave generator 2.45 GHz with controlled output power in range of 200 W to 3 kW was applied. Sewage sludges with moisture content up to 60% were heated by microwaves to temperature from 250°C to 350°C with pressure ca 300 Barr. After heating by 15 - 20 minutes inside of vessel fluid like oil was obtained with solid particles in form of carbon black. Fluid after separation of water contains hydrocarbons – with biodiesel structure. The similar process with conventional heating by metallic walls of vessel needs much longer time – about 40 minutes, and higher energy consumption.In the next stage a semi-industrial system was designed with process reactor in form of ceramic tube located inside of metallic cavity with two single mode microwave radiators connected to microwave generators of 2.45 GHz and with output power 3 kW (CW) each.Heating process is provided in stop/flow system: biomass inside of high pressure cavity is heated by microwaves to adjusted temperature (280 -350°C) and product is transported by heat exchanger to separator. At the same time next portion of biomass is injected to the cavity. During the process reflected microwave power was recorded. When treated material was in very high pressure, close to subcritical state, specific fluctuations of reflected power level ware observed. Water in subcritical condition lose polar structure and dielectric constants change, but in the hydrothermal conversion process another chemical compounds are formed (for example diesel like hydrocarbons) and treated material still effectively absorb microwaves. In the described system ca 60 – 80 kg of wet biomass (with 50 – 55% of water) was treated and ca 8 – 15 kg of diesel – like fluid was obtained. Basing on the preliminary results a new industrial scale system was designed and actually is under construction. In industrial scale installation a microwave heating system of 60 kW, 915 MHz is planned, with two radiators installed along ceramic tube. Estimated efficiency of the system is in range of 200 to 400 kg of biomass treated in hour.

We report a microwave heating system with a carbon heating tube (CHT) made by a 4-mm diameter quartz tube filled carbon particles and Ar gas at 1400 Pa. 2.45-GHz microwave at 200 W was introduced to a 300-dimameter metal cavity, in which 60-mm-long CHT was set at the central position. The numerical simulation with a finite element moment method resulted in the standing wave of the electric field caused by three dimensional Fresnel interference effect with low high electric field intensity ranging from from 1 to 6 kV/m because of effective absorption of microwave power by the CHT. The lowest average electrical field intensity of 5 kV/m in the cavity space was given by the electrical conductivity of carbon ranging from 10 to 55 S/m. The CHT with 55 S/m heated to 1200oC by microwave irradiation at 200 W. This heating method was applied to activate 1.0x1015-cm-2 boron and phosphorus implanted regions in n-type crystalline silicon substrate to fabricate pn junction and solar cells. The CHT heating at 1200oC realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3x1011 and 9.2x1010 cm-2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.

Due to their acid characteristics and pore structure, which can induce high product selectivity; zeolite catalysts are used extensively in industry to catalyse reactions involving hydrocarbons. However, these catalysts can suffer from deactivation due to cracking reactions that result in the deposition of carbon leading to poisoning of the acid sites and blocking of the pores [1]. Depending upon the reaction and the particular catalyst involved this deactivation may take place over several months or even years but in some cases occurs in minutes. Therefore, zeolite catalysts are frequently reactivated / regenerated. This generally involves a thermal treatment involving air which results in oxidation of the carbon [2]. However, the oxidation of carbon is highly exothermic, and if not carefully controlled, results in the generation of exceedingly high localized temperatures which can destroy the zeolite structure and result in subsequent loss of catalyst activity. More conservative thermal treatments can result in incomplete regeneration and again a catalyst displaying inferior activity. This paper explores the use of non-thermal plasma which had been either generated using microwaves or via a barrier discharge to regenerate spent zeolite catalysts. The catalyst, H-mordenite, was tested for the disproportionation of toluene (Figure 1) using conventional heating. The spent catalyst was then regenerated using a plasma or conventional thermal treatment before having its activity re-evaluated for the toluene disproportionation reaction as previous. Fig. 1. Reaction Scheme for Toluene Disproportionation. Interestingly, not only is plasma regeneration highly effective but also catalysts can be regenerated in greatly reduced times. There is an additional advantage in that plasma regeneration can impart physical properties that result in a zeolite that is resistant to further deactivation. However, the results are highly dependent upon the experimental conditions involved for plasma regeneration. References Wu J, Leu L., Appl. Catal., 1983; 7 :283-294. M. Guisnet and P. Magnoux, Deactivation of Zeolites by Coking. Prevention of Deactivation and Regeneration. In: Zeolite Microporous Solids: Synthesis, Structure, and Reactivity. E.G. Derouane, F Lemos, C. Naccache, F. Ramoa Ribeiro, Eds. Pages 437-456. Springer 1992.

[EN] In the field of ceramic-based materials processing the last three decades has been marked by significant academic and industry interest in Additive Manufacturing (AM) technology due to its capability to produce ceramic parts with complex geometry and customizable materials properties. Conceptually, AM technology is a layer-by-layer fabrication of three dimensional physical parts directly from computer-aided design [1]. Solidification of the parts prepared from substances containing ceramic powder may be performed either by conventional heat treatment of a part as whole or by directed energy deposition. Both these strategies can be implemented using gyrotron-based millimeter-wave facilities allowing alternatively both the uniform heating of large-size parts in multi-mode cavities and local heating by focused wave-beams [2]. Hydroxyapatite- and yttria-stabilized zirconia-based ceramics are widely used in biomedical applications due to their high biocompatibility. The knowledge of their microwave absorption variation with temperature and porosity as the materials are densified, is necessary to optimize the scheme of microwave heating. 8 mm diameter disks for the measurements were prepared by uniaxial compacting from commercially available hydroxyapatite (HA) powder and yttria-stabilized zirconia (3YSZ) powder (Tosoh corp.). The measurements were performed at 24 GHz 3 kW gyrotron system. Samples for measurements were placed into the gyrotron system applicator and surrounded with porous alumina based thermal insulation. The design of the applicator and insulation allowed performing optical measurements of both the sample size and temperature distribution over the surface of the sample using a digital monochrome CCD camera. Measurements were made by the calorimetric method, when the microwave power absorbed in the sample is determined basing on the difference of the heating/cooling rates at the moments of intentional abrupt change of the microwave power at different sample temperatures. Absorption coefficient was determined as a division of the absorbed power to the incident microwave power. Special calibration experiments were made for determining microwave power density in the applicator and inside the thermal insulation. The method allows to measure absorption coefficients in situ during the sintering process. Absorption coefficients of HA were obtained in the range of 200 C - 1200 C, and for 3YSZ - in the range of 400 C - 1400 C both in situ during sintering and for as sintered samples. Dependencies of the absorption coefficients on the temperature and porosity are discussed., This research was supported by Russian Basic Research Foundation, grant # 18-29-11045.

Lentil is one of the important pulse crops in the world with a high proportion of easily digestible protein. However, there are several pests and pathogens which cause losses during crop growth, harvesting and post-harvest storage. Microwave processing has shown great potential to eradicate pests and pathogens from grains; however, there is still concerns about its heat uniformity, which is of crucial importance in pest and pathogen control. Fluidization using forced hot air is one of the potential solutions for having uniform temperature during microwave processing. In this study, a single mode microwave cavity, with a 2.45 GHz microwave source, was modified to have a microwave fluidized bed and used to evaluate its potential to eliminate the Botrytis grey mold (BGM) pathogen, which is one of the important seed-borne pathogens of lentil crops in Australia. Air speed was maintained to be constant during the experiment and was just enough to fluidize 100g of red lentils in the sample holder. Two wet based (w.b.) seed moisture contents (m.c.) of 10.5% and 18.5% were prepared and the process parameters were selected as: air temperature at 50 and 60°C; microwave power at 0, 300, 400 W for 18.5% m.c. and 0, 400, 500 W for 10.5% m.c.; and exposure times of 5 and 10 min. These parameters were chosen to reach the final temperature of below 70°C. The effect of process parameters on seed moisture loss, seed germination, electrical conductivity of seed soaking water and percentage of infected seeds (IS%) were analyzed using general factorial regression and analysis of variance. The results showed that the most effective factors on moisture loss, after seed moisture content, was exposure time, followed by microwave power and air temperature. While final bed temperature was affected mostly by air temperature, and then by microwave power. Furthermore, based on general full factorial regression and pareto chart of standardized effects, moisture content had by far the most influence on the reduction of IS%. Seed pathogen inoculum reduction, without significant seed viability loss, was obtained by applying microwave power of 300W and set air temperature of 60°C (actual inlet air temperature of 57±1°C) on seeds with m.c. of 18.5% for 10 min. This gave a 27% reduction in IS% (from 82% to 55%).

[EN] At present, ZrTiO4 nanopowders are used as a dielectric in the electroceramic field, applications of catalysis, microwave telecommunications devices, pigments, composites, etc. One of the most interesting applications is the potential as structural material and similar applications that require a high thermal resistance. However, all the properties of zirconium titanate are still a subject of interest for the industrial field.12 There are several routes of synthesis of ZrTiO4; among them is the sol-gel method and lyophilization. These methods have been used to make powders or small pieces of zirconium titanate. However, structural applications require materials in large quantities, so it is necessary to identify the differences between the methods of synthesizing and allowing the preparation of powders suitable for the generation of green materials for subsequent sintering.3 To develop a new generation of nanomaterials with microstructural differences it is necessary to innovate in the sintering process. Years ago, the use of conventional oven for sintering material was the usual procedure. Nowadays, non-conventional methods as Microwave sintering (MW) are a bright way to produce high dense materials, using heating rates in reduce dwell times and lower consumption using 70%-80% less energy. 4 This reactive sintering technique achieves excellent mechanical properties, homogeneous microstructure employing lower sintering temperatures. All these energy and economic advantages generate a new vision for the future on ceramic materials and their industrial production. The main objective of this study is to make a comparison of the mechanical properties of the materials synthesized by sol-gel method and lyophilization and sintered by microwaves., The authors would like to thank to the Generalitat Valenciana for financial support received for Santiago Grisolía program scholarship (GRISOLIAP/2018/168). A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her RyC contract (RYC-2016-20915).

In contrast to RF produced plasmas, in the case of microwave plasmas the energy from the electromagnetic (EM) field is communicated only to electrons since ions, being a few thousand times much heavier than electrons, cannot respond to the periodic changes in the direction of the E-field of microwaves (typical frequency range 100 MHz-300 GHz) and therefore cannot gain energy in the EM field. The energy of electrons is essentially transferred to heavy particles either through numerous enough collisions during the E-field period (high enough gas pressures) or through electron-cyclotron resonance (pressures below mTorr) sustaining in this way the gas discharge. This had led to introduce the concept of power absorbed per electron qA and power loss on a per electron basis qL [1]. Under steady-state conditions and when the plasma volume (the volume in which plasma particles recombine and, thus, power is lost) is equal to the volume in which power is absorbed from the MW field, we have the power balance qA = qL, which can be shown to be much informative than the usual global power balance. qA is defined as where n is the electron collision frequency for momentum transfer, w, the wave angular frequency, e/me, the electron charge to mass ratio, and , the mean squared value of the EM E-field. The value of qA (absorbed power) is shown to adjust so as to compensate exactly for qL (power losses), which is thus the dominant power parameter; as a result, the intensity of the maintenance E-field sustaining the discharge comes out as an internal parameter, i.e., it is operator-independent, in contrast to what is generally believed whatever the kind of E-field sustained discharges. Other related features are: i) whenever this can be achieved, the smaller the volume in which power is absorbed with respect to the volume in which it is spent, the higher the intensity of the maintenance E-field: this leads to higher atomic (molecular) excitation rates inside than outside the absorption region (such is the case in micro-discharges); ii) an interesting fact as far as understanding RF and MW discharge properties is concerned is that the value of qL decreases with increasing frequency from the RF domain to that of MWs; iii) similarity laws, initially derived with DC discharges, are generalized to include RF and microwave discharges. For example, qA/p as a function of pR (p is gas pressure and R discharge-tube inner radius) replaces advantageously the widely used E/p vs. pR similarity law since qA is more easily measured than E2 and further it avoids considering the latter as an external parameter, etc.; iv) using the power per electron balance, it can be proved that the EM E-field intensity under electron cyclotron resonance (ECR) condition passes through a minimum, not a maximum, contrary to what is generally claimed; v) the E-field intensity under pulsed regime can be maximized under short enough pulse length and long enough off-time in between.

[EN] The importance of microwave assisted thermal processing for the food industry relies on the fact of the procedure being economical and swift along with ensuring high quality product. The sample has been assumed as a porous solid food with meat being the continuous phase and oil or water being the dispersed phase. The resultant matrix of meat-oil or meat-water is considered to be a 2D cylinder being subjected to microwave irradiation in two different interaction schemes i.e. lateral and radial. The thermal effect of the interaction is calculated by applying Galerkin finite element analysis to simultaneously solve the Maxwell's equation and heat transfer equation using pertinent boundary conditions. The preliminary solution gives the value of average power absorption at different sample sizes which exhibit few peak points depicting enhanced heating and power absorption. Further study consists of analyzing the spatial distribution of power and temperature along with the transient temperature difference and mean temperature evolution within the sample corresponding to designated observation points. The heating strategy exhibiting high heating rate and low thermal nonuniformity is recommended as the preferred optimum condition. For both meat-oil and meatwater porous solids, the radial irradiation is recommended as the optimal heating strategy corresponding to smaller sample diameter (OP: 1) whereas lateral irradiation is recommended for larger sample diameter (OP: 2). Overall the present work serves as a guide for enhanced microwave assisted heating of porous food samples in the shape of 2D cylinders.

It has been realized that various chemical reactions are accelerated under irradiation of MW. Such Microwave chemistry is known as time-saving, clear and eco-friendly. MW ovens are world-wide domestic tools for cooking which can serve meals quickly. Regardless of its convenience, few understand the essential mechanism of MW ovens. For better understanding of MW chemistry, authors think it is necessary for to introduce elementary knowledge by holding a 1-day program of experiments by using microwave (MW) ovens.“Science with microwave oven”, 1-day program which we developed and named “Hirameki Tokimeki Science” was supported by Japan Society for the promotion of Science, has been performed over four years.More than 100 students of elementary and junior-high school have joined the program.Here we report the program, response from students.Program of experiments: “1: Dyeing handkerchief with onion peer (*1), 2: Cooking of pizza quickly yeast-leavened, 3: Preparation of shining slime with fluorescein dye synthesized in nonsolvent reaction. 4. Plasma in MW oven (*2), etc.”Students realized how MW accelerated chemical reactions and that dyeing under MW was faster and more fixed compared with the conventional methods. Besides, they could enjoy lunch with pizza and dealing with the slime, both they made. They had a good time with a bit of scientific knowledge. Through 1-day program, we can make science more familiar with students, and it will cause young students to become more interested in science, lead them to future research workers.In addition to the “Hirameki Tokimeki (Inspiration and Spark) Program, we have doneVolunteer activities at Ishinomaki, one of the most damaged cities at the Higashi Nihon Big Earthquake, in 2011.“Science with microwave oven” program surely gives students mysterious interest anddream for Science. That is “Inspire and Spark!” (*1) (*2)

[EN] Over the last ten years the concept of self healing in asphalt mixtures for roads pavements has been reaching great importance due to the fact that this capability allows a material to recuperate original properties after failure. This new generation of asphalt paving materials would allow road agencies to save no renewable resources as aggregates and bitumen, making the road investments more efficient. By the moment, there are two mechanisms to promote self healing in asphalt pavement: the incorporation in the asphalt mixtures of capsules containing a rejuvenating agent, or the heating of the pavement, especially the surface layer, to melt the asphalt binder, that gets liquid and refills the cracks in the material, recuperating a part of its initial structural parameters. Probably the most promising method for the in situ heating of the pavements is the radiation by microwaves. Unfortunately, asphalt mixture components (aggregates and binder) are low sensitive to microwave energy. This is why it may be advantageous to incorporate in the mixture additives to improve the sensibility to the radiation with microwaves. In this investigation two additives were studied: graphene and EAF slag coming from the steel industry. These additives were incorporated at several contents and the efficiency of the heating process was evaluated by the ratio kwh/kg/ºC in order to optimize the content of the additive in the asphalt mixture. Additionally, an evaluation of the electrical conductivity of the asphalt mixture at different contents of additives was carried out to study the possible relation between the conductivity of the mixture and its sensibility to microwave radiation. As a result of the investigation, it seems that microwave radiation can be a real option to promote in situ self healing of asphalt pavements. References J. Gallego, M.A. del Val, V. Contreras, A. Páez. Use of additives to improve the capacity of bituminous mixtures to be heated by means of microwaves, Materiales de Construcción. Vol. 67, Issue 325, January–March 2017, e110. http://dx.doi.org/10.3989/mc.2017.00416 …, The collaboration for this investigation between the University of Lisbon and the Technical University of Madrid was possible thanks to Grant n. PDI-18-0HXIUI-55-QZMWQL for Investigation Stays of Senior Researchers in Foreign Universities and an additional Grant for PhD students by the Agustín of Betancourt Foundation.

Nanoscale tungsten carbide WC powders are of practical interest for the creation of nanostructured hard alloys with enhanced physical and mechanical characteristics, wear-resistant nanostructured coatings, electrocatalysts in fuel cells, metal melt modifiers [1]. An efficient method for producing tungsten carbide nanopowder is a plasma-chemical synthesis of a multi-component powder nanocomposite system W-C in combination with its subsequent heat treatment [2]. Experimental studies have shown the possibility of producing tungsten carbide WC nanopowder by this method. But the transformation of the nanocomposite in the target product is accompanied by an increase in the size of nanoparticles. We assume that this growth is associated with prolonged heating (several hours) in an electric furnace at a temperature of about 1000 ° C. This time is necessary for the complete transformation of the nanocomposite into the target product. The aim of the work was an experimental study of the formation of tungsten carbide nanopowder WC when processing a multi-component powder nanocomposite system W-C in an electromagnetic field with a frequency of 24 GHz. A multipurpose gyrotron system with a nominal power of 7 kW with at a frequency of 24 GHz was used for the experiments. The microwave application system described in [3]. The powders were treated in an argon flow. The experiments were carried varying exposure time and microwave power. The samples of nanopowders obtained in the experiments were analyzed using the following methods: XRD, TEM, SEM, BET, LDA, CEA. It was established that microwave radiation with a frequency of 24 GHz allows heating samples of powders to a temperature of 1100-1200 C almost immediately (after 1-2 s) after switching on. The tungsten carbide WC is formed in a few minutes under the exposure to microwave radiation of the original W-C nanocomposite system. There is only a slight increase in the average particle size from 20 to 30 nm. The investigations showed that the synthesis of tungsten carbide WC under the microwave heating as compared to conventional heating in an electric furnace may be carried out for significantly less time while maintaining the particles in the nanometer range.The work was carried out within the framework of the Program #14 "Physical chemistry of adsorption phenomena and actinide nanoparticles" of the Presidium of the Russian Academy of Sciences.References Z. Zak Fang, Xu Wang, et al. Int. Journal of Refractory Metals & Hard Materials, 2009, 27, 288–299.Samokhin A., Alekseev N., et al. Plasma Chem. Plasma Proc., 2013, 33, 605–616.Samokhin A., Alekseev N., et al. J. Nanotechnol. Eng. Med., 2015, 6, 011008.

[EN] Concentration of microwave E-field between material particles is considered to cause the enhancement of sintering1 and chemical reaction under microwave irradiation. For example, it is usually required 1700 °C to synthesize AlN by carbothermal reduction method using Al2O3 as a starting material, but microwave processing can proceed this process at 1200 °C2. To understand this phenomenon, it is necessary to understand an occurrence behavior of plasma and a chemical reaction related to radical species generated by a local E-field concentration. In addition, in material synthesis using a raw material powder of several mm, it is suggested that a selective heating in the powder scale occurs. However, to discuss this selective heating behavior on this scale, it is necessary to realize a quantitative temperature measurement system with independent of the emissivity of the material and several mm spatial resolution. In this study, we conducted an in-situ spectroscopy and two-color thermography to verify these non-equilibrium effects during microwave irradiation. For example, in the iron making process, it was investigated that CN plasma was generated, and this CN radical contributed to the reduction reaction (Fig. 1(a))3. In addition, the developed two-dimensional two-color thermography system with a high resolution of 8.8 mm/pixel was enable to discuss local temperature gradients quantitatively (Fig. 1(b))., This work was supported by a JSPS Grant-in-Aid for Scientific Research (S) No. JP17H06156.

The reduction of CO 2 concentration in our atmosphere consists in a big challenge for researchers, who are trying to explore novel technologies in order to transform CO 2 into high added-value products. CO 2 conversion into methane using microwave plasma (MWP) manifests as a very promising solution due to the ease of transport of methane and its storage. Microwave plasma represents a source of high-energy electrons, active ions and radicals that enhance or enable chemical reaction. It can be supplied by electricity generated from renewable resources. Then, MWP does not require any electrode to be generated and thus, the cost of those electrodes and of maintenance is reduced compared to glow discharge or DBD plasmas. MWP also can be generated over wide range of pressure (between 10 mbar-1bar). In addition, in the case of MWP, more electrons and active species are produced in comparison with other type of plasma[1–4]. MWP is a very suitable medium for this chemical reaction and leads to an efficient dissociation of CO 2 . The catalytic reduction of CO 2 with H 2 using MWP has been investigated in this work and the synergetic effects between the plasma and several catalysts were studied. First, the reaction was carried out without any catalysts and the effect of CO 2 /H 2 ratio, total flow rate and input energy were evaluated. Then, a microwave generated plasma process was coupled with several Nickel catalysts that we prepared and characterized [5] in order to lead the reaction into methane formation. Multiple configurations were studied by changing the position of the catalyst bed. Obtained results were compared with conventional catalytic tests made with the same catalysts. It was found that the conversion of CO 2 and energy efficiency increased using plasma assisted catalytic methanation of CO 2 in comparison with conventional process. Operating conditions were studied in order to optimize methane production and energy efficiency of Plasma-catalytic process. References Qin, Y., G. Niu, X. Wang, D. Luo, Y. Duan, J. CO 2 Util., 2018, 28, 283–291. De la Fuente, J.F., S.H. Moreno, A.I. Stankiewicz, G.D. Stefanidis, Int J Hydrogen Energy, 2016, 41, 21067–21077. Ashford, B., X. Tu, Curr Opin Green Sustain Chem, 2017, 3, 45–49. Vesel, A., M. Mozetic, A. Drenik, M. Balat-Pichelin, Chem Phys., 2011, 382, 127–131. Alrafei, B., I. Polaert, A. Ledoux, F. Azzolina-Jury, Catal. Today, Available online 12 March 2019, In Press, Accepted Manuscript. https://doi.org/10.1016/j.cattod.2019.03.026

The permittivity of a material can be obtained from resonant measurements in an accurate way [1] at a single frequency (where the resonance occurs). In figure (1) results for the Debye Model at 298K temperature can be seen in the 10MHz-50GHz frequency band for distilled water. In this work we explore the possibilities of obtaining the permittivity of materials from resonant measurements in a certain frequency bandwidth around the resonance frequency. With this purpose a Debye model jointly with a certain conductivity useful for polar liquids [1], are studied to evaluate this possibility jointly with inverse techniques.

[EN] Linear even-carbon-number alpha-olefins (LAO) with four or more carbon atoms are important compounds of high demand in chemical industry as precursors of a wide range of value-added chemicals [1]. LAO are used as co-monomers for polyethylene production, for the production of alcohols (mainly in detergents and plasticizers) and for synthesis of polyalphaolefins (used in synthetic lubricants). Alpha-olefins (C4, C6, C8 and C10) are mainly used to produce poly(vinyl chloride) plasticizers, high-density and linear low-density polyethylene to impart the stress-crack resistance. C10–C14 alpha-olefins can be used to synthesize linear alkylbenzene sulfonates (synthetic detergents). A conventional route to produce alpha-olefins is oligomerization of ethylene. The process provides production of high quality alpha-olefins but is very costly. If not oligomerization, LAO can be produced by thermal cracking of waxy paraffins but the product is not pure and contains numerous internal olefins, dienes and paraffin impurities. The process is conducted in the vapor phase at relatively low cracking temperatures and needs rapid quenching to prevent side reactions such as isomerization or cyclization. In our previous work [2], we showed that the selectivity to alpha-olefins can be increased considerably via catalytic cracking of n-alkanes under selective MW heating of catalysts. In the present work, the general regularities of MW cracking of n-alkanes are presented. Porous ceramic matrix Al2O3/Al composites (ceramometals) and various carbon materials (CM) having high dielectric losses were studied as supports of the catalysts. MW cracking was conducted with n-C16H34 and n-C28H58. The influence particle size and surface morphology of ceramometals and CM on the structural and group composition of the products was studied. It was established that LAO (C2-C23) and n-alkanes (C2-C26) were the main cracking products under selective MW heating of the used supports. The quantitative analysis of the products demonstrated that the liquid-phase process is more selective to alpha-olefins at the MW catalytic cracking than at the convectional thermal cracking. Silica modification of the surface of CM was shown to suppress spark discharge (usually observed at MW heating of CM); hence, the thermal cleavage of C-C bonds on the CM surface but not in the plasma discharge contributes the most to the formation of radicals. It was shown that the selectivity to liquid alpha-olefin could be more than 85 % under MW heating of cermets in region of the E - field node and decrease considerably in the region of H - field node., The research was supported by RSF (project No. 17-73-30032).

For drying building structures [1], dielectric heating using RF energy (in this case 13.56 MHz) is an efficient and fast alternative to conventional heating methods based on heat transfer from the surface to the interior of the masonry. Another innovative application of volumetric RF heating is the chemical-free pest control in wood-based materials [2]. For such applications where the RF systems often are not completely shielded, the propagation or coupling of the electromagnetic wave into wires that are placed inside the field cannot be neglected which represents a certain risk. Depending on the different electromagnetic coupling mechanisms, several interference signals can be generated. In order to protect electrical equipment in the surrounding, these interferences have to be significantly reduced by electrical filters. For this purpose, initially a cost-effective (at least in comparison to standard RF measurement systems) and more robust measuring concept was developed. With the help of this system, the common mode (I_CM) interference could be identified as the dominant part and the differential mode (I_DM) interference as a minor disturbance. Based on the experimental evaluation, a cost-effective filter for the respective disturbance was constructed and successfully tested.

[EN] The objectives fixed by world’s governments concerning energy transition have aroused interest on lignocellulosic biomass utilization for bioenergy and green chemistry applications. However, due to their resistant structure, deconstructive pretreatments are necessary to render possible biological conversions of these lignocellulosic residues. Microwave (MW) treatment has been reported as efficient in many biotechnology fields; biomass pretreatment for biorefinery purposes is another possible application. This work presents the effects of MW pretreatment on underexploited natural agri-food biomass of economic interest: wheat bran, miscanthus stalks and corn stalks. Various parameters were studied including solvent, power density, treatment duration, pressure. Effects were evaluated by a complete biomass characterization before and after treatment, with main focus on phenolic acids release. In the tested conditions and when compared to the high NaOH consumption reference extraction method for phenolic acids, the atmospheric pressure (open vessel) microwave treatment did not allow attaining high acid yields (Fig.1). The most important parameters for improving treatment efficiency were power density and solvent. In order to increase yields, microwave treatments under pressure were carried out to reach higher temperatures while taking care as to not exceed the acid denaturation temperature (150°C) and to avoid the formation of inhibitors. Phenolic acids yields and biomass composition are currently being processed and will be discussed., Authors would like to thank Nicolas Holfeltz, NH Verre France for his help in designing the microwave reactor. The authors also thank Yannick Sire from INRA Pech Rouge for phenolic acids analysis.

[EN] Microwave-material interactions and electromagnetic propagation phenomena are important to optimize the microwave heating process of food samples. In this study, a 3D numerical modelling of a TE10 rectangular waveguide including microwave antenna and impedance matching elements is proposed. The microwave applicator is aimed to process both solid and liquid food samples. The model illustrates the standing wave patterns and microwave absorbed power within the cavity by taking into account the influence of the screw tuner, quartz windows, shorting plunger, and additional dielectric support plates. The results reveal the importance to consider the real cavity design and the precise dielectric characterization to predict accurate temperature profiles within the food product during the microwave heating. Such a model can be now be used to optimize the food sample geometry to achieve minimum reflected power and better heating uniformity., The authors are grateful to the National Council for Scientific and Technological Development (CNPq, Brazil) for Clarissa Detomi Albuquerque’s PhD scholarship and financial support (process number 232767/2014-9). The authors would also like to thank O. Tantot (XLIM, UMR CNRS 7252) for the dielectric characterization of materials.

[EN] Algae are very effective in capturing the sun's energy, carbon dioxide from the atmosphere, and nutrients to turn them into useful substances (carbohydrates, oils, proteins, etc.). Besides the main metabolites, there are also secondary metabolites, such as carotenoids (astaxanthin, β-carotene, lutein, lycopene, and canthaxanthin [1]). Both major and compounds existing in small amounts in algae are useful. Oils and carbohydrates could provide biofuels, proteins can get products with nutritional value and from carotenoids can be prepared food supplements. Obtaining biofuel from algae has not yet proved to be economically viable [2, 3]. A much higher interest might be getting food supplements from algae. To increase their value as ingredients for food supplements, algal oils should have a higher degree of unsaturation (rich in omega 3) and an increased carotenoid content to be an important additional benefit in over all processing of algae. There are studies that refer to the influence of environmental factors on algae composition [2], but the microwave influence on algae growth, especially algal metabolites composition change is very poor studied. In this paper, besides the experiments for the activation of algal growth in discontinuous reactors [4] additional work was conducted in a continuous photobioreactor. The goal was checking not only the growth of microalgae but also their content in polyunsaturated oil and in carotenoids. By microwave-controlled irradiation of the nutrient and algae flux, which is recirculated through the photobioreactor and through a glass reactor located in a TE-type monomod cavity, the lipid content of the algae increased, but only, the modification of the lipid fraction content was significantly increased in the concentration of polyunsaturated acids with 16 and 18 carbon atoms. As far as carotenoids are concerned, the algae nannochloris has a higher carotenoid content over many known vegetables holding carotene or lycopene (carrots or tomatoes). Besides oil increasing microwave treatment produced a significant increase in carotenoid content of algae. They can be extracted together with omega-3-rich algal oil and are the basis of very valuable dietary supplements., The authors acknowledge the financial support received from the Competitiveness Operational Programme 2014-2020, Action 1.1.4: Attracting high-level personnel from abroad in order to enhance the RD capacity, project: P_37_471, „Ultrasonic/Microwave Nonconventional Techniques as new tools for nonchemical and chemical processes”, financed by contract: 47/05.09.2016

Ryszard Parosa, Andrzej Brożyński, Piotr Grześkowiak, Krzysztof Kowalczyk, Marek Natoński, Piotr Ziętek and Janusz Żytkiewicz PROMIS-TECH Poland Keywords: microwave treatment, low pressure heating, microwave drying Uniquely favourable characteristics of biological product can be obtained through the use of the microwave method in vacuum heating process. Microwave-vacuum drying is superior to other methods in terms of dried products' structure, flavour, colour and biological active compounds contents. But applications of such a methods seems to be much wider: drying of fruits and vegetables for consumption, drying of herbs for extraction of valuable biological compounds, for modification of seed structure (sunflowers seeds, pumpkin seeds), for pasteurisation etc. A universal system was designed for testing such processes in laboratory scale and several industrial scale system have been developed. Process of thermal treatment can be carried out with plastic drum installed inside of multi-mode microwave cavity and cavity which is connected by microwave line with reflectometer and circulator - to microwave generator. In laboratory unit generator 2.45 GHz with controlled power (from 50W to 800W) was applied. System was equipped with vacuum pump with pressure control and is controlled by computer. Most important technical parameters, like: microwave power, time of treatment, pressure inside of drum, temperature of steam – are controlled and recorded. Laboratory scale unit is shown below. Basing on laboratory scale test several technologies in industrial scale was developed. Industrial scale unit equipped with 8 generators of 3 kW (2.45 GHz) was constructed and for last 8 years has been successfully used for “production” of crispy chips which are now popular in Polish marked. Exemplary industrial scale installation is shown in photo below. Multi – drum microwave drier. Two cavity microwave industrial drier Another system for modification od seed is now constructed – ordered by big industrial producer of batons and sweet snacks. Process will be carried our inside of dielectric drum in low pressure and reactor will be equipped with 8 generators of 3 kW (2.45 GHz). Treatment time will be reduced to 3-4 minutes and next material (seeds) will be cooled down. Last project which now realized is connected with drying of wood flour applied in composite material production. System will work continuously with two airlocks and with dielectric drum and will be connected with 4 microwave generators (3 kW, 2.45 GHz). In next step planed installation will be equipped with microwave high power generator ca. 60 kW with frequency 915 MHz.

Supersonic gas flows activated by microwave discharge are commonly used to obtain thrust for spacecraft. When using a mixture of hydrocarbons and hydrogen as a working gas, the proposed method generates high-speed plasma streams with a high concentration of radicals, allowing it to be used for efficient deposition of diamond films . To optimize diamond synthesis processes, it is necessary to study the effect of various system parameters (geometrical dimensions, radiation power, pressure and others). This abstract presents a numerical simulation of the formation of high-speed gas flow activated by a microwave discharge. The conjugate problem of hydrodynamics and plasma dynamics was solved in the continuum approximation, taking into account impact ionization and thermal dissociation, due to microwave heating of the gas. The simulations were carried out in an axisymmetric formulation. The region of plasma flow formation was a cylindrical chamber (radius 5 cm, height 7 cm). At this stage, hydrogen was chosen as the working gas. The flow outlet is a hole at the center of the lower boundary with fixed pressure of 2 torr. The gas entered the domain at a constant flow rate of 20 l/min through the openings in side wall along its normal. Such flow rate sustained the mean pressure in the chamber at the level 200 torr. Microwave radiation was injected by a coaxial port located above the plasma chamber. The geometrical dimensions of the resonant chamber were selected in order to form the maximum of the electric field intensity over the gas outflow region (total deposited power 1000W). The distributions of velocity, temperature, and concentrations of all components of the hydrogen plasma were estimated. Optimal characteristics of the system were found to reach a high mole fraction of atomic hydrogen, necessary diamond deposition.

[EN] Nowadays, strengthening and refurbishing of existing structures on urban areas has gained interest in order to reduce costs by avoiding both the use of construction raw materials and the disposal of construction and demolition waste on landfill. Usually, existing structures need to be locally demolished in order to replace either the existing corroded reinforcement or strengthen the existing structure. Among all the existing demolition methods, microwave and induction heating have been proven as a good alternative to generate a local damage with little noise and dust production, which is a desirable feature when structures are in urban areas. However, there is a lack of information about the behaviour of both damaging methods when steel fibre-reinforced concretes are involved. This paper studies the influence of the steel fibre addition on the damaging capacity of both microwave and induction heating demolition methods. For that purpose, mortars containing two different steel fibres (steel fibres used for concrete reinforcement and brass covered steel needles used for mortar reinforcement) were added in three different proportions (0%, 0.5% and 1% by unit volume of mortar) and exposed to up to 10 min of either microwave heating (0.003-0.03 W/mm3, 2.45 GHz) or induction heating (0.016-0.023 W/mm3, 18 kHz). With the aim of evaluating the damage caused by the heating methods, test specimens were visually checked, and mechanical properties were determined via flexural and compressive strength tests. According to the results, mortars exposed to either microwave or induction heating suffered a sudden, violent disintegration without noticing any previous damage on the mortar specimens. Results proved that pressure increment on water-saturated pores caused the failure no matter the fibre type used as a reinforcement. However, for microwave heating, the reflection of microwaves on the fibres tended to concentrate the heating effect on the specimen surface, resulting in higher surface temperatures, but lower damaging potential of the demolition method. Furthermore, similar failure mechanism was observed on oven-dried mortars exposed to microwave heating. Nevertheless, oven dried mortars exposed to induction heating suffered a highly variable, silent and controlled damage, presenting a highly varying quantity of fracture planes that decreased its flexural and compressive strengths by up to 38% and 31%, respectively., This work has been partly financed within the European Horizon 2020 Joint Technology Initiative Shift2Rail through contract no.730841 (IN2TRACK) and no. 826255 (IN2TRACK2). This work was also co-financed with the projects Elkartek 2018 ref. KK2018/00073 (GOLIAT) and Elkartek 2019 ref. KK-2019/00023 (GOLIAT2). The authors also wish to thank the Basque Government for financial assistance through IT919-16.

[EN] This paper describes the application of dielectric resonators (DR) to the measurements of surface impedance of microwave susceptors. We demonstrate that the single-post (SiPDR) configuration is applicable to plain susceptors before use, while the split-post (SPDR) configuration - to crazed susceptors after use. Attention is given to the full characterisation of active packaging, that is, the influence of paper support on the overall electric losses is also investigated. The measurements can be preformed with various form-factor VNAs, including benchtop VNAs and hand-held FieldFox, though the most economical setup is constructed with a dedicated computer-controlled microwave signal oscillator system available under the name of Q-Meter. Finally, an extension of dielectric resonator measurements to surface imaging is presented, achieved by incorporating the resonator in a 2D automatic scanner., This project has received funding from the European Union’s Horizon 2020 research and innovation programme (H2020-NMBP-07-2017) under grant agreement MMAMA No. 761036.

[EN] The literature related to microwave and ultrasound working simultaneously is rather infrequent. The reason is obvious: microwave irradiation is of electromagnetic origin while ultrasound is a mechanical vibration energy. Moreover, the optimal settings for ultrasound propagation throughout a reaction media do not coincide with the conditions required for application of microwaves. Therefore, the challenge is to find a way to best combination of these sources of energy into one apparatus to allow researchers to take advantage of the features of each technology. The oldest paper describing such a combination – microwave and ultrasound is having just 20 years [1] and describe an apparatus which uses a probe system delivering ultrasound through decalin to a vessel holding the reagents dipped in the MW cavity (fig. 1a). Another possibility using a normal MW oven is described by Peng [2] (fig.1b), but this setup is having radiation leakage problems and needs a proper protection. Ragaini et all proposed another type of setup [3] (fig. 1c), not easy to reproduce, but describing calibration and parameters which show an additive increase of thermal energy delivered when MW and US works simultaneous. Insert here uploaded pictures Figure 1. Some MW-US simultaneous setups Few years ago, Cravotto and Cintas [4], disccussed for the first time the potential of using MW and US in sequential or tandem setups. Their paper discuss all possible setups for using mostly glass probe for devlivery of ultrasonic energy or classical setup (fig. 1a). Slowly the concept gain popularity and the paper of Lionelly and Mason [5] prompts to the potential industrial applications, naming the combination of microwave with ultrasound a hybrid technology. The challenge in using this “hybrid technology” is to find a vesatile and reproducible apparatus able to deliver both microwave and ultrasound at a full controlable parameters. In our laboratory we have and use the setup like in the fig. 1a, but the ultrasonic energy is delivered by an ultrasonic cleaning device attached to microwave device (SAIREM Miniflow 200SS). To achieve the above mentioned outcome launched a project to build a device which could work with MW and US in tandem (as Cravotto mentioned [4]) using an US device able to deliver more than a single ultrasonic frequency at a full controlled power. It is our believe that such a device could significantly contribute to MW-US tandem equipment development. Based on our expertise and potential proposed interaction of US with reagents [6] we will investigate the influence (if any) of ultrasound upon MW field. In this paper we will present the earlier results of “Tandem Microwave Ultrasound” energy influence on chemical reagents. References 1. Lagha, A., et al., Analusis, 1999. 27(5): p. 452-457. 2. Peng, Y. and G. Song, Green Chemistry, 2001. 3(6): p. 302-304. 3. Ragaini, V., et al., Ultrasonics Sonochemistry, 2012. 19(4): p. 872-876. 4. Cravotto, G. and P. Cintas, Chemistry - A European Journal, 2007. 13(7): p. 1902-1909. 5. Leonelli, C. and T.J. Mason, Chemical Engineering and Processing: Process Intensification, 2010. 49(9): p. 885-900. 6. Vinatoru, M. and T.J. Mason, Ultrasonics Sonochemistry, 2018., The authors acknowledge the financial support received from the Competitiveness Operational Programme 2014-2020, Action 1.1.4: Attracting high-level personnel from abroad in order to enhance the RD capacity, project: P_37_471, „Ultrasonic/Microwave Nonconventional Techniques as new tools for nonchemical and chemical processes”, financed by contract: 47/05.09.2016