Microwave Sintering of Lunar Soil: Properties, Theory, and Practice

The unique properties of lunar regolith make for the extreme coupling of the soil to microwave radiation. Space weathering of lunar regolith has produced myriads of nanophase-sized Fe0 grains set within silicate glass, especially on the surfaces of grains, but also within the abundant agglutinitic glass of the soil. It is possible to melt lunar soil (i.e., 1,200–1,500°C) in minutes in a normal kitchen-type 2.45?GHz microwave, almost as fast as your tea-water is heated. No lunar simulants exist to study these microwave effects; in fact, previous studies of the effects of microwave radiation on lunar simulants, MLS-1 and JSC-1, have been misleading. Using real Apollo 17 soil has demonstrated the uniqueness of the interaction of microwave radiation with the soil. The applications that can be made of the microwave treatment of lunar soil for in situ resource utilization on the Moon are unlimited.     

复杂目标RCS预估及其高分辨率成像

复杂目标雷达散射截面（ＲＣＳ）的高频预估方法、ＲＣＳ高分辨率成像原理及其测量系统的简述．对××目标分别进行了实时成像和预估计算机模拟；所得到的图像正确反映了目标ＲＣＳ的空间分布情况，预估模拟结果与实测结果吻合良好．     

Microwaves for microscopy

Sample preparation for microscopy is based on physical and chemical processes. These processes can be influenced by microwave irradiation. The prerequisite for the development of good microwave procedures is knowledge of histochemistry combined with understanding of the physics of microwave irradiation. Examples of superior results of fixation, processing, and (immuno) staining performed in the microwave oven are presented, both for light- and electron microscopy.     

Microwave power absorption profile of detergent surfactant agglomerates during microwave heating

The microwave energy absorption behavior of the linear alkylbenzene sulfonate (LAS) surfactant detergent agglomerates was studied while considering changes in the physical properties of the samples. Microwave heating was used to change the internal structure of the agglomerates to make a reduced density (fluffy) product. The absorption of energy within LAS samples indicated fluctuating trends as microwave heating progressed. This was associated with the dielectric properties of the material which are strongly dependent upon the nature (“free” or “bound”) and quantity of water present in them at any instant which changes during heating. Therefore, complete profiles of the energy absorbed by the samples have been recorded to determine their actual power absorption behavior/total energy consumption over time. The bulk density of the agglomerates decreased significantly when exposed to microwave fields. Hot air drying can be combined with microwave heating to reduce the total heating time. It has been observed that the pre-heating of the samples reduces the total heating time and microwave energy requirement. This is due to the temperature-dependent decomposition of hydrates releasing more “free” water.     

Large signal modelling of GaAs/AlGaAs HBT's with separation of the surface recombination current

The effects of surface recombination on an AlGaAs/GaAs HBT have been investigated. Studies of Gummel-plots for devices with different sized base emitter junctions made it possible to separate the surface recombination from the bulk current. An extension of the Gummel–Poon model that includes this surface recombination current is suggested. The large-signal performance was evaluated by two methods, power spectrum characteristics and by design and characterization of a power amplifier. For these two measurement set-ups, measured data was compared with simulations of the model both including and excluding the surface recombination current. It is clearly seen that without including the surface recombination current, it is impossible to correctly represent the large-signal performance. The model is also verified with DC characteristics and S-parameters.     

Ni-Al-Ti coatings obtained by microwave assisted SHS: Oxidation behaviour in the 750-900 °C range

Microwaves have been used to ignite the Self-propagating High-temperature Synthesis (SHS) of Ni and Al powder mixtures to produce a duplex intermetallic coating on Ti substrates. Due to the high exothermic nature of the reaction, the newly formed NiAl is in the liquid phase and can react with the underlying Ti to form a tough ternary intermediate layer, belonging to the Ti-Ni-Al system, in a one step process. Aim of this work is to assess the high-temperature performances of the Ti-Ni-Al layer, compared to NiAl coating and Ti. Experimental results demonstrate that the ternary layer presents oxidation resistance comparable to NiAl up to 750 °C. In this condition, the thick Ti-Ni-Al layer could replace the functionality of hard and brittle NiAl coatings. At 900 °C, instead, NiAl oxidation resistance results higher, and this can be ascribed to the relatively low Al content in the studied ternary compound, which hinders the formation of a continuous and protective scale.     

Microwave-Enhanced Thermal Desorption of Polyhalogenated Biphenyls from Contaminated Soil

The effect of microwave (MW) field on the rate of thermal desorption of polychlorinated biphenyls (PCBs) from long-term contaminated soil was examined in the laboratory environment. For these purposes a modified MW oven was used, with a uniformly extended MW field and a power consumption of 200–600 W. The weight of the soil samples was 100 g, the sum of concentrations of seven indicative congeners of PCB Nos. 28, 52, 101, 118, 153, 138, and 180 was, on average, 264 mg/kg of dry matter. It was experimentally proven that the efficiencies of PCB desorptions were high, over 99.9%. The maximal desorption temperature of 600°C was reached within 15–17 min. It came to light that the presence of alkaline additives in the soil (such as carbonates and alkaline metal hydroxides) did not have an apparent effect on the desorption of PCBs under those conditions. The results concerning the efficiency of PCB separations are in agreement with our previous findings regarding the efficiency of thermal desorption without using MWs in the pilot (input 35 kg) and industrial (input 15 t) desorption chambers with a stationary layer of the same type of contaminated soil. The main disadvantage of experiments with thermal desorption without the action of MWs was the low rate of heating up the soil. This study was focused to solve the problem of contamination in a complex way; we also studied the effect of MWs on the rate of the deterioration of the separated PCBs in aqueous condensates, the deterioration of PCBs in contaminated waste water containing alkaline agents (soda and lye), and on the catalytic reductive dechlorination of PCBs in the system Pd supported on active coal with sodium formate as the hydrogen donor. Experiments with the MW-enhanced catalytic reductive oxidation show over 98.5% reduction in the concentration of PCBs. An important and new finding is the more than 98% reduction in the concentration of PCBs when the MW field was applied on the contaminated water into which only 2.5% of Na2CO3 was added. Further studies on possible influences of MWs on the reaction kinetic are needed. Meanwhile we attribute the positive MW effects to their thermal properties rather than to their influence on the reaction mechanism.     

Scale Continuous Microwave Dry‐Media Reactor – Part II: Application to Waxy Esters Production

The solvent free esterification reaction between stearic acid and stearyl alcohol has been examined with a montmorillonite clay as catalyst. To aim for industrial application the system has been studied on reaction rate, product purity, catalyst behavior and water removal as function of the process conditions. To avoid an etherification side reaction and to aim for the highest reaction rate, the temperature should be strictly maintained at 170 °C. This is provided on larger scale by the application of microwave heating. Although the examined Brønsted acid clay was found to lose its catalytic activity at very low water activities, a yield of 95 % pure stearyl stearate can be obtained by simply filtering of the clay without solvent extraction or distillation. The “waxy” esterification reaction was investigated with the pilot plant continuous microwave dry‐media reactor (CMDR). The reaction time needed for 95 % yield was reduced by a factor 20–30 in comparison with industrial conventional reactors. This was due to the more homogeneous heat transfer of microwaves, which allows to reach a higher bulk temperature.     

Case study of surface micro-waves in ultra-precision raster fly cutting

In ultra-precision raster fly cutting (UPRFC), very high frequency microwaves in the range of 3.42 MHz–6.36 MHz are found on the machined surface. This study conducted a series of theoretical and experimental investigations to discover the origin of these microwaves and how they might be suppressed. Research results show that: (i) microwaves on the machined surface are caused by the material sliding during the chip formation in UPRFC; (ii) owing to the inconsistent thickness of chips along their length direction, the microwaves accumulate at the surface-exit in each feed length; and (iii) chip thickness and tool wear change the length and distribution of the microwaves. This research provides a deep insight into the formation of microwaves along with suggestion on how to suppress them.     

The effect of microwave treatment on the immunoreactivity of gliadin and wheat flour

Commercial gliadins and wheat flour were exposed to microwaves at power distribution of 70, 200, and 500 W for different time periods to achieve a level of applied energy doses up to 150 kJ. Ethanolic extracts (40 vol.% ethanol/water) of microwave treated samples were analyzed by ELISA with the use of either monoclonal antibodies against -gliadin or polyclonal anti-gliadin antibodies and by electrophoresis followed by immunoblotting. A significant increase in reactivity, almost 210% over the untreated control sample, was observed for gliadins exposed to the energy dose of 40 kJ. Gliadins treated with higher energy doses showed a drop in an immune response independent of monoclonal or polyclonal antibodies used in ELISA. Gliadin fractions extracted from wheat flour treated with microwaves demonstrated similar immunoreactivity changes vs applied energy, although the maximum of reactivity appeared at 30 kJ. The increase in immune response of microwave irradiated gliadins was also confirmed by immunoblotting assay with the use of sera of patients susceptible to wheat flour allergy. Reversed phase HPLC elution profiles of treated gliadins showed that the content of all gliadin fractions in microwave treated samples decreased with the increase of the dose of applied energy.