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Efficient reduction of graphene oxide to obtain high-quality graphene nanosheets is desirable for energy storage, catalysis, electronics and environmental remediation. In this brief review, we mainly focus on the microwave-assisted production of reduced graphene oxide in three categories: (1) microwave-assisted chemical reduction of graphene oxide; (2) microwave-assisted thermal reduction of graphene oxide; (3) microwave-assisted simultaneous thermal exfoliation & thermal reduction of graphite oxide. We also summarize common techniques for characterizing reduction efficiency and quality of as-obtained rGO.

The ternary transitional metal oxide NiCo 2 O 4 is a promising anode material for sodium ion batteries due to its high theoretical capacity and superior electrical conductivity. However, its sodium storage capability is severely limited by the sluggish sodiation/desodiation reaction kinetics. Herein, NiCo 2 O 4 double-shelled hollow spheres were synthesized via a microwave-assisted, fast solvothermal synthetic procedure in a mixture of isopropanol and glycerol, followed by annealing. Isopropanol played a vital role in the precipitation of nickel and cobalt, and the shrinkage of the glycerol quasi-emulsion under heat treatment was responsible for the formation of the double-shelled nanostructure. The as-synthesized product was tested as an anode material in a sodium ion battery, was found to exhibit a high reversible specific capacity of 511 mAh g -1 at 100 mA g -1 , and deliver high capacity retention after 100 cycles.

Microwaves have been widely used in the treatment of different materials. However, the existing adjustable power thermostatic reactors cannot be used to analyze materials characteristics under microwave effects. In this paper, a microwave thermostatic chemical reactor for processing liquid materials is proposed, by controlling the velocity of coolant based on PLC (programmable logic controller) in different liquid under different constant electric field intensity. A nonpolar coolant (Polydimethylsiloxane), which is completely microwave transparent, is employed to cool the liquid materials. Experiments are performed to measure the liquid temperature using optical fibers, the results show that the precision of temperature control is at the range of ±0.5 °C. Compared with the adjustable power thermostatic control system, the effect of electric field changes on material properties are avoided and it also can be used to detect the properties of liquid materials and special microwave effects.

Objectives: To improve its phosphate accumulating abilities for phosphate recycling from wastewater, a magnetotactic bacterium, Magnetospirillum gryphiswaldense, was genetically modified to over-express polyphosphate kinase., Results: Polyphosphate kinase was over-expressed in the bacterium. The recombinant strain accumulated ninefold more polyphosphate from synthetic wastewater compared to original wild type. The magnetic property of the recombinant M. gryphiswaldense strain was retained., Conclusions: The recombinant M. gryphiswaldense can be used for phosphate removal and recovery in bioremediation.

Dynamic control transmission and polarization properties of electromagnetic (EM) wave propagation is investigated using chemical reconfigurable all-dielectric metasurface. The metasurface is composed of cross-shaped periodical teflon tubes and inner filled chemical systems (i.e., mixtures and chemical reaction) in aqueous solution. By tuning the complex permittivity of chemical systems, the reconfigurable metasurface can be easily achieved. The transmission properties of different incident polarized waves (i.e., linear and circular polarization) were simulated and experimentally measured for static ethanol solution as volume ratio changed. Both results indicated this metasurface can serve as either tunable FSS (Frequency Selective Surface) or tunable linear-to-circular/cross Polarization Converter at required frequency range. Based on the reconfigurable laws obtained from static solutions, we developed a dynamic dielectric system and researched a typical chemical reaction with time-varying permittivity filled in the tubes experimentally. It provides new ways for realizing automatic reconfiguration of metasurface by chemical reaction system with given variation laws of permittivity.

Traditional permittivity measurements in microwave chemistry have some limitations on bandwidth and probe erosion. To resolve these problems, in this note, an apparatus that realizes a real-time wide-band non-contact measurement is proposed. Scattering parameters are obtained from measurements made using the proposed coaxial apparatus. These parameters are used to reconstruct the permittivities of several solutions using artificial neural networks. The maximum deviations in measured permittivity at 2.45 and 5.8 GHz are within 5% of results from the literature, showing the obvious advantages of coaxial apparatus with artificial neural network reconstruction over conventional apparatus.

A number of studies have achieved the consensus that microwave thermal technology can regenerate the granular activated carbon (GAC) more efficiently and energy-conservatively than other technologies. In particular, in the microwave heating industry, permittivity is a crucial parameter. This paper developed two equivalent models to establish the relationship between effective complex permittivity and pore volume of the GAC. It is generally based on Maxwell-Garnett approximation (MGA) theory. With two different assumptions in the model, two quantificational expressions were derived, respectively. Permittivity measurements and Brunauer-Emmett-Teller (BET) testing had been introduced in the experiments. Results confirmed the two expressions, which were extremely similar. Theoretical and experimental graphs were matched. This paper set up a bridge which links effective complex permittivity and pore volume of the GAC. Furthermore, it provides a potential and convenient method for the rapid assisted characterization of the GAC in its adsorption performance.

Microwaves have been widely used in the treatment of materials, such as heating, drying, and sterilization. However, the heating in the commonly used microwave applicators is usually uneven. In this paper, a novel multi-material turntable structure is creatively proposed to improve the temperature uniformity in microwave ovens. Three customized turntables consisting of polyethylene (PE) and alumina, PE and aluminum, and alumina and aluminum are, respectively, utilized in a domestic microwave oven in simulation. During the heating process, the processed material is placed on a fixed Teflon bracket which covers the constantly rotating turntable. Experiments are conducted to measure the surface and point temperatures using an infrared thermal imaging camera and optical fibers. Simulated results are compared qualitatively with the measured ones, which verifies the simulated models. Compared with the turntables consisting of a single material, a 26%-47% increase in temperature uniformity from adapting the multi-material turntable can be observed for the microwave-processed materials.

Microwave processing of materials has been found to deliver enormous advantages over conventional processing methods in terms of mechanical and physical properties of the materials. However, the non-uniform temperature distribution is the key problem of microwave processing, which is related to the structure of the cavity, and the placement and physical parameters of the material. In this paper, a new microwave cavity structure with a sliding short based on phase-shifting heating is creatively proposed to improve the temperature uniformity. An electronic mathematical model based on the Finite Element Method (FEM) is built to predict the temperature distribution. Meanwhile, a new computational approach based on the theory of transformation optics is first provided to solve the problem of the moving boundary in the model simulation. At first, the experiment is carried out to validate the model, and heating results from the experiment show good agreement with the model's prediction. Based on the verified model, materials selected among a wide range of dielectric constants are treated by stationary heating and phase-shifting heating. The coefficient of variation (COV) of the temperature and temperature difference has been compared in detail between stationary heating and phase-shifting heating. A significant improvement in heating uniformity can be seen from the temperature distribution for most of the materials. Furthermore, three other materials are also treated at high temperature and the heating uniformity is also improved. Briefly, the strategy of phase-shifting heating plays a significant role in solve the problem of non-uniform heating in microwave-based material processing. A 25%-58% increase in uniformity from adapting the phase-shifting method can be observed for the microwave-processed materials.

The aim of this work is to investigate the dielectric polarization in polar-molecule reactions in the liquid phase theoretically. On the basis of the modified Smoluchowski equation, the analytic expression of the polarization is derived. The result shows that the expression of the polarization in polar-molecule reactions is quite different from the one in the Debye model. For general reactions, two vectors, the rotational diffusion vector and the component concentration vector, are proposed to describe the polarization. For fast reactions, the conception of relative permittivity will be nonexistent due to the effect of the component concentration vector on the frequency of the applied field, and the dielectric behavior may only be analyzed in the time domain. On the contrary, for slow reactions, the relative permittivity will be concentration-dependent.

The aim of this communication is firstly to describe the effective permittivity of the biodiesel reaction for multiphysics calculation of microwave heating. An innovatively method was proposed to get the effective permittivity of the biodiesel reaction solution through one measurement, which can be directly applied for the thermal analysis of microwave heating on biodiesel reaction based on the multiphysics calculation. The effective permittivity of biodiesel reaction at any temperature and concentration obtained in this paper. The maximum relative error of real part is 4.10%, and 5.65% for imaginary part. The calculated results also show good agreement with the measured results at constant temperature., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

Nonequilibrium molecular dynamics (NMD) simulations of the N, N-dimethylformamide (DMF) aqueous solution have been performed in the canonical ensemble (NVT) in both the absence and presence of external electromagnetic (E/M) field, using the SPC/E model for water and the optimized potentials for liquid simulations-all atom (OPLS-AA) model for DMF. The electromagnetic wave propagates in the z-axis direction with a frequency of 10 GHz, and the intensity of the electromagnetic field in the range 0 to 3 x 10(9) V/m is assumed in the simulation. The results indicate that as the intensity of the electromagnetic field increased, the dipole alignment of the DMF aqueous solution molecules became more pronounced and the molecular polarizability gradually increased. In addition, the hydration number and the static dielectric constant of DMF aqueous solutions decreased as the intensity of the electromagnetic field increased.

It is the intent of this study to estimate the progression or regression of edema at the bedside continuously. Based on the theoretic model, the Adaptive Genetic Algorithm (AGA) has been applied in the calculation of conductivity reconstruction. Dynamic crossover and mutation operators which are based on Haiming Distance are brought forward in this paper to maintain generation's diversity. Then, both AGA and Standard GA (SGA) have been applied in the conductivity reconstruction of edema in human brain. It is shown that AGA not only has attained a higher degree of efficiency but also has enhanced the capability to converge to the best answer.

A wide-band patch probe excited by coaxial line, which is useful for noninvasive measurement of superficial tissues at high frequencies, is presented in this paper. Optimization of the probe is performed by genetic algorithm (GA) combined with Finite Difference Time Domain (FDTD). Then the optimized round patch probe is used to measure reflection coefficient for 1-7 GHz. The measured results show some interesting phenomena, which are very useful for reconstruction of electric properties of superficial tissues.

Microwave imaging for dielectric objects was considered in this paper. Applying Bayesian approach to represent prior information about permittivity distribution of observed object by prior probability density and combine measurements information of scattering field, we obtained posterior probability density that included synthetic information about the observed object. And then, Gibbs sampler, one of Markov Chain Monte Carlo method, was used to sample the posterior probability density. The sample mean was regarded as an evaluation of the permittivity distribution. The results of simulation imaging with "blocky" objects showed that this set of methods made good use of information and had the advantages of feasibility and very strong anti-noise ability. In addition,it is capable of describing (definite or indefinite) prior information in a convenient and controllable way, as well as capable of giving the "complete" solution, i.e., the occurrence probability of every permittivity distribution.

It is the intent of this paper to locate the activation point in Transcranial Magnetic Stimulation (TMS) efficiently. The schemes of coil array in torus shape is presented to get the electromagnetic field distribution with ideal focusing capability. Then an improved adaptive genetic algorithm (AGA) is applied to the optimization of both value and phase of the current infused in each coil. Based on the calculated results of the optimized current configurations, ideal focusing capability is drawn as contour lines and 3-D mesh charts of magnitude of both magnetic and electric field within the calculation area. It is shown that the coil array has good capability to establish focused shape of electromagnetic distribution. In addition, it is also demonstrated that the coil array has the capability to focus on two or more targets simultaneously.

This paper presents a coupling method of the finite element method and the boundary element method to compute the transmembrane potential (TMP) of an erythrocyte in a low-frequency electric field. We compute an in vitro erythrocyte's TMP induced by external electric fields by this hybrid method. It takes advantage of the homogeneous characteristics from both intracellular region and extracellular region. Moreover, we may use a fine three-dimensional (3-D) mesh around the thin membrane and avoid 3-D meshes in other regions. Numerical results of a spherical cell show that the hybrid method is accurate. The computed threshold of the applied electric field for membrane electric breakdown agrees well with those experimental results. Numerical results can also guide us to locate the maximum induced TMP on the erythrocyte membrane in various electric fields. Some further applications of the hybrid method are also discussed.