Papers by Keyword: Microwave

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Authors: Theofano M. Kollatou, Stylianos D. Assimonis, Christos S. Antonopoulos
Abstract: The purpose of this paper is to present efficient models of new octagonal split ring resonant (O-SRR) periodic structures that can offer practical applications for electromagnetic compatibility (EMC) engineers in the area of absorbing materials. The model of an ultra-thin, compact O-SRR absorber for operation at microwave frequencies is introduced, exhibiting very high absorptive regions. The idea is extended to multi-band performance, where two different setups are demonstrated and analyzed. The physics behind the absorption mechanism for the multi-band structures is explained through the surface mechanism.
Authors: Hong Fu Guo, Chao Xu, Cai Xiang Xu, Gui Hua Gao
Abstract: This paper proposes a matter of permittivity measurement method which based on the microwave antennas resonant characteristics. The basic principle of measuring permittivity was analyzed by the antenna resonance theory. The simulation model has been build and analyzed by Ansoft HFSS simulation software. The relationship between different permittivity and the antennas resonant frequency was given. The experimental model was designed and the experimental data of sample was measured. The experimental and simulation data are compared and discussed. Results show that the simulation and experimental results are consistent well; the antenna resonance method to measure the permittivity is feasible.
Authors: Ling Xu, Hai Yan Xu, Hao Wang
Abstract: Well-dispersed nanocrystalline TiO2 powders with the average size of about 4 nm have been synthesized by a simple and rapid microwave irradiation method. The as-obtained TiO2 nanoparticles displayed obvious quantum size effects characterized by Raman spectroscopy.
Authors: Zhi Wen Luo, Zhong Chen, Su Hong Liu
Abstract: Diatomite was modified by microwave treatment to increase their utilization value, using modified diatomite to treat ammonia-nitrogen wastewater. The experiment indicated that adsorption process of modification of the modified time by microwaves and microwave power is the impact of ammonia adsorption of the main factors. Through modification experiments by raising the capacity of diatomite adsorption ammonia nitrogen, adsorption of ammonia nitrogen increase over one time. Langmuir and Freundlich isotherms were used to fit and the experimental results show that the modified diatomite adsorption onto ammonia nitrogen accords with Langmuir and Freundlich isotherm. The maximum theoretical adsorption capacities are 5.81083mg/g.
Authors: Lan Zhang, Atsushi Hosoi, Yang Ju
Abstract: Using the microwave atomic force microscope (M-AFM) measuring system, the sample of Au nanowires arranged on glass wafer was sensed with three kinds of scanning speed. As the results shown, the spatial resolution of topographies is increased with the decrease of scanning speed. However, the precision of microwave images is not changed much with decreasing the scanning speed. Since M-AFM with the compact microwave instrument can always implement the real time measurement, the variation of scanning speed will not affect the microwave measurement.
Authors: Sang An Ha, Mi Young You, Jei Pil Wang
Abstract: The objective of this study is to investigate and evaluate the thermal desorption process to treat soil contaminated with high concentration of oil by applying microwave and high temperature heating element. It was found that TPH (Total Petroleum Hydrocarbon) was achieved below 2,000 mgkg-1 of Korea criterion at 8kW of microwave powder and 700°C of processing temperature for 20 minutes. In addition, the rate of thermal desorption was also the highest value to be 0.09711 at 8kW of microwave powder and 700°C of processing temperature. Compared to other cases, the thermal desorption process applied by microwave had faster desorption rate of oil than conventional heat treatment process indicating that it would shorten processing time to treat oil-contaminated soil.
Authors: Tang Kai, Yan Jie, Huang Xin
Abstract: In this paper, microwave-surfactant assisted extraction of saponin from Momordica Charantia.L was studied. The content of saponin was determined by the method of vanillin-acetic acid and perchloric which were used as developer. Four main factors including extraction powder, extraction time, ratio of solid to liquid and surfactant concentration were studied by orthogonal experiments. Results showed that extraction powder was the most significant influential factor, followed by extraction time and ratio of solid to liquid. Surfactant concentration showed the minimum influence. The optimum extraction conditions were: extraction powder 400W, extraction time 5min, ratio of solid to liquid 1:12g/mL and surfactant concentration 0.03mol/L, under which the extraction yield of saponin reached 4.69%.
Authors: Shao Hao Chen, Cheng Chun He, Chao Yin Kuo
Abstract: This study investigates the activation of waste carbon fiber by microwave heating and potassium hydroxide and the adsorption of aqueous dye RB19 using said modified waste carbon fiber. Heating was performed in a microwave that was set to 900 W from 20 to 60 minutes (M20, M40, and M60). The specific surface areas of the original waste carbon fiber (WCF), M20, M40, and M60were 2 to489 m2/g. M40 had the highest specific surface area and an acceptable yield of 62%. In adsorption experiments at 57°C, the original waste carbon fiber adsorbed only 15 mg of dye/g of fiber. The results reveal that the capacity of adsorption increased when the waste carbon fibers were modified by activation with microwave and potassium hydroxide. Remarkably, M40 was the most suitable absorbent of aqueous dye RB19 and it had the highest capacity of 202 mg/g.
Authors: Hong Chen, Chen Hong Zhang, Tao Wang
Abstract: To fully utilize the residual of microwave-heated pyrolysis, the char was activated by vapor and used as adsorbent. Langmuir and Freundlich model were applied to adsorption for methylene blue, and the Freundlich gave a better fitting results. The high amount of adsorbent and temperature were favorable to adsorption, and the adsorbent showed high adsorption capacity in the pH range of 48. These results indicate the activated char have a greatly potential in treatment of dye wastewater.
Authors: Agus Setiabudi, Nisa Nashrah, Hanifah Permana Putri, Galuh Yuliani
Abstract: Being abundant and hazardous solid waste, the utilization of fly ash was sought. This study aimed to convert coal fly ash into zeolite using reflux method combined with microwave and ultrasonic pretreatments. Fly ash was reacted with NaOH 2 M, ultrasonicated for 30 minutes and irradiated using microwave for 45 minutes. The resulting solution was then refluxed for 24 hours. The zeolite formation was confirmed by FTIR and XRD analysis. The zeolite was then activated by 20% HCl for 2 hours. Fly ash, zeolites and activated zeolite were characterized for their adsorptive properties using a cationic dye via batch experiment. The maximum adsorption capacity (Qm) of fly ash, zeolite, and acid activated zeolite were 0.0003 mg g, 51 mg/g, and 101 mg/g, respectively. BET analyses indicated that the surface area of fly ash was 7 m2/g, while that for zeolite and acid activated zeolite were 82.4 m2g and 82.6 m2/g, respectively. The FTIR showed the Si-OH groups were significantly enhanced upon acid activation indicated by absorption peak at 960-1100 cm-1. It can be concluded that the chemisorption via cation-exchange or monolayer interaction played a major role in the adsorption mechanism of zeolite, supported by the allignment of the adsorption data plots to Langmuir isoterm adsorption model.
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