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666 results on '"Huang, Wanxia"'

263. Study on shielding functionally gradient materials with low reflection loss and high absorption loss for electromagnetic wave

Author

Huang Wanxia, Jiang Yu, Mao Jian, Cheng Jia-Zhao, TU Mingjing, and Guan Deng-Gao

Subjects
Materials science, business.industry, Reflection loss, Composite number, Impedance matching, chemistry.chemical_element, Electromagnetic radiation, Nickel, Optics, chemistry, Electromagnetic shielding, Computational electromagnetics, Composite material, business, Electrical impedance
Abstract

In this paper, the double gradient model for shielding functionally gradient materials (SFGMs) with low reflection loss and high absorption loss in less than 1 GHz is put forward to reduce pollution of the electromagnetic wave. In SFGMs, double impedance matching layers on the surface and high absorption layer in center and double impedance transition layers between the surface and center are designed. The based on nickel and (Ni,Zn)Fe/sub 2/O/sub 4/ gradient composite shielding coatings are prepared. The test results of the coatings showed that, the reflection loss was decreased 6/spl sim/8 dB and the absorption loss was increased 6/spl sim/14 dB.

Published
2003

272. Curing kinetics, mechanical properties and thermal stability of epoxy/graphene nanoplatelets (GNPs) powder coatings.

Author

Zhi, Maoyong and Huang, Wanxia

Abstract

Epoxy/graphene nanoplatelets (GNPs) powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy (FT-IR) with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy (FE-SEM) after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis (TGA). The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading (1 wt %), indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability. [ABSTRACT FROM AUTHOR]

Published
2016
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274. Preparation and phase transition properties of Ti-doped VO films by sol-gel process.

Author

Shi, Qiwu, Hu, Yanyan, Huang, Wanxia, Zhu, Hongfu, Yue, Fang, Xiao, Yang, Liang, Shan, and Lu, Tiecheng

Abstract

Pure and Ti-doped vanadium dioxide (VO) thin films were deposited on muscovite substrates using an inorganic sol-gel method. The crystallinity, stoichiometry, surface morphology and phase transition properties of the films were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and in situ FTIR measurement, respectively. The results indicated that all the VO films exhibited polycrystalline structure, with a (011) preferred orientation. But Ti doping affected the morphology of the films remarkably, which then led to varied phase transition properties. Particularly, the phase transition temperature elevated by increasing the doping concentration of Ti (from 61 °C for pure film to 71.5 °C for the film doped with 2.8 at.% Ti), and the hysteresis loop decreased simultaneously. This study proposed a new method to prepare Ti-doped VO film and provided considerable insights for the application of Ti-doped VO film due to its unique phase transition properties. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Published
2016
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283. Grain nucleation and growth behavior of a Sn-Pb alloy affected by direct current: An in situ investigation.

Author

Yang, Fenfen, Chen, Zongning, Cao, Fei, Fan, Rong, Kang, Huijun, Huang, Wanxia, Yuan, Qingxi, Xiao, Tiqiao, Fu, Yanan, and Wang, Tongmin

Subjects
NUCLEATION, LEAD alloys, DIRECT current circuits, SOLIDIFICATION, GRAIN genetics
Abstract

In situ synchrotron X-ray radiography was used to study the effect of direct current (DC) on the grain nucleation and growth of Sn-50 wt.%Pb alloy. The results showed that applying DC adequately during solidification could effectively enhance the grain nucleation and inhibit its growth. Imaging of comparative experiments with varying DC intensity indicated that the final grain size, determined by the competition between grain nucleation and growth, was sensitively dependent on the DC intensity. It was found that the average grain size was decreased from 1632 to 567 μm with DC density of 1.5 A/mm 2 compared to the case without DC. Beyond this value, raising the current density may cause a significant decrease in the nucleation rate, and thus lead to a coarsening of the grain structure. [ABSTRACT FROM AUTHOR]

Published
2017
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