Chu Zengyong

Effect of surface modification on microwave absorbing properties of magnetic metal fibers

In order to avoid forming an electrical conductive network due to surface connections, the magnetic metal fibers were coated with SiO2 for surface modification by the sol-gel process. The microstructure, composition and electromagnetic characteristics of SiO2-coated and uncoated metal fibers were studied using SEM, EDAX, and a voter network analyzer. The reflectivity was simulated using the RAMCAD software. The electromagnetic parameters and absorption properties of SiO2-coated metal fibers were improved greatly due to optimal impendence matching and the electric conductivity decreased, compared to those of uncoated materials.

Defects of polymer-derived Si−C−O fibers and their originations

Defects of polymer-derived Si−C−O fibers were intensively studied by the SEM and TEM techniques and their originations were also discussed on the basis of factors experiments. The defects were found mainly in the form of strumaes, pits and splits on surfaces as well as microflaw networks, porosity clusters and inclusions in the bulk. Factors experiments reveal that a nonuniform or an insufficient curing would result in larger-sized strumaes or interior microflaws. Gas evolution rates due to different firing rates have a great influence on the formation of internal microflaws or porosity clusters and some oxidation-induced pits or splits may be formed on surfaces because of a trace of oxygen or water vapor accumulated from the flowing inert atmosphere during pyrolysis.

PAN预氧丝BCl 3 气氛中的碳化及其吸波性能的研究

PAN预氧丝在BCl 3 气氛中进行碳化处理, 研究了处理温度与时间对纤维B元素含量的影响. 采用X射线光电子能谱(XPS)、傅立叶红外分析(FTIR)、扫描电镜(SEM)对碳化后纤维的形貌与结构进行表征, 并对其吸波性能进行分析. 结果表明: PAN预氧丝在BCl 3 气氛下碳化后, 纤维表面生成了BCN包状附着物, 纤维中有B?N键的生成. 与氮气中碳化的碳纤维相比, 纤维的介电常数有所降低, 介电常数虚部降低得较快, 有利于改善纤维的吸波性能.PAN预氧丝在BCl 3 气氛中进行碳化处理, 研究了处理温度与时间对纤维B元素含量的影响. 采用X射线光电子能谱(XPS)、傅立叶红外分析(FTIR)、扫描电镜(SEM)对碳化后纤维的形貌与结构进行表征, 并对其吸波性能进行分析. 结果表明: PAN预氧丝在BCl 3 气氛下碳化后, 纤维表面生成了BCN包状附着物, 纤维中有B?N键的生成. 与氮气中碳化的碳纤维相比, 纤维的介电常数有所降低, 介电常数虚部降低得较快, 有利于改善纤维的吸波性能.