Papers by Author: Fang He

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Authors: Fang He, Hai Lei Zhao, Xian Hui Qu, Wei Hua Qiu, Wei Jiang Wu
Abstract: Silica aerogels were synthesized from hybrid silicon sources of TEOS and acid silica sol by two-step sol-gel method and supercritical drying. Different chemical compositions of the starting solution were altered in order to make an insight into the relationship between process parameters and the microstructural characteristics of resulting silica aerogels. The results indicate that a certain amount of acid silica sol may promote the gelation process while excessive nano-scaled silica particles easily result in dense structure and low specific surface area. The gelation time increases with the increasing water amount. Excessive water will lead to weak network structure of silica gels and thus larger shrinkage and lower porosity of the resulting silica aerogels.
1509
Authors: Xiao Meng Zhang, Li Hua Xu, Hong Shun Hao, Jian Ying Yang, Fang He
Abstract: Silicon carbide powders were prepared by the carbothermal reduction method. The starting powders used were iron tailings and graphite. The XRD results showed that the main crystal phase was SiC and the main impurity was FexSiy in as-fabricated silicon carbide. The SEM results revealed that the grains of SiC-phase in as-fabricated silicon carbide were flaky-like or globular-like. It is found that the carbon addition and the reaction temperature play a key role to obtain SiC-phase, while the holding time and argon flow rate had a little effect on the yield of SiC as the excessive carbon addition are used. The optimum sintering temperature, holding time, argon flowing rate, the ratio of n(C): n(SiO2) are 1500 °C, 8 h, 0.6 L/min, 5:1, respectively.
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