Papers by Author: X.H. Zhang

Abstract: In alkaline earth aluminoborosilicate glasses CaO-B₂O₃-Al₂O₃-SiO₂, the changes of structure and properties caused by variations in the ratio Al₂O₃/B₂O₃ were investigated. The structure was investigated by Fourier transform infrared spectroscopy. The dielectric constant and tangent loss were measured at 1 MHz. Chemical durability was evaluated by weight losses of glass samples after immersion in HCl and NaOH solutions. The results indicated that the fraction of four-coordinated boron atoms (N₄), chemical durability and dielectric properties increased with increasing Al₂O₃/B₂O₃ replacements.

Abstract: In alkaline earth aluminoborosilicate glasses CaO-B₂O₃-Al₂O₃-SiO₂, the changes of structure and properties caused by variations in the ratio SiO₂/B₂O₃ were investigated. The structure was investigated by Fourier transform infrared spectroscopy. The dielectric constant and tangent loss were measured at 1 MHz. Chemical durability was evaluated by weight losses of glass samples after immersion in HCl and NaOH solutions. The results indicated that the fraction of four-coordinated boron atoms (N₄), chemical durability and dielectric properties increased with increasing SiO₂/B₂O₃ replacements.

Abstract: The forsterite-structure Mg₂SiO₄ was successfully synthesized by the aqueous sol-gel method using Si sols dioxide and magnesium nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized Mg₂SiO₄ powders were successfully obtained at 850 °C with particle size of 60~80 nm.

Abstract: Tool material has been one of the focuses in tool research. Diamond and cubic boron nitride (c-BN) are materials of exceptional and very similar properties that make them extremely valuable not only for the aesthetics of diamond. C-BN is a material synthesized rather recently that has rapidly spurred technological and scientific interest. Presently, both materials have found commercial applications. There is still a long way for the practical application of cBN film. The main problems are such as adhesion, thickness, purity, nucleating, and growth mechanism. We will develop a new way of DC plasma jet CVD way to synthesis the cBN film. The deposition of cBN films can be performed in a DC jet plasma CVD reactor by using an Ar-N2-BF3-H2 gas mixture, on the basis of deposition of diamond has been achieved.

Abstract: To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.