Research On The Solid Solution And Composite Of Double Ionic Substitute Negative Thermal Expansion Compound Zr_1-xAl_xMoW_1-y V_yO₈

This paper has mainly introduced the developing course, the research present situation in Domestic and foreign and the applying area of the negative thermal expansion (NTE) materials, and has also analysed the prepareing method and the negative thermal expansion mechanics. In this paper, the double ionic substitute method was applied to modify the properties of ZrMoWO8 based on the reported information. Composite material was prepared from the ZrMoWO8 solid solution and plate alumina. And it is characterized through modern analytic technique. The main researching points in this paper are as follows:The Zr1-xAlxMoW1-yVyO8 solid solution was prepared by co-precipitation method. The sintered behavior was analysed by SEM which exhibited that the samples of the modified ZrMoWO8 showed a compact structure, low porosity and a good fired behavior with the content of V5+ rising up to a certain concentration. While, the fired behavior would get worse when the content exceeded the concentration. The XRD data showed that the crystal structure has not been changed, the lattice parameter was rose firstly and then stabilized with the rising of the content of V5+. Bisides the expansion coefficient was also rose.The molten salt method method was adopted to prepare plate alumina. Through the characterization of SEM and XRD, the best experiment conditions were got as follows: the sintered temperature is 1200℃, sintering time is 3h, and the best salt is NaCl+KCl with the weight ratio of 1:1. The prepared plate alumina has the properties of uniform size and regular shape, and the ratio of the diameter and thickness of the samples is about 20. Its crystal structure isα–Al₂O₃ which is the most stabilized alumina.The binder is a low melting point glass material, which can be used to prepare composite matrial through the mixing with ZrMoWO8 and plate alumina and being molten at low temperature. Both of ZrMoWO8 and plate alumina are binded together with the binder through ionic and covalent bond. The TG-DTA data showed that the melting point of this binder is 550℃which would meet the requirement of the preparation of composite.The composite material was prepared by mixing the tow materials and binder suficently and sintered at low tempareture. Through the analytic technique of SEM and XRD, the best experiment conditions were got as follws: the sintered temperature is 650℃, sintering time is 1h, the contents of plate alumina and binder are 40% and 25%. The XRD data showed that the crystal structure of each raw material has not been changed.Though there are still a few single plate alumina existing and inefficient binding effect, it has meet the requirement the NTE composite material.