Research Of Preparation And Properties Of Ultra High Temperature Materials

Ultra-high materials have become a hot research topic in recent years, among which ZrB₂ has become the focus of research because of its preeminent physical and chemical properties. In the 60’s of last century,the preparation technology of ZrB₂ has been very mature, but the existence of ZrB₂ stable covalent bond makes it difficult to sintering, easy to oxidation in the air,add to other shortcomings has become the obstacle to its application. Based on ZrB₂ full investigation, In this paper, the preparation of micron ZrB₂, sintering property and sintering of SPS material density is analyzed and explored. In order to get a better antioxidant properties of ZrB₂ compsites,the SPS sintering proceeds bulk ZrB₂-Si C layer oxide structure to improve the antioxidant properties of materials were studied, and ZrB₂-Si C bulk composites electrical properties the analysis and inquiry.In this paper, the influence of the sol-gel process on the preparation of ZrB₂ particles was studied, and the suitable experimental conditions were selected in four different raw materials ratio. Study found that in the sucrose 2.5g, and zirconium propoxide 5.3g, raw material distribution of boric acid 2.97 g get the more pure boron powder of zirconium, ZrB₂ prepared for rod like particles 10 microns size; and calcinations holding long time will contribute to the particles of irregular growth.This article focuses on the ZrB₂ oxidation characteristics, first of ZrB₂ particles and block in the air oxidation temperature do the quantitative analysis. Experimental results show that the granular and block are oxidation in 600 to 700℃, but block below 1000℃ for passivating oxide, has the effect of hinder the oxidation. Based on the sintering behavior, using the sintered densities, we chose the ZrB₂-10mol%Si C to study the oxidative, ZrB₂-10mol%Si C with increasing oxidation temperature, the surface will be gradually formation layer composed of Zr O2 protective layer to prevent the further oxidation; in the course of low temperature oxidation, oxidation of long for oxidation effect is not obvious. ZrB₂-10mol%Si C in high temperature oxidation, due to the volatility of B2O3 will form three layers of block structure, the first layer is the protection of Si O2 and Zr O2 layer, the second layer of Si O2 and Zr O2, ZrB₂-Si C mixed layer, and the third layer is the ZrB₂-Si C material layer.At the same time, we use the SPS sintering proceeds of ZrB₂ samples to study the electrical properties of ZrB₂ material. Experimental results tell us that the resistivity at room temperature of 8.062 μΩ · cm; resistivity of ZrB₂-Si C composites with Si C addition amount increases gradually, at room temperature, the resistivity of ZrB₂-10mol%Si C、ZrB₂-20mol%Si C、ZrB₂-30mol%Si C respectively is 9.836 μΩ·cm、13.987 μΩ·cm、15.124 μΩ·cm.