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Ultra-high Temperature Ceramic Material-Zirconium Diboride

wallpapers Industry 2020-07-21

Ultra-high temperature ceramics are transition metal borides, carbides, and nitrides with a high melting point above 3000°C and excellent high-temperature oxidation resistance, ablation resistance, and thermal shock resistance. They are expected to be used in space rockets. The engine, the heat protection system, and propulsion system of the space shuttle and the hypersonic vehicle, as well as the electrodes, crucibles, and related parts for high-temperature smelting and continuous casting of metals, heating elements, etc. The performance of ultra-high temperature ceramics depends on factors such as the quality of high-purity ultra-fine raw materials, powder morphology and reactivity, degree of densification, sintering methods, and systems, and microstructure control. High-temperature performance includes high-temperature strength, thermal shock resistance, and Oxidation, and ablation resistance is the key to the application of UHT ceramics to high-temperature structural material engineering components.

Researchers have analyzed the phase equilibrium relationship, powder synthesis, molding process, sintering, microstructure control and ultrastructure analysis, high-temperature strength, the resistance of ultra-high temperature ceramics based on zirconium boride (ZrB2) and hafnium boride (HfB2). Systematic in-depth research on oxidation and ablation resistance has been carried out, and fruitful research results have been obtained.

Using commercial powders as raw materials, high-purity and ultra-fine ZrB2 and HfB2 powders were obtained through various preparation methods. The research results showed that the obtained powders have good sintering activity. At the same time, a variety of sintering processes were used to prepare ultra-high temperature ceramics, and the densification mechanism of the material was studied; transmission electron microscopy was used to study the distribution of oxygen pollution on the surface of ZrB2 powder particles, and the removal mechanism; grouting or gel injection was used Mold forming combined with pressureless sintering process to prepare ultra-high temperature ceramic parts with complex shapes.

To further improve the general performance of ultra-high temperature ceramics, various microstructure control methods are used, and the external field (strong magnetic field and stress field) auxiliary methods are proposed and used, including practices such as strong magnetic field orientation and hot forging, to obtain a highly oriented texture. Boride-based ultra-high temperature ceramics, the hardness, thermal conductivity, and oxidation resistance of the material are significantly improved in a specific direction, which maximizes the best performance of the ceramic material in a particular crystal plane direction, to further enhance the ultra-high temperature ceramics The performance provides a new way. Simultaneously, the mechanical properties, high-temperature thermophysical properties, and high-temperature stability of the microstructure of the material were evaluated, and a transmission electron microscope studied the initial depletion layer of the hafnium boride-silicon carbide (HfB2-SiC) composite ceramic. Formation mechanism and put forward a new point of view to evaluate the oxidation resistance of materials based on the thickness of the depletion layer; systematically studied the chemical reaction and reliable solution mechanism of different carbide additives in the sintering process.

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Tag: Zirconium Diboride