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Study on the oxidation resistance of HfB2 ultra high-temperature ceramics

wallpapers News 2021-12-29
The development cyclically or for a long period depends on the development of new materials that can withstand the harsh aerodynamic thermal environment of certain parts of the vehicle during flight.HfB2 ultra-high temperature ceramic material can be used in high ultrasonic speed flying vehicle wing edge, nose cone, engine mouth, and other high-temperature parts. In practical application, the surface temperature of the hypersonic vehicle can reach 1 500 ° C and W when the hypersonic vehicle enters and exits the large air layer. The fuel inlet temperature of the leading edge of the flying wing, the engine rectifier hood, and the combustion chamber of the super combustion engine can even reach 2 000. In this extremely harsh environment, the high-temperature stability of materials is extremely important, because the high-temperature oxidation resistance is an important index to measure the properties of ultra-high temperature materials.
The ultra-high temperature ceramic material that has been studied most is HfB2 composite material with various sintering additives, among which the most common sintering additive is SIC. At atmospheric pressure and sintering temperature higher than 900 ° C, SiC can react with HfB2 and B2O3 to form SIC and CO gas bodies. The gas body is discharged from the furnace cavity by a mechanical pump during the sintering process. In the early stage of heating, the restricted SiO2 liquid phase can inhibit the volatilization of B2O3 to a certain extent and can react with B2O3 to form a borate liquid phase between grains. It also greatly prevented the continuous diffusion of oxygen into the inner part of the material and improved the antioxidant property of the material when it was sintered and densified. In addition, other sintering AIDS such as TaSi2 can also effectively improve the oxidation resistance of HfB2 ceramic materials.

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