Impact of a Supersonic Dissociated Air Flow on the Surface of HfB2-30 vol % SiC UHTC Produced by the Sol-Gel Methodстатья
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Дата последнего поиска статьи во внешних источниках: 26 декабря 2018 г.
Аннотация:A new method to produce ultra-high-temperature ceramic composites under rather mild conditions (1700 degrees C, 30 MPa, treatment time 15 min) was applied to synthesize a relatively dense ((rel) = 84.5%) HfB2-30 vol % SiC material containing nanocrystalline silicon carbide (average crystallite size approximate to 37 nm). The elemental and phase compositions, microstructure, and some mechanical properties of this material and also its thermal behavior in an air flow within the temperature range 20-1400 degrees C were investigated. Using a high-frequency induction plasmatron, a study was made of the effect of a supersonic dissociated air flow on the surface of the produced ultra-high-temperature ceramic composite shaped as a flat-end cylindrical sample installed into a copper water-cooled holder. On 40-min exposure of the sample to the supersonic dissociated air flow, the sample did not fail, and the weight loss was 0.04%. Although the heat flux was high, the temperature on the surface did not exceed 1400-1590 degrees C, which could be due to the heat transfer from the sample to the water-cooled model. The thickness of the oxidized layer under these conditions was 10-20 m; no SiC-depleted region formed. Specific features of the microstructure of the oxidized surface layer of the sample were noted.