S042011 2000K以上での使用を目的としたZrB_2-SiC-ZrCの耐酸化性評価([S042]セラミックスおよびセラミックス系複合材料)

Abstract

ZrB_2-SiC-ZrC(ZSZ) with four different compositions containing 16 vol% SiC were sintered by hot pressing and spark plasma sintering. In this study, ZSZs were oxidized in the ultra-high temperature range by two different tests. Firstly, ZSZs were oxidized at 1973 K in an airflow by an IR image furnace for several minutes. The result showed that ZSZs have oxidation resistance in this temperature range due to formation of oxide scale which acts as a barrier against oxygen diffusion into the unoxidized area. Moreover, ZSZ containing more ZrC formed ZrO_2 rich scale, whereas ZSZ containing more ZrB_2 formed SiO_2 rich scale. These results suggested that the highest oxidation resistance would berealized if the silica scale is formed with ZrO_2 rigid skelton. In the next step, ZSZ, ZrB_2-SiC and monolithic SiC were oxidized continuously up to 2073 K in air by a ZrO_2 furnace to compare their oxidation resistance. The results revealed that oxide scale disappeared from monolithic SiC surface, whereas ZSZ and ZrB_2-SiC maintained their oxide scaleduring the oxidation test. Comparing ZSZ with ZrB_2-SiC, ZSZ formed silica scale with ZrO_2 skelton, whereas no ZrO_2 skelton was formed in the silica scale of ZrB_2-SiC. The IR image furnace test implied that it is important to have not only high oxidation resistant SiO_2 layer but also coexistence rigid oxide scale. Therefore, it is suggested that ZSZ is more attractive candidate for the advanced aerospace heat-resistant material than SiC and ZrB_2-SiC.