In this work, the ablation behavior of monolith ZrB2-30 vol%SiC (Z30S) composites were studied under various oxy-acetylene flame angles. Typical oxidized microstructures (SiO2/SiC-depleted/ZrB2-SiC) were observed when the flame to Z30S was arranged vertically. However, formation of the outmost glassy SiO2 layer was hindered when the Z30S was tilted. The SiC-depleted region was fully exposed to air with reduced thickness when highly tilted. Traces of the ablated and island type SiO2 were observed at intermediate flame angles, which clearly verified the effect of flame angle on the ablation of the SiO2 layer. Furthermore, the observed maximum surface temperature of the Z30S gradually increased up to 2,200 °C proving that surface amorphous silica was continuously removed while monoclinic ZrO2 phase began to be exposed. A proposed ablation mechanism with respect to flame angles is discussed. This observation is expected to contribute to the design of complex-shaped UHTC applications for hypersonic vehicles and re-entry projectiles.

This paper reports the microstructures and thermal conductivities of -SiC composite ceramics with size and amount of SiC. We fabricated sintered bodies of -x vol.% SiC (x=10, 20, 30) with submicron and nanosized SiC densified by spark plasma sintering. Microstructure retained the initial powder size of especially SiC, except the agglomeration of nanosized SiC. For sintered bodies, thermal conductivities were examined. The observed thermal conductivity values are 40~60 W/mK, which is slightly lower than the reported values. The relation between microstructural parameter and thermal conductivity was also discussed.

This paper reports the effect of sintering processes and additives on the microstructures and mechanical properties of -SiC composite ceramics. We fabricated sintered bodies of -20 vol.% SiC with or without sintering additive, such as C or , densified by spark plasma sintering as well as hot pressing. While almost full densification was achieved regardless of sintering processes or sintering additives, significant grain growth was observed in the case of spark plasma sintering, especially with . With sintered bodies, mechanical properties, such as flexural strength and Vickers hardness, were also examined.