Effect of B₄C Addition on the Microstructures and Mechanical Properties of ZrB₂-SiC Ceramics

Abstract

ZrB 2 has a melting point of 3245 o C and a relatively low density of 6.1 g/cm 3 , which makes this a candidate for application to ultrahigh temperature environments over 2000 o C. Beside these properties, ZrB 2 is known to have excellent resistance to thermal shock and oxidation compared with other non-oxide engineering ceramics. In order to enhance such oxidation resistance, SiC was frequently added to ZrB 2 -based systems. Due to nonsinterability of ZrB 2 -based ceramics, research on the sintering aids such as B 4 C or MoSi 2 becomes popular recently. In this study, densification and high-temperature properties of ZrB 2 -SiC ceramics especially with B 4 C are investigated. ZrB 2 -20 vol% SiC system was selected as a basic composition and B 4 C or C was added to this system in some extents. Mixed powders were sintered using hot pressing (HP). With sintered bodies, densification behavior and high-temperature (up to 1400 o C) properties such as flexural strength, hardness, and so on were examined.

Thermal and Mechanical Properties of ZrB2-SiC Ceramics Fabricated by Hot Pressing with Change in Ratio of Submicron to Nano Size of SiC

“…ZrB 2 분말은 공유결 합의 특성이 강하여 입내/입계 확산속도가 매우 낮으므로 치밀화하기 위해 상당한 고온이 필요하며, 7) 이러한 난소 결 특성으로 인하여 ZrB 2 -계 세라믹스는 고온가압소결, 방 전플라즈마소결, 반응고온가압소결, 무가압소결 등 다양 한 공정으로 치밀화되고 있다. 4,7,8) 또한, ZrB 2 -계 세라믹 스의 산화저항성을 향상하기 위해 SiC가 첨가 4,7,9,10) 되는 데, SiC 첨가는 산화저항성 외에 ZrB 2 -계 세라믹스의 기 계적, [11][12][13] 열적 특성의 향상…”