ZrO2 removing reactions of Groups IV-VI transition metal carbides in ZrB2 based composites

In this paper, ZrO2 removing reactions of Groups IV-VI transition metal carbides (MCs, M = Hf, Nb, Ta, W, Ti and V) in ZrB2 based ultra-high temperature ceramics (UHTCs) are investigated. Distinct roles of various MCs were observed during this process. According to thermodynamic analysis and experiment verifications, the sequence for oxide removing ability of different MCs is WC>VC>NbC>TaC>HfC>TiC. The importance of this study concerns the establishment of a map of reactivity of the transition metal carbides against ZrO2, in order to choose the proper additive for the densification of ZrB2-composites. Utilizing right reactions and controlling proper sintering atmospheres, high density ZrB2-SiC ceramic could be eventually obtained by pressureless sintering at temperatures (around 2000-2200 degrees C). (C) 2010 Elsevier Ltd. All rights reserved.