Reaction Mechanism of Combustion Synthesized ZrC–2ZrB₂-Based Cu Cermets

Abstract

The reaction process of ZrC–2ZrB₂-based Cu cermets from the (1 − x wt.%)(1B₄C–3Zr)–x wt.%Cu system (Zr/B₄C = 3 in molar ratio) was explored. Results showed that ZrC and ZrB₂ were mostly produced through the dissolution of B₄C into a preformed Zr–Cu liquid. With an increase in x, the synthetic ZrC–2ZrB₂ and generated heat were reduced. This effect decreased an ability for Zr–Cu liquid to propagate in the reactants, and restrained the dissolution Zr. As a result, the complete synthesis of ZrC–2ZrB₂ failed in the systems with a higher Cu content (e.g., 50 wt.%). Furthermore, after the precipitation of ZrC and ZrB₂, the liquid surrounding would prevent ZrC and ZrB₂ from growing. Increasing Cu content enhanced the amount of Zr–Cu melt. This behavior contributed to a decline in ZrC–2ZrB₂ particle sizes, and the production of fine ceramic particles (∼200 nm). It is also revealed that the formation of ZrC–2ZrB₂ is a multistep process, which results in the inhomogeneity of ZrC–2ZrB₂ particle sizes. A valuable approach was proposed to explore the relationship between reaction process and synthesized products of combustion synthesis-related technique.

Fig. 3 XRD patterns of (a) BZC50 and (b) BZC30 quenched from different temperatures.