Combustion and formation behavior of hybrid ZrB2 and ZrC particles in Al–Zr–B4C system during self-propagation high temperature synthesis

Abstract

Hybrid ZrB2 and ZrC particles were prepared by self-propagation high temperature synthesis (SHS) using Al, Zr and B4C powders as starting reactants. As effective diluents, Al play an important role in the SHS reactions, during which the solid Al and Zr reacted in the first instance followed by melting of Al that reacted with Zr to generate ZrAl3. Meanwhile, due to the heat generated by the reactions, C and B atoms were dissolved into the Zr–Al liquid, leading to the precipitation of ZrB2 and ZrC out of the supersaturated liquid phases. In the case of samples with Al content of 30wt.%, ZrB2 particles exhibit typical hexagonal and rectangular shapes, whilst a spherical shape was displayed with ZrC particles. The synthesized structure of the ZrB2 and ZrC can be as fine as nanoscale. Not only prevented the synthesized products from growing, the Al addition also promoted the SHS reaction.