Mechanical activation assisted self-propagating high-temperature synthesis of ZrC and ZrB2 in air from Zr/B/C powder mixtures

When the powder mixture of Zr/B/C=1/1/1 in molar ratio was mechanically activated by grinding in a planetary ball mill and then exposed to air, it self-ignited spontaneously and the self-propagating high-temperature synthesis (SHS) of ZrC and ZrB2 was simultaneously occurred. In this mechanical activation assisted self-propagating high-temperature synthesis in air (MA-SHS in Air), it was found that high reactivity of disordered carbon formed by mechanical activation of graphite played a decisively important role. On the other hand, the isothermal solid-state reaction of the unground powder mixture of Zr/B/C=1/1/1 in argon formed ZrB2 at 800 °C and then ZrC at 1000 °C. The reaction mechanism and the morphology of the products in both processes are discussed. The product with fine, homogeneous microstructure obtained in MA-SHS in Air is expected to be a promising candidate as precursor of ZrC–ZrB2 composites.