A method to synthesize ultrafineTiB2 and ZrB2 powders

Abstract

In this work, the ultrafine TiB2 and ZrB2 powders were prepared using TiO2, ZrO2, C, B4C, and Ca as the raw materials. The process consisted of steps of carbothermic pre-reduction of oxide, boronization and decarburization reactions in Ca melt, wet leaching as well as deep deoxidation. The pre-deoxidation by carbothermic reduction successfully avoids the problem of evaporation loss of boron source in traditional borothermal reduction method to prepare borides due to the generation of boride oxide. Because of the strong exothermic behavior, the adiabatic temperatures in boronization-decarburization step as well as wet leaching step were calculated, and the results show that these reactions are mild and controllable. Furthermore, it was found that the high oxygen contents in as-prepared TiB2 and ZrB2 powders were resulted from the high temperature and low pH value during water leaching and acid leaching processes. After deep deoxidation at 1673 K in vacuum by mixture of C and B4C, the particle sizes of the final TiB2 and ZrB2 powders were about 200 nm, and the oxygen contents were 1.26 wt% and 0.92 wt%, respectively.