Synthesis of fine ZrB2 powders by new borothermal reduction of coarse ZrO2 powders

Effects of ZrO2 particle size (similar to 50 nm and similar to 2 mu m) on synthesis of ZrB2 powders via conventional or new borothermal reduction were investigated. The conventional process was a one-step heat treatment at 1600 degrees C in vacuum. The newly developed process consisted of two-step heat treatment (first-step at 1000 degrees C and second-step at 1600 degrees C) plus intermediate step of water washing. Micron-sized ZrB2 powders were prepared by conventional process, independent of initial ZrO2 particle size. Based on new process, submicrometric ZrB2 powders were synthesized using nano-size ZrO2. However, submicrometric ZrB2 could also be synthesized using micron-size ZrO2 by prolonging the holding time during first-step heat treatment. Therefore, results of present study suggested that fine ZrB2 powders could be synthesized by controlling the time of first-step heat treatment of the new borothermal reduction process by converting ZrO2 as completely as possible independent of initial particle size. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.