A universal method for the synthesis of refractory metal diborides

Abstract

Abstract Refractory metal diboride is a kind of excellent ultra-high temperature ceramics and could be applied as thermal shielding material for supersonic aircraft. In this paper, a two-step reaction process for the synthesis of refractory metal diboride powders was proposed using refractory metal oxide, carbon black (C), B4C, and calcium Ca as raw materials. Firstly, the carbothermal reduction reaction between oxides and C was taken place at 1773\xa0K; and then, the reduction product was reacted with B4C and Ca for the purposes of boronization and decarburization. After acidic leaching, pure diboride was prepared. The experimental results indicated that diborides of Ti, Zr, Hf, V, Nb and Ta with low residual carbon content can be prepared by this method. In addition, the inheritance relationship of particle size between raw oxide and finally prepared diboride was revealed. By this method, ultra-fine TiB2 (123\xa0nm) and ZrB2 (76\xa0nm) powders were also successfully prepared, with the raw materials of nano TiO2 and nano ZrO2, respectively.