1992 Volume 100 Issue 1158 Pages 172-177
The reactivity of starting materials and heat treatment conditions for the preparation of ZrB2 fine powders using a thermite method were examined in the ZrO2-B2O3-Mg and ZrO2-B-Mg systems. The removal treatment of by-products was also investigated. In the ZrO2-B2O3-Mg and ZrO2-amorphous B-Mg systems, the reduction of ZrO2 and B2O3 by Mg and the boriding reaction of α-Zr and Mg occurred concurrently. The ZrB2 fine powders of single phase were successfully prepared at 1100°C in the ZrO2-B2O3-9Mg (molar ratio) system and at temperatures above 700°C in the ZrO2-2B-5Mg (molar ratio) system. Washing of the products with deoxidized acidic solutions in nitrogen atmosphere was effective to separate ZrB2 from MgO and MgB2, and to inhibit the oxidation of the ZrB2, too. Mg content in the powders after the acid treatment was 0.6-1.0wt%.