Synthesis of zirconium, hafnium and their ternary borides by a polymer complex route

Submicrometer (100–500 nm) zirconium diboride powders were synthesized by a polymer complex route using simple and mainly nontoxic starting reagents. In this aqueous process, chitosan was used as a coordinating polymer to immobilize the metal ion and boric acid in the molecular so as to inhibit the segregation of various components in the dried gel. This zirconium-based precursor (4 B/metal molar ratios) was thus completely transformed into ZrB2 after 1400 °C heat treatments. As a comparison, synthesis of zirconium diboride using phenolic resin with poor complexation ability was also conducted, and the results showed that the final products comprised of a mixture of boride and a considerable amount of carbide phase in spite of the excess of boron source. Moreover, HfB2 and the ternary boride powders were also synthesized by the polymer complex method and had a submicrometer size; moreover, the ternary boride showed a single phase AlB2-type products. Thus, the polymer complex method was demonstrated to be a more effective method to synthesize boride particles.