Studies on the formation of TiB2 through carbothermal reduction of TiO2 and B2O3

Formation of titanium di-boride (TiB2) whiskers through carbothermal reduction of TiO2 and B2O3 has been studied from 900 to 1600degreesC in 1 arm argon. K2CO3, which forms a low melting liquid by reacting with TiO2, and NiCl2, which catalyses the carbon gasification, were used to aid the whisker formation by a vapor-liquid-solid (VLS) growth mechanism. TiO2, NiCl2, K2CO3, carbon black and B2O3 were reacted in a molar ratio (TiO2:NiCl2:KCO3:C:B2O3 = x:0.15:0.144:4:1), where x = 1/0.5/0.25. Irrespective of TiO2 content, TiB2 was formed as the major phase. Small quantities of TiC were also formed in the system containing 1 mol of TiO2 Whiskers of TiB2 were observed at 940-1200degreesC. Above 1400degreesC, the formation of particulate was the dominant process. Upon decreasing the TiO2 content to 0.5 mol, a single phase TiB2 was formed. Further decrease in the TiO2 content to 0.25 mol, resulted in the formation of B4C apart from TiB2. The B4C had appeared mainly as platelets. A vapour-liquid-solid growth mechanism was identified for TiB2 whisker formation. (C) 2003 Elsevier B.V All rights reserved.