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

Abstract Formation of titanium di-boride (TiB 2 ) whiskers through carbothermal reduction of TiO 2 and B 2 O 3 has been studied from 900 to 1600 °C in 1 atm argon. K 2 CO 3 , which forms a low melting liquid by reacting with TiO 2 , and NiCl 2 , which catalyses the carbon gasification, were used to aid the whisker formation by a vapor–liquid–solid (VLS) growth mechanism. TiO 2 , NiCl 2 , K 2 CO 3 , carbon black and B 2 O 3 were reacted in a molar ratio (TiO 2 :NiCl 2 :K 2 CO 3 :C:B 2 O 3 = x :0.15:0.144:4:1), where x =1/0.5/0.25. Irrespective of TiO 2 content, TiB 2 was formed as the major phase. Small quantities of TiC were also formed in the system containing 1 mol of TiO 2 . Whiskers of TiB 2 were observed at 940–1200 °C. Above 1400 °C, the formation of particulate was the dominant process. Upon decreasing the TiO 2 content to 0.5 mol, a single phase TiB 2 was formed. Further decrease in the TiO 2 content to 0.25 mol, resulted in the formation of B 4 C apart from TiB 2 . The B 4 C had appeared mainly as platelets. A vapour–liquid–solid growth mechanism was identified for TiB 2 whisker formation.