Formation of TiN whiskers through carbothermal reduction of TiO2

Formation of TiN whiskers through carbothermal reduction of TiO2 in nitrogen was studied. Effect of (i) addition of potassium (K2CO3) and nickel (NiCl2), (ii) reaction temperature on the formation of whiskers was studied. Addition of K2CO3 has strong influence on the formation whiskers. The yield of whisker was maximum at 920-1000degreesC. At higher temperatures, formation of particulates of TiN was the dominant process. Increase in K2CO3 concentration increased the formation of (i) whiskers at low temperatures 815degrees-920degreesC, (ii) particulates at high temperatures 1000degrees-1100degreesC. A vapor-liquid-solid growth mechanism of whisker formation was identified. K2CO3 has been identified as an essential constituent for the formation of a low melting liquid by reaction with TiO2 and NiCl2. Continuous supply of TiO, nitrogen and CO to this complex K-Ni-Ti liquid droplet lead to the precipitation of TiN whisker. (C) 2002 Kluwer Academic Publishers.