Coating and spark plasma sintering of nano-sized TiN on Y-α-sialon

Abstract

TiN coating on Y-α-sialon was accomplished by depositing TiO 2 on their particle surfaces through controlled hydrolysis of TiCl 4 and Ti(O- i-C 3H 7) 4 and subsequent nitridation with NH 3 gas at 1000 °C. TiN particles covering Y-α-sialon were about 20 nm in size. Spark plasma sintering (SPS) of TiN/Y-α-sialon particles produced composite ceramics with continuous TiN networks at 1400 °C, but with TiN grains isolated in elongated β-sialon grains at 1600 °C. The relative density and Vickers hardness of TiN/sialon ceramics SPSed at 1400–1600 °C containing 25 vol.% TiN were measured. The electrical resistivity was in a wide range of 10 −4 to 10 0 Ω cm for the ceramics sintered at 1400 °C, but lowered to the order of magnitude of 10 −1 and 10 5 Ω cm at higher temperatures ≥1500 °C. It was found that the complete transition to β-sialon increased the resistivity to 10 3 to 10 5 Ω cm, due to breaking up continuous TiN layers by elongated β-sialon grains.