Coating and spark plasma sintering of nano-sized TiN on alumina particles of different size, shape and structure

TiN-coated Al₂O₃ particles of different size, shape and crystal structure were prepared by depositing nano-size TiO₂ on the Al₂O₃ surfaces from Ti(O-i-C₃H ₇)₄ solution (TiO₂ precursor) by controlled hydrolysis, then nitrided with NH₃ at 1000°C. Irrespective of the source of Al₂O₃ particles, a homogeneous TiO₂ coating was achieved by heating from 10 to 40°C an ultrasonic suspension of the Al₂O₃ particles containing the precursor with 1.0 vol% H₂O. After nitridation, the Al₂O₃ grains were coated with 10-20 nm TiN particles. Spark plasma sintering of the TiN/Al ₂O₃ particles at 1500°C and 1600°C yielded the composite ceramics with a relative density of 94-97%. Composite TiN/Al ₂O₃ ceramics with an electrical resistivity of ∼10^-2 Ω. cm were obtained at 25 vol% TiN composition.