Dense and homogenous Si3N4-TiN composites (5 vol% TiN) were prepared by using in situ
synthesis method from Si3N4, AlN and TiO2 mixtures, containing Y2O3 and Al2O3 as sintering aids. In
the prepared Si3N4-TiN composites, TiN grains were formed from TiO2 and AlN powders during the
sintering process, in which ammonium citrate was used as a dispersant for raw TiO2 powders. The
microstructures of the Si3N4-TiN composites with the increase of ammonium citrate were
investigated by scanning electron microscopy (SEM). Citrate ions modified on the surface of TiO2
particles and protected the TiO2 particles in the mixed slurry to reduce the aggregations of TiO2
powders, and homogenous Si3N4-TiO2-AlN composite powder was prepared for sintering. The
microstuctures of Si3N4-TiN were developed after sintering with the uniform distribution of TiN
grains in the Si3N4 ceramics. It was found that the microstructure of Si3N4-TiN composite was
improved significantly with 0.20 g ammonium citrate in the system, TiN grains with 0.2-0.3 μm in
diameter distributed throughout Si3N4 matrix. It was a practical and useful way to improve the
microstructure of Si3N4-TiN composite without the alteration of the preparation procedure.
In situ Synthesis of Nano-sized ZrC and Its Formation Mechanism by Combustion Synthesis from Zr–C–Cu System
