Effect of different Si_3N_4 structure state on synthesis of Sialon by spark plasma sintering

Using nanometer amorphous Si3N4,micrometer-Si3N4,micrometer AlN,nanometer Al2O3 and nanometer Y2O3 powders as starting materials,Sialon ceramics are prepared using spark plasma sintering technology.The effect of various Si3N4 structures on the synthesis of Sialon is discussed.The sintered samples are characterized by X-ray diffraction and scanning electron microscopy.Furthermore,the mechanical properties such as hardness and fracture toughness are determined by Vickers indentation method.Also the density is measured in terms Archimedes's principle and the flexural strength is tested by three-point bending method.The results show that when-Si3N4 is used as starting material,α / β-Sialon ceramics can be prepared by SPS;while when partial α-Si3N4 powder is replaced by nanometer amorphous Si3N4 powder,the relative content of α-Sialon phase in the sintered samples decrease.When α-Si3N4 of formula is totally replaced by nanometer non crystal Si3N4,only β-Sialon phase can be obtained in the sintered samples.