(In situ preparation of α-SiAlON-SiC composite)

The objective of this work is to obtain in situ α-SiAlON-SiC composites, by silicon nitride solid solution development, during sintering, using rare earth and yttrium oxide mixture (CRE 3 O 3 ) as stabilizer of the α-Si 3 N 4 phase. A fraction of 20 vol.% of AlN-CRE 2 O 3 mixture was mixed to 80 vol.% of Si 3 N 4 . Different contents of β-SiC powders were mixed to the Si 3 N 4 -AlN-CRE 2 O 3 powder mixture. The powder mixtures were milled and compacted by uniaxial and cold isostatic pressing. The green bodies were sintered at 1950 °C during 1 h under 1 MPa of N 2 pressure. The sintered samples were characterized by X-ray diffraction and scanning electron microscopy, in order to assess the crystalline phases and microstructural aspects, respectively. The results revealed the presence of α-SiAlON and β-SiC as the only crystalline phases present in the material. No partial crystallization of remaining intergranular phase was detected. No α-SiAlON solubility variation was observed by the use of different SiC contents, but different grain of α' grains are related to SiC addition in the mixtures.