SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature ...SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.展开更多
Ⅰ. INTRODUCTIONMgO was first used as a sintering additive in the fabrication of Si<sub>3</sub>N<sub>4</sub> ceramics. Another common sintering additive Al<sub>2</sub>O<sub>3&...Ⅰ. INTRODUCTIONMgO was first used as a sintering additive in the fabrication of Si<sub>3</sub>N<sub>4</sub> ceramics. Another common sintering additive Al<sub>2</sub>O<sub>3</sub> combined with AIN can be accommodated in β-Si<sub>3</sub>N<sub>4</sub> structure to form β-sialon. A thorough understanding of the effect of those combined additives depends on the knowledge of the phase relationships in the system Mg-Si-Al-O-N.展开更多
文摘SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids(12H and 21R)as the bonding phases were prepared using SiC fine powder,MgAl_(2)O_(4)fine powder and Al powder as raw materials.The effects of the firing temperature and the mass ratio of SiC to MgAl_(2)O_(4) on the formation of SiAlON polytypoids as well as on the properties of samples were studied.The formation mechanism of SiAlON polytypoids was discussed.The results show that firing at 1650℃in the nitrogen atmosphere,SiC-MgAl_(2)O_(4) composites with SiAlON polytypoids can be obtained.With the gradual increase of the mass ratio of SiC to MgAl_(2)O_(4) in the raw materials,12H forms first,and then coexists with 21H,finally,all 12H converts into 21R in samples.Both phases are plate crystals with flat and smooth edges.Compared with 21R,12H is conducive to improving the density and the cold mechanical properties of materials.After firing at 1650℃in the nitrogen atmosphere,with the mass ratio of SiC to MgAl_(2)O_(4) of 6:4,the sample has the cold modulus of rupture of 27 MPa,showing the optimal performance.
文摘Ⅰ. INTRODUCTIONMgO was first used as a sintering additive in the fabrication of Si<sub>3</sub>N<sub>4</sub> ceramics. Another common sintering additive Al<sub>2</sub>O<sub>3</sub> combined with AIN can be accommodated in β-Si<sub>3</sub>N<sub>4</sub> structure to form β-sialon. A thorough understanding of the effect of those combined additives depends on the knowledge of the phase relationships in the system Mg-Si-Al-O-N.
