SiC-Al_2O_3 Nanocomposites Superfast Densified by SPS

Heterogeneous precipitation methods were used to produce 5 vol % SiC-Al2O3 nanocompositepowder, from aqueous suspension of Nano-SiC (70 nm), aqueous solution of aluminium chlorideand ammonia. The SiC-A12O3 nanocomposites were superfast densified by spark plasma sintering(SPS) process with heating to a sintering temperature range from 1350 to 1550℃, at a heatingrate of 600℃/min, without holding time, and then fast cooling to 600℃ within 2-3 minutes;and high density nanocomposites were obtained. The expermental results show that bendingstregth of 5 vol% SiC-A12O3 nanocomposites sintered at 1450℃ is as high as 1000 MPa, whileviaaers hardness about 19 GPa. fracture toughness of the sample sintered at 1500 ℃ is about 4MPa.ml/2, a little bit higher than that of A12O3 ceramics. Microstructure studies show that nanoSiC particles are mainly located in Al2O3 grains and the fracture mode of the nanocompositesis mainly transgranular fracture. Due to the eXPansion coefficient mismatch and most' of SiCparticles located in Al2O3 gains, the tensile stress, which weakens matrix grains and originates thetransgranular fracture, will appear when the samples cool down from the sintering temperature.