Mechanical properties and microstructure of nano-SiC-Al2O3 composites densified by spark plasma sintering

Heterogeneous precipitation method has been used to produce 5 vol% SiC-Al2O3 powder, from aqueous suspension of nano-SiC, aqueous solution of aluminium chloride and ammonia. The resulting gel was calcined at 700 degrees C. Nano-SiC-Al2O3 composites were densified using spark plasma sintering (SPS) process by heating to a sintering temperature at 1350, 1400, 1450, 1500 and 1550 degrees C, at a heating rate of 600 degrees/min, with no holding time, and then fast cooling to 600 degrees C within 2-3 min. High density composites could be achieved at lower sintering temperatures by SPS, as compared with that by hot-press sintering process. Bending strength of 5 vol% SiC-Al2O3 densified by SPS at 1450 degrees C reached as high as 1000 MPa. Microstructure studies found that the nano-SiC particles were mainly located within the Al2O3 grains and the fracture mode of the nanocomposites was mainly transgranular fracture, (C) 1999 Elsevier Science Limited. All rights reserved.