Low-Temperature Spark Plasma Sintering of a SiC Nanopowder with a Very Thin Al-Based Layer

摘要

A SiC nanopowder with an Al-based layer synthesized by means of laser pyrolysis was used to fabricate bulk SiC using spark plasma sintering (SPS) at 1600 - 1800 degrees C. The surface structure of the novel SiC nanopowder was analyzed by means of field-emission scanning/transmission electron microscopy (FE-SEM/TEM), while the surface chemistry was characterized using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). The average particle size was around 45 nm with a very thin ( 5 nm) coating of Al-containing compounds. The effect of the SPS temperature on the density and mechanical and thermal properties of bulk SiC was investigated. Sintered densities above 96 % were obtained at temperatures as low as 1700 degrees C. Toughened microstructures, which consisted of platelets and relatively small equiaxed SiC grains incorporating crystalline Al4O4C, were observed after SPS treatment at 1800 degrees C. The samples fabricated by means of SPS at 1800 degrees C had a typical bending strength of 592 MPa, fracture toughness of 5.4 MPam(1/2), and thermal conductivity of 80 W/mK.