Al_2O_3-Coated Nano-SiC Particles Reinforced Al_2O_3 Matrix Composites

摘要

Properties of Al_2O_3-coated nano-SiC have been compared with those of as-received SiC. The isoelectric point (IEP) of SiC changed from pH3.4 to pH7.3 after coating with the alumina precursor, which is close to that of alumina. Because both surfaces of coated SiC and Al_2O_3 possess higher positive charge at pH=4.5 ～ 5.0, they are uniformly dispersed in the two-phase aqueous suspensions, Then a mixed powder containing nano-SiC dispersed homogeneously into the Al_2O_3 matrix was achieved from flocculating the two-phase suspension. Finally, Al_2O_3/SiC nanocomposites were obtained by coating nano-SiC with Al_2O_3, in which the majority of SiC particles were located within the Al_2O_3 grains. The observation by transmission electron microscopy (TEM) and the analysis by the X-ray photoelectron spectroscopy (XPS) showed that cracks propagated towards the intragranular SiC rather than along grain boundaries.