Processing of SiC whisker-reinforced mullite ceramic composites

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(1) Dispersion of ceramic powder and SiC whisker in slurryDispersion behavior of mullite and SiC whisker in slurry was evaluated by the measurement of zeta potential in aqueous solution and sedimentation velocity in aqueous solution and ethanol. Good dispersion state for mullite was obtained in aqueous solution adjusted above pH=9 and in ethanol. On the other hand, dispersion for SiC whisker was improved only by addition of deflocculant.(2) Relation between powder mixing and slurry drying processes and microstructure of ceramic compositesThe effects of mixing and drying methods to density, microstructure and flexural strength was studied. Ceramic composites of high density and high strength was obtained by the combination of powder-mixing in ethanol containing deflocculant by ball-milling and drying by rotary-evaporator(3) Flexural strength and fracture toughnessThe effects of whisker diameter and carbon-coating to whisker on the flexural strength and fracture toughness of SiC whisker-reinforced mullite were studied. The flexural strength and fracture toughness increased with increasing SiC whisker contents. The flexural strength and fracture toughness were little affected by changing whisker diameter. The flexural strength slightly decreased by coating whisker with carbon. It is concluded that the toughening mechanism of SiC whisker-reinforced mullite is in load transfer to whisker.