| 摘要 |
A silicon-containing composite body that would otherwise be brittle can be engineered to exhibit enhanced fracture toughness. Specifically, a silicon ceramic reinforced silicon carbide composite body is produced, preferably by a reactive infiltration technique. The ceramic is selected such that it has a higher coefficient of thermal expansion (CTE) than does the silicon phase. A t least at some point during processing, the silicon phase is at temperature above its normal ductile/brittle transition temperature of about 500~C, and preferably above its melting point. The formed composite body containing the silicon phase is then cooled below its ductile/brittle transition. During cooking the ceramic phase shrinks more than does the silicon phase, thereby placing the latter in a state of compressive stress. By the time the composi te body has cooled to substantially ambient temperature, the induced compressiv e stress in the silicon phase is sufficient as to impart a measurable degree o f semi-ductile character to the silicon phase. This pseudo-ductility manifests itself in the composite body as a significant increase in the fracture toughness of the body. For example when the ceramic reinforcement of the carbide (which has a CTE similar to that of silicon), fracture toughness increased by almost30 percent.
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