| 摘要 |
<p>A fully densified, self-reinforced silicon nitride ceramic body of high fracture toughness and high fracture strength is disclosed comprising (a) β-silicon nitride in the form of whiskers having an average aspect ratio of at least 2.5, and (b) a crystalline grain boundary phase having an oxynitride apatite structure, as determined by X-ray crystallography. A process for preparing the above-identified silicon nitride body comprises hot-pressing a powder mixture containing silicon nitride; silica; a densification aid including strontium oxide; a conversion aid, such as, yttrium oxide; and a compound, such as, calcium oxide which enhances growth of β-silicon nitride whiskers, under conditions such that densification and the in situ formation of β-silicon nitride whiskers having a high aspect ratio occur, and thereafter annealing the densified composition for a time sufficient to produce a crystalline grain boundary phase having an oxynitride apatite structure.</p> |
