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    • 4. 发明公开
    • SINTERED SILICON NITRIDE OF HIGH TOUGHNESS, STRENGTH AND RELIABILITY
    • 烧结氮化硅高韧性,强度和可靠性。
    • EP0636112A1
    • 1995-02-01
    • EP93909491.0
    • 1993-04-08
    • AlliedSignal Inc.
    • LI, Chien-WeiGOLDACKER, Jeffrey, A.
    • C04B35
    • C04B35/806C04B35/5935
    • A silicon nitride sintered body has a composition consisting essentially of 85 to 94 % by weight beta silicon nitride, 6 to 15 % by weight grain boundary phase consisting essentially of (i) at least two rare earth elements, wherein yttrium is considered a rare earth, and, optionally, strontium which, calculated as SrO, is 0 to 2 percent by weight of the total body, and (ii) at least two of Si, N, O and C, and an additive consisting essentially of a metal carbon compound present in the amount of about 0.2 to 3.5 % by volume. The additive is substantially homogeneously dispersed within the sintered body. The sintered body has a microstructure wherein (i) the beta silicon nitride grains are acicular and have an average grain width ranging from 0.5 to 1.5 mu m, (ii) at least 25 % of the grains have width greater than 0.7 mu m, and at least 10 % of the grains have width greater than 1 mu m, and (iii) no more than 5 % of grains have width greater than 3.5 mu m and apparent aspect ratio greater than 5, with the proviso that the average aspect ratio is at least 1.8 and a fracture origin, at least 90 % of which is comprised of large acicular beta Si3N4 grains, the average size of which ranges from about 15 to 50 mu m. Such a ceramic has high strength, high toughness and long term durability, and is especially suited for industrial applications such as components for gas turbine and automotive engines.