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Filament-containing composite

  • US 5,330,854 A
  • Filed: 09/24/1987
  • Issued: 07/19/1994
  • Est. Priority Date: 09/24/1987
  • Status: Expired due to Fees
First Claim
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1. A process for producing a composite with a porosity of less than about 10% by volume comprised of boron nitride-coated filaments and a matrix phase, said filament component of said coated filaments comprising at least about 10% by volume of the composite, said matrix phase containing silicon carbide formed in situ in an amount of at least about 5% by volume of the composite and elemental silicon in an amount of at least about 1% by volume of the composite, which comprises the following steps:

  • (a) providing a filament selected from the group consisting of elemental carbon, a SiC-containing material containing at least about 50% by weight silicon and at least about 25% by weight carbon, and a combination thereof, said filament having a diameter of at least about 50 microns;

    (b) depositing a coating of boron nitride on said filament leaving no significant portion thereof exposed;

    (c) providing infiltration-promoting material in the form of particulates and/or fibers, said infiltration-promoting material containing elemental carbon;

    (d) contacting a plurality of said boron nitride-coated filaments with said infiltration-promoting material to produce a preform wherein said infiltration-promoting material envelops each coated filament preventing contact therebetween and wherein said coated filaments are at least substantially parallel to each other, said preform having an open porosity ranging from about 25% by volume to about 85% by volume of the preform;

    (e) contacting said preform with silicon-associated infiltrating means whereby said silicon is infiltrated into said preform;

    (f) heating the resulting structure in a partial vacuum to a temperature at which said silicon is molten and infiltrating said molten silicon into said preform to produce an infiltrated product having the composition of said composite, said preform containing sufficient elemental carbon to react with said silicon to form said composite, said partial vacuum being at least sufficient to remove gas from said preform so as to allow said molten silicon to infiltrate said preform; and

    (g) cooling said product to produce said composite, said boron nitride-coated filaments being enveloped by said infiltration-promoting material to enable said infiltration by molten silicon.

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