Preparation of substantially polycrystalline silicon carbide fib

Details Preparation of substantially polycrystalline silicon carbide fib Preparation of substantially polycrystalline silicon carbide fib

1991-01-31

1992-12-01

Lorin, Hubert C.

Plastic and nonmetallic article shaping or treating: processes

Carbonizing to form article

Agglomeration or accretion

264 25, 264 292, 264 296, 264 56, 264 83, 264184, 264205, 26421115, 26421116, 26421117, 501 95, D01F 910

Patent

active

051678810

ABSTRACT:
A process for the preparation of substantially polycrystalline silicon carbide fibers are provided. The fibers may be fabricated to have a small diameter and are thermally stable at high temperature. The process is carried out by initially forming fibers from a preceramic polymeric precursor comprising phenyl-containing polyorganosiloxane resins. The fibers are then infusibilized to render them nonmelting followed by a pyrolysis step in which the fibers are heated to a temperature in excess of 1600.degree. C. in a nonoxidizing atmosphere to form substantially polycrystalline silicon carbide fibers. The substantially polycrystalline silicon carbide fibers which are formed have at least 75% crystallinity and have a density of at least about 2.9 gm/cm.sup.3. The polymeric precursor or the fibers contain, or have incorporated therein, at least about 0.2 % by weight boron. This incorporation of boron may be accomplished either prior to or during formation of the fibers or during at least one of the infusibilizing or pyrolyzing steps of the process.

REFERENCES:
patent: 3971840 (1976-07-01), Economy et al.
patent: 4424145 (1984-01-01), Sara
patent: 4904424 (1990-02-01), Johnson

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