Dow Corning Corporation

Paul P Lu

Jonathan Lipowitz

James A Rabe

David C DeLeeuw

Gregg A Zank

Gary T Burns

David Charles Deleeuw

A process for the preparation of substantially polycrystalline silicon carbide fibers is provided. The fibers may be fabricated to have a small diameter and are thermally stable at high temperatures. The process is carried out by initially forming fibers from a preceramic polymeric precursor comprising methylpolysilane 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 by the process of the present invention 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.

Preparation of substantially polycrystalline silicon carbide fibers from

This invention relates to the preparation of thermally stable, substantially polycrystalline silicon carbide ceramic fibers derived from a polycarbosilane resin. The unexpected thermal stability of these fibers is achieved by the incorporation of boron prior to ceramification.

Polycrystalline silicon carbide fibers

Preparation of substantially crystalline silicon carbide fibers from

A rapid method of infusibilizing (curing) preceramic polymers comprising treatment said polymers with gaseous nitrogen dioxide. The infusibilized polymers may be pyrolyzed to temperatures in excess of about 800.degree. C. to yield ceramic materials with low oxygen content and, thus, good thermal stability. The methods are especially useful for the production of ceramic fibers and, more specifically, to the on-line production of ceramic fibers.

Curing preceramic polymers by exposure to nitrogen dioxide

A method is disclosed for the preparation of ceramic materials or articles by the pyrolysis of preceramic polymers wherein the preceramic polymers are rendered infusible prior to pyrolysis by exposure to gaseous nitric oxide. Ceramic materials with low oxygen content, excellent physical properties, and good thermal stability can be obtained by the practice of this invention. This method is especially suited for the preparation of ceramic fibers.

Infusible preceramic polymers via nitric oxide treatment

Halogenated polycarbosilanes are prepared by reacting a polycarbosilane containing at least 0.1 weight percent Si-H groups with a halogenating reagent selected from the group consisting of chlorine, bromine, phosphorous pentachloride, phosphorous pentabromide, antimony pentachloride, N-chlorosuccinimide, N-bromosuccinimide, sulfonyl chloride, and mixtures of CH.sub.e X.sub.f and a free radical initiator where e is 0 or 1, f is 3 or 4, the sum (e+f) is 4, and X is chlorine or bromine. The halogenated polycarbosilanes can be further treated to produce other derivatized polycarbosilanes. The halogenated and derivatized polycarbosilanes can be converted to silicon carbide-containing ceramic materials by pyrolysis at elevated temperatures under an inert atmosphere.

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Hacienda Heights, CA, United States of America

Paul P Lu