Preparation of substantially polycrystalline silicon carbide fibers from polyorganosiloxanes

US5167881A · kind A · utility

Assignee

• Dow Corning Corporation · US

Inventors

• William H. Atwell · Midland, US
• Duane R. Bujalski · Auburn, US
• Eric Jude Joffre · Midland, US
• Gary E. LeGrow · Midland, US
• Jonathan Lipowitz · Midland, US
• James A. Rabe · Midland, US

Key dates

• Filing date: Jan 31, 1991
• Grant date: Dec 1, 1992
• Expiry date: Jan 31, 2011

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C04B35/571
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

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.