Dow Corning Corporation

Jonathan Lipowitz

James A Rabe

Duane R Bujalski

Paul P Lu

Robert E Kalinowski

William H Atwell

David C DeLeeuw

Gary E LeGrow

Kimmai Thi Nguyen

Thomas Duncan Barnard

Thomas F Lim

Richard E Jones

Eric Jude Joffre

John C Saam

Kai Su

James R Falender

Chandan K Saha

Donald M Bartos

Gary E Le Grow

Gregg Alan Zank

Patrick J Harder

Neal Roger Langley

David Charles Deleeuw

Chi-Tang Li

Harvey A Freeman

Sheryl A Bowman

A process for producing polycrystalline silicon carbide by heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor

A process for producing polycrystalline silicon carbide includes heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

Process to produce silicon carbide fibers using a controlled

The present invention relates to a method for preparing a ceramic fiber from alkenyl or alkynyl functional resins and to the ceramic fibers produced therefrom. The method comprises (A) forming a fiber from a siloxane resin comprised of R.sup.1.sub.a R.sup.2.sub.b RSiO.sub.(3-a-b)/2 units wherein R is an unsaturated carbon group; each R.sup.1 is selected from the group consisting essentially of an aryl group having from 6 to 10 carbon atoms and functional derivatives thereof; each R.sup.2 is selected from the group consisting essentially of an alkyl group having from 1 to 4 carbon atoms and functional derivatives thereof; a has a value of 0, 1 or 2; b has a value of 0, 1, or 2 with the proviso that a+b &lt;2; (B) curing the fiber by exposing the fiber to high energy radiation to render it non-fusible; and (C) heating the non-fusible fiber in an inert environment to a temperature above about 800.degree. C. to convert it to a ceramic fiber.

Amorphous silicon oxycarbide and crystalline silicon carbide fibers from

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

Disclosed is a process for the formation of silicon carbide powder in which vaporized polysiloxanes are reacted and pyrolyzed in a single heating step to form the silicon carbide powder. The process is simple and inexpensive and yields powder having desirable characteristics.

Process for preparing silicon carbide powder from vaporized polysiloxanes

This invention relates to the preparation of polycrystalline silicon carbide fibers from ceramic fiber. The process involves heating the ceramic fiber in an environment containing a volatile sintering aid to a temperature sufficient to convert the ceramic fiber to the polycrystalline silicon carbide fiber.

Polycrystalline silicon carbide fibers

This invention relates to the preparation of polycrystalline silicon carbide fibers from ceramic fibers. The process involves heating the ceramic fiber in an environment containing a volatile sintering aid to a temperature sufficient to convert the ceramic fiber to the polycrystalline silicon carbide fiber.

Preparation of polycrystalline ceramic fibers

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 methylpolydisilylazane 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/cc. 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.

The present invention relates to ceramic fibers of the Si-C-N-O series with a diameter less than about 20 micrometers. It has been unexpectedly found that the thermal stability of these fibers can be increased by minimizing the impurity content, primarily the content of metals or metallic compounds. Such fibers with low levels of contaminants retain greater than about 60 percent of their initial tensile strength when subjected to temperatures of 1300.degree.-1400.degree. C. for at least 30 minutes in a non-oxidative environment.

Polymer derived ceramic fibers having improved thermal stability

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.

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.

The elastic modulus and density of an amorphous, ceramic article derived from a resinous organosilicon polymer and having a composition consisting essentially of silicon, nitrogen and/or carbon are increased while substantially maintaining or improving tensile strength by heat treating the ceramic article at an elevated temperature under superatmospheric nitrogen pressure to increase its density while avoiding crystallization. During heat treatment, at least some of the conditions of time, temperature, heating rate, cooling rate, pressure and atmosphere are controlled to minimize erosion of the article which could otherwise occur due to the loss to the surrounding atmosphere, as a gas or gaseous component, of at least one of nitrogen, silicon and carbon. The heat treated, ceramic article is amorphous and non-crystalline and has a density substantially greater than 2.5 g/cc together with desirable values of tensile strength and elastic modulus.

Method for densification of amorphous ceramic material

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.

Growing community of inventors

Midland, MI, United States of America

Jonathan Lipowitz