Barrier coated ceramic fiber and coating method
AssigneeThe Boeing Company
InventorsFrederick H. Simpson, Juris Verzemnieks
Life of this patent
Estimating the term…
Abstract
Oxide-based ceramic fibers are treated in a novel process to create a substantially uniform boron nitride barrier coating at their surface. The process includes the step of heating the fiber, preferably an aluminoborosilicate fiber like NEXTEL, for between about 5-90 minutes in a nitriding atmosphere of ammonia, hydrogen and nitrogen at a temperature of between about 2200.degree.-2600.degree. F. to diffuse boron from the fiber to the surface of the fiber where it reacts to form the boron nitride coating.
Claims24
A method for coating a ceramic fiber that contains boron with boron nitride comprising the step of heating the fiber in the presence of a nitriding atmosphere to diffuse boron in the fiber to the fiber surface without forming liquid boron oxide or boric acid that can degrade the fiber and to react the boron at the surface with a suitable source of nitrogen in the atmosphere, the reaction occuring at a temperature of at least about 2200.degree. F.
A method for forming a substantially uniform barrier coating about an oxide-based ceramic fiber in a fiber cloth, the fiber containing boron, comprising the steps of:
- (a) heating the fiber in the presence of a nitriding atmosphere at a temperature of between about 2200.degree.-2600.degree. F. to diffuse boron in the fiber to the surface of the fiber without forming liquid boron oxide or boric acid that can degrade the fiber;
- and
- (b) maintaining the temperature in the range for between about 5-90 minutes to react the boron at or near the surface with a reactive nitrogen source in the atmosphere to form a substantially uniform boron nitride coating on the surface of the fiber.
A method for forming a substantially uniform barrier coating about aluminoborosilicate ceramic fibers in a fiber cloth wherein the fiber contains boria, comprising the steps of:
- (a) heating the fibers to a temperature of about 2200.degree.-2600.degree. F. in the presence of a nitriding atmosphere that contains an effective amount of NH.sub.3, the heating causing boron in the fibers to diffuse to the fiber surface without forming liquid boron oxide or boric acid that can degrade the fiber;
- and
- (b) maintaining the temperature in the range for between about 5-90 minutes to allow formation of a substantially uniform barrier coating of boron nitride at each fiber surface in the cloth.
A method for coating a ceramic fiber that contains boron with a substantially uniform boron nitride comprising the step of exposing the uncoated fiber to a heated atmosphere containing ammonia at a temperature of about 2200.degree.-2600.degree. F. for about 5-90 minutes to cause boron in the fiber to diffuse to the surface and to react at or near the surface to form boron nitride without forming liquid boron oxide or boric acid.
Dependencies are inferred from the claim text.