Method of forming in-situ boron nitride for ceramic matrix composite environmental protection

1. A method for forming in situ a boron nitride reaction product locally on a reinforcement phase of a ceramic matrix composite material, said method comprising:

providing a ceramic matrix composite material having a fiber reinforcement material;

providing a B4C material and a Si3N4 material and depositing a layer of said B4C material and a layer of said Si3N4 material on said fiber reinforcement material wherein said layer of said B4C material and said layer of said Si3N4 material are deposited sequentially; and

heating said B4C material and said Si3N4 material to a temperature above 1200 degrees Centigrade to form a hexagonal boron nitride reaction product in situ on the fiber reinforcement material by the reaction between B4C and Si3N4.

2. The method of claim 1 , wherein said forming step comprises forming said layer of boron nitride solely on a surface of the fiber reinforcement material.

3. The method of claim 1 , wherein said forming step comprises forming said layer of boron nitride so that said layer of boron nitride solely surrounds the fiber reinforcement material.

4. The method of claim 1 , wherein said providing step comprises providing a silicon based ceramic matrix composite material having a plurality of silicon based reinforcement fibers.

5. The method of claim 4 , wherein said providing step comprises providing said silicon based ceramic matrix composite material with a plurality of fibers selected from the group consisting of silicon carbide (SiC), Si—C—O, Si—N—C—O, Si—B—C—N, carbon, aluminum oxide, zirconium oxide, glass, mullite, and silicon nitride fibers.

6. The method of claim 1 , wherein said heating step comprises heating to a temperature in the range of from 1400 degrees Centigrade to 1500 degrees Centigrade to form said boron nitride reaction product.