PRODUCTION OF BN COMPOSITE MATERIALS

The invention comprises a process comprising infiltrating or infiltrating and coating a substrate with a boron comprising precursor and contacting the boron comprising precursor with a nitrogen comprising reactant to convert the boron comprising precursor to BN or other a boron nitrogen reaction product in the surface porosity or in the surface porosity and on the surface of the substrate. Composite materials comprising as one phase a substrate and BN or other a boron nitrogen reaction product as a further phase in surface porosity or in surface porosity and on a surface of the substrate are claimed.