The present approach relates to the fabrication of a composite material via a multi-step heating process. In one heating stage an internal region of a preform is heated by application of electro-magnetic radiation. In another heating stage, a region near the surface of the preform is heated from the exterior inward.

A method of preparing a boron nitride material, such as boron nitride (BN) or boron carbonitride (BCN), is provided. The method may include providing a substrate, and sublimating an amine borane complex onto the substrate to obtain the boron nitride material. The amine borane complex may include, but is not limited to, borazine, amino borane, trimethylamine borane and triethylamine borane. In addition, the temperature at which the sublimating is carried out may be varied to control composition of the boron nitride material formed. In addition, various morphologies can be obtained by using the present method, namely films, nanotubes and porous foam.