Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent

A 3 nm coronene coating and a 4 nm amorphous carbon coating with uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process, where coronene is directly mixing with boron particles without a solvent, and heated at 520 {\deg}C for 1 h or at 630 {\deg}C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and inside agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method is possibly applied to many other powders, thus it has potential applications in many fields with low cost.