  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.
