Insight into combustion characteristics of micro- and nano-sized boron carbide

The combustion characteristics of micro- and nano-sized boron carbide (B4C) powders were investigated to exploit the role of carbon atoms on combustion. Various combustion parameters had been evaluated for B4C powders. Results demonstrated a direct correlation between the gas oxide of carbon atoms with the morphology of condensed combustion products. The thrust generated when the gas diffused from the B4C matrix to the environment could not only disperse the burning B4C powder, but also break through the liquid oxide layer and leave holes on the surface of micro-sized B4C. The formed holes on the surface were considered oxygen diffusion channels to the interior of B4C particle, which accelerated the mass transfer rate and improved the oxidation efficiency. The evolution images of confined combustion and the characterizations of condensed combustion products suggested that the B4C powder released most of energy potential after stable combustion and transformed into boron oxide. Given the combustion process, the B4C powders exhibited the higher combustion heat and the larger peak area of combustion pressure than boron powders with similar diameter distribution, and the B4C powders in nano-sized generated strongest energy output among all samples.