In-situ heteroatoms stabilization of zero-dimensional boron nanospheres for high-energy nanofluid fuels combustion enhancement

Since boron powder has the highest volume energy density, it has long been desired for use as fuel in aerospace and other fields. However, boron has poor ignition performance and low combustion efficiency due to uneven microstructure and oxide layers of boron. Here, we report a facile strategy to prepare zero-dimensional boron nanospheres from micrometer-scale amorphous boron through ultrasound-assisted in-situ stabilization of heteroatoms for inhibition of boron oxide layer by using hexachlorocyclotriphosphazene (HCCP) and 4,4′-sulfonyldiphenol (BPS) polycondensation and carbonization. The diameter of the obtained boron nanospheres was in the range of 500–800 nm, which is the smallest reported diameter of regular boron nanoparticles. The initial reaction temperature of CPZS@B-1.0 decreased from 791.1 to 641.7 °C, and the ignition delay time of 20 wt% CPZS@B-1.0/RP-3 nanofluid fuel decreased to 393 ms. The addition of CPZS@B promoted RP-3 oxidation at both low temperatures (<200 °C) and high temperatures (>200 °C) by in-situ FTIR analysis. Notably, the prepared zero-dimensional nano-boron exhibited removal of surface oxidation and complete combustion degree (from 42.06 % to 80.36 %). This work provides a new method for the preparation of nano-boron and a solution for increasing the fuel energy density of hydrocarbon fuels.