Boron has a promising application in the field of propellants due to its high calorific value. However, the difficulty of ignition and the poor combustion efficiency of boron (B) have severely limited its efficient application. In response to this issue, this paper proposes to improve the ignition and combustion performance of micron-sized boron by the Polyvinylidene Fluoride (PVDF) coating. The effect of PVDF content on the B combustion performance was systematically studied using a Thermogravimetry-Differential Scanning Calorimetry (TG-DSC), a Transmission Electron Microscope (TEM), an X-Ray Diffractometer (XRD), a laser Particle Size Analyzer (PSA), and a high-speed camera. The results show that PVDF can significantly reduce the initial oxidation temperature of B powder and increase its reaction heat. When the PVDF content is 23wt%, the reaction heat and the combustion intensity of B powder reach the maximum and are significantly higher than those of the uncoated B powder. Moreover, the fluorination reaction that occurs during the combustion process not only can effectively shorten the combustion time of B powder, but also has a positive effect on its flame intensity and propagation speed, and it significantly reduces B particle agglomeration, which improves the combustion efficiency significantly. This study lays the foundation for the application of PVDF modified B in B-based solid propellants.

This paper presents how the combustion performance of nano-sized aluminum (nAl) powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.