Improving effect of boron carbide on the combustion and thermal oxidation characteristics of amorphous boron

Abstract

Boron carbide (B4C) is one of the main products from the primary combustion of boron (B)-based propellants and has a significant influence on the secondary combustion of B. To systematically evaluate its effects on the secondary combustion of B, mixtures of B4C and B in different mass ratios were prepared. To study the ignition temperatures and combustion flames of the samples, a xenon lamp ignition experimental system and a flame shape test system were designed, respectively. A thermogravimetry–differential scanning calorimetry–Fourier transform infrared spectroscopy combined thermal analysis system was used to study the thermal oxidation characteristics and analyze the gaseous products of the samples. The results indicate that B4C reduces the heat absorption at the beginning of the ignition, but subsequently prevents the rapid rise of sample temperature. During the stable combustion stage, the maximum flame length under optical density 10−4 (OD4) filter was 20.4 mm, and the maximum flame length under 580 nm + OD4 filters (represents the combustion of B element) was 16.7 mm. The samples contained a small amount of HBO2 and H3BO3, which led to slight mass loss during the low temperature section of the thermal oxidation process. During the high temperature section, the oxidation of B and B4C caused considerable mass gain. The gaseous products of the thermal oxidation process include CO2, CO, and H2O. In general, the B content of 60% was the most beneficial to decrease the oxidation temperature, increase the combustion intensity, and improve the heat-releasing ability of the samples.