Effect of metal ultrafine powders on the HEM combustion characteristics

The results of thermodynamic calculations and experimental study of metal additive effect on the combustion characteristics of high-energy materials based on ammonium perchlorate, butadiene rubber and aluminum powder are presented in this paper. It is found that partial or complete replacement of aluminum by metal additives (B, Mg, AlB$_2$, Al/Mg, Cu, Fe, Ti and Zr) in the HEM composition leads to a reduction in the specific impulse values and the combustion temperature. It was shown that the partial replacement of Alex aluminum by iron UFP in HEM leads to 1.3–1.4 fold increase in the burning rate in the pressure range of 2.2–7.5 MPa. Thus some agglomeration of metal fuel is enhanced: the mean particle diameter of agglomerates is increased up to 1.2 fold, and their content is increased up to 1.4 fold. Upon partial replacement of Alex by boron UFP the burning rate is practically unchanged as compared with that for basic propellant with Alex. However the agglomeration is significantly enhanced, which is manifested at the increase in the agglomerate particles content in CCPs by 1.8–2.2 times, increase by 1.6–1.7 times in the agglomerates mean diameter and increase in the unburned metal fraction in agglomerates by 1.6–1.9 times. The content and the mean diameter of the oxide particles are reduced more significantly than in the case of iron introduction, namely, by 20–30 % and 30–40 %, respectively.