Formation of condensed products during combustion of boron-based high-energy compositions

The methods and results of measuring the burning rate and quenching and sampling of the condensed combustion products (CCPs) near the combustion surface for high-energy compositions (HECs), containing various dispersed boron-based fuels as B, Al/B mixture, AlB 2 , and AlB 12 , are presented. The sampling of the CCPs formed during the combustion of HEC sample was carried out in a constant-pressure cylindrical flow chamber with a filter system. It was found that at a chamber pressure of 4 MPa, the highest burning rate is typical for HECs with B and mixture Al/B powder due to their higher specific surface area and particle reactivity. For HECs with AlB 2 and AlB 12 , the burning rate is 10% lower than the maximum rate. The combustion of the boron particles or a mixture of Al and B particles in the HEC reaction layer is accompanied by conglomeration, which increases the average particle size of CCPs by 5.5–6.5 times compared to the initial average particle size of the dispersed metal fuel. During combustion of the AlB 2 and AlB 12 particles, both simple and complex (5Al 2 O 3 ·B 2 O 3 , borate) crystalline oxides are formed in the surface reaction layer of the HEC. The proportion of fine oxide particles increases, while the average size of the CCP particles is 6.6 µm and 9.4 μm, respectively.