Combustion Characteristics of Boron-Iron Powder with Micro-Zone Compounding

Boron-iron composite powders with a D50 value of < 0.5 mu m and iron contents of 5, 10, and 20 wt.% were prepared via a combination of electro-explosive and roll-grinding methods. High-resolution transmission electron microscopy and electron probe X-ray microanalysis revealed evidence of boron-ion micro-zone composites. Ignition tests using a 150-W laser in a pure oxygen atmosphere indicated that the boron-iron composite powder effectively reduced the ignition delay of boron (224.8 ms), with 5 wt.% boron-iron composite powder exhibiting a reduced ignition delay of 106.1 ms. Thermal analysis tests in a pure oxygen atmosphere indicated that iron not only promoted the exothermic reaction of boron but also significantly promoted its oxidation. A comparison of the oxygen bomb calorific values of the composite powder, the original boron powder, and simple mixed powder revealed that the simple mixed iron did not improve the combustion performance of boron, whereas the composite powder generally improved the boron calorific value (12967 J/g), with the 10 wt.% boron-iron composite powder exhibiting a boron calorific value of 21,189 J/g. The addition of iron improved the combustion behavior, stabilized the combustion flame, and improved the combustion quality. An elevated iron content resulted in an increased sensitivity of the powder to the ambient pressure, and an elevated pressure effectively increased the burning rate. The experimental results indicated that iron generally improved the ignition and combustion performance of boron with low and high iron contents, respectively.