Improving the Energy Characteristics of Aluminum Diboride and Increasing the Safety of Its Use by Producing Microcapsules with a Fluoropolymer
J.-F. Wang1, Z.-Q. Qin1, Y.-P. Ou1, Q.-J. Jiao1, T. Yan2
1School of Mechatronical Engineering, Beijing Institute of Technology, Beijing, China
2College of Aerospace and Civil Engineering, Harbin Engineering University, Harbin, China
Keywords: aluminum diboride, core-shell structure, metallic fuel, ignition and combustion
Abstract
Aluminum diboride (AlB2) microcapsules coated with polyvinylidene difluoride (PVDF), fabricated by a simple rotary evaporation method, were studied. According to the morphology study, PVDF forms an intact outer shell on the surface of each individual AlB2 particle. Compared with uncoated AlB2, the AlB2@PVDF microcapsule has a shorter ignition time, more intense combustion, and faster pressure build-up. At an appropriate PVDF content, the measured heat of combustion is higher than that of the composition with unencapsulated AlB2, due to a higher heat release efficiency during combustion --- 92.3% (the efficiency of the composition with unencapsulated AlB2 is 85.2%). Mechanistic study shows that the PVDF decomposition product likely accelerates the oxidation of AlB2 at several reaction stages, providing higher reactivity of the AlB2@PVDF microcapsules. The use of AlB2@PVDF in explosives increases density, detonation velocity, and heat release with good component compatibility, while maintaining acceptable mechanical sensitivity. Therefore, AlB2@PVDF microcapsules are a promising metallic fuel in composite energetic materials.
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