Science and Technology of Energetic Materials

Vol.62, No.1 (2001)

Research paper

Effect of coating on the reactivity of boron powder
Hidetsugu Nakamura, Osamu Nakazono, Miyako Akiyoshi,
and Yasutake Hara


Thermal analysis and combustion experiments were carried out to study the effect of the surface properties of boron on the thermal reaction and combustion reaction of boron and its mixture with potassium nitrate.The obtained results are as follows.
Boron powder was not completely oxidized in air because of its stable oxide layer on the suface. Fluororesin - coated boron underwent oxidation at a lower temperature, but showed a smaller fractional oxidation. Uncoated boron had a large hygroscopicity and formed boric acid if in contact with moisture. Surface coated - boron prevented the absorption of water.
The thermal reactivity and ignitability of boron - potassium nitrate mixtures were different with the composition and species of boron. Boron - rich condition caused higher thermal reactivity. The mixture that contained fluororesin - coated boron showed a lower initiation temperature of the exothermic reaction and ignition temperature than the other ones. The coating caused decrease in the linear burning rate and the drop hammer sensitivity of the mixture. For electrostatic sensitivity, the fluororesin coated - boron containing mixtures had a lower sensitivity and the epoxy resin coating showed a higher sensitivity compared to the mixture containing uncoated boron.

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