Suppressing H₂ Evolution by Silicon Powder Dispersions

Abstract

Silicon dispersions in water are used to produce pyrotechnic time delay compositions. The propensity of the silicon to react with water and to produce hazardous hydrogen gas must be suppressed. To this end, the effect of surface modifications and medium pH on the rate of corrosion of silicon was studied at ambient temperature. It was found that the rate of hydrogen evolution increased with increasing pH. Silanes proved to be more effective silicon corrosion inhibitors than alcohols, with vinyl tris (2-methoxyethoxy) silane producing the best results. Differential thermal analysis (DTA) studies were performed using a near-stoichiometric amount of lead chromate as oxidant. Comparable combustion behavior was observed when both the fuel and the oxidant powders were either uncoated or silane modified. Mixtures of neat oxidant with silane-coated silicon showed poor burn behavior and this was attributed to poor particle–particle mixing due to the mismatch in surface energies.

Keywords:

• oxidation
• pyrotechnic
• silicon
• water

Acknowledgments

Financial support from the THRIP programme of the Department of Trade and Industry and the National Research Foundation as well as AEL is gratefully acknowledged.

Notes

^a Surface area coverage data supplied by manufacturer.