1Suppressing H2 Evolution by Silicon Powder Dispersions

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 were 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. DTA studies were performed using a near-stoichiometric amount of lead chromate as oxidant. Comparable combustion behaviour 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 behaviour and this was attributed to poor particle-particle mixing owing to the mismatch in surface energies