The Preparation Of Nano Porous Silicon And Its Application In Energetic Materials Field

The nano porous silicon is a kind of base material which haveporous structure on the surface. Since its invention in the last century, porous silicon had been widely applied in electronic components, light-emitting component, biosensor and mems energetic equipment. It was Prof. Bard who first discovered the explosion at low temperature of porous silicon. After that, the porous silicon has been considered as a kind of new materials was being used in energetic materials field.In this paper, the nano porous silicon particle was prepared from polycrystalline silicon powder by chemical etching. The adsorption-desorption technique, scanning electron microscopy, thermal gravity-differential scanning calorimetry and X-ray diffraction were used to evaluate the structure and surface functional groups. The effects of the concentration of HNO3, etching time and particle diameter of silicon powder on the physiochemical properties upon the nPS were investigated, then the optimal synthesized conditions were studied in the experiments. The composite energetic material was prepared with NaC104 as oxidizer and porous silicon as agents, the flame temperature was tested by thermal mapper and thetest of DSC-TG reveal the combustion mechanisms.nPS/BaCrO4delay composition was prepared by coprecipitation and the burning rates of delay compositions was measured. These concrete works are the following:(1) The SEM showed that after chemical etching there were lots of nano size pores on the surface of the nPS powder.Itsspecific surface area of was increased greatly, and there were lots of hydrogen bonds on its surface.The nitric acid concentration was the major factor for affecting the size and the distribution of pore diameter. Specific surface area couled be increased with the increasing of etching time and the reduction of particle size of Si powder. The optimum preparation were obtained through experiments.Thermal analysis data show that the Si-Hx bonds were oxidized at 400℃ on the condition of enough oxygen.(2) nPS/NaClO4 composite energetic material (in ratio of 1:1)was parepared by ultrasound filling technique.The phenomenon of deflagration was occurred during combustion of nPS/NaC104. Compared with the Si/NaC104 composite, the combustion mechanism of nPS/NaC104 was analyzed using the DSC-TG technology, which was proved rationality by X-ray diffractometer of combustion product.(3) Compared with Si/NaClO4, the flame sensitivity of nPS/NaClO4 unchanged, but the friction sensitivity enhanced by 63.6% than Si/NaClO4 and the impact sensitivity reduced by 60%.(4) nPS/BaCrO4 delay composition was prepared by coprecipitation.Based on the zero oxygen balance, five formulas were chosen. The NH3H2O as pH regulator could effectively improve the mass fraction of the BaCrO4.The new type of microchannel combustion abrasive was designed and the burning rate of five formulas were tested at 20℃.The test result showed that at a mixing weight ratio(the weight of nPS to BaCrCO4) of 22/78, the best delay precision was obtained.(5) After stabilized at high temperature, the composition was not changed but the partial Si-Hx bonds were replaced by Si-O bonds. The result indicated that,the delay precision had been increased through the stabilized and the influencing extend of the burning rate on the environment temperature was reduced.