Characterization of Porous Silicon for Micropyrotechinc Applications

The high reactivity of nanoscale composites can be exploited to form a new class of energetic materials known as nanoenergetic materials. Porous silicon is a nanoenergetic material that can store more energy than conventional energetic materials and can be used in innovative ways to tailor the release of this energy. This material attracts the attention of many researchers due to the possibility of developing PS based devices. Due to its high energy density, PS can be integrated into microscale devices as an on-board energy source and such integration is known as micropyrotechnics. Porous silicon is formed by electrochemical dissolution of selective atoms in hydrofluoric acid based electrolytes, which results in high surface areas ̴ 1000 m²/g. The pore morphology is strongly affected by the etch parameters such as electrolyte composition, current density, etch duration and also the substrate properties such as dopant type and concentration. The changes in the porous structure strongly affect the reactive properties of energetic composites formed. Flame propagation speeds were found to be up to three orders of magnitude due to variation in the porous structure. The goal of this project is to etch and characterize the porous layers formed on substrates with different dopant types and concentrations. This information will be used to adjust the etch parameters to yield samples with specific porous layer structure which will enable a parametric study of the flame propagation to understand the important physical effects and help formulate models to explain how the propagation rates can be tuned.