Combustion and Material Characterization of Highly Tunable On‐Chip Energetic Porous Silicon

Abstract

AbstractWe present a comprehensive investigation into the tunable combustion of on‐chip porous silicon energetic materials. The exothermic reaction occurs between high surface area nanoscale porous silicon and a solution‐deposited sodium perchlorate oxidizer that penetrates each pore. The resulting burn rates spanned three orders of magnitude, from 5.2 to 1950 m s−1. Material properties of the porous silicon films were characterized using gas adsorption porosimetry, SEM, and profilometry, over specific surface areas between 191 and 901 m2 g−1, and porosities between 49 and 80 %. Combustion events were characterized using high speed imaging and bomb calorimetry. Results revealed that combustion depended on several material properties including surface area and porosity of the porous silicon substrate, with the peak flame speed occurring at 895 m2 g−1 specific surface area, 3.32 nm pore size, and 72 % porosity. Measured heat of combustion increased with porosity over the range of 65–75 %, up to 22.5 kJ g−1 of porous silicon at 75 % porosity. These measurements along with gravimetric determinations of oxidizer pore loading suggest that the system was typically fuel rich, with macroscopic morphology and porous silicon film mechanical integrity generally limiting the realistic range of porosity values to less than stoichiometric conditions.