A Metal Inorganic Framework Designed as a Propellant Burn Rate Modifier

Abstract

The kinetics of a strategically synthesized burn rate enhancer (BRE) are investigated in its reaction with ammonium perchlorate (AP). The BRE is designed for multifunctionality by 1) producing reactive gases that couple with AP gas production; 2) trapping reactive gases with high surface area; and 3) exposing metal cations to incite exothermic reactions at a temperature coincident with AP decomposition. This study advances inorganic synthesis by introducing a metal inorganic framework (MIF) composed of an aluminum cation (Al+3) surrounded by inorganic “linker” molecules of oxidizing species. To increase surface area, a porous, amorphous MIF (a‐MIF) is synthesized by controlling solution properties of an acid–base precipitation reaction. Upon gas generation, high surface area and aluminum‐rich surface of a‐MIF accelerate AP decomposition and induce an exothermic reaction that is otherwise endothermic in thermal equilibrium analysis. AP decomposition rate is advanced by reducing peak onset temperature and increasing decomposition rate with addition of a‐MIF (i.e., from 17% min−1 at 401 °C to 18% min−1 at 365 °C). Enthalpy of AP decomposition increases from +240 J g−1 to −1040 J g−1. Results introduce an approach for increasing the decomposition rate of solid oxidizers by demonstrating a recipe for designing and synthesizing an MIF.