Concerted Effects of Cobalt Nitrate Hexahydrate on Ammonium Nitrate/Ammonium Perchlorate Dual Oxidizer‐Based Composite Solid Propellants

ABSTRACT

Ammonium nitrate (AN) is a prominent environment‐friendly oxidizer, but it suffers from drawbacks such as combustion instability, hygroscopicity, and phase transitions at room temperature. To address these challenges, an extensive, combined theoretical and experimental study was performed on ammonium‐nitrate/ammonium‐perchlorate (AN/AP) composite solid propellants to assess the impact of a dual‐oxidizer formulation containing AN and AP with cobalt nitrate hexahydrate (CNH) as a catalytic additive. Propellant formulations were evaluated using NASA CEA thermochemical calculations, x‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high‐pressure burn‐rate tests, mechanical characterization (including Young's modulus), density measurements, heat‐of‐combustion determinations, chloride‐ion analysis, and detailed kinetic modeling. The optimized AN/AP/CNH formulation exhibited a 1419.87% increase in burn rate at 4.14 MPa and a 24.85% increase in Young's modulus relative to pure AN‐based propellant. Addition of CNH to the dual‐oxidizer matrix also reduced the experimentally measured chloride content by 22.8% compared with AP‐only propellants. Thermal decomposition kinetic analysis showed that the activation energy was also drastically decreased with CNH, showing that their decomposition behavior is improved. Based on the overall results, it is concluded that the combined incorporation of AP and CNH is associated with improved ballistic, thermo‐mechanical, and combustion performance of AN‐based propellants, which makes it promising for high‐performance solid rocket applications with reduced toxicity.