Kinetics of Nano Titanium Dioxide Catalyzed Thermal Decomposition of Ammonium Nitrate and Ammonium Nitrate‐Based Composite Solid Propellant

Abstract

Abstract This study deals with the influence of nanosized titanium dioxide (TiO 2 ) catalysts on the decomposition kinetics of ammonium nitrate (AN) and ammonium nitrate‐based composite solid propellant. TiO 2 nanocatalyst with an average particle size of 10 nm was synthesized by sol‐gel method using titanium alkoxide as precursor. Formation of nanostructured TiO 2 and presence of its anatase and brookite phases was confirmed by powder X‐ray diffraction (PXRD) and selected area diffraction (SAED) studies. Nano TiO 2 was further characterized by transmission electron microscopy (TEM), infrared (IR) spectroscopy, and thermogravimetry. The catalytic effect of TiO 2 nanocatalysts on the solid state thermal decomposition reaction of AN and nonaluminized HTPB/AN propellant was evaluated. To ascertain the effectiveness of the TiO 2 nanocatalyst, the thermal kinetic constants for the catalytic and non‐catalytic decomposition of AN and AN propellant samples were computed by using a nonlinear integral isoconversional method. Catalytic influence was evident from the lowering of activation energy for the catalyzed decomposition reactions. Apparently, the nanocatalysts provide Lewis acid and/or active metal sites, facilitating the removal of AN dissociation products NH 3 and HNO 3 and thereby enhance the rate of decomposition. The changes in the critical temperature of thermal explosion of AN and AN propellant samples due to the addition of TiO 2 nanocatalyst were also computed and the possible reasons for the changes are discussed.