Combustion synthesis and effect of LaMnO3 and LaOCl powder mixture on HMX thermal decomposition

LaOCl powder mixture and perovskite-type LaMnO3 were prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. LaOCl powder mixture was a mixture of LaOCl and significant amounts of amorphous materials. When heated at 973.15 K, the mixture was found to be converted into single-phase perovskite-type LaMnO3. The catalytic activities of LaOCl powder mixture and LaMnO3 were investigated for octahydro-1,3.5,7-tetranitto-1,3,5,7-tetrazociine (HMX) thermal decomposition by thermal gravity (TC) and thermogravimetry-evolved gas analysis (TC-EGA) techniques. The experimental results show that both the mixture and LaMnO3 have catalytic activities for the thermal decomposition of HMX, and LaOCl powder mixture has much higher catalytic activity than LaMnO3 on the early stages of HMX thermal decomposition. That could be attributed to the higher surface adsorption oxygen (O-ad) and hydroxyl as well as its high specific Surface area. LaMnO3 can obviously reduce activation energy of HMX thermal decomposition than LaOCl powder mixture. This may be due to its catalytic activity on the oxidation reaction of CO and the reaction between CO and NO during HMX thermal decomposition. (C) 2009 Elsevier B.V. All rights reserved.