Full Paper Nanocrystalline Transition Metal Oxides as Catalysts in the Thermal Decomposition of Ammonium Perchlorate Inder Pal Singh Kapoor, Pratibha Srivastava, Gurdip Singh* Department of Chemistry, DDU Gorakhpur University, Gorakhpur-273 009, India Received: April 11, 2008; revised version: July 12, 2008 DOI: 10.1002/prep.200800025 Abstract Nanocrystalline transition metal oxides (NTMOs) have been successfully prepared by three different methods: novel quick precipitation method (Cr 2 O 3 and Fe 2 O 3 ); surfactant mediated method (CuO), and reduction of metal complexes with hydrazine as reducing agent (Mn 2 O 3 ). The nano particles have been characterized by X-ray diffraction (XRD) which shows an average particle diameter of 35 – 54 nm. Their catalytic activity was measured in the thermal decomposition of ammonium perchlo- rate (AP). AP decomposition undergoes a two step process where the addition of metal oxide nanocrystals led to a shifting of the high temperature decomposition peak toward lower temperature. The kinetics of the thermal decomposition of AP and catalyzed AP has also been evaluated using model fitting and isoconver- sional method. Keywords: Ammonium Perchlorate, Catalytic Activity, Metal Oxide, Thermal Decomposition 1 Introduction Powders with particles of uniform shape and narrow size distribution lying in the nanometer range have been shown to possess interesting properties. Nanoscale metal oxide particles are gaining increasing technical importance for classical areas of application such as catalysts, passive electronic components, or ceramic materials [1]. At present, preparation methods of nanosized transition metal oxides comprise solid state reaction, thermal decomposition of metal salts, mechanical milling of commercial powders, sol – gel method, hydrothermal process, and others [2 – 4]. Never- theless, most methods reported for the preparation of nanocrystalline transition metal oxides (NTMOs) required large amounts of organic solvents and expensive ultrasonic equipment. It is preferred to have very easy and low cost preparative methods for NTMOs. In the present communi- cation, we systematically studied the preparation of oxides of first row transition metals using three different methods such as a novel quick precipitation method, reduction of metal complexes in aqueous solution at low temperature with hydrazine as the reducing agent, and a surfactant- mediated method. Ammonium perchlorate (AP) is the most common oxidizer in composite solid propellants (CSPs). Thermal decomposition characteristics of AP influence the combus- tion behavior of the propellants. The catalytic thermal decomposition of AP is remarkably sensitive to metal oxide additives [5 – 11]. Several researchers have studied the surface structure of solid catalysts with particular reference to the identification of the active sites responsible for the catalytic activity (C A ) [6 – 11]. Moreover, the semiconduct- ing properties of the simple oxides were found to play a major role in the decomposition of AP [11]. The catalytic effect of NTMOs on the decomposition of AP was studied in detail. 2 Experimental 2.1 Materials AP, obtained from CECRI, Karaikudi, was used as received without further purification. Crystals of AP were ground into fine powder using a pestle and mortar and sieved to 100 – 200 mesh. Acetates of Cr, Fe, and glacial acetic acid were purchased from sd-fine chemicals Ltd., and KMnO 4 , CuCl 2 , Cetyl trimethyl ammonium bromide (CTAB), and NaOH were obtained from Merck. All these chemicals were used as received. 2.2 Preparation of Metal Oxide Nanocrystals Cr 2 O 3 and Fe 2 O 3 NTMOs were prepared by a novel quick precipitation method as reported earlier [12] which involves mixing of the corresponding metal acetate aqueous solution and glacial acetic acid under reflux condition followed by * Corresponding author; e-mail: gsingh4us@yahoo.com 351 Propellants Explos. Pyrotech. 2009, 34, 351 – 356  2009 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim