Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

Abstract

Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride. Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedman's differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods. To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method. The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism. The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD). The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO₂ shows no influence on the rate of decomposition. Possible explanations for these results are discussed.

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Keywords:

• ammonium nitrate
• copper oxide
• decomposition kinetics
• lithium fluoride
• thermal properties
• titanium dioxide

Acknowledgments

The authors thank Dr. V. N. Krishnamurthy and Professor S. P. Tewari for fruitful discussions, DRDO for financial support to ACRHEM, and A. Rajesh, CIL, University of Hyderabad, for collecting the thermal analysis data.