Abstract:

High-performance solid propellants are very important for the development of modern weapons. Aside from their high energy and high burning rate, safety performance is regarded as the most important factor that should be considered whenever a new solid propellant recipe is formulated. Therefore, exploring a new type of combustion catalyst that can improve both catalytic activity and reduce the sensitivity of the energetic component is significant. Traditionally, transition metals or metal oxides are used as a combustion catalyst for accelerating the thermal decomposition of energetic components. However, the existing problem of these catalysts is the aggregation of particles accompanied by poor surface area. Coupling metal oxides with graphene is a promising approach to obtain a binary composite with stable structure and large specific surface area. In this work, rod-like and granular Fe₂O₃ nanoparticles were synthesized using a hydrothermal method. Then, the two as-prepared Fe₂O₃ nanoparticles were coupled with graphene sheets using an interfacial self-assembly method, which can effectively prevent the aggregation of Fe₂O₃ particles and simultaneously increase the active sites that participate in the reaction. X-ray diffraction and X-ray photoelectron spectroscopy were used to identify the phase states and chemical compositions of the prepared samples. The morphology and internal structures were further demonstrated through scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption tests. Both phase analysis and structure identification indicate that the prepared Fe₂O₃/G has high purity and high surface area. The catalytic performance of the prepared Fe₂O₃ and Fe₂O₃/G in the thermal decomposition of hexanitrohexaazaisowurtzitane (CL-20) was evaluated based on thermal gravimetric analysis-infrared spectroscopy (TGA-IR) and differential scanning calorimetry (DSC) tests. The non-isothermal decomposition kinetics of CL-20, Fe₂O₃/CL-20, and Fe₂O₃/G/CL-20 were further studied by DSC. The results reveal the excellent catalytic activity of Fe₂O₃/G in the thermal decomposition of CL-20, which is attributed to the presence of abundant pore structure and large surface area. The reaction mechanisms of the exothermic decomposition process of CL-20, Fe₂O₃/CL-20, and Fe₂O₃/G/CL-20 were obtained by the logical choice method, and the composites all followed same mechanism function model as CL-20. Through comparison, the rod-like Fe₂O₃ coupled with graphene was found to have the best catalytic activity in the thermal decomposition of CL-20. Thus, the rod-like Fe₂O₃ and its Fe₂O₃/G composite were used to investigate their influence on the impact sensitivity of CL-20 by fall hammer apparatus. The results show that rFe₂O₃/G can effectively decrease the impact sensitivity of CL-20 compared with pure CL-20 and rFe₂O₃/CL-20. Therefore, rFe₂O₃ coupled with graphene not only promotes the thermal decomposition but also improves the safety performance of CL-20.

Key words: Fe₂O₃/graphene, Three-dimensional net structure, Catalytic activity, Thermal decomposition, Kinetics