MgAl2O4nanoparticles: A new low-density additive for accelerating thermal decomposition of ammonium perchlorate

Abstract

Developing low-density additives with high activities is significantly important for thermal decomposition of ammonium perchlorate and the relative technical applications. In this paper, nanoparticles of magnesium aluminate (MgAl₂O₄) with a low density of 3.02–3.17 g cm⁻³ were synthesized by a self-generated template path, in which citric acid was introduced to ensure homogeneous distribution of metal cations at atomic level and serve as the carbon source of the self-generated carbon template. Carbon template was generated by pyrolysis and carbonization of citrate after calcinations at 800 °C in N₂, and then removed with annealing in air at high temperatures, resulting in porous MgAl₂O₄ with a specific surface area as high as 291 m² g⁻¹. Depending on the annealing temperatures, the primary sizes of MgAl₂O₄ nanoparticles that built up the porous structures were adjusted from 6.2 to 24.7 nm. The structural characteristics of MgAl₂O₄ nanoparticles were systematically studied by X-ray diffraction, transmission electron microscopy, Braun-Emmet-Teller analysis, and the catalytic role were evaluated by thermal decomposition of ammonium perchlorate. All samples were indicated to be X-ray-pure MgAl₂O₄, among which MgAl₂O₄ nanoparticles with a largest surface area of 291 m² g⁻¹ and pore volume of 0.24 cm³ g⁻¹ was proved to have an optimum catalytic activity: exothermic peaks of AP thermal decomposition shifted towards the lower temperatures by 78.3 °C for high-temperature decomposition process. The relative kinetic process was also investigated.