MgAl2O4 nanoparticles: 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 (MgAl 2 O 4 ) with a low density of 3.02-3.17 g cm 23 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 selfgenerated carbon template. Carbon template was generated by pyrolysis and carbonization of citrate after calcinations at 800 uC in N 2 , and then removed with annealing in air at high temperatures, resulting in porous MgAl 2 O 4 with a specific surface area as high as 291 m 2 g 21 . Depending on the annealing temperatures, the primary sizes of MgAl 2 O 4 nanoparticles that built up the porous structures were adjusted from 6.2 to 24.7 nm. The structural characteristics of MgAl 2 O 4 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 MgAl 2 O 4 , among which MgAl 2 O 4 nanoparticles with a largest surface area of 291 m 2 g 21 and pore volume of 0.24 cm 3 g 21 was proved to have an optimum catalytic activity: exothermic peaks of AP thermal decomposition shifted towards the lower temperatures by 78.3 uC for high-temperature decomposition process. The relative kinetic process was also investigated.

Preparation of Aluminum/Boron/Iron-Oxide Nanothermites and Catalytic Activity for Ammonium Perchlorate

“…From Fig. 5a, the DSC curve for thermal decomposition of pure AP shows three processes that are similar to the previous results [17][18][19][20]. The endothermic peak on the DSC curve at about 249°C belongs to a phase transition of AP from orthorhombic to cubic.…”

Catalytic Activity of Co3O4 Nanomaterials with Different Morphologies for the Thermal Decomposition of Ammonium Perchlorate

“…The above results indicate that Co 3 O 4 particles have a significant effect on the decomposition temperature of AP and Co 3 O 4 nanomaterials with different morphologies for decreasing the decomposition of AP are proportional to their BET surface area and pore volume. It is known that specific surface area and pore volume can be the primary reasons for the catalytic role, since more reactive sites can be generated [12,20,21]. Thus, Co 3 O 4 nanorods with larger BET surface area and pore volume have the most effective catalytic activity and the thermal decomposition temperature of AP shifted downward about 148.8 ∘ C.…”

Solvent-Tuned Synthesis of Mesoporous Nickel Cobaltite Nanostructures and Their Catalytic Properties

“…The E a was calculated to be 317 kJ mol −1 , which is larger than reported activation energy (100-130 kJ mol −1 ) of pure AP [30]. The increased activation energy for AP decomposition has been observed in several metal oxide additives such as CoO [24], CuO [31], and MgAl 2 O 4 [32], which is ascribed to the kinetic compensation effect [31]. Though nanostructures, which facilitates the gas diffusion and provides more active sites for AP thermal decomposition [30].…”