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Applied Clay Science, Volumes 65–66, September 2012, Pages 14-20
Zhiwei Li, Xu Xiang, Lu Bai, Feng Li
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, PR China
Key Laboratory of Fine Petrochemical Engineering of Jiangsu Province, Changzhou, 213164, PR China
Abstract
Ammonium perchlorate (AP), known as a common oxidizer, plays a key role in composite solid propellants (CSP). The performance of CSP is strongly dependent on the thermal decomposition of AP, which is greatly affected by solid additives or catalysts. Metal oxides have been widely used as catalysts to improve thermal decomposition of AP. Layered double hydroxides (LDHs) or hydrotalcite-like materials belong to a family of anionic clay with a brucite-like layered structure. LDHs can be ideal precursors to obtain various mixed-metal oxides (MMO) with regular compositions upon heating. Herein, we have established a green synthetic strategy to layered double hydroxide/carbon (LDH/C) nanocomposite by simultaneous occurrence involving crystallization of NiAl-LDH and carbonization of non-toxic glucose under mild hydrothermal conditions. The nanocomposites calcined in air lead to porous NiAl-MMO with tunable surface areas. The porosity of resultants is ascribed to the templating effect, resulting from the depletion of carbonaceous products with the elevating temperature. The specific surface areas of products are sensitive to carbonaceous product content in the composite precursor, Ni/Al ratio and as well the calcination temperature. The specific surface area reaches a maximum under medium carbon content in the precursor and decreases with the increasing calcination temperature. On a basis of the nature of metal oxides and their high surface areas, the MMOs are utilized for catalytic thermal decomposition of ammonium perchlorate (AP) and exhibit excellent catalytic activity. The peak temperature of AP decomposition was greatly decreased compared to that of pure AP. And the temperature is strongly dependent on the surface areas of MMO. Furthermore, the decomposition activation energy of AP with the mixed oxide additives was calculated to be 74.6 and 80.4 kJ mol-1 by two methods of kinetics, respectively, both of which are smaller than that of pure AP.
The MMO derived from LDH/C nanocomposites can be a promising candidate for catalytic decomposition of thermally volatile substances (solid propellants or energetic materials), which may open up new opportunities in the fields of aerospace or safety such as high-energy propellants or emergency gas generators.
