Preparation And Characterization Of Three-Dimensionally Ordered Macroporous Metallic Oxides/Al Nanoenergetic Composites

Miniaturized size was one of the characteristics of MEMS Pyrotechnics device which caused low energy output, the researchers considered the integration of micro-and nano energetic materials into the device in order to improve its ignition output energy. Therefore, nano-thermite films with high output energy and compatible with MEMS process had become a foucs. Recently, nano-thermite films such as CuOx/Al multilayer foils, were fabricated by alternatively depositing Al and copper oxide layers with well-defined thicknesses under high vacuum, but this fabrication process is costly, time-consuming and difficult to scale up. In this study, we have introduced a new method to prepare nanoenergetic material. First, a facile procedure to prepare three-dimensionally ordered macroporous (3DOM) Fe2O3membrane is presented. Then, Al was deposited onto3DOM Fe2O3by magnetron sputtering method.The Polystyrene spheres (PS) colloidal spheres were synthesized via the emulsion polymerization method. The PS colloidal spheres had an average diameter of280nm. This was achieved by strictly controlling the synthesis conditions. The resulting PS spheres are monodispersed to a high degree. The PS colloidal spheres were assembled into a three-dimensional ordered colloidal crystal template via natural sedimentation. Metal nitrate hydrate (1.0M) was dissolved in ethylene glycol (EG) by slow stirring at room temperature until all of the nitrate salt had dissolved. Then the PS template was soaked in the solution for several minutes. The obtained sample was allowed to dry in air at room temperature overnight and calcined in an oven. The temperature was raised at a rate of1℃/min to500℃and held for5h. The obtained sample was characterized by SEM、TEM、EDS、XRD and nitrogen adsorption-desorption. The3DOM material was α-Fe2O3with pore diameter about130±20nm and the wall thickness was approximately30nm. Meanwhile, the3DOM material had large BET surface area about44.59m2/g which provided the conditions for further Al deposition on porous iron oxide skeleton.Al was coated on the wall of3DOM Fe2O3membrane via magnetron sputtering method. The molar ratio between Al and Fe2O3increased with the extending of deposition time. From SEM image, we can see the wall thickness of Fe2O3/Al energetic nanocomposite increased with the extending of deposition time, but for pore size the opposite is the case. When the molar ratio reaches0.59, the heat of reaction equal to2831J·g-1.XRD was used to analyze the phase of product after DSC test. The results indicating that the product was Fe and there was no Al or Fe2O3left. Meanwhile, the Fe2O3with special3DOM structure made it easy to contact with nano-Al. Therefore, enhanced contact, reduced impurities and optimal fuel/oxidizer equivalence ratio result in high heat output.Ignition tests were applied by thermal ignition of Nichrome wire bridge initiating device. Self-propagating reaction was observed and Fe2O3/Al energetic nanocomposite burned vigorously with flame spills phenomenon, while the burning time last more than0.12seconds.In summary, Fe2O3/Al energetic membrane have some advantages such as high energy output, excellent ignition performance and compatible with MEMS process. It can be used as an ideal ignition material in micro-detonation system.