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Electrical Initiation Mechanism Of Chemical Reaction In Reactive Multilayer Films

Posted on:2021-09-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:S FuFull Text:PDF
GTID:1481306512481144Subject:Ordnance Science and Technology
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Reactive multilayer films(RMFs)consisting of alternating layers of the reactants is a relatively new form of energetic materials.These RMFs with two-dimensional laminated structures have received much attention because of their high energy density and fast energy release due to their uniform distribution and good contact between layers.RMFs react either by thermal explosion or by a self-propagating exothermic reaction once it is initiated.Thermal explosion occurs under the rapid and high current density,which is often realized by capacitor discharge.Integrated RMFs have been shown to be an effective method for increasing the output energy of micro-chip initiators without increasing the input energy.At present,remarkable progress has been made in the preparation and characterization,reaction path,and welding application of RMFs.However,there have been few investigations of the electrical initiation of RMFs under the rapid and high current density,which may be important for initiator and pyrotechnic applications of RMFs.In this study,the typical Al/Ni RMFs(intermetallic reaction)and Al/Cu O RMFs(oxidation-reduction reaction)were described systematically.The particular research contents and conclusions are as follows:(1)Al/Ni and Al/Cu O RMFs of nano modulation periods were fabricated by magnetron sputtering,respectively.The as-deposited RMFs were characterized by varied analytical techniques,including FESEM,XRD,DSC,and so on.The results showed that the RMFs with distinct layer structure,good contact between layers,and no obvious blisters and fragments.The heat releases of chemical reaction of Al/Ni and Al/Cu O RMFs are 1135J/g and 1956J/g,respectively.The equiaxed and fibrous grain structures were formed in the Al and Ni layers in Al/Ni RMFs,respectively.The equiaxed and columnar grain structures were formed in the Al and Cu O layers in Al/Cu O RMFs,respectively.In addition,there is 30%of the Cu O was reduced to Cu2O because that some oxygen was lost during deposition.(2)The electrical resistivity model of the Al/Ni RMFs was established based on F-S and M-S models.A metal-interlayer-metal(MIM)structure samples were designed to investigate the breakdown properties of Al/Cu O RMFs.The results showed that the resistivity of the Al/Ni RMFs is mainly dominated by grain boundary scattering,because the thicknesses of the Al and Ni layers in the RMFs are much larger than the corresponding electron mean free path.The Al/Cu O RMFs are not discharged until the external electric field exceeds the breakdown field strength of the Al/Cu O RMFs.A theoretical model indicates that the thermal conductivity and number of grain boundaries are crucial parameters for the breakdown of Al/Cu O RMFs.The EB of the Al/Cu O RMFs can be improved by Al layers in the RMFs.(3)The micro-initiators realized by integrating Al/Ni and Al/Cu O RMFs were fabricated by using microsystem techniques that allow batch fabrication and high level of integration.The electrical explosion performance of the Al/Ni RMFs initiator and MIM-Al/Cu O RMFs initiators was characterized under capacitor discharge conditions.Results show that the energy released by exothermic reaction is able to help generating high-temperature products on the initiators.The ejected products can ignite the attached energetic materials even if the initiators make no physical contact to the energetic materials.In addition,the initiation of MIM-Al/Cu O RMFs initiators is found to occur through the rapid formation of single-hole breakdowns in their Al/Cu O RMFs interlayer,then the materials evaporate around the breakdown holes and form a high-temperature plasma,which results in their initiation times(<1.0?s)are much smaller than that of conventional Al film initiator(2?s?4?s).
Keywords/Search Tags:reactive multilayer films, electrical resistivity, breakdown characteristics, initiators and pyrotechnics, electrical-explosion characteristics
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