Preparation Of Nanocomposites And Their Catalytic Thermal Decomposition And Combustion Performance

Soild propellants is an important class of special energy materials,which is widely used in aerospace,weapon systems and other fields.Combustion catalyst is a vital component of solid propellant formulation and plays a momentous role in adjusting burning rate s,reducing pressure index and improving plume characteristics.Aluminum powder（Al）has abundant reserves and high combustion enthalpy,is a high-energy fuel commonly used in propellant formulations.Metastable intermixed composites（MICs）which is normally composed of a metal oxide and a fuel is an important kind of high-energy composite combustion catalysts,and has larger energy release and more excellent catalytic combustion performance compared with traditional CHON energetic compounds.It has been widely studied and applied in propellants,explosives and pyrotechnics.The design and development of new composite catalysts to enhance energy release and the combustion performance of propellants are hotspots in recent years.In this thesis,a series of composites were prepared by different method,and their catalytic thermal decomposition and combustion characteristics were investigated.The main research contents are as follows:（1）Two kinds of ferrite/graphene oxide（GO）nanocomposites with enhanced dispersity and improved catalytic performance were prepared by in-situ growth method,their effects on the thermal decomposition of Ammonium perchlorate（AP）,5,5′-bistetrazole-1,1′-diolate（TKX-50）and Cyclotrimethylenetrinitramine（RDX）were evaluated by DSC.The results reveal that the composites can significantly reduce the thermal decomposition temperature and apparent activation energy of single energetic materials,which can be attributed to the improved dispersity and the enhanced“synergistic catalytic effect”between nanoparticles and GO.It is found that Mg Fe₂O₄-GO composite by in-situ growth presents high catalytic activity for the thermal decomposition of AP and RDX.Under the catalytic of Mg Fe₂O₄-GO,the thermal decomposition temperature and apparent activation energy of AP are decreased by100.3℃and 46.4 k J/mol,respectively,and those of RDX are decreased to 234.6℃and141.6 k J/mol.While Zn Fe₂O₄-GO show better catalytic activity for TKX-50,which reduces its thermal decomposition temperature and apparent activation energy by 47.4℃and 28.6k J/mol.In addition,the enhanced catalytic decomposition mechanism of AP and TKX-50 by in-situ growth composites was discussed,and the kinetic equations of catalytic decomposition of Mg Fe₂O₄-GO/RDX and Zn Fe₂O₄-GO/RDX were obtained by the kinetic calculation.（2）A novel Al/Cu Fe₂O₄@NC composite with high-energy and insensitivity,which has a theoretical enthalpy of 3977.25 J/g,was successfully assembled by electrospray.Its thermochemical reactivity,sensitivity,laser ignition and combustion performance were investigated and compared with traditional thermite composites of Al/Cu O（4088.91 J/g）and Al/Fe₂O₃（3939.57 J/g）.The results show that the interfacial contact and oxidizer in composites have significant effects on the energy release,sensitivity and combustion properties.Al/Cu Fe₂O₄@NC composite has short ignition delay time（～4.5 ms）,low friction（360 N）and electrostatic spark sensitivity（11.25 m J）,moderate energy release and combustion characteristics.Its burning rate can be adjusted in range of～0.39-1.77 m/s by varying the interfacial contact between components.In addition,Al/Cu Fe₂O₄@NC can significantly reduce the thermal decomposition temperature and apparent activation energy of RDX and TKX-50,showing high catalytic decomposition performance.（3）Al/B/Cu Fe₂O₄@NC nanocomposites with different Al/B mole ratio were fabricated by electrospray,the effects of Al/B mole ratio on thermochemical reactivity,electrostatic sensitivity,laser ignition delay and combustion performance of composites were studied.The results show that compared with Al/Cu Fe₂O₄@NC composite,B/Cu Fe₂O₄@NC has higher thermite reaction temperature（603.3℃）and larger heat release（1569.8 J/g）of solid-solid phase reaction,which is ascribed to the high oxidation temperature and theoretical enthalpy of nano B.The thermite reaction properties,laser ignition delay and flame propagation velocity of Al/B/Cu Fe₂O₄@NC composites are significantly improved with the increase of Al/B mole ratio,while high content of nano B is beneficial to reduce the electrostatic spark sensitivity of composite,showing the adjustment of reactivity and combustion performance of composites can be achieved by incorporation of different fuel.The catalytic decomposition performance of composites for RDX and TKX-50 was investigated,and it is found that metal composite oxide played a leading role in the thermal decomposition of single energetic materials.In addition.the enhanced catalytic decomposition mechanism of TKX-50 was discussed.（4）Using the components of the composite modified double-based propellant（CMDB）as the basic unit,a series of energetic nanocomposites of NC/Al、NC/RDX and NC/Al/RDX with different mass loadings were fabricated by electrospinning,and their thermal behavior,laser ignition and combustion performance were investigated and compared with each other.The results reveal that nano Al particles have largely positive effects on promoting the thermal decomposition,laser ignition and combustion reaction of composites,and the composite fibers containing Al have a short ignition delay time（～23 ms）and a high flame propagation velocity.The burning rates of NC/Al（6.44 cm/s）and NC/Al/RDX（6.23 cm/s）composites are～2 times higher than that of PM.NC+Al（3.03 cm/s）,showing that the enhanced interfacial contact and improved dispersity of nano Al by electrospinning are beneficial to enhance the ignition and combustion of composites.In addition,the DSC results show that Cu Fe₂O₄nanoparticles can significantly promote the thermal decomposition of RDX,NC/RDX and NC/Al/RDX,reducing their thermol decomposition temperature and activation energy and presenting good catalytic performance.