Preparation And Properties Of Rare Earth Metal Composite Oxides

Solid propellant,as one of the key technologies in the launcher,plays an important role in aerospace technology and military.Its key point is combustion.In order to achieve efficient and full combustion,the addition of combustion catalyst is an effective way.Composite metal oxides are increasingly used because their high thermal stability and good chemical stability.The core-shell structure on the metal composite oxide can further improve its catalytic performance.In this paper,a series of rare earth metal composite oxides were synthesized by different methods,and the core-shell structure loading was carried out on the basis of solvothermal preparation of metal composite oxides.The catalytic thermal decomposition of the energetic components ammonium perchlorate?AP?and HNIW?CL-20?by the as-prepared particles was further analyzed.?1?LaFeO₃ with perovskite structure was successfully synthesized by using one-step solvothermal method.The MnO₂@LaFeO₃ with core-shell structure was synthesized by using the above-prepared LaFeO₃ as the nucleus and KMnO₄ as the raw material.The material composition,crystal form and morphology were characterized.?2?Firstly,template polystyrene?PS?microspheres were synthesized by emulsification method,and then four perovskite rare earth metal complexes were prepared by using PS as template method,namely LaFeO₃,LaCoO₃,LaNiO₃,La₂CuO₄,and further it was characterized by XRD,XPS,FT-IR and SEM.?3?The effects of LaFeO₃ and MnO₂@LaFeO₃ on the thermal decomposition behavior of AP,CL-20 and octogen?HMX?were studied.The results show that MnO₂@LaFeO₃ exhibits the best catalytic activity,which can reduce the maximum decomposition peak temperature of AP by 122.34°C,and reduce the apparent activation energy by 27.1 kJ/mol.The results show that the catalytic activity of the core-shell structure MnO₂@LaFeO₃ is higher than that of the single LaFeO₃ composite.The mechanism is that the interaction between the core and the shell causes the charge on both surfaces to shift,and the lattice is distorted,further increasing the active site on the metal surface.At the same time,the thermal catalytic performance of LaFeO₃,LaCoO₃,LaNiO₃ and La₂CuO₄ prepared by template method was studied.The results show that the synthesized rare earth metal complexes have certain catalytic effects on CL-20,The catalytic effect is LaFeO₃>LaCoO₃>LaNiO₃>La₂CuO₄.?4?The effects of the above synthesized materials on the thermal decomposition of AP and CL-20 were studied by DSC method.The non-isothermal reaction kinetic parameters were calculated by thermal behavioral kinetics:apparent activation energy?E?and pre-exponential factor?A?.Determine the kinetic mechanism function of its thermal decomposition reaction.The corresponding thermal decomposition kinetic of MnO₂@LaFeO₃/APis is:d?/dT=4(10^7.59/?)?1-??^3/4exp??-11231?/RT? The corresponding thermal decomposition kinetic of LaFeO₃/CL-20 is:d?/dT=3(10^12.4/?)?1-??[-ln?1-??]^2/3exp??-14782?/RT?.