Synthesis And Combustion Catalysis Of Nanoporous Composite Materials

Ammonium perchlorate(AP)/hydoxyl-terminated polybutadiene(HTPB) composite solid propellants are composed of 15 wt%HTPB as a polymeric matrix,additive with 70 wt%AP solid powder as a oxidizer,10 wt%metal powder as a secondary fuel component, and 5 wt%low-molecular-weight species such as catalyst,plasticizer,and curing agent. Though catalysts are in minute quantities,they play an important role in the performance of propellant,catalysts are required to increase the burning rate of composite solid propellant,as they have low inherent burning rate.Nanometer sized metal particles and metal oxides particles are good burning rate enhancer for composite solid propellants due to their smaller size and larger surface area.Unfortunately,the high viscosity during the propellant molding process made these nanoparticles hardly dispersed in HTPB,which diminished their catalytic effect.The ferrocene(Fc) and its derivatives are other kind of good burning rate enhancers for AP/HTPB composite solid propellants,however some defects limited the use of ferrocene derivatives as burning rate catalyst,such as their migration to insulation during curing and storage,evaporation or sublimation loss during processing,and phase separation by crystallization in low temperature applications or storage.To disperse the nanosized particle and block the migration of Fc,composite powder technology was developed in this paper,nanoporous composite powder was prepared and its catalytic activity on the thermal decomposition of AP and the combustion of AP/HTPB propellant was studied.In chapter 3,CuO/SBA-15 composites were prepared by impregnation method using as-prepared SBA-15(template concluded) as support.The resulting sample was characterized by X-ray diffraction and N₂ adsorption to evaluate the textural properties of these composites.TG-DSC was used to survey the catalysis function of the sample to the decomposition of ammonium perchlorate(AP).Results indicated that CuO was well dispersed on the surface of SBA-15,and these materials shown significant catalytic effect on the decomposition of AP.The decomposition temperature of AP containing 2wt%CuO/ SBA-15 decreased by 146℃as compared with the decomposition temperature of pure AP. Moreover,the burning rate of AP based propellant increased 9.5%and pressure exponent decreased 17%after addition of 1 wt%CuO/SBA-15 composites.A non-migration catalyst was developed by grafting ferrocene on SBA-15 in chapter 3. The grafted catalyst has been characterized by small angle X-ray diffraction(SAXRD), infrared spectra(IR),N₂ adsorption,and the atomic absorption spectrophotometry (AAS).The migration behavior has been assessed by AAS and the catalysis on the thermal decomposition of AP has been studied with differential scanning calorimetry analysis (DSC).XRD and N₂ adsorption indicated that grafting of Fc caused the decrease of BET surface area and pore diameter,but the structure of SBA-15 was not destroyed.Fe content in HTPB slides at various distances from the interface between the non-additive and additive showed that grafted Fc was a non-migration catalyst.DSC curves indicated that grafted Fc decreased the thermal decomposition temperature of AP.Burning rate test indicated that grafted Fc increased the burning rate of AP/HTPB composite propellant and decreased the pressure exponent value.Since SBA-15 is non-energetic,it is therefore highly desirable that using energetic material as carrier for nanometal and organic ferrocene.In chapter 4,nanometer sized copper/active carbon(AC) composite material was prepared by H₂ deoxidization at 500℃. Results show that the best dispersion acquired when the copper content is 10wt%.Cu/AC composite materials have significant catalytic activity on the decomposition of AP.The decomposition temperature of AP containing 2wt%Cu/AC decreased by 124℃as compared with the decomposition temperature of pure AP.Moreover,the burning rate of AP based propellant increased 25%and pressure exponent decreased 8%after addition of 1 wt%Cu/AC(10) composites.Another non-migration catalyst was developed by grafting ferrocene on carbon nanotube(CNT) in chapter 4.The grafted catalyst has been characterized by Raman spectra and Infrared spectra.The migration behavior has been assessed by AAS and the catalysis on the thermal decomposition of AP has been studied with differential scanning calorimetry analysis(DSC).Raman spectra and Infrared spectra indicated that Fc has been grated on CNT,Fe content in HTPB slides at various distances from the interface between the non-additive and additive showed that grafted Fc was a non-migration catalyst.DSC curves indicated that grafted Fc decreased the thermal decomposition temperature of AP by 106℃.Burning rate test indicated that grafted Fc increased the burning rate of AP/HTPB composite propellant and decreased the pressure exponent value.The better catalytic activity compared with Fc-SBA-15 may be attributed to the better heat conduction with the addition of CNT.In chapter 5,three kinds of manganese oxide octahedral molecular sieves(OMS) were prepared and the catalytic activity of OMS on the thermal decomposition of ammonium perchlorate(AP) has been briefly studied.Results show that OMS plays a catalytic role on the thermal decomposition of AP,and the most effective is OMS-2.The decomposition temperature of AP has been decreased 145℃and the heat of decomposition has been increased 0.66 kJ·g^-1 with the addition of 2wt%OMS-2.Such effects are mainly attributed to the mixed valence of Mn³⁺ and Mn⁴⁺ existing in OMS-2 material and its high surface area.Doping with Cu²⁺,Ni²⁺ and Co²⁺ does not improve the catalytic activity of OMS.