Combustion Mechanisms Of Fullerenes In The New Promising High Energetic Fuel

NEPE propellant is a new type of nitrate ester plasticized polyether solid rocket propellant.It concentrates both the advantages of double base(DB)and composite solid propellants.It not only has high energy,large low temperature elongation,but also has good technical process and safe property,which are better than other current equipped propellants.The N-15 propellant is a kind of the highest energetic propellants equipped in the modern world.But there are some problems to be solved about its combustion characteristics,such as higher pressure exponent,the contradiction between energy performance and combustion characteristics and the contradiction between burning rate and pressure exponents,etc.Thus its unique combustion mechanism leads to the invalidation of the traditional combustion mechanisms used in investigating DB and composite solid propellants.The fullerene catalysts are one of the most popular materials used in recent years,and the unique enclosed spherical structure promotes the catalytic ability in many fields.The fullerenes used as burning rate catalysts in solid propellant have very dramatic effects. This dissertation includes the effects of fullerenes on the thermal decomposition of the main oxides and binders,and the effects of fullerenes on the burning rates and pressure exponents of NEPE propellants.According to the results of these investigations,a small amount of fullerene soot(FS)could obviously promote the thermal decomposition of ammonium perchlorate(AP)and inhibit the aging process of polyethylene glycol(PEG).One 0.5%FS/2.5%lead phthalic acid(Φ-Pb)/0.5% copper adipic acid(J-Cu)composite catalysts which could effectively decrease the pressure exponents of cyclotrimethylene trinitramine(RDX)/AP-composite modified double-base(CMDB)propellant have been obtained,and another AP+PEG/ nitroglycerin(NG)/1,2,4- butantriol trinitrate(BTTN)+2%FS propellant which has large combustion heat,high buming rate and low pressure exponent is also gained.(1)From the results of the effects of fullerenes and carbon black(CB)catalysts on the thermal decomposition of AP,one could see that the initial decomposition temperature(T₀),low and high temperature decomposition peak temperature(T_L and T_H)of AP were advanced 32℃,34℃and 45℃by 5%FS catalyst.Also,the T₀,T_L, and T_H of AP were advanced 11℃,27℃and 44℃by 5%CB catalyst.Therefore,the T₀,T_L,and T_H of AP were affected a little by 5%EFS and 5%C₆₀.The effects of FS and CB contents on the thermal decomposition of AP indicated that both FS and CB showed splendid catalytic effects on the thermal decomposition of AP,and the effect of FS was better.The initial decomposition,low and high temperature decomposition processes of AP were promoted by 3%FS,and the higher of FS contents,the better of the catalytic effects were.The low and high temperature decomposition processes of AP were overlapped by adding 8%or 10%FS.The To of AP was not affected,but the low temperature decomposition processes was inhibited by 3%CB.Therefore,these three decomposition processes of AP were promoted by 5%,8%and 10%CB.Also,the low and high temperature decomposition processes of AP were overlapped by adding 8%or 10%CB.(2)A comparison of the thermal decomposition dynamics parameters of AP+5%FS and AP+5%CB indicated that the thermal decomposition activation energy of AP were lowered by 5%FS and 5%CB.The thermal decomposition activation energy of AP was lowered about 37%and 34%by 5%FS and 5%CB respectively.The thermal decomposition activation energy of AP+5%FS was a little smaller than that of AP+5%CB showed the better catalytic effect of FS.The pre-exponential factor of AP thermal decomposition was increased by these two catalysts,and this phenomenon showed the percentage of active molecules was increased by 5%FS and 5%CB.The ignition temperatures of AP were lowered about 5.6℃,9.7℃and 12.3℃by 5%EFS, 5%C₆₀and 5%CB respectively.Among all catalysts,FS showed the best effect and the ignition temperature of AP was lowered about 47.4℃by 5%FS.(3)The investigation of the effects of fullerenes(or CB)/Φ-Pb composite catalysts on the thermal decomposition characteristics of AP showed that the initial decomposition process of AP was apparently promoted by these composite catalysts, among which FS/Φ-Pb showed the best catalytic effect,and the T₀ of AP was decreased about 40℃by 5%FS/15%Φ-Pb composite catalysts.The T₀ of AP was decreased about 8℃when the content of FS was increased from 5%to 15%.The combustion heat of 70%AP/15%Φ-Pb/15%FS and 70%AP/15%Φ-Pb/15%CB were increased about 146%and 115%when compared to that of pure AP.(4)The effects of fullerenes and CB on the thermal decomposition characteristics of cyclotetramethylenete tranitramine(HMX)and hexanitrohexaaza-isowurtzitane (CL-20)were investigated by TG-DTG,DTA,and PDSC.The results showed that the initial decomposition temperature of HMX was advanced 46℃by 5%FS,and the decomposition peak temperature of HMX was lowered about 15℃by 15%FS.The initial decomposition temperature,decomposition peak temperature and the decomposition terminated temperature of CL-20 were obviously promoted by FS.The thermal decomposition of pure CL-20 didn't depend on the carrier gases and it was nitrogen not air atmosphere that was in favor of the catalytic ability of FS.(5)The results of the effects of fullerenes on the thermal decomposition and pyrolysis characteristics of HTPB showed the thermal decomposition dynamic characteristic of HTPB is only depending on the main-chain structure of HTPB.The pyrolysis-GC/MS results of HTPB at 280,320,350 and 380℃showed that there exists 16 main products at all four different temperatures,including 4-ethenyl-cyclohexene,styrene,etc.The thermal decomposition results of glycidyl azide polymer(GAP)showed that the low temperature decomposition of GAP was not affected by 10%FS.Therefore,that of GAP were advanced 6℃and 9℃by 30%FS and 50%FS.(6)The effects of fullerenes on the thermal decomposition of PEG have been investigated by TG,in-situ FTIR and pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).The results showed that the addition of fullerenes obviously restrained the thermal decomposition of PEG.The initial decomposition temperatures and maximum decomposition peak temperatures were evidently postponed by FS.There is no chemical reaction between FS and PEG,no new functional group with IR absorptive activity,but only vander's force between FS and PEG.FS didn't alter the thermal decomposition mechanism of PEG,but restrained the thermal decomposition of PEG.The effect of FS on the condense phase decomposition of PEG was not obvious,but FS made the increase of the gaseous decomposition temperature of PEG.This is mainly because the absorbance of gaseous decomposition products of PEG covered the surface of PEG.(7)According to the results of the effects of fullerenes or CB/Φ-Pb/J-Cu composite catalysts on the combustion characteristics of RDX/AP-CMDB propellant, we found that the thermal decomposition of RDX/AP-CMDB propellant wasn't affected by these composite catalysts,but only the solid phase decomposition of nitrocellulose(NC)and liquid phase decomposition of RDX were slightly promoted by fullerenes/Φ-Pb/J-Cu composite catalysts.The combustion heat of RDX/AP-CMDB propellant was slightly decreased by fullerenes and the combustion heat values of RDX/AP-CMDB propellant with different catalysts are HX-013(EFS)＞HX-014(C₆₀)=HX-009(CB)＞HX-011(FS).Compared to the basis formulation,the pressure exponent of HX-010 was lowered about 20%by 0.5%FS/2.5%Φ-Pb/0.5%J-Cu,and among all composite catalysts this is the best one.(8)The results of the effects of FS on the thermal decomposition,combustion heats and burning rates of AP+GAP/NG/BTTN,HMX/AP+GAP/NG/BTTN, AP+PEG/NG/BTTN and HMX/AP+ PEG/NG/BTTN propellants showed that the thermal decomposition processes of these four propellants were benefitted with the addition of HMX and the burning rates of these four propellants were benefitted with the addition of AP.The combustion heats and buming rates of HMX/AP+GAP/NG/BTTN and HMX/AP+PEG/NG/BTTN propellants were benefitted by 2%FS with respect to 1%FS+1%PbO.When using 2%FS instead of 1%FS+1%PbO,the combustion heats of AP+GAP/NG/BTTN,HMX/AP+ GAP/NG/BTTN,AP+PEG/NG/BTTN and HMX/AP+PEG/NG/BTTN propellants were increased 321 J·g^-1,851 J·g^-1,201 J·g^-1and 153 J·g^-1respectively.Also the burning rates of AP+PEG/NG/BTTN propellant were increased about 78.4%,72.2%, 55.5%and 50.2%at 2.94MPa,4.90MPa,6.86MPa and 8.83MPa when using 2%FS instead of 1%FS+1%PbO.