Study Of Catalytic Effects Of Metal Oxides And Oxalates On The Thermal Decomposition Of TEGDN/NC Propellant

Combustion properties of propellants are the key performance for weapons to obtain stability and controllable ballistic characteristics, and the investigation on combustion properties is usually started from the study of thermal decomposition process. Adding combustion catalysts into the propellants is one way of regulating and improving the decomposition and combustion propertises of propellants. This dissertation contains three aspects of works. Firstly, thermal decomposition characteristics of the double-base propellant containing triethylene glycol dinitrate (TEGDN) and nireocellulose (NC) are analyzed by thermal analysis. Secondly, a series of metal oxides including NiO, Fe₂O₃, et al and micro-sized oxalates including nickel oxalate, ferrous oxalate, et al are prepared and their catalytic effects on TEGDN/NC propellant as well as the catalytic mechanism are studied. This work affords the experimental and theoretical basis for regulating and improving the decomposition and combustion propertises of TEGDN/NC propellant. Thirdly, the atomic cluster catalytic mechanism of NiO on thermal decomposition of main components of TEGDN/NC propellant is studied, to afford a new way of studying the mechanism of solid catalysts on thermal decomposition of energetic compounds. Main research contents are shown as follows.The thermal decomposition processes of TEGDN, NC and TEGDN/NC propellant were studied by derivative thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC) experiments. It was shown that the thermal decomposition of TEGDN/NC propellant proceeded in two steps. The first step was caused by the evaporation and thermal decomposition of TEGDN, while the second step was mainly caused by the thermal decomposition of NC. The DTG peak points were respectively at 192?and 205?. There was only an exothermic peak in the DSC curve during thermal decomposition of TEGDN/NC propellant. The peak temperature of DSC curve was about 215?and the released heat was approximately 1612 J·g-1. According to the thermogravimetry-mass (TG-MS) analysis, the gaseous products evolved during the thermal decomposition of TEGDN/NC propellant were H₂O?HCN?CO?N2?HCHO?NO?HCNO?CO₂?NO₂ and HCOOH?NiO was prepared by a solid-state reaction and was characterized by XRD, FT-IR and TEM analysis. The catalytic effect of NiO on thermal decomposition of TEGDN/NC propellant was studied via DSC/TG-MS method. It was found that decomposition process of TEGDN/NC propellant with 2% NiO particles was accelerated and preceded in one step. The DTG peak point was at around 188?From the DSC analysis, it can be seen that adding NiO to TEGDN/NC propellant decreased the decomposition temperature and increased the decomposition heat from 1612 J·g-1 to 1720 J·g-1.From the TG-MS analysis, it can be easily found that after adding 2% NiO to TEGDN/NC propellant, the ion currents of the evolved products during thermal decomposition attained the peak values at lower temperatures and their maximum ion intensities were increased obviously. The thermal decomposition of nitrate esters involves fission of the oxygen-nitrogen bond as the first and rate determing step, leading to the generation of NO₂. Then NO₂ reacts with the condensed phase, leading to the generation of other gaseous products. According to the MS cuves of gaseous products, it can be found that adding NiO accelerated the cleavage of O-NO₂ bond and NO₂ was produced at lower temperature. Then large amount of NO₂ was detained in condensed phase and reacted with the condensed phase, so the decomposition process of TEGDN/NC propellant was promoted. The integral intensities of individual ions were calculated and it was found that the addition of NiO resulted in the increase of intensity of m/z=27 (HCN+),28 (CO+, N2+) and 30 (HCHO+) MS signals, but the decrease of the intensity of m/z=18(H₂O+),30 (NO+) and 44 (CO₂+) MS signals during the thermal decomposition of TEGDN/NC propellant.Cr₂O₃, Fe₂O₃, CuO, SnO₂ and CdO nanoparticles were prepared by precipitation method and were characterized by XRD, FT-IR and TEM techniques. The catalytic effects of these catalysts on thermal decomposition of TEGDN/NC propellant were analyzed by TG-DTG and DSC method. It was found that Cr₂O₃ had little influence on the decomposition process of TEGDN/NC propellant while the other catalysts depressed the decomposition reaction, which implied that these catalysts were unfavorable for the thermal decomposition process of TEGDN/NC propellant.Nickel oxalate (NiC2O4·2H₂O), ferrous oxalate (FeC2O4·2H₂O), cobalt oxalate (CoC2O4·2H₂O) and copper oxalate (CuC2O4·xH₂O) were prepared by precipitation method and were characterized by XRD, FT-IR, Raman, SEM. laser granularity measurement device, elemental analysis and TG-DTG techniques. The catalytic effects of micro-sized oxalates on thermal decomposition of TEGDN/NC propellant were analyzed by TG-DTG and DSC method. It was found that adding NiC2O4·2H₂O accelerated the decomposition process of TEGDN/NC propellant and decreased the second DTG peak temperature from 205?to about 198?. However, the addition of FeC₂O₄·2H₂O, CoC₂O₄·2H₂O and CuC2O4·xH₂O depressed the decomposition reaction of TEGDN/NC propellant and obviously decreased the decomposition heat.The influence of NiC2O4·2H₂O on the gaseous products evolved during the thermal decomposition of TEGDN/NC propellant was studied via TG-MS techniques. It was found that the addition of NiC2O4·2H₂O accelerated the evolution of gaseous products and the maximum ion intensities of gaseous products were obviously increased. The integral intensities of individual ions were calculated and it was found that NiC2O₂·2H₂O resulted in the increase of HCHO formation but decrease the production of CO₂ during the thermal decomposition of TEGDN/NC propellant.The atom cluster catalytic effects of NiO on thermal decomposition of NC and TEGDN were respectively studied by XRD and SEM method. It was found that the addition of 2% NiO can promote the decomposition process. The XRD and SEM results revealed that NC reacted completely and NiO which participated in reaction was transformed into Ni.10% NiO was added into TEGDN and the mixture was reacted. The XRD and SEM analysis of the reaction residue showed that NiO was completely transformed into Ni and the morphology of particles was obviously changed. Meanwhile,10% Ni powder was added into TEGDN and the mixture was reacted. The XRD and SEM analysis of the reaction residue showed that the morphology of Ni powder was changed although the crystalline structure of Ni was not altered. The reaction systems of NiO with TEGDN and Ni with TEGDN were treated by chloroform respectively. The extract liquid was characterized by UV-Vis and FT-IR, and it was found that both the reaction systems contained the intermediate state which was similar with Ni(CO)₄.The effects of NiO and NiC₂O₄·2H₂O on the combustion properties of TEGDN/NC propellant were respectively studied by closed bomb test. It was found that the addition of NiO and NiC2O4·2H₂O can prolong the combusting time, decrease the maximum pressure, improve the burning rate in the pressure range of 30?180 MPa and obviously decrease the pressure exponent of TEGDN/NC propellant. Experimental results revealed that the addition of 1% NiO decreased the pressure exponent from 0.9814 to 0.9445, while the addition of 1.5% NiC2O4·2H₂O decreased the pressure exponent from 0.9814 to 0.9095.