Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculation...Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.展开更多
Perfluorolyether is characterized by highly chemical inertness, oxidative stability, anticorrosion as well as radiation resistance. It can be used as lubricant especially in harsh environmental conditions. In this wor...Perfluorolyether is characterized by highly chemical inertness, oxidative stability, anticorrosion as well as radiation resistance. It can be used as lubricant especially in harsh environmental conditions. In this work, hexafluoropylene oxide was catalytically polymerized at low temperature using the methods of anionic polymerization, and perfluorolyethers were obtained with number-average degree of polymerization more than 15. CsF and RbF were used as catalysts and their catalytic activities were investigated. Experimental results show that perfluorolyethers with number-average molar masses up to 3 000 g/mol could be obtained using the two kinds of catalysts, respectively. As compared to CsF, the number-average degree of polymerization is higher and the relative molecular mass distribution interval is narrower when RbF is used as catalyst. The effect of factors such as impurities＇ content, reaction temperature and reaction time on the number-average degree of polymerization was also investigated. It is found that low impurities＇ content and low temperature are beneficial to the generation of high number-average degree of perfluorolyethers. The optimization reaction time is 24 h, and fiarther increase of reaction time does not significantly affect the average relative molecular mass. The product was characterized by IR, 19F NMR and GC-MS, and the catalytic mechanism was analyzed finally.展开更多
The properties of dissolution in different solvents,the specific heat capacity and thermal decomposition process under the non-isothermal conditions for energetic triazole ionic salts 1,2,4-triazolium nitrate(1a),1,2,...The properties of dissolution in different solvents,the specific heat capacity and thermal decomposition process under the non-isothermal conditions for energetic triazole ionic salts 1,2,4-triazolium nitrate(1a),1,2,3-triazolium nitrate(1b),3,4,5triamino-1,2,4-triazolium nitrate(2a),3,4,5-triamino-1,2,4-triazolium dinitramide(2b)were precisely measured using a Calvet Microcalorimeter.The thermochemical equation,differential enthalpies of dissolution(△difH m ),standard molar enthalpies of dissolution(△difH m ),apparent activation energy(E),pre-exponential constant(A),kinetic equation,linear relationship of specific heat capacity with temperature over the temperature range from 283 to 353 K,standard molar heat capacity(C p,m)and enthalpy,entropy and Gibbs free energy at 283–353 K,taking 298.15 K as the benchmark for 1a,1b,2a and 2b were obtained with treating experimental data and theoretical calculation method.The kinetic and thermodynamic parameters of thermal decomposition reaction,critical temperature of thermal explosion(Tb),self-accelerating decomposition temperature(TSADT)and adiabatic time-to-explosion(t)of 1a,1b,2a and 2b were calculated.Their heat-resistance abilities were evaluated.Information was obtained on the relation between molecular structures and properties of 1a,1b,2a and 2b.展开更多
基金Project(51004034)supported by the National Natural Science Foundation of ChinaProject(N090302009)supported by the Fundamental Research Funds for the Central Universities,China
文摘Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.
基金Project(53110704012) supported by the Fundamental Research Funds for the Central Universities,China
文摘Perfluorolyether is characterized by highly chemical inertness, oxidative stability, anticorrosion as well as radiation resistance. It can be used as lubricant especially in harsh environmental conditions. In this work, hexafluoropylene oxide was catalytically polymerized at low temperature using the methods of anionic polymerization, and perfluorolyethers were obtained with number-average degree of polymerization more than 15. CsF and RbF were used as catalysts and their catalytic activities were investigated. Experimental results show that perfluorolyethers with number-average molar masses up to 3 000 g/mol could be obtained using the two kinds of catalysts, respectively. As compared to CsF, the number-average degree of polymerization is higher and the relative molecular mass distribution interval is narrower when RbF is used as catalyst. The effect of factors such as impurities＇ content, reaction temperature and reaction time on the number-average degree of polymerization was also investigated. It is found that low impurities＇ content and low temperature are beneficial to the generation of high number-average degree of perfluorolyethers. The optimization reaction time is 24 h, and fiarther increase of reaction time does not significantly affect the average relative molecular mass. The product was characterized by IR, 19F NMR and GC-MS, and the catalytic mechanism was analyzed finally.
基金supported by the National Natural Science Foundation of China (20573098)the Science and Technology Foundation of National Key Lab of Science and Technology on Combustion and Explosion in China (9140C3503030805)
文摘The properties of dissolution in different solvents,the specific heat capacity and thermal decomposition process under the non-isothermal conditions for energetic triazole ionic salts 1,2,4-triazolium nitrate(1a),1,2,3-triazolium nitrate(1b),3,4,5triamino-1,2,4-triazolium nitrate(2a),3,4,5-triamino-1,2,4-triazolium dinitramide(2b)were precisely measured using a Calvet Microcalorimeter.The thermochemical equation,differential enthalpies of dissolution(△difH m ),standard molar enthalpies of dissolution(△difH m ),apparent activation energy(E),pre-exponential constant(A),kinetic equation,linear relationship of specific heat capacity with temperature over the temperature range from 283 to 353 K,standard molar heat capacity(C p,m)and enthalpy,entropy and Gibbs free energy at 283–353 K,taking 298.15 K as the benchmark for 1a,1b,2a and 2b were obtained with treating experimental data and theoretical calculation method.The kinetic and thermodynamic parameters of thermal decomposition reaction,critical temperature of thermal explosion(Tb),self-accelerating decomposition temperature(TSADT)and adiabatic time-to-explosion(t)of 1a,1b,2a and 2b were calculated.Their heat-resistance abilities were evaluated.Information was obtained on the relation between molecular structures and properties of 1a,1b,2a and 2b.
