The Synthetic Optimization Of DNTF And Thermal Decomposition Behavior Of Its Reaction Intermediates

3,4-bisnitrofurazanfuroxan（DNTF）is a high energy density compound with good thermal stability and can be used in explosives and propellants.This work summarized the synthesis and application of DNTF.The synthetic procedure,the thermal behavior of the synthetic reaction,the exothermic decomposition process and the application of DNTF were studied in this work.The effects of material ratio,reaction temperature and time on the yield and purity of DNTF and its intermediates were investigated using single-factor method.After optimizing the reaction conditions,the yield of DNTF was stable,and the purity of the final product and reaction intermediates were improved while the synthetic route was simplified and shortened.The solubilities of DNTF in ethanol,acetic acid,acetic acid/water and the relationship between crystallization conditions and the grain sizes of DNTF were investigated.The technology conditions of producing DNTF with three different grain sizes wereobtained.The thermal behaviors of the syntheses of 3-amino-4-aminoxinidofurazan（DAOF）and 3,4-bis（4-aminofurazan-3-yl）-furoxan（DATF）were studied with power compensation method.In the synthesis of malononitrileoxime and hydroxylamine,the heat was mainly released during the addition of the sodium nitrite solution.The reaction temperature and dosing rate did not affect the total thermal release behavior significantly.The maximal thermal release power increased with the increasing of dosing rate.A similar phenomenon was also found in the case of DATF.A quarter of the whole heat was release during the holding period.With the reaction temperature increased,heat release mainly happened in the adding period.In a specific range,the maximal thermal release power displayed a linear dependence on the dosing rate.In order to explore the thermal stability of DAOF and DATF,their adiabatic decomposition processes were studied by accelerating reaction calorimetry（ARC）.The decomposition temperature,pressure and temperature rise rate were obtained.The initial decomposition temperature was 197.4 ℃,showing the good thermal stability of DAOF.The values of apparent activation energy and pre-exponential factor were achieved as 226.15 kJ·mol^-1and 4.64 × 10²⁰s^-1,respectively.The initial decomposition temperature of DATF was 166.70 ℃,the maximum heating rate was 25.19 ℃·min^-1and the adiabatic temperature rise was 3506.00 ℃.The apparent activation energy,and pre-exponential factor were 205.20 kJ·mol^-1,4.99 × 10¹⁹s^-1,respectively.The reaction function of DAOF and DATF was f（α）=（1-α）².ARC was used to study the adiabatic thermal decomposition of DNTF.The apparent activation energy,pre-exponential factor and reaction function were recorded as 215.65 kJ·mol^-1,5.69 × 10¹⁸s^-1and f（α）=（1-α）²,respectively.Results showed that the initial decomposition temperature was between 2-methyl-1,3-5-trinitrobenzene（TNT）and 1-methoxy-2,4-dinitrobenzene（DNAN）,and the decomposition heat was higher than DNAN and TNT.All of above data indicated that DNTF was more powerful than DNAN and TNT and showed better thermal stability and shorter self-accelerating period.The molecular configuration of DNTF was calculated by density functional theory（DFT）at the B3LYP/6 – 311 + G（d,p）level.The optimized geometries of these compounds showed that no imaginary frequency was found and it was stable on the potential energy surface.Natural bond orbital（NBO）analyses were performed to reveal the origin of intermolecular interaction between DNTF and 5,5’-bistetrazole-1,1’-diolate（TKX-50）,3-nitro-1,2,4-triazole-5-one（NTO）,and octogen（HMX）,respectively.The hydrogen bonds contributed to the interaction energies dominantly.Its thermal stability was investigated by vacuum stability test.DNTF performed good compatibility with commonly used energetic materials.The performance of DNTF-based explosives were further calculated and compared to TNT-based explosives,which would be useful for the application of DNTF-based explosives.