Adsorption and Decomposition Mechanism of 1,1-Diamino-2,2-dinitroethylene on A1（111） Surface by Periodic DFT Calculations

The adsorption of 1,1-diamino-2,2-dinitroethylene （FOX-7） molecule on the AI（I 11） surface was investigated by the generalized gradient approximation （GGA） of density functional theory （DFT）. The calculations employ a supercell （4 × 4 × 2） slab model and three-dimensional periodic boundary conditions. The strong attractive forces between oxygen and aluminum atoms induce the N--O bond breaking of the FOX-7. Subsequently, the dissociated oxygen atoms and radical fragment of FOX-7 oxidize the AI surface. The largest adsorption energy is --940.5 kJ/mol. Most of charge transfer is 3.3 le from the A1 surface to the fragment of FOX-7 molecule. We also investi- gated the adsorption and decomposition mechanism of FOX-7 molecule on the AI（111） surface. The activation en- ergy for the dissociation steps of P2 configuration is as large as 428.8 kJ/mol, while activation energies of other configurations are much smaller, in range of 2.4 to 147.7 kJ/mol.

Thermochemical Properties, Thermal Behavior and Decomposition Mechanism of 1,1-Diamino-2,2- dinitroethylene （DADE）

The constant-volume combustion energy, △cU （DADE, s, 298.15 K）, the thermal behavior, and kinetics and mechanism of the exothermic decomposition reaction of 1,1-diamino-2,2-dinitroethylene （DADE） have been investigated by a precise rotating bomb calorimeter, TG-DTG, DSC, rapid-scan fourier transform infrared （RSFT-IR） spectroscopy and T-jump/FTIR, respectively. The value of △cHm （DADE, s, 298.15 K） was determined as （-8518.09±4.59） j·g^-1. Its standard enthalpy of combustion, △cU （DADE, s, 298.15 K）, and standard enthalpy of formation, △fHm （DADE, s, 298.15 K） were calculated to be （-1254.00±0.68） and （- 103.98±0.73） kJ·mol^-1, respectively The kinetic parameters （the apparent activation energy Ea and pre-exponential factor A） of the first exothermic decomposition reaction in a temperature-programmed mode obtained by Kissinger＇s method and Ozawa＇s method, were Ek=344.35 kJ·mol^-1, AR= 1034.50 S^-1 and Eo=335.32 kJ·mol^-1, respectively. The critical temperatures of thermal explosion of DADE were 206.98 and 207.08 ℃ by different methods. Information was obtained on its thermolysis detected by RSFT-IR and T-jump/FTIR.

四硝基乙酰胺酸(TNAA)的合成及热性能

以1,1'-二氨基-2,2'-二硝基乙烯(FOX-7)为原料,经浓硝酸硝化及有机溶剂萃取得到高氧平衡化合物——四硝基乙酰胺酸(TNAA)。对比了四种有机萃取溶剂(二氯甲烷、氯仿、四氯化碳和乙酸乙酯)所得TNAA的收率及纯度。采用DSC和TG研究了TNAA的热行为。结果表明,确定二氯甲烷为最佳萃取溶剂,其收率为95.0%,纯度为99.4%。升温速率10 K·min^(-1)下,TNAA熔化吸热峰的初始温度、峰值温度分别为84.8℃和87.8℃,熔融焓为61.7 J·g^(-1);分解放热峰的初始温度、峰值温度分别为117.7℃和131.4℃,分解热为934.8 J·g^(-1)。采用Kissinger方法得到的TNAA的热分解反应活化能E为124.7 k J·mol^(-1),指前因子A为10^(16.1)s^(-1)。自加速分解温度T_(SADT)为102.3℃、热爆炸临界温度T_b为112.2℃、T=Tp时TNAA热分解反应的热力学参数ΔH~≠、ΔS~≠以及ΔG~≠,分别为121.5 k J·mol^(-1)、61.2 J·K^(-1)·mol^(-1)和98.0 k J·mol^(-1)。

Synthesis, Crystal Structure and Thermal Behavior of 4,5-Diacetoxyl-2-（dinitromethylene）-imidazolidine

A new energetic material, 4,5-diacetoxyl-2-（dinitromethylene）-imidazolidine （DADNI）, was synthesized by the reaction of 4,5-dihydroxyl-2-（dinitromethylene）-imidazolidine （DDNI） and acetic anhydride, and characterized by single crystal X-ray diffraction. Crystal data for DADNI are monoclinic, space group C2/c, a= 15.9167（3）A, b= 8.6816（4）A, c=8.5209（3） A, t= 103.294（9）°, V= 1145.9（3） A3, Z=4,A=0.150 mm 1, F（000）=600, Dc= 1.682 gocm-3, R] =0.0565 and wR2=0.1649. Thermal decomposition behavior of DADNI was studied and an intensely exothermic process was observed. The kinetic equation of the decomposition reaction is：exp（-1.582 ×10^5/RT）. The critical temperature of thermal explosion is 163.76℃. The specific heat capacity of DADNI was studied with micro-DSC method and theoretical calculation method. The molar heat capacity is 343.30 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of DADNI was calculated to be 87.7 s.

Effect of Aluminum on FOX-7 Structure

The effect of aluminum on FOX-7 structure was considered. Density functional approach at the level of unrestricted B3LYP/6-311++G(d,p) level was adopted. The model considered 1-4 aluminum atoms per FOX-7 molecule. The results show that the molecular geometries as well as many molecular orbital characteristics of FOX-7 molecule are subjected multiplicity of the composites, FOX-7 + n Al ( n =1-4). In the case of n =1-2, some conformational changes occur. In the presence of three aluminum atoms, the quartet state of the composite is stable but in the doublet state, one of the N—O bonds ruptures. As for the n =4 case the singlet and triplet states are stable but in the quintet state one of the N—O bonds cleaves. As the number of aluminum atoms increases, the HOMO-LUMO energy gap decreases generally.

Non-isothermal Decomposition Kinetics of [Cu（en）2H2O] （FOX-7）2·H2O

The thermal behavior and non-isothermal decomposition kinetics of [Cu（en）2H2O]（FOX-7）2·H2O （en=ethylenediamine） were studied with DSC and TG-DTG methods.The kinetic equation of the exothermal process is dα/dt=（10^17.92/β）4α^3/4exp（-1.688×10^5/RT）.The self-accelerating decomposition temperature and critical temperature of the thermal explosion are 163.3 and 174.8 ℃,respectively.The specific heat capacity of [Cu（en）2H2O]（FOX-7）2·H2O was determined with a micro-DSC method,with a molar heat capacity of 661.6 J·mol^-1·K^-1 at 25 ℃.Adiabatic time-to-explosion was also estimated as 23.2 s.[Cu（en）2H2O]（FOX-7）2·H2O is less sensitive.

Preparation and Properties of PBXs Based on FOX-7 in Controlled Fragmentation Warhead Application

Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU)based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively.Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU(GAP/HTPB)with 14% binder.The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied,in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel,with dimensions(100 mm length,30 mm outer diameter and 3 mm thickness).Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively.Its friction sensitivity is the same as that of PBXGR4.It has better performance,in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4.It was concluded that PBXGF4 which based on FOX-7 bonded with PU/GAP matrix has good characteristics as PBX,specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive fragmentation warheads.

An integrated theoretical and experimental investigation of insensitive munition compounds adsorption on cellulose,cellulose triacetate, chitin and chitosan surfaces

This manuscript reports results of combined computational chemistry and batch adsorption investigation of insensitive munition compounds, 2,4-dinitroanisole（DNAN）, triaminotrinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（FOX-7） and nitroguanidine（NQ）, and traditional munition compound 2,4,6-trinitrotoluene（TNT） on the surfaces of cellulose, cellulose triacetate, chitin and chitosan biopolymers. Cellulose,cellulose triacetate, chitin and chitosan were modeled as trimeric form of the linear chain of4 C1 chair conformation of β-D-glucopyranos, its triacetate form, β-N-acetylglucosamine and D-glucosamine, respectively, in the 1 ？ 4 linkage. Geometries were optimized at the M062 X functional level of the density functional theory（DFT） using the 6-31 G（d,p） basis set in the gas phase and in the bulk water solution using the conductor-like polarizable continuum model（CPCM） approach. The nature of potential energy surfaces of the optimized geometries were ascertained through the harmonic vibrational frequency analysis. The basis set superposition error（BSSE） corrected interaction energies were obtained using the 6-311 G（d,p）basis set at the same theoretical level. The computed BSSE in the gas phase was used to correct interaction energy in the bulk water solution. Computed and experimental results regarding the ability of considered surfaces in adsorbing the insensitive munitions compounds are discussed.