Thermal Decomposition of Energetic Materials 83. Comparison of the Pyrolysis of Energetic Materials in Air versus Argon

T‐Jump/FTIR spectroscopy was employed to flash pyrolyze a series of energetic compounds in an air atmosphere for comparison with an argon atmosphere. The O‐NO₂ compounds (NG, NC, and PETN), N‐NO₂ compounds (RDX and HMX), and C‐NO₂ compounds (DNT, TNT, and NTO) were studied. The effect of the surrounding atmosphere on the pyrolysis gases roughly correlates with the trend in the vapor pressure of the parent energetic material (i. e. DNT>NG>TNT>NTO>PETN≈RDX>NC≈HMX). For high vapor pressure compounds, the gaseous phase reactions dominate and the dependence on the surrounding atmosphere is strong. For low vapor pressure compounds, the condensed phase decomposition dominates and the dependence on the surrounding atmosphere is weak. That is, the extent of condensed phase vs. gas phase decomposition is the major factor in the effect of the surrounding atmosphere on the decomposition gases. The main reactions in the air are CO with O₂ which is fast, and NO with O₂, which is slow. However, these pyrolysis products for the nitrate esters, the nitramines, and the C‐NO₂ compounds behave differently suggesting that a common process, such as surface catalysis, is not responsible for the behavior seen. There is little effect of the relative humidity (0–60% range) except in the case of HMX.     

Thermal Decomposition of Energetic Materials 57. Products of some self-igniting fuel-HNO3 Systems

Exothermic reactions of some self igniting fuel-HNO₃ systems have been examined by the rapid-scan FIR/thermal profiling technique. A sudden rise in temperature is observed when the liquid oxidizer is dropped onto the solid fuel. Simultaneous monitoring of the gas products of the reaction occurring between p-phenylenediamine and HNO₃ reveals the formation of Co₂, NO₂ and HONO. Immediate evolution of NO₂ is observed in the synergistically igniting systems comprised of substituted anilines, Mg and HNO₃. Thiocarbohydrazide and its acetone and benzaldehyde monoderivatives on reacting with HNO₃ produce SO₂, NO₂ and, possibly, OCS. The results are explained in terms of the oxidation and nitration reactions occurring in these systems.     

Thermal Decomposition of Energetic Materials. 47. A trigger linkage study of high-nitrogen content nitraminotetrazoles and nitramino-1,2,4-triazoles

The thermal decomposition of six related nitraminotctrazoles and nitramino-1, 2, 4-triazoles at slow (5°C/min, DSC) and fast (⪈ 70°C/s, FTIR/temperature profiling) heating rates is described. The nitramine protion of the molecule appears to initiate the degradation in all cases except 5-nitraminotetrazole (5-NATZ) where the tetrazole ring is the trigger linkage. The crystal structures of DNTP and 5-NATZ are described and help explain the decomposition process. DNTP contains one of the longest N-NO₂ bonds known for a nitramine (1.49 Å). 5-NATZ was found to be a nitrimine rather than a nitramine.     

Thermal Decomposition of Energetic Materials 78. Vibrational and Heat of Formation Analysis of Furazans by DFT

Density functional theory (DFT) was used to calculate the heats of formation and infrared active vibrational frequencies of twelve furazan compounds. The absolute values of the heats of formation are unreliable but the trends with systematic variations of the bridge and terminal groups are reasonable. The assignments of the vibrational motions to IR frequencies based on a force field analysis are given to clarify the complex coupling in these molecules.     

Thermal Decomposition of Energetic Materials. 43. Fast thermolysis of cubylammonium nitrate and cubane-1,4-diammonium dinitrate

The rapid thermal decomposition (dT/dt ≥ 70°C/s) of eubylammonium nitrate (CUBAN) and cubane-1, 4-diammonium dinitrate (CUBDAN) is described in terms of the temperature profile and gas products as a function of pressure (1-200 psi Ar). In this environment the full strain energy of cubane is not released simultaneously with the redox reactions that involve the ammonium nitrate site because C₂H₄ and/or C₂H₂ are evolved. No large hydrocarbons form during rapid thermolysis, although both salts sublime to some extent below 7 psi Ar. CUBDAN is the only alkyldiammonium dinitrate salt that we have found to sublimduring fast thermolysis. An estimated gas phase basicity of about 215 kcal/mol for the cubylamines is obtained from the tendency to release HNO₃(g). This value is surprising in light of the basicity values for other primary amines.     

Thermal Decomposition of Energetic Materials XXVIII. Predictions and results for nitramines of bis-imidazolidinedione: DINGU,TNGU and TDCD

Structural/thermal decomposition relationships are assessed in this project. The relative concentrations of the first observed, infrared-active gas products generated by fast thermolysis (dT/dt = 110 K/s) of 2,5-dioxo-1,3,4,6-tetranitro-tetrahydrocyclobutan[1,2-d : 3,4-d′]diimidazole (TDCD) and 1,3,4,6-tetranitroglycoluril (TNGU) were successfully predictable from structure/thermal decomposition relationships. The predictions for 1,4-dinitroglycoluril (DINGU) were only partly successful. The departures from expection appear to originate from the different degree of stability of the non-energetic backbone of these molecules. The dependence of the first-observed gas products on pressure from these molecules was qualitatively predicted from the nature of the products liberated at atmospheric pressure.     

金属氢化物在含能材料中的燃烧、热分解及应用研究进展

为了促进金属氢化物材料在含能材料中的研究应用,从金属氢化物在含能材料中的燃烧、热分解和应用3个方面对金属氢化物在含能材料(EMs)中的研究现状和前景进行了概述。结果表明,在含能材料中加入适量的金属氢化物可以有效地改善混合体系的燃烧热、能量水平等其他方面的性能指标。将金属氢化物添加在含能材料中具有巨大的潜力,但金属氢化物与含能材料间的相容性及金属氢化物本身的稳定性等阻碍了金属氢化物在含能材料中的应用。其中,开发具有适当热稳定性的金属氢化物较为迫切。掺杂和纳米晶化是提高金属氢化物热力学性能最有效的两种方法。     

Thermal Decomposition of Energetic Materials. XV. Evidence that decomposition initiates deflagration: high-rate thermolysis of FEFO,TEFO, and DITEFO

The thermal decomposition of three energetic materials containing the formal group, FEFO, TEFO, and DITEFO have been studied by rapid-scan infrared spectroscopy. The five gem-trinitro compounds studied to date all display a transition from decomposition to deflagration according to the gas products evolved during the first second of rapid thermolysis. FEFO is the first compound without a gem-trinitro group to exhibit this transition in the same experiment. These results provide convincing evidence that decomposition occurs in advance of deflagration and imply that decomposition studies are relevant to understanding the initiation of combustion. Under directly comparable conditions fluorodinitro compounds are confirmed to be more thermally stable than the analogous gem-trinitro compounds. Also, DTA and IR spectroscopy show that DITEFO has solid-solid phase transitions between 295 K and its melting point.     

Thermal Decomposition of Energetic Materials 41. Fast thermolysis of cyclic and acyclic ethanediammonium dinitrate salts and their oxonium nitrate double salts,and the crystal structure of piperazinium dinitrate

Fast thermolysis/FTIR spectroscopy of [H₃NCH₂CH₂NH₃]-(NO₃)₂ (EDD), [H₂N(CH₂CH₂)₂NH₂](NO₃)₂ (PIPDN), and [HN(CH₂CH₂)₃NH](NO₃)₂(DABCOD) and new oxonium nitrate (H₃O⁺NO⁻³) double salts of PIPDN and DABCOD is described. EDD initially yields HNO₃ and then small molecule decomposition products from redox reactions when heated at ≥ 100°C (dcc.). PIPDN initially yields HNO₃, but then generates a significant amount of N,N′-dinitrosopiperazine along with small molecule fragments. DABCOD produces no HNO₃(g), but instead gives CH₂O, N,N′-dinitrosopiperazine and small molecule products. These patterns are entirely consistent with the behavior observed for primary, secondary and teritary ammonium mononitrate salts in our previous work. The presence of nitrosamines strongly increases the health hazard of the matcrials upon heating. No nitramines were detected as thermolysis products. Thermolysis of the oxonium nitrate double salts liberates HNO₃ and H₂O at a relatively low temperature (≥ 60 °C). Above this temperature, the thenmolysis proceeds in the same way as that of pure PIPDN and DABCOD. The crystal structure of PIPDN is described.     

Thermal Decomposition of Energetic Materials 81. Flash Pyrolysis of GAP/RDX/BTTN Propellant Combinations

The pyrolysis of a 50/50 mixture of RDX/GAP‐diol cured with the isocyanate compound N‐100, and a 70/21/9 mixture of RDX/BTTN/ GAP‐polyol cured with HMDI were studied by the T‐jump/FTIR spectroscopy technique. To understand the behaviors better, pyrolysis was also conducted on pure N‐100, pure BTTN, GAP‐diol cured with N‐100, and 70/30 BTTN/GAP‐polyol cured with HMDI. Pure N‐100 and the cured propellants liberate a large quantity of HMDI upon pyrolysis. This result reveals that the urethane bonds break early in the reaction sequence and the curing agent begins to vaporize from the matrix. The 50/50 RDX/GAP mixture decomposed with relatively little smoke or residue, which sharply contrasts with its reported behavior upon combustion. The difference can be attributed to the mismatch between the heating rates of flash pyrolysis and combustion. During pyrolysis the RDX and GAP are able to remain in contact longer such that fuel‐oxidizer reactions occur between them. During combustion the two compounds may segregate due to evaporation of most of the RDX. Hence the GAP decomposes in the condensed phase giving smoke and residue without the benefit of oxidation by NO₂ from the RDX. This discrepancy does not exist with the more fuel‐oxidizer balanced 70/21/9 mixture of RDX/BTTN/GAP, where the interaction of the fuel and oxidizer species is strong.     

静态与动态高压对含能材料热分解的影响

利用常压和高压差示扫描量热仪（DSC、PDSC）在动态和静态状下研究了CL-20、HMX、RDX、NC、NG、NG NC等几种含能材料的热分解,探讨了常压与高压条件下,静态与动态对这些含能材料热分解的影响。结果显示含能材料热分解受压力和动态气氛的影响有三种情况：1、热分解同时受到压力和动态气氛的影响;2、热分解既不受压力也不受动态气氛的影响;3、热分解只受压力的影响而不受动态气氛的影响。     

Thermal Decomposition of Energetic Materials XVIII. Bis (cyanomethyl)nitramine and Bis(cyanoethyl)nitramine

The crystal structures of two potentially useful cyanonitramines are reported. Bis(cyanomethyl)nitramine (BCMN), (NCCH₂)₂NNO₂: monoclinic, C2, a = 10.247(1), b = 7.771(1), c = 12.230(2) [Å], β = 107.45 (2)^°, Z = 6, D_calc = 1.502 g.cm⁻³, R_F = 2.8%, R_wF = 3.1%. A syn (C₂) and anti (C_s) isomers of BCMN crystallize together in a 2:1 ratio in the unit cell. Bis(cyanoethyl)nitramine (BCEN), (NCCH₂CH₂)NNO₂: monoclinic, P2₁/c, a = 7.512(2), b = 10.840(3), c = 10.181(3) [Å], β = 97.39(2)^°, Z = 4, D_cale = 1.357 g.cm⁻³, R_F = 4.6%, R_wF = 4.7%. Only one conformation of the BCEN molecule having no symmetry is present in the unit cell. The IR spectrum shows that BCEN forms an amorphous phase when the melt is cooled or when an acetone or acetonitrile solution is rapidly evaporated. The amorphous phase slowly crystallizes at room temperature. High-rate thermolysis of BCMN liberates NO₂ as the predominant initial product. This difference is qualitatively predictable on the basis of the variation in the N-N bond distance in these two compounds.     

Thermal Decomposition of Energetic Materials 56. On the fast thermolysis mechanism of ammonium nitrate and its mixtures with mangnesium and carbon

Fast thermolysis studies of ammonium nitrate (AN) and its mixtures with magnesium and activated charcoal have been carried out by the Fourier transform infrared spectroscopy/temperature profiling technique. When subjected to rapid heating (ca. 80°C/s), AN Sublimes/decomposes around 300°. Sublimation dominates at ambient pressures. The IR-active products of decomposition are NH₃, NO₂, N₂O and H₂O. Reaction schemes accounting for the products are proposed which involve proton transfer leading to NH₃ by the decomposition products of HNO₃. The decomposition of AN is significantly enhanced when AN is mixed with magnesium powder or charcoal, and occurs at as low a temperature as 135°C. Whereas NH₃ is the major product of decomposition of AN Mg mixtures, no NH₃ is observed from AN C mixtures. The results are explained by the reaction of HNO₃ and NH₃ with Mg or C.     

Thermal Decomposition of Energetic Materials 86. Cryogel Synthesis of Nanocrystalline CL‐20 Coated with Cured Nitrocellulose

An unusual energetic composite, in which spherical nano‐dimensional particles of CL‐20 were uniformly coated with HDI‐cross‐linked nitrocellulose, was synthesized by the sol‐gel to cryogel method. Up to 90% solid loading was achieved. The particle size of CL‐20 was determined to be in the range of 20–200 nm by transmission electron microscopy, atomic force microscopy, and X‐ray powder diffraction. The decomposition characteristics of the composite were investigated by DSC and T‐jump/FTIR spectroscopy. The decomposition properties were controlled mostly by nitrocellulose until the percentage of CL‐20 was well above 50%. The drop weight impact sensitivity of the cryogels was essentially independent of the composition.     

含能功能化氧化石墨烯的制备、热分解行为及其对AP热分解的催化作用

为了提高氧化石墨烯(GO)对高氯酸铵(AP)热分解反应的催化活性,以GO和2,4,6-三硝基苯胺(TNA)为原料,N,N-二甲基甲酰胺、三乙胺为溶剂和酸束缚剂,合成一种新型含能功能化氧化石墨烯(EFGO);采用HRTEM、FT-IR、Raman和XPS表征了EFGO结构;采用TG-DTG和DSC分析了EFGO的热分解行为及EFGO对AP热分解反应的催化作用。结果表明,TNA通过共价键修饰至GO片层表面,其中,TNA分子中的—NH2与GO片层表面的C—O—C发生开环反应,生成C—NH键;EFGO热稳定性高,在143.8~770.0℃范围内发生了非常缓慢的失重过程,最大失重率发生在约172.1℃,整个过程失重21.2%;EFGO质量分数分别为2.5%、5%和10%时,可使AP在高温阶段的分解峰温分别降低25.6、48.0和113.1℃,表观分解放热量分别增加371、1499和2693J/g;表明EFGO对AP热分解反应的催化活性相对于GO得到显著提高,将其作为非金属含能催化剂应用于AP基固体推进剂具有潜在的应用前景。     

Thermal Decomposition of Energetic Materials 77. Behavior of N‐N Bridged Bifurazan Compounds on Slow and Fast Heating

Nine energetic furazan (1,2,5‐oxadiazole) compounds were flash‐heated by the use of T‐jump/FTIR spectroscopy. Thermodynamically relatively stable gaseous products are formed, which reflect several patterns in the stoichiometry of the parent compound. The hydrazo‐bridged furazans lose H₂ to form the azo‐bridged analog before the ring decomposes. The melting point and sublimation properties qualitatively relate to the crystal structure and hydrogen bonding potential in these compounds. The synthesis of dinitrohydrazofurazan is given for the first time.     

A New Computer Code for Assessment of Energetic Materials with Crystal density,Condensed Phase Enthalpy of Formation,and Activation Energy of Thermolysis

Crystal density and enthalpy of formation of the condensed phase of energetic compounds are two important input parameters for the performance prediction in several computer codes for rapid hazard assessment of energetic materials. A novel easy‐to‐handle user‐friendly computer code in Visual Basic is introduced to predict these parameters for various energetic compounds including nitroaliphatics, nitrate esters, nitramines, polynitroarenes, and polynitroheteroarenes. The calculated values can be used as inputs for other thermochemical/hydrodynamic computer codes. This computer code is also able to calculate the activation energies of thermal decomposition of polynitroarenes and nitramines in condensed state. The number of carbon, hydrogen, oxygen, and nitrogen atoms and specification of some molecular fragments are input parameters for this code without using any experimental data. The new algorithms on the base of easy‐to‐get input parameters are tested for some new energetic compounds, which provide more reliable results as compared to the best available methods.     

Thermal Decomposition of Energetic Materials 69. Analysis of the kinetics of nitrocellulose at 50 °C–500 °C

Kinetic constants for decomposition of nitrocellulose in the 50 °C to 500°C range are analyzed. At T < 100°C, three processes (depolymerization, peroxide formation, and hydrolysis) are consistent with the reported kinetics. For T = 100°C–200°C, 28 of 30 previously reported kinetic measurements can be organized clearly into two categories by the use of the kinetic compensation effect. These two groups fit the first-order and autocatalytic processes. Conflicting interpretations are reconciled by this approach. At T > 200°C, the kinetics are consistent with the existence of the first-order step and desorption of the products as two parallel processes which, together, control the rate. Time-to-exotherm and mass burning rate kinetics are compared as temperature-dependent reaction-desorption events.     

覆碳铁、钴、镍纳米复合材料对AP的催化热分解

通过400℃,500℃、600℃热解含Fe,Co,Ni的高聚物前驱体（M-PAA,M为Co,Fe,Ni）制备覆碳的Fe,Co,Ni纳米复合材料（M／C）,研究了其对AP热分解的影响。XRD和TEM结果表明,500℃热解M-PAA均可获得纳米Fe（Co或Ni）／C材料,热解产物中Co,Fe,Ni颗粒的平均粒径分别为13nm,18nm和20nm。DTA研究结果表明,添加500℃热解所得的M／C（M／C-500）对AP的热分解有明显的催化作用,其催化作用随着M／C-500添加量的增加而增加,Ni／C-500,Fe／C-500,Co／C-500分别使AP高温分解峰最大可降低54．5℃,79．3℃和156．2℃。其中Co／C-500可使AP的高温和低温分解峰发生重叠。