铝粉粒度对高氯酸铵热分解动力学的影响

采用热重-差示扫描量热(TG-DSC)联合技术研究了10.7 μm, 2.6 μm和40 nm铝粉对高氯酸铵(AP)热分解的影响. 结果表明, 铝粉的加入对AP的低温放热峰有抑制作用, 对高温放热分解反应有促进作用, 并且随铝含量的增加和铝粒径的减小这种作用更强烈. 采用多元非线性拟合技术对不同升温速率下TG-DSC实验数据进行拟合, 结果表明, 质量分数为40%的不同粒径铝粉的加入对AP的热分解三阶段(A→B→C→D)反应模型无影响, 但反应机理函数发生了改变. 纯AP, AP/Al(10.7 μm), AP/Al(2.6 μm)及AP/Al(40 nm)的反应机理函数组合分别为C1/D1/D1, C1/D1/D3, C1/D1/D4和C1/D1/F2.     

Thermal decomposition of RDX/AP by TG–DSC–MS–FTIR

The method of TG–DSC–MS–FTIR simultaneous analysis has been used to study the thermal decomposition mechanism of the RDX/AP (1/2) mixture. TG–DSC showed that there were two mass loss processes for thermal decomposition of RDX/AP. The first one was mainly ascribed to the thermal decomposition of RDX. Addition of AP to RDX causes decomposition to take place abruptly, after melting, resulting in a very sharp and strong peak at lower temperature. The apparent activation energies, calculated by model-free Friedman method, of this process were negative. The second mass loss process of RDX/AP was confirmed to be the thermal decomposition of AP, catalyzed by RDX. This process can be divided into three stages, which were an nth-order autocatalytic and two one-dimensional diffusion stages, respectively. There was a competition among the formation reactions of N₂O, HNCO, and HCl for the first stage and between NO₂ and N₂O for the later two stages. The production of N₂O dominated in the second stage, while NO₂ did in the third stage.     

Thermal behavior of ammonium perchlorate and metal powders of different grades

The effects of aluminum (Al) and nickel (Ni) powders of various grain sizes on the thermal decomposition of ammonium perchlorate (AP) were investigated by TG and DSC in a dynamic nitrogen atmosphere. The TG results show that Al powders have no effect on the thermal decomposition of AP at conventional grain size, while the nanometer-sized Ni powders (n-Ni) have a great influence on the thermal decomposition of AP with conventional and superfine grain size. The results obtained by DSC and an in situ FTIR analysis of the solid residues confirmed the promoting effects of n-Ni. The effects of n-Ni have been ascribed to its enhancement on the gas phase reactions during the second step decomposition of conventional grain size AP.     

Thermal decomposition of energetic materials. 5. reaction processes of 1,3,5-trinitrohexahydro-s-triazine below its melting point

Through the use of simultaneous thermogravimetry modulated beam mass spectrometry, optical microscopy, hot-stage time-lapsed microscopy, and scanning electron microscopy measurements, the physical and chemical processes that control the thermal decomposition of 1,3,5-trinitrohexahydro-s-triazine (RDX) below its melting point (160-189 degrees C) have been identified. Two gas-phase reactions of RDX are predominant during the early stages of an experiment. One involves the loss of HONO and HNO and leads to the formation of H2O, NO, NO2, and oxy-s-triazine (OST) or s-triazine. The other involves the reaction of NO with RDX to form NO2 and 1-nitroso-3,5-dinitrohexahydro-s-triazine (ONDNTA), which subsequently decomposes to form a set of products of which CH2O and N2O are the most abundant. Products from the gas-phase RDX decomposition reactions, such as ONDNTA, deposit on the surface of the RDX particles and lead to the development of a new set of reaction pathways that occur on the surface of the RDX particles. The initial surface reactions occur on surfaces of those RDX particles in the sample that can accumulate the greatest amount of products from the gas-phase reactions. Initial surface reactions are characterized by the formation of islands of reactivity on the RDX surface and lead to the development of an orange-colored nonvolatile residue (NVR) film on the surface of the RDX particles. The NVR film is most likely formed via the decomposition of ONDNTA on the surface of the RDX particles. The NVR film is a nonstoichiometric and dynamic material, which reacts directly with RDX and ONDNTA, and is composed of remnants from RDX and ONDNTA molecules that have reacted with the NVR. Reactions involving the NVR become dominant during the later stage of the decomposition process. The NVR reacts with RDX to form ONDNTA via abstraction of an oxygen atom from an NO2 group. ONDNTA may undergo rapid loss of N2 and NO2 with the remaining portion of the molecule being incorporated into the dynamic NVR. The dynamic NVR also decomposes and leads to the formation of H2O, CH2O, N2O, NH2CHO, (CH3)2NCHO, (CH3)2NNO, C2H2N2O, and (CH3)3N or CH3NCH2CH3. The competition between reaction of the dynamic NVR with RDX and its own thermal decomposition manifests itself in a rapid increase in the rate of evolution of the NVR decomposition products as the amount of RDX remaining in the sample nears depletion. The reactions between the NVR film and RDX on the surface of the RDX particles leads to a localized environment that creates a layer of molten RDX on the surface of the particles where reactions associated with the liquid-phase decomposition of RDX may occur. The combination of these reaction processes leads to an acceleration of the reaction rate in the later stage of the decomposition process and creates an apparent reaction rate behavior that has been referred to as autocatalytic in many previous studies of RDX decomposition. A reaction scheme summarizing the reaction pathways that contribute to the decomposition of RDX below its melting point is presented.     

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

A new energetic material, 4,5-dimethoxy-2-(dinitromethylene)imidazolidine(DMDNI), was synthesized by the reaction of 4,5-dihydroxyl-2-(dinitromethylene)-imidazolidine(DDNI) and methanol, and structurally characterized by single crystal X-ray diffraction. DMDNI crystallized in triclinic space group P, with crystal data a=0.4324(4) nm, b=1.3599(11) nm, c=1.7503(14) nm, α=77.406(14)°, β=84.494(15)°, γ=87.976(14)°, V=0.9997(14) nm³, Z=4, μ＝0.140 mm^-1, F(000)=488, D_c=1.556 g/cm³, R₁=0.0773 and wR₂=0.1574. Thermal decomposition of DMDNI was studied, and its thermal decomposition process was divided into two stages. The first stage was a mel- ting process and the second stage was an exothermic decomposition process. The enthalpy, apparent activation energy and pre-exponential constant of the exothermic decomposition reaction are -491.5 J/g, 142.3 kJ/mol and 10^14.24 s^-1, respectively. The critical temperature of thermal explosion is 162.47℃. DMDNI has a lower thermal stability than DDNI but it is close to that of 4,5-diacetoxyl-2-(dinitromethylene)-imidazolidine(DADNI).     

超级铝热剂Al/Fe2O3的制备、表征及对环三亚甲基三硝胺热分解的影响

采用水热法制备了中空短棒状纳米Fe2O3,并用超声分散法将其与纳米Al颗粒复合为单金属氧化基超级铝热剂.利用X射线粉末衍射(XRD)、傅里叶变换红外(FTIR)光谱、扫描电镜及能量散射光谱仪(SEM-EDS)对样品进行表征.并运用差示扫描量热法(DSC)对比研究了超级铝热剂Al/Fe2O3、Al粉和纳米Fe2O3对环三亚甲基三硝胺(RDX)热分解特性的影响.结果表明:超级铝热剂的加入改变了RDX的热分解过程,并加剧了RDX的二次气相反应;随着超级铝热剂含量的增加,RDX的分解峰峰形发生了明显的改变;Al/Fe2O3、Al粉和Fe2O3对RDX热分解的作用主要表现为二次分解峰逐渐明显且峰温降低.     

Dinuclear (Ferrocenylmethyl)imidazolium Ionic Compounds with Polycyano Anions. Characterization,Migration, and Effects during Combustion

Alkyl‐substituted ferrocene‐based burning rate catalysts exhibit high migration and volatility during curing process and prolonged storage of the composite solid propellants. To deal with the drawbacks twenty‐one dinuclear (ferrocenylmethyl)imidazolium compounds paired with polycyano anions, were synthesized and characterized by ¹H NMR, ¹³C NMR, UV/Vis, elementary analysis, and both 2 and 11 were further characterized by single‐crystal X‐ray diffraction. The migration test revealed that the compounds have excellent anti‐migration ability. The cyclic‐voltammetry results suggested that they are quasi‐reversible or irreversible redox systems. The TG/DSC analyses showed that the compounds are highly thermal stable. Their effects on the thermal decomposition of ammonium perchlorate (AP) and 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX) were additionally examined. The results showed that the new compounds have strong effects on the thermal decomposition of both AP and RDX during combustion. Both 13 and 21 are more excellent than catocene for increasing the released heats of AP and can be used as alternatives of catocene in the composite solid propellants.     

竹材非等温热解动力学

利用热重分析技术对竹材在高纯N2条件下,从室温至1273K进行了非等温热解分析,研究了升温速率(5、10、20和40K/min)对热解过程的影响,探讨了其热解机理。研究表明,竹材非等温热解过程主要分为失水干燥、快速热解和缓慢分解三个阶段组成,其中第二阶段是整个过程的主要阶段,析出大量挥发分造成明显失重。升温速率对热解过程有显著影响,随着升温速率的增加,最大热解速度增大,对应的峰值温度升高,热滞后现象加重,热解各阶段向高温侧移动。热解机理满足一维扩散Parabolic法则,反应机理函数为g(α)=α2。不同升温速率下活化能为75.32-82.99kJ.mol-1,指前因子为1.17×105-1.12×106min-1。     

The two steps thermal decomposition of titanium hydride and two steps foaming of Al alloy

1 Introduction Al alloy foam with closed pores prepared by melt foaming, realizing the lightness, high specific strength and multifunction of structure material, is becoming one of the hotspots[1―11]. In order to meet the demand of high-tech, preparing s…     

Thermal Behavior and Non-isothermal Decomposition Reaction Kinetics of NEPE Propellant with Ammonium Dinitramide

Thermal decomposition behavior and non‐isothermal decomposition reaction kinetics of nitrate ester plasticized polyether NEPE propellant containing ammonium dinitramide (ADN), which is one of the most important high energetic materials, were investigated by DSC, TG and DTG at 0.1 MPa. The results show that there are four exothermic peaks on DTG curves and four mass loss stages on TG curves at a heating rate of 2.5 K·min^?1 under 0.1 MPa, and nitric ester evaporates and decomposes in the first stage, ADN decomposes in the second stage, nitrocellulose and cyclotrimethylenetrinitramine (RDX) decompose in the third stage, and ammonium perchlorate decomposes in the fourth stage. It was also found that the thermal decomposition processes of the NEPE propellant with ADN mainly have two mass loss stages with an increase in the heating rate, that is the result of the decomposition heats of the first two processes overlap each other and the mass content of ammonium perchlorate is very little which is not displayed in the fourth stage at the heating rate of 5, 10, and 20 K·min^?1 probably. It was to be found that the exothermal peak temperatures increased with an increase in the heating rate. The reaction mechanism was random nucleation and then growth, and the process can be classified as chemical reaction. The kinetic equations of the main exothermal decomposition reaction can be expressed as: dα/dt=10^12.77(3/2)(1?α)[?ln(1?α)]^1/3 e^{?1.723×104/T}. The critical temperatures of the thermal explosion (T_be and T_bp) obtained from the onset temperature (T_e) and the peak temperature (T_p) on the condition of β→0 are 461.41 and 458.02 K, respectively. Activation entropy (ΔS^≠), activation enthalpy (ΔH^≠), and Gibbs free energy (ΔG^≠) of the decomposition reaction are ?7.02 J·mol^?1·K^?1, 126.19 kJ·mol^?1, and 129.31 kJ·mol^?1, respectively.     

The influence of reagents solvation on enthalpy change of glycine-ion protonation and silver(I) glycine-ion complexation in aqueous-dimethylsulfoxide solutions

The thermal decomposition process and non-isothermal decomposition kinetic of glyphosate were studied by the Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA). The results showed that the thermal decomposition temperature of glyphosate was above 198?°C. And the decomposition process was divided into three stages: The zero stage is the decomposition of impurities, and the mass loss in the first and second stage may be methylene and carbonyl, respectively. The mechanism function and kinetic parameters of non-isothermal decomposition of glyphosate were obtained from the analysis of DTA?CTG curves by the methods of Kissinger, Flynn?CWall?COzawa, Distributed activation energy model, Doyle and ?atava-?esták, respectively. In the first stage, the kinetic equation of glyphosate decomposition obtained showed that the decomposition reaction is a Valensi equation of which is two-dimensional diffusion, 2D. Its activation energy and pre-exponential factor were obtained to be 201.10?kJ?mol^?1 and 1.15?×?10¹⁹?s^?1, respectively. In the second stage, the kinetic equation of glyphosate decomposition obtained showed that the decomposition reaction is a Avrami?CErofeev equation of which is nucleation and growth, and whose reaction order (n) is 4. Its activation energy and pre-exponential factor were obtained to be 251.11?kJ?mol^?1 and 1.48?×?10²¹?s^?1, respectively. Moreover, the results of thermodynamical analysis showed that enthalpy change of ??H ^??, entropy change of ??S ^?? and the change of Gibbs free energy of ??G ^?? were, respectively, 196.80?kJ?mol^?1,107.03?J?mol^?1?K^?1, and 141.77?kJ?mol^?1 in the first stage of the process of thermal decomposition; and 246.26?kJ?mol^?1,146.43?J?mol^?1?K^?1, and 160.82?kJ?mol^?1 in the second stage.     

纳米晶镁铝水滑石的制备及其热分解机理

研究了无机阻燃剂镁铝水滑石纳米晶的制备及其热分解机理.采用常压下,一步反应的液相法制备镁铝水滑石试样，用XRD和TEM测试试样的相组成和形貌，针状镁铝水滑石纳米晶体的长度约80 nm.依据DSC和DTA-TG测试结果，发现镁铝水滑石纳米晶的热分解由两个阶段组成:第一个吸热峰出现在220 ℃左右，第二个吸热峰出现在380 ℃左右.研究了反应时间对所得镁铝水滑石试样的热分解性能的影响，发现延长反应时间，镁铝水滑石试样的第一次、第二次热分解的起始温度升高,第一次热分解的失重值增大，最后剩余氧化物的量增大，从而增强镁铝水滑石阻燃剂的阻燃性能.根据不同升温速率下获得的DSC测试数据，应用Achar微分法、Šatava-Šesták积分法和Ozawa积分法对镁铝水滑石纳米晶热分解的第二个阶段进行了动力学计算和分析，确定该段的热分解机理函数积分式为(1－α)－1－1.     

A study of the sensitivity and decomposition of 1,3,5-trinitro-2-oxo-1,3,5-triazacyclo-hexane

The thermal decomposition and thermal stability of 1,3,5-trinitro-2-oxo-1,3,5-triazacyclohexane (keto-RDX or K-6) was studied. The keto-RDX synthesis is described, mass spectra (electron impact (70 eV) and chemical ionization) similar to RDX spectra registered under identical conditions are presented, and mass spectroscopy fragmentation paths are proposed. The LI-MS (laser induced/mass spectroscopic) results imply that the first step in the decomposition of keto-RDX is the elimination of NO₂ or HONO and subsequent breakdown of the triazacyclohexane ring. The thermal stability, activation energy (E_a = 140 kJ mol⁻¹), and frequency factor (K₀ = 9 × 10⁹ s⁻¹) in the temperature interval 90-120°C were measured using chemiluminescence (NO detection only). The activation energy was also determined from DSC data using the ASTM method E 698-79, and was found to be 280 kJ mol⁻¹ with a frequency factor of 7.0 × 10²⁹ s⁻¹ in the temperature interval 175-200°C. Microcalorimetry, drop-weight test, friction test, and ignition temperature (Wood's metal bath) measurements were also conducted. Quantum mechanical calculations (semi-empirical method with PM3 set at the unrestricted Hartree-Fock level) were conducted to correlate the sensitivity and thermal decomposition with those of RDX. No significant differences in bond-breaking energies for RDX and keto-RDX were found. Conclusions drawn from the experiments are that the decomposition of keto-RDX is auto-catalytic, and that the sensitivity of keto-RDX is not connected with the initial bond-breaking step. More than one method for measuring the risk involved in handling an explosive is necessary since the sensitivity depends on different stages in the decomposition.     

Dynamic pressure thermal analysis of double-base propellants containing RDX

The thermal decomposition of five double-base propellants modified with RDX was studied by dynamic pressure thermal analysis to determine the effect of RDX content (20–60 wt.%) on performance. All have good stability. Both stability and activation energy increase as RDX increases from 20% to 50% then decrease; 50% RDX performs best. The decomposition mechanism is affected by RDX content and temperature. Increasing temperature induces autocatalysis and accelerates decomposition.      

Differential thermal analysis and thermogravimetry of ammonium perchlorate at pressures up to 51 ATM

The thermal decomposition of pure ammonium perchlorate (AP)was investigated in various gaseous atmospheres at pressures up to 51 atm, using a technique of thermal analysis. It is concluded that the first and second stage decompositions of AP in an atmosphere of oxygen or nitrogen are appreciably accelerated as the pressure is increased. Platinum has a catalytic effect in the high-temperature decomposition and suppresses the sublimation of AP at high temperature ranges in helium atmosphere even at 1 atm. The reaction heat for the high-temperature decomposition of AP in the platinum cell was calculated from the peak temperatures of DTA curves at various pressures to be 77.9 kcal mol^?1. The activation energies of the sublimation in helium at 1 atm and of the high-temperature decomposition in the platinum cell at various pressures of helium have also been obtained, giving similar values of 23–25 kcal mol^?1.     

Thermal decomposition properties of double-base propellant and ammonium perchlorate

The thermal decomposition properties and the heat of combustion (ΔH) of samples with different ammonium perchlorate (AP)/double base propellant (DB) mass ratios under argon atmosphere were studied by the thermogravimetry–differential scanning calorimetry–mass spectrometry–Fourier transform infrared spectroscopy (TG–DSC–MS–FTIR) and automatic calorimeter method. The results show that decomposition process of AP/DB samples in negative and zero oxygen balance (OB) is different from that in positive OB. With the increasing of AP in the AP/DB samples, the decomposition of the samples becomes more and more severe. When the OB of the samples is positive, the phenomenon of deflagration or explosion could be observed in the decomposition process. The sample with OB = 0 has the greatest heat of combustion.     

Facile Fabrication of Cu-doped Carbon Aerogels as Catalysts for the Thermal Decomposition of Ammonium Perchlorate

We report a simple and effective method to produce copper-doped carbon aerogel (Cu-CA) using sodium alginate as a carbon precursor through ion crosslinking and high-temperature carbonization. Results indicate that Cu-alginate has a 3D scaffold structure with pores. The effect of using different metal salt mass ratios of Cu-CA on the catalytic thermal decomposition of AP is also investigated. The thermal decomposition temperature of AP decreases by 94.24 °C, and the activation energy of the decomposition reaction is reduced by 45.7 kJ/mol. These results demonstrate that the composite exhibits superior catalytic performance compared with a single-component transition metal salt.     

Preparation,characterization and compatibility studies of poly(DFAMO/AMMO)

Poly(3-difluoroaminomethyl-3-methyl oxetane (DFAMO)/3-azidomethyl-3-methyl oxetane (AMMO)) (PDA) can be used as an energetic pre-polymer in the binder systems of solid propellants and polymer-bonded explosives (PBXs). The cationic solution polymerization affords PDA using butane diol (BDO) and boron trifluride etherate (TFBE) as initiator and catalyst, separately. Its molecular structure is characterized and thermal decomposition behavior is investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The copolymer has good thermal stability and exhibits a three-step mass-loss process with the first two steps mainly belonging to the thermal decomposition of difluoroamino and azido groups, respectively. DSC method is performed to evaluate the compatibility of PDA with some energetic components and inert materials. More than half of the selected materials are compatible with PDA, which including cyclotrimethylenetrinitramine (RDX), 2,4,6-trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), pentaerythritol tetranitrate (PETN), ammonium perchlorate (AP), ammonium nitrate (AN), potassium nitrate (KNO₃), aluminum powder (Al), aluminum oxide (Al₂O₃), 2-nitrodiphenylamine (NDPA) and 1,3-diethyl-1,3-diphenyl urea (C₁).     

Phase transition and thermal decomposition of [Al(DMSO)<Subscript>6</Subscript>]Cl<Subscript>3</Subscript>

Phase transition and thermal decomposition of hexadimethylsulfoxidealuminium chloride were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and simultaneous differential thermal analysis (SDTA). The gaseous products of the decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In the temperature range of 95–300 K, [Al(DMSO)₆]Cl₃ indicates one phase transition at T _c^h=244.96 K (on heating) and at T _c^c=220.87 K (on cooling). Large thermal hysteresis of the phase transition (∼24 K) indicates its first order character. Large value of transition entropy (ΔS≈40 J mol⁻¹ K⁻¹) suggests its configurational character. Thermal decomposition of the title compound proceeds in four main stages. In the first stage, which starts just above ca. 300 K, the compound loses two DMSO molecules per one formula unit and undergoes into [Al(DMSO)₄]Cl₃. In the second stage, the next three DMSO ligands are released and simultaneously decomposed. The third stage, which continues up to ca. 552 K, is connected with a loss of the last DMSO ligand and the formation of AlCl₃. In the fourth stage AlCl₃ reacts with carbon monoxide that originates from the decomposition of DMSO, and first aluminium oxychloride and next solid Al₂O₃ plus carbon are created.     

Ferrocenyl Ionic Compounds Containing [Fe(CN)6]3– Anions: Synthesis,Characterization, and Catalytic Effects during Combustion

Twenty‐eight novel ferrocenyl ionic compounds, composed of mononuclear 1‐ferrocenylmethylalkyldimethylammoniums, 1‐ferrocenylmethyl‐3‐alkylimidazoliums, or their dinuclear analogs and [Fe(CN)₆]^3– anion, were designed and synthesized to tackle significant volatility and migration tendency of ferrocene‐based burning rate catalysts (BRCs) used currently in the composite solid propellants. The new compounds were characterized by UV/Vis, FT‐IR, and elementary analysis. The crystal structures of compounds 2· 5H₂O and 3· CH₂Cl₂ · 4H₂O verified the successful preparation of the desired ionic compounds. The TG tests at 70 °C for 24 h revealed that the new compounds exhibit lower volatility than catocene. The cyclic‐voltammetry results suggested that new compounds are quasi‐reversible or irreversible redox systems. TheTG/DSC analyses exhibited that the compounds are of highly thermal stability. Their catalytic effects on the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazacyclooctane (HMX) were investigated. The results showed that most of the compounds exert great effects on the thermal degradation of AP and RDX during combustion. 11 and 2 are comparable to catocene in the thermal decomposition of AP and RDX, respectively, and can therefore be used as alternatives of catocene in a composite solid propellant. Some new compounds are unexpectedly active in promoting the thermal disintegration of HMX.