Thermal Decomposition Of HMX Research Articles

Energetic Cuprous Azide Complex: Synthesis, Crystal Structure and Effection on the Thermal Decomposition of HMX

A novel energetic cuprous azide complex with the formula of [Cu2(dmpyz)(N3)2] n (1) (dmpyz: 2,5-dimethylpyrazine) has been synthesized through hydrothermal method by utilizing the reducibility of H3PO3 and structurally characterized by X-ray single crystal diffraction method. Single crystal X-ray diffraction analysis reveals complex (1) featuring a two-dimensional layer structure constructed from copper(I) atoms bridged by azide anion and further connected by pyrazine ligand to form a 3D network. The result of catalysis research reveals it can promote the burning rate of main component of rocket propellants.

Comparative study of HMX and CL-20

This study deals with a well-known monocyclic nitramine HMX and a relatively new polycyclic strained-cage nitramine CL-20. Experimental data on the powder morphology, simultaneous thermal analysis (STA) and burning rate of binary formulations Al/HMX and Al/CL-20 are presented. Kinetic modelling for HMX and CL-20 are considered based on analysis of STA data obtained for low heating rates. The processing of STA data by the Kissinger method was shown to need to be supplemented with the construction of a thermokinetic model. The thermal decomposition of HMX is reliably described by the reaction of the first order with the autocatalysis. Obtained kinetic parameters of the HMX thermal decomposition correlate with literature-known data on kinetics of the lead stage of HMX combustion. Two types of aluminium powder, i.e. micron-sized and ultrafine, are used to investigate the interaction with both nitramines. Thermal analysis revealed the higher Al oxidation ability of the solid compounds produced at CL-20 thermolysis, than that one of HMX. Burning rate experiments show the differences in the combustion parameters between CL-20- and HMX-based formulations, specifically along with the burn rate level increase for CL-20 monopropellant as compared to HMX one, the pressure exponent and effect of the aluminium particle size variation are also distinct. Results are analyzed and compared to available literature data.

Effects of Defects on Thermal Decomposition of HMX via ReaxFF Molecular Dynamics Simulations

Effects of molecular vacancies on the decomposition mechanisms and reaction dynamics of condensed-phase β-HMX at various temperatures were studied using ReaxFF molecular dynamics simulations. Results show that three primary initial decomposition mechanisms, namely, N-NO(2) bond dissociation, HONO elimination, and concerted ring fission, exist at both high and lower temperatures. The contribution of the three mechanisms to the initial decomposition of HMX is influenced by molecular vacancies, and the effects vary with temperature. At high temperature (2500 K), molecular vacancies remarkably promote N-N bond cleavage and concerted ring breaking but hinder HONO formation. N-N bond dissociation and HONO elimination are two primary competing reaction mechanisms, and the former is dominant in the initial decomposition. Concerted ring breaking of condensed-phase HMX is not favored at high temperature. At lower temperature (1500 K), the most preferential initial decomposition pathway is N-N bond dissociation followed by the formation of NO(3) (O migration), although all three mechanisms are promoted by molecular vacancies. The promotion effect on concerted ring breaking is considerable at lower temperature. Products resulting from concerted ring breaking appear in the defective system but not in the perfect crystal. The mechanism of HONO elimination is less important at lower temperature. We also estimated the reaction rate constant and activation barriers of initial decomposition with different vacancy concentrations. Molecular vacancies accelerate the decomposition of condensed-phase HMX by increasing the reaction rate constant and reducing activation barriers.

Combustion Synthesis of La 0.8Sr 0.2MnO 3 and Its Effect on HMX Thermal Decomposition

Perovskite-type La 0.8Sr 0.2MnO 3 was prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scaning electron micrograph (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of La 0.8Sr 0.2MnO 3 was investigated on thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by thermal gravity-differential scanning calorimetry (TG-DSC) techniques. The experimental results show that La 0.8Sr 0.2MnO 3 is an effective catalyst for HMX thermal decomposition. The surface-adsorbed species such as H 2O, OH − and adsorbed oxygen (O ad) could result in an advance in the onset temperature of HMX thermal decomposition. The mixture system of Mn 3+ and Mn 4+ ions and lattice oxygen could play key roles for the increase of the decomposition heat of HMX because these exothermic reactions could be catalyzed by La 0.8Sr 0.2MnO 3 between CO and NO x (from the thermal decomposition of HMX) and the oxidation reaction of CO. According to the previous researches and our results, perovskite-type La 0.8Sr 0.2MnO 3 may be used as a novel catalyst or modifier for nitrate ester plasticized polyether (NEPE) propellant.

Combustion synthesis and effect of LaMnO 3 and LaOCl powder mixture on HMX thermal decomposition

LaOCl powder mixture and perovskite-type LaMnO 3 were prepared by stearic acid gel combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. LaOCl powder mixture was a mixture of LaOCl and significant amounts of amorphous materials. When heated at 973.15 K, the mixture was found to be converted into single-phase perovskite-type LaMnO 3. The catalytic activities of LaOCl powder mixture and LaMnO 3 were investigated for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) thermal decomposition by thermal gravity (TG) and thermogravimetry-evolved gas analysis (TG–EGA) techniques. The experimental results show that both the mixture and LaMnO 3 have catalytic activities for the thermal decomposition of HMX, and LaOCl powder mixture has much higher catalytic activity than LaMnO 3 on the early stages of HMX thermal decomposition. That could be attributed to the higher surface adsorption oxygen (O ad) and hydroxyl as well as its high specific surface area. LaMnO 3 can obviously reduce activation energy of HMX thermal decomposition than LaOCl powder mixture. This may be due to its catalytic activity on the oxidation reaction of CO and the reaction between CO and NO during HMX thermal decomposition.

Combustion Synthesis and Catalytic Activity of LaCoO3 for HMX Thermal Decomposition

AbstractPerovskite‐type LaCoO3 was prepared by stearic acid solution combustion method and characterized by XRD, DSC‐TG, and XPS techniques. The catalytic activities of LaCoO3 for HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) thermal decomposition were investigated. The as‐prepared LaCoO3 shows higher activity than the calcined one. This could be due to higher concentration of surface‐adsorbed oxygen and hydroxyl species as well as higher BET surface area of the as‐prepared LaCoO3.

Preparation and catalytic activities of LaFeO 3 and Fe 2O 3 for HMX thermal decomposition

Perovskite-type LaFeO 3 and α -Fe 2O 3 with high specific surface areas were directly prepared with appropriate stearic acid–nitrates ratios by a novel stearic acid solution combustion method. The obtained powders were characterized by XRD, FT-IR and XPS techniques. The catalytic activities of perovskite-type LaFeO 3 and α-Fe 2O 3 for the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were investigated by TG and TG–EGA techniques. The experimental results show that the catalytic activity of perovskite-type LaFeO 3 was much higher than that of α -Fe 2O 3 because of higher concentration of surface-adsorbed oxygen (O ad) and hydroxyl of LaFeO 3. The study points out a potential way to develop new and more active perovskite-type catalysts for the HMX thermal decomposition.

Particle Size Effects on Thermal Decomposition of Energetic Material

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by differential scanning calorimetry (DSC) under nonisothermal conditions, with heating rates from 5 to 20°C min−1. The influence of the particle size in the thermal decomposition of HMX was verified. The activation energy for the decomposition of each sample was calculated using the peak temperature shift methods, proposed by Kissinger and Ozawa. A significant variation in the results was observed according to the range of the particle size used. The results showed that, as the particle size of HMX increased, the thermal decomposition temperature of HMX and the decompositional activation energies ranges enhanced. At the same time, at a constant heating rate, the decomposition temperatures of the smaller particles were lower than those of larger ones. The critical temperature for thermal explosion of each sample was calculated. Also, the values of ΔS#, ΔH#, and ΔG# of reaction for each particle size were computed.

Effect of Metal Formiates and Oxalates on HMX Decomposition

Metal formiates and oxalates applied onto HMX increase the initial rate and decrease the induction period of thermal decomposition of HMX. The activity of sodium oxalates, which contain crystal water, is much lower than that of anhydrous formiates of the same metals. The possible reasons of the catalytic effect of the additives on the thermal decomposition of are discussed.

Thermal decomposition of HMX influenced by nano-metal powders in high energy fuel : Li, S. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2002, 47, (2), 596–597

Thermal decomposition of HMX influenced by nano-metal powders in high energy fuel : Li, S. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2002, 47, (2), 596–597

Influence of the heating rate in the thermal decomposition of HMX

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (HMX) by differential scanning calorimetry (DSC) in non-isothermal conditions, with heating rates from1 to 25°C min−1. The influence of the heating rate, the particle and the sample size were verified. The activation energy was calculated using the peak temperature shift method, proposed by Ozawa and a significant variation in the results was observed according to the range of the used heating rates. As the heating rate was increased, different conversions and self-heating effects were observed at the respective DSC peaks, indicating that the use of this method was inadequate and it may lead to incorrect results, which, in turn, could explain the wide range of activation energy values published in literature. At lower heating rates HMX decomposition occurs on the solid state and at higher ones decomposition occurs after melting practically at the same temperature, which does not depend on the heating rate.

Effect of propionitrile nitramine salts on the thermal decomposition of HMX

The thermal decomposition of HMX with additives of metal salts of propionitrile nitramine is studied. The process goes with acceleration by a complex mechanism, in which the interaction of HMX with propionitrile imine and its oligomer formed in the reaction plays an important role. The initial rate of HMX decomposition correlates with the mass fraction of the anion in the salt.

Kinetics and mechanism of thermal decomposition of HMX with metal cupferronate additives

The kinetic features of the thermal decomposition of HMX with metal cupferronate additives, in which the nucleophilic detachment of a proton in HMX by a phenylnitric-oxide anion-radical plays an important role, are established. The logarithms of the rate constants for the decomposition of HMX correlate with the ratio of the charge of the metal cation in the cupferronate to its radius, which indicates a different reactivity of the anion-radical owing to the polarizing effect of the cation.

Thermal Decomposition of HMX and Mixtures

AbstractThermal decomposition of pure HMX shows DSC endothermic peaks at 210°C from β to γ phase transformation and at 285°C from the HMX melting followed by an instantaneous exothermic decomposition leading to a strong peak at 290°C and a very strong DTG peak at 325°C with a mass loss of 95%. However, the GS‐2 mixture shows two DSC exothermic peaks at 225°C and 270°C assigned to nitroguanidine etc. and HMX decomposition. Addition of NH4ClO4 to HMX causes the decomposition to take place before melting and decomposition peak is lowered to 230°C. However in the case of GS‐2, a strong effect was observed and the amount of the mixture was to be decreased to obtain a reasonable DSC curve. This shows that the addition of NH4CIO4 to HMX increases the decomposition of HMX, however this effect is more pronounced in GS‐2 mixture. Even the minimum concentration of NH4CIO4 tested (10%) shows strong effect.The addition of NH4NO3 to HMX and GS‐2 shows DSC exothermic decomposition peaks at 272°C and 245°C, showing a contribution from NH4NO3 decomposes near to the decomposition of HMX, it does not show a strong effect on the decomposition of HMX/GS‐2 as compared to NH4ClO4. Addition of KClO4, NaClO4 and KNO3 don't show any effect in these thermoanalytical studies.

Thermal Decomposition of HMX: Low Temperature Reaction Kinetics and their Use for Assessing Response in Abnormal Thermal Environments and Implications for Long-Term Aging

AbstractThe thermal decomposition of HMX between 175°C and 200°C has been studied using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) apparatus with a focus on the initial stages of the decomposition. The identity of thermal decomposition products is the same as that measured in previous higher temperature experiments. The initial stages of the decomposition are characterized by an induction period followed by two acceleratory periods. The Arrhenius parameters for the induction and two acceleratory periods are (Log(A)= 18.2 ± 0.8, Ea = 48.2 ± 1.8 kcal/mole), (Log (A) = 17.15 ± 1.5 and Ea = 48.9 ± 3.2 kcal/mole), (Log (A) = 19.1 ± 3.0 and Ea = 52.1 ± 6.3 kcal/mole), respectively. The data can be used to calculate the time and temperature required to decompose a desired fraction of a test sample that is being prepared to test the effect of thermal degradation on its sensitivity or burn rates. It can also be used to estimate the extent of decomposition that may be expected under normal storage conditions for munitions containing HMX. The data, along with previous mechanistic studies conducted at higher temperatures, suggest that the process that controls the early stages of decomposition of HMX in the solid phase is scission of the N-NO2 bond, reaction of the NO2 within a “lattice cage” to form the mononitroso analogue of HMX and decomposition of the mononitroso HMX within the HMX lattice to form gaseous products that are retained in bubbles or diffuse into the surrounding lattice.

Mass spectrometric studies of the thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX)

The sublimation and thermal decomposition of HMX were studied by means of Langmuir evaporation and effusion mass spectrometry in the temperature range 175–275°C. Langmuir experiments showed that the primary mechanism for thermal decomposition is ring cleavage to two equal 148 amu species. Decomposition within the effusion cell produced numerous smaller molecules and free radicals due to the decomposition of the 148 amu molecule.

Thermal Decomposition Process of HMX

AbstractThe thermal decomposition of HMX has been investigated using thermoanalytical techniques and infrared spectroscopic study at both above and below its melting point. The weight loss phenomenon that occurs as the temperature is elevated at a constant heating rate has been clearly separated into four elementary processes which are induction period, sublimation, first order solid phase reaction, and highly exothermic liquid phase reaction by plotting them against the logarithm of the heating rate versus the reciprocal temperature. Hydroxymethyl formamide has been shown to be a major product of the liquid phase decomposition, which suggests that the decomposition of HMX in the liquid phase should be initiated by the N‐N bond scission but not by the C‐N bond scission.