Decomposition Of Energetic Materials Research Articles

Thermal recombination strategy designed R-CN as active shell to improve catalyst activity

A new recombinant CN material (R-CN) was prepared with g-C3N4 as precursor by hydrothermal method combined with thermal recombination method, which has 2D ultra-thin structure, nanoscale folds, graphite-like texture and some pores, and has richer N and O elements than g-C3N4. R-CN can reduce high temperature decomposition peak of ammonium perchlorate (AP) to 356.06 oC, and its promoting effect is obviously better than that of g-C3N4. Based on specific structural composition and physicochemical properties of R-CN, a novel R-CN@MWO composite with core-shell was designed, which was applied to catalytic decomposition of AP and pressure enlarging effect during combustion process of cyclotrimethylenetrinitramine (RDX)+nitrocellulose (NC). With the introduction of R-CN@MWO, decomposition peak temperature and activation energy of AP are reduced by 104.67oC and 59.24 kJ mol−1, and peak pressure and pressurization rate of RDX+NC constant volume combustion test are increased by 11.33 and 118.54 times, respectively. Moreover, the combustion rate of R-CN@MWO-AP/HTPB propellant is 3.23 times that of AP/HTPB propellant. To sum up, R-CN as a coating layer can significantly enhance catalytic activity of MgWO4 for thermal decomposition of energetic materials.

Descriptors applicability in machine learning-assisted prediction of thermal decomposition temperatures for energetic materials: Insights from model evaluation and outlier analysis

Machine learning is an emerging approach to predict thermal decomposition temperature in the field of energetic materials, while an assessment of the descriptor applicability is still lacking. In this work, we have systematically established 5 general descriptor sets for 1091 compounds and combined them with 9 algorithms to construct a suite of predictive models with mean absolute error ranging 41–29 K, which is comparable to the cutting-edge endeavors. Our study emphasizes the significant influence of multi-level structural interactions on the thermal stability and decomposition of energetic materials, contributing insights conducive to the development of corresponding descriptors.

Evaluating shock sensitivity and decomposition of energetic materials by ReaxFF molecular dynamics

Evaluating shock sensitivity and decomposition of energetic materials by ReaxFF molecular dynamics

Research on catalytic performance of transition-metal-based MOFs towards thermal decomposition of RDX

It is beneficial for the efficient energy utilization of propellants to develop high - efficiency catalysts for thermal decomposition of energetic materials. Herein, catalytic characteristics of different transition-metal-based MOFs on thermal decomposition of cyclotrimethylenetriamine (RDX) were studied, such as [Zn2(atz)3(N3)]n, MIL-88B and ZIF-67. ZIF-67 was found to exhibit superior properties therein. On this basis, size effect of ZIF-67 when catalyzing the thermal decomposition of RDX was further investigated. It has been found that the catalytic performance can be boosted as the size of ZIF-67 is reduced. However, the performance will decline when the size is ulteriorly reduced into nanoscale. Besides, the doping of Ni, Cu or Zn into ZIF-67 has little effect on the promotion of the catalytic performance. Among all the catalysts, ZIF-67-S shows the best catalytic performance for the thermal decomposition of RDX, which is superior to most existing catalysts. Specifically, it can reduce the thermal decomposition peak temperature of RDX by 22.4 °C and enhance the apparent decomposition heat by 59.9%. As a consequence, it is expected to be used as a combustion catalyst in propellants such as 3D printing gun propellants with high RDX contents.

Microfluidic preparation and thermal properties of HMX@PDA@MO

Metal oxides can effectively promote the thermal decomposition of energetic materials. However, the traditional physical mixing process has potential safety hazards and cannot achieve uniform and stable coating. To address this issue, this study provides adhesion sites for metal oxides through the rough coating formed by polydopamine on the surface of HMX, which improves the coating stability. Taking advantage of the safety and efficient mixing of microfluidic technology, HMX@PDA@MO samples with good dispersion were prepared. The samples were characterized by SEM-EDS, XRD and DSC. The XRD results demonstrate the successful preparation of HMX@PDA@CuO and HMX@PDA@PbO samples. SEM-EDS images show that polydopamine forms a rough coating on the surface of HMX, and the increase in the total flow rate is beneficial to enhance the dispersion of metal oxides. The DSC data showed that the addition of 3% and 20% CuO advanced the thermal decomposition temperature and apparent activation energy of HMX@PDA by 0.3K, 40.13 kJ·mol−1 and 2K, 108.83 kJ·mol−1, respectively, PbO is 0.1K, 111.94 kJ·mol−1, and 4.5K, 205.02 kJ·mol−1. It shows that the increase of metal oxide content will promote thermal decomposition. For HMX, PbO has better catalytic activity than CuO. PbO has better catalytic activity than CuO for HMX.

Design and performance of a novel high-efficiency WO3-based combustion catalyst and its catalytic mechanism

To develop efficient combustion catalyst for solid propellants, a novel WO3-based composite (CuX-WO3/Biochar) was designed by the method of doping and loading. As a dopant, Cu has the advantages of producing multiple bands, inhibiting grain growth and restraining exciton–exciton collisions. Meanwhile, biochar is cheap and available as a carrier, which can effectively inhibit the agglomeration of nanomaterials. Therefore, in this work, Cu-doped WO3 nanoparticles were uniformly anchored on surface of biochar by in-situ solvothermal reaction combined calcination method, which significantly increased the surface-active area, and was firstly applied to catalytic decomposition and laser ignition of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 5,5′-bistetrazole-1,1′-diolate (TKX-50). With the introduction of CuX-WO3/Biochar, decomposition peak temperature of AP, RDX and TKX-50 diminished by 97.0, 6.7 and 37.9℃, and activation energy decreased by 14.4, 93.5 and 22.6 kJ mol−1, respectively. Simultaneously, flame brightness, flame area and flame propagation speed during combustion of RDX and TKX-50 were evidently improved after CuX-WO3/Biochar was added. Finally, electron transfer mechanism of catalytic thermal decomposition of energetic materials was deduced based on Density Functional Theory (DFT) calculation and characterization analysis. This study will provide a new insight into development of combustion catalysts.

Hematite: A Good Catalyst for the Thermal Decomposition of Energetic Materials and the Application in Nano-Thermite

Metal oxides (MOs) are of great importance in catalysts, sensor, capacitor and water treatment. Nano-sized MOs have attracted much more attention because of the unique properties, such as surface effect, small size effect and quantum size effect, etc. Hematite, an especially important additive as combustion catalysts, can greatly speed up the thermal decomposition process of energetic materials (EMs) and enhance the combustion performance of propellants. This review concludes the catalytic effect of hematite with different morphology on some EMs such as ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenete-tranitramine (HMX), etc. The method for enhancing the catalytic effect on EMs using hematite-based materials such as perovskite and spinel ferrite materials, making composites with different carbon materials and assembling super-thermite is concluded and their catalytic effects on EMs is also discussed. Therefore, the provided information is helpful for the design, preparation and application of catalysts for EMs.

Nitrocellulose-based propellants: elucidation of the mechanisms of the diphenylamine stabilizer employing density functional theory

ABSTRACT The decomposition of energetic materials, especially propellants, produces nitrous gas and free acid nitrates which accelerates its rate velocity. To inhibit this inconvenient autocatalytic reaction, molecules known as stabilizers are usually included in their composition. One of them, diphenylamine (DPA), is primarily used in single-base compositions. In this work, we used density functional theory, with the RI-B2PLYP-D3BJ exchange-correlation functional, to investigate the N-nitrosation mechanism corresponding to a reaction between DPA and a nitro compound producing N-nitroso-diphenylamine (NNDPA). For this purpose, geometry optimizations (equilibrium and transition states), minimum energy paths, Gibbs free activation energies, and rate constants of four reaction mechanisms were computed both in the gas phase and simulating the nitrocellulose environment, which produced similar results. We found that the N-nitrosation mechanism with HNO2 is the most favored, with a rate constant of 5.3 × 10 −4 g·µmol −1 ·s −1. In contrast, the formation of NNDPA is less likely to depend on NO+ in agreement with the experimental results. Cationic reaction mechanisms are hardly viable, whereas interactions with NO or N2O3 are possible. Nonetheless, the former is too slow (1.02 × 10 −35 g·µmol −1 ·s −1) and the latter depends on the scarcely available nitro compound as a reactant, despite being considerably fast (1.61 × 104 g·µmol−1 ·s−1).

Atomistic insight into enhanced thermal decomposition of energetic material on graphene oxide

Graphene oxide (GO)-based nanocomposites are promising additives for practical applications of cyclotrimethylenetrinitramine (RDX). GO is not only an excellent support for nanoparticles, but also has independent catalytic activities, which have not been well understood. In this study, the reactive molecular dynamics simulation method is employed to investigate the kinetics and fundamental catalytic mechanisms of the thermal decomposition of RDX on GO. The RDX decomposition reaction is found to be enhanced in the presence of GO and the catalytic effect is better at low than at high temperatures. Additionally, GO addition lowers the activation energy by 11.35% compared with the thermal decomposition of pure RDX. The study shows that the catalytic capabilities of GO primarily originate from its functional groups that promote both the initiation and intermediate reactions. Furthermore, the H exchange process between the functional groups on GO and RDX/RDX intermediates plays an important role in the reaction. GO is further oxidized with more functional groups during the reaction, which are also involved in the catalytic activities. Finally, the energy barrier of functional group-participated reactions is found to be lower than their corresponding unimolecular decomposition leading to enhanced thermal decomposition of RDX. The proposed catalytic mechanisms in the present research should also be applicable to other energetic materials of the same class with a similar structure as RDX.

Temperature and Pressure Effects on HMX/Graphene via ReaxFF Molecular Dynamics Simulations

Studying the thermal decomposition of energetic materials at high temperatures can provide detailed reaction and mechanistic information, which is critical for understanding the reactivity of energetic materials, designing mixed explosives, and achieving improved safety. In this work, the effects of temperature and pressure on graphene (Gr)-based HMX crystals were investigated using ReaxFF molecular dynamics simulations. The thermal decomposition processes of perfect HMX crystals, HMX crystals with (001), (010), or (100) crystal planes, and HMX/Gr mixed systems were studied at high temperatures and pressures. In the mixed systems, different configurations of HMX molecules adsorbed on the Gr surface were confirmed by theoretical calculation methods. With the pressure ranging from atmospheric pressure to 31 GPa, 3, 5, and 3 configurations of HMX adsorbed on the Gr surface were identified for the (001)/Gr, (010)/Gr, and (100)/Gr systems, respectively. The time-dependent curves for the evolution of fragments, intermediates, and pyrolysis products were analyzed. The rate constant for the thermal decomposition of HMX was found to be significantly affected by the addition of Gr. In particular, the thermal decomposition reaction was strongly inhibited in the (010)/Gr system. This result indicates that Gr promotes an anisotropic thermal effect, resulting from the steric hindrance of the NO2 functional groups and the interaction between Gr and HMX molecules. Gr also affected the initial reaction pathway of homolytic N–NO2 bond cleavage, with C=O, C–OH, and C–OC bonds on the Gr surface participating in the formation of nitro radicals and HONO.

Autocatalytic decomposition of energetic materials: interplay of theory and thermal analysis in the study of 5-amino-3,4-dinitropyrazole thermolysis.

A reliable kinetic description of the thermal stability of energetic materials (EM) is very important for safety and storage-related problems. Among other pertinent issues, autocatalysis very often complicates the decomposition kinetics of EM. In the present study, the kinetics and decomposition mechanism of a promising energetic compound, 5-amino-3,4-dinitro-1H-pyrazole (5-ADP) were studied using a set of complementary experimental (e.g., differential scanning calorimetry in the solid state, melt, and solution along with advanced thermokinetic models, accelerating rate calorimetry, and evolved gas analysis) and theoretical techniques (CCSD(T)-F12 and DLPNO-CCSD(T) predictive quantum chemical calculations). The experimental study revealed that the strong acceleration of the decomposition rate of 5-ADP is caused by two factors: the progressive liquefaction of the sample directly observed using in situ optical microscopy, and the autocatalysis by reaction products. For the first time, the processing of the non-isothermal data was performed with a formal Manelis-Dubovitsky kinetic model that accounts for both factors. With the aid of quantum chemical calculations, we have rationalized the autocatalysis present in the formal kinetic models at the molecular level. Theory revealed an unusual primary decomposition channel of 5-ADP, viz., the two subsequent sigmatropic H-shifts in the pyrazole ring followed by the C-NO2 bond scission yielding a pyrazolyl and nitrogen dioxide radicals as simple primary products. Moreover, we found the secondary reactions of the latter radical with the 5-ADP to be kinetically unimportant. On the contrary, the substituted pyrazolyl radical turned out to undergo a facile addition to 5-ADP, followed by a fast exothermic elimination of another ˙NO2 species. We believe the latter process to contribute remarkably to the observed autocatalytic behavior of 5-ADP. Most importantly, the calculations provide detailed mechanistic evidence complementing the thermoanalytical experiment and formal kinetic models.

Effect of Bi2WO6/g-C3N4 composite on the combustion and catalytic decomposition of energetic materials: An efficient catalyst with g-C3N4 carrier

An effective strategy involving a suitable carrier is needed to improve the dispersion, combustion and catalytic performances of catalyst nanoparticles. Herein, a Bi2WO6/g-C3N4 composite employing g-C3N4 as the catalyst carrier was prepared by a one-step in situ hydrothermal method, which was used as the combustion catalyst of solid propellants. The catalyst’s structure, morphology and its catalytic decomposition on several energetic materials were characterized by a series of analyses. The optimal ratio of g-C3N4 and Bi2WO6 was systematically determined. The results demonstrate that Bi2WO6/g-C3N4 (4:6) composite can diminish the decomposition temperatures of ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) and cyclotrimethylenetrinitramine + nitrocellulose (RDX + NC) by 25.0, 5.2, 24.0 and 1.2 (4.9) ° C, and reduce their apparent activation energy by 59.5, 116.7, 11.6 kJ mol-1, respectively. Moreover, the laser ignition tests indicate that Bi2WO6/g-C3N4 can effectively promote the ignition performance of RDX and RDX + NC. A possible mechanism of Bi2WO6/g-C3N4 on AP was proposed. The g-C3N4 catalyst carrier is superior to GO carrier due to its low cost, simple synthesis process, improved combustion and catalytic performances, as well as high N content. These make it have broad engineering application prospects in solid propulsion and other energetic materials.

Decomposition mechanism on different surfaces of copper azide

Copper azide, a potential primary explosives that may replace traditional primers such as lead azide, mercury fulminate and silver azide, has received widespread attention, but its decomposition mechanism remains unclear. Here, based on first-principles calculations, (010)N3, (100)N3 and (001) facets with a copper/nitrogen atom ratio of 1/6 are found to be the most stable surfaces of copper azide crystal. Through transition state (TS) calculations, we find that during the decomposition process on the surface, there is a synergy effect between two Cu–N1–N2–N3 chains, where the terminal N2–N3 bonds on two chains break simultaneously, and the dissociated N3 atom bonds with another N3′ atom of adjacent chain to form a N2 molecule. Next, the Cu–N bond will rupture, and two more N2 molecules (N1–N2, N1′–N2′) desorb from the surface. The overall reaction releases above 4 eV energy at a barrier of 1.23 eV on (001) surface. Electronic structure calculations reveal that the TS of N2–N3 rupture is more stabilized than that of N1–N2. According to the above results, we propose a new decomposition mechanism based on simulations of N–N bond breaking on different surfaces of copper azide. The results underscore the surface effect in decomposition of energetic materials.

Graphene-based Composites for the Thermal Decomposition of Energetic Materials

Owing to its remarkable mechanical, electrical and thermal properties, graphene has been a hot area of composites research in the past decade, including the field of energetic materials. Graphene has been widely applied in enhancing the physical properties of energetic materials, such as solid composite propellants. Through the way of adding different forms of graphene into the matrix of solid propellants, their thermal decomposition performance can be effectively improved. In this paper, we reviewed the status and challenges of the application of graphene in the thermal decomposition of composite solid propellant. Moreover, the main preparation methods and material structures of graphene are reviewed. We can conclude that graphene and its derivatives can enhance the catalytic effect remarkably, which can be attributed to the large specific surface area of graphene that makes the uniformly dispersed catalyst particles and the more catalyst active sites. Meanwhile, graphene possesses the high thermal conductivity, making the rapider heat diffusion, which can promote the decomposition reactions of the energetic components in solid propellants. Graphene and catalyst work synergistically in their thermal decomposition. More than this, the main methods to improve the thermal decomposition of energetic components of composite propellants and their effects on decomposition temperature reduction are systematically summarized, respectively.

Correlation between the self-sustaining ignition ability and the impact sensitivity of energetic materials

Sensitivity is one of the most important characteristics of energetic materials (EMs), and uncovering the sensitivity mechanism is still a challenge. In this work, we find that the self-sustaining ignition ability is a predominant factor governing the impact sensitivity, and propose the self-ignition propagation coefficient (SIPC) to represent the capability for molecular decomposition of energetic materials based on heat release and energy barrier. A higher correlation of the SIPC with the impact sensitivity measured experimentally is validated by applying it to more than 150 energetic compounds with a high diversity of components, structures and impact sensitivity, in contrast to those of the existing molecule-based models. The advantage of the SIPC can be attributed to the fact that it combines thermodynamics and kinetics and better represents the impact sensitivity. Moreover, the SIPC with a physical meaning can be encoded in a program for the high-throughput design of energetic compounds due to its high accessibility on the molecular level and high reliability for fast screening.

Molecular Dynamics Insight into the Evolution of Al Nanoparticles in the Thermal Decomposition of Energetic Materials

It has become increasingly important to add Al nanoparticles (ANPs) into energetic materials (EMs) to overcome the issue of Al particles aggregation and promote the efficiency of heat release. Neve...

Thermal Decomposition of Ammonium Perchlorate in the Presence of Cobalt Hydroxyl@Nano-Porous Polyaniline

In this report, nanoporous polyaniline (NP-PANi) as an intrinsic conductive polymer (ICPs) was sonochemically synthesized and coated by Cobalt Hydroxyl nanoparticles using precipitation method. The prepared Cobalt Hydroxyl@NP-PANi (CoPANi) merged two separated peaks of AP into a width peak revealed at 297 °C, and drastically increased the area under the peak about 90–334%. Dependency of activation energy (Eα) to the reaction progress (α) was investigated by Starink method and results showed that in the presence of CoPANi throughout the reaction, Eα of AP decomposition was completely shifted to the lower values. The thermal decomposition mechanisms of samples were evaluated by Complementary method using a MATLAB code. The best decomposition reaction model obtained for AP was Avrami Erofeyev (A2) which CoPANi changed it to (A4); this caused Ea reduced from 161 (KJ/mol) to 113 (KJ/mol). Reaction rate constant, pre-exponential factor, Characteristic temperatures (TSADT and Tb) and thermodynamic parameters have been also calculated, the noted parameters presented a descending trend when the CoPANi was used. As the results confirmed the strong modifying effect of Cobalt Hydroxyl@NP-PANi on AP decomposition reaction, this report would be helpful for further application of M(OH)x@ICPs as a new family of burning rate modifier materials used for decomposition of energetic material.

Use of Terahertz Spectrometry to Study the Mechanisms of Thermal Decomposition of Energetic Materials

Use of Terahertz Spectrometry to Study the Mechanisms of Thermal Decomposition of Energetic Materials

Investigation of the Kinetics of Thermal Decomposition of Energetic Materials Using High-resolution Terahertz Frequency Spectroscopy

Investigation of the Kinetics of Thermal Decomposition of Energetic Materials Using High-resolution Terahertz Frequency Spectroscopy

1T/2H multi-phase MoS2 heterostructures: synthesis, characterization and thermal catalysis decomposition of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate

Dependence of ln(β/Tp2) on 1/Tp for TKX-50 and mixtures with 10 wt% 2H-MoS2 and 1T/2H-MoS2.