Thermal Decomposition Mechanism of Ammonium Nitrate on the Main Crystal Surface of Ferric Oxide: Experimental and Theoretical Studies.

Understanding the decomposition process of ammonium nitrate (AN) on catalyst surfaces is crucial for the development of practical and efficient catalysts in AN-based propellants. In this study, two types of nano-Fe2O3 catalysts were synthesized: spherical particles with high-exposure (104) facets and flaky particles with high-exposure (110) facets. Through thermal analysis and particle size analysis, it was found that the nanosheet-Fe2O3 catalyst achieved more complete AN decomposition despite having a larger average particle size compared to nanosphere-Fe2O3. Subsequently, the effects of AN pyrolysis on the (110) and (104) facets were investigated by theoretical simulations. Through studying the interaction between AN and crystal facets, it was determined that the electron transfer efficiency on the (110) facet is stronger compared to that on the (104) facet. Additionally, the free-energy step diagrams for the reaction of the AN molecule on the two facets were calculated with the DFT + U method. Comparative analysis led us to conclude that the (110) facet of α-Fe2O3 is more favorable for AN pyrolysis compared to the (104) facet. Our study seeks to deepen the understanding of the mechanism underlying AN pyrolysis and present new ideas for the development of effective catalysts in AN pyrolysis.

Comparing the Catalytic Effect of Metals for Energetic Materials: Machine Learning Prediction of Adsorption Energies on Metals.

Energetic materials (EMs) and metals are the important components of solid propellants, and a strong catalysis of metals on EMs could further enhance the combustion performance of solid propellants. Accordingly, the study on the adsorption of EMs such as octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and ammonium dinitramide (ADN) on metals (Ti, Zr, Fe, Ni, Cu, and Al) was carried out by density functional theory (DFT) to reveal the catalytic effect of metals. The deep dissociation of EMs on Ti and Zr represents a stronger interaction and corresponds to the rapid thermal decomposition behavior of the EMs/metal composite in the experiment. It is expected that DFT calculation can be selected instead of experiments to compare the catalytic effect of metals and preliminarily screen out potential high-performance metals. Based on the data set of the calculated adsorption energy, further machine learning (ML) was used to predict the adsorption energy of EMs on metals for a convenient comparison of the catalytic effect of metals, since a quite high adsorption energy value represents a more thorough dissociation. The kernel ridge regression (KRR) method shows the best performance on predicting adsorption energy and helps to choose the metals for efficiently catalyzing ammonium nitrate (AN) and hexanitrohexaazaisowurtzitane (CL-20). Such adsorption computation and ML not only reveal the decomposition mechanism of EMs on metals but also provide a simple underlying method to predict the catalytic effect of metals.

Correlation of Efficient Dispersion and Catalytic Performance of Nanocombustion Catalysts in Energetic Materials: A Case Study of the Nanocopper Oxide Catalyst with Superfine Ammonium Perchlorate.

Obviously, the dispersion of nanocatalytic materials has significant influence on their catalytic performance. In this study, an evaluation method for the dispersion of nanomaterials was established according to the different solid UV absorptions of different substances by taking the dispersion of nanocopper oxide (nano-CuO) in superfine ammonium perchlorate (AP) as an example. The nano-CuO/superfine AP composites with different nano-CuO dispersions can be obtained by changing the process parameters, such as varying the grinding method, the grinding strength, and the grinding time. Three replicate experiments were carried out for different composites to derive the average values of absorbance at 212 nm, and the dispersion of nano-CuO in superfine AP was calculated using the difference equation, as the solid UV curves at 210-214 nm were almost identical for each sample, especially at 212 nm. The properties of different samples were tested by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and thermogravimetry-mass spectrometry (TG-MS). The results show that the particle size and structure of superfine AP in the composites prepared by different methods were not changed. The XRD and IR techniques in this study were unable to characterize the dispersion of nano-CuO in the composites due to its low content. The dispersion of nano-CuO in the nano-CuO/superfine AP composites was significantly enhanced with the increase of grinding strength and grinding time, and the dispersion of nano-CuO was positively correlated with its catalytic performance, which means that the thermal decomposition performance of different composites improved with the increasing dispersion of nano-CuO. Highly dispersed nano-CuO exhibited a significant catalytic effect on superfine AP in TG-MS. The above conclusions demonstrate the accuracy of the difference equation for evaluating the dispersion of nanomaterials based on solid UV curves, which is expected to be used extensively in evaluating the dispersion of nanocatalytic materials in energetic materials.

Long-Distance Continuous Self-Transport of a Droplet by Merging Droplets on a Graphene-Covered Multibranch Gradient Groove Surface.

Although the self-transport of liquid droplets by a gradient-textured substrate can break away from the energy input, the long distance and even continuous spontaneous motion of droplets will be limited by the length in the surface-gradient direction. This article introduces a novel design with a monolayer graphene-covered multibranch gradient groove surface (GMGGS). The design aims to achieve long-distance, continuous self-transport of a mercury (Hg) droplet by merging with other mercury droplets, and the process is carried out using molecular dynamics (MD) simulation. This method achieves the merging of mercury droplets through the structure of multibranch gradient grooves, and we have observed that the merged mercury droplet can be reaccelerated in the gradient groove. The results demonstrate that droplet merging allows for control over the surface morphology variations of mercury droplets within the gradient groove. This creates a forward pressure difference, which leads to reacceleration of the mercury droplets. In light of this mechanism, the trunk droplet can achieve long-distance continuous self-transport on the GMGGS by continuously merging with branch droplets. These findings will broaden our comprehension of droplet merging and self-transport behavior, offering corresponding theoretical support for the long-distance continuous self-transport of droplets.

The positive correlation between the dispersion and catalytic performance of Fe2O3 nanoparticles in nano-Fe2O3-ultrafine AP energetic composites supported by solid UV-vis spectroscopy.

Recently, the widespread use of nanocatalytic materials has contributed to an enormous improvement in the performance of energetic materials, especially, highly dispersed nanomaterials. However, the lack of quantitative methods for analyzing the dispersion of nanomaterials limits their further widespread use. Although various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), etc. are used to analyze the relative dispersion of nanomaterials, it is not possible to quantitatively analyze their dispersion. Therefore, there has been an effort to develop new methods for the quantitative analysis of nanocatalytic materials. Fortunately, we were able to analyze the dispersion of nanocatalytic materials using the difference in their UV absorbance. More importantly, we established the corresponding difference equation to quantify the dispersion of nanocatalytic materials, which is capable of quantifying the dispersion of nano-Fe2O3 in nano-Fe2O3-ultrafine AP composites. The accuracy of the difference equation was verified using a variety of techniques and the desired results were obtained. Based on the above conclusions, the quantitative analysis method for the dispersion of nanomaterials that we established is expected to be widely used and promote the development of energetic materials.

AP-HTPB propellant combustion under strain conditions with laser absorption spectroscopy.

Understanding the combustion behaviors of solid propellant with different levels of strains is of practical interest. In this work, an experimental study of the effects of static and dynamic strains on the burning rate, temperature, CO, and C O 2 formation of aluminized ammonium perchlorate (AP)-hydroxyl terminated poly-butadiene (HTPB) propellant combustion was presented at initial pressures of 0.1 MPa, 0.2 MPa, and 0.5 MPa. The strains were being applied onto solid propellant by exerting static and cyclic loadings. The propellant burning rate was acquired by a 4 kHz high-speed photography system, and the combustion temperature, CO, and C O 2 column densities were measured at 10 kHz through laser absorption spectroscopy (LAS). At atmospheric pressure, it was demonstrated that the propellant burning rate increased with tensile stress and decreased with compressive stress. The measured flame temperature showed a similar correlation with strains as compared to the propellant burning rate. At elevated pressures, the increase of the propellant burning rate due to tensile stress was more evident, while the difference in combustion temperatures was less significant. For the cyclic strain condition, the variations of the measured C O 2 and CO column densities were consistent with the static strain condition.

Cysteine dioxygenase and taurine are essential for embryo implantation by involving in E2-ERα and P4-PR signaling in mouse.

BACKGROUND: Taurine performs multiple physiological functions, and the maintenance of taurine level for most mammals relies on active uptake from diet and endogenous taurine synthesis through its synthesis enzymes, including cysteine dioxygenase (CDO). In addition, uterus tissue and uterus fluid are rich in taurine, and taurine synthesis is regulated by estrogen (E2) and progesterone (P4), the key hormones priming embryo-uterine crosstalk during embryo implantation, but the functional interactions and mechanisms among which are largely unknown. The present study was thus proposed to identify the effects of CDO and taurine on embryo implantation and related mechanisms by using Cdo knockout (KO) and ovariectomy (OVX) mouse models. RESULTS: The uterine CDO expression was assayed from the first day of plugging (d 1) to d 8 and the results showed that CDO expression level increased from d 1 to d 4, followed by a significant decline on d 5 and persisted to d 8, which was highly correlated with serum and uterine taurine levels, and serum P4 concentration. Next, Cdo KO mouse was established by CRISPER/Cas9. It was showed that Cdo deletion sharply decreased the taurine levels both in serum and uterus tissue, causing implantation defects and severe subfertility. However, the implantation defects in Cdo KO mice were partly rescued by the taurine supplementation. In addition, Cdo deletion led to a sharp decrease in the expressions of P4 receptor (PR) and its responsive genes Ihh, Hoxa10 and Hand2. Although the expression of uterine estrogen receptor (ERα) had no significant change, the levels of ERα induced genes (Muc1, Ltf) during the implantation window were upregulated after Cdo deletion. These accompanied by the suppression of stroma cell proliferation. Meanwhile, E2 inhibited CDO expression through ERα and P4 upregulated CDO expression through PR. CONCLUSION: The present study firstly demonstrates that taurine and CDO play prominent roles in uterine receptivity and embryo implantation by involving in E2-ERα and P4-PR signaling. These are crucial for our understanding the mechanism of embryo implantation, and infer that taurine is a potential agent for improving reproductive efficiency of livestock industry and reproductive medicine.

Dense, Three-Dimensional, Highly Absorbent, Graphene Oxide Aerogel Coating on ZnCo2O4/ZnO Particles Exerts a Synergistic Catalytic Effect for Ammonium Perchlorate Thermal Decomposition.

As a new type of carbon material, graphene oxide aerogel (GA) is widely used in catalysis due to its porous structure, high-efficiency adsorption, and superb conductivity. In this study, GA was prepared into a dense coating layer surrounding ZnCo2O4/ZnO particles to form a composite GA-ZnCo2O4/ZnO by means of a hydrothermal, blast drying, and vacuum-freeze-drying approach applied to catalyze the thermal decomposition of ammonium perchlorate (AP). The physicochemical properties of the obtained GA-ZnCo2O4/ZnO were characterized by different analytical methods. Scanning electron microscopy (SEM) analysis exhibited that GA is coated on the surface of ZnCo2O4/ZnO, forming a dense layer. Brunner Emmet Teller (BET) measurement results show that GA-ZnCo2O4/ZnO has a smooth macropore distribution curve and a larger specific surface area. Moreover, The catalytic effect investigation on AP with GA-ZnCo2O4/ZnO: the high temperature decomposition (HTD) peak temperature of AP in the presence of 5 wt % GA-ZnCo2O4/ZnO was reduced from 441 to 294 °C, and the exotherm of AP was expanded from 205 to 1275 J/g at a heating rate of 15 °C/min. Through the calculation, GA-ZnCo2O4/ZnO makes the activation energy and Gibbs free energy of the AP pyrolysis lower so that the reaction is easier to occur. Thermogravimetric-mass (TG-MS) spectrometry revealed that during thermal decomposition of AP, GA-ZnCo2O4/ZnO leveraged the synergistic catalysis of ZnCo2O4/ZnO and GA that boosted the flow of electrons from ClO4- to O2 and increased the absorption of the gas product to accelerate the AP pyrolysis. These results provided a facile strategy to prepare GA-based composite catalysts with extraordinary application prospects in the domain of solid propellants.

Significantly Enhanced Thermal Decomposition of Mechanically Activated Ammonium Perchlorate Coupling with Nano Copper Chromite.

In this article, nano-CuCr2O4 (copper chromite)/ultrafine ammonium perchlorate (AP) composites were prepared by a ultrasonic dispersion method and a mechanical grinding method. A series of nano-CuCr2O4/ultrafine AP composites with different dispersions were prepared by controlling the compounding time to study the best catalytic effect of nano-CuCr2O4 on the ultrafine AP. The microstructures, surface elements, and morphologies of samples were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersion X-ray spectroscopy. The catalytic effect of nano-CuCr2O4 on the thermal decomposition of AP was investigated by differential scanning calorimetric techniques and thermogravimetric analysis. The results indicated that the mechanical ball milling method could make nano-CuCr2O4 more evenly dispersed on the ultrafine AP, and with the increase in the milling time, the uniformity of nano-CuCr2O4 on the ultrafine AP was better. When the milling time was 6-12 h, nano-CuCr2O4 was most evenly dispersed on the ultrafine AP. At this time, the decomposition temperature and Gibbs free energy of the nano-CuCr2O4/ultrafine AP composite were the lowest, which decreased by 78.1 °C and 25.16 kJ/mol compared with those of ultrafine AP, respectively. Moreover, the mechanical sensitivity of nano-CuCr2O4/ultrafine AP composites was lower than that of ultrafine AP. It showed that ball milling for 6-12 h could make nano-CuCr2O4 evenly dispersed on the ultrafine AP, and nano-CuCr2O4 could play the best catalytic effect on the ultrafine AP.

Pb Single Atoms Enable Unprecedented Catalytic Behavior for the Combustion of Energetic Materials.

Manipulating the thermal decomposition behavior of energetic materials is the key to further pushing the combustion performance of solid rocket propellants. Herein, atomically dispersed Pb single atoms on polydopamine (PDA-Pb) are demonstrated, which display unprecedented catalytic activity toward the thermal decomposition of cyclotrimethylenetrinitramine (RDX). Impressively, RDX-based propellants with the addition of PDA-Pb catalyst exhibit substantially enhanced burning rates (14.98 mm s-1 at 2 MPa), which is 4.8 times faster than that without PDA-Pb and represents the best catalytic performance among Pb-based catalysts. Moreover, it also possesses low-pressure exponents in broad pressure ranges, which can enable more stable and safer combustion in solid rocket engines. Theoretical calculation unravels the efficient catalytic activity is stemmed from the enhanced interfacial electronic coupling between RDX and PDA-Pb via orbital level engineering. More importantly, PDA-Pb also presents similar catalytic behavior toward the decomposition of nitrocellulose, suggesting its broad catalytic generality. This work can open up new opportunities in the field of energetic compound combustion by exploring Pb-based single atom catalysts and beyond.

Ellipsoidal magnetite nanoparticles: a new member of the magnetic-vortex nanoparticles family for efficient magnetic hyperthermia.

The development of magnetic iron oxide nanoparticles with novel topological magnetic domain structures, such as the vortex-domain structure, is a promising strategy for improving the application performance of conventional superparamagnetic iron oxides while maintaining their good biocompatibility. Here, we fabricated a new kind of magnetic-vortex nanoparticles, i.e., ellipsoidal magnetite nanoparticles (EMPs), for cancer magnetic hyperthermia. The magnetization configurations and switching behaviours of the EMPs were analyzed by analytical simulations and Lorentz TEM, demonstrating the magnetic vortex structures of both single and coupled EMPs. The EMP treatment of 4T1 cells exposed to an alternating magnetic field (AMF) induced a significant decrease in the cell viability by ∼51.5%, which indicated a much higher cytotoxic effect in comparison with commercial superparamagnetic iron oxides (Resovist, ∼12.0%). In addition, the in vivo high efficacy of 4T1 breast tumor inhibition was also achieved by using EMP-mediated magnetic hyperthermia. Our results not only provide a new type of magnetic-vortex nanoparticles for efficient hyperthermia but also enrich the family of magnetic iron oxide nanoparticles for various biomedical applications.

Shape- and size-dependences of gold nanostructures on the electrooxidation of methanol under visible light irradiation.

Plasmonic metal nanocatalysts have excellent light trapping properties and high chemical reactivity. Impressively, Au nanostructures can absorb a wide array of visible light by tuning their morphology. In this work, spherical gold nanoparticles (Au NSs), multi-branched gold nanoparticles (Au NMs) and gold nanorods (Au NRs) were successfully synthesized; the shape- and size-dependences of these gold nanocatalysts on the methanol oxidation reaction (MOR) under light irradiation were studied. It is worth mentioning that Au NRs have the highest anode peak current density under dark conditions due to the exposure of highly active facets. A similar enhancement effect was obtained for Au NSs and Au NMs under visible light irradiation, which is due to the generation of a high concentration of energetic charge carriers on these Au nanostructures. The size dependences of Au NSs on the MOR showed that a larger electrochemically active surface area (ECSA) was obtained for small nanoparticles, which is due to the surface effect. In addition, the catalytic performance, durability and anti-CO stripping of these Au nanocatalysts under visible light irradiation, as well as the effect of light intensity and wavelength were described in detail. This work provides an insight into the mechanism of plasmon enhanced electrocatalysis by Au nanostructures with different sizes and shapes.

Interface self-assembly preparation of multi-element doped carbon nanobowls with high electrocatalysis activity for oxygen reduction reaction.

Developing an efficient, stable and low cost oxygen reduction reaction electrocatalyst is desirable for fuel cells and metal-air batteries. Here, we have successfully prepared multi-element doped carbon nanobowls by simply mixing the porous carbon nanobowls and sulfur doped graphitic carbon nitride quantum dots in FeCl3 solution and subsequent high temperature treatment processes. Compared with the commercial Pt/C electrocatalyst, the multi-element doped carbon nanobowls display a comparable half-wave potential of 0.82 V, much larger limiting diffusion current density (0.4-0.8 V), better methanol-tolerance and higher long-term stability for the oxygen reduction reaction in alkaline media. The robust three-dimensional porous structure of carbon nanobowls and multiple active centers derived from Fe, N, S and O co-doping are responsible for the excellent performance. This work suggests that such multi-element doped carbon nanobowls can be a promising alternative for Pt-based catalysts in fuel cells.

Nonisothermal decomposition and safety parameters of HNIW/TNT cocrystal.

To explore the thermal decomposition behavior and evaluate the thermal safety of the cocrystal 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW)/2,4,6-trinitrotoluene (TNT), its thermal and kinetic behaviors were studied by differential scanning calorimetry (DSC) technique. With the help of onset temperature (T e) and maximum peak temperature (T p) from the non-isothermal DSC curves of HNIW/TNT cocrystal at different heating rates (ß), the following were calculated: the value of specific heat capacity (C p) and the standard molar enthalpy of formation , the apparent activation energy (E K and E O) and pre-exponential constant (A K) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method, density (ρ) and thermal conductivity (λ), the decomposition heat (Q d, as half-explosion heat), Zhang-Hu-Xie-Li's formula, Smith's equation, Friedman's formula, Bruckman-Guillet's formula, Frank-Kamenetskii's formula and Wang-Du's formulas, the values (T e0 and T p0) of T e and T p corresponding to ß â†’ 0, thermal explosion temperature (T be and T bp), adiabatic time-to-explosion (t tiad), 50% drop height (H 50) for impact sensitivity, critical temperature of hot-spot initiation (T cr), thermal sensitivity probability density function [S(T)] vs. temperature (T) relation curves with radius of 1 m and ambient temperature of 300 K, the peak temperature corresponding to the maximum value of S(T) vs. T relation curve (T S(T)max), safety degree (SD) and critical ambient temperature (T acr) of thermal explosion. Results show that the kinetic equation describing the exothermic decomposition reaction of HNIW/TNT cocrystal is The following thermal safety parameters for the HNIW/TNT cocrystal are obtained: T e0 = 464.45 K; T p0 = 477.55 K; T be = 472.82 K; T bp = 485.89 K; t tiad = 4.40 s, 4.42 s, and 4.43 s for n = 0, 1, and 2, respectively; T cr = 531.90 K; H 50 = 19.46 cm; and the values of T acr, T S(T)max, SD and P TE are 469.69 K, 470.58 K, 78.57% and 21.43% for sphere; 465.70 K, 470.58 K, 78.17% and 21.83% for infinite cylinder; and 459.39 K, 464.26 K, 77.54% and 22.46% for infinite flat.

High electrocapacitive performance of bowl-like monodispersed porous carbon nanoparticles prepared with an interfacial self-assembly process.

Bowl-like monodispersed porous carbon nanoparticles (BMPCNs) have been successfully prepared with a facile and scalable approach, and the as-prepared BMPCNs are examined thoroughly by various physical characterizations. Physical measurements display that BMPCNs have the high surface area (1255m2g-1), hierarchical porosity, a certain amount of oxygen-containing groups and high graphitization degree. These unique structure features endow BMPCNs with a high capacitance (281Fg-1 at 0.5Ag-1), excellent rate capability (209Fg-1 at 50Ag-1), and outstanding cycling stability (94.8% capacity retention after 10,000 cycles at 10Ag-1) in electrochemical double-layer capacitors, suggesting its promising applications in field of energy conversion and storage. Further, the studies on formation mechanism of BMPCNs suggest that, the CTAB wormlike micelles assembling with silica/resorcinol-formaldehyde oligomers at the interface of tetraethyl orthosilicate droplets under Stöber condition determines the morphology of BMPCNs.

Boosting one-step conversion of cyclohexane to adipic acid by NO2 and VPO composite catalysts.

We demonstrate VPO composites as efficient catalysts for highly selective oxidation of cyclohexane to adipic acid with NO2. In particular, the Ni-Al-VPO composite catalyst exhibits the striking conversion of cyclohexane (60.6%) and exceptionally high selectivity towards adipic acid (85.0%). Moreover, N2O is an environmentally harmful gas, and its yield in the present process is only 0.03 t/t adipic acid, which is far below that obtained using the industrial method (0.3 t/t adipic acid). This work provides a new strategy for the one-step synthesis of dicarboxylic acids from cycloalkanes.

DFT studies of the adsorption and dissociation of H2O on the Al13 cluster: origins of this reactivity and the mechanism for H2 release.

A theoretical study of the chemisorption and dissociation pathways of water on the Al13 cluster was performed using the hybrid density functional B3LYP method with the 6-311+G(d, p) basis set. The activation energies, reaction enthalpies, and Gibbs free energy of activation for the reaction were determined. Calculations revealed that the H2O molecule is easily adsorbed onto the Al13 surface, forming adlayers. The dissociation of the first H2O molecule from the bimolecular H2O structure via the Grotthuss mechanism is the most kinetically favorable among the five potential pathways for O-H bond breaking. The elimination of H2 in the reaction of an H2O molecule with a hydrogen atom on the Al cluster via the Eley-Rideal mechanism has a lower activation barrier than the elimination of H2 in the reaction of two adsorbed H atoms or the reaction of OH and H. Following the adsorption and dissociation of H2O, the structure of Al13 is distorted to varying degrees.

Non-isothermal decomposition kinetics, heat capacity and thermal safety of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture.

The specific heat capacity (C(p)) of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was determined with the continuous C(p) mode of microcalorimeter. The equation of C(p) with temperature was obtained. The standard molar heat capacity of GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was 1.225 J mol(-1)K(-1) at 298.15K. With the help of the peak temperature (T(p)) from the non-isothermal DTG curves of the mixture at different heating rates (ß), the apparent activation energy (E(k) and E(o)) and pre-exponential constant (A(K)) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method. Using density (ρ) and thermal conductivity (λ), the decomposition heat (Q(d), taking half-explosion heat), Zhang-Hu-Xie-Li's formula, the values (T(e0) and T(p0)) of T(e) and T(p) corresponding to ß â†’ 0, thermal explosion temperature (T(be) and T(bp)), adiabatic time-to-explosion (t(TIad)), 50% drop height (H(50)) of impact sensitivity, and critical temperature of hot-spot initiation (T(cr,hot spot)) of thermal explosion of the mixture were calculated. The following results of evaluating the thermal safety of the mixture were obtained: T(be) = 441.64K, T(bp) = 461.66 K, t(Tlad) = 78.0 s (n = 2), t(Tlad) = 74.87 s (n = 1), t(Tlad) = 71.85 s (n = 0), H(50) = 21.33 cm.

Non-isothermal thermal decomposition reaction kinetics of 2-nitroimino-5-nitro-hexahydro-1,3,5-triazine (NNHT).

The thermal behavior and decomposition reaction kinetics of 2-nitroimino-5-nitro-hexahydro-1,3,5-triazine (NNHT) were investigated by TG-DTG and DSC under atmospheric pressure and flowing nitrogen gas conditions. The results show that the thermal decomposition process of NNHT has two mass loss stages. The exothermic decomposition reaction mechanism obeys chemical reaction rule. The kinetic parameters of the reaction are E(a)=131.77 kJ mol(-1), lg(A/s(-1))=12.56, respectively. The kinetic equation can be expressed as: dalpha/dt = 10(12.86)(1-alpha)(3/2)3(-1.5849 x 10(4)/T)). The critical temperature of thermal explosion of NNHT obtained from the peak temperature (T(p)) is T(bp)=467.22K. The entropy of activation (DeltaS( not equal)), enthalpy of activation (DeltaH( not equal)), and free energy of activation (DeltaG( not equal)) of the reaction are -7.978 J mol(-1)K(-1), 127.99 kJ mol(-1) and 131.62 kJ mol(-1), respectively.

Effects of pressure and TEGDN content on decomposition reaction mechanism and kinetics of DB gun propellant containing the mixed ester of TEGDN and NG.

The effects of pressure and triethyleneglycol dinitrate (TEGDN) content on the decomposition reaction mechanism and kinetics of the double-base (DB) gun propellant composed of mixed ester of TEGDN and nitroglycerin (NG), and nitrocellulose (NC) were investigated by high-pressure differential scanning calorimetry (PDSC). The results show that the high pressure can decrease the DSC peak temperature, increase the decomposition heat; with the increase in the content of TEGDN, the decomposition heat decreases below 2MPa and rises at 4MPa. The high pressure can change the decomposition reaction mechanism and the kinetics of the DB gun propellant under 0.1MPa; the high TEGDN content does not change the mechanism functions, and the kinetic equation has a little difference between the sample and the control propellant; the high pressure makes the critical temperature (T(be)) of thermal explosion of the sample decrease, while the high TEGDN content make it present a increasing trend, and the DB gun propellant containing high content of TEGDN has a better thermal stability.