Critical Temperature Of Thermal Explosion Research Articles

Simulation of thermal hazards risk in octogen based on non-isothermal DSC data

To evaluate the possible thermal risks associated with the storage of octogen (HMX), non-isothermal differential scanning calorimetry (DSC) experiments were conducted in order to ascertain the kinetic model and parameters governing its thermal decomposition. DSC measurements indicate that HMX underwent a crystal transformation prior to thermal decomposition. A kinetic model for the autocatalytic thermal decomposition process was developed through the analysis of its primary exothermic peaks. Subsequently, numerical simulations were performed using the aforementioned kinetic model to assess the potential thermal explosion hazard of HMX under two distinct storage conditions. The comparison was made between the models of HMX autocatalytic decomposition temperature and thermal explosion critical temperature under two distinct storage conditions. The prediction of the influence of ambient temperature on the critical temperature of thermal explosion is conducted simultaneously. Finally, the thermal hazard parameters of HMX under different package quality are given.

Novel azide polymer/NC/RDX composite microspheres: low sensitivity and excellent thermal stability

ABSTRACT The high sensitivity of nitramine explosives limits their wide application, and an effective way to reduce the sensitivity is to coat them. In this study, four types of azide polymers (GAP, GAPA, GAPE, GAP-ETPE) and nitrocellulose (NC) were selected as the coating materials to coat RDX by the solvent evaporation method. The morphology, structure, dimensions and coating quality of the composite microspheres were investigated by SEM, laser particle size measurement, XRD, XPS and FT-IR. The results indicated that uniformly coated RDX composite microspheres with high sphericity and uniform particle size distribution were prepared. In addition, the thermal stability of the composite microspheres was further analyzed by DSC. The results showed that the critical temperature of thermal explosion (T b ) and self-accelerated decomposition temperature (T SADT ) of the azide polymer/NC/RDX composite microspheres were increased from 211.92°C and 198.49°C to 218.82°C and 206.19°C, respectively. In addition, mechanical sensitivity tests showed that the friction sensitivity and impact sensitivity of the composite microspheres were reduced by 24% ~36% and 35% ~58%, respectively.Therefore, this work demonstrates the beneficial effects of azide polymers and NC as coating materials for nitramine explosives and provides a reference for the desensitization research of nitramine explosives.

Study on Thermal Decomposition and Thermal Safety of Mixtures of Highly Active Aluminum Powder and Nitramine Explosive

The newly prepared and stored highly active aluminum powder were mixed with common nitramine explosives HMX and CL-20 at a mass ratio of 1:1, respectively. The effects of the two kinds of high active aluminum powder on the thermal decomposition properties of HMX and CL-20 were investigated by differential scanning calorimetry (DSC). The thermal explosion critical temperature of the mixture of high active aluminum powder and nitramine explosive was calculated. The result shows that after joining highly active aluminium powder, highly active aluminium/nitramine explosive mixture, moderate and apparent activation energy decrease thermal decomposition peak suggests that highly active aluminium can contribute to the thermal decomposition of HMX and CL-20, compared with highly active aluminium stored after a certain period of time, the new system is highly active aluminum powder with a mixture of nitramine explosives with lower apparent activation energy, At the same time, the critical temperature of thermal explosion also decreased significantly, which indicated that the newly prepared high-activity aluminum powder had higher chemical reactivity, but its thermal safety was reduced.

Thermal Analysis and Pyrolytic Behavior of Bimetal and Double Oxidant Thermite Al/Mg/MoO3/CuO

AbstractIn order to study the effect of fuel Mg and metal oxide CuO on the reaction of thermite, different proportions of Al‐Mg alloys and MoO3‐CuO metal oxides were prepared by mechanical ball milling, and then the samples of Al1‐xMgx/(MoO3)1‐xCuOx composite thermite were prepared by ultrasonic dispersion method. The samples were characterized by SEM, TG‐DSC, and constant pressure combustion experiments. The results show that in quaternary thermite, adding CuO increases initial exothermic temperature, but increases exothermic heat in high‐temperature regions, and effectively reduces the activation energy of the thermite reaction. On the contrary, adding Mg reduces exothermic heat in the high‐temperature areas, but reduces initial exothermic temperature. After calculation, the quaternary thermite with the best exothermic performance is Al0.8Mg0.2/(MoO3)0.5CuO0.5. Its initial reaction temperature is only 614 °C, but the heat release is up to 2217 J/g. Its activation energy is only 106.7 kJ/mol, but the critical temperature of thermal explosion is up to 927.9 K. At the same time, Al0.8Mg0.2/(MoO3)0.5CuO0.5 has better combustion performance. During combustion, the flame is jet‐like, and the main products are Al2O3, Mo and Cu. This work provides a reference for studying the thermal safety and combustion performance of quaternary thermite.

Thermal studies of novel heat-resistant 3,6-dinitropyrazolo[4,3-c]pyrazole-based energetic materials

1,4-Bis(2′,4′,6′-trinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DTNBDNP) is a newly developed heat-resistant explosive exhibiting superior properties to most traditional heat-resistant energetic materials with a significantly high thermal decomposition temperature of 410 °C. Detailed thermal behaviors and nonisothermal decomposition kinetics of DTNBDNP and 1,4-bis(2′,4′-dinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DDNBDNP) were investigated using a differential scanning calorimeter (DSC), and the thermal safety was evaluated by different criteria, including the self-accelerating decomposition temperature and critical temperature of thermal explosion. Their thermodynamic functions were also obtained based on the specific heat capacity data determined using a micro-DSC method. Further studies on the thermal decomposition mechanism were carried out through condensed-phase thermolysis/Fourier transform infrared (in situ FTIR) spectroscopy and the combination of differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectroscopy (DSC–TG–MS–FTIR) techniques. The experimental results prove that the decomposition of DTNBDNP and DDNBDNP is most likely to begin with a ring-opening reaction of the fused-heterocycle backbone. In addition, the main gaseous products, including NO, CO2, N2O, and NO2, are released from the decomposition of DTNBDNP and DDNBDNP.

Bis(5-nitroimino-1,2,4-triazole-3-yl) methane-based energetic salts: Synthesis, crystal structure, thermal behavior and catalytic activity

Four energetic ionic salts of bis(5-nitroimino-1,2,4-triazole-3-yl) methane (BNTM) potassium (KBNTM), ammonium (A2BNTM), hydroxylamine ((HA)2BNTM), 1,3-diaminoguanidine ((DAG)2BNTM) have been synthesized and characterized by Elemental analysis(EA), Fourier infrared(FI) and Nuclearmagnetic resonance(NMR). Fortunately, the single crystals available for determination of KBNTM was acquired by slow evaporation of solvent method and its structure was discussed. The thermal behaviors of them were explored by Differential Scanning Calorimetry(DSC) and Thermogravimetry/ Derivative Thermogravimetry (TG/DTG) technique, and the result displayed that all of them had good thermal stability. The most possible mechanism function of main exothermic decomposition process were obtained (No.35 for KBNTM, No.6 for A2BNTM, No.24 for (HA)2BNTM, No.14 for (DAG)2BNTM). In addition, (HA)2BNTM has the best thermal safety, followed by KBNTM and A2BNTM according to the calculated value of self-accelerating decomposition temperature (TSADT) and critical temperature of thermal explosion (Tb). Moreover, the catalytic effects of four ionic salts on Cyclotrimethylenetrinitramine(RDX) and Octogen(HMX) were investigated respectively. The consequent showed that (HA)2BNTM accelerated the thermal decomposition of RDX and HMX, and reduced the decomposition temperature and apparent activation energy of RDX and HMX by 6.94 °C, 17.37 kJ·mol−1 and 4.17 °C, 2.77 kJ·mol−1, respectively. Surely, the thermal decomposition mechanism function of (HA)2BNTM/RDX was different from that of RDX (No.5, f(α)=6(1-α)2/3 [1-(1-α)1/3]1/2). In summary, (HA)2BNTM can be regarded as a potential energetic combustion catalyst with insensitive to physical impact (IS=16 J).

Fabrication and properties of sphere CL-20/RDX composites with different molar ratios

ABSTRACT Micronsized spherical CL-20/RDX composites with uniform size were prepared by an electrospray method. After preparation, the morphology, crystal structure, thermal decomposition property, explosion performance and mechanical sensitivity were characterized. Different structures existed in the CL-20/RDX composites with different molar ratios. The CR11e composites had the lowest apparent activation energy and the lowest critical temperature of thermal explosion. The explosion pressure and mechanical sensitivity of CL-20/RDX composites were lower than that of raw CL-20 and decreased with increasing RDX content.

Comparative investigations of ternary thermite Al/Fe2O3/CuO and Al/Fe2O3/Bi2O3 from pyrolytic, kinetics and combustion behaviors

To develop new energy enhancement energetic materials with great combustion performance and thermal stability, two kinds of ternary thermite, Al/Fe2O3/CuO and Al/Fe2O3/Bi2O3, were prepared and analyzed via mechanical ball milling. The samples were characterized by SEM, XRD, TG-DSC, constant volume and constant pressure combustion experiments. The first exothermic peaks of Al/Fe2O3/CuO and Al/Fe2O3/Bi2O3 appear at 579 °C and 564.5 °C, respectively. The corresponding activation energies are similar. The corresponding mechanism functions are set as G(α)=[−ln(1−α)]3/4 and G(α)=[−ln(1−α)]2/3, respectively, which belong to the Avrami-Erofeev equation. Al/Fe2O3/CuO has better thermal safety. For small dose samples, its critical temperature of thermal explosion is 121.05 °C higher than that of Al/Fe2O3/Bi2O3. During combustion, the flame of Al/Fe2O3/CuO is spherical, and the main products are FeAl2O4 and Cu. The flame of Al/Fe2O3/Bi2O3 is jet-like, and the main products are Al2O3, Bi and Fe. Al/Fe2O3/Bi2O3 has better ignition and gas production performance. Its average ignition energy is 4.2 J lower than that of Al/Fe2O3/CuO. Its average step-up rate is 28.29 MPa/s, which is much higher than 6.84 MPa/s of Al/Fe2O3/CuO. This paper provides a reference for studying the thermal safety and combustion performance of ternary thermite.

On the Promotion of TKX‐50 Thermal Activity with Aluminum

AbstractIt is significant to investigate the effect of aluminum (Al) on the thermal activity of Dihydroxylammonium 5, 5′‐bistetrazole‐1, 1′‐diolate (TKX‐50) for the application of TKX‐50‐based composite solid propellant. In this work, TKX‐50/Al composites with different particle sizes and contents of Al were blended, and the thermal decomposition and combustion properties were investigated by differential scanning calorimetry (DSC), thermal decomposition kinetic methods, laser ignition experiments, and constant‐volume combustion cell test. The results showed that the exothermic peak temperatures for thermal decomposition of TKX‐50 were gradually advanced with the decrease of Al particle size. With the increase of Al nanoparticles (nAl) content, the peak temperatures of TKX‐50 first decreased and then increased. As the content of nAl was 50 %, the activation energy of TKX‐50 changed from 226.51 kJ ⋅ mol−1 to 215.23 kJ ⋅ mol−1, and the critical temperature of thermal explosion decreased by 13.54 °C after the addition of nAl. In addition, a small amount of nAl could promote the combustion of TKX‐50 that is reflected on the accelerated burning rate, increased maximum combustion pressure and pressurization rate. Overall, nAl with high specific surface area and high reactivity is a great thermal activity enhancement additive for TKX‐50.

Thermodynamic properties, decomposition kinetics of 2-(5-amino-2H-tetrazol-1-yl)-4-amine-3,5-dinitropyridine

A novel energetic material 2-(5-amino-2H-tetrazol-1-yl)-4-amine-3,5-dinitropyridine (ATDP) was synthesized and characterized by 1H NMR, 13C NMR, mass spectroscopy, and elemental analysis. The research by differential scanning calorimetry (DSC) shows that ATDP decomposed about 290°C. The calculating results of kinetic parameters using Ozawa method, Kissinger method, and Starink method were quite consistent. Self-accelerated decomposition temperature (TSADT), thermal ignition temperature (TTIT), and critical temperature of thermal explosion (Tb) were 272.55°C, 121.71°C, and 137.67°C, respectively. Geometric optimization, heat of formation, detonation velocity (D), detonation pressure (P), bond dissociation energy (BDE), and electrostatic potential (ESP) were explored using Gaussian 16. The results show that ATDP has a much larger ΔHf,gas value than HMX(272.6kJmol-1). The D and P are predicted with the value of 7.50kms-1 and 24.47 GPa, respectively. The relatively high BDE value (270.77kJmol-1) indicates that ATDP has moderate thermal stability.

Thermal Safety Analysis of On-Site Emulsion Explosives Mixed with Waste Engine Oil

The study of the thermal safety of emulsion explosives mixed with waste engine oil is very important for the safety of these types of explosives used in mine blasting. In order to study the thermal safety of emulsion explosives mixed with waste engine oil, thermal safety tests were carried out using a Differential Scanning Calorimeter (DSC), non-isothermal kinetics, and the Flynn–Wall–Ozawa method. The results show that the minor particle impurities in the filtered waste engine oil are mainly combustibles; after adding different amounts of waste engine oil, the activation energy of the emulsion matrix decreases from 110.33 kJ/mol to 75.39 kJ/mol, 74.50 kJ/mol, and 82.23 kJ/mol, and the critical temperature for thermal explosion changes from 194.16 °C to 169.73 °C, 227.47 °C, and 208.78 °C. The addition of waste engine oil reduces the activation energy of emulsion explosives. The waste engine oil is negatively correlated with the activation energy and the thermal explosion reaction temperature of emulsion explosives, and the correlation coefficient is −0.686 and −0.333. The emulsifier is positively correlated with the critical temperature of thermal explosion of emulsion explosives, and the correlation coefficient is 0.251. The small particles in the waste engine oil create a hot spot in the emulsion explosives, which reduces the thermal safety of the emulsion explosives mixed with waste engine oil. The emulsifier reduces the droplet size of the emulsion explosive, improves the oil-water interface strength, and improves the thermal safety of the emulsion explosives mixed with waste engine oil. The thermal safety of emulsion explosives mixed with waste engine oil can be improved by reducing the proportion of the sensitizer and increasing the proportion of the emulsifier.

Hermetic thermal decomposition behaviors and specific heat capacity of 2,4,6-triazido-1,3,5-triazine (TAT)

In view of the volatile quality of 2,4,6-triazido-1,3,5-triazine (TAT) after melting, a special high-pressure hermetic crucible was used to analyze the compound's thermal decomposition behaviors. The complete exothermic decomposition process of TAT was obtained, and the extrapolated onset temperature, peak temperature, and decomposition enthalpy at a heating rate of 10.0 °C/min were measured as 195.1 °C, 221.4 °C and -3753.0 J/g, respectively. The hermetic thermal decomposition kinetic equation was thus obtained. The self-accelerating decomposition temperature and critical temperature of thermal explosion for TAT were 173.7 °C and 186.6 °C, respectively. The specific heat capacity of TAT was determined, and the molar heat capacity was 234.67 J/(mol · K) at 298.15 K. It can be observed that TAT possesses a high thermal decomposition temperature and a drastic heat release.

5,7-diamine-2-nitro-1,2,4-triazolo[1,5-a]-1,3,5-triazine (ANTT): A nitrogen-rich compound suitable for gas generators

For the development of safe, non-toxic and environmentally friendly gas generators, a nitrogen-rich compound 5,7-diamine-2-nitro-1,2,4-triazolo[1,5-a]-1,3,5-triazine (ANTT) was synthesized from 3,5-diamine-1,2,4-triazole in two steps. The structure of ANTT was comprehensively characterized and well investigated by X-ray diffraction. The thermal stability, detonation properties and mechanical sensitivities of ANTT were finely studied. ANTT, enjoyed with a high content of nitrogen (57.13%), as well as a high decomposition temperature of 358.5 °C, high self-accelerating decomposition temperature of 340.3 °C, high critical temperature of thermal explosion 342.2 °C, high apparent activation energy of 512.23 kJ•mol−1 and low sensitivity toward destructive mechanical stimuli (IS > 60 J; FS > 360 N), is promising candidate as gas generator.

Thermal Decomposition Kinetics and Compatibility of 3,5-difluoro-2,4,6-trinitroanisole (DFTNAN).

In this paper, the thermal decomposition behavior of 3,5-difluoro-2,4,6-trinitroanisole (DFTNAN) was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) by using different heating rates (2, 5, 10, 15 °C·min−1). Subsequently, the kinetic and thermodynamic parameters of non-isothermal thermal decomposition of DFTNAN were calculated. The critical temperature of thermal explosion () and self-accelerating decomposition temperature () were determined to be 249.03 °C and 226.33 °C, respectively. The compatibility of DFTNAN with a number of high explosives (cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-tetracyclo-[5.5.0.05,9.03,11]-dodecane (CL-20) and dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate (TKX-50)) was studied at different mass ratios using DSC. The criteria to judge the compatibility between the materials were based on a standardization agreement (STANAG 4147). The thermodynamic study results revealed that DFTNAN possessed superior thermal safety and stability. The experimental of compatibility results indicated that the mass ratios of the high explosives in the DFTNAN/RDX, DFTNAN/HMX and DFTNAN/CL-20 compositions more than 40%, 60% and 70% exhibited good compatibility, whereas DFTNAN/TKX-50 demonstrated poor compatibility.

Evaluation of thermal hazards based on thermokinetic parameters of 2,4-dinitroanisole

ABSTRACT As a high-energy insensitive explosive which is expected to replace 2,4,6-trinitrotoluene (TNT), it is necessary to evaluate the thermal risk of 2,4-dinitroanisole (DNAN). In this article, the thermal performance of DNAN was tested using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC). According to the test results, the decomposition activation energy (E), the pre-exponential constant (A), activation entropy (ΔS ≠), activation enthalpy (ΔH ≠), activation Gibbs free energy (ΔG ≠) at T P0 of the reaction and the critical temperature of thermal explosion (T b) were obtained. The kinetic model under adiabatic conditions was established. The thermal hazard assessment of DNAN was carried out according to the thermodynamic parameters, and the assessment results are of great significance to the application of DNAN.

Synthesis and Properties of Hydrazine Picrate

Picric acid was reacted with liquid propellant anhydrous hydrazine to synthesize anhydrous hydrazine picrate. Its structure was characterized by elemental analysis, infrared spectrum analysis, nuclear magnetic resonance, and its thermal decomposition performance was analyzed by TG-DTG and DSC. The thermal decomposition of anhydrous hydrazine picrate was studied by using Kissinger method and its activation energy was calculated. The critical temperature of thermal explosion was calculated by using the characteristic data of non-isothermal DSC curve. The results shows that the thermal decomposition of anhydrous hydrazide is mainly between 179.8∼200.9°C, the decomposition process is exothermic reaction, the melting point is about 140°C, the non-isothermal kinetic equation is ln(β/T p 2 )=-17652 (1/T p)+28.009, the activation energy of thermal decomposition is E=146.76kJ/mol, pre-exponential factor lnA=30.34, and the critical temperature of thermal explosion T b=175.3°C. Anhydrous hydrazine picrate has the characteristics of simple synthesis, rapid reaction and good thermal stability. It provides a new way for the disposal and reuse of anhydrous hydrazine.

Effect of Acid Concentration on Thermal Stability of nitrocellulose (NC) for Civil Use

The effect of acid concentration in nitrocellulose (NC) on thermal stability of NC for civil use was studied using differential scanning calorimeter (DSC). The thermal explosion temperature (Tb) and kinetic parameters of NC thermal decomposition were calculated using different methods based on the thermal decomposition behaviors of NC in high pressure-gold plated stainless steel crucible at different heating rates. The results show that acid content in NC reduces the stability of NC remarkably, including reducing the characteristic decomposition temperature such as peak temperature (Tp), onset temperature (Tonset), initial temperature (T0) and critical temperature of thermal explosion (Tb). The big difference between NC with different acid content is that the relative quantity of activation energy and the change trend of activation energy. The most interesting thing is that NC with more acid content has the lower characteristic temperature but higher calculated activation energy.

Energetic properties, thermal behavior and thermal safety of 4-(2,2,2-trinitroethyl)-2,6,8,10,12-pentanitro-2,4,6,8,10,12-hexaazaisowurtzitane

The physicochemical and energetic properties of 4-(2,2,2-trinitroethyl)-2,6,8,10,12-pentanitro-2,4,6,8,10,12-hexaazaisowurtzitane (1) are investigated. The energetic cage compound exhibits detonation properties comparable to those of HMX, and its impact sensitivity is higher than that of ε-CL-20. It shows a significantly higher thermal stability with a decomposition temperature of 227.6 °C than those of the other trinitromethyl-substituted energetic compounds. Its thermal behavior is further investigated using differential scanning calorimetry and accelerating rate calorimetry. The non-isothermal and adiabatic decomposition reaction kinetics of compound 1 are studied, and its thermal safety is evaluated using different criteria including the self-accelerating decomposition temperature, critical temperature of thermal explosion, and five-second delay exploding point.

Preparation and molecular dynamics simulation of spherical β-HMX by spray drying technology

ABSTRACT In this paper, the optimal temperature in an HMX spray-drying process was determined by molecular dynamics simulations and verified using experiments. Using the optimal spray-drying temperature determined by simulations, spherical β-HMX with a uniform particle size distribution was obtained by spray-drying. Performance characterization and thermal analysis of β-HMX were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The impact sensitivity of β-HMX was also measured and analyzed. The molecular dynamics simulations and experimental results both indicated that the optimum spray-drying temperature of HMX was 57°C. At this temperature, an HMX particle diameter range of 1 µm – 5 µm was obtained, and the particles tended to be smooth spheroids. Compared with raw HMX, the T p0 and critical temperature of thermal explosion of HMX-1 increased by 0.9°C and 0.94°C, respectively. The characteristic drop height of impact sensitivity increased by 32% from 32.05 cm to 42.28 cm.

A novel energetic composite with a special sandwich microstructure: RDX/expanded graphite intercalation composite

In this paper, the RDX/expanded graphite (EG) intercalation composites were prepared by solvent/anti-solvent process to recrystallize RDX crystals into the holes, gaps and grooves of EG with controllable embedding ratio (maximum 87.0 wt%) and crystal size. RDX in the composites was in the most stableα-phase, which was benefit for its further application in the military industry. The stability and sensitivity of RDX were improved with higher melting and thermolysis temperature, activation enthalpy (ΔH ≠), critical temperature of thermal explosion (T b) and lower mechanical sensitivity. The advanced half-coated parallel multi-sandwiches microstructure of RDX/EG intercalation composites possessed two effects: (i) high heat conduction and (ii) hot spots isolation of the carbon microstructure, which were the key to higher performance.