Critical Temperature Of Thermal Explosion Research Articles

Preparation, crystal structure, thermal decomposition, quantum chemical calculations on [K(ZTO)⋅H2O]∞ and its ligand ZTO

A novel potassium complex has been synthesized and characterized under the non-isothermal conditions by DSC and TG-DTG method. The 4,4-azo-1,2,4-triazol-5-one (ZTO) has the molecular formula C4H4N8O2. The thermodynamic parameters, HOMO–LUMO energy gap, total energy and electrostatic potential (MEP) of ZTO are conducted by density functional theory DFT/B3LYP calculation method with 6-311G basis set. In the coordination polymer, with the ligand anion (ZTO−) as space linkers, two types of potassium atoms centers are joined together to form three-dimensional frameworks. The enthalpy, apparent activation energy and pre-exponential factor of the second exothermic decomposition reaction are 85.43kJmol−1, 414.4kJmol−1and 1037.92s−1, respectively. The critical temperature of thermal explosion (Tb) for [K(ZTO)⋅H2O]∞ is 275.08°C. [K(ZTO)⋅H2O]∞ CCDC: 902339.

Structural and Thermal Characterization of A Novel High Nitrogen Energetic Material: (NH4 )2 DNMT

1,4-Dihydro-5H-(dinitromethylene)-tetrazole ammonium salt ((NH4)2DNMT), a high nitrogen energetic compound, was synthesized and structurally characterized by single-crystal X-ray diffraction. The thermal behavior of (NH4)2DNMT was studied with DSC and TG-DTG methods. The kinetic equation of the thermal decomposition reaction is: dα/dT=1013.17/3β(1−α)−2 exp(−1.388×105/RT). The critical temperature of thermal explosion is 182.7 °C. The specific heat capacity of (NH4)2DNMT was determined and the molar heat capacity is 301 J mol−1 K−1 at 298.15 K. The adiabatic time-to-explosion of (NH4)2DNMT was calculated to be 277 s. The detonation velocity and detonation pressure were also estimated. All results showed that (NH4)2DNMT presents good performance.

Structural and Thermal Characteristics of a High-Nitrogen Energetic Material: G(AHDNE)

A high-nitrogen energetic salt, 1-amino-1-hydrazino-2,2-dinitroethylene guanidine salt [G(AHDNE)], was synthesized by reacting of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE) and guanidine hydrochloride in sodium hydroxide aqueous solution. The theoretical investigation on G(AHDNE) was carried out by B3LYP/<TEX>$6-311+G^*$</TEX> method. The thermal behaviors of G(AHDNE) were studied with DSC and TG-DTG methods, and the result presents an intense exothermic decomposition process. The enthalpy, apparent activation energy and pre-exponential constant of the process are <TEX>$-1060J\;g^{-1}$</TEX>, <TEX>$148.7kJ\;mol^{-1}$</TEX> and <TEX>$10^{15.90}s^{-1}$</TEX>, respectively. The critical temperature of thermal explosion of G(AHDNE) is <TEX>$152.63^{\circ}C$</TEX>. The specific heat capacity of G(AHDNE) was studied with micro-DSC method and theoretical calculation method, and the molar heat capacity is <TEX>$314.69J\;mol^{-1}K^{-1}$</TEX> at 298.15 K. Adiabatic time-to-explosion of G(AHDNE) was calculated to be a certain value between 60-72 s. The detonation velocity and detonation pressure were also estimated. G(AHDNE) presents good performances.

Molecular structure, quantum chemical investigation, and thermal behavior of (DNAZ-CO)2

Bis-(3,3-dinitroazetidinyl)-oxamide ((DNAZ-CO)2) is an acyl derivative of 3,3-dinitroazetidine (DNAZ). It is prepared and its crystal structure is determined. The crystal is orthorhombic, Fdd2 space group, a = 13.136(14) A, b = 19.48(3) A, c = 10.326(14) A, V = 2642 (6) A3, Z = 8. A density functional theory (DFT) method of the Amsterdam Density Functional (ADF) package is used to calculate the geometry, frequencies, and properties. The optimized geometry, frontier orbital energy, and main atomic orbital percentage are obtained. The thermal behavior is studied under a non-isothermal condition by DSC and TG/DTG methods. The apparent activation energy (E a) and pre-exponential factor (A) of the exothermic decomposition reaction of (DNAZ-CO)2 are 164.10 kJmol−1 and 1013.38 s−1 respectively. The critical temperature of thermal explosion is 272.20°C. The values of ΔS ≠, ΔH ≠, and ΔG ≠ of this reaction are 6.44 Jmol−1·K−1, 163.76 kJmol−1 and 160.34 kJmol−1 respectively.

Specific Heat Capacity, Thermal Behavior, and Thermal Hazard of 2,4‐Dinitroanisole

AbstractThe thermal hazard of 2,4‐dinitroanisole (2,4‐DNAN) was evaluated by microcalorimetry methods. The specific heat capacity, melting enthalpy, and the solidification heat of 2,4‐DNAN were determined with a Micro‐DSCIII calorimeter. The thermal decomposition behavior of 2,4‐DNAN at four different heating rates was studied by using a C‐500 type calvet microcalorimeter. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow data. The critical temperature of thermal explosion (Tb) and the initial decomposition temperature (Tp0) were determined to distinctly evaluate the thermal hazard of 2,4‐DNAN.

A feature on ensuring safety of superfine explosives

To probe the dependence of particle size on the safety of nitroamine explosives, coarse RDX and HMX were comminuted to nanometer particles by an improved superfine mill. Their thermolysis characteristics were studied by thermal analysis and described via calculating some thermodynamic and kinetic parameters such as the activation free-energy (ΔG≠), activation enthalpy (ΔH≠), activation entropy (ΔS≠), apparent activation energy (E), critical temperature of thermal explosion (Tb), and critical heating rate of thermal explosion (\( ({\text{d}}T/{\text{d}}t)_{{T_{\text{b}} }} \)). After comminuted, the values of Tb and \( ({\text{d}}T/{\text{d}}t)_{{T_{\text{b}} }} \) were increased. However, the values of ΔH≠, ΔS≠, ΔG≠, and E for nanoexplosives were close to those of microexplosives, which mean decreasing particle size into nanometer did not distinctly influence the thermolysis characteristic of nitroamines. The safety of the nanoexplosives was practically assessed by testing their impact, friction, and shock sensitivities. Results indicated that nano nitroamines presented obviously higher safety than the micro-counterparts. Especially in Small Scale Gap Test, the shock sensitivity of nano-RDX and nano-HMX decreased by about 45 and 56% compared with that of micro-RDX and micro-HMX, respectively.

Synthesis, crystal structure, thermal decomposition, and non-isothermal reaction kinetic analysis of an energetic complex: [Mg(CHZ)3](ClO4)2 (CHZ = carbohydrazide)

An energetic complex [Mg(CHZ)3](ClO4)2 was synthesized by the reaction of carbohydrazide (CHZ) with magnesium perchlorate. The product was characterized by X-ray single-crystal diffraction, elemental analysis, and IR spectroscopy. The crystal belongs to the monoclinic system with space group P2(1)/n. Cell parameters: a = 10.034(2) Å, b = 8.5069(16) Å, c = 21.285(4) Å, β = 100.901(3)°, V = 1784.1(6) Å3, Z = 4. The central magnesium is six-coordinate with three oxygen atoms of carbonyl groups and three terminal nitrogen atoms of the hydrazine groups from three CHZs to form a distorted octahedron. Differential scanning calorimetry and thermogravimetric-differential thermogravimetric analysis were applied to assess the thermal decomposition behavior. The kinetic parameters were obtained by non-isothermal reaction kinetics. The equation can be expressed as . Moreover, the values of critical temperature of thermal explosion, ΔS≠ , ΔH≠ , ΔG≠ , and the energy of combustion were obtained as 284°C, −169.76 J mol−1 K−1, 65.46 kJ mol−1, 154.27 kJ mol−1, and 6759 kJkg−1, respectively.

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

AbstractStudy on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (Tb) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS#, ΔH#, and ΔG# of its decomposition reaction were calculated.

Thermal decomposition behavior, kinetics, and thermal hazard evaluation of CMDB propellant containing CL-20 by microcalorimetry

The thermal decomposition behavior of composite modified double-base propellant containing hexanitrohexaazaisowurtzitane (CL-20/CMDB propellant) was studied by microcalorimetry. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The effect of different proportion of CL-20 to the thermal decomposition behavior, kinetics, and thermal hazard was investigated at the same time. The critical temperature of thermal explosion (Tb), the self acceleration decomposition temperature (TSADT), and the adiabatic decomposition temperature rise (ΔTad) were calculated to evaluate the thermal hazard of the CL-20/CMDB propellant. It shows that the CMDB propellant with 38% CL-20 has relative lower values of E and lgA, and with 18% CL-20 has the highest potential hazard.

Synthesis, Crystal Structure and Thermal Behavior of 4,5‐Diacetoxyl‐2‐(dinitromethylene)‐imidazolidine

AbstractA new energetic material, 4,5‐diacetoxyl‐2‐(dinitromethylene)‐imidazolidine (DADNI), was synthesized by the reaction of 4,5‐dihydroxyl‐2‐(dinitromethylene)‐imidazolidine (DDNI) and acetic anhydride, and characterized by single crystal X‐ray diffraction. Crystal data for DADNI are monoclinic, space group C2/c, a=15.9167(3) Å, b=8.6816(4) Å, c=8.5209(3) Å, β=103.294(9)°, V=1145.9(3) Å3, Z=4, µ=0.150 mm−1, F(000)=600, Dc=1.682 g·cm−3, R1=0.0565 and wR2=0.1649. Thermal decomposition behavior of DADNI was studied and an intensely exothermic process was observed. The kinetic equation of the decomposition reaction is: dα/dT=(1016.64/β)×4α3/4exp(−1.582×105/RT). The critical temperature of thermal explosion is 163.76°C. The specific heat capacity of DADNI was studied with micro‐DSC method and theoretical calculation method. The molar heat capacity is 343.30 J·mol−1·K−1 at 298.15 K. The adiabatic time‐to‐explosion of DADNI was calculated to be 87.7 s.

Synthesis and thermal behavior of a new high-energy organic potassium salt

A new high-energy organic potassium salt, 1-amino-1-hydrazino-2,2-dinitroethylene potassium salt [K(AHDNE)], was synthesized by reacting of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE) and potassium hydroxide in methanol aqueous solution. The thermal behavior of K(AHDNE) was studied using DSC and TG/DTG methods and can be divided into three obvious exothermic decomposition processes. The decomposition enthalpy, apparent activation energy and pre-exponential factor of the first decomposition process were −2662.5 J g−1, 185.2 kJ mol−1 and 1019.63 s−1, respectively. The critical temperature of thermal explosion of K(AHDNE) is 171.38 °C. The specific heat capacity of K(AHDNE) was determined using a micro-DSC method, and the molar heat capacity is 208.57 J mol−1 K−1 at 298.15 K. Adiabatic time-to-explosion of K(AHDNE) was also calculated. K(AHDNE) presents higher thermal stability than AHDNE.

Thermal Behaviors of 2‐(Dinitromethylene)‐1,3‐diazacycloheptane (DNDH)

Abstract2‐(Dinitromethylene)‐1,3‐diazacycloheptane (DNDH) was prepared by the reaction of 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) with 1,4‐diaminoethane in NMP. Thermal decomposition behavior of DNDH was studied under the non‐isothermal conditions with DSC method, and presents only one intensely exothermic decomposition process. The kinetic equation of the decomposition reaction is dα/dT=1033.88×3α2/3exp(−3.353×105/RT)/β. The critical temperature of thermal explosion is 215.97°C. Specific heat capacity of DNDH was studied with micro‐DSC method and theoretical calculation method, and the molar heat capacity is 215.40 J·mol−1·K−1 at 298.15 K. Adiabatic time‐to‐explosion was calculated to be 92.07 s. DNDH has same thermal stability to FOX‐7.

Structural Characterization and Thermal Behavior of a Novel Energetic Material: 1-Amino-1-(2,4-dinitrophenylhydrazinyl)-2,2-dinitroethylene

A novel energetic material, 1-amino-1-(2,4-dinitrophenylhydrazinyl)-2,2-dinitroethylene (APHDNE), was synthesized by the reaction of 1,1-diamino-2,2-dinitroethylene (FOX-7) and 2,4-dinitrophenylhydrazine in N-methyl pyrrolidone (NMP) at 110 <TEX>$^{\circ}C$</TEX>. The theoretical investigation on APHDNE was curried out by B3LYP/6-311+<TEX>$G^*$</TEX> method. The IR frequencies analysis and NMR chemical shifts were performed and compared with the experimental results. The thermal behavior of APHDNE was studied by DSC and TG/DTG methods, and can be divided into two crystal phase transition processes and three exothermic decomposition processes. The enthalpy, apparent activation energy and pre-exponential factor of the first exothermic decomposition reaction were obtained as -525.3 kJ <TEX>$mol^{-1}$</TEX>, 276.85 kJ <TEX>$mol^{-1}$</TEX> and <TEX>$10^{26.22}s^{-1}$</TEX>, respectively. The critical temperature of thermal explosion of APHDNE is 237.7 <TEX>$^{\circ}C$</TEX>. The specific heat capacity of APHDNE was determined with micro-DSC method and theoretical calculation method, and the molar heat capacity is 363.67 J <TEX>$mol^{-1}K^{-1}$</TEX> at 298.15 K. The adiabatic time-to-explosion of APHDNE was also calculated to be a certain value between 253.2-309.4 s. APHDNE has higher thermal stability than FOX-7.

Synthesis, Crystal Structure and Thermal Behavior of GZTO·H2O

AbstractGuanidimium‐4,4‐azo‐1‐hydro‐1,2,4‐triazol‐5‐one (GZTO·H2O) was synthesized from 4‐amino‐1,2,4‐triazol‐5‐one as a starting material by two‐step including oxidation coupling using acid KMnO4 and reaction with (NH2)2CNH·HNO3 (GN) in KOH solution. The single crystal of the title compound was obtained by slow evaporation method at room temperature, and its structure was firstly determined with X‐ray single‐crystal diffractometer. It is a orthorhombic crystal, space group Pbca with cell dimensions of a=1.0459(2) nm, b=1.3584(3) nm, c=1.6103(3) nm, α=90.00(10)°, β=90.00(11)°, γ=90.00(11)°, V=2.2878(8) nm3, Z=8, Dc=1.587 g·cm−3, F(000)=1136, µ=0.132 mm−1, R1=0.0455, wR2=0.1397. The thermal behavior of GZTO·H2O was studied under a non‐isothermal condition by DSC‐TGA method, and its thermal decomposition process can be divided into three stages, and the first stage is an intense exothermic decomposition process. The second stage and the third stage are slow exothermic decomposition processes. The critical temperature of thermal explosion is 237.74°C.

A new method based on the non-isothermal kinetic equation to estimate the critical temperature of thermal explosion for energetic materials using non-isothermal DSC

A method for estimating the critical temperature of thermal explosion for energetic materials using differential scanning calorimetry (DSC) measurement is derived from the Semenov’s thermal explosion theory and the non-isothermal kinetic equation based on Harcourt-Esson’s kinetic equation. The result obtained from this method coincides completely with that of the Hu-Yang-Liang-Wu method.

Thermochemical properties and thermokinetic behavior of energetic triazole ionic salts

The properties of dissolution in different solvents, the specific heat capacity and thermal decomposition process under the non-isothermal conditions for energetic triazole ionic salts 1,2,4-triazolium nitrate (1a), 1,2,3-triazolium nitrate (1b), 3,4,5-triamino-1,2,4-triazolium nitrate (2a), 3,4,5-triamino-1,2,4-triazolium dinitramide (2b) were precisely measured using a Calvet Microcalorimeter. The thermochemical equation, differential enthalpies of dissolution (ΔdifHmΘ), standard molar enthalpies of dissolution (ΔdifHmΘ), apparent activation energy (E), pre-exponential constant (A), kinetic equation, linear relationship of specific heat capacity with temperature over the temperature range from 283 to 353 K, standard molar heat capacity (Cp,mΘ) and enthalpy, entropy and Gibbs free energy at 283–353 K, taking 298.15 K as the benchmark for 1a, 1b, 2a and 2b were obtained with treating experimental data and theoretical calculation method. The kinetic and thermodynamic parameters of thermal decomposition reaction, critical temperature of thermal explosion (Tb), self-accelerating decomposition temperature (TSADT) and adiabatic time-to-explosion (t) of 1a, 1b, 2a and 2b were calculated. Their heat-resistance abilities were evaluated. Information was obtained on the relation between molecular structures and properties of 1a, 1b, 2a and 2b.

Synthesis and thermal behavior of 4,5-dihydroxyl-2-(dinitromethylene)-imidazolidine (DDNI)

A novel energetic material, 4,5-dihydroxyl-2-(dinitromethylene)-imidazolidine (DDNI), was synthesized by the reaction of FOX-7 and glyoxal in water at 70 °C. Thermal behavior of DDNI was studied with DSC and TG-DTG methods, and presents only an intense exothermic decomposition process. The apparent activation energy and pre-exponential factor of the decomposition reaction were 286.0 kJ mol−1 and 1031.16 s−1, respectively. The critical temperature of thermal explosion of DDNI is 183.78 °C. Specific heat capacity of DDNI was studied with micro-DSC method and theoretical calculation method, and the molar heat capacity is 217.76 J mol−1 K−1 at 298.15 K. The adiabatic time-to-explosion was also calculated to be a certain value between 14.54 and 16.34 s. DDNI presents lower thermal stability, for its two ortho-hydroxyl groups, and its thermal decomposition process becomes quite intense.

Thermal behavior of 1,2,3-triazole nitrate

The thermal decomposition behaviors of 1,2,3-triazole nitrate were studied using a Calvet Microcalorimeter at four different heating rates. Its apparent activation energy and pre-exponential factor of exothermic decomposition reaction are 133.77 kJ mol−1 and 1014.58 s−1, respectively. The critical temperature of thermal explosion is 374.97 K. The entropy of activation (ΔS ≠), the enthalpy of activation (ΔH ≠), and the free energy of activation (ΔG ≠) of the decomposition reaction are 23.88 J mol−1 K−1, 130.62 kJ mol−1, and 121.55 kJ mol−1, respectively. The self-accelerating decomposition temperature (T SADT) is 368.65 K. The specific heat capacity was determined by a Micro-DSC method and a theoretical calculation method. Specific heat capacity equation is \( C_{\text{p}} \left( {{\text{J mol}}^{ - 1} {\text{ K}}^{ - 1} } \right) = - 42.6218 + 0.6807T \) (283.1 K < T < 353.2 K). The adiabatic time-to-explosion is calculated to be a certain value between 98.82 and 100.00 s. The critical temperature of hot-spot initiation is 637.14 K, and the characteristic drop height of impact sensitivity (H 50) is 9.16 cm.

Thermal Safety Study on TEGDN/NG/NC Gun Propellant

The self-accelerating decomposition temperature (TSADT), critical temperature of thermal explosion (Tb), adiabatic time to explosion (tTIad), 50% drop height of impact sensitivity (H50), critical temperature of hot spot initiation caused by impact (Tcr,hotspot), safety degree (Sd), critical thermal explosion ambient temperature (Tacr), and thermal explosion probability (PTE) of the gun propellant composed of triethyleneglycol dinitrate (TEGDN), nitroglycerin (NG), and nitrocellulose (NC) were studied. The results of thermal safety evaluation on the gun propellant were obtained: (1) T00 = 433.4 K, TSADT = Te0 = 441.1 K, Tb = Tbp0 = 468.4 K; (2) when Ek = 205.3 × 103 J mol −1 and Ak = 1020.62 s −1, tTIad = 48.3 s, H50 = 17.93 cm, Tcr, hotspot = 634.9 K; for a sphere sample, TS(T)max = 369.0K, Tacr = 364.2 K, Sd = 65.03%, PTE = 34.96%.

Thermal behavior of 3,4,5-triamino-1,2,4-triazole nitrate

The thermal decomposition behaviors of 3,4,5-triamino-1,2,4-triazole nitrate were studied using a C-500 type Calvet Micro-calorimeter at four different heating rates. Its apparent activation energy and pre-exponential factor of exothermic decomposition reaction are 137.16 kJ mol −1 and 10 10.03 s −1. The critical temperature of thermal explosion is 441.37 K. The entropy of activation (Δ S ≠ ), enthalpy of activation (Δ H ≠ ), and free energy of activation (Δ G ≠ ) of the decomposition reaction are −65.65 J mol −1 K −1, 132.97 kJ mol −1 and 166.35 kJ mol −1, respectively. The self-accelerating decomposition temperature ( T SADT) is 429.56 K. The specific heat capacity was determined with a Micro-DSC method and a theoretical calculation method. Specific heat capacity (J g −1 K −1) equation is C p = 0.356 + 2.957 × 10 −3 T (283.1 K < T < 353.2 K). The adiabatic time-to-explosion is calculated to be a certain value between 702.22 s and 712.22 s. The critical temperature of Hot-Spot initiation is 600.325 °C, and the characteristic drop height of impact sensitivity ( H 50) is 27 cm.