Hongxu Gao

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.

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.

Nonisothermal Thermal Decomposition Reaction Kinetics of Double-base Propellant Catalyzed with Lanthanum Citrate

Abstract The decomposition reaction kinetics of the double-base (DB) rocket propellant composed of the mixed ester of triethyleneglycol dinitrate (TEGDN) and nitroglycerin (NG), and nitrocellulose (NC) with lanthanum citrate as a combustion catalyst was investigated by thermogravimetry and differential thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) under atmospheric pressure and flowing nitrogen gas conditions. The results showed that the thermal decomposition processes of DB propellant had two mass loss stages: volatilization and decomposition of the mixed ester in the first-stage and exothermic decomposition reaction in the second-stage. The exothermic decomposition reaction mechanism obeyed the third-order chemical reaction rule. The kinetic parameters of the reaction were: Ea=231.14 kJ·mol–1, A=1023.29 s–1. The kinetic equation can be expressed as: dα/dt=1022.99(1–α)3e–2.78×104/T. The critical temperatures of the thermal explosion of the DB propellant obtained from the onset temperature (Te) and the peak temperature (Tp) were: Tbe=463.62 K, Tbp=477.88 K. The entropy of activation (ΔS≠), enthalpy of activation (ΔH≠), and free energy of activation (ΔG≠) of the reaction were 219.75 J·mol–1·K–1, 239.23 kJ·mol–1, and 135.96 kJ·mol–1, respectively.

Catalytic action of nano Bi2WO6 on thermal decompositions of AP, RDX, HMX and combustion of NG/NC propellant

Nano Bi2WO6 was prepared by hydrothermal method and characterized by XRD, SEM and EDS. Catalytic decomposition effects of nano-Bi2WO6 on AP, RDX and HMX were studied by DSC method. Nano Bi2WO6 can reduce the decomposition temperature and apparent activation energy of decomposition process. The thermal behaviors of Bi2WO6-DB propellant were studied. The self-accelerating decomposition temperature and critical temperature of thermal explosion are 168.3 and 178.1 °C, respectively. Nano Bi2WO6 used as burning catalyst of NG/NC propellant can greatly increase the burning rate, decrease the pressure exponent and form specific high-pressure “platform” at 16–22 MPa. Nano Bi2WO6 exhibits good application performance in solid propellant.

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 (β), the apparent activation energy (E(k) and E(o)) and pre-exponential constant (A(K)) of thermal decomposition reaction obtained by Kissingers method and Ozawas method. Using density (ρ) and thermal conductivity (λ), the decomposition heat (Q(d), taking half-explosion heat), Zhang-Hu-Xie-Lis formula, the values (T(e0) and T(p0)) of T(e) and T(p) corresponding to β → 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.

Dissolution properties of ammonium dinitramide in N -methyl pyrrolidone

The dissolution properties of ammonium dinitramide (ADN) in N-methyl pyrrolidone (NMP) were studied with a RD496-2000 Calvet microcalorimeter at four different temperatures under atmospheric pressure. The heat effects were determined for ADN in NMP. The molar enthalpies and the differential molar enthalpies for ADN in NMP were also obtained at the same time. The corresponding kinetic equations that describe the four dissolution processes are discussed.

Thermochemical properties of 2,4-dinitroanisole in N-methyl pyrrolidone and dimethyl sulfoxide

The thermochemical properties of 2,4-dinitroanisole (DNAN) in N-methy pyrrolidone (NMP) and dimethyl sulfoxide(DMSO) were studied using a RD496-2000 Calvet microcalorimeter at four different temperatures. The heat effects were measured for DNAN dissolved in NMP and DMSO and the relationships between the heat effects and the amounts of the substance were determined. The molar enthalpies and the differential molar enthalpies of dissolution processes were also obtained from the experimental data. The corresponding kinetic equations describing the two dissolution processes at different temperatures were discussed.

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 (Te) and maximum peak temperature (Tp) from the non-isothermal DSC curves of HNIW/TNT cocrystal at different heating rates (β), the following were calculated: the value of specific heat capacity (Cp) and the standard molar enthalpy of formation , the apparent activation energy (EK and EO) and pre-exponential constant (AK) of thermal decomposition reaction obtained by Kissingers method and Ozawas method, density (ρ) and thermal conductivity (λ), the decomposition heat (Qd, as half-explosion heat), Zhang–Hu–Xie–Lis formula, Smiths equation, Friedmans formula, Bruckman–Guillets formula, Frank-Kamenetskiis formula and Wang–Dus formulas, the values (Te0 and Tp0) of Te and Tp corresponding to β → 0, thermal explosion temperature (Tbe and Tbp), adiabatic time-to-explosion (ttiad), 50% drop height (H50) for impact sensitivity, critical temperature of hot-spot initiation (Tcr), 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 (TS(T)max), safety degree (SD) and critical ambient temperature (Tacr) 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: Te0 = 464.45 K; Tp0 = 477.55 K; Tbe = 472.82 K; Tbp = 485.89 K; ttiad = 4.40 s, 4.42 s, and 4.43 s for n = 0, 1, and 2, respectively; Tcr = 531.90 K; H50 = 19.46 cm; and the values of Tacr, TS(T)max, SD and PTE 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.

Effect of rGO–Fe2O3 nanocomposites fabricated in different solvents on the thermal decomposition properties of ammonium perchlorate

rGO–Fe2O3 composites were prepared using different solvents (distilled water, ethanol, N-methylpyrrolidone, ethyl acetate, n-butyl alcohol and N,N-dimethylformamide) via a simple solvothermal method and characterized by SEM, TEM, XRD, FT-IR, Raman and XPS techniques. Then, the catalytic action of rGO–Fe2O3 composites (prepared in different solvents), GO, rGO and pristine Fe2O3 on the thermal decomposition of ammonium perchlorate (AP) were studied using a TG-DSC instrument. DSC results showed that GO, rGO, pristine Fe2O3 and rGO–Fe2O3 composites could effectively promote the thermal decomposition of AP. Additionally, rGO–Fe2O3 fabricated in N,N-dimethylformamide (DMF) solvent possesses the best catalytic performance among the investigated materials. This result can be attributed to the better dispersibility of Fe2O3 nanoparticles on graphene oxide prepared in DMF solvent, which was confirmed by SEM and TEM imaging. The high temperature decomposition exothermic peak (HTP) and the apparent activation energy of AP are reduced by 119.6 °C and 173.3 kJ mol−1, respectively, in the presence of Fe2O3–rGO (DMF) composite.

Effects of Nano PbZrO 3 on the Decompositions of AP, RDX, HMX and the Combustion of (NG/NC) Propellant

Nanoscale lead zirconate (PbZrO3) was prepared by using co-precipitation method, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The catalytic performances of PbZrO3 on the decomposition of ammonium perchlorate (AP), cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) were examined by differential scanning calorimetry (DSC). The thermal behaviors, nonisothermal decomposition kinetics of nitroglycerin/nitrocotton (NG/NC) double-base propellant with nano PbZrO3 (PbZrO3-DB) were also studied. The results show that PbZrO3 presents a typical perovskite structure. Nano PbZrO3 can remarkably reduce the thermal decomposition temperature and apparent activation energy of decomposition process(reduced by 21, 7.4 and 15 kJ/mol respectively). The thermal decomposition of PbZrO3-DB propellant is heterogeneous. Thermal decomposition mechanism of PbZrO3-DB propellant is a contracting cylinder with phase boundary reaction, and the kinetic equation is: