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Uranyl ion (UO22+) is both radiotoxic and chemically toxic, which has harmful effects on the ecological environment and human health. This work presents a novel material called two-dimensional photonic crystal polyacrylic acid hydrogel (2D-PCPAAH), which contains massive carboxyl groups that can bind to UO22+ by strong coordination interaction. UO22+ can be combined with multiple ligand groups, causing the shrinkage of the 2D-PCPAAH which results in a reduction in particle spacing and a color change. Via measuring the Debye diffraction ring diameter using a ruler, the particle spacing can be easily obtained and the UO22+ concentration can be determined. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

During application, energetic materials may suffer different temperature environmental stimulation. In order to study the influence of temperature environmental on performance of HNIW/FOX-7 based PBXs, HNIW/FOX-7 based PBX modeling powders and PBX columns were treated by LT (low temperature), HT (high temperature), HLC (high-low temperature cycle) and HLS (high-low temperature shock). Then scanning electron microscope (SEM), infrared spectra (IR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to study the variation of PBX modeling powders after LT, HT, HLC and HLS treatments; in addition, the mass, size and mechanical properties of PBX columns were characterized after different temperature adaptability treatments as well. The results indicate that the change ratios of mass and size of HNIW/FOX-7 based PBX columns are less than 1%, illustrating that mass and size of PBX columns are at acceptable level after different temperature adaptability treatments. The unevenness degree of the surface of PBX modeling powders followed the order of HLC > HT > LT > HLS, which agrees well with mass loss order. Moreover, IR and XRD results indicated that the molecular structure and crystal form of HNIW and FOX-7 did not change after different temperature adaptability treatments. Additionally, thermal stabilities of PBX modeling powders are decreased after different temperature adaptability treatments, among which HLS has the largest influence on HNIW/FOX-based PBX modeling powders. The compression strengths and elastic moduli of HNIW/FOX-based PBX columns are enhanced after different temperature adaptability treatments, among which the strength of PBX columns after HLC has the maximum increase, indicating that HLC has more significant effect on mechanical property. [ABSTRACT FROM AUTHOR]

Quantum–mechanical transition states can aid in the identification of promising catalysts for methane C–H activation and functionalization. However, only a limited amount of the vast metal–ligand chemical space has been computationally evaluated. To begin to solve this problem, we showcase a workflow that combines automated construction of Pt(II)-ligand combinations and automated transition-state searching with machine learning to maximize the generation of fully optimized transition states. [ABSTRACT FROM AUTHOR]

1,1-Diamino-2,2-dinitroethylene (FOX-7) is well-known as one high-energy insensitive material. The size effect of the nano-crystal on the pyrolysis are extremely important for ignition and reaction pathways under extreme conditions. The thermal decomposition of nano-FOX-7 was investigated utilizing molecular dynamics method with reactive force field. The pyrolysis simulation showed that the potential barrier of nano-FOX-7 at 3000 K are higher than that at 2000 K. The temperature distribution of nano-FOX-7 in the temperature-rise periods shows that the decomposition occurs first at the central part of the crystal. Based on the analysis of chemical species, three types of initial reaction pathways were identified, among which the fission of the C–NH2 bond may be a new reaction pathway. A decomposition network from initial reactant to the main products was proposed to provide insights into the decomposition mechanism on atomic level. The mass distribution of products showed that the clusters among the decomposition products can inhibit the violent reaction to a certain extent. In addition, the analysis of the nano-crystal effect on the FOX-7 decay shows that the numbers of N2 and CO2 are related to the nanoparticle size. [ABSTRACT FROM AUTHOR]

Sodium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (Na2DNABT) and rubidium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (Rb2DNABT) were synthesized and characterized by IR spectroscopy and 1H/13C NMR. Rb2DNABT was characterized by single-crystal X-ray diffraction. The thermal decomposition kinetics and thermal hazards of Na2DNABT and Rb2DNABT were investigated by difference scanning calorimeter (DSC) and accelerating rate calorimeter (ARC). The thermal decomposition kinetics (activation energy, pre-exponent, reaction model) were evaluated by Thermal Safety Software (TSS) on DSC and ARC tests. The activation energy of Na2DNABT and Rb2DNABT by DSC test was also calculated by Starink method, which consistent with the simulated activation energy by TSS. Time to maximum rate (TMR), reaction temperature at which TMR is 24 h (TD24) and time conversion limit (TCL) were simulated by TSS, too. The TD24 of Na2DNABT and Rb2DNABT were calculated as 215.86 and 141.95 °C, respectively, and their TCL at 200 °C was calculated as 24.00 and 4.56 h, respectively. Na2DNABT is a stable and safety compound compared with Rb2DNABT. [ABSTRACT FROM AUTHOR]

Ammonium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (ADNABT) was synthesized and characterized by IR spectroscopy, 1H/13C NMR and single-crystal X-ray diffraction. The thermal decomposition of ADNABT was investigated by thermogravimetry–differential thermal analysis (TG–DTA) and accelerating rate calorimeter (ARC). The kinetic parameters (activation energy, pre-exponential factor, mechanism functions) by DTA and ARC tests were simulated by Thermal Safety Software (TSS). The simulated results revealed that the exothermic decomposition of ADNABT under non-isothermal and adiabatic conditions all followed a full autocatalysis model. In order to ensure the safety of production, transportation and storage, several thermal hazard indicators such as time to maximum rate (TMR), reaction temperature at which TMR is 24 h (TD24), time to conversion limit and self-accelerating decomposition temperature (SADT) were also simulated by TSS on the kinetic model. The TD24 and SADT50 kg were calculated as 183.37 and 167.00 °C, respectively. [ABSTRACT FROM AUTHOR]

Thermal decomposition study of diammonium 5,5′-bistetrazole-1,1′-diolate (ABTOX) was investigated by using DSC. The result showed that ABTOX is less thermal sensitive than TKX-50. The kinetic parameters (E = 139.82 kJ mol−1 and lgA = 12.75 s−1) for thermal decomposition reaction of ABTOX were obtained. The compatibility of ABTOX with 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaza-isowurtzitane (CL-20), 3-nitro-1,2,4-triazol-5-one (NTO), 1,1-diamino-2,2-dinitroethene (FOX-7), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), aluminum powder (Al), Estane-TPU-5702 and two kinds of fluoropolymers (F-2311 and F-2603) were evaluated by using DSC. The results showed that CL-20/ABTOX, FOX-7/ABTOX and F-2603/ABTOX were exhibiting good compatibility and RDX/ABTOX and Al/ABTOX had moderate compatibility. In addition, the compatibility of ABTOX with Estane-TPU-5702 and F-2311 was not good. HMX/ABTOX, NTO/ABTOX and LLM-105/ABTOX had poor compatibility. Furthermore, the self-accelerating decomposition temperature was calculated to be 152 °C and 150 °C in commercial wooden and PE cylinder, respectively. [ABSTRACT FROM AUTHOR]

The primary decomposition product (TKX-50-M) of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) was obtained under adiabatic condition by using accelerating rate calorimeter (ARC). Meanwhile, diammonium 5,5′-bistetrazole-1,1′-diolate (ABTOX) was confirmed as the main component of TKX-50-M. Specific heat capacity of TKX-50-M and ABTOX was studied from 0 to 45 °C. In addition, the thermal decomposition of TKX-50-M and ABTOX was studied under adiabatic condition. The experiment results revealed that TKX-50-M were more thermal sensitive than ABTOX. Furthermore, ABTOX exhibited much violent than that of TKX-50-M during decomposition. [ABSTRACT FROM AUTHOR]

Attachment energy model was adopted to research the influence of external growth environments on ε-HNIW crystal morphology. The morphology of ε-HNIW crystal in acetone-cyclohexane binary systems was simulated with cyclohexane mass fraction of 0.05, 0.10, 0.15 and 0.20, respectively. The influences of 0.80 acetone on ε-HNIW morphology were studied in the acetone-toluene, acetone-benzene and acetone-dichloromethane binary system. Besides, the effects of the temperature and supersaturation on ε-HNIW crystal morphology were also examined in the acetone-cyclohexane system. The simulation results reveal that ε-HNIW crystal morphology almost maintains consistent with the increase in cyclohexane ratio. Contrarily, the variations of the anti-solvent, the temperature and the supersaturation affect ε-HNIW crystal morphology dramatically. Furthermore, the influence of model dimension on the attachment energy was discussed, and a reasonable model size was obtained. The radial distribution function analysis was performed to explore the adsorption and diffusion behaviours of the solvent molecules on the ε-HNIW surfaces. Overall, the simulation results can provide some guidance for the crystallization process of ε-HNIW. [ABSTRACT FROM AUTHOR]

TKX-50-based PBX (PBX-T) is prepared by solution–water suspension method using dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) as the explosive. The thermal behavior of PBX-T is investigated under a nonisothermal condition by using TG-DTG and DSC method. The kinetic parameters (Ea = 167.98 kJ mol−1 and A = 1016.05 s−1) for the main thermal decomposition reaction of PBX-T are calculated from the analysis of DSC curves by differential method and integral method, and the nonisothermal kinetic equation of the exothermic process is dα/dT=1016.05/2β51-α-ln1-α3/5exp(-2.0204×104/T), suggesting that the main exothermic decomposition reaction mechanism of PBX-T is classified as Avrami–Erofeev equation. The specific heat capacity (Cp) of PBX-T is measured using continuous Cp mode of C80 micro-calorimeter. Depending on the thermal decomposition parameters and Chinese Military Standards GJB 772A-97 method, the adiabatic time, self-accelerating decomposition temperature, sensitivities, and 5-second flash point on of PBX-T are obtained. [ABSTRACT FROM AUTHOR]

Thermogravimetric-differential scanning calorimeter and accelerating rate calorimeter (ARC) were performed to study the thermal characteristics and kinetics of energetic 5,5′-bistetrazole-1,1′-diolate (1,1-BTO). The DSC measurements showed one endothermic peak and one exothermic peak with decomposition occurring at 219.1, 227.2, 234.0 and 244.1 °C at different heating rates (2, 4, 8 and 15 °C min). The value of critical temperature of thermal explosion ( T ) and kinetics parameters was calculated, suggesting that 1,1-BTO is stable below the temperature of 175.36 °C. The thermal behavior under adiabatic condition was studied by ARC, depicting that onset temperature was 176.61 °C and the thermal decomposition ended at 215.93 °C, within the time span of 49.04 min. In addition, the thermo-kinetic parameters such as the activation energy E and pre-exponential factor A under adiabatic condition were also obtained. [ABSTRACT FROM AUTHOR]

The enthalpies of dissolution for dihydroxylammonium 5, 5′-bistetrazole-1,1′-diolate (TKX-50) in water were measured using a C-80 Calvet microcalorimeter at four different temperatures under atmospheric pressure. Differential enthalpies (Δ H) and molar enthalpies (Δ H) of dissolution were calculated. The corresponding kinetic equations that describe the dissolution rate at the four experimental temperatures are d α/d t = 10(1 − α) ( T = 298.15 K), d α/d t = 10(1 − α) ( T = 303.15 K), d α/d t = 10(1 − α) ( T = 308.15 K), d α/d t = 10(1 − α) ( T = 313.15 K). In addition, the determined values of the activation energy E and pre-exponential factor A for the dissolution process are 25.08 kJ mol and 21.98 s, respectively. [ABSTRACT FROM AUTHOR]

The thermal behavior and decomposition kinetics of CL-20-based plastic-bonded explosives (PBXs) composed of main explosive CL-20 and additives were first time explored by means of DSC, TG and ARC techniques. The DSC study at different heating rates was performed and showed the effect of the additives on the exothermic peaks of CL-20-based PBXs. The thermal stability of CL-20-based PBXs was evaluated by DSC, TG and ARC, indicating that the largest influence on lowering the activation energy is the presence of plasticizer. The kinetic parameters after addition of additives were compared with those of raw CL-20 by means of Kissinger and Ozawa methods. Moreover, the mechanical sensitivities of investigated CL-20-based PBXs were supported, which was well consistent with the data from DSC and ARC measurements. [ABSTRACT FROM AUTHOR]

The heat effects in the case of manufacture process of nitration 1,2,4-triazol-5-one (TO) in nitric acid solution were distinguished and determined using the calorimeters of DSC200F3, C80 and E856; the influence of these heats on the total exothermic effect during manufacture process was examined. Five kinds of thermal effects were differentiated and measured: the heat of process of dosing TO (Δ H ), the heat of dissolution TO (Δ H ), the heat of reaction (Δ H ), the heat of crystallization of NTO (Δ H ) and the heat ( $$\Delta H_{{{\text{HNO}}_{{\text{3}}} }}$$ ) caused by changes in concentration of nitric acid. The data on dissolution heats of TO and NTO in nitric acid with different concentrations in the 0-98.4 % range and isobaric heat capacity of TO over the temperature range of 0-90 °C are determined. The main results of examination showed: The Δ H was the main contribution to the total exothermic effect during synthesis processes in 66-96 % HNO; the contribution ability rank of other four thermal effects varied based on the concentration of HNO adopted. [ABSTRACT FROM AUTHOR]

The enthalpies of dissolution for 5,5′-Bistetrazole-1, 1′-dihydroxy ((HO)BTO) and disodium 5,5′-Bistetrazole-1,1′-diolate ([Na(HO)]BTO) in dimethyl sulfoxide (DMSO) at 298.15 K were studied by using a C-80 Calvet microcalorimeter. Empirical formulae for the calculation of the molar enthalpies of dissolution (Δ H), relative partial molar enthalpies (Δ H ), and relative apparent molar enthalpies (Δ H ) were deduced by the experimental results of the dissolution processes of (HO)BTO and [Na(HO)]BTO in DMSO. Finally, the corresponding kinetic equations describing the dissolution processes were dα/dt = 10(1− α) for the dissolution of (HO)BTO in DMSO, and dα/dt = 10(1− α) for the dissolution of [Na(HO)]BTO in DMSO. [ABSTRACT FROM AUTHOR]

Thermal decomposition study of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) was investigated by using TG-DTG and TG-IR-MS and found that N, NO, NH and HO were the main products during the decomposition process. The kinetic parameters ( Ea = 138.96 kJ mol and A = 10 s) for thermal decomposition reaction of TKX-50 were obtained from DSC profile by differential method and integral method, and the nonisothermal kinetic equation of the exothermic process was $${\text{d}}\alpha /{\text{d}}T = (10^{12.93} /\beta )3(1 - \alpha )[ - \ln (1 - \alpha )]^{2/3} \exp ( - 1.6713 \times 10^{4} /T),$$ suggesting that the main exothermic decomposition reaction mechanism of TKX-50 was classified as Avrami-Erofeev equation. In addition, the theoretical detonation velocity ( D = 8804 m/s) of TKX-50 at 298.15 K was calculated by a simple method. Finally, the safety parameters of TKX-50 (25 kg) including time to maximum rate under adiabatic conditions and self-accelerating decomposition temperature were calculated to be 142.12 and 129.01 °C by using AKTS software. [ABSTRACT FROM AUTHOR]

4,4-azo-bis(1,2,4-triazol-5-one) (ZTO) and its solvent adducts have been reported, and the single crystal X-ray measurements indicated that the ZTO crystals appeared as a monoclinic system with space group P2(1)/c, while ZTO·2HO and ZTO·2DMF displayed as monoclinic with space group P2(1)/n and triclinic with space group Pī, respectively. In addition, the thermal decomposition process of the three crystals was studied by thermogravimetric differential analysis (TG-DTA), and the result showed that only one exothermic peak was found in each case of ZTO, ZTO·2HO, and ZTO·2DMF, and the peak temperature ( T) are observed at 292.36, 291.82, and 272.73 °C, respectively. [ABSTRACT FROM AUTHOR]

The crystal and molecular structure of an interesting cage compound is described. Crystal data: C48H36N6O6·(CH3)2CO; monoclinic; space group: P21 /n; a = 14.948(3) Å, b = 15.079(3) Å, c = 19.539(4)Å, β = 93.93(3)°, V = 4394(2)Å3; and Z = 4. [ABSTRACT FROM AUTHOR]

Molecular dynamic (MD) simulations were applied to investigate the binding energies and mechanical properties of 1,1-diamino-2,2-dinitroethene (FOX-7) based polymer bonded explosives (PBXs) with ethylenevinylacetate copolymer (EVA), fluorine (F2641), hydroxyl-terminated polybutadiene (HTPB), and styrene butadiene styrene block copolymer (SBS). The binding energies between FOX-7 and the four polymer binders are different, of which the descending order is FOX-7/HTPB ≈ FOX-7/SBS > FOX-7/EVA > FOX-7/F2641. Furthermore, the (002) surface of FOX-7 has the strongest interaction with the four polymers. The mechanical properties (elastic moduli and Poisson’s ratio) of pure FOX-7 and FOX-7 based PBXs were obtained. The results show that the descending order of the ability of polymer binders to improve plasticity of PBXs is SBS > F2641 > EVA > HTPB. The formability of FOX-7 based PBXs is better than that of pure FOX-7, as the order of FOX-7/SBS > FOX-7/EVA > FOX-7/F2641 > FOX-7/HTPB > FOX-7 shows. Poisson’s ratio of SBS is the highest. The calculated detonation performances for pure FOX-7 and FOX-7 based PBXs show that the detonation properties of explosives slightly decreases when the mass ratio of binder is about 5%. All the theoretical detonation velocities of FOX-7 based PBXs are higher than 8500 m/s. [ABSTRACT FROM AUTHOR]