Jinshan Li

A multivariate relationship for the impact sensitivities of energetic N-nitrocompounds based on bond dissociation energy

The ZPE-corrected N-NO(2) bond dissociation energies (BDEs(ZPE)) of a series of model N-nitrocompounds and typical energetic N-nitrocompounds have been calculated using density functional theory methods. Computed results show that using the 6-31G** basis set the UB3LYP calculated BDE(ZPE) is similar to the B3PW91 but is less than the UB3P86 and that for both UB3P86 and UB3PW91 methods the 6-31G(**) calculated BDE(ZPE) is close to the 6-31++G(**). For the series of model N-nitrocompounds it is drawn from the NBO analysis that at the UB3LYP/6-31G(**) level the order of BDE(ZPE) is not only in line with that of bond order but also with that of the energy gap between N-NO(2) bond and antibond orbitals. For the typical energetic N-nitrocompounds the impact sensitivity is strongly related to the BDE(ZPE) indeed, and based on the BDEs(ZPE) calculated at different density functional theory levels this work has established a good multivariate correlation of impact sensitivity with molecular parameters, which provides a method to address the sensitivity problem.

Molecular dynamic simulations on the structures and properties of ɛ-CL-20(0 0 1)/F2314 PBX

Molecular dynamical (MD) simulations with the COMPASS force field were employed to investigate the influences of temperature (T), the concentration of F(2314) binder (W%), and crystal defects on the mechanical properties, binding energy (E(bind)), and detonation properties of epsilon-CL-20(001)/F(2314) PBX (polymer bonded explosives). T was found to have some influences on the mechanical properties, and the PBX at 298 K was considered with better mechanical properties. By radial distribution function g(r) analysis the three types of hydrogen bonds, H...O, H...F, and H...Cl were predicted as the main interaction formats between F(2314) and epsilon-CL-20, and the strength of these interactions changed with temperature changing. The isotropic properties of the PBX increased with W% increasing, but each modulus and E(bind) did not monotonously vary with W% increasing. The detonation properties of the PBX decreased with the increasing W%, and the PBX with 4.69% F(2314) was regarded with good detonation properties. The existence of crystal defects (vacancy or adulteration) might increase the elasticity but destabilize the system to some extent, and the mechanical properties of PBX were chiefly determined by the main body explosive. The above information was thought guidable for practical formulation design of PBX.

A quantitative relationship for the shock sensitivities of energetic compounds based on X-NO2 (X = C, N, O) bond dissociation energy

The ZPE-corrected X-NO(2) (X=C, N, O) bond dissociation energies (BDEs(ZPE)) of 11 energetic nitrocompounds of different types have been calculated employing density functional theory methods. Computed results show that using the 6-31G** basis set the UB3LYP calculated BDE(ZPE) is less than the UB3P86. For these typical energetic nitrocompounds the shock-initiated pressure (P(98)) is strongly related to the BDE(ZPE) indeed, and a polynomial correlation of ln(P(98)) with the BDE(ZPE) has been established successfully at different density functional theory levels, which provides a method to address the shock sensitivity problem.

Research on KOH/La-Ba-Al2O3 catalysts for biodiesel production via transesterification from microalgae oil

Alumina supports modified by lanthanum (La) and barium (Ba) were prepared by peptization. Catalysts with different KOH contents supported on modified alumina were prepared by impregnation method. Various techniques, including N2 adsorption-desorption (Brunauer-Emmet-Teller method, BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and fourier transform infrared absorption spectroscopy (FT-IR). Catalytic activity for microalgae oil conversion to methyl ester via transesterification was evaluated and analyzed by GC-MS and GC. BET results showed that the support possessed high specific surface area, suitable pore volume and pore size distribution. Activity results indicated that the catalyst with 25 wt% KOH showed the best activity for microalgae oil conversion. XRD and SEM results revealed that Al–O–K compound was the active phase for microalgae oil conversion. The agglomeration and changing of pore structure should be the main reasons for the catalyst deactivation when KOH content was higher than 30 wt%.

Prediction of the properties and thermodynamics of formation for energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate-based anions

Density functional theory and volume‐based thermodynamics calculations were performed to study the effects of different substituents and linkages on the densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of energetic nitrogen‐rich salts composed of triaminoguanidinium cation and 5‐nitroiminotetrazolate anions. The results show that the NO2, NF2, or N3 group is an effective substituent for increasing the densities of the 5‐nitroiminotetrazolate salts, whereas the effects of the bridge groups on the density are coupled with those of the substituents. The substitution of the group NH2, NO2, NF2, N3, or the nitrogen bridge is helpful for increasing the HOFs of the salts. The calculated energetic properties indicate that the NO2, NF2, N3, or NN group is an effective structural unit for improving the detonation performance for salts. The thermodynamics of formation of the salts show that all the salts may be synthesized easily by the proposed reactions. The structure‐property relationships provide basic information for the molecular design of novel high‐energy salts.

Structures, photoluminescence and photocatalytic properties of two novel metal–organic frameworks based on tetrazole derivatives

Two novel metal–organic frameworks, [Ag(ATZ)]n (1) (ATZ = 5-amino-tetrazole) and [Ag2(en)2(AT)]n (2) (en = ethylenediamine, AT = 5,5′-azotetrazolate), were prepared from corresponding Ag(I) salts and have been structurally characterized by elemental analysis, Fourier transform infrared spectroscopy and single crystal and powder X-ray diffraction. The structures of both compounds consist of 2-D three-connected layers that are linked by π–π overlap interactions between the tetrazolate fragments in neighbouring layers to form a 3-D supramolecular structure. The photoluminescence properties of solid samples of 1 and 2 at room temperature and their photocatalytic performance have also been reported and discussed. The results indicate that 1 seems to be a good candidate for a novel inorganic–organic photoactive material with high quantum yield. Moreover, compounds 1 and 2 represent the first examples of coordination polymers with a Ag ion that exhibit high, efficient photocatalytic abilities for dye degradation under UV light and show good stability toward photocatalysis.

Two nitrogen-rich Ni(II) coordination compounds based on 5,5′-azotetrazole: synthesis, characterization and effect on thermal decomposition for RDX, HMX and AP

Two novel multiligand coordination complexes of Ni(II), [Ni(en)3]AZT·THF (1) (en = ethylene diamine, THF = tetrahydrofuran) and [Ni(AZT)(pn)2]n (2) (pn = propylene diamine), were prepared from the corresponding Ni salts and have been structurally characterized by elemental analysis, Fourier transform infrared spectroscopy and single crystal X-ray diffraction. The results show that both 1 and 2 crystallize in the triclinic space group P. 1 presents a zero-dimensional unit, while 2 exhibits a one-dimensional zigzag chain. Under nitrogen, the thermal decomposition process and the kinetic parameters of the two complexes were studied by TG-DTG and DSC technologies. The non-isothermal kinetic parameters were calculated by Kissingers and Ozawa–Doyles methods. Furthermore, the compounds were explored as additives to promote the thermal decomposition of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX) and ammonium perchlorate (AP) by differential scanning calorimetry.

Influence of crystal characteristics on the shock sensitivities of cyclotrimethylene trinitramine, cyclotetramethylene tetranitramine, and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetra-cyclo[5,5,0,03,1105,9]dodecane immersed in liquid

The shock sensitivities of differently qualified cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine(HMX), and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetra-cyclo[5,5,0,03,1105,9]dodecane (CL-20) immersed in liquid were determined by the large-scale gap tests, for systemic discussion on the influences of crystal characteristics on them. As a result, it shows that (1) the immersion of crystals in liquid leads to an obvious sensitivity decrease; (2) for all three explosives, their shock sensitivities are lowered with increasing their crystal apparent densities or decreasing their particle sizes, and almost not affected by particle morphologies; (3) the crystal twins are readily formed for HMX and the most distinct factor influencing its shock sensitivities; (4) it is found that the crystal apparent density affects most obviously the shock sensitivities for RDX and CL-20; and (5) CL-20, HMX, and RDX are less and less sensitive to shock, suggesting chemical components are also a dete...

5,6-Di(2-fluoro-2,2-dinitroethoxy)furazano[3,4- b ]pyrazine: a high performance melt-cast energetic material and its polycrystalline properties

5,6-Di(2-fluoro-2,2-dinitroethoxy)furazano[3,4-b]pyrazine was synthesized in a three-step process starting from 3,4-diaminofurazan (DAF) including a significant nucleophilic substitution reaction under the catalytic effect of trisodium phosphate dodecahydrate. Characterization of this molecule indicates that it possesses a higher crystal density than that of 2,4,6-trinitrotoluene (TNT) at ambient temperature with acceptable melting-point and energetic properties approaching those of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) but with a higher thermal stability and lower sensitivity towards impact and friction. To investigate its polycrystalline properties, differential scanning calorimetry (DSC), powder-X-ray-diffraction (PXRD) and ab initio calculation using the Viena Ab initio simulation package (VASP) were employed.

Comparative theoretical studies on energetic substituted 1,2,4-triazole molecules and their corresponding ionic salts containing 1,2,4-triazole-based cations or anions

We have studied the densities, heats of formation, energetic properties, and thermodynamics of formation for a series of substituted 1,2,4-triazole molecules and their corresponding ionic salts containing 1,2,4-triazolium cations or 1,2,4-triazolide anions using density functional theory and volume-based thermodynamics method. The results show that when the 1,2,4-triazole molecules lose a proton to form corresponding 1,2,4-triazole-based anions, their salts have smaller densities than corresponding molecules. When the molecules get a proton to form the 1,2,4-triazole-based cations, their salts have higher densities than corresponding molecules. The transformation of the 1,2,4-triazole derivatives from nonionic molecules to corresponding cations or anions are very helpful for increasing their heats of formation. Changing the 1,2,4-triazole derivatives into corresponding cations or anions produce different effects on their heats of detonation. Overall, as the compound numbering varies, the evolution trend of heat of detonation is very similar to heat of formation. The salts containing the 1,2,4-triazolide anions have smaller detonation velocities and pressures than corresponding 1,2,4-triazole molecules, whereas the salts containing the 1,2,4-triazolium cations have higher detonation velocities and pressures than corresponding molecules. Finally, the lattice enthalpies and entropies were used to construct a thermodynamic cycle for salt formation to predict the possibility to synthesize the salts.