Shijin Chu

Two important factors influencing shock sensitivity of nitro compounds: Bond dissociation energy of X–NO2 (X = C, N, O) and Mulliken charges of nitro group

DFT/BLYP/DNP is employed to calculate bond dissociation energy of X-NO(2) (X = C, N, O) and Mulliken charges of nitro group of 14 kinds of nitro compounds, and partial least squares approximation is applied to linearly fit their shock initiation pressure (p(90%,TMD)). It is found that the fitted values are in good agreement with the experimental shock initiation pressures. The fitted model is used to predict the shock initiation pressures of two kinds of explosives, TNB and TNETB. The predictive values are in accordance with experimental ones. It reflects that bond dissociation energy of X-NO(2) (X = C, N, O) and Mulliken charge of nitro groups may be the important factors influencing the shock sensitivity of nitro compounds. On the basis of the fitted model, bond dissociation energy of X-NO(2) (X = C) and Mulliken charges of nitro groups of another 14 kinds of heterocyclic nitro compounds are in consideration to predict shock sensitivity. This work is meaningful in further understanding the shock mechanism and helpful to the design and synthesis of novel energetic materials.

On the shock sensitivity of explosive compounds with small-scale gap test.

In this work an improved set of small-scale gap tests was applied to measure the shock sensitivity of 13 explosive compounds, and a Mn-Cu manometer was also employed to measure the output pressures of shock waves passed through aluminum gaps with different thicknesses to draw a standard curve. The critical initiation thicknesses of aluminum gaps of different explosive compounds (244 shots in total) were treated according to statistical method, and the Mulliken charges of nitro groups, bond dissociation energies of X-NO(2) (X = C, N), resonance energies, and ring strain energies of these explosive compounds were calculated with the means of DFT/BLYP/DNP calculations and homodesmotic reactions designs. Genetic function approximation was used to construct a relationship between the critical initiation thicknesses of aluminum gaps of different explosive compounds and their forementioned molecule structural parameters.

Synthesis, characterization, thermal stability and mechanical sensitivity of polyvinyl azidoacetate as a new energetic binder

A new azide polymer, polyvinyl azidoacetate (PVAA), was synthesized through the initial polymerization reaction and subsequent azidation reaction of vinyl chloroacetate. By controlling the appropriate reaction conditions, the PVAA can be prepared with a number average molecular weight in the range of 1.54 × 104~4.02 × 104 and polydispersity index in the range of 2.0~4.0. The structure of PVAA was confirmed by elemental analysis, 1H NMR, 13C NMR and ATR-FTIR techniques. The glass transition temperature of PVAA was evaluated by DSC method and the thermal stability of PVAA was tested by DTA and TGA methods. The results show that PVAA has a single glass transition temperature and exhibits a good stability. In addition, the sensitivity properties of PVAA were measured by the China national military standard methods and the compatibilities of PVAA with the energetic components of TNT–based melt cast explosives were studied using the non-isothermal DSC method. The results indicate that PVAA is an insensitive energetic polymer and can be safely used in melt cast explosives.

Preparation of He@C60 and He2@C60 by an explosive method

We developed an explosion-based method for preparing non-metal endohedral fullerenes. Fullerenes, an explosive and a noble gas are contained in an enclosed space. A flying plate within the apparatus is used to convert the explosion energy into kinetic energy of the gas molecules, which in turn bombard the fullerenes. Through adjusting the quantity of explosive, the gas molecules obtain sufficient energy to penetrate the fullerene surface and then become incarcerated forming endohedral fullerenes. Our technique was successfully applied to the production of He@C60 and He2@C60. However, it may be extendable to other endohedral fullerenes by employing other fullerenes, other inert gases (such as Ne, Ar, Kr, Xe), and an appropriate quantity of explosive.

Synthesis and Characterization of a New Energetic Plasticizer: Acyl-Terminated GAP

A new energetic plasticizer, acyl-terminated glycidyl azide polymer (GAP), was synthesized through the reaction between 2,4,6-trinitrobenzoyl (TNB) chloride and GAP. The TNB-GAP structure was confirmed by FT-IR, UV-vis, 1H NMR, and 13C NMR. The glass transition temperature (T g ) of TNB-GAP was evaluated by differential scanning calorimetry (DSC), and the thermal stability of TNB-GAP was tested by thermogravimetric analysis (TGA). DSC traces showed that TNB-GAP had a T g of −46.01°C. TGA curves showed that the thermo-oxidative degradation of TNB-GAP in air was a two-step reaction, and the percentage of degraded TNB-GAP nearly reached 100% at 650°C. Exothermic decomposition reaction kinetic parameters of TNB-GAP were also studied using the non-isothermal DSC method. Results indicated that the values of apparent activation energy of TNB-GAP were 80.16 and 162.92 kJ/mol, and the values of the pre-exponential constant were 1.75 × 1010 and 1.22 × 1016.

Synthesis, characterization, and thermal stability properties of PVTNP-co-PVAA through the azidoacetylation of polyvinyl 2,4,6-trinitrophenylacetal

AbstractA new energetic polymer, poly(vinyl 2,4,6-trinitrophenylacetal)-co-poly(vinyl acetate azide) (PVTNP-co-PVAA), was synthesized by a two-step process involving initial chloroacetylation and subsequent azidation of poly(vinyl 2,4,6-trinitrophenylaceta). The synthesized polymers were characterized by elemental analysis, UV-Vis, ATR-FTIR, and 1H NMR techniques. The glass-transition temperature of PVTNP-co-PVAA was evaluated by differential scanning calorimetry (DSC), and the thermal stability of PVTNP-co-PVAA was tested by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). DSC traces showed that PVTNP-co-PVAA had two glass-transition temperatures at −27.53 and 67.05 °C, respectively. DTA and TGA curves showed that the thermo-oxidative degradation of PVTNP-co-PVAA in air was a two-step reaction, and the percentage of degraded PVTNP-co-PVAA reached nearly 100% at 600 °C.

High mobility ZnO nanowires for terahertz detection applications

An oxide nanowire material was utilized for terahertz detection purpose. High quality ZnO nanowires were synthesized and field-effect transistors were fabricated. Electrical transport measurements demonstrated the nanowire with good transfer characteristics and fairly high electron mobility. It is shown that ZnO nanowires can be used as building blocks for the realization of terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave (∼0.3 THz) induced photovoltages were obtained at room temperature with varying incidence intensities. Further analysis showed that the terahertz photoresponse is closely related to the high electron mobility of the ZnO nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.

An important factor in relation to shock-induced chemistry: resonance energy

With density function theory BLYP/DNP method, together with homodesmotic reactions and isodesmic reactions, we calculated the resonance energies of some explosives, including eight nitro compounds which contains benzene rings, three nitro compounds which contains azaheterocycles (2,4-dinitroimidazole (2,4-DNI), 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) and 2,4,6-trinitro-1,3,5-triazine) and one nitrogen-rich energetic compound of 3,3’-azobis(6-amino-s-tetrazine) (DAAT). The results indicate that their resonance energies are in relation to their shock sensitivity which measuring their threshold pressures of initiation, that is, the lower the resonance energy is, the higher the shock sensitivity of the explosive behaves. And this measuring method according to resonance energy is based on the global property of the molecule instead of the local one, such as one nitro group in the molecule. It is meaningful to calculate resonance energies of these kind of compounds quickly and accurately because resonance structures exist widely in these organic compounds and resonance energies may play a significant role in determining their shock sensitivity, and it is helpful in the rational design or synthesis of high energy and insensitive materials.

Solvent-Free Synthesis of N-Arylfulleropyrrolidine Derivatives Without Using Phase-Transfer Catalyst Under Microwave Irradiation

Several N-arylfulleropyrrolidine derivatives were synthesized via the direct solvent-free reactions of N-unsubstituted fulleropyrrolidines and nitrochlorobenzenes under microwave irradiation in the absence of phase-transfer catalysts. Their structures were confirmed by ultraviolet–visble, Fourier transform–infrared, 1H NMR, and mass spectrometry.

Large-area snow-like MoSe2 monolayers: synthesis, growth mechanism, and efficient electrocatalyst application

This study explores the large-area synthesis of controllable morphology, uniform, and high-quality monolayer. MoSe2 is essential for its potential application in optoelectronics, photocatalysis, and renewable energy sources. In this study, we successfully synthesized snow-like MoSe2 monolayers using a simple chemical vapor deposition method. Results reveal that snow-like MoSe2 is a single crystal with a hexagonal structure, a thickness of ∼0.9 nm, and a lateral dimension of up to 20 μm. The peak position of the photoluminescence spectra is ∼1.52 eV corresponding to MoSe2 monolayer. The growth mechanism of the snow-like MoSe2 monolayer was investigated and comprised a four-step process during growth. Finally, we demonstrate that the snow-like MoSe2 monolayers are ideal electrocatalysts for hydrogen evolution reactions (HERs), reflected by a low Tafel slope of ∼68 mV/decade. Compared with the triangular-shaped MoSe2 monolayer, the hexangular snow-like shape with plentiful edges is superior for perfect electrocatalysts for HERs or transmission devices of optoelectronic signals.