Rufang Peng

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.

Synthesis of [60]Fullerene-Fused Tetrahydrobenzooxepine and Isochroman Derivatives via Hydroxyl-Directed C–H Activation/C–O Cyclization

The palladium-catalyzed hydroxyl-directed C-H activation/C-O cyclization reaction of [60]fullerene with 2-phenylethyl alcohols and benzyl alcohols afforded [60]fullerene-fused tetrahydrobenzooxepine and isochroman derivatives in up to 43% yield. A plausible reaction mechanism is proposed, and the electrochemistry was also investigated.

Facile Access to Novel [60]Fullerenyl Diethers and [60]Fullerene–Sugar Conjugates via Annulation of Diol Moieties

A general and facile annulation of various diol motifs to [60]fullerene has been developed. This protocol can afford not only 6- to 10-membered-ring fullerenyl diethers in one step from simple acyclic diols but also directly couple [60]fullerene with a variety of structurally diverse sugars. The [60]fullerene-sugar conjugates formed do not require any linker moiety and maintain their inherent structural integrity. The electrochemistry of the fullerenyl diethers and [60]fullerene-sugar conjugates has also been investigated.

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.

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.

Nitrogen-Rich Energetic Metal-Organic Framework: Synthesis, Structure, Properties, and Thermal Behaviors of Pb(II) Complex Based on N,N-Bis(1H-tetrazole-5-yl)-Amine

The focus of energetic materials is on searching for a high-energy, high-density, insensitive material. Previous investigations have shown that 3D energetic metal–organic frameworks (E-MOFs) have great potential and advantages in this field. A nitrogen-rich E-MOF, Pb(bta)·2H2O [N% = 31.98%, H2bta = N,N-Bis(1H-tetrazole-5-yl)-amine], was prepared through a one-step hydrothermal reaction in this study. Its crystal structure was determined through single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, and elemental analysis. The complex has high heat denotation (16.142 kJ·cm−3), high density (3.250 g·cm−3), and good thermostability (Tdec = 614.9 K, 5 K·min−1). The detonation pressure and velocity obtained through theoretical calculations were 43.47 GPa and 8.963 km·s−1, respectively. The sensitivity test showed that the complex is an impact-insensitive material (IS > 40 J). The thermal decomposition process and kinetic parameters of the complex were also investigated through thermogravimetry and differential scanning calorimetry. Non-isothermal kinetic parameters were calculated through the methods of Kissinger and Ozawa-Doyle. Results highlighted the nitrogen-rich MOF as a potential energetic material.

Nitrogen-rich energetic salts of 1H,1′H-5,5′-bistetrazole-1,1′-diolate: synthesis, characterization, and thermal behaviors

A series of nitrogen-rich heterocyclic 1H,1′H-5,5′-bistetrazole-1,1′-diolate salts, namely, 1,2,4-triazolium (2), 3-amino-1,2,4-triazolium (3), 4-amino-1,2,4-triazolium (4), 3,5-diamino-1,2,4-triazolium (5), 2-methylimidazolium (6), imidazolium (7), pyrazolium (8), 3-amino-5-hydroxypyrazolium (9), dicyandiamidine (10), and 2,4-diamino-6-methyl-1,3,5-triazin (11), was synthesized with cations. These energetic salts were fully characterized through FT-IR, 1H NMR, 13C NMR, and elemental analysis. The structures of 2, 3·7H2O, 6·2H2O, 8, and 10·4H2O were further confirmed through single crystal X-ray diffraction. Their thermal stabilities were investigated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results indicated that all of the salts possess excellent thermal stabilities with decomposition temperatures ranging from 225.7 °C to 314.0 °C. On the basis of the Kamlet–Jacobs formula, we carefully calculated their detonation velocities and detonation pressures. All of the salts, except 11, exhibit promising detonation performances with a detonation pressure of 20.23–28.69 GPa and a detonation velocity of 7050–8218 m s−1. These values are much higher than those of TNT. The impact sensitivities of the compounds were determined via a Fall hammer test. All of the compounds show excellent impact sensitivities of >50 J, and this finding is higher than that of TATB (50 J). Therefore, these ionic salts with excellent energetic properties could be applied as new energetic materials.

Terahertz photodetector arrays based on a large scale MoSe2 monolayer

Large domains of monolayered transition-metal dichalcogenides (TMDCs) have emerged as exciting materials because of their potential to provide a platform for ultrathin circuits and optoelectronics systems. Herein, we report ambient pressure chemical vapor deposition (CVD) growth of large scale MoSe2 film for terahertz (THz) applications. Arrays of 100 × 60 μm MoSe2 rectangle layers were etched out and field effect transistors (FETs) were fabricated on these arrays. The device exhibits current on/off ratio of ∼104. The THz photoresponse of the devices was studied and a THz responsivity of ∼38 mV W−1 was demonstrated, suggesting that TMDCs can be promising materials for long wavelength optoelectronic applications.

Terahertz detectors arrays based on orderly aligned InN nanowires.

Nanostructured terahertz detectors employing a single semiconducting nanowire or graphene sheet have recently generated considerable interest as an alternative to existing THz technologies, for their merit on the ease of fabrication and above-room-temperature operation. However, the lack of alignment in nanostructure device hindered their potential toward practical applications. The present work reports ordered terahertz detectors arrays based on neatly aligned InN nanowires. The InN nanostructures (nanowires and nano-necklaces) were achieved by chemical vapor deposition growth, and then InN nanowires were successfully transferred and aligned into micrometer-sized groups by a “transfer-printing” method. Field effect transistors on aligned nanowires were fabricated and tested for terahertz detection purpose. The detector showed good photoresponse as well as low noise level. Besides, dense arrays of such detectors were also fabricated, which rendered a peak responsivity of 1.1 V/W from 7 detectors connected in series.