Fengsheng Li

Molecular dynamics study of the structures and properties of RDX/GAP propellant.

Molecular dynamics simulations have been performed to investigate well-known energetic material cyclotrimethylene trinitramine (RDX) crystal, glycidyl azide polymer (GAP) and RDX/GAP propellant. The results show that the binding energies on different crystalline surface of RDX change in the order of (0 1 0) > (1 0 0) > (0 0 1). The interactions between RDX and GAP have been analyzed by means of pair correlation functions. The mechanical properties of RDX/GAP propellant, i.e., elastic coefficients, modulus, Cauchy pressure, and Poissons ratio, etc., have been obtained. It is found that mechanical properties are effectively improved by adding some amounts of GAP polymer, and the overall effect of GAP on three crystalline surfaces of RDX changes in the order of (1 0 0) > (0 1 0) > (0 0 1). The energetic properties of RDX/GAP propellant have also been calculated and the results show that compared with the pure RDX crystal, the standard theoretical specific impulse (I(sp)) of RDX/GAP propellant decrease, but they are still superior to those of double base propellant.

Synthesis of Nano-sized Yttria via a Sol-Gel Process Based on Hydrated Yttrium Nitrate and Ethylene Glycol and Its Catalytic Performance for Thermal Decomposition of NH4ClO4

Abstract Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70 °C, dried at 90 °C, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 ∼ 350 °C and 400 ∼ 470 °C into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g −1 . It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5% nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7 °C by reduction of 114.6 °C and increases the apparent decomposition heat from 515 to 1240 J·g −1 , reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.

Massive Preparation of Reduced-Sensitivity Nano CL-20 and Its Characterization

Nano 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) was produced massively by ball milling. One thousand grams of the raw CL-20 were used per batch. The product was characterized using laser granularity measurement, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results show that the pulverized particles were pseudo-spheres with an average particle size (d50) of 200 nm, and the thermal decomposition peak temperature of the nano CL-20 was 239.61°C lower than that of the micrometer-sized CL-20 at a heating rate of 15°C · min−1. Furthermore, compared with the raw CL-20, the impact and friction sensitivities of the nano CL-20 were considerably reduced by 116.2 and 22%, respectively, indicating the great improvement in safety of CL-20.

Novel Salt-Assisted Combustion Synthesis of High Surface Area Ceria Nanopowders by An Ethylene Glycol-Nitrate Combustion Process

A novel salt-assisted combustion process with ethylene glycol as a fuel and nitrate as an oxidant to synthesize high surface area ceria nanopowders was reported. The effects of various tunable conditions, such as fuel-to-oxidant ratio, type of salts, and amount of added salts, on the characteristics of the as-prepared powders were investigated by X-ray diffraction, transmission electron microscopy and BET surface area measurement. A mechanism scheme was proposed to illustrate the possible formation processes of well-dispersed ceria nanoparticles in the salt-assisted combustion sunthesis. It was verified that the simple introduction of leachable inert inorganic salts as an excellent agglomeration inhibitor into the redox mixture precursor leads to the formation of well-dispersed ceria particles with particle size in the range of 4 ∼ 6 nm and a drastic increase in the surface area. The presence of KCl results in an over ten-fold increment in specific surface area from 14.10 m2·g−1 for the produced ceria powders via the conventional combustion synthesis process to 156.74 m2·g−1 for the product by the salt-assisted combustion synthesis process at the same molar ratio of ethylene glycol-nitrate.

A feature on ensuring safety of superfine explosives

To probe the dependence of particle size on the safety of nitroamine explosives, coarse RDX and HMX were comminuted to nanometer particles by an improved superfine mill. Their thermolysis characteristics were studied by thermal analysis and described via calculating some thermodynamic and kinetic parameters such as the activation free-energy (ΔG≠), activation enthalpy (ΔH≠), activation entropy (ΔS≠), apparent activation energy (E), critical temperature of thermal explosion (Tb), and critical heating rate of thermal explosion (

Preparation and characterization of Fe3O4@TiO2 shell on polystyrene beads

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A Fractal Approach to Assess the Risks of Nitroamine Explosives

). After comminuted, the values of Tb and