Crystalline behaviors of HMX-Al composites in solvents: A molecular dynamics and experimental study
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NANOCRYSTALLINE HIGH ENTROPY MATERIALS: PROCESSING CHALLENGES AND PROPERTIES
Crystalline behaviors of HMX-Al composites in solvents: A molecular dynamics and experimental study Jun Tao1,a) Xiaofeng Wang1,b) 1
Xi’an Modern Chemistry Research Institute, Xi’an, Shaanxi 710065, People’s Republic of China Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] a)
Received: 13 August 2018; accepted: 3 December 2018
Herein, in order to research the crystalline behaviors of cyclotetramethylenetetranitramine-aluminum (HM-Al) composites in solvents, the modified attachment energy model was applied to predict the morphologies of HMX in vacuum, dimethyl sulfoxide (DMSO), and ethanol. Then HMX-Al composites with Al coated and noncoated were prepared via solvent–nonsolvent method, and the morphologies were characterized. Results show that HMX interacts with DMSO and ethanol mainly via van der Waals force and electrostatic force. HMX grows into polyhedral crystals in two solvents. However, the shapes and the crystalline surface area distributions of the polyhedrons are different for two solvents. There are many aluminum particles embedded in HMX crystals of HMX-Al composite particles prepared via solvent–nonsolvent method, but Al particles cannot embed in HMX crystals in the existence of fluoropolymer. The crystal morphology predicted is consistent with the experimental results.
Introduction As a kind of metal fuels with high calorific value, aluminum powder owns a wide range of sources and low cost, and it has been widely used in kinds of explosive formulations. However, because of the dense oxide layer on its surface, the ignition threshold and reaction completeness of aluminum powder are seriously restricted [1, 2, 3]. In order to improve the reaction completeness and promote energy release of aluminum powder in the detonation zone via rapid oxidation reaction, scientists from various countries have done some related work. One of the effective methods is combining the aluminum powder and the oxidant together. The reaction properties of thermobaric explosives with aluminum powder coated with nickel were researched [4]. The results showed that nickel could reduce the ignition temperature of aluminum powder, enhance the combustion efficiency of fuel particles, and increase the impulse and temperature field during detonation. The reaction kinetics of fluoropolymer-aluminum composite particles were investigated by Pantoya et al. [5]. The reaction characteristics of the composite particles with different aluminum powder sizes were quite different. The reaction heat of the composite particles containing aluminum powders with a size of 15 nm was three
ª Materials Research Society 2019
times more than the composite particles containing 50 nm aluminum powders. Dolgoborodov et al. [6] studied the detonation performance of Al-polytetrafluoroethylene (PTFE) composite particles experimentally, and it was found that the composite particles can reach steady state detonation. The de
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