Baoyun Ye

Preparation and Properties of Surface-Coated HMX with Viton and Graphene Oxide

To improve the safety performance of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) particles, the new carbon material graphene oxide (GO) and Viton were used to coat HMX via a solvent–slurry process. For comparison, the HMX/Viton/graphite (HMX/Viton/G) and HMX/Viton composites were also prepared by the same process. Atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC) were employed to characterize the morphology, composition, and thermal decomposition of samples. The impact sensitivity and shock wave sensitivity of HMX-based composites were also measured and analyzed. The results of SEM, XRD, and XPS indicate that the cladding layer of HMX-based composites is successfully constructed. HMX/Viton/GO composites exhibit better thermal stability compared to HMX and HMX/Viton. The results show that both impact and shock wave sensitivities of HMX/Viton/GO composites are much lower than that of HMX/Viton. In addition, GO sheets exhibit a better desensitizing effect than G sheets. These combined properties suggest that nano-GO has good compatibility with explosives and can be utilized as a desensitizer in HMX particles.

Nano-CL-20/HMX Cocrystal Explosive for Significantly Reduced Mechanical Sensitivity

Spray drying method was used to prepare cocrystals of hexanitrohexaazaisowurtzitane (CL-20) and cyclotetramethylene tetranitramine (HMX). Raw materials and cocrystals were characterized using scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, Raman spectroscopy, and Fourier transform infrared spectroscopy. Impact and friction sensitivity of cocrystals were tested and analyzed. Results show that, after preparation by spray drying method, microparticles were spherical in shape and 0.5ź5źµm in size. Particles formed aggregates of numerous tiny plate-like cocrystals, whereas CL-20/HMX cocrystals had thicknesses of below 100źnm. Cocrystals were formed by CźHźO bonding between źNO2 (CL-20) and źCH2ź (HMX). Nanococrystal explosives exhibited drop height of 47.3źcm, and friction demonstrated explosion probability of 64%. Compared with raw HMX, cocrystals displayed significantly reduced mechanical sensitivity.

Formation and properties of HMX-based microspheres via spray drying

Herein, we report a facile strategy to prepare a novel HMX-based microspheres by coating a layer of energetic binders on HMX. HMX-based microspheres were synthesized and compared by different dissolution methods by spray dying. The HMX-based composites were also prepared by a water-suspension method. The formation mechanism of the hollow structure and core–shell structure is proposed. The as-prepared HMX/NC/GAP microspheres synthesized by suspension spray drying were found to possess a solid core–shell structure, display a β-form, lower impact sensitivity and higher energy performance.

Preparation and Characterization of the Solid Spherical HMX/F2602 by the Suspension Spray-Drying Method

Solid spherical octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine/fluororubber2602 (HMX/F2602) was prepared by the suspension spray-drying method as follows: firstly, thinning octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was obtained by a solvent–anti-solvent method. Secondly, thinning HMX suspended in ethyl acetate solvent in a solution of a binder—F2602—was made into a suspension. Finally, the samples were prepared by spray drying. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), and Fourier transform infrared (FTIR), and its thermal stability as well as mechanical and spark sensitivities were measured. The results of SEM showed that the grain of HMX/F2602 was solid spherical and the particle distribution was homogeneous. The results of XPS indicated that F2602 can be successfully coated on the surface of HMX crystals. Compared to raw HMX, th characteristic drop height was increased from 19.60 to 40.37 cm, an increase of 79.10%. The friction sensitivities of HMX reduced from 100 to 28% and the spark sensitivity of HMX/F2602 increased. The critical explosion temperatures of raw HMX and HMX/F2602 were 275.43 and 274.30°C, respectively. The amount of gas evolution of raw HMX and HMX/F2602 was 0.15 and 0.12 ml·(5 g)−1, respectively. The results of DSC and vacuum stability tests (VSTs) indicate that the thermal stability of HMX/F2602 was equal to that of raw HMX and HMX and F2602 had good compatibility.

One-Step Ball Milling Preparation of Nanoscale CL-20/Graphene Oxide for Significantly Reduced Particle Size and Sensitivity

A one-step method which involves exfoliating graphite materials (GIMs) off into graphene materials (GEMs) in aqueous suspension of CL-20 and forming CL-20/graphene materials (CL-20/GEMs) composites by using ball milling is presented. The conversion of mixtures to composite form was monitored by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The impact sensitivities of CL-20/GEM composites were contrastively investigated. It turned out that the energetic nanoscale composites based on CL-20 and GEMs comprising few layers were accomplished. The loading capacity of graphene (reduced graphene oxide, rGO) is significantly less than that of graphene oxide (GO) in CL-20/GEM composites. The formation mechanism was proposed. Via this approach, energetic nanoscale composites based on CL-20 and GO comprised few layers were accomplished. The resulted CL-20/GEM composites displayed spherical structure with nanoscale, ε-form, equal thermal stabilities, and lower sensitivities.

Carbon-coated copper nanoparticles prepared by detonation method and their thermocatalysis on ammonium perchlorate

Carbon-coated copper nanoparticles (CCNPs) were prepared by initiating a high-density charge pressed with a mixture of microcrystalline wax, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and copper nitrate hydrate (Cu(NO3)2·3H2O) in an explosion vessel filled with nitrogen gas. The detonation products were characterized by transmission electron microcopy (TEM), high resolution transmission electron microcopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy. The effects of CCNPs on thermal decomposition of ammonium perchlorate (AP) were also investigated by differential scanning calorimeter (DSC). Results indicated that the detonation products were spherical, 25-40 nm in size, and had an apparent core-shell structure. In this structure, the carbon shell was 3-5 nm thick and mainly composed of graphite, C8 (a kind of carbyne), and amorphous carbon. When 5 wt.% CCNPs was mixed with 95 wt.% AP, the high-temperature decomposition peak of AP decreased by 95.9...

Nano-HNS Particles: Mechanochemical Preparation and Properties Investigation

Nano-2,2′,4,4′,6,6′-hexanitrostilbene (HNS) particles were successfully prepared by a mechanochemical (i.e., high energy milling) process without an organic solvent, which can be viewed as a green technology. The particle size, morphology, specific area, crystal phase, thermal decomposition properties, impact sensitivity, and short duration shock initiation sensitivity were characterized and tested. The diameter of milling HNS is about 89.2 nm with a narrow size distribution and without agglomeration of particles. The formation mechanism of nano-HNS can be viewed as the transformation from thin HNS sheets with a one-dimensional nanostructure to three-dimensional nanoparticles. The nano-HNS particles present a much higher and lower impact sensitivity than purified HNS, revealing the outstanding safety properties. From the results of the short duration shock initiation sensitivity, 50% and 100% initiation voltages are decreased compared with those of HNS-IV, indicating the higher initiation sensitivity.

One-step synthesis of graphene nanosheets through explosive process

ABSTRACT Herein, we report a facile process to prepare graphene nanosheets through explosive method. The explosive products were characterized by using XRD, TEM, AFM, Raman and XPS. The results show that the obtained materials have a perfect sheet-like structure, and vary in the two-dimensional plane at the macron scale and in thickness at the nanoscale. This technique may offer a low-cost, energy-saving, and efficient way to prepare graphene materials.