Bing Gao

Facile, continuous and large-scale synthesis of CL-20/HMX nano co-crystals with high-performance by ultrasonic spray-assisted electrostatic adsorption method

High-performance of CL-20/HMX nano co-crystals is readily synthesized by ultrasonic spray-assisted electrostatic adsorption method. This facile and continuous approach reduces handling time, minimizes the potential of aggregation via the electrostatic repulsive force among nano co-crystal particles and opens up new perspectives in fabricating various organic nano-sized co-crystals on a large-scale.

Preparation and characterization of nano-1,1-diamino-2,2-dinitroethene (FOX-7) explosive

Nano-1,1-diamino-2,2-dinitroethene (FOX-7) explosive particles were successfully prepared via an ultrasonic spray-assisted electrostatic adsorption (USEA) method and sub-micro FOX-7 was also obtained by recrystallization (using absolute ethyl alcohol as the solvent) for comparison. The samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and particle size and size distribution. The results showed that there were two groups of size distribution. For the nano-sized FOX-7, prepared by the USEA method, the size distribution was in the range of 30 to 200 nm and the average particle size of FOX-7 was approximately 78 nm. While, sub-micro FOX-7 particles obtained via recrystallization had a single size distribution of 200–450 nm. The particles were cubic and spheroidal, respectively. Whats more, their thermal properties were also investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). For nano-sized FOX-7, the first exothermic peak (267.4 °C) was increased by 45 °C and had a faster energy releasing efficiency and released more energy compared to original and sub-micro particle crystals (222.7 °C). There is a potential alternative application for micro-electromechanical systems (MEMS), micro thrusters and so on.

Controlled synthesis of porous Co3O4–C hybrid nanosheet arrays and their application in lithium ion batteries

Two-dimensional Co3O4 nanostructures with porous architectures are experiencing rapid development in functional material fields for their unique structures and properties. Porous Co3O4–C hybrid nanosheet (NS) arrays grown directly on various conducting substrates are synthesized by a controlled method for the first time via a facile hydrothermal synthesis approach in combination with heat treatment. These NS arrays reveal uniform hexagonal morphology and have combined properties of quasi-single-crystallinity and a pore network inside the architecture. A four-step formation mechanism is proposed to understand the growth process of nanosheet arrays grown on the substrate based on the change of morphology. Both the concentration of Co2+ and poly(vinylpyrrolidone) (PVP) play key roles in the formation of NS arrays. When tested as an anode material in lithium-ion batteries, the porous Co3O4–C hybrid NS arrays exhibit improved electrochemical properties of cyclic performance and high coulombic efficiency compared with the commercial Co3O4 and Co3O4/carbon nanocomposites. This approach, porous Co3O4–C NS arrays grown directly on different substrates (wafer, foam, alloy net, foil, especially flexible carbon cloth), provides an efficient route to produce NS arrays to meet the demand for diversity, and may be extended to synthesize other transition metal oxide materials for other applications.

a novel preparation method for drug nanocrystals and characterization by ultrasonic spray-assisted electrostatic adsorption

Purpose The purpose of this study was to develop a novel and continuous method for preparing a nanosized particle of drug crystals and to characterize its properties. Materials and methods A new apparatus was introduced to crystallize nanosized drug crystals of amitriptyline hydrochloride as a model drug. The samples were prepared in the pure state by ultrasonic spray, and elaborated deposition was completed via electrostatic adsorption. Scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy were used to characterize the size of the particles; this was subsequently followed by differential scanning calorimetry. Results and discussion Nanoparticles of drug crystals were successfully prepared. The size of the drug crystals ranged from 20 nm to 400 nm; the particle size of amitriptyline hydrochloride was approximately 71 nm. The particles were spherical and rectangular in shape. Moreover, the melting point of the nanoparticles decreased from 198.2°C to 196.3°C when compared to raw particle crystals. Furthermore, the agglomeration effect was also attenuated as a result of electrostatic repulsion among each particle when absorbed, and depositing on the inner wall of the gathering unit occurred under the electrostatic effect. Conclusion Ultrasonic spray-assisted electrostatic adsorption is a very effective and continuous method to produce drug nanocrystals. This method can be applied to poorly water-soluble drugs, and it can also be a very effective alternative for industrial production. Once the working parameters are given, drug nanocrystals will be produced continuously.

Facile, continuous and large-scale production of core–shell HMX@TATB composites with superior mechanical properties by a spray-drying process

The increasing high-energy-density requirements of energetic materials as well as the concerns over safety problems have accelerated the development of insensitive high explosives (IHEs). Recently, studies focused on the fabrication of advanced combinations of materials such as coating a moderately powerful and extremely insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) onto the surface of a high-energy but sensitive explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) have attracted a large amount of attention. However, the reported results on the construction of this core–shell structure show a low utilization of shell material due to the unconfined synthesis environment. In this report, a facile and effective spray-drying route was employed to achieve a coating of TATB nanoparticles onto pre-modified HMX crystals. The utilization of TATB shell was significantly improved due to the self-assembly in confined droplets during spray-drying process, thus leading to the decrease of shell content and further enhancement of explosive performance. Both field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of the core–shell HMX@TATB composites with a uniform and compact shell layer. The influence of various experimental parameters on the core–shell structure of final products was also examined. The impact and friction sensitivity results showed that superior mechanical properties of these core–shell microparticles can be maintained. Furthermore, such a facile, continuous, and one-step synthesis strategy opens up new perspectives on the large-scale production of core–shell energetic–energetic composites.

Formulation and performance of functional sub-micro CL-20-based energetic polymer composite ink for direct-write assembly

Direct writing deposition of energetic materials has been an area of interest for fuzing applications, novel initiation/booster trains, and for studying small scale detonations. Herein, we present a simple and efficient strategy to fabricate a high explosive ink formulation with good stability as well as excellent performance. Sub-micro CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) was prepared by the ball milling method and then mixed with an energetic binder consisting of GAP (glycidyl azide polymer binder) and N100 (polyisocyanate). The emulation curing process of GAP and N100 was illustrated by FT-IR spectra. Sub-micro CL-20 based ink shows wettability and good uniformity without cracks, porosity and voids. Moreover, the printed sample has lower sensitivity for impact heat stability than pure CL-20. A directly deposited sample in small grooves can provide steady detonation at a size of under 0.4 × 0.4 mm.

Preparation of CL-20 Explosive Nanoparticles and Their Thermal Decomposition Property

Herein, we develop a novel method for preparing nanohexanitrohexaazaisowurtzitane nano-CL-20 via ultrasonic spray-assisted electrostatic adsorption USEA technology. Various experimental conditions which influence safety factors and the crystallization process were studied. Meanwhile, the prepared nano-CL-20 particles were characterized by field emission scanning electron microscopy FE-SEM, X-ray diffraction XRD, and Fourier transform infrared FT-IR spectroscopy. The results show that the obtained nano-CL-20 showed a wide size distribution in the range from 150 to 600 nm with an average of 270 nm. Moreover, their thermal properties were also investigated by differential scanning calorimetry DSC and thermogravimetry TG. For nano-CL-20, the exothermal peak is 232.9°C increased by 12°C compared with conventionally manufactured CM CL-20, and they exhibit fast energy release efficiency as well as more energy release. The simple and continuous approach presented here is expected to be an attractive potential for fabricating other organic nanoparticles.

Synthesis, Characterization, and Sensitivity of a CL-20/PNCB Spherical Composite for Security

Highly energetic materials have received significant attention, particularly 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). However, the application of this material was limited due to its high sensitivity. It is well known that the shape, size, and structure of energetic materials (EMs) significantly influence their sensitivity. At present, there are several ways to reduce the sensitivity of CL-20, such as spheroidization, ultrafine processing, and composite technology. However, only one or two of the abovementioned methods have been reported in the literature, and the obtained sensitivity effect was unsatisfactory. Thus, we tried to further reduce the sensitivity of CL-20 by combining the above three methods. The as-prepared composite was precipitated from the interface between two solutions of water and ethyl acetate, and the composite was insensitive compared with other reported CL-20-based EMs. The H50 value for the composite ranged up to 63 cm. This approach opens new prospects for greatly reducing the sensitivity of high Ems.