Zhiqiang Qiao

Fabrication of FOX-7 quasi-three-dimensional grids of one-dimensional nanostructures via a spray freeze-drying technique and size-dependence of thermal properties.

1,1-Diamino-2,2-dinitroethylene (C(2)H(4)N(4)O(4), FOX-7) quasi-three-dimensional (3D) grids, a promising high-energy-density material with superior sensitivity properties, were synthesized by a spray freeze-drying technique. The FOX-7 3D grids were constructed from one-dimensional nanostructures. The sizes and structures of the FOX-7 3D grids strongly depend on the concentration of the aqueous solution of FOX-7. A possible formation mechanism of this structure was proposed in detail. Thermal analysis reveals that decrease in average particle sizes of FOX-7 grids results in a lower decomposition temperature and a much higher decomposition rate, which is in agreement with those reported about inorganic nanomaterials.

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.

Controlled synthesis of Co3O4 single-crystalline nanofilms enclosed by (111) facets and their exceptional activity for the catalytic decomposition of ammonium perchlorate

Single-crystalline, thermally stable Co3O4 (111) nanofilms have been successfully synthesized without any surfactant. The catalytic activity of Co3O4 nanofilms was investigated via the thermal decomposition of ammonium perchlorate (AP). AP exhibited unprecedentedly low decomposition temperatures and fast reaction rates in the catalyzed formations, making the Co3O4 (111) nanofilms an effective catalyst.

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.

Self-assembly of TATB 3D architectures via micro-channel crystallization and a formation mechanism

Three-dimensional (3D) hierarchical nanostructures with a controlled morphology and dimensionality represent one kind of important materials and have received enormous attention for a series of applications. We demonstrate a micro-channel directional crystallization process to assemble TATB 3D architectures. Chrysanthemum-like 3D architectures with a size of 2 μm were self-assembled by many TATB nanorods, of which the length and diameter is ∼1 μm and ∼40 nm, respectively. A 1D nanorod structure was formed due to the driving-force gradient of an initial crystallite and further growth along a certain direction. The nanostructure of TATB can be tuned by changing the diameter of the micro-channel and a 3D microsphere assembled by nanowires with a diameter of ∼30 nm and a 1D shuttle-like nanostructure with a diameter of ∼50 nm can be successfully prepared. The nanostructure of TATB has a great influence on the thermal decomposition and kinetics of TATB due to its high surface area that contributes to efficient mass transfer and heat transfer, thus leading to numerous activated molecules being involved in the reaction. We believe that this approach will open doors to a range of interesting studies related to nano-energetic material fabrication.

Core–Shell Al-Polytetrafluoroethylene (PTFE) Configurations to Enhance Reaction Kinetics and Energy Performance for Nanoenergetic Materials

The energy performance of solid energetic materials (Al, Mg, etc.) is typically restricted by a natural passivation layer and the diffusion-limited kinetics between the oxidizer and the metal. In this work, we use polytetrafluoroethylene (PTFE) as the fluorine carrier and the shielding layer to construct a new type of nano-Al based fuels. The PTFE shell not only prevents nano-Al layers from oxidation, but also assists in enhancing the reaction kinetics, greatly improving the stability and reactivity of fuels. An in situ chemical vapor deposition combined with the electrical explosion of wires (EEW) method is used to fabricate core-shell nanostructures. Studies show that by controlling the stoichiometric ratio of the precursors, the morphology of the PTFE shell and the energy performance can be easily tuned. The resultant composites exhibit superior energy output characters than that of their physically mixed Al/PTFE counterparts. This synthetic strategy might provide a general approach to prepare other high-energy fuels (Mg, Si).

Enhanced Thermal Decomposition Properties of CL-20 through Space-Confining in Three-Dimensional Hierarchically Ordered Porous Carbon

High energy and low signature properties are the future trend of solid propellant development. As a new and promising oxidizer, hexanitrohexaazaisowurtzitane (CL-20) is expected to replace the conventional oxidizer ammonium perchlorate to reach above goals. However, the high pressure exponent of CL-20 hinders its application in solid propellants so that the development of effective catalysts to improve the thermal decomposition properties of CL-20 still remains challenging. Here, 3D hierarchically ordered porous carbon (3D HOPC) is presented as a catalyst for the thermal decomposition of CL-20 via synthesizing a series of nanostructured CL-20/HOPC composites. In these nanocomposites, CL-20 is homogeneously space-confined into the 3D HOPC scaffold as nanocrystals 9.2-26.5 nm in diameter. The effect of the pore textural parameters and surface modification of 3D HOPC as well as CL-20 loading amount on the thermal decomposition of CL-20 is discussed. A significant improvement of the thermal decomposition properties of CL-20 is achieved with remarkable decrease in decomposition peak temperature (from 247.0 to 174.8 °C) and activation energy (from 165.5 to 115.3 kJ/mol). The exceptional performance of 3D HOPC could be attributed to its well-connected 3D hierarchically ordered porous structure, high surface area, and the confined CL-20 nanocrystals. This work clearly demonstrates that 3D HOPC is a superior catalyst for CL-20 thermal decomposition and opens new potential for further applications of CL-20 in solid propellants.