Jinpeng Shen

Highly exothermic and superhydrophobic Mg/fluorocarbon core/shell nanoenergetic arrays.

Mg/fluorocarbon core/shell nanoenergetic arrays are prepared onto silicon substrate, with Mg nanorods as the core and fluorocarbon as the shell. Mg nanorods are deposited by the glancing angle deposition technique, and the fluorocarbon layer is then prepared as a shell to encase the Mg nanorods by the magnetron sputtering deposition process. Scanning electron microscopy and transmission electron microscopy show the core/shell structure of the Mg/fluorocarbon arrays. X-ray energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy are used to characterize the structural composition of the Mg/fluorocarbon. It is found that the as-prepared fluorocarbon layer consists of shorter molecular chains compared to that of bulk polytetrafluoroethylene, which is proven beneficial to the low onset reaction temperature of Mg/fluorocarbon. Water contact angle test demonstrates the superhydrophobicity of the Mg/fluorocarbon arrays, and a static contact angle as high as 162° is achieved. Thermal analysis shows that the Mg/fluorocarbon material exhibits a very low onset reaction temperature of about 270 °C as well as an ultrahigh heat of reaction approaching 9 kJ/g. A preliminary combustion test reveals rapid combustion wave propagation, and a convective mechanism is adopted to explain the combustion behaviors.

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.

Bottom‐Up Fabrication of Single‐Layered Nitrogen‐Doped Graphene Quantum Dots through Intermolecular Carbonization Arrayed in a 2D Plane

A single-layered intermolecular carbonization method was applied to synthesize single-layered nitrogen-doped graphene quantum dots (N-GQDs) by using 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as the only precursor. In this method, the gas produced in the pyrolysis of TATB assists with speeding up of the reactions and expanding the layered distance, so that it facilitates the formation of single-layered N-GQDs (about 80 %). The symmetric intermolecular carbonizations of TATB arrayed in a plane and six nitrogen-containing groups ensure small, uniform sizes (2-5 nm) of the resulting products, and provide high nitrogen-doping concentrations (N/C atomic ratio ca. 10.6 %). In addition to release of the produced gas, TATB is almost completely converted into aggregated N-GQDs; thus, relatively higher production rates are possible with this approach. Investigations show that the as-produced N-GQDs have superior fluorescent characteristics; high water solubility, biocompatibility, and low toxicity; and are ready for potential applications, such as biomedical imaging and optoelectronic devices.

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.

Microstructured Al/Fe2O3/Nitrocellulose Energetic Fibers Realized by Electrospinning

At present, metastable intermolecular composites (MICs) have been widely studied for their potential in high-density energetic materials and nanotechnology, but the relatively low-pressure discharge in a short period of time and the oxidation of Al powders have seriously impeded their applications in rocket solid fuels and explosives. In this work, the authors successfully fabricated microstructured Al/Fe2O3/nitrocellulose (Al/Fe2O3/NC) fibers via simple electrospinning, introducing nitrocellulose (NC), a gas generator to MICs. In view of previous reports, wrapping nAl in NC fibers might reduce their further oxidation during storage. In addition, the thermal properties and elastic modulus of NC fibers were measured before and after adding Al/Fe2O3.

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).