Weidong Wu

Three-Dimensional Macroassembly of Sandwich-Like, Hierarchical, Porous Carbon/Graphene Nanosheets towards Ultralight, Superhigh Surface Area, Multifunctional Aerogels.

A new, ultralight, superhigh surface area, multifunctional aerogel, which is macroassembled from sandwich-like, hierarchical, porous carbon/graphene nanosheets, is described. The multifunctional aerogel was characterized by means of XRD, SEM, TEM, Raman spectroscopy, and UV/Vis absorption spectroscopy. The multifunctional aerogel had an ultralow density of 8u2005mgu2009cm(-3) and a superhigh surface area of 2650u2005m(2) u2009g(-1) . The multifunctional aerogel was thermal stability and compressible. Meanwhile, the multifunctional aerogel exhibited high capacity for the adsorption of oils and organic solvents, unexpectedly high hydrogen adsorption and good electrochemical performance.

Efficient generation and transportation of energetic electrons in a carbon nanotube array target

Laser-driven energetic electron propagation in a carbon nanotube-array target is investigated using two-dimensional particle-in-cell simulations. Energetic electrons are efficiently generated when the array is irradiated by a short intense laser pulse. Confined and guided transportation of energetic electrons in the array is achieved by exploiting strong transient electromagnetic fields created at the wall surfaces of nanotubes. The underlying mechanisms are discussed in detail. Our investigation shows that the laser energy can be transferred more effectively to the target electrons in the array than that of in the flat foil due to the hole structures in the array.

Facile fabrication of ultra-low density, high-surface-area, broadband antireflective carbon aerogels as ultra-black materials

Carbon aerogels with various densities, even as low as 20xa0mg/cm3, were fabricated by pyrolysis of organic aerogels formed by aqueous condensation of resorcinol and formaldehyde. It was found that carbon aerogels with the density below 70xa0mg/cm3 exhibited the total reflectance values of typically less than 0.24xa0% across wavelengths in the range of 400–2000xa0nm. The change of antireflective properties between the lowest-density carbon aerogel monolith and its powder coating was discussed. Furthermore, we studied the effect of the density on the structure and antireflective property of carbon aerogels. As a result, the low-density carbon aerogels showed broadband low-reflectivity and high absorption to incident light.

Fabrication of Graphene-Based Nanostructured Thin Films with Mid-Infrared Photoresponse Properties

Graphene shows great potential as an advanced building block for fabricating varied graphene based nanostructured films together with other metal and metal oxide nanomaterials. In the current work, a new approach was developed to fabricate flexible, transparent conductive films via layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxide (RGO) nanosheets. We further fabricated transparent conductive hybrid films via LbL assembly of oppositely charged RGO nanosheet and platinum (Pt) nanoparticle as well as silica (SiO2) nanoparticle. It was found that the graphene based nanostructured films showed different mid-infrared photoresponse properties. Moreover, the photoresponse performance could be manipulated by the power and distance between two electrodes.

The collimation of intense relativistic electron beams generated by ultra-intense femtosecond laser in nanometer-scale solid fiber array

A scheme to collimate the ultra-intense laser generated MeV electrons by nanometer-scale solid fiber array is proposed. Unlike previous resistivity-structured target schemes, not the magnetic field but the electric field due to the anisotropic resistivity acts to collimate the divergent fast electrons. This concept is well supported by analytical estimation and numerical calculation. The measurements of collimated MeV electron beams at rear of carbon nanotube arrays irradiated by intense femtosecond laser show the viability of this scheme. These results indicate that potential applications include radiography, fast electron beam focusing, and perhaps the electron collimation for fast ignition of inertial confined fusion.

Fabrication of Ultra-Low Density, High Surface Area Carbon Aerogels and their Application in Supercapacitors

The ultra-low density carbon aerogel, as low as 20 mg/cm3, was fabricated by pyrolysis of the organic aerogel formed by aqueous condensation of resorcinol and formaldehyde. Its surface area was as high as 1783 m2/g and it was used for investigation of electrochemical capacitive behaviours. The ultra-low density carbon aerogel displayed capacitive performance (110 F/g at 0.2 A/g) in 6 M KOH aqueous solution. Additionally, over 98% of the initial capacitance was retained after repeating the cyclic voltammetry test for 1000 cycles. The electrochemical performance might be attributed to the combination of three dimensional “opened” structure and high surface area of the carbon aerogel.

Influence of annealing temperature on microstructures and resistivity of FexAl1-x films

In this paper, FeXAl1-X films have been deposited on silicon substrates using electron beam evaporation, which have been not reported to prepare FeXAl1-X films before. Subsequently, the films were annealed in vacuum better than 3×10-4Pa for 1 hour at 100°C, 280°C, 330°C, 450°C and 500°C, respectively. Electrical resistivities of the samples were been measured by four point probe, and microstructures of the samples were characterized by X-ray diffraction(XRD). The results show that, the resistivity of films reduces gradually with increasing of the annealing temperature, and the structure of films can be improved after annealing. In addition, the resistivity of film reduces gradually with increasing thickness and comes closed to the that of bulk when the film thickness becomes thicker than 100nm.

The influence of the substrate temperature variation on FexAl1-x thin films deposition

FexAl1-x thin films had been prepared on Si (100) substrates by electron beam evaporation. The substrate temperature was varied from room temperature to 450°C at an interval of 100°C. The crystalline orientation of deposited FexAl1-x thin films had been characterized by X-ray diffraction (XRD) and the thickness was measured by Atomic profiler. The results show that the crystalline orientation of FexAl1-x thin films depends on the substrate temperature. The thin films are crystal at different substrate temperatures. The deposition rate becomes bigger from 30°C to 250°C and smaller from 250°C to 450°C. The surface morphology of deposited FexAl1-x thin films had been investigated by atomic force microscopy (AFM). The results show that the surface roughness increases with increasing the substrates temperature to 450°C.

Fabrications of Metallic Oxide Doped Polystyrene Shells via Emulsion Techniques

Abstract New-type metallic oxide (M2O3 M = Cr, Al) doped plastic shells used for inertial confinement fusion experiments are fabricated with emulsion techniques. Three different phases of solution (W1, O, and W2) are adopted for the fabrication process. The W1 phase is 1 wt% of sodium lauryl sulfate in water. The W1 phase solution is mixed with a 3 wt% M2O3-PS solution in benzene-dichloroethane (O phase) while stirring. The mixed emulsion (W1/O) is then poured into a 3 wt% aqueous polyvinyl alcohol solution (W2 phase) while stirring. The resulting emulsion (W1/O/W2) is heated to evaporate benzene and dichloroethane, and thus, a solid M2O3-PS shell is formed. The diameter and wall thickness of the shells are 300 and 5 μm, respectively. The average surface roughness of the final products is <30 nm. Other parameters, uniformity and sphericity, are 98.9 and 99.6%, similar to or better than that of the usual PS shells.