P.X. Yan

Nanoparticles and 3D sponge-like porous networks of manganese oxides and their microwave absorption properties.

Hydrohausmannite nanoparticles (approximately 10 nm) were prepared by the hydrothermal method at 100 degrees C for 72 h. Subsequent annealing was done in air at 400 degrees C and 800 degrees C for 10 h, Mn(3)O(4) nanoparticles (approximately 25 nm) and 3D Mn(2)O(3) porous networks were obtained, respectively. The products were characterized by XRD, TEM, SAED and FESEM. Time-dependent experiments were carried out to exhibit the formation process of the Mn(2)O(3) networks. Their microwave absorption properties were investigated by mixing the product and paraffin wax with 50 vol%. The Mn(3)O(4) nanoparticles possess excellent microwave absorbing properties with the minimum reflection loss of -27.1 dB at 3.1 GHz. In contrast, the Mn(2)O(3) networks show the weakest absorption of all samples. The absorption becomes weaker with the annealing time increasing at 800 degrees C. The attenuation of microwave can be attributed to dielectric loss and their absorption mechanism was discussed in detail.

Copper nitride thin film prepared by reactive radio-frequency magnetron sputtering

Copper nitride (Cu3N) thin films were deposited on glass substrates by reactive radio-frequency magnetron sputtering of a pure copper target in a nitrogen/argon atmosphere. The deposition rate of the films gradually decreased with increasing nitrogen flow rate. The color of the deposited films was a reddish dark brown. The Cu3N films obtained by this method were strongly textured with crystal direction [100]. The grain size of the polycrystalline films ranged from 16 to 26 nm. The Hall effect of the copper nitride (Cu3N) thin films was investigated. The optical energy gap of the films was obtained from the Hall coefficient and found to vary with the nitrogen content. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. The copper nitride thin films are unstable and decompose into nitrogen and copper upon heat treatment when annealed in vacuum with argon protected at 200 °C for 1 h.

Fabrication, structure, magnetic properties of highly ordered cobalt disulfide nanowire arrays

Highly ordered arrays of parallel CoS2 nanowires with a diameter of about 50 nm and a length up to about 50μm were synthesized by two electrical fields in an anodized aluminum oxide film. In this letter, fabrication, structure, magnetic properties of highly ordered magnetic cobalt disulfide nanowires arrays were studied. Also, a growth mechanism has been speculated.

Structure and Properties of Cobalt Disulfide Nanowire Arrays Fabricated by Electrodeposition

Highly ordered arrays of parallel cobalt disulfide nanowires with a diameter of about 40 nm and a length up to several tens of micrometers were synthesized by two electrical fields in an anodized aluminum oxide film. The cobalt disulfide nanowires have a cubic pyrite structure. In the study of electrochemical properties, it is found that the reaction of cobalt disulfide is an intercalation reaction in the range of 1.6-3.0 V, while a redox reaction in the range of 0.02-1.6 V is probable. The CoS 2 nanowires are ferromagnetic and the easy magnetization direction is along the nanowire axes.

Characterization of the single crystalline iron sulfide nanowire array synthesis by pulsed electrodeposition

Magnetic material Fe7S8 nanowire arrays have been successfully synthesized by pulsed electrodeposition in porous anodized aluminum oxide template. X-ray diffraction results show that the as-synthesized nanowires are single crystalline and have a highly preferential orientation. Scanning electron microscopy and transmission electron microscopy observations indicate that the ordered Fe7S8 nanowire arrays are uniform with a diameter of 50nm and length up to several tens of micrometers. The temperature variation of the magnetic properties has also been studied.

Overgrowing single crystalline ZnB2O4 on multiwall carbon nanotubes: Straightening the curly tubes

Single crystals of ZnB2O4 have been grown from a supercooled molten ZnO-B2O3 system on multiwall carbon nanotubes. Transmission electron microscopy investigations indicated that the originally curly carbon nanotubes were well straightened after the single-crystal coating. The coating and straightening mechanism are discussed.

Study on the structure, morphology and properties of Fe-doped Cu3N films

Fe-doped Cu3N films were prepared by cylindrical magnetron sputtering equipment at room temperature. The doping of Fe with the proper concentration results in a change in the preferred growth orientation from the Cu-rich plane (1 1 1) to the N-rich plane (1 0 0), which relates to the evolution of the surface grain shape from pyramid to sphere. Excessive doping of Fe is not favourable for the crystallization of Cu3N films. The cross-sections of the doped films with preferred growth orientations of [1 0 0] exhibit regular columnar grains. The variation between the lattice constant and the XPS results reveals that Fe probably replaces the position of Cu atoms in the lattice or is segregated in the grain boundaries. Weaker bonding of Cu–N results in a reduction of thermal stability for Fe-doped Cu3N films. And the incorporation of Fe can effectively modify the energy gap. According to the variations in the mean grain size, the peak of N1s and the energy gap, it is inferred that a doping limitation exists around 2.0 at%.

Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction (XRD), BET equation, transmission electron microscopy (TEM), and the corresponding selected area electron diffraction (SAED). The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11m^2/g, the particle size distribution is 30 to 90nm, and the average particle size is about 67nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.

Processing parameters for Cu nanopowders prepared by anodic arc plasma

Abstract Copper nanopowders were successfully prepared by anodic arc discharging plasma method with home-made experimental apparatus. The effects of various processing parameters on the particle size of Cu nanopowders were investigated in the process, and the optimum processing parameters were obtained. In addition, the morphology, crystal structure, particle size distribution of the nanopowders were characterized via X-ray diffraction(XRD), transmission electron microscopy(TEM) and the corresponding selected area electron diffraction(SAED). The experimental results show that the crystal structure of the samples is the same fcc structure as that of the bulk materials. The processing parameters play a major role in controlling the particle size. The particle size increases with the increase of the arc current or gas pressure.

A comparative study of the properties of TiN films deposited by MAIP and FCAP

Abstract In this study two types of TiN films were prepared, one using the filtered cathodic arc plasma (FCAP) technique with an in-plane “S” filter, and the other using the multi-arc ion-plating (MAIP), and both deposited under the same parameters. Comparisons of the texture, hardness, roughness, tribological and electrochemical corrosion behaviors of the two types of TiN films were given. The TiN films obtained by the FCAP technology were found to be highly uniform, smooth and macroparticle-free. The TiN films deposited by FCAP had a (111) preferred orientation, while there was no texture in the films deposited by MAIP. Under low load the two kinds of TiN coatings had very different wear mechanisms; the films of FCAP had a lower wear rate and friction coefficient compared with the TiN films deposited by the MAIP technique. The dense and hole-free structure of TiN films of FCAP could effectively avoid the avalanche of TiN films from the substrate during corrosion tests.