Advanced Materials Research Vols. 535-537

Abstract: Different morphologies of molybdenum trioxide have been synthesized via low-temperature liquid phase method, hydrothermal synthesis and the direct decomposition method. Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to characterize the as-synthesized products and the photo catalytic degradation properties were studied for different nitrogen of dyes. The results indicate that the discoloration rate of methylene red was the best and it could be more than 90 percent in the same conditions. Therefore, the synthesized MoO3 powder is a kind of photocatalayst with excellent performance.

Abstract: Silver selenide nanopowder was prepared by a room temperature conversion method, in which selenide powder(Se) and ethylenediamine (NH₂CH₂CH₂NH₂) were used as precursors. Chemical mechanism were studied by several comparative experiments. It was found that chemical reaction was taken place between Se and Ag ions through ethylenediamine. The influence of the chemical reaction time on the phase and microstructure was investigated. The results showed that the reaction was not completely if the reaction time was lower than 4h, on the contrary, some plane begin to split if the reaction time was longer than 12h. While the size and lattice parameter increase firstly with increasing time and then reduce. The results were discussed and the optimum condition was obtianed.

Abstract: A fully dense nanocrystalline Ni-Co alloy with 18 nm grain size exhibited high strength of about 2200 MPa and ductility of 8.19.2% at strain rates of 1.04×10-5 to 1.04 s-1 and room temperature. The alloying of Co element induces the grain refinement, solid solution hardening and decrease of stacking fault energy should contribute to the favorable combination of mechanical performance. The obvious distinctions of fracture-surface morphologies with strain rate alteration were attributed to underlying deformation mechanism transition. The high strain rate sensitivity exponent and small activation volume indicate that grain boundary activity may be expected in this alloy.

Abstract: Magnesium oxychloride (MOC,5Mg(OH)2•MgCl2•8H2O,phase 5) nanowhiskers were synthesized via a reverse microemulsion method by suing cetyltrimethyl ammonium bromide (CTAB)/n-butanol (C4H10O)/cyclohexane (C6H12)/water as soft-template. Aqueous solution of magnesium chloride (MgCl2) and MgO powder were suing as reactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Results indicated that MOC nanowhiskers can be obtained when the mass ratio of MgO, magnesium chloride hexahydrate and water is 1:1:0.64. The aspect ratio of MOC nanowhisker is more than 100 with an average diameter of 50-90 nm. The influence of size of MgO particles and mass ratio of MgCl2 solution to CTAB on morphology of whiskers was investigated. The growth mechanism of the MOC nanowhisker was also supposed in this study.

Abstract: Metal assisted chemical etching of heavily doped p-type Si(100) wafer was investigated in a solution containing HF and hydrogen peroxide using Pt nanoparticles as catalyst. The Pt nanoparticles were formed on Si(100) substrate by magnetron sputtering and post-deposition annealing. In a solution containing low concentration HF, formation of cylindrical nanoholes are unstable in the early stage of the etching process. After that, nanoholes with diameters ranging from 40 to 50 nm are stably formed in silicon substrate and the calculated growing rate is 60 nm/min. Instead, in a solution containing high concentration HF, cylindrical nanoholes with a diameter of about 10 nm can be stably produced in silicon substrate all the time and the growing rate is increased to as fast as 160 nm/min. In both cases, no Pt nanoparticles are observed at the bottom of the nanoholes. Finally, the underlying mechanisms of the aforementioned phenomena are also discussed.

Abstract: The highly ordered silver nanowire arrays were fabricated successfully by an easily produced and handled approach with the assistance of nanoporous anodized aluminum oxide(AAO) template. The silver nanowires with uniform diameters are highly ordered and parallel to each other. A broad UV-visible absorption band with a center at 401nm of silver nanowire arrays were detected. Optimized surface enhanced Raman scattering(SERS) signals of crystal violet molecules(CV) were recorded. It was found that the substrate exhibits strong enhancement properties due to the surface plasma resonance(SPR) of highly ordered silver nanowire arrays. The enhancement factor was calculated as 3.5×106. In addition, the results offered a simple technique in preparing highly ordered nanowire arrays which can be used as negative-refractive-index material as well as excellent SERS substrate.

Abstract: A facile one-pot hydrothermal synthesis approach has been developed to prepare hierarchical and well-defined cobalt sulfide nanostructures. Different solvents (methanol, ethanol, glycol, propyl alcohol and butyl alcohol) were applied to investigate the influence of solvent on the morphologies evolution procedures. Morphologies such as sphere-, cube-, flake-like cobalt sulfide structures can be obtained, the surface appearance of the cobalt sulfide nanostructure also can be controlled by changing the solvent. The as-prepared products were characterized by Field-emission scanning electron microscope and the influence of different kinds of alcoholic solvents on the hierarchical CoS nanostructures was studied. It can affect the electrochemical capacitance performances directly and may have a potential application in electrical fields.

Abstract: Novel K2Ti6O13 nanobelts, as one-dimensional nanomaterials, were synthesized by a simple hydrothermal method at 200°C for 12h, using TiO2 nanoparticles and KOH aqueous as raw materials. The crystal structure and morphology of K2Ti6O13 nanobelts were characterized by a series of methods including XRD, FESEM, EDS, TEM and HRTEM. The results indicated that K2Ti6O13 nanobelts synthesized were single crystals. The typical width is about 5-10nm and the length is in the range of from hundreds of nanometers up to tens of micrometers. The novel structure exhibits excellent flexibility. From the experimental results, it can be concluded that well crystallized and single phase K2Ti6O13 can be obtained under the certain temperature and KOH concentration. The size of TiO2 nanoparticles has an effect on the hydrothermal reaction rate and morphology control of the products.

Abstract: Well-defined ZnO nanostructures and their self-assembly have been fabricated directly on Zn foil via a hydrothermal synthesis method. (NH4)2S2O8 was introduced as the controllable reagent for the growth of ZnO. Nanorod-, nanowire- and nanobranch-like ZnO can be easily prepared. The experiment results indicated that the zinc oxide morphology and thier self-assemblied structures can be controlled by changing the reaction conditions. The effects of the concentration of NaOH, reaction temperature on the morphology of these nanostructures were investigated, and the possible mechanism of the ZnO nanostructures was proposed.

Abstract: In this report, the polyol process was used for preparing silver nanowires. In this improved method, the silver nanowires with high purity, high yield and high sensitive surface enhanced Raman scattering (SERS) activity were synthesized mainly by sealed heating. Then the samples were characterized by scanning electron microscopy (SEM). Its optical absorption properties were measured by UV-Vis spectrophotometer; furthermore, SERS spectra of R6G molecule on the single nanowire was obtained and systematically studied by excitation wavelength 532nm. Our experimental results showed that the length of nanowires by our improved method is uniform and has high yield, high purity and higher SERS enhancement effect. The UV-Vis absorption spectrum of the samples displayed the transverse and longitudinal plasma resonance (SPR) absorption bands of silver nanowires which are located at 358nm and 416nm, respectively. Also single nanowire SERS activities which are dependent on the different substrates were researched.