Advanced Materials Research Vols. 284-286

Abstract: In this paper, a rapid, facile and green strategy — electron beam irradiation has been developed to prepare CdSe nanoparticles. 10 mA GJ-2-II electronic accelerator was applied as radiation resource. CdSe nanoparticles were synthesized using NH₃ as complexing agent by electron beam method in a colloid system, which used Cd(Ac)₂ and Na₂SeO₃ as raw materials. Nanocrystalline CdSe was prepared rapidly at room temperature under atmospheric pressure. The structure and morphology of prepared CdSe nanoparticles were analyzed by X-ray diffraction and transmission electron microscopy. UV–vis spectroscopy (U-3010, Japan Hitachi) and photoluminescence spectroscopy (PL, F-7000, Japan Hitachi) were used to investigate the optical properties of the CdSe nanoparticles. The effects of radiation dose on the formation of CdSe nanocrystallines were discussed. The possible mechanism of the CdSe grain growth by electron beam irradiation method was proposed.

Abstract: The growth of carbon nanofibers (CNFs) with ordered macroscopic structures could be achieved by CVD technique. Silica fiber, alumina fiber, and AAO membrane were selected as the typical ordered macroscopic substrates for CNFs growth. It turned out that silica fiber could act as the promising and effective substrate for CNFs growth on its surface. While alumina fiber and AAO membrane could also be expected to act as the potential substrates for CNFs growth on their surface.

Abstract: CuO-CoO-MnO/SiO2 nanocomposite aerogel as catalysts carrier was prepared via sol-gel process and CO₂ supercritical drying (SCD) technique. Catalyst supported by the nanocomposite aerogel was prepared via impregnation method. The catalyst was used for the synthesis of diphenyl carbonate (DPC), and the yield of DPC in mass is up to 26.31%. The catalysis system of PdCl₂/Co(OAc)₂-Cu(OAc)₂-Mn(OAc)₂/TBAB/H₂BQ is favorable to the synthesis of DPC. PdCl₂, acetates of transition metals and H₂BQ were the key catalyst, inorganic cocatalyst and organic cocatalyst, respectively. TBAB was the surface active agent of Pd⁰ and stabilizer of Pd²⁺ in the catalysis system.

Abstract: In this paper, we discuss the theory research and testing methods of a grating coupler. The grating coupling efficiency of parameters and the corresponding theoretical simulation was studied systematically. Meanwhile, the coupling efficiency in theory can be improved to 76% using an optimized grating design. The fabrication of the couplers in silicon-on-insulator is focusing on ion beam method (FIB). Using the tunable NewFocus laser with an adjustable extent of 1520~1570nm as the sources, Si waveguide grating is achieved vertical coupler through coupling a single-mode fiber with the diameter of 10.4. In the experiment, when the input wavelength is 1550nm, the maximum coupling efficiency is measured approximately 31% and 1 dB bandwidth is approximately 30 nm.

Abstract: Novel doughnut-like loop structures of silicon oxynitride were grown over a Si substrate via self-assembly of ordered nanowires. These hierarchical structures were formed by metallic gallium-catalyzed vapor-liquid-solid growth at high temperature under a flow of NH₃ gas. The product was characterized by XRD, SEM, EDS mapping and XPS techniques. XRD characterization confirms the formation of Si₃N₄ and silicon oxynitride phases. The silicon oxynitride loop structures assembled by ordered nanowires have outer diameters of 10-14 mm and wall thickness of 2-3 mm. The nanowire bundles in a single loop exhibit a petal-like growth mode. EDS mapping verifies the elemental distribution over the structure. XPS analyses disclose the binding contribution from Si₃N₄, silicon oxynitride and silicon oxide. The formation mechanism of the self-assembled structures was analyzed based on the growth process.

Abstract: Manganese tungstate nano-particles were successfully synthesized at low temperatures by molten salt method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet visible spectra techniques (UV-vis), respectively. The effects of calcining temperatures and salt quantity on the crystallization and development of MnWO₄ crystallites were studied. Experimental results showed that the well-crystallized MnWO₄ nano-particles with about 40 nm in diameter could be prepared at 270°C with 3:1 mass ratio of the salt to MnWO₄ precursor for a holding time of 4 h. XRD analysis evidenced that the product was a pure monoclinic phase of MnWO₄ with wolframite structure. UV-vis spectrum revealed that MnWO₄ nano-particles had strong light absorption properties in both ultraviolet and visible light region.

Abstract: The 0.4mol•L^-1CuSO₄ liquor and 5mol•L^-1NaOH liquor were prepared by CuSO₄·5H₂O and NaOH as raw materials. The Cu₂O powders were prepared by dextrose reducer and PVP dispersant. The Cu₂O oxidation reaction DTA-TG-DTG curves were obtained by SDT 2960 simultaneous DSC-TGA analysis apparatus. The mensuration condition were that rise temperature velocity 15°C·min^-1 and deoxidize gas air. The Cu₂O oxidation reaction kinetics was calculated by DTA-TG-DTG curves data. The results indicate that the cuprous oxide powders shape were spherical, their particle’ sizes were 100,200,1000nm. Their apparent activation energy were 164.38, 175.54, 282.65 KJ·mol^-1, the apparent activation energy increase with Cu₂O particle’ size. Their frequency factors were 1.22×10¹³, 1.40×10¹³, 2.88×10²⁰, the frequency factors increase with particle’ size Cu₂O. Their reaction progressions were 1.02, 1.00, 0.96, the reaction progression increase with Cu₂O particle’ size decreased.

Abstract: Nanocrystalline MgCr₂O₄ with a crystal size of about 20nm is synthesized by citrate sol-gel process, which is characterized by X-ray diffraction (XRD), thermogravimetry coupled with differential thermal analysis (TG-DTA) and field emission scanning electron microscopy (FE-SEM). The initial crystallization temperature of MgCr₂O₄ spinel was at about 550°C, whereas that of the fully crystallized magnesium chromate spinel appeared at about 600°C. The crystal grain size increases with the annealing temperature and holding time.

Abstract: Monophasic orthorhombic InVO₄ was synthesized using InCl₃ and NH₄VO₃ as starting materials by a hydrothermal approach. The as-prepared InVO₄ product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectroscopy (DRS). It was found that the as-prepared InVO₄ shows strong visible-light absorption with absorption onset of 515 nm, indicating a narrow optical band gap of 2.4 eV. Furthermore, the as-prepared InVO₄ shows high visible-light photocatalytic activity for decomposition of methyl orange, which is ascribed to the strong visible-light absorption.

Abstract: TiO₂ nanocrystalline powders with high specific area were prepared using urea as the template by the sol-gel method. The samples were characterized by X-ray diffraction, N₂ adsorption isotherms, and transmission electron microscopy. Urea plays a key role in the preparation process of TiO₂ nanocrystalline powders. Large amounts of small urea aggregates were formed in the sol-gel process and decomposed during the calcination process, which results in the formation of large amounts of mesopores. Urea also inhibits the agglomeration and growth of the TiO₂ nanoparticle, which facilitates the preparation of a TiO₂ powder with smaller nanocrystal size. The above effects of urea may be the main reason of the as-prepared sample with very high specific surface area.