材料期刊网

SYNTHESIS OF INTERMETALLICS BY MECHANICAL ALLOYING

F. H.(Sam) Froes , C. Suryanarayana , and D. Mukhopadhyay (Institute for Materials and Advanced Processes (IMAP) , University of Idaho , Moscow , ID 83844-3026 , USA)C-G. Li(BlM , P.O. Box 81 , Beijing , 100095 , P.R. CHINA)K. Brand(On leave from Institut fur Werkstoffwissenshaft , Technische Universitst Dresden , 07062 Dresden , Germany , at IMAP)

金属学报(英文版)

Mechanical alloying (MA), a solid-state powder processing method, is a "far from equilibrium" synthesis technique which allows development of novel crystal structures and microstructures, leading to enhanced physical and mechanical properties. The ability to synthesize a variety of alloy phases including supersaturated solid solutions, nanocrystalline structures, amorphous phases and intermetallic compounds themselves is discussed. No extension of solubility using MA has been observed in the intermetallics studied. Nanostructured grains were observed in all compositions. Long time milling generally resulted in amorphous phase formation in large part because of the increase in grain boundary energy/mole with reduced grain size; good agreement with the Miedema model for amorphization was obtained in the Al-Fe system. Generally an anneal was required to form the intermetallic after MA; however,intermetallics with a large negative enthalpy of formation were detected in the MA condition. A study of the hot isostatic pressing of γ-TiAl powders produced by MA demonstrated that full density can be achieved at least 400℃ below the normal temperature required for conventional powder, that is 725℃ or below. Nanometered sized grains (≤100nm)were observed after HIP'ing up to 850℃.

关键词: : Intermetallics , null , null

Nobel Prize for Our Advisor, Gerhard Ertl, Germany

催化学报

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Controlled synthesis of cobalt flowerlike architectures by a facile hydrothermal route

European Journal of Inorganic Chemistry

Cobalt flowerlike architectures composed of hexagonal nano-platelets have been synthesized by a simple hydrothermal. reduction method. The architectures are fabricated by the reaction Of COCl2 with NaOH at 140-180 degrees C in the presence of sodium dodecyl benzenesulfonate (SDBS), with NaH2PO2 center dot H2O as reducing agent. The diameters of the flowers range from 8 to 10 mu m, and the average thickness of the hexagonal sheets is about 100 nm. Higher reaction temperatures and the proper concentration of sodium hydroxide (NaOH) are key requirements for the fabrication of the flowerlike architectures. A growth mechanism for these architectures is proposed on the basis of the characterization by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The magnetic hysteresis loops at 5 K and 295 K of the cobalt flowerlike architectures show ferromagnetic characteristics with coercivities of 371 Oe and 197 Oe, respectively. Our work may shed light on the designed fabrication of complex 3D architectures of other materials. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008.

关键词: hydrothermal synthesis;cobalt;nanostructures;magnetic properties;gold nanoparticle arrays;anisotropic growth;self-organization;nanoplatelets;superlattices;nanocrystallites;superstructures;nanostructures;construction;aggregation

Hydrothermal Synthesis of Three-Dimensional Hierarchical CuO Butterfly-Like Architectures

European Journal of Inorganic Chemistry

Uniform 3D hierarchical CuO butterfly-like architectures were fabricated by a surfactant-assisted hydrothermal oriented attachment route. This route included the formation of CuO butterfly-like architectures in a solution of cupric chloride (CuCl(2)center dot 2H(2)O) and sodium hydroxide (NaOH) at 100 degrees C for 15 h by using sodium dodecyl benzenesulfonate (SDBS) as surfactant. The as-prepared CuO architecture was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The CuO butterfly-like architectures, with lengths of about 6 pm and widths of 2-4 mu m, were assembled from several tens of oriented attachment rhombic nanosheets with a thickness of about 60 nm. A growth mechanism for the formation of the CuO butterfly-like architectures was proposed on the basis of time-dependent. experiments. The synthetic parameters such as reaction temperature, the concentration of sodium hydroxide and reaction time all affected the morphology of the CuO architectures. The synthetic strategy could be extended to assemble 3D architectures of other materials. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451. Weinheim, Germany, 2009)

关键词: Hydrothermal synthesis;Copper oxide;Nanostructures;Self-assembly;large-scale synthesis;catalytic-properties;cu(oh)(2) nanowires;oriented attachment;formation mechanism;room-temperature;field-emission;hollow spheres;simple route;nanostructures