Campbell Laird(Dept. of Materials Science & Engineering
,
University of Pennsylvania
,
Philadelphia
,
PA 19104-6272
,
USA)Pedro Peralta(Center for Materials Science
,
Los Alamos National Laboratory
,
MaU Stop K765
,
Los Alamos
,
NM 87545-0001
,
USA)
材料科学技术（英文）
The mechanisms of fatigue crack propagation are breifly reviewed in relation to Professor McClintock's contributions to the early development of the field. The most securely established understanding has been obtained for those mechanisms of propagation involving plasticity-inducedgeometrical changes to the crack tip during tensile and compressive straining (the plastic blunting process). The roles of more complex factors in controlling the kinetics of crack propagation,which cause the magnitude of the Paris exponent to exceed 2, remain to be elucidated. Recentlyobtained results revealing the interconnection between the slip behaviour at the crack tip, theplastic blunting process and the dislocation structures present in the material before the crackencounters them are reported.
关键词:
WU Chuansong
,
CAO Zhenning
,
WU Lin Harbin Institute of Technology
,
Harbin
,
China
金属学报(英文版)
A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China
关键词:
KEY WORDS TIG weld pool
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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
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
International Journal of Hydrogen Energy
Various carbon additives were mechanically milled with LiBH(4)/MgH(2) composite and their hydrogen storage behaviors were investigated. It was found that most of the carbon additives exhibited prominent effect on the host material. Among the various carbon additives, purified single-walled carbon nanotubes (SWNTs) exhibited the most prominent effect on the kinetic improvement and cyclic stability of Li-Mg-B-H system. Results show that LiBH(4)/MgH(2) composite milled with 10 wt.% purified SWNTs additive can release nearly 10 wt.% hydrogen within 20 mm at 450 degrees C, which is about two times faster than that of the neat LiBH(4)/MgH(2) sample. On the basis of hydrogen storage behavior and structure/phase investigations, the possible mechanism involved in the property improvement upon carbon additives was discussed. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
关键词:
Hydrogen storage;Lithium borohydride;MgH(2);Carbon;Mechanical;milling;arc-discharge method;libh4;nanotubes;composites;hydride
