Papers by Keyword: Bulk

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Authors: Ludovic Charpentier, Francis Baillet, Didier Chaussende, Etienne Pernot, Michel Pons, Roland Madar
87
Authors: Frédéric Mercier, Shin Ichi Nishizawa
Abstract: We investigated with ab initio calculations the 3C-, 6H-, 4H- and 2H-SiC polytypes. We discuss the geometry and the energetics of bulk and surface relaxed structures ((0001) Si face and the (000-1) C face surfaces). The polytype stability is discussed regarding the bulk and surface effects.
41
Authors: Jozef Miškuf, Kornel Csach, Alena Juríková, Mária Huráková, Martin Miškuf, Elena D. Tabachnikova
Abstract: In metallic glasses plastic deformation occurs via the creation and the propagation of a softened region in the shear bands. Some of the high strength metallic glasses (as Zr-based metallic alloys) exhibit complex shear band topography and the final failure respects the allocation of the shear bands. We studied the differences in the fracture surfaces of Zr-and Mg-based amorphous alloys. Ductile behaviour of the shear bands in Zr-based amorphous alloy tends to the dimple creation during the failure. On the fracture surfaces the vein pattern morphology manifestations were present. Conchoidal fracture was typical for Mg-based amorphous glass. Two different surface morphologies, plumes and rib marks ornament the fracture surfaces.
504
Authors: Wei Bo Guan, Xiao Ying Zhang
Abstract: The denier of raw silk is enlarged by selected high denier cocoon silk and combined silk filament. The silk impregnating agent was mixed with hot water in order to enhance the softness of silk when reeling silk. After reeling, the silk and polyester partially oriented yarn(POY)were combined and textured by mechanical force and heat, and the silk multifilament with physic mechanical and geometric distortion was produced. Several silk multifilaments were fed together into the yarn carrier of coarse V-bed flat machine and grey cloth was knitted. The silk knitting fabrics with coarse style were produced through refining and drying. Such fabric, which bulkiness, elasticity and drapability are excellent, is suitable for kinds of knitting outer wear.
284
Authors: Frédéric Mercier, Shin Ichi Nishizawa
Abstract: We investigated numerically fluid dynamics and carbon transport in a 2 inches SiC solution growth with the presence of alternative magnetic fields. Buoyancy and Marangoni convection are taken into account. Our numerical results revealed that the magnetic field parameters have a strong impact on the melt convection. We also propose a solution to increase the mass transfer at the crystal growth front.
32
Authors: Akari Fujii, Yoshihisa Kimoto, Shin Wakayama, Yorinobu Takigawa, Tokuteru Uesugi, Kenji Higashi
Abstract: Many studies have been conducted on mechanical properties in nanocrystalline Ni-W alloys. However, since these results are obtained in the specimens whose thickness is less than 100 μm and whose homogeneity is not strictly controlled, an inherent potential of the nanocrystalline Ni-W alloy may be hidden. Therefore, it is necessary to fabricate the bulk Ni-W alloy with sufficient thickness and homogeneity. In the present study, we develop novel electroforming process and fabricate the homogeneous nanocrystalline Ni-W alloys. The homogeneities of W-concentration in micrometer scale are confirmed by the W-concentration profiles obtained by the linear analyses of the energy dispersed spectroscopy (EDS). The single-phase nanocrystalline bulk Ni-W alloy with the thickness above 2 mm and minimized W-concentration gradient and fluctuation is featured for the first time.
691
Authors: Shin Wakayama, Yoshihisa Kimoto, Yorinobu Takigawa, Tokuteru Uesugi, Kenji Higashi
Abstract: A 2mm-thick bulk amorphous Ni-W alloy is formed by applying a new electroforming process and its states are investigated by the XRD analyses and the EDS measurement. The homogeneities of the electroformed alloys are evaluated by the linear analyses on the cross sections of the sample. The fluctuation of the millimeter-scale W-concentration of the bulk amorphous alloy obtained in the present work is reduced to almost the same as that of the bulk nanocrystalline alloy reported in the previous work. Compared to the thin-film specimen produced by the conventional electroplating processes, the gradient of W-concentration of the bulk amorphous specimen can be reduced to two-fifth in the micrometer-scale profiles. Therefore new electroforming process can be successfully applied to the fabrication of the bulk amorphous Ni-W alloy.
1375
Authors: Bin Lu, Dan Qing Yi, Biao Yan, Jun Lin Yin, Yan Liu, Hui Qun Liu, Biao Li Wu, Xiao Li Chen
Abstract: Mechanical alloying(MA) technique and single-roller melt spinning technique were used to prepare Fe86Zr5.5Nb5.5B3 nanocrystalline and amorphous powders, bulk alloys were prepared by cryogenically high-pressure quick sintering. The results showed that: (1) after MA process for 15 hours, the grain size of α-Fe phase was ≤10nm; (2) melt spinning powders were fragmented by ball milling, but remained amorphous state. The crystallization temperature of this amorphous powder was about 500°C. Apparent activation energy of the amorphous crystallization was E=294.1KJ/mol; (3) under the quick sintering conditions of P=5.5GPa/t=3min/Pw≥1050W, single phaseα-Fe nanocrystalline(8~15nm) bulk alloys with relative density≥98.7% can be obtained.
3467
Authors: Jozef Miškuf, Kornel Csach, Alena Juríková
Abstract: The main limitation of bulk metallic glasses for their application as structural materials is the large brittleness under the external loading. We analyzed the failure characteristics of Co43Fe20Ta5.5B31.5 (at.%) bulk metallic glass deformed in a compression at the room temperature and a low strain rate. Under loading the amorphous structure can store high elastic energy. During the failure this energy is released and the alloy breaks into small particles or powder exhibiting a fragmentation mode. The nanoscale fracture surface morphology respects the micromechanisms of failure of the amorphous structure. The fracture surface consists of a smooth mirror cleavage zone and a river pattern zone with the nanosized dimples arranged in lines respecting the periodic corrugation zones oriented perpendicular to the crack propagation direction.
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Authors: Gabriel Ferro, Carole Balloud, Sandrine Juillaguet, Patrice Vicente, Jean Camassel, Yves Monteil
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