Papers by Keyword: Nano-Structured

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Authors: Daniel Salcedo, C.J. Luis-Pérez, Javier León, Rodrigo Luri, Ignacio Puertas
Abstract: ECAE process is a novel technology which allows us to obtain materials of sub-micrometric and/or nanometric grain size as a result of accumulating very high levels of plastic deformation in the presence of high hydrostatic pressure. This avoids the material being fractured and permits very high values of plastic deformation to be obtained (ε>>1). Therefore, these nanostructured materials can be used as starting materials for other manufacturing processes such as: extrusion, rolling and forging among others; with the advantage of providing nanostructure and hence improving the mechanical properties. In this present study, forging by finite element of materials that have been previously predeformed by ECAE is analysed. MSC.MarcTM software will be employed with the aim of analysing the possibility of manufacturing mechanical components (spur gears) from materials nanostructured by ECAE.
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Authors: Xiao Ping Wu
Abstract: Because of the unique optical properties, titanium dioxide (TiO2) has been widely used as a white pigment over several decades. The numerous and diverse applications of TiO2 can be found in many common products such as paints, plastics, paper, sunscreens, etc. In the past decades, the emergence of nanotechnology and the discovery of some of the key application potentials of TiO2 have spurred the enormous interests to study TiO2, particularly, nano-structured TiO2, as the functional materials. Since then, substantial advances have been made in the fabrication, characterization, fundamental understanding of TiO2 nano-materials, and their promising applications in a number of areas such as energy and environment. This review will discuss the properties of nano-structured TiO2 and highlight the recent development of their applications.
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Authors: Ge Qin, Hao Xue Li, Meng Die Ma, Juan Juan Li, Ya Fei Deng
Abstract: This paper studied the growth morphology of the cells on the nanostructured surfaces of the bio-electrodes implanted in human patients. A transition model of the cells on those surfaces, which is the W model or C-B model, was deduced according to the effect of the microstructures on the wetting characteristics and the solid-liquid contact angle models of the microstructured surface. According to the contact angle formula of the model of the droplet on the solid surface, the formula was derived to describe the morphology of the ells on the nanostructured surface. The results of the experiments showed the impact of nanostructured to the morphology of the cells. The changes of the cell morphology on the smooth surface and the nanostructured surface showed that the cell morphology was affected by the nanostructures of solid surface, and the growth shape of cell was different when the sizes were different.
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Authors: G.B. Pinto, S.R.S. Soares, Uilame Umbelino Gomes, Rubens Maribondo Nascimento, Antonio Eduardo Martinelli, José F. Silva Jr
Abstract: High-energy milling has been used for production of nano-structured WC-Co powders. During the High-Energy Milling, the powders suffer severe high-energy impacts in the process of ball-to-ball and ball-to-vial wall collisions of the grinding media. Hard metal produced from nanostructured powders have better mechanical properties after appropriate sintering process. During the milling the particles size of WC and Co can be reduced and plastic deformed. In the present work, a mixture of WC-10%Co was produced by high energy milling. The starting powders of the WC (0.87 μm - Wolfran Bergau) and Co (0.93 μm - H.C.Starck) were used to produce the hard metal. The influence of the milling time on the particle size distributions and in the lattice strain was investigated. Milling time of the 2, 10, 20, 50, 70, 100 and 150 hours were used. The powders after milling were characterized by X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM). The results show that 10 h milling were enough to reduce the crystallite size of WC and the increase of the milling time reduces the crystallite size.
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Authors: Takayuki Kitamura, Akihiro Kushima, Yoshitaka Umeno
Abstract: The ideal strength of a nano-component, which is the maximum stress of the structure, provides an insight into the mechanical behavior of minute material. We conducted tensile simulations for cylindrical-shaped Cu nano-wires composed of an atomic chain as a core wrapped around by shell(s) with the structure of (111) layers in an fcc crystal. The results are compared with Cu atomic chain and sheet which are components of the nanowire. Young’s moduli and the ideal strengths of the wires are less than a single atomic chain and a sheet. The mechanical strength of the wire is weakened by the following three factors: (A) Change in electron arrangement caused by combining core and shell; (B) Larger interatomic distance (inherent tensile strain) of the outer shell introduced by the mismatch of atomic layers due to the curvature difference; (C) Mismatch between shells due to curvature difference. Factor (A) reduces the bonding strength in the shell(s) that occupy a greater part of the wire. 5-1 wire, which consists of a core and a shell, is weaker than the single atomic chain and the single sheet due to (A) and (B). 10-5-1 wire, consisting of a core and two shells, has less strength than 5-1 wire due to (C) in addition to (A) and (B).
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Authors: C.C. Fu, L.J. Chang, Y.C. Huang, P.W. Wong, Jason S.C. Jang
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Authors: Xin Wang, Dian Tang, Jing En Zhou
Abstract: Sn is one of the most important elements for the Cl2-evolving anode coatings, but it always used as a minor additive. In this paper, an Sn-based ternary oxide coating with its composition of SnO2-23wt%TiO2-21wt%RuO2 was prepared by a sol-gel technique through etching, painting, sintering and annealing. The differential thermal analysis (DTA) shows that the crystallization behavior of the ternary xerogel is more similar to that of pure xerogels SnO2. X-rays diffraction (XRD) indicates that the coating is composed of rutile phase (Sn,Ti,Ru)O2. Any other undesired phases, for example, anatase TiO2 and metallic ruthenium phases are not found in the coatings. The microstructure and the morphologies were studied by a transmission electron microscope (TEM) and a scanning electron microscope (SEM). The results of energy dispersive spectrometer (EDS) indicate Sn content in the coatings remain at high level and coincident with the nominal composition. The grain sizes in the coatings are around 4 nm. The voltage of Cl2-evolution and O2-evolution shows the ternary coating has good electrochemical properties.
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Authors: M. Abdus Salam, Suriati Sufian, T. Murugesan
Abstract: Nano-structured hydrotalcite based mixed oxides have been synthesized using coprecipitation method under variable pH and low supersaturation condition. XRD technique has been used to confirm the hydrotalcite structure and its derived different phase of mixed oxides. The metal dispersion of mixed oxides was analyzed using ICP-MS. The nanostructures of the mixed oxides have been investigated using FESEM and HRTEM. The textural properties of mixed oxides were analyzed using N2 adsorption-desorption (BET) technique. The Characterizations have revealed that the developed mixed oxides were consisted with hexagonal/rhombohedral well dispersed nano-particles. Polycrystalline mixed oxides formed mesopore surface and narrower pore size distribution.
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Authors: Hong Sheng Ding, Zhi Fang Cheng, Hui Rong, Lin Lu
Abstract: Nano-structured Al2O3-13%TiO2 coating was deposited by air plasma spraying. Wear properties of the coatings under different load trough SRV friction and wear testing machine were studied, the results showed that wear mass loss of Al2O3-13%TiO2 coating by plasma spraying slide with ZrO2 and Si3N4 increase with load increasing, but the difference is that wear loss of coaing slide with Si3N4 ¬is lower than the coating slide with ZrO2 when load is less than 40N. Opposite phenomenon will occur when load is higher than 40N.The wear surface morphology was analyzed trough scanning electron microscopic, the results showed that coating slided with Si3N4 ball when matching at low loads, with a shallow furrow shape grinding. There were wide and deep furrows while at higher loads. Coating slide with ZrO2 ball has no obvious cracks, no layer spalling.Wear was occurred by micro cutting.
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