Papers by Author: Yu Cheng Wu

Abstract: Powder metallurgy method was used to prepare copper alloy nanocomposites (CuCrZr/AlN) with high strength and conductivity. The morphologies and structures of the CuCrZr/AlN nanocomposites were analyzed using scanning electronic microscope (SEM) and transmission electronic microscope (TEM). The impact of aging treatment on mechanical properties of CuCrZr/AlN nanocomposites was studied. The result showed that dislocation density of the sample decreased and the solid solution atoms precipitated after aging treatment. The micro-hardness of the sample decreased and Brinell hardness increased after aging treatment.

Abstract: Highly ordered TiO₂ nanotube arrays (NTAs) modified with Pt nanoparticles (Pt/TiO₂ NTAs) have been prepared by anodization of Ti foils followed by electrochemical deposition and employed to improve the performance of the low-overpotential determination of H₂O₂ in solution. Morphologies of TiO₂ and Pt/TiO₂ NTAs were observed by SEM and TEM. The electrochemical behaviors of TiO₂ and Pt/TiO₂ NTAs were compared by cyclic voltammograms (CVs) in phosphate buffer solutions in absence and prensence of 10 mM H₂O₂, which showed that Pt nanoparticles can enhance the electrochemical activities of TiO₂ NTAs and achieve low-overpotential determination of H₂O₂. Amperometric method with an applied potential of-100 mV was used for H₂O₂ detemination, which demonstrated a good H₂O₂ sensing with sensitivity of 5.4 μAcm^-2mM^-1.

Abstract: The compression deformation processes of powder particles were investigated by the way of mesoscopic simulation based on finite element method of discrete body. The strain process of the particles in typical position, the deformation difference of the particles in different positions and the strain status of particles were investigated under various compacting pressure. The results show that the deformation process of the compressed powder particles consisted of three stages, which were the initial stage of small deformation, the major stage of the sharply changes of strain and the ultimate stage of strain tending to stable state. The interface friction has a significant influence on the deformation and pressed density of particles close to die wall. The density can not be increased with the increase of compacting pressure of compaction infinitely.

Abstract: To obtain a large surface area, the aluminum electrode foils (AEF) were etched by direct current (DC) in hot chloride solution to get lots of vertical [001] tunnels. Whereas, because of the defects as rolling trace, distorted oxidation film, non-uniform organization, pollution layer on the surface of the aluminum foil, and the easy corrosion in hot Cl- acid solution, the etch pits are disorder and merged. These merged pits cause laterally directed dissolution and excessive dissolution on the aluminum surface, which limited the surface enlarging and decreased the strength of the aluminum foils. In this paper, we adopted anodic oxidation to fabricate the porous anodic alumina (PAA) on the high-purity electronic aluminum foils with 99.99% purity, and polarized by a negative voltage in the KCl solution. The result showed that several nanopores combined together to form a large open holes without barrier layers. With this membrane on, the foils were etched in 70°C HCl+H2SO4 solution, and the etch pits were just generated in the combining-nanopores. The etch pits grew into tunnels respectively without merged, and the surface was also smooth.

Abstract: Highly ordered TiO₂ nanotube arrays (TNTAs) with smooth walls and uniform diameter were prepared by electrochemical anodization. And then solution deposition process was adopted for the modification of the TNTAs with nanoscaled CdSe. The materials obtained were characterized by field emission scanning electron microscopy, UVvisible spectroscopic and photoelectrochemical techniques. The results revealed that the morphologies and growth mechanism for CdSe/TNTAs composites varied with the reaction time in Se^2- solutions (c=1.2 mol/L) when nanotubes were firstly imported with Cd²⁺ ions. Optical absorption behavior of the CdSe/TNTAs composites increased with more CdSe nanoparticles. And the photo-response of the obtained nanomaterials was first strengthened and then declined with the sustained increase of the deposited CdSe.

Abstract: Nylon 6/MgAl-LDH nanocomposites had been successfully prepared by In situ hydrolyzed ring opening polymerization in this work. The structures and properties of Nylon 6/MgAl-LDH nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The nanodispersion of exfoliated MgAl-LDH layers in nylon 6 matrix has been verified by the observation of TEM image in Nylon 6/MgAl-LDH nanocomposites with 0.3 wt% MgAl-LDH (MANM-0.3). The XRD results showed that the exfoliated MgAl-LDH favored the formation of the γ-crystalline of nylon 6 form. DSC data showed that the exfoliated MgAl-LDH layers play the role of nucleating agents with strong heterogeneous nucleation effect on the crystallization of nylon 6. But TAG results showed the thermal stability of nylon 6/MgAl-LDH nanocomposites were worse than that of neat nylon 6.

Abstract: Au-Cu alloy nanowires with diameters 50-100nm and lengths of 500nm have been obtained by direct electrochemical deposition.The fabrication of highly ordered Au-Cu alloy nanowires arrays was used as a Anodic aluminum oxide (AAO) template. This template was fabricated with two-step anodizing method. In this paper, we report electrochemical deposition fabrication of Au–Cu alloy nanowire arrays by AAO. Use SEM, TEM can detect morphology of Au-Cu alloy nanowires, And use EDS to analyse the elements.The electrocatalytic activities of the Au-Cu alloy nanowires for the oxidation of ethanol in acidic medium were investigated by cyclic voltammetry.

Abstract: The Cu-40wt%Zn-1.0wt%Bi-1.0wt%Mn bismuth-brass was prepared by casting and annealing. The microstructure was investigated by scanning electron microscopy (SEM), the phase composition was analyzed by X-ray diffraction (XRD), and the properties of mechanics and cutting were tested, too. The results show that the bismuth-rich phase is mainly distributed in the grain boundary as the shape of granules, which lead to the mechanics property and cutting property of bismuth-brass can basically reach the requirements of replace the traditional cutting-free brasses.

Abstract: Cu-0.2wt%Cr-0.5wt%Zr-0.1wt%RE(La) was prepared by casting, quenching, rolling and aging. The microstructure was studied by electron microscope and the texture components were studied by electron backscattered diffraction. In the cast alloy, pure chromium distributed near the grain boundary as a strip shaped and Cu5Zr phase distributed in the interior of grain as a shape of granules. The texture components of the rolled plate include {110} and {112}. With the rolling ratio increased, {112} texture component became the primary rolling texture component. The strengthening effect was attributed to the refinement of the grain size. The electron conductivity was mainly affected by the misorientation of the grain size with a high rolling ratio.

Abstract: In this paper, we systematically investigated the influence of SiC particle size on the wear properties of the SiC particle reinforced Cu matrix composite prepared by powder metallurgy process. Under low load (≤120N), the increase of the SiC particle size contributes to the improvement of the abrasive resistance and the main abrasion mechanism is abrasive wear. With the increase of the load, the large SiC particle is easy to break and exfoliate, leading to delamination wear and the decrease of the strength. Under higher load (≥120N), the small size of the SiC reinforcement particle which can reduce the plastic deformation of the subsurface efficiently has significant enhancement effect of the SiC/Cu composite, avoiding delamination fracture.