Papers by Author: Yu Cheng Wu

Abstract: The as-cast microstructures and mechanical properties of Al-Si-Mg-Cu-Ti alloys with and without Sc were investigated by metallographic microscope, field emission scanning electron microscope, energy spectrum analysis, transmission electron microscope and universal testing machine. The result shows that adding 0.20wt.% Sc into the casting alloy can refine the grain, change the growth morphology from dendrite to fine equiaxed grain, and the morphology of eutectic Si by rough laminar structure into fine fibrous. The tensile strength of alloy with 0.20wt.% Sc is up to 304.4 MPa after T6 heat treated, which is close to that of 6061 forging aluminum alloy.

Abstract: W–Cu (0, 0.25, 0.75, 1.5, and 3 wt.%)/Lu₂O₃ composite materials were prepared through electroless plating with simplified pretreatment method and powder metallurgy. The phases and morphologies of the W–Cu/Lu₂O₃ composites were characterized by X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The relative density, microhardness, electrical conductivity, and bending strength of the sintered samples were examined. The experimental results show that W–Cu composites with uniform structures can be obtained with pretreated W using the simplified method, followed by electroless Cu plating. The microstructure and properties of the composites were significantly affected by the addition of Lu₂O₃ nanoparticles, resulting in high electrical conductivity and strength. The electrical conductivity of W–Cu/1.5 wt.% Lu₂O₃ composites reached 63.3%, which is higher than the national standard value of 50.71%. The bending strength of W–Cu/1.5 wt. % Lu₂O₃ reached 1306.7 MPa, which is 65.41% higher than the national standard. These results may be attributed to the uniform distribution of refined particles with Lu₂O₃ content increased to 1.5 wt. %.

Abstract: The Self-Organizing Anodic Aluminium Oxide(AAO) Template Is Widely Used to Construct the Nanomaterials. but the AAO Film Is Very Thin and Brittle, the AAO Templates Are Easily Been Destroied when Widening and Opening the Nanopores. the Nanorods/wires Constructed by this Template Likely Aggregate because of the High Activity of Nano-Surface at Short Range. this Paper Proposed a Novel Image of AAO Template in which Several Nanopores Combined Together to Form a Large Open Holes without Widening the Cells and Opening Barrier Layers. the Electronic Aluminium Foils with 99.99% Purity Is Anodized in Phosphoric Acid by Two-Steps, then Polarized under a Negative Voltage in the Kcl Solution. the Result of Experiment Demostrated the Possibility of the Formation Mechanism of this New Templates.

Abstract: The stability of mold oscillation can directly influence on slab surface quality and operational safety in continuous casting. In recent years, the hydraulic oscillation is developed and applied as the driven equipment of mold oscillation. In the present work, based on the slab continuous caster of hydraulic oscillations, the displacement and other parameters of hydraulic oscillator are measured and the evaluation method of oscillation is studied. The displacement difference and phase difference of oscillation with sinusoidal waveform and non-sinusoidal waveform are analyzed. Especially, the dynamic characteristics of the driving force of left and right cylinders are evaluated. The results indicated that the hydraulic oscillator is quite a good device in terms of precision. The method proposed may be useful for evaluating oscillators.

Abstract: A series of binuclear metal (II) phthalocyanine hexasulphonates, (M-M)Pc, including (Co-Co)Pc, (Co-Zn)Pc, (Co-Mn)Pc, (Zn-Zn)Pc, (Zn-Mn)Pc and (Mn-Mn)Pc were synthesized and immobilized on nanocrystalline TiO2 thin films. The nanocrystalline TiO₂ thin film was characterized by SEM, XRD and profilometer. The catalytic activity of various (M-M)Pc/nanocrystalline TiO₂ thin films was evaluated by the degradation of methylene blue (MB) with air as the oxidant under visible light irradiation and dark condition. The results indicated that the prepared nanocrystalline TiO₂ thin film had good crystalline and uniform particle size distribution. According to the degradation results of MB, various homo/hetero (M-M)Pc can sensitize nanocrystalline TiO₂ thin films and improve their photocatalytic activity under visible light irradiation. The catalytic activity of hetero (M-M)Pc/nanocrystalline TiO₂ thin films were more effective than that of homo (M-M)Pc under both visible light irradiation and dark condition, and the air purging was essential in degradation of MB. Therefore, these (M-M)Pc/nanocrystalline TiO₂ thin films can be applied to the degradation of MB as a promising catalyzer.

Abstract: Copper and copper alloys had various applications in tremendous areas due to their unique properties, such as good conductivity, good thermal conductivity and so on. However, applications of copper and copper alloys were severely restricted as the result of the limited strength at room temperature and poor wear-resistance at high temperature. In this paper, we investigated the preparation of Cu-Cr-Zr/AlN nanocomposites by mechanical alloying process and then powder metallurgy technology. XRD and SEM were performed for the phase and morphology characterization. The conductivity properties were also tested and the results showed that Cu-Cr-Zr/AlN nanocomposites exhibited excellent conductivity behavior.

Abstract: Anodic aluminium oxide(AAO) templates were fabricated by a two-step anodization method utilizing high purity aluminium sheets. On the basis of getting the optimum preparation parameters of AAO templates, effects of the pretreatment and the first anodization time on morphology of AAO templates were studied. Field emission scanning electron microscope(FESEM) was used to investigate surface morphology of AAO templates. The SEM images indicated that both pretreatment and the first anodization time had a significant influence on morphology of AAO templates. Meanwhile,effect mechanism of pretreatment and the first anodization time on AAO templates morphology was elucidated.

Abstract: In this paper, highly-ordered TiO2 nanotube arrays (TNAs) were firstly fabricated by electrochemical anodization. Secondly, the as-prepared TNAs were used as precursors for hydrothermal treatment and large percentage of nanoparticles with special shape were achieved. Their photocatalytic activity was evaluated based upon the removal of methylene blue (MB) dye in the aqueous solution. In order to enhance the photocatalytic properties, we added a certain amount of AgNO3 solution (0.1M) in the hydrothermal treatment process and the experiment demonstrated that the addition of AgNO3 solution displayed an excellent improvement for the photocatalytic activity. Under sunlight irradiation, the methylene blue pollutant of 1×10−5M was almostly completely degraded by Ag -TiO2 nanoparticles within 300 min.

Abstract: Fly ash particles reinforced aluminum matrix composites were fabricated by powder metallurgy method. The influence of different fly ash content on hardness, the friction and wear behavior of the composites were investigated at a constant sliding velocity of 400r/min. The worn surfaces of composites were observed by scanning electron microscope, and worn mechanism of composites was discussed. The results showed that the hardness of composites increased first and then decreased with fly ash content increasing. Under the lower loads and at the lower fly ash content, the friction co-efficient is steadily lower than that of Al alloy matrix. The wear resistance of composites increased with the volume fraction of fly ash particles and the wear mechanism was characterized as abrasive wear and adhesive wear.On the other hand, the wear mechanisms in the composites have been transformed with increasing load and fly ash volume; it mainly was delamination wear and abrasive wear.

Abstract: TiO2 shows a high efficiency in Photocatalysis, however, the recycling of TiO2 is difficult, composite coating is prepared by simultaneous elecroless deposition of NiP and TiO2 on substrates, surface topography and hardness of composite coating are investigated by metalloscope, SEM, EDS and Vickers microhardness; The relation between absorbence of methyl orange and time is researched by 723# spectrophotometer. The results show when TiO2 content in bath is 4g/L, plating speed is most fast and amount to 12.2μm/h, the photocatalytic effect is best. by comparing the microhardness of heat-treated compound coating and the Ni-P alloy coating, the maximum microhardness of the former appears in 500°C and achieves HV1180, and the latter appears in 400 °C and achieves HV950.