Abstract: In this paper a special At.f (Acidthiobacillus ferrooxidans) modified carbon powder microelectrode was prepared, and a series of electrochemical measurements were conducted to study ferrous ion Fe2 + oxidation mechanism on the electrode. CV (cyclic voltammetry) studies show that this oxidation reaction is reversible when c (Fe2 +) is lower than 0.16mol/L. At higher speed scanning, the currents through the electrode include two parts of the micro disc current and the thin layer current, while at lower speed scanning of steady state process the current provided by thin layer could be ignored, the whole oxidation reaction was controlled by diffusion process, and the calculated diffusion coefficient D0 is about 6. 25 ×10 - 6cm2.s – 1. The transient potential stair step studies also have been conducted. The results are consistence with steady state ones although thin layer currents should be taken in to account.
Abstract: For removing impurities to improve luminescence properties, Eu2+- activated Sr2Si5N8 red phosphor for white light-emitting diodes (LEDs) was prepared by multiple heat-treatment synthesis which includes carbothermal reduction and nitridation. The X-ray diffraction (XRD) patterns were showed the standard single phase of Sr2Si5N8. With an optimized amount of Eu2+ (2 at. %) dopant, the broad excitation band of Sr2Si5N8:Eu2+ indicated that the phosphor was suitable for application of white LEDs with UV or blue chip, and red emission peak at 628 nm in spectra originating from the 4f65d1→4f7 transition of Eu2+ ion. After third heating process, luminescence properties of the obtained phosphor were improved obviously and higher than commercial YAG:Ce3+ phosphor.
Abstract: Based on making principle of aluminum foams and semi-soild forming technology, a two-stage foaming process for Al-Si alloy foam named Semi-Solid Foaming (SSF) was put forward in this paper in order to control the cell structure of closed-cell aluminum foam. On the basis of introducing basic technology of SSF, effects of process parameters on foaming process and cell structure was investigated to obtain optimal parameters. The results show that the decomposing time of TiH2 can be controlled and two-stage foaming process, i.e. SSF, has been realized, to obtain Al-Si alloy foam of relatively homogenious cell structure with porosity of 74.6%, cell diameter ranging from 2.1mm to 3.2mm（average value is 2.3mm），and average circularity of 0.812. It is clarified that optimal parameters are as follows:agitation temperature is 580,the mixing time is 0.5min,the mixing speed is 1200r/min，re-foaming temperature of furnace is 720 and the heating time is 15min on condition of experiment.
Abstract: Huge rectangular ingots becomes crying needs in the condition of lots of heavy plate mills more than 5m have been in operation. In this paper, a special method of wind cooling outside mould has been presented and applied to produce 60t rectangular ingot. Mathematical simulation results tell us that by wind cooling, the solidification time of the 60t ingot can be shortened by 67 minutes, internal soundness can be ensured. The wind cooling process can obviously improve microstructure and preventing skull patch by increasing the thickness of solidified shell. A 60 tons huge rectangular ingot is successfully produced by wind cooling, the surface quality of is very well and the internal soundness should be improved further.
Abstract: In order to join the automotive radiator pipe with high-quality and high-efficiency, flame and induction brazing experiments of steel radiator were carried out using Cu-Zn alloy. Results show that Cu-Zn brazing filler metal can wet the steel well under different heating conditions. The average tensile-shear strength of the brazed joints was more than 400MPa. Brazing experiments of automotive radiator pipe were carried out for comparing the heating methods. Results show that the joints acquired by the induction brazing method were much better in the appearance, further; the amounts of brazing alloy were relatively less. Brazed radiator pipes were then electroplated, and sealability tests of the brazed pipe were investigated, which indicated the pipes and joints remained in good condition after the tests.
Abstract: This paper has systematically investigated the effects of 13 metal ion dopants on the photoreactivity and UV adsorption of TiO2 nanoparticle. The pure and ion-doped TiO2 nanoparticles were prepared using so-gel method. The absorption spectra of the TiO2 nanoparticles were obtained using UV-Visible spectrometer. The wavelength of the absorption edge of TiO2 was calculated using the tangent method. In general, different doping ion types were observed to exhibit different effects on the absorption spectra and photoreactivity of TiO2 nanoparticles. Ion concentrations were also shown to play a important role in the photoreactivity of the catalyst except Ag+, La3+, Zn2+ ions. Results reveal that red shift occurred to all ion-doped TiO2 nanoparticles with absorption edge ranging from 426 nm to 437 nm under optimal ion concentrations. Photocatalysis was shown to be inversely proportional to the amount of red shift of the absorption edge of implanted TiO2. Among the ions investigated, Ni-doped TiO2 nanoparticles have shown highest photoreactivity at the ion concentration 6.04×1017cm-3. The research results may provide references about enhancing the photoreactivity of TiO2 nanoparticles by applying metal ion doping.
Abstract: The effect of heat treatment on phase transformation, precipitation behavior and micro-hardness response of Cu40Zn-1.0Ti brass was investigated via powder metallurgy method. The volume fraction of α phase increased with elevated temperature, equaled to that of β phase at 400 °C, and reached to a maximum value of 55.9% at 500 °C. The solid solubility of Ti in Cu40Zn brass matrix decreased with elevated heat treatment temperature, showed high chemical potential for precipitates reaction in Cu40Zn brass. The micro-hardness of the BS40-1.0Ti brass was primarily dependent on the solid solubility of Ti, but also dependent on the phase ratio of α and β phase.
Abstract: Highly uniform and monodisperse KY3F10 nanospheres, with an average diameter of 300 nm, have successfully prepared through a simple solution method employing the reaction of Ln(NO3)3 and KBF4 under ambient conditions, without any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The SEM images illustrate that these spheres were actually composed of randomly aggregated nanoparticles.
Abstract: There were carried on experiment in zinc sulfate and selenite sodium electrolyte solution. To further studying the influence of the ZnSe films ingredient and the appearance influence of electrochemical formation ZnSe thin films, the deposition parameters, which are the pH, Zn2+/SeO32- molar ratio, complexing agent sodium citrate, bath temperature and current density, are studied by the orthogonal experiment, the influence on Zn of the parameters from strong to weak are attained.
Abstract: With water as solution, ferric chloride (FeCl3∙6H2O) as oxidant, sulfuric acid (SA) as dopant, prepared polypyrrole/montmorillonite (PPy/MMT) via chemical oxidation polymerization. We researched the effect that the content of the polypyrrole to the conductivity of composite in the condition of n (Py): n (FeCl3∙6H2O): n (SA) =1: 1: 0.5. Using IR, XRD, IR, TEM and SEM modern characterization methods to characterize internal structure of composites, the results show PPy were intercalated into the inner space of MMT. The surfaces of MMT intercalated are coated by conductive polypyrrole particles with equal size and uniform arrangement. MMT dispersed among conductive polypyrrole matrix and overlapped each other, which formed a conductive network. Using percolation theory, we analyzed the conductivity of composites that conform to the classical statistical percolation theory.