Photocatalytic activity of porous TiO2 films prepared by anodic oxidation

Anatase titanium dioxide is an active photocatalyst, however, it is difficult to be immobilized on the substrate. The crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation. The film was then used for photocatalysis via the methyl orange degradation method. The effects of anodization voltage, pH value, TiO2 film area and degradation time on the photocatalyst were investigated respectively by UV-visible spectrum. It was indicated that the TiO2 film prepared by anodic oxidation at 140 V had the best photocatalysis capability and the degradation of methyl orange was accelerated with acid addition.     

Enhancement of porous silicon photoluminescence by chemical and electrochemical infiltration of conducting polymers

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多孔阳极氧化铝膜的制备及电化学阻抗谱分析

在8℃、40V直流电压、0.3 mol/L的草酸电解液中,采用两步阳极氧化法用高纯度铝箔制备多孔阳极氧化铝（AAO）膜。用场发射扫描电子显微镜观察多孔阳极氧化铝膜的形貌。采用电化学交流阻抗法测量多孔阳极氧化铝膜制备过程中一次氧化和二次氧化后的电化学阻抗谱。试验结果表明,所制备的多孔阳极氧化铝膜为高度有序排列的纳米孔洞阵列。根据试验得到的电化学阻抗谱建立了R（QR）（QR）等效电路,该等效电路能较好地表征多孔阳极纳米氧化铝膜的电化学特性,进而找到了等效电路中电学元件与草酸电解液、多孔氧化铝膜的特性及界面电荷转移的关系。该研究有助于研究多孔阳极氧化铝膜的生长过程及形成机理。     

Electrolyte composition and galvanic corrosion for ruthenium/copper electrochemical mechanical polishing

Electrochemical mechanical polishing(ECMP)is a new and highly promising technology.A specific challenge for integrating Ru as barrier in Cu interconnect structures is the galvanic corrosion of Cu that occurs during ECMP.To mitigate the problem,the benzotriazole(BTA)and ascorbic acid(AA) were chosen as selective anodic and cathodic inhibitors for Cu and Ru,respectively.The optimization of electrolytes at different pHs including BTA,hydroxyethylidenediphosphoric acid(HEDP),and AA were investigated...     

Anisotropic etching and electrochemical etch-stop properties of silicon in TMAH:IPA:pyrazine solutions

Anisotropic etching and electrochemical etch-stop properties of single-crystal silicon in tetramethylammonium hydroxide (TMAH): isopropyl alcohol (IPA) solutions containing pyrazine were investigated. With the addition of IPA to TMAH solution, an improvement in flatness on the etching front and a reduction in undercutting were observed, but the etch rate on (100) silicon decreased. However, the (100) silicon etch rate is improved by the addition of pyrazine. An etch rate of 0.8 μm/min on (100) silicon, which is faster by 13% than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH:0.005g/ml pyrazine solutions, but the etch rate on (100) silicon is decreased if there is an increase in the amount of pyrazine in the solution. With the addition of pyrazine to a 25 wt.% TMAH solution, no significant variations in flatness on the etching front were observed and the undercutting ratio was reduced by 30∼50%. The addition of pyrazine to TMAH:IPA solutions increased the etch rate of (100) silicon, thus the time required by the etch-stop process was shortened. The current-voltage (I–V) characteristics of n- and p-type silicon in TMAH:IPA:pyrazine solutions were obtained. The passivation potential (PP) of n- and p-type silicon was obtained and the applied potential was selected between n- and p-type silicon PPs. The electrochemical etch-stop method was applied to the fabrication of 801 silicon microdiaphragms of 20 μm thickness on a 5-inch silicon wafer. The average thickness of fabricated 801 microdiaphragms on one wafer was 20.03 μm and the standard deviation was ±0.26 μm. The silicon surface of the etch-stopped microdiaphragms was extremely flat with no noticeable taper or non-uniformity. The benefits of the electrochemical etch-stop method for the anisotropic etching of silicon in TMAH:IPA:pyrazine solutions become apparent when reproducibility of silicon microdiaphragm thickness for mass production is realized. The results indicate that use of the electrochemical etch-stop method for the anisotropic etching of silicon in TMAH:IPA:pyrazine solutions provides a powerful and versatile alternative process for fabricating high-yield silicon microdiaphragms.     

Effect of heat-treatment on the nanostructural change of W-Cu powder prepared by mechanical alloying

W-30wt.%Cu powder prepared by mechanical alloying (MA) was annealed at various temperatures to investigate the structural change of MA W-Cu powder. From differential scanning calorimeter analysis and transmission electron microscope observation, it was revealed that the recovery of W in MA W-30wt.%Cu powder occurred at 700°C and the W grain started growing also at this temperature. The W grain had grown significantly after annealing at 900°C, and the Cu phase in the MA powder was found to act as liquid melt near 900°C. The microstructure of the sintered specimen was similar to that of the W-Cu alloy via liquid phase sintering. This microstructure, even at temperatures below Cu melting, was the new feature observed in the MA W-Cu powder. This suggests that such a microstructure is closely related to the inherent high diffusivity of the nanosized W crystallites as well as the liquid-like behavior of the Cu phase.     

Graphene-encapsulated blackberry-like porous silicon nanospheres prepared by modest magnesiothermic reduction for high-performance lithium-ion battery anode

Porous silicon(Si) nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.However,fabrication of porous structures tends to be difficult to control and complex,so,the final electrochemical performance can be compromised.Herein,a modest magnesiothermic reduction(MMR) reaction is demonstrated to produce blackberry-like porous Si nanospheres(PSSs) controllably using magnesium silicide(Mg_2 Si) as Mg source and SiO_2 nanospheres as the reactant.This improved MR method provides good control of the kinetics and heat release compared to the traditional MR(TMR) method using Mg powder as the reactant.The PSSs obtained by MMR reaction has higher structural integrity than that fabricated by TMR.After encapsulation with reduced graphene oxide,the Si/C composite exhibits superior cycling stability and rates such as a high reversible capacity of 1034 mAh·g~(-1) at0.5 C(4200 mAh·g~(-1) at 1.0 C) after 1000 cycles,capacity retention of 79.5%,and high rate capacity of 497 mAh·g~(-1)at 2.0 C.This strategy offers a new route to fabricate highperformance porous Si anodes and can be extended to other materials such as germanium.     

Preparation and characterization of Ni nanopowders prepared by anodic arc plasma

Ni nanopowders were successfully prepared in large quantities by anodic arc discharged plasma method with homemade experimental apparatus in inert gas. The particle size, microstructure and morphology of the particles were characterized via X-ray diffractometry (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffractometry(SAED). The specific surface area and pore parameters were investigated by nitrogen sorption isotherms at 77 K with Brunauer-Emmett-Teller(BET) equation and Barrett-Joyner-Halenda (BJH) method. The chemical compositions were determined by X-ray energy dispersive spectrometry(XEDS) and element analysis. The experimental results indicate that this method is convenient and effective, and the nanopowders with uniform size, higher purity, weakly agglomerated and spherical chain shape are gotten. The crystal structure of the samples is FCC structure as the bulk materials, the particle size distribution ranges from 20 to 70 nm, and the average particle size is about 46 nm obtained by TEM and confirmed by XRD and BET results. The specific surface area is 14.23 m^2/g, specific pore volume is 0.09 cm^3/g and average pore diameter is 23 nm.     

Growth mechanism of Cu nanopowders prepared by anodic arc plasma

1 Introduction In recent years, the research and development for metal nanopowders has attracted significant interest and it is still the subject of intense investigation owing to their intriguing properties and extensive prospects [1-5]. Metal nanopowder…     

Theoretical analysis of silicon surface roughness induced by plasma etching

A theoretical study of single-crystal silicon surface roughness induced by SF₆ plasma has been carried out by means of atomic force microscopy. Plasma which contains the velocity shear instability has been used to study the relation between the plasma parameters and subsequent surface roughness. The surface roughness has been examined in the dependence on experimental parameters. The results obtained by theoretical calculations are identical to the experimental ones. The present paper has quantified the influence of a DC electric field values on plasma parameters such as the ratio of ion flux to the neutral reactant flux (J ⁺/J _F), exposure time, DC electric field, magnetic field and inhomogeneity. Theoretical investigation shows that the roughness of silicon surface increases with the increase of the values of J ⁺/J _F, exposure time, of magnetic field, of inhomogeneity in a DC electric field and decreases through increasing the value of a DC electric field.     

Micro-machinability of monocrystal silicon by direct etching using excimer laser

The high flexibility of laser direct writing and its potential capability of fabricating micro-mechanical structure are discussed. Aiming at providing knowledge for micro-engineering application, experiments on direct etching of monocrystal silicon with focusing KrF excimer laser beam (λ = 248 nm) were carried out. The validity of non-thermal excimer laser material processing was examined by SEM observation on the “heat-affected zone (HAZ)”. An empirical formula establishing the relationship of etching depth versus laser energy per pulse and the number of laser pulses has been derived from the experiments. Impact damage at the underside of silicon wafer has been observed. Its relevant causes are analyzed.     

Morphology and characterization of the anodic coating on galvanized steels prepared by alternating currents

A novel technique for producing anodic coatings on galvanized steels was developed in this study. Several coloured coatings, with thickness varying from 20 to 50 μm, were produced by adding a specific transition metal salt to the basic electrolyte of silicate. The anodic coating was composed mainly of silicon, zinc, sodium and oxygen, doped with transition metal ions. Results from electron probe microanalysis and X-ray diffraction studies indicated that the island-like structure is silicon-enriched and that a fused glass structure is a major part of the anodic coating. The colour imparted to the anodic coating depended on the specific metal incorporated during its formation. The coating significantly increased the corrosion resistance of galvanized steels.     

Preparation and particle size characterization of Cu nanopartides prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.     

Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

1. Introduction Metal nanoparticles exhibit novel physical and chemical properties owing to the small size effect, surface effect, quantum size effect, and quanta tun-nel effect [1-4]. In recent years, the research and de-velopment for metal nanoparticles have attracted significant interest and is still the subject of intense investigation owing to their intriguing properties and various potential applications [5-7]. Because the properties depend strongly on the details of particle size, speci…     

阳极氧化法构筑的铝基超疏水表面及其耐蚀性能

通过接触角测量仪、扫描电镜、红外光谱、电化学工作站对经阳极氧化及低表面能物质修饰相结合处理的7075铝合金的表面的形貌、化学成分和耐蚀性能进行了表征.结果表明:阳极氧化法构筑的珊瑚状微纳结构和低表面能十四酸的协同效应赋予了7075铝合金表面超疏水性能.当草酸浓度40 g/L、电流密度20 A/dm2、阳极氧化时间10 ...     

Preparation and crystalline phase of a TiO2 porous film by anodic oxidation

Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy （FESEM） and X-ray Diffraction （XRD）. The effects of the parameters of anodic oxidation （such as voltage, the concentration of sulphuric acid, anodization time and current density） on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed.     

Microstructures and properties of porous TiAl-based intermetallics prepared by freeze-casting

Preparation of porous TiAl-based intermetallics with aligned and elongated pores by freeze-casting was investigated. Engineering Ti−43Al−9V−1Y powder (D₅₀=50 μm), carboxymethyl cellulose, and guar gum were used to prepare the aqueous-based slurries for freeze-casting. Results showed that the porous TiAl was obtained by using a freezing temperature of −5 °C and the pore structure was tailored by varying the particle content of slurry. The total porosity reduced from 81% to 62% and the aligned pore width dropped from approximately 500 to around 270 μm, with increasing the particle content from 10 to 30 vol.%. Furthermore, the compressive strength along the aligned pores increased from 16 to 120 MPa with the reduction of porosity. The effective thermal conductivities of porous TiAl were lower than 1.81 W/(m·K) and showed anisotropic property with respect to the pore orientation.     

Fabrication of a probe needle using a tubular cathode by electrochemical etching

To fabricate a probe needle, a tubular cathode was applied by electrochemical etching. A tungsten wire was used as an anode, and a stainless steel tube was used as a cathode, respectively. The stainless steel tube was partially immersed into a sodium hydroxide solution. After the tungsten wire was aligned at the center of the stainless steel tube, electricity was supplied from an external power source. During the experiment, the level of solution that was inside the stainless steel tube rose higher than that of the outer solution of the stainless steel tube, due to bubbles generated on the inner surface of the stainless steel tube, and the inner solution increased in volume. Using this process, the length of the probe needle tapering could be controlled without using a vertical loading system or controller.     

Influence of copper on the morphology of porous anodic alumina

Sputtering-deposited Al-Cu alloy layers and an Al-Cu/Al bi-layer are used to investigate the influences of copper on the morphology of porous anodic alumina films formed galvanostatically in either sulphuric or phosphoric acid electrolyte. The results reveal development of an irregular morphology of pores during anodizing of the alloy layers, contrasting with the linear porosity of films formed on aluminium. Further, the rates of film growth and alloy consumption are relatively low, since oxygen is generated following enrichment of copper in the alloy and incorporation of copper species into the anodic film. The linear morphology is re-established following depletion of the copper in the bi-layer and at the same time, film growth accelerates as oxygen evolution diminishes. The irregular pore morphology is considered to arise from stress-driven pore development influenced by effects of oxygen bubbles within the anodic alumina.     

Ionic transport in amorphous anodic titania stabilised by incorporation of silicon species

Incorporation of silicon species from an alloy substrate into anodic titania is shown to stabilise the structure of the film, facilitating investigation of the ionic transport processes in amorphous titania grown at high efficiency. Thus, an amorphous anodic film developed on a sputtering-deposited Ti-6 at.%Si alloy formed to 100 V in phosphoric acid electrolyte in contrast to a partially crystalline film developed on relatively pure titanium at <20 V. Silicon species, which are immobile and act as marker species in the growing film, are present in the inner 58% of the film thickness. Evidently, the film material forms simultaneously at the film/electrolyte and alloy/film interfaces by co-operative transport of cations and anions, as is usual in amorphous anodic oxides. The phosphate anions incorporated from the electrolyte migrate inward at 0.34 times the rate of O²⁻ ions and hence are present in the outer 62% of the film thickness.