Effect of the crystal face orientation and alloying with gold on the properties of thin anodic films of Ag(I) oxide: I. Photocurrent

The anodic formation of nano-size anodic films of Ag(I) oxide on polycrystalline silver and Ag-Au alloys, as well as on low-index monocrystalline silver faces in 0.1 M KOH, is studied. Based on the data of photocurrent measurements, the n-kind of the oxide film conductivity is determined. Replacing the polycrystalline silver with monocrystals, as well as adding a small amount of gold atoms to its lattice (X _[Au] <= 4 at. %), results in substantial structure ordering of the oxide due to the decrease in the deviation from the stoichiometric composition. The structure-dependent parameters of Ag(I) oxide (the optical absorption coefficient α, the concentration of donor defects N _D, the width of the spatial charge region W, and the Debye screening length L _D) are determined by the silver crystal face orientation, the gold content, and the film formation potential. At E = 0.52 V, the series of changes in these characteristics correlate with the series of reticular density. An increase in E breaks the series and increases the deviation of the composition from the stoichiometric Ag₂O composition.     

Effect of orientation of crystal face of silver and its alloying with gold on properties of thin anodic Ag(I) oxide films: II. Photopotential

The current efficiency of the formation of anodic oxide on polycrystalline silver is shown to decrease with an increase in the concentration of KOH solutions, while the rate-limiting stage remains the solid-phase mass transfer. Photopotential in nano-size Ag(I) oxide films anodically formed on polycrystalline silver is independent of the OH⁻ ion concentration, which means that a photoresponse is generated in the bulk oxide. The n-type conductivity of oxide films on silver, Ag-Au alloys, and low-index silver crystal faces, which was determined previously when measuring photocurrent, is confirmed. Replacing polycrystalline silver with its monocrystals results in a substantial decrease in the photopotential amplitude due to the decrease in the deviation from a stoichiometric composition. The electron mobility and the partial electronic photoconductivity in the anodic Ag(I) oxide depend on the orientatinon of the crystal face in silver and the gold content. At E = 0.56 V, a series of changes in these characteristics correlates to the changes in other structure-dependent parameters of Ag₂O oxide (the optical absorption coefficient α, the concentration of donor defects N _D, the width of the spatial charge region W, and the Debye screening length L _D).     

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。     

Adsorption of Ag（Ⅰ） on H2TiO3 from aqueous solutions

Adsorption of silver ions from aqueous solution onto H2TiO3 was studied. Equilibrium experimental studies were performed to determine the adsorption capacity of H2TiO3 for silver ion at various pH values. Batch experiments were conducted in the range of pH value 3-7 and silver ions concentration 10-200 mg/L. The results show that the adsorption is strongly dependent on pH value. The equilibrium absorption capacity of H2TiO3 increases significantly with the increase of pH value from 3 to 7. The adsorption of silver ion obeys the Langmuir isothermal equation well in the concentration range studied, the adsorption constant is 0.054 7, 0.052 4, 0.0881 at pH 5, 6 and 7, respectively, and the maximum adsorption capacities are 23.64, 29.76 and 40.82 mg/g.     

Luminescence from band-gap photo-excitation of titanium anodic oxide films

Luminescence light from the anodic thin oxide films formed on titanium in neutral phosphate solution was measured by photo-excitation of ultra-violet light irradiation with 3.82 eV energy. The luminescence light is observed with a peak of about 3 eV energy that corresponds to the band-gap energy of the n-type semiconductive TiO₂ oxide. It can therefore be presumed that the luminescence is induced by de-excitation or recombination between electrons in the conduction band and holes in the valence band. The peak wavelength of the luminescence light changes with the formation potential of the oxide film from 409 nm at 1 V to 425 nm at 6 V. The shift of the peak may reflect an amorphous-crystalline transition with increase of potential.     

Fabrication of nano-sized oxide composite coatings and photo-electric conversion/electron storage characteristics

Titanium dioxide TiO₂ can be used as a photo-anode to give generated electrons to the metal substrate under illumination. The transition metal oxide such as iron oxide Fe₂O₃ can be used to store electrons generated by the photo-electric conversion function of TiO₂ under the illuminated situation while the electrons are discharged from the transition metal oxide to the metal substrate in the dark. In this paper, coatings of nano-sized composite of TiO₂ and Fe₂O₃ were fabricated by the Warm Spray process, in which the feedstock powder is accelerated by a supersonic gas jet with speed above 1.0 km s^- 1 and temperature between 800 and 2500 K, and then impacted onto the target substrate continuously to form coatings. The coatings of TiO₂ and Fe₂O₃ nano-composite fabricated by Warm Spray showed no thermal deterioration such as phase transformation and particle growth of the feedstock during the spray process. The coatings fabricated by the Warm Spray had larger photo-current and the electron charge/discharge capacity than that by a conventional HVOF process. In addition, these characteristics were improved by decreasing the primary particle size of TiO₂ and Fe₂O₃.     

腐蚀铝箔高压阳极氧化膜微观结构与电化学特征

将高压铝电解电容器用腐蚀铝箔在硼酸电解质溶液中进行530 V阳极氧化,应用透射电镜与交流阻抗研究了所形成的高压阳极氧化膜的微观结构与电化学特征。结果表明:高压阳极氧化膜具有明显的层状结构特征,各层的结晶程度与缺陷特征不同,外层晶化程度较低、缺陷较少;中层与内层晶化程度较高、缺陷较多;铝箔表面微孔诱发弥散效应,交流阻抗频谱的等效电路可用膜QOX与膜电阻ROX并联,再与电解液电阻RS串联来表征,容抗行为显著接近界面电容元件特性,膜电阻处于氧化膜非晶质层电阻与结晶质层电阻之间而偏向结晶质层电阻。     

改性竹炭对银（I）的吸附性能与机理

研究了改性竹炭对银(I)的吸附性能与机理.研究表明:竹炭对银(I)有良好的吸附性能,平衡吸附量为45.2 mg/g;竹炭对银的吸附动力学可用准一级动力学描述,表观吸附速率常数k298=3.29×10-4 s-1,表观吸附活化能为:Ea=36.1 kJ·mol-1;银在竹炭上的吸附符合Langmiur吸附等温线,吸附系数KL(298 K)为24.427 L·mg-1,饱和吸附量Q∞为62.7 mg/g;温度升高,吸附量减小,表明吸附为放热过程;测得吸附热力学参数为:ΔH= -40.9 kJ·mol-1,ΔG=-36.6 kJ·mol-1,ΔS=-14.46 J·K-1·mol-1.机理研究表明:竹炭对银(I)的吸附主要为还原吸附.     

Reflectance spectroscopy of oxide films. I. A theoretical study

Theoretical reflectance spectra for a thin film on an infinite substrate (such as an oxide layer on a metal) have been calculated, to assess the combined effects of absorption bands, interference and surface structure on film identification and the accuracy of film thickness measurements.     

Review of porous anodic aluminium oxide (AAO) applications for sensors,MEMS and biomedical devices

Anodising of aluminium is one of the simplest metal surface finishing processes, and results in a porous anodic aluminium oxide (AAO) which is integral with the parent metal. Pore size, interpore spacing and thickness of the porous oxide film can be controlled by careful selection of the anodising electrolyte (type and concentration), and the operating parameters (voltage, temperature, time) employed. A self-ordered nanoporous AAO can be obtained without the need for expensive or complex processes required for traditional materials employed in microelectronics and MEMS applications (e.g. photolithography in the production of porous silicon). Planar and curved AAO surfaces can be manufactured. The simple and low-cost process for the production of AAO has enabled this material to gain inroads in the manufacture of various sensors and MEMS devices. This review paper discusses the anodising process and the resulting AAO structures tailored for MEMS, sensors, biomedical and nanotechnology fabrication.     

氧化铁皮相结构的光电子能谱分析

通过光电子能谱（XPS）对氧化铁皮层相结构进行的分析,可以有效定性分析热轧板卷表面的氧化物结构相构成,再通过拟合不同峰位下高斯线型峰的面积,可计算各种Fe化合价含量比,并且通过刻蚀在厚度方向定量分析各种氧化物的含量对比,可有效表征氧化铁皮结构相的分布状态。通过检测表明：最表层Fe3O4占据主导地位,随着深度的增加,Fe3O4逐渐减少,同时FeO的比重开始增加,在整个氧化铁皮层中存在含量较低的单质Fe,表明氧化铁皮层中存在有共析的Fe3O4+αFe相。     

Surface characteristics and bioactivity of oxide films formed by anodic spark oxidation on titanium in different electrolytes

Porous oxide films were fabricated on commercially pure titanium (CP-Ti) using an anodic spark oxidation technique with different electrolytes, 1 M H₂SO₄, 1 M H₃PO₄, and 1 M CH₃COOH. The micro-morphology, surface roughness, and crystalline structure were evaluated by scanning electron microscopy, profilometry, and X-ray diffraction, respectively. The chemical composition and binding state of the specimen groups were evaluated by X-ray photoelectron spectroscopy (XPS). TiO₂ films were observed on the specimens anodized in the acetic acid and sulfuric acid electrolytes. However, a TiP₂O₇ film was mainly observed on the specimen anodized in the phosphoric acid electrolyte. The dominant Ti⁴⁺ peaks for all sample groups and the additional Ti³⁺ peaks for the groups anodized in the acetic and phosphoric acid electrolytes were detected by high-resolution XPS. The effects of the surface characteristics of the specimens on the bioactivity were examined using an immersion test in a minimum essential medium (MEM) solution. There was a higher level of calcium formed on the anodized specimens than on the as-received titanium while there was no significant difference in the calcium content between the anodized specimen groups. Fourier transform infrared spectroscopy showed a different content of chemical function groups in the deposits formed in MEM according to the type of electrolyte used. These results were attributed to the different surface chemical states of the oxide films.     

Adsorption behavior and mechanism of amino methylene phosphonic acid resin for Ag（ Ⅰ ）

1 Introduction Many efforts have been made on using ion exchange resin to separate and concentrate certain metal cations [1?11]. However, less research for using it to adsorb noble metal Ag(Ⅰ), and much less research for commercializa- tion has been don…     

Thermal desorption spectroscopy (TDS) method for hydrogen desorption characterization (I): theoretical aspects

We present a theoretical study of thermal desorption spectroscopy applied to the characterization of hydrogen desorption kinetics from hydride forming materials. We propose a model that considers bulk and surface processes during desorption in the solid solution+hydride field of a metal–hydrogen system. We consider as possible rate limiting steps: diffusion, phase transformation, bulk to surface passage and two-atom recombination on the surface of the sample.     

纳米Ni(OH)2的制备及其电化学性能

采用固相法制备了纳米β-Ni(OH)2, 采用Scherrer公式由其中一样品的(100)、 (101)及(110)晶面参数计算得到晶粒尺寸分别为11.1 nm、 3.6 nm和12.1 nm. 采用循环伏安、恒电流充放电等技术对其电化学性能进行了初步研究, 结果表明 纳米Ni(OH)2的活性比较高, 其首次容量达207.9 mA*h*g-1, 第2周期容量即达到最大值240.4 mA*h*g-1, 但其容量衰退较快.     

Post-functionalization of poly(3-hexylthiophene) via anodic chlorination

Selective anodic chlorination of a poly(3-hexylthiophene) was successfully carried out by electrochemical polymer reaction. NMR and EDX analyses revealed the selective and sufficient substitution of chlorine atom at the 4-position of the repeating thiophene ring. GPC measurement of the polymer before and after electrolysis indicated that neither decomposition nor propagation of the polymer occurred even after passage of the excess charge. The optical and electrochemical properties of the obtained chlorinated polymer were investigated in detail.     

Synthesis of a boron-containing conducting polymer from the anodic oxidation of Tris(pyrrolyl)borane

The electrochemical oxidation of Tris(N-pyrrolyl)borane (1) in THF yielded a conducting polymer film with an electron conductivity of ca. 7×10⁻⁴ S cm⁻¹. The coulometric measurements indicated that the three pyrrolyl units were not totally coupled during the electropolymerization reaction. From further UV–VIS and FT-IR spectroscopy data, a structure of poly(1) was then proposed.     

Simultaneous plasma-electrolytic anodic oxidation (PAO) of Al-Mg compounds

A process for the simultaneous plasma-electrolytic anodic oxidation (PAO) of a compound consisting of an Al (AlMgSi1) and Mg (AZ31) alloy is introduced. Using this process, an almost uniformly thick, compact oxide coating on both compound partners can be produced provided that the narrow window of this process is determined and kept. The most important parameters for the simultaneous plasma anodizing are the composition and conductivity of the used electrolyte, the current density and the process time. A short-time process using high current densities has been found suitable. This process is a promising procedure for the protection of Al- and Mg-based compound surfaces.     

Wear characteristics of Fe-based diamond composites with cerium oxide (CeO2) reinforcements

To obtain better wear resistance for the metal bond diamond grinding tools, cerium oxide (CeO₂) with different contents were introduced into Fe-based diamond composites. A pin-on-disc wear test was performed to assess the wear properties of the fabricated specimens, and the morphological properties of the worn surface and corresponding wear debris were evaluated to examine the wear mechanism. Results show that the Fe-based diamond composites with CeO₂ addition exhibited an improvement in the densification, mechanical properties and wear resistance. The original long rod-shaped CeO₂ particles converted into the spherical particles <1 μm, dispersing in the Sn phase. The cerium oxide acted as a sintering aid, promoting the diffusion of Fe in the Sn phase during the sintering process. The dominant wear mechanism of the specimen with CeO₂ addition was the adhesive wear, compared with the abrasive wear in the specimen without CeO₂. With the increase in CeO₂ addition amount, the wear rate decreased. But an excessive amount of CeO₂ was detrimental to mechanical and wear performances. The optimal amount of cerium oxide to achieve the best wear resistance was investigated to be 0.8 wt%.     

Adsorption properties of Ag（Ⅰ）, Au（Ⅲ）, Pd（Ⅱ） and Pt（Ⅳ） ions on commercial 717 anion-exchange resin

The adsorption properties of the four precious metal ions (Ag(I), Au(II), Pd(III) and Pt(IV)) on the commercial Cl^?-form 717 strongly basic anion-exchange resin were studied in detail. The effects of the contact time, solution acidity, and concentrations of Cl^? and Pb²⁺ ions on the adsorption properties were studied by the batch method. Then, the column method was conducted under the optimized adsorption conditions (pH=3.0). The effects of the sample loading flow rate and the length-to-diameter ratios of the columns were investigated. The precious metal ions adsorbed could not be eluted completely after the saturated adsorption because the precious metal ions were found to be reduced to their metallic states during the adsorption process. So, it is recommended that the commercial Cl^?-form 717 strongly basic anion-exchange resin should be decomposed directly to recovery the precious metals after the saturated adsorption.