Distinguishing nanowire and nanotube formation by the deposition current transients

ABSTRACT: High aspect ratio Ni nanowires (NWs) and nanotubes (NTs) were electrodeposited inside ordered arrays of self-assembled pores (approximately 50 nm in diameter and approximately 50 um in length) in anodic alumina templates by a potentiostatic method. The current transients monitored during each process allowed us to distinguish between NW and NT formation. The depositions were long enough for the deposited metal to reach the top of the template and form a continuous Ni film. The overfilling process was found to occur in two steps when depositing NWs and in a single step in the case of NTs. A comparative study of the morphological, structural, and magnetic properties of the Ni NWs and NTs was performed using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively.     

Study on the activity and stability of urease immobilized onto nanoporous alumina membranes

Nanoporous alumina membranes were employed as substrate materials for urease immobilization. Anodic porous alumina was prepared by the two-step anodization of high purity aluminum. By controlling anodization conditions, the nanoporous structure with desired dimension was obtained. Urease immobilization onto nanoporous alumina membranes was performed by four different protocols. Effect of pore diameter, pore length and immobilization methods on the activity and stability of immobilized enzyme was discussed in detail. The results show that the enzymes immobilized onto porous alumina with big pore diameter possess high activity and poor stability as compared to small pore diameter. The effect of pore length is complicated, the activity of enzyme increases with the increasing pore length for big pore size; while for correspondingly small pore size, enzymatic activity slightly depends on pore length. The immobilization methods have a slight effect on enzymatic activity, whereas enzyme immobilization by chitosan coating and reticulation with glutaraldehyde exhibits a good long-term stability as compared to that only via physical adsorption.     

阳极氧化工艺对氧化铝纳米孔膜形成过程及结构的影响

采用高纯度的铝片为阳极，以铂网为阴极，在3％～5％草酸溶液中，电压在30～70V，温度控制在17～25℃范围内进行恒压阳极氧化制备氧化铝膜，并采用环境扫描电镜观察纳米孔形貌，金相显微镜测量氧化膜厚度。研究了电解电压、电解液浓度、温度等条件对氧化铝多孔膜结构的影响。结果表明：氧化膜形成速度、纳米孔孔径、胞径、孔壁厚度、氧化膜厚度受电解电压影响显著，随着电解液浓度和温度的增大，氧化膜生长速度加快，纳米孔孔径、孔壁厚度等都随之增大，在相同时间内生成的氧化膜厚度增大。     

废镍触媒的综合利用工艺研究

扼要介绍了工业废镍催化剂的综合利用工艺研究。对其主成分Ni和Al均加以回收利用,分别制取结晶硫酸镍、氢氧化铝及氧化铝。产品质量达国家工业标准。Ni回收率高达90％。     

直接电沉积法制备纳米银修饰丝网印刷电极及其对H2O2电催化性能的研究

采用直接电沉积法制备了纳米银修饰丝网印刷电极,利用扫描电子显微镜对电极表面纳米银颗粒进行了表征。实验结果表明,电极表面纳米银颗粒的尺寸和覆盖度随电沉积的时间而增加。研究了修饰电极的电化学性质,该电极对H2O2的电还原过程具有明显的催化作用。通过测量该还原电流,可以实现对10—3mmol／L范围内的H2O2进行测定。     

脉冲与直流电沉积RE-Ni-W-P-SiC复合镀层性能研究

采用脉冲与直流电沉积，研究了RE—Ni—W—P—SiC复合镀层的性能。结果表明：在相同的条件下，采用脉冲电流得到的复合镀层比直流电流得到的镀层有更高的硬度、沉积速度，同时耐磨、耐蚀性也得到提高。     

超声波对硫酸盐镀镍及镀层性能的影响研究

研究了硫酸盐镀镍过程中施加超声波对阴极极化能力、阴极电流效率、分散能力、电化学反应阻抗、镀层内应力和硬度的影响。结果表明,镀镍过程中施加超声波能够降低阴极极化、提高阴极电流效率、改善电解液的分散能力、减小镍沉积阻抗;还能细化镀层晶粒、降低镀层内应力、提高镀层的硬度。     

Effect of electrode configuration and mode of deposition on magnetoresistance in electrodeposited Co/Cu multilayers on n-Si by a fully electrochemical method

Electrodeposition of metallic multilayers on Si is normally preceded by the vapour deposition of a metallic layer. Since vapour deposition produces an additional step in the production process, direct electrodeposition of multilayers on Si is desirable. However, direct electrodeposition on Si has resulted in low magnetoresistance (MR) - of the order of 1% - at room temperature. With the use of (i) electroless plated copper back contact, (ii) composite potentiostatic pulses, (iii) horizontal electrode configuration and (iv) non-continuous mode of deposition, a room temperature MR of 5.8% has been achieved.     

铝合金换向电流法氧化发色工艺的研究

采用周期换向电流法对铜较高的铝合金进行电解氧化发色。分别对温度与氧化电流密度等影响氧化膜生长速度与质量的工艺条件做了分析研究,取得了实用的工艺操作作规程。研究结果表明：应用周期换向电流法可以在硫酸溶液中对较难氧化着色的铝铜合金进行氧化发色,得到黄－黄绿－绿－黑绿－黑系列颜色的氧化膜。     

Fabrication of integrated arrays of ultrahigh density magnetic nanowires on glass by anodization and electrodeposition

Integrated nanowire arrays of Fe-Pt, Co-Pt, and Ni-Pt alloys were successfully fabricated on glass substrates by successive anodization and electrodeposition. Porous alumina films, which were formed from an aluminum layers sputter-deposited on glass substrates covered with transparent oxide conductive films, were used as template-electrodes to deposit various magnetic alloys (Fe-Pt, Co-Pt, and Ni-Pt) in the nanopores by a cathodic electrodeposition, thus leading to integrated nanowire arrays with ultrahigh densities of (0.6-2.1) × 10¹⁵ wire m⁻². The as-deposited nanowires of Fe-Pt, Co-Pt, and Ni-Pt alloys are polycrystalline and composed of fine crystals (4-7 nm across) of chemically ordered tetragonal FePt, CoPt, or NiPt phase. The integrated nanowire arrays may be the promising candidate materials for ultrahigh density perpendicular magnetic recording media in terabits per square inch regime, due to the predictable enhanced perpendicular magnetic performance after appropriate annealing.     

Effect of Pyridine and its Derivatives on the Electrodeposition of Nickel from Aqueous Sulfate solutions Part I: Current Efficiency, Surface Morphology and Crystal Orientation

The effects of pyridine and its derivatives on current efficiency, surface morphology and crystallographic orientations of electrodeposited nickel from acidic sulfate solutions were investigated. The results indicated that the presence of pyridine and picolines had no significant effect on current efficiency. The deposits obtained were smoother, more compact and uniform with picolines than with pyridine. A significant change in surface morphology of the electrodeposits was observed and picolines were found to be better additives than pyridine, 4-picoline being the best. X-ray diffraction revealed that the (200) plane was the most preferred plane and was not affected by the presence of any of these additives in the electrolyte.     

工艺条件及镀液杂质对瓦特镍镀层内应力的影响

为控制生产中瓦特镍镀层的内应力,利用条形阴极法测试了镀液的温度、pH及镀液中的杂质等对瓦特镍镀层内应力的影响。结果表明,镀镍液θ为50℃,pH为4.0时,镀层内应力最小;随着镀液中Cu~(2+)、Zn~(2+)金属杂质含量的增加,镀层内应力均增加;另外,在生产中为降低镀层的内应力,还需严格控制硫酸镍品质。     

Electrodeposition of Ag and Pd on a reconstructed Au(1 1 1) electrode surface studied by in situ scanning tunneling microscopy

Electrochemical deposition of Ag and potential-induced structural change of the deposited Ag layer on a reconstructed surface of Au(1 1 1) electrode were followed by in situ scanning tunneling microscope (STM). A uniform Ag monolayer was formed on a reconstructed Au(1 1 1) surface in a 50-mM H₂SO₄ solution at +0.3 V (vs. Ag/AgCl) after adding a solution containing Ag₂SO₄ so that the concentration of Ag⁺ in the STM cell became ca. 2 μM. No characteristic height corrugation such as the Au reconstruction was observed on the surface, indicating that the lifting of the substrate Au reconstruction occurred by Ag deposition. The formed Ag monolayer was converted to a net-like shaped Ag nano-pattern of biatomic height when the potential was stepped from +0.3 to −0.2 V in the solution containing 2 μM Ag⁺. This result indicates that the substrate Au(1 1 1)-(1 × 1) surface was converted to the reconstructed surface even in the presence of Ag adlayer. Quite different structure was observed for Pd deposition on a reconstructed surface of Au(1 1 1) electrode at +0.3 V and the origin for this difference between Ag and Pd deposition is discussed.     

Adsorption Studies of Heavy Metal Cations on Silica Flat Bed Induced with Microcrystalline Cellulose Gels: Quantitative Determination of Cobalt and Nickel by Optical Scanning Densitometry

Silica gel H impregnated with microcrystalline cellulose gel in alkaline medium was used as a stationary phase for the thin layer chromatography of heavy metal cations. A mixture of 10% aqueous potassium thiocyanate and triton X-100 in 1:1 v/v has been identified as the best combination of mobile phase for achieving selective separation of cobalt from nickel. The efficacy of the chromatographic system has been investigated by monitoring reproducibility of R_F values and spot compactness with respect to the change in sample concentration and matrix effect. The improved selectivity of impregnated silica gel H was expounded by SEM and FTIR studies. The typical surface modification as well as the chemical changes in impregnated silica gel H was attributed. Chromatograms of the cations were quantitatively evaluated by scanning densitometry in comparison with ICP elemental analysis. The proposed method is applied for the determination of cobalt and nickel cations in spiked samples of geological and industrial origin.