Improving the electrochemistry and microstructure of nickel electrode by deposition on anodized titanium substrate for the electrocatalytic oxidation of methanol and ethanol

The electrodeposition process of nickel and the substrate used for the electrodeposition can be improved to obtain an effective catalyst for methanol oxidation. Thus, nanoparticles of nickel have been uniformly electrodeposited on the surface of previously anodized titanium at 5 V during 1 h. The optimized microstructure has been studied by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XPS and argon-ion etching experiments have revealed the composition profile of the titanium/titania/nickel thin film electrode. Metallic Ni is detected by XRD. The nickel particles dispersed in a porous TiO₂ substrate have great catalytic activity for methanol oxidation in basic solution and through the redox couple NiO(OH)/Ni(OH)₂. The optimized titania substrate yields to electrodes (crystalline titanium/amorphous titania/nanocrystalline nickel) with higher catalytic activity than non-anodized metallic titanium (titanium/nickel). However, further oxidation and thickening of the titania film drives to poorer electrochemical behavior. The SEM and EDS results show that the nickel particles exhibit certain tendency to agglomerate and to form spherical particles of around 2 μm. This electrode material also is active to oxidize ethanol, but this activity is poorer.     

Study on the adhesion mechanism of electrodeposited nickel clusters on carbon substrates

Growth and adhesion mechanisms of Ni clusters electrodeposited on three different carbon-based substrates have been studied. Glassy carbon, carbon paper and PAN-based fibres have been used as working electrodes and Ni clusters have been electrodeposited from a NiCl₂·6H₂O. Ni reduction on carbon substrates has been studied by cyclic voltammetry, chronocoulometry and in situ SERS, whereas the morphological and structural characterization of the interface between Ni clusters and carbon-based substrates has been performed by High Resolution TEM.From our results we can conclude that the precipitation of Ni hydroxides and basic salts in the unbuffered catholyte promotes the adhesion of Ni clusters on the carbon-based substrates considered in this study. This feature of the investigated Ni clusters electrodeposition suggests that it may be a suitable fabrication route for applications in catalytic processes, such as metal-particle catalysed growth of carbon nanotubes.     

Electrodeposition of magnesium film from BMIMBF4 ionic liquid

In this paper, we reported for the first time magnesium electrodeposition and dissolution processes in the ionic liquid of BMIMBF₄ with 1 M Mg(CF₃SO₃)₂ at room temperature. Our study found that complete electrochemical reoxidation of the electrodeposited magnesium film was feasible only on Ag substrate, comparing with the Pt, Ni, and stainless-steel. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) results showed that magnesium was found in the deposited film and the deposits were dense. The electrodeposition of magnesium on Ag substrate in the ionic liquid was considered to be a reversible process by cyclic voltammetry. Plots of peak current versus the square root of the scan rate were found to be linear, which indicates that the mass-transport process of electroactive species was mainly diffusion controlled. The diffusion coefficient D values of electroactive species were calculated from cyclic voltammetry and chronoamperometry, respectively.     

Electrodeposition of well adherent metallic clusters on carbon substrates

The good adhesion of electrodeposited Ni clusters on carbon supports was demonstrated; the metallic clusters were deposited on recompressed graphite (Papyex) and PAN-based fibres (Toray T300) by electrodeposition technique. For both substrates, the process parameters were optimized in order to obtain a uniform and dense spatial distribution of the Ni clusters with narrow size distribution peaked around 50 nm. The morphology of the Ni clusters was characterized by SEM and AFM.The cluster adhesion to the substrates was tested with several experiments: Ni coated carbon substrates were dipped into different liquids, processed with a variety of treatments (immersion, magnetic stirring, centrifugation and ultrasonic bath) and then observed with SEM. Moreover, nano-scratch tests were performed on Ni coated supports by means of an AFM equipped with a diamond tip.     

Electrodeposition and magnetic properties of Ni nanowire arrays on anodic aluminum oxide/Ti/Si substrate

Ni nanowire arrays with different diameters have now been extended to directly fabricate in porous anodic alumina oxide (AAO) templates on Ti/Si substrate by direct current (DC) electrodeposition. An aluminum film is firstly sputter-deposited on a silicon substrate coated with a 300 nm Ti film. AAO/Ti/Si substrate is synthesized by a two-step electrochemical anodization of the aluminum film on the Ti/Si substrate and then used as template to grow Ni nanowire arrays with different diameters. The coercivity and the squareness in parallel direction of Ni nanowires with about 10 nm diameters are 664 Oe and 0.90, respectively. The Ni nanowire arrays fabricated on AAO/Ti/Si substrates should lead to practical applications in ultrahigh-density magnetic storage devices because of the excellent properties.     

Magnetoelectric Effect in Gallium Arsenide–Nickel–Tin–Nickel Multilayer Structures

Experimental data have been presented for the magnetoelectric effect in nickel–tin–nickel multilayer structures grown on a GaAs substrate by cathodic electrodeposition. The method of fabricating these structures has been described, and the frequency dependence of the effect has been demonstrated. It has been shown that tin used as an intermediate layer reduces mechanical stresses due to the phase mismatch at the Ni–GaAs interface and, thus, makes it possible to grow good structures with a 70-μm-thick Ni layer. The grown structures offer good adhesion between layers and a high Q factor.     

铀矿坑水样中铀电沉积层的表征

描述了硫酸铵溶液中铀矿坑水样品中铀的电沉积层特性。 电沉积液为10 ml 0.8 M的硫酸铵溶液, 电流密度0.6 A/cm2, pH值为2.5, 电镀1 h。 电沉积经化学分离后的水样品和电沉积的纯硝酸铀酰样品进行了比较, 并对二者分别做了红外(IR)光谱、 扫描电镜(SEM)、 元素分析以及α能谱测量。 IR谱上铀酰离子的反对称伸缩振动峰在887 cm-1附近, 使电沉积在不锈钢片上的铀主要以铀酰离子水合物的形式存在, 有一部分NH+4以NH3的形式替代水合物中的水, 使电沉积层中铀的化合物形式为UO2(OH)2·xNH3·yH2O或者UO2(OH)2-x·(ONH4)x·yH2O, 铀酰离子通过链的形式形成聚合结构。 SEM照片显示电沉积层均匀, 没堆积成团现象出现。 α谱表明电沉积层中铀的同位素主要是238U和234U, 相应的α能量峰4198和4773 keV很显著, 没其它峰的干扰。 Characteristics of electrodeposited uranium films of uranium ore water sample in ammonium sulphate was investigated in this work. The optimized electrodeposited conditions were as follows: electrolyte was ammonium sulphate of 0.8 M, and current density at the cathode was 0.6 A/cm2, electrolyte pH value was 2.5, the time of plating on the electrodeposition was 1 h. In this situation, the uniform, thin and adheresive films were produced by electrodeposition method. Two samples were made, one electrodeposition of pure uranyl nitrate, and another electrodeposition of uranium ore water sample after chemical separation. Characteristics of electrodeposited uranium films of uranium ore water sample after chemical separation was studied, making comparisons with electrodeposited films of uranyl nitrate. The analysis of film characteristics was done through infrared (IR) spectrum, scanning electron microscopy(SEM), element analysis and α spectrum measurment. According to Fourier transform infrared spectra, the asymmetric stretching vibration band of uranyl group is around 887 cm-1. In addition, according to IR spectrum, we know that uranium exists mainly as the form of hydrated polymeric compound in the film. Electrodeposited uranium films also included many NH+4. Polymeric structures of variable composition were present in the electrodeposited samples, with the unit monomeric formula UO2(OH)2·xNH3·yH2O or UO2(OH)2-x·(ONH4)x·yH2O. Scanning electron microscopy shows that the two samples have similar surface characteristics and no cluster is observed. The samples were also measured by spectrometer equipped with Passivated Implanted Planar Silicon(PIPS) detector. From the α spectrum, we know that isotopes of uranium in the film are 238U and 234U. 235U is not found in the α spectrum. It also shows that the chemical separation process can isolate uranium from other interfering elements effectively, the result of chemical separation is very satisfactory and electrodeposited process is rather efficient. Source electrodeposited in ammonium sulphate through optimized conditions satisfies the need of high resolution α spectrum.     

Magnetostriction and magnetoresistance in nanocontacts

Ni nanocontacts have been grown by electrodeposition using a self-terminating technique in a single electrolyte bath based on nickel sulfate, nickel chloride and boric acid. Resistance measurements performed on different samples presented two kinds of obviously different magnetoresistance effects. The analysis of the data sets showed that magnetostriction might play a key role in magnetoresistance of the electrodeposited Ni nanocontacts.     

Characterization of thin Zn-Ni alloy coatings electrodeposited on low carbon steel

The characteristics of initial layer formation in alkaline bath for Zn-Ni (12-15%) alloy electrodeposition on low carbon steel plates are detected in a nanometric thickness range by electron probe microanalysis (EPMA), with both bulk sample and thin film on substrate correction procedure, glow discharge optical emission spectroscopy (GDOES) and gracing incidence X-ray diffraction (GIXRD). The Zn-Ni coatings were elaborated using either intensiostatic or potentiostatic mode. A preferential deposition of Ni, in the initial thin layer, is detected by these analyses; according to EPMA and GDOES measurements, a layer rich in nickel at the interface substrate/deposit is observed (90 wt.% Ni) and approved by GIXRD; the thin layer of Ni formed in the first moments of electrolysis greatly inhibits the Zn deposition. The initial layer depends upon the relative ease of hydrogen and metal discharge and on the different substrate surfaces involved. The electrodeposition of zinc-nickel alloys in the first stage is a normal phenomenon of codeposition, whereby nickel - the more noble metal - is deposited preferentially.     

Friction and wear properties of the co-deposited Ni-SiC nanocomposite coating

Ni-SiC nanocomposite coatings were produced by electrodeposition from a nickel sulfate bath containing SiC nanoparticles with an average particle size of 30 nm. The characteristics of the coatings were assessed by scanning electron microscopy and microhardness test. The friction and wear performance of Ni-SiC nanocomposite coatings and Ni film were comparatively investigated sliding against Si₃N₄ ceramic balls under non-lubricated conditions. The results indicated that compared to Ni film, Ni-SiC nanocomposite coating exhibited enhanced microhardness and wear resistance. The effect of SiC nanoparticles on the friction and wear resistance is discussed in detail.     

Hall Mobility of As‐Grown Cu2O Thin Films Obtained Via Electrodeposition on Patterned Au Substrates

Hall measurement of an electrodeposited Cu₂O film is rendered difficult as the bilayer structure of semiconductor on top of a conductive substrate obviates the measurement. Here, we propose the use of a patterned Au on glass substrate in line/space configuration for the Hall measurement of electrodeposited Cu₂O. A continuous, (111) oriented Cu₂O film was electrodeposited on 8 μm/2 μm Au‐line/space on glass substrate and Hall measurement was performed. The room temperature Hall measurement of the Cu₂O film on the patterned substrate indicates p‐type conduction with a hole concentration of 2.2 × 10¹⁷ cm^?3 and mobility of 4.7 × 10^?3 cm² V^?1 s^?1. Additionally, the temperature dependent resistivity exhibits a negative slope that is characteristic of a semiconductor. Therefore, the measured electrical characteristics can be attributed to the electrodeposited Cu₂O semiconductor film rather than the conductive substrate. This method can be applied for the Hall measurement of any other electrodeposited semiconductor by optimizing the line/space geometry of the conductive substrate.     

The influence of pH electrolyte on the electrochemical deposition and properties of nickel thin films

Ni thin films were electrodeposited on gold substrate from chloride solution with different pH at room temperature. The effect of electrolyte pH on Ni coatings was studied by using the cyclic voltammetry, the scanning electron microscopy (SEM), x-ray diffraction, and alternating gradient force magnetometer measurements. From electrochemical measurements, the onset potential for reduction of Ni was gradually shifted towards more cathodic scan with increase in pH; this is due to the protons in the case of low pH values and to the hydroxide ions in the case of higher pH values. The SEM study showed that a granular and compact structure of the electrodeposited Ni layers and the variation of film morphology with bath pH are established. The x-ray diffraction spectra revealed the formation of fcc structure Ni thin films with a preferential orientation along the Ni(111). The size of the deposited crystals in both the cases has been found to be in the range of 49–153 nm. Magnetic properties such as coercivity and saturation magnetization showed strong dependence on the electrolyte solution pH and consequently the crystallite size. Coercivity higher than 130–160 Oe was achieved for a pH value of 4 to 5. The differences observed in the magnetic properties were attributed to the structural changes caused by the electrolyte pH.     

衬底材料对制备立方氮化硼薄膜的影响

较系统地研究了不同衬底材料对制备氮化硼薄膜的影响。用热丝增强射频等离子体CVD法,以NH3,B2H6和H2为反应气体,在Si,Ni,Co和不锈钢等衬底材料上,成功生长出高质量的立方氮化硼薄膜,还用13.56MHz的射频溅射系统将c-BN薄膜沉积在Si衬底上,靶材为h-BN(纯度为99.99％）,溅射气体为氩气和氮气的混合气体,所得到的氮化硼薄膜中立方相含量高于90%,用X射线衍射谱和傅里叶变换红谱对样品进行了分析表明,衬底材料与c-BN的晶格匹配情况,对于CVD生长立方氮化硼薄膜影响很大,而对溅射生长立方氮化硼薄膜影响不大。     

Structure and phonon spectrum of a submonolayer Ni film on the surface of Cu(100)

The equilibrium atomic structure and the phonon spectra of a submonolayer (θ = 0.5 monolayer) Ni film deposited on the surface of Cu(100) are calculated using the potentials obtained by the embedded atom method. We consider atomic relaxation, the vibrational state density distribution on Ni and substrate atoms, and polarization of vibrational modes. Variation of the phonon spectrum upon segregation of Cu atoms on the film surface is considered. It is shown that mixing of vibrations of Ni adatoms with vibrations of substrate atoms occurs in the entire frequency range, leading to a frequency shift of the vibrational modes of the substrate and to the occurrence of new vibrational states atypical of a clean surface. The Cu(100)–c(2 × 2)–Ni structure is dynamically stabler when placed in the subsurface layer of the substrate.     

Surface morphology and local magnetic properties of electrodeposited thin iron layers

Thin iron layers with different thickness were prepared by electrodeposition on the polycrystalline substrate. The surface morphology of the layers, their structure and local magnetic properties were studied using scanning tunneling microscopy (STM), X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS). STM studies revealed the granular structure of the surface of the electrodeposited iron layers with the roughness up to 10 nm. XRD analysis proved that these layers were highly strained. The CEMS spectra showed an in-plane magnetic anisotropy in the iron layers. Isomer shift of the electrodeposited iron was different than that of the -Fe. This difference was attributed to the internal stresses existing in the electrodeposited layers.     

Physical and electrochemical characterizations of Ni-SiO2 nanocomposite coatings

Advances in materials performance often require the development of composite system. In the present investigation, SiO₂-reinforced nickel composite coatings were deposited on a mild steel substrate using direct current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of the Ni and Ni-SiO₂ nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of SiO₂ particles in the Ni nanocomposite coating on the microhardness and corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon oxide particles were obtained. The preferred growth process of the nickel matrix in crystallographic directions <111>, <200> and <220> is strongly influenced by SiO₂ nanoparticles. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~23 nm for electrodeposited nickel and ~21 nm for Ni-SiO₂ nanocomposite coatings. The crystallite structure was fcc for electrodeposited nickel and Ni-SiO₂ nanocomposite coatings. The incorporation of SiO₂ particles into the Ni matrices was found to improve corrosion resistance of pure Ni coatings. The corrosion potential (E _corr) in the case of Ni-SiO₂ nanocomposite coatings had shown a negative shift, confirming the cathodic protective nature of the coating. The Ni-SiO₂ composite coatings have exhibited significantly improved microhardness (615 HV) compared to pure nickel coatings (265 HV)     

Anomalous scaling for thick electrodeposited films

Anomalous surface roughness scaling, where both the local and the large-scale roughness show a power-law dependence on the film thickness, has been widely observed. Here we show that the value of the local roughness exponent in the early stages of Cu electrodeposition depends on the deposition potential. However, initial anomalous scaling can lead to two qualitatively different types of behavior for large film thickness (t>/ or =4 microm). For Cu films electrodeposited with forced convection at high potential and current density, the anomalous scaling is transient: the local roughness saturates for the thickest films studied. When Cu films are electrodeposited at similar potential and current density but with reduced convection, no saturation of the local roughness is observed. Instead the film forms overhangs such that the surface height becomes a multivalued function of the lateral position.     

Oxygen separation induced by Xe ion beam upon electrodeposited oxygen-nickel and oxygen-chromium systems on iron substrate studied by conversion electron Mössbauer spectroscopy

Nickel was electrodeposited on one side and chromium on the other side of a sheet of α-iron enriched (∼85%) with⁵⁷Fe. The electrodeposited Ni and Cr contained oxygen and it could be separated by 500 keV xenon implantation. The separated oxygen formed an amorphous metal-oxide interphase at the interface of iron substrate and electrodeposited Ni or Cr.     

Selective electroplating of copper lines on pre-patterned tantalum oxide thin films

Direct selective metal deposition on semiconductors is of interest to electronic device technology, in particular for interconnects and Schottky devices. In this study, we investigate selective copper electrodeposition on patterned tantalum oxide thin films. Cyclic voltammetry studies show that thick tantalum oxide thin films have insulating properties while oxide films thinner than a critical value are semiconductors. Copper films electrodeposited on tantalum oxide thin films are known to form Schottky contacts. We demonstrate the formation of copper patterns on pre-patterned tantalum oxide films by a simple process: an insulating tantalum oxide film was grown electrochemically, the film was then mechanically scratched followed by mild oxidation to produce a thin tantalum oxide film inside the scratch. Based on the differential behavior of thin and thick tantalum oxide films, metal lines were electrodeposited selectively under formation of Schottky junctions. The process demonstrated in this paper is compatible to standard processes for semiconductor device fabrication while permitting flexible prototyping for research at small scales.     

Improving nucleation in the fabrication of high-quality 3D macro-porous copper film through the surface-modification of a polystyrene colloid-assembled template

A new approach is developed to the fabrication of high-quality three-dimensional macro-porous copper films. A highly-ordered macroporous copper film is successfully produced on a polystyrene sphere (PS) template that has been modified by sodium dodecyl sulfate (SDS). It is shown that this procedure can change a hydrophobic surface of PS template into a hydrophilic surface. The present study is devoted to the influence of the electrolyte solution transport on the nucleation process. It is demonstrated that the permeability of the electrolyte solution in the nanochannels of the PS template plays an important role in the chemical electrodeposition of high-quality macroporous copper film. The permeability is drastically enhanced in our experiment through the surface modification of the PS templates. The method could be used to homogeneously produce a large number of nucleations on a substrate, which is a key factor for the fabrication of the high-quality macroporous copper film.