Laser-enhanced electrodeposition of nickel coatings

Optimal conditions for a laser-enhanced electrodeposition of nickel coatings have been specified. Comparative results of structure and mechanical properties of electrically deposited nickel coatings produced by a laser-enhanced galvanostatic method and without laser emission were analysed. It was found that laser medium wave IR radiation has a local thermal effect on the process of electrodeposition and stimulates formation of a nickel coating structure which is of a more equilibrium state, less defective and has reduced internal stress in the area of local laser heating. Studies of plating rate showed a 1.4 times increase for nickel coatings in conditions of laser-enhanced electrodeposition due to reduction of common cathode overpotentional and increase of cathode metal efficiency, that involves generation of a more coarse microcrystal structure. Results of studies of the laser radiation effect on structure and properties of nickel coatings show potential for increased adhesion of electrodeposited coatings with a copper substrate.     

Microstructure and properties of nanocrystalline nickel coatings prepared by pulse jet electrodeposition

The fabrication of nanocrystalline nickel coatings was conducted by pulse jet electrodeposition on the substrate of 45# carbon steel. The effects of average current density on the surface morphology, microstructure, average grain size and microhardness of nickel coatings were investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and microhardness measurement. In addition, the corrosion resistances of coating and substrate were compared. It is revealed that the nickel coatings prepared by pulse jet electrodeposition exhibit a fine-grained structure with a smooth surface and a high density, although some pores and defects are still present in coatings. With the increase of average current density, the average grain size of nickel coatings is reduced at first and then increased. The coating with the optimum compactness, the smallest average grain size (13.7 nm) and the highest microhardness are obtained at current density of 39.8 A/dm2. The corrosion resistance is obviously increased for the coatings prepared by pulse jet electrodeposition; however, the corrosion rate is increased after a certain period due to the penetration of the corrosive media.     

电镀金刚石线锯快速植砂工艺研究

为了提高电镀金刚石线锯的制备效率,通过金刚石微粉表面化学镀镍、钢丝基体磁化处理等方式改进上砂工艺,结合SEM、EDS及高斯计等研究不同工艺因素对电镀线锯的制备效率及耐用度的影响。结果表明:基体磁感应强度、金刚石质量浓度及上砂时间对线锯制备效率及耐用度有重要影响;采用磁化基体制备线锯的最佳上砂工艺参数为:电流密度5 A/dm2、基体磁感应强度0.6mT、上砂槽金刚石质量浓度15g/L、上砂时间30s、温度45℃。采用最佳工艺参数制备线锯的上砂时间缩减为金刚石及钢丝基体没有处理时制备线锯的上砂时间的1/20,制备效率可提高81%,同时还能保持较高的耐用度。      

Plating by electric explosion of conductors

The influence of the energy characteristics of the electric explosion of metal conductors on the structure and stability of a coating applied on a substrate has been studied experimentally. It is established that, at ω = ω_c, the nickel coating consists of chaotically placed hardened metal drops and is unsteady. The coating formed by fine-dispersed nickel particles deposited from the gaseous phase in the course of an electroexplosion at ω = 2ω_c is uniform and resistant to mechanical impacts.     

Studies on the Mechanism,Structure and Microhardness of Ni-W Alloy Electrodeposits

The electrodeposition of Ni-W alloy has been studied on the glassy carbon electrode by the cyclic voltammetry and potentiostatic step methods. It has been found that electrodeposition of Ni-W alloy involves an intermediate valence tungsten oxide which inhibits hydrogen evolution. Ni-W alloy electrodeposition occurs by a mechanism involving progressive nucleation followed by three dimensional growth.

The structures of nickel-tungsten alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD results from Ni-W alloy deposits reveal a face-centered cubic solid solution, the microstructure of the deposits exhibit (111) preferred orientation. The lattice constant and microhardness of Ni-W alloy deposit increase as the tungsten content increases, the XPS results of Ni-W alloy deposits indicate that the nickel and tungsten of the deposits exist in the metallic state, but the Ni-W alloy deposit with a tungsten content of 40.7% is an intermetallic compound. The XPS results of the deposit with tungsten content of 40.7% show that the atomic ratio of Ni to W is 4:1, so β-Ni₄ W alloy can be obtained by electrodeposition and its microhardness (Hv) is as high as 672.8.     

Fabrication of tunable pore size of nickel membranes by electrodeposition on colloidal monolayer template

Large-area nickel patterned membranes with tunable pore size are prepared by the combination of self-assembly nanosphere lithography and electrodeposition. The morphology of the nickel membranes exhibits a honeycomb or egg-shell-roofed structure depending on the deposition time and the electrostatic-induced absorption effect. With an increase of electrodeposition time, the movement of polystyrene spheres caused by metal-filling gradually changes the contact evolution between the spheres and the substrate from facet contact to quasi-point contact, until complete lift from the substrate. Hence, the pore size can be controlled by varying the deposition time; i.e., by controlling the contact area between the polystyrene spheres and the substrate. Such membranes can be useful as templates for nanofabrication. The site and density control of one-dimensional nanostructures, depending on the distance and the size of the pore, is a critical issue in many potential applications, such as optical antennas, biosensors and bioprobes, and field emission devices.     

Excellent mechanical properties of three-dimensionally ordered macroporous nickel photonic crystals

High quality three-dimensionally ordered macroporous (3DOM) nickel photonic crystals (PCs) are fabricated using the polystyrene template-assisted electrodeposition method on nickel alloy substrate. The Ni²⁺ in solution will firstly arrive in the electrode (nickel alloy substrate) and occupy the interstices among the PS template spheres; when enlarge the deposition time to 5 min, 3DOM nickel PCs will be achieved. The 3DOM nickel PCs grow firmly on the substrate due to the similar bounds between the PCs and substrate. Excellent mechanical properties are observed in the 3DOM nickel PCs, which may promote the practical applications of PCs.     

The Structure and Protective Properties of Zinc and Nickel Alternate Electrodeposits

A NEW TYPE of coatings consisting of a large numberof laminar deposits has been the keen subject of muchresearch,because these layered-structure coatingspossess improved properties or novel phenomenon suchas increased mechanical strength,micro-hardness,giantmagnetoresistance and corrosion resistance[1"6'.Thesecoating systems with individual layers making upoverall structure are also called compositionallymodulated multilayer(CMM)coatings'3"5'.In view ofthe plating historical use of surface…     

In situ electrochemical wet cell transmission electron microscopy characterization of solid-liquid interactions between Ni and aqueous NiCl2

Electrodeposition and electropolishing of nanograined nickel has been observed using an in situ electrochemical wet cell developed for transmission electron microscopy. The cell employs two thin film nickel electrodes in a 0.1 M aqueous NiCl₂ electrolyte, which were biased at ±1 V. Anisotropic electrodeposition was observed in which growth of the nickel film across the substrate occurred much more rapidly than growth perpendicular to the substrate. The anisotropic behavior results from relatively equiaxed nanograins nucleating at the growth front with little subsequent coarsening. Grains were observed to nucleate ahead of the growth front, suggesting a new mechanism for electrochemically driven growth across a substrate which depends on ionic surface adsorption ahead of the growth front. During electropolishing the dissolution of nickel tended to occur more isotropically. The film thinned relatively uniformly until certain regions displayed Rayleigh instabilities. At this point the film broke up and some regions coarsened rapidly and/or were subject to electromigration.     

电沉积工艺对铁—镍—磷合金磁参量影响的研究

本文通过对电沉积铁-镍-磷合金磁性能的的测定,探讨了不同电沉积工艺参数及施加磁场电沉积对合金主要技术磁参量(μ_0、H_c、B_r、Ph及Bs)的影响规律;并获得具有较佳磁性能的电沉积工艺参数。研究结果表明,随pH值的增大,非晶合金的B_s增大,H_c、B_r、Ph等呈下降趋势。随D_k的增大,非晶合金的B_s不断增大,μ_o持续下降,H_c、B_r、Ph等呈上升趋势。当pH=1.5、D_k=10A/dm~2左右时,非晶合金具有较佳的软磁特性。外加磁场电沉积可有效的调整铁-镍-磷合金的磁性能。     

摩擦辅助喷射电沉积纳米晶镍的电化学腐蚀行为

采用摩擦辅助喷射电沉积工艺和传统喷射电沉积工艺制备纳米晶镍,用TEM对比分析了二者的组织结构,用电化学极化法研究了2种纳米晶镍层在3.5%NaCl(质量分数)溶液及1 mol/L H2SO4溶液中的腐蚀行为。结果表明,摩擦辅助喷射电沉积结晶过程更加均匀,制备的纳米晶镍层组织致密,晶粒细小,平均晶粒达到9.77 nm;在2种腐蚀溶液中,摩擦辅助喷射电沉积制备的纳米晶镍的电化学腐蚀性能均优于传统喷射电沉积;在NaCl溶液中,摩擦辅助喷射电沉积所制纳米晶镍在腐蚀过程中有钝化膜产生。并指出晶粒大小与微观缺陷是影响纳米晶镍耐腐蚀性能的2个重要因素     

Effect of the Current Density on Morphology,Porosity, and Tribological Properties of Electrodeposited Nickel on Copper

In the steel industry, nickel coating on copper has increased the lifespan of continuous ingot casting molds. The objective of this work is to estimate the porosity of nanocrystalline nickel electrodeposited onto copper. Characteristics of nickel coating such as hardness, wear resistance, porosity, morphology, and adhesion are very important for maximum performance of molds. The effective porosity in nickel coating was determined by using anodic voltammetry. The porosity of electrodeposited nickel onto copper increased from 0.16% up to 6.22% as the current density increased from 1.5 up to 8.0 A dm⁻². The morphology of the nickel electrodeposited at lower current densities was more compact. Tribological properties were studied using hardness measurements, and calotest. Results of calotest indicated a wear coefficient of 10⁻⁶ for all samples. An extremely low friction coefficient of 0.06-0.08 was obtained for the sample deposited with a current density of 1.5 A dm⁻², and a friction coefficient of 0.15-0.21 was measured for the nickel coating electrodeposited at a current density of 5 A dm⁻². Effects of the current density of the electrodeposition process on the morphology, porosity, and tribological properties were evaluated.     

Evaluation of effect of grain size on mechanical and tribological properties of pulse electrodeposited nanocrystalline nickel using nanoindentation techniques

Abstract

Pulse electrodeposition of nanocrystalline nickel has been carried out on AA 6061 substrate from a modified Watt’s bath using saccharin as a grain refining additive. By varying the concentration of saccharin and other operating parameters, nanocrystalline nickel electrodeposits of varying average grain sizes (from 115 down to 17 nm) have been obtained. Nanoindentation was employed for studying the effect of average grain size on the mechanical and tribological properties of the electrodeposits, with emphasis on hardness, elastic modulus, wear resistance and coefficient of friction. The study confirms that the hardness of nanocrystalline nickel electrodeposits increases as the average grain size decreases and a value as high as 7·2 GPa is obtained for a coating having an average grain size of 17 nm. No inverse Hall–Petch relationship is observed for the entire range of grain sizes studied. The elastic modulus of the electrodeposits remained almost constant (between 150 and 160 GPa), irrespective of the average grain size and a coefficient of friction value of 0·25 has been obtained for a deposit having an average grain size of 17 nm.     

Formation of ferromagnetism in pseudobinary PrNi<Subscript>5 − <Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (2.5 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 5) solid solutions

The structure and magnetic properties of the PrNi_{5 − x} Cu _x alloys have been studied in a composition range of 2.5 ≤ x ≤ 5. Single-phase solid solutions with a hexagonal structure of the CaCu₅ type have been shown to be realized within this composition range. It has been found that upon the introduction of nickel into the Van Vleck paramagnet PrCu₅ the ground state of the alloys with x ≤ 4.3 becomes ferromagnetic. All the compositions under study exhibit high magnetocrystalline anisotropy of the “easy-basal-plane” type. With allowance for the literature data available, a complete magnetic phase diagram of the PrNi_{5 − x} Cu _x system was constructed; it is characterized by two maxima in the compositional dependence of the Curie temperature. The earlier suggested model of the effect of local random crystal fields on the magnetic state of Pr³⁺ ions in alloys with low copper contents was shown to be applicable also for the explanation of magnetic properties of alloys with low nickel contents. The results of this study confirm the hypothesis about the determining role of local irregular crystal fields in the formation of the magnetic properties of the pseudobinary PrNi_{5 − x} Cu _x intermetallic compounds.     

Studies of Structure and Electrocatalytic Hydrogen Evolution on Electrodeposited Nanocrystalline Ni-Mo Alloy Electrodes

Nanocrystalline Ni-Mo alloy deposits were obtained by electrodeposition. The structures of the alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD shows that Ni-Mo alloy deposit with 15·2% molybdenum exhibits (111) preferred orientation, the lattice constant is larger than that of nickel metal. The XPS results on nanocrystalline Ni-Mo alloy deposits indicate that the nickel and molybdenum of the deposits exist in the metallic state, the binding energy of the alloyed elements increase to some extent. The nanocrystalline Ni-Mo alloy deposit electrode may offer better electrocatalytic activity than the polycrystalline nickel electrode. The electrochemical impedance spectra from the nanocrystalline Ni-Mo alloy electrode indicate that hydrogen evolution in 30% (m/m) KOH is in accordance with the Volmer-Heyrovsky mechanism.     

Jet electrodeposition multilayer nickel on the surface of sintered NdFeB and corrosion behaviours

Sintered neodymium (NdFeB) magnet material is highly vulnerable to corrosion. To solve this problem, three kinds of structures (dark nickel, bright nickel, and multilayered nickel) were produced efficiently and quickly by using jet electrodeposition technology. The structure and microstructure of the coatings were analysed by X-ray diffraction and field-emission scanning electron microscopy, respectively. The corrosion resistance of the samples was evaluated by potentiodynamic polarisation (Tafel). By comparing the corrosion behaviours of different structures, we found that the corrosion resistance of multilayered structure nickel coating was much higher than that of single layered nickel and the surface quality was significantly improved compared with dark nickel, which can better protect the NdFeB material.     

The Use of Crystal Orientation in Mapping the Electrodeposition of Cobalt and Copper

The orientation of the substrate used in electrodeposition has a significant effect on the distribution and morphology of the deposit. This may be particularly important in producing multilayered structures with a short repeat distance.

It has been shown that on a multi-crystalline copper substrate the deposition of cobalt takes place preferably on certain orientations, and that little deposition takes place on other orientations. The electrodeposited Co may be either hcp or fcc. When copper is deposited on cobalt, the distribution of growth is relatively independent of the substrate orientation. In this study scanning Auger spectroscopy complemented crystal orientation mapping.     

超亲水/超疏水镍-纳米三氧化钨复合镀层的制备及特性分析

硬度高、寿命长、适用范围广的金属基自清洁表面的制备是国内外研究的热点和难点。以镍为金属基体,纳米三氧化钨（WO₃）作为功能性材料,采用复合电沉积法在金属基底上制备出超亲水或超疏水可选择的镍-纳米三氧化钨自清洁镀层。使用SEM、S-neox 三维光学轮廓仪、EDS、接触角测量仪等测量其表面形貌特征、力学性能、表面润湿性及光催化性能。结果表明：WO₃质量分数为17%时的镍-纳米三氧化钨复合镀层表面呈现典型的微纳米分级结构特征和超亲水润湿特性,并具有光催化降解甲基橙溶液能力;经氟化处理,复合镀层由超亲水转变为超疏水,接触角高达156.5°;经电化学刻蚀-氟化处理,复合镀层的疏水能力更强,光催化性更好;制备的复合镀层具备超亲水或超疏水特性,具有硬度高、与金属基体结合力大、光催化降解有机物等更加优异的自清洁性能。     

Electrolytic Codeposition of Nickel and Phosphorus from Methanesulfonate Electrolyte

The characteristics of Ni–P alloy electrodeposition from a methanesulfonate electrolyte have been investigated. It has been found that the phosphorus content of the alloy increases with increasing the concentration of sodium hypophosphite in the electrolyte and reducing the electrodeposition current density. A mechanism of codeposition of nickel and phosphorus has been suggested. It is shown that phosphorus was formed by electrochemical reduction of hypophosphite anions and their disproportionation at a catalytically active surface of a nickel cathode. It has been shown quantitatively that the most likely path for the formation of phosphorus through the electrochemical mechanism is the direct electrochemical reduction of a hypophosphite anion to atomic phosphorus. The rate of phosphorous formation from hypophosphite anions is dependent on the concentration of hydrogen ions in the near-electrode layer. Therefore, the phosphorus content of the coatings obtained from the methanesulfonate electrolyte is slightly decreased as compared with that from the sulfate electrolyte which exhibits higher buffering properties. It has been revealed that codeposition of nickel and phosphorus reduces the kinetic difficulties of electrochemical reduction of the nickel ions. This might be due to an increased near-electrode concentration of nickel hydroxyl complexes discharging at the cathode, which is the result of an increased near-electrode pH caused by the reactions involving hypophosphite anions and hydrogen ions.     

Crystallization behavior of electroless Co-Ni-B alloy plated in magnetic field in presence of cerium

1 Introduction Electroless Co-Ni-B soft magnetic thin film has the property of high microhardness, wearability and excellent soft magnetism[1, 2], and possesses many advantages such as simple preparation and low cost. It can be used as a new type of soft …