Electrodeposition and morphology of Ni, Co and Ni-Co alloy powders: Part II. Ammonium chloride supporting electrolyte

Polarization characteristics of the processes of Ni and Co powders and Ni-Co alloy powders electrodeposition from ammonium chloride containing supporting electrolyte and their morphologies are investigated as a function of Ni²⁺ and Co²⁺ ions concentrations. It is found that the shape of the polarization curves in all cases is practically defined by the shape of the polarization curve for hydrogen evolution. It is shown that correct polarization curves, as well as the morphology of electrodeposited powders are sensitive to the ratio of Ni²⁺/Co²⁺ ions concentration. Characteristic feature of powder particles obtained from chloride containing electrolytes is the presence of cone-shaped cavities. In the case of Ni powder cauliflower and spongy type particles are detected, while Co powder contains only spongy type particles. In all cases of alloy powder formation anomalous type of co-deposition is detected.     

电沉积Ni－Co合金及其结构研究

采用硫酸盐体系电沉积Ｎｉ－Ｃｏ合金，研究了电镀工艺参数对镀层组成及电流效率的影响，测定了镀层结构。实验发现：在Ｎｉ－Ｃｏ合金镀层中，当Ｃｏ含量低于７６ｗｔ％时，合金由两种面心立方结构的固溶体组成；Ｃｏ含量介于７６～９０ｗｔ％之间时，由面心立方和六方密排两种结构的固溶体组成；Ｃｏ含量超过９０ｗｔ％时，合金只由一种六方密排结构的固溶体相成。     

低速电沉积钯镍合金工艺的研究

通过极化曲线研究了钯、镍的电沉积行为.讨论了钯镍浓度比、pH值、电流密度、沉积电势等工艺参数对低速电沉积钯镍合金组成的影响.结果表明:与钯相比,镍的极化大,极化度也大;电沉积合金时,钯催化镍的沉积,而镍阻化钯的沉积.合金组成是各工艺参数的函数,镀液中钯、镍离子浓度比是影响合金成分的主要因素.随着镀液中Ni/Pd值的增大,合金中镍含量呈线性增加;pH值升高,合金中镍含量降低;电流密度增大或者沉积电势负移,合金中镍含量增加;沉积电势对合金成分的影响更显著,成分更易控制.     

Electrodeposition and characterization of Cu-Ni-Zn and Cu-Ni-Cd alloys

The electrodeposition of ternary Cu-Ni-Zn and Cu-Ni-Cd alloys was investigated in acidic sulphate electrolytes. The influence of Zn²⁺ and Cd²⁺ ions concentrations as well as the effect of current density on the surface appearance and the deposits’ composition was examined. Sodium dithiolate (NaS)₂CC(CN)₂·3H₂O was used as surface active substance (SAS), and the effect of the SAS on the alloys composition and surface morphology was also investigated. No significant effect of SAS on the alloy composition, however, apparently effect on the deposits surface morphology was observed. It was also noticed that on increasing Zn²⁺ (or Cd²⁺) concentration in the bath, a depletion in the nickel content in the deposit occurred. Deposits obtained were characterized from the structural and morphological points of view. It was found that the structure and morphology of the deposited alloys are mainly controlled by both the applied current densities and the bath composition.     

脉冲镀Ni-Co合金镀层内应力及钴含量的研究

研究了脉冲镀Ni-Co合金的工艺,讨论了脉冲电镀中占空比及频率对镀层内应力及钴含量的影响.实验结果表明:镀层内应力随占空比的增加而降低,随脉冲峰值电流密度增加而升高,随温度的升高而降低.镀层中Co的质量分数则随温度的升高而升高.     

Characterization of electrodeposited powders of the system Ni-Mo-O

The electrodeposition of the Ni-Mo-O alloy powders from ammonium chloride containing electrolytes for different Ni/Mo ions concentration ratios was investigated by the polarization measurements. The morphology, chemical composition and phase composition of the electrodeposited Ni-Mo-O alloy powders were investigated using DSC, TGA, SEM, EDS and XRD analysis. According to the EDS results, the powder composition depends on the Ni/Mo ions concentration ratio. However, some deviations in the composition of the as-deposited powders, as the result of the position of the EDS analysis, revealed that the composition of such powders is not homogeneous. The as-deposited alloy powders were nanocrystalline showing only one broad XRD peak around 44°. Their morphology was found to depend on the Ni/Mo ions concentration ratio. After annealing of the Ni-Mo-O powders for 2 h in N₂ atmosphere at 600 °C, well-defined crystals for all powders were detected by SEM. The presence of the NiMoO₄ phase only or NiMoO₄ and MoO₃ phases in these powders (XRD), depending on the Ni/Mo ions concentration ratio, was identified. The additional EDS analysis on different recrystallized grains revealed the influence of the annealing on a composition of the alloy powders.     

Effects of some plating variables on the electrodeposition of catalytically active nickel-thallium alloy powders

The electrodeposition of nickel-thallium alloy powders was investigated from a selected bath of the composition 0.0125 NiSO₄·6H₂O, 0.01 TICI, 0.10 (NH₄)₂SO₄, 0.10 H₃BO₃ and 0.07 Na₂SO₄·10 H₂O (mol dm^?3). The effects of the pH of the bath, deposition current density and deposition time on the cathodic polarisation, current efficiency and composition of the electrodeposited alloy were determined. The properties of the electrodeposits examined, as a function of the above-mentioned variables, were surface morphology and catalytic activity towards the decomposition of 0.4% H₂O₂ solution. It was found from this investigation that the operating variables influence to a great extent the current efficiency, composition and surface morphology of the electrodeposited alloys; and the catalytic activity is primarily controlled by the surface morphology.     

非晶态Ni—Mo合金的电沉积

从含有NiSO_4、(NH_4)_6Mo_7O_(24)、NaCl、Na_3C_6H_5O_7和NH_3·H_2O的镀液中电沉积具有金属光泽并略带银灰色的非晶态Ni-Mo合金.研究了镀液的组成、pH值及阴极电流密度等对阴极电流效率、合金组成以及合金结构的影响.合金最大钼含量为29.4at%.当镀层中钼含量大于约25at%时,为非晶态结构.此外,还研究了Ni-Mo合金的析氢催化特性.     

Characterization of electrodeposited Cd–Co alloy coatings by anodic linear sweep voltammetry

The electrodeposited Cd–Co alloys were characterized by the anodic linear sweep voltammetry (ALSV) technique in the solution of 1 M NaCl (pH 2). It is shown that Cd–Co alloys could be deposited with high current efficiency (>90%) from the solution containing 0.2 M boric acid, low concentration of cadmium sulfate (0.01 M and 0.02 M) and high concentration of cobalt sulfate (0.2 M and 0.4 M) under the conditions of convective diffusion (RPM = 1000). The ALSVs were characterized by the presence of three peaks: one corresponding to the dissolution of pure Cd, one corresponding to the dissolution of pure Co and one corresponding to the dissolution of unknown phase formed in the system Cd–Co (since the phase diagram of the Cd–Co system does not exist in the literature). Depending on the charge and on the alloy composition (amount of Cd and Co) the peak of the unknown phase can either be hardly seen, or can prevail on the ALSV. This phase is formed mainly on the account of Co, but certain limiting amount of Cd must be deposited for the unknown phase to be formed and seen on the ALSV.     

Raney Ni catalysts derived from different alloy precursors (I) morphology and characterization

Ni-Al alloys containing 41.3, 49.2 and 59.9 wt% Ni were leached by reaction with 20 wt% aqueous NaOH solution under different temperature and time. The reactivities of alloys and morphologies of resultant catalysts were investigated. A large difference in reactivities of alloys toward alkali solution was revealed according to the composition of the alloy. As Al content in precursor alloy increased, the reactivity of alloy toward alkali solution increased. It was shown that, during leaching, reaction in Ni 41.3 wt% alloy is restricted to reaction interface, whereas that in Ni 49.9 wt% alloy occurs throughout the product layer. Surface area and pore size distribution were seen to be strongly dependent upon leaching conditions and relatively independent of the composition of precursor alloy. This paper was prepared at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November 3 and 4, 2004.     

Electrochemical deposition and characterization of ZnCo alloys and corrosion protection by electrodeposited epoxy coating on ZnCo alloy

ZnCo alloys electrochemically deposited on steel under various deposition conditions were investigated. The influence of deposition current density, temperature and composition of deposition solution on the phase structure and corrosion properties of ZnCo alloys were studied. It was found that ZnCo alloy obtained from chloride solution at 5 A dm⁻² showed the best corrosion properties, so this alloy was chosen for further examination. Epoxy coating was electrodeposited on steel and steel modified by ZnCo alloy using constant voltage method. The effect of ZnCo alloy on the corrosion behavior of the protective system based on epoxy coating is interpreted in terms of electrochemical and transport properties, as well as of thermal stability.     

Electrodeposition of Zn–Co alloy coatingsfrom sulfate–chloride electrolytes

The composition, surface morphology and appearance of Zn–Co alloy deposits as a function of current density, electrode potential and Co2+ concentration in the electrolyte was studied. It was found that coatings of good quality with low (1%) Co content are formed at a current density of 0.2Adm–2 and with high (6.5%) Co content at 2Adm–2 from electrolytes containing 1.0M Co2+ under galvanostatic conditions. The potentiodynamic dissolution of coatings with Co content of 6.5% indicates successive deposition of Co enriched phases and a pure Zn phase. The Zn–Co alloys are more corrosion resistant than zinc but are less resistant than cobalt.     

Spark plasma assisted carbothermal reduction-nitridation synthesis of (Ti,W, Mo)(C,N)-(Ni,Co) powders

Ultrafine (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders were rapidly synthesized from various metal oxides, mainly anatase-TiO₂, by spark plasma assisted carbothermal reduction-nitridation (SPCRN) at low temperature. The phase evolution of the SPCRN reaction was investigated using X-ray diffraction (XRD) and the microstructure of the product powders was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). NiO, Co₃O₄ and MoO₃ were converted to Ni, Co and Mo₂C by CR reaction at temperatures below 900 °C. WO₃ was successively transformed from W₂C to WC by CR reaction up to 1100 °C. Finally, at up to 1350 °C, (Ti, W, Mo)(C, N) formed into the sequence of TiO₂, Ti₄O₇, Ti₃O₅, Ti(O, N), Ti(C, N), (Ti, W)(C, N) and (Ti, W, Mo)(C, N). The crystal structure of (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders was analyzed by the Rietveld method and transmission electron microscopy (TEM). The findings demonstrated that the pure (Ti, W, Mo)(C, N)-(Ni, Co) cermet powders with grain size of below 0.5 µm were synthesized from metal oxides by SPCRN reaction at 1400 °C for 10 min.     

化学镀非晶态Co-Ni-P薄膜磁性的研究

化学镀Ｃｏ－Ｎｉ－Ｐ薄膜镀态下为非晶态结构,Ｃｏ－Ｎｉ－Ｐ薄膜的矫顽力较低,矩形比较高,其易磁化方向与膜面垂直。薄膜越厚,矫顽力越高,矩形比越低;镀液的ｐＨ值越高,矫顽力越高;当以化学镀Ｎｉ－Ｐ合金作为中间镀层时,可获得较高的矫顽力和矩形比。     

电镀Ni—Co合金及其电催化性能的研究

研究了以钛和铁为基体的Ｎｉ－Ｃｏ合金电镀，镀层紧密细致，结合力强，耐高温，耐腐蚀，硬度大，并具有优良的电催化性能。     

电沉积Ni-S-Co/ZrO2复合电极及其催化析氢性能

在镀液中悬浮粒径约为200~400 nm 的ZrO2固体颗粒,以电沉积方法制备了Ni-S-Co/ZrO2复合电极。XRD和SEM测试结果表明,沉积层由非晶态的Ni、Co、S和单斜晶型的ZrO2粒子组成。镀层表面呈团粒状结构,无裂隙,与基体结合牢固。电化学测试结果表明,25 ℃时,Ni-S-Co/ZrO2复合电极在28％NaOH溶液中,在电流密度100 mA•cm-2下的超电势为145 mV,与未复合纳米ZrO2粒子的Ni-S-Co电极相比降低了50 mV。表明超细ZrO2的掺入有效提高了电极对析氢反应的催化效果。实验表明,沉积的最佳电流密度为70 mA•cm-2,最适宜的ZrO2用量为15 g/L,采用Ni-S-Co作为过渡层可以显著改善复合镀层与基体的结合。     

Study of Methane Decomposition on Fe/MgO-Based Catalyst Modified by Ni,Co, and Mn Additives

Catalytic decomposition of methane (CDM) generates clean hydrogen and carbon nanomaterials. In this study, methane decomposition to hydrogen and carbon was investigated over Ni-, Co-, or Mn-doped Fe/MgO catalysts. The doping effect of different metals, varying from 3 to 10?wt%, was investigated. The catalytic performance of the obtained materials (noted 15%Fe+x%metal/MgO) revealed that the doping effect of Ni, Co, and Mn significantly improved the activity of Fe/MgO. Among the Ni-doped catalyst series, the 15%Fe+3%Ni/MgO catalyst performed better than the rest of the Ni catalysts. The 6%Co-containing catalyst remained the best in terms of activity in the Co-doped catalyst series and the 15%Fe+6%Mn/MgO solid showed better methane conversion for the Mn-doped series. Overall, 3%Ni-containing catalyst displayed the best catalytic performance among all Ni-, Co-, and Mn-doped catalysts. XRD, N₂ sorption, and H₂ temperature-programmed reduction (TPR), Laser–Raman spectroscopy, thermogravimetric analysis (TGA) under air, and temperature-programmed oxidation (TPO) were used for catalyst characterization. The results revealed that all the doped catalysts exhibited better metallic active site distribution than 15%Fe/MgO and proved that metal doping played a crucial role in catalytic performance.     

离子交换树脂回收钴镍技术进展

随着钴与镍资源的日益枯竭，它们的回收与分离变得十分重要。通过对近20a的相关文献进行调研，总结了目前国内外钴与镍的回收与分离技术的发展趋势：目前常用的方法有化学沉淀法、萃取法和树脂法，但较好的方法是树脂法。简要介绍了离子交换法分离钴镍离子技术工艺的特点，重点阐述了各种树脂在钴镍离子回收的实践和科研中进展情况。     

电沉积Ni-Ru合金及其结构和性能研究

在(25±2)℃下,从含有50 g/L RuCl3·nH2O、30.0 g/L乙酸钠、30.0 g/L二水合柠檬酸钠和15.0～50.0 g/L NiSO4·6H2O的溶液(pH 3.0)中,以1O～90 mA/cm2在铜基底上电沉积制备了Ru含量为5%～70%(原子分数)的Ni-Ru合金.采用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学方法,研究了镀液中NiSO4质量浓度和电流密度对沉积层组成、表面形貌、结构及电催化析氢活性的影响.结果表明,溶液中Ru优先析出并能促进Ni的沉积,镀层中Ru含量随着镀液中Ni2 质量浓度的提高而降低,低电流密度有利于获得Ru含量高的镀层.随着镀液中Ni2 质量浓度的降低或电流密度的提高,镀层表面形貌由较为平整、均匀变为多孔的颗粒状.镀层主要呈现面心立方Ni结构特征,且晶粒尺寸随镀层中Ru含量的增加而变小.Ni-Ru合金电极的析氢活性优于纯Ni,当镀层的Ru原子分数超过15%时,其析氢活性与纯Ru电极接近.