A Study into the Electrodeposition Mechanisms of Zinc-Nickel Alloys from an Acid-Sulphate Bath

Zinc-nickel alloys were electrodeposited under galvanostatic conditions from a sulphate based electrolyte. The effect of deposition current density on alloy composition was determined for an electrolyte containing 0.58 mol/l nickel and 0.92 mol/l zinc (as sulphates). At current densities exceeding 0.01 A/dm², a transition from normal deposition to anomalous co-deposition (ie where the less noble metal deposits preferentially) was observed and alloys rich in zinc were obtained. The transition current density was observed to increase with an increase in electrolyte temperature or a decrease in electrolyte pH.

The electrodeposition mechanism for zinc-nickel alloys in the transition regions was studied in detail using potentiodynamic cathodic polarisation techniques. The results were consistent with the suppression of nickel deposition due to the precipitation of zinc hydroxide on the cathode surface. This was supported by pH measurements made in the vicinity of the cathode where a rise in pH was detected as the transition current density was approached and exceeded the critical pH for zinc hydroxide precipitation.     

Preparation of Al-Si Master Alloy by Electrochemical Reduction of Fly Ash in Molten Salt

An electrochemical method on preparation of Al-Si master alloy was investigated in fluoride-based molten salts of 47.7wt.%NaF-43.3wt.%AlF₃-4wt.%CaF₂ containing 5 wt.% fly ash at 1233 K. The cathodic products obtained by galvanostatic electrolysis were analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy, and energy-dispersive spectrometry. The result showed that the compositions of the products are Al, Si, and Al_3.21Si_0.47. Meanwhile, the cathodic electrochemical process was studied by cyclic voltammetry, and the results showed the reduction peak of aluminum deposition is at ?1.3 V versus the platinum quasi-reference electrode in 50.3wt.%NaF-45.7wt.%AlF₃-4wt.%CaF₂ molten salts, while the reduction peak at ?1.3 V was the co-deposition of aluminum and silicon when the fly ash was added. The silicon and iron were formed via both co-deposition and aluminothermic reduction. In the electrolysis experiments, current efficiency first increased to a maximum value of 40.7% at a current density of 0.29 A/cm², and then it decreased with the increase of current density. With the electrolysis time lasting, the content of aluminum in the alloys decreased from 76.05 wt.% to 48.29 wt.% during 5 h, while the content of silicon increased from 15.94 wt.% to 37.89 wt.%.     

泡沫铝表面Ni-W共沉积及性能研究

目的 进一步提高泡沫铝材料的强度及耐蚀特性，同时明确金属涂覆泡沫铝材料的综合耗能指标。方法 对泡沫铝表面预镀镍层后，在硫酸盐体系下，利用脉冲电镀进行镍钨合金共沉积。通过准静态压缩测试及扫描电镜分析，得到泡沫铝、预镀镍泡沫铝及镍钨共沉积泡沫铝材料的特征曲线及变形模式，综合分析材料的增强机理及综合耗能指标。采用电化学测试对比分析材料耐蚀特性。结果 泡沫铝表面共沉积镍钨合金层后，其峰值应力比镀镍泡沫铝平均提高了10%，较基体泡沫铝平均提高了约45%。强度提高来源于变形过程中包覆金属的支撑及铝基体-镍镀层界面处的拉伸撕裂。镍钨合金共沉积使泡沫铝的能量吸收增加38%，吸能效率有所提升，且其自腐蚀电位较镀镍泡沫铝及基体泡沫铝明显正移，腐蚀倾向及腐蚀速率降低。结论 泡沫铝表面镍钨合金共沉积使其强度、耐蚀性较镀镍泡沫铝进一步提高。由于特征曲线及变形模式的改变，镍钨共沉积泡沫铝的耗能特性提升明显。     

B含量对Al-Zn-Sn系阳极材料组织与性能的影响

在Al-Zn-Sn系阳极材料的基础上添加不同含量的B,研究B对合金组织性能的影响,运用电化学测试、扫描电镜技术,研究合金的组织和电化学性能.结果表明:硼含量主要影响合金的品粒大小、枝晶形态、第二相的数量和分布,进而影响合金表面溶解均匀性和电流效率;合金在B含量为0.0155%时,即按B、Ti质量比为1:3.22的比例添加B,可获得良好的电化学性能.     

新一代激光冲击强化系统对5052铝合金电化学性能的实验研究

利用新一代激光冲击强化系统对5052铝合金试样进行了激光冲击强化处理,通过实验研究了试样的电化学性能,并对材料的物相、表面硬度、腐蚀形貌进行了检测与分析。结果表明:经过激光冲击强化一次、两次后,材料没有发生相变,表面硬度分别提高了7.0%和19.8%,腐蚀速率分别下降了27.0%和35.0%。因此,激光冲击强化处理能有效抑制腐蚀裂纹的扩展,显著提高材料的耐腐蚀性。     

铝合金表面BTSE硅烷化处理研究

通过极化曲线与电化学阻抗谱(EIS)等技术对LY12铝合金表面形成的BTSE硅烷膜在NaCl溶液中的性能进行了研究．结果表明，硅烷膜的存在，一方面很大程度上增大了铝合金的耐蚀性，另一方面并不影响合金电极在腐蚀介质中的电极动力学．这意味着BTSE膜对侵蚀粒子仅起到阻挡层的作用．提出了硅烷化试样在测试溶液中的合理等效电路，并对EIS数据进行了拟合．采用正交设计方法对硅烷化工艺参数进行了优化，其中采用电极体系的极化电阻(由EIS拟合得出)来量化硅烷膜的耐蚀性．文中还对各因素对膜性能的影响规律进行了初步探讨。     

Electrodeposition of zinc and composite zinc–yttria stabilized zirconia coatings

Pure zinc and composite coatings of zinc and nano-sized yttria stabilized zirconia (YSZ) particles were prepared by cathodic electrodeposition from zinc sulphate-based electrolytes containing gelatin. The effects of gelatin on the morphology, crystallographic orientation of the zinc coatings and deposition mechanism of the composite Zn–YSZ coatings were studied. The coatings obtained were studied by scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), X-ray diffraction and potentiodynamic polarization measurements. It was shown that the addition of gelatin to the electrolyte significantly changed the microstructure and crystallographic orientation of the zinc deposits and improved the coating microhardness. In the case of the composite coating co-deposition process, the YSZ particles were found to preferentially rest on the edges or macrosteps of the deposited zinc crystals. The incorporation of YSZ particles into the composite coating was enhanced by reducing the solution pH and through the addition of gelatin. The mechanical and electrochemical properties of conventional zinc coatings were observed to be significantly improved by the incorporation of YSZ particles.     

镍-铝复合涂层的电沉积机理

在改进的Watts溶液中电沉积镍-铝复合涂层。采用Z电位分析、伏安法和电化学阻抗谱（EIS）,研究涂层的电化学行为。结果发现,铝颗粒的Z电位是-4 mV,与氧化铝的非常接近。添加导电铝颗粒到电解液中,导致极化曲线向负电位方向移动,且EIS曲线的环路尺寸增大。结果表明,镍-铝复合层的共沉积行为服从Guglielmi模型。加入的导电铝颗粒起惰性粒子的作用,证实在铝颗粒表面存在薄的氧化铝层。     

Ce对Zn-Al合金组织性能的影响

研究了Ｃｅ对ＺｎＡｌ合金（ＺＡ２７、ＺＡ４３）的力学性能、淬火时效特性及耐磨性的影响。结果表明,Ｃｅ能明显细化合金的铸态组织,提高其强度和塑性。当ＺＡ２７和ＺＡ４３中含Ｃｅ量分别为０．１０％和０．１５％时,获得最佳的力学性能。提出了Ｃｅ细化ＺｎＡｌ合金的机理,加Ｃｅ后成分过冷效应所引起的枝晶熔断脱落对细化α相起主要作用。     

铝合金大气腐蚀综合加速试验方法的研究

采用电化学技术、扫描电子显微镜等方法研究了铝合金大气腐蚀的综合加速试验,并同盐雾试验做了比较.结果表明：降雨/盐雾模式的综合加速试验较好地模拟了大气腐蚀过程中干/湿循环和电化学特点,也较好地模拟了铝合金大气腐蚀的形貌和动力学特征.因此降雨/盐雾模式综合环境试验更好地模拟了铝合金的大气腐蚀.     

铝合金电镀工艺研究

铝及铝合金性质活泼，需经预处理才能进行电镀。采取二次浸锌的方法，在铝合金表面形成了一层锌层，再电镀暗镍、亮铜及装饰铬，得到了质量较高的镀层，并对实验过程进行了分析和讨论。     

Zinc–nickel alloy coatings electrodeposited from a chloride bath using direct and pulse current

Zinc–nickel alloys were electrodeposited on steel from chloride bath by direct and pulse current. Some electric variables (average current density, pulse frequency, duty cycle) and some important bath conditions (ratio of Ni²⁺/Zn²⁺ in bath, temperature) on chemical compositions, current efficiency, microhardness and surface appearance of coatings were studied. At low current densities, transition from anomalous to normal co-deposition was observed for both direct and pulse current. Pulse current seems to increase brightness of the coating and to decrease the precipitation of zinc hydroxide at the cathode surface. In addition, applied pulse current increases the percentage of nickel in deposits. Pulse frequency and duty cycle had little effect on the chemical composition of deposits. The polarization curve of zinc–nickel deposition with pulse current is shifted to positive potentials in comparison with direct current curves. The temperature of the plating bath had a very strong effect on the composition of the deposits. This is primarily the result of intrinsically slow nickel kinetics. The hardness of Zn–Ni alloy coatings (approx. 220 VHN) was greater than the hardness of zinc coating (approx. 161 VHN). The hydroxide suppression mechanism for Zn–Ni co-deposition has been confirmed.     

压铸技术的发展与应用

简述了压铸技术发展的历史及发展状况。叙述了压铸铝合金、镁合金、锌和锌铝合金的研究开发与应用状况。提出了若干压铸合金有待进一步研究开发的问题。     

Fe替代Co对AB5型贮氢合金循环稳定性的影响

用铸造及快淬的方法制备了稀土基AB5型Mm（NiMnSiAl）4．3Co0.6-xFex（x=0，0．1，0．2，0．3，0．4，0．5，0．6）贮氢合金，用XRD。TEM及SEM观测了铸态及快淬态的微观结构，测试了合金在铸态及快淬态下的电化学循环稳定性。研究了Fe替代Co对铸态及快淬态贮氢合金微观结构及循环稳定性的影响。研究结果表明，Fe替代Co对铸态及快淬态合金的相结构没有明显影响，但对合金的循环稳定性产生显著影响。Fe替代Co能不同程度地改善铸态及快淬态合金的循环稳定性，但对快淬态合金循环寿命的改善更加显著，导致这一结果的主要原因是Fe替代Co使快淬态合金的微观组织显著细化。     

水下机器人的电化学防护研究

研究了我国水下机器人用材ＰＯＤ９１９与ＬＤ３１铝合金２在３．５％ＮａＣｌ溶液中的腐蚀性能,测定了铝合金的阴极保护参数及不同系列的牺牲阳极的电化学性能,并选择了合适的牺牲阳极。针对机器人内部构件的紧凑性与复杂性,研究了隙缝尺寸对实施阴极选择的影响,提出了对不同构件采用的电化学保护措施。     

球磨时间对Mg2-xZrxNi(x=0～0.6)电极合金微观结构及电化学性能的影响

在不同的球磨时间下,应用机械合金化法制备出Mg2-xZrxNi(x=0,0.15,0.3,0.45,0.6)电极合金.系统地测试了合金的微观结构及电化学性能,研究了球磨时间对合金微观结构及电化学性能的影响.XRD及 TEM的分析结果表明,合金中的非晶相随球磨时间的延长而增加.电化学测试的结果显示,随球磨时间的增加,合金的循环稳定性及放电电压特性得到显著改善.球磨时间对合金容量的影响与合金的成分相关,对于x≤0.3的合金,其放电容量随球磨时间的延长而单调增加;而对于x>0.3的合金,放电容量随球磨时间的增加有一个极大值.     

Cr和Zn元素对AA3xxx合金均质化热处理微观组织演化的模拟研究

Cr和Zn作为杂质或添加合金元素对铝合金产品的最终性能有很大影响。采用基于热力学与扩散动力学的KWN模型，研究了这两种元素对AA3xxx合金均质化热处理过程中弥散相形成的影响。该研究的目的是展示数学模型对铝合会成分及工艺设计的指导作用。     

Gelatin as corrosion inhibitor for aluminum and aluminum silicon alloys in sodium hydroxide solutions

The corrosion behavior of aluminum and aluminum silicon alloys in 0.1 M NaOH solution in the absence and presence of gelatin was studied using potentiostat polarization, electrochemical impedance spectroscopy (EIS), cyclic voltammetry and potentiodynamic anodic polarization techniques. The percentage inhibition efficiency increases with increasing the concentration of gelatin and with decreasing temperature as well as Si content. This was attributed to a lower affinity of the inhibitor to adsorb on Si than on Al. The inhibitory action of gelatin was explained in terms of adsorption of gelatin on the surface of Al or Al–Si alloys forming a barrier of mass and charge transfer leading to protect the metal surface from the aggressive ones. The adsorption of gelatin on the metal surface follows Freundlich isotherm. Some activated thermodynamic parameters were calculated and discussed.     

Density and solidification feeding model of vacuum counter-pressure cast aluminum alloy under grade-pressuring conditions

The density of vacuum counter-pressure cast aluminum alloy samples under grade-pressuring condition was studied. The effect of grade pressure difference and time on the density of aluminum alloys was discussed, and the solidification feeding model under grade-pressuring condition was established. The results indicate the grade-pressured solidification feeding ability of vacuum counter-pressure casting mainly depends on grade pressure difference and time. With the increase of grade pressure difference, the density of all the aluminum alloy samples increases, and the trend of change in density from the pouring gate to the top location is first decreasing gradually and then increasing. In addition, in obtaining the maximum density, the optimal grade-pressuring time is different for samples with different wall thicknesses, and the solidification time when the solid volume fraction of aluminum alloy reaches about 0.65 appears to be the optimal beginning time for gradepressuring.     

生物浸出体系中中等嗜热菌对锌冶炼窑渣中金属的提取及其电化学特性的影响(英文)

研究中等嗜热菌对锌冶炼窑渣中金属提取的影响以及生物浸出过程中锌冶炼窑渣碳糊电极的电化学特性。结果表明,在矿浆浓度2%、pH1.0、温度65°C、转速为120r/min的浸出条件下,去除生物浸出体系中吸附菌后,废渣中Fe、Cu和Zn的浸出率分别为86.7%、90.3%和66.7%,而在没有去除吸附菌体系中3种金属的浸出率分别为91.9%、96.0%和84.5%。对生物浸出渣和酸浸渣表面细菌分泌物进行FT-IR测试分析可知,生物浸出渣颗粒表面出现了新的官能团振动峰,如1007cm1和1193cm1处的峰,间接说明残渣颗粒表面吸附细菌的存在。生物浸出体系和空白体系的循环伏安曲线和塔菲尔曲线特性进一步表明生物浸出体系中细菌促进了锌冶炼窑渣中有价金属的溶出。