铝合金微弧氧化过程的特性研究及机理分析

在硅酸钠和氢氧化钾电解液中利用微弧氧化方法,在2024铝合金上制备了陶瓷膜层.测定了膜层的厚度,考察了微弧氧化过程中放电参数及形成陶瓷膜速率的规律,用X射线衍射仪(XRD)观察分析了其成分及组成,对陶瓷膜的摩擦性能进行了研究,推断了在电极上发生的反应,对陶瓷膜的成膜机理进行了分析.结果表明,随着时间的进行,阴阳极电压逐步升高,开始时膜厚增加较快,以后逐渐变慢,膜层厚度随时间变化不是简单的线性关系.陶瓷膜内含有γ-Al2O3和α-Al2O3相,膜层内外两相含量差异较大,主要是由于冷却速率不同的原因.陶瓷层表面经历了一个熔融、凝固和冷却的过程.陶瓷层由内向外可以分为过渡层、致密层和疏松层,陶瓷膜与基体的结合非常牢固,属于冶金结合.溶液内的Si、K元素和基体内的合金元素Cu在陶瓷膜中都有存在,阴极成分Fe也存在于陶瓷膜中,放电通道中在高的能量密度下生成了Si-Al-O三重复杂化合物.     

Galvanic Corrosion of a Carbon Steel-Stainless Steel Couple in Sulfide Solutions

The galvanic corrosion behavior of carbon steel-stainless steel couples with various cathode/anode area ratios was investigated in S ²⁻-containing solutions, which were in equilibrium with air, by electrochemical measurements, immersion test, and surface characterization. It is found that the galvanic corrosion effect on carbon steel anode increases with the cathode/anode area ratios, and decreases with the increasing concentration of S²⁻ in the solution. A layer of sulfide film is formed on carbon steel surface, which protects it from corrosion. When the cathode/anode area ratio is 1:1, the potentiodynamic polarization curve measurement and the weight-loss determination give the identical measurement of the galvanic corrosion effect. With the increase of the cathode/anode area ratio, the electrochemical method may not be accurate to determine the galvanic effect. The anodic dissolution current density of carbon steel cannot be approximated simply with the galvanic current density.     

Corrosion Behavior of an Abradable Seal Coating System

A novel NiTi/BN composite abradable coating and two traditional Ni/C and Ni/BN coatings were manufactured with NiAl as the bond layer using thermal spray technology and their corrosion behaviors were investigated. In salt spray corrosion testing of the Ni/BN coating, defective sites of the metal matrix were corroded preferentially. Simulated occlusion experiments and electrochemical tests indicated that migration of ions resulted in pH decrease and Cl^? enrichment in defects, and a more aggressive electrolyte led to a decrease of the corrosion potential of the metal inside defects but an increase of the corrosion current density, representing an autocatalytic corrosion process. Moreover, galvanic corrosion between the top and bond coatings of the abradable system was studied via the electrochemical technique. The results showed that, for the NiTi/BN, Ni/BN, and Ni/graphite coatings with a NiAl bond coating, current flow was generated between the anode and cathode. The NiTi/BN coating acted as the cathode due to its passivation, while the Ni/BN and Ni/graphite coatings acted as the anode because of their lower corrosion potential compared with the NiAl coating. The anode suffered serious corrosion damage due to galvanic corrosion, while the cathode corroded only slightly.     

基于渐变孔隙正极和叉指型流道主动式锂空气液流电池电化学性能理论研究

提出了具有渐变孔隙正极结构的主动式锂空气液流电池,利用溶液泵驱动电解液循环,结合渐变孔隙正极结构,强化电极内部Li^+和O2扩散和结合能力,减弱电极钝化。基于COMSOL Multiphysics 5.3,建立二维电化学模型,用Darcy定律、Butler-Volmer方程和组分输运公式描述在渐变孔隙正极结构(ε=0.55+αX等)下电极内部电解液流动、正负极电化学反应及电解液中Li^+和O2浓度场分布。由于Li2O2积聚在正极孔隙内,电极比表面积下降,采用Carman-Kozeny方程修正渗透率K。研究渐变孔隙率、压强差、氧气参数、正极厚度及动力学速率系数对该电池放电性能影响。结果表明:在放电电流密度0.1 mA/cm^2,电池比电容量是被动式结构的2.5倍;与ε=0.85-0.1X相比,采用ε=0.55+αX结构的电化学性能较佳;在放电电流密度0.1 mA/cm^2下,正极厚度为500^750μm,电池放电性能较好。     

电迁移诱发镀层锡须生长行为分析

分析了0.3×104 A/cm2恒定电流密度和四种不同加载时间（0,48,144和240 h）电迁移条件对6.5 μm厚镀锡层表面锡须生长行为的影响,以及不同电流密度对阴极裂纹宽度的影响.结果表明,电迁移加速了镀层表面锡须的形成与生长,随着电迁移时间的延长,锡须长度不断增加.此外,电迁移导致在阴极首先出现了圆形空洞,随后在两极均形成了圆形空洞,并且在阴极处还发现有微裂纹存在,随着电流密度增加,阴极裂纹宽度也随之增加,电流密度为0.5×104 A/cm2时,平均最大裂纹宽度约为9.2 μm.     

Effect of backfilled stone/brine media on the initial electrochemical performance of aluminum sacrificial anode

Aluminum alloy sacrificial anodes applied to protect the subsea immersed tunnels' steel shells are buried in an unfamiliar inhomogeneous backfilled stone/brine media. To verify its influence, the effect of the backfilled stone (10–12, 6–10, and 3–6 mm)/brine (40 Ω cm) media, denoted as Stone 1, Stone 2, and Stone 3, on the initial electrochemical performance of an Al─Zn─In─Si─Sn─Ti anode is investigated by electrochemical and surface analysis techniques. With decreasing the stone size, the Stones 1–3 media's resistivity increases to 100, 125, and 150 Ω cm, respectively. The backfilled stone/brine media inhibits the anode′s free corrosion and pitting process and accelerates its activation in the initial period. The anode′s capacity and current efficiency decrease slightly; however, the anode′s output current and its transmission are depressed more heavily by decreasing the backfilled stone size. Also, the backfilled stone shields parts of the cathode surfaces, decreases dissolved oxygen concentration, and blocks the diffusion of the anode's dissolution product in the media, resulting in the change of the anode's protective effect.     

某420 kA大型电解槽电热场测试和分析

针对某铝厂420 kA大型铝电解槽进行了全面的电、热场测试,对该槽型的运行情况进行分析。测试了该电解槽阳极、阴极、母线等各部分的欧姆压降,并和设计值进行了比较。测试并计算了立柱母线、阴极、阳极电流分布,比较了和设计值的偏差。测试了该槽型的炉膛形状,分析了高电流密度电解槽的炉膛形成规律。对电解槽的散热和能量平衡进行了详细的计算分析,为大型槽的内衬设计提供了依据。测试发现,该420 kA电解系列由于采用了保温型的设计,电解槽各部分散热比例和传统散热型电解槽有非常大的差异,特别是槽底部,只占电解槽散热的3%以内,比传统7%的散热比例要小得多。结合各项测试内容和生产情况,针对我国大型电解槽的设计提出改进建议。     

Preparation and characterization of tungsten nanopowders from WC scrap in molten salts

Tungsten carbide (WC) scrap was used as a consumable anode to prepare tungsten powder in NaCl–KCl melt at 1023 K for the first time. The electrolysis process was investigated. Results showed that the tungsten component in WC anode was dissolved as W^2 + into the NaCl–KCl melt. The cathode reaction was controlled by the diffusion of tungsten ions. The effect of electrolysis parameters, including the anode–cathode distance, cathode current density and different electrolysis ways (galvanostatic and potentiostatic electrolysis), on the purity and grain size of the cathode deposits was studied. It showed that a large anode–cathode distance was beneficial to the formation of pure tungsten powder at the cathode. With increasing the cathode current density, the tungsten grain size first decreased and then increased. When the cathode current density was 0.125 A cm^− 2, tungsten powder with a diameter of smaller than 100 nm was obtained. Deposits prepared through galvanostatic and potentiostatic electrolysis was compared in the end.     

双膜三室电沉积金属锰联产EMD的离子传输过程

针对传统单槽电解金属锰或二氧化锰存在能耗高、资源利用率低、环境污染严重等问题,提出双膜三室电解法实现阴极电沉积锰同时阳极联产电解二氧化锰,中隔室电化学再生硫酸。通过分析各隔室离子浓度变化,探究双膜三室电解法技术可行性,并对比三种离子交换膜对电沉积效果的影响。结果表明:双膜三室电解法电沉积金属锰同时联产电解二氧化锰可以实现,并且阴极电流效率可达80%以上,阳极电流效率可达60%以上,中隔室酸回收率高于65%;与Ionsep-HC、LANRAN-AM相比,TRJM-10W均相膜槽压最低,电解12h后,阴极电流效率为86.25%,阳极电流效率为70.6%,中隔室酸回收率可达73.08%,但阴极液pH增幅最大,中间液Mn²⁺浓度最高。     

Electrical Characteristics of a Glow Discharge in Air over the Surface of Aluminum Sulfate Aqueous Solution

The paper presents the current?voltage characteristics, the magnitudes of cathode potential drop, the dependences of the total and specific glow discharge power which is injected into the plasma from the discharge current, as well as the density of electrons in the glow discharge in air at atmospheric pressure with the cathode based on 1?10% solutions of aluminum sulfate in distilled water. The distance between the electrolytic liquid cathode and the metal anode is varied from 1 to 10 mm at an average discharge current of 8?36 mA. The discharge is promising for the synthesis of nanostructures of aluminum and aluminum oxide which are formed when processing the solutions with a glow discharge.     

含砂海水中环氧树脂/Q235钢体系的冲刷腐蚀行为研究

目的 研究环氧树脂/Q235钢体系在含砂流动海水中的耐冲刷腐蚀性能.方法 采用旋转冲刷腐蚀试验装置进行不同流速、不同含砂量下环氧树脂/Q235钢体系的冲刷腐蚀试验,利用表面观测、电化学测试以及扫描开尔文探针(SKP)技术研究冲刷腐蚀后体系的腐蚀规律.采用计算流体动力学(CFD)方法模拟计算冲刷流场和砂粒分布.结果 高流...     

In‐situ investigation of the surface‐topography during anodic dissolution of copper under near‐ECM conditions

Electrochemical machining is characterized by deliberate high speed anodic dissolution. The distance between anode and cathode are only a few hundred microns. Additionally, the electrolyte flow rate is in the range of approximately meter/second. A special electrochemical cell design was developed to investigate the surface topography during the anodic dissolution simultaneously and in‐situ under near‐ECM conditions. The anode was directly placed under the cathode with a gap of 350 µm. We carried out pulse experiments at 15 A/cm² and 25 A/cm² with an electrolyte flow rate of 4m/s. First‐time it was possible to observe the surface changing of the anode directly during current pulses by using a video camera. Different stages e.g. roughening, film formation or gas evolution could be distinguished.     

钢筋混凝土结构中阴极保护用MMO涂层钛阳极的研究

采用热分解法制备了IrTa-X混合金属氧化物（MMO）涂层钛阳极。通过极化曲线研究了钛阳极的电化学性能，用SEM观察了涂层形貌，研究了阳极寿命与涂层厚度和电流密度之间的关系，并与国外阳极试样的寿命做了一对比。结果表明，所研制的涂层钛阳极具有良好的电化学性能和较长的使用寿命，是钢筋混凝土结构外加电流阴极保护中比较理想的辅助阳极。     

Fabrication of complex shape electrodes by localized electrochemical deposition

Localized electrochemical deposition (LECD) is a promising technology for fabrication of high-aspect ratio electrode of various materials. This technology is found to be one of the simple and inexpensive ways to fabricate electrodes for micro-EDM. This study presents a novel method to manufacture electrodes with complex cross-section using mask of non-conductive material. In this study, the mask is placed between the anode and cathode, which is immersed in mixed electrolyte of copper sulfate, 1.0 M sulfuric acid and as an additive agent 0.04 g/l of thiourea. The deposition of copper is localized on the cathode surface using a mask and applying ultra short voltage pulses between the anode and cathode. In this setup the cathode is placed above the anode and mask, so that the deposited electrode can be used directly for EDM or any application without changing tool orientation. The deposition characteristics such as size, shape, surface, and structural density according to gap between the anode and mask, applied voltage, pulse frequency and duty ratio have been investigated in this study. Finally, appropriate conditions have been found out for effective fabrication of smooth and fine-grained deposited electrodes based on the findings of the various experiments.     

电流密度对Cu/Sn-9Zn/Ni焊点液-固电迁移行为的影响

采用同步辐射实时成像技术对比研究了不同电流密度对Cu/Sn-9Zn/Ni焊点液-固电迁移行为和界面反应的影响。结果表明,当电流密度为5.0×10~3A/cm~2时,无论电子方向如何,钎料中的Zn原子均定向扩散至Cu侧界面参与界面反应,导致Cu侧界面处金属间化合物(intermetallic compounds,IMC)的厚度大于Ni侧界面处IMC的厚度;而当电流密度升高至1.0×10~4和2.0×10~4 A/cm~2时,钎料中的Zn原子均定向扩散至阴极界面,界面IMC的生长表现为"反极性效应",电流密度越高界面IMC的"反极性效应"越显著。液-固电迁移过程中Cu基体消耗明显,特别是在高电流密度条件下,电子从Ni侧流向Cu侧时,Cu基体的溶解厚度与时间呈现线性关系,电流密度越高Cu基体的溶解速率越快。此外,基于焊点中原子电迁移通量J_(em)和化学势通量J_(chem)对Zn原子和Cu在不同电流密度下的迁移行为进行了研究。     

镀铂多孔金属钛性能的研究

钛镀铂作为不溶性阳极、阴极,已广泛应用于电解工业。采用电镀技术在多孔钛表面沉积了均匀的铂金属层,分析了多孔钛镀铂后的表面状态及电化学性能,并与IrTi涂层阳极及镀铂钛网阴极进行比较,结果显示：多孔钛板开孔孔隙表面可均匀沉积结合力良好的铂层,镀层厚度为2μm;镀铂多孔钛阴极析氢电位比镀铂钛网高,且在大电流下,阳极析氧电位比IrTi涂层阳极高。因此采用这种方法制备出的电极可大幅降低能耗,使用寿命得以延长,对电解工业节能具有重要意义。     

交流电频率对X80管线钢在酸性土壤模拟溶液中腐蚀行为的影响

通过电化学测试、浸泡实验和表面分析技术研究了交流电频率(50~400 Hz)对X80钢在鹰潭酸性土壤模拟溶液中腐蚀行为的影响。结果表明,随交流电频率的增加,X80钢的腐蚀速率逐渐减小,腐蚀程度减弱。交流电作用下X80钢生成的腐蚀产物疏松、裂纹多,对基体的保护性很差。X80钢的腐蚀电位偏移量随交流电频率的增大而减小。随交流电频率的增大,阴、阳极极化曲线的振荡幅度逐渐减弱。交流电的施加不仅使阴、阳极的电流密度增大,还使阴极反应由混合控制逐渐向活化控制转变。     

Spatially resolved Langmuir probe measurements of a magnetically enhanced hollow cathode arc plasma

Hollow cathode arc discharges are efficient plasma sources and are applied in substrate pretreatment or plasma-activated deposition processes. In order to generate large volume homogeneous plasmas to guarantee uniformity of plasma activation and coating properties, in the presented configuration a ring-shaped anode is positioned coaxially around the hollow cathode tube. A magnetic field is applied, which is axial within the cathode tube and spreads out in the deposition chamber. In order to characterize the hollow cathode plasma, spatially resolved Langmuir probe measurements have been carried out. The charge carrier density maximum on the cathode tube axis reaches values up to 10¹³ cm^? 3. With increasing distance from the plasma source, the plasma density decreases and shows a smoother lateral profile. Maxwellian electron energy distribution functions are observed with spatially homogeneous electron temperatures in the range 1–4 eV. Increasing the chamber pressure leads to higher plasma densities and lower electron temperatures. Reduction of the gas flow through the hollow cathode tube results in a strong rise of the plasma density over two orders of magnitude. The magnetic field supports the low gas flow mode and leads to higher plasma densities, too. The results of the Langmuir probe measurements are discussed by means of the active zone model and are further related to optical emission measurements performed in the vicinity of the hollow cathode orifice.     

Investigation of the plasma electrolytic oxidation of Ti6Al4V under single-pulse power supply

Plasma electrolytic oxidation (PEO) was studied using electrochemical impedance spectroscopy (EIS) and transient waveform analysis. First, EIS measurements on coatings prepared under constant current density were conducted in the working electrolyte. The EIS analysis showed that the coating structure changed with the termination voltage. Second, the pulse waveform of the power supply was recorded during the PEO process. It showed that a charging process occurred across the breakdown coating at the beginning of the pulse. The present study analysed this charging process in detail.     

恒电位对TiAlN涂层在海水环境中磨蚀性能的影响

目的研究不同恒电位对TiAlN涂层在海水环境中磨蚀性能的影响,分析其腐蚀磨损行为。方法用PVD多弧离子镀技术在316不锈钢上沉积TiAlN涂层。通过XRD测试、硬度测试、结合力测试、电化学工作站测试、不同恒电位下磨蚀测试及磨痕截面轮廓测试,分别评价TiAlN涂层的相结构、表面硬度、结合力、电化学性能、摩擦系数和磨损率,通过扫描电子显微镜观察涂层磨痕形貌并分析其磨蚀损伤机理。结果 TiAlN涂层在海水环境下的抗腐蚀性优于基体316不锈钢。在阴极电位下,恒电位增加使涂层的摩擦系数逐渐降低。阳极电位为0.5 V时,摩擦形成的TiO_2基含水化合物颗粒可作为润滑剂,使涂层的摩擦系数迅速降低至0.45。TiAlN涂层在干摩擦条件下的磨损率为5.5678×10-5 mm3/(N·m),在阴极保护电位为-1 V下的磨损率为2.2909×10-6 mm3/(N·m),在开路电位(OCP)下的磨损率为7.4881×10-5 mm3/(N·m)。结论随着加载电位(SCE)的升高,涂层的腐蚀效应愈发明显。涂层在阴极电位下的磨蚀机理主要为塑性变形,在阳极电位下的磨蚀机理主要为疲劳点蚀。