多孔阳极氧化铝膜的制备及电化学阻抗谱分析

在8℃、40V直流电压、0.3 mol/L的草酸电解液中,采用两步阳极氧化法用高纯度铝箔制备多孔阳极氧化铝（AAO）膜。用场发射扫描电子显微镜观察多孔阳极氧化铝膜的形貌。采用电化学交流阻抗法测量多孔阳极氧化铝膜制备过程中一次氧化和二次氧化后的电化学阻抗谱。试验结果表明,所制备的多孔阳极氧化铝膜为高度有序排列的纳米孔洞阵列。根据试验得到的电化学阻抗谱建立了R（QR）（QR）等效电路,该等效电路能较好地表征多孔阳极纳米氧化铝膜的电化学特性,进而找到了等效电路中电学元件与草酸电解液、多孔氧化铝膜的特性及界面电荷转移的关系。该研究有助于研究多孔阳极氧化铝膜的生长过程及形成机理。     

纳米多孔氧化铝膜的制备与结构表征

采用二次阳极氧化法,以草酸为电解液,制备纳米多孔氧化铝膜。利用扫描电镜、原子力显微镜和X射线衍射仪对氧化铝薄膜的微观形貌和相组成进行了表征,研究了二次阳极氧化法制备纳米多孔氧化铝膜的过程和成膜机理。结果表明:二次阳极氧化制备的纳米多孔氧化铝膜为非定型态,所得孔洞排列规则且分布均匀,平均孔径约为29 nm,孔密度为1.74×1010个/cm2。纳米多孔氧化铝膜的形成经历了阻挡层形成、微孔层形成和多孔层形成与长大等阶段。     

铝阳极氧化膜在NaCl溶液中的电化学性能

采用交流阻抗法研究了工业纯铝L3阳极氧化膜在中性NaCl溶液中交流阻抗谱的变化规律, 比较了未封闭处理与沸水封闭处理后氧化膜的交流阻抗谱的差异, 并结合等效电路分析了氧化膜多孔层与阻挡层电化学参数的变化.结果表明, 未封闭的阳极氧化膜在NaCl溶液中浸泡初期存在一个自封闭过程, 封闭处理明显提高氧化膜多孔层的初始Rp值并降低初始CPEp值; 溶液中侵蚀性离子浓度越高, 封闭处理提高铝阳极氧化膜的耐蚀性能作用越明显.     

电化学法研究铝阳极氧化膜的抗腐蚀性

工业纯铝L2在硫酸溶液中进行阳极氧化制得阳极氧化膜,测试了此阳极氧化膜在NaCl溶液中的电化学性能。通过动态极化法和交流阻抗法对阳极氧化膜进行分析,发现阳极氧化膜的制备条件(电解液浓度、时间、电压等)不同时,膜的抗腐蚀性能也不同。电化学阻抗法测定表明,随浸泡时间的增加,膜阻抗值明显增大,可能是多孔膜在介质溶液中存在一个自然水合封闭的过程。     

阳极氧化法制备多孔氧化铝模板

采用阳极氧化法，以硫酸为电解液制备了多孔氧化铝模板。讨论了氧化电压和电解液温度对多孔阳极氧化铝膜的孔径的影响。试验结果表明，当氧化时间为6h时，氧化膜厚度达到最大值35．6μm。XRD分析结果证实，多孔氧化铝膜由非晶态的Al2O3组成。     

镁合金阳极氧化膜成膜过程的交流阻抗谱研究

采用阳极氧化工艺对AZ31镁合金进行表面处理,利用交流阻抗技术(EIS)研究了阳极氧化膜的成膜过程。结果表明,不同氧化时间氧化膜的阻抗谱变化具有明显的规律性,可以划分为4个阶段,并且各阶段之间存在显著差异。利用R(C(R(QR)))(CR)模型进行计算机拟合,得到的等效电路元件拟合值显示:随着氧化时间的延长,膜表面孔洞增多,粗糙度也随之增大;氧化膜阻挡层和多孔层的生长并不同步,而是一个动态变化的过程。     

多孔阳极氧化铝膜的制备及应用研究

详细研究了合成条件对制备多孔阳极氧化铝膜的影响,以所制备的多孔阳极氧化铝膜为模板,初步研究了氧化铁纳米线的制备。实验1.带基体的多孔AAO模板的制备。铝片预处理。实验铝片纯度为99.99%,厚度0.3mm。将铝片依次在丙酮、乙醇和蒸馏水中超声清洗去除表面的油污。然后     

铝阳极氧化膜在去离子水中的自封闭效应

采用交流阻抗法研究了工业纯铝L3阳极氧化膜在去离子水中的自封闭效应,并结合等效电路分析了氧化膜多孔层与阻挡层电化学参数的变化。结果表明,未封闭的阳极氧化膜在去离子水中浸泡初期存在一个明显的自封闭过程,导致阳极氧化膜在浸泡初期的耐蚀性提高。     

《电镀与精饰》2009年第11期摘要

多孔阳极氧化铝模板制备工艺的研究以硫酸为电解液,采用二次阳极氧化工艺制备高度有序的多孔阳极氧化铝模板。研究了电解液浓度、阳极氧化电压和制备温度对多孔阳极氧化铝模板形貌和孔洞尺寸的影响,并以高氯酸和丙酮的混合溶液为电解液,利用第三次阳极氧化,一步实现了多孔阳极     

腐蚀铝箔高压阳极氧化膜微观结构与电化学特征

将高压铝电解电容器用腐蚀铝箔在硼酸电解质溶液中进行530 V阳极氧化,应用透射电镜与交流阻抗研究了所形成的高压阳极氧化膜的微观结构与电化学特征。结果表明:高压阳极氧化膜具有明显的层状结构特征,各层的结晶程度与缺陷特征不同,外层晶化程度较低、缺陷较少;中层与内层晶化程度较高、缺陷较多;铝箔表面微孔诱发弥散效应,交流阻抗频谱的等效电路可用膜QOX与膜电阻ROX并联,再与电解液电阻RS串联来表征,容抗行为显著接近界面电容元件特性,膜电阻处于氧化膜非晶质层电阻与结晶质层电阻之间而偏向结晶质层电阻。     

EIS characterisation of anodic films formed on 2024 aluminium alloy, in sulphuric acid containing molybdate or permanganate species

Electrolytes composed of sulphuric acid and corrosion inhibitors (molybdate or permanganate species) were proposed in order to replace chromic acid for the anodising of 2024 aluminium alloy. The electrochemical impedance spectroscopy (EIS) method was used to visualise the correlation between the corrosion performance in NaCl and the morphology of these new anodic layers. From an appropriate equivalent circuit, EIS parameters concerning the porous and barrier layers were detected. Their evolution during corrosion tests was discussed. The results indicate that the morphology and the corrosion resistance of anodic films formed in acid sulphuric with molybdate species remain unchanged. On the contrary, morphological properties of anodic films formed in presence of permanganate species are modified, favouring their corrosion performance. EIS analyses were completed with SEM technique.     

The electrochemical behaviour of Ti‐13Nb‐13Zr alloy in various solutions

The electrochemical behaviour of a near‐β Ti‐13Nb‐13Zr alloy for the application as implants was investigated in various solutions. The electrolytes used were 0.9 wt% NaCl solution, Hanks' solution and a culture medium known as minimum essential medium (MEM) composed of salts, vitamins and amino acids, all at 37 °C. The electrochemical behaviour was investigated by the following electrochemical techniques: open circuit potential measurements as a function of time, electrochemical impedance spectroscopy (EIS) and determination of polarisation curves. The obtained results showed that the Ti alloy was passive in all electrolytes. The EIS results were analysed using an equivalent electrical circuit representing a duplex structure oxide layer, composed of an inner barrier layer, mainly responsible for the alloy corrosion resistance, and an outer and porous layer that has been associated to osteointegration ability. The properties of both layers were dependent on the electrolyte used. The results suggested that the thickest porous layer is formed in the MEM solution whereas the impedance of the barrier layer formed in this solution was the lowest among the electrolytes used. The polarisation curves showed a current increase at potentials around 1300 mV versus saturated calomel electrode (SCE), and this increase was also dependent on the electrolyte used. The highest increase in current density was also associated to the MEM solution suggesting that this is the most aggressive electrolyte to the Ti alloy among the three tested solutions.     

Influence of copper on the morphology of porous anodic alumina

Sputtering-deposited Al-Cu alloy layers and an Al-Cu/Al bi-layer are used to investigate the influences of copper on the morphology of porous anodic alumina films formed galvanostatically in either sulphuric or phosphoric acid electrolyte. The results reveal development of an irregular morphology of pores during anodizing of the alloy layers, contrasting with the linear porosity of films formed on aluminium. Further, the rates of film growth and alloy consumption are relatively low, since oxygen is generated following enrichment of copper in the alloy and incorporation of copper species into the anodic film. The linear morphology is re-established following depletion of the copper in the bi-layer and at the same time, film growth accelerates as oxygen evolution diminishes. The irregular pore morphology is considered to arise from stress-driven pore development influenced by effects of oxygen bubbles within the anodic alumina.     

Surface Characteristics and Electrochemical Impedance Investigation of Spark-Anodized Ti-6Al-4V Alloy

In this study, the surface characteristic of oxide films on Ti-6Al-4V alloy formed by an anodic oxidation treatment in H₂SO₄/H₃PO₄ electrolyte at potentials higher than the breakdown voltage was evaluated. Morphology of the surface layers was studied by scanning electron microscope. The results indicated that the diameter of pores and porosity of oxide layer increase by increasing the anodizing voltage. The thickness measurement of the oxide layers showed a linear increase of thickness with increasing the anodizing voltage. The EDS analysis of oxide films formed in H₂SO₄/H₃PO₄ at potentials higher than breakdown voltage demonstrated precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. X-ray diffraction was employed to exhibit the effect of anodizing voltage on the oxide layer structure. Roughness measurements of oxide layer showed that in spark anodizing, the Ra and Rz parameters would increase by increasing the anodizing voltage. The structure and Corrosion properties of oxide layers were studied using electrochemical impedance spectroscopy (EIS) techniques, in 0.9 wt.% NaCl solution. The obtained EIS spectra and their interpretation in terms of an equivalent circuit with the circuit elements indicated that the detailed impedance behavior is affected by three regions of the interface: the space charge region, the inner compact layer, and outer porous layer.     

Pore development in anodic alumina in sulphuric acid and borax electrolytes

The formation of porous anodic films on an Al-3.5 at.%W alloy is compared in sulphuric acid and borax electrolytes in order to investigate pore development processes. The findings disclose that for anodizing in sulphuric acid, the pores develop mainly due to the influences of field-induced plasticity of the film and growth stresses; in borax, field-assisted dissolution dominates. The films formed in sulphuric acid are consequently much thicker than the layer of oxidized alloy and tungsten species are retained in the film. In contrast, with borax, the films and oxidized alloy layers are of similar thickness and tungsten species are lost to the electrolyte. Efficiencies of film growth are also significantly different, about 65% in sulphuric acid and about 52% in borax. The retention of tungsten species during anodizing in sulphuric acid is due to the localization of tungsten in the inner regions of the barrier layer and cell walls, with a layer of anodic alumina separating the tungsten-containing regions from the electrolyte. For borax, the tungsten is distributed more uniformly through the film material, enabling loss of tungsten species to the electrolyte from the pore base.     

Alumina nanostructures prepared by two-step anodization process

Alumina nanostructures were obtained by two-step anodization process.The porous anodic aluminum oxide(AAO)membranes were anodized in oxalic acid,which was subsequently treated with chemical etching process with 1.0 mol/L sodiumhydroxide solution,or mixed solution of phosphoric acid(6.0%)and chromic acid(1.8%),respectively.Field emission scanningelectron microscopy(FE-SEM)and transmission electron microscopy(TEM)were employed to character the morphology andstructure of the obtained alumina nanostructure.It is found that alumina nanowires are generated in the acidic chemical etchingsolution,while nanotube structures are formed in the alkaline solution.The influence of acid and alkaline solution on aluminamorphologies in the chemical etching process was discussed.     

硼酸对7050铝合金硼酸-硫酸阳极氧化膜结构及耐蚀性的影响(英文)

通过 AFM、交流阻抗谱及扫描 Kelvin 探针技术,研究硼酸对 7050 铝合金硼酸?硫酸阳极氧化膜结构及耐蚀性的影响。结果表明,在硼酸-硫酸阳极氧化体系中,硼酸不会改变氧化膜阻挡层的结构,但会显著影响氧化膜多孔层的结构形式,进而影响氧化膜的耐蚀性。在 0～8 g/L 的范围内,随着电解液中硼酸含量的增加,氧化膜的多孔层电阻增大,电容减小,表面势正移,孔径缩小,耐蚀性变好。在高于 8 g/L 时,随着硼酸含量的增加,氧化膜的孔隙变大,阻抗变小,电子逸出功降低,耐蚀性变差。     

Sealing of Porous Anodic Films on Aluminium

The sealing of porous anodic films, formed on aluminium in sulphuric acid, has been examined using electrochemical impedance spectroscopy. In contrast to many previous studies, distilled water has been used, and measurements have been made both at room temperature and at the boiling point of water. The latter approach has formed the basis of the assessment of impedance spectroscopy as an on-line monitoring technique for the effectiveness of sealing of porous anodic films on aluminium.

Studies using interruption of the seating process have revealed the importance of pore hydration resistance in determining the extent of sealing after the bridging or plugging over of the pore mouths. This has led to a refinement of the basic equivalent circuit of sealed anodic films. For continuous impedance measurements at the sealing temperature, a further modification of the equivalent circuit is necessary to allow simulation of the impedance response. The modified response indicates the importance of gel-like material development within the pore volume at the sealing temperature. The consequence of reduction in temperature, from that of boiling water to ambient temperature, is the compaction of the gel-like material in the form of more crystalline hydrated aluminas which contribute an enhanced resistance to the measured impedance.     

铝阳极氧化膜的显微组织与性能研究

研究了ＬＹ１１硬铝合金硫酸法阳极氧化膜的组织结构及其性能,讨论了电解液组成和工艺条件对它们的影响。结果表明,电解液中Ｈ２ＳＯ４浓度增大,易得到较厚的多孔型氧化膜;而稀Ｈ２ＳＯ４（１０％体积比）电解液,可获得致密、无孔洞的相对较薄的氧化膜,其耐蚀性、电绝缘性和表面硬度均明显改善。工艺操作参量中,保持较低的电解液温度、合适的阳极电流密度及氧化时间,有利于膜层综合性能的提高。     

Electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing hydrogen peroxide

The aim of this study is to evaluate the electrochemical corrosion behaviour of Incoloy 800 in sulphate solutions containing H₂O₂ in the temperature range of 25–80 °C. The open circuit potential measurements, cathodic and anodic polarization and electrochemical impedance spectroscopy (EIS) were used to characterize the corrosion behaviour. The results provide kinetic data for reduction of hydrogen peroxide on Pt surface. The anodic polarization curves for Incoloy at different pH, temperature and H₂O₂ concentration are presented. EIS data generally confirm the polarization interpretations about the effects of various parameters. An equivalent circuit was used to fit all the acquired data.