【作者】 梁坤；

【导师】 梁成浩；

【作者基本信息】 大连理工大学 ， 化学工程， 2009， 博士

【摘要】 多孔阳极氧化铝膜是理想的合成纳米线结构的模板材料。然而通常的氧化铝模板制备较困难,合成纳米线的工艺复杂。采用交流电沉积的方法,在未去处铝基体的情况下,使金属沉积到氧化膜孔中合成纳米线的工艺较简单,可省去减薄氧化膜阻挡层并与基体分离、喷镀导电金属层等工序。然而施加交流电时,金属离子在氧化膜孔中的沉积过程变得复杂。所以,交流电沉积条件下,探讨金属离子在多孔氧化膜的沉积历程具有重要的意义。本文采用电化学技术,在硫酸、草酸和磷酸溶液中通过对铝及其合金实施阳极氧化处理,制备了多孔阳极氧化铝膜。在上述三种溶液里恒压氧化过程中,初始阶段电流密度迅速下降,随后转为升高,最后趋于平稳。20℃时,稳定时的电流密度值与氧化电压均呈指数变化关系。硫酸溶液中电流密度i与电压V的关系为:i=1.056e^0.1676V;草酸为:i=2.763e^0.037V;磷酸为:i=0.446e^0.024V。高纯铝经电化学抛光后,通过阳极氧化得到有序的多孔结构的氧化膜。硫酸氧化膜的平均孔径约为20nm,草酸氧化膜的约为40nm,而磷酸氧化膜的孔径为50nm到120nm。经XRD分析,铝合金在硫酸溶液中所得到的氧化膜为非晶的α-Al₂O₃。U-I特性曲线测试发现,高纯铝阳极氧化膜具有单向导通的性质。氧化膜的阴极极化过程可分为三个阶段:初始时,电流密度变化较小而电位迅速负移,为克服氧化膜阻挡层电阻阶段;电流密度迅速增大而电位变化较小的析氢阶段;之后电流密度变化较小而电位迅速负移的受氢离子扩散控制阶段。氧化膜阻抗的大小由氧化膜阻挡层决定,阻挡层愈厚,氧化膜阻抗愈大。氧化电压与阻挡层的厚度成正比,在硫酸、草酸和磷酸溶液中的阻挡层成长率约为1nm/V。LY12铝合金磷酸氧化膜和复合氧化膜在含25g/L的ZnSO₄·7H₂O、25g/LH₃BO₃、1g/L的（NH₄）₂SO₄与N（CH₂COOH）₃的溶液中,施加15V交流电压,室温下制备了含锌粒子的复合膜。其中,LY12铝合金复合氧化膜在溶液中交流电沉积300s时,沉积在氧化膜孔中的锌粒子为单质锌,主要分布在氧化膜孔底约2μm内,沉积量为31.404μg/cm²。沉积过程中,沉积量C与沉积时间s呈对数关系:C=7.6537ln（s）-12.388。首次采用交流电沉积的方法在LY12铝合金硫酸氧化膜上制备了Ce复合膜。工艺条件为:在1 g/L CeCl₃·7H₂O和10 mL/L H₂O₂的水溶液,施加10 V电压,室温下沉积5 min。实验发现,只有氧化膜的厚度大于6.8μm时,才能形成均匀的Ce复合膜,Ce复合膜表面稀土Ce的平均含量为1.70（wt）%,且分布均匀,Ce主要以非晶态的Ce³⁺和Ce⁴⁺氢氧化物分布在氧化膜多孔层的表层,分布深度约为1.51μm。采用交流电沉积的方法,1235铝合金硫酸氧化膜在硫酸铜溶液中电沉积得到金属Cu,草酸氧化膜在硝酸银溶液中电沉积得到金属Ag。Cu和Ag主要沉积于氧化膜孔底,氧化膜其他地方分布相对较少。交流电沉积过程中发现,峰值电流发生剧烈变化区域,发生金属离子和氢离子的还原反应,峰值电流稳定时则发生金属离子的还原反应,而氢离子的还原反应受到抑制。而且,电沉积过程中,阴极的峰值电流比阳极的峰值电流大。更多还原

【Abstract】 Porous anodic alumina films are used as the ideal templates to synthesize the nanowire arrays materials. However, the common synthetic processes are long and complex through direct current（D.C） deposition into the porous alumina films. If the direct currentdeposition method is replaed by an alternative current （A.C）.ones, a simple process will be obtained for some procedures are canceled, such as separation from the barrier layer and aluminum, spray conductive metal on the film. However, the reactions become more complex during the application of A.C. deposition. Therefore, it is of great significance to study the process of metal ions A.C. deposited into the porous alumina film.In this paper, electrochemical technique is applied on aluminum and its alloy to anodize in sulfuric, oxalic and phosphoric acid solution to form porous anodic alumina films. During the constant voltage process of anodize, the current densities decline rapidly in the initial stage, then rise and finally become steady.When the high pure aluminum is anodized in the given solution at 20℃, current densities i change with voltage V are index relationship. For sulfate acid: i = 1.056e^0.1676V; for the oxalic acid: i= 2.763e^0.037V; and for phosphoric acid: i= 0.446e^0.024V.After electrochemical polishing and anodization, the anodic alumina films of high pure aluminum appear orderly porous structure. The average pore diameter is about 20nm, about 40nm, and 50-120nm, respectively, for anodizing in sulfuric, oxalic and phosphoric acid solution. Analysis by XRD, the film is the amorphousα-Al₂O₃ for anodizing in sulfate acid solution.U-I curve testt finds that the porous anodic alumina film has a semiconductor performance. The cathode polarization process applied on the films can be divided into three stages. Initially, current densities change slightly and potentials shift to negative rapidly. It is the stage of overcoming the barrier resistors of oxide film. Secondly, current densities grow quickly while potentials increase little. It is the hydrogen evolution stage. And the last stage is the current densities are nearly changed but potentials shift to negative rapidly. Is is the diffusing control step of hydrogen ions. The impedance of alumina film depends on the thickness of the barrier layer. The impedance increases with the barrier layer becoming thicker. The anodizing voltage proportional to the thickness of the barrier layer, and the anodizing ratio is about 1nm / V in sulfuric, phosphoric and oxalic acid solutions. The composite film contained zinc particle is prepared by A.C.deposition method. The solution contains 25g/LZnSO₄ ? 7H₂O, 25g/LH₃BO₃ and 1g/L additives（（NH₄）₂SO₄ and N（CH₂COOH）₃ ） . When the alumina film is applied 15V A.C. deposition in the given solution for 300s the deposition sediment in the pores of oxide film is metal zinc, which is mainly distributed at the bottom of porous anodic alumina film with the thickness about 2um. And the amount of deposited zinc is about 31.404μg/cm². During A.C. deposition process, the amount of sediment C and the time s are fit to the formula: C = 7.6537 ln（s） -12.388.It is the first time to prepare Ce composite film in porous anodic alumina film by A.C. deposition method. Process conditions are as follows: the solution containing 1g/LCeCl₃·7H₂O and 10 mL/L H₂O₂, 10V（A.C） voltage applied at room temperature for 5 min. It is found that to obtain a uniform Ce composite film the thickness of the porous anodic alumina film must over 6.8μm. Ce sediment is distributed evenly on the inner surface of porous alumina film with the average content of 1.70 （wt）%. And Ce is mainly at the form of the amorphous Ce³⁺ and Ce⁴⁺ hydroxide, with the depth about 1.5μm.Ag and Cu composite films are prepared by A.C. deposition method. The metal of Ag and Cu are mainly deposition at the bottom of porous alumina film and there are some metal being distributed in the other place. It is found in the process of A.C. deposition, the region of the peak current dramatic changes, reduction of metal ions and hydrogen ions take place at the same time. When the peak current stable the mainly reaction is metal ions reduction, while, hydrogen ions reduction would be inhibited, In addition, during A.C. deposition process, the cathodic peak current is larger than that of anodic current.更多还原