不同孔径高度有序多孔阳极氧化铝模板的制备与稳定氧化过程添加剂的研究

【作者】 高玉波；

【导师】 彭智；

【作者基本信息】 青岛大学 ， 材料学， 2007， 硕士

【摘要】 阳极氧化铝(AAO)模板法制备纳米材料以其独特的性能和简单的工艺越来越赢得人们的青睐。本文通过对以草酸为电解液的AAO模板进行研究，以此出发，用不同方法成功制备了以硫酸和磷酸为电解液的模板，并对不同制备方法的机理进行了探索。此外，我们还对稳定氧化过程添加剂进行了初步探索。1．恒压法氧化法AAO模板的制备(1)在草酸电解液中，制备了孔径70-120nm，厚度25-175μm的AAO模板，随着电压的升高，孔径和厚度不断增大；温度的升高会使孔径和厚度变大，但孔的有序性变差；随着电解液浓度的增大，孔径会在小范围内使有所提高，厚度变化不大。(2)在磷酸电解液中，制备了孔径100-300nm的AAO模板，随着电压的升高，孔径不断增大，有序度有一定提高，膜的厚度在不断降低，但总体膜厚都较薄。(3)在硫酸电解液中，制备了孔径20-35nm，厚度5-20μm的AAO模板，随着电压的升高，孔径不断增大，但有序度较差，膜在高压时破裂。2．恒流氧化法AAO模板的制备(1)以草酸为电解液，随着电流密度的增大，孔径提高较大，厚度增大；随着氧化时间的延长，孔径会有小范围的提高，但不明显，但孔的有序程度会有所提高，膜的厚度在一定范围内，也会有较大提高，但时间提高到到一定程度时，膜厚将不再增长发生溶解。恒流一定值后模板的有序性会下降，但总体效果还是不错的，厚度大，有序性高。(2)以磷酸为电解液，孔径随电流密度的增大而不断增加，但电流密度增大到一定程度，孔径会有所下降，而膜的厚度随电流密度的增大而降低；随着氧化时间的延长，孔径会有小范围的提高，但不明显，孔会随之变得规整有序。膜的厚度在一定范围内，也会稍有变化，但时间提高到到一定程度时，膜厚将不再增长。(3)以硫酸为电解液，随着电流密度的增加，AAO模板的孔径逐渐增加，厚度增大，孔隙率变大，而孔密度急剧降低；随着氧化时间的增大，孔径会有小范围的提高，孔会随之变得规整有序，膜的厚度在一定范围内，也会稍有增加，但时间提高到到一定程度时，膜厚将不再增长。3．稳定氧化过程添加剂AAO模板的制备(1)在草酸电解液中，随着乙醇的加入，模板孔的有序性明显得到提高，但孔径大小几乎不发生变化，大约都在90nm左右；侧面都变得光滑有序，孔道之间平行排列，而厚度也发生一定的变化，模板的厚度随乙醇加入量，成线性降低。(2)在磷酸电解液中，随着乙醇和磷酸的比例的增大，发现孔径变化不是很明显，但孔的结构形状发生变化，分别出现孔壁破裂、大孔套小孔现象、以及正六边形结构；随着乙醇加入量的增加模板厚度变化不大，但侧面的有序程度有相应的增加。4．氧化机理的研究(1)恒流法发生电化学溶解的条件比较温和，膜孔出现阶段时氧化电压要求较低，因而不易对膜孔的有序性造成破坏，膜孔的形成也就较为规整；相反，在恒压法中，电压保持不变，初始电化学溶解电流也就比较大，膜孔的形成条件比较剧烈，膜孔极易被破坏，因而膜孔的形成会比较杂乱。(2)添加乙醇后，在非水溶剂中，无机酸的酸度会发生明显的变化，对氧化膜的溶解能力也有所改变。其原因是改变水的含量，本质上就是调节了电解质中载流子的数量，氧化电流随着体系中水含量的降低而降低。氧化速率与溶解速率同时降低保证了电氧化过程在相当长的时间内能够稳定进行。与水溶液电解质体系相比，该反应条件更加温和，因而会比较容易形成有序性好，厚度大的AAO模板。更多还原

【Abstract】 The method of anodic aluminum oxide (AAO) is more and more popular in preparingnanomaterials because of its special performance and simple techniques. AAOtemplates were prepared in sulfuric acid and phosphoric acid electrolyte by differentmethods, and the mechanism of oxidation was discussed. Moreover, the additivewhich can keep the process of oxidation steady was investigated.1. The preparation of AAO by constant voltage(1) AAO templates with their diameter from 70nm to 120nm and thickness from25μm to 175μm were prepared in oxalic acid. The diameter and thickness willaccrete with the increasing voltage. The diameter and thickness will also be largerand larger with the increasing temperature, while the regularity will be worse andworse. The consistency of electrolyte also has much influence on AAO.(2) AAO templates with their diameter from 100nm to 300nm were prepared inphosphoric acid. The diameter will accrete with the increasing voltage, and theregularity will be improved. On the contrary, the thickness of the AAO will bethinner and thinner.(3) AAO templates with their diameter from 25nm to35nm and thickness from5μm to 25pro were prepared in sulphuric acid. The diameter and thickness willaccrete with the increasing voltage, while the regularity will be worse and worse.The AAO template will be destroyed when the voltage is high.2. The preparation of AAO by constant current density(1) The diameter and thickness will accrete with the increasing current density inoxalic acid. They will be bigger with the increasing oxidation time, while theregularity will be better. Though regularity will be worse after the current densitygetting a high value, the whole quality is good.(2) The diameter will accrete with the increasing current density in phosphoricacid, but the thickness has the opposite change. The diameter and thickness will bebigger and thicker with the increasing oxidation time, while the regularity will bebetter. After a long time of oxidation, the thickness of the film will stop growing.(3) The diameter, thickness and porosity will accrete with the increasing currentdensity, while pore density drops in sulphuric acid. The diameter and thicknesswill be bigger and thicker with the increasing oxidation time, but after a long timeof oxidation, the thickness of the film will stop growing.3. Add the additive to prepare AAO (1) The regularity will be improved in oxalic acid after adding some ethanol. Thethickness will have a linear relation with the quantity of the ethanol, while thediameter of the pores keeps the value 90nm.(2) The structure of pores will be changed added some ethanol in phosphoric acid.The thickness of the films will have little change when we add some ethanol, butthe regularity will be better after adding the ethanol.4. The research of oxidation mechanism(1) The condition of electrochemistry dissolution by constant current densitymethod is soft. The regularity will not be destroyed because of its low voltage atthe time of the little pores’ appearance. So the film will have highly orderedstructure by this method. On the contrary, the condition of electrochemistrydissolution by constant voltage method needs high current density. It will destroythe regularity of AAO, and have bad ordered structure.(2) The capability of dissolving the AAO has changed, because the consistency ofinorganic acid has changed in solvent without water after adding some ethanol.The essence is that can adjust the content of the water, reduce the value of currentdensity and the velocity of oxidization and dissolution. So it will form a kind of highly ordered and thick AAO templates, because of’the soft condition.更多还原