| In recent years, with the development of nano-technology, the research and preparation of porous anodic alumina membranes with nano-pore structure is attracting more and more people's attention. Porous anodic alumina (PAA, porous anodic alumina) membranes with a good many advantage, such as preparation easy, process simple, performance predominant and price cheap, are widely used in various fields.Firstly, in this paper the small area anodic aluminum oxide (AAO, anodic aluminum oxide) templates were prepared by one-step and two-step anodization in given oxalic acid and sulfuric acid electrolyte respectively, and the two methods were compared. The influence of various factors, including voltage, temperature, electrolyte concentration and kinds, pretreatment and so on, was researched. By scanning electron microscope (SEM, scanning electron microscope), the microstructure of alumina membranes prepared under different conditions was observed. The experimental results show that: oxidation voltage is the main influencing factors of aperture and pore density; Electrolyte concentration and current density are the main influencing factors of thickness. All things considered, the technological conditions of high voltage, low temperature, and low electrolyte concentration will be advantageous to the formation of alumina membranes with uniform aperture and good corrosion resistance.Secondly, in view of the alumina membranes mostly smaller and the price higher on the market, its application is limited, so we explored the preparation technology of large area AAO templates. Of course, we also encountered many difficulties during the course of exploratory work. For example:(1) Lack theoretical guidance. There are not reports on the preparation of large area AAO templates at home and abroad by now.(2) Lake support of fund. We must save the fund as far as possible.(3) Need new equipments. We need to design and manufacture a new anodic oxidation device, and we don't know whether the original voltage-stabilized power will be able to withstand the higher voltage and current.Facing these questions, we first took the theory of preparing small area AAO templates as a guide, and modeling on their design proposal of oxidation device, we manufactured a set of oxidation device whose effective oxidized area approximate 5 times of original oxidation device. The results showed that the initial current had achieved the limit of voltage-stabilized power and was too big—aluminum plate was soon penetrated—to prepare the big area AAO template. Aiming at this problem, we studied the growth mechanism of alumina membranes in detail, and found that the thickness of barrier layer and voltage are proportional—the thickness of barrier layer and resistance increase when the voltage rises. Therefore we adopted gradually voltage-rising method. Gradually voltage-rising method slowed down the fluctuation which was caused by the rapid increase of voltage, playing a "buffer" role. At last, we successfully prepared large area AAO templates whose effective oxidized area was 1960 mm~2. Then we designed a cassette-type oxidation device which can prepare AAO templates whose effective oxidized area reaches 7500 mm~2 and had also obtained success.Subsequently, we observed the membranes and found large area AAO templates compared with the small area AAO templates almost have the same order degree and pore density. But the aperture of templates gets smaller.Finally, in order to further optimize the existing anodic oxidation device of preparing large area AAO templates, we analyzed and summarized anodic oxidation devices used to prepare small area AAO templates by each domestic research institution, unified their merits and designed preferable new anodic oxidation device. |
PDF Full Text Request