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Porous Alumina Films with Width-Controllable Alumina Stripes.

Huang K, Huang SM, Pu L, Shi Y, Wu ZM, Ji L, Kang JY - Nanoscale Res Lett (2010)

Bottom Line: The width of the alumina stripes increases proportionally with the anodizing voltage.And the pores tend to be initiated close to the alumina stripes.These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

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ABSTRACT
Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

No MeSH data available.


a The surface morphology of the porous alumina films under the anodizing voltage of 5 V, b the surface morphology of the porous alumina films under the anodizing voltage of 15 V, c schematic diagram of the barrier layer structures formed at the initial stage of anodizing at a relatively low voltage
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Figure 5: a The surface morphology of the porous alumina films under the anodizing voltage of 5 V, b the surface morphology of the porous alumina films under the anodizing voltage of 15 V, c schematic diagram of the barrier layer structures formed at the initial stage of anodizing at a relatively low voltage

Mentions: While the applying anodizing voltage is rather low, the surface morphology of the porous alumina films become totally different. Figure 5a shows the surface SEM image of the porous alumina under a very low anodizing voltage of 5 V. It can be distinguished that there are protuberant stripes showed in the surface (i.e., quadrilateral marked in Fig. 5a). But pores do not avoid the stripe region as discussed above. By contraries, there are a lot of pores located at the midline of the stripes (i.e., pore indicated in Fig. 5a). Figure 5b shows the differentiation of the surface morphology of the porous alumina under the anodizing voltage of 15 V. Some pores form at the border of the stripes (pore A) and there are still some pores locating at the middle of the stripes (pore B). When the anodizing voltage is relatively low (lower than R2/1.1 nm/V), it can be deduced that the barrier layer forms the structure as Fig. 5c. Under the static electric field assumption, the electric charge density on the region R2 is much bigger than on the region R1. Therefore, the electric field intensity is bigger on region R2. The thickness of the barrier can be estimated by the equation ∫E·dl = V. Thus, we can draw the conclusion that the barrier layer on region R2 is much thinner than that on region R1. Along with the anodizing proceeding, microcracks caused by the stress and the heat on region R2 can be much easier to impenetrate the hole barrier layer and then form the pores. That is, in the case of a rather small anodizing voltage, the pores tend to initiate on the positive curvature region i.e., on the stripes.


Porous Alumina Films with Width-Controllable Alumina Stripes.

Huang K, Huang SM, Pu L, Shi Y, Wu ZM, Ji L, Kang JY - Nanoscale Res Lett (2010)

a The surface morphology of the porous alumina films under the anodizing voltage of 5 V, b the surface morphology of the porous alumina films under the anodizing voltage of 15 V, c schematic diagram of the barrier layer structures formed at the initial stage of anodizing at a relatively low voltage
© Copyright Policy
Related In: Results  -  Collection

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Figure 5: a The surface morphology of the porous alumina films under the anodizing voltage of 5 V, b the surface morphology of the porous alumina films under the anodizing voltage of 15 V, c schematic diagram of the barrier layer structures formed at the initial stage of anodizing at a relatively low voltage
Mentions: While the applying anodizing voltage is rather low, the surface morphology of the porous alumina films become totally different. Figure 5a shows the surface SEM image of the porous alumina under a very low anodizing voltage of 5 V. It can be distinguished that there are protuberant stripes showed in the surface (i.e., quadrilateral marked in Fig. 5a). But pores do not avoid the stripe region as discussed above. By contraries, there are a lot of pores located at the midline of the stripes (i.e., pore indicated in Fig. 5a). Figure 5b shows the differentiation of the surface morphology of the porous alumina under the anodizing voltage of 15 V. Some pores form at the border of the stripes (pore A) and there are still some pores locating at the middle of the stripes (pore B). When the anodizing voltage is relatively low (lower than R2/1.1 nm/V), it can be deduced that the barrier layer forms the structure as Fig. 5c. Under the static electric field assumption, the electric charge density on the region R2 is much bigger than on the region R1. Therefore, the electric field intensity is bigger on region R2. The thickness of the barrier can be estimated by the equation ∫E·dl = V. Thus, we can draw the conclusion that the barrier layer on region R2 is much thinner than that on region R1. Along with the anodizing proceeding, microcracks caused by the stress and the heat on region R2 can be much easier to impenetrate the hole barrier layer and then form the pores. That is, in the case of a rather small anodizing voltage, the pores tend to initiate on the positive curvature region i.e., on the stripes.

Bottom Line: The width of the alumina stripes increases proportionally with the anodizing voltage.And the pores tend to be initiated close to the alumina stripes.These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
Porous alumina films had been fabricated by anodizing from aluminum films after an electropolishing procedure. Alumina stripes without pores can be distinguished on the surface of the porous alumina films. The width of the alumina stripes increases proportionally with the anodizing voltage. And the pores tend to be initiated close to the alumina stripes. These phenomena can be ascribed to the electric field distribution in the alumina barrier layer caused by the geometric structure of the aluminum surface.

No MeSH data available.