| 1. |
- Evertsson, Jonas, et al.
(författare)
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Self-organization of porous anodic alumina films studied in situ by grazing-incidence transmission small-angle X-ray scattering
- 2018
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Ingår i: RSC Advances. - 2046-2069. ; 8:34, s. 18980-18991
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Tidskriftsartikel (refereegranskat)abstract
- Self-ordered porous anodic alumina (PAA) films are studied extensively due to a large number of possible applications in nanotechnology and low cost of production. Whereas empirical relationships between growth conditions and produced oxides have been established, fundamental aspects regarding pore formation and self-organization are still under debate. We present in situ structural studies of PAA films using grazing-incidence transmission small-angle X-ray scattering. We have considered the two most used recipes where the pores self-organize: 0.3 M H2SO4 at 25 V and 0.3 M C2H2O4 at 40 V. During anodization we have followed the evolution of the structural parameters: average interpore distance, length of ordered pores domains, and thickness of the porous oxide layer. Compared to the extensively used ex situ investigations, our approach gives an unprecedented temporal accuracy in determination of the parameters. By using of Al(100), Al(110) and Al(111) surfaces, the influence of surface orientation on the structural evolution was studied, and no significant differences in the interpore distance and domain length could be observed. However, the rate of oxide growth in 0.3 M C2H2O4 at 40 V was significantly influenced by the surface orientation, where the slowest growth occurs for Al(111). In 0.3 M H2SO4 at 25 V, the growth rates were higher, but the influence of surface orientation was not obvious. The structural evolution was also studied on pre-patterned aluminum surfaces. These studies show that although the initial structures of the oxides are governed by pre-patterning geometry, the final structures are dictated by the anodization conditions.
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| 2. |
- Vinogradov, Nikolay A., et al.
(författare)
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Observation of Pore Growth and Self-Organization in Anodic Alumina by Time-Resolved X-ray Scattering
- 2018
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 1:3, s. 1265-1271
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Tidskriftsartikel (refereegranskat)abstract
- The anodic oxidation of metals such as aluminum and titanium can lead to the development of self-ordering pores. These pores make excellent templates for a range of nanoscale objects with many applications in nanoscience. Theoretical studies on pore formation have proposed several models for the establishment, growth, and ordering of these pores; however, experimental verification has mostly been limited to ex situ measurements. Here we show that the lateral and vertical pore structure can be probed in situ with high precision, using grazing transmission X-ray scattering. By making use of the high flux available at modern synchrotrons and fitting only the difference between scattering patterns we show the nearly real-time evolution of the pore’s arrangement. We observe no dependence on the substrate crystallographic orientation for domain size or pore separation. We do however observe an anisotropy in the oxide growth rate for the different substrate surfaces. This experimental approach can be applied to the study of a large variety of electrochemically produced materials such as magnetic nanowires, novel solar cell designs, and catalysts.
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