Leszek Zaraska

GridSpace2 virtual laboratory case study: implementation of algorithms for quantitative analysis of grain morphology in self-assembled hexagonal lattices according to the hillebrand method

This work presents the implementation of a method, originally proposed by Hillebrand et al. [1], of quantitative analysis of the grain morphology in self-assembled hexagonal lattices. This method can be effectively used for investigation of structural features as well as regular hexagonal arrangement of nanoporous alumina layers formed on the metal surface during the self-organized anodization process. The method has been implemented as a virtual experiment in the GridSpace2 Virtual Laboratory [15] which is a scientific computing platform developed in the scope of the PL-Grid [9] project. The experiment is a GridSpace2 pilot and therefore made available to the wider community of PL-Grid users. It is both editable and executable through a web portal offered by the GridSpace2 Experiment Workbench [17], dedicated to PL-Grid users. Moreover, since all GridSpace2 experiments are embeddable on arbitrary web sites owing to the Collage [16] feature, the final version of the experiment has been published as an executable publication [18] with execution rights granted to all PL-Grid users.

Properties of nanostructures obtained by anodization of aluminum in phosphoric acid at moderate potentials

The influence of the process duration, anodizing potential and methanol addition on the structural features of porous anodic alumina formed in a 0.3 M H3PO4 solutions by two# s tep self#organized anodizing was investigated for potentials ranging from 100 to 170 V. The structural features of porous structures including pore diameter and interpore distance were evaluated from FE#SEM top#view images for samples anodized in the presence and absence of methanol. For the highest studied anodizing time and methanol volume fraction, an excellent agreement between experimental values of the interpore distance and theoretical predictions was observed. The pore arrangement regularity was analyzed for various electrolyte compositions and anodizing potentials. It was found that the regularity ratio of porous alumina increases linearly with increasing anodizing potential and time. The addition of methanol improves the quality of nanostructures and especially better uniformity of pore sizes is observed in the presence of the highest studied methanol content.

Formation of Nanoporous Tin Oxide Layers on Different Substrates during Anodic Oxidation in Oxalic Acid Electrolyte

Nanoporous tin oxide layers were obtained on various Sn substrates including high- and low-purity foils and wire by one-step anodic oxidation carried out in a 0.3 M oxalic acid electrolyte at various anodizing potentials. In general, amorphous oxide layers with the atomic ratio of Sn : O (1 : 1) were grown during anodization, and a typical structure of the as-obtained film consists of the “outer” layer with less regular, interconnetted pores and the “inner” layer with much more uniform and regular channels formed as a result of vigorous gas evolution. It was found that the use of electrochemical cell with the sample placed horizontally on the metallic support and stabilized by the Teflon cover, instead of the typical two-electrode system with vertically arranged electrodes, can affect the morphology of as-obtained layers and allows fabrication of nanoporous oxides even at anodizing potentials up to 11 V. An average pore diameter in the “outer” oxide layer increases with increasing anodizing potential, and no significant effect of substrate purity on the structure of anodic film was proved, except better uniformity of the oxides grown on high-purity Sn. A strong linear relationship between the average steady-state current density and anodizing potential was also observed.

Synthesis of Nanoporous Anodic Alumina by Anodic Oxidation of Low Purity Aluminum Substrates

The aim of this chapter is to present some recent findings on the fabrication of anodic aluminum oxide (AAO) layers by anodization of low purity aluminum substrates. The use of low purity, technical aluminum alloys, instead of high purity substrates, can significantly reduce the cost of AAO fabrication, however, this can also affect the structure and properties of as produced alumina layers. Here, we focused on the comparison of oxide layer growth on substrates with different Al contents, as well as on the new procedures used for the synthesis of well-ordered nanoporous oxides from technical aluminum alloys. Some applications of the formed nanoporous AAO layers are presented.

AAO templates with different patterns and channel shapes

Nanoporous anodic aluminum oxide (AAO) membranes formed by anodic oxidation of metallic Al have become one of the most popular templates for the fabrication of diverse range of nanostructured materials in the form of nanodots, nanowires, and nanotubes. A key advantage of using AAO instead of other templates is a highly ordered and close-packed distribution of pores within the template. In addition, the fabrication of porous AAO membrane via electrochemical anodization is relatively simple and inexpensive. All structural features of anodic oxide templates, such as pore diameter, pore-to-pore distance, thickness of the template, pore density, porosity, etc., can be easily controlled by anodizing conditions, especially type of electrolyte, potential applied, temperature and duration of the process. For the preparation of porous AAO templates, two different approaches can be distinguished: a pre-patterned guided anodization and a self-organized two-step anodization. In the first case, a pre-patterned (pre-textured) aluminum substrate is used for anodization, while the latter is based on a self-organized pre-patterning of Al during the first anodizing step and the removal of irregular oxide layer before the final (second) anodization. The pre-patterned guided anodization results in a perfectly arranged pore lattice formed over a surface area defined by the dimensions of the previously prepared stamp (mold) or indented Al surface. The pre-pattern guided anodization can result in pore shapes and cell configurations different from the pattern with circular and hexagonally arranged pores, which is typically observed for self-organized AAO templates. In particular, complex nontypical regular pore patterns on AAOs (e.g., square, triangle, diamond, triangle–diamond, checkerboard, etc.) can be formed. The self-organization process of AAO formation can occur over a macroscopic surface area, however it always results in a non-perfectly ordered hexagonal arrangement of pores. A typical self-organized anodization results in porous AAO layers with straight cylindrical nanochannels parallel to each other. However, a great variety of procedure modifications was recently proposed. They allow for the fabrication of anodic alumina films with a more complex internal architecture (e.g., Y-branched, multilevel Y-branched, and multi-branched nanochannels) and various nanochannel shapes (e.g., conical, step-shaped, serrated, periodically branched, and modulated nanochannels).