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Preparation of nanoporous alumina by means of anodic oxidation in a solution of 5-sulfosalicylic acid

Krzysztof Librant

Abstract

Introduction Nanoporous alumina in recent years have been attracting considerable attention among others as a reinforcing filler of plastics and as a matrix which, when doped with ions of rare earth metals and suspended in the polymer has interesting fluorescent properties. Nanoporous alumina is derived by the controlled hydrolysis of metal-organic compounds. This method is however difficult to provide a product with reproducible properties. Therefore in this work it was decided to use the existing knowledge in obtaining membranes with porous alumina by electrochemical oxidation of aluminum (Anopore type membrane) [1]. The main task of this study was to obtain the thinnest possible and easily separated anodic oxide layer (AAO layer), by application of the 5-sulfosalicylic acid solution as electrolyte, whereas the maximum simplicity of the method used [2]. The effect of shape of anode used, anodizing process parameters and initial preparation of surface of aluminum in the process of DC and an AC [3], on ease of separation of oxide layers from the electrode surface were also investigated. With the help of advanced electron microscopy micro- and nanostructure of the the produced layers were examined. Results and Discussion In this study nanoporous alumina in the form of thin (>10 µm), centimeter-sized flakes was obtained. Failed to obtain a material with nanometric thickness. The separation of layers in the process of an AC have also failed. This is probably because evolution of hydrogen during the anodizing process made separation of layers by cathodic polarization ineffective. Decreasing the anode surface roughness using both mechanical polishing with fine sandpaper and by electropolishing, greatly facilitated the separation of the oxide layer from the substrate, so it became easier to obtain intact porous membranes. Among the shapes of used aluminum electrodes, plate and the disk showed the greatest usefulness. For these shapes there were no troubles with separation of oxide layer, as was the case with the coil of wire. The thicker aluminum foil anodization was partly successful, because of the inability to completely remove remaining aluminium from anode interior. Experiments with oxidizing of the thinner foil were abandoned due to problems with elimination of the through-oxidation-on-the-waterline issues. Heating in 1200°C did not damaged the 20 µm thick anodized layer, but instead partly revealed its polycrystalline structure. Conclusions Main aim of this work was reached. With use of very simple laboratory equipment and by using basic methods, anodic layer was obtained and detached from metallic subtrate. Thin AAO membranes from 5-sulfosalicylic acid solution may find its application as nanoporous material under the condition, that some type of physical disintegration will be performed. Initial heat treating of the layer had shown, that more intensive heating can and should be applied, to bring the layer’s properties as near the ceramic material as it is possible.
Record ID
WUT827ca28b2c2c46e390f301169b24be08
Diploma type
Master of Science
Author
Krzysztof Librant Krzysztof Librant,, Undefined Affiliation
Title in Polish
Otrzymywanie nanoporowatego tlenku glinu w procesie utleniania anodowego w roztworze kwasu 5-sulfosalicylowego
Supervisor
Wojciech Fabianowski (FC/CPCT) Wojciech Fabianowski,, Chair Of Polymer Chemistry And Technology (FC/CPCT)Faculty of Chemistry (FC)
Certifying unit
Faculty of Chemistry (FC)
Affiliation unit
Chair Of Polymer Chemistry And Technology (FC/CPCT)
Study subject / specialization
, Technologia Chemiczna
Language
(pl) Polish
Status
Finished
Defense Date
03-01-2012
Issue date (year)
2012
Keywords in Polish
-
Keywords in English
-
Abstract in Polish
urn:pw-repo:WUT827ca28b2c2c46e390f301169b24be08