THERMAL STUDIES OF POROUS ALUMINUM OXIDE MEMBRANES

Изучение оптических свойств наноразмерных мембран пористого анодного оксида алюминия позволяет значительно расширить области применения данного материала. В работе представлены результаты тепловизионных исследований мембран пористого анодного оксида алюминия с различными структурными параметрами. Построены профили распределения температуры для мембран, полученных в различных электролитах на основе серной, щавелевой и ортофосфорной кислотах. Установлено, что экранирование ИК излучения сильнее (примерно на 30%) проявляется у мембран с меньшим диаметром пор d ≈ 20 нм по сравнению с мембранами, у которых d ≈ 200 нм. Это связано с рассеиванием теплового излучения на неоднородностях структуры, которых значительно больше в мембранах пористого анодного оксида алюминия, полученных на серной кислоте. В качестве источников неоднородности выступают поры малого диаметра, недотравленные области и дефекты. Также, за счет повышенной активности серной кислоты по сравнению с другими используемыми кислотами большее количество анионов встраивается в структуру образца. Study of optical properties of nanoscale membranes of porous anodic alumina can significantly expand the scope of this material. The paper presents the results of thermal imaging studies of porous anodic alumina membranes with various structural parameters. Temperature distribution profiles for membranes obtained in various electrolytes based on sulfuric, oxalic and orthophosphoric acids have been constructed. It was found that the shielding of IR radiation is more pronounced (approximately 30 %) in membranes with a smaller pore diameter d ≈ 20 nm compared to membranes with a larger pore diameter d ≈ 200 nm. This is due to the scattering of thermal radiation on structural inhomogeneities, which are much higher in porous anodic alumina membranes obtained with sulfuric acid. Small-diameter pores, under-etched areas and defects act as sources of inhomogeneity. Also, due to the increased activity of sulfuric acid in comparison with other acids used, more anions are incorporated into the structure of the sample.

Study of coloured anodized coatings on aluminum alloy by electrochemical impedance spectroscopy

Anodizing, porous anodic alumina, electrochemical impedance spectroscopy, electrolytic coloring, hydrothermal sealing, equivalent electrical circuit, simulation.

Study of electric parameters of thin porous anodic alumina layers

Currently, the study of the electric parameters of porous anodic alumina (PAA) layers is of interest for sensor applications (humidity, DNA, etc.). PAA layers are synthesized using electrochemical anodizing of aluminum foil in potentiostatic mode with an aqueous solution of sulfuric acid and glycerin as an electrolyte. The surface morphology of the layers was studied by atomic force microscopy. The electric characteristics were studied using impedance spectroscopy at room temperature and under heating. An increase in the impedance of the heat-treated PAA sample was found, as well as an increase in the impedance with an increase in the measurement temperature. The results are explained by the influence of adsorbed water molecules on the electric characteristics of porous layers.

Uniform arrays of gold nanoelectrodes with tuneable recess depth

Nanoelectrode arrays are much in demand in electroanalytical chemistry, electrocatalysis, and bioelectrochemistry. One of the promising approaches for the preparation of such systems is templated electrodeposition. In the present study, porous anodic alumina templates are used to prepare Au nanoelectrode arrays. Multistage electrodeposition is proposed for the formation of recessed electrodes with the ability to tune the distance between the surface of the porous template and the top surface of the nanoelectrodes. A set of complementary techniques, including chronoamperometry, coulometry, and scanning electron microscopy, are used to characterize the nanoelectrode arrays. The number of active nanoelectrodes is experimentally measured. The pathways to further improve the recessed nanoelectrode arrays based on anodic alumina templates are discussed.