NDTnet 1998 Aug, Vol.3 No.8

Abstract

The investigation of dielectric characteristics of the system aluminium/oxide layer/electrolyte enables the explanation of the structure, i.e. of the characteristics of the anodic layer in relation to the conditions of the electrochemical process. It also gives possibility of the insight of the behaviour boundary phase solid/liquid in relation to the electrolyte composition.

The samples to be investigated were anodically oxidized in the solution of borates at 100 V up to achieving the constant values for current density of 15 m A/dm². The resistant and capacitive impendance component of the system aluminium/anodic oxide layer/electrolyte was measured by Wien system in the frequency area 50 - 20000 Hz. The solution with the concentration of 6,7 10^-2 moldm^-3 in regard to BO₃ ^3- HpO₄² and H₂PO₄^- of various pH values was used as electrolyte. In the same experimental conditions the contact angle was measured by the dipping method.

The results obtained by impendance measuring were used for calculating the characteristical parameters for non-ideal condenser tg , C_p and R_p values for real and imaginary components of dielectric constant ' and " whose frequency dependence can point at los type in the dielectricum of the non-ideal condenser and enable the formation of the conclusion about the mechanisms responsible for the determined behaviour of the phase layer.

The investigation results point at the differences in system behaviour in dependence on pH values of electrolytes. In the acid area the relations tg - log , ' - log , " - log and " - ' characterize the appearance of the relaxing process. Based on the investigation results is could be concluded that the relaxation time decreases and the contact angle increases with the increase of pH in the acid area, with means that by the increase of pH the strength of adsorption bound decreases.

The obtained results have been discussed in the context of adsorption and desorption of the species from the solution and in regard to the possible energetic conditions.

The used measuring methods have been experienced as sensitive and reliable ones for registration of changes on the boundary anodized aluminium/electrolyte and they are specially suitable for studying process on the offset printing form as well as for the follow of quality of the offset printing surfaces.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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