The present brief research deals with the appearance of voltage oscillations during galvanostatic anodization of Zn in the NaOH electrolyte. Hence, this research aims to describe the observed voltage oscillations, giving the most probable explication for their occurrence. Following previous results, the anodization was performed at 30 or 50 mA•cm-2 in diluted 0.002 M NaOH aqueous solution for 100 or 240 s at room temperature. The respective voltage alterations were recorded and submitted for further analysis. The obtained curves and the probable reasons for the observed voltage oscillations were analyzed in detail. The main research result has become a concept for the correlation between the oscillations and the alteration of the growing layer resistivity. This suggests that the resistivity alters due to local heating effects inside the film. These effects probably cause irreversible structural changes in the bulk of the growing film, obviously related to the occurrence of oxygen vacations. In this sense, this study initiates an entirely new field of investigation regarding the phenomena related to the Zn anodization in alkaline media at high current densities.
Dependence of photocatalytic reaction rate on the depth of the solution in case of small depths was studied. To the best of our knowledge, there are no reports on depth dependence of the photocatalytic reaction rate in literature. The study of reaction rate on the solution depth can play an important role in the development of systems for photodecomposition of organic pollutants. The model for photodegradation with a modified rate constant, which was developed in our previous work was generalized for the application of the catalyst in both plate and powder form. The applicability of the model was proved on the methylene blue discoloration by ZnO photocatalyst powder and plates.
The work presents preparation, structural investigation and optical properties characterization of composite films based on the azopolymer (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2- ethanediyl, sodium salt]), shortly PAZO, doped with 1 wt.% particles of the previously synthesized by us new tellurium containing chalcogenide system (GeTe4)100-xCux, where x = 5, 10, 15 and 20 mol.%. X-Ray diffraction (XRD) was applied to analyze the structure of the chalcogenide bulk material. Transmission electron microscopy (TEM) has been used to study the particles and the composite films morphology. The transmittance coefficient (T), the reflectance coefficient (R), the refractive index (n), the extinction coefficient (k), the optical absorption coefficient (α) and the optical band gap (E_g^opt) of the composite films were determined. Birefringence was induced by a He-Cd laser with a wavelength 442 nm and measured with probe Diode Pumped Solid State (DPSS) laser at 635 nm. The influence of the dopants concentration on the optical performance of the composite films has been discussed.
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