Showing papers by "Kirill S. Napolskii published in 2016"

Optical properties of one-dimensional photonic crystals based on porous films of anodic aluminum oxide

Abstract: The optical properties of one-dimensional photonic crystals based on porous anodic aluminum oxide films have been studied by measuring transmittance and specular reflectance spectra in the visible and UV spectral regions. Angular dependences of the spectral positions of optical stop bands are obtained. It is shown that the reflectance within the first stop band varies from point to point on the sample surface, reaching a level of 98–99% at some points. The dispersion relation for electromagnetic waves in the model of infinite periodic structure is calculated for the samples under study. The possibility of using models with an infinite or finite number of layers to calculate reflectance spectra near the first optical stop band is discussed.

Crystallography-induced correlations in pore ordering of anodic alumina films

Abstract: A crystallographic approach to tailoring the morphology and ordering degree of the porous structure of alumina films obtained by anodization of single-crystalline aluminum is discussed. The examination of porous structure of anodic alumina films formed on low-index and vicinal planes of Al single crystals under self-ordering conditions by high-resolution small-angle X-ray scattering revealed the existence of two pore growth directions on vicinal facets. The inclination of channels from the normal to the metal surface is explained by the competitive impact of electromigration driving force and the crystallographic anisotropy of the substrate. It was also shown that pores growing in different directions during anodization retain hexagonal domains with various in-plane orientations. These results for the first time demonstrate the strong correlations between the longitudinal alignment and in-plane packing options of pores in anodic alumina films.

Morphology of anodic alumina films obtained by hard anodization: Influence of the rate of anodization voltage increase

Abstract: The influence of the anodization voltage ramp on the morphology and thickness homogeneity of porous anodic alumina films was studied. The samples were prepared in the oxalic acid at 120 V during the hard anodization process. As a nondestructive characterization method, the smallangle Xray scattering technique was used. The analysis of diffraction patterns allows determining the mean value and dispersion of interpore distance and the channel tortuosity with high accuracy. The increase of voltage ramp at the initial stage of hard anodization process was shown to lead to reduction of mechanical deformation (tortuosity) of anodic alumina film during crystallization.

Preparation of Thin Anodic Alumina Membranes and Their Utilization for Template Electrodeposition

Abstract: A method for the preparation of arrays of anodic aluminium-oxide porous films on a metal frame is proposed. The suggested approach makes it possible to obtain very thin porous-oxide films possessing a high mechanical strength, which are suitable for various practical applications such as templates for the formation of one-dimensional nanostructures or membranes for gas separation and liquid filtration. To demonstrate the possibility of the utilization of thin anodic alumina films as the templates for nanowire formation, cobalt nanowires with 50 nm diameter are prepared using 5 μm thick alumina membranes.

Simple phase transfer of nanoparticles from aqueous to organic media using polymer colloids as carriers

Abstract: A new simple and versatile technique for the phase transfer of nanoparticles from water to water-immiscible organic solvents is presented. The proposed method is based on using charged colloids as carriers for the transfer of nanoparticles with opposite surface charge. The method has been successfully applied for the transfer of SrFe12O19 nanoplatelets and CdTe nanoparticles.