Some Aspects Regarding I. R. Absorbing Materials Based On Thin Alumina Films for Solar-Thermal Energy Conversion, Using X-Ray Diffraction Technique
Solar energy is the most “available”, ecological and clean energy. This energy can be used in active or passive mode. The active mode implies the transformation of solar energy into a useful energy. The solar energy can be transformed into thermal energy, using solar collectors. In these collectors, the active and the most important element is the absorber, material which performs the absorption of solar radiation and, in at the same time, limits its reflection. The paper presents some aspects regarding the IR absorbing material – a type of cermets, used as absorber in the solar collectors, by X Ray Diffraction Technique (XRD) characterization. Keywords—Alumina films, solar energy, X-ray diffraction.
Structural characteristics of Al2O3 thin films prepared by spray pyrolysis
The crystalline and structural characteristics of aluminium oxide (Al2O3) thin films deposited by ultrasonic spray pyrolysis have been analysed using conventional and high resolution transmission electron microscopy. The aluminium oxide films were deposited on silicon (100) wafers, using a solution of aluminium acetylacetonate in dimethylformamide. The films were deposited with and without the addition of water mist generated in parallel to the spraying solution. The substrate temperatures during deposition of the films were in the range of 500-650 °C. The results indicate that the thin films deposited without water mist have an amorphous structure, while those films deposited with the addition of water mist show a two-face nature, formed by small crystallites embedded in an amorphous matrix. The crystalline phase has been determined, through the indexing of the electron diffraction patterns. It is found that it corresponds to 5Al2O3 · H2O in a Tohdite hexagonal structure with unit cell lattice constants a = 5.575 A and c = 8.76 A.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).