Papers by Author: L.L. Pranevičius

Abstract: Yttria-stabilized zirconia (YSZ) coatings were synthesized using dc magnetron sputter deposition of Y/Zr layers followed by thermal treatment in the range of temperatures 600-1000 °C at atmospheric pressure in air. The characterization of YSZ coating structure was carried out by X-ray diffraction. The secondary ion mass-spectrometry analysis was used for the recording of depth profiles of the most important elements in coatings and at interface. The conducted analysis showed that processes on the surface play a dominant role in the synthesis mechanism of YSZ coatings homogeneous in structure and composition during the thermal oxidation. The excess of surface thermodynamic potentials supports an intensive intermixing across Y/Zr layers with continuous supply of oxygen through the surface. Under highly non-equilibrium conditions on the surface, the adatoms are driven into grain boundaries of crystallites and result in high compressive stress in grains. The stress relaxation initiates the plastic flow of matrix material with incorporation of oxygen atoms. Thermally activated dislocation glide is considered as the dominant plasticdeformation mechanism in these materials.

Abstract: Surface atoms are activated as result of replacement collisional sequences in solids by incident ions. In dependence on theirs threshold (displacement) energy and angular distribution they may be sputtered (removed) or laterally relocated on the surface. The relocation length distribution depends on the energy and angular distributions of activated atoms and interaction atom-solid potential. The process of lateral relocation of surface atoms is considered as a sequence of stochastic removal and adsorption processes. The rate equations describing processes of sputtering, relocation and thermal diffusion are built and steady state solutions are presented for multielemental solids. The mechanisms of stochastic mixing of atoms and roughening of surface is discussed.

Abstract: The behaviors of hydrogen in Al, Mg and MgAl thin films on stainless steel substrate were investigated in this work. The hydrogen ions extracted from plasma were used to load hydrogen into the film material. Glow discharge optical emission spectroscopy (GDOES) was applied to obtain the hydrogen depth profiles in Al films versus hydriding parameters. The MgH2, AlH3 and Mg(AlH4)2 hydrides were identified in plasma hydrided films using X-ray diffraction (XRD). It is shown that efficient supply transport of hydrogen from the surface into the bulk for Mg films takes place at temperature above 100 °C and ion irradiation intensity above 1 mAcm-2.

Abstract: Thin films of ZrO₂-8mol%Y₂O₃ have been deposed by pulsed DC magnetron sputtering method. The substrates of Ni-cermet and alloy-600 for the films were used. The results of the investigation of the X-ray diffraction patterns and SEM showed that the films are nanocrystalline and belong to cubic symmetry. The relaxation process is related to the ion transport in thin films. The results of the investigation of the temperature dependencies of thin films ionic conductivity (σ) showed that the dependence σ(T) is caused by the temperature dependence of oxygen vacancy mobility, while the number of charge carriers remains constant with temperature.