Interaction on surfaces of technically important alloys

The doctoral thesis is devoted to surface study of Heusler alloys and their properties. Main attention is paid to alloys based on Ni-Mn-Ga and Fe-Zr-Si. The work deals with the dynamics of martensitic transformation on macro- and mesoscopic scales of Ni-Mn-Ga system. The chemical state, morphology, as well as magnetic and surface structure are monitored at particular stages of the phase transition. Induced by radiation heating, the transformation from martensite to austenite takes place separately at the surface and in the bulk. The surface analysis of the Ni49.7Mn29.1Ga21.2 (100) single crystal alloy reports on the significant difference between surface and bulk in martensitic phase with respect to the twin microstructure and the arrangement of magnetic domains. The second part of the work deals with corrosion protective layers of zirconium cladding in nuclear industry applications and initial stages of the FeZrSi alloys formation on the Zr surface. The corrosion experiments were carried out in autoclave conditions with an in-situ electrochemical impedance spectroscopy. These experiments show that the thicker Si overlayer successfully suppresses oxygen uptake of the underlying Zr material by forming a diffusion barrier. A similar barrier effect of the Si film was also confirmed for hydrogen diffusion. The FeZrSi Heusler alloy was formed by sequential deposition of Fe and Si layers on a clean Zr surface. The structure of the surface was analyzed by LEED and XPS. Two different chemical states on the clean Zr surface were detected. The third part of the doctoral thesis is devoted to study of the Zr surface protection by means of polycrystalline diamond coating. Hydrogen adsorption on the Zr surface is treated in the final part of this thesis.

Supervisor specialist: Ing. Vladimír Cháb, CSc.
Supervisor: Doc. RNDr. Petr Sajdl, CSc.