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Precipitation processes in light hardenable alloys and the possibilities for integrating thermal analysis into physics education on high school
Kodetová, Veronika ; Vlach, Martin (advisor) ; Černošková, Eva (referee) ; Svoboda, Pavel (referee)
The doctoral thesis is divided into two parts - Thermal analysis in physics education on high school and Material research of Al-Zn-Mg(-Cu-Sc-Zr) alloys. Within the first part, the areas of crystallization and/or melting of selected foods were determined using differential scanning calorimetry. A practical lesson for high school physics has been created and tested. The study text focused mainly on differential scanning calorimetry and its use was made. In the second part of the doctoral thesis, there was analysed thermal evolution of the phase transformation in the Al- Zn-Mg(-Cu) alloys with Sc and Zr addition. The effect of (cold and hot) deformation on the decomposition sequences was studied. The hardening effect after annealing above 300 řC in the Sc and Zr alloys is caused by the precipitation of the secondary Al3Sc,Zr) particles. These particles were observed by transmission electron microscopy after annealing up to 360 řC in all studied AlZnMg(Cu)ScZr alloys. In the AlZnMgCu alloy the partial recrystallization was observed after annealing at 350 řC/10 hours and after annealing at 450 řC/10 hours the grain size was 50-200 m (depending on the treatment of the alloy). The addition of Sc, Zr in the AlZnMgCuScZr stabilizes grains and there is no recrystallization in the AlZnMgCuScZr alloy at temperature...
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Selected glasses of Ge-Se-Te system
Černošková, E. ; Hejdová, M. ; Černošek, Z. ; Holubová, J. ; Todorov, R. ; Vlček, Milan
Bulk glasses Ge30Se70-xTex for (x = 0, 10, 20) were prepared by direct synthesis. Thermal evaporation was used for preparation of thin films. The glass transition temperature of the bulk samples and decrease with increasing Te, but Tg of films with tellurium was not found. Crystallization temperature, Tc, for both bulk samples and films were close each to other. Comparing of Raman spectra - the corresponding Raman bands showed that medium-range order of bulks and thin films are partly different. 77Se MAS NMR of Ge30Se70 glass detected resonance of only Ge-Se-Ge (420 ppm, 98 %) and Se-Se-Se (837 ppm, 2 %), eliminating outrigger raft model and the structure of the studied glasses is probably close to Continuous Random Model.
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