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Mathematical modelling diffusion of metal ions in humic gel
Masár, Lukáš ; Ing. Eva Gregorová,CSc. (referee) ; Klučáková, Martina (advisor)
The subject of this bachelor thesis was simulation of diffusion processes proceeding in the reactive gelous media using the COMSOL Multiphysics software. The aim of this study was to develop a comprehensive set of models available for the interpretation of experimental data obtained in the study of metal ions transport in the humic acids hydrogel. The main consideration was given to the influence of porosity modelling and chemical interactions on the diffusion characteristics (mainly diffusion flow). Within the simulation of the influence of chemical reactions, different kinetic models were used (one-way reaction of first and second order and reverse reaction).
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Diffusion of cupric ions in humic gel
Kalina, Michal ; Gregorová,, Eva (referee) ; Klučáková, Martina (advisor)
The bachelor´s thesis deals with the study of non–stationary diffusion of copper (II) ions in humic gel. The objective of the study was to validate that the diffusion is influenced by the volume of cupric ions solution and by the length of tubes filled with humic gel. Diffusion was characterized by the value of diffusion flux and by the copper (II) ionic concentration profiles in humic gel. The data necessary for calculation were obtained by spectrophotometric measuring of the extracts of each slice after diffusion.
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Comparison of Dry and Wet Oxidation Process during Low Pressure Boron Diffusion with BBR3 in Solar Cell Production
Mojrová, B.
This paper deals with replacing a dry oxidation with a wet oxidation process during low pressure diffusion using boron tribromide (BBr3) in solar cell production. Because the liquid boron trioxide (B2O3), a product of a chemical reaction during diffusion, condenses apart from wafers on walls of quartz tube, it is essential to clean the tube after diffusion. This could be done by evaporation of water into the tube after unload or, in order to make the production time shorter, by replacing the dry oxidation with wet oxidation process. In this paper a comparison of the wet and dry oxidation is given with regard to the solar cell production.
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CARBON DIFFUSION IN CARBON-SUPERSATURATED 9CR-1MO STEEL: ANOMALOUS TEMPERATURE DEPENDENCE OF CARBON DIFFUSIVITY
Čermák, Jiří ; Král, Lubomír
Carbon diffusion was studied in temperature interval 573 - 1073 K in carbon-supersaturated surface layer of 9Cr–1Mo steel P91 and in model Fe-15Cr binary alloy. Extremely low carbon diffusion coefficient D (by 3 orders of magnitude lower than the value D eq in material with equilibrium carbon concentration) was observed in carburized surface region of Fe-15Cr. Similar results were obtained for P91 above the temperature T n ~ 800 K. However, below T n , the values of D measured in P91 increased and approached the value of D eq . It seems that the non-Arrhenius behaviour of P91 steel around T n may be ascribed to the α → α + α’ phase decomposition. Possible effect of nitrogen upon the low-temperature increase in D in P91 steel was excluded.
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Initial Stage of Mutual Diffusion of Carbide in Iron
Čermák, Jiří ; Král, Lubomír
Initial stage of mutual diffusion close to carbon/iron interface was investigated in the present work. SIMS technique of concentration profiles enabled to study the carbon redistribution in the very early stages, when the diffusion process occurs – at least partly – in regions, where the carbon concentration exceeds the carbon concentration limit. It was observed that carbon diffusion coefficients are much lower under such conditions, than in Fe matrix with equilibrium carbon concentration. The measured carbon diffusion coefficients approached values reported for carbon diffusion in carbides.
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Jednoduchá metoda pro difúzní měření využívající zbytkové aktivity
Rothová, Věra
A simple and sensitive technique using the liquid scintillation (LS) counter has been developed which is based on a solid scintillator in place of the commonly used LS cocktail. As a test case, the method was applied to the successful determination of the Ni-63 self-diffusion profile in commercial purity nickel by means of the Gruzin's residual activity technique.
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