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Le sujet de la thèse initié dans le cadre de l'ANR UV-Borate s'inclut dans le projet UV-Conversion labellisée par 2 pôles de compétitivité (Matériala - Lorraine - et Route des lasers - Aquitaine -) soumis à l'ANR en 2011. Les études se portent particulièrement sur les borates YxLaySc4-(x+y)(BO3)4 (LYSB) et YAl3(BO3)4 (YAB), cristaux Optiques Non Linéaires (ONL) possédant la même structure cristallographique (R32). La croissance de ces cristaux est effectuée par les collaborateurs industriels et universitaires de l'ANR. Ces deux matériaux présentent en effet des possibilités de conversion de fréquence jusqu'à des longueurs d'onde λ < 300 nm, de plus une non hygroscopicité procure une plus grande durée de vie des échantillons et par conséquent un net intérêt pour les applications industrielles. L'endommagement laser étant lié à l'absorption et ainsi, en partie, aux impuretés, une étude de la qualité cristalline et de l'homogénéité de nos cristaux a été effectuée. Les résultats ont permis de relier des défauts de structure (dislocations et etch pits) à la croissance de la maille rhomboédrique via des caractérisations par ombre portée (Photography Schlieren) et par attaque chimique suivi d'une observation par microscopie optique, MEB et MFA. Par ailleurs, des études théoriques et expérimentales d'accord de phase (détermination de θ et φ) lors de conversions de type I principalement ont été réalisées sur les cristaux de YAB, LYSB ainsi que sur des cristaux de référence tel que β-BaB2O4 (β-BBO). L'aspect de l'endommagement laser dans les matériaux ONL a été abordé dans les locaux de l'Institut Fresnel de Marseille au sein de l'équipe Interaction Laser Matière (ILM) sur des échantillons de Li2B4O7 (LTB). L'équipe a effectivement développé un dispositif de mesure de la probabilité d'endommagement laser et de mesure de tenue du seuil d'endommagement laser des matériaux optiques. Par ailleurs, un effort a été mené dans la conception d'un dispositif de mesure de la transmission optique et absorption à température ambiante et aux basses températures afin de révéler des défauts absorbants. Des premiers résultats ont été obtenus et discutés sur des échantillons de β-BBO et LYSB.

We investigated from the point of view of optical and vibrational the matrix 60B203 - (20 - x)Na2O - 10PbO - 10Al2O3 : xTiO2, with x= 0, 1, 2, 3, 4, e 5 mol% glasses, in order to understand the changes brought with the substitution of sodium oxide Na2O titanium oxide per TiO2. We performed measurements of X-ray diffraction, which revealed homogeneous amorphous structures throughout the composition range. The absorption spectra showed that the energy of the optical band gap (∆Eopt) and Urbach energy (UE) decreased with increased concentration of oxide TiO2. By using Vibrational Raman Spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy, we have observed changes in the spectra, which indicated a relationship with the effect conversion BO4 to BO3 groups and the appearance of “loose” BO4, indicating that ions titanium acted as a modifier of the vitreous network. Subsequently, we investigated the effect of substitution of Na2O per TiO2 on the point of view of structural features and spectroscopic oxide dopant Nd2O3 the following borate glass matrix 60B2O3 - (20 - x)Na2O - 10PbO - 10Al2O3 : xTiO2 : yNd2O3. Were measured from X-ray patterns, temperatures glass (Tg), vibrational spectroscopy and Raman and Infrared measurements of optical absorption and emission spectra. The tendency of the glass transition temperature (Tg), Judd-Ofelt parameters, Ω(2;4;6) and the ratio for Nephelauxetic with increasing concentration TiO2 and Nd2O3 were interpreted quantitatively and qualitatively in terms of connections and coordination number. Measurements of glass transition temperature (Tg) for the entire series of glass system doped with neodymium ions (Nd3+) for different concentrations of titanium (Ti) suggested changes in the rigidity of the matrix due to the change coordinating boron oxide resulting from the effect of converting BO4 to BO3. The variation of the Judd-Ofelt parameters Ω 2 and Ω 4 indicated that the average radius of the rare earth-ligand decreased creating a distribution of electron density when the ion concentration of neodymium (Nd3+) increases. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Investigamos sob o ponto de vista Óptico e vibracional a matriz vÍtrea 60B203 — (20 — x)Na2O —10PbO —10Al2O3 : xTiO2, com x= 0, 1, 2, 3, 4, e 5 mol%, a fim de compreender as mudanças causadas com a substituição de óxido de sódio (Na2O) por óxido de titânio (TiO2). Realizamos medidas de difração de Raio-X, as quais revelaram estruturas amorfas homogêneas em toda a faixa de composição. Os espectros de absorção mostraram que a energia da largura da banda óptica (∆Eopt) e a Energia de Urbach (UE) diminuíram à medida que aumentamos a concentração do óxido de titânio (TiO2). Ao utilizarmos a Espectroscopia Vibracional Raman e Infravermelho por Transformada de Fourier, observamos alterações nos espectros, as quais, indicaram uma relação com o efeito de conversão de BO4 para BO3 e o aparecimento de grupos BO4 livres, indicando que os íons de titânio atuaram como um modificador da rede vítrea. Posteriormente, investigamos as modificações nas propriedades estruturais causadas com a substituição de óxido de sódio (Na2O) por óxido de titânio (TiO2), utilizando como ponto de vista as propriedades espectroscópicas do íon dopante Nd3+ da seguinte matriz vítrea borato 60B2O3 — (20 — x)Na2O — 10PbO — 10Al2O3 : xTiO2 : yNd2O3, com x= 0, 1, 2, 3, 4, 5 mol% e y= 1, 2, 3, 4, 5 peso%. A tendência da temperatura de transição vítrea, dos parâmetros Judd-Ofelt, (2;4;6) e da razão nefelauxética em função do aumento da concentração dos óxidos de titânio (TiO2) e dos óxidos de neodímio (Nd2O3) foram interpretados quantitativamente e qualitativamente em termos das ligações da rede e do número de coordenação. As medições da temperatura de transição vítrea para toda a série do sistema vítreo dopada com íons de neodímio (Nd3+) em diferentes concentrações de óxidos de titânio (TiO2) sugeriram mudanças na rigidez da matriz, devido à mudança de coordenação do óxido de boro, resultante do efeito da conversão do BO4 para o BO3. A variação dos parâmetros de Judd-Ofelt indicaram que o raio médio do íon terra rara-ligante diminuiu criando uma redistribuição da densidade eletrônica quando a concentração do íon de neodímio (Nd3+) aumenta.

This work specifies the synthesis and the characterization of amorphous powders belonging to the Y2O3 - Al2O3 - B2O3 system. The main objective of this work was to develop amorphous powders near the YAl3(BO3)4 composition without any rare earth as doping for the development of a new family of phosphors for solid state lighting systems excited by near ultra-violet light. The sol-gel and polymeric precursor methods were applied in order to produce these powders. After these syntheses we optimized several parameters such as thermal treatments: two different routes were tested: direct calcination and pyrolytic decomposition followed by calcination. The temperature, annealing time, heating rate and the effects of impurities on the photoluminescence (PL) were studied. A comparison between these two synthesis methods was done. The powder samples were characterized by thermal analysis technique, X-ray diffraction, photoluminescence and infra-red spectroscopies, transmission and scanning electron microscopy, elemental analysis and electron probe microanalyses, nuclear magnetic resonance, cathodoluminescence, electronic paramagnetic resonance. From the thermal analyzes, it was observed that the powder prepared by polymeric precursor method shows a glass transition temperature (Tg) around 740 °C and crystallization temperatures (Tx) at 815, 850 and 900 °C. Amorphous powder showing high photoluminescence emission (between 400 and 750 nm) and quantum yields higher than 90% at 365 nm excitation, without any phase segregation were obtained when the samples are annealed at temperatures at around Tg, above this temperatures the powder start to crystallize decreasing their PL properties. Other compositions were studied by increasing the relative amounts of Y2O3, Al2O3 and B2O3, by removing the yttrium, addition of SiO2. Finally, the first measurements of color coordinates and the preliminary tests on the thermal and photo stability have been done. / Ce travail de these porte sur la synthèse et la caractérization de poudres amorphes en appartenant système Y2O3 - Al2O3 - B2O3. L'objectif principal du travail a été de préparer des poudres amorphes dont la composition est proche de YAl3(BO3)4 sans terre rare en vue la réalisation de phosphores pour des dispositif d'éclairage solide à base de LED emmetant dans le proche UV. Pour la synthèse des poudres les methodes sol-gel et celles des precurseurs polymériques ont été utilisées. Nous avons ensuite optimizé les paramètres thermiques, en utilisant deux stratégies: la calcination directe et la pyrolyse suivrie d'une seconde étape de calcination. La température, le temps de recuit, vitesse de chauffage et les effect des impurities sur la photoluminescence ont été étudié. Les échantillons en poudre ont été caractérisés par les techniques d'analyse thermiques, diffraction des rayons X, la spectroscopie de photoluminescence et la spectroscopie infra-rouge, microscopies électronique à balayage et en transmission, les méthodes des analyses élémentaire et microsonde électronique, la résonance magnétique nucléaire, cathodoluminescence et le résonance paramagnétique électronique. Par l'analyse thermique, on a observé que la poudre préparée par la méthode de précurseur polymère a une température de transition vitreuse (Tg) autour de 740 ° C et des températures de cristallisation (Tx) à 815, 850 et 900 ° C. Les poudres amorphes presentent de larges bandes d'émission de photoluminescence (entre 400 et 750 nm) avec des rendements quantiques supérieurs à 90% pour une excitation de 365 nm. De plus, les poudres microscopiques obtenu sont chimiquement homogene avec des composition très proche de celle initialmente visée YAl3(BO3)4 lorsque les échantillons sont recuits à des températures voisine du Tg. Au-dessus de cette température, la poudre commence à se cristalliser conduisant à réduction de l'intensité de PL. D'autres compositions ont été étudiées en augmentant la quantité relative de Y2O3, Al2O3 et B2O3, en éliminant complètement l'yttrium, ou en ajutant SiO2. Finalement, les premiers mesures de coordonnées de couleur et les essais préliminaires sur la stabilité thermique et photométrique sont très prometeur. En effet, outres les rendemente specifiques de luminescence très elevés ces luminophores émitent de lumiére très chaudes.

Resumo: Para conhecer o potencial de plantas de cobertura no fornecimento de nitrogênio para o milho, em sistema de plantio direto, foi avaliado o N potencialmente mineralizável (N0) do solo por meio de ensaio de incubação aeróbia de longa duração e o N disponível por meio dos extratores químicos KCl a quente, Dakota do Sul modificado e tampão fosfato borato a pH 11,2. Foram utilizadas amostras de solo de experimento a campo, instalado em área de Latossolo Vermelho argiloso e conduzido em delineamento em blocos casualizados, com cinco tratamentos: testemunha com vegetação espontânea, sorgo, milheto, mucuna-preta e feijão-de-porco, e cinco repetições. A coleta de solo nas parcelas foi feita após a dessecação das plantas de cobertura e antes do cultivo de milho, nos anos agrícolas de 2007/2008 e 2008/2009. O solo coletado, representativo da profundidade de 0 a 10 cm, foi utilizado no ensaio de incubação aeróbia, em experimento em vasos, com milho, e para as análises químicas. A eficiência dos extratores foi avaliada por meio de testes de correlação, empregando como variáveis de referência o N0 e o N mineralizado acumulado por 30 semanas, obtidos no ensaio de incubação aeróbia, e a produção de matéria seca e o N acumulado na parte aérea do milho, obtidos no experimento em vasos. As plantas de cobertura não diferem entre si quanto ao potencial de fornecimento de N para o milho. O método do KCl a quente é capaz de predizer a mineralização de N, porém os métodos químicos avaliados para predizer o N disponível não são eficientes / Abstract: Aiming to determine the potential of cover crops to supply nitrogen for corn in no-tillage system, it was evaluated the soil potentially mineralizable N (N0) by long-term aerobic incubation and available N by chemical extractants (hot KCl, modified South Dakota and pH 11.2 phosphate-borate buffer). Soil samples were collected from a field experiment, installed in an Udox and carried out in a randomized block design with five treatments (control with spontaneous vegetation, Sorghum bicolor, Pennicetum glaucum, Mucuna aterrima and Canavalia ensiformis) and five replications. Plots soil sampling was made after the cover crops desiccation and before growing the corn in the agricultural seasons of 2007/2008 and 2008/2009. Soil samples collected from 0 to10 cm depth were used for long-term aerobic incubation, pots experiment with corn, and for soil chemical analysis. Extractants efficiency was evaluated by correlation tests, using as reference the N0 and the mineralized accumulated N over 30 weeks obtained from long-term aerobic incubation, dry matter production and N accumulated in maize shoots, obtained from pots experiment. Cover crops do not differ in their potential to supply nitrogen for corn. Hot KCl is able to predict the N mineralization but the chemical methods evaluated to predict the available nitrogen are not efficients / Orientador: Manoel Evaristo Ferreira / Coorientador: Mara Cristina Pessôa da Cruz / Banca: André César Vitti / Banca: José Frederico Centurion / Mestre

Este trabalho teve como principal objetivo o estudo sistemático da obtenção da fase beta-BaB204 (beta-BBO) a partir de uma fase vítrea do sistema BaO-B2O3-TiO2. Foram estudadas amostras contendo entre 4 e 16% de TiO2. A avaliação das propriedades térmicas, estruturais e microestruturais das amostras foi realizada empregando as técnicas de Analise Térmica Diferencial (DTA), Difração de Raios-X (DRX), Microscopia óptica (MO), Microscopia Eletrônica de Varredura (MEV), Espectroscopia Raman, Absorção e Transmissão óptica no Infravermelho, Espectroscopia de Absorção de Raios-X (XAS) e Ressonância Magnética Nuclear (RMN). O coeficiente de Geração de Segundo Harmônico (GSH) foi obtido através das medidas do loci de casamento de fase e da Franja de Maker. O estudo do processo de cristalização revelou que em todas as amostras prevaleceu o mecanismo de cristalização superficial. Nas amostras contendo 4 e 8% de TiO2 foi observada a cristalização da fase beta-BBO enquanto que nas amostras contendo 15 e 16% de TiO2, foi observado que o processo de cristalização se inicia pela fase BaTi(BO3)2 e que somente após longos tempos de tratamento, a fase beta-BBO se toma a fase predominante. A identificação da fase BaTi(BO3) somente foi possível com a utilização da técnica de Espectroscopia Raman. O estudo da estrutura local através das técnicas de XAS e RMN mostrou que a estrutura local ao redor dos átomos de titânio, bário e boro nas amostras cristalizadas é pouco afetada quando a quantidade de TiO2 passa de 4 para 16%. A análise dos resultados da medida de geração de segundo harmônico mostrou que nas amostras contendo uma camada da superfície cristalizada, o valor do coeficiente de geração de segundo harmônico (deff) é equivalente ao do quartzo monocristalino e na amostra contendo 16% de TiO2, corresponde a 70% do valor observado na fase beta-BBO em sua forma monocristalina / This work consists of a systematic study of the beta-BaB2O4 (beta-BBO) crystalline phase obtained from the BaO-B2O3-TiO2 glass system containing amounts of titanium varying from 4 to 16 mol%. The thermal, structural and microstructural properties of the samples were evaluated by the following techniques: Differential Thermal Analysis (DTA), X-Ray Diffraction (XRD), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Raman Spectroscopy, Infrared Optical Absorption Spectroscopy, X-Ray Absorption Spectroscopy (XAS) and Nuclear Magnetic Resonance (NMR). The Second Harmonic Generation (SHG) coefficient (def) was obtained from the phase matching Loci and Maker fringe curves. A study of the crystallization process revealed that the surface crystallization mechanism predominated in each of the samples. Only the beta-BBO phase was observed in the samples containing 4 and 8 mol% of TiO2. However, in the samples containing 15 and 16 mol% of TiO2, crystallization of the BaTi(BO3)2 occurred first and was followed by crystallization of the P-BBO phase, which subsequently became the main phase as the period of heat treatment increased. The identification of the BaTi(BO3)2 phase in the early stage of the crystallization process was only possible by using the Raman spectroscopy technique. Based on the results obtained from the XAS and NMR techniques, it was found that the increasing the titanium concentration does not affect significantly the short-range order around Ti, Ba and B atoms. An analysis of the SHG data obtained from the crystallized surface of the glassy samples indicated that the SHG coefficient, def, was comparable to that of the z-quartz monocrystalline sample and, in the sample containing 16 mol% of TiO2, it corresponded to 70% of the value observed for the monocrystalline beta-BBO sample

Le but de ce travail est d'étudier l'effet de la teneur en cuivre et de la valence des atomes de cuivre sur la structure et les propriétés mécanique du verre. Des verres de zinc- et plomb- cuivre borate ont été étudiés. Les changements structurels avec le remplacement de PbO ou ZnO par CuO sont observés par réflectance infrarouge et Raman. L'état d'oxydation, l'environnement du site et la liaison caractéristique d'ions de cuivre ont été étudiés par spectroscopie optique et de résonance de spin électronique. Les propriétés mécaniques ont été déterminées et corrélées à la structure du verre et à sa composition, en mettant l'accent sur les propriétés élastiques, le comportement d'indentation (dureté et micro-fissures), la ténacité et la dépendance à la température de l'élasticité. Le cuivre a une tendance à stabiliser le bore en coordinence trigonale et donne une structure de type métaborate plus homogène. L'ajout d'ions de cuivre au verre métaborate améliore les performances mécaniques (modules d'élasticité et dureté), et diminue la sensibilité à la température ainsi que le taux de ramollissement des verres au plomb. Toutefois, l'ajout d'ions de cuivre dans les verres au zinc a des effets opposés sur ces propriétés. Les changements chimiques à la surface des verres de borates de cuivre et de zinc après traitement thermique sont également étudiés. L'étude par nanoindentation et par rayage montre que la couche cristallisée améliore la résistance mécanique de la surface du verre. / The aim of this work is to study the effect of copper content and copper valence on the structural and mechanical properties of glass. Zinc- and lead- copper borate glasses were studied. Their structural changes with the substitution of CuO for ZnO or PbO are followed by Raman and reflectance infrared. The oxidation state, site environment and bonding characteristic of copper ions are studied by optical and electron spin resonance spectroscopy. The mechanical properties were determined and correlated to the glass structure and composition, with a particular emphasis on the elastic properties, sharp indentation behavior (hardness and micro-cracking), toughness and temperature dependence of elasticity. Copper tends to stabilize trigonal boron and gives a more homogeneous metaborate structure. Adding copper ions to the metaborate glass clearly improves the mechanical performance (elastic moduli and hardness), in the meantime decreases the temperature sensitivity and soften rate of lead borate glasses. However, adding copper ions in zinc borate glasses has opposite effects on these properties. The chemistry changes at zinc-copper-borate glass surface after heat-treatment are also studied. Investigation of the nanoindentation and scratch behavior show that the crystallized layer improves the mechanical resistant of glass surface.

Physical properties of materials and their constituents are interrelated. Though the basic structural unit involved also plays a role in deciding the properties, this can be manipulated to a certain extent, by carefully selecting the basic ingredients or by varying the composition. In order to tailor the properties of the materials according to the need, the relationship between the properties and the structure has to be established. Glasses, due to their inherent disorder, don’t have the privilege of using symmetry as enjoyed by their crystalline counterparts. Given their components and composition there is no immediate and easy way of predicting all the observed properties of glasses. This is not considering computer simulations and DFT calculations. Hence we go back to play with nature, i.e., do experiments. Technological applications like LASERs, optic fibers, photosensitive semiconducting thin films, solid state batteries for energy storage etc. have greatly increased the interest in the fundamental properties of disordered materials. Large coefficient of linear expansion of germanate glasses is made use in glass-to-metal seals for ultra high vacuum. More over, many germanate based glasses with specially tailored dispersion properties have been developed. GeO2 based glasses are in fibre optics in the IR region of 1.5 to 1.8 microns. Borate glasses are resistant to thermal and chemical attack. They lower the melting temperature of glasses thus facilitating large scale production.Both borates and germanates have been worked upon extensively. Alkali boro germanate systems are interesting inherently. Borates and Germanates both are glass formers by themselves. The continuous random network formed by this base glass is modified by the presence of alkali ions. It is interesting to see to what extent the alkali ions can maintain the local charge neutrality in their neighborhood by creating non bridging oxygen atoms and how the presence of two formers is stabilizing the glass matrix. Present Work This thesis work is an attempt to understand the structure of alkali borogermanate glasses 25R2O-25GeO2-(50-x)B2O3-xNd2O3:(R=Li, Na, K and Rb; x=0,0.5). A variety of experimental techniques are available to give a good insight of the structure of glass systems. In this thesis, we have carried out  Optical studies at room temperature to probe the environment of RE ion  AC conductivity at high temperature to probe the alkali ion dynamics  11B MASS NMR of doped systems at room temperature to probe the Boron sites  Raman and Mid-IR experiments at room temperature to probe the various structural groups to get a comprehensive understanding of the structure of these glasses. To facilitate the analysis of the data and discussion of the results from these experiments, the thesis is divided in to four chapters excluding the introduction as categorized above and is presented accordingly. The second chapter begins with the preparation of the glass samples and their characterization. We have used Differential Scanning Calorimetry (DSC), powder XRD and elemental analysis using ICP-OES for characterizing the sample. We have also measured the density and refractive index of the glasses under study. After this section, we describe the results from Optical Absorption and Photoluminescence studies. A brief description of Judd-Ofelt (JO) theory used for the analysis of the results is given. We have calculated the optical parameters and JO parameters and the energy levels of Nd ions in the glass matrix based on absorption studies using program written in Matlab. The procedure to calculate these parameters and their relevance in estimating the important quantities like radiative transfers, branching ratios are discussed. The effect of variation of the alkali ions on these properties is also discussed. In the third chapter, we have investigated AC conductivity in these glasses. These experiments are carried out both as a function of frequency (40 Hz - 15 MHz) and temperature (220 C – 500 C) using a home made portable furnace with a temperature controller. The cable compensation using open and short standards were done at the high temperature end. The data has been analyzed in Electric modulus (M*) formalism using Kohlrausch William Watts (KWW) function. The other basic models used in the literature like Debye, Cole-Cole, Cole Davidson and Havriliak Negami are briefly discussed. The frequency dependence of conductivity in these systems has been ascribed to the hopping motion of the alkali ions. Non-symmetric nature of the imaginary part of M* shows an evidence of non-exponential relaxation. Activation energies were estimated from the temperature variation of the KWW and DC. The fit parameters KWW and KWW shows interesting behavior. KWW in LGBNd and NGBNd show an initial increase with increasing temperature reaching a value of 1, while a contrasting behavior is observed in KGBNd and RGBNd. Barton-Nakajima-Namikawa (BNN) plot of the present study gives a value of 0.67 and 0.7 for the slope parameter p for doped and un-doped samples respectively. BNN plot is used to correlate the ac and dc conductivities in the sample. The deviation of the slope parameter from unity may be an indication of different charge carriers for ac and dc transport. Fourth Chapter describes the room temperature 11B MASS NMR studies in Nd doped glass system. The relevant theory of Zeeman, Dipolar, Quadrupolar and Chemical shift interactions are discussed briefly before the results. The principle used in obtaining high resolution NMR in solids by means Sample spinning is also described. NMR line shape for the central transition (1/2  -1/2) of I=3/2 nuclei (11B) was simulated in Mathematica and fitting was tried in Matlab. Using this background we have analyzed the line shape. In the next part, the results of 11B MASS NMR experiments of doped glasses carried out using Bruker DSX300 at 96.3MHz are presented. The fraction of contribution from four and three co-ordinated 11B to NMR line-shape were identified and calculated. The results show unambiguously the presence of two 3 coordinated 11B sites which were differentiated on the basis of the quadrupolar parameters. In the last chapter we discuss the results of Raman and Mid-IR investigations carried out in these glasses at room temperature. These two important techniques are well established in identifying the structural groups in glass systems. Raman bands observed in the range 200 cm-1 to 1600 cm-1 in these glasses are deconvoluted using gaussian peaks and they have been assigned to various modes of possible structural groups. Two broad MIR absorption bands were observed between 600cm-1 - 1600cm-1 in both doped and undoped glasses. Each band was resolved into gaussian peaks. The band shifts and the changes in the intensities are ascribed to the effects of variation of alkali, as the presence of GeO2 (up to 25mol%) is known not to affect the borate bands as it is a former by itself.

No description available.

Chiral separation systems in capillary electrophoresis are in the scope of interest of many research groups all over the world. Therefore, the need to develop reliable theoretical models, which would help to explain phenomena connected with chiral separations or optimization of separation conditions, is obvious. In this thesis several mathematical models and approaches that can fulfill these requirements are presented. First part of the thesis deals with the determination of rate constants of interconversion of enantiomers by means of dynamic capillary electrophoresis. We focused on mixtures of chiral selectors and formulated a mathematical model, which enables to determine rate constants of interconversion in such systems. Mixtures of chiral selectors are very popular in separation practice due to their enhanced enantioselectivity. The theoretical model established in the thesis is able to explain the separation mechanisms of multi-chiral selector systems and to propose and verify possible ways of their optimization. In addition, the separation mechanism in systems with simultaneous cyclodextrin and borate complexation was revealed. Finally we present the complete mathematical model of electromigration in systems with complexation agents. The model is implemented into our simulation tool Simul 5...