A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor. / Natural Sciences and Engineering Research Council of Canada (NSERC)

A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor. / Natural Sciences and Engineering Research Council of Canada (NSERC)

This work presents theoretical background for the investigation of nanostructure formation in alkali-metal doped fullerene layers. A number of computational methods are used to describe structural transformation in the fullerene layer. They include tight-binding molecular dynamics, empirical molecular dynamics, Monte-Carlo calculations as well as other methods. The doped fullerene layers show the highest superconducting critical temperature among organic superconductors. A new electrochemical method of synthesis of potassium and rubidium fullerides has been recently developed by Professor Dunsch and coworkers in the department of electrochemistry and conductive polymers at IFW Dresden. The process of electrochemical doping is accompanied by several side effects, and one of them is nanostructure formation at the surface of the fullerene layer. In the present work an explanation is given for the nanostructure formation observed recently by scanning tunnel microscopy. The corresponding model is based on the concept of spontaneous phase separation that has been realized by kinetic Monte Carlo calculations. These calculations predict instability of initially homogeneous alkali-doped fullerene layers. Due to the significant gap in the Madelung energy formation of an alkali-poor and an alkali-reach phase is expected. The results of the Monte Carlo simulations point out that the particle size of the corresponding phases remains in the nanometer range. Interpretation of experimental data for metal deposition on fullerene substrates can be easily given in the framework of the phase separation concept as well. Metal clusters of the size order 50 to 100 nm emerge in course of electrochemical copper deposition on alkali-doped fullerene layers. The electrically conductive paths through the insulating fullerene layer are probably responsible for the inhomogeneous copper deposition under electrochemical conditions. A novel computer program has been developed in course of this work, which is designed as a distributed application. It can be used for diverse conventional and kinetic Monte Carlo calculations. / Die vorliegende Arbeit präsentiert theoretische Arbeiten, die das Ziel haben, die Nanostrukturbildung in dotierten Fullerenschichten zu verstehen. Diverse Rechenmethoden wurden verwendet, um die strukturellen Umwandlungen in der Fullerenschicht zu beschreiben. Die Tight-Binding-Molekulardynamik, die empirische Molekulardynamik und Monte-Carlo-Berechnungen sowie andere Methoden sind eingeschlossen. Die dotierten Fullerenschichten zeigen die höchste supraleitende kritische Temperatur unter den organischen Supraleitern. Eine neue elektrochemische Methode der Synthese von Kalium- und Rubidium-Fulleriden wurde vor kurzem von Professor Dunsch und Mitarbeitern in der Abteilung Elektrochemie und leitfähigen Polymere am IFW Dresden entwickelt. Der Prozess der elektrochemischen Dotierung wird von mehreren Nebenprozessen begleitet, und einer davon ist die Nanostrukturbildung an der Oberfäche der Fullerenschicht. In der vorliegenden Arbeit wird eine Erklärung für die Herausbildung der Nanostrukturen, die mit Hilfe von Rastertunnelmikroskopie beobachtet wurden, gegeben. Das entsprechende Modell basiert auf dem Konzept der spontanen Phasenentmischung und wird durch kinetische Monte-Carlo-Simulationen realisiert. Diese Simulationen sagen Instabilität der zunächst homogenen Alkali-dotierten Fullerenschichten voraus. Wegen des wesentlichen Unterschieds in der Madelungenergie ist die Herausbildung einer Alkalimetall-armen und einer Alkalimetall-reichen Phase zu erwarten. Die Ergebnisse der Monte-Carlo-Simulationen weisen darauf hin, dass die Teilchengröße der entsprechenden Phasen im Nanometer-Bereich bleibt. Im Rahmen des Phasenentmischungskonzepts können auch experimentelle Daten zur Metallabscheidung auf Fullerensubstraten problemlos interpretiert werden. Bei elektrochemischer Kupferabscheidung auf Alkali-dotierten Fullerenschichten entstehen Metallcluster der Größenordnung von 50 bis 100 nm. Die elektrisch leitfähige Pfade, die in einer isolierenden Matrix auftreten, sind wahrscheinlich für die ungleichmäßige Kupferabscheidung unter elektrochemischen Bedingungen verantwortlich. Ein neuartiges Computerprogramm wurde im Rahmen dieser Arbeit entwickelt, das als eine verteilte Anwendung entworfen ist. Damit können diverse konventionelle und kinetische Monte-Carlo-Simulationen durchgeführt werden.

Aqueous solutions were studied using photoelectron and Auger spectroscopy, based on synchrotron radiation and a liquid micro-jet setup. By varying the photon energy in photoelectron spectra, we depth profiled an aqueous tetrabutylammonium iodide (TBAI) solution. Assuming uniform angular emission from the core levels, we found that the TBA+ ions were oriented at the surface with the hydrophobic butyl arms sticking into the liquid. We investigated the association between ions and their neighbors in aqueous solutions by studying the electronic decay after core ionization. The (2p)−1 decay of solvated K+ and Ca2+ ions was studied. The main features in the investigated decay spectra corresponded to two-hole final states localized on the ions. The spectra also showed additional features, related to delocalized two-hole final states with vacancies on a cation and a neighboring water molecule. These two processes compete, and by comparing relative intensities and using the known rate for the localized decay, we determined the time-scale for the delocalized process for the two ions. We compared to delocalized electronic decay processes in Na+, Mg2+, and Al3+, and found that they were slower in K+ and Ca2+, due to different internal decay mechanisms of the ions, as well as external differences in the ion-solute distances and interactions. In the O 1s Auger spectra of aqueous metal halide solutions, we observed features related to delocalized two-hole final states with vacancies on a water molecule and a neighboring solvated anion. The relative intensity of these feature indicated that the strength of the interaction between the halide ions and water correlated with ionic size. The delocalized decay was also used to investigate contact ion pair formation in high concentrated potassium halide solutions, but no concrete evidence of contact ion pairs was observed. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 726

A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor. / Natural Sciences and Engineering Research Council of Canada (NSERC)

The Phthalocyanines (Pc’s) are a group of macro-cyclic molecules, widely investigated due to the possibility to use them in a variety of applications. Electronic and geometrical structure investigations of molecular model systems of Pc’s adsorbed on surfaces are important for a deeper understanding of the functionality of different Pc-based devices. Here, Pc’s monolayers and films, deposited on different surfaces, were investigated by X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS) and Scanning Tunneling Microscopy (STM). In addition Density Functional Theory (DFT) simulations were performed. For molecular films of Metal-free (H2Pc) and Iron (FePc) Pc’s, on surfaces, it is found that the intermolecular interaction is weak and the molecules arrange with their molecular plane mainly perpendicular to the surface. Several monolayer systems were characterized, namely H2Pc and FePc adsorbed on Graphite, ZnPc on InSb(001)-c(8x2), H2Pc on Al(110) and on Au(111). For all the studied monolayers it was found that the molecules are oriented with their molecular plane parallel to the surface. The electronic structure of the molecules is differently influenced by interaction with the surfaces. For H2Pc adsorbed on Graphite the nearly negligible effect of the surface on the molecular electronic structure allowed STM characterization of different molecular orbitals. A strong interaction is instead found in the case of H2Pc on Al(110) resulting in molecules strongly adsorbed, and partly dissociated. Modifications of the electronic and geometrical structure induced by alkali doping of H2Pc films and monolayers were characterized. It is found both for the H2Pc film on Al(110) and monolayer adsorbed on Au(111), that the molecular arrangement is changed upon doping by Potassium and Rubidium, respectively. Potassium doping of the H2Pc films results in a filling of previously empty molecular orbitals by a charge transfer from the alkali to the molecule, with significant modification of the molecular electronic structure.

A reação álcali-agregado - RAA é uma patologia de ação lenta que tem sido observada em construções de concreto capaz de comprometer suas estruturas. Sabe-se que a reação álcali-agregado é um fenômeno bastante complexo em virtude da grande variedade de rochas na natureza que são empregadas como agregados no preparo do concreto, podendo cada mineral utilizado afetar de forma distinta a reação ocorrida. Em função dos tipos de estrutura, das suas condições de exposição e dos materiais empregados, a RAA não se comporta sempre da mesma forma, em virtude disto a pesquisa constante neste tema é necessária para o meio técnico e a sociedade. Pesquisas laboratoriais, empíricas e experimentais tem sido rotina em muitos dos estudos da RAA dada ainda à carência de certas definições mais precisas a respeito dos métodos de ensaio, mas também em função da necessidade do melhor conhecimento dos materiais de uso em concretos como os agregados, cimentos, adições, aditivos entre outros e do comportamento da estrutura. Embora técnicas de prevenção possam reduzir significativamente a incidência da RAA, muitas estruturas foram construídas antes que tais medidas fossem conhecidas, havendo no Brasil vários casos de estruturas afetadas, sendo custosos os reparos dessas estruturas. Em estudos recentes sobre o tamanho das partículas de álcali-agregado e sua distribuição foi concluído que o tamanho do agregado está relacionado com o potencial danoso da RAA. Existem ainda indícios de que o tamanho e a distribuição dos poros do concreto também sejam capazes de influenciar o potencial reativo do concreto. Neste trabalho desenvolvemos um Sistema de Visão Artificial (SVA) que, com o uso de técnicas de Processamento de Imagens, é capaz de identificar em imagens de concreto, agregado e poros que atendam em sua forma, às especificações do usuário, possibilitando o cálculo da porosidade e produzindo imagens segmentadas à partir das quais será possível extrair dados relativos à geometria desses elementos. Serão feitas duas abordagens para a obtenção das imagens, uma por Escâner Comercial, que possui vantagens relacionadas à facilidade de aquisição do equipamento, e outra por micro tomógrafo. Uma vez obtidas informações sobre as amostras de concreto, estas podem ser utilizadas para pesquisar a RAA, comparar estruturas de risco com estruturas antigas de forma a melhorar a previsão de risco de ocorrência, bem como serem aplicadas a outras no estudo de outras patologias do concreto menos comuns no nosso país, como o efeito gelo/degelo. / The alkali-aggregate reaction - RAA is a condition of slow action that has been observed in concrete constructions that could affect their structures. It is known that the alkali-aggregate reaction is a very complex phenomenon because of the great variety of rocks in nature that are used as aggregates for concrete, and each mineral used differently affects the reaction occurred. Depending on the type of structure, its exposure conditions and the materials used, this phenomenon does not always behaves the same way, because of this, constant research in this area is needed for the technical means and the society. Laboratory, empirical and experimental research has been routine in many of the RAA studies still given the lack of certain more precise definitions concerning the testing methods, but also because of the need for better understanding of the use of materials in concrete as aggregate, cement, additions, additives etc. and structure behavior. Prevention techniques could significantly reduce the incidence of RAA. Still, many structures were built before such measures were known, several cases of affected structures were discovered in Brazil, all with large spending on repairs of the affected structures. In recent studies on the particle size of the alkaliaggregate and its distribution was concluded that the aggregate size is related to the damaging potential of the RAA. There are also indications that the size and distribution of concrete pores are also capable of influencing the reactive potential of the concrete. In the present work we developed an Artificial Vision System ( VAS ) that uses image processing techniques to identify aggregate and pores in hardened concrete images, enabling the calculation of porosity and producing segmented images that can be used to investigate data about the geometry of these elements. Were made two approaches for obtaining the images, one by Scanner Commercial, which has related advantages will ease the acquisition of equipment, and other micro CT scanner. Once obtained information on the concrete samples, these can be used to search the AAR compared risk structures with old structures so as to enhance the occurrence of risk prediction, as well as be applied to other concrete in the study of other pathologies less common in our country, as ice effect / thaw.

Borate glasses and glass-nano/microcrystal composite fabrication and investigations into their physical properties, have been interesting from their multifunctionalities view point. Certain borate structural units possess high hyperpolarizabilities and give rise to high nonlinear optical effects. High refractive index materials are important for photonic applications. Heavy metal oxide (Bi2O3) containing compounds have high refractive indices. Glasses embedded with wide band-gap semiconducting oxide crystals such as TiO2 received much attention due to their easy processing, stability and promising physical properties. Though TiO2 is used as nucleating agent to fabricate glass-ceramics of various phases, crystallization of TiO2 in glass matrices is difficult and the data are scarce in the literature. Therefore it was worth attempting to find glass compositions in which one can obtain TiO2 crystallization in large volume fractions. Towards this TiO2 crystallization was accomplished in BaO-TiO2-B2O3 glass matrix over wide composition ranges by tuning the concentration of BaO-TiO2 content in B2O3 network. The physical properties of these glasses of various compositions and glass-nanocrystal composites of TiO2 phase (anatase) were investigated. Interestingly BaO-TiO2-B2O3 glasses found to be hydrophobic in nature. The results obtained in the present research work are classified into five chapters apart from the Introduction, Materials and Methods chapters. Chapter 1 constitutes preface to oxide glasses, principles of glass formation and structural criteria followed by crystallization kinetics. In addition, principles of dielectric, optical and mechanical phenomena in glasses are discussed, since the present thesis focuses on the aforesaid physical properties. This chapter concludes with scope of the present thesis. Chapter 2 includes the detailed description concerning the fabrication techniques of materials under study and various characterization methods that have been employed at various stages of the present research work. The principles and experimental tools adopted for the structural and microstructural studies of materials were illustrated. Measurement techniques and experimental setup used to study physical parameters such as dielectric, optical, mechanical etc. were elaborated. Chapter 3 comprises structural, dielectric, electrical transport characteristics and optical studies of mixed alkali borate glasses in the 0.5Li2O-0.5M2O-2B2O3 (M=Li, Na and K) system. Transparent glasses in the Li2O-2B2O3 (LBO), 0.5Li2O-0.5Na2O-2B2O3 (LNBO) and 0.5Li2O-0.5K2O-2B2O3 (LKBO) were fabricated via the conventional melt quenching technique. Amorphous and glassy nature of the samples was confirmed via the X-ray powder diffraction and the differential scanning calorimetry, respectively. LKBO glass was found to have high thermal stability than that of LBO and LNBO. The frequency and temperature dependent characteristics of the dielectric relaxation and the electrical conductivity were investigated in the 100 Hz - 10 MHz frequency range. The relaxation and conductivity were rationalized using impedance and modulus formalism. Imaginary part of the electric modulus spectra was modelled using an approximate solution of Kohlrausch-Williams-Watts relation. The stretching exponent, β, was found to be temperature independent for LNBO glasses. Activation energies for conduction and relaxation process were calculated using the Arrhenius relation. The activation energy was found to be higher (1.25eV) for LKBO glasses than that of the other glass systems under study. This is attributed to the mixed cation effect. It has wide optical transmission window and optical band gap. Urbach energies were calculated for all these glasses. LBO, LNBO and LKBO glass compositions were found to crystallize in Li2B4O7, LiNaB4O7 and LiKB4O7 phases respectively upon heat treatment at appropriate temperatures. Transparent glass-micro crystal composites of LiKB4O7 were fabricated from LKBO glasses and found to be SHG active. BaO-TiO2-B2O3 Chapter 4 delineates the evolution of nanocrystalline TiO2 phase (Anatase) in BaO-TiO2-B2O3 (BTBO) glasses. Transparent colourless glasses in the ternary system were fabricated via conventional melt-quenching technique. The glasses with certain molar concentrations of BaO and TiO2 upon heat treatment at appropriate temperatures yielded nanocrystalline phase of TiO2 associated with the crystallite size in the 5-15 nm range. Nanocrystallized glasses exhibited high refractive index (no=2.15) at λ=543nm. These glasses were found to be hydrophobic in nature associated with the contact angle of 90o. These high index glass nanocrystal composites would be of potential interest for optical device applications. Crystallization kinetics of anatase phase in BTBO glasses were studied using non-isothermal Differential Scanning Calorimetry (DSC) at three different heating rates (10, 20 & 30 K/min). Scanning Electron Microscopy (SEM) carried out on heat treated (at 920 K) glasses confirmed bulk nucleation and three-dimensional growth. Johnson-Mehl-Avrami model could not be applied for this system suggesting considerable overlap of the nucleation and growth involving complex transformation process. However, modified Kissinger and Ozawa models were used to calculate the effective activation energy associated with anatase crystallization. The kinetic exponent n was found to be temperature dependent indicating the change in the crystallization mechanism. This is attributed to the high entropy fusion of anatase phase, fast crystallization rate and nano dimension of the anatase phase. Chapter 5 illustrates structural changes that occur in the x(BaO-TiO2)-B2O3 (x=0.25, 0.5, 0.75 &1 mol.) system on increasing the x apart from the details concerning some physical property correlations. Thermal stability and glass forming ability as determined by Differential Thermal Analysis (DTA) were found to increase with increasing BaO-TiO2 (BT) content. However, there was no noticeable change in the glass transition temperature (Tg). This was attributed to the active participation of TiO2 in the network formation especially at higher BT contents via the conversion of the TiO6 structural units into TiO4 units which increased the connectivity and resulted in an increase in crystallization temperature. Dielectric and optical properties at room temperature were studied for all the glasses under investigation. Interestingly, these glasses were found to be hydrophobic. The results obtained were correlated with different structural units present in the glass and their connectivity. These glasses exhibited low loss (tan δ≈0.002), frequency (10 kHz- 10 MHz) and temperature independent (or very weak temperature response) flat-dielectric response. Crossover temperature was encountered between flat response and Jonscher’s universal response. The cross-over temperature and cross-over energy barrier from flat dielectric response to Jonscher’s response was deduced for all the glasses in the present investigation. Electric modulus formalism was invoked to rationalize the relaxation phenomena. The observed dielectric response and conduction process in these glasses were attributed to the local vibration and switching of non-bridging oxygen ions in their potential cage and hopping over distributed energy barriers above the crossover temperature. Chapter 6 depicts the dielectric and mechanical properties of glasses embedded with TiO2 nanocrystals. BaO-TiO2-B2O3 glasses on subjecting to appropriate heat treatment temperature yielded TiO2 nano crystalline anatase phase. NMR studies carried out on the as-quenched glasses facilitated the estimation of fraction of tetrahedral and trigonal borate units. Poisson’s ratio and Young’s modulus were evaluated through theoretical expressions proposed by Makishima and Mackenzie. Nano-indentation and micro-indentation studies were carried out on the as-quenched glasses and glass-nanocrystal composites to examine mechanical characteristics. Estimated and indentation Young’s modulus of glasses were found to be in reasonable agreement. Hardness and Young’s modulus increased with increasing fraction of nano crystallites whereas fracture toughness was found to depend strongly on surface conditions. The results were corroborated by the structural units and particulates present in these glasses. Dielectric constant increased with increasing volume fraction of the nanocrystals which was rationalized via mixture rule. Chapter 7 describes the dielectric properties, electrical conduction and electric relaxation phenomena in 2Bi2O3-B2O3 (BBO) glasses followed by thier linear and nonlinear optical characteristics. Glasses in BBO system were obtained via melt-quenching technique. X-ray diffraction and differential scanning calorimetry were used to study the structural characteristics. Dielectric studies carried out on these glasses revealed near constant loss (NCL) response in the 1 kHz to 1 MHz frequency range at moderately high temperatures (300-450 K) accompanied by relatively low loss (tan δ=0.006, at 1 kHz & 300 K) and high dielectric constant (ε' =37, at 1 kHz & 300 K). The variation in AC conductivity with temperature at different frequencies showed a cross over from NCL response characterized by local ion vibration within the potential well to universal Jonscher’s power law dependence triggered by ion hopping between potential wells or cages. Thermal activation energy for single potential well was found to be 0.48±0.05 eV from cross over points. Ionic conduction and relaxation processes were rationalized by modulus formalism. The promising dielectric properties (relatively high ε' and low tan δ) of the BBO glasses were attributed to high density (93 % of its crystalline counterpart), high polarizability and low mobility associated with heavy metal cations, Bi3+. Optical band gap obtained for BBO glasses was found to be 2.6 eV. The refractive index measured for these glasses was 2.25±0.05 at λ=543 nm. Nonlinear refraction and absorption studies were carried out on BBO glasses using z-scan technique at λ=532 nm of 10 ns pulse width. The nonlinear refractive index obtained was n2=12.1x10-14 cm2/W and two-photon absorption coefficient was β=15.2 cm/GW. The n2 and β values of the BBO glasses were higher than that reported for high index bismuth based oxide glass systems in the literature. These were attributed to the high density, high linear refractive index, low band gap and two-photon absorption associated with these glasses. The electronic origin of large nonlinearities was discussed based on bond-orbital theory. Thesis ends with summary and conclusions followed by prospective views, though each chapter comprises conclusions associated with complete list of references. Patent, publications and conference proceedings that are listed below are largely based on the studies conducted as a part of the research work reported in the present thesis.

This diploma thesis is focused on composition and processing of cellulose fibers and their usage in cementitious composites. It describes key attributes of cellulose fibers, which has to be acquired for effective use in cement composites. There are stated effects of cellulose fibers on concrete properties, such as workability, physical and mechanic attributes and freeze-thaw resistance. In experimental part is designed a mixture with portion of cellulose fibers. There has been performed various tests to define the effect of cellulose fibers. There was designed experiment to determine its alkali resistance for fibers itself, and possible changes in microstructure of fibers were analyzed by optic and electron scanning microscope.

This doctoral thesis is focused on the possibilities of alkali-activated slag (AAS) shrinkage reduction, which would together with the use of waste sludge from waterglass production contribute to wider practical utilization of this interesting material. Besides the influence on AAS dimensional changes also effect of various factors on workability, setting time and mechanical properties was investigated. Obtained results were supported by the application of instrumental techniques like izotermal calorimetry, mercury intrusion porosimetry, scanning electron microscopy and X-ray diffraction. The results show the possibilities of reduction of AAS drying shrinkage related to its cracking tendency through the combination of increased dose of waterglass and reduced water to slag ratio (w/b), partial replacement of slag by pulverized fly ash or cement by-pass dust and application of organic admixtures, where significant effect on AAS hydration was observed. On the basis of the obtained results concrete mixtures, where the whole activator was replaced by the waste sludge form waterglass production, were designed and optimized in terms of shrinkage, mechanical properties and price. Selected concretes were also tested in semi-operating conditions.