One of the most important and interesting unsolved problems of science is the nature of glassy dynamics and the glass transition. It is quite an old problem, and starting from the early20th century there have been many efforts towards a sound understanding of the phenomenon. As a result, there are a number of theories in the field, which do not entirely contradict each other, but between which the connection is not entirely clear. In the last couple of decades or so, there has been significant progress and currently we do understand many facets of the problem. But a unified theoretical framework for the varied phenomena associated with glassiness is still lacking. Mode-coupling theory, an extreaordinarily popular approach, came from Götze and co-workers in the early eighties. The theory was originally developed to describe the two¬ step decay of the time-dependent correlation functions in a glassy fluid observed near the glass transition temperature(Tg). The theory went beyond that and made a number of quantitative predictions that can be tested in experiments and simulations. However, one of the drawback of the theory is its prediction of a strong ergodic to non-ergodic transition at a temperature TMCT; no such transition exists in real systems at the temperatures at which MCT predicts it. Consequently, the predictions of the theory like the power-law divergences of the transport quantities (e.g., viscosity and relaxation time) fail at low enough temperature and the theory can not be used below TMCT. It is well understood now that MCT is some sort of a mean-field theory of the real phenomenon, and in real systems the transition predicted by MCT is at best avoided due to finite dimensions and activated processes, neither of which is taken into account in standard MCT. Despite its draw backs, even the most severe critic of the theory will be impressed by its power and the predictions in a regime where it works. Even though the non-ergodic transition predicted by the theory is averted, the MCT mechanism for the increase of viscosity and relaxation time is actually at work in real systems. The status of MCT for glass transition is ,perhaps, similar to the Curie-Weiss theory of magnetic phase transition and it will require hard work and perhaps a conceptual breakthrough to go beyond this mean-field picture. Discussion of such a theoretical framework and its possible directions are, however, beyond the scope of this thesis. In the first part of this work, we have extended the mode coupling theory to three important physical situations: the properties of fluids under strong confinement, a sheared fluid and for the growth kinetics of glassy domains. In the second part, we have studied a different class of non equilibrium phenomenon in arrested systems, the fluctuation relations for yielding. In the first chapter, we talk about some general phenomenology of the glass transition problem and a few important concepts in the field. Then we briefly discuss the physical problems to be addressed in detail later on in the thesis followed by a brief account of some of the important existing theories in the field. This list is by no means exhaustive but is intended to give a general idea of the theoretical status of the problem. We conclude this chapter with a detailed derivation of MCT and its successes and failures. This derivation is supposed to serve as a reference for the details of the calculations in later chapters. The second chapter deals with a simple theory of an important problem of lubrication and dynamics of fluid at nanoscopic scales. When a fluid is confined between two smooth surfaces down to a few molecular layers and an normal force is applied on the upper surface, it is found that one layer of fluid gets squeezed out of the geometry at a time. The theory to explain this phenomenon came from Persson and Tosatti. However, due to a mathematical error, the in-plane viscosity term played no role in the original calculation. We re-do this calculation and show that the theory is actually more powerful than was suggested originally by its proponents. In the third chapter, we work out a detailed theory for the dynamics of fluid under strong planar confinement. This theory is based on mode-coupling theory. The walls in our theory enter in terms of an external potential that impose a static inhomogeneous background density. The interaction of the density fluctuation with this static background density makes the fluid sluggish. The theory explains how the fluid under strong confinement can undergo a glassy transition at a higher temperature or lower density than the corresponding bulk fluid as has been found in experiments and simulations. One of the interesting findings of the theory is the three-step relaxation that has also been found in a variety of other cases. The fourth chapter consists of a mode-coupling calculation of a sheared fluid through the microscopic approach first suggested by Zaccarelli et al[J. Phys.: Condens. Matter 14,2413(2002)]. The various assumptions of the theory are quite clear in this approach. The main aim of this calculation is to understand how FDR enters with in the theory. The only new result is the modified form of Yvon-Born-Green(YBG) equations for a sheared fluid. Then we extend the theory for the case of a confined fluid under steady shear and show that a confined fluid will show shear thinning at a much lower shear rate than the bulk fluid. When a system is quenched past a phase transition point, phase ordering kinetics begins. The properties of the system show “aging” with time, and the characteristic length scale of the quenched system grows as one waits. The analogous question for glasses has also been asked in the contexts of various numerical and experimental works. We formulate a theory in chapter five for rationalizing these findings. We find that MCT, surprisingly, offers an answer to this key question in glass forming liquids. The challenge of this theory is that care must be taken in using some equilibrium relations like the fluctuation-dissipation relation(FDR), which is one of the key steps in most of the derivations of MCT. We find that the qualitative, and some times even the quantitative, picture is in agreement with numerical findings. A similar calculation for the spin-glass case also predicts increase of the correlation volume with the waiting time, but with a smaller exponent than the structural glass case. We extended this theory to the case of shear and find that shear cuts off the growth of the length-scale of glassy correlations when the waiting time becomes of the order of the inverse shear rate. For the case of sheared fluid, if we take the limit of the infinite waiting time, the system will reach a steady state. Then, the resulting theory will describe a fluid in sheared steady state. The advantage of this theory over the existing mode-coupling theories for a sheared fluid is that FDR has not been used in any stage. This is an important development since the sheared steady state is driven away from equilibrium. Interestingly, the theory captures a suitably-defined effective temperature and gives results that are consistent with numerical experiments of steady state fluids(both glass and granular materials). We give the details of a theoretical model for jamming and large deviations in micellar gel in the sixth chapter. This theory is motivated by experiments. Through the main ingredient of the attachment-detachment kinetics and some simple rules for the dynamics, the theory is capable of capturing all the experimental findings. The novel prediction of this work is that in a certain parameter range, the fluctuation relations may be violated although the large deviation function exists. We argue that a wider class of physical systems can be understood in terms of the present theory. In the final chapter, we summarize the problems studied in this thesis and point out some future directions.

On considère l'évolution adiabatique des états vitreux sous perturbations extérieures. Bien que le formalisme que nous utilisons soit très général, nous nous concentrons ici sur les sphères dures en dimension infinie où une analyse exacte est possible. Nous considérons perturbations de la frontière, notamment compression ou cisaillement simple et nous calculons la réponse des états vitreux à ces perturbations : pression et contrainte de cisaillement. Nous constatons un dépassement des deux quantités avant que l'état vitreux ne devienne instable à un point spinodal, où il fond dans le liquide (ou cède). Nous estimons également la limite d'élasticité du verre. Enfin, nous étudions la stabilité des bassins vitreux vers la rupture en sous-bassins, correspondant à une transition de Gardner. Nous constatons que près de la transition dynamique, les verres subissent une transition de Gardner après une perturbation infinitésimale. Nous étudions ensuite le régime de haute pression et haut cisaillement au-delà de la transition de Gardner. / We consider the adiabatic evolution of glassy states under external perturbations. Although the formalism we use is very general, we focus here on infinite-dimensional hard spheres where an exact analysis is possible. We consider perturbations of the boundary, i. e. compression or (volume preserving) shear-strain, and we compute the response of glassy states to such perturbations: pressure and shear-stress. We find that both quantities over shoot before the glass state becomes unstable at a spinodal point where it melts into a liquid (or yields). We also estimate the yield stress of the glass. Finally, we study the stability of the glass basins towards breaking into sub-basins, corresponding to a Gardner transition. We find that close to the dynamical transition, glasses undergo a Gardner transition after an infinitesimal perturbation. We then study the high-pressure and high-strain regime beyond the Gardner transition.

The possibility to extract bio-SNG from the product gas obtained from gasification of biofuel with a pressurized, oxygen-blown CFB gasifier connected to a heat and power station using only membrane separation was theoretically investigated. Selling the methane, instead of feeding it to the plant’s turbine(s), might mean that overall profitability is increased. The considered product gas mainly consists of H2, CO, CO2, H2O and CH4. By doing a literature review different membrane types were studied and it was concluded that for now only polymers may be of interest, due to high production costs for other membranes or for the fact they are still at laboratory stage. It was further determined though that neither membranes made of glassy polymers (fixed polymer chains) nor rubbery polymers (mobile polymer chains) are probably capable of separating the methane from the other gas components on their own. Glassy membranes will most likely have trouble separating CO from CH4 due to similarity in size of the two molecules, while a separation using rubbery membranes will result in at least H2 accompanying the methane. The rubbery polymers’ incapability of separating H2 from CH4 despite greatly differing condensation temperatures between the two components can be explained by the fact that rubbery membranes, apart from condensation temperature, also separate according to molecular diffusivity. If a multistep process with recirculation that combines both glassy and rubbery polymers is applied, satisfying results may be obtained. This, however, builds on a higher separation of CH4 and CO with rubbery membranes than condensation data indicates and needs to be further investigated with help of real life experiments and more advanced computation programs than used in this study.

<p>Cilj ovog rada bio je da se ustanovi da li dolazi do elektrohemijskog taloženja&nbsp; niobijuma i aluminijuma iz hloroaluminatnih rastopa obogaćenih niobijumom na podlogama od staklastog&nbsp; ugljenika, platine i zlata. Nadalje, ako dolazi do rečenog&nbsp; taloženja, da li pri tome dolazi i do formiranja legura niobijuma sa izabranim podlogama kao i da li dolazi do formiranja legura niobijuma sa zajednički taloženim aluminijumom. I na kraju,&nbsp; cilj je&nbsp; bio da se navedeni fenomeni ostvare na &scaron;to nižim temperaturama.</p><p>Nb&nbsp; i&nbsp; Al&nbsp; su elektrohemijski taloženi na staklastom ugljeniku, platini i zlatu pri 200&nbsp; &deg;C, pod atmosferom argona, iz rastopa napravljenog od ekvimolarne sme&scaron;e AlCl₃ + NaCl kome&nbsp; je dodat niobijum.</p><p>U istraživanjima su kori&scaron;ćene: linearna&nbsp; i&nbsp; ciklička voltametrija, metoda potenciodinamičke polarizacione krive, metoda &bdquo;otvorenog kola&ldquo;,&nbsp; hronoamperometrija,&nbsp; SEM,&nbsp; EDS, AFM&nbsp; i XRD analiza.</p><p>Elektrohemijsko taloženje Nb i Al iz primenjenih rastopa pri potpotencijalima uočeno je na podlozi od zlata. Taloženje niobijuma pri potpotencijalima na zlatu je novost, a taloženje Al na zlatu pri&nbsp; potpotencijalima poznato je od ranije. Elektrotaloženje&nbsp; Al&nbsp; i&nbsp; Nb&nbsp; iz primenjenih rastopa pri potpotencijalu na zlatu prethodi procesima elektrotaloženja niobijuma i aluminijuma pri natpotencijalima.&nbsp; Rezultat ovih procesa su Nb/Au i Al/Au legure nastale zajedničkim taloženjem i interdifuzijom istaloženog Nb, odnosno&nbsp; Al i podloge&nbsp; -&nbsp; zlata (AlAu,&nbsp; AlAu₂ , AlAu₄, AlNb₂ , AlNb₃ , Au₂Nb, Au₂Nb₃ , AuNb₃ , AlNb₃).</p><p>Elektrohemijsko taloženje Nb iz primenjenih rastopa pri potpotencijalima uočeno je na platini i prethodi procesima elektrotaloženja&nbsp; Nb&nbsp; i&nbsp; Al. Rezultat su formirane Nb/Pt legure nastale interdifuzijom&nbsp; istaloženog Nb i podloge&nbsp; -&nbsp; platine (Nb₃Pt). Pri natpotencijalima aluminijuma na&nbsp; platini dolazi do taloženja metalnog niobijuma, metalnog aluminijuma i zajedničkog taloženja Nb i Al. Kao posledica&nbsp; ovih procesa dolazi i do formiranja legura (AlNb₃, Al₃Pt₅ ,&nbsp; Nb₃Pt).</p><p>Elektrohemijsko taloženje niobijuma iz primenjenih rastopa na izabranim podlogama odigrava se na potencijalima koji su pozitivniji od potencijala&nbsp; elektrotaloženja aluminijuma.</p><p>Sve dobijene legure formirane su pri temperaturi od 200 &deg;C &scaron;to je nekoliko stotina stepeni niže od odgovarajućih temperatura potrebnih da se formiraju termičkim putem.&nbsp;</p> / <p>The aim of this study was to establish electrodeposition of niobium and aluminium from chloroaluminate melt (AlCl₃ + NaCl) enriched with niobium onto gold, platinum and glassy carbon substrates. Furthermore, if such deposition is shown to occur,&nbsp; to&nbsp; assess if it can lead to formation ofniobium alloys with chosen substrates or&nbsp; formation of Nb/Al alloys as a result of codeposition. And finally, if the deposition is indeed confirmed,&nbsp; to&nbsp; establish the lowest operational temperature at which it is possible.</p><p>Niobium and aluminium were electrodeposited onto glassy carbon, gold and platinum at&nbsp; 200 &deg;C, under an argon atmophere&nbsp; from the melt made of&nbsp; equimolar mixture AlCl₃ + NaCl with niobium being added.</p><p>Research methods used were:&nbsp; cyclic voltammetry, potentiodynamic polarization curves, &quot;open circuit&rdquo;, chronoamperometry,&nbsp; SEM,&nbsp; EDS, AFM and&nbsp; XRD&nbsp; analysis. Underpotential deposition of&nbsp; Nb&nbsp; and Al&nbsp; from the melt onto gold substrate was observed. Of the two, niobium deposition is a novelty, while alumininum deposition has been previously studied.&nbsp; Underpotential deposition of&nbsp; NB and Al onto gold from given melt precedes the overpotential deposition of aluminium and niobium onto gold. The result of these processes are Nb/Au and Al/Au alloys formed by codeposition of the two metals&nbsp; and&nbsp; interdiffusion between the Nb and Al deposits and the substrate -gold (AlAu, AlAu₂, AlAu₄, AlNb₂, AlNb₃,&nbsp; Au₂Nb, Au₂Nb₃, AuNb₃, AlNb₃). Underpotential deposition of niobium onto platinum from used melts was recorded and it precedes the&nbsp; processes of overpotential deposition of niobium and aluminium. The result is formation of Nb/Pt alloys as a consequence of&nbsp; interdiffusion between the substrate and the deposited Nb (Nb₃Pt). The potentials more negative than the aluminium deposition potential in the used system lead to deposition of niobium and aluminium&nbsp; individually and jointly. Thus, a number of alloys are formed (AlNb₃, Al₃Pt₅, Nb₃Pt).&nbsp; Niobium electrodeposition onto chosen substrates from the melt applied takes place at potentials which are more positive than the potential of electrodeposition of aluminium. Formation of&nbsp; the&nbsp; obtained alloys occurred at a temperature of 200 &deg;C which is several hundred degrees lower than the temperatures needed for their formation by thermal methods.</p>

Beaucoup de systèmes qui ont un certain degré de désordre ont des similaritésdans leur structure: le paysage énergétique est aléatoire et il a plusieursminima locaux de l’énergie. Quand on ajoute une petite perturbation externeau système à basse temprature, il est raisonnable d’attendre que la dynamiqueconduira le système d’un minimum à l’autre, et ça donne lieu à une réponsealéatoire et saccadé. Les sautes discontinus que l’on observe sont appelésavalanches, et l’intérêt de ce travail est le calcul de leur distribution. Undes résultats est en effet le développement d’un cadre pour calculer cettedistribution dans des systèmes en dimension infinie qui peuvent être décritsavec le replica symmetry breaking. Nous appliquons les résultats à l’un desmodèles les plus simples des verres structuraux, c’est à dire les empilementsdenses de sphères molles avec répulsion harmonique, avec une déformation(shear strain) du volume comme perturbation. Nous soutenons que, quandla déformation est suffisamment petite, une portion de la distribution desavalanches devient une loi de puissance, dont l’exposant peut être directementlié au paramètre d’ordre de la brisure de symétrie de replica. Cet exposant estégalement lié à la distribution des forces de contact (au moins entre certainessphères), dont le comportement asymptotique on sais que ne dpends pasfortement de la dimension spatiale; pour cette raison nous comparons lesprdictions de champ moyen en dimension infinie avec des simulation du mêmesystème en dimension trois et, remarquablement, on trouve un bon accord.Dans le reste de la thèse nous discutons aussi les similarités avec des travauxprécédents et quelques consquences que la distribution des avalanches donnesur les propriétés élastiques de la matière granulaire dense. / Many systems that are somehow characterized by a degree of disorder sharea similar structure: the energy landscape has many sample-dependent localenergy minima. When a small external perturbation is applied to the systemat low temperature, it is reasonable to expect that the dynamics will leadthe system from a minimum to another, thus displaying a random and jerkyresponse. The discontinuous jumps that one observes are called avalanches,and the focus of this work is the computation of their distribution. Oneof the results is indeed the development of a framework that allows thecomputation of this distribution in infinite-dimensional systems that canbe described within a replica symmetry breaking ansatz. We apply theresults to one of the simplest models of structural glasses, namely densepackings of (harmonic) soft spheres, either at jamming or at larger densities,subject to a shear transformation that induces jumps both in the totalenergy and in the shear stress of the system. We argue that, when theshear strain is small enough, the avalanche distribution develops a power-lawbehavior, whose exponent can be directly related to the functional orderparameter of the replica symmetry breaking solution. This exponent is alsorelated to the distribution of contact forces (or at least of the contact forcesbetween some of the spheres), whose asymptotic behavior is known not todepend strongly on the spatial dimension; for this reason, we compare theinfinite-dimensional prediction with three dimensional simulations of thesame systems and, remarkably, we find a good agreement. In the rest of thethesis we compare our results with previous works, and we also discuss someof the consequences that the avalanche distribution lead to, concerning thestatistical elastic properties of dense granular media.

Συστηματική μελέτη πυριτικών, πυριτίου-ασβεστίου και φωσφοπυριτικών γυαλιών, με σύσταση 80 SiO2 - (20-x) Na2O - x Me2O (όπου x=0, 10 και Me=Li ή K), 48.7SiO2 - 26.9CaO - (24.4-x) Na2O - x Me2O (όπου x=0, 12.2 και Me=Li ή K) και 46.1 SiO2 - 2.6 P2O5 - 26.9 CaO - (24.4-x) Na2O - x Me2O (όπου x=0, 12.2 και Me=Li ή K), γίνεται με φασματοσκοπικές τεχνικές πυρηνικού μαγνητικού συντονισμού MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance) και MQ–MAS NMR (Multiple Quantum-MAS NMR). Η 29Si MAS NMR ανάλυση του Na2O πυριτικού γυαλιού έδειξε την ύπαρξη δύο κορυφών, οι οποίες αποδίδονται σε Q3 και Q4 πυριτικές δομές. Η υποκατάσταση Na από Κ διατηρεί τις Q3 και Q4 δομές ενώ στο Na2O-Li2O γυαλί, παρατηρήθηκαν τρεις κορυφές, οι οποίες αποδίδονται σε Q3, Q4-3 και Q4-4 πυριτικές δομές. H Q4-4 είναι σχετικά στενή και υποδηλώνει έναρξη κρυστάλλωσης του δικτύου λόγω της μικρής έντασης του σήματος. Στο γυαλί Na2O πυριτίου-ασβεστίου, η ανάλυση οδήγησε σε δυο κορυφές οι οποίες αποδίδονται σε Q1 και Q2 δομές, ενώ στο Na2O-K2O γυαλί, το φάσμα αναλύθηκε μόνο μια κορυφή που αντιπροσωπεύει Q2 πυριτικές δομές. Από την άλλη, στο γυαλί Na2O-Li2O, παρατηρήθηκαν δύο κορυφές οι οποίες αντιστοιχούν σε Q2 και Q3 δομές. Στο Na2O φωσφοπυριτικό γυαλί, η ανάλυση οδήγησε στις κορυφές που αποδίδονται σε Q2 και Q3 δομές. Η 23Na MQ-MAS NMR ανάλυση στο Na2O πυριτικό γυαλί οδήγησε στην παρουσία δύο ιοντικών περιοχών νατρίου (site 1: δiso= 5.1 ppm, CQ= 0.96 MHz, ΔCS= 20 ppm και site 2: δiso= 1.9 ppm, CQ= 3.06 MHz, ΔCS= 20 ppm). Η υποκατάσταση Na από Li ή Κ διατηρεί τις δύο ιοντικές περιοχές στα γυαλιά. Στο γυαλί Na2O πυριτίου-ασβεστίου, η ανάλυση οδήγησε μόνο σε μια ιοντική περιοχή η οποία είναι η site 2 (δiso= 5.4 ppm, CQ= 2.83 MHz, ΔCS= 17 ppm). Στα υπόλοιπα γυαλιά δεν παρατηρούνται διαφορές κατά την υποκατάσταση Na από Li ή Κ. Στο 24.4 Na2O φωσφοπυριτικό γυαλί παρατηρήθηκαν τρεις ιοντικές περιοχές (site 1: δiso= 6.0 ppm, CQ= 1.4 MHz, ΔCS= 20 ppm, site 2: δiso= 6.8 ppm, CQ= 2.6 MHz, ΔCS= 20 ppm, και site 3: δiso= 6.6 ppm, CQ= 1.2 MHz, ΔCS= 1 ppm). Η υποκατάσταση Na από Li ή Κ οδήγησε στην απουσία της τρίτης και πιο ισχυρής ιοντικής περιοχής (site 3). Πιθανολογούμε ότι η απουσία της σχετίζεται με την τροποποίηση του δικτύου που προέρχεται από την εισαγωγή του φωσφόρου στο υαλώδες δίκτυο. Η μελέτη μας επεκτάθηκε και στην μοριακή προσομοίωση των γυαλιών των τριών οικογενειών με την βοήθεια του προγράμματος Gaussian 03W. Πρώτα έγινε η γεωμετρική προσομοίωση του πλέγματος και μετά η προσομοίωση των NMR παραμέτρων με την χρήση της DFT μεθόδου (Density Functional Theory) και με τις βάσεις 6-311++G, 6-31G και 3-21++G. Οι δομές που προέκυψαν έδωσαν μια εικόνα του πυριτικού, πυριτίου-ασβεστίου και φωσφοπυριτικού υαλώδους δικτύου. Οι δομές των αλκαλίων αποτελούνται από τετραεδρικής, εξαεδρικής και οκταεδρικής συμμετρίας κυψελίδες. Μετά από υπολογισμούς διαφόρων πιθανών δομών καταλήξαμε στις δομές για την ερμηνεία των φασμάτων σε εκείνες που υπάρχει καλή συμφωνία μεταξύ των θεωρητικών και πειραματικών 23Na NMR αποτελεσμάτων. Συγκεκριμένα, η site 2 προέρχεται από ένα 23Na σε XXX-εδρικό περιβάλλον. Η site 3 μπορεί να προέρχεται από οκταεδρικούς σχηματισμούς υψηλής συμμετρίας των ιόντων Na γιατί αυτές οι περιοχές οδηγούν με βάση τους υπολογισμούς μας σε περιβάλλον με αυξημένη ιοντική ισχύ και συμμετρία. / Silicate, calcium-silicate and phosphosilicate glasses of the composition 80 SiO2 - (20-x) Na2O - x Me2O (where x=0, 10 and Me=Li or K), 48.7SiO2 - 26.9CaO - (24.4-x) Na2O - xMe2O (where x=0, 12.2 and Me=Li or K) and 46.1 SiO2 - 2.6 P2O5 - 26.9 CaO - (24.4-x) Na2O - x Me2O (where x=0, 12.2 and Me=Li or K), have been investigated using the advanced NMR methods of MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance) and MQ-MAS NMR (Multiple Quantum-MAS NMR). The 29Si MAS NMR analysis of the sodium silicate glass revealed two lines attributed to Q3 and Q4 silicate species. Substitution of Na with K conserves the Q3 and Q4 species while in the Na2O-Li2O glass, three lines were obtained attributed to Q3, Q4-3 and Q4-4 species. The Q4-4 signal is attributed to initial stage of crystallization due to the narrow size distribution and low intensity. In the sodium calcium-silicate glass, two lines were resolved assigned to Q1 and Q2, while in the Na2O-K2O glass, only one line was resolved attributed to Q2 species. For the Na2O-Li2O glass, two lines were revealed assigned to Q2 and Q3. In the sodium phosphosilicate glass, the analysis revealed two lines ascribed to Q2 and Q3. The 23Na MQ-MAS NMR analysis in the sodium silicate glass exhibits two Na ionic sites (site 1: δiso= 5.1 ppm, CQ= 0.96 MHz, ΔCS= 20 ppm and site 2: δiso= 1.9 ppm, CQ= 3.06 MHz, ΔCS= 20 ppm). Substitution of Na with Li or K conserves the two sites in the glasses. For the sodium calcium-silicate glass, the analysis revealed only one site (site 2: δiso= 5.4 ppm, CQ= 2.83 MHz, ΔCS= 17 ppm). No difference was observed by the substitution of Na with Li or K in the glasses. In the 24.4 Na2O phosphosilicate glass three sites were obtained with: site 1 (δiso= 6.0 ppm, CQ= 1.4 MHz, ΔCS= 20 ppm), site 2 (δiso= 6.8 ppm, CQ= 2.6 MHz, ΔCS= 20 ppm), site 3 (δiso= 6.6 ppm, CQ= 1.2 MHz, ΔCS= 1 ppm). The substitution of Na with Li or K resulted in the absence of the third and most ionic site, which is probably associated with the presence of phosphorus in the glassy network. Our study was completed by the molecular simulation of the three types of glasses, for which the Gaussian 03W program was used. For the geometrical optimization and the optimization of the NMR parameters was used the DFT (Density Functional Theory) method and the 6-311++G, 6-31G, and 3-21++G basis sets. The resulting structures gave an insight into the silicate, calcium-silicate and phosphosilicate glassy network. These structures consist of tetrahedral, hexahedral, and octahedral symmetry shells which enclose the alkali ions. The good agreement between the theoretical and experimental 23Na NMR results leads to the depiction of the Na ionic sites and especially of site 2. This site was attributed to sodium in XXX-coordination. Concerning site 3, was observed that the increased ionic strength of the site could possible be ascribed to high symmetry octahedral configurations of Na ions.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-18T15:31:59Z No. of bitstreams: 1 VANUCIA SANTOS DIAS - DISSERTAÇÃO PPG-CEMat 2014..pdf: 3639913 bytes, checksum: 915ca6c2f3b8eced104eb3bd31c33dd3 (MD5) / Made available in DSpace on 2018-04-18T15:31:59Z (GMT). No. of bitstreams: 1 VANUCIA SANTOS DIAS - DISSERTAÇÃO PPG-CEMat 2014..pdf: 3639913 bytes, checksum: 915ca6c2f3b8eced104eb3bd31c33dd3 (MD5) Previous issue date: 2014-08-29 / Um dos grandes problemas sanitários está na disposição final dos resíduos gerados pela população e pelas indústrias. No estado da Paraíba, são coletados diariamente 2.754 toneladas de resíduos sólidos urbanos, destes 30,9% têm destinação final em aterros sanitários, 36,9% destinam-se para aterros controlados e 32,2% têm como destino final os lixões. O reaproveitamento do vidro indica 100% de reprocessamento. Além de ser 100% reciclável, o vidro, quando reaproveitado, resulta em redução do impacto ambiental e ainda contribui para diversificação da fabricação de produtos e para diminuição dos custos finais de sua produção. Este trabalho objetiva estudar o processo de recozimento de resíduos vítreos, visando contribuir para o desenvolvimento de uma tecnologia social de reciclagem de vidros para as trabalhadoras do CAVI - Associação de Catadores e Recicladores de Vidros e outros Materiais. Para isso foram utilizados resíduos de vidros planos e ocos submetidos a cinco processos de fusão e recozimento com diferentes níveis de temperatura, empregando técnicas de reciclagem de vidro a quente (vitrofusão e termoformado). Foram utilizados moldes de cerâmica para os estudos iniciais e de gesso para a confecção dos corpos de prova. A resistência após o recozimento foi analisada por meio de ensaios de impacto, em que pode ser constatado que as amostras submetidas ao tratamento térmico estudado apresentaram maior resistência ao impacto quando comparadas às amostras que não receberam tratamento térmico durante o processo de fusão. As fraturas obtidas após os ensaios foram analisadas macroscopicamente. / One of the major health problems is the disposal of waste generated by the population and industries. In the state of Paraíba, are collected daily 2,754 tons of municipal solid waste, 30.9% of these have final disposal in landfills, 36.9% intended to controlled landfills and 32.2% have a final destination landfills. Recycling of glass indicates 100% reprocessing. Besides being 100% recyclable glass, when reused, resulting in reduced environmental impact and still contributes to diversification of manufacturing products and to decrease the final cost of its production. This work aims to study the process of annealing of glassy waste, aiming to contribute to the social development of a recycling technology for glass workers CAVI - Association of Collectors and Recyclers of Glass and other Materials. For this waste flat glass and hollow undergone five mergers and annealing with different temperature levels were used, employing techniques of recycling glass hot (fusing and slumping). Ceramic molds for the initial studies and gypsum for the manufacture of test specimens were used. The resistance after annealing was examined by impact tests, it can be seen that the samples subjected to the heat treatment study had higher impact resistance compared to samples which received no heat treatment during the melting process. The fractures obtained after the tests were analyzed macroscopically.

Philosophiae Doctor - PhD / The thesis presents a simple, sensitive, low cost and a novel graphenated polyaniline doped tungsten trioxide nanocomposite, as an electrochemical sensor for the detection and quantitative and determination of PAHs, which are ubiquitous, toxic, as well as dangerous organic pollutant compounds in the environment. The selected PAHs (anthracene, phenanthrene and pyrene) in wastewater were given priority as a result of their threat to human nature and that of the environment. In order for a healthy, non-polluted and well sustainable environment, there is need for an instrument that is capable of detecting and quantifying these organic pollutants onsite and also for constant monitoring. The nanocomposites were developed by chemical and electrochemical methods of preparations, exploiting the intrinsic properties of polyaniline, graphene and tungsten trioxide semiconducting materials. Chemically, graphene-polyaniline (GR-PANI) nanocomposite was synthesised by in situ polymerisation method, then casted on a surface of glassy carbon electrode to form GR-PANI modified electrode. The properties of the prepared electrode were investigated through morphological and spectroscopic techniques, which confirmed the formation of the composite. The electroactivity of the prepared modified electrode revealed great improvement in cyclic and square wave voltammetric response on anthracene. A dynamic range of 2.0 × 10-5 to 1.0 × 10-3 M and detection limit of 4.39 x 10-7 M was established.

À la différence des liquides simples, les solides amorphes, une vaste catégorie de matériaux allant des verres métalliques aux émulsions concentrées, ne se mettent à s'écouler qu'au-delà d'une contrainte finie. Notre thèse a pour objet la modélisation de cet écoulement, dans un cadre général et avec un accent mis sur les hétérogénéités. En premier lieu, notre travail a porté sur l'inclusion d'inhomogénéités dans le cadre de la théorie de couplage de modes appliquée à la rhéologie et nous avons notamment obtenu une équation générale d'évolution des inhomogénéités de densité. À basse température, l'écoulement est en effet fortement hétérogène : des phases de déformation élastique sont entrecoupées de réarrangements de particules, brusques et localisés, qui interagissent par le biais des déformations élastiques qu'ils génèrent. En second lieu, nous avons donc considéré un modèle calqué sur ce scénario et affiné ses éléments constitutifs pour rendre compte de la compétition entre cisaillement appliqué et réarrangements locaux, à l'origine de la courbe d'écoulement des matériaux athermiques. Cette dernière a été reproduite de manière satisfaisante. Pour ce qui est des corrélations spatiales dans l'écoulement, nous avons montré qu'il n'existe pas de loi d'échelle universelle dans les modèles élasto-plastiques, malgré la présence d'une classe de longueurs de corrélation décroissant comme dot{gamma}^{ icefrac{-1}{d}} en d dimensions, dans le régime dominé par le cisaillement. Par ailleurs, dans diverses variantes du modèle, le cisaillement se trouve localisé dans une région du matériau. Ce phénomène apparaît dès lors que les blocs élasto-plastiques sont durablement fragilisés à la suite d'un événement plastique. Enfin, les prédictions du modèle ont été directement mises en regard avec des expériences sur l'écoulement en microcanal d'émulsions concentrées et des simulations de dynamique moléculaire à température nulle. Les écarts observés nous ont poussé à développer et implémenter un code plus flexible, qui s'appuie sur une routine simplifiée d'Éléments Finis et rend mieux compte du désordre structurel et des effets inertiels. / Contrary to the case of simple fluids, a finite stress is required to initiate the flow of amorphous solids, a broad class of materials ranging from bulk metallic glasses to dense emulsions. The objective of this thesis is to model the flow of these materials in a general framework, with an emphasis on heterogeneities. In a first approach, using the liquid regime as a starting point, I have investigated to what extent inhomogeneities can be accommodated in the framework of the mode-coupling theory of rheology. A generic equation for the evolution of density inhomogeneities has been derived. At low temperatures, the flow is indeed quite heterogeneous: it consists of periods of elastic deformation interspersed with swift localised rearrangements of particles, that induce long-range elastic deformations and can thereby spark off new rearrangements. In a second approach, a model rooted in this scenario has been refined so as to reflect the interplay between the external drive and the localised rearrangements, which is at the origin of the flow curve of athermal solids. The latter has been reproduced satisfactorily. Turning to spatial correlations in the flow, we have shown that there exists no universal scaling for these correlations in elastoplastic models, although a broad class of correlation lengths scale with dot{gamma}^{ icefrac{-1}{d}} in the shear-dominated regime in d dimensions. Besides, shear localisation has been observed in diverse variants of the model, whenever blocks are durably weakened following a plastic event. Finally, we have directly compared model predictions to experimental results on the flow of dense emulsions through microchannels and to athermal molecular dynamics simulations. Spurred on by the observation of some discrepancies, we have developed and implemented a more flexible code, based on a simplified Finite Element routine, which notably provides a better account of structural disorder and inertial effects.

The objective of the present work is the study of the electrochemical behaviour of two diagnostic tumor markers of great importance, vanillylmandelic acid (VMA) and homovanillic acid (HVA), on carbon-based electrodes by using cyclic and differential pulse voltammetry. A comparison was made among non-modified glassy carbon electrode (GCE) and GCE modified by multi-walled carbon nanotubes, Nafion (Nafion/GCE) and poly(neutral red) (PNR/GCE), and further boron doped diamond (BDD) electrode which was activated by anodic polarization (Eakt = +2,4 V, t = 30 s) or by polishing on alumina slurry. Significant differences in the voltammetric responses of VMA and HVA were found, not only among utilized electrode materials which also influenced the way of controlling the oxidation process, but also they depend on the pH value of aqueous media in which these acids occurred. An acidic environment is the most suitable for their determination. Calibration dependences were measured in 0.1 mol∙l−1 phosphate buffer pH 3.0 which was chosen as an optimal supporting electrolyte for differential pulse voltammetric determination. Achieved detection limits were 0.6, 0.9, 0.8 and 1.2 μmol∙l−1 for HVA and 0.4, 1.5, 2.4 and 1.1 μmol∙l−1 for VMA at BDD electrode, non-modified GCE, Nafion/GCE and PNR/GCE, respectively. Limits...