Tesi sul tema "Glasses"
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1
Leuzzi, Luca. "Thermodynamics of glassy systems glasses, spin glasses and optimization /". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/66345.
Testo completo
2
Wootton, Andrew Michael. "Silicon oxycarbide glasses and glass-ceramics". Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310015.
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3
Rappensberger, Csaba Ferenc. "Novel rare-earth aluminosilicate glasses and glass-ceramics". Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/56937/.
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4
Zhang, Endang. "Fibre reinforcement of oxynitride glasses and glass-ceramics". Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320017.
Testo completo
5
Conca, Luca. "Mechanical properties of polymer glasses : Mechanical properties of polymer glasses". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1050/document.
Testo completoAbstract (sommario):
Ce manuscrit présente des récentes extensions au modèle PFVD, basé sur l'hétérogénéité de la dynamique des polymères vitreux à l'échelle de quelques nanomètres et résolu par simulation en 3D, afin de fournir une description physique unifiée des propriétés mécaniques et dynamiques des polymères vitreux soumis à déformation plastique. Trois sujets principaux sont traités : La plastification. Sous déformation, les polymères atteignent le seuil de plasticité (yield) à quelques pourcents de déformation et quelques dizaines de MPa. Nous proposons que l'énergie élastique absorbée à l'échelle des hétérogénéités dynamiques accélère la dynamique locale. On observe contraintes ultimes de quelques dizaines de MPa à quelques pourcents de déformation et que la plastification est due à un nombre relativement petit d'événements locaux. Il a été observé que la dynamique devient plus rapide et homogène dans le régime plastique et que la mobilité moyenne atteint une valeur stationnaire, linéaire avec le taux de déformation. Nous proposons que la contrainte locale stimule la diffusion de monomères des domaines lents à ceux rapides (mécanisme de facilitation) et accélère dynamique locale. Ceci permets d'observer l'homogénéisation de la dynamique, avec des caractéristiques proches de l'expérience. L'écrouissage, dans les polymères enchevêtrés ou réticulés. A grande déformation, la contrainte augmente avec une pente caractéristique d'ordre 10 – 100 MPa au-dessous de la transition vitreuse. De manière analogue à une théorie récente, nous proposons que la déformation locale oriente les monomères dans la direction d'étirage et ralentie la dynamique, suite à l'intensification des interactions locales. Les modules d'écrouissage mesurés, les effets de la réticulation et du taux de déformation sont comparables aux données expérimentales. En outre, on trouve que l'écrouissage a un effet stabilisateur sur les phénomènes de localisation et sur les bandes de cisaillementThis manuscript presents recent extensions to the PFVD model, based on the heterogeneity of theh dynamics of glassy polymers at the scale of a few nanometers et solved by 3D numerical simulation, which aim at providing a unified physical description of the mechanical and dynamical properties of glassy polymers during plastic deformation. Three main topics are treated: Plasticization. Under applied deformation, polymers undergo yield at strains of a few percent and stresses of some 10 MPa.We propose that the elastic energy stored at the scale of dynamical heterogeneities accelerates local dynamics. We observe yield stresses of a few 10 MPa are obtained at a few percent of deformation and that plastification is due to a relatively small amount of local yields. It has been observed that dynamics becomes faster and more homogeneous close to yield and that the average mobility attains a stationary value, linear with the strain rate. We propose that stress-induced acceleration of the dynamics enhances the diffusion of monomers from slow domains to fast ones (facilitation mechanism), accelerating local dynamics. This allows for obtaining the homogeneisation of the dynamics, with the same features observed during experiments. Strain-hardening, in highly entangled and cross-linked polymers. At large strain, stress increases with increasing strain, with a characteristic slope (hardening modulus) of order 10 – 100 MPa well below the glass transition. Analogously to a recent theory, we propose that local deformation orients monomers in the drawing direction and slows dows the dynamics, as a consequence of the intensification of local interactions. The hardening moduli mesured, the effect of reticulation and of strain rate are comparable with experimental data. In addition, strain-hardening is found to have a stabilizing effect over strain localization and shear banding
6
Brüning, Ralf. "Structural relaxation and the glass transition in metallic glasses". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74345.
Testo completoAbstract (sommario):
This thesis presents for the first time direct structural measurements of both reversible and irreversible structural relaxation and the glass transition in the metal-metalloid glass Pd$ sb{40}$Ni$ sb{40}$P$ sb{20}$. The techniques have been x-ray diffraction and Mossbauer spectroscopy, and a new analysis method for changes of amorphous diffraction patterns was developed.It is found that irreversible relaxation proceeds by many local shear-type motions involving the metal atoms, and that it is accompanied by a small densification. Reversible relaxation at high annealing temperatures entails the same microscopic processes, but it does not change the density of the glass. The type of atomic processes changes continuously as the annealing temperature is lowered, and at sufficiently low temperatures the distribution of metal atoms remains constant, so that reversible relaxation then proceeds via rearrangement of the metalloid atoms. This rearrangement leads to more ordered, but less isotropic atomic sites.
The second part of the thesis is concerned with the motion of the atoms in a metallic glass below and above the glass transition. Mossbauer spectroscopy allows the direct measurement of vibrational and diffusional motion. The increase of the amplitude of atomic vibration has the same temperature dependence as the increase in volume that marks the glass transition, thus the two processes are governed by the same mechanism. The directly measured diffusional motion is in agreement with macroscopic measurements of diffusion.
7
De, Mestral François. "Calcium phosphate glasses and glass-ceramics for medical applications". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65405.
Testo completo
8
Kansal, Ishu. "Diopside-fluorapatite-wollastonite based bioactive glasses and glass-ceramics". Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14827.
Testo completoAbstract (sommario):
Doutoramento em Ciência e Engenharia dos MateriaisBioactive glasses and glass–ceramics are a class of biomaterials which elicit special response on their surface when in contact with biological fluids, leading to strong bonding to living tissue. This particular trait along with good sintering ability and high mechanical strength make them ideal materials for scaffold fabrication. The work presented in this thesis is directed towards understanding the composition-structure-property relationships in potentially bioactive glasses designed in CaOMgOP2O5SiO2F system, in some cases with added Na2O. The main emphasis has been on unearthing the influence of glass composition on molecular structure, sintering ability and bioactivity of phosphosilicate glasses. The parent glass compositions have been designed in the primary crystallization field of the pseudo-ternary system of diopside (CaO•MgO•2SiO2) – fluorapatite (9CaO•3P2O5•CaF2) – wollastonite (CaO•SiO2), followed by studying the impact of compositional variations on the structure-property relationships and sintering ability of these glasses. All the glasses investigated in this work have been synthesized via melt-quenching route and have been characterized for their molecular structure, sintering ability, chemical degradation and bioactivity using wide array of experimental tools and techniques. It has been shown that in all investigated glass compositions the silicate network was mainly dominated by Q2 units while phosphate in all the glasses was found to be coordinated in orthophosphate environment. The glass compositions designed in alkali-free region of diopside – fluorapatite system demonstrated excellent sintering ability and good bioactivity in order to qualify them as potential materials for scaffold fabrication while alkali-rich bioactive glasses not only hinder the densification during sintering but also induce cytotoxicity in vitro, thus, are not ideal candidates for in vitro tissue engineering. One of our bioglass compositions with low sodium content has been tested successfully both in vivo and in preliminary clinical trials. But this work needs to be continued and deepened. The dispersing of fine glass particles in aqueous media or in other suitable solvents, and the study of the most important factors that affect the rheology of the suspensions are essential steps to enable the manufacture of porous structures with tailor-made hierarchical pores by advanced processing techniques such as Robocasting.
Os vidros e vitrocerâmicos bioactivos são uma classe de biomateriais que induzem uma resposta especial à sua superfície quando em contacto com fluidos biológicos que conduz a uma forte ligação ao tecido vivo. Esta característica particular conjugada com uma boa aptidão para a sinterização e elevada resistência mecânica torna estes materiais ideais para a fabricação de estruturas de suporte à regeneração óssea. O trabalho apresentado nesta tese pretende dar um contributo para uma melhor compreensão das relações entre composição-estrutura-propriedades em vidros potencialmente bioactivos com composições no sistema CaOMgOP2O5SiO2F, em alguns casos com a adição de Na2O. O estudo da influência exercida pela composição do vidro na estrutura molecular, capacidade de sinterização e nível de bioactividade dos vidros fosfosilicatados foi objecto de especial atenção. As composições vítreas foram concebidas no campo da cristalização primária do pseudo sistema ternário do diópsido (CaO•MgO•2SiO2) – fluorapatite (9CaO•3P2O5•CaF2) – wollastonite, e estudou-se o impacto das variações composicionais na estrutura, nas propriedades e na capacidade de sinterização destes vidros. Todos os vidros investigados neste trabalho foram preparados por fusão e fritagem e caracterizados quanto à sua estrutura molecular, capacidade de sinterização, degradação química e bioactividade, usando uma grande variedade de técnicas experimentais. Ficou demonstrado que em todas as composições de vidro investigadas a rede de silicato era dominada principalmente por unidades Q2 enquanto o fosfato se encontrava coordenado em ambiente de ortofosfato. As composições de biovidros isentas de alcalinos do sistema diópsido–fluorapatite demonstram possuir excelente capacidade de sinterização e elevados níveis de bioactividade, atributos que os qualificam como materiais promissores para a fabricação de estruturas de suporte à regeneração de tecidos ósseos, enquanto os vidros bioactivos contendo alcalinos foram mais difíceis de densificar durante a sinterização e induziram citotoxicidade in vitro, não sendo candidatos ideais para a engenharia de tecidos. Uma das nossas composições de biovidro com um baixo teor de sódio foi testada com sucesso tanto in vivo como em ensaios clínicos preliminares. Mas este trabalho precisa de ser continuado e aprofundado. A dispersão de fritas moídas em meio aquoso ou outros solventes adequados, e o estudo dos factores mais relevantes que condicionam a reologia das suspensões são etapas essenciais para viabilizar o processo de fabrico de suportes porosos com estruturas hierárquicas de poros feitas por medida através de técnicas de processamento avançadas tais como o Robocasting.
9
Goel, Ashutosh. "Clinopyroxene based glasses and glass-ceramics for functional applications". Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2323.
Testo completoAbstract (sommario):
Doutoramento em Ciência e Engenharia de MateriaisAs piroxenas são um vasto grupo de silicatos minerais encontrados em muitas rochas ígneas e metamórficas. Na sua forma mais simples, estes silicatos são constituídas por cadeias de SiO3 ligando grupos tetrahédricos de SiO4. A fórmula química geral das piroxenas é M2M1T2O6, onde M2 se refere a catiões geralmente em uma coordenação octaédrica distorcida (Mg2+, Fe2+, Mn2+, Li+, Ca2+, Na+), M1 refere-se a catiões numa coordenação octaédrica regular (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), e T a catiões em coordenação tetrahédrica (Si4+, Al3+, Fe3+). As piroxenas com estrutura monoclínica são designadas de clinopiroxenes. A estabilidade das clinopyroxenes num espectro de composições químicas amplo, em conjugação com a possibilidade de ajustar as suas propriedades físicas e químicas e a durabilidade química, têm gerado um interesse mundial devido a suas aplicações em ciência e tecnologia de materiais. Este trabalho trata do desenvolvimento de vidros e de vitro-cerâmicos baseadas de clinopiroxenas para aplicações funcionais. O estudo teve objectivos científicos e tecnológicos; nomeadamente, adquirir conhecimentos fundamentais sobre a formação de fases cristalinas e soluções sólidas em determinados sistemas vitro-cerâmicos, e avaliar a viabilidade de aplicação dos novos materiais em diferentes áreas tecnológicas, com especial ênfase sobre a selagem em células de combustível de óxido sólido (SOFC). Com este intuito, prepararam-se vários vidros e materiais vitro-cerâmicos ao longo das juntas Enstatite (MgSiO3) - diopsídio (CaMgSi2O6) e diopsídio (CaMgSi2O6) - Ca - Tschermak (CaAlSi2O6), os quais foram caracterizados através de um vasto leque de técnicas. Todos os vidros foram preparados por fusão-arrefecimento enquanto os vitro-cerâmicos foram obtidos quer por sinterização e cristalização de fritas, quer por nucleação e cristalização de vidros monolíticos. Estudaram-se ainda os efeitos de várias substituições iónicas em composições de diopsídio contendo Al na estrutura, sinterização e no comportamento durante a cristalização de vidros e nas propriedades dos materiais vitro-cerâmicos, com relevância para a sua aplicação como selantes em SOFC. Verificou-se que Foi observado que os vidros/vitro-cerâmicos à base de enstatite não apresentavam as características necessárias para serem usados como materiais selantes em SOFC, enquanto as melhores propriedades apresentadas pelos vitro-cerâmicos à base de diopsídio qualificaram-nos para futuros estudos neste tipo de aplicações. Para além de investigar a adequação dos vitro-cerâmicos à base de clinopyroxene como selantes, esta tese tem também como objetivo estudar a influência dos agentes de nucleação na nucleação em volume dos vitro-cerâmicos resultantes á base de diopsídio, de modo a qualificá-los como potenciais materiais hopedeiros de resíduos nucleares radioactivos.
The pyroxenes are a wide spread group rock-forming silicate minerals found in many igneous and metamorphic rocks. They are silicates that, in their simplest form, contain single SiO3 chains of linked SiO4 tetrahedra. The general chemical formula for pyroxenes is M2M1T2O6, where M2 refers to cations in a generally distorted octahedral coordination (Mg2+, Fe2+, Mn+, Li+, Ca2+, Na+), M1 to cations in a regular octahedral coordination (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), and T to tetrahedrally coordinated cations (Si4+, Al3+, Fe3+). Monoclinic pyroxenes are called clinopyroxenes. The stability of clinopyroxenes over a broad spectrum of chemical compositions, in conjunction with the possibility of achieving desired physical properties and high chemical durability, has generated a worldwide interest due to their applications in material science and technology. The present work deals with the development of clinopyroxene based glasses and glass-ceramics for functional applications. The objective of the study was dual, both scientific and technological; particularly to gain fundamental knowledge on the formation of crystalline phases and solid solutions in selected glass-ceramic systems, and to evaluate the feasibility for application of new materials in different technological areas with emphasis on sealing in solid oxide fuel cells (SOFC). In this pursuit, various glasses and glass-ceramics along Enstatite (MgSiO3) - Diopside (CaMgSi2O6) and Diopside (CaMgSi2O6) – Ca – Tschermak (CaAlSi2O6) joins have been prepared and characterized by a wide array of characterization techniques. All the glasses were prepared by melt-quenching technique while glass-ceramics were produced either by sintering and crystallization of glass powders or by nucleation and crystallization in monolithic glasses. Furthermore, influence of various ionic substitutions/additions in Alcontaining diopside on the structure, sintering and crystallization behaviour of glasses and properties of resultant glass-ceramics has been investigated, in relevance with final application as sealants in SOFC. It has been observed that enstatite based glasses/glass-ceramics do not exhibit requisite characteristics in order to qualify for the job of sealing in SOFC while the superior properties exhibited by diopside based glass-ceramics qualify them for further experimentation as SOFC sealants. Apart from investigating the suitability of clinopyroxene based glass-ceramics as sealants, this thesis also aims to study the influence of nucleating agents on the volume nucleation in the resultant diopside based glass-ceramics so as to qualify them for further experimentation as hosts for radioactive nuclear wastes.
10
Parupudi, Aarti. "Singing wine glasses". Kansas State University, 2015. http://hdl.handle.net/2097/19706.
Testo completoAbstract (sommario):
Master of ScienceComputing and Information Sciences
Daniel A. Andresen
One among the many inventions of Benjamin Franklin is the Glass Armonica, a musical instrument whose sound source was a series of resonating glass vessels. However, the Irish musician Richard Pockrich is typically credited as the first to play an instrument composed of glass vessels, called the Glass Harp in 1741, by rubbing his fingers around the rims. In this project “Singing Wine Glasses”, the principle of Franklin’s glass armonica is demonstrated with a wine glass. One hand is used to hold the glass steady at the base. The rim of glass is gently pressed with a moistened finger of the other hand and drawn in a circle around. When the pressure and amount of moisture are just right, the slight friction between the finger and the rim of glass causes vibrations in the sides of the glass. At a particular frequency, called the resonant frequency, the sides of the glass will vibrate most easily. The resonant frequency of wine glasses is typically within the range of human hearing (20-20,000 Hz), so the resulting resonant vibration is heard as a tone. The glass starts to sing when the vibration gets the molecules moving at their natural frequency. The resonant frequency changes with the amount of water filled in the glass. This android application deals with virtual glasses that serve the purpose of wine glasses filled with different amounts of water. Swiping on the glass edges would produce music, as per Franklin’s principle. The users would be free to select the number of glasses they want to play, and the amount of water-level in each glass. This application would also come with an enhanced feature of sustaining a particular note until the finger is released from the glass.
11
Mancino, Amerigo. "Putting on Glasses". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14814/.
Testo completoAbstract (sommario):
Scanning people and generating realistic face models is becoming nowadays an important branch in Computer Graphics.
The main applications are the creation of 3D selfies that can be immediately viewed or printed in 3D, the creation of 3D avatars for augmented or virtual reality applications, content creation for games or movies, or the developing of 3D face authentication algorithms (more robust respect to the 2D counterpart).
This thesis provides an overview on a common issue that arises when scanning people wearing glasses and in turn proposes different solutions to solve or at least bypass the original problem, showing the strengths and the weaknesses.
Distinct techniques for automatically putting a pair of glasses on a human face are also present.
Furthermore, a study on the physical properties of glasses is documented, involving both the frame and the lenses, along with a brief description of the Blender software and its main features that were essential during the development.
12
Masood, Ansar. "Functional Metallic Glasses". Doctoral thesis, KTH, Teknisk materialfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101901.
Testo completoAbstract (sommario):
For decades, Metallic Glass, with its isotropic featureless structure while exhibiting outstanding mechanical properties was possible only at a high rate of quenching and with at least one dimension in the submicron regime. This limitation was overcome with the discovery of Bulk Metallic glasses, BMGs, containing three or more elements following the additional two empirical rules of optimum geometric size differences and negative energy of mixing among the constituent elements. Since then thousands of Fe-, Ni-, Al-, Mg-, Ti- based BMGs have been discovered and comprehensively investigated mainly by groups in Japan and USA. Yet the discovery of new combinations of elements for BMGs is alchemy. We do not know with certainty which element when added will make possible a transition from being a ribbon to a bulk rod. In this thesis we report a discovery of castable BMGs rods on substitution of Fe by nickel in an alloy of FeBNb which could otherwise have been only melt-spun into ribbons. For example, we find that substitution of just 6 at.% of Fe raises the glass forming range, GFA, to as much as ∆Tx =40K while the other parameters for GFA like Trg, γ, and δ reach enhanced values 0.57, 0.38, and 1.40 respectively. Furthermore, the electrical conductivity is found to increase by almost a factor of two. Magnetically it becomes softer with coercivity 260mOe which further reduces to much lower values on stress relaxation. Ni does not seem to carry a magnetic moment while it enhances the magnetic transition temperature linearly with Ni concentration. We have investigated the role of Ni in another more stable BMGs based FeBNbY system in which case ∆Tx becomes as large as 94K with comparable enhancement in the other GFA parameters. Due to the exceptional soft magnetic properties, Fe-based bulk metallic glasses are considered potential candidate for their use in energy transferring devices. Thus the effect of Ni substitution on bulk forming ability, magnetic and electrical transport properties have been studied for FeBNb and FeBNbY alloy systems. The role of Ni in these systems is densification of the atomic structure and its consequence. We have exploited the superior mechanical properties of BMGs by fabricating structures that are thin and sustainable. We have therefore investigated studies on the thin films of these materials retaining their excellent mechanical properties. Magnetic properties of FeBNb alloy were investigated in thin films form (~200-400nm) in the temperature range of 5-300K. These Pulsed Laser deposited amorphous films exhibit soft magnetism at room temperature, a characteristic of amorphous metals, while they reveal a shift in hysteresis loop (exchange anisotropy, HEB=18-25Oe), at liquid helium temperature. When thickness of films is reduced to few nanometers (~8-11nm), they exhibit high transparency (>60%) in optical spectrum and show appreciably high saturation Faraday rotation (12o/μm, λ= 611nm). Thin films (~200-400nm) of Ni substituted alloy (FeNiBNb) reveal spontaneous perpendicular magnetization at room temperature. Spin-reorientation transition was observed as a function of film thickness (25-400nm) and temperature (200-300K), and correlated to the order/disorder of ferromagnetic amorphous matrix as a function of temperature. These two phase films exhibits increased value of coercivity, magnetic hardening, below 25K and attributed to the spin glass state of the system. Using the bulk and thin films we have developed prototypes of sensors, current meters and such simple devices although not discussed in this Thesis. Ti-based bulk metallic glasses have been attracting significant attention due to their lower density and high specific strength from structural application point of view. High mechanical strength, lower values of young’s modulus, high yield strength along with excellent chemical behaviors of toxic free (Ni, Al, Be) Ti-based glassy metals make them attractive for biomedical applications. In the present work, toxic free Ti-Zr-Cu-Pd-Sn alloys were studied to optimize their bulk forming ability and we successfully developed glassy rods of at least 14mm diameter by Cu-mold casting. Along with high glass forming ability, as-casted BMGs exhibit excellent plasticity. One of the studied alloy (Ti41.5Zr10Cu35Pd11Sn2.5) exhibits distinct plasticity under uniaxial compression tests (12.63%) with strain hardening before failure which is not commonly seen in monolithic bulk metallic glasses.QC 20120906
Hero-m
13
Nobre, Fernando Dantas. "Planar spin glasses". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47590.
Testo completo
14
Zamfir, Pompiliu Manuel. "Spherical spin glasses /". May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Testo completo
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Medina, Francelys A. Lanagan Michael Thomas. "Impedance spectroscopy studies of silica-titania glasses and glass-ceramics". [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-4566/index.html.
Testo completo
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Mao, Ming. "Structural relaxation and the glass transition in metal-metal glasses". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41708.
Testo completoAbstract (sommario):
This thesis presents the results of a systematic study on the structural relaxation and the glass transition of ternary metal-metal glasses Zr$ sb{67}$(Ni$ sb{1-x}$Cu$ sb{x}) sb{33}$. Differential scanning calorimetry provides macroscopic evidence of structural changes from the compositional and temperature dependence of enthalpy change. Results from high precision x-ray diffraction and Mossbauer spectroscopy, performed mainly on $ rm Zr sb{67}Ni sb{10}Cu sb{23}$ (x = 0.7), complete the picture of structural changes at the atomic level.Irreversible structural relaxation leads to densification and enthalpy release. Shear-like atomic motion enhances local atomic order, highlighting the atomic processes during the irreversible relaxation. Reversible structural relaxation involves two partly overlapping processes initiated at different temperatures, which are characterized by the solid and liquid atomic mobilities, respectively. Interatomic positional exchanges between Cu and Ni atoms change the local structure and are active during the reversible relaxation at low temperatures, which are also partly responsible for the irreversible relaxation. Above 500 K, shear-like atomic movements characterize the reversible relaxation, involving all three atomic species in a length scale of a few near-neighbor atomic shells. The overall density is unchanged during reversible relaxation.
The strong compositional dependence of the glass transition in the ternary glasses indicates an intimate association of the glass transition with interatomic bondings among different atomic species. The atomic motion from room temperature up to above the glass transition temperature, measured by the Mossbauer spectroscopy, is macroscopically tracked by the volume expansion and the enthalpy evolution. The glass transition occurs when the length scale of the atomic motion expands so rapidly that the interatomic potential can no longer maintain the on-site atomic vibration. The rapid development of translational atomic motion upon approaching the glass transition is reflected by the dramatic enhancement of the diffusive atomic motion.
17
Żalin̄ska, Beata. "Bismuth-based glasses, glass-ceramics and composites for microwave applications". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537987.
Testo completo
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Beatty, Kirk Matthew 1962. "Processing of copper aluminosilicate glasses to produce glass-copper structures". Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278284.
Testo completoAbstract (sommario):
Copper aluminosilicate (composition Cu₂O·Al₂O₃·6SiO₂) glass was melted in an alumina crucible at 1500°C and air cooled in situ. A layer of cupric oxide was grown on the polished glass surface and its thickness measured using a scanning electron microscope (SEM). The thickness of the oxide layer was found to increase parabolically with time, with a temperature dependency that was compatible with the diffusion of copper through the layer. The cupric oxide layer was reduced to copper on roughened and polished glass surfaces using a gas mixture of 3% H₂ and 97% N₂, resulting in a glass substrate coated by copper. Adherence of the copper layer to the polished glass substrate was found to be poor. However, adherence was found to increase by roughening the surface before oxidation. Additions of NiO and CaO to the base glass were not detrimental to the production of the copper film.
19
MUZI, ELISA. "Advanced nanostructured optical glasses and glass-ceramics for photonic applications". Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2970993.
Testo completo
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De, Villiers Daniel Robert. "Non-silicate porous glasses obtained by the leaching of borate-rich glasses". Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22327.
Testo completoAbstract (sommario):
Bibliography: pages 62-65.Glasses of the composition Na₂O-B₂O₃-X-Y and Na₂O-B₂O₃-Al₂o₃-X-Y were made where X and Y are two of the oxides CeO₂, HfO₂, ThO₂,Y₂O₃,ZrO₂ or Ga₂O₃. The glasses were either quenched or heat treated to promote phase separation and/or crystallization. The materials were subsequently leached in distilled water for periods of up to 96 hours. Leaching resulted in porous glasses or porous crystalline materials. The porous materials had high surface areas and good alkali resistance. A wide variety of compositions of these porous materials had BET surface areas between 100 and 413 m²/g. Selected porous glasses were chemically analysed. The heat resistances of two porous glasses were evaluated by observing the temperatures necessary for densification. Electron micrographs and X-ray diffraction scans were taken where necessary. Part of the glass forming regions for quenched samples of the system Na₂O-B₂O₃-Ga₂O₃-Y₂O₃ having Ga₂O₃ : Y₂O₃ ratios of either 3 : 1 or 3 : 2 were investigated. Part of the glass forming region for quenched samples of the Na₂O-B₂O₃-Y₂O₃ system was also investigated.
21
Woldt, E. "Relaxation in metallic glasses". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382709.
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22
Pizzey, Keiron. "Glasses under extreme conditions". Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687334.
Testo completoAbstract (sommario):
The method of in-situ high-pressure neutron diffraction was used to measure the structural transformations that take place upon cold-compression of several network-forming amorphous materials. The chalcogenide glasses GeSe2, GeSe4, and As2Se3, and the silicate glass CaSiO3, were investigated using a Paris-Edinburgh press to provide compression. Where possible, the neutron diffraction results were compared to experimental results and molecular dynamics (MD) simulations provided by other research groups. Amorphous GeSe2 was studied at pressures up to 16.1 GPa using a combination of neutron diffraction, neutron diffraction with isotope substitution (NDIS), and first-principles molecular dynamics (FPMD) simulations. It was found that the network transformations occurred in two stages. In the first stage up to ∼ 8 GPa, the structure re-arranged on an intermediate length scale by re-organising corner and edge-sharing GeSe4 tetrahedra. Above 8 GPa, both 5- and 6-fold coordinated Ge atoms began to form as the mean nearest-neighbour coordination number n and mean nearest-neighbour bond distance r both increased. A disagreement between the neutron diffraction and FPMD results above 8.5 GPa is attributed to the presence of an energy barrier. This barrier inhibits structural rearrangement in a cold-compression diffraction experiment, but allows them to occur via a high-temperature annealing stage in the simulations. Amorphous GeSe4 was studied at pressures up to 14.4 GPa using a combination of neutron diffraction and FPMD. The nearest-neighbour coordination environment was found to vary little across the measured pressure range, but structural transformations took place on an intermediate length scale as seen by the pressure-dependence of the second nearest-neighbour distance in the neutron diffraction results. The new experimental results are in accord with FPMD results and with those obtained from a study using x-ray diffraction (XRD). There are, however, major inconsistencies with the results obtained from a different study in which XRD was combined with empirical potential structure refinement (EPSR). It is hypothesised that this disagreement is due to the difficulty of modelling XRD results with EPSR for glasses in the Ge-Se system, where the x-ray atomic form factors of Ge and Se are similar. The reduced-density ρ/ρ0 dependence of the results was compared to that obtained for amorphous GeSe2, where ρ is the atomic number density at pressure and ρ0 is the atomic number density at ambient pressure. It was found that for both materials the local coordination environment does not change for ρ/ρ0 < 1.6. Amorphous As2Se3 was studied at pressures up to 14.4 GPa using a mixture of neutron diffraction, NDIS, and FPMD. At the total structure factor level, no change was observed to the nearest-neighbour coordination environment. The NDIS results do, however, suggest a change to the nearest-neighbour coordination environment beginning at 6 GPa. The results were compared to those found for two crystalline polymorphs of As2Se3, one prepared at ambient pressure and the other recovered to ambient conditions from high-pressure and -temperature. The differences between the coordination environments of these crystalline polymorphs pointed to some possible densification mechanisms in the glass. Ambient-pressure NDIS was also used to measure the full set of partial pair-distribution functions. Amorphous CaSiO3 was studied at pressures up to 17.5 GPa using neutron diffraction. The Si-O coordination number started to increase beyond a threshold pressure of 13 GPa, as compared to 15 GPa for amorphous SiO2. The results were used to test the validity of two sets of MD simulations that used different interatomic potentials and thermal processes for producing the glass. The results were found to agree with the MD simulations that used a cold-compression protocol.
23
Lee, Joo Hee. "Structural studies of glasses". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627292.
Testo completo
24
Emms, S. "Crystallisation of PFA glasses". Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/8485.
Testo completoAbstract (sommario):
Bibliography: leaves 79-81.Glasses with various compositions, falling in the CaO-AI20rSi02 and MgO-CaOAI20rSi02 systems were made, using pulverised fuel ash and silica, hydrated lime, kaolin and magnesium carbonate. Titania or ferric oxide and chromia were used as nucleants. Various crystallisation heat treatments were carried out and the nucleation and crystallisation behaviour was studied. A minimum MgO:CaO was found to be necessary for bulk nucleation to occur. The activation energy for viscous flow decreased with increased MgO:CaO ratios. This was accompanied by an increase in the surface crystal growth rates and a decrease in the activation energy for surface crystal growth. Titania also lowered the activation energies for viscous flow and surface crystal growth and caused an increase in the surface crystal growth rates.
25
Huang, Hong. "Synthesis and devitrification of high glass-forming ability bulk metallic glasses". Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/842676/.
Testo completoAbstract (sommario):
In this thesis, literature on the production, microstructures and properties of bulk metallic glasses (BMG) has been reviewed with particular reference to glass forming ability (GFA) and alloys of the Fe-Zr-B and Zr-based BMG systems. The experimental procedures used in the research are presented and the results for the amorphous Fe80Zr12B8 ribbon and the Zr57Ti5Al10Cu20Ni8, Zr57Nb5Al10Cu20Ni8, Zr53Nb2Al8Cu30Ni7 BMGs are given and discussed. Wedge-shaped ingots of the Zr-based BMGs were produced by casting in air or water cooled copper moulds. The Zr-based BMGs were fully amorphous up to 2 mm thickness of the wedge. In the Fe80Zr12B8 alloy and the Zr-based BMGs the glass transformation and crystallization temperatures increased with increasing temperature increase rate in the DSC. This shows that atom mobility dominates the onset of crystallization. Using XRD and TEM, the crystallization of the Fe80Zr12B8 amorphous alloy was studied from room temperature to 1273 K. The phase evolution path during continuous heating was: Amorphous → amorphous + alpha-Fe → amorphous + alpha-Fe + Fe23Zr6 (Fe3Zr) → amorphous + alpha-Fe + Fe23Zr6 (Fe3Zr) + Fe2Zr → amorphous + alpha-Fe + Fe23Zr6 (Fe3Zr) + Fe2Zr + Fe3B. In the air-cooled Zr57Ti5Al10Cu20Ni8 alloy the A1 rich Zr3Al2 and the bcc Al1.5(Cu+Ni)3(Zr+Ti)5 phases were quenched in the amorphous matrix and as the temperature decreased nanocrystalline Zr3Al2 phase nucleated. It is suggested that A1 is critical regarding GFA. The main crystalline phase that contained Zr, Ti, Al, Cu and Ni was the tetragonal (Zr, Ti)2(Cu, Al, Ni) phase, which is isomorphous with the Zr2Cu phase. Compared with the air-cooled alloy, the water-cooled amoiphous Zr57Ti5Al10Cu20Ni8 alloy has a larger supercooled liquid region and the same reduced glass transition temperature. This would suggest that fine crystallites were probably present in the air-cooled amorphous Zr57Ti5Al10Cu20Ni8 alloy. Thermal stability and GFA increased with the substitution of Ti with Nb in Zr57Nb5Al10Cu20Ni8 and the increase of the Cu/Nb ratio in Zr53Nb2Al8Cu30Ni7. Increase of the Cu/Nb ratio in Zr-based BMGs improved the GFA criteria, the thermal stability, hardness and eliminated crack formation. It is suggested that the Zr-Ti/Nb-Al-Cu-Ni BMGs with high glass forming ability can be obtained over a wide composition range Zr = 50-60 at.%, Ti or Nb = 2-5 at.%, A1 ≤ 8 at.%, Cu+Ni ≥ 30 at.%. On the basis of the results of this study on the formation of the primary crystallization phase, it is suggested that atomic packing close to the amorphous phase, high melting temperature and strong bonding among component elements lead to the ease of formation of the primary phase. In terms of reliability and applicability, good glass formers should capture the following features: low Ti, high Tg and high (Tx-Tg). Good indicators are made of ratios and sums of ratios that reflect these features. New GFA indicators are proposed namely: Tx/Tg + Tx/T1, Tx/(T1-Tg) + Tx/Tg, Tx/Tg + Tg/T1 +Tx/T1, (Tx-Tg)/T1 + Tx/T1. Casting at specific cooling rate or annealing at temperature between the glass transition temperature (Tg) and onset crystallization temperature (Tx), especially annealing near Tx for enough time, leads to the formation of nanoparticles in an amorphous matrix.
26
Ponsot, Inès. "Glasses and Glass-Ceramic Components from Inorganic Waste and Novel Processing". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424636.
Testo completoAbstract (sommario):
Thanks to European environmental rules and regulations establishment, waste recycling has become a more and more relevant problematic. For manufacturing plants, especially those producing hazardous wastes, expenses linked to waste production have drastically increased over the last decades. In the proposed work, various hazardous and non-hazardous wastes, among: soda-lime and borosilicate glass cullet, cathode ray tubes glass, exhausted lime from fume abatement systems residues, sludge and slags from ferrous and non-ferrous metallurgy, and pre-stabilized municipal solid waste incinerators ashes are used to elaborate several compositions of glass-ceramics. High-temperature treatment (minimum 800 °C) associated to a Direct Sintering process (30 min) was an efficient way to stabilize chemically the final products. The impact of each waste on the final product’s mechanical properties was studied, but also their synergies between each other, when mixed together. Statistic mixture designs enabled to develop interesting products for modern building applications, such as porous tiles and lightweight panels destined to insulation, with a purpose of fulfilling multifunctional properties.Grazie alle regole e normative ambientali europee istituite, il riciclaggio dei rifiuti è diventato una problematica sempre più rilevante. Per gli impianti di produzione, in particolare quelli che producono rifiuti pericolosi, le spese connesse allo smaltimento sono drasticamente aumentate negli ultimi decenni. Nel lavoro proposto, vari rifiuti, pericolosi o no, vengono utilizzati per elaborare diverse composizioni di vetroceramiche. Si distinguono rottami di vetro della produzione di finestre, di contenitori farmaceutici e di tubi catodici. I rifiuti non vetrosi invece sono calce esausta da residui di sistemi di filtrazione di fumi, scorie metallurgiche da leghe ferrose e non e ceneri da inceneritori. E' presentata nel presente lavoro la ricerca di un metodo di trattamento ad alta temperatura (minima 800 ° C) efficace per stabilizzare chimicamente il prodotto finale, tramite i diversi processi di sinterizzazione diretta, sinter-cristallizzazione e vetrificazione. Sono stati studiati gli effetti di ogni rifiuto sulle proprietà meccaniche del prodotto finale, ma anche le nuove funzionalità ottenute attraverso le sinergie risultanti dalla loro miscela. Miscele calibrate hanno permesso di sviluppare prodotti interessanti per applicazioni edilizie moderne, come le piastrelle porose e pannelli leggeri destinati all’isolamento.
27
Avila-Coronado, Karina E. "Triangular Relations in Structural Glasses". Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1273602464.
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28
Dahlberg, Joakim. "Eye Tracking with Eye Glasses". Thesis, Umeå University, Department of Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-32868.
Testo completoAbstract (sommario):
This study is concerned with the negative effects of wearing corrective lenses while using eye trackers, and the correction of those negative effects. The eye tracker technology studied is the video based real-time Pupil Center and Corneal Reflection method. With a user study, the wearing of eyeglasses is shown to cause 20 % greater errors in the accuracy of an eye tracker than when not wearing glasses. The error is shown to depend on where on the eye tracker viewing area the user is looking.
A model for ray refraction when wearing glasses was developed. Measurements on distortions on the image of the eye caused by eyeglass lenses were carried out. The distortions were analyzed with eye tracking software to determine their impact on the image-to-world coordinates mapping. A typical dependence of 1 mm relative distance change on cornea to 9 degrees of visual field was found.
The developed mathematical/physiological model for eyeglasses focuses on artifacts not possible to accommodate for with existing calibration methods, primarily varying combinations of viewing angles and head rotations. The main unknown in the presented model is the effective strength of the glasses. Automatic identification is discussed. The model presented here is general in nature and needs to be developed further in order to be a part of a specific application.
29
Damart, Tanguy. "Energy dissipation in oxide glasses". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1189/document.
Testo completoAbstract (sommario):
L'atténuation d'ondes à basse et haute fréquences dans les verres n'est pas encore bien comprise en grande partie car les phénomènes à l'origine de cette dissipation varient grandement en fonction de la fréquence. L’existence de structures complexes et organisation multi échelle dans les verres favorise l'apparition de temps de relaxation allant de la seconde à la femtoseconde et de corrélation prenant place de l’Angström à la centaine de nanomètre. A basse fréquence, une meilleur compréhension de ces phénomènes de dissipation serait bénéfique à de nombreux domaines. Par exemple, les multi-couches recouvrants les miroirs des interféromètres servant à détecter les ondes gravitationnelles sont réalisées à partir de verres d'oxyde (SiO2 et Ta2O5) qui sont une source majeur de dissipation. A haute fréquence, l'étude de la dissipation pose des questions théoriques sur le lien entre asymétrie locale et atténuation acoustique.Durant cette étude, nous avons réalisé une analyse approfondie de l'interaction entre ondes mécaniques et structure des verres en utilisant des techniques de simulations telle que la dynamique moléculaire. En partant de la synthèse de verres de SiO2 et Ta2O5, nous nous sommes appliqués à trouver l'origine structurelle de la dissipation aux différentes échelles de fréquence. A basse fréquence nous avons été capable de catégoriser les déplacements atomiques à l'origine de la dissipation en utilisant la théorie des états à deux niveaux. A haute fréquence, nous avons utilisé une technique de spectroscopie mécanique appuyé par un développement analytique pour montrer l'importance du désordre local dans l’existence de dissipationThe origin of sound attenuation at low and high frequency in glasses stays elusive mainly because of the complex temperature and frequency dependence of the phenomena at its root. Indeed, the presence of complex structures and multi-scale organizations in glasses induce the existence of relaxation time ranging from the second to the femto-second and of spatial correlation ranging from the Angström to a hundred nanometers. At low-frequency, a better understanding of the phenomena at the origin of dissipation would be beneficial to several applications. For example, the multi-layers coating the mirrors of gravitational waves detectors consists of a superposition of two oxide glasses: silicate (SiO2) and tantalum pentoxide (Ta2O5), are an important source of dissipation. At high frequency, the study of dissipation raises theoretical questions about the link between attenuation and dissipation as well as between loclt asymmetry and dissipation. In the present study, we conducted an analysis of the interaction between mechanical waves and the structure of two oxide glasses using simulation techniques such as non-equilibrium molecular dynamics. At high-frequencies, we implemented and used mechanical spectroscopy to measure dissipation numerically and performed in parallel an analytical development based on the projection of the atomic motion on the vibrational eigenmodes. At low-frequencies, we used molecular dynamics to gather sets of thermally activated events that we classed in three categories based on topologically distinct atomic motions and from which we predicted dissipation numerically using a refreshed TLS model
30
Serral, Gracià Rubèn. "Spin bosons and spin glasses". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/76076.
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31
Cambron, André. "Hydrogen in NiZr metallic glasses". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66070.
Testo completo
32
Verrall, Diane Jane. "Structural studies of chalcogenide glasses". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333353.
Testo completo
33
Gladden, L. F. "Structural studies of inorganic glasses". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233932.
Testo completoAbstract (sommario):
The present work has been concerned with a study of the structure of germanium and silicon dichalcogenide glasses. Initially, the aim of this research was to obtain direct structural evidence of reversible photostructural changes in bulk germanium chalcogenide glasses. However, having confirmed the existence of such changes using EXAFS and neutron scattering techniques, it became obvious that a more comprehensive understanding of the as-quenched, annealed glass structure is required before a valid interpretation of the data can be made; in particular, the extent of medium-range order in these systems is of interest. Although limited to few examples at the moment, the potenital of both structural modelling and NMR studies for solving such problems has been investigated in a variety of inorganic glass systems, and these approaches can now be extended to those glasses exhibiting photostructural changes. Modelling studies of the structure of a-SiSe2 have shown that the total correlation function T(r) is sensitive to different structural features in the generated glass structure. The present studies heavily favour a structure based on chains of edge-sharing (SiSe4) tetrahedra. A degree of spatial correlation is required between the chains, such as can only be obtained by short lengths of parallel chains 'pinned' by corner-sharing tetrahedra. 29Si NMR studies of vitreous silica have shown that water, incorporated into the SiO2 network as OH, acts as a major source of spin-lattice relaxation in this system. Numerical methods of self-calibration ('phasing') and removal of data truncation and lineshape apodization effects have been investigated, thereby enabling quantitative information concerning the Si-O-Si bond-angle distribution in silica to be obtained. Although these algorithms are presented with reference to NMR spectroscopy, their extension to other branches of spectroscopy is obvious. NMR has also been used to probe defect states in a-Se. 77Se spin-lattice relaxation time data provide evidence of a defect state (perhaps a VAP) in equilibrium with C10 centres in the glass.
34
Gillin, Peter. "Statistical mechanics of multispin glasses". Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393228.
Testo completo
35
Sears, Adam J. "The characterisation of stannosilicate glasses". Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364575.
Testo completo
36
Colborne, S. G. W. "Numerical studies of spin glasses". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233056.
Testo completo
37
Viana, L. "Phase diagrams for spin glasses". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356116.
Testo completo
38
Harris, Bridget. "Sites in oxidic network glasses". Thesis, University of Aberdeen, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244312.
Testo completoAbstract (sommario):
Chemically reactive sites in oxidic networks are discussed in terms of the electron densities provided at the sites using the optical basicity model. Ultraviolet/visible/near-infrared spectroscopy has been used to identify sites for metalions. The effect of glass composition on the coexistence and availability of these sites is considered with reference to the structure of the network and sites identified using far-infrared spectroscopy. Ultraviolet spectra of lead(II) ions indicate the existence of two types of site for Pb2+ in borate and phosphate networks. The switchover from one site to the other coincides with major changes in the network structure. Remarkably, the natures of the Pb2+ sites in all of the binary alkali systems studied are independent of the identify of the alkali. Moreover, data for lead(II) ions in xLi2O.(1-x)Cs2O.2B2O3 systems indicate that the natures of the Pb2+ sites change when more than one alkali is present. The influence of the modifier cation charge on the sites for Pb2+ ions has also been investigated. Data for barium, calcium and zinc systems are reported. The possibility of using vanadyl and cobalt(II) ions to quantify the basicities of glasses with poor ultraviolet transparence has been considered. The response of the Co2+ ion in borate systems gave the best fit with the optical basicity model. Approximate values have been assigned to the basicities of Tl2O, PbO, Bi2O3 and Ag2O by comparing the spectra of the Co2+ ion in borate glasses containing these oxides to those of Co2+ in the equimolar alkali glasses. The results provide an insight into the site selectivity of Tl+, Pb2+ and Bi2+ probe ions. Basicity changes in AgI.Ag2O.B2O3 and NaI.Na2O.B2O3 systems have also been investigated. Ligand field data for Ti3+, V3+, Cr3+, Ni2+ and Cu2+ ions in oxidic glasses have been collected from the literature with a view to correlating the ligand field parameters Dq and B with optical basicity.
39
Theodorou, Doros Nicolas. "Molecular modelling of polymeric glasses". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15293.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 193-199.
by Doros Nicolas Theodorou.
Ph.D.
40
Middleton, Thomas Ferguson. "Energy landscapes of model glasses". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619844.
Testo completo
41
Madge, Shantanu V. "Magnesium-based bulk metallic glasses". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619797.
Testo completo
42
Zhang, Yi. "Inhomogeneous deformation in metallic glasses". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613414.
Testo completo
43
Pham, Khoa Nguyen. "Glasses in colloid-polymer mixtures". Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/15644.
Testo completo
44
Zubair, Muhammed 1962. "Aluminoborophosphosilicate glasses for microelectronics packaging". Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277898.
Testo completoAbstract (sommario):
Glasses are used in microelectronic packaging for insulation and passivation purposes. To optimize the performance of these packages, it is necessary to investigate new glasses or improve on properties of the glasses in use. The insulating glass should have low dielectric constant, low dissipation factor, low glass transition temperature, high chemical resistivity, and a thermal expansion coefficient matching the substrate. In this study, various aluminoborophosphosilicate glasses containing Ca(Mg)O, Ca(Mg)F₂, and AlF₃ as flux were investigated. Processing temperatures for these glasses range from 1300°C to 1500°C. The coefficients of thermal expansion range from 4.52 μ/°C to 9.39 μ/°C. The dielectric constant as a function of frequency and composition is in the range of 4.1 to 5.2. The index of refraction for these glasses is in the range of 1.52 to 1.58. Glass transition and softening temperatures as low as 538°C and 622°C, respective, were found. Results of this investigation are discussed in terms of the possible use of aluminoborophosphosilicate glasses in microelectronic packaging.
45
Forto, Chungong Louis. "Structural characterisation of bioactive glasses". Thesis, Aston University, 2018. http://publications.aston.ac.uk/37835/.
Testo completoAbstract (sommario):
Bioactive glasses are of great importance for orthopaedic and dental applications. The macroscopic properties of bioactive glasses, and in particular the rate of dissolution, can be tailored for specific applications by altering the compositions. It is therefore important to understand a compositional-structural-relationship as this will help when predicting glass properties and for optimising the design of future glasses for clinical applications. This thesis focused on the structural-characterisation of a wide range of bioactive glasses that are important for orthopaedic and dental applications. Experimental probes including neutron diffraction, high energy X-ray diffraction, solid-state NMR, supported by complimentary techniques such EXAFS, FTIR, XPS and XRD were used to characterise these glasses. A series of halide containing (CaF2 and CaCl2) bioactive glasses were successfully synthesised and characterised. Despite conflicting reports in the literature, the present study strongly suggests that minimal Si-Cl or Si-F bonds are present in these glasses. Instead halide ions were found to surround calcium ions. The silica network is therefore unaffected by the addition of halides ions. A series of novel zinc silicate-germanate glasses, with potential applications for bone cements, were investigated structurally. Studies revealed both Zn and Ge cations are in a tetrahedra coordination with no evidence of 5, 6-fold coordinations. An increase in the network connectivity of the glass will significant reduce its dissolution. The impact of incorporating Mg and Zn into bioglass was studied since both these ions can act as network intermediates. Whilst Zn was found to be solely tetrahedral Mg had significant fractions of 5 and 6-fold coordinations. The structure of Mg-BMG were investigated using neutron diffraction and molecular dynamics to help deconvolved overlapping partial structure factors. Isotopic neutron diffraction was further used to simplify the individual partial structure factors to further understand the structure of the glasses which is important to optimise its properties.
46
Sahar, Md Rahim. "A study on oxyhalide glasses". Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/106571/.
Testo completoAbstract (sommario):
Oxychloride glasses in the ternary system Sb2O3 - PbCl2 - ZnCl2 have been prepared. The thermal properties and the crystallisation behaviour of these glasses have been investigated by differential scanning calorimetry, viscometry, x-ray diffraction, scanning electron microscopy with energy dispersive x-ray analysis and infra-red spectroscopy. Thermal stability gaps, T1 - T4 up to 149°C are observed. The predominant crystal phases formed, depending on composition, are ZnCl2, Sb2O3 and a lead antimony oxychloride Sillan phase whose stoichiometry varies with glass composition from PbSb2O2.Cl2 to PbSb1O2.Cl. Relative crystal growth rates for the glasses have also been measured and values up to 0.16 μm sec−1 are observed. These values are found to be strongly dependent on the chlorine content of the glasses as are also the viscosity characteristics. The chemical durability of the glasses has also been studied under various conditions. Initial water dissolution rates between 10−2 to 10−4 gm cm day were observed. The corrosion rates were found to be chlorine content dependent and reaction mechanisms are suggested. The introduction of a heavy metal chloride such as BlCl2 or TlCl, as a fourth component, was found to increase the chlorine content without much affecting the thermal stability. However, an excessive amount of chlorine makes the glass less durable.
47
Lopatchenko, T. "How 3D without glasses work". Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/44881.
Testo completoAbstract (sommario):
The technology of 3D without glasses is called autostereoscopy. Because this kind of three dimensional technology doesn't utilize special spectacles or headgear it became also known as glasses-less 3D or glasses free 3D. The methods of 3D technology without glasses include a parallax barrier, volumetric and holographic techniques.
48
Magkiriadou, Sofia. "Structural Color From Colloidal Glasses". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226099.
Testo completoAbstract (sommario):
When a material has inhomogeneities at a lengthscale comparable to the wavelength of light, interference can give rise to structural colors: colors that originate from the interaction of the material's microstructure with light and do not require absorbing dyes. In this thesis we study a class of these materials, called photonic glasses, where the inhomogeneities form a dense and random arrangement. Photonic glasses have angle-independent structural colors that look like those of conventional dyes. However, when this work started, there was only a handful of colors accessible with photonic glasses, mostly hues of blue.
We use various types of colloidal particles to make photonic glasses, and we study, both theoretically and experimentally, how the optical properties of these glasses relate to their structure and constituent particles. Based on our observations from glasses of conventional particles, we construct a theoretical model that explains the scarcity of yellow, orange, and red photonic glasses. Guided by this model, we develop novel colloidal systems that allow a higher degree of control over structural color. We assemble glasses of soft, core-shell particles with scattering cores and transparent shells, where the resonant wavelength can be tuned independently of the reflectivity. We then encapsulate glasses of these core-shell particles into emulsion droplets of tunable size; in this system, we observe, for the first time, angle-independent structural colors that cover the entire visible spectrum. To enhance color saturation, we begin experimenting with inverse glasses, where the refractive index of the particles is lower than the refractive index of the medium, with promising results. Finally, based on our theoretical model for scattering from colloidal glasses, we begin an exploration of the color gamut that could be achieved with this technique, and we find that photonic glasses are a promising approach to a new type of long-lasting, non-toxic, and tunable pigment.
49
Wood, David John. "Fundamental studies on ionomer glasses". Thesis, University of Greenwich, 1993. http://gala.gre.ac.uk/6347/.
Testo completoAbstract (sommario):
Composition-structure-property relationships were studied in glasses of the type used to produce glass lonomer dental cements. These materials are currently being developed as a bone cement in joint replacement surgery. Initially, a simple quaternary (25i02-Al203-CaO-CaF2) glass was produced and was found to undergo minimal fluorine loss. This results in a glass whose composition is reproducible between batches. This composition, however, was too reactive to form a glass ionomer cement. A glass-ceramic approach was pursued to deactivate the glass and following heat treatments, cements were produced whose properties varied depending upon the precise heat treatment used. The heat treatments above the glass transition temperature resulted in amorphous phase separation, probably by a spinodal decomposition mechanism, followed by a two stage crystallization of calcium fluoride (fluorite) and anorthite. The anorthite phase crystallized from fluorite nuclei and, in effect, crystallization occurred by a bulk nucleation mechanism. The glass will also undergo significant crystallization to fluorite below the glass transition temperature, with surface nucleation the dominant mechanism. This explains the deactivation of ionomer glasses used commercially to control the setting properties of dental glass ionomer cements. The structural role of fluorine in these glasses was also investigated. It seems that fluorine is present in the glass network, rather than existing as a discreet entity bonded to a modifying cation. There is evidence that the fluoride ions are bonded only to aluminium sites and act to disrupt network connectivity. A commercial glass was examined and was found to be clearly phase separated. This glass was found to crystallize to apatite and mullite. Apatite is the mineral phase of bone and enamel and this may explain the excellent biocornpatability of glass ionomer cements. Glasses containing sodium and phosphate ions have also been produced. The sodium containing glasses were all found to crystallize from the melt to calcium fluoride. The phosphate containing glasses formed cements without any subsequent modification, and following a simple heat treatment, all of the phosphate containing glasses were found again to crystallize initially to an apatite phase. Selected compositions additionally crystallized to mullite. These glass-ceramics were tougher than the base glasses and this is attributed to the presence of interlocking needles of the two phases. Some of the glasses were easily castable to produce optically clear glasses, and in addition the glasses underwent bulk nucleation via prior amorphous phase separation, to give needles of apatite and mullite. These glass-ceramics thus show tremendous potential for use as a bloactive bone substitute material or as a castable crown.
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Fitzgerald, Victoria. "Structural characterisation of bioactive glasses". Thesis, University of Kent, 2007. https://kar.kent.ac.uk/38707/.
Testo completoAbstract (sommario):
Melt-quenched glasses containing SiO2, CaO, Na2O and P2O5, and sol-gel derived glasses containing SiO2 and CaO are known to have bioactive properties. Foaming of binary sol-gel derived bioactive glasses containing SiO2 and CaO can be used to produce 3D porous scaffolds which mimic the structure of trabecular bone, increasing the potential for these glasses to be used as bioactive bone-regenerative materials. A range of experimental techniques have been used to investigate the atomic scale structure of these materials, and also to observe the reaction mechanisms which occur when these materials are immersed in a simulated physiological solution (simulated body fluid, SBF) and a standard cell culture medium (tris buffer solution, TBS). A robust structural model of the most bioactive of the melt-quenched glasses, namely Bioglass®, has been produced by combining high energy X-ray and neutron diffraction data, magic angle spinning nuclear magnetic resonance (MAS NMR) and reverse Monte Carlo (RMC) modelling. It has been shown that Ca clustering occurs in the glass, which is of direct relevance to the understanding of the facile nature of calcium within such glasses giving rise to its relatively rapid diffusion from the solid into solution. Hydroxyapatite has been confirmed as the calcium phosphate phase which grows on the surface of Bioglass® when immersed in the standard cell culture medium, TBS. A new method which can be used for in-situ time resolved high-energy X-ray diffraction studies of reaction mechanisms, such as those involved when a bioactive glass is immersed in a simulated physiological solution, is decribed in this thesis. Small-angle X-ray scattering has enabled the growth of mesopores to be observed during the foamed sol-gel stabilisation process. In-situ simultaneous small and wide angle X-ray scattering measurements of a foam in SBF have shown that the mesoporous network facilitates the rapid growth of relatively high-density HCA, which will therefore eventually replace the initial silicate glass as the material bounding the macropores. The data presented herein reveal the structure of highly important materials in the field of biomaterials and enable a link to be made between the atomic scale structure of the materials and their bioactive properties.