Rozprawy doktorskie: „Disordered Materials - Properties”

1

Belk, Nathan. "Electronic transport and magnetic properties of disordered high-Tc materials". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10745.

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Murai, Syunsuke. "Studies on photonic materials having disordered structures and tailored light scattering properties". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/147363.

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3

Li, Yuting. "Simulations and Electronic Structure of Disordered Silicon and Carbon Materials". Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1395410498.

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4

Valkovskii, Vitalii [Verfasser], i Sergei [Akademischer Betreuer] Baranovskii. "Optical and Transport Properties of Disordered Materials by Computer Simulation / Vitalii Valkovskii ; Betreuer: Sergei Baranovskii". Marburg : Philipps-Universität Marburg, 2018. http://d-nb.info/1170321275/34.

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5

Timothy, Jithender J. [Verfasser], Günther [Gutachter] Meschke i Christian [Gutachter] Hellmich. "Analytical and computational models for the effective properties of disordered microcracked porous materials / Jithender J. Timothy ; Gutachter: Günther Meschke, Christian Hellmich". Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1125106603/34.

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6

Lebihain, Mathias. "Large-scale crack propagation in heterogeneous materials : an insight into the homogenization of brittle fracture properties". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS522.

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La compréhension du comportement macroscopique d'un matériau à partir de la donnée de ses constituants à l'échelle microscopique a toujours été le Saint Graal en science des matériaux dans la mesure où elle fournit les éléments essentiels à la prédiction de la résistance d'une structure et au développement de matériaux aux propriétés innovantes. Si la théorie de l'homogénéisation constitue un cadre théorique établi pour prédire la réponse effective d'une vaste classe de comportements matériaux, elle ne permet pas à l'heure actuelle de prédire les propriétés effectives en rupture fragile. S'attaquer à cette question suppose de tirer profit des caractéristiques uniques de la rupture fragile qui est (i) un problème d'évolution dissipatif, (ii) localisé en pointe de fissure et (iii) relié à un problème de structure. Dans ce travail, nous proposons un formalisme théorique fondé sur une approche perturbative de la mécanique de la rupture afin de (i) modéliser la propagation de fissure dans les milieux désordonnés de grande taille. L'implémentation numérique de ce modèle nous permet (ii) d'étudier en détail les mécanismes dissipatifs mis en jeu en pointe de fissure lorsqu'une fissure interagit avec des hétérogénéités. Leur contribution au renforcement du matériau à l'échelle macroscopique est finalement (iii) estimée à partir de la résolution du problème de structure à l'aide d'outils empruntés à la physique statistique. Les apports théoriques et numériques de la thèse sont finalement confrontés aux résultats d'expériences de fissuration de polymères hétérogènes imprimés 3D, extraits d'outils de corrélation d'image
Being able to predict the macroscopic response of a material from the knowledge of its constituent at a microscopic or mesoscopic scale has always been the Holy Grail pursued by material science, for it provides building bricks for the understanding of complex structures as well as for the development of tailor-made optimized materials. The homogenization theory constitutes nowadays a well-established theoretical framework to estimate the overall response of composite materials for a broad range of mechanical behaviors. Such a framework is still lacking for brittle fracture, which is a dissipative evolution problem that (ii) localizes at the crack tip and (iii) is related to a structural one. In this work, we propose a theoretical framework based on a perturbative approach of Linear Elastic Fracture Mechanics to model (i) crack propagation in large-scale disordered materials as well (ii) the dissipative processes involved at the crack tip during the interaction of a crack with material heterogeneities. Their ultimate contribution to the macroscopic toughness of the composite is (iii) estimated from the resolution of the structural problem using an approach inspired by statistical physics. The theoretical and numerical inputs presented in the thesis are finally compared to experimental measurements of crack propagation in 3D-printed heterogeneous polymers obtained through digital image correlation

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7

Penfold, Ian Timothy. "Structural properties of chalcogenide material". Thesis, University of East Anglia, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278073.

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8

Yu, Tae-Hwan. "Electrical properties and structural disorder in stannate pyrochlores". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40609.

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9

Shrestha, Kiran (Engineer). "Electrical Conduction Mechanisms in the Disordered Material System P-type Hydrogenated Amorphous Silicon". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700106/.

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The electrical and optical properties of boron doped hydrogenated amorphous silicon thin films (a-Si) were investigated to determine the effect of boron and hydrogen incorporation on carrier transport. The a-Si thin films were grown by plasma enhanced chemical vapor deposition (PECVD) at various boron concentrations, hydrogen dilutions, and at differing growth temperatures. The temperature dependent conductivity generally follows the hopping conduction model. Above a critical temperature, the dominant conduction mechanism is Mott variable range hopping conductivity (M-VRH), where p = ¼, and the carrier hopping depends on energy. However, at lower temperatures, the coulomb interaction between charge carriers becomes important and Efros-Shklosvkii variable hopping (ES-VRH) conduction, where p=1/2, must be included to describe the total conductivity. To correlate changes in electrical conductivity to changes in the local crystalline order, the transverse optical (TO) and transverse acoustic (TA) modes of the Raman spectra were studied to relate changes in short- and mid-range order to the effects of growth temperature, boron, and hydrogen incorporation. With an increase of hydrogen and/or growth temperature, both short and mid-range order improve, whereas the addition of boron results in the degradation of short range order. It is seen that there is a direct correlation between the electrical conductivity and changes in the short and mid-range order resulting from the passivation of defects by hydrogen and the creation of trap states by boron. This work was done under the ARO grant W911NF-10-1-0410, William W. Clark Program Manager. The samples were provided by L-3 Communications.

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10

Shaw, Stephanie M. "Frequency Response of Synthetic Vocal Fold Models with Linear and Nonlinear Material Properties". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2433.

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Previous studies have shown the importance of cricothyroid muscle activation in altering fundamental frequency in the human voice. Other studies have investigated the non-linear properties of vocal fold tissue and the impact of this non-linearity on frequency response. Several physical models of the vocal folds have been made for research purposes. However, all have been isotropic in nature with linear stress-strain properties. The purpose of this study was to create a physical model with non-linear stress-strain properties to investigate the frequency response of the model as cricothyroid muscle activation was simulated (in other words, as the vocal folds were stretched in an anterior-posterior dimension). In this study the physical models of the vocal folds were stretched in 1 mm increments and the fundamental frequency (F0) was recorded at each position. Subglottal pressure was also monitored and phonation threshold pressures were recorded for each adjustment in length and vocal fold tension, because this can influence F0. Results were obtained for models with and without non-linear properties for comparison. Tensile tests were also conducted for the linear and non-linear synthetic vocal folds. Results indicate that non-linear models demonstrated a more substantial frequency response than linear vocal fold models and a more predictable F0 increase with respect to increasing vocal fold length. Phonation threshold pressures also increased with increasing vocal fold length for non-linear vocal fold models. This trend was reversed for linear vocal fold models, with phonation threshold pressures decreasing with increasing vocal fold length. These results indicate that the non-linear vocal fold models more accurately represent the human vocal folds than do linear models. This study serves as the foundation for future research to quantify the impact of non-linear tissue properties versus active tensioning (through antagonistic thyroarytenoid muscle activation) on F0 response and phonation threshold pressure.

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11

Narayanan, Rajesh. "Influence of rare regions on the critical properties of systems with quenched disorder /". view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9948028.

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Thesis (Ph. D.)--University of Oregon, 1999.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 165-166). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948028.

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12

Panzer, Fabian [Verfasser], i Anna [Akademischer Betreuer] Köhler. "Understanding the impact of order-disorder phenomena on the optical properties of photoactive semiconducting materials / Fabian Panzer ; Betreuer: Anna Köhler". Bayreuth : Universität Bayreuth, 2016. http://d-nb.info/1115250280/34.

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13

Mortensen, Clay Dustin. "The effect of grain size, alloy composition and turbostratic disorder on the thermal and electrical properties of Bi₂Te₃ based materials /". Connect to title (abstract only) online (ProQuest), 2008. http://proquest.umi.com/pqdweb?did=1690937581&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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14

Langenfeld, Annette. "Etude de corrélations électroniques dans des systèmes désordonnés". Grenoble 1, 1993. http://www.theses.fr/1993GRE10081.

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Cette these est faite de deux parties independantes. La premiere partie traite les corrections quantiques a l'effet hall anormal. On peut montrer que les termes de l'anomalie coulombienne se compensent mutuellement en considerant la diffusion asymetrique des electrons de conduction par les moments magnetiques d'une couche metallique desordonnee. La contribution venant de la localisation faible est coupee par la diffusion asymetrique qui brise la coherence de phase. Les resultats sont en bon accord avec une experience recente sur des couches minces de fer desordonnees et ferromagnetiques. Dans la seconde partie, on etudie la formation de moments magnetiques localises dans des systemes comme des semiconducteurs dopes en phase metallique. Le calcul est base sur le modele de hubbard avec desordre hors-diagonal. En examinant le modele a une seule impurete faiblement rattachee au reseau, on trouve un moment magnetique localise, et cela meme dans l'approximation de hartree-fock pour la repulsion locale u. On associe a ce moment magnetique un effet kondo dont la nature et la dependance par rapport au desordre sont discutees. Les resultats sont compares a une experience recente mesurant le pouvoir thermoelectrique du si:p. La correspondance est satisfaisante

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15

Isotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4". Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.

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To support the growing global demand for energy, new sustainable solutions are needed both economically and environmentally. Thermoelectric waste heat recovery and energy harvesting could contribute by increasing industrial process efficiency, as well as powering stand-alone devices, microgenerators, and small body appliances.The structural complexity of quaternary chalcogenide materials provides an opportunity for engineering defects and disorder, to modify and possibly improve specific properties. Cu2ZnSnS4 (CZTS, often kesterite), valued for the abundance and non-toxicity of the raw materials, seems particularly suited to explore these possibilities, as it presents several structural defects and polymorphic phase transformations. The aim of this doctoral work is to systematically investigate the effects of structural polymorphism, disorder, and defects on the thermoelectric properties of CZTS, with particular emphasis to their physical origin. A remarkable case is the order-disorder transition of tetragonal CZTS, which is found responsible for a sharp enhancement in the Seebeck coefficient due to a flattening and degeneracy of the electronic energy bands. This effect, involving a randomization of Cu and Zn cations in certain crystallographic planes, is verified in bulk and thin film samples, and applications are proposed to exploit the reversible dependence of electronic properties on disorder. Low-temperature mechanical alloying is instead discovered stabilizing a novel polymorph of CZTS, which disordered cubic structure is studied in detail, and proposed deriving from sphalerite-ZnS. The total cation disorder in this compound provides an uncommon occurrence in thermoelectricity: a concurrent optimization of Seebeck coefficient, electrical and thermal conductivity. These findings, besides providing new and general understanding of CZTS, can cast light on profitable mechanisms to enhance the thermoelectric performance of semiconducting chalcogenides, as well as delineate alternative and fruitful applications.

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16

Isotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4". Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.

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To support the growing global demand for energy, new sustainable solutions are needed both economically and environmentally. Thermoelectric waste heat recovery and energy harvesting could contribute by increasing industrial process efficiency, as well as powering stand-alone devices, microgenerators, and small body appliances. The structural complexity of quaternary chalcogenide materials provides an opportunity for engineering defects and disorder, to modify and possibly improve specific properties. Cu2ZnSnS4 (CZTS, often kesterite), valued for the abundance and non-toxicity of the raw materials, seems particularly suited to explore these possibilities, as it presents several structural defects and polymorphic phase transformations. The aim of this doctoral work is to systematically investigate the effects of structural polymorphism, disorder, and defects on the thermoelectric properties of CZTS, with particular emphasis to their physical origin. A remarkable case is the order-disorder transition of tetragonal CZTS, which is found responsible for a sharp enhancement in the Seebeck coefficient due to a flattening and degeneracy of the electronic energy bands. This effect, involving a randomization of Cu and Zn cations in certain crystallographic planes, is verified in bulk and thin film samples, and applications are proposed to exploit the reversible dependence of electronic properties on disorder. Low-temperature mechanical alloying is instead discovered stabilizing a novel polymorph of CZTS, which disordered cubic structure is studied in detail, and proposed deriving from sphalerite-ZnS. The total cation disorder in this compound provides an uncommon occurrence in thermoelectricity: a concurrent optimization of Seebeck coefficient, electrical and thermal conductivity. These findings, besides providing new and general understanding of CZTS, can cast light on profitable mechanisms to enhance the thermoelectric performance of semiconducting chalcogenides, as well as delineate alternative and fruitful applications.

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17

Atmani, Hassane. "Investigations dans le domaine des comportements thermiques de matériaux désordonnés : application au sélénium et aux mélanges Se-Bi à faible concentration en bismuth". Rouen, 1988. http://www.theses.fr/1988ROUES009.

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18

Salamone, Salvatore. "Propriétés physiques des empilements de fibres macroscopiques : une approche expérimentale, théorique et numérique". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAE007/document.

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L'objectif de ce travail est de comprendre comment la forme intrinsèque des fibres individuelles contrôle les propriétés collectives des empilements, en particulier leurs propriétés mécaniques (élasticité) et électriques. Nous nous intéressons à des fibres longues, alignées selon une direction privilégiée et présentent un désordre de forme important. Notre étude est expérimentale et numérique. Nous proposons un modèle à deux dimensions, de champ moyen auto-cohérent, décrivant l'élasticité collective de l'empilement à partir des propriétés individuelles des fibres : leurs distribution de désordre ainsi que leurs module de courbure. Nous obtenons une équation d'état qui décrit avec un bon accord l'élasticité de nos empilements de fibres, sans paramètre ajustable, mais à un facteur multiplicatif près. Nous obtenons des résultats comparables entre les études expérimentale et numérique
The purpose of this work is to understand how intrinsic shape of individual fibers controls the collective behavior of fiber stacks, in particular the mechanical (elasticity) and electrical properties. We consider long fibers, aligned towards one preferential direction with a significant disorder shape. Our study is experimental and numerical. We propose a two dimensions self consistent mean field model which describes the collective elasticity from the individual properties of fibers : the disorder distribution and the bending modulus. We obtain an equation of state which describes with a good agreement the stacks elasticity, without any fit parameters, however up to a multiplicative constant. We obtain similar results between experimental and numerical studies

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19

Zhang, Xiaodong. "Flow properties and fracture in disordered media". Phd thesis, 1996. http://hdl.handle.net/1885/143813.

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20

Holliday, Kito S. "The mechanical and optical properties of ordered and disordered materials". 2005. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-822/index.html.

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21

Daga, Vikram Kumar. "Role of strongly interacting additives in tuning the structure and properties of polymer systems". 2011. https://scholarworks.umass.edu/dissertations/AAI3482604.

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Block copolymer (BCP) nanocomposites are an important class of hybrid materials in which the BCP guides the spatial location and the periodic assembly of the additives. High loadings of well-dispersed nanofillers are generally important for many applications including mechanical reinforcing of polymers. In particular the composites shown in this work might find use as etch masks in nanolithography, or for enabling various phase selective reactions for new materials development. This work explores the use of hydrogen bonding interactions between various additives (such as homopolymers and non-polymeric additives) and small, disordered BCPs to cause the formation of well-ordered morphologies with small domains. A detailed study of the organization of homopolymer chains and the evolution of structure during the process of ordering is performed. The results demonstrate that by tuning the selective interaction of the additive with the incorporating phase of the BCP, composites with significantly high loadings of additives can be formed while maintaining order in the BCP morphology. The possibility of high and selective loading of additives in one of the phases of the ordered BCP composite opens new avenues due to high degree of functionalization and the proximity of the additives within the incorporating phase. This aspect is utilized in one case for the formation of a network structure between adjoining additive cores to derive mesoporous inorganic materials with their structures templated by the BCP. The concept of additive-driven assembly is extended to formulate BCPadditive blends with an ability to undergo photo-induced ordering. Underlying this strategy is the ability to transition a weakly interacting additive to its strongly interacting form. This strategy provides an on-demand, non-intrusive route for formation of well-ordered nanostructures in arbitrarily defined regions of an otherwise disordered material. The second area explored in this dissertation deals with the incorporation of additives into photoresists for next generation extreme ultra violet (EUV) photolithography applications. The concept of hydrogen bonding between the additives and the polymeric photoresist was utilized to cause formation of a physical network that is expected to slow down the diffusion of photoacid leading to better photolithographic performance (25-30 nm resolution obtained).

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