Dissertations / Theses: 'Amorphous structure'

1

Gibson, Andrew Stephen. "The electronic structure of amorphous graphite." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335747.

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Walters, Jennifer. "The structure of amorphous hydrogenated carbon." Thesis, University of Kent, 1995. https://kar.kent.ac.uk/38837/.

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The structure of several amorphous hydrogenated carbon (a-C:H) samples has been studied in detail using time-of-flight neutron diffraction, inelastic neutron scattering, infrared spectroscopy and reverse Monte Carlo (RMC) computer modelling. Supplementary work has also included combustion analysis. The results are presented as evidence for a new structural model for a-C:H. The high-resolution real-space neutron diffraction data allows direct determination of the single:double bond ratio, and also shows the presence of sp1 hybridised carbon bonding environments in some samples. There is limited evidence for the presence of molecular hydrogen "trapped" within the amorphous network. The spectroscopic data is then used to provide information on the C-H bonding environments, so that using a combination of experimental techniques a detailed picture of the atomic scale structure has been produced. For the hand carbon samples, prepared using acetylene and propane, the carbon-atom sites are found to be predominantly sp2 bonded, with a single:double bond ratio for carbon-carbon bonds of about 2.5:1. The effect of beam energy on the structure of the material is also investigated, and comparison made between samples prepared using a fats-atom (neutral particle)source and those prepared by plasma enhanced chemical vapour deposition, from acetylene. The results show that in both deposition methods, increasing the beam energy produces a lower total sp2 hybridised carbon content in the material with evidence for a shift from pure olefinic to some aromatic/graphitic bonding in one sample. This trend to a more aromatic bonding environment is also observed in samples prepared from a cyclohexane precursor. The spectroscopy results show that for all samples the hydrogen bonding environments are similar, although there is some evidence for changes in the distribution of hydrogen within the network with deposition energy. The spectra for all the samples show similarities to those for the polymeric materials, polyethylene and rubber. In addition, the results of a study of the structure of a-C:H up to a maximum of 1000c are presented. The data show clearly the effect on atomic correlations of elevated temperatures, with the initial room-temperature amorphous network (a mixture of single bonds and olefinic double bonds) becoming progressively aromatic, the graphite as hydrogen is evolved. Infrared spectroscopy results would seem to indicate that sp3 CH is the primary source of hydrogen for effusion, such that, on annealing, molecular hydrogen is formed wherever there are two neighboring hydrogen atoms. Structural transformations are seen to occur throughout the heating process. Finally, the RMC method has been used to produce a model for the structure of a-C:H, by fitting to experimental data from neutron and X-ray diffraction experiments. The RMC method was implemented with the introduction of additional constraints on the minimum number of atoms in a ring, and on the maximum coordination number. Once the data has been fitted, it is possible to generate model partial pair distribution functions, bond angle distributions, coordination number distributions, etc. By fitting all the experimental data sets simultaneously, there is sufficient information to generate a viable "physical" model for the structure of these materials. The effects of increasing number density within the model have also been investigated, and this confirmed that the density is a crucial parameter in the modelling process.

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3

Gilbert, D. G. "Fracture and deformation of amorphous polymers." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354673.

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4

Edwards, Ann M. "The structure of amorphous semiconductor:metal thin-films." Thesis, University of Kent, 1989. https://kar.kent.ac.uk/38702/.

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A transition from semiconducting to extend state conduction may be induced in certain amorphous semiconductor:metal alloys by increasing the metal concentration above a critical limit. Descriptions of the processes involved in such a transition have generally been based around investigations on electronic properties. However, without a knowledge of the atomic-scale structure of the alloys, it is difficult to ascribe a mechanism to an observed transition. In order to increase the understanding of such processes in semiconductor:metal systems, thin-film samples of three alloy systems (a-Si:Ni:H, a-Si:Sn:H and a-Ge:Au) have been prepared by rf co-sputtering over pertinent composition ranges, and micro-structural studies have been performed using extended X-ray absorption fine structure spectroscopy and other complementary techniques. For low metal concentrations (<20at.%), both a-Si:Ni:H and a-Ge:Au appear to consist of two separate phases: regions of an amorphous Ni:Si or a partially crystalline Au:Ge alloy being embedded in the remaining, modified amorphous matrix provided by a-Si:H and a-Ge respectively. In contrast, Sn atoms appear to substitute randomly into the a-Si:H network. The implications of these results for the interpretation of electrical conductivity data is discussed.

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Abtew, Tesfaye Ayalew. "Structure and Carrier Transport in Amorphous Semiconductors." Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1174329920.

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6

Bhattarai, Bishal. "Ab initio Structure Inversion for Amorphous Materials." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1537349044469989.

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7

Lowe, A. J. "Photostructural changes and defects in amorphous materials." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355260.

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Zeidler, Anita. "Ordering in amorphous binary systems." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501637.

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In this work the method of isotopic substitution in neutron diffraction is used to measure the partial structure factors of several binary systems. Molten sodium chloride at 820(5) °C is investigated and an improvement is made on the previously available data. The applicability of a simple model pair potential for the asymptotic decay of the pair correlation functions is discussed. The glass forming system zinc chloride is also investigated in both the molten phase at 332(5) °C and the glassy phase at 25(1) °C. The measured partial pair distribution functions show that the zinc atoms are fourfold coordinated in both the glass and the liquid and that the first sharp diffraction peak in the total structure factor is mainly due to the zinc-zinc correlations. A simple ionic model can account for several factors associated with the ultimate decay of the partial pair correlation functions.

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Atta-Fynn, Raymond. "Theory of localized electron states and novel structural modeling of amorphous silicon /." View abstract, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3203330.

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Godwin, Paul D. "Structure and properties of diamond-like carbon." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360316.

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Simmons, Jane. "The structure and function of amorphous calcium phosphate biominerals." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339520.

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12

Pickup, David M. "The structure and characterisation of amorphous transition-metal chalcogenides." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308039.

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13

Wallis, David John. "The structure of amorphous oxides and nitrides of silicon." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337313.

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14

Chen, Hsiung. "Preparation, properties, and structure of hydrogenated amorphous carbon films." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054566593.

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15

Singh, Anirudh. "The structure and optical properties of amorphous oxide films." Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/35786.

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The structure and optical bandgap properties of amorphous oxide films are studied by reference to the specific examples of r.f.-sputtered ternary a-Cex Siy Oz and binary a-SiOx : Hy thin films. Atomic structure is investigated by IR, EXAFS and Urbach edge measurements, while the bandgaps are determined from the optical absorption edge. In addition, details of the X-ray edge structure are used for the first time to obtain structural information further to that derived from EXAFS. The EXAFS study of the ternary system indicates that most films favour a continuous-random-network structure. Comparison of the optical bandgaps with the coordination numbers shows that it is the nearest-neighbour environment of Si, not Ce, that determines the former quantities. The downward shift of the IR O-stretch wSO peak position with Ce addition in these films is probably due to Ce-Si bond formation. The IR results of the a-SiOx :Hy films show a rapid reduction in film H content as the oxygen content increases, and indicates H bonded in both the mono- and di-hydride geometries. Analysis of the Si-H stretch peak fine structure points explicitly to the presence of specific tetrahedral units comprising the film structures. A combination of IR and EXAFS techniques is suggested for obtaining a detailed picture of the distribution of such microstructural units. The sensitivity of the X-ray edge features to the Si environment is used to detect small changes in its coordination due to H incorporation, as well as re-affirming the general coordination picture obtained from EXAFS. The trends in the bandgaps of the binary films with hydrogenation is shown, after a consideration of the calculated DOS in the gap region, to be due to the passivation of Si dangling bonds and replacement of weak Si-Si bonds. Oxygen 2p lone-pair interactions are identified as the major cause of bandtailing in the non-stoichiometric films, and the variation of Eo with the O/Si ratio is explained in terms of a change in connectivity of the structures. The anomalous behaviour of the stoichiometric ternary structures is attributed to the passivation of non-bridging oxygen centres by cerium.

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Elgun, Nese. "Structure and electronic properties of sputtered amorphous gap films." Thesis, University of Leicester, 1994. http://hdl.handle.net/2381/35876.

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Stoichiometric amorphous GaP films have been prepared by RF sputtering on to substrates held at temperatures from 20°C to 200 °C. Some room-temperature deposited samples were annealed at higher temperatures (200-400 °C) in vacuum. Structural, optical and electrical characterisation of these films was carried out by means of a variety of experimental techniques. Electron microscopy experiments, using both transmission electron microscope (TEM) and scanning electron microscope together with energy dispersive X-ray analyser (SEM-EDAX) have revealed that, while on the macroscopic scale the samples are homogeneous, continuous and smooth, on the microscopic scale they contain structural inhomogeneities, namely voids, and a small degree of compositional non-uniformity. Extended X-ray absorption fine structure (EXAFS) spectroscopy has provided information on the atomic structure of the films, in particular on the short-range order around both Ga and P atoms. It was found that the a-GaP network is four-fold coordinated and chemically ordered, i.e. wrong bonds, Ga-Ga and P-P bonds, do not exist. In addition the technique revealed very little disorder in the bond length but wide distributions in the bond angles, the latter being more pronounced around P atoms than around Ga atoms. Information on the short-range atomic structure has been obtained from infrared (IR) spectroscopy through the identification of the vibrational modes of the bonds. The main finding of these measurements was that the a-GaP network is chemically ordered, which is consistent with the EXAFS work. From a combination of conventional reflection-transmission (R-T) and the most recently developed photothermal deflection spectroscopy (PDS) techniques, the absorption coefficient in the range of 10 cm-l < 10.;5 cm-1, the refractive index and values ofthe optical gap were determined. The results are explained in terms of the nature and distribution in energy of the density of states (DOS) in the forbidden gap. The DOS in the conduction band is also extracted from the X-ray absorption near edge structure (XANES) data, which is combined with the DOS-valence band information taken from the literature to obtain full details of the electronic structure of a-GaP. D.c conductivity measurements at high- and low-temperatures showed a continuously varying activation energy. This was interpreted as a transport mechanism taking place in a band tail but in which the conduction path moves downwards in the tail as T is lowered.

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17

Mountjoy, Gavin. "Diffraction and microscopy studies of the structure of amorphous solids." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362969.

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Wetherall, Kate M. "The Structure of Amorphous Calcium Phosphate and othe phosphate materials." Thesis, University of Kent, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520863.

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19

Hellrup, Joel. "Pharmaceutical Nanocomposites : Structure–Mobility–Functionality Relationships in the Amorphous State." Doctoral thesis, Uppsala universitet, Institutionen för farmaci, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-300159.

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Amorphous materials are found in pharmaceutical formulations both as excipients and active ingredients. Indeed, these formulations are becoming an essential strategy for incorporating drugs into well-performing solid dosage forms. However, there is an unmet need of better understanding of the microstructure and component interactions in amorphous formulations to be able to design materials with improved functionalities. The aim of this thesis is to give deepened knowledge about structure-mobility-functionality relationships in amorphous for-mulations by studying composites produced from sugars and filler particles. The structure, the mobility, and physical stability of the composite materials were studied using calorimetry, X-ray diffraction, microscopy, spectroscopy, and molecular dynamics simulations. Further, the moisture sorption of the composites was determined with dynamic vapor sorption. The compression mechanics of the composites was evaluated with compression analysis. It was demonstrated that fillers change the overall properties of the amorphous material. Specifically, the physical stability of the composite was by far improved compared to the amorphous sugar alone. This effect was pronounced for formulations with 60 wt% filler content or more. Amorphous lactose that normally recrystallizes within a few minutes upon humidity exposure, could withstand recrystallization for several months at 60% RH in composites with 80 wt% cellulose nanocrystals (CNC) or sodium montmorillonite (Na-MMT). The increased physical stability of the amorphous sugars was related to intra-particle confinement in extra-particle voids formed by the fillers and to immobilization of the amorphous phase at the surface of the fillers. Also, the composite formation led to increased particle hardness for the lactose/CNC and the lactose/Na-MMT nanocomposites. The largest effect on particle hardness was seen with 40-60 wt% nanofiller and could be related to skeleton formation of the nanofillers within the composite particles. The hygroscopicity for the lactose/Na-MMT nanocomposites decreased as much as 47% compared to ideal simple mixtures of the neat components. The nanofillers did not influence the water sorption capacity in the amorphous domains; however, lactose (intercalated into Na-MMT) interacted with the sodium ions in the interlayer space which led to the lowered hygroscopicity of this phase. The thesis advanced the knowledge of the microstructure of amorphous pharmaceutical com-posites and its relationship with pharmaceutical functionalities. It also presented new approaches for stabilizing the amorphous state by using fillers. The concept illustrated here might be used to understand similar phenomena of stabilization of amorphous formulations.

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Liu, Richard Yufeng. "Oxygen Transport as a Structure Probe for Amorphous Polymeric Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1103694304.

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21

Choi, Jaeho. "Structure and properties of amorphous GexSe1-x and related alloys." Thesis, University of Leicester, 1996. http://hdl.handle.net/2381/35855.

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Un-hydrogenated and hydrogenated a-GexSe1-x films (0.2 x 1) have been prepared by radio-frequency sputtering at room temperature employing an r.f. power of 240 W and an Ar pressure of 3-6 mTorr. Zn-alloyed films, a-GexSeyZnz, were deposited under the same conditions, with Zn concentrations up to 27%. The compositions of the films were determined by an energy dispersive X-ray analyser (SEM-EDAX) attached to a scanning electron microscope. Optical absorption edges of the a-GexSe1-x samples have been deduced from reflection-transmission (R-T) spectra and photo-thermal deflection spectroscopy (PDS) measurements. The optical bandgaps, other parameters related to the edges, and the real part of the refractive index were determined and analysed. The effects of hydrogenation on the a-GexSe1-x films are investigated by analysing their optical absorption edges and measurements of the d.c. electrical conductivity as a function of temperature. The optical and electrical properties of a-GexSeyZnz films were studied and the effects of Zn addition to GeSe films analysed from the behaviour of the optical gap and the activation energy in the d.c. electrical conductivity. Extended X-ray absorption fine structure (EXAFS) measurements have been performed on both a-GexSe1-x and a-GexSeyZnz films. Information on the local atomic structure, e.g. the nearest-neighbour bond length and the coordination number, has been extracted from the data and is discussed in detail. In particular, the experimentally determined partial coordination numbers are compared with those predicted by two models, the chemically ordered bond network (OBN) and random bond network (RBN) structures. The results reveal that the a-GexSe1-x films have a chemically ordered 4-2 covalent bond network structure throughout the whole composition range and that Zn replaces the Ge atoms and is four-fold coordinated. The dielectric functions of the a-GexSe1-x alloys is modelled and the calculated optical properties compared with the experimental results. Good agreement is found.

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22

Miller, Jason. "Devitrification Effects on the Structure and Corrosion of an Fe-based Bulk Metallic Glass." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1252371978.

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Thesis(M.A.)--Case Western Reserve University, 2010
Title from PDF (viewed on 2010-01-28) Department of Materials Science and Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center

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23

Ludl, Adriaan-Alexander. "Etude du diagramme de phases des solutions d'électrolytes sous conditions extrêmes." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066303/document.

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L’étude des phases amorphes et cristallines de solutions permet est d'un fort intérêt pour la biologie et la planétologie. Le but de cette thèse est l’exploration du diagramme de phase des solutions d’électrolytes (LiCl et NaCl dans l’eau) sous des conditions de pression et température typiques des corps glacés tels Europe et Ganymède (de 77 à 300 K et jusqu’à 5 GPa). Nous avons étudié des phases de glaces amorphes et cristallines pouvant incorporer des quantités considérables de sel (jusqu’à 10 % de masse de sel). En outre de la mise en évidence de phases de glace salées, nous avons caractérisé deux propriétés exotiques induites sous pression, à savoir le polyamorphisme et l’inclusion des ions dans le réseau de la glace. Nous avons produit des échantillons de phase amorphe de solutions de NaCl dans l’eau par trempe rapide à 77 Kelvin. Nos expériences de diffraction de neutron et de rayons X montrent que la structure locale de cette phase amorphe est très similaire de celle de la phase haute densité de l’eau pure. Nos expériences haute pression avec la presse Paris-Edinbourg et nos calculs de dynamique moléculaire montrent que la densité et la structure évoluent de manière continue en compression jusqu’à 4 GPa. La possibilité d’inclusion du sel (NaCl) dans le réseau de la glace VII sous pression dans nos expériences est analysée en comparaison avec des simulations utilisant la théorie de la densité fonctionnelle. La glace VII qui cristallise dans nos expériences est soit pure, soit elle contient une fraction faible des ions de la solution mère. Il est possible que des quantités de sel plus grandes puissent être incorporées à des pressions plus élevées
The study of amorphous and crystalline phases of solutions gives essential insight on the behaviour of water under conditions relevant for biology and planetary science. The aim of this work is the exploration of the phase diagram of common electrolyte solutions (LiCl-water, NaCl-water) under pressure and temperature conditions (from 77 K to 330 K and up to 5 GPa) relevant for icy bodies such as Europe and Ganymede. In experiments and simulations we search for crystalline phases of ice at high-pressure, which can contain considerable amounts of salt in their lattice (up to 10 % of by weight). We probe the existence of these salty ices, and characterize two exotic, pressure induced properties, polyamorphism and ionic inclusions in the ice lattice. We have produced highly concentrated amorphous solutions of NaCl in water by fast quenching to liquid nitrogen temperature. Our neutron and X-ray diffraction experiments show that the local structure of this amorphous solution at ambient pressure is very similar to the high density amorphous structure of pure water. Our high-pressure experiments with the Paris-Edinburgh cell and our classical Molecular Dynamics calculations show only smooth structure and density changes during compression up to 4 GPa. We discuss the possibility of salt (NaCl) inclusions in the ice VII lattice at high pressure in our experiments by complementary calculations based on Density Functional Theory. The ice VII which crystallized in our experiments is either pure ice, or it contains only a small fraction of the ions from the solution. It may be possible that ions can be included in larger quantities at higher pressures

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24

Yasuda, Kazuharu. "Development of controlled structure polymers : physical property and microstructure control of injection mouldings." Thesis, Brunel University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311274.

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Castano, Fernando J. "Structure and thermo-magnetic properties of amorphous thin films and multilayers." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267189.

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Stephan, Uwe. "Theoretical methods and results for electronic-structure investigations of amorphous carbon." [S.l. : s.n.], 1996. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10324488.

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Edling, Hans Eliot. "Synthesis and Structure-Property Relationships of Polyesters Containing Rigid Aromatic Structures." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/95029.

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Polyesters are an attractive class of polymer that can be readily modified with a wide range of different comonomers, during polymerization or with melt blending, to achieve a wide variety of physical properties. This research primarily focuses on polyesters that incorporate rigid aromatic structures that have excellent potential to enhance thermal and mechanical properties. Copolyesters were prepared through melt polycondensation of diesters and diols in the presence of an exchange catalyst. Monomer incorporation was verified with nuclear magnetic resonance (NMR) and molecular weights were obtained by measuring inherent viscosity (ninh). Physical properties were assessed with thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheology. Mechanical properties were assessed with tensile and impact testing. Copolyesters of poly(ethylene terephthalate) (PET) were synthesized by substituting dimethyl terephthalate (DMT) with dimethyl 4,4'-biphenyldicarboxylate (4,4'BB) resulting in enhanced glass transition (Tg) temperatures relative to PET while affording melting temperatures (Tm) low enough to allow facile melt processing. Further modification with dimethyl isophthalate (DMI) or dimethyl 3,4'-biphenyldicarboxylate (3,4'BB) slowed crystallization sufficiently to allow biaxial orientation, leading to further studies assessing the permeability of oriented films. Novel amorphous polyesters were synthesized with 3,4'BB or 4,4'BB in combination with neopentyl glycol (NPG), 1,4-cyclohexandimethanol (CHDM) and ethylene glycol (EG). Use of multiple diols produced clear, amorphous copolyesters with Tgs as high at 129 C. A series of novel high temperature(Tm) copolyesters were synthesized from dimethyl 2,6-naphthalenedicarboxylate (DMN) and 4,4'BB combined with CHDM. Studies were performed with standard DSC and thin film calorimetry to show the convergence of multiples melting endotherms in an effort to determine their origin. Preliminary work was performed on the modification of poly(1,4-cyclohexylenedimethylene terephthalate) (PCT), poly(1,4-cyclohexylenedimethylene 2,6-naphthalate) (PCN) and poly(1,4-cyclohexylenedimethylene 4,4'-bibenzoate) (PCB) with dimethyl p-terphenyl-4,4''-dicarboxylate.
PHD

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Cai, Bin. "Model Design and Analysis for Amorphous Materials." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1311192632.

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Rapold, Roland Fritz. "Atomistic simulation of the structure and ring motion of dense, amorphous polystyrene /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10308.

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Walton, Richard I. "The characterisation and structure of amorphous and poorly crystalline transition-metal chalcogenides." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388467.

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Erslev, Peter Tweedie 1979. "The electronic structure within the mobility gap of transparent amorphous oxide semiconductors." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10566.

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xix, 142 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Transparent amorphous oxide semiconductors are a relatively new class of materials which show significant promise for electronic device applications. The electron mobility in these materials is at least ten times greater than that of the current dominant material for thin-film transistors: amorphous silicon. The density of states within the gap of a semiconductor largely determines the characteristics of a device fabricated from it. Thus, a fundamental understanding of the electronic structure within the mobility gap of amorphous oxides is crucial to fully developing technologies based around them. Amorphous zinc tin oxide (ZTO) and indium gallium zinc oxide (IGZO) were investigated in order to determine this sub-gap structure. Junction-capacitance based methods including admittance spectroscopy and drive level capacitance profiling (DLCP) were used to find the free carrier and deep defect densities. Defects located near insulator-semiconductor interfaces were commonly observed and strongly depended on fabrication conditions. Transient photocapacitance spectroscopy (TPC) indicated broad valence band-tails for both the ZTO and IGZO samples, characterized by Urbach energies of 110±20 meV. These large band-tail widths imply that significant structural disorder exists in the atomic lattice of these materials. While such broad band-tails generally correlate with poor electronic transport properties, the density of states near the conduction band is more important for devices such as transistors. The TPC spectra also revealed an optically active defect located at the insulator-semiconductor junction. Space-charge-limited current (SCLC) measurements were attempted in order to deduce the density of states near the conduction band. While the SCLC results were promising, their interpretation was too ambiguous to obtain a detailed picture of the electronic state distribution. Another technique, modulated photocurrent spectroscopy (MPC), was then employed for this purpose. Using this method narrow conduction band-tails were determined for the ZTO samples with Urbach energies near 10 meV. Thus, by combining the results of the DLCP, TPC and MPC measurements, a quite complete picture of the density of states within the mobility gap of these amorphous oxides has emerged. The relationship of this state distribution to transistor performance is discussed as well as to the future development of device applications of these materials.
Committee in charge: Stephen Kevan, Chairperson, Physics; J David Cohen, Member, Physics; David Strom, Member, Physics; Jens Noeckel, Member, Physics; David Johnson, Outside Member, Chemistry

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Lee, Sang Joon. "Structure and Interaction Energies of Kr Atoms Adsorbed on Graphitic Amorphous Carbon." DigitalCommons@USU, 1995. https://digitalcommons.usu.edu/etd/2091.

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The physisorption of Kr on graphitic amorphous carbon (g-C) has been investigated using a statistical approach. The interaction energy calculation process (i) established a structural model of g-C and (ii) determined the adsorbate-adsorbate and the adsorbate-substrate interaction potentials on g-C. The structural model of g-C was divided into three regions. For the interaction potential between a Kr atom and a carbon atom the short and medium range order of g-C was described with a discrete medium model based on three ring clusters using ring statistics from Beeman's continuous random network C1120 model of g-C. For the intermediate distance region, Beeman's radial distribution function was used to model g-C. A homogenous and isotropic continuous medium model was used at large distances. The Kr-Kr and Kr-g-C interaction potentials used for Kr on g-C, which are pair-wise Lennard-Jones 6-12 potentials, are similar to Kr on graphite potentials. the validity of the model for g-C and the potentials were verified though calculations for Kr on graphite. Results compared favorably with recent literature values. The interaction energy calculation results for Kr on a g-C substrate assert that (i) Kr adlayers will form on g-C, (ii) the structure of the Kr adlayer is governed by the substrate corrugation at low coverage and by the Kr-Kr interaction at high coverage, and (iii) there is no direct relation between the structure of Kr adlayers on g-C and those on graphite. The average binding energy of Kr on g-C is comparable with that on graphite, but the corrugation of g-C is perhaps six times that of a graphite substrate. The wrinkling of the g-C surface, due to the presence of a distribution of 5-, 6-, and 7- membered rings, is responsible for this large corrugation of the g-C substrate.

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33

Hassanali, Ali. "WATER AT MOLECULAR INTERFACES: STRUCTURE AND DYNAMICS NEAR BIOMOLECULES AND AMORPHOUS SILICA." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275314943.

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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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Kang, Yixiu. "Deposition and Characterization of Amorphous GaN Thin Films." Ohio University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1020266055.

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36

Zeagler, Andrew. "Structure and Processing Relations in Ni-W Amorphous Particle Strengthened Ni Matrix Composites." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/36084.

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Reinforcing metals with compositionally similar amorphous particles has been found to create composites with good interfacial bonding. It is conceivable that significant additional strengthening in amorphous reinforced composites can be realized by creating high-aspect ratio reinforcements; attritor milling holds promise in this regard. In this work, mechanical alloying was used to produce equimolar Ni-W powder that became a composite of amorphous Ni-W with undissolved W crystallites. A mixture of nickel powder and ten volume percent amorphous Ni-W powder was blended by attritor milling for either one or three hours, compacted by combustion-driven compaction and sintered for up to fifty hours at 600ÂºC. Prolonged times at elevated temperatures led to crystallization of the amorphous reinforcement particles and dissolution of tungsten into the matrix. Vickers macrohardness tests on the sintered composites yielded lower-than-expected values. Microscopy after hardness testing revealed sliding of particles at their boundaries, indicating poor bonding between them. It is believed that the sintering process was compromised by contamination from organic vapor present in the tube furnace used. While attritor milling effected smaller reinforcement particles, the small increase in aspect ratio would likely have been insufficient to cause significant strengthening by shear load transfer.
Master of Science

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37

Palma, Joseph John. "X-ray Diffraction Studies of Amorphous Materials." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/231213.

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Physics
Ph.D.
This thesis presents a study on two types of X-ray diffraction methodologies applied to the characterization of amorphous materials. The purpose of this study was to assess the feasibility of measuring the diffractive spectrum of amorphous materials by Energy-Dispersive X-ray Diffraction (EDXRD) utilizing Cadmium Zinc Telluride detectors. The total scattering intensity (coherent plus incoherent scatter) spectra precisely measured by high-energy Wide-Angle X-ray Scattering (WAXS) were compared to the EDXRD spectra to determine the level of agreement between the two techniques. The EDXRD spectra were constructed by applying a spectra fusing technique which combined the EDXRD spectra collected at different scattering angles rendering a continuous total scattering spectrum. The spectra fusing technique extended the momentum transfer range of the observed scattered spectrum beyond the limitations of the X-ray source and CZT detection efficiencies. Agreement between the WAXS and fused EDXRD spectra was achieved. In addition, this thesis presents the atomic pair correlation functions and coordination numbers of the first coordination shell for four hydrogen peroxide solutions of varying mass concentrations using Empirical Potential Structural Refinement (EPSR). The results are compared to the state-of-the art ad initio quantum mechanical charge field molecular dynamics (QMCF MD) model of the hydrogen peroxide in solution to support the model's predictions on why hydrogen peroxide is stable in water. The EPSR results using the coherent scattering intensity calculated from the WAXS data set predicts a hydration shell of 6.4 molecules of water surrounding hydrogen peroxide. The results also indicate that hydrogen peroxide is more likely to behave as a proton donor than acceptor. These findings are in agreement with QMCF MD model of aqueous hydrogen peroxide.
Temple University--Theses

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38

Hardian, Rifan. "Interplay between structure, texture, and reactivity in MOFs in the case of amorphous, defective, and composite materials." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0419/document.

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Metal-Organic Frameworks (MOFs) sont constitués de clusters métalliques connectés dans les ligands organiques. L'objectif principal de ma thèse était de caractériser la texture, la structure et la réactivité des MOFs dans le cas de systèmes présentant des défauts, amorphes et composites.La première étude est centrée sur les propriétés de la famille Fe-BTC et ce travail a été réalisé en collaboration avec l'Université d'Utrecht et l'Université d'Oxford. Une étude comparative entre le MIL-100(Fe) et son homologue commercial Basolite F300 (BASF) qui est amorphe ont été évaluées par l’adsorption de méthanol et d'autres techniques de caractérisation. De plus, les deux matériaux ont été testés pour être utilisés comme support pour l'imprégnation des métaux.Dans la deuxième étude, le broyage à la bille est utilisé comme stratégie de modification post-synthèse de MOFs. Le matériau ZIF-8 a été sélectionné de cas car il s'agit d'un MOF disponible dans le commerce (Basolite Z1200) et qui est en train de devenir de référence dans ce domaine. Ce chapitre examiner des propriétés flexibles, de la texture, de la structure, et la réactivité.Les MOFs UiO-66 et MOF-808 sont également analysées. Ces études ont été réalisées en collaboration avec l'Université Technique de Munich. UiO-66 contenant différents défauts d'ingénierie sont examinées. Nous avons démontré que les mesures d’adsorption de vapeur peuvent être un outil précieux pour accéder à la chimie des défauts. Le deuxième système est la série MOF-808 qu’une étude complète est présentée allant des diverses stratégies de synthèse de MOFs défectueux et composites jusqu'à leur propriété d'adsorption et de réactivité
Metal-organic frameworks (MOFs) are a class of porous materials that constructed from metal clusters connected with organic linkers. The main objective of my PhD was to characterize the texture, structure, and reactivity of MOFs materials with a particular focus on defective, amorphous and composite materials. The first study is centered on the properties of the Fe-BTC family and this work was realized in collaboration with Utrecht University and the University of Oxford. A comparative study between crystalline MIL-100(Fe) and its commercial counterpart amorphous Basolite F300 (BASF) were studied by using methanol adsorption to predict the reactivity. Other characterization methods are introduced to investigate both materials which were further tested to be used as supports for metal-impregnation. In the next study, ball-milling was employed as a post-synthesis strategy for MOF modification. This ZIF-8 material was selected since it is commercially available (Basolite Z1200) and is becoming one of the reference materials in this area. Extensive studies including flexibility, textural, structural, as well as reactivity of different milling products is presented. Zirconium-based MOFs (UiO-66 and MOF-808) were also examined in this thesis. These studies were performed in collaboration with TU Munich. UiO-66 series containing engineered defects are first examined. We demonstrated that vapor adsorption measurement is a valuable tool to access the chemistry of the defects. The second studied system is MOF-808 series, where a comprehensive study is presented starting from synthesis strategies of defective and composite MOFs up to adsorption properties and reactivity

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39

Ali, Fatmah Abdullah Haider. "Examination of atomic scale structure and dynamics of amorphous materials by solid state NMR." Thesis, University of Kent, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481489.

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Mead, Robert Nielle. "Molecular dynamics modelling of the amorphous calcium silicate and titania silicate atomic-scale structure." Thesis, University of Kent, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443767.

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41

Tanaka, Katsuhisa. "ESR AND MOSSBAUER STUDIES ON STRUCTURE AND MAGNETIC PROPERTIES OF IRON-CONTAINING AMORPHOUS OXIDES." Kyoto University, 1990. http://hdl.handle.net/2433/74576.

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42

Van, Order Jon P. "Molecular modeling of intermediate order in polymer glasses." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10134.

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43

Liu, Yanchun. "Synthesis and Characterization of Amorphous Cycloaliphatic Copolyesters with Novel Structures and Architectures." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77999.

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A series of random and amorphous copolyesters containing different cycloaliphatic rings within the polymer chains were prepared by melt polycondensaton of difunctional monomers (diesters and diols) in the presence of a catalyst. These polyesters were characterized by nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile tests and/or dynamic mechanical analysis (DMA). The copolyester based on dimethyl bicyclo[2.2.2]octane-1,4-dicarboxylate (DMCD-2) was observed to have a higher Tg, about 115ºC, than the other copolyesters with the same compositions in this study. For copolyesters containing different compositions of dimethyl-1,4-cyclohexane dicarboxylate (DMCD) and DMCD-2, the Tg increased linearly with the increase of DMCD-2 mole content. DMA showed that all of the cycloaliphatic copolyesters had secondary relaxations, resulting from conformational transitions of the cyclohexylene rings. The polyester based on DMCD-3 in the hydrolytic tests underwent the fastest hydrolytic degradation among these samples. A new triptycene diol (TD) was synthesized and incorporated into a series of cycloaliphatic copolyester backbones by melt condensation polymerization. Straight chain aliphatic spacers, including ethylene glycol (EG), 1,4-butanediol (BD) and 1,6-hexanediol (HD), were used as co-diols to explore their effects on polyester properties. An analogous series of non-triptycene copolyesters based on various hydroxyethylated bisphenols were also prepared for comparison. The results revealed that the TD-containing polymers had higher thermal stability and higher Tg's than the corresponding non-TD analogs. For TD-containing copolyesters, the mechanical properties were found to be dependent on the types and compositions of the co-diols. A 1,4-butanediol-based triptycene copolyester was observed to have a significantly increased Tg and modulus while maintaining high elongation at ambient temperature. Furthermore, it was demonstrated that the triptycene polyester exhibited higher Tg and modulus than those containing bisphenol derivatives. However, all of the 1,4-butanediol based copolyesters were brittle and had comparable moduli at low temperatures (-25°C or -40 °C). Melt polycondensation was also used to prepare a series of all-aliphatic block and random copolyesters including the following aliphatic monomers: trans-DMCD, DMCD-2, neopentyl glycol (NPG), diethylene glycol (DEG) and dimethyl succinate (DMS). The polymer compositions were determined by 1H NMR, and the molecular weights were determined using SEC. The polyesters were also characterized by TGA, DSC, DMA and tensile tests. Phase separation was not observed in these block copolyesters. However, the block copolyester containing DMCD-2 and NPG was observed to have a higher Tg than the block copolyester based on trans-DMCD and NPG. In addition, these block copolyesters were found to have better mechanical properties than the corresponding random copolyesters.
Ph. D.

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44

Vrana, Semir [Verfasser], and Helmut [Akademischer Betreuer] Kohl. "Characterization of amorphous materials using the three particle structure factor / Semir Vrana ; Betreuer: Helmut Kohl." Münster : Universitäts- und Landesbibliothek Münster, 2021. http://d-nb.info/1236632389/34.

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45

Mohamed, Raja Roslan Raja. "Structure-property relationships in biaxially stretched amorphous PET applicable to thermoforming and stretch blow moulding." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728400.

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In thermoforming and Injection stretch blow moulding, amorphous Polyethylene terephthalate (aPET) is stretched to form products. While stretching, the microstructures change and have influence on final product properties. Therefore, the main aim of this work was to provide a fundamental understanding of microstructures evolvement during biaxial stretching of aPET in conditions applicable to thermoforming and injection stretch blow moulding as well as their effect on thermal and mechanical properties. Specimens were cut out from a commercial grade extruded aPET sheets which has a similar intrinsic viscosity to injection stretch blow moulding (ISBM) aPET and stretched using Queen's Biaxial Stretching machine under various sets of parameters namely temperature, strain rate, stretch ratio and mode of stretching, whilst mimicking the industrial processing conditions. The stress-strain behaviour during stretching was then analysed. The stretched specimens were then characterised employing a Fourier Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) for gauche and trans conformers, a Differential Scanning Calorimeter for heat-crystallisable content, crystallinity and thermal properties, FTIR-ATR with polariser for orientation parameters, and a tensometer for mechanical properties. Statistical tools were also employed to determine the significance of changes and correlate the structural changes as well as the thermal and mechanical properties. The onset of strain hardening that impedes viscous flow during stretching can be attributed to the intermolecular attractions between the aligning and orientating chain. This is a new perspective on what may cause strain hardening. The structural changes may have good linear correlation between each other, depending on the stretching parameters employed. The heat-crystallisable region was found to be the determining factor in strain induced crystallisation as well as the stretching parameters. The relationship between the properties, thermal and mechanical, is determined by complex interactions between the measured structural characteristics.

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46

Srivastava, Deepansh. "NMR methods and analysis for determining correlated structural distributions in amorphous solids." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531928644070636.

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47

Sagnes, Emmanuel. "Influence of DC saddle-field discharge deposition parameters on the structure of hydrogenated amorphous carbon semiconductor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0008/NQ41501.pdf.

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48

Jensen, Anders Christian Solberg [Verfasser], and Markus [Akademischer Betreuer] Antonietti. "Structure and dynamics of amorphous carbonates related to biomineralization / Anders Christian Solberg Jensen ; Betreuer: Markus Antonietti." Potsdam : Universität Potsdam, 2018. http://d-nb.info/1219077933/34.

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49

Sapelkin, Andrei V. "Structure of and phase transformations in bulk amorphous (GaSb)â†1â†-â†x(Geâ†2)â†x." Thesis, De Montfort University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391341.

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50

Triana, Carlos A. "Atomic short-range order, optical and electronic properties of amorphous transition metal oxides : An experimental and theoretical study of amorphous titanium aTiO2 and tungsten aWO3 solid thin-film oxides." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-318193.

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Amorphous transition metal oxides [aTMOs], have emerged as innovative functional materials for wide-ranging electronic, optical and energy-related applications. However, no systematic and broadly applicable method exists to assess their atomic-scale correlations, and since the optical and electronic processes are local structure-dependent, still there are not well-stablished mechanisms that suitably explain the physical properties of aTMOs. This thesis presents experimental and theoretical studies of the atomic short-range order, optical and electronic properties, and state-defects induced by Li+-ion-intercalation and oxygen-vacancies in amorphous titanium aTiO2 and tungsten aWO3 thin-film oxides. Those properties play a key role for application in high energy-density Li+-ion batteries and in switchable dynamical modulation of solar-irradiation transmittance for energy efficient "smart windows", where the disorder-dependent Li+-ion-intercalation and oxygen-vacancy-induced defect-states influence charge-carrier transfer mechanisms. After introducing the scope of this thesis, the fundamental theoretical concepts describing the experimental findings on amorphous solids are reviewed. Thereafter, a comprehensive analysis on the optical absorption phenomena experimentally observed in oxygen-deficient and Li+-ion-intercalated aLixTiO2−y and aLixWO3−y thin-films and a discussion on the electrochromic properties are presented. The optical absorption is described in the framework of the small polaron absorption model. Finally, a state-of-the-art systematic procedure involving theory and experiment in a self-consistent computational framework is implemented to unveil the atomic-scale structure of aTiO2 and aWO3, and its role for the electronic properties. The procedure is based in Reverse Monte Carlo [RMC] and Finite Difference Method [FDM] simulations of X-ray-Absorption spectra to construct a disordered theoretical model having the same bonding and coordination distribution as the experimental system. Ab-initio molecular dynamics simulations and density functional theory are then used to assess defect-states induced by Li+-ion-intercalation and oxygen-vacancies in aTiO2 and aWO3 oxides. The schemes introduced in this study offer a consistent route to experimentally and theoretically assess the role of the atomic-scale structure on the optical and electronic properties of aTiO2 and aWO3 and could be extended to the study of other aTMOs. The final results provide crucial insight towards the understanding of optical and electronic mechanisms where disorder-dependent ion-intercalation and oxygen-vacancy-induced localized defect-states influence charge transfer mechanisms of crucial importance for wide ranging optical and energy-related application of aTiO2 and aWO3 oxides.

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Dissertations / Theses on the topic 'Amorphous structure'

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