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1
Maggio, Mario. « Carbon-based nanomaterials ». Doctoral thesis, Universita degli studi di Salerno, 2017. http://hdl.handle.net/10556/2482.
Texte intégralRésumé :
2014 - 2015New layered carbon-based materials were prepared and exhaustively characterized exploiting different characterization techniques, such as thermogravimetry (TGA), differential thermal calorimetry (DSC), Fourier transform infrared (FTIR) and wide angle X-ray diffraction (WAXD). Pristine graphite (G) with high surface area and carbon black (CB) samples with different surface areas were selected as starting materials to prepare the corresponding oxidized samples, i.e. graphite oxide (GO) and carbon black oxide (oCB), with the Hummers’ method. Thanks to the strong hydrophilicity and to the lamellar structure of oxidized carbon-based materials, a rich intercalation chemistry is permitted. In fact, after treatments of GO and oCB by strong basis, ordered intercalation compounds have been obtained, not only if the starting material is crystalline like graphite oxide, but also if it is completely amorphous like oxidized carbon black. Starting basified GO, free-standing papers can be obtained by vacuum filtration, as well as by casting procedure, of colloidal dispersions of graphene oxide sheets. The use of basified GO leads to more flexible, solvent resistant and thermally stable GO papers. Spectroscopic analyses of the obtained papers have been conducted aiming to a possible rationalization of the observed behavior. [edited by author]
Per questo lavoro di tesi di dottorato, sono stati preparati nuovi nanomateriali basti su carbonio ed esaustivamente caratterizzati con tecniche quali termogravimetria (TGA), calorimetria a scansione differenziale (DSC), spettroscopia infrarossa (FT-IR) e diffrazione dei razzi X (WAXD). I materiali di partenza utilizzati per questo lavoro di tesi, sono stati la grafite ad alta area superficiale e carbon black con differenti valori di area superficiale, al fine di ottenere i corrispondenti materiali ossidati quali ossido di grafite (GO) e carbon black ossidato (oCB). Il metodo utilizzato per le ossidazioni dei suddetti starting materials è quello di Hummers. Grazie alla forte idrofilicità ed alla struttura lamellare posseduta dai materiali carboniosi ossidati, è possibile ottenere svariati composti di intercalazione trattando il GO (cristallino) e l’oCB(amorfo) con basi forti e con conseguente funzionalizzazione ionica con cationi di natura organica. Inoltre, partendo da dispersioni di GO basificato, sono stati ottenuti fogli di ossido di grafite e di grafene mediante filtrazione e/o per lenta evaporazione del solvente. Utilizzando una base nella procedura di ottenimento dei cosiddetti fogli di ossido di grafite/grafene, sono stati preparati campioni free-standing con elevata flessibilità, resistenza ai solventi e alle alte temperature. [a cura dell'autore]
XIV n.s.
2
Chatakondu, Kalyan. « Organometallic intercalation chemistry ». Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258017.
Texte intégral
3
Duggan, Andrew Charles. « Fullerene intercalation chemistry ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298749.
Texte intégral
4
Henry, Paul Francis. « Fullerene intercalation chemistry ». Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363757.
Texte intégral
5
Saidi, Mohammed-Yazid. « Electrochemistry of intercalation ». Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/845.
Texte intégral
6
Laugaa, Philippe. « De la mono-intercalation à la tris-intercalation dans l'ADN : aspects physicochimiques et biologiques ». Paris 6, 1988. http://www.theses.fr/1988PA066666.
Texte intégral
7
Formstone, Carl. « Electronic structure of intercalation compounds ». Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276842.
Texte intégral
8
Denning, Mark Simon. « Intercalation chemistry of higher fullerenes ». Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343444.
Texte intégral
9
Wu, Qi-Hui. « Photoelectron Spectroscopy of Intercalation Phases ». Phd thesis, [S.l. : s.n.], 2003. http://tuprints.ulb.tu-darmstadt.de/342/1/Wu-Qihui-diss.pdf.
Texte intégralRésumé :
V2O5 and LiMn2O4 are promising cathode materials for lithium-ion batteries due to their high capacities and battery voltages. The several work was mainly focused on the study of electrochemical and structural properties during lithium intercalation. But there is no detailed knowledge of the changes in electronic structure and the intercalation mechanism itself. Especially no general agreement has been reached on the nature and the extent of the interactions between host material and alkali guest atoms. This thesis addresses the electronic stucture of transition-metal oxides and its changes during the intercalation of alkali metals. The intercalation of Na and Li into V2O5 thin films and LiMn2O4 powder samples have been studied mainly using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and resonant photoemission spectroscopy (RPES). The PVD prepared V2O5 thin films are nearly stoichiometric with only about 4% oxygen deficiency. After deposition onto the HOPG substrate, the oxide surface is smooth and polycrystalline. The valence band of V2O5 is formed by the hybridisation of the O2p and V3d electron states. It has been shown by RPES that the V3d admixture to the valence band is about 20%. Therefore, the real electron occupation number of the 3d electron state of the V ions in V2O5 is about 2 instead of 0, and the simple ionic model is not valid. The influence of heating on the V2O5 films has also been studied. Elevated temperatures lead to sub-stoichiometric V2O5-x that can be probed by chemically shifted components in the V2p3/2 emission line, and a decrease of O1s/V2p intensity ratios. Annealing of the sub-stoichiometric films at 400°C in an oxygen atmosphere lead to the reoxidation of vanadium to its higher oxidation state. The alkali metals are instantaneously intercalated into V2O5 when they are deposited onto the surface at room temperature. Only a small amount (about 10%) of the alkali metal atoms remain adsorbed on the surface due to the intercalation kinetics. The results obtained in this work demonstrate that the electrons of intercalated alkali metals s orbitals are mostly transferred to the transition-metal 3d orbitals and cause the reduction of the transition-metal ions as proven by the XPS and UPS data. The values of effective electron transfer for Na3s and Li2s are about 0.42 and 0.55 electrons per alkali atom, respectively. With low content of intercalated alkali metals, the electronic and crystalline structure of the host do not change considerately. For Na, an alkali saturation concentration of V2O5 films can be reached as Na1.4V2O5 without decomposition of the host, for Li, this saturation value is about Li2.5V2O5. When this limit for alkali intercalation is reached, further deposition of alkali atoms will not intercalate into the host but form oxides, peroxides and even metallic alkali on the surface. The formation of surface oxide films on the electrodes would have a severe impact on battery performance. A better understanding of such films can be essential to solve the stability problem of lithium-ion batteries, such as capacity loss, power-fade, poor cyclability, and self-discharge. After the over-intercalated samples have been kept in the ultra-high vacuum chamber for few days, the alkali metal will react further with vanadium oxides and form alkali oxides and peroxides on the surface. In this work, we have clearly demonstrated the formation of alkali oxides and peroxides species, which are probably part of the so-called solid electrode interface (SEI) layers. Finally, the electronic structure and surface composition of LiMn2O4 powder has been studied. The results show that manganese ions exist in two oxidation states: a trivalent state (Mn3+) as well as a tetravalent state (Mn4+). The photoemission intensity ration of Mn3+ to Mn4+ is about 0.9, so that the average oxidation state is 3.55 which is a little higher than the expected value of +3.5 which is probably due to small amounts of lithium oxides formed on the surface. UPS and RPES indicate that the Mn ions are in a high spin configuration, and O2p and Mn3d orbitals are strongly hybridised.
10
Schelfhout, Carla Roberta Maria. « Intercalations in Dutch ». [S.l. : Nijmegen : s.n.] ; UB Nijmegen [Host], 2006. http://webdoc.ubn.ru.nl/mono/s/schelfhout_c/inteindu.pdf.
Texte intégral
11
Mulhern, Peter John. « Lithium intercalation in crystalline Li MoS₂ ». Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27148.
Texte intégralRésumé :
This thesis reports the first successful synthesis of highly crystalline Li[sub x]MoS₂, and describes the electrochemical and structural properties of this material. Five crystal phases were found when the lithium content was varied between x≃O and x-1 by electrochemical intercalation. Each phase existed over a small range of x, and the crystal lattices were found to have small triclinic or monoclinic distortions from 1T-hexagonal symmetry.
These discoveries have resolved a controversy in the literature. Many references have claimed that crystalline MoS₂ disproportionates when the lithium content exceeds x≃0.2, while others have claimed an electrochemically produced MoS₂ polytype is an intercalation host with Δx≃1. A strong correspondence has been found between the properties of the electrochemically produced host and the crystalline 1T- Li[sub x]MoS₂.Science, Faculty of
Physics and Astronomy, Department of
Graduate
12
Evans, John Simon Owen. « Structural studies on layered intercalation compounds ». Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386747.
Texte intégral
13
Allen, Katharine M. « Intercalation chemistry of alkali metal fullerides ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390457.
Texte intégral
14
Burch, Damian. « Intercalation dynamics in lithium-ion batteries ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54233.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 153-160).
A new continuum model has been proposed by Singh, Ceder, and Bazant for the ion intercalation dynamics in a single crystal of rechargeable-battery electrode materials. It is based on the Cahn-Hilliard equation coupled to reaction rate laws as boundary conditions to handle the transfer of ions between the crystal and the electrolyte. In this thesis, I carefully derive a second set of boundary conditions--necessary to close the original PDE system--via a variational analysis of the free energy functional; I include a thermodynamically-consistent treatment of the reaction rates; I develop a semi-discrete finite volume method for numerical simulations; and I include a careful asymptotic treatment of the dynamical regimes found in different limits of the governing equations. Further, I will present several new findings relevant to batteries: Defect Interactions: When applied to strongly phase-separating, highly anisotropic materials such as LiFePO4, this model predicts phase-transformation waves between the lithiated and unlithiated portions of a crystal. This work extends the analysis of the wave dynamics, and describes a new mechanism for current capacity fade through the interactions of these waves with defects in the particle. Size-Dependent Spinodal and Miscibility Gaps: This work demonstrates that the model is powerful enough to predict that the spinodal and miscibility gaps shrink as the particle size decreases. It is also shown that boundary reactions are another general mechanism for the suppression of phase separation.
(cont.) Multi-Particle Interactions: This work presents the results of parallel simulations of several nearby crystals linked together via common parameters in the boundary conditions. The results demonstrate the so-called "mosaic effect": the particles tend to fill one at a time, so much so that the particle being filled actually draws lithium out of the other ones. Moreover, it is shown that the smaller particles tend to phase separate first, a phenomenon seen in experiments but difficult to explain with any other theoretical model.
by Damian Burch.
Ph.D.
15
Wong, John T. M. Eng Massachusetts Institute of Technology. « Shape morphing structures via intercalation compounds ». Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42153.
Texte intégralRésumé :
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (leaves 35-36).
Recent research has allowed the use of electrode-active materials as actuators by harnessing reversible volumetric change due to intercalation during charging and discharging. These actuators provide a relatively large strain, 2-3%, while requiring less than ten volts to operate with a cycle time on the order of one hundred seconds. This technology can be used in any moderate bandwidth, high-force, high-strain application, including shape-morphing helicopter blades, boat hulls, satellites, and any other structure that benefits from shape change. An analysis is performed on the state of the technology, the intellectual property held, and the potential markets that exist. A recommendation is made to pursue the technology, while cognizant of the fact that it is still in a seed stage and requires significant time and financial investment before entering production. Two business models are proposed and rough market calculations are also presented. The basis of this project is work done at the Massachusetts Institute of Technology by Professor Yet-Ming Chiang and Professor Steven Hall. Industrialists, including but not limited to, William Fallon and Dan Ursenbach of Sikorsky Aircraft in Stratford, Connecticut are also involved in the project.
by John T. Wong.
M.Eng.
16
Han, Kyoo-Seung. « Intercalation du lithium dans FeWO4C1 ; intercalation d'entités vanadates dans des hydroxydes doubles lamellaires dérivés de Ni(OH)2 ». Phd thesis, Université Sciences et Technologies - Bordeaux I, 1996. http://tel.archives-ouvertes.fr/tel-00150393.
Texte intégralRésumé :
Ce travail est consacré a l'intercalation de deux typesC d'éspèces dans des structures lamellaires : d'une part de lithium dans FeWO4C1, d'autre part des ions complexes vanadate dans des hydroxydes doubles lamellaires. La réaction du lithium dans FeWO4C1 est réversible dans le domaine de composition FeWO4C1. L'analyse structurale sur monocrstal de FeWO4C1 et de l'affinement par la methoe de rietveld une foorte modification de l'environnement du fer lors de l'intercalation.Des hydroxydes doubles lamellaires dérivés de Ni(OH)2 contenant des chaînes métavanadate intercalées ont été préparés par la chimie douce. Ces matériaux ont été caractérisés par diffraction des rayons X, spectroscopie infrarouge, analyser thermogravimétrique, analyse chimique et RMN du vanadium. L'étude du processus d'intercalation montre que des ions diperoxovanadate sont insérés de prime abord pouis polycondensent spontanément pour donner des chaînes métavanadate. La RMN du vanadium met en évidence le couplage de ce comportement à un phénomène de greffage, également spontané, des entités insérées aux feuillets.
17
Kyoo-Seung, Han. « Intercalation du lithium dans FeWO₄Cl : intercalation d'entités vanadates dans des hydroxydes doubles lamellaires dérivés de Ni(OH)₂ ». Bordeaux 1, 1996. http://www.theses.fr/1996BOR10585.
Texte intégralRésumé :
Ce travail est consacré a l'intercalation de deux typesC d'éspèces dans des structures lamellaires : d'une part de lithium dans FeWO₄Cl, d'autre part des ions complexes vanadate dans des hydroxydes doubles lamellaires. La réaction du lithium dans FeWO₄Cl est réversible dans le domaine de composition FeWO₄Cl. L'analyse structurale sur monocrstal de FeWO₄Cl et de l'affinement par la methoe de rietveld une foorte modification de l'environnement du fer lors de l'intercalation. Des hydroxydes doubles lamellaires dérivés de Ni(OH)₂ contenant des chaînes métavanadate intercalées ont été préparés par la chimie douce. Ces matériaux ont été caractérisés par diffraction des rayons X, spectroscopie infrarouge, analyser thermogravimétrique, analyse chimique et RMN du vanadium. L'étude du processus d'intercalation montre que des ions diperoxovanadate sont insérés de prime abord pouis polycondensent spontanément pour donner des chaînes métavanadate. La RMN du vanadium met en évidence le couplage de ce comportement à un phénomène de greffage, également spontané, des entités insérées aux feuillets.
18
Rolseth, Erlend Granbo. « Carbon Dioxide Intercalation in Sodium Fluorohectorite Clay ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12793.
Texte intégralRésumé :
Wide angle X-ray Scattering (WAXS) measurements of the layered synthetic silicatesodium fluorohectorite (NaFh) when exposed to pressurized carbon dioxideare reported. With a custom made sample holder placed on top of a coolingsystem, measurements of the NaFh were taken at diferent conditions for temperatureand pressure. The interlamellar spacing of the clay particles is observedto expand approximately 2:4Å in the 001-direction when the sample is held at -20 degrees Celsius and exposed to 15 bar of CO2 for over 9 days, indicating the intercalation of CO2. The d-spacing after intercalation is indistinguishable from the d-spacing of NaFh in the 1WL hydration state. The rate of intercalation process is reported to be dependent on the temperature and the pressure of CO2, with the decreaseof temperature and the increase of pressure beeing favorable for intercalatingCO2. Through various measurements the possibillity of water as the observedintercalated guest substance has been ruled out. Molecular models based onthe swelling free energy are proposed to explain some of the features observedin the experiment.
19
Khan, Aamir I. « Novel intercalation chemistry of layered double hydroxides ». Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413071.
Texte intégral
20
Carreyette, Shuaijin Chen. « Solid intercalation to produce polymer/clay nanocomposites ». Thesis, Nottingham Trent University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396366.
Texte intégral
21
Kosidowski, Maria-Laura S. « The preparation and characterisation of intercalation compounds ». Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/584.
Texte intégral
22
Suter, Theo M. « Crystalline carbon nitrides : characterisation, intercalation and exfoliation ». Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10045282/.
Texte intégralRésumé :
In recent years there has been significant interest in, and research into, carbon nitride materials for use in applications such as photocatalysis. The most commonly described C/N materials are referred to as graphitic carbon nitride (gCN), though due to the layered amorphous nature structural characterisation is difficult. Polytriazine imide (PTI) is a crystalline layered carbon nitride that is less explored within the literature compared to gCN due to its more difficult synthetic procedure. In this thesis the synthesis, characterisation, intercalation chemistry and exfoliation of PTI is explored. The synthesis of a related material, triazine based graphitic carbon nitride (TGCN) is explored and the product characterised in detail. PTI refers to the carbon, nitrogen and hydrogen framework (C6N9H3) within which different ionic intercalants can be accommodated; then give rise to several different crystalline materials with the same underlying carbon nitride backbone. The structure of these crystalline, layered PTI was synthesised by reversibly removing and replacing the intercalated ions without affecting the carbon nitride structure. The structures of these new materials was investigated and how changing the intercalant can be used to tune the structures and properties. This methodology may facilitate the fine-tuning and optimisation of carbon nitrides for a number of applications. I have also explored the exfoliation of the layered PTI materials. A number of methods have been used including intercalation and ultrasonication. Remarkably, however I found that the PTI gently, and even spontaneously dissolves to form solutions in highly polar organic solvents and even in water. This process takes place without the need for mechanical mixing, sonication or centrifugation. The resultant separated nanosheets solutions are characterised indepth. Few layer stacks of undamaged crystallites are observed. The photoluminescence of the nanosheets have been found to depend on the number of stacked layers, presenting exciting opportunities for optoelectronic devices.
23
Gummow, Rosalind June. « Lithium intercalation reactions with transition metal oxides ». Doctoral thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/19039.
Texte intégralRésumé :
An investigation of several lithium transition metal oxide systems has been undertaken with the aim of synthesising an optimised LiM0₂ compound (M = Mn, Co or Co/Ni mixtures) for application as a cathode in rechargeab1e lithium batteries. Attention has been focused on systems which show promise for application as cathodes in rocking-chair cells which do not contain metallic lithium anodes. A novel lithium cobalt oxide, LT-LiCoO₂ (LT for low temperature), has been synthesised at 400°C. This compound has near-cubic symmetry and can be indexed to either a trigonal unit cell (space group R3m) with a=2.830(1)Å and c=l3.875(8) Å, or to a face-centred cubic unit cell (space group Fd3m) with a=8.002(1)A. The near-cubic symmetry is maintained on delithiation. Neutron and X-ray powder diffraction refinement of the LT-LiCoO₂ sample has shown it to be best described as a layered structure (R3m symmetry) with approximately 6% of the cobalt cations in the predominantly lithium layer and vice versa. An acid-leached sample LT-Liₒ₄.4CoO₂ was, however, shown to have a defect spinel structure.
24
Wang, Ying. « Enhanced Li-ion intercalation properties of vanadium oxides / ». Thesis, Connect to this title online ; UW restricted, 2006. http://hdl.handle.net/1773/10561.
Texte intégral
25
Dahn, Douglas Charles. « Low temperature specific heat of LixNbS2 intercalation compounds ». Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25563.
Texte intégralRésumé :
This thesis describes a study of the low temperature specific heat of LiⅹNbS₂, where x is between 0 and 1. Samples were prepared by intercalating lithium into niobium disulfide in electrochemical cells. Structural data obtained by x-ray diffraction are presented. These, together with electrochemical measurements, show that staged phases exist for some values of x. The electronic specific heat of LiⅹNbS₂, is consistent with complete charge transfer from the intercalated lithium to the bands of the NbS2 host. The lattice specific heat also shows large changes as a function of x. A discussion of the data in terms of continuum elasticity theory suggests that intercalation produces large changes in the shear elastic constant C₄₄ . A brief discussion of superconductivity in LiⅹNbS₂, is also included.Science, Faculty of
Physics and Astronomy, Department of
Graduate
26
Colbow, Kevin Michael. « Lithium intercalation in titanium based oxides and sulfides ». Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27860.
Texte intégralRésumé :
The Li-Ti-S ternary system was investigated. The elements and/or compounds, such as lithium sulfide, titanium disulfide and titanium trisulfide, were combined at high temperature (typically 500-900°C). The synthesized compounds containing one or more phases were structurally characterized using x-ray powder diffraction. When Lix TiS₂, (0 ≤ x ≤ 1) was synthesized at elevated temperature, a new polytype, 3R-LixTiS₂, was found for some values of x. The regions of stability of the 3R polytype and the well known 1T polytype are presented. Lithium can be intercalated or de-intercalated from both polytypes at room temperature. Ambient temperature Li/3R-LixTiS₂ cells have higher average voltages than Li/1T-Li TiS₂, cells.
The lithium spinel oxides are another class of
materials receiving attention as cathode materials in
lithium secondary batteries. LiTi₂0₄ is metallic, has the
cubic spinel structure and reacts with one further lithium
atom to form Li₂Ti₂0₄. The related spinel Li₄/₃Ti₅/₃⁰₄͵
which is electrically insulating, also reacts reversibly
with one lithium atom. Both Li₂Ti₂0₄ and Li₄/₃Ti₅/₃⁰₄͵
cells cycle reversibly, but have subtle differences in their
voltage profiles. The difference in cell behaviour was
interpreted based on the band structure of Li₁˖xTi₂₋x⁰₄.
The mixed spinels LiMnyTi₂₋y⁰₄ (0 ≤ y ≤ 2) were also investigated. These compounds were synthesized at high temperature but their performance as cathodes in lithium batteries was not encouraging.Science, Faculty of
Physics and Astronomy, Department of
Graduate
27
Latieule, Sylvie. « Intercalation de dérivés d'acides aminés dans la Montmorillonite ». Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7542.
Texte intégralRésumé :
La Montmorillonite-sodium est une argile gonflante de la famille des Smectites qui presente la propriete de pouvoir echanger les cations sodium, situes dans ses espaces interlamellaires. Grace a cette propriete, nous avons pu concevoir des argiles organiques, par association entre de la Montmorillonite-sodium avec des cations organiques derives d'acides amines et fonctionnalises par esterification. Ces nouveaux materiaux ont ete caracterises par determination des isothermes d'adsorption et de desorption des cations organiques et sodium, respectivement, ainsi que par mesure des espaces interlamellaires des argiles organiques par diffraction de rayons. X. Parmi les applications possibles de ces nouveaux materiaux, on peut citer la resolution de melanges de gaz par chromatographie en phase gazeuse. Une etude menee sur la separation de melanges CO$\sb2$, CH$\sb4$, O$\sb2$, N$\sb2$, en utilisant differents supports, a ete interpretee en termes de taille et forme de cavites creees au niveau de l'argile, comparees aux molecules de gaz. Autre application, la resolution de melanges racemiques d'acides amines a ete investiguee en chromatographie en phase liquide.
28
Uribe, Calderón Jorge Alonso. « Melt intercalation andor exfoliation of polystyrene-montmorillonite nanocomposites ». Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79267.
Texte intégralRésumé :
Thermal stability of organoclays and polystyrene (PS) intercalation in organoclays by melt processing were studied. The effects of polymer viscosity, processing conditions, type of mixing and the type of fillers on the intercalation process were evaluated. The resulting nanocomposites were tested to characterize structure, thermal stability and mechanical properties.Two new organoclays were used in this study exhibited good thermal stability. This suggested their potential use in the preparation polymer nanocomposites at high processing temperatures.
Batch mixing promoted polymer intercalation in most cases. PS nanocomposites showed a combination of intercalated and unintercalated or collapsed structures. In general, thermal stability and mechanical properties of PS were enhanced by incorporation of organoclays. Processing conditions in the batch mixer had only a small influence on intercalation behavior. However, they had a strong effect on thermal stability and mechanical properties. The degree of intercalation was dependant on the type of organoclay. As a result thermal stability and mechanical properties were influenced by the type of organoclay used. The best mechanical properties were obtained with Cloisite 10-A.
Mixing in the twin screw extruder promoted intercalation of low viscosity PS. Thermal stability was increased in all cases, but mechanical properties did not improve significantly.
The tensile modulus of nanocomposites was calculated using five models reported in the literature. The results were compared to experimental data obtained in this study. Up to 1% wt Cloisite 10-A content, the experimental results showed very good agreement with the predictions of the Halpin-Tsai and Brune models, which predicted the highest modulus values. The experimental values fell rapidly bellow theoretical predictions above 1% wt clay content.
29
Fogg, Andrew Michael. « Structural, kinetic and synthetic studies of intercalation compounds ». Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297906.
Texte intégral
30
Trouw, F. R. « The structure and dynamics of graphite intercalation compounds ». Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371585.
Texte intégral
31
Pavitt, David. « Few-layer transition metal chloride graphene intercalation compounds ». Thesis, University of London, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603531.
Texte intégralRésumé :
Few-layer transition metal chloride graphene intercalation compounds have becJI fabricated by the mechanical exfoliation of graphite intercalation compounds (GTCs) containing CoC12 , NiCh, CuCl2 , MnCh and FeC13 . The number of graphene layers and the distribution of the intercalate in the few-layer graphene intercalation compounds (FLGICs) have been characterised using the optical contrast of the FLGICs against the Si02 substrate and the G-peak of the Raman spectrum. FLGICs containing CL single intercalate layer surrounded by two graphene layers have been fabricated and characterised, which are an ideal system to study 2D magnetic phase transitions.
32
Blakeslee, Pamela Lené Washington. « Oxygen intercalation in electrochemically-doped La₂CuO₄₊[delta] ». Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43295.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1997.On t.p. ["delta"] appears as the lower case Greek letter.
Includes bibliographical references (157-163).
by Pamela Lené Washington Blakeslee.
Ph.D.
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Woodford, William Henry IV. « Electrochemical shock : mechanical degradation of ion-intercalation materials ». Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80889.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 173-195).
The ion-intercalation materials used in high-energy batteries such as lithium-ion undergo large composition changes-which correlate to high storage capacity-but which also induce structural changes and stresses that can cause performance metrics such as power, achievable storage capacity, and life to degrade. "Electrochemical shock"-the electrochemical cycling-induced fracture of materials-contributes to impedance growth and performance degradation in ion-intercalation batteries. Using a combination of micromechanical models and in operando acoustic emission experiments, the mechanisms of electrochemical shock are identified, classified, and modeled in targeted model systems with different composition and microstructure. Three distinct mechanisms of electrochemical shock in ion-intercalation mate- rials are identified: 1) concentration-gradient stresses which arise during fast cycling, 2) two- phase coherency stresses which arise during first-order phase-transformations, and 3) inter-granular compatibility stresses in anisotropic polycrystalline materials. While concentration- gradient stresses develop in proportion to the electrochemical cycling rate, two-phase coherency stresses and intergranular compatibility stresses develop independent of the electro- chemical cycling rate and persist to arbitrarily low rates. For each mechanism, a micromechanical model with a fracture mechanics failure criterion is developed. This fundamental understanding of electrochemical shock leads naturally to microstructure design criteria and materials selection criteria for ion-intercalation materials with improved life and energy storage efficiency. In a given material system, crystal symmetry and phase-behavior determine the active mechanisms. Layered materials, as exemplified by LiCoO₂, are dominated by intergranular compatibility stresses when prepared in polycrystalline form, and two-phase coherency when prepared as single crystal powders. Spinel materials such as LiMn₂O₄, and LiMn₁.₅Ni₀.₅O₄ undergo first-order cubic-to-cubic phase- transformations, and are subject to two-phase coherency stresses even during low-rate electrochemical cycling. This low-rate electrochemical shock is averted in iron-doped material, LiMn₁.₅Ni₀.₄₂Fe₀.₀₈O₄, which has continuous solid solubility and is therefore not subject to two-phase coherency stresses; this enables a wider range of particle sizes and duty cycles to be used without electrochemical shock. While lithium-storage materials are used as model systems, the physical phenomena are common to other ion-intercalation systems, including sodium-, magnesium-, and aluminum-storage compounds.
by William Henry Woodford IV.
Ph.D.
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Khoshnevisan, B., et H. Pourghasemian. « Nanoporous Ag-Cnts foamed electrode for lithium intercalation ». Thesis, Sumy State University, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20610.
Texte intégralRésumé :
Intercalation of lithium into Ag-CNTs sample is reported here. We have used a
nano- porous silver foam as a frame for deposition of the CNTs inside the pores by
electrophoresis deposition (EPD) technique. By using chronopotentiometry method, we
have noticed that the Li storage capacity of the prepared Ag-CNTs electrode was im-
proved noticeably in comparison with literature. In addition, a very good functional
stability for the prepared electrode has been tested during subsequent cycles of charge /
discharge (C&D) procedures. By scanning the cycle's regulated current from 0.2 up to
1.0 mA , it was shown that in the range of 0.4 - 0.6 mA the Li storage capacity and
reversibility of the C&D cycles became optimum, as well.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20610
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Nhlapo, N. S. (Nontete Suzan). « Intercalation of fatty acids into layered double hydroxides ». Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/28361.
Texte intégralRésumé :
Surfactant-mediated intercalation of aliphatic fatty acids into a commercial,layered double hydroxide (LDH) with the approximate composition of [Mg0.689Al0.311(OH2)] (CO3)0.1569nH2O was explored. The reactions were conducted at elevated temperatures with the LDH powder suspended in a fatty acid oil-water emulsion. The acidic fatty acid, e.g. stearic acid, reacts with the basic carbonate anions from LDH-CO3. In the process, CO2 is released as a gas and the fatty acids are intercalated as a bilayer. A high concentration of anionic or non-ionic surfactants, i.e. sodium dodecylsulphate or Tween 60, facilitates the intercalation process by emulsifying the molten fatty acids and dispersing the LDH particles. The presence of carboxylate anions in the interlayer region was confirmed by the carboxylate absorption peaks observed in the region 1700–1000 cm-1 on Fouriertransform infrared spectroscopy (FT-IR). Several bands were observed, i.e. ionised and non-ionised. An increase in the d-spacing of the d003 plane of the brucite-like LDH layers was observed on X-ray diffraction (XRD) analysis of all the LDH intercalates. The d-spacing increased linearly with the length of the carboxylic acid chain. Sharp reflection peaks were obtained on XRD, showing the high crystallinity of the LDH intercalates. The thermal decomposition of these materials was explored on thermogravimetric or differential thermogravimetric analysis (TGA/DTA) and temperature-scanned XRD. The mole ratio of Mg to Al was obtained by XRF and the morphology by scanning electron microscopy (SEM). The present method works well with long-chain aliphatic fatty acids at temperatures above or at the melting point of the desired acid. Temperature proved to be the most important parameter to control during the preparation process, i.e. at low temperatures incomplete reactions were obtained. The method is convenient, economical and environmentally friendly. It employs the readily available carbonate form of LDH as a starting reagent, water is used as medium rather than organic solvents, there are no high-temperature calcinations, and an inert atmosphere is not required. CopyrightDissertation (MSc)--University of Pretoria, 2008.
Chemistry
unrestricted
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Nhlapo, Nontete Suzan. « Intercalation of fatty acids into layered double hydroxides ». Pretoria : [s. n.], 2008. http://upetd.up.ac.za/thesis/available/etd-10022009-193152.
Texte intégral
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Seyller, Thomas, Sarah Roscher, Felix Timmermann, Marcus V. Daniel, Florian Speck, Martina Wanke, Manfred Albrecht et Susanne Wolff. « Quasi-Freestanding Graphene on SiC(0001) by Ar-Mediated Intercalation of Antimony : A Route Toward Intercalation of High-Vapor-Pressure Elements ». Wiley-VCH Verlag, 2019. https://monarch.qucosa.de/id/qucosa%3A35599.
Texte intégralRésumé :
A novel strategy for the intercalation of antimony (Sb) under the (6√3 × 6√3)R30° reconstruction, also known as buffer layer, on SiC(0001) is reported. Using X-ray photoelectron spectroscopy, low-energy electron diffraction, and angle-resolved photoelectron spectroscopy, it is demonstrated that, while the intercalation of the volatile Sb is not possible by annealing the Sb-coated buffer layer in ultrahigh vacuum, it can be achieved by annealing the sample in an atmosphere of Ar, which suppresses Sb desorption. The intercalation leads to a decoupling of the buffer layer from the SiC(0001) surface and the formation of quasi-freestanding graphene. The intercalation process paves the way for future studies of the formation of quasi-freestanding graphene by intercalation of high-vapor-pressure elements, which are not accessible by previously known intercalation techniques, and thus provides new avenues for the manipulation of epitaxial graphene on SiC.
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Horowitz, Eric D. « Intercalator-mediated assembly of nucleic acids ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33937.
Texte intégralRésumé :
The RNA World hypothesis suggests that RNA, or a proto-RNA, existed in an early form of life that had not yet developed the ability to synthesize protein enzymes. This hypothesis, by some interpretations, implies that nucleic acid polymers were the first polymers of life, and must have therefore spontaneously formed from simple molecular building blocks in the "prebiotic soup." Although prebiotic chemists have searched for decades for a process by which RNA can be made from plausible prebiotic reactions, numerous problems persist that stand in the way of a chemically-sound model for the spontaneous generation of an RNA World (e.g., strand-cyclization, heterogeneous backbones, non-selective ligation of activated nucleotides). The Molecular Midwife hypothesis, proposed by Hud and Anet in 2000, provides a possible solution to several problems associated with the assembly of the first nucleic acids. In this hypothesis, nucleic acid base pairs are assembled by small, planar molecules that resemble molecules which are known today to intercalate the base pairs of nucleic acid duplexes. Thus, the validity and merits of the Molecular Midwife hypothesis can be, to some extent, explored by studying the effects of intercalation on the non-covalent assembly of nucleic acids.
In this thesis, I explore the role of the sugar-phosphate backbone in dictating the structure and thermodynamics of nucleic acid intercalation by using 2′,5′-linked RNA intercalation as a model system of non-natural nucleic acid intercalation. The solution structure of an intercalator-bound 2′,5′ RNA duplex reveals structural and thermodynamic aspects of intercalation that provide insight into the origin of the nearest-neighbor exclusion principle, a principle that is uniformly obeyed upon the intercalation of natural (i.e. 3′,5′-linked) RNA and DNA. I also demonstrate the ability of intercalator-mediated assembly to circumvent the strand-cyclization problem, a problem that otherwise greatly limits the polymerization of short oligonucleotides into long polymers. Together, the data presented in this thesis illustrate the important role that the nucleic acid backbone plays in governing the thermodynamics of intercalation, and provide support for the proposed role of intercalator-mediated assembly in the prebiotic formation of nucleic acids.
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Al-Yamani, Faisal M. « A route to enhanced intercalation in rubber-silicate nanocomposites ». Akron, OH : University of Akron, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1124544242.
Texte intégralRésumé :
Thesis (M.S.)--University of Akron, Dept. of Polymer Engineering, 2005."August, 2005." Title from electronic thesis title page (viewed 11/28/2005) Advisor, Lloyd Goettler; Faculty Reader, Avraam I. Isayev; Department Chair, Sadhan C. Jana; Dean of College, Frank N. Kelley; Dean of Graduate School, George R. Newkome. Includes bibliographical references.
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Borralleras, Mas Pere. « Intercalation mechanism of polycarboxylate-based superplasticizers into montmorillonite clays ». Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667977.
Texte intégralRésumé :
The presence of clays in the sands used for concrete production interferes with the development of the fluidity of concrete, producing an instantaneous slump loss just after batching and the premature loss of fluidity. This interference occurs with all types of additives and clays but is especially problematic when combining sands containing expansive clays such as montmorillonites with new-generation high water-reducer/superplasticizer admixtures based on polycarboxylate polymers (PCE).
Water-reducers based on PCE polymers offer much better performance than traditional superplasticizers based on sulfonated naphthalene polymers (BNS) and sulfonated melamine polymers (MNS), making great advances in concrete technology, both from the technical and economical point of view as in reducing the environmental impact associated to concrete. However, these advantages are inhibited when sands contain clays of the expansive type in their composition.
All the preventive or corrective measures to mitigate the harmful effect of clays contained in sands result in increases of production costs and in greater environmental impact. For this reason, during the last years it has been tried to develop polymeric structures that offer the same benefits than polymers PCE but with improved tolerance against clays of the expansive type, such as montmorillonite clays, but without getting to reach solutions with guarantees of success, due to the complexity of the interaction process between PCE polymers and montmorillonite clays.
This doctoral thesis aims to deepen knowledge about the mechanism of interaction between PCE polymers and montmorillonite clays, assuming that the deep understanding of the interaction mechanism is the essential previous step to finally develop high-performance, clay-insensitive superplasticizers for concrete. For this, the research is structured in three parts, motivated by the discrepancies that the current model of interaction proposed shows with the experimental results of sorption and fluidity loss.
In the first part, it is intended to develop a test method that allows to observe the real expansion profiles of the clays in such a way that the mentioned discrepancies can be clarified.
Secondly, with the proposed test method, it is intended to identify how the structure of PCE polymers, as well as the dosage used, influences on the expansion of montmorillonite clays produced by the absorption of polymer. And, thirdly, to identify how the properties of clay affect the interaction process.
The first phase of the research campaign has made it possible to propose an improved test method for the d-spacing determination that revealed the real intercalation behavior, by which the number of PCE side chains intercalated into the interlaminar space of montmorillonite clays is up to ten times higher than that deducted from the traditional analytical method. And from the new test method proposed it has been possible to clarify the role of the different structures of PCE polymers and the properties of montmorillonite clays in the intercalation mechanism, in agreement with the experimental results of fluidity loss and of sorption behavior.
Based on the mentioned achievements, an extended model for the intercalation mechanism has been proposed, whereby montmorillonite clays inhibit the dispersing capacity of PCE polymers, being able to identify the parts and properties of both the clay and the PCE polymers that control this process.
With this contribution, the knowledge of the intercalation mechanism is extended to understand how the interaction between PCE polymers and montmorillonite clays is developed, which is the main objective of this research.La presencia de arcillas en las arenas empleadas para producir hormigón interfiere en el desarrollo de la fluidez de los hormigones, produciendo una pérdida de cono instantánea tras el amasado y la pérdida prematura de fluidez. Esta interferencia se produce con todos los tipos de aditivos y de arcillas, pero es especialmente problemática cuando se combinan arenas que contienen arcillas expansivas del tipo montmorillonita con aditivos superplastificantes de nueva generación basados en polímeros de policarboxilato (PCE). Este tipo de aditivos superplastificantes basados en polímeros de PCE ofrecen prestaciones muy superiores a las de los superplastificantes tradicionales basados en polímeros de naftalensulfonatos (BNS) y melaminas sulfonadas (MNS), aportando grandes mejoras en la tecnología del hormigón, tanto desde el punto de vista técnico y económico como en la reducción del impacto ambiental asociado al hormigón. Sin embargo, estas ventajas quedan inhibidas cuando las arenas contienen arcillas del tipo expansivo en su composición. Todas las medidas preventivas o correctivas aplicadas para mitigar el efecto dañino de las arcillas contenidas en las arenas acarrean incrementos de coste de producción y mayor impacto ambiental. Por este motivo, durante los últimos años se ha intentado desarrollar estructuras poliméricas que ofrezcan las mismas prestaciones que los polímeros de PCE pero con mayor tolerancia frente a arcillas del tipo expansivo, como por ejemplo las montmorillonitas, pero sin llegar a alcanzar soluciones con garantías de éxito, debido a la complejidad del proceso de interacción entre los polímeros de PCE y las arcillas montmorillonitas. Esta tesis doctoral pretende profundizar en el conocimiento en torno al mecanismo de interacción entre los polímeros de PCE y las arcillas montmorillonita, entendiéndose que la comprensión del mecanismo de interacción es la etapa previa esencial para lograr, finalmente, desarrollar aditivos superplastificantes de altas prestaciones e insensibles a las arcillas. Para ello, la investigación se estructura en tres partes, motivado por las discrepancias que el actual modelo de interacción propuesto muestra con los resultados experimentales de sorción y de pérdida de fluidez. En primer lugar, se pretende desarrollar un método de ensayo que permita observar el perfil de expansión de la arcilla real de tal modo que las discrepancias mencionadas puedan ser clarificadas. En segundo lugar, con el método de ensayos propuesto, se pretende identificar como influye la estructura del polímero de PCE, así como su dosificación, en la expansión de la arcilla producida por la absorción de polímero. Y, en tercer lugar, identificar como influyen las propiedades de la arcilla en el proceso de interacción. La primera fase de investigación ha permitido proponer un método de ensayo para el factor de expansión d-spacing que vislumbra que el número de cadenas laterales del polímero de PCE intercaladas dentro del espacio interlaminar de las montmorillonitas es hasta más de diez veces superior al deducido con el método analítico tradicional. Y a partir del nuevo método de ensayo ha sido posible clarificar el rol de las diferentes estructuras de los polímeros de PCE y de las propiedades de la arcilla en el mecanismo de intercalación, en consonancia con los resultados de fluidez y de sorción. A partir de los logros mencionados, se ha propuesto un modelo extendido del mecanismo de intercalación por el cual las arcillas montmorillonitas inhiben el efecto dispersante de los polímeros de PCE, pudiendo identificar cuáles son las partes y propiedades tanto de la arcilla como de los polímeros de PCE que controlan este proceso. Con esta aportación, se amplía el conocimiento para comprender como se desarrolla la interacción entre los polímeros de PCE y las arcillas montmorillonitas, que es el objetivo principal de esta investigación.
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Wang, Chang. « Mathematical modelling of lithium intercalation dynamics in battery electrodes ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:2e259d53-c9f1-4d1f-8aa9-48e857ad553b.
Texte intégralRésumé :
This thesis discusses mathematical models for phase separation pattern in electrode materials for lithium ion batteries. The material is assumed to be composed of discrete "compartments", which might model individual particles in nanoparticle Lithium Iron Phosphate cathode material, for example, or individual layers in graphite anode material. We first present deterministic ODE models to describe quasi-equilibrium and out-of-equilibrium lithiation/delithiation of such systems. In sequence, we examine a single compartment under voltage-control, a multicompartment system under current-control, and a multicompartment system under voltage-control. We show that the dynamics of a single compartment can be reduced to rapid switching between an "empty" state and a "full" state, and we identify the critical voltage at which the switch occurs under both static and dynamic conditions. We also identify the critical voltages for the multicompartment system to change stage. We find that the multicompartment system supports a large number of stable states in quasiequilibrium, and we further reveal that its dynamics may be extremely sensitive to initial conditions and control parameters. We also explore how the dynamics are affected by discreteness and thermal noise by investigating the probability distribution of the lithium concentration. We first study a single-compartment and two-compartment systems, and then extend the analysis to more interacting compartments. We start with the discrete chemical master equations, and then derive a discrete-to-continuum model to explore the probability distribution during dynamic lithiation/delithiation. We identify distinct asymptotic regimes in which either discreteness and thermal noise are important or the dynamics is well captured by the deterministic model. We then compare the different phase-separation patterns predicted by the deterministic model and by the stochastic model, for quasi-equilibrium and out-of-equilibrium evolutions. Finally, we explore how different interaction laws could impact the observed phase-separation pattern.
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Dube, Paul A. « Properties of magnetic transition metal-bromide graphite intercalation compounds / ». *McMaster only, 2002.
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Price, Stephen John. « Kinetic and synthetic studies of intercalation by layered materials ». Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339054.
Texte intégral
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Dean, M. P. M. « Superconductivity and electron-phonon interactions in graphite intercalation compounds ». Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598476.
Texte intégralRésumé :
Systematic Raman scattering experiments were performed to compare the phonon properties in series of GICs BaC6, SrC6, YbC6 and CaC6. The key difference induced by changing the ions in this order is a reduction in the separation of the graphene layers, which is concurrent with an increase in the superconducting transition temperature Tc from < 80 mK to 11.5 K. It was possible to correlate the increase in Tc with a softening of an out-of-plane carbon related phonon, which was explained in terms of increased charge in the carbon-related electronic band. This provides evidence that the carbon-related phonons and electronic-bands are crucial to the superconductivity in these compounds. An in-plane carbon phonon was also measured, which was shown not to follow the Born-Oppenheimer approximation. Recent theoretical attempts to explain these effects cannot fully account for the observed electron-phonon scattering rate. Neutron scattering was also used to measure the high energy carbon-related phonons in CaC6. Due to the highly textured nature of the samples, special analytical techniques were developed to allow for the comparison between experiment and density functional theory (DFT). Overall, a good level of agreement between experiment and theory is found, which is significant in light of several other measurements of phonon related properties of CaC6, which disagree with the theoretical predictions. YbC6 was studied as a function of pressure to investigate the changes induced by reducing the layer separation. Tc initially increases consistent with the idea that moving the graphene layers closer increases Tc, however, at higher pressures Tc decreases disappearing at 7 GPa. These effects are discussed in light of a possible valence transition in YbC6.
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Narayanan, Nair Maya. « Functionalization of epitaxial graphene by metal intercalation and molecules ». Phd thesis, Université de Haute Alsace - Mulhouse, 2013. http://tel.archives-ouvertes.fr/tel-01064523.
Texte intégralRésumé :
In this thesis, we have explored the possibilities to realize a Graphene Based Hybrid structures (GBHs) by the functionalization of a graphene layer on both sides. The first chapter gives a general introduction about graphene and a literature review of different metal intercalations on graphene. The second chapter explains the experimental techniques used in this work. In chapter 3, we studied the functionalization of epitaxial graphene on SiC(0001) by gold intercalation. With the help of Scanning Tunneling Microscopy, we have evidenced and characterized different intercalation modes such as the formation of aggregates of individual gold atoms and the formation of a continuous gold layer between the top graphene and the buffer layer. The free standing nature of the intercalated gold atoms was examined by differential charge density plot, projected density of states calculations and further by X-ray photoelectron spectroscopy. The band structure modification of graphene due to these intercalated gold atoms was evidenced by Angle-resolved photoemission spectroscopy, which reveals a strong Van Hove extension and an increase of the Fermi velocity. Extend to this research, to obtain an extended Van Hove singularity usually observed in highly doped graphene; we studied highly electron donor molecules, TetraThioFullvalene (TTF) on pristine and gold intercalated graphene and on graphite (chapter 4). The dependence of charge transfer of these molecules with their conformation and the reactivity of photochromic with conjugated molecules on graphene were also discussed. To understand the structural properties of these molecules photophysical measurements were performed in chapter 5.
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Morris, M. « The intercalation chemistry of alpha-vanadyl phosphate£t dihydrate ». Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384060.
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Locke, Ian Wyn. « Preparation and computational study of novel fullerene intercalation compounds ». Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299956.
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Ghorayeb, A. M. « Charge transfer in the intercalation complexes of layered compounds ». Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373249.
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Zhang, Renyan. « Intercalation induced superconductivity in MoS2, black phosphorus and Bi2Se3 ». Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/intercalation-induced-superconductivity-in-mos2--black-phosphorus-and-bi2se3(bd6767e7-79b2-46ac-bdd8-d78322a54d7b).html.
Texte intégralRésumé :
Intercalation is known to be an efficient method for tuning the band structure of layered materials to bring out superconductivity, without significantly altering the crystal structure of the host material. Graphite intercalation compounds and intercalated transitional metal dichalcogenides (TMDs) are two most studied representatives. This thesis presents an experimental study of several new superconductors obtained by intercalation of layered materials, including MoS2, black phosphorus and a topological insulator Bi2Se3. Polymorphism is an essential feature of MoS2. While, superconductivity in doped 2H-MoS2 has been extensively studied. Superconductivity in its 1T and 1T' counterparts has been neither observed, nor even predicted theoretically. In this thesis, we have investigated potassium (K)-intercalated MoS2 and found that doping with K induces both structural and superconducting phase transitions. We demonstrate that all three phases of MoS2 - 2H, 1T and 1T'- become superconducting as a result of intercalation, with critical temperature Tc of 6.9 K, 2.8 K and 4.6 K, respectively. Black phosphorus has been 'rediscovered' in the last few years due to its layered structure and unique electronic properties. This thesis describes successful intercalation of black phosphorus with several alkali metals (Li, K, Rb, Cs) and alkaline earth metal Ca, with all five compounds showing superconductivity. Importantly, and very unexpectedly, the found superconductivity of intercalated black phosphorus is independent of the intercalant, with all five compounds having exactly the same superconducting characteristics (Tc, critical fields, anisotropy). We suggest that the superconductivity is due to heavily doped phosphorene layers, with alkali metal atoms acting mainly as charge reservoirs. Superconducting topological insulators, such as Bi2Se3, are regarded as the most promising candidates for topological superconductivity. However, the nature of superconductivity in doped Bi2Se3, such as CuxBi2Se3, SrxBi2Se3 and NbxBi2Se3, remains controversial and so far no convincing evidence of topological superconductivity has been reported for these materials. In this thesis, we report superconductivity in a new family of superconductors derived from Bi2Se3, by intercalation with K, Rb and Cs metals. All three superconductors exhibit qualitatively identical but highly anomalous behaviour of magnetisation, with several new features consistent with the properties of topological superconductors. Specifically, the new materials exhibit a highly unusual extra diamagnetic screening in the Meissner state and two coexisting superconducting phase, including surface superconductivity that we attribute to heavily doped surface states of the original topological insulator (Bi2Se3). This work provides a new platform in the study of the interplay between the topological and superconducting orders. In conclusion, superconductivity has been induced in MoS2, black phosphorus and Bi2Se3 through alkali or alkaline earth metal intercalation. The study of these new superconducting materials has been summarised in the thesis.
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Mead, Kevin. « Graphene growth on SiC under Arambient and H-intercalation ». Thesis, KTH, Rymd- och plasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177645.
Texte intégralRésumé :
We grow epitaxial graphene on 6H-SiC (0001) substrates in Ar background and intercalatehydrogen to reform the carbon bu↵er layer into single and multilayered graphene. We willanalyze the graphene using a combination of techniques including optical microscopy,micro-Raman spectroscopy, Atomic Force Microscopy (AFM), and reflectance mappingand contactless measurements of sheet carrier density and charge carrier mobility. We havestudied in detail, the influence of growth parameters and in-situ surface preparation ofsubstrate on the thickness uniformity and surface morphology of graphene. Additionally,as-grown graphene layers were intercalated with H to obtain quasi-free standing layers ofgraphene with enhanced charge carrier mobility.