Global ETD Search
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Showing 1 to 16 of 16 for “"Negative thermal expansion"”.
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Epoxy coating systems: Probing negative thermal expansion with zinc cyanide
The purpose of this document is two-fold. First, as a formal written submission of the work completed for my degree, but secondly, as a useful reference for myself as I continue to work in the line of composite materials and any others who venture into this area. As such, Chapter 1 gives the …
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Negative Thermal Expansion in Zincblende Structure: an EXAFS study of CdTe
… In this work an accurate evaluation of the bond thermal expansion, parallel and perpendicular MSRDs and distribution asymmetry of the first shell of CdTe has been made, obtaining a good agreement between two different procedures of the data analysis (i) ratio method (ii) FEFF6-FEFFIT method. The …
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An in-situ synchrotron study of low positive and negative thermal expansion ceramics
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-12-04 without embargo terms
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Structural studies on Functional Materials using Solid-State NMR, Powder X-ray Diffraction and DFT Calculations
… 17O solid state NMR experiments highlight subtle thermally induced structural changes in (MoO2)2P2O7 pyrophosphate, tungsten trioxide WO3 and negative thermal expansion ZrW2O8. DFT methods using CASTEP software to calculate 31P and 17O NMR parameters are performed on these structures and discussed …
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Lattice parameter and thermal expansion in solid methane
… position and width was verified by independent thermal arrest measurements. The average entropy discontinuity was 0.65 cal/mole/deg. A phenomenological study of the data in the range 2.5 to 12 K was made to gain some understanding of the observed negative thermal expansion below 9.75 K. The …
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Structural, vibrational and thermodynamic properties of carbon allotropes from first-principles : diamond, graphite, and nanotubes
… data. The vibrational free energy and the thermal expansion, the temperature dependence of the elastic moduli and the specific heat are calculated using the quasi-harmonic approximation. Graphite shows a distinctive in-plane negative thermal-expansion coefficient that reaches its lowest …
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Molecular Dynamics Simulations of Structural Transitions in Crystalline and Amorphous Inorganic Compounds
… as an increase of the mechanical moduli upon expansion. Irreversible polyamorphic transitions occur under large compressive stresses provided adequate thermal activation for the necessary bond exchanges to take place. This leads to a permanent densification of silica glass. In addition to …
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Topology Optimization and Analysis of Thermal and Mechanical Metamaterials
… possessing unique thermoelastic properties. A thermal and mechanical stress analysis formulation based on homogenization theory is developed and is used in a regional scaled aggregation stress constraint method, and a method of worst-case stress minimization is also included to efficiently …
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Structural and chemical characterization of complex nanomaterials at atomic resolution
… dynamics were characterized in the form of negative thermal expansion (NTE) and abnormal levels of disorder. To examine a less complex system, electrocatalytically-active, core-shell nanostructures assembled from Pt and Pd were synthesized and subsequently examined using spherical …
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Θεωρητική και πειραματική μελέτη της απόκρισης ζεολίθων σε μεταβολές θερμοκρασίας, πίεσης και συγκέντρωσης ροφημένων ουσιών
Οι ζεόλιθοι ανήκουν στα νανοπορώδη υλικά ή αλλιώς και μοριακά κόσκινα. Βρίσκουν δε εφαρμογή σε πληθώρα εφαρμογών, καλύπτοντας ένα μεγάλο θερμοκρασιακό φάσμα. Η γνώση της απόκρισής τους κατά τις μεταβολές της θερμοκρασίας είναι καθοριστικής σημασίας για την αποδοτικότητά τους, ακόμα περισσότερο όταν …
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Embedded-fragment studies of ice, water, and molecular cluster cations
… water ice Ih were investigated with BIM-MP2. The negative thermal expansion and pressure-induced amorphization of ice Ih were computationally observed and linked to hydrogen bond-bending acoustic phonons that soften with increasing pressure. The anomalous volume isotope effect, where D2O possesses …
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A new class of auxetic lattices
In this work we have studied the mechanical and thermal behavior of a new class of auxetic lattices. We have started introducing a novel two-dimensional lattice family with three different realizations that leads to a Poisson's ratio arbitrarily close to the thermodynamic limit corresponding to ν = …
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Computational Study of Two-Dimensional Materials for Energy Applications
… In this thesis, the mechanical, vibrational, thermal, and electronic properties of several 2D materials are explored and their possible application to devices is examined. The work was carried out in collaboration with experimentalists at several institutions with theoretical calculations …
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Materials development for multicomponent systems with variable oxidation states
… the M1Ti2(PO3)4 (M1= Li, Na, K,) family, their thermal expansion behavior were studied by means of high resolution (synchrotron radiation) in-situ high temperature X-ray diffraction, Rietveld refinement and the coefficient of thermal expansion analysis suite (CTEAS) software developed at UIUC. …
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The Structure of the RC-LH1 Complex from Rps. acidophila: Optical Single-Molecule Spectroscopy and Numerical Simulations
… local pressure is conceivable, since, due to a negative thermal expansion coefficient for thin polymer films below the glass transition temperature, an expansion rather than a contraction of the PVA-film is expected upon temperature reduction. In low-temperature single-molecule measurements it …