Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Lattice Thermal Conductivity"”.
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Lattice thermal conductivity of copper alloys below 2 K
Thermal conductivity measurements have been made between 0.06 and 2 K on copper samples containing either 10 atomic percent aluminum, 30 atomic percent zinc, or 4 atomic percent nickel. These samples were studied in both annealed and heavily deformed conditions. No unusual behavior has been …
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Lattice thermal conductivity of bulk and polycrystalline PbTe from computer simulations
… in its pristine form, largely due to its low lattice thermal conductivity. Several studies have been proposed to analyse this thermal conductivity, but their range of application is usually limited: first-principles simulations do not allow for the study of intrinsic defects in large …
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Theoretical Investigations of the Electronic, Magnetic, and Thermoelectric Properties of Transition-Metal Based Compounds
… with full electron spin polarization. The lattice thermal conductivity (κL) was found to decrease for these alloys as the temperature increases. The present investigation indicated that the phonon optical modes have a major contribution to the total κL as compared to the acoustic modes. It …
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Study of Thermoelectric and Lattice Dynamics Properties of 2D Layered MX (M = Sn, Pb; X = S, Se, Te) and ZrS2 Compounds using First-principles Approach
… is the investigation of thermoelectric and lattice dynamics properties of two-dimensional (2D) MX (M = Sn, Pb; X = S, Se, Te) and ZrS2 compounds based on the first-principles density functional theory. The dimensionality reduction (e.g., using 2D structure) of bulk materials is found to have …
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Theoretical Investigations of the Structural, Dynamical, Electronic, Magnetic, and Thermoelectric Properties of CoRhYSi (Y = Cr, Mn) Quaternary Heusler Alloys
… compute the Seebeck coefficient (S), electrical conductivity (σ), and electronic thermal conductivity (k_e) of CoRhYSi (Y = Cr, Mn) alloys, whereas Slack's equation was used to get the lattice thermal conductivity (k_L).</p>
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Thermoelectric properties in gallium telluride-gallium antimonide vacancy compounds
… large Seebeck coefficient, large electrical conductivity and low thermal conductivity, are of great importance in solid state cooling and power generation. Solid solution formation is one effective method to achieve low thermal conductivity by phonon scattering due to mass and strain field …
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Advancing the computational exploration for thermoelectric materials
… models take into account both electronic and thermal properties since good thermoelectric materials must maintain a difficult balance between the two to achieve high efficiency. In this vein, one route which has proven particularly insightful is to rank materials by their intrinsic …
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Nanoscale electron, phonon and spin transport in thermoelectric materials
… as a candidate technology to harvest energy from thermal sources, such as the sun and terrestrial heat sources, as well as improve the efficiency of existing energy systems by recycling the inevitable waste heat. The bottleneck that prevents large-scale deployment of thermoelectric modules so far, …
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Study of phonon-dislocation interaction in LiF and KCl crystals
… of crystalline solids. The low-temperature thermal conductivity of electrically insulating crystals is strongly influenced by dislocations. Measurement of the lattice thermal conductivity, therefore, provides a useful tool for the study of phonon-dislocation interaction. In this thesis, …
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Atomistic and ab initio prediction and optimization of thermoelectric and photovoltaic properties
… computation. In this thesis we investigate lattice thermal conductivities KL and electronic band gaps E,, which are relevant to thermoelectric and photovoltaic applications, respectively, and develop or modify computational tools for predicting and optimizing these properties. For lattice …
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Advancing Nontoxic, Antimony-based 1–2–2-type Thermoelectric Zintls
… unusual transport behaviors regarding electrical conductivity, carrier concentration, or lattice thermal conductivity among these compounds have been identified, and we also present their rationales in depth. Thirdly, we conceived a new method to design a series of 1–2–2-type Zintl compositions …
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Lattice Dynamics in Temperature-driven and Photo-induced Phase Transitions
… the significance of phonon anharmonicity in the thermal phase transition, as well as the lattice dynamics of photo-excited crystals, specifically in VO2 and SnS/SnSe single crystals.</p><p>The thermal transport behavior and thermodynamics of VO2, which exhibits a well-studied metal-insulator …
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Cooling and crystallization of komatiite flows.
… constrained crystallization arising from strong thermal pradients and the high lattice thermal conductivity and near-infrared transparency of olivine (3-5 times greater than that of the surrounding melt). Such crystals exhibit a very strong preferred orientation with the a crystallographic axis …
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Improving supervised machine learning for materials science
… experimentally measured formation enthalpy and lattice thermal conductivity as case studies to exam the usefulness of information transfer and understand where and why information transfer helps. For situations where expansion of datasets is necessary, we propose to use active learning/Bayesian …
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Functional materials for thermal regulation
Developing thermal management materials with greater functionality for the control of heat dissipation and regulation is a fundamental step to improve the performance in many engineering systems. This dissertation presents experimental studies of heat conduction in distinctive thermal functional …
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Synthesis and thermoelectric properties of Mg2Si-Mg2Sn solid solutions for waste heat recovery
… model has been established to extract of the lattice contribution from the total thermal conductivity. The calculation results indicate that Ge substitutions slightly reduce the lattice thermal conductivity of Mg2Si0.4Sn0.6. Mg vacancies can be introduced in Mg2SixSn1−x due to Mg evaporation …
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Thermal conductivity and electrical resistivity of cemented carbides, titanium diboride and high temperature ceramic superconductors
… were studied via measurement and analysis of thermal conductivity and electrical resistivity from 15-1400 oK. It has been reported that YB8:2CU:-sO-7--,.. exhibits a significant rise in thermal conductivity just below the superconducting transition temperature, Te. This rise, or phonon bump, …
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Modeling microstructural effects of deformation resistance and thermal conductivity
… carrying out MD simulations to calculate its lattice thermal conductivity, I obtain the first quantitative evidence ever that the vibrational contribution is only a small part of the total thermal conductivity of refractory carbides at realistic carbon vacancy concentrations. This is a …
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Ultra low thermal conductivity in layered disordered crystalline materials
… an alternative route to achieve ultralow thermal conductivity in a dense solid. Thin films of disordered layered crystalline materials were deposited using Modulated Elemental Reactants (MER) method. Cross-plane thermal conductivity was measured using Time-Domain Thermo Reflectance (TDTR) …
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Studying phonon mean free paths at the nanoscale : modeling and experiments
… contributions of different phonon MFPs to thermal conductivity is termed thermal conductivity accumulation function. In this thesis, we advance a thermal conductivity spectroscopy technique based upon experimental observation of non-diffusive thermal transport using wire grid linear …
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