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Title:Mapping the thermal conductivity of SiC/SiC composites
Author(s):Brethauer, John
Advisor(s):Cahill, David G.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Silicon carbide (SiC)
Thermal conductivity
Abstract:This thesis investigates the uses of time-domain thermoreflectance (TDTR) to map the thermal conductivity of SiC/SiC composites that are being considered for use as replacement materials in current light-water reactors (LWR), and also as materials for use in next generation nuclear reactors. The thermonuclear properties of the SiC/SiC composites can be tuned to particular situations by varying how the composite is formed. To this end, computational methods are used to predict the properties of these composites. However, currently these methods only take into account the thermal properties of the constituent components of the composite prior to being integrated, potentially missing information on how the thermal properties of the components change post-composite-integration. Additionally, they do not take into account the interfacial thermal conductance between the fiber, interphase, and matrix, and the interphase is typically calculated based on the through-plane thermal conductivity of the matrix, if it is calculated at all. This thesis uses TDTR to map Hi-Nicalon Type S fiber, CVI matrix SiC/SiC composites, enabling the measurement additional thermal information than can be obtained by measuring the matrix or fibers of a composite individually. The thermal conductivity of the interphase is also measured. Crystalline 6H and 4H SiC wafers have their thermal conductivity measured using TDTR, and their phases are confirmed through Raman spectroscopy. The effects of irradiation on SiC is investigated by using TDTR mapping to measure the thermal conductivity of a 6H SiC wafer that has been implanted with He ions. Additional uses of TDTR mapping are explored by measuring the thermal conductivity of hybrid superlattice structures, and beam offset measurements are used to measure the in-plane thermal conductivity of a MEMS infrared detector device.
Issue Date:2017-04-27
Rights Information:Copyright 2017 John Brethauer
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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