자료유형  

 학위논문

Control Number  

0017161784

International Standard Book Number  

9798382584010

Dewey Decimal Classification Number  

539.76

Main Entry-Personal Name  

Quillin, Kyle Matthew.

Publication, Distribution, etc. (Imprint  

[S.l.] : The University of Wisconsin - Madison., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

246 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-11, Section: B.

General Note  

Advisor: Sridharan, Kumar.

Dissertation Note  

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2024.

Summary, Etc.  

요약The development of advanced cladding and fuel materials is central to enhancing the safety and accident tolerance of light water reactors (LWRs). Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC-SiCf), on account of their superior high temperature strength and steam oxidation resistance, as well as acceptable irradiation damage resistance and neutronic characteristics, are being considered as potential accident tolerant fuel cladding materials for LWRs. However, the hydrothermal corrosion of SiC at normal reactor operating conditions presents a challenge toward its implementation. Protective corrosion-resistant coatings deposited on the outer surface of the SiC cladding offer a potential solution to addressing this challenge.For a coating material to serve as a corrosion barrier, it must effectively passivate when in contact with high temperature water. To this end, the coating should also possess a combination of mechanical characteristics including good adhesion to the substrate, a compressive residual stress state, and ductility to maintain its mechanical integrity during in-reactor service. The coating will be required to withstand the harsh environment inside the reactor core and be compatible with the underlying SiC at elevated temperature and under irradiation. Cr was selected as the coating material for investigation in this research as it has the potential to address these requirements, if a more fundamental understanding of the deposition processes, structure, properties, and performance can be achieved.A variety of magnetron sputtering technologies were used to deposit Cr films 5-10 µm in thickness on SiC substrates to understand the effects of process parameters on the structure of the films and their interface with the substrate, as well as their performance in harsh environments. Six types of sputtering processes were investigated, including (i) standard direct current magnetron sputtering (S-DCMS), (ii) pulsed DCMS (P-DCMS), (iii) ion-assisted DCMS (I-DCMS), and (iv) pulsed ion-assisted DCMS (PI-DCMS), (v) high-power impulse magnetron sputtering (HiPIMS), and (vi) bipolar HiPIMS (B-HiPIMS). The DCMS processes are characterized by low power densities, minimal atomic mobility during film growth, and negligible ionization of the sputtered flux prior to impingement on substrate surface. HiPIMS processes (both conventional and B-HiPIMS) involve much higher power densities and ionization levels, and consequently impart greater surface atomic mobilities than the DCMS processes. The research employs multi-scale materials characterization and testing approaches in harsh conditions to understand multiple scientific phenomena and themes that fundamentally govern the relationships between the deposition process and coating structure and properties with respect to the important performance considerations necessary for a materials system inside a reactor core. The first topic is understanding how energetics of deposition manifest in the coatings' structure, residual stress state, and mechanical behavior. The second relates to ion irradiation effects, from low energy (on the order of eV) during deposition (film evolution and growth) to high energy (on the order of MeV) ion beam irradiation experiments (to induce radiation damage) that provide insights into morphological evolution and compositional redistribution in the coating and coating-substrate interface in different energy regimes. The third theme involves elucidating interfacial phenomena including deposition-induced atomic mixing, coating-substrate interdiffusion and chemical interaction at elevated temperatures, interfacial evolution under irradiation, and mechanical behavior at the interface. Lastly, aspects specifically related to the Cr-SiC materials system, such as corrosion, phase equilibria, and amorphization under high energy irradiation are elucidated. Transmission electron microscopy (TEM) was used to characterize the structural features of the coatings at a nanoscale, including porosity, and grain size and orientation. Regardless of the specific process variant used, DCMS coatings exhibited fibrous grains separated by nanoscale porosity. The additional energetic ion bombardment in the two types of HiPIMS deposition processes and associated enhanced mobility resulted in coatings with fully dense microstructures and smoother surfaces. However, the morphology and grain size in the conventional HiPIMS and B-HiPIMS coatings were quite different and found to be dependent on substrate temperature and different characteristics of the ionized sputtered flux. High-resolution TEM (HRTEM) imaging of the interface revealed that a Cr-SiC mixed region about 2 nm in thickness formed at the coating-substrate interface for B-HiPIMS but was not evident for the DCMS coating. The observation of the mixed interfacial region in the B-HiPIMS coating was supported by a dynamic Monte Carlo simulation of interfacial composition evolution during the early stages of deposition. Using spatially resolved electron energy loss spectroscopy (EELS), it was determined that the mixed region formed on the Cr-rich side of the interface and contained a significant amount of carbon. Analysis of the fine structure of core-loss ionization edges supported with statistical compositional profiling of the interface revealed. (Abstract shortened by ProQuest).

Subject Added Entry-Topical Term  

Nuclear engineering.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Applied physics.

Subject Added Entry-Topical Term  

Engineering.

Index Term-Uncontrolled  

Accident tolerant fuels

Index Term-Uncontrolled  

Electron microscopy

Index Term-Uncontrolled  

Nuclear materials

Index Term-Uncontrolled  

Physical vapor deposition

Index Term-Uncontrolled  

SiC fuel cladding

Added Entry-Corporate Name  

The University of Wisconsin - Madison Materials Science and Engineering

Host Item Entry  

Dissertations Abstracts International. 85-11B.

Electronic Location and Access  

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Control Number  

joongbu:657474