Scholars' Mine Doctoral Dissertations Student Theses and Dissertations Fall 2019 Microstructural evolution of zirconium carbide (ZrCₓ) ceramics under irradiation conditions Raul Florez Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Materials Science and Engineering Commons, and the Nuclear Engineering Commons Department: Nuclear Engineering and Radiation Science Recommended Citation Florez, Raul, "Microstructural evolution of zirconium carbide (ZrCₓ) ceramics under irradiation conditions" (2019). Doctoral Dissertations. 2821. https://scholarsmine.mst.edu/doctoral_dissertations/2821 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. i MICROSTRUCTURAL EVOLUTION OF ZIRCONIUM CARBIDE (ZrCx) CERAMICS UNDER IRRADIATION CONDITIONS by RAUL FERNANDO FLOREZ MEZA A DISSERTATION Presented to the faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfilment of the Requirements for the Degree DOCTOR OF PHILOSOPHY In NUCLEAR ENGINEERING 2019 Approved by: Joseph T. Graham, Advisor William G. Fahrenholtz Gregory E. Hilmas Miguel L. Crespillo Carlos H. Castano iii PUBLICATION DISSERTATION OPTION This dissertation consists of four manuscripts that were prepared for publication as follows. The paper entitled, “The irradiation response of ZrC ceramics at 800o C” (Paper I, Pages 28–59), was submitted to the Journal of the European Ceramic Society and is currently under revision. The manuscript entitled “Early stage oxidation of ZrCx under ion-irradiation at elevated temperatures” (Paper II: Pages 60–101) was submitted to the Journal of Corrosion Science. The manuscript entitled “Sequential Ion-Electron Irradiation of Zirconium Carbide Ceramics: Microstructural Analysis” (Paper III: Pages 102–137) was prepared for submission to the Journal of Nuclear Materials. The manuscript entitled “Fabrication and Microstructural Analysis of Hot-Pressed ZrCx with low Hf-content” (Paper IV: Pages 144–172) is intended for submission for publication in the Journal of Nuclear Materials following revision based on the recommendations of the dissertation committee and review by the authors. iv ABSTRACT A comprehensive understanding of the microstructural evolution of Zirconium Carbide (ZrCx) ceramics under irradiation conditions is required for their successful implementation in advanced Gen-IV gas-cooled nuclear reactors. The research presented in this dissertation focusses on elucidating the ion and electron irradiation response of ZrCx ceramics. In the first part of the research, the microstructural evolution was 3+ characterized for ZrCx ceramics irradiated with 10 MeV Au ions up to doses of 30 displacement per atom (dpa) at 800 ºC. Coarsening of the defective microstructure, as a function of dose, was revealed by transmission electron microscopy analysis. The lack of change in the irradiated microstructure, at doses above 5 dpa, indicated that a balance between irradiation damage accumulation and dynamic annealing of defects was reached. It was also found that concurrent oxidation occurred during the ion irradiation. The effects of irradiation on the morphology and microstructure of the initial oxide formed on the surface of ZrCx were investigated. The concomitant reduction in size and surface coverage of the oxide nodules at high doses, indicated that oxide dissolution was the predominant mechanism under irradiation conditions. In the second part of the research, Zirconium Carbide (ZrCx) was irradiated with 10 MeV Au3+ ions to a dose of 10 dpa and subsequently with 300 keV electrons in a transmission electron microscope (TEM). It was found that high-energy electron irradiation of pre-damaged ZrCx foils induce atomic mixing via radiation enhanced diffusion (RED), producing surface oxidation of the TEM foil. v ACKNOWLEDGEMENTS I would like to start by expressing my sincere gratitude to my advisor Dr. Joseph Graham for his continuous support through my doctoral studies and related research. Certainly, this work would not been possible without his motivation, guidance, and patience. I would also like to thank Dr. William Fahrenholtz and Dr. Gregory Hilmas for providing their unending advice and expertise to my work, in addition to their modelling of several qualities I hope to emulate in all facets of my life. Thanks to Dr. Miguel Crespillo for conducting the ion irradiation experiments and for showing me that the biggest factor limiting my research was myself. I am also grateful for everything Dr. Carlos Castano did for me over the last four years. I would be remiss if I did not thank Dr. Xiaoqing He at the Electron Microscopy Core (EMC) at the University of Missouri, Columbia. In addition to teaching me how to effectively utilize the electron microscopes, he has been a mentor and brainstorming partner for the last two years. His encouragement for my attending conferences and applying to fellowships has tremendously expanded my understanding on electron microscopy techniques. I would like to thank my friends and fellow students for all their help and support. Many people have helped me with this research, and I will not list the names for fear of omitting someone. Finally, my deepest gratitude goes to my parents, Raul and Ingrid, my siblings, Paula and Andres, and my little niece Juliana. Without your unconditional support, I would not been able to be where I am today. I love you all very much. vi TABLE OF CONTENTS Page PUBLICATION DISSERTATION OPTION ................................................................... iii ABSTRACT ....................................................................................................................... iv ACKNOWLEDGMENTS ...................................................................................................v LIST OF FIGURES .......................................................................................................... xii LIST OF TABLES ........................................................................................................... xvi SECTION 1. INTRODUCTION ...................................................................................................... 1 1.1. RESEARCH SCOPE AND CONTRIBUTIONS ............................................... 4 1.2. DISSERTATION OUTLINE ............................................................................. 5 2. STATE OF KNOWLEDGE ....................................................................................... 7 2.1. CRYSTAL STRUCTURE AND PHASE DIAGRAM ...................................... 7 2.2. PROCESSING OF ZIRCONIUM CARBIDE CERAMICS ............................ 10 2.2.1. Solid Phase Reaction. ............................................................................. 10 2.2.2. Solution Based Fabrication. ................................................................... 11 2.2.3. Vapor Phase Fabrication. ....................................................................... 12 2.3. THERMOMECHANICAL PROPERTIES ...................................................... 13 2.4. MAJOR DEGRADATION MODES ................................................................ 15 2.4.1. Radiation Damage. ................................................................................. 15 2.4.2. Chemical Compatibility with Coolant. ................................................... 22 2.4.3. Air Ingress Accident. .............................................................................. 23 vii 2.4.4. Other Degradation Mechanisms ............................................................. 27 PAPER I. THE ION IRRADIATION RESPONSE OF ZrC CERAMICS AT 800 ºC ............. 28 ABSTRACT ................................................................................................................. 28 1. INTRODUCTION .................................................................................................... 29 2. EXPERIMENTAL PROCEDURE AND METHODS............................................. 33 2.1. SAMPLE PREPARATION .............................................................................. 33 2.2. ION IRRADIATION ........................................................................................ 34 2.3. MATERIAL CHARACTERIZATION ............................................................ 36 2.3.1. Grazing Incidence X-Ray Diffraction (GIXRD). ................................... 36 2.3.2. Line Profile Analysis. ............................................................................. 37 2.4. ELECTRON MICROSCOPY .......................................................................... 37 2.5. RAMAN SPECTROSCOPY ............................................................................ 38 3. RESULTS AND DISCUSSION .............................................................................. 39 3.1. CONTROL SPECIMEN ................................................................................... 39 3.2. IRRADIATED SPECIMENS ........................................................................... 41 3.2.1. GIXRD and TEM Analysis. ................................................................... 41 3.2.2. Raman Spectroscopy. ............................................................................. 46 4. CONCLUSIONS .....................................................................................................