Scholars' Mine Masters Theses Student Theses and Dissertations Summer 2020 Intrinsic mechanical properties of zirconium carbide ceramics Nicole Mary Korklan Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Ceramic Materials Commons Department: Recommended Citation Korklan, Nicole Mary, "Intrinsic mechanical properties of zirconium carbide ceramics" (2020). Masters Theses. 7956. https://scholarsmine.mst.edu/masters_theses/7956 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]. INTRINSIC MECHANICAL PROPERTIES OF ZIRCONIUM CARBIDE CERAMICS by NICOLE MARY KORKLAN A THESIS Presented to the Faculty of the Graduate School of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY In Partial Fulfillment of the Requirements for the Degree MASTERS OF SCIENCE IN CERAMIC ENGINEERING 2020 Approved by: Gregory E. Hilmas, Advisor William G. Fahrenholtz Jeremy L. Watts iii PUBLICATION THESIS OPTION This thesis consists of the following manuscripts which have been or will be submitted for publication as follows. Paper I: Pages 17-30 entitled “Processing and Room Temperature Properties of Zirconium Carbide” has been submitted to the Journal of the American Ceramic Society and is in review. Paper II: Pages 31-43 entitled “Ultra High Temperature Strength of Zirconium Carbide” is being drafted for publication. iv ABSTRACT This research focuses on the processing and mechanical properties of zirconium carbide ceramics (ZrCx). The first goal of this project was to densify near stoichiometric (i.e., x as close to 1 as possible) and nominally phase pure ZrCx. The maximum stoichiometry achieved for the ZrCx (C/Zr ratio of 0.92) was measured using gas fusion analysis. Hot pressing was used to obtain dense ZrCx. Archimedes was used to determine the relative density of hot pressed ZrCx at >95%. Scanning electron microscopy (SEM) was used to determine the overall microstructure of the hot pressed ZrCx. The measured porosity was ~4 vol% and additional unreacted carbon was observed in SEM images. The average grain size was 2.7 ± 1.4 pm with a maximum observed grain size of 17.5 pm. The second goal of the project was to measure the hardness, flexure strength, and fracture toughness of ZrCx at room temperature. Flexure strength at elevated temperatures, from 1600 to 2400°C, was also measured. Vickers’ hardness was measured at two different loads and decreased from 19.5 GPa at a load of 0.5 kgf to 17.0 GPa at a load of 1 kgf. Flexure strength was 362.3 ± 46 MPa at room temperature and was roughly constant up to 2200°C where the strength decreased to 283 ± 34 MPa. Fracture toughness was determined to be 2.9 ± 0.1 M Pam1/2 at room temperature. A Griffith-type analysis was used in determining the strength limiting flaws in the room temperature tests which was determined to be the largest grains of ZrC in the microstructure. The test bars used in the high temperature tests showed a slight increase in the average grain size but still within the standard deviation of the room temperature test bars. v ACKNOWLEDGEMENTS First, I would like to thank my advisor, Dr. Gregory Hilmas, for his guidance and patience throughout my graduate studies and research. Next, I would like to thank Dr. William Fahrenholtz for providing advice and direction in my research. I would also like to thank Dr. Jeremy Watts for his assistance in the laboratory. I would like to thank NSF for providing the funding for this research with grant number DMR-1742086. I would like to thank my peers in 307 for all there help and support. At the start of my graduate research they taught me how to operate the equipment needed for my research. They provided advice and kept me on track when I needed it most. Finally, I would like to thank my family for their unending support and always believing in me. Without your support I would not have made it to where I am today. Thank you. vi TABLE OF CONTENTS Page PUBLICATION THESIS OPTION...................................................................................iii ABSTRACT.......................................................................................................................iv ACKNOWLEDGEMENTS................................................................................................v LIST OF ILLUSTRATIONS.............................................................................................ix LIST OF TABLES..............................................................................................................x SECTION 1. INTRODUCTION...................................................................................................... 1 2. LITERATURE REVIEW........................................................................................... 3 2.1 CRYSTAL STRUCTURE.................................................................................... 3 2.2 PROCESSING OF ZIRCONIUM CARBIDE CERAMICS................................ 6 2.2.1 Solid Phase Reaction.................................................................................... 7 2.2.2 Solution-Based Fabrication............................................................................ 9 2.2.2 Vapor Phase Fabrication...............................................................................10 2.3 SINTERING AND DENSIFICATION.............................................................. 10 2.3.1 Pressureless Sintering...................................................................................12 2.3.2 Hot Pressing..................................................................................................12 2.3.3 Reactive Hot Pressing...................................................................................13 2.3.4 Spark Plasma Sintering.................................................................................14 2.4 MECHANICAL PROPERTIES..........................................................................14 2.4.1 Room Temperature.....................................................................................15 vii 2.4.2 Elevated Temperature................................................................................ 15 PAPER I. PROCESSING AND ROOM TEMPERATURE PROPERTIES OF ZIRCONIUM CARBIDE.......................................................................................... 17 ABSTRACT.................................................................................................................. 17 1. INTRODUCTION.................................................................................................... 17 2. EXPERIMENTAL PROCEDURE............................................................................19 2.1 PROCESSING.................................................................................................... 19 2.2 CHARACTERIZATION.................................................................................... 20 2.3 MECHANICAL TESTING................................................................................ 22 3. RESULTS AND DISCUSSION............................................................................... 23 3.1 DENSITY AND MICROSTRUCTURE............................................................ 23 3.2 MECHANICAL PROPERTIES......................................................................... 24 4. SUMMARY.............................................................................................................. 26 ACKNOWLEDGEMENTS.......................................................................................... 26 REFERENCES ............................................................................................................ 29 II. ULTRA HIGH TEMPERTURE STRENGTH OF ZIRCONIUM CARBIDE.......31 ABSTRACT................................................................................................................. 31 1. INTRODUCTION.................................................................................................... 31 2. EXPERIMENTAL PROCEDURE........................................................................... 33 2.1 PROCESSING.................................................................................................... 33 2.2 CHARACTERIZATION.................................................................................... 34 2.3 MECHANICAL TESTING 35 viii 3. RESULTS AND DISCUSSION............................................................................... 35 3.1 DENSITY AND MICROSTRUCTURE............................................................ 35 3.2 MECHANICAL PROPERTIES......................................................................... 36 3.3 SURFACE MICROSTRUCTURE..................................................................... 39 4. SUMMARY.............................................................................................................. 40 ACKNOWLEDGEMENTS.......................................................................................... 40 REFERENCES ............................................................................................................ 43 SECTION 3. CONCLUSIONS ..................................................................................................... 44 4. FUTURE WORK.....................................................................................................