UNIVERSITY OF CALIFORNIA, SAN DIEGO Particle size/ grain size correlation and mechanical properties of spark plasma sintered 8Y-ZrO2, MgAl2O4, and Al2O3 based composites A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Engineering Science (Mechanical Engineering) by Keyur Kashinath Karandikar Committee in charge: Professor Olivia Graeve, Chair Professor Shengqiang Cai Professor Robert Continetti Professor Joanna McKittrick Professor Martha Mecartney 2018 Copyright Keyur Kashinath Karandikar, 2018 All rights reserved. The Dissertation of Keyur Kashinath Karandikar as it is listed on UCSD Academic Records is approved, and it is acceptable in quality and form for publication on microfilm and electronically: ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ Chair University of California, San Diego 2018 iii TABLE OF CONTENTS SIGNATURE PAGE................................................................................................................. iii TABLE OF CONTENTS...........................................................................................................iv LIST OF FIGURES...................................................................................................................vii LIST OF TABLES....................................................................................................................xii ACKNOWLEDGEMENTS.....................................................................................................xiv VITA........................................................................................................................................xvi ABSTRACT OF DISSERTATION........................................................................................xvii CHAPTER 1: INTRODUCTION AND MOTIVATION.............................................................. 1.1 Ceramic oxide materials............................................................................................1 1.2 Oxide ceramics surrogate for nuclear project.............................................................2 1.3 Significance of particle size and grain size................................................................4 CHAPTER 2: PARTICLE SIZE DISTRIBUTION....................................................................... 2.1 Motivation for particle size distribution studies.........................................................8 2.2 Powder information and properties............................................................................9 2.3 Powder characterization methods and experiments.................................................12 2.4 Particle size distribution results...............................................................................21 2.5 Effect of milling in particle size distribution............................................................24 2.6 Particle size measurements and milling of multiphase powder mixtures.................30 2.7 Conclusion.............................................................................................................. 33 CHAPTER 3: SINTERING RESULTS & PARTICLE-GRAIN SIZE CORRELATION............. 3.1 Spark Plasma Sintering: Background and motivation..............................................34 3.2 Experimental setup and sintering load diagrams.....................................................37 iv 3.3 Post-sintering characterization: Density, X-ray diffraction, Polishing, Imaging.....43 3.4 Sintering results: Grain size distribution in single/multiphase composites..............47 3.5 Sintering results: Densification tendency in single/multiphase composites.............50 3.6 Results: particle size/grain size correlation – “size ratio” ........................................51 3.7 Discussion of sintering results: Grain growth/Densification...................................60 3.8 Sintering of ceramic oxides of two different powder sizes.......................................70 3.9 Discussion: Sintering of ceramic oxides of two different powder sizes...................75 3.10 Significance of current study as compared to previous literature...........................82 3.11 Conclusion.............................................................................................................91 CHAPTER 4: MECHANICAL PROPERTIES AND MICROSTRUCTURAL CHARACTERIZATION.............................................................................................................. 4.1 Motivation and Background....................................................................................93 4.2 Experimental Setup.................................................................................................95 4.3 Results: Hardness of single/multiphase composites................................................99 4.4 Results: Fracture toughness of single/multiphase composites...............................105 4.5 Results: Fracture surface characterization of single/multiphase oxides.................109 4.6 Discussion of hardness results in Single phase ceramic oxides..............................113 4.7 Comparisons of mechanical properties among single phase materials...................115 4.8 Fracture toughness vs. grain size tendency............................................................117 4.9 Fractal Micrography discussion studies.................................................................119 4.10 Comparative studies between single and multiphase composites........................121 4.11 Significance of the present study.........................................................................124 4.12 Conclusion...........................................................................................................129 v CHAPTER 5: HEATING RATE AND MASTER SINTERING CURVE.................................. 5.1 Experimental Set-up, Results, and Discussion.......................................................131 5.2 Master Sintering Curve: Theory and Procedure.....................................................141 5.3 Conclusion ............................................................................................................153 REFERENCES........................................................................................................................153 vi LIST OF FIGURES Figure 1.1 Model multiphase fine-grained ceramic oxide surrogate material for advance inert matrix fuel ...................................................................................................................................4 Figure 1.2 Schematics of ceramic sintering process ...................................................................5 Figure 2.1 Dynamic light characterizing technique used for particle size distribution.34, 35 Figure A highlights the schematics of laser diffraction system with laser pulse scattered by resulting particles and collected by a detector at an angle ϴ.. ..................................................12 Figure 2.2 Change in zeta potential concerning to pH in solution and respective stability of the suspension. The isoelectric point is the point where zeta potential is 0mV, i.e., the solution undergoes maximum deagglomeration. ....................................................................................14 Figure 2.3 Zeta potential (mV) vs. pH values for increasing concentrations of YSZ-3Y or 3Y- ZrO2 by volume % ....................................................................................................................18 Figure 2.4 Zeta potential (mV) vs. pH values at various concentrations (vol %) of YSZ-8Y or 8Y-ZrO2 ....................................................................................................................................18 Figure 2.5 Zeta potential (mV) vs. pH values at various concentrations of monoclinic ZrO2 .19 Figure 2.6A Particle size distribution by DLS of individual sample powder of (Al2O3)3 (Fig. E, F) single phase ceramic size powders. The results about change in particle sizes before and after milling are highlighted. .....................................................................................................27 Figure 2.7 SEM micrographs of as received(left) and milled powder(right) of single-phase ceramic oxides of 8Y-ZrO2 (in the previous page), MgAl2O4 and Al2O3 (present page)......29 Figure 2.8 Particle size distribution results obtained by DLS of binary sample powder of (8Y- ZrO2)1/(MgAl2O4)1, (8Y-ZrO2)2/(Al2O3)3, and (8Y-ZrO2)2/(MgAl2O4)1/(Al2O3)2 ternary phase ceramic size powders. .........................................................................................32 Figure 3.1 Timeline diagram regarding the background and the history of spark plasma sintering process. 61, 62 ............................................................................................................34 Figure 3.2 Publication history and trends related to use of spark plasma sintering to process potential advanced engineering materials.63 ............................................................................34 Figure 3.3 Principle set up for spark plasma sintering furnace .................................................36 Figure 3.4 Photograph of spark plasma sintering furnace at Alfred University,