University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School 7-7-2008 Mechanical Properties of Particulate-Reinforced Boron Carbide Composites Lorenzo W. Hankla University of South Florida Follow this and additional works at: https://scholarcommons.usf.edu/etd Part of the American Studies Commons Scholar Commons Citation Hankla, Lorenzo W., "Mechanical Properties of Particulate-Reinforced Boron Carbide Composites" (2008). Graduate Theses and Dissertations. https://scholarcommons.usf.edu/etd/278 This Thesis is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Mechanical Properties of Particulate-Reinforced Boron Carbide Composites by Lorenzo W. Hankla A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Department of Mechanical Engineering College of Engineering University of South Florida Major Professor: Ashok Kumar, Ph.D. Nathan Crane, Ph.D. Muhammad Rahman, Ph.D. Makoto Hirai, Ph.D. Ramachandran Radhakrishnan, Ph.D. Date of Approval: July 7, 2008 Keywords: B4C, silicon carbide, SiC, titanium diboride, TiB2, microhardness, fracture toughness, flexure strength, modulus of rupture, elastic modulus, Plasma Pressure Compaction, P2C ©Copyright 2008, Lorenzo W. Hankla To Dad, Laura, Amanda, Beth, and, of course, my favorite Mom. ACKNOWLEDGEMENTS Earning a postgraduate is not an easy task and, as such, I would like to express my sincere gratitude to the large number of people who helped me along the way. First, I would like to extend my appreciation to my major professor, Dr. Ashok Kumar, for his aid and support throughout this investigation. I know few are given the chance to conduct research in an industrial environment and I am thankful for being given the chance to do just that. I would also like to thank my committee members Dr. Nathan Crane and Dr. Muhammad Rahman for taking the time to review this manuscript and provide me with their valuable feedback. Special thanks goes out to Dr. Makoto Hirai for taking the time to sit on my committee and help me with all of the scanning electron microscope images seen in this manuscript. I would also like to extend appreciation to everyone at Materials Modification Inc. in Fairfax, Virginia for the constant help and support provided to me throughout this research endeavor. Without the helpful guidance and support from Dr. Ramachandran Radhakrishnan, Mr. Jim Intrater, and Dr. T. S. Sudarshan, this research would have never been possible. Finally, I would like to thank my family and close friends for their constant support, love, and encouragement throughout this research process: thank you all! TABLE OF CONTENTS LIST OF TABLES .........................................................................................................iv LIST OF FIGURES........................................................................................................vi ABSTRACT...................................................................................................................xi CHAPTER 1: INTRODUCTION ....................................................................................1 CHAPTER 2: LITERATURE REVIEW..........................................................................6 2.1. CERAMICS..................................................................................................6 2.1.1. HISTORY .........................................................................................8 2.1.2. STRUCTURAL CERAMICS ................................................................10 2.2. POWDER PROCESSING...........................................................................11 2.2.1. POWDER SYNTHESIS ......................................................................11 2.2.1.1. Boron Carbide................................................................12 2.2.1.2. Silicon Carbide...............................................................13 2.2.1.3. Titanium Diboride..........................................................14 2.2.2. POWDER BLENDING .......................................................................15 2.2.3. FORMING.......................................................................................16 2.2.4. SINTERING.....................................................................................18 2.2.4.1. Plasma Pressure Compaction..........................................22 2.2.5. FINISHING .....................................................................................24 2.3. STRUCTURE OF CERAMICS...................................................................25 2.3.1. CHEMICAL BONDING .....................................................................25 2.3.2. CRYSTALLINE STRUCTURE.............................................................26 2.3.2.1. Boron Carbide................................................................29 2.3.2.2. Silicon Carbide...............................................................35 2.3.2.3. Titanium Diboride..........................................................40 2.3.3. MICROSTRUCTURE.........................................................................43 2.3.3.1. Grain-Size Reduction .....................................................43 2.4. MECHANICAL PROPERTIES OF CERAMICS........................................44 2.4.1. MICROHARDNESS ..........................................................................44 2.4.1.1. Mechanical Theory.........................................................45 2.4.1.2. Testing Methods.............................................................47 2.4.2. FRACTURE TOUGHNESS .................................................................50 2.4.2.1. Mechanical Theory.........................................................50 i 2.4.2.2. Testing Methods.............................................................54 2.4.3. FLEXURE STRENGTH......................................................................58 2.4.3.1. Mechanical Theory.........................................................58 2.4.3.2. Testing Methods.............................................................60 2.4.4. ELASTIC MODULUS........................................................................62 2.4.4.1. Mechanical Theory.........................................................62 2.4.4.2. Testing Methods.............................................................65 2.4.5. BORON CARBIDE ...........................................................................66 2.4.6. SILICON CARBIDE ..........................................................................67 2.4.7. TITANIUM DIBORIDE......................................................................68 2.5. TOUGHENING MECHANISMS ...............................................................69 2.5.1. GRAIN BOUNDARY STRENGTHENING..............................................69 2.5.2. CRACKTIP INTERACTION ................................................................70 2.5.2.1. Crack Bowing ................................................................70 2.5.2.2. Crack Deflection ............................................................72 2.5.2.3. Ultra-Tough Particulate Reinforcement ..........................74 2.5.3. CRACKTIP SHIELDING ....................................................................79 2.5.3.1. Transformation Toughening ...........................................79 2.5.3.2. Microcracking................................................................81 2.5.4. CRACK BRIDGING..........................................................................83 CHAPTER 3: EXPERIMENTAL METHODOLOGY...................................................86 3.1. POWDER PROCESSING...........................................................................86 3.1.1. RAW CERAMIC POWDERS...............................................................86 3.1.2. POWDER BLENDING .......................................................................88 3.1.3. FORMING.......................................................................................90 3.1.4. SINTERING.....................................................................................92 3.1.5. FINISHING .....................................................................................93 3.2. MATERIAL CHARACTERIZATION........................................................94 3.2.1. DENSITY MEASUREMENTS .............................................................95 3.2.2. POROSITY......................................................................................96 3.2.3. PHASE IDENTIFICATION..................................................................96 3.2.4. MICROSTRUCTURAL CHARACTERIZATION ......................................97 3.2.4.1. Grain-Size......................................................................97 3.2.4.2. Fractography ..................................................................98 3.3. MECHANICAL PROPERTIES ..................................................................99 3.3.1. VICKERS MICROHARDNESS ............................................................99 3.3.2. FOUR-POINT BEND TESTS ............................................................100 3.3.2.1. Fracture Toughness ......................................................102 3.3.2.2. Flexure Strength...........................................................103