University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2010 LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS Ding Li University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Li, Ding, "LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS" (2010). University of Kentucky Doctoral Dissertations. 91. https://uknowledge.uky.edu/gradschool_diss/91 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Ding Li The Graduate School University of Kentucky 2010 LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS ABSTRACT OF DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Engineering at the University of Kentucky By Ding Li Lexington, Kentucky Director: Dr. Fuqian Yang, Professor of Materials Engineering Lexington, Kentucky 2010 Copyright © Ding Li 2010 ABSTRACT OF DISSERTATION LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS Bioactive glasses react with the human physiological solution in control of their biofunctionality. The stress state in bioactive glasses determines the chemomechanical reaction and their biofunctionality. Using the microindentation technique, the effect of the indentation deformation on the surface damage and material dissolution of 45S5 bioglass was investigated. The indentation-induced residual stresses were calculated. Complete anelastic recoveries of the indentation depths and the impression marks were observed for the first time, which was likely driven by the stored strain energy over the anelastic deformation zone. The indentation-induced local surface damages were revealed before and after the immersion tests in phosphate buffer solution (PBS). The growth of the cracks in the PBS solution displayed the stress-corrosion behavior with the crack-growth speed being a linear function of the indentation load. 45S5-bioglass was crystallized at temperature of 650 ºC. Microindentation technique also was used to study the localized mechanical behavior of the crystallized 45S5-bioglass. The crystallization had little effect on the indentation hardness, and the indentation hardness of the crystallized 45S5-bioglass is the same as that of the corresponding material in vitreous state. The fracture toughness is about 3 times less than that of annealed 45S5-bioglass in vitreous state, suggesting the preference of using bioactive glasses of vitreous state in the implant applications. Also, the effect of crystallization on the material dissolution was examined in phosphate buffer solution. We also studied the growth and mechanical behaviors of the Ca-P precipitate layers formed on 45S5 bioglass in simulated body fluid. The thickness of the Ca-P precipitate layers was proportional to the square root of the immersion time, and the ratio of Ca/P in the Ca-P precipitate layers increased with the immersion time and approached 1.67, corresponding to the stoichiometric hydroxyapaptite (HA).Using the indentation technique, the indentation behavior of the Ca-P precipitate layers was investigated. The indentation hardness of the HA layers formed in SBF was found to be 0.40 GPa, and the contact modulus was 12.0 GPa. The contact modulus of 12.0 GPa is close to that of cortical bone. In this thesis, the primary mechanical properties of the non-crystalline and crystalline bioglass 45S5 were revealed. The relationship between the dissolution rate and localized residual stresses are discussed. With such knowledge, the evaluation of implants with respect to manufacturing processes, control, and service conditions now has another variable to consider and evaluate against performance. KEYWORDS: Bioglass, Residual stress, Crystallinity, Indentation, Bioactivity ____Ding Li ______ ________ 04/01/2010 LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS By Ding Li _____Fuqian Yang___________ Director of Dissertation ___ Stephen Rankin_ _______ Director of Graduate Studies _____04/01/2010____________ Date RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor’s degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgements. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date DISSERTATION Ding Li The Graduate School University of Kentucky 2010 LOCALIZED MECHANICAL DEFORMATION AND DISSOLUTION OF 45S5 BIOGLASS DISSERTATION A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College of Engineering at the University of Kentucky By Ding Li Lexington, Kentucky Director: Dr. Fuqian Yang, Professor of Materials Engineering Lexington, Kentucky 2010 Copyright © Ding Li 2010 DEDICATED TO MY FAMILY ACKNOWLEDGEMENT Firstly I would like to sincerely thank my advisor Dr. Fuqian Yang for his invaluable guidance, continuous encouragement and constructive instructions. I am grateful to Dr. John Nychka, Dr. Y. T. Cheng, Dr. Stephen Rankin, Dr. David Puleo and Dr. Richard Eitel for their helpful insight and supervision. I also appreciate the support from Dr. Yuming Zhang. In addition I want to thank all of my colleagues in the Lab: Rong Chen, Juchuan Li, Hongmei Dang, Yan Li, Ning Zhang, and Ming Liu for their helpful suggestions for my work. In addition, I want to give my thanks to my parents for their endless love and support throughout all my life. Lastly I’d like to express my great appreciation to my Husband, Kun Qian, for bringing me and sharing with me so many wonderful moments in my life. iii TABLE OF CONTENTS Acknowledgments…………………...……………………………………………….iii List of Tables……………………….………………………………………………...vii List of Figures……………………………………………………………………….viii Chapter 1 Introduction and Overview............................................................................1 1.1 Fundamental of Bioglass..........................................................................................1 1.1.1 Concept, classification, and applications of bioglass........................................1 1.1.2 Bioglass reaction and definition of bioactivity..................................................2 1.1.3 Processing techniques........................................................................................4 1.2 Factors affecting the Bioactivity of Bioglass...........................................................5 1.2.1 Porous characteristics........................................................................................5 1.2.2 Surface Morphology..........................................................................................7 1.2.3 Residual Stresses .............................................................................................10 1.2.4 Crystallinity.....................................................................................................18 1.3. Experimental objectives and scope of this dissertation ........................................19 Chapter 2 Anelastic Indentation Recovery of Bioglass at Room Temperature............30 2.1 Introduction............................................................................................................30 2.2. Experimental.........................................................................................................31 2.3 Results and Discussion ..........................................................................................32 2.4 Summary................................................................................................................35 Chapter 3 Surface Morphological Changes Accompanying Dissolution of Bioactive Glass: Effect of Residual Stress...................................................................40 3.1. Background...........................................................................................................40 3.2．Experimental.......................................................................................................41 3.2.1 Sample Preparation..........................................................................................41 3.2.2Indentation........................................................................................................41 3.2.3 Immersion in vitro ...........................................................................................42 3.2.4 Materials Characterization ..............................................................................42 3.3. RESULTS AND DISCUSSION............................................................................42 3.3.1 Indentation Characteristics..............................................................................42 iv 3.3.2 Residual Energy...............................................................................................46