The Microstructure and Properties of Transition Metal Nitride Nanocrystalline Coatings
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The Microstructure and Properties of Transition Metal Nitride Nanocrystalline Coatings By Song Xu A thesis in fulfilment of the requirements for the degree of Doctor of Philosophy School of Material Science and Engineering Faculty of Science April 2016 PLEASE TYPE THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Xu First name: Song Other name/s: Abbreviation for degree as given in the University calendar: Ph.D. School: Materials Science & Engineering Faculty: Science Title: The microstructure and properties of transition metal nitride nanocrystalline coatings Abstract 350 words maximum: (PLEASE TYPE) The composition, microstructure, mechanical properties and biocompatibility of a number of tantalum nitride coatings, deposited on Ti-Al-V substrates by the double cathode glow discharge technique, were investigated. With increasing nitrogen partial pressure, the composition of the tantalum nitride coatings changed from hexagonal Ta2N to fcc TaN. Both coatings exhibited a nanoporous structure comprising fine (~ 10 nm) equiaxed grains together with a homogenous distribution of (~5-10 nm) nanopores. The relatively high hardness and low elastic modulus of these coatings led to improved damage resistance and wear resistance for these tantalum nitride coatings. Further, Ta2N-based coatings also showed good compatibility with hydroxyapatite. However, the introduction of oxygen during the deposition process led to significant degradation of the coating hardness, wear resistance and damage resistance of these coatings. This was due to the presence of Ta2O5 and an amorphous tantalum oxynitride phase arising from the higher oxygen pressure during deposition. In addition to these tantalum nitride coatings, the composition, microstructure, and mechanical properties of zirconium nitride coatings again deposited by double cathode glow discharge technique were also investigated. Zirconium nitride coatings were deposited on both stainless steel and Ti-Al-V substrates. The zirconium nitride coatings on the stainless steel substrates exhibited a bimodal microstructure with both fine grains and more elongated coarser grains. In contrast, the coatings on the Ti-Al-V substrates showed a uniform microstructure comprising fine equiaxed grains and together with a number of nanopores. All these coatings showed comparable hardness values, but lower elastic modulus values, compared with zirconium nitride coatings deposited by other deposition techniques. Therefore, a relative high wear resistance and damage resistance may be expected for the zirconium nitride coatings studied in this thesis. By exploring the influence of nanopores on the mechanical properties of nanocrystalline Ta2N coatings, it was found that the presence of nanoporosity may increase wear resistance and damage resistance of these coatings by significantly reducing elastic modulus without greatly decreasing hardness. This suggests a promising new strategy for improving the mechanical properties of nanocrystalline coatings. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). ……………………………………… ………………… ……………………………… ……..…………………….……………… Signature Witness Signature Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: THIS SHEET IS TO BE GLUED TO THE INSIDE FRONT COVER OF THE THESIS COPYRIGHT STATEMENT ‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.' Signed ……………………………………………........................... Date ……………………………………………........................... AUTHENTICITY STATEMENT ‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’ Signed ……………………………………………........................... Date ……………………………………………........................... ORIGINALITY STATEMENT I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged Signed …………………………………………….............. Date …………………………………………….............. i ACKNOWLEDGEMENT Writing an “Acknowledgements” for a thesis is like writing down the last period at the end of a story. I thought about this time for a few times, however, when it really comes, I feel a little bit hesitating. This three years journey is a difficult but fantastic adventure for me. I can’t reach the destination without the kind help of a number of individuals. I owe them my deepest gratitude and best wishes. I would like to acknowledge their contributions here with my sincere thankfulness. Firstly, I would like to give my deepest gratitude to my supervisor Prof. Paul Munroe for his guidance and support in these three years. I am so fortunate to have Paul as my supervisor. I have to say I came to this university with only curiosity and passion, Paul taught me how to be an independent researcher. He dedicates a lot of energy in guiding me, and also taught me how to write academically with great patience. He also encouraged me to start a project on my own interest. I really learned a lot from His profound knowledge and critical attitude. I appreciate his untiring effort in reviewing my paper and thesis. I hope I could have the opportunity to work with him in the future. I would like to thank Prof. Jiang Xu for providing transition metal nitride specimens and for reviewing the manuscripts of my papers. We worked together in several projects. From him, I learned many strategies and experiences in paper writing and project designing. I also need to thank Dr. Zonghan Xie for his valuable comments during the paper writing stage. He did a lot of work in reviewing the manuscripts of my papers. I am so grateful for the kind help come from the technical and administrative staff at UNSW. Dr. Bill Joe spent a lot of time with me in the Nanomechanics Testing Lab in these three years. His patience and endeavor deeply impressed me. I want to give my heartfelt respect to Dr. George Yang for his efficiency and professionalism. I would like to give my thanks to the staffs in EMU, especially Dr. Charlie Kong, Mr. Sean Lim, and Ms. Katie Levick, they were always there when I needed help. I need to thank Dr. Bill Gong, Dr. Yu Wang and Dr. Anne Rich for their kind assistance. They help me a lot in my sample ii characterization. I also want to give my appreciation to Ms. Joanne Hallis, Dr. Anthony Zhang, Mr. Danny Kim, Ms. Laura McNally, Mr. Alan Chow, Ms. Lana Strizhevsky and Ms. Lucy Zhang from the School of Materials Science and Engineering. Only with their support, I can enjoy my three-year-life in UNSW. I also want to say thank you to all my friends. I know they will never ask for my thanks. The courage and concern they gave to me supported me in those good and bad times. To those of my brothers and sisters in “Playing Mafia Day and Night” group, I don’t know how to express my gratitude to you guys. I am so lucky to have you. I will always remember the happiness we created together. Youran, three years long-distance relationship, we made it. Thank you for your understanding and company. At last, I will give my heartfelt thanks to my parents. They brought me into this world, and give me all their love. They encouraged me to start this adventure three years ago, and supported me from beginning to end. “Thank you” is not nearly enough to express my gratitude to them. iii ABSTRACT The composition, microstructure, mechanical properties and biocompatibility of a number of tantalum nitride coatings, deposited on Ti-Al-V substrates by the double cathode glow discharge technique, were investigated.