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by Li, Kowk Cheung = 利用木材製作具有生物形態的碳化矽 / 李國彰. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Abstracts in English and Chinese. / by Li, Kwok Cheung = Li yong mu cai zhi zuo ju you sheng wu xing tai de tan hua xi / Li Guozhang. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of contents --- p.vi / List of figure captions --- p.x / List of table captions --- p.xiv / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Biomorphic products and their potential applications --- p.1 / Chapter 1.2 --- Structures and mechanical behaviors of wood --- p.1 / Chapter 1.3 --- Characteristics and applications of SiC --- p.2 / Chapter 1.4 --- Common methods of producing biomorphic SiC from wood --- p.2 / Chapter 1.4.1 --- Chemical vapor deposition --- p.3 / Chapter 1.4.2 --- Melt infiltration --- p.3 / Chapter 1.4.3 --- Sol-gel process --- p.4 / Chapter 1.5 --- Carbothermal reduction process of silica --- p.5 / Chapter 1.6 --- Objectives of present work --- p.5 / Chapter 1.6.1 --- Comments on the previous works --- p.5 / Chapter 1.6.2 --- Current approaches --- p.6 / References --- p.8 / Chapter Chapter 2 --- Experimental procedures / Chapter 2.1 --- Wood biotemplates --- p.10 / Chapter 2.1.1 --- Balsa --- p.10 / Chapter 2.1.2 --- Flame tree --- p.10 / Chapter 2.2 --- Sol Gel process --- p.11 / Chapter 2.2.1 --- Precursor --- p.11 / Chapter 2.2.2 --- Reaction mechanisms --- p.11 / Chapter 2.2.3 --- "Effects of pH, temperature, and environment" --- p.12 / Chapter 2.3 --- Preparation of biomorphic SiC / Chapter 2.3.1 --- HC1 pretreatment --- p.13 / Chapter 2.3.2 --- Infiltration of silica via sol gel process --- p.13 / Chapter 2.3.2.1 --- Balsa --- p.14 / Chapter 2.3.2.2 --- Flame tree --- p.15 / Chapter 2.3.3 --- Sintering --- p.15 / Chapter 2.3.4 --- Removal of carbon --- p.15 / Chapter 2.4 --- Characterization methods --- p.16 / Chapter 2.4.1 --- Scanning electron microscope and energy dispersive x-ray spectroscopy --- p.16 / Chapter 2.4.2 --- X-ray diffractometry --- p.16 / Chapter 2.4.3 --- Differential thermal analysis --- p.16 / Chapter 2.4.4 --- Compressive strength analysis --- p.17 / Chapter 2.5 --- Summary --- p.17 / References --- p.18 / Figures --- p.19 / Chapter Chapter 3 --- Results and discussions / Chapter 3.1 --- Balsa --- p.21 / Chapter 3.1.1 --- HC1 pretreatment --- p.21 / Chapter 3.1.2 --- Infiltration behaviors --- p.21 / Chapter 3.1.2.1 --- By the standard method --- p.21 / Chapter 3.1.2.2 --- Modified sol-gel process --- p.21 / Chapter 3.1.3 --- SiC products --- p.22 / Chapter 3.1.3.1 --- Volumetric shrinkage and weight loss --- p.22 / Chapter 3.1.3.2 --- Compositions --- p.23 / Chapter 3.1.3.3 --- Morphology and structure --- p.24 / Chapter 3.1.4 --- Optimal infiltration conditions --- p.25 / Chapter 3.2 --- Flame tree --- p.25 / Chapter 3.2.1 --- HC1 pretreatment --- p.26 / Chapter 3.2.2 --- Infiltration behaviors --- p.26 / Chapter 3.2.3 --- SiC products --- p.26 / Chapter 3.2.3.1 --- Volumetric shrinkage and weight loss --- p.26 / Chapter 3.2.3.2 --- Composition --- p.27 / Chapter 3.2.3.3 --- Morphology and structure --- p.27 / Chapter 3.3 --- Mechanisms for the formation of SiC cell walls --- p.30 / Chapter 3.4 --- Compressive strength --- p.31 / Chapter 3.5 --- Summary --- p.34 / References --- p.35 / Tables --- p.36 / Figures --- p.38 / Appendix --- p.65 / Chapter Chapter 4 --- Conclusions and future works / Chapter 4.1 --- Summary --- p.67 / Chapter 4.2 --- Suggestions for future work --- p.68 / References --- p.70

Solid oxide fuel cells (SOFC) in a flat-plate configuration require a hermetic seal between the fuel and air sides of the electrodes, and this seal must withstand a variety of thermally-induced stresses over the lifetime of the cell. In this study, quantitative microstructure-property relationships are developed to predict optimum seal structures for mechanical properties and thermal expansion coefficient criteria. These relationships are used to create an inverse approach to characterizing the processing method from the desired microstructure. The main focus of the work concentrates on providing tools to enable macroscopic property predictions from the constituent properties using homogenization techniques based on the individual phase properties and microstructure morphology. The microstructure is represented by two-point correlation functions. Statistical continuum mechanics models were then employed and developed to predict the mechanical and thermal properties of the material. The models enable the prediction of elastic modulus and coefficient of thermal expansion of the multi-phase material. The inelastic mechanical behavior was also studied, indicating microstructure dependence. These models will aid in predicting the a proper seal microstructure (with desired elastic stiffness, coefficient of thermal expansion, and viscoelastic behaviors) based on a desired level of crystallization glass-ceramic materials.

Ein Schwerpunkt der Arbeit ist die lokale Phasenanalyse keramischer Systeme mittels EBSD. Insbesondere bei MMC auf der Basis von TRIP-Stahl/Mg-PSZ ist die Ortsauflösung der bisher üblichen XRD-Phasenanalyse nicht ausreichend. Das gilt auch für die Analyse von Grenzflächenreaktionen, wie sie zum Beispiel bei Korrosionsprozessen auftreten. Es wurde eine Methode der Probenpräparation entwickelt und erfolgreich für unterschiedliche keramische Systeme eingesetzt. Ein Ergebnis ist der Nachweis von spannungs-assistierten Phasenumwandlungen in Mg-PSZ. Zweiter Schwerpunkt ist die Entwicklung einer in situ Druckverformungsapparatur für einen Labor-Röntgen-Tomographen. Mit dieser Apparatur können Druckverformungskräfte bis 100 kN erreicht werden. Tomographische Untersuchungen werden unter Druckspannung durchgeführt. Im Rahmen der Arbeit wurde insbesondere das Verformungs- und Schädigungsverhalten von MMC in Form von Schäumen und Wabenkörpern detailliert untersucht.