Ph.D., Faculty of Engineering and the Built Environment, University of the Witwatersand, 2012 / This thesis focuses on the boron suboxide B6O, a boron-rich super-hard ceramic material. With hardness values previously reported between 24 GPa and 45 GPa, B6O is one of the hardest known materials. Although first reports on boron suboxides date back as far as 1909 (Weintraub E., Transactions of the American Electrochemical Society, 16 (1909) 165), it is the B6O-based composites that have attracted considerable interest in recent years due to their enormous technological potential, especially as an alternative to polycrystalline diamond and polycrystalline cubic boron nitride for wear and abrasive applications. Investigations into the properties of B6O itself appear to have been neglected in favour of the improvement of densification and fracture toughness of the composites. The B6O samples used for the work reported in this work was hot-pressed was prepared under an argon environment at 1800 C and 50 MPa for 20 minutes followed metallographical preparation. The density of the hot-pressed compacts measured 2.44 g/cm3. The starting B6O powder material was supplied from the Fraunhofer Institute for Ceramic Technologies and Systems, Dresden. This thesis primarily seeks to generate and report as much practical data for polycrystalline B6O materials prepared by uniaxial hot-pressing as possible from a variety of characterization techniques. Firstly, the Raman spectra of hot-pressed B6O, which was until now poorly understood, was investigated using using a 514.5 nm green Ar+ laser excitation source. Secondly, the fundamental nature of some mechanical properties of hot-pressed B6O were investigated by means of Vickers and Berkovich indentation techniques. New approaches for data analysis, especially the investigations of the nanomechanical properties of hot-pressed B6O by Berkovich nanoindentation, were also suggested. Thirdly, the intrinsic hardness of hot-pressed B6O was investigated by means of a comprehensive inter-model comparison study. Fourthly, a combined experimental and simulation approach for determining mechanical properties of hot-pressed B6O by nanoindentation was also carried out, based on the outcomes of the study, the deformation response of the material under dynamic indentation was investigated at di erent stages using a custom developed finite element model. Finally, based on the preliminary ab initio density functional calculations of the structural properties of B6O conducted by Lowther showing that the presence of a high electronegativity interstitial in the B6O structure could enhance the strength of the bonding in B6O, fluorine ion implantation into B6O were conducted. The e ects to the structural and the nanomechanical properties of radiation damage induced by ion implantation was investigated. The possible formation of novel nanostructures in the ion-irradiated B6O matrix near-surface was also investigated. Results obtained from this study provides a vast amount of practical data for hot-pressed B6O materials as well as a number of novel analysis approaches for the extraction useful properties from the measured raw data. Firstly, using an automated background subtraction method, observable first- and second-order Raman spectra of B6O were obtained. A comparative analysis with previously reported spectra of other -rhombohedral boron-rich ceramic materials demonstrate a good agreement. Results also confirm the existence of highly resolved Raman modes measured at ambient conditions using a green Ar+ excitation source which is contrary to the conventional understanding. Secondly, results from the micro-indentation investigations indicate the measured microhardness exhibits indentation load dependence. A model inter-comparison study of indentation size e ects in the microhardness measurements of hot-pressed B6O is comprehensively discussed. Thirdly, the intrinsic hardness value of 30 GPa was deduced. Fourthly, a quantitative analysis approach was developed to simulate multi-cycling loading load-displacement curves from a single measured load-displacement nanoindentation curve. Based on the results, the nature of the indentation size e ect in the nanoindentation hardness as well as the intrinsic nanomechanical properties of hot-pressed B6O were established. Fifthly, a combined experimental and finite element method simulation approach for determining mechanical properties of hot-pressed B6O by nanoindentation was developed. Based on the outcomes of the combined experimental and simulation studies, the deformation response of the material under dynamic indentation was also investigated at di erent stages using a custom developed finite element model. Finally, results from the structural characterization of the ion implanted B6O material demonstrates the formation of novel nanostructures by means of the ion bombardment of B6O. In addition, the study presented here also seeks to investigate the e ects of the fluorine ion implantation on the near-surface nanomechanical properties of hot-pressed B6O. The principal conclusions that the study provide are both comprehensive practical data for B6O materials prepared by uniaxial hot-pressing. A number of properties, including the Raman spectra, the intrinsic hardness, and the radiation resistance and the e ects of radiation damage are reported in the thesis.

SC-15 epoxy is used in many industrial applications and it is well known that the mechanical and viscoelastic properties of epoxy can be signicantly enhanced when reinforced with nanofillers. In this work, SC-15 epoxy is reinforced by loading with magnetically-active nanofillers and cured in a modest magnetic field. Because of the signicant magnetic response of the nanofillers, this is a low cost and relatively easy technique for imposing a strong magnetic anisotropy to the system without the need of a superconducting magnet. It is also found that this method is an effective way of enhancing the mechanical properties of epoxy. Three systems were prepared and studied. The first is a dilute system of various concentrations of Fe2O3 nanoparticles in SC-15 epoxy. The second system is a combination of Fe2O3 nanoparticles and chemically-functionalized single-walled carbon nanotubes (SWCNT(COOH)s) in SC-15 epoxy. The third is a dilute system of SWCNT(COOH)s decorated with Fe3O4 particles t hrough a sonochemical oxidation process in SC-15 epoxy. Samples have an initial cure of 6 hrs in a magnetic led of 10 kOe followed by an additional 24 hours of post curing at room temperature. These are compared to the control samples that do not have initial field curing. Tensile and compressive stress-strain analysis of the prepared systems shows that mechanical properties such as tensile strength, tensile modulus and compressive strength are enhanced with the inclusion of these nanofillers. It is also found that there is an anisotropic enhancement of these properties with respect to the imposed curing field. An interesting phenomenon is observed with the increase in modulus of toughness and fracture strain with nanotube inclusion. / These parameters are drastically enhanced after curing the systems in a magnetic field. While there is a modest shift in glass transition temperature during viscoelastic analysis, the thermal stability of the created systems is not compromised. Results of these mechanical enhancements will be compared with other nanoloading techniques from literature. / by Olga Malkina. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

O presente trabalho busca o entendimento do aparecimento da fase cristalina em compósitos de polipropileno isotático, que contém carbonato de cálcio, em presença ou não de polipropileno modificado com anidrido maléico (PPMA). Vários tipos de CaCO3 foram utilizados: com diâmetros médios de 0,9 m, com e sem tratamento superficial, 2,5 m e 3,0 m. As duas séries de compósitos, com e sem PPMA, denominadas iPP/CaCO3/PPMA e iPP/CaCO3, foram formuladas com as seguintes razões mássicas, 94,5/5/0,5% e 95/5, respectivamente. Em ambas as séries, observou-se a ocorrência das fases cristalinas e do polipropileno; entretanto, a concentração relativa variou de acordo com o tipo de compósito. A caracterização das fases cristalinas presentes nos compósitos foi realizada utilizando a difratometria de raio-x (DRX) e análises térmicas, principalmente, calorimetria diferencial exploratória (DSC). As análises por DSC incluíram o estudo cinético da cristalização isotérmica e não isotérmica dos compósitos. Os resultados obtidos permitiram identificar os compósitos com maior concentração de fase cristalina e relacionar a sua formação com os constituintes presentes nos compósitos. / The present work aims to understand the occurrence of the beta crystalline phase in composites of isotactic polypropylene with calcium carbonate in the presence or not of polypropylene grafted maleic anhydride (PPMA). CaCO3 having different average diameter were used: 0.9 m with and without surface treatment, 2.5 m and 3.0 m. Both series of composites, one with PPMA and another without, named iPP/CaCO3/PPMA and iPP/CaCO3, were formulated at the following mass proportions: 94.5/5/0.5% and 95/5, respectively. The presence of the e crystalline phases in polypropylene were observed. However, the relative concentration of such phases depended on the composite composition. The characterization of the crystalline phases in composites were performed by using x-ray diffraction (DRX) and thermal analyses, mainly, differential scanning calorimetry (DSC). DSC analysis was used to investigate isothermal crystallization kinetic and nonisothermal crystallization kinetic. The results allowed the identification of the composites with higher concentration of crystalline phase and it was possible to attribute the phase occurrence to the presence of specific constituents of the composites.

by Chan Man-ng. / Thesis (M.Ph.)--Chinese University of Hong Kong. / Bibliography: l. 108.

by Fung-luen Kwong. / Thesis submitted in: August 1998. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 130-131). / Text in English; abstract also in Chinese. / by Fung-luen Kwong. / Acknowledgements --- p.i / Abstract --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Development of ceramic materials --- p.1 / Chapter 1.2 --- Alumina-Zirconia advanced ceramics --- p.2 / Chapter 1.3 --- About this thesis --- p.3 / Chapter 2 --- Related work and Motivation --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- Powder synthesis --- p.7 / Chapter 2.2.1 --- Mechanical milling --- p.7 / Chapter 2.2.2 --- Sol-gel methods --- p.8 / Chapter 2.2.3 --- CVD methods --- p.12 / Chapter 2.2.4 --- Hydrothermal processing --- p.12 / Chapter 2.2.5 --- Wear of Zr02 milling media --- p.14 / Chapter 2.3 --- Powder fabrication --- p.14 / Chapter 2.3.1 --- Dry pressing --- p.14 / Chapter 2.3.2 --- Isostatic pressing --- p.19 / Chapter 2.3.3 --- Hot pressing --- p.23 / Chapter 2.4 --- Sintering mechanism --- p.26 / Chapter 2.4.1 --- Solid state sintering --- p.26 / Chapter 2.4.2 --- Liquid state sintering --- p.36 / Chapter 2.5 --- Toughening mechanism --- p.39 / Chapter 2.5.1 --- Stress-induced transformation toughening --- p.39 / Chapter 2.5.2 --- Microcrack toughening --- p.42 / Chapter 2.6 --- Motivation --- p.42 / Chapter 3 --- Experiments --- p.45 / Chapter 3.1 --- Methodology --- p.45 / Chapter 3.1.1 --- Procedures --- p.45 / Chapter 3.1.2 --- Verified parameters and potential difficulties --- p.53 / Chapter 3.2 --- Instrumentation --- p.56 / Chapter 3.2.1 --- Electronic balance --- p.56 / Chapter 3.2.2 --- Instron 4486 loading machine --- p.60 / Chapter 3.2.3 --- High temperature furnace --- p.63 / Chapter 3.2.4 --- Scanning electron microscope (SEM) --- p.65 / Chapter 3.2.5 --- Hardness tester --- p.67 / Chapter 3.2.6 --- X-ray powder diffraction --- p.69 / Chapter 4 --- Results ´ؤ The effects of conditions in fabrication --- p.71 / Chapter 4.1 --- Wet chemical reaction --- p.71 / Chapter 4.2 --- Pressure dependence analysis --- p.75 / Chapter 4.3 --- Sintering behavior --- p.80 / Chapter 4.3.1 --- Sintering temperature analysis --- p.80 / Chapter 4.3.2 --- Sintering duration analysis --- p.85 / Chapter 4.3.3 --- Program for counting pores --- p.94 / Chapter 5 --- Results ´ؤ The effects of Additives to Al203 - ZrO2 --- p.96 / Chapter 5.1 --- Introduction --- p.96 / Chapter 5.1.1 --- Effects of adding metal aluminum --- p.97 / Chapter 5.1.2 --- Effects of adding magnesium oxide --- p.103 / Chapter 6 --- Conclusions --- p.108 / Source code of the programs for counting pores --- p.111 / TIFF 6.0 --- p.124 / Bibliography --- p.131

Yuen, Kin Pong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 93-95). / Yuen, Kin Pong. / Contents --- p.i / Abstract --- p.iv / Acknowledgement --- p.v / List of Figures --- p.vi / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Optically Bistable Behavior --- p.5 / Chapter 2.1 --- Bistable behavior of two component composites --- p.5 / Chapter 2.1.1 --- Formalism --- p.6 / Chapter 2.1.2 --- Results and Discussion --- p.7 / Chapter 2.1.3 --- Stability analysis --- p.9 / Chapter 2.2 --- Bistable behavior of three component composites: Nonlinear dielec- tric core embedded in a metallic shell --- p.11 / Chapter 2.2.1 --- Spectral representation of the local field --- p.11 / Chapter 2.2.2 --- The onset of bistable behavior --- p.20 / Chapter 2.2.3 --- The extinction coefficient and reflectance at normal incidence --- p.24 / Chapter 2.2.4 --- Discussion and Conclusion --- p.28 / Chapter 2.3 --- Bistable behavior of three component composites: Metallic core em- bedded in a nonlinear dielectric shell --- p.30 / Chapter 2.3.1 --- Linear response of spherical inclusions and concentric spheres --- p.31 / Chapter 2.3.2 --- Onset of bistable behavior --- p.35 / Chapter 2.3.3 --- Results and Discussion --- p.41 / Chapter 2.4 --- Possible development of the spectral representation --- p.44 / Chapter Chapter 3. --- Optical Repsonse of a Nonlinear Composite Film --- p.45 / Chapter 3.1 --- Enhanced nonlinear response of coated spheres --- p.46 / Chapter 3.2 --- Solution of nonlinear wave equation --- p.48 / Chapter 3.3 --- Results and Discussion --- p.49 / Chapter 3.4 --- Conclusion --- p.52 / Chapter 3.5 --- Transfer matrix formalism for transmittance: Possible control over the size of a photonic band gap --- p.52 / Chapter 3.5.1 --- Transfer matrix method --- p.54 / Chapter Chapter 4. --- Bounds and Estimates for Nonlinear Composites --- p.59 / Chapter 4.1 --- Linear response of spherical inclusions --- p.60 / Chapter 4.2 --- Strongly nonlinear response of spherical inclusions --- p.61 / Chapter 4.3 --- Linear response of concentric spheres --- p.64 / Chapter 4.4 --- Strongly nonlinear response of concentric spheres --- p.66 / Chapter 4.5 --- Some exactly solvable cases --- p.68 / Chapter 4.6 --- Concentric spheres with nonlinear shell embedded in a linear dielec- tric host --- p.71 / Chapter 4.7 --- Discussion and Conclusion --- p.73 / Chapter 4.8 --- Small contrast expansion --- p.75 / Chapter 4.9 --- Hashin-Shtrikman microgeometry --- p.78 / Chapter 4.10 --- Exact bounds for linear composites --- p.79 / Chapter 4.11 --- Variational approach for Hashin-Shtrikman microstructure --- p.82 / Chapter 4.12 --- Improved variational approach --- p.85 / Chapter 4.13 --- Discussion and Conclusion --- p.87 / Appendix A. Derivation of the Energy Functional --- p.88 / Chapter A.1 --- The energy functional --- p.88 / Chapter A.2 --- Effect of higher order terms to the energy functional --- p.91 / Bibliography --- p.93

O presente trabalho busca o entendimento do aparecimento da fase cristalina em compósitos de polipropileno isotático, que contém carbonato de cálcio, em presença ou não de polipropileno modificado com anidrido maléico (PPMA). Vários tipos de CaCO3 foram utilizados: com diâmetros médios de 0,9 m, com e sem tratamento superficial, 2,5 m e 3,0 m. As duas séries de compósitos, com e sem PPMA, denominadas iPP/CaCO3/PPMA e iPP/CaCO3, foram formuladas com as seguintes razões mássicas, 94,5/5/0,5% e 95/5, respectivamente. Em ambas as séries, observou-se a ocorrência das fases cristalinas e do polipropileno; entretanto, a concentração relativa variou de acordo com o tipo de compósito. A caracterização das fases cristalinas presentes nos compósitos foi realizada utilizando a difratometria de raio-x (DRX) e análises térmicas, principalmente, calorimetria diferencial exploratória (DSC). As análises por DSC incluíram o estudo cinético da cristalização isotérmica e não isotérmica dos compósitos. Os resultados obtidos permitiram identificar os compósitos com maior concentração de fase cristalina e relacionar a sua formação com os constituintes presentes nos compósitos. / The present work aims to understand the occurrence of the beta crystalline phase in composites of isotactic polypropylene with calcium carbonate in the presence or not of polypropylene grafted maleic anhydride (PPMA). CaCO3 having different average diameter were used: 0.9 m with and without surface treatment, 2.5 m and 3.0 m. Both series of composites, one with PPMA and another without, named iPP/CaCO3/PPMA and iPP/CaCO3, were formulated at the following mass proportions: 94.5/5/0.5% and 95/5, respectively. The presence of the e crystalline phases in polypropylene were observed. However, the relative concentration of such phases depended on the composite composition. The characterization of the crystalline phases in composites were performed by using x-ray diffraction (DRX) and thermal analyses, mainly, differential scanning calorimetry (DSC). DSC analysis was used to investigate isothermal crystallization kinetic and nonisothermal crystallization kinetic. The results allowed the identification of the composites with higher concentration of crystalline phase and it was possible to attribute the phase occurrence to the presence of specific constituents of the composites.

Thesis (M.S. in materials science and engineering)--Washington State University, December 2007. / Includes bibliographical references.

Thesis (M.D.S.)--University of Hong Kong, 1994. / Includes bibliographical references. Also available in print.

Thesis (M.S. in biological systems engineering)--Washington State University, December 2007. / Includes bibliographical references (p. 41-45).