Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 97-108). Also available in print.

Polyetheretherketone (PEEK), a polymer with mechanical strength comparable to human bone, is gaining popularity in the orthopedic field because it can potentially relieve the clinical complications, such as stress shielding effect and inevitable implantation failure, which are caused by the mismatch of the mechanical strength between the current metallic implants and the implantation sites. However, it is bio-inert and requires supplementary modification. Plasma immersion ion implantation (PIII) has been well documented that it is a good way to improve the bioactivity of a biomaterial. It is a method that introduces new elements to the biomaterial, generating bio-functional groups on the material surface without altering its mechanical properties. Hence, the aim of this study is to improve the bioactivity of PEEK by modifying its surface chemistry with the use of water (H2O) and ammonia (NH3) plasma immersion ion implantation (PIII) without altering its mechanical properties. After PIII treatment, a series of surface characterization tests that provide information about the surface properties, such as surface energy, roughness, surface chemical composition and crystallinity of PIII-treated PEEK were carried out. Results show that both H2O PIII and NH3 PIII-treated PEEK had significantly higher surface energy and roughness than untreated PEEK. There was also no significant change in the crystallinity of the PIII-treated PEEK, indicating that PIII treatment will not alter the mechanical properties of PEEK. Improvement in wetting properties of PEEK samples suggest the formation of polar functional groups on the PIII-treated PEEK materials, while the increased in surface roughness may be due to the energetic bombardments of plasma ions on the material surface. The in vitro bioactivity of plasma-treated PEEK was investigated and confirmed with hMSC-TERT. Initial cell attachment, cell spreading area, cell proliferation and differentiation were studied. Cell adhesion and cell spreading were enhanced on PIII-treated PEEK, and higher cell viability was observed on PIII-treated PEEK. Moreover, cell proliferation was promoted on early time point and cell differentiation was also enhanced particularly on day 7 by measuring the alkaline phosphatase activity. Therefore, H2O-PIII and NH3-PIII treatments were able to promote the bioactivity of PEEK samples. / published_or_final_version / Orthopaedics and Traumatology / Master / Master of Philosophy

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A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of Ce02 powders produced from dissolved cerium nitrate salts. The reactor minimized particle recirculation and provided a highly symmetric and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of Ce02 powders. The sampling probe provided in-situ sampling of in-flight CeCb particles and allowed continuous sampling without cross contamination. The sampled particles were collected using a wet collection system composed of a mist atomizer acting as a scrubber and a custom-made spray chamber. The entire collection system is portable and it was tested in the particle range of 20 nm to 100 jam. This information provided a picture of how Ce02 particles were formed. A numerical simulation of different plasma operating parameters using Fluent was presented. A comprehensive droplet-to-particle formation mechanism was deduced based on calorimetry. thermodynamics of Ce02 formation, numerical simulations and collected particles. The effect of adding water soluble fuels (alanine and glycine) to the original cerium nitrate solutions was investigated. Fuel addition decreased the temperature of CeC>2 formation by acting as a local heat source as a result of fuel auto-ignition. The addition of fuel caused “particle size discrimination’*, and a single mode particle size distribution centered between 50-140 nm was achieved along the centerline of the reactor. [...] / Un nouveau reacteur et une technique innovatrice d’echantillonnage in situ furent developpes pour etudier la synthese de poudres de Ce02 produites a partir de sels de nitrate de cerium dissous. Le reacteur minimise la recirculation des particules et fournit un plasma non perturbe et grandement symetrique approprie pour l’analyse des phenomenes affectant la formation de poudres de Ce02. De plus, une sonde permet un echantillonnage in situ et en vol des particules de Ce02 et ce, en continu et sans contamination croisee. Les particules ainsi captees sont recueillies grace a un systeme de collecte par voie humide qui est compose d’un atomiseur de brume (mist atomizer) qui joue le role d’un recureur (scrubber) et d’une chambre d’atomisation (spray chamber) maison. Le systeme d’echantillonnage est mobile et fut teste sur des particules ayant des tailles de 20 nm a 100 jam. C’est grace a l’analyse des particules ainsi recueillies que nous sommes en mesure de comprendre comment les particules de Ce02 sont formees. Nous presentons aussi une simulation numerique, effectuee avec le logiciel Fluent, qui utilise les differents parametres d’experimentation. Le mecanisme detaille de la formation des particules a partir de gouttelettes fut deduit grace a des etudes calorimetriques, a une etude thermodynamique de la formation du Ce02, a des simulations numeriques et a l’analyse des particules recueillies. Nous avons aussi etudie l’effet d’un ajout de combustibles hydrosolubles (l’alanine et la glycine) a la solution originale de nitrate de cerium. Cette addition de combustibles diminue la temperature de formation du Ce02 en agissant comme une source locale de chaleur resultant de 1’auto-ignition du combustible. Aussi, le combustible cause une « segregation des particules » selon leur taille.

A new reactor and a novel in-situ sampling technique were developed for the study of the synthesis of CeO2 powders produced from dissolved cerium nitrate salts. The reactor minimized particle recirculation and provided a highly symmetric and undisturbed plasma flow suitable for the analysis of the phenomena affecting the formation of CeO2 powders. The sampling probe provided in-situ sampling of in-flight CeO2 particles and allowed continuous sampling without cross contamination. The sampled particles were collected using a wet collection system composed of a mist atomizer acting as a scrubber and a custom-made spray chamber. The entire collection system is portable and it was tested in the particle range of 20 nm to 100 mum. This information provided a picture of how CeO2 particles were formed. A numerical simulation of different plasma operating parameters using Fluent was presented. A comprehensive droplet-to-particle formation mechanism was deduced based on calorimetry, thermodynamics of CeO2 formation, numerical simulations and collected particles. The effect of adding water soluble fuels (alanine and glycine) to the original cerium nitrate solutions was investigated. Fuel addition decreased the temperature of CeO2 formation by acting as a local heat source as a result of fuel auto-ignition. The addition of fuel caused "particle size discrimination", and a single mode particle size distribution centered between 50-140 nm was achieved along the centerline of the reactor. / Also, heat and mass transfer effects were numerically investigated in evaporating solution droplets (20-40 mum in diameter) containing dissolved hexahydrated cerium nitrate in a stationary rf Ar-O2 thermal plasma. This model was developed to study the evaporation of a solution droplet surrounded by a porous crust in a stagnant rf Ar-O2 thermal plasma under reduced pressure. It considered a three phase system: a liquid core of dissolved Ce(NO 3)3.6H2O in water, a dry porous crust of homogeneously precipitated spherical crystals of equal size, and an Ar-O2 plasma under reduced pressure. The impact of different plasma operating parameters on the temperature and dissolved solid content profiles in the droplet was studied, i.e. surrounding plasma temperature, initial salt content and droplet size, plasma gas composition, and system pressure. Temperature and composition dependant thermophysical properties were used. The model was solved in a moving boundary frame using an ALE approach and considering Stefan flow. It provided the necessary information to understand the droplet to particle transformation steps in regions where in-flight probing was unfeasible, i.e. torch zone.

Thesis (Ph.D.)--McMaster University (Canada), 1992. / Source: Dissertation Abstracts International, Volume: 54-08, Section: B, page: 4217. Adviser: J. S. Chang.

Thesis (Ph. D.)--University of Sydney, 2004. / Title from title screen (viewed 5 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Degree awarded 2004; thesis submitted 2003. Includes bibliographical references. Also available in print form.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / Said I. Abdel-Khalik, Committee Chair ; Sheldon M. Jeter, Committee Member ; Minami Yoda, Committee Member. Includes bibliographical references.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Herbert L. Berk. Vita. Includes bibliographical references.