Surface temperature and heat flux measurements were made in a single cylinder SI engine piston when uncoated and with two different surface coatings: a metal TBC and YSZ. A new thermocouple was developed to accurately measure surface temperatures. The engine was operated in a standard full load mode and a knock promoting mode featuring heated intake air and advanced spark timing. Cylinder pressures were measured to quantify knock. It was found that average heat flux into the piston substrate was 33 % higher with the metal TBC and unchanged with the YSZ relative to the uncoated surface. The increase with the metal TBC was attributed to its surface roughness. However, the metal TBC and YSZ reduced peak heat flux by 69 and 77 %, respectively. Both the metal TBC and YSZ reduced knock compared to the uncoated surface. After testing, the metal TBC was undamaged and the YSZ was slightly chipped.

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Advancement in biotechnology has successfully converted the conventional bearing couples into artificial joints. Materials used today, however, have not been satisfactory. Problems such as osteolysis and aseptic loosening lead to failure of artificial joints and also the lifespan of these joints is to be further improved. This research targets two issues related to the problem: coatings and design of new generation biofluids. Superior to metals and polymers, ceramics are hard and biocompatible and exhibit low wear and friction. The ceramic-on-ceramic bearing pair could last for a long time which could be beneficial to younger and active patients who need a bearing pair which would last for more than 15 years to avoid the possibility of a revision surgery. The first part of this thesis deals with studying the microstructure-property relationship of new ceramic-based materials and coatings. Specifically, alumina (ceramic) coatings at different current intensities were tested in order to determine their feasibility as a biomaterial for artificial joints. In order to find a new avenue for developing biofluids, the second part of this thesis focuses on the failure of artificial joints under inadequate lubrication. Also due to osteoarthritis, synthetic biofluid is injected into joints to help relieve pain but it works for only 6-9 months. We propose a new method using noble gold nanoparticles to modify fluids. This was accomplished by mixing different concentration of nanoparticles with biofluid. This thesis consists of 6 sections. The first section is an introduction to tribology, biotribology and artificial joints which is followed by the second section which discusses the objectives of the research. The third section describes the materials and methods used in the research. The tribological characterization of MAO alumina coatings is discussed in the fourth section and the fifth section discusses the effect of nanoparticles on fluid lubrication. The last section is the conclusion.

Thermal barrier coatings (TBCs) have become an important part of turbine technology by providing thermal protection to the underlying metallic components. These coatings are typically made from a zirconia-based ceramics which have a low thermal conductivity and thermal expansion coefficients similar to those of the superalloys. Early failure in these coatings is most often due to foreign object damage and erosion resulting in delamination and spallation. To protect against these types of failure, new materials with increased toughness are needed. There are two main toughening mechanisms in ceramics: transformation toughening, which is limited to low temperature applications and ferroelastic toughening which is accessible at all temperatures. Ferroelastic toughening occurs when the c-axis of the tetragonal grain undergoes reorientation under the application of an external stress. In this study, ferroelastic toughening is examined by Raman spectroscopy. It is shown that by using polarized confocal Raman spectroscopy one can not only observed the ferroelastic process, but also measure the parameters that control the increase in toughness observed. Ferroelastic toughening was observed in two ways in the 18mol% ceria stabilized zirconia (18CSZ) samples studied here. Samples were either exposed to indentation damage or uniaxial loading. In both of these cases maps of the ceramic surface were taken using Raman spectroscopy following loading and the relative intensities of the tetragonal peaks were analyzed. The resulting intensity profiles were used to monitor the reorientation of domains corresponding to ferroelastic toughening. Changes in domain orientation were observed that corresponded to the reorientation of domains along cracks as well as on a larger scale along those cracks. Domain reorientation was also observed under uniaxial loading and the stresses required for domain formation and movement were measured.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 184-189).

Thesis (Ph. D.)--Lehigh University, 2001. / Includes bibliographical references and vita.