Precision surface finishes are used in a wide variety of applications. From bearing races and rolling elements to parallel slide ways, the frictional characteristics of these surfaces are critical to the performance of the products. Experimental trial and error has shown that certain surfaces outperform others in certain applications, but the specific surface characteristics that make this true have yet to be fully understood. The research goal was to develop an apparatus that can test the coefficient of rolling/sliding friction of different precision machined surfaces and to combine this data with topographic analysis of the surfaces to correlate specific 3-D parameters with the frictional performance of a surface. The sample treatments consisted of four different surface textures (hard-turned, ground, honed and isotropic finish) and four different relative surface speeds. By monitoring the torque in the sample-mounting shaft under lubricated conditions the coefficient of rolling/sliding friction of each surface was found. Utilizing white light interferometry measurement of the surfaces, a highly detailed map of each surface was obtained. Using different characteristic values of each machined surface (RMS roughness, asperity density, lay direction, etc.), the frictional behavior of the surfaces were compared to the surface characteristics yielding insight into the relationship between surface finish and friction in rolling/sliding contact. Friction coefficient was found to correlate most strongly with RMS roughness (Sq) and density of surface summits (Sds). These parameters govern mechanical interference of asperities and surface adhesion respectively. These findings suggest that friction coefficients of surfaces could be optimized through manipulation of three-dimensional surface parameters.

The complex interrelations among the different physical processes involved in acid fracturing make it difficult to design, and later, to predict the outcome of stimulation jobs. Actual tendencies require the use of computational models to deal with the dynamic interaction of variables. This thesis presents a new study of acidized surface textures by means of a laser profilometer to improve our understanding of the remaining etched surface topography and its hydraulic response. Visualization plots generated by the profilometer identified hydrodynamic channels that could not be identified by the naked eye in acidized surfaces. The plots clarified the existence of rock heterogeneities and revealed how the processes of dissolution function in chalk rock. Experimental data showed clearly that the effect of dissolution depends on the type of rock and the fluid system; dolomite, for example, dissolves more rapidly but more roughly than limestone. Fluid leakoff rate and temperature also affect the dissolution. Further research is necessary to clarify the effects of conductivity.

An apparatus intended to measure the pressure oscillations generated by nanoparticle suspensions in response to an AC electric field was designed and made operational. Electroacoustic measurements were performed on nanoparticle systems covering a range of particle sizes and zeta-potentials, determined using typical particle characterization techniques. The results of the electroacoustic experiments were mapped to the hydrodynamic size and zeta-potentials of the various nanoparticle systems. It was determined that while the electroacoustic technique can be used successfully to measure the motion of nanoparticles in response to an AC electric field, additional improvements to the electroacoustic apparatus are required to allow for a more rigorous mapping of electroacoustic measurements to particle hydrodynamic size and zeta-potential.

No description available.

This research studies the chemical nature of zirconia and the complex surface chemistry of zirconia in order to better comprehend its behavior under chromatographic conditions. This research shows how the physical and chemical properties of zirconia depend strongly on the thermal treatment during synthesis. The morphology of the samples was also studied. The absorption capability of Adenosine Triphosphate (ATP) on zirconia was also monitored and spectrally characterized. The results of this research showed how the properties of zirconia vary with thermal treatment. It was observed that the zirconia prepared at a higher temperature had lower surface area, lower pore size and pore volume as compared to the zirconia prepared at a lower temperature. The morphology studies showed the porosity of the zirconia. The results from the absorption experiments showed that zirconia prepared at a higher temperature absorbed more ATP than the zirconia prepared at a lower temperature. Significant changes were also observed on the pellets of zirconia pre and post absorption experiments. I hope that this research sheds more light on the complex properties of zirconia’s surface chemistry and the results of this study could better help in the application and use of zirconia in chromatography to separate proteins.

Humic-based organic compounds containing phenol or benzoic acid groups strongly compete with phosphates for specific binding sites on the surface of these colloidal particles. To study the interactions between phenol groups and the surface binding sites of unmodified or modified colloidal particles, chemical force spectrometry (CFS) was used as a tool to measure the adhesion force between an atomic force microscopy (AFM) tip terminated with a phenol self-assembled monolayer and colloidal particles under varying pH conditions. Two modification methods, co-precipitation and post-precipitation, were used to simulate the naturally-occurring phosphate and humic-acid adsorption process. The pH dependence of adhesion forces between phenol-terminated tip and colloidal particles could be explained by an interplay of electrostatic forces, the surface loading of the modifying phosphate or humic acid species and ionic hydrogen bonding. Polydimethylsiloxane (PDMS) is a widely-used polymer in microfluidic devices. PDMS surfaces are commonly modified to make it suitable for specific microfluidic devices. We studied the surface modification of PDMS using four perfluoroalkyl-triethoxysilane molecules of differing length of perfluorinated alkyl chain. The results show that the length of fluorinated alkyl chain has important effects on the density of surface modifying molecules, surface topography and surface zeta potential. The perfluorinated overlayer makes PDMS more efficient at supporting electroosmotic flow, which has potential applications in microfluidic devices. The kinetic study of RNase A, lysozyme C, α-lactalbumin and myoglobin at different concentrations adsorbed on the self-assembled monolayers of 1-octanethiol (OT-Au) and 1H, 1H, 2H, 2H-perfluorooctyl-1-thiol (FOT-Au) has been carried out. The results show a positive relationship between the lower protein concentration and the increased adsorption rate constant (ka) on both surfaces. At low concentrations, the protein adsorption on an OT-Au surface has greater ka than it on a FOT-Au surface. Comparing ka values for four proteins on OT-Au and FOT-Au surface demonstrates that hard proteins (lysozyme and RNase A) have larger ka than soft proteins (α-lactalbumin and myoglobin) on both surfaces. The discussion is based on the hydrophobicity of OT-Au and FOT-Au surfaces, as well as average superficial hydrophobicity, flexibility, size, stability, and surface induced conformation change of proteins. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-10-14 21:08:31.617

Theoretical and experimental results show that the performance of a load-bearing surface in hydrodynamic lubrication may be enhanced by engineering a definable surface texture onto the surface. These surface textures are in the form of protrusions (positive asperities) or cavities (negative asperities) of known size and geometry. The benefits of such surface textures include lower friction torque, higher load capacity and lower operating temperatures. This Thesis details a fabrication process to manufacture such surface textures/asperities on flat surfaces. The asperities are fabricated using a UV photolithography process followed by electroplating. A complete surface characterization is done to evaluate the effectiveness of the manufacturing process. From the characterization results, some errors in asperity geometry are identified and statistically quantified. These errors are found to be normally distributed and the random surface roughness is 1 to 3 orders of magnitude less than the deterministic feature size. The accuracy of the manufacturing process for fabricating the asperities was found to lie within 6.5 % of the desired value over all the errors studied. Finally, a sensitivity analysis is done to theoretically evaluate the effect of some of these errors in the hydrodynamic lubrication regime.

The deterministic microasperities play a vital role in reducing the coefficient of friction and wear of thrust surfaces and improve the tribological properties of the surfaces. Deterministic microasperities have a specific pattern in terms of size, shape and spacing. These specified geometries are controllable and repeatable. The microasperities are micron scaled asperities and cavities on a surface that form the surface roughness. The present thesis shows the detailed process to fabricate the deterministic microasperities on thrust surfaces, i.e. stainless substrate, using micro-fabrication processes such as lapping and ultra-violet photolithography in combination with an electroplating (nickel) process. A Novel alignment technique is used to align the photomask with the substrate to get repeatable and aligned patterns on the thrust surface. Deterministic microasperities are characterized by using precision instruments such as an Optical profilometer, Scanning Electron Microscope (SEM) and Optical microscope to study the various surface parameters such as Average roughness (Ra), Root mean square value (rms) and Peak value (PV) of the thrust surface.

No description available.

The rechargeable Li-O2 battery has attracted interest due to its high theoretical energy density (about 10 times better than today’s Li-ion batteries). In this PhD thesis the cycling instability of the Li-O2 battery has been studied. Degradation of the battery has been followed by studying the interface between the electrodes and electrolyte and determining the chemical composition and quantity of degradation products formed after varied cycling conditions. For this in-house and synchrotron based Photoelectron Spectroscopy (PES) were used as a powerful surface sensitive technique. Using these methods quantitative and qualitative information was obtained of both amorphous and crystalline compounds. To make the most realistic studies the carbon cathode pore structure was optimised by varying the binder to carbon ratio. This was shown to have an effect on improving the discharge capacity. For Li-O2 batteries electrolyte decomposition is a major challenge. The stability of different electrolyte solvents and salts were investigated. Aprotic carbonate and ether based solvents such as PC, EC/DEC, TEGDME, and PEGDME were found to decompose during electrochemical cycling of the cells. The carbonate based electrolytes decompose to form a 5-10 nm thick surface layer on the carbon cathode during discharge which was then removed during battery charging. The degradation products of the ether based electrolytes consisted mainly of ether and carbonate based surface species. It is also shown that Li2O2 as the final discharge product of the cell is chemically reactive and decomposes carbonate and ether based solvents. The stability of lithium electrolyte salts (such as LiPF6, LiBF4, LiB(CN)4, LiBOB, and LiClO4) was also studied. The PES results revealed that all salts are unstable during the cell cycling and in contact with Li2O2. Decomposition layers thinner than 5 nm were observed on Li2O2. Furthermore, it is shown that the stability of the interface on the lithium anode is a chief issue. When compared to Li batteries (where oxygen levels are below 10 ppm) working in the presence of excess oxygen leads to the decomposition of carbonate based electrolytes to a larger degree.