Global ETD Search

21	The Effects of Material Treatments on the Surface Properties of Polymeric Biomaterials Vase, Ajoy 01 May 2007 (has links) This work examines the chemical and physical effects of a material treatment process on the biopolymers PEEK, POM-h, POM-c, PTFE and UHMWPE. The polymers are analyzed physically and chemically using atomic force microscopy, profilometry, scanning electron microscopy, optical microscopy, contact angle measurement, FT infra-red spectroscopy and energy dispersive X-ray spectrometry. PEEK is found to be the most suitable polymer and FT Infra-red spectroscopy an informative analytic tool. Biomedical engineering Biomedical materials Bioreactors Biopolymers Polytef Ultra high molecular weight polyethylene Polyoxymethylene Polyethers Artificial corneas Surfaces (Technology)-Analysis
22	Probing the influence of bimetallic composition on the Pd/Au catalysed synthesis of vinyl acetate monomer Haire, Andrew Richard January 2010 (has links) Scanning Tunnelling Microscopy (STM) was utilised together with the high resolution depth-profiling capabilities of Medium Energy Ion Scattering (MEIS), a technique traditionally associated with single crystal substrates, to probe the mean size and depth dependent composition profile of bimetallic PdAu nanoparticles on planar oxide surfaces as functions of the starting composition and annealing temperature. In order to fit composition profiles to experimental MEIS data, a new analysis tool has been designed that models the particles as flat-topped structures with a hexagonal base which can be divided into a number of shells, each shell corresponding to a particular ion pathlength inside the material. The reliability of this method will be discussed in detail. Fitting results show that the surface layers are always significantly enriched in Au compared to the bulk alloy composition. By comparing MEIS data for clean surfaces data for modified surfaces it was found that Pd generally segregates towards the particle surface on adsorption of acetic acid. The interaction of potassium acetate with Au/Pd{111} alloy surfaces of varying composition has been investigated using Temperature Programmed Desorption (TPD) and Reflection Absorption Infra Red Spectroscopy (RAIRS). At lower coverage, potassium acetate reacts reversibly with the surface to form CO and carbonate. Formation of surface acetate is observed on Pd-rich surfaces only. At higher coverage, acetate is the major surface species formed on all samples examined. 541.39
23	The effect of materials preparation on polymer surfaces Vase, Ajoy January 2007 (has links) This work examines the chemical and physical effects of a material treatment process on the biopolymers PEEK, POM-h, POM-c, PTFE and UHMWPE. The polymers are analyzed physically and chemically using atomic force microscopy, profilometry, scanning electron microscopy, optical microscopy, contact angle measurement, FT infra-red spectroscopy and energy dispersive X-ray spectrometry. PEEK is found to be the most suitable polymer and FT Infra-red spectroscopy an informative analytic tool.
24	High throughput characterization of cell response to polymer blend phase separation Zapata, Pedro José 12 July 2004 (has links) Combinatorial techniques, which overcome limitations of actual models of material research permitting to effectively address this large amount of variables, are utilized in this work to prepare combinatorial libraries of the blend of the biodegradable polymers Poly(e-caprolactone) and Poly(lactic acid). These libraries present continuous composition and temperature gradients in an orthogonal fashion that permit to obtain multiple surface morphologies with controllable microstructures due to the blends low critical solution phase behavior (LCST). The goal of this study is to investigate the effect of surface morphology (surface chemical patterning and surface topography) on cell behavior. The varied surface topography of the libraries is used as a valuable tool that permits to assay the interaction between MC3T3-E1 cells and hundreds of different values of critical surface properties, namely, surface roughness and microstructure size. The outcome of this tool is a rapid screening of the effect of surface topography on cell behavior that is orders of magnitude faster than the standard 1-sample for 1 measurement techniques. The results obtained show that cells are very sensitive to surface topography, and that the final effect of surface properties on cell function is intimately related with the stage of the cell developmental process. Meaning that, for example, areas with optimal characteristics to elicit enhancement of cell attachment is not necessarily the same that promotes cell proliferation. This study imparts an improved understanding of an often neglected factor in biomaterials performance: surface morphology (particularly surface topography). The results provide a new insight into the importance of taking into consideration both chemistry and physical surface features for superior biomaterial design. Combinatorial Phase separation Polymers Biomaterials Tissue engineering Osteoblast Cell-surface interaction High throughput Tissue engineering Surfaces (Technology) Analysis Polymers Biodegradation Combinatorial chemistry Cells Morphology Biomedical materials Design Biodegradable plastics
25	Nanolithography on thin films using heated atomic force microscope cantilevers Saxena, Shubham 01 November 2006 (has links) Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported. Characterization Deflection Setpoint Grain rearrangement Array Precise positioning Metrology Explosion Explosives Data storage Material Image processing Slow scan disabled Temperature Tip Local In-situ Nanoscale Electrical circuit fabrication Repair Co-polycarbonate Polymers Polycarbonates Energetic materials PETN Simulation Interface Nano-manufacturing Experiment Calibration Raman Frequency Deflagration Decomposition Detonation Build up Pile-up End capped End capping Cross linked Cross-linked Conductivity Microscale MEMS Microcantilever NEMS DPN tDPN Silicon Glass Peak InVOLS Manipulation AFM Atomic force microscope Defense Nanoscale Surface Stiffness Force Scan size Thermal cantilevers Imaging Lithography Nanolithography Thin films Cantilevers Heaters Technology Nanotechnology Scan velocity Scan rate Bake Anneal Pentaerythritol tetranitrate Thin films Thermal properties Atomic force microscopy Microlithography Nanotechnology Surfaces (Technology) Analysis

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