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Electro-spinning of poly (ethylene-co-vinyl alcohol) (EVOH) nanofibres for medical applications and its mechanical propertiesXu, Chao January 2012 (has links)
Skin wound healing is an urgent problem in clinical treatment, in particular, with a military context. Although significant advances have been made in treating skin wounds, traditional methods face several challenges, e.g., limited donor skin tissue for transplants and inflammation over the period of long term healing. To address these challenges, in this study we present a method to fabricate Poly (ethylene-co-vinyl alcohol) (EVOH) nanofibres encapsulated with the Ag nanoparticle, using the electro-spinning technique. The manufacturing process of nanofibres by electro-spinning is the subject of the present research. Electro-spinning is a process which produces nanofibres through the electrically charged jet of a polymer solution. While the principle has long been understood, the process of forming them still remains difficult to control. In its simplest form, the technique consists of a pipette to hold the polymer solution, two electrodes and a DC voltage supply over a 10 KV range. The polymer dropping from the tip of the pipette is drawn into a jet which is electrically charged and spun into fine fibres by the electronic field. An appropriate combination of the control parameters, such as the charge voltage, density and viscosity of the polymer solution and the travel distance of the jet, etc. will lead to the production of fibres with diameters in the range of 10-7~8 meters. The fibres can then be collected on the surface of a grounded target. regulating three main parameters, namely, a concentrated EVOH solution, the electric voltage and the distance between the injection needle tip (high voltage point) and the fibre collector. Ag was added to the nanofibres to offer long term anti-inflammation properties by the slow release of Ag nanoparticles through the gradual degradation of the EVOH nanofibre. The method developed here could lead to new dressing materials for the treatment of skin wounds. The thin EVOH nanofibre sheets obtained from electro-spinning were tested in uniaxial tension for their mechanical properties, with a view to the possibilities of using them as wound dressings. It was found that the sheets show a mild hardening behaviour with extensive elongation and necking before failure in multiple fractures at random locations. The failure is not simply fibre breakage. Due to the random orientation of the continuing fibres in the sheet, detachment, shear, straightening and twinning. etc., among the fibres all occur at the same time to different extents. The Young’s modulus and the yield stress (at 0.4~0.5% proof strains) are predominately affected by the diameters of the fibres. The latter are largely insensitive to strain rate over the range tested.
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Electrical, Optical and Thermal Investigations of Cobalt Oxide-Antimony Doped Tin Oxide (CoO-ATO) Thin Films and Nanofiber MembranesRoy, Nirmita 02 November 2017 (has links)
The main aim of this thesis work is to investigate the electrical, optical and thermal impact characteristics of cobalt oxide doped antimony tin oxide (CoO-ATO) in the form of thin films and nanofiber membranes. CoO-ATO is a novel composite material that has the potential to be used as reinforced aircraft coatings, military garment coatings, or more specifically as an anti-reflective (AR) top coating for photovoltaic (PV) cells. This work will be critical in determining the effectiveness of using a CoO-ATO layer in these applications. Electrospun nanofibers and spin coated thin films consisting of a polymeric solution of CoO-ATO will be used. Thin films are created using spin coating techniques, and nanofiber membranes are created using an electrospinning technique. Polystyrene (PS) will be used as a solute, and chloroform as a solvent, to create the solution. It is hypothesized that coatings of this material will have improved optical characteristics as compared to traditional ATO coatings and minimum impact from thermal cycling making it a favorable candidate for PV cells. This work will do an electrical, optical and thermal cycling impact characterization of CoO-ATO thin films and nanofiber membranes for a doping range of x% CoO where x ranged from 0.2
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