Zugl.: Duisburg, Universiẗat, Diss., 2001.

Freiburg (Breisgau), University, Diss., 2001.

Thin self-supporting deuterated polyethylene targets for use with the reaction 2ʜ(3ʜe,p)⁴He have been investigated. Both pouring and evaporating techniques for the construction of the polyethylene film were tested. Stable targets, capable of withstanding 690 keV ³He beam current densities of more than 10 μA/cm², were constructed by evaporating 10 μg/cm² thick carbon layers onto both sides of the (C₂D₄)n film ("sandwich" targets). Targets prepared by the pouring technique were found to be mechanically stronger than the "sandwich" targets prepared by evaporation of (C₂D₄)n. The targets exhibit an initial rapid decrease in the deuterium content during the first 150 μc of ³He beam on the target. This effect is attributed to breakdown of the C₂D₄ molecules into their atomic constituents and subsequent diffusion of the deuterium out of the target. After this initial effect, the targets deteriorate by less than 0.05% per μc. The targets were developed for use for total proton reaction cross section measurements by the associated particle technique. The beam profiles of the 15.8 MeV protons from the reaction ²H (³He,p)⁴He, which are relevant to this technique, were measured. The amount of elastic scattering suffered by the protons in the present targets was smaller than that observed with the copper backed heavy ice targets used in previous cross section measurements (Ho 68). The deuterium content of the target was found to be a linear function of the thickness of the carbon layers comprising the target "sandwich". The alpha yield from the reaction ²H (³He,p)⁴He increased by a factor of 1.83 ± 0.35 per 10 μg/cm² carbon layer on the "back" of the target, and by a factor of 1.38 ± 0.26 per 10 μg/cm2 carbon layer on the "front" of the target. As a possible explanation of this effect it is proposed that deuterium, repleased from the polyethylene by the beam, diffuses throughout the target and is trapped by the carbon to a concentration of 0.11 deuterium atoms per carbon atom. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Thesis (Ph.D.)--York University, 2004. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 160-172). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99168

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

No description available.

The aim of this thesis is to investigate the possibility of enhancing the dielectric breakdown strength (DBS) of low density polyethylene (LDPE) with addition of voltage stabilizing additives. In the first part of the thesis, the influence of various process parameters on the alternating current DBS of pure LDPE and LDPE containing either 3 or 30 wt% magnesium oxide nanoparticles was investigated. It was found that the influence of moisture, crystalline structure and process stabilizing additives did not affect the DBS. In the second part of the thesis the effect of five different voltage stabilizing additives was investigated to enhance the DBS. No significant improvement in DBS could be seen for additives mixed with neat LDPE or LDPE nanocomposites by extrusion (typical DBS values ranged between 109-116 kV/mm for neat LDPE). However, the compounding by extrusion resulted in better stability of the breakdown data. A method to swell voltage stabilizing additives into the polymer matrix with solvents have been developed and evaluated. No significant improvements in breakdown strength could be seen for neat LDPE, but the DBS was increased by 15-20 % at low probability of failure for the LDPE nanocomposites. Further work is required to investigate if this increase is significant. It is believed that it is critical to dissolve a higher amount of the voltage stabilizing additives into the polymer matrix. The actual concentrations of the additives need to be quantified with chromatographic methods or infrared spectroscopy.

Tsui Sai Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves i-ii.

Thesis (MTech. degree in Polymer Technology)--Tshwane University of Technology, 2008. / Aims to determine the effect of the introduction of oxo-biodegradable polymers on the quality of both linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) recycling streams.