Grain orientated magnetic steels have applications in the electrical industry as components of power transformers. Power losses are observed in these devices due to the magnetostrictive effect. Aluminium phosphate coatings are applied to the steel to impart a tensile strength to the steel inhibiting the effects of magnetostriction, reducing losses. This thesis examines the development and application of aluminium metaphosphate coatings with the aim of improving the currently used aluminium orthophosphate coatings. The experiments described here show that aluminium metaphosphate can be formed using a variety of readily available aluminium precursors and that the products are stable to the effects of thermal hydration. A combination of bulk and surface analysis techniques suggest that there is need to re-examine the accepted assignments of the O(1s) region of the XPS for aluminium metaphosphates. The testing of the applications of the metaphosphates as stress coatings has yielded results indicating improved performances over the orthophosphate coatings. SEM analysis has shown that this is due to the formation of a phosphate film across the surface of the substrate imparting a greater degree of tension than orthophosphate coatings. Investigations examined the proposal that the low temperature synthesis of mullite (Al6Si2O13) is facilitated through the addition of Jahn-Teller active complexes. The findings showed that the addition of stable low-spin complexes resulted in the formation of mullite by 800 oC. Also, tested was the hypothesis that this synthesis route resulted in the formation of nano-scale mullite, but SEM image data has discounted this.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:732263 |
| Date | January 2017 |
| Creators | Thomas, Matthew Gareth |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/107820/ |
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