Over three quarters of the world's flat glass is produced by the float method, in which molten glass is solidified on large baths of liquid tin. Sulphur is a major contaminant in these baths, causing a defect known as top speck. This dissertation describes the design, construction and evaluation of a sensor based upon a solid electrolyte, intended for use in the detection of this sulphur. Three solid electrolytes were produced: strontium and sodium β-alumina by direct methods, and silver β-alumina by ion exchange. The effects of material composition and sintering cycle on density were investigated, and conductivities, atomic structures and microstructures were characterised and shown to agree with published data. A number of cell designs were constructed to investigate the electrolytes' responses to different partial pressures of sulphur and oxygen, which were produced using mixtures of the metals copper, iron and molybdenum with their respective sulphides and oxides. A non-equilibrium electrolyte response was observed, caused by slow interaction between the electrolyte and the metals. A mixture of molten tin and solid tin sulphide was investigated using a silver-referenced, silver β-alumina cell, and reproducible emfs corresponding to thermodynamic expectations were observed. A non-unity value was determined for the activity of a proposed silver sulphide auxiliary layer at the surface of the β-alumina and shown to be in agreement with a theoretically-calculated value. Experiments were carried out using this cell in molten tin baths of varying sulphur content. Results were generally consistent with the previously-determined values of silver sulphide activity; however, at low sulphur values this activity was not constant and decreased to zero. The minimum level of sulphur which could be detected by this technique was calculated and tested both in laboratory molten tin and in industrial trials.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597897 |
| Date | January 2000 |
| Creators | Connolly, William John Cleveland |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.repository.cam.ac.uk/handle/1810/251711 |
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