Developing alternative sealing materials in fabrication of evacuated glazing at low temperature

• Main Author: Arya, Farid
• Format: Dissertation
• Language: English
• Published: University of Ulster 2014

Very low heat transfer rates through multiple glass pane windows can be achieved by creating a vacuum between the glass panes and depositing low emittance coatings on the glass surface. This involves forming a vacuum tight seal around the periphery of the glazing, and creating a high vacuum (, 10-5 mbar) within the glazing. Arrays of tiny support pillars are placed between the glass panes to maintain the separation between the panes which would otherwise touch under atmospheric pressure. To date there are two principal methods reported in the literature which are widely used in the fabrication of functioning vacuum glazing i.e. solder glass and metal sealing techniques. Since the solder glass sealing process is usually a high temperature process (450°C-530°C) it restricts the use of tempered glass in the fabrication of vacuum glazing. Alternatively, metal sealing techniques are typically low temperature processes (<200°C) which enables the use of tempered glass panes in the fabrication of vacuum glazing. However, the high price and availability of these semi-precious metals makes this method of fabricating vacuum glazing less economically viable. The aim of this project is to develop a novel method of fabrication for a new generation of vacuum glazing which have a high thermal performance, a potential life span of more than 20 years and a process capable of being exploited by industry in cost effective manner. In order to achieve this goal the main focus is to develop an alternative sealing system and the required fabrication methodology. An analysis of the current sealing methodologies which have been adopted for vacuum glazing has been undertaken. Improving and optimizing the current metal based sealing methodology has been undertaken. Characterisation of the thermal performance of vacuum glazing samples using a hot box calorimeter was undertaken. An optical system was developed which provides a quick and easy way to study the internal pressure of vacuum glazing and characterise their thermal performance. A crucial step in this project was to develop a new reliable and effective pump out system and pump-out hole sealing methodology for vacuum glazing. A range of double, triple and hybrid vacuum glazing using indium sealing techniques and annealed glass panes were fabricated and their thermal performance was characterised.