Abstract
AbstractThis paper embraces two different approaches for the joining of materials through glass sealants. First, the conventional method of furnace sealing in which paste technology is normally employed. The glass sealant is applied in powder form mixed with agglomerant and with the help of dispenser robots, tape casting, or screen printing. Glass‐ceramics for sealing of solid oxide fuel cells (SOFC) are described as an example of this type of processing. Glass composition, thermal properties, particle size of the glass powder, sintering and crystallization competition, and final crystalline phases together with a suitable chemical compatibility with the metallic and ceramic elements to be sealed need to be carefully adjusted for this specific application. Second, laser welding is presented as an alternative sealing technology. A general overview about laser welding through glass sealants is presented. Particularly, the welding of sapphire and fused silica glass through a BTS.2SiO2 thin film glass sealant by employment of a nanosecond‐pulsed laser is detailed. Laser parameters (frequency, power, scan speed, and number of passes) were optimized to get the best molten conditions of the BTS thin film, while allowing its crystallization. BTS crystallization upon laser welding leads to a strong blue emission upon UV excitation. Finally, both processing technologies were compared.
Highlights
The term sealing glass, more than a composition or specific property, describes the use of glass to create a hermetic seal
The starting system is BaO–MgO–SiO2, the glass-forming region in this system was deeply studied in Ref. (31) together with the definition of compositions with more suitable dilatometric properties
One of the main reasons for selecting this system was the good fit of TEC of barium silicate phases with those of the cell components
Summary
The term sealing glass, more than a composition or specific property, describes the use of glass to create a hermetic seal. For sealing, a paste obtained from glass powder mixed with alcohol and a binder is prepared and applied to the parts to be sealed; after that, the entire stack is heated up at temperatures between 800°C and1000°C in an electrical furnace for few hours.[2,3] Normally, the application of the glass powder takes place with the help of dispenser robots, tape casting, or screen printing.[4] This is a typical example of conventional furnace sealing In this case, glass composition, thermal properties, particle size of the glass powder, sintering and crystallization competition, and final crystalline phases together with a suitable chemical compatibility with the metallic and ceramic elements to be sealed need to be carefully adjusted. The results aim to consolidate the feasibility of the employment of BTS-based thin film glass sealants for the welding of transparent dissimilar substrates, by using a nanosecond pulsed laser, different to the lasers conventionally used (Table 1)
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