Reactive air brazing for sealing mixed ionic electronic conducting hollow fibre membranes. (15th April 2015)

• Record Type: Journal Article
• Authors: Chen, Hong; Li, Leijun; Kemps, Raymond; Michielsen, Bart; Jacobs, Marijke; Snijkers, Frans; Middelkoop, Vesna
• Is Part Of: Acta materialia. Volume 88(2015)
• Page Start: 74
• Page End: 82
• Publication Date: 2015-04-15
• Subjects: Reactive air brazing -- Ceramic-metal interfacial bonding -- High-temperature joining and sealing -- Gas-separation systems -- Mixed ionic–electronic conducting hollow fibre membranes; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.01.029
• Languages: English
• ISSNs: 1359-6454

Abstract

Graphical abstract: Abstract: Mixed ionic–electronic conducting (MIEC) ceramic membranes and high-temperature alloys are candidate materials for applications in high-temperature gas separation systems and solid oxide fuel cells (SOFCs). Ensuring a gas-tight seal between the components is of paramount importance in the operation of such devices. This paper investigates the wettability and joining of representative ceramic-to-ceramic and ceramic-to-metal components by reactive air brazing (RAB) using Ag–Cu alloys. The correlation of the interfacial reaction (including wettability) to the hermeticity of the joints has been demonstrated by elemental mapping using Electron Probe Micro-Analysis with wavelength dispersive spectrometry (EPMA-WDS). The wettability studies described herein demonstrate that RAB is a reliable method to achieve strong, gas-tight bonding between the dissimilar materials. These are the first reported results of successful air-brazed joints between La0.6 Sr0.4 Co0.2 Fe0.8 O3-δ (LSCF) and BaCo0.4 Fe0.4 Zr0.2 O3-δ (BCFZ) hollow fibre membranes to FeCrAlloy components using a 4 mol.% Cu in Ag filler metal composition which delivered an impressive runtime of up to 2000 h (for LSCF). It has been demonstrated that these RAB joints are hermetic and resistant to thermal ageing, making them suitable for membrane-based gas-separation applications. Post-operation EPMA-WDS analysis of the microstructures and compositional distribution of the brazed seals has revealed that their performance is largely dependent upon a reaction zone and an interfacial oxide layer adherent to the FeCrAlloy surface.