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Title Metal Glass Adhesion in SOFC Applications
Author Nielsen, Sofie Birkedal Lund (Materialeteknologi og -udvikling, Institut for Produktion og Ledelse, Danmarks Tekniske Universitet, DTU, DK-2800 Kgs. Lyngby, Denmark)
Supervisor Somers, Marcel A. J. (Materials Science and Engineering, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Solvang, Mette (Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2006
Abstract Class or glass ceramic is a good candidate as a sealant between Fe22Cr interconnector steel and cell components in Solid Oxide Fuel Cells (SOFCs). The Adhesion between two different glass sealants and three different types of interconnector steel (Crofer22APU, Sandvik 1C44Mo20 and Sandvik 350) was tested by heat treatment of stacks of alternate layers of glass and steel under a small load. The interfaces were then investigated in a Scanning Electorn Microscope (SEM). The thermal expansion characteristics of the two glasses, a sodium alumino silicate (NAS) glass and a calcium alumino boro silicate (CAS) glass, were adjusted to match those of the interconnector steels by addition (either 0, 10 or 39wt%) of a MgO filler with a higher thermal expansion coefficient (TEC) than the glass. Etching, sanding, pre-oxidation or coatings of metal or metal oxide, which wrer all believed to help facilitate good bonding between glass and steel, were applied to steel surfaces. The nonding an microstucture of the interfaces between glass/composite seals and interconnector steels were investigated as a function of steel composition, durface treatment/coating of the steel surface, glass matrix compositon, filler concentration in the glass seal and sealing temperature (850oC or 950oC). Only the interface between Sandvik 1C44Mo20 steel and CAS glass showed an improvement in adhesion when raising the sealing temperature from 850oC to 950oC. Other interfaces, tested at both temperatures, did not show any difference in adhesion when raising the sealing temperature. Etching, sanding or pre-oxidation of steel surfaces did not change surface conditions of the steel plates and the performance of surface treated steel/glass interfaces were no different than with untreated steel plates. Adhesion in interfaces between Sandvik 1C44Mo20 and CAS glass was generally better when no MgO particles were added to the glass. At interfaces between Crofer 22APU and CAS glass, a better adhesion was observed when 10 wt% MgO was added to the glass as compared to no filler in the glass. The Sandvik 350 steel did not show any trend in a general better adhesion to CAS glass with or without filler in the glass. NAS glass was only tested with MgO particles in the glass and there did not seem to be a general difference in adhesion betw3een interfaces with 10 wt% MgO compared to 39 wt% MgO in the glass. Application of transition metal oxide coatings on etched surfaces of Crofer 22 APU steel showed a significant improvement in the development of a gradual transition in chemical bonding between steel an glass. Coatings of MN3O4 and NiO to the steel gave the best results against CAS glass and coatings of NiO and Co3O4 gave the best results against NAS glass. Wxcellent bonding was seen at interfaces between untreated or pre-oxidized Sandvik 1C44Mo20 steel and CAS glass and also between MN3O4 or NiO coated Crofer 22APU steel and CAS composite with 10 wt% MgO.
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Admin Creation date: 2007-07-25    Update date: 2011-09-27    Source: dtu    ID: 201786    Original MXD