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    Effect of binder burnout on the sealing performance of glass ceramics for solid oxide fuel cells
    (ELSEVIER SCIENCE BV, 2013) Ertugrul, Tugrul Y.; Celik, Selahattin; Mat, Mahmut D.
    The glass ceramics composite sealants are among few materials suitable for the solid oxide fuel cells (SOFC) due to their high operating temperatures (600 degrees C-850 degrees C). The glass ceramics chemically bond to both the metallic interconnector and the ceramic electrolyte and provide a gas tight connection. A careful and several stages manufacturing procedure is required to obtain a gas tight sealing. In this study, effects of binder burnout process on the sealing performance are investigated employing commercially available glass ceramic powders. The glass ceramic laminates are produced by mixing glass ceramic powders with the organic binders and employing a tape casting method. The laminates are sandwiched between the metallic interconnectors of an SOFC cell. The burnout and subsequent sealing quality are analyzed by measuring leakage rate and final macrostructure of sealing region. The effects of heating rate, dead weight load, solid loading, carrier gas and their flow rates are investigated. It is found that sealing quality is affected from all investigated parameters. While a slower heating rate is required for a better burnout, the mass flow rate of sweep gas must be adequate for removal of the burned gas. The leakage rate is reduced to 0.1 ml min(-1) with 2 degrees C min(-1) + 1 degrees C min(-1) heating rate, 86.25% solid loading, 200 N dead weight load and 500 ml min(-1) sweep gas flow rate. (C) 2013 Elsevier B.V. All rights reserved.
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    Electrochemical behaviour and sulfur tolerance of VxMo(1-x)Oy as solid oxide fuel cell anode
    (ELSEVIER SCI LTD, 2013) Beyribey, Berceste; Timurkutluk, Bora; Ertugrul, Tugrul Y.; Timurkutluk, Cigdem; Mat, Mahmut D.
    Vanadium molybdenum oxide system (VxMo(1-x)Oy for x <= 0.13) is synthesized through reducing acidified vanadate and molybdate solution at 60 degrees C by passing hydrogen sulfide gas through the solution. The electrochemical performance of the mixed oxide is tested at various operation temperatures as an anode material for intermediate temperature solid oxide fuel cell (IT-SOFC) under pure and 50 ppm H2S-containing hydrogen fuel. The highest cell performance of 0.18 W cm(-2) peak power is reached at an operation temperature of 750 degrees C for dry H-2. It is found that the addition of 50 ppm H2S to the anode gas causes a 22% decrease in the cell peak power. The loss in the cell performance is attributed to both gas conversion and diffusion. Short-term regeneration tests indicate that 1 h-exposure to sulfur-free gas is insufficient for the reactivation of the cell performance. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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    Optimum processing parameters to improve sealing performance in solid oxide fuel cells
    (ELSEVIER SCI LTD, 2015) Ertugrul, Tugrul Y.; Celik, Selahattin; Mat, Mahmut D.
    Glass ceramic composites are among the favorable candidates as a sealing material for solid oxide fuel cells (SOFC). In order to obtain a reliable, robust and hermetic sealing, the glass ceramics must chemically bond to both the metallic interconnector and the ceramic electrolyte. A high-bonding strength and good wetting, which strongly depend on the thermal treatment, are always preferred to ensure gas-tight sealing. The thermal treatment involves three stages: binder burnout (stage-I), sintering (stage-II), and cooling (stage-III). This study investigates effects of various parameters on the sealing quality at the sintering stage. The effects of sintering temperature, clamping pressure and sealant thickness are considered. The glass ceramic laminates are produced employing a tape casting method. The sealing quality is evaluated by measuring leakage and final macro-structure of the sealing region. It is suggested that a 900-930 degrees C sintering temperature and 1.5-7.6 N cm(-2) clamping pressure ranges are better for successful sealing. The initial thickness of glass ceramic laminates is also desired to be between 0.25-0.5 mm thickness range for both a cost-effective and reliable sealing. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.