The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Jeffry W Stevenson - One of the best experts on this subject based on the ideXlab platform.

  • Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: Sealing Glass stability, microstructure and interfacial reactions
    Journal of Power Sources, 2014
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    Abstract A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part II of the work examined the Sealing Glass stability, microstructure development, interfacial reaction, and volatility issues of a 3-cell stack with LSM-based cells. After 6000 h of testing, the refractory Sealing Glass YSO7 showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified. In addition, no Glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the Sealing Glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the Glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar Glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time weight loss of refractory Sealing Glass YSO77 was estimated to be less than 0.1 wt%.

  • Surfaces, Interfaces, and the Science of Ceramic Joining - Glass Sealing in Planar SOFC Stacks and Chemical Stability of Seal Interfaces
    Ceramic Transactions Series, 2012
    Co-Authors: Zhenguo Yang, Kerry D Meinhardt, K. Scott Weil, Guanguang Xia, Jeffry W Stevenson
    Abstract:

    In intermediate temperature planar SOFC stacks, the interconnect, which is typically made from cost-effective oxidation resistant high temperature alloys, is typically sealed to the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a Sealing Glass. To maintain the structural stability and minimize the degradation of stack performance, the Sealing Glass has to be chemically compatible with the PEN and alloy interconnects. In the present study, the chemical compatibility of a barium-calcium-aluminosilicate (BCAS) based Glass-ceramic (specifically developed as a sealant in SOFC stacks) with a number of selected oxidation resistant high temperature alloys, as well as the YSZ electrolyte, was evaluated. This paper reports the results of that study, with a particular focus on Crofer22 APU, a new ferritic stainless steel that was developed specifically for SOFC interconnect applications.

  • Evaluation of a single cell and candidate materials with high water content hydrogen in a generic solid oxide fuel cell stack test fixture, Part II: materials and interface characterization
    International Journal of Applied Ceramic Technology, 2012
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    A generic solid oxide fuel cell (SOFC) test fixture was developed to evaluate candidate materials under realistic operating conditions. A commercial 50 mm × 50 mm NiO-YSZ anode-supported thin YSZ electrolyte cell with lanthanum strontium manganite (LSM)/YSZ cathode was tested to evaluate the stability of candidate materials. The cell was tested in two stages at 800°C: stage I with low (~3% H2O) humidity and stage II with high (~30% H2O) humidity hydrogen fuel in constant voltage or constant current mode. Part I of the work, published previously, provided information regarding the generic test fixture design, materials, cell performance, and optical post-mortem analysis. In part II, detailed microstructure and interfacial characterizations are reported regarding the SOFC candidate materials: (Mn,Co)-spinel conductive coating, alumina coating for Sealing area, ferritic stainless steel interconnect, refractory Sealing Glass, and their interactions with each other. Overall, the (Mn,Co)-spinel coating was very effective in minimizing Cr migration. No Cr was identified in the cathode after 1720 h at 800°C. Aluminization of metallic interconnects also proved to be chemically compatible with alkaline-earth silicate Sealing Glass. The details of interfacial reaction and microstructure development are discussed.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective alumina coating on electrical stability in dual environment
    International Journal of Hydrogen Energy, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Jeffry W Stevenson
    Abstract:

    Abstract An alkali-containing silicate Glass was recently proposed as a potential sealant for solid oxide fuel cells (SOFC). The Glass contains appreciable amount of alkalis and retains its Glassy microstructure at elevated temperatures over time. It is more compliant as compared to conventional Glass–ceramics sealants and could potentially heal cracks during thermal cycling. In previous papers the thermal cycle stability, thermal stability and chemical compatibility were reported with yttria-stabilized zirconia (YSZ) electrolyte and YSZ-coated ferritic stainless steel interconnect. In this paper, we report the electrical stability of the compliant Glass with aluminized AISI441 interconnect material under DC load in dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-point method for the Glass sealed between two aluminized AISI441 metal coupons as well as plain AISI441 substrates. The results showed good electrical stability with the aluminized AISI441 substrate, while unstable behavior was observed for un-coated substrates. In addition, interfacial microstructure was examined with scanning electron microscopy and correlated with the measured resistivity results. Overall, the alumina coating demonstrated good chemical stability with the alkali-containing silicate Sealing Glass under DC loading.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective YSZ coating on electrical stability in dual environment
    Journal of Power Sources, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Edwin C. Thomsen, Jeffry W Stevenson
    Abstract:

    Abstract Recently, compliant Sealing Glass has been proposed as a potential candidate sealant for solid oxide fuel cell (SOFC) applications. In a previous paper, the thermal stability and chemical compatibility were reported for a compliant alkali-containing silicate Glass sealed between anode supported YSZ bi-layer and YSZ-coated stainless steel interconnect. In this paper, we will report the electrical stability of the compliant Glass under a DC load and dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-ponit method for the Glass sealed between two plain SS441 metal coupons or YSZ-coated aluminized substrates. The results showed instability with plain SS441 at 800 °C, but stable behavior of increasing resistivity with time was observed with the YSZ coated SS441. In addition, results of interfacial microstructure analysis with scanning electron microscopy will be correlated with the measured resistivity results. Overall, the YSZ coating demonstrated chemically stability with the alkali-containing compliant silicate Sealing Glass under electrical field and dual environments.

Yeongshyung Chou - One of the best experts on this subject based on the ideXlab platform.

  • Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: Sealing Glass stability, microstructure and interfacial reactions
    Journal of Power Sources, 2014
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    Abstract A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part II of the work examined the Sealing Glass stability, microstructure development, interfacial reaction, and volatility issues of a 3-cell stack with LSM-based cells. After 6000 h of testing, the refractory Sealing Glass YSO7 showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified. In addition, no Glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the Sealing Glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the Glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar Glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time weight loss of refractory Sealing Glass YSO77 was estimated to be less than 0.1 wt%.

  • Evaluation of a single cell and candidate materials with high water content hydrogen in a generic solid oxide fuel cell stack test fixture, Part II: materials and interface characterization
    International Journal of Applied Ceramic Technology, 2012
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    A generic solid oxide fuel cell (SOFC) test fixture was developed to evaluate candidate materials under realistic operating conditions. A commercial 50 mm × 50 mm NiO-YSZ anode-supported thin YSZ electrolyte cell with lanthanum strontium manganite (LSM)/YSZ cathode was tested to evaluate the stability of candidate materials. The cell was tested in two stages at 800°C: stage I with low (~3% H2O) humidity and stage II with high (~30% H2O) humidity hydrogen fuel in constant voltage or constant current mode. Part I of the work, published previously, provided information regarding the generic test fixture design, materials, cell performance, and optical post-mortem analysis. In part II, detailed microstructure and interfacial characterizations are reported regarding the SOFC candidate materials: (Mn,Co)-spinel conductive coating, alumina coating for Sealing area, ferritic stainless steel interconnect, refractory Sealing Glass, and their interactions with each other. Overall, the (Mn,Co)-spinel coating was very effective in minimizing Cr migration. No Cr was identified in the cathode after 1720 h at 800°C. Aluminization of metallic interconnects also proved to be chemically compatible with alkaline-earth silicate Sealing Glass. The details of interfacial reaction and microstructure development are discussed.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective YSZ coating on electrical stability in dual environment
    Journal of Power Sources, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Edwin C. Thomsen, Jeffry W Stevenson
    Abstract:

    Abstract Recently, compliant Sealing Glass has been proposed as a potential candidate sealant for solid oxide fuel cell (SOFC) applications. In a previous paper, the thermal stability and chemical compatibility were reported for a compliant alkali-containing silicate Glass sealed between anode supported YSZ bi-layer and YSZ-coated stainless steel interconnect. In this paper, we will report the electrical stability of the compliant Glass under a DC load and dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-ponit method for the Glass sealed between two plain SS441 metal coupons or YSZ-coated aluminized substrates. The results showed instability with plain SS441 at 800 °C, but stable behavior of increasing resistivity with time was observed with the YSZ coated SS441. In addition, results of interfacial microstructure analysis with scanning electron microscopy will be correlated with the measured resistivity results. Overall, the YSZ coating demonstrated chemically stability with the alkali-containing compliant silicate Sealing Glass under electrical field and dual environments.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective alumina coating on electrical stability in dual environment
    International Journal of Hydrogen Energy, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Jeffry W Stevenson
    Abstract:

    Abstract An alkali-containing silicate Glass was recently proposed as a potential sealant for solid oxide fuel cells (SOFC). The Glass contains appreciable amount of alkalis and retains its Glassy microstructure at elevated temperatures over time. It is more compliant as compared to conventional Glass–ceramics sealants and could potentially heal cracks during thermal cycling. In previous papers the thermal cycle stability, thermal stability and chemical compatibility were reported with yttria-stabilized zirconia (YSZ) electrolyte and YSZ-coated ferritic stainless steel interconnect. In this paper, we report the electrical stability of the compliant Glass with aluminized AISI441 interconnect material under DC load in dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-point method for the Glass sealed between two aluminized AISI441 metal coupons as well as plain AISI441 substrates. The results showed good electrical stability with the aluminized AISI441 substrate, while unstable behavior was observed for un-coated substrates. In addition, interfacial microstructure was examined with scanning electron microscopy and correlated with the measured resistivity results. Overall, the alumina coating demonstrated good chemical stability with the alkali-containing silicate Sealing Glass under DC loading.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: Combined stability in isothermal ageing and thermal cycling with YSZ coated ferritic stainless steels
    Journal of Power Sources, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Edwin C. Thomsen, Jeffry W Stevenson
    Abstract:

    Abstract An alkali silicate Glass (SCN-1) is being evaluated as a candidate sealant for solid oxide fuel cell (SOFC) applications. The Glass contains about 17 wt.% alkalis (K + Na) and has low Glass transition and softening temperatures. It remains vitreous and compliant after Sealing without substantial crystallization, as contrary to conventional Glass–ceramic sealant. The Glassy nature and low characteristic temperatures can reduce residual stresses and result in the potential for crack healing. In a previous study, the Glass was found to have good thermal cycle stability and was chemically compatible with yttria stabilized zirconia (YSZ) coating during short term testing. In this study, the compliant Glass was further evaluated in a more realistic way in that the sealed couples were first isothermally aged for 1000 h followed by thermal cycling. High temperature leakage was measured. Chemical compatibility was also investigated with powder mixtures to enhance potential interfacial reaction. In addition, interfacial microstructure was examined with scanning electron microscopy and evaluated with regard to the leakage and chemical compatibility results. Overall the compliant Sealing Glass showed desirable chemical compatibility with YSZ coated metallic interconnect of minimum reaction and hermetic behavior at 700–750 °C in dual environment.

Jung-pyung Choi - One of the best experts on this subject based on the ideXlab platform.

  • Long-term evaluation of solid oxide fuel cell candidate materials in a 3-cell generic short stack fixture, Part II: Sealing Glass stability, microstructure and interfacial reactions
    Journal of Power Sources, 2014
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    Abstract A generic solid oxide fuel cell stack test fixture was developed to evaluate candidate materials and processing methods under realistic conditions. Part II of the work examined the Sealing Glass stability, microstructure development, interfacial reaction, and volatility issues of a 3-cell stack with LSM-based cells. After 6000 h of testing, the refractory Sealing Glass YSO7 showed desirable chemical compatibility with YSZ electrolyte in that no discernable interfacial reaction was identified. In addition, no Glass penetration into the thin electrolyte was observed. At the aluminized AISI441 interface, the protective alumina coating appeared to be corroded by the Sealing Glass. Air side interactions appeared to be more severe than fuel side interactions. Metal species such as Cr, Mn, and Fe were detected in the Glass, but were limited to the vicinity of the interface. No alkaline earth chromates were found at the air side. Volatility was also studied in a similar Glass and weight loss in a wet reducing environment was determined. Using the steady-state volatility data, the life time weight loss of refractory Sealing Glass YSO77 was estimated to be less than 0.1 wt%.

  • Evaluation of a single cell and candidate materials with high water content hydrogen in a generic solid oxide fuel cell stack test fixture, Part II: materials and interface characterization
    International Journal of Applied Ceramic Technology, 2012
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Jung-pyung Choi
    Abstract:

    A generic solid oxide fuel cell (SOFC) test fixture was developed to evaluate candidate materials under realistic operating conditions. A commercial 50 mm × 50 mm NiO-YSZ anode-supported thin YSZ electrolyte cell with lanthanum strontium manganite (LSM)/YSZ cathode was tested to evaluate the stability of candidate materials. The cell was tested in two stages at 800°C: stage I with low (~3% H2O) humidity and stage II with high (~30% H2O) humidity hydrogen fuel in constant voltage or constant current mode. Part I of the work, published previously, provided information regarding the generic test fixture design, materials, cell performance, and optical post-mortem analysis. In part II, detailed microstructure and interfacial characterizations are reported regarding the SOFC candidate materials: (Mn,Co)-spinel conductive coating, alumina coating for Sealing area, ferritic stainless steel interconnect, refractory Sealing Glass, and their interactions with each other. Overall, the (Mn,Co)-spinel coating was very effective in minimizing Cr migration. No Cr was identified in the cathode after 1720 h at 800°C. Aluminization of metallic interconnects also proved to be chemically compatible with alkaline-earth silicate Sealing Glass. The details of interfacial reaction and microstructure development are discussed.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective YSZ coating on electrical stability in dual environment
    Journal of Power Sources, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Edwin C. Thomsen, Jeffry W Stevenson
    Abstract:

    Abstract Recently, compliant Sealing Glass has been proposed as a potential candidate sealant for solid oxide fuel cell (SOFC) applications. In a previous paper, the thermal stability and chemical compatibility were reported for a compliant alkali-containing silicate Glass sealed between anode supported YSZ bi-layer and YSZ-coated stainless steel interconnect. In this paper, we will report the electrical stability of the compliant Glass under a DC load and dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-ponit method for the Glass sealed between two plain SS441 metal coupons or YSZ-coated aluminized substrates. The results showed instability with plain SS441 at 800 °C, but stable behavior of increasing resistivity with time was observed with the YSZ coated SS441. In addition, results of interfacial microstructure analysis with scanning electron microscopy will be correlated with the measured resistivity results. Overall, the YSZ coating demonstrated chemically stability with the alkali-containing compliant silicate Sealing Glass under electrical field and dual environments.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: The effect of protective alumina coating on electrical stability in dual environment
    International Journal of Hydrogen Energy, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Jeffry W Stevenson
    Abstract:

    Abstract An alkali-containing silicate Glass was recently proposed as a potential sealant for solid oxide fuel cells (SOFC). The Glass contains appreciable amount of alkalis and retains its Glassy microstructure at elevated temperatures over time. It is more compliant as compared to conventional Glass–ceramics sealants and could potentially heal cracks during thermal cycling. In previous papers the thermal cycle stability, thermal stability and chemical compatibility were reported with yttria-stabilized zirconia (YSZ) electrolyte and YSZ-coated ferritic stainless steel interconnect. In this paper, we report the electrical stability of the compliant Glass with aluminized AISI441 interconnect material under DC load in dual environment at 700–800 °C. Apparent electrical resistivity was measured with a 4-point method for the Glass sealed between two aluminized AISI441 metal coupons as well as plain AISI441 substrates. The results showed good electrical stability with the aluminized AISI441 substrate, while unstable behavior was observed for un-coated substrates. In addition, interfacial microstructure was examined with scanning electron microscopy and correlated with the measured resistivity results. Overall, the alumina coating demonstrated good chemical stability with the alkali-containing silicate Sealing Glass under DC loading.

  • Compliant alkali silicate Sealing Glass for solid oxide fuel cell applications: Combined stability in isothermal ageing and thermal cycling with YSZ coated ferritic stainless steels
    Journal of Power Sources, 2012
    Co-Authors: Yeongshyung Chou, Jung-pyung Choi, Edwin C. Thomsen, Jeffry W Stevenson
    Abstract:

    Abstract An alkali silicate Glass (SCN-1) is being evaluated as a candidate sealant for solid oxide fuel cell (SOFC) applications. The Glass contains about 17 wt.% alkalis (K + Na) and has low Glass transition and softening temperatures. It remains vitreous and compliant after Sealing without substantial crystallization, as contrary to conventional Glass–ceramic sealant. The Glassy nature and low characteristic temperatures can reduce residual stresses and result in the potential for crack healing. In a previous study, the Glass was found to have good thermal cycle stability and was chemically compatible with yttria stabilized zirconia (YSZ) coating during short term testing. In this study, the compliant Glass was further evaluated in a more realistic way in that the sealed couples were first isothermally aged for 1000 h followed by thermal cycling. High temperature leakage was measured. Chemical compatibility was also investigated with powder mixtures to enhance potential interfacial reaction. In addition, interfacial microstructure was examined with scanning electron microscopy and evaluated with regard to the leakage and chemical compatibility results. Overall the compliant Sealing Glass showed desirable chemical compatibility with YSZ coated metallic interconnect of minimum reaction and hermetic behavior at 700–750 °C in dual environment.

Teng Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Structural transformation-induced surface strengthening of borosilicate Sealing Glass for solid oxide fuel cells
    Ceramics International, 2019
    Co-Authors: Yan Jiajia, Dewei Lin, Hongbing Zhan, Haiyan Zhuang, Teng Zhang
    Abstract:

    Abstract In solid oxide fuel cells (SOFCs), it is important that the Sealing Glass has adequate mechanical strength (rigidity) to withstand stack loads while simultaneously having appropriate resiliency to release the internal stress and thus resist cracking. However, at present, Sealing Glass is either resilient or rigid. Animal teeth exhibit a bilayer structure that combines remarkable surface hardness to withstand mastication loads with the high resiliency of the inner layer to resist crack propagation. Drawing from this, in this study, we selected a heat-treatment temperature of 700 °C to simulate the operating temperature of the Sealing Glass and SOFCs, and carried out experimental and theoretical investigation of a typical borosilicate Sealing-Glass system. The results revealed that surface strengthening occurs within 200 nm depth as the heat-treatment time increases; that is, there is a gradient change in the mechanical property from the surface to the interior of Glass, indicating that the surface has greater hardness and elastic modulus to bear stack loads, while the interior has better resiliency and may help resist crack initiation and propagation. A possible mechanism for this strengthening is proposed. The 4-coordinated B and Al centred BO4 and AlO4 can form a Glass network structure with SiO4 (i.e., B–O–Si, Al–O–Si), which may lead to surface strengthening due to the increase in the degree of network crosslinking.

  • Improving the Sealing performance of Glass-ceramics for SOFCs applications by a unique ‘composite’ approach: A study on Na2O-SiO2 Glass-ceramic system
    Journal of the European Ceramic Society, 2018
    Co-Authors: Dewei Lin, Yan Jiajia, Dian Tang, Lin Fen, Hsiwen Yang, Shengwei Tan, Dong Zhengwei, Kongfa Chen, Teng Zhang
    Abstract:

    Abstract The rigid nature of Sealing Glass-ceramics restricts the thermal cycling stability of Solid Oxide Fuel Cells (SOFCs), which thus evokes an interest in designing a Sealing Glass without crystallization under the operational condition of SOFCs. In this paper, we report that the Sealing performance of 30Na2O-70SiO2 (in mole%) Glass-ceramic can be significantly improved by Fe2O3 dopant through a composite approach. In particular, the crystallization in Glass can be suppressed by appropriate Fe2O3 dopant amount (8 mol%), which results in the improved Sealing property of Glass. In addition, the Glass modified with Fe2O3 shows good chemical compatibility with 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte and metallic interconnect (430 stainless steel) in dual atmospheres. The possible mechanism for the improved Sealing performance of 30Na2O-70SiO2 Glass-ceramic by this unique composite approach is also discussed.

  • Controlling the reaction between boron-containing Sealing Glass and a lanthanum-containing cathode by adding Nb2O5
    Journal of Power Sources, 2016
    Co-Authors: Dandan Zhao, Dian Tang, Fang Lihua, Teng Zhang
    Abstract:

    Abstract In solid oxide fuel cell (SOFC) stacks, the volatile boron species present in the Sealing Glass often react with the lanthanum-containing cathode, degrading the activity of the cathode (this phenomenon is known as boron poisoning). In this work, we report that this detrimental reaction can be effectively reduced by doping bismuth-containing borosilicate Sealing Glass-ceramic with a niobium dopant. The addition of Nb 2 O 5 not only condenses the [SiO 4 ] structural units in the Glass network, but also promotes the conversion of [BO 3 ] to [BO 4 ]. Moreover, the Nb 2 O 5 dopant enhances the formation of boron-containing phases (Ca 3 B 2 O 6 and CaB 2 Si 2 O 8 ), which significantly reduces the volatility of boron compounds in the Sealing Glass, suppressing the formation of LaBO 3 in the reaction couple between the Glass and the cathode. The reported results provide a new approach to solve the problem of boron poisoning.

  • Reducing the reaction between boron-containing Sealing Glass-ceramics and lanthanum-containing cathode: Effect of La2O3
    Journal of the European Ceramic Society, 2016
    Co-Authors: Honglin Liu, Dian Tang, Wei Luo, Chunxiang Lin, Du Xinhang, Hsiwen Yang, Teng Zhang
    Abstract:

    Abstract The volatile boron species from Sealing Glass-ceramics have a significant poisoning effect on the electrochemical activity of Solid Oxide Fuel Cell (SOFC) cathodes. The reaction between boron-containing Sealing Glass-ceramics and cathodes thus presents a challenge for the development of SOFC. Here we report for the first time that the addition of La 2 O 3 can significantly reduce the boron volatility from Sealing Glass-ceramics and consequently the formation of LaBO 3 in reaction couple between Glass and (La,Sr)(Co,Fe)O 3 (LSCF) cathode. In particular, the boron volatility can be reduced by about 6 times with the addition of 4 mol.% La 2 O 3 (3.7 × 10 −3 vs. 0.6 × 10 −3 %). The addition of La 2 O 3 condenses the structure of Glasses and Glass-ceramics, contributing to the decrease in boron volatility from Glass-ceramics. In addition, La 2 O 3 dopant favors the formation of boron-containing phase (La 5 SiBO 13 ) in Glass-ceramics, which dramatically reduces the boron volatility. The reported results provide an effective approach for solving the Sealing challenge.

  • Improving the electrical property of CeO2-containing Sealing Glass–ceramics for Solid Oxide Fuel Cell applications: Effect of HfO2
    Journal of the European Ceramic Society, 2016
    Co-Authors: Honglin Liu, Dandan Zhao, Hsiwen Yang, Jinwan Huang, Teng Zhang
    Abstract:

    Abstract The electrical property of Sealing Glass–ceramics is of great importance for Solid Oxide Fuel Cell (SOFC) applications. In spite of their good sintering property, CeO 2 -containing Glass–ceramics often lack in sufficient electrical resistance, due to the formation of CeO 2 as a conductive phase. Here we report for the first time that the electrical conductivity of CeO 2 -containing Glass–ceramics can be reduced by an order of magnitude with HfO 2 dopant. A mechanism on the improved electrical property has also been proposed in terms of the structural change in HfO 2 -doped Glass–ceramics. In addition, the relationship between phase evolution of HfO 2 -doped Glass–ceramics and the change in conductivity with operational time has been systematically investigated. Moreover, HfO 2 -doped Glass–ceramics show good chemical compatibility with 8 mol.% yttria-stabilized zirconia (8YSZ) electrolyte, after held at 750 °C for 500 h. The reported results support the suitability of prepared Glass–ceramics as Sealing materials for SOFC applications.

Zhenguo Yang - One of the best experts on this subject based on the ideXlab platform.

  • Surfaces, Interfaces, and the Science of Ceramic Joining - Glass Sealing in Planar SOFC Stacks and Chemical Stability of Seal Interfaces
    Ceramic Transactions Series, 2012
    Co-Authors: Zhenguo Yang, Kerry D Meinhardt, K. Scott Weil, Guanguang Xia, Jeffry W Stevenson
    Abstract:

    In intermediate temperature planar SOFC stacks, the interconnect, which is typically made from cost-effective oxidation resistant high temperature alloys, is typically sealed to the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a Sealing Glass. To maintain the structural stability and minimize the degradation of stack performance, the Sealing Glass has to be chemically compatible with the PEN and alloy interconnects. In the present study, the chemical compatibility of a barium-calcium-aluminosilicate (BCAS) based Glass-ceramic (specifically developed as a sealant in SOFC stacks) with a number of selected oxidation resistant high temperature alloys, as well as the YSZ electrolyte, was evaluated. This paper reports the results of that study, with a particular focus on Crofer22 APU, a new ferritic stainless steel that was developed specifically for SOFC interconnect applications.

  • Electrical stability of a novel Sealing Glass with (Mn,Co)-spinel coated Crofer22APU in a simulated SOFC dual environment
    Journal of Power Sources, 2010
    Co-Authors: Yeongshyung Chou, Jeffry W Stevenson, Guanguang Xia, Zhenguo Yang
    Abstract:

    Abstract A novel alkaline-earth silicate (Sr–Ca–Y–B–Si–Zn) Sealing Glass was developed for solid oxide fuel cell (SOFC) applications. The Glass was sandwiched between two metallic interconnect plates and tested for electrical stability in a dual environment at elevated temperatures of 800–850 °C. A ferritic stainless steel (Crofer22APU) was used as the metallic interconnect material in the as-received state and coated with (Mn,Co) 3 O 4 spinel. The isothermal aging results showed stable electrical resistivity at 800–850 °C for ∼500–1000 h. The electrical resistivities at 800 or 850 °C of the spinel coated samples were lower than the as-received ones; however, they were still several orders of magnitude higher than typical SOFC functional parts. Interfacial microstructure was characterized and possible reactions are discussed.

  • chemical stability of Glass seal interfaces in intermediate temperature solid oxide fuel cells
    Journal of Materials Engineering and Performance, 2004
    Co-Authors: Zhenguo Yang, Kerry D Meinhardt, Scott K Weil, Jeff W Stevenson
    Abstract:

    In intermediate temperature planar solid oxide fuel cell (SOFC) stacks, the interconnect, which is typically made from cost-effective, oxidation-resistant, high-temperature alloys, is typically sealed to the ceramic positive electrode-electrolyte-negative electrode (PEN) by a Sealing Glass. To maintain the structural stability and minimize the degradation of stack performance, the Sealing Glass has to be chemically compatible with the PEN and alloy interconnects. In the present study, the chemical compatibility of a barium-calcium-aluminosilicate (BCAS) based Glass-ceramic (specifically developed as a sealant in SOFC stacks) with a number of selected oxidation resistant high temperature alloys (and the yttria-stabilized zirconia electrolyte) was evaluated. This paper reports the results of that study, with a particular focus on Crofer22 APU, a new ferritic stainless steel that was developed specifically for SOFC interconnect applications.

  • chemical compatibility of barium calcium aluminosilicate based Sealing Glasses with the ferritic stainless steel interconnect in sofcs
    Journal of The Electrochemical Society, 2003
    Co-Authors: Zhenguo Yang, Kerry D Meinhardt, Jeff W Stevenson
    Abstract:

    In most planar SOFC stack designs, the interconnect, which is typically made from a ferritic stainless steel, is hermitically sealed to the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a Sealing Glass. To maintain the structural stability and minimize degradation of the stack performance, the Sealing Glass must be chemically compatible with the stainless steel interconnect. In this study, a barium-calcium-aluminosilicate (BCAS) based Glass-ceramic, specifically developed as a sealant in SOFC stacks, and a ferritic stainless steel (446) were selected as examples to increase the understanding the chemical compatibility issues in SOFC. Evaluation of the interfaces of coupon joints indicated that interactions between the BCAS Glass-ceramic and the ferritic stainless steel was dependent on the exposure conditions. At the edges of joints, where oxygen or air was accessible, the interaction often led to the formation of BaCrO4, while in the interior of the joints, chromium or chromia dissolved into the Glass to form a thin layer of chromium rich solid solution. It was also found that, in the interior of the joints, the interaction often resulted in the formation of pores aligned along the interface. It appears the pore formation along the interface can be avoided through a pre-heat treatment.

  • Chemical interactions of barium–calcium–aluminosilicate-based Sealing Glasses with oxidation resistant alloys
    Solid State Ionics, 2003
    Co-Authors: Zhenguo Yang, Jeff W Stevenson, Kerry D Meinhardt
    Abstract:

    Abstract In most planar solid oxide fuel cells (SOFC) stack designs, the interconnect, which is typically made from an oxidation resistant alloy, potentially including austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, has to be hermitically sealed to its adjacent components, usually by a Sealing Glass. To maintain the structural stability and minimize the degradation of stack performance, the Sealing Glass must be chemically compatible with the alloy used for the interconnect. In this work, Nicrofer6025, AISI446 and a Fecralloy were selected as examples of austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, respectively. Their chemical compatibility with a barium–calcium–aluminosilicate (BCAS)-based Glass, specifically developed as a sealant in SOFC stacks, was evaluated. It was found that the BCAS Sealing Glass interacted chemically with both the chromia-forming alloys and the alumina-forming alloys. The extent and nature of the interactions and their final products depended on the matrix alloy compositions, the exposure conditions and/or proximity of the Glass/alloy interface to the ambient air. These interactions and their mechanisms will be discussed with the assistance of thermodynamic modeling.