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Sealant properties of CaO- and SrO-containing BaO–B2O3–SiO2 and BaO–ZnO–B2O3–SiO2 glasses were first reported in this work. CaO and SrO were used as glass modifiers to improve thermal properties and optimize CTE value and possess a good joining interface between SOFC components. Addition of CaO and SrO enhanced the glass transition and softening temperature due to the higher ionic field strength of Ca and Sr ions promoting the boroxol ring formation and a denser glass network. IR spectra confirmed a less significant effect of CaO and SrO in the glass structures. Addition of doubled CaO and SrO retained the compatibility of CTE to that of SDC electrolyte and Crofer22APU interconnect. Crystalline phases with compatible CTE were formed in the CaO- and SrO-containing glass ceramics. This provided good adhesion without defects at the interface, which is close to the electrolyte and interconnect after prolonged operation at 800°C for 50 h. [ABSTRACT FROM AUTHOR]

This paper presents a hermitic fiber sensor packaging technique that enables fiber sensors to be embedded in energy systems for performing multi-parameter measurements in high-temperature and strong radiation environments. A high-temperature stable Intrinsic Fabry–Perot interferometer (IFPI) array, inscribed by a femtosecond laser direct writing scheme, is used to measure both temperature and pressure induced strain changes. To address the large disparity in thermo-expansion coefficients (TECs) between silica fibers and metal parts, glass sealants with TEC between silica optical fibers and metals were used to hermetically seal optical fiber sensors inside stainless steel metal tubes. The hermetically sealed package is validated for helium leakages between 1 MPa and 10 MPa using a helium leak detector. An IFPI sensor embedded in glass sealant was used to measure pressure. The paper demonstrates an effective technique to deploy fiber sensors to perform multi-parameter measurements in a wide range of energy systems that utilize high temperatures and strong radiation environments to achieve efficient energy production. [ABSTRACT FROM AUTHOR]

Although various additive manufacturing techniques are used intensively to mold materials for solid oxide fuel cell (SOFC) applications, 3D printing has not been applied to obtain sealants which are crucial components for SOFC stacking. It is essential to develop different methods for molding sealing products based on glasses and glass-ceramics which are the most promising materials for SOFC stacking. This study reveals the potential of fused deposition modeling (FDM) for the production of complex shape objects for the sealing of tubular SOFC in the example of the composition based on thermoplastic, thermoplastic elastomer, oil, and a filler (glass sealant). The highest filler content in the mixture is 63 wt %. Two aluminosilicate sealants of different compositions are used as the filler and the printed products are successfully applied for tubular supporting anode|sealant|steel joints. • FDM is successfully used to obtain products for tubular SOFC sealing. • Bubbles in the sealant volume do not violate the sealing. • Tubular supporting anode|sealant|steel joints are prepared using printed products. [ABSTRACT FROM AUTHOR]

This paper presents a hermitic fiber sensor packaging technique that enables fiber sensors to be embedded in energy systems for performing multi-parameter measurements in high-temperature and strong radiation environments. A high-temperature stable Intrinsic Fabry–Perot interferometer (IFPI) array, inscribed by a femtosecond laser direct writing scheme, is used to measure both temperature and pressure induced strain changes. To address the large disparity in thermo-expansion coefficients (TECs) between silica fibers and metal parts, glass sealants with TEC between silica optical fibers and metals were used to hermetically seal optical fiber sensors inside stainless steel metal tubes. The hermetically sealed package is validated for helium leakages between 1 MPa and 10 MPa using a helium leak detector. An IFPI sensor embedded in glass sealant was used to measure pressure. The paper demonstrates an effective technique to deploy fiber sensors to perform multi-parameter measurements in a wide range of energy systems that utilize high temperatures and strong radiation environments to achieve efficient energy production.

Chemical compatibility in oxidizing and reducing environments between sealants and interconnects for planar solid oxide fuel cells (SOFC) are investigated. (Co,Mn) 3 O 4 , Co-Mn, and Al coatings were prepared on the FeCr-based ferritic-stainless-steel (SUS430). The (Co,Mn) 3 O 4 coating exhibited water vapor bubble formation at the outer sealing edges when exposed to H 2 , indicating reactions between the coating and sealant. Co-Mn metal coating was found readily oxidized in an oxidizing environment. The glass with 5 wt% Al 2 O 3 addition helped mitigate the Cr diffusion into sealant based on bare SUS430 substrate. Moreover, the Al metal layer effectively blocked the diffusion of Cr into the sealant at the interface and environment for 100 h, with a thickness of only 1 µm. At the constant discharge current of 24 A, the voltage is stabilized at about 4.2 V for 48 h using H 2 as fuel gas in 5-cell stack. [ABSTRACT FROM AUTHOR]

A low leakage rate sealant of 10 wt% ZrO 2 -added CaO–K 2 O–Na 2 O–BaO silicate glass for SOFC has been studied. The structure of the sealant is stable at high temperatures with leakage rates less than 10−4 sccm∙cm−1, and no crystal except for ZrO 2 is found in XRD analysis after heating at 800 °C for 100 h. ZrO 2 is distributed in the glass matrix and plays a supporting role in avoiding over-softening at operating temperature. Good compatibility in both oxidizing and reducing atmospheres between the sealant and SUS430 interconnect was proved by SEM at 750 °C for 100 h. A fully coupled 3D Multiphysics button SOFC is constructed for mechanical analyses. The results show that the increase of ZrO 2 in the sealant will decrease the stress and displacement in the SOFC. Besides, the width of the sealant also affects the stress value and distribution. The results show that GZ10 is a competitive sealing material compared with other ZrO 2 -added sealants. [ABSTRACT FROM AUTHOR]

In this work, the thermal stability of a BaO–CaO–SiO 2 –B 2 O 3 glass sealant, named "H", was investigated by differential scanning calorimetry (DSC). The crystallization behavior of glass H as the sealant matrix was investigated by a combination of experimental X-ray diffraction (XRD) analysis and thermodynamic simulation with the FactSage package. A good agreement was found between the Rietveld refinement of XRD experiments and the FactSage simulation. Particular attention was also given to the influence of the Sr 2 SiO 4 filler added to the glass matrix "H" on the thermal expansion and microstructures of glass-Sr 2 SiO 4 composites by means of dilatometry and scanning electron microscopy (SEM). The reinforced 20 wt% Sr 2 SiO 4 composite (HS2S20) showed excellent properties and, thus, its joining performance was investigated using SrTi 0.75 Fe 0.25 O 3-δ (STF25) and Aluchrom as promising oxygen transport membrane (OTM) and counterpart, respectively. The joining behaviors were investigated by comparing different joining temperatures. 920 °C is the best joining temperature for HS2S20 sealant. [ABSTRACT FROM AUTHOR]

Three new BaO–SrO–SiO2–B2O3 (BS) glasses with different SrO contents (6–25 mol%) are developed for oxygen transport membrane (OTM) joining application. The content of strontium is investigated first in terms of its effect on the glass‐forming tendency, thermal expansion coefficient, crystallization, shrinkage behavior, and viscous flow properties. Differential scanning calorimetry (DSC) is carried out. Dilatometric tests are performed to obtain coefficients of thermal expansion (CTEs) of BS glasses. The crystallization behavior of the BS glasses is investigated by X‐ray powder diffraction (XRD). Sinking dilatometric measurements simulate the joining procedure and observe the shrinkage behavior of the BS glasses. The viscous flow behavior of the BS glasses is examined via hot stage microscopy. The glass with 15 mol% SrO (BS15) glass shows the best glass‐forming tendency, most matching CTE (11.9 × 10−6 K−1), densest microstructure, highest shrinkage rate (24%), and good viscous behavior at high joining temperatures compared with other BS glasses. BS15 glass is chosen for helium leak test and assembly test joining with Aluchrom and SrTi0.75Fe0.25O3−δ membrane (STF25). The sandwiched sample with two Aluchrom plates sealed by BS15 glass at 1075 °C for 5 min achieves good gas‐tightness with low helium leakage rate <10−9 mbar·l s−1. [ABSTRACT FROM AUTHOR]

The creation of gas‐tight connections in solid oxide fuel cells (SOFCs) requires finding a suitable glass sealant composition and developing high‐tech approaches to sealant molding. 3D printing has been used successfully to mold SOFC functional materials (anode, electrolyte), and this study tests its applicability to glass sealant printing. We have found the composition of the glass‐filled polymer compound to print glass sealants for tubular SOFCs: the polycaprolactone/filler ratio is 60/40 wt%. Silica has been shown to be a good model filler to polish the 3D printing technology. Polymer decomposition during sealing leads to the formation of voids and seal failure, which indicates that the filler content of 40 wt % is insufficient for such purposes. [ABSTRACT FROM AUTHOR]

The influence of the gradual replacement of Al 2 O 3 with Y 2 O 3 in alkali-containing silica glass sealants is studied with a detailed discussion of crystallization kinetics. Such substitution has a complex effect on T g , T sphere , T HS , and T flowing which might be connected with the role of yttrium in the glass network. An increase in the Y 2 O 3 content is found to intensify crystallization, causing the growth of the crystalline phase fraction. At the same time, intense crystallization appears to have no pronounced effect on the coefficient of thermal expansion: its average increment after 1000 h of exposure at 850 °C in air atmosphere is <1‧10−6 K −1. The only crystalline phase observed in samples with Y 2 O 3 content greater than 2 wt % is suggested to be Na 0.8 Ca 0.3 Y 0.4 Zr 0.22 Si 2.13 O 6 which is the Ca2+- and Zr4+-substituted isomorph of NaYSi 2 O 6. [ABSTRACT FROM AUTHOR]

The behaviour of the promising glass sealant 54.4SiO 2 -13.7Na 2 O-1.7K 2 O-5.0CaO-12.4MgO-0.6Y 2 O 3 -11.3Al 2 O 3 -0.9B 2 O 3 for solid oxide fuel cells (SOFCs) under SOFC operating conditions was studied. First, the kinetics of the crystallisation processes at the operating temperature (850 °C) was discussed (maximum exposure time of 1000 h), and the effect of crystallisation on the coefficient of thermal expansion (CTE) of the sealant was studied. Furthermore, the degradation processes at the interface of the glass sealant and functional SOFC materials (Crofer 22 APU, YSZ, and NiO(Ni)-YSZ) during exposure to 850 °C in oxidising and reducing atmospheres for 500 h were studied. The tests demonstrated good performance of the sealant studied and possibility of its application in SOFCs. [ABSTRACT FROM AUTHOR]

The development of electrochemical generators based on solid oxide fuel cells requires the development of sealant materials that would ensure gastight junction of separate components and be chemically and thermally compatible with other functional materials. This study deals with the effect of small additions of Cr2O3 on the thermal properties and chemical stability of a glass sealant of the composition 54.39SiO2–13.78Na2O–1.67K2O–5.02CaO–12.37MgO–0.61Y2O3–11.26Al2O3–0.9B2O3. Introduction of chromium oxide increases the coefficient of linear thermal expansion relative to the initial composition but does not affect the sealing temperature and phase composition of the glass ceramic. The materials developed exhibit good chemical stability in contact with Crofer22APU chromium-containing alloy and can be recommended for use as sealants for solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

The joining of ceramic and metal (interconnect) parts is one of the main challenges in the development of solid oxide fuel cells (SOFC). A promising approach to solving this problem is the use of glassy sealants. In this work, we investigated the effect of yttria additions on the properties of SiO 2 –Al 2 O 3 –CaO–Na 2 O–ZrO 2 –Y 2 O 3 glass sealants. An increase in the concentration of yttria is shown to reduce the tendency of the glasses under study to crystallisation. A glass containing 4 wt% of Y 2 O 3 is found to be amorphous, even after exposure at 850 °C for 100 h. Moreover, the defectiveness of the glass microstructure, after sealing, is found to decrease along with a growth in the Y 2 O 3 concentration. The developed non-crystallising sealant was successfully applied for joining a YSZ ceramic and an Fe–Ni–Co alloy having the phase transition of around 500 °C. The use of the non-crystallising sealant allows us to join materials with very different thermal expansion coefficients and to avoid cracking under cooling, which might occur due to a large difference in thermal expansion coefficients. [ABSTRACT FROM AUTHOR]

The present paper describes the electrochemical results and the post exposure microstructural characterization by means of SEM/EDS of a four layer SOFC stack after 34,000 h operation under load at 700 °C, showing low voltage degradation rate less than 0.3% per 1,000 h. Emphasis was put on the behavior of the ferritic interconnect steel and its interaction with glass sealants as well as contacting and coating materials. The interconnect steel had formed thin protective chromia scales. Gas distributing steel foils of 200 µm showed in some locations breakaway type oxidation. It was related to local overheating caused by locally occurring combustion of a defective cell. The interaction of the steel with the glass sealant showed good adhesion. Interdiffusion at the joint between nickel contact and steel interconnect at the anode side resulted in minor oxide formation on the Ni wires and in austenite formation in the steel without formation of σ‐FeCr formation at the steel/austenite interface. The steel showed excellent compatibility with the Manganese‐Cobalt‐Ferrite (MCF) chromium retention coatings. Chromium enriched phases were found near the interface between MCF coating and perovskite contact layer. Excess glass sealing material interacted with the contact layer without showing obvious detrimental effects. [ABSTRACT FROM AUTHOR]

Abstract SiO 2 -Al 2 O 3 -B 2 O 3 -Na 2 O based glass sealant compositions were designed for the development of GMJ using extreme vertices methodology. The effect of the glass sealant individual constituent on wettability, Glass transition temperature (T g), Crystallization temperature (T c), thermal conductivity, and density was analyzed with the help of analysis of variance technique (ANOVA). The increase in SiO 2 constituent in glass sealant decreased the spreading area (mm2) of glass sealant and increased the value of contact angle (θ) formed by glass sealant over the SS304 metal substrate. The T g and T c of glass sealant also increased as SiO 2 content increased. The addition of B 2 O 3 and Na 2 O in glass sealant system reduced the T g and T c of glass sealant. The developed regression model was validated and it was observed that the experimental and predicted results nearly matched with an error less than 5% in most of the cases. [ABSTRACT FROM AUTHOR]

Laser welding of dissimilar materials is challenging, due to their difference in coefficients of thermal expansion (CTE). In this work, fused silica-to-sapphire joints were achieved by employment of a ns laser focused in the intermediate Si-enriched fresnoitic glass thin film sealant. The microstructure of the bonded interphase was analyzed down to the nanometer scale and related to the laser parameters used. The crystallization of fresnoite in the glass sealant upon laser process leads to an intense blue emission intensity under UV excitation. This crystallization is favored in the interphase with the silica glass substrate, rather than in the border with the sapphire. The formation of SiO 2 particles was confirmed, as well. The bond quality was evaluated by scanning acoustic microscopy (SAM). The substrates remain bonded even after heat treatment at 100 °C for 30 min, despite the large CTE difference between both substrates. [ABSTRACT FROM AUTHOR]

Glass-ceramics are commonly used as sealing materials for planar solid oxide fuel cells (SOFCs). The major requirements of stack and module builders for these materials are the stability of the coefficient of thermal expansion (CTE), the excellent bonding (sticking) behaviour and the absence of volatile ingredients, which can lead to changes of the material properties and the sealing ability. In this study, the thermal stability of glasses in the BaO-Al2O3-La2O3-B2O3-SiO2 system was investigated, to develop a suitable sealing glass for planar solid oxide fuel cell operating at 800-850°C. The developed glasses were characterised through measurement of different properties, coefficient of thermal expansion (CTE), glass transition temperature (Tg), dilatometric softening temperature (Td), crystallisation behaviour during prolonged heat-treatment, density etc. At a target operating temperature of 750°C, the long-term coefficient of thermal expansion (CTE) of one particular composition (G4) was found to be particularly stable, due to devitrification to a mixture of glasses and ceramic phases. [ABSTRACT FROM AUTHOR]

High temperature hermetic sealants are required for the stability and good efficiency of the solid oxide fuel cells (SOFCs). Glass and glass ceramics are promising sealant materials due to their desirable properties and flexible compositions. In the present study, the novel glass series (10 + x) CaO-(10 − x) MgO-10SrO-10B 2 O 3 -20Al 2 O 3 -40SiO 2 (x = 0, 2.5, 5, 7.5) has been synthesized via melt quenching route. These glass/glass ceramics are characterized by X-ray diffraction to evaluate the amorphous nature and phase formation, respectively. The activation energy has been analyzed by using three different theoretical models – Kissinger Model, Moynihan Model and Augis and Benett Model. In addition to this, the characteristic glass temperatures and coefficient of thermal expansion (CTE) have been obtained from DTA, differential DTA (DDTA) and Dilatometry. Various stability parameters like Hruby parameter, Saad Parameter, fluctuation free volume (f g ) and bulk thermal expansion coefficient (α f ) are also calculated with varying CaO/MgO ratio (R). Furthermore, to analyze the stability of the glasses with varying CaO/MgO ratio over a broader range of temperature, k parameters i.e. k b (T) and k f (T) are also evaluated for different heating rates. The diffusion couples of glasses with pre oxidized Crofer 22APU and YSZ fabricated at 850 ° C for 500 h have been characterized using scanning electron microscopy (SEM) and X-ray dot mapping to investigate the sealing characteristics with varying CaO/MgO ratio. The glass series 15 CaMg is very stable and promises to be a good sealant for solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Sealing performance and chemical compatibility of SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glass sealants with bare and Mn–Co spinel coated SUS430 ferritic alloys are investigated. The low–SrO glasses (≤40 mol%) show good wettability and adherence to the bare SUS430 alloy due to their lower viscosity and negligible reactions with the alloy. The high–SrO glass (e.g. 45 mol%) exhibits higher viscosity and more serious reactions with the bare SUS430 alloy. The formation of SrCrO 4 with higher CTE causes obvious delamination and dramatic oxidation of the alloy at the glass/alloy interface. In contrast, Mn–Co spinel coating has good compatibility with both SrO–La 2 O 3 –Al 2 O 3 –SiO 2 glasses and Fe–Cr ferritic alloy. Moreover, the Mn–Co spinel coating on the alloy can effectively restrain the diffusion of Fe and Cr and the reactions between the glasses and the alloy. Due to the ameliorated interfacial microstructure, sealing performance can be improved by applying the Mn–Co spinel coating on SUS430 alloy, especially for the bonded couple with high–SrO glass. [ABSTRACT FROM AUTHOR]

The broad and widespread commercialisation of solid oxide fuel cells still requires a lot of research and development. Since the fuel cell consists of several components, compatibility of these components is necessary. Because structural, thermal or chemical changes in any of the cell components affect the overall working of the cell. In the present work, perovskite structured SrZr 0.85 Cu 0.15 O 3- δ (cathode) and a glass sealant, 45SiO 2 –40BaO–10B 2 O 3 –5ZrO 2 , are mixed in the ratio of 70:30 wt %, respectively and heat-treated at 800 °C for 1, 10, 100 and 500 h in the air. The X-ray diffraction results show the presence of some minor amounts of detrimental phases, i.e. BaSrSi 2 O 6 and SiO 2. However, the presence of these phases is minute compared to the major crystalline phase (SrZrO 3). Grain size increases with increasing heat-treatment duration with a well-connected cathode-sealant interface. The coefficient of thermal expansion is in the required range as prescribed for solid oxide fuel cells even after 500 h of heat treatment of the diffusion couple at 800 °C. • Interaction study between glass sealant and cathode. • Both XRD and SEM confirm the diffusion among the glass sealant and cathode. • No distinct fracture or delamination at the interface of the cathode and sealant. • CTE is compatible with other SOFC components after 500 h of interaction in air. [ABSTRACT FROM AUTHOR]

The chemical interaction study of AO-SiO2-B2O3-Y2O3 (A = Ba, Sr) (BaY, SrY) glass with high-temperature electrolyte yttria-stabilized zirconia (YSZ 8 mol%) is reported as a function of different heat treatment durations. The as-prepared glass with 10 mol% of yttria shows limited amount of crystallization at 800 °C. Due to this yttria-based glasses BaY and SrY have been chosen to make diffusion couples with high-temperature electrolyte and interconnect material. These diffusion couples have been heat treated at 850 °C, for 100, 200, and 500 h. The heat-treated diffusion couples have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Microstructural analysis of diffusion couples shows absence of any undesired oxides and detrimental reaction products at the interface. The glass has shown good bonding characteristics and absence of cracks, pores, or any kind of delamination from YSZ. Apart from this, SrY and BaY glass seals have also shown good adhesion characteristics with Crofer 22 APU, even after 500 h at 850 °C. The morphology and microstructure of the glass matrix suggest limited amount of devitrification in the glass. [ABSTRACT FROM AUTHOR]

Conductive Ag-precipitated glass powder was prepared by a heat reduction process of the glass/AgCl composite powder and its electrical conductivity was compared to conventional Ag-particle mixed glass powder. The Ag-precipitated glass powder with 30wt.% dispersed Ag particles of diameter of 20 to 300nm and the baked film made of the powder showed a good electrical conduction from 400°C to 700°C. On the other hand, the baked films made of the Ag-particle mixed glass powders of Ag particle size of 300nm with 35wt.% Ag content and that of size of 20nm with 30wt.% Ag content showed a poor electrical conduction. The electrical conduction of the film of Ag-precipitated glass powder resulted from a uniform dispersion of Ag particles. Since no continuous network of Ag particles was found in the microstructure observation of the glass powders, or films, the origin of the electrical conduction was considered to be due to a tunneling effect between the well-dispersed Ag particles. [ABSTRACT FROM AUTHOR]

Laser joining of ZrO2 ceramics using glasses and glass ceramics as sealing components requires optimized systems. The ternary systems SiO2–BaO–B2O3 and BaO–SrO–SiO2 were selected as a basis for development of suitable glass compositions for the laser joining process. Additives such as CaO, TiO2, Al2O3, and MgO were used to control the crystallization processes and hence the thermal expansion coefficients during glass synthesis. The glass viscosity, the strength of the ceramic-glass-ceramic joint, and the joint tightness are other important glass properties which were optimized for the laser process. For glass G018-345, this yielded strengths of up to 225MPa (Weibull modulus of m =8.6) and He leak rates of up to 4.3×10−5 mbar ls−1. Because of the varying viscosities obtained, the optimized glass systems could be used selectively in a temperature range of 700–900°C. [ABSTRACT FROM AUTHOR]

Abstract: A strontiumlanthanumaluminoborosilicate based intermediate temperature solid oxide fuel cell (IT-SOFC) glass sealant has been investigated for isothermal devitrification under accelerated conditions. Sintering of the glass up to 100 h at 1000 °C, results in the formation of two crystalline phases evidenced by X-ray diffraction (XRD) analysis. Hexacelsian phase evolves from the initial hours of sintering; however, lanthanum silicate phase appears at longer hours of sintering. Quantitative XRD of the glass ceramics reveals that hexacelsian occupies majority of the crystalline phases and lanthanum silicate is occupying minor quantity. Formation of crystalline phases has been reconfirmed by microstructure analysis of glass ceramics through Scanning Electron Microscopy (SEM) and elemental analysis of phases by energy dispersive spectroscopy (SEM-EDS). Crystalline phases in the glass ceramics have been quantified by analysis of SEM images through Imagepro plus software. At different stages of sintering, CTE of the glass ceramics has been measured by dilatometer. Correlation of CTE with crystalline phases in the glass ceramics indicates that with formation of hexacelsian phase CTE of the glass ceramics increases, however, formation of lanthanum silicate phase reduces the CTE of the glass ceramics. Phase property correlation indicates that after 100 h of accelerated devitrification at 1000 °C, the glass ceramics attains phase stability therefore the CTE stabilizes and the value remains well within the requirement limit of SOFC sealant. [Copyright &y& Elsevier]

Abstract: The impact of volatile boron species on the microstructure and performance of nano-structured (Gd,Ce)O2-infiltrated (La,Sr)MnO3 (GDC-LSM) cathodes of solid oxide fuel cells is studied for the first time. The results indicate that after the heat treatment of the cathodes at 800°C in air for 30days in the presence of borosilicate glass significant grain growth and agglomeration of infiltrated GDC nanoparticles are observed. The electrode polarization resistance of the GDC–LSM cathode after the heat treatment in the presence of glass is 3.15Ωcm2 at 800°C, substantially higher than 0.17Ωcm2 of the cathode heat-treated in the absence of glass under identical conditions. ICP-OES analysis shows the deposition of boron species in the cathodes after sintering in the presence of glass powder. The results demonstrate the significant detrimental effect of volatile boron species on the microstructure and activity of nano-structured GDC–LSM cathode. [Copyright &y& Elsevier]

Abstract: Strontium–lanthanum–aluminoborosilicate (SrO–La2O3–Al2O3–B2O3–SiO2) (SLABS) glass was prepared for sealant material in planar Solid Oxide Fuel Cells (pSOFC). Differential Thermal Analysis of the glass showed the formation of two crystalline phases, first one 807 °C and the second phase at 1021 °C. Crystallization kinetic of the first crystalline phase was investigated by differential thermal analysis (DTA) and using the JMA-kinetic model. The activation energy for crystallization was calculated to be 114.04 kJ/mol with frequency factor 5.9 × 103. Coefficient of Thermal Expansion (CTE) of the glass was measured to be 9.72 × 10−6/°C. Optical band gap of the glass was measured to be 3.07 eV. Conductivity measured by Impedance spectroscopy found to be 5.68 × 10−7 S cm−1 at 600 °C and it increased with temperature to 2.68 × 10−6 S cm−1 at 800 °C. Activation energy for electrical conduction was measured to be 66.12 kJ/mol. Wetting behavior of the glass on a ferritic steel substrate was investigated under hot stage microscopy. It showed initial deformation temperature (IDT) 754 °C, softening temperature (ST) 840 °C, hemispherical temperature (HT) 1108 °C and flow temperature (FT) 1279 °C. [Copyright &y& Elsevier]

Abstract: Effects of crystallization on the high-temperature mechanical properties of a newly developed silicate-based glass sealant (GC-9) are investigated for use in planar solid oxide fuel cell (pSOFC). The aged, crystallized GC-9 glass is produced by heat treatment of the original GC-9 glass at 900°C for 3h. Not only crystalline phases are formed but the residual glass is also changed in the aged GC-9 glass after the heat treatment. Mechanical properties of the aged GC-9 glass are determined by four-point bending technique at temperature from 25°C to 750°C. The glass transition temperature of the given glass is reduced but the softening temperature is increased by such a crystallization heat treatment. The aged GC-9 glass exhibits a greater flexural strength and Young''s modulus than the non-aged one at temperature below 650°C due to the existence of crystalline phases. At temperature of 700°C and 750°C, a greater extent of stress relaxation is found in the aged GC-9 glass such that its strength and stiffness are much lower than those of the non-aged one. The changes in the thermal and mechanical properties through the given aging treatment are favorable for application of the GC-9 glass sealant in pSOFC. [Copyright &y& Elsevier]

Abstract: A method for oxygen leak rate testing was presented based on oxygen pump technique. In this method, using the theory of oxygen pump and oxygen sensor, a formula for the calculation of leak rate was derived from Nernst equation, Faraday law and ideal gas law. In the gas leakage testing, a glass sealant based on SiO2–B2O3–Al2O3–BaO–PbO2–ZnO (named AF8) was used to seal two yttria stabilized zirconia (YSZ) plates together to form a small gas chamber, one plate worked as oxygen pump and the other worked as oxygen sensor. Constant current was applied on the oxygen pump to take out/into oxygen from the gas chamber resulting in its oxygen partial pressure change, the corresponding concentration voltage data were collected continuously for the calculation of the oxygen leak rate. With this method, the calculated leak rate of AF8 was 8.2×10−8 mbar l s−1 cm−1 at 800 °C which was smaller than the required value of 10−7 mbar l s−1 cm−1. [Copyright &y& Elsevier]

Abstract: Yttrium-doped barium cerate, BaCe0.85Y0.15O3−α (BCY15), membranes are proton-conducting electrolytes for intermediate-temperature protonic ceramic fuel cells (IT-PCFC), useful for, among other processes, co-production of power and ethylene by dehydrogenation of ethane. BCY15 membranes showed good conductivity at intermediate temperatures, 15 and 20mScm−1 at 700 and 750°C, respectively. Maximum power density was 174mWcm−2 at 700°C, with a corresponding current density of 320mAcm−2, using a C2H6,Pt/BCY15/Pt,O2 fuel cell, with a ca. 0.5mm thick membrane, producing 34% ethane conversion with 96% ethylene selectivity Comparison of performances using vertical and horizontal set-ups showed that horizontal set-ups are subject to torsional strain, causing reduced cell performance resulting from even minor leakage at the glass seal. [Copyright &y& Elsevier]

Abstract: A glass system based on SiO2–B2O3–Al2O3–BaCO3–PbO2–ZnO was prepared and a sort of compounding was optimized to determine the composition with best performance named AF8. The technical thermal expansion coefficient (t-TEC) is 10.58×10−6 K−1 between 323 and 773K. The resistivity of AF8 is 1.95×104 Ωcm at 800°C. The optimum sealing temperature range was 850–880°C. AF8 glass sealant could adhere with electrolyte of yttria stabilized zirconia (YSZ) well and there were no perforative pores in the sealant. The leak rate of AF8 glass was 0.81×10−7 mbarls−1 cm−1 at 800°C tested by oxygen coulometric titration which was closed to the required value. Around the sealing temperature, contact angle of AF8 on YSZ is about 110°. This angle can make them adhere well under a suitable pressure, and also avoids glass spreading freely on surface of the electrolyte. All measured results approved that AF8 may become a practical sealant for SOFCs. [Copyright &y& Elsevier]