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Metallic interconnects represent the main component of a solid oxide fuel cell (SOFC) stack in terms of weight and volume. They are typically made of ferritic stainless steel (FSS) coated on the air side. At the stack operating conditions, the interconnect is exposed to a dual atmosphere: air at the cathode side; fuel (a hydrogen-rich mixture) at the anode side. The stacks considered in this study were field operated in reformed natural gas for 5000, 9000 and 20,000 h respectively. The analyzed interconnects are made from CROFER22APU and coated on the air side with Co-Mn base spinel. One interconnect has been studied for each stack by sampling and preparing cross section the inlet and outlet positions. The samples were characterized by SEM-EDXS in order to investigate the evolution of the interconnect at the air side. The interaction between the metal substrate and the coating is investigated highlighting the formation of chromia based thermal grown oxide (at the FSS/coating interface) and the solid-state diffusion of Cr and Fe from the metal into the coating. The microstructural features evolving as a function of time are also quantified.

The possible interactions near the triple-phase boundaries (TPB) metal/glass/air, and their effects on joint strength are investigated. Two types of samples (joined couples and glass coated coupons) are prepared with the coupon of AISI 430 (nickel plated and uncoated) and a slurry of compliant silicate sealing glass (SCN-1). The joined and coated samples are heated at 850 °C for 1000 h in air. The joined couples are cooled using two different schedules and then tested in uniaxial tension. For investigating the metal-oxides precipitation procedure in glass near the TPB, glass coated coupons are either cooled at the rate of 5 °C min −1 or water-quenched from aging temperature. The mechanical test results and microstructural observations show that the spread and accelerated breakaway oxidation near TPB, which is due to continuous oxidation and dissolution of ferritic stainless steel (FSS) into the glass, leads to decreased and scattered low temperature joint strengths. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the surface compressive stress (CS) on the hardness and Young's modulus of the ion-exchanged aluminosilicate float glass on air and tin sides are investigated. The hardness and Young's modulus are experimentally measured by nanoindentation. As a result, the surface hardness and Young's modulus of aluminosilicate float glass can be enhanced by chemical strengthening. The hardness increases with an increase in the CS, whereas Young's modulus is not obviously influenced by CS. The hardness and Young's modulus on the air and tin sides are almost the same before ion exchange. However, the tin side always has greater hardness than the air side after the ion exchange. The results would be useful in guiding the strengthening process of float glass by one step ion-exchange or two step ion-exchange to obtain engineered stress profile (ESP) glasses. [Copyright &y& Elsevier]

Abstract: The difference between the inter-diffusion kinetics of K+–Na+ in the air and tin sides of an ion-exchanged float aluminosilicate glass was investigated as a function of the exchange temperature and time. The potassium concentration profiles of the ion-exchanged glass surface were experimentally measured by electron microprobe analysis, and the diffusion coefficient was calculated by the Boltzmann-Montano approach. On the tin side of the ion-exchanged glass, the diffusion of K+–Na+ ions is hindered by tin. The diffusion coefficient is also more sensitive to temperature and time on the tin than on the air sides. The results would be useful in guiding the strengthening process of float glass by one step ion-exchange or two step ion-exchange to obtain engineered stress profile (ESP) glasses. [Copyright &y& Elsevier]

Abstract: Optical properties of soda-lime glass manufactured by the float process were investigated using spectroscopic ellipsometry and intensity transmission measurements. Thickness and optical properties of surface layers on the air and tin sides were determined with ellipsometry. The tin side surface layer shows a graded refractive index with a non-linear profile. Intensity transmission data were used to quantify absorption in the bulk glass. Transmission-mode generalized ellipsometry characterized residual birefringence in the bulk glass. Birefringence effects on ellipsometric delta data were corrected using a simple empirical offset with 1/wavelength dependence. A general optical model for soda-lime glass is presented which can be used for subsequent analysis of coated soda-lime glass and other transparent substrates. [Copyright &y& Elsevier]

Abstract: The present paper reports results from an investigation of the air side thermal performance of fin-and-tube coils with herringbone-wavy and convex-louver fins. The tube diameter of the tested coils was 12.7mm. Coils with different fin pitch and tube rows have been tested in order to determine their effect over the thermal performance. In addition, the performance of the convex-louver fins has been evaluated with respect to that of the wavy fins according to the Webb VG1 procedure. The collar diameter Reynolds number covered in the tests varied from 1000 to 6000, corresponding to face velocities of 1–6m/s. It has been found that the fin pitch affects lightly the heat transfer coefficient, its value being incremented of the order of 10% by reducing the fin pitch from 3.17mm to 1.81mm. Opposite trends have been found for the friction factor of wavy and louver fins regarding the effect of the fin pitch. The thermal performance is not affected by the number of tube rows in either of the fin configurations in coils for more than two rows. One and two row coils present non-negligible differences either with respect to the Colburn or friction factors. It has been found that area reductions in louver with respect to wavy fins can attain values of the order of 30% for Reynolds number of the order of 1000 and fin pitch of 3.17mm. [Copyright &y& Elsevier]

Metallic interconnects represent the main component of a solid oxide fuel cell (SOFC) stack in terms of weight and volume. They are typically made of ferritic stainless steel (FSS) coated on the air side. At the stack operating conditions, the interconnect is exposed to a dual atmosphere: air at the cathode side; fuel (a hydrogen-rich mixture) at the anode side. The stacks considered in this study were field operated in reformed natural gas for 5000, 9000 and 20,000 h respectively. The analyzed interconnects are made from CROFER22APU and coated on the air side with Co-Mn base spinel. One interconnect has been studied for each stack by sampling and preparing cross section the inlet and outlet positions. The samples were characterized by SEM-EDXS in order to investigate the evolution of the interconnect at the air side. The interaction between the metal substrate and the coating is investigated highlighting the formation of chromia based thermal grown oxide (at the FSS/coating interface) and the solid-state diffusion of Cr and Fe from the metal into the coating. The microstructural features evolving as a function of time are also quantified. [ABSTRACT FROM AUTHOR]