A variety of seals such as metal–metal, metal–ceramic, and ceramic–ceramic are required for a functioning solid oxide fuel cells (SOFC). These seals must function at high temperatures between 600 and 900°C and in oxidizing and reducing environments of the fuels and air. Among the different type of seals, the metal–ceramic and ceramic–ceramic seals require significant attention, research, and development because the brittle nature of ceramics and glasses can lead to fracture and loss of seal integrity and functionality. This paper addresses the needs and possible approaches for high‐temperature ceramic–metal seals for SOFC and seals fabricated using some of these approaches. A new concept of self‐healing glass seals is proposed, developed, and used for making metal—glass–ceramic seals for potential application in SOFC in order to enhance the reliability and life of a cell. In this study, glasses displaying self‐healing behavior are investigated and used to fabricate seals. The performance of these seals under long‐term exposure at higher temperatures coupled with thermal cycling is characterized by leak tests. The self‐healing ability of these glass seals is also demonstrated by leak tests along with the long‐term performance.

The kinetics and mechanism of reaction of glassy carbon with a pure silicon melt or a Si + Mo melt were investigated.The results showed that the growth of a continuous reaction-formed S i c layer followed a fourth-power rate law in the temperature range of 1430" to 1510°C. A model that could explain the fourth-power rate law was developed. In this model, an internal electric field was assumed to be set up over the reaction-formed S i c layer through a negative space charge, and then the diffusion of the carbon-ion vacancies across this layer, driven predominately by this electric field, was considered as the rate-limiting step for the SIC growth. Neither an increase in the processing temperature nor an addition of 10 wt% Mo into the silicon melt had a significant influence on the reaction kinetics. X-ray diffraction analysis revealed that the reaction products were p-Sic, and P-SiC + MoSi, for the Si-C and Si-C-Mo reactions, respectively.

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The electric field-induced antiferroelectric (AFE) to ferroelectric (FE) phase transition in lead strontium zirconate titanate (PSZT) ceramics was studied by means of dielectric, polarization, and strain hysteresis measurements. PSZT compositions with varying strontium and Zr/Ti ratio, located in the ferroelectric, antiferroelectric phase regions, and near the AFE/FE phase boundary were prepared. Dielectric properties were measured as a function of temperature for different compositions. The electric field required for AFE–FE phase transition and hysteresis were affected by the temperature and composition. The entropy change during phase transition and the field-induced strain were also measured and discussed.

The thermal shock behavior of three types of two‐dimensional woven, continuous fiber‐reinforced (NextelTM 312 (3M Co., St. Paul, MN) or NicalonTM (Nippon Carbon, Tokyo, Japan)) ceramic matrix (silicon carbide matrix that had been processed by chemical vapor infiltration or polymer impregnation and pyrolysis) composites was studied using the water‐quench technique. Thermal‐shock‐induced damage was characterized by a destructive technique of four‐point flexure and a nondestructive technique of Young's modulus measurement by the dynamic resonance method. Compared with monolithic ceramics, the continuous fiber‐reinforced ceramic composites were capable of preventing catastrophic failure that was caused by thermal shock. Analysis of the results that were based on the stresses that were generated by thermal shock and the mismatch of thermal expansion between fibers and matrices suggested possible mechanisms of the thermal shock damage. Preliminary results showed evidence of matrix cracking and delamination because of the thermal shock damage. The feasibility of using the nondestructive technique to detect thermal shock damage also was demonstrated.