The oxidation of ferritic stainless steels has been studied under solid oxide fuel cell ͑SOFC͒ interconnect ''dual'' exposure conditions, i.e., simultaneous exposure to air on one side of the sample, and moist hydrogen as the fuel on the other side. The scales grown on the air side under these dual exposure SOFC conditions can be significantly different from scales grown on samples exposed to air on both sides. In contrast, no substantial difference was observed between scales grown on the fuel side of the dual atmosphere samples and scales grown on samples exposed to moist hydrogen on both sides. The anomalous oxidation of stainless steels at the air side depends on both alloy composition and thermal history. AISI430, with 17% Cr, suffered localized attack via formation of Fe 2 O 3 hematite-rich nodules on the air side of dual exposure samples, while the spinel top layer of the air side scale of Crofer22 APU ͑23% Cr͒ was enriched in iron. For E-brite, with the highest Cr content ͑27%͒, no unusual phases were found in the scale on the air side, but the air side scale was less dense and appeared to be more prone to defects than the scale grown in air only. Increasing temperature and thermal cycling both accelerated the anomalous oxidation, which appeared to be related to the transport of hydrogen through the steel and its subsequent presence in the air side scale.
Measurements of the heat capacity, thermal expansion, and thermal conductivity on synthetic crystals of undoped and neodymium-doped fluorapatite are reported. Fitting the low-temperature specific heat data to a Debye model yields a Debye temperature of 550 o K. At 25°C the thermal expansion coefficients are 10.0X1()-6 °K-l and 9.4X 1()-6 oK-I, respectively, along the [0001J and [10IOJ directions. The thermalexpansion measurements yield a Debye temperature of 500 o K. A typical value of the thermal conductivity is 0.020 W cm-1 °K-l at room temperature. The thermal conductivity is only feebly temperature dependent and, similar to the thermal-expansion coefficient, shows very little crystallographic anisotropy.
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