One of the critical components of a planar solid oxide fuel cell (SOFC) stack is the interconnect, an electronically conducting plate in contact with the cathode of one cell and the anode of the adjacent cell. The interconnect physically separates the anodic and the cathodic gases. Thus, the interconnect is a bipolar plate which connects cells in series. The interconnect can, in principle, be made of an electronically conducting ceramic or a metallic alloy. Ceramic materials are brittle and their thermomechanical properties are an important consideration. Ceramic materials such as doped-LaCrO 3 are currently being explored. However, their brittleness, materials cost, and manufacturing cost are significant impediments to their use as interconnect materials in planar SOFCs. However, a ceramic interconnect in the form of a thin strip is ideally suited for tubular SOFCs. Metallic alloys are potential candidates provided they meet certain requirements. A prospective metallic alloy for application as an interconnect must be 1. Oxidation-resistant in both cathodic (air) and anodic (fuel gas plus water vapor) atmospheres.2. Impermeable to both anodic and cathodic gases.3. The oxide scale must be a good electronic conductor. 4. Strongly adherent to the alloy substrate. 5. Flexible enough to withstand thermal expansion mismatches. Or, if it is brittle, it must have a thermal expansion coefficient similar to that of the cell components.6. Inexpensive. The last requirement is very important from a practical standpoint. Platinum may be an ideal material based on the physical requirements alone. Its high cost, however, precludes its use as an interconnect material. An obvious choice for planar SOFCs would be one or more of the nickel-based superalloys which are known to exhibit excellent oxidation resistance at temperatures as high as 900ЊC. Most of the literature on the oxidation behavior of superalloys is from the standpoint of structural applications. The electronic conductivity of the oxide scale is usually not investigated. Many structural alloys contain aluminum which forms a protective alumina layer at high temperatures. The requirement of good electronic conductivity of the oxide scale, however, precludes the use of alloys which form a contiguous alumina scale or other insulating oxide scales.The typical partial pressure of oxygen in the fuel used in a solid oxide fuel cell ranges between 10 Ϫ22 and 10 Ϫ17 atm, depending upon the temperature and fuel composition. By contrast, the equilib-rium partial pressure of oxygen for Cr/Cr 2 O 3 is several orders of magnitude lower (10 Ϫ28 atm at 800ЊC). Thus, oxidation of chromium occurs readily in the fuel atmosphere as well. Therefore, its application in solid oxide fuel cells requires due consideration of the oxidative effects in fuel. The present work describes the results of studies of oxidation in air. The focus of a subsequent manuscript will be on oxidation in a fuel atmosphere.

Foil specimens of Haynes 230, Hastelloy X, Inconel 718, and Inconel 625 of 4.5 mil ͑ϳ113 m͒ thickness were oxidized in wet hydrogen for several hundred hours at temperatures between 700 and 1100°C. Chromia was determined to be the predominant oxide phase in the scales of these alloys, consistent with the results of a previous study 1 of these alloys in air, as shown using X-ray diffraction and electron probe microanalysis. The oxidation kinetics of all the alloys, investigated by thermogravimetry, in a wet hydrogen atmosphere exhibited parabolic behavior. Haynes 230 and Hastelloy X exhibited the slowest oxidation kinetics of all the alloys studied. Further, the oxidation kinetics of all the alloys were faster at 800°C in a wet hydrogen atmosphere compared to oxidation in air at 800°C. However, the oxidation kinetics of these alloys in a wet hydrogen atmosphere were slower than those in air at 1100°C. The oxide scale formed in wet hydrogen exhibited a higher resistance than that formed in air. This result is attributed to the expected p-type conductivity of the oxide scales formed in both air and wet hydrogen.

The genomic transferrin receptor genes (tbpA and tbpB) from two strains of Haemophilus influenzae type b (Hib) and two strains of non-typable H. influenzae (NTHi) have been cloned and sequenced. The deduced protein sequences of the H. influenzae tbpA genes were 95-100% conserved and those of the tbpB genes were 66-100% conserved. The tbpB gene from one strain of NTHi was found to encode a truncated Tbp2 protein. The tbpB genes from four additional NTHi strains were amplified by the polymerase chain reaction (PCR) utilizing primers derived from the conserved N-terminal sequences of Tbp1 and Tbp2 and were found to encode full-length proteins. Although several bacterial species express transferrin receptors, when the Tbp1 and Tbp2 sequences from different organisms were compared, there was only limited homology. Recombinant Tbp1 and Tbp2 proteins were expressed from Escherichia coli and antisera were raised to the purified proteins. There was significant antigenic conservation of both Tbp1 and Tbp2 amongst H. influenzae strains, as determined by Western blot analysis. In a passive model of bacteraemia, infant rats were protected from challenge with Hib after transfer of anti-rTbp2 antiserum, but not after anti-rTbp1 antiserum.

We have cloned and sequenced the d15 gene from two strains of Haemophilus influenzae type b (Hib) and two strains of nontypeable H. influenzae (NTHI). The nucleotide and deduced protein sequences of d15 are highly conserved, with only a small variable region identified near the carboxyl terminus of the protein. Analysis of upstream sequences revealed that the H. influenzae d15 gene may be part of a large potential operon of closely spaced open reading frames, including one with significant homology to the Escherichia coli cds gene encoding CDP-diglyceride synthetase. Southern blot analysis demonstrated that the d15 gene is also present in H. influenzae types a, c, d, e, and f and in Haemophilus parainfluenzae. A recombinant D15 (rD15) protein was expressed in good quantity in E. coli from the inducible T7 promoter, and monospecific anti-rD15 antibodies were raised. Immunoblot analysis of H. influenzae serotypes a, b, c, d, e, and f, NTHI, and H. parainfluenzae lysates revealed that they all expressed a cross-reactive D15-like protein. Purified rD15 was found to be highly immunogenic in mice, guinea pigs, and rabbits, and passive transfer of anti-rD15 antibodies protected infant rats from challenge with H. influenzae type b or type a in infant rat models of bacteremia. Thus, D15 is a highly conserved antigen that is protective in animal models and it may be a useful component of a universal subunit vaccine against Haemophilus infection and disease.

Heat is fundamental to power generation and many industrial processes, and is most useful at high temperatures because it can be converted more efficiently to other types of energy. However, efficient transportation, storage and conversion of heat at extreme temperatures (more than about 1,300 kelvin) is impractical for many applications. Liquid metals can be very effective media for transferring heat at high temperatures, but liquid-metal pumping has been limited by the corrosion of metal infrastructures. Here we demonstrate a ceramic, mechanical pump that can be used to continuously circulate liquid tin at temperatures of around 1,473-1,673 kelvin. Our approach to liquid-metal pumping is enabled by the use of ceramics for the mechanical and sealing components, but owing to the brittle nature of ceramics their use requires careful engineering. Our set-up enables effective heat transfer using a liquid at previously unattainable temperatures, and could be used for thermal storage and transport, electric power production, and chemical or materials processing.