In the current study, Ag–CuO, a reactive air brazing alloy was evaluated for brazing Ba0.5Sr0.5Co0.8Fe0.2O(3−δ) (BSCF). In situ contact angle tests were performed on BSCF using Ag–CuO binary mixtures at 950 and 1000 °C, and the interfacial microstructures were evaluated. Wetting contact angles (θ < 90°) were obtained at short times at 950 °C, and the contact angles remained constant at 1000 °C for 1, 2, and 8 mol% CuO contents. Microstructural analysis revealed the dissolution of copper oxide into the BSCF matrix to form copper–cobalt–oxygen rich dissolution products along the BSCF grain boundaries. The formation of a thick interfacial reaction product layer and ridging at the sessile drop triple point indicate that the reaction kinetics are very rapid and that it will require careful process control to obtain the desired thin but continuous interfacial product layer.

Thermo-mechanical processing was performed on two titanium alloy billets, a beta-titanium alloy (Ti1Al8V5Fe) and an alpha-beta titanium alloy (Ti6Al4V), which had been produced using a novel low-cost powder metallurgy process that relies on the use of TiH2 powder as a feedstock material. The thermomechanical processing was performed in the beta region of the respective alloys to form 16-mm diameter bars. The hot working followed by the heat treatment processes not only eliminated the porosity within the materials but also developed the preferred microstructures. Tensile testing and rotating beam fatigue tests were conducted on the as-rolled and heat-treated materials to evaluate their mechanical properties. The mechanical properties of these alloys matched well with those produced by the conventional ingot processing route.

Several advanced air separation unit (ASU) designs being considered for use in coal gasification rely on the use of solid state mixed ionic and electronic conductors. Nicrofer-6025HT, a nickel-based alloy, has been identified as a potential manifold material to transport the hot gases into the ASUs. In the current study, isothermal oxidation tests were conducted on Nicrofer-6025HT in the temperature range of 700–900 °C for up to 24 h. The evolution of oxide scale was evaluated using SEM, XRD, and XPS. The composite surface oxide layer that formed consisted of an outer chromia-rich scale and an inner alumina scale. For the longer times at the higher temperatures evaluated, a NiCr2O4 spinel phase was located at the interface between the alumina and chromia. Based on the experimental results a four-step oxidation model was proposed.

One of the keys to developing viable solid oxide fuel cell (SOFC) systems is to first develop reliable and inexpensive stack sealing technology. Three general approaches are currently being pursued: rigid bonded sealing, compressive sealing, and compliant bonded sealing. This review highlights the advantages and limitations of each option, discusses some of the leading concepts, and out-lines the future steps that need to be taken in their development.

The study reported here examines wetting between Al2O3 and a series of AgCuO air braze filler metals. Based on in-situ contact angle measurements, two transitions in wetting behavior were identified in the composition range of 040mol% CuO. The first transition occurs directly at the miscibility gap boundary composition (for a given temperature) of the AgCuO phase diagram and is attributable to the presence of two liquid phases, one of which is rich in copper oxide and preferentially wets the alumina substrate via the mechanism predicted by Cahn's critical point wetting theory. The second transition occurs at a filler metal composition that falls well within the miscibility gap for the AgCuO system and may occur due to the formation of a reaction product between the substrate and the molten filler metal, as denoted by small, discontinuous reaction regions.

In March 2012, a group of researchers met to discuss emerging topics in ceramic science and to identify grand challenges in the field. By the end of the workshop, the group reached a consensus on eight challenges for the future:—understanding rare events in ceramic microstructures, understanding the phase-like behavior of interfaces, predicting and controlling heterogeneous microstructures with unprecedented functionalities, controlling the properties of oxide electronics, understanding defects in the vicinity of interfaces, controlling ceramics far from equilibrium, accelerating the development of new ceramic materials, and harnessing order within disorder in glasses. This paper reports the outcomes of the workshop and provides descriptions of these challenges.

The goal of the US Department of Energy (DOE) hydrogen production portfolio is to research and develop low-cost, highly efficient and environmentally friendly production technologies based on diverse, domestic resources. The DOE Hydrogen Program integrates basic and applied research, as well as technology development and demonstration, to adequately address a diverse range of technologies and feedstocks. The program encompasses a broad spectrum of coordinated activities within the DOE Offices of Energy Efficiency and Renewable Energy (EERE), Nuclear Energy (NE), Fossil Energy (FE), and Science (SC). Hydrogen can be produced in small, medium, and larger scale facilities, with small-scale distributed facilities producing from 100 to 1,500 kilograms (kg) of hydrogen per day at fueling stations, and medium-scale (also known as semi-central or city-gate) facilities producing from 1,500 to 50,000 kg per day on the outskirts of cities. The largest central facilities would produce more than 50,000 kg of hydrogen per day. Specific technologies currently under program development for distributed hydrogen production include bio-derived renewable liquids and water electrolysis. Centralized renewable production pathways under development include water electrolysis integrated with renewable power (e.g., wind, solar, hydroelectric, or geothermal), biomass gasification, solar-driven high-temperature thermochemical water splitting, direct photoelectrochemical water splitting, and biological production methods using algal/bacterial processes. To facilitate commercialization of hydrogen production via these various technology pathways in the near and long terms, a "Hydrogen Production Roadmap" has been developed which identifies the key challenges and high-priority research and development needs associated with each technology. The aim is to foster research that will lead to hydrogen production with near-zero net greenhouse gas emissions, using renewable energy sources, nuclear energy, and/or coal (with carbon capture and storage). This paper describes the research and development needs and activities by various DOE offices to address the key challenges in the portfolio of hydrogen production technologies.

Nicrofer-6025HT (Nicrofer) has been selected as a potential manifold material for advanced air separation units that use mixed ionic and electronic conductors (MIECs). Reactive air brazing (RAB) is a recently developed joining technique that has the potential to obtain high-quality joints with the required hermeticity between Nicrofer and the MIEC. Successful RAB joining of these two distinct materials requires an alumina surface layer on the Nicrofer. To aluminize the surface of Nicrofer, a recently developed reactive air aluminizing (RAA) technique was used. The current work demonstrated the feasibility of preparing RAA coatings on Nicrofer and compared the effect of aluminum powder size on the RAA process.

Niobium (Nb) sputter coated 316L stainless steel (SS) is investigated as an alternative to a previously developed Nb clad 304L SS material for use in a bipolar plate component of a polymer electrolyte membrane fuel cell (PEMFC) stack. The electrochemical properties of the Nb sputter coated 316L SS are evaluated via static corrosion and interfacial contact resistance testing and through potentiodynamic and potentiostatic measurements conducted under half-cell environments of a standard PEMFC stack. The experimental results show that the electrochemical properties of the sputtered Nb coatings are quite viable for the PEMFC bipolar plate application, while the thickness of the sputtered Nb coating is substantially thinner than that of the roll clad Nb coating.

In the present study, the properties of non-platinum based nanoscale tantalum oxide/tungsten oxide-carbon composite catalysts were investigated for potential use in catalyzing the oxygen reduction reaction on the cathode side of a PEM fuel cell. All of the tantalum oxide-based catalysts exhibit high ORR on-set potentials, comparable with the commercial Pt/C catalyst even though oxygen reduction current was limited. The tungsten oxide doping to tantalum oxide improved catalytic performance. The performance enhancement was due to a decrease in resistance polarization with increasing tungsten content mainly due to the decrease in resistance polarization. XPS results indicate that the oxidation state of tungsten is +6 and that of the tantalum is +5, suggesting that excess oxygen is generated in the resulting oxide structure. This compositional effect seems to reduce resistance polarization by altering the surface chemistry of the tantalum oxide and enhancing the reaction steps such as surface diffusion. Maximum performance was achieved with a catalyst containing 32mol% of tungsten oxide, reaching a mass specific current density of ∼7% that of the commercial Pt/C catalyst at 0.6V vs. NHE and ∼35% at 0.2V vs. NHE. In term of area-specific current density, five-fold increase in loading of the doped catalyst leads to a 4–4.5 fold increase in area specific current density at 0.6V vs. NHE, reaching 66% that of the Pt/C catalyst at 100rpm and 35% at 2400rpm.

Chromia-forming ferritic stainless steels find widespread use as interconnect materials in SOFCs at operating temperatures below 800 degrees C, because of their thermal expansion match and low cost. However, volatile Cr-containing species originating from this scale can poison the cathode material in the cells and subsequently cause power degradation in the devices. To prevent this, a conductive manganese cobaltite spinel coating has been developed, but unfortunately; this coating is not compatible with glass-based seals between the interconnect or cell frame components and the ceramic cell due to reactions between the coating and the glass. Thus, a new aluminizing process has been developed to improve the stability of the sealing regions of these components, as well as for other metallic stack and balance-of-plant components. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

This chapter contains sections titled: Introduction Basic Phenomena in Ceramic Joining Methods of Joining Conclusions References

Chromia forming ferritic stainless steels (SS) exhibit many desirable qualities for intermediate temperature solid oxide fuel cell interconnect applications. However, with these alloys, there is a need to prevent chromia volatilization and the associated chromium poisoning at the cathode-electrolyte interface, while ensuring low interfacial electrical resistance with the cell electrodes; a need that has generated renewed interest in the development of oxidation resistant, electrically conductive coatings. In the present study, screen printed (Mn,Co)(3)O(4) coatings were applied to a newly developed ferritic SS alloy, Sanergy HT(Cr-21.9%, Ni-0.5%, Mo-0.88%, Nb-0.60%, and Si-0.05%). The oxidation behavior of both the coated alloy and the bare alloy were evaluated at 800 degrees C in air for exposures times up to 1500 h. The oxidation kinetics, investigated using weight gain and scale thickness measurements, exhibited parabolic behavior for the bare alloy. The oxidation behavior of the coated material could not be explained by a single parabolic mechanism. The calculated parabolic thickening rate constants were compared with published data on other ferritic SS alloy compositions.