Hexagonal and cubic phases of manganese oxide mesoporous structures (MOMS) have been prepared by means of the oxidation of Mn(OH) 2 . The hexagonal MOMS materials form a hexagonal array of pores with an open porous structure, thick walls (1.7 nanometers), and exceptional thermal stability (1000°C). The walls of the mesopores are composed of microcrystallites of dense phases of Mn 2 O 3 and Mn 3 O 4 , with MnO 6 octahedra as the primary building blocks. The calcined hexagonal MOMS have an electrical conductivity of 8.13 × 10 −6 per ohm·centimeter, an average manganese oxidation state of 3.55, and a band gap of 2.46 electron volts. Catalytic oxidations of cyclohexane and n -hexane in aqueous solutions in a batch reactor show conversions of ∼10 and ∼8 percent, respectively. Characterization and catalytic data suggest that MOMS systems show significant enhancement in thermal stability with respect to octahedral molecular sieve materials.

ÐMuch emphasis is now placed on chip-multiprocessor (CMP) architectures for exploiting thread-level parallelism in an application. In such architectures, speculation may be employed to execute applications that cannot be parallelized statically. In this paper, we present an efficient CMP architecture for speculative execution of sequential binaries without source recompilation. We present the software support that enables identification of threads from a sequential binary. The hardware includes a memory disambiguation mechanism that enables the detection of interthread memory dependence violations during speculative execution. This hardware is different from past proposals in that it does not rely on a snoopy-based cache-coherence protocol. Instead, it uses an approach similar to a directory-based scheme. Furthermore, the architecture includes a simple and efficient hardware mechanism to enable register-level communication between on-chip processors. Evaluation of this software-hardware approach shows that it is quite effective in achieving high performance when running sequential binaries.

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The deposition, stability, and function of carbonaceous films formed by exposing porous yttria-stabilized zirconia ͑YSZ͒ anodes in YSZ-based solid oxide fuel cells ͑SOFCs͒ to n-butane at elevated temperatures was studied using a combination of four-probe conductivity, impedance spectroscopy, and cell polarization measurements. The carbonaceous deposits were found to have high electronic conductivity and to be relatively stable for steam-to-carbon ratios as high as 3.75. Comparison of the performance of cells in which carbon films were used as the sole current collector in the anode with anodes containing both Cu and carbon films indicated that in the latter case, the carbon layer plays an important role in providing electronic conductivity near the three-phase boundary.Metal-ceramic ͑cermet͒ composites, with Ni as the metal, are the most commonly used materials for solid oxide fuel cells SOFC anodes. 1,2 In these composites Ni provides high electronic conductivity, reasonably good high temperature stability, and high catalytic activity for steam reforming. The latter allows for some internal reforming when methane or syngas is used as the fuel. Unfortunately, Ni also catalyzes the formation of carbon fibers if insufficient amounts of steam are present along with methane or CO. 3-5 The problem of carbon fiber formation is particularly severe for hydrocarbons larger than methane. It is well known from the steamreforming literature that high H 2 O:C ratios must be maintained, 3,5,6 higher even than that predicted from thermodynamic considerations, 6 in order to avoid plugging the reactor with carbon while operating with higher hydrocarbon fuels.While it is theoretically possible to operate an SOFC directly on hydrocarbon fuels, this requires replacement of Ni with other electronically conductive materials that do not catalyze carbon formation. In our laboratory, we have been studying Cu-based cermets 7,8 for this purpose. While Cu-YSZ ͑yttria-stabilized zirconia͒ composites are stable in hydrocarbon fuels, it is necessary to add a catalyst, ceria, to the anode in order to achieve reasonable performance. 9,10 Furthermore, the fabrication of Cu-based anodes has required the development of synthetic methods that are different from those used to produce Ni ceramic-metallic ͑cermet͒ composites, because CuO and Cu 2 O melt at the temperatures required for processing YSZ. 8 Rather than calcining mixtures of CuO x and YSZ, the Cu cermets are fabricated by first producing a highly porous YSZ matrix and then adding Cu to the matrix by impregnation with Cu salts.We have recently shown that exposure of Cu-ceria-YSZ anodes to n-butane at 973 K can lead to a large increase in performance due to the formation of carbonaceous residues within the anode. 11 Based on the fact that the enhancement is large for anodes with low Cu contents and small for anodes with high Cu contents, it was concluded that the carbonaceous residues enhance electronic conductivity within the anodes. Analysis of the compounds formed by passing n-butane over ...

Metal‐supported solid oxide fuel cells (MSCs) offer certain strategic advantages over the more conventional solid oxide fuel cells (SOFCs), which comprise only ceramic materials. Since alloys such as ferritic steels are very similar in their coefficient of thermal expansion (CTE) with ceramic components, viz., cerias, zirconias, and nickel oxide doped with either of them, they could provide excellent thermal cyclability while maintaining a strong interlayer bond. Therefore, in an anode‐supported cell the entire NiO‐ceramic support can be replaced by a ferritic steel porous support—the catalytically active NiO is therefore, a functional layer only. A huge savings in materials cost is achievable, because cerias and zirconias [usually doped with Y, Gd, Sm rare earth (RE) elements] are considerably more expensive that ferritic steels. Lowering the capital costs for SOFCs is an extensive global undertaking with US Department of Energy (DOE) laying down targets such as ~$ 200/kW for the stack itself, in order for SOFCs to become competitive with grid power costs and to offer a power source that promises 24 × 7 power supply for critical applications. This will eventually lead to a premier electricity generation device in the distributed power space, with the highest known electrical efficiencies (>50%). MSCs need very robust, high precision, and cost‐effective manufacturing techniques, which are scalable to high volumes. One of the main goals in this review is to showcase some of the work done in this area since the last review (2010), and to assess the technology challenges, and new solutions that have emerged over the past few years. WIREs Energy Environ 2017, 6:e246. doi: 10.1002/wene.246 This article is categorized under: Fuel Cells and Hydrogen > Science and Materials