共查询到20条相似文献，搜索用时 31 毫秒
1.
Fuel cells are uniquely capable of overcoming combustion efficiency limitations (e.g., the Carnot cycle). However, the linking of fuel cells (an energy conversion device) and hydrogen (an energy carrier) has emphasized investment in proton-exchange membrane fuel cells as part of a larger hydrogen economy and thus relegated fuel cells to a future technology. In contrast, solid oxide fuel cells are capable of operating on conventional fuels (as well as hydrogen) today. The main issue for solid oxide fuel cells is high operating temperature (about 800°C) and the resulting materials and cost limitations and operating complexities (e.g., thermal cycling). Recent solid oxide fuel cells results have demonstrated extremely high power densities of about 2 watts per square centimeter at 650°C along with flexible fueling, thus enabling higher efficiency within the current fuel infrastructure. Newly developed, high-conductivity electrolytes and nanostructured electrode designs provide a path for further performance improvement at much lower temperatures, down to ~350°C, thus providing opportunity to transform the way we convert and store energy. 相似文献
2.
Hibino T Hashimoto A Inoue T Tokuno J Yoshida S Sano M 《Science (New York, N.Y.)》2000,288(5473):2031-2033
The performance of a single-chamber solid oxide fuel cell was studied using a ceria-based solid electrolyte at temperatures below 773 kelvin. Electromotive forces of approximately 900 millivolts were generated from the cell in a flowing mixture of ethane or propane and air, where the solid electrolyte functioned as a purely ionic conductor. The electrode-reaction resistance was negligibly small in the total internal resistances of the cell. The resulting peak power density reached 403 and 101 milliwatts per square centimeter at 773 and 623 kelvin, respectively. 相似文献
3.
Garcia-Barriocanal J Rivera-Calzada A Varela M Sefrioui Z Iborra E Leon C Pennycook SJ Santamaria J 《Science (New York, N.Y.)》2008,321(5889):676-680
The search for electrolyte materials with high oxygen conductivities is a key step toward reducing the operation temperature of fuel cells, which is currently above 700 degrees C. We report a high lateral ionic conductivity, showing up to eight orders of magnitude enhancement near room temperature, in yttria-stabilized zirconia (YSZ)/strontium titanate epitaxial heterostructures. The enhancement of the conductivity is observed, along with a YSZ layer thickness-independent conductance, showing that it is an interface process. We propose that the atomic reconstruction at the interface between highly dissimilar structures (such as fluorite and perovskite) provides both a large number of carriers and a high-mobility plane, yielding colossal values of the ionic conductivity. 相似文献
4.
Methane was oxidatively coupled to ethylene with an ethylene yield up to 85 percent and a total C(2) hydrocarbon yield up to 88 percent in a gas recycle high-temperature (800 degrees C) electrocatalytic or catalytic reactor where the recycled gas passes continuously through a molecular sieve trap in the recycle loop. Oxygen is supplied either electrocatalytically by means of the solid electrolyte support of the silver-based catalyst or in the gas phase. The C(2) products are obtained by subsequent heating of the molecular sieve trap. The selectivity to ethylene is up to 88 percent for methane conversion up to 97 percent. 相似文献
5.
A solid electrolyte fuel cell operating on ammonia fuel has been constructed and tested. The yield of nitric oxide can exceed 60 percent with simultaneous electric energy production. Two dimensionless numbers have been identified which govern the product selectivity and power output of this fuel cell. The cell appears to be a promising candidate for nitric acid and electric energy cogeneration. 相似文献
6.
Sorbent materials that allow for high-temperature, regenerative desulfurization of fuel gas streams for the anode of a solid oxide fuel cell have been developed. Reversible adsorption of H2S on cerium and lanthanum oxide surfaces is demonstrated over many cycles at temperatures as high as 800 degrees C, on both fresh or presulfided sorbents, and at very high space velocities. The adsorption and desorption processes are very fast, and removal of H2S to sub-parts per million levels is achieved at very short (millisecond) contact times. Any type of sulfur-free gas, including water vapor, can be used to regenerate the sorbent surface. Preferably, the anode off-gas stream is used to sweep the desorbed H(2)S to a burner. 相似文献
7.
Diffusion couples, consisting of sapphire and fused silica, which were annealed in the temperature range from 1678 degrees to 2003 degrees C and analyzed by electron beam microprobe, have provided data on the stable phase equilibrium of the silica-alumina system. Under stable equilibrium conditions, the intermediate compound of this system, mullite (3Al(2)O(3) . 2SiO(2)), melts incongruently at 1828 degrees +/- 10 degrees C and its solid solution field extends from 70.5 to 74.0 percent (by weight) alumina. The stable phase diagram is a composite of the two binary eutectic diagrams: silica-mullite in the absence of alumina and silica-alumina in the absence of mullite. Under metastable conditions, mullite melts congruently at approximately 1890 degrees +/- 10 degrees C and its solid solution field extends to approximately 83.2 percent (by weight) alumina. 相似文献
8.
Extensive efforts to develop a solid-oxide fuel cell for transportation, the bottoming cycle of a power plant, and distributed generation of electric energy are motivated by a need for greater fuel efficiency and reduced air pollution. Barriers to the introduction of hydrogen as the fuel have stimulated interest in developing an anode material that can be used with natural gas under operating temperatures 650 degrees C < T < 1000 degrees C. Here we report identification of the double perovskites Sr2Mg(1-x)MnxMoO(6-delta) that meet the requirements for long-term stability with tolerance to sulfur and show a superior single-cell performance in hydrogen and methane. 相似文献
9.
Stamenkovic VR Fowler B Mun BS Wang G Ross PN Lucas CA Marković NM 《Science (New York, N.Y.)》2007,315(5811):493-497
The slow rate of the oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cell (PEMFC) is the main limitation for automotive applications. We demonstrated that the Pt3Ni(111) surface is 10-fold more active for the ORR than the corresponding Pt(111) surface and 90-fold more active than the current state-of-the-art Pt/C catalysts for PEMFC. The Pt3Ni(111) surface has an unusual electronic structure (d-band center position) and arrangement of surface atoms in the near-surface region. Under operating conditions relevant to fuel cells, its near-surface layer exhibits a highly structured compositional oscillation in the outermost and third layers, which are Pt-rich, and in the second atomic layer, which is Ni-rich. The weak interaction between the Pt surface atoms and nonreactive oxygenated species increases the number of active sites for O2 adsorption. 相似文献
10.
Solid tumors grew in the chorioallantois of chick embryos after the topical inoculation of ascites tumor cells. The microscopic character of the growth varied depending on the temperature of incubation. At 32.5 degrees C a sarcomatous appearance was prominent; at 37.5 degrees C carcinomatous structure in several alveolar patterns predominated; at 42.5 degrees C growth was that of a "giant cell" carcinoma. 相似文献
11.
Release of protoplasts in the yeast phase of Histoplasma capsulatum without added enzyme 总被引：2，自引：0，他引：2
Cells of the yeast phase of the dimorphic systemic fungus pathogen Histoplasma capsulatum readily released large numbers of intact protoplasts without degradation of their cell walls by snail or microbial enzymes, previously regarded as a requirement for all yeast and mycelial fungal forms. Over 90 percent of "B" type yeast cells in the early logarithmic phase of growth released living protoplasts when incubated at 37 degrees C with 2 molar magnesium sulfate, whereas "A" type yeast cells required prior exposure for 24 hours to 2-deoxy-D-glucose before incubation in the 2 molar magnesium sulfate. 相似文献
12.
Carbon from the Allende meteorite is not graphite but carbyne (triply bonded elemental carbon), inasmuch as on heating to 250 degrees to 330 degrees C it releases mainly triply bonded fragments: -(C identical withC)(n),- with n = 1 to 5, and -(C identical withC)(n)-CN, with n = 1 to 3. Although carbynes have been known to form only by condensation of carbon vapor above 2600 K or by explosive shock of > 600 kilobars, it is found that they also form metastably by the reaction 2CO --> CO(2) + C (solid) at 300 degrees to 400 degrees C in the presence of a chromite catalyst. Such low-temperature formation by surface catalysis may be the dominant source of carbynes on the earth and in meteorites, and a major source of interstellar carbynes and cyanopolyacetylenes. 相似文献
13.
Field measurement of slow metamorphic reaction rates at temperatures of 500 degrees to 600 degrees C
High-temperature metamorphic reaction rates were measured using strontium isotopic ratios of garnet and whole rock from a field site near Simplon Pass, Switzerland. For metamorphic conditions of cooling from 612 degrees +/- 17 degrees C to 505 degrees +/- 15 degrees C at pressures up to 9.1 kilobars, the inferred bulk fluid-rock exchange rate is 1.3(-0.4)(+1.1) x 10(-7) grams of solid reacted per gram of solid per year, several orders of magnitude lower than laboratory-based estimates. The inferred reaction rate suggests that mineral chemistry may lag the evolving conditions in Earth's crust during mountain building. 相似文献
14.
固态电解质具有优异的安全性能、工作温度范围宽、回收方便等优点,已成为新一代柔性电子器件中最具前景的电解质材料.为探索兼具高离子电导率和优良机械性能的固态电解质,将无机活性陶瓷锂镧锆氧（Lithium lanthanum zirconium oxide,LLZO）与改性聚离子液体复合,制备了一种性能优异的复合固态电解质.研究了LLZO与复合材料间结构的差异、LLZO的含量对复合固态电解质在离子电导率、机械性能的影响以及其抗压能力.结果表明,聚离子液体粘结剂的加入,赋予了固态电解质良好的柔顺性,并显著地提升了电解质的离子传输效率. 当复合固态电解质中LLZO为质量分数50%时,复合固态电解质的室温离子电导率达到最高值（1.45×10-4 S·cm-1）,比单一的LLZO固态电解质的离子电导率高了一个数量级以上. 用维氏硬度来表征复合固态电解质的抗压能力,发现当LLZO为质量分数50%时,复合固态电解质的硬度可以达到0.45 gf/μm2. 相似文献
15.
Single-crystal films are essential for devices because the intrinsic properties of the material, rather than its grain boundaries, can be exploited. Cubic bismuth oxide has the highest known oxide ion mobility, which makes it useful for fuel cells and sensors, but it is normally only stable from 729 degrees to 825 degrees C. The material has not been previously observed at room temperature. Single-crystal films of the high-temperature cubic polymorph of bismuth oxide were epitaxially electrodeposited from an aqueous solution onto single-crystal gold substrates. The 35.4 percent lattice mismatch was accommodated by forming coincidence lattices in which the bismuth oxide film was rotated in relation to the gold substrate. These results provide a method for producing other nonequilibrium phases that cannot be accessed by traditional thermal processing. 相似文献
16.
Saunders DS 《Science (New York, N.Y.)》1973,181(4097):358-360
Females of the parasitic wasp Nasonia vitripennis raised from the egg stage in the total absence of light but subjected to daily temperature cycles (13 degrees to 23 degrees C), are able to distinguish a "short-day" thermoperiod ( 13 hours at 23 degrees C per day) from a "long-day" thermoperiod ( 13 hours at 23 degrees C per day) and produce diapausing or developing progeny accordingly. 相似文献
17.
Crystals of a high-pressure form of benzene (benzene 11) were grown in the diamond-anvil pressure cell at elevated temperature and pressure from the transition of solid I to solid II. X-ray precession data were obtained from a single-crystal in the high-pressure cell. At 21 degrees C and about 25 kilobars, benzene II crystallizes in the monoclinic system with a = 5.417 +/- 0.005 angstroms (S.D.), b = 5.376 +/- 0.019 angstroms, c = 7.532 +/- 0.007 angstroms, beta = 110.00 degrees +/- 0.08 degrees , space group P2(1)/ c, Pc= 1.26 grams per cubic centimeter. The crystal structure was solved by generating all possible molecular packing configurations and calculating structure factors, reliability factors, and packing energies for each configuration. This procedure produced a unique solution for the molecular packing of benzene II. 相似文献
18.
There are substantial barriers to the introduction of hydrogen fuel cells for transportation, including the high cost of fuel-cell systems, the current lack of a hydrogen infrastructure, and the relatively low fuel efficiency when using hydrogen produced from hydrocarbons. Here, we describe a solid oxide fuel cell that combines a catalyst layer with a conventional anode, allowing internal reforming of iso-octane without coking and yielding stable power densities of 0.3 to 0.6 watts per square centimeter. This approach is potentially the basis of a simple low-cost system that can provide substantially higher fuel efficiency by using excess fuel-cell heat for the endothermic reforming reaction. 相似文献
19.
Leveiller F Jacquemain D Lahav M Leiserowitz L Deutsch M Kjaer K Als-Nielsen J 《Science (New York, N.Y.)》1991,252(5012):1532-1536
A crystalline counterionic layer at the interface between an electrolyte solution and a charged layer of insoluble amphiphilic molecules was observed with grazing incidence synchrotron x-ray diffraction. Uncompressed arachidic films spread over 10(-3) molar cadmium chloride solution (pH 8.8) spontaneously form crystalline clusters with coherence lengths of approximately 1000 angstroms at 9 degrees C. Ten distinct diffraction peaks were observed, seven of which were attributed to scattering only from a crystalline Cd(2+) layer and the other three to scattering primarily from the arachidate layer. The reflections from the Cd(2+) layer were indexed according to a 2 x 3 supercell of the arachidate lattice with three Cd(2+) ions per cadmium unit cell. 相似文献
20.
采用固相法、燃烧法和溶解-凝胶法等3种制备固体氧化物燃料电池阴极材料的常用方法合成了La0.7Sr0.3MnO3（LSM）材料．合成的粉体成,钙钛矿结构,没有杂相生成．采用三电极法对阴极材料的电化学性能进行了研究;同时将制备的3种LSM阴极材料应用于阳极支撑型固体氧化物燃料电池,组装成单电池,采用四电极法对单电池的输出性能进行了测试和比较．结果表明,溶胶-凝胶法合成的LSM阴极材料在800℃下界面电阻最小。约为3Ω·cm^2,表现出良好的电性能．溶胶-凝胶法合成的LSM阴极材料制备的单电池电化学性能优良,在800℃时,输出功率密度达745mW／cm^2． 相似文献