While it is well-established that ionic conduction in lithium aluminosilicates proceeds via hopping of Li ions, the nature of the various hoping-based mechanisms in different temperature regimes has not been fully elucidated. The difficulties associated with investigating the conduction have to do with the presence of grains and grain boundaries of different orientations in these usually polycrystalline materials. Herein, we use electrochemical impedance spectroscopy (EIS) to investigate the ion conduction mechanisms in beta-eucryptite, which is a prototypical lithium aluminosilicate. In the absence of significant structural transitions in grain boundaries, we find that there are three conduction regimes for the one-dimensional ionic motion along the c axis channels in the grains, and determine the activation energies for each of these temperature regimes. Activation energies computed from molecular statics calculations of the potential energy landscape encountered by Li ions suggest that at temperatures below 440 degrees C conduction proceeds via cooperative or correlated motion, in agreement with established literature. Between 440 degrees C and 500 degrees C, the activation barriers extracted from EIS measurements are large and consistent with those from atomistic calculations for uncorrelated Li ion hopping. Above 500 degrees C the activation barriers decrease significantly, which indicates that after the transition to the Li-disordered phase of beta-eucryptite, the Li ion motion largely regains the correlated character.

Protonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency 1 , 2 . Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon- and/or sulfur-containing fuels, resulting in severe performance degradation over time 3 – 6 . Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells 2 , 7 , 8 , there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n -butane, i -butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.

Knowledge of accurate values of elastic modulus of (Al 1-x Sc x )N is required for design of piezoelectric resonators and related devices.Thin films of (Al 1-x Sc x )N across the entire composition space are deposited and characterized.Accuracy of modulus measurements is improved and quantified by removing the influence of substrate effects and by direct comparison of experimental results with density functional theory calculations.The 5%-30% Sc compositional range is of particular interest for piezoelectric applications and is covered at higher compositional resolution here than in previous work.The reduced elastic modulus is found to decrease by as much as 40% with increasing Sc concentration in the wurtzite phase according to both experimental and computational techniques, whereas Sc-rich rocksalt-structured films exhibit little variation in modulus with composition.

BaCo0.4Fe0.4Zr0.1Y0.1O3−δis applied for the first time as a cathode for low-temperature solid oxide fuel cells (LT-SOFCs) with high power densities below 500 °C and 2500 hours stable performance.

Certain alumino-silicates display exotic properties enabled by their framework structure made of corner-sharing tetrahedral rigid units. Using in situ diamond-anvil cell x-ray diffraction (XRD), we study the pressure-induced transformation of β eucryptite, a prototypical alumino-silicate that undergoes a phase transformation at moderate pressures. The atomic structure and symmetry group of the new pressure-stabilized phase has not yet been reported. Based on density functional theory studies and Rietveld analysis of XRD patterns, we find that the new phase belongs to the Pna21 space group and report its atomic structure. Furthermore, we discover two other possible pressure-stabilized polymorphs, P1c1 and Pca21.

Austenitic Stainless Steel is regarded as an important stainless steel in the nuclear industry,and it has excellent property of corrosion resistance. However,there are some non-standard machining,transportation and assembly that can decrease the property of corrosion resistance of austenitic stainless steel during the nuclear main pump production procession,one of the most serious factors affecting the property of corrosion resistance of austenitic stainless steel is the iron contamination of austenitic stainless steel. Thus,it is pivotal to know the source of iron contamination in order to reach the stringent requirements of nuclear power equipment and safe operation of nuclear power station is essential. Therefore,this work summarized the source of iron contamination and its protective measures.