Low-temperature solid oxide fuel cells with La1−xSrxMnO3 as the cathodes

La_1−xSr_xMnO₃ (LSM) has been widely developed as the cathode material for high-temperature solid oxide fuel cells (SOFCs) due to its chemical and mechanical compatibilities with the electrolyte materials. However, its application to low-temperature SOFCs is limited since its electrochemical activity decreases substantially when the temperature is reduced. In this work, low-temperature SOFCs based on LSM cathodes are developed by coating nanoscale samaria-doped ceria (SDC) onto the porous electrodes to significantly increase the electrode activity of both cathodes and anodes. A peak power density of 0.46 W cm⁻² and area specific interfacial polarization resistance of 0.36 Ω cm² are achieved at 600 °C for single cells consisting of Ni-SDC anodes, LSM cathodes, and SDC electrolytes. The cell performances are comparable with those obtained with cobalt-based cathodes such as Sm_0.5Sr_0.5CoO₃, and therefore encouraging in the development of low-temperature SOFCs with high reliability and durability.     

制备负载型纳米TiO_2的研究进展

介绍了纳米TiO2光催化剂负载技术的研究进展,负载载体玻璃材料、金属物质、天然矿物等的应用概况以及各种载体的特点.并对常用负载方法及存在的问题进行了简述.     

Structure and properties of dispersion-strengthened-with-nanosized particles refractory hard material TiC—Ni-alloy

Some particularities of the effect of nanocomponents such as ZrO₂,Al₂O₃, W, WC, WC—Co, NbC, Si₃N₄ on the combustion process, the structure, and mechanical properties of a novel electrode dispersion-strengthened alloy TiC—40% Ni have been studied. The refractory hard alloy based on titanium and a nickel alloy has been produced by the method of self-propagating high-temperature synthesis. It has been shown that introduction of a nanosized powder causes reduction of the combustion velocity depending on the specific surface area of the additive. It has been found that upon introduction of nanodispersed powders into the green mixture the product structure undergoes significant modification. The ZrO₂ and NbC additives produce a positive effect on the main mechanical characteristics of the alloy (its strength, hardness, and crack resistance). In contrast, these properties are negatively affected by the Al₂O₃ and Si₃N₄ nanopowders. Enhancement of the material bending strength and crack resistance can be achieved by respective addition of WC—Co and W, WC. © 2003 Elsevier Ltd. All rights reserved.     

Effects of Nb on stress corrosion cracking of high-strength low-alloy steel in simulated seawater

In this study, simulated heat-affected zone (HAZ) of Nb-free and Nb-bearing steel were obtained, and SEM, TEM, and slow strain rate tensile (SSRT) tests were performed to investigate the effect of Nb on the stress corrosion cracking (SCC) behavior of high-strength low-alloy (HLSA) steel in simulated seawater with or without hydrogen charging. The addition of Nb significantly refined the grains and uniformed the microstructure of HLSA. Nb hardly affected the SCC susceptibility of BM and HAZ without hydrogen-charging. However, after charging with 10 mA cm⁻², the SCC resistance of Nb-bearing steel, especially the coarse grain HAZ (CGHAZ) improved drastically, and the process of crack initiation and propagation was inhibited owing to the hydrogen trap function of NbC precipitates.     

Multifunctional macroporous solid oxide fuel cell anode with active nanosized ceramic electrocatalyst

In this work, an alternative anode material, consisting of perovskite-type manganese-doped lanthanum aluminate (La_1.5Al_0.33Mn_0.17O₃), was proposed and implemented. The solid oxide fuel cell anode was produced by the wet impregnation of nanoparticles into a macroporous electrolyte-based scaffold material. The produced cell was characterized by X-ray diffraction and scanning electron microscopy, from which the morphology of the scaffold, the particle size distribution, and porosity were extensively performed and discussed. Electrochemical and electrocatalytic tests were accounted by recording i-V plots with hydrogen or methane as fuels, and by measuring methane conversion rates and C₂ hydrocarbons selectivity.The particle size distribution was confirmed to be submicrometric with the presence of nanoparticles. High levels of porosity (30–35%) were achieved at the scaffold and the cells were able to operate with hydrogen and methane as fuels delivering a power density of around 150 mW.cm⁻² and yielding 30–70% C₂ hydrocarbons selectivity, depending on operational conditions.     

Rethink about electrolyte: Potassium fluoride as a promising additive to an electrolyte for the water oxidation by a nanolayered Mn oxide

Water oxidation is a bottleneck of the hydrogen production through the water-splitting reaction. Herein, the promising role of fluoride on the water-oxidizing activity of a nanolayered Mn oxide under the electrochemical condition is reported. The experiments show the increase of the water-oxidizing activity of the nanolayered Mn oxide under an electro-water oxidation circumstance in the presence of potassium fluoride as a promising additive to an electrolyte. As a result, the required overpotential is decreased and the yield of oxygen evolution raised in the water-oxidation reaction.     

纳米TiO2光催化材料研究新进展

纳米级TiO2作为一种光催化材料,具有广阔的应用领域。优化TiO2的光催化活性,拓宽其应用领域是当今研究的热点。综述了近几年来利用掺杂改性来改善二氧化钛光催化性方面所取得的进展及其在相关领域的应用。     

On the Reliability of Sensitivity Test Methods for Submicrometer‐Sized RDX and HMX Particles

Submicrometer‐sized RDX and HMX crystals were produced by electrospray crystallization and submicrometer‐sized RDX crystals were produced by plasma‐assisted crystallization. Impact and friction sensitivity tests and ballistic impact chamber tests were performed to determine the product sensitivity. Rather than reflecting the quality of the particles, we found the sensitivity tests to be unreliable for submicrometer particles. The used impact test was not accurate enough, while in the friction and ballistic impact chamber tests the submicrometer‐sized crystals were distributed among the grooves of the porcelain plate or among the grains of the sandpaper used in these tests. These observations stress the need for revisiting the current standards used for determining the hazardous properties like friction and impact sensitivity of energetic materials in the case, where the sample consists of submicrometer‐sized crystals. Recommendations were suggested to develop new test methods that only use the interactions between the particles and therefore allow the application of sensitivity tests for submicrometer/nano‐sized energetic materials.     

The application of nanosized silver colloids in far infrared low-emissive coating

In this study, far infrared low-emissive coatings have been prepared using a spin-coated 2-μm layer of commercial inorganic binder under a spin-coat produced from nanosized silver solution, resulting in Ag films of thicknesses between 0.1 and 1 μm. The bilayer coatings were baked at various temperatures for 30 min in air. The 1-μm Ag film baked at 150 °C exhibited an extremely low emissivity of 0.04 in the far infrared range wavelengths of 8 to 14 μm. In addition, this nano-silver paint showed good adhesive strength and the capability to withstand a neutral salt test.     

The photocatalytic activity and stability of a nanosized TiO2 film prepared by carbon black modified method

Regard to the poor adsorbability of the fixing film photocatalyst, we prepared a new nanosized TiO₂ thin film modified by carbon black acting as the pore-forming agent and baked by a kind of new method. The film was characterized by XRD, TEM, SEM, DRS and FT-IR techniques. The results showed that the prepared TiO₂ films were mainly anatase structure, containing a little rutile. Their mean sizes of crystal grains are about 20–30 nm. Comparing to the ordinary TiO₂ film, we found that both carbon black modification and new baking method could make the characteristics of films change, such as more pores, looser structure, smaller crystal grains and longer excitation wavelength. It should be owed to these advantaged characteristics that the photocatalytic activity of the new film was largely improved during the degradation of benzamide. Furthermore, it also had wonderful stability, keeping its activity for 4 months applied to degrade reactive brilliant red X-3B in the continuous flow reactor.