Ti/SnO_2+Sb_2O_4+GF/PbO_X电极的制备及电催化性能研究

采用热分解和电沉积相结合方法制备了Ti/SnO2＋Sb2O4＋GF/PbOX电极,采用三电极体系测定了上述电极在不同溶液中的循环伏安曲线,同时利用循环伏安曲线求得了电极表面的分形维数、活化能和动力学参数等。结果表明该电极电催化性能优于传统电极,是一种优良的电催化剂。     

YBa_(1-x)Ca_xCo_2O_(5+δ)(x=0,0.1,0.15,0.2,0.25,0.3)体系的制备和物性研究

用溶胶凝胶法制备了钙钛矿钴氧化物YBa1-xCaxCo2O5+δ(x=0,0.1,0.15,0.2,0.25,0.3),系统研究了材料的热膨胀性能和电输运性质.结果表明,热膨胀系数随着Ca的掺杂量x的增加而减小,x=0.30掺杂样品在400℃-800℃温区内具有最小的平均热膨胀系数约为12.34×10-6K-1;掺杂样品在中低温下的电输运机制符合小极化子模型,x=0.30掺杂样品也具有较高的电导率约为126Scm-1,在800℃时的热膨胀系数与固体电解质YSZ最相近.     

电弧炉粉尘球团直接还原的热传导模型

对电弧炉炼钢粉尘加上还原剂碳混合制粒成的球团还原过程的热传导行为进行了研究,根据实验推导了球团导热模型的结构参数,并试图建立热传导模型。     

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al-Mg alloys

The mechanisms involved in the grain refinement of Al-Mg alloys through varying the Mg content and applying intensive melt shearing were investigated. It was found that the oxide formed in Al-Mg alloys under normal melting conditions is MgAl₂O₄, which displays an equiaxed and faceted morphology with {1 1 1} planes exposed as its natural surfaces. Depending on the Mg content, MgAl₂O₄ particles exist either as oxide films in dilute Al-Mg alloys (Mg < 1 wt.%) or as naturally dispersed discrete particles in more concentrated Al-Mg alloys (Mg > 1 wt.%). Such MgAl₂O₄ particles can act as potent sites for nucleation of α-Al grains, which is evidenced by the well-defined cube-on-cube orientation relationship between MgAl₂O₄ and α-Al. Enhanced heterogeneous nucleation in Al-Mg alloys can be attributed to the high potency of MgAl₂O₄ particles with a lattice misfit of 1.4% and the increased number density of MgAl₂O₄ particles due to either natural dispersion by the increased Mg content or forced dispersion through intensive melt shearing. It was also found that intensive melt shearing leads to significant grain refinement of dilute Al-Mg alloys by effective dispersion of the MgAl₂O₄ particles entrapped in oxide films, but it has marginal effect on the grain refinement of concentrated Al-Mg alloys, where MgAl₂O₄ particles have been naturally dispersed into individual particles by the increased Mg content.     

Comparison of anodised aluminium surfaces from four fabrication methods

This study presents a comparative analysis of surface characteristics and properties of anodised aluminium cylinders produced by sand casting, permanent mould casting, extrusion, and high pressure die casting. Differences in micro structure and distribution of silicon particles in the aluminium, due to the fabrication method and the silicon content in the alloy, resulted in varying thickness of the oxide layers (mean thicknesses between 7 and 19 μm) and surface topography. The oxide layer was unevenly thick for the permanent mould cast and the sand cast cylinders, resulting in a surface with higher plateaus and lower areas. This was more prominent for the sand cast surface. The oxide of the extruded cylinder was thick and even and its surface was smooth. The high pressure die cast surface had an oxide that was very thin and uneven. The surfaces displayed different results in the scratch test due to the variations in the surface structure. For the permanent mould cast and the sand cast surfaces the silicon particles present in the oxide deflected the cracks that were formed during the scratching. This resulted in smaller wear debris. The nanohardness values of the oxides had a large scattering due to the inhomogeneous nature of the oxide layers, with pores and particles. However, the highest nanohardness values were between 5000 and 6000 MPa for the four surfaces, which is significantly lower than that of sintered alumina. In the micro abrasion test the wear mechanism for all four surfaces was microcutting resulting in chippings.     

穿孔顶头表面氧化膜浅析

分析了穿孔顶头表面氧化膜的形成过程、性质、作用、界面行为，以及对顶头使用寿命的影响。指出了提高该氧化膜耐久性的途径。     

稀土镧、钇对蓝色氧化钨氢还原的影响

借助于ＳＥＭ、Ｘ射线衍射技术及ＩＰＰ粉末粒度仪等系统地研究了稀土镧、钇对蓝色氧化钨（ＢＯ）氢还原的影响。结果表明：稀土元素镧、钇在蓝色氧化钨的还原钨粉中以氧化物及钨酸盐形式存在；还原后所得的钨粉颗粒大多为规则形状的多面体；稀土镧、钇和铝相似，强烈地抑制ＢＯ氢还原钨粉颗粒的长大，而且钇的作用更为显著。     

Thermal behavior of the amorphous precursors of the ZrO2–GaO1.5 system

The amorphous precursors of the ZrO₂–GaO_1.5 system on the ZrO₂-rich side of the concentration range were prepared by co-precipitation from aqueous solutions of the corresponding salts. Thermal behavior of the amorphous precursors was monitored using differential thermal analysis (DTA), X-ray powder diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). Crystallization temperature of the amorphous precursors rose with an increase in the GaO_1.5 content, from 405 °C (0 mol% GaO_1.5) to 720 °C (50 mol% GaO_1.5). The results of Rietveld refinements indicated that the maximum solubility of Ga³⁺ ions in the ZrO₂ lattice (43 mol%) occurred in the metastable products obtained after crystallization of the amorphous precursors. Further thermal treatment caused a decrease of the solubility limits, which became negligible after calcination at 1100 °C. The results of Raman spectroscopy showed that the incorporation of Ga³⁺ ions partially stabilized the tetragonal polymorph of ZrO₂, but could not stabilize its cubic polymorph. The incorporation of Ga³⁺ ions caused a linear decrease in the unit-cell volume of the ZrO₂-type solid solutions, but the rate of the decrease turned out to be smaller than the rate obtained after the incorporation of bigger Fe³⁺ ions.     

Studies on Composite Cathode with Nanostructured Ce0.9Sm0.1O1.95 for Intermediate Temperature Solid Oxide Fuel Cells

A kind of nanostructured Ce_0.9Sm_0.1O_1.95 is prepared by a hydrothermal method. It exhibits large Brunauer‐Emmett‐Teller area (>120 m² g^–1), open mesoporous structure and nanocrystalline sheets. This material shows high activity for oxygen reduction. An area specific resistance below 0.6 Ω cm² at 600 °C is achieved when it is mixed with Ag paste as a composite cathode in a symmetric cell. This is attributed to its large triple phase boundary area and good ionic conducting property. The influences of microstructure, doping, loading effects of silver nanoparticles and the temperature dependence on oxygen reduction kinetics are investigated by the impedance spectroscopy. Although some further optimisations are still required, this special Ce_0.9Sm_0.1O_1.95 material reported here exhibits promising features of applications in the composite electrodes for intermediate temperature solid oxide fuel cells (IT‐SOFCs).     

The interaction of spherical Al2O3 particles with molten Al2O3-CaO-FeOx-SiO2 slags

The present paper investigates the rate of chemical dissolution of Al₂O₃ particles in synthetic Al₂O₃-CaO-FeO_x-SiO₂ slags as a function of time under an atmosphere where Fe²⁺ would be the stable state for iron ions dissolved in the slag. Two aspects of the interaction between the Al₂O₃ spheres and slags were studied, namely (i) the speed at which the particle sinks into the slag and (ii) how rapidly the particles dissolve. The objectives are to elucidate interactions between oxide particulate material, either from the refractory wall or from the mineral constituents in the fuel feedstock, with the slag formed at the wall in entrained-slagging gasifiers.The particle settling was found to proceed first rapidly, but subsequently slowing down and this behavior was in qualitative agreement with model predictions based on a balance between gravity-, drag-, capillary-, and added mass forces. The effect of increasing temperature and FeO_x content are investigated and it is shown that both contribute towards increasing the dissolution rate. The rate appears to be governed by a combination of the driving force for dissolution and transport properties in the slag.