Exploring single electrode reactions in polymer electrolyte fuel cells

Utilising a pseudo-reference electrode in polymer electrolyte fuel cells allows for the separation of anodic and cathodic contributions to the entire cell impedance. Modelling the impedance responses by using equivalent circuits inhibits the investigation of kinetic parameters of the basic electrochemical reactions, which take place at single electrode-electrolyte interfaces. Therefore, we evaluate single electrode impedance measurements by a kinetic model, which is based on specific reaction pathways, either for the oxygen reduction reaction (ORR) or the hydrogen oxidation reaction (HOR). As a consequence, it is possible to obtain kinetic parameters for the specific reaction of interest. Furthermore, the information gained from the single electrode impedance measurements and the kinetic model can give insight into single reactions steps. In particular, the ORR has to include a chemical step in the reaction pathway.     

Preparation of NaBiO3 and the electrochemical characteristic of manganese dioxide doped with NaBiO3

NaBiO₃ crystal of high purity has been synthesized through chemical oxidization. The morphology and thermal stability of NaBiO₃ were examined with scanning electron microscope (SEM) and thermogravimetry-differential scanning calorimetry (TG-DSC). The electrochemical properties of MnO₂ electrodes with and without doping NaBiO₃ were studied through galvanostatic charge/discharge and cyclic voltammetry. The results indicate that the MnO₂ electrode doped with NaBiO₃ possesses remarkably higher discharge voltage and capacity and better reversibility than the pure MnO₂ electrode and Bi₂O₃ doping MnO₂ electrode.     

苎麻落麻纤维增强热固性树脂复合材料的制备及性能研究

本文介绍了落麻纤维、落麻热压毡、落麻无纺毡制备热固性树脂复合材料的工艺过程;比较了这三种复合材料的力学性能;结果表明,用无纺毡制备复合材料的方法可较大幅度提高纤维含量,能较好地解决落麻纤维在复合材料中的分散问题.     

Preparation of a Novel Composite Material Based on a Nafion® Membrane and Polypyrrole for Potential Application in a PEM Fuel Cell

The process of embedding polypyrrole (PPy) on the surface of a Nafion^® membrane was studied. Three methods of PPy synthesis directly on the membrane surface were compared. The diffusion method based on the separation of monomer and oxidant (peroxidisulphate) solutions by the membrane to be modified is proposed as the most promising one. The monomer diffuses through the membrane to the oxidant side, where it is polymerized. In this case sulphate is incorporated into the film as a counter-ion. PPy film prepared in this way adheres well to the Nafion^® surface and shows promising electrochemical activity. The permeability of the composite for monomer in comparison to self-standing Nafion^® film is reduced significantly. This may be important for the potential application of this composite, especially in a direct methanol fuel cell, as an alternative membrane-electrode assembly (MEA), particularly with regard to the currently used MEA’s permeability for fuel.     

Flow pattern measurement in a full scale silo containing iron ore

The flow pattern in a silo is important because it affects both the recovery of solids and the pressures on the silo wall during discharge. Wherever mass flow is not achieved, the boundary of the flow channel has significant implications for both the functional and structural design of the silo. Many techniques have been used for the study of flow patterns in model silos, but most cannot be used at full scale, and very few quality measurements at full scale have ever been made. This paper outlines a full scale experimental study in which the patterns of solids flow and the flow channel boundaries are reliably quantified.The full scale silo was specially designed, constructed and instrumented to exhibit funnel flow and to make observations of the solids flow pattern and the silo wall pressures. It had three outlets: one concentric, one fully eccentric and one in between. Three materials were used: iron ore pellets, slag fines and crushed basalt. This paper describes experiments involving iron ore pellets. The silo was seeded with radio frequency tags whose residence times were measured by detecting them on exit during discharge. The residence time data were studied to deduce the discharge flow pattern. This paper presents the results of three different flow pattern interpretation techniques: the best of them (mass-time relationships) is shown to give a very clear identification of the solids flow pattern and the flow channel boundary.     

Ni/Al_2O_3覆膜方法

阐述了Ni/Al2 O3 复合颗粒在生产中的应用 ,讨论了在Al2 O3 陶瓷颗粒上形成Ni膜的三种方法 ,分析了这些方法的优缺点。     

矿渣复合助磨剂的实验研究

在相同的粉磨条件下，研究了数种复合助磨剂（三乙醇胺十无机盐类）对矿渣的助磨效果，每隔0．5h测定其比表面积并与空白样品对比；然后对所得矿粉用图像分析仪和扫描电镜进行了形貌分析。同时又研究了三乙醇胺系复合助磨削时矿渣-水泥体系的标准稠度用水量、凝结时间、胶砂强度等性能的影响。结果表明：（1）复合矿渣助磨剂的助磨效果优于单一助磨剂，对矿渣水泥的性能无损害且能够提高胶砂强度；（2）无机盐的取代在一定程度上能够降低助磨剂的成本。     

气干型不饱和聚酯树脂

气干型不饱和聚酯树脂是常温交联的热固性树脂。其性能优良，光泽度高，丰满度好，是优良的饰面材料。它的组成的原子灰，是理想的更新换代产品，广泛适合于金属基材的嵌填。     

Surface modification of macroporous Al2O3 tubes with carbon-doped TiO2 intermediate layer and preparation of highly permeable palladium composite membranes for hydrogen separation

ABSTRACT

To prepare H₂-permeable palladium composite membranes, a novel carbon-doped microporous TiO₂ intermediate layer was introduced to modify the surface of macroporous Al₂O₃ substrates. The Pd/TiO₂–C/Al₂O₃ membrane was prepared via electroless plating, and thereafter, carbon residue in the intermediate layer was removed by calcination in air, yielding a Pd/TiO₂/Al₂O₃ membrane. Experimental results indicate that the carbon residue shrinks the pore size of the intermediate layer and facilitates a decrease of membrane defects. Additionally, carbon removal induces a higher effective membrane area at the permeate side, which enhances hydrogen permeability. Furthermore, the apparent activation energy (E_A) and stability of the as-prepared Pd/TiO₂/Al₂O₃ membrane were investigated.     

Cinétique de dégagement des matières volatiles lors de la pyrolyse d'électrodes de carbone industrielles

In aluminium plants, the anode baking process is associated with an important release of volatile combustible matter. It is the purpose of this study to investigate the kinetics of the evolution of these volatiles. A large thermogravimetry set-up has been designed in such a way that it could simulate real plant conditions. Samples of two distinct masses have been subjected to pyrolysis at different heating regimes. The loss of weight together with the concentrations of the released gases were recorded on a continuous basis during the temperature rise. Kinetic results were found for methane, hydrogen and tar. No variation of the order of reaction with the heating rate was observed, whereas the activation energy and the pre-exponential factor increased. Furthermore, for the range of sample dimensions studied, it was found that the mass of the solid had no significant influence on the kinetic parameters.