Study of the oxygen electrode reaction using mixed conducting oxide surface layers. Part I: Experimental methods and current-overvoltage experiments

The oxygen gas electrode has been studied for a number of mixed conducting oxide surface layers on top of Gd2Zr2O7 (TGZO) solid electrolytes. In part II of this paper we present the results of frequency dispersion measurements for the electrode reaction, supplying additional information to the results of current-overvoltage experiments presented in part I. For both kinds of experiments the same trends were observed for the electrode polarization. Best results are obtained for a surface layer of TGZO, while p-type mixed conducting oxides give less decreased values of the electrode polarization. High electrode capacitances were found in the case of mixed conducting surface layers (about 700 F/m2). The electrode reactions follow a Butler-Volmer type of equation. Most probably a diffusion process is rate controlling the overall charge transfer process

Oxygen ion and mixed conductivity in compounds with the fluorite and pyrochlore structure

The effect of pyrochlore order in solid solutions with the defect fluorite structure was studied. The amount of order was changed by various heat treatments or by varying the cation composition. Examples of short range order and microdomain-formation have been observed in Tb2Zr2O7+x and Gd2Zr2O7. Pyrochlore order results in a decrease of the activation enthalpy and pre-exponential factor for oxygen ion conduction. The results are explained by a model based on the occurrence of a preferential diffusion path with a low strain energy component in ΔH. Optimal conductivity is achieved in materials which are not completely ordered. Mixed conductivity in Ln2Zr2O7 with P structure can be realized by partial replacement of Ln by Tb. This results in good ionic as well as electronic conductivities

Study of the oxygen electrode reaction using mixed conducting oxide surface layers. Part II: Small signal analysis

The oxygen gas electrode has been studied for a number of mixed conducting oxide surface layers on top of Gd2Zr2O7 (TGZO) solid electrolytes. In part II of this paper we present the results of frequency dispersion measurements for the electrode reaction, supplying additional information to the results of current-overvoltage experiments presented in part I. For both kinds of experiments the same trends were observed for the electrode polarization. Best results are obtained for a surface layer of TGZO, while p-type mixed conducting oxides give less decreased values of the electrode polarization. High electrode capacitances were found in the case of mixed conducting surface layers (about 700 F/m2). The electrode reactions follow a Butler-Volmer type of equation. Most probably a diffusion process is rate controlling the overall charge transfer process

Electric and electrochemical properties of catalytically active oxygen electrode materials

The electrical conductivity has been investigated of some oxygen ion and mixed conducting materials. Electrodes are prepared from thin sputtered layers of these oxides combined with a small Au or Pt strip. The kinetics of the oxygen reaction has been studied for temperatures of 820–1020 K and PO2 values of 10−4 - 1 atm. respectively.\ud Highest oxygen ion conductivities are found in solid solutions of 0.7 Bi2O3−0.3 Tb2O3.5 followed by 0,7 CeO2 - 0.3Tb2O3.5 (CT-30) and (TbxGd1−x) with pyrochlore structure and x=0 (TGZ-0). Highest, p-type, electronic conductivities are found in CT-30 and TGZ with x=1. TGZ-0 was used in all experiments as the solid electrolyte.\ud Combined current-overvoltage (ν) and impedance measurements show that with Au strips the nature of the oxidic materials has a pronounced effect on especially the cathodic polarization, the effect being larger with larger ν. Introduction of p-type conductivity does not decrease the electrode resistance. The Butler-Volmer equation is obeyed with effective cathodic and anodic transfer coefficients close to 0.5 and 1.5 respectively while the effective exchange current varies as the 0.5 power of PO2. These results can be interpreted by a mechanism where charge transfer in the metal-oxide region is rate controlled by surface diffusion on the oxide

Treatment of imported severe malaria with artesunate instead of quinine--more evidence needed?

Rapid and fast acting anti-malarials are essential to treat severe malaria. Quinine has been the only option for parenteral therapy until recently. While current evidence shows that intravenous artesunate is more effective than quinine in treating severe malaria in endemic countries, some questions remain regarding safety profiles and drug resistance. For imported severe malaria, additional unanswered questions are related to generalizability of the findings from endemic countries and to legal aspects, as there is no Good Manufacturing Practice-conform drug available yet. Here, the implications of existing evidence for the treatment of imported severe malaria are discussed

Wet verplichte ggz biedt meer mogelijkheden om zwangeren te begeleiden

Effective Protection of Fundamental Rights in a pluralist worldCoherent privaatrech