Influence of the La6W2O15 Phase on the Properties and Integrity of La6-xWO12-x Based Membranes

The aim of the present work is to evaluate the influence of La6W2O15 secondary phase on the properties and integrity of La6-xWO12-δ–based membranes. Structural, microstructural and thermo–chemical study was carried out evidencing significant crystallographic and thermal expansion anisotropy: the reason for poor thermo–mechanical stability of La6W2O15. Conductivity of La6W2O15 was one to two orders of magnitude lower compared to the phase pure La6-xWO12-δ in the range of 300 to 900 °C. The relaxation study showed that the hydration process was faster for the La6W2O15 compared to the LWO phase, due to the higher electronic contribution to the total conductivity. Short–term stability tests in H2 at 900 °C and in a mixture of CO2 and CH4 at 750 °C were conducted and material remained stable. Remarkable reactivity with NiO and YSZ at elevated temperatures was further evidenced compared to the relative inert behavior towards MgO and CGO.Ivanova, ME.; Seeger, J.; Serra Alfaro, JM.; Solis Díaz, C.; Meulenberg, WA.; Fischer, W.; Roitsch, S.... (2012). Influence of the La6W2O15 Phase on the Properties and Integrity of La6-xWO12-x Based Membranes. Chemistry and Materials Research. 2(1):56-81. http://hdl.handle.net/10251/80837S56812

Internal capsule size associated with outcome in first-episode schizophrenia

Subtle structural brain abnormalities are an established finding in first-episode psychosis. Nevertheless their relationship to the clinical course of schizophrenia is controversially discussed. In a multicentre study 45 first-episode schizophrenia patients (FE-SZ) underwent standardized MRI scanning and were followed up to 1 year. In 32 FE-SZ volumetric measurement of three regions of interests (ROIs) potentially associated with disease course, hippocampus, lateral ventricle and the anterior limb of the internal capsule (ALIC) could be performed. The subgroups of FE-SZ with good (12 patients) and poor outcome (11 patients), defined by a clinically relevant change of the PANSS score, were compared with regard to these volumetric measures. Multivariate analysis of covariance revealed a significant reduced maximal cross sectional area of the left ALIC in FE-SZ with clinically relevant deterioration compared to those with stable psychopathology. There were no differences in the other selected ROIs between the two subgroups. In conclusion, reduced maximal area of ALIC, which can be interpreted as a disturbance of fronto-thalamic connectivity, is associated with poor outcome during the 1 year course of first-episode schizophrenia

Entwicklung und Erprobung einer Anlage zur Untersuchung der Permation von Wasserstoffisotopen unter nuklearen Prozeßgasbedingungen

The concept and the effort of the research installation, designed for simulation of the permeation of hydrogen isotopes (protium and tritium) through the elements of heat exchanger of a HTR-process heat system, are presented. The experimental results show that the thin oxide scale in situ grown on the surfaces of austenitic high temperature resistant alloys can hinder the hydrogen permeation up to the level above three orders of magnitude. The enhancement of this effect due to oxidation of both surfaces of investigated materials, as deduced from the previous model calculations can be also conluded from the presented results

Wasserstoffpermeation durch Chrom

Steady state and non-steady state measurements of hydrogen permeation through metallic chromium are reported. The experimentshave been conducted by use of hydrogen and deuterium within a pressure range of 10$^{-8}$ - 1 bar and temperatures between 600 - 800 ° C. Numerical values for the physical quantities permeability, diffusion constant and solubility could be derived. At an upstream pressure above around 10$^{-3}$ bar classical Sieverts-low was found (permeation rate $\backsim$ $\sqrt{p}$) with activation energies Q$_{perm}$ - 65 kJoule/mole, Q$_{Diff}$ = 4-8 kJoule/mole, Q$_{Sol}$ = 57-61 kJoule/mole for the respective processes involved. The isotopic effect between H and D of the permeabilities could be represented by a factor of 1,5 indepent on temperature. All non steady-state measurements could be approximated reasonably well by classical diffusion kinetics. Below up-stream pressures of $\backsimeq$ 10$^{-7}$ bar the kinetics was no longer diffusion controlled, the dependence on up-stream pressure changed from $\sqrt{p}$ $\rightarrow$ p, the activatian energy for permeation increased to 127 kJoule/mole and - the isotopic factor resulted in about 2-3

Effects of production method and space holder material on microstructure of porous titanium

The use of space holder particles is now a well-known and common method for production of porous titanium implants. It is possible to control porosity and pore structure by the use of a variety of spacer materials available. However, adaptation of the space holder method to near net-shape processing techniques such as metal injection molding (MIM), necessitates some specifications for space holder selection. In this work, those specifications for MIM processing were defined and the use of alternative space holders was investigated. Titanium foams were produced via two different methods, namely, warm pressing in the presence of a binder system and cold isostatical pressing without binders. Microstructures of the titanium foams produced via different methods and varying space holders were comparatively examined

Ein Versuch zur phänomenologischen Beschreibung der Wasserstoffpermeation durch Stähle und ihre Behinderung durch Oxidfilme

Experiments are presented investigating the action of corrosion scales on several steels against hydrogen and tritium permeation. We are interested in such model experiments to learn how to prevent tritium permeation from the primary circuit of an HTR to the secondary side. The same problem might be of some importance in later fusion reactor technology. Our corrosion scales were formed in a temperature range between 500° C and 950° C under varying steam hydrogen mixtures. Thickness of the scales was up to several ym. By adequate choice of the "process" parameters we succeeded to produce oxid scales with relativ high reduction factors for hydrogen permeation as compared with the permeation through the blank metal surfaces. Such scales also show a linear correlation between hydrogen pressure and permeation and an increased activation energy for permeation as compared to that of the blank metal. Our observations cast doubt on elder theories trying to explain the action of oxide films. We try here to apply a formalism presented first by Ash and Barrer to describe our findings. According to our experiments we believe that oxide scales formed under the conditions prevailing here act rather as a "dissociationbarrier" than as a "diffusionbarrier". We try here for the first time to describe the influence of the hydrogen permeation on the tritium permeation of the opposite side, (this is exactly the problem we normally encounter in the case of an HTR for process heat application). Our theoretical explanation shows on the one hand possibilities for producing very high reduction factors e.g. by producing oxide scales on both sides of a heat exchanger tube whereby tritium permeation may be reduced to acceptable levels in a HTR process heat plant, on the other side the models described here, give a sounder base to calculate tritium release in such plants and may be in later fusion reactor blanket configurations

Review of physical properties of NASICON materials for use in sodium batteries

The environmental concerns about the use of fossil fuels and their resource constraints have led to a great interest in renewable energy sources and new electrical energy storage systems. One promising solution is the electrochemical storage of electricity in batteries. Among all rechargeable battery technologies, the Li-ion cells offer the largest energy density and output voltage. But recently, Na-ion batteries are back in the focus of interest due to the abundant availability of Na instead of the limited resources of Li. However, much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. NASICON materials (sodium super ionic conductors) are a thoroughly-studied class of solid electrolytes for Na-ion batteries. In this study, their structure, compositional diversity and ionic conductivity are reviewed in order to correlate the lattice parameters and specific crystal structure data with the sodium mobility and the activation energy. For approximately 150 structures with the general formula Na1+x+yMxM’2-xSiyP3-yO12 (M and M’ di-, tri-, tetra- or pentavalent cations) an optimal size for M and M’ could be found and the impact on the conductivity of the amount of Na per formula unit could be pointed out. This understanding will be useful for the search of new and improved NASICON materials. An extensive study of the size of the structural bottleneck for the sodium conduction (formed by triangles of oxygen ions) has been made to validate the influence of this geometrical parameter on the sodium mobility