Thermoelectric properties of CoSb3 with maize‐like structure

Maize‐like CoSb₃ powders were obtained via the chemical alloying method. After the consolidation of the nanopowder using hot press, the CoSb₃ compact shows a higher Seebeck coefficient and lower thermal conductivity. For the investigated CoSb₃, a ZT of 0.15 at 673 K is shown. Though the achieved ZT does not reach the optimal value (0.17 to 0.18) for pure CoSb₃, due to its lower electrical conductivity, the novel structure fabrication provides an interesting and promising approach to enhancing the thermoelectric performance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of hydrothermally formed corrosion layers in Ni‐base alloy 625 by combined FE‐SEM and EDXS

During experiments simulating the destruction of organic waste or the conversion of biomass with water at supercritical water conditions (SCW, T > 374 °C, p > 22.1 MPa), severe corrosion phenomena were observed. Depending on the experimental conditions applied, scale formation and precipitation of corrosion products occurred. The harsh conditions and the chemical properties of the feed solutions lead to consecutive chemical reactions with the materials involved. To study such hydrothermal reactions on simplified model systems, tubular reactors made of Ni‐based alloys were exposed to feed solutions composed of water, methanol and alkaline salts. After each experiment, the reaction tubes were cut and examined by optical microscopy. Hydrothermally formed corrosion layers were studied by field emission electron microscopy and combined energy dispersive X‐ray spectroscopy. Element line scans and mappings were performed which depicted selective dissolution of alloying elements (dealloying of Ni, Fe, Mo). The formation of the corrosion layers was accompanied by a subsequent reduction of the tube wall diameter. Atomic force microscopy gained additional morphological information; a Monte Carlo programme was applied to simulate X‐ray line scans. Copyright © 2011 John Wiley & Sons, Ltd.     

Strength and fatigue of some binary and ternary silicate glasses

A survey represented mainly by means of glasses of the borosilicate system shows the generally valid limits of the applicability of the crack growth model and the essential influence of the corrosion of glasses on fatigue. A close correlation between macroscopic crack growth and fatigue was affirmed for samples with fresh, slightly corroded cracks. If the state of corrosion of the samples is advanced, the influence of region 2 is reduced and the fatigue limit is increased. Processes of corrosion during the measurement influence the fatigue curve prevailingly in the range of great time-to-failure, in particular the slope in region 1. The results indicate the high complexity of the effective chemomechanical processes during the fatigue measurements.