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There exists concern that glass-ceramic seal materials may not tolerate the high temperature gaseous environment in solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) applications, potentially leading to the poisoning of electrodes by silica and ultimate loss of hermeticity. A mechanism for the loss of silicon from glass seals has been proposed by other workers. To address this concern, material samples of proprietary glass-ceramics were exposed to steam/hydrogen atmospheres at 800 °C for up to 1000 h. The mass losses of the samples were measured at intervals and their changes in surface chemistry were analyzed using techniques such as X-ray photoelectron spectroscopy and dynamic secondary ion mass spectroscopy. It was shown that the extent of corrosion depends on composition and surface microstructure and that some glass-ceramics are particularly resistant to steam/hydrogen corrosion.

Mo x S 8 (0 ≤ x ≤ 4). -The title compounds are synthesized from mixtures of the elements (1000°C, 96 h) and characterized by high-resolution neutron powder diffraction, powder XRD, thermogravimetry, and magnetic measurements. The compounds crystallize in the cubic space group F43m at ambient temperature. GaV4S8 and GaMo4S8 exhibit a distortion to rhombohedral (R3m) symmetry at low temperatures. Suppression of this distortion at the B-site in GaB 4 S 8 (B: V, Mo) prevents the establishment of a magnetically ordered state in the quaternaries. -(POWELL*, A. V.; MCDOWALL, A.; SZKODA, I.; KNIGHT, K. S.; KENNEDY, B. J.; VOGT, T.; Chem. Mater. 19 (2007) 20, 5035-5044; Dep. Chem., Heriot-Watt Univ., Riccarton, Edinburgh EH14 4AS, UK; Eng.) -W. Pewestorf 49-005

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Single crystals of four erbium-chromium sulfides have been grown by chemical vapor transport using iodine as the transporting agent. Single-crystal X-ray diffraction reveals that in Er(3)CrS(6) octahedral sites are occupied exclusively by Cr(3+) cations, leading to one-dimensional CrS(4)(5-) chains of edge-sharing octahedra, while in Er(2)CrS(4), Er(3+), and Cr(2+) cations occupy the available octahedral sites in an ordered manner. By contrast, in Er(6)Cr(2)S(11) and Er(4)CrS(7), Er(3+) and Cr(2+) ions are disordered over the octahedral sites. In Er(2)CrS(4), Er(6)Cr(2)S(11), and Er(4)CrS(7), the network of octahedra generates an anionic framework constructed from M(2)S(5) slabs of varying thickness, linked by one-dimensional octahedral chains. This suggests that these three phases belong to a series in which the anionic framework may be described by the general formula [M(2n+1)S(4n+3)](x-), with charge balancing provided by Er(3+) cations located in sites of high-coordination number within one-dimensional channels defined by the framework. Er(4)CrS(7), Er(6)Cr(2)S(11), and Er(2)CrS(4) may thus be considered as the n = 1, 2, and infinity members of this series. While Er(4)CrS(7) is paramagnetic, successive magnetic transitions associated with ordering of the chromium and erbium sub-lattices are observed on cooling Er(3)CrS(6) (T(C)(Cr) = 30 K; T(C)(Er) = 11 K) and Er(2)CrS(4) (T(N)(Cr) = 42 K, T(N)(Er) = 10 K) whereas Er(6)Cr(2)S(11) exhibits ordering of the chromium sub-lattice only (T(N) = 11.4 K).

The mechanical properties of magnesium aluminium silicate (MAS) and lithium aluminium silicate (LAS) single fibers were investigated. The fibers were prepared using different methods namely melt drawing (MAS) and continuous drawing (LAS) respectively. The glass ceramic fibers were subjected to the optimized thermal treatments and tested using the single fiber test method (SFT) in order to obtain and evaluate their mechanical properties before and after crystallization. The tested fibers were further characterized by scanning electron microscopy (SEM) and the results showed that the average tensile strength values were a function of the gage length and the fiber diameters.

Phase equilibria established in the PbO -BiVO 4 system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using DTA and XRD.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.