Isotopic investigations of Chinese ceramics

This chapter provides insights into Chinese ceramic technologies of both bodies and glazes as well as provenance by using isotopes applied to a number of case studies. The use of Sr isotopes to investigate Chinese high-fired Celadon wares and blue-and-white Jingdezhen porcelain (Jiangxi province) has revealed a clear distinction associated with the fluxes used in the glazes: plant ash in celadons and limestone in Jingdezhen glazes, something that is not clear from major element analysis. Furthermore, the technique is able to suggest by implication the nature of the silica source used in the glazes—normally weathered granitic rocks or metamorphic rocks (porcelain stone) which also contains Sr. This leads to an isotopic mixing line of the 2 Sr-rich components and is proof that 2 Sr-rich components were mixed in the manufacture of limestone glaze. This is not the case for plant ash glazes. Eventually, the technique may be used in provenance studies. Like Sr isotope analysis, lead isotope analysis relies on there being a lack of or a minimal change in the isotope ratios when the raw materials are heated. Lead isotope analysis links the use of lead in glazes to the original metal ore and if a kiln uses a distinctive lead source in its glazes, it can provide a provenance for the pottery. This has been very successful in distinguishing Chinese Tang sancai wares made in the Huangye, Huangbao, Liquanfang and Qionglai kilns

Analyse der Entwicklung der mit Neutronenbeugung gemessenen Texturen und des Mikrogefueges von experimentell verformten, polykristallinem Pyrrhotin, Fe(1-x)S Schlussbericht

Available from TIB Hannover: DtF QN1(38,11) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Heteroepitaxial growth of GaN on sapphire substrates by high temperature vapor phase epitaxy

This paper presents recent progress in the development of the high temperature vapor phase epitaxy (HTVPE) for a direct deposition of GaN layers on sapphire substrates and the impact of the improved deposition technique on the quality of the HTVPE GaN layers. This technique uses an improved HTVPE reactor for a better control of the growth process. The reactor contains a newly designed Ga evaporation cell made of refractory metals, which significantly reduces the concentration of process-induced impurities. As a result, the impurity concentrations in the HTVPE layers were reduced to or below 1016 cm−3. For a direct deposition of GaN on (0001)-oriented sapphire, a multi-step process was developed that includes the growth of a nucleation layer and a seed layer, which can be used as a template for further overgrowth with an increased growth rate to produce several ten µm thick GaN layers. The properties of the HTVPE layers are characterized by optical and scanning electron microscopy, glow discharge mass spectrometry, Raman spectroscopy, X-ray diffraction, and photoluminescence. The residual stresses and dislocation densities are presented for seed and overgrown layers, and compared with the properties of layers grown by established methods of chemical vapor phase epitaxy. In this context, challenges and prospects of the HTVPE method are discussed

Synthesis of nanostructured chitin-hematite composites under extreme biomimetic conditions

Chitin of poriferan origin is a unique and thermostable biological material. It also represents an example of a renewable materials source due to the high regeneration ability of Aplysina sponges under marine ranching conditions. Chitinous scaffolds isolated from the skeleton of the marine sponge Aplysina aerophoba were used as a template for the in vitro formation of Fe2O3 under conditions (pH similar to 1.5, 90 degrees C) which are extreme for biological materials. Novel chitin-Fe2O3 three dimensional composites, which have been prepared for the first time using hydrothermal synthesis, were thoroughly characterized using numerous analytical methods including Raman spectroscopy, XPS, XRD, electron diffraction and HR-TEM. We demonstrate the growth of uniform Fe2O3 nanocrystals into the nanostructured chitin substrate and propose a possible mechanism of chitin-hematite interactions. Moreover, we show that composites made of sponge chitin-Fe2O3 hybrid materials with active carbon can be successfully used as electrode materials for electrochemical capacitors