In: Lithos, 2010, p. -
Oldoinyo Lengai and the volcanic centres of the Lake Natron–Engaruka province contain melilite as a widespread mineral. Extraordinarily Na–Al-rich melilites (up to 6 wt.% Na₂O and 9 wt.% Al₂O₃) from recent explosive eruptions are among the most Na-rich ever reported. Their unusual mineral composition leads to optical properties with vivid birefringence colours of 2nd order. The...
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In: Clays and Clay Minerals, 2009, vol. 57, no. 2, p. 139-149
The influence of Cu(II) on the hydrothermal and thermal transformations of a synthetic hectorite was investigated by a combined approach using mainly X-ray diffraction, thermal analyses, and electron paramagnetic resonance spectroscopy. The presence of Cu(II) during hydrothermal treatment increased the crystallite size. Copper (II) was both structure-bound and associated with the inner surfaces...
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In: Mineralogical Magazine, 2009, vol. 73, no. 3, p. 373-384
Alumoåkermanite, (CaNa)₂(Al,Mg,Fe²⁺)(Si₂O₇), is a new mineral member of the melilite group from the active carbonatite-nephelinite-phonolite volcano Oldoinyo Lengai, Tanzania. The mineral occurs as tabular phenocrysts and microphenocrysts in melilite-nephelinitic ashes and lapilli-tuffs. Alumoåkermanite is light brown in colour; it is transparent, with a vitreous lustre and the streak...
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In: Fuel Cells, 2009///doi: 10.1002/fuce.200800118
Solid oxide electrolyser cells (SOECs) have great potential for efficient and economical production of hydrogen fuel. Element diffusion between the Ni-cermet electrode and the metal substrate of metal supported cells (MSC) is a known problem in fuel cell and electrolysis technology. In order to hinder this unintentional mass transport, different ceramic diffusion barrier layers (DBLs) are...
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In: Advanced Engineering Materials, 2009, vol. 11, no. 8, p. 659 - 666
The infiltration mechanism of X3CrNi13-4 in titanium activated porous alumina preforms has been studied. Investigations revealed isolated steel-covered titanium particles beyond the infiltration front. The only transport path possible for the steel to form such wetted islands is through the gas phase. Supersaturation due to the mixing of the steel gas phase with the titanium rich gas phase...
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In: Advanced Engineering Materials, 2008, vol. 10, no. 5, p. 471 - 475
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In: Ceramics International, 2008, vol. 34, no. 6, p. 1459-1472
The distributions of general and coincidence site lattice (CSL) grain boundaries (GBs) in texture-free alumina and zirconia ceramics sintered at two different temperatures were investigated based on electron backscatter diffraction (EBSD) measurements. Results were compared with the distributions obtained from random 2D spatial models and with calculated random distributions reported in the...
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In: Terra Nova, 2007, vol. 19, no. 4, p. 240-244
For two decades, considerable efforts have been made to explain the formation of snowball garnets by either the rotational or non-rotational models. On the basis of morphological, chemical and crystallographic evidence, this paper presents new data on snowball garnets showing that the formation of these microstructures can be explained by the combination of the two previously proposed mechanisms...
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In: Journal of Materials Research, 2007, vol. 22, no. 5, p. 1414-1424
X-ray computed micro tomography (CT) is an alternative technique to the classical methods such as mercury intrusion (MIP) and gas pycnometry (HP) to obtain the porosity, pore-size distribution, and density of porous materials. Besides the advantage of being a nondestructive method, it gives not only bulk properties, but also spatially resolved information. In the present work, uniaxially pressed...
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Thèse de doctorat : Université de Fribourg, 2002 ; no 1391.
La presente ricerca concerne lo studio dei prodotti ceramici provenienti dai due siti lacustri, del Neolitico finale, di Portalban e St. Blaise, in Svizzera occidentale, relativamente al gruppo culturale "Auvernier-cordé" (2700–2400 a.C.). Questi due importanti siti fanno parte della sequenza della Regione dei Tre Laghi (Neuchâtel, Bienne e Morat), la quale include la completa stratigrafia...
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