Journal ArticleDOI
Transmission electron microscope studies on Li-doped MgO
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In this article, as-grown Li-doped MgO have revealed the presence of precipitates with an average size of 220 A. Detailed micro-diffraction studies and moire pattern analyses have identified these precipitates as Li2O with the cubic fluorite structure.Abstract:
Transmission electron microscope investigations of as-grown Li-doped MgO have revealed the presence of precipitates with an average size of 220 A. Detailed micro-diffraction studies and moire pattern analyses have identified these precipitates as Li2O with the cubic fluorite structure. Exposures of Li-doped MgO crystals either to high temperatures in air for 10 min followed by quenching or to a large dose of ionizing radiation at ambient temperature leads to a reduction in the precipitate size. These results lend support to our previous conjecture from optical and magnetic resonance studies that localized lithium-rich environments are responsible for the stable [Li]0 centres and that the source of these lithium ions are the precipitates.read more
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Journal ArticleDOI
A Critical Assessment of Li/MgO-Based Catalysts for the Oxidative Coupling of Methane
S. Arndt,Guillaume Laugel,Sergey V. Levchenko,Raimund Horn,Manfred Baerns,Matthias Scheffler,Robert Schlögl,Reinhard Schomäcker +7 more
TL;DR: Li/MgO is one of the most frequently investigated catalysts for the oxidative coupling of methane as mentioned in this paper, and it is a suitable system to perform surface science experiments and quantum chemical calculations, which is not possible for many other active catalysts.
Journal ArticleDOI
Analytical electron microscopic studies and positron lifetime measurements in Al‐doped MgO crystals
TL;DR: In this article, large spinel (MgO Al2O3) precipitates were observed in samples with high contents of Al and a well-defined crystallographic relationship between the precipitates and the matrix was found.
Journal ArticleDOI
Computational approaches to the determination of active site structures and reaction mechanisms in heterogeneous catalysts
TL;DR: This work applies quantum chemical methods to the study of active site structures and reaction mechanisms in mesoporous silica and metal oxide catalysts using density functional theory (DFT) and the embedding matrix simulated by shell model potentials.
Journal ArticleDOI
The relationship between catalyst morphology and performance in the oxidative coupling of methane
TL;DR: In this article, a detailed study of the oxidative coupling of methane over magnesium oxide and lithium-doped MgO catalysts is presented, and the morphology of a number of different catalysts has been examined by detailed transmission electron microscopy and the results have been correlated with catalyst performance.
Book ChapterDOI
Surface-Generated Gas-Phase Radicals: Formation, Detection, and Role in Catalysis
TL;DR: In this article, the formation, detection, and role in catalysis of surface-generated gas-phase radicals are discussed, as well as experimental evidence for a radical mechanism and a means of determining the rate limiting step of a catalytic cycle.
References
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Book
Electron Microscopy of Thin Crystals
TL;DR: Hirsch et al. as mentioned in this paper described further experiments on the preparation of thin film sections of embedded Backscatter Kikuchi diffraction in the SEM for identification of crystallographic thin films by electron microscopy.
Journal ArticleDOI
Growth of High‐Purity and Doped Alkaline Earth Oxides: I. MgO and CaO
TL;DR: In this article, a new variation of the carbon arc-fusion technique is reported which makes possible the growth of large, high-purity MgO and CaO single crystals which are free of microbubbles.
Journal ArticleDOI
Stable (Li)/sup 0/ defects in MgO single crystals
TL;DR: The (Li)/sup 0/center has been formed in lithium-doped single crystals of MgO by high temperature quenching as mentioned in this paper, which is stable at room temperature.
Journal ArticleDOI
Trapped-hole centers containing lithium in MgO, CaO and SrO
TL;DR: In this paper, an ESR investigation of a S = 1 2 center in MgO, CaO and SrO consisting of an O − ion neighbored by a substitutional Li + ion is presented.