Search results for " oxides"

The F-type centres in YAG crystals

2001

The comparative study of optical properties of thermochemically reduced undoped YAG (Y3Al5O12) crystals is reported. A particular type of the centres often observed in YAG crystals synthesized as w...

Optically detected magnetic resonance studied via the blue luminescence of Ti-doped

1998

The UV-excited blue and green luminescence bands of Ti:sapphire are characterized by ODMR. These emission bands are attributed to two centres, which show very similar properties and are created as a result of a charge-transfer transition of an electron from to ions. In both centres, the d electron of and the hole of are strongly coupled and form triplet states. Doublet systems can be ruled out as sources of the blue-green luminescence. The angular dependence of the ODMR can be explained with an appropriate spin Hamiltonian assuming orthorhombic local symmetry. The orientation of the principal axes of the g-tensor and the crystal-field tensor, found for both centres, suggest that the hole is…

Influence of melt flow and temperature on erosion of refractory and deposit formation in aluminium melting furnaces

2002

The deposition and erosion mechanism in induction-channel furnace for Al melting in alumino-silicate refractory is considered. The possibility of simultaneous erosion and deposition in the same cross-section of the channel is shown. The chemical reaction model causing the erosion of refractory is proposed. The erosion process is described by chemically active aluminium oxides while the deposition is caused by chemically stable aluminium oxides. The variations of erosion and deposition in the same cross-section of the channel are explained by variation of the thickness of laminar sub-layer along the perimeter.

Reaktionen an Aluminiumoxiden. 5. Mitt.: Umsetzungen von Cyclohexanon an Aluminiumoxid

1974

Die Umsetzungen von Cyclohexanon (1) an verschiedenen Aluminiumoxiden wurden bei unterschiedlichen Bedingungen untersucht. Die dabei entstandenen Stoffe wurden durch Vergleichssubstanzen mit Hilfe der DC und GC nachgewiesen. Reactions on Aluminium Oxides The reactions of cyclohexanone (1) on various aluminium oxides were investigated under different conditions. The resulting products were identified using synthesized compounds by aid of TLC and GLC.

Properties of native ultrathin aluminium oxide tunnel barriers

2003

We have investigated planar metal–insulator–metal tunnel junctions with aluminium oxide as the dielectricum. These oxide barriers were grown on an aluminium electrode in pure oxygen at room temperature till saturation. By applying the Simmons model we derived discrete widths of the tunnelling barrier, separated by Δs ≈ 0.38 nm. This corresponds to the addition of single layers of oxygen atoms. The minimum thickness of s0 ≈ 0.54 nm is then due to a double layer of oxygen. We found a strong and systematic dependence of the barrier height on the barrier thickness. Breakdown fields up to 5 GV m−1 were reached. They decreased strongly with increasing barrier thickness. Electrical breakdown could…

Cu–Cu interactions in the transparent p-type conductors: CuAlO2 and SrCu2O2

2003

Abstract Electronic structures of the p-type Transparent Conducting Oxides (TCO): CuAlO2 and SrCu2O2 are calculated using the Tight Binding Linearized Muffin Tin Orbital within the Atomic Sphere Approximation method (TB-LMTO-ASA). The band structures indicate two gaps for CuAlO2 (an indirect one with ΔE≈0.45 eV and a direct one with ΔE≈1.25 eV) and one direct gap for SrCu2O2 (with ΔE≈2 eV). In both oxides the Cu states are dominant at the top of the valence band, close to the Fermi level and the existence of weak Cu–Cu bonding interactions is revealed through the Integrated Crystal Orbital Hamiltonian Population (ICOHP). The presence of such interactions suggests that for the hole doped oxi…

New chiral α-aminophosphine oxides and sulfides: an unprecedented rhodium-catalyzed ligand epimerization

2001

International audience; New chiral α-aminophosphine oxide N,P(O) and sulfide N,P(S) ligands have been prepared in one-pot syntheses by addition of Ph2PH to (S)-PhCH[double bond, length half m-dash]NCH(Ph)CH3, followed by oxidation with O2 or S8. Crystallization from cold methanol leads to the isolation of an enantiomerically pure single N,P(O) diastereomer and to a 1 : 1 mixture of the two N,P(S) diastereomers. The coordination chemistry of these ligands with [RhCl(COD)]2 and [RhCl(CO)2]2 has been investigated under argon and syngas. At high temperatures, a P–C oxidative addition of the N,P(O) ligand followed by imine elimination leads to several hydrido rhodium species. The complexes conta…

Characterization of Anodic Oxides on Titanium by Photocurrent and Differential Admittance Techniques

2010

Characterization of Anodic Oxides on Magnetron Sputtered Ta-Nb Alloys by Photocurrent Spectroscopy and Differential Admittance Measurements

2010

Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts

2009

[EN] Alkali metal-doped MoVSbO catalysts have been prepared by impregnation of a MoVSbO-mixed oxide (prepared previously by a hydrothermal synthesis) and finally activated at 500 or 600 degrees C in N-2. The catalysts have been characterized and tested for the selective oxidation of propane and propylene. Alkali-doped catalysts improved in general the catalytic performance of MoVSbO, resulting more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free MoVSbO catalysts. However, the specific behaviour strongly depends on both the alkali metal added and/or the final activation temperature. At isoconversion conditions, catalysts activated at 600 degrees…