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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical chemistry accounts 72 (1987), S. 485-496 
    ISSN: 1432-2234
    Schlagwort(e): Chemisorption ; TiH ; Electronic structure of metal surfaces ; Hydrogen adsorption ; Titanium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of hydrogen chemisorption on the strength of Ti-Ti bonds is studied byab initio configuration interaction techniques using an embedding theory to describe the electronic structure. A Ti adatom on Ti(0001) is modelled by a Ti20H cluster with boundary potentials determined from the embedding treatment. Hydrogen atom chemisorption is highly exothermic for adsorption atop the adatom, a three-fold site formed by the adatom and in the interstitial site below the adatom. Compared to the planar Ti(0001) surface the adatom region binds hydrogen much more strongly. Removal of Ti from the surface is energetically much more favorable if H remains on the surface as opposed to the removal of TiH. The exchange reaction Ti20+H→Ti19H+Ti is endothermic by 0.3 eV. These results suggest high reactivity of the adatom region on Ti(0001) but not such that the surface is more easily fragmented by removal of Ti or TiH.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 697-703 
    ISSN: 0570-0833
    Schlagwort(e): Chinese porcelain manufacture ; Porcelain ; Intercalation ; Silicates ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The secret of old Chinese porcelain is the technique by which a material, capable of forming extremely thin-walled articles, was obtained from a slightly plastic kaolin. Intercalation compounds, which form by treating kaolinite with decaying urine, give the key to the preparation of this material.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 32-41 
    ISSN: 0570-0833
    Schlagwort(e): Polymerization ; Polyethylene ; Titanium ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A two-component organometallic catalyst of composition CH3TiCl3·CH3AlCl2 effects high-speed polymerization of ethylene in the presence of chlorinated hydrocarbons at low temperatures. The catalyst does not undergo any alteration in the process. In contrast to the Ziegler catalysts, the titanium remains quadrivalent. Olefins of low-molecular-weight and with branched structures are produced. It proved possible to isolate the primary products of the polymerization at -50 to -100°C and to elucidate the mode of their formation from a knowledge of their structures. The findings are incompatible with either a cationic or anionic reaction mechanism. A novel type of mechanism is proposed, whereby the catalyst is supposed to have an ionic structure and molecular growth proceeds via π-complex formation of the olefin with the titanium cation. The formation of ethylene/olefin copolymers is also discussed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 4
    ISSN: 0570-0833
    Schlagwort(e): Silicates ; Silicon ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Starting from a consideration of the “undisturbed” Si—O—Si bond in the modification of silicic acid, the types of bonds present in silicates with polymeric Si—O—Si groups are discussed, taking into consideration the inductive effect of the metal cations. Experimental data on the influence of various substituents in organopolysiloxanes form the basis for this discussion. The bonds in silicates differ by direction and character and are determined by the relative ability of the metal atoms to act as donors and by the degree of condensation of the Si—O—Si bond. It is shown that on this basis, it is possible to explain, for example, why silicates differ in their atomic distances, susceptibility to cleavage by acids, stability relationships, and other properties.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 0570-0833
    Schlagwort(e): Cyclooligomerization ; Butadiene ; Titanium ; Cyclododecatriene ; Cyclooctadiene ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Advances in the fields of synthesis and reactions of some medium-sized hydrocarbon rings are reported and in connection therewith on novel π-complexes of transition metals. Catalytic syntheses yield 1,5,9-cyclododecatriene, 1,5-cyclooctadiene, and 1,5-cyclodecadiene either from butadiene or from butadiene and ethylene. The reactions proceed very readily.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 134-144 
    ISSN: 0570-0833
    Schlagwort(e): Mica-type layered silicates ; Silicates ; Montmorillonite ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Mica-type layer-silicates such as montmorillonite and vermiculite are capable of exchanging their cations for other (including organic) cations, just like the zeolites. These derivatives swell in a variety of liquids. This paper presents a survey of the structures of organic derivatives of mica-type layer-silicates and illustrates some possibilities for their industrial utilization.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 2 (1963), S. 704-714 
    ISSN: 0570-0833
    Schlagwort(e): Titanium ; Alkenes ; Polymerization ; Titanium ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: At low temperatures, ethylene and α-olefins (Δ1-olefins or 1-alkenes) are rapidly converted into oligomrs by the two-component organometallic catalyst CH3TiCl3·CH3AlCl2. To achieve smooth oligomerizations, aromatic or chlorinated hydrocarbons must be used as solvents. Although the activity of the titanium-carbon bond is enhanced by the aluminum component of the catalyst, the aluminum and its methyl group do not participate in the reaction proper; the latter proceeds exclusively at the titanium-carbon bond. The reaction will olefins can be used as an analytical method for the quantitative determination of the titanium-carbon bond in admixture with the organoaluminum component. It is thus possible to follow the reaction leading to formation of the catalyst from titanium tertrachloride, as well as the processes occurring at the titanium-carbon bond during the oligomerization of olefins. All the observations indicate that the catalyst possesses an ionic structure which is determined by the solvent. It is shown that the initial reaction step probably involves formation of a complex between the olefin and the alkyltitanium cation. The reaction scheme proposed is based on organometallic reactions which are characterized by carbanion and hydride transfers within the olefin-cation complex. This mechanism, which is unusual for Ziegler catalysts, is due to the predominance of hydride transfers.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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