Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Activation possibilities and geochemical correlations of photoluminescing carbonates, particularly calcites (1975)
    Springer
    Mineralium deposita 10 (1975), S. 216-227 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract We studied carbonates of mainly postmagmatic origin. As a result of extensive measurements of the absorption spectra, light of λ=253 nm of a Xenon lamp was used for excitation. The emitted luminescence was measured by a photometer. Luminescence of considerable intensity is exhibited by calcites, aragonites, smithsonites, strontianites as well as by witherites and cerussites. Calcites have the most strongly differentiated spectrum. Each of their five different luminescence types is caused by a special activation. Particularly characteristic are calcites, whose luminescence is activated (a) by lattice defects and/or Zn-contents (broad emission band with maximum at about 420 nm), (b) by Mn/Pb-substitution (maxima at 325 and 420 nm), (c) by REE (maxima at 340–360, 480, 545, 575, 623 and 670 nm). The other, also luminescing carbonates, show a close relationship to the calcite of the ‘fundamental type’ (a) but with varying position of their emission maxima. Also most of the phosphorescing samples of calcite are of this type (a). The majority of these calcites originate from telethermal, surface-near formation regions and from resolutions, respectively. Fe, Ni, and in the case of smithsonite also Cu, are ‘killing elements’, which are less efficient by REE-activation than by Mn/Pb-activation. In particular phosphorescence and activation by lattice defects will be disturbed. The luminescence analysis represents a possibility for mineral identification. Furthermore it gives criteria for chemical homogenity of minerals, and locates concentrations of certain elements in inhomogeneous samples. For the most important activators it is a tool for qualitative element detection, especially in the case of REE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207138
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    NMR-spectroscopy of synthetic potassium-bearing cordierites (1992)
    Springer
    Physics and chemistry of minerals 18 (1992), S. 383-388 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Potassic cordierites with the chemical composition K x Mg2Al4+x Si5−xO18 (x = 0.00, 0.10, 0.20, and 0.25) were synthesized by annealing glasses at 1290° C for different lengths of time. The procedure resulted in cordierites with different states of Al,Si-order for the tetrahedral sites in the structure. The dependence between the potassium-content and the state of order on one side and between annealing time and the state of order on the other side was then studied using 29Si MAS nuclear magnetic resonance (NMR) spectroscopy. The spectra show that the state of order is a continuous function of annealing time for all compositions considered, but the rate of ordering decreases with increasing K-content. Since the substitution K+Al →Si leads to higher Al/Si-ratios; the lower rate of ordering is discussed as a consequence of changed statistics for Al, Si site exchanges. The Al atoms replacing silicon in the structure to balance the charge of potassium cations are not located close to the potassium ion but at a maximum distance from it. This is shown to be a consequence of an improvement in coordination of all oxygen atoms in the cordierite framework.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199420
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    NMR, XRD and IR study on microcrystalline opals (1994)
    Springer
    Physics and chemistry of minerals 21 (1994), S. 166-175 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Microcrystalline opal-CT and opal-C were investigated by 29Si MAS NMR and 29Si {1H} cross polarisation MAS NMR spectroscopy, X-ray small angle scattering, X-ray powder diffraction and infrared absorption spectroscopy. The results are compared with those for non-crystalline precious opal (opal-AG), non-crystalline hyalite (opal-AN), moderately disordered cristobalite and with well ordered low-cristobalite and low-tridymite. Opal-C is confirmed to be strongly stacking disordered low-cristobalite with about 20 to 30% probability for tridymitic stacking. More extensively stacking disordered opal-CT does not contain detectable domains of low-cristobalite or low-tridymite. The stacking sequence is close to 50% cristobalite and 50% tridymitic. The local order decreases with increasing stacking disorder, so that the structural state of microcrystalline opals lies between cristobalite, tridymite and non-crystalline opals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203147
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    1-Aminoadamantane as guest molecule in dodecasil 1H: an X-ray crystallographic study (1986)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 4 (1986), S. 85-91 
    Details
    ISSN: 1573-1111
    Keywords: clathrasil ; tectosilicate ; 1-aminoadamantane ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dodecasil 1H, 34SiO2 · 3M12 · 2M12′ · 1M20 with M12, M12′=N2 and M20=1-aminoadamantane, is hexagonal witha=13.825(2) Å,c=11.189(2) Å and crystallizes in space groupP6/mmm. With 767 unique reflexions the structure has been refined to a weighted reliability factorR w =0.054. The three-dimensional four-connected host framework is built by corner sharing [SiO4] tetrahedra and shows three types of cagelike voids, [512] cages, [435663] cages and [51268] cages, the latter housing the 1-aminoadamantane guest molecule. Difference Fourier synthesis ρ(obs)-ρ(calc(Si,O)) delineate the guest molecules within the different types of cage. Residual electron densities reveal positional disorder of the 1-aminoadamantane guest molecule. Four crystallographically different preferred orientations for the 1-aminoadamantane guest molecule are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00662085
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Studies on clathrasils VIII. Nonasils-[4158], 88SiO2 · 8M8 · 8M9 · 4M20: Synthesis, thermal properties, and crystal structure (1986)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 4 (1986), S. 339-349 
    Details
    ISSN: 1573-1111
    Keywords: Clathrasil ; nonasil ; synthesis ; crystal structure ; porous silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nonasils-[4158], 88SiO2·8M8·8M9·4M20, have been synthesized with 2-methylpyrrolidine, hexamethyleneimine, 2-(aminomethyl)-tetrahydrofuran, 1,2-diaminocyclohexane, 2-methylpiperidine, 2-methylpiperazine, 1-aminobutane, 2-aminobutane, and 2-aminopentane as guest molecules, M20. The samples have been prepared from aqueous silicate solutions which were sealed in silica tubes and heated at about 200°C for several weeks. These clathrasils crystallize in space groupFmmm. For the nonasil with 2-aminopentane as the guest molecule and the unit cell dimensionsa o=22.232(6) Å,b 0=15.058(4) Å, andc o=13.627(4) Å, the structure has been refined using 550 non-equivalent single crystal reflexions to a reliability factorR w =0.125. The 3-dimensional 4-connected silica host framework has three types of cage-like voids, [5464], [4158], and [58612], the latter housing the structure-controlling guest molecules, M20. The non-spherical shape of the guest molecules is the most important factor for the formation of nonasils-[4158]. On heating nonasils-[4158] up to 950°C the organic guest species are driven out and the pure silica form of nonasil is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656161
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Synthesis, crystallographic, and thermal properties of a new porous silica (1987)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 5 (1987), S. 283-287 
    Details
    ISSN: 1573-1111
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new porous tectosilicate has been synthesized in the presence of boric acid and 1, 2, 2, 6, 6-pentamethylpiperidine as guest molecules. It crystallizes in the monoclinic system with ao=9.91 (1) Å, bo=20.62 (3) Å, co=9.80 (2) Å, and β-99.7 (2)0. After heat treatment at 820°C for 1 hour the guest molecules are set free whereas the silica host framework is retained. From crystal morphology and thermal behaviour it is concluded that the new material possesses channel-like voids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655666
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Studies on clathrasils: VII. A new clathrate compound of silica: Synthesis, crystallographic, and thermal properties (1984)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 2 (1984), S. 275-278 
    Details
    ISSN: 1573-1111
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using l-aminoadamantane a new type of silica host framework has been stabilized. The clathrasil is rhombohedral with a=13.887Å and c=40.989Å for the hexagonal unit cell. Heating the compound on a thermal analyser shows that from 500°C on the guest molecule evaporates. The silica framework only very slowly breaks down when heated at 1100°C for several hours yielding cristobalite. Since l-aminoadamantane stabilizes, at higher temperatures of synthesis, dodecasil 1H the new clathrasil is regarded as low temperature form for this particular guest molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00663266
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    A29Si NMR study of natural and synthetic melanophlogites, the silica analogues of the clathrate hydrates of type I (1990)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 8 (1990), S. 235-239 
    Details
    ISSN: 1573-1111
    Keywords: Melanophlogite ; 29Si NMR ; phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 29Si MAS NMR spectra of natural melanophlogite as well as of synthetic melanophlogite indicate that the room temperature lattice structure has lower symmetry than expected from its proposed crystal structure. On heating the samples to temperatures above room temperature, the structure undergoes a reversible phase transition with a transition temperature characteristic of the locality. For the synthetic melanophlogite, the transition is over the range 298 K to 338 K. From low temperature NMR spectra it is concluded that the low temperature forms of synthetic melanophlogite and of melanophlogite from Sicily differ in their crystal lattice symmetries due to their characteristic guest species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01131300
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Chemisches Kolloquium Marburg-L (1951)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 63 (1951), S. 312-313 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19510631307
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Studies on Clathrasils. X. The effect of “help gases” on the formation and stability of clathrasils (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 546 (1987), S. 189-198 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen an Clathrasilen. X. Der Einfluß von Hilfsgasen auf die Bildung und Stabilität von ClathrasilenEs wurden Vertreter jeder der bisher bekannten Clathrasil-Familien unter Hydrothermalbedingungen aus wäßrigen Kieselsäure-Lösungen in Gegenwart ihrer charakteristischen Gastmoleküle und unter Ausschluß von Luft synthetisiert. Die kleinen Käfige im Tetraedergerüst dieser Produkte sind leer, während sie bei Synthesen in Anwesenheit von Luft mit Stickstoff gefüllt sind. Außer den Clathrasilen wurde Silica-ZSM-48 erhalten, wenn unter Luftausschluß Pyrrolidin als Gastmolekül verwendet wurde. Es zeigt sich, daß die kleinen Moleküle von „Hilfsgasen“ wie Stickstoff nur einen geringen Einfluß auf die Stabilisierung der Clathrasil-Gerüste haben. Dies steht im Gegensatz zur Bedeutung von „Hilfsgasen“ für die Stabilisierung einiger Clathrathydrate. Die Bildungsgeschwindigkeit von Clathrasilen bei Synthesen in Gegenwart und unter Ausschluß von Luft werden miteinander verglichen.
    Notes: Members of all known clathrasil families have been synthesized from aqueous silica solutions under hydrothermal conditions in the presence of their characteristic guest molecules and in the absence of atmospheric gases. The small cages of the products, otherwise filled with nitrogen, were found to be empty. In addition to clathrasils, silica-ZSM-48 was obtained as a reaction product in the absence of atmospheric gases and pyrrolidine as the guest. It appears that small “help gas” molecules such as nitrogen play only a minor role in the stability of clathrasil frameworks unlike in the case of some clathrate hydrates. A comparison of rates of formation of clathrasils synthesized in air and in the absence of “help gases” is also presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19875460321
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...