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  • 1
    Electronic Resource
    Electronic Resource
    TiO2-Based Porous Materials Obtained from Gels, in Different Experimental Conditions (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 249-253 
    Details
    ISSN: 1573-4846
    Keywords: porous materials ; TiO2 films ; titanium isopropoxide ; sol-gel method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gels which are precursors of TiO2 porous materials are prepared by the controlled hydrolysis-condensation of titanium isopropoxide by polymeric method. In the present work, a study of the influence of different experimental conditions (water/alkoxide ratio, solvent/alkoxide ratio and temperature) on the structure and texture of the polymeric gels obtained with the same type of alkoxide has been investigated. The structural and textural modifications for the unsupported materials have been detected using DTA/TGA, XRD, specific surface area and pore size computerized measurements. The optical properties of the supported materials deposited on silicon wafers have been investigated using ellipsometric method. Supported and unsupported porous materials with different structure and texture have been obtained depending on different experimental and thermal treatment conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026449910325
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Hydrolysis-Polycondensation in Binary Phosphorus Alkoxides—TEOS System Studied by GC-MS (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 59-63 
    Details
    ISSN: 1573-4846
    Keywords: SiO2-P2O5 sol-gel system ; P-precursor reactivity ; GC-MS investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is well known that various phosphorus precursors exhibit different reactivities towards hydrolysis-polycondensation in acidic media. The hydrolysis-condensation in binary P-alkoxides—TEOS system was studied by GC-MS, in relation to the mentioned reactivity. As P-precursors, the following reagents were used: PO(OMe)3, PO(OEt)3, PO(OBu)3, P(OEt)3 and HOP(OMe)2. PO(OMe)3, PO(OEt)3 and PO(OBu)3 do not hydrolyze, but change the TEOS hydrolysis-polycondensation ratio. P(OEt)3 partially hydrolyzes and transforms into a very stable HOP(OEt)2 form, while HOP(OMe)2 reacts very fast with nonparental solvent and undergoes transesterification. Si–O–P bonds have not been observed in early stages of hydrolysis-polycondensation. However, the gelling tendency is strongly influenced by the P-precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026438820378
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Solid State Phase Formation in the Bi2O3-PbO-CaO System (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 125-130 
    Details
    ISSN: 1572-8943
    Keywords: Bi2O3-PbO-CaO system ; DTA ; solid-state reactions ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Following our previous research, this work is dedicated to the study of phase formation in the subsolidus domain of the Bi2O3-PbO-CaO system. Former investigations performed by DTA/TGA and XRD have pointed out that under non-isothermal conditions only the formation of binary compounds occurs. Under such conditions these compounds could be non-equilibrium phases. In order to establish the conditions of formation of equilibrium phases, a study of the Bi2O3-PbO-CaO system, in isothermal conditions, was carried out. The results obtained in isothermal conditions have confirmed the presence of Bi2O3-rich solid solutions and Ca2PbO4 as main equilibrium phases. An attempt to represent the phase relations of the mentioned system at 700°C should be equally mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010199728644
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of the decomposition of calcium carbonate in the presence of Bi2O3 (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 569-575 
    Details
    ISSN: 1572-8943
    Keywords: Bi2O3 ; CaCO3 decomposition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3. The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983998
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal Stability of SiO2-Based Inorganic-Organic Hybrid Materials (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 191-198 
    Details
    ISSN: 1572-8943
    Keywords: inorganic-organic hybrids ; molecular species ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrolysis-polycondensation of organically modified Si-alkoxides leads to the obtaining of inorganic-organic hybrid materials in which the organic moieties remain as permanent groups bonded to the inorganic network. The molecular species previously determinated by GC-MS during the gelation process have been significantly different according to the type of the alkoxide used. In the present work, thermal stability of SiO2-based inorganic-organic hybrid materials starting with TEOS (tetraethoxysilan), MTEOS (triethoxymethylsilan), VTEOS (triethoxyvinylsilan) and MTMOS (trimethoxymethylsilan) was studied. The molecular structure of the gels obtained determines differences in their thermal behaviour. Gels obtained starting with MTEOS show the highest thermal stability, while gels obtained using VTEOS the lowest, among the substituted alkoxides. A particular behaviour presents the gel obtained with MTMOS that decomposes in four steps. This could be explained by the presence in the gel of some prevalent types of molecular species with different thermal stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010132703144
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Contributions to the Gelling Process in the Bi-Sr-Ca-Cu-O System, Via Acetate Route (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; acetates ; Bi-based superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metal acetates represent suitable precursors in the sol-gel method. Generally, acetates are used in multicomponent systems with alkoxides or other carboxylic salts. However, Bi-Sr-Ca-Cu-O superconductors have been obtained by the sol-gel method starting only from acetate mixture. This work was intended to study the gelling process of acetates involved in the formation of bismuth-based superconducting phases, both individually and in the bi- and multicomponent systems. Probably, copper acetate is mainly responsible for the gel formation in these systems. The gelling process was monitored by measuring the pH, density and viscosity changes. The gels obtained were characterized by UV-VIS and IR spectra, DTA/TGA and powder X-ray diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018388730256
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    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Hydrolysis-polycondensation in binary phosphorus alkoxides—TEOS system studied by GC-MS (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 59-63 
    Details
    ISSN: 1573-4846
    Keywords: SiO2−P2O5 sol-gel system ; P-precursor reactivity ; GC-MS investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is well known that various phosphorus precursors exhibit different reactivities towards hydrolysis-polycondensation in acidic media. The hydrolysis-condensation in binary P-alkoxides—TEOS system was studied by GC-MS, in relation to the mentioned reactivity. As P-precursors, the following reagents were used: PO(OMe)3, PO(OEt)3, PO(OBu)3, P(OEt)3 and HOP(OMe)2. PO(OMe)3, PO(OEt)3 and PO(OBu)3 do not hydrolyze, but change the TEOS hydrolysis-polycondensation ratio. P(OEt)3 partially hydrolyzes and transforms into a very stable HOP(OEt)2 form, while HOP(OMe)2 reacts very fast with nonparental solvent and undergoes transesterification. Si−O−P bonds have not been observed in early stages of hydrolysis-polycondensation. However, the gelling tendency is strongly influenced by the P-precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436818
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    TiO2-based porous materials obtained from gels, in different experimental conditions (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 249-253 
    Details
    ISSN: 1573-4846
    Keywords: porous materials ; TiO2 films ; titanium isopropoxide ; sol-gel method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gels which are precursors of TiO2 porous materials are prepared by the controlled hydrolysis-condensation of titanium isopropoxide by polymeric method. In the present work, a study of the influence of different experimental conditions (water/alkoxide ratio, solvent/alkoxide ratio and temperature) on the structure and texture of the polymeric gels obtained with the same type of alkoxide has been investigated. The structural and textural modifications for the unsupported materials have been detected using DTA/TGA, XRD, specific surface area and pore size computerized measurements. The optical properties of the supported materials deposited on silicon wafers have been investigated using ellipsometric method. Supported and unsupported porous materials with different structure and texture have been obtained depending on different experimental and thermal treatment conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436848
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Contributions to the gelling process in the Bi−Sr−Ca−Cu−O system, via acetate route (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; acetates ; Bi-based superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metal acetates represent suitable precursors in the sol-gel method. Generally, acetates are used in multicomponent systems with alkoxides or other carboxylic salts. However, Bi−Sr−Ca−Cu−O superconductors have been obtained by the sol-gel method starting only from acetate mixture. This work was intended to study the gelling process of acetates involved in the formation of bismuth-based superconducting phases, both individually and in the bi-and multicomponent systems. Probably, copper acetate is mainly responsible for the gel formation in these systems. The gelling process was monitored by measuring the pH, density and viscosity changes. The gels obtained were characterized by UV-VIS and IR spectra, DTA/TGA and powder X-ray diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436922
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    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Structure and phase diagram of the Na2B4O7-Na3AlF6 system (1999)
    Springer
    Journal of materials science 34 (1999), S. 3923-3929 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A complex study was carried out on Na2B4O7-Na3AlF6 binary system by means of differential thermal analyses (DTA), X-ray diffraction as well as infrared (IR), and Raman spectroscopy. Although the system exhibits a simple eutectic at 83 wt % Na2B4O7 and Te = 642°C, interesting structural changes of borate glasses formed have been evidenced by means of IR and Raman spectroscopy. Over 80–100 wt % Na2B4O7 range AlF6 3− anions are diluted in the vitreous matrix without significant structural changes while the further increase of Na3AlF6 content diminishes the concentration of BO4 groups and promotes the appearance of complex anions AlFx (x−3)− (x = 6, 5, 4) as well as the possible new BF4 − and/or BO3F4− species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004635109184
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    Paper (German National Licenses)
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