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  • 1
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    Land Use Planning in Drylands: Participatory Processes in Diagnosing the Physical-Biological Subsystem (2020)
    Springer
    Details
    Publication Date: 2020-07-28
    Print ISSN: 1874-463X
    Electronic ISSN: 1874-4621
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Springer
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Effect of the Measurement Temperature on the Dispersive Component of the Surface Free Energy of a Heat Treated SiO2 Xerogel (2000)
    Springer
    Journal of sol gel science and technology 18 (2000), S. 115-118 
    Details
    ISSN: 1573-4846
    Keywords: heat treated silica xerogel ; gas chromatography ; surface energy ; dispersive component ; surface enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The surface free energy of a monolithic silica xerogel treated at 1000°C has been measured by inverse gas chromatography in the temperature range 25–150°C using n-alkanes. Values of the dispersive component, γS D, vary from 49.07 mJ·m−2 at 25°C to 17.20 mJ·m−2 at 150°C. The γS D value obtained at 25°C is lower than that found for amorphous and crystalline silicas but higher than that found for glass fibres meaning that the heat treatment at 1000°C changes drastically the structure of the silica xerogel showing a surface similar to a glass. However, the higher value of γS D in comparison to glass fibres can be attributed to the mesoporous structure present in the silica xerogel. In the temperature range of 60–90°C there exists an abrupt change of the γS D values as well as in the dispersive component of the surface enthalpy, h S D. Such abrupt change can be attributed to an entropic contribution of the surface free energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008756718043
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of TiO2 on the Pore Structure of SiO2-PDMS Ormosils (2000)
    Springer
    Journal of sol gel science and technology 18 (2000), S. 105-113 
    Details
    ISSN: 1573-4846
    Keywords: mercury porosimetry ; titanium ormosils ; pore structure ; interconnection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work, pore structure evolution of Ormosils containing TBT (Tetrabutyl titanate) has been characterized by means of mercury porosimetry, nitrogen adsorption and helium pycnometry. These ormosils have been prepared by the sol-gel method by the reaction of TEOS (tetraethoxysilane), PDMS (polydimethylsiloxane, silanol terminated) and TBT under acid-catalyzed conditions. The addition of TiO2 increases the volume and specific surface of secondary micropores and at the same time decreases the corresponding volumes of mesopores and macropores. The presence of TiO2 gives also a continuous decreasing in the pore connectivity being 9.7 for the ormosil without TiO2 and 4.4 for that of the higher concentration of TiO2. However, the pore length shows a significant decrease with the first addition of TiO2 changing from 9.1 to 2.2 at the higher TiO2 concentration. Pore volumes show a decrease as the TiO2 concentration is increased in the ormosil. On the other hand, density increases and porosity decreases with the TiO2 concentration. These results are in accordance with the presence of TiO2 nanoparticles in the ormosil and the size of such nanoparticles increases with the TiO2 concentration. Fractal constant has a low value, close to 2, for all different samples meaning that these ormosils can be considered as low surface roughness materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008704701204
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  • 4
    Electronic Resource
    Electronic Resource
    Surface Energy Changes of Heat Treated TEOS Derived Silica Xerogels (1997)
    Springer
    Journal of sol gel science and technology 10 (1997), S. 31-44 
    Details
    ISSN: 1573-4846
    Keywords: silica xerogels ; gas chromatography ; surface energy ; acid index ; basic index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The surface energy of monolithic silica xerogels was examined by measuring the interaction of organic probes with xerogels heated at temperatures close to the gel-to-glass transition temperature. Values of the dispersive component of the surface energy, γ $$_S^D $$ , between 60 and 80 mJ ⋅ m-2 have been observed using n-alkanes for silica xerogels heated at 700, 800 and 900°C. At 1000°C, γ $$_S^D $$ decreases to 8.37 mJ · m-2. Also the differential heat of adsorption, variation of standard free energy and entropy of adsorption decrease when the silica xerogel is heated at 1000°C, showing a lower interaction potential of the organic probes with the silica surface. For the silica xerogels heated between 700 and 900°C, the acid character varies in accordance with the variation of the chemical nature of the silica. Upon heating at 1000°C, both acid and base characters are very close in accordance with a neutral surface. Within the experimental conditions used in this work, the surface of the obtained monolithic silica xerogels behaves as a glass surface when the treating temperature is 1000°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018380004857
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  • 5
    Electronic Resource
    Electronic Resource
    Further Insights into the Porous Structure of TEOS Derived Silica Gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 159-163 
    Details
    ISSN: 1573-4846
    Keywords: TEOS ; SiO2 ; heat ; fractal ; percolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The porous structure of TEOS derived silica gels was studied using nitrogen adsorption at 77 K. Silica gels were prepared using TEOS, H2O and ethanol for different molar ratios. No catalyst was used in this study. Silica gels were also heat treated up to 1000°C. The nitrogen sorption isotherms were analyzed by two models: Fractal and Percolation Theories. Using the fractal analysis approach, the surface roughness of the porous structure of silica gels was determined. The surface fractal dimension depends on the hydrolysis conditions and heat treatment. The surface fractal dimension decreases with increasing H2O/TEOS molar ratio or heating temperature. For the silica gels studied, the surface fractal dimension changed from 2.6 to 2.5 after heating the gels, and from 2.4 to 2.6 with decreasing H2O/TEOS ratio. Using the Percolation theory, we have determined the connectivity of the porous structure of silica gels. The extent of sorption hysteresis of the nitrogen isotherms reflects the connectivity of the pore network. The mean coordination number (connectivity) Z, and the linear dimension of the network, L, have been calculated from the hysteresis of the isotherms. For the as-prepared silica gels, Z was about 8 and L close to 2. On heating the gels, Z decreases to 4 and L increases to 7, results which are in accordance with the collapse of the porous network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026408802147
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  • 6
    Electronic Resource
    Electronic Resource
    Further insights into the porous structure of TEOS derived silica gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 159-163 
    Details
    ISSN: 1573-4846
    Keywords: TEOS ; SiO2 ; heat ; fractal ; percolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The porous structure of TEOS derived silica gels was studied using nitrogen adsorption at 77 K. Silica gels were prepared using TEOS, H2O and ethanol for different molar ratios. No catalyst was used in this study. Silica gels were also heat treated up to 1000°C. The nitrogen sorption isotherms were analyzed by two models: Fractal and Percolation Theories. Using the fractal analysis approach, the surface roughness of the porous structure of silica gels was determined. The surface fractal dimension depends on the hydrolysis conditions and heat treatment. The surface fractal dimension decreases with increasing H2O/TEOS molar ratio or heating temperature. For the silica gels studied, the surface fractal dimension changed from 2.6 to 2.5 after heating the gels, and from 2.4 to 2.6 with decreasing H2O/TEOS ratio. Using the Percolation theory, we have determined the connectivity of the porous structure of silica gels. The extent of sorption hysteresis of the nitrogen isotherms reflects the connectivity of the pore network. The mean coordination number (connectivity) Z, and the linear dimension of the network,L, have been calculated from the hysteresis of the isotherms. For the as-prepared silica gels, Z was about 8 andL close to 2. On heating the gels, Z decreases to 4 andL increases to 7, results which are in accordance with the collapse of the porous network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436834
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  • 7
    Electronic Resource
    Electronic Resource
    Tribological improvement of aluminium infiltrated with zirconia nanoparticles (2000)
    Springer
    Materials research innovations 4 (2000), S. 42-44 
    Details
    ISSN: 1433-075X
    Keywords: Keywords Zirconia ; Aluminium ; Composites ; Infiltration ; Nanoparticles ; Tribology ; Martensitic ; Tetragonal ; Monoclinic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Aluminium matrix-zirconia nanoparticles-reinforced composites were prepared by the infiltration technique. The metallic matrix for these composites stabilizes the tetragonal phase of zirconia at low temperature (450 °C) whereas at 610 °C a mixture of tetragonal and monoclinic was obtained. The wear resistance of zirconia-modified aluminium was significantly improved due to the presence of the ceramic nanoparticles embedded into the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190000066
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  • 8
    Electronic Resource
    Electronic Resource
    Palladium(II) and platinum(II) dichloro complexes containing diamine-estrone derivatives (1983)
    Springer
    Monatshefte für Chemie 114 (1983), S. 535-540 
    Details
    ISSN: 1434-4475
    Keywords: Diamine estrogenic complexes ; Palladium(II) complexes ; Platinum(II) complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird über die Darstellung voncis-Dichlor-Pt(II)- undcis-Dichlor-Pd(II)-Komplexen mitN-[3-Hydroxyestra 1:3:5 (10)trien-17β]ethylendiamin,N-[3-Hydroxyestra 1:3:5 (10) trien-17β]1,3-propylendiamin undN-[3-Hydroxyestra 1:3:5 (10)trien-17β]2-aminomethylpyridin berichtet. Die Komplexe wurden mittels chemischer Analyse, IR und Leitfähigkeitsmessungen charakterisiert.
    Notes: Abstract The preparation ofcis-dichloro Pt(II) andcis-dichloro Pd(II) complexes ofN-[3-hydroxyestra 1:3:5 (10)trien-17β]ethylendiamine,N-[3-hydroxyestra 1:3:5 (10)trien-17β]1,3-propylendiamine, andN-[3-hydroxyestra 1:3:5 (10)trien-17β]2-aminomethylpyridine is reported. The complexes have been characterized by chemical analysis, infrared spectroscopy and molar conductivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798607
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of Reaction Parameters on the Hydrolysis of Zirconium Propoxide. A Study by Infrared Spectroscopy (1998)
    Springer
    Journal of materials science 17 (1998), S. 1839-1842 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006678125381
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  • 10
    Electronic Resource
    Electronic Resource
    Corrosion of SiC fibres with HNO3 (1991)
    Springer
    Journal of materials science 26 (1991), S. 2841-2845 
    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 The corrosion of SiC fibres with HNO3 has been studied. Characterization has been carried out by means of infrared spectroscopy, scanning electron microscopy and adsorption of nitrogen and benzene. Corrosion attack changes the specific surface area of the fibres and increases the surface roughness along the fibres. The microstructure of the fibres is not modified by the attack. The surface heterogeneity of the original fibres shows a different feature when the fibres have been corroded; the distribution of active sites on the surface of the fibres is changed by acid attack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01124810
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