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  • 1
    Electronic Resource
    Electronic Resource
    Conventional and Microwave-Hydrothermal Synthesis of TiO2 Nanopowders (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The objective of this study was to compare the conventional and microwave hydrothermal treatment of TiOCl2 solutions. Colloidal titania suspensions were prepared by forced hydrolysis at 195°C for different times ranging from 1 to 32 h for the conventional synthesis and from 5 min to 1 h for the microwave ones. The effect of the microwave technology on both the synthesis conditions and titania nanoparticles properties has been evaluated. Particles morphology and crystallinity were studied by using transmission electron microscopy and X-ray diffraction. The thermal and chemical stability of the obtained powders were determined by TG/DTA analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00474.x
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave-Hydrothermal Synthesis of Nanocrystalline Zirconia Powders (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nanosized zirconium oxide (ZrO2) powders were prepared by adding NaOH to a zirconyl chloride aqueous solution under microwave-hydrothermal conditions. The obtained results showed that the tetragonal polymorph increased with increasing NaOH concentration in the starting solution and reached the maximum value by using 1M ZrOCl2. The microwave-assisted hydrothermal synthesis is expected to be able to process continuously, and may lead to energy savings because of rapid heating to temperature and increased kinetics of crystallization. This method is very simple and can lead to powders with desirable characteristics such as very fine size, narrow size distribution, and good chemical homogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01084.x
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic Structure of F and V Centers on the MgO Surface (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 17010-17018 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100046a029
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  • 4
    Electronic Resource
    Electronic Resource
    Surface reactivity of MgO oxygen vacancies: electrostatic mechanisms in the formation of O2− and CO− species (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 2066-2078 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction of O2 and CO gas-phase molecules with oxygen vacancies on the MgO (100) surface has been studied by means of cluster models and ab initio wave functions. It is found that the surface oxygen vacancies, or Fs centers, exhibit a high reactivity toward O2 and CO at variance with the regular MgO surface. The reaction proceeds through the formation of radical anions, O2− and CO−, via the transfer of one electron trapped in the surface cavity to the empty levels of the adsorbed molecule. The resulting surface complexes, X−/Fs+ or X−/Fs2+ (X=O2 or CO), are bound by electrostatic forces. Although the mechanism of the interaction is the same for the two molecules, the details of the energetics are different. O2 spontaneously removes the electrons trapped in the MgO oxygen vacancies to form the stable O2− superoxide anion. On the contrary, CO− forms only at finite temperatures and is a metastable species. The different behavior can be rationalized in terms of electron affinities of the two molecules. The calculations are useful also for the spectroscopic characterization of the radical anions at the surface. The calculations of electron paramagnetic resonance (EPR) hyperfine coupling constants and, for CO, of the vibrational frequencies indicate that the experimental spectra are consistent with the existence of O2− and CO− surface species. The analysis of the vibrational shifts shows that the coordination mode of CO is C-down and not O-down. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474557
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  • 5
    Electronic Resource
    Electronic Resource
    On the role of electrostatics in the heterolytic splitting of covalent bonds at defective oxide surfaces (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 509-518 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A model is proposed for the heterolytic dissociation of covalent bonds at the surface of perfect or defective oxide surfaces essentially based on the analysis of the electrostatic potential and its gradient at the bare surface. It permits us to obtain in a semiquantitative way the equilibrium geometry of the fragments and the reaction energy, and gives clues for the identification of the reaction path and for a rough estimate of the related activation energy. The predictive ability of the model has been verified by performing a number of calculations to simulate H2 dissociation at various defects at MgO and CaO: the isolated oxygen vacancy, the divacancy at the (100) face, the infinite edge and the divacancy at the edge. All calculations have been performed at an ab initio Hartree–Fock level of approximation, using the CRYSTAL program for the periodic structures and the EMBED program for the local defects. Generally satisfactory agreement is found between the model predictions and the results of actual calculations. The model could be useful for predicting with low cost computations if and how a local structure at a defective oxide surface is capable or not of heterolytically dissociating strong covalent bonds. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378308
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  • 6
    Electronic Resource
    Electronic Resource
    The Anorthite–Diopside System: Structural and Devitrification Study. Part II: Crystallinity Analysis by the Rietveld–RIR Method (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crystallization behavior of 10 binary glasses belonging to the CaO–MgO–Al2O3–SiO2 quaternary system and two glasses corresponding to anorthite and diopside composition was investigated by X-ray diffraction, thermal, and thermomechanical analyses, and scanning electron microscopy. Particular emphasis is laid on the quantitative X-ray diffraction analysis by the Rietveld–reference intensity ratio combined procedure, which seems to be a useful tool to obtain time–temperature–transformation diagrams. Results showed that to obtain glass–ceramics with a significant crystalline phase presence, it is necessary to treat samples at 1000°C for 4 h or at 1100°C for 1 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00578.x
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  • 7
    Electronic Resource
    Electronic Resource
    Environmental Scanning Electron Microscopy (ESEM) Investigation of the Reaction Mechanism in Praseodymium-Doped Zircon (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The formation mechanism of praseodymium-doped zircon stain was studied, using environment scanning electron microscopy (ESEM) primarily. The significance of ESEM as a processing tool for studying chemical and morphologic dynamic changes under controlled temperature conditions was evaluated, with respect to the traditional investigation methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01420.x
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  • 8
    Electronic Resource
    Electronic Resource
    New Glass–Ceramic Inclusion Pigment (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Recently, the traditional ceramic industry has demonstrated increased interest in obtaining inclusion pigments to stabilize unstable chromophores, such as hematite or cadmium sulfoselenide, at firing temperature and in studying the actions of molten glasses. This present work focuses on a new method for synthesizing hematite–zircon inclusion pigments from an unconventional mixture of precursors. For this purpose, a glassy composition that belongs to the LiO2–ZrO2–SiO2 system and that crystallizes into zircon during the calcination step has been chosen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00217.x
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  • 9
    Electronic Resource
    Electronic Resource
    Reaction Mechanism in Alumina/Chromia (Al2O3–Cr2O3) Solid Solutions Obtained by Coprecipitation (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The aim of this work is to study the structural characteristics and properties of the solid solution (Al,Cr)2O3. XRD analysis, 27Al MAS-NMR measurements, and microstructural characterization were used to determine the relationship between color and crystallochemical properties of the compounds formed. In particular, to determine more accurately the mechanism of solid solution formation above the miscibility gap of the system, the marker technique was used. In order to define the behavior of the system for temperatures below the miscibility gap at 1 bar pressure, the composition Al2O3:Cr2O3 1:1 was studied with high-temperature XRD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01508.x
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  • 10
    Electronic Resource
    Electronic Resource
    Microwave-Hydrothermal Synthesis and Hyperfine Characterization of Praseodymium-Doped Nanometric Zirconia Powders (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This work focuses on the microwave-assisted hydrothermal synthesis of praseodymium-doped zirconia and on the subsequent evaluation of the effect of synthesis conditions on powder properties. Pure and 10 mol% Pr-doped zirconia samples have been analyzed by X-ray diffraction (XRD) and the perturbed angular correlations hyperfine technique, which probes the nearest environments of zirconium ions. At atomic scale, as determined from perturbed angular correlation data, the XRD amorphous fraction of the as-obtained powders exhibits a tetragonal-like structure. The pure powder becomes partially stabilized and the doped powder is a substitutional solid solution of praseodymium in tetragonal zirconia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00093.x
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