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  • 1990-1994  (10)
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  • 1
    Digitale Medien
    Digitale Medien
    Generation of homogeneous rhodium particles by photoreduction of rhodium(III) on titania colloids grafted on silica (1993)
    s.l. : American Chemical Society
    Langmuir 9 (1993), S. 121-125 
    Details
    ISSN: 1520-5827
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/la00025a028
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  • 2
    Digitale Medien
    Digitale Medien
    Low-temperature photoassisted generation of a strong metal-support interaction in a rhodium/titania catalyst (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 3350-3354 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100115a043
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  • 3
    Digitale Medien
    Digitale Medien
    XPS and ISS study of NiTiO3 and PbTiO3 subjected to low-energy ion bombardment. I. Influence of the type of ion (Ar+ and O2+) (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 941-948 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Compositional and chemical changes in PbTiO3 and NiTiO3 induced by 3.5 keV Ar+ and O2+ ion bombardment have been studied quantitatively by XPS and ISS. Whereas in NiTiO3 the Ti/Ni ratio determined by XPS remained practically constant, a preferential loss of lead was observed in PbTiO3 during ion bombardment. In that case, Ar+ removed lead more effectively than O2+ ions. Argon ion bombardment induced strong chemical changes in both titanates: Ni2+ and Pb2+ species were nearly totally reduced to the metallic state, while Ti4+ species were partially reduced to Ti3+ and Ti2+ oxidation states. This reduction is more efficient in PbTiO3 than in NiTiO3. The preferential loss of lead in PbTiO3 and the removal at equivalent rates of Ti and Ni in NiTiO3 are discussed within the context of the chemical stability and physical constants of the compounds by assuming a chemically guided lattice relaxation of the bombarded targets. The possibility that solid-state reactions play a role in the control of some of the results is stressed. Other possible effects, such as agglomeration or surface enrichment, are discussed by using the ISS results.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740201203
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  • 4
    Digitale Medien
    Digitale Medien
    Chemical changes in titanate surfaces induced by Ar+ ion bombardment (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 286-290 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The reduction effects and compositional changes induced by 3.5 keV Ar+ bombardment of several titanates (i.e. SrTiO3, Al2TiO5 and NiTiO3) have been quantitatively investigated by XPS.In all the samples studied here the original Ti4+ species were reduced to lower oxidation states (i.e. Ti3+ and Ti2+), although to a lesser extent than in pure TiO2. On the contrary, whereas Sr2+ and Al3+ seem to remain unaffected by Ar+ bombardment, in agreement with the behaviour of the respective oxides (i.e. SrO and Al2O3), Ni2+ appears more easily reducible to Ni0 in NiTiO3 than in NiO. In addition, other specific differences were observed between the titanates, which reveal the existence of interesting chemical effects related to the presence of the different counter-ions in the titanates.In the case of Al2TiO5, its Ar+-induced decomposition to form TiO2 + Al2O3 could be followed by XPS.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740190154
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  • 5
    Digitale Medien
    Digitale Medien
    Use of XPS and Ar+ depth profiling to determine the dispersion degree of Ni in Ni/TiO2 and Ni/SiO2 catalysts (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 508-512 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Two series of Ni/TiO2 and Ni/SiO2 catalysts prepared by different methods have been characterized by XPS and Ar+ sputtering. Depth profiles have been obtained from the intensity of the Ni 2p photoelectron peaks as a function of the sputtering time. The analysis has been carried out for samples in their precursor, calcined and reduced states, in order to obtain information on the changes in dispersion of the active phase through the whole activation process. In the case of reduced Ni/SiO2 catalysts, comparison with results by other techniques (i.e. H2 chemisorption, x-ray diffraction and transmission electron microscopy) has shown that the sputtering method may give a semi-quantitative assessment on the dispersion degree of nickel. However, for Ni/TiO2 catalysts in the SMSI state after reduction in H2 at 773 K only the Ar+ sputtering method was able to provide information on the distribution of nickel. In this case the depth profiles were consistent with partial solution of the nickel in the TiO2 matrix.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740190194
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  • 6
    Digitale Medien
    Digitale Medien
    Use of XAS and chemical probes to study the structural damage induced in oxide ceramics by bombardment with low-energy ionsPaper presented at ECASIA 93, Catania, Sicily, 4-8 October 1993. (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 418-424 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A preliminary study by x-ray absorption spectroscopy (XAS) of the structural modifications induced in mixed oxides by low-energy (1-5 keV) Ar+ bombardment is presented in this paper. The analysis of the extended x-ray adsorption fine structure (EXAFS) and x-ray adsorption near-edge structure (XANES) spectra recorded for bombarded Al2TiO5 and BaTiO3 has shown the randomization of the atomic network and the formation of TiO2 in the outermost layers of these materials. On the other hand, SO2 is proposed as a probe molecule to asess semiquantitatively the extent of structural damage in the surface layers of bombarded oxides. The incorporation of sulphur into this zone has been proved by depth profiling with XPS and Ar+ ions of 0.5 keV. In BaTiO3 the incorporation of sulphur increases with the energy of the primary ions. This fact suggests that the concentration of defects increases with the energy of the Ar+ beam and that the most disordered surface layers are more reactive towards SO2. A similar effect is not observed with TiO2 and Al2TiO5 because in these materials, where a considerable reduction of titanium to Tin+ (n 〈 4) species is produced by the preferential removal of oxygen, an overlay of elemental sulphur is formed by the reaction of SO2 with these species. This overlay prevents the diffusion of SO2 and therefore the incorporation of sulphur into the damaged layer of those samples.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740210617
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  • 7
    Digitale Medien
    Digitale Medien
    Charging and mixing effects during the XPS analysis of mixtures of oxides (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 22 (1994), S. 111-114 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: In this article we present an XPS analysis of mixtures of Al2O3 and TiO2 powders of different relative size in order to study differential charging effects. To illustrate some of the possible situations we have studied the behaviour of three different samples: (1) very large (microns) and porous particles of Al2O3 supporting TiO2 particles of relatively small size (300 Å); (2) Al2O3 and TiO2 particles of similar size (300 Å); and (3) very small particles (20-30 Å) of TiO2 dispersed in Al2O3 particles of 300 Å. The observed effects are then analysed by using Auger parameters and relative binding energies and discussed in terms of the different morphologies of the samples, as determined by TEM. The influence on charging of an electron flood gun and of Ar+ sputtering is also presented. In addition, ion-induced mixing effects have been clearly observed in the case of very small particles of TiO2 dispersed on alumina.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740220127
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  • 8
    Digitale Medien
    Digitale Medien
    XPS intensities and binding energy shifts as metal dispersion parameters in Ni/SiO2 catalysts (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 375-379 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A set of Ni/SiO2 catalysts with metal loadings between 1 and 8% by weight has been prepared by several methods. Metal dispersions have been determined by H2 chemisorption and x-ray line broadening analysis, giving metal particle sizes from ∼30 to 250 Å.XPS analysis of the samples has been recorded after reduction in situ and the data correlated with the metal loading and metal dispersion. When comparing the Ni 2p intensities, a good relationship has been obtained with metal surface concentration, showing the existence of two well-defined set of catalysts with particles of quite different sizes. However, a single linear relationship is obtained for all the samples when the Ni 2p binding energies are plotted against the metal dispersion calculated from H2 chemisorption. The origin of the binding energy shift and its relation with metal dispersion is discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740160179
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  • 9
    Digitale Medien
    Digitale Medien
    Interpretation of surface textural changes in SrTiO3 ex-oxalate samples using XPS and IR spectroscopies (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 693-697 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: XPS, IR and x-ray diffraction (XRD) have been used to study high-surface-area ‘ex-oxalate’ polycrystalline SrTiO3 materials. Changes of surface area and pore size distribution are induced during lixiviation with a 0.1 M HCl solution, which removes carbonate impurities. The study shows the presence in the original sample of a microcrystalline SrCO3 phase at its surface and isolated CO32- species, these latter remaining even after outgassing at 773 K for 15 h. However, a complete elimination of the SrCO3 and other carbonate species at the surface is achieved by heating the acid-lixiviated sample at 773 K, although carbonate species still remain in the bulk of the SrTiO3 material after this treatment. The usefulness of the combined use of XPS and IR for the characterization of surface and bulk species in this type of powdered material is pointed out during this study.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740151109
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  • 10
    Digitale Medien
    Digitale Medien
    Size and support effects in the photoelectron spectra of small TiO2 particles (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 392-396 
    Details
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Three different TiO2 samples in the form of bulk material, colloidal particles and small clusters supported on SiO2 have been studied by extended x-ray adsorption fine structure (EXAFS), UV-visible, transmission electron microscopy (TEM) and XPS. The different values of the Ti 2p binding energies and the Auger parameter of Ti found for each sample show that the photoemission processes in these oxide materials are influenced by size and support effects. A difference in the relaxation energy of -1.1 eV is found for the TiO2/SiO2 sample with respect to TiO2, which is attributed to an effect of the silica support.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/sia.740180604
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