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  • 1
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ti-Al-O layers were deposited on Si-〈100〉 wafers at 500 °C by means of reactive magnetron sputtering ion plating (R-MSIP). An Al-target was sputtered in rf-mode and a Ti-target in dc-mode simultaneously by an oxygen/argon plasma. The influence of the Al- and Ti-sputter powers on composition, structure, and morphology of the Ti-Al-O layers and the binding states of the components were investigated. The analysis with EPMA, XPS, AES and TEM yielded the following results: Ti-Al-O coatings with different Ti, Al, and O contents in the range of TiO2 to Al2O3 were grown. TEM structure analysis revealed: the pure TiO2 film consisted of the tetragonal phases rutile and anatase; the two structures were found in the titanium-rich Ti-Al-O film, too, but with significant smaller lattice constants. The aluminium-rich Ti-Al-O film displayed the same cubic structure of γ-Al2O3 as determined for the pure Al2O3 film, but the lattice constant is significant lower. Evaluation of the TEM pattern of the film with a Ti/Al ratio of 0.8 indicates a hexagonal structure with lattice constants similar to those of κ′-Al2O3. All films are nanocrystalline and not textured.
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  • 2
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation behavior of cubic Ti1-xAlxN films was improved by decreasing the Ti/Al ratio from 50/50 in the direction of the phase transition between cubic and hexagonal structure. Metastable, polycrystalline, single-phase Ti1-xAlxN films were deposited on high speed steel (HSS) substrates by reactive magnetron sputtering ion plating (MSIP). The composition of the bulk was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). A Ti1-xAlxN film with a Ti/Al atomic ratio of 38/62 was deposited in cubic NaCl structure, whereas a further decrease of the Ti/Al ratio down to 27/73 led to a two-phase film with both cubic and hexagonal constituents. The Ti0.38Al0.62N film was oxidized in synthetic air for 1 h at 800 °C. The oxidic overlayer was analyzed by X-ray photoelectron spectroscopy (XPS) sputter depth profiling, EPMA crater edge linescan analysis, and secondary neutrals mass spectroscopy (SNMS). Scanning electron microscopy (SEM) micrographs of the cross sectional fracture were taken for morphological examination. With higher Ti content, the Ti1-xAlxN formed a TiO2-x rich sublayer beneath an Al2O3 rich toplayer, whereas the oxide layer on the Ti0.38Al0.62N film consisted of pure Al2O3. The thickness of the oxide layer was determined to 60–80 nm, about a quarter of the oxide layer thickness detected on Ti0.5Al0.5N films. The absence of a TiO2-x sublayer was also confirmed by XRD. The results show a distinct improvement of the oxidation resistance of cubic Ti1-xAlxN films by increasing the Al content from x = 0.5 to 0.62, whereas a further increase leads to the hexagonal structure, which is less suitable for tribological applications due to its tendency to form cracks during oxidation.
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  • 3
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural transitions of metastable Ti1–xAlxN coatings on technically relevant substrates were determined as a function of the Ti/Al ratio. Ti1–xAlxN films with different Ti/Al ratios were deposited on high speed steel (HSS) substrates at substrate temperatures of 300 ° and 500 °C by means of reactive magnetron sputtering ion plating (MSIP). A Ti/Al compound target was used as well as a cluster arrangement of one Ti and one Al target for comparison. The composition of the films was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). The analyses revealed that films deposited with Ti/Al ratios of 44/56 and 36/64 had grown in cubic NaCl structure, a film with a Ti/Al ratio of 32/68 was two-phase, and a Ti/Al ratio of 25/75 led to a hexagonal film in wurtzite structure. Only small differences of the lattice parameters could be observed in dependence of temperature: At 300 °C the lattice parameters of the cubic structure corresponded exactly to Vegard‘s law, whereas they slightly decreased in the films deposited at 500 °C. The application of a cluster arrangement instead of a compound target resulted in nearly the same lattice parameters and peak shapes.
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  • 4
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Due to its high surface sensitivity, electron spectroscopy has proven to be a powerful tool for the determination of binding states and electronic structures of thin films. The principal processes of electrons and photons interacting with a surface are briefly discussed. Special attention is paid to the determination of binding states, near range orders and the electronic structures in ceramics by Auger- and Photoelectron Spectroscopy (AES and XPS) as well as Electron Energy Loss Spectroscopy (EELS). The particularities of electron spectroscopy of metastable ternary ceramic solution phases which have been deposited by means of reactive magnetron sputtering are described. Because of their continuous change in composition and, thus, in chemical environment, these solution phases are attractive systems for the analysis of the effects of chemical environment upon binding states and the electronic structure of ceramics.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 15 (1992), S. 119-123 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thermodynamic data bank system THERDAS [1, 2] has been used in conjunction with the program ChemSage [3] to calculate the conditions necessary for the formation of 2,3,7,8-TCDD (tetrachlorodibenzodioxin). The stability ranges of both gaseous and condensed dioxin are presented as functions of the chlorine content, C/H mole ratio, oxygen partial pressure and temperature of the system.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 1436-5073
    Keywords: (Ti,Al)N ; Ti1−x Al x N ; hard coating ; metastable ceramic phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metastable, single phase, polycrystalline Ti1−x Al x N hard layers were deposited on HSS-substrates with reactive magnetron sputtering ion plating (MSIP). The substrate temperature was 400 °C, the bias −60 V, the argon pressure 1.2 Pa and the sputter power 6 W cm−2. Compound targets with a Ti:Al ratio of 75/25, 50/50 and 25/75, expressed in at-%, were sputtered. The nitrogen reactive gas pressure during sputtering was 8.4 × 10−2 Pa for the 75∶25 target and 1.08 × 10−1 Pa for the 50∶50 and 25∶75 targets. The Ti1−x Al x N layers grew with x=0.26, 0.54 and 0.75, as determined with EPMA. Thin film XRD and HEED structure analysis showed that the Ti0.74Al0.26N layer had grown as B1 structure (a0∶0.4214 nm) with [211] texture, the Ti0.46Al0.54N layer likewise as B1 structure (a0∶0.4154) with [111] texture, but the Ti0.25Al0.75N as B4 structure (a0∶0.317 nm and c0∶0.5014 nm) with [110] texture. Pronounced columnar growth was observed with HR-SEM in the fractured surface of the cubic layers. The mean grain size, and consequently the surface roughness, diminished with increasing Al-content of the layer.
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  • 7
    ISSN: 1436-5073
    Keywords: Key words: (Al ; Cr)2O3; PVD; metastable solid solutions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  (Al,Cr)2O3 layers were deposited on cemented carbide insert tips at a substrate temperature of 500 °C by means of reactive magnetron sputtering. An Al target was sputtered in RF mode and a Cr target in DC mode simultaneously in an oxygen/argon plasma. The influence of the Al and Cr sputter power and of the oxygen partial pressure on composition and structure of the (Al,Cr)2O3 layers as well as on the binding states of their components were investigated. Special attention was paid to the interpretation of the O ls and O-KLL fine structure and peak shifts. For the binary phases γ-Al2O3 and Cr2O3, a good agreement with literature values was observed in each case. In case of the ternary phases a continuous shift of the energetic position of the O1s peak, the O-KL23L23 transition and the modified Auger parameter α ′ of oxygen between the two binary phases γ-Al2O3 and Cr2O3 could be detected, indicating a wide range of solid solubility between Al2O3 and Cr2O3. As revealed by grazing incidence X-ray diffraction, the crystallinity of the ternary phases is less pronounced as compared to the binaries and increases with increasing oxygen flow rate.
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  • 8
    ISSN: 1436-5073
    Keywords: Key words: Optical data storage; copper nitride; PVD.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  Cu3N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For basic investigations concerning the composition and structure of Cu3N, Si wafers were used as substrate material. To study the suitability of Cu3N as an optical data storage medium under technical conditions, Cu3N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The decomposition of Cu3N into metallic copper and nitrogen was induced and characterized with a dynamic tester consisting of an optical microscope with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity photo detector. Optimized Cu3N films could be decomposed into metallic copper at pulse lengths of 200 ns. The reflectivity change from 3.2% to 33.2% for completely transformed areas and to 12% for single bits as well as the maximum write data rate of 3.3 Mbit/s demonstrated the suitability of Cu3N for write once optical data storage. Especially the carrier to noise ratio of 41 dB shows an increase of a factor of 3 for this novel material as compared to conventional optical data storage media.
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  • 9
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die Umsetzung von gelöstem Kohlenmonoxid mit Wasser zu Wasserstoff und Kohlendioxid erfolgt in wäßriger Phase als homogene Reaktion gemäß - dcCO/dt = k1cCO. Bei der Reduktion von Kobalt-Ionen aus acetat-haltigen Lösungen mit Kohlenmonoxid reagiert zunächst gelöstes CO mit H2O zu H2 und CO2, anschließend wird das Kobalt mit diesem intermediär gebildeten H2 reduziert. Für die heterogen an Kobalt-Pulver (Fläche F) im Lösungsvolumen Vli ablaufende Kobalt-Reduktion mit H2 gilt - dcCo2+/dt = (k2F/Vli)pH2. Die Kobalt-Reduktion mit CO (Anfangsdruck pCO0) läßt sich durch die Gleichung - (dcCo2+/dt) Vli = k3pCO0 beschreiben. Bei ausreichendem Angebot an Fremdkeimen gilt in guter Nährung - dcCo2+/dt ∼ k1pCO0, d. h. die Wassergas-Reaktion bestimmt die Geschwindigkeit der Kobalt-Fällung.
    Additional Material: 10 Ill.
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