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  • 2000-2004  (1)
  • 1985-1989  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 28 (1987), S. 1-16 
    ISSN: 1573-4889
    Schlagwort(e): Silicon oxidation ; tracer ; double oxidation ; oxygen diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract This work focuses on the thermal oxidation of silicon near 1273 K using the double-tracer oxidation method. The results confirm that oxidation occurs by the transport of electrically neutral non-network oxygen through the interstitial space of the vitreous silica (ν-SiO2) scale. Simultaneously, self- (or isotopic-) diffusion occurs in the network, resulting in characteristic isotopic fraction distributions near the gas-scale interface. The self-diffusion coefficients calculated from these profiles agree with those reported for tracer diffusion in ν-SiO2, and the diffusion coefficient calculated from the scale growth is consistent with reported O2 permeation data. An important parameter that describes the double-oxidation behavior is the ratio of the value of Δ/√(D nt′),where Δ is the scale thickness grown during the second oxidation, Dn is the network self-diffusion coefficient for oxygen, and t′ is the time of the second oxidation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 27 (1987), S. 143-155 
    ISSN: 1573-4889
    Schlagwort(e): double-oxidation ; O-18 ; tracer concentration profile ; diffusion model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Two methods are presented for the analysis of oxygen tracer isotope “double oxidation” experiments. Mass balance criteria are presented for inferring oxide growth mechanisms from the oxygen isotope profile. For the case of inward growing scales, a diffusion model is presented which describes the tracer distribution as a function of lattice and grain boundary diffusivities, grain size and the parabolic growth rate.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 35 (2000), S. 3365-3371 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Preferred orientation was measured in Si3N4/BN fibrous monolithic ceramics using x-ray diffraction. The materials were manufactured by co-extrusion of polymer binder/ceramic blends which were subsequently pyrolized and then hot-pressed to produced a fully dense ceramic composite. A very strong modified wire texture was present in the BN with the basal planes aligned parallel to the axis of extrusion due to shear-induced reorientation of the platelet-shaped BN particles during co-extrusion. Texture was also observed in the Si3N4 and was attributed to a combination of co-extrusion and hot-pressing. After hot pressing, the basal planes of the rod-shaped β-Si3N4 were observed to be preferentially aligned perpendicular to the extrusion direction. Measurements prior to hot-pressing revealed that a small amount (≈5%) of β-Si3N4 was present in the α-Si3N4 starting powder. Although texturing of the predominant α-Si3N4 did not occur during co-extrusion, significant texturing of the β-Si3N4 was observed. During subsequent hot-pressing, the pre-existing textured β-Si3N4 particles appeared to act as seeds for transformation and preferred growth of rod-shaped β grains parallel to the axis of extrusion.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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