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  • TEM  (3)
  • FeCrAl  (1)
  • Key words Palmaz-Schatz-Stent – AVE-Micro-Stent – restenosis-rate – high pressure implantation – morphology of stenosis  (1)
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  • 1
    ISSN: 1573-4889
    Keywords: HIGH-RESOLUTION SIMS ; TEM ; ALUMINA SCALES ; FeCrAl ; Y SEGREGATION
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of undoped and Y-dopedhigh-purity FeCrAl at 1200°C was investigated. Thescale-growth processes were studied using two-stage16O/18O experiments andhigh-resolution imaging SIMS. SEM, TEM, and scanning transmission electronmicroscopy-electron-dispersive X-ray spectrometry(STEM-EDS) studies were performed in order to determinethe microstructure of the oxide and the chemistry of the metal-oxide interface. An equiaxedα-Al2O3 scale was found togrow by simultaneous outward Al and inward oxygendiffusion on the undoped FeCrAl. In contrast, a columnarα-Al2O3 grain structure on the Y-doped FeCrAl was produced by inwardoxygen diffusion; outward Al diffusion was suppressed.Y was shown to segregate toα-Al2O3 grain boundaries andto the metal-oxide interface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 50 (1998), S. 269-307 
    ISSN: 1573-4889
    Keywords: TITANIUM ALUMINIDE ; NITROGEN EFFECT ; SURFACE FINISH EFFECT ; Al-DEPLETION ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The microstructural development of oxidizedγ-TiAl is presented with a focus on oxidation inair. The investigations were carried out usingconventional, analytical, and, especially,energy-filtered transmission electron microscopy (EFTEM). Threeimportant points were studied in detail: (1) the“nitrogen effect,” (2) the“surface-finish effect,” and (3) thesubsurface zone. Nitrogen leads to the formation of TiN andTi2AlN at the metal-scale interfaceinterrupting alumina and thereby preventing thedevelopment of a continuous alumina layer. TheAl-depletion layer formed during the oxidation process develops from a single-phaselayer, consisting of a cubic phase, to a two-phaselayer, consisting of the cubic phase andα2-Ti3Al. The cubic phase isnot known in the system Ti-Al-O-N. Oxidation in oxygen depends on the surfacepreparation of the sample with rapid oxidation kineticsfor fine polishing and slow kinetics for a 600-gritSiC-paper finish. The rougher surface finish leads to the development of a recrystallization zonenear the surface and supports the formation of acontinuous alumina layer in the early stages ofoxidation. As for the oxidation in air, the cubic phaseis formed first underneath the oxide scale,followed by α2-Ti3Alformation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 43 (1995), S. 157-172 
    ISSN: 1573-4889
    Keywords: oxidation ; NiAl ; ion implantation ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of Y-ion implantation on the oxidation of β-NiAl single crystals has been investigated using SEM, TEM, and STEM. Y ions having an energy of 70 keV were implanted with a concentration of 5×1016 ions/cm2. The oxidation experiments were performed in air at 1223 K. Y-ion implantation resulted in a 45-nm disordered layer. Oxidation of Y-implanted β-NiAl leads to the formation of a fine-grain layer, consisting of γ-Al2O3 containing Y and a θ-Al2O3 layer. After further oxidation the metastable Al2O3 transformed into α-Al2O3, which started at the metal-oxide interface. Y-Al-garnet (YAG) particles were observed and Y segregation to α-Al2O3 grain boundaries has been detected.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1285
    Keywords: Key words Palmaz-Schatz-Stent – AVE-Micro-Stent – restenosis-rate – high pressure implantation – morphology of stenosis ; Schlüsselwörter Palmaz-Schatz-Stent – AVE-Micro-Stent – Restenoserate – Hochdruckimplantation – Stenosemorphologie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Late results of interventional procedures utilizing coronary stents are largely determined by the rate of restenosis. So far few data are available addressing the effect of stent design, implantation pressure and morphologic factors on this crucial variable. Therefore we analyzed the coronary angiogramms obtained in 259 patients before, immediately after and at 3 to 6 months following stent implantation for obstructive coronary disease. A total of 196 AVE-Micro-Stents and 142 Palmaz-Schatz-Stents were implanted into 307 stenoses. In 126 stenoses there were implanted only Palmaz-Schatz-Stents, in 170 only AVE-Micro-Stents and in 11 Stenoses there were implanted Palmaz-Schatz- as well as Micro-Stents. Restenosis was defined as an over 50% stenosis at follow up. No significant difference was detected with regard to global restenosis rate at an average of 4 months following implantation (Palmaz-Schatz 33%, Micro-Stent 27%). If results were analzyed according to implantation pressure however, there was a significantly lower restenosis rate for AVE Micro-Stens implanted with 〉 10 atm (17%) as compared to ≤ 10 atm (35%, p 〈 0.02) and as compared to Palmaz-Schatz-Stents (34%, p 〈 0.02), which were also implanted with high pressure over 10 atm. In addition to implantation pressure, vessel segment and morphology of stenosis proved to be important determinants of late results. In this series of patients the AVE-Micro-Stent compared favourably to the Palmaz-Schatz-Stent not only with respect to a significantly lower restenosis rate, when implanted with pressures 〉 10 atm, but also with regard to its superior flexibility and handling characteristics.
    Notes: Zusammenfassung Der Langzeiterfolg einer Stent-Implantation wird im wesentlichen durch die Restenoserate bestimmt. Bisher sind noch nicht alle Faktoren geklärt, welche die Restenoserate beeinflussen. Daher wurde in der vorliegenden Studie der Einfluß zweier unterschiedlicher Stentdesigns, der Implantationsart (Hochdruckimplantation 〉 10 atm, Niederdruckimplantation ≥ 10 atm), der Lokalisation der Stenose sowie der Stenose-Morphologie untersucht. Hierzu wurden die koronarangiographischen Untersuchungen von 259 Patienten, bei denen in 307 Stenosen insgesamt 196 Micro- und 142 Palmaz-Schatz-Stents implantiert worden waren, quantitativ vor, direkt nach und 3-6 Monate nach Stent-Implantation retrospektiv ausgewertet. Es fand sich zwischen den beiden Stent-Typen kein signifikanter Unterschied in der Restenoserate (Palmaz-Schatz 33%, Micro 27%). Bei Hochdruckimplantation des Micro-Stents mit Drucken von 〉 10 atm zeigte sich jedoch eine signifikant niedrigere Restenoserate sowohl im Vergleich zu den mit niedrigen Drucken implantierten Micro-Stents (17% versus 35%, p 〈 0,02) als auch im Vergleich zu den nahezu ausnahmslos mit Hochdruck implantierten Palmaz-Schatz-Stents (17% versus 34%, p 〈 0,02). Lediglich 11 Palmaz-Schatz-Stents wurden mit einem Druck von ≥ 10 atm implantiert. Ein Grund hierfür war aus den Untersuchungsprotokollen retrospektiv nicht zu entnehmen. In der LAD lag die Restenoserate mit 39% signifikant höher als in der RCX (21%) und RCA (22%, p 〈 0,02). Bei komplexen Typ-C-Stenosen zeigt sich eine höhere Restenoserate (39%) als bei Typ-A- (17%) und Typ-B-Stenosen (26%, p 〈 0,05). Insgesamt zeigt diese Studie Vorteile für den mit Hochdruck implantierten AVE-Micro-Stent aufgrund seiner geringeren Restenoserate im Vergleich zum Palmaz-Schatz-Stent.
    Type of Medium: Electronic Resource
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