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  • Polymer and Materials Science  (12)
  • Industrial Chemistry and Chemical Engineering  (1)
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 21 (1990), S. 35-35 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: SiC-Fiber Reinforced Ti 6 Al4 V Alloy: Effect of TiC and TiN Interlayers on the Reaction Zone.Processing and properties of SiC-fiber reinforced Ti 6 Al4 V alloys are briefly summarized. In order to avoid the degradation of the SiC-fibers caused by interfacial reactions, TiC and TiN interlayers were incorporated and their influence on the formation of the reaction zone was investigated. The reaction fiber-matrix was determinated by high temperature X-ray diffraction and Auger electron depth profiling.Coating with TiC and TiN cannot completely avoid fiber damage and interfacial reactions. However, due to the low reaction rate, at short process times (ca. 〈 1 h) the formation of titanium silicides can be prevented. Based on these results, the coating of the SiC-fibers by TiN, but especially TiC, gives positive aspects for further improving these composites.
    Notes: Es wird ein kurzer Überblick über Herstellung und Eigenschaften von SiC-faserverstärkten Ti 6 Al4 V-Verbundwerkstoffen gegeben. Um die durch Reaktionen im Grenzflächenbereich verursachte Schädigung der SiC-Fasern zu vermeiden, wurden TiC- und TiN-Schichten zwischen Faser und Matrix eingebracht und deren Einfluß auf die Ausbildung der Reaktionszone untersucht. Zum Nachweis der Reaktionen zwischen Faser und Matrix wurden die Röntgen-Hochtemperatur-Diffraktometrie und Auger-Elektronen-Tiefenprofilanalyse eingesetzt.Durch Aufbringen von TiC- und TiN-Zwischenschichten können der Faserangriff und die Grenzflächenreaktionen nicht vollständig verhindert werden. Bedingt durch die langsame Reaktionsgeschwindigkeit kann allerdings bei kurzen Haltezeiten (bis etwa 〈 1 h) die Ausbildung der schädlichen Titansilicide vermieden werden. Nach den bisher vorliegenden Ergebnissen liefert die Beschichtung der SiC-Fasern mit TiN, insbesondere aber mit TiC, positive Ansätze für die Weiterentwicklung dieser Verbundwerkstoffe.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 11 (1997), S. 181-194 
    ISSN: 0268-2605
    Keywords: synthesis ; silazanes ; polymer pyrolysis ; non-oxide ceramics ; Si3N4 ; SiC ; crystallization ; ceramic matrix composites ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The goal of this investigation was to optimize the synthesis of silazane-based polymers for processing fibre-reinforced ceramic matrix composites (CMCs). Liquid oligomeric silazanes were synthesized by ammonolysis of chlorosilanes and characterized spectroscopi- cally (FTIR, NMR) as well as by elemental analysis. The silazanes were obtained in high yield and purity. Different functional groups (system S1: Si - H, Si - CH3, Si - CH=CH2) and different degrees of branching in the Si - N backbone [system S2; Si(NH)3, Si(NH)2] were realized in order to study the properties of the silazanes that are dependent on the molecular structure.For processing ceramics via pyrolysis of pre-ceramic oligomers, molecular weight, rheological behaviour, thermosetting and ceramic yield were investigated systematically and correlated with the molecular structure of the silazanes. Low molecular weights (500-1000 g mol-1) as well as low viscosity values (0.1-20 Pa s) enable processing of the silazanes in the liquid phase without any solvent. Due to the latent reactivity of the functional groups, curing of the polymers via hydrosilylation is achieved.Structural changes and weight loss during polymer curing as well as the organic/inorganic transition were monitored by FTIR spectroscopy and differential thermogravimetric analysis. With increasing temperature (room temperature to 800 °C) the hydrogen content decreases from 7 to 〈 0.5 wt% due to the formation of gaseous molecules (NH3, CH4, H2). High ceramic yields up to 80% were reached by branching the oligomers, thus reducing the amount of volatile precursor fragments.Up to 1300 °C, ceramic materials remained amorphous to X-rays. At higher temperatures (1400-1800 °C) either SiC or SiC/Si3N4 composites were selectively crystallized, depending on the pyrolysis conditions. The utility of the optimized precursors for CMCs has been demonstrated by infiltration of fibre preforms and subsequent pyrolysis. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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