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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 255-257 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Reinforcement effects in composites are widely influenced by fibre coatings. A detailed understanding of their microstructure and chemical composition is of great interest. Boron nitride films were deposited continuously on fibre rovings of various ceramics in CVD reactors of vertical as well as horizontal position. XPS depth profilings show that the film compositions are close to stoichiometric BN with carbon and oxygen impurities in the range of 10 at%. Cross-sections of separated fibres were investigated by HREM and TEM diffraction. All BN films are hexagonal turbostratic. The (002) layers with an increased distance (about 0.36 nm) showed a mean stacking sequence near to graphite and a characteristic orientation to the fibre in the interface region. We assume the gas flow type and hence the exchange rate of matter and energy determines the film structure in this region. With increasing film thickness the (002) layers fold randomly in all directions or form nanocrystals at elevated temperatures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 31 (1996), S. 5979-5984 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Carbon fibres were coated with layers of silicon carbide (SiC) and boron nitride (BN) by conventional chemical vapour deposition. The SiC films were deposited by thermal decomposition of methyltrichlorosilane, whereas the BN films were deposited using the stepwise disproportion reaction of boron chloride with ammonia. Samples for electron microscopic investigations were prepared by separating film from fibre or by conventional mechanical thinning and subsequent ion milling of cross sections of coated fibres. Bright- and dark-field images of both planar and cross-sectional electron microscopic investigations on the fibre coatings gave detailed information on film thickness and morphology. High-resolution images improved the structural information of electron diffraction patterns. Crystal dimensions in the SiC film vary between 10 and 40 nm. Electron diffraction revealed the crystal structure to be a mixture of disordered hexagonal 2H-SiC and cubic β-SiC. High-resolution images showed the (1 1 1)-planes to be preferred for deposition. In BN films, a hexagonal turbostratic structure similar to turbostratic carbon was observed. Apart from amorphous regions, nanocrystalline parts were detected, which have a higher structural perfection in the stacking sequence of their (0 0 2)-planes compared to the (0 0 2)-planes of the turbostratic carbon fibre. High-resolution images located the film-fibre interface that was confirmed by electron energy loss spectroscopy.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 133-135 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The analytic characterisation of various layers and layer systems on fibrous materials are presented. The layers, deposited by an isothermal CVD process, consisting mainly of pyrolytic carbon, hexagonal boron nitride and silicon carbide were characterised by different analytical methods, especially by Raman spectroscopy [1]. The surface enhanced Raman spectroscopy (SERS) was used first time for the investigation of boron nitride (BN) coatings on fibres.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 361 (1998), S. 653-655 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Investigations on CVD boron nitride films on fibres by means of photoelectron and X-ray spectroscopy resulted in B/N ratios above the stoichiometric value 1 and oxygen contents up to 25 at%. Compared to the hydrolytic rate of the films an apparent dependence was found on the deposition rate and some evidence of the oxygen concentration. CVD fibre coatings exhibit a hexagonal turbostratic structure with extremely small atomic layer plane dimensions, which was proved by transmission electron microscopy. Corresponding to oxygen concentrations in pyrolytic carbon films with similar structure a model is proposed, where the small atomic layers with dimensions of some nanometers cause a relatively high oxygen concentration in the boron nitride films. The oxygen atoms saturate the dangling bonds. Moreover the B/N ratio extents the expected stoichiometric ratio due to the oxygen atoms at nitrogen sites.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 349 (1994), S. 181-181 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pyrolytic BN-films have been prepared continuously on HT-carbon fibres by conventional CVD using the reaction of BCl3 with NH3 at temperatures between 700–1000° C and at ambient pressure. The film thickness varied with the N: B ratio, the dilution of the reactant gases, the flow conditions in the reactor tube and the velocity of roving. Good infiltration was obtained up to a thickness of about 50 nm at a speed of roving of 5 m/h. The coatings were characterized by XPS, TEM, REM, X-ray diffraction and thermogravimetric analysis.
    Type of Medium: Electronic Resource
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