Aluminum Oxide and Chromium Oxide Coatings on Ceramic Fibers via MOCVD

Abstract

The overall strength and toughness of ceramic matrix composites is very much affected by the interfacial properties that govern the bonding between the reinforcing fibers and the matrix. The ability to control this interaction is very important. One method involves coating the ceramic fibers with an appropriate material. There is a definite advantage in using lower-temperature processes to produce the coatings: fibers subjected to high-temperature coating processes are more prone to degradation due to microstructure and crystallization changes. Matrix and fiber materials could also react at high temperatures to form a strong bond at the interface making the composite brittle. Metal−organic precursors were used to produce aluminum oxide and chromium oxide coatings on SiC and Al2O3−SiO2 based ceramic fibers. These metal oxides were deposited on the reinforcing fibers by the pyrolysis in air of their respective metal acetylacetonates at temperatures of 500 °C or less. The coated ceramic fibers showed some reduction in tensile strength but still had considerable strength for use in composites.

Fluidization and coating of very dense powders by Fluidized Bed Chemical Vapour Deposition

“…The relative comparison of the EDS spectra of uncoated and coated particles indicates that, on these latter, an alumina film with carbon impurities was obtained. This result is in good accordance with previous works reported in literature, as already mentioned (Minkina, 1993;Nable et al, 2003).…”

“…However, several works, in which alumina coatings were obtained from aluminium acetylacetonate precursor in our range of temperature, i.e. 390-450 • C, have reported that obtained films exhibited orange-claret (Minkina, 1993), golden brown (Nable et al, 2003) or tan and dark tan (Nguyen et al, 2002) tints. These colours could be explained by an alumina film contamination due to carbon and pyrolysis by-products incorporation.…”

A single-molecular pathway from heterometallic MM′ (M = Baii, Mnii; M′ = Criii) oxalato complexes to intermetallic composite oxides

“…7 Recent research in chromium-based composite oxides has revealed their functions in alkane oxidation, 8 ammoxidation, 9 dental materials, 10 etc. These oxides are typically prepared from thermal 11 and sol-gel 12 techniques, or as thin films from MO-CVD 13 and pulsed laser desorption (PLD). 14 Little is known about their syntheses from well-defined single-molecular sources, although there are a few intermetallic molecular complexes that could serve as precursors to mixed-metal or alloy materials.…”

Fabrication of porcelain foam substrates coated with SiC, Ni, and Cr using the dip-coating technique

“…Futhermore, some advanced processes such as the atomic layer deposition [13], chemical vapour deposition (CVD) [14], physical vapour deposition (PVD) [15], electrodeposition [16], and magnetron sputtering [17] techniques can be found in the literature.…”