In-situ processing of carbon coatings on the surface of SiC-based fibers

Abstract

Carbon coatings have been formed on the surface of free carbon containing Tyranno ZMI and Nicalon SiC-based fibers by reaction with chlorine gas (chlorination) in the temperature range 550-675 °C. The kinetics and growth mechanisms have been investigated for both fibers. Results have shown that, for similar experimental conditions, the reactivity of both fibers displayed noticeable discrepancies. It has thus been observed that the Nicalon fiber was more prone to chlorine-based treatment and displayed a thicker carbon coating than the ZMI fiber. These results have also revealed that, in both case, these thicknesses can be closely monitored by physical parameters such as temperature and aging duration. The nature of the obtained coating has also been investigated by various experimental devices. AES, SEM and TEM analyses have thus evidenced that these carbon coatings were uniform and well adherent whereas AFM showed that the chlorine-based treatments resulted in a nanometer-range roughness at the fiber surface. Adsorption gas analyses also revealed a microporosity coupled with a high specific surface area. The chemical composition of the final products was determined by XPS and Mass Spectroscopy. Finally, the oxidation behaviour which was investigated by thermogravimetric analysis revealed that oxidation occurs at a quite low temperature (225°C).

In situ preparation of C–SiCxOy coatings with controllable composition on continuous oxygen-enriched SiC fibres

“…The SSA of the coating increases with elevating temperature, which is in accordance with the results in ref. 18. However, since the thickness of the CDC coatings obtained at various temperatures is different, the true weight percentage of the porous region (CDC coating in the bre) is changeable and unmeasurable for different samples.…”

“…[14][15][16][17] A. Delcamp et al reported the kinetics of the growth of the CDC coating on two types of the SiC-based bres, Tyranno ZMI and Nicalon. 18 In the temperature range of 550-675 C, the coating thickness is found to increase linearly with the etching time (in Cl 2 environment), suggesting that the coating growth is controlled by interfacial reaction. It should be noted that oxygen of $9 at% and $14 at% is present in the Tyranno ZMI and Nicalon bre, respectively.…”

Study of TiC Coatings on Nicalon Fibre Prepared by Pressure-Pulsed Reactive Chemical Vapour Deposition at Low Pressure

“…The process is detailed by Delcamp and al. (7). After the chlorination treatment, the thickness of the carbon coating surrounding the fibre is about 200 nm.…”

Study of TiC Coatings on Nicalon Fiber Prepared by Pressure-Pulsed Reactive Chemical Vapor Deposition at Low Pressure

“…The nanoporous carbon coating was formed at the surface of the Nicalon fibre by extraction of Si from SiC of the fibre with pure chlorine according to the following equation: SiC(s) + 2Cl 2 (g) = C(s) + SiCl 4 (g) equation 1 The process is detailed by Delcamp and al. [3]. After the chlorination treatment, the thickness of the carbon coating surrounding the fibre is about 200 nm.…”