Carbon fibres coated with titanium carbide using the liquid metal transfer agent technique

Abstract

Protective coatings of titanium carbide were applied to PAN type carbon fibres by a liquid metal transfer agent (LMTA) technique using tin as a transfer agent. The effect of the coating on the strength of the fibres was evaluated by performing single fibre tensile tests. The coatings were examined metallographically, by X-ray diffractometry, and by scanning electron microscopy. Carbide coating thicknesses obtained ranged from approximately 0.05 to 0.5#m and the coatings were found to be uniform and adherent to the fibres. It was found that wetting of the fibres by the tin alloy is associated with the spontaneous formation of a carbide layer with a thickness dependent upon the melt temperature, after which the carbide layer was found to grow parabolically with time and with an apparent activation energy of 187kj mo1-1. The strength of the carbon fibres decreased with increasing coating thickness according to a Griffith relation.

Tensile strength, oxidation resistance and wettability of carbon fibers coated with a TiC layer using a molten salt method

“…In all cases the normalized tensile strength of the coated carbon fibers decreases with the increasing coating thickness. However, the decrease in strength with coating thickness in the present study is comparable to or much less than that observed with coated fibers synthesized by CVD [15] and LMTA technique [4], indicating that the molten salt method is very promising in terms of preserving the tensile strength of the carbon fibers while obtaining a TiC coating with an appropriate thickness on them.…”

“…The cracks will eventually propagate into the fiber under further loading if the bonding between the coating and the fiber is strong enough to withstand the shear stress at the interface [4]. Obviously, these cracks in the coating act as stress raisers which reduce the tensile strength of the fibers.…”

“…These mechanical and physical properties are quite attractive for structural, thermal and electrical applications. However, the development of carbon fiber reinforced metal matrix composites has been hindered by the low oxidation resistance of carbon fibers, poor wetting characteristics of carbon fiber by liquid metal, as well as the chemical reaction between carbon fibers and many metals, which introduce many difficulties in the fabrication and high temperature application of these composites [4]. To promote wetting and simultaneously provide a barrier against excessive interfacial reaction between the fibers and the matrix metal during the fabrication of the composites, it is necessary to develop a suitable protective coating on the carbon fiber surface [5].…”

Influence of Hot Extrusion on Microstructure and Hardness of SiC Particle Reinforced Al-Zn-Mg-Cu Alloy Matrix Composite

“…Methods improving the wettability of SiCp-Al and interfacial reaction in the preparation of aluminum composite reinforced by SiCp, mainly are high temperature oxidation, surface coating(Cu, Ni, Ag et al), alloy element adding(Mg, Li, Be et al)and stirring et al [17][18][19]. Usually, only the combination of these methods can make good SiCp-Al interfacial bonding and well property of aluminum composite [19].…”