Carbide Coatings on Graphite Fibers by Liquid Metal Transfer Agent Method

Abstract

Titanium and zirconium carbide layers were produced on the surface of graphite fibers. The process allows a controlled reaction of the fibers with the carbide-forming elements dissolved in a molten tin bath, which acts as the transferring medium. The coatings were analyzed by optical and scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. It was found that they consist of two distinct layers, one with the binary carbide composition in contact with the fiber core and an exterior one having a ternary carbide composition. The coatings are brittle, continuous, and uniform along and across the fibers and show good adherence to the carbon core. The carbide growth process is difF'usion-controlled with an activation energy of 184 kJ/mol. The coated fibers are readily wetted by molten aluminum.

Carbon Materials Reinforced Aluminum Composites: A Review

“…TiC coating is studied because it is theoretically more stable than Al 4 C 3 and would not be degraded by contact with aluminum [46,58]. Meanwhile, TiC coating can be produced by a liquid metal transfer agent method which is schematically shown in Fig.…”

“…This method is effective but the matrix composition is modified, which may affect the overall properties of the composites. (3) Coating the carbon materials to produce diffusional barriers to prevent interfacial reactions and/or improve wettability, such as Ni [24,[27][28][29][30][31][32][33][34][35], Cu [27][28][29][36][37][38][39], W [40], Ti [41][42][43], SiC [44][45][46][47][48], TiC [44,46,[49][50][51][52][53], Al 2 O 3 [54,55], TiO 2 [29,56], ZrO 2 [57,58] and pyrolytic carbon [44,59,60] coatings. This method is effective and widely accepted, and it will be discussed in detail later.…”

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

“…However, this method is inapplicable in the case of carbon fibers, because this method requires a flat substrate that can hold a complete drop of molten metal [12]. In this study, the wettability measurement process was carried out using the method similar to that reported in literature [5]. The fibers were stacked in alternate layers with Mg granules inside a graphite crucible or with Al granules inside an alumina crucible.…”

“…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]. The coating layer must have high enough temperature stability and reasonable strength and adherence to permit good load transfer between fibers and matrix.…”

“…The coating layer must have high enough temperature stability and reasonable strength and adherence to permit good load transfer between fibers and matrix. Among the numerous coatings proposed in the literature, TiC is especially attractive for its stability, low density and excellent wettability by molten Mg and Al [5,6]. Generally, used as titanium source) and the high reaction temperature (above 1100°C) may damage carbon fibers in the coating process [7].…”