Electrical energy can be converted into heat energy through ohmic joule heating. Metallic materials are typically used in electrical heating elements because of their great electrical conductivity. However, metallic materials have several weaknesses, such as corrosion sus-ceptibility, heavy weight, high manufacturing costs, and electromagnetic wave emissions [1,2]. To resolve these problems, carbon materials with good electrical conductivity, such as carbon fibers, graphite fibers, carbon nanotubes, and carbon black, have been examined as heating materials [3,4]. Among these carbon materials, graphite fibers possess many advan-tages compared to carbon fibers such as good mechanical and electrical properties, excellent chemical stability, high thermal conductivity, and so on [5-7]. However, the electrical con-ductivity of graphite fibers is much lower than that of copper, which is too low to improve the heating properties. Therefore, metal-incorporated graphite fibers have been considered as attractive materials to achieve improved heating properties [8,9]. Metal can be incor-porated into carbon structures using several different methods, such as electrodeposition, electroless deposition, doping, and impregnation. Among these methods, impregnation by stirring in a metal solution is a simple, easy, and cost-effective method, but this method incorporates less metal into the structure than that of other methods [10,11]. To overcome this limitation, ultrasonication has been used to impregnate metal atoms in a solution, which can attach more metal atoms on the surface of supporters than that of previous impregnation methods because it provides more opportunities for reactions between supporters and metal atoms. Moreover, when a solution is exposed to ultrasonication, high temperature and pres-sure fields accelerating the chemical reaction may be produced at the centers of the generated bubbles in a solution. Therefore, ultrasonication treatment has become probably the most widely used and effective mechanical technique [12].