“…The absence of carbidic phase is expected, as Ni carbide is not stabile at 550 o C [76]. Similarly the presence of metallic state and the absence of carbidic phase of Ni catalyst were previously reported after deactivation from the catalytic carbon support gasification, after graphitization of the amorphous carbon film, and during and after CNT growth [44,63,65,[77][78][79][80][81]. Catalytic gasification, CNT and CNF growth, and catalytic graphitization presumably involve a similar general mechanism of carbon atoms dissolutions, diffusion and precipitation from the catalyst Ni particles [56,65].…”