Catalytic growth of nickel-encapsulated and hollow graphitic carbon nanoparticles during laser vaporization of cellulose char containing nickel

Nickel-encapsulated and hollow graphitic carbon nanoparticles (CNPs) with diameters of up to 200 nm were fabricated from cellulose char containing nickel, by continuous wave Nd:YAG laser vaporization. The relative yields of the Ni-encapsulated and hollow CNPs strongly depended on the laser power density and the quantity of Ni in the cellulose char. The hollow CNPs with yields of up to 90% were successfully formed with increasing laser power density. A net-like structure composed of small fragments of bending graphitic layers was also produced under an excess condition of the cellulose char. We discuss the formation mechanisms of the CNPs, in which the growth of graphitic layers around Ni particles and their separation repeatedly occur after the start of laser irradiation.