Synthesis Of Metal-carbon Composites Via Laser Irradiation

As a composite with a unique core-shell structure, carbon encapsulated metalparticles(CEMPs) posess excellent electrical conductivity, magnetic property,biocompatibility, and can be applied in chemistry, materials, physics, biology fields.So far, many techniques have been developed to coat carbon layer over metalnanoparticles，among which laser technique exhibits a number of advantages, such assimple processing, green synthesis, short experimental period, few impurities. In thisthesis, CEMPs were fabricated by pulsed laser ablation of metal target in liquid, andthe formation mechanisms of these CEMPs were discussed.Carbon encapsulated nickel microparticles(CENMPs) were obtained by1064nmmillisecond pulsed laser ablation of nickel powders in anhydrous ethanol. Laserablation can heat nickel powders to a temperature over melting point, and thendecompose ethanol, the generated carbon atoms were adsorbed by nickel droplets andthen precipitated to form CENMPs. The product possessed high purity and exhibitedexcellent magnetic properties.Carbon encapsulated iron nanoparticles(CEINPs) with good dispersion werefabricated by1064nm nanosecond pulsed laser ablation of iron target in anhydrousethanol, using oleic acid as the surfactant. The dispersion of CEINPs could beimproved by empolying lower laser energy and surfactant concentration.Finally, we made primary investigation on the material synthesis by doublepulsed lasers where millisecond pulsed laser was combined with nanosecond pulsedlaser to irradiate a reaction system. The nanosecond laser excitated and decomposedraw materials for generating active reactants, at the same time the millisecond laserwas used for selective heating the products to control particle growth and achievieuniform nanoparticles.