Synthesis and properties of nickel-dispersed carbons by pressure pyrolysis of nickelocene-divinylbenzene

Nickel-dispersed carbon was synthesized by pressure pyrolysis of nickelocene-divinylbenzene at temperatures below 700° C at 125 MPa. The carbon so produced contained uniformly dispersed metallic nickel particles less than 40 nm in size with low crystallinity. The magnetization of nickelocene-divinylbenzene polymer increased abruptly at 280° C. The morphology of carbon changed from coalescing polyhedra to filaments via coalescing spherulites as the temperature increased from 550 to 700° C. Carbon tubes of 30 nm diameter were formed by pyrolysis of nickelocene-divinylbenzene at 650° C and 125 MPa. The Curie point of nickel-dispersed carbon was 360° C. The uniform dispersion of nickel with comparable crystallinity in the carbon matrix gave a linear relation between the saturation magnetization and the nickel concentration. The saturation magnetization of nickel-dispersed carbons synthesized at temperatures below 650° C and at 700° C were 60 and 85% of the theoretical value, respectively. The saturation magnetization of the nickel-dispersed carbon could be increased to reach 90% of the theoretical value with an increase in the crystallinity of dispersed nickel particles by subsequent heat treatment at 700° C for 7 h.