Preparation, Characterization, and Surface Modification of Carbon-Encapsulated Nickel Nanoparticles

Carbon-encapsulated nanonickel particles were prepared by heating nickel acetate highly dispersed in cured phenolic resin at 673 K in N2. The metallic nickel cores were about 50—80 nm in diameter, completely encapsulated with carbon shells about 10 nm thick. No byproduct, such as carbides, carbon rods, and carbon fibers, were formed in the samples prepared this way. The carbon shells prevented the metallic nickel cores from oxidation by air at high temperatures. The metallic cores remained even after the encapsulated particles were treated with 6 M hydrochloric acid solution for 24 h. The surface of the encapsulated particles was originally hydrophobic due to the hydrophobic property of the carbon shells formed under the high carbonization temperature. The treatment of the encapsulated particles with O3 at room temperature generated substantial amounts of carboxylic groups on the outer surface of carbon shells, leading to the hydrophilic surface of the encapsulated nanonickel particles.