Effects of specific surface area of metallic nickel particles on carbon deposition kinetics

Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature pro-graming oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I(D)/I(G) of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homo-geneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nick-el powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.