INFLUENCE OF COPPER ON THE STRUCTURAL CHARACTERISTICS OF CARBON NANOFIBERS PRODUCED FROM THE COBALT-CATALYZED DECOMPOSITION OF ETHYLENE

We have used a combination of techniques to examine modifications in t he structural characteristics of carbon nanofibers produced from the i nteraction of cobalt and copper-cobalt powders with ethylene at temper atures over the range 425 to 700 degrees C. The nanofibers generated f rom the interaction of cobalt with ethylene at 600 degrees C were foun d to be highly crystalline in nature. Incorporation of as little as 2% copper into the cobalt created a major modification in the conformati on of the solid carbon deposit, which was composed of multiple nanofib er limbs emanating from a single catalyst particle, and in this state the carbon structures tended to be disordered. As the composition of t he bimetallic was progressively changed to the point where copper beca me the major component, there was a significant increase in the degree of crystalline perfection of the nanofibers even though they maintain ed their multidirectional form. The transformation in structural chara cteristics of the carbon nanofibers is rationalized, according to a co ncept wherein the crystalline order of the deposit is related to the w etting properties of the bimetallic particles with graphite.