A method for characterization and quantification of platelet graphite nanofiber edge crystal structure

Abstract

Platelet graphite nanofibers are materials produced from the decomposition of carbon monoxide and hydrogen over iron powders. The surface consists of terminated graphite edges, differing from traditional graphite materials in which basal plane graphite surfaces dominate. The 3-dimensional morphology and crystal face exposure on the nanofiber surface was determined by selected area electron diffraction studies. From orientation of the 〈 1 0 1 ¯ 0 〉 “zigzag” and 〈 1 1 2 ¯ 0 〉 “armchair” directions, the concentration of { 1 1 2 ¯ 0 } and { 1 0 1 ¯ 0 } face families on the fiber surface, along with the overall geometry and shape of the nanofibers, were determined. To overcome the problem of large aspect ratio in such materials, the fibers were cleaved along the basal plane, which was oriented perpendicular to the fiber axis. Effectively, the materials were transformed into multiple single crystal graphite structures. The cleaved samples, because of the decreased depth of field, were then observed end on using transmission electron microscopy techniques. It was found that the zigzag/armchair face ratio for most observed structures was ∼1.7/1, but some samples deviated from this ratio. Such knowledge is useful in discerning types of graphite surfaces are exposed when nanostructured carbons are used as catalysts and catalyst supports.