Synthesis of Vapor-Grown Carbon Fibers Using Nanocrystalline Fe₇₅Si₁₅B₁₀ Alloy as a Catalyst

Abstract

The synthesis of vapor-grown carbon fibers (VGCFs) using the nanocrystalline Fe₇₅Si₁₅B₁₀ alloy as a novel catalyst has been investigated, and the growth process of VGCFs was discussed. The nanocrystalline Fe₇₅Si₁₅B₁₀ alloy with fine bcc-Fe grains less than about 20 nm was prepared by the melt spinning technique followed by annealing. VGCFs with a diameter of less than about 40 nm were successfully prepared using the nanocrystalline Fe₇₅Si₁₅B₁₀ catalyst at 773 K under 80%CO–20%H₂ atmosphere. High-resolution transmission electron microscopic characterization indicated that the VGCFs catalytically generated over the Fe₇₅Si₁₅B₁₀ nanocrystal surfaces at both 773 K and 873 K most likely have a tubular-type structure, in which the graphite sheets were stacked parallel to the fiber axis. The Fe₇₅Si₁₅B₁₀ catalyst particles appear to be made of the single-phase Fe₃C grains, which is in contrast to the Fe₉₁Zr₇B₂ catalyst particles previously studied by us. The formation of Fe₃C leads to the brittleness of catalyst particles and results in a growth of filamentous carbon.