Expanded carbon fiber product and composite using the same

An expanded stacked cup carbon nanofiber product comprising a vapor grown coaxial stacking morphology of truncated conical tubular graphene layers,

• wherein each of the truncated conical tubular graphene layers includes a hexagonal carbon layer and has a large ring end at one end and a small ring end at the other end in an axial direction,
• wherein at least part of edges of the hexagonal carbon layers are exposed at the large ring ends,
• wherein the stacked cup carbon nanofiber has a round cross-section,
• wherein a plurality of gaps between the hexagonal carbon layers is larger than the gaps between the hexagonal carbon layers at the time of vapor growth due to an expansion treatment applied to the carbon fibers, and
• wherein the plurality of gaps between the hexagonal carbon layers after expansion treatment are about 100 to about 1000 times larger than the gaps between the hexagonal carbon layers prior to expansion treatment, and the gaps between the hexagonal carbon layers prior to treatment are about 3 Å to about 4 Å.