Carbon nanofiber, method for production thereof, method for production of carbon fiber composite material using carbon nanofiber, and carbon fiber composite material

A method of producing a carbon fiber composite material comprising:

• providing first carbon nanofibers produced by a vapor growth method;
• oxidizing the first carbon nanofibers and reducing the mass of the first carbon nanofibers by 2 to 20% to obtain second carbon nanofibers having an oxidized surface, the second carbon nanofibers having a surface oxygen concentration measured by X-ray photoelectron spectroscopy (XPS) of 2.6 to 4.6 atm % and the second carbon nanofibers having a ratio (D/G) of a peak intensity D at around 1300 cm−1 to a peak intensity G at around 1600 cm−1 measured by Raman scattering spectroscopy of 0.12 to 0.22;
• and
• mixing the second carbon nanofibers into an elastomer, and uniformly dispersing the second carbon nanofibers in the elastomer by applying a shear force to obtain a carbon fiber composite material.

A method of producing a carbon fiber composite material comprising:

• providing first carbon nanofibers produced by a vapor growth method;
• oxidizing the first carbon nanofibers to obtain second carbon nanofibers having an oxidized surface, the second carbon an having a surface oxygen concentration measured by X-ray photoelectron spectroscopy (XPS) of 2.6 to 4.6 atm % and the second carbon nanofibers having a specific surface area by nitrogen adsorption of 34 to 58 m2/g;
• and
• mixing the second carbon nanofibers into an elastomer, and uniformly dispersing the second carbon nanofibers in the elastomer by applying a shear force to obtain a carbon fiber composite material.