Based on a novel solvent-free coextrusion and melt-spinning of polypropylene/(phenol formaldehyde-polyethylene)-based core/sheath polymer blends, a series of activated carbon nanofibers (ACNFs) have been prepared and their morphological and microstructure characteristics analyzed by scanning electron microscopy, atomic force microscopy (AFM), Raman spectroscopy, and X-ray diffractometry with particular emphasis on the qualitative and quantitative AFM analysis. The effect of activating agent, potassium hydroxide, and phosphorous acid is compared, and factors affecting the surface morphology and microstructure of ACNF are analyzed.