This study elucidates the stabilization and activation in forming activated carbon fibers (ACFs) from ultra-thin polyacrylonitrile (PAN) fibers. The effect of stabilization time on the properties and structure of resultant stabilized fibers was investigated by thermal analysis, X-ray diffraction (XRD), elemental analysis, and scanning electron microscopy (SEM). Stabilization was optimized by the pyrolysis of ultra-thin PAN fibers in air atmosphere at 280 degrees C for 15 min, and subsequent activation in steam at 1000 degrees C for 0.75 to 15 min. Resultant ACFs were characterized by N-2 adsorption at 77 K to evaluate pore parameters, XRD to evaluate structure parameters, and field entission scanning electron microscopy (FESEM) to elucidate surface morphology. The produced ACFs had surface areas of 668-1408 m(2)/g and a micropore volume to total pore volume ratio from 78 to 88%. Experimental results demonstrate the surface area and micropore volume of 1408 m(2)/g and 0.687 cm(3)/g, respectively, following activation at 1000 degrees C for 10 min. (c) 2008 Wiley Periodicals, Inc.