The carbon nanomaterials are synthesized at 800-1000 degrees C using paper phenolic (PP) board and NiCl2 aqueous solution as the carbon source and catalyst precursor, respectively. The products include hollow-cored, multi-walled carbon nanofibers (CNFs), platelet-stacked-type CNFs, nanocapsules, and cup-stacked-type CNFs. It is suggested that the catalyst shape plays an important role in the microstructure of the carbon nanomaterials. Since the PP board is used as the insulating substrate of printed circuit board (PCB), the results of this study show that recycling the waste PCBs and using their PP boards to synthesize valuable carbon nanomaterials are of high feasibility. (C) 2011 Elsevier B.V. All rights reserved.