Highly graphitized carbon from non-graphitizable raw material and its formation mechanism based on domain theory

This work demonstrates conversion of non-graphitizable carbon (NGC) to graphitizable carbon (GC) by NaOH treatment of carbonized spherical phenol resin (SPR). The degree of graphitization of the studied SPRs was confirmed using X-ray diffraction and Raman spectroscopy, and their morphologies were observed with scanning electron microscopy and scanning tunneling microscopy. Graphitization of amorphous carbonized SPR at 2800 degrees C was performed; however, the degree of graphitization was low to indicate that carbonized SPR was non-graphitizable. NaOH treatment of carbonized SPR endowed fairly high degree of graphitization; graphitization of carbonized SPR following NaOH activation improved the degree of graphitization. Thus NaOH treatment was demonstrated to convert non-graphitizable SPR to graphitizable one. The role of NaOH was suggested in terms of hierarchical domain structure model. NaOH treatment could successfully destroy micro-domains of carbonized SPR via sodium intercalation/deintercalation and catalytic gasification with deintercalated sodium atoms with releasing hydrogen and gaseous carbon oxides and decreasing alkyl groups, and reconstruct the new larger clusters and microdomains merged together to relieve the distortion stresses. Thus merged micro-domains would be critical in the conversion of NGC to GC. The presented findings open up a possibility to control the properties of carbon materials by manipulation of their domain structures. (C) 2017 Elsevier Ltd. All rights reserved.