Graphitization behavior of carbon nanofibers derived from bacteria cellulose

Bacteria cellulose was prepared from nata de coco which is composed of pure cellulose nanofibers. The nanofibers were dispersed in ethanol or distilled water and were stirred and then filtered to obtain paper-like sheets. The diameters of the nanofibers were in the range of 30 to 60 nm. The sheets were carbonized and then heat-treated at temperatures between 2400 and 3200 °C in a high purity Ar flow under atmospheric pressure, and the texture and structure of the heat-treated sheets were investigated. Cellulose-based carbon materials are known to be one of the nongraphitizing carbons. However, graphitization of the carbon sheets was observed as a result of the heat treatment, and was especially apparent for those from the nanofibers dispersed in ethanol. The development of a graphite structure in the carbon nanofibers of the sheets seems to be attributed to graphitization on the surface of nongraphitizing carbon, and the surface graphitization seems to extend to the inside of the carbon nanofibers with very thin diameters of 30–60 nm. The graphitization degree of the 3200 °C-treated sheet derived from the nanofibers dispersed in ethanol was nearly comparable to that for a commercial graphite nanofiber powder VGCF®. However, the improvement in structural perfection with heat treatment for the carbon sheets was less remarkable in comparison with that for typical graphitizing carbons. The limited graphitization behavior of the heat-treated sheets may be attributed to their heterogeneous structure.