Catalytic graphitization of carbons by borons

Boron is known as a unique graphitization catalyst, because it accelerates the homogeneous continuous graphitization process of the entire carbon without any formation of specific carbon components such as graphitic carbon. This study uses various amounts of boron and several kinds of carbon in an attempt to reveal whether the boron exhibits other kinds of catalytic effect. For the non-graphitizing phenol-formaldehyde resin carbon, a boron addition of 1 wt % accelerates the homogeneous continuous graphitization process of the entire carbon at heat-treatment temperatures from 1800 to 2600 °C. As the amount was increased to 5 and 10 wt %, the boron catalysed the formation of specific turbostratic carbon (no three-dimensional ordered structure, d002 3.38 Å, Lc 200 Å∗) at 2200 °C, and graphitic carbon (three-dimensional ordered structure, d002 3.36 Å, Lc 1000 Å) above 2400 °C, besides the homogeneous effect, which was enhanced by increased heat-treatment temperature and an increase in the amount of boron. For the graphitizing 3,5-dimethylphenol-formaldehyde resin carbon, only the homogeneous acceleration was catalysed by 1 wt % boron. Additions of 5 and 10 wt % boron resulted in the formation of graphitic carbon above 2400 °C in addition to the homogeneous effect observed above 1800 °C. Turbostratic carbon was never found. The catalytic mechanisms for these effects are discussed.