RELATIONSHIP BETWEEN REFLECTANCE AND STRUCTURE OF HIGH-SURFACE-AREA CARBONS

Reflectance measurements have been used to try to track the structural alterations during activated carbon synthesis by chemical activation. H3PO4 has been used as a chemical reagent with white oak, subbituminous coal and a bituminous coal, and KOH with a bituminous coal. The reflectance of thermally treated carbons follows a single correlation with heat treatment temperature (HTT), consistent with thermally induced increases in aromaticity and structural order. For chemically activated carbons, the relationship between reflectance and HTT depends upon the precursor-activant combination that is used. At low HTT, chemically activated carbons have higher reflectance than their thermally treated counterparts, due to accelerated chemical change. At higher HTT this situation is reversed, despite further increase in aromaticity. It is proposed that the development of significant porosity (principally in pores 2-50 nm in diameter) reduces the measured reflectance by contributing to the scattering of incident light.