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, subbitumino us coal and a bituminous coal, and KOH with a bituminous coal. The ref lectance of thermally treated carbons follows a single correlation wit h heat treatment temperature (HTT), consistent with thermally induced increases in aromaticity and structural order. For chemically activate d carbons, the relationship between reflectance and HTT depends upon t he precursor-activant combination that is used. At low HTT, chemically activated carbons have higher reflectance than their thermally treate d 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 contri buting to the scattering of incident light.