Comparative investigation of defects on carbon black surfaces by nitrogen adsorption and SIMS

Abstract

Defects on carbon black surfaces are studied by low-pressure nitrogen adsorption at 77 K. The shape of the experimental carbon black isotherms and simulated isotherms on defect graphite surfaces [Carbon 36 (1998) 1439] are in good agreement. Surface defects cause a reduced nitrogen adsorption for P/ P 0 from ∼5×10 −5 to ∼0.1. This decrease can be used as a measure of the surface defect concentration. The adsorption potential distribution (APD), calculated from the adsorption data, also depends on the concentration of surface defects. It is possible to use the area of the monolayer formation peak in the APD as another measure of the concentration of surface defects. Both measures correlate well with the concentration of surface defects determined by surface spectroscopy (SIMS). Thermal carbon blacks produced from natural gas exhibit a higher concentration of surface defects than furnace blacks and thermal blacks produced from oil feedstock. However, important differences exist, even for carbon blacks of the same grade.