THE MICROSTRUCTURE OF CARBON-BLACK INVESTIGATED BY ATOMIC-FORCE MICROSCOPY

Using the optical lever technique we have developed an atomic force microscope (AFM) which can also detect the friction force. In contrast to the scanning tunneling microscope (STM) the AFM is able to measure both conductive and nonconductive surfaces at resolutions down to the atomic level. This technique has been applied to two carbon blacks (N110, N762) produced by oilfurnace process. The structural investigations of carbon black particles with the AFM show quasi-spheroidal particles fused together to form aggregates. The measured diameters of the particles are in good agreement with the data of the manufacturer. At higher magnification of the particle surface the images show individual particles consisting of graphite layer stacks organized in a concentric way around the center of the particle. A step-like structure of the surface is clearly shown by the AFM, arising from layer stacks tilted with respect to each other. The lateral size of the layers changes with the variation of the investigated carbon blacks. A value of 1.0-1.5 nm was found for the lateral layer size of N110 and 1.8-2.5 nm for N762. The lateral dimensions and the tilt of the graphite layer stacks could be significant parameters with regard to the reinforcing effect of carbon black.