Transmission electron microscopy studies on carbon materials prepared by mechanical milling

Abstract

The effects of mechanical milling on the multiscale organization (structure and microtexture) of various carbon materials were investigated by means of Transmission Electron Microscopy. We show that mechanical grinding generates an increasing amount of disordered carbon at a rate depending on the type of grinding mode used (shear- or shock-type grinding). When the shock-type grinding is used, the triperiodic structure and the lamellar microtexture of the graphite completely break down to give microporous and turbostratic carbons made of misoriented nanometric Basic Structural Units (BSUs). Graphite grinding permits the elaboration of disordered carbons. The involved mechanism is different from a simple reverse graphitization, since not only structure but also microtexture are strongly modified by the grinding. After heat treatment at 2800°C, the graphite organization is not recovered, and a mesoporous turbostratic carbon is mainly obtained. All the carbon precursors studied, submitted to strong grinding, leads to similar microporous carbons. Shear grinding is less effective since remnants of graphitic carbon are still present within the disordered carbon.