Graphitization studies of anthracites by high resolution electron microscopy

Thirteen anthracites of various origin were studied by modern electron microscopy techniques, microdiffraction, bright field, dark field and lattice imaging in the raw and progressively heat-treated state. The anthracites are known to behave like hard carbons below HTT 2000°C and like soft carbons above 2500°C. We have found that flattening of the pores, which is not present in hard carbons, occurs in anthracites and that this flattening induces a preferred orientation of the carbon planes above 1700°C, which in turn allows graphitization. This evolution of the carbon structure, demonstrated for the first time, is the essential phenomenon for anthracites. It becomes hidden by the promoting effect of impurities included in anthracites, if their concentration is too high.