Development of graphite-like particles from the high temperature treatment of carbonized anthracites

Abstract

Abstract The aim of this study is the optical and structural (micro-Raman spectroscopy and X-ray diffraction) characterization of particles formed during the high temperature treatment (HTT) of anthracites. Two anthracites of different rank, from the Penarroya–Belmez–Espiel Basin (PBEB, Spain) (Rr = 2.62%), and the Douro Basin (DB, Portugal) (Rr = 6.25%), were carbonized at 1000 °C in a tube furnace, under nitrogen flow, and then treated at temperatures of 2000 °C and 2500 °C, in a graphite furnace. After treatment at these high temperatures, the residues obtained show various graphite structures, namely, flakes, microspheres and crystalline aggregates, in percentages that depend on type of the precursor (carbonized anthracite) and temperature. These structures grow from the dense particles, which are the major component of the studied samples. Flakes, microspheres and crystalline aggregates develop and acquire their properties at 2000 °C, and minor changes occurring with the rise in temperature. Moreover, theses structures exhibit similar characteristics to those of graphite edge planes. Dense particles from both samples show an improvement in their microstructure with the rise in temperature. This improvement is greater in dense particles from the carbonized DB anthracite. In fact at 2500 °C these dense particles show optical and structural properties similar to those found in natural graphite. This was not found in the case of dense particles from the carbonized PBEB anthracite. These observations are also supported by the X-ray diffraction parameters which confer the highest degree of crystallinity for the carbonized DB sample at 2500 °C.