Influence of Inherent Coal Mineral Matter on the Structural Characteristics of Graphite Materials Prepared from Anthracites

Abstract

Anthracites with different mineral matter content and composition but similar organic matter composition and, therefore, microtexture were obtained by consecutive immersion in mixtures of organic liquids of increasing density from an anthracite with a low degree of graphitizability, thus reducing the characteristics of the anthracite that affect the graphitization process to the mineral matter. Graphite materials were then prepared by heating the anthracites in the temperature interval of 2400−2600 °C for the purpose of studying the influence of the anthracite mineral matter (amount and composition) on their ability to graphitize. The interlayer spacing ( d 002 ) and crystallite sizes (along the c -axis ( L c ) and along the a -axis ( L a )), calculated from X-ray diffractometry (XRD), as well as the relative intensity of the Raman D-band ( I D / I t ), were used to assess the degree of structural order of the materials. A progressive increase in this degree of structural order with increasing mineral matter content of the anthracite was observed. The catalytic effect of the mineral matter on the graphitization of the anthracites relies mainly on promotion of the growth of the crystallites along the basal plane. Reasonably good linear correlations between the mineral matter content and the L a value of the material were attained. Among the different constituents of the mineral matter, the clay mineral illite and the iron carbonates ankerite and siderite were observed to be the main active catalyst compounds during the graphitization of anthracites. In addition to the amount and composition of the mineral matter, the distribution of the mineral matter also influences the graphitization process of the anthracite. A fine distribution in the organic matter, such as that in the case of the iron compounds, was observed to improve the catalytic effect of the mineral matter.