Characteristics of graphite mineral raw materials

Graphite is one of the crystalline minerals of carbon element, with lubrication, chemical stability, high temperature resistance, electrical conductivity, special thermal conductivity and plasticity, coating and other excellent properties, its application areas are very extensive. Graphite is mainly used as refractory materials in the metallurgical industry; used as casting molds and anti-rust coatings in the foundry industry; used in the electrical industry for the production of carbon electrodes, electrode carbon rods, batteries, graphite milk made of graphite milk can be used as a television picture tube coating, made of carbon products can be used for generators, motors, communication equipment and many other aspects; in the machinery industry as a lubricant for high-speed running machinery such as airplanes, ships, trains; used in the chemical industry for the manufacture of various anti-corrosion utensils and equipment In the nuclear industry, it can be used as a neutron moderator and protective material in atomic reactors; in the aerospace industry, it can be used as a tail nozzle throat liner for rocket engines, thermal insulation and heat-resistant materials for rockets and missiles, and radio connection signals and conductive structural materials on artificial satellites. In addition, graphite is a polishing agent and rust inhibitor for glass and paper in light industry, and is a raw material for the manufacture of pencils, inks, black paints, inks and synthetic diamonds. With the development of modern science and technology and industry, the application field of graphite is still expanding, and has become an important raw material for new composite materials in the field of high technology, and plays an important role in the national economy. 

The chemical composition of graphite is carbon (C). Naturally produced graphite is rarely pure, often containing 10% to 20% impurities, including SiO2, Al2O3, MgO, CaO, P2O5, CuO, V2O5, H2O, S, FeO and H, N, CO2, CH4, NH3 and so on. Graphite minerals are iron black, steel gray, strip marks bright black; metallic luster, cryptocrystalline aggregate gloss dull, opaque; cleavage {0001} complete, hardness is heterodirectional, vertical cleavage surface is 3~5, parallel cleavage surface is 1~2; soft, density is 2.09~2.23g/cm3, there is a sense of slippery, easy to contaminate fingers. Mineral flakes are generally opaque under transmitted light, very thin sheets can transmit light, showing light greenish gray, one-axis crystal, refractive index 1.93 ~ 2.07, light brown gray under reflected light, reflective polychromaticity is obvious, Ro gray with brown, Re dark blue gray, reflectivity Ro23 (red), Re5.5 (red), reflective color, double reflection are significant, strong heterogeneity, polarization color is straw yellow. Graphite belongs to the compound hexagonal double conical crystals, along the {0001} is a hexagonal plate-like crystal, the common monoform has parallel double-sided, hexagonal double cone, hexagonal column, but the intact crystal shape is rare, generally scaly or plate-like, the aggregate is dense block, soil or spherical. 

Graphite crystals have a typical layered structure, with carbon atoms arranged in a hexagonal network layer, and carbon atoms on the surface mesh nodes relative to the center of the upper and lower adjacent meshes. The repeating layer of 2 is graphite 2H multitype, which belongs to the hexagonal crystal system, that is, the graphite commonly referred to; if the repeating layer is 3, it is graphite 3R multitype, which belongs to the tripartite crystal system, but cannot be separated separately in the natural graphite structure. In the graphite crystal structure, the coordination number of carbon atoms in the layer is 3, with covalent metal bonds, the spacing is 0.142nm, and the layers are connected by molecular bonds, the spacing is 0.340nm, and this special crystal structure and chemical bonding make graphite have some special process properties.