Natural flake graphite powder is a kind of natural phanero-crystalline graphite, which is similar to fish phosphorus in shape and belongs to hexagonal crystal system with layered structure. It has high oxidation resistance, electrical conductivity, thermal conductivity, self-lubrication, plasticity and acid and alkali resistance.
Graphite can be sourced either organically or inorganically, with most commercially significant graphite deposits being of organic origin. It is available in a wide range of purity levels, from around 80% carbon to 99+% carbon. The higher the carbon content, the more expensive the material will be. Flake graphite is a very fine powder, and can be used for many different applications. The most common applications are as an electrode for the production of alumina-graphite crucibles to melt steel, graphite gaskets to seal high temperature equipment, and as a pencil lead in light bulbs (also known as arc lamp electrodes) and carbon rods in mercury positive brushes.
It is also an excellent lubricant, which has a low coefficient of friction and enables a high level of performance under load. Flake graphite is also a very good conductive material, with its ability to conduct electricity being due to the large number of electron delocalization within the carbon layers – a phenomenon called aromaticity.
Typical commercial flake graphite is produced by grinding, sizing and flotation. This can be done in hard-rock or soft-rock mining techniques, depending on the location of the ore deposit. Flotation is typically done using the froth method, with the resulting concentrate being sized and purified by other methods.