the nature of the graphite:
the mineral graphite is one of the allotropes of carbon. there are two principal types of natural graphite, each occurring in different types of ore deposit: crystalline flake graphite occurs as isolated, flat, plate-like particles with hexagonal edges and when broken the edges can be irregular or angular; amorphous graphite occurs as fine particles and is the result of thermal metamorphism of coal, the last stage of coalification.
graphite is a layered compound, and has special atomic structures. therefore, graphite has physical properties as following: high-temperature resistance, good conductivity of heat and electricity, excellent lubrication, good chemical stability, plasticity and thermal shock resistance and much more.
uses of natural graphite:
crystalline flake graphite is widely used in many areas such as metallurgy, machinery, petroleum, chemicals,nuclear industry and national defence. its main applications are as follows:
this end-use begins before 1900 with the graphite crucible used to hold molten metal; this is now a minor part of refractories. in the mid 1980s, the carbon-magnesite brick became important, and a bit later the alumina-graphite shape. currently the order of importance is alumina-graphite shapes, carbon-magnesite brick, and then crucibles.
zinc-carbon batteries, electrode, electric motor brushes, carbon tube and coating used in television kinescope.
foundry facings and lubricants：
a foundry facing or mold wash is a water-based paint of fine flake graphite.painting the inside of a mold with it and letting it dry leaves a fine graphite coat that will ease separation of the object cast after the hot metal has cooled.graphite lubricants are specialty items for use at very high or very low temperatures, as an antiseize agent, a gear lubricant for mining machinery, and to lubricate locks.
natural graphite has found used as the marking material in common pencils, in steel-making, in brake linings, and in seal rings.