Graphite is an allotrope of elemental carbon, where each carbon atom is surrounded by three other carbon atoms (arranged in a honeycomb like pattern with multiple hexagons) that are covalently bonded to form covalent molecules.

Graphite has the following special properties due to its special structure:

1) High temperature resistance: The melting point of graphite is 3850 ± 50 ℃, and the boiling point is 4250 ℃. Even after being burned by an ultra-high temperature arc, the weight loss is very small, and the coefficient of thermal expansion is also very small. The strength of graphite increases with temperature, and at 2000 ℃, the strength of graphite doubles.

2) Conductivity and thermal conductivity: The conductivity of graphite is one hundred times higher than that of general non-metallic minerals. The thermal conductivity exceeds that of metal materials such as steel, iron, and lead. The thermal conductivity decreases with increasing temperature, and even at extremely high temperatures, graphite becomes an insulator. Graphite can conduct electricity because each carbon atom in graphite only forms three covalent bonds with other carbon atoms, and each carbon atom still retains one free electron to transfer charges.

3) Lubricity: The lubrication performance of graphite depends on the size of the graphite flakes. The larger the flakes, the smaller the friction coefficient, and the better the lubrication performance.

4) Chemical stability: Graphite has good chemical stability at room temperature, and can withstand acid, alkali, and organic solvent corrosion.

5) Plasticity: Graphite has good toughness and can be ground into very thin sheets.

6) Thermal shock resistance: Graphite can withstand drastic temperature changes without damage when used at room temperature. When the temperature suddenly changes, the volume of graphite does not change much and will not crack.

Usage:
1. Used as refractory material: Graphite and its products have the properties of high temperature resistance and high strength. They are mainly used in the metallurgical industry to manufacture graphite crucibles. In steelmaking, graphite is commonly used as a protective agent for steel ingots and as a lining for metallurgical furnaces.

2. As a conductive material: used in the electrical industry to manufacture electrodes, brushes, carbon rods, carbon tubes, positive electrodes for mercury rectifiers, graphite gaskets, telephone parts, coatings for television tubes, etc.

3. As a wear-resistant lubricating material: Graphite is often used as a lubricant in the mechanical industry. Lubricating oil often cannot be used under high speed, high temperature, and high pressure conditions, while graphite wear-resistant materials can work without lubricating oil at high sliding speeds at temperatures of 200-2000 ℃. Many devices that transport corrosive media widely use graphite materials to make piston cups, sealing rings, and bearings, which do not require the addition of lubricating oil during operation. Graphite emulsion is also a good lubricant for many metal processing (wire drawing, tube drawing).
4. Graphite has good chemical stability. Specially processed graphite, with characteristics such as corrosion resistance, good thermal conductivity, and low permeability, is widely used in the production of heat exchangers, reaction tanks, condensers, combustion towers, absorption towers, coolers, heaters, filters, and pump equipment. Widely used in industrial sectors such as petrochemicals, hydrometallurgy, acid-base production, synthetic fibers, and papermaking, it can save a large amount of metal materials.

The variety of impermeable graphite varies in corrosion resistance due to the different resins it contains. Phenolic resin impregnators are acid resistant but not alkali resistant; Furfuryl alcohol resin impregnators are both acid and alkali resistant. The heat resistance of different varieties also varies: carbon and graphite can withstand 2000-3000 ℃ in a reducing atmosphere, and begin to oxidize at 350 ℃ and 400 ℃ in an oxidizing atmosphere, respectively; The variety of impermeable graphite varies with the impregnating agent, and it is generally heat-resistant to below 180 ℃ by impregnating with phenolic or furfuryl alcohol.

5. Used for casting, sand turning, molding, and high-temperature metallurgical materials: Due to the small coefficient of thermal expansion of graphite and its ability to withstand changes in rapid cooling and heating, it can be used as a mold for glassware. After using graphite, black metal can obtain castings with precise dimensions, smooth surface, and high yield. It can be used without processing or slight processing, thus saving a large amount of metal. Powder metallurgy processes such as producing hard alloys typically use graphite materials to make ceramic boats for pressing and sintering. The crystal growth crucible, regional refining container, support fixture, induction heater, etc. of monocrystalline silicon are all processed from high-purity graphite. In addition, graphite can also be used as a graphite insulation board and base for vacuum smelting, as well as components such as high-temperature resistance furnace tubes, rods, plates, and grids.

6. Used in the atomic energy industry and national defense industry: Graphite has excellent neutron moderators used in atomic reactors, and uranium graphite reactors are a widely used type of atomic reactor. The deceleration material used in atomic reactors for power should have high melting point, stability, and corrosion resistance, and graphite can fully meet the above requirements. The purity requirement for graphite used in atomic reactors is very high, and the impurity content should not exceed dozens of PPMs. Especially, the boron content should be less than 0.5PPM. In the national defense industry, graphite is also used to manufacture nozzles for solid fuel rockets, nose cones for missiles, components for space navigation equipment, insulation materials, and anti radiation materials.

7. Graphite can also prevent boiler scaling. Relevant unit tests have shown that adding a certain amount of graphite powder (about 4-5 grams per ton of water) to water can prevent boiler surface scaling. In addition, graphite coating on metal chimneys, roofs, bridges, and pipelines can prevent corrosion and rust.

Graphite can be used as a pencil lead, pigment, and polishing agent. After special processing, graphite can be used to produce various special materials for relevant industrial sectors.