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Note: Graphite is an allotrope of elemental carbon, and each carbon atom is surrounded by three other carbon atoms (multiple hexagons arranged in a honeycomb pattern) to covalently key Combine to form covalent molecules.
Since each carbon atom emits an electron, those electrons can move freely, so graphite is a conductor. Graphite is one of the softer minerals. Its uses include making pencil lead and lubricants. Carbon is a non-metallic element, located in the IVA family of the second cycle of the periodic table. The Latin word is Carbonium, which means "coal, charcoal". The Chinese character "carbon" is composed of the word "charcoal" of charcoal and the word "stone" beside it.
Chemical formula: C
Molecular weight: 12.01
Melting point: 3652 ℃
Boiling point: 4827 ℃
Water solubility: insoluble in water
Appearance: black solid
Applications: pencil lead, refractory materials, conductive materials, lubricating materials, carbon manufacturing, anti radiation materials, etc
purpose
Traditional use
1. As refractory materials: graphite and its products have the properties of high temperature resistance and height. It is mainly used to make graphite crucibles in the metallurgical industry. In steelmaking, graphite is often used as the protective agent for steel ingots and the lining of metallurgical furnaces.
2. As conductive material: it is used in the electrical industry to manufacture electric comparator, brush, carbon rod, carbon tube, mercury positive current device, graphite Washer , telephone parts, Television Coating of picture tube, etc.
3. As wear-resistant lubricating material: graphite is often used as lubricant in the machinery industry. Lubricating oil can not be used at high speed, high temperature and high pressure, while graphite wear-resistant material can work without lubricating oil at high sliding speed at 200~2000 ℃. Many equipment transporting corrosive media widely use graphite materials to make pistons cup The sealing ring and bearing do not need to add lubricating oil when they are running. 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 corrosion resistance, good thermal conductivity and low permeability, is widely used in making heat exchangers, reaction tanks, condensers and combustion Pagoda Absorber, cooler, heater, filter, pump equipment. It is widely used in petrochemical industry, hydrometallurgy, acid-base production, synthetic fiber, paper making and other industrial sectors, which can save a lot of metal materials.
The types of impermeable graphite have different corrosion resistance due to different resins. For example, phenolic resin impregnator is acid resistant, but not alkali resistant; Those impregnated with furfuryl alcohol resin are resistant to both acid and alkali. The heat resistance of different varieties is also different: carbon and graphite can withstand 2000~3000 ℃ in reducing atmosphere, and begin to oxidize at 350 ℃ and 400 ℃ respectively in oxidizing atmosphere; The type of impermeable graphite varies with impregnating agent. Generally, the heat resistance of phenolic or furfuryl alcohol impregnated graphite is below 180 ℃.
5. Casting, sanding, die casting and high temperature metallurgical materials: due to the small thermal expansion coefficient of graphite and its ability to withstand rapid changes in cooling and heating, it can be used as the casting mold of glassware. After using graphite, the ferrous metal can obtain accurate casting size, high yield of smooth surface, and can be used without processing or slightly processing, thus saving a lot of metal. In the production of cemented carbide and other powder metallurgy processes, graphite materials are usually used to make ceramic boats for pressing and sintering. Single crystal silicon crystal growth crucibles, regional refining containers, support fixtures, induction heaters, etc. are all processed with high-purity graphite. In addition, graphite can also be used as graphite insulation plate and base for vacuum smelting, high temperature resistance furnace tube, rod, plate, grid and other components.
6. For atomic energy industry and national defense industry: graphite has good neutron retarder for use in atomic reactors, and uranium graphite reactor is a kind of atomic reactor that is widely used. As the deceleration material in the atomic energy reactor used for power, it should have high melting point, stability and corrosion resistance. Graphite WAN can all meet the above requirements. The purity of graphite used for atomic reactor is very high, and the impurity content should not exceed dozens of PPM. In particular, the boron content shall be less than 0.5PPM. In the national defense industry, graphite is also used to make nozzles of solid fuel rockets, nose cones of missiles, parts of current market navigation equipment, thermal insulation materials and radiation shielding materials.
7. Graphite can also prevent boiler scaling. Relevant unit tests show 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.
8. Graphite can be used as pencil lead, pigment and polishing agent. After special processing, graphite can be made into various special materials for relevant industrial departments.
