Graphite Hot Zone

Excellent properties of carbon graphite materials：
1. Conductivity: Among non-metallic materials, carbon-graphite materials are good conductors of electricity, and graphite materials are basically the best conductors of non-metallic materials.
2. Thermal conductivity: The thermal conductivity of graphite material is good, which is 3-4 times that of steel (normal temperature) and 1/2-1/3 of copper.
3. Heat resistance: it does not melt under normal pressure, sublimates into carbon vapor at temperatures above 3500°C, is not easy to soften and deform at high temperature, has no conversion process from solid to liquid, and has excellent thermal shock resistance and rapid cooling and rapid heating resistance .
4. Corrosion resistance: excellent, acid and alkali corrosion resistance under normal temperature and pressure, and molten metal is difficult to wet.
5. High high temperature strength: the strength at room temperature is 1/20-1/30 of steel, but it increases with the rise of temperature before 2500 °C (strength at 2500 °C is twice as the normal temperature value) and Does not soften.
6. Lubricity: Graphite material has good lubricity and anti-friction properties.
7. Thermal expansion: The thermal expansion coefficient is small, only about 1/6 of that of steel and about 2/3-3/4 of that of refractory bricks. The physical size of carbon-graphite materials changes little at high temperatures.
8. Hardness: The graphite material is soft, the Mohs hardness is 2-3, the Shore hardness is 20-70, and the hardness of the graphite material can be designed and adjusted according to the different use environments.
9. Density: light weight, the bulk density is usually in the range of 1.4-1.8g/cm3, the lowest is 0.8g/cm3, the highest is 1.95g/cm3, which is 1/4-1/5 of steel and 2/3 -3/4 of refractory brick. It is a lightweight material.
10. Machinability: Graphite materials are easy to machine, can be precision machined, and can be machined into various complex shapes.
11. Purity: The ash content of graphite materials is usually 0.01-0.3%, which is easy to be refined to achieve high purity (ash content below 10ppm). This property is beneficial for applications in the semiconductor industry.
12. Nuclear physical properties: graphite material has a large scattering cross section for neutrons, a small absorption cross section, and can withstand the bombardment of fast neutrons and other high-energy particles for a long time with little change. Good chemical stability, no chemical reaction with substances in the fission zone. And the production cost is low, so it can be used as a deceleration material for nuclear reactors.
13. Biocompatibility: The biocompatibility of carbon material is very good, and it can be used as a patch material for the human body.
It can be seen from the above. Carbon materials are similar to metal materials in terms of electrical conductivity and thermal conductivity, and have commonalities with ceramic materials in terms of heat resistance and corrosion resistance, and are similar to organic polymer materials in terms of light weight, reducibility and molecular structure diversity. This shows that the carbon material has the characteristics of three solid materials of metal, ceramic and organic polymer. And it has other properties that cannot be replaced by other materials, such as high elastic modulus, high specific strength, large shock absorption rate, good biocompatibility, self-lubrication and neutron deceleration ability.

Classification of graphite materials by use：
1. Conductive carbon/graphite materials: such as graphite electrodes for electric arc furnace steelmaking, anodes for molten salt electrolytic cells, etc.
2. Carbon/graphite materials for high temperature refractory materials: such as bottom blocks for aluminum electrolytic cells, semi-graphite carbon blocks, silicon-containing carbon blocks and graphite blocks, etc.
3. Wear-resistant carbon/graphite materials: such as carbon, graphite, resin-impregnated, metal-impregnated carbon/graphite materials, and carbon/carbon composite materials that match different friction pairs.
4. Graphite materials for high temperature molds: such as graphite for black or non-ferrous metal continuous casting; high temperature hot pressing molds above 1000 °C; boats and dishes for smelting cemented carbide; graphite molds for precision casting; Sintering molds for semiconductors and integrated circuits and mold electrodes for EDM, etc.
5. For electric heating elements: such as graphite heating rod, graphite heating tube, graphite fiber belt heating element.
6. As high temperature thermal insulation materials: such as thermal insulation materials that can be used for 1800-3000 °C carbon felt, graphite felt and foam carbon, etc.
7. As bioengineering materials: such as carbon artificial heart valve, carbon artificial bone, carbon artificial joint, carbon fiber artificial ligament and artificial trachea, etc.
8. Structural materials for nuclear reactors: such as graphite moderated materials, graphite reflective materials, pyrolytic carbon-coated fuel balls, etc.
9. As a high temperature lubricant: such as graphite emulsion and fluorinated graphite for metal drawing.
10. As adsorption material: such as activated carbon and activated carbon fiber.
11. Chemical carbon/graphite corrosion-resistant materials: such as graphite heat exchangers, graphite pumps, graphite absorption towers and corrosion-resistant linings for chemical containers.
12. As a reinforcing material for advanced composite materials: such as carbon fiber, carbon cloth, three-way and multi-directional carbon fiber braid.
13. Carbon graphite materials are used as positive and negative electrode materials in the battery industry;
14. Used as anode in electrolysis industry; used as electrode in EDM;
15. Used as sacrificial anode in underground pipeline anticorrosion;
16. Used as electrodes in electric arc furnace for industries like steelmaking, ferromanganese, ferrosilicon, calcium carbide, industrial silicon, yellow phosphorus, corundum and other industries;
17. Used as crucibles, boats, dishes, etc. in melting and refining rare metals;
18. Casting molds, molds, molds, etc. in the foundry industry;
19. Used as molds, fine blow pipes and agitators in the aluminum alloy industry;
20. In the electrical industry as carbon brushes, collectors and collector rings, electric shocks, lightning rods, etc.;
21. Used as corrosion-resistant heat exchangers, synthetic hydrochloric acid equipment, various pumps, valves, pipes, etc. in the chemical industry;
22. Used as structural and functional materials in various industrial kilns above 1800°C;
In addition, carbon graphite materials are widely used in the fields of semiconductor, communication, and electronic equipment manufacturing; in the fields of nuclear energy and radioactive energy, in the fields of aerospace and navigation, in the fields of nuclear energy, wind energy, solar energy, and in the military industry.