Graphite felt definition
Graphite felt graphite felt
Carbon felt in the vacuum or inert atmosphere after more than 2000 degrees under high temperature treatment for graphite felt, carbon content is higher than the carbon felt, up to 99%. At the end of 60s the world has a graphite felt goods supply. Because of the different selection of raw graphite felt felt for PAN based graphite felt and viscose based graphite felt two.
The process of polyacrylonitrile based carbon felt or rayon based carbon felt is cut into the required size, the container into a cylinder made of a graphite, graphite container in a high temperature furnace (high temperature furnace for graphite tube furnace, intermediate frequency and high frequency induction furnace or other heating in the form of Gao Wenlu), with the vacuum or protection of high purity inert gas, heating rate from 100 to 300 DEG /h heating to 2200 to 2500 DEG C, natural cooling to 100 DEG C to obtain.
Properties of graphite brittle graphite
The unique structure of graphite has special properties. It is widely used in industry. It is mainly used in the following properties:
(1) lubrication. Because the bonding strength between layers of graphite material is very small, when it is friction with the metal, the metal surface is easy to form graphite film, it can play a role in reducing friction. For surface polished steel, the dynamic friction coefficient of high strength graphite at room temperature and atmosphere is about 0.35. Therefore, graphite is often used as a lubricant, manufacturing graphite bearings, graphite, such as graphite.
(2) thermal expansion is small. Generally at 20 degrees to 200 degrees Celsius, extrusion molding graphite products, along the extrusion direction of the coefficient of thermal expansion (2 ~ 1) * 10-6/ degrees Celsius, perpendicular to the extrusion direction (2 ~ 3) * 10-6/. The thermal expansion coefficient of the expanded graphite plate is larger, such as the direction of the expansion plate is 5 * 10-6/, and the thickness is 100 * 10-6/. Graphite products with high thermal shock resistance, such as the use of electric furnace steel graphite electrode to withstand the urgent need for cooling, heat, and so on.
(3) good thermal conductivity and electrical conductivity. Generally, the conductivity is much larger than that of the plane in the direction of the crystal. But the graphite thermal conductivity and resistance are affected by temperature, such as the coefficient of resistance in 700K ~ 900K is negative, 900K above is positive, the thermal conductivity at a certain temperature reached the maximum value, and the rest will fall. Due to the good thermal conductivity and conductivity of the anisotropic material, the graphite is used as a refractory material, a heat insulating material and a graphite electrode.
(4) the availability of a wide range of temperature zones. The melting point of graphite is 38.50 degrees Celsius, the boiling point of 4250 degrees Celsius, so it can be used in the air to -200~450 C, in a vacuum or reducing atmosphere available to -200 ~ 3000. The strength and hardness of graphite increase with the increase of temperature. (5) stable and non toxic chemical properties. Graphite is non-toxic to human body. It begins to oxidize at 400 degrees C, and can react with water vapor at 700. 900 C above can be reacted with CO2, more than 1000 C before the reaction with hydrogen. In addition to aqua regia, chromic acid, concentrated sulfuric acid and nitric acid, which can resist erosion various acid, alkali and organic solvent. At high temperatures, the graphite can react with many metals or non metals or their oxides. Due to the radiation resistance and thermal neutron cross section of graphite, it becomes the only slow material in nuclear reactor.
(6) other characteristics. Graphite is a kind of important carbon source, which has the characteristics of good application, light weight, easy processing and forming. It can provide a high purity carbon in various materials.
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