Carbon felt in the vacuum or inert atmosphere after more than 2000 degrees under high temperature treatment for graphite felt, carbon content than carbon felt, up to more than 99%. At the end of 60s the world has a graphite felt good supply. Because of the different selection of raw graphite felt for pitch based and PAN based graphite felt and viscose based graphite felt three.

　　The Japan Kureha chemical as a representative of the asphalt in the insulation industry mainstream, Europe and the United States insulation felt basically to adhesives based, and China is most clear polypropylene based as raw material. Process of polyacrylonitrile based carbon felt or rayon based carbon felt cut into the desired size, rolled into a cylindrical shape is arranged in a graphite material container, graphite container is placed in a high temperature furnace (high temperature furnace graphite tube furnace, medium frequency, high-frequency induction furnace or other forms of heating furnace), vacuum pumping or through a high purity inert gas protection, to 100 to 300 DEG / h of the heating rate of heating to 22 to 25 DEG C; and naturally cooling to 100 DEG C to obtain.

　　PAN based graphite felt than viscose base graphite felt strong and strong antioxidant capacity, but poor flexibility, volume density, good insulation properties. They have the advantages of high purity, high temperature resistance, corrosion resistance, non melting and so on, but also can be flexible, can be folded, cut and can be used with graphite yarn stitching and so on. Graphite felt is mainly used as a single crystal silicon smelting furnace insulation, thermal insulation materials. In the chemical industry can be used as a filter material of high purity corrosive chemical reagents. Under the condition of non oxidizing atmosphere, the temperature of graphite felt is up to 3000.

　　Used in the vanadium redox flow battery,is one of the most useful application of carbon felt/graphite felt.If other materials are used in the vanadium redox flow battery,something will happen,like: the electric current density of vanadium redox flow battery is very low,only about 20mA/cm2 or even lower,but the vanadium redox flow battery with carbon felt/graphite felt can be about 80mA/cm2,and at the same time,the service life of the carbon plate used as bipolar plate is very short and it will lead to the service life of vanadium redox flow battery is very short.

　　So the vanadium battery system must use the carbon felt/graphite felt as electrode materials.

　　The electrode material which is used in the vadadium system divided into two types,one is graphite felt,and another one is carbon felt.To the graphite felt,the baking temperature is higher,and the degree of graphitization is also higher,accordingly,the graphite felt has a higher cost and price than carbon felt.

　　The felt used for electrode material in the vanadium battery mainly divided into PAN base and RAYON base,the rayon ones are more expensive than the PAN ones,but the property of vanadium battery depends on the design of the battery system.

　　Among so many carbon electrode materials ,the graphite felt holds greatest promise. The structure cross section as below:

　　PAN base graphite felt is the first choice to be used in the vanadium redox flow battery,but it still has some disadvantage such as the hydrophilic property can not meet the battery requirement,and the chemical activity can not make it ether. So the research and development of PAN carbon/graphite felt is more and more important.

　　Carbon felt is made up of carbon fiber and felt like,it divided into two categories,classificated by raw materials. RAYON and PAN.

　　Carbon felt has the properities as the bulk graphite,such as: high temperature resistance,corrosion resistance,non melting etc.meanwhile,it’s also low density,flexible, elastic, collapsible, clipping, suture as the fiber.

　　Carbon felt is widely used as the high temperature heat insulation material for high temperature furnace(eg.high temperature carbon tube furnace), high temperature induction furnace and vacuum coating furnace.as it has a low invasion with molten metal,ceramic and glass etc.so it could be used as a surface coverings of these material,to reduce the heat loss.The fiber in the carbon felt whose diameter is less than 10μm,so it’s also good using as catalyst carrier.

　　The carbon carbon composite material products used with carbon felt could be used as nose cone, throat material in the aerospace industry.The main specification of carbon felt are:bulk density,carbon contant,ash,strength, thermal conductivity, oxidative weightlessness, tensile strength etc.

　　Graphite felt need the carbon felt under vacuum conditions and with 2000 degrees Celsius heat treatment.the carbon contant is higher than carbon felt,more than 99%.the technology is that fill the RAYON carbon felt or PAN carbon felt in to a graphite material container and put the container into high temperature furnace,meanwhile, ensure that the vacuum in the furnace or inert gas is filled, heating-up the temperature to 2200~2500 degrees celsius,and then chill-down 100 degrees celsius,the graphite felt is done.

　　The main use of graphite felt is heat insulating material of Single crystal silicon smelting furnace,It also could be used as filter material.the working temperature could get 3000 degrees celsius under non oxidizing atmosphere.