The graphite gasket is made of the flexible graphite,also called expandable graphite,it’s one of the new type carbon materials since 1960s,and it first come from the patent of Union Carbine Co USA. After that,with the development of petroleum chemical industry and nuclear power industry,the need for sealing material is also more strict,and the flexible graphite sealing material replace the asbestos material.

　　The flexible graphite has the similar properties with the natural graphite on the structure.and it has many good properties such as high thermal resistance,corrosion resistance,resilience, radiation resistance,high purity etc.

　　The purity of the flexible graphite has a big influence to the sealing property,the Sulpher in the graphite will separate out and make the surface corrosion of the metal,and weak the sealing effect,and to the nuclear industry,the Sulpher content is more important to control,or it will make the pollution to the reaction medium and lead to the system paralysis,so the low S and even no S products are more and more popular,many scholars around the world do this research. Now the main technique to process flexible graphite is : chemical oxidation process, electrochemical method, microwave method, explosive method and gas diffusion method etc.The way to get low S: the key point is to reduce the dosage of sulfuric acid in the intercalation agent and use the organic acid as the intercalator. By this way,it can reduce the content of the sulpher.

　　The way to get no S: it’s use the nitric acid, sulfuric acid, perchlorate or mixed acid as the intercalation. By this way,it can get the no S flexible graphite. And we should also pay attention on the raw graphite powder, it should be no S content raw material, so we could get the 100% no S flexible graphite. Then we could get the low S or no S flexible graphite gasket.

　　High pure graphite generally refers to the amount of carbon in the 99.99% above the stone ink, in the organization structure can be divided into three kinds of coarse grain structure, fine particle structure and ultrafine particles structure, high pure graphite is used in a large number of single crystal silicon furnace. The base material for integrated circuit is mainly silicon single crystal chip, the silicon single crystal growth process is mainly uses the Czochralski (CZ), and other methods of magnetic Czochralski method (MCZ), regional (Fz) method and double crucible pulling method, Czochralski silicon accounted for about 80% of the total amount of silicon single crystal for the global electronics industry, Czochralski silicon furnace graphite piece is a consumable by high pure graphite material processing into Czochralski silicon furnace heating system. In 2005 China needs to use graphite about 800 t in the single crystal furnace.

　　Another important purpose of high pure graphite is processed into various kinds of crucible, used in the production of precious metals, rare metals or high purity metals, non-metallic materials. The graphite electrode is also a kind of high purity graphite, which can be used for the analysis of the spectra of all the elements except carbon. Impurities of finished product should be not more than 6 * 10 in spectrum analysis in preparation of standard sample and catch impurities set required spectral pure carbon powder or spectral pure graphite toner by chemical method and. These two kinds of high purity materials of impurity content requirements are in 6 * 10; in some uses, the need to contain carbon content up to 99.9995%, total ash content of less than 5 * 10. There are three kinds of molding methods of high purity graphite, such as extrusion molding, molding, and so on.

　　The foundry industry in the machinery industry uses graphite material as the pressure casting, centrifugal casting, super hard alloy hot extrusion and other processing of the mold, big to the train wheel, small to precision parts can be used graphite mold. Graphite mold can be used repeatedly, after the release of the casting has a high degree of finish, some without further processing can be used. Graphite materials used in the casting mold should be of high quality, low thermal expansion coefficient and good oxidation resistance. Graphite can be used in the casting of large size. China for the manufacture of a large number of graphite mold, in 2005, the continuous casting of graphite about 1500t, the use of graphite in the production of 4000t.

　　In the mould graphite metal continuous casting graphite quality requirements of the most stringent requirements for its high thermal conductivity, thermal stability and thermal shock resistance, good lubrication, and molten metal infiltration, not with the cast metal reaction, easy to process into the size of the mold. The characteristics of continuous casting graphite are as follows: bulk density 1.7-1.9g/cm, flexural strength 30-40MPa, tensile strength 20-30MPa, thermal conductivity 100 W/ (K - M).

　　X mm 280 X MM 200 mm 1260 mm 240 mm 1000 X mm 70 X casting speed according to the size of the cast plate 0.7 m/min ~4. Fine structure graphite or other static pressure forming graphite can be processed into metal continuous casting graphite pieces.

       The graphite material plate has a good electrical conductivity,thermal conductivity,and corrosion resistance,so it’s widely used as the bipolar plate of full cell. However,there are some small hole,during the production process,and the size of the holes are different. The main reason is that some coal tar which is used as binder will be oxidation or volatilization during the making process. And this situation will have a bad influence on the graphite plate The porosity of graphite plate is about 18.2%~24.4%.

　　Now,the most common method is using some organic compound to fill in the hole of graphite plate,such as phenolic resin, paraffin, asphalt, polymer, etc. to achieve the purpose of sealing,but it can increase the resistance of graphite plate. The new way to meet the requirement is to use the

　　Na2SiO3 solution, acid leaching and heating to treat the graphite plate,it can improve the fuel cell performance and reduce the porosity.

　　The immersion time and pressure have a big influence to the result. the effect will be better with the pressure increasing and the time extending. However ,the higher pressure need higher strength and better sealing effect,and also difficult to operate.

　　By this way,the porosity can down to 3.3% from 18.2%,and it will not influence the resistance. Some scholars did the testing on the different resistance between the before and after dipping,it’s about 6.34ρ /( Ψ ·cm) before impregnation and it’s about 6.36ρ /( Ψ ·cm) after the impregnation.

　　The properties of the graphite plate after impregnation is better than the ones before impregnation,and it also can be proved by the electric reactor performance test.

　　The graphite plate after impregnation can increase the voltage to 40mV above,it’s under the same situation with the same current density to the graphite plate without impregnation,it can guarantee the fuel cell property.

　　Forging graphite emulsion (forging demoulding agent) is a compounded with graphite and other polymer materials of water-based release agent, is black, non-ferrous metal hot and cold working mould release lubricant. Forged sub micron graphite emulsion is a high-end products in the forging of graphite, metal precision forging, when its very fine graphite particles attached to the surface of the mold, can form a layer of thin film solid adhesion on metal mold surface, this film has excellent lubrication, high temperature resistance.

　　The product is mainly used for forging forging, metal mold machining, heat extrusion processing (such as aluminum, copper and other non-ferrous metals), molten steel casting, pure silicon smelting and other fields.

　　Main ingredients

　　Graphite, inorganic film forming material, organic water soluble polymer (which has the function of protecting and dispersing the colloid), and the water, etc.. The specific formulation and production technology vary with the application field.

　　Environmental protection

　　In the course of the use of water, there is no harmful gas emissions in the process of the use of graphite milk.

　　Using method

　　1 、The use of the first should be a mix of forged graphite milk. After a long period of time, there may be a small amount of solid material precipitation, but after mixing can restore the original suspension uniform state, without reducing the use of results.

　　2、 Users can according to different requirements or experience, decided on whether liquid dilution and dilution ratio, the following reference;

　　(1) The shape of the forging is complex and difficult to release, in which a large and small dilution 3-5 times; medium and small water diluted 5-10 times;

　　(2) General forging and forging water 5-15 times;

　　(3) Roll forging process can be diluted 20-30 times;

　　(4) The requirements for special processes may not be diluted and used directly

The graphite felt used for vanadium redox flow battery need to be modified,to improve the chemical activity,and find out the influence factors in graphite felt electrode,we could use different treatments on the graphite felt electrode material. Below treatments are heating treatment and acid treatment,we use polarization curve, cyclic voltammetry and AC impedance to describe the electrochemical properties of the graphite felt electrode,and describe the differences between the chemical treatment before and after,and we need to use XPS,SEM and

　　There are different ways to treat the graphite felt electrode,such as : heating treatment,acid treatment, electrochemical treatment,etc.

　　Put the PAN graphite felt on the crucible and put it into the muffle furnace,under the 500 C°,after 0.5 h calcinations,make it natural cooling;and on the other hand,put the graphite felt into 85 C°concentrated acid,and after 4 hours immersion,then use the distilled water to make it clean.

　　After polarization curve analysis,we could find that the corrosion current of untreat graphite felt electrode is highest,and the polarization resistance of it is the lowest. As for the heating treatment and acid treatment graphite felts,they are almost the same,and two times higher than the untreat one. The result show that the corrosion resistance of treated graphite felt is better than the untreated ones,and the acid treatment graphite felt is the best of all.

　　After cyclic voltammetry,the result shows that the reactive activity and reversibility of the acid treatment is better than the heating treatment and the untreated graphite felts. The SEM result shows that,the heating treatment can make cause surface damage of the carbon fiber,so it will make the resistance more higher,however,after acid treatment,the acid can make the carbon fiber surface smoothly,it will also make the resistance increase. Although the resistance will increase after acid and heating treatment,but it will not have any influence on the reactivity and reversibility.

　　Special graphite covers a wide range, the Chinese electrical carbon products industry, natural graphite products industry and metallurgy with carbon products industry in this regard have different understanding and classification methods, metallurgical carbon products industry classification of habits explain, special graphite mainly refers to the high strength, high density, high purity graphite products (referred to as Sangao graphite). Sangao graphite from the organization of the material can be divided into coarse grain structure, fine grain structure and fine grain structure, from forming method of distinguish main molding special graphite, extrusion molding special graphite and static pressure molding special graphite three categories. In addition, vibration molding can also be used for the production of special graphite. High quality specialty graphite, an isotropic graphite, is a special kind of graphite used in static pressure.

　　Not all special graphite must achieve the same high density, high strength, high purity index, using in different occasions of special graphite with strength and the density of specific requirements, strength, density index is not the same. Many special graphite does not need to reach high purity, ash is not the main quality index. Some special graphite does not require high strength, high density but need high purity. Some special graphite such as electric spark machining graphite according to different processing technology and processing object need different physical and chemical index of fine particles of graphite or special fine particles structure graphite.

      As the top graphite manufacturer of China,We have widely ranged of graphite products production capacity,includes wide range of carbon and graphite products.Graphite and carbon carbon composites products if you have needs, we are dedicated to providing high-quality products and services.

　　The ablation of carbon carbon composite material throat is mainly from complex gas environment,and the main reason includes: carbon sublimation, surface chemical reaction, mechanical erosion,and the fiber properties, prefabricated structure,material density, porosity, matrix carbon, degree of graphite, impurity,and there are some factors that affect the interaction.

　　Carbon carbon composite material has many good properties,such as high specific strength, high specific modulus, high temperature resistance, corrosion resistance, thermal shock resistance,and chemical stability. Now the carbon carbon composite material is double functional composite material with structure material and thermal protection materials,and it’s already widely used in aerospace industry and other industrial system.

　　Carbon carbon composite material now is the preferred material for nozzle throat. During the working state,the carbon carbon nozzle throat is under the very bad thermal environment,under the high temperature and high pressure,the caliber of the throat will be enlarge,the surface will be out-of-flatness,and it will have a big influence to the work pressure of the engine and it will also reduce the working efficiency of the nozzle,it will even make the engine failure.

　　The mechanical properties and ablation properties most depends on the different type and quality of the carbon fiber. The carbon fiber used for carbon carbon composite material has many different kinds,such as :PAN base,pitch base etc.and each different kinds of the carbon fiber can be divided into a number of series.

　　The difference from matrix carbon, physical and mechanical properties, the arrangement of carbon fiber, production technology,so the mechanical erosion will also be different,some can be erosion in partical state,and some can be erosion in big piece. So we need to confirm the raw material,the structure of matrix carbon and different production technology to improve the properties of carbon carbon composite material.

  Guide with new type of knitting process can be enhanced by carbon fiber knitted fabric, the fabric is woven from a carbon fiber filament continuous, it can replace mutual enhancement or woven fabric reinforced material, and the knitting technology can provide can be formed and costs are relatively cheap products.

　　Reinforcing knitted fabric from the matrix resin and any limitations of presoak process, a certain stability, fiber distribution can be obtained the permanent and certain tensile properties of the composites, the composite material due to the organizational structure of reinforced material apparent anisotropy, but its space deformation may be woven or orientation enhanced composite materials, the stereo configuration of the knitting knitting circle more effectively prevent the up layer phenomena of the material.

　　Carbon fiber knitted fabric is used as the reinforced material disadvantage is that its performance by the matrix resin adhesive ability, the direction of the knitted yarn circle and draft form and the degree of influence. At present, the carbon fiber nonwoven fabric, woven fabric, the research and development of 3 d work is to further strengthen, also the clip the versatile of its products.

　Graphite (siliconized) is a kind of composite material which is made of silicon carbide coating on the surface of graphite material. The hardness of silicon carbide is the hardness of SiC, it is only after diamond, boron nitride, boron carbide, the hardness is higher than that of tungsten carbide, three aluminum oxide, two. Silicified graphite used as phosphoric acid, hydrofluoric acid and amine and phosphorus bearing pump. In addition, the semiconductor industry, as silicon epitaxial growth of the heating sheet matrix and fixture and manufacture of artificial joint, artificial heart valve, artificial root and so on

　　There are three methods to make the production of siliconized graphite : chemical vapor deposition (CVD), Chemical vapor reaction method (CVR), and liquid silicon infiltration reaction.

　　Chemical vapor deposition (CVD) method

　　The gas containing silicon and carbon was decomposed by the high temperature graphite matrix, and the SiC was deposited on the surface of graphite matrix. Raw materials for the three (CH3SiC3), four hydrogen chloride, hydrogen, silicon vapor, etc.. The deposition temperature range is wide, from 1175 to 1775. The SiC layer generated by this method is very compact, uniform thickness, average thickness is about 0.1 ~ 0.3mm. But SiC and graphite matrix with pure mechanical binding, the binding force is weak, in temperature blast SiC layer prone to cracking and spalling.

　　Chemical vapor reaction method (CVR)

　　Raw material for coke powder and excessive amounts of quartz sand or no amorphous silica fume, when heated to 2000 degrees occurred chemical reaction to generate the SiO vapor. SiO vapor and carbon matrix reaction to generate SiC. SiC layer and the carbon matrix without obvious interface, are firmly combined, under high load and sudden changes in temperature will not fall off, but CVR method is SiO gas infiltration of carbon base body reaction, therefore, still retains the porous carbon matrix, when used as a sealing material, need resin dip stains or CVD pore filling.

　　liquid silicon infiltration reaction.

　　liquid silicon infiltration reaction.is also a kind of CVR. Under the vacuum condition, the carbon matrix is directly immersed into the molten silicon liquid by heating up to 1700-1900, and liquid silicon is gradually infiltrated into the carbon matrix, and the reaction is generated by SiC. Raw materials for 99.9999% of pure silicon. The thickness of SiC layer is 3.5mm. After the reaction, the carbon matrix contains about 17% of the free silicon in the matrix, so that the matrix becomes dense and opaque. However, the corrosion resistance and high temperature oxidation resistance of silicon carbide were decreased by the presence of free silicon.