High purity graphite refers to the carbon content of >99.99% graphite, widely used in metallurgical industry of high-grade refractory materials and coatings, military industrial explosive materials stabilizer, light industry, electrical industry pencil brush, industrial battery electrode, additives and catalyst in chemical fertilizer industry.

　　High purity graphite

　　Performance: flake crystal integrity, thin and good toughness, excellent physical and chemical properties, good thermal conductivity, temperature resistance, self lubrication, conductivity, thermal shock resistance, corrosion resistance and other properties.

　　Description: high pure graphite (also known as: flake high thermal conductivity toner) has the advantages of high strength, good thermal shock resistance, high temperature resistance, oxidation resistance, resistance coefficient, corrosion resistance, easy machining and other advantages, is the ideal inorganic non-metallic materials. For the manufacture of electric heating elements, the structure of die casting, high pure metal smelting crucible boat, crystal furnace heater, EDM graphite, sintering mold, tube anode, metal coating, semiconductor technology with graphite crucible, electron tube, thyratron and mercury arc rectifier with graphite anode, grid etc..

　　The characteristics and application of high pure graphite with high strength, high density, high purity, high chemical stability, high temperature resistance, compact and uniform structure, high conductivity, good wear resistance, self lubrication and easy processing characteristics, widely used in metallurgy, chemical, aerospace, electronics, machinery, nuclear power and other industrial areas. In particular, the large size and high quality high purity graphite, as an alternative material, has a broad application space in the fields of high technology and new technology, and has broad application prospects. [1]

　　Purification method

　　It is divided into two categories: one is wet purification, including flotation, acid and alkali, hydrofluoric acid; the two is the purification of the fire, including chlorination roasting and high temperature method

　　High purity graphite

　　Widely used in metallurgical industry of high-grade refractory materials and coatings, military industrial explosive materials stabilizer, light industry, electrical industry pencil brush, industrial battery electrode, additives and catalyst in chemical fertilizer industry. High purity graphite after processing, and production of graphite, graphite sealing material and composite material, graphite products, graphite antifriction additives and other high-tech products, various industrial sectors become important non-metallic mineral raw materials.

　　High purity graphite: graphite content of more than 99.9% of graphite called high pure graphite. Is an ideal inorganic non metal crucible boat, crystal furnace heater, EDM graphite, sintering mold, tube anode, metal coating, semiconductor technology with graphite crucible, electron tube, thyratron and mercury arc rectifier with graphite anode, grid etc..

　　High purity graphite has the advantages of small resistance coefficient, high temperature resistance, corrosion resistance, oxidation resistance, good thermal shock resistance, electrical conductivity, thermal conductivity, small coefficient of expansion, self lubrication, easy machining precision and so on.

　　1) high temperature resistant graphite melting point of 3850 - 50 DEG C, the boiling point of 4250 DEG C, even after the ultra high temperature arc ignition, the weight loss is very small, the thermal expansion coefficient is small. The graphite strength increases with the increase of temperature, and at 2000 DEG C, the graphite strength is doubled.

　　2) conductivity, thermal conductivity: the conductivity of graphite is one hundred times higher than the general non-metallic minerals. Thermal conductivity of steel, iron, lead and other metal materials. The thermal conductivity decreases with the increase of temperature, even in high temperature, graphite as insulator. Graphite is able to conduct electricity because each carbon atom in graphite has only

　　3 covalent bonds with other carbon atoms, and each carbon atom retains 1 free electrons to transfer the charge.

　　3 lubrication: graphite lubrication performance depends on the size of the graphite flake, the larger the size, the smaller the friction coefficient, the better the lubrication performance.

　　4) chemical stability: graphite has good chemical stability at room temperature, acid and alkali corrosion resistance to organic solvents.

　　Graphite is an important strategic resource，and China’s graphite resource reserves and production rank the first in the world. High purity graphite has excellent performance and graphite products are widely used. Purification of graphite is the premise and basis of graphite products application，therefore the performance and application of graphite products are directly affected by the purity of graphite. Graphite resource and production and consumption in China and the rest of the world are presented. The main methods for purification of graphite are discussed，and the research progress of graphite purification are reviewed from several aspects，including flotation method， alkali-acid processing method，hydrofluoric acid washing，chloridizing roasting and high temperature purification. After comparing the advantages and disadvantages of each method，the development direction and prospect of graphite purification is put forward. Grinding and flotation technology for protection of larger graphite flake，less fluoride or fluoride-free graphite purification and cost-effective high temperature graphite purification will be the new technologies in the future.

　　As the purification of graphite is the prerequisite and basis for the development and application of graphite materials, the demand for high purity graphite will be increased with the improvement of the application level of graphite. The purification of graphite should be adapted to local conditions, and the development of resource saving and environment friendly.

　　Graphite as a kind of important strategic resource and our country's advantage resources, need to develop the deep processing and application of graphite industry. Graphite purification technology to floatation purification technology as the foundation, according to the graphite product application field and application way requirements, in order to deepen the alkali acid, hydrofluoric acid, high temperature method and purification technology. The development trend of the purification technology will be the development of high temperature purification technology with the protection of large scale integrated grinding flotation technology, the low fluorine and fluorine free purification of acid and alkali substitution technology and the realization of superior cost-effective.

　　High purity graphite generally refers to the amount of carbon containing more than 99.99% of graphite in the organizational structure can be divided into three categories: coarse grain structure, fine grain structure and fine grain structure. The base material for integrated circuits is mainly single crystal silicon chip, silicon single crystal growth process is currently mainly used in Czochralski (CZ) method, and other methods of magnetic Czochralski method (MCZ), regional (FZ) method and double crucible pulling method, the total amount of single crystal silicon 80% monocrystalline silicon with the global electronics industry. Czochralski graphite furnace is monocrystalline silicon using consumables, high purity graphite materials into the heating system of monocrystalline silicon furnace. In 2005 China needs to be directly drawn silicon single crystal furnace with graphite about 800 t. [1]

　　Another important use of high purity graphite is processed into various kinds of crucible, used for the production of precious metals, rare metals or high pure metal, non-metallic materials. Graphite electrode is also a kind of high purity graphite, which can be used for the spectral analysis of all elements except for carbon. The impurity content of finished product should be less than 6*10 were prepared by chemical method and standard sample collection for impurity spectrum of pure carbon powder or graphite pure spectrum in spectrum analysis, the two kinds of high purity materials of impurity content requirements are at 6 *10; in some cases, to the carbon content reached 99.9995% the total ash content of less than 5 *10. The molding methods of high purity graphite include three kinds of forming methods, such as extrusion, molding, and static pressing. Table 9 the physical and chemical properties of high purity graphite products made in China

　　The high purity and high strength graphite are commonly used in nuclear reactor and rocket structure material and the parts and devices required in fabrication of high purity metal, semiconductor materials and rare metal .

　　The high purity graphite used in semiconductor consumption , the high purity graphite used in single crystal furnace, the crucible boat and dish of semiconductor materials smelting and the devices in smelting high pure metal . The impurity content of this kind of graphite material is requested by <0.01%; the bulk density is 1.55 ~1.75g/cm3. Its production process is generally the same compared with ordinary graphite process ,but we must choose the ash content is less than 0.05% of the raw materials for the graphite material which formed by molded or isostatic pressure , high graphitization temperature and and accessing the halogen gas during the graphitization process ,we coat the pyrolysis graphite which the thickness in 10~20Hm on the surface of some high purity graphite devices in order to improve the oxidation resistance.

　　The high strength graphite used in the rocket engine , it is mainly used as the throat lining materials. It is necessary to meet the following severe working conditions: 2ooo degrees centigrade ~ 35 degrees Celsius temperature, the thermal shock caused by high-speed heating , the thermal stress caused by the maximum thermal gradients , sharply increased pressure; exposed in the high-speed corrosive gas for several minutes. The advantages of this kind of high strength graphite is relatively light, high temperature resistance and thermal stability.

　　The nuclear graphite, the nuclear graphite is used in nuclear reactor as the slowing down material and reflection material . It must have the performance of four aspects: high purity (0.5 xlO-6 boron content gas ni0.1) and high bulk density (1.65 -1.80g/cm3), high mechanical strength (compressive strength can reach 88.2 ~ 98.IMPa), low porosity and low gas permeation rate.

　　The high purity graphite products are widely used in metallurgy, machinery, electronics, chemical, electrical, food and other industrial fields. For emitting an electron tube, thyratron, mercury arc rectifier with graphite plate,the grid plate; semiconductor technology with graphite boat dish, the crucible, heating element, single crystal furnace heater, metal gasification with graphite ware, continuous casting mold, pressure sintering graphite template, electric spark machining of the graphite electrode. Faced with so many applications,Just only one way to prepare high purity graphite is clearly not enough, the following are the high purity graphite preparation methods which given by we , the graphite products manufacturer :

　　1).The theory of high temperature process for the preparation of high purity graphite: we can utilize the low boiling point nature of the impurities to make the impurities first gasification and removal of insulation via heating the graphite materials to 2700 DEG C degrees above, for a certain period of time, it can get rid of all impurities. the carbon content of graphite was 99.99% or more when the graphite was purified by high temperature graphite method.

　　2).The flotation process for the preparation of high purity graphite: the flotation method is mainly used on the graphite preliminary purification, the purity is not high after purification, it shall be by chemical or thermal methods to further remove impurities from the graphite if we need to improve graphite grade. That graphite products processing factory in flake graphite fast flotation experimental study on process flow: fast flotation process can make the taste for 4.35% of the ore grade is 91.89%, recovery rate was 92.52% graphite concentrate. Compared with the ordinary flotation method, the grade of graphite concentrate in the fast flotation process was increased by 1.15%, the recovery rate was increased by 4.28%, and the graphite large yield was also improved significantly.

　　3). The chlorination roasting method to prepare high purity graphite: the chlorination roasting method is make the graphite roasted under the high temperature and a certain atmosphere , then passing into the chlorine for chemical reaction , the impurities in the graphite by chlorination reaction, gas generation phase or condensed chloride and complex (lower melting point and boiling point) to escape so as to achieve the purpose of purification. The chlorination roasting method has the characteristics of high recovery rate and low cost. We put one or several of the inert gas, chlorine, freon and tetrafluoroethane in the closed graphitizing furnace for purification of graphitization, we can get the high purity graphite which the ash content is less than 50 ppm.

　　Our company also can provide the high purity graphite under 20PPm,please contact us if you have the demand of these high purity graphite material or products.

　　1).The High Purity Graphite

　　The high purity graphite generally refers to the amount of carbon containing more than 99.99% of graphite and in the organizational structure it can be divided into three categories: coarse grain structure, fine grain structure and ultra-fine grain structure. The basic material of the integrated circuit is mainly silicon single crystal chip, at present silicon single crystal growth process is mainly uses in Czochralski (CZ), Czochralski silicon accounted for about 80% of the total amount of silicon in the global electronics industry, the graphite piece in Czochralski silicon furnace is a consumable,we use the high purity graphite material to process the Czochralski silicon furnace heating system.

　　Another important use of high purity graphite is process various kinds of crucibles which are used for the production of precious metals, rare metals or high pure metal, non-metallic materials. The graphite electrode used in sectral analysis is also a kind of high purity graphite, which can be used for the spectral analysis of all elements except for carbon. The extrusion method is used for the graphite electrode for spectrum analysis ,the impurities of finished product should be not more than 6*10-5 ,in spectrum analysis in preparation of standard sample and catching impurities set required spectral pure carbon powder or spectral pure graphite toner by chemical method. These two kinds of high purity materials of impurity content requirements are in 6*10-5; in some application,it need the carbon content up to 99.9995% and total ash content less than 5 * 10-6. The molding methods of high purity graphite include three kinds of forming methods, such as extrusion, molding, and isostatic pressing.

　　2). The Graphite Material Used in Nuclear Power

　　The graphite is one of the materials used in the construction of nuclear reactors and one of reflective materials,the early reactors are graphite reactor. The graphite as the structural material of nuclear reactor is more strict and expensive in the selection of raw materials, process control, product inspection than the graphite electrode, the grphite used in a nuclear reactor must have the following properties: the little absorption for slow neutron , good high temperature strength, high thermal shock resistance, the good deceleration performance for the fast neutron, stable dimension under irradiation, impurity content rarely. For Boron, Cadmium and other easy absorb elements in the neutron ,we must control the content strictly. The nuclear graphite must have higher bulk density, The bulk density is one of the main indicators of nuclear graphite, The porosity and permeability must be reduced to a certain level. The mechanical strength of graphite is also related to its bulk density. The bulk density of graphite used in the normal graphite reactor is 1.7-1.75g/cm3.

　　3).The Homogeneous Graphite

　　Although the definition of homogeneous graphite need to be defined in the world, the general is measuring the diameter direction and lengthwise direction of some physical properties of the index and calculate the ratio, some with thermal expansion coefficient ratio, the most simple one is expressed as a ratio of the resistivity, the difference to referred to in ~ 1.1 range for isotropic products, more than 1.1 called the anisotropy product. Japan and other industrial technology advanced countries use static pressure molding method of large-scale production of isotropic graphite and the diameter can reach 1.5m, length of 3%, the volume density reached 1.95-2.0g/cm3, the anisotropy ratio reduced to 1.05. In addition to the use of general petroleum coke, the use of modified pitch coke, natural pitch coke, oxidized petroleum coke, calcined petroleum coke, natural graphite, etc., are also used in the manufacture of homogeneous graphite.

　　High purity graphite is a graphite with a carbon content of more than 99.99%. High purity graphite with high temperature resistance, corrosion resistance, thermal shock resistance, thermal expansion coefficient is small, self lubrication, resistance coefficient is small and easy to processing machinery, and other advantages, is widely used in metallurgical, mechanical, environmental, chemical, electronic, medical, military and aerospace fields, the position in the national economy is becoming more and more important, especially in the solar photovoltaic industry. The global photovoltaic industry average annual growth rate of 40%, China as the world's largest producer of solar photovoltaic, 70% of its share to the global, high-grade graphite materials consumed by the industry in 2011 reached 2.3 million T to expected future photovoltaic industry of silicon and polysilicon demand of high purity graphite materials will be at the speed of 20% ~ 25% a year growth

　　The future development direction of high purity graphite will be the production of structural and performance integration, and the comprehensive performance of a good product. At present, the production of high purity graphite defects and future requirements based on the need in the future research, strengthen academic exchanges between enterprises and international cooperation, cooperation, optimize some key technology, in order to obtain the best process parameters; in countries and jointly support the relevant enterprises, construction engineering technology center, actively carry out new technologies new product research and development work; International Association founded the production process of high-purity graphite, annual meetings, research progress of high purity graphite production process; to strengthen the basic theory research; using computer simulation technology to simulate and optimize the production process also will be the future development direction of hot spot.

　　　　High purity graphite is refers to the carbon content is more than 99. 99% which is high strength, high density, high purity, high chemical stability, compact structure, high temperature resistance and high conductive rate,also has a good wear resistance.

　　High purity graphite is widely used in metallurgy, chemical industry, aerospace, Electronics, Mechanics, Nuclear power industry etc.

　　Graphite purification method is mainly divided into two categories,one is the wet purification, including flotation, acid-alkali, hydrofluoric acid.The other is the fire purification method, including chlorination roasting method and high temperature method.In addition,with petroleum coke as raw materials to produce high grade fine particles of high purity graphite is also widely used.

　　The production process is:

　　Raw material→calcinations→crocus→ingredients→mix and knead→fine powder→molding→baking→dipping→graphitization.

　　Under the 2000~2800℃ high temperature, freon gases and chlorine gas are bubbled into it,to make impurity elements form chloride and fluoride volatile escape,when the temperature dropped to1800℃,pure nitrogen is bubbled into,and excess chlorine, fluorine gas discharged,to get the purpose of purification.

　　The fine structure and high purity graphite’s particle size is going to be smaller and smaller, particles of 5~l0μm structure of the graphite material has been industrialized production. Small pitch mesophase sphere as raw material to make the fine structure of high purity graphite which has been used.

　　When choosing purification methods, should consider the nature of the raw material, process characteristics and environmental factors.