As for graphite and carbon, we always think that they are the same substance. Today, let's explain them:

Introduction to graphite and carbon materials

React with oxygen at different temperatures to form carbon dioxide or carbon monoxide; Among halogens, only fluorine can react directly with carbon; Under heating, graphite powder is easy to be oxidized by acid; At high temperatures, it can also react with many metals to form metal carbides, and can smelt metals at high temperatures.

Material characteristics

Graphite is a substance with very sensitive chemical reactions. In different environments, its resistivity will change, that is, its resistance value will change, but one point will not change. Graphite powder is one of the good non-metallic conductive materials. As long as the graphite powder is guaranteed to be uninterrupted in an insulated object, it will also be electrified like a thin wire. However, there is no accurate number for the resistance value, Because the thickness of graphite powder is different, the resistance value of graphite powder used in different materials and environments will also be different. Graphite has the following special properties due to its special structure:
1) High temperature resistant type: the melting point of graphite is 3850 ± 50 ℃, and the boiling point is 4250 ℃. Even if it is burned by ultra-high temperature arc, the weight loss is very small, and the coefficient of thermal expansion is also very small. The strength of graphite increases with the increase of temperature. At 2000 ℃, the strength of graphite is doubled.
2) Conductivity and thermal conductivity: the conductivity of graphite is 100 times higher than that of general non-metallic minerals. Its thermal conductivity exceeds that of metal materials such as steel, iron and lead. The thermal conductivity decreases with the increase of temperature, and even at extremely high temperatures, graphite becomes an insulator.
3) Lubricity: the lubricity of graphite depends on the size of graphite scales. The larger the scales, the smaller the friction coefficient, and the better the lubricity.
4) Chemical stability: graphite has good chemical stability at normal temperature, and can resist acid, alkali and organic solvent corrosion.
5) Plasticity: graphite has good toughness and can be connected into very thin flakes.
6) Thermal shock resistance: when graphite is used at normal temperature, it can withstand drastic changes in temperature without damage. When the temperature changes abruptly, the volume of graphite changes little and cracks will not occur.

Application case

1. As refractory material: graphite and its products have the properties of high temperature resistance and high strength. They are mainly used to make graphite crucibles in the metallurgical industry. In steel-making, graphite is often used as a protective agent for steel ingots and as the lining of metallurgical furnaces.
2. As a conductive material: used in the electrical industry to manufacture electrodes, brushes, carbon rods, carbon tubes, positive electrodes of mercury positive current devices, graphite gaskets, telephone parts, coatings of TV picture tubes, etc.
3. As wear-resistant lubricating material: graphite is often used as a lubricant in the machinery industry. Lubricating oil can not be used at high speed, high temperature and high pressure, while graphite wear-resistant materials can work without lubricating oil at (I) 200 ~ 2000 ℃ at very high sliding speed. Many equipment conveying corrosive media widely use graphite materials to make piston cups, sealing rings and bearings, which do not need to add lubricating oil during operation. Graphite emulsion is also a good lubricant for many metal processing (wire drawing and pipe drawing).

Classification of graphite

High purity submicron graphite particles have a very wide range of applications: electronic information picture tubes, black background conductive coatings in the display manufacturing industry, devices composed of liquid crystal displays, photosensitive black coatings used on sensors and color decomposers, color liquid crystal plasma tricolor boundary in flat panel displays for improving emission effect and color contrast, ultra-fine tungsten, molybdenum wire drawing and other coatings, High purity submicron graphite particles are widely used in many industries, such as advanced lubricating oil and grease manufacturing, foam iron nickel manufacturing for high-performance battery, and photosensitive film.
The ultra-fine powder of high-purity graphite has colloidal graphite powder, which is mainly used for pens, powder metallurgy, lubricating oil, grease, dry batteries, conductive coatings, lubricating coatings, scientific research by the Commission of science, technology and industry for national defense, scientific research institutions, civil nuclear power, aerospace, strategic power interference weapons, smoke screen weapons, etc, Colloidal graphite powder produced in China is an industry pacesetter for the development of China's graphite industry, and some technologies have reached the international leading level.
Performance and application of Glan powder (sealing and anti sticking grease): it can withstand high temperature of 3000 ℃ and high pressure of 40kg. It is used for sealing and anti sticking of metal joint surfaces and flange joint parts of ships, aircraft, locomotives, automobiles, construction machinery and various large petroleum, chemical and electrical machinery.
Special graphite coatings: water-based graphite coatings, conductive graphite coatings, dissolved graphite coatings, internal and external graphite coatings, wiredrawing graphite coatings, lubricating graphite coatings, glass fiber coatings, TV graphite coatings and special coatings, various non-metallic materials, nano materials production processes and design schemes. Handle all kinds of anti-corrosion equipment, and undertake all kinds of anti-corrosion equipment treatment. The variety is diverse and the specifications are complete. The products comply with the national standards of the people's Republic of China. Special machinery design and manufacture of various fine chemical equipment, various mills and formula processes.

Use of graphite

Industry
Graphite has good chemical stability. Specially processed graphite, which has the characteristics of corrosion resistance, good thermal conductivity and low permeability, is widely used to make heat exchangers, reaction tanks, condensers, combustion towers, absorption towers, coolers, heaters, filters and pumps. It is widely used in petrochemical industry, hydrometallurgy, acid-base production, synthetic fiber, paper making and other industrial sectors, which can save a lot of metal materials.
As casting, foundry, die casting and high-temperature metallurgical materials: because graphite has a small coefficient of thermal expansion and can withstand rapid cooling and heating changes, it can be used as a mold for glassware. After graphite is used, ferrous metal castings have accurate dimensions, smooth surface and high yield. It can be used without processing or a little processing, thus saving a lot of metal. In the production of cemented carbide and other powder metallurgy processes, graphite materials are usually used to make dies and ceramic boats for sintering. Single crystal silicon crystal growth crucibles, regional refining vessels, support fixtures, induction heaters, etc. are all made of high-purity graphite. In addition, graphite can also be used as graphite insulation board and base for vacuum smelting, furnace tube, rod, plate, lattice and other components of high-temperature resistance furnace.
Graphite can also prevent boiler scaling. Tests by relevant units show that adding a certain amount of graphite powder to water (about 4-5g per ton of water) can prevent boiler surface scaling. In addition, graphite can be coated on metal chimneys, roofs, bridges and pipes to prevent corrosion and rust.
Graphite can be used as pencil lead, pigment and polishing agent. After special processing, graphite can be made into various special materials for use in relevant industrial departments.
In addition, graphite is also a polishing agent and rust inhibitor for glass and paper in light industry, and an indispensable raw material for manufacturing pencils, ink, black paint, ink, artificial diamonds and diamonds. It is a very good energy-saving and environmental friendly material, and the United States has used it as a car battery. With the development of modern science, technology and industry, the application of graphite is still expanding. It has become an important raw material for new composite materials in the high-tech field and plays an important role in the national economy.

national defense
Used in the atomic energy industry and national defense industry: graphite has a good neutron moderator for use in atomic reactors, and uranium graphite reactors are widely used. As the deceleration material in the nuclear reactor for power, it should have high melting point, stability and corrosion resistance. Graphite can fully meet the above requirements. The purity of graphite used for atomic reactors is very high, and the impurity content should not exceed tens of ppm. In particular, the boron content should be less than 0.5ppm. In the national defense industry, graphite is also used to make nozzles of solid fuel rockets, nose cones of missiles, parts of aerospace equipment, heat insulation materials and radiation protection materials.

Graphite conductive principle

Generally, rubber is insulated. If it needs to be conductive, it needs to add conductive substances. Graphite powder has excellent conductivity and lubrication demoulding property. Processing graphite into graphite powder has excellent lubrication and conductivity. The higher the purity of graphite powder, the better the conductivity. Many special rubber products factories need conductive rubber. Can graphite powder be added to rubber to conduct electricity? The answer is yes, but there is also a question, what is the proportion of graphite powder in rubber? Some enterprises use a proportion of no more than 30%, which is used in wear-resistant rubber products, such as automobile tires, and so on. There are also special rubber factories with a proportion of 100%. Only in this way can the conductor conduct electricity. The basic principle of conduction is that the conductor can not be interrupted, just like a wire. If it is interrupted, it will not be electrified. The conductive graphite powder in the conductive rubber is a conductor. If the graphite powder is separated by the insulating rubber, Then it will not conduct electricity, so if the proportion of graphite powder is small, the conductive effect is probably not good.

heat conduction

Heat conduction of graphite
When there is a temperature gradient in graphite, heat flows from high temperature to low temperature. The parameter characterizing the thermal conductivity of graphite is thermal conductivity. The thermal conductivity is a proportional coefficient between the amount of heat Q (heat flux) per unit area and the temperature gradient grad t per unit time.
q=– λ grad T
(1) Where a negative sign indicates that the heat flow direction is opposite to the temperature gradient direction. Formula (1) is often referred to as Fourier's law of heat conduction. If the cross-sectional area perpendicular to the x-axis direction is Δ S. The temperature gradient of the material along the x-axis direction is DT / DX Δτ In time, it flows in the positive direction of the X axis Δ The heat of section s is: Δ Q. In the stable heat transfer state, formula (1) has the following form:
(2) The legal unit of thermal conductivity is w · m · K. For unstable heat transfer process, that is, the temperature varies with time. For objects that have no heat exchange with the outside and have temperature gradients, the temperature gradients will tend to zero with the passage of time, that is, the temperature at the hot end will continue to decrease and the temperature at the cold end will continue to increase, and finally reach a consistent equilibrium temperature. In this unstable heat transfer process, the temperature change rate per unit area of the object at any time is:
(3) Where: τ Is time, ρ Is the density, CP is the constant pressure heat capacity of mass. λ/ρ CP is often called the thermal diffusivity or thermal conductivity of graphite, and the common unit is cm / s.
Heat conduction is realized by the movement of the heat conducting carrier. The heat conduction carriers of graphite include electrons, phonons (lattice vibration waves), photons, etc. The thermal conductivity of graphite can be expressed as the superposition of the contributions of various heat conducting carriers:
(4) Where VI, Li and CI are the moving speed, average free path and specific heat capacity per unit volume of the heat conducting carrier I, respectively. Various heat conduction carriers of graphite interact and restrict each other. For example, phonons of different frequencies collide with each other and scatter, and phonons scatter with grain boundaries, lattice defects and impurities, affecting their average free path. Therefore, the heat conduction of graphite is a very complex physical process. Theoretically, it has been a long and hard work to accurately predict the thermal conductivity of various graphites and their changes with temperature, but only limited achievements have been made. Roughly speaking, at normal temperature and not too high temperature (less than 2000K), phonon thermal conductivity is dominant, and the thermal conductivity of electrons and photons can be ignored. At very low temperatures (less than 10k), the electronic thermal conductivity occupies a certain component. Photonic thermal conductivity does not appear until at very high temperatures (above 2000K). The thermal conductivity of graphite increases with the increase of its conductivity (see Weidman Franz's law).

Crystalline graphite

single crystal
Graphite single crystal pure natural flake graphite and highly oriented pyrolytic graphite. These graphite crystals have fewer defects and larger sizes, which can generally be considered as relatively perfect graphite single crystals. There have been many studies on the thermal conductivity of this kind of graphite. Under compressive stress, the bulk density of pyrolytic graphite treated at more than 3000K is 2.25g/cm, which is close to the theoretical density of single crystal of 2.266g/cm. The angular spread at half width of (002) diffraction peak is only 0.4 ° (mosaic angle), which is also very close to the theoretical value of zero degrees. The thermal conductivity of this graphite is shown in Table 1. These values are generally considered to represent the corresponding values of single crystal graphite. Thermal conductivity along the two main directions: the thermal conductivity along the plane is λ a. Those along and perpendicular to the plane are recorded as: λ c。
At normal temperature λ A ratio λ C is about 200 times larger. As the temperature rises, the ratio will decrease, but it is still very large. Therefore, the thermal conductivity of polycrystalline graphite composed of microcrystals is the thermal conductivity of microcrystal layer λ A, λ C can be almost ignored. Natural flake graphite λ A is 280 ~ 500W / (m · K) at normal temperature, and the ratio λ a/ λ When C is between 3 and 5, it can be seen that the perfection of its crystal is far less than that of highly oriented pyrolytic graphite.
Pyrolytic graphite with highly regular crystal structure, La above 2000Nm, from low temperature to high temperature, its thermal conductivity changes with temperature in a bell jar shape, as shown in Fig. 1 and Fig. 2.
The temperature is much lower than the characteristic temperature of thermal conductivity at the graphite crystal level θλ Below:
λ a∝exp(– θλ/ bT) (5)
Where B is about 2, θλ It is sometimes called Debye temperature, but it is different from the Debye temperature that characterizes the heat capacity (see the heat capacity of carbon materials and graphite materials). At temperatures much higher than θλ When
λ a∝T(6)
According to formula (5), λ A increases with the increase of temperature T; According to formula (6), λ A decreases with the increase of temperature. Between low temperature and high temperature, both formulas (5) and (6) work, and when these two effects rival each other, λ A reaches the maximum value. This is why the bell shaped curve is formed.
At not too low temperature, the heat conduction carrier of graphite crystal is phonon, and formula (3) can be simplified as:
λ=γρ Where cvvl (7) ρ Is the density, CV is the constant volume heat capacity of the mass, V is the phonon propagation speed, l is the average free path between two phonon scattering or collision, γ Is the scale coefficient. At low temperature, the size of L is controlled by grain boundary scattering, and the size of L is equivalent to that of microcrystals. therefore λ The height and position of the peaks of the A-T curves are controlled by the size of the graphite crystal (the diameter La of the microcrystals in the a direction). The higher the annealing temperature of pyrolytic graphite, the more perfect the crystal, and the Greater LA, so the thermal conductivity λ A increases, the peak increases, and the peak position moves to the low temperature side (Fig. 3).
For the two kinds of graphite crystals, the grain diameter in the a direction is la. 1 and La. 2, and the thermal conductivity peak positions are TM. 1 and TM. 2, respectively. The relationship between these parameters is as follows:
(8) A method for estimating La from thermal conductivity data is provided. The La value obtained by this method is approximately equivalent to that obtained by X-ray diffraction.

Thermal conductivity ellipsoid
The thermal conductivity of the crystal in two main directions is λ (a) and λ c. In either direction Ф The thermal conductivity of λФ，Ф Is the intersection angle between this direction and the crystal axis C, and
λФ=λ asin Ф+λ ccos Ф (9)
In formula (9), Pt is represented graphically by a rotating ellipsoid with the long diameter as the axis of rotation (Fig. 4). The semimajor diameter of the ellipsoid is λ c. Half short diameter λ a。 This ellipsoid is called the thermal conductivity ellipsoid of graphite. Thermal conductivity in any direction λФ， The radius of the ellipsoid in this direction can be determined by γФ To represent:
λФ= 1/ γФ (10)
The shorter the radius in this direction, the greater the thermal conductivity.
Polycrystalline graphite
The thermal conductivity of polycrystalline graphite is affected by many factors: the type and proportion of aggregate and binder, forming conditions, heat treatment temperature and other manufacturing processes have significant effects; The size and distribution of microcrystals, the number and shape of pores and other structural factors are particularly prominent. The thermal conductivity varies greatly among different graphite varieties. Even for the same graphite, there are considerable differences between different batches. Although there are many influencing factors, the basic law of controlling thermal conductivity remains unchanged. In the temperature region dominated by phonon thermal conductivity, it is still controlled by the law indicated by formula (7).
Polycrystalline graphite is composed of many microcrystals. The thermal conductivity of polycrystalline graphite is transferred through the microcrystalline layer (a-direction thermal conductivity), because the λ A ratio λ C is about two orders of magnitude larger, and the thermal conductivity in direction C can be ignored, as shown in Fig. 6. At moderate temperature, microcrystalline λ A is mainly controlled by two scattering processes: 1. Thermal conductivity controlled by grain boundary scattering λ B. The larger the crystallite size La, λ The larger B is. 2. Thermal conductivity controlled by scattering caused by collision between phonons λ u. The higher the temperature, λ U decreases with the increase of temperature. λ a、 λ B、 λ U has the following relationship:
1/ λ a=1/ λ B+1/ λ u
(15) Thermal conductivity in either direction (x direction) λ X depends on the orientation and distribution of microcrystals in polycrystalline graphite. As the path of heat transfer is tortuous, amorphous and imperfect crystalline carbon substances and transitional carbon substances may exist between microcrystals, λ X and λ A) a correction factor shall be included in the relationship between: α x. Namely:
(16) Through theoretical analysis, λ The change data of u with temperature are listed in Table 3. Then compare the measured data of thermal conductivity at different temperatures with the theoretical formula (16), and we can get λ B and α x。 The comparison between the measured and calculated values of thermal conductivity of an extruded core graphite PGA and a molded ZTA graphite is shown in Fig. 7.
Table 3 λ U change with temperature

The change of thermal conductivity with temperature is shown in Fig. 8 and Fig. 9 for several kinds of molded graphite, λ– T curves are bell shaped& nbsp;

  Thermal conductivity theory

The theory of thermal conductivity of graphite crystal is very complicated. With the help of computer, much progress has been made, but there are still many problems to be further explored. Here, the thermal conductivity of the ideal graphite crystal without defects is only taken as the plane thermal conductivity λ Taking a as an example, the lattice vibration wave is quantized, and the vibration wave is vividly called phonon. The vibration wave is a vector, which can be called a wave vector. The energy and state of the wave vector are functions of the reciprocal lattice of the crystal. The reciprocal lattice of the whole crystal can be represented by a small region; This area is called Brillouin area. As long as the energy and state of phonons in this region are clear, the situation of phonons in the whole crystal will be well understood.
The Brillouin region of the graphite crystal is a hexagonal prism (Fig. 5). If only the thermal conductivity at the graphite crystal level is discussed, as a simplified model, it is enough to only discuss the motion of Phonons on the regular hexagonal plane in Fig. 5. This two-dimensional situation greatly simplifies the problem and makes it more convenient to deal with it. N represents the wave number. On the [NX, NY] plane, the area of the hexagonal cross-section can be represented by a circular surface with a radius of nm, as shown in Fig. 5:
(11)
In formula (11), a is a lattice parameter of graphite, a = 0.246 × 10cm。 Nm is the maximum wave number of phonon vibration, that is, the number of phonon vibrations per unit length. The product of the phonon velocity V and the wave number n is the phonon frequency, and the phonon energy is proportional to the frequency. The maximum angular frequency of phonon WM = 2 π vnm, and 2 π nm is called the maximum angular wave number, often referred to as QM. qm=1.55X10cm。
The motion of phonons is classified. Each category is called a phonon branch, and each branch is given a code. There are several phonon branches on the regular hexagonal plane of Brillouin region, mainly including three: longitudinal branch, with maximum frequency of 37thz and velocity of VL = 2.36 × 10cm/s； 2. TA, lateral branch, maximum frequency of 25thz, velocity of VT = 1.59x10cm/s; 3. Low TA branch, also known as bending vibration branch, has a maximum frequency of 14thz and a speed of VB = 0.53 × 10cm/s。 In addition, there are folded La branches, lateral optical branches to, etc. the frequency of these non main branches is lower than 4thz, and they strongly interact with other branches, so they are less than 4thz, that is, the angular frequency is less than WC = 2.5 × These branches of 10s play little role in heat transfer and can be ignored. WC is called the lower limit of phonon angular frequency. The speed of the low TA branch is much lower than that of La and Ta, and may not be considered. In this greatly simplified case, only la and Ta branches are considered, and only thermal conductivity is considered, not heat capacity. This is the so-called two-dimensional phonon gas model. Thus, a Debye velocity VD can be defined:
(12) From the data listed above, Debye speed VD = 1.86 × 10cm / s, and the maximum angular frequency of phonon WM = vddqm = 2.88x10s.
When the thermal conductivity carrier is monopolized by phonons, that is, at normal temperature and not too high temperature, the layer thermal conductivity of ideal graphite crystal is λ， be
(13) Where: ρ The density of ideal graphite crystal is 2.266 g / cm, γ Is the green eyson coefficient (see the heat capacity of graphite), which can be taken as γ= 2. Thus
=5.73/T × 10 (14)
This formula is simple and clear, and obviously provides a theoretical basis for the T relationship of formula (6). See Table 2 for the comparison between the thermal conductivity calculated by this formula and the measured value of highly perfect high directional pyrolytic graphite.
The measured values are generally in accordance with the theoretical values, and the results obtained from the very simplified theoretical model are in such good agreement with the actual ones. The average ratio of the two is 0.94, which indicates that even such graphite crystals still have shortcomings in their perfection compared with ideal crystals.

High thermal conductivity graphite

Thermal conductivity and density

As early as the middle of the 19th century, J.C. Maxwell, a famous physicist and founder of electromagnetic wave theory, was born. In his famous book electromagnetic wave theory (1873), he pointed out that for materials with pores, assuming that pores are uniformly dispersed in the material in the form of equal diameter small balls, the conductivity (electrical conductivity or thermal conductivity) of the material can be theoretically calculated by the following formula:
(17)
Where p is porosity, λ 0 is the thermal conductivity without holes (P = 0). This formula has historical significance. For graphite, the pores are not spherical, much less EQUIDIAMETER, and this formula is certainly not applicable. But it shows that the larger the porosity (i.e., the smaller the density), the smaller the thermal conductivity. This qualitative conclusion is correct. A kind of extruded nuclear graphite with different impregnation treatments. At normal temperature, its thermal conductivity λ The change with porosity conforms to the following relationship:
λ ∥= λ 0exp(–bP) (18)
Where: λ 0 = 1280w / (m · K), which is the ultimate thermal conductivity without pores, constant b = 7.00.
For the same type of graphite, the thermal conductivity increases with the increase of its density. Fig. 11 shows the thermal conductivity of hdfg homogeneous graphite λ Relationship with density.
Heat treatment temperature polycrystalline graphite is mostly made of roasted blanks after high-temperature heat treatment. The higher the heat treatment temperature, the more perfect the development of microcrystals, the increase of La, and the increase of thermal conductivity. The La values of calcined petroleum needle coke and medium temperature coal tar pitch, which are extruded into baking sticks, are shown in Table 4 after different heat treatments (HTT). Its axial thermal conductivity λ ∥ see Fig. 12 for the change with temperature. Reciprocal of thermal conductivity 1/ λ Called thermal resistance. At different heat treatment temperatures, the axial thermal resistance of this graphite is 1/ λ// See Fig. 13 for its relationship with L / LA. It is also another extruded graphite made of petroleum coke and medium temperature coal tar pitch. Fig. 14 shows its λ ∥ depending on LA. For a molded graphite λ ⊥ and htt are shown in FIG. 15.
Thermal diffusion coefficient α Also known as the thermal conductivity coefficient, α=λ/ρ cp。 (see formula (3)). It represents the ability of the material to make the temperature of each part tend to be the same during heating or cooling; It is a characteristic parameter that describes the speed of temperature change in the unstable heat transfer process. The higher the thermal conductivity of the material, the greater the propagation speed of the internal temperature of the material, and the smaller the temperature difference in the material. A high density, ρ= 1.81g/cm ³、 Isotropic fine grain graphite EK – 98, which α See FIG. 16 for the change with temperature.
Heat dissipation coefficient ε A comprehensive parameter characterizing the thermal performance of graphite materials, which is closely related to the thermal conductivity. It is defined as:
ε= ( λ cp ρ) (19)
In the legal system of units, ε The unit of is WS · m · K, which represents the heat dissipation or absorption capacity of the material surface. The variation of heat dissipation coefficient of ek-98 graphite with temperature is shown in FIG. 17.
Anisotropy of thermal conductivity: the anisotropy of graphite material is shown as the thermal conductivity along the direction parallel to the axis of symmetry λ ‖ and thermal conductivity along the vertical direction λ ⊥. In general, for extruded graphite λ ∥> λ ⊥, put λ ∥/ λ ⊥ this ratio is called thermal conductivity anisotropy; For molded graphite, λ ⊥> λ ∥, the ratio λ ⊥/ λ It is called thermal conductivity anisotropy; That is, the degree of anisotropy is at least 1 (isotropy). Let the orientation parameter along the symmetry axis oz of graphite be Roz, and the correction parameters in parallel and vertical directions be γ ‖ and γ ⊥ (see anisotropy of graphite) are:
Due to microcrystalline λ c/ λ a<& lt; 1. The above two expressions can be reduced to
Yes, a lot of graphite γ ∥≈ γ ⊥, from (21):
This is the famous expression for estimating orientation parameters from thermal conductivity data. For example, for nuclear graphite PGA, the R measured by conventional X-ray diffraction is 0.78, and the R measured by thermal conductivity data is 0.77, which are in good agreement.

Development prospect

It is expected that in the next ten years, as long as the whole market is sufficient to support, mining and expansion are successful, the capacity of graphite powder will continue to grow. The new graphite production capacity will make up for the current production capacity of 100000 tons of flake graphite lost due to mining due to engineering errors. According to the analysis of insiders, global graphite product research and development will be carried out in ten fields. At the same time, as the largest graphite producer in the world, China's output accounts for 40% ~ 50% of the world's total output according to the original national building materials administration. India, the world's second largest producer, has accounted for about 15% of graphite production in the past decade. Other producers are Brazil (7%), Mexico (6%), and North Korea (6%). The total graphite output of the above five countries accounts for more than 75% of the world's total output.
If the world graphite market environment continues to develop in a favorable direction in the future, the graphite output will increase, especially in Brazil, Canada, China, India and Mexico. The total volume is expected to increase by 120000 tons. Under the guidance of the graphite deep processing direction proposed in the 10th five year plan, the graphite deep processing products to be developed in China in the next five years are special-shaped carbon, fluorinated graphite, siliconized graphite, graphite emulsion for picture tubes, lithium-ion batteries, carbon materials, fuel cell carbon materials, etc.
In addition, there is still a large gap in the production of graphite deep-processing products in China, and the development work is promising. For example, there are 1000 nuclear power stations in the world, but there are only three in China at present, and 23 are planned to be built by the state. Basically, all the nuclear pure graphite used depends on imports.
At present, with the globalization of economic development, product research and development of the global graphite industry will be carried out in ten fields:
1. High performance seals and products, with a transaction volume of US $10 billion in the world, the highest grade graphite products for nuclear reaction are US $1.2 million / ton. There are four key technologies in this product, insertion technology, expanded sulfur technology, composite reinforcement technology and molding technology.
2. High performance conductive materials: one is to make interlayer compounds; Second, high performance and stability; The third is process repairability.
3. Battery materials.
4. Environmental protection materials.
5. Biomaterials.
6. Sound and heat insulation materials.
7. Protective safety materials.
8. Shielding material.
9. Arts and crafts materials.
10. Catalyst.