合成黒鉛：総合ガイド

Synthetic graphite is also another term for artificial graphite. They come in many types and have excellent performance. They are indispensable carbon-based materials for industrial production. In the future, you can see that synthetic graphite may develop towards innovation and greening!

Synthetic Graphite Definition

Synthetic graphite is an amorphous carbon material that has been artificially synthesized and modified. It is usually produced with carbonaceous raw materials (such as coal, petroleum coke, etc.) through high-temperature treatment and graphitization processes. It has similar electrical, thermal, and high-temperature resistance characteristics as natural graphite, but the purity and structure can be changed for need.

Synthetic graphite properties

Physical properties

Synthetic graphite has excellent electrical and thermal conductivity. It is a very suitable material for making electrodes, batteries and thermal management. Besides, synthetic graphite is able to withstand extreme high-temperature environments. This means that you can use it as a refractory material and high-temperature furnace lining in the metallurgical and chemical industries. Furthermore, the relatively low density of it helps to reduce structural weight. At the same time, it maintains a high specific surface area, enhancing its performance in catalysis and adsorption processes.

Chemical properties

Synthetic graphite has excellent corrosion resistance and chemical stability. For example, it resists to a wide range of acids, bases, and organic solvents. So it is suitable for use in the manufacture of linings and storage tanks for chemical equipment. In addition, synthetic graphite can retain the stability of chemical structure and exhibit good oxidation resistance at high temperatures. This is particularly important in high-temperature applications, such as in high-temperature furnaces and heat treatment equipment.

Mechanical properties

Synthetic graphite has high strength and hardness so it can withstand large mechanical loads and resist wear. This makes synthetic graphite very useful in the manufacture of mechanical components, structural materials, and wear-resistant materials. At the same time, the plasticity of synthetic graphite allows it to be made into a variety of shapes and sizes through different processing techniques, increasing its flexibility in industrial applications. The abrasion resistance of it also makes it ideal for the manufacture of brake pads, seals, and other friction materials.

Natural graphite VS synthetic graphite

構造

Natural graphite is composed of single carbon element, and its crystal structure belongs to the hexagonal crystal system, which is a hexagonal layered structure.

Synthetic graphite is similar to polycrystalline in crystallography and can also be seen as a multiphase material. After graphitization, synthetic graphite has a more orderly arrangement of carbon atoms and interlayer spacing than natural graphite.

Thermal conductivity

The thermal conductivity of natural graphite is generally better than that of synthetic graphite, and can theoretically reach 2000 W/m·K, depending on the purity and crystal structure of the graphite. Its layered structure makes heat conducted quickly within the layer, so it is excellent in high-temperature applications.

The thermal conductivity of synthetic graphite is generally between a few hundred and 1000 W/m·K. This often depends the production process and the quality of the raw material.

Electrical conductivity

The electrical conductivity of natural graphite is typically between 10^4 and 10^6 S/m, relating to its crystal structure and impurity content. Natural graphite has a high electrical conductivity, especially in the plane direction, because electrons can move freely between layers.

The electrical conductivity of synthetic graphite is generally between 10^3 and 10^5 S/m, usually lower than that of natural graphite. This is because the structure and degree of graphitization of synthetic graphite may not be as perfect as that of natural graphite, resulting in certain restrictions on the movement of electrons.

Synthetic graphite manufacturing process

1. Raw material mixing

We select petroleum coke, needle coke, etc. which have high purity and good crystallinity as aggregates. Then mix them with binders such as coal, tar, pitch, etc. in a certain proportion and knead in the kneading equipment at a temperature of 150 – 200°C. In this way, the binder is evenly wrapped on the surface of the aggregate particles, forming a plastic paste. Typically, we define pitch as a binder for synthetic graphite.

2. Molding

Compression molding: We put the paste into the mold and apply a pressure of 10 – 50MPa to make the paste form into the desired shape in the mold, such as block, plate, etc.

Extrusion molding: For products such as electrodes, we extrude the paste through the mold of an extruder to form a cylindrical or other specific shape of green body.

3. Heat treatment

Carbonization: We put the shaped green billet into the carbonization furnace. Then, heat it to 800 – 1000°C at a heating rate of 1 – 5 °C/min under the protection of inert gases such as nitrogen or argon. In this process, the non-carbon elements in the binder escape in the form of a gas, and the remaining carbon further binds the aggregate particles.

黒鉛化: Then place the carbonized body in a graphitization furnace and heat it to 2500 – 3000°C at a heating rate of 5 – 10 °C/min. At this high temperature, the carbon atoms rearrange and the crystal structure gradually shifts to a graphite structure.

Synthetic graphite uses

– Battery industry:

Synthetic graphite anodes have high theoretical specific capacity, good cycling stability and low lithium intercalation potential. They are widely used in various lithium-ion battery products, which play a vital role in improving the overall performance of batteries. In addition, graphite is used to electrolyze the cathode of electrolytic cells for magnesium, aluminum, etc.

– Steelmaking and metallurgical industry:

You can use graphite as a carburant in the steelmaking industry. In the electric arc furnace steelmaking process, the graphite electrode acts as a conductive electrode to transmit electrical energy to the furnace, creating an electric arc that melts the charge. It  has good electrical conductivity, high temperature resistance and chemical stability. Therefore it can withstand harsh conditions such as strong currents and slag erosion in electric arc furnaces. In the modern steel industry, graphite electrodes are indispensable key materials for the production of high-quality steels such as special steels and alloy steels.

– Friction Materials:

Graphite is used in the manufacture of clutches in mechanical transmission systems, brake pads in automobiles, and high-temperature lubricant friction materials. For example, the lubricity and heat resistance of synthetic 黒鉛粉 can reduce the coefficient of friction, reduce wear. Thereby improving the service life and performance of friction materials. This ensure the normal operation of braking and transmission systems of automobiles, trains and other vehicles. In addition, the emerging synthetic graphite granules brake pads are more outstanding in friction and braking performance. This type of brake pad is made of resin and graphite synthesis.

– Heat Dissipation and Lighting Materials:

In power electronics such as power transistors, rectifiers, inverters, etc., you will use synthetic graphite sheet to dissipate heat. These devices generate a lot of heat when they are working. Therefor, and good heat dissipation helps to improve the reliability and efficiency of the equipment. Meanwhile, it reduces failures and performance degradation caused by overheating. For instance, LED lights will generate heat during the working process, and if they cannot dissipate heat in time, it will affect the luminous efficiency and life of the LED. Synthetic graphite sheets can be attached to LED chips or heat dissipation substrates to effectively dissipate heat. This ensures the normal operation of LED lighting systems, and improve lighting quality and energy-saving effects.

– Aerospace and defense industries:

With a high melting point, strong resistance to thermal shock, and corrosion resistance. It can be used as nuclear fuel and as a cladding material in high-temperature gas-cooled reactors. In addition, graphite is also used to manufacture nozzles for space rockets, aerospace engine parts, and thermal insulation structural materials.

National Synthetic Graphite Production

China is the world’s largest graphite manufacturer. In 2023, the graphite output has reached 2.612 million tons, of which synthetic graphite production accounts for 53.75% and natural graphite accounts for 46.25%. Chinese’s exports and net exports of synthetic graphite is continuing to grow, and the trade surplus shows an expanding trend.

In 2021, the synthetic graphite anode material market accounted for 97.58% of the market. From the market situation, the mainstream price range of mid-range products in the synthetic graphite anode market is US$2,700-4,100 per ton. Among them, the mainstream price range of high-end power products is US$3,700-4,700 per ton. The mainstream price range of low-end products is US$2,100-3,10o per ton.