Given that graphite prepared from natural graphite is typically what is referred to in the narrow sense as synthetic graphite, this article focuses solely on analyzing and discussing the differences and connections between natural graphite and synthetic graphite in the narrow sense.

Crystal structure

Natural graphite has a more developed crystal structure, and the graphitization degree of natural flake graphite typically ranges from... 98% Above,   Meanwhile, the graphitization degree of natural microcrystalline graphite typically ranges from... 93% The following.

The degree of crystalline development in synthetic graphite depends on the raw materials and the heat-treatment temperature. Generally speaking, the higher the heat-treatment temperature, the greater the degree of graphitization. Currently, in industrial production, the degree of graphitization in synthetic graphite typically falls below... 90%。

Organizational Structure

Natural flake graphite is a single crystal with a relatively simple microstructure, containing only crystallographic defects (such as point defects, dislocations, and stacking faults). On a macroscopic scale, it exhibits anisotropic structural characteristics. Natural microcrystalline graphite, on the other hand, has smaller crystallites that are randomly arranged and contain pores left after impurities have been removed. On a macroscopic scale, it displays isotropic structural characteristics.

Artificial graphite can be regarded as a multiphase material, comprising carbonaceous particles such as petroleum coke or pitch coke.   Graphite phases formed by particle transformation, graphite phases formed by the conversion of coal pitch binder coating around the particles, and pores generated by particle packing or thermal treatment of the coal pitch binder, among others.

Physical form

Natural graphite typically exists in powder form and can be used on its own, but it is usually employed in composite form with other materials.

Artificial graphite comes in various forms, including powdery, fibrous, and block-like. However, in a narrow sense, artificial graphite typically refers to the block-like form, which needs to be processed into a specific shape before use.

Physicochemical Properties

Natural graphite and synthetic graphite share certain common characteristics but also exhibit differences in performance. For instance, both natural graphite and synthetic graphite are excellent conductors of heat and electricity. However, for graphite powders of the same purity and particle size, natural flake graphite boasts the best thermal and electrical conductivity, followed by natural microcrystalline graphite, while synthetic graphite has the lowest conductivity.

Graphite exhibits good lubricity and a certain degree of plasticity. Natural flake graphite has well-developed crystals, a lower coefficient of friction, the best lubricity, and the highest plasticity. Dense crystalline graphite and cryptocrystalline graphite rank second, while synthetic graphite is inferior.

Application areas

Graphite possesses numerous excellent properties, and as a result, it is widely used in various industrial sectors including metallurgy, mechanical engineering, electrical engineering, chemical industry, textile industry, and national defense. While there is some overlap in the application areas of natural graphite and synthetic graphite, there are also distinct differences between the two.

In the metallurgical industry, natural flake graphite, due to its good antioxidant properties, can be used to produce refractory materials such as magnesia-carbon bricks and alumina-carbon bricks.

Artificial graphite can be used as electrodes for steelmaking, whereas electrodes made from natural graphite are less suitable for use in steelmaking electric furnaces with more demanding operating conditions.

In the mechanical industry, graphite materials are commonly used as wear-resistant and lubricating materials. Natural flake graphite has excellent lubricity and is often used as an additive in lubricating oils.

For equipment used to convey corrosive media, piston rings, seals, and bearings made of synthetic graphite are widely employed; these components require no lubricant during operation.

Natural graphite-polymer resin composites can also be used in the aforementioned fields, but their wear resistance is inferior to that of synthetic graphite.

Artificial graphite features corrosion resistance, excellent thermal conductivity, and low permeability, making it widely used in the chemical industry for manufacturing equipment such as heat exchangers, reaction vessels, absorption towers, and filters.

Natural graphite compounded with polymer resin   Composite materials can also be used in the aforementioned fields, but their thermal conductivity and corrosion resistance are inferior to those of artificial graphite.

Develop artificial graphite using natural graphite as a raw material.

In fact, developing new graphite products by drawing on the preparation processes used for synthetic graphite has long been no longer a novel topic in the synthetic graphite industry. Many carbon-graphite products—prepared using natural graphite as the primary or auxiliary raw material according to synthetic graphite production processes—have already emerged, and some have even grown into sizable industries.

Zinc-manganese battery carbon rods: Carbon rods for zinc-manganese batteries (commonly known as dry cells), produced through a series of processes including mixing, extrusion molding, roasting, machining, and wax impregnation, using natural microcrystalline graphite and coal tar pitch as the primary raw materials.

It primarily leverages the high conductivity and low cost of natural microcrystalline graphite. While it does not have stringent requirements for ash content, it does impose strict limits on impurities such as iron and sulfur.

Natural graphite brush   Made primarily from natural flake graphite and coal pitch, the material undergoes mixing, rolling into sheets, grinding into powder, mold pressing, and firing (with graphitization treatment required in certain cases).   Motor brushes produced through processes such as machining and finishing.

It primarily leverages the high conductivity and high orientation of natural flake graphite, with requirements for relatively low impurity levels of elements such as iron and sulfur.   Low and ash content no higher than 2% During machining, pay attention to the orientation of flake graphite.

Mechanical Carbon-Graphite Materials   A block-shaped material produced through processes including mixing, rolling into sheets, grinding into powder, mold pressing, and firing, using natural graphite and coal pitch as the primary raw materials.   Precision machining is required according to the usage requirements.

It primarily leverages the lubricating properties of natural graphite, as well as its high-temperature resistance and corrosion resistance, while placing stringent requirements on ash and impurity content.

As can be seen from the examples above, compared with narrowly defined synthetic graphite, carbon-graphite products prepared using natural graphite as the primary or auxiliary raw material according to synthetic graphite production processes exhibit the following differences in terms of both production processes and product performance:  ：

( 1 ) The former usually requires going through 2500 Graphitization treatment at temperatures above ℃ is performed to achieve the desired physicochemical properties; the latter can either undergo graphitization treatment or remain untreated.

To reduce production costs, graphitization is typically not performed; therefore, the microstructure contains a “carbon” phase formed by the transformation of the binder pitch.

This is located within the graphite particles.   The carbon surrounding and binding the graphite particles together has higher hardness and significantly lower conductivity than natural graphite, thus having a substantial impact on the product’s performance.

( 2 ) Since natural graphite typically exists in powder form and has poor bonding strength with coal tar pitch, carbon-graphite products made from natural graphite often suffer from drawbacks such as high porosity, low mechanical strength, and poor oxidation resistance and thermal shock resistance. Consequently, the product specifications cannot be too large, and their application fields are significantly limited.

Based on the analysis and discussion above, the author believes that when developing synthetic graphite using natural graphite as a raw material, the following technical issues should be given particular attention:  ：

Surface modification of natural graphite. Compared with carbonaceous raw materials such as petroleum coke and pitch coke, natural graphite has fewer oxygen-containing functional groups on its surface, lower reactivity, and weaker binding affinity with coal tar pitch.

Therefore, carbon-graphite products prepared using natural graphite—particularly natural flake graphite—as the primary raw material according to artificial graphite production processes inevitably suffer from poor mechanical performance. It is necessary to subject the natural graphite to appropriate surface treatment to increase the content of oxygen-containing functional groups on its surface.

Purification of natural graphite. Carbonaceous raw materials such as petroleum coke and pitch coke have relatively high purity, with ash content typically below: 0.5% However, natural graphite processed by flotation has lower purity, with a carbon content typically ranging from... 90% The following,

Therefore, carbon-graphite products prepared from natural graphite are often limited in their application fields due to their relatively low purity and inferior overall performance. One approach to addressing this issue is to subject natural graphite to high-purity purification treatment.

Chemical purification is relatively low in cost, but it consumes large amounts of water during the washing process and causes significant pollution. On the other hand, high-temperature purification suffers from higher costs. Some also suggest first preparing block-shaped graphite using the production process for synthetic graphite, and then proceeding with... 2500 High-temperature heat treatment above ℃,

While carbon is being graphitized, impurities in the natural graphite phase are removed. However, this process not only increases production costs but also often leads to defects caused by the volatilization of impurities, which in turn can degrade product performance.

Particle size of natural graphite. To improve process performance and product quality, most carbon-graphite products—except for fine-structured carbon-graphite products—require the use of carbonaceous raw materials with different particle sizes during the batching process. For certain large-sized products, the particle size of the carbonaceous raw materials can even reach... 16 Millimeters; meanwhile, natural graphite processed by flotation typically appears as a fine powder with particle sizes ranging from only tens to hundreds of micrometers. Therefore, using natural graphite as a raw material is limited to the preparation of carbon-graphite products with fine microstructures.

Although natural microcrystalline graphite of varying particle sizes can be obtained, due to its relatively low purity and the high cost of high-temperature purification, there have been no reports yet on the preparation of coarse-structured carbon-graphite products using natural microcrystalline graphite as a raw material.   To address the shortage of large-particle natural graphite, it is recommended to adopt carbon processing methods used in the synthetic graphite industry.   The “secondary coking” process during the use of black raw materials.

Volume shrinkage during the preparation process. During the preparation of synthetic graphite, especially during the graphitization process, the volume shrinkage of the product is significant because the arrangement of carbon atoms gradually transitions toward a more ordered graphite structure.

The advantage of this volume shrinkage is that it can increase the density of the product. However, when the shrinkage is uneven, the product is prone to cracking. On the other hand, when natural graphite is used as the raw material, because the volume shrinkage during carbonization and graphitization is relatively small, the resulting product exhibits lower density and mechanical properties.

In addition, when developing synthetic graphite from natural graphite as a raw material, it is also necessary to take into account the issue of overall production costs.

Since the price of naturally flaked graphite after flotation is comparable to that of calcined petroleum coke and pitch coke, and after further purification to achieve a carbon content of... 98% At present, the price of natural graphite has nearly doubled that of calcined petroleum coke and pitch coke. Consequently, in addition to the several carbon-graphite products mentioned earlier that have already developed into sizable industries, most proposed technological approaches and technical measures will significantly increase production costs.

Conclusion     language

In summary, developing synthetic graphite products from natural graphite is indeed an important approach for expanding the application fields of natural graphite.

Natural graphite has long been used as an auxiliary raw material in the production of some synthetic graphite products; however, there are still many issues that need to be addressed when developing synthetic graphite products using natural graphite as the primary raw material.

Fully recognizing and leveraging the structure and properties of natural graphite, and employing suitable process routes and methods to produce synthetic graphite products with special structures, properties, and applications, should be the best approach to achieving this goal.