What is the density of graphite?

Graphite is very important in industrial production and daily life. Different types of graphite have different densities, and it is important to understand the influencing factors of graphite density, measurement methods, etc. as it has meaningful importance in industrial production.

What is the density of various types of graphite?

Natural graphite

– Flake graphite: generally around 2.09 – 2.23 g/cm³.

– Earthy graphite (microcrystalline graphite): generally around 2.0 – 2.2 g/cm³.

Artificial graphite

– Isostatic pressure graphite: high density reaching around 1.7 – 1.9g/cm³. Due to its isotropic characteristics, isostatic graphite can achieve a high level after special process treatment, which helps to improve its properties such as strength, electrical conductivity and thermal conductivity.

– Molded graphite: typically range between 1.6 – 1.85 g/cm³. Its density is affected by factors such as molding pressure, raw materials and binders, and the densities in this range can meet the basic requirements of various application scenarios such as mechanical seals and electrodes.

– Extruded graphite:  around 1.5 – 1.7 g/cm³. In the extrusion process, the particle arrangement and compaction degree of the raw material will affect the final density. Extruded graphite in this density range shows good performance in applications such as electrode materials and brushes.

Factors that affect density

1.Raw materials:

The nature of the raw material of graphite can influence densities of the final products. For example, the particle size, shape, purity, etc. of the raw material will affect the bulk density and crystallinity of graphite.

2.Molding methods:

Different molding methods, such as molding, extrusion, isostatic pressing, etc., will have an impact. For example, isostatic compression molding can achieve higher densities of graphite products because the method allows the pressure to be applied evenly to the graphite material, thereby reducing internal porosity.

3.Sintering temperature and time:

During the sintering process, the control of temperature and time has an important impact. Higher sintering temperature and proper holding time can promote the crystallization and fusion of graphite particles, reduce porosity, and thus increase densities.

4.Porosity:

The porosity in graphite directly affects its density. The higher the porosity, the lower the density. The formation of pores may be related to factors such as the characteristics of the raw material, the discharge of gases during preparation, and the shrinkage during sintering.

5.Impurity content:

If graphite contains more impurities, it will affect the integrity and compactness of its crystal structure, resulting in a decrease in density.

6.Degree of graphitization:

The higher the degree of graphitization, the more complete the crystal structure of graphite, and the density will increase accordingly.

Methods for measuring the density of graphite

1. Archimedes’ principle (drainage method).

According to Archimedes’ principle, the buoyant force experienced by an object in a liquid is equal to the weight it displaces from the liquid. By measuring the weight of graphite in air and its weight in water (buoyancy), the volume of graphite can be calculated. Then combined with its mass, the result is derived.

2. Pycnometer method

By measuring the mass of a known volume of pycnometer when it is filled with a liquid (such as water) and the mass remaining after the liquid overflows after filling the liquid, the volume of the graphite sample can be calculated, so as the density.

3. Direct measurement method (for regularly shaped graphite samples)

For graphite samples with regular shapes (e.g., cubes, cuboids, cylinders, etc.), the size can be directly measured, and the volume can be calculated. Then the density can be calculated in combination with the mass.

Comparison of the density of graphite with the same type of carbon material

Activated charcoal VS Graphite

Activated carbon is a carbon material with a highly porous structure. Due to its large number of pore structures, the density of activated carbon is relatively low, generally around 0.5 – 0.9 g/cm³. In contrast, graphite is much denser than activated carbon.

Diamond VS Graphite

At room temperature and pressure, the density of diamond is about 3.5 – 3.53 g/cm³. Therefore, the density of diamond is greater than that of graphite.

Carbon fiber VS Graphite

The density of carbon fiber is usually between 1.7 and 2.2 g/cm³, but its density will vary depending on the type of fiber and the preparation process. Therefore, graphite partially overlaps with carbon fiber in the density range.

Carbon nanotubes VS Graphite

Carbon nanotubes are a tubular carbon material, and their density depends on factors such as tube diameter, tube wall thickness, etc. The density of single-walled carbon nanotubes is about 1.3 – 1.4 g/cm³. Graphite is denser than carbon nanotubes.

The importance of graphite density in industrial production

Performance evaluation: The density of graphite is closely related to its physical properties. Higher density usually means better mechanical strength, wear resistance, electrical conductivity, etc. By measuring the density of graphite, its performance in a specific application can be preliminarily evaluated, providing a basis for selecting the right graphite material.

Quality control: In the production process of graphite products, density is an important quality indicator. By controlling the production process parameters to ensure that the graphite product reaches the expected density range, the quality stability and consistency of the product can be guaranteed. Products with unsatisfactory densities may affect their performance and longevity in service.

Conclusion

To sum up, the density of graphite is a crucial determinant of its mechanical properties and, consequently, its industrial applications. With its potential applications expanding into various sectors, its prominence in the industrial landscape continues to rise.