Physical and chemical indicators of graphite materials ：Structural

A. Bulk density
Bulk density is a physical quantity that characterizes the macroscopic structure of a material. The higher the bulk density, the denser the macroscopic structure of the material, and the lower the bulk density, the looser the macroscopic structure of the material.
Calculation formula: bulk density = mass / volume
The unit of bulk density is: g / cm 3 (g / cm3)
The unit of mass is: gram (g)
The unit of volume is: cm3 (cm3)
Unit conversion:
1 ton = 1000 kg (kg), 1 kg (kg) = 1000 g (g),
1 g (g) = 1000 mg (mg),
1 mg (mg) = 1000 micrograms (μg)
1 km (km) = 1000 m (m)
1 m (m) = 10 decimeters (dm) = 100 cm (cm) = 1000 mm (mm),
1 mm (mm) = 10 filament meters (dmm) = 100 mm (cmm) = 1000 micrometers (μm)
1 micron (μm) = 1000 nanometers (nm)
1 nanometer (nm) = one hundred millionth of a meter (m), if the nanometer is regarded as table tennis, then the size of the rice is about the size of the earth.
We can calculate according to the different units given by different users at home and abroad into gram / cm 3 (g / cm3), compare the industry standards and internal physical and chemical indicators of the enterprise, so that we can know how to communicate with users.
The cylinder product is calculated as follows:
Bulk density = mass ÷ diameter ÷ diameter ÷ 0.785 ÷ length
The cuboid product is calculated as follows:
Bulk density = mass ÷ length ÷ width ÷ height (thickness)
If the volume density of various shaped products can be calculated, the volume is calculated accurately after calculation. If the volume cannot be accurately calculated, the volume is approximated by the drainage method and then calculated.
Because the bulk density directly reflects the compactness of the macroscopic structure of the material, and indirectly reflects the strength of the material, etc., is an important physical quantity, so it occupies a very important position in the user’s requirements.
However, because the carbon graphite material is very different in the whole manufacturing process due to the difference in raw materials, formulation, molding method, heat treatment temperature, immersion treatment, process equipment, personnel quality, management level, etc., the bulk density varies greatly. Generally, the bulk density of artificial graphite fluctuates in the range of 1.50 to 1.85 g/cm3, and the specially treated product can reach 1.90-2.20 g/cm3.
B. True density
It is a physical quantity that characterizes the microstructure of a material. The higher the true density, the better the microstructure of the material, the lower the true density, and the less perfect the microstructure of the material.
The unit of true density is the same as the volume density
The true density is measured by an experimental method, and is determined by a solvent replacement method in production, and is scientifically determined by an X-ray diffraction method.
The true density directly reflects the perfection of the microstructure of the material, and indirectly reflects the heat treatment temperature of the material, which has an important influence on the electrical conductivity, thermal conductivity, oxidation resistance, high temperature resistance and acid and alkali corrosion resistance of the material.
The true density of the ideal graphite is 2.265 g/cm3, the true density of various artificial graphite materials is usually 2.16-2.23 g/cm3, and the high density nuclear graphite and pyrolytic graphite are 2.24-2.25 g/cm3.
C, porosity
The pores of the carbon material are divided into open pores, closed pores, and through pores. Therefore, the porosity is also divided into the total porosity and the apparent porosity, and the apparent porosity does not include closed pores.
The formula for calculating the total porosity of carbon materials is as follows:
Full porosity = (true density – volume density) / true density Χ 100%
The full porosity of several carbon materials is as follows:
Carbon electrode: 17-25%, graphite electrode: 22-30%, carbon block: 15-0%,
Filter material: 30-60%, impregnated structural material: 0-3%, carbon material: 10-20%
The porosity of carbon materials reflects the specific gravity of the pores of the material. The size of the porosity determines the applicable range of the material. For structural materials, the porosity is harmful. For some functional materials (such as filtration material) It is beneficial to have a large porosity. The size of the porosity reflects the ability of the material to pass through gases, liquids, and melts. Generally, when the porosity is large, the strength of the material is low, the electrical and thermal conductivity is poor, the oxidation resistance, the corrosion resistance, and the leakage resistance are poor.