Graphite is a mineral, stable crystalline modification of carbon. It retains its original properties under standard conditions. The material is refractory, quite dense and has high electrical conductivity. It turns out by heating anthracite without air. It is used in foundry, in the manufacture of steel, as well as for lubrication in the rolling industry. But these areas do not cover all areas of use.
Basic properties
If you are interested in the question of what is the density of graphite, you should know that this parameter is 2230 kg / m 3 . Another allotropic form of carbon is diamond, so graphite is sometimes compared with it. The latter has electrically conductive characteristics and acts as a semimetal. This property has found its application in the production of electrodes.
Graphite density is not all you need to know if you are interested in this mineral. It is necessary to take an interest also in other properties. For example, this crystalline modification of carbon does not melt, and when exposed to a temperature of 3500 ° C, it ignites. The material passes the liquid phase, passing into a gaseous state.
However, if the conditions provide for an increase in pressure up to 90 MPA, as well as temperature, then melting can be achieved. This discovery was made when studying the properties of diamond when they tried to synthesize it. But to obtain this material from molten graphite failed.
Crystal cell
The crystal lattice of graphite provides for the presence of carbon atoms. It has a layered structure. The distance between the individual layers can reach 0.335 nm. In the lattice, carbon atoms bind to three other carbon atoms.
The lattice can be hexagonal and rhombohedral. In each layer, carbon atoms are located opposite the central parts of the hexagons. The latter are in adjacent layers, then the position of the layers is repeated, which happens through one.
Artificial Graphite Production
Graphite and its properties are not the only things you should know if you are interested in this mineral. It is important to take an interest in the production of the artificial variety. It differs from natural material in that during the synthesis a substance with specified parameters is obtained.
Waste from petroleum coke and coal sand goes into production. The mixture of fine-grained elements is fired, and then cooled for about 5 weeks. The influence of temperature in the first stage is accompanied by its increase to 1200 ° C.
To increase the theoretical density of graphite, the workpieces are impregnated with sand. At the final stage, graphitization takes place, it provides for the heat treatment of the material in a special furnace, where the temperature reaches 3000 ° C. In this case, it is possible to form a crystal lattice.
Such graphite has high thermal conductivity and excellent electrical conductivity. Anisotropic properties are inherent in the mineral obtained by extrusion. Today, a newer technology called isostatic pressing is also used. This allows you to make a material that has a low coefficient of friction. It has isotropic properties.
The density of graphite (g / cm3), which is obtained during the extrusion process, reaches 2.23. The same indicator for an isostatic recrystallized variety, depending on the brand, can reach 5 g / cm 3 . Such material is used for the manufacture of large-sized blanks, the length and diameter of which are 1000 and 500 mm, respectively, as well as for the production of foundry parts and molds that have antifriction properties.
Major brands
Today, the possibility of synthesis with different grain sizes is used. As a result, graphite can be classified into:
- coarse-grained;
- medium grained;
- fine-grained;
- fine-grained.
Elements of the first reach a diameter of 3,000 microns. If we are talking about a medium-grained variety, then the grain size is 500 microns. Fine-grained graphite of the MPG brand with a grain size of up to 50 microns is distinguished. There is also a fine-grained isotropic mineral of the MIG-1 brand, the particles of which have sizes from 30 to 150 microns. Fine-grained graphite and isostatic graphite have grains up to 30 microns in size, their minimum diameter is 1 micron.
The use of artificial graphite
The density of graphite is already known to you. However, it is important to study the area of use of the artificial variety. It is used in all industries. Coarse-grained electrodes are made. Fine-grained structural is used for the production of shaped products that have a complex shape.
The use of artificial mineral allowed to achieve high accuracy in the manufacture of parts. Today, equipment is produced that fully complies with the standards of this century.
Additional Density and Thermal Expansion Information
Depending on the additive, the highest density of graphite can be 5 g / cm 3 . The minimum value is 2. It is inherent in recrystallized graphite. Single crystals have high anisotropy, this is due to the structure of the crystal lattice. In the basal planes, the thermal expansion is negative up to 427 ° C. This suggests that the mineral is being compressed.
With increasing temperature, its absolute value decreases. At the aforementioned temperature level, thermal expansion is positive. It is directed perpendicular to the basal planes. The temperature coefficient of expansion is almost independent of temperature and exceeds the value by more than 20 times in comparison with the average absolute coefficient for the basal planes.
What else you need to know about strength
The strength and density of graphite change with increasing temperature. For most artificial graphites, tensile strength increases 2.5 times with increasing temperature. The maximum value reaches at 2800 ° C.
The compressive strength increases by 1.6 times when the temperature reaches 2,200 ° C. Shear and elastic moduli increase 1.6 times when the temperature reaches a value of 1,600 ° C.
Finally
The form determines the varieties of graphite, which can be: lamellar, flaky and spherical. Flaky is also called carbon annealing. Graphite is also a microstructural component of ductile, gray ductile iron and vermicular graphite iron. In this case, it consists of carbon and predetermines the specific properties of cast iron.
This material was used to create inscriptions and drawings about 4,000 years ago. Its name comes from the word "write." Deposits are located where deposits of bitumen and coal were exposed to high temperatures.