What are the uses of graphite?

Ores of almost all graphite deposits can rarely be used raw by consumers. Virtually all of them are subjected to a particular pretreatment in order to convert the ore into finished products.

The technological classification of graphite ores coincides with the classification of natural types.

Explicitly crystalline ores are processed mainly by flotation schemes due to the good flotation of graphite.

The cryptocrystalline graphite raw material is represented by finely dispersed minerals in a very complex germination with empty rocks. Therefore, such types of graphite ores almost do not lend itself to mechanical enrichment. They are mainly used in ore mining and, in special cases, methods of chemical, thermal or other processing methods. Due to the fact that these processes are expensive, it is rarely used.

The main indicators on which graphite products are evaluated are: texture-structural, carbon, ash, moisture, volatile components, harmful impurities (iron, sulfur, copper, etc.), granulometric composition.

In the foundry industry preference is given to cryptocrystalline graphite, since for this production the dispersion of the powder is important, providing a smooth surface of the molds and facilitating the removal of the castings after cooling.

High-quality, clearly crystalline graphites are widely used in special steel casting.

Crucible graphite is represented by three brands. Zoning does not exceed 7, respectively; 8.5 and 10%, the mass fraction of iron in terms of Fe2O3 for all brands is not more than 1.6%, volatiles – less than 1.5%; Moisture – no more than 1%.

For the production of graphite-ceramic melting crucibles and refractories, high-quality, clearly crystalline graphite is used.
In accordance with the requirements for lubricating graphite, the products are manufactured in the form of several grades, each of which has its own direction of application and is characterized by a number of indicators. Common to all brands are only indicators of the concentration of hydrogen ions of water extract and humidity.

The production of pencils, as well as the electro-carbon, makes the highest demands on the quality of graphite. In the world practice for the best varieties of pencils used a mixture of Ceylon and other crystalline or cryptocrystalline graphite, which is most often used for the production of ordinary varieties of pencils.

In the electric coal industry, graphite of three types is used: natural fine and concealed and artificial and artificial. Artificial graphite has become widespread due to its high purity and consistency of composition.

In the production of lubricants as solid substances, natural crystalline graphite is widely used and, together with it, graphite is artificial. This production requires graphite of usually high purity and very fine grinding, sometimes of colloidal dimension. Lubricants are most often aqueous or oil suspensions made of natural crystalline and artificial graphite.

A number of graphite grades do not allow clogging impurities, including graphite from other deposits. These grades include crucible, elemental and electro-carbon graphite.

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What are the uses of diamonds in industry?

Jewelery diamonds. The main area of ‚Äč‚Äčapplication of diamonds in value terms is cutting into diamonds.

Technical diamonds. Technical dark crystals with cracks and other defects, as well as various fragments, twins, splices, etc., from which it is impossible to produce a faceted crystal, belong to technical ones. Depending on the quality and purpose, technical diamonds can be conditionally divided into the following groups:

– diamonds undergoing processing to obtain grains of a certain geometric shape. These include diamonds intended for the manufacture of cutters, drills, tips, glass cutters, bearings, etc .;
– diamond crystals used in raw form in drill bits, diamond-metal pencils, etc .;
– Abrasive diamonds are mainly small crystals that have significant defects and are suitable only for grinding into powder.

Diamond powders are indispensable in the processing of sub-miniature parts, such as watch stones from ruby, bearings from topaz, beryl and sapphire, whose hardness is close to the hardness of corundum. Only the use of diamond powders ensures high purity of the processed microsurfaces, on which the accuracy of the micro components work in apparatuses and devices depends.

Tools from diamond powders. For cutting hard rocks, alloys and other hard materials, the industry produces diamond discs and various diamond saws. Are widespread abrasive diamond tools in the mandrel, which are widely used in the metalworking industry for dressing grinding wheels. Also used are diamond-metal pencils, which are pressed inserts from a diamond powder of a hard alloy.

Tools from single crystals of diamond. Cutters, needles, glass cutters, dies (lamellar diamonds with the finest holes drilled in them) and another tool are made from individual diamond crystals or parts thereof. Diamond needles are crystals of diamonds with a natural sharp tip or fragments with a sharp edge fixed in metal rods. Diamond needles are widely used for making taps on thread grinders. Diamond needles of conical shape with a spherical head are used in profilometers and profilographs, which serve to measure the smallest irregularities and surface cleanliness of various parts. Widely used diamonds for the manufacture of spinnerets in the production of wire from hard materials, especially small diameters for electronics.

Diamond rock cutting tool. The use of diamonds for the reinforcement of drill bits has increased the productivity of drilling rigs by a factor of 1.5-2 compared to non-diamond drilling.

Other areas of use of diamonds. Diamond is an excellent optical material for all kinds of ditches and windows, capable of withstanding high pressures and pressure of substances of any degree of aggressiveness and being simultaneously transparent over a wide range of wavelengths.

The diamond substrate of semiconductor circuits, providing their excellent insulation, diverts the heat several times faster than, for example, copper, significantly increasing the efficiency of the responsible parts of electronic circuits. The ability to count nuclear particles with diamonds in conditions of aggressive media and high mechanical loads, diamond is used in special counters.

The structure of consumption of technical diamonds by highly developed countries is as follows, (%):
– Grinding, sharpening of tools and parts of cars from hard alloys – 60-70;
– mandrel of grinding wheels – 10-12;
– drilling of wells – 10;
– Wire drawing – 10;
– cutting and grinding of parts and products from glass, ceramics, marble, drilling and finishing of carbide parts, processing of watch and jewelry – 10-12.

General characteristic of diamond

Once people who hunted for diamonds, and did not suspect that the object of their passion is crystalline carbon, which forms soot, soot and coal. This was first proved by Lavoisier. He put the experience of burning a diamond, using an incendiary machine specially built for this purpose. It turned out that the diamond burns in air at a temperature of about 850-1000 * C, leaving no solid residue, like ordinary coal, and burns at a temperature of 720-800 * C in a jet of pure oxygen. When heated to 2000-3000 * C without access to oxygen, it passes into graphite (this is explained by the fact that the homopolar bonds between the carbon atoms in the diamond are very strong, which causes a very high melting point.

Diamond – a colorless, transparent crystalline substance, extremely refracting rays of light.
The carbon atoms in the diamond are in a state of sp3-hybridization. In the excited state, valence electrons are vaporized in carbon atoms and four unpaired electrons are formed.
Each carbon atom in a diamond is surrounded by four others, located away from it in the direction from the center at the tops of the tetrahedron.
The distance between atoms in tetrahedra is 0.154 nm.
The strength of all bonds is the same.
The whole crystal is a single three-dimensional skeleton.

At 20C, the density of the diamond is 3.1515 g / cm. This explains its exceptional hardness, which on the edges is different and decreases in sequence: octahedron – rhombododecahedron – cube. At the same time, the diamond has perfect cleavage (in the octahedron), and its flexural and compressive strength is lower than that of other materials, so the diamond is brittle, it breaks with a sharp impact and turns into powder when it is crushed. The diamond has maximum rigidity. The combination of these two properties makes it possible to use it for abrasive and other tools operating at a significant specific pressure.

The refractive index (2.42) and dispersion (0.063) of diamond are much higher than those of other transparent minerals, which, combined with maximum hardness, determines its quality as a precious stone.

Diamonds contain impurities of nitrogen, oxygen, sodium, magnesium, aluminum, silicon, iron, copper and others, usually in thousandths of a percent.

The diamond is extremely resistant to acids and alkalis, it is not wetted by water, but has the ability to adhere to some fatty mixtures.

Diamonds in nature occur both in the form of well-defined individual crystals and polycrystalline aggregates. Correctly formed crystals have the form of polyhedra with planar faces: octahedron, rhombododecahedron, cube and combinations of these forms. Very often on the faces of diamonds there are numerous stages of growth and dissolution; If they are indistinguishable to the eye, the faces appear curved, spherical, in the form of an octahedroid, hexahedroid, cuboid and their combinations. The different shape of the crystals is due to their internal structure, the presence and nature of the distribution of defects, and also the physicochemical interaction with the surrounding medium.

Among the polycrystalline formations, ballas, carbonado, and beads are distinguished.

Ballas are spherulite formations with radial-radiant structure. Carbonado – cryptocrystalline aggregates with the size of individual crystals of 0.5-50 microns. Board – clear aggregates. Ballas and especially carbonado have the highest hardness from all types of diamonds.