The main component is carbon (C). Graphite produced in nature is formed during reduction under high-temperature conditions. Graphite is widely distributed due to sedimentary metamorphism, which is formed by regional metamorphism of sedimentary rocks rich in organic matter or carbonaceous matter. For example, coal seams or carbonaceous sedimentary rocks can produce graphite through metamorphism; when magma rocks come into contact with limestone, CO2 decomposed from limestone can also form graphite through reduction. Graphite is rarely pure and often contains large amounts of mechanical admixtures, such as quartz, mica, salt, iron oxide, magnesium oxide, calcium oxide, phosphorus pentoxide, etc. Sometimes there are gases such as CO2, CO, H2, CH4, N2, water, and asphalt. Graphite crystal is a layered lattice, which is composed of many regular hexagonal rings of carbon atoms connected to form a huge planar network, which is parallel and overlapping with each other. The more common graphite crystals belong to the hexagonal crystal system. Complete crystals are rare and usually appear in the form of plates and scales. Amorphous graphite is often in the form of lumps and powders. When the crystal diameter of natural graphite is less than 1 μm, and its crystal form is difficult to see under a general microscope, the dense graphite aggregate is called microcrystalline graphite (also known as amorphous graphite or earthy graphite).
The color of graphite ranges from iron gray to steel gray, with black streaks. It has significant optical inhomogeneity, hardness inhomogeneity, and is opaque and has metallic luster. Aphanitic crystals are dull. The hardness is 1 to 2, the specific gravity is 2.09 to 2.23, and the specific gravity of inferior graphite is 1.84 to 1.98. (The change in specific gravity is determined by the number of bubbles.) The sheets can bend, have a slippery feel, and can stain paper and fingers. Graphite has strong heat conductivity (higher than copper and aluminum), high electrical conductivity, and can withstand high temperatures above 3000°C. It has a melting point of 3800°C and a boiling point of 4250°C. It has plasticity, strong chemical stability, and is insoluble in acids and alkalis.
1. Manufacturing electrical smelting furnaces, electrolytic cells, arc lamps and arc welding electrodes and generators, motor brushes, resistors, and carbon rods for telephones, etc.
2. Manufacture various metallurgical crucibles.
3. Because graphite can absorb a large number of neutrons, it can be used as a moderator in atomic piles, but it must be highly pure crystalline graphite.
4. Used as coating for sand casting mold surfaces, anti-rust coating, machine lubricant, and bearing lubricant.
5. Mixtures of various refractory materials and refractory insulating materials.
6. Make corrosion-resistant paint.
7. Make pencil refills and use them as black coloring materials.
8. After special chemical treatment, it can be made into a flexible sealing material.