Classification of Carbon Materials

Classification of Carbon Materials

Classification of Carbon Materials

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Classification of Carbon MaterialsCarbon material, according to the arrangement of its atoms in the structure, carbon has three allotropes, namely diamond, gra

Classification of Carbon Materials

Carbon material, according to the arrangement of its atoms in the structure, carbon has three allotropes, namely diamond, graphite and amorphous carbon, their physical properties, chemical properties and uses are also different.

1. Diamond: it is the hardest substance known in nature, and its crystal structure is basically face-centered cubic lattice. Each carbon atom is surrounded by four carbon atoms around it, connected by covalent bonds. When diamond contains trace impurities, it has the performance of semiconductor and can be used as high temperature rectifier or solid microwave device.

Natural diamonds are precious stones (diamond diamonds). There are three types of diamonds: type ⅰ, type ⅱ and hexagonal. The impurity content of type ⅰ is higher, in which the nitrogen content is 0.0025% ~ 0.2%. Most natural diamonds belong to this type. Type ⅱ is extremely pure diamond, complete crystal, nitrogen content less than 0.001%, good thermal conductivity, with semiconductor properties. 1% ~ 2% of natural diamonds belong to this type. Non-diamond structure of carbon can be converted into diamond by special artificial methods (such as ultra-high pressure and high temperature method), that is, artificial diamond.

2, graphite: carbon atoms to four coordination polyhedra composed of network layer, between the network layer to molecular bonds, forming hexagonal wafer. Graphite is a special inorganic nonmetallic material, both metal and plastic properties and a series of other characteristics, in metallurgy, chemical, power and electronics, machinery, textile and atomic energy and other industrial sectors have been widely used.

The use of graphite is closely related to its properties.

(1) High temperature resistance, good thermal stability, at 3600℃ does not melt, so used in the metallurgical industry crucible (see color picture), refractory materials in the furnace.

(2) Has good thermal conductivity and electrical conductivity (4 times higher than stainless steel), conductivity coefficient decreases with temperature rise. Used for manufacturing electrodes, brushes, carbon rods, heat exchangers, coolers, etc.

③ Good chemical stability, can resist the erosion of acid, alkali and organic media, widely used to manufacture heat exchanger, combustion tower, reaction tank, cooler, absorber, pump and heater in acid and alkali industry, petrochemical industry, textile, papermaking and other industries.

(4) Lubrication performance and molybdenum disulfide similar, wear resistance, friction coefficient is less than 0.1, can be used at -200 ~ 2000℃ and 100m/s speed, used to make seals and bearings, do not add lubricant.

(5) Good plasticity, can be extended into transparent, breathable sheet.

⑥ Has good neutron deceleration, used as deceleration material in atomic reactors. In addition, they are also used as nozzles in solid fuel rockets, spare parts for space equipment, heat insulation and radiation protection materials. The biggest disadvantage of graphite is that it is easy to oxidize at high temperature and needs to be used in a protective atmosphere.

Graphite ore has crystalline and cryptocrystalline points. Crystalline graphite ore has two kinds of dense crystal and flake crystal, the former grain is larger than 0.1mm, carbon content in 60% ~ 65%, even up to 80% ~ 90%, but poor plasticity, flotation. Although the grade of flake crystalline graphite is low (3%-5% or 10%-25%), it has good properties. Cryptocrystalline graphite, also known as earthy graphite, can contain more than 90% carbon, but its performance is poor. Half of the graphite produced in the world is earthy.

The Soviet Union is the country with the largest graphite reserves and production. China's graphite resources are also rich, mostly scale and cryptocrystalline ink. Because graphite ore grade is not high, need to be beneficiated and purified, commonly used flotation method (graphite hydrophobicity) and gravity separation method (graphite relative density is small, 1.9 ~ 2.3), can make the carbon content in the finished product up to 90%, some products also need to use chemical purification, so that the carbon content increased to 97% ~ 99% or high temperature purification to 99.9%.

3. Amorphous carbon: the carbon atoms are disordered, or the grains are too small. Amorphous carbon obtained by carbonization of coal, natural gas, petroleum or other organic matter at about 1000℃ is porous material with a large surface area. Products are carbon black, activated carbon and so on. [1]

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    www.chinaelectrodes.

    2022-03-23 01:58:10

    Generally, when the cathode carbon block is lower than its roasting temperature, it shows a positive coefficient of thermal expansion as the temperature increases, while the ramming paste will shrink from curing temperature to the maximum roasting temper

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    www.chinaelectrodes.

    2022-03-21 03:57:32

    From 1954 to 1976, calcined petroleum was widely used in aluminum plants. On the one hand, the carbon plant of aluminum factory produces anode paste, using local materials; On the other hand, there were no more effective pastes.

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    www.chinaelectrodes.

    2022-03-19 13:55:29

    An important index to measure the performance of calcined pet coke is the content of volatiles in calcined pet coke. If the content of volatiles in calcined pet coke is too high, the shrinkage ratio of raw anode will be large in the roasting process, and

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