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carbon black,mixture of partially burned hydrocarbons. Carbon black is produced by partial combustion of natural gasnatural gas,
natural mixture of gaseous hydrocarbons found issuing from the ground or obtained from specially driven wells. The composition of natural gas varies in different localities.
..... Click the link for more information. . It is used as a black pigment for inks and paints, and is used in large amounts by the tire industry in the production of vulcanized rubber. Lampblack resembles carbon black, but is produced by burning liquid hydrocarbons, e.g., kerosene; it is often somewhat oily, is duller than carbon black, and may have a bluish undertone. It is sometimes used in making contact brushes for electrical apparatus.
a dispersible carbon product resulting from the partial combustion or thermal decomposition of hydrocarbons. Carbon black occurs in the form of black, spherical particles with an average size ranging from 100 to 3,500 angstroms (Å). The particles are made up of layers of carbon atoms similar to the layers in graphite. The layers themselves consist of hexagons with carbon atoms situated at the vertices and separated from adjacent atoms by a distance of 1.42 Å. Unlike graphite, however, the layers in carbon black are curved rather than flat, which accounts for the spherical surfaces of the particles. The density of the particles is approximately 2 g/cm3; the density in bulk, depending on the extent of packing, ranges from 0.05 to 0.5 g/cm3. The surface of the particles can be smooth or rough.
Starting materials for the production of carbon black include natural gas, acetylene, and liquid hydrocarbons and coal tars and residues from petroleum distillation containing large amounts of condensed aromatic compounds.
Depending on the method of production, carbon black is classified as channel black, furnace black, or thermal black.
Channel (contact) black is obtained from the incomplete combustion of natural gas or a mixture of natural gas and an oil, such as anthracene oil in combustion chambers fitted with slotted burners. Carbon black is deposited when the flame impinges on cool surfaces placed inside the chamber.
Furnace black is obtained from the incomplete combustion of oil, natural gas, or a mixture of the two in a reactor (furnace). Combustion is triggered by a flame issuing from a special device. Carbon black in the form of an aerosol leaves the reactor with the combustion products and is collected by special filters.
Thermal black is produced in special reactors by the thermal decomposition of natural gas in the absence of oxygen.
The yield of carbon black depends on its dispersibility and on the type of the starting material; the yield of finely dispersed carbon black is lower than that of the coarser product. Industrial carbon black usually contains more than 98 percent carbon, 0.2–0.5 percent hydrogen, and minor sulfur and mineral impurities. In certain special varieties, chemisorbed oxygen is present in concentrations of up to 10 percent (by weight).
Carbon black is widely used in many branches of industry. More than 90 percent of the carbon black produced is used in the rubber industry, primarily for tire manufacture. The tensile strength and durability of rubber increase sharply with the addition of carbon black. Carbon black is widely used in the manufacture of black lacquers and enamels and black printing inks. It serves as a filler in the fabrication of plastic items and also has uses in the production of carbon paper, typewriter ribbons, shoe polish, theatrical makeup, and cosmetic pigments. Acetylene black, obtained through the thermal or explosive decomposition of acetylene, is distinguished by its more developed secondary structure and high electric conductivity and is used in the manufacture of dry cells. The heating procedures employed in many furnaces, particularly in open-hearth furnaces, involve measures to increase the concentration of carbon black in the flames because the thermal and luminous radiation of the flames derives from the presence of this material.
The carbon black generated during combustion in industrial and residential furnaces and in the operation of internal-combustion engines (diesel engines) is expelled along with combustion products into the atmosphere as a harmful smoke. Carbon black particles do not react with atmospheric oxygen and therefore are removed from the air only through coagulation and settling, processes that proceed very slowly. Strict controls over the completeness of fuel combustion are therefore necessary if the quality of the environment is to be safeguarded.
“White carbon black” is a conventional name for finely dispersed amorphous silicon dioxide (powdered silica gel), Si02, which is used as an active filler in special types of rubber, such as organosilicon compounds, and in the manufacture of white and colored rubber.
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P. A. TESNER