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What is diamond?

Diamond is what we often say diamonds (diamonds is its common name), it is a kind of pure carbon composed of minerals. Diamond is the hardest material in nature, and therefore has many important industrial applications, such as fine grinding materials, high hard cutting tools, all kinds of drill, drawing die. It is also used as part of many precision instruments.


    Diamond has a variety of colors, from colorless to black have to colorless for the special good. They can be transparent or translucent or opaque. Most diamonds are mostly yellow. Diamond's refractive index is very high, dispersion performance is also very strong, which is why the diamond will reflect the colorful flash reasons. Diamond in the X-ray irradiation will be issued under the blue-green fluorescence. The diamond is only produced in the Kimberley rocket. Kimberley rock is their original rock, other parts of the diamond are by rivers, glaciers and other handling in the past. Diamond is generally granular. If the diamond is heated to 1000 ° C, it will slowly become graphite.


    In 1977, a villager in Changlin, Lushi County, Shandong Province, discovered the largest diamond in China (about egg yolk size, right). The world's largest industrial diamond and gem-grade diamonds are produced in Brazil, all over 3100 carats (1 carat = 200 mg). The size of the gem-quality diamond is 10 × 6.5 × 5 cm, called "Cullinan", found in 1905 in South Africa's Premy rock pipe. China Chang Lin Diamond, weighing 158.786 karats, found in Shandong Linshu County in 1977, as the world famous drill. The world's major diamond origin of Australia, Zaire, Botswana, the former Soviet Union.


    Diamond and graphite belong to the same element of carbon. Is a super-hard, wear-resistant, heat-sensitive, heat conduction, semiconductor and beyond the excellent physical properties, known as "the king of hardness" and the king of precious stones, diamond crystal angle is 54 degrees 44 Min 8 sec. The last century 50's, the United States to graphite as raw materials, high temperature and pressure in the successful manufacture of synthetic diamond. Artificial diamonds are now widely used in production and life, but it is difficult to create large particles of diamonds.


Diamond - the characteristics of mineral raw materials

    Natural diamond diamond chemical composition of C, and graphite with carbon isomorphic variants. In the mineral chemical composition, the total containing Si, Mg, Al, Ca, Mn, Ni and other elements, and often contain Na, B, Cu, Fe, Co, Cr, Ti, N and other impurity elements, and carbohydrates.


    Diamond crystal structure is equiaxed system with the same electrode tetrahedral structure. The carbon atom is located at the corner and center of the tetrahedron and has a high degree of symmetry. The carbon atoms in the unit cells are connected with the same polar bonds, the distance is 1.54  (10-10m). Common crystal form octahedron, diamond dodecahedron, cube, tetrahedron and six octahedron and so on.


    Diamond Mohs hardness of 10, micro hardness of 98 654.9MPa (100060kg / mm2), the absolute hardness is greater than 1000 times the quartz, 150 times greater than corundum.


    Mineral brittle, shell-like or staggered fracture, in the absence of impact will be cleaved along the crystal cleavage surface, with parallel octahedral medium or complete cleavage, parallel dodecahedric incomplete cleavage. Mineral pure, the density is generally 3 470-3 560kg / m3.


    The color of the diamond depends on the purity level, the type and content of the impurity elements contained, the very pure colorless, generally different degrees of yellow, brown, gray, green, blue, white and purple; pure transparent, with impurities Translucent or opaque; in the cathode ray, X-ray and ultraviolet light, will emit a different green, sky blue, purple, yellow-green and other color fluorescence; in the sun exposure to the dark room after the light blue blue phosphorescence; Grease or metallic luster, high refractive index, generally 2.40-2.48.


    Diamond thermal conductivity is generally 136.16w / (m · k), where Ⅱ a diamond thermal conductivity is extremely high, 25 times the liquid nitrogen temperature, and with the temperature rise sharply decreased, such as at room temperature The specific heat capacity increases with the temperature, such as at -106 ℃ when the 399.84J / (kg · k), 107 ℃ when the 472.27J / (kg · k); thermal expansion coefficient is very small, with the temperature Ascending and increased, such as at -38.8 ℃ when the 0,0 ℃ when the 5.6 × 10-7; in pure oxygen in the ignition point of 720 ~ 800 ℃, in the air 850-1 000 ℃, under the oxygen 2 000 -3 000 ℃ into graphite.


    The chemical properties of diamond are stable, with acid resistance and alkali resistance. Under high temperature, it does not react with concentrated HF, HCl and HNO3. Only when the mixture of Na2CO3, NaNO3, KNO3, or with K2Cr2O7 and H2SO4 is boiled, Slightly oxidized; in O, CO, CO2, H, Cl, H2O, CH4 high temperature gas corrosion.


    Diamond also has non-magnetic, poor conductivity, lipophilic hydrophobicity and friction and so on. The only type IIb diamond has a good semiconductor performance. According to the difference of nitrogen impurity content and heat, electricity and optical properties of diamond, diamond can be divided into two types: Ⅰ and Ⅱ, and further subdivided into Ⅰa, Ⅰb, Ⅱa, Ⅱb four subclasses. Type I diamonds, especially the Ⅰa subtype, are common diamond, accounting for about 98% of the total natural diamond. Type I diamonds contain a certain amount of nitrogen, with good thermal conductivity, poor conductivity and good crystal form. Type II diamond is extremely rare, with little or no nitrogen, with good thermal conductivity and surface characteristics of the crystal. Ⅱb ​​subtype diamond with semiconductivity. Due to the excellent performance of type Ⅱ diamond, it is used for space technology and cutting-edge industry.

Reproduced from: interactive encyclopedia

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