Beryllium

The crystal of beryllium

BERYLLIUM, Be (Latin "Beryllium" * EN: berillium; DE: Beryllium; FR: beryllium; ES: berilio; RU: бериллий) is the chemical element of the Group II of the Periodic System by Mendeleev, the atomic number is 4, the atomic mass is 9.0122. It has one stable isotope 9Be. It has been discovered during the 1798 by the French chemist L. Vauquelin in the form of the BeO oxide, which has been isolated from beryl. There have independently obtained the metallic beryllium during the 1828 the German chemist F. Wöhler and the French chemist A. Bussy.

Beryllium is the lightweight pale-gray metal. The crystal structure of the alpha-Be (269-1254 degrees Celsius) is hexagonal; of the beta-Be (1254-1284 degrees Celsius) is the body-centered, cubic. The density is 1844 kilograms per cubic metre, the temperature of the melting point is 1287 degrees Celsius, the temperature of the boiling point is 2507 degrees Celsius. It has the highest among all metals specific heat capacity of 1.80 kilojoules per kilogram-kelvin, high thermal conductivity of 178 watts per metre-kelvin at 50 degrees Celsius, low specific electrical resistivity (3.6-4.5) • 10 ohm-metre at 20 degrees Celsius; the coefficient of the thermal linear expansion is 10.3-13.1 • 10^-6 per degree (at 25 - 100 degrees Celsius). Beryllium is brittle metal; the toughness is 10-50 kilojoules per square metre. Beryllium possesses small cross section for the capture of the thermal neutrons.

Beryllium is the typical amphoteric element with high chemical activity; the compact beryllium is stable within the air thanks to the forming of the BeO film; the oxidation state of beryllium is +2. During the heating, it combines with oxygen, halogens, and other non-metals. It forms with oxygen the BeO oxide, with nitrogen the Be3N2 nitride, with carbon the Be2C carbide, with sulfur the BeS sulfide. It is soluble within alkalies (with the forming of the hydroxide-beryllates) and most acids. At the high temperatures, beryllium interacts with most metals, forming beryllides. The molten beryllium interacts with oxides, nitrides, sulfides, and carbides. Of the beryllium compounds, there have the greatest industrial importance the BeO, Be(OH)2, fluoroberyllates, for example the Na2[BeF4], and others. The volatile beryllium compounds and the dust, which is containing beryllium and its compounds, are toxic.

Beryllium is the rare (the Clarke number is 6 • 10^-4%), typically lithophilic element, which is characteristic for the acidic and alkaline rocks. Of the 55 own minerals of beryllium, 50% belong to silicates and beryllium silicates, 24% belong to phosphates, 10% belong to oxides, and the remaining ones belong to the borates, arsenates, carbonates. The approximate equality of the ionization potentials determines the affinity of beryllium and zinc within the alkaline environment, so that they are simultaneously located within certain hydrothermal deposits, and also belong to the composition of the same mineral, namely, genthelvite. Within the neutral and acidic environments, the migration paths of beryllium and zinc diverge sharply. Certain dispersion of beryllium within rocks is determined by its chemical similarity with Al and Si. These elements are especially similar in the form of the [BeO4]6-, [AlO4]5-, and [SiO4]4- tetrahedral groups. There manifests itself the greater affinity of beryllium to silicon within granites, and to aluminium within the alkaline rocks. Because there is energetically more favourable the substitution of the Al3+IV by the Be2+IV, than of the Si4+IV by the Be2+IV, the isomorphic dispersion of beryllium within the alkaline rocks is, as a rule, higher than within the acidic ones. The geochemical migration of beryllium is associated with fluorine, with which it forms very stable [BeF4]2-, [BeF3]1-, [BeF2]0, [BeF]1+ complexes. During the increase of temperature and alkalinity, these complexes are easily hydrolyzed to [Be(OH)F]0, [Be(OH)2F]1- compounds, in the form of which beryllium migrates.

About the major genetic types of the deposits of beryllium, and for the schemes of beneficiation, see within the "Beryllium ores" article. Within the industry, they obtain the metallic beryllium by the thermal reduction of the BeF2 by magnesium, the beryllium of the high purity by the remelting within vacuum, and by the vacuum distillation.

They use beryllium and its compounds within the engineering (more than 70% of the total consumption of the metal), as the alloyant for the alloys, which are based on Cu, Ni, Zn, Al, Pb, and other non-ferrous metals. They use the Be and BeO within the nuclear engineering as the reflectors and moderators for neutrons, and also as the source of neutrons. The low density, high strength and heat resistance, high modulus of elasticity, and good thermal conductivity, permit to use beryllium and its alloys as the construction material within the aircraft, rocket, and space engineering. The alloys of beryllium and beryllium oxide comply with the requirements for strength and corrosion resistance as the materials for the claddings of the nuclear fuel rods. Beryllium serves for manufacturing of the X-ray tube windows, for the coating of the solid diffuse layer onto the surface of steel (beryllization), as the dopants for the rocket fuel. The electrical engineering and radio-electronics also are the consumers of the Be and BeO; they use the BeO as the material for the casings, heat sinks, and insulators of the semiconductor devices. Thanks to its high fire resistance, inertness in relation to most molten metals and salts, the beryllium oxide is used for the manufacturing of the crucibles and special ceramics.