bore

Traductions

• anglais

  Date : 1983

  Définition

  An element. State: solid; group: IIIA; atomic no.: 5; atomic wt.: 10.81; valence: 3; isotopes: 2 stable. Boron is a hard, nonmetallic solid, m.p. 2300 °C (4172 °F), obtained from the ores colemanite and kernite. It may be either a crystalline solid or an amorphous powder, depending on the method of production. It can be produced in several ways: by reduction of boron oxide with magnesium or aluminum; (b) by electrolysis of fused potassium halide salts in which boron-containing compounds are dissolved; (c) by passing gaseous boron compounds and hydrogen over heated metal wires, upon which pure boron deposits. This method is unique, but is slow and expensive.
  
  A chemical element, boron is a light, hard non-metal. It appears as a yellowish brown crystalline solid or an amorphous greenish brown powder.

  Note :

  Boron has a number of unusual properties. The 10 isotope has the highest neutron-absorbing capacity of any known substance. In addition to forming conventional chemical compounds with hydrogen, nitrogen, oxygen, and the halogens, boron combines with carbon and silicon to form carbides, carborane, and various borosilicates. In combination with metals, it also forms a large array of refractory borides, which are crystalline structures in which the boron atoms are uniquely bonded to produce extremely hard, stable materials of high thermal conductivity and very high melting points. The elemental uses of boron include high-strength filaments used in composites, neutron-absorbing devices for nuclear reactor control, alloying agent with iron, manganese and other metals, and deoxidizing additive in steels and copper. It is an essential plant micronutrient and is nontoxic in low concentrations.

  Termes :

  1. boron
  2. B

  [B] Symbol for the element boron, the name apparently being a transliteration of an Arabic word, baurach, for borax or a similar compound.