See also: Boron (homonymy)
It is a trivalent Métalloïde , which is abundantly in nature in the form of Borax. There are two allotropic forms boron; amorphous boron is a brown powder, but metal boron is black. The metal form is hard (9,3 on the scale of hardness Mohs) and with room temperature is a bad driver of electricity.
Boron, having an Orbital-p vacuum, is defective in electron S (from where its use in doping of pure silicon of the photovoltaic cells). The compounds of boron often behave like acid of Lewis, easily binding with species rich in electrons in order to make up its electronic deficit.
Boron is transparent with the light Infrarouge. With room temperature, boron is a bad conducting electric but is a good driver with high temperature.
Boron with the tensile strength highest of all the known elements.
The Boron nitride can be employed to make materials which are as hard as the Diamant. The nitride also acts as an insulator electrical but conducted the heat like a metal. This element also has qualities of lubricant similar to the Graphite. Boron is also similar to the Carbone because it with the possibility of forming stable molecular networks by covalent bonds.
It is present in the Lessive S what makes of it a tracer of urban Pollution in the networks of Assainissement.
Curiously, boron uses the composition only of only one molecule having a known biological role: AI-2 ( autoinducer 2 ), discovered in 1994 by Bonnie L. Bassler, is an agent which makes it possible bacteria to communicate between them to evaluate their number and to start certain actions (as luminescence) only if they are comparatively numerous; it consists of a sugar which encloses a boron atom.
The compound of boron having the greattest economic importance is the Borax or tetraborate of sodium Na 2B4 O 7 5 H2O, which is used for the manufacture of insulating glass fiber, and of bleaching agent.
thanks to its green color in the flame, boron Amorphe is used in the pyrotechnical effects;
- the boric Acid is an important compound in the textile products;
- the compounds of boron are used in organic synthesis and in the Verre S borosilicates like the Pyrex;
- some boron compounds are used as protective agents of wood, and have the advantage of having a low toxicity;
- the 10B is used in the moderation of the nuclear reactors, like shield against the radiations and in the detectors of Neutron S
- one finds it out of alloy with the Fer and the Néodyme (Nd2Fe14B) in powerful permanent Aimant S.
The boron compounds are studied for a very great number of applications as in the permeable membranes to sugar, the sensors of carbohydrate.
boron is used also much in the industry of the Semi-conducteur S. It is useful in, general of doping agent acceptor (typify), in particular in the Silicium.
The compounds of boron (Arab بورون - buraq , Persan burah “shining”), are known since thousands of years. In the ancient Egypt, the process of momification depended on the Natron, an ore containing of borates as well as other more common salts. The Chinese used a borax clay since − 300 and the Romains used boron compounds for the manufacture of glass.
This element was insulated only in 1808 by Sir Humphry Davy, Gay-Lussac and the baron Louis Jacques Thénard, which obtained a purity of 50 %. They did not identify however the substance like a élément.
It was Jöns Jacob Berzélius which in 1824 identified boron like an element. The first pure boron sample was obtained by the American chemist W. Weintraub in 1909.
The the United States and the Turkey are the two larger boron producers. Turkey holds close to 63 % of world reserves. One does not find boron in nature in his elementary form, but in form combined for example in the Borax (tinkalite), the boric acid, the Colémanite, the Kernite, the Ulexite and the borates. One finds sometimes acid boric in the sources of volcanic water. Ulexite is a boron ore which has the properties of fiberoptic naturally.
The most important sources economically are the ore of rasorite and the borax ore which one can find in the Désert of Mojaves in California. Turkey is another country where large borax deposits are found.
Pure boron is not easy to prepare. The first methods implied the reduction of the boric acid with a metal such as the Magnésium or the Aluminum. However the product is almost always contaminated by metal borides. Very pure boron is prepared by reducing volatile boron halides with Hydrogène at high temperature.
- Boron - health and environment summarized of GreenFacts of a report/ratio of the International Program on the Chemical Safety of WHO
Simple: Boron Zh-yue: 硼
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