The nature and purpose of elemental boron

The natural boron has two isotopes: boron 10 and boron 11, boron 10 is the most important. Boron is non-metallic element. Elemental boron has amorphous boron powder and crystalline boron two kinds. The former is brownish black to black powder; the latter was jet-black to silver-gray, remarkable metallic luster, close to the hardness of diamond, but there is a very high resistance, the electrical conductivity increases with the increasing temperature. Amorphous boron powder density is 2.3 g / cm 3 (25-27 ° C); crystalline elemental boron density is 2.31 g / cm 3. Boron’s melting point is 2300°C, boiling point is 2550°C. Boron has extensive application. Boron in combination with plastic or aluminum is an effective neutron shielding material; boron steel used in the reactor as a control rod; boron fibers for manufacturing a composite material and so on.

Boron is relatively stable at room temperature, even long-term boiling in hydrochloric acid or hydrofluoric acid does not work. Boron can combine with halogen group elements to form a boron halide. Boron in 600 ~ 1000°C can react with sulfur, tin, phosphorus, arsenic; in 1000 to 1400°C, react with the nitrogen, carbon, silicon effects, under high temperature boron also react with many metals and metal oxides, formed metal borides. These compounds are generally with high hardness, resistance to melt, high electrical conductivity, and chemically inert substances, often with special properties. 1702 French doctors first from borax made of boric acid, called sedation salt. In 1741, French chemist pointed out that the borax react with sulfuric acid not only get boric acid, but also get sodium. In 1789, scientists included boric acid group in the table of elements. 1808 British chemist and France chemist use potassium to restore boric acid obtained boron.

Amorphous boron powder at room temperature oxidized in air slowly, at about 800 can be spontaneous firing. Boron with hydrochloric acid or hydrofluoric acid, even though long-term boiling could not react. It can be slow eroded and oxidized by a mixture of hot concentrated nitric acid and sodium dichromate and sulfuric acid. Hydrogen peroxide and ammonium persulfate also can be slow oxidized crystalline boron. These reagents react with amorphous boron is fierce. Eutectic with the alkali metal carbonates and hydroxides mixture, all the various forms of boron are completely oxidized. Chlorine, bromine, fluorine react with boron to form the corresponding boron halide. Boron and sulfur intense reaction at 600 to form a sulfurized boron mixture. Boron in a nitrogen or ammonia gas heated to above 1000 can form boron nitride, above 1800-2000 boron and hydrogen is still not react, boron and silicon above 2000 can react to generate boride silicon. At high temperatures, the boron can react with many metal powder and metal oxides to generate metal boride.

Boron is mainly used in metallurgy (eg, in order to increase the hardness of steel) produce borax and boric acid and elemental boron, because it absorb neutrons ability is strong. Boron at high temperatures is particularly lively, so it was used for metallurgical heat treatment getter, wrought iron heated process, increased high temperature alloy steel rugged, boron is also used in nuclear reactors and high-temperature technology. Rod and strip boron steel is widely used as control rods in a nuclear reactor. Due to the nature of boron has low density, high strength and a high melting point, it can be used to produce some of the structural materials in missile rocket. Boron compounds in agriculture, medicine, glass industry is widely used. Therefore, boron resources development, utilization, for the development of modern industry has an increasingly important role.

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