Beryllium

Beryllium. Chemical element, Be, atomic number 4, with an atomic weight of 9.0122. Beryllium, a rare metal, is one of the lightest structural metals, its density is about a third of that of aluminum . Some of the important physical and chemical properties of beryllium are given in the table. Beryllium has a number of unusual and even special properties.

The main use of metallic beryllium is in the manufacture of beryllium- copper alloys and in the development of moderator and reflective materials for nuclear reactors. The addition of 2% beryllium to copper forms a non-magnetic alloy six times stronger than copper. These beryllium-copper alloys have numerous non-sparking applications in the tool industry, in critical moving aircraft parts, as well as in key components of precision instruments, mechanical computers, electrical relays, and camera shutters.. Beryllium-copper hammers, wrenches, and other tools are used in oil refineries and other plants where a spark from steel parts can cause an explosion or fire.

Summary

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  • 1 Main features
  • 2 Applications
  • 3 Metallurgy
  • 4 History
  • 5 Abundance and obtaining
  • 6 Isotopes
  • 7 Precautions
  • 8 Health effects
  • 9 Sources

Main features

Beryllium has one of the highest melting points among the light metals . Its modulus of elasticity is approximately 33% greater than that of steel. It has excellent thermal conductivity, is non-magnetic, and resists attack with nitric acid.

It is highly permeable to X-rays and, like radium and polonium, releases neutrons when bombarded with alpha particles (on the order of 30 neutrons per million alpha particles). Under normal conditions of pressure and temperature, beryllium resists oxidation in air , although the property of scratching glass is probably due to the formation of a thin oxide layer.

Applications

  • Alloy element, in copper-beryllium alloys with a wide variety of applications.
  • In X-ray diagnosis, thin sheets of beryllium are used to filter visible radiation, as well as in X-ray lithography for the reproduction of integrated circuits.
  • Neutron moderator in nuclear reactors.
  • Due to its rigidity, lightness and dimensional stability, it is used in the construction of various devices such as gyroscopes, computer equipment, clock springs and various instruments.
  • Beryllium oxide is used when high thermal conductivity and mechanical properties, high melting point and electrical insulation are required.
  • Beryllium compounds were once used in fluorescent tubes, a use abandoned by berylliosis.
  • Manufacture of Tweeters in speakers of the High-End class, due to its great rigidity.

Metallurgy

Beryllium metallurgy involves two processes to extract beryllium oxide or hydroxide from ore. There are also two methods to reduce BeO to metallic beryllium. The two extraction methods are based on dissolving the oxide as fluoride or as sulfate. The reduction is achieved thermally with the addition of magnesium to beryllium fluoride, and electrolytically with beryllium chloride. More than 90% of the metal is obtained by the thermal process.

Vacuum cast beryllium ingots are either produced as raw material for the powder metallurgy process, which accounts for 90% of the material produced, or are cast directly for further processing. Machined parts are generally made from metal powder products, while beryllium ingots are rolled or otherwise worked.

Beryllium can be welded autogenously, by brazing, brazing, or bonded in plastic form, with strong binders and plastics, as well as with mechanical fasteners, all of which are the usual production methods. Surface protection of polished beryllium surfaces can be provided by anodizing, optical polishing, or using common or conversion coatings. Chemical machining and milling are used to obtain surfaces with minimal etching and damage.

Beryllium has a long history in nuclear energy as a neutron source , reflector, and moderator in thermal and intermediate reactors. Beryllium aerospace applications provide weight savings of up to 60% over other materials and using the same design. The wide use of beryllium in protective material for re-entry into the atmospherein spacecraft structures it is due to its resistance to high temperatures and its thermal capacity. The transparency of the metal to radiation (this is why it is used in X-ray windows), is also important in directed projectile structures (missiles or rockets), which must resist electromagnetic pulses created by anti-projectile tactics. Finally, its ability to be machined to very close tolerances, coupled with its dimensional stability, have led to beryllium being used almost exclusively in inertial guidance navigation and control devices.

History

Beryllium (from the Greek βερυλλoς beryl) or glucinium (from the English glucinium and this one from the Greek γλυκυς, sweet) due to the taste of its salts, was discovered by Vauquelin in 1798 in the form of oxide in beryl and emerald. Friedrich Wöhler and AA Bussy independently isolated the metal in 1828 by reacting potassium with beryllium chloride.

Abundance and obtaining

Beryllium is found in 30 different minerals, the most important being beryl and bertrandite, the main sources of commercial beryllium, chrysoberyl and phenakite. Currently most of the metal is obtained by reducing beryllium fluoride with magnesium . The precious forms of beryl are aquamarine and emerald .

Geographically, the largest reserves are in the United States, which also leads the world production of beryllium (65%), followed by Russia (40%) and China (15%). World reserves are estimated to exceed 80,000 tons.

Isotopes

Be-9 is the only stable isotope. Be-10 is produced in Earth’s atmosphere by bombarding cosmic radiation with oxygen and nitrogen.

Since beryllium tends to exist in aqueous solution with pH levels lower than 5.5, this atmospheric beryllium formed is carried away by rainwater (whose pH is usually lower than 5.5); once on the ground, the solution becomes alkaline precipitating the beryllium that is stored in the soil for a long time (half-life of 1.5 million years) until its transmutation into B-10. Be-10 and its daughter products have been used to study erosion processes, formation from regolith and development of lateritic soils, as well as variations in solar activity and the age of frozen masses.

The fact that Be-7 and Be-8 are unstable has profound cosmological consequences, as it means that elements heavier than beryllium could not be produced by nuclear fusion in the big bang. Furthermore, the nuclear energy levels of Be-8 are such that they allow the formation of carbon and with it life (see triple alpha process).

Precautions

Beryllium and its salts are toxic and potentially carcinogenic. Chronic berylliosis is a lung condition caused by exposure to beryllium dust, classified as an occupational disease. The first cases of acute chemical pneumonitis due to exposure to beryllium occurred in 1933 in Europe and in 1943 in the United States; In 1946 , the first cases of berylliosis were described among workers at a fluorescent tube manufacturing plant in Massachusetts.

Berylliosis resembles sarcoidosis in many ways, making diagnosis difficult at times. Although the use of beryllium compounds in fluorescent lamps was discontinued in 1949 , occupational exposure occurs in the nuclear and aerospace industries, in metal refining and melting of its containing alloys, in the manufacture of electronic devices and in the handling of other materials containing beryllium.

Beryllium and its compounds should be handled carefully, extreme caution when during activity may be generated beryllium powder as prolonged exposure to beryllium dust can cause cancer of lung . The substance can be handled safely as long as certain procedures are followed. If these are unknown, the manipulation of beryllium should not be attempted.

Health effects

The effects depend on the level and duration of the exposure. If the level is high enough, above 1000 μg / m3 in the breathed air, it can cause acute beryllium disease or acute berylliosis, which causes severe inflammation of the lungs; In general, the limit values ​​for atmospheric beryllium contemplated in the industrial hygiene legislation, which set the maximum levels of occupational exposure, allow this risk to be controlled effectively. Between 1 and 15% of the exposed population develops sensitization to beryllium.

These people can develop inflammatory processes of the respiratory system (chronic beryllium disease or chronic berylliosis) that can manifest years after occupational exposure when it has exceeded the recommended exposure levels (0.2 μg / m3). The risk of the general population to contract these diseases is very low since the levels of beryllium in non-work environments are very low (0.00003-0.0002 μg / m3).

Poisoning by ingestion of beryllium is not known since the amount of beryllium absorbed by the body through this route is very small, although ulcers have been observed in dogs after ingesting beryllium. Contact of beryllium with the skin after a scratch or cut can cause eczema and skin ulcers. Long-term exposure increases the risk of lung cancer . The International Agency for Research on Cancer has determined that beryllium is a human carcinogen.

 

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