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= Beryllium =
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Introduction
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Beryllium is a chemical element; it has symbol Be and atomic number 4.
It is a steel-gray, hard, strong, lightweight and brittle alkaline
earth metal. It is a divalent element that occurs naturally only in
combination with other elements to form minerals. Gemstones high in
beryllium include beryl (aquamarine, emerald, red beryl) and
chrysoberyl. It is a relatively rare element in the universe, usually
occurring as a product of the spallation of larger atomic nuclei that
have collided with cosmic rays. Within the cores of stars, beryllium
is depleted as it is fused into heavier elements. Beryllium
constitutes about 0.0004 percent by mass of Earth's crust. The world's
annual beryllium production of 220 tons is usually manufactured by
extraction from the mineral beryl, a difficult process because
beryllium bonds strongly to oxygen.
In structural applications, the combination of high flexural rigidity,
thermal stability, thermal conductivity and low density (1.85 times
that of water) make beryllium a desirable aerospace material for
aircraft components, missiles, spacecraft, and satellites. Because of
its low density and atomic mass, beryllium is relatively transparent
to X-rays and other forms of ionizing radiation; therefore, it is the
most common window material for X-ray equipment and components of
particle detectors. When added as an alloying element to aluminium,
copper (notably the alloy beryllium copper), iron, or nickel,
beryllium improves many physical properties. For example, tools and
components made of beryllium copper alloys are strong and hard and do
not create sparks when they strike a steel surface. In air, the
surface of beryllium oxidizes readily at room temperature to form a
passivation layer 1-10 nm thick that protects it from further
oxidation and corrosion. The metal oxidizes in bulk (beyond the
passivation layer) when heated above 500 C, and burns brilliantly when
heated to about 2500 C.
The commercial use of beryllium requires the use of appropriate dust
control equipment and industrial controls at all times because of the
toxicity of inhaled beryllium-containing dusts that can cause a
chronic life-threatening allergic disease, berylliosis, in some
people. Berylliosis is typically manifested by chronic pulmonary
fibrosis and, in severe cases, right sided heart failure and death.
Physical properties
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Beryllium is a steel gray and hard metal that is brittle at room
temperature and has a close-packed hexagonal crystal structure. It has
exceptional stiffness (Young's modulus 287 GPa) and a melting point of
1287 °C. The modulus of elasticity of beryllium is approximately 35%
greater than that of steel. The combination of this modulus and a
relatively low density results in an unusually fast sound conduction
speed in beryllium - about 12.9 km/s at ambient conditions.
Among all metals, beryllium dissipates the most heat per unit weight,
with both high specific heat () and thermal conductivity ().
Beryllium's conductivity and relatively low coefficient of linear
thermal expansion (11.4 × 10−6 K−1), make it uniquely stable under
extreme temperature differences.
Nuclear properties
====================
Naturally occurring beryllium, save for slight contamination by the
radioisotopes created by cosmic rays, is isotopically pure
beryllium-9, which has a nuclear spin of −. The inelastic scattering
cross section of beryllium increases with relation to neutron energy,
allowing for significant slowing of higher-energy neutrons. Therefore,
it works as a neutron reflector and neutron moderator; the exact
strength of neutron slowing strongly depends on the purity and size of
the crystallites in the material.
The single primordial beryllium isotope 9Be also undergoes a (n,2n)
neutron reaction with neutron energies over about 1.9 MeV, to produce
8Be, which almost immediately breaks into two alpha particles. Thus,
for high-energy neutrons, beryllium is a neutron multiplier, releasing
more neutrons than it absorbs. This nuclear reaction is:
: + n → 2 + 2 n
Neutrons are liberated when beryllium nuclei are struck by energetic
alpha particles producing the nuclear reaction
: + → + n
where is an alpha particle and is a carbon-12 nucleus.
Beryllium also releases neutrons under bombardment by gamma rays.
Thus, natural beryllium bombarded either by alphas or gammas from a
suitable radioisotope is a key component of most radioisotope-powered
nuclear reaction neutron sources for the laboratory production of free
neutrons.
Small amounts of tritium are liberated when nuclei absorb low energy
neutrons in the three-step nuclear reaction
: + n → + , → + β−, + n → +
has a half-life of only 0.8 seconds, β− is an electron, and has a
high neutron absorption cross section. Tritium is a radioisotope of
concern in nuclear reactor waste streams.
Optical properties
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As a metal, beryllium is transparent or translucent to most
wavelengths of X-rays and gamma rays, making it useful for the output
windows of X-ray tubes and other such apparatus.
Isotopes and nucleosynthesis
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Both stable and unstable isotopes of beryllium are created in stars,
but the radioisotopes do not last long. It is believed that the
beryllium in the universe was created in the interstellar medium when
cosmic rays induced fission in heavier elements found in interstellar
gas and dust, a process called cosmic ray spallation. Natural
beryllium is solely made up of the stable isotope beryllium-9.
Beryllium is the only monoisotopic element with an even atomic number.
About one billionth () of the primordial atoms created in the Big Bang
nucleosynthesis were 7Be. This is a consequence of the low density of
matter when the temperature of the universe cooled enough for small
nuclei to be stable. Creating such nuclei requires nuclear collisions
that are rare at low density. Although 7Be is unstable and decays by
electron capture into 7Li with a half-life of 53 days, in the early
universe this decay channel was unavailable due to atoms being fully
ionized. The conversion of 7Be to Li was only complete near the time
of recombination.
The isotope 7Be (half-life 53 days) is also a cosmogenic nuclide, and
also shows an atmospheric abundance inversely proportional to solar
activity. The 2s electrons of beryllium may contribute to chemical
bonding. Therefore, when 7Be decays by L-electron capture, it does so
by taking electrons from its atomic orbitals that may be participating
in bonding. This makes its decay rate dependent to a measurable degree
upon its chemical surroundings - a rare occurrence in nuclear decay.
8Be is unstable but has a ground state resonance with an important
role in the triple-alpha process in helium-fueled stars. As first
proposed by British astronomer Sir Fred Hoyle based solely on
astrophysical analysis, the energy levels of 8Be and 12C allow carbon
nucleosynthesis by increasing the contact time for two of the three
alpha particles in the carbon production process. The main
carbon-producing reaction in the universe is
where 4He is an alpha particle.
Radioactive cosmogenic 10Be is produced in the atmosphere of the Earth
by the cosmic ray spallation of oxygen. Then the 10Be accumulates at
the soil surface, where its relatively long half-life (1.36 million
years) permits a long residence time before decaying to boron-10.
Thus, 10Be and its daughter products are used to examine natural soil
erosion, soil formation and the development of lateritic soils, and as
a proxy for measurement of the variations in solar activity and the
age of ice cores. The production of 10Be is inversely related to solar
activity, because increased solar wind during periods of high solar
activity decreases the flux of galactic cosmic rays that reach the
Earth. Nuclear explosions also form 10Be by the reaction of fast
neutrons with 13C in the carbon dioxide in air. This is one of the
indicators of past activity at nuclear weapon test sites.
The exotic isotopes 11Be and 14Be are known to exhibit a nuclear halo.
This feature can be understood as the nuclei of 11Be and 14Be have,
respectively, 1 and 4 neutrons orbiting substantially outside the
expected nuclear radius.
Occurrence
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Beryllium is found in over 100 minerals, but most are uncommon to
rare. The more common beryllium-containing minerals include:
bertrandite (), beryl (), chrysoberyl () and phenakite (). Precious
forms of beryl are aquamarine, red beryl and emerald.
The green color in gem-quality forms of beryl comes from varying
amounts of chromium (about 2% for emerald).
The two main ores of beryllium, beryl and bertrandite, are found in
Argentina, Brazil, India, Madagascar, Russia and the United States.
Total world reserves of beryllium ore are greater than 400,000 tonnes.
The Sun has a concentration of 0.1 parts per billion (ppb) of
beryllium. Beryllium has a concentration of 2 to 6 parts per million
(ppm) in the Earth's crust and is the 47th most abundant element. It
is most concentrated (6 ppm) in the soils. Trace amounts of 9Be are
found in the Earth's atmosphere. The concentration of beryllium in sea
water is 0.2-0.6 parts per trillion. In stream water, however,
beryllium is more abundant, with a concentration of 0.1 ppb.
Extraction
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The extraction of beryllium from its compounds is a difficult process
due to its high affinity for oxygen at elevated temperatures, and its
ability to reduce water when its oxide film is removed. Currently the
United States, China and Kazakhstan are the only three countries
involved in the industrial-scale extraction of beryllium. Kazakhstan
produces beryllium from a concentrate stockpiled before the breakup of
the Soviet Union around 1991. This resource had become nearly depleted
by mid-2010s.
Production of beryllium in Russia was halted in 1997, and is planned
to be resumed in the 2020s.
A bead of beryllium from a melt
Beryllium is most commonly extracted from the mineral beryl, which is
either sintered using an extraction agent or melted into a soluble
mixture. The sintering process involves mixing beryl with sodium
fluorosilicate and soda at 770 C to form sodium fluoroberyllate,
aluminium oxide and silicon dioxide. Beryllium hydroxide is
precipitated from a solution of sodium fluoroberyllate and sodium
hydroxide in water. The extraction of beryllium using the melt method
involves grinding beryl into a powder and heating it to 1650 C. The
melt is quickly cooled with water and then reheated 250 to in
concentrated sulfuric acid, mostly yielding beryllium sulfate and
aluminium sulfate. Aqueous ammonia is then used to remove the
aluminium and sulfur, leaving beryllium hydroxide.
Beryllium hydroxide created using either the sinter or melt method is
then converted into beryllium fluoride or beryllium chloride. To form
the fluoride, aqueous ammonium hydrogen fluoride is added to beryllium
hydroxide to yield a precipitate of ammonium tetrafluoroberyllate,
which is heated to 1000 C to form beryllium fluoride. Heating the
fluoride to 900 C with magnesium forms finely divided beryllium, and
additional heating to 1300 C creates the compact metal. Heating
beryllium hydroxide forms beryllium oxide, which becomes beryllium
chloride when combined with carbon and chlorine. Electrolysis of
molten beryllium chloride is then used to obtain the metal.
Chemical properties
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A beryllium atom has the electronic configuration [He] 2s2. The
predominant oxidation state of beryllium is +2; the beryllium atom has
lost both of its valence electrons. Lower oxidation states complexes
of beryllium are exceedingly rare. For example, a stable complex with
a Be-Be bond, which formally features beryllium in the +1 oxidation
state, has been described. Beryllium in the 0 oxidation state is also
known in a complex with a Mg-Be bond. Beryllium's chemical behavior is
largely a result of its small atomic and ionic radii. It thus has very
high ionization potentials and does not form divalent cations. Instead
it forms two covalent bonds with a tendency to polymerize, as in solid
.. Its chemistry has similarities to that of aluminium, an example of
a diagonal relationship.
At room temperature, the surface of beryllium forms a 1−10 nm-thick
oxide passivation layer that prevents further reactions with air,
except for gradual thickening of the oxide up to about 25 nm. When
heated above about 500 °C, oxidation into the bulk metal progresses
along grain boundaries. Once the metal is ignited in air by heating
above the oxide melting point around 2500 °C, beryllium burns
brilliantly, forming a mixture of beryllium oxide and beryllium
nitride. Beryllium dissolves readily in non-oxidizing acids, such as
HCl and diluted , but not in nitric acid or water as this forms the
oxide. This behavior is similar to that of aluminium. Beryllium also
dissolves and reacts with alkali solutions.
Binary compounds of beryllium(II) are polymeric in the solid state.
has a silica-like structure with corner-shared tetrahedra. and have
chain structures with edge-shared tetrahedra. Beryllium oxide, BeO, is
a white refractory solid which has a wurtzite crystal structure and a
thermal conductivity as high as some metals. BeO is amphoteric.
Beryllium sulfide, selenide and telluride are known, all having the
zincblende structure. Beryllium nitride, , is a high-melting-point
compound which is readily hydrolyzed. Beryllium azide, is known and
beryllium phosphide, has a similar structure to . A number of
beryllium borides are known, such as , , , , and . Beryllium carbide,
, is a refractory brick-red compound that reacts with water to give
methane. Beryllium silicides have been identified in the form of
variously sized nanoclusters, formed through a spontaneous reaction
between pure beryllium and silicon. The halides (X = F, Cl, Br, and
I) have a linear monomeric molecular structure in the gas phase.
Beryllium is a strong electron acceptor leading to Be bonding effects
similar to hydrogen bonding.
Aqueous solutions
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Solutions of beryllium salts, such as beryllium sulfate and beryllium
nitrate, are acidic because of hydrolysis of the ion. The
concentration of the first hydrolysis product, , is less than 1% of
the beryllium concentration. The most stable hydrolysis product is the
trimeric ion . Beryllium hydroxide, , is insoluble in water at pH 5 or
more. Consequently, beryllium compounds are generally insoluble at
biological pH. Because of this, inhalation of beryllium metal dust
leads to the development of the fatal condition of berylliosis.
dissolves in strongly alkaline solutions.
Beryllium(II) forms few complexes with monodentate ligands because the
water molecules in the aquo-ion, are bound very strongly to the
beryllium ion. Notable exceptions are the series of water-soluble
complexes with the fluoride ion:
:{{chem2|[Be(H2O)4](2+) + 'n' F- <->
Be[(H2O)_{2-'n'}F_{'n'}](2-) + 'n' H2O}}
Beryllium(II) forms many complexes with bidentate ligands containing
oxygen-donor atoms. The species is notable for having a 3-coordinate
oxide ion at its center. Basic beryllium acetate, , has an oxide ion
surrounded by a tetrahedron of beryllium atoms.
With organic ligands, such as the malonate ion, the acid deprotonates
when forming the complex. The donor atoms are two oxygens.
:
:
The formation of a complex is in competition with the metal
ion-hydrolysis reaction and mixed complexes with both the anion and
the hydroxide ion are also formed. For example, derivatives of the
cyclic trimer are known, with a bidentate ligand replacing one or more
pairs of water molecules.
Aliphatic hydroxycarboxylic acids such as glycolic acid form rather
weak monodentate complexes in solution, in which the hydroxyl group
remains intact. In the solid state, the hydroxyl group may
deprotonate: a hexamer, , was isolated long ago. Aromatic hydroxy
ligands (i.e. phenols) form relatively strong complexes. For example,
log K1 and log K2 values of 12.2 and 9.3 have been reported for
complexes with tiron.
Beryllium has generally a rather poor affinity for ammine ligands.
There are many early reports of complexes with amino acids, but
unfortunately they are not reliable as the concomitant hydrolysis
reactions were not understood at the time of publication. Values for
log β of ca. 6 to 7 have been reported. The degree of formation is
small because of competition with hydrolysis reactions.
Organic chemistry
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Organometallic beryllium compounds are known to be highly reactive.
Examples of known organoberyllium compounds are dineopentylberyllium,
beryllocene (), diallylberyllium (by exchange reaction of diethyl
beryllium with triallyl boron), bis(1,3-trimethylsilylallyl)beryllium,
Be(mes)2, and (beryllium(I) complex) diberyllocene. Ligands can also
be aryls and alkynyls.
History
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The mineral beryl, which contains beryllium, has been used at least
since the Ptolemaic dynasty of Egypt. In the first century CE, Roman
naturalist Pliny the Elder mentioned in his encyclopedia 'Natural
History' that beryl and emerald ("smaragdus") were similar. The
Papyrus Graecus Holmiensis, written in the third or fourth century CE,
contains notes on how to prepare artificial emerald and beryl.
Early analyses of emeralds and beryls by Martin Heinrich Klaproth,
Torbern Olof Bergman, Franz Karl Achard, and always yielded similar
elements, leading to the mistaken conclusion that both substances are
aluminium silicates. Mineralogist René Just Haüy discovered that both
crystals are geometrically identical, and he asked chemist
Louis-Nicolas Vauquelin for a chemical analysis.
In a 1798 paper read before the Institut de France, Vauquelin reported
that he found a new "earth" by dissolving aluminium hydroxide from
emerald and beryl in an additional alkali. The editors of the journal
'Annales de chimie et de physique' named the new earth "glucine" for
the sweet taste of some of its compounds. The name 'beryllium' was
first used by Friedrich Wöhler in 1828. Both beryllium and glucinum
were used concurrently until 1949, when the IUPAC adopted beryllium as
the standard name of the element.
Friedrich Wöhler and Antoine Bussy independently isolated beryllium in
1828 by the chemical reaction of metallic potassium with beryllium
chloride, as follows:
:
Using an alcohol lamp, Wöhler heated alternating layers of beryllium
chloride and potassium in a wired-shut platinum crucible. The above
reaction immediately took place and caused the crucible to become
white hot. Upon cooling and washing the resulting gray-black powder,
he saw that it was made of fine particles with a dark metallic luster.
The highly reactive potassium had been produced by the electrolysis of
its compounds. He did not succeed to melt the beryllium particles.
The direct electrolysis of a molten mixture of beryllium fluoride and
sodium fluoride by Paul Lebeau in 1898 resulted in the first pure
(99.5 to 99.8%) samples of beryllium. However, industrial production
started only after the First World War. The original industrial
involvement included subsidiaries and scientists related to the Union
Carbide and Carbon Corporation in Cleveland, Ohio, and Siemens &
Halske AG in Berlin. In the US, the process was ruled by Hugh S.
Cooper, director of The Kemet Laboratories Company. In Germany, the
first commercially successful process for producing beryllium was
developed in 1921 by Alfred Stock and Hans Goldschmidt.
A sample of beryllium was bombarded with alpha rays from the decay of
radium in a 1932 experiment by James Chadwick that uncovered the
existence of the neutron. This same method is used in one class of
radioisotope-based laboratory neutron sources that produce 30 neutrons
for every million α particles.
Beryllium production saw a rapid increase during World War II due to
the rising demand for hard beryllium-copper alloys and phosphors for
fluorescent lights. Most early fluorescent lamps used zinc
orthosilicate with varying content of beryllium to emit greenish
light. Small additions of magnesium tungstate improved the blue part
of the spectrum to yield an acceptable white light.
Halophosphate-based phosphors replaced beryllium-based phosphors after
beryllium was found to be toxic.
Electrolysis of a mixture of beryllium fluoride and sodium fluoride
was used to isolate beryllium during the 19th century. The metal's
high melting point makes this process more energy-consuming than
corresponding processes used for the alkali metals. Early in the 20th
century, the production of beryllium by the thermal decomposition of
beryllium iodide was investigated following the success of a similar
process for the production of zirconium, but this process proved to be
uneconomical for volume production.
Pure beryllium metal did not become readily available until 1957, even
though it had been used as an alloying metal to harden and toughen
copper much earlier. Beryllium could be produced by reducing beryllium
compounds such as beryllium chloride with metallic potassium or
sodium. Currently, most beryllium is produced by reducing beryllium
fluoride with magnesium. The price on the American market for
vacuum-cast beryllium ingots was about $338 per pound ($745 per
kilogram) in 2001.
Between 1998 and 2008, the world's production of beryllium had
decreased from 343 to about 200 tonnes. It then increased to 230
metric tons by 2018, of which 170 tonnes came from the United States.
Etymology
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Beryllium was named for the semiprecious mineral beryl, from which it
was first isolated. Martin Klaproth, having independently determined
that beryl and emerald share an element, preferred the name
"beryllina" due to the fact that yttria also formed sweet salts.
Although Humphry Davy failed to isolate it, he proposed the name
'glucium' for the new metal, derived from the name 'glucina' for the
earth it was found in; altered forms of this name, 'glucinium' or
'glucinum' (symbol Gl) continued to be used into the 20th century.
Radiation windows
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Because of its low atomic number and very low absorption for X-rays,
the oldest and still one of the most important applications of
beryllium is in radiation windows for X-ray tubes. Extreme demands are
placed on purity and cleanliness of beryllium to avoid artifacts in
the X-ray images. Thin beryllium foils are used as radiation windows
for X-ray detectors, and their extremely low absorption minimizes the
heating effects caused by high-intensity, low energy X-rays typical of
synchrotron radiation. Vacuum-tight windows and beam-tubes for
radiation experiments on synchrotrons are manufactured exclusively
from beryllium. In scientific setups for various X-ray emission
studies (e.g., energy-dispersive X-ray spectroscopy) the sample holder
is usually made of beryllium because its emitted X-rays have much
lower energies (≈100 eV) than X-rays from most studied materials.
Low atomic number also makes beryllium relatively transparent to
energetic particles. Therefore, it is used to build the beam pipe
around the collision region in particle physics setups, such as all
four main detector experiments at the Large Hadron Collider (ALICE,
ATLAS, CMS, LHCb), the Tevatron and at SLAC. The low density of
beryllium allows collision products to reach the surrounding detectors
without significant interaction, its stiffness allows a powerful
vacuum to be produced within the pipe to minimize interaction with
gases, its thermal stability allows it to function correctly at
temperatures of only a few degrees above absolute zero, and its
diamagnetic nature keeps it from interfering with the complex
multipole magnet systems used to steer and focus the particle beams.
Mechanical applications
=========================
Because of its stiffness, light weight and dimensional stability over
a wide temperature range, beryllium metal is used for lightweight
structural components in the defense and aerospace industries in
high-speed aircraft, guided missiles, spacecraft, and satellites,
including the James Webb Space Telescope. Several liquid-fuel rockets
have used rocket nozzles made of pure beryllium. Beryllium powder was
itself studied as a rocket fuel, but this use has never materialized.
A small number of extreme high-end bicycle frames have been built with
beryllium. From 1998 to 2000, the McLaren Formula One team used
Mercedes-Benz engines with beryllium-aluminium alloy pistons. The use
of beryllium engine components was banned following a protest by
Scuderia Ferrari.
Mixing about 2.0% beryllium into copper forms an alloy called
beryllium copper that is six times stronger than copper alone.
Beryllium alloys are used in many applications because of their
combination of elasticity, high electrical conductivity and thermal
conductivity, high strength and hardness, nonmagnetic properties, as
well as good corrosion and fatigue resistance. These applications
include non-sparking tools that are used near flammable gases
(beryllium nickel), springs, membranes (beryllium nickel and beryllium
iron) used in surgical instruments, and high temperature devices. As
little as 50 parts per million of beryllium alloyed with liquid
magnesium leads to a significant increase in oxidation resistance and
decrease in flammability.
The high elastic stiffness of beryllium has led to its extensive use
in precision instrumentation, e.g. in inertial guidance systems and in
the support mechanisms for optical systems. Beryllium-copper alloys
were also applied as a hardening agent in "Jason pistols", which were
used to strip the paint from the hulls of ships.
In sound amplification systems, the speed at which sound travels
directly affects the resonant frequency of the amplifier, thereby
influencing the range of audible high-frequency sounds. Beryllium
stands out due to its exceptionally high speed of sound propagation
compared to other metals. This unique property allows beryllium to
achieve higher resonant frequencies, making it an ideal material for
use as a diaphragm in high-quality loudspeakers.
Beryllium was used for cantilevers in high-performance phonograph
cartridge styli, where its extreme stiffness and low density allowed
for tracking weights to be reduced to 1 gram while still tracking high
frequency passages with minimal distortion.
An earlier major application of beryllium was in brakes for military
airplanes because of its hardness, high melting point, and exceptional
ability to dissipate heat. Environmental considerations have led to
substitution by other materials.
A metal matrix composite material combining beryllium with aluminium
developed under the trade name AlBeMet for the high performance
aerospace industry has low weight but four times the stiffness of
aluminum alone.
Mirrors
=========
Large-area beryllium mirrors, frequently with a honeycomb support
structure, are used, for example, in meteorological satellites where
low weight and long-term dimensional stability are critical. Smaller
beryllium mirrors are used in optical guidance systems and in
fire-control systems, e.g. in the German-made Leopard 1 and Leopard 2
main battle tanks. In these systems, very rapid movement of the mirror
is required, which again dictates low mass and high rigidity. Usually
the beryllium mirror is coated with hard electroless nickel plating
which can be more easily polished to a finer optical finish than
beryllium. In some applications, the beryllium blank is polished
without any coating. This is particularly applicable to cryogenic
operation where thermal expansion mismatch can cause the coating to
buckle.
The James Webb Space Telescope has 18 hexagonal beryllium sections for
its mirrors, each plated with a thin layer of gold. Because JWST will
face a temperature of 33 K, the mirror is made of gold-plated
beryllium, which is capable of handling extreme cold better than
glass. Beryllium contracts and deforms less than glass and remains
more uniform in such temperatures. For the same reason, the optics of
the Spitzer Space Telescope are entirely built of beryllium metal.
Magnetic applications
=======================
Beryllium is non-magnetic. Therefore, tools fabricated out of
beryllium-based materials are used by naval or military explosive
ordnance disposal teams for work on or near naval mines, since these
mines commonly have magnetic fuzes. They are also found in maintenance
and construction materials near magnetic resonance imaging (MRI)
machines because of the high magnetic fields generated.
Nuclear applications
======================
High purity beryllium can be used in nuclear reactors as a moderator,
reflector, or as cladding on fuel elements.
Thin plates or foils of beryllium are sometimes used in nuclear weapon
designs as the very outer layer of the plutonium pits in the primary
stages of thermonuclear bombs, placed to surround the fissile
material. These layers of beryllium are good "pushers" for the
implosion of the plutonium-239, and they are good neutron reflectors,
just as in beryllium-moderated nuclear reactors.
Beryllium is commonly used in some neutron sources in laboratory
devices in which relatively few neutrons are needed (rather than
having to use a nuclear reactor or a particle accelerator-powered
neutron generator). For this purpose, a target of beryllium-9 is
bombarded with energetic alpha particles from a radioisotope such as
polonium-210, radium-226, plutonium-238, or americium-241. In the
nuclear reaction that occurs, a beryllium nucleus is transmuted into
carbon-12, and one free neutron is emitted, traveling in about the
same direction as the alpha particle was heading. Such alpha
decay-driven beryllium neutron sources, named "urchin" neutron
initiators, were used in some early atomic bombs. Neutron sources in
which beryllium is bombarded with gamma rays from a gamma decay
radioisotope are also used to produce laboratory neutrons.
Beryllium is used in fuel fabrication for CANDU reactors. The fuel
elements have small appendages that are resistance brazed to the fuel
cladding using an induction brazing process with Be as the braze
filler material. Bearing pads are brazed in place to prevent contact
between the fuel bundle and the pressure tube containing it, and
inter-element spacer pads are brazed on to prevent element to element
contact.
Beryllium is used at the Joint European Torus nuclear-fusion research
laboratory, and it will be used in the more advanced ITER to condition
the components which face the plasma. Beryllium has been proposed as a
cladding material for nuclear fuel rods, because of its good
combination of mechanical, chemical, and nuclear properties. Beryllium
fluoride is one of the constituent salts of the eutectic salt mixture
FLiBe, which is used as a solvent, moderator and coolant in many
hypothetical molten salt reactor designs, including the liquid
fluoride thorium reactor (LFTR).
Acoustics
===========
The low weight and high rigidity of beryllium make it useful as a
material for high-frequency speaker drivers. Because beryllium is
expensive (many times more than titanium), hard to shape due to its
brittleness, and toxic if mishandled, beryllium tweeters are limited
to high-end home, pro audio, and public address applications. Some
high-fidelity products have been fraudulently claimed to be made of
the material.
Some high-end phonograph cartridges used beryllium cantilevers to
improve tracking by reducing mass.
Electronic
============
Beryllium is a p-type dopant in III-V compound semiconductors. It is
widely used in materials such as GaAs, AlGaAs, InGaAs and InAlAs grown
by molecular beam epitaxy (MBE). Cross-rolled beryllium sheet is an
excellent structural support for printed circuit boards in
surface-mount technology. In critical electronic applications,
beryllium is both a structural support and heat sink. The application
also requires a coefficient of thermal expansion that is well matched
to the alumina and polyimide-glass substrates. The beryllium-beryllium
oxide composite "E-Materials" have been specially designed for these
electronic applications and have the additional advantage that the
thermal expansion coefficient can be tailored to match diverse
substrate materials.
Beryllium oxide is useful for many applications that require the
combined properties of an electrical insulator and an excellent heat
conductor, with high strength and hardness and a very high melting
point. Beryllium oxide is frequently used as an insulator base plate
in high-power transistors in radio frequency transmitters for
telecommunications. Beryllium oxide is being studied for use in
increasing the thermal conductivity of uranium dioxide nuclear fuel
pellets. Beryllium compounds were used in fluorescent lighting tubes,
but this use was discontinued because of the disease berylliosis which
developed in the workers who were making the tubes.
Medical applications
======================
Beryllium is a component of several dental alloys. Beryllium is used
in X-ray windows because it is transparent to X-rays, allowing for
clearer and more efficient imaging. In medical imaging equipment, such
as CT scanners and mammography machines, beryllium's strength and
light weight enhance durability and performance. Beryllium is used in
analytical equipment for blood, HIV, and other diseases. Beryllium
alloys are used in surgical instruments, optical mirrors, and laser
systems for medical treatments.
Toxicity and safety
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Biological effects
====================
Approximately 35 micrograms of beryllium is found in the average human
body, an amount not considered harmful. Beryllium is chemically
similar to magnesium and therefore can displace it from enzymes, which
causes them to malfunction. Because Be2+ is a highly charged and small
ion, it can easily get into many tissues and cells, where it
specifically targets cell nuclei, inhibiting many enzymes, including
those used for synthesizing DNA. Its toxicity is exacerbated by the
fact that the body has no means to control beryllium levels, and once
inside the body, beryllium cannot be removed.
Inhalation
============
Chronic beryllium disease (CBD), or berylliosis, is a pulmonary and
systemic granulomatous disease caused by inhalation of dust or fumes
contaminated with beryllium; either large amounts over a short time or
small amounts over a long time can lead to this ailment. Symptoms of
the disease can take up to five years to develop; about a third of
patients with it die and the survivors are left disabled. The
International Agency for Research on Cancer (IARC) lists beryllium and
beryllium compounds as Category 1 carcinogens.
Occupational exposure
=======================
In the US, the Occupational Safety and Health Administration (OSHA)
has designated a permissible exposure limit (PEL) for beryllium and
beryllium compounds of 0.2 μg/m3 as an 8-hour time-weighted average
(TWA) and 2.0 μg/m3 as a short-term exposure limit over a sampling
period of 15 minutes. The National Institute for Occupational Safety
and Health (NIOSH) has set a recommended exposure limit (REL)
upper-bound threshold of 0.5 μg/m3. The IDLH (immediately dangerous to
life and health) value is 4 mg/m3. The toxicity of beryllium is on par
with other toxic metalloids/metals, such as arsenic and mercury.
Exposure to beryllium in the workplace can lead to a sensitized immune
response, and over time development of berylliosis. NIOSH in the
United States researches these effects in collaboration with a major
manufacturer of beryllium products. NIOSH also conducts genetic
research on sensitization and CBD, independently of this
collaboration.
Acute beryllium disease in the form of chemical pneumonitis was first
reported in Europe in 1933 and in the United States in 1943. A survey
found that about 5% of workers in plants manufacturing fluorescent
lamps in 1949 in the United States had beryllium-related lung
diseases. Chronic berylliosis resembles sarcoidosis in many respects,
and the differential diagnosis is often difficult. It killed some
early workers in nuclear weapons design, such as Herbert L. Anderson.
Beryllium may be found in coal slag. When the slag is formulated into
an abrasive agent for blasting paint and rust from hard surfaces, the
beryllium can become airborne and become a source of exposure.
Although the use of beryllium compounds in fluorescent lighting tubes
was discontinued in 1949, potential for exposure to beryllium exists
in the nuclear and aerospace industries, in the refining of beryllium
metal and the melting of beryllium-containing alloys, in the
manufacturing of electronic devices, and in the handling of other
beryllium-containing material.
Detection
===========
Early researchers undertook the highly hazardous practice of
identifying beryllium and its various compounds from its sweet taste.
A modern test for beryllium in air and on surfaces has been developed
and published as an international voluntary consensus standard, ASTM
D7202. The procedure uses dilute ammonium bifluoride for dissolution
and fluorescence detection with beryllium bound to sulfonated
hydroxybenzoquinoline, allowing up to 100 times more sensitive
detection than the recommended limit for beryllium concentration in
the workplace. Fluorescence increases with increasing beryllium
concentration. The new procedure has been successfully tested on a
variety of surfaces and is effective for the dissolution and detection
of refractory beryllium oxide and siliceous beryllium in minute
concentrations (ASTM D7458). The NIOSH Manual of Analytical Methods
contains methods for measuring occupational exposures to beryllium.
Further reading
======================================================================
*
* Mroz MM, Balkissoon R, and Newman LS. "Beryllium". In: Bingham E,
Cohrssen B, Powell C (eds.) 'Patty's Toxicology', Fifth Edition. New
York: John Wiley & Sons 2001, 177-220.
* Walsh, KA, [
https://books.google.com/books?id=3-GbhmSfyeYC
'Beryllium Chemistry and Processing']. Vidal, EE. et al. Eds. 2009,
Materials Park, OH:ASM International.
*
[
https://web.archive.org/web/20190207015758/http://www.bjorklundnutrition.net/2011/11/belpt/
Beryllium Lymphocyte Proliferation Testing (BeLPT).] DOE Specification
1142-2001. Washington, DC: U.S. Department of Energy, 2001.
External links
======================================================================
* [
https://www.atsdr.cdc.gov/csem/csem.html ATSDR Case Studies in
Environmental Medicine: Beryllium Toxicity] U.S. Department of Health
and Human Services
* [
http://education.jlab.org/itselemental/ele004.html It's Elemental -
Beryllium]
* MSDS:
[
https://web.archive.org/web/20070928003708/http://espi-metals.com/msds%27s/beryllium.pdf
ESPI Metals]
* [
http://www.periodicvideos.com/videos/004.htm Beryllium] at 'The
Periodic Table of Videos' (University of Nottingham)
* [
https://www.cdc.gov/niosh/topics/beryllium/ National Institute for
Occupational Safety and Health - Beryllium Page]
* [
http://www.orau.org/nssp/ National Supplemental Screening Program
(Oak Ridge Associated Universities)]
*
[
http://minerals.usgs.gov/minerals/pubs/commodity/beryllium/100798.pdf
Historic Price of Beryllium in USA]
License
=========
All content on Gopherpedia comes from Wikipedia, and is licensed under CC-BY-SA
License URL:
http://creativecommons.org/licenses/by-sa/3.0/
Original Article:
http://en.wikipedia.org/wiki/Beryllium
