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For micro chips.
(L. silex, silicis, flint) Davy in 1800 thought silica to be a compound and not an
element; later in 1811, Gay Lussac and Thenard probably prepared impure amorphous silicon
by heating potassium with silicon tetrafluoride.
In 1824 Berzelius, generally credited with the discovery, prepared amorphous silicon by
the same general method and purified the product by removing the fluosilicates by repeated
washings. Deville in 1854 first prepared crystalline silicon, the second allotropic form
of the element.
Silicon is present in the sun and stars and is a principal component of a class of
meteorites known as aerolites. It is also a component of tektites, a natural glass
of uncertain origin.
Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant
element, being exceeded only by oxygen. Silicon is
not found free in nature, but occurs chiefly as the oxide and as silicates. Sand, quartz,
rock crystal, amethyst, agate, flint, jasper, and opal are some of the forms in which the
oxide appears. Granite, hornblende, asbestos, feldspar, clay, mica, etc. are but a few of
the numerous silicate minerals.
Silicon is prepared commercially by heating silica and carbon in an electric furnace,
using carbon electrodes. Several other methods can be used for preparing the element.
Amorphous silicon can be prepared as a brown powder, which can be easily melted or
vaporized. The Czochralski process is commonly used to produce single crystals of silicon
used for solid-state or semiconductor devices. Hyperpure silicon can be prepared by the
thermal decomposition of ultra-pure trichlorosilane in a hydrogen atmosphere, and by a
vacuum float zone process.
Silicon is one of man's most useful elements. In the form of sand and clay it is used
to make concrete and brick; it is a useful refractory material for high-temperature work,
and in the form of silicates it is used in making enamels, pottery, etc. Silica, as sand,
is a principal ingredient of glass, one of the most inexpensive of materials with
excellent mechanical, optical, thermal, and electrical properties. Glass can be made in a
very great variety of shapes, and is used as containers, window glass, insulators, and
thousands of other uses. Silicon tetrachloride can be used as iridize glass.
Hyperpure silicon can be doped with boron, gallium, phosphorus, or arsenic to produce
silicon for use in transistors, solar cells, rectifiers, and other solid-state devices
which are used extensively in the electronics and space-age industries.
Hydrogenated amorphous silicon has shown promise in producing economical cells for
converting solar energy into electricity.
Silicon is important to plant and animal life. Diatoms in both fresh and salt water
extract Silica from the water to build their cell walls. Silica is present in the ashes of
plants and in the human skeleton. Silicon is an important ingredient in steel; silicon
carbide is one of the most important abrasives and has been used in lasers to produce
coherent light of 4560 A.
Silcones are important products of silicon. They may be prepared by hydrolyzing a
silicon organic chloride, such as dimethyl silicon chloride. Hydrolysis and condensation
of various substituted chlorosilanes can be used to produce a very great number of
polymeric products, or silicones, ranging from liquids to hard, glasslike solids with many
Crystalline silicon has a metallic luster and grayish color. Silicon is a relatively
inert element, but it is attacked by halogens and dilute alkali. Most acids, except
hydrofluoric, do not affect it. Elemental silicon transmits more than 95% of all
wavelengths of infrared, from 1.3 to 6.y micro-m.
Regular grade silicon (99%) costs about $0.50/g. Silicon 99.9% pure costs about $50/lb;
hyperpure silicon may cost as much as $100/oz.
Miners, stonecutters, and others engaged in work where siliceous dust is breathed into
large quantities often develop a serious lung disease known as silicosis.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.
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