| Identification | More | [Name]
Silicon | [CAS]
7440-21-3 | [Synonyms]
111>
Silicon
SI002050
SI007908
SI007915
SI002011
SI002012
SI002015
SI003077
SI002080
SI003050
SI003100
SI003052
SI007916
SI007931
SI006820
SI007920
SI007918
SI003078
SI002076
SI002010
SI007910
SI003120
SI003140
SI007930
SI003051
SI002013
SI003121
SI007940
SI007926
SI003101
SI002090
SI007905
OXALATEE
gSilicon
silicium
SIMP AX05
SIMP AX10
SIMP AX20
Silicon 6N
defoamers-10
SILICON,LUMP
silicon atom
PERCHLORATEE
Siliconwafer
Silicon grain
Silicon in B5
Defoamer S-10
Silica powder
SILICON METAL
SiliziumMetall
silicon,powder
Silicon in B20
Silicon 99.99%
Silicon in B100
SILICON 99.999%
SiliconchipsNmm
Silicon granules
SILICON-29 METAL
Silicon solution
SILICON STANDARD
elementalsilicon
Silicon, -325 mesh
Silica micropowder
Silicon nanopowder
SiliconpowderNmesh
PURE SILICON METAL
Silicon powder (Si)
Silicon wafer, <
Silicon shot,1-6MM.
Silicon300Mesh99.9%
SILICON AA STANDARD
Siliconpowder(99+%)
SILICON METAL POWDER
SILICON ICP STANDARD
SILICON POWDER , 2N+
Silicon (low oxygen)
Silicon Metal, Lumps
SILICON, LUMP, 98.5%
SILICON 0.02-1.5 MM
SIMVASTATIN CAPSULES
SILICON powder 98.5%
Tennant Silicon Metal
Silicon Powder < 4 mm
silicon nanoparticals
SILICON, 99% powder
Siliconpowder(99.999%)
Silicon, powder, 99.9%
Silicon Powder, 150 μm
Silicon Pieces < 10 mm
SiliconrandompiecesNcm
Silicon Monocrystalline
monocrystalline silicon
polycrystalline silicon
Siliconwaferorientation
silicon，momocrystalline
Silicon respirable dust
siliconpowder,amorphous
silicon [atomamorphous]
Silicon chips (99.9999%)
SILICON ICP/DCP STANDARD
SILICON: 99.9999%, LUMPS
Silicon, Powder 100 Mesh
Silicon, pieces,99.9999%
SILICON NANOPOWDER, 98+%
SILICON, PIECES, 99.999+%
Silicon solution 1000 ppm
Silicon sputtering target
SILICON STANDARD SOLUTION
Silicon(Metal)Powder98.5%
Silicon (3 oxygen levels)
Silicon, For analysis APS
Silicon crystalline powder
Silicon, -60 mesh, 99.999%
NIST SRM 57a silicon metal
Silicon Disc 0.625 x 125 mm
Silicon Powder < 160 micron
Silicon ISO 9001：2015 REACH
96067 SILICON (LOW OXYGEN)
SILICON CHIPS: 99.9999%, 6N
polyeristallinesiliconpowder
Silicon powder , sphere (Si)
Silicon total inhalable dust
Silicon, 100-200 Mesh, Powder
Silicon random pieces (99.5%)
SILICON POWDER TECHNICAL 97.5%
Silicon, Powder 100 Mesh 99.9%
SILICON, AAS STANDARD SOLUTION
SILICON: 99.99%, PIECES, -15MM
SILICON SINGLE ELEMENT STANDARD
silicon coating quality balzers
SILICON, POWDER, -325 MESH, 99%
Silicon wafer <111> orientation
90960 SILICON (3 OXYGEN LEVELS)
Silicon, 99+%, powder, -325 mesh
SILICON FINEST POWDER, TECHNICAL
SILICON STANDARD SOLUTION 100 ML
SILICON STANDARD SOLUTION 500 ML
Silicon, +12 Mesh to 1 in., LuMp
Silicon, powder, -325 mesh, 99+%
SILICON METALLO-ORGANIC STANDARD
SILICON PLASMA EMISSION STANDARD
SILICON, PLASMA STANDARD SOLUTION
SILICON WAFER, (111), 2 IN. DIAM.
SILICON WAFER, (111), 3 IN. DIAM.
"Silicon Pieces, polycrystalline"
SILICON WAFER, (100), 2 IN. DIAM.
SILICON WAFER, (100), 3 IN. DIAM.
SILICON, POWDER, -60 MESH, 99.999%
SILICON ATOMIC ABSORPTION STANDARD
HIGH VACCUM GREASE(SILICON GREASE)
SILICON AA SINGLE ELEMENT STANDARD
Silicon rod, 2.5cm (0.98 in.) dia.
Silicon rod, 5.08cm (2.0 in.) dia.
Silicon powder, Plasma Synthesized
Silicon granular, Virgin poly fines
SILICON: 99.995%, POWDER, -8 MICRON
Silicon Sputtering target 4 x 50 mm
Silicon powder (aMorphous), Min. 97%
SILICON ATOMIC SPECTROSCOPY STANDARD
SILICON, OIL BASED STANDARD SOLUTION
Silicon rod, 0.828cm (0.326 in.) dia.
Silicon plate, 9.5mm (0.37 in.) thick
Silicon plate, 12.5mm (0.5 in.) thick
SILICON WAFER <100> orientation, 76mm
SILICON, RANDOM PIECES, OPTICAL GRADE
Silicon, powder, 99.9995% metals basis
Silicon plate, 6.35mm (0.25 in.) thick
SILICON SINGLE ELEMENT PLASMA STANDARD
SILICON COATING QUALITY UMICORE, 1-5 MM
Silicon wafer <100> orientation P-doped
SILICON WAFER, DOPED (N-TYPE), (111) 3 &
SILICON WAFER, DOPED (N-TYPE), (100) 3 &
SILICON WAFER, DOPED (P-TYPE), (100), 2&
SILICON WAFER, (111), DOPED (P-TYPE), 3&
SILICON WAFER, DOPED (N-TYPE), (100), &
SILICON WAFER, DOPED (P-TYPE), (100), 3&
SILICON WAFER, (111), DOPED (P-TYPE), 2&
SILICON WAFER, DOPED (N-TYPE), (111), &
Silicon, powder,99.999%,powder, -60 mesh
SILICON ICP STANDARD TRACEABLE TO SRM FR
N-type, diam. x thickness 2 in. x 0.5 mm
SILICON AA/ICP CALIBRATION/CHECK STANDARD
SILICON RANDOM PIECES: 99.5%, 2N5, 2-8 CM
Silicon, powder, powder, -60 mesh, 99.999%
Silicon powder (nanocrystalline), Min. 97%
Silicon wafer (single side polished), <
SILICON ATOMIC ABSORPTION STANDARD SOLUTION
SILICON WAFER <100> ORIENTATION, 76MM WAFER
SILICON WAFER <111> ORIENTATION, 76MM WAFER
Silicon powder, crystalline, APS ≤50nm, 98%
Silicon rod, Unpolished, 1.6cm (0.6 in.) dia.
SILICON WAFER <100> ORIENTATION UNDOPED, 76MM
SILICON WAFER <100> ORIENTATION N-DOPED, 76MM
SILICON PLASMA EMISSION SPECTROSCOPY STANDARD
SILICON WAFER <100> ORIENTATION P-DOPED - 76MM
Silicon standard solution, 1 mg/ml Si in 2% NaOH
Certified Reference MateriaI for Silicon Isotope
Silicon powder, -325 Mesh, 99.999% (Metals basis)
SILICON ATOMIC ABSORPTION SINGLE ELEMENT STANDARD
Silicon powder, -325 Mesh, 99% trace Metals basis
Standard solution for the determination of silicon
Silicon lump, 0.1-2.5cm, 99.9999% trace metals basis
Silicon powder, APS 1-5 Micron, 99.9% (Metals basis)
Silicon powder, -60 mesh, 99.999% trace metals basis
Silicon lump, 10cm (3.9in) & down, 98.4% (metals basis)
Silicon nanopowder, <100 nm (BET), <3% oxygen passivation
Silicon lump, 15cm (5.9in) & down, 99.999+% (metals basis)
Silicon powder, crystalline, -140 Mesh, 98% (Metals basis)
N-type, contains No dopant, diam. x thickness 3 in. x 0.5 mm
N-type, contains No dopant, diam. x thickness 2 in. x 0.5 mm
silicon, containing by weight not less than 99.99 % of silicon
Silicon Optical Window, 50.8mm (2.0in) dia x 2mm (0.08in) thick
Silicon Optical Window, 25.4mm (1.0in) dia x 1mm (0.04in) thick
Silicon Optical Window, 25.4mm (1.0in) dia x 2mm (0.08in) thick
Silicon Optical Window, 50.8mm (2.0in) dia x 1mm (0.04in) thick
Silicon powder, crystalline, -325 mesh, 99.5% trace metals basis
Silicon slugs, 9.5mm (0.375 in.) dia. x 9.5mm (0.375 in.) length
Silicon powder, crystalline, -100 mesh, 99.9% trace metals basis
SILICON 99.999%SILICON, 99.999%SILICON, 99.999%SILICON, 99.999%
Silicon
elemental silicon
polyeristalline silicon powder
silicium
Silicon powder, crystalline, APS ^=100nM, 99%, PlasMa Synthesized
Silicon99.999%polycrystalinediscandsputteringtargetsavailablealso
Silicon powder, crystalline, -100+200 mesh, 99.99% (metals basis)
P-type, contains boron as dopant, diam. x thickness 2 in. x 0.3 mm
Silicon powder, crystalline, -325 mesh, 99.999% trace metals basis
P-type, contains boron as dopant, diam. x thickness 2 in. x 0.5 mm
P-type, contains boron as dopant, diam. x thickness 3 in. x 0.5 mm | [EINECS(EC#)]
231-130-8 | [Molecular Formula]
H4Si | [MDL Number]
MFCD00085311 | [Molecular Weight]
32.12 | [MOL File]
7440-21-3.mol |
| Chemical Properties | Back Directory | [Definition]
Nonmetallic element Atomic number 14, group IVA
of the periodic table, aw 28.086, valence = 4, three
stable isotopes. It is the second most abundant ele-
ment (25% of the earth’s crust) and is the most
important semiconducting element; it can form
more co | [Appearance]
Silicon is a nonmetallic element which is known as silicon metal. Not occur freely in nature, but is found in silicon dioxide (silica) and in various silicates. It is a steel-gray crystalline solid or a black-brown amorphous material. | [Melting point ]
1410 °C(lit.)
| [Boiling point ]
2355 °C(lit.)
| [density ]
2.33 g/mL at 25 °C(lit.)
| [storage temp. ]
Flammables area | [solubility ]
insoluble in H2O, acid solutions; soluble in alkaline solutions | [form ]
powder
| [color ]
White | [Specific Gravity]
2.42 | [Odor]
Odorless | [PH]
13.5 (H2O, 20°C) | [Stability:]
Stable. Fine powder is highly flammable. Incompatible with oxidizing agents, bases, carbonates, alkali metals, lead and aluminium oxides, halogens, carbides, formic acid. | [Water Solubility ]
INSOLUBLE | [Crystal Structure]
Cubic, Diamond Structure - Space Group Fd3m | [Sensitive ]
Air Sensitive | [Merck ]
13,8565 | [Dielectric constant]
2.4（Ambient） | [Exposure limits]
ACGIH: TWA 2.5 mg/m3
NIOSH: IDLH 250 mg/m3; TWA 2.5 mg/m3 | [InChIKey]
BLRPTPMANUNPDV-UHFFFAOYSA-N | [History]
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.
Berzelius, generally credited with the discovery, in
1824 succeeded in preparing amorphous silicon by the same
general method as used earlier, but he 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. Natural silicon contains three isotopes.
Twenty-four other radioactive isotopes are recognized. 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. Crystalline silicon has a metallic luster and grayish
color. 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. This product
can be doped with boron, gallium, phosphorus, or arsenic to
produce silicon for use in transistors, solar cells, rectifiers, and
other solid-state devices that 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 a relatively
inert element, but it is attacked by halogens and dilute alkali.
Most acids, except hydrofluoric, do not affect it. Silicones 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 useful properties. Elemental silicon
transmits more than 95% of all wavelengths of infrared, from
1.3 to 6.7 μm. 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 to iridize glass. Silicon
is important in plant and animal life. Diatoms in both fresh
and salt water extract silica from the water to build up their
cell walls. Silica is present in 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 remarkable
material, first discovered in 1930, is Aerogel, which is now
used by NASA in their space missions to collect cometary
and interplanet dust. Aerogel is a highly insulative material
that has the lowest density of any known solid. One form of
Aerogel is 99.9% air and 0.1% SiO2 by volume. It is 1000 times
less dense than glass. It has been called “blue smoke” or “solid
smoke.” A block of Aerogel as large as a person may weigh less
than a pound and yet support the weight of 1000 lbs (455 kg).
This material is expected to trap cometary particles traveling
at speeds of 32 km/sec. Aerogel is said to be non-toxic and
non-inflammable. It has high thermal insulating qualities that
could be used in home insulation. Its light weight may have
aircraft applications. Regular grade silicon (99.5%) costs about
$160/kg. Silicon (99.9999%) pure costs about $200/kg; hyperpure
silicon is available at a higher cost. Miners, stonecutters,
and other engaged in work where siliceous dust is breathed in
large quantities often develop a serious lung disease known
as silicosis. | [Uses]
Silicon is usually available as electronic-grade, high-quality, high-purity single crystalline material in the form of wafers (round, surface-polished slices typically of 4–12 inches in diameter and a few hundreds of micrometers to millimeters in thickness). The biggest advantage of using silicon for microfluidic applications is the availability of a mature processing technology inherited from the microelectronics IC industry as well as the possibility of defining very small structures that can be cointegrated with the electronics on the same chip. Some of the disadvantages of using silicon as a structural material are linked to the polar nature of the silicon crystal resulting in undesirable adsorption of molecules in microfluidic systems. Furthermore, the higher cost of silicon as substrate material without any specific advantages from microfluidic systems standpoint makes it less attractive as a substrate material unless integration of on-chip electronic circuits is a strong requirement for the particular microsystem design. The typical cost of an average quality silicon substrate is about 0.25 U.S. cents/cm2. | [CAS DataBase Reference]
7440-21-3(CAS DataBase Reference) | [NIST Chemistry Reference]
Silicon(7440-21-3) | [EPA Substance Registry System]
7440-21-3(EPA Substance) |
| Safety Data | Back Directory | [Hazard Codes ]
T,F | [Risk Statements ]
R11:Highly Flammable. | [Safety Statements ]
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S36/37:Wear suitable protective clothing and gloves .
S45:In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) .
S7/9:Keep container tightly closed and in a well-ventilated place .
S33:Take precautionary measures against static discharges .
S16:Keep away from sources of ignition-No smoking .
S36:Wear suitable protective clothing . | [RIDADR ]
UN 2922 8/PG 2
| [WGK Germany ]
2
| [RTECS ]
VW0400000
| [Autoignition Temperature]
780°C | [TSCA ]
Yes | [HazardClass ]
4.1 | [PackingGroup ]
III | [HS Code ]
28046900 | [Safety Profile]
A nuisance dust. Moderately toxic by ingestion. An eye irritant. Does not occur freely in nature, but is found as sdicon dioxide (sdtca) and as various shcates. Elemental Si is flammable when exposed to flame or by chemical reaction with oxidlzers. Violent reactions with alkali carbonates, oxidants, (A1 + PbO), Ca, Cs2C2, Cl2, CoF2, F2, IFs, MnF3, Rb2C2, FNO, AgF, NaK alloy. When heated it will react with water or steam to produce H2; can react with oxidizing materials. See also various silica entries, SILICATES, and POWDERED METALS. | [Hazardous Substances Data]
7440-21-3(Hazardous Substances Data) |
| Hazard Information | Back Directory | [General Description]
A dark brown powder. Insoluble in water and denser than water. Burns readily when exposed to heat or flames, and may be difficult to extinguish. Water may not be effective in extinguishing flames. Used to make computer microchips. | [Reactivity Profile]
SILICON POWDER, AMORPHOUS(7440-21-3) is a reducing agent. Ignites in fluorine gas at ordinary temperatures [Mellor 2:11-13 1946-47]. Burns spontaneously in gaseous chlorine. A mixture of silicon, aluminum, and lead oxide explodes when heated [Mellor 7:657 1946-47]. When heated with an alkali carbonate, a vigorous reaction attended by incandescence occurs [Mellor 6:164 1946-47]. Reacts violently with silver fluoride [Mellor 3:389 1946-47]. Reacts with sodium-potassium alloy to form sodium silicide, which is spontaneously flammable in air [Mellor 2 Supp. 2:564 1961]. | [Air & Water Reactions]
Highly flammable. Insoluble in water. A significant dust explosion hazard. | [Hazard]
Flammable in powder form.
| [Health Hazard]
Oxides from metallic fires are a severe health hazard. Inhalation or contact with substance or decomposition products may cause severe injury or death. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may cause pollution. | [Potential Exposure]
Silicon may be used in the manufacture of silanes, silicon tetrachloride, ferrosilicon, silicones. It is used in purified elemental form in transistors and photovoltaic cells. | [Fire Hazard]
May react violently or explosively on contact with water. Some are transported in flammable liquids. May be ignited by friction, heat, sparks or flames. Some of these materials will burn with intense heat. Dusts or fumes may form explosive mixtures in air. Containers may explode when heated. May re-ignite after fire is extinguished. | [First aid]
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure. Transfer promptly to a medical facility. | [Shipping]
UN1346 Silicon powder, amorphous requires, Hazard Class: 4.1; Labels: 4.1-Flammable solid. | [Incompatibilities]
Dust or powder may form explosive mixture with air. A strong reducing agent. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, calcium, carbonates, chlorine, fluorine, oxidizers, cesium carbide; alkaline carbonates. | [Chemical Properties]
grey lustrous solid or grey powder | [Chemical Properties]
Silicon is a nonmetallic element which is known as silicon metal. Not occur freely in nature, but is found in silicon dioxide (silica) and in various silicates. It is a steel-gray crystalline solid or a black-brown amorphous material. | [Physical properties]
Silicon does not occur free in nature, but is found in most rocks, sand, and clay. Siliconis electropositive, so it acts like a metalloid or semiconductor. In some ways silicon resemblesmetals as well as nonmetals. In some special compounds called polymers, silicon will act inconjunction with oxygen. In these special cases it is acting like a nonmetal.
There are two allotropes of silicon. One is a powdery brown amorphous substance bestknown as sand (silicon dioxide). The other allotrope is crystalline with a metallic grayishluster best known as a semiconductor in the electronics industry. Individual crystals of siliconare grown through a method known as the Czochralski process. The crystallized siliconis enhanced by “doping” the crystals (adding some impurities) with other elements such asboron, gallium, germanium, phosphorus, or arsenic, making them particularly useful in themanufacture of solid-state microchips in electronic devices.
The melting point of silicon is 1,420°C, its boiling point is 3,265°C, and its density is2.33 g/cm3. | [Isotopes]
There are 21 isotopes of silicon, three of which are stable. The isotope Si-28makes up 92.23% of the element’s natural abundance in the Earth’s crust, Si-29 constitutes4.683% of all silicon found in nature, and the natural abundance of Si-30 ismerely 3.087% of the stable silicon isotopes found in the Earth’s crust. | [Origin of Name]
Silicon was named after the Latin word silex, which means “flint.” | [Occurrence]
Silicon, in the form of silicon dioxide (SiO2), is the most abundant compound in theEarth’s crust. As an element, silicon is second to oxygen in its concentration on Earth, yet it is only the seventh most abundant in the entire universe. Even so, silicon is used as the standard(Si = 1) to estimate the abundances of all other elements in the universe. For example, hydrogenequals 40,000 times the amount of silicon in the cosmos. Hydrogen is the most abundantof all elements in the universe, and carbon is just three and half times as abundant as siliconin the entire universe. On Earth silicon accounts for 28% of the crust, oxygen makes up 47%of the crust, and much of the rest of the crust is composed of aluminum.
It is believed that silicon is the product of the cosmic nuclear reaction in which alpha particleswere absorbed at a temperature of 109 Kelvin into the nuclei of carbon-12, oxygen-16,and neon-20. Pure elemental silicon is much too reactive to be found free in nature, but it doesform many compounds on Earth, mainly oxides as crystals (quartz, cristobalite, and tridymite)and amorphous minerals (agate, opal, and chalcedony). Elemental silicon is produced byreducing silica (SiO2) in a high-temperature electric furnace, using coke as the reducing agent.It is then refined. Silicon crystals used in electronic devices are “grown” by removing startercrystals from a batch of melted silicon. | [Characteristics]
The characteristics of silicon in some ways resemble those of the element germanium,which is located just below it in the carbon group.
Flint is the noncrystalline form of silicon and has been known to humans since prehistorictimes. When struck with a sharp blow, flint would flake off sharp-edged chips that were thenused as cutting tools and weapons.
In addition to silica (silicon dioxide SiO2), the crystal form of silicon is found in severalsemiprecious gemstones, including amethyst, opal, agate, and jasper, as well as quartz of varyingcolors. A characteristic of quartz is its piezoelectric effect. This effect occurs when thequartz crystal is compressed, producing a weak electrical charge. Just the opposite occurs whenelectric vibrations are fed to the crystal. These vibrations are then duplicated in the crystal.Quartz crystals are excellent timekeeping devices because of this particular characteristic. | [Reactions]
Si is a little soluble in water (Solubility: 0.005 g/100 g H2O (298 K)). It reacts strongly with F at room temperature, Cl at 430℃, Br at 500℃, O at 400℃, and N2 at 1000℃ to form compounds of SiF4 , SiCl4 , SiBr4 , SiO2 , SiO, and Si3N4 , respectively. | [Flammability and Explosibility]
Nonflammable | [Agricultural Uses]
Some plants need silicon (Si) in addition to micro and
macro nutrients. It is one of the most abundant elements
absorbed by plants. Silicon belongs to Group 14
(formerly IVB) of the Periodic Table. It is an
essential trace element for the normal growth of higher
animals, as it is involved in the formation of bones and
cartilages. Crops grown in the absence of soluble silica
are more prone to mildews than those provided with
soluble silica. Rice, cucumber, gherkin and barley
require silicon. Silicon improves the growth of sugar
cane. Silicon corrects soil toxicities arising from the
presence of excessive quantities of Mn, Fe and active Al.
The oxidizing power of rice roots and their tolerance to
the high level of iron and manganese are attributed to
silicon nutrition.
In a field trial, when parts of a rice crop had a silica to
nitrogen ratio of 11:2, 10 tons/ha of extra rice was
produced. Silicon helps to (a) maintain the erectness of
rice leaves, (b) increase resistance to insect pests, (c)
improve photosynthesis, (d) increase the number of
stems, and (e) improve the fresh as well as dry weights of
rice plants. If silica is withheld during the reproductive
period, the number of spikelets per panicle and the
ripened grain percentage decreases.
Silicon contributes to the structure of cell wall, thus
(a) making the cell wall more immune to diseases, (b)
improving the stalk strength, and (c) increasing the
resistance to lodging. Rice and sugar cane respond
favorably to silicon fertilizers. Enzyme-silicon
complexes formed in sugar cane act as protectors or
regulators of photosynthesis and enzyme activity. By
suppressing the invertase activity in sugar cane, silicon
increases sugar production.
Silicon and oxygen occupy 75% of the earth's crust,
of which silicon alone is 27.7%. Silica, which occurs to
the extent of 60 to 80% as insoluble quartz silica, is in the
form of mono-silicic acid [Si(OH)4], the availability of
which increases with increasing soil pH and temperature.
Roughly, 130 ppm silicon (SO2) is the critical limit of the
available silicon in air-dry soil for maximizing wetland
rice yield; the critical limit is raised by adding silicon (as
SiO2).
Silicon uptake by plants differ with plant species.
Gramineae contains 10 to 20 times more silicon than that normally found in legumes and dicotyledons. Paddy
contains 4.6 to 7.0% of silicon in the straw. Oxides of
iron and aluminum, liming, flooding and nutrient supply
influence silicon-uptake; high soil-water content
increases the uptake in rice, barley, oats, sorghum and
sugar cane.
The quantity of silica fertilizer to be added to the soil
is guided by the ratio of the available silica to organic
matter, which if less than 100, warrants the use of
fertilizer; if the ratio is more than 100, it calls for the
addition of organic matter; if less than 50, it indicates that
the soil is suffering from silicon shortage. For a silicondeficient
area, the addition of 2 todha of silica fertilizer
is recommended. Freckling, which is a necrotic leaf spot
condition, is a symptom of low levels of silicon in a sugar
cane plant that receives direct sunlight, the ultraviolet
(W) radiation in sunlight being the causative agent.
Sufficient quantities of silicon in a sugar cane plant filters
out harmful UV radiation.
Major silica fertilizers include calcium silicate slag,
calcium silicate and sodium meta-silicate. 1.5 to 2.0 tons
of silicate slag per hectare usually provides sufficient
silicon for rice crops produced in low-silicon soils.
Silicate fertilizers serve as a source of silicon and a liming
material in acid soils. Slags from the steel industry,
ground basic-slag (containing varying quantities of Al,
Ca, Fe, Mn, Mg and Si), and wollastonite (Ca-Mg
silicate) are all silicate fertilizers.
Sodium silicate increases the crop yield in phosphatedeficient
soils, possibly because silicates help increase
the assimilation of phosphoric acid by the plant and not
the soil. However, according to some, silicate increases
the amount of available soil phosphate. Heavy
applications of nitrogen make the rice plant more
susceptible to fungal attack because of the decreased
silicon concentration in the straw. | [Industrial uses]
Silicon is, after oxygen, the second most abundant element in the earth s crust. It occurs in a range of minerals and sand (SiO2, quartz). Silicon can be extracted from silicates or sand by reducing SiO2 with coke at high temperatures at around 3000°C.Silicon is used in a wide variety of applications. In nature, silicon does not exist as the pure metal and most commonly occurs in silica (including sand) and silicates. Silicon dioxide, also known as silica, is a hard substance with a high melting temperature and clearly very different from carbon dioxide. Molten silica can be used to make glass, an extremely useful material, which is resistant to attack by most chemicals except fluorine, hydrofluoric acid and strong alkalis. Silicon atoms can also be found in the class of compounds called silicones. Pure silicon metal is used in semiconductors, the basis of all electronic devices, and is most well known for its application in solar panels and computer chips. |
| Questions And Answer | Back Directory | [Description]
Gay Lussac and Thenard in 1809 obtained very impure amorphous silicon by passing silicon tetrafluoride over heated potassium. Berzelius in 1823 prepared elemental silicon in high purity by the same method. He also obtained silicon by heating potassium fluosilicate with potassium metal. Deville produced crystalline silicon in 1854 by electrolysis of a molten mixture of impure sodium aluminum chloride containing 10% silicon and a small quantity of aluminum.
Silicon is the second most abundant element on earth after oxygen. It occurs in nature combined with oxygen in various forms of silica and silicates. Silicates have complex structures consisting of SiO4 tetrahedral structural units incorporated to a number of metals. About 90% of the earth’s crust is made up of silica and naturally-occurring silicates. Silicon is never found in nature in free elemental form. Among all elements silicon forms the third largest number of compounds after hydrogen and carbon. There are well over 1,000 natural silicates including clay, mica, feldspar, granite, asbestos, and hornblende. Such natural silicates have structural units containing orthosilicates, SiO44– , pyrosilicates Si2O76– and other complex structural units, such as, (SiO3)n2n– that have hexagonal rings arranged in chains or pyroxenes (SiO32– )n and amphiboles, (Si4O116– )n in infinite chains. Such natural silicates include common minerals such as tremolite, Ca2Mg5(OH)2Si8O22; diopside, CaMg(SiO3)2; kaolin, H8Al4Si4O18; montmorillonite, H2Al2Si4O12; talc, Mg3[(OH)2 SiO10]; muscovite ( a colorless form of mica), H2KAl3(SiO4)3; hemimorphite, Zn4(OH)2Si2O7•H2O; beryl, Be3Al2Si6O18; zircon, ZrSiO4; benitoite, BaTiSi3O9; feldspars, KAlSi3O8; zeolites, Na2O•2Al2O3•5SiO2•5H2O; nephrite, Ca(Mg,Fe)3(SiO3)4; enstatite, (MgSiO3)n; serpentine, H4Mg3Si2O9; jadeite, NaAl(SiO3)2; topaz, Al2SiO4F2; and tourmaline, (H,Li,K,Na)9 Al3(BOH)2Si4O19. Many precious gemstones are silicate based. Such gems include beryl, emerald, aquamarine, morganite, topaz, tourmaline, zircon, amazon stone and moonstone.
| [Crystal System]
?The space lattice of Si belongs to the cubic system, and its diamond structure has a lattice constant of a=0.543072 nm (258℃) and Si–Si=0.235 nm. | [Uses]
Elemental silicon has some of the most important applications in this electronic age. One of the major applications is in computer chips. The single crystals of crystalline silicon are used for solid-state or semiconductor devices. Silicon of hyperpurity, doped with trace elements, such as boron, phosphorus, arsenic, and gallium is one of the best semiconductors. They are used in transistors, power rectifiers, diodes and solar cells. Silicon rectifiers are most efficient in converting a-c to d-c electricity. Hydrogenated amorphous silicon converts solar energy into electricity.
| [Production Methods]
Elemental silicon is produced commercially by heating silica with carbon (coke) in an electric furnace using carbon electrodes:
SILICON 819SiO2 + C → Si + CO2
The product obtained is about 96 to 98% purity. Repeated leaching forms about 99.7% purified product. Alternatively, lower grade silicon is converted to its halide or halosilane, which is then reduced with a high purity reducing agent. Hyperpure silicon for semiconductor applications can be made by several methods. Such processes include reduction of silicon tetrachloride with highly pure zinc:
SiCl4 + 2Zn → Si + 2ZnCl2
or by reducing trichlorosilane with hydrogen at 1,150°C using a silicon filament on which deposition of silicon occurs:
SiHCl3 + H2 → Si + 3HCl
or by heating silane or silicon tetraiodide to elevated temperatures:
SiH4 → Si + 2H2
SiI4 → Si + 2I2
or by reducing silicon tetrafluoride with sodium:
SiF4 + 4Na → Si + 4 NaF
Several processes are known to achieve growth of single crystals of silicon for semiconductors. One such method developed in 1918 is known as Czocharlski process or Teal-Little method. The process involves dipping a single crystal “seed” into molten silicon held at the melting point. The seed is properly oriented by rotation and the molten silicon is allowed to freeze gradually over it and the seed is slowly withdrawn. The growth rate is controlled by melt temperature and heat losses from the crystal. Growth rates are usually in the range of 2.5 cm/hour but can vary with diameter. Crystals of varying sizes have been produced by this method. The common sizes of crystals usually range between 75 to 125 mm in diameter and about 100 cm long. Pure quartz crucibles or silicon pedestals are employed to carry out single crystal’s growth.
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