SILICA

Silica, also known as Silica dioxide (SiO₂), is a natural compound made of Silica and oxygen. 
Silica's one of the most abundant minerals found on Earth, commonly occurring in nature as Silica, which is a key component of sand, rock, and soil.
Silica is a chemical compound comprised of oxide and Silica elements. 

CAS Number: 14808-60-7
Molecular Formula: O2Si
Molecular Weight: 60.08
EINECS Number: 215-684-8

Synonyms: Silica DIOXIDE: Silica, Dioxosilane, Silica, 7631-86-9, Cristobalite, Tridymite, 112945-52-5, 14808-60-7, 112926-00-8, Silicic anhydride, Sand, Aerosil, Diatomaceous silica, 14464-46-1, 60676-86-0, Wessalon, Silica(IV) oxide, Zorbax sil, Silica, amorphous, Silica (SIO2), Dicalite, Ludox, Nyacol, Amorphous silica, Synthetic amorphous silica, Cristobalite (SiO2), Cab-O-sil, SILICA, VITREOUS, Sillikolloid, Extrusil, Santocel, Sipernat, Superfloss, Acticel, Carplex, Neosil, Neosyl, Porasil, Silikil, Siloxid, Zipax, Aerosil-degussa, Aerosil 380, Silica sand, Rose Silica, Silica particles, Cab-o-sil M-5, Snowtex O, Silica, colloidal, Tokusil TPLM, Dri-Die, Manosil vn 3, Colloidal Silica dioxide, Ultrasil VH 3, Ultrasil VN 3, Aerosil bs-50, Carplex 30, Carplex 80, Snowtex 30, Zeofree 80, Aerosil K 7, Cabosil N 5, Syton 2X, Amorphous silica gel, Positive sol 232, Siliziumdioxid, Aerogel 200, Aerosil 300, Chalcedony, Diatomite, Ludox hs 40, Silanox 101, Silica (SiO2), Vitasil 220, Agate, Positive sol 130M, Silica vitreous, Silica dioxide (amorphous), Aerosil A 300, Aerosil E 300, Aerosil M-300, colloidal silica, Fused silica, Silica glass, Silica slurry, Silica dioxide, fumed, Silicae dioxide, Nalfloc N 1050, Quso 51, Silica, amorphous fused, Nalco 1050, Quso G 30, 15468-32-3, Hydrophobic silica 2482, Kieselsaeureanhydrid, Min-U-Sil, SiO2, CCRIS 3699, Silica Gel, 40-63 Micron Particles, Silica aerogel, (SiO2)n, UNII-ETJ7Z6XBU4, ETJ7Z6XBU4, Silica Dioxide, Amorphous, Silica 2482, hydrophobic, Silica dioxide, chemically prepared, 15723-40-7, 99439-28-8, EINECS 231-545-4, CAB-O-SIL N-70TS, EPA Pesticide Chemical Code 072605, CI 7811, Aerosil 200, 13778-37-5, CHEBI:30563, AI3-25549, Crystalline silica, N1030, U 333, Silica gel 60, 230-400 mesh, MFCD00011232, MFCD00217788, Celite, Silica dioxide, colloidal, ENT 25,550, [SiO2], Silica, crystalline - fused, Silica, fumed, Calcined diatomite, Silica gel, pptd.,cryst.-free, 13778-38-6, 17679-64-0, Christensenite, Crystoballite, Silica gel desiccant, indicating, INS-551, Silica, amorphous,fumed, cryst.-free, Silica, mesostructured, Amethyst, Aquafil, Cataloid, Crysvarl, Flintshot, Nalcoag, Novaculite, Silikill, Vulkasil, Cherts, Snowit, Imsil, Metacristobalite, silica sand, Silica silica, alpha-Silica, Fossil flour, Fumed silica, Silica dust, Rock crystal, Silica dust, White carbon, SIMETHICONE COMPONENT Silica DIOXIDE, Chromosorb P, Tiger-eye, E-551, Vulkasil S, Celite superfloss, Cristobalite dust, Corasil II, Silver bond B, Cab-O-sperse, alpha-Cristobalite, alpha-Crystobalite, Gold bond R, (SiO2), Cabosil st-1, Silica Standard: SiO2 @ 100 microg/mL in H2O, Sil-Co-Sil, Silica Standard: SiO2 @ 1000 microg/mL in H2O, Siderite (SiO2), Tridymite 118, J-002874, Sand, white Silica, >=99.995% trace metals basis, Silica gel, large pore, P.V. ca. 1cc/g, 8 mesh, Silica gel, technical grade, 1-3 mm particle size, Silica gel, technical grade, 3-6 mm particle size, Silica gel, with moisture indicator (blue), coarse, Silica oxide nanopowder (Non-porous) (10-20 nm), Celpure(R) P65, meets USP/NF testing specifications, Micro particles based on Silica dioxide, size: 2 mum, Micro particles based on Silica dioxide, size: 3 mum, Micro particles based on Silica dioxide, size: 4 mum, Micro particles based on Silica dioxide, size: 5 mum, Silica gel 60, 0.060-0.2mm (70-230 mesh), Silica gel desiccant, indicating, <1% Cobalt chloride, Silica gel, -60-120 mesh, for column chromatography, Silica(IV) oxide, 30% in H2O, colloidal dispersion, Celpure(R) P100, meets USP/NF testing specifications, Celpure(R) P1000, meets USP/NF testing specifications, Celpure(R) P300, meets USP/NF testing specifications, Micro particles based on Silica dioxide, size: 0.5 mum, Micro particles based on Silica dioxide, size: 1.0 mum, Silica Dispersion (SiO2, Aqueous Dispersion, Amorphous), Silica gel 60, 0.032-0.063mm (230-450 mesh), Silica gel 60, 0.036-0.071mm (215-400 mesh), Silica gel 60, 0.040-0.063mm (230-400 mesh), Silica gel desiccant, indicating, -6+16 mesh granules, Silica gel, with moisture indicator (blue), -6-20 mesh, Silica, mesostructured, MSU-H (large pore 2D hexagonal), Silica, mesostructured, SBA-15, 99% trace metals basis, Silica Dioxide (Silica) Nanodispersion Type A (20nm), Silica Dioxide (Silica) Nanodispersion Type B (20nm), Silica dioxide, -325 mesh, 99.5% trace metals basis, Silica dioxide, washed and calcined, analytical reagent, Silica(IV) oxide, amorphous fumed, S.A. 85-115m2/g, Synthetic - fused silica: Trade Names: Suprasil; TAFQ, Zeolite - Mesoporous Silica Nanopowder (SBA-15 Type), Chromosorb(R) W, AW-DMCS, 100-120 mesh particle size, Micro particles based on Silica dioxide, size: 0.15 mum, Silica gel orange, 2-5 mm, with colour indicator, pearls, Silica gel, high-purity grade (15111), pore size 60 ??, Silica Slurry (SiO2, Purity: 99%, Diameter: 15-20nm), Silica, mesoporous, 1 mum particle size, pore size ~2 nm, Silica, mesoporous, 1 mum particle size, pore size ~4 nm, Silica, mesoporous, 2 mum particle size, pore size ~2 nm, Silica, mesoporous, 2 mum particle size, pore size ~4 nm, Silica, mesoporous, 3 mum particle size, pore size ~2 nm, Silica, mesoporous, 3 mum particle size, pore size ~4 nm, Silica,fumed, hydrophilic, specific surface area 200 m2/g, Silica,fumed, hydrophilic, specific surface area 400 m2/g, Silica dioxide; synthetic amorphous Silica dioxide (nano), Silica(IV) oxide, amorphous fumed, S.A. 350-420m2/g, Amorphous silica: Vitreous silica, Silica glass, fused silica, LUDOX(R) AM colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) CL colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) CL-X colloidal silica, 45 wt. % suspension in H2O, LUDOX(R) LS colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) SM colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) TMA colloidal silica, 34 wt. % suspension in H2O, Silica gel orange, with moisture indicator free of heavy metals, Silica gel, high-purity grade, FIA according to DIN 51791, Silica, mesoporous, 0.5 mum particle size, pore size ~2 nm, Silica, mesoporous, 0.5 mum particle size, pore size ~4 nm, Silica dioxide, acid washed and calcined, Analytical Reagent, Silica dioxide, crystalline (fine), coating quality, >=99.9%, Chromosorb(R) P, NAW, 60-80 mesh particle size, bottle of 100 g, Chromosorb(R) W, AW, 80-100 mesh particle size, bottle of 100 g, Chromosorb(R) W, HP, 60-80 mesh particle size, bottle of 100 g, LUDOX(R) AS-30 colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) AS-40 colloidal silica, 40 wt. % suspension in H2O, LUDOX(R) HS-30 colloidal silica, 30 wt. % suspension in H2O, LUDOX(R) HS-40 colloidal silica, 40 wt. % suspension in H2O, LUDOX(R) TM-40 colloidal silica, 40 wt. % suspension in H2O, LUDOX(R) TM-50 colloidal silica, 50 wt. % suspension in H2O, Silica gel, Davisil(R) grade 22, pore size 60 ??, 60-200 mesh, Silica gel, high-purity grade, 60??, 35-60 mesh particle size, Silica gel, high-purity grade, pore size 60 ??, 70-230 mesh, Silica gel, HPLC grade, spherical, 3 micron APS, 120 angstroms, Silica gel, technical grade (w/ fluorescent indicator), 60 F254, Silica gel, Type H, without binder, for thin layer chromatography, Silica gel, Type II, 3.5 mm bead size, Suitable for desiccation, Silica, fumed, powder, 0.2-0.3 mum avg. part. size (aggregate), Silica Dioxide Dispersion (SiO2, Aqueous Dispersion, Amorphous), Silica dioxide, for cleaning of platinum crucibles, calcined, crude, Silica dioxide, fused (pieces), 4 mm, 99.99% trace metals basis, Silica oxide nanopowder , modified with amino group (10-20 nm), Silica oxide nanopowder , modified with double bond (10-20 nm), Silica oxide nanopowder , modified with double layer (10-20 nm), Silica oxide nanopowder , modified with epoxy group (10-20 nm), Silica oxide, catalyst support, high surface area, S.A.250m2/g, Zeolite - Mesoporous Silica Nanopowder (1D-Hexagonal SBA-41 Type), Zeolite - Mesoporous Silica Nanopowder (3D-Cubic MCM-48 Type), Celatom(R), acid-washed, for use in Total Dietary Fiber Assay, TDF-100A, Chromosorb(R) G, HP, 100-120 mesh particle size, bottle of 100 g, Chromosorb(R) P, AW-DMCS, 80-100 mesh particle size, bottle of 100 g, Chromosorb(R) W, AW, 100-120 mesh particle size, bottle of 100 g, Chromosorb(R) W, HP, 100-120 mesh particle size, bottle of 100 g, NBS 28 (Silica and oxygen isotopes in silica sand), NIST(R) RM 8546, Pyrogenic or fumed silica: Trade Names: Aerosil; Cab-O-Sil; HDK; Reolosil, Silica microscope slide, fused, 25.4x25.4x1.0mm (1.0x1.0x0.0394in), Silica microscope slide, fused, 50.8x25.4x1.0mm (2.0x1.0x0.0394in), Silica gel 60, 0.105-0.2mm (70-150 mesh), S.A. 500-600m2/g, Silica gel, high purity, 90??, 35-70 mesh, for column chromatography, Silica gel, high-purity grade (7734), pore size 60 ??, 70-230 mesh, Silica gel, high-purity grade (7754), pore size 60 ??, 70-230 mesh, Silica gel, high-purity grade, 40, >=400 mesh, for column chromatography, Silica gel, high-purity grade, 40, 35-70 mesh, for column chromatography, Silica gel, high-purity grade, 40, 70-230 mesh, for column chromatography, Silica gel, high-purity grade, 90, Silica (SiO2);Rose Silica, silica, crystalline(asrespirable, silica, crystalline(asrespirabledust), Silica oxide, Silica, P 820 A, Silica, CRYSTAL LASER GRADE;Silica CALIBRATION PLATE 17°.

Silica is insoluble in water or acids except hydrofluoric acid. 
Silica appears as transparent to gray, tasteless crystal which is widely presented in nature as sand or Silica. 
It is also one of the most abundant mineral existing in Earth’s crust. 

Silica has wide applications in various fields as below: as the precursor to glass and Silica; for sand casting; as a additive to food and pharmaceutical products; for production of cement and refractory materials; as the medium for conversion of energy.
Extraction of DNA and RNA; as a defoamer component. 
There are many ways for production of Silica. 

The most common way is through mining and purification of Silica.
Silica dioxide, also known as silica, is an oxide of Silica with the chemical formula SiO2, commonly found in nature as Silica.
In many parts of the world, silica is the major constituent of sand. 

Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. 
Examples include fused Silica, fumed silica, opal, and aerogels. 
Silica is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. 

All forms are white or colorless, although impure samples can be colored.
Silica is a common fundamental constituent of glass.
Silica is a colorless solid that exists in numerous crystalline forms. 

Oxygen and Silica are the two most common elements in the earth's crust, and Silica is the principal component of sand. 
Silica is used biologically, most notably by phytoplankton diatoms and the zooplankton radiolarians in their shells. 
Silica, SiO2, should not be confused with Silica or Silicaes. 

Silica contain the basic tetrahedral unit SiO44-bonded to metal ions such as aluminum, iron, sodium, magnesium, calcium, and potassium to form numerous Silica minerals. 
Silicaes are synthetic polymers made of monomers with at least two Silica atoms combined with an organic group and generally containing oxygen.
Silica is the oxide of the nonmetallic element Silica, is the commonest of minerals, and appears in a greater number of forms than any other. 

Its formula is SiO2. Silica commonly occurs in prismatic hexagonal crystals terminated by a pyramid. 
This pyramid is due to the equal development of two rhombohedrons, and may be observed in cases where one rhombohedron predominates. 
Cleavage is not observed; the fracture is typically conchoidal; hardness is 7; specific gravity, 2.65; luster, vitreous to greasy or dull; colorless to white, pink, purple, yellow, blue, green, smoky brown to nearly black; transparent to opaque.

Silica is a component of many mineral dusts and materials which melts to a glass at very high temperature.
Silica can exist in either a crystalline or noncrystalline form. 
In Silica, SiO2 exists in the natural crystalline state and possesses long-range order, with the Silica atom covalently bonded to oxygen atoms in a tetrahedral arrangement in a regular repeating pattern. 

Glass is an example of noncrystalline Silica. 
Although natural glasses exist, Silica glasses are produced when Silica is heated to an elevated temperature and then rapidly cooled. 
The rapid cooling does not allow the SiO2 to form a regular crystalline structure with long-range order. 

The result is a solid that behaves like a viscous liquid when heated.
Glass is sometimes called a solid solution and fl ows at a very slow rate. 
This can sometimes be seen in old window glass where the bottom is slightly thicker than the top. 

The actual structures form a three-dimensional tetrahedral pattern. 
Silica is sold as sand and its main uses are for glass; ceramics; foundry sand, a source of Silica in the chemical industry; as a filtration media; a filler/extender; an abrasive; and as an adsorbent.
Silica is another name for the chemical compound composed of Silica and oxygen with the chemical formula SiO2, or Silica dioxide. 

There are many forms of silica. All silica forms are identical in chemical composition, but have different atom arrangements. 
Silica compounds can be divided into two groups, crystalline (or c-silica) and amorphous silica (a-silica or non-crystalline silica). 
Silica compounds have structures with repeating patterns of Silica and oxygen.

Silica chemical structures are more randomly linked when compared to c-silica. 
All forms of silica are odorless solids composed of Silica and oxygen atoms. 
Silica particles become suspended in air and form non-explosive dusts. 

Silica may combine with other metallic elements and oxides to form silicates.
In the majority of Silica dioxides, the Silica atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atom (see 3-D Unit Cell). 
Thus, SiO2 forms 3-dimensional network solids in which each Silica atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms.

In contrast, CO2 is a linear molecule. 
The starkly different structures of the dioxides of carbon and Silica are a manifestation of the double bond rule.
Based on the crystal structural differences, Silica dioxide can be divided into two categories: crystalline and non-crystalline (amorphous). 

In crystalline form, this substance can be found naturally occurring as Silica, tridymite (high-temperature form), cristobalite (high-temperature form), stishovite (high-pressure form), and coesite (high-pressure form). 
On the other hand, amorphous silica can be found in nature as opal and diatomaceous earth. 
Silica glass is a form of intermediate state between these structures.

All of these distinct crystalline forms always have the same local structure around Si and O. 
In α-Silica the Si–O bond length is 161 pm, whereas in α-tridymite it is in the range 154–171 pm. 
The Si–O–Si angle also varies between a low value of 140° in α-tridymite, up to 180° in β-tridymite. 

In α-Silica, the Si–O–Si angle is 144°.
SiO2 is most commonly encountered in nature as Silica, which comprises more than 10% by mass of the Earth's crust.
Silica is the only polymorph of silica stable at the Earth's surface. 

Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism. 
The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks. 
In many parts of the world, silica is the major constituent of sand.

Even though it is poorly soluble, silica occurs in many plants such as rice. Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates. 
Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by herbivores may have developed as a defense mechanism against predation.
Silica is also the primary component of rice husk ash, which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing.

Silicification in and by cells has been common in the biological world and it occurs in bacteria, protists, plants, and animals (invertebrates and vertebrates).
Silica, also called Silica dioxide, compound of the two most abundant elements in Earth’s crust, Silica and oxygen, SiO2.
The mass of Earth’s crust is 59 percent silica, the main constituent of more than 95 percent of the known rocks.

Silica has three main crystalline varieties: Silica (by far the most abundant), tridymite, and cristobalite.
Other varieties include coesite, keatite, and lechatelierite.
Silica sand is used in buildings and roads in the form of portland cement, concrete, and mortar, as well as sandstone.

Silica also is used in grinding and polishing glass and stone; in foundry molds; in the manufacture of glass, ceramics, Silica carbide, ferroSilica, and Silicaes; as a refractory material; and as gemstones.
Silica gel is often used as a desiccant to remove moisture.
It can also be produced by vaporizing Silica sand in a 3000 °C electric arc. 

Both processes result in microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles, a white powder with extremely low bulk density (0.03-0.15 g/cm3) and thus high surface area.
The particles act as a thixotropic thickening agent, or as an anti-caking agent, and can be treated to make them hydrophilic or hydrophobic for either water or organic liquid applications.
Silica fume is an ultrafine powder collected as a by-product of the Silica and ferroSilica alloy production. 

Silica consists of amorphous (non-crystalline) spherical particles with an average particle diameter of 150 nm, without the branching of the pyrogenic product. 
The main use is as pozzolanic material for high performance concrete. 
Fumed silica nanoparticles can be successfully used as an anti-aging agent in asphalt binders.

Silica, either colloidal, precipitated, or pyrogenic fumed, is a common additive in food production. 
Silica is used primarily as a flow or anti-caking agent in powdered foods such as spices and non-dairy coffee creamer, or powders to be formed into pharmaceutical tablets.
It can adsorb water in hygroscopic applications. 

Colloidal silica is used as a fining agent for wine, beer, and juice, with the E number reference E551.
In cosmetics, silica is useful for its light-diffusing properties and natural absorbency.
Diatomaceous earth, a mined product, has been used in food and cosmetics for centuries. 

Silica consists of the silica shells of microscopic diatoms; in a less processed form it was sold as "tooth powder".
Manufactured or mined hydrated silica is used as the hard abrasive in toothpaste.
Silica is the name given to a group of minerals composed of Silica and oxygen, the two most abundant elements in the earth's crust.

Silica is found commonly in the crystalline state and rarely in an amorphous state.
Silica is composed of one atom of Silica and two atoms of oxygen resulting in the chemical formula SiO2.
The rst industrial uses of crystalline silica were probably related to metallurgical and glass making activities in three to ve thousand years BC.

Silica has continued to support human progress throughout history, being a key raw material in the industrial development of the world especially in the glass, foundry and ceramics industries.
Silica contributes to today's information technology revolution being used in the plastics of computer mouses and providing the raw material for Silica chips.
Silica has widespread industrial applications including use as a food additive, i.e., anti-caking agent, as a means to clarify beverages, control viscosity, as an anti-foaming agent, dough modier, and as an excipient in drugs and vitamins.

Chemically, silica is an oxide of Silica, viz., Silica dioxide, and is generally colorless to white and insoluble in water.
When associated with metals or minerals the family of silicates is formed.
There are several water soluble forms of silica referred collectively to as silicic acid (ortho, meta, di, and tri-silicates), which are present in surface and well water in the range of 1--100 mg/L.

Orthosilicic acid is the form predominantly absorbed by humans and is found in numerous tissues including bone, tendons, aorta, liver and kidney.
Compelling data suggest that silica is essential for health although no RDI has been established.
Silica gel from Merck is a powerful drying agent suitable for drying practically all gases and liquids.

Silica can thus be used in a wide range of applications, for instance in desiccators packed drying towers, for protecting moisturesensitive substances during storage and transport or for maintaining the dryness of anhydrous solvents.
Silica gel has a high adsorptive capacity for moisture, and its performance is practically temperature-independent up to approx. 65°C.
Another advantage of silica gel is its ease of use and disposal thanks to its high chemical inertness and non-toxicity.

In addition to white silica gel as granulates in dierent sizes or beads, Merck also provides self-indicating silica gel with iron salt moisture indicator in beaded or granular form.
Fumed silica is a mineral mixture composed of submicron particles of amorphous Silica dioxide (100 to 150 times smaller than a grain of cement)
Silica strengthens steel corrosion in concrete due to its extremely low permeability to chloride-ion ingress and high electrical resistance.

When added to ready-mixed concrete and ready-mixed concrete, silica fumed produces high-performance, high-strength concretes that extend the service life and increase the structural economy. 
Silica prevents the ingress of moisture, chemicals and other contaminants and provides more sealing.

Provides signicantly greater resistance to corrosion, abrasion and erosion, chemical attack and freeze/thaw damage.
Silica is more ecient in precast concrete (made in the production environment) and saves cost and time.

Melting point: 1610 °C (lit.)
Boiling point: 2230 °C
Density: 2.6 g/mL at 25 °C (lit.)
Bulk density: 1400 kg/m³
Refractive index: n20/D 1.544 (lit.)
Storage temp.: no restrictions.
Solubility: insoluble in H₂O, acid solutions; soluble in HF
Form: powder
Color: white
Specific Gravity: 2.2-2.6
pH: 5-8 (400g/l, H₂O, 20℃) (slurry)
Water solubility: insoluble
Crystal structure: Silica type
Crystal system: Three sides
Space group: P3221
Dielectric constant: 4.2 (0.0℃)
Exposure limits: ACGIH: TWA 0.025 mg/m³, OSHA: TWA 50 μg/m³, NIOSH: IDLH 50 mg/m³; TWA 0.05 mg/m³
Stability: Stable
InChIKey: VYPSYNLAJGMNEJ-UHFFFAOYSA-N
Hardness, Vickers: 1103 - 1260
Hardness, Mohs: 7.0
Hardness, Knoop: 666 - 902
Drilling Hardness: 7648

Silica is found naturally in the environment. 
Silica is a compound made from Silica and oxygen and can come in different forms. 
All silica forms are made from the same chemicals but can have different structures. 

Silica is divided into two main groups, crystalline silica and amorphous silica (non-crystalline silica). 
The most common type of crystalline silica is Silica. 
Other types also exist, but they are less common.

Silica compounds are found throughout the environment in rocks, sand, clay, soil, air, and water. 
Silica is used in many commercial products, such as bricks, glass and ceramics, plaster, granite, concrete, cleansers, skin care products, and talcum powder. 
Some forms of amorphous silica are used as food additives, food wrappings, toothpaste and cosmetics.

Silica nanostructures nd applications in drug delivery, catalysis, and composites, however, understanding of the surface chemistry, aqueous interfaces, and biomolecule recognition remain dicult using current imaging techniques and spectroscopy.
A silica force eld is introduced that resolves numerous shortcomings of prior silica force elds over the last 30 years and reduces uncertainties in computed interfacial properties relative to experiment from several 100% to less than 5%.
In addition, a silica surface model database is introduced for the full range of variable surface chemistry and pH (Q2, Q3, Q4 environments with adjustable degree of ionization) that have shown to determine selective molecular recognition.

The force eld enables accurate computational predictions of aqueous interfacial properties of all types of silica, which is substantiated by extensive comparisons to experimental measurements.
The parameters are integrated into multiple force elds for broad applicability to biomolecules, polymers, and inorganic materials (AMBER, CHARMM, COMPASS, CVFF, PCFF, INTERFACE force elds).
The systematic analysis of binding conformations and adsorption free energies of distinct peptides to silica surfaces will be reported separately in a companion paper.
 
Also called silica sand or Silica sand, silica is Silica dioxide (SiO2). 
Silica compounds are the most significant component of the Earth’s crust. 
Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of Silica. 

The metamorphic rock, Silicaite, is another source.
Silica (Si) is a semi-metallic or metalloid, because it has several of the metallic characteristics. 
Silica is never found in its natural state, but rather in combination with oxygen as the silicate ion SiO44- in silica-rich rocks such as obsidian, granite, diorite, and sandstone. 

Feldspar and Silica are the most significant silicate minerals. 
Silica alloys include a variety of metals, including iron, aluminum, copper, nickel, manganese and ferrochromium.
A variety of chalcedony thatforms in rock cavities and has a patternof concentrically arranged bandsor layers that lie parallel to the cavitywalls. 

These layers are frequently alternatingtones of brownish-red.
Moss agate does not show the samebanding and is a milky chalcedonycontaining mosslike or dendritic patternsformed by inclusions of manganeseand iron oxides. 
Agates areused in jewellery and for ornamentalpurposes.

The most abundant andcommon mineral, consisting of crystallinesilica (Silica dioxide, SiO2),crystallizing in the trigonal system. 
Silica has a hardness of 7 on the Mohs’scale. 
Well-formed crystals of Silicaare six-sided prisms terminating insix-sided pyramids. 

Silica is ordinarily colourless and transparent, in which form it is known as rock crystal.
Coloured varieties, a number ofwhich are used as gemstones, includeamethyst, citrine Silica (yellow),rose Silica (pink), milk Silica(white), smoky Silica (grey-brown),chalcedony, agate, and jasper.
Silica occurs in many rocks, especiallyigneous rocks such as graniteand Silicaite (of which it is the chiefconstituent), metamorphic rockssuch as gneisses and schists, and sedimentary rocks such as sandstone andlimestone. 

The mineral is piezoelectricand is used in oscillators. 
Silica isalso used in optical instruments andin glass, glaze, and abrasives.
Silica is the second-most abundant element on Earth, behind oxygen. 

Almost 30% of our planet’s crust is made of the stuff, so it isn’t surprising that it’s also found in food.
However, Silica is rarely found on its own. Instead, it combines with oxygen and other elements to form silicate materials, which are the largest class of rock-forming materials on Earth and compose 90% of the Earth’s crust. 

One such material is silica, or Silica dioxide, which is the most common component of sand.
Silica is also found naturally in some foods, and it is added to many food products and supplements. 
It is commonly used in the form of Silica dioxide as an anti-caking agent in foods and supplements to keep ingredients from clumping up or sticking together, and it’s sometimes added to liquids and beverages to control foaming and thickness.

Silica is one of the most common hazards on a worksite, particularly in the construction, oil and gas, manufacturing, and agriculture industries. 
Silica dust can cause silicosis, a serious and irreversible lung disease. 
It can also cause lung cancer. Cutting, breaking, crushing, drilling, grinding, or blasting concrete or stone releases the dust. 

As workers breathe in the dust the silica settles in their lungs.
Silica was not mutagenic in bacterial assays; both positive and negative results have been reported in a wide variety of in vivo and in vitro genotoxic assays.
Alpha Silica is the most stable form of solid SiO2 at room temperature. 

The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than Silica. 
The transformation from α-Silica to beta-Silica takes place abruptly at 573 °C. 
Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature limit.

The high-pressure minerals, seifertite, stishovite, and coesite, though, have higher densities and indices of refraction than Silica.
Stishovite has a rutile-like structure where Silica is 6-coordinate. 
The density of stishovite is 4.287 g/cm3, which compares to α-Silica, the densest of the low-pressure forms, which has a density of 2.648 g/cm3.

The difference in density can be ascribed to the increase in coordination as the six shortest Si–O bond lengths in stishovite (four Si–O bond lengths of 176 pm and two others of 181 pm) are greater than the Si–O bond length (161 pm) in α-Silica.
The change in the coordination increases the ionicity of the Si–O bond.
Silica, another polymorph, is obtained by the dealumination of a low-sodium, ultra-stable Y zeolite with combined acid and thermal treatment. 

The resulting product contains over 99% silica, and has high crystallinity and specific surface area (over 800 m2/g).
Silica has very high thermal and acid stability. 
For example, it maintains a high degree of long-range molecular order or crystallinity even after boiling in concentrated hydrochloric acid.

Silica exhibits several peculiar physical characteristics that are similar to those observed in liquid water: negative temperature expansion, density maximum at temperatures ~5000 °C, and a heat capacity minimum.
Its density decreases from 2.08 g/cm3 at 1950 °C to 2.03 g/cm3 at 2200 °C.
The molecular SiO2 has a linear structure like CO2. 

Silica has been produced by combining Silica monoxide (SiO) with oxygen in an argon matrix. 
The dimeric Silica dioxide, (SiO2)2 has been obtained by reacting O2 with matrix isolated dimeric Silica monoxide, (Si2O2). 
In dimeric Silica dioxide there are two oxygen atoms bridging between the Silica atoms with an Si–O–Si angle of 94° and bond length of 164.6 pm and the terminal Si–O bond length is 150.2 pm. 

The Si–O bond length is 148.3 pm, which compares with the length of 161 pm in α-Silica. 
The bond energy is estimated at 621.7 kJ/mol.
Silica is the primary ingredient in the production of most glass. 

As other minerals are melted with silica, the principle of freezing point depression lowers the melting point of the mixture and increases fluidity. 
The glass transition temperature of pure SiO2 is about 1475 K.
When molten Silica dioxide SiO2 is rapidly cooled, it does not crystallize, but solidifies as a glass.

Because of this, most ceramic glazes have silica as the main ingredient.
The structural geometry of Silica and oxygen in glass is similar to that in Silica and most other crystalline forms of Silica and oxygen, with Silica surrounded by regular tetrahedra of oxygen centres. 
The difference between the glass and crystalline forms arises from the connectivity of the tetrahedral units: Although there is no long-range periodicity in the glassy network, ordering remains at length scales well beyond the SiO bond length. 

One example of this ordering is the preference to form rings of 6-tetrahedra.
The majority of optical fibers for telecommunications are also made from silica. 
Silica is a primary raw material for many ceramics such as earthenware, stoneware, and porcelain.

The solubility of Silica dioxide in water strongly depends on its crystalline form and is three to four times higher for amorphous silica than Silica; as a function of temperature, it peaks around 340 °C (644 °F).
This property is used to grow single crystals of Silica in a hydrothermal process where natural Silica is dissolved in superheated water in a pressure vessel that is cooler at the top. 
Crystals of 0.5–1  kg can be grown for 1–2 months.

These crystals are a source of very pure Silica for use in electronic applications.
Above the critical temperature of water 647.096 K (373.946 °C; 705.103 °F) and a pressure of 22.064 megapascals (3,200.1 psi) or higher, water is a supercritical fluid and solubility is once again higher than at lower temperatures.
Silica compounds are the most signicant component of the Earth’s crust.

Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of Silica.
The metamorphic rock, Silicaite, is another source.
Silica (Si) is a semi-metallic or metalloid, because it has several of the metallic characteristics.

Silica is never found in its natural state, but rather in combination with oxygen as the silicate ion SiO44- in silica-rich rocks such as obsidian, granite, diorite, and sandstone.
Feldspar and Silica are the most signicant silicate minerals.
Silica alloys include a variety of metals, including iron, aluminum, copper, nickel, manganese and ferrochromium.

Besides being the most abundant mineral on the Earth, it is also very important to life on our planet.
Diatoms, a type of phytoplankton forming the base of the ocean’s food chain, have skeletons composed of silica.

Many plants use silica to stien stems for holding fruit and to form external needles for protection.
The role of silica is less obvious in animals, but each one of us contains about half a gram of silica – without which our bones, hair, and teeth could not be formed.

Uses:
As the art of glass making developed, individuals discovered how to produce different glasses by adding various substances to the Silica melt. 
The addition of calcium strengthened the glass, and other substances imparted color to the glass. 
Iron and sulfur give brown glass, copper produces a light blue color, and cobalt a dark blue color. 

Manganese was added to produce a transparent glass, and antimony to clear the glass of bubbles. 
Most modern glass produced is soda-lime glass and consists of approximately 70% SiO2, 15% Na2O (soda), and 5% CaO (lime). 
Borosilicate glass is produced by adding about 13% B2O3. 

Borosilicate glass has a low coeffi cient of thermal expansion and is therefore very heat resistant. 
Silica is used extensively in laboratory glassware and in cooking where it is sold under the brand name Pyrex. 
Because of Silica's high melting point, it is ideal for making molds for metal casting. 

Silica is regularly used to form iron, aluminum, and copper items. 
Silica is the primary filter medium used in wastewater treatment. 
Filtration systems often modify Silica physically and chemically to produce activated Silica formulations. 

Besides water treatment, activated Silica gels used for chromatography in chemistry laboratories. 
In the construction industry, Silica glass is used as fiber glass insulation, Silica sand is a basic ingredient in cement and concrete, and is used indirectly in building products. 
Silica is used as filler in paints, adhesives, rubber, and coatings. 

Silica is added to personal care products such as tooth polishes.
Formulators may select Silica as an alternative to diatomaceous earth or clay, particularly when developing mineral make-up, pressed or loose powders. 
Silica has abrasive, absorbent, and anti-caking properties, and can also reduce the transparency of a formulation. 

Silica is the U.S. name for what is known as solum diatomeae.
Electronic components; piezoelectric control in filters, oscillators, frequency standards, wave filters, radio and TV components; barrel-finishing abra- sive.
Sand, white silica has been employed as a solid sample to evaluate the pore-volume variations during fluid-rock interaction experiments.

Silica is an anticaking agent, carrier, and dispersant that can absorb approximately 120% of its weight and remain free flowing. 
Silica is used in salt, flours, and powdered soups to prevent caking caused by moisture. 
It is also used in powdered coffee whitener, vanilla powder, baking powder, dried egg yolk, and tortilla chips. 

Silica is also termed silica, amorphous.
Crushed and graded Silica is used as the abrasive in flint sandpapers. 
Almost any deposit of massive white Silica is suitable. 

Being the cheapest of all the abrasive-coated paper, this product is still sold in fair amounts, mainly in hardware stores and by small jobbers. 
Silica is made only in the form of paper, not as cloth. 
True chalk flint from England and France is used extensively for this purpose in Europe; it has better cutting qualities and longer life than ordinary Silica. 

Crushed and ground sand, sandstone, powdered Silica, and silt are sometimes used in hand soaps, scouring compounds, and harsher metal polishes.
Cristobalite is used in the manufacture of water glass, refractories, abrasives, ceramics and enamels. 
Silica is used as a mineral, natural or synthetic fiber. 

Tridymite is used as a filtering and insulating media and as a refractory material for furnace linings.
Workers are potentially exposed to crystalline silica in such industries as granite quarrying and cutting, foundry operations; metal, coal, dentistry, painting, and nonmetallic mining; and manufacture of clay and glass products.
About 95% of the commercial use of Silica dioxide (sand) is in the construction industry, e.g. in the production of concrete (Portland cement concrete).

Certain deposits of silica sand, with desirable particle size and shape and desirable clay and other mineral content, were important for sand casting of metallic products.
The high melting point of silica enables it to be used in such applications such as iron casting; modern sand casting sometimes uses other minerals for other reasons.
Crystalline silica is used in hydraulic fracturing of formations which contain tight oil and shale gas.

Hydrophobic silica is used as a defoamer component.
In its capacity as a refractory, it is useful in fiber form as a high-temperature thermal protection fabric.
Silica is used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes.

Silica aerogel was used in the Stardust spacecraft to collect extraterrestrial particles.
Pure silica (Silica dioxide), when cooled as fused Silica into a glass with no true melting point, can be used as a glass fibre for fibreglass.
One of the most common uses of silica is in the production of glass. 

Silica is a major component of the raw materials used in making glass, such as windows, bottles, and fiberglass. 
Silica’s high melting point and durability make it ideal for this purpose, allowing glass to withstand high temperatures and external stresses.
In the electronics industry, silica is used to produce semiconductors and other components found in computer chips, transistors, and photovoltaic cells. 

High-purity silica is required in these applications because of its excellent insulating properties, which are essential for the functioning of electronic devices.
Silica is a key ingredient in cement, concrete, and mortar, making it essential for construction and building materials. 
It contributes to the strength, durability, and hardness of concrete, which is why it is used extensively in building foundations, roads, bridges, and other structures. 

Additionally, silica sand is used to produce tiles, bricks, and other architectural elements.
In the paint and coatings industry, silica is used as a filler, thickener, and anti-settling agent. 
Silica improves the texture and consistency of paints, helping them to adhere to surfaces and resist wear and tear. 

Silica also enhances the durability of coatings, making them resistant to weathering, corrosion, and abrasion.
Silica is widely used in the cosmetics industry, particularly in skincare and makeup products. 
It acts as an absorbent to control moisture, oil, and sweat, and is used in products like powders, foundations, and deodorants. 

Silica also helps improve the spreadability and texture of formulations, ensuring that products apply smoothly to the skin.
Due to its porous structure, silica is used in filtration systems, particularly for water purification. 
Silica sand is commonly used in filters for swimming pools, drinking water treatment plants, and industrial applications. 

The fine particles of silica can trap impurities and particles, improving the quality of the water being filtered.
In the production of rubber and plastic materials, silica is used as a reinforcing agent. 
Silica improves the mechanical properties of rubber, such as its strength, durability, and wear resistance. 

Silica is also used in the manufacture of tires, as it helps reduce rolling resistance and improves fuel efficiency in vehicles.
Silica is used in the food industry as an anti-caking agent to prevent the clumping of powders, such as powdered sugar, salt, and spices. 
It helps maintain the flowability of these products, ensuring that they remain free-flowing and easy to use.

Silica is a critical material in the production of ceramics, such as porcelain, tiles, and pottery, due to its heat resistance and stability. 
It is also used in the manufacture of refractories, which are materials designed to withstand high temperatures in industrial furnaces and kilns. 
Silica’s high melting point makes it ideal for these applications.

Silica is used in agriculture as a soil conditioner and a source of nutrients for plants. 
It helps improve the structure of the soil, making it more fertile and resistant to erosion. 
Silica also contributes to the strengthening of plant cell walls, enhancing their resistance to pests, diseases, and environmental stress.

Safety Profile:
Confirmed carcinogen with experimental carcinogenic, tumorigenic, and neoplastigenic data. 
Experimental poison by intratracheal and intravenous routes.
Human systemic effects by inhalation: cough, dyspnea, liver effects. 

Incompatible with OF2, vinyl acetate. 
Inhaling finely divided crystalline silica dust can lead to silicosis, bronchitis, or lung cancer, as the dust becomes lodged in the lungs and continuously irritates the tissue, reducing lung capacities.
When fine silica particles are inhaled in large enough quantities (such as through occupational exposure), it increases the risk of systemic autoimmune diseases such as lupus and rheumatoid arthritis compared to expected rates in the general population.

Silica is an occupational hazard for people who do sandblasting or work with powdered crystalline silica products. 
Amorphous silica, such as fumed silica, may cause irreversible lung damage in some cases but is not associated with the development of silicosis. 
Children, asthmatics of any age, those with allergies, and the elderly (all of whom have reduced lung capacity) can be affected in less time.

Crystalline silica is an occupational hazard for those working with stone countertops because the process of cutting and installing the countertops creates large amounts of airborne silica.
Crystalline silica used in hydraulic fracturing presents a health hazard to workers.

Inhaling finely divided crystalline silica can lead to severe inflammation of the lung tissue, silicosis, bronchitis, lung cancer, and systemic autoimmune diseases, such as lupus and rheumatoid arthritis. 
Inhalation of amorphous silica, in high doses, leads to non-permanent short-term inflammation, where all effects heal.

Health Hazard:
Exposure to Silica can result in the disease called silicosis. 
Silicosis is a disabling, nonreversible, and sometimes fatal lung disease caused by overexposure to respirable crystalline Silica. 
In silicosis, Silica particles enter the lung where they become trapped, producing areas of swelling. 

The swelling results in nodules that become progressively larger as the condition worsens. 
Silicosis is defined at several levels of severity: chronic silicosis, accelerated silicosis, and acute silicosis. 
Chronic silicosis results from long-term (20 years) exposure to low concentrations of Silica, whereas acute silicosis is the result of a short-term exposure (a year or less) to high concentrations. 

Symptoms may not be obvious in cases of chronic silicosis and x-ray screening is recommended for at-risk groups. 
These include sand-blasters, miners, laborers who regularly saw, drill, and jack-hammer concrete, and general construction such as tunnel drilling. 
In advanced stages of silicosis, individuals have difficulty breathing, especially when active.