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CAS NO.: 112945-52-5
EC/LIST NO .: 231-545-4
Silica is the name given to a group of minerals composed of silicon 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 silicon and two atoms of oxygen resulting in the chemical formula SiO2.
The first industrial uses of crystalline silica were probably related to metallurgical and glass making activities in three to five 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 silicon chips.
silica, also called silicon dioxide, compound of the two most abundant elements in Earth’s crust, silicon 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: quartz (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, silicon carbide, ferrosilicon, and silicones; as a refractory material; and as gemstones.
Silica gel is often used as a desiccant to remove moisture.
Silica is one of the most common minerals in the earth's crust.
Glass, beach sand, silicon, and granite are all silica materials.
There are two forms of silica - crystalline and non-crystalline
The most common form of crystalline silica is quartz, which is found in sand, gravel, clay, granite, diatomaceous earth, and many other rock forms.
Non-crystalline silica is found in glass, silicon carbide, and silicon.
Silica is a sodium silicate produced in a laboratory environment, which prevents the deterioration of foods, vegetable products, leather goods, chemical dyes and many perishable things in daily life by absorbing moisture.
This substance was patented in 1919 by Walter A. Patrick, a professor at Johns Hopkins University.
The substance has a large sandy structure.
The substance changes color with moisture.
This substance is placed next to medicines in daily life, absorbs its moisture and thus prevents it from spoiling, at the same time, most plant-based industrial products and foods are protected in this way.
Leather and living-based items are also protected from rotting in this way.
This substance changes color by absorbing the moisture in the environment where it is placed.
Today, it is offered for sale in different sizes.
multiple forms of silica exist in nature and silicon, a component, is the second most prevalent element after oxygen.
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 modifier, and as an excipient in drugs and vitamins.
Chemically, silica is an oxide of silicon, viz., silicon 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 moisture-sensitive 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 different 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 silicon 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 significantly greater resistance to corrosion, abrasion and erosion, chemical attack and freeze/thaw damage.
Silica is more efficient in precast concrete (made in the production environment) and saves cost and time.
FUME SILICA provides high early and higher ultimate compressive strength.
Eliminates steam cure.
Silica saves on heating costs.
In shotcrete applications, there is less material waste and greater product use efficiency.
FUME SILICA provides high electrical resistance and impermeability.
Mitigating factors that strengthen steel corrosion.
Enhanced bonding strength. Provides thicker applications with each nozzle pass.
Crystalline silica (or silicon dioxide, SiO2) is a mineral that is naturally found in the Earth’s crust and whose three main forms are quartz, cristobalite and tridymite.
Crystalline silica, and notably quartz, can be found in many rocks (sandstone, granite, sand, etc.) at varying concentrations.
Sand is almost exclusively made of quartz and is therefore a source of crystalline silica.
Crystalline silica has a 3-dimensional structure that forms crystalline domains, which means that the presence of crystals can be observed on the microscopic level.
Amorphous silica is also a compound with the formula SiO2 but its atom arrangement is more chaotic – on the microscopic level, they do not form a well-arranged structure and do not have any particular order.
This structural difference has a major impact on the toxicity of silica.
Silica is therefore important to check what kind of silica is being used.
The different kinds of crystalline and amorphous silica are presented in .
Silicates (sodium silicate, calcium silicate, magnesium silicate, potassium silicate, etc.) are derivatives of silica.
The SiO2 groups are bound to other atoms, such as Al, Ca, Mg, K, etc. Thus they are not the same chemical entity and have different toxicity.
Silica is a natural substance found in varying amounts in most rocks, sand and clay. For example, sandstone contains more than 70% silica, whereas granite might contain 15-30%. Silica is also a major constituent of construction materials such as bricks, tiles, concrete and mortar.
You generate dust from these materials during many common construction tasks.
These include cutting, drilling, grinding and polishing.
Some of this dust is fine enough to get deep into your lungs.
The fine dust is known as respirable crystalline silica (RCS) and is too fine to see with normal lighting.
Silica is commonly called silica or silica dust.
Millions of U.S. workers are exposed to respirable crystalline silica, also known as silica dust, in a variety of industries, including construction, mining, oil and gas extraction, stone countertop fabrication, foundries and other manufacturing settings.
Silica dust is made up of small particles that become airborne during various work activities including cutting, drilling, chipping, sanding, or grinding materials that contain crystalline silica.
These materials can include sand, concrete, brick, block, stone, and mortar.
Silica dust (crystalline silica) is found in some stone, rock, sand, gravel and clay.
The most common form is quartz. Silica dust can also be found in the following products:
bricks
tiles
concrete
some plastic material.
When these materials are worked on, silica is released as a fine dust known as respirable crystalline silica or silica dust.
Also called silica sand or quartz sand, silica is silicon dioxide (SiO2).
Silicon 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 silicon.
The metamorphic rock, quartzite, is another source.
Silicon (Si) is a semi-metallic or metalloid, because it has several of the metallic characteristics.
Silicon 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 quartz are the most significant silicate minerals.
Silicon 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 stiffen 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.
Not only does silica play an important role in biology, it had played an important role in civilization.
Flint is a form of silica that was used in ancient tools.The sand used in pottery is also a form of silica.
Two-thousand year-old Roman cement contains amorphous silica from volcanic ash which helps give it high strength and durability.
Present technology would be very different without the silica used to create the catalysts of our oil refineries, bind the molds for casting super-alloys, form modern glass and ceramics, and polish electronic materials.
Silica is another name for silicon oxides - the most prevalent type being SiO2.
Silica can be found in nature in crystalline form (as quartz sand), and it is the most abundant component of the earth's crust.
Amorphous silica, on the other hand, is industrially manufactured in a variety of forms - including silica gels, precipitated silica, fumed silica, and colloidal silica.
Silica is the common name for silicon dioxide, a white or colorless crystalline compound found naturally in sand, granite and many other types of rocks.
Concrete and masonry products, the primary materials used in road construction, contain both silica sand and rock containing silica.
Silica is a natural compound, found all around us in nature.
Silica makes up over a quarter of the planet's crust and can be found in most rocks, clays and sands.
Silicas forms include emerald, quartz, clay and glass.
Silica has multiple uses in industry – for example, in concrete – and in foods, including as an anti-caking agent.
There's lots of evidence that its water-soluble form, which is found in certain plants – including the herb horsetail3 – is highly beneficial to health.
Traditionally, horsetail has been used to treat wounds, strengthen connective tissue and support the kidneys
Quartz is the most common form of crystalline silica and is the second most common mineral on the earth’s surface.
Silica is found in almost every type of rock i.e. igneous, metamorphic and sedimentary.
Since it is so abundant, quartz is present in nearly all mining operations.
Cristobalite is scarce in nature. Some volcanic rocks and meteorites may contain small amounts of it.
Cristobalite may also form when quartz is heated at high temperatures starting at 450°C.
This is especially true during production and use of refractory materials and/or during calcination of silica (between 800 and 1110°C).
As a result, there is a likelihood of exposure to cristobalite in occupational settings
Tridymite is also a scarce mineral that is only found in nature in volcanic rocks and meteorites.
Tridymite, however, differs from cristobalite in that it is not stable during quartz and refractory materials heating processes at conventional process temperatures.
As a result, exposures are very unlikely to occur in occupational or other settings.
The respirable dust fraction corresponds to the proportion of an airborne particle, which penetrates to the pulmonary alveolar region of the lungs.
Respirable crystalline silica is the respirable dust fraction of crystalline silica which enters the body by inhalation.
This term applies to workplace atmospheres.
The three major forms of crystalline silica -quartz, tridymite and cristobalite- are stable at different temperatures and have subdivisions.
For instance, geologists distinguish between alpha and beta quartz.
When low temperature alpha quartz is heated at atmospheric pressure it changes to beta quartz at 573oC.
At 870oC tridymite is formed and cristobalite is formed at 1470oC.
The melting point of silica is 1610oC, which is higher than iron, copper and aluminium, and is one reason why it is used to produce moulds and cores for the production of metal castings.
The crystalline structure of quartz is based on four oxygen atoms linked together to form a three-dimensional shape called a tetrahedron with one silicon atom at its centre.
Myriads of these tetrahedrons are joined together by sharing one another's corner oxygen atoms to form a quartz crystal.
Quartz is usually colourless or white but is frequently coloured by impurities, such as iron, and may then be any colour.
Quartz may be transparent to translucent, hence its use in glassmaking, and have a vitreous lustre.
Quartz is a hard mineral owing to the strength of the bonds between the atoms and it will scratch glass.
It is also relatively inert and does not react with dilute acid. These are prized qualities in various industrial uses.
Depending on how the silica deposit was formed, quartz grains may be sharp and angular, sub-angular, sub-rounded or rounded.
Foundry and filtration applications require sub-rounded or rounded grains for best performance.
Silica is a naturally occurring material in minerals, flint and in some plants in crystalline phase.
Silica commonly used in industries is in synthetic form.
Surface area, pore volume, pore size and particle size are independently controllable to some extent.
The crystalline silica may be classified based on atmospheric pressure as:
a. Quartz: = 1143K
b. Tridymite: 1143 - 1743K
c. Cristobalite: = 1743, over 1973K it forms amorphous vitreous silica glass.
Silicas chemical formula is SiO2.
Silica is volatile because of its very light specific gravity.
This substance, which has an amorphous structure, is a hydrophilic fuming crystalline fine powder of silicon dioxide with a specific surface of 200 m2/g.
Silica is used as a thixotropy provider and thickening agent in the polyester resin industry.
When used correctly, it prevents the resin from flowing from vertical surfaces.,
Silica exists in nine different crystalline forms or polymorphs with the three main forms being quartz, which is by far the most common, tridymite and cristobalite.
Silica also occurs in a number of cryptocrystalline forms.
Fibrous forms have the general name chalcedony and include semi-precious stone versions such as agate, onyx and carnelian.
Granular varieties include jasper and flint. There are also anhydrous forms - diatomite and opal.
Quartz is the second most common mineral in the earth's crust.
Silica is found in all three of the earths rock types - igneous, metamorphic and sedimentary.
Silica is particularly prevalent in sedimentary rocks since it is extremely resistant to physical and chemical breakdown by the weathering process.
Since it is so abundant, quartz is present in nearly all mining operations.
Silica is present in the host rock, in the ore being mined, as well as in the soil and surface materials above the bedrock, which are called the overburden.
Most of the products sold for industrial use are termed silica sand.
The word "sand" denotes a material whose grain size distribution falls within the range 0.06-2.00 millimetres.
The silica in the sand will normally be in the crystalline form of quartz.
For industrial use, pure deposits of silica capable of yielding products of at least 95% SiO2 are required.
Often much higher purity values are needed.
Silica sand may be produced from sandstones, quartzite and loosely cemented or unconsolidated sand deposits.
High grade silica is normally found in unconsolidated deposits below thin layers of overburden.
Silica is also found as "veins" of quartz within other rocks and these veins can be many metres thick.
On occasions, extremely high purity quartz in lump form is required and this is produced from quartzite rock.
Silica is usually exploited by quarrying and it is rare for it to be extracted by underground mining.
Silica scaling has the following features:
The solubility of silica depends on the system pH and temperature.
Low temperature operation, i.e., below 10 °C, and silica saturation below 120 ppm allows for operation with brine solutions supersaturated in silica with little or no silica scaling.
Operation at higher concentrations or temperature enhances the silica scaling process.
Silica forms complex precipitates with iron, aluminum, and magnesium hydroxides.
The most effective method to prevent silica scaling is to maintain its concentration below the saturation limit, which is strongly affected by the system temperature.
Silica nanostructures find applications in drug delivery, catalysis, and composites, however, understanding of the surface chemistry, aqueous interfaces, and biomolecule recognition remain difficult using current imaging techniques and spectroscopy.
A silica force field is introduced that resolves numerous shortcomings of prior silica force fields 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 field 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 fields for broad applicability to biomolecules, polymers, and inorganic materials (AMBER, CHARMM, COMPASS, CVFF, PCFF, INTERFACE force fields).
We also explain mechanistic details of molecular adsorption of water vapor, as well as significant variations in the amount and dissociation depth of superficial cations at silica–water interfaces that correlate with ζ-potential measurements and create a wide range of aqueous environments for adsorption and self-assembly of complex molecules.
The systematic analysis of binding conformations and adsorption free energies of distinct peptides to silica surfaces will be reported separately in a companion paper.
The models aid to understand and design silica nanomaterials in 3D atomic resolution and are extendable to chemical reactions.
Silica was used in synthesis of silicalite. Silica was used to assist the catalytic growth of oxide and nitride nanowires.
silica is an ultra-fine thixotropy additive used to reduce flowability in resin systems.
Silica can be used to make a resin gelcoat. It is a good filling material for structural adhesives.
Silica is an ideal choice for surfaces where non-abrasion is required.
Silica sanding is required, it should not be used more than this product.
Sanding is difficult due to its high abrasion resistance.
In ready-mixed concrete and mortars
In the refractory industry
in marine structures
Dams, tunnels, bridges and roads
On industrial floors
In Shotcrete applications
in concrete pipes
In the precast and prefab industry
Advantages:
Silica significantly increases the compressive strength of high performance concretes.
By imparting excellent abrasion and friction resistance, it seriously increases the permanence of surfaces in high traffic areas.
Silica increases the impermeability up to 100 times, making the use of microsilica ideal especially for areas exposed to chemicals.
Silica significantly reduces the corrosion effect caused by sulfate and chlorine.
Reduces rebound rate by 50% by increasing adhesion in shotcrete applications
Silica deposits are normally exploited by quarrying and the material extracted may undergo considerable processing before sale.
The objectives of processing are to clean the quartz grains and increase the percentage of silica present, to produce the optimum size distribution of product depending upon end use and to reduce the amount of impurities, especially iron and chromium, which colour glass.
Cleaning the quartz grains and increasing silica content is achieved by washing to remove clay minerals and scrubbing by attrition between particles.
Production of the optimum size distribution is achieved by screening to remove unwanted coarse particles and classification in an upward current of water to remove unwanted fine material.
Quartz grains are often iron stained and the staining may be removed or reduced by chemical reaction involving sulphuric acid at different temperatures.
Impurities present as separate mineral particles may be removed by various processes including gravity separation, froth flotation and magnetic separation.
For the highest purity, for electronics applications, extra cleaning with aggressive acids such as hydrofluoric acid combined with thermal shock may be necessary.
After processing, the sand may be dried and some applications require it to be ground in ball mills to produce a very fine material, called silica flour.
Also, quartz may be converted to cristobalite in a rotary kiln at high temperature, with the assistance of a catalyst.
Some specialist applications require the quartz to be melted in electric arc furnaces followed by cooling and grinding to produce fused silica.
The demand for long-term data storage in the cloud is reaching unprecedented levels, and continues to grow into the zettabytes.
Existing storage technologies do not provide a cost-effective solution for storing long-lived data.
Operating at such scales in the cloud requires a fundamental re-thinking of how we build large-scale storage systems, as well as the underlying storage technologies that underpin them.
Project Silica is developing the first-ever storage technology designed and built from the media up, for the cloud.
We are leveraging recent discoveries in ultrafast laser optics to store data in quartz glass by using femtosecond lasers, and building a completely new storage system designed from scratch around this technology.
This opens up an incredibly exciting opportunity to challenge and completely re-think traditional storage system design, and to co-design the future hardware and software infrastructure for the cloud.
IUPAC NAME:
Amorphous Colloidal Silica
AMORPHOUS SILICA
Amorphous Silica
Amorphous silica
amorphous silica
Amorphous silico dioxide
Amorphous silicon dioxide hydrate
Dioxide de silicium
DIOXOSILANE
Dioxosilane
dioxosilane
dioxoslian
Fumed Silica
JIOS Aerova aerogel powder
Kieselgel
Kieselsäuren, amorphe
N.A.
oxid křemičitý (amorfní)
Precipitated amorphous silica
Quarz
sand
SYNONYMS:
Silicon dioxide
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