Silica is Silicon Dioxide is an oxide of Silicon with the chemical formula SiO2 and they are most commonly found in the nature as Quartz, and also in various living organisms. In major parts of the word, This is a major constituent of Sand. It is one of the most complex but abundant material families and exists as a compound of several minerals and also as a synthetic product. Examples are fused quartz, silica gel, fumed silica, aerogels etc. They are also used in the food industry, as electrical insulator etc.
SiO2 has many crystalline forms but however they have the same local Si and O structure.
In major silicates the atoms of silica will show the tetrahedral coordination with four oxygen atom and has one central Si atom. They have three-dimensional network in which each of the silicon atom is covalently bonded to four oxygen atoms. However in the CO2 it is a linear structure.
Natural occurrence for SiO2: They are mostly present as Quartz and by mass is about 10 percent of the earths crust. It is a polymorph of silica stable and during metamorphism they form high impacting structures and it is associated with Eclogites. The high temperature forms of tridymite and are known from silica rich volcanic rocks. Silica is a major constituent of Sand.
For Biology standpoint: Silica occur in many plants and plant with big silica appear to be important to grazing animals from chewing insects to others. Silica accelerates tooth wearing and high silica levels are used in plants are eaten by animals which in turn form a defence mechanism against predators. Silica is used for filtration and cement manufacturing. In modern world it is available in Bacteria single celled organisms and other plants. Also present in Rice husk and dicotyledons.
In the natural environment, the minerals are crystallised and that is undersaturated with respect to silicon, and under conditions of neutral pH and low temperature. Silica is important for animal nutrients. It certainly does occur in the living body, creating the challenge of creating silica-free controls. It is important for the growth, strength and management for many tissues and also important for biochemistry of many sub cellular enzyme containing structures.
Uses Of Silica:
- Silica is most used for industrial and commercial use for the production of concrete which is the Portland concrete Cement.
- They are also used for sand casting for metallic products and since sometimes the silica have desirable particle size, shape and clay in them that is why it helps in such productions.
- Silica has very high melting point hence it is used for iron casting, modern sand casting and also sometimes uses other minerals together for this.
- Crystal Silica is used for hydraulic fracturing of oil and gas shales.
- In Cosmetics, Silica is used for light diffusing and high absorbency properties.
- This is also used for elemental silicon production and this process thus uses carbothermic reduction in an electric arc furnace.
- Silicon Dioxide is a major constituent for raw material in Porcelain, Earth Ware, Stone Ware, Ceramics.
- Many telecommunication optic fibres uses Silica as its component.
- Colloidal Silica is used as a fining agent in Wine, Beer etc
- They are a common addition to the food industry and and food production, It s used as a anti caking agent and powdered foods to spices, non dairy coffee creamer etc.
- Glass is primarily made by Silica and as other minerals melt with Silica the principle of freezing point lower the mixture melting point and thus the fluid structure increases. When we cool down the molten form of SiO2 it will not crystalline but it rather solidifies as Glass. Thus most of the Ceramic Glazes have Silica as main ingredient.
- The diatomaceous earth is used for food and cosmetics industries for centuries and it consists of Silica Shells and diatoms. In the less processed form it is sold as Tooth Powder and sometimes the hydrated Silica is used as toothpaste as an abrasive.
- The structural geometry of Silicon and Oxygen in the glass is very same to Quartz and most other crystalline forms of silicon and oxygen that has silicon that is surrounded by tetra hedra of oxygen. Thus the basic structure of Glass and others it is the connectivity to the tetrahydra units.
Polymorphism Of Silica:
Alpha Quartz is the most stable form of Solid SiO2 at the room temperature. The high temperature ones which are Tridymite and cristobalite have low densities and refraction of indices than the regular quartz. Learn When alpha quartz is heated to 575^(0) C it changes to?
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