CPU? Sand? What associations do you have with this word? Or maybe Silicon Valley?
Be that as it may, we come across silicon every day, and if you are interested in finding out what Si is and what it is eaten with, please refer to the cat.

Introduction

As a student at one of the Moscow universities, with a specialty in Nanomaterials, I wanted to introduce you, dear reader, to the most important chemical elements of our planet. I spent a long time choosing where to start, carbon or silicon, and still decided to stop at Si, because the heart of any modern gadget is based on it, so to speak, of course. I will try to express my thoughts in an extremely simple and accessible way. By writing this material, I was counting mainly on beginners, but more advanced people will also be able to learn something interesting. I would also like to say that the article was written solely to broaden the horizons of those interested. And so let's get started.

Silicium

Silicon (lat. Silicium), Si, chemical element Group IV periodic table Mendeleev; atomic number 14, atomic mass 28.086.
In nature, the element is represented by three stable isotopes: 28Si (92.27%), 29Si (4.68%) and 30Si (3.05%).
Density (at no.) 2.33 g/cm?
Melting point 1688 K


Powder Si

Historical reference

Silicon compounds, widespread on earth, have been known to man since the Stone Age. The use of stone tools for labor and hunting continued for several millennia. The use of Silicon compounds associated with their processing - glass production - began around 3000 BC. e. (V Ancient Egypt). Before others known compound Silicon - oxide SiO2 (silica). In the 18th century, silica was considered simple body and were classified as “lands” (as reflected in its name). The complexity of the composition of silica was established by I. Ya. Berzelius. For the first time, in 1825, he obtained elemental silicon from silicon fluoride SiF4, reducing the latter with potassium metal. The new element was given the name “silicon” (from the Latin silex - flint). The Russian name was introduced by G. I. Hess in 1834.

Silicon is very common in nature as part of ordinary sand.

Distribution of Silicon in nature

Silicon is the second most abundant element in the earth's crust (after oxygen), its average content in the lithosphere is 29.5% (by mass). In the earth's crust, Silicon plays the same primary role as carbon in animals and flora. For the geochemistry of silicon, its extremely strong connection with oxygen is important. About 12% of the lithosphere is silica SiO2 in the form of the mineral quartz and its varieties. 75% of the lithosphere is composed of various silicates and aluminosilicates (feldspars, micas, amphiboles, etc.). The total number of minerals containing silica exceeds 400.

Physical properties of Silicon

I don’t think there’s much point in stopping here, that’s all physical properties are freely available, but I will list the most basic ones.
Boiling point 2600 °C
Silicon is transparent to long-wave infrared rays
Dielectric constant 11.7
Silicon Mohs hardness 7.0
I would like to say that silicon is a brittle material; noticeable plastic deformation begins at temperatures above 800°C.
Silicon is a semiconductor, which is why it is widely used. The electrical properties of silicon are very dependent on impurities.

Chemical properties of Silicon

There’s a lot that could be said here, of course, but I’ll focus on the most interesting. In Si compounds (similar to carbon) 4-valentene.
In air, silicon is stable even at elevated temperatures due to the formation of a protective oxide film. In oxygen it oxidizes starting at 400 °C, forming silicon oxide (IV) SiO2.
Silicon is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids, and easily dissolves in hot alkali solutions with the release of hydrogen.
Silicon forms 2 groups of oxygen-containing silanes - siloxanes and siloxenes. Silicon reacts with nitrogen at temperatures above 1000 °C. Of great practical importance is the nitride Si3N4, which does not oxidize in air even at 1200 °C, is resistant to acids (except nitric) and alkalis, as well as to molten metals and slags, which makes it is a valuable material for the chemical industry, as well as for the production of refractories. Silicon compounds with carbon (silicon carbide SiC) and boron (SiB3, SiB6, SiB12) are characterized by high hardness, as well as thermal and chemical resistance.

Obtaining Silicon

I think this is the most interesting part, let’s take a closer look here.
Depending on the purpose there are:
1. Electronic quality silicon(so-called “electronic silicon”) - the highest quality silicon with a silicon content of over 99.999% by weight, the electrical resistivity of electronic quality silicon can be in the range from approximately 0.001 to 150 Ohm cm, but the resistance value must be ensured exclusively a given impurity, i.e., the entry of other impurities into the crystal, even if they provide a given electrical resistivity, is, as a rule, unacceptable.
2. Solar grade silicon(so-called “solar silicon”) - silicon with a silicon content of over 99.99% by weight, used for the production of photovoltaic converters (solar batteries).


3. Technical silicon- silicon blocks of polycrystalline structure obtained by carbothermic reduction from pure quartz sand; contains 98% silicon, the main impurity is carbon, characterized by a high content of alloying elements - boron, phosphorus, aluminum; mainly used to produce polycrystalline silicon.

Technical purity silicon (95-98%) is obtained in an electric arc by reducing silica SiO2 between graphite electrodes. In connection with the development of semiconductor technology, methods for producing pure and highly pure silicon have been developed. This requires the preliminary synthesis of the purest initial silicon compounds, from which silicon is extracted by reduction or thermal decomposition.
Polycrystalline silicon (“polysilicon”) is the purest form of industrially produced silicon - a semi-finished product obtained by purifying technical silicon using chloride and fluoride methods and used for the production of mono- and multicrystalline silicon.
Traditionally, polycrystalline silicon is obtained from technical silicon by converting it into volatile silanes (monosilane, chlorosilanes, fluorosilanes), followed by separation of the resulting silanes, rectification purification of the selected silane and reduction of the silane to metallic silicon.
Pure semiconductor silicon is obtained in two forms: polycrystalline(reduction of SiCl4 or SiHCl3 with zinc or hydrogen, thermal decomposition of SiI4 and SiH4) and monocrystalline(crucible-free zone melting and “pulling” a single crystal from molten silicon - Czochralski method).

Here you can see the process of growing silicon using the Czochralski method.

Czochralski method- a method of growing crystals by pulling them upward from the free surface of a large volume of melt with the initiation of crystallization by bringing a seed crystal (or several crystals) of a given structure and crystallographic orientation into contact with the free surface of the melt.

Application of Silicon

Specially doped silicon is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, thyristors; solar photocells used in spaceships, as well as a lot of other things).
Since silicon is transparent to rays with wavelengths from 1 to 9 microns, it is used in infrared optics.
Silicon has diverse and expanding applications. In metallurgy Si
used to remove oxygen dissolved in molten metals (deoxidation).
Silicon is integral part large number alloys of iron and non-ferrous metals.
Typically, Silicon gives alloys increased resistance to corrosion, improves their casting properties and increases mechanical strength; however, at higher levels Silicon can cause brittleness.
The most important are iron, copper and aluminum alloys containing silicon.
Silica is processed by glass, cement, ceramics, electrical and other industries.
Ultra-pure silicon is primarily used for the production of single electronic devices (for example, your computer processor) and single-chip microcircuits.
Pure silicon, ultra-pure silicon waste, purified metallurgical silicon in the form of crystalline silicon are the main raw materials for solar energy.
Monocrystalline silicon - in addition to electronics and solar energy, is used to make gas laser mirrors.

Ultrapure silicon and its products

Silicon in the body

Silicon is found in the body in the form of various compounds, mainly involved in the formation of hard skeletal parts and tissues. Some marine plants (for example, diatoms) and animals (for example, siliceous sponges, radiolarians) can accumulate especially large amounts of silicon, forming thick deposits of silicon (IV) oxide when they die on the ocean floor. In cold seas and lakes, biogenic silts enriched with silicon predominate; in tropical seas, calcareous silts with a low silicon content predominate. Among terrestrial plants, cereals, sedges, palm trees, and horsetails accumulate a lot of silicon. In vertebrates, the content of silicon (IV) oxide in ash substances is 0.1-0.5%. IN the largest quantities silicon is found in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 g of silicon. When there is a high content of silicon (IV) oxide dust in the air, it enters the human lungs and causes the disease silicosis.

Conclusion

Well, that's all, if you read to the end and delve a little deeper, then you are one step closer to success. I hope I didn’t write in vain and at least someone liked the post. Thank you for your attention.

Silicon in free form was isolated in 1811 by J. Gay-Lussac and L. Thénard by passing silicon fluoride vapor over metallic potassium, but it was not described by them as an element. The Swedish chemist J. Berzelius in 1823 gave a description of the silicon he obtained by treating the potassium salt K 2 SiF 6 with potassium metal at high temperature. The new element was given the name “silicon” (from the Latin silex - flint). The Russian name "silicon" was introduced in 1834 by the Russian chemist German Ivanovich Hess. Translated from ancient Greek. krhmnoz- "cliff, mountain."

Being in nature, receiving:

In nature, silicon is found in the form of dioxide and silicates of various compositions. Natural silica occurs primarily in the form of quartz, although other minerals such as cristobalite, tridymite, kitite, and cousite also exist. Amorphous silica is found in diatom deposits on the bottom of seas and oceans - these deposits were formed from SiO 2, which was part of diatoms and some ciliates.
Free silicon can be obtained by calcining fine white sand with magnesium, which chemical composition is almost pure silicon oxide, SiO 2 +2Mg=2MgO+Si. In industry, technical grade silicon is obtained by reducing the SiO 2 melt with coke at a temperature of about 1800°C in arc furnaces. The purity of silicon obtained in this way can reach 99.9% (the main impurities are carbon and metals).

Physical properties:

Amorphous silicon has the form of a brown powder, the density of which is 2.0 g/cm 3 . Crystalline silicon is a dark gray, shiny crystalline substance, brittle and very hard, crystallizing in the diamond lattice. This is a typical semiconductor (it conducts electricity better than an insulator like rubber, and worse than a conductor like copper). Silicon is fragile; only when heated above 800 °C does it become a plastic substance. Interestingly, silicon is transparent to infrared radiation, starting at a wavelength of 1.1 micrometers.

Chemical properties:

Chemically, silicon is inactive. At room temperature it reacts only with fluorine gas, resulting in the formation of volatile silicon tetrafluoride SiF 4 . When heated to a temperature of 400-500 °C, silicon reacts with oxygen to form dioxide, and with chlorine, bromine and iodine to form the corresponding highly volatile tetrahalides SiHal 4. At a temperature of about 1000°C, silicon reacts with nitrogen to form the nitride Si 3 N 4, with boron - the thermally and chemically stable borides SiB 3, SiB 6 and SiB 12. Silicon does not react directly with hydrogen.
For silicon etching, a mixture of hydrofluoric and nitric acids is most widely used.
Silicon dissolves in hot alkali solutions: Si + 2KOH + H 2 O = K 2 SiO 3 + 2H 2
Silicon is characterized by compounds with an oxidation state of +4 or -4.

The most important connections:

Silicon dioxide, SiO 2- (silicon anhydride), colorless. christ. substance, refractory (1720 C), with high hardness. Acidic oxide, chemically inactive, interacts with hydrofluoric acid and alkali solutions, in the latter case forming salts of silicic acids - silicates. Silicates are also formed when silicon oxide fuses with alkalis, basic oxides and some salts
SiO 2 + 4NaOH = Na 4 SiO 4 + 2H 2 O; SiO 2 + CaO = CaSiO 3;
Na 2 CO 3 + CaCO 3 + 6SiO 2 = Na 2 CaSi 6 O 14 + 2CO 2 (mixed sodium-calcium silicate, glass)
Silicic acids- weak, insoluble, formed when acid is added to a silicate solution in the form of a gel (gelatin-like substance). H 4 SiO 4 (orthosilicon) and H 2 SiO 3 (metasilicon, or silicon) exist only in solution and are irreversibly converted to SiO 2 when heated and dried. The resulting solid porous product is silica gel, has a developed surface and is used as a gas adsorbent, desiccant, catalyst and catalyst carrier.
Silicates- salts of silicic acids for the most part (except for sodium and potassium silicates) are insoluble in water. Soluble silicates in solution undergo severe hydrolysis.
Hydrogen compounds- analogues of hydrocarbons, silanes, compounds in which silicon atoms are connected by a single bond, strong, if the silicon atoms are connected by a double bond. Like hydrocarbons, these compounds form chains and rings. All silanes can spontaneously ignite, form explosive mixtures with air and easily react with water: SiH 4 + 2H 2 O = SiO 2 + 4H 2
Silicon tetrafluoride SiF 4, a gas with an unpleasant odor, poisonous, is formed by the action of hydrofluoric acid on silicon and many of its compounds, including glass:
Na 2 SiO 3 + 6HF = 2NaF + SiF 4 + 3H 2 O
Reacts with water to form silicon and hexafluorosilicon(H 2 SiF 6) acids:
3SiF 4 + 3H 2 O = 2H 2 SiF 6 + H 2 SiO 2
H 2 SiF 6 is close in strength to sulfuric acid, the salts are fluorosilicates.

Application:

Silicon finds its greatest use in the production of alloys for imparting strength to aluminum, copper and magnesium and for the production of ferrosilicides having important in the production of steels and semiconductor technology. Silicon crystals are used in solar cells and semiconductor devices - transistors and diodes. Silicon also serves as a raw material for the production of organosilicon compounds, or siloxanes, obtained in the form of oils, lubricants, plastics and synthetic rubbers. Inorganic compounds silicon is used in ceramics and glass technology, as an insulating material and piezocrystals

Silicon is important for some organisms biogenic element. It is part of the supporting structures in plants and skeletal structures in animals. Silicon is concentrated in large quantities by marine organisms - diatoms, radiolarians, sponges. Large amounts of silicon are concentrated in horsetails and cereals, primarily in the subfamilies of Bamboo and Rice, including rice. Human muscle tissue contains (1-2)·10 -2% silicon, bone tissue - 17·10 -4%, blood - 3.9 mg/l. Up to 1 g of silicon enters the human body with food every day.

Antonov S.M., Tomilin K.G.
HF Tyumen State University, 571 group.

Sources: Silicon Wikipedia; Silicon in the Online Encyclopedia "Around the World", ;
Silicon on site

Silicon (Si) is the second most abundant nonmetal in the earth's crust after oxygen. In nature, it is found in compounds and is rarely found in pure form. The structure of the silicon atom determines the properties of the element.

Structure

Silicon - element 14 periodic table Mendeleev, located in the third period, in group IV. Relative atomic mass - 28.

Rice. 1. Position in the periodic table.

The nucleus of a silicon atom contains 14 protons and 14 neurons and has a positive charge of +14. Around the core there are three electronic shells, which contains 14 electrons. The outer energy level is occupied by four electrons, which determine the valence of the element. Silicon exhibits the +2 oxidation state because the 3p level has two unpaired electron. An element can enter an excited state due to a vacant 3d orbital, exhibiting an oxidation state of +4.

Rice. 2. The structure of the atom.

The structure diagram of the silicon atom is 1s 2 2s 2 2p 6 3s 2 3p 2 or +14 Si) 2) 8) 4.

Physical properties

Silicon is a hard, dark gray element with a metallic luster. Is a semiconductor. It has one modification, similar in structure to the allotropic modification of carbon - diamond. However, the bonds between silicon atoms are not as strong as those between carbon atoms.

Rice. 3. Silicon.

Silicon occurs naturally in sand, clay, quartz, and silicates. Silicon dioxide (SiO 2) - sand. Silicon is obtained by calcining sand with carbon (coal) or metals:

• 2C + SiO 2 t˚→ Si + 2CO;
• 3SiO 2 + 4Al → 3Si + 2Al 2 O 3;
• 2Mg + SiO 2 t˚→ Si + 2MgO.

Silicon is used for the production of radioelements, photocells, and in the production of heat-resistant materials.

Chemical properties

Thanks to electronic structure Silicon is capable of reacting with other elements by accepting or donating electrons. In reactions with metals it acts as a reducing agent, and in reactions with non-metals it acts as an oxidizing agent. Under optimal conditions, silicon reacts only with fluorine:

Si + 2F 2 → SiF 4 .

When heated it reacts:

• with oxygen (600°C) - Si + O 2 → SiO 2 ;
• with chlorine (400°C) - Si + 2Cl 2 → SiCl 4 ;
• with carbon (2000°C) - Si + C → SiC;
• with nitrogen (1000°C) - 3Si + 2N 2 → Si 3 N 4.

It is an oxidizing agent in reactions with metals:

Si + 2Mg → Mg 2 Si.

Can react with concentrated alkalis to release hydrogen:

Si + 2NaOH + H 2 O → Na 2 SiO 3 + 2H 2.

Silicon does not react directly with hydrogen and acids, except for hydrofluoric acid HF: Si + 6HF → H 2 + 2H 2 or Si + 4HF → SiF 4 + 2H 2. A compound with hydrogen - silane (SiH 4) - is obtained by decomposition of the salt with acid - Mg 2 Si + 2H 2 SO 4 → SiH 4 - + 2MgSO 4.

What have we learned?

Silicon is a non-metal of the fourth group of the periodic table. The outer energy level of an atom contains four electrons. Has an oxidation state of +2. In nature, it is found in compounds in the form of clay, sand, quartz and other substances. There is only one modification of silicon, similar to diamond. Silicon is obtained by heating sand with coal or metals. The element reacts with non-metals, metals and alkalis. Does not react with hydrogen and acids (except for HF).

Element characteristics

14 Si 1s 2 2s 2 2p 6 3s 2 3p 2

Isotopes: 28 Si (92.27%); 29 Si (4.68%); 30 Si (3.05%)

Silicon is the second most abundant element in the earth's crust after oxygen (27.6% by mass). It is not found in a free state in nature; it is found mainly in the form of SiO 2 or silicates.

Si compounds are toxic; inhalation tiny particles SiO 2 and other silicon compounds (for example, asbestos) cause a dangerous disease - silicosis

In the ground state, the silicon atom has valence = II, and in the excited state = IV.

The most stable oxidation state of Si is +4. In compounds with metals (silicides) S.O. -4.

Methods for obtaining silicon

The most common natural silicon compound is silica (silicon dioxide) SiO 2 . It is the main raw material for producing silicon.

1) Reduction of SiO 2 with carbon in arc furnaces at 1800 "C: SiO 2 + 2C = Si + 2CO

2) High-purity Si from a technical product is obtained according to the scheme:

a) Si → SiCl 2 → Si

b) Si → Mg 2 Si → SiH 4 → Si

Physical properties of silicon. Allotropic modifications of silicon

1) Crystalline silicon - a silvery substance - gray with a metallic sheen, crystal cell type of diamond; m.p. 1415"C, boiling point 3249"C, density 2.33 g/cm3; is a semiconductor.

2) Amorphous silicon - brown powder.

Chemical properties of silicon

In most reactions, Si acts as a reducing agent:

At low temperatures, silicon is chemically inert; when heated, its reactivity increases sharply.

1. Reacts with oxygen at temperatures above 400°C:

Si + O 2 = SiO 2 silicon oxide

2. Reacts with fluorine already at room temperature:

Si + 2F 2 = SiF 4 silicon tetrafluoride

3. Reactions with other halogens occur at temperature = 300 - 500°C

Si + 2Hal 2 = SiHal 4

4. With sulfur vapor at 600°C it forms a disulfide:

5. Reaction with nitrogen occurs above 1000°C:

3Si + 2N 2 = Si 3 N 4 silicon nitride

6. At temperature = 1150°C reacts with carbon:

SiO 2 + 3C = SiC + 2CO

Carborundum is close to diamond in hardness.

7. Silicon does not react directly with hydrogen.

8. Silicon is resistant to acids. Interacts only with a mixture of nitric and hydrofluoric (hydrofluoric) acids:

3Si + 12HF + 4HNO 3 = 3SiF 4 + 4NO + 8H 2 O

9. reacts with alkali solutions to form silicates and release hydrogen:

Si + 2NaOH + H 2 O = Na 2 SiO 3 + 2H 2

10. The reducing properties of silicon are used to isolate metals from their oxides:

2MgO = Si = 2Mg + SiO 2

In reactions with metals, Si is an oxidizing agent:

Silicon forms silicides with s-metals and most d-metals.

The composition of silicides of a given metal may vary. (For example, FeSi and FeSi 2 ; Ni 2 Si and NiSi 2 .) One of the most well-known silicides is magnesium silicide, which can be obtained by direct interaction of simple substances:

2Mg + Si = Mg 2 Si

Silane (monosilane) SiH 4

Silanes (hydrogen silicas) Si n H 2n + 2, (cf. alkanes), where n = 1-8. Silanes are analogues of alkanes; they differ from them in the instability of the -Si-Si- chains.

Monosilane SiH 4 is a colorless gas with an unpleasant odor; soluble in ethanol, gasoline.

Methods of obtaining:

1. Decomposition of magnesium silicide hydrochloric acid: Mg 2 Si + 4HCI = 2MgCI 2 + SiH 4

2. Reduction of Si halides with lithium aluminum hydride: SiCl 4 + LiAlH 4 = SiH 4 + LiCl + AlCl 3

Chemical properties.

Silane is a strong reducing agent.

1.SiH 4 is oxidized by oxygen even at very low temperatures:

SiH 4 + 2O 2 = SiO 2 + 2H 2 O

2. SiH 4 is easily hydrolyzed, especially in an alkaline environment:

SiH 4 + 2H 2 O = SiO 2 + 4H 2

SiH 4 + 2NaOH + H 2 O = Na 2 SiO 3 + 4H 2

Silicon (IV) oxide (silica) SiO 2

Silica exists in the form various forms: crystalline, amorphous and glassy. The most common crystalline form is quartz. When quartz rocks are destroyed, quartz sands are formed. Quartz single crystals are transparent, colorless (rock crystal) or colored with impurities in various colors (amethyst, agate, jasper, etc.).

Amorphous SiO 2 is found in the form of the opal mineral: silica gel is artificially produced, consisting of colloidal particles of SiO 2 and being a very good adsorbent. Glassy SiO 2 is known as quartz glass.

Physical properties

SiO 2 dissolves very slightly in water, and is also practically insoluble in organic solvents. Silica is a dielectric.

Chemical properties

1. SiO 2 is an acidic oxide, therefore amorphous silica dissolves slowly in aqueous solutions of alkalis:

SiO 2 + 2NaOH = Na 2 SiO 3 + H 2 O

2. SiO 2 also interacts with basic oxides when heated:

SiO 2 + K 2 O = K 2 SiO 3;

SiO 2 + CaO = CaSiO 3

3. Being a non-volatile oxide, SiO 2 displaces carbon dioxide from Na 2 CO 3 (during fusion):

SiO 2 + Na 2 CO 3 = Na 2 SiO 3 + CO 2

4. Silica reacts with hydrofluoric acid, forming hydrofluorosilicic acid H 2 SiF 6:

SiO 2 + 6HF = H 2 SiF 6 + 2H 2 O

5. At 250 - 400°C, SiO 2 interacts with gaseous HF and F 2, forming tetrafluorosilane (silicon tetrafluoride):

SiO 2 + 4HF (gas.) = SiF 4 + 2H 2 O

SiO 2 + 2F 2 = SiF 4 + O 2

Silicic acids

Known:

Orthosilicic acid H 4 SiO 4 ;

Metasilicon (silicic) acid H 2 SiO 3 ;

Di- and polysilicic acids.

All silicic acids are slightly soluble in water and easily form colloidal solutions.

Receipt methods

1. Precipitation with acids from solutions of alkali metal silicates:

Na 2 SiO 3 + 2HCl = H 2 SiO 3 ↓ + 2NaCl

2. Hydrolysis of chlorosilanes: SiCl 4 + 4H 2 O = H 4 SiO 4 + 4HCl

Chemical properties

Silicic acids are very weak acids(weaker than carbonic acid).

When heated, they dehydrate to form silica as the final product.

H 4 SiO 4 → H 2 SiO 3 → SiO 2

Silicates - salts of silicic acids

Since silicic acids are extremely weak, their salts in aqueous solutions are highly hydrolyzed:

Na 2 SiO 3 + H 2 O = NaHSiO 3 + NaOH

SiO 3 2- + H 2 O = HSiO 3 - + OH - (alkaline medium)

For the same reason, when passing carbon dioxide Through silicate solutions, silicic acid is displaced from them:

K 2 SiO 3 + CO 2 + H 2 O = H 2 SiO 3 ↓ + K 2 CO 3

SiO 3 + CO 2 + H 2 O = H 2 SiO 3 ↓ + CO 3

This reaction can be considered as qualitative reaction to silicate ions.

Among silicates, only Na 2 SiO 3 and K 2 SiO 3 are highly soluble, which are called soluble glass, and their aqueous solutions- liquid glass.

Glass

Ordinary window glass has the composition Na 2 O CaO 6 SiO 2, i.e., it is a mixture of sodium and calcium silicates. It is obtained by fusing Na 2 CO 3 soda, CaCO 3 limestone and SiO 2 sand;

Na 2 CO 3 + CaCO 3 + 6SiO 2 = Na 2 O CaO 6SiO 2 + 2СO 2

Cement

A powdery binding material that, when interacting with water, forms a plastic mass that turns over time into a solid, stone-like body; main building material.

The chemical composition of the most common Portland cement (in% by weight) is 20 - 23% SiO 2; 62 - 76% CaO; 4 - 7% Al 2 O 3; 2-5% Fe 2 O 3; 1-5% MgO.

Description and properties of silicon

Silicon - element, fourth group, third period in the table of elements. Atomic number 14. Silicon formula- 3s2 3p2. Defined as an element in 1811, and in 1834 received Russian name“silicon”, instead of the previous “sicily”. Melts at 1414º C, boils at 2349º C.

Molecular structure it resembles, but is inferior to it in hardness. Quite fragile, when heated (at least 800º C) it becomes plastic. Translucent infrared radiation. Monocrystalline silicon has semiconductor properties. According to some characteristics silicon atom similar to the atomic structure of carbon. Silicon electrons have the same valence number as with the carbon structure.

Workers properties of silicon depend on the content of certain contents in it. Silicon has different types of conductivity. In particular, these are the “hole” and “electronic” types. To obtain the first, boron is added to silicon. If you add phosphorus, silicon acquires the second type of conductivity. If silicon is heated together with other metals, specific compounds called “silicides” are formed, for example, in the reaction “ magnesium silicon«.

Silicon used for electronics needs is primarily assessed by the characteristics of its upper layers. Therefore, it is necessary to pay attention to their quality, it directly affects general indicators. The operation of the manufactured device depends on them. To obtain the most acceptable characteristics of the upper layers of silicon, they are treated with various by chemical means or exposed to radiation.

Compound "sulfur-silicon" forms silicon sulfide, which easily interacts with water and oxygen. When reacting with oxygen, under temperature conditions above 400º C, it turns out silica. At the same temperature, reactions with chlorine and iodine, as well as bromine, become possible, during which volatile substances are formed - tetrahalides.

It will not be possible to combine silicon and hydrogen by direct contact; for this there are indirect methods. At 1000º C, a reaction with nitrogen and boron is possible, resulting in silicon nitride and boride. At the same temperature, by combining silicon with carbon, it is possible to produce silicon carbide, the so-called “carborundum”. This composition has a solid structure, the chemical activity is sluggish. Used as an abrasive.

In connection with iron, silicon forms a special mixture, this allows the melting of these elements, which produces ferrosilicon ceramics. Moreover, its melting point is much lower than if they are melted separately. At temperatures above 1200º C, the formation of silicon oxide, also under certain conditions it turns out silicon hydroxide. When etching silicon, alkaline water-based solutions are used. Their temperature must be at least 60º C.

Silicon deposits and mining

The element is the second most abundant on the planet substance. Silicon makes up almost a third of the volume earth's crust. Only oxygen is more common. It is predominantly expressed by silica, a compound that essentially contains silicon dioxide. The main derivatives of silicon dioxide are flint, various sands, quartz, and field . After them come silicate compounds of silicon. Nativeness is a rare phenomenon for silicon.

Silicon Applications

Silicon, Chemical properties which determines the scope of its application, is divided into several types. Less pure silicon is used for metallurgical needs: for example, for additives in aluminum, silicon actively changes its properties, deoxidizers, etc. It actively modifies the properties of metals by adding them to compound. Silicon alloys them, changing the working characteristics, silicon A very small amount is enough.

Also, higher quality derivatives are produced from crude silicon, in particular, mono and polycrystalline silicon, as well as organic silicon - these are silicones and various organic oils. It has also found its use in the cement production and glass industries. It did not bypass brick production; factories producing porcelain also cannot do without it.

Silicon is part of the well-known silicate glue, which is used for repair work, and previously it was used for office needs until more practical substitutes appeared. Some pyrotechnic products also contain silicon. Hydrogen can be produced from it and its iron alloys in the open air.

What is better quality used for? silicon? Plates Solar batteries also contain silicon, naturally non-technical. For these needs, silicon of ideal purity or at least technical silicon of the highest degree of purity is required.

So-called "electronic silicon" which contains almost 100% silicon, has much better performance. Therefore, it is preferred in the production of ultra-precise electronic devices and complex microcircuits. Their production requires high-quality production circuit, silicon for which should go only highest category. The operation of these devices depends on how much contains silicon unwanted impurities.

Silicon occupies an important place in nature, and most living beings constantly need it. For them, this is a kind of building composition, because it is extremely important for the health of the musculoskeletal system. Every day a person absorbs up to 1 g silicon compounds.

Can silicon be harmful?

Yes, for the reason that silicon dioxide is extremely prone to dust formation. It has an irritating effect on the mucous surfaces of the body and can actively accumulate in the lungs, causing silicosis. For this purpose, in production related to the processing of silicon elements, the use of respirators is mandatory. Their presence is especially important when it comes to silicon monoxide.

Silicon price

As you know, all modern electronic technology, from telecommunications to computer technology, is based on the use of silicon, using its semiconductor properties. Its other analogues are used to a much lesser extent. Unique properties Silicon and its derivatives are still unrivaled for many years to come. Despite the decline in prices in 2001 silicon, sales quickly returned to normal. And already in 2003, trade turnover amounted to 24 thousand tons per year.

For latest technologies, requiring almost crystal purity of silicon, its technical analogues are not suitable. And due to him complex system cleaning price accordingly increases significantly. The polycrystalline type of silicon is more common; its monocrystalline prototype is somewhat less in demand. At the same time, the share of silicon used for semiconductors takes up the lion's share of trade turnover.

Product prices vary depending on purity and purpose silicon, buy which can start from 10 cents per kg of crude raw materials and up to $10 and above for “electronic” silicon.