EntranceVasily 3 the last collector of the Russian land presentation. Grand Duke Vasily III Ivanovich. Annexation of Smolensk and Ryazan
CPU? Sand? What associations do you have with this word? Or maybe Silicon Valley?
Be that as it may, we encounter silicon every day, and if you are interested in knowing what Si is and what it is eaten with, please under cat.
Introduction
As a student of one of the Moscow universities with a degree in Nanomaterials, I wanted to introduce you, dear reader, to the most important chemical elements of our planet. I chose for a long time where to start, carbon or silicon, and yet I decided to focus on 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 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. So let's get started.Silicium
Silicon (lat. Silicium), Si, a chemical element of group IV of the periodic system of 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 (N.C.) 2.33 g/cm³
Melting point 1688 K
Powder Si
History reference
Silicon compounds, widely distributed 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 - the manufacture of glass - began around 3000 BC. e. (in ancient Egypt). The earliest known Silicon compound is SiO2 oxide (silica). In the 18th century, silica was considered a simple body and referred to as "earths" (which is reflected in its name). The complexity of the composition of silica was established by I. Ya. Berzelius. He was the first, in 1825, to obtain elemental silicon from silicon fluoride SiF4, reducing the latter with metallic potassium. The name "silicon" was given to the new element (from Latin silex - flint). The Russian name was introduced by G.I. Hess in 1834.
Silicon is very common in nature in the composition of ordinary sand.
Distribution of silicon in nature
In terms of prevalence in the earth's crust, silicon is the second (after oxygen) element, 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 the animal and plant kingdoms. For the geochemistry of silicon, its exceptionally strong bond 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 think it’s not worth dwelling here, 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 of great use. The electrical properties of silicon are highly dependent on impurities.
Chemical Properties of Silicon
There's a lot to be said, of course, but I'll focus on the most interesting. In Si compounds (similar to carbon) is 4-valent.Due to the formation of a protective oxide film, silicon is stable in air even at elevated temperatures. In oxygen, it oxidizes starting from 400 °C, forming silicon oxide (IV) SiO2.
Silicon is resistant to acids and dissolves only in a mixture of nitric and hydrofluoric acids, easily dissolves in hot alkali solutions with hydrogen evolution.
Silicon forms 2 groups of oxygen-containing silanes - siloxanes and siloxenes. Silicon reacts with nitrogen at temperatures above 1000 °C. Si3N4 nitride, which does not oxidize in air even at 1200 °C, is resistant to acids (except nitric acid) and alkalis, as well as to molten metals and slags, is of great practical importance its 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, here we will stop in more detail.Depending on the purpose, there are:
1. Silicon of electronic quality(so-called "electronic silicon") - the highest quality silicon with a silicon content of more than 99.999% by weight, the electrical resistivity of electronic quality silicon can be in the range from about 0.001 to 150 ohm cm, but the resistance value must be provided exclusively a given impurity, i.e., the ingress of other impurities into the crystal, even if they provide a given electrical resistivity, as a rule, is unacceptable.
2. Solar Grade Silicon(the so-called "solar silicon") - silicon with a silicon content of more than 99.99% by weight, used for the production of photovoltaic converters (solar batteries).
3. Technical silicon- silicon blocks of polycrystalline structure obtained by carbothermal reduction from pure quartz sand; contains 98% silicon, the main impurity is carbon, it has a high content of alloying elements - boron, phosphorus, aluminum; mainly used to obtain polycrystalline silicon.
Silicon of technical purity (95-98%) is obtained in an electric arc by the reduction of silica SiO2 between graphite electrodes. In connection with the development of semiconductor technology, methods have been developed for obtaining pure and extra pure silicon. This requires a preliminary synthesis of the purest initial silicon compounds, from which silicon is extracted by reduction or thermal decomposition.
Polycrystalline silicon ("polysilicon") - the purest form of industrially produced silicon - a semi-finished product obtained by cleaning technical silicon by chloride and fluoride methods and used for the production of mono- and multi-crystalline 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, distillation 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" of a single crystal from molten silicon - the 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 up from the free surface of a large volume of the melt with the initiation of the onset 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.
Silicon Application
Specially doped silicon is widely used as a material for the manufacture of semiconductor devices (transistors, thermistors, power rectifiers, thyristors; solar photocells used in spacecraft, as well as many other things).Since silicon is transparent to rays with a wavelength of 1 to 9 microns, it is used in infrared optics.
Silicon has diverse and ever-expanding applications. In metallurgy Si
used to remove oxygen dissolved in molten metals (deoxidation).
Silicon is an integral part of a large number of iron and non-ferrous alloys.
Silicon usually 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, ceramic, electrical and other industries.
Ultra-pure silicon is mainly used for the production of single electronic devices (for example, your computer's processor) and single-chip microcircuits.
Pure silicon, ultra-pure silicon waste, refined 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, it is used to make mirrors for gas lasers.
Ultrapure silicon and its product
Silicon in the body
Silicon is found in the body in the form of various compounds involved mainly in the formation of solid skeletal parts and tissues. Especially a lot of silicon can be accumulated by some marine plants (for example, diatoms) and animals (for example, silicon-horned sponges, radiolarians), which form powerful deposits of silicon oxide (IV) when dying on the ocean floor. In cold seas and lakes, biogenic silts enriched with silicon predominate, in tropical seas - calcareous silts with a low content of silicon. Among terrestrial plants, cereals, sedges, palms, and horsetails accumulate a lot of silicon. In vertebrates, the content of silicon oxide (IV) in ash substances is 0.1-0.5%. Silicon is found in the largest quantities in dense connective tissue, kidneys, and pancreas. The daily human diet contains up to 1 g of silicon. With a high content of silicon oxide (IV) dust in the air, it enters the lungs of a person and causes a disease - silicosis.Conclusion
Well, that's all, if you read to the end and delved a little, then you are one step closer to success. I hope I wrote not in vain and at least someone liked the post. Thank you for your attention.Monosilane SiH 4 . The ancestor of the homologous series of silicon hydrogens Si n H 2n+2. It is a very poisonous colorless gas with an odor reminiscent of AsH 3 and H 2 S. t pl \u003d -185 o C, t kip \u003d -112 o C. In air, it ignites spontaneously, since its ignition temperature is below room temperature. Decomposes when heated. Does not dissolve in cold water. Very reactive. Strong reducing agent. Obtained by the action of dilute hydrochloric acid on magnesium silicide.
Silicon (II) oxide (silica) SiO 2 . It occurs mainly as the mineral quartz. Contaminated with impurities, quartz - ordinary sand - is one of the main products of the destruction of rocks. Colorless, very refractory solid. Practically insoluble in water. Does not affect silica and acids, except for HF. Alkalis are gradually transferred into solution, forming the corresponding salts of silicic acid. Obtained by the interaction of silicon and oxygen. Used as building material.
Silicic acid H 2 SiO 3 . Almost insoluble in water (in the form of a true solution). Easily forms colloidal solutions and therefore precipitates only partially. The precipitate has the appearance of a colorless jelly, and its composition corresponds not simply to the formula H 2 SiO 3 or H 4 SiO 4 , but to the more general nSiO 2 . mH 2 O with n and m values varying with precipitation. Silicic acid is very weak.
Glass Na 2 CaSi 6 O 14 or Na 2 O. CaO. 6SiO2. Quite close to this composition is the usual window glass. It is practically insoluble, but water partially decomposes from its surface, washing out mainly sodium. Obtained from soda, limestone and sand.
Silicon carbide (carborundum) SiC. Solid, refractory substance. Its crystal lattice is similar to that of diamond. It is a semiconductor. It reacts intensively with molten alkalis (in the presence of oxygen), above 600 ° C it interacts with chlorine. Receive in large quantities in electric furnaces at 2300 about With the interaction of excess carbon with silicon oxide.
53) Natural silicon compounds. The use of silicon in modern construction.
Natural silicon compounds:
silicates. Among them, aluminosilicates are the most common (it is clear that these silicates contain aluminum). Aluminosilicates include granite, various types of clays, and mica. An aluminium-free silicate is, for example, asbestos.
SiO2 oxide is essential for plant and animal life. It gives strength to the stems of plants and the protective covers of animals. Fish scales, insect shells, butterfly wings, bird feathers and animal fur are strong because they contain silica.
3) Rhinestone
Rock crystal is a colorless, transparent, usually chemically pure, almost free of impurities, a kind of low-temperature modification of quartz - SiO2, which crystallizes in a trigonal system. It occurs in the form of single or prismatic-hexagonal crystals collected in druses, sometimes weighing a ton or more.
Quartz is one of the most common minerals in the earth's crust, a rock-forming mineral of most igneous and metamorphic rocks. Chemical formula: SiO2.
Varieties of quartz: colorless, rose quartz, "hairy", carnelian, agate, "tiger's eye", polished pebbles.
5) Carnelian Formula - SiO2, a kind of chalcedony. Chemical composition - SiO2 content - 90-99%; Fe2O3, Al2O3, MgO, CaO, H2O impurities are noted. Carnelian, like agate, is an aggregate of essentially chalcedonic composition with a complex structure.
Jasper is an opaque variety of quartz - silicon dioxide SiO2 - with a fibrous structure that includes a wide variety of minerals: garnets, hematite, pyrite, etc. Therefore, jasper is distinguished by a great variety of its color, including all tones except pure blue.
7) Amethyst
Amethysts are considered purple or reddish quartz crystals, which are silicon dioxide and belong to the trigonal system.
Opal is an amorphous variety of quartz SiO2 with a variable water content (6-10%). Opal's chemical name is silicon dioxide polyhydrate. The main advantage of opal is the ability to emit successively different rays under the influence of sunlight, to cause a varied play of colors. Three types of opal are known: black opal, which has a very dark blue color with "flashes" of colors; orange-red fire opal and white opal.
7) Citrine The name of the stone, derived from the word citreus - "lemon", indicates the yellow tint of this variety of quartz, which is given to citrine by impurities of ferric iron. Citrine is good for concentration, concentration.
Jade is a translucent mineral of white and green color. From a mineralogical point of view, jade is a silica compound.
9) Agate is a kind of translucent quartz. Chemical formula: SiO2.
Application of silicon compounds:
Silicon is used in the silicate industry:
Natural silicon compounds - sand (SiO2) and silicates are used for the production of ceramics, glass and cement.
Silicate glue is widely known, used in construction as a desiccant, and in pyrotechnics and in everyday life for gluing paper.
Silicone oils and silicones, materials based on organosilicon compounds, have become widespread.
54) Physical and chemical bases of corrosion of concrete and mineral materials.
Concrete corrosion is the main enemy of all mineral building materials and structures (concrete, reinforced concrete, brick, asbestos cement, silicate, foam concrete and aerated concrete blocks). The most serious problem is the influence of the atmospheric-chemical factor - the impact of aggressive atmospheric substances (carbonates, sulfates, chlorides), as well as frequent freeze-thaw cycles.
Mineral-based building materials are capillary-porous. As a result of aggressive atmospheric action, crystals are formed inside the porous structure, the growth of which leads to the appearance of cracks. As a result of exposure to water, salts and carbon dioxide - corrosion of concrete and destruction of building structures.
Protection of mineral surfaces is a global task in the design, construction and operation of any facilities. It is relevant for all types of buildings, structures and structures used in modern construction.
Silicon (Si) - stands in period 3, group IV of the main subgroup of the periodic system. Physical properties: silicon exists in two modifications: amorphous and crystalline. Amorphous silicon is a brown powder with a density of 2.33 g/cm3, which dissolves in metal melts. Crystalline silicon is dark gray crystals with a steel luster, hard and brittle, with a density of 2.4 g/cm3. Silicon consists of three isotopes: Si (28), Si (29), Si (30).
Chemical properties: electronic configuration: 1s22s22p63 s23p2 . Silicon is a non-metal. At the external energy level, silicon has 4 electrons, which determines its oxidation states: +4, -4, -2. Valence - 2, 4. Amorphous silicon has a greater reactivity than crystalline. Under normal conditions, it interacts with fluorine: Si + 2F2 = SiF4. At 1000 °C, Si reacts with non-metals: with CL2, N2, C, S.
Of the acids, silicon interacts only with a mixture of nitric and hydrofluoric acids:
With respect to metals, it behaves differently: it dissolves well in molten Zn, Al, Sn, Pb, but does not react with them; with other melts of metals - with Mg, Cu, Fe, silicon interacts with the formation of silicides: Si + 2Mg = Mg2Si. Silicon burns in oxygen: Si + O2 = SiO2 (sand).
Silicon dioxide or silica- stable connection Si, is widely distributed in nature. It reacts with its fusion with alkalis, basic oxides, forming salts of silicic acid - silicates. Receipt: in industry, pure silicon is obtained by reduction of silicon dioxide with coke in electric furnaces: SiO2 + 2С = Si + 2СO?.
In the laboratory, silicon is obtained by calcining white sand with magnesium or aluminum:
SiO2 + 2Mg = 2MgO + Si.
3SiO2 + 4Al = Al2O3 + 3Si.
Silicon forms acids: H2 SiO3 - meta-silicic acid; H2 Si2O5 is two metasilicic acid.
Finding in nature: quartz mineral - SiO2. Quartz crystals have the shape of a hexagonal prism, colorless and transparent, called rock crystal. Amethyst - rock crystal, dyed purple with impurities; smoky topaz is painted brownish; agate and jasper are crystalline varieties of quartz. Amorphous silica is less common and exists in the form of the mineral opal, SiO2 nH2O. Diatomaceous earth, tripolite or kieselguhr (diatomaceous earth) are earthy forms of amorphous silicon.
42. The concept of colloidal solutions
Colloidal solutions– highly dispersed two-phase systems consisting of a dispersion medium and a dispersed phase. Particle sizes are intermediate between true solutions, suspensions and emulsions. At colloidal particles molecular or ionic composition.
There are three types of internal structure of primary particles.
1. Suspensoids (or irreversible colloids)– heterogeneous systems, the properties of which can be determined by a developed interfacial surface. Compared to suspensions, they are more highly dispersed. They cannot exist for a long time without a dispersion stabilizer. They are called irreversible colloids due to the fact that their precipitation after evaporation again does not form sols. Their concentration is low - 0.1%. They differ slightly from the viscosity of the dispersed medium.
Suspensoids can be obtained:
1) dispersion methods (grinding large bodies);
2) condensation methods (obtaining insoluble compounds by means of exchange reactions, hydrolysis, etc.).
The spontaneous decrease in dispersion in suspensoids depends on the free surface energy. To obtain a long-lasting suspension, conditions are necessary for its stabilization.
Stable disperse systems:
1) dispersion medium;
2) dispersed phase;
3) stabilizer of the dispersed system.
The stabilizer can be ionic, molecular, but most often high-molecular.
Protective colloids- macromolecular compounds that are added for stabilization (proteins, peptides, polyvinyl alcohol, etc.).
2. Associative (or micellar colloids) - semicolloids arising at a sufficient concentration of molecules consisting of hydrocarbon radicals (amphiphilic molecules) of low molecular weight substances during their association into aggregates of molecules (micelles). Micelles are formed in aqueous solutions of detergents (soaps), organic dyes.
3. Molecular colloids (reversible or lyophilic colloids) - natural and synthetic high molecular weight substances. Their molecules have the size of colloidal particles (macromolecules).
Dilute solutions of colloids of macromolecular compounds are homogeneous solutions. When strongly diluted, these solutions obey the laws of dilute solutions.
Non-polar macromolecules dissolve in hydrocarbons, polar ones - in polar solvents.
Reversible colloids- substances, the dry residue of which, when a new portion of the solvent is added, again goes into solution.
After oxygen silicon is the most abundant element in the earth's crust. It has 2 stable isotopes: 28 Si, 29 Si, 30 Si. Silicon is not found in free form in nature.
The most common are: salts of silicic acids and silicon oxide (silica, sand, quartz). They are part of mineral salts, mica, talc, asbestos.
Allotropy of silicon.
At silicon There are 2 allotropic modifications:
Crystalline (light gray crystals. The structure is similar to the crystal lattice of diamond, where the silicon atom is covalently bonded to 4 identical atoms, and is itself in sp3 - hybridization);
Amorphous (brown powder, more active form than crystalline).
silicon properties.
At temperature, silicon reacts with atmospheric oxygen:
Si + O 2 = SiO 2 .
If there is not enough oxygen (lack), then the following reaction may take place:
2 Si + O 2 = 2 SiO,
Where SiO- monoxide, which can also be formed during the reaction:
Si + SiO 2 = 2 SiO.
Under normal conditions silicon may react with F 2 , when heated - with Cl 2 . If the temperature is increased further, then Si will be able to interact with N and S:
4Si + S 8 = 4SiS 2;
Si + 2F 2 \u003d SiF 4.
Silicon is able to react with carbon, giving carborundum:
Si + C = SiC.
Silicon is soluble in a mixture of concentrated nitric and hydrofluoric acids:
3Si + 4HNO 3 + 12HF = 3SiF 4 + 4NO + 8H 2 O.
Silicon dissolves in aqueous solutions of alkalis:
Si + 2NaOH + H 2 O \u003d Na 2 SiO 3 + H 2.
When heated with oxides, silicon disproportionates:
2 MgO + 3 Si = mg 2 Si + 2 SiO.
When interacting with metals, silicon acts as an oxidizing agent:
2 mg + Si = mg 2 Si.
Application of silicon.
Silicon finds the greatest use in the production of alloys for giving strength to aluminum, copper and magnesium and for the production of ferrosilicides, which are 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 silicon compounds are used in ceramic and glass technology as an insulating material and piezocrystals.