Simple silicon is a relatively active nonmetallic element, which can form compounds with 64 of 96 stable elements. The main use of silicon depends on its semi-conductivity.

Silicon is the most important semiconductor material at present. At present, the annual output of the world is about 3× 106kg. A silicon wafer with a diameter of 75mm can integrate tens of thousands to hundreds of thousands or even millions of components to form microelectronics, resulting in microcomputers and microprocessors. Due to the development of information engineering, silicon is mainly used in microelectronics technology. The components of power semiconductor devices, mainly silicon thyristors, are getting bigger and bigger. Compared with silicon transistors, integrated circuits are just the opposite. On a silicon wafer with a diameter of 75mm, only one module can withstand thousands of amperes of current and thousands of volts. This component has penetrated into the fields of electronics, power and control, forming a new discipline-power electronics.

In order to adapt to the development of large-scale integrated circuits, monocrystalline silicon is developing in the direction of large diameter, high purity, high uniformity and no defects. The largest silicon wafer diameter reaches 150mm, and the high-purity silicon in the laboratory is close to the theoretical limit purity.

At present, the commonly used solar cells are silicon cells. If the area of 1 m2 is covered with silicon solar cells, the power of 100W can be obtained. Monocrystalline silicon solar cells have stable performance, high conversion efficiency, small size and light weight, and are very suitable for use as power sources on space spacecraft. The large spacecraft space laboratory in the United States is equipped with four solar panels, which are composed of 147840 single crystal silicon solar cells with the size of 8 square centimeters, and the power generation is about 12KW.

Crystalline silicon includes monocrystalline silicon and polycrystalline silicon. The preparation method of crystalline silicon is to reduce SiO2 _ 2 to Si with carbon, and then purify it with HCl to obtain high purity polysilicon. The preparation method of monocrystalline silicon is usually to prepare polycrystalline silicon or amorphous silicon first, and then grow rod-shaped monocrystalline silicon from the melt by Czochralski method or suspension zone melting method. Silicon single crystal has a basically complete lattice structure. Different directions have different properties, so they are good semiconductor materials. The purity requirement is 99.9999%, even above 99.9999%. Used for manufacturing semiconductor devices, solar cells, etc. It is extracted from high-purity polysilicon in a single crystal furnace. When molten elemental silicon solidifies, silicon atoms are arranged into many crystal nuclei in the diamond lattice. If these crystal nuclei grow into grains with the same crystal plane orientation, these grains combine in parallel and crystallize into monocrystalline silicon. Monocrystalline silicon has the physical properties of metalloid and weak conductivity, and the conductivity increases with the increase of temperature, so it has obvious semiconductivity. Ultrapure monocrystalline silicon is an intrinsic semiconductor. Doping trace amounts of group Ⅲ A elements, such as boron, into ultra-pure single crystal silicon can improve its conductivity and form a P-type silicon semiconductor. If a small amount of ⅴ A group elements, such as phosphorus or arsenic, are added, the conductivity can also be improved and N-type silicon semiconductors can be formed. The preparation method of monocrystalline silicon is usually to prepare polycrystalline silicon or amorphous silicon first, and then grow rod-shaped monocrystalline silicon from the melt by Czochralski method or suspension zone melting method. Monocrystalline silicon is mainly used to manufacture semiconductor components.

silicon dioxide

Properties: silica is also called silica. It is widely distributed in nature, such as timely and quartz sand. White or colorless, light yellow, with high iron content. The density is 2.2 ~ 2.66. Melting point 1670℃ (tridymite); 17 10℃ (in time). The boiling point is 2230℃. Insoluble in water, slightly soluble in acid, particles can react with melt and alkali. Used for making glass, water glass, pottery, enamel, refractory, ferrosilicon, molding sand, elemental silicon, etc. Silicon dioxide CASNo. : 763 1-86-9 molecular shape: tetragonal system molar mass: 60. 1 g mol- 1 chemical formula SiO2 _ 2, the molecular formula is 60.08.

Also known as silica, it is a hard and insoluble solid. It often appears in three varieties: Yishi, tridymite and Fang Yingshi. From the underground to 16 km, almost 65% is silica ore. Natural silica can be divided into crystalline silica and amorphous silica, and crystalline silica is mainly produced in Yingshi mining area. Pure time is colorless crystal, while large and transparent prismatic time is crystal. Silicon dioxide is an atomic crystal with tetrahedral structure formed by silicon atoms and four oxygen atoms, and the whole crystal can be regarded as a huge molecule. Silicon dioxide is the simplest form and does not mean a single molecule. The density is 2.32g/cm3, the melting point is1723 5℃, and the boiling point is 2230℃.

Amorphous silica is a white solid or powder. The chemical properties are very stable. Insoluble in water, does not react with water. It is an acidic oxide and does not react with ordinary acids. Gaseous hydrogen fluoride or hydrofluoric acid reacts with silicon dioxide to generate gaseous silicon tetrafluoride. React with hot alkali solution or molten alkali to generate silicate and water. React with various metal oxides at high temperature to form silicates. It is used to make timely glass, optical instruments, chemical utensils, ordinary glass, refractories, optical fibers, ceramics and so on.

Silicon dioxide is inactive in nature, and does not react with halogen, hydrogen halide and hydrogen halide, sulfuric acid, nitric acid and perchloric acid except fluorine, hydrogen fluoride and hydrofluoric acid. Hydrogen fluoride (hydrofluoric acid) is the only acid that can dissolve silicon dioxide and produce water-soluble fluorosilicic acid. In order to measure the specific surface area of silica, an automatic BET specific surface area tester F-Sorb 2400 was used. SiO _ 2+4hf = SiF4 =+2H2O silica and alkaline oxide SiO _ 2+Cao = (at high temperature) SiO _ 3 silica can be dissolved in strong alkaline solution: SiO _ 2+2NaOH = Na2SiO _ 3+H2O (reagent bottle containing alkali can replace glass stopper with rubber stopper) Silica can be reduced by carbon, magnesium and aluminum at high temperature: SiO _ 2+2C = Si+2co =.

Although the melting time is not long-range ordered, it presents a short-range ordered structure, which can be considered as four oxygen atoms on the foot of a triangle polygon. The center of the polyhedron is a silicon atom. In this way, every four oxygen atoms are bonded to silicon atoms with a valence of about * * *, which satisfies the valence layer of silicon. If each oxygen atom is a part of two polyhedrons, the valence of oxygen is also satisfied, and the result is a regular crystal structure, which is called synchronization. In the melting process, some oxygen atoms become oxygen bridges and combine with two silicon atoms. Some oxygen atoms have no oxygen bridge and only bond with one silicon atom. It can be considered that thermally grown silica is mainly composed of polyhedral networks with human orientation. Compared with the anaerobic bridge, the larger the aerobic bridge, the greater the adhesion of the oxide layer and the less the tendency of damage. The ratio of aerobic bridge to anaerobic bridge in dry oxygen oxidation layer is much larger than that in wet oxygen oxidation layer. Therefore, it can be considered that SiO2 is more similar to ionic crystals than atomic crystals. The valence bond between oxygen atom and silicon atom is transformed into ionic bond.

Silicon dioxide is the raw material for making glass, timely glass, water glass, optical fiber and refractory. When the silicon dioxide crystal is perfect, it is a crystal; Silica becomes agate after gelatinization and dehydration; Water-containing silica gel becomes opal after solidification; When the particle size of silica is less than several microns, chalcedony, flint and secondary quartzite are formed. Mineral resources with very stable physical and chemical properties, crystals belong to ternary oxide minerals, that is, low-temperature response time (a- response time), which is the most widely distributed mineral species in response time minerals. Generalized response time also includes high temperature response time (b- response time). Timely block, also known as silica, is mainly the raw material for producing quartz sand, as well as the raw material for timely refractory and ferrosilicon firing.

Silicate mineral is an oxyacid salt mineral formed by the combination of metal cation and silicate. Widely distributed in nature, it is the main mineral that constitutes the crust and upper mantle, accounting for more than 90% of the whole crust. Stone meteorites and moon rocks are also abundant here. There are about 800 known mineral species, accounting for about 1/4 of the total mineral species. Many silicate minerals such as asbestos, mica, talc, kaolinite, montmorillonite and zeolite are important nonmetallic mineral raw materials and materials. Some are extracting main minerals such as metal potassium and aluminum and rare metals such as lithium, beryllium, zirconium, rubidium and cesium, such as nepheline, lepidolite, beryl, zircon and Tianhe stone. There are many silicate minerals such as jadeite, aquamarine and jadeite, which are precious gem minerals.

Characteristics of chemical composition: There are more than 40 elements that make up silicate minerals. In addition to Si and O necessary for silicate, inert gas ions (such as Na+, K+, Mg2+, Ca2+, Ba2+, Al3+, etc. ) and some transition ions (such as Fe2+, Fe3+, Mn2+, Mn3+, Cr3+, Ti3+, etc. ) exists in the form of metal cations. In addition, (OH)-, O2-, F-, C 1-, [CO3 ]2-, [SO4] 2- exist in the form of additional anions. Isomorphic substitution widely exists in the chemical composition of silicate minerals. In addition to the substitution between metal cations, Al3+, Be2+ or B3+ often replace Si4+ in silicate free radicals, thus forming aluminosilicate, beryllium silicate and borosilicate minerals respectively. In addition, in a few cases, there may be (OH)- instead of O2- in silicate.