Silicon (Taiwan, Hong Kong called silicon xī) is a chemical element, its chemical symbol is Si, formerly known as silicon. Atomic number 14, relative atomic mass 28.0855, with amorphous silicon and crystalline silicon two isomorphic bodies, belonging to the periodic table on the third cycle, IVA family of metal elements. Silicon is also a very common element, but it rarely appears in the form of simple matter in nature, but in the form of complex silicate or silica, widely present in the rock, gravel, dust. Silicon reserves in the universe ranked eighth. In the crust, it is the second rich element that constitutes 26.4% of the total mass of the crust, second only to the first oxygen (49.4%).
There are two kinds of allotropes of amorphous silicon and crystalline silicon. Crystalline silicon is gray-black, amorphous silicon is black,
Density of 2.32-2.34 g / cm3, the melting point of 1410 ℃, the boiling point of 2355 ℃, crystalline silicon is the atomic crystal. Do not dissolve in water, nitric acid and hydrochloric acid, soluble in hydrofluoric acid and lye. Hard and metallic luster.
1, high purity monocrystalline silicon is an important semiconductor material. Doped with a trace amount of Group IIIA elements in monocrystalline silicon to form p-type silicon semiconductors; and incorporation of trace amounts of Group VA elements to form n-type semiconductors. P-type semiconductor and n-type semiconductor together to form p-n junction, can be made of solar cells, the radiation energy into electrical energy. In the development of energy is a very promising material. Also widely used in the diode, transistor, thyristor, FET and a variety of integrated circuits (including people inside the computer chips and CPU) are made of silicon raw materials.
2, cermet, an important material for aerospace navigation. The ceramic and metal mixed sintering, made of cermet composite, it is high temperature, toughness, can be cut, both inherited the advantages of metal and ceramics, but also make up for both the inherent defects. Can be applied to the manufacture of military weapons. The first space shuttle "Columbia" can withstand the high-speed wear through the dense atmosphere of friction generated by the high temperature, thanks to it that thirty thousand thousand pieces of silicon tile into the shell.
3, optical fiber communication, the latest modern means of communication. With pure silica can be drawn out of high transparency of glass fiber. Laser can be in the glass fiber path, the occurrence of countless total reflection and forward transmission, instead of the cumbersome cable. Fiber optic communication capacity is high, a hair so fine glass fiber, you can simultaneously transmit 256 phone; and it is not subject to electricity, magnetic interference, not afraid of eavesdropping, with a high degree of confidentiality. Fiber communication will make the 21st century human life revolution.
4, excellent performance of silicon organic compounds. For example, silicone plastic is an excellent waterproof coating material. Spraying silicone on the walls of the underground railway can solve the problem of water seepage once and for all. In the ancient artifacts, sculpture appearance, coated with a thin layer of silicone plastic, can prevent the moss breeding, against wind and rain and weathering. Tiananmen Square, the People's Heroes Monument, is the surface through the silicone plastic treatment, so always white, fresh.
5, due to the unique structure of silicone, both inorganic materials and organic materials performance, with a low surface tension, viscosity coefficient is small, high compressibility, high gas permeability and other basic properties, and has high and low temperature, electrical insulation, It is widely used in aerospace, electrical and electronic, construction, transportation, chemical, textile, food, light industry, medical treatment, etc., and so on. It is widely used in aerospace, electronic and other fields, such as oxidation stability, weatherability, flame resistance, hydrophobic, corrosion resistance, non-toxic and tasteless and physiological inertness. Industry, which is mainly used in silicone sealing, bonding, lubrication, coating, surface activity, stripping, defoaming, foam suppression, waterproof, moisture, inert filling. With the continuous growth of the number and variety of organic silicon, the application field has been widened to form an important product system which is unique to the new materials industry. Many varieties are indispensable and indispensable for other chemicals.
6, silicon can increase the hardness of plant stalk, pest feeding and digestion to increase the difficulty. Although silicon is not an essential element in plant growth and development, it is also a chemical element necessary for plants to resist adversity and regulate the relationship between plants and other organisms.
Silicon has a great effect on improving plant resistance to abiotic and biotic stress. For example, silicon can improve the resistance of plants to drought, salt stress, ultraviolet radiation and pests and diseases. Silicon can improve the resistance of rice to Cnaphalocrocis medinalis. After applying silicon, the defense response to pest feeding is rapidly increasing, and silicon plays a protective role in plant defense.
When the rice is attacked by insect pests, silicon can alert the rice to the rapid activation of the jasmonic acid pathway associated with stress resistance. The jasmonic acid signal, in turn, promotes the absorption of silicon. The interaction of silicon and jasmonic acid signaling pathways affects the resistance of rice to pests.