News

      The electrical field of the application of various types of materials referred to. Including the conductive material, semiconductor materials, insulating materials, and other dielectric materials, magnetic materials. These materials are electrical or magnetic properties. Specific electrical materials are generally classified by purpose. Such as ferrite, by permeability stars, for the magnetic circuit is a magnetic material; resistivity stars, when used for the circuit is a semiconductor material.

      In the field of engineering, materials occupy an important position. Various technologies must be achieved through certain devices, the devices need to use a specific material. No corresponding material, even if it is a viable technologies and products on the principle, also can not be achieved. The emergence of new materials can often bring significant technical progress. Is also the case of the electrical field. For example, the emergence of the silicon steel sheet greatly improve the efficiency of the rotary motors and transformers, larger capacity, thereby promoting long-distance transport of electricity and extensive application; the emergence of a high coercive force and a high remanence NdFeB material meet permanent magnet synchronous motors need strong magnet, so that such motor drive occupies an important position in the micro-motor, and is still expanding its scope of application. Since 1986, the breakthrough of high critical temperature superconducting materials, to show industrial scale transmission and energy storage prospects for low-power (or loss), caused the attention of the world physics community, electrician profession. The development of various applicable electrician new material is an important task of the electrical field.

      Conductive material having a high electrical conductivity of the material used in electrical equipment as a conductor, such as copper, aluminum, etc., and typical article is wire, cable, the conductive core wire. Also belonging to the conductive material used for manufacturing an electrical contact, thermoelement, fuses and other materials. These materials in addition to high conductivity, there are a number of other specific properties, such as the manufacture of the fuse material having a relatively low melting point; contact material requires a high arc resistance performance.

High resistance alloy, such as nickel-chromium, chromium-nickel, iron, manganese, copper, constantan also belong to a conductive material, which may be used for the purpose of the heating element, the energy is converted into heat, or for manufacturing a resistor.

      Graphite is a special kind of conductor, although low conductivity, but due to its chemical inertness and a high melting point, and its products have a low coefficient of friction, a certain mechanical strength, is widely used as a brush, electrodes, etc..

      Also belonging to the conductive material of low temperature conductive material and superconducting material. For example, aluminum at 20K, the liquid hydrogen temperature range is the best low-temperature conductive material; beryllium at 77K or so that the liquid nitrogen temperature resistivity is only less than one-thousandth to one ten thousandth of the room temperature . The superconducting material is generally in the work, the temperature of the proximity 0K its resistance rate undetectable. The 1980s have been found on thousands of superconducting materials, in which elements of the class, there are compounds. The practical Nb3Sn, Nb3Al. Discovered in 1986, barium, yttrium, copper oxide ceramics that have superconducting at liquid nitrogen temperature (77K), which will bring the popularity of superconductivity technology, even to have a profound impact on human civilization.

      The conductivity of semiconductor material between the conductive material and insulating material is approximately between 105 to 10-7 the West / m material. Can be the band gap of the band theory for the conductivity of the electron (hole) may be defined, and its value is about 0.08 to 3 electron volts (also suggested that the upper limit thereof should be 1.5 or 2 electron volts). The semiconductor and the electric conductor except smaller conductivity, its conductivity increases with temperature increases, and the conductivity of the conductor with increasing temperature dropped.

      The nature of the semiconductor with the defect and impurity content and a significant change, it is possible to use doped to control its performance. Such as silicon, germanium, phosphorus, arsenic, antimony and other elements can be made of the electronic type (N-type) semiconductor, the incorporation of boron, aluminum, gallium, indium, and other elements can be made of a hole-type (P-type) semiconductor incorporating. Use of different combinations of the N-type and P-type, rectifying and amplifying effect can be obtained, as in Electrical power and control and adjustment purposes.

      The conductivity of the semiconductor is extremely sensitive to external factors, to a series of physical phenomena can be observed in its role. Can produce a photoelectric effect, for example, in the light of different wavelengths, when the electron absorption light, resulting in free carrier concentration increases, so that the conductivity increases, called photoconductivity. Using this nature, can be made of the photosensitive member. In addition, the thermoelectric effect, Hall effect, magnetoresistance effect, piezoelectric effect, FET and the tunnel effect, etc. can be utilized.

      Semiconductor can be divided into two types of organic and inorganic chemical composition, mainly inorganic semiconductor. Inorganic semiconductors can be further divided into elemental and compound type. The latter can be divided into component elements such as binary, ternary, has developed rapidly in recent years. Semiconductor can also be its morphology is divided into crystalline the Semiconductor and amorphous semiconductor. More generally the use of the former, but the latter being vigorously developed since the 1970s.

      The electrically insulating or dielectric material a resistivity of approximately 1010 Omri more materials. Practical excellent insulation resistivity of the material at room temperature greater than 1012 Omri. Insulating materials are generally used contains impurities, the resistance or conductance at the working temperature of the metal ion type. The insulating material of the electronic type for conductance is generally believed that the band gap in the 2 to 3 electron volts or more.

      The characteristics of the dielectric material is the polarization in the electric field can occur. Most of the dielectric is an excellent insulating material, the two are often used as synonyms.

Insulating materials often their aggregation state into solid, liquid and gaseous. Most of the insulating material is solid. Liquid and gaseous insulating material generally can not play a supporting role on the mechanics, so less alone.

      The gas-insulated material is characterized by low conductivity, dielectric constant and dielectric loss, breakdown strength is generally much lower than the liquid and solid insulating material, but after the breakdown of self-restoring insulation, self-healing. Sulfur hexafluoride (SF6) gas has a high breakdown strength, widely used as a closed electrical insulation.

      Liquid insulating material is generally used instead of the pores in the air, space filled electrical equipment or impregnation equipment insulated structure. It also can play a role in addition to insulation, heat or interrupter role. Consider it under the action of the electric field of the stability, thermal stability, viscosity, flash point, the acid value, the base value, impurity content, water content, coefficient of thermal expansion, and compatibility with other insulating and structural materials in the liquid insulating material is selected should be and so on. The most widely used liquid insulation material is mineral insulating oil. In order to ensure a pure liquid material composition, the current development of a variety of synthetic insulating oil, silicone oil, such as high temperature and dodecylbenzene.

      Solid insulating materials can be divided into natural and synthetic. Natural cotton yarn, silk, paper, shellac, bitumen, mineral oil, rubber, asbestos, mica, etc., used in electrical equipment has begun in the 19th century. Synthetic materials, particularly polymer materials, have developed rapidly in the 20th century. The reason is that the vast majority of polymeric material having a high resistivity, and a polymer material (including plastics, synthetic rubber and synthetic fibers, and many other species) can meet a variety of usage occasions claim. The polymer material has excellent dielectric properties, mechanical properties and resistance to high temperature compared with the corresponding natural materials, occupies an important position in the insulation material. Important polymer materials, polyethylene, polystyrene, polypropylene, poly vinyl chloride, polyester and unsaturated polyester, epoxy resin, silicone resin, and polyimide as represented by an aromatic heterocyclic polymer materials.

      Inorganic insulating materials, there are also significant progress. Example, made of a mica paper, to solve the mica insufficient resources; emergence of the glass fiber cloth, so that the heat level of the fibers greatly improved; ceramic varieties developed to meet the requirements of high mechanical strength, high temperature and a high dielectric constant . Due to the rapid development of superconducting technology, the low-temperature electrical materials made significant progress. Cryogenic electrically insulating paint gum and adhesives, electrical film and laminate, and the low-temperature inorganic insulating material, such as glass, quartz, ceramics, etc., there are a great development.