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Electrical insulators and dielectric materials are ceramics with intrinsically low electrical conductivity. Internal porosity lowers bulk electrical conductivity. Insulators for DC or low frequency AC devices must have a high resistivity, good thermal resistivity, and low dilation coefficient in order to have sufficient resistance to thermal shock. The porosity must be very low. The surface vitrification must be perfect to avoid water absorption and improve mechanical resistance. The most commonly used materials are porcelains, mainly ternary compounds (Al2O3-SiO2-MgO). Such insulators are used especially as supports for electric oven resistors or heating elements. Ceramics used for high frequency insulator applications require a low dielectric constant and a small loss tangent. The careful choice of raw materials saves the surface from having to be vitrified. A vitrified surface would increase the value of the dissipation factor. For very high frequencies (VHF), high-purity dense alumina, fired at temperatures above 1600°C, is generally used. For powerful tubes, large alumina insulators must be assembled on metallic electrodes. This application is used for television or satellite transmitter tubes, for microwave generators used for heating, and for powerful lasers. Products & Services
Industrial ceramic materials are non-metallic, inorganic compounds that include oxides, carbides, or nitrides. They have high melting points, low wear resistance, and a wide range of electrical properties.
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Ceramic tube and ceramic rod products are suitable for use in applications requiring high temperature strength, erosion resistance, electrical or thermal insulation, and other specialized characteristics.
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Ceramic balls are rolling, spherical elements that are used in check and ball valves, bearings, and other mechanical devices that provide rotary or linear motion. They can provide higher stiffness, lower thermal expansion, lighter weight, increased corrosion resistance, and higher electrical resistance than comparable steel products.
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Specialty ceramics include nitrides, borides, carbon or graphite and silicides as well as other specialized non-metallic compounds.
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Aluminum oxide and alumina ceramics have excellent wear characteristics, chemical resistance, compressive strength, high-temperature properties, and dielectric strength.
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Topics of Interest
10.1 OVERVIEW
Electrical circuits use insulator materials in various forms. Capacitors use dielectrics as a medium. The dielectric materials, which are also known as insulators, constitute a very...
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7.3 Electrostaticity
The electrical charge capacity of an item depends on the condition of its surface, on the dielectric constant, the surface resistivity, and the relative humidity of the...
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Zirconia or zirconium oxide (ZrO2) is an extremely refractory compound of zirconium and oxygen. Zirconia may have additions of calcia, magnesia or baria to stabilize the structure into a cubic...
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All materials can be characterized as either electrical conductors or as electrical insulators. A conductor is a material through which an electrical current can pass and an insulator is a material...
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