What is Mica
Types of Mica
Properties of Mica
Mica is a naturally occurring mineral, based on a group of silicate minerals composed of varying amounts of aluminum, potassium, magnesium, iron and water having thin sheet-like or plate-like structure with different composition and physical properties. All Mica form flat six-sided monoclinic crystals with a remarkable cleavage in the direction of large surfaces, which permits them to be easily cleaved into optically flat films. When cleaved into thin films, they remain tough and elastic even at high temperatures. Mica possesses some of the most outstanding combinations of chemical, physical, electrical, thermal and mechanical properties which cannot found in any other insulating product.
Mica is a biaxial birefringent crystal. Its average refractive index in the visible spectrum is about 1.6. Because of its birefringence, it can be used to cause a phase delay between two orthogonal components of an input linear polarization and thus can be used as a retardation device. For same physical thickness, optical thickness of Mica can vary because its birefringence is not constant. Mica has absorption of 2 to 5% in the visible spectrum.
Physically: Mica is transparent, optically flat, easily split into thin films along its cleavage, colorless in thin sheets, resilient and incompressible.
Chemically: It is a complex hydrous silicate of aluminum, containing potassium, magnesium, iron, sodium fluorine and/or lithium and also traces of several other elements. It is stable and completely inert to the action of water, acids (except hydrofluoric and concentrated sulphuric), bases, alkalies, conventional solvents, oil and virtually unaffected by atmospheric action.
Electrically: Mica has the unique combination of great dielectric strength, uniform dielectric constant and capacitance stability, low power loss (high Q factor), high electrical resistance or resitivity and low temperature coefficient and capacitance. It is noted for its resistances to arc and corona discharge with no permanent injury.
Thermally: Mica is fire proof, infusable, incombustible, non- flammable and can resist temperatures of up to 1000 degrees Celsius/1832 degrees Fahrenheit, depending on the type of Mica. It has low heat conductivity, excellent thermal stability and may be exposed to high temperatures without noticeable effect.
Mechanically: Mica is highly elastic, flexible and tough, having high tensile strength. It has great compression strength and can be hand cut, machined or die-punched.
Typical End uses of natural sheet Mica:
*Electrical apparatus, heaters, hair dryers, etc.
*Electric heating appliances
*Electrical lighting equipment
*Industrial electric heating appliances
*Radio, radar, television etc.
*Motors, generators, load centers, etc.