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德语Magnets produce a force at a distance that attracts or repels charged particles, electric currents and other magnets. They are essential for the generation of electric power, for motors and generators and many labor-saving electromechanical devices, for information storage and recording and numerous specialized applications such as seals on refrigerator doors. Magnets are made of various materials including iron, nickel, cobalt, neodymium and gadolinium (rare earth metals) and are commonly found as natural lodestones or the magnetite in iron ore, ferrite in ceramics and some alloys of these metals and the synthetic rare earth material barium ferrite.
The strongest magnets are created from rare-earth metals such as neodymium, samarium and cobalt. They are called permanent magnets because they retain their magnetic properties over long periods of time and can withstand high temperatures.
These magnets are manufactured by a complex series of steps that include sintering, annealing, grinding and polishing the raw materials. All these processes must be carefully monitored to ensure that the chemical composition and physical properties remain stable and consistent. This is important because if the magnetic and non-magnetic qualities are compromised it may affect the performance of the finished product.
Samarium-cobalt (SmCo) magnets, introduced in the 1970’s, are the first commercially available rare earth magnets and were initially ranked similarly to neodymium magnets in terms of strength, but have better temperature ratings and higher coercivity (the resistance to demagnetization). They can withstand temperatures down to -273 degC which is close to absolute zero, and they also provide excellent corrosion resistance.
In addition to these benefits, samarium-cobalt magnets have several advantages over neodymium magnets including their lower cost and smaller size. These attributes make SmCo magnets a popular choice for many applications that require high operating temperatures. They are used in generators, motors, pumps, couplings and sensors in the automotive, aerospace, military, marine and food and manufacturing industries.
The magnetic attraction of these magnets is created by the fact that their unpaired electron spins are oriented in such a way that they align themselves with each other. This is the process of magnetization and this phenomenon occurs in all ferromagnetic substances such as steel, aluminum, copper and some alloys of these metals. The iron oxides in lodestone and magnetite are naturally (and comparatively weakly) magnetic as is the neodymium iron boron in junkyard cranes, particle accelerators and other powerful magnet configurations such as quadrupole magnets for focusing particle beams.
Magnets can also be produced artificially by assembling the right combination of iron and other elements. For example, iron-cobalt alloys can be forged to produce extremely strong, compact magnets. A number of industrial applications use this technology, but the most prominent application of magnets is in the levitation and propulsion of trains, called maglev trains, that operate using pulsed magnetic fields to levitate and propel them over a track without touching it and generating mechanical friction or noise. The same principles could be applied to the propulsion of space vehicles to enable them to reach orbit without the need for booster rockets.
Permanent Magnet Coupling Manufacturers
