澳门金沙平台开户网址是多少:Making complex magnets the easy way

 作者:酆樨藐     |      日期:2019-03-08 06:10:20
COMPLEX magnets similar to those used to build computer disc drives can be made in a flash and at a fraction of the normal cost simply by setting light to a mixture of powders. Conventional methods for making the ceramic-like magnetic materials called ferrites involve several stages. Oxides of iron and other elements such as chromium, barium or strontium must be ground together, heated and then cooled. After the process has been repeated several times, the material is turned into a magnet by placing it in a strong magnetic field. In the one-step process devised by Ivan Parkin and Quentin Pankhurst of University College London, ferrite magnets are made directly from a mixture of metallic iron and metal oxides. The mix, known as a thermite mixture, is placed in a magnetic field and set alight. This starts a self-propagating reaction that generates high temperatures that force the components to react and form a ferrite which is magnetised by the external field. By carefully controlling the magnetic field they applied to the mixture, the researchers found they could create a single magnet with regions of different field strength and polarity. Sophisticated magnets such as these are used in a variety of applications, including the motors inside computer disc drives and particle accelerators. They are normally made by gluing several single magnets together. Making these complex magnets with the thermite technique is not only quicker and cheaper, it also produces a better result. “The strength of these magnets is much greater than when you glue separate magnets together,