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discovered_02_2013

discovered 02.13 FOCUS WWW.Hzdr.DE as part of the sawdust ought to be re-molten, ideally separated out by type. Which is why we have to first separate them from the fluid that is used as part of the sawing process. Next, the dust is condensed and molten. However, the resulting dust contains impurities. Since the chippings' surface is large compared to their volume, oxidation takes place such that a lot of silicon dioxide is allowed to build up. In addition, carbon particles end up in the sawdust and, during melting, silicon carbide is produced as an unwanted waste product. Our goal is to come up with an economically feasible process for industrial recycling of silicon waste." Magnetic fields are the key The ultimate goal is to develop an industry-compatible process by the end of the three-year period the EU project is scheduled to last. Electromagnetic stirring and separating figures are prominently in the picture. Magnetic fields have long been used to grow crystals, for instance, in the production of silicon monocrystals with diameters of up to 300 millimeters, like those used in modern-day chip production. The effects of a non-contact, externally applied magnetic field on the flow of an electrically conductive molten metal is considerable: Molten metals can be stirred, calmed, decelerated, even swirled. The HZDR researchers have several years' worth collective know-how under their belts, especially when it comes to dirt particles embedded within molten metals. "We're mostly preoccupied with the question of how the magnetic field and coil have to be configured in order to effectively stir the contaminated mixture. Imagine a bucket containing a liquid and flakes of dirt. You might try and stir it so the flakes get spread out evenly so that you could live with it. Or you try and separate out the dirt by stirring and allowing it to deposit on the edge where you're able to fish it out of the liquid," Sven Eckert explains. WITHOUT A SINGLE TOUCH: Magnetic fields stir liquid metals but they are also capable of flow deceleration and acceleration. Josef Pal is seen here conducting an experiment at the HZDR’s MULTIMAG (Multi Purpose Magnetic Field System). Photo: Frank Bierstedt

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