Inclusion Optimized Silicon for the Production of Silicones
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One of the challenges with silicones production is the accumulation ofimpurities from metallurgical grade silicon (MG-Si) in the reactor. Size, shapeand density of the intermetallics affect the accumulation, and their sizedistribution is also dependent on the thermal history of silicon. Differentannealing treatments were carried out on MG-Si in order to investigate the reorderingof the intermetallics from liquid state. The surfaces of the sample wereanalyzed with BSE-SEM images and the computer program ImageJ®. Theresults show that the size of the intermetallics increases with time andtemperature, whereas aspect ratio and inclusions number have the oppositetrend. Temperature above 850°C is a necessary condition for transformations tostart. The composition was changed after a melting step was performed in air. XRFchemical analysis confirm the effects of refining and segregation. The softwareSiStruc® calculated expected contents of phases based on thermodynamics only.EPMA and BSE-SEM image analysis estimated the phase composition on auntreated sample and on a treated one. It can be stated that there could bereactions between intermetallic phases. The effects of the annealing andrefining on the composition are compared to the expected change on reactivityand selectivity in the silicones production.