X-ray Microprobe Investigation of Iron During a Simulated Silicon Feedstock Extraction Process
- PDF / 2,371,276 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 4 Downloads / 131 Views
TION
EXTRACTION of silicon from raw feedstocks requires carbothermic reduction, industrially performed in submerged electric arc furnaces.[1,2] Production of alkyl-chlorosilane/chlorosilane, aluminum alloys, and solar-grade silicon used for photovoltaic applications are major examples of applications sensitive to the presence of unintentional metallic impurities. In the following, the latter application is used as exempli gratia.
SARAH BERNARDIS, formerly Doctoral Student with the Massachusetts Institute of Technology, Cambridge, MA, is now Research Engineer with the French Commission for Atomic and Alternative Energies (CEA), Le Bourget du Lac, France. Contact e-mail: [email protected] SIRINE C. FAKRA, Principal Associate Beamline Scientist, is with the Lawrence Berkeley National Laboratory, Berkeley, CA. ELENA DAL MARTELLO, formerly Doctoral Student with the Norwegian University of Science and Technology, Trondheim, Norway, is now Project Engineer with BundeGruppen AS, Oslo, Norway. RUNE B. LARSEN, Professor, is with Geology and Mineral Resources Engineering, Norwegian University of Science and Technology, Trondheim, Norway. BONNA K. NEWMAN, formerly Postdoctoral Fellow with the Massachusetts Institute of Technology, is now Researcher with Energy Research Centre of the Netherlands (ECN), Petten, The Netherlands. DAVID P. FENNING, formerly Doctoral Student with the Massachusetts Institute of Technology, is now Assistant Professor with the University of California, San Diego, CA. MARISA DI SABATINO, Associate Professor, is with the Materials Science and Engineering Department, Norwegian University of Science and Technology, Trondheim, Norway. TONIO BUONASSISI, Associate Professor, is with the Massachusetts Institute of Technology. Manuscript submitted October 9, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
In silicon used for photovoltaic applications, metallic impurities are subject of extensive research: they can enter the production chain via the initial raw feedstock materials[3–6] as well as via furnace crucible and/or crucible lining materials or via material handling; and they are still present in the silicon and solar cells.[7–17] Often, post-reduction silicon refining is the only method sought to reduce unwanted impurities, directing efforts to understand their behavior to a certain step of the extraction process onwards. Yet impurities are already present in the raw feedstocks and they interfere with the silica reduction processes and the kinetics of the entire process. Several theoretical[2,18–20] and experimental[21–24] studies are dedicated to the Si-C-O system and proposed chemical reactions during silica reduction. However, industrial submerged arc furnaces operate outside equilibrium conditions in dynamic cycles of charging (inserting raw material in the furnace), stocking (breaking the crust formed at the top of the furnace), and tapping (extracting silicon metal from the furnace bottom). These cycles influence chemical speciation, temperature, and pressure.[25,26] Industrial furnaces are co
Data Loading...
