Metallurgical and Materials Transactions B

, Volume 47, Issue 6, pp 3565–3574

X-ray Microprobe Investigation of Iron During a Simulated Silicon Feedstock Extraction Process

  • Sarah Bernardis
  • Sirine C. Fakra
  • Elena Dal Martello
  • Rune B. Larsen
  • Bonna K. Newman
  • David P. Fenning
  • Marisa Di Sabatino
  • Tonio Buonassisi
Article

DOI: 10.1007/s11663-016-0795-6

Cite this article as:
Bernardis, S., Fakra, S.C., Dal Martello, E. et al. Metall and Materi Trans B (2016) 47: 3565. doi:10.1007/s11663-016-0795-6
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Abstract

Elemental silicon is extracted through carbothermic reduction from silicon-bearing raw feedstock materials such as quartz and quartzites. We investigate the micron-scale distribution and valence state of iron, a deleterious impurity in several iron-sensitive applications, in hydrothermal quartz samples of industrial relevance during a laboratory-scale simulated reduction process. We use X-ray diffraction to inspect the quartz structural change and synchrotron-based microprobe techniques to monitor spatial distribution and oxidation state of iron. In the untreated quartz, most of the iron is embedded in foreign minerals, both as ferric (Fe3+, e.g., in muscovite) and ferrous (Fe2+, e.g., as in biotite) iron. Upon heating the quartz to 1273 K (1000 °C) under industrial-like conditions in a CO(g) environment, iron is found in ferrous (Fe2+) particles. At this temperature, its chemical state is influenced by mineral decomposition and melting processes, whereas at higher temperatures it is influenced by the silicate melts. As the quartz grains partially transform to cristobalite 1873 K (1600 °C), iron diffuses towards liquid–solid interfaces forming ferrous clusters. Silica is liquid at 2173 K (1900 °C) and the iron migrates towards the interfaces between gas phases and the silicate liquid.

Copyright information

© The Minerals, Metals & Materials Society and ASM International 2016

Authors and Affiliations

  • Sarah Bernardis
    • 1
    • 2
  • Sirine C. Fakra
    • 3
  • Elena Dal Martello
    • 4
    • 5
  • Rune B. Larsen
    • 6
  • Bonna K. Newman
    • 1
    • 7
  • David P. Fenning
    • 1
    • 8
  • Marisa Di Sabatino
    • 9
  • Tonio Buonassisi
    • 1
  1. 1.Massachusetts Institute of TechnologyCambridgeUSA
  2. 2.French Commission for Atomic and Alternative Energies (CEA)Le Bourget du LacFrance
  3. 3.Lawrence Berkeley National LaboratoryBerkeleyUSA
  4. 4.Norwegian University of Science and TechnologyTrondheimNorway
  5. 5.BundeGruppen ASOsloNorway
  6. 6.Geology and Mineral Resources EngineeringNorwegian University of Science and TechnologyTrondheimNorway
  7. 7.Energy research Centre of the Netherlands (ECN)PettenNetherlands
  8. 8.University of CaliforniaSan DiegoUSA
  9. 9.Materials Science and EngineeringNorwegian University of Science and TechnologyTrondheimNorway

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