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Title: The effects of glass doping, temperature and time on the morphology, composition, and iron redox of spinel crystals

Precipitation of large crystals/agglomerates of spinel and their accumulation in the pour spout riser of a Joule-heated ceramic melter during idling can plug the melter and prevent pouring of molten glass into canisters. Thus, there is a need to understand the effects of spinel-forming components, temperature, and time on the growth of crystals in connection with an accumulation rate. In our study, crystals of spinel [Fe, Ni, Mn, Zn, Sn][Fe, Cr]₂O₄ were precipitated from simulated high-level waste borosilicate glasses containing different concentrations of Ni, Fe, and Cr by heat treating at 850 and 900°C for different times. These crystals were extracted from the glasses and analyzed with scanning electron microscopy and image analysis for size and shape, with inductively coupled plasma-atomic emission spectroscopy and atom probe tomography for concentration of spinel-forming components, and with wet colorimetry and Mössbauer spectroscopy for Fe²⁺/Fetotal ratio. High concentrations of Ni, Fe, and Cr in glasses resulted in the precipitation of crystals larger than 100 µm in just two days. Crystals were a solid solution of NiFe₂O₄, NiCr₂O₄, and -Fe₂O₃ (identified only in the high-Ni-Fe glass) and also contained small concentrations of less than 1 at% of Li, Mg, Mn, and Al.
 [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Office of River Protection, Richland, WA (United States)
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Conference: Advances in Materials Science for Environmental and Energy Technologies III, October 27-31, 2013, Montreal, Quebec, Canada. Ceramic Transactions, 250:147-156
T Ohji, et al; John Wiley & Sons, Inc., Hoboken, NJ, United States(US).
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States
HLW; spinel crystals; iron redox; chemical analysis; SEM