The Structure of the Molten FeO-SiO 2 System
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RAY diffraction techniques have been used extensively for the study of glass structures ," During the past few years, we have been engaged in the study of the structure of molten silicates by means of high temperature X-ray diffraction. The results of the molten binary alkali and alkaline earth silicates, Li 20, Na 20, K20, CaO and MgO have been reported,"? All these systems exhibited the fotlowing three characteristic features: 1) Molten silicates containing up to 60 mole pct M20 or MO, where M denotes the alkali or alkaline earth metal, mainly consist of Si0 4 tetrahedral units, 2) On addition of M20 or MO, the Si0 4 tetrahedral units become more loosely packed due to the breaking of the three dimensional network structure of pure silica, and 3) The structure of molten silicates is insensitive to temperature at least within the temperature range investigated. However, there is a difference in the root mean square displacements of the correlation in the near neighbor distance. These conclusions were based on studies confined to the lower melting acid region of the respective binary silicate systems since these compositions were more amenable to experimentation. In the baste region of silicate melts, it is expected that the Si04 tetrahedral units may exist individually. To test the applicability of these conclusions to the more basic region of silicate melts, the FeO-Si0 2 system was investigated by means of a high temperature X - ray diffraction technique. The composition range studied was from 0 to 44 mole pet Si02. II. EXPERIMENTAL The experimental arrangements, including calibration of temperature, operating procedures for the X-ray intensity measurements of high temperature YOSHIO WASEDA and J. M. TOGURI are Visiting Professor and Professor and Chairman, respectively, Department of Metallurgy and Materials Science, University of Toronto, Toronto, M5S 1A4, Canada. Manuscript submitted January 24, 1978.
melts and the correction of the observed intensity data were almost identical to those described previously.2,3 The Compton scattering was eliminated experimentally by using the usual diffracted beam moncchromator J':" Depending on temperature and slag composition, either an iron or molybdenum cell was used. The sample was melted by a molybdenum heater. The heater-sample holder assembly was enclosed under a purified dry argon atmosphere in which the oxygen partial pressure was 10- 9 atm. Measurements were also carried out under an argon atmosphere in which the oxygen partial pressure was 10-7 atm, and under an argon-3 pet H2 mixture in which the oxygen partial pressure was 10- 11 atm. These oxygen partial pressures were determined by using a calcia stabilized zirconia electrolyte. The temperature was controlled to within ±5 degrees of the desired temperatures. FeO was prepared by melting a mixture of high purity Fe and Fe 203 powders (Wacoh Chemical Company) in an iron crucible, then rapidly quenching the melt into water. The quenched sample was ground to - 100 mesh and then passed through a magnetic separator to
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