1. Phase-separation transformation behaviors in NiO bearing Na2O-B2O3-SiO2 glass and melt through high-temperature Ni K-edge XAFS and time-resolved SAXS measurements.
- Author
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Tomita, Kana, Kishi, Tetsuo, Osaka, Keiichi, Matsumura, Daiju, and Yano, Tetsuji
- Subjects
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BOROSILICATES , *TIME-resolved measurements , *LIGAND field theory , *PHASE separation , *HEAT treatment , *PYROMETRY - Abstract
• High-temperature in-situ XAFS and SAXS measurements of nio-doped sodium borosilicate glass and melt were successfully carried out under controlled thermal history. • The Ni2+ ions in borosilicate glass were 6-coordinated (O h) and showed green appearance. The coordination number decreased rapidly when heated above 1000 °C under in-situ measurement. The coordination number seemed to be turned smaller than 5, as the glass quenched from 1000 °C was brown-colored. • High-temperature in-situ time-resolved SAXS measurements show a rapid decrease in scattering intensity during heating from 800 °C up to 1000 °C as the fractionated glass is heated. This is in good agreement with the rapid change in the coordination number of Ni2+, suggesting that the compositional heterogeneity caused by the phase separation affected the ligand field of Ni2+. High-temperature in-situ Ni-K edge XAFS and SAXS measurements were conducted on borosilicate glasses with low alkali content with/without phase separation tendency, which have been investigated to understand immiscibility into silica-rich phase and borate-rich one on the samples heat-treated at certain temperature followed by fast quenching. In this work, using in-situ analyzing techniques, in-situ time-domain evolution of phases along temperature and time was obtained to understand high-temperature behavior. Ni2+ ion probes phase separation behavior using its high selectivity favoring borate-rich phase and sensitivity to electron donating ability of surrounding oxygens. Taking advantage of these characters, local compositional change was tracked during phase separation under heat treatment. Time-resolved SAXS profiles revealed the speed of phase transformation in addition to changes of morphology at respective temperature. The phase-separation transformation mechanism via different phase separation scheme (homogeneous → spinodal → binodal →homogeneous) was clearly described, revealing effect of NiO clustering at higher temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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