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• 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]

• Na 2 O-B 2 O 3 -SiO 2 glass plate phase separated in spinodal was partially remelted and homogenized by laser heating, using embedded NiO as CW-laser (λ=1064 nm) absorber and heat center. • The laser irradiated area of glass turned brown with high chemical durability, indicating the local environment change of Ni2+ ion along with miscibility change. • Similar color change was observed when the glass is water-quenched from 1000°C melt, which has homogeneous structure frozen at room temperature. • The color of Ni2+ ion reflects miscible-immiscible behavior of sodium borosilicate glass. Na 2 O-B 2 O 3 -SiO 2 glass plate phase separated in spinodal was partially remelted and homogenized by laser heating. As heat generation source, 0.8 mol% NiO was added to absorb continuous-wave laser with λ=1064 nm. After acid leaching, borate phase with NiO was remaining partially in laser irradiated area. Smooth, non-porous surface was found at cross section of laser irradiated area below surface, and nano-scale porous structure was found at non-irradiated area observed by scanning electron microscopy (SEM). X-ray Absorption Fine Structure (XAFS) spectra revealed that Ni2+ in laser irradiated area showed coordination change from 6 coordinated octahedral to 5 coordinated in square pyramid along with apparent color change from green to brown. Similar change was observed in water-quenched specimen from 1000°C. Ni2+ transition gave additional structural information in phase separate / homogeneous glass, which was difficult to be distinguished by spectroscopy which focuses on covalent bonding of glass network. [ABSTRACT FROM AUTHOR]

Photon emission (PE) at wavelength ranges of 430–490 nm (B-PE), 500–600 nm (G-PE) and 610–680 nm (R-PE) caused by brittle fracture was simultaneously measured in the nanosecond-to-microsecond and millisecond time domains for two types of borosilicate glasses: Pyrex-type Tempax glass and BK7 glass. The results were compared to those for silica and soda lime glasses. The time dependence of the PE of Tempax glass was similar to that of silica glass, while the PE intensity was lower. Because Tempax glass contains both silica-rich and borate-rich amorphous phases, the PE must be mainly produced by the fracture of the silica-rich phase. Moreover, the proportion of B-PE of Tempax glass was higher than that of silica glass. This suggests that the measured B-PE might also include very weak PE caused by the fracture of the borate-rich phase. The PE time dependence of BK7 glass was similar to that of soda lime glass, which was different from the case for Tempax glass. The PE intensity of BK7 glass was slightly higher than that of soda lime glass, but much lower than that of Tempax glass. The result indicates that non-bridging oxygen in the glasses affects crack propagation behavior and reduces the PE. [ABSTRACT FROM AUTHOR]