Sohei Sukenaga

The effect of adding R2O (R=Li, Na and K) or RO (R=Ba, Mg) on the viscosities of CaO–SiO2–Al2O3 (CaO/SiO2=0.67, 1.00 or 1.22, Al2O3=20 mass%) melts has been measured by rotating crucible viscometer. In addition, structural characterizations of these quenched vitreous samples have been investigated by 27Al and 29Si MAS-NMR spectra.The viscosities of CaO–SiO2–Al2O3–R2O quaternary melts decreased with increasing the additive content of Li2O or Na2O. However, the viscosity of the melts increased wit

In the present work, we measured the density and the surface tension of CaO–SiO2–Al2O3–R2O (CaO/SiO2=0.67, Al2O3=20 mass%, R2O=10.8 mol%, R=Li, Na, K) quaternary melts at elevated temperature using the double-bob Archimedean method and the ring method, respectively. The density of the CaO–SiO2–Al2O3–R2O melts decreased with temperature due to the thermal expansion of the melts. In addition, the density of the CaO–SiO2–Al2O3 ternary melt decreased with the addition of the alkali oxides. We conver

The effect of the CaO/SiO2 molar ratio on the surface tension of calcium aluminosilicate melts containing magnesia (CaO–SiO2–Al2O3–MgO) has been explored using a ring method at 1723–1823 K; the Al2O3 and MgO contents were approximately 12 and 8 mol%, respectively. The CaO/SiO2 molar ratio of the samples was varied in the range of 1.1–1.7. The surface tension of the CaO–SiO2–Al2O3–MgO system simultaneously increased upon increasing the CaO/SiO2 molar ratio. The present data were compared with the

The description of the structure of aluminosilicate glasses is more often centered on its cationic constituents, and oxygen ions determine their connectivity, directly impacting the physical properties of those disordered materials. A very powerful approach to ascertain this short- to medium-range order is to use ¹⁷O NMR, but up to now the speciation of the chemical bonds was only ambiguously achieved for multicomponent glasses. Here, we propose to directly probe the very scarcely exp

The thermal conductivity of silicate melts and glasses is an important physical property for understanding the temperature distribution in high-temperature metallurgical processes; however, the mechanism of heat conduction in these non-crystalline materials remains unclear. Two types of vibration modes must be considered to understand the mechanism of heat conduction, namely, propagative and diffusive vibration modes. In the present study, we carefully derived the thermal conductivity of pure si

In the present study, we measured the viscosity change with the melting time (melting temperature: 1873 K, 1773 K or 1673 K, atmosphere: air) of calcium ferrite (CaO·Fe2O4(CF)) based slags (CF, CF–5wt%SiO2 and CF–5wt%Al2O3) by the rotating crucible method. Moreover, the viscosity changes were discussed from the viewpoints of the iron oxidation states (Fe2+ and Fe3+) and the coordination number of Fe3+.Viscosity of the CF based slags decreased with the melting time at all the temperature (1673 K,

Abstract Optimizing the concentration of molybdenum incorporated in a borosilicate glass matrix is essential in the vitrification of high‐level radioactive waste. However, the incorporation limit of MoO 3 in fundamental borosilicate systems has been rarely correlated with the local structure of the molybdenum cations. This study investigates the variations in the incorporation limit of MoO 3 in ternary sodium borosilicate glass upon varying the B 2 O 3 /(SiO 2 + B 2 O 3 ) ratio (i.e., B ) . The

Viscosity of multi-phases fluids, suspensions of spherical polyethylene beads dispersed in silicone oils, has been measured by rotating cylinder method. Results were obtained as functions of the volume fraction and the average particle size of dispersed beads, the viscosity of silicone oil and shear rate at the surface of rotating spindle. In addition, the rheological characterization of the multi-phase fluids was examined from the relationship between the shear rate and the shear stress calcula

Fluorine and nitrogen are important elements of metallurgical slags and fluxes. Studies on their viscosity have often focused on the additive effect of fluoride and nitride compounds (e.g., CaF2 and Si3N4), whereas the influence of anionic composition (i.e., oxygen, fluorine, and nitrogen concentrations) with a fixed cationic composition remains unclear. The present study reports the scarcely quantified viscosity variations due to changes in the anionic composition of a simple sodium silicate sy

Aluminum cations are generally present in four-fold ([4]Al3+) or five-fold coordination ([5]Al3+) in aluminosilicate slags, where the concentration of [5]Al3+ varies depending on the type of charge compensator, for example, Mg2+ and Ca2+. Although it has been reported that the amount of [5]Al3+ species increases with the replacement of CaO with MgO in the CaO–MgO–SiO2–Al2O3 system, the detailed mechanism underlying the change in the local structure near the aluminum cations remains unclear. Beca

Abstract Lithium disilicate (LS2) has been a crucial parent composition for glass‐ceramics since the 1950s because of its excellent chemical and physical durability. In addition, a wide range of electrical properties can be obtained by changing the composition and crystallinity. Bandgap energy is one of the critical electrical properties for designing new lithium silicate‐based materials. In this study, the bandgap energy of a synthesized LS2 crystal is evaluated using electron energy‐loss spect