Structure–property relationship amphoteric oxide systems via phase stability and ionic structural analysis

• Published in: Journal of the American Ceramic Society Vol. 104; no. 1; pp. 140 - 156
• Main Authors: Choi, Joon Sung, Park, Tae Jun, Min, Dong Joon
• Format: Journal Article
• Language: English
• Published: Columbus Wiley Subscription Services, Inc 01.01.2021
• Subjects: Activation energy; aluminosilicates; Aluminum oxide; Amphoterics; Basicity; Calcium oxide; Iron; Phase diagrams; Phase stability; Raman spectroscopy; Rotating cylinders; silicates; Silicon dioxide; Slag; slags; Stability analysis; Structural analysis; Structural stability; Viscosity; Wollastonite
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.17432

The effects of basicity and amphoteric oxides (Al2O3 and FetO) on the structure–property relationships of CaO–SiO2–(Al2O3 and FetO) and CaO–SiO2–Al2O3–FetO slags were investigated to determine the constitutional effects on the structure of high‐temperature ionic melts. The proportion of Qn species, which is determined by Raman spectroscopy, and the viscosity measured by the rotating cylinder method are both correlated and shown together with the slag structure index (NBO/T) concept. The NBO/T of CaO‐SiO2 binary slags showed a linear relationship with basicity (CaO/SiO2), including an inflection point at CaO/SiO2 = 1.0 resulting from the stability and Qn‐dominant unit of the melt, which changes close to the wollastonite (CaSiO3) congruent point. This inflection point changes with the increasing amphoteric oxide content (Al2O3 and FetO) because of the change in the dominant polymeric unit (Si4+–O–Si4+→M4+–O–Si4+; M: Al and Fe), in accordance with the equilibrated primary phases. As the Al2O3 content increased, the viscosity and activation energy of slags both drastically increased owing to the change in the flow unit (Si–O–Si, Al–O–Si, and Al–O–Al). In contrast, as FetO increased, the viscosity and activation energy (Eη) of slags decreased because of the change in the flow unit (Si–O–Si, Fe–O–Si, and Fe–O–Fe). Ultimately, the flow unit (T–O–T; T = Si, Al, and Fe) and activation energy of the slags were found to be closely related to the solid primary phase on the phase diagram, and the physical‐property–structure relationship was determined from the phase stability.