J. Korean Ceram. Soc. > Volume 31(7); 1994 > Article
 Journal of the Korean Ceramic Society 1994;31(7): 695.
 소량의 $SiO_2$가 첨가된 Calcium Aluminate 유리의 특성 및 구조 심성헌, 허종, 김유성 포항공과대학교 재료금속공학과 Characteristics and Structural Evolution of Low-Silica Calcium Aluminate Glasses ABSTRACT Current study was undertaken to explain the structural evolution and corresponding changes in the properties of calcium aluminate glasses with the variation of SiO2 doping concentration. Calcium aluminate glasses in the compositional ranges of (100-x)(0.6CaO+0.4Al2O3)+xSiO2(where x=0~60) were fabricated. DTA analysis confirmed an anomalous behavior in glass transition temperature (Tg) with the maximum of 887$^{circ}C$ and minimum of 859$^{circ}C$ when x=5 and 50, respectively. densities and refractive indices monotonically decreased with increasing SiO2 content and IR transmitting cutoff shifted to shorter wavelength side when the amount of added SiO2 exceeded 5 mole%. IR fundamental vibration absorption peaks showed the change that NBOs were inclined to SiO4 tetrahedron in the low-silica region and NBO per SiO4 tetrahedra changed from 2 to 0 with increasing silica content. Based on the analysis of IR fundamental vibration absorption peaks, the model of the structural change can be proposed in three step: 1) SiO4 scavenged the NBOs located at AlO4-tetrahedra, which resulted in the increased of Tg values, 2) NBOs located in the main network again with a decrease in Tg, and 3) dominated by the decrease in the relative amount of NBOs in the glass system, where Tg re-increased.
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