분자동력학법에 의한 (1-x)CaO·xAl_(2)O_(3) 유리의 구조 연구
(A) Study on the Structures of (1-x)CaO·xAl_(2)O_(3) Glasses by Molecular Dynamics Method
분자동력학법 유리구조 세라믹공학;
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Calcium aluminate glasses have been proposed as materials for low-loss infrared opical fibers. CaO·Al2O3 system glasses are also of intrinsic scientific interest because they do not contain any of the traditional glass forming. Molecular dynamics simulation of xAl2O3·(1-x)CaO glasses has been carried out using empirical potentials with the covalent term. The potential model and parameters used were correctly reproduced by the neutron TCF(Total Correlation Function) of structure of 62CaO·38Al2O3 glass and some properties such as elastic properties. The data show that the calcium atoms are octahedrally coordinated by oxygen and at least two calcium atoms in AlO4 structural units are bound by two oxygen atoms. The X-ray photoelectron spectroscopy(XPS) was used to study NBO/BO ratios of 62CaO·38Al2O3 glasses. As the concentration of Al2O3 were increased, the number of Q4 was increased suddenly because it was included to Ⅴ,Ⅵ coordination of Al. while the number of Q2 ,Q1 were decreased. The viscosity was calculated to diffusion coefficient by Stokes-Einstein relation equation. And the intermediate range order of structure was analyzed into ring size distribution(RDS). When Al2O3 content decreases, calcium aluminate liquid transfers gradually into fissured liquid, the average ring size increases, and alumina network gradually loses its connectivity. Also it is expected that glass forming range is limited to near eutectic compositions.