Molecular Dynamics Study of the Structural Properties of Calcium Aluminosilicate Slags with Varying Al2O3/SiO2 Ratios

Abstract

Molecular dynamics simulation was explored to investigate the change of structure of calcium aluminosilicate slags with varying Al2O3/SiO2 ratios at a fixed CaO content. In practice the results of the study are relevant to the significant changes in slag structure caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum. It was found that Q 4 tetrahedral species (tetrahedron with four bridging oxygens) increase while NBOs (non-bridging oxygen) decreases with increasing Al2O3/SiO2 mole ratio, suggesting that a more polymerized network was formed. The concentration of oxygen tricluster increased dramatically up to 24% with increasing Al2O3/SiO2 mole ratio, and the coordination number for Al (CNAl-O) was also observed to increase from 4.02 for sample CAS1 to 4.11 for sample CAS11, suggesting that high coordination number of Al presents in the slag melt with the substitution of [AlO4] for [SiO4]. NBOs prefer to be coordinated with Si and Al tends to be localized in more polymerized environment as network intermediate phases. The degree of Al avoidance was calculated and the Al avoidance principle is applicable in the SiO2 rich regions.KEY WORDS: molecular dynamics; calcium aluminosilicate slag; slag structure; Al2O3/SiO2 ratio.

Structure Analysis of CaO–SiO2–Al2O3–TiO2 Slag by Molecular Dynamics Simulation and FT-IR Spectroscopy

“…The values of Si-O, Al-O, Ti-O and Ca-O are 1.6, 1.75, 1.9 and 2.3 Å, respectively. The bond length of Si-O, Al-O, Ti-O and Ca-O are in accordance with previous results although in different slag systems, 24,25,29,31) indicating that the strong stability of shortrange order less than 6 Å despite of different systems. The combining capacity between cations and O 2-were also presented by comparing the bond length and it can be obviously seen that the rank of stability is Si-O > Al-O > Ti-O > Ca-O, which is opposite to the rank of their lengths.…”

“…The second item on the right hand denotes the short-range repulsion interaction between two atoms which are determined by parameters of Bij and Rij. The parameters were adopted from Zheng's work 25) as well as our previous study 26) to insure the accuracy. The parameters Bij and Rij, corresponding to the short-range repulsion interaction between two atoms, were listed in Table 1.…”

“…24) Zheng et al have also revealed the effect of Al2O3/SiO2 ratios on the structure of calcium aluminosilicate slags by MD simulation. 25) In our previous work, 26) the structure in CaO-SiO2-TiO2 system has been investigated with different additions of TiO2 at a fixed CaO/SiO2 ratio. In the present work, the MD simulation and FT-IR were combined to investigate the information of the structure in CaO-SiO2-14 mass% Al2O3-TiO2 slag with varying additions of TiO2 as well as different CaO/TiO2 ratios.…”

Molecular Dynamics Analysis of the Microstructure of the CaO-P₂O₅-SiO₂ Slag System with Varying P₂O₅/SiO₂ Ratios

“…16,22) However, in this CaO-P 2 O 5 -SiO 2 slag system, oxygen tricluster was not found, this is probably because the content of CaO is high, which increases the difficulty of forming complicated clusters and anions. The distributions of the BO, NBO and O 2¹ are presented in Fig.…”

Thermal Conductivity of Molten Slags: A Review of Measurement Techniques and Discussion Based on Microstructural Analysis

“…Zheng et al confirmed this microstructural modification of the CaOAl2O3-SiO2 system with composition variation using Molecular Dynamics simulation. 51) This found that although the SiO4 network may be depolymerized by initial Al2O3 addition, Si and Al are likely to subsequently coordinate together to form a new network cluster. By careful analyses of the microstructure of molten slags, the amphoteric behavior could be clearly understood and an interrelationship among the thermophysical properties of the molten silicate was verified.…”