Molecular dynamics simulation is applied to investigate the mechanism and variation of self-diffusion in calcium aluminosilicate slags. The self-diffusion coefficients are calculated for eleven slag compositions with varying Al 2 O 3 /SiO 2 ratios at a fixed CaO content. In practice , the results of the study are relevant to the significant changes in transport phenomenon caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum. The cooperative movement between O atoms and network formers is discussed since [AlO 4 ] and [SiO 4 ] tetrahedra are the elementary structural units in the CaO-Al 2 O 3 -SiO 2 (CAS) slag system. The diffusivities for four atomic types are affected by the degree of polymerization (DOP) of slag network characterized by the proportions of non-bridging oxygen (NBO) and Q n species in the system. On the other hand, a sudden increase in 5-coordinated Al as network modifiers in high alumina regions slightly increases the self-diffusion coefficient for Al. As another structural defect, oxygen tricluster plays an important role in the behavior of self-diffusion for O atoms, while the diffusivity for Ca is deeply influenced by its bonding and coordinating conditions.
KeywordsMolecular DynamicsSelf-DiffusionDegree of PolymerizationStructural DefectsAl<sub>2</sub>O<sub>3</sub>/SiO<sub>2<
D. R. Neuville, L. Cormier, B. Boizot and A.-M. Flank, “Structure of β-Irradiated Glasses Studied by X-Ray Absorption and Raman Spectroscopies,” Journal of NonCrystalline Solids, Vol. 323, No. 1-3, 2003, pp. 207-213. http://dx.doi.org/10.1016/S0022-3093(03)00308-9
M. E. Lines, “Photoelastic Trends from Halides to Pnictides by a Bond-Orbital Method,” Journal of Applied Physics, Vol. 60, No. 4, 1986, pp. 1472-1478. http://dx.doi.org/10.1063/1.337274
H. Hosono, K. Yamazaki and Y. Abe, “Reversible Optical Change of Amorphous Red Phosphorus in Reduced Phosphate Glasses,” Journal of the American Ceramic Society, Vol. 68, No. 1, 1985, pp. C304-C305. http://dx.doi.org/10.1111/j.1151-2916.1985.tb15242.x
Z. T. Zhang, G. H. Wen, P. Tang and S. Sridhar, “The Influence of Al2O3/SiO2 Ratio on the Viscosity of Mold Fluxes,” ISIJ International, Vol. 48, No. 6, 2008, pp. 739-746. http://dx.doi.org/10.2355/isijinternational.48.739
P. B. Debenedetti and F. H. Stillinger, “Supercooled Liquids and the Glass Transition,” Nature, Vol. 410, No. 6825, 2001, pp. 259-267. http://dx.doi.org/10.1038/35065704
Y. Liang, F. M. Richter, A. M. Davis and E. B. Watson, “Diffusion in Silicate Melts: I. Self Diffusion in CaOAl2O3-SiO2 at 1500°C and 1 GPa,” Geochimica et Cosmochimica Acta, Vol. 60, No. 22, 1996, pp. 4353-4367. http://dx.doi.org/10.1016/S0016-7037(96)00288-8
K. G. Ewsuk, S. J. Glass, R. E. Loehman, A. P. Tomsia and W. G. Fahrenholtz, “Microstructure and Properties of Al2O3-Al(Si) and Al2O3-Al(Si)-Si Composites Formed by in Situ Reaction of Al with Aluminosilicate Ceramics,” Metallurgical and Materials Transactions A, Vol. 27, No. 8, 1996, pp. 2122-2129. http://dx.doi.org/10.1007/BF02651867
D. Nevins and F. J. Spera, “Molecular Dynamics Simulations of molten CaAl2Si2O8: Dependence of Structure and Properties on Pressure,” American Mineralogist, Vol. 83, No. 11-12, 1998, pp. 1220-1230.
A. Whittington, P. Richet and F. Holtz, “Water and the Viscosity of Depolymerized Aluminosilicate Melts,” Geochimica et Cosmochimica Acta, Vol. 64, No. 21, 2000, pp. 3725-3736. http://dx.doi.org/10.1016/S0016-7037(00)00448-8
G. Gruener, P. Odier, D. De Sousa Meneses, P. Florian and P. Richet, “Bulk and Local Dynamics in Glass-Forming Liquids: A Viscosity, Electrical Conductivity, and NMR Study of Aluminosilicate Melts,” Physical Review B, Vol. 64, No. 2, 2001, pp. 024206(1-5).
V. V. Hoang, “Dynamical Heterogeneity and Diffusion in High-Density Al2O3d2SiO2 Melts,” Physica B, Vol. 400, No. 1-2, 2007, pp. 278-286. http://dx.doi.org/10.1016/j.physb.2007.07.023
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N. A. Morgan and F. J. Spera, “A Molecular Dynamics Study of the Glass Transition in Ca Al2Si2O8,” American Mineralogist, Vol. 86, No. 4, 2001, pp. 915-926.
J. Horbach, W. Kob and K. Binder, “Molecular Dynamics Simulation of the Dynamics of Supercooled Silica,” Philosophical Magazine Part B, Vol. 77, No. 2, 1998, pp. 297-303. http://dx.doi.org/10.1080/13642819808204955
B. Sauerhammer, M. Spiegel, D. Senk, E. Schmidt, S. Sridhar and M. Safi, “Effect of Liquid Phase on Scale Formation during High-Temperature Oxidation of AlSiTransformation-Induced Plasticity Steel Surfaces,” Metallurgical and Materials Transactions B, Vol. 36, No. 4, 2005, pp. 503-512.
A. Tandia, N. T. Timofeev, J. C. Mauro and K. D. Vargheese, “Defect-Mediated Self-Diffusion in Calcium Aluminosilicate Glasses: A Molecular Modeling Study,” Journal of Non-Crystalline Solids, Vol. 357, No. 7, 2011, pp. 1780-1786. http://dx.doi.org/10.1080/13642819808204955
B. T. Poe, P. F. McMillan, D. C. Rubie, S. Chakraborty, J. Yarger and J. Diefenbacher, “Silicon and Oxygen SelfDiffusivities in Silicate Liquids Measured to 15 Gigapascals and 2800 Kelvin,” Science, Vol. 276, No. 5316, 1997, pp. 1245-1248. http://dx.doi.org/10.1126/science.276.5316.1245
S. K. Lee and J. F. Stebbins, “Disorder and the Extent of Polymerization in Calcium Silicate and Aluminosilicate Glasses: O-17 NMR Results and Quantum Chemical Molecular Orbital Calculations,” Geochimica et Cosmochimica Acta, Vol. 70, No. 16, 2006, pp. 4275-4286. http://dx.doi.org/10.1016/j.gca.2006.06.1550
M. J. Toplis, D. B. Dingwell and T. Lenci, “Peraluminous Viscosity Maxima in Na2O-Al2O3-SiO2 Liquids: The Role of Triclusters in Tectosilicate melts,” Geochimica et Cosmochimica Acta, Vol. 61, No. 13, 1997, pp. 2605-2612. http://dx.doi.org/10.1016/S0016-7037(97)00126-9
J. F. Stebbins, J. V. Oglesby and S. Kroeker, “Oxygen Triclusters in Crystalline CaAl4O7 (Grossite) and in Calcium Aluminosilicate Glasses: 17O NMR,” American Mineralogist, Vol. 86, No. 3, 2001, pp. 1307-1311.
D. R. Neuville, L. Cormier, V. Montouillout and D. Massiot, “Local Al Site Distribution in Aluminosilicate Glasses by 27Al MQMAS NMR,” Journal of Non-Crystalline Solids, Vol. 353, No. 2, 2007, pp. 180-184. http://dx.doi.org/10.1016/j.jnoncrysol.2006.09.035
S. Sen and R. E. Youngman, “High-Resolution Multinuclear NMR Structural Study of Binary Aluminosilicate and Other Related Glasses,” The Journal of Physical Chemistry B, Vol. 108, No. 23, 2004, pp. 7557-7564. http://dx.doi.org/10.1021/jp031348u
T. Matsumiya, A. Nogami and Y. Fukuda, “Applicability of Molecular Dynamics to Analyses of Refining Slags,” ISIJ International, Vol. 33, No. 1, 1993, pp. 210-217. http://dx.doi.org/10.2355/isijinternational.33.210
P. Ganster, M. Benoit, W. Kob and J.-M. Delaye, “Structural Properties of a Calcium Aluminosilicate Glass from Molecular-Dynamics Simulations: A Finite Size Effects Study,” The Journal of Chemical Physics, Vol. 120, No. 21, 2004, pp. 10172-10181. http://dx.doi.org/10.1063/1.1724815
F. J. Spera, D. Nevins, M. Ghiorso and I. Cutler, “Structure, Thermodynamic and Transport Properties of CaAl2Si2O8 Liquid. Part I: Molecular Dynamics Simulations,” Geochimica et Cosmochimica Acta, Vol. 73, No. 22, 2009, pp. 6918-6936. http://dx.doi.org/10.1016/j.gca.2009.08.011
K. Zheng, Z. T. Zhang, F. H. Yang and S. Sridhar, “Molecular Dynamics Study of the Structural Properties of Calcium Aluminosilicate Slags with Varying Al2O3/SiO2 Ratios,” ISIJ International, Vol. 52, No. 3, 2012, pp. 342349.
N. A. Morgan and F. J. Spera, “Glass Transition, Structural Relaxation, and Theories of Viscosity: A Molecular Dynamics Study of Amorphous CaAl2Si2O8,” Geochimica et Cosmochimica Acta, Vol. 65, No. 21, 2001, pp. 4019-4041. http://dx.doi.org/10.1016/j.gca.2009.08.011
K. D. Vargheese, A. Tandia and J. C. Mauro, “Origin of Dynamical Heterogeneities in Calcium Aluminosilicate Liquids,” The Journal of Chemical Physics, Vol. 132, No. 19, 2010, pp. 194501(1-9).
C. M. Scarfe and D. J. Cronin, “Viscosity-Temperature Relationships at I atm in the System Diopside-Anorthit,” American Mineralogist, Vol. 68, No. 11-12, 1983, pp. 1083-1088.
V. Petkov, T. Gerber and B. Himmel, “Atomic ordeRing in Cax/2AlxSi1-xO2 Glasses (x =0, 0.34, 0.5, 0.68) by Energy-Dispersive x-Ray Diffraction,” Physical Review B, Vol. 58, No. 18, 1998, pp. 11982-11989. http://dx.doi.org/10.1103/PhysRevB.58.11982
J. F. Stebbins and Z. Xu, “NMR Evidence for Excess Non-Bridging Oxygen in an Aluminosilicate Glass,” Nature, Vol. 390, No. 6655, 1997, pp. 60-62. http://dx.doi.org/10.1038/36312
J. R. Allwardt, S. K. Lee and J. F. Stebbins, “Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from 17O MAS and 3QMAS NMR on Calcium Aluminate and Low-Silica Ca-Aluminosilicate Glasses,” American Mineralogist, Vol. 88, 2003, pp. 949-954.
V. Petkov, S. J. L. Billinge, S. D. Shastri and B. Himmel, “Polyhedral Units and Network Connectivity in Calcium Aluminosilicate Glasses from High-Energy X-Ray Diffraction,” Physical Review Letters, Vol. 85, No. 16, 2000, pp. 3436-3439. http://dx.doi.org/10.1103/PhysRevLett.85.3436
M. Schmucker and H. Schneider, “New Evidence for Tetrahedral Triclusters in Aluminosilicate Glasses,” Journal of Non-Crystalline Solids, Vol. 311, No. 2, 2002, pp. 211-215. http://dx.doi.org/10.1016/S0022-3093(02)01632-0
D. R. Neuville, L. Cormier and D. Massiot, “Al coordination and Speciation in Calcium Aluminosilicate Glasses: Effects of Composition Determined by 27Al MQ-MAS NMR and Raman Spectroscopy,” Chemical Geology, Vol. 229, No. 1-3, 2006, pp. 173-185. http://dx.doi.org/10.1016/j.chemgeo.2006.01.019
A. C. Hannon and J. M. Parker, “The Structure of Aluminate Glasses by Neutron Diffraction,” Journal of NonCrystalline Solids, Vol. 274, No. 1-3, 2000, pp. 102-109. http://dx.doi.org/10.1016/j.chemgeo.2006.01.019
L. Cormier, D. Ghaleb, D. R. Neuville, J.-M. Delaye and G. Calas, “Chemical Dependence of Network Topology of Calcium Aluminosilicate Glasses: A Computer Simulation Study,” Journal of Non-Crystalline Solids, Vol. 332, No. 1-3, 2003, pp. 255-270. http://dx.doi.org/10.1016/j.jnoncrysol.2003.09.012