Time Resolved Very High Temperature NMR Study of the Cooling Process of CaO-Al2O3 Liquids

Massiot, Dominique; Touzo, Bruno; Trumeau, Dominique; Farnan, Ian; Rifflet, Jean-Claude; Bessada, Catherine; Douy, André; Coutures, Jean-Pierre

doi:10.1007/978-3-642-80432-8_7

Cited by 2 publications

(3 citation statements)

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“…Containerless processing enables the fabrication of glasses that cannot be formed using traditional methods by eliminating the possibility of chemical reactions between high temperature liquid oxides and containment materials and suppressing heterogeneous nucleation to promote deep supercooling. Using aerodynamic levitation with laser-heating, it is possible to extend this glass forming region to 0.37 x 0.75 [10] (figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…A Vogel-Tammann-Fulcher [16][17][18] fit to the macroscopic viscosity data of liquid CaAl 2 O 4 Figure 1. Liquidus (black curve) [9], conventional glass-forming region (hatched area) [2], and extended glass forming region by containerless processing (solid filled area) [10] for the system (CaO)x(Al 2 O 3 ) 1−x . Using rapid (splat) quenching it is possible to extend the glass-forming region further to x = 0.18 [11].…”

Section: Introductionmentioning

confidence: 99%

“…A subtraction of the measured diraction patterns allows the complex overlapping g αβ (r) functions involving the substituted elements to be unraveled, providing highly-detailed information on liquid structure [14,36]. The results of these scattering techniques in turn provide a rigorous test of the ecacy of [9], conventional glass-forming region (hatched area) [2], and extended glass forming region by containerless processing (solid filled area) [10] for the system (CaO) x (Al 2 O 3 ) 1−x . Using rapid (splat) quenching it is possible to extend the glass-forming region further to x = 0.18 [11].…”

Section: Introductionmentioning

confidence: 99%

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Configurational constraints on glass formation in the liquid calcium aluminate system

Drewitt¹,

Jahn²,

Hennet³

2019

J. Stat. Mech.

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We report new time-resolved synchrotron x-ray diffraction (SXRD) measurements to track structural transformations in calcium-aluminate (CaO)x(Al 2 O 3 ) 1−x liquids during glass formation, and review recent progress in neutron diffraction with isotope substitution (NDIS) experiments, combined with aspherical ion model molecular dynamics (AIM-MD) simulations, to identify the atomic-scale configurational constraints on glass-forming ability. The time-resolved measurements reveal substantial changes in ordering on short-and intermediate-range occurring during supercooling. In the equimolar composition x = 0.5 (CA), the liquid undergoes a remarkable structural re-organisation on vitrification as over coordinated AlO 5 polyhedra and oxygen triclusters breakdown to form a network of predominantly corner-shared AlO 4 tetrahedra. This is accompanied by the formation of branched chains of edge-and face-sharing Cacentred CaOy polyhedra contributing to cationic ordering on intermediate lengthscales. The Ca-rich end-member of the glass-forming system x = 0.75 (C3A) is largely composed of AlO 4 tetrahedra, but ∼ 10 % unconnected AlO 4 monomers and Al 2 O 7 dimers are present, representing a threshold after which the glass can no longer support the formation of an infinitely connected network. Overall, the AIM-MD simulations are in excellent agreement with the SXRD and NDIS experiments suggesting an accurate potential model. However, small discrepancies between the simulated glass structures and experimental measurements are apparent indicating a small degree of liquid-like ordering persists in the simulated glass trajectories. This may be due to the short simulation time-scales which are unrepresentative of the viscous kinetic processes involved in supercooling and glass formation. One approach to improve future models could be the integration of rare event sampling techniques into MD simulation codes to massively extend equilibration time-scales and more accurately model vitrification and structural configurations in real glass systems.

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Section: Introductionmentioning

confidence: 99%