Temperature-dependent structural heterogeneity in calcium silicate liquids

Benmore, C. J.; Weber, Jacques; Wilding, Martin C.; Du, Jincheng; Parise, John B.

doi:10.1103/physrevb.82.224202

Cited by 54 publications

(69 citation statements)

References 35 publications

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“…For instance, the peaks positioned at ~3.6 Å and 3.8 Å are associated with Si–Ca/Si–O and Ca–Ca next nearest neighbors, respectively. These peaks are assigned on the basis of their crystalline analogs Tobermorite and Jennite and on the basis of MD simulations of calcium silicate glasses …”

Section: Resultssupporting

confidence: 92%

Compositional Evolution of Calcium Silicate Hydrate (C–S–H) Structures by TotalX‐Ray Scattering

et al. 2011

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High‐energy X‐ray diffraction was employed to study the structural characteristics of a set of C–S–H samples with 0.6 ≤ C/S ≤ 1.75. It has been observed that Si is tetrahedrally coordinated to O for all samples irrespective of chemical composition and the Ca–O coordination number gradually decreases from ~7 to ~6 with increasing C/S ratio. This suggests that the C–S–H structure evolves from a tobermorite‐like structure into a jennite‐like structure as a function of increasing C/S ratio as the interlayer space decreases from ~1.3 to ~1 nm. Evolution of these short‐ and medium‐range order structural characteristics in the C–S–H system is associated with the alteration of the Ca–O layers and silicate depolymerization with increasing C/S.

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Section: Resultssupporting

confidence: 92%

Compositional Evolution of Calcium Silicate Hydrate (C–S–H) Structures by TotalX‐Ray Scattering

et al. 2011

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“…The only published simulations of liquid TiO 2 were made by Hoang [44,45], using the potentials of Matsui and Akaogi (MA) [46], which were those recommended after a review, by Collins et al [47], of the existing potentials at the time (1996). We also assess the more recent potentials of Pedone et al [48] (Pedone hereafter) and the rigid ion potentials of Teter [49], the latter of which are unpublished, but have been used extensively in the literature, particularly for the simulation of silicate glasses [49,50] and melts [51,52] …”

Section: Molecular Dynamicsmentioning

confidence: 99%

Structure of molten titanium dioxide

et al. 2014

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The x-ray structure factor of molten TiO 2 has been measured for the first time, enabled by the use of aerodynamic levitation and laser beam heating, to a temperature of T = 2250(30) K. Ti-O coordination number in the melt is close to n TiO = 5.0(2), with modal Ti-O bond length r TiO = 1.881(5) Å, both values being significantly smaller than for the high temperature stable Rutile crystal structure (n TiO = 6.0, r TiO = 1.959 Å). The structural differences between melt and crystal are qualitatively similar to those for alumina, which is rationalized in terms of the similar field strengths of Ti 4+ and Al 3+. The diffraction data are used to generate physically and chemically reasonable structural models, which are then compared to the predictions based on various classical molecular dynamics (MD) potentials. New interatomic potentials, suitable for modelling molten TiO 2 , are introduced, given the inability of existing MD models to reproduce the diffraction data. These new potentials have the additional great advantage of being able to predict the density and thermal expansion of the melt, as well as solid amorphous TiO 2 , in agreement with published results. This is of critical importance given the strong correlation between density and structural parameters such as n TiO . The large thermal expansion of the melt is associated with weakly temperature dependent structural changes, whereby simulations show that n TiO = 5.85(2) -(3.0(1) x 10 -4 )T (K, 2.75 Å cut-off). The TiO 2 liquid is structurally analogous to the geophysically relevant high pressure liquid silica system at around 27 GPa. We argue that the predominance of 5-fold polyhedra in the melt implies the existence of as yet undiscovered TiO 2 polymorphs, based on lowerthan-octahedral coordination numbers, which are likely to be metastable under ambient conditions. Given the industrial importance of titanium oxides, experimental and computational searches for such polymorphs are well warranted.

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“…Recent work on molten oxides shows that the liquids can significantly restructure when they are supercooled (Benmore et al 2010). In molten calcium silicates, the extent to which CaO 6 polyhedra edge-share increases when the liquid is supercooled (Benmore et al 2010). A recent theoretical analysis suggests that structural changes are a general property of liquids when they are supercooled to a glass.…”

Section: Discussionmentioning

confidence: 96%

“…Making similar measurements at lower temperatures will help to develop a comprehensive understanding of the way in which molecular liquids transform into glasses. Recent work on molten oxides shows that the liquids can significantly restructure when they are supercooled (Benmore et al 2010). In molten calcium silicates, the extent to which CaO 6 polyhedra edge-share increases when the liquid is supercooled (Benmore et al 2010).…”

Section: Discussionmentioning

confidence: 98%

“…Work is in progress to investigate the effects of stabilizers on the glass-forming tendency and the stability of glassy and amorphous pharmaceutical products made from levitated liquids and solutions. Structural evolution in high temperature liquids has been studied extensively by use of in-situ X-ray and neutron measurements of structure (Benmore et al 2010;Drewitt et al 2011). Making similar measurements at lower temperatures will help to develop a comprehensive understanding of the way in which molecular liquids transform into glasses.…”

Section: Discussionmentioning

confidence: 99%

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Acoustic levitation: recent developments and emerging opportunities in biomaterials research

et al. 2011

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Containerless sample environments (levitation) are useful for study of nucleation, supercooling, and vitrification and for synthesis of new materials, often with non-equilibrium structures. Elimination of extrinsic nucleation by container walls extends access to supercooled and supersaturated liquids under high-purity conditions. Acoustic levitation is well suited to the study of liquids including aqueous solutions, organics, soft materials, polymers, and pharmaceuticals at around room temperature. This article briefly reviews recent developments and applications of acoustic levitation in materials R&D. Examples of experiments yielding amorphous pharmaceutical materials are presented. The implementation and results of experiments on supercooled and supersaturated liquids using an acoustic levitator at a high-energy X-ray beamline are described.

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Temperature-dependent structural heterogeneity in calcium silicate liquids

Cited by 54 publications

References 35 publications

Compositional Evolution of Calcium Silicate Hydrate (C–S–H) Structures by TotalX‐Ray Scattering

Compositional Evolution of Calcium Silicate Hydrate (C–S–H) Structures by TotalX‐Ray Scattering

Structure of molten titanium dioxide

Acoustic levitation: recent developments and emerging opportunities in biomaterials research

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