Confinement effects on freezing and melting

Christenson, Hugo K.

doi:10.1088/0953-8984/13/11/201

Cited by 582 publications

(634 citation statements)

References 201 publications

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“…Environment is particularly important for the many crystallization processes -such as frost heave, the templated growth of nanomaterials and biomineralization -which occur within confined volumes. It is well-recognized that confinement can affect many features of crystal growth, such as the size and morphology, polymorph, orientation and single-crystal vs. polycrystalline structure of crystals, although most work has focused on the freezing transitions of liquids, 3 or the crystallization of organic/ molecular crystals. 4,56 A perfect example of a process which occurs in confinement is biomineralization.…”

Section: Introductionmentioning

confidence: 99%

Confinement Increases the Lifetimes of Hydroxyapatite Precursors

2014

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The mineral component of bone is a carbonated, non-stoichiometric hydroxyapatite (calcium phosphate) that forms in nanometer confinement within collagen fibrils, the principal organic constituent of bone. We here employ a model system to study the effect of confinement on hydroxyapatite precipitation from solution under physiological conditions. In common with earlier studies of calcium carbonate and calcium sulfate precipitation, we find that confinement significantly prolongs the lifetime of metastable phases, here amorphous calcium phosphate (ACP) and octacalcium phosphate (OCP). The effect occurs at surprisingly large separations of up to 1 m, and at 0.2 m the lifetime of ACP is extended by at least an order of magnitude. The soluble additive poly(aspartic acid), which in bulk stabilizes ACP, appears to act synergistically with confinement to give a greatly enhanced stability of ACP. The reason for the extended lifetime appears to be different from that found with CaCO 3 and CaSO 4 , and underscores both the variety of mechanisms whereby 2 confinement affects the growth and transformation of solid phases, and the necessity to study a wide range of crystalline systems to build a full understanding of confinement effects. We suggest that in the case of ACP and OCP the extended lifetime of these metastable phases is chiefly due to a slower transport of ions between a dissolving metastable phase, and the more stable, growing phase. These results highlight the potential importance of confinement on biomineralisation processes.3

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Section: Introductionmentioning

confidence: 99%

Confinement Increases the Lifetimes of Hydroxyapatite Precursors

2014

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“…There are many experimental and theoretical studies reporting that phase behavior of a fluid in such extreme confinement is qualitatively different from, and often much richer than, that of the bulk counterpart. [1][2][3][4][5] It is as yet difficult to predict phase behavior of a confined fluid even if the bulk phase behavior is completely known and the pore confining the fluid is fully characterized. 6,7 A main reason is that we still do not know how these fundamental characteristics of the pore alter the thermodynamic properties of the fluid.…”

Section: Introductionmentioning

confidence: 99%

Phase equilibria and interfacial tension of fluids confined in narrow pores

Hamada

Koga

Tanaka

2007

The Journal of Chemical Physics

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Correlation between phase behaviors of a Lennard-Jones fluid in and outside a pore is examined over wide thermodynamic conditions by grand canonical Monte Carlo simulations. A pressure tensor component of the confined fluid, a variable controllable in simulation but usually uncontrollable in experiment, is related with the pressure of a bulk homogeneous system in equilibrium with the confined system. Effects of the pore dimensionality, size, and attractive potential on the correlations between thermodynamic properties of the confined and bulk systems are clarified. A fluid-wall interfacial tension defined as an excess grand potential is evaluated as a function of the pore size. It is found that the tension decreases linearly with the inverse of the pore diameter or width.

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“…[1][2][3]. The interplay of finite size and surface effects strongly modifies the phase behavior of such confined fluids [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] in comparison with the bulk. The vapor to liquid transition is shifted ("capillary condensation"), as well as critical points [3,4,9,12].…”

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Rounding of Phase Transitions in Cylindrical Pores

et al. 2010

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Phase transitions of systems confined in long cylindrical pores (capillary condensation, wetting, crystallization, etc.) are intrinsically not sharply defined but rounded. The finite size of the cross section causes destruction of long range order along the pore axis by spontaneous nucleation of domain walls. This rounding is analyzed for two models (Ising/lattice gas and Asakura-Oosawa model for colloid-polymer mixtures) by Monte Carlo simulations and interpreted by a phenomenological theory. We show that characteristic differences between the behavior of pores of finite length and infinitely long pores occur. In pores of finite length a rounded transition occurs first, from phase coexistence between two states towards a multi-domain configuration. A second transition to the axially homogeneous phase follows near pore criticality. PACS numbers: 64.75Jk, 64.60.an, 05.70Fh, 02.70Tt Fluids and fluid mixtures in nano-and microporous materials (pore diameters from 1 nm to 150 nm) play important roles in various industries (extracting oil and gas from porous rocks; use as catalysts or for mixture separation in the chemical and pharmaceutical industry; nanofluidic devices, etc.) [1][2][3]. The interplay of finite size and surface effects strongly modifies the phase behavior of such confined fluids [1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] in comparison with the bulk. The vapor to liquid transition is shifted ("capillary condensation"), as well as critical points [3,4,9,12]. Effects of wetting [20] on phase coexistence give rise to interesting patterns (plugs versus capsules versus tube structures etc. [7]). However, although various phase diagrams (different from the bulk) have been proposed (e.g. [1,3,7,9,12,13,17]), many aspects hitherto are not well understood. E.g., the "critical point" where adsorption/desorption hysteresis vanishes seems to be systematically lower than the critical temperature where the density difference between the vapor-like and liquid-like states vanishes [12], in contrast to what theories have predicted [14].However, a crucial aspect (stressed only in a few pioneering studies [3,8], and in the context of Ising/lattice gas models [21][22][23]) is the rounding of all transitions, caused by the quasi-one-dimensional character of a fluid in a long cylindrical pore with cross-sectional radius R. With the current progress of producing pores of wellcontrolled diameter varying from the nanoscale (carbon nanotubes [23][24][25]) to arrays of pores in silicon wafers [26], up to 150 nm wide and of well-controlled length, experiments become feasible which are not plagued by effects of random disorder, which occur in porous glasses [1,27]. Thus, it is important to understand the phase transitions in pores more precisely, considering both the radius R and the length L of the pore as variables (the important role of L has so far been largely disregarded). In the present Letter, we elucidate the rounding of vaporliquid type transitions in cylindrical pores, based on Monte Carlo sim...

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Confinement effects on freezing and melting

Cited by 582 publications

References 201 publications

Confinement Increases the Lifetimes of Hydroxyapatite Precursors

Confinement Increases the Lifetimes of Hydroxyapatite Precursors

Phase equilibria and interfacial tension of fluids confined in narrow pores

Rounding of Phase Transitions in Cylindrical Pores

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