The melting behavior of organic materials confined in porous solids

Jackson, Christian; McKenna, Gregory B.

doi:10.1063/1.459240

Cited by 804 publications

(678 citation statements)

References 32 publications

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“…The shift, now known as the Gibbs-Thomson effect, has been studied with a variety of substances dispersed on inert substrates or confined in porous media. A sampling is given in the references in four groups: weakly interacting molecular species such as rare gas atoms in porous media ͑Brewer et Tell and Maris, 1983;Liezhao et al, 1986;Shimoda et al, 1986;Kondo et al, 1987;Brown et al, 1988;Bruschi et al, 1988;Hiroi et al, 1989;Jackson and McKenna, 1990;Rall et al, 1991;Duffy et al, 1995;Beaudoin et al, 1996͒, ice in porous media ͑Blachere andYoung, 1972;Gay et al, 1992;Maruyama et al, 1992;Ishizaki et al, 1996;Mori et al, 1996͒, dispersed metal particles ͑Takagi, 1954Gladkich et al, 1966;Wronski, 1967;Coombes, 1972;Peppiatt and Sambles, 1975;Buffat andBorel, 1976͒, andice in soils ͑Hoekstra andDelaney, 1974;Konrad and Morgenstern, 1981;Smith and Tice, 1988͒. The typical behavior of the first group is that melting begins appreciably below the bulk transition when the pores are filled. Although the first one or two adsorbed layers prefreeze, due to substrate attractive forces stronger than the interactions within the material.…”

Section: Porous Mediamentioning

confidence: 99%

The physics of premelted ice and its geophysical consequences

2006

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The surface of ice exhibits the swath of phase-transition phenomena common to all materials and as such it acts as an ideal test bed of both theory and experiment. It is readily available, transparent, optically birefringent, and probing it in the laboratory does not require cryogenics or ultrahigh vacuum apparatus. Systematic study reveals the range of critical phenomena, equilibrium and nonequilibrium phase-transitions, and, most relevant to this review, premelting, that are traditionally studied in more simply bound solids. While this makes investigation of ice as a material appealing from the perspective of the physicist, its ubiquity and importance in the natural environment also make ice compelling to a broad range of disciplines in the Earth and planetary sciences. In this review we describe the physics of the premelting of ice and its relationship with the behavior of other materials more familiar to the condensed-matter community. A number of the many tendrils of the basic phenomena as they play out on land, in the oceans, and throughout the atmosphere and biosphere are developed.

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Section: Porous Mediamentioning

confidence: 99%

The physics of premelted ice and its geophysical consequences

2006

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“…there is large and important group of restricted geometry objects, namely materials confined within porous media (hereinafter we will call them confined materials -CM). In recent years properties of CM and in particular various types of phase transitions (PT) (superconducting [1,2], superfluid [3,4], melting-freezing [5,6,7,8,9,10,11] and others PTs [12,13,14,15,16,17,18,19,20,21,22] in different CM have been extensively studied by different experimental methods including calorimetry [5,7,20], NMR [9,21], ultrasonic [8,9] and dielectric [12,14,15] measurements, Raman [10,13], X-ray [12,16,17,18] and neutron scattering [10,14,22,23,24,25,26], differential thermal analysis [19] etc. It has been shown that CM can form either a system of isolated particle...…”

Section: Introductionmentioning

confidence: 99%

Temperature Evolution of Sodium Nitrite Structure in a Restricted Geometry

et al. 2002

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The NaNO2 nanocomposite ferroelectric material in porous glass was studied by neutron diffraction. For the first time the details of the crystal structure including positions and anisotropic thermal parameters were determined for the solid material, embedded in a porous matrix, in ferroand paraelectric phases. It is demonstrated that in the ferroelectric phase the structure is consistent with bulk data but above transition temperature the giant growth of amplitudes of thermal vibrations is observed, resulting in the formation of a "premelted state". Such a conclusion is in a good agreement with the results of dielectric measurements published earlier.

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“…25 It has also been shown that the melting transition of some confined organic molecules has the opposite behavior than the one found here. 26,27 Results for the effect of confinement on the glass transition appear to be more complicated, with different behaviors observed for the same material depending on the experimental methods used. 1 In conclusion, we have developed a procedure for direct synthesis of Ag 2 Se inside the pores of a mesoporous silica containing an ordered array of pores with a diameter between 2 and 10 nm, and found a steady decrease in the temperature of the β→α transition with decreasing pore size.…”

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Effect of nanoscale confinement on the β−α phase transition in Ag2Se

León

Ren

Saboungi

2008

Journal of Applied Physics

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The confinement of silver selenide was investigated using mesoporous silica. Results from x-ray diffraction and electron microscopy show that the confined material still exhibits a β to α transition similar to the one that takes place in the bulk crystalline state but with a transition temperature that depends significantly on the confinement conditions. Decreasing the pore size leads to an increase of the transition temperature, opposite to the behavior of the melting point observed in several metallic and organic materials. In the free particles, on the other hand, no size dependence is observed with particle sizes down to 4 nm.A recent review by Alcoutlabi and McKenna 1 has summarized the state of the art of nanoscale confinement effects on the first-order thermodynamics in confined geometries and shown that the Gibbs-Thomson equation is suitable for describing the changes in melting phenomena observed in the literature due to nanometer scale confinement. They also discussed the more challenging issue of the glass transition for confined systems under different geometrical conditions. However, to our knowledge the problem of the changes in solid-solid phase transitions due to confinement has not been addressed. Some silver ionic salts as well as silver chalcogenides undergo a relatively low-temperature solid-solid transition with dramatic differences between the two phases, e.g., transition from an ordered to a disordered phase with changes in the nature of the conduction mechanism in each phase. 2,3 The structure and spectroscopic properties of various Se based compounds confined in cages of zeolites have been studied, 4 but no attempts have been made to investigate changes induced by the confinement on firstorder transitions. Silver selenide, Ag 2 Se, is such an example and here we focus uniquely on this compound. At room temperature, Ag 2 Se is a narrow band-gap semiconductor with high carrier mobility and without magnetoresistance (MR) and undergoes a phase transition in the solid state. 5,6 The lowtemperature phase, designated as β−Ag 2 Se with an orthorhombic structure, has been widely used as a photosensitizer in photographic films and thermochromic materials. The transition to the hightemperature phase α−Ag 2 Se takes place accompanied by a decrease in volume and has been reported with values of the transition temperature T βα ranging from 127 °C to 143 °C. 7,8 The high-temperature phase is a superionic conductor with mobile Ag + ions used as the solid electrolyte in photochargeable secondary batteries. 9 In the liquid state, it has been shown that the temperature dependence of the conductivity is negative, which is unusual for liquids with a conductivity in the range typical for liquid semiconductors in the narrow definition of Mott. 10,11 Moreover, β−Ag 2 Se has been recently shown to exhibit a significant magnetoresistance (MR) by manipulating small departures from stoichiometry. 12 This large magnetic response, a near-linear increase of the resistance with the applied magnetic field witho...

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The melting behavior of organic materials confined in porous solids

Cited by 804 publications

References 32 publications

The physics of premelted ice and its geophysical consequences

The physics of premelted ice and its geophysical consequences

Temperature Evolution of Sodium Nitrite Structure in a Restricted Geometry

Effect of nanoscale confinement on the β−α phase transition in Ag2Se

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