Phase transitions for gallium microparticles in a porous glass

Borisov, B. F.; Charnaya, E. V.; Kumzerov, Yu. A.; Раджабов, А. К.; Shelyapin, AV

doi:10.1016/0038-1098(94)90492-8

Cited by 27 publications

(18 citation statements)

References 10 publications

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“…Examples of confinement effect include anomalous and lamellar diffusion, enhancement of correlation times, shift of melting and freezing temperatures, as well as the change of the very character of phase transition occurring in a space having dimension less than three (fractal path). , In particular geometrical restrictions are found to favor an increased microviscosity that causes a more hindered diffusion in the imbibed liquids and a molecular reorientation time longer than in the bulk state. The excluded volume effects (i.e., physical traps) on the radial distribution functions have a physical origin that can be explained taking into account that the local number density n l for an atom in the liquid phase in a pore is generally higher than the average number density of the liquid in the whole system n̄ , because the regions of the sample occupied by the substrate are forbidden for the atoms (frustration).…”

Section: General Considerationsmentioning

confidence: 99%

Diffusive Relaxations and Vibrational Properties of Water and H-bonded Systems in Confined State by Neutrons and Light Scattering: State of the Art

et al. 2000

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A detailed spectroscopic analysis is presented in order to study the reorientational and vibrational dynamics of water and other fundamental H-bonded systems: ethylene glycol (HO−CH2−CH2−OH) and its homologous species, such as ethylene glycol monomethyl ether (CH3O−CH2−CH2−OH) and ethylene glycol dimethyl ether (CH3O−CH2−CH2−OCH3), propylene glycol (HO−CH(CH3)−CH2−OH) and its oligomers, that are confined in a matrix of sol−gel porous glasses with 26 Å interconnected cylindrical pores. The use of different spectroscopic techniques, light scattering (Rayleigh wing and Raman scattering), FT-IR absorption, neutron scattering (incoherent quasi elastic and inelastic neutron scattering, IQENS and IINS, respectively) allow the marking of different dynamical parameters, with different probes being used to investigate H-bonded systems. The clear influence of the confinement on the mobility of the studied liquids, with a dramatic frozen-in observed effect respect to the bulk state, is evidenced and compared with literature results. Furthermore, a surface−liquid potential well induces strong modifications of the local symmetry of the vibrational groups (e.g., the active OH stretching groups) involved in the interaction, giving rise to anharmonic effects (red shift, band enlargement) that depend on the nature of the surface (hydrophobic or hydrophilic) and on the nature of guest liquids (wetting or nonwetting).

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Section: General Considerationsmentioning

confidence: 99%

Diffusive Relaxations and Vibrational Properties of Water and H-bonded Systems in Confined State by Neutrons and Light Scattering: State of the Art

et al. 2000

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“…The high surface to volume ratio in porous materials permits studying the surface interactions of nematogens, in particular aligning properties of the surface material on the confined molecules [1,2]. Furthermore, the confining cavity sizes can influence the temperatures [3,4] and the very character [5,6,7] of phase transitions in the confined material. New thermodynamic phases can be induced or bulk phases suppressed in the confining geometry [8,9], and order and orientation of the confined liquid crystalline mesophases can be changed.…”

Section: Introductionmentioning

confidence: 99%

Measurement of orientational order and mobility of a nematic liquid crystal in random nanometer confinement

Cramer

Kremer

et al. 1997

The Journal of Chemical Physics

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Confinement of a nematogen in submicrometer cavities can produce substantial effects on the nematic-isotropic phase transition and on order and orientation of the nematic phase. We combine the methods of 13 C-and 1 H-NMR and broadband dielectric spectroscopy to probe liquid crystalline order and molecular mobility. We find that the dynamics of mesogenic molecules (5CB) in the free volume of nanoporous sol-gel glass (5nm pore diameter) is as fast as in the free bulk phase. In addition, a boundary layer of molecules with reduced mobility covers the pore walls. Isotropicnematic transition as well as crystallization of the confined nematogen are considerably suppressed. In order to extract the temperature dependence of the nematic order parameter from NMR data, a mathematical model is applied which describes the combined influences of orientational order and diffusional averaging in randomly oriented pores on NMR spectra of the nematogens.

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“…Large quantities of Ga nanoparticles can be obtained by soaking porous matrices in liquid gallium. Via this route, it is possible to obtain particles with diameters of 422 or 8 nm 17. Mixing liquid gallium thoroughly with epoxy resin results in particles with sizes of 100 to 1000 nm 23.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Supported Ga Nanodrops by a Bottom‐up Route

Armbrüster

Cardoso‐Gil

2015

Zeitschrift anorg allge chemie

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Nanoparticulate gallium can be obtained in an unconfined state by reduction of gallium-acetylacetonate with LiAlH4. The products were analyzed by scanning electron microscopy, elemental analysis together with X-ray diffraction, and thermal analysis. EXAFS investigations reveal, in accordance with the results from thermal analyses, that the particles are liquid at room temperature. The reason for the lower melting point could not be clarified within this study and might be caused either by the lower melting point of -gallium or by the small particle size of 10-20 nm. Upon cooling, several of the low-temperature modifications of gallium are observed depending on cooling-rate and temperature

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Phase transitions for gallium microparticles in a porous glass

Cited by 27 publications

References 10 publications

Diffusive Relaxations and Vibrational Properties of Water and H-bonded Systems in Confined State by Neutrons and Light Scattering: State of the Art

Diffusive Relaxations and Vibrational Properties of Water and H-bonded Systems in Confined State by Neutrons and Light Scattering: State of the Art

Measurement of orientational order and mobility of a nematic liquid crystal in random nanometer confinement

Synthesis of Supported Ga Nanodrops by a Bottom‐up Route

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