Étude par absorption hertzienne de l'eau adsorbée sur un gel de silice

Kamyoshi, Kan-Tchi; Ripoche, Jean

doi:10.1051/jphysrad:019580019012094300

Cited by 13 publications

(11 citation statements)

References 4 publications

(2 reference statements)

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“…The above behavior can be understood easily by plotting the characteristic frequency for the observed relaxation in the Arrhenius form, as shown in Figure . If a linear relationship is established, then the activation energy for the observed relaxation can be estimated from the slope of the straight line. ,− In the present case, it is important to note that the Arrhenius plots give a nonlinear relationship. In the lower coverage, e.g., θ = 0.6, the f m value decreases with decreasing temperature.…”

Section: Resultsmentioning

confidence: 98%

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface

Kuroda¹,

Watanabe²,

Yoshikawa³

et al. 1997

Langmuir

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The dielectric behavior of Ag2O samples with different amounts of adsorbed H2O was investigated in the temperature range from 308 to 200 K and in the frequency region from 0.1 Hz to 5 MHz. A large relaxation is observed in these ranges, and it is explained by the interfacial polarization due to the heterogeneity of the system. The characteristic frequency (f m) for this relaxation is lowered with decreasing temperature until a complete monolayer is established. However, such a behavior of fm in the region beyond the surface coverage of ca. 1 reveals a new specific feature; the fm value gives a maximal frequency at around 278 K. The cause of this behavior is explored through the measurements of the differential adsorption heat, water content, and Clausius-Clapeyron plots (ln p vs 1/T). As a result, a new phenomenon observed in the Ag 2O-H2O system can be explained by considering that the continuous phase change occurs at around 278 K in the adsorbed layer higher than the monolayer; the cluster-like structure formed on the OH groups at a temperature higher than 278 K is transferred to the two-or three-dimensional network structure formed by H-bonding between adsorbed H 2O molecules in the lower temperature region.

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Section: Resultsmentioning

confidence: 98%

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface

Kuroda¹,

Watanabe²,

Yoshikawa³

et al. 1997

Langmuir

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“…This can be compared with the activation energies of 18 kJ/mol for liquid water and 53 kJ/mol for ice. 39,40,[42][43][44][45] It is clear that the ∆E q value for the Cr 2 O 3 -H 2 O system is close to that for ice; the water molecule adsorbed on the Cr 2 O 3 surface takes the icelike (solid) state, though β in eqs 6-8 was estimated to be ca. 0.5 at a coverage of 1.1 ML, being different from that of pure ice.…”

Section: Resultsmentioning

confidence: 99%

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

et al. 1999

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The dynamic properties of water molecules adsorbed on the hydroxylated chromium(III) oxide surface, whose two-dimensional critical temperature was 303 K, were investigated at around the two-dimensional critical temperature by FT-IR, quasielastic neutron scattering, and dielectric relaxation techniques. The Cr 2 O 3 sample covered with monolayer water gives an IR band having a broad nature at ∼3400 cm -1 , due to the mutual hydrogen bonding among the adsorbed water molecules. The quasielastic neutron scattering data have revealed that the motion of the adsorbed water molecules changes across the two-dimensional critical temperature, ranging from the motion of the supercritical fluid to that of a solidified phase with decreasing temperature. The dielectric spectra observed at 298 K and at the coverage of 1.1 monolayers have been interpreted in terms of the presence of two relaxations due to the interfacial and orientational polarizations. The characteristic frequency of the relaxation for the latter polarization was estimated to be ca. 300 Hz. It is concluded from these findings that the two-dimensionally condensed waters adopt the mutually hydrogen-bonded solid state having a commensurate structure with the hydroxylated (001) Cr 2 O 3 surface below the two-dimensional critical temperature of this system. In addition, the interfacial polarization was explained in terms of a hopping model of protons of the adsorbed molecules. The behavior of conductivity arising from this proton hopping also indicates the morphology of the two-dimensionally condensed water below the monolayer coverage: the small clusters of water are formed on the Cr 2 O 3 surface.

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“…5 gives the plot of AE (= E , -E,) of arc I11 us. 8. Eqn (6) has so far been corroborated indirectly by plotting the increment of the dielectric permittivity against 8.…”

Section: Discussionmentioning

confidence: 83%

Dielectric behaviour of adsorbed water. Part 2.—Measurement at low temperatures on TiO2

Iwaki¹,

Morimoto²

1987

J. Chem. Soc., Faraday Trans. 1

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On TiO, samples with controlled amounts of chemisorbed and physisorbed H,O, the dielectric permittivity and dielectric loss have been measured at frequencies from 0.1 Hz to 5 MHz at temperatures from room temperature to 77 K. As a result, three kinds of relaxations have been discovered and the crude Cole-Cole plots have been analysed into three arcs I, I1 and 111; relaxation I is due to interfacial polarization as reported in our previous paper. The arcs I1 and I11 are assigned to the relaxations due to surface hydroxyls and physisorbed H,O, respectively. It is found that arc I1 decreases with increasing coverage 8 of physisorbed H,O and becomes extinct at 6 > 1. Furthermore, both the chord length of arc I11 and the dielectric activation energy of the relaxation 111 reveal a similar variation as 6 increases: first they increase linearly until 8 = 2 is reached and then the slope of each curve becomes more gradual. Finally, the dielectric activation energy of adsorbed H,O approaches that of ice. These phenomena are explained on the basis of the proposed models of H,O adsorbed on TiO,.

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Étude par absorption hertzienne de l'eau adsorbée sur un gel de silice

Cited by 13 publications

References 4 publications

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

Dielectric behaviour of adsorbed water. Part 2.—Measurement at low temperatures on TiO2

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Étude par absorption hertzienne de l'eau adsorbée sur un gel de silice

Cited by 13 publications

References 4 publications

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag2O Surface

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag2O Surface

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

Dielectric behaviour of adsorbed water. Part 2.—Measurement at low temperatures on TiO2

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Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface

Specific Feature of Dielectric Behavior of Water Adsorbed on Ag₂O Surface