scholarly journals The mobility of sodium on tungsten

1935 ◽  
Vol 150 (869) ◽  
pp. 58-76 ◽  
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Work Function ◽  
Direct Measurement ◽  
Diffusion Coefficients ◽  
Condensation Coefficient ◽  
Alkali Earth ◽  
Adsorbed Films ◽  
A Value ◽  
Two Phases

Although the existence as well as some of the properties of adsorbed films of alkali and alkali earth metals on metals of higher work function have long been known, it is only recently that these films have been shown to be capable of migrating over the surface of the adsorbent, and that attempts have been made to measure diffusion coefficients and the activation energy associated with the diffusion. Langmuir and Taylor, investigating the properties of cæsium films, found it necessary to postulate that the cæsium was mobile in order to account for the high value (α ≅ 1.0) for the condensation coefficient on quite concentrated films. Later they were able to make a direct measurement of the diffusion coefficient. They obtained a value of D at 812° K of 3.4 x 10 -5 cm 2 secs -1 , and an activation energy of 0.61 volt. Langmuir has also shown that cæsium films exist in two phases and has measured the diffusion coefficient by following the movement of the boundary between these two phases.

Induced polarization and pore radius — A discussion

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D519-D526 ◽  
Author(s):  
Andreas Weller ◽  
Zeyu Zhang ◽  
Lee Slater ◽  
Sabine Kruschwitz ◽  
Matthias Halisch
Keyword(s):  
Diffusion Coefficient ◽  
Relaxation Time ◽  
Diffusion Coefficients ◽  
Pore Radius ◽  
Mercury Porosimetry ◽  
Induced Polarization ◽  
Reliable Estimate ◽  
Characteristic Relaxation Time ◽  
A Value ◽  
Apparent Diffusion

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time [Formula: see text] is related to the effective hydraulic radius [Formula: see text] controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of [Formula: see text] and [Formula: see text] for an extensive database of sandstone samples, in which mercury porosimetry data confirm that [Formula: see text] is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with [Formula: see text] and the specific surface area per unit pore volume [Formula: see text]. Two scenarios can explain our findings: (1) the length scale defined by [Formula: see text] is not equal to [Formula: see text] and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of [Formula: see text] (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study.

Oxygen Chemical Diffusion Coefficients of (U, Pu)O2-x

2017 ◽  
Vol 375 ◽  
pp. 84-90 ◽  
Author(s):  
Masashi Watanabe ◽  
Takeo Sunaoshi ◽  
Masato Kato
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Surface Reaction ◽  
Chemical Diffusion ◽  
Chemical Diffusion Coefficient ◽  
Thermo Gravimetry ◽  
Metal Ratio

The oxygen chemical diffusion coefficient in (U, Pu)O2-x was determined by thermo-gravimetry as functions of the Pu content, oxygen-to-metal ratio and temperature. The surface reaction was considered in the diffusion coefficient determination. The activation energy for the chemical diffusion coefficient was 60 kJ/mol and 65 kJ/mol, respectively, in (U0.8Pu0.2)O2-x and (U0.7Pu0.3)O2-x.

scholarly journals Studies on Transformations of Hemophilus influenzae

1961 ◽  
Vol 44 (6) ◽  
pp. 1229-1239 ◽  
Author(s):  
Sol H. Goodgal ◽  
Roger M. Herriott
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Sedimentation Coefficient ◽  
Close Correlation ◽  
Erythromycin Resistance ◽  
Hemophilus Influenzae ◽  
A Value ◽  
Transforming Activity ◽  
Separation Cell ◽  
And Diffusion

The sedimentation and diffusion coefficients have been determined for Hemophilus influenzae transforming activity and DNA using P32-labeled DNA. The methods employed the Spinco fixed boundary separation cell for measurements of the sedimentation coefficient and the Northrop-Anson diffusion cell to determine the diffusion coefficient. There was a very close correlation between the amount of DNA and transforming activity sedimented or diffused. The sedimentation coefficient (s20°), for both biological activity and DNA was 27 and the diffusion coefficient (D20°) 1 x 10-8 cm2/sec. The molecular weight calculated from these coefficients gave a value of 16 million. There was no difference in the sedimentation coefficients for the two unlinked markers, streptomycin and erythromycin resistance, and the diffusion coefficients for single markers or the linked markers, streptomycin and cathomycin, were the same.

Fe tracer diffusion in L10 ordered FePt

2002 ◽  
Vol 753 ◽  
Author(s):  
Y. Nosé ◽  
T. Ikeda ◽  
H. Nakajima ◽  
K. Tanaka ◽  
H. Numakura
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Single Crystal ◽  
Diffusion Coefficients ◽  
Ion Beam ◽  
Tracer Diffusion ◽  
Ordered Structure ◽  
Tracer Diffusion Coefficient ◽  
Exponential Factor ◽  
Axis Direction

ABSTRACTTracer diffusion coefficient of 59Fe in FePt with the tetragonal L10 ordered structure has been measured by an ion-beam sputter-sectioning technique in the temperature range from 1173 to 1374 K. Anisotropy in diffusion has been studied using single-variant single-crystal specimens. The diffusion coefficient in the direction perpendicular to [001] axis (in the a-axis direction), Da, is larger than that in the [001] (c-axis) direction, Dc, as expected from the atomic arrangement of the L10 ordered structure. The ratio of the diffusion coefficients, Da/Dc, is 1.33.6 for Fe42Pt58 and smaller at higher temperatures. The activation energy for the diffusion is 259 ± 1 kJ/mol for Da and 309 ± 18 kJ/mol for Dc, while the pre-exponential factor is and , respectively in Fe42Pt58.

Infrared absorption spectroscopy of hydrogen and deuterium in CaO and SrO crystals

1989 ◽  
Vol 4 (1) ◽  
pp. 224-231 ◽  
Author(s):  
J. L. Park ◽  
R. González
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Absorption Spectra ◽  
Infrared Absorption ◽  
Diffusion Coefficients ◽  
Elevated Temperatures ◽  
Arrhenius Equation ◽  
Lithium Concentration ◽  
Infrared Absorption Spectroscopy ◽  
Infrared Absorption Spectra

Infrared absorption spectra have been used to characterize OH− and OD− ions at the surface and the bulk of undoped CaO, lithium doped CaO, and SrO crystals. Diffusion of deuterons from D2O vapor into these crystals was performed at elevated temperatures. Diffusion coefficients were obtained to be D (CaO) = 3 ⊠ 10−6 cm2/sec at 1773 K and D (SrO) = 4 ⊠ 10−7 cm2/sec at 1523 K. For the doped CaO crystal with lithium concentration of 310 ppm, the diffusion coefficient was measured to be D (CaO:Li) = 4 ⊠ 10−7 cm2/sec at 1473 K and the activation energy in the Arrhenius equation was estimated to be 1.7 eV.

Radiotracer Measurements of Sulfur Diffusion in Rubbers

1971 ◽  
Vol 44 (5) ◽  
pp. 1307-1315 ◽  
Author(s):  
M. Mozisek
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Temperature Dependence ◽  
Diffusion Coefficients ◽  
Elemental Sulfur ◽  
Butyl Rubber ◽  
In Cis ◽  
Sulfur Diffusion

Abstract The object of measurement was the diffusion of elemental sulfur labeled with the radioisotope S in representative types of rubber. The highest values of diffusion coefficient were found in cis-1,4 polybutadiene. The lowest measured value was found for butyl rubber. The activation energy, expressing the temperature dependence of the diffusion coefficients, ranges from 4 to 10 kcal mol-1. For some rubbers studied, the activation energy is to a certain degree dependent upon temperature. The values of the diffusion coefficients and the characteristic constants for their temperature dependence are related to the mobility of the macromolecular segments.

scholarly journals Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4030
Author(s):  
Gengbiao Chen ◽  
Zhiwen Liu
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Surface Effect ◽  
Bulk Water ◽  
Self Diffusion ◽  
Average Diffusion Coefficient ◽  
Average Diffusion ◽  
Chain Lengths ◽  
Fluid Diffusion ◽  
Self Diffusion Coefficient

The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH2)3CH3, –(CH2)7CH3, and –(CH2)11CH3 nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the z direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy.

scholarly journals Surface Thermodynamics, Viscosity, Activation Energy of N-Methyldiethanolamine Aqueous Solutions Promoted by Tetramethylammonium Arginate

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1337
Author(s):  
Xiangfeng Tian ◽  
Lemeng Wang ◽  
Pan Zhang ◽  
Dong Fu
Keyword(s):  
Activation Energy ◽  
Surface Tension ◽  
Diffusion Coefficient ◽  
Aqueous Solutions ◽  
Quantitative Relationship ◽  
Viscosity Data ◽  
Surface Thermodynamics ◽  
Surface Entropy ◽  
Operation Conditions ◽  
Surface Enthalpy

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

scholarly journals Time-Dependent Diffusion Coefficients for Chaotic Advection due to Fluctuations of Convective Rolls

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 99 ◽  
Author(s):  
Kazuma Yamanaka ◽  
Takayuki Narumi ◽  
Megumi Hashiguchi ◽  
Hirotaka Okabe ◽  
Kazuhiro Hara ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Liquid Crystals ◽  
Diffusion Coefficients ◽  
Coarse Graining ◽  
Chaotic Advection ◽  
Time Dependent ◽  
Local Order ◽  
Weak Turbulence ◽  
Normal Diffusion ◽  
Convective Rolls

The properties of chaotic advection arising from defect turbulence, that is, weak turbulence in the electroconvection of nematic liquid crystals, were experimentally investigated. Defect turbulence is a phenomenon in which fluctuations of convective rolls arise and are globally disturbed while maintaining convective rolls locally. The time-dependent diffusion coefficient, as measured from the motion of a tagged particle driven by the turbulence, was used to clarify the dependence of the type of diffusion on coarse-graining time. The results showed that, as coarse-graining time increases, the type of diffusion changes from superdiffusion → subdiffusion → normal diffusion. The change in diffusive properties over the observed timescale reflects the coexistence of local order and global disorder in the defect turbulence.

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