Diffusion of He, Ne, and Ar in Vitreous and Partially Devitrified Germani um Dioxide

1972 ◽  
Vol 27 (4) ◽  
pp. 617-623
Author(s):  
W.W. Brandt ◽  
B. Rauch ◽  
J. Wagner
Keyword(s):  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Diffusion Mechanism ◽  
Preexponential Factor ◽  
Activation Energies ◽  
Transition Range ◽  
Critical Dimensions ◽  
Glass Transition Range ◽  
Diffusion Paths ◽  
Solubility Coefficients

Abstract The diffusion coefficients of He, Ne, and Ar in various samples of GeO2 and approximate values for the corresponding solubility coefficients were obtained from nonisothermal and isothermal desorption experiments. The data show trends similar to those obtained on fused SiO2 , and are interpreted by assuming that the glasses contain many interstices of different critical dimensions and a variety of diffusion paths corresponding to a range of activation energies. Some annealed and partially devitrified samples were studied and the activation energies of diffusion were found to be relatively high. In a few cases, the measurements were extended into and above the glass transition range (∼570°) ; the resulting activation energy and the preexponential factor of the Arrhenius equation for the diffusion coefficient were markedly increased, indicating that the diffusion mechanism is probably drastically changed.

Pressure effects on the diffusion of boron and phosphorus in silicon

2019 ◽  
Vol 33 (23) ◽  
pp. 1950267
Author(s):  
Phan Thi Thanh Hong ◽  
Vu Van Hung ◽  
Nguyen Van Nghia ◽  
Ho Khac Hieu
Keyword(s):  
Diffusion Coefficients ◽  
Activation Volume ◽  
Ambient Pressure ◽  
Diffusion Mechanism ◽  
Potential Method ◽  
Activation Energies ◽  
Pressure Effects ◽  
Arrhenius Behavior ◽  
Work Pressure ◽  
Phosphorus In Silicon

In this work, pressure effects on the diffusion of boron and phosphorus in silicon have been investigated by using the statistical moment method. We consider the diffusion of boron and phosphorus in silicon for wide temperature and pressure ranges revealing the Arrhenius behavior of diffusion coefficients. Activation energies of diffusion of boron and phosphorus in silicon are derived, respectively, as 3.41 and 3.20 eV at ambient pressure. Our work shows that when pressure increases, the diffusivity of B is enhanced characterized by an activation volume of [Formula: see text] ([Formula: see text] is the atomic volume) at temperature 1083 K; and the diffusivity of P is reduced indicated by an activation volume of [Formula: see text] at 1113 K. Our results of activation energies and diffusion coefficients are in agreement with recent experimental measurements and ab initio calculations. This work proposes a potential method to investigate the diffusion mechanism in silicon solar cell.

scholarly journals Migration of mineral oil in elastomers

2021 ◽  
Author(s):  
Tobias Förster ◽  
Artur Blivernitz
Keyword(s):  
Diffusion Coefficients ◽  
Mineral Oil ◽  
Activation Energies ◽  
Concentration Profiles ◽  
Small Reservoir ◽  
Experimental Procedure ◽  
Mineral Oils ◽  
The Absolute ◽  
Suitable Measure

AbstractThis work describes a newly introduced experimental procedure to quantify the diffusion progress of mineral oils locally resolved in NBR. Diffusion of reference oils IRM 901, IRM 902 and IRM 903 in NBR with various acrylonitrile contents was investigated. Classical sorption experiments were performed as a basic characterization and compared to the newly introduced method. Here, elastomer specimens are only being dipped with the bottom in a relatively small reservoir of mineral oil. This provides a determination of locally resolved concentration profiles of mineral oils, and the calculation of diffusion coefficients. These diffusion coefficients follow the same trends like those determined via sorption experiments. Despite differences in the absolute numbers, activation energies of diffusion can be applied as a suitable measure for the compatibility of elastomers and fluids.

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

The Sequence of the Phase Growth during Diffusion in Ti-Based Systems

2019 ◽  
Vol 38 (2019) ◽  
pp. 151-157 ◽  
Author(s):  
Bartek Wierzba ◽  
Wojciech J. Nowak ◽  
Daria Serafin
Keyword(s):  
Theoretical Analysis ◽  
Entropy Production ◽  
Diffusion Coefficients ◽  
Intermetallic Phase ◽  
Intermetallic Phases ◽  
Diffusion Couples ◽  
Intrinsic Diffusion ◽  
Phase Growth ◽  
Diffusion Paths

AbstractThe interdiffusion in Ti-based alloys was studied. It was shown that during diffusion at 1,123 K formation of four intermetallic phases occurs. The diffusion paths for six different diffusion couples were determined. Moreover, the entropy production was calculated – the approximation used for determination of the sequence of intermetallic phase formation. In theoretical analysis, the intrinsic diffusion coefficients were determined from the modified Wagner method.

Some thermodynamic and kinetic properties of H2SO4–H3PO4–H2O–Fe(III) system

2021 ◽  
pp. 1-9
Author(s):  
Ya.G. Avdeev ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Platinum Electrode ◽  
Molar Fraction ◽  
Redox Couple ◽  
Kinetic Properties ◽  
Cyclic Voltammogram ◽  
Electrode Potentials ◽  
Half Wave ◽  
Sulfate Complexes

The values of the electrode potentials of the redox couple Fe(III) / Fe(II) and the half-wave potentials of the reactions Fe3+ + e– = Fe2+ и Fe2+ — e– = Fe3+ on the cyclic voltammogram of a platinum electrode in acid solutions containing Fe(III) salts have been measured to characterize the oxidizing ability of the H2SO4—H3PO4—H2O—Fe(III) system. The values of these experimentally obtained parameters are close. A decrease in the oxidizing ability of H2SO4 and H3PO4 mixtures containing Fe(III) with an increase in the molar fraction of H3PO4 in them occurs due to the formation of Fe(III) complexes with phosphate anions which are inferior to their hydrate and sulfate complexes in the oxidizing ability. The temperature coefficients of the electrode potential (dE / dt) of the redox couple Fe(III) / Fe(II) in the H2SO4—H2O, H2SO4—H3PO4—H2O and H3PO4–H2O systems were determined experimentally. The diffusion coefficients of Fe(III) in the studied solutions were calculated based on the Randles—Shevchik equation. The temperature dependence of the diffusion coefficients of Fe(III) cations is satisfactorily described by the Arrhenius equation. The parameters of this equation are calculated.

scholarly journals Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1778
Author(s):  
Jürgen E. K. Schawe ◽  
Claus Wrana
Keyword(s):  
Glass Transition ◽  
Structural Relaxation ◽  
Random Sequence ◽  
High Sensitivity ◽  
Random Copolymers ◽  
High Time Resolution ◽  
Scanning Calorimetry ◽  
Transition Range ◽  
Glass Transition Range ◽  
And Control

Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF.

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