The Vacancy-Wind Factor and the Manning Factor Occurring in Interdiffusion and Ionic Conductivity in Solids

2019 ◽  
Vol 22 ◽  
pp. 170-183
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Ionic Conductivity ◽  
Radiation Damage ◽  
Driving Force ◽  
Transport Coefficients ◽  
Equilibrium Concentration ◽  
Wind Effect ◽  
Crystalline Solids ◽  
Net Flux ◽  
The 1960S ◽  
Correlation Factors

In crystalline solids, during such processes as chemical interdiffusion in alloys, ionic conductivity and the annealing out of radiation damage there will inevitably be a net flux of vacancies. In most cases, when different species of atoms have different jump rates with vacancies within a net flux of vacancies, the phenomenon of the vacancy-wind effect will occur. This effect was first discovered in the 1960s by the late Dr John Manning. It is a subtle phenomenon that comes about because of the local redistribution of the equilibrium concentration of vacancies with respect to two or more species of drifting atoms in a driving force. The effect is captured in various ‘vacancy-wind factors’ (some of which are now sometimes called Manning factors) which formally arise from non-zero off-diagonal Onsager phenomenological transport coefficients and non-unity values of the tracer correlation factors. In this paper, the effect is reviewed and discussed.

scholarly journals Visualization of the Vacancy-Wind Effect Occurring in Chemical Diffusion and Ionic Conductivity in Solids

2008 ◽  
Vol 273-276 ◽  
pp. 431-444 ◽  
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Computer Simulation ◽  
Ionic Conductivity ◽  
Radiation Damage ◽  
Chemical Diffusion ◽  
Wind Effect ◽  
Net Flux ◽  
First Time ◽  
Net Fluxes

Net fluxes of vacancies commonly occur during chemical interdiffusion in alloys, ionic conductivity and the annealing out of radiation damage. When atoms with different jump rates diffuse in a net flux of vacancies the phenomenon of the vacancy-wind effect will occur. This effect, first discovered by the late Dr John Manning, is a subtle phenomenon arising from a disturbed distribution of vacancies with respect to a given moving atom or species of atom. In this paper, the vacancy-wind effect is discussed and its visualization, performed for the first time by computer simulation, is demonstrated.

scholarly journals Non-Random Interaction of Vacancies with Atoms during Interdiffusion and Ionic Conductivity in Materials

2007 ◽  
Vol 266 ◽  
pp. 119-130
Author(s):  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Ionic Conductivity ◽  
Random Distribution ◽  
Historical Context ◽  
Good Deal ◽  
Ternary Alloys ◽  
Wind Effect ◽  
Random Interaction ◽  
Ionic Systems ◽  
Net Flux ◽  
Made In

The non-random interaction of vacancies with atoms during interdiffusion and ionic conductivity is referred to as the vacancy-wind effect. This effect, first discovered by the late Dr John Manning, is a subtle phenomenon arising from the non-random distribution of vacancies with respect to a given moving atom within a net flux of vacancies. Recently, a good deal of progress has been made in determining accurate expressions for vacancy-wind factors in binary and ternary alloys, and in mixed cation ionic systems. The present paper provides an overview of these recent findings and puts them into a broader and historical context.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

scholarly journals Six-Jump-Cycle Mechanism for Collective Correlations in Nonstoichiometric Intermetallic Compounds

2006 ◽  
Vol 251-252 ◽  
pp. 59-68
Author(s):  
K.L. Gosain ◽  
D.K. Chaturvedi ◽  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Transport Coefficients ◽  
Fundamental Unit ◽  
Jump Frequency ◽  
Frequency Model ◽  
The Mean ◽  
The Individual ◽  
Jump Frequencies ◽  
Regular Site ◽  
Correlation Factors ◽  
Good Agreement

The six-jump-cycle (6JC) mechanism is used to derive expressions for collective correlation factors in a nonstoichiometric binary intermetallic compound AB. The 6JC is used as a fundamental unit for the cycle involving a perfectly ordered configuration and a two-jumpcycle (2JC) as a fundamental unit for the cycle involving existing antistructural atoms. The jump frequency for the 6JC is calculated in terms of a four-frequency-model using the mean first passage concept of Arita et al., while the jump frequency for the 2JC is taken to be the harmonic mean of the individual jump frequencies. The expressions for phenomenological transport coefficients are obtained through the linear response approximation using the kinetic equation approach. The results for collective correlation factors are compared with Monte Carlo simulation and are found to be in reasonably good agreement when the ratio of jump frequencies of regular site and antistructural atoms is of the order of 10-1.

Collective Correlation Factors in Random Non-Stoichiometric Inermetallic Compounds

2005 ◽  
Vol 247-248 ◽  
pp. 1-8 ◽  
Author(s):  
I.S. Sandhu ◽  
D.K. Chaturvedi ◽  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Linear Response ◽  
Transport Coefficients ◽  
Nearest Neighbour ◽  
Equation Approach ◽  
Frequency Model ◽  
Random Alloy ◽  
Simulation Results ◽  
Jump Frequencies ◽  
B2 Structure ◽  
Correlation Factors

In this paper Manning random alloy model has been extended to the binary nonstoichiometric intermetallic compound of the B2 structure. Two sub-lattices, that are dynamically independent in six-jump cycle (6JC) mechanism, are coupled together by taking into consideration the vacancy motion as a sequence of nearest neighbour jumps in random directions. The linear response expressions for the phenomenological transport coefficients are evaluated making use of the kinetic equation approach. The expressions for collective correlation factors are derived in terms of the equilibrium partial atomic concentrations and jump frequencies. Results are compared with Monte Carlo simulation results using the four-frequency model.

Possibility and Hope: Getting from Here to There

2015 ◽  
Vol 66 (8) ◽  
pp. 30
Author(s):  
Pete Seeger ◽  
Linda C. Forbes
Keyword(s):  
Natural Environment ◽  
Driving Force ◽  
Index Volume ◽  
Hudson River ◽  
Unique Form ◽  
Monthly Review ◽  
Hudson River School ◽  
Citizen Activism ◽  
The 1960S

Pete Seeger is an environmental advocate who understands the transforming power of immersion in nature. However, his desire to restore his cherished Hudson River posed a monumental challenge in the 1960s. The Hudson River, once so majestic that it inspired the Hudson River School painters, had become a sewer for the communities and commercial industries that populated its shoreline. Seeger&rsquo;s approach to reversing the degradation of the Hudson River involved a unique form of advocacy and organizing. He envisioned healing the Hudson through immersion. His approach involved bringing people back to the river aboard a 106-foot replica of a Hudson River sloop (a single-masted sailboat), one that resembled the boats that traversed the Hudson in centuries past. By 1969, with Seeger as the driving force behind its creation, the sloop Clearwater was constructed and launched. It still sails today and serves as an inspiring symbol of citizen activism on behalf of the natural environment.<p class="mrlink">This article can also be found at the <a href="http://monthlyreview.org/index/volume-66-number-7" title="Vol. 66, No. 7: January 2015" target="_blank"><em>Monthly Review</em> website</a>, where most recent articles are published in full.</p><p class="mrpurchaselink"><a href="http://monthlyreview.org/index/volume-66-number-7" title="Vol. 66, No. 7: January 2015" target="_self">Click here to purchase a PDF version of this article at the <em>Monthly Review</em> website.</a></p>

Free fatty acid uptake by polyethylene: what can one learn from this?

1991 ◽  
Vol 261 (6) ◽  
pp. G896-G906
Author(s):  
A. J. Schwab ◽  
C. A. Goresky
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Aqueous Phase ◽  
Present Report ◽  
Equilibrium Concentration ◽  
Fatty Acid Uptake ◽  
Unstirred Layer ◽  
Acid Uptake ◽  
Net Flux ◽  
Rate Limiting

Previous experiments have shown that fatty-acid uptake by isolated hepatocytes is inhibited by albumin, but this inhibition was less than expected from the decrease in the equilibrium concentration of fatty acid. The possible explanation of this observation by the effects of codiffusion of protein-bound and unbound fatty acid across the unstirred layer surrounding these isolated cells has recently been challenged on the basis of experiments in which uptake by monolayers of hepatocytes was compared with that by a polyethylene sheet [F.J. Burczynski et al., Am. J. Physiol. 257 (Gastrointest. Liver Physiol. 20): G584-G593, 1989]. In the present report, we reevaluate the theoretical basis for interpretation of these experiments by solving the differential equations describing diffusion into a sheet behind a linear barrier. The diffusion coefficient for palmitate in polyethylene is estimated to be approximately 10(-9) cm2/s. We conclude that when proteins are absent from the aqueous phase, diffusion across the unstirred layer is rate limiting for removal of fatty acids by cellular monolayers, and also rate limiting for net flux across the water-polyethylene interface. In contrast, if the aqueous phase contains either 5 microM albumin or 125 microM beta-lactoglobulin, diffusion within the polyethylene sheet will become rate limiting. The net flux of fatty acids into a polyethylene sheet becomes insensitive to an increase in protein concentration if the latter rises above a certain threshold. The polyethylene data provide no additional insight into the manner in which hepatocytes take up free fatty acids.

scholarly journals Die Evolution der bundesdeutschen Forschungs- und Technologiepolitik: Rückblick und Bestandsaufnahme

2002 ◽  
Vol 3 (3) ◽  
pp. 279-301 ◽  
Author(s):  
Andreas Fier ◽  
Dietmar Harhoff
Keyword(s):  
Economic Theory ◽  
Economic Analysis ◽  
Driving Force ◽  
Comprehensive Evaluation ◽  
State Of The Art ◽  
Policy Instruments ◽  
Cost Benefit ◽  
Policy Practice ◽  
Federal Research ◽  
The 1960S

Abstract We consider the development of German federal research and technology (R&T) policies since the 1960s and sketch the evolution of today's highly differentiated and complex set of policy instruments. Advances from economic theory and empirical results are reflected in this evolution, but have not necessarily been the driving force. In some instances, innovative policy instruments have been introduced in order to accommodate the state of the art in economic analysis; in other cases, such innovations have preceded a thorough analysis of the respective policy instruments. A major point of concern is the lack of comprehensive evaluation and cost-benefit analyses in R&T policies. In this regard, German policy practice lags behind well-established procedures in other countries.

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