Concentration gradient and diffusion potential in colloidal electrolyte solutions

Magnesium alloys have low density densities and high specific strengths that are comparable to steels and titanium alloys. Therefore, they are widely used as structural materials in the automotive and aerospace industries. However, the use of magnesium alloys is hindered by the fact that they offer insufficient resistance against corrosion, even in diluted electrolyte solutions. We examined alloys from the Mg-Y-RE-Zr and Mg-Al-RE systems (WE43 and AE44) that are used in the domestic and international automotive and aerospace industries. In these applications, the alloys are exposed to corrosion in environments containing electrolytes. It is commonly known that hydrogen is the main corrosive factor, appearing during chemical reactions between magnesium and water in an electrolyte solution. Selecting rare earth-containing magnesium alloys allows us to analyse the various effects of hydrogen on these materials. Hydrogen interacts with the selected alloys in a manner that depends strongly on alloy structure and chemical composition—these factors cause variations in the concentration, solubility, and diffusion rate of hydrogen in the host material. After hydrogen uptake, the cracking velocity of each alloy phase is different and is related to cracking micromechanisms. Our results show that when samples were immersed in 0.1M sodium sulfate solution, hydrogen atoms diffused into the material and enriched the intermetallic phases. With increased immersion time, magnesium hydride fractures in a brittle manner when the inner stress caused by hydrogen pressure and the expansion stress due to the formation of magnesium hydride are higher than the fracture strength.

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Interaction effects of clay swelling and dispersion and CaCO3 content on saturated hydraulic conductivity

Soil Research ◽

10.1071/sr02102 ◽

2003 ◽

Vol 41 (5) ◽

pp. 979 ◽

Cited By ~ 26

Author(s):

Rami Keren ◽

Meni Ben-Hur

Keyword(s):

Hydraulic Conductivity ◽

Concentration Gradient ◽

Soil Aggregates ◽

Electrolyte Solutions ◽

Saturated Hydraulic Conductivity ◽

Reference Solution ◽

Clay Dispersion ◽

Clay Swelling ◽

Caco3 Content ◽

Steep Concentration Gradient

Typic Chromoxeret-sand and Lithic Ruptic Xerochrept-sand mixtures, of high sodicity, and containing 8 and ~0% CaCO3, respectively, were packed in columns and leached with electrolyte solutions. When a reference solution of 500 mmol/L was replaced successively with solutions containing 100, 50, 10, 5, and 1 mmol/L and then with deionised water (gradual leaching), the saturated hydraulic conductivity (Ks) decreased gradually to steady-state values, and no clay was observed in the leachate. Under deionised leaching, the relative Ks (Ks/Ks0) (the ratio between the observed Ks and that under leaching with the reference solution) in the Chromoxeret mixture at exchangeable sodium percentages (ESPs) of 30, 38, and 63 was 0.83, 0.47, and 0.41, respectively, and that in the Xerochrept mixture at ESPs of 23, 28, and 36 were 0.82, 0.71, and 0.39 respectively. When a solution of 50 mmol/L was replaced directly with deionised water (abrupt leaching), the Ks/Ks0 of the Chromoxeret mixture at the above ESPs dropped sharply to minimum values of 0.25, 0.18, and 0.11, respectively, and that of the Xerochrept mixture to 0.42, 0.04, and 0.13, respectively, and dispersed clay was observed in the leachate. It is hypothesised that the abrupt leaching with deionised water generated a steep concentration gradient between the solutions within and around the aggregates, leading to clay dispersion and rapid Ks/Ks0 reduction; under gradual leaching, no steep concentration gradient developed, there was no clay dispersion, and clay swelling caused gradual Ks/Ks0 reduction. In the Chromoxeret, the CaCO3 decreased the clay swelling and dispersion, and probably acted as a cementing agent that stabilised the soil aggregates against slaking during the initial wetting of the mixture.

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Electrolyte Solutions: The Measurement and Interpretation of Conductance, Chemical Potential and Diffusion in Solutions of Simple Electrolytes (Second Edition)

Journal of The Electrochemical Society ◽

10.1149/1.2427802 ◽

1960 ◽

Vol 107 (8) ◽

pp. 205C ◽

Cited By ~ 9

Author(s):

R. A. Robinson ◽

R. H. Stokes ◽

Roger G. Bates

Keyword(s):

Chemical Potential ◽

Electrolyte Solutions ◽

And Diffusion

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Network Dynamics

The Oxford Handbook of Analytical Sociology ◽

10.1093/oxfordhb/9780199215362.013.19 ◽

2011 ◽

Author(s):

Peter Dodds ◽

Duncan J. Watts

Keyword(s):

Social Relations ◽

Network Dynamics ◽

Dynamic Networks ◽

Network Evolution ◽

Diffusion Potential ◽

Edge Based ◽

And Diffusion ◽

Over Time ◽

Network Diffusion

This article explores dynamic networks and diffusion, with particular emphasis on evolving traces of enacted social relations. It begins with a review of models for the evolution of networks over time — making a distinction between ‘node-based’ and ‘edge-based’ models — and more specifically how and why networks change. It then considers how network timing affects the flow of things across networks, focusing on how edge timing reshapes the set of paths potentially useful for diffusion. It also discusses the structure requirements for network diffusion and shows how these requirements are affected when we assume edges come and go over time. Finally, it describes the effect of tie order on diffusion potential as well as the correlation between network evolution and diffusion.

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