Diffusion in Glassy Metals

Mehrer, H.

doi:10.4028/www.scientific.net/df.1.125

Cited by 3 publications

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“…The fairly significant metastability of conventional metallic glasses leads to various atomic rearrangement processes already below the crystallisation temperatures, which also calls for an understanding of the diffusion behaviour of glassy metals (see, e.g. [1,4]).…”

Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

“…For more details about metallic glasses we refer the reader to a chapter about Diffusion in Glassy Metals by the present author in a recent volume of Diffusion Foundations [4].…”

Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

“…Sectioning techniques are either mechanical or sputtering procedures (see, e.g. [1,4]). For ionconducting glasses both techniques are applicable, depending on the magnitude of the diffusivity and the chosen annealing treatment.…”

Section: Tracer Diffusionmentioning

confidence: 99%

“…High-pressure studies have played key roles in the identification of diffusion mechanisms of crystalline metals, semiconductors, ionic crystals and glassy metals (see e.g. [1,4,8]). In the case of interstitial diffusion, such as carbon diffusion in iron, small activation volumes of migration of about 0.1 atomic volume are associated with the jump process, because interstitial diffusion occurs without thermal defects like vacancies.…”

Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

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Diffusion and Ion Conduction in Cation-Conducting Oxide Glasses

Mehrer

2016

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In this Chapter we review knowledge about diffusion and cation conduction in oxide glasses. We first remind the reader in Section 1 of major aspects of the glassy state and recall in Section 2 the more common glass families. The diffusive motion in ion-conducting oxide glasses can be studied by several techniques – measurements of radiotracer diffusion, studies of the ionic conductivity by impedance spectroscopy, viscosity studies and pressure dependent studies of tracer diffusion and ion conduction. These methods are briefly reviewed in Section 3. Radiotracer diffusion is element-specific, whereas ionic conduction is not. A comparison of both types of experiments can throw considerable light on the question which type of ions are carriers of ionic conduction. For ionic conductors Haven ratios can be obtained from the tracer diffusivity and the ionic conductivity for those ions which dominate the conductivity.In the following sections we review the diffusive motion of cations in soda-lime silicate glass and in several alkali-oxide glasses based mainly on results from our laboratory published in detail elsewhere, but we also take into account literature data.Section 4 is devoted to two soda-lime silicate glasses, materials which are commonly used for window glass and glass containers. A comparison between ionic conductivity and tracer diffusion of Na and Ca isotopes, using the Nernst-Einstein relation to deduce charge diffusivities, reveals that sodium ions are the carriers of ionic conduction in soda-lime glasses. A comparison with viscosity data on the basis of the Stokes-Einstein relation shows that the SiO2 network is many orders of magnitude less mobile than the relatively fast diffusing modifier cations Na. The Ca ions are less mobile than the Na ions but nevertheless Ca is considerably more mobile than the network.Section 5 summarizes results of ion conduction and tracer diffusion for single Na and single Rb borate glasses. Tracer diffusion and ionic conduction have been studied in single alkali-borate glasses as functions of temperature and pressure. The smaller ion is the faster diffusing species in its own glass. This is a common feature of all alkali oxide glasses. The Haven ratio of Na in Na borate glass is temperature independent whereas the Haven ratio of Rb diffusion in Rb borate glass decreases with decreasing temperature.Section 6 reviews major facts of alkali-oxide glasses with two different alkali ions. Such glasses reveal the so-called mixed-alkali effect. Its major feature is a deep minimum of the conductivity near some middle composition for the ratio of the two alkali ions. Tracer diffusion shows a crossover of the two tracer diffusivities as functions of the relative alkali content near the conductivity minimum. The values of the tracer diffusivities also reveal in which composition range which ions dominate ionic conduction. Tracer diffusion is faster for those alkali ions which dominate the composition of the mixed glass.Section 7 considers the pressure dependence of tracer diffusion and ionic conduction. Activation volumes of tracer diffusion and of charge diffusion are reviewed. By comparison of tracer and charge diffusion the so-called Haven ratios are obtained as functions of temperature, pressure and composition. The Haven ratio of Rb in Rb borate glass decreases with temperature and pressure whereas that of Na in Na borate glass is almost constant.Section 8 summarizes additional common features of alkali-oxide glasses. Activation enthalpies of charge diffusion decrease with decreasing average ion-ion distance. The Haven ratio is unity for large ion-ion distances and decreases with increasing alkali content and hence with decreasing ion-ion distance.Conclusions about the mechanism of diffusion are discussed in Section 9. The Haven ratio near unity at low alkali concentrations can be attributed to interstitial-like diffusion similar to interstitial diffusion in crystals. At higher alkali contents collective, chain-like motions of several ions prevail and lead to a decrease of the Haven ratio. The tracer diffusivities have a pressure dependence which is stronger than that of ionic conductivity. This entails a pressure-dependent Haven ratio, which can be attributed to an increasing degree of collectivity of the ionic jump process with increasing pressure. Monte Carlo simulations showed that the number of ions which participate in collective jump events increases with increasing ion content – i.e. with decreasing average ion-ion distance. For the highest alkali contents up to four ions can be involved in collective motion. Common aspects of the motion process of ions in glasses and of atoms in glassy metals are pointed out. Diffusion in glassy metals also occurs by collective motion of several atoms.Section 10 summarizes the major features of ionic conduction and tracer diffusion and its temperature and pressure dependence of oxide glasses.

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Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

“…For more details about metallic glasses we refer the reader to a chapter about Diffusion in Glassy Metals by the present author in a recent volume of Diffusion Foundations [4].…”

Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

Section: Tracer Diffusionmentioning

confidence: 99%

Section: Progress In Ion Transport and Structure Of Ion Conducting Co...mentioning

confidence: 99%

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Diffusion and Ion Conduction in Cation-Conducting Oxide Glasses

Mehrer

2016

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“…56 La descripción del flujo (J) de una especie química, en función de la variación de la concentración de dicha especie a lo largo de una coordenada espacial x, está dada por la primera ley de Fick,…”

Section: Difusión: Fundamentos Teóricosunclassified

Difusión Selectiva de Hidrocarburos en Zeolitas de Poro Pequeño a Partir de Técnicas de Simulación Molecular

Combariza¹,

Aldo²

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A Germán Sastre, director de mi tesis, por su incondicional apoyo y por su excepcional trabajo como tutor de mi trabajo doctoral.A Avelino Corma, por darme la oportunidad de trabajar en el ITQ, y por ser una fuente inagotable de inspiración.A Amparo Mifsud, por su ayuda y disposición, y por hacer del ITQ un lugar mucho mas amable.A Jaime Primo, un agradecimiento especial por su paciencia y por sus consejos.A Mónica, Inma y Marcos: su trabajo es altamente apreciado, su colaboración, sin duda alguna, hace mas fácil el camino.A José Sanchez Marín, profesor de la Universidad de Valencia, por su diligencia y colaboración.Un agradecimiento especial a Diego Gómez, por las muchas y fructíferas conversaciones sobre ciencia y computadores, pero sobre todo por ser un excelente compañero.A Siris, Peter, Angeles, Mer, Tirso, Adela por hacer del laboratorio un lugar de trabajo muy agradable.A Peter Vennestrøm una mención especial por su colaboración por hacer que el primer contacto que un grupo muy especial de niños tuvo con la ciencia fuera tan divertido y seguramente inolvidable.The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny ...' Isaac Asimov II Un agradecimiento muy especial a Yuriy Bushuev, por las enriquecedoras conversaciones que tuvimos mientras estuvo en el ITQ, y las que sin ninguna duda se darán en el futuro.Mis agradecimientos no estarían completos si no incluyeran a la persona que me abrió las puertas de la química teórica y computacional, a Scott M. Auerbach, por mostrarme el camino que seguramente seguiré recorriendo en el futuro.

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Charge attachment–induced transport: toward new paradigms in solid state electrochemistry

Weitzel

2021

Current Opinion in Electrochemistry

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Diffusion in Glassy Metals

Cited by 3 publications

References 44 publications

Diffusion and Ion Conduction in Cation-Conducting Oxide Glasses

Diffusion and Ion Conduction in Cation-Conducting Oxide Glasses

Difusión Selectiva de Hidrocarburos en Zeolitas de Poro Pequeño a Partir de Técnicas de Simulación Molecular

Charge attachment–induced transport: toward new paradigms in solid state electrochemistry

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