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Letteratura scientifica selezionata sul tema "Zn diffusion"

Autore: Grafiati

Pubblicato: 10 dicembre 2022

Ultima modifica: 28 gennaio 2023

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Articoli di riviste sul tema "Zn diffusion"

1

Khoulif, S., E. B. Hannech e N. Lamoudi. "Study of Reactive Diffusion in Cu/Zn Diffusion Couple". Indian Journal Of Science And Technology 15, n. 48 (27 dicembre 2022): 2740–47. http://dx.doi.org/10.17485/ijst/v15i48.13.

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2

Mittal, Jagjiwan, e Kwang-Lung Lin. "Diffusion of elements during reflow ageing of Sn-Zn solder in liquid state on Ni/Cu substrate – theoretical and experimental study". Soldering & Surface Mount Technology 30, n. 3 (4 giugno 2018): 137–44. http://dx.doi.org/10.1108/ssmt-10-2017-0035.

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Purpose This paper aims to study the diffusion of Zn, Ni and Sn in the liquid state during the reflow ageing of the Sn-Zn solder above its melting point on an Ni/Cu substrate in relation to the formation of intermetallic compounds (IMCs). Design/methodology/approach The Sn-Zn solder is reflowed on Ni/Cu substrates and is aged at 503 K. The formation of IMCs and their composition is characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Diffusion coefficients and diffusion distances of Zn, Ni and Sn in the liquid state during reflow and ageing are theoretically calculated. Both experimental and theoretical behaviours for Ni and Zn diffusions are compared. Findings Calculations show a linear increment in the liquid-state diffusion coefficients of Ni, Zn and Sn in the solder matrix with a rise in temperature, but they remained constant during ageing. However, diffusion distances increased slowly with temperature but manifold with ageing time. The experimental results revealed segregation of Zn and Ni at the interface in the as-reflow aged specimens. The Zn was concentrated at the solder–substrate interface and it reacted with Ni diffusing from the substrate to form Ni-Sn-Zn IMCs. The rapid diffusion of Zn and Ni with the increase in ageing time increased their atomic concentrations in the IMCs against the reduction in Sn concentration owing to a comparatively slower diffusion. Originality/value The novelty of the paper is the detailed study of theoretical diffusion of Zn, Sn and Ni in the liquid state during reflow ageing of Sn-Zn above its melting points on a Ni/Cu substrate. This is compared with values obtained experimentally and related to the mechanisms of IMC formation.

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3

Sadaiyandi, K., e K. Ramachandran. "Zn Diffusion in ZnTe". physica status solidi (b) 170, n. 2 (1 aprile 1992): K77—K81. http://dx.doi.org/10.1002/pssb.2221700235.

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4

LIANG, LIU, YA-LING LIU, YA LIU, HAO-PING PENG, JIAN-HUA WANG e XU-PING SU. "EFFECT OF Mg AND TEMPERATURE ON Fe–Al ALLOY LAYER IN Fe/(Zn–6%Al–x%Mg) SOLID–LIQUID DIFFUSION COUPLES". Surface Review and Letters 24, Supp01 (31 ottobre 2017): 1850010. http://dx.doi.org/10.1142/s0218625x18500105.

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Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe–Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe–Al alloy layer. It was found that the Fe2Al5Znxphase layer forms close to the iron sheet and the FeAl3Znxphase layer forms near the side of the melted Zn–6%Al–3%Mg in diffusion couples. When the Fe/(Zn–6%Al–3%Mg) diffusion couple is kept at 510[Formula: see text]C for more than 15[Formula: see text]min, a continuous Fe–Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples, the Fe–Al alloy layer on the interface of the Fe/(Zn–6% Al–3% Mg) diffusion couple is the thinnest. The Fe–Al alloy layer forms only when the diffusion temperature is above 475[Formula: see text]. These results show that the Fe–Al alloy layer in Fe/(Zn–6%Al–[Formula: see text]%Mg) solid–liquid diffusion couples is composed of Fe2Al5Znxand FeAl3Znxphase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe–Al alloy layer. When the Mg content in the Fe/(Zn–6%Al–[Formula: see text]%Mg) diffusion couples is 3%, the growth of the Fe–Al alloy layer is inhibited. These results may explain why there is no obvious Fe–Al alloy layer formed on the interface of steel with a Zn–6%Al–3%Mg coating.

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5

Dayananda, Mysore A. "Selected Analyses and Observations in Multicomponent Diffusion". Defect and Diffusion Forum 297-301 (aprile 2010): 1451–60. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.1451.

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Selected isothermal diffusion studies in ternary and quaternary systems are reviewed in order to present analytical and experimental approaches adopted for the determination of interdiffusion fluxes of components, interdiffusion coefficients, diffusional interactions among components, and internal consistency in the experimental data. Several interesting phenomena and observations including uphill diffusion, zero-flux planes and flux reversals, and double serpentine diffusion paths are illustrated with selected single phase Cu-Ni-Zn, Fe-Ni-Al and Cu-Ni-Zn-Mn diffusion couples. The main challenges involved in the experimental determination of interdiffusion data from multicomponent diffusion couples and in the application of such data are also addressed.

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6

Gramlich, A., S. Tandy, E. Frossard, J. Eikenberg e R. Schulin. "Diffusion limitation of zinc fluxes into wheat roots, PLM and DGT devices in the presence of organic ligands". Environmental Chemistry 11, n. 1 (2014): 41. http://dx.doi.org/10.1071/en13106.

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Environmental context Zinc is an essential micronutrient for plants and many arid areas of the world have zinc-deficient soils. The bioavailability of Zn to plants is influenced by diffusion limitations and complex lability in the soil solution. To identify the relative importance of these two factors, we investigated the influence of diffusion layer thickness on Zn uptake by wheat and by two bio-mimetic devices in the presence of ethylenediaminetetraacetic acid and two natural ligands found in soil. Abstract Organic ligands can increase metal mobility in soils. The extent to which this can contribute to plant metal uptake depends among others, on complex lability and diffusion limitations in solute transfer from the soil solution to root uptake sites. We investigated the influence of diffusion layer thickness on zinc uptake by wheat seedlings in the presence of ethylenediaminetetraacetic acid (EDTA), citrate and histidine with similar free Zn by measuring 65Zn uptake from stirred, non-stirred and agar-containing solutions. Analogous experiments were performed using permeation liquid membranes (PLM) and ‘diffusive gradients in thin films’ (DGT) probes as bio-mimetic devices. In treatments with low EDTA concentrations (~2µM) or ligand-free Zn solution, increasing diffusion layer thickness reduced Zn fluxes into roots to a similar extent as into PLM and DGT probes, indicating reduced uptake attributable to diffusion limitation. In the citrate treatments root Zn influx was similar to EDTA treatments under stirred conditions, but increasing diffusion layer thickness did not affect Zn uptake. This suggests complex dissociation compensated for reduced Zn2+ diffusion and that the entire complexes were not taken up. The Zn root influxes in the histidine treatments were found to be on average by a factor of 2.5 higher than in the citrate treatments and they also showed no decrease in non-stirred and agar treatments. Dissociation kinetics inferred from PLM measurements explained a large part, although not all, of the increased Zn uptake by the plants in the presence of histidine. The difference may be a result of the uptake of neutral or positive Zn–histidine complexes. The results of this study confirm that labile complexes can contribute to Zn uptake by wheat either through diffusion limitation and complex dissociation or through uptake of entire complexes, depending on the nature of the ligands.

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Das, Sazol Kumar, Young Min Kim, Tae Kwon Ha, Raynald Gauvin e In Ho Jung. "Anisotropic Diffusion Behaviour of Al and Zn in HCP Mg: Diffusion Couple Experiment Using Mg Single Crystal". Materials Science Forum 765 (luglio 2013): 516–20. http://dx.doi.org/10.4028/www.scientific.net/msf.765.516.

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Diffusion couple experiments for Mg-Al and Mg-Zn were carried out with Mg single crystal to determine the anisotropic diffusion coefficients of Al and Zn in hcp Mg at the temperature range between 553 and 693 K. Based on the experimental results, anisotropic diffusion coefficients of Al and Zn were calculated using multiphase diffusion simulations. Al diffusion in hcp Mg is slightly faster than Mg self-diffusion itself, but the diffusion of Zn is slightly slower than Mg self-diffusion. The diffusion coefficients of Al and Zn along the a-axis (basal plane) of hcp Mg is slightly higher (1.1-1.4 times) than those along the c-axis (normal to the basal plane), which is also similar to Mg self-diffusion behaviour.

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8

Hu, Zhihua. "Study on microstructure and properties of Zn-Sn coating on sintered Nd-Fe-B magnets by grain boundary diffusion process". Anti-Corrosion Methods and Materials 68, n. 4 (10 agosto 2021): 340–45. http://dx.doi.org/10.1108/acmm-02-2021-2440.

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Purpose The microstructure and properties of Zn-Sn coating on sintered Nd-Fe-B magnets were investigated by the grain boundary diffusion process, to improve the corrosion resistance of magnet surface and explore the feasibility of realizing the lower-temperature grain boundary diffusion. Design/methodology/approach The Zn-Sn coating was deposited on sintered Nd-Fe-B magnets by magnetron sputtering, and then the Zn-Sn coated magnets were put into the vacuum tube furnace for grain boundary diffusion process. The morphology and structure of Zn-Sn coating as well as its mechanical properties and corrosion resistance were investigated. Findings Results showed that the particle size of vacuum diffusion-treated Zn-Sn coating increased and the particle agglomeration was weakened with increasing diffusion temperature, and the non-vacuum diffusion-treated Zn-Sn coating was oxidized to generate SnO2 and ZnO compounds. The binding force of coating first increased and then decreased with increasing diffusion temperature, and the maximum binding force was obtained at 540 °C. The binding force and corrosion resistance of non-vacuum diffusion-treated Zn-Sn coating were higher than the vacuum diffusion-treated Zn-Sn coating at the same diffusion temperature. Originality/value The Zn-Sn coating after diffusion treatment can provide complete protection, and the coating elements diffusion can be carried out at the same temperature as the secondary aging of sintered Nd-Fe-B magnets. Simultaneously, further diffusion process optimization needs to be completed because the diffusion depth is very low and only about 10 µm, which does not meet the requirements of traditional grain boundary diffusion method.

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9

Kim, Seon Tai, e Dong Chan Moon. "Zn Diffusion in In1-xGaxP". Japanese Journal of Applied Physics 29, Part 1, No. 4 (20 aprile 1990): 627–29. http://dx.doi.org/10.1143/jjap.29.627.

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10

Tong, Jianbin, Yi Liang, Shicheng Wei, Hongyi Su, Bo Wang, Yuzhong Ren, Yunlong Zhou e Zhongqi Sheng. "Microstructure and Corrosion Resistance of Zn-Al Diffusion Layer on 45 Steel Aided by Mechanical Energy". Materials 12, n. 18 (18 settembre 2019): 3032. http://dx.doi.org/10.3390/ma12183032.

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In harsh environments, the corrosion damage of steel structures and equipment is a serious threat to the operational safety of service. In this paper, a Zn-Al diffusion layer was fabricated on 45 steel by the Mechanical Energy Aided Diffusion Method (MEADM) at 450 °C. The microstructure and composition, the surface topography, and the electrochemical performance of the Zn-Al diffusion layer were analyzed before and after corrosion. The results show that the Zn-Al diffusion layer are composed of Al2O3 and Γ1 phase (Fe11Zn40) and δ1 phase (FeZn6.67, FeZn8.87, and FeZn10.98) Zn-Fe alloy. There is a transition zone with the thickness of about 5 μm at the interface between the Zn-Al diffusion layer and the substrate, and a carbon-rich layer exists in this zone. The full immersion test and electrochemical test show that the compact corrosion products produced by the initial corrosion of the Zn-Al diffusion layer will firmly bond to the Zn-Al diffusion layer surface and fill the crack, which plays a role in preventing corrosion of the corrosive medium and reducing the corrosion rate of the Zn-Al diffusion layer. The salt spray test reveals that the initial corrosion products of the Zn-Al diffusion layer are mainly ZnO and Zn5(OH)8Cl2H2O. New corrosion products such as ZnAl2O4, FeOCl appear at the middle corrosion stage. The corrosion product ZnAl2O4 disappears, and the corrosion products Zn(OH)2 and Al(OH)3 appear at the later corrosion stage.

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Più fonti

Tesi sul tema "Zn diffusion"

1

Peksa, Mikulás̆, Sareeya Bureekaew, Rochus Schmid, Jan Lang e Frank Stallmach. "On the nature of adsorption sites for CO 2 in MOF Zn 2 (bdc) 2 dabco". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183198.

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2

Wehring, Markus, Saeed Amirjalayer, Rochus Schmid e Frank Stallmach. "Anisotropic self-diffusion of guest molecules in Zn 2 (bdc) 2 dabco". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185473.

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3

Wehring, Markus, Saeed Amirjalayer, Rochus Schmid e Frank Stallmach. "Anisotropic self-diffusion of guest molecules in Zn 2 (bdc) 2 dabco". Diffusion fundamentals 16 (2011) 60, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13803.

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4

Seehamart, Kompichit, Tanin Nanok, Jörg Kärger, Christian Chmelik, Rajamani Krishna e Siegfried Fritzsche. "Examining the reason of the observed influence of the lattice flexibility on the diffusion of ethane in Zn(tbip)". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189728.

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5

Peksa, Mikulás̆, Sareeya Bureekaew, Rochus Schmid, Jan Lang e Frank Stallmach. "On the nature of adsorption sites for CO 2 in MOF Zn 2 (bdc) 2 dabco". Diffusion fundamentals 20 (2013) 55, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13631.

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6

Seehamart, Kompichit. "Investigation of the diffusion mechanisms of several hydrocarbons in the Metal-Organic-Framework Zn(tbip)". Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-68125.

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Most of the computer simulations of molecules in Metal-Organic Frameworks (MOFs) to be found in the literature are done with rigid framework. But, Molecular Dynamics (MD) simulations of the self-diffusivity, Ds, of ethane within the one-dimensional 4.5 Å channels of the MOF type Zn(tbip)(H2 tbip = 5-tert-butyl isophthalic acid) presented in this work have shown not only quantitative, but also qualitative, differences in the Ds values for fixed and flexible lattices. Particularly, the dependence of Ds upon the concentration of molecules, c, is strongly influenced by the lattice flexibility. The reasons for this influence are investigated with the aid of probability density plots, free energy landscapes and barriers, along with a determination of the structural changes accompanying increasing c. It is found that for flexible lattices, the tighter, more constrained parts of the channels become wider at higher c; this allows more molecules to diffuse in the central region of the channels. The investigations for Zn(tbip) have been extended to three equimolar mixtures of ethane/ethane, CO2/ethane and CO2/methanol. The simulations take into account the lattice flexibility. The diffusional characteristics are discussed in relation to molecule properties and lattice geometry. The results show that Zn(tbip) may be a useful material for separating methane/ethane and CO2/ethane mixtures at low concentrations, and CO2/methanol mixtures at high concentrations. The temperature and concentration dependence of the self-diffusivity of propane diffusion in Zn(tbip) have been investigated as well by performing normal MD and hyper-MD with bias potential simulations. The obtained temperature dependence of the self-diffusivities is analyzed using an Arrhenius relationship, yielding the activation energy to be 9.53 kJ/mol and the pre-exponential factor to be 4.48×10-9 m2s-1. Using this hyper-MD method, interesting mechanisms of the propane molecules able to pass each other and exchange their sites in the channels can be observed. Because of mutual hindrance of propane molecules, the propane self-diffusivities decrease with increasing concentration.

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7

Seehamart, Kompichit, Tanin Nanok, Jörg Kärger, Christian Chmelik, Rajamani Krishna e Siegfried Fritzsche. "Examining the reason of the observed influence of the lattice flexibility on the diffusion of ethane in Zn(tbip)". Diffusion fundamentals 11 (2009) 38, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A13988.

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8

Gumbmann, Eva Maria. "The effect of minor alloying elements (Mg, Ag, Zn) on the nucleation and precipitation behaviour in AlCuLi alloys". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI092.

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Les alliages Al-Cu-Li sont particulièrement attractifs pour les applications aéronautiques du fait de leur faible densité, haute limite d'élasticité et bonne ténacité. Ils reçoivent une attention particulièrement importante actuellement, depuis le développement de la troisième génération qui contient des concentrations relativement élevées pour le cuivre et relativement basses pour le Li. Ces nouveaux alliages sont caractérisés par une dureté élevée, une bonne résistance à la fatigue et une bonne stabilité thermique. La phase principale de durcissement est la phase T1 – Al2CuLi qui se présente sous la forme de plaquettes d'environ 1 nm d'épaisseur et 50 nm de diamètre, situées sur les plans {111} de la matrice avec une structure hexagonale. La germination efficace de cette phase durcissante entre en compétition avec d'autres précipités des sous-systèmes constituant ces alliages (comme Al-Cu et Al-Li), et nécessite des conditions particulières, en particulier la présence de dislocations (introduites par pré-déformation) et d'éléments d'alliage mineurs (Mg, Ag, Zn). Bien qu'il soit connu depuis longtemps que l'addition de ces éléments favorise la cinétique de précipitation dans ces alliages et le durcissement associé, leurs mécanismes d'action sont encore très mal compris.Dans ce contexte, l'objectif de la thèse est d'évaluer systématiquement l'effet des additions mineures de Mg, Ag et Zn sur la germination, la cinétique de précipitation et le durcissement correspondant. La caractérisation détaillée de la microstructure est utilisée pour comprendre les mécanismes de modification de la microstructure par les éléments mineurs. Les mesures de la diffusion des rayons X à petits angles et la DSC fournissent respectivement la cinétique de précipitation et la séquence de formation des phases. La microscopie électronique en transmission, utilisée en mode conventionnel, en résolution atomique et en mode de cartographie chimique met en évidence la structure et la distribution spatiale des phases. La dureté donne accès au durcissement. Des matériaux à gradient de concentration ont été élaborés et caractérisés pour évaluer l'effet de la concentration des alliages sur la précipitation et le durcissement.Les résultats mettent en évidence que le Mg est l'élément le plus efficace pour accélérer la cinétique de précipitation et de durcissement. L'addition d'Ag et de Zn augmente également la cinétique de précipitation mais dans une moindre mesure. L'addition de Mg change la séquence de précipitation tout au long de la séquence de vieillissement. La différence principale liée à la présence de Mg pour les premiers stades de traitement thermique est observée par rapport à la précipitation sur les dislocations. Dans les alliages qui contiennent du Mg, les dislocations sont décorées par des phases précurseur contenant de Cu et Mg. Par contre dans les alliages sans Mg celles-ci sont associés à des zones GP qui évoluent ensuite en précipités θ'. Cette différence est attribuée à la germination favorable de T1 sur les phases précurseur de Cu/Mg dans les alliages contenant du Mg, et par la saturation des sites de germination hétérogène par θ' dans les alliages sans Mg.L'augmentation de dureté associée à l'addition d'Ag et Zn est attribuée à une fraction volumique plus élevé de la phase T1. Ag est ségrège à l'interface entre T1 et la matrice et Zn est incorporé dans la structure de T1. Ces résultats suggèrent que les additions de Zn et Ag stimulent la formation de T1.L'influence de la concentration en éléments d'addition mineurs a été caractérisée par une approche résolue en temps et en espace, sur les matériaux contenant un gradient en composition. Cela révèle que l'effet de l'addition de Mg sur la précipitation se produit à une valeur seuil de ~0.1% en poids, suggérant que cela est la concentration nécessaire pour germer des phases précurseur sur les dislocations dans les premiers stades de la précipitation
Al-Cu-Li alloys are very attractive for aerospace applications alloys due to their low density, high modulus and high strength. They are experiencing a strong interest since the so-called 3rd generation alloys, with relatively high Cu and low Li content, have been developed with high toughness, fatigue resistance and thermal stability. The main precipitating phase in these alloys is the T1-phase which precipitates on {111}Al-planes with a hexagonal structure. It is known that obtaining a fine dispersion of T1, and hence a high strength requires the presence of dislocations as nucleation sites. In addition, commercial Al-Cu-Li alloys contain several minor alloying elements such as Mg, Ag and Zn, which help reaching the desired properties. Although the effect of these minor additions on precipitation of T1 has been characterized, it has not been understood yet.In this context the aim of this thesis is to systematically investigate the effect of minor additions of Mg, Ag and Zn on precipitation nucleation, precipitation kinetics and related strengthening, and to use a detailed characterization of the microstructure to understand the mechanisms by which the modifications induced by these minor additions take place. In-situ Small-Angle X-ray Scattering and Differential Scanning Calorimetry provide the precipitation kinetics and sequence, respectively. Transmission Electron Microscopy, both in conventional mode, atomically-resolved and in chemical mapping mode, reveals the structure and distribution of phases. Hardness gives access to the strengthening. Compositionally gradient materials are fabricated and characterized to evaluate the effect of alloy composition on precipitation and strengthening.The results reveal that Mg is most effective in order to enhance precipitation kinetics and hardening. Additional Ag and Zn further enhance precipitation kinetics but to a lower extent. The addition of Mg changes the precipitation sequence at all times of ageing. The main differences in early aging conditions are observed with respect to precipitation on dislocations. In Mg-containing alloys, dislocations are decorated by Cu-Mg precursor phases, whereas dislocations in Mg-free alloys are mainly associated to GP-zones which evolve subsequently into θ'-phase. In fully precipitated conditions the microstructure of Mg-containing alloys is dominated by the T1 phase, whereas that of Mg-free alloys is dominated by the θ'-phase. This difference is attributed to the favourable nucleation of T1 on Mg-Cu precursor phases in the Mg-containing alloys, and to the consumption of T1-heterogeneous nucleation sites by the θ'-phase in the Mg-free alloys.The increase of hardness associated to the addition of Ag and Zn is associated to a higher volume fraction of the T1-phase. Ag was found to segregate at the T1/matrix interface and Zn was incorporated into the T1-phase, so that it is assumed that their additions stimulate the formation of T1.The influence of the concentration of the minor solute additions has been characterised by combined space and time-resolved experiments on compositionally gradient materials. It reveals that the effect of an Mg addition on precipitation occurs at a threshold level of ~0.1wt%, suggesting that this concentration is that necessary to form the precursor phase at the dislocations during early ageing

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Degaga, Gemechis D. "Physicochemical, Spectroscopic Properties, and Diffusion Mechanisms of Small Hydrocarbon Molecules in MOF-74-Mg/Zn| A Quantum Chemical Investigation". Thesis, Michigan Technological University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791501.

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In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic bricks connected by organic linkers. From a crystal engineering stand point, MOFs are advantageous in creating a range of microporous (0.2–2.0 nm) to mesoporous (>50 nm) void cavities, presenting unique opportunities for the functionalization of both the organic linkers and the void. Of significant importance is the MOF-74-M family (M = metal), characterized by a high density of open metal sites, that is not fully coordinated metal centers. This family of MOF is also known as CPO-27-M. MOF-74 have demonstrated more separation potential than other known MOFs and zeolites. Density functional theory (DFT), as implemented within a linear combination of atomic orbital (LCAO) approach, has been used to investigate the selective sorption of C1-C4 hydrocarbons in MOF-74-Mg/Zn. The study was first implemented by adopting a molecular cluster approach, and later by applying periodic boundary conditions (PBC). While both modellistic approaches agree in showing significant differences in binding energies between olefins and paraffins adsorbed at the MOFs’ open metal sites, results reported at the molecular cluster level show underestimation when compared to those obtained at the PBC level. The use of PBC models allow for the correcting of binding energies for basis set superposition error (BSSE), molecular lateral interaction (LI), zero-point energy (ZPE), and thermal energy (TE) contributions. As such, results obtained at the PBC level are directly comparable to experimental calorimetric values (i.e., heat of adsorptions). This work discusses, for the first time, the origin of the fictitious agreement between binding energies obtained with molecular clusters and experimental heats of adsorption, identifying its origin as due to compensation of errors. Spectroscopy studies based on the intensities and frequency shifts with respect to the molecules in the gas phase are presented as a further investigation of the interaction of the small hydrocarbons (C₁-C₂) with the open metal sites in MOF-74-Mg. In an attempt to provide a more comprehensive description of the behavior of the hydrocarbon molecules, results from diffusion mechanism studies are also presented. The investigations of the diffusion mechanisms are based on the use of climbing-image nudge elastic band (CI-NEB) simulations, coupled with van der Waals functional (vdW-DF) and ultra-soft pseudopotentials as implemented within the plane-wave (PW) DFT approach. The CI-NEB studies showed that paraffin molecules are more energetically favored to diffuse within and along the cavity of MOF-74-Mg with respect to their olefin counterparts.

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10

Landaverde, Alvarado Carlos Jose. "Sorption, Transport and Gas Separation Properties of Zn-Based Metal Organic Frameworks (MOFs) and their Application in CO₂ Capture". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73214.

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Adsorption, separation and conversion of CO₂ from industrial processes are among the priorities of the scientific community aimed at mitigating the effects of greenhouse gases on the environment. One of the main focuses is the capture of CO₂ at stationary point sources from fossil fuel emissions using porous crystalline materials. Porous crystalline materials can reduce the energy costs associated with CO₂ capture by offering high adsorption rates, low material regeneration energy penalties and favorable kinetic pathways for CO₂ separation. MOFs consist of polymeric inorganic networks with adjustable chemical functionality and well-defined pores that make them ideal for these applications. The objective of this research was to test the potential for CO₂ capture on Zn-based MOFs by studying their sorption, transport and gas separation properties as adsorbents and continuous membranes. Three Zn-based MOFs with open Zn-metal sites were initially studied. Zn4(pdc)4(DMF)2•3DMF (1) exhibited the best properties for CO₂ capture and was investigated further under realistic CO₂ capture conditions. The MOF exhibited preferential CO₂ adsorption based on a high enthalpy of adsorption and selectivity of CO₂ over N₂ and CH₄. Sorption dynamics of CO₂ indicated fast adsorption and a low activation energy for sorption. Diffusion inside the pores is the rate-limiting step for diffusion, and changes in the process temperature can enhance CO₂ separation. Desorption kinetics indicated that CO₂ has longer residence times and lower activation energies for desorption than N₂ and CH₄. This suggests that the selective adsorption of CO₂ is favored. MOF/Polymer membranes were synthesized via a solvothermal method with structural defects sealed by a polymer coating. This method facilitates the permeation measurements of materials that cannot form uniform-defect-free layers. The membrane permeation of CO₂, CH₄, N₂ and H₂ exhibited a linear relation to the inverse square root of the molecular weight of the permanent gases, indicating that diffusion occurs in the Knudsen regime. Permselectivity was well-predicted by the Knudsen model with no temperature dependence, and transport occurs inside the pores of the membrane. MOF (1) exhibits ideal properties for future applications in CO₂ capture as an adsorbent.
Ph. D.

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Capitoli di libri sul tema "Zn diffusion"

1

Mazilkin, A. A., B. Baretzky, S. Enders, Olga A. Kogtenkova, Boris Straumal, Eugen Rabkin e Ruslan Z. Valiev. "Hardness of Nanostructured Al-Zn, Al-Mg and Al-Zn-Mg Alloys Obtained by High-Pressure Torsion". In Defect and Diffusion Forum, 155–60. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-17-5.155.

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El-Hofy, M. "Grain Boundary Defects Induced Switching in Zn- Bi- Mo Ceramic". In Defect and Diffusion Forum, 13–20. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-28-0.13.

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Čermák, Jiří, e Ivo Stloukal. "Zn Diffusion in Binary Base of Light Mg-Al Alloys". In Defect and Diffusion Forum, 165–70. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-35-3.165.

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Murashov, Vladimir, Boris Straumal e Pavel Protsenko. "Grain Boundary Wetting in Zn Bicrystals by a Sn-Based Melt". In Defect and Diffusion Forum, 235–38. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-17-5.235.

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Torres, Vitor J. B., J. Coutinho e Patrick R. Briddon. "Local Vibrational Modes of Zn-H-P in GaP, InP and ZnTe". In Defect and Diffusion Forum, 31–36. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-37-x.31.

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Brennan, Sarah, Katrina Bermudez, Nagraj Kulkarni e Yongho Sohn. "Diffusion couple investigation of the Mg-Zn system". In Magnesium Technology 2012, 323–27. Cham: Springer International Publishing, 2012. http://dx.doi.org/10.1007/978-3-319-48203-3_59.

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Brennan, Sarah, Katrina Bermudez, Nagraj Kulkarni e Yongho Sohn. "Diffusion Couple Investigation of the Mg-Zn System". In Magnesium Technology 2012, 323–27. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118359228.ch59.

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Chaubey, Anil K., S. Mohapatra, B. Bhoi, J. L. Gumaste, B. K. Mishra e P. S. Mukherjee. "Effect of Cerium Addition on the Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy". In Defect and Diffusion Forum, 97–103. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-61-2.97.

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Chen, Y. C., H. Z. Cui, J. Ding e Y. B. Chen. "Experiments Proving the Mixed Control of the Reactive Diffusion System Zn/Fe₃Si with Clamp Press". In Defect and Diffusion Forum, 59–62. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-36-1.59.

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Suarez, Lucia, F. Leysen, C. Masquelier, D. Warichet e Yvan Houbaert. "Effects of Mg Additions on Surface Morphology and Corrosion Resistance of Hot-Dipped Zn Coatings". In Diffusion in Solids and Liquids III, 300–305. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-51-5.300.

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Atti di convegni sul tema "Zn diffusion"

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Liu, Jian-Chun, Long Xiao, Zhi-Jun Yue e Gong Zhang. "Atomic diffusion of Zn in Sn-Zn based solder joints subjected to high temperature aging". In 2017 IEEE Electrical Design of Advanced Packaging and Systems Symposium (EDAPS). IEEE, 2017. http://dx.doi.org/10.1109/edaps.2017.8277008.

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Cheng, Chen-Lung, N. Ledentsov, M. Agustin, J. R. Kropp, N. N. Ledentsov, Z. Khan e Jin-Wei Shi. "Ultra-Fast Zn-Diffusion/Oxide-Relief 940 nm VCSELs". In Optical Fiber Communication Conference. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/ofc.2019.w3a.2.

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Kitatani, Takeshi, Kaoru Okamoto, Kenji Uchida e Shigehisa Tanaka. "Long tail Zn diffusion in InGaAsP and InGaAlAs quaternary alloys". In 2016 Compound Semiconductor Week (CSW) [Includes 28th International Conference on Indium Phosphide & Related Materials (IPRM) & 43rd International Symposium on Compound Semiconductors (ISCS)]. IEEE, 2016. http://dx.doi.org/10.1109/iciprm.2016.7528577.

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Hoxha, Adhurim, Heinrich Oettel, Dietrich Heger, Angelos Angelopoulos e Takis Fildisis. "Calculation Of The Interdiffusion Coefficient In The Cu-Zn Diffusion Couple". In ORGANIZED BY THE HELLENIC PHYSICAL SOCIETY WITH THE COOPERATION OF THE PHYSICS DEPARTMENTS OF GREEK UNIVERSITIES: 7th International Conference of the Balkan Physical Union. AIP, 2010. http://dx.doi.org/10.1063/1.3322515.

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Schlegl, T. "The Influence of Surface Preparation on Zn-Diffusion Processes in GaSb". In THERMOPHOTOVOLTAIC GENERATION OF ELECTRICITY: Sixth Conference on Thermophotovoltaic Generation of Electricity: TPV6. AIP, 2004. http://dx.doi.org/10.1063/1.1841918.

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Sulima, Oleg V. "Diffusion of Zn in TPV materials: GaSb, InGaSb, InGaAsSb and InAsSbP". In THERMOPHOTOVOLTAIC GENERATION OF ELECTRICITY: Fifth Conference on Thermophotovoltaic Generation of Electricity. AIP, 2003. http://dx.doi.org/10.1063/1.1539395.

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Wada, Morio, Katsutoshi Sakakibara e Yoichi Sekiguchi. "A new method of Zn diffusion into InP for optical device fabrication". In Advanced processing and characterization technologies. AIP, 1991. http://dx.doi.org/10.1063/1.40637.

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GRABOWSKI, S., e P. ENTEL. "ELEMENTARY DIFFUSION PROCESSES IN AL-CU-ZN ALLOYS: AN AB INITIO STUDY". In From Atoms, Molecules and Clusters in Complex Environment to Thin Films and Multilayers. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812793652_0005.

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Shishiyanu, S. T., e T. S. Shishiyanu. "Impact of light quantum in Rapid Photothermal Diffusion of Zn IN GaAs". In 2010 International Semiconductor Conference (CAS 2010). IEEE, 2010. http://dx.doi.org/10.1109/smicnd.2010.5650620.

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Shima, A., T. Kamizato, A. Takami, S. Karakida, K. Isshiki, H. Matsubara e H. Kumabe. "A Very Low Threshold Current, 780 nm Diffusion Stripe Laser Fabricated by Open-tube, Two-step Zn Diffusion Technique". In 1989 Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 1989. http://dx.doi.org/10.7567/ssdm.1989.d-7-4.

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Rapporti di organizzazioni sul tema "Zn diffusion"

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Kammerer, Catherine, Nagraj S. Kulkarni, Robert J. Bruce Warmack, Kelly A. Perry, Irina Belova, Prof Graeme Murch e Yong Ho Sohn. Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples. Office of Scientific and Technical Information (OSTI), agosto 2013. http://dx.doi.org/10.2172/1095717.

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Norseng, Marshall Stephen. Ga self-diffusion in isotopically enriched GaAs heterostructures doped with Si and Zn. Office of Scientific and Technical Information (OSTI), dicembre 1999. http://dx.doi.org/10.2172/760338.

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3

Dakshinamurthy, S., S. Shetty, I. Bhat, C. Hitchcock, R. Gutmann, G. Charache e M. Freeman. Fabrication and characterization of GaSb based thermophotovoltaic cells using Zn diffusion from a doped spin-on glass source. Office of Scientific and Technical Information (OSTI), giugno 1998. http://dx.doi.org/10.2172/307843.

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