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1
Khrapak, Sergey A. "Self-Diffusion in Simple Liquids as a Random Walk Process." Molecules 26, no. 24 (December 11, 2021): 7499. http://dx.doi.org/10.3390/molecules26247499.
Анотація:
It is demonstrated that self-diffusion in dense liquids can be considered a random walk process; its characteristic length and time scales are identified. This represents an alternative to the often assumed hopping mechanism of diffusion in the liquid state. The approach is illustrated using the one-component plasma model.
2
Pham Huu, Kien, Linh Nguyen Hong, Hien Pham Xuan, Linh Nguyen Thi Thuy, Quang Phan Dinh, and Trang Giap Thi Thuy. "Molecular dynamics simulation for structural heterogeneity and diffusion process in liquid GeO2." Journal of Science Natural Science 66, no. 1 (March 2021): 42–48. http://dx.doi.org/10.18173/2354-1059.2021-0005.
Анотація:
In this paper, we perform a simulation about liquid GeO2. The structure and diffusion process are analyzed through the radial distribution function, the distribution of GeOx (x = 4, 5, 6) structural units, length distribution, angle distribution, and data visualization. Simulation results show that the structure of liquid GeO2 composes clusters of GeO4, GeO5, or GeO6. These clusters have sizes depending on pressure and are distributed heterogeneously in space. This result confirms the origin of dynamical heterogeneity in the liquid oxide systems. In addition, the diffusion coefficient of Ge and O decreases upon pressure. We show that the diffusion relates to the breaking bond Ge-O.
3
Senn, S. M., and D. Poulikakos. "Multiphase Transport Phenomena in the Diffusion Zone of a PEM Fuel Cell." Journal of Heat Transfer 127, no. 11 (June 20, 2005): 1245–59. http://dx.doi.org/10.1115/1.2039108.
Анотація:
In this paper, a thorough model for the porous diffusion layer of a polymer electrolyte fuel cell (PEFC) is presented that accounts for multicomponent species diffusion, transport and formation of liquid water, heat transfer, and electronic current transfer. The governing equations are written in nondimensional form to generalize the results. The set of partial differential equations is solved based on the finite volume method. The effect of downscaling of channel width, current collector rib width, and diffusion layer thickness on the performance of polymer electrolyte membrane (PEM) fuel cells is systematically investigated, and optimum geometric length ratios (i.e., optimum diffusion layer thicknesses, optimum channel, and rib widths) are identified at decreasing length scales. A performance number is introduced to quantify losses attributed to mass transfer, the presence of liquid water, charge transfer, and heat transfer. Based on this model it is found that microchannels (e.g., as part of a tree network channel system in a double-staircase PEM fuel cell) together with diffusion layers that are thinner than conventional layers can provide substantially improved current densities compared to conventional channels with diameters on the order of 1 mm, since the transport processes occur at reduced length scales. Possible performance improvements of 29, 53, and 96 % are reported.
4
Dong, F. T., Xiang Yi Xue, Hong Chao Kou, Jun Wang, C. X. Niu, and J. S. Li. "Diffusion Bonding of Fe-Based Amorphous Ribbon to Crystalline Cu." Materials Science Forum 745-746 (February 2013): 788–92. http://dx.doi.org/10.4028/www.scientific.net/msf.745-746.788.
Анотація:
A copper rod/FeSiB amorphous ribbon/copper rod sandwich laminated composite material has been successfully fabricated by co-pressing at temperatures within supercooled liquid region. The bonding interface has been characterized by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Results showed that a good bonding interface could be obtained only when the initial surface were carefully polished. The diffusion zone confirmed by EDS is about 60nm, indicating the bonding is in atomic metallurgical level via limited diffusion. The present results show that even the diffusion length is very small, diffusion bonding in the supercooled liquid region could be an effective way for fabricating Fe-based metallic glass/Cu laminated composites
5
Pratt, F. L., F. Lang, S. J. Blundell, W. Steinhardt, S. Haravifard, S. Mañas-Valero, E. Coronado, B. M. Huddart, and T. Lancaster. "Studying spin diffusion and quantum entanglement with LF-µSR." Journal of Physics: Conference Series 2462, no. 1 (March 1, 2023): 012038. http://dx.doi.org/10.1088/1742-6596/2462/1/012038.
Анотація:
Abstract LF-µSR studies have previously been used to study the diffusive 1D motion of solitons and polarons in conducting polymers. This type of study was also applied to investigating the diffusive motion of spinons in spin-1/2 antiferromagnetic chains. Recently the method has been extended to examples of 2D layered triangular spin lattices which can support quantum spin liquid states, such as 1T-TaS2 and YbZnGaO4. These systems are found to show spin dynamics that matches well to 2D spin diffusion, such a model being found to provide a much better fit to the data than previously proposed models for spin correlations in such systems. In YbZnGaO4 the diffusion rate shows a clear crossover between classical and quantum regimes as T falls below the exchange coupling J. That the spin diffusion approach works well in the high T classical region might be expected, but it is found that it also works equally well in the low T quantum region where quantum entanglement controls the spin dynamics. Measurement of the diffusion rate allows a T dependent length scale to be derived from the data that can be assigned to a quantum entanglement length ξ E. Another entanglement measure, the Quantum Fisher Information F Q can also be obtained from the data and its T dependence is compared to that of ξ E.
6
Gomez, Houari Cobas, Jéssica Gonçalves da Silva, Jocasta Mileski Machado, Bianca Oliveira Agio, Francisco Jorge Soares de Oliveira, Antonio Carlos Seabra, and Mario Ricardo Gongora-Rubio. "LTCC 3D FLOW FOCALIZATION DEVICE FOR LIQUID-LIQUID PARTIAL SOLVENT EXTRACTION." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2016, CICMT (May 1, 2016): 000111–17. http://dx.doi.org/10.4071/2016cicmt-wa23.
Анотація:
Abstract The present work shows a ceramics microfluidic device for partial solvent extraction scheme. The technology used for device fabrication was Low Temperature Cofired Ceramics (LTCC) which allows us for complex and chemical resistant 3D microfluidic devices. The proposed system aims to partially extract the solvent present in a mixture containing aqueous and organic phases. This scheme uses a 3D flow focalization in order to improve the solvent diffusion into the external aqueous phase. The device is composed by three different parts, the input channels distribution, the main channel and the output channels distribution. The designed input channels distribution ensures a centered 3D focalized solvent stream along the main channel. The focalized solvent mixes with the surrounding water thanks to diffusion. Projected output channels take the central fluid out separately from the surrounding. Thus the device has two different outputs, one for the focalized fluid and another one for the waste fluid, which is the aqueous phase plus solvent. For a device concept proof, acetone and water were used as organic and aqueous phases, respectively. COMSOL Multiphysics was used for device microfluidics and chemical transport simulation. The extraction efficiency was the variable used as indicator for device performance validation. The flow rate ratio between phases, total flow rate, main channel length and focalized stream channel output hydraulic diameter (ODH) were used as process variables for simulation purposes. A factorial experimental planning was used in order to analyze the extraction efficiency taking into account process variables effects. From simulation results it was determined main channel length and ODH as the variables with stronger effect on extraction efficiency. Obtained simulated efficiencies were as high as 80.6%. Considering previous results observations a microfluidic device was fabricated with a main channel length of 21,4 mm and ODH of 214,63 μm. Gas chromatography was used to measured acetone concentration in outputs samples and from here the extraction efficiency. Experimental results were in agreement with simulation, returning extraction efficiencies in the order of 80.8% ± 2.2%.
7
Zhang, Guoyan, Shengyong Liu, Jie Lu, Jiong Wang, and Yongtao Ma. "Numerical Simulation of Diffusion Absorption Refrigerator." E3S Web of Conferences 233 (2021): 01044. http://dx.doi.org/10.1051/e3sconf/202123301044.
Анотація:
Based on Fluent software, a mathematical model of thermosyphon pump is established and numerical simulation is carried out to study the influence of riser tube length, tube diameter and immersion ratio on liquid lifting capacity and efficiency. The results showed that: the liquid lifting volume increased with the increase of immersion ratio, whereas the lifting efficiency showed a trend of increasing followed by decreasing. The highest lifting efficiency for a 340mm long, 6mm diameter riser achieved when the immersion ratio is 0.35. With the increasing of the height in riser, the velocity of the gas phase close to the wall in the thermosyphon pump was higher than the velocity along the radial direction. In order to enhance fluid interchange, corners of the refrigeration box were designed to be arc-shaped with a higher corner speed and lower temperature.
8
Ward, P., N. Collings, and N. Hay. "A Comparison of Simple Models of Turbulent Droplet Diffusion Suitable for Use in Computations of Spray Flames." Journal of Engineering for Gas Turbines and Power 107, no. 3 (July 1, 1985): 690–94. http://dx.doi.org/10.1115/1.3239790.
Анотація:
An exact analysis of the diffusion of droplets in turbulent flow, taking account of the random nature of the flow and the range of length and time scales, is very involved and the equations derived are not necessarily solvable. For this reason spray models have usually not included liquid turbulent diffusion effects. Simpler models of turbulent diffusion of droplets are compared in this paper and equations suitable for insertion into existing spray models that require little extra computational effort are derived.
9
Suwannakham, Parichart, and Kritsana Sagarik. "Dynamics of structural diffusion in phosphoric acid hydrogen-bond clusters." RSC Advances 7, no. 35 (2017): 21492–506. http://dx.doi.org/10.1039/c7ra01829k.
Анотація:
For protonated H3PO4 clusters, the Eigen–Zundel–Eigen mechanism is enhanced by fluctuations in the H-bond chain length and local-dielectric environment, and can proceed without the reorientation of H3PO4 molecules as in the case of neat liquid H3PO4.
10
Jüngling, E., K. Grosse, and A. von Keudell. "Propagation of nanosecond plasmas in liquids—Streamer velocities and streamer lengths." Journal of Vacuum Science & Technology A 40, no. 4 (July 2022): 043003. http://dx.doi.org/10.1116/6.0001669.
Анотація:
Nanosecond plasmas in liquids are often generated by applying a short high voltage pulse to an electrode immersed in a liquid for biomedical or environmental applications. The plasmas appear as streamers that propagate through the liquid. The understanding of the ignition of these nanosecond plasmas in liquids, however, is an open question. The occurrence of any traditional gas phase ignition mechanism is unlikely, because the formation of a gas bubble prior to ignition is suppressed by the inertia of the liquid. Therefore, either electron multiplication inside nanopores that are induced by an electric field pressure gradient or field effects at the tip and at the ionization front of the liquid streamer may act as electron generation mechanisms. A deeper understanding can be achieved by comparing the velocity and dynamic of the plasma propagation with modeling, where the individual mechanisms and transport coefficients can be analyzed. Here, we are using intensified charge-coupled device imaging to investigate the time dependence of the streamer dynamic and compare this with a 1D fluid code for negative voltages. It is shown that the maximum streamer length scales with the applied electric field, indicating that an electric stability field in the liquid streamer channel is important, as known for gas streamers. The 1D fluid code can reproduce the proper streamer velocities, if transport coefficients for hydrated electrons are chosen. The model suggests that the propagation of liquid streamers is dominated by the local ionization rate at the ionization front rather than by advection or diffusion of electrons as in gases. This also explains the finding that positive and negative streamers exhibit almost identical electron densities.
11
Chen, W. T., H. Carduner, J. P. Cussonneau, J. Donnard, S. Duval, A. F. Mohamad-Hadi, J. Lamblin, et al. "Measurement of the Transverse Diffusion Coefficient of Charge in Liquid Xenon." Defect and Diffusion Forum 326-328 (April 2012): 567–72. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.567.
Анотація:
Liquid xenon (LXe) is a very attractive material as a detection medium for ionization detectors due to its high density, high atomic number, and low energy required to produce electron-ion pairs. Therefore it has been used in several applications, like γ detection or direct detection of dark matter. Now Subatech is working on the R & D of LXe Compton telescope for 3γ medical imaging, which can make precise tridimensional localization of a (β+, γ) radioisotope emitter. The diffusion of charge carriers will directly affect the spatial resolution of LXe ionization signal. We will report how we measure the transverse diffusion coefficient for different electric field (0.5 ~ 1.2 kV/cm) by observing the spray of charge carriers on drift length varying until 12 cm. With very-low-noise front-end electronics and complete Monte-Carlo simulation of the experiment, the values of transverse diffusion coefficient are measured precisely.
12
Chang, Qinghua, Peikai Gao, Junyi Zhang, Yiqang Huo, Zheng Zhang, and Jingpei Xie. "Numerical Simulation of Copper-Aluminum Composite Plate Casting and Rolling Process and Composite Mechanism." Materials 15, no. 22 (November 16, 2022): 8139. http://dx.doi.org/10.3390/ma15228139.
Анотація:
This paper uses ANSYS Workbench platform to simulate the casting and rolling composite process, taking the horizontal type casting and rolling machine as the research object, and conducts the numerical simulation study of copper-aluminum composite solid-liquid casting and rolling heat-flow coupling, mainly to study different walking speed, aluminum pouring temperature, casting and rolling zone length, heat transfer coefficient on the temperature field, liquid phase rate influence law, and use it as a theoretical guide for copper-aluminum solid-liquid casting. The experiments of copper-aluminum solid-liquid casting-rolling composite were carried out to optimize the process parameters and to verify the experiments, so as to prepare a well-bonded copper-aluminum composite plate. The composite mechanism in the preparation of copper-aluminum composite plate was analyzed, and it was clarified that the interfacial layer was formed through four stages: contact between copper and aluminum surfaces, contact surface activation, mutual diffusion of copper and aluminum atoms, and reaction diffusion.
13
Kien, P. H. "The structural phase-transition pathway under compression and dynamic properties in liquid GeO2." Modern Physics Letters B 34, no. 17 (March 31, 2020): 2050187. http://dx.doi.org/10.1142/s0217984920501870.
Анотація:
We perform a simulation of the structural phase-transition pathway under compression and dynamic properties in liquid germania (GeO2). The structure of liquid GeO2 is clarified through the pair radial distribution function (PRDF), distribution of GeO[Formula: see text] [Formula: see text] units, bond angle and length distribution, and three-dimensional (3D) visualization. The result shows that the structure of liquid GeO2 is built by GeO4, GeO5 and GeO[Formula: see text]units, which are linked to each other via common oxygen atoms. The GeO[Formula: see text] units lead to form into the separate GeO4-, GeO5- and GeO6-phases. The existence of separate phases is evidence of dynamical heterogeneity (DH) in liquid GeO2. The atoms in GeO5-phase are more mobile compared to other ones. The variation of the self-diffusions of Ge and O atoms under pressure is examined via the characteristics of separate GeO4-, GeO5- and GeO6-phases. We found that under compression, there is diffusion anomaly in liquid GeO2. This is suggested to be related to the very high mobility of Ge and O atoms in the GeO5-phase compared to GeO4- and GeO6-phase.
14
Hicks, Peter D., and Richard Purvis. "Liquid–solid impacts with compressible gas cushioning." Journal of Fluid Mechanics 735 (October 22, 2013): 120–49. http://dx.doi.org/10.1017/jfm.2013.487.
Анотація:
AbstractThe role played by gas compressibility in gas-cushioned liquid–solid impacts is investigated within a viscous gas and inviscid liquid regime. A full analysis of the energy conservation in the gas is conducted for the first time, which indicates that both thermal diffusion across the gas film and viscous dissipation play an important role in gas cushioning once gas compression becomes significant. Consequently existing models of gas compressibility based on either an isothermal or an adiabatic equation of state for the gas do not fully reflect the physics associated with this phenomenon. Models incorporating thermal diffusion and viscous dissipation are presented, which are appropriate for length scales consistent with droplet impacts, and for larger scale liquid–solid impacts. The evolution of the free surface is calculated alongside the corresponding pressure, temperature and density profiles. These profiles indicate that a pocket of gas can become trapped during an impact. Differences between the new model and older models based on isothermal and adiabatic equations of state are discussed, along with predictions of the size of the trapped gas pocket.
15
Yeganegi, Saeid, Azim Soltanabadi, and Davood Farmanzadeh. "Molecular Dynamic Simulation of Dicationic Ionic Liquids: Effects of Anions and Alkyl Chain Length on Liquid Structure and Diffusion." Journal of Physical Chemistry B 116, no. 37 (September 5, 2012): 11517–26. http://dx.doi.org/10.1021/jp3059933.
16
Shahar, A., Z. Feit, and A. Zussman. "Diffusion length and lifetime in highly Ga‐doped PbSnTe layers grown by liquid‐phase epitaxy." Journal of Applied Physics 66, no. 6 (September 15, 1989): 2455–57. http://dx.doi.org/10.1063/1.344256.
17
Cousin Saint Remi, Julien, Gino V. Baron, and Joeri F. M. Denayer. "Nonuniform Chain-Length-Dependent Diffusion of Short 1-Alcohols in SAPO-34 in Liquid Phase." Journal of Physical Chemistry C 117, no. 19 (May 2013): 9758–65. http://dx.doi.org/10.1021/jp312287k.
18
MATSUMOTO, TOSHITATSU, NOBUYUKI HIDAKA, HIROSHI KAMIMURA, MIHOKO TSUCHIYA, TAKASHI SHIMIZU, and SHIGEHARU MOROOKA. "Turbulent mixing-length model for axial turbulent diffusion of liquid in three-phase fluidized bed." Journal of Chemical Engineering of Japan 21, no. 3 (1988): 256–61. http://dx.doi.org/10.1252/jcej.21.256.
19
von Kurnatowski, Martin, and Klaus Kassner. "Selection Theory of Dendritic Growth with Anisotropic Diffusion." Advances in Condensed Matter Physics 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/529036.
Анотація:
Dendritic patterns frequently arise when a crystal grows into its own undercooled melt. Latent heat released at the two-phase boundary is removed by some transport mechanism, and often the problem can be described by a simple diffusion model. Its analytic solution is based on a perturbation expansion about the case without capillary effects. The length scale of the pattern is determined by anisotropic surface tension, which provides the mechanism for stabilizing the dendrite. In the case of liquid crystals, diffusion can be anisotropic too. Growth is faster in the direction of less efficient heat transport (inverted growth). Any physical solution should include this feature. A simple spatial rescaling is used to reduce the bulk equation in 2D to the case of isotropic diffusion. Subsequently, an eigenvalue problem for the growth mode results from the interface conditions. The eigenvalue is calculated numerically and the selection problem of dendritic growth with anisotropic diffusion is solved. The length scale is predicted and a quantitative description of the inverted growth phenomenon is given. It is found that anisotropic diffusion cannot take the stabilizing role of anisotropic surface tension.
20
Howard, Riley L., Francesca Bernardi, Matthew Leff, Emma Abele, Nancy L. Allbritton, and Daniel M. Harris. "Passive Control of Silane Diffusion for Gradient Application of Surface Properties." Micromachines 12, no. 11 (November 4, 2021): 1360. http://dx.doi.org/10.3390/mi12111360.
Анотація:
Liquid lithography represents a robust technique for fabricating three-dimensional (3D) microstructures on a two-dimensional template. Silanization of a surface is often a key step in the liquid lithography process and is used to alter the surface energy of the substrate and, consequently, the shape of the 3D microfeatures produced. In this work, we present a passive technique that allows for the generation of silane gradients along the length of a substrate. The technique relies on a secondary diffusion chamber with a single opening, leading to a directional introduction of silane to the substrate via passive diffusion. The secondary chamber geometry influences the deposited gradient, which is shown to be well captured by Monte Carlo simulations that incorporate the passive diffusion and grafting processes. The technique ultimately allows the user to generate a range of substrate wettabilities on a single chip, enhancing throughput for organ-on-a-chip applications by mimicking the spatial variability of tissue topographies present in vivo.
21
Prasad, Arvind, Lang Yuan, Peter D. Lee, Mark Easton, and David St John. "On the Solute Diffusion Length in the Interdependence Model: Dendritic versus Non-Dendritic Interface." Materials Science Forum 828-829 (August 2015): 461–67. http://dx.doi.org/10.4028/www.scientific.net/msf.828-829.461.
Анотація:
The Interdependence model currently uses an analytical expression for a moving planar interface to calculate the solute diffusion length designated as x’dl in the model. Upon nucleation within an alloy melt (i.e. when the solid embryo starts to grow), the interface grows with a spherical front which then breaks down into a dendritic interface. The time required for this breakdown is a subject for separate research. In this paper, we explore the validity of using a planar interface in the early stages of nucleation and growth of metal alloys as used in the Interdependence model. The diffusion field ahead of a planar interface, in theory, has an exponentially changing composition of infinite length. In the Interdependence model, x’dl is assumed to be where this exponentially decreasing composition profile in the liquid ahead of the interface (for k < 1) reduces to within 1% of a quantity proportional to the nominal alloy composition, C0, far from the interface. A numerical solidification model, μMatIC, is used to simulate the growth of a single grain with a dendritic interface in 2D and 3D. The numerical model is capable of generating the solute profile ahead of the growing grain which is used to evaluate the solute diffusion length that can be compared with the results obtained from the planar interface model. The comparisons were made with both 1% and 0.1% cut-off criteria. The results indicate that the 1% assumption being used in the planar front diffusion length calculation is a good approximation for the Interdependence model.
22
Ahmed, Tanvir, N. Colby Fleming, and Ayman I. Hawari. "Effects of Hydrogen Bonding on Nuclear Data Development of Liquid Anhydrous HF." EPJ Web of Conferences 284 (2023): 17003. http://dx.doi.org/10.1051/epjconf/202328417003.
Анотація:
Anhydrous Hydrogen Fluoride (HF) at high temperatures and pressures is used to process and manufacture nuclear fuel. As HF is often used directly with uranium, correct neutron thermal scattering cross sections are crucial to criticality safety applications. Classical molecular dynamics (CMD) simulation of the flexible HF system was used to create the thermal scattering law (TSL) and cross sections. The initial 2-site model is used in LAMMPS, and it can not capture the H-bond. To correctly represent the H-bond effects, a second, 3-site model was constructed in GROMACS. The 3-site model handled H-bonds by connecting a massless charge to the molecule. Key model parameters were compared to experimental data to verify the approach and models. To get the normalized VACF, the model was compared using hydrogen and fluorine bond length, density, potential energy, and diffusion coefficient. The phonon DOSs for both models were derived from the normalized VACF. DOSs were used to estimate the TSL (S(α,β)) and neutron thermal scattering cross sections for hydrogen in HF. The TSLs were evaluated using the FLASSH code with the Schofield diffusion model. It was observed that the representation of the hydrogen bonding changes the TSL's diffusional contributions. This is represented in the low energy scattering cross section, where intermolecular binding effects shift the cross section.
23
DUBROVSKII, V. G., I. P. SOSHNIKOV, A. A. TONKIKH, V. M. USTINOV, G. E. CIRLIN, and YU B. SAMSONENKO. "MBE GROWTH OF GaAs NANOWHISKERS STIMULATED BY THE ADATOM DIFFUSION." International Journal of Nanoscience 06, no. 03n04 (June 2007): 225–31. http://dx.doi.org/10.1142/s0219581x07004626.
Анотація:
The growth mechanisms of GaAs nanowhiskers (NWs) during molecular beam epitaxy (MBE) are studied theoretically and experimentally. A kinetic model of the diffusion-induced NW growth is presented that allows one to predict the dependence of NW length on the drop radius and on the technologically controlled MBE growth conditions. The results of scanning electron microscopy studies of GaAs NWs grown at different conditions on the GaAs (111) B surface activated by Au are presented and analyzed. It is shown that the length of NWs increases with decreasing the drop radius and with decreasing the deposition rate of GaAs , while its temperature dependence has a certain maximum. The aspect ratio of MBE-grown GaAs NWs is higher than 100. The maximum length of NWs is several times larger than the effective thickness of the deposited GaAs . The obtained results demonstrate that the NW growth is controlled by the adatom diffusion toward their tip rather than by the adsorption-induced vapor–liquid–solid mechanism. The growth conditions' influence on the NW morphology may be used for the controlled fabrication of NWs by MBE for different applications.
24
Li, Lei, Yuliang Su, Han Wang, Guanglong Sheng, and Wendong Wang. "A New Slip Length Model for Enhanced Water Flow Coupling Molecular Interaction, Pore Dimension, Wall Roughness, and Temperature." Advances in Polymer Technology 2019 (December 17, 2019): 1–12. http://dx.doi.org/10.1155/2019/6424012.
Анотація:
In this paper, a slip length model is proposed to analyze the enhanced flow based on the Hagen–Poiseuille equation. The model considers the multimechanisms including wall-water molecular interactions, pore dimensions, fractal roughness, and temperature. The increasing wall-water interactions result in the greater slip length and flow enhancement factor. The increased temperature enhances the kinetic energy of water molecules that leads to great surface diffusion coefficient and small work of adhesion. The wall roughness can decrease the slip length and flow enhancement factor in hydrophilic nanopores. This work studies the effects of multimechanisms on slip length and flow enhancement factor theoretically, which can accurately describe the liquid flow in nanopores.
25
Zheng, Hongyu, Jingwen Sun, Na Guo, and Mingjie Wang. "Atomic Research on the Diffusion Behavior, Mechanical Properties and Fracture Mechanism of Fe/Cu Solid–Liquid Interface." Coatings 12, no. 9 (September 4, 2022): 1299. http://dx.doi.org/10.3390/coatings12091299.
Анотація:
A molecular dynamics simulation was applied to investigate the diffusion behavior and mechanical properties of a Fe/Cu solid–liquid interface with different orientations, temperatures, and strain rates. The results show that the displacement distance of Fe atoms’ diffusion into the Cu matrix was obviously larger than that of Cu atoms’ diffusion into the Fe matrix at any diffusion temperature and diffusion time. Moreover, the diffusion coefficient and diffusion distance both increase with temperature and time, and reach the highest value when the temperature and diffusion time are 1523 K and 3 ns, respectively. Additionally, the diffusion coefficients of the Fe atoms are arranged in the following order: Fe (100) < Fe (110) < Fe (111). The diffusion coefficients of the Cu atoms are arranged in the following order: Cu (110) > Cu (111) > Cu (100), when temperature and time are 1523 K and 3 ns, respectively. The yield strength and fracture strain of the bimetallic interface is positively correlated with the strain rate, but negatively correlated with the tensile temperature. Moreover, the yield strength of the three orientations can be arranged as follows: Fe (110)/Cu (110) > Fe (100)/Cu (100) > Fe (111)/Cu (111), and the yield strength and fracture strain of Fe (110)/Cu (110) diffusion interface are 12.1 GPa and 21% when the strain rate was 1 × 109/s and the tensile temperature was 300 K. The number of stacking faults and dislocations of the diffused Fe/Cu interface decreased significantly in comparison to the undiffused Fe/Cu interface, even in the length of Stair-rod dislocation and Shockley dislocation. All these results lead to a decrease in the tensile yield strength after interface diffusion.
26
Rybka, Julia, Alexandra Höltzel, Nicole Trebel, and Ulrich Tallarek. "Stationary-Phase Contributions to Surface Diffusion in Reversed-Phase Liquid Chromatography: Chain Length versus Ligand Density." Journal of Physical Chemistry C 123, no. 35 (August 13, 2019): 21617–28. http://dx.doi.org/10.1021/acs.jpcc.9b06160.
27
Magin, Richard L., and Ervin K. Lenzi. "Fractional Calculus Extension of the Kinetic Theory of Fluids: Molecular Models of Transport within and between Phases." Mathematics 10, no. 24 (December 16, 2022): 4785. http://dx.doi.org/10.3390/math10244785.
Анотація:
The application of fractional calculus in the field of kinetic theory begins with questions raised by Bernoulli, Clausius, and Maxwell about the motion of molecules in gases and liquids. Causality, locality, and determinism underly the early work, which led to the development of statistical mechanics by Boltzmann, Gibbs, Enskog, and Chapman. However, memory and nonlocality influence the future course of molecular interactions (e.g., persistence of velocity and inelastic collisions); hence, modifications to the thermodynamic equations of state, the non-equilibrium transport equations, and the dynamics of phase transitions are needed to explain experimental measurements. In these situations, the inclusion of space- and time-fractional derivatives within the context of the continuous time random walk (CTRW) model of diffusion encodes particle jumps and trapping. Thus, we anticipate using fractional calculus to extend the classical equations of diffusion. The solutions obtained illuminate the structure and dynamics of the materials (gases and liquids) at the molecular, mesoscopic, and macroscopic time/length scales. The development of these models requires building connections between kinetic theory, physical chemistry, and applied mathematics. In this paper, we focus on the kinetic theory of gases and liquids, with particular emphasis on descriptions of phase transitions, inter-phase mixing, and the transport of mass, momentum, and energy. As an example, we combine the pressure–temperature phase diagrams of simple molecules with the corresponding anomalous diffusion phase diagram of fractional calculus. The overlap suggests links between sub- and super-diffusion and molecular motion in the liquid and the vapor phases.
28
Laghaei, Rozita, and Afshin Eskandari Nasrabad. "The Influence of Bond Angle on Thermophysical Properties of Three-Center Lennard-Jones Fluids: Computer Simulation and Theory." Zeitschrift für Physikalische Chemie 233, no. 4 (April 24, 2019): 551–76. http://dx.doi.org/10.1515/zpch-2018-1199.
Анотація:
Abstract We carry out extensive computer simulations to study the phase equilibrium, thermodynamics, and diffusion coefficient of three-center Lennard-Jones (3CLJ) fluids with an emphasis on the effects of bond angle on these properties. We take into account several bond angles ranging from θ0 = 60 to 180 degrees and two equilibrium bond elongations le = 1.0 and 0.5 (in Lennard-Jones length unit). Moreover, we study the fully flexible (FF) 3CLJ fluids for molecules with bond length 1.0. Gibbs ensemble Monte Carlo (MC) simulations are performed to compute the densities of the vapor-liquid coexisting phases and the vapor pressure, and direct three-phase (vapor-liquid-vapor) molecular dynamics (MD) simulations are carried out to calculate the surface tension. We then apply constant NVT MC simulations to obtain the internal energy, the pressure, and the pair correlation function, and utilize equilibrium MD simulations to compute the diffusion coefficient of systems with le = 1.0. In addition to MD simulations, the modified Cohen-Turnbull (mCT) theory is used to to compute the diffusion coefficient and the mean free volume appearing in the mCT relation is provided by the results of the Generic van der Waals (GvdW) theory. We show that the mCT theory is capable of reproducing the MD simulation values quite well over a wide range of density with slight overestimations at medium range. The angle dependence of different thermophysical properties are analyzed and discussed in details.
29
Weiss, V., J. Svobodova, and J. Cais. "The Crystal Segregation During Casting of the Alloy AlZn5.5Mg2.5Cu1.5." Archives of Foundry Engineering 14, no. 2 (June 1, 2014): 63–68. http://dx.doi.org/10.2478/afe-2014-0038.
Анотація:
Abstract In the course of homogenizing annealing of aluminium alloys being cast continually or semi-continually it appears that chemical inhomogenity takes off within separate dendritic cells (crystal segregation). It is about a diffusion process that takes place at the temperature which approaches the liquid temperature of the material. In that process the transition of soluble intermetallic compounds and eutectic to solid solution occurs and it suppresses crystal segregation significantly [1]. The temperature, homogenization time, the size of dendritic cells and diffusion length influences homogenizing process. The article explores the optimization of homogenizing process in terms of its time and homogenizing annealing temperature which influence mechanical properties of AlZn5,5Mg2,5Cu1,5 alloy.
30
Wu, Jie, Jia Wang, Haiou Ni, Guimin Lu, and Jianguo Yu. "Investigation of Microscopic Structure and Ion Dynamics in Liquid Li(Na, K)EutecticCl Systems by Molecular Dynamics Simulation." Applied Sciences 8, no. 10 (October 10, 2018): 1874. http://dx.doi.org/10.3390/app8101874.
Анотація:
Molten chloride salts are the main components in liquid metal batteries, high-temperature heat storage materials, heat transfer mediums, and metal electrolytes. In this paper, interest is centered on the influence of the LiCl component and temperature on the local structure and transport properties of the molten LiCl-NaCl-KCl system over the temperature range of 900 K to 1200 K. The liquid structure and properties have been studied across the full composition range by molecular dynamics (MD) simulation of a sufficient length to collect reliable values, such as the partial radial distribution function, angular distribution functions, coordination numbers distribution, density, self-diffusion coefficient, ionic conductivity, and shear viscosity. Densities obtained from simulations were underestimated by an average 5.7% of the experimental values. Shear viscosities and ionic conductivity were in good agreement with the experimental data. The association of all ion pairs (except for Li-Li and Cl-Cl) was weakened by an increasing LiCl concentration. Ion clusters were formed in liquids with increasing temperatures. The self-diffusion coefficients and ionic conductivity showed positive dependences on both LiCl concentration and temperature, however, the shear viscosity was the opposite. By analyzing the hydrodynamic radii of each ion and the coordination stability of cation-anion pairs, it was speculated that ion clusters could be the cation-anion coordinated structure and affected the macro properties.
31
Khanal, Ohnmar, Vijesh Kumar, Fabrice Schlegel, and Abraham M. Lenhoff. "Estimating and leveraging protein diffusion on ion-exchange resin surfaces." Proceedings of the National Academy of Sciences 117, no. 13 (March 16, 2020): 7004–10. http://dx.doi.org/10.1073/pnas.1921499117.
Анотація:
Protein mobility at solid–liquid interfaces can affect the performance of applications such as bioseparations and biosensors by facilitating reorganization of adsorbed protein, accelerating molecular recognition, and informing the fundamentals of adsorption. In the case of ion-exchange chromatographic beads with small, tortuous pores, where the existence of surface diffusion is often not recognized, slow mass transfer can result in lower resin capacity utilization. We demonstrate that accounting for and exploiting protein surface diffusion can alleviate the mass-transfer limitations on multiple significant length scales. Although the surface diffusivity has previously been shown to correlate with ionic strength (IS) and binding affinity, we show that the dependence is solely on the binding affinity, irrespective of pH, IS, and resin ligand density. Different surface diffusivities give rise to different protein distributions within the resin, as characterized using confocal microscopy and small-angle neutron scattering (length scales of micrometer and nanometer, respectively). The binding dependence of surface diffusion inspired a protein-loading approach in which the binding affinity, and hence the surface diffusivity, is modulated by varying IS. Such gradient loading increased the protein uptake efficiency by up to 43%, corroborating the importance of protein surface diffusion in protein transport in ion-exchange chromatography.
32
Sun, Gang, Alexander Hawken, and Peter Harrowell. "The displacement field associated with the freezing of a melt and its role in determining crystal growth kinetics." Proceedings of the National Academy of Sciences 117, no. 7 (February 3, 2020): 3421–26. http://dx.doi.org/10.1073/pnas.1915806117.
Анотація:
The atomic displacements associated with the freezing of metals and salts are calculated by treating crystal growth as an assignment problem through the use of an optimal transport algorithm. Converting these displacements into timescales based on the dynamics of the bulk liquid, we show that we can predict the activation energy for crystal growth rates, including activation energies significantly smaller than those for atomic diffusion in the liquid. The exception to this success, pure metals that freeze into face-centered cubic crystals with little to no activation energy, are discussed. The atomic displacements generated by the assignment algorithm allows us to quantify the key roles of crystal structure and liquid caging length in determining the temperature dependence of crystal growth kinetics.
33
Lacroix, Christian, Jaël Giguère, Simon-Mathieu Bergeron Hartman, Haïfa Ben Saad, Anthony Martin, Thomas Leduc, Maxime Gendron-Paul, et al. "Normal zone propagation in various REBCO tape architectures." Superconductor Science and Technology 35, no. 5 (March 30, 2022): 055009. http://dx.doi.org/10.1088/1361-6668/ac56ff.
Анотація:
Abstract The normal zone propagation velocity (NZPV) of three families of REBCO tape architectures designed for superconducting fault current limiters and to be used in high voltage direct current transmission systems has been measured experimentally in liquid nitrogen at atmospheric pressure. The measured NZPVs span more than three orders of magnitude depending on the tape architectures. Numerical simulations based on finite elements allow us to reproduce the experiments well. The dynamic current transfer length (CTL) extracted from the numerical simulations was found to be the dominating characteristic length determining the NZPV instead of the thermal diffusion length. We therefore propose a simple analytical model, whose key parameters are the dynamic CTL, the heat capacity and the resistive losses in the metallic layers, to calculate the NZPV.
34
Sepeai, Suhaila, Saleem Hussain Zaidi, M. Yusof Sulaiman, Kamaruzzaman Sopian, M. Adib Ibrahim, M. Khairunaz Mat Desa, and Mat Daud Norizam. "Detailed Analysis of Shallow and Heavily-Doped Emitters for Al-BSF Bifacial Solar Cells." Advanced Materials Research 896 (February 2014): 459–63. http://dx.doi.org/10.4028/www.scientific.net/amr.896.459.
Анотація:
A selective emitter structure is a promising approach to improve the cell efficiency of industrial type silicon solar cells by minimizing the losses at the front surface and in the emitter. Selective emitters can be produced by numerous processing sequences, resulting in different doping profiles. This paper focuses on the analysis of emitter formation for bifacial solar cell application. In this research, liquid phosphorus oxy-trichloride (POCl3) has been used as a diffusion source for emitter formation. The diffusion temperature was varied from 800 to 900 °C in order to determine an optimum diffusion profile. In this study, the mask-free diffusion process forms diffused emitter on both side of Si wafer. In order to determine the emitter characteristics, the sheet resistance of Si wafer after POCl3 diffusion process was measured using a four-point probe. Based on the sheet resistance value of ~47 ohm/sq, the emitter has been classified as heavily-doped emitter. The performance analysis using surface photovoltage (SPV) and spectral response presents a diffusion length of 2.19 μm. The POCl3-diffusion and screen printed Al-BSF led to bifacial solar cells with a front surface efficiency of 12.8 % and back surface efficiency of 5.08 %.
35
Rauber, Daniel, Andreas Hofmann, Frederik Philippi, Christopher W. M. Kay, Tatiana Zinkevich, Thomas Hanemann, and Rolf Hempelmann. "Structure-Property Relation of Trimethyl Ammonium Ionic Liquids for Battery Applications." Applied Sciences 11, no. 12 (June 19, 2021): 5679. http://dx.doi.org/10.3390/app11125679.
Анотація:
Ionic liquids are attractive and safe electrolytes for diverse electrochemical applications such as advanced rechargeable batteries with high energy densities. Their properties that are beneficial for energy storage and conversion include negligible vapor-pressure, intrinsic conductivity as well as high stability. To explore the suitability of a series of ionic liquids with small ammonium cations for potential battery applications, we investigated their thermal and transport properties. We studied the influence of the symmetrical imide-type anions bis(trifluoromethanesulfonyl)imide ([TFSI]−) and bis(fluorosulfonyl)imide ([FSI]−), side chain length and functionalization, as well as lithium salt content on the properties of the electrolytes. Many of the samples are liquid at ambient temperature, but their solidification temperatures show disparate behavior. The transport properties showed clear trends: the dynamics are accelerated for samples with the [FSI]− anion, shorter side chains, ether functionalization and lower amounts of lithium salts. Detailed insight was obtained from the diffusion coefficients of the different ions in the electrolytes, which revealed the formation of aggregates of lithium cations coordinated by anions. The ionic liquid electrolytes exhibit sufficient stability in NMC/Li half-cells at elevated temperatures with small current rates without the need of additional liquid electrolytes, although Li-plating was observed. Electrolytes containing [TFSI]− anions showed superior stability compared to those with [FSI]− anions in battery tests.
36
Lee, Antony, Karen Caicedo, Quentin Grésil, Pierre Bon, and Laurent Cognet. "Measure and Analysis of Carbon Nanotube Diffusion in 3D." ECS Meeting Abstracts MA2022-01, no. 9 (July 7, 2022): 716. http://dx.doi.org/10.1149/ma2022-019716mtgabs.
Анотація:
Measuring carbon nanotube diffusion is complex in 3D liquid environments. Single molecule fluorescence microscopy commonly provides nanotube trajectories in the 2D imaging plane with nanometer precisions but assessing the third dimension is more challenging task. To this aim, We will present two strategies based on point-spread function (PSF) engineering [1] or self-interfering PSF [2]. Because nanotubes are not spherical objects, 3D angular diffusion of the nanotubes shall also be considered. We will show that using a high-frame rate imaging (kHz) of nanotube movements, the autocorrelation time of nanotube fluorescence intensity can be computed in order to measure the rotational diffusion coefficient of the nanotubes. This further allows to estimate the length of the nanotubes either from the rotational diffusion coefficients alone, or by combining translational and rotational diffusion coefficients which has the advantage to avoid the requirement of knowing the solution viscosity or the SWCNT hydrodynamic diameter [3]. References [1] Gresil, Lee, et al. In preparation [2] Caceido, Lee, et al. In preparation [3] Lee & Cognet J. Appl. Phys. 128 (2020) 224301
37
Williams, H. A. R., and O. E. Jensen. "Surfactant Transport Over Airway Liquid Lining of Nonuniform Depth." Journal of Biomechanical Engineering 122, no. 2 (November 18, 1999): 159–65. http://dx.doi.org/10.1115/1.429637.
Анотація:
Numerous effects (e.g., airway wall buckling, gravity, airway curvature, capillary instabilities) give rise to nonuniformities in the depth of the liquid lining of peripheral lung airways. The effects of such thickness variations on the unsteady spreading of a surfactant monolayer along an airway are explored theoretically here. Flow-induced film deformations are shown to have only a modest influence on spreading rates, motivating the use of a simplified model in which the liquid-lining depth is prescribed and the monolayer concentration satisfies a spatially inhomogeneous nonlinear diffusion equation. Two generic situations are considered: spreading along a continuous annular liquid lining of nonuniform depth, and spreading along a rivulet that wets the airway wall with zero contact angle. In both cases, transverse averaging at large times yields a one-dimensional approximation of axial spreading that is valid for the majority of the monolayer. However, a localized monolayer remains persistently two dimensional in a region at its leading edge having axial length scales comparable to the length scale of transverse depth variation. It is also shown how the transverse spreading of a monolayer may be arrested as it approaches a static contact line at the edge of a rivulet. Implications for Surfactant Replacement Therapy are discussed. [S0148-0731(00)00202-8]
38
Kien, P. H., P. M. An, G. T. T. Trang, and P. K. Hung. "The structural transition under compression and correlation between structural and dynamical heterogeneity for liquid Al2O3." International Journal of Modern Physics B 33, no. 31 (December 20, 2019): 1950380. http://dx.doi.org/10.1142/s0217979219503806.
Анотація:
This study reported a simulation of structural transition and correlation between structural and dynamical heterogeneity (DH) for liquid Al2O3. Structural characteristics of liquid Al2O3 were clarified through the pair radial distribution functions, the distribution of [Formula: see text] and [Formula: see text] ([Formula: see text], 4, 5, 6; [Formula: see text], 2, 3) basic structural units, angle and bond length distribution and 3D visualization. Simulation results revealed that network structure of liquid Al2O3 is built mainly by AlO3, AlO4, AlO5 and AlO6 units that are linked to each other through common oxygen atoms. We found the existence of separate AlO4-, AlO5- and AlO6-phases where the mobility of atoms can be determined. The atoms in AlO4-phase are more mobile than the ones in AlO5- and AlO6-phases. The existence of separate phases is evidence of DH in liquid Al2O3. Moreover, the self-diffusion of Al and O atoms was also discussed via characteristics of separate AlO4-, AlO5- and AlO6-phases.
39
Wieczorek, L., T. Katzwinkel, M. Blüm, M. Löwer, and A. Röttger. "Supersolidus Liquid Phase Sintering and Heat Treatment on Atomic Diffusion Additive Manufacturing Produced Ledeburitic Cold Work Tool Steel*." HTM Journal of Heat Treatment and Materials 77, no. 4 (August 1, 2022): 269–83. http://dx.doi.org/10.1515/htm-2022-1019.
Анотація:
Abstract In this work, the possibility of manufacturing complex-shaped components from a carbon-martensitic hardenable cold-work steel (1.2379; X153CrMoV12; D2) is investigated. For this purpose, cube-shaped samples with an edge length of 10 mm were produced using the fused-filament fabrication process, which were post-compacted after solvent debinding by supersolidus liquid-phase sintering. Using the knowledge of liquid phase volume content as a function of temperature, supersolidus liquid phase sintering experiments were performed. The microstructure formation process was characterized by electron microscopy and X-ray diffraction. The microstructure and hardness of the processed samples were compared in the heat-treated condition with the properties of the same steel 1.2379 (X153CrMoV12; D2) in the as-cast, deformed and heat-treated condition. The results demonstrate effective post-densificationc close to theoretical density of cold-work tool steel samples fabricated by fused-filamet fabrication using supersolidus liquid-phase sintering at 1280 °C. The defect-free microstructure in the heat-treated state is characterized by a martensitic matrix and eutectic Cr-rich M7 C3 and small amounts of V-rich MC carbides. The hardness of the annealed Supersolidus liquid phase sintering samples are 681 ± 5 HV10, which is above the level of the reference material 1.2379 (629 ± 7 HV10) in the as-cast, formed and heat-treated condition.
40
Perakis, Fivos, Katrin Amann-Winkel, Felix Lehmkühler, Michael Sprung, Daniel Mariedahl, Jonas A. Sellberg, Harshad Pathak, et al. "Diffusive dynamics during the high-to-low density transition in amorphous ice." Proceedings of the National Academy of Sciences 114, no. 31 (June 26, 2017): 8193–98. http://dx.doi.org/10.1073/pnas.1705303114.
Анотація:
Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.
41
Gorodetsky, V. O., S. O. Semenikhin, N. I. Kotlyarevskaya, and M. M. Usmanov. "Improvement of the liquid-jet sulfitators construction to increase the efficiency of sulfitation treatment of sugar production liquids." New Technologies 17, no. 4 (November 12, 2021): 53–61. http://dx.doi.org/10.47370/2072-0920-2021-17-4-53-61.
Анотація:
The article discusses and analyzes the construction of liquid-jet sulfitators used in the beet sugar industry. The importance of sulfitation treatment in the sugar beet processing and raw cane sugar technology is noted and the main advantages of its use at various technological stages are given, namely, preparation of extractant used for diffusion sucrose extraction out of beet cossettes, thin juice processing, thick juice with B- and C-remelts processing, as well as raw cane sugar remelt processing. The advantages and disadvantages of liquid-jet sulfitators in comparison with other constructions are noted and criteria for their improvement are given. It has been noted that the created ejection, which sucks in the sulphitation gas into the contacting chamber, and the fact that the absorption of sulfur dioxide occurs on a larger surface than in other types of structures the main advantages of liquid-jet sulphitators. The main disadvantages are the short length of the contacting chamber, which is insufficient for ensuring complete absorption of sulfur dioxide, as well as instability of the generated ejection when the productivity changes. This determines the criteria given in the article for the improvement of liquid-jet sulfitators. The description of the developed construction of the sulphitator centrifugal-jet nozzle of sugar production liquids is given, which provides: the stability of the sulphitation gas supply in a wide range of plant productivity; stability of the hydroaerodynamic regime of the system «treated liquid – sulphitation gas» inside the sulphitator; sufficient contact time for complete dissolution in the treated liquid of the sulfur anhydride contained in the sulphitation gas. The advantages of the developed centrifugal-jet sulfitators in comparison with typical liquid-jet sulfitators are noted: ensuring the operation range of 50-120% of the nominal capacity (plant production capacity); significant reduction in the technical sulfur consumption for the sulphur anhydride production, which is used as a reagent for the sulfitation treatment of liquids in beet sugar processing; reduction of harmful emissions into the atmosphere due to 100 % sulfur anhydride dissolution in the treated liquid.
42
Wu, Rui, and Feng Chen. "Interplay between salt precipitation, corner liquid film flow, and gas–liquid displacement during evaporation in microfluidic pore networks." Journal of Applied Physics 133, no. 7 (February 21, 2023): 074701. http://dx.doi.org/10.1063/5.0135135.
Анотація:
Visualization experiments with microfluidic pore networks are performed in this work to disclose interplay between salt precipitation, the corner liquid film flow, and gas–liquid displacement during evaporation. Two forms of salt precipitation are revealed: aggregated polycrystalline structures and large bulk crystals. It is found that gas bubbles can be formed because of imbibition of liquid into aggregated polycrystalline structures. The length of a corner liquid film can affect the direction of growth of the aggregated polycrystalline structures connected to the corner liquid film. Discontinuous corner liquid films can be transformed to continuous ones when they are touched by growing aggregated polycrystalline structures. The “sleeping” aggregated polycrystalline structures at the open surface of a microfluidic pore network, i.e., efflorescence, can grow again if they are touched by growing aggregated polycrystalline structures inside the microfluidic pore network, i.e., subflorescence. Because of efflorescence, the evaporation rate from a microfluidic pore network can increase first and then decrease. Moreover, a theoretical model is developed for the coupled transport of vapor diffusion in the gas zone and liquid flow as well as transport of dissolved salt in the corner liquid films in a capillary tube of square cross section so as to disclose the key parameters controlling the transport processes.
43
Yamamoto, Takao. "Relationship between Rate-Limiting Process and Scaling Law in Gel Growth Induced by Liquid-Liquid Contact." Gels 9, no. 5 (April 24, 2023): 359. http://dx.doi.org/10.3390/gels9050359.
Анотація:
Gelation through the liquid-liquid contact between a polymer solution and a gelator solution has been attempted with various combinations of gelator and polymer solutions. In many combinations, the gel growth dynamics is expressed as X∼t, where X is the gel thickness and t is the elapsed time, and the scaling law holds for the relationship between X and t. In the blood plasma gelation, however, the crossover of the growth behavior from X∼t in the early stage to X∼t in the late stage was observed. It was found that the crossover behavior is caused by a change in the rate-limiting process of growth from the free-energy-limited process to the diffusion-limited process. How, then, would the crossover phenomenon be described in terms of the scaling law? We found that the scaling law does not hold in the early stage owing to the characteristic length attributable to the free energy difference between the sol-gel phases, but it does in the late stage. We also discussed the analysis method for the crossover in terms of the scaling law.
44
Corcione, Massimo, Antonio Natale, Alessandro Quintino, and Vincenzo Andrea Spena. "Buoyancy-Driven Convection from a Vertical Heated Plate Suspended Inside a Nanofluid-Filled Cooled Enclosure." Journal of Nanofluids 9, no. 1 (March 1, 2020): 56–65. http://dx.doi.org/10.1166/jon.2020.1729.
Анотація:
Buoyancy-driven convection from a heated vertical plate suspended inside a nanofluid-filled square enclosure cooled at the walls, is studied numerically using a two-phase model based on the double-diffusive approach. The study is conducted under the assumption that the Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum and energy for the nanofluid, and continuity for the nanoparticles, is solved by a computational code which incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity and the coefficient of thermophoretic diffusion, all based on a high number of literature experimental data. The SIMPLE-C algorithm is used to handle the pressure-velocity coupling. Numerical simulations are executed using alumina-water nanofluids for different values of the diameter and the average volume fraction of the suspended nanoparticles, the plate length and position, the cavity width, the average temperature of the nanofluid, and the temperature difference imposed between the plate and the boundary walls of the enclosure. It is found that the impact of the nanoparticle dispersion into the base liquid increases remarkably with increasing the average temperature, whereas, by contrast, the other controlling parameters have just moderate effects. Moreover, when the top and bottom walls of the enclosure are cooled, keeping the sidewalls adiabatic, a periodic flow is detected, whose main features will be discussed.
45
Ren, Wang, Ying Zhang, and Min Jiao Li. "Electrodeposition of Cobalt Nanoparticles from Mixture of 1-Butyl-3-Methylimidazolium Chloride Ionic Liquid and Urea." Applied Mechanics and Materials 117-119 (October 2011): 773–76. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.773.
Анотація:
The electrodeposition of cobalt nanoparticles from mixture of 1-butyl-3- methylimidazolium chloride (BMIC) ionic liquid and urea was investigated. The results from the cyclic voltammetry (CV) show that the reduction of Co(II) to cobalt is an irreversible process and controlled by the diffusion of Co(II) on Pt working electrode. The cobalt nanoparticles prepared by direct current (DC) electrodeposition method at 70 °C were characterized by scanning electron microscope (SEM). Test results indicate that the Co nanoparticles are grain-like arrays and link together because of their magnetic property. The average length of these particles is about 100 nm.
46
Kousar, Ayesha, Ishan Pande, Emilia Peltola, and Tomi Laurila. "(Digital Presentation) Effect of the Length of Carbon Nanofibers on Selective Dopamine Sensing." ECS Meeting Abstracts MA2022-01, no. 50 (July 7, 2022): 2119. http://dx.doi.org/10.1149/ma2022-01502119mtgabs.
Анотація:
The engineering of carbon nanofibers (CNFs) has recently received extensive attention in the field of biosensors due to their high surface area, rich nanoscale geometries, ability to selectively detect the analyte of interest (e.g., dopamine) in the presence of interfering molecules that exist in biological environment and inherent resistance to biofouling1 - 3. CNFs with the individual fiber length/size adjusted to the diffusion layer thickness can confine the analyte molecules within the nanostructures and result in the formation of a thin liquid layer, increasing their sensitivity 4. This points towards the potential of altering the aspect ratios and growth densities of CNFs to tune their biosensing properties. Thus, here we aim to evaluate the effect of the length, distribution, and microstructure of fibers on their electrochemistry and how this affects the sensitivity and selectivity for dopamine (DA) detection. Herein, CNFs of varying lengths have been grown on a silicon substrate using the thin layers of Ni and Cr as catalysts. Samples with different length and distribution of CNFs have been synthesized by controlling the duration of the growth phase. The length and the detailed structure of the CNFs have been investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The lengths of CNFs were found to be in the range of 900 nm-1µM, 500-600 nM, 200-300 nM, and <150 nM for 30 mins, 10 mins, 5 mins and 1 min growth times, respectively. Cyclic voltammetry measurements showed that the double-layer capacitance (Cdl) and oxidation current (Ipa) of dopamine increase continuously with the increase in the length of fibers indicating the increase in the surface area (Figure 1A). DA reaction kinetics tend to be reversible for the longest fibers and becomes slightly more sluggish with the decrease in the fiber length. However, it should be noted that carbon nanofiber length (hundreds of nM to 1µm) may match the diffusion layer thickness at certain scan rates, causing the thin liquid layer electrochemical behavior to contribute to the total kinetics. This implies that the variations in the peak separation (ΔEp) can be due to the combined changes in reaction kinetics and geometry. CNFs grown for 30 mins, 10 mins, 5 mins, and 1 min exhibited log Ipa vs v slope of 0.72, 0.63, 0.62 and 0.51, indicating that contribution of adsorption/thin layer formation is coming into effect with the increase in fiber length (Table 1). Washout experiments will be performed to distinguish further between thin layer and adsorption behavior affecting the electrochemistry of DA. It appears that DA reaction kinetics is fully under semi-infinite linear diffusion-control only at 1 min grown CNFs due to the relatively smooth surface of the electrode material. The selectivity of dopamine in the presence of physiological concentrations of ascorbic acid (AA) and uric acid (UA) greatly improves with the increase in the length of the fibers (Figure 1B). Electrodes with 1 min grown CNFs possessing metal particles and exhibiting little CNF growth did not show selectivity towards DA. Interestingly, with the increase in the growth time and consequently the length of the fiber, well-defined oxidation peaks of AA and DA and UA are observed. Moreover, the position of the oxidation potential appears to be affected both by the fiber length and presence/absence of other molecules, and often in the opposite directions (Table 1, Figure 1). The results discussed above point towards the significance of matching the CNF length with the scan rate used for in vivo detection of DA for optimized sensitivity and selectivity. References 1 S. Sainio, T. Palomäki, N. Tujunen, V. Protopopova, J. Koehne, K. Kordas, J. Koskinen, M. Meyyappan and T. Laurila, Mol. Neurobiol., 2015, 52, 859–866. 2 S. Sainio, E. Leppänen, E. Mynttinen, T. Palomäki, N. Wester, J. Etula, N. Isoaho, E. Peltola, J. Koehne, M. Meyyappan and others, Mol. Neurobiol., 2020, 57, 179–190. 3 A. Kousar, E. Peltola and T. Laurila, ACS omega, 2021, 6, 26391–26403. 4 Q. Cao, Z. Shao, D. K. Hensley, N. V Lavrik and B. J. Venton, Langmuir, 2021, 37, 2667–2676. Figure 1
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Sun, Qi, Zhicheng Xu, Qingtao Gong, Wangjing Ma, Zhiqiang Jin, Lei Zhang, and Lu Zhang. "The Study of Interfacial Adsorption Behavior for Hydroxyl-Substituted Alkylbenzene Sulfonates by Interfacial Tension Relaxation Method." Molecules 28, no. 11 (May 24, 2023): 4318. http://dx.doi.org/10.3390/molecules28114318.
Анотація:
In order to explore the interface adsorption mechanism of hydroxyl-substituted alkylbenzene sulfonates, the interfacial tension relaxation method was used to investigate the dilational rheology properties of sodium 2-hydroxy-3-octyl-5-octylbenzene sulfonate (C8C8OHphSO3Na) and sodium 2-hydroxy-3-octyl-5-decylbenzene sulfonate (C8C10OHphSO3Na) at the gas–liquid interface and oil–water interface. The effect of the length of the hydroxyl para-alkyl chain on the interfacial behavior of the surfactant molecules was investigated, and the main controlling factors of the interfacial film properties under different conditions were obtained. The experimental results show that for the gas–liquid interface, the long-chain alkyl groups adjacent to the hydroxyl group in the hydroxyl-substituted alkylbenzene sulfonate molecules tend to extend along the interface, showing strong intermolecular interaction, which is the main reason why the dilational viscoelasticity of the surface film is higher than that of ordinary alkylbenzene sulfonates. The length of the para-alkyl chain has little effect on the viscoelastic modulus. With the increase in surfactant concentration, the adjacent alkyl chain also began to extend into the air, and the factors controlling the properties of the interfacial film changed from interfacial rearrangement to diffusion exchange. For the oil–water interface, the presence of oil molecules will hinder the interface tiling of the hydroxyl-protic alkyl, and the dilational viscoelasticity of C8C8 and C8C10 will be greatly reduced relative to the surface. The main factor controlling the properties of the interfacial film is the diffusion exchange of surfactant molecules between the bulk phase and the interface from the beginning.
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Yelisieiev, Volodymyr, Vasyl Lutsenko, Tetiana Ruzova, Bahram Haddadi, and Michael Harasek. "Stefan flow-inclusive mass transfer in a narrow cylindrical channel with a two-layer medium." IOP Conference Series: Earth and Environmental Science 1348, no. 1 (May 1, 2024): 012051. http://dx.doi.org/10.1088/1755-1315/1348/1/012051.
Анотація:
Abstract The exploration and extraction of oil, coal, and gas reserves are closely tied to mass transfer phenomena within porous and fractured rock formations. Frequently, these processes involve the adsorption or desorption, dissolution, or evaporation of certain components on the surface of the pore channels. In these cases, Stefan hydrodynamic flows arise, and although they may be individually small, they can have a noticeable impact on mass transfer and flow structure considering particular length of the channel. The authors explore the issue of inert component diffusion from the surface of a capillary into a suspension flow. The analysis involves a two-layer flow, including a central two-phase (liquid and particles) component and a near-wall flow of the fluid carrier. A certain component from the channel’s surface permeates deep into the flow without interacting with the solid phase. In this research the authors solve a diffusion problem with boundary conditions that consider the presence of Stefan hydrodynamic flows. The calculations reveal that, depending on the magnitude of the Stefan flows and the length of the affected area, the porosity, and consequently, the viscosity of the two-phase flow zone can undergo significant variations.
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SHEN, M. Y., M. ODA, T. GOTO, and T. YAO. "DYNAMICAL PROCESS OF PHOTOIONIZATION IN SEMICONDUCTOR NANOCRYSTALS." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3574–78. http://dx.doi.org/10.1142/s0217979201008184.
Анотація:
When quantum dots (QDs) or nanocrystals (NCs) are photoionized, great changes of electric fields exerted on QDs occur, then photodarkening, photobrightening, and persistent hole burning effects may be macroscopically observed in QD system, and luminescence spectral diffusion and on/off behavior may be microscopically observed in a single QD. The dynamics of the emitted carrier from the QD by photoionization governs the properties of these phenomena. The photoionization process has been directly found in CdTe nanocrystals embedded in TOPO by measuring the temperature dependence of their photocurrent and photoluminescence. The phase transition of the matrix TOPO from amorphous solid to liquid makes the diffusion length of the emitted carriers outside the nanocrystals increase abruptly, resulting in a steep rise in both the photocurrent and the photoluminescence. Photoionization of a QD is fundamentally important to its optical properties
50
Hosangadi, Ashvin, and Vineet Ahuja. "Numerical Study of Cavitation in Cryogenic Fluids." Journal of Fluids Engineering 127, no. 2 (March 1, 2005): 267–81. http://dx.doi.org/10.1115/1.1883238.
Анотація:
Numerical simulations of cavitation in liquid nitrogen and liquid hydrogen are presented; they represent a broader class of problems where the fluid is operating close to its critical temperature and thermal effects of cavitation are important. A compressible, multiphase formulation that accounts for the energy balance and variable thermodynamic properties of the fluid is described. Fundamental changes in the physical characteristics of the cavity when thermal effects become significant are identified; the cavity becomes more porous, the interface less distinct, and it shows increased spreading while getting shorter in length. The heat transfer model postulated in variants of the B-factor theory, where viscous thermal diffusion at the vapor-liquid interface governs the vaporization, is shown to be a poor approximation for cryogenic fluids. In contrast the results presented here indicate that the cavity is sustained by mass directly convecting into it and vaporization occurring as the liquid crosses the cavity interface. Parametric studies for flow over a hydrofoil are presented and compared with experimental data of Hord (1973, “Cavitation in Liquid Cryogens II—Hydrofoil,” NASA CR-2156); free-stream velocity is shown to be an independent parameter that affects the level of thermal depression.