Liquid Migration Research Articles

Understanding Ag liquid migration in SiC through ex-situ and in-situ Ag-Pd/SiC interaction studies

The effective containment of fission products (FPs) within tri-structural isotropic (TRISO) fuel particles is crucial for the safety and efficiency of High Temperature Gas-cooled Reactors (HTGRs). Combining multi-scale (µm to nm) and multi-dimensional (2D and 3D) analysis, this study focuses on the migration mechanisms of silver (Ag), for which the Ag-110 m FP isotope is radiotoxic, facilitated by reactions with palladium (Pd) alloys and the silicon carbide (SiC) layer at elevated temperatures (1300–1500 °C). Three primary pathways for Ag migration are identified: (1) diffusion in solid palladium silicide to form (Pd,Ag)2Si, (2) infiltration through cracks and pores in the carbon phase, and (3) liquid phase migration along SiC grain boundaries. Especially at temperatures above the melting point of Pd2Si (1404 °C), a ‘dissolution-recrystallisation’ mechanism is proposed of the Ag-Pd-Si liquid phase migrating along SiC grain boundaries. The study employs state-of-the-art in-situ heating transmission electron microscopy (TEM) techniques to directly observe the dynamic migration processes of Pd silicide within SiC, providing unprecedented insights into the liquid behaviour in TRISO fuel. These findings highlight the significant role of liquid phases in determining the transport of FPs through the TRISO-SiC which is vital for developing strategies that enhance the safety and efficacy of HTGRs.

Thermal performance of energy piles in unsaturated soils: Experiment, simulation, and case study

The operation of energy piles in unsaturated soils involves coupled heat and moisture transfer, demanding further detailed investigation. In this paper, laboratory tests were conducted to validate a numerical model that incorporated vapor and liquid migration, convection, and latent heat transfer in unsaturated soils. Moreover, this model captured the dynamic variation in characteristic parameters of unsaturated soils. Building upon this observation, this study delved into the thermal performance of the energy pile under ten-year cooling and heating cycles, specifically focusing on the temperature, heat exchange rate, volumetric water content, and thermal conductivity. It is demonstrated that the imbalanced cooling and heating load adversely affects the long-term operation. In particular, the cooling power experiences a reduction of 15.1% after ten years of operation. The results indicate that higher soil temperatures positively impact the heat exchange rate in heating mode, while rainfall facilitates heat transfer in both seasons. Furthermore, a case study of an energy pile system was carried out, encompassing load calculation, pile group simulation, economic analysis, and design optimization. A comprehensive evaluation of the technical and economic feasibility demonstrates that the system exhibits excellent performance, particularly when the ratio of cooling and heating loads ranges from 1.1 to 1.3.

Co-hydrothermal carbonization of waste biomass and phosphate rock: promoted carbon sequestration and enhanced phosphorus bioavailability

Co-hydrothermal carbonization (co-HTC) of phosphorus rock (PR) and corn straw (CS) was investigated to prepare hydrochar-based materials as soil conditioners, focusing on the morphological transformation and solid–liquid migration of carbon and phosphorus. Various analytical methods, including elemental analysis, chemical quantification, FT-IR, XRD, 3D-EEM, TG, and XANES, were used to understand the synergistic interactions of PR and CS during co-HTC and determine the properties of the resultant products. The results indicated the acidic solution and humic acid-like substances produced by HTC of CS reduced the crystallinity of the PR and served as the activating agent for PR, allowing the PR to be easily dissolved and reconstituted, producing calcium carbonate and apatite-like materials, and the formation of C–O–PO3, C–PO3, C=O, and O=C–O chemical bonds. At 220 °C, adding 5% PR significantly promoted a 10.3% rise in the yield of CS hydrochar, a 4.3% rise in carbon recovery of CS, and a 4.8% rise in carbon sequestration potential of CS. The formation of Ca–P was notably promoted and the content of AP in co-HTC hydrochar was up to 89.9%, with 39% Hydro-P and 33% CaHPO4. In the case of artificial humic acid (HAa), its content was also remarkably increased by 5.9% in the hydrochar by co-HTC. In addition, the hydrochar produced by co-HTC of CS and PR was composed of carbon with an increased aromatic degree, rich organic matter, and biologically effective mineral nutrient elements and exhibited high stability. The present study provided a promising approach for value-added utilization of waste biomass and low-grade PR towards soil application.Graphical

New insights into the parameterization of the dry surface layer and its hydrogeochemical mechanism: An experimental study

Knowledge of the parameterization of the dry surface layer (DSL) is essential for evaluating near-surface water flow and water balance in arid and semi-arid areas. Existing studies have parameterized DSL thickness and vapor flow as functions of the soil moisture content (SMC) in the surface layer to predict soil evaporation. However, hydrochemical processes related to DSL development have been ignored, including changes in hydrochemistry, the underlying hydrochemical mechanism, and the role of dissolved substances in the DSL development. Herein, we performed a series of soil evaporation experiments for 260 days and explored the factors influencing DSL development (e.g., soil texture, atmospheric temperature, SMC, solutes). Evaporation experiments were performed using silty loess, sandy loess, and fine sand with a 60-cm water table. Results showed that the cumulative evaporation of silty loess, sandy loess, and fine sand over the experimental period were 1,391.52, 460.10, and 185.53 mm, respectively, which determined by the maximum height of liquid flow continuity. The content of total dissolved solids (TDS) and major ions at the surface soil were significantly higher than the values at deep depths of 5‒55 cm, which largely depend on evaporative water loss. Evolutionary trends of chemical facies in sand media along the liquid water migration were from HCO3-Ca type to SO4·Cl-Na type. This was attributed to mineral dissolution at a depth of 5–55 cm and their transport with liquid water, resulting in the precipitation of salt crystals at the surface soil. Furthermore, a consolidated DSL with a thickness of 3.0–3.5 cm in the sandy loess and a loose DSL with a thickness of 1.5–2.0 cm in fine sand were observed at the end of the experiments. The accumulation of solutes at the surface leads to a reduction in effective porosity and the aggregation of soil particles during continuous drying, which facilitates the consolidation of DSL in sandy loess. This overestimated the DSL thickness, resulting in a difference between the experimental and predicted evaporation rates by Fick's law. Overall, these results highlight the limitations of considering DSL thickness as a function of SMC only, providing new insights into hydrochemical processes and dissolved solutes involving DSL parameterization during continuous soil drying.

Linking formulation feedstock to printability by robocasting: A case study of eco-friendly alumina pastes

Robocasting stands as a pertinent additive manufacturing technique for producing intricate ceramic parts. Amidst stricter environmental regulations, the adoption of natural additives becomes imperative. This study investigates the influence of plant-based additives on the rheology and printability of eco-friendly pastes.Various 50 vol%-alumina pastes were formulated using natural binders, plasticizers and dispersants (e.g., lignosulfonate, polysaccharides, glycerol) and then assessed through oscillation and flow rheological analyses. Paste viscosity and rigidity often deviated from printability maps reported in the literature, showing the complexity of defining universal printability criteria. A comprehensive investigation was conducted on the water retention capabilities of additives, liquid phase migration and paste drying kinetics.This paper highlights the critical importance of constraining liquid phase migration within eco-friendly ceramic pastes and the crucial role of polymer chain reorientation under shear. Consequently, this research lays diversifying formulations, offering sustainable solutions for industrial ceramic applications.

Analisis of Liquid Migration as a Manifestation of Migration-based Lifestyle in the Third Millennium Using a Qualitative Approach

Analisis of Liquid Migration as a Manifestation of Migration-based Lifestyle in the Third Millennium Using a Qualitative Approach

The impact of intersecting crises on recent intra‐EU mobilities: The case of Spaniards in the UK and Germany

AbstractThis article contributes to two interconnected fields of study: recent literature on intra‐EU migration, specifically South–North flows; and scholarship into the impact of intersecting crises on (im)mobilities. Interest in intra‐EU mobilities has increased with the expansion of the EU and especially since the 2008 Great Recession, with a focus mostly on young people and East–West flows. However, based on a mixed‐methods research approach, this article looks at the recent migration of individuals and families from Spain to the UK and Germany, two of the main destinations in Europe. It explores the impacts on (im)mobility strategies of three intersecting “crises”: starting with emigration since 2008, including the erosion of EU mobile citizens' rights culminating in “Brexit,” and ending with the effects of COVID‐19. Our analysis situates these migrant experiences in the interplay between core‐periphery theories and the concept of liquid migration, highlighting how crises accentuate vulnerabilities but can also generate opportunities.

Isothermal experiments on eutectic and oxidation reactions of Cr-coated Zr alloy cladding in steam at 1350 ℃: Behavior, mechanism and kinetics

The isothermal steam oxidation experiments of Cr-coated Zr alloy cladding at 1350 ℃ were conducted, and the influence of Cr-Zr eutectic reaction on the oxidation behavior was investigated. The oxidation duration, ranging from 50 s to 3600 s, covers the cases from the initial formation of eutectic liquid to the complete oxidation of the cladding. The microstructures of the coating and the substrate were characterized. The eutectic-oxidation degradation mechanism of the coating is summarized. The migration of the eutectic liquid and the evolution of Cr-rich phases in the post-oxidation eutectic structure are studied and discussed, confirming the process of ZrCr2 reacting with α-Zr(O) to form Zr3Cr3O. The degraded Cr coating and the Cr retained in ZrO2 during the migration of the eutectic liquid can hardly affect the oxidation of cladding substrate. However, the Cr-rich phases, which eventually aggregated in the radial center of the cladding, can reduce the oxidation rate.

Application of template method in fabricating ordered gas diffusion layer of PEMFC

ABSTRACT As a core component of proton exchange membrane fuel cell (PEMFC), gas diffusion layer (GDL) takes an important role in the migration of gas, liquid, heat, and electrons. Optimizing GDL microstructure is crucial to improve the gas-liquid flowing behavior and enhance PEMFC performance. Therefore, an ordered GDL is designed by coupling the template method and stacking multiple fiber layers method to provide the large holes for water elimination and the small pores for gas delivery. The ordered GDL possesses excellent mass transfer capacity, which can improve the PEMFC performance compared with commercial GDL under high relative humidity (RH). At RH 100% and 70°C, the PEMFC with ordered GDL achieves the maximum peak power density of 0.92 W cm−2, which realizes an increment of 10.8% compared with commercial GDL. However, with a decrease in RH, the ohmic loss gradually occupies the primary contribution to the performance compared with the mass transfer capacity, resulting in a downward trend of the performance of PEMFC with ordered GDL. This work provides a simple and efficient strategy to design the ordered pore structure of GDL, and the outcomes have the potential of being implemented in the future PEMFC vehicles.

Effects of sintering temperature on the microstructure evolution and mechanical properties of TiB2-20 wt% CoNi cermets

Microstructure evolution and mechanical properties of TiB2-CoNi cermets at different sintering temperatures were investigated. A small amount of liquid phase appeared between 1362 ºC and 1398 ºC. Solid phase sintering mainly occurred below this temperature range, while liquid phase sintering mainly occurred above this temperature range. At around 1460 ºC, dissolution and re-precipitation occurred around TiB2 particles due to liquid phase migration. Only TiB2 and CoNi phases were detected on XRD patterns at different sintering temperatures. As the sintering temperature increased, the relative density, fracture toughness, transverse fracture strength, and hardness of cermets increased, while their porosity decreased. The main influencing factors on the properties of cermets sintered at 1460 ºC and above were the interface bonding strength and the grain size, while the porosity was the main influencing factor for cermets sintered below 1460 ºC.

Simulation of phase change during the freezing of unsaturated porous media by using a coupled lattice Boltzmann model

PurposeThe purpose of this paper is to develop a coupled lattice Boltzmann model for the simulation of the freezing process in unsaturated porous media.Design/methodology/approachIn the developed model, the porous structure with complexity and disorder was generated by using a stochastic growth method, and then the Shan-Chen multiphase model and enthalpy-based phase change model were coupled by introducing a freezing interface force to describe the variation of phase interface. The pore size of porous media in freezing process was considered as an influential factor to phase transition temperature, and the variation of the interfacial force formed with phase change on the interface was described.FindingsThe larger porosity (0.2 and 0.8) will enlarge the unfrozen area from 42 mm to 70 mm, and the rest space of porous medium was occupied by the solid particles. The larger specific surface area (0.168 and 0.315) has a more fluctuated volume fraction distribution.Originality/valueThe concept of interfacial force was first introduced in the solid–liquid phase transition to describe the freezing process of frozen soil, enabling the formulation of a distribution equation based on enthalpy to depict the changes in the water film. The increased interfacial force serves to diminish ice formation and effectively absorb air during the freezing process. A greater surface area enhances the ability to counteract liquid migration.

Influence of the electrolyte concentration and amount on the performance of textile electrodes in electrostimulation: A systematic study

BackgroundTextile-based stimulation electrodes are a fast-growing research area. With their advantages including flexibility, reusability and the possibility for integration into garments, textile electrodes open up new possibilities that are not yet feasible today, e.g. various self-administrated treatments and rehabilitation based on neuromuscular electrical stimulation (NMES) or transcutaneous electrical nerve stimulation (TENS). So far, most research has shown that textile-based stimulation electrodes perform more reliable when wetted with an electrolyte. However, there is no systematic investigation about which type and amount of electrolyte to use. MethodsIn this study, double-layered textile electrodes have been produced by machine knitting with a size of 3 × 3 cm2. The electrodes were wetted stepwise with a liquid amount from 5 µL up to 320 µL; four levels of sodium chloride (NaCl) concentrations, i.e. 0.9%, 1.5%, 5% and 35%, plus pure deionized water as a reference liquid were chosen. The study analyzed the behavior of the skin-electrode impedance when changing the moisture content and NaCl concentration. In addition, equivalent circuits were modelled for deeper insights into the mechanisms causing an impedance change. ResultsResults showed that the impedance was greatly influenced by the liquid amount with amounts of 5 µL already significantly reducing the impedance compared to dry electrodes, caused by a substantial reduction in resistance. The reactance, on the other hand, was only partly influenced by the liquid amount showing a reduction upon higher liquid amounts only within a range of 5 – 40 µL. Further, a significant influence on the impedance by the presence of ions was found where the skin-electrode systems wetted with NaCl solution were showing generally lower impedances than systems wetted with deionized water. However, within this, no remarkable influence of the NaCl concentration could be observed. As the impedance was found to be very sensitive to the moisture content in the system, it is recommended to introduce standardizations for impedance testing of wet textile electrodes with precisely controlled electrolyte volumes and liquid migration properties to make independent studies of textile electrodes more comparable.

Reimagining “Integration” in the Light of the New Forms of Mobility

There is a growing awareness in migration research that traditional interpretations and approaches to measuring and evaluating integration do not adequately fit the increasingly fluid and unpredictable patterns of migration observed today. Focusing on the transnational and liquid migration characteristic of Eastern European migrants, we propose a new conceptual framework that explains contemporary processes of migrant incorporation from the perspective of migrants themselves. Our model accounts for the “breadth and depth” of integration and contrasts deep integration and assimilation with functional adaptation, and integration into a certain group or network with integration into society as a whole. The analysis is based on comprehensive mixed-design research of Latvian migrants which includes a survey of 6,242 Latvian emigrants, as well as 15 in-depth interviews with internationally-mobile global talents. The bottom-up perspective that we employ sheds new light on how migrants themselves think about, and experience integration in their everyday lives.

Metallurgical interactions in solid/liquid diffusion couples of AA4343/AA3xxx/AA4343 layered aluminum sheet

The effect of pre-stretching on solid-liquid interaction, microstructure and brazing performance of AA4343/AA3xxx/AA4343 layered aluminum sheet during brazing at the atomic level (solid solution), nanoscale (dislocation) and micron level (grain boundary) are studied by glow discharge optical emission spectrometry (GDOES), scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The microstructure after brazing largely depends on the forming condition. The driving force of liquid film migration (LFM) is the reduction of stored deformation energy. The interaction between the liquid clad and solid core layers changes the elemental distribution and microstructure, which in turn affects the brazing performance of the sheet. The results reveal the mechanism of solid-liquid interaction of layered aluminum sheet during brazing and clarify the driving force of LFM of layered aluminum sheet during brazing. Consequently, these results provide important insights for the design and theoretical research of functional layered aluminum sheet.

Liquid migration revisited: Reflections on Brazilian mobilities to Australia

AbstractThis paper discusses whether liquid migration, a framework developed to theorise recent patterns of intra‐European migration, is a suitable lens to analyse contemporary migration in other regions of the Western world. It does so by drawing on findings from ethnographic research conducted on the Brazilian migration to Australia, a recent migration wave whose patterns are embedded in a transformed migration context and paradigm. The reflections suggest that, notwithstanding a few differences and nuances inherent to the migration regime in question, the original framing of liquid migration is helpful to analyse and understand contemporary patterns of Brazilian migration to Australia. The contributions of this paper include a reframing of the original dimensions of liquid migration based on contemporary migration patterns to Australia. Based on the Australian case, this paper proposes a new dimension of liquid migration—namely, fluid visa journeys—which addresses some of the critiques of the original formulation of the concept. Finally, this paper argues that the fluidity of contemporary migration patterns to Australia is not a condition migrants pursue willingly, but rather one they are ‘trapped into’.

A comparative study of DNAPL migration and transformation in confined and unconfined groundwater systems

To explore the migration and transformation process of dense non-aqueous liquid (DNAPL) pollutants’ multiphase flow, specifically nitrobenzene (NB), in confined groundwater (CG) versus unconfined groundwater (UG), a two-dimensional sandbox experimental device was designed and constructed. This involved constructing a vadose zone-UG- aquitard-CG structure, which was then subjected to different scenarios. Real-time analysis and numerical simulation methods were established and employed, with a particular focus on the detailed investigation results of actual contaminated site. The study found that when the same amount of NB was injected, the special structure of the CG layer resulted in a more pronounced reverse diffusion of NB in both the dissolved and NAPL phases. This was especially true for the dissolved phase, which was more likely to diffuse reversely. Meanwhile, CG did not directly interact with the vadose zone, and there was no loss of gas phase NB after the leakage in CG. As a result, higher concentrations of dissolved phase NB were generated, leading to the emergence of a larger area of NB contaminant plumes with CG flow. Importantly, the simulation study of the actual site and the laboratory experimental results were found to be validated, further validating the conclusion that direct leakage of NB into CG results in a higher concentration and larger area of dissolved phase contaminant plume, causing more serious pollution to the groundwater environment.

The inhibit behavior of fluids migration on gas hydrate re-formation in depressurized-decomposed-reservoir

Hydrate re-formation can lead to the blockage of gas recovery during natural gas hydrates production process. However, the hydrate re-formation induced by fluid migration is ignored. In this work, hydrate re-formation behaviors in porous media were investigated via two types of the fluid migration: gas migration and liquid migration. The gas migration was conducted by the following two ways: migration from top to bottom, and migration from bottom to top. The marine soil from South China sea was utilized to reconstruct hydrate samples. The results indicated that the average temperature rise with liquid migration is twice as large as that of the gas migration. What's more, the maximum temperature increment of decomposed-reservoir reaches 9 K. In addition, it was found that there was a duration of 60 min until hydrate re-formation at the end of the liquid migration process. Surprisingly, the fluid migration had a positive influence on inhibiting hydrate re-formation. The findings of this study suggest that the fluid migration could inhibit the hydrate re-formation in depressurized-decomposed-reservoir.

Variation and prediction of unfrozen water content in different soils at extremely low temperature conditions

The unfrozen water content in frozen soil is the critical factor for liquid water migration, frost heaving and thawing settlement during freeze–thaw process, and its content largely depends on soil texture and temperature. Herein, the unfrozen water content in different soils was measured by low-field nuclear magnetic resonance (NMR) at extremely low temperature ranging from −80 to 0 °C. The effect of soil properties on the variation of pore water in soil during freezing is analysed by combining T2 relaxation curve and freezing characteristic curve. The results indicate that soil properties affect the phase transition process between liquid water and solid ice in frozen soil, and the pore size distribution plays a leading role in capillary water freezing in the severe phase transformation zone. When unfrozen water develops from the transitional phase transformation zone to the frozen stability zone, the freezing of adsorbed water in soil is affected by clay content. In addition, by analogy with the soil freezing characteristic curve, a prediction model of unfrozen water content of soil is established in accordance with the phase transition process of liquid water, and the accuracy of the model is further confirmed by comparing the test results. Sensitivity analysis of the proposed model parameters revealed that the parameters are closely related to the pore size distribution and the clay content. The proposed model expands the response range between the variation of unfrozen water and temperature by experimental means, and realizes the prediction of unfrozen water content in different types of soil at extremely low temperature. This study would provide significant reference for exploring the heat-moisture migration and mechanical strength in frozen soil.

Effect of cerium on the primary carbides and inclusions in electroslag remelted M35 high speed steel

To restrain the formation of primary carbides in M35 high speed steel, the present work investigated the effect of cerium on the microstructure, primary carbides and inclusions in electroslag remelted M35 high speed steel based on experimental characterizations and thermodynamic calculations. The primary carbides in M35 high speed steel are M2C-type carbides with orthorhombic crystal structure and MC-type carbides with FCC crystal structure. M2C-type carbides are the dominant carbides, whose precipitation is prior to the MC-type carbides. With adding cerium content to 0.0230wt%, the evolutionary process of inclusions is: MgO∙Al2O3→Ce2O3, CeAlO3 and Ce2O2S→Ce2O3, Ce2O2S and Ce2O3 core surrounded by Ce–As–P layer. Adding cerium content from 0 to 0.0230wt% causes the secondary dendrite arm spacing to decrease from 36.8 μm to 29.4 μm, as the heterogeneous nucleation of Ce2O3, Ce2O2S and CeAlO3 inclusions, as well as the effect of dissolved cerium including the increase in the constitutional undercooling and the drag on the migration of liquid–solid interface. Ce2O3, Ce2O2S and CeAlO3 are the less effective heterogeneous nucleation cores for M2C-type and MC-type primary carbides precipitation than MgO∙Al2O3 inclusions, which is conducive to the decrease in the area fraction of primary carbides with adding 0.0067wt% cerium. Further increasing cerium content to 0.0230wt%, the formation of Ce–As–P inclusions surrounding Ce2O3 promotes the precipitation of M2C-type primary carbides, causing the increase in the area fraction of primary carbides.

Migration of DNAPL in Saturated Porous Media: Validation of High-Resolution Shock-Capturing Numerical Simulations through a Sandbox Experiment

This paper shows a comparison between experiments carried out in a laboratory-scale sandbox where the migration of a dense nonaqueous phase liquid (DNAPL), hydrofluoroether (HFE-7100), in a saturated porous medium was investigated, and validation was performed using high-resolution shock-capturing numerical simulations to resolve the nonlinear governing coupled partial differential equations of a three-phase immiscible fluid flow. The contaminant was released using a colored fluid as a tracer for a fixed time and pressures different from the atmospheric one into the saturated zone, first by using a column laboratory experiment, and then a sandbox-scale example with a hydraulic gradient. A digital image analysis procedure was used to determine the saturation distribution of the contaminant during its migration. These results are compared with the values determined for a DNAPL migration in a similar porous media through a numerical simulation. They show good agreement with the experimental results and also show that CactusHydro can follow the migration of a plume evolution very precisely and can also be used to evaluate the effects and environmental impacts deriving from leaks of DNAPL in saturated zones.