Solute Trapping Research Articles

Surface amorphization of bulk NiTi induced by laser radiation

Surface amorphization of bulk NiTi induced by laser radiation

Morphological stability of solid-liquid interfaces under additive manufacturing conditions

Understanding rapid solidification behavior at velocities relevant to additive manufacturing (AM) is critical to controlling microstructure selection. Although in-situ visualization of solidification dynamics is now possible, systematic studies under AM conditions with microstructural outcomes compared to solidification theory remain lacking. Here we measure solid-liquid interface velocities of Ni-Mo-Al alloy single crystals under AM conditions with synchrotron X-ray imaging, characterize the microstructures, and show discrepancies with classical theories regarding the onset velocity for absolute stability of a planar solid-liquid interface. Experimental observations reveal cellular/dendritic microstructures can persist at velocities larger than the expected absolute stability limit, where banded structure formation should theoretically appear. We show that theory and experimental observations can be reconciled by properly accounting for the effect of solute trapping and kinetic undercooling on the velocity-dependent solidus and liquidus temperatures of the alloy. Further theoretical developments and accurate assessments of key thermophysical parameters - like liquid diffusivities, solid-liquid interface excess free energies, and kinetic coefficients - remain needed to quantitatively investigate such discrepancies and pave the way for the prediction and control of microstructure selection under rapid solidification conditions.

A Method for Calibrating the Transient Storage Model from the Early and Late-Time Behavior of Breakthrough Curves

Solute transport in rivers is controlled by mixing processes that occur over a wide spectrum of spatial and temporal scales. Deviations from the classic advection–dispersion model observed in tracer test studies are known to be generated by the temporary trapping of solutes in storage zones where velocities and mixing rates are relatively small. In this work, the relation between the early and late-time behavior of solute breakthrough curves (BTCs) and the key parameters of the Transient Storage Model (TSM) is analyzed using non-asymptotic approximations of the model equations. Two main slopes are identified corresponding to the rising and decreasing limbs of the BTCs which are linked by specific relationships to transport and storage parameters. The validity of the proposed approximations is demonstrated with both synthetic and experimental data. Consistent with the TSM assumptions, the range of validity of the proposed approximations represents the limit of separability between surface dispersion and transient storage and can be expressed as a function of a nondimensional parameter. The results of this work can help environmental scientists identify solute transport and transient storage parameters and support the design of enhanced field tracer experiments.

Solute trapping and solute drag during non-equilibrium solidification of Fe–Cr alloys

Solute trapping and solute drag during non-equilibrium solidification of Fe–Cr alloys

Solute Trapping and the Mechanisms of Non‐Fickian Transport in Partially Saturated Porous Media

AbstractWe study the upscaling of pore‐scale solute transport in partially saturated porous media at different saturation degrees. The interaction between structural heterogeneity, phases distribution and small‐scale flow dynamics induces complex flow patterns and broad probability distributions of flow, which control key aspects of transport, such as residence and arrival times, dispersion, and spatial solute distributions, as well as chemical reactions. A continuous‐time random walk (CTRW) framework that integrates the processes of advection, diffusion, and trapping in immobile zones is used to upscale and evaluate the transport of diluted solutes. Results of this model were compared to direct numerical simulations solving the advection‐diffusion equation in experimental saturation patterns. The comparison between simulations results, with different Péclet numbers (Pe), and the physics‐based upscaled CTRW approach allows for a quantitative analysis of the governing factors of transport in partially saturated porous media. This analysis shows that the fluid phase saturation decreases the advective tortuosity, the media's characteristic length, the fraction of the immobile region, and the mean trapping time. At the same time, for a given saturation degree, the normalized mean trapping time is proportional to the Pe. This suggests that the characteristic trapping length is proportional to the media's characteristic (correlation) length. Moreover, the trapping frequency decreases with increasing Pe.

Localization of Multiple Hydrogels with MultiCUBE Platform Spatially Guides 3D Tissue Morphogenesis In Vitro

AbstractLocalization of multiple hydrogels is expected to develop the structure of 3D tissue models in a location‐specific manner. Here, 3D tissue morphogenesis is spatially guided by localizing different hydrogel conditions at different parts of a tissue. To achieve the localization, a unit‐based scaffold is developed with a unique frame design to trap hydrogel solutions inside their designated units. An optimal range of unit dimensions and surface wettabilities enables a solution trapping up to several cubic millimeters without any need for chemical additives. This capability allows spatial organization of biomolecular compositions and physical conditions of hydrogels, as well as the relative position of biological samples (cells, spheroids, and reconstituted tissues) within the scaffold. Successful localization of branching development on reconstituted human epithelial tissues is achieved by localizing growth factors or cross‐linked matrix proteins within hydrogels, demonstrating a direct dependence on local hydrogel conditions. Unlike 3D‐bioprinting or microfluidic techniques, this scaffold‐based localization of hydrogels requires only a manual pipetting and no specialized tools, making it ready‐to‐use for researchers from any field. This localization technique provides a new promising route to spatially control morphogenesis, differentiation, and other developmental processes within 3D organoids or tissue models for practical biomedical applications in the future.

CO2 concentration and water availability alter the organic acid composition of root exudates in native Australian species

PurposeRoot exudation of organic acids (OAs) facilitates plant P uptake from soil, playing a key role in rhizosphere nutrient availability. However, OA exudation responses to CO2 concentrations and water availability remain largely untested.MethodsWe examined the effects of CO2 and water on OA exudates in three Australian woodland species: Eucalyptus tereticornis, Hakea sericea and Microlaena stipoides. Seedlings were grown in a glasshouse in low P soil, exposed to CO2 (400 ppm [aCO2] or 540 ppm [eCO2]) and water treatments (100% water holding capacity [high-watered] or 25–50% water holding capacity [low-watered]). After six weeks, we collected OAs from rhizosphere soil (OArhizo) and trap solutions in which washed roots were immersed (OAexuded).ResultsFor E. tereticornis, the treatments changed OArhizo composition, driven by increased malic acid in plants exposed to eCO2 and increased oxalic acid in low-watered plants. For H. sericea, low-watered plants had higher OAexuded per plant (+ 116%) and lower OArhizo per unit root mass (–77%) associated with larger root mass but fewer cluster roots. For M. stipoides, eCO2 increased OAexuded per plant (+ 107%) and per unit root mass (+ 160%), while low-watered plants had higher citric and lower malic acids for OArhizo and OAexuded: changes in OA amounts and composition driven by malic acid were positively associated with soil P availability under eCO2.ConclusionWe conclude that eCO2 and altered water availability shifted OAs in root exudates, modifying plant–soil interactions and the associated carbon and nutrient economy.

Microstructural Pattern Formation during Far-from-Equilibrium Alloy Solidification.

We introduce a new phase-field formulation of rapid alloy solidification that quantitatively incorporates nonequilibrium effects at the solid-liquid interface over a very wide range of interface velocities. Simulations identify a new dynamical instability of dendrite tip growth driven by solute trapping at velocities approaching the absolute stability limit. They also reproduce the formation of the widely observed banded microstructures, revealing how this instability triggers transitions between dendritic and microsegregation-free solidification. Predicted band spacings agree quantitatively with observations in rapidly solidified Al-Cu thin films.

Microstructure and mechanical properties of multi-scale α-Fe reinforced Cu–Fe composite produced by vacuum suction casting

Cu–10Fe composites were produced by the vacuum suction casting and traditional vacuum mold casting, respectively. The evolution of microstructure and properties of the composites during cold rolling and aging processes was analyzed. Compared with the traditional mold-casted Cu–Fe composites, the suction-casted Cu–Fe composite had better mechanical properties, with microhardness, tensile strength and elongation of 148 HV, 526 MPa and 23.7%, respectively. The softening temperature of the suction-casted Cu–Fe composite was 520 °C, which was 200 °C higher than that of traditional mold-casted Cu–Fe composite. The good performance of the suction-casted Cu–Fe composite was mainly attributed to the refinement of the Cu matrix and the formation of the multi-scale α-Fe particles caused by the effect of solute trapping during vacuum suction casting. The yield strength of the composites was mainly attributed to the contribution of Orowan strengthening, refinement strengthening and dislocations strengthening, which count for 31.1%, 25.8% and 24.1%, respectively.

Investigation of a new approach for 36Cl determination in solid samples using plastic scintillators

This work reports a new approach for the determination of 36Cl in radioactive waste samples from nuclear decommissioning, wherein novel plastic scintillator (PS) materials were used for the concentration of 36Cl prior to the detection with scintillation counting. Different plastic scintillator (PS) materials were tested for their selective absorption and detection of 36Cl activity in solid samples. PS microspheres (PSm), cross-linked PSm (CPSm) and PS resin have been investigated. PS resin was identified as the most suitable material for 36Cl analysis. Pyrolysis and subsequent trapping of the volatile elements in a bubbler was used. The trapping solution was finally loaded onto a cartridge of the PS resin. Scintillation counting and ion chromatography were used to determine the activity concentration and the chemical recovery, respectively.

MTNet: Mutual tri-training network for unsupervised domain adaptation on person re-identification

MTNet: Mutual tri-training network for unsupervised domain adaptation on person re-identification

Variational Theory of Crystal Growth in Multicomponent Alloys

The provisions for a new variational theory of crystal growth in multicomponent metal melts were formulated. The developed theory is the generalization of the previously conducted studies of crystal growth under conditions of deviation from local equilibrium at the phase boundary. The description of the methods of non-equilibrium thermodynamics of interrelated physico-chemical processes occurring in the initial phase, on the interface of phases and inside the growing crystal, was compared with the variational description of the crystal growth as a macrobody. The developed approach made it possible to find the general expression for the crystal growth rate, considering the influence of thermal and diffusion processes, as well as taking into account the influence of nonstationary effects associated with deviation from the local equilibrium on the surface of the growing nucleus. The justification of the new method showed that when the condition of the local equilibrium on the surface of the growing crystal is satisfied, the resulting equations take the form of expressions that can be obtained by constructing the equation of a mass and internal energy balance for the system under consideration. As an example, the problem of crystal growth from a melt of eutectic composition was considered. The equation of the growth rate of the two-component nucleus of the stoichiometric composition was obtained, taking into account the influence of the local non-equilibrium effects on growth. The expressions obtained were compared with the known equations of the solute trapping theory.

Mechanical design of plate-fin heat exchangers for industry using social learning chaotic based Kho-Kho optimization

The success of a new mechanical device is very much dependent on its design. To attract users, product design should be better than the present by its design as well as performance within proper cost. Here, a mechanical model is carried out for optimal designing of the Plate-fin heat exchangers (PFHE) to minimize five objective functions such as total heat transfer rate, total weight, total mass flow rate, number of entropy generation unit, and total annual cost. In this paper, a novel Social Learning based Chaotic Kho-Kho (SL-C-KKO) optimization approach is proposed to design PFHE. Among social animals, social learning plays an important role in behaviour learning. It helps people to learn from other’s actions (behaviour) without incurring the price of specific trials and errors by avoiding the learning complexity. Chaos is simple to set up and avoids the need for a local trapping solution. The chaotic search initialization method is used in this research to initialize the population for the KKO. As a result, it takes significantly less time to converge and able to reach global optimality. Using the proposed SL-C-KKO, optimal value of total heat transfer rate, total weight, mass flow rates at the hot region, mass flow rate at the cold region, number of entropy generation and total annual cost are obtained as 1107.1 Watt, 22.7 kg, 1.84 Kg/s, 2.01 Kg/s, 0.1321, and 823 $ respectively. The obtained results are compared with some existing results. • Design an optimal Plate-fin heat exchanger (PFHE). • Development of SL-C-KKO optimizer to improve the performance of the PFHE. • Five practical thermo-mechanical issues of PFHE are optimized. • PFHE performance in terms of five objectives is improved by the proposed method.

Macro-Micro Coupled Simulation of SLM Process with Inconel 718 Superalloy

As an increasingly mature additive manufacturing technology for metal materials, Selective Laser Melting (SLM) technology has become a hot topic in many application fields. However, due to the fast-moving velocity and small scale of the laser beam in the SLM process, it is very difficult to directly observe the microstructural changes in the SLM additive manufacturing process. In this study, a macro-micro coupled simulation model of Inconel 718 SLM process was established to study the solidification behavior of the molten pool. The macro temperature field is obtained by the finite difference method based on the birth and death grid algorithm. The local temperature intercepted from the macro temperature field is employed as the input condition for phase field microstructure calculation. Dendrite morphology, intercellular spacing, and microsegregation are simulated under the coupled model. The result shows that the solidification structure of IN718 alloy in the micro molten pool formed by SLM grows in the form of a non-flat interface. The primary dendrite spacing predicted by the simulation is in good agreement with Hunt model at the initial stage of solidification. The solute trapping caused by non-equilibrium solidification makes dendrites dissolve more Nb, resulting in microsegregation.

Fundamental Studies on Electron Dynamics in Exact Paraxial Beams with Angular Momentum

Classical electromagnetic radiation with orbital angular momentum (OAM), described by nonvanishing vector and scalar potentials (namely, Lorentz gauge) and under Lorentz condition, is considered. They are employed to describe paraxial laser beams, thereby including non-vanishing longitudinal components of electric and magnetic fields. The relevance of the latter on electron dynamics is investigated in the reported numerical experiments. The lowest corrections to the paraxial approximation appear to have a negligeable influence in the regimes treated here. Incoherent Thomson scattering (TS) from a sample of free electrons moving subject to the paraxial fields is studied and investigated as a beam diagnosis tool. Numerical computations elucidate the nature and conditions for the so called trapped solutions (electron motions bounded in the transverse plane of the laser and drifting along the propagation direction) in long quasi-steady laser beams. The influence of laser parameters, in particular, the laser beam size and the non-vanishing longitudinal field components, essential for the paraxial approximation to hold, are studied. When the initial conditions of the electrons are sufficiently close to the origin, a simplified model Hamiltonian to the full relativistic one is introduced. It yields results comparing quite well quantitatively with the observed amplitudes, phase relationships and frequencies of oscillation of trapped solutions (at least for wide laser beam sizes). Genuine pulsed paraxial fields with OAM and their features, modeling true ultra-short pulses are also studied for two cases, one of wide laser beam spot (100 μm) and other with narrow beam size of 6.4 μm. To this regard, the asymptotic distribution of the kinetic energy of the electrons as a function of their initial position over the transverse section is analyzed. The relative importance of the transverse structure effects and the role of longitudinal fields is addressed. By including the full paraxial fields, the asymptotic distribution of kinetic energy of an electron population distributed across the laser beam section, has a nontrivial and unexpected rotational symmetry along the optical propagation axis.

Size dependence of solute’s translational jump-diffusion in solvent: Relationship between trapping and jump-diffusion

Previous studies, explaining the breakdown of Stokes-Einstein relation using the translational jump-diffusion (TJD) approach, hinted an important relationship between the strength of solute trapping inside solvent cage and the contribution of jump-diffusion to the total diffusion. To generalize the above picture we simulate here a simple solute–solvent model system with different solute sizes. It has been observed that the jump-diffusion contribution is negligible when the solute particles are weakly trapped within the solvent cage and vice versa. This study, therefore, suggests that strong caging induces jump-diffusion of a particle, which is responsible for the breakdown of Stokes-Einstein relation.

An effective iterative greedy algorithm for distributed blocking flowshop scheduling problem with balanced energy costs criterion

With the increase in production levels, a pattern of industrial production has shifted from a single factory to multiple factories, resulting in a distributed production model. The distributed flowshop scheduling problem (DPFSP) is of great research significance as a frequent pattern in real production activities. In this paper, according to real-world scenarios, we have added blocking constraints and sequence-dependent setup times (SDST) to the DFSP and proposed a distributed blocking flowshop scheduling problem with sequence-dependent setup times (DBFSP_SDST). In a distributed environment, the allocation of resources and utilization have become an urgent problem to be solved. In addition, scheduling problems related to resource conservation have also attracted increasing attention. Therefore, we study DBFSP_SDST and consider minimizing the energy consumption cost of the critical factory (critical factory is the factory with maximum energy consumption cost) under resource balance. To tackle this problem, an effective iterated greedy algorithm based on a learning-based variable neighborhood search algorithm (VNIG) is proposed. In VNIG, an efficient construction heuristic is well designed. Two different local searches based on the characteristics of the proposed problem are developed to enhance the local exploitation by neighborhood searching. A learning-based selection variable neighborhood search strategy is designed to avoid the solution trapping in local optima. By conducting extensive simulation experiments, the proposed VNIG shows superior performance compared with artificial chemical reaction optimization (CRO, 2017), the discrete artificial bee colony algorithm (DABC, 2018), the iterative greedy algorithm with a variable neighborhood search scheme (IGR, 2021), and the evolution strategy approach (ES, 2022). • A mathematical model of an energy-balance DBFSP_SDST is formulated. • An efficient heuristic is presented to generate a high-quality initial solution. • Two different local searches based on the characteristics of the proposed problem are developed. • A learning-based selection variable neighborhood search is designed. • The VNIG shows superior performance compared with four algorithms on 90 instances.

Ammoniacal nitrogen recovery from pig slurry using a novel hydrophobic/hydrophilic selective membrane

The implementation of the circular economy paradigm in intensive pig farming requires technologies able to recover ammoniacal nitrogen from pig slurries. This research explores the feasibility of a novel hydrophobic/hydrophilic non-porous membrane to recover ammoniacal nitrogen from pig slurry at ambient temperature and using a H 2 SO 4 solution as trapping agent. The influence of (i) the pH of the feed solution, (ii) the volume ratio between feed and trapping solution, and (iii) the trapping solution concentration on nitrogen recovery and flux were evaluated using a synthetic solution and pig slurry. The best performance was achieved when the pH of the feed solution was controlled at 9.0, where average fluxes of 145 and 116 g N/(m 2 ·day) were achieved for the synthetic solution and pig slurry after 24 h, respectively. Decreasing the feed-to-trapping volume ratio improved the recovery efficiency after 24 h from 62% to 74% for the synthetic solution and from 32% to 46% for pig slurry. However, renewing the H 2 SO 4 concentration of the trapping solution only led to minor improvements despite the higher reagent consumption. The diffusion coefficients of NH 3 and NH 4 + through the membrane at pH 9.0 were (7.3 ± 0.2)·10 –11 and (2.1 ± 0.1)·10 –11 m 2 /s for the synthetic solution and (2.7 ± 0.1)·10 –11 and (1.0 ± 0.1)·10 –11 m 2 /s for the pig slurry, respectively. The capacity of ions to diffuse through the membrane is a distinctive feature of this membrane and allowed recovering 33% of potassium and 21% of phosphate in pig slurry after 24 h. • The performance of a novel ammonia selective membrane was evaluated. • The highest nitrogen flux was obtained when the pH of the feed solution was 9.0. • For pig slurry, 46% and 59% of the nitrogen was recovered in 24 and 48 h. • A trapping solution concentrated in NPK and free of heavy metals was obtained. • A model was used to calculate NH 3 and NH 4 + diffusion coefficients at each condition.

Microstructure evolution of Inconel 625 alloy during single-track Laser Powder Bed Fusion

Elemental microsegregation and precipitate formation are inevitable during solidification of Additive Manufacturing (AM) parts. In this study, single-track Laser Powder Bed Fusion (LPBF) has been combined with optical and electron microscopy, as well as thermodynamic (CALPHAD) simulations, to evaluate the solidified microstructure and also the formation of the precipitates in an as-built LPBF microstructure of Inconel625 (IN625). It is shown that the microstructure consists mainly of columnar Nickel–Chromium ( γ -FCC) cell-like dendrites which grew epitaxially from the substrate. Utilizing Scanning Transmission Electron Microscopy (STEM) with Energy-Dispersive X-ray Spectroscopy (EDS) and High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM), we have detected NbC, γ ′ ′ -Ni 3 Nb, and laves precipitates embedded into the interdendritic regions. The level of microsegregation and the microsegregation patterns during the solidification of primary arms are obtained by STEM-EDS, and calculated using the Scheil–Gulliver (with solute trapping) and DIffusion-Controlled TRAnsformations (DICTRA) methods. Good agreement is seen between the Scheil–Gulliver predictions and STEM-EDS observations of microsegregation, however the level of elemental microsegregation was overestimated in DICTRA simulations as compared to the experimental result. The formation of precipitates was also evaluated computationally by calculation of driving force for the nucleation of the precipitates from the last solidified liquid where the composition and thermal information for the last solidified liquid extracted from the Scheil solidification simulation. The precipitates predicted via CALPHAD were compared with the precipitates identified via HAADF-STEM analysis inside the interdendritic region.

Irradiation-induced solute trapping by preexisting nanoprecipitates in high-strength low-alloy steel

In the present study, a nanoprecipitate-strengthened high-strength low-alloy steel was irradiated by high-energy Au2+ ions with a peak dose of ∼70 displacements per atom (dpa) at room temperature. The formation of nanoprecipitates, dislocation loops, elemental segregation and mechanical properties before and after irradiation were carefully characterized using atom probe tomography (APT), transmission electron microscopy (TEM) and nanoindentation. The mechanism of precipitation and coarsening of these nanoprecipitates and the effect of the dose on irradiation-induced solute capture were studied. The results show that, different from a simple aging-induced precipitation of Cu-rich nanoprecipitates, coprecipitation of Cu/Ni nanoprecipitates occurred under irradiation. With increasing dose, the nanoprecipitates coarsened. Although irradiation induced the formation of small dislocation loops together with new nanoprecipitates, the abnormal softening that occurred after irradiation can be attributed to the coarsening of the preexisting nanoprecipitates. These studies and discoveries are expected to provide unique and important information for the design of new structural alloys with enhanced radiation resistances.