Homogeneous Diffusion Research Articles

Ternary Interdiffusion Coefficients in BCC Ti-Al Based Alloys and Their Application in Simulations of Homogenization and Finite Diffusion Couples

Ternary Interdiffusion Coefficients in BCC Ti-Al Based Alloys and Their Application in Simulations of Homogenization and Finite Diffusion Couples

Insights into calculating Reference Discontinuity Factors with Serpent Monte Carlo code

This study explores the calculation of Reference Discontinuity Factors (RDFs) using the Serpent Monte Carlo code, focusing on the methodology and potential pitfalls. In two-step reactor analyses, consistently generated RDFs are crucial for aligning homogeneous nodal diffusion results with the reference heterogeneous transport solution. However, the Serpent internal diffusion solver, based on the Analytic Function Expansion Nodal (AFEN) method, may not be compatible with other nodal methods such as the Nodal Expansion Method (NEM). Additionally, the solver can suffer from instabilities, particularly in multi-group calculations, leading to erroneous RDFs. Despite these challenges, Serpent can generate the necessary raw data for RDF calculation, which can be accurately processed using external diffusion solvers. Two numerical examples − a 1D fuel-reflector model and a 2D SMR core model − illustrate the effects of consistent and inconsistent RDFs on simulation accuracy. The study emphasizes the importance of using compatible diffusion solvers and thoroughly assessing RDFs to avoid errors in reactor simulations.

Diffusive micromixing combined with dynamic in situ laser scattering allows shedding light on lipid nanoparticle precipitation

Pharmaceutical formulations are increasingly based on drug nanoparticles or carrier nanoparticles encapsulating drugs or mRNA molecules. Sizes and monodispersity of the nanoparticles regulate bioavailability, pharmacokinetics and pharmacology. Microfluidic mixers promise unique conditions for their continuous preparation. A novel microfluidic antisolvent precipitation device was realized by two-photon-polymerization with a mixing channel in which the organic phase formed a sheet with a homogeneous thickness of down to 7 μm completely wrapped in the aqueous phase. Homogeneous diffusion through the sheet accelerates mixing. Optical access was implemented to allow in-situ dynamic light scattering. By centering the thin sheet in the microchannel cross-section, two important requirements are met. On the one hand, the organic phase never reaches the channel walls, avoiding fouling and unstable flow conditions. On the other hand, in the sheet positioned at the maximum of the parabolic flow profile the nanoparticle velocities are homogenized which enables flow-compensated Dynamic Light Scattering (flowDLS). These unique features allowed in-situ particle size determination for the first time. Monitoring of lipid nanoparticle precipitation was demonstrated for different rates of solvent and antisolvent flows. This breakthrough innovation will not only enable feedback control of nanoparticle production but also will provide new insights into the dynamics of nanoparticle precipitation.

Regulating Zn2+ Migration-Diffusion Behavior by Spontaneous Cascade Optimization Strategy for Long-Life and Low N/P Ratio Zinc Ion Batteries.

Parasitic side reactions and dendrite growth on zinc anodes are formidable issues causing limited lifetime of aqueous zinc ion batteries (ZIBs). Herein, a spontaneous cascade optimization strategy is first proposed to regulate Zn2+ migration-diffusion behavior. Specifically, PAPE@Zn layer with separation-reconstruction properties is constructed in situ on Zn anode. In this layer, well-soluble poly(ethylene oxide) (PEO) can spontaneously separation to bulk electrolyte and weaken the preferential coordination between H2O and Zn2+ to achieve primary optimization. Meanwhile, poor-soluble polymerized-4-acryloylmorpholine (PACMO) is reconstructed on Zn anode as hydrophobic flower-like arrays with abundant zincophilic sites, further guiding the de-solvation and homogeneous diffusion of Zn2+ to achieve the secondary optimization. Cascade optimization effectively regulates Zn2+ migration-diffusion behavior, dendrite growth and side reactions of Zn anode are negligible, and the stability is significantly improved. Consequently, symmetrical cells exhibit stability over 4000 h (1 mA cm-2). PAPE@Zn//NH4 +-V2O5 full cells with a high current density of 15 A g-1 maintains 72.2 % capacity retention for 12000 cycles. Even better, the full cell demonstrates excellent performance of cumulative capacity of 2.33 Ah cm-2 at ultra-low negative/positive (N/P) ratio of 0.6 and a high mass-loading (~17 mg cm-2). The spontaneous cascade optimization strategy provides novel path to achieve high-performance and practical ZIBs.

A novel surface molecularly imprinted polymer based on the natural biological macromolecule sporopollenin for the specific and efficient adsorption of resveratrol from Polygonum cuspidatum extracts

Sporopollenin is a natural biological macromolecule consisting of highly cross-linked carbon, hydrogen, and oxygen atoms, with a highly porous structure and multifunctional groups. In this work, a novel surface molecularly imprinted polymer based on magnetically aminated cattail sporopollenin (MACSp-SMIP) was prepared for the specific and efficient adsorption of resveratrol, with the aim of purifying resveratrol from Polygonum cuspidatum extracts. MACSp-SMIP was found to have a porous structure covered with the multi-layered sponge-like imprinted polymers. MACSp-SMIP had a high adsorption capacity for resveratrol (65.77 mg·g−1) and excellent selectivity (imprinting factor 5.64). The adsorption of resveratrol by MACSp-SMIP was a homogeneous diffusion dominated by chemical adsorption with three stages of external diffusion, internal diffusion, and micropore diffusion. MACSp-SMIP was used as an adsorbent in molecularly imprinted solid-phase extraction for the purification of resveratrol from P. cuspidatum extracts, achieving a resveratrol recovery of 94.33 % and a purity of 76.67 % in the final products. MACSp-SMIP maintained a satisfactory recovery of resveratrol (88.18 %) after six cycles. Overall, this work developed a promising biological macromolecule-based adsorbent MACSp-SMIP for the specific and efficient adsorption of resveratrol, and also provided an efficient and simple approach for the selective purification of resveratrol from P. cuspidatum extracts for food/nutraceutical applications.

Effects of storage period and season on the microecological characteristics of Jiangxiangxing high-temperature Daqu

Metagenomics, non-targeted metabolomics, and metaproteomics were employed to analyze the microecological succession of high-temperature Daqu during storage, elucidate the adaptation mechanism of the microbial community of Daqu to storage environments, and clarify the microecological characteristics of Daqu during different seasons. During storage, the relative abundances of Bacillus, Oceanobacillus, Staphylococcus, and Aspergillus in Daqu had significantly increased, while those of Kroppenstedtia, Saccharopolyspora, Thermoascus, and Thermomyces had significantly decreased. During the first 3 months of storage, compound metabolism of Daqu was primarily dominated by generation of small molecular substances and then shifted to metabolism of amino sugars. During the storage process, homogeneous selection (15.57 %) and homogeneous diffusion (14.86 %) of the microbial communities of Daqu were much larger than during the fermentation process, while the variable selection assembly (29.43 %) was smaller than during the fermentation process. Among the 2509 proteins identified in the four-season Daqu, bacterial protein expression was 1.46-fold greater than that of fungi. Seasonal factors influenced the function of Daqu by alterations to Bacillus subtilis, Oceanobacillus iheyensis, and Aspergillus nidulans and other microbial functions. Carbon and benzoic acid metabolism of Daqu was relatively increased during the spring, while metabolism of alkaloids and tyrosine was upregulated during the summer, amino acid synthesis and starch metabolism were enriched during the autumn, and peptidoglycan synthesis was relatively greater during the winter. Adjusting the moisture content of Daqu during the storage period was shown to reduce microecological differentiation caused by seasonal temperature variations.

Study by transmition electron microscopy of Co-WC/Ni interface produced by solid state bonding

The microstructure of the interface and inter-diffusion behavior during bonding plays an important role to understand and to control the joining process for better mechanical properties of an interface. In this work, the microstructure of the formed interlayer between cermet WC-Co and metallic Ni after solid state bonding (the WC-Co/Ni interface) was analyzed by scanning (SEM) and transmission (TEM) electron microscopy, and characteristic energy dispersive x-ray spectroscopy (EDS). The WC-Co/Ni joint was produced at 980°C for 25 minutes in argon atmosphere. For SEM observation, the samples were mechanically polished and etched. TEM samples were produced parallel (sample P), perpendicular (sample T) and oblique (sample TP) to the interface by focused ion beam (FIB). The EDS results indicate the inter-diffusion at the interface of W, Ni, Co and C and the segregation of Ni and Co, together with the formation of crystalline phases and an amorphous carbon layer. W follows a homogeneous diffusion while Ni and Co show a non-homogeneous diffusion behavior.

Effect of chemical reactions and melting heat on the dynamics of maxwell nanofluid flow

AbstractThis study investigates the electrically conducting Maxwell fluid flow over a stretching sheet with the effects of homogeneous‐heterogeneous chemical reactions, thermal radiation, and melting heat. The nanomaterial characteristics are analyzed considering Brownian motion and thermophoresis (Buongiorno's model). Irreversibility analysis is conducted to assess entropy generation. The governing equations of the problem are transformed into dimensionless equations through appropriate similarity transformations. The graphical and tabular numerical solutions are attained through NDSolve via Mathematica. The study examines how various parameters affect the velocity, concentration, temperature, and entropy generation within the flow. This study provides insights into isothermal chemical processes which contribute to the optimization of industrial and engineering applications. It is seen that heterogeneous diffusion parameter increases molecular disorder and rate of irreversible processes, whereas homogeneous diffusion parameter shows opposite trend.

Finite difference analysis for entropy optimized nanomaterial Darcy-Forchheimer flow with homogeneous and heterogeneous reactions

Hybrid nanoliquids are not underestimated for their involvement in microelectronics, transportation, coolant processes, ships, biological processes and power generation. Hence motivation for current work is to examine homogeneous-heterogeneous reactions in entropy optimized flow by curved sheet stretched with nonlinear velocity. Trihybrid nanoliquid is synthesized through 2 % of ferrous oxides(Fe3O4), 2 % of silver(Ag) and 2 % of copper(Cu). Kerosene oil is employed as the base fluid. These specific kinds of nanoparticles are taken into consideration because of their numerous applications in heat dissipation, air filters, dynamic sealing, biosensors and catalysts process. Kerosene oil may have applications in many different domains such as energy storage, cleaning agent, portable heaters, fuel additive and industrial lubricants. Darcy-Forchheimer model is employed. Analysis in presence of radiation, dissipation, Ohmic heating, entropy generation and heat generation/absorption are organized. Unlike the previous considerations, the thermal expression here consists of impacts through Darcy-Forchheimer relation. Adequate transformations are implemented. Computations have been arranged by applying finite difference technique (FDM) using MATLAB. Quantities for physical interest are addressed. The presented analysis may have relevance for solar systems, chemical reacting processes, cooling towers and polymer data processes. The conclusions are also organized for important key findings. It is noticed that trihybrid nanomaterial has more entropy rate when compared with hybrid and classical nanoliquids when volume fraction is chosen as 2 % for trihybrid fluid. It is proposed that the ability to transfer heat is enhanced when nanoparticles are added to conventional fluids. Decay in concentration is noticed for both homogeneous and heterogeneous parameters. Reduction for Bejan number is noticed through homogeneous diffusion factor. Comparison with previous study is also presented and found great consensus between them.

Mitigating Zn Dendrite Growth and Enhancing the Utilization of Zn Electrode in Aqueous Zn-Ion Batteries.

In spite of extensive research and appreciable progress, in aqueous zinc-ion batteries, Zn metal anode is struggling with low Zn utility and poor cycling stability. In this study, a 3D "electrochemical welding" composite electrode is designed by introduction of ZnO/C nanofibers film to copper foils as an anode according to pre-electrodeposition active Zn (Zn@ZnO/C-Cu). The flow of Zn2+ through carbon fiber layer is regulated by zincophilic ZnO, promoting homogeneous diffusion of Zn2+ to Cu foil. In subsequent Zn deposition/stripping processes, the hydrophobicity of ZnO/C fiber layer reduces water at the interface of Zn@ZnO/C-Cu and results in uniform electric field significant suppressing growth of Zn dendritic and side reactions. Thus, pre-electrodeposition active Zn electrochemical welds ZnO/C nanofibers and Cu foil collectively provide stable charge/electron transfer and stripping/plating of Zn with low polarization and excellent cycling performance. The assembled symmetrical batteries exhibit stable cycling performance for over 470 h under 20% utilization of Zn at 5mA cm-2, and an average coulombic efficiency of 99.9% at low negative/positive capacity ratio (N/P = 1) after 1000 cycles in the Zn@ZnO/C-Cu||Na2V6O16·1.5H2O full cell.

Intermittent cluster dynamics and temporal fractional diffusion in a bulk metallic glass

Glassy solids evolve towards lower-energy structural states by physical aging. This can be characterized by structural relaxation times, the assessment of which is essential for understanding the glass’ time-dependent property changes. Conducted over short times, a continuous increase of relaxation times with time is seen, suggesting a time-dependent dissipative transport mechanism. By focusing on micro-structural rearrangements at the atomic-scale, we demonstrate the emergence of sub-diffusive anomalous transport and therefore temporal fractional diffusion in a metallic glass, which we track via coherent x-ray scattering conducted over more than 300,000 s. At the longest probed decorrelation times, a transition from classical stretched exponential to a power-law behavior occurs, which in concert with atomistic simulations reveals collective and intermittent atomic motion. Our observations give a physical basis for classical stretched exponential relaxation behavior, uncover a new power-law governed collective transport regime for metallic glasses at long and practically relevant time-scales, and demonstrate a rich and highly non-monotonous aging response in a glassy solid, thereby challenging the common framework of homogeneous aging and atomic scale diffusion.

A novel Adomian natural decomposition method with convergence analysis of nonlinear time-fractional differential equations

ABSTRACT The objective of the current article is to use the Banach fixed point theorem to present proofs for the existence and uniqueness theorems for a nonlinear time-fractional differential equation, namely, the linear and nonlinear, homogeneous and nonhomogeneous time-fractional diffusion equations. In addition, we explore exact solutions to nonlinear time fractional partial differential equations using an effective method called the Adomian natural decomposition method (ANDM), which is a combination of the Adomian decomposition method (ADM) and the natural transform method (NTM). To demonstrate the effectiveness of the suggested scheme, three examples are provided along with graphs and numerical tables to support our work. The outcomes demonstrate how effortless and effective the ANDM is for addressing fractional partial differential equations in multi-dimensional spaces, some of which we examined in this study as special cases. AMS Classifications 34A08, 65P99, 49J15, 35R11, 26A33, 74G10.

Competitive sorption of low and high molecular weight proteins in model mixtures by Q HyperZ chromatographic medium. Part II: Mass transfer mechanisms

The kinetic uptake of Bovine Serum Albumin (BSA) and ferritin in mixtures by the composite anion exchanger Q HyperZ was studied. Transient adsorption experiments were performed to investigate the dominant resistance between external and internal mass transfer in simultaneous and sequential adsorption experiments. From the evolution of protein solution concentration with time, the external mass transfer coefficients determined were very low in simultaneous (7.1 10−7 and 1.1 10−7 m/s for BSA and ferritin respectively) and sequential (4.6 10−7 and 2.5 10−7 m/s for BSA and ferritin respectively) adsorption systems which is in agreement with the low agitation speed used. From the transient protein uptakes, the internal mass transfer was studied and the homogenous diffusion model applied provides a good predictability in single as well as in simultaneous and sequential adsorption experiments. The effective diffusion coefficients were determined in sequential (6.4 10−14 m2/s and 3.8 10−14 m2/s for BSA and ferritin respectively) and simultaneous (4.2 10−14 m2/s for both proteins) systems. In multi-component adsorption system, it was found that BSA was slowed down upon the presence of ferritin on mixture solutions contrarily to ferritin protein. This phenomenon, known as electrostatic coupling effect, indicates that diffusion of charged proteins in ion exchangers are not independent.

Modelling competitive adsorption of organic micropollutants onto powdered activated carbon in continuous stirred tank reactors for advanced wastewater treatment

This work investigates the validation and application of a competitive model approach for full-scale wastewater treatment plants (WWTP) with external recirculation of partially loaded powdered activated carbon (PAC) for removal of organic micropollutants (OMP). It is based on the ideal adsorbed solution theory (IAST) for multisolute mixtures combined with calibration of fictive organic components and correction of single-solute model parameters for OMP by use of the tracer model (TRM). Adsorption kinetics are represented by a pseudo first order reaction (PFO) and compared to mass transfer calculated with the homogenous surface diffusion model (HSDM). Model validation with operational data from two different WWTPs showed a strong dependency of model results on the batch sample quality used for model calibration. In contrast, the kinetic approach is of less importance for predicting full-scale OMP removal with long PAC sludge retention times. Further model application demonstrated that external PAC recirculation significantly improves the OMP removal with regard to both adsorption capacity and compensation of competitive effects of Dissolved Organic Carbon (DOC).

Removal of antibiotics, bacterial toxicity, and occurrence of antibiotic resistance genes in secondary hospital effluents treated with granular activated carbon and the impact of preceding chlorination

This comprehensive investigation highlighted the complex adsorption behaviors of antibiotics onto granular activated carbon (GAC), the effectiveness of this adsorption in reducing bacterial toxicity, and the reduction of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) in hospital wastewater (HWW) effluents. Six GACs were characterized for their physicochemical properties, and their ability to adsorb six antibiotics in the background matrix of actual HWW was evaluated. Coconut shell-derived GAC (Co-U), which had the highest hydrophobicity and lowest content of oxygen-containing acidic functional groups, demonstrated the highest adsorption capacities for the tested antibiotics. Bacterial toxicity tests revealed that GACs could eliminate the bacterial toxicity from antibiotic intermediates present in chlorinated HWW. By contrast, the bacterial toxicity could not be removed by GACs in non-chlorinated HWW due to the greater presence of intermediate components identified by LC-MS/MS. The intraparticle diffusion coefficient of antibiotics adsorbed onto Co-U could be calculated by adsorption kinetics derived from the linear driving force model and the homogenous intraparticle diffusion model associated with the linear adsorption isotherms (0–150 μg/L). Meropenem and sulfamethoxazole exhibited the highest adsorption capacities in a single-solute solution compared to penicillin G, ampicillin, cetazidime, and ciprofloxacin. However, the greater adsorption capacities of meropenem and sulfamethoxazole disappeared in mixed-solute solutions, indicating the lowest adsorption competition. GAC can eliminate most ARGs while also promoting the growth of some ARB. Chlorination (free chlorine residues at 0.5 mg Cl2/L) did not significantly affect the overall composition of ARGs and ARB in HWW. However, the accumulation of ARGs and ARB on GAC in fixed bed columns was lower in chlorinated HWW than in non-chlorinated HWW due to an increase in the adsorption of intermediates.

Regularised Diffusion–Shock Inpainting

We introduce regularised diffusion–shock (RDS) inpainting as a modification of diffusion–shock inpainting from our SSVM 2023 conference paper. RDS inpainting combines two carefully chosen components: homogeneous diffusion and coherence-enhancing shock filtering. It benefits from the complementary synergy of its building blocks: The shock term propagates edge data with perfect sharpness and directional accuracy over large distances due to its high degree of anisotropy. Homogeneous diffusion fills large areas efficiently. The second order equation underlying RDS inpainting inherits a maximum–minimum principle from its components, which is also fulfilled in the discrete case, in contrast to competing anisotropic methods. The regularisation addresses the largest drawback of the original model: It allows a drastic reduction in model parameters without any loss in quality. Furthermore, we extend RDS inpainting to vector-valued data. Our experiments show a performance that is comparable to or better than many inpainting methods based on partial differential equations and related integrodifferential models, including anisotropic processes of second or fourth order.

Mechanism insight of sorption of Er(III) and Nd(III) ions onto Aluminium barium tungstate synthesized via streamlined sol–gel technique: Time-transient study

Aluminium barium tungstate powder (ABT) was chemically synthesized via streamlined sol–gel technique and exploited as a sorbent material for sorption of erbium and neodymium ions from aqueous solutions under simulated conditions using batch technique. The pH influence, time and temperature factors have been studied. The sorption of neodymium ions was found to be marginally higher than that of erbium ions and the apparent sorption capacity has a progressive influence with temperature. Thermodynamic parameters such as Gibbs free energy change (ΔG◦), enthalpy change (ΔH◦) and entropy change (ΔS◦) were calculated. The negative ΔG◦ values declines with an increase in temperature value, demonstrating that the sorption reaction for both studied ions was spontaneous and more promising at greater temperature. The positive ΔH◦ values affirm that the nature of the sorption processes is endothermic. The comparison of different time transient models applied to the sorption data was assessed for the pseudo first-order (PFO), the pseudo second-order, (PSO) and homogeneous particle diffusion (HPD) models. The results revealed that both PSO and HPD models were found to best correlate the experimental sorption rate data and a monolayer model was adopted as the best suitable model to explore the sorption mechanism for both studied ions. The attained particle diffusion coefficients and rate constant values were acquired from the graphical illustration of the anticipated models. Activation energy change (Ea) and activation entropy change (ΔS±) were also calculated from the linearized Arrhenius model and indicated that the binding process between the sorbent and the studied ions occurred through chemisorption and the sorption of both ions onto synthetic sorbent took place through associative mechanism.

Enabling Uniform and Stable Lithium-Ion Diffusion at the Ultrathin Artificial Solid-Electrolyte Interface in Siloxene Anodes.

Constructing a stable and robust solid electrolyte interphase (SEI) has a decisive influence on the charge/discharge kinetics of lithium-ion batteries (LIBs), especially for silicon-based anodes which generate repeated destruction and regeneration of unstable SEI films. Herein, a facile way is proposed to fabricate an artificial SEI layer composed of lithiophilic chitosan on the surface of two-dimensional siloxene, which has aroused wide attention as an advanced anode for LIBs due to its special characteristics. The optimized chitosan-modified siloxene anode exhibits an excellent reversible cyclic stability of about 672.6 mAh g-1 at a current density of 1000mA g-1 after 200 cycles and 139.9 mAh g-1 at 6000mA g-1 for 1200 cycles. Further investigation shows that a stable and LiF-rich SEI film is formed and can effectively adhere to the surface during cycling, redistribute lithium-ion flux, and enable a relatively homogenous lithium-ion diffusion. This work provides constructive guidance for interface engineering strategy of nano-structured silicon anodes.

Narrowing the pore size distribution of a piperazine-based ultrathin polyamide film with the addition of 1,3-diamino-2-propanol (DAP)

Sharpening the pore size distribution is challenging but highly efficacious to boost the performance of polyamide (PA) membranes in nanofiltration (NF). Herein, a facile and applicable strategy for narrowing the pore size distribution of a piperazine (PIP)-based NF membrane is proposed by introducing 1,3-diamino-2-propanol (DAP) into the aqueous phase. The results show that the selective layer can be effectively remodeled via the incorporation of DAP. A thicker, rougher and more hydrophilic selective layer with a narrowed pore size distribution can be attained by adding 0.03 w/v% DAP to the 0.1 w/v% PIP solution, which exhibited a pure water permeance (PWP) of 20.7 L m−2 h−1·bar−1 and a MgSO4 rejection up to 97.4 %. This transformation can be attributed to the stronger polarity and higher reactivity of DAP compared to PIP. During the IP process modified by DAP, the strong polarity of DAP could result in a slower and more homogeneous diffusion of PIP into the organic phase through hydrogen interaction to facilitate a uniform interfacial polymerization reaction. Meanwhile, the higher reactivity of DAP could remedy the probably produced defects. This work provides a straightforward route for the regulation of NF membrane structure and performance.

Decay estimates in time for fractional evolution equations

We consider the homogeneous time-fractional diffusion equation \partial^{\alpha} (u-u_0)(t)+A u(t)=0, \quad t\text{-a.e.} Here, \partial^{\alpha} denotes the Riemann–Liouville fractional derivative of order \alpha \in (0,1) with respect to time and A is a uniformly elliptic operator on \mathbb{R}^d . We prove decay estimates in time and other regularity properties for the solution of the above equation.