Immiscible Components Research Articles

Engineering the Atomic Interface of Refractory‐Metal‐Reinforced Copper Matrix Using Direct Ink 3D Printing

Herein, 3D printing involving metallic materials with substantially distinct melting temperatures and their immiscibility presents a formidable challenge. Nevertheless, it may be possible to overcome this challenge using the direct ink writing (DIW) method within such immiscible systems. In this article, a successful fabrication of Cu‐based composites utilizing the additive manufacturing process that is DIW technique, followed by a post‐sintering process, is presented. The secondary addition to the Cu–matrix includes tantalum (Ta), tungsten (W), and niobium (Nb). The rheological properties of the composite inks are also analyzed for the DIW technique. The underlying reasons behind the increased mechanical, wear, and thermal properties are assessed through experimental and molecular dynamics simulations. Microstructural analysis is conducted using optical and scanning electron microscopes. Mechanical, electrical, thermal, and wear properties are evaluated at ambient temperature, and comparisons are established with DIW‐processed pure Cu. Elemental mapping through energy‐dispersive spectroscopy and high‐resolution transmission electron microscopy confirm the distribution of W, Ta, and Nb particles within the composite. The 3D printing of immiscible alloy components opens new avenues for exploring novel material properties, mixtures, and composite materials, thus fostering the development of innovative materials.

Получение композиционных материалов при аддитивном производстве

The main possibilities of obtaining new composite materials are presented. Due to the high dynamics of thermal deformation processes in the molten bath of a thin layer of the grown part, we obtain a new material structure from immiscible components. Another direction of obtaining a new composite material in the growing process is the reinforcement of the matrix with high-strength elements, which can be present, including in the form of a solid phase under melting and crystallization of the material. This allows predicting in advance new qualitative properties of the grown part - increased strength, weight reduction, etc. Additive technology is being developed for growing parts and products made of tungsten, molybdenum, tantalum, niobium and other hard-melting metals that are poorly treated through mechanical methods. In this case, heating is used within growing process. The successful application of additive technologies is used in medicine in the manufacture of implants made of molybdenum, tantalum and their alloys, which have high biocompatibility and no toxic property. It becomes possible to manufacture an implant grown according to a specific model for a given individual. The main directions of the additive manufacturing development are the creation of more productive complexes and the expansion of construction materials powders range, used when forming new composite materials in the growing process.

Liquid-liquid equilibrium of FAEs – glycerol phase – ethanol in the ethanol regeneration and FAE separation stage

Extraction and purification of biofuel components are as important as their synthesis. Synthesis of fatty acid esters in a molar excess of ethanol above 1:30 results in the formation of a homogeneous phase including the ester and glycerol phases dissolved in ethanol. It was observed that when excess ethanol was removed, the separation of the system into ester and glycerol phases did not always occur. To improve the biodiesel purification process the experimental binodal curve for the FAE-ethanol-glycerol phase system was obtained in the synthesis of biodiesel from rapeseed oil. The data was obtained from homogeneous alkaline synthesis of FAE with molar excess of ethanol 1:50. The pseudocomponent glycerol phase contains glycerol and unreacted oil (triglycerides (TGA)). The calculated liquid-liquid equilibrium (LLE) data for FAE – ethanol – glycerol and FAE – ethanol – TGA ternary mixtures were obtained by the UNIFAC (UNIQUAC Functional-group Activity Coefficients) model and compared with experimental diagram. It was found that glycerol and unreacted triglycerides affect the behavior of the system by preventing or promoting the mixing of immiscible components. The obtained results show that, depending on the conversion, the phase behavior of the FAE-ethanol-glycerol phase system will correspond to the ternary system FAE-ethanol-glycerol or FAE-ethanol-TGA. The obtained data help to predict the separation of glycerol and ester phases at the ethanol recovery stage knowing the degree of rapeseed oil conversion at the synthesis stage. Successful separation of the glycerol and FAE phases is possible at oil conversion above 53 %.

Selective Multiphase-Assisted Oxidation of Bio-Sourced Primary Alcohols over Ru- and Mo- Carbon Supported Catalysts.

The oxidation of representative bio-based benzyl-type alcohols has been successfully carried out in a multiphase (MP) system comprised of three mutually immiscible liquid components as water, isooctane, and a hydrophobic ionic liquid as methyltrioctylammonium chloride ([N8881][Cl]), a heterogeneous catalyst (either ad-hoc synthesized carbon-supported Mo or a commercial 5% Ru/C), and air as an oxidant. The MP-reaction proceeded as an interfacial process with Mo/C or Ru/C perfectly segregated in the ionic liquid phase and the reactant(s)/products(s) dissolved in the aqueous solution. This environment proved excellent to convert quantitatively benzyl alcohols into the corresponding aldehydes with a selectivity up to 99%, without overoxidation to carboxylic acids. The nature of the catalyst, however, affected the operating conditions with Ru/C active at a lower T and t (130 °C, 4-6 h) compared to Mo/C (150 °C, 24 h). The phase confinement was advantageous also to facilitate the products isolation and the recycle of the catalyst. Notably, in the Mo/C-catalyzed oxidation of benzyl alcohol, benzaldehyde was achieved with unaltered selectivity (>99%) at complete conversion, for 5 subsequent reactions through a semicontinuous procedure in which the catalyst was reused in-situ, without ever removing it from the reactor or treating it in any way.

Ti/Mg dissimilar joining by eutectic-melting-induced liquid metal dealloying

Ti and Mg alloys, which have thermodynamically immiscible main components, have been chemically joined in previous work using a third element with high affinity for both elements. However, this strategy is challenging in precisely controlling brittle intermetallic compounds formed at a joint interface. In this study, we mechanically joined pure Ti and pure Mg without brittle layers by forming bicontinuous microstructure, 3D entanglement of immiscible phases, at the joint interface. We butt-joined pure Mg and Ti–Cu alloy interlayer, which we pre-diffusion bonded to the pure Ti and heated at 813 K and 20 MPa for 5 min. At the joint interface, Cu and Mg eutectic melted, which induced liquid metal dealloying of the interlayer. The entire Ti–Cu interlayer is dealloyed, and a byproduct (Mg–Cu phase) is removed by pressurization during melting. These brittle layer removal processes left only α-Ti/Mg–Cu phase bicontinuous microstructure at the joint interface, improving the joint strength. Ti/Mg joints fractured at the Mg base metal at ca. 90 MPa by tensile tests. The findings of this study provide the basis for achieving immiscible alloy joining, for which effective joining methods have not yet been established.

Electrospark alloying of 30KhGSN2A stee l with alloy based on systems of immiscible components

The studies of the influence of the parameters of the electrospark alloying mode (EIL) on the properties of steel coated on the basis of copper alloys made it possible to determine not only the change in the mechanical and fatigue properties of the material, but also to choose rational technological modes. The rational modes of electrospark coating of bronze VBr5М and BrAZhMCz10-3-1.5, as well as an alloy based on the Cu—Pb system on the surface of parts made of steel 30KhGSN2A at the installation are determined ELFA-512M in automatic processing. It is shown that in order to eliminate the burnout of phosphorus during EIL of parts with bronze grade VBr5M, it is necessary to carry out the process in an inert gas (argon). It has been established that the coating applied by the electrospark method based on bronze does not affect the strength and plastic properties of steel 30KhGSN2A. At the same time, EIL bronze leads to a decrease in the low-cycle fatigue of samples made of steel 30KhGSN2A. Based on the results of studies of the coefficient of friction and wear of samples under dry friction conditions after EIL for the manufacture of parts operating under high loads under sliding friction conditions, taking into account the data of mechanical tests, it is possible to recommend for use bronze grade BrAZhMCz10-3-1.5 and a composite material based on immiscible components of the system 64 % Cu—36 % Pb.

Особенности фазовых и структурных превращений в композиционных материалах на основе систем несмешивающихся компонентов при воздействии концентрированных потоков энергии

The features of phase and structural transformations in composite materials based on systems of immiscible components Al – Be, Al – Be – Mg, Fe – Cu, Fe – Cu – Pb under the influence of concentrated heat sources — electric arc, electron and laser beams — are considered. It is shown that when materials of the Al – Be, Al – Be – Mg systems are exposed to an electric arc plasma and an electron flow, they are melted and subsequently cooled by grain grinding, formation of a zone of thermal influence and crystallization of the resulting new structures and phases. In zone of thermal influence, the enrichment of the aluminum matrix with Be particles is observed due to the thermal diffusion processes of their movement. When plasma is exposed to an arc discharge, pulsed and continuous laser radiation, as well as the flow of electrons on the composition Fe – Cu, Fe – Cu – Pb, a change in the morphology of the near-surface layer is observed: the irradiated material in the melt zone is exfoliated and in the process of crystallization the stratified phases are fixed in a solid state. The mechanism of stratification formation is associated with the limited solubility of the elements that make up the composition in the liquid and solid states.

Deposition-controlled phase separation in CuNb metallic alloys

Vapor co-deposited metal nanocomposites with immiscible components have shown to have several superior properties including mechanical performance, radiation tolerance, and enhanced functionalities. The morphology and structural design of these nanocomposites are important in determining the expression of these properties. The conditions used to deposit thin film nanocomposites are the governing factors in determining the final nanostructure. In this work, we link the effects of process gas pressure, substrate temperature, and sputtering target power on resultant Cu/Nb thin film nanostructures. We find that for films with equiatomic phase fractions of Cu and Nb, inhomogeneous precipitate segregation dominated the structure at lower substrate temperature depositions while higher temperatures distributed the Cu and Nb phases more uniformly. Increasing process gas pressure during deposition lead to a spatially homogeneous, nanocrystalline structure of Cu/Nb. In situ annealing of this sample shows that the phase separated morphology of the two immiscible materials depends on the initial composition. Finally, compositions of Cu and Nb that were highly disparate lead to interface segregation of the minority phase. The morphological evolution observed in the Cu/Nb system is compatible with modified structural zone models for immiscible thin film systems.

Preparation and Characterization of Novel Green Seaweed Films from Ulva rigida.

Ulva rigida green seaweed is an abundant biomass consisting of polysaccharides and protein mixtures and a potential bioresource for bioplastic food packaging. This research prepared and characterized novel biodegradable films from Ulva rigida extracts. The water-soluble fraction of Ulva rigida was extracted and prepared into bioplastic films. 1H nuclear magnetic resonance indicated the presence of rhamnose, glucuronic and sulfate polysaccharides, while major amino acid components determined via high-performance liquid chromatography (HPLC) were aspartic acid, glutamic acid, alanine and glycine. Seaweed extracts were formulated with glycerol and triethyl citrate (20% and 30%) and prepared into films. Ulva rigida films showed non-homogeneous microstructures, as determined via scanning electron microscopy, due to immiscible crystalline component mixtures. X-ray diffraction also indicated modified crystalline morphology due to different plasticizers, while infrared spectra suggested interaction between plasticizers and Ulva rigida polymers via hydrogen bonding. The addition of glycerol decreased the glass transition temperature of the films from -36 °C for control films to -62 °C for films with 30% glycerol, indicating better plasticization. Water vapor and oxygen permeability were retained at up to 20% plasticizer content, and further addition of plasticizers increased the water permeability up to 6.5 g·mm/m2·day·KPa, while oxygen permeability decreased below 20 mL·mm/m2·day·atm when blending plasticizers at 30%. Adding glycerol efficiently improved tensile stress and strain by up to 4- and 3-fold, respectively. Glycerol-plasticized Ulva rigida extract films were produced as novel bio-based materials that supported sustainable food packaging.

Interfacial adhesion of immiscible component polymers of isoprene rubber and α‐olefin copolymer by chemical reaction using peroxide crosslinking agent

AbstractWe investigated the interfacial adhesion of immiscible component polymers of isoprene rubber (IR) and α‐olefin copolymer (αOC) by chemical reaction using peroxide crosslinking agent which was used for the crosslinking of IR. Fibrillar structure of the IR elongated from the αOC domains was observed by scanning electron microscope and the tensile stress of the IR was enhanced without sacrifice of the excellent elongation in the two‐phase blends of IR and αOC obtained after crosslinking reaction, suggesting that adhesion exists at the interface. The confocal‐Raman imaging of the bilayer films of IR and αOC revealed that mixed layer having a distance about 358 nm was formed at the interface by the chemical reaction. Owing to the existence of the mixed layer at the interface, the adhesion strength was larger as the mixed layer at the interface was thicker. Thus interfacial adhesion exists in the immiscible component polymers of IR and αOC by the chemical reaction and the tensile stress was enhanced without sacrifice of the excellent elongation.

Pressure relaxation in some multiphase flow models

We consider in this paper multiphase flow models involving two, three or four fields, in total mechanical and thermodynamical disequilibrium. Thus several pressure fields arise, and we precisely focus here on the pressure relaxation process, while restricting to four distinct multiphase flow models. The first two models only involve immiscible compressible components, while the last two hybrid models involve both miscible and immiscible components. It is shown that some -weak- restrictions may occur on pressure gaps, which are unlikely to appear in practice. Evenmore, three-phase flow models may involve a non-monotone behaviour in the return to pressure equilibrium.

On the conservative phase-field method with the N-component incompressible flows

This paper presents a conservative Allen–Cahn model coupled with the incompressible Navier–Stokes equation for tracking the interface with the N-component immiscible fluids system. The proposed conservative phase-field model can track the interface with large deformation in divergence-free velocity fields. The erroneous estimation of the normal vector is a challenging numerical issue for the interface capturing due to the appearance of spurious oscillations. The improved phase-field-based method combines the nonlinear preprocessing operation guided by the level-set method with local artificial viscosity stabilization to improve the computation of the discrete normal vector. The interfaces between different immiscible components are replaced by the transition region with finite thickness in the continuous phase field. The surface tension effects are represented with the continuous surface tension force in the system, which is not limited by the number of components. The third-order Runge-Kutta time discretization and second-order spatial discretization are applied for the multi-component system. To eliminate the spurious oscillations caused by discontinuous and steep gradient for capturing the shocks and sharp interfaces, we apply the third-order weighted essentially non-oscillatory method for the advection term. Several quantitative results of numerical tests, such as error estimation with the proposed method, comparative tests with different methods, and convergence rate for classical benchmark test, have been performed to illustrate that our method works well for the interface tracing issue with high numerical accuracy. In addition, various representative qualitative tests have been presented to demonstrate the applicability of our method.

Comment on “Progress and investigation on lattice Boltzmann modeling of multiple immiscible fluids or components with variable density and viscosity ratios”

We briefly comment on the generalized analytical solution for the multilayered Couette flow presented in the paper “Progress and investigation on lattice Boltzmann modeling of multiple immiscible fluids or components with variable density and viscosity ratios”.

Domain walls in fractional media.

Currently, much interest is drawn to the analysis of optical and matter-wave modes supported by the fractional diffraction in nonlinear media. We predict a new type of such states in the form of domain walls (DWs) in the two-component system of immiscible fields. Numerical study of the underlying system of fractional nonlinear Schrödinger equationsdemonstrates the existence and stability of DWs at all values of the respective Lévy index (α<2), which determines the fractional diffraction, and at all values of the XPM/SPM ratio β in the two-component system above the immiscibility threshold. The same conclusion is obtained for DWs in the system which includes the linear coupling, alongside the XPM interaction between the immiscible components. Analytical results are produced for the scaling of the DW's width. The DW solutions are essentially simplified in the special case of β=3, as well as close to the immiscibility threshold. In addition to symmetric DWs, asymmetric ones are constructed too, in the system with unequal diffraction coefficients and/or different Lévy indices of the two components.

Immiscible Polymer Blends Compatibilized through Noncovalent Forces: Construction of a “Quasi-Block/Graft Copolymer” by Interfacial Stereocomplex Crystallites

Interfacial compatibilization is acknowledged to be the most effective approach to improve interfacial strength between the thermodynamically immiscible components of polymer blends. However, the compatibilizer, mainly achieved by graft or block copolymers, necessarily connected by covalent bonds, can rarely be satisfied presently. Herein, we propose a concept of “quasi-block/graft copolymer” to compatibilize the immiscible polyolefin elastomer (POE) and poly(styrene-acrylonitrile-glycidyl methacrylate) (SAG) blends. The quasi-block/graft copolymer was achieved by the stereocomplex crystals (SC) of poly-l-lactic acid (PLLA) and poly-d-lactic acid (PDLA) moieties that reactively grafted on the main chains of the components. By taking advantage of the interfacial compatibilization through noncovalent forces, the microphase morphology of the blend can be adjusted and the mechanical properties can be improved: firstly, the curvature of the phase interface decreases significantly, facilitating co-continuous morphology on account of the “rigid” interfacial layers; secondly, the tensile strength and modulus of the blend are obviously improved; thirdly, the original phase structure of the blend can be well maintained during long-term annealing due to the high melting point of the interfacial SC. This strategy of compatibilizing immiscible blends by using the hydrogen bonding force of the stereocomplex opens up an idea for interfacial compatibilization.

Fully-decoupled, energy stable second-order time-accurate and finite element numerical scheme of the binary immiscible Nematic-Newtonian model

We consider the numerical approximation of a two-phase complex fluid flow model that couples the immiscible liquid crystal fluid component immersed in the ambient free flow field, where the free interface motion between the two fluids is simulated by using the phase-field approach via the energy variational method. The model is a highly nonlinear coupling system, which is composed of the Navier–Stokes equations for the flow field, the Cahn–Hilliard equations for the free moving interface, and the constitutive equation for the nematic liquid crystal. This paper proposes an effective full-discrete finite element numerical scheme to solve the model and makes the scheme not only have the characteristics of linearity, second-order time accuracy, unconditional energy stability, decoupling structure but also only need to solve a few constant-coefficient elliptic equations at each time step. The unconditional energy stability of the scheme and the detailed implementation process are further given. Various numerical experiments including the well-known “beads-on-string” phenomena are also simulated to illustrate the effectiveness of the scheme.

Pseudo-potential lattice Boltzmann model for large density and viscosity ratio fluids

The flow of two immiscible fluid components with large density and viscosity ratios is considered. Using the pseudo-potential lattice Boltzmann model with a non-ideal equation of state and a mixture viscosity formulation, we can develop a model that successfully passes a series of benchmark tests, most importantly co-current layered flows, with no discontinuities in the velocity profiles at interfaces. The model is then applied to applications of bubbles rising in denser fluids and shows good quantitative agreement with previous numerical and experimental results. The model is also applied to the flow of two immiscible fluids in a porous medium and shows characteristics that are physically consistent with established experimental observations.

A phase field model for compressible immiscible fluids with a new equation of state

In this paper, we propose a new compressible phase field model of two different immiscible fluid components, in which the density of each phase is variable. In order to establish the compressible phase field model, a new P-V-T equation of state is introduced to solve the pressure. The new model is derived by the physics law of conservation, and conforms to the second law of thermodynamics. The model adopts an innovative expression of Helmholtz free energy, taking into account the new state equation of pressure and the varying material properties of each phase. A high-order accurate numerical scheme is introduced to solve the model equations. The convection terms of the governing equations are discretized by the fifth-order WENO scheme, and the residual terms are discretized by the Lax–Friedrichs method. Finally, the reliability and validity of the compressible two-phase model are verified by numerical simulations.

A fully-discrete decoupled finite element method for the conserved Allen–Cahn type phase-field model of three-phase fluid flow system

In this article, we develop and analyze a novel fully discrete decoupled finite element method to solve a flow-coupled ternary phase-field model for the system consisting of three immiscible fluid components. Based on the L2-gradient flow approach, the conserved Allen–Cahn type dynamics is used to describe the free interface motion, where multiple nonlocal type Lagrange multipliers are used to accurately conserve the volume of each phase. The scheme is also linear, second-order time accurate, and unconditionally energy stable, due to the combination of several effective numerical techniques, including the two-step backward differentiation scheme, finite element discretization, explicit-SAV (scalar auxiliary variable) method for handling the nonlinearity, and projection method of Navier–Stokes equation. At each time step, the non-local splitting technique only requires solving several decoupled constant-coefficient elliptic equations. The implementation issues are discussed in detail. The solvability and the unconditional energy stability of the scheme are rigorously proved. Plenty of 2D and 3D numerical simulations are carried out to numerically demonstrate the accuracy, energy stability, and applicability of the proposed scheme.

Efficient, second-order in time, and energy stable scheme for a new hydrodynamically coupled three components volume-conserved Allen–Cahn phase-field model

In this paper, we establish a new hydrodynamically coupled phase-field model for three immiscible fluid components system. The model consists of the Navier–Stokes equations and three coupled nonlinear Allen–Cahn type equations, to which we add nonlocal type Lagrange multipliers to conserve the volume of each phase accurately. To solve the model, a linear and energy stable time-marching method is constructed by combining the stabilized-Invariant Energy Quadratization (S-IEQ) approach and the projection method. The well-posedness of the scheme and its unconditional energy stability are rigorously proved. Several numerical simulations in 2D and 3D are carried out, including spinodal decomposition, dynamical deformations of a liquid lens and rising liquid drops, to validate the model and demonstrate the efficiency and energy stability of the proposed scheme, numerically.