Interfacial Phenomena Research Articles

(Invited) Gravitational Level Effects on Electrochemical Interfacial Phenomena

Electrochemical copper refining technology invented in Niagara area made a great progress over more than 100 years through better understanding of natural convection phenomena. Ionic mass-transfer rate enhanced by natural convection developing along 1m high vertical electrode surfaces has been unconsciously utilized by trial-and-error method. As the local electrolyte composition is partly stratified in an electrolytic cell (roughly 5m long x 1.3m wide x 1.3m depth). The industrial electrolytic tank house is composed of about 1000 cells through which the electrolyte is continuously supplied. Thus, the electrolyte circulation is a key technology in industrial copper refining processes as well as appropriate selection of effective additive and stable sedimentation of anode slime containing precious metals on the electrolytic tank bottom.On the other hand, Cu nanowire arrays were electrodeposited potentiostatically with PC filter template in two kinds of electrolytic cell configurations: cathode over anode (C/A) and anode over cathode (A/C). The effect of gravitational level on the coupling phenomena between the morphological variation and the ionic mass transfer rate in nanosized pores(a mesoscopic scale of a fewμm high and 30nm in diameter) was also found. Hitherto, the coupling phenomena accompanied with the electrochemical interfacial reactions confined in such a mesoscopic space has not been studies in spite of the great technological interest for the production of micro- or meso-scale fabrication techniques encountered in microelectronics and energy conversion & storage technology field. The initial stage including nucleation and growth process during electrochemical phase transformation reactions must be at first focused to profoundly comprehend the present subject in order to reasonably design such an advanced device technology.Fundamental aspects in electrochemical processes in microgravity environments have not been frequently reported. However, Artemis projects may provide the large opportunities on the energy storage and power generation, as well as materials processing. The effects of gravitational level and magnetic field gradient on the electrochemical interfacial phenomena should be understood. The drop tower facility surely offers the appropriate & “unique” experimental opportunities to propose such research program in the future space engineering fields. Electrocrystallization of metals is selected as a good subject for starting direction of research. Its reaction mechanism is relatively simple, the deposition rate can be easily varied by changing the current density or potential, and a smooth copper film is deposited so long as it is not too thick.By the way, the damascene process has been introduced to copper wiring process in ULSI field by IBM almost 25 years ago. It is important to control the nucleation and crystal growth in the initial stages of electrodeposition process. For this purpose, many effects of additive have been intensively examined. However, few quantitative examinations have been reported on the coupling phenomena of ionic mass transfer and nucleation and crystal growth. In the present work, we introduce various gravitational levels as new parameters into the nonequilibrium electrochemical processing in order to create or tailor the unique physical properties in nano space field. It is fruitful in terms of physicochemical hydrodynamics that the experiments are done under various gravitational levels. In fact, it has been confirmed that the gravitational levels as well as the magnetic field introduce the intensified effects from that under 1 G normal environment. Here is a report to analyze the effect of gravitational level on the initial stages of Cu electrodeposition on TaN or TiN substrate.

Unveiling the Dynamics of Solid Electrolyte Interphase Evolution in Li-Ion Batteries Via Operando X-Ray Reflectivity: Experimental Insights for Advanced Energy Storage

The Solid-Electrolyte-Interphase (SEI) is a crucial component of Li-ion batteries (LIBs), as it passivates the highly reactive electrode from the electrolyte and helps to stabilize the electrode/electrolyte interface. However, the SEI formation and evolution can also limit the cycling performance and the capacity retention of the battery. Accurate electrochemical models must therefore account for the SEI and properly simulate it. In order to investigate experimentally the SEI, various techniques have been deployed, including electron microscopy1, X-ray photoelectron spectroscopy (XPS)2,3 and Nuclear magnetic resonance (NMR)4.Providing reliable information on the SEI evolution during cycling, and thus benchmarking models, is challenging with these ex-situ or destructive techniques, as they hardly allow in situ observation. On the other hand, synchrotron X-ray reflectivity (XRR) can be used for the operando investigation of interfacial phenomena. It provides information on the thickness, density, and roughness of the SEI, as well as their changes upon (de)lithiation or in out-of-equilibrium conditions. Moreover, operando XRR can be performed under controlled battery operating conditions, providing relevant information on the SEI. Recently, several works reported that operando XRR experiment can provide in situ structural information of the formation and the growth of SEI with sub-nanometer resolution during the cycling5–7.Herein, we report the results of operando XRR experiments performed at the beamline BM32 of the European Synchrotron Radiation Facility (ESRF) to investigate the SEI on Si anode using novel, sustainable fluorine-free electrolytes. Indeed, in the quest for environmentally friendly and safe LIBs, removing the fluorinated electrolytes that are toxic and release corrosive compounds is a necessary step. One way to enhance the safety and sustainability of LIBs is to replace the conventional fluorinated electrolytes by fluorine-free alternatives. A F-free composition based on the lithium bis(oxalato) borate (LiBOB) salt recently showed promising performance in commercially relevant cell configurations8. As with conventional electrolytes, the F-free electrolyte reacts at the surface of the electrodes during the first charge, thus forming the SEI. Characterizing the F-free SEI growth and stability is thus key to understand its behavior and to improve the cell performance for this promising green electrolyte.In this work, operando XRR experiments were performed in electrochemical cells with different electrolyte compositions: 1 M LiPF6 in ethylene carbonate (EC):ethyl methyl carbonate (EMC) = 3:7 vol % (LP57), 0.7 M LiBOB in EC:EMC = 3:7 vol % (LiBOB), and 0.7 M LiBOB in EC:EMC = 3:7 vol % with 2 wt% vinylene carbonate (LiBOB-VC) during at least three cycles. XRR data show that the formations of SEI layers and their evolutions during the cycling for these two types of electrolytes are different. Furthermore, a layer with low electron density (ED) is still present after total delithiation in the LiBOB-cells, while the ED evolutions are generally reversible for LP57 cell. This suggests that the F-free SEI has different properties during cycling than the SEI formed with conventional salt LiPF6.In summary, operando XRR is a powerful technique for investigating the impact of new electrolyte chemistry and formulation on the SEI properties, which significally influence batteries performances. Moreover, the in situ and in real-time experimental insights with sub-nanometer resolution from this technique provides valuable information for the development of more accurate and predictive models for the SEI evolution. Its unique capabilities make it an essential tool for advancing the understanding of SEI behavior and designing more efficient and stable energy storage systems.Figure 1: (a) Principle of operando X-ray reflectometry. (b) XRR data and fit-derived EDP of LiBOB cell upon lithiation. Figure 1

(Invited) Lithium Battery Interfacial Engineering with Thin Conformal Polymer Coatings

Coupled chemical and mechanical phenomena at electrode interfaces largely govern the reversibility and long term stability of lithium ion and lithium metal batteries. A well-known example in lithium ion batteries is the formation of the electrically insulating, ionically conductive, continuous solid electrolyte interface (SEI) on graphitic anodes, which passivates the electrode against further electrochemical reduction of the electrolyte. Unfortunately, this stable passivation does not occur in Si and Li metal anodes. High voltage cathodes are also prone to detrimental interfacial processes, resulting in electrolyte oxidation, gas formation, and transition metal dissolution. In response, a myriad of coating technologies has been developed to mitigate and control these interfacial phenomena and enable next-generation electrodes. These technologies must provide thin, conformal coatings over the entire electrochemically active surface area of the electrode; the coatings must also possess the requisite mechanical properties to accommodate volume dilation due to lithium insertion/extraction.This presentation will describe the development of conformal, compliant polymer thin film coatings for lithium battery electrodes. The polymer thin films are prepared by initiated chemical vapor deposition (iCVD), which provides exquisite control over film composition and morphology by facilitating heterogeneous free-radical polymerization of vinyl monomers with thickness precision on the order of 1 nm. Poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) (pV4D4) was deposited onto silicon thin film electrodes using iCVD. 25 nm-thick pV4D4 films on Si electrodes improved initial coulombic efficiency by 12.9% and capacity retention over 100 cycles by 64.9% relative to untreated electrodes. PV4D4 coatings also improved rate capabilities, enabling higher lithiation capacity at all current densities. Post-cycling FTIR and XPS showed that pV4D4 inhibited electrolyte reduction and altered the SEI composition, with enrichment in LiF. In another example, thin conformal coatings of perfluorinated polymer were deposited onto battery-grade Cu current collectors to function as an artificial solid electrolyte interface. The effect of the film thickness on Li cycling reversibility was characterized. By galvanostatically cycling Li in an asymmetric Li||Cu cell using 1M LiFSI in a 1:1 (v/v) mixture of dioxolane:dimethoxyethane at 30°C, it was shown that the average coulombic efficiency averaged over 50 cycles increased from 98.36% for bare, untreated Cu to 99.08% for Cu coated with 25 nm of the fluoropolymer. Moreover, the 25 nm coating suppressed interfacial impedance growth on the current collector; the resistance of the coated Cu was 40% lower than the untreated Cu after 100 cycles. The mechanism by which the polymer coating enhances coulombic efficiency and suppresses side reactions will be discussed, along with discussion of the performance in practical anode-free lithium metal batteries.

Effect of Fission Products on Molten Salt Corrosion for Nuclear Reactor Applications

Molten halide salts are used in various technologically important applications like molten salt reactors and concentrated solar power. A major challenge of molten salts is their corrosivity towards structural materials. However, most of the complex interfacial phenomena related to molten salt corrosion are not well understood, primarily due to the complex impact of salt chemistry on structural material interface. Structural material corrosion is influenced by salt redox potential, fission product buildup, presence of impurities and moisture. Given the huge dependence of operations on salt chemistry, understanding the interactions between soluble fission products and structural alloys is of great importance. EuCl3 is one of the primary fission products and shown EuCl3 to cause accelerated corrosion of structural alloys in molten chloride salts. Given the more positive formal oxidation potential of Eu(III)/Eu(II) compared to nickel, iron, and chromium that are major components of the structural alloys, Eu(III) species act as a strong oxidant to cause the dissolution of these metals. This talk will highlight utilization of novel in situ optical spectroscopy technique to study time-dependent evolution of corrosion damage of metals in presence of EuCl3 as well as the EELS technique to identify changes in oxidation states of dissolved alloying elements.

(Invited) Design of Surface Oxidation and Nitridation Reactions on 4H-SiC for the Advanced SiC Gate Stack Formation Processes

Silicon carbide (SiC) MOSFETs are expected to replace Si bipolar transistors partially in applications such as automotive, railroad, and other high-voltage applications. But the resistance of the MOS inversion layer channel limits the performance of MOSFETs. It has been clarified that the effective carrier density in the inversion channel is significantly reduced by the carrier trapping by the high density of defect states distributed nearby SiO2/SiC interface. In this study, our understanding of oxidation and nitridation reactions of SiC for designing the gate stack formation processes to improve the MOS interface characteristics is presented.Choosing SiO2 as a gate dielectric for SiC is favorable from various aspects including its ability to form a thermodynamically stable interface with SiC, which is free of reactions at the process temperature. However, from a microscopic point of view, Si-O bond alone cannot cover the whole surface of SiC and the excess C atoms on the surface causes the formation of defect states. One of the possible approaches has been employing an appropriate thermal oxidation condition to enhance the excess carbon elimination by forming CO. For example, we have experimentally demonstrated a significant reduction of Dit by employing high-temperature thermal oxidation with a rapid heating furnace [1]. However, such approach seems to bring a serious drawback such as defect formation in the surface region of SiC, experimentally detected by a lattice distortion in the beneath of SiO2 after high-temperature oxidation [2]. One of the possible reasons for such deterioration would be an invasion of activated oxygen atoms into the surface region of SiC [3]. A possible approach to avoid such drawback of high-temperature oxidation process would be utilizing H2O vapor for the formation of SiO2/SiC interface at relatively lower temperature while avoiding the damages on SiC surface [4], since H2O oxidation was found to be advantageous to remove CO more efficiently than O2 oxidation even at low temperature.On the other hand, another approach to passivate SiC surface is the surface nitridation technique, which is the most common way in industry to fabricate SiC MOS interface typically achieved by high-temperature annealing in NO gas [5]. Nitridation can replace the topmost C sites with N without inducing significant distortion in the SiC surface structure, to suppress the C-related defect formation at the interface. The advantage of this reaction is that it proceeds self-limited manner and N atoms are introduced only on the topmost surface of SiC. Note that NO gas triggers the surface nitridation by removing the surface C atoms in the form of CO by oxidation. Actually, a very similar reaction occurs even when SiC is annealed in N2 [6] ambient with a slight addition of O2. We experimentally found that the surface N density saturated with different values when we employed various N2+O2 atmosphere with different O2 concentration. Therefore we setup a simple model to describe the saturation behavior, which is determined by the balance between the rate of N uptake (N+) and the rate of N desorption (N‒) mainly due to the oxidation reaction [7]. This model was found to represent the time-dependent change of surface N density well, by assuming that N+ remained constant during the reaction and N‒ was proportional to both the reaction rate of interface oxidation and the surface N density [8]. Based on this simplified model, it is possible to design a process to tune the N density. By choosing appropriate temperature and oxygen partial pressure we can increase N density at the surface to minimize the interface trap density. Further improvement of surface N density would be achieved by further controlling of the blance between N uptake and N desorption reactions.As we have discussed so far, the role of materials science to clarify the interface phenomena is significantly important to achieve a further improved SiC MOS interface characteristics for the next generation SiC power MOSFET process technology. [1] R. Kikuchi and K. Kita, Appl. Phys. Lett. 105, 032106 (2014).[2] A. D. Hatmanto and K. Kita, Appl. Phys. Express 11, 011201 (2018).[3] A. D. Hatmanto and K. Kita, Jpn. J. Appl. Phys. 59, SMMA02 (2020).[4] H. Hirai and K. Kita, Appl. Phys. Lett. Appl. Phys. Lett. 113, 172103 (2018).[5] J. Rozen et al., J. Appl. Phys. 105, 124506 (2009).[6] A.Chanthaphan et al., AIP Adv. 5, 097134 (2015).[7] T. Yang and K. Kita, Jpn. J. Appl. Phys. 61, SC1077 (2022).[8] T. Yang and K. Kita, SSDM 2023, Chiba.

Interfacial Phenomena in Additively Manufactured Stainless Steel 316L/Inconel 718 Multi-Material Structures

Interfacial Phenomena in Additively Manufactured Stainless Steel 316L/Inconel 718 Multi-Material Structures

On-water surface synthesis of electronically coupled 2D polyimide-MoS2 van der Waals heterostructure

The water surface provides a highly effective platform for the synthesis of two-dimensional polymers (2DP). In this study, we present an efficient on-water surface synthesis of crystalline monolayer 2D polyimide (2DPI) through the imidization reaction between tetra (4-aminophenyl) porphyrin (M1) and perylenetracarboxylic dianhydride (M2), resulting in excellent stability and coverage over a large area (tens of cm2). We further fabricate innovative organic-inorganic hybrid van der Waals heterostructures (vdWHs) by combining with exfoliated few-layer molybdenum sulfide (MoS2). High-resolution transmission electron microscopy (HRTEM) reveals face-to-face stacking between MoS2 and 2DPI within the vdWH. This stacking configuration facilitates remarkable charge transfer and noticeable n-type doping effects from monolayer 2DPI to MoS2, as corroborated by Raman spectroscopy, photoluminescence measurements, and field-effect transistor (FET) characterizations. Notably, the 2DPI-MoS2 vdWH exhibits an impressive electron mobility of 50 cm2/V·s, signifying a substantial improvement over pristine MoS2 (8 cm2/V·s). This study unveils the immense potential of integrating 2D polymers to enhance semiconductor device functionality through tailored vdWHs, thereby opening up exciting new avenues for exploring unique interfacial physical phenomena.

The Nanoscale Wetting Parameter and Its Role in Interfacial Phenomena: Phase Transitions in Nanopores.

Through analysis of the statistical mechanical equations for a thin adsorbed film (gas, liquid, or solid) on a solid substrate or confined within a pore, it is possible to express the equilibrium thermodynamic properties of the film as a function of just two dimensionless parameters: a nanoscale wetting parameter, αw, and pore width, H*. The wetting parameter, αw, is defined in terms of molecular parameters for the adsorbed film and substrate and so is applicable at the nanoscale and for films of any phase. The main assumptions in the treatment are that (a) the substrate structure is not significantly affected by the adsorbed layer and (b) the diameter of the adsorbate molecules is not very small compared to the spacing of atoms in the solid substrate. We show that different surface geometries of the substrate (e.g., slit, cylindrical, and spherical pores) and various models of wall heterogeneity can be accounted for through a well-defined correction to the wetting parameter; no new dimensionless variables are introduced. Experimental measurements are reported for contact angles for various liquids on several planar substrates and are shown to be closely correlated with the nanoscale wetting parameter. We apply this approach to phase separation in nanopores of various geometries. Molecular simulation results for the phase diagram in confinement, obtained by the flat histogram Monte Carlo method, are reported and are shown to be closely similar to experimental results for capillary condensation, melting, and the triple point. The value of the wetting parameter, αw, is shown to determine the qualitative behavior (e.g., increase vs decrease in the melting temperature, capillary condensation vs evaporation), whereas the pore width determines the magnitude of the confinement effect. The triple point temperature and pressure for the confined phase are always lower than those for the bulk phase for all cases studied.

Liquid crystal-based label-free low-cost sensing platform: Engineering design based on interfacial interaction and transport phenomena

Typically, the detection methods of chemical species in sensing platform involves the use of labelling agents. Even though it is selective, the process is complex and time consuming. Liquid crystals (LC) are sensitive and rapidly responsive to the presence of any foreign species. When a LC layer interacts with aqueous (ionic surfactant) solution, there is homeotropic alignment of the director orientation due to the anisotropic interactions at the interface. This leads to the dark birefringence patterns observed in polarised microscope under cross polarisation. In the presence of H+ in the aqueous layer, the LC orientation is distorted resulting in a change of the birefringence patterns in the polarised micrographs. We have prepared an optical cell where the aqueous solution can interact with the LC layer confined within micrometre sized grids. The flow arrangement and the associated mass transfer process is optimised for enhanced interaction. The elastic interactions of the LC layer with H+ at the interface distorts the director orientation, and the birefringence pattern is captured with polarised microscope (cross-polarisation). There is a correlation between the polarised micrographs and the concentration of the H+, which forms the basis of detection principle. The detection of H+ has no interference with salts. The present method can be used for recognition of (bio-) chemical reactions releasing H+. The developed optical flow cell is inexpensive, less than $1. The outcome of the present work may be useful for technological adaption and prospective use in point-of-care devices and field test kits.

Investigation of the interfacial phenomena in the presence of nonionic surfactants and a silica nanoparticle at the n-decane-water interface: Insights from molecular dynamics simulation

In chemical enhanced oil recovery (EOR), the nanoparticles can be employed as conveyors to transfer the surfactants and impede the reduction of surfactant concentration. Here, a set of molecular dynamic simulations were carried out to examine the ability of hydrophobic silica nanoparticle (NP) to deliver the nonionic surfactant (Triethylene glycol monododecyl ether; C12E3) into the n-decane-water interface. Another set of simulations in which only surfactant molecules are initially located at the interface was performed in order to better characterize the influence of NP on the surfactant adsorption film.The NP exhibited high efficiency in delivering surfactant molecules to the n-decane-water interface. In addition, for the C12E3-NP and n-decane-NP, the Coulombic interactions are weaker than the van der Waals interactions confirming the nonpolar property of the silica nanoparticle. The density profiles indicate that as the concentration of surfactants increases at the interface, NP separates more from the surfactant layer. The interfacial tension (IFT) of n-decane-water systems containing only surfactants decreases as the surface coverage of the surfactants increases. Moreover, it was also proved that the intrinsic width of the interface increases with an increment in the surface coverage of surfactants. The surfactant molecules exhibit a great tendency to contribute as acceptors to the formation of hydrogen bonds with water molecules. With an increment in the surface coverage of surfactant molecules, the 2D radial distribution functions between the centers of mass (COMs) of surfactant tails show oscillations. Appeared oscillations represent the correlation between the surfactant tails. Presence of NP causes the oscillations start at lower surfactant coverage than without NP. The surfactant tails choose a random distribution at the low surface coverage of surfactants. In addition, they tend to be oriented partially perpendicular to the interface with an increase in surfactant surface coverage. Besides, NP causes the surfactant tails to orient more perpendicular to the interface than surfactants alone.

“Depo-all-around”: A novel FIB-based TEM specimen preparation technique for solid state battery composites and other loosely bound samples

Interfacial phenomena between active cathode materials and solid electrolytes play an important role in the function of solid-state batteries. (S)TEM imaging can give valuable insight into the atomic structure and composition at the various interfaces, yet the preparation of TEM specimen by FIB (focused ion beam) is challenging for loosely bound samples like composites, as they easily break apart during conventional preparation routines. We propose a novel preparation method that uses a frame made of deposition layers from the FIB's gas injection system to prevent the sample from breaking apart. This technique can of course be also applied to other loosely bound samples, not only those in the field of batteries.

Determination of Hansen Solubility Parameters of Raw Muscovite

AbstractMuscovite has been used increasingly as a substrate in flexible electronics and fillers in high-performance nanocomposites. Muscovite-based interfacial interactions play a crucial rule in material fabrication. Hansen solubility parameters (HSPs) have proven useful in characterizing molecular interactions within/between condensed phases. The present study aimed to determine the HSPs of raw muscovite (RM) and to investigate solvent dispersion mechanisms of RM. To achieve this, the solubilities of RM in 17 solvents were evaluated by dispersion tests, and the HSPs of RM were calculated as the center of the optimal solubility rotated-ellipsoid in HSP space, which included all good solvents, had the smallest number of outliers, and had the smallest volume. The resulting dispersion, polar, and hydrogen bonding components of RM were 18.301, 2.366, and 3.727 MPa1/2, respectively. By considering the HSPs and Kamlet-Taft's solvatochromic parameters of solvents, we concluded that the low polarity of RM is due to hindered K+/H+ exchange on the RM surface, resulting from limited water/moisture contact. For solvent dispersion of RM, essential conditions include strong dispersion forces and weak polar forces, finely tuned to match the surface property of RM at a certain hydration level. The HSPs of RM determined from dispersion tests were restricted to predicting/characterizing RM-based interfacial phenomena in an environment with strictly controlled water/moisture content. The HSP calculation method proposed herein was applicable to any clay mineral.

Investigation on the oil bridge between air bubble and glass surface in water: Formation, deformation, mechanical force and implications for froth flotation

In froth flotation, the insoluble oil as a liquid bridge between an air bubble and a solid surface in water is a common and important interface phenomenon. This paper investigated the impact of the oil bridge between an air bubble and a glass plane from aspects of mechanical forces acting on complex interfaces. An air bubble was pulling towards an oil droplet anchored on a flat glass slide under water compulsively. In this process, the high-speed camera was applied to observe the deformation of the interfaces and the mechanical forces were measured using a micro-force sensor. It was found that the air-water-oil (A-W-O) three-phase contact line (TPL) can form, expand and become stable rapidly within 85.0 ms when the bubble is attached to the oil droplet. The expansion of the A-W-O TPL provides an extra adhesion force to the air bubble. The oil formed an oil bridge connecting the bubble and the solid surface which shortened the attachment distance and extended the detachment distance. The mechanical force resulting from the oil bridge acting on the air bubble is equivalent to an air bubble directly adhering to a hydrophobically modified surface. The capillary force and pressure force were calculated and were found to be the major components of the mechanical force in the detaching process. This mechanical force was directly influenced by the interfacial tension vectors, the interface curvatures, and the TPL radius. The deformation on the interface, especially the A-W interface, is significant to the detachment process and related mechanical forces.

A research article on polymeric surfactant and its applications

Polymeric surfactants represent a distinctive class of amphiphilic compounds that combine the versatility of polymers with the surfactant properties crucial for interfacial phenomena. This research article will focus on the basis of polymeric surfactants and their applications in various domains. Characterisation techniques, including spectroscopy, microscopy, and rheology, are employed to elucidate polymeric surfactants' structural features and self-assembly behaviour. Understanding these characteristics is pivotal for optimising their performance in diverse applications. The applications of polymeric surfactants span a broad spectrum, focusing on their use in emulsion polymerisation, drug delivery, enhanced oil recovery, and environmental remediation. Their unique structure imparts advantages such as improved stability, controlled release, and enhanced efficiency in various processes.

Interfacial mechanism of hydrogel with controllable thickness for stable drag reduction

Surface wettability plays a significant role in reducing solid-liquid frictional resistance, especially the superhydrophilic/hydrophilic interface because of its excellent thermodynamic stability. In this work, poly(acrylic acid)-poly(acrylamide) (PAA–PAM) hydrogel coatings with different thicknesses were prepared in situ by polydopamine (PDA)-UV assisted surface catalytically initiated radical polymerization. Fluid drag reduction performance of hydrogel surface was measured using a rotational rheometer by the plate-plate mode. The experimental results showed that the average drag reduction of hydrogel surface could reach up to about 56% in Couette flow, which was mainly due to the interfacial polymerization phenomenon that enhanced the ability of hydration layer to delay the momentum dissipation between fluid layers and the diffusion behavior of surface. The proposed drag reduction mechanism of hydrogel surface was expected to shed new light on hydrogel-liquid interface interaction and provide a new way for the development of steady-state drag reduction methods.

Unveiling the Role of Nonionic Surfactants in Enhancing Cefotaxime Drug Solubility: A UV-Visible Spectroscopic Investigation in Single and Mixed Micellar Formulations.

This study reports the interfacial phenomenon of cefotaxime in combination with nonionic surfactants, Triton X-100 (TX-100) and Tween-80 (TW-80), and their mixed micellar formulations. Cefotaxime was enclosed in a micellar system to improve its solubility and effectiveness. TX-100 and TW-80 were used in an amphiphilic self-assembly process to create the micellar formulation. The effect of the addition of TX-100, a nonionic surfactant, on the ability of TW-80 to solubilize the drug was examined. The values of the critical micelle concentration (CMC) were determined via UV-Visible spectroscopy. Gibbs free energies (ΔGp and ΔGb), the partition coefficient (Kx), and the binding constant (Kb) were also computed. In a single micellar system, the partition coefficient (Kx) was found to be 33.78 × 106 and 2.78 × 106 in the presence of TX-100 and TW-80, respectively. In a mixed micellar system, the value of the partition coefficient for the CEF/TW-80 system is maximum (5.48 × 106) in the presence of 0.0019 mM of TX-100, which shows that TX-100 significantly enhances the solubilizing power of micelles. It has been demonstrated that these surfactants are effective in enhancing the solubility and bioavailability of therapeutic compounds. This study elaborates on the physicochemical characteristics and solubilization of reactive drugs in single and mixed micellar media. This investigation, conducted in the presence of surfactants, shows a large contribution to the binding process via both hydrogen bonding and hydrophobic interactions.

Effect of Cr2O3 Addition on Sintering Behavior of Novel Chromite‐Based Ladle Filler Sand

Developing novel filler sands has garnered significant interest in improving the ladle's free‐opening rate and enhancing the cleanliness of high‐Mn and high‐Al steel. Laboratory studies explore the effect of adding Cr2O3 powder on the sintering behavior of chromite‐based filler sands. Furthermore, interfacial phenomena are examined between the sands and the steel grades, varying in Mn contents. The results demonstrate that adding Cr2O3 power plays a role in inhibiting the liquid phase formation in the sand. With a 16% addition, the steel (Mn mass% = 30) reacts with the sand, leading to the shape of a spinel phase, specifically (Mn, Fe, Mg)O·(Al, Cr)2O3, which facilitates the separation of the liquid phase. The reduction of FeO to Fe by Mn, Al, and C in steel, especially Al, is hindered by adding Cr2O3, resulting in a suitable sintering degree that ultimately benefits ladle free‐opening. SiO2 is crucial for forming the liquid phase during the sintering process. The SiO2 content of the sand should be about 20% to achieve optimal sintering effects. Chromite sand for casting is not suitable for the steels. The mixed sand presented in the current study demonstrates potential as a suitable filler sand for the steel (20 ≤ Mn mass% ≤ 30).

Pore-scale study of the effects of DTPA chelating agent flooding on oil recovery utilizing a clay-coated micromodel

The use of diethylenetriaminepentaacetic acid (DTPA) chelating agent has shown promising results for enhanced oil recovery (EOR) in prior research. Several mechanisms, mainly resulting from rock-fluid interaction, have been proposed for chelating agent flooding; however, little attention has been paid to fluid-fluid interaction thus far. The assessment of these mechanisms has primarily relied on macroscopic techniques such as core flooding. This paper aims to investigate the injection of DTPA brine and its dominant mechanisms at the pore scale using a clay-coated micromodel. The micromodel tests were performed under oil-wet and water-wet states. For a more precise examination of fluid/fluid interactions, the dynamic interfacial tension (IFT) and Zeta potential were measured. It was observed that the injection of DTPA brine in water-wet state changed the saturation distribution and increased oil recovery. Based on visual inspections, this change in saturation distribution could potentially be linked to the formation of micro-dispersions and viscoelastic interfacial phenomena. Micro-dispersions facilitate flow to unswept areas, and viscoelastic interface formation reshapes the interface between oil and brine, causing disconnected oil droplets to coalesce and thus increase recovery. Under the oil-wet state, the micro-dispersion formation and wettability alteration can be the dominant mechanisms, and the amount of recovered oil was higher than that observed in the water-wet state. Furthermore, Zeta potential measurements at the interface between brine and oil showed a more negative value for DTPA brine, which is effective in wettability alteration and micro-dispersions stability. The results indicate that IFT reduction was not significant enough to be considered the dominant mechanism, although it assists in DTPA brine penetration into the crude oil and subsequent micro-dispersion formation.

Interfacial Micro-heterogeneous Surface Phenomenon in the Oxidative Transformation of 2-Phenylethanol by Ce(IV)

Interfacial Micro-heterogeneous Surface Phenomenon in the Oxidative Transformation of 2-Phenylethanol by Ce(IV)

Synthesis, dielectric, and magneto – dielectric properties of carbon quantum dots/ZnFe2O4 hybrid nanocomposite

Carbon quantum dots doped ZnFe2O4 Spinel Ferrite, that is, CQD-ZSF hybrid nanocomposite was thrivingly synthesised exploiting sol-gel based synthesis technique. Structural assessment supports Fd-3m space group with cubic spinel structure with mean size of 10.33 nm as obtained from Scherrer formula. Raman spectra confirmed the existence of CQD in ZSF. The samples contained a variety of vibration bands, according to the FT-IR analysis. The dielectric permittivity (ε) and tangent losses (tan δ) was conducted with frequency from 100 Hz to 1 MHz range at different temperatures ranging from 300 to 773 K. It was found that ε as well as tan δ receded monotonously with extending frequency. This information reveals a space or interfacial dipolar relaxation phenomenon. The electrical properties and the ion hopping dynamics were probed with the assistance of an AC-electrical conductivity (σac) analysis. Frequency-dependent σac heeded Jonscher’s law of power. The advent of arcs semicircular by nature in cole-cole plot indicates cloud of electronic process occurring within sample. At 300 K, by applying an external magnetic field varying till 1.5 Tesla magnetic field, the magneto-dielectric effects of the sample were measured by obtaining ε and tan δ versus frequency values displaying negative ML% (magneto-loss) and MD% (magneto-dielectric) coupling of −32.57% and −58.13%, respectively.