Interfacial Phenomena Research Articles

Origin of the time-dependent corrosion behavior of biodegradable Mg-Si-Zn alloys in simulated body fluid

The corrosion behavior of Mg‐0.6%Si‐2%Zn alloys in simulated body fluid was studied to understand the time-dependent processes and interfacial phenomena. The alloy's microstructure includes Mg-rich dendrites within eutectic microconstituent. Electrochemical responses showed minimal dependence on dendritic-spacing. Initial immersion (12.2-hour) formed a protective layer, indicated by potential elevation, polarization resistance escalation, and changes in Nyquist and Bode plots. However, between 12.2- and 168.4-hour, the protective layer integrity decreased, with observable corrosion. The corrosion mechanism involved protective layer formation followed by cracking induced by Pilling-Bedworth ratio and high H2 evolution kinetics. This time-dependent corrosion resistance resembles both corrosion-resistant and corrosion-sensitive Mg alloys, showcasing challenges in accurate assessment.

3D Printed Drug Delivery Systems in Action-Magnetic Resonance Imaging and Relaxometry for Monitoring Mass Transport Phenomena.

The hypothesis of the study was that (1) 3D printed drug delivery systems (DDS) could be characterized in situ during drug release using NMR/MRI techniques in terms of mass transport phenomena description (interfacial phenomena), particularly for systems dealing with two mobile phases (e.g., water and low molecular weight liquid polymer); (2) consequently, it could be possible to deduce how these interfacial mass transport phenomena influence functional properties of 3D printed DDS. Matrix drug delivery systems, prepared using masked stereolithography (MSLA), containing poly(ethylene glycol) diacrylate (PEGDA) and low molecular weight polyethylene glycol (PEG) with ropinirole hydrochloride (RH) were studied as example formulations. The PEGDA to PEG (mobile phase) concentration ratio influenced drug release. It was reflected in spatiotemporal changes in parametric T2 relaxation time (T2) and amplitude (A) images obtained using magnetic resonance imaging (MRI) and T1-T2 relaxation time correlations obtained using low-field time-domain nuclear magnetic resonance (LF TD NMR) relaxometry during incubation in water. For most of the tested formulations, two signal components related to PEG and water were assessed in the hydrated matrices by MRI relaxometry (parametric T2/A images). The PEG component faded out due to outward PEG diffusion and was gradually replaced by the water component. Both components spatially and temporally changed their parameters, reflecting evolving water-polymer interactions. The study shows that dynamic phenomena related to bidirectional mass transport can be quantified in situ using NMR and MRI techniques to gain insight into drug release mechanisms from 3D printed DDS systems.

Revisiting the mechanism of rapid gas decompression failure in silica-reinforced NBR composites: Effect of interfacial phenomena

Sudden pressure drop in elastomers saturated with high temperature-high pressure gas produces a type of failure known as Rapid Gas Decompression (RGD). Understanding the relationship between the RGD and the material behaviour paves the way for better control of the RGD. It is the aim of the present work to study the effect of rubber-silica interfacial phenomena on the RGD resistance of nitrile butadiene rubber (NBR) composites. By grafting various degrees of a long-chain monofunctional silane onto the silica surface, composites having distinct levels of filler-induced mobility restrictions, and also controlled levels of interface strength were prepared. Also, to find the underlying mechanism responsible for controlling the RGD failure, an analysis of silica morphology, the cavitation strength, and the tear strength was performed for the composites. The RGD resistance was assessed under mild (70 MPa) and severe (cyclic test, 150 MPa) testing conditions using carbon dioxide gas. The obtained trend of the RGD damage was roughly correlated to the cavitation test, showing a higher resistance for the silica system having high filler-polymer interaction and bound rubber. It was suggested that the trend of RGD is more complicated to fully capture by a single physico-mechancial mechanism. Alternatively, inspired by the theory of fracture mechanics, it was suggested that the RGD can be better realized if the factors governing the driving force of RGD damage and the factors responsible for the resistance against the RGD are separated.

Single iron particle combustion - A morphology study of partially oxidized iron particles

In recent years, metal fuels were discussed as a contribution to meeting the challenges of the energy transition to a climate-friendly, sustainable energy economy. One material system with high potential to store and release a large amount of energy is iron powder and its reducible solid product iron oxide powder. In this study, the evolution of the particle morphology during single particle combustion in a laminar flow reactor is analyzed. Partially oxidized iron particles are sampled at different heights above the burner and their internal morphological structure is revealed qualitatively and quantitatively by tomography and microscopy methods (μCT, SEM, EDX, EBSD). The findings show that interfacial phenomena might play a major role when describing single particle combustion as the existence of two liquid phases with emulsification phenomena can be detected. Based on the results, a morphological description of the oxidation progress is proposed within the frame of this work.

Comprehensive Review on the Role of Nanoparticles and Nanofluids in Chemical Enhanced Oil Recovery: Interfacial Phenomenon, Compatibility, Scalability, and Economic Viability

Comprehensive Review on the Role of Nanoparticles and Nanofluids in Chemical Enhanced Oil Recovery: Interfacial Phenomenon, Compatibility, Scalability, and Economic Viability

Xanthan gum modification to surface and interfacial properties between soil‐based matrixes and petroleum oils to minimize soil pollution

AbstractA novel approach exploiting surfaces and interfaces between liquid oils and porous soil media was used to investigate the role of xanthan gum (XG) in minimizing the spread of petroleum oil spills on land. 1.6 wt% XG added to soil‐based mixture matrixes (topsoil, sand, clay, and moisture) resulted in a 50% reduction in oil spreading area at 0 and 5 wt% moisture content, at 1.3 cm depth of soil matrix. Also recorded was a 45% increase in time taken for the low‐ and medium‐viscosity oils to penetrate this soil depth. XG alters the surface energy and roughness of the soil matrixes, which additionally contributes to a reduction in oil spreading capabilities. Interfacial phenomena between individual oil droplets and soil matrixes demonstrated variable findings of droplet spreading and penetration with XG, depending upon the heterogeneity of the soil matrix itself. XG assisted a reduced lateral spread in heterogeneous soil matrixes and a reduced vertical penetration in clay‐based matrixes. These interfacial results highlighted the often‐observed differing transport phenomena at the interface compared with the bulk. This initial study demonstrates a novel approach to incorporate surface energy phenomena into the suite of soil remediation efforts by introducing natural biopolymers in high‐risk land oil‐spill areas to slow oil contaminant spread. Future studies will further characterize the benefits of XG in containing oil flow.

Marangoni flows triggered by cationic-anionic surfactant complexation

HypothesisThe gradients in surfactant distribution at a fluid-fluid interface can induce fluid flow known as the Marangoni flow. Fluid interfaces found in biological and environmental systems are seldom clean, where mixtures of various surfactants are present. The presence of multi-component surfactant mixtures introduces the possibility of interactions among constituents, which may impact Marangoni flows and alter flow dynamics. ExperimentsWe employed flow visualization, surface tension and reaction kinetic measurements, and numerical simulations to quantitatively investigate the Marangoni flows induced by the reacting surfactant mixtures. Different binary surfactant mixtures were utilized for comparative analysis. FindingsThe impact of surfactant interactions on Marangoni flows is confirmed through the observation of diverse complex flow patterns that result from the combination of oppositely charged surfactants in varying composition ratios and concentrations. Unique flow patterns originate from the composition-dependent interfacial phenomena upon mixing surfactants. Our findings provide vital insights that could be used to guide the development of effective oil remediation or the spreading of waterborne pathogens in contaminated regions.

The interface between ice and alcohols analyzed by atomic force microscopy.

This study investigates the interface between ice and organic solvents using atomic force microscopy (AFM). Atomically flat ice surfaces were prepared and observed by AFM in 1-octanol, 1-hexanol, and 1-butanol. The results show differences in surface roughness influenced by the interaction of ice and alcohols. Young's modulus of ice was analyzed by force curve measurements, providing valuable insights into the properties of ice in liquid environments. The results showed the characteristics of the ice surface in different solvents, suggesting potential applications in understanding surface and interface phenomena associated with ice under realistic conditions.

Enhanced comprehension of the cross-scale forming mechanism in CF/PEEK resistance welding: Analysis of temperature gradients and meso–microscopic phase transitions

Resistance welding technology is an effective solution for connecting thermoplastic composites. However, limited research on non-uniform distribution of interfacial temperature and complex evolution mechanism of phase-change molding hinders its application. This reliance on traditional experimental and trial-and-error methods severely impedes its development. Therefore, this study employed a novel cross-scale numerical simulation method, being applied for the first time in the field of resistance welding for elucidating the underlying mechanism of joint formation through multi-component phase transformation. The constructed model accurately represented the transient heat transfer of a realistic wire mesh structure in three dimensions, while incorporating complex gradient effects arising from both spatial and temporal variations in heating element temperature due to air interference. Further, melting, flow, and consolidation behavior of the resin matrix in resistance welding of carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composite was investigated herein at a mesoscopic scale. To accomplish this objective, a three-phase flow spatial forming and evolution model for resistance welding was developed at the mesoscopic scale by integrating principles from fluid dynamics. Interestingly, introduction of an air phase reinstated the spatial voids formation and flow in resistance welding, providing robust evidence for the initiation mechanism of internal defects. Moreover, this study revealed variations in the melting mode of PEEK resin across different regions within the weld and highlighted distinct distributions of voids resulting from uneven heat transfer. The interfacial phenomenon and flow diffusion mechanism between components in resistance welding tests were further verified and discussed through analyzing scanning electron microscopy and energy dispersive spectroscopy results. Temporal and spatial correlation in void distribution within the welding zone was observed, which was found to be consistent with simulation results. Specifically, with the progress of the welding process, air near the wire mesh gradually dispersed into the laminate, with significantly more voids at weld seam edges than in central regions. This research methodology based on stepwise scale reduction offers a promising avenue for investigating resistance welding and other connection forming applications, in particular, within the context of engineering underlying logical behavior.

Insight into material behavior via surface free energy calculations for common energetic materials

AbstractThe Gibbs Free energy is a driving force for equilibrium crystal shapes and the formation of crystal facets in molecular crystals. Orientation dependence of interfacial properties is linked to surface free energy (SFE). Prediction of orientation‐dependent properties such as thermal stability, mechanical response, and compatibility with binders require a systematic approach to the quantification of SFE. In molecular crystals, entropy has a much larger contribution among all ordered crystalline materials. In this paper, we extend our previously developed method to quantify SFE and entropy of β‐HMX to other common energetic materials–TATB, α‐RDX, and PETN. Two complimentary approaches, Nonequilibrium Thermodynamic Integration (NETI) and Steered Molecular Dynamics (SMD) methods are used to obtain insight into interfacial phenomena along with surface free energy estimates. We discuss the relevance of surface free energy and the importance of surface entropy for facetted molecular crystals in understanding crystal properties, activation of slip planes, and potential pathways for fracture. These values allow us to predict theoretical crystal shape using Wulff Construction, better understand the effect of hydrogen bonding on SFE, and the diversity of bonding environment in energetic crystals. In particular, in crystals with low stacking fault energy, the SMD values can be inconclusive due to the triggering of slip plane motions. In cases where SMD simulations lead to large deformations and high uncertainty, the NETI approach can still provide SFE estimates.

Crude oil displacement enhanced by interfacially active nanoparticles and their coupling effect with low-salinity brines

From the microscopic scale to the petroleum-reservoir scale, the interfacial phenomena of a crude oil–water-rock system crucially control immiscible flow in a porous reservoir. One of the key mechanisms is crude oil droplet displacement dynamics, which can be optimized by manipulating the oil–water interfacial tension and the three-phase contact angle by means of chemical injection. Oil film displacement was enhanced by adding interfacially active nanoparticles, namely poly(N-isopropylacrylamide) or pNIPAM (43–48 nm hydrodynamic diameter and 0.0005–0.0050 wt% concentration range), accelerating the oil droplet receding rate (up to 5.66°/s) and greater degree of oil film dewetting (37.0° contact angle). Such behavior was attributed to nanoparticle-induced structural disjoining pressure between the oil–water and water–solid interfaces. The coupling effect of pNIPAM nanoparticles with low-salinity brines was studied, revealing discrepancy in different valency brines. Coupling with divalent CaCl2 led to much slower oil droplet receding dynamics (2.58°/s, and 58.7° contact angle) since oil-substrate bridging is formulated and promoted by the divalent cation. However, a positive synergy was observed with a monovalent NaCl blend. The crude oil dewetting dynamics were enhanced (9.55°/s) owing to the combined salt-induced hydration and nanoparticle-induced structural forces. The contact angle reduced to 21.5° before eventually detaching from the substrate after a relatively short period (156 s). These findings highlight the coupling effects of nanoparticles and low-salinity brine to enhance dewetting of heavy crude oil. Adding nanoparticles to an ‘optimal’ brine could be an option for faster and greater fluid displacement, which is not limited to oil production applications but several others, such as detergency and other forms of geological storage.

Understanding of Lanthanide-Doped Core-Shell Structure at the Nanoscale Level.

The groundbreaking development of lanthanide-doped core-shell nanostructures have successfully achieved precise optical tuning of rare-earth nanocrystals, leading to significant improvements in energy transfer efficiency and facilitating multifunctional integration. Exploring the atomic-level structural, physical, and optical properties of rare-earth core-shell nanocrystals is essential for advancing our understanding of their fundamental principles and driving the development of emerging applications. However, our knowledge of the atomic-level structural details of rare-earth nanocrystal core-shell structures remains limited. This review provides a comprehensive discussion of synthesis strategies, characterization techniques, interfacial ion-mixing phenomena, strain effects, and spectral modulation in core-shell structures of rare-earth-doped nanocrystals. Additionally, we prospectively discuss the challenges encountered in studying the fine structures of rare-earth-doped core-shell nanocrystals, particularly the increasing demand for researchers to integrate interdisciplinary knowledge and utilize high-end precision instruments.

Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques

Diffuse soft matter interfaces take many forms, from end-tethered polymer brushes or adsorbed surfactants to self-assembled layers of lipids. These interfaces play crucial roles across a multitude of fields, including materials science, biophysics, and nanotechnology. Understanding the nanostructure and properties of these interfaces is fundamental for optimising their performance and designing novel functional materials. In recent years, reflectometry techniques, in particular neutron reflectometry, have emerged as powerful tools for elucidating the intricate nanostructure of soft matter interfaces with remarkable precision and depth. This review provides an overview of selected recent developments in reflectometry and their applications for illuminating the nanostructure of diffuse interfaces. We explore various principles and methods of neutron and X-ray reflectometry, as well as ellipsometry, and discuss advances in their experimental setups and data analysis approaches. Improvements to experimental neutron reflectometry methods have enabled greater time resolution in kinetic measurements and elucidation of diffuse structure under shear or confinement, while innovation in analysis protocols has significantly reduced data processing times, facilitated co-refinement of reflectometry data from multiple instruments and provided greater-than-ever confidence in proposed structural models. Furthermore, we highlight some significant research findings enabled by these techniques, revealing the organisation, dynamics, and interfacial phenomena at the nanoscale. We also discuss future directions and potential advancements in reflectometry techniques. By shedding light on the nanostructure of diffuse interfaces, reflectometry techniques enable the rational design and tailoring of interfaces with enhanced properties and functionalities.

A Hydridoaluminate Additive Producing a Protective Coating on Ni‐Rich Cathode Materials in Lithium‐Ion Batteries

AbstractTo enhance the energy density of Li‐ion batteries, high‐capacity and high‐voltage cathode materials are needed. Recently, Ni‐rich layered oxides have attracted attention as they can offer ≈200 mAh g−1 when cycled up to 4.3 V. However, cycling these materials in their full capacity range often leads to excessive reactivity with the electrolyte, resulting in particle cracking, transition metal dissolution, and oxygen loss. In this study, the use of lithium hydridoaluminates as electrolyte additives is explored for lithium‐ion batteries based on nickel‐rich cathode materials. Being mild reducing agents, these additives act as HF scavengers, avoiding transition metal dissolution from the cathode. Additionally, their oxidation results in the formation of an Al‐rich protective layer on the cathode, which dampens the surface reactivity, preventing surface reconstruction and impedance build‐up. This study further stresses the important role of the cathode‐electrolyte interface phenomena on the capacity degradation of Ni‐rich cathode materials and provides a novel avenue for controlling this reactivity, thus extending their cycling life.

Mo–Si Alloys Studied by Atomistic Computer Simulations Using a Novel Machine‐Learning Interatomic Potential: Thermodynamics and Interface Phenomena

Mo–Si Alloys Studied by Atomistic Computer Simulations Using a Novel Machine‐Learning Interatomic Potential: Thermodynamics and Interface Phenomena

Correction to “A correlation between morphology and mechanical performance of injected‐molded PE/EVA/clay nanocomposites: Insight into phase miscibility and interfacial phenomena”

Correction to “A correlation between morphology and mechanical performance of injected‐molded <scp>PE</scp>/<scp>EVA</scp>/clay nanocomposites: Insight into phase miscibility and interfacial phenomena”

High-efficient acetylene synthesis by selective electrochemical formation of CO2-derived CaC2

Acetylene can be used as feedstock for various chemical products, but its raw material has been a fossil fuel, which poses an environmental challenge. One way to address the challenge is to form CaC2 from CO2, which reacts with water to form acetylene. This study demonstrated the selective formation of CaC2 from CO2 by an electrochemical process in NaCl-KCl-CaCl2-CaO melt at 823 K to produce C2H2 with high current efficiency. The CaC2 was formed through two reactions: the carbon electrodeposition from CO2-derived CO32− (Step 1) and the electrochemical reduction of Ca(II) ion on the carbon (Step 2). These two reactions could be controlled by conducting potentiostatic electrolysis under CO2 and Ar atmospheres, resulting in acetylene synthesis with a maximum current efficiency of 92 %. Each electrochemical reaction agreed with the thermodynamic electrode potential. The electrolysis on carbon electrodes revealed that the higher the crystallinity of carbon, the more selectively CaC2 was formed. The CaC2 formation was induced by the reduction of Ca(II) ions on the basal plane of the graphite layer rather than the edge plane. The unique interfacial phenomenon between high-temperature melt and a carbon electrode surface will contribute to realizing a highly efficient CO2 conversion process to acetylene.

Wettability of molten CaO-Al2O3-MgO slag on some refractory materials at 1773K

The interface characteristic of molten slag has an important effect on the interface phenomenon and reaction between molten slag and molten metal/refractory. The wettability of molten CaO-MgO-Al2O3 slag on some refractory materials (including Mo, graphite, boron nitride (BN), MgO and Al2O3) was studied in argon atmosphere at 1773 K. The contact angle between molten slag and substrate material was measured by the sessile drop method; the interfacial tension and work of adhesion were calculated by Young equation and Young-Dupré equation, respectively. The results showed that, except for graphite, the molten slag can well wet these materials, and the contact angle decreases with increasing temperature and eventually converges to a stable equilibrium value. The interfacial tension of different substrate materials is very different, and the interfacial tension between the slag and reactive substrate MgO, Al2O3 and graphite is small, ranging from 71 to 205 mN/m. The molten slag-Mo of the non-reactive substrate is 1323 mN/m and the molten slag-BN is 7297 mN/m. The adhesion work between molten slag and substrate is in the range of 800–1100 mJm−2 except graphite, which is 400 mJm−2.

Activated carbon-reinforced polyurethane composite foams with hierarchical porosity for broadband sound absorption

The generation of various noise has caused severe noise pollution issues across a wide frequency spectrum, urgently requiring the development of sound-absorbing materials. Herein, we introduce composite polyurethane (PU) foams incorporating extremely nanoporous activated carbon (AC) including both meso- and macro-sized pores as an eco-friendly sound-absorbing material with superior and broadband sound absorption capabilities. The composite foam absorbs 95.8 % of the incident acoustic waves in the 2,000–5,000 Hz frequency range, i.e., the most sensitive range for the human auditory system, far outperforming pristine PU foam, which absorbs only 70.6 %. We demonstrate that sound absorption properties can be fine-tuned by adjusting the pore type and content of the AC. Significantly, the optimized composite foam structure absorbs 100 % of the incident waves at a specific frequency of 2,550 Hz. Collectively, we propose a master curve for the sound absorption properties derived from various composite foams, demonstrating that the properties can be precisely predictable and subsequently used for designing the pore characteristics and content of AC. Incorporating AC can also improve the mechanical properties of foams through interfacial adhesion phenomena. Our methodology provides valuable insights into the fabrication of composite foams with tunable sound absorption properties as a promising solution to noise pollution.

Quasi-operando Transmission Electron Microscopy Diagnostics for Electrocatalytic Processes in Liquids.

The need to relate the mechano-physico-chemical phenomena in liquid-based electrocatalysts to the stages of start-up, operation, and shut-down phases is one of the major challenges that the energy community is facing. Understanding these phenomena will pave the way for the tailor-made design of efficient, commercially viable electrocatalytic systems. Transmission electron microscopy plays an important role in the investigation of local electrocatalytic effects, complementing other operando characterization techniques. Herein, after attempting to define the meaning of operando methodologies in relation to electron microscopy studies, the progress in the field is reviewed in terms of the knowledge gained about the catalysts, the solid-liquid interfaces, and the solid-liquid-gas interfacial phenomena for several electrocatalytic reactions. Finally, the parameters that require consideration in operando ec-LPTEM studies of electrocatalytic systems are discussed.