Interfacial Phenomena Research Articles

The Effects of Degradation Phenomena of the Steel-Concrete Interface in Reinforced Concrete Structures

Reinforced concrete (RC) constructions are the innovation of sustainable constructions replacing masonry constructions. Despite this, the use of concrete and steel to improve the performance of structural members in service is a recurring problem due to the immediate or overtime appearance of cracks. The objective of this work was therefore to assess the damage phenomena of the steel-concrete interface in order to assess the performance of an RC structure. Samples of approximately 30 cm of reinforcement attacked by rust were taken from broken reinforced concrete columns and beams in order to determine the impact of corrosion on high adhesion steel (HA) and therefore on its ability to resist. The experimental results have shown that the corrosion degradation rates of reinforcing bars of different diameters increase as the diameter of the reinforcing bars decreases: 5% for HA12; 23.75% for HA8 and 50% for HA6. Using the approach proposed by Mangat and Elgalf on the bearing capacity as a function of the progress of the corrosion phenomenon, these rates made it possible to assess the new fracture limits of corroded HA steels. For HA6 respectively HA8 and HA12, their initial limit resistances will decrease by 4/4, 3/4 and 1/4. Based on the results of this study and in order to guarantee their durability, an RC structure can be dimensioned by taking into account the effects of reinforcement corrosion.

Controlled release of microcargo from water-in-liquid crystal emulsions via interfacial shear induced by synthetic microstirrers.

Past studies demonstrated that the microcargo carrying aqueous droplets trapped in LCs through elastic stresses can be triggered to release by applying shear to LC-bulk interfaces. Herein, we report our investigations on the release mechanisms of such microcargo entrapped in aqueous droplets of W-in-LC emulsions via interfacial shear caused by the synthetic micro-stirrer microparticle assemblies of iron oxide particles rotated with a magnetic field. We show that a three fold control over the release rate of the tracer molecules is possible that have initial release rates of 14.3 ± 2.5 μg cm-2 h-1, 26.5 ± 3.4 μg cm-2 h-1, and 46.9 ± 4.6 μg cm-2 h-1 when the rotation of magnetic flux was 250, 500 and 1000 rpm, respectively. We measure the release rates to reduce to 5.4 ± 1.2 μg cm-2 h-1, 6.3 ± 0.7 μg cm-2 h-1, and 20.0 ± 3.2 μg cm-2 h-1 after 60 min of shearing at 250, 500 and 1000 rpm, respectively. We present evidence for the release mechanism resulting in such temporal release profiles that correlate with the magnitude of the shear applied to the interface, interfacial coverage of the microstirrers, and the creaming effect of the aqueous droplets doped with tracers. We also report that the influence of the interfacial density of the microparticles that showed an intermediate areal density is required to achieve a maximized release rate. Additionally, we found evidence of the influence of the droplet charge that critically determines the release. This study highlights the importance of the colloidal and interfacial phenomena in the release profiles of the dispersed droplets present in a LC medium.

Phononic thermal conduction and thermal regulation in low-dimensional micro-nano scale systems: Nonequilibrium statistical physics problems from chip heat dissipation

“Heat death”, namely, overheating, which will deteriorate the function of chips and eventually burn the device and has become an obstacle in the roadmap of the semiconductor industry. Therefore, heat dissipation becomes a key issue in further developing semiconductor. Heat conduction in chips encompasses the intricate dynamics of phonon conduction within one-dimensional, two-dimensional materials, as well as the intricate phonon transport through interfaces. In this paper, the research progress of the complexities of phonon transport on a nano and nanoscale in recent three years, especially the size dependent phonon thermal transport and the relationship between anomalous heat conduction and anomalous diffusion are summarized. Further discussed in this paper is the fundamental question within non-equilibrium statistical physics, particularly the necessary and sufficient condition for a given Hamiltonian whose macroscopic transport behavior obeys Fourier’s law. On the other hand, the methods of engineering the thermal conduction, encompassing nanophononic crystals, nanometamaterials, interfacial phenomena, and phonon condensation are also introduced. In order to comprehensively understand the phononic thermal conduction, a succinct overview of phonon heat transport phenomena, spanning from thermal quantization and the phonon Hall effect to the chiral phonons and their intricate interactions with other carriers is presented. Finally, the challenges and opportunities, and the potential application of phonons in quantum information are also discussed.

Energy landscapes on polymerized liquid crystal interfaces.

We measure and model monolayers of concentrated diffusing colloidal probes interacting with polymerized liquid crystal (PLC) planar surfaces. At topological defects in local nematic director profiles at PLC surfaces, we observe time-averaged two-dimensional particle density profiles of diffusing colloidal probes that closely correlate with spatial variations in PLC optical properties. An inverse Monte Carlo analysis of particle concentration profiles yields two-dimensional PLC interfacial energy landscapes on the kT-scale, which is the inherent scale of many interfacial phenomena (e.g., self-assembly, adsorption, diffusion). Energy landscapes are modelled as the superposition of macromolecular repulsion and van der Waals attraction based on an anisotropic dielectric function obtained from the liquid crystal birefringence. Modelled van der Waals landscapes capture most net energy landscape variations and correlate well with experimental PLC director profiles around defects. Some energy landscape variations near PLC defects indicate either additional local repulsive interactions or possibly the need for more rigorous van der Waals models with complete spectral data. These findings demonstrate direct, sensitive measurements of kT-scale van der Waals energy landscapes at PLC interfacial defects and suggest the ability to design interfacial anisotropic materials and van der Waals energy landscapes for colloidal assembly.

Electrical conductivity and interface phenomena in thin-film heterostructures based on lithium niobate and lithium tantalate

Electrical conductivity and interface phenomena in thin-film heterostructures based on lithium niobate and lithium tantalate

Interface chemistry and displacement of porphyrin macrocycles on semiconductor quantum dot surface

Here, we present comparative experimental data and results of quantum chemical calculations (method MM+) describing electrostatic interactions of positively charged 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin molecules with negatively charged glutathione stabilized core/shell semiconductor quantum dots (QD) AgInS/ZnS leading to the formation of stable QD-porphyrin nanoassemblies in water (pH 7.5) at ambient temperature. Based on steady-state absorption/ photoluminescence, time-resolved experiments (TCSPC), and Raman spectroscopy, interface phenomena and changes in spectral properties for interacting subunits in nanoassemblies are analyzed. Using an elaborated size-consistent quantum chemical atomistic 3D model for glutathione stabilized AgInS/ZnS QD, we propose a detailed physico-chemical mechanism for the interaction of the porphyrin molecule with the QD surface. It includes electrostatic interactions of the positively charged porphyrin free base molecule with negatively charged capping ligand (glutathione), followed by a very fast metalation of porphyrin free base (formation of ligated Zn-porphyrin complex) which is directly fixed on the QD surface. These results highlight the complexity of interface processes in “QDs – porphyrin” nanoassemblies and provide valuable strategies for the detailed analysis of the excitation energy relaxation in the systems under study.

Performance of Rhodamine-Sensitized Solar Cells Fabricated with Silver Nanoparticles

A plasmonic effect of silver nanoparticles (AgNPs) in dye-sensitized solar cells (DSSCs) is studied. In this investigation, the efficiency of dye-sensitized solar cells has been remarkably increased by infusion of synthesized silver nanoparticles into the TiO2 photoanode. Rhodaminederivative RdS1 was synthesized by microwave-assisted condensation of hydrazide and 3-for-mylchromone. The synthesized silver nanoparticles were characterized with UV/Vis absorption spectroscopy and transmission electron microscopy. The interfacial charge transport phenomena of the dye-sensitized solar cell (DSSCs) are determined by electrochemical impedance spectroscopy and the corresponding efficiencies are calculated using current-voltage (I-V) curve. The solar cell photoanode with silver nanoparticles infused with RdS1 in titanium dioxide had the highest solar-to-electric power efficiency at 0.17%.

The Morphology of al Droplet in an Ultrasonic Oscillation Field: Kinetic and Equilibrium Thermodynamic Analysis

Wetting of metal droplet on the solid substrate is a fundamental phenomenon which is applicable to the surface chemistry. When an oscillation field is included in the wetting condition, the wetting process shows significant advancing and receding behaviors. Also, the use of ultrasonic oscillation field is promising in welding. However, some odd morphologies led by the ultrasonic-treatment have shown wetting kinetics which have not been fully investigated. The high frequency ultrasonic vibration brings hysteresis to the contact angle, whose extra energy is attributed by the oscillation field. The ultrasonic wetting process is excited by the 20 kHz frequency periodic oscillation, during which droplet is swaying cyclically. However, after capturing the transformation of droplet morphologies, it is found that the frequency of each swaying cycle is identified to be 180 ms. Theoretical investigations have also quantitively proved that the energy for the contact angle decrease origins from the ultrasonic field, and the wettability is in a great enhancement. Thermal and kinetic effects of ultrasonic are investigated by making theoretical calculations, the 20 kHz ultrasonic field lasting for 5 seconds. Thermodynamics, vibrational mechanics, and interfacial phenomena affect the sonochemistry of wetting.

Oscillating rheological behavior of Turbatrix aceti nematodes

We present an experimental investigation of the rheological aspects of collective motion by the swimming Turbatrix aceti nematodes. We discover that these nematodes can significantly change the rheological properties of the suspension due to their body oscillations and form synchronized waves, which produce strong fluid flows. The strength of the collective state changes the shape of the interface where they swim in synchronization. We unravel that the effective viscosity of the nematode suspension at higher shear rates shows steady viscous behavior with time, where no significant effect of nematode activity is observed. For the first time, we have reported that at low shear rates, the activity effect is significant enough to generate oscillating viscous effects. In addition, we also measured the influence of the nematode concentration on suspension viscosity. This work opens a new way for understanding the rheological aspects of active matter under low and high shear rates. We illustrate these dynamics by showing that the force generated by these nematodes is sufficient to change the suspension rheology. The various aspects of nematodes, especially their large size and ease of culturing, make them a good model organism for experimental investigation as active fibers with oscillations. The oscillating behavior regulates the interfacial phenomenon and produces oscillatory rheological dynamics at low shear rates. The results of our work can be utilized to further study the novel metamaterials with negative viscosity, which have applications in healthcare and energy systems.

Asymmetric membranes for gas separation: interfacial insights and manufacturing.

State-of-the-art gas separation membrane technologies combine the properties of polymers and other materials, such as metal-organic frameworks to yield mixed matrix membranes (MMM). Although, these membranes display an enhanced gas separation performance, when compared to pure polymer membranes; major challenges remain in their structure including, surface defects, uneven filler dispersion and incompatibility of constituting materials. Therefore, to avoid these structural issues posed by today's membrane manufacturing methodologies, we employed electrohydrodynamic emission and solution casting as a hybrid membrane manufacturing method, to produce ZIF-67/cellulose acetate asymmetric membranes with improved gas permeability and selectivity for CO2/N2, CO2/CH4, and O2/N2. Rigorous molecular simulations were used to reveal the key ZIF-67/cellulose acetate interfacial phenomena (e.g., higher density, chain rigidity, etc.) that must be considered when engineering optimum composite membranes. In particular, we demonstrated that the asymmetric configuration effectively leverages these interfacial features to generate membranes superior to MMM. These insights coupled with the proposed manufacturing technique can accelerate the deployment of membranes in sustainable processes such as carbon capture, hydrogen production, and natural gas upgrading.

Возможный способ защиты оптики космических аппаратов от микрометеорной эрозии

There is a huge potential in Russia for the application of space technology in exploration, especially in the oil and gas sector. Images from space are a valuable source of information for geological predictions. How long can optics last in space and provide high-quality images when exposed to a micrometeor shower? The article proposes a new way to protect optical instruments from micrometeor erosion. The method is based on the use of a self-healing surface of a thin layer of a special liquid applied to the surface to be protected. Liquid resistant to solar and cosmic radiation. The implementation of the method is possible due to the physics of interfacial phenomena under microgravity conditions in space. The technical details of the proposal are being discussed.

Active self-assembly of colloidal machines with passive rotational parts via coordination of phoresis and osmosis.

The organization of microscopic objects into specific structures with movable parts is a prerequisite for building sophisticated micromachines with complex functions, as exemplified by their macroscopic counterparts. Here we report the self-assembly of active and passive colloids into micromachinery with passive rotational parts. Depending on the attachment of the active colloid to a substrate, which varies the degrees of free freedom of the assembly, colloidal machines with rich internal rotational dynamics are realized. Energetic analysis reveals that the energy efficiency increases with the degrees of freedom of the machine. The experimental results can be rationalized by the cooperation of phoretic interaction and osmotic flow encoded in the shape of the active colloid, which site-specifically binds and exerts a torque to passive colloids, supported by finite element calculations and mesoscale simulations. Our work offers a new design principle that utilizes nonequilibrium interfacial phenomena for spontaneous construction of multiple-component reconfigurable micromachinery.

Molecular modeling of interfacial properties of the hydrogen + water + decane mixture in three-phase equilibrium.

The understanding of interfacial phenomena between H2 and geofluids is of great importance for underground H2 storage, but requires further study. We report the first investigation on the three-phase fluid mixture containing H2, H2O, and n-C10H22. Molecular dynamics simulation and PC-SAFT density gradient theory are employed to estimate the interfacial properties under various conditions (temperature ranges from 298 to 373 K and pressure is up to around 100 MPa). Our results demonstrate that interfacial tensions (IFTs) of the H2-H2O interface in the H2 + H2O + C10H22 three-phase mixture are smaller than IFTs in the H2 + H2O two-phase mixture. This decrement of IFT can be attributed to C10H22 adsorption in the interface. Importantly, H2 accumulates in the H2O-C10H22 interface in the three-phase systems, which leads to weaker increments of IFT with increasing pressure compared to IFTs in the water + C10H22 two-phase mixture. In addition, the IFTs of the H2-C10H22 interface are hardly influenced by H2O due to the limited amount of H2O dissolved in nonaqueous phases. Nevertheless, positive surface excesses of H2O are seen in the H2-C10H22 interfacial region. Furthermore, the values of the spreading coefficient are mostly negative revealing the presence of the three-phase contact for the H2 + H2O + C10H22 mixture under studied conditions.

First-principles investigation of interface phenomena in hafnium-based metal-insulator-metal diodes.

Metal-insulator-metal (MIM) diodes are very interesting in many different applications exploiting environment-friendly renewable energy solutions. Moreover, since the dimensions of such devices are at the nanoscale, the size and the characteristics of their constitutive elements can drastically influence their macroscale performance. As it could be difficult to describe in detail the physical phenomena occurring among materials in nanoscale systems, in this work first-principles calculations have been used to study the structural and electrical properties of three different hafnium oxide (HfO2)-MIM diodes. These devices have been simulated at the atomistic level by interposing 3 nm of HfO2 between drain and source electrodes made of gold and platinum, respectively. The monoclinic and orthorhombic polymorphs of HfO2 have been considered to model different types of MIM diodes, and the interface geometries have been optimized to compute the current-voltage characteristics, reflecting the tunneling mechanisms occurring in such devices. The calculation of the transmission pathways has also been carried out to investigate the effects of atomistic coordinates despite the use of the same material. The results demonstrate the role of the Miller indices of metals and the influence of the HfO2 polymorphs on the MIM properties. In this study, the importance of interface phenomena on the measurable properties of the proposed devices has been investigated in detail.

Revealing the effect of LiOH on forming a SEI using a Co magnetic “probe”

The effect of LiOH on SEI stability is elucidated systematically. These findings can provide important guidance for SEI design and protection, as well as a reference for the study of complex interface phenomena.

Aerosols and human health – A multiscale problem

Chemical engineering is a scientific discipline that uses physicochemically based quantitative analysis of the momentum, energy, and mass transfer to design and optimize industrial processes. Technical issues are considered on different scales, starting from the molecular interactions, through the nano- and micrometric levels up to the design and control of the full-scale equipment and industrial installations. Such a multi-scale approach is needed to identify the critical factors of any process. In a similar way, chemical engineering can solve problems of physiology and medicine. This paper is focused on pulmonary drug delivery, which needs using a combination of the knowledge of lung physiology with the quantitative description of aerosol generation, multi-phase flow and interfacial phenomena in the respiratory system. The scientific evidence of the effectiveness of this approach has been referred to the extensive studies of the author's research team working in the field of chemical and process engineering.

Macroscopic Supramolecular Assembly of Rigid Building Blocks Facilitated by Layer-By-Layer Assembled Microgel Film

Macroscopic supramolecular assembly (MSA) of building blocks larger than 1 μm provides new methodology for fabrication of functional supramolecular materials and a platform for mechanism investigation of interfacial phenomena. Most reports on MSA are restricted to soft hydrogels, and supramolecular groups can be directly integrated into a hydrogel matrix to generate sufficient attraction for maintaining macroscopic assemblies. For non-hydrogel stiff building blocks, two layer-by-layer modification processes consisting of flexible spacing coating and additional interacting groups are necessary to enable MSA, which is laborious and time-consuming. Approaches for highly efficient MSA based on flexible spacing coating are desired. In this work, MSA of polydimethylsiloxane (PDMS) building blocks is demonstrated by inducing microgel films that serve as both flexible spacing coating and surface functional groups, thus avoiding a two-step LbL modification process. By the varying bilayer number of microgel films, the MSA probability of modified PDMS increases from 54% at 3 bilayers to 100% at 6 bilayers. Control experiments and in situ force measurement strongly support the obtained MSA results and verify the dominant role of the microgel film as a flexible spacing coating and a supramolecularly interactive layer in achieving MSA. Moreover, the underlying mechanism is interpreted as low Young's modulus microgel films rendering surface groups highly mobile to enhance the multivalent interfacial binding. Taken together, this work has demonstrated the feasibility of MSA of rigid building blocks assisted by microgel films as flexible spacing coating and supramolecularly interactive layer simultaneously, which may extend the application fields of microgel materials to interfacial adhesion and advanced manufacturing with MSA methodology.

3D High-Resolution Chemical Characterization of Sputtered Li-Rich NMC811 Thin Films Using TOF-SIMS.

Massive demand for Li-ion batteries stimulates the research of new materials such as high-capacity cathodes, metal anodes, and solid electrolytes, which should ultimately lead to new generations of batteries such as all-solid-state batteries. Such material discovery often requires knowledge on lithium's content and local distribution in complex Li-containing systems, which is a challenging analytical task. The state-of-the-art time-of-flight secondary-ion mass spectrometry (TOF-SIMS) is one of the few chemical analysis techniques allowing for parallel detection of all sample components and representing their distributions in 3D with nanoscale resolution. In this work, we explore the outstanding potential of TOF-SIMS for comprehensive chemical and nano-/micro-structural characterization of novel Li-rich nickel manganese cobalt oxide thin films, which are potential cathode materials for the future generation batteries. Off-stoichiometric thin films of Li- and Ni-rich layered oxide with the composition of LixNi0.8Mn0.1Co0.1O2 (LR-NMC811, x > 1) were deposited using reactive magnetron sputtering. Such thin films do not contain any conductive additives or binders and therefore serve as model 2D systems to investigate compositional fluctuations, surface and interface phenomena, and their aging. TOF-SIMS revealed the presence of 400 ± 100 nm overlithiated grains and 100 ± 30 nm nanoparticles with an increased 7Li16O+ ion content in the buried part of LR-NMC811. The Li-rich agglomerates could potentially serve as Li reservoirs for compensating Li losses during cathode fabrication and cell operation. Interestingly, these sub-micron structures decomposed in time upon exposure to ambient conditions for 30 days.

Obtaining Niobium Nitride on n-GaN by Surface Mediated Nitridation Technique

In this work the n-GaN(1000) surface is used as a source of nitrogen atoms in order to obtain niobium nitride film by a surface-mediated nitridation technique. To this end, the physical vapor deposition of the niobium film on GaN is followed by sample annealing at 1123 K. A thermally induced decomposition of GaN and interfacial mixing phenomena lead to the formation of a niobium nitride compound, which contains Nb from thin film and N atoms from the substrate. The processes allowed the obtaining of ordered NbNx films on GaN. Structural and chemical properties of both the GaN substrate and NbNx films were studied in-situ by surface-sensitive techniques, i.e., X-ray and UV photoelectron spectroscopies (XPS/UPS) and a low-energy electron diffraction (LEED). Then, the NbNx/GaN surface morphology was investigated ex-situ by scanning tunneling microscopy (STM).

Proximity induced moment at Pt/Co interfaces and isolated skyrmion bubble stabilization at zero magnetic field

Magnetic multilayers with heavy metal/ferromagnetic interfaces play an important role in data storage and spintronics due to magnetic phenomena such as perpendicular magnetic anisotropy (PMA) and magnetic skyrmion stabilization. Properties such as saturation magnetization (Ms), PMA, and interfacial Dzyaloshinskii–Moriya interaction (iDMI) can be tuned by stacking engineering to tailor the multilayer magnetic ground state. Here, it is demonstrated that isolated skyrmion bubbles can be stabilized at zero magnetic field in nominally symmetric Pt/Co/Pt multilayers grown by magnetron sputtering. Interface disorder and asymmetry are strongly enhanced as the Co layer is thinned, leading to nonzero iDMI and Pt proximity induced moment (PIM) that affects both the multilayer Ms and PMA. The interplay between PIM and the iDMI is behind the nucleation of skyrmion bubbles, highlighting the importance of controlling the interface phenomena to develop devices for future applications. These results also manifest the importance of considering the PIM to determine the correct magnetic parameters of ultrathin films on the zero-field spin textures stability.