Thin Solution Layer Research Articles

A versatile electrochemical cell for in-situ GI-XRD measurements on lab-scale XRD devices

In-situ X-ray diffraction (XRD) cells for electrochemical experiments suffer from strong attenuation of primary and diffracted beams within the electrolyte solution. To reduce the intensity loss of the X-rays, the use of a thin layer of electrolyte solution is an essential element of the conventional cell design. On the other hand, the thin layer electrolyte geometry is a considerable limitation for electrochemical measurements. To overcome these drawbacks a versatile electrochemical cell for in-situ GI-XRD measurements was constructed and used for the electrodeposition of Cu2O thin films on a copper substrate.In this design, a thin copper metal film working electrode is applied on a polyimide foil and then backside-illuminated in GI-XRD geometry. In this way, the XRD pattern is measured from the electrolyte/electrode interface of the working electrode. The X-rays only have to penetrate the polymer foil and the sputtered metal layer, resulting in high-intensity signals.In this work, we demonstrate the abilities of the in-situ cell with quantitative measurements of cathodic deposition of Cu2O thin layers. The results show a good agreement between the diffracted X-ray peak intensities and the calculated and measured thicknesses of the oxide layers. The cell design allows the structural characterization of electrode surfaces during electrochemical measurements without the disadvantages of thin layer cells and therefore does not require high intensity synchrotron radiation to perform X-ray diffraction during electrochemical investigations.

The velocity field behavior and the nature of deposition of microparticles in a thin layer of colloidal solution at wall heating from one and two laser beams

To date, heat transfer, convection and particle deposition have been mainly investigated for the case of homogeneous wall heating. Convection and particle deposition during local heating, when there are one or more local heating sources, have not been practically studied. Experimental studies of free convection and particle deposition in a layer of colloidal solution have been carried out. Convection was created by heating the liquid using one and two laser beams. The colloidal solution consisted of water and microscopic TiO2 particles. The novelty of the work is the demonstration of the effectiveness of local heating in creating high rates of convection and particle deposition at low energy costs. With two-point laser heating, the convection rate is higher than with single-point heating. When using two laser beams, the Marangoni number increases in comparison with single-point laser heating. As a result, the Bo number becomes lower than the critical value and the stability of the velocity field increases. In contrast to single-point heating, the use of two laser beams does not change the vortex flow pattern with increasing layer height. The particle deposition rate is higher when using a single laser beam than when using two beams and is two orders higher than the deposition without convection. An expression linking the deposition rate with time, layer height and fluid velocity is derived. The obtained results on the use of local heating sources are applicable for enhancing convection, as well as in technologies for cleaning solutions from solid impurities.

Electrosynthesis and Microanalysis in Thin Layer: An Electrochemical Pipette for Rapid Electrolysis and Mechanistic Study of Electrochemical Reactions.

Electrochemistry represents unique approaches for the promotion and mechanistic study of chemical reactions and has garnered increasing attention in different areas of chemistry. This expansion necessitates the enhancement of the traditional electrochemical cells that are intrinsically constrained by mass transport limitations. Herein, we present an approach for designing an electrochemical cell by limiting the reaction chamber to a thin layer of solution, comparable to the thickness of the diffusion layer. This thin layer electrode (TLE) provides a modular platform to bypass the constraints of traditional electrolysis cells and perform electrolysis reactions in the timescale of electroanalytical techniques. The utility of the TLE for electrosynthetic applications benchmarked using NHPI-mediated electrochemical C-H functionalization. The application of microscale electrolysis for the study of drug metabolites was showcased by elucidating the oxidation pathways of the paracetamol drug. Moreover, hosting a microelectrode in the TLE, was shown to enable real-time probing of the profiles of redox-active components of these rapid electrosynthesis reactions.

Photochemical Metallization: Advancements in Polypropylene Surface Treatment.

The work was devoted to the development of technology for applying metal coatings to the surface of polypropylene products. At the same time, the main stages of the technology were carried out using the influence of electromagnetic waves of light radiation. So, to obtain an electrically conductive silver layer, after mechanical treatment, etching and activation, the polymer was immersed for several minutes in a solution containing 10-20 g/L of silver nitrate and equivalent amounts of ascorbic acid, and a thin layer of solution was obtained on the surface of the polymer. A sample with such a sorption film was exposed to electromagnetic waves of light radiation at a flux density of 700-1100 W/m2. The small thickness of the sorption film facilitated the penetration of these waves directly onto the polymer surface and ensured the photochemical process of silver reduction with the formation of active centers. At the same time, electromagnetic waves acting on ascorbic acid transferred it to an excited state. As a result, the chemical reduction of silver in the space between the active centers became possible. In this case, the film obtained within 15-20 min had the necessary electrical conductivity. The suitability of these films for galvanic metallization of the polymer surface was shown.

Electrosynthesis and Microanalysis in Thin Layer: An Electrochemical Pipette for Rapid Electrolysis and Mechanistic Study of Electrochemical Reactions

Electrochemistry represents unique approaches for the promotion and mechanistic study of chemical reactions and has garnered increasing attention in different areas of chemistry. This expansion necessitates the enhancement of the traditional electrochemical cells that are intrinsically constrained by mass transport limitations. Herein, we present an approach for designing an electrochemical cell by limiting the reaction chamber to a thin layer of solution, comparable to the thickness of the diffusion layer. This thin layer electrode (TLE) provides a modular platform to bypass the constraints of traditional electrolysis cells and perform electrolysis reactions in the timescale of electroanalytical techniques. The utility of the TLE for electrosynthetic applications benchmarked using NHPI‐mediated electrochemical C‐H functionalization. The application of microscale electrolysis for the study of drug metabolites was showcased by elucidating the oxidation pathways of the paracetamol drug. Moreover, hosting a microelectrode in the TLE, was shown to enable real‐time probing of the profiles of redox‐active components of these rapid electrosynthesis reactions.

Janus Distillation Membrane via Mussel-Inspired Inkjet Printing Modification for Anti-Oil Fouling Membrane Distillation

In this work, inkjet printing technology was used to print a thin layer of a hydrophilic solution containing polydopamine as a binder and polyethyleneimine as a strong hydrophilic agent on a commercial hydrophobic membrane to produce a Janus membrane for membrane distillation. The pristine and modified membranes were tested in a direct-contact membrane distillation system with mineral oil-containing feedwater. The results revealed that an integrated and homogenous hydrophilic layer was printed on the membrane with small intrusions in the pores. The membrane, which contained three layers of inkjet-printed hydrophilic layers, showed a high underwater oil contact angle and a low in-air water contact angle. One-layer inkjet printing was not robust enough, but the triple-layer coated modified membrane maintained its anti-oil fouling performance even for a feed solution containing 70 g/L NaCl and 0.01 v/v% mineral oil concentration with a flux of around 20 L/m2h. This study implies the high potential of the inkjet printing technique as a facile surface modification strategy to improve membrane performance.

Thin-layer solutions to the Helmholtz equation in three dimensions

This paper gives a brief overview of how boundary layer solutions of Helmholtz equation can reveal the structure of planar layers, caustics and foci in three dimensions. In particular, it describes solutions that are localised near straight lines, smooth and cusped caustics and hyperbolic umbilic points as well as solutions localised near smooth prescribed boundaries.

Experimental Investigations and Modeling of Atmospheric Water Generation Using a Desiccant Material

Harvesting atmospheric water by solar regenerated desiccants is a promising water source that is energy-efficient, environmentally clean, and viable. However, the generated amounts of water are still insignificant. Therefore, more intensive fundamental research must be undertaken involving experiments and modeling. This paper describes several experiments, which were conducted to predict and improve the behavior of water absorption/desorption by the Calcium Chloride (CaCl2) desiccant, where the uncertainty did not exceed ±3.5%. The absorption effect in a deep container was studied experimentally and then amplified by pumping air into the solution. The latter measured water absorption/desorption by a thin solution layer under variable ambient conditions. Pumping air inside deep liquid desiccant containers increased the water absorption rate to 3.75% per hour, yet when using a thin layer of the solution, it was found to have increased to 6.5% per hour under the same conditions. The maximum amount of absorbed water and water vapor partial pressure relation was investigated, and the mean absolute error between the proposed formula and measured water content was 6.9%. An empirical formula, a one-dimensional mathematical model, was then developed by coupling three differential equations and compared to experimental data. The mean absolute error of the model was found to be 3.13% and 7.32% for absorption and desorption, respectively. Governing mathematical conservation equations were subsequently formulated. The mathematical and empirical models were combined and solved numerically. Findings obtained from the simulation were compared to experimental data. Additionally, several scenarios were modeled and tested for Jeddah, Saudi Arabia, under various conditions.

Visualization of Coupling Current and Immersion Potential of Iron Surface Corroding Beneath the Ice in the Temperature Cycling under the Freezing Point

A test specimen, comprising 100 iron wires of 1 mmφ diameter arranged in a 10 × 10 matrix, was exposed to temperature cycling between 0°C and −20°C. NaCl solution (0.1 wt%) was dropped on the surface to form an ice droplet, and the coupling current of each iron electrode against the other 99 electrodes was measured sequentially to obtain a coupling current map. The average coupling current of 100 electrodes varied with temperature cycling. The coupling current increased at a relative humidity > 65% in the absence of an ice droplet, which was similar to atmospheric corrosion at a room temperature higher than the freezing point. When an ice droplet exists, the coupling current increased with increasing temperature and did not depend on relative humidity. This behavior was interpreted as the formation of a thin solution layer of concentrated NaCl solution at the interface between the electrode surface and ice due to the exclusion of NaCl from the growing ice crystal of pure water. From the coupling current map, the inner area of the iron electrodes beneath the ice droplet tended to be a cathode, whereas the outer and surrounding area tended to be an anode. An open circuit potential map was also measured using a quasi-Ag/AgCl electrode placed on the specimen surface. The potential of the inner area was less noble than the outer and surrounding areas and shifted in a less noble direction with temperature. The ice droplet shrank during the temperature cycling and left rust on the surface.

Vertical dynamic impedance of a sand-filled nodular pile in saturated soil

A new type of composite pile called a sand-filled nodular (SFN) pile has been increasingly used as a foundation element in the southeast coastal region of China. This paper derives an analytical solution of the vertical dynamic impedance of a SFN pile in saturated soil. The accuracy of the derived solution was verified by degenerating the SFN pile into a general pipe pile. The feasibility of incorporating the thin-layer assumption in Biot theory was then examined and the results suggested that for soft soils with shear modulus less than 5 MPa, the thin-layer solution is sufficiently accurate to estimate the vertical dynamic impedance of a pile in saturated soil. A parametric study was further conducted to provide insight into the influences of pile geometries and sand fill properties on the vertical dynamic impedance of the pile. The results indicated that the pile geometries have considerable influence on the vertical dynamic impedance of SFN piles where pile rib length plays a most significant role.

Increased Sensitivity of Ascorbate Detection by Mediated Oxidation in Confined Electrochemical Cells

AbstractIn this work, the EC’ mechanism involving ascorbate (AA−) and the oxidized form of ferrocenemethanol (FcMeOH) was explored as an analytical strategy to monitor AA− at low concentration levels. The feasibility of this approach was investigated at different mass transport regimes utilizing macro‐ (glassy carbon) and ultramicroelectrodes (5 μm radius carbon disk). Cyclic voltammograms (CV) were recorded in acetate buffer solution (pH 3.7) using a glassy carbon electrode, and an expressive increase in the anodic peak current (and decrease in the cathodic peak) was noticed in the CV in a solution containing both FcMeOH and ascorbate, confirming the presence of an electrocatalytic process (EC’). The current increase was more pronounced when the reactants and products were confined in a thin solution layer, which was created by approaching an ultramicroelectrode close to an insulator surface. At optimized experimental conditions, a correlation between ascorbate concentration and the steady‐state current measured at the ultramicroelectrode was established, allowing the development of an analytical method for ascorbate detection in the micromolar range. The proposed approach was used to quantify ascorbate in a commercial juice sample.

Selective Ion Capturing via Carbon Nanotubes Charging.

We present a phenomenon consisting of the synergistic effects of a capacitive material, such as carbon nanotubes (CNTs), and an ion-selective, thin-layer membrane. CNTs can trigger a charge disbalance and propagate this effect into a thin-layer membrane domain under mildly polarization conditions. With the exceptional selectivity and the fast establishment of new concentration profiles provided by the thin-layer membrane, a selective ion capture from the solution is expected, which is necessarily linked to the charge generation on the CNTs lattice. As a proof-of-concept, we investigated an arrangement based on a layer of CNTs modified with a nanometer-sized, potassium-selective membrane to conform an actuator that is in contact with a thin-layer aqueous solution (thickness of 50 μm). The potassium ion content was fixed in the solution (0.1–10 mM range), and the system was operated for 120 s at −400 mV (with respect to the open circuit potential). A 10-fold decrease from the initial potassium concentration in the thin-layer solution was detected through either a potentiometric potassium-selective sensor or an optode confronted to the actuator system. This work is significant, because it provides empirical evidence for interconnected charge transfer processes in CNT–membrane systems (actuators) that result in controlled ion uptake from the solution, which is monitored by a sensor. One potential application of this concept is the removal of ionic interferences in a sample by means of the actuator to enhance precision of analytical assessments of a charged or neutral target in the sample with the sensor.

Повышение теплотехнической однородности стен из ячеистобетонных блоков

The development of effective protecting structures is currently one of the most popular areas in the construction industry. Masonry made of aerated concrete blocks is used in conditions of ensuring energy efficiency and environmental safety in the construction of civil buildings as enclosing structures. It has high thermal protection properties. The issue of filling through seams of aerated concrete masonry is acute, since adhesive and cement-sand mortars in masonry have low thermal conductivity and are temperature bridges. The authors have developed a two-row energy-efficient wall masonry made of aerated concrete blocks using polyurethane glue as a filler for through and dressing joints. The article discusses the effect of horizontal through joints made of cement-sand mortar and blocking of blocks on the resistance to heat transfer of masonry from aerated concrete blocks. In addition, it presents a study of the reduced resistance to heat transfer of the enclosing structure, taking into account heat-conducting inclusions, presented in the form of a traditional two-row aerated concrete masonry through a row, made on a thin-layer adhesive solution, as well as the masonry developed by the authors. It is concluded that the energy efficiency of the developed wall fencing is ensured due to the increased thermal homogeneity of the masonry.

Effects of a Corrosion Inhibitor on the Corrosion of Steels under Thin Solution Layers

薄い液膜下における鋼の腐食に及ぼす腐食抑制剤（以下「抑制剤」と略記する）の影響を調査した．抑制剤として0.5 mmol L－1モリブデン酸ナトリウムと0.5 mmol L－1乳酸アルミニウムを10 mmol L－1 NaCl溶液に添加して用いた．サイフォン式膜厚制御セルを用いて試料上に1.0～0.2 mmの厚さの液膜を形成し電気化学測定を実施した．動電位分極測定では，拡散限界電流（jlim）及びアノード電流（janode）を測定し，抑制剤添加による変化を調べた．抑制剤添加によるjlimの変化は見られなかったが，janodeは減少したことから用いた抑制剤はアノード反応を抑制することが示された．また，電気化学インピーダンス測定では，溶液に試料を完全に浸漬させた場合と比較して，液膜下においてインピーダンスの挙動が異なることから，液量に応じて抑制剤の保護層の形態が変化することが示唆された．

Numerical simulation and experimental verification of pitting corrosion propagation in sweet pipeline service

This paper has numerically simulated and experimentally verified the pitting corrosion propagation inside a low-alloy carbon steel pipeline for sweet (CO2) petroleum service. In this study, a Finite-Element-Analysis-based mechanistic model was first developed to predict the transient dissolution rate of iron ion (Fe2+) from a pre-existing pit through solving the Nernst-Planck Equation. Specifically, the computational domain combines a hemispherical-shaped pit and a thin laminar boundary layer of an electrolyte solution. The mesh was generated using quadratic triangular elements in the Cartesian Coordinate System, and a moving mesh method was deployed to track the dynamic pitting propagation. The velocity distribution of the electrolyte solution was computed through solving the Navier-Stokes Equations. Distribution of electrochemical potentials was determined based on the Poisson Equation in consideration of electroneutrality whereas a Debye-Hückel approximation was applied to describe the variation of the potentials at the metal-solution interfaces by reason of the existence of the Electrical Double Layer. The distribution of the ionic concentrations of each participating chemical species was obtained through solving Fick’s Second Law. To verify the developed pitting propagation model, a laboratory testing system was established and a series of experimental tests were performed. The results demonstrate that the predicted pitting corrosion growth rates agree well with the experimental observations. The model described herein is able to predict pitting corrosion rates and induction times for the onset of pitting attack or passivation in a given sweet pipeline system set of operating conditions.

Collective motion of self-propelled chemical garden tubes.

In H2O2 solutions, manganese-containing chemical garden tubes can self-propel due to the catalytic production and ejection of oxygen bubbles. Here, we investigate the collective behavior of these self-assembled precipitate tubes. In thin solution layers, the tubes show definite autonomous dynamics with only weak interactions that result from fluid motion around the moving units and directional changes during collisions. In thick solution layers with convex menisci forcing spatial confinement, the tubes undergo cycles of self-assembly and dispersion. This collective motion results from the rhythmic creation of a large master bubble around which the tubes align tangentially.

Bright and Stable Light-Emitting Diodes Based on Perovskite Quantum Dots in Perovskite Matrix.

Light-emitting diodes (LEDs) based on metal halide perovskite quantum dots (QDs) have achieved impressive external quantum efficiencies; however, the lack of surface protection of QDs, combined with efficiency droop, decreases device operating lifetime at brightnesses of interest. The epitaxial incorporation of QDs within a semiconducting shell provides surface passivation and exciton confinement. Achieving this goal in the case of perovskite QDs remains an unsolved challenge in view of the materials' chemical instability. Here, we report perovskite QDs that remain stable in a thin layer of precursor solution of perovskite, and we use strained QDs as nucleation centers to drive the homogeneous crystallization of a perovskite matrix. Type-I band alignment ensures that the QDs are charge acceptors and radiative emitters. The new materials show suppressed Auger bi-excition recombination and bright luminescence at high excitation (600 W cm-2), whereas control materials exhibit severe bleaching. Primary red LEDs based on the new materials show an external quantum efficiency of 18%, and these retain high performance to brightnesses exceeding 4700 cd m-2. The new materials enable LEDs having an operating half-life of 2400 h at an initial luminance of 100 cd m-2, representing a 100-fold enhancement relative to the best primary red perovskite LEDs.

Quartz Transformation into Opal at the Water–Vapor Interface

The kinetics of reactions between minerals and water vapor or two water phases simultaneously (liquid + vapor) is still understood inadequately poorly, and the absence of these data disable realistic and comprehensive quantitative description of the evolution of hydrothermal system after its fluid heterogenizes. To bridge this gap, we have conducted quenching experiments with quartz crystals and water at 300°C and Psat = 86 bar. In addition to usually applied analytical techniques (ICP-AES, SEM, XRD, and optical microscopy), we used 3d scanning of the crystals, measured their surface areas, and plotted the changes in the crystal sizes because of dissolution and deposition reactions. In the experimental runs with the crystal occurring in the vapor phase, the first ever data were acquired on the rate constant of quartz dissolution for saturated water vapor (Psat = 86 bar) at 300°C (2.7 nmol m–2 s–1). The constant turned out to be 630 times lower than that for pure water. Calculations indicate that equilibrium between quartz and water and vapor is established during comparable time spans, but quartz recrystallization in vapor due to the temperature gradient proceeds two orders of magnitude more slowly than in water. In the runs with the crystal occurring in both water and vapor, not only the stable quartz dissolved, but also metastable cristobalite-tridymite opal was formed. The opal was deposited on the autoclave walls and even on the quartz itself above the water surface, and the silica concentration in the water remained remarkably lower that the quartz solubility. The rate of opal formation (10–7.5 mol m–2 s–1) was 3.5 orders of magnitude higher than the quartz recrystallization rate (which is the only process possible in this system according to the traditional geochemical approach). This disagreement is explained within the framework of the distillation hypothesis, which is based on the preferential evaporation of the thin (<100 nm) solution layer at the meniscus edge. The system is found out to be able to evolve according to two scenarios, which result in the scattered and compact opal deposition because of the different ratios of the ascent velocity of the solution film and the evaporation rate. This phenomenon may explain the asymmetry of naturally occurring crystallization cavities, whose lower parts dissolved, and minerals were deposited in the upper parts.

Constructing compatible interface between Li7La3Zr2O12 solid electrolyte and LiCoO2 cathode for stable cycling performances at 4.5 V.

With high theoretical capacity and tap density, LiCoO2 (LCO) cathode has been extensively utilized in lithium-ion batteries (LIBs) for energy storage devices. However, the bottleneck of structural and interfacial instabilities upon cycling severely restricts its practical application at high cut-off voltage. From another perspective, the compatibility between the electrode and electrolyte is highly valued in the development of all-solid-state batteries. Herein, we construct a compatible interface between Li7La3Zr2O12 (LLZO) and LCO through a facile surface modification strategy, which significantly improves the cycling stability of LCO at a high cut-off voltage of 4.5 V. Characterization results demonstrate that the LCO@1.0 LLZO sample delivers a desirable capacity retention of 76.8% even after 1000 cycles at 3.0-4.5 V with the current density of 1 C (1 C = 274 mA g-1). Further investigation indicates that the LLZO modification layer could protect the LCO electrode through effectively alleviating the side reactions, which not only facilitates the Li+ transportation at the interface but also mitigates the bulk structure degradation. Moreover, it is also established that a small amount of La and Zr ions could gradiently migrate into the surface lattice of LCO to generate a thin layer of the surface solid solution Li-Co-La-Zr-O. Thus formed pinning region between surface modified LLZO and LCO cathode could contribute both to their mechanical compatibility and Li+ kinetics behavior upon repeated cycling. This work not only provides a strategy in broadening the operation potential and extracting higher capacity of LCO but also sheds light on constructing compatible interfaces in LIBs, especially for all-solid-state energy storage and conversion devices.

Effect of Layer Thickness and Temperature Difference on Oxygen Diffusion Behavior in Thin Solution Layer Formed on Metal

Effect of Layer Thickness and Temperature Difference on Oxygen Diffusion Behavior in Thin Solution Layer Formed on Metal