Increasing Solution Concentration Research Articles

Biosorption of Triphenyl Methane Dyes (Malachite Green and Crystal Violet) from Aqueous Media by Alfa (Stipa tenacissima L.) Leaf Powder.

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch mode. The effect of experimental parameters such as initial dye concentration (10-40 mg/L), contact time (0-300 min), biosorbent dose (2.5-5.5 g/L), initial pH (2-8), temperature (298-328 K), and ionic strength on dye sorption was investigated. The results of both dyes show that the increase in initial concentration, contact time, temperature, and initial pH of solution leads to an increase in biosorbed quantity, unlike the effect of ionic strength. The biosorption kinetics for triphenylmethane dyes on ALP was analyzed by pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models proposed by the Weber-Morris equation. Equilibrium sorption data were analyzed by six isotherms, namely the Langmuir, Freundlich, Harkins-Jura, Flory-Huggins, Elovich, and Kiselev isotherms. The thermodynamic parameters were evaluated for both dyes. The thermodynamic results suggest that both dyes' biosorption is a typical physical process, spontaneous and endothermic in nature.

Experimental and numerical investigations on damage evolution of concrete under sulfate attack and freeze-thaw cycles

The macro-microstructure tests of concrete under the alternating action of salt freezing (ASF) were conducted to investigate the macro-mechanical properties and microstructure pore evolution patterns of concrete. Combined with CT scanning and 3D pore model reconstructing technologies, we present the evolution equation of concrete porosity and the quantitative relation between the fractal dimension of concrete pores and the macroscopic strength under the ASF. Then, a macro-microscopic damage evolution model of concrete was proposed to study the structural performance evaluation of an aqueduct. The results show that the compressive strength (fc), splitting tensile strength (ft), and relative dynamic modulus (Erd) of concrete specimens under the ASF show a decreasing trend as a whole, and the mechanical properties of concrete gradually decrease with the increase of sulfate solution concentration. With the increase of the cycles of salt freezing alternation, the pore fractal dimension of the concrete gradually decreases and the porosity gradually increases. After the cycle of 8 times, the pore fractal dimension decreases by 6.06%, and the porosity increases by 7.30% compared with the initial state. The porosity of concrete is negatively correlated with the strength, while the fractal dimension of the pore structure is positively correlated with the strength. When the ASF reaches 8 times, the maximum compressive stress and tensile stress of the groove body are 9.48 MPa and 3.13 MPa, respectively, which appear at the ends of the lower chord. The displacements of the bottom and side wall plates are 0.384 mm and 3.289 mm, respectively. The penetrating cracks appear at the junction, and the structure severely deteriorates.

Investigating the impact of flow rate and moisture content for different concentration of liquid desiccant solution

The desiccant air conditioning system consists of two processes, namely cooling and dehumidification, in which the air temperature and humidity are controlled in order to provide comfortable thermal conditions. A typical system includes a dehumidifier, indirect evaporative cooler, and regenerator. The desiccant is selected depending on its ability to absorb water vapor present in the air. In this study, calcium chloride solution was used as a desiccant for the desiccant solution regeneration process, and a flat plate solar collector was employed. Different variables, such as the primary air flow rate, desiccant flow rate, and the concentration of the desiccant solution, were changed during the experiments. The impact of these variables on the performance parameters of the desiccant system such as moisture removal rate, moisture efficiency, enthalpy efficiency, sensible heat ratio, and the mass transfer coefficient was studied. The obtained results revealed that as the solution concentration and the flow rate of primary air increase, the moisture removal rate, sensible heat ratio, and mass transfer coefficient increase. A particular value of inlet primary air flow rate (0.18Kg/s), an increase in the inlet concentration of calcium chloride solution from 0.85 to 0.95 leads to a rise in moisture removal rate, sensible heat ratio, and mass transfer coefficient of (1.1 _1.65) g/s, (0.18-0.25), and (0.01075-0.0123) m/s respectively. While at a certain inlet concentration of a desiccant solution (0.95), increasing the inlet primary air flow rate from 0.1Kg/s to 0.18Kg/s leads to an increase in the moisture removal rate, sensible heat ratio, and mass transfer coefficient o (0.94-1.26) g/s, (0.24-0.26), and(0.0038 -0.011) m/s respectively.

Experimental studies on strength and durability of alkali activated slag and coal bottom ash based geopolymer concrete

This thesis work describes the experimental evaluation of the durability and strength properties of nominally mixed conventional concrete of grade M35, Alkali Activated Slag Based Geopolymer Concrete. Research on Rapid Chloride Permeability Test (RCPT) durability properties has been conducted. Sodium hydroxide (NaOH) and sodium Chloride (NaCl) must be mixed in a 2.5:1 M ratio and at molarities of 12 and 16, respectively, in order to make alkali activators, with dry curing and open-air curing serving as distinct curing regimes. NaOH concentrations of 12 M and 16 M were used to make nine distinct mixes, one of which was designated as the control mix. Then, these mixtures were cured at room temperature in the open air. Prior to the testing day, they were maintained at room temperature after a 24-hour dry curing procedure at 90 °C in a hot air oven. Each of the nine mixes underwent split tensile and flexural strength and durability testing after 90 days. Compressive strength tests are conducted at 28, 56, and 90 days. The results show that tensile strength increases as NaOH solution concentration decreases, but compressive and flexural strength increase as NaOH solution concentration increases. However, it was discovered that the Geopolymer concrete made from Alkali Activated Slag and Coal Bottom Ash (CBA) did not perform well in tests of water fast chloride penetrability because surface cracking predominated. When compared to the results of the control mix, the Alkali Activated Slag and Coal Bottom Ash (CBA)-based geopolymer concrete mix shows a superior improvement in strength measures than standard concrete. At this time, it seems that making geopolymer concrete costs less than regular concrete.

A Mathematical Simulation of Copper and Nickel Ions Separation Using Prepared Nanocellulose Material.

Environmental risks can arise from the existence of heavy metals in wastewater and their land disposal. To address this concern, a mathematical technique is introduced in this article that enables the anticipation of breakthrough curves and the imitation of copper and nickel ion separation onto nanocellulose in a fixed-bed system. The mathematical model is based on mass balances for copper and nickel and partial differential equations for pore diffusion in a fixed bed. The study evaluates the impact of experimental parameters such as bed height and initial concentration on the shape of the breakthrough curves. At 20 °C, the maximum adsorption capacities for copper and nickel ions on nanocellulose were 5.7 mg/g and 5 mg/g, respectively. The breakthrough point decreased with increasing solution concentration at higher bed heights, while at an initial concentration of 20 mg/L, the breakthrough point increased with bed height. The fixed-bed pore diffusion model showed excellent agreement with the experimental data. The use of this mathematical approach can help alleviate the environmental hazards that arise from the presence of heavy metals in wastewater. The study highlights the potential of nanocellulose as a material for membrane technology, which can effectively address these risks.

Study on Compatibility between Complex Mode Micropore Structure and Polymer Solution of Different Formulation for Conglomerate Reservoir

In this paper, the conglomerate reservoir is selected as the object to investigate the micropore structure and the compatibility of polymer solutions. Firstly, the characteristics of complex mode pore structure are analyzed based on casting thin sections, scanning electron microscope, and capillary pressure curve. Then the conglomerate reservoir is divided into five types by use of the K-means clustering algorithm, and the differences in micropore structure among the different reservoir types are also clarified. Secondly, the dynamic light scattering technology is used to directly determine the hydrodynamic diameter of different polymer formulations. As the polymer molecular weight increases, the average hydrodynamic diameter becomes larger, and with the same polymer molecular weight, the average hydrodynamic diameter becomes gradually larger as the solution concentration increases. Based on the above research results, the matching relationship between five reservoir types and polymer solutions is determined through laboratory experiments. The experimental results show that when the polymer molecular weight is determined, the volume of pore volume that can be effectively swept by polymer hydration molecules gradually decreases as the concentration of the solution increases. When the polymer molecular weight and its concentration are both determined, the pore volume of effective displacement of polymer-hydrated molecules also gradually reduces with becoming worse reservoir pore structure. The scope of application of different polymer formulations becomes progressively smaller as the microscopic pore structure of type I to type V reservoirs becomes deteriorated. The compatibility between the micropore structure of different conglomerate reservoir types and polymer solution is determined to provide the geological basis for the reasonable formulation of the polymer flooding scheme.

Determination of the supramolecular arrangement of Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene films fabricated by Physical Vapor Deposition and possible implications for electronic devices

Organic thin films have been used as active layers and are an alternative to inorganic materials in order to improve the performance of electronic devices. Recently, Dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) became an important compound in organic electronics due to its optical and electrical properties, which are dependent on the supramolecular arrangement. Thus, in this work we determined the supramolecular arrangement of organic thin films of DNTT (DNTT PVD films) fabricated by Physical Vapor Deposition (PVD). Ultraviolet-visible absorption spectra showed the controlled growth of the films within the range from 17 to 120 nm and the formation of aggregates (J- and H-), as the H-aggregate was favored by the thickness. The emission spectra revealed that excimers are responsible for the emission in DNTT PVD films and the increase in solution concentration led to the formation of H-aggregates primarily. The molecular organization of the films, determined by selection rules of Fourier Transform Infrared absorption spectroscopy, suggested that the molecules had a preferential chain-on organization for 120 nm thickness film. Complementary, X-Ray Diffraction data showed that DNTT PVD film was practically monocrystalline with monoclinic cell unit, also determined for the 120 nm thickness film. Atomic Force Microscopy measurements revealed that DNTT film had a homogeneous surface (roughness around 6 nm for the film with 120 nm thickness) with grains of uniform size and geometry. Thus, based on the characteristics of the supramolecular arrangement (especially the molecular organization and increase of H-aggregates with the thickness of DNTT PVD film and the results found in the literature), it was possible to analyze probable implications of chain-on molecular organization and the increase of H-aggregates with the film thickness on the mobility of charge carriers of devices, such as diodes and transistors, in which they are applied.

Effects of N-Alkanol Adsorption on Bubble Acceleration and Local Velocities in Solutions of the Homologous Series from Ethanol to N-Decanol

The influence of n-alkanol (C2-C10) water solutions on bubble motion was studied in a wide range of concentrations. Initial bubble acceleration, as well as local, maximal and terminal velocities during motion were studied as a function of motion time. Generally, two types of velocity profiles were observed. For low surface-active alkanols (C2-C4), bubble acceleration and terminal velocities diminished with the increase in solution concentration and adsorption coverage. No maximum velocities were distinguished. The situation is much more complicated for higher surface-active alkanols (C5-C10). In low and medium solution concentrations, bubbles detached from the capillary with acceleration comparable to gravitational acceleration, and profiles of the local velocities showed maxima. The terminal velocity of bubbles decreased with increasing adsorption coverage. The heights and widths of the maximum diminished with increasing solution concentration. Much lower initial acceleration values and no maxima presence were observed in the case of the highest n-alkanol concentrations (C5-C10). Nevertheless, in these solutions, the observed terminal velocities were significantly higher than in the case of bubbles moving in solutions of lower concentration (C2-C4). The observed differences were explained by different states of the adsorption layer in the studied solutions, leading to varying degrees of immobilization of the bubble interface, which generates other hydrodynamic conditions of bubble motion.

Adsorption of Methyl Orange and Amoxicillin from Water using Metal-organic Framework Prepared from Solvothermal Mixing of Zn ions and 1,4-Benzenedicarboxylic Acid Moieties

In this study, we determined the capacity of metal organic framework, which we prepared by the solvothermal mixing of Zn ions and 1,4-benzenedicarboxylic acid (Zn/BDC) moieties to adsorb methyl orange (MO), and amoxicillin (AMX). Results obtained show that MO and AMX adsorption capacity by Zn/BDC (mg/g) was found to increase with increase in solution concentration, for each contaminant type. Three isotherm models were applied to the adsorption data: Freundlich, Langmuir, and Temkin. R2 values obtained for the adsorption of MO, 0.9778, 0.8589 and 0.9038 for Freundlich, Langmuir and Temkin plots respectively, indicates that all three models fit the adsorption data appreciably good, with the Freundlich isotherm providing the best fit. Those for AMX, 0.6737, 0.0616, and 0.5300 indicated a poor fit, but the Freundlich isotherm came out as best fitting isotherm for AMX, an indication of a multilayer adsorption process. Maximum possible amount of contaminant adsorbed per gram of Zn/BDC deduced from the Langmuir isotherm for the adsorption of both contaminants were 93.46 mg/g and 18.41 mg/g for MO and AMX respectively. This, among other indicators, showed the preference of Zn/BDC for MO relative to AMX. Adsorption kinetic models: pseudo first order, pseudo second order, and Weber-Morris intraparticle diffusion models, gave R2 values that indicate that intraparticle diffusion dominated the adsorption of MO, while the adsorption of AMX followed pseudo second order kinetics, an indicator of chemisorptive mechanism. Calculated Qe values, were in close agreement with experimental values.

OBTAINING AND PROPERTIES OF THE IMPLANT FILM MADE WITH CARBOXYMETHYLCELLULOSE CONTAINING SILVER NANOPARTICLES USED FOR TREATMENT OF BURN WOUNDS

This article studies feasibilities of making an implant-film for treatment of burn wound, based on silver nanoparticles (AgNPs) stabilized by sodiumcarboxymethylcellulose (Na-CMC) with degrees of substitution (DS) 0.65-0.90 and polymerization (DP) 200-600 synthesized using a photochemical method. The structural, physical and chemical, and physicalmechanical, burn wound healing properties as well as antimicrobial effects of implant-films containing the Na-CMC and AgNPs have been investigated. The shape, quantity, and size of the AgNPs embedded into the Na-CMC films were determined by UV-Vis spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). It was found that the increase of silver nitrate concentration in solution of Na-CMC followed by photoirradiation leads to changes of AgNPs size and shape. It was found out that Na-CMC films containing AgNPs in the size ranging from 5 to 35 nm had enhanced the microbicide effects and burn wound healing properties within 14 days.

Effect of Different Draw Solutions on Concentration Polarization in a Forward Osmosis Process: Theoretical Modeling and Experimental Validation

Forward osmosis (FO) is a promising membrane technology to promote water sustainability. However, the concentration polarization (CP) effects, including external (ECP) and internal concentration polarization (ICP), are critical issues reducing FO efficiency. In this study, a solution diffusion model was built to investigate the effects of different draw solutions (NaCl, KCl, Na2SO4, and MgCl2) on the intrinsic CP effects, and results were experimentally validated in a laboratory-scale FO system. The modeling results showed a significant loss of a draw solution’s theoretical osmotic pressure (OP) (up to 50–90%) in the CP effects, especially ICP (up to 40–72%). Among the various draw solutes, the solute with fewer ions dissociated (NaCl and KCl), a higher diffusion coefficient, and a low viscosity allowed solutes to diffuse more freely and maintain a higher effective OP with much lower CP. The ECP effects could be mitigated by increasing the flow rate, which improves mixing and reduces the boundary layer. The CP effects, ICP effect particularly, became more prominent when increasing the draw solution concentration. The in-depth analysis of the relationship among ICP, ECP, and water flux confirmed that the increase in draw solution concentration resulted in a significant loss of OP because of the CP effects. Apart from the membrane properties, it is vital to control the CP effects by selecting a draw solution with a greater diffusion coefficient to maintain a higher effective OP.

Enhanced inactivation of Escherichia coli by ultrasound combined with peracetic acid during water disinfection

Peracetic acid (PAA) is a desirable disinfectant for municipal wastewater because of its potent disinfection performance and limited toxic by-products. This study explored the efficiency and mechanism of Escherichia coli inactivation by PAA combined with ultrasound simultaneously (ultrasound + PAA) or (ultrasound → PAA) sequentially. The result showed that 60 kHz ultrasound combined with PAA sequentially (60 kHz → PAA) had excellent inactivation performance on E. coli, up to 4.69-log10. The result also showed that the increase of pH and humic acid concentration in solution significantly reduced the inactivation efficiency of 60 kHz → PAA treatment. We also observed that the increase of temperature was beneficial to the disinfection, while anions (Cl−; HCO3−) had little effect. With 60 kHz → PAA, the PAA and the synergism between PAA and ultrasound played major contribution to the inactivation, which we assumed might be due to both the diffusion of PAA into the cells and the damage to the cytomembrane by ultrasound, as evidenced through the laser confocal microscopy (LSCM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The inactivation mechanism involved the destruction of cell membrane and loss of intracellular material. Empirically, 60 kHz → PAA was found to be effective for the inactivation of E. coli in actual wastewater, and the regrowth potential of E. coli treated by 60 kHz → PAA was significantly lower than that treated only by PAA.

The Characteristics of the Metal-Free and Non-Conjugated Polymer Film with Self-Assembled Nanoparticles.

It is shown in this paper that a polymer, MA-PEG 1000-DGEBA (MP1D), exhibits antireflection, substrate-dependent photoluminescence (SDP), wide band-gap, and photoconduction characterization. MP1D was synthesized from maleic anhydride, polyethylene glycol 1000, and bisphenol-A diglycidyl ether. Self-assembled nanoparticles embedded in MP1D film and ranging from 2.5 to 31.6 nm are observed, which could be expected as scatterers to enhance light trapping and extraction. The size of the nanoparticle increases with the concentration of the MP1D solution. Besides solution concentration, the nanoparticle dimension could be modified by the chain length of polyethylene glycol in the polymer synthesis. The effects of solution concentration, annealing temperature, annealing period, and substrate on the photoluminescence (PL) of MP1D films are examined. Increasing solution concentration increases PL intensity. However, aggregation-caused quenching is explicit as the solution concentration exceeds 100 mM. PL intensity increases with annealing temperature, which could be attributed to crystallinity improvement. PL intensity increases with increasing the annealing period from 0.5 to 2 h. Nonetheless, as the annealing period exceeds 2 h, PL quenching is emerging, which could be due to aggregation. It is expected that MP1D could be a promising candidate for host materials and MP1D film could play a multifunctional role (antireflective and light-trapping functions) in optoelectronics.

The evolution and morphological stability of a particle in a binary alloy melt

The evolution and morphological stability of a particle in a binary alloy melt is re-examined using the asymptotic method. The resulting asymptotic solution of the dynamics model of the particle reveals that the temporal evolution and morphological stability of the particle vary continuously as functions of solute concentration. In particular, (1) the critical nucleation radius of the particle in the binary alloy melt is determined. When solute is rejected from solid phase to liquid phase, the initial concentration increases the critical nucleation radius and depresses the growth velocity of the particle. When solute is incorporated into the solid, the initial concentration decreases the critical nucleation radius. (2) The absolute and relative stability criteria of the particle in the binary alloy melt are shown on the basis of Mullins and Sekerka’s work in the pure melt. The critical stability radii for the absolute and relative stability criteria of the particle in the binary alloy melt are determined. The growth ratio of the critical stability radius to the critical nucleation radius in the binary melt does not exceed that in the pure melt. (3) When the segregation coefficient is less than one, with the growth of the particle, the initial concentration in the binary alloy melt first suppresses and then enhances the morphological stability of the particle. There exists a minimum solute concentration in the binary alloy melt such that when the initial concentration is lower than the minimum solute concentration, the stability of the particle decreases with the increase of solute concentration, whereas when the initial concentration is higher than the minimum solute concentration, the stability of the particle increases with the solute concentration. As the initial concentration increases, the critical stability radius first decreases to the minimum solute concentration at a certain solute concentration, and then increases with the solute concentration. This may control the morphological stability of particles by changing the addition of solute in the alloy melt.

Investigation on the reduction effect of QAs1 on the adhesion force between methane hydrate particles and wall droplets

The adhesion force between methane hydrate particles and wall droplets is an important reference for studying the behavior of hydrate particles accumulating or detaching from the tube wall. In this work, a high pressure visualization microscopic force testing system was built to evaluate the effect of hydrate anti-agglomerants (AAs) in the methane gas phase. It was found that the hydrate adhesion force reached its lowest value at the QAs1 solution concentration of 0.2 wt% (CMC), and the adhesion force was 589.81 mN/m under 1 subcooling condition and 1123.63 mN/m under 10 subcooling condition. It was found that the mechanism of QAs1 in reducing adhesion force under lower levels of subcooling conditions is mainly to reduce the gas–water interfacial tension. The mechanism of action of QAs1 in reducing adhesion force under higher levels of subcooling conditions is mainly due to the steric hindrance effect of QAs1 molecules. The presence of QAs1 molecules on the droplet surface leads to the slowdown of tangential growth of hydrate film and the slowdown of thickening of hydrate film, resulting in a reduction in adhesion force. When the concentration of QAs1 solution is higher than the CMC, the steric hindrance effect of QAs1 molecules is no longer enhanced with the increase of QAs1 solution concentration, while the presence of micelles makes the hydrate easier to nucleate and makes the adhesion force gradually increase. These research data are useful to study the mechanism of action of quaternary ammonium salts as hydrate anti-agglomerants (AAs) and provide a basis for determining the optimal amount of additives for AAs used to prevent hydrate accumulation in natural gas pipelines, and for optimizing hydrate prevention solutions in deep-water gas wells.

Solvent extraction of nickel from iron and cobalt containing sulfate solutions

In this study, solvent extraction is applied for extracting nickel from sulfate solutions containing iron and cobalt ions. This process can also be applied for the cleaning of waste solutions and for increasing solution concentrations after the leaching of low-grade nickel ores. Di-2-Ethylhexyl phosphoric acid (D2EHPA) was used as an extractant for this purpose. Effects of pH, aqueous/organic (A/O) phase ratio, iron, and cobalt ion contents of the solution on nickel extraction efficiency were investigated. The McCabe-Thiele diagrams for extraction and stripping steps were developed to determine the number of stages required. A total of two stages were required for 96.3% of Ni extraction and a total of two stages to strip nickel with 98% efficiency.

Fabrication and Properties of a Hybrid Biocompatible Nanofiber Mesh Constituted of Polycaprolactone and Self-Assembly Peptide

Conventional therapeutic methods for organ and tissue deficiencies include surgical reconstruction, organ transplantation, medical devices treatment, synthetic prosthesis and so on, of which the application is limited when donors exhibit a low availability and impaired organs and tissues cannot well perform their functions. Tissue Engineering (TE) can harmonize with regional organs or tissues, ensure optimal degradation time for novel structure rebirth, facilitate cell adhesiveness, contribute to cell procreation and differentiation in tissue scaffolds, etc., making it an alternative option for treating pathological obstacles. Artificial polymers such as polycaprolactone (PCL) and nature materials such as peptides are adopted for the fabrication of nanofiber scaffolds. The study first engineered porous PCL scaffolds for examining the fiber morphology and the diameter alternations considering the change of single variable condition of the solution concentration, voltage and electrode distance, etc., thereby finding the basic conditions for producing nanofiber scaffolds with good formation. With the increase in solution concentration, the more obvious molecule entanglement can limit the jet stretching, thereby enlarging the fiber diameters. Voltage negatively impacts the fiber diameters, and elevated voltage can strengthen the electric intensity, thereby leading to a complete stretching of cone jets and making fiber diameters thinner. Besides, increased electrode distance is followed by expanded flight distance and decreased electrode intensity (constant voltage), as a result, fibers become narrower. Nanofiber substance exhibits the optimal performance under the condition of solution concentration: 6%, voltage: 50kV, and electrode distance: 150mm. Subsequently, nanofiber scaffolds were fabricated based on the respective preparation of PCL/P11-4 and PCL/P11-8 polymer solutions. Both P11-4 and P11-8 presented uneven distribution in PCL scaffolds, which involved various PCL nanofiber substances with abundant peptides. PCL nanofiber scaffolds saw the breakage of P11-4 and P11-8 fibers.

Effect of Na2SiO3 concentration on corrosion resistance and wear resistance of MAO ceramic film on the Al‐Mg‐Sc alloy

AbstractAlthough Al‐Mg‐Sc alloy was widely applied to aviation aerospace field, they were vulnerable to local corrosion and wear in the process of long‐term service in severe environmental conditions. In this paper, micro‐arc oxidation (MAO) ceramic films on Al‐Mg‐Sc alloy substrate were prepared in electrolyte solutions with different Na2SiO3 concentrations, and the corrosion resistance and wear resistance of the MAO samples were studied. The experimental results of potentiodynamic polarization (PDS) and long‐term immersion tests indicated that the MAO ceramic film prepared in 10 g/L Na2SiO3 electrolyte solution had the best corrosion resistance, as manifested by no obvious cracks, serious collapse and corrosion products on the sample surface and no deep cracks and corrosion paths in the cross‐sectional area. The increase of Na2SiO3 concentration in electrolyte solution also improved the wear resistance of MAO ceramic film, as manifested by low wear depth (10 μm)and width (1 mm) of the MAO ceramic film prepared in 10 g/L Na2SiO3 electrolyte solution against GCr15 steel ball. Studies in mechanisms suggested that as the Na2SiO3 concentration in the electrolyte increased, the MAO ceramic film became denser, which could prevent the penetration of corrosive medium, promote the generation of the anti‐wear layer with SiO2 as the main component to enhance the wear resistance. MAO ceramic film formed in Na2SiO3 electrolyte solution provided good protective performance for Al‐Mg‐Sc alloy in the corrosion and wear conditions, which had a broader application prospect.

Structural analysis of potassium borate solutions.

In this work, H/D isotopic substitution neutron diffraction was combined with empirical potential structure refinement (EPSR) and DFT-based quantum calculations to study the interactions between B(OH)3 boric acid molecules, B(OH)4- metaborate ions, water molecules, and potassium cations in borate solutions. The results show that the solute ions and molecules have a marked effect on the second coordination shell of the water molecules, causing a greater deviation from a tetrahedral structure than is observed for pure water. Potassium ions and trans-B(OH)3 tend to form a monodentate contact ion pair (MCIP) with a K-B distance ∼3.8 Å, which remains constant upon changing the solution concentration. Potassium ions and cis-B(OH)3 form both a MCIP at K-B ∼3.8 Å and a bidentate contact ion pair (BCIP) at K-B ∼3.4 Å. As the solution concentration increases, there is a BCIP to MCIP transformation. Boric acid molecules can undergo hydration in one of three ways: direct hydration, interstitial hydration, and axial hydration. The energetic hydration preference is direct hydration → interstitial hydration → axial hydration. Nine water molecules are required when all water molecules directly interact with the -OH groups of B(OH)4-, and a tenth water molecule is located at an interstitial position. The hydrogen bonding between boric acid molecule/metaborate ion and water molecules is stronger than that between water molecules in the hydration layer.

Mode switching of active droplets in macromolecular solutions.

Typical bodily and environmental fluids encountered by biological swimmers consist of dissolved macromolecules such as proteins or polymers, rendering them even non-Newtonian at times. Active droplets mimic the essential propulsive characteristics of several biological swimmers, and serve as ideal model systems to widen our understanding of their locomotive strategies. Here, we investigate the motion of a micellar solubilization driven active oil droplet in an aqueous medium consisting of polymers as macromolecular solutes. Experiments reveal extreme sensitivity of the droplet motion to the presence of macromolecules in its ambient medium. Through in situ visualization of the self-generated chemical field around the droplet, we notice unexpectedly high diffusivity of the filled micelles in the presence of high molecular weight polymeric solutes. This highlights the breakdown of continuum approximation due to a significant size difference between the macromolecular solutes and the micelles. It is shown that the Péclet number, defined based on the experimentally determined filled micelle diffusivity (taking into account the local solvent viscosity) successfully captures the transition from smooth to jittery propulsion mode for both molecular and macromolecular solutes. With an increase in macromolecular solute concentration, particle image velocimetry reveals another mode switching from the conventional pusher mode to puller mode of propulsion, characterized by a more persistent droplet motion. By doping the ambient medium with suitable choice of macromolecules, our experiments unveil a novel route to orchestrate complex transitions in active droplet propulsion.