NaCl Aqueous Solution Research Articles

Thermodynamic characterization of aqueous solutions of NaCl, KCl, MgCl2 and CaCl2: volumetric, acoustic, viscometric and computational analysis

The volumetric and acoustic properties of alkali and alkaline earth metal salts are ubiquitous in numerous biological and non-biological processes and accurate formulation of their thermophysical properties is a fundamental prerequisite for complete exploration of their diverse applications. To meet this purpose, in this investigation, we herewith report the systematic data of densities ρ, speed of sound u and viscosity η of aqueous binary solutions of the prominent alkali and alkaline earth metal salts viz. NaCl, KCl, MgCl2, and CaCl2 at seven different temperatures T = (288.15–318.15 K) and ambient pressure over the wide concentration range of (0.002–1) mol∙kg−1.These experimental data have been further employed to obtain some important thermodynamic parameters, viz, the apparent molar volume of solute Vϕ, limiting apparent molar volume of solute Vϕ0, isentropic compressibility of solution κS, apparent molar isentropic compression of the solute KS,ϕ, limiting apparent molar isentropic compression of solute KS,ϕ0 and apparent molar expansibility Eϕ0. Further, the coefficient of thermal expansion α*, the second-order derivative of limiting apparent molar volume ∂2Vϕ0/∂T2, Jones-Dole equation viscosity A, B, D coefficients, temperature derivative of B coefficient i.e. dB/dT, activation parameters for viscous flow and hydration number nH have also been computed. The results obtained have been used to elucidate different interactions taking place in the aqueous electrolytic solutions. To corroborate the experimental results, quantum chemical calculations were performed using density functional theory (DFT) by Gaussian software package. The calculations included an analysis of molecular orbitals, with particular emphasis on the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Tribocorrosion behaviors of VNbMoTaWCr high entropy alloy coatings

In this work, four BCC-structured VNbMoTaW and VNbMoTaWCr high entropy alloy (HEA) coatings with different Cr contents were fabricated on the surface of 304 stainless steel (304SS) plates by a pulsed DC magnetron sputtering system. In addition to the dry pin-on-disk wear test and pure corrosion test, two kinds of tribocorrosion tests were performed. For the tribocorrosion test without applied potential, the HEA coatings were immersed in a 3.5 wt% NaCl aqueous solution at room temperature under 1 N load using a pin-on-disk tribometer. For the tribocorrosion test with applied potentials, the potentiodynamic polarization test was conducted to investigate the effects of external potentials and sliding loads on the corrosion current density, polarization resistance, and wear rates of HEA coatings. The hardness, corrosion resistance, and tribocorrosion (without applied potential) resistance of VNbMoTaWCr HEA coatings increased with increasing Cr content. The VNbMoTaWCr coatings with higher than 24.7 at.% Cr had a high hardness of 16.4 to 16.5 GPa and excellent corrosion resistance in pure corrosion and tribocorrosion without applied potential. On the other hand, as the tribocorrosion was executed with an applied potential higher than the breakdown potential and high current density, the tribocorrosion resistance of HEA coatings was greatly influenced by its protection degradation ratio, Pdr (the polarization resistance ratio between pure corrosion and tribocorrosion setup 2). Finally, the lowest wear rate of 2.55 × 10−5 mm3N−1 m−1, which was 1.4 times better than 304SS, was obtained for the VNbMoTaWCr coating containing 11.65 at.% Cr after the tribocorrosion test with applied high potential because of its lower Pdr value and less decay of corrosion protection ability.

Hydrogen generation by hydrolysis of ultrafine microstructure Mg[sbnd]10Ni alloy wire

This work presents a MgNi alloy wire prepared by a combination of extrusion and multi-pass hot drawing for fast hydrogen generation from aqueous NaCl solution. The results showed that the hydrogen generation rates of the wire were significantly improved compared to the as-cast alloy. The hydrolysis of the MgNi alloy wire produced 820 ml g−1 hydrogen in 16 min and the maximum hydrogen generation rates reached 67.86 ml g−1 min−1 in 3.5 % NaCl solution and at 25 °C. The improved hydrogen production properties can be attributed to the increase in specific surface area and the ultrafine microstructure with highly dispersed submicron Mg2Ni particles of the MgNi alloy wire.

Corrosion Resistance of Fe-Cr-Al Intermetallic Coatings Obtained by Aluminizing

The growing interest in intermetallic and metal–intermetallic materials and coatings is based on the number of favorable properties they possess, primarily mechanical. However, the lack of data on their corrosion resistance has largely limited their scope of application. In this study, the corrosion destruction mechanisms of coatings formed on substrates made of AISI 321 steel and Aluchrom W (fechralloy) were investigated. The coatings were created by alloying in an aluminum melt followed by diffusion annealing to form the ultimate intermetallic structure. Corrosion resistance was studied under cyclic exposure to a humid marine atmosphere simulator and potentiostatic tests in an aqueous NaCl solution. Corrosion destruction parameters were determined, and mechanisms for each type of coating were revealed. The conducted studies allowed us to determine the electrochemical parameters of the corrosion destruction process and its mechanisms. It was shown that the corrosion rates during potentiostating for coatings on substrates Cr15Al5 and 12Cr18Ni10Ti differed by almost twofold. Two different mechanisms of corrosion are proposed. The first is associated with the formation of Al2O3 and MgO oxide films, which at the initial stage protect only local areas of the coating surface on Cr15Al5. The second is determined by the diffusion of titanium atoms during annealing to the coating surface on a 12Cr18Ni10Ti steel substrate with the formation of TiC carbide at the grain boundaries.

Morphological and biochemical variations caused by salinity stress in some varieties of Pennisetum glaucum L.

The salinity of the soil is a severe challenge to the sustainability of agricultural production. It causes significant loss in the productivity of crop plants. To overcome this problem, one of the possible solutions could be the identification and cultivation of salinity tolerant crop plants in salt affected land. Therefore, this study was designed to screen some varieties of Pearl Millet (Pennisetum glaucum L. Family Poaceae), an equally important cereal crop for food and forage, for salinity tolerance in a pot experiment. Some eighteen varieties of Pearl Millet were utilized to investigate the morphometric and biochemical variations induced by saline stress. The plants were grown for three weeks under normal conditions in sand culture in disposable PVP cups with three inches diameter. Afterwards, the plants were challenged with salinity stress (aqueous solution of NaCl applied in successive steps of 50, 100, 150 and 200 mM with Hoagland’s nutrients). The plants adopted salinity stress after one week and harvested for various physio-biochemical attributes. The results showed that the varieties YBS-93, YBS-94, YBS-95 and YDR-8-1 exhibited tolerance toward salinity stress as their shoot length, root length, biomass production and K+ was maintained under salt stress. The levels of proline contents and free amino acids in their leaves were relatively higher under salt stress as compared with other varieties. The accumulation of Na+ in theses varieties was lower as compared to other varieties under saline stress. These findings indicated their potential strategy to cope with salinity stress. While theYBS-83, YBS-98, YCMP-19 and YCMP-34 varieties among the subjected eighteen varieties of Pearl Millet were screened as most sensitive varieties to salinity stress in these experimental conditions. Because these varieties had reduction in shoot length, root length biomass production and K+. Other varieties did not show any significant success in salinity stress management. This study has provided significant preliminary screening data of morphological and biochemical aspects of eighteen varieties of Pearl Millet for their capability of salinity tolerance. Further molecular investigations are underway which will be helpful in revealing insights of the salt tolerance mechanism and signaling pathways in the screened salt tolerant varieties.

Impact of Ionic Strength and Charge Density on Donnan Potential in the NaCl-Cation Exchange Membrane System

This work aims to theoretically investigate the effect of both the fixed charge density of ion exchange membranes and the ionic strength of the treated aqueous NaCl solution on the generated Donnan potential at thermodynamic equilibrium conditions. The direct objective of our work is to calculate the equilibrium concentration of the Cl− co-ion inside a swelled cation-exchange membrane equilibrated with a water/NaCl system. Two activity coefficient models are employed, i.e., the Debye–Huckel (DH) model (as a reference model) and the Meissner model, which is known for its applicability in treating concentrated solutions. Experimental data available in the literature for Donnan potential are used to verify model predictions. Our study confirms that a high fixed charge density is required to counterbalance the deterioration in membrane selectivity encountered in high-salinity systems. The DH model can be safely used to predict the Donnan potential for feed compositions up to 0.1 M. At higher compositions, the DH model significantly overestimates the predicted (absolute) Donnan potential compared to the Meissner model. The osmotic pressure resulting from the difference in ionic concentration between the membrane phase and the feed phase is found to have insignificant effects on the Donnan potential. The equilibrium computations and methodology are presented in a general way that enables handling multivalent electrolyte systems such as CaCl2.

Enhancing Surface Integrity of Micro-Holes Machined on Inconel 718 using Shaped Tube Electrochemical Machining via Hydroxide Mixing

This research explores enhancing surface integrity of high aspect ratio (AR>5) micro-holes machined on Inconel 718 using Shaped Tube Electrochemical Machining (STEM) by mixing limited amount of metal hydroxides in the different electrolyte solutions. Typically, STEM employs hazardous acid solutions. These solutions cause machine corrosion, environmental risks, and harm to operators. This research aims to explore eco-friendly and safe alternatives. The efficacy of adding NaOH or KOH to eco-friendly neutral aqueous solutions of NaCl, KBr, and NaNO3 on machined surfaces is expounded. We assess electrolyte mixing parameters, including concentration and composition, and explore the effects of varying electrolyte temperature, voltage, and tool feed rate. Surface assessment uses SEM, EDX, XRD, and profilometry. Results reveal that adding hydroxides to neutral salt solutions improves surface roughness and reduces pitting. Hydroxide ions aid in dissolving oxide films during STEM of Inconel 718. Under specific conditions (9 g l−1, 18°C, 8 V, 0.8 mm min−1), NO3│OH yielded the lowest Ra (1.64 μm), while Br│OH resulted in the highest Ra (2.14 μm) with pitting, cracks, and deposits. NO3│OH exhibited a 25% decrease in Ra when a hydroxide concentration rise from 3 g l−1 to 15 g l−1. This research supports eco-friendly STEM for improved surface quality without process performance compromise.

Pre-oxidized ultramicroporous carbon cloth with ultrahigh volumetric capacity and ultralong lifespan for capacitive desalination

Capacitive deionization is a promising desalination technique to tackle with freshwater scarcity, due to its facile, energy-efficient and eco-friendly operation. Carbon materials are primary electrode materials in capacitive deionization devices; however, their practical applications are limited by the low salt adsorption capacity and poor cycling stability. Here, we report a pre-oxidized strategy to significantly improve the salt adsorption capacity and cycling lifespan of carbon clothes. By the simple pre-oxidation treatment, it creates abundant ultramicropores and a superhydrophilic surface, which lead to a high salt adsorption capacity (31.5 mg g−1 and 13 mg cm−3) in 0.01 M NaCl aqueous solution. Moreover, the surface of each carbon fiber is oxidized, combined with a high mechanical strength, resulting in a stable surface during the cycling process. The retention rate is 74% even after 5000 adsorption/desorption cycles in diluted seawater. This work provides a new avenue to the design of high-performance, low-cost, and durable electrodes for capacitive deionization applications.

Anti-Corrosion Properties of Polyaniline/Polyurethane Composite Coatings on Mild Steel Using Coconut-Based/PPG Blend Polyols

Polyurethane coating has been widely used as a protective coating due to its wide range of mechanical strength, excellent abrasion resistance, toughness, low-temperature flexibility, and chemical resistance, simplicity in production and application, and superior protection on corrosion to mild steel. No studies have been reported utilizing coconut-based/PPG blend polyols to produce polyurethane-based protective coatings on mild steel. Therefore, in this work, we fabricated polyurethane-based protective coating using coconut-based/PPG blend polyols for anti-corrosion application. Due to low adhesion strength of Polyurethane-based protective coating, the incorporation of nano-fillers into the polymer matrix improved the adhesion strength of the coating due to its functional benefits and its effects gave rise to increased intermolecular bonding, hydrogen bonding, van der waals, magnetism, and surface energy. Therefore, we fabricated PANI/PU composite coatings with varied amounts of polyaniline nanoparticles on mild steel using coconut-based/PPG blend polyols exposed in 3.5 wt% NaCl aqueous solution for anti-corrosion application. Characterizations like Fourier Transform Infrared Spectroscopy (FTIR), Potentiodynamic Polarization (Tafel plot), contact angle, adhesion test, FESEM, XRD, and UV-VIS were used in this study. Tafel plot revealed that PU-based and PANI/PU composite coatings exhibited a significant reduction in corrosion current density (Icorr), perhaps due to the adsorption of inhibitor in the surface of the mild steel which reduced corrosion rate of the metal by retarding the anodic process and impeding the corrosive species from the surroundings. Among all fabricated coatings, 0.5-PANI/PU composite coating was the best, having a less corrosion rate of 5.66x10-5 mmpy compared to others. In addition, its surface was more compact, smooth, rigid, and no voids present at the interface according to the result of FESEM, suggesting better corrosion protection to mild steel. Hence, PU-based protective coating and PANI/PU composite coatings using coconut-based/PPG blend polyols inhibited the penetration of the corrosive species and served as an adequate barrier protection against corrosion for mild steel.

Artificial water channels-embedded PVDF membranes for direct contact membrane distillation and ultrafiltration

Innovative self-supported flat-sheet polyvinylidene fluoride (PVDF) membranes were developed incorporating amphiphilic I-quartet Artificial Water Channels (AWCs) and applied for membrane distillation (MD) and Dyes Ultrafiltration (UF). The presence of AWCs was aimed to increase the amount of water within hydrophobic PVDF pores increasing water permeability and preserving high selectivity and consequently to improve the MD and dyes UF performances. We explored novel strategies in which water channels structures contribute to water cluster stabilization and the increase of water (vapors or liquid) within hydrophobic pore structures. With this novel strategy in mind, three PVDF polymer grades with different molecular weights as well as the variation of their mass concentration as well as of AWCs were studied to shed in light their influence on the water permeability using a dead-end filtration setting. An enhanced water permeability of 75.3 L.m−2.h−1.bar−1 was attained for the PVDF-AWC hybrid membrane prepared using 16 wt% PVDF (530,000 g/mol) and 0.05 wt% AWCs when compared with a reference membrane with a water permeability of 30.6 L.m−2.h−1.bar−1. The MD performances of both membranes were assessed using a 35 g/L NaCl aqueous solution to yield a salt rejection of 95.3% and 85.2%, respectively. Furthermore, both the reference and the PVDF-AWC membranes showed improved separation performance in terms of rejection efficiency and dye permeability for binary dyes mixture as compared to single dyes. Among all the tested membranes, while methylene blue was completely removed in both cases, the 14 wt% PVDF membrane incorporating 0.075 wt% AWC showed a methyl orange rejection efficiency of up to 99.8% compared to 98.4% for its reference membrane. This hybrid membrane also displayed an almost doubled filtered dye feed permeability of 84 L.m−2.h−1.bar−1, compared to 40 L.m-2.h−1.bar−1 for its 14 wt% PVDF reference membrane.

Discharge in electrospraying of highly conductive aqueous solution coated with outer ionic liquid

Discharge in electrospraying can be applied in water decontamination, dental sterilization, and spectrometry of biological samples. The discharge in electrospraying of a single liquid like the aqueous solution or the ionic liquid has been investigated, which presents different discharge characteristics such as patterns, currents and frequencies. This paper puts forward a way to actively control the discharge characteristics of liquids electrospray beyond the limitation of their own physical properties, which was accomplished by utilizing the technique of coaxial electrospray to coat the concentrated sodium chloride (NaCl) aqueous solution with a layer of ionic liquid. Previously we used this method to suppress the discharge of NaCl solution and stably electrosprayed the NaCl solution. The discharge characteristics of coaxial electrospray and the effect of the applied voltage and the flow rates of both liquids on the discharge was investigated in detail. When being electrosprayed, the NaCl solution alone discharged with pre-onset mode, pulseless corona discharge mode and streamer discharge mode, while the ionic liquid and the coaxial electrospray only discharged with the streamer discharge mode with a conical liquid shape, and less droplets were formed during the transient cone-jet emission. After being coated with the outer ionic liquid, the current, frequency and onset voltage of the discharge of the inner aqueous solution all increased. The current and frequency of the discharge of the coaxial electrospray all increased as the applied voltage increased. In addition, a numerical simulation has been conducted, which confirmed that the inner aqueous solution was strongly shielded from the external electric field by the outer ionic liquid layer. Therefore, it is plausible to actively control the discharge characteristics of the liquids through adjusting the flow rates of both liquids, the applied voltage and choosing the suitable outer liquid.

The Role of the Gravitational Field in Generating Electric Potentials in a Double-Membrane System for Concentration Polarization Conditions.

Electric potentials referred to as the gravielectric effect (∆ΨS) are generated in a double-membrane system containing identical polymer membranes set in horizontal planes and separating non-homogenous electrolyte solutions. The gravielectric effect depends on the concentration and composition of the solutions and is formed due to the gravitational field breaking the symmetry of membrane complexes/concentration boundary layers formed under concentration polarization conditions. As a part of the Kedem-Katchalsky formalism, a model of ion transport was developed, containing the transport parameters of membranes and solutions and taking into account hydrodynamic (convective) instabilities. The transition from non-convective to convective or vice versa can be controlled by a dimensionless concentration polarization factor or concentration Rayleigh number. Using the original measuring set, the time dependence of the membrane potentials was investigated. For steady states, the ∆ΨS was calculated and then the concentration characteristics of this effect were determined for aqueous solutions of NaCl and ethanol. The results obtained from the calculations based on the mathematical model of the gravitational effect are consistent with the experimental results within a 7% error range. It has been shown that a positive or negative gravielectric effect appeared when a density of the solution in the inter-membrane compartment was higher or lower than the density in the outer compartments. The values of the ∆ΨS were in a range from 0 to 27 mV. It was found that, the lower the concentration of solutions in the outer compartments of the two-membrane system (C0), for the same values of Cm/C0, the higher the ∆ΨS, which indicates control properties of the double-membrane system. The considered two-membrane electrochemical system is a source of electromotive force and functions as an electrochemical gravireceptor.

High-Throughput Aqueous Electrolyte Structure Prediction Using IonSolvR and Equivariant Graph Neural Network Potentials.

Neural network potentials have recently emerged as an efficient and accurate tool for accelerating ab initio molecular dynamics (AIMD) in order to simulate complex condensed phases such as electrolyte solutions. Their principal limitation, however, is their requirement for sufficiently large and accurate training sets, which are often composed of Kohn-Sham density functional theory (DFT) calculations. Here we examine the feasibility of using existing density functional tight-binding (DFTB) molecular dynamics trajectory data available in the IonSolvR database in order to accelerate the training of E(3)-equivariant graph neural network potentials. We show that the solvation structure of Na+ and Cl- in aqueous NaCl solutions can be accurately reproduced with remarkably small amounts of data (i.e., 100 MD frames). We further show that these predictions can be systematically improved further via an embarrassingly parallel resampling approach.

Solid dispersion complex triclabendazole preparations with succinic acid and their fasciolocidal activity

The purpose of the research is to test the efficacy of triclafascid and two solid dispersion complex preparations based on the triclabendazole substance against fasciolosis in cattle and sheep. Materials and methods. Complex preparations of triclabendazole (TCB) formulations: Succinic Acid (SA): Polyvinylpyrrolidone (PVP) (1: 1 : 8) and TCB: SA: Arabinogalactan (AG) (1: 1 : 8) were obtained by combined solid-stategrinding of the components in a fiber drum on an LE-101 ball mill at a roll rotation speed of 60 rpm with a process module of 1: 17 for 1 to 6 hours with sampling for analysis (HPLC) for changes in the TCB solubility. A comparative test of the efficacy of triclafascid and new solid dispersions (SD) of TCB complexes with SA against fascioliasis of sheep and cattle was conducted in the North-Eastern Federal District of the Caucasus in March-April 2023. To determine the Fasciola infection rate in animals, fecal samples were individually taken and examined by the Fülleborn methods using saturated aqueous NaCL solution and sequential washing. The drug efficacy was recorded at 25-30 days after deworming in analogy with "critical test". The results were statistically processed by the Student-Fisher method using Microsoft Excel 2007. Results and discussion. The resulting TCB and SA complexes with polymers had an increased solubility (up to 59–70 times) that depended on the polymer nature. The efficacy of new TCB dosage forms against fascioliasis in sheep at a dose of 1.5 mg/kg, i.e. 0.5 mg/kg less than the therapeutic dose as compared with oral triclafascid was 90.0 and 100%, respectively, and 85.7% in cattle at a dose of 2.0 mg/kg for the active substance.

Novel bipolar membrane electrolyzer for CO2 reduction to CO in organic electrolyte with Cl2 and NaOH produced as byproducts

Electrochemical reduction of CO2 to valuable products, powered by renewable energy, provides a promising strategy for reducing our dependence on fossil fuels. But up to now, no technology has been implemented for large-scale industrial applications. Without massive utilization of CO2, many vital practical problems, such as reducing CO2 emissions, storing renewable energy, and alleviating environmental pollution, cannot be resolved through this route. Herein, we propose a novel electrolyzer for CO2 electro-reduction, which is separated into three chambers by a bipolar membrane and a cation exchange membrane. In the cathodic chamber, CO2 is reduced to CO in organic electrolytes. In the anodic chamber, Cl- is oxidized to Cl2 in NaCl aqueous solution. In the central chamber, NaOH is obtained. The generated CO and Cl2 can be used as feedstock to produce phosgene (CO+Cl2 =COCl2). Through this route, phosgene can be produced from CO2 and NaCl, with NaOH generated as a byproduct. By substantially increasing the product value, we can promote CO2 electro-reduction technology to industrial applications.

Advanced Janus membrane (MXene/CoAl-LDH) for efficient asymmetric ion transport and nanofluidic energy harvesting

Two-dimensional (2D) material membranes with nanometer or sub-1 nanometer confined space present enormous potential for water permeation, ion sieving and transport. In addition, electrolyte flowing through the asymmetric channels exhibits ion asymmetric transport behavior which provides a basis to control the ion flow. Therefore, it is an opportunity to develop Janus membranes by 2D materials for alleviating the concentration polarization and enhancing the performance in nanofluidic energy harvesting. Whereas the previously reported 2D material-based Janus laminated membranes were adjusted interlayer charge distribution by modifying positively charged polymer, due to the intrinsically negative surface charge of these 2D nanosheets. Thus, design of 2D/2D Janus membrane from positive and negative changed 2D materials will have great opportunity for efficient asymmetric ion transport and nanofluidic energy harvesting. In this work, Janus MXene/LDH (MXLDH) membranes containing negatively charged MXene and positively charged CoAl-LDH were designed without additional modifying process for efficient ion asymmetric transport and neutralization energy harvesting. The ratio of MXene/LDH draws a significant effect on ion rectification factor, osmotic voltage, ion selectivity and energy conversion efficiency. The Janus membrane with 86 wt% LDH (MXLDH-86) revealed the highest rectification factor of ∼6.2 in 0.1 mM NaCl aqueous solution. And the osmotic power density of MXLDH-86 under 1 M HCl/ 1 M NaOH can reach ∼8.75 W/m2, ∼17.7 % higher than that of the pristine MXene membrane, indicating that the Janus membrane with asymmetric charges is a promising material for harvesting neutralization energy.

Analysis of a Double Aging Process in a Maraging 300 Steel Fabricated by Selective Laser Melting, Using the Design of Experiments Technique

This study aims to optimize the aging treatment of a maraging 300 steel, without prior austenitizing, manufactured by the selective laser melting (SLM) technique. The study includes the analysis of a double aging process. In addition, the impact of the aging treatment on corrosion resistance in 3.5 wt.% NaCl solution was analyzed. The research technique followed was a factorial design of experiments with three factors and two levels, performing one replicate of each experiment. The results show that excellent mechanical properties can be achieved by omitting the solubilization treatment prior to aging. The highest hardness and tensile strength were achieved by performing a double aging at 460 °C for 8 h. Under these conditions, the maximum hardness exceeded 615 HV and the tensile strength was over 2140 MPa. Aging at 520 °C caused the formation of reverse austenite. The aging temperature was the only factor that had a significant effect on the formation of reverse austenite. It should be noted that the holding time at this temperature did not have a significant effect. The corrosion resistance, in 3.5 wt.% NaCl aqueous solution, increased in the aged samples compared to the as-printed sample. Samples overaged at 520 °C showed the best corrosion resistance. It can be concluded that the predominant cathodic reaction taking place is the reduction of oxygen dissolved in the electrolyte.

Transport Properties of NaCl in Aqueous Solution and Hydrogen Solubility in Brine.

Ion transport properties and hydrogen solubility in brine play pivotal roles in various engineering and scientific scopes including chemical, physical, geochemical, and geothermal domains. Molecular dynamics simulations were performed to obtain transport properties of NaCl in the binary H2O + NaCl system using different force fields. Brine density, ion diffusivity, molar conductivity, conductivity, and hydrogen solubilities were obtained as functions of temperature and salt concentration. We compared the performance of different force fields against the experimental correlation model and developed three mathematical models. The first was the modified brine density model based on the simulated brine density over a wide range of salinity levels, and the second and third analytical mathematical models were derived for the ion diffusivity and molar conductivity as a function of salinity and temperature. The results of this study illustrated that the modified brine density model not only produced the same results of the previous model for lower salinity levels but also applied well to predict the brine density for a higher salinity level. The derived mathematical models indicated that the ion diffusivity and molar conductivity decreased linearly with salinity, and the slope and y-intercept of the lines of diffusivity and molar conductivity versus temperature were third-order polynomials of temperature. The developed models provided the mechanism for the behavior of decreasing molar conductivity with increasing salinity and increasing conductivity with increasing salinity. The directions of the effect of salinity on the molar conductivity and conductivity were opposite. The molar conductivity increased with a decreasing salinity level. However, the conductivity increased with increasing salinity, as the contribution of the ion concentration or salinity level to conductivity dominated over that of the ion movement.

Mechanical Properties and Corrosion Resistance of AlCrNbSiTiN High Entropy Alloy Nitride Coatings

High-entropy alloy (HEA) nitride coatings have been extensively studied due to their desirable properties of high hardness, thermal stability, and corrosion resistance. Among HEA nitride thin films, the AlCrNbSiTiN coatings exhibit very good hardness, high temperature strength, and thermal stability. In this study, six AlCrNbSiTiN HEA coatings with different Al and Cr contents were synthesized using a co-sputtering system with a high-power impulse magnetron sputtering (HiPIMS) power connected to an Al70Cr30 target and a mid-frequency power connected with an Al4Cr2NbSiTi2 high-entropy alloy target. The input power of the Al70Cr30 target was adjusted to obtain AlCrNbSiTiN coatings with different Al and Cr contents. It is observed that the sum of the Al and Cr contents and the (Al + Cr)/(Al + Cr + Nb + Si + Ti) ratio of the AlCrNbSiTiN coatings increased from 59 to 91 at.% when the input power of the Al70Cr30 target increased from 700 W to 1100 W. The single NaCl-type (B1) face-centered cubic (FCC) phase was observed for each coating. The hardness of the coatings increased from 21.2 to 28.2 GPa with increasing Al and Cr contents due to the grain size refinement effect brought by the increasing HiPIMS power. The wear depth and wear rate of the coatings sequentially decreased from 544 to 24 nm and from 2.79 × 10−5 to 2.63 × 10−7 mm3N−1m−1, respectively. Although the adhesion slowly decreased with increasing Al and Cr contents and the hardness of the coating, there was adequate adhesion with a minimum LC3 critical load of 36.1 N. The corrosion resistance of 304 stainless steel in a 3.5 wt.% NaCl aqueous solution was improved by deposition of the AlCrNbSiTiN coating. In this work, the high-entropy AlCrNbSiTiN nitride coating with a (Al + Cr)/(Al + Cr + Nb + Si + Ti) ratio of 91% exhibited excellent surface roughness, the highest hardness of 28.2 GPa, adequate adhesion, and the lowest wear rate of 2.63 × 10−7 mm3N−1m−1 due to its grain refinement effect by the ion bombardment generated with HiPIMS.

Effect of Al Content on Microstructure, Mechanical, and Corrosion Properties of (Fe33Cr36Ni15Co15Ti1)100−xAlx High‐Entropy Alloys

(Fe33Cr36Ni15Co15Ti1)100−xAlx (x = 0, 3, 5, 6, 7, 8) high‐entropy alloys (HEAs) are prepared by arc melting. The influence of Al element addition on the microstructure, mechanical properties, and anticorrosion in 3.5 wt% NaCl aqueous solution is systematically investigated. The microstructure analysis indicates that HEAs possess varying phases from face center cubic/face‐centered cubic (FCC) + sigma to FCC + body‐centered cubic (BCC) and then FCC + BCC +sigma, the last to BCC + sigma with the increase of Al content. The compressive results suggest that the Al addition exhibits a significant elevation in strength. Particularly, Al7 alloy shows a superior strength and plasticity, which presents a yield strength of 1315.3 MPa and a compressive strain over 50%. Order strengthening and coherent strengthening of nanosized phase are regarded as main strengthening effects. In addition, Al element is harmful for the corrosion resistance of (Fe33Cr36Ni15Co15Ti1)100−xAlx HEAs system, which is ascribed to the weakened passive film stability. It is also noted that pits tend to be initiated in relatively Cr‐depleted phases (FCC or B2 phase) due to the inhomogeneous elemental distribution‐induced galvanic corrosion. In spite of this, all HEAs exhibit superior corrosion resistance than that of 304SS.