Concentrated Sodium Chloride Solution Research Articles

Laboratory study on the transformation of oil-water interface properties under direct current electric field

Interface tension is one of the important mechanisms that affect crude oil recovery and plays an important role in the development of tight oil reservoirs. Electrical-enhanced oil recovery can be used as a technology to reduce interfacial tension and improve crude oil recovery. In the previous research process of Electrical-enhanced oil recovery, the focus was more on the influence of electric field on wettability, and the understanding of the changes in interfacial tension under electric field action is not yet comprehensive. This article designs an orthogonal experiment to study the effect of electric field on oil-water properties. The degree of influence of three factors, namely sodium chloride solution concentration (C), direct current voltage (V), and voltage action time (t), on interfacial tension is studied. Gas chromatography, four component analysis, and Fourier transform infrared spectroscopy are combined to discuss the mechanism of the influence of changes in solution pH, crude oil components, and oil phase functional groups on interfacial tension. The results show that an external electric field can effectively reduce the interfacial tension between oil and water, and the maximum change in interfacial tension after the experiment can be reduced from 23.21 mN/m to 0.37 mN/m; Through range analysis, it can be concluded that the concentration of sodium chloride solution has the greatest impact on interfacial tension, followed by DC voltage and voltage action time. The optimal experimental conditions are 0.5mol/L sodium chloride solution, 10V DC voltage, and a voltage action time of 18 hours, and the change in interfacial tension is related to the increase in pH value. The change in crude oil composition is also an important reason for the decrease in interfacial tension under external electric fields. Finally, Fourier transform infrared spectroscopy was used to determine that under the action of an electric field, the increase in pH of the sodium chloride solution resulted in the formation of carboxylate salts through chemical reactions between alkaline substances of solution and acidic substances of the oil, which were the key factors in reducing interfacial tension. This study helps to understand and explore the principles and mechanisms of Electrical-enhanced oil recovery in improving oil recovery, with the aim of contributing to the development and promotion of Electrical-enhanced oil recovery technology.

Temperature compensation measurements in the detection of glucose and sodium chloride solution concentration based on SPR in the optical fiber

The temperature variation is one of the main error factors in the process of glucose and sodium chloride solution concentrations detection based on optical fiber sensor. In this paper, we proposed a sensor with temperature compensation, which can detect the temperature while measuring the concentrations of glucose or sodium chloride solution. The dual-channel design enables the sensor to obtain accurate measurement results of glucose and sodium chloride concentrations, and also to monitor the environmental temperature simultaneously. The deposition of zinc oxide film not only enhances the sensitivity of the sensor but also prevents oxidation of the silver film. The high stability of polydimethylsiloxane (PDMS) ensures that the two sensing channels of the sensor do not interfere with each other. The proposed dual-channel sensor offers advantages of low cost, a simple structure, and high sensitivity, with potential applications in the fields of food science and biochemistry.

A simple electrode insulation and channel fabrication technique for high-electric field microfluidics

A simple and robust electrode insulation technique that can withstand a voltage as high as , which is equivalent to an electric field strength of MV m−1 across a channel filled with an electrolyte of conductivity S m−1, i.e. higher than sea water’s conductivity, is introduced. A multi-dielectric layers approach is adopted to fabricate the blocked electrodes, which helps reduce the number of material defects. Dielectric insulation with an exceptional breakdown electric field strength for an electrolyte confined between electrodes can have a wide range of applications in microfluidics, like high electric field strength-based dielectrophoresis. The voltage-current characteristics are studied for various concentrations of sodium chloride solution to estimate the insulation strength of the proposed materials, and the breakdown strength is calculated at the point where the electrical insulation failed. A detailed adhesion technique is also demonstrated, which will reduce the ambiguity around the fabrication of a sealed channel using SU-8.

Concentration of sodium chloride solutions in the processing of concentrates for reverse osmotic water desalification

The paper examines the processes of concentrating sodium chloride solutions by the electrodialysis method. Given the shortage of reagents and their high prices, this electrodialysis method can be implemented to obtain acid and alkali from solutions of sodium sulfate, alkali, aluminum and iron coagulants. Today, the technologies that, as a result of the process, allow us to obtain valuable materials, substances, products, coagulants as a secondary product, are very justified, economically feasible and, most importantly, allow us to successfully implement the principles of low-waste production. The essence of the process is the use of sodium chloride solutions, which are formed during the desalination of water by reverse osmosis in the form of concentrates. The concentration process was implemented in a three-chamber electrolyzer, in the cathode, anode and working areas, a sodium chloride solution with a concentration of 360 mmol/dm3 was placed. An alkali solution with a concentration of 480 mg-eq/dm3 was used in the anode area. During electrolysis, alkali was formed in the cathode area, due to the diffusion of sodium in the working area and the cathodic reduction of water. Chlorides from the working area moved to the anode area. Hydroxide anions on the anode were oxidized to oxygen, chlorides with sodium formed sodium chloride, the concentration of which increased to 660 mg-eq/dm3. Alkalinity decreased to 68-70 mg-eq/dm3. When changing cathodes and anodes, the process was repeated in some places until the alkalinity in the cathode zone and the concentration of chlorides in the anode zone increased. . A solution of sodium chloride with a concentration of 360 mmol/dm3 was added to the working area where water desalination took place. After nine cycles of electrolysis, a sodium chloride solution with a concentration of 100-150 g/dm3 was obtained. The residual content of sodium chloride in desalinated water reached 50-100 mg/dm3. Sodium chloride solutions with a concentration of 4 to 30 g/dm3 can be used for concentration. It should be noted that after conducting nine cycles of the experiment, we can state that the process of concentration by this electrodialysis method does not lead to an increase in system resistance and energy consumption.

Insight into Anti-Corrosion Behavior and Mechanism of 8-Hydroxyquinoline Inhibitor on AZ91D Alloy in Different Concentrations of Sodium Chloride Solution

The inhibition behavior of the promising eco-friendly inhibitor 8-hydroxyquinoline (8HQ) in two concentrations of sodium chloride solution was studied by hydrogen evolution, scanning electron microscope (SEM), three-dimensional morphology, electrochemical testing, and computational calculations. The results indicated that the 8HQ inhibitor showed satisfactory inhibition effect due to its fast, excellent adsorption capacity and self-healing ability. The corrosion inhibition effect is related to the concentration of the inhibitor. There was a competitive adsorption relationship between 8HQ and [Cl−], and the adsorption morphology was obviously affected by the concentration of [Cl−]. At the lower concentration of NaCl solution, the adsorption of 8HQ was more orderly, faster, and the adsorption amount was larger, which led to the formation of a denser protective layer. Density functional theory (DFT) results showed that the most stable adsorption configuration of 8HQ was NO-Top. N and O atoms are the active sites, and there is a strong coupling between them and Mg atoms, which is consistent with the experimental results.

Polymorph and Morphology Formation of Cerium Carbonate from Reactive Crystallization

Semibatch reactive crystallization and hydrothermal reaction of cerium carbonate were investigated with cerium chloride and sodium carbonate as the reactants in order to determine the key factor and the foremost step that affect the polymorph and morphology. Pure Ce2(CO3)3·8H2O, pure CeCO3OH, and the concomitant polymorphism of the two were obtained at different temperatures and the concentrations of cerium chloride solution. The relative stability of Ce2(CO3)3·8H2O and CeCO3OH, the solubilities of the two forms in low concentration of sodium chloride solution and the dehydration and decomposition processes with heating were first discussed in this study. Rodlike forms, short rodlike forms, platelike aggregations or blocks, regular intercrescence, and regular spindle morphology of cerium carbonate crystals were obtained from semibatch and hydrothermal reactive crystallization, respectively. Raman spectroscopy and a focused beam reflection measuring (FBRM) instrument were applied in situ to monitor the reaction, nucleation, and growth processes. It was found that CeCO3OH is more stable than Ce2(CO3)3·8H2O. The thermodynamics driving force of supersaturation of cerium carbonate generated from the reaction between cerium chloride and sodium carbonate at different temperatures contributed mainly to the nucleation, which, in turn, controls the crystal phase formation and the morphology of cerium carbonate. Finally, the routes for cerium chloride and sodium carbonate to transform into cerium oxide were summarized.

Hydrate phase equilibria of carbon dioxide/propane gas mixture in concentrated aqueous sodium chloride solutions: Experimental data and prediction

The information on hydrate equilibrium conditions of gas hydrate formers in concentrated NaCl solutions are the prerequisites for hydrate-based desalination methods. Hydrate dissociation conditions for CO2-C3H8 mixture, as a good candidate for this application, were measured for the temperature and pressure ranges of 269–283 K and 0.3–3.4 MPa, respectively using an isochoric pressure-search method. The used gas mixture was a solution of 10 mol% C3H8 + 90 mol% CO2 and NaCl concentrations varied between 8 and 12 wt%. The promoting effect of propane was obviously observed from the experimental data. This promoting effect nearly balanced the inhibitory effect of 12 wt% NaCl. A thermodynamic model was applied to predict the experimental data using SRK, PR, and VPT EOSs. All EOSs had accurate results for prediction of CO2 hydrate equilibrium pressures, with the best result by PR EOS. The overall average absolute percent deviation (AAPD) of PR EOS in pure water and 8 wt% NaCl solution were 5.29 and 3.8 %, respectively. For gas mixture (CO2-C3H8) in pure water, the best accuracy was obtained by using SRK EOS with AAPD of 4.44 %. However, the results of VPT and PR for gas mixture in NaCl solutions, were more accurate than SRK with AAPDs equal to 7.47 and 7.75 %, respectively.

Improved Spectral Interrogation of Tilted Fiber Bragg Grating Refractometer Using Residual Convolutional Neural Networks

This paper proposes a new approach of demodulating the spectra of tilted fiber Bragg grating (TFBG) based refractive-index (RI) sensor by employing convolutional neural networks (CNN) with residual blocks. The proposed residual CNN model was trained and tested by over 5500 samples recorded at different concentrations of sodium chloride solution, whose RI ranged from 1.3350 to 1.3790 RIU, and the raw spectral data can be directly utilized to train the residual CNN without any pre-processing. Results show that the coefficient of determination could reach 99.82% and the mean square error (MSE) achieves 2.818 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−7</sup> RIU. The well-trained model could be applied to demodulate other similar sensors through transfer learning, which demonstrates its good generalization capability of the proposed method. Additionally, the proposed method could maintain high MSE (i.e., 2.938 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−7</sup> RIU) although the interrogator with poorer resolution (20 times less) was utilized, showing high potential to reduce the cost of the interrogation hardware.

Rapid Detection of Clenbuterol Residues in Pork Using Enhanced Raman Spectroscopy.

Clenbuterol (CB) is a synthetic β-receptor agonist which can be used to improve carcass leanness in swine, but its residues in pork also pose health risks. In this report, surface-enhanced Raman scattering (SERS) technology was used to achieve rapid detection and identification of clenbuterol hydrochloride (CB) residues. First, the effects of several different organic solvents on the extraction efficiency were compared, and it was found that clenbuterol in pork had a better enhancement effect using ethyl acetate as an extraction agent. Then, SERS signals of clenbuterol in different solvents were compared, and it was found that clenbuterol had a better enhancement effect in an aqueous solution. Therefore, water was chosen as the solvent for clenbuterol detection. Next, enhancement effect was compared using different concentration of sodium chloride solution as the aggregating compound. Finally, pork samples with different clenbuterol content (1, 3, 5, 7, 9, and 10 µg/g) were prepared for quantitative analysis. The SERS spectra of samples were collected with 0.5 mol/L of NaCl solution as aggregating compound and gold colloid as an enhanced substrate. Multiple scattering correction (MSC) and automatic Whittaker filter (AWF) were used for preprocessing, and the fluorescence background contained in the original Raman spectra was removed. A unary linear regression model was established between SERS intensity at 1472 cm-1 and clenbuterol content in pork samples. The model had a better linear relationship with a correlation coefficient R2 of 0.99 and a root mean square error of 0.263 µg/g. This method can be used for rapid screening of pork containing clenbuterol in the market.

Computational Intelligence Powered Performance Analysis on Phase Change Heat Storage Air Source Heat Pump System.

Aiming at the performance deterioration of air source heat pump at low temperature in cold area, an air source heat pump system with sodium chloride aqueous solution as low temperature phase change heat storage material was proposed to increase the air inlet temperature of the unit under low temperature conditions and improve the low temperature performance of the heat pump unit. The system form, unit energy consumption model, and economic model were given, and the operating economy of the traditional electric auxiliary heat air source heat pump system and the phase change heat storage air source heat pump system were compared through computational intelligence powered methods. On this basis, the operation economy of the heat pump system using different concentrations of sodium chloride solution as the heat storage material was simulated and optimized, and the operation efficiency and energy-saving performance of the system were analyzed by taking an actual residential building in a cold area as an example. The simulation results showed that the Heating Seasonal Performance Factor (HSPF) of the heat pump system using 8.5% sodium chloride aqueous solution as the heat storage material is 2.24, and the HSPF of the traditional electric auxiliary heat pump system is 1.83. Compared with the traditional electric auxiliary heat pump system, the phase change heat storage heat pump system saves heating energy consumption by 19.6% and defrosting energy consumption by 38.8%. The heat pump system using 10% sodium chloride aqueous solution as the heat storage material has the best operating economy, and the system HSPF is 2.33, which saves heating energy consumption by 23.2% and defrosting energy consumption by 34% compared with the traditional heat pump system. The operation condition of phase change heat storage air source heat pump system is stable, and the system performance is significantly improved.

Physicochemical model for simulating the chemical processes during the crystallization of minerals from spent ion exchange regenerant

Traditionally, industrial processes produce wastes that, even though often containing useful materials, are discarded, contributing to environmental pollution and depletion of natural resources. An example of such wastes are brines, flows of concentrated salts, produced in water treatment processes, which are now routinely discharged into receiving water bodies. Brines however can also be considered as flows of reusable materials which should be recovered, and the Zero Brine cooperation project aims to develop processes for that purpose. For a demineralized water production plant in the port of Rotterdam (the Netherlands), a closed water processing cycle was proposed to treat the large volume of spent Ion Exchange (IEX) regenerant brine which, apart from recovering demineralized water, is also intended to produce magnesium (Mg2+) and calcium (Ca2+) salts, with the highest purity possible, from the otherwise discharged brine. The process scheme includes nanofiltration (NF) for separating mono- and multivalent ions, followed by sequential chemical precipitation of Mg2+ and Ca2+ ions from the NF concentrate, and production of demineralized water by evaporation of the NF permeate. The concentrate of monovalent ions produced in the evaporator, essentially a concentrated sodium chloride solution, in its turn might be reused for IEX regeneration. Part of the supernatant of the sequential precipitation may be fed to the evaporator as well, but bleeding the other part of this supernatant is essential in order to maintain process stability, avoid accumulation of minor pollutants, and reduce scaling. In this study, various scenarios to operate the process were modeled, using PHREEQC and Excel. According to the simulation results, recovery of ≈97% of Mg2+ and Ca2+ is possible, the latter with a higher purity than the former. The main factors affecting the results are the concentration of carbonate present in the spent IEX regenerant, as well as characteristics of the NF membrane and the dosing of sodium hydroxide in the sequential precipitation steps. The results of the simulations were used for the design and operation of a pilot plant, comprising all mentioned process steps.

Physicochemical parameters of a hydrochemical technology employing sodium chloride to obtain cryolite used in aluminium production

The paper aims to study the physicochemical parameters of a hydrochemical technology employing hydrofluoric acid and local mineral resources (sodium chloride) to obtain cryolite used in the electrolysis of cryolite-alumina melts. In order to determine the elemental chemical and phase compositions of initial, intermediate, and final products, titration and X-ray diffraction analysis (using an upgraded Dron-2 unit) were employed. The conducted studies indicate that the proposed process of cryolite production from hydrofluoric acid at 28–30 % concentration using aluminium hydroxide and a concentrated sodium chloride solution occurs at 25 °С for 10–15 min. The yield of cryolite reaches 87.6 %, while ~12 % of cryolite remains dissolved in the hydrochloric acid solution. With the temperature rising from 25°С to 95°С, the cryolite yield is shown to decrease from 87.6 % to 69.3 % due to its higher solubility in the formed hydrochloric acid. The cryolite production process was validated via X-ray diffraction analysis. The analysed sample was found to be consistent with the cryolite reference, i. e., indicating an interaction between sodium chloride and fluoroaluminic acid. The conducted studies served as a basis for developing a process flow diagram of hydrochemical cryolite production using hydrofluoric acid, aluminium hydroxide, and sodium chloride. The conducted studies revealed that the technology of cryolite production employing sodium chloride is easy to implement and cost-effective due to the use of local mineral resources and low energy consumption.

Evaluation of the efficacy of alkylimidazolines in reducing the corrosion aggressiveness of oil-containing waters

The subject of the study is the study of corrosion processes of non-alloy steel St 3 in water-oil mixtures to create effective compositions of corrosion inhibitors for oil and oil refining industries. Corrosion aggressiveness of commodity and formation waters, waters present in crude oil, due to their high mineralization, the presence of various sulfur compounds, as well as acidification due to the formation of carboxylic acids and other acidic compounds. High corrosion activity of water-oil mixtures causes rapid destruction of equipment and pipelines. This not only significantly affects the economic performance of production due to the cost of replacing metal structures, but also causes great environmental damage due to environmental pollution by both petroleum products and highly mineralized waters.&#x0D; Therefore, one of the most important tasks is the protection of metal structures from corrosion in mineralized waters and water-oil mixtures.&#x0D; Given the prospects for the use of corrosion inhibitors of non-alloy steel, the effectiveness of alkylimidazolines (C15-C20) in water-oil mixtures depending on the characteristics of aquatic environments and the parameters of corrosion processes was studied. Given that the real formation waters of Ukraine's oil fields differ significantly in chemical composition and are difficult to model in the laboratory, a 3 % solution of sodium chloride with acetic acid, sulfite and sodium metabisulfite was used. Aqueous solutions were mixed with oil in a ratio of 140:10–180:10. The concentration of sodium chloride solution (3 %) is due to the high corrosion activity of this solution to ferrous metals, including solutions with a high level of mineralization. The choice of alkylimidazolines is due to the fact that they are promising inhibitors in both aqueous media in the presence of oil and in oil in the presence of mineralized waters in a wide range of temperatures.&#x0D; There are almost no data in the literature on the effect of pH, petroleum products, sulfites on the corrosion activity of mineralized media against non-alloy steel. There are no data on the effect of these parameters on the effectiveness of imidazoline corrosion inhibitors of steel.&#x0D; The processes of corrosion of steel St3 in 3 % solution of sodium chloride and its mixtures with oil at temperatures from 20 to 85 oC at pH change from 2.65 to 6.25 at concentrations of imidazolines from 2 to 50 mg/dm3 were studied. &#x0D; The impact on the corrosion of sodium sulfite and bisulfite in the presence of alkylimidazolines was evaluated. The effectiveness of alkylimidazolines in the aqueous medium as bactericidal inhibitors under anaerobic conditions has been determined.&#x0D; It is shown that corrosion aggressiveness in water-oil mixtures increases with decreasing medium pH and increasing temperature. A significant reduction in the corrosion rate was achieved with the use of alkylimidazolines. In some cases, the values of the degree of protection of steel against corrosion at the level of 80-90% at doses of inhibitor up to 50 mg/dm3. The use of imidazolines in the composition with sodium sulfite helps to increase the effectiveness of steel protection against corrosion. Alkylimidazolines (C15-C20) provided a high level of protection of steel from biocorrosion under anaerobic conditions.

Experimental Study on Damage Characteristics of Solidified Mud under Coupling Action of Freeze-Thaw Cycle and Chloride Salt

The physical properties of solidified mud will deteriorate under the combined action of freezing-thawing cycle and chlorine salt, which will affect the safety and stability of solidified mud engineering. In order to study the damage characteristics of solidified mud under the action of freeze-thaw cycle and chloride salt, the solidified mud samples were soaked in different concentrations of sodium chloride solution and treated with freeze-thaw cycle. Besides, the unconfined compressive strength test was carried out to study the damage characteristics of the samples caused by different concentrations of sodium chloride solution and freeze-thaw cycles. The test results show the following. (1) Under the action of freeze-thaw cycle and sodium chloride solution, the surface of the sample deteriorated in varying degrees. With the increase in freeze-thaw cycle times and sodium chloride solution concentration, the mass loss of the sample was greater. (2) Under the action of chlorine salt and freeze-thaw cycle, the strength of the sample decreases with the increase in freeze-thaw cycle times. With the increase in the concentration of sodium chloride solution, the strength of the sample decreases and the damage degree increases gradually. (3) Under the action of freeze-thaw cycle, the internal pores of the samples gradually expand and more honeycomb holes appear, and the content of hydration products is higher. As the concentration of sodium chloride solution increases, the particle connection inside the sample gradually weakens, and the sample is more likely to be damaged.

Effect of Corrosive Medium and Surface Defect-Energy on Corrosion Behavior of Rolled ZK61M Alloy.

Magnesium alloys have been widely used as lightweight engineering structural materials, but their service performances are severely restricted by corrosion failure. In this paper, the influence of corrosive medium and surface defect energy on the corrosion behavior of rolled ZK61M alloy was investigated. The corrosion tests were conducted in different concentrations of sodium chloride solution for different durations, and the polarization curves and electrochemical impedance spectroscopy were reported. The surface morphology of rolled ZK61M alloy before and after corrosion tests were analyzed. The results showed that the corrosion tendency became stronger with the increase of the concentration of corrosive medium and the number of surface defects of ZK61M alloy. Moreover, the initial corrosion pattern was the pitting caused by micro galvanic corrosion at the surface defect, which gradually developed into uniform corrosion. Furthermore, the main damage occurred at the grain boundary, resulting in the destruction of grain bonding force and the removal of material along the rheological layer. The oxidation corrosion mechanism was mainly the anodic dissolution mechanism.

Methylenedisalicylic Acid as a Biocorrosion Inhibitor for Aluminum in Concentrated Sodium Chloride Solutions.

3,3′-Methylenedisalicylic acid (MDS) was synthesized and ascertained on the basis of elemental analyses (C, H) and spectral measurements (IR, mass, 1H NMR, and UV–vis). Moreover, the prepared MDS compound has been assayed for its antimicrobial action against the growth of fungi as well as Gram-positive and Gram-negative bacteria. The results demonstrated the possibility of its usefulness to restrain the growth of both fungi and bacteria, whereas MDS showed its best impact against Candida albicans. The inhibitive impact of MDS on the corrosion of aluminum (Al) in concentrated sodium chloride solution (3.5 wt % NaCl) has been investigated. The corrosion work was done by potentiodynamic cyclic polarization, electrochemical impedance spectroscopy, and chronoamperometric current–time measurements and complemented by scanning electron microscopy and energy-dispersive X-ray investigations. It was found that MDS molecules protect the aluminum against corrosion, and its ability increases with the increase of concentration from 5 × 10–5 to 1 × 10–4 M and further to 5 × 10–4 M. The electrochemical results were supported by the morphological analysis and proved that the presence of MDS inhibits the uniform and pitting corrosion of Al in the chloride solutions.

Microwave irradiation spectrum of graphene oxide paper regulated by Na ions

In this paper, we found that the presence of sodium chloride (NaCl) can effectively inhibit the diffusion of graphene oxide (GO) in water. Based on this discovery, we reported a simple preparation method of GO paper regulated by Na ions. By adjusting the drying temperature and the mass fraction of NaCl solution, the preparation and complete stripping of GO paper can be easily completed, thereby obtaining free-standing GO paper. Further, we also found that the introduction of sodium ions would cause changes in the microwave irradiation spectrum of GO paper, and the change was related to the mass fraction of NaCl solution used, which could be used to detect sodium ions and the concentration of NaCl solution. Besides, our study also showed that MWRGO paper with NaCl solution treatment can more effectively remove methylene blue in water, compared with MWRGO paper without NaCl solution treatment. This study provides the possibility of the preparation of GO paper based on seawater and also provides a new method for the detection of sodium ions and determination of sodium chloride solution concentration. It has important application prospects in the preparation of GO paper, sensor and water treatment.

Study on Deterioration Law and Mechanism of Gray Brick Due to Salt Crystallization.

Salinization has an important impact on the degradation of ancient masonry buildings, and systematically mastering the law of salt migration and degradation of ancient masonry buildings is an important part of the protection of ancient buildings. In this paper, the damage law of gray bricks under the action of salt crystallization is studied. The orthogonal test method is used to carry out cyclic degradation tests on gray bricks. The nominal strength is proposed as a mechanical parameter to measure the structural damage of grey bricks, and the change in compressive strength and crystallization pressure of the samples after the test is measured and analyzed. The results show that the damage of different salts in the gray bricks shows a certain difference. Magnesium sulfate and sodium chloride cause significant damage to the surface of the gray bricks, while calcium chloride does not cause significant damage to the surface of the gray bricks. When the concentrations of sodium chloride solution, calcium chloride solution and magnesium sulfate solution are less than 13.73 mol/L, 11.47 mol/L and 17 mol/L, respectively, the nominal strength of gray brick samples increases; In the range of 9.9 mol/L and 4.73–8.94 mol/L, the crystallization pressure began to appear inside the sample. The research results provide an important scientific basis for evaluating the damage caused by salting to the damage of porous ancient building materials such as masonry.

Polyvinyl Alcohol/Graphene Oxide Conductive Hydrogels via the Synergy of Freezing and Salting Out for Strain Sensors.

Hydrogels of flexibility, strength, and conductivity have demonstrated broad applications in wearable electronics and soft robotics. However, it is still a challenge to fabricate conductive hydrogels with high strength massively and economically. Herein, a simple strategy is proposed to design a strong ionically conductive hydrogel. This ion-conducting hydrogel was obtained under the synergistic action by salting out the frozen mixture of polyvinyl alcohol (PVA) and graphene oxide (GO) using a high concentration of sodium chloride solution. The developed hydrogel containing only 5 wt% PVA manifests good tensile stress (65 kPa) and elongation (180%). Meanwhile, the PVA matrix doped with a small amount of GO formed uniformly porous ion channels after salting out, endowed the PVA/GO hydrogel with excellent ionic conductivity (up to 3.38 S m−1). Therefore, the fabricated PVA/GO hydrogel, anticipated for a strain sensor, exhibits good sensitivity (Gauge factor = 2.05 at 100% strain), satisfying working stability (stably cycled for 10 min), and excellent recognition ability. This facile method to prepare conductive hydrogels displays translational potential in flexible electronics for engineering applications.

Effect of niobium oxide thin film on the long-term immersion corrosion of the 2198-T851 aluminium alloy

This work aims to study the effect of niobium oxide coating on the long-term immersion corrosion of the 2198-T851 aluminium alloy. The niobium oxide thin film was successful obtained on freshly plates of 2198-T851 alloy by reactive sputtering technique. Scanning vibrating electrode tests, electrochemical impedance spectroscopy and immersion tests measurements were used to reveal the insights of global and localised corrosion behaviour of the functionalised material in different concentrations of sodium chloride solution. The electrochemical impedance spectroscopy spectra showed that the coating significantly influenced on the corrosion resistance of the 2198-T851 alloy, since the functionalised alloy immersed in 0.6 mol L−1 NaCl solution during 720 h (30 days) displays the same result as the bare material for 3 h of immersion. The scanning vibrating electrode tests demonstrated the coated material was free of local corrosive attack by the electrolyte in the first 10 h of immersion, whilst the bare alloy exhibited active anodic and cathodic sites over the surface with increasing current density values for longer immersion times. The deposited coating was able to increase the corrosion resistance of the 2198-T851 aluminium alloy used as fuselage skin material by the aeronautical industry as verified by the immersion tests. Finally, experimental results confirm the extraordinary properties of niobium oxide as-deposited coating.