Aqueous NaNO3 Research Articles

Iodine Adsorption in Nanoporous Carbon to Fabricate Assimilated Battery Electrodes for Durable Hybrid Supercapacitors.

A hybrid supercapacitor is designed by coupling a battery electrode with a capacitive electrode in a single device/cell to enhance energy density. In iodine-based hybrid supercapacitors, the nanoporous carbon serves as the electrode material; however, the cathode or positive electrode is charged with iodine via electrodeposition from a redox aqueous electrolyte, while a negative electrode stores charges at the electric double-layer. In this work, iodine is loaded via physical adsorption into the porosity of a carbon electrode, keeping the aqueous electrolyte free from iodide redox moieties. By this way, the risk of polyiodide (I3- and I5-) generation at the positive electrode leading to a shuttling-related performance loss of the hybrid supercapacitor is prevented. Chemical interactions of iodine with the carbon surface and within the pores have been investigated with Raman spectroscopy, thermogravimetry and electron microscopy. Electrochemical methods have been used to test individual electrodes and hybrid supercapacitors in aqueous NaNO3 and aqueous LiTFSI at 5 mol/L concentration for performance parameters such as energy efficiency, capacitance, self-discharge and cyclability. The hybrid supercapacitor in aqueous LiTFSI exhibits stable capacitance and energy efficiency during long-term aging tests at 1.5 V. Carbon nanoarchitecturing with iodine as shown in the present work offers an economical approach to enhance the performance of hybrid supercapacitors.

The effect of ion shape and concentration on tunable wetting of water droplets on graphite surfaces

We study the wetting behaviors of aqueous NaCl and NaNO3 electrolyte nano-droplets on graphite surfaces by molecular dynamics simulations. Despite the same ion charge and similar Stokes radii, while the contact angle increases with NaCl concentration up to 3 M, the contact angle decreases with NaNO3 concentration up to 3 M. We show that while the liquid/vapor surface tension increases with both NaCl and NaNO3 concentrations, the solid/liquid interfacial tension varies with NaCl and NaNO3 concentrations oppositely. The Cl− ions are depleted from the first dense water layer at the graphite/water interface, leading to an increasing interfacial tension and an increasing contact angle with ion concentration. Beyond 3 M NaCl, the ionic double layer at the interface counteracts the depletion of ions at the immediate graphite/water interface. Therefore, the contact angle saturates beyond around 3 M NaCl. By contrast, the planar NO3− ions are adsorbed in the dense water layer at the immediate graphite/water interfaces, conform to the interface, and form excessive hydrogen bonds with water at the interface. Consequently, the interfacial tension is decreased with increasing NaNO3 concentrations, leading to a decreasing contact angle up to around 3 M NaNO3. At NaNO3 concentrations beyond 3 M, the interfacial tension no longer decreases, likely due to the saturation of NO3− in the dense region; therefore, the contact angle slightly increases with NaNO3 concentration due to the increasing liquid/vapor surface tension. Our research sheds light on the mechanisms of the effect of ion shape and concentration on droplet wetting on solids.

Analysis of Mechanisms Affecting the Tool in Pulsed Electrochemical Machining

Electrochemical machining (ECM) is an important technology in machining difficult-to-cut materials. The contactless nature of ECM and anodic dissolution of the workpiece propound no tool ablation. Nevertheless, in a few studies, tool damages, namely the formation of pits and geometrical changes, have been observed, which is the investigative goal of this work. This study considers three hypotheses to investigate tool changes during pulsed electrochemical machining (PECM) which are hydrogen embrittlement, cavitation erosion, and cathodic corrosion. A systematic study of monitoring possible tool (1.4112 martensitic stainless steel) changes during ECM and PECM in aqueous NaNO3 electrolyte is performed. Experimental results of this study show that hydrogen embrittlement and cavitation erosion are not the reason for causing changes in the tool. Cathodic corrosion might be the reason for the changes in the tool in this study; however, more investigation is needed. The approach in this study is investigating the microstructure of the tool regarding different aspects before and after ECM and PECM, as the microstructure stores information regarding phenomena occurring during any process.

Zavitsas’ model of aqueous NaF solution activities utilizing hydration numbers reported from Dielectric Relaxation spectroscopy

Dielectric Relaxation Spectroscopy (DRS) measures the number of water molecules irrotationally bound to electrolytes, which is a similar concept to the hydration number in Zavitsas’ model of electrolyte solution thermodynamics. Zavitsas’ model assumes that some water molecules are bound to electrolytes so strongly that they act as part of the electrolyte rather than the solvent. Most monovalent electrolytes have linear water activity versus concentration plots at low concentrations and many sparingly soluble electrolytes like NaF are only soluble in the linear region. Multiparameter models fit to this data are statistically overparametrized. The present study relieves overparameterization by substituted the number of irrotationally bound water molecules determined by DRS for the hydration number in Zavitsas’ model and then optimized the NaF extent of dissociation (ie) to best fit water activity data. This ie value was consistent with and could be predicted by The Law of Matching Water Affinities. Using the resulting model parameters, the solubility of NaF was predicted in aqueous NaNO3 solutions without having to optimize any parameters to the solubility data. These results demonstrates that DRS can be used to parametrize Zavitsas’ model.

Ion-dipole complex effect on activity coefficient of L-methionine in aqueous NaCl and NaNO3 solutions

Ion-dipole complex effect on activity coefficient of L-methionine in aqueous NaCl and NaNO3 solutions

Study of the electrochemical dissolution behavior of Nitinol shape memory alloy in different electrolytes for micro-ECM process

Nickel-titanium alloy (Nitinol) is an excellent shape memory alloy (SMA) for microelectro-mechanical systems (MEMS) particularly in biomedical applications owing to its three excellent features shape memory effect (SME), superelasticity, and biocompatibility. The temperature-dependent material transformation properties of Nitinol SMAs make conventional machining difficult. Micro-ECM, a non-conventional machining process for conductive materials regardless of their strength and hardness, has the potential to fabricate microfeatures on Nitinol. This study presents the investigation on the electrochemical dissolution behavior of Nitinol in different electrolytes for micro-ECM. The influence of electrolytes on the nature of dissolution of Nitinol was studied by fabricating microchannels in three levels of parameters containing applied voltage and electrolyte concentration. The first three electrolytes were all aqueous neutral electrolytes, i.e., NaCl, NaNO3, and NaBr. The aqueous NaNO3 was successful in fabricating microchannels at all levels of process parameters. However, aqueous electrolytes form relatively a huge amount of sludge on the machined surface reducing both dissolution efficiency and machining accuracy. Thus, ethylene glycol-based NaNO3 was used to fabricate microchannels with lower depth overcut (DOC), width overcut (WOC), and length overcut (LOC) with respect to aqueous NaNO3 electrolyte. The potentiodynamic polarization (PDP) tests of Nitinol through cyclic voltammetry (CV) shows passive dissolution in aqueous electrolyte and active dissolution in non-aqueous electrolyte.

In situ spatiotemporal solute imaging of metal corrosion on the example of magnesium

Visualization and quantification of corrosion processes is essential in materials research. Here we present a new approach for 2D spatiotemporal imaging of metal corrosion dynamics in situ. The approach combines time-integrated Mg2+ flux imaging by diffusive gradients in thin films laser ablation inductively coupled plasma mass spectrometry (DGT LA-ICP-MS) and near real-time pH imaging by planar optodes. The parallel assessment of Mg2+ flux and pH distributions on a fine-structured, bare Mg alloy (b-WE43) showed intense Mg dissolution with Mg2+ flux maxima up to 11.9 ng cm−2 s−1 and pH increase >9 during initial corrosion (≤15 min) in aqueous NaNO3 solution (c = 0.01 mol L−1). The techniques visualized the lower initial corrosion rate in buffered synthetic body fluid (Hank's balanced salt solution; pH 7.6) compared to unbuffered NaNO3 (pH 6.0), but precise localization of Mg corrosion remains challenging under these conditions. To further demonstrate the capability of DGT LA-ICP-MS for spatiotemporal metal flux imaging at the microscale, a coated Mg alloy (c-WE43) with lower reactivity was deployed for ≤120 min. The high spatial resolution (∼10 μm × 80 μm) and low limits of detection (≤0.04 ng cm−2 s−1, t = 60 min) enabled accurate in situ localization and quantification (Urel = 20%, k = 2) of distinct Mg2+ flux increase, showing micro-confined release of Mg2+ from surface coating defects on c-WE43 samples. The presented approach can be extended to other metal species and applied to other materials to better understand corrosion processes and improve material design in technological engineering.

The NaxMnO2 materials prepared by a glycine-nitrate method as advanced cathode materials for aqueous sodium-ion rechargeable batteries

Cathodic material for sodium-ion rechargeable batteries based on NaxMnO2 were synthesized by glycine nitrate method and subsequent annealing at high temperatures. Different crystal structures with different morphologies were obtained depending on the annealing temperature: hexagonal layeredα-Na0.7MnO2.05 nanoplates were obtained at 850 °C, while 3-D tunnel structured Na0·4MnO2 and Na0·44MnO2, both with rod-like morphology, were obtained at 800 °C and 900 °C, respectively. The investigations of the electrochemical behavior of obtained cathodic materials in aqueous NaNO3 solution have shown that Na0·44MnO2 obtained at 900 °C has shown the best battery performance. Its initial discharge capacities are 123.5 mA h/g, 113.2 mA h/g, and 102.0 mA h/g at the high current densities of 1000, 2000 and 5000 mA/g, respectively.

Highly Stable Silver(I) Complexes with Cyclen-Based Ligands Bearing Sulfide Arms: A Step Toward Silver-111 Labeled Radiopharmaceuticals.

With a half-life of 7.45 days, silver-111 (βmax 1.04 MeV, Eγ 245.4 keV [Iγ 1.24%], Eγ 342.1 keV [Iγ 6.7%]) is a promising candidate for targeted cancer therapy with β– emitters as well as for associated SPECT imaging. For its clinical use, the development of suitable ligands that form sufficiently stable Ag+-complexes in vivo is required. In this work, the following sulfur-containing derivatives of tetraazacyclododecane (cyclen) have been considered as potential chelators for silver-111: 1,4,7,10-tetrakis(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO4S), (2S,5S,8S,11S)-2,5,8,11-tetramethyl-1,4,7,10-tetrakis(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO4S4Me), 1,4,7-tris(2-(methylsulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane (DO3S), 1,4,7-tris(2-(methylsulfanyl)ethyl)-10-acetamido-1,4,7,10-tetraazacyclododecane (DO3SAm), and 1,7-bis(2-(methylsulfanyl)ethyl)-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). Natural Ag+ was used in pH/Ag-potentiometric and UV–vis spectrophotometric studies to determine the metal speciation existing in aqueous NaNO3 0.15 M at 25 °C and the equilibrium constants of the complexes, whereas NMR and DFT calculations gave structural insights. Overall results indicated that sulfide pendant arms coordinate Ag+ allowing the formation of very stable complexes, both at acidic and physiological pH. Furthermore, radiolabeling, stability in saline phosphate buffer, and metal-competition experiments using the two ligands forming the strongest complexes, DO4S and DO4S4Me, were carried out with [111Ag]Ag+ and promising results were obtained.

Immobilization of Polyiodide Redox Species in Porous Carbon for Battery-Like Electrodes in Eco-Friendly Hybrid Electrochemical Capacitors.

Hybrid electrochemical capacitors have emerged as attractive energy storage option, which perfectly fill the gap between electric double-layer capacitors (EDLCs) and batteries, combining in one device the high power of the former and the high energy of the latter. We show that the charging characteristics of the positive carbon electrode are transformed to behave like a battery operating at nearly constant potential after it is polarized in aqueous iodide electrolyte (1 mol L−1 NaI). Thermogravimetric analysis of the positive carbon electrode confirms the decomposition of iodides trapped inside the carbon pores in a wide temperature range from 190 °C to 425 °C, while Raman spectra of the positive electrode show characteristic peaks of I3− and I5− at 110 and 160 cm−1, respectively. After entrapment of polyiodides in the carbon pores by polarization in 1 mol L−1 NaI, the positive electrode retains the battery-like behavior in another cell, where it is coupled with a carbon-based negative electrode in aqueous NaNO3 electrolyte without any redox species. This new cell (the iodide-ion capacitor) demonstrates the charging characteristics of a hybrid capacitor with capacitance values comparable to the one using 1 mol L−1 NaI. The constant capacitance profile of the new hybrid cell in aqueous NaNO3 for 5000 galvanostatic charge/discharge cycles at 0.5 A g−1 shows that iodide species are confined to the positive battery-like electrode exhibiting negligible potential decay during self-discharge tests, and their shuttling to the negative electrode is prevented in this system.

Chain conformation and biological activities of hyperbranched fucoidan derived from brown algae and its desulfated derivative

A fucoidan derived from marine brown algae has great potential in biomedical filed. Herein, the fucoidan was successfully isolated and purified by using chitosan microspheres, resulting in the sulfate fucoidan (CF) with degree of sulfation (DS) of 0.94. CF was identified to be highly branched, consisting of fucose (77.4%) and galactose (13.9%), etc., supported by the results of GCMS and light scattering with the structure-sensitive parameter of 0.98 in 0.15 M aqueous NaNO3. The individual CF and its desulfated derivative chains adopted sphere-like conformation in water, observed by atomic force microscopy. CF exhibited higher antiangiogenesis than the desulfated one and strong antileukemia activities through inhibiting cell proliferation and inducing cell apoptosis via cell cycle arrest at G1 phase in vitro. This work provided important information that ester sulfate groups of polysaccharide played an important role in the enhancing of bioactivities of fucoidan, and put forward to a potential drug to treat acute myelocytic leukemia (AML) and tumors.

Novel route to synthesize CaAl- and MgAl-layered double hydroxides with highly regular morphology

A facile, sol–gel method was developed to obtain Al-containing layered double hydroxides (LDHs) with Ca or Mg divalent cations. Ca- and Al-alkoxide were added to aqueous NaNO3 solution, and, after rapid gelation, a solid product, phase-pure, highly crystalline CaAl–LDH was formed with exceptionally regular morphology without impurities for the first time with sol–gel method. The lack of salt in the solution used for the hydrolysis resulted in a non-desirable by-product (katoite). For the sol–gel synthesis of MgAl–LDH, it was found that its formation was less sensitive to the presence of nitrate ions, and pure water or aqueous NaOH worked equally well. The product was also a highly crystalline material with thin, plate-like morphology as revealed by X-ray diffractometry and scanning electron microscopy. IR measurements indicate the lack of organic substance in the interlamellar space for both materials.

Role of temperature in de-mixing absorbance spectra composed of compound electrolyte solutions.

This work is focused on the role of temperature in the de-mixing of absorbance spectra measured in mixed aqueous Na2SO4 and NaNO3 solutions. First, the influence of temperature on the absorbance spectrum of demineralized water was determined. Second, the absorbance spectra of five separate electrolytes (NaNO2, NaNO3, CaCl2, K2CO3, and NaOH) at three temperatures (4°C, 25°C, and 50°C) for concentrations ranging from 0.0625M to 0.5M were examined. These five electrolytes show similar temperature dependencies. Finally, absorbance spectra of mixed solutions were investigated at temperatures of 5°C, 15°C, 25°C, 35°C, and 45°C for concentrations ranging from 0.0625M to 0.5M per electrolyte in the mixture. The spectral window from 650 to 1100nm was utilized to observe the ionic and temperature influences on the vibrational modes of the OH bond in the solvent molecules. The effects of dissolving Na2SO4 and NaNO3 are nonlinearly cumulative at lower temperatures indicating extended alteration of the water structure beyond the first hydration shell. A similar trend was observed for a mixture of Na2CO3 and NaCl. Furthermore, it was found that higher temperatures are better for recovering the separate component absorption signatures of an electrolyte mixture. The near-infrared spectral regime is well suited for integrated sensing, and therefore these results can help in designing an integrated sensor to identify inorganic species in water.

Facile Deposition of Cu−SnOx Hybrid Nanostructures on Lightly Boron‐Doped Diamond Electrodes for CO2 Reduction

AbstractIn this work, we report a facile synthesis of Cu−SnOx hybrid nanostructures on lightly boron‐doped diamond (BDDL) electrodes by a potentiodynamic electrodeposition method. The deposition potential for Cu−SnOx hybrid nanostructures was cycled between 0 to −1.0 V vs Ag/AgCl for five consecutive runs at a scan rate of 50 mV/sec. The growth of the Cu−SnOx hybrid nanostructures on BDDL was optimized by varying the number of potentiodynamic deposition cycles and precursor concentration. A uniform particle size distribution of Cu−SnOx was obtained on BDDL using 10 mM CuSO4 and 5 mM SnCl2 in 50 mM aqueous NaNO3. Detail of surface morphology and surface elemental composition of the optimized Cu−SnOx hybrid nanostructures modified BDDL electrodes were characterized. The optimized Cu−SnOx hybrid nanostructures on BDDL were found to be in the size range of 50 to 100 nm with a 3 to 10 nm SnOx‐rich shell. This optimized Cu−SnOx modified BDDL electrode was tested for electrochemical CO2 reduction reaction in aqueous electrolyte and found to produce primarily CO with a Faradaic Efficiency of up to 82.5 % at −1.6 V vs Ag/AgCl.

The relative viscosity of NaNO3 and NaNO2 aqueous solutions

In aqueous solution, both nitrate and nitrite are planar, monovalent, and have the same elements but different sizes and charge densities. Comparing the viscosity of NaNO2 and NaNO3 aqueous solutions provides an opportunity to determine the relative importance of anion size versus strength of anion interaction with water. The viscosity of aqueous NaNO2 and NaNO3 were measured over a temperature and concentration range relevant to nuclear waste processing. The viscosity of NaNO2 solutions was consistently larger than NaNO3 under all conditions, even though nitrate is larger than nitrite. This was interpreted in terms of quantum mechanical charge field molecular dynamics calculations that indicate that nitrite forms more and stronger hydrogen bonds with water per oxygen atom than nitrate. These hydrogen bonds inhibit rotational motion required for fluid flow, thus increasing the nitrite solution viscosity relative to that of an equivalent nitrate solution.

Solvation Thermodynamics of DL-Phenylalanine in Aqueous NaNO3 Solution at 298.15 K

By “formol titrimetry” method solubilities of DL-phenylalanine (PA) in aqueous NaNO3 solution were measured at 298.15 K. The standard Gibbs energy of PA in aqueous and aqueous NaNO3 solution and also transfer free energy of PA was evaluated. The thermodynamic parameters: molar volume, densities, dipole moment and solvent diameter of aqueous solution of NaNO3 have also been reported. Electrolyte effects on the solubility and relative stability of PA is guided by different types of interactions which are explained in this manuscript.

Influence of Metallic Ions on the Aggregation of Soft Colloidal Polysaccharides

The aggregation behavior of carboxymethyldextran, a soft and anionic polysaccharide, was studied in the presence of divalent cation Cd2+ in aqueous NaNO3 electrolyte. The experimental destabilization conditions of this colloidal suspension have determined by turbidimetric method and the kinetics of aggregation and the characteristics of aggregates were analyzed through Dynamic Light Scattering measurements. The aggregates are derived from very attractive interactions, which are modulated by the metallic ion to carboxymethylextran ratios and their feature indicates a mechanism characterized by a diffusion-limited aggregation.

Effect of Polarisation Mimicking Cathodic Electrodeposition Coating on Industrially Relevant Metal Substrates with ZrO2‐Based Conversion Coatings

AbstractModern ZrO2‐based conversion coatings were deposited on an aluminium alloy (AA6014), a cold‐rolled steel, a zinc electrogalvanised steel and a Sendzimir zinc hot‐dip galvanised steel. Pretreated substrates were subjected to galvanostatic polarisation in aqueous NaNO3 to mimic deposition conditions of cathodic electrodeposition coatings. No significant structural modification of the conversion coatings was found with Raman or photoluminescence (PL) spectroscopy. After treatment, increased PL indicated an increased number of point defects. Downstream monitoring of dissolved Zr indicated an insignificant totally dissolved fraction of 0.01 % after 5 s of polarisation, which may occur through vacancy‐pair coalescence with concurrent oxide dissolution, as discussed for transpassive dissolution. Overall, the ZrO2 films remained intact after polarisation.

Solubility of glycine and DL-nor-valine in aqueous solutions of NaNO3 and KNO3 and measurements of transfer thermodynamics

The solubility and solvation thermodynamics of the amino acids in aqueous solutions are related to their biochemical and biophysical actions in human physiology. This makes such studies to be highly relevant for academia, health and industry. In the present work solubilities of glycine and DL-nor-valine were measured under different experimental conditions by an analytical gravimetric method in aqueous NaNO3 and KNO3 solutions and the results were employed as an input in theoretical solvation investigations. Thermodynamic parameters like standard transfers Gibbs energies and entropies and other important physicochemical parameters such as molar volume, density, dipole moment, mixed solvent diameter, etc., of the experimental solutions were evaluated at 298.15K and compared with earlier values. Finally the above mentioned parameters were used to conclude ΔGt,ch0(i) i.e. chemical effects of the transfer Gibbs energies and ΤΔSt,ch0(i) i.e. chemical effects of the transfer entropy. Different factors such as nature of solute and solvent, interactions between solute and solvents, etc., which are influencing the solvation of glycine and DL-nor-valine were also characterized by different physical and analytical techniques.

Ratiometric detection of Raman hydration shell spectra

The micro-structure of hydration shell of solute in water is significant for understanding the properties of aqueous solutions. However the spectra of hydration shell are difficult to be obtained. Herein, a novel Raman ratio spectra, which is obtained through dividing the Raman spectra of aqueous solutions from the spectrum of water, was applied to deduce the spectra of hydration shell of organic (acetone-D6) and inorganic compounds (NaNO3, NaSCN, NaClO4, Na2SO4, NaCl) in water. Those spectra of the hydration shell were employed to study the micro-structures of the first hydration shells of anions, the number of water molecules in the first hydration shell of free anions and acetone-D6, and the aggregation behavior of ions in the concentrated aqueous NaNO3. The number of water molecules in the hydration shell was supported by our molecular dynamic simulations. The Raman ratio spectra can be widely employed to obtain the spectra of the first hydration shell, and it is helpful to understand the micro-structure of aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.