NaX Solutions Research Articles

Corrosion behaviors of Mg−39Pb−11.5Al−1B−0.4Sc alloy in 3.5 wt.% NaX (X=F, Cl, Br and I) solutions

Mg−39Pb−11.5Al−1B−0.4Sc alloy was prepared by melting method, and the corrosion behaviors and mechanisms in 3.5 wt.% NaX (X = F, Cl, Br, and I) solutions were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), polarization curve test, and electrochemical impedance spectroscopy (EIS). The results show that the phases of Mg−39Pb−11.5Al−1B alloy are α-Mg, Mg2Pb, Mg17Al12 and AlB2. The addition of Sc can refine the microstructure significantly. The corrosion resistance of Mg−39Pb−11.5Al−1B−0.4Sc alloy in NaX solutions is in the order of NaCl < NaBr < NaI < NaF. During the corrosion process in NaX (X=Cl, Br, and I) solutions, Mg is first dissolved, then Mg2Pb is dissolved, and finally Mg17Al12 is fallen off from matrix. The corrosion products of Mg and Mg2Pb are Mg(OH)2 and MgO, respectively.

Compression icing of room-temperature NaX solutions (X = F, Cl, Br, I).

In situ Raman spectroscopy revealed that transiting H2O/NaX (∼64) solutions into an ice VI phase and then into an ice VII phase at a temperature of 298 K requires excessive pressures with respect to pure water. The increase of the critical pressures varies with the solute type in the Hofmeister series order: X = I > Br > Cl > F ∼ 0. The results suggest that the solute hydration creates electric fields that lengthen and soften the O:H nonbond and meanwhile shorten and stiffen the H-O bond through O-O Coulomb repulsion. Compression, however, does the opposite to solute electrification upon the O:H-O bond relaxation. Therefore, compression of the aqueous solutions recovers the electrification-deformed O:H-O bond first and then proceeds to the phase transitions, which requires excessive energy for the same sequence of phase transitions. Ice exclusion of solute disperses the frequencies of characteristic phonons and the critical pressures with unlikely new bond formation.

Glancing-angle Raman spectroscopic probe for reaction kinetics at water surfaces

We report glancing-angle Raman spectra acquired at the surface of aqueous dimethyl sulfoxide solutions and demonstrate that this technique can be used to measure the surface concentration of solutes. The presence of some solute molecules at the surface suppresses the intensity of the OH-stretching band of water there. We used this phenomenon to study the interfacial reaction of gas-phase ozone with aqueous NaX solutions (X = Br, I) by monitoring the decrease in intensity of the OH-stretching band of water over time. UV-VIS analysis of the product solutions indicates that X(3)(-), formed from X(2) evolved in the ozonation reaction, is the species most likely responsible for the decrease in OH-stretching intensity at the surface. The dependence of the rate of OH-Raman signal loss at the water surface on the bulk halide concentration is well described by a Langmuir-Hinshelwood kinetic model. The Langmuir-Hinshelwood parameters indicated that iodide has a approximately 50 times greater propensity for the surface compared to bromide.

The limiting partial molar volume and transfer partial molar volume of glycylglycine in aqueous sodium halide solutions at 298.15 K and 308.15 K

Apparent volumes V Φ of glycylglycine in aqueous NaX (X = F −, Cl −, and Br −) solutions have been obtained from densities of their solutions at 298.15 K and 308.15 K measured by using a precise vibrating-tube digital densimeter. These values have been utilized in conjunction with the values in water to deduce partial molar volumes of transfer Δ trs V Φ ∘ from water to different aqueous NaX solutions. Δ trs V Φ ∘ values are positive. The interpretation is that these results arise from the dominant interaction of the NaX with the charged centers of glycylglycine. The results show that Δ trs V Φ ∘ depend less on the temperature. Hydration numbers and interaction coefficients have been calculated from V Φ ∘ and Δ trs V Φ ∘ values and the values have been interpreted in terms of various interactions.

Electronic Transport in Molten Salt Rich Na — NaX Solutions (X = Br, I)

AbstractThe electronic conductivity of liquid Na—Nal and Na—NaBr has been measured over a wide concentration range from dilute to concentrated nonmetallic solutions at different temperatures between 700 and 900°C. Two methods have been applied, the Wagner polarization technique at low metal activities and an ac‐technique at high activities where the concentration has been varied by coulometric titration. A thermodynamic defect model previously used for solids is developed and extended to liquid solutions. It quantitatively describes the concentration and temperature dependence of the thermodynamic properties as well as the charge carrier concentration in these nonmetallic systems. The electronic mobility has been determined and the transport mechanism approaching the nonmetal‐metal transition is discussed.

Preparation and Solid-phase Thermal cis-α↔cis-β Isomerization of the Chromium(III) Triethylenetetramine Complexes

Abstract Heating of a mixture of CrCl3·6H2O and triethylenetetramine (trien) produced violet products which gave cis-α-[Cr2(OH)2trien2]X4·2H2O and cis-α-[Cr(OH)(H2O)trien]X2·H2O (X=Cl, Br or I) on treatment with aqueous NaX solutions. cis-α-[CrCl2trien]Cl·2H2O were obtained in the presence of a trace amount of water. Absolutely dry conditions are necessary for the preparation of cis-β-[CrCl2trien]Cl. The thermally induced reversible cis-α↔cis-β isomerization was detected in the complexes cis-α-[Cr(OH)(H2O)trien]Cl2·H2O and cis-β-[CrCl2-trien]Cl by means of derivatography and high-temperature IR spectroscopy. The former cis-α-hydroxoaqua complex was found to be converted irreversibly into cis-β-form above 225 °C in the solid-phase. The cis-β-form obtained readily isomerized to cis-α-form in aqueous media. The dimeric cis-α-[Cr2(OH)2trien2]4+ was converted gradually into the monomeric cis-α-[Cr(OH)(H2O)trien]2+ in water.