Thermodynamics and vacuum distillation studies of liquid Al–Ga and In–Sn alloys

Activities of components in liquid Al–Ga and In–Sn alloys, the separation coefficients and vapour–liquid phase equilibrium in vacuum distillation were predicted using the molecular interaction volume model as a function of the activity coefficients. The results indicated that both Al and In are preferentially volatilised into vapour phase while Ga and Sn remain in residue. Similarly, we found that both the mass fraction and the content of Al and In in vapour phase increase as distillation temperature increases such that when the content of Al is 0.005985 wt% and In is 0.004141 wt% in vapour phase, respectively, in liquid phase, it was 70 wt% at T = 1073 K for both. The calculated values of activity and activity coefficients at various temperatures are presented. Comparison of the predicted values with experimental data indicates good agreement, thus verifying from statistical thermodynamics viewpoint that the model is stable and reliable.     

Adsorption of Cl−, Br−, and I− ions from 0.1 M solutions in methanol on Ga, (In-Ga), and (Tl-Ga) electrodes

Adsorption of Cl^?, Br^?, and I^? (Hal^?) ions from 0.1 M solutions in methanol (MeOH) is studied on the liquid renewable Ga, (In-Ga), and (Tl-Ga) electrodes by the methods of differential capacitance and jet electrode. It is shown that the adsorption parameters and the series of surface activity of halide ions in MeOH essentially depend on the metal nature. On the (In-Ga) and (Tl-Ga) electrodes, as well as on the Hg electrode, the surface activity of halide ions increases in the series: Cl^? < Br^? < I^?; on the Ga electrode, it varies in another series: Br^? < Cl^? < I^?. The data for the Ga/MeOH interface support the result, which was first obtained on the Ga/N-methyl formamide (N-MF) interface, that the effect of inversion of surface activity series can be observed not only in the aprotic solvents, but also in the protic solvents. The data, which were obtained in MeOH, are compared with the corresponding data, which were obtained in N-MF, dimethyl formamide (DMF), acetonitrile (AN), and water. For Ga, (In-Ga), and (Tl-Ga) electrodes, the adsorption of Hal^? varies in the series: H₂O < MeOH ≈ N-MF < DMF < AN. The data obtained in MeOH indicate that the energy of metal-Hal^? interaction (ΔG _M-Hal) increases in the series (Tl-Ga) < (In-Ga) < Ga as the electronic work function increases. This is in agreement with the data, which were obtained in other solvents, and is the evidence for the donor-acceptor nature of metal-Hal^? interaction, where the Hal^? ions are the donors of electron pair with respect to the metal.     

Electrical conductivity and thermoelectric power of liquid Co–Sn alloys

The electrical conductivity and thermoelectric power of liquid Co–Sn alloys were investigated in a wide concentration and temperature range. It was shown that the electrical conductivity of the melts decreased with an increase of the Co content. The results are interpreted in the context of the s–d hybridisation model. The corresponding behaviour is caused by sharing electrons from one metal to another one. This is in agreement with the concept of Fermi enthalpy, according to which up to two electrons from Sn transfer to the uppermost bands of Co.     

Predicting the formation enthalpies of Cd–Ga–In–Sn–Zn liquid alloys by the limiting partial enthalpies

The formation enthalpies of Cd–Ga–Sn, In–Sn–Zn, Cd–Ga–In–Sn, Ga–In–Sn–Zn and Cd–Ga–In–Sn–Zn liquid alloys are calculated by molecular interaction volume model (MIVM), which only using the limiting partial enthalpies of binary systems and the coordination numbers of the constituent elements in liquid alloys. The predicted values are compared with the experimental data and the values calculated using Hoch–Arpshofen model, which indicate that the model is reliable and convenient.     

Thermodynamic evaluation of viscosity in In–Zn and Sn–Zn liquid alloys

A theoretical formalism that links thermodynamic properties to transport properties has been used to study the viscosity of Sn–Zn and In–Zn liquid alloys at various temperatures. The formalism was successful at describing the thermodynamic properties of these alloys and showed a better estimation of the viscosity of the Sn–Zn alloy than that of the In–Zn alloy.     

Thermodynamic and surface properties of Ge–Ga and Ge–Sb liquid alloys

Thermodynamic and surface properties of Ge–Ga and Ge–Sb liquid alloys have been studied using statistical mechanical formulations based on complex formation and that based on the concept of layered structure near the interface. The study showed that low level of complex formation of the form Ge _{2 Sb} exists in Ge–Sb toward the Ge-rich end of the concentration range and the surface properties of Ge–Ga are almost equal to their corresponding bulk equivalent.     

Donor–acceptor interactions between resonance-excited silver nanoparticles and halide ions in water solutions

Donor–acceptor interactions between silver nanoparticles (NPs), resonance-excited by optical quanta of light, and halide ions are studied in aqueous solutions. It is shown that deactivation of the plasmon excitation of Ag NP proceeds according to the exchange mechanism of electron transfer. Plasmon excitation quenching constants are determined and a correlation between quenching and the donor properties of halide ions is found. The efficiency of electrostatic interaction between resonantly-excited Ag NPs and halide ions is studied, and their dipole moment is determined.

     

Characterization of SEI layer formed on high performance Si–Cu anode in ionic liquid battery electrolyte

Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of > 1620 mAhg^? 1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries.     

The abnormal changes of electrical resistivity in liquid Pb–In alloys

Electrical resistivity of liquid lead and indium (Pb–In) alloys with different compositions has been measured using the four-probe method in a large temperature range. Marked turning points on each resistivity–temperature (ρ–T) curve of the liquid Pb–In alloys can be observed far above the liquidus. The unusual variation of the resistivity of Pb–In melts suggests a structural transition of these melts, for resistivity is a sensitive parameter to the structure. Moreover, the DSC experiment of Pb–In melts supports the existence of a liquid–liquid (L–L) structure transition in Pb–In melts. Such a L–L structural transition can be described in terms of the gradual disappearance of atomic bonds corresponding to the crystal structure and/or to a reduction of the size of pre-formed atomic clusters. This implies an increase of disorder in the high temperature melts. The transition temperatures depend on the composition of Pb–In melts and the onset transition temperatures of the intermediate phase (α) Pb–63%In and Pb–70.6%In melts are higher than that of other compositions.     

Thermodynamic studies of the surface and transport properties in Ag–In and Ag–Sb liquid alloys

The surface tension, surface concentration, viscosity and mutual diffusion co-efficients of the Ag–In and Ag–Sb liquid alloys have been calculated using energetics and derivables from a statistical mechanical framework which recognises the formation of atom clusters of self associates. Our calculations suggest the existence of some form of local order in the systems. Ag–In showed higher tendencies to heterocoordination in the bulk-manifested higher values of mutual diffusion coefficient throughout the concentration range. The viscosity values of Ag–In and Ag–Sb were calculated using the expression reported by Kucharsky which relates the viscosity of a liquid binary alloy to the activity coefficients of the liquid alloy components that are raised to some power m. This exponent m is a fitted parameter. The calculated viscosity values for Ag–Sb had some reasonable agreement with experiment above 0.5 atomic fraction of Sb, using a fitted parameter value of m = 4.5. The fitted parameter value for the viscosity of Ag–In is expected to be in the range 1.5 ≤ m ≤ 3.5.     

Electrical double layer on (111) and (100) faces of silver single crystals in solutions containing ClO4− and F−

The differential capacitance-potential dependence C(E) of electrolytically grown (111) and (100) faces of silver single crystals in diluted solutions of NaClO₄ and KF was studied. Comparison with results obtained in KF solutions shows a concentration-independent shift of E_min to more negative potentials and higher values of the reciprocal slope of the C⁻¹ vs. C_d⁻¹ plots. The data obtained have been explained as due to a weak specific adsorption of ClO₄⁻ which is stronger on the (100) face. The influence of water in the double layer on the adsorption has been discussed.     

Study on surface adsorption from cationic surfactant–electrolyte mixed aqueous solution including BF 4 − ion

The surface tension of aqueous mixtures of dodecyltrimethylammonium tetrafluoroborate (DTABF₄) and sodium tetrafluoroborate (NaBF₄) was measured as a function of total molality and composition of DTABF₄ at 298.15 K. The results were analyzed by originally developed thermodynamic equations and compared with those of dodecyltrimethylammonium bromide (DTAB)–sodium bromide (NaBr) mixed system. It was indicated that BF₄⁻ ions reduce the repulsion between DTA⁺ ions more effectively than Br⁻ ions in the adsorbed film. To investigate this difference more closely, the surface tension of DTAB–NaBF₄ and DTABF₄–NaBr mixed system was also measured. The data analysis revealed that BF₄⁻ ions are adsorbed positively even for the pure NaBF₄ system and preferentially to Br⁻ ions in these mixtures. Furthermore, it was concluded that the side-by-side arrangement suggested in the adsorbed film of 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF₄) is due to not only the positive adsorption of BF₄⁻ ions but also the capability of hydrogen bond formation between imidazolium ion and BF₄⁻ ions.     

Electrical Double Layer Structure in Surface-Inactive Electrolytes on a Liquid Cd–Ga Electrode in Methanol and Propylene Carbonate

Differential capacitance curves and potentials of zero charge are obtained for liquid Cd–Ga electrodes in methanol and propylene carbonate solutions of a surface-inactive electrolyte. It is found that double-layer characteristics of the Cd–Ga electrode differ from those of a Ga electrode both in nonaqueous solutions and in water. The lyophilic nature of the Cd–Ga electrode, relative to methanol and propylene carbonate, is shown to approach that of the In–Ga electrode. In the absence of a metal–solvent chemisorption interaction, the difference between reciprocal metallic capacitances for Cd–Ga and Hg electrodes is independent of the solvent nature. The chemisorption interaction between the solvents and Cd–Ga, Ga, and In–Ga electrodes increases with the solvents' donor number.     

Evaluation of AMP–PAN composite for adsorption of Cs+ ions from aqueous solution using batch and fixed bed operations

Ammonium molybdophosphate–polyacrylonitrile (AMP–PAN) as an organic–inorganic composite ion exchanger was synthesized and investigated for adsorption of cesium from aqueous solutions. The synthesized composite was characterized by various techniques including X-ray powder diffraction, Fourier Transform Infrared Spectroscopy, thermogravimetry-differential scanning calorimetry, specific surface analysis, scanning election microscopy, X-ray fluorescence spectroscopy and CHN elemental analysis. The cesium adsorption on composite adsorbent was studied as a function of contact time, pH, temperature, and presence of various cations. In addition, adsorption thermodynamic parameters were determined and it was observed that the adsorption of cesium on the adsorbent is an endothermic and spontaneous process. The Langmuir and Freundlich adsorption isotherms were fitted to the adsorption data and the results showed that the Langmuir model best predicates the cesium adsorption on the adsorbent. The dynamic behavior of cesium adsorption on AMP–PAN ion exchanger was also investigated for a fixed bed column and desorption was carried out.     

Study on the microstructure and liquid–solid correlation of Al–Mg alloys

Based on the available structural models and theories of electrical resistivity (ER) of liquid alloys, the structure and the liquid–solid correlation of Al _(100-x) Mg_x (x = 0, 10, 20, 30, 40, 50) alloys have been qualitatively studied by measuring the ER during the heating/cooling process using the direct-current (DC) four-probe method, as well as by characterizing the solidification morphology and testing the hardness. The result shows that the ER of Al–Mg alloys increases with the increasing temperature and the Mg content; thermal state and history have an effect on the solidification structure and properties: the ER of Al–Mg alloys exhibits a lag phenomenon of structure change during the heating/cooling process. A higher heating/cooling rate contributes to the more obvious relaxation effect of ER and the more uniform structure. Furthermore, higher pouring temperature (PT) leads the melts and solidification structure to be more homogeneous, which increases the hardness.     

Effect of electrolyte and agitation on the anomalous behavior and morphology of electrodeposited Co–Ni alloys

This study continues previous work which showed that the anomalous behavior of Co–Ni deposition could be alleviated or eliminated through use of cyclic voltammetry (CV) or pulse reverse (PR) plating. The research focuses on aspects not considered in this previous work: the effects of the anion and agitation in the plating bath. A comparison is made of Co–Ni electrodeposition using the CV and PR techniques in sulfate and chloride baths at pH 3 containing equimolar Co(II) and Ni(II) concentrations under both stirred and unstirred conditions. The anomalous behavior can be significantly suppressed and even eliminated with current efficiencies above 90 % through use of PR plating, in particular, but only if carried out in a chloride solution under quiescent conditions. Both metal ion reduction during the cathodic portion and oxidation of the coating during anodic polarization are accelerated in the chloride solution relative to that in the sulfate solution. Electrolyte agitation exacerbates anomalous deposition and reduces the current efficiency by enhancing mass transport of Co(II) and H⁺ to and from the electrode. The origin of anomalous deposition and effects of the chloride ion are examined in terms of coordination chemistry and ligand field theory. This analysis suggests that oxidation of the Co–Ni coating in the chloride solution during anodic polarization of the PR and CV cycles when cobalt preferentially dissolves is crucial to suppressing the anomalous behavior. Examination of the coatings shows that the anion type, degree of agitation of the electrolyte, and electroplating technique significantly affects their microstructure and roughness.     

Structure of Electrical Double Layer on Liquid Pb–Ga Alloy in Aqueous Electrolytes

A new electrode, which is a liquid Pb–Ga alloy (0.06 at. % Pb), is developed and studied. It is shown that the alloy's double-layer characteristics dramatically differ from characteristics of a Ga electrode and are practically identical to characteristics of a Pb electrode. Hence, the Pb–Ga electrode in fact models electrochemical properties of a liquid Pb electrode. It is established that the metallic capacitance of the Pb–Ga electrode occupies an intermediate position between values of metallic capacitance of Ga and Hg electrodes, provided the metal–water chemisorption interaction is absent and the electrode charge is fixed. Hydrophilicity of the Pb–Ga electrode is substantially lower than hydrophilicity of a Ga electrode and coincides with hydrophilicity of an Hg electrode. It is shown that In–Ga, Cd–Ga, and Pb–Ga electrodes have close values of the electrochemical work function, and the chemisorption potential drop of the solvent in them increases in the series Pb–Ga < In–Ga < Cd–Ga with decreasing distance of closest approach of water molecules to the ionic core of the metal. The absorbability of anions at the Pb–Ga electrode increases in the series BF^– ₄= SO^2– ₄< Cl^–< Br^–< I^–.     

Adsorption of Cd2+ and Cu2+ ions from aqueous solutions by a cross-linked polysulfonate–carboxylate resin

A new cross-linked polyzwitterion (CPZ) was synthesized through cyclocopolymerization of 3-[diallyl(carboxymethyl)ammonio]propane-1-sulfonate (92.5 mol%), and a cross-linker 1,1,4,4-tetraallylpiperazine-1,4-diium chloride (7.5 mol%) in the presence of tert-butylhydroperoxide. The cross-linked polyzwitterion/anion (CPZA) was obtained by the basification of CPZ with NaOH. The adsorption data fit both Temkin and Freundlich isotherm models. The adsorption trend on CPZA is as Cu²⁺ > Cd²⁺ and both followed pseudo-second-order kinetic model. The negative ΔG and positive ΔH values ascertained the spontaneous and endothermic nature of the adsorption process. The effectiveness of a zwitterionic–anionic motif consisting of quaternary nitrogen, sulfonate and carboxylate groups has been tested for the first time for capturing Cd²⁺ and Cu²⁺ ions at low concentrations.     

Pitting of Al and Al–Si alloys in KSCN solutions and the effect of light

The pitting corrosion susceptibility of pure Al and three Al-Si alloys, namely (Al-6%Si), (Al-12%Si) and (Al-18%Si) has been studied in 0.04 M KSCN solution. Measurements were carried out under the effect of various experimental conditions using cyclic polarization, potentiostatic and galvanostatic techniques. In all cases, the potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of a thin film of Al₂O₃ on the anode surface. The passive region is followed by pitting corrosion, at a certain critical potential, pitting potential (E_pit), as a result of breakdown of the passive film by SCN^? anions. Cyclic polarization measurements allowed the determination of the pitting corrosion parameters, namely the pitting potential and the repassivation potential (E_rp). Alloyed Si decreased the passive current (j_pass) and shifted both E_pit and E_rp towards more positive values. Thus alloyed Si suppressed pitting attack. The effect of illumination on passivity and the initiation of pitting corrosion on Al in KSCN solutions was also studied. It is observed that illumination of Al leads to an increase in its pitting corrosion resistance-apparent from j_pass, E_pit, and E_rp measurements in aggressive KSCN solutions.