Corrosion behaviour of carbon materials exposed to molten lithium chloride–potassium chloride salt

The corrosion behaviour of four carbon materials namely low density graphite, high density graphite, glassy carbon and pyrolytic graphite were investigated in molten LiCl–KCl electrolyte medium at 600 °C for 2000 h under high pure argon atmosphere. Structural and microstructural changes in the carbon materials after exposure to molten chloride salt were investigated from the weight change and using scanning electron microscopy, atomic force microscopy, X-ray diffraction and laser Raman spectroscopic techniques. Microstructural analysis of the samples revealed the poor corrosion resistance of high density and low density graphite and severe attack was observed at several places on the surface. On the other hand, glassy carbon and pyrolytic graphite were relatively inert, while pyrolytic graphite showed the best corrosion resistance to molten salt attack. In the order of increasing corrosion resistance to molten salt, the carbon materials were found to follow the sequence: low density graphite < high density graphite < glassy carbon < pyrolytic graphite.     

Unique and contrasting mixed-metal lithium–calcium and lithium–barium hexamethyldisilazide complexes

Addition of lithium hexamethyldisilazide to calcium or barium bis(hexamethyldisilazide) in THF resulted in the synthesis of two unique but very different mixed-metal complexes: X-ray crystallography shows these to be, respectively, the heterobimetallic complex [Ca{N(SiMe₃)₂}₃Li(THF)] (1), containing two calcium–lithium bridging amide ligands and the remarkable co-crystalline compound [Ba{N(SiMe₃)₂}₂(THF)₃][Li₂{N(SiMe₃)₂}₂(THF)₂] (2).     

Product of dissolution of V2O5 in the choline chloride–urea deep eutectic solvent

The previously reported high solubility data for V₂O₅ in the deep eutectic solvent of choline chloride and urea (ChCl–urea) is the result of forming [H₂V₁₀O₂₈]^4 − complex anion.Storing this as-prepared solution for about three months at 20 °C, a new compound, [(CH₃)₃N(CH₂)₂OH]₄[H₂V₁₀O₂₈]·2(NH₂)₂CO (1), was obtained. The solid-state structure is assembled of dihydrogendecavanadate(V) anions, choline cations and molecules of urea. The crystal structure is further stabilized by electrostatic interactions and by O–H⋯O and N–H⋯O hydrogen bonds. The ⁵¹V NMR spectroscopy detected the decavanadate anion in the as-prepared solution.     

Electrochemical preparation of a lithium–graphite-intercalation compound in a dimethyl sulfoxide-based electrolyte containing calcium ions

Electrochemical preparation of lithium–graphite-intercalation compound in dimethyl sulfoxide (DMSO)-based electrolytes containing calcium salt was studied. Intercalation of DMSO-solvated cation took place in 1.0 mol dm⁻³ lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) + 1.5 mol dm⁻³ calcium bis(trifluoromethanesulfonyl)amide (Ca(TFSA)₂)/DMSO, whereas intercalation of Li⁺ ions without solvent took place in 1.0 mol dm⁻³ LiTFSA + 2.5 mol dm⁻³ Ca(TFSA)₂/DMSO. Raman spectroscopic study suggests absence of free DMSO in 1.0 mol dm⁻³ LiTFSA + 2.5 mol dm⁻³ Ca(TFSA)₂/DMSO, which can lead to different solvation structure of Li⁺ from the one in 1.0 mol dm⁻³ LiTFSA + 1.5 mol dm⁻³ Ca(TFSA)₂/DMSO. Factors that are responsible for co-intercalation and only Li⁺ ion intercalation are discussed based on the Li⁺ ion solvation structures.     

The role of chloride ions and pH in the corrosion and pitting of Al–Si alloys

The role of chloride ions in the pitting corrosion of some Al–Si alloys was investigated by chemical, polarization and EIS measurements, as well as SEM studies. Differences in corrosion rates of pure aluminium and the alloys are discussed. The capacitive behaviour of the oxide covered surface is replaced by resistive behaviour as immersion time increases in HCl solutions. At neutral pH corrosion currents increase then decrease with chloride ion concentrations. Pitting by chloride ions initiates more readily in acidic media.     

Synthesis and characterization of potassium humate–acrylic acid–acrylamide hydrogel

A novel potassium humate–acrylic acid–acrylamide (KHA–AA–AM) superabsorbent polymer was prepared from the reaction among leonardite potassium humate, acrylic acid and acrylamide by free radical initiating process using ammonium persulfate as the initiator and N, N′-methylene bisacrylamide as the crosslinker. Various effects of synthesis conditions on superabsorbent polymer were studied and the optimal reaction condition was obtained with crosslinker concentration 0.44–0.74 wt%, initiator concentration 1.12–2.22 wt%, n(KOH)/n(AA) 0.51–0.70, monomer concentration 10.95–12.59 wt%, graft reaction temperature 83 ± 1°C, monomer mole ratio of acrylic acid to acrylamide 1.42–2.30, and potassium humate content 17.54 wt%. Under the optimal conditions, the solution absorbency of KHA–AA–AM superabsorbent polymer to deionized water, tap water, 0.5% carbamide solution and 0.9% NaCl solution were 733–756, 161–284, 786–825, and 76–83 g/g, respectively.     

Structure and in vivo anticalcification properties of a polymeric calcium–sodium–phosphocitrate organic–inorganic hybrid

This paper describes the synthesis, characterization and crystal structure of an organic–inorganic polymeric hybrid composed of Ca, Na, and phosphocitrate (CaNaPC). CaNaPC is synthesized by reaction of CaCl₂·2H₂O and Na₄(HPC)·3H₂O in water, at pH 2. Its structure is polymeric with Ca(PC)₂(H₂O) “monomers” connected through Na⁺ bridges. The 9-coordinate Ca occupies the center of an irregular polyhedron defined by four phosphate, four carbonyl, and one H₂O oxygens. CaO(C) distances are in the 2.446(2)–2.586(2) Å range. There is a short distance of 2.477(1) Å between Ca and the ester O from C–O–PO₃H₂. All –COOH groups are protonated. There are three dissociated protons per two PC molecules, all coming from –PO₃H₂. Na ions are six-coordinate surrounded by –COOH’s. The anticalcification properties of CaNaPC on plaque growth were studied in vivo using rats as model systems. Na–phosphocitrate is an effective inhibitor, but its effectiveness diminishes when a lower dose is used (9.7 mg as H₅PC), resulting in only 30% plaque reduction. Superior inhibition activity becomes evident by following treatment with CaNaPC, at an equal dose (9.6 mg as H₅PC) giving nearly quantitative (95%) plaque inhibition.     

Sol–gel preparation and characterization of nano-crystalline lithium–mica glass–ceramic

The nano-crystalline lithium–mica glass–ceramic with separated crystallite size of 13 nm was prepared using sol–gel technique. In such a process, the structural evolutions and microstructural characteristics of the synthesized samples were investigated through X-ray diffraction, transmission electron microscopy, thermal analysis and Fourier transform infrared spectroscopy. It was found that the crystallite size of the mica obtained from sol–gel method is smaller than the one synthesized via conventional melted method. The XRD results also showed that the crystallization of mica occurred above 675 °C and it could originate from MgF₂ so that the next stage will also be the transformation from mica to norbergite and norbergite to chondrodite. The activation energy of the crystallization and Avrami factor were measured as 376.7 kJ mol^?1 and 2.3, respectively. It is found that the bulk crystallization could be considered as the predominant crystallization mechanism for the glass–ceramic.     

Experimental investigation and thermodynamic simulation of the uranium oxide–zirconium oxide–iron oxide system in air

The behavior of melts and the phase composition of crystallization products of six compositions in the uranium oxide-zirconium oxide-iron oxide system in air have been investigated. It has been revealed that crystallized samples containing 20–50 wt % uranium oxide and 25–80 wt % iron oxide (the rest is zirconium oxide) consist of five crystalline phases and involve two types of eutectic structures. The possible factors responsible for this phenomenon have been considered.     

Preparation and phosphorus recovery performance of porous calcium–silicate–hydrate

Porous calcium–silicate–hydrate was synthesized and used to recover phosphorus from wastewater. The principal objective of this study was to explore the phosphorus recovery performance of porous calcium–silicate–hydrate prepared by different Ca/Si molar ratios. Phosphorus recovery mechanism was also investigated via Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrum (EDS), Brunauer–Emmett–Teller (BET) and X-ray Diffraction (XRD). The law of Ca²⁺ release was the key of phosphorus recovery performance. Different Ca/Si molar ratios resulted in the changes of pore structures. The increase of specific surface area and the increase in concentration of Ca²⁺ release were well agreement together. The Ca/Si molar ratio of 1.6 for porous calcium–silicate–hydrate is more proper to recover phosphorus. The pore structure of porous calcium–silicate–hydrate provided a local condition to maintain a high concentration of Ca²⁺ release. Porous calcium–silicate–hydrate could release a proper concentration of Ca²⁺ and OH^? to maintain the pH values at 8.5–9.5. This condition was beneficial to the formation of hydroxyapatite. Phosphorus content of porous calcium–silicate–hydrate reached 18.64% after phosphorus recovery.     

Palladium-catalyzed efficient Suzuki–Miyaura reaction of potassium aryltrifluoroborates in water

An efficient and environment-friendly protocol has been developed for the palladium-catalyzed Suzuki–Miyaura reaction of potassium aryltrifluoroborates with (hetero)aryl halides in water without any additive. This method allows the preparation of a variety of biaryls and heterobiaryls in excellent yields. In addition, the cross-coupling product can be isolated in good yields and high purity by simple filtration and recrystallization as the reaction was performed on gram scale.     

Electrochemical reduction of solutions of ReF6 in fused LiF–NaF–KF eutectic mixture

Electrolyte was prepared by introducing gaseous ReF₆ into the molten LiF–NaF–KF eutectic at 600 °C. The electrochemical properties of the solutions were studied by voltammetric techniques. The reduction of ReF₈ ^2– to Re occurred via a single irreversible step with diffusion controlled mass transfer. The diffusion coefficient of ReF₈ ^2– was 8 × 10^–10 m² s^–1 and the cathodic transfer coefficient was 0.13. Well-crystallized pure rhenium layers, up to 50 m thick, were obtained on W, Ag, graphite and vitreous carbon substrates and were examined by SEM and X-ray diffraction techniques.     

Electrochemical behaviour of LaCl3 at tungsten and aluminium cathodes in LiCl–KCl eutectic melt

The electrochemical behaviour of lanthanum was studied at inert tungsten electrode and reactive aluminium electrode in LiCl–KCl eutectic melt in the temperature range 698–798 K using transient electrochemical techniques. Reduction of La(III) to La(0) at the tungsten electrode takes place in a single step. The reduction shows quasi-reversible behaviour for polarization rates, 25 ≤ ν ≤ 150 mV s^?1 and is predominantly controlled by charge transfer of La(III) ions for scan rates higher than 75 mV s^?1. The heterogenous rate constant of the process was estimated from impedance spectroscopy and from the semi-integrals of the cyclic voltammograms. The redox potential of the La(III)/La couple at the Al electrode was observed to be more positive than that at the inert electrode. This potential shift is due to the lowering of the activity of La in the metal phase caused by the formation of the intermetallic compound Al₁₁La₃. Thermodynamic properties such as Gibbs energy of formation of Al₁₁La₃, excess Gibbs energy and the activity coefficient of La in Al were calculated from the open circuit potential measurement.     

The development and challenges of rechargeable non-aqueous lithium–air batteries

Lithium–air (Li–air) batteries have recently received much attention due to their extremely high theoretical energy densities. The significantly larger theoretical energy density of Li–air batteries is due to the use of a pure lithium metal anode and the fact that the cathode oxidant, oxygen, is stored externally since it can be readily obtained from the surrounding air. However, before Li–air batteries can be realized as high-performance, commercially viable products there are still numerous scientific and technical challenges that must be overcome, from designing the cathode structure, to optimizing the electrolyte compositions and elucidating the complex chemical reactions that occur during charge and discharge. The scientific obstacles that are related to the performance of Li–air batteries open up an exciting opportunity for researchers from many different backgrounds to utilize their unique knowledge and skills to bridge the knowledge gaps that exist in current research projects. This review article is a summary of the most significant developments and challenges of practical Li–air batteries and the current understanding of their chemistry.     

Sol–gel synthesis and characterization of lithium aluminate (L–A–H) and lithium aluminosilicate (L–A–S–H) gels

Hydrous lithium aluminosilicate (L–A–S–H) and lithium aluminate (L–A–H) gels are candidate precursors for glass-ceramics and ceramics with potential advantages over conventional processing routes. However, their structure before calcination remained largely unknown, despite the importance of precursor structure on the properties of the resulting materials. In the present study, it is demonstrated that L–A–S–H and L–A–H gels with Li/Al ≤ 1 can be produced via an organic steric entrapment route, while higher Li/Al ratios lead to crystallization of gibbsite or nordstrandite. The composition and the structure of the gels was studied by thermogravimetric analysis, X-ray diffraction, ²⁷Al and ²⁹Si magic-angle spinning nuclear magnetic resonance, and Raman spectroscopy. Aluminium was found to be almost exclusively in six-fold coordination in both the L–A–H and the L–A–S–H gels. Silicon in the L–A–S–H gels was mainly in Q⁴ sites and to a lesser extent in Q³ sites (four-fold coordination with no Si–O–Al bonds). The results thus indicate that silica-rich and aluminium-rich domains formed in these gels.     

Chemical vapor deposition of ordered structures in YAG–alumina eutectic system

The eutectic structure of metals and ceramics is the result of a self-organization phenomenon in which multiple solid phases solidify with an ordered structure from a liquid phase. Hence, a melt-solidification process was the only way to generate ordered structures in a ceramic eutectic system. Here, we prepared ordered structures of Y₃Al₅O₁₂ (YAG)–Al₂O₃ composites via chemical vapor deposition in the YAG–Al₂O₃ eutectic system. Spatially periodic YAG rod and lamellar structures were generated in an alumina matrix homoepitaxially grown on the sapphire substrates on the Al₂O₃-rich side of the eutectic composition, whereas α-Al₂O₃ rod and lamellar structures were generated in a YAG matrix on the Y₂O₃-rich side. The results reveal that the pattern formation of ordered structures in a ceramic eutectic system can occur not only during in the melt-solidification process but also during the vapor deposition process. The Ce³⁺-doped YAG–Al₂O₃ composite film converts some of the blue light into yellow light, allowing some of it to pass through, and emitting white light. The Eu³⁺-doped YAG–Al₂O₃ composite film can be utilized as a scintillation screen for a high-resolution X-ray imaging test to see though a semiconductor storage device.