Effect of Heat Treatment on the Composition of Surface Layers in Lithium Silicate Glass Exposed to Acid and Salt Solutions

The concentration distribution of lithium ions in the surface layers of the 27Li₂O–73SiO₂ (mol %) glass samples subjected and unsubjected to heat treatment under different conditions after exposure to 0.1 M HCl + y M LiCl (y = 0, 1.0, 5.0, and 10) solutions is studied by the HF-sectioning technique. It is found that the specific (molded) layer formed on the glass surface upon pouring of a glass melt into a cooled mold affects the leaching processes in both the initial and phase-separated glasses. In the absence of the molded layer, the leaching rate of the initial glass in the acid is lower than that of the phase-separated glass and higher than that of the crystallized glass. The leaching rate of the phase-separated and crystallized samples in the acid with an salt additive is higher than that of the initial salt. Chlorine ions in the acid solution bring about a weakening of the silicon–oxygen network. The profiles of the dissolution rate of glass in a 1% HF solution correlate with the concentration profiles of lithium.     

The effect of dominant ions on solvent extraction of lithium ion from aqueous solution

Solvent extraction of lithium ion using kerosene as solvent is proposed. The extraction of lithium ion using various mixed extractants of β-diketone and neutral ligand in kerosene was performed to find the optimum extractant combination. Considering the extraction efficiency, the optimum extractant combination was 0.02 M TTA and 0.04M TOPO. For the development of lithium extraction from seawater, the effects of dominant ions in seawater were examined in various extraction conditions. The extraction efficiencies generally decreased with the concentration of dominant metallic ions and increased with pH of the aqueous solutions, but Cl^? ion showed only minor effect on the efficiency, even up to its concentration in seawater. Except for Mg²⁺ ion, more than 70% of lithium ions could be extracted at pH 10.6 from aqueous solutions with a dominant ion at its concentration in seawater.     

Early detection of aluminum corrosion via “turn-on” fluorescence in smart coatings

In the present work we describe the successful application of spiro[1H-isoindole-1,9′-[9H]xanthen]-3(2H)-one, 3′,6′-bis(diethylamino)-2-[(1-methylethylidene)amino](“FD1”) as a “turn-on” early aluminum corrosion detector in epoxy coatings. Electrospray ionization mass spectrometry (ESI-MS) and ¹H NMR investigations have revealed that the non-fluorescent FD1 is sensitive to low pH due to its acid-catalyzed hydrolysis to Rhodamine B hydrazide (RBH) that subsequently becomes protonated to its fluorescent ring-opened form. Both clear and filled FD1-containing smart epoxy coatings were capable of sensing acidic pH produced at the anodic site of localized aluminum corrosion at a low indicator concentration (0.5 wt%), which was demonstrated by the observation of fluorescent, bright-orange areas corresponding to localized pitting corrosion of the aluminum substrate illuminated by a handheld UV lamp. Therefore, early corrosion of aluminum can be easily and nondestructively detected via our “turn-on” fluorescence strategy.     

Electroless oxidation of diamond surfaces in ceric and ferricyanide solutions: An easy way to produce “C-O” functional groups

Despite many works are devoted to oxidation of diamond surfaces, it is still a challenge, to successfully produce well defined “C-O” functions, particularly for functionalization purposes. In this paper we describe and compare, for the first time, the “electroless” oxidation of as-deposited polycrystalline boron-doped diamond (BDD) films in ceric and ferricyanide solutions at room temperature. Both reactions efficiently generate oxygen functionalities on BDD surface. While a higher amount of “C-O” moieties is produced with Ce⁴⁺ as oxidizing agent, the use of ferricyanide specie seems the most interesting to specifically generate hydroxyl groups. Additionally, this easy to perform oxidative method appears not damaging for diamond surfaces and adapted to conductive or non-conductive materials. The resulting surfaces were characterized using X-ray photoelectron spectroscopy, contact angle and capacitance-voltage analysis.     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

IR spectroscopic investigation of interaction between sodium aluminosilicate electrode glasses and aqueous solutions

The effect of introduction of aluminum oxide into the composition of sodium silicate glasses has been studied by IR absorption and reflection spectroscopy. The change in the spectroscopic characteristics of glasses after their treatment with HNO₃ and AgNO₃ aqueous solutions is analyzed. The concentration profiles of Na₊ and Ag₊ ions in the surface layers of these glasses are determined by the HF-sectioning technique. It is found that silver ions predominantly interact with the [AlO_4/2]^- groups in the glass. The leaching of sodium ions, formation of amorphous silica in the surface layers of the treated glass samples, and exchange of sodium ions by hydrogen ions are revealed from changes in the spectra.     

Spectroscopic and structural studies of di-ureasils doped with lithium perchlorate

Di-urea cross-linked POE/siloxane hybrid ormolytes (di-ureasils) doped with a wide concentration range of lithium perchlorate trihydrate (LiClO₄·3H₂O) (200 ≥ n ≥ 0.5, where n expresses the salt content in terms of the number of ether oxygen atoms per Li⁺ ion) have been analysed by Fourier transform infrared and Raman (FT-IR and FT-Raman, respectively) spectroscopies and X-ray diffraction (XRD). The results obtained lead us to conclude that the xerogels with n ≥ 5 are totally amorphous. At n ≤ 1 free salt is observed. “Free” ClO₄⁻ ions appear to be the main charge carriers at the conductivity maximum located within the 25 ≤ n ≤ 8 composition range of this family of ormolytes. At n = 15 ClO₄⁻ ions coordinated in mono/tridentate (C_3v symmetry) and bidentate (C_2v symmetry) configurations were detected. In salt-rich samples with n < 15 there is a marked tendency for ionic association. The resulting decrease that occurs in the concentration of “free” ions is consistent with the observed significant decrease of the ionic conductivity. The analysis of the “amide I” and “amide II” regions provided solid proof that the Li⁺ ions bond to the urea carbonyl oxygen atoms over the entire range of salt concentration studied.     

An urchin-like graphite-based anode material for lithium ion batteries

In situ preparation of carbon nanotubes on the surface of spherical graphite particles is made by chemical vapor deposition, resulting in an “urchin-like” hybrid material. TEM and SEM images show that carbon nanotubes are herringbone with turbulent layered structure, less than 100 nm in diameter and several micrometers in length in the average. The hybrid's use as an anode material in lithium ion batteries is examined using constant current charge-discharge tests, which prove that carbon nanotubes oriented on the surface effectively improve the reversible capacity. Cyclic voltammogram shows that there is no cathodic peak for the reaction of the Fe catalyst with Li⁺ in the charge-charge process in 0.0-1.6 V vs. Li/Li⁺ potential range.     

Na and Li ion diffusion in modified ASTM C 1260 test by Magnetic Resonance Imaging (MRI)

In the current study, MRI was applied to investigate lithium and sodium ion diffusion in cement paste and mortars containing inert sand and borosilicate glass. Paste and mortars were treated by complying with ASTM C 1260. Lithium and sodium distribution profiles were collected at different ages after different treatments. Results revealed that sodium ions had a greater diffusion rate than lithium ions, suggesting that Na reaches the aggregate particle surface before Li. Results also showed that Na and Li ions had a competitive diffusion process in mortars; soaking in a solution with higher [Li] favored Li diffusion but hindered Na diffusion. In mortars containing glass, a substantial amount of Li was consumed by the formation of ASR products. When [Li] in soaking solution was reduced to 0.37 N, a distinctive Na distribution profile was observed, indicating the free-state Na ions were continuously transformed to solid reaction products by ASR. Hence, in the modified ASTM C 1260 test, [Li] in the storage solution should be controlled at 0.74 N, in order to completely prevent the consumption of Na ions and thus stop ASR.     

pH sensing in aqueous solutions using a MnO2 thin film electrodeposited on a glassy carbon electrode

An electrolysis technique at a constant potential was used to develop a highly reproducible and fast elaboration method of adherent manganese dioxide thin films on a glassy carbon electrode from aqueous solutions containing sulfuric acid and manganese sulfate. The resulting films were found to have a nanostructured character presumably due rather to birnessite (δ-MnO₂) than to γ-MnO₂, as suggested by their Raman and XRD signatures. They lead to modified electrodes that present an obvious although complex pH dependent potentiometric response. This sensor indeed showed a single slope non-Nernstian linear behaviour over the 1.5–12 pH range for increasing pH direction (“trace”), whereas a Nernstian two slopes linear behaviour was observed for decreasing pH direction (“re-trace”). Preliminary EIS experiments carried out at a pH value of 1.8 seem to reveal a sensitivity mechanism based on proton insertion process at least at highly acidic pH values.     

Design and synthesis of novel fluorescence sensing perylene diimides based on photoinduced electron transfer

Two novel tetraester- and PAMAM-branched perylene diimides were synthesized and configured as “fluorophore-spacer-receptor” systems based on photoinduced electron transfer. Due to their long alkylester and alkylamine terminal groups the examined compounds were well soluble in organic solvents. Photophysical characteristics of the dyes were investigated in DMF and water/DMF (1:1, v/v) solution. The ability of the synthesized perylene diimides to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions (Zn²⁺, Co²⁺, Cu²⁺, Fe³⁺, Pb²⁺, Hg²⁺, Ag⁺ and Ni²⁺) and protons. The dyes under study displayed “off-on” switching in its fluorescence as a function of pH, which is attributed to disallowing photoinduced electron transfer from the receptor moiety to the fluorophore. PAMAM-branched dye displayed a good pH sensor activity (FE = 6.4), however the pH sensing ability of tetraester was substantially higher (FE = 184). In the presence of Cu²⁺ and Pb²⁺ ions tetraester quenched its fluorescence intensity (FQ = 22 and 12 respectively), while PAMAM-branched dye enhanced its fluorescence intensity with pronounced selectivity to Cu²⁺ and Fe³⁺ (FE = 3.2 and 4.9, respectively). The results obtained indicate the potential of the novel compounds as fluorescent detectors for metal ions with pronounced selectivity towards Cu²⁺, Pb²⁺ and Fe³⁺ ions and highly efficient “off-on” pH switches, especially a tetraester-branched perylene diimide.     

Mechanism of lithium electrosorption by activated carbons

Sorption of Li⁺ ions from diluted aqueous medium has been investigated on activated carbons. The pure chemical sorption is controlled by pH of the solution as well as by the nature and concentration of surface groups, showing cation-exchanger properties of the carbon substrate. Lithium sorption is enhanced by applying a cathodic polarization to the activated carbon, and reversing voltage allows a full desorption of trapped lithium. In the selected conditions of investigation, the electrostatic attraction is not responsible of ions sorption as demonstrated by the low values of capacitance measured at constant potential or current. Our experiments proved that local high pH values at the carbon cathode, due to reduction of water, are the cause for increasing the dissociation of surface groups and consequently the amount of adsorbed lithium ions. On the other hand, with positive polarization, water is oxidized at the carbon surface, and proton exchange favors the release of lithium ions to the solution.     

Adsorption behavior of fluoride ions using a titanium hydroxide-derived adsorbent

The removal behavior of fluoride ions was examined in aqueous sodium fluoride solutions using a titanium hydroxide-derived adsorbent. The adsorbent was prepared from titanium oxysulfate (TiOSO₄·xH₂O) solution, and was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry-differential thermal analysis, Fourier transform infrared spectrum and specific surface area. Batchwise adsorption test of prepared adsorbent was carried out in aqueous sodium fluoride solutions and real wastewater containing fluoride ion. The absorbent was the amorphous material, which had different morphology to the raw material, titanium oxysulfate, and the specific surface area of the adsorbent (96.8 m²/g) was 200 times higher than that of raw material (0.5 m²/g). Adsorption of fluoride on the adsorbent was saturated within 30 min in the solution with 200 mg/L of fluoride ions, together with increasing pH of the solution, due to ion exchange between fluoride ions in the solution and hydroxide ions in the adsorbent. Fluoride ions were adsorbed even in at a low fluoride concentration of 5 mg/L; and were selectively adsorbed in the solution containing a high concentration of chloride, nitrate and sulfate ions. The adsorbent can remove fluoride below permitted level (< 0.8 mg/L) from real wastewaters containing various substances. The maximum adsorption of fluoride on the adsorbent could be obtained in the solution at about pH 3. After fluoride adsorption, fluoride ions were easily desorbed using a high pH solution, completely regenerating for further removal process at acidic pH. The capacity for fluoride ion adsorption was almost unchanged three times after repeat adsorption and desorption. The equilibrium adsorption capacity of the adsorbent used for fluoride ion at pH 3 was measured, extrapolated using Langmuir and Freundlich isotherm models, and experimental data are found to fit Freundlich than Langmuir. The prepared adsorbent is expected to be a new inorganic ion exchanger for the removal and recovery of fluoride ions from wastewater.     

Hydronium Ions in Soda‐lime Silicate Glass Surfaces

The presence of leachable alkali ions, or their hydrated sites in the glass, is believed to be a determining factor for the interfacial water structure at the glass surface, influencing the surface properties of glass. The interfacial water structure on soda‐lime silicate glass in humid ambience at room temperature was analyzed with sum‐frequency‐generation (SFG) vibration spectroscopy, which can probe the interfacial water layer without spectral interferences from the gas phase water. The soda‐lime glass surface exposed to water vapor shows three sharp SFG peaks at 3200, 3430, and 3670 cm^?1 in SFG, which is drastically different from the SFG spectra of the water layers on the fused quartz glass surface and the liquid water/air interface. The sharp peak at 3200 cm^?1 is believed to be associated with the hydronium ions in the Na⁺‐leached silicate glass surface. The 3200 cm^?1 peak intensity varies with the relative humidity, indicating its equilibrium with the gas phase water. It is proposed that the hydronium ions in the Na⁺‐leached sites produce compressive stress in the silicate glass surface; thus the growth of hydronium ions with increasing humidity might be responsible for the increased wear resistance of soda‐lime glass surfaces in near‐saturation humidity conditions.     

Compatibility of quaternary ammonium-based ionic liquid electrolytes with electrodes in lithium ion batteries

Electrochemical intercalation/deintercalation behavior of lithium into/from electrodes of lithium ion batteries was comparatively investigated in 1 mol/L LiClO₄ ethylene carbonate-diethyl carbonate (EC-DEC) electrolyte and a quaternary ammonium-based ionic liquid electrolyte. The natural graphite anode exhibited satisfactory electrochemical performance in the ionic liquid electrolyte containing 20 vol.% chloroethylenene carbonate (Cl-EC). This is attributed to the mild reduction of solvated Cl-EC molecules at the graphite/ionic electrolyte interface resulting in the formation of a thin and homogenous SEI on the graphite surface. However, rate capability of the graphite anode is poor due to the higher interfacial resistance than that obtained in 1 mol/L LiClO₄/EC-DEC organic electrolyte. Spinel LiMn₂O₄ cathode was also electrochemically cycled in the ionic electrolyte showing satisfactory capacity and reversibility. The ionic electrolyte system is thus promising for 4 V lithium ion batteries based on the concept of “greenness and safety”.     

Ion transport properties of lithium ionic liquids and their ion gels

A new series of lithium ionic liquids were prepared by introducing of two electron-withdrawing trifluoroacetyl groups in borate salts containing two methoxy-oligo(ethylene oxide) groups in the structures. Successive substitution reactions of oligo-ethylene glycol monomethyl ether and trifluroacetic acid from LiBH₄ yielded the lithium salts, which were clear and colorless liquids at room temperature. The fundamental physicochemical properties, such as density, thermal property, viscosity, ionic conductivity, self-diffusion coefficients, and electrochemical stability, were measured. The lithium ionic liquids had self-dissociation ability and conducted ions even in the absence of organic solvents. New polymer electrolytes, named ‘ion gels’, were prepared by radical cross-linking reactions of a poly(ethylene oxide-co-propylene oxide)tri-acrylate macromonomer in the presence the lithium ionic liquid. An increase in the glass transition temperatures (T_g) of the ion gels was very small even with increasing lithium ionic liquid concentration, and the T_g's were lower than that of the ionic liquid itself. The ionic conductivity of the ion gels surpassed that of the lithium ionic liquid in the bulk at certain compositions.     

Modification of polyimide coatings by high energy ion bombardment

Exposure of 25-μm films of polyimide and polyamideimide to high doses (> 10¹⁵/cm²) of energetic ions (energy ≥ 100 keV) resulted in physical and chemical modification of the film surface. Cross-section microscopy revealed damaged layers extending beyond the projected ion range; conductivity in this damaged layer was found to be as high as 10³ω^?1 cm^?1. Surface conductivity was found to be a function of ion energy and dose, with an exponential energy dependence from 200 to 900 keV. The temperature dependence and thermal stability of the surface conductivity were determined.     

铝在含锂盐的碱性溶液中稳定性的研究

为了解铝在锂盐溶液中的钝化行为,通过失重法研究了溶液pH值、温度、浸泡时间及氯离子浓度等因素对钝化膜形成及稳定性的影响。结果表明,溶液pH值和温度对钝化膜的和稳定性影响最大。为获得稳定的钝化膜,锂离子的浓度应随pH值的增大而增大,含锂钝化膜对氯离子的局部腐蚀有较强的抑制作用。     

Thermal Poling of Soda‐Lime Silica Glass with Nonblocking Electrodes—Part 2: Effects on Mechanical and Mechanochemical Properties

The mechanical and mechanochemical properties of soda lime silica (SLS) glass surfaces can vary with the sodium ion (Na⁺) concentration in the subsurface region. Changes in these properties were studied upon modification of Na⁺ concentrations in the SLS glass by thermal poling. In Part‐1, it is found that the Na⁺‐depleted and Na⁺‐gradient layers could be formed at the anode and cathode sides, respectively. Here in Part‐2, we show that Na⁺ ions play a pivotal role in the mechanochemical wear property upon lateral shear stress. The Na⁺‐depleted glass wear more readily as relative humidity (RH) increases, while Na⁺‐gradient glass becomes resistant to wear at high RH. It is also found that the Na⁺‐gradient glass surface has a higher elastic modulus and hardness with very little change in fracture toughness compared to the pristine surface. The Na⁺‐depleted glass surface shows a lower elastic modulus and hardness; but its fracture toughness is significantly improved, which might be due to a larger densification capacity of Na⁺‐depleted layer.