LiOH Aqueous Solution Research Articles

Long lifetime in concentrated LiOH aqueous solution of air electrode protected with interpenetrating polymer network membrane

Solid anion-exchange membranes that display interpenetrating polymer network (IPN) architecture were developed to be assembled on air electrode surface to improve its electrochemical stability in alkaline environment. The IPN membranes associate an anionic conducting polyepichlorohydrin network entangled within a cross-linked poly(2-hydroxyethyl methacrylate) in different mass proportions. The membranes possess suitable mechanical and thermal properties, an ionic conductivity of about 1×10−3Scm−1 and suitable cation selectivity. The electrochemical behaviour of the air electrode/IPN membrane assemblies (AEMA) were then evaluated in LiOH 5M. The polarization curves indicate that a good electrochemical interface was established between the electrode and the IPN membranes. Moreover, the AEMA exhibits a discharge stability in LiOH 5M ten times higher compared to a bare electrode under the same conditions.

加工工艺对N18锆合金在360 ℃/18.6 MPa LiOH水溶液中腐蚀行为的影响

The effect of thermal processing on corrosion behavior of N18 alloy has been inves- tigated by autoclave tests in 0.01 mol/L LiOH aqueous solution at 360 and l8.6 MPa, and the microstructures of these specimens were examined by TEM and SEM. The results show that the cor- rosion resistance of specimens is improved obviously by β phase quenching before cold rolling and annealing due to nano second phase particles (SPPs) precipitated dispersively, but when the inter- mediate annealing temperature increased to 740 before cold rolling and annealing, the corrosion resistance is lowered greatly due to SPPs coarsened to several hundred nanometers, where the cor- rosion rate accelerates markedly after the corrosion transition at 150 d exposure. The existence of β-Zr phase in the microstructures of specimens treated at 780 and 800 for 2 h in dual phase region is harmful to the corrosion resistance, but the corrosion resistance returns to a better level after the decomposition of β-Zr phase during the following processes of cold rolling and annealing at 580 to obtain fine SPPs.

Optimization for the Formation of Metal Hydride Electrode Used in Ni/MH Batteries

The effect of charging current, temperature, concentrations of KOH and LiOH, soaking time and temperature on the utilization of metal hydride (MH) electrode in the formation of Ni/MH battery is investigated by the conventional experimental design. The experimental results indicate that the optimal charging conditions are the charging time ratio of 9/1 with 0.1 and 1.0 C-rates. The other optimal conditions for the formation of MH electrode re 25°C, 8.02 M KOH and 0.48 M LiOH aqueous solution. The steady utilization of MH electrode is 83.52% for the soaking temperature of 45°C and the soaking time greater than 24 h, respectively. According to the Taguchi's orthogonal arrays, the relationship between the utilization of metal hydride electrode (y) and the formation factors is obtained to be y = 75.52 - 6.58A + 3.98C + 5.09E + 6.71F - 1.32AC + 2.57BC + 5.62E2 - 10.67F2 where A, B, C, E and F are the charging current, the charging temperature, the concentration of KOH in the electrolyte, the soaking time and temperature, respectively. Under the optimal formation conditions, the utilization of MH electrode is increased from 87.25% to the steady value of 98.50% by increasing the charging/discharging cycle from 1 to 4.

Model description of the equivalent electroconductivity of aqueous solutions of alkali metal hydroxides over a wide range of concentrations and temperatures

The possibility of a quantitative theoretical description of the λ(c) dependence for aqueous solutions of alkali metal hydroxides in a wide concentration (from 0.0001 to 12 M) and temperature (from 0 to 100°C) was considered on the basis of concept suggested earlier. Effectiveness of the description of characteristics analyzed was illustrated on the examples of the calculation of electroconductivity values for aqueous LiOH, NaOH, KOH, RbOH, and CsOH solutions and comparison of them with experimental values taken from published data. The suggestion on different H+ and OH− ion migration mechanism was made on the basis of the model used for description of λ(c).

β 相水淬对Zr-4合金在LiOH水溶液中耐腐蚀性能的影响

To investigate the effect ofβ-quenching on the corrosion behavior,Zr-4 specimens wereβ-quenched and subsequently annealed at 480—600℃for 2—200 h.The corrosion tests were carried out in 0.01 mol/L LiOH aqueous solution at 360β/18.6 MPa.The microstructure of Zr-4 specimens and fracture surface morphology of oxide films on the corroded specimens were observed by TEM and HRSEM,respectively.The results show that Zr-4 specimens exhibit excellent corrosion resistance as Zr-Sn-Nb alloys in LiOH aqueous solution after increasing the solid solution content of Fe and Cr inα-Zr matrix by suitable quenching rate fromβ-phase to avoid the formation ofβ-Zr. When the cooling rate is too fast,the specimens show worse corrosion resistance due to the formation ofβ-Zr.After annealing at 480—600℃,the better corrosion resistance of Zr-4 specimens can be obtained with increasing annealing temperture and time due to the decomposition ofβ-Zr.

What Does LiOH Treatment Offer for Lyocell Fibers? Investigation of Structural Changes

Lyocell fibers, regenerated cellulosic fibers spun from cellulose/N-methylmorpholine-N-oxide hydrate solution by wet spinning, were treated with LiOH aqueous solution at concentrations of up to 7.5 M to study the inter- and intrafibrillar changes. Wide-angle X-ray diffraction analyses were applied to identify the crystallinity index and crystallite size. Inverse size-exclusion chromatography was applied to study the pore structure of the swollen fibers. The mean pore diameter was found to increase after the LiOH treatment. The carboxyl content, measured by methylene blue sorption, decreased slightly. The water retention value, depth of color measured after dyeing with CI Direct Red 81, and weight loss of fibers changed gradually after LiOH treatment at concentrations up to ca. 5 M. The treated fibers became brittle as a result of both inter- and intrafibrillar swelling and the deep penetration ability of LiOH treatments above 5 M.

Lithium Intercalation Properties of Lithium Tetratitanate Obtained by Nanosheets Process

Lithium intercalation properties of lithium tetratitanate obtained by nanosheets process (NS-LT4) was examined and compared with those of conventional lithium tetratitanate. NS-LT4 was prepared by restacking of tetratitanate nanosheets with LiOH aqueous solution. NS-LT4 exhibited a reversible capacity of approximately 140 mAh g-1, which corresponds to approximately two Li insertions per formula unit. Two Li insertions per formula unit mean that half of the Ti atoms were reduced from a tetravalent state to a trivalent state. The quasi open-circuit voltage of NS-LT4 was comparable with that of conventional lithium tetratitanate, and the voltage change of NS-LT4 as the change in lithium composition was greater than that of conventional lithium tetratitanate. This potential behavior would be caused by the unique stacking structure with stacking fault and random rotation in nanosheet-plane generated during the restacking of nanosheets.

Pressure-induced phase transition of ice in aqueous LiOH solution

I have examined the changes in in situ Raman spectra of ice in aqueous LiOH solution as a function of pressure at liquid nitrogen temperature (77 K). Here, I have shown the possibility that ice in aqueous LiOH solution transforms to a high-density amorphous like phase at around 0.9 GPa. I have mentioned that the results show differences strongly depending on the salts dissolved in the aqueous solutions.

수열합성법을 이용한 이트륨 산화물 나노와이어의 합성

<TEX>$Y(OH)_3$</TEX> nanowires were synthesized by a hydrothermal reaction of metallic Y with aqueous solution of LiOH. The morphology and the size of the nanowires changed with varying the volume of the LiOH solution inside the autoclave. <TEX>$Y(OH)_3$</TEX> nanowires transformed to <TEX>$Y_2O_3$</TEX> by a subsequent heat-treatment without morphological change. By a proper control of hydrothermal reaction parameter and heat-treatment, the yield of pure <TEX>$Y_2O_3$</TEX> nanowires up to 97% was attained.

A study on lithium/air secondary batteries—Stability of the NASICON-type lithium ion conducting solid electrolyte in alkaline aqueous solutions

The stability of the high lithium ion conducting glass ceramics, Li 1+ x+ y Ti 2− x Al x Si y P 3− y O 12 (LTAP) in alkaline aqueous solutions with and without LiCl has been examined. A significant conductivity decrease of the LTAP plate immersed in 0.057 M LiOH aqueous solution at 50 °C for 3 weeks was observed. However, no conductivity change of the LTAP plate immersed in LiCl saturated LiOH aqueous solutions at 50 °C for 3 weeks was observed. The pH value of the LiCl–LiOH–H 2O solution with saturated LiCl was in a range of 7–9. The molarity of LiOH and LiCl in the LiOH and LiCl saturated aqueous solution were estimated to be 5.12 and 11.57 M, respectively, by analysis of Li + and OH −. The high concentration of LiOH and the low pH value of 8.14 in this solution suggested that the dissociation of LiOH into Li + and OH − is too low in the solution with a high concentration of Li +. These results suggest that the water stable LTAP could be used as a protect layer of the lithium metal anode in the lithium/air cell with LiCl saturated aqueous solution as the electrolyte, because the content of OH − ions in the LiCl saturated aqueous solution does not increase via the cell reaction of Li + 1/2O 2 + H 2O → 2LiOH, and LTAP is stable under a deep discharge state.

An optical humidity sensor based on Li 3PO 4 hollow nanospheres

Orthorhombic Li 3PO 4 hollow nanospheres and solid particles have been successfully prepared respectively via a simple neutralization reaction between H 3PO 4 and LiOH aqueous solutions, by just changing the adding sequence of H 3PO 4 and LiOH aqueous solutions (with PVP) in dropwise. Transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM) images display Li 3PO 4 hollow nanospheres with average diameters of about 400 nm and wall thickness of about 50 nm which is actually composed of nanoparticles with sizes of 20–50 nm, and Li 3PO 4 solid particles with lengths of 100–500 nm and widths of 100–250 nm. The photoluminescence (PL) properties of the samples reveal that the Li 3PO 4 hollow nanospheres show stronger PL intensity than the Li 3PO 4 solid particles. Furthermore, an adapted photoluminescence-type gas sensor based on Li 3PO 4 hollow nanospheres has been devised and its sensing property to humidity has also been investigated. This novel sensor exhibits good sensitivity, ideal linearity, quick response/recovery, and reliable repeatability in a very wide humidity range at room temperature.

Elucidation of the electrochromic mechanism of nanostructured iron oxides films

Nanostructured hematite thin films were electrochemically cycled in an aqueous solution of LiOH. Through optical, structural, morphological, and magnetic measurements, the coloration mechanism of electrochromic iron oxide thin films was elucidated. The conditions for double or single electrochromic behavior are given in this work. During the electrochemical cycling, it was found that topotactic transformations of hexagonal crystal structures are favored; i.e. α-Fe 2O 3 to Fe(OH) 2 and subsequently to δ-FeOOH. These topotactic redox reactions are responsible for color changes of iron oxide films.

IN SITU IMPEDANCE CHARACTERISTICS OF ZIRCONIUM ALLOY CORROSION IN HIGH TEMPERATURE AND PRESSURE WATER ENVIRONMENT

The electrochemical impedance spectroscopy (EIS) was used to analyze the corrosion evolution of pre- and post-transition of the annealed Zr-4 alloy in 0.01 mol/L LiOH aqueous solution at 360 /18.6 MPa. The results show that oxidation weight gain of Zr-4 alloy increases slowly before corrosion transition. When Zr is oxidized into ZrO2, the stress appears in the oxide film due to volume expansion. With gradually thickening of the oxide film, accumulation of micro-defects will relax the stress in outer layer of oxide film. As a result, the uniform and compact oxide layer turns into double layer with a porous outer layer and a dense inner one. Meanwhile the impedance spectra evolve from single arc into double capacitive arcs. When the oxide film forms macro-defects such as cracks, corrosion transition takes place, giving rise to an acceleration of oxidation weight gain and the rapid drop of impedance and corrosion potential. Corrosion potential and electrochemical impedance spectroscopy are able to obtain in situ some information of the transition point.

Hydrothermally Processed Oxide Nanostructures and Their Lithium-ion Storage Properties.

Y- and Si-based oxide nanopowders were synthesized by a hydrothermal reaction of Y or Si powders with NaOH or LiOH aqueous solution. Nanoparticles with different morphology such as elongated nanospheres, flower-like nanoparticles and nanowires were produced by a control of processing parameters, in particular, the starting composition of solution. The preliminary result of electrochemical examination showed that the hydrothermally processed nanowires exhibit high initial capacities of Li-ion storage: 653 mAh/g for Y2O3 nanowires as anode materials and 186 mAh/g for Li2Si2O5 nanowires as cathode materials in a Li secondary cell. Compared to the powder with elongated sphere or flower-like shapes, the nanowires showed a higher Li-ion capacity and a better cycle property.

Effect of magnesium on the electrochemical behavior of lithium anode in LiOH aqueous solution used for lithium–water battery

The effect of adding magnesium to lithium on lithium electrochemical behavior in 4 mol L −1 LiOH is studied using electrochemical techniques. The results show that the hydrogen evolution rate is decreased with increasing Mg content. Through theoretical analysis and X-ray (XRD) investigation, MgH 2 and Mg(OH) 2 are created on the surface film of lithium–magnesium alloys after discharge. The porosity of the lithium surface film is decreased by MgH 2, Mg(OH) 2 combined with LiOH and LiOH·H 2O and the hydrogen evolution rate is decreased effectively. Magnesium addition to lithium reduces the extent of hydrogen evolution by alteration of the hydride–hydroxide layer also reduces the extent of anodic dissolution without a significant change in the system efficiency.

A convenient method for the reductive degradation of mono-, di-, and tribromodiphenyl ethers, tetrabromo- and tetrachlorobisphenol A with Raney Ni-Al alloy

Raney Ni-Al alloy in a dilute aqueous alkaline solution of NaOH, KOH, CsOH, LiOH, or Ca(OH)2, or of alkali metal carbonates such as Na2CO3, K2CO3 and Cs2CO3, becomes a very powerful reducing agent and dehalogenates mono-, di and tribromodiphenyl ethers (BDPEs), tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) effectively. Polybromodiphenyl ethers are reduced to give diphenyl ether as sole product. TBPPA and TCPPA are debrominated to bisphenol A and other dehalogenated compounds. The C-C bond of bisphenol A is broken easily under the reaction conditions. An almost quantitative removal of halogen from BDPEs, TBBPA and TCPPA can be realized in aqueous media under mild reaction conditions without the use of organic solvents. The reductive dehalogenation of TBBPA and TCBPA with a Raney Ni-Al alloy under ultrasonication is also described.

New design of electric double layer capacitors with aqueous LiOH electrolyte as alternative to capacitor with KOH solution

Activated carbon (AC) fiber cloths and a hydrophobic microporous polypropylene (PP) membrane, both modified with lithiated acetone oligomers, were used as electrodes and a separator in electric double layer capacitors (EDLCs) with aqueous lithium hydroxide (LiOH) as the electrolyte. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge cycle tests and impedance spectroscopy (EIS), compared with a case of the capacitor with aqueous potassium hydroxide (KOH) as an electrolyte. As a result, the capacitor with LiOH aqueous solution and a modified separator and electrodes was found to exhibit higher specific capacitance, maximum energy stored and maximum power than that with KOH aqueous solution.

Preparation and Characterization of Microporous Layers on Titanium

Microporous layers on titanium (Ti) are formed by chemical treatment in highly concentrated alkaline media, and their properties and growth mechanism are examined using electrochemical techniques, in situ resistometry, scanning electron microscopy (SEM), grazing-incident X-ray diffraction (GIXRD), and glow discharge optical emission spectroscopy (GD-OES). Chemical treatment in a 5 M aqueous KOH solution yields results superior to those from the same treatment in a 5 M aqueous NaOH solution, while a 3 M aqueous LiOH solution does not produce porous layers. The cation constituting the solution plays a vital role in the process. An SEM analysis reveals that the KOH solution is the most effective in forming microporosity and that the longer the treatment time, the more porous the near-surface layer. The results of GIXRD analysis show the presence of Na(2)Ti(5)O(11) and K(2)Ti(6)O(13) in the layers formed in the NaOH and KOH solutions, respectively; in the case of the LiOH solution, TiO(2) is formed. Chemical treatment in the NaOH and KOH solutions resembles a general corrosion process with the existence of local cathodic and anodic sites. The reduction reaction produces H(2), some of which becomes absorbed in the near-surface region of Ti, while the oxidation reaction produces the above-mentioned compounds and/or an oxide layer. The presence of hydrogen (H) within the solid is detected using GD-OES. The H-containing near-surface layer partially dissolves, yielding a microporous structure. The development and dissolution of the H-containing near-surface layer of Ti upon chemical treatment in the NaOH and KOH solutions are confirmed by resistometry measurements. They point to the formation of a compact passive layer on Ti upon exposure to the LiOH solution.

Nano-sized lithium manganese oxide dispersed on carbon nanotubes for energy storage applications

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 °C for 30 min using MnO 2-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.

An experimental study on the preparation of tochilinite-originated intercalation compounds comprised of Fe 1−xS host layers and various kinds of guest layers

Tochilinite represents a mineral group of ordered mixed-layer structures containing alternating Fe 1− x S layers with mackinawite-like structure and metal hydroxide layers with Mg(OH) 2-like structure. In this article, we report the preparation of a series of tochilinite-originated (or Fe 1− x S-based) intercalation compounds (ICs). According to their preparation procedures, these ICs can be divided into four kinds. The first kind of IC was sodium tochilinite (Na-tochilinite), which was prepared by the hydrothermal reaction of metallic Fe particles with concentrated Na 2S·9H 2O aqueous solutions. The hydroxide layer of the Na-tochilinite was a mixed hydroxide of Na + ions along with a certain amount of Fe 2+ ions. When the hydroxide layer of the Na-tochilinite completely dissolved in aqueous solutions, a Fe-deficient mackinawite-like phase Fe 1− x S was obtained, which was probably an electron-deficient p-type conductor. The second kind of ICs was prepared by ‘low-temperature direct intercalation in aqueous solutions, using Na-tochilinite as a parental precursor. When the Na-tochilinite was ultrasonicated in aqueous solutions containing Lewis basic complexing agents (like NH 3, N 2H 4, 2,2′-bipyridine (bipy), and 1,10-phenanthroline (phen)), the Na + ions of the Na-tochilinite were removed and the Lewis basic complexing agents entered the hydroxide layer of the Na-tochilinite and became coordinated with the Fe 2+ ions, and the second kind of ICs was thus produced. The second kind of ICs includes NH 3 IC, N 2H 4 IC, N 2H 4-NH 3 IC, [Fe(bipy) 3] 2+-containing IC and [Fe(phen) 3] 2+-containing IC. The third kind of ICs, which includes NH 3 IC, N 2H 4–NH 3 IC and N 2H 4-LiOH (NaOH) IC, was prepared by the hydrothermal reaction of metallic Fe particles with (NH 4) 2S aqueous solution, S (elemental) + N 2H 4·H 2O aqueous solution, and S + N 2H 4·H 2O + LiOH (NaOH) aqueous solution, respectively. The third kind of ICs has a close relationship with the second kind of ICs both in composition and structure. The fourth kind of ICs was prepared by the oxidation and reduction of some of the N 2H 4-containing ICs mentioned above, which include N 2H 2 (diazene or diimide) IC, N 2 (dinitrogen) IC and NH 3 IC. The N 2H 2 IC was prepared by mild air oxidation of the N 2H 4-LiOH IC. The N 2 IC was prepared by strong air oxidation of the N 2H 4-LiOH IC, however, we have not been able to separate the pure phase N 2 IC. Hydrothermal reduction of the N 2H 4 IC made by the direct intercalation method in strong reducing environment by H 2S + Fe (metal) led to the production of the NH 3 IC of the fourth kind of ICs. The NH 3 ICs prepared by the three methods had similar compositions and structures. As almost all the ICs reported in this paper were extremely sensitive both to air and to the electron beam, they were mainly characterized by XRD. The properties and interrelationships (or mutual transformations) of the Fe 1− x S-based ICs revealed novel chemistry occurring in the sub-nanoscopic space between the micrometer- to nanometer-sized electron-deficient Fe 1− x S layers. An important finding of this novel chemistry was that the Fe 1− x S-based ICs tended to oxidize or reduce the intercalated species when the redox state of their environments varied. The results of our experiments potentially have many cosmochemical implications. The most important implication is that our experimental results, along with previous studies, strongly suggested that some of the ammonium salts, ammonia and carbonates existing in the matrix of the CM carbonaceous chondrites may have been formed by abiotic reactions employing molecular nitrogen as the nitrogen source and carbon monoxide as the carbon source and iron sulfide and/or iron hydroxide as catalysts.