LiOH Concentration Research Articles

Properties of nickel hydroxide electrode in formation of Ni/MH battery

Nickel metal hydride (Ni/MH) batteries are presently as the promising high capacity power sources applied in the various portable electronic devices and the hybrid electric vehicles. After a Ni/MH battery was assembled, the forming process was carried out to assure its performances, which included the high charge/discharge capacity, the good cycle durability, and the low internal resistance. The effect of charging current, charging temperature, concentration of KOH, concentration of LiOH, soaking time, and soaking temperature on the formation of a Ni/MH battery was investigated in the present work. The experimental results indicate that the best utilization of the positive electrode is found to be 86.3% at the conditions of 0.2C charging current, 25 °C, 7.129 M KOH and 0.477 M LiOH for the battery soaked at 30 °C for 12 h. The electrochemical properties of Ni/MH battery are investigated by AC impedance, and the elements of equivalent circuit for various forming conditions are evaluated by using the complex nonlinear least square (CNLS) technique. The active material β-Ni(OH)2 in the positive electrode is transformed to β-NiOOH and γ-NiOOH in the forming process observed by the X-ray diffraction (XRD) analysis. When the soaking time and temperature of the forming process increase, the utilization of positive electrode increases due to the increase in its electroactive area and fraction of γ-NiOOH.

The effect of alkalinity and temperature on the performance of lithium-air fuel cell with hybrid electrolytes

A lithium-air fuel cell combined an air cathode in aqueous electrolyte with a metallic lithium anode in organic electrolyte can continuously reduce O 2 to provide capacity. Herein, the performance of this hybrid electrolyte based lithium-air fuel cell under the mixed control of alkalinity and temperature have been investigated by means of galvanistatic measurement and the analysis of electrochemical impedance spectra. Electromotive force and inner resistance of the cell decrease with the increase of LiOH concentration in aqueous electrolyte. The values ranged from 0.5 to 1.0 M could be the suitable parameters for the LiOH concentration of aqueous electrolyte. Environment temperature exhibited a significant influence on the performance of lithium-air fuel cell. The lithium-air fuel cell can provide a larger power at elevated temperature due to the decrease of all resistance of elements.

Malonic acid: A potential reagent in decontamination processes for Ni-rich alloy surfaces

The ability of malonic acid as a dissolution agent toward synthetic Ni ferrite and Alloy 600 and 800 corrosion products was explored. Its performance in the dissolution kinetics of Ni ferrite powders was compared with the one of oxalic acid. Kinetic parameters were obtained and the dependency on external Fe(II) was modelled. Oxidized samples used in descaling tests were prepared by exposure of coupons of both alloys to lithiated aqueous solutions, under hydrothermal conditions and hydrogen overpressure, simulating PHWR conditions. Oxide layer morphology, the influence of exposure time to corrosive medium and LiOH concentration on its thickness were characterized. Descaling tests consisting on a two-stage method (a first oxidizing step with alkaline permanganate followed by a reducing step with oxalic or malonic acid were carried out). Results were compared to those obtained with a well known chemical cleaning formulation (APAC: Alkaline Permanganate Ammonium Citrate) used in decontamination of several reactors and loops and the competitiveness of malonic acid was demonstrated.

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.

Structure, Size, and Morphology Control of Nanocrystalline Lithium Cobalt Oxide

Hydrothermal synthesis of nanocrystalline LiCoO2 from CoOOH and LiOH is studied by in situ powder X-ray diffraction. The study confirms that transformation from CoOOH to LiCoO2 takes place through a dissolution−recrystallization process, where the dissolution step is rate determining. Therefore, a high solubility of CoOOH is needed to ensure a fast reaction, and this can be achieved by increasing the temperature or the pH value. The growth rates and the final sizes of the LiCoO2 nanoparticles are observed to be highly dependent on the synthesis temperature. The nanoparticles are disk shaped, and the in situ data show that the degree of anisotropy in the morphology is temperature dependent. Thus, not only particle size but also morphology is controllable. The in situ data also show that at low temperature and low LiOH concentration, the Fd3m polymorph of LiCoO2 is first crystallized, but sustained reaction leads to a transformation to the R3̅m polymorph. At other conditions the R3̅m polymorph forms directly within the time resolution (10 s). Finally, the unit cell is observed to change significantly with particle size. However, at low LiOH concentrations peculiar anisotropic unit cell changes are observed, which cannot be explained by particle size effects or Li defects.

Hydrothermal Synthesis of a Nanosized LiNi0.5Mn1.5O4 Cathode Material for High Power Lithium-Ion Batteries

A material for use as a spinel cathode for lithium-ion batteries was synthesized for the first time using a hydrothermal approach. The effects of the LiOH concentration and hydrothermal temperature on the hydrothermal products were investigated systematically, where the LiOH concentration (e.g., ) was proven critical to successfully synthesize the spinel. At low LiOH concentrations (e.g., ), the obtained products may be MnOOH, , and spinel, while high concentrations (e.g., ) favor the phase. The particle size of the as-prepared spinel is ca. , and its formation is associated with the dissolution-recrystallization mechanism from an amorphous precursor. Cell tests show that the as-prepared material obtained at exhibits a capacity of ca. at a current density of , where ca. above . Such a material shows an excellent rate capability with a capacity of ca. delivered at , 73% of that obtained at .

Enhanced photoluminescence of ZnO–SiO2 nanocomposite particles and the analyses of structure and composition

Abstract Stable blue-green photoluminescent ZnO–SiO2 nanocomposite particles exhibiting quantum efficiency as high as 34.8% under excitation at 360 nm were prepared using a spray-drying process from a feed solution that contained both luminescent ZnO nanoparticles synthesized by a sol–gel method and commercially-available SiO2 nanoparticles. The effects of silica nanoparticle size and SiO2-to-ZnO concentration ratio on the PL properties of the composite particles were investigated. The internal structure and chemical composition were investigated in detail using elemental mapping, which revealed that ZnO nanoparticles were well-dispersed within silica nanoparticle matrix. At a LiOH concentration of 0.23 M, the predicted ZnO crystallite diameter before and after spray drying was approximately constant at 3.3 and 3.6 nm, respectively. This result indicates that ZnO particle growth was inhibited and therefore the PL property of ZnO nanoparticles was stably preserved in the composite.

Hydrothermal Synthesis and Characterization of LiREF4 (RE = Y, Tb−Lu) Nanocrystals and Their Core−Shell Nanostructures

In this paper, a water-ethanol-oleic acid system was developed to prepare LiREF(4) nanocrystals with a controlled size and shape. The influence of LiOH concentration and temperature on the phase and shape evolution of the LiREF(4) nanocrystals was systematically investigated and discussed. It was found that the LiOH concentration was the key factor responsible for the shape evolution and phase control for LiREF(4) nanocrystals at selected temperatures. The LiYF(4)-LiLuF(4) core-shell nanostructure was synthesized and characterized.

Semicontinuous Automated Measurement of Organic Carbon in Atmospheric Aerosol Samples

A fully automated measurement system for ambient aerosol organic carbon, capable of unattended operation over extended periods, is described. Particles are collected in a cyclone with water as the collection medium. The collected sample is periodically aspirated by a syringe pump into a holding loop and then delivered to a wet oxidation reactor (WOR). Acid is added, and the WOR is purged to measure dissolved CO(2) or inorganic carbonates (IC) as evolved CO(2). The IC background can often be small and sufficiently constant to be corrected for, without separate measurement, by a blank subtraction. The organic material is now oxidized stepwise or in one step to CO(2). The one-step oxidation involves UV-persulfate treatment in the presence of ozone. This treatment converts organic carbon (OC) to CO(2), but elemental carbon is not oxidized. The CO(2) is continuously purged from solution and collected by two sequential miniature diffusion scrubbers (DSs), a short DS preceding a longer one. Each DS consists of a LiOH-filled porous hydrophobic membrane tube with terminal stainless steel tubes that function as conductance-sensing electrodes. As CO(2) is collected by the LiOH-filled DSs, hydroxide is converted into carbonate and the resulting decrease in conductivity is monitored. The simultaneous use of the dual short and long DS units bearing different concentrations of LiOH permits both good sensitivity and a large dynamic range. The limit of detection (LOD, S/N = 3) is approximately 140 ng of C. With a typical sampling period of 30 min at a sampling rate of 30 L/min, this corresponds to an LOD of 160 ng/m(3). The approach also provides information on the ease of oxidation of the carbonaceous aerosol and hence the nature of the carbon contained therein. Ambient aerosol organic carbon data are presented.

Disordered lithium niobate rock-salt materials prepared by hydrothermal synthesis

An investigation of the one-step hydrothermal crystallisation of lithium niobates reveals that reaction between Nb(2)O(5) and aqueous LiOH at 240 degrees C yields materials with a disordered rock-salt structure where the metals are statistically distributed over the cation sites. This contrasts with the well-studied reaction between Nb(2)O(5) and NaOH or KOH that produces ANbO(3) (A = Na, K) perovskites. Powder neutron diffraction shows that materials prepared at short reaction times and lower LiOH concentration (2.5 M) are lithium deficient and have a slight excess of niobium, but that at longer periods of reaction in 5 M LiOH, close to the ideal, stoichiometric Li(0.75)Nb(0.25)O composition is produced. Upon annealing this phase cleanly transforms into the known ordered rock-salt material Li(3)NbO(4), a process we have followed using thermodiffractometry, which indicates that transformation begins at approximately 700 degrees C. Solid-state (93)Nb and (7)Li NMR of the disordered and ordered rock-salt phases shows that both contain single metal sites but there is clear evidence for local disorder in the disordered samples. For the ordered material, NMR parameters derived from experiment are also compared to those calculated using density functional theory and are shown to be in good agreement.

Adsorption of Ions on Zirconium Oxide Surfaces from Aqueous Solutions at High Temperatures

Surface titrations were carried out on suspensions of monoclinic ZrO2 from 25 to 290 °C slightly above saturation vapor pressure at ionic strengths of 0.03, 0.1 and 1.0 mol⋅kg−1(NaCl). A typical increase in surface charge was observed with increasing temperature. There was no correlation between the radius of the cations, Li+, Na+, K+ and (CH3)4N+, and the magnitude of their association with the surface. The combined results were treated with a 1-pKa MUSIC model, which yielded association constants for the cations (and chloride ion at low pH) at each temperature. The pH of zero-point-charge, pHzpc, decreased with increasing temperature as found for other metal oxides, reaching an apparent minimum value of 4.1 by 250 °C. Batch experiments were performed to monitor the concentration of LiOH in solutions containing suspended ZrO2 particles from 200 to 360 °C. At 350 and 360 °C, Li+ and OH− ions were almost totally adsorbed when the pressure was lowered to near saturation vapor pressure. This reversible trend has implications not only to pressure-water reactor, PWR, operations, but is also of general scientific and other applied interest. Additional experiments probed the feasibility that boric acid/borate ions adsorb reversibly onto ZrO2 surfaces at near-neutral pH conditions as indicated in earlier publications.

The preparation of LiCoO2 nanoplates via a hydrothermal process and the investigation of their electrochemicalbehavior at high rates

We report an alternative hydrothermal process for the preparation of pure phaseLiCoO2 cathodematerial for potential application under high rates. By adjusting the hydrothermal conditions, nanoplate-likeLiCoO2 crystals were obtained, with grain size about 200 nm. It was found in the experiment that theH2O2 concentration and hydrothermal temperature were the two key factors that influence the phasepurity and crystal shape, while LiOH concentration has only a slight effect on the crystal size ofthe product. The electrochemical test revealed a good rate behavior of the synthesized pure phaseLiCoO2 nanoplates, demonstrating a potential of the hydrothermal process for mass production.

One-step hydrothermal routine for pure-phased orthorhombic LiMnO 2 for Li ion battery application

This paper reports a simple one-step hydrothermal routine to prepare orthorhombic LiMnO 2 powder for Li ion battery application. Employing Mn 2O 3 and LiOH as the starting materials, hydrothermal reaction operated under 160 °C for 12 h generated pure-phased o-LiMnO 2 powder. The morphological change and reduction in grain size between the reagent and the resultant were revealed by SEM observation, which indicated that LiOH played two important roles in the process, one as the Li ion source to form orthorhombic LiMnO 2 by intercalation and the other as the corrosive medium to control the morphology and reduce the particle size. Detailed investigation showed that the LiOH concentration and the hydrothermal temperature were two key factors influencing phase purity of the final product. Pure-phased o-LiMnO 2 prepared under optimized hydrothermal conditions showed higher capacity and better cyclical performance than the commonly prepared o-LiMnO 2 powder, and therefore promised potential application for lithium ion secondary batteries.

Ultrasound assisted synthesis of nano-sized lithium cobalt oxide

Nano-sized HT-LiCoO 2 powders were prepared by sonochemical synthesis in an aqueous solution of lithium hydroxide containing cobalt hydroxide at ∼80 °C without any further heat treatment at high temperature. The effects of the LiOH concentration, oxidation conditions, ultrasound irradiation time and temperature on the formation of the nano-sized HT-LiCoO 2 phase were investigated. The formation of the HT-LiCoO 2 phase was confirmed by X-ray diffraction and Raman spectroscopy. The TEM images showed the presence of HT-LiCoO 2 aggregates with a mean particle diameter of ∼20 nm. The reaction mechanism of the ultrasound assisted synthesis of nano-sized LiCoO 2 was proposed on the basis of the XRD, X-ray absorption spectroscopy analysis and TEM observation of the reaction products taken during the course of the synthesis.

Mechanistic study of the reduction of copper oxides in alkaline solutions by electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy was used to study the mechanism by which copper oxides are reduced in alkaline solutions. For the reductions of CuO and Cu 2O, a capacitive loop and also an inductive loop under certain conditions were observed in the complex plane. The electrochemical impedance for CuO reduction was not greatly dependent on the solution alkalinity and the kind of alkali hydroxide. However, the electrochemical impedance for Cu 2O reduction was considerably affected by the kind and concentration of alkali hydroxide. The diameter of the capacitive loop, i.e., the charge-transfer resistance ( R ct), was increased with increase in solution alkalinity. It should also be noted that R ct was increased in the order of KOH < NaOH < LiOH. These dependences were consistent with the good separation between the reduction potentials of CuO and Cu 2O in chronopotentiometric and voltammetric measurements with strongly alkaline electrolytes containing Li +. The inductive loop observed for the Cu 2O reduction at higher concentrations of KOH (>6 M) and LiOH (>0.2 M) suggested the existence of an intermediate species (probably CuOH). The specific inhibitory effect of Li + ions on the reduction of Cu 2O might be explained by a possible stabilization of CuOH by Li + ions.

Evidence of Ni 2FeBO 5 and m-ZrO 2 precipitates in fuel rod deposits in AOA-affected high boiling duty PWR core

This paper describes the characteristics of corrosion product deposits found in upper regions of high axial offset anomaly (AOA) once-burnt fuel assemblies after Cycle 9 in the Callaway pressurized water reactor (PWR). The ∼100-μm-thick deposits consisted of a new type of highly porous and structured Ni-, Fe-, B-, and Zr-rich material. The analyses showed that deposits contain a large amount (about 50 wt%) of Ni–Fe oxyborate (Ni 2FeBO 5, mineral name bonaccordite), in the form of matted ∼0.1-μm-thick and ∼10-μm-long, needle-like particles. An especially high density of Ni 2FeBO 5 needles was found in a 30–40-μm-thick zone on the clad side of the deposits. This compound has not previously been reported as a component of PWR fuel crud. Common fuel crud components such as nickel ferrite and nickel oxide were observed only in small quantities (about 10 wt%). Reference samples of Ni 2FeBO 5 were obtained by hydrothermal reactions in alkaline aqueous solutions starting from about 400 °C, or by sintering at about 1000 °C. Formation of Ni 2FeBO 5 has been identified as a new mechanism for boron retention and neutron absorption on PWR fuel. Aggregates of apparently hydrothermally precipitated ∼0.1–0.3-μm-sized particles of monoclinic m-ZrO 2(∼30 wt%) were found in the deposits, which is indicative of a dissolution–precipitation process at the cladding surface. This process may be enhanced by a LiOH concentration mechanism in crud, which is a result of both sub-cooled nucleate boiling and 10B(n,α) 7Li reactions. Consistently, the isotopic abundance of 10B in Ni 2FeBO 5 in crud samples was reduced to about 10% of the total boron.

Electrophoretic Deposition of Template-Free ZnO Nanorod Films

ZnO nanorods were synthesized by hydrothermal coarsening of quantum dots. The length of the nanorods and degree of asymmetry increased with higher Zn and LiOH concentrations. Particles were deposited by cathodic electrophoresis on transparent conductive oxide substrates from isopropanolic suspensions. As particle asymmetry increased, homogeneous films were deposited with preferred horizontal orientation. Commercially available ZnO nanopowders yielded inhomogeneous films and showed no preferred orientation with electrophoretic deposition.

Studies on the morphologies of LiCoO 2 films prepared by soft solution processing

Lithium cobalt oxide films were prepared on nickel plates and foam nickel by soft solution processing method. The films were characterized by chemical analysis, X-ray diffraction, scanning electron microscopy, and atomic force microscopy. It was found that growth of LiCoO 2 crystal on polished nickel plates and foam nickel led to different morphologies of LiCoO 2. A compact LiCoO 2 film was formed on smooth nickel plates while some grassy LiCoO 2 crystals formed and scattered on the surface of foam nickel, which indicates different mechanism of films growth. Formation of LiCoO 2 crystal on nickel plates shows the characteristic of two-dimensional nucleation while on foam nickel shows the characteristic of preferential nucleation. Further, increase of LiOH concentration in the soft solution results in morphological change of LiCoO 2 film from hexagonal platelets to spherical grains. In addition, the larger the current density, the less the grain size and the porosity inside grains are.

Generating Blue and Red Luminescence from ZnO/Poly(ethylene glycol) Nanocomposites Prepared Using an In‐Situ Method

AbstractThe peak of the luminescence spectrum of zinc oxide (ZnO) is usually observed above 500 nm (yellow region). By in‐situ growth of ZnO nanoparticles in a poly(ethylene glycol) (PEG) matrix, we have succeeded in producing ZnO/polymer composites with stable luminescence peaks down to 465 nm (blue region). The unbalanced precursor molarity approach, where the molarity of one precursor (LiOH) is several times larger than the molarity represented by a chemical reaction balance, was used. The blue luminescence, which was accompanied by an enhancement of luminescence intensity, was observed at very high LiOH concentrations. This was probably due to the simultaneous reduction in the crystalline size and improvement in the crystallinity. Doping ZnO nanoparticles with europium also generated a red luminescence at 616 nm, due to the 5D0 →7F2 transition of Eu ions.

Molten Ba(OH) 2·8H 2O as an etchant for CR-39 detector

Systematic studies were carried out to discover/unveil a best etchant for CR-39, polymeric nuclear track detector. In this context, different concentrations of NaOH, KOH, LiOH and Ba(OH) 2·8H 2O were used at different temperatures. For these etchants, bulk-etching rate, track etching rate and efficiency of the CR-39 were determined using track diameter method. Activation energies for bulk and track etching processes as well as induction time of the etchants were also studied. The results obtained were compared with that of the 6 M NaOH at 70°C. Our study showed that molten Ba(OH) 2·8H 2O yields excellent etching properties with drastically reduced etching time and relatively higher efficiency.