LiOH Solution Research Articles

Zeta potential of microarc oxidation film on zirlo alloy in different aqueous solutions

Zeta potentials of the bare Zirlo alloy and its microarc oxidation (MAO) film in KCl, NaCl, H3BO3 and LiOH solutions were measured. Their corrosion behavior in different solutions were evaluated by electrochemical impedance spectroscopy (EIS). The correlation between zeta potential and corrosion behavior was also analyzed. The MAO treatment shifted the iso-electric point (IEP) to a higher pH value in 1500 ppm B3+ and 2.3 ppm Li+ mixed aqueous solution for simulating normal water chemistry in nuclear reactors. Besides, MAO film with higher zeta potential could reduce the adsorption of lithium ions, which improved the corrosion resistance of Zirlo alloy.

Improvement of the Catalytic Efficiency of Butene Oligomerization Using Alkali Metal Hydroxide-Modified Hierarchical ZSM-5 Catalysts

Oligomerization of light olefin is an effective method to produce plentiful liquid fuels. However, oligomerization processes using microporous zeolites have severe problems due to steric hindrance. In this paper, oligomerization of butene using a series of new types of hierarchical HZSM-5 zeolite catalysts is studied. To obtain the modified HZSM-5 catalysts, HZSM-5 is treated with the same concentration of LiOH, NaOH, KOH, and CsOH aqueous solutions, respectively. It is demonstrated that the alkali treatment can effectively modify the acidity properties and hierarchical structure of the HZSM-5 catalyst, which is confirmed by X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Nitrogen Adsorption-desorption Measurements, Transmission Electron Microscopy Investigations (TEM), Ammonia Temperature-programmed Desorption Method (NH3-TPD), Pyridine FT-IR, and Thermogravimetric Analysis (TGA). The results show that hierarchical catalysts with interconnected open-mesopores, smaller crystal size, and suitable acidity can better prolong the catalyst lifetime during butene oligomerization. Particularly, the HZSM-5 catalysts treated with CsOH aqueous solution (ATHZ5-Cs) proved to be the most effective catalyst, resulting in approximately 99% conversion of butene and exhibiting C8+ selectivity of 85% within 12 h. Thus, an appropriate hierarchical catalyst can satisfy the oligomerization process and has the potential to be used as a substitute for the commercial ZSM-5 catalyst.

Preparation of Lithium Ion Adsorbent Using Low-Grade Pyrolusite: Preparation Method and Adsorption Performance

A lithium ion adsorbent was prepared using low-grade pyrolusite by the following steps: (1) Manganese rich material (MRM) with higher Mn content was prepared by pyrolusite–NaOH molten salt roasting and washing processes to remove impurities in pyrolusite, such as silicon, iron, aluminum, etc. (2) the lithium ion adsorbent was obtained by extraction of lithium with hydrochloric acid from the precursor, which was synthesized via the solid-phase reaction between MRM and LiOH. Compositions of low-grade pyrolusite, MRM, precursor and lithium ion adsorbent were characterized by powder x-ray diffraction and x-ray photoelectron spectroscopy. Adsorption properties and selectivity of the adsorbent are also discussed. The results showed that in the NaOH roasting process, manganese was transformed to Na0.7MnO2.05 and silicon, iron, and aluminum became hydrosoluble Na2SiO3, Na2Al5.2O9.4 and Na3FeO3, respectively. The manganese content in MRM increased from 24.6% to 50% in the conditions of a 600°C 2 h roasting temperature, and the NaOH–pyrolusite mass ratio was 1.5, after the washing process. The Li1.27Mn1.73O4 precursor was synthesized at 750°C with good crystallization yielding a Li/Mn molar ratio of 3 via the LiOH and MRM roasting process. The value of Li+ extraction from the Li1.27Mn1.73O4 precursor reached a maximum in the condition of 0.3 mol/L HCl solution at 40°C for 6 h. Before and after adsorption of Li+, the spinel structure of the adsorbent was not changed. The Li+ adsorption capacity of the obtained adsorbent reached 36.5 mg/g in a LiOH solution, which contained 2 g/L Li+ and remained at 34–35 mg/g after several cycles. The lithium ion adsorbent had better Li+ selectivity in the synthetic salt-lake brine solution, and the separation coefficients of Li+ to Na+ and K+ reached 44.15 and 33.56, respectively.

Lithiation Effect of the Poly(Acrylic Acid) Binders on the Silicon Anode of Lithium-Ion Batteries

The exploration for the next generation of anode materials in the lithium-ion batteries is a vital subject in the past few years due to the huge demand of high capacity batteries. Silicon (Si) stands out as a promising anode material due to its high theoretical specific capacity (4200 mAh/g), enviroment friendliness and low costs. However, Si nanoparticles (NPs) experience severe volume changes up to 300 % during the lithiation/delithiation process, which leads to dramatic particle degradation and thus capacity loss. Novel polymeric binders with enhanced mechanical properties have been identified as one effective approach to alleviate this issue, and some examples include carboxymethyl cellulose (CMC), alginate, and poly(acrylic acid) (PAA), etc. By using those binders, cell performance has been greatly improved as compared to the conventional polyvinylidene fluoride (PVDF) binder. Among those candidates, PAA outperforms others possibly due to its superior mechanical properties. In this report we have attempted to investigate the lithiation effect of the PAA binders. Lithiating PAA binders could benefit the electrode laminate processing as well as cycling performance. A commercially available PAA sample with a characterized Mn of 147 kDa was used in this study. By titrating with LiOH solution, we controlled the pH of 10 wt% PAA solutions as well as the lithiation ratio (Table 1). Those binder solutions were used to fabricate silicon/ graphite composite electrodes that composed of 10 % PAA, 73 % Hitachi MagE, 15 % Si NPs (NanoAmour, 70-130 nm), and 2 % Timcal C45. Half-cell cycling results (Figure 1) indicated that different lithiation of PAA binders has dramatic impact on their corresponding cycling performance. Lower lithiation tends to afford higher initial specific capacities and better capacity retentions. Actually, the best performer is PAA binder with no lithiation at all. This result is a little contradicting to previous study but we reason that our lithiation agent, LiOH, may have side reasons with silicon particles, as evidenced by the dramatic decrease of the silicon capacity. Full cell cycling as well as further characterization of electrode surface is ongoing. Table 1. The calculated mol% of LiOH (to AA monomer) and the resulting pH values of the final PAA solutions. LiOH % 0 25 50 75 85 90 91 92.5 95 100 pH 2.08 4.22 4.84 5.49 5.97 6.97 10.03 11.96 12.28 12.59 Figure 1. Specific discharge capacity and Coulombic efficiency of PAA binders with different pH values. Figure 1

Rapid hydrogen generation through aluminum-water reaction in alkali solution

The effects of CaO and waste lithium foil on the aluminum-water reaction are investigated in this study. When CaO and waste lithium foil are added to deionized water, the pH of the solution rises above 12 and the Al–H2O reaction is noticeably affected. Two rapid hydrogen generation processes and a passivation process are observed in CaO/Ca(OH)2 suspension. A slow reaction follows the rapid hydrogen generation in LiOH solution. At the beginning of the process, the rapid reaction in CaO/Ca(OH)2 suspension and LiOH solution corresponds the rapid consumption of OH– ions. A similar tendency as the hydrogen generation process in CaO/Ca(OH)2 is detected by the in–situ open circuit potential. Solutions of LiOH and CaO/Ca(OH)2 initially present a difference in the rate of hydrogen generation, but they demonstrate a similar behavior after the consecutive addition of Al batches. This may be due to the synergistic reaction of OH– ions and the self-catalytic behavior of Al(OH)3, formed as a by product of the reaction.

Correlation Between Microstructure and Corrosion Behavior of Zr-0.8Sn-1Nb-0.3Fe Alloy

Abstract Zr-0.8Sn-1Nb-0.3Fe zirconium alloy sheets were prepared by different heat treatment processes. Then OM and TEM were used to analyze the microstructure of the samples, and static autoclave tests were carried out in 360 °C/18.6 MPa/0.01 mol/L LiOH solution and 400 °C/10.3 MPa superheated steam to investigate the corrosion behavior. The results show that the second phase particles (SPPs) are mainly C14 type Zr(Nb, Fe)2 with a HCP structure, and the uniformity of SPPs distribution gradually becomes worse when the hot-rolling temperature increases from 600 to 700 °C. Aging treatment before hot-rolling not only improves the uniformity of SPPs distribution, but also promotes the diffusion of Nb, which increases the amount of βNb SPPs. Extension of final annealing time has little influence on size and distribution of the SPPs, but increases the Nb/Fe ratio in the SPPs. After long time corrosion tests, the corrosion resistance becomes worse when the hot-rolling temperature increases in both corrosion conditions. Aging treatment before hot-rolling can increase the corrosion resistance. Extension of final annealing time can also increase the corrosion resistance in LiOH solution, but decrease the corrosion resistance in superheated steam. The relationship between microstructure and corrosion resistance was discussed, and the size, distribution and the Nb content of SPPs are considered to be the main reason for the difference of the corrosion resistance of Zr-Sn-Nb-Fe zirconium alloys.

Facile synthesis of lithium carbonate nanoparticles with potential properties for bone repair applications

Lithium carbonate nanoparticles were synthesized by facile chemical route in the presence of organic capping agents. Nanosized Li2CO3 particles of ∼86 nm in size were produced from LiOH solution and preferably using PVA as a capping agent. FTIR-ATR analysis revealed that Li2CO3 phase is formed during calcination of the freeze-dried synthesis product. In vitro tests shown that nanoparticle concentrations up to 600 µg/mL do not disturb cell viability and promote the osteogenic differentiation of stem cells by Li+ ions (9.7 mM) leached from the nanoparticle. The biological properties exhibited by the Li2CO3 nanoparticles make of them attractive for bone repair applications.

Yolk-shell structured composite for fast and selective lithium ion sieving

Yolk-shell structured C@Li4Ti5O12 microspheres composed of carbon core (ca. 500 nm) and sea urchin-like Li4Ti5O12 shell (ca. 400–500 nm) are formed by hydrothermally treating the core–shell structured C@TiO2 in the EtOH/H2O solution of LiOH and calcining it in N2 atmosphere. Yolk-shell structured TiO2-type lithium ion sieve is further transformed from C@Li4Ti5O12 through the acid treatment, which have a high specific surface area of 201.74 m2/g. The composite shows adsorption capacity towards Li+ proportional to the pH value in the range of 7–13. The adsorption reaches equilibrium within 2 h with a high equilibrium adsorption capacity of 28.46 mg/g under alkaline conditions, which is ca. 8 times the value of ordinary TiO2 lithium ion sieve with comparable size and surface area, demonstrating the enhanced adsorption is attributed to the generation of more accessible surficial voids by replacing internal part with light carbon core. The adsorption follows Freundlich and pseudo-second-order kinetic models with a high rate constant of 0.015 g/(mg·min). The selective adsorption to Li+ is verified in the presence of K+, Na+, Ca2+ and Mg2+.

New methodology for automated SPOT synthesis of peptides on cellulose using 1,3,5-triazine derivatives as linkers and as coupling reagents.

Two new rigid bi-aromatic linkers for synthesis of peptide arrays by SPOT methodology were obtained from cellulose treated with 2,4-dichloro-6-methoxy-1,3,5-triazine. Reaction with m-phenylenediamine gave non-cleavable TYPE I linker which enabled attachment of the peptides via resistant to harsh reaction conditions amide, ether, and amine bonds. Reaction with 3-Fmoc-aminobenzoic acid followed by thermal isomerization of the intermediate "superactive" ester producing an amide-like bond gave TYPE II linker that was very stable during peptide synthesis. However, the peptide was cleavable, with fragment of the linker, in the presence of 1M LiOH solution. The uniform loading of the cellulose and efficient synthesis of the peptide array was achieved by using N-(4,6-dimethoxy-1,3,5-triazin-1-yl)-N-methylmorpholinium 4-toluenesulfonate as the coupling reagent.

Effects of sulfate and nitrate anions on aluminum corrosion in slightly alkaline solution

The corrosion mechanisms and kinetics of AA1085 in Li2SO4 and LiNO3 aqueous rechargeable lithium-ion battery electrolytes were investigated at pH 11 using chronoamperometry. The corrosion kinetics of AA1085 is controlled by the electrolyte concentration level and the anodic potentials. AA1085 is susceptible to crystallographic pitting corrosion in Li2SO4 electrolytes. The rates of pit nucleation and pit growth both decreased at higher Li2SO4 concentrations or at lower anodic potentials. AA1085 passivates against pitting corrosion in LiNO3 electrolytes due to the formation of a thick, uniform corrosion product layer. The growth rate of the passive film was slightly enhanced by increasing the electrolyte concentration and anodic potentials. X-ray photoelectron spectroscopy spectra showed the formation of a thin sulfate-incorporated passive film on the electrode, which comprises Al2(SO)418H2O, Al(OH)SO4 and Al(OH)3, before the occurrence of pitting growth in 2 M Li2SO4 electrolyte. The thick corrosion product layer formed in 5 M LiNO3 electrolyte was composed of Al(OH)3 and AlOOH. Raman spectroscopy on deionized water, LiOH solution, Li2SO4 and LiNO3 electrolytes depicted changes of solution structure with increasing electrolyte concentration. The influence of extrinsic and intrinsic factors on the corrosion kinetics of AA1085 in Li2SO4 and LiNO3 electrolytes at pH 11 are discussed in detail.

THE CORROSION BEHAVIOR AND WEAR RESISTANCE OF GRAY CAST IRON

Gray cast iron has many applications as pipes, pumps and valve bodies where it has influenced by heat and contact with other solutions . This research has studied the corrosion behavior and Vickers hardness of gray cast iron by immersion in four strong alkaline solutions (NaOH, KOH, Ca(OH)2, LiOH)with three concentrations (1%,2%,3%) of each solution. Dry sliding wear has carried out before and after the heat treatments (stress relief, normalizing, hardening and tempering). In this work, maximum wear strength has obtained at tempered gray cast iron and minimum corrosion rate has obtained in LiOH solution by forming protective white visible oxide layer.

High-rate Li4Ti5O12/porous activated graphene nanoplatelets composites using LiOH both as lithium source and activating agent

The Li4Ti5O12/activated graphene nanoplatelets (Li4Ti5O12/a-GNPs) composites are prepared via a low-cost, green, one-pot hydrothermal process by using LiOH both as lithium source and activating agent for the first time. The LiOH solution concentration and hydrothermal time are optimized to obtain the pure Li4Ti5O12/a-GNPs. The synergistic effects of the nanosized Li4Ti5O12 and the three-dimensional porous a-GNPs endow the composites with convenient lithium ion diffusion channels and efficiently conductive structures for electron and ion transport. As anticipated, the Li4Ti5O12/a-GNPs deliver an outstanding rate capability of 125 and 113 mA h g−1 at 80 and 100 C, respectively, and an excellent cycling stability with 90.21% capacity retention after 2000 cycles at 10 C. These results are much better than those of the Li4Ti5O12/GNPs and pure Li4Ti5O12, demonstrating Li4Ti5O12/a-GNPs are promising anode materials for lithium-ion batteries of high current density applications.

Ultralong cycling stability of cotton fabric/LiFePO4 composites as electrode materials for lithium-ion batteries

Cotton fabric/LiFePO4 cathode material was synthesized via a conventional solvothemal method. XRD results revealed that all the patterns could be indexed as the olivine-type structured LiFePO4 with the space group of Pnma. SEM images showed that the obtained samples presented plate-type morphology. When the cotton fabric (soaked in the 0.1 M LiOH solutions)/LiFePO4 used as the cathode material for lithium-ion battery, it showed excellent cycle stability, i.e., an extremely low loss in the capacity of 7.8% after 200 cycles at 2 C, due to the enhanced electronic conductivity and Li-ion diffusion processes as also proved by the electrochemical impedance spectroscopy (EIS). Thus, this low cost cotton fabric decorated LiFePO4 composite is a promising cathode material for high-performance lithium-ion battery.

Superior lithium adsorption and required magnetic separation behavior of iron-doped lithium ion-sieves

The recent research on adsorption-based lithium recovery from lithium-containing solutions has been centred on adsorption capacity and separation of lithium ion-sieves powder from solutions. Herein, an effective iron-doped lithium titanium oxide (Fe-doped Li2TiO3) was synthesized by Fe-doping via solid state reactions followed by acid treatment to form iron-doped lithium ion-sieves (Fe/Ti-x(H)). The resulting solid powder displays both superior adsorption capacity of lithium and high separation efficiency of the adsorbent from the solutions. SEM imaging and BET surface area measurement results showed that at Fe doping levels x≤0.15, Fe-doping led to grain shrinkage as compared to Li2TiO3 and at the same time the BET surface area increased. The Fe/Ti-0.15(H) exhibited saturated magnetization values of 13.76emug−1, allowing effective separation of the material from solid suspensions through the use of a magnet. Consecutive magnetic separation results suggested that the Fe/Ti-0.15(H) powders could be applied at large-scale and continuously removed from LiOH solutions with separation efficiency of 96% or better. Lithium adsorption studies indicated that the equilibrium adsorption capacity of Fe/Ti-0.15(H) in LiOH solutions (1.8gL−1 Li, pH 12) reached 53.3mgg−1 within 24h, which was higher than that of pristine Li2TiO3 (50.5mgg−1) without Fe doping. Competitive adsorption and regeneration results indicated that the Fe/Ti-0.15(H) possessed a high selectivity for Li with facile regeneration. Therefore, it could be expected that the iron-doped lithium ion-sieves have practical applicability potential for large scale lithium extraction and recovery from lithium-bearing solutions.

Homojunction Cu2O Solar Cells Fabricated with Various Impurity-Doped Epitaxially Grown n-Type Cu2O Thin Film By Electrochemical Deposition

This paper describes the photovoltaic properties of a homojunction Cu2O solar cells fabricated with a various impurity-doped epitaxially grown n-type Cu2O thin-film by electrochemical deposited (ECD) method. The various impurity-doped n-type Cu2O thin film layer was prepared on thermally oxidized polycrystalline p-type sodium-doped Cu2O (p-Cu2O:Na) sheet substrates under various deposition conditions using the following ECD process. Initially, an acetic acid and Copper (II) acetate aqueous solution was prepared with 0.08 M acetic acid, 0.02 M Copper (II) acetate and de-ionized water; then a 0.1-1.0×10-5 M CuCl2, InCl3, CdCl2, ZnCl2 or MnCl2 aqueous solution was added to the solution as a doping impurity; and after that, a 3 M LiOH, NaOH or KOH aqueous solution was added to adjust the pH. Next, a p-Cu2O:Na sheet substrate was immersed in the above solution at a temperature of 60-90 oC; a Pt plate and the p-Cu2O:Na sheet substrate were used as the anode and cathode electrodes, respectively, of the ECD. Finally, the deposition was carried out under various current densities of 0.1-2.0 mA/cm2 for durations of 1-30 min. In addition, various n-type oxide semiconductor, such as GaXAl1-X-O or Zn1-XGeX-O multicomponent oxide thin films and an Al-doped ZnO (AZO) thin film were deposited at room temperature using a pulsed laser deposition or magnetron sputtering methods as the n-type semiconductor layer and the transparent electrode, respectively. The solar cells were fabricated by forming an AZO/n-oxide semiconductor/various impurity-doped n-type Cu2O/p-Cu2O:Na structure on the front surface of the Cu2O:Na sheets and an Au ohmic electrode on the back surface (the sheets function as the active layer as well as the substrate). The photovoltaic properties of the resulting solar cells were measured under AM1.5G solar illumination. For example, the Cu2O homojunction solar cells was fabricated by epitaxialiy growing a Cl-doped Cu2O (Cu2O:Cl) thin film on p-Cu2O:Na (with a hole concentration of 1015-1019 cm-3) sheets by ECD. Significantly enhanced open circuit voltage (VOC) and conversion efficiency (η) were achieved in AZO/n-Cu2O:Cl/p-Cu2O:Na heterojunction solar cells fabricated by Cu2O:Cl thin-film as the n-type layer by using ECD; these values were higher than those obtained in AZO/p-Cu2O and AZO/n-ZnO/p-Cu2O solar cells. The obtained enhanced Voc and η suggest that the Cu2O:Cl thin-film n-type layer acts as an appropriate active layer. In addition, significant improvement of photovoltaic properties was achieved in heterojunction solar cells fabricated with a Ga1-XAlX-O or Zn1-XGeX-O multicomponent oxide thin film n-type semiconductor window layer prepared by optimizing the chemical composition (the Ga or Ge content). Note that the photovoltaic properties obtained in AZO/Ga0.975Al0.025-O or Zn0.38Ge0.62-O/n-Cu2O:Cl/p-Cu2O:Na (with a hole concentration on the order of 1015 cm-3) heterojunction solar cells could be controlled by changing the Cl content doped into the Cu2O:Cl thin film.

Preparation and characterisation of lithium ion exchange composite for the recovery of lithium from brine

ABSTRACTThis paper presents the characterisation and application of a new ion exchange composite, manufactured by poly vinylidene fluoride (PVDF) for recovery of lithium from natural brine. Synthesised MnO2 nano particles (HMO, final MnO2 ion-sieve) having high selectivity for lithium adsorption were used as inorganic ion-exchange adsorbent. Subsequently, the lithium ion exchange composite (CHMO, final MnO2 ion exchange composite) was prepared by dissolving PVDF in N-methyl-2-pyrrolidone, and mixing with (HMO) in equal ratios. The produced polymeric solution acts as a binder and support to closely bond HMO together into a homogeneous three-dimensionally interpenetrating network after drying at 220°C. This composite presents a mesoporous/macroporous structure which allows free channel of the solution. It exhibits considerable Li+ adsorption capacities of 19.22 and 11.06 mg(Li+) g−1 (CHMO) in LiOH solution and lithium-enriched Lake Urmia, respectively. Efforts for improvement of the overall performances of CHMO are still in progress.

Molten salt synthesis and characterization of fast ion conductor Li6.75La3Zr1.75Ta0.25O12

The limited electrochemical stability and the flammability of the liquid electrolytes presently used in Li-ion batteries stimulates the search for alternatives including ceramic solid electrolytes. Moreover, solid electrolytes also fulfil crucial functions in various large-scale energy storage systems, e.g. as anode-protecting membranes in aqueous Li-air batteries. Here, the processing of the solid electrolytes Li7La3Zr2O12 is studied for applications in Li-air batteries. Molten salt method (MSM) was adopted previously on synthesis of simple oxides; to the best of our knowledge, we report for the first time the adaptation of the MSM to prepare this class of solid electrolytes. As a model compound, we prepared the garnet-related Li6.75La3Zr1.75Ta0.25O12. It has been prepared by using stoichiometric amounts of La2O3, ZrCl4, and Ta2O5 in excess 0.88 M LiNO3:0.12 M LiCl molten salt. Subsequently, samples were heated to various temperatures in the range 600–900 °C for 6 h in air in a recrystallized alumina crucible and finally washed with distilled water to remove excess salts. The obtained Li6.75La3Zr1.75Ta0.25O12 electrolyte powder was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and impedance spectroscopy as well as surface area measurements. The cubic single phase was obtained for samples prepared at temperatures ≥700 °C. The effects of washing with water or aqueous LiOH solution on the structure and conductivity of the phases will be discussed.

A new electroplated Ir/Ir(OH) x pH electrode and its application in the coastal areas of Newport Harbor, California

Resulting from the rising levels of atmospheric carbon, ocean acidification has become a global problem. It has significant impacts on the development, survival, growth and physiology of marine organisms. Therefore, a high-precision sensor is urgently needed to measure the pH of sea-water. Iridium wire with a diameter of 0.25 mm is used as the substrate, and an Ir/Ir(OH) x pH electrode is prepared by a one-step electrochemical method in a LiOH solution at the room temperature. A scanning electron microscope (SEM) observation reveals that it is coated with nanoscale particles. In laboratory tests, the electrode exhibits a very promising pH response, with an ideal Nernst slope (56.14–59.52), fast response, good stability and long life-span in tested pH buffer solutions. For a sea trial, four pH electrodes and one Ag/AgCl reference electrode are integrated with a self-made chemical sensor, and a profile detection of nearly 70 m is implemented near Newport Harbor, California on August 3, 2015. The results reflect that the pH value measured by the sensor is very close to the data given by Sea-Bird 911 plus CTD, with a difference value ranging from 0.000 075 to 0.064 719. And the sensor shows a better data matching degree in 0–40 m water depth. In addition, the high precision and accuracy of the sensor make it possible to use in the ocean observation field.

Degradation and structure evolution in corrosive LiOH solution of microarc oxidation coated Zircaloy-4 alloy in silicate and phosphate electrolytes

To improve the corrosion resistance of zirconium alloys, two separate coatings with distinct structure were prepared on Zircaloy-4 alloy by microarc oxidation in alkaline phosphate and silicate electrolytes, respectively. The coating formed in silicate solution has more dense and homogeneous structure than the other, thus it shows better corrosion resistance. According to the electrochemical impedance spectroscopy of the two samples immersed in LiOH solution for different time periods, the coating formed in phosphate solution is able to protect the substrate alloy from corrosion for 30days, while the coating formed in silicate can provide sufficient protection to the substrate up to 50days.

New Low-Sn Zr Cladding Alloys with Excellent Autoclave Corrosion Resistance and High Strength

It is expected that low-Sn Zr alloys are a good candidate to improve the corrosion resistance of Zr cladding alloys in nuclear reactors, presenting excellent corrosion resistance and high strength. The present work developed a new alloy series of Zr-0.25Sn-0.36Fe-0.11Cr-xNb (x = 0.4~1.2 wt %) to investigate the effect of Nb on autoclave corrosion resistance. Alloy ingots were prepared by non-consumable arc-melting, solid-solutioned, and then rolled into thin plates with a thickness of 0.7 mm. It was found that the designed low-Sn Zr alloys exhibit excellent corrosion resistances in three out of pile autoclave environments (distilled water at 633 K/18.6 MPa, 70 ppm LiOH solution at 633 K/18.6 MPa, and superheated water steam at 673 K/10.3 MPa), as demonstrated by the fact of the Zr-0.25Sn-0.36Fe-0.11Cr-0.6Nb alloy shows a corrosion weight gain ΔG = 46.3 mg/dm2 and a tensile strength of σUTS = 461 MPa following 100 days of exposure in water steam. The strength of the low-Sn Zr alloy with a higher Nb content (x = 1.2 wt %) is enhanced up to 499 MPa, comparable to that of the reference high-Sn N36 alloy (Zr-1.0Sn-1.0Nb-0.25Fe, wt %). Although the strength improvement is at a slight expense of corrosion resistance with the increase of Nb, the corrosion resistance of the high-Nb alloy with x = 1.2 (ΔG = 90.4 mg/dm2 for 100-day exposure in the water steam) is still better than that of N36 (ΔG = 103.4 mg/dm2).