Electrochemical behavior of mesh and plate oxide coated anodes during zinc electrowinning

The catalytic performance of two oxides coated anodes （OCSs） meshes and one OCA plate was investigated in a zinc electrowinning electrolyte at 38 ℃. Their electrochemical behaviors were compared with that of a conventional Pb-0.7%Ag alloy anode. Electrochemical measurements such as cyclic voltammetric, galvanostatic, potentiodynamic, open-circuit potential （OCP） and in situ electrochemical noise measurements were considered. After 2 h of OCP test, the linear polarization shows that the corrosion current density of the Ti/（IrO2-Ta2O5） mesh electrode is the lowest （3.37μA/cm^2） among the three OCAs and shows excellent performance. Additionally, after 24 h of galvanostatic polarization at 50 mA/cm^2and 38 ℃, the Ti/MnO2mesh anode has the highest potential （1.799 V）, followed by the Ti/（IrO2-Ta2O5） plate （1.775 V） and Ti/（IrO2-Ta2O5） mesh （1.705 V） anodes. After 24 h of galvanostatic polarization followed by 16 h of decay, the linear polarization method confirms the sequence obtained after 2 h of OCP test, and the Ti/（IrO2-Ta2O5） mesh attains the lowest corrosion current density. The Ti/（IrO2-Ta2O5） mesh anode also shows better performance after 24 h of galvanostatic polarization with the overpotential lower than that of the conventional Pb-Ag anode by about 245 mV.

Removal of Uranium（Ⅵ） by Fixed Bed Ion-exchange Column Using Natural Zeolite Coated with Manganese Oxide

The adsorption of uranium(Ⅵ)on the manganese oxide coated zeolite(MOCZ)from aqueous solution was investigated in a fixed-bed column.The experiments were conducted to investigate the effects of bed height,flow rate,particle size,initial concentration of uranium(Ⅵ),initial pH,presence of salt and competitive ions.The U-uptake by MOCZ increased with initial uranium(Ⅵ)concentration and bed height,but decreased as the flow rate and particle size increased.In the presence of salt and competitive ions,the breakthrough time was shorter.The adsorption capacity reached a maximum at pH of 6.3.The Thomas model was applied to the experimental data to determine the characteristic parameters of the column for process design using linear regression.The breakthrough curves calculated from the model were in good agreement with the experimental data.The BDST model was used to study the influence of bed height on the adsorption of uranium(Ⅵ).Desorption of uranium(Ⅵ)in the MOCZ column was investigated.The column could be used for at least four adsorption-desorption cycles using 0.1mol.L-1 NaHCO3 solution as the elution.After desorption and regeneration with deionized water,MOCZ could be reused to adsorb uranium(Ⅵ)at a comparable capacity.Compared to raw zeolite,MOCZ showed better capacity for uranium(Ⅵ)removal.

Oxide Coated Cathode Plasma Source of Linear Magnetized Plasma Device

Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm2 to 6 A/cm2 in pulsed mode within pulse length 5-20 ms. A 10 cm diameter, 2 m long plasma column with density 10is m-3 to 1019 m3 and electron temperature Te --~ 3-7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper.

Adsorption and Desorption Mechanisms of Methylene Blue Removal with Iron-Oxide Coated Porous Ceramic Filter

Adsorption and desorption mechanisms of methylene blue (MB) removal with iron-oxide coated porous ce-ramics filter (IOCPCF) were investigated in batch and column mode. The results revealed that MB removal mechanisms included physical adsorption and chemical adsorption, of which chemical adsorption by surface ligand complex reaction played a dominant role after infrared spectrum analysis. Recycling agents were se-lected from dilute nitric acid (pH=3), sodium hydroxide solution (pH=12) and distilled water. Among three agents, dilute metric acid (pH=3) was the best recycling agent. Regeneration rate of IOCPCF arrived at 82.56% at batch adsorption and regeneration was finished in 75min at column adsorption. Adsorp-tion-desorption cycles of IOCPCF after batch and column adsorption were four and three times, respectively. Further, compared with fresh IOCPCF, MB removal rate with these desorbed IOCPCF adsorption only slightly decreased, which suggested that IOCPCF should be used repeatedly.

Preparation, Characterization, and Application of Manganese Oxide Coated Zeolite as Adsorbent for Removal of Copper(II) Ions from Seawater

The present study is aimed to examine the adsorption characteristics of Cu(II) by using the novel cellulose acetate composite and to apply it for the removal of Cu(II) from real wastewater samples. In order to achieve this objective, ethylenediamine, diethylenetriamine, triethylenetetramine and te-traethylenepentanene were used for immobilization of grafted cellulose acetate-nanoscale manganese dioxide. Cellulose was extracted from mangrove species Avicennia marina and converted to cellulose acetate then it was formed composite with nano-manganese dioxide via precipitation of nano-manganese dioxide on it. The composite was grafted with acrylamide monomer before immobilization. The synthesized compounds were used for adsorption of Cu(II) and characterized by FT-IR, TGA and SEM. The adsorption characteristics of synthesized sorbents were optimized. Langmuir and Freundlich models were used to establish sorption equilibria. The analytical applications of these modified materials were applied successfully for the removal of Cu(II).

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density.However,low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application.Herein,a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the electrochemical performance is improved.The modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of~233 m Ah/g at0.1 C and 174 m Ah/g at 1 C after 150 cycles in the voltage range of 3.0 V–4.4 V at 45℃,and it also exhibits an enhanced rate capability with 118 m Ah/g at 5 C.The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.

Formation process of composite plasma electrolytic oxidation coating containing zirconium oxides on AM50 magnesium alloy

The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation （PEO） in a K 2 ZrF 6 electrolyte solution were studied by scanning electron microscope （SEM） and energy dispersive X-ray spectroscope （EDX）. Electrochemical impedance spectroscopy （EIS） tests were used to study the variation of the corrosion resistance of the coating during the PEO treatment. The results show that the coating formed on Mg alloy is mainly composed of MgO and MgF 2 when the applied voltage is lower than the sparking voltage, and zirconium oxides start to be deposited on Mg substrate after the potential exceeding the sparking voltage. The corrosion resistance of the coating increases with increasing the applied voltage.

Preparation and oxidation resistance of B_2O_3-coated boron-modified carbon foams

To improve the oxidation resistance of boron-modified carbon foams, the B2O3 coating was prepared on boron-modified carbon foams by low-cost slurry method. The microstructures and phase compositions of the coated carbon foams were characterized by scanning electron microscopy and X-ray diffraction, respectively. Oxidation resistances of uncoated and coated boron-modified carbon foams were investigated at 873 K in air. The results showed that as-received B2O3 coating could protect boron-modified carbon foams from oxidation at 873 K. B2O3-coated carbon foam doped with 7% B2O3 （mass fraction） （BO-7） had better oxidation resistance, exhibiting mass loss of 17.40% after oxidation at 873 K for 120 min. The melting glass layer formed on the surface of BO-7 could prevent oxygen from diffusing into boron-modified carbon foams substrate during oxidation to some extent.

Synthesis and characterization of LiFePO_4 coating with aluminum doped zinc oxide

Aluminum doped zinc oxide （AZO）, as an electrically conductive material, was applied to coating on the surface of olivine-type LiFePO4 synthesized by solid-state method. The charge-discharge test results show that the rate performance and low-temperature performance of LiFePO4 are greatly improved by the surface treatment. Even at 20C rate, the discharge specific capacity of 100.9 mA.h/g was obtained by the AZO-coated LiFePO4 at room temperature. At -20 ℃, the discharge specific capacity at 0.2C for un-coated LiFePO4 and the coated one are 50.3 mA.h/g and 119.4 mA.h/g, respectively. It should be attributed to the electrically conductive AZO-coating which increases the electronic conductivity of LiFePO4. Furthermore, the surface-coating increases the tap-density of LiFePO4. The results indicate that the AZO-coated LiFePO4 is a good candidate of cathode material for applying in lithium power batteries.

Thermal conductivity of (Sm_(1-x)La_x)_2Zr_2O_7 (x=0,0.25,0.5,0.75 and 1) oxides for advanced thermal barrier coatings

Pyrochlore oxides of general compositions, A2Zr2O7, where A is a 3＋ cation （La to Lu）, are promising candidate materials for applications as high temperature thermal barrier coatings because of their high melting points, high thermal expansion coefficients, and low thermal conductivities. In this study, oxides of Sm2Zr2O7, （Smo.75La0.25）2Zr2O7, （Sm0.5 La0.5）2 ZreO7, （Sm0.25La0.75）eZr2O7 and La2Zr2O7 were prepared by solid reactions at 1600℃ for 10 h using Sm2O3, La2O3 and ZrO2 as the reactants. The phase compositions of these ceramic materials were analyzed by X-ray diffractometer （XRD） and fourier transform infrared spectroscopy （FT-IR） methods, respectively. The microstructure was observed by scanning electron microscope （SEM）. The thermal conductivities of these ceramic materials were measured using laser-flash method. XRD and FT-IR results showed that pure ceramic materials with pyrochlore structure were prepared successfully. SEM results indicated that microstructures of these ceramic materials were dense and grain boundaries were very clean. The La2O3 doped Sm2Zr2O7 pyrochlores （Sm0.75 La0.25）2Zr2O7 and （Sm0.5 La0.5）2 Zr2O7 had lower thermal conductivity than the undoped Sm2Zr2O7. The thermal conductivity of （Sm0.25La0.75）2Zr2O7 was found to be lower than that of La2Zr2O7. The results showed that these ceramic materials had the potential to be used as candidate materials for TBCs.

Scavenging of Cd through Fe/Mn oxides within natural surface coatings

The dynamics of Cd scavenging from solutions by Fe/Mn oxides in natural surface coatings （NSCs） was investigated under laboratory conditions. Selective extraction methods were employed to estimate the contributions of Fe/Mn oxides, where hydroxylamine hydrochloride （0.01 mol/L NH2OH-HCl ＋ 0.01 mol/L HNO3）, sodium dithionite （0.4 mol/L Na2S2O4） and nitric acid （10% HNO3） were used as extraction reagents. The Cd scavenging was accomplished with developing periods of the NSCs （totally 21 data sets）. The resulting process dynamics fitted well to the Elovich equation, demonstrating that the amount of Cd scavenged was proportional to the increments of Fe/Mn oxides that were accumulated in the NSCs. The amount of Cd bound to Fe oxides （MCdFe） and Mn oxides （MCdMn） could be quantified by solving two equations based on the properties of two extraction reagents. The amount of Cd scavenged by Fe/Mn oxides could also be estimated using MCdFe and MCdMn divided by the total amounts of Fe and Mn oxides in the NSCs, respectively. The results indicated that the Cd scavenging by Fe/Mn oxides was dominated by Fe oxides, with less roles attributed to Mn oxides. The estimated levels of Cd scavenging through Fe and Mn oxides agreed well with those predicted through additive-adsorption and linear-regression models.

Measurement of Atrazine Adsorption onto Surficial Sediments(Natural Surface Coatings)——New Evidence for the Importance of Fe Oxides

To reveal the relative contribution of the components, Fe, Mn oxides or organic materials（OMs） in the surficial sediments（SSs）, and the natural surface coating samples（NSCSs） to adsorbing atrazine（AT）, a selective chemical extraction technique was employed, to remove the different components, and the adsorption characteristics of AT on the SSs and the NSCSs were investigated. The observed adsorptions of AT on the original and extracted SSs and NSCSs were analyzed by nonlinear least squares fitting（NLSF） to estimate the relative contribution of the components. The results showed that the maximum adsorption of AT on the NSCSs was greater than that in the SSs, before and after extraction treatments, implying that the NSCSs were more dominant than the SSs for organic pollutant adsorption. It was also found that the Fe oxides, OMs, and residues in SSs（NSCSs） facilitated the adsorption of AT, but Mn oxides directly or indirectly restrained the interaction of AT with SSs（NSCSs） particles. The contribution of the Fe oxides to AT adsorption was more than that of OMs; the greatest contribution to AT adsorption on a molar basis was from the Fe oxides in the nonresidual fractions, indicating that the Fe oxides played an important role in controlling the environmental behavior of AT in an aquatic environment.

Coating Carbon Nanotubes with Europium Oxide

Carbon nanotubes (CNTS) coating with europium oxide by a simple method is reported in this letter for the first time. The CNTS were refluxed in a solution of nitric acid containing europium nitrate, and the pH value was subsequently ajusted with ammonia solution. At last, the mixture was filtered and annealed. The TEM micrograph showed that the CNTS were covered with a uniform thin layer with thickness of about 15 nm. The XRD results revealed that the CNTS were coated with europium oxide.

Studies on thermally grown oxide as an interface between plasma-sprayed coatings and a nickel-based superalloy substrate

A thermally grown oxide layer formed by hot corrosion was investigated as an interface between plasma-sprayed coatings and a nickel-based superalloy substrate. The hot corrosion mechanism of NiCr–Cr_2O_3 and Al_2O_3–40wt% TiO_2(A40T) plasma coated Inconel 617 was evaluated. The experiments were carried out at 1000°C using a combination of Na_2SO_4, NaCl, and V_2O_5 salts to simulate the conditions of a gas turbine in a marine environment. The hot corrosion results revealed the spallation and dissolution of oxides upon prolonged exposure. Optical images and scanning electron micrographs of the exposed samples revealed the formation of oxide scale and provided details of its morphology in NiCr–Cr_2O_3 coated samples. Microstructure characterization of A40T coatings demonstrated a thermally grown oxide(TGO) layer at 1000°C. Increasing the thickness of the TGO layer decreased the corrosion resistance. The elemental analysis and image mapping revealed the migration of active elements from the substrate and coatings toward the corrosive environment.

Structure and Oxidation Behavior of a Plasma Sprayed Yttrium Silicates Coated SiC-C/C with a Glass Outer Sealant from 1573K to 1873K

Different compositions of yttrium silicates coatings were deposited on SiC-C/C by plasma spraying and an outer borosilicate glass was applied on the yttrium silicates coatings surfaces. The structure of the multi-layer coatings was characterized by XRD and SEM analyses. High temperature oxidation behavior of the multi-layer coatings coated C/C composites was investigated. Results show that SiC/2SiO2 Y2O3/1.5SiO2 Y203/ SiO2 Y2O3/glass multi-layer coating has better high temperature oxidation resistance, protecting carbon/ carbon composites from oxidation at 1 773 K in air for 164 h with the weight loss of 1.65%. The oxidation weight loss of the coated C/C with time accorded with parabolic rule in the temperature range 1 573 K-1 873 K; and the corresponding oxidation activation energy of the coated carbon/carbon composites is 132.2 kJ/mol.

Improvement of thermally grown oxide layer in thermal barrier coating systems with nano alumina as third layer

A thermally grown oxide （TGO） layer is formed at the interface of bond coat/top coat. The TGO growth during thermal exposure in air plays an important role in the spallation of the ceramic layer from the bond coat. High temperature oxidation resistance of four types of atmospheric plasma sprayed TBCs was investigated. These coatings were oxidized at 1000 °C for 24, 48 and 120 h in a normal electric furnace under air atmosphere. Microstructural characterization showed that the growth of the TGO layer in nano NiCrAlY/YSZ/nano Al2O3 coating is much lower than in other coatings. Moreover, EDS and XRD analyses revealed the formation of Ni（Cr,Al）2O4 mixed oxides （as spinel） and NiO onto the Al2O3 （TGO） layer. The formation of detrimental mixed oxides （spinels） on the Al2O3 （TGO） layer of nano NiCrAlY/YSZ/nano Al2O3 coating is much lower compared to that of other coatings after 120 h of high temperature oxidation at 1000 °C.

Enhanced high-temperature performance of Li-rich layered oxide via surface heterophase coating

Li-rich layered oxides have become one of the most concerned cathode materials for high-energy lithiumion batteries, but they still suffer from poor cycling stability and detrimental voltage decay, especially at elevated temperature. Herein, we proposed a surface heterophase coating engineering based on amorphous/crystalline Li3 PO4 to address these issues for Li-rich layered oxides via a facile wet chemical method. The heterophase coating layer combines the advantages of physical barrier effect achieved by amorphous Li3 PO4 with facilitated Li+diffusion stemmed from crystalline Li3 PO4. Consequently, the modified Li(1.2) Ni(0.2) Mn(0.6) O2 delivers higher initial coulombic efficiency of 92% with enhanced cycling stability at 55 °C(192.9 mAh/g after 100 cycles at 1 C). More importantly, the intrinsic voltage decay has been inhibited as well, i.e. the average potential drop per cycle decreases from 5.96 mV to 2.99 mV. This surface heterophase coating engineering provides an effective strategy to enhance the high-temperature electrochemical performances of Li-rich layered oxides and guides the direction of surface modification strategies for cathode materials in the future.

Micro and nano-enabled approaches to improve the performance of plasma electrolytic oxidation coated magnesium alloys

Magnesium(Mg)and its alloys have become a hot research topic in various industries owing to the specific physical and chemical properties.However,high corrosion rate is considered the key lifetime-limiting.Plasma electrolytic oxidation(PEO)method is a simple strategy to deposit an oxide layer on the surface of light metals such as magnesium alloys,to control corrosion rate and promote some other properties,depending on their performances.Nevertheless,their features including their micropore size,distribution,and interconnectivity,and microcracks have not been improved to an acceptable level to support long-term performances of the magnesium-based substrates.Studies have introduced micro/nano-enabled approaches to enhance various properties of PEO coatings such as corrosion resistance,tribological properties,self-healing ability,bioactivity,biocompatibility,antibacterial properties,or catalytic performances.These strategies consist of incorporating of micro and nanoparticles into the PEO layers to produce multi-functional surfaces or the formation of multi-layered coatings to cover the defects of PEO coatings.In this perspective,the present paper aims to overview various nano/micro-enabled strategies to promote the properties of PEO coatings on magnesium alloys.The main focus is given to the functional changes that occurred in response to the incorporation of various types of nano/micro-structures into the PEO coatings on magnesium alloys.

Surface encapsulation of layered oxide cathode material with NiTiO_(3) for enhanced cycling stability of Na-ion batteries

In Na-ion batteries,O3-type layered oxide cathode materials encounter challenges such as particle cracking,oxygen loss,electrolyte side reactions,and multi-phase transitions during the charge/discharge process.This study focuses on surface coating with NiTiO_(3) achieved via secondary heat treatment using a coating precursor and the surface material.Through in-situ x-ray diffraction(XRD)and differential electrochemical mass spectrometry(DEMS),along with crystal structure characterizations of post-cycling materials,it was determined that the NiTiO_(3) coating layer facilitates the formation of a stable lattice structure,effectively inhibiting lattice oxygen loss and reducing side reaction with the electrolyte.This enhancement in cycling stability was evidenced by a capacity retention of approximately 74%over 300 cycles at 1 C,marking a significant 30%improvement over the initial sample.Furthermore,notable advancements in rate performance were observed.Experimental results indicate that a stable and robust surface structure substantially enhances the overall stability of the bulk phase,presenting a novel approach for designing layered oxide cathodes with higher energy density.