Electrochemical decolorization of dye wastewater by surface-activated boron-doped nanocrystalline diamond electrode

Complex organics contained in dye wastewater are difficult to degrade and often require electrochemical advanced oxidation processes（EAOPs） to treat it. Surface activation of the electrode used in such treatment is an important factor determining the success of the process.The performance of boron-doped nanocrystalline diamond（BD-NCD） film electrode for decolorization of Acid Yellow（AY-36） azo dye with respect to the surface activation by electrochemical polarization was studied. Anodic polarization found to be more suitable as electrode pretreatment compared to cathodic one. After anodic polarization, the originally H-terminated surface of BD-NCD was changed into O-terminated, making it more hydrophilic.Due to the oxidation of surface functional groups and some portion of sp2 carbon in the BD-NCD film during anodic polarization, the electrode was successfully being activated showing lower background current, wider potential window and considerably less surface activity compared to the non-polarized one. Consequently, electrooxidation（EO） capability of the anodically-polarized BD-NCD to degrade AY-36 dye was significantly enhanced, capable of nearly total decolorization and chemical oxygen demand（COD） removal even after several times of re-using. The BD-NCD film electrode favored acidic condition for the dye degradation; and the presence of chloride ion in the solution was found to be more advantageous than sulfate active species.

Influence of Concentrations of KOH and Na_2SiO_3 Electrolytes on the Electrochemical Behavior of Ceramic Coatings on 6061 Al Alloy Processed by Plasma Electrolytic Oxidation

In this study,ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation（PEO）technique,and the effect of concentrations of KOH and Na_2SiO_3 as electrolytes for PEO process was studied on microstructure,chemical composition,and electrochemical behavior of PEO coatings formed on the 6061 Al alloy.The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte.Consequently,the breakdown voltage reduced,which in turn improved the surface quality and the corrosion behavior.Moreover,the increase in concentration of Na_2SiO_3 resulted in the increase in incorporation of Si in the coating,which led to a higher corrosion potential in the concentration of 4 g L^（-1）.According to this investigation,the best protection behavior of coatings can be obtained when the KOH and Na_2SiO_3 concentrations in PEO electrolyte are equal to 4 g L^（-1）.

Effect of solution pH,Cl- concentration and temperature on electrochemical behavior of PH13-8Mo steel in acidic environments

The effect of solution pH,Cl;concentration and temperature on the electrochemical corrosion behavior of PH13-8Mo steel in acidic solution was investigated by using the electrochemical tests,scanning electron microscopy and X-ray photoelectron spectroscopy.The PH13-8Mo martensitic precipitation hardened stainless steel is in the passivity state when the pH value is above 3.0,below which the anodic polarization curves of the steel are actively dissolved.The corrosion current density gradually decreases with increasing the solution pH and decreasing Cl;concentration and solution temperature.Pits are initiated on the sample surface in the presence of the Cl;and gradually developed into uniform corrosion with increasing the Cl;concentrations.Moreover,the corrosion is more serious with an increase in solution temperature.

Doping strategy on improving the overall cathodic performance of double perovskite LnBaCo_(2)O_(5+σ)(Ln=Pr,Gd)as potential SOFC cathode materials

A series of single-phase double perovskite Pr1-xGdxBaCo_(2)-yFeyO_(5+σ)(x=0,0.5 and 1,0≤y≤1)materials were engineered through A/B site co-doping strategy to improve the mechanical,electrical and electrochemical properties as potential cathode materials for the application of intermediate solid oxide fuel cells(IT-SOFCs).The corresponding thermochemical stability,thermal expansion behavior,electrical conductivity and cathodic polarization resistance of the materials were systematically investigated.It was found that the A-site dual lanthanide doped Pr_(0.5)Gd_(0.5)BaCo_(2)O_(5+σ)(PGBCO)exhibits improved electrical conductivity,reduced thermal expansion,and comparatively low electrochemical polarization resistance versus single lanthanide double perovskite,PrBaCo_(2)O_(5+σ)(PBCO)and GdBaCo_(2)O_(5+σ)(GBCO)materials.Further investigation on the effect of B-site Fe-doping on Pr_(0.5)Gd_(0.5)BaCo_(2)-yFeyO_(5)+σ(PGBCF-y,0≤y≤1)reveals that all the PGBCF-y compositions exhibit excellent chemical stability with Gd-doped ceria(GDC)at operating temperatures not higher than 1100℃.Besides,doping of Fe in B-site can effectively reduce the thermal expansion coefficients(TECs)of the Pr_(0.5)Gd_(0.5)BaCo_(2)O_(5)+σceramics at 30e1000℃.And the electrochemical impedance spectra(EIS)results show that the PGBCF-y|GDC|PGBCF-y symmetric cells have acceptable low area specific polarization resistances.Further examination of the cathodic polarization and characteristic capacitance from the AC impedance spectra by employing the relaxation time distribution(DRT)method demonstrated that charge transfer is the dominating subprocess for the oxygen transport through the materials.

Effect of Heat Treatment on Corrosion Behaviour of Amorphous Metal Fibers

Amorphous metal fiber has high corrosion resistance and excellent mechanical properties, making it a kind of good material for reinforcing concrete matrix. The effect of heat treatment on the corrosion behaviour of Fe73- Cr6C9Si1P11 amorphous metal fibers in 0.5 mol/L He SO4 solution was investigated by electrochemical polarization analysis. Differential scanning calorimetry （DSC） was used to measure the thermal properties. The evolution of the crystallization process after heat treatment was identified by X-ray diffraction （XRD）. The results show that the α- Fe, Fe2 P and Fea P crystalline phases individually precipitate in the amorphous matrix with increasing annealing temperature. The as prepared amorphous sample shows high corrosion resistance with a lower passivation current density and a wider passive region. The corrosion resistance dramatically decreases after the annealing temperature is higher than 400 ℃.

Corrosion Evolution of Low Alloy Steel in Deaerated Bicarbonate Solutions

Corrosion evolution during immersion tests （up to 43 days） of NiCu steel in deaerated 0.1 mol/L bicarbonate solutions was investigated by electrochemical measurements, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Results show that NiCu steel transformed from the anodic dissolution in the early stage of immersion to a metastable passive state in the final stage as the open-circuit potential value shifted positively, which was aroused by the precipitation of corrosion products. This process was mainly promoted by the trace amount of oxygen. Simultaneously, dominant cathodic reaction transformed from the hydrogen evolution in early stage to reduction processes of corrosion products in later stages. Possible corrosion processes were discussed with the assistance of a corresponding Pourbaix diagram.