Passivation process of X80 pipeline steel in bicarbonate solutions

The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electrochemical impedance spectroscopy (DEIS), and Mott-Schottky measurements. The results show that the shape of polarization curves changes with HCO₃⁻ concentration. The critical ‘passive’ concentration is 0.009 mol/L HCO₃⁻ for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in HCO^3/− solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the HCO^3/− concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L HCO₃⁻ solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.     

Conductive and corrosion behaviors of silver-doped carbon-coated stainless steel as PEMFC bipolar plates

Ni–Cr enrichment on stainless steel SS316L resulting from chemical activation enabled the deposition of carbon by spraying a stable suspension of carbon nanoparticles; trace Ag was deposited in situ to prepare a thin continuous Ag-doped carbon film on a porous carbon-coated SS316L substrate. The corrosion resistance of this film in 0.5 mol·L-1 H₂SO₄ solution containing 5 ppm F- at 80℃ was investigated using polarization tests. The results showed that the surface treatment of the SS316L strongly affected the adhesion of the carbon coating to the stainless steel. Compared to the bare SS316L, the Ag-doped carbon-coated SS316L bipolar plate was remarkably more stable in both the anode and cathode environments of proton exchange membrane fuel cell (PEMFC) and the interface contact resistance between the specimen and Toray 060 carbon paper was reduced from 333.0 mΩ·cm2 to 21.6 mΩ·cm2 at a compaction pressure of 1.2 MPa.     

Electrochemical corrosion behavior of the cobalt modified aluminide coating in 3.5 wt% NaCl solutions

In this paper, we achieved the Co modified aluminide coating on nickel base superalloys by pack cementation process. The corrosion currents(i_(corr)) of coated and uncoated substrate after 1 h of immersion tested by potentiodynamic polarization in 3.5 wt% NaCl solutions are 9.73 b × 10~(-7) A/cm~2 and 1.31 × 10~(-6) A/cm~2, respectively. With the immersion time extension, the icorrof the coating decreases and the values of |Z| by EIS increase, indicating that the electrochemical reaction rate of the coating becomes slower. The coating presents good corrosion resistance due to the Al_2O_3 formed on the surface.     

Short-term exposure of low-alloyed steels in Qinghai Salt Lake atmosphere

The rusts formed on carbon steel and weathering steel exposed in Qinghai Salt Lake atmosphere for 6 months were characterized by X-ray diffraction （XRD）, infrared transmission spectroscopy （iRS）, scanning electron microscopy （SEM）, electron probe micro analyzer （EPMA） and electrochemical po- larization techniques. The two kinds of steels showed the similar corrosion rate, corrosion product composition and electrochemical polarization behavior. Their rusts were mainly composed of β-FeOOH, Fe8（O,OH）16Cl1.3 and a little γ-FeOOH. Cl^- played an important role during the corrosion process of low-alloyed steels. The alloyed elements Cr, Ni and Cu in weathering steel were detected in the rusts; however, they showed no remarkable protective ability.     

Effect of heating rate on the electrochemical performance of MnO X @CNF nanocomposites as supercapacitor electrodes

Carbon nanofibers （CNFs） and MnOjc@CNF nanocomposites （MCNFs） are fabricated by electrospin- ning and investigated as free-standing electrodes for sup- ercapacitor. This work presents the effect of heating rate during carbonization on the electrochemical behavior of the as-prepared MCNFs electrodes in 6 mol/L KOH elec-trolyte. Results show that the MCNFs electrodes carbon- ized by relatively slower heating rate exhibit higher specific capacitance. The electronic conductivity of the slow heated MCNFs electrodes is better than that of the fast heated electrodes due to the better crystallinity of the MnOx nanoparticles and the graphitic carbon layers forming on the surface of the Mn-loaded CNFs. These MCNFs electrodes demonstrate elevated rate capability and improved cycling performance without adding any polymer binder or electronic conductor.     

The voltammetric behavior of concanavalin a at bare silver electrode and analytical application

The voltammetric behavior of concanavalin A at the bare silver electrode is described. Cyclic voltammograms show a pair of well-defined redox peaks for concanavalin A in the medium of phosphate buffer(pH=7.0) with electrochemical reaction rate constant ofK ₂=0.053 s^?1 and electron transfer number ofn=2. Moreover, both the oxidation currents and the reduction currents have linear relationship with concanavalin A concentrations in the range of 1.0×10^?6～2.0×10^?5 mol/L, which can be used as an analytical method for determining concanavalin A concentration.     

Synthesis of antiferroelectric (Bi0.534Na0.5)0.94Ba0.06TiO3 ceramics with high phase transition temperature and broad temperature range by a solid-state reaction method

Antiferroelectric 0.94(Bi 0.534 Na 0.5 )TiO 3 -0.06BaTiO 3 ceramics were prepared using a solid-state reaction method, involving the addition of excessive amounts of Bi2O3 . The resulting ceramics featured a very high phase transition temperature (Tm～330°C), from the antiferroelectric to the paraelectric phase, and a low depolarization temperature (Td<25°C). The broad temperature range, within which antiferroelectric properties are retained, of the prepared materials indicates their higher potential over lead-based antiferroelectric ceramics such as PZT-based materials that exhibit a lower T m ≤170°C. The lower Td and higher T m obtained val- ues, relative to those reported in the literature, are believed to be due to the formation of A-site vacancies originating from the incorporation of excess Bi into the perovskite structure of the studied sample. In addition, the synthesized sample shows a high dielectric constant of ～1460, in a temperature range of 50-150°C at 1 kHz, and a high energy storage density of 0.71 J/cm 3 , which is an asset in energy storage capacitor applications.     

An ultra-sensitive non-enzymatic hydrogen peroxide sensor based on SiO2-APTES supported Au nanoparticles modified glassy carbon electrode

A novel electrochemical sensor based on (3-aminopropyl)triethoxysilane (APTES) functionalized SiO₂ supported Au nanoparticles and Nafion (Nf) as the protective membrane was fabricated for the electrochemical determination of H₂O₂ in contact lens-cleaning solution. The modification steps of glassy carbon working electrode (GCE) were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The amperometric results showed that Nf/[email protected]₂-APTES/GCE sensor can be used to determine H₂O₂ in contact lens solutions with the linear ranges of 14–180 μM and 0.18–7.15 mM, excellent sensitivities of 2514.6 and 894.2 μA mM cm^?2, and a low limit of detection (LOD) of 4.25 μM depending upon signal-to-noise ratio of 3. Nf/[email protected]₂-APTES/GCE exhibited excellent repeatability with relative standard deviation (RDS) of 2.66% and acceptable reproducibility with RSD of 3.35%. The sensor displayed reasonable selectivity in the presence of uric acid, dopamine, ascorbic acid, glucose, mannose, glycine, fructose, histidine, and arginine with RSD less than 2.5%. The fabricated Nf/[email protected]₂-APTES/GCE sensor has been successfully applied to detect H₂O₂ in contact lens cleaning solutions.     

Photocatalytic activity of ferric oxide/titanium dioxide nanocomposite films on stainless steel fabricated by anodization and ion implantation

A simple surface treatment was used to develop photocatalytic activity for stainless steel. AISI 304 stainless steel specimens after anodization were implanted by Ti ions at an extracting voltage of 50 kV with an implantation dose of 3 × 1015 atoms·cm?2 and then annealed in air at 450℃ for 2 h. The morphology was observed by scanning electron microscopy. The microstructure was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The photocatalytic degradation of methylene blue solution was carried out under ultraviolet light. The corrosion resistance of the stainless steel was evaluated in NaCl solution (3.5 wt%) by electrochemical polarization curves. It is found that the Ti ions depth profile resembles a Gaussian distribution in the implanted layer. The nanostructured Fe₂O₃/TiO₂ composite film exhibits a remarkable enhancement in photocatalytic activity referenced to the mechanically polished specimen and anodized specimen. Meanwhile, the annealed Ti-implanted specimen remains good corrosion resistance.     

Elastic anomalies near phase transitions of lead-free （Na,Bi）TiO3 and （Ba,Zr）TiO3 ferroelectric ceramics

We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus exhibits minimal change in elastic modulus up to 90°C,while the elastic modulus of the BaZr0.07Ti0.93O3(BZT-7)shows 12.5%change at the phase transition temperature of70°C and that of the BaZr0.15Ti0.85O3(BZT-15)ceramics shows 34.6%change at the phase transition temperature of60°C.The variations of elastic modulus will affect the temperature stability of devices made by these lead-free ferroelectric ceramics.     

低浓度白芨葡甘聚糖溶液的流变性研究

研究了低浓度白芨葡甘聚糖(BSG)溶液的流变性与多糖浓度、外加电解质浓度、pH值及温度等的相关性。结果表明,BSG水溶液在2～16g.L-1时是假塑性流体。在低剪切速率下(γ.1s-1),溶液的表观黏度η迅速降低;剪切速率增大(γ.1s-1),溶液的η达到稳定(ηs)。在高剪切速率下溶液的ηs随浓度的增加而增加。向溶液中加入电解质,或者改变pH值,都不会影响ηs。对质量浓度为16g.L-1的BSG溶液,升高温度,η降低,η与温度的关系符合Arrhenius方程。     

Thermodynamic functions and growth constants of web-like ZnO nanostructures

Web-like ZnO nanostructures have been successfully synthesized using the potassium nitrate route at various temperatures to simplify conventional preparation methods. The structures and morphologies of the as-prepared products were characterized by X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The results showed that the reaction temperature was an important parameter, and that there was a feedback effect between nano-structure and growth parameters, combined with in situ micro-calorimetry, the reaction rate constants of the three systems were found to have been: 2.43×10-6, 2.70×10-8 and 3.12×10-7s-1 respectively. Furthermore, based on the relationship governing the potential differences between nanoand bulk ZnO, thermodynamic functions of nano-ZnO such as standard molar entropy (Sm,ZnO(nano)), standard molar Gibbs free energy of formation (△rGm,ZnO(nano)), and standard molar enthalpy of formation (△rHm,ZnO(nano)) have been calculated by the electrochemical method.     

Antibacterial and corrosive properties of copper implanted austenitic stainless steel

Copper ions were implanted into austenitic stainless steel (SS) by metal vapor vacuum arc with a energy of 100 keV and an ions dose range of (0.5-8.0)×1017 cm-2. The Cu-implanted SS was annealed in an Ar atmosphere furnace. Glancing X-ray diffraction (GXRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) were used to reveal the phase compositions, microstructures, and concentration profiles of copper ions in the implanted layer. The results show that the antibacterial property of Cu-implanted SS is attributed to Cu_9.9Fe_0.1, which precipitated as needles. The depth of copper in Cu-implanted SS with annealing treatment is greater than that in Cu-implanted SS without annealing treatment, which improves the antibacterial property against S. aureus. The salt wetting-drying combined cyclic test was used to evaluate the corrosion-resistance of antibacterial SS, and the results reveal that the antibacterial SS has a level of corrosion-resistance equivalent to that of un-implanted SS.     

Highly stable N-containing polymer-based Fe/Nx/C electrocatalyst for alkaline anion exchange membrane fuel cell applications

A cost-effective electrocatalyst with high activity and stability was developed. The Fe-Nx and pyridinic-N active sites were embedded in nitrogen-doped mesoporous carbon nanomaterial by carbonization at high temperature. The electrocatalyst exhibited excellent electrochemical performance for the oxygen reduction reaction, with high onset potential and half-wave potential values (E_onset = 1.10 ?V and E_1/2 ?= ?0.944 ?V) than 20 ?wt % Pt/C catalyst (1.04 and 0.910 ?V). The mass activity of the Schiff base network (SNW) based SNW-Fe/N/C@800° electrocatalyst (0.64 ?mA ?mg^?1 @ 1 ?V) reached about half of the commercial Pt/C electrocatalyst (1.35 ?mA ?mg^?1 @ 1 ?V). The electrocatalyst followed the 4-electron transfer mechanism due to very low hydrogen peroxide yield (H₂O₂ ?< ?1.5%) was obtained. In addition, this electrocatalyst with dual active sites showed high stability during cyclic voltammetry and chronoamperometry measurements. More importantly, the electrocatalyst also demonstrated the power density of 266 ?mW ?cm^?2 in the alkaline anions exchange membrane fuel cell (AEMFC) test, indicating its prospective application for fuel cells.     

High density methane inclusions in Puguang Gasfield: Discovery and a T-P genetic study

Based on measurement of homogenization temperature of inclusions and Raman spectral analysis, high density methane inclusions were discovered in the Triassic reservoirs of Puguang Gasfield. The methane inclusions show a homogenization temperature Th = -117.5― -118.1℃, a corresponding density of 0.3455―0.3477 g/cm3, and a Raman scatter peak v1 shift varying between 2911―2910 cm-1, which signifies a very high density of methane inclusions. The salt water inclusions paragenetic with methane inclusions show a homogenization temperature Th=170―180℃. Based on the composition of methane inclusions as determined by Raman spectra, PVTsim software was used to simulate the trapping pressure for high density methane inclusions in geologic history, and the trapping pressure was found to be as high as 153―160 MPa. Even though Puguang Gasfield is currently a gas pool of normal pressure, and the fluid pressure for the gas pool ranges between 56―65 MPa. However, data from this study indicates that remarkable overpressure may be generated at the stage of mass production of gas cracked from oils in Cretaceous, as high density methane inclusions constitute key evidence for overpressure in gas pool in geologic history. Meanwhile, discovery of small amounts of H2S, CO2 or heavy hydrocarbon in part of the high density methane inclusions indicates that the geochemical environment for trapping of inclusions may be related to formation of H2S. Therefore, the observation results can help to explore the thermochemical sulfate reduction （TSR） conditions for oil cracking and H2S formation.     

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe₄₄Al₃₄Ti₇N₁₅ and Al₆₁Ti₁₁N₂₈) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH₄Cl ​+ ​Na₂S₂O₃) solution revealed lower corrosion current (I_corr) (0.42 ​± ​0.02 ​μA/cm² and 0.086 ​± ​0.001 ​μA/cm² Vs. 0.76 ​± ​0.05 ​μA/cm²), lower passivation current (I_pass) (1.45 ​± ​0.03 ​μA/cm² and 1.83 ​± ​0.07 ​μA/cm² Vs. 1.98 ​± ​0.04 ​μA/cm²), and approximately six-fold higher breakdown potential (E_bd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (R_ct), 7- and 2.5-times higher film resistance (R_f), lower film capacitance values (Q_f) (10 ​± ​2.4 ​μS-s^acm^-2, and 5.41 ​± ​0.8 ​μS-s^acm^-2 Vs. 18 ​± ​2.21 ​μS-s^acm^-2), and lower double-layer capacitance values (Q_dl) (31.33 ​± ​4.74 ​μS-s^acm^-2, and 15.3 ​± ​0.48 ​μS-s^acm^-2 Vs. 43 ​± ​4.23 ​μS-s^acm^-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.     

Improvement in hydrogen storage performance of Mg by mechanical grinding with molten salt etching Ti3C2Clx

Mg-based materials are currently a hot research topic as hydrogen storage materials due to their considerable theoretical hydrogen storage capacity. However, the kinetic performance of hydrogen absorption and desorption of Mg is too slow and requires high temperature, which seriously hinders the application of this material. MXene is a new type of two-dimensional material with significant role in improving thermodynamics and kinetics. In this experiment, a two-dimensional layered MXene containing Cl functional group was prepared by molten salt etching using the Ti-containing MAX phase as the raw material. Then different ratios of Ti₃C₂Cl_x were uniformly dispersed onto the surface of Mg by high energy ball milling. The samples were characterized by hydrogen absorption and desorption kinetics, SEM, XRD, XPS, and DSC to investigate the effect of Ti₃C₂Cl_x on the hydrogen absorption and desorption performance of Mg. The onset hydrogen absorption temperature can be reduced to room temperature and the hydrogen release temperature is reduced by 200 ​°C by doping Ti₃C₂Cl_x. And there is also 5.4 ​wt% hydrogen storage in the isothermal hydrogen absorption test at 400 ​°C. The results of DSC demonstrate that the E_a of Mg+15 ​wt% Ti₃C₂Cl_x was reduced by 12.6% compared to pristine Mg. The ΔH is almost invariable. The results of XPS show that the presence of multivalent Ti promotes electron transfer and thus improves the conversion between Mg²⁺/Mg and H⁻/H. This study provides a guideline for further improving the hydrogen absorption and desorption performance of Mg-based hydrogen storage materials.     

Mangosteen peel-derived activated carbon for supercapacitors

This work reports the effects of activation temperatures on the porous development and electrochemical performance of activated carbons. Herein, activated carbons were prepared from the biowaste of mangosteen peel by using KOH activation at temperatures of 400, 600, and 800 ?°C. The results demonstrate that the specific surface area increases with increasing the activation temperatures in which the well-developed porous structure after KOH activation at 800 ?°C provides the highest specific surface area of 1039 ?m² ?g^?1. At 600 ?°C, the activated carbon delivers the highest specific capacitance value of 182 ?F ?g^?1 ?at a current density of 0.5 ?A ?g^?1 in 3 ?M KOH aqueous electrolyte. This is correlated well with its high micropore fractions (99%). Moreover, it was found that the activation temperature changes the major contribution of oxygen-containing functional group on surface of activated carbon, which is beneficial for the enhancement of the specific capacitance value of activated carbon at the temperature of 600 ?°C. This work suggests that the activation temperature is a key to optimizing the electrochemical performance of activated carbons. Overall, our activated carbons can be considered as a strong candidate for use as electrode materials in supercapacitors.     

Preparation and application of electrochemical barbital sensor based on molecularly imprinting technique

A molecularly imprinted electrochemical sensor was prepared based on poly folic acid(PFA) for rapid detection of barbital(BAR). The PFA membrane was obtained via directly electropolymerization technique on the surface of chemically modified Au electrode(Au/CME) by means of cyclic voltammetry(CV) in the potential range between-0.4 and 1.0 V in phosphate buffer solution(PBS) pH 7.04. The molecularly imprinted polymers(MIP) membrane was synthesized with BAR as template molecules and folic acid(FA) as the functional monomer. The performance and surface feature of the proposed imprinted sensor were investigated using CV, differential pulse voltammetry(DPV), electrochemical impedance spectroscopy(EIS) and scanning electron microscope(SEM). Under the optimized conditions, the peak current decrease(ΔI_p) was proportional to the BAR concentration in the range of 1.00×10~(–7)-1.00×10~(–4) mol/L(R~2=0.998 2) with a detection limit(S/N=3) of 4.65×10~(–8) mol/L. The results indicated that the imprinted sensor exhibited an excellent selectivity for BAR and it was successfully used to determine BAR in real samples with recoveries of 94.7%-106.2% by using the standard addition method.     

Study on the corrosion inhibitor and fog suppressor for chemical pickling of iron and steel

A new type of corrosion inhibitor and fog suppressor composed of Nitrogen-containing alkaloid, water-soluble butadiene lower polymer, and inorganic electrolyte has been investigated by gravimetric and electrochemical method. Effects of this chemicals on pickling rate and hydrogen penetration into iron and steel material in 50∼150 g/L HCl or/and H₂SO₄ solutions at 20∼70°C temperature were examined. The amount of acid fog escaping from the surface of air-liquid was determined by chemical titration. The results indicate that the efficiency of inhibition and suppression depends on film properties by which mean a barrier film on the interface of bare mild steel/solution or an unsolvable liquid membrane as hydrophibic effect. In present work the film-forming mechanism by in situ and chemistry-mechanics effect is also discussed. Supported by the National Natural Science Foundation of China Tao Yingchu, born in Jun. 1943, Prof.