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951.
New steels with different carbon contents were self-developed by thermo-mechanical controlled processing.The effects of the carbon content and the microstructure on the corrosion properties of new steels were investigated by immersion test and SEM.The results indicated that the ferrite phase(both the proeutectoid and eutectoid ferrite) dissolved preferentially.Cementite reserved and accumulated on the surface.As carbon content increased,the content of ferrite decreased and cathode/anode area ratio increased.Therefore,the corrosion rate of new steels increased from 0.30 to0.90 mm/years when the carbon content rose from 0.05 to 0.13 wt%.The corrosion process of new steels was studied using electrochemical impedance spectroscopy experiments during 72 h.It indicated that the impedance modulus |Z|0.01 Hz of the new steels reduces with the increase of the immersion time.While the corrosion process of the new steel with 0.11 wt%C developed faster than that with 0.07 wt%C,although their |Z|0.01 Hz was similar at the initial stage. 相似文献
952.
研究了无镍高氮奥氏体不锈钢的脆韧转变(BDT)。在176 K、273 K和336 K进行的落锤试验结果表明,尽管Fe-25Cr-1.1N(质量分数,%)是面心立方结构的奥氏体合金钢,但仍展现出显著的脆韧转变现象。对冲击试验试样的塑性变形观察表明,BDT是由于低温下差的延展性所致,这与铁素体钢的情况是一致的。为了测量BDT的激活能,利用4点弯曲试验研究了应变速率与BDT温度的关系。研究发现,BDT温度与应变速率之间的依赖关系不显著,且BDT温度对应变率的Arrhenius曲线表明Fe-25Cr-1.1N钢BDT的激活能比低碳铁素体钢的高得多。从滑移位错与溶质氮原子发生交互作用导致低温下位错可动性降低这一角度,本文探讨了高氮钢特有的BDT及其高激活能的本质原因。 相似文献
953.
S. Girija 《腐蚀工程科学与技术》2014,49(5):335-344
The paper focuses on corrosion monitoring of 304L stainless steel (SS) (solution annealed, sensitised) in nitric acid (4, 8 and 12M) at 298 and 323 K electrolyte temperatures, and simulated high level waste (HLW, 323 K), using electrochemical noise (EN) measurements. Double loop electrochemical potentiokinetic reactivation test was conducted to assess the degree of sensitisation. Electrochemical noise records revealed passivation process during the monitoring period, under all conditions studied, except for the sensitised specimen in 4M nitric acid (323 K), which showed localised attack. The results showed an inverse relation between EN resistance and corrosion activity. An increase in nitric acid concentration resulted in an increase in corrosion activity, while increasing the electrolyte temperature increased the corrosion activity marginally. A profound increase in corrosion activity occurred for the sensitised specimen in nitric acid when compared to the solution annealed specimen, but the increase was marginal in simulated HLW. The results are detailed in the paper. 相似文献
954.
The present work is focused in the study of the bimetallic Cu–Co formulation combined with CeO2 as SOFC anode, at 750 °C, direct feed of methane and two different fuel mixtures that simulate biogas. Additionally, the sulphur tolerance of new anode material has been evaluated. Its single cell evaluation, based on a samaria doped ceria (SDC) solid electrolyte and a LSM perovskite cathode, together with the electrochemical characterisation and catalytic activity tests, have allowed to demonstrate the ability of this material to operate directly with simulated biogas mixtures without loss of single cell performance due to the formation of carbon deposits or sulphur anode poisoning. The activity of this material for the exothermic oxidation of methane reduces the energy requirement of the endothermic internal methane reforming process. The cobalt doping of basic copper–ceria formulation enhanced sulphur and carbon coking tolerance of the SOFC anode material. 相似文献
955.
Electrochemical Impedance Spectroscopy (EIS) is a suitable and powerful diagnostic testing method for fuel cells because it is non-destructive and provides useful information about fuel cell performance and its components. In this work, EIS measurements were carried out on a 300 W stack with 20 elementary cells. Electrochemical impedance spectra were recorded either on each cell or on the stack. Parameters of a Randles-like equivalent circuit were fitted to the experimental data. In order to improve the quality of the fit, the classical Randles cell was extended by changing the standard plane capacitor into a constant phase element (CPE). The effects of output current, cell position, operating temperature and humidification temperature on the impedance spectra were studied. 相似文献
956.
957.
Philippe Perret Zohreh Khani Thierry Brousse Daniel Bélanger Daniel Guay 《Electrochimica acta》2011,56(24):8122
A new hybrid electrochemical capacitor based on an activated carbon negative electrode, lead dioxide thin film and nanowire array positive electrode with an electrolyte made of a lead salt dissolved in methanesulfonic acid was investigated. It is shown that the maximum energy density and specific capacity of the C/PbO2 nanowire system increase during the first 50 cycles before reaching their maximum values, which are 29 Wh kg−1 and 34 F g−1, respectively, at a current density of 10 mA cm−2 and a depth of discharge (positive active electrode material) of 3.8%, that corresponds to a 22C rate. This is 7–8 times higher than the corresponding maximum values reached with a C/PbO2 thin film cell operated in the same conditions. After an initial activation period, the performances of the C/PbO2 nanowire system stay constant and do not show any sign of degradation during more than 5000 cycles. For comparison, the C/PbO2 thin film system exhibits a 50% decrease of its performances in similar conditions. 相似文献
958.
To produce a Nd1.8Ce0.2CuO4±δ solid solution, the oxide form of the reagents were milled for 36 h and sintered at 1173 K for 8 h in a microwave furnace. The transition from a negative temperature coefficient (NTC) of conductivity to a positive temperature coefficient (PTC) was suppressed due to the submicron size of the crystallites. The low-frequency response in the complex impedance plane fit the Gerischer element. At 973 K, the area specific resistance (ASR) of Nd1.8Ce0.2CuO4±δ/GDC/Nd1.8Ce0.2CuO4±δ sintered at 1073 K for 2 h was 1.92 ohm cm2. 相似文献
959.
Anodic oxidation of molybdenum in weakly acidic, nearly neutral and weakly alkaline electrolytes was studied by voltammetric and electrochemical impedance spectroscopic measurements in a wide potential and pH range. Current vs. potential curves were found to exhibit two pseudo-Tafel regions suggesting two parallel pathways of the dissolution process. Electrochemical impedance spectra indicated the presence of at least two reaction intermediates. X-ray photoelectron spectroscopic (XPS) results pointed to the formation of an oxide containing Mo(IV), Mo(V) and Mo(VI), the exact ratio between different valence states depending on potential and pH of the solution. A physico-chemical model of the processes is proposed and a set of kinetic equations for the steady-state current vs. potential curve and the impedance response are derived. The model is found to reproduce quantitatively the current vs. potential curves and impedance spectra at a range of potentials and pH and to agree qualitatively with the XPS results. Subject to further improvement, the model could serve as a starting point for the optimization of the electrochemical fabrication of functional molybdenum oxide coatings. 相似文献
960.
The performance of mixed bi-material electrodes composed of the battery material, LiMn2O4, and the electrochemical capacitor material, activated carbon, for hybrid electrochemical energy storage devices is investigated by galvanostatic charge/discharge and pulsed discharge experiments. Both, a high and a low conductivity lithium-containing electrolyte are used. The specific charge of the bi-material electrode is the linear combination of the specific charges of LiMn2O4 and activated carbon according to the electrode composition at low discharge rates. Thus, the specific charge of the bi-material electrode falls between the specific charge of the activated carbon electrode and the LiMn2O4 battery electrode. The bi-material electrodes have better rate capability than the LiMn2O4 battery electrode. For high current pulsed applications the bi-material electrodes typically outperform both the battery and the capacitor electrode. 相似文献