scholarly journals Electrochemical Promotion of Nanostructured Palladium Catalyst for Complete Methane Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Yasmine M. Hajar ◽  
Balaji Venkatesh ◽  
Elena A. Baranova
Keyword(s):  
Anodic Polarization ◽  
Reaction Rate ◽  
Electrochemical Promotion ◽  
Open Circuit ◽  
Current Application ◽  
Faradaic Efficiency ◽  
Reaction Rate Increase ◽  
Structured Catalysts ◽  
Different Temperatures ◽  
Electrochemical Promotion Of Catalysis

Electrochemical promotion of catalysis (EPOC) was investigated for methane complete oxidation over palladium nano-structured catalysts deposited on yttria-stabilized zirconia (YSZ) solid electrolyte. The catalytic rate was evaluated at different temperatures (400, 425 and 450 °C), reactant ratios and polarization values. The electrophobic behavior of the catalyst, i.e., reaction rate increase upon anodic polarization was observed for all temperatures and gas compositions with an apparent Faradaic efficiency as high as 3000 (a current application as low as 1 μA) and maximum rate enhancement ratio up to 2.7. Temperature increase resulted in higher enhancement ratios under closed-circuit conditions. Electrochemical promotion experiments showed persistent behavior, where the catalyst remained in the promoted state upon current or potential interruption for a long period of time. An increase in the polarization time resulted in a longer-lasting persistent promotion (p-EPOC) and required more time for the reaction rate to reach its initial open-circuit value. This was attributed to continuous promotion by the stored oxygen in palladium oxide, which was formed during the anodic polarization in agreement with p-EPOC mechanism reported earlier.

Heat Treatment Influence on the Corrosion Resistance of a Cu-Al-Fe-Mn Bronze

2018 ◽  
Vol 69 (5) ◽  
pp. 1055-1059 ◽  
Author(s):  
Mariana Ciurdas ◽  
Ioana Arina Gherghescu ◽  
Sorin Ciuca ◽  
Alina Daniela Necsulescu ◽  
Cosmin Cotrut ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Structural Changes ◽  
Heating Temperature ◽  
Galvanic Corrosion ◽  
Cooling Water ◽  
Open Circuit ◽  
Water Quenching ◽  
Heat Treated ◽  
Different Temperatures

Aluminium bronzes are exhibiting good corrosion resistance in saline environments combined with high mechanical properties. Their corrosion resistance is obviously confered by the alloy chemical composition, but it can also be improved by heat treatment structural changes. In the present paper, five Cu-Al-Fe-Mn bronze samples were subjected to annealing heat treatments with furnace cooling, water quenching and water quenching followed by tempering at three different temperatures: 200, 400 and 550�C. The heating temperature on annealing and quenching was 900�C. The structure of the heat treated samples was studied by optical and scanning electron microscopy. Subsequently, the five samples were submitted to corrosion tests. The best resistance to galvanic corrosion was showed by the quenched sample, but it can be said that all samples are characterized by close values of open-circuit potentials and corrosion potentials. Concerning the susceptibility to other types of corrosion (selective leaching, pitting, crevice corrosion), the best corrosion resistant structure consists of a solid solution, g2 and k compounds, corresponding to the quenched and 550�C tempered sample.

scholarly journals Corrosion Behaviour of 316L Stainless Steel in CNTs–Water Nanofluid: Effect of Temperature

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 119
Author(s):  
Dana H. Abdeen ◽  
Muataz A. Atieh ◽  
Belabbes Merzougui
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Corrosion Behaviour ◽  
Gum Arabic ◽  
Steel Sample ◽  
Open Circuit ◽  
Deionized Water ◽  
Effect Of Temperature ◽  
Different Temperatures ◽  
In Series

The inhibition behavior of carbon nanotubes (CNTs) and Gum Arabic (GA) on the corrosion of 316L stainless steel in CNTs–water nanofluid under the effect of different temperatures was investigated by electrochemical methods and surface analysis techniques. Thereby, 316L stainless steel samples were exposed to CNTs–water nanofluid under temperatures of 22, 40, 60 and 80 °C. Two concentrations of the CNTs (0.1 and 1.0 wt.% CNTs) were homogenously dispersed in deionized water using the surfactant GA and tested using three corrosion tests conducted in series: open circuit test, polarization resistance test, and potentiodynamic scans. These tests were also conducted on the same steel but in solutions of GA-deionized water only. Tests revealed that corrosion increases with temperature and concentration of the CNTs–water nanofluids, having the highest corrosion rate of 32.66 milli-mpy (milli-mil per year) for the 1.0 wt.% CNT nanofluid at 80 °C. In addition, SEM observations showed pits formation around areas of accumulated CNTs that added extra roughness to the steel sample. The activation energy analysis and optical surface observations have revealed that CNTs can desorb at higher temperatures, which makes the surface more vulnerable to corrosion attack.

scholarly journals Effects of laminating and co-firing conditions on the performance of anode-supported Ce0.8Sm0.201.9 film electrolyte

2011 ◽  
Vol 43 (3) ◽  
pp. 305-312 ◽  
Author(s):  
X. Li ◽  
J. Lu ◽  
H. Wang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Flexural Strength ◽  
Single Cell ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Maximum Power Density ◽  
Film Electrolyte ◽  
Different Temperatures

In order to evaluate the laminating and co-firing technique on the performance of anode-supported Ce0.8Sm0.2O1.9 (SDC) film electrolyte and its single cell, NiO-YSZ and NiOSDC anode-supported SDC film electrolytes were fabricated by laminating 24 sheets of anode plus one sheet of electrolyte and co-firing. La0.4Sr0.6Co0.2Fe0.8O3-? (LSCF)-SDC cathode was coated on the SDC electrolytes to form a single cell. The lamination was tried at different laminating temperatures and pressures and the co-firing was carried out at different temperatures. The results showed that the laminating temperature should above the glass transition temperature (Tg) of the binder. The laminating pressure of 70 MPa resulted in warp of the samples. The best co-firing temperature of the anode-supported SDC film electrolyte was 1400?C. The SDC film electrolyte formed well adherence to the anode. The NiO-YSZ anode had larger flexural strength than the NiO-SDC anode. The NiO-YSZ anode-supported SDC film electrolyte single cell had an open circuit voltage of 0.803 V and a maximum power density of 93.03 mW/cm2 with hydrogen as fuel at 800?C.

scholarly journals Electrochemical behavior of AgCu50 in alkaline media in the presence of chlorides and 2-mercaptobenzothiazole

2017 ◽  
Vol 53 (3) ◽  
pp. 349-356 ◽  
Author(s):  
V. Grekulovic ◽  
M. Rajcic-Vujasinovic ◽  
A. Mitovski
Keyword(s):  
Electrochemical Behavior ◽  
Electrode Surface ◽  
Anodic Polarization ◽  
Pure Copper ◽  
Inhibitory Effect ◽  
Open Circuit ◽  
Alkaline Media ◽  
Nacl Solution ◽  
Pure Silver ◽  
Current Densities

Electrochemical behavior of an alloy AgCu50, pure copper, and pure silver, respectively, was investigated by measuring the open circuit potentials using anodic potentiodynamic polarization and potentiostatic method in 0.1 moldm-3 NaOH + 0.02 moldm-3 NaCl solution, without and with adding 2-mercaptobenzothiazole in various concentrations (0.00001 - 0.001 moldm-3). Anodic polarization curves for AgCu50 alloy, showed four current peaks. Potentiostatic curves showed that values of the stationary current densities drop down with the increase of 2-mercaptobenzothiazole concentration in the electrolyte. The electrode surface was analyzed by optical microscopy after the potentiostatic oxidation. Micrographs confirmed that 2-mercaptobenzothiazole has got the inhibitory effect by forming the film of CuMBT and AgMBT which protect the electrode surface from corrosion.

scholarly journals Effect of Sterilization on the Properties of a Bioactive Hybrid Coating Containing Hydroxyapatite

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
E. K. K. Baldin ◽  
C. F. Malfatti ◽  
V. Rodói ◽  
R. N. Brandalise
Keyword(s):  
Electrochemical Behavior ◽  
Morphological Changes ◽  
Xrd Analysis ◽  
Dip Coating ◽  
Open Circuit ◽  
Hybrid Coating ◽  
Mechanical Resistance ◽  
X Ray Diffraction ◽  
Wear Performance ◽  
Different Temperatures

The objective of this study was to evaluate the influence of sterilization on a hybrid coating obtained from a sol composed of alkoxysilane tetraethoxysilane (TEOS) and organoalkoxysilane methyltriethoxysilane (MTES) containing 10% (mass) of hydroxyapatite particles. The coating was obtained by dip coating, by applying two layers (protective/bioactive), which were cured at different temperatures (450°C and 60°C). The effects of sterilization on the superficial, electrochemical, bioactive, and mechanical properties of the coating were evaluated by performing different sterilization processes, namely, steam autoclave, hydrogen peroxide plasma, and ethylene oxide. Subsequently, the coating was characterized by using scanning electron microscopy (SEM/FEG), and FTIR measurements were performed to characterize the chemical structure. The bioactivity and degradability of the coating were analyzed by mass variation after immersion in SBF and X-ray diffraction (XRD) analysis. The electrochemical behavior was assessed by open circuit potential (OCP) and potentiodynamic polarization curves and the mechanical behavior by wear resistance. Results showed that all sterilization processes caused significant morphological changes in the hybrid coating. The autoclaved sample presented the highest structural chemical changes, and, consequently, the highest degradability, even though it had a superior bioactive behavior in relation to the other samples. In addition, the sterilization processes influenced the electrochemical behavior of the hybrid coating and altered the mechanical resistance to abrasion, thus presenting lower wear performance in relation to the nonsterilized sample.

scholarly journals An External Energy Independent WO3/MoCl5 Nano-Sized Catalyst for the Superior Degradation of Crystal Violet and Rhodamine B Dye

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 642 ◽  
Author(s):  
Dongin Kim ◽  
Geonwoo Kim ◽  
Hyeonbin Bae ◽  
Eunwoo Kim ◽  
Byunghyun Moon ◽  
...  
Keyword(s):  
Crystal Violet ◽  
Rhodamine B ◽  
Degradation Product ◽  
Reaction Rate ◽  
Advanced Oxidation Process ◽  
Reaction Rate Constant ◽  
Thermal Method ◽  
External Energy ◽  
Superior Result ◽  
Reaction Rate Increase

In this study, the synthesis of a novel catalyst WO3/MoCl5 was carried out by the thermal method. The method gave an entirely different product compared to previous studies that doped Mo on the surface of semiconductor metal oxides. The degradation reaction of crystal violet (CV) and rhodamine B (RB) dye were done without any energy source. The results showed an incomparably superior result for degradation, with a reaction rate constant of 1.74 s−1 for 30 ppm CV, 1.08 s−1 for 30 ppm RB, and a higher value than 1 s−1 for both cases of 50 ppm dye solution. To the author’s knowledge, this catalyst has the highest reaction rate compared to other studies that targeted CV and RB, with an immense reaction rate increase of more than 100 times. Reusability of the three trials was verified, and the only process required was washing the catalyst after the reaction. One of the drawbacks of the advanced oxidation process (AOP), which has a degradation percent limit, has been solved, since 100% mineralization of the dye was available using this catalyst. FT-IR spectroscopy revealed that W-O-Mo linkage was successfully processed while Mo-Cl linkage has retained. 1H-NMR spectroscopy results confirmed that the degradation product of the dye treated by simple MoCl5 and WO3/MoCl5 was different. Deep inspection of specific regions of NMR fields gave necessary information about the degradation product using WO3/MoCl5.

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