Search results for "passiv"
showing 10 items of 512 documents
Investigation of the kinetics of growth of anodic oxide films on niobium by galvanostatic and tensiodynamic experiments
1990
Abstract The kinetics of growth of anodic oxide films on niobium has been investigated by interferometric methods. Tensiodynamic experiments allow the growth of the films at constant rate. Photoeffects during the growth of the films under absorbed light give additional information on the growth process.
Two birds with one stone: dual grain-boundary and interface passivation enables >22% efficient inverted methylammonium-free perovskite solar cells
2021
Advancing inverted (p���i���n) perovskite solar cells (PSCs) is key to further enhance the power conversion efficiency (PCE) and stability of flexible and perovskite-based tandem photovoltaics. Yet, the presence of defects at grain boundaries and in particular interfacial recombination at the perovskite/electron transporting layer interface induce severe non-radiative recombination losses, limiting the open-circuit voltage (VOC) and fill factor (FF) of PSCs in this architecture. In this work, we introduce a dual passivation strategy using the long chain alkylammonium salt phenethylammonium chloride (PEACl) both as an additive and for surface treatment to simultaneously passivate the grain b…
Repassivation of the damage generated by cavitation on UNS N08031 in a LiBr solution by means of electrochemical techniques and Confocal Laser Scanni…
2010
Abstract The objective of this work is to study the influence of cavitation on the corrosion behaviour of Alloy 31, a highly-alloyed austenitic stainless steel (UNS N08031), in a LiBr heavy brine solution (992 g/L) at 25 °C. The presence of cavitation shifted the OCP value towards the active direction by 708 mVAg/AgCl, increased anodic current densities and passivation current density, ip, and reduced the pitting potential, Ep. Repassivation behaviour of Alloy 31 has been investigated by using potentiostatic tests at different potentials. The current density transient obtained after interrupting cavitation was used to obtain the repassivation index, n, provided by the slope of the log i(t) …
Monolayer black phosphorus by sequential wetchemical surface oxidation
2018
We report a straightforward chemical methodology for controlling the thickness of black phosphorus flakes down to the monolayer limit by layer-by-layer oxidation and thinning, using water as solubilizing agent.
Influence of sulphite on the passivation of iron
1991
Abstract Mossbauer spectroscopy and electrochemical measurements were used to study the passivation of iron and steels in a sulphite containing solution. The potentiodynamic curves show that passivation occurs at −140 mV potential vs saturated calomel electrode ( sce ). The main phase of the passive layer was found to be γ-FeOOH, while FeSO 4 ·H 2 O on the surface and FeSO 3 ·3H 2 O inside the layer were identified as minor phases in the case of polarization in a solution of pH 3.37. Only γ-FeOOH was observed on the surface of samples polarized at pH 6.6.
Study of Passive Films Formed on AISI 316L Stainless Steel in Non-Polluted and Underwater-Volcano-Polluted Seawater
2014
This work studies the semiconducting behavior of passive films formed on AISI 316L (UNS S31603) in two different sea-water solutions, non-polluted and polluted, collected from the volcano of El Hierro Island. Polarization measurements, potentiostatic passivation tests, electrochemical impedance spectroscopy, and capacitance measurements were performed. Results show that the polluted seawater worsens passivation kinetics. Additionally, passive films formed on AISI 316L stainless steel in polluted seawater have been found to be less protective than those formed in non-polluted seawater, showing a more defective structure, owing to the acidity of the polluted medium.
Investigation of pitting resistance of titanium based on a modified point defect model
2011
Abstract The pitting resistance of titanium was studied under potential control in solutions containing chloride ions. The results evidenced that Cl − concentration had an effect on the metastable pitting intensity, but no significant influence on the uniform corrosion. XPS characterization revealed that some Cl − ions were present in the outer hydroxide layer, but few in the inner oxide layer, indicating that the inner oxide layer was impervious to Cl − ions. A cation–anion-vacancy condensation mechanism was considered for pit initiation based on the point defect model (PDM). The experimental results analyzed by the charge integration technique were in agreement with the derived relations.
Evaluation of metastable pitting on titanium by charge integration of current transients
2010
Abstract The metastable pitting of titanium has been studied under potentiostatic control in solutions containing chloride ions. An approach based on the charge integration of current transients was proposed for a quantitative determination of metastable pitting. A pit density (dmpit) was defined as the number of metastable pits per unit area per unit time (cm−2 h−1) with a typical size, instead of a size distribution. The calculated dmpit of titanium at 0.5 VSCE in 0.6 M NaCl was about 1.0 × 103 cm−2 h−1 with a typical radius of 0.12 μm. An exponential potential dependence of dmpit was obtained through the integration approach.
Electrochemical impedance spectroscopy for studying passive layers on steel rebars immersed in alkaline solutions simulating concrete pores
2007
Present paper deals with the use of the electrochemical impedance spectroscopy to identify different processes in the passive layer growth over steel rebar surface immersed in an alkaline media simulating the concrete pore solution. Two cases have been considered: a passive layer spontaneously grown in a high alkaline media and a passive layer assisted by the application of an anodic potential in the same media. The application of electric equivalent circuits allows distinguishing between the different mechanisms occurring in this passive layer when grows in different conditions. An electric equivalent circuit with two RC loops connected in parallel is often used for fitting the EIS diagram…
Electrochemically-induced TiO2 incorporation for enhancing corrosion and tribocorrosion resistance of PEO coating on 7075 Al alloy
2018
Abstract 7075 Al alloy was PEO-treated in a silicate based electrolyte containing 3 g l-1 potassium titanyl oxalate using unipolar and bipolar pulsed current waveforms. The coating formed by the bipolar waveform with the wider cathodic pulses showed volcano-like surface morphology with no evidence of large pores at the metal/coating interface. It revealed the highest corrosion performance due to the synergistic effect of TiO2 incorporation and structural/morphological features along with a better passivation behavior indicating no pitting susceptibility. For this coating, the tribocorrosion tests showed no potential drop during sliding under 1 N with the lowest volume loss of 0.022 mm3.