Measurement of polarization effects in dual-phase ceria-based oxygen permeation membranes using Kelvin probe force microscopy

In this study, a dual phase composite (CSO-FC2O) consisting of 60 vol % Ce0.8Sm0.2O1.9 as oxygen-conductive phase and 40 vol % FeCo2O4 as electron-conductive phase was synthesized. TEM measurements showed a relatively pure dual-phase material with only minor amounts of a tertiary (Sm,Ce)(Fe,Co)O3 perovskite phase and isolated residues of a rock salt phase at the grain boundaries. The obtained material was used as a model to demonstrate that a combination of polarization relaxation measurements and Kelvin probe force microscopy (KPFM)-based mapping of the Volta potential before and after the end of polarization can be used to determine the chemical diffusion coefficient of the ceria component of the composite. The KPFM measurements were performed at room temperature and show diffusion coefficients in the range of 3 × 10−13 cm2·s−1, which is comparable to values measured for single-phase Gd-doped ceria thin films using the same method.

Focusing on the relationship between the precipitated phases and the pitting corrosion of ZL101A aluminum alloy

The pitting corrosion behavior of ZL101A aluminum alloy in simulated marine environment was investigated for guiding the composition design. The Volta potential of the precipitated phases was mainly characterized via the in-situ SKPFM technique. The obtained results indicated that the precipitated phases of ZL101A were composed of Al-Si phase, Si-Mg-Fe phase and Si-rich/Al-poor phase, accelerating the formation of corrosion pits during immersion test. Both Al-Si phase and Si-Mg-Fe phase accelerated the corrosion process through the self-dissolution and the galvanic effect, respectively, which can be contributed to the high corrosion sensitivity of the two phases. Si-rich/Al-poor phase presented high corrosion resistance, which should be related to the deficiency of impure elements such as Mg and Fe.

Using SKPFM to Determine the Influence of Deformation-Induced Dislocations on the Volta Potential of Copper

The variation rule of the Volta potential on deformed copper surfaces with the dislocation density is determined in this study by using electron back-scattered diffraction (EBSD) in conjunction with scanning Kelvin probe force microscopy (SKPFM). The results show that the Volta potential is not linear in the dislocation density. When the dislocation density increases due to the deformation of pure copper, the Volta potential tends to a physical limit. The Volta potential exhibits a fractional function relationship with the dislocation density only for a relatively low shape variable.

Zn-Co-CeO2 vs. Zn-Co Coatings: Effect of CeO2 Sol in the Enhancement of the Corrosion Performance of Electrodeposited Composite Coatings

Electrodeposition and characterization of novel ceria-doped Zn-Co composite coatings was the main goal of this research. Electrodeposited composite coatings were compared to pure Zn-Co coatings obtained under the same conditions. The effect of two ceria sources, powder and home-made sol, on the morphology and corrosion resistance of the composite coatings was determined. During the electrodeposition process the plating solution was successfully agitated in an ultrasound bath. The source of the particles was found to influence the stability and dispersity of plating solutions. The application of ceria sol resulted in an increase of the ceria content in the resulting coating and favored the refinement from cauliflower-like morphology (Zn-Co) to uniform and compact coral-like structure (Zn-Co-CeO2 sol). The corrosion resistance of the composite coatings was enhanced compared to bare Zn-Co as evidenced by electrochemical impedance spectroscopy and scanning Kelvin probe results. Zn-Co doped with ceria particles originating from ceria sol exhibited superior corrosion resistance compared to Zn-Co-CeO2 (powder) coatings. The self-healing rate of artificial defect was calculated based on measured Volta potential difference for which Zn-Co-CeO2 (sol) coatings exhibited a self-healing rate of 73.28% in a chloride-rich environment.

Effect of Temperature and Composition on Corrosion Behavior of Medium Cr Steel in Salt Solution Containing CO₂

In this paper, the corrosion behavior of three kinds of medium Cr low C steels in the simulated service environment of the transport pipeline was investigated through accelerated corrosion experiments, and the corrosion resistance mechanism of these experimental steels at different temperatures was investigated by electrochemical means. Finally, the reasons for the difference in corrosion behavior were analyzed from the grain boundary and surface Volta potential. The results show that as the temperature rised, the corrosion rate of 5Cr specimens increased sharply, the corrosion type developed from slight general corrosion to severe general corrosion; 7Cr specimen was less sensitive to temperature, and the type of corrosion changed from slight general corrosion to local corrosion; 9Cr specimen was not sensitive to temperature, and the type of corrosion was always local corrosion. 5Cr steel could form a protective product film at 30 °C. As the temperature rised, the protective ability of the product film decreased, and the matrix dissolved easily. The film of 7Cr and 9Cr samples had not yet precipitated and the matrix was difficult to dissolve at 30 °C. However the matrix dissolved easily at 50 °C, and the product film had formed, which played a major role. At 70 °C, the protective effect of the product film decreased, and the gap between the 7Cr and 9Cr samples began to appear. The increase of Cr content helped to refine grains and increased the proportion of low-angle grain boundaries. At the same time, the increase of Cr element helped to increase the maximum Volta potential of the experimental steel and increased the Volta potential difference. As a result the test steel was shown to be resistant to uniform corrosion, but it also increased the risk of pitting corrosion.