| 1. |
- Chen, Dihao, et al.
(author)
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Correlation between pitting susceptibility and surface acidity, point of zero charge of passive film on aluminum: Influence of alloying elements
- 2024
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In: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 227
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Journal article (peer-reviewed)abstract
- The pitting potential, intrinsic surface acidity, point of zero charge of passive film on Al are studied using first-principles calculations to establish their relationships. Influences of alloying elements Zn, Cr, Nb, Si, Mo and Sc on adsorption of NH3 and NaCl, pHpzc of Al2O3 and pitting susceptibility of Al are investigated. The efficiency for enhancing pitting resistance of Al is evaluated, yielding the ratios Si: Zn: Cr: Mo: Nb: Sc = 1.8: − 0.3: 1: 1.9: 1.4: 0.2. A model for the dependence of pitting potential on the concentration of alloying elements in Al alloy matrix is developed, based on effects of alloying elements on the surface charge of passive film. The effects of Sc on pitting potential and pHpzc of Al oxide are predicted based on the calculated results, which are supported by electrochemical measurement, XPS analysis and contact angle titration.
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| 2. |
- Chen, Dihao, et al.
(author)
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Development of the General Methodology for Determining the Point of Zero Charge of Oxide Films by Contact Angle Titration
- 2023
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In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
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Journal article (peer-reviewed)abstract
- The point of zero charge (pH(pzc)) is one of the most important properties in determining the nature of the surface charge on oxide films in contact with aqueous solutions. Contact angle titration is a simple, rapid and direct surface titration approach to determine the pH(pzc) of oxide films, compared with mass titration, potentiometric titration and batch equilibration method. Although contact angle titration has been an effective method to estimate the pH(pzc) in the past, there are some limitations in previous methodologies for the correlation between the contact angle and the surface charge density, due to the consideration of only the negative charged OH- at surface or the absence of a vital part of solution potential for the electrochemical potential of H+ in electrolyte. Based on the work of many previous contributors, two general thermodynamic methods for determining the pHpzc of oxide films by contact angle titration are developed here. The methods provide precise, fundamental understandings of the variation of the contact angle with surface charge density, which is of great significance for interfacial science.
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| 3. |
- Yue, Xiaoqi, et al.
(author)
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In depth analysis of the passive film on martensitic tool alloy: Effect of tempering temperature
- 2024
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In: Corrosion Science. - : Elsevier. - 0010-938X .- 1879-0496. ; 234
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Journal article (peer-reviewed)abstract
- Effect of tempering temperature on the composition of the passive film of a martensitic tool alloy was studied by synchrotron-based hard/soft X-ray photoelectron spectroscopy and electrochemical analyses. The contents of Cr and Mo in the passive film are affected by precipitation of tempering carbides. Increase of tempering temperature from 200 to 525°C leads to enhanced formation of Cr/Mo-rich tempering carbides and Cr depletion. Tempering at 525°C results in a Cr content < 11 at% in the underlying metallic layer and formation of a Cr-deficient defective passive film, and thus loss of passivity for the tool alloy in corrosive conditions.
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| 4. |
- Yue, Xiaoqi, et al.
(author)
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Unveiling nano-scale chemical inhomogeneity in surface oxide films formed on V- and N-containing martensite stainless steel by synchrotron X-ray photoelectron emission spectroscopy/microscopy and microscopic X-ray absorption spectroscopy
- 2025
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In: Journal of Materials Science & Technology. - : Chinese Society of Metals. - 1005-0302. ; 205, s. 191-203
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Journal article (peer-reviewed)abstract
- Nano-scale chemical inhomogeneity in surface oxide films formed on a V- and N-containing martensite stainless steel and tempering heating induced changes are investigated by a combination of synchrotron- based hard X-ray Photoelectron emission spectroscopy (HAXPES) and microscopy (HAXPEEM) as well as microscopic X-ray absorption spectroscopy (μ-XAS) techniques. The results reveal the inhomogeneity in the oxide films on the micron-sized Cr2N- and VN-type particles, while the inhomogeneity on the martensite matrix phase exists due to localised formation of nano-sized tempering nitride particles at 600 °C. The oxide film formed on Cr2N-type particles is rich in Cr2O3 compared with that on the martensite matrix and VN-type particles. With the increase of tempering temperature, Cr2O3 formation is faster for the oxidation of Cr in the martensite matrix than the oxidation of Cr nitride-rich particles.
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