Jinshan Pan - Academia.edu (original) (raw)

Papers by Jinshan Pan

The reformation and characterization of the passive film formed on ultra-thin 316L after hydrogen... more The reformation and characterization of the passive film formed on ultra-thin 316L after hydrogen charging was investigated by combining EBSD, TMDS, XRD, Synchrotron-based XPS, and electrochemical experiments. The results show that ultra-thin foil reforms a passive film after 12 hours of hydrogen release in NaCl solution. The reformed passive film was half the thickness of the as-received passive film and was dominated by Cr oxides/hydroxides. The lattice extension caused by residual hydrogen accelerated Cr migration to form Cr2O3; while the diffusible hydrogen occupied the cation vacancies and resulted in high defect density for the reformed passive film within 12 hours.

The behavior of oxygen (O) atoms on the surface as well as the subsurface of (111), (001), and (1... more The behavior of oxygen (O) atoms on the surface as well as the subsurface of (111), (001), and (110) orientations of aluminum (Al) during initial-stage oxidation is studied by using density-functional theory (DFT), focusing on adsorption energy, work function, surface relaxation/reconstruction, surface complex formation with evolving structural parameters with increasing coverage of adsorbing O up to two-monolayer. The energetics of O adsorption indicate a favorable oxidation behavior with a large work function increase induced by O on Al(111) and (110). The structural as well as electron re-distribution analyses reveal that spontaneous O ingress into (110) leads to an “intercalating” oxidation mode, which may also result in a much faster surface oxidation process, whereas the oxidation on Al(111) and (001) proceeds similarly in a “layer-by-layer” mode with a slower oxidation rate. Moreover, different complexes of Al-O are formed depending on the availability of O towards Al on diff...

Journal of Alloys and Compounds, 2021

The surface chemistry and thickness of the native oxide, hydroxide, and modified sub-surface laye... more The surface chemistry and thickness of the native oxide, hydroxide, and modified sub-surface layer of three Ni superalloys (alloy 59, 625, and 718) were determined by synchrotron X-ray Photoelectron Spectroscopy (XPS) and X-ray Reflectivity (XRR). Taking advantage of the synchrotron radiation techniques, a procedure for normalizing the photoelectron intensity was employed, which allowed for accurate quantitative analysis revealing a total oxide thickness for all samples of 12-13 A, a hydroxide layer of 2-3 A, and a thickness of the sub-surface alloy layer of 20-35 A. The thickness results were compared to structural atomic models suggesting that the oxide thickness corresponds to four planes of metal cations in the oxide matrix. The XPS data revealed that the native oxides were enriched in Cr3+, Mo-(4,Mo-5,Mo-6)+, and Nb5+, while no Ni oxide was detected. The hydroxide layer mainly contained Ni2+ and Cr3+ hydroxide. The sub-surface layer was enriched in Ni and depleted in Cr, Fe, Mo, and Nb. The obtained oxide composition can be explained using thermodynamics, and it was found that the oxide composition correlates with the enthalpy of oxide formation for the metal elements in the alloys. Finally, the advantages of synchrotron radiation for composition and thickness determination are discussed

$Research paper thumbnail of Towards understanding hydrogen embrittlement of duplex atainless steel using operando high-energy X-ray diffraction and digital image correlation technique$

Corrosion Engineering Science and Technology, Feb 20, 2019

Colloids and Surfaces A: Physicochemical and Engineering Aspects, Aug 1, 2023

npj Materials Degradation

A finite element model is developed to study dynamics of atmospheric corrosion of carbon steel, f... more A finite element model is developed to study dynamics of atmospheric corrosion of carbon steel, focusing on the influence of thin electrolyte film thickness under varying corrosion product porosity. Calculations have been done to evaluate the impact of electrolyte film thickness and corrosion product porosity on oxygen diffusion path, and the hindrance effect of corrosion products on the metal surface activity. The time evolution of corrosion current density and controlling steps in the corrosion process are explored. When the corrosion products are loose, oxygen diffusion is the dominant controlling step, and the thicker the electrolyte film, the lower the corrosion rate. When they are dense, the corrosion process is controlled by the mixture of oxygen diffusion and the surface discharge. The oxygen diffusion path is determined only by the corrosion product porosity, and therefore the corrosion rate is not affected by the electrolyte film thickness.

Engineering of Biomaterials, 2010

In-situ AFM and Electrochemical AFM Investigation of Corrosion Protection of Solventborne Alkyd :... more In-situ AFM and Electrochemical AFM Investigation of Corrosion Protection of Solventborne Alkyd : Polyaniline Composite Coating for Carbon Steel

Journal of The Electrochemical Society, 2008

For patients suffering bradycardia, i.e., too slow heart rhythm, the common treatment is having a... more For patients suffering bradycardia, i.e., too slow heart rhythm, the common treatment is having a pacemaker implanted. The pacemaker system consists of the pacemaker and a pacing lead. The pacing lead is connected to the pacemaker and at the other end there is a stimulation electrode. The most common conductor material is a cobalt-based super alloy (MP35N® or 35N LT®), with the main constituents Ni, Co, Cr and Mo. The pacemaker electrode is often made of a substrate material with a rough surface coating. The substrate materials are predominantly platinum/iridium alloy and titanium. The material choice is of great importance for the performance and stability during long-term service. Excellent corrosion resistance is required to minimize elution of metal ions in the human body. In this thesis, the electrochemical behaviour and corrosion resistance of the Co-based alloys and Ta (as electrode substrate), in a phosphate buffer saline (PBS) solution with and without addition of H2O2, was investigated by means of potentiodynamic polarization, cyclic voltammetry, electrochemical impedance spectroscopy and simulated pacemaker pulsing. The metal release from the Co-based alloy during the passivation treatment and exposure in the synthetic biological media was measured by using inductive coupled plasma - atomic emission spectroscopy (ICP-AES). Moreover, surface composition was analyzed by using x-ray photoelectron spectroscopy. The results show that the chemical passivation of Co-based alloy 35N LT® increased the corrosion resistance and reduced Co release significantly, even in more hostile environment, i.e. PBS with addition of H2O2. The increased corrosion resistance is due to the Cr enrichment in the surface layer. The reduced Co release is due to a preferential dissolution of Co from the surface oxide layer during the chemical passivation. The electrochemical investigation of uncoated and rough TiN coated Ta show that uncoated Ta is not suitable electrode material due to formation of a highly resistive surface oxide film. Whereas the rough TiN coated Ta exhibits desirable electrochemical performance for pacemaker electrodes. The addition of H2O2 in the PBS has a large influence on the electrochemical behaviour of Ta, but the influence is small on the rough TiN coated Ta.

Meeting abstracts, 2007

not Available.