On the Interface between Plasma Fluorocarbon Films and 316L Stainless Steel Substrates for Advanced Coated Stents

2011 ◽  
Vol 409 ◽  
pp. 117-122 ◽  
Author(s):  
Maxime Cloutier ◽  
Stéphane Turgeon ◽  
P. Chevallier ◽  
D. Mantovani
Keyword(s):  
Stainless Steel ◽  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Corrosion Behaviour ◽  
Drug Carrier ◽  
Native Oxide ◽  
Interfacial Region ◽  
Native Oxide Layer ◽  
Corrosion Performance ◽  
Stent Restenosis

As intravascular biomedical devices, metallic stents are particularly susceptible to corrosion induced by the physiological environment, causing the degradation of mechanical properties and leading to the release of toxic and carcinogenic ions from the SS316L bulk. Therefore, several works have been focused on the development of an ultra-thin fluorocarbon coating that could act both as a drug-carrier for in-stent restenosis and as an anti-corrosion barrier. However, the increase of the corrosion performance was limited by the inevitable permeability of the coating, which exposed some of the sensitive interfacial region to the corrosive environment. Indeed, in previous works, adhesion and growth rate of the film were promoted by the removal of the native oxide layer of the stainless steel which is inhomogeneous, brittle and mechanically unstable. Further refinements of the interface are therefore required in order to enhance the overall corrosion performance without compromising the fluorocarbon film properties and adhesion. Hence, the aim of this work was to enhance the corrosion behaviour of coated SS316L by the creation of a controlled interfacial oxide layer. The native oxide layer was first removed under vacuum and the bare metal surface was subjected to a plasma-reoxidation treatment. Tafel measurements were used to assess the corrosion rates of the specimens. Coated and uncoated modified interfaces were also characterized by X-Ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM).

Nano-Thick Amorphous Oxide Layer Produced by Plasma on Type 316L Stainless Steel for Improved Corrosion Resistance Under Plastic Deformation

CORROSION ◽  
10.5006/2674 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 1011-1022 ◽  
Author(s):  
Megan Mahrokh Dorri ◽  
Stéphane Turgeon ◽  
Maxime Cloutier ◽  
Pascale Chevallier ◽  
Diego Mantovani
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Oxide Layer ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Localized Corrosion ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Amorphous Oxide ◽  
Amorphous Oxide Layer

Localized corrosion constitutes a major concern in medical devices made of stainless steel. The conventional approach to circumvent such a problem is to convert the surface polycrystalline microstructure of the native oxide layer to an amorphous oxide layer, a few micrometers thick. This process cannot, however, be used for devices such as stents that undergo plastic deformation during their implantation, especially those used in vascular surgery for the treatment of cardiac, neurological, and peripheral vessels. This work explores the feasibility of producing a nano-thick plastic-deformation resistant amorphous oxide layer by plasma-based surface modifications. By varying the plasma process parameters, oxide layers with different features were produced and their properties were investigated before and after clinically-relevant plastic deformation. These properties and the related corrosion mechanisms were mainly evaluated using the electrochemical methods of open-circuit potential, cyclic potentiodynamic polarization, and electrochemical impedance spectroscopy. Results showed that, under optimal conditions, the resistance to corrosion and to the permeation of ions in a phosphate buffered saline, even after deformation, was significantly enhanced.

scholarly journals Эволюция физико-химических свойств поверхности GaSb(100) в растворах сульфида аммония

2019 ◽  
Vol 53 (7) ◽  
pp. 908
Author(s):  
М.В. Лебедев ◽  
Т.В. Львова ◽  
А.Л. Шахмин ◽  
О.В. Рахимова ◽  
П.А. Дементьев ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Treatment Time ◽  
Solution Concentration ◽  
Native Oxide ◽  
Semiconductor Surface ◽  
Native Oxide Layer ◽  
Force Microscopy ◽  
Fermi Level Pinning ◽  
Ammonium Sulfide

AbstractVarious conditions of passivation of the GaSb(100) surface by ammonium sulfide ((NH_4)_2S) solutions depending on the solution concentration, solvent, and treatment time are investigated by X-ray photoelectron spectroscopy and atomic-force microscopy. It is shown that treatment of the GaSb(100) surface by any (NH_4)_2S solution leads to removal of the native oxide layer from the semiconductor surface and the formation of a passivating layer consisting of various gallium and antimony sulfides and oxides. The surface with the lowest roughness (RMS = 0.85 nm) is formed after semiconductor treatment with 4% aqueous ammonium sulfide solution for 30 min. Herewith, the atomic concentration ratio Ga/Sb at the surface is ~2. It is also found that aqueous ammonium sulfide solutions do not react with elemental antimony incorporated into the native-oxide layer. The latter causes a leakage current and Fermi-level pinning at the GaSb(100) surface. However, a 4% (NH_4)_2S solution in isopropanol removes elemental antimony almost completely; herewith, the semiconductor surface remains stoichiometric if a treatment duration is up to 13 min.

Nano-Scale Native Oxide on 6H-SiC Surface and its Effect on the Ni/Native Oxide/SiC Interface Band Bending

2014 ◽  
Vol 778-780 ◽  
pp. 566-570 ◽  
Author(s):  
Wei Huang ◽  
Xi Liu ◽  
Xue Chao Liu ◽  
Tian Yu Zhou ◽  
Shi Yi Zhuo ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Interface Energy ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Band Bending ◽  
X Ray ◽  
Vacuum Chambers ◽  
Transmission Electron ◽  
Electron Transport Properties

Native oxide layer with thickness of about 1 nm was found easy to form on 6H-SiC surface during transporting from cleaning process to vacuum chambers, which was examined by x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The interface band bending was studied by synchrotron radiation photoelectron spectroscopy (SRPES). For the native-oxide/SiC surface, after Ni deposition, the binding energy of Si 2p red-shifted about 0.34 eV, which suggested the upward bending of the interface energy band. Therefore, the native oxide layer should be considered on the study of SiC devices because it may affect the electron transport properties significantly.

scholarly journals Composition and band structure of the native oxide nanolayer on the ion beam treated surface of the GaAs wafer

2018 ◽  
Vol 52 (5) ◽  
pp. 506
Author(s):  
V.M. Mikoushkin ◽  
V.V. Bryzgalov ◽  
S.Yu. Nikonov ◽  
A.P. Solonitsyna ◽  
D.E. Marchenko
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Ion Beam ◽  
Native Oxide ◽  
Chemical Compositions ◽  
Native Oxide Layer ◽  
Band Diagram ◽  
Clean Surface ◽  
Gaas Wafer ◽  
Dielectric Layers

AbstractDetailed information on GaAs oxide properties is important for solving the problem of passivating and dielectric layers in the GaAs-based electronics. The elemental and chemical compositions of the native oxide layer grown on the atomically clean surface of an n -GaAs (100) wafer etched by Ar^+ ions have been studied by synchrotron-based photoelectron spectroscopy. It has been revealed that the oxide layer is essentially enriched in the Ga_2O_3 phase which is known to be a quite good dielectric as compared to As_2O_3. The gallium to arsenic ratio reaches the value as high as [Ga]/[As] = 1.5 in the course of oxidation. The Ga-enrichment occurs supposedly due to diffusion away of As released in preferential oxidation of Ga atoms. A band diagram was constructed for the native oxide nanolayer on the n -GaAs wafer. It has been shown that this natural nanostructure has features of a p–n heterojunction.

scholarly journals Magnetic and Structural Characterization of Mechanically Alloyed Fe50co50 Samples

2012 ◽  
Vol 15 ◽  
pp. 41-47
Author(s):  
Germán A. Pérez Alcázar ◽  
Ligia Edith Zamora ◽  
José Francisco Marco ◽  
Juan José Romero ◽  
Jesús María González ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Field Distribution ◽  
Photoelectron Spectroscopy ◽  
Hyperfine Magnetic Field ◽  
Complete Removal ◽  
Milling Process ◽  
Native Oxide ◽  
Nominal Composition ◽  
Native Oxide Layer ◽  
X Ray

Samples of nominal composition Fe50Co50 were produced by mechanical alloying byusing a planetary ball mill and different milling times. The samples were studied via X-raydiffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy to characterize thephase distribution resulting from the milling process. The Mössbauer data indicated that Co startsdiffusing into Fe after 8 h of milling. Between t = 8h and t = 24 h the sample has a heterogeneouscomposition, presenting a bimodal hyperfine field distribution with maxima centred at 34.3 T and35.8 - 36.4 T, compatible with the presence of different Fe environments (richer in Co and richerin Fe, respectively). After 48 h of milling, the sample presents a more homogeneous compositionshowing an almost symmetric hyperfine magnetic field distribution centred at H=34.9 T,indicating that a disordered equiatomic FeCo solid solution has already been formed. The X-rayphotoelectron spectroscopy data indicate that the native oxide layer formed on the freshly milledsamples contains Co2+, Fe2+ and Fe3+ oxides. After complete removal of this native oxide layer byAr ion bombardment, X-ray photoelectron spectroscopy analysis yields the composition of thenominal equiatomic Fe50Co50 alloy.

Alloy Compositional Gradation in Surface Layer and Oxidation Resistance on Chemical Synthesized FeCo Nanoparticles

2009 ◽  
Vol 631-632 ◽  
pp. 507-512 ◽  
Author(s):  
G.B. Chon ◽  
D. Kodama ◽  
Kozo Shinoda ◽  
Shigeru Suzuki ◽  
Balachamdran Jeyadevan
Keyword(s):  
Oxide Layer ◽  
Oxidation Resistance ◽  
Photoelectron Spectroscopy ◽  
Surface Composition ◽  
Particle Surface ◽  
Atmospheric Environment ◽  
Atomic Diffusion ◽  
Native Oxide ◽  
Alloy Nanoparticles ◽  
Native Oxide Layer

X-ray photoelectron spectroscopy (XPS) has been used for analyzing the surface composition of polyol process-derived Fe30Co70, Fe50Co50, and Fe70Co30 alloy nanoparticles with diameters 50, 100 and 150 nm, respectively. These Fe-Co alloy particles have high oxidation resistance in the atmospheric environment even though their particle size is so small. The XPS results revealed that the concentration of iron at the surface of the as-synthesized Fe-Co alloy nanoparticles was lower than that in bulk and increased with increasing bulk cobalt composition, although the surface of nanoparticles was covered with native oxide layer formed during their exposure to atmosphere. This low concentration of iron and very thin oxide layer at the surface are considered to protect the particle from oxidation. The concentration of iron at the surface of Fe70Co30 nanoparticles increased when they were annealed at 573 K in N2 and H2 atmosphere. The results indicate that nonuniformity of the chemical composition between particle surface and core occurs during the formation of the same in polyol, and atomic diffusion at the surface of particle can occur even at relatively low temperature. The above is considered to arise from the difference in the chemical characteristics of iron and cobalt during co-precipitation in the polyol.

Wettability in pressure infiltration of SiC and oxidized SiC particle compacts by molten Al and Al-12wt%Si alloy

2007 ◽  
Vol 22 (8) ◽  
pp. 2273-2278 ◽  
Author(s):  
J.M. Molina ◽  
J. Tian ◽  
C. Garcia-Cordovilla ◽  
E. Louis ◽  
J. Narciso
Keyword(s):  
Contact Angle ◽  
Oxide Layer ◽  
Low Temperatures ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Threshold Pressure ◽  
Pressure Infiltration ◽  
Surface Conditions ◽  
Infiltration Behavior ◽  
Sic Particle

The infiltration behavior of compacts of SiC particles in two surface conditions, as-received and thermally oxidized, was investigated by using pure Al and Al-12wt%Si as infiltrating metals. Analysis of the threshold pressure for infiltration revealed that the process is governed by the same contact angle for all different systems, no matter the metal or particle condition. This leads to the conclusion that oxidation does not modify the wetting characteristics of the particles, most probably because they are already covered by a thin native oxide layer that remains unaltered in processing routes involving short contact times and low temperatures, such as actual conditions of pressure infiltration at 700 °C.

The Effect of Surface States on Secondary Electron (SE) Dopant Contrast from Silicon p-n Junctions

2007 ◽  
Vol 1026 ◽  
Author(s):  
Augustus K. W. Chee ◽  
Conny Rodenburg ◽  
Colin John Humphreys
Keyword(s):  
Oxide Layer ◽  
Computer Modelling ◽  
Surface States ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Element Analysis ◽  
Surface Band ◽  
Band Bending ◽  
Wide Range ◽  
Se Doping

AbstractDetailed computer modelling using finite-element analysis was performed for Si p-n junctions to investigate the effects of surface states and doping concentrations on surface band-bending, surface junction potentials and external patch fields. The density of surface states was determined for our Si specimens with a native oxide layer. Our calculations show that for a typical density of surface states for a Si specimen with a native oxide layer, the effects of external patch fields are negligible and the SE doping contrast is due to the built-in voltage across the p-n junction modified by surface band-bending. There is a good agreement between the experimental doping contrast and the calculated junction potential just below the surface, taking into account surface states, for a wide range of doping concentrations.

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