Effect of sulfide pollution on the stability of the protective film of benzotriazole on copper

Benzotriazole (BTAH) is an excellent inhibitor for the corrosion of copper and many of its alloys in unpolluted media. Protection is attributed to the formation of a film of Cu(I)BTA. Injection of sulfide ions into a benzotriazole inhibited salt water damages the protective Cu(I)BTA film very rapidly, increases the corrosion rate and leads to the formation of copper sulfide. This effect is quite marked at a sulfide concentration as low as 10⁻⁵ M (about 0.3 ppm sulfur) in the presence of 10⁻² M BTAH, which is 1000-fold greater than that of the sulfide ion. The intensity of sulfide attack increases with its concentration.Prolonged pre-passivation of copper in the BTAH protected medium even at high concentration does not markedly improve the resistance of the protective film to sulfide attack. This finding is contrary to a well-documented phenomenon in unpolluted media where the inhibiting efficiency of BTAH increases with the time of immersion and the concentration of the inhibitor. X-ray photoelectron spectroscopy (XPS) reveals the presence of both sulfide and BTAH on the corroded surface indicating that sulfide attack is localized.     

Adsorption and film growth of N-methylamino substituted triazoles on copper surfaces in hydrocarbon media

The adsorption of benzotriazole (BTA), tolyltriazole (TTA) and two different N-methylaminosubstituted triazoles on copper surfaces in hydrocarbon media has been examined by in situ ellipsometry and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). All four triazoles were found to form films and from the ellipsometric study were the film thicknesses estimated to be in the range of 0.5-2 nm after 1000 min exposure time. The layers formed from BTA and TTA were thicker (up to 2 nm) than the layers from N-aminomethyl substituted triazoles (roughly 0.5 nm). Desorption was studied qualitatively and 20% or less of the adsorbed material were found to desorb. The ToF-SIMS study showed that while BTA and TTA adsorbed intact did the N-aminomethyl substituted triazoles appear to loose their aminomethyl tails on binding since only signals corresponding to triazole moieties of the compounds were detected.     

New route to form micro-pores on 316L stainless steel surface

In order to seek an effective way for preventing restenosis after coronary stent implantation, a proposal of increasing the amount of loaded drug without changing the size of struts was given. Thereafter, a process of fabricating in-situ formed sub-micro-pores on 316L stainless steel (316L SS) was demonstrated. An aluminum thin film was deposited by magnetron sputtering on a 316L substrate. The aluminum film was then anodized in different acids (0.3 M oxalic and 10 vol.% sulfuric) by regulating direct current power supply. Through an appropriate chemical dissolution, the anodic alumina film was removed and the underlying porous 316L was obtained. The morphology of the porous 316L surface was examined by scanning electron microscope and the composition of the pores was investigated by energy dispersive X-ray analysis. The corrosion behavior of the porous 316L was evaluated by the polarization measurement. The results indicate that the shape and size of pores could be affected evidently by the acids used in anodization. The pores density is found to change with variation of the applied voltage in anodization. The corrosion current of the anodized specimens decrease and the corrosion voltage increase, compared with the untreated specimens.     

Influence of zinc ion implantation on surface nanomechanical performance and corrosion resistance of biomedical magnesium-calcium alloys

It is believed that magnesium and its alloys may find applications in biomedical fields as implants, bone fixation devices, and tissue engineering scaffolds. However, their corrosion rate must be controlled. In this study, biomedical magnesium-calcium (Mg-Ca) alloys were ion-implanted with zinc. The surface nanomechanical performance and corrosion behavior of the ion-implanted Mg-Ca alloys are determined. The results show that zinc ion implantation at a dose of 0.9 × 10¹⁷ ions/cm² significantly improves the surface hardness and modulus. However, the results on corrosion resistance reveal that zinc ion implantation degrades the corrosion behavior of Mg-Ca alloys. Thus, zinc is not a favorable element for the ion implantation treatment of biomedical Mg-Ca alloys.     

Electroless plating of silver on cenosphere particles and the investigation of its corrosion behavior in composite silicon rubber

In this paper, silver coating on the surface of cenosphere particles was prepared by electroless plating method. The adhesion, oxidation resistance and corrosion resistance properties of silver coating mixed in silicone rubber were investigated. The corrosion characteristic of silver coating was evaluated by anodic polarization curves of the silicone rubber composite in sulfuric acid solution. The results showed that the silver coating on the surface of cenosphere particles was smooth and uniform. The silver film was not oxidized and peeling off during preparation of composite silicone rubber. The adhesion between the cenosphere particle and silver film was good enough. The anodic polarization curves of the silicone rubber composite showed typical activation and passivation transformation. The values of corrosion potential, the initiating passive potential and maintaining passivity potential of composites filled with different contents of Ag-coated cenosphere particles were the same and related to the nature of silver coating. The passive current density of composite increased with increase of the amount of Ag-coated cenosphere particles and was inversely proportional to the resistance of silicone rubber composite. The better the conductivity of silicone rubber composite is, the higher corrosion rate will be.     

Electrochemical behavior and microstructural characterization of 1026 Ni-B coated steel

Ni-B coatings have been deposited on the surfaces of commercial steels (SAE-1026). The depositions were carried out using the electroless plating technique employing a nickel chloride solution with borane-dimethylamine as the reducing agent. These specimens were subsequently heat treated at different temperatures (300-500 °C) and different periods of time. The obtained coating thickness was in the order of approximately 1.5 μm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterize the structure and superficial morphology of the coatings. Phases like Ni, Ni₃B and Ni₄B₃ were observed through X-ray diffraction and confirmed by differential scanning calorimeter (DSC) studies. Some of the precipitated phases have been structurally characterized. The corrosion behavior of the coated surfaces was carried out by electrochemical impedance spectroscopy (EIS) using electrolytic sodium chlorine solutions with pH 2 and 7. The EIS results showed an active corrosion mechanism in acid solution while diffusion-reaction phenomena are predominant in neutral solution.     

Effect of NaAlO2 concentrations on microstructure and corrosion resistance of Al2O3/ZrO2 coatings formed on zirconium by micro-arc oxidation

In this study, Al₂O₃/ZrO₂ composite coatings were prepared on Zr substrates by micro-arc oxidation (MAO) in the NaAlO₂-containing electrolytes, and the effect of NaAlO₂ concentration on the microstructure, bond strength, microhardness and corrosion resistance of coatings was systematically investigated. The study reveals that the adequate NaAlO₂ in the electrolyte (>0.2 M) is essential to the formation of needle-like α-Al₂O₃ in the coatings, and the amount of α-Al₂O₃ rises with the increase of the NaAlO₂ concentration. m-ZrO₂ and t-ZrO₂ are present in all of the coatings, but their relative amount largely depends on the amount of Al₂O₃. It is also found that as the NaAlO₂ concentration increases from 0.2 to 0.3 M, the coating becomes denser and thicker, and its bond strength, maximum microhardness and corrosion resistance increases as well. The coating formed at 0.3 M NaAlO₂ demonstrates the highest bond strength of 52 MPa, the maximum microhardness of 1600 Hv_0.2N and the superior corrosion resistance. However, the overhigh concentration of NaAlO₂ (0.35 M) is found harmful to the coating's microstructure and properties.     

Structural characterization and properties of lanthanum film as chromate replacement for tinplate

Sulfide-stain resistance of La-passivated, unpassivated and Cr-passivated tinplate was measured using a cysteine tarnish test. Corrosion behavior of these tinplates was investigated using electrochemical impedance spectroscopy (EIS) measurement. The morphology, composition and thickness of lanthanum film were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence spectrometry (XRF), respectively. La-passivation treatment remarkably enhances sulfide-stain resistance of tinplate, and sulfide-stain resistance of La-passivated tinplate is slightly higher than that of Cr-passivated tinplate. La-passivation treatment also significantly improves corrosion protection property of tinplate. In contact with 3.5% NaCl solution, corrosion resistance of La-passivated tinplate is close to that of Cr-passivated tinplate, and in contact with 0.1 M citric-citrate buffer solution, corrosion resistance of La-passivated tinplate is higher than that of Cr-passivated tinplate. Lanthanum film is composed of spherical particles about 50-1000 nm in diameter, while most part of tinplate's surface is covered with the small particles about 50-200 nm. The film mainly consists of lanthanum and oxygen, which mainly exist as La₂O₃ and its hydrates such as La(OH)₃ and LaOOH. The amount of lanthanum in the film is about 0.0409 g/m².     

The influence of dew point during annealing on the power loss of electrical steel sheets

Decarburization is a necessary part of the processing of electrical steels if their carbon content is above a certain level. The process is usually carried out in a wet hydrogen–nitrogen atmosphere. Having a high dew point has a negative influence on the power loss, though. This is due to oxidation of the steel, which hinders domain wall motion near the surface. In this study, an increase of the power loss was only observed at a fairly high dew point (>20 °C). It was also only at these high dew points where a subsurface oxide layer was observed. The surfaces of samples with and without this layer were etched in steps. The magnetic properties of the etched samples corresponded well with the expected behavior based on GDOES profiles of the samples.     

Composition, structure and morphology of oxide layers formed on austenitic stainless steel by oxygen plasma immersion ion implantation

Oxygen ions were implanted in to austenitic stainless steel by plasma immersion ion implantation at 400 °C. The implanted samples were characterized by XPS, GIXRD, micro-Raman, AFM, optical and scanning electron microscopies. XPS studies showed the presence of Fe in elemental, as Fe²⁺ in oxide form and as Fe³⁺ in the form of oxyhydroxides in the substrate. Iron was present in the oxidation states of Fe²⁺ and Fe³⁺ in the implanted samples. Cr and Mn were present as Cr³⁺ and Mn²⁺, respectively, in both the substrate and implanted samples. Nickel remained unaffected by implantation. GIXRD and micro-Raman studies showed the oxide to be a mixture of spinel and corundum structures. Optical and AFM images showed an island structure on underlying oxide. This island structure was preserved at different thicknesses. Further, near the grain boundaries more oxide growth was found. This is explained on the basis of faster diffusion of oxygen in the grain boundary regions. Measurement of total hemispherical optical aborptance, α and emittance, ? of the implanted sample show that it has good solar selective properties.     

Epitaxy of m ‐plane ZnO on (112) LaAlO3 substrate

Heteroepitaxial growth of non‐polar m ‐plane (10 0) ZnO has been demonstrated on (112) LaAlO₃ single crystal substrates using the pulsed laser deposition method. X‐ray diffraction, reflection high energy electron diffraction, and cross‐sectional transmission electron microscopy with selected‐area diffraction, have been used to characterize the structural properties of deposited ZnO films. The epitaxial relationship between ZnO and LAO is shown to be (10 0)_ZnO ∥ (112)_LAO, (11 0)_ZnO ∥ ( 1)_LAO and [0001]_ZnO ∥ [ 10]_LAO. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of a Lennard-Jones fcc structure melting to the corresponding frozen liquid: Differences between the bulk and the surface

We computed a Lennard-Jones frozen liquid with a free surface using classical molecular dynamics. The structure factor curves on the free surface of this sample were calculated for different depths knowing that we have periodic boundary conditions on the other parts of the sample. The resulting structure factor curves show an horizontal shift of their first peak depending on how deep in the sample the curves are computed. We analyze our resulting curves in the light of spatial correlation functions during melting. The conclusion is that the differences between bulk and surface are quite small during melting and that at the end of melting, only the very surface happens to be less dense than the bulk. This result is intrinsic to the shape of the Lennard-Jones potential and does not depend on any other parameter.     

Selective vapor phase etching of SiGe by HCl in a RPCVD reactor

Chemical vapor phase etching of epitaxial SiGe by HCl was investigated using a single wafer reduced pressure CVD (RPCVD) system. For the sample preparation, patterning and dry etching were performed on the Si substrate with SiGe buried layers to open the sidewalls of the buried SiGe layers. The etchrate of the lateral direction was measured. The etchrate of SiGe is increasing with increasing SiGe thickness saturating at SiGe thicknesses higher than ∼25 nm. This result could be caused by diffusion effects of molecules in the narrow trenches during the etching. At the same SiGe thickness, the etchrate of SiGe is increasing with increasing etching temperature. B doping does not affect the etchrate of SiGe. P doping is increasing and C doping is decreasing the etchrate. Facet formation of the etchfront of Si and SiGe depends on initial surface orientation. These results enable improved process controllability of the etching process using doped layers for different applications.     

Comparative examination of the microstructure and high temperature oxidation performance of NiCrBSi flame sprayed and pack cementation coatings

Coatings formed from NiCrBSi powder were deposited by thermal spray and pack cementation processes on low carbon steel. The microstructure and morphology of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Flame sprayed coatings exhibited high porosity and were mechanically bonded to the substrate while pack cementation coatings were more compact and chemically bonded to the substrate. The microhardness and the high temperature oxidation resistance of the coated samples were evaluated by a Vickers microhardness tester and by thermogravimetric measurements (TG), respectively. Pack cementation coatings showed higher hardness and were more protective to high temperature environments than the flame sprayed coatings.     

Growth process and wear resistance for ceramic coatings formed on Al-Cu-Mg alloy by micro-arc oxidation

The growth process, distribution of chemical elements, phase constitutions and relative wear resistance of the ceramic coatings formed on Al-Cu-Mg alloy by ac micro-arc oxidation are investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDX), X-ray diffraction (XRD) and reciprocating friction and wear tests. The results indicate that there are three stages with the formation of the ceramic coatings: (1) the formation of ceramic particles, (2) sintering growth in sawtooth structure, (3) the increase of thickness by remolting and sintering. The ceramic coatings are made up of a mixture of α-alumina, γ-alumina and amorphous alumina, whose relative contents varied with the position in the ceramic coatings, respectively. The chemical elements altered in ceramic coatings produced in different electrolytes and varied along the depth in ceramic coatings obtained in phosphate electrolyte. Meanwhile, the results of friction and wear tests against Gr15 after 16 h indicate that the weight loss of ceramic coatings became almost unchanged.     

Relative roles of acetic acid, dodecyl sulfate and benzotriazole in chemical mechanical and electrochemical mechanical planarization of copper

The efficiency of chemical mechanical or electrochemical mechanical planarization (CMP or ECMP) carried out in the fabrication of integrated circuits is largely governed by the functional chemicals used in these processes. In this work, we study the individual and combined chemical and electrochemical effects of a selected set of such chemicals that can potentially support both CMP and ECMP of copper. These chemicals include acetic acid (HAc) as a complexing agent, H2O2 as an oxidizer, and ammonium dodecyl sulfate (ADS) as a dissolution inhibitor. Surface passivating effects of ADS under both CMP (open circuit) and ECMP (voltage activated) conditions are compared with those of a standard dissolution inhibitor for Cu, benzotriazole (BTAH), and the combined effects of a BTAH-ADS mixture also are explored. The experiments are performed in the absence of mechanical polishing using static and rotating Cu disc electrodes, and electro-dissolution of Cu for ECMP is activated using a voltage pulse modulation technique. A mechanism of surface reactions is proposed to describe the relative roles of HAc, H2O2, ADS and BTAH as electrolyte components for CMP and ECMP of Cu.     

Characterization and luminescent properties of SiO2:ZnS:Mn and ZnS:Mn nanophosphors synthesized by a sol-gel method

ZnS and SiO₂-ZnS nanophosphors, with or without different concentration of Mn²⁺ activator ions, were synthesized by using a sol-gel method. Dried gels were annealed at 600 °C for 2 h. Structure, morphology and particle sizes of the samples were determined by using X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The diffraction peaks associated with the zincblende and the wurtzite structures of ZnS were detected from as prepared ZnS powders and additional diffraction peaks associated with ZnO were detected from the annealed powders. The particle sizes of the ZnS powders were shown to increase from 3 to 50 nm when the powders were annealed at 600 °C. An UV-Vis spectrophotometer and a 325 nm He-Cd laser were used to investigate luminescent properties of the samples in air at room temperature. The bandgap of ZnS nanoparticles estimated from the UV-Vis data was 4.1 eV. Enhanced orange photoluminescence (PL) associated with ⁴T₁→⁶A₁ transitions of Mn²⁺ was observed from as prepared ZnS:Mn²⁺and SiO₂-ZnS:Mn²⁺ powders at 600 nm when the concentration of Mn²⁺ was varied from 2-20 mol%. This emission was suppressed when the powders were annealed at 600 °C resulting in two emission peaks at 450 and 560 nm, which can be ascribed to defects emission in SiO₂ and ZnO respectively. The mechanism of light emission from Mn²⁺, the effect of varying the concentration on the PL intensity, and the effect of annealing are discussed.     

Growth and real time corrosion resistance monitoring of lead decanoate coatings

Lead is very susceptible to corrosion in the presence of organic acids and humidity. A potential countermeasure is to apply a lead carboxylate coating by immersing the metal in a sodium carboxylate solution/suspension. In this work we report on the degree of surface coverage and the corrosion resistance of a lead decanoate Pb(C₁₀)₂ coating as a function of treatment time. Results show that the surface coverage reaches 91% after 15 min and about 100% after 1 h in a 0.05 M sodium decanoate solution. The corrosion resistance, as indicated by electrochemical impedance spectroscopy, continues to increase even after 6 h of immersion. In addition, we show that in the case of planar transport, a diffusion layer of 17 mm thickness exists, wherein the sodium decanoate concentration drops linearly from its bulk value to almost zero at the solid/surface interface.     

Microstructure evolution occurring in the modified surface of 316L stainless steel under high current pulsed electron beam treatment

High current pulsed electron beam (HCPEB) surface treatment of 316L stainless steel (SS) was carried out with a wide spectrum of treating parameters. Microstructure changes occurring in the modified surface were characterized with microscopy, X-ray diffractometry and electron backscatter diffractometry (EBSD) techniques. The evolution regularities of surface craters and microstructure refinement, as well as preferred orientation of (1 1 1) crystal planes were discussed on considering the coupled temperature-stress fields formed in surface layers after an absorption of HCPEB energy.     

Electrochemical and quantum chemical studies of some Schiff bases on the corrosion of steel in H2SO4 solution

The efficiency, as steel-corrosion inhibitors in 0.1 M and 1 M H₂SO₄, of two Schiff bases, 2-{[(4-methoxyphenyl)imino]methyl}phenol and 1-{[(4-methoxyphenyl)imino]methyl}-2-naphthol, (abbreviated SB-1 and SB-2, respectively) was investigated by Tafel extrapolation and linear polarization methods. Corrosion parameters and adsorption isotherms were determined from current-potential curves. It was found that the percent inhibition efficiencies (η%) and surface coverage (θ) increase with an increases in the concentrations of inhibitors. The results showed that these compounds act as good corrosion inhibitors especially at high concentrations. The adsorption of used compounds on the steel surface obeys Langmuir's isotherm. Obvious correlation was found between corrosion inhibition efficiency and quantum chemical parameters obtained by B3LYP/6-31g(d) method. The obtained theoretical results have been compared with the experimental findings.