AES- und XPS-Untersuchungen zum Einflu? von Chrom, Nickel und Molybd?n auf das Korrosionsverhalten von rostfreien St?hlen in S?uren

Summary The alloys Fe17.8Cr, Fe16Cr2.4Mo and Fe18Cr14Ni2.5Mo (at%) were polarized in 0.5 mol/l H₂SO₄ or in 0.1 mol/l HC1 + 0.4 mol/l NaCl. The composition of the oxide layer and of the metallic layer beneath the oxide and the kinetics of the passive layer formation were determined by AES and XPS. In the active region, selective dissolution of Fe leads to an enrichment of Cr, Ni and Mo at the metal/electrolyte interface. In the passive region, the thickness of the rapidly formed passive layer is determined by the potential. The chromium content of the passive layer approaches a stationary, high value. The passive layer essentially consists of the anions O^2- and OH^– and of the cations of Cr, Fe, Mo, whereas Ni — and less pronounced Mo — are enriched below the layer.     

Cyclic voltammetric generation and electrochemical quartz crystal microbalance characterization of passive layer of nickel in a weakly acid medium

The electrochemical quartz crystal microbalance results show that nickel electrodissolution and nickel passivation occur simultaneously. Besides, the anodic transferred charge decreases and the passive layer thickness increases with the number of successive voltammetric cycles. Mass balances across the metal/passive layer/solution have been done from the instantaneous F(dm/dQ) function. A dynamic process for generation of an inner NiO and a Ni(OH)₂ outer passive layers is suggested.     

Pt–Ni alloy nanoparticles supported on multiwalled carbon nanotubes for methanol oxidation in alkaline media

The Pt–Ni alloy nanoparticles with different Pt/Ni atomic ratios supported on functionalized multiwalled carbon nanotubes surface were synthesized via an impregnation-reduction method. The nanocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. XRD demonstrated that Pt was alloyed with Ni. TEM showed that the Pt–Ni alloy nanoparticles were uniformly dispersed on the multiwalled carbon nanotubes (MWCNTs) surface, indicating appropriate amount of Ni in Pt–Ni alloy which facilitates the dispersion of nanoparticles on the MWCNT surface. XPS revealed that the Pt 4f peak in Pt–Ni/MWCNT (4:1) catalyst shifted to a lower binding energy compared with Pt/MWCNT catalyst, and nickel oxides/hydroxides such as NiO, Ni(OH)₂, and NiOOH were on the surface of Pt–Ni nanoparticles. Electrochemical data based on cyclic voltammetry and chronoamperometric curves indicated that Pt–Ni (4:1) alloy nanoparticles exhibited distinctly higher activity and better stability than those of Pt/MWCNTs toward methanol oxidation in alkaline media.     

EIS and XPS studies on passive film of AISI 304 stainless steel in dilute sulfuric acid solution

Electrochemical impedance spectroscopy and XPS studies on AISI 304 stainless steel in naturally aerated 0.5 M H₂SO₄ solution were carried out at room temperature. The valuable model of the metal/solution interphase was established, and the reliable equivalent electrical circuits in the solution were presented. The analysis of the chemical composition of passive film on AISI 304 stainless steel was carried out by XPS. The passive film of AISI 304 stainless steel is composed of oxyhydroxides, Fe₂O_3, FeO, Cr₂O₃, NiO, sulfate, sulfite, and sulfide (FeS, NiS). It is reported that the ferrous sulfide film formed on AISI 304 stainless steel in the dilute sulfuric acid solution. The possible process in which sulfuric acid is reduced to sulfite and sulfide is proposed. The galvanic interaction of sulfide inclusions with the base alloy is introduced. Copyright © 2011 John Wiley & Sons, Ltd.     

Interaction of water with clean and oxygen precovered nickel surfaces

The adsorption of water on a Ni(111) single crystal surface, clean as well as precovered with oxygen, has been investigated with thermal desorption spectroscopy (TDS) and measurements of the adsorption-desorption equilibrium combined with XPS (X-ray photoelectron spectroscopy). The measurements have been carried out with water pressures up to 10^–5 mbar on surfaces, which have been either clean or precovered with oxygen. On the clean Ni(111) surface the first adsorbate layer with a maximum coverage of 0.42 ML (monolayers) has a desorption energy of 52 kJ/mol and a preexponential factor of desorption of 10¹⁶s^–1. A second water layer adsorbs with the desorption energy of the ice multilayer but with first order kinetics. On Ni(111) precovered with chemisorbed oxygen an additional state of molecular, more strongly bound water is found, but no dissociation. For higher oxygen precoverages where NiO islands are formed on the surface, also the water dissociation product OH is found adsorbed. On a sample covered with a closed NiO layer, adsorbed OH and molecular water in an energetically not well-defined state are found. High doses of water on oxygen-precovered Ni(111) induce a slow surface modification leading to water dissociation.     

Effect of surface finishing on the formation of nanostructure and corrosion behavior of Ni–Ti alloy

In the present work, we have investigated the formation of nanostructured oxide layers by anodic oxidation on different surface finished (mirror finished, 600 and 400 grit polished) nickel–titanium alloy (Ni–Ti) in electrolyte solution containing ethylene glycol and NH₄F_. The anodized surface has been characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X‐ray photoelectron spectroscopy (XPS). The corrosion behaviors of the Ni–Ti substrate and anodized samples have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in simulated body fluid (Hanks' solution). The results show that the native oxide on the substrate is replaced by nanostructures through anodization process. XPS of Ni–Ti substrate shows the presence of Ni⁰, NiO, Ti⁰ and TiO₂ species, whereas Ni₂O₃ and Ni(OH)₂ and TiO₂ are observed in the samples after anodization. Corrosion resistance of the anodized sample is comparable with that of the untreated sample. Copyright © 2016 John Wiley & Sons, Ltd.     

NiO纳米片和多孔纳米片自组装的空心微球的无模板水热法制备与磁学性质

报道一种非常简单的制备NiO和Ni(OH)₂空心微球的无模板水热法, 即通过NiCl₂与氨水在140 ℃水热反应12 h, 制备了Ni(OH)₂纳米片自组装的空心微球, 经400 ℃热处理2 h得到了NiO空心微球. 采用X射线衍射仪、扫描电镜和透射电子显微镜对产物进行表征, 并在室温下测试了它的磁学性能, 结果表明, Ni(OH)₂空心微球的直径约为3～4 μm, 它是由尺寸1.1～1.3 μm左右的六方相结构的Ni(OH)₂纳米片组装而成; NiO空心微球是由立方相纳米片和多孔纳米片组装而成, 它具有弱的铁磁性, 其矫顽力为583 Oe, 剩余磁化强度为0.213 emu/g. 研究了氨在Ni(OH)₂纳米片的形成与组装过程中的作用, 提出了可能的生长机理.     

Characterization of non‐Cr‐based deoxidizers on Al alloy 7475‐T7651

The effects of three non‐chromate‐based deoxidizers, namely NaBrO₃/HNO₃, (NH₄)₄Ce(SO₄)₄/H₂SO₄ and Fe(III)/HF/HNO₃, on the Al alloy 7475‐T7651 were investigated. Several analytical methods were employed, including SEM, AES, transmission electron microscopy (TEM), electron energy‐loss spectroscopy (EELS) and glow discharge optical emission spectrometry (GDOES), to study the effects on the surface of this alloy after each treatment compared with the as‐received and alkaline‐cleaned alloy surfaces. The untreated alloy was found to have a thick oxide of 200–320 nm, consisting mainly of MgO. Alkaline cleaning results in an etching effect that thins the oxide and also deposits a thin silicate layer on the surface. In the case of the deoxidizers, there is significant removal of the native oxide of the alloy by the NaBrO₃/HNO₃ deoxidizer. There is also evidence of intermetallic attack on the alloy. The (NH₄)₄Ce(SO₄)₄/H₂SO₄ deoxidizer, which is a low‐etch‐rate deoxidizer, resulted in a slight thinning of the oxide. However, the effect was not significantly greater than with alkaline cleaning alone. The most effective deoxidizer in reducing the oxide thickness of the alloy is Fe(III)/HF/HNO₃, in which the etch rate was sufficiently high to remove completely the native oxide. In this case, equilibrium between oxide removal and the formation of new oxides on the alloy surface was achieved. Copyright © 2004 John Wiley & Sons, Ltd.     

Growth behaviour of cerium-based conversion coating on Zn-5%Al alloy

Cerium-based conversion coatings were deposited on a Zn-5%Al alloy by immersing the alloy in cerium nitrate aqueous solutions with various immersion times. The growth behaviour of the cerium-based conversion coating on the Zn-5%Al alloy was investigated by the electrochemical impedance spectroscopy (EIS), SEM, energy dispersive spectroscopy (EDS), and XPS techniques. The results reveal that the coating mainly consists of ZnO, Zn(OH)₂, Ce(OH)₄, Ce(OH)₃, CeO₂, and Ce₂O₃. The growth of the cerium-based conversion coating is accompanied by metal dissolution. The dissolution mainly occurs on the η-Zn surface of the phase boundary and continues to extend to the Zn-rich phase as the coating grows. EIS results show that with increasing immersion time, the corrosion resistance of the Ce conversion coating gradually increases in the early growth stage and then decreases when the cracks appear.     

State of Supported Nickel Nanoparticles during Catalysis in Aqueous Media

The state of Ni supported on HZSM‐5 zeolite, silica, and sulfonated carbon was studied during aqueous‐phase catalysis of phenol hydrodeoxygenation using in situ extended X‐ray absorption fine structure spectroscopy. On sulfonated carbon and HZSM‐5 supports, NiO and Ni(OH)₂ were readily reduced to Ni⁰ under reaction conditions (≈35 bar H₂ in aqueous phenol solutions containing up to 0.5 wt. % phosphoric acid at 473 K). In contrast, Ni supported on SiO₂ was not stable in a fully reduced Ni⁰ state. Water enables the formation of Ni^II phyllosilicate, which is more stable, that is, difficult to reduce, than either α‐Ni(OH)₂ or NiO. Leaching of Ni from the supports was not observed over a broad range of reaction conditions. Ni⁰ particles on HZSM‐5 were stable even in presence of 15 wt. % acetic acid at 473 K and 35 bar H₂.     

Studying the fine microstructure of the passive film on nanocrystalline 304 stainless steel by EIS,XPS, and AFM

The fine microstructure of the passive films on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SSs) in 0.5 M H₂SO₄ were investigated by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The results indicate that the passive film on both CC and NC SSs exhibits a two-layer microstructure consisting of a compact inner layer and a porous outer layer. Some hydrated compounds (HC) were present in the porous outer layer of NC SS but not CC SS in 0.5 M H₂SO₄ solution. The pores in the outer layer of the NC SS were observed to be in the nanoscale by AFM. HC filling of the pores in the passive film on NC SS may occur due to capillary forces endowed by the nanosize pores. XPS analysis of the passive films on both CC and NC SSs, however, does not show such a composition difference which is attributed to dehydration occurring in the XPS vacuum chamber. Both the inner and outer layers of the NC SS were determined by EIS analysis to be more compact and protective than the corresponding films on CC SS as evidenced by the lower Q value, higher n, and much higher R value in the corresponding layer.     

Nickel particles with increased catalytic activity towards hydrogen evolution reaction

Nickel particles are synthesized by a modified polyol method using 1 at. % of Pd as nucleation agent (Ni₉₉Pd₁) followed by an electrochemical sinusoidal wave treatment in 0.1 M Na₂SO₄ + 30 mM ascorbic acid. This treatment proved to significantly enhance the catalytic activity of Ni towards the hydrogen evolution reaction (her). After treatment, the current density of her increases almost four times and is accompanied by the onset potential shift to more positive values. From SEM, no visible changes in Ni particle size and shape were observed after treatment. XPS analysis of the surface of as-prepared Ni particles reveals that it contains Ni⁰, NiO, NiOOH and Ni(OH)₂, whereas after treatment Ni atoms exist mainly in the metallic form and as NiOOH. The increase in the activity of Ni particles after the treatment might be due to the higher amount of Ni⁰ at the surface.     

Effect of atomic-layer-deposited TiO2 on carbon-supported Ni catalysts for electrocatalytic glycerol oxidation in alkaline media

Thin TiO₂ layers were deposited onto a carbon-supported Ni catalyst (Ni/C) through atomic layer deposition (ALD) and the resulting TiO₂-coated Ni/C (ALD(TiO₂)-Ni/C) was utilized for electrochemical glycerol oxidation in alkaline media. X-ray photoelectron spectroscopy analysis demonstrated that the Ni surface phase of ALD(TiO₂)-Ni/C mainly consisted of Ni(OH)₂ while that of uncoated Ni/C was a mixed phase of NiO and Ni(OH)₂. The ALD(TiO₂)-Ni/C exhibited electrocatalytic activity at least 2.4 times higher than that of Ni/C. Density functional theory calculations were used to investigate how the modified Ni surface with the TiO₂ coating affects the adsorption/desorption of glycerol.     

Corrosion of Al85Ni9Ce6 amorphous alloy in the first hours of immersion in 3.5-wt% NaCl solution: The role of surface chemistry

AbstractThe surface chemistry and corrosion behavior of Al₈₅Ni₉Ce₆ melt-spun ribbons were studied after the first hours of immersion in 3.5-wt% NaCl solution at room temperature. X-ray photoelectron spectroscopy (XPS) was used to assess the chemical states of Al, Ce, Ni, and O. Electrochemical impedance spectroscopy was used to assess the corrosion resistance of the Al₈₅Ni₉Ce₆ ribbons. The alloy remained immersed for up to 48 hours. The results showed that hydroxide species in the passive film play a central role in the corrosion behavior of the Al₈₅Ni₉Ce₆ alloy.     

非晶Fe40Ni40P14B6合金阳极钝化膜的电子能谱研究

应用表面分析技术XPS和AES（包括深度分布）分析了非晶Fe40Ni40P14B6合金在H3BO3－Na2B4O7（pH＝9．20）缓冲溶液中不同钝化势或不同钝化时间形成的阳极钝化膜的元素化学状态、结构和化学组成，探讨了加入Ⅲ、Ⅴ族B、P对非晶FeNi基合金钝化成膜的影响，并给出了阳极钝性成膜的一种机制．     

Synthesis and Enhanced Photocatalytic Activity of a Hierarchical Porous Flowerlike p–n Junction NiO/TiO2 Photocatalyst

Hierarchical flowerlike β‐Ni(OH)₂ superstructures composed of intermeshed nanoflakes are synthesized by hydrothermal treatment with a mixed solution of C₂H₄(NH₂)₂, NaOH, and Ni(NO₃)₂. The as‐prepared β‐Ni(OH)₂ superstructures could be easily changed into NiO superstructures without great morphology change by calcination at 400 °C for 5 h. Furthermore, the TiO₂ nanoparticles can be homogeneously deposited on the surface of NiO superstructures by dispersing β‐Ni(OH)₂ powders in Ti(OC₄H₉)₄–C₂H₅OH mixed solution and then vaporizing to remove the ethanol at 100 °C, and finally calcination at 400 °C for 5 h. The prepared NiO/TiO₂ p–n junction superstructures show much higher photocatalytic activity for photocatalytic degradation of p‐chlorophenol aqueous solution than conventional TiO₂ powders and NiO superstructures prepared under the same experimental conditions. An obvious enhancement in the photocatalytic activity can be related to several factors, including formation of hierarchical porous structures, dispersion of TiO₂ particles on the surface of NiO superstructures, and production of a p–n junction. Further results show that NiO/TiO₂ composite superstructures can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and re‐used, compared with conventional powder photocatalysts. After many recycling experiments for the photodegradation of p‐chlorophenol, the NiO/TiO₂ composite sample does not exhibit any great activity loss, confirming that NiO/TiO₂ sample is stable and not photocorroded.     

非晶Fe40Ni40P14B6合金阳极钝化膜的电子能谱研究

应用表面分析技术ＸＰＳ和ＡＥＳ（包括深度分布）分析了非晶Ｆｅ４０Ｎｉ４０Ｐ１４Ｂ６合金在Ｈ３ＢＯ３－Ｎａ２Ｂ４Ｏ７（ＰＨ＝９．２０）缓冲溶液中不同钝化时间形成的阳极钝化膜的元素化学状态、结构和化学组成，探讨了加入Ⅲ、Ｖ族Ｂ、Ｐ对非晶ＦｅＮｉ基合金钝化金钝化成膜的影响，并给出了阳极钝性成膜的一种机制。     

介孔氧化镍的合成、表征和在电化学电容器中的应用

以十二烷基硫酸钠为模板剂, 采用尿素为沉淀剂, 用均匀沉淀法, 适当控制尿素的水解速度, 制备具有介孔结构的氢氧化镍胶体, 在不同温度下焙烧处理得到孔分布集中的氧化镍介孔分子筛. 结果表明, 在523 K下焙烧得到的氧化镍BET比表面达到477.7 m²•g^－1. 结构表征还显示, 介孔氧化镍的孔壁为多晶结构, 其孔结构形成机理应为准反胶束模板机理. 循环伏安法表明用NiO介孔分子筛制备的电极有很好的电容性能. 与浸渍法和阴极沉淀法制得的NiO相比, 这种介孔结构的NiO能够大量用来制作电化学电容器电极, 并且保持较高的比电容量和良好的电容性能.     

Oxidation behavior of NiAl alloy at low temperatures

Oxidation behavior of NiAl alloy at low temperatures was studied. A NiAl plate was oxidized by exposure to ambient atmosphere at room temperature, heated at 473 K in air, and heated at 773 K in air. The oxide formed on the NiAl surface was investigated by angle‐resolved X‐ray photoelectron spectroscopy (AR‐XPS). Chemical composition and atomic concentration in the oxide layer were analyzed with factor analysis of XPS spectra. Exposure of the NiAl plate to the ambient atmosphere resulted in the formation of an Al₂O₃ layer along with a small amount of NiO. Oxidation of the NiAl plate at 473 K in air formed a film of double‐layered oxide; the top layer consisted of NiAl₂O₄ and a small amount of NiO, and the second layer was Al₂O₃. Successive oxidation at 773 K only changed the oxide‐layer thickness without changing the structure. Formation of oxide observed in the present study corresponds to the thermodynamic prediction for the oxidation behavior of NiAl at 1373 K. Copyright © 2007 John Wiley & Sons, Ltd.     

The Inherent Electrochemistry of Nickel/Nickel‐Oxide Nanoparticles

The direct detection of nanoparticles is at the forefront of research owing to their environmental and toxicological applications. Herein, we studied the inherent electrochemistry of Ni and NiO nanoparticles and proposed a simple and direct electrochemical method for the determination of the concentrations of both nickel (Ni) and nickel oxide (NiO) nanoparticles in alkaline solution. A highly sensitive voltammetry technique was used to measure the oxidative signal of Ni(OH)₂ that formed spontaneously on the surface of Ni and NiO nanoparticles in alkaline media. Detection limits of 220 μg mL^?1 for Ni and 13 μg mL^?1 for NiO nanoparticles were obtained. Ni and NiO nanoparticles are used as electrode modifiers or as electrochemical signal labels in various biosensing applications. Therefore, methods to rapidly quantify the amount of Ni and NiO nanoparticles are of widespread potential use.