Quantitative determination of the composition of nitrided layers on iron using AES

Within the framework of the study of industrial nitriding of steel, AES was chosen as the principle analysis technique. In order to characterise the nitrided layers quantitatively, reliable sensitivity factors were needed. For that purpose, different reference samples containing the pure γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases were prepared by gaseous nitriding of pure iron. The characterisation of these references by means of electron probe microanalysis (EPMA) is discussed. The first sample contained a nitrided layer with large γ′‐Fe₄N_1?x grains (～30 µm) with 19.6 at.% nitrogen on top of an iron substrate. The second one contained an ε‐Fe₂N_1?z outer layer (～6 µm) with 26 at.% nitrogen, on a γ′‐Fe₄N_1?x layer (～4 µm) with 19.8 at.% nitrogen, created on top of an iron substrate. In this study, Fe LMM and N KLL Auger electron spectral lines were acquired on the pure γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases of these two reference samples in order to calculate the sensitivity factors of iron and nitrogen. Different Auger intensities were considered and compared. It was decided to use the peak areas of the direct Auger electron spectral lines. The values of the sensitivity factors are 0.74 for iron and 0.33 for nitrogen. Finally, a set of three independent and well‐characterised samples containing the γ′‐Fe₄N_1?x and ε‐Fe₂N_1?z phases was used to validate the elaborated quantification procedure. Copyright © 2007 John Wiley & Sons, Ltd.     

Recent progress in quantitative and high spatial resolution AES

Progress in high resolution Auger electron spectroscopy (HR-AES or scanning Auger microscopy, SAM) during the past few years is characterized by the use of efficient field emission electron sources, parallel detection capabilities and improved data acquisition, storage and processing, thus enhancing spatial resolution (to about 10 nm), signal to noise figure and quantification of elements in different chemical bonding states, e.g. by routinely using factor analysis. Optimized ion sputtering facilities, particularly sample rotation, enable depth profiling with high, depth independent resolution. The basic features of SAM are discussed with respect to EPMA (electron probe micro-analysis), emphasizing fundamental limitations and future developments.     

Post‐oxidizing effects on surface characteristics of salt bath nitrocarburized AISI 02 tool steel type

The effect of post‐oxidizing treatment on the characteristics of modified surface layers produced by salt bath nitrocarburizing on the industrial American Iron and Steel Institute (AISI) 02 tool steel types is investigated. Nitrocarburizing treatment is performed for 6 h and 8 h at 570 °C and post‐oxidizing treatment for 30, 60 and 90 min at 520 °C, using argon–steam mixture. Formed layers are characterized by their basic properties such as thickness layer, depth, surface hardness and wear resistance. Detailed estimation of the modified metal surface quality, in terms of chemical composition, formed phases, microstructures and diffusion mechanisms are performed by metallographic techniques, EDX, X‐ray diffraction, scanning electron microscopy (SEM) and glow discharge optical electron spectroscopy (GDOES). The corrosion resistance was investigated in 0.4 M H₂SO₄ solutions, using steady‐state electrochemical polarization methods. The obtained results revealed the existence of a superficial oxide layer which consists of magnetite (Fe₃O₄) and hematite (Fe₂O₃) and the presence of an ε‐phase associated with a small amount of γ′‐phase. Important improvements in wear, microhardness and corrosion resistance occur after these treatments and it is specifically concluded that the sole application of a nitrocarburizing treatment does not significantly ameliorate the corrosion resistance of the as‐received steel. In fact, post‐oxidation treatment contributes to increase corrosion resistance by forming a dense magnetite layer and at the same time, it partially covers the compound layer pores. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of a laser‐nitrided titanium alloy by electron backscattered diffraction and electron probe microanalysis

After a laser gas nitriding treatment of the Ti‐7.5Al (atom %) titanium‐based alloy, we used a combination of electron backscattered diffraction (EBSD) in scanning electron microscope and electron probe microanalysis (EPMA) techniques in order to efficiently characterize the different phases in the resolidified layer. Representative measurements of chemical composition and reliable determination of crystal structure were possible for each phase of the complex microstructure. The reaction zone is formed by a mixture of isostructural TiN phases with dendritic and/or ‘coarse’ needles morphology, fixed into a α′‐Ti matrix (martensite) with a thin needle aspect. The nitrogen solubility was found to remain very low in the α′‐Ti matrix (up to 2–3 atom %), while in the TiN phase, an aluminum solubility as high as 4 atom % was measured, reducing drastically the nitrogen content into a Ti₇₉N₁₇Al₄ chemical composition. Copyright © 2005 John Wiley & Sons, Ltd.     

Characterization of native and heterooxide layers on compound semiconductors by combined use of surface analysis methods

Summary Structure, formation and interface reactions of anodic oxides and SiO₂ on Cd_xHg_1–xTe have been studied by means of SIMS, AES, XPS, TDMS and the electron microprobe as an example for the application of surface analysis to compound and semiconductor passivation systems.

---

Charakterisierung von Eigenoxid- und Heterooxidschichten auf Mehrkomponentenhalbleitern durch kombinierten Einsatz oberflächenanalytischer Verfahren

Zusammenfassung Aufbau, Bildungsmechanismus und Grenzflächenreaktionen von anodischen Oxiden und Quarz auf Cd_xHg_1–xTe wurden mit SIMS, AES, XPS, TDMS, SNMS und der Elektronenstrahlmikrosonde untersucht.

     

Surface characteristics analysis of nitrocarburized (Tenifer) and carbonitrided industrial steel AISI 02 types

Generally, tool steels for cold work are obtained by rolling and forging processes. They are treated to have a structure conferring to the material a high toughness limit in terms of wear resistance and endurance. The objective of this study is the thermochemical heat treatment of industrial steel blades made of AISI 02 types, intended for polymer crushing. The effects of nitrocarburizing (Tenifer) and gaseous carbonitriding processes on surface characteristics are considered. These surface treatments increase the usefulness of properties, that is, fatigue strength, wear and corrosion resistance of this microalloyed steel. The influence of treatment duration and the thickness of the layers on surface properties are investigated. The analysis and characterization are carried out using physical analysis [optical microscopy, scanning electron microscopy, X‐ray diffraction and glow discharge optical emission spectroscopy (GDOES) techniques] and mechanical measurements (microhardness, weight loss and residual stresses) of treated material. The results are intended to contribute in defining and optimizing the adequate choice of treatments for this type of steel in industrial conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization and use of crystalline bacterial cell surface layers

Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air–water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.     

The segregation of As,Sb and Bi in Cr-Ni steels and alloys with different Ni contents investigated using AES

This paper reports on an AES study of grain boundary segregation in five kinds of Cr-Ni corrosion-resistant steels and alloys with different Ni contents that were enriched by As, Sb or Bi. The results show that all mentioned impurities segregate to the grain boundaries and that the segregation level depends on the type of the impurity. The highest amount of segregant atoms was found in the case of Bi, while it appeared to be substantially lower for As and Sb. The segregation level of each impurity grows also with the Ni content. This increase is more pronounced for Bi and Sb than for As. In particular the results demonstrate that the enrichment of grain boundaries by a given impurity is strongly connected to the solubility of this element in the matrix.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

应用渐进因子分析法研究SiO_2/Si样品俄歇深度剖析

首次利用渐进因子分析法对ＳｉＯ２／Ｓｉ样品俄歇深度剖析过程进行研究，发现ＳｉＯ２／Ｓｉ界面处有ＳｉＯｘ成分存在，ｘ值在１０～１５之间，厚度约为３０ｎｍ，含量接近５０％。Ａｒ＋离子束的轰击使得ＳｉＯ２薄膜内分解产生亚稳态ＳｉＯ２，含量在１７％左右。研究结果表明，渐进因子分析法非常适合于俄歇深度剖析的化学态分析。     

Investigations of the distribution of elements in phases present in G-AlMg5Si cast alloy with EDX/WDX spectrometers and AES

The mechanical properties of most aluminium alloys depend heavily on chemical composition, casting methods and heat treatment. Alloys of type G-AlMg₅Si are known for good corrosion resistance and mechanical properties at elevated temperatures. Under the designation Hydronalium (Hy 511) they are used for the production of heads for air cooled Diesel engines. To obtain better mechanical characteristics, titanium is added to the alloy. This paper deals with the results obtained during investigations of the distribution of elements in binary eutectic Mg₂Si and ternary eutectic as well as the distribution of titanium in samples of Hy 511, obtained during casting of cylinder heads. Studies of the distribution of the elements were performed using EDX/ WDX spectrometry, and the distribution of titanium was studied also with Auger electron spectroscopy.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

X-ray photoelectron spectra and Auger studies of the surface oxidation of cobalt

Surface oxidation of Co has been investigated at different temperatures in the 300–600 K range at oxygen exposures upto 10⁶ L by XPES and AES techniques. In the XPES, both the valence band and core level bands have been employed to monitor the oxidation while in the AES, metal Auger intensity ratios as well as O(KLL)/Co(L₂₃M₄₅M₄₅) ratios have been examined. Only CoO is formed on the surface at high oxygen exposures at and above 500 K. Communication No. 62 from the Solid State and Structural Chemistry Unit.     

Behavior of nitrided and carburized AISI 904 L stainless steels under severe light ion beam irradiation with plasma focus

Superaustenitic stainless steels have become of growing interest in industrial and technological fields, but there is not a complete understanding on their fundamental properties and their performances. For this paper, AISI 904 L superaustenitic samples were nitrided and carburized in order to study the expanded austenite stability under severe deuterium and helium ion bombardment. Surface treatments were conducted using pulsed plasma glow discharges in a low pressure atmosphere, and a dense plasma focus device was used to irradiate the samples. Characterization techniques used were focused ion beam/SEM, energy‐dispersive X‐ray spectroscopy, and grazing incidence X‐ray diffraction. Our results showed in carburized samples lattice expansion growth with the time treatment, but in nitrided samples, an expanded austenite reduction with time treatment was observed due to the formation of nitride nanoagglomerates. Moreover, this ion impingement provoked surface melting and a severe collision cascade, and a damaged bead located under the craters composed solely of minor alloying atoms. Furthermore, nitrided samples were more stable following ion bombardment than the carburized ones. When helium ions were used, the loss of expansion (triggered by diffusion processes of N or C to deeper regions) was more pronounced in the expanded austenite, but when deuterium ions were used to bombard the sample, there was a crystallite development of stressed austenite, which provoked a diffraction peak arousal at 43.3°. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative surface analysis by X-ray photoelectron spectroscopy and X-ray excited auger electron spectroscopy

It is shown that X-ray excited KLL Auger electron spectra allow it to describe measured signal strengths similarly to X-ray photoelectron signals, thus offering valuable information on the quantitative surface composition of a solid sample. The principal equation and corresponding fundamental parameters are discussed. As a result Auger spectra of C, N, O, F, and Na can be easily used in a multiline approach for quantitative analysis. LMM and MNN spectra give rise to more problems, due to their more complicated structure, uncertainties with regard to the background and the influence of Coster-Kronig transitions. These problems are overcome by the use of empirical ratios of the strongest lines of 2p/LMM or 3d/MNN. Since these ratios are independent of sample composition, they allow it to transform the Auger signal into the corresponding photoelectron signal, provided that a standard sample has been measured. Thus a true additional information is obtained and moreover difficulties in cases of photoelectron spectra with overlapping lines from other chemical elements can be overcome.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

SIMS and Auger investigation of oxygen adsorption on polycrystalline nickel surface

As it is known, the secondary ion yields increase stepwise upon increasing O₂ exposure, during SIMS measurements on metal samples in an oxygen atmosphere. Taking Auger spectra at varying oxygen exposure, the variation of satellite peaks and the chemical shift has been monitored, and a similar step-like dependence at the same range of oxygen exposures was found. This shows, that the discontinuous increase in the secondary ion intensity is due to the different types of oxides formed on the metal surface. Identification of these oxides are discussed.     

Characterization of surface modifications of stainless steel samples after electron and ion bombardment by SEM, AES, and XPS

The interaction of inert or reactive gas plasmas with the surface of stainless steel has been investigated with the aim, to modify the surface and hence to reduce the outgassing rate of the material, an important factor for the production of an ultrahigh vacuum. The plasma treatments investigated may be an alternative to the common used in situ baking. The samples have been exposed to electrons, argon and oxygen ions either in a DC glow discharge or in a microwave discharge. The DC glow discharge in Ar/O₂, the most effective plasma treatment reduces the outgassing rate by a factor of 10. After this treatment the surfaces of the samples have been investigated with respect to the topography and the chemical composition (depth profile) by Secondary Electron Microscopy (SEM), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS), respectively. The surface modifications resulting from the different treatments of the samples have been correlated to the outgassing rate.     

Structural and electrochemical characterization of sputter-deposited nitrided NiCr alloys

Nickel-based coatings are potential candidates for the protection of electrochemical dissolution of steel surfaces. Such coatings, elaborated by magnetron sputtering in a nitrogen atmosphere, offer good corrosion protection, good adherence as well as stability for metallic structures. NiCr alloys with almost constant composition have been deposited with different nitrogen contents on stainless steel and carbon steel surfaces. The coating uniformity, homogeneity, composition and crystallinity have been studied by scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy and X-ray diffraction techniques. The corrosion degradation behavior of all the samples was tested in NaCl and NaCl and CO₂ mixture exposures using electrochemical impedance spectroscopy measurements. Nitrided NiCr alloys on a stainless steel substrate resulted with better adhesion than carbon steel, by delaying the corrosion mechanism when exposed to NaCl and CO₂ solution. A comparison of the corrosion resistive behavior of the substrates (stainless steel, carbon steel) and the coatings is made by using the electrical capacitance concept from a double-layer model for the coating–metal interface.     

Investigation of surface and thermogravimetric characteristics of carbon-coated iron nanopowder

Demand for high-density press and sinter components is increasing day by day. Of the different ways to improve the sinter density, the addition of nanopowder to the conventional micrometer-sized metal powder is an effective solution. The present investigation is aimed at studying the surface chemistry of iron nanopowder coated with graphitic carbon, which is intended to be mixed with the conventional iron powder. For this purpose, iron nanopowder in the size range of 30 nm to submicron (less than 1 micron) was investigated using thermogravimetry at different temperatures: 400°C, 600°C, 800°C, 1000°C, and 1350°C. The X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and high-resolution scanning electron microscopy (HR-SEM) were used for characterizing the powder as well as samples sintered at different temperatures. The presence of iron, oxygen, carbon, chromium, and zinc were observed on the surface of the nanopowder. Iron was present in oxide state, although a small metallic iron peak at 707 eV was also observed in the XPS spectra obtained from the surface indicating the oxide scale to be maximum of about 5 nm in thickness. For the sample treated at 600°C, presence of manganese was observed on the surface. Thermogravimetry results showed a two-step mass loss with a total mass loss of 4 wt.% when heated to 1350°C where the first step corresponds to the surface oxide reduction.     

Enhanced infrared ATR spectra of surface layers of polymers using metal films

Enhanced infrared ATR spectra were measured for Langmuir films of CuPc deposited on PE and PVdC overlaid on PET, by using thin metal (Ni or Ag) films. The apparent intensity ratios for the bands ascribed to the upper layer were much larger than for those of the lower layer. The ratio depended on the nature as well as the mass thickness of the metal films. The mechanism of the enhancement was discussed in terms of SPP and multiple reflection effects.     

Properties of proton-conducting Nafion-type membranes with Nanometer-thick polyaniline surface layers

The study is directed to the improving of proton-conducting Nafion-type membranes for using in fuel cells with direct oxidation of liquid fuels. Nanometer-thick layer of polyaniline (in its conducting emerald-dine form) was deposited onto the membrane surface by in situ polymerization. The structure of the polyaniline layer is studied, as well as the properties of thus modified membranes (electronic and proton conduction, permeability for methanol, thermal stability). A method of platinum catalyst deposition onto the Nafion-modifying polyaniline layer is developed.     

Intercalation of diamines into zirconium phosphate-phosphite: A layered compound with asymmetric layers

Many primary diamines H₂N(CH₂)_nNH₂ (all the members withn ranging from 0 to 12 with the exception ofn =I 1) have been intercalated within the phosphate regions of layered zirconium phosphate-phosphite. As a general rule, intercalation occurs in two steps that are not well differentiated. The first one leads to intercalation compounds in which the diamines are arranged with their alkyl chain oriented parallel to the layers; the second one to the fully intercalated compounds. These latter compounds have composition Zr(HPO₄)_0.7(HPO₃)1,3-yNH₂(CHn2)·NH₂, withy ranging from 0.36 to 0.49 depending on the nature of the diamine. Not all the diamine molecules are thus diprotonated and they show a tendency to reach a y value of 0.5, corresponding to the total occupancy of the crystal sites available for intercalation. Diamines are arranged as a monolayer of extended molecules and an evident even-odd alternation of the interplanar spacing has been observed.A comparison with the intercalation of-zirconium phosphate for the same diamines is also made.