In-situ fracture investigations of MgLi-carbon fibre composite materials by AES and data analysis by means of factor and cluster analysis

Uncoated and 300 nm pyrocarbon coated polyacrylonitril (PAN) based T300 type carbon fibres were pressure infiltrated with molten Mg8Li and Mg12Li alloys at 903 K and 963 K, respectively, and at contact times of 4 s and 30 s. The fracture surfaces were characterized by in-situ Auger electron spectroscopy (AES) to investigate the reason for differences in mechanical properties, which were obtained by tensile strength experiments. Pressure increase occurred during the fracture of all the MgLi samples under ultra high vacuum conditions in the analyzer chamber of the AES apparatus, indicating porosity probably due to poor wetting of the fibres during the infiltration process. As visible in the scanning electron micrographs, the pyrocarbon coated carbon fibres were less attacked by the molten MgLi than the uncoated fibres. The damage seemed to increase, the higher the Li contents, the higher the contact time and the higher the temperature were chosen, whereas pyrocarbon coating may retard this affection. Characteristic objects of the sample fracture surfaces (fibre fracture surface, fibre jacket surface, fibre impression surface and matrix) were investigated by laterally high resolution Auger electron spectroscopy. Oxygen was found to be distributed all over the fracture surfaces of the as-fractured samples, and Mg/Li were identified in a chemically bound form. On all the characteristic objects carbide (Li₂C₂) formation has been detected. Factor analysis was performed to exctract the principal components from the whole set of differentiated Auger electron spectra in the Mg/Li, C and O spectral regions, respectively. Cluster analysis of the weighting factors (the factor loadings) of the most important principal components lead to a separation of the data set into two main groups due to the presence or absence of a strong carbide C (KVV) peak as result of Ar⁺ sputter removal of the covering oxide layer; no separation of the objects concerning the reaction conditions was found. Received: 18 June 1996 / Revised: 26 July 1996 / Accepted: 30 July 1996     

XPS and SIMS Examination of Alumina Fibres Affected with Mg and MgLi Melt

 Fibre/matrix interfaces in δ-Al₂O₃/Mg8Li and δ-Al₂O₃/Mg composites have been investigated using XPS and SIMS analysis of extracted δ-Al₂O₃ fibres in context with previous XRD observations. Results obtained indicate that in MgLi based composites lithium enters preferentially the interfacial redox reactions producing Li⁺ ions that occupy vacant cation positions in the defect δ-Al₂O₃ lattice which results in a strong fibre/matrix interfacial bond. On the other hand, in Mg matrix composites the magnesium oxide appears to be the final reaction product that does not enter the solid state reaction with adjacent δ-Al₂O₃ fibre during the melt infiltration process, so that only relatively weak interfacial bond is created.     

Controllable Hydrolysis Performance of MgLi Alloys and Their Hydrides

Theoretically, the hydrolysis of MgLi and MgH₂−LiH can produce 9.6 and 17.5 wt.% hydrogen (water is not included in the calculation), respectively. The ball-milling method is commonly used to refine the particle size and thus may improve hydrolysis kinetics. However, Mg and Li will be easily agglomerated, which means that direct ball-milling could not refine MgLi. In this work, we introduced 10 wt.% expanded graphite into the ball-milling process to synthesize refined MgLi alloy samples. Further studies showed that MgLi-10 wt.% expanded graphite can produce 966 mL/g hydrogen within 3 min in 0.5 M MgCl₂ solution. The MgLi hydrides were synthesized by reactive ball milling under 3 MPa H₂ and their hydrolysis performance was investigated. Moreover, the sawed powder was milled in 3 MPa H₂ for 6 h and then hydrogenated in 3 MPa H₂ at 380 °C; it can produce 1542 and 1773 mL/g (15.8 wt.%) hydrogen in 5 and 30 min with mild kinetics, respectively, and the activation energy of the hydrolysis reaction is 24.6 kJ/mol in 1 M MgCl₂ solution. The findings here open a new avenue to the development of refined MgLi alloys and hydrides for hydrogen generation through a controllable hydrolysis process.     

Oxidation, Diffusion and Segregation in CuNi(Mn) Films Studied by AES

 The surface and in-depth compositions of sputter-deposited Cu_0.57Ni_0.42Mn_0.01 thin films were studied by Auger electron depth profiling after thermal treatment. The samples were thermally cycled to maximum temperatures of 300 °C to 550 °C in air, argon and forming gas (N₂, 5 vol. % H₂). Linear least-squares fit to standard spectra and factor analysis were applied to separate the overlapping Auger transitions of Cu and Ni. Under bombardment by 4 keV argon ions, CuNi(Mn) layers display bombardment-induced surface enrichment of Ni in the same extent as binary CuNi alloys. At sufficiently high oxygen partial pressures, a duplex oxide layer is formed and a thick surface copper oxide overgrows the initial nickel oxide. In reducing atmosphere selective oxidation of manganese takes place. A capping NiCr layer prevents CuNi(Mn) from being oxidized, but the film configuration is degraded with increasing annealing temperature due to formation of a surface chromium oxide and diffusion of Ni from the CuNi(Mn) layer into the NiCr/CuNi(Mn) interface.     

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.     

In-depth compositional analysis of ceramic (Bi2O3)0.75(Er2O3)0.25 by AES and XPS

The chemical composition of dense ceramics of erbia-stabilized -Bi₂O₃ was analyzed by Auger electron spectroscopy (AES) depth profiling using Ar⁺ ion sputtering. The relative sensitivity factors (rsf) and sputter rates of bismuth and erbium in this material have been determined by electron probe microanalysis (EPMA) and chemical analysis. These results, supplemented by data from angle resolved X-ray photoelectron spectroscopy (ARXPS), shows a bismuth enrichment at the surface. Evidence has been found for reduction of the bismuth-oxide at the outermost part of the surface layer.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Study of stressed hard coatings and of their abrasive particles by AES and REM

Chromium nitride and chromium oxide were deposited by arc PVD and APS on steel substrates to be worn in a testing set up simulating the abrasion process of a screw rotor compressor. The damage of Cr _x N is more severe than that of Cr₂O₃. The abrasive particles were collected on glassy carbon with a Batelle impactor and analyzed by AES and REM. Particles from the Cr _x N coating are totally oxidized, in contrast to particles from Cr₂O₃ which are not chemically influenced. No oxidation can be detected on the surface of the treated Cr _x N coating. The Cr₂O₃ coating is not affected either.Dedicated to Professor Dr. rer. nat. Dr.h.c. Hubertus Nickel on the occasion of his 65th birthday     

Characterization of metallic layer composites by means of AES/depth profile analysis

The adherence mechanism of arc sprayed Ni layers on structure steel St37 is investigated. AES depth profiles are obtained on single Ni particles still adhering to the substrate after the Ni layer has been separated from it. A comparison of interface shapes and results of adherence measurements reveals Fe-Ni layered structures for the best adhering layers, whereas less adhering layers are characterized by narrower interfaces caused by diffusion. Areas with no adherence are covered with oxidic layers.     

Improving surface‐analysis methods for characterization of advanced materials by development of standards,reference data,and interlaboratory comparisons

This paper summarizes the results of two surveys examining current needs for improved analyses of surfaces. Surfaces and interfaces are increasingly important to science and technologies associated with nanoparticles, nano‐structured materials and other complex materials including those associated with information systems and medical or biological applications. Adequate characterization of advanced materials frequently requires application of more than one analysis method along with the need to analyze data in increasingly sophisticated and sometimes interrelated ways. It is useful for both new and experienced analysts to have ready access to best practices for obtaining accurate and useful information from a variety of different analysis tools. The International Organization for Standardization (ISO) Committee TC 201 on surface chemical analysis and the ASTM Committee E‐42 on surface analysis are working to address these needs by assembling guides and standards reflecting the collective experience and wisdom of experts in this community. Published in 2007 by John Wiley & Sons, Ltd     

Grass fiber reinforced phenol formaldehyde resin composite: preparation,characterization and evaluation of properties of composite

There is a growing interest in the development of new materials through utilization of natural resources. This paper describes evaluation of water leached and alkali treated chopped grass fiber reinforced phenol formaldehyde composite. Here alkali treatment of grass fiber was carried out by varying the concentration of sodium hydroxide. The thermal stability of the composite was assessed by thermogravimetric analysis (TGA). Fourier transformation infrared spectroscopic study of both water leached and alkali treated grass fiber‐phenolic resin composite was also performed. Water absorption and swelling behavior of grass fiber phenolic resin composites in water were studied and the alkali treated grass fiber‐resin composite showed less water absorption and swelling. A composite prepared from 1% alkali treated grass fiber and 55% resin, showed the highest tensile strength whereas a composite prepared from 5% alkali treated grass fiber and 55% resin, showed maximum flexural properties. Copyright © 2006 John Wiley & Sons, Ltd.     

氢化物发生ICP-AES法测定药用植物中的痕量锗

本文应用氢化物发生ＩＣＰ－ＡＥＳ法研究了药用植物样品中痕量锗的测定方法，系统地研究了ＩＣＰ－ＡＥＳ仪器参数及氢化物发生条件对锗谱线信背比的影响，考察了１３种共存元素的干扰，并比较了植物样品的３种前处理方法。选定Ｈ３ＰＯ４－ＨＮＯ３－Ｈ２Ｏ２消化，在３ｍｏｌ／ＬＨ３ＰＯ４介质中，以１５ｇ／ＬＮａＢＨ４还原，测定药用植物样品中的锗，相对标准偏差≤２．９％，回收率为９４％～１０３％。方法检出限达０．１３μｇ／Ｌ。     

Distribution and thickness of the surface contaminations on STM tungsten tips,studied by AES/SEM and ARXPS

The combination of Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and angle resolved X-ray photoelectron spectroscopy (ARXPS) has been applied to the analysis of the distribution of elements at the surface region of electrochemically etched tungsten tips and the determination of the thickness of a layer with oxygen and carbon contamination. Auger line profiling revealed a homogeneous distribution of oxygen and significant enrichment of carbon on the W tip between 0 and 1.5 m from the top. The thickness of the contamination layer on various W materials, electrochemically etched, was found to be 1.35±0.15 nm as measured using ARXPS, and was estimated to be about 1–3 nm as measured by AES.     

XPS and AES surface analysis of WC-Co-(Cr) cemented carbide after immersion in neutral solution

The binder phase Co in WC-Co cemented carbide is dissolved easily in corrosive media (even in neutral solution), which has limited its application in a wider range. In this paper, the influence of Cr on corrosion resistance of WC-Co immersed in neutral solution was studied, with a focus on the surface chemistry of the corrosion product. The results show that in neutral solution, the corrosion is mainly caused by the selective dissolution of Co and the dominant surface corrosion product after immersion is Co (OH)₂. The corrosion resistance of WC-Co cemented carbide can be improved by the addition of Cr. This can be explained by the formation of more protective chromium containing oxide on the binder phase of WC-Co-Cr alloy, leading to reduced corrosion rate.     

Multivariate comparison of concentration profiles in materials analysis

Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were applied to find groups between similar depth-profiles in thin-layers investigated by Rutherford backscattering spectrometry (RBS).HCA yields in one run an objective hierarchy of similarity for several profiles. Among the similarity coefficients examined the linear measure, the Euclidean distance and the exponential measure respond with different sensitivity to overall shifts in direction of the concentration axis, whereas the correlation measure relates to parallelism of the profiles.For agglomerative HCA with Euclidean distance, a lowest significant linkage level has been defined by use of Fisher'sF-test. For divisive HCA based also on Euclidean distance, the maximum of a separating function marks the most separating cluster step. The outcomes of both proposals agree for the data set investigated.PCA is useful for verifying the results of HCA and yields additional information about the data structure. In the actual example quite different positions of features (concentrations at definite depths) in the space of the two first principal components hint at peculiarities during the metallurgical coating process.     

Resolving co-eluting chromatographic patterns by means of dissimilarity analysis in iterative target transformation factor analysis

The initialization of concentration vector for iterative target transformation factor analysis (ITTFA) and identification of pure or key variables are the important issue in MCR. In this study, dissimilarity analysis and evolving factor analysis (EFA) are combined to find the selective or key variables and subsequently obtain initial estimates of the concentration vectors for resolution of gas chromatography/mass spectrometry (GC/MS) data by ITTFA. For systems containing components with highly similar mass spectra, a new constraint setting the elements out of elution window to 0 is used to improve convergence rate and accuracy of results. Tested by standard mixture of two wax esters and real GC/MS data of gasoline 97#, dissimilarity based ITTFA could obtain accurate results (average Dot product of concentration vectors, average deviation of peak area ratio and average similarity of mass spectra are 0.9929, 0.0228 and 981.0, respectively).     

Synthesis and characterization of polypyrrole/graphite oxide composite by in situ emulsion polymerization

This work demonstrates a feasible route to synthesize the layered polypyrrole/graphite oxide (PPy/GO) composite by in situ emulsion polymerization in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) as emulsifier. AFM and XRD results reveal that the GO can be delaminated into nanosheets and well dispersed in aqueous solution in the presence of CTAB. The PPy nanowires are formed due to the presence of the lamellar mesostructured (CTA)₂S₂O₈ as a template. The results of the PPy/GO composite indicate the PPy insert successfully into GO interlayers, and the nanofiber‐like PPy are deposited onto the GO surface. Owing to π–π electron stacking effect between the pyrrole ring of PPy and the unoxided domain of GO sheets, the electrical conductivity of PPy/GO composite (5 S/cm) significantly improves in comparison with pure PPy nanowires (0.94 S/cm) and pristine GO (1 × 10^?6 S/cm). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1329–1335, 2010     

Oxide and nitride protective layers on stainless steel studied by AES,WDS and XPS

Protective surface layers on AISI 321 stainless steel were prepared by thermal treatments at two different temperatures in air and two controlled atmospheres. Different oxide and/or nitride layers were formed. Surface morphology of the layers was investigated by scanning electron microscopy (SEM). Auger electron spectroscopy (AES) depth profiling of the samples was performed. Since depth profiling suggested layer thicknesses of the order of hundreds of nanometres, an attempt was made to obtain some fast, averaged information about the layer compositions using wavelength dispersive spectroscopy (WDS) at two different beam energies to obtain probing depths best suited to the layer thickness. X‐ray photoelectron spectroscopy (XPS) profiling of one layer was also performed to obtain information about the chemical states of the elements inside the layer. The analysed samples showed considerable differences with respect to their surface morphology, oxide/nitride layer thicknesses, compositions and layer–metal interface thickness. Copyright © 2007 John Wiley & Sons, Ltd.     

ARL—3520AES电感耦合等离子体发射光谱仪疑难故障的分析与排除

介绍了在瑞士ＡＲＬ公司生产的ＩＣＰ－３５２０ＡＥＳ型电感耦合等离子体原子发射光谱仪上存在的一种疑难故障的分析与排除过程，对同类型仪器的故障分析有借鉴作用。     

Enhanced target factor analysis

Target testing or target factor analysis, TFA, is a well-established soft analysis method. TFA answers the question whether an independent target test vector measured at the same wavelengths as the collection of spectra in a data matrix can be excluded as the spectrum of one of the components in the system under investigation. Essentially, TFA cannot positively prove that a particular test spectrum is the true spectrum of one of the components, it can, only reject a spectrum. However, TFA will not reject, or in other words TFA will accept, many spectra which cannot be component spectra. Enhanced Target Factor Analysis, ETFA addresses the above problem. Compared with traditional TFA, ETFA results in a significantly narrower range of positive results, i.e. the chance of a false positive test result is dramatically reduced. ETFA is based on feasibility testing as described in Refs. [16–19]. The method has been tested and validated with computer generated and real data sets.     

Quantitative Analysis of Ti-Si-Ge/Si-Ge/Si Structures by EDS and AES

 A method for quantitative analysis of Ti-Si-Ge/Si-Ge/Si structures with submicron thick layers by energy dispersive spectroscopy (EDS) in transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) was developed. Quantitation of the results of both AES and EDS techniques was performed on the basis of a single reference specimen for the Ti-Si-Ge system comprising a uniform layer of the Ti(Si_0.85Ge_0.15)₂ phase on a silicon substrate. The reference sample was prepared by the same procedure as the samples used in the study, and was thoroughly characterized by X-ray diffractometry, transmission electron microscopy and energy dispersive spectroscopy in scanning electron microscopy. Using this reference sample the elemental sensitivity factors relative to Si were found for both techniques, which enable us to obtain the elemental depth distributions for the studied samples. Good agreement between the results obtained by EDS/TEM, AES and supplementary techniques was found.