Phosphorus as sintering activator in powder metallurgical steels: characterization of the distribution and its technological impact

Powder metallurgy is a highly developed method of manufacturing reliable ferrous parts. The main processing steps in a powder metallurgical line are pressing and sintering. Sintering can be strongly enhanced by the formation of a liquid phase during the sintering process when using phosphorus as sintering activator. In this work the distribution (effect) of phosphorus was investigated by means of secondary ion mass spectrometry (SIMS) supported by Auger electron spectroscopy (AES) and electron probe micro analysis (EPMA). To verify the influence of the process conditions (phosphorus content, sintering atmosphere, time) on the mechanical properties, additional measurements of the microstructure (pore shape) and of impact energy were performed. Analysis of fracture surfaces was performed by means of scanning electron microscopy (SEM). The concentration of phosphorus differs in the samples from 0 to 1% (w/w). Samples with higher phosphorus concentrations (1% (w/w) and above) are also measurable by EPMA, whereas the distributions of P at technically relevant concentrations and the distribution of possible impurities are only detectable (visible) by means of SIMS. The influence of the sintering time on the phosphorus distribution will be demonstrated. In addition the grain boundary segregation of P was measured by AES at the surface of in-situ broken samples. It will be shown that the distribution of phosphorus depends also on the concentration of carbon in the samples.     

硼镁合金粉中硼的测定

报道了酸碱滴定法测定硼镁合金中的硼。确定了试样的溶解方法,建立了合理的分析步骤。对3个试样进行分析测定。其方法的回收率为98%～103%,RSD为10%。     

Characterization of the Element Distribution Within TiN Coatings with SIMS

 The distribution of the relevant elements within TiN coatings, made with two different physical deposition methods as the conventional dc vacuum arc method and the filtered high current pulsed arc method (Φ-HCA) are characterized and finally compared. Despite the rougher surface of the dc-arc produced TiN layer, which is due to accumulated droplets, there is no evidence of different stoechiometric composition of Ti and N on the surface. The interface of the dc-arc produced TiN layer (600 nm) is 10 times wider than the one made with the new filtered high current pulsed arc method (60 nm). However the TiN layer made by Φ-HCA shows an inhomogeneous distribution of aluminum and chlorine in the vertical direction, whereas the dc-arc sample is homogeneous. Furthermore, the TiN layer made by Φ-HCA shows vertically an obvious local maximum of chlorine at a depth of about 130 nm. This vertical local maximum has an homogeneous distribution in horizontal direction, which means that a thin, chlorine enriched layer has been incorporated inside the TiN layer. Nevertheless, quantification by SIMS shows that aluminum as well as chlorine concentrations of both samples are too low to influence any TiN properties. Received January 3, 2000. Revision April 4, 2000.     

Simultaneous SIMS/AES Measurements for the Characterization of Multilayer Systems

The interface region of silicon dioxide layers deposited on indium phosphide was investigated by simultaneous secondary ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES) depth profile measurements. The results of such measurements depend strongly on the ion species used for sputtering. With Ar⁺ primary ions an enhancement of the P- and In-SIMS signals occurs in the mixing zone at the interface. This effect can be explained by an increase of the ionization yield of In and P in the presence of oxygen from the SiO₂. The use of O₂ ⁺ as sputter ions enlarges the phosphorus peak at the interface while the enhancement of the In-signal diminishes. The simultaneously measured AES spectra give clear evidence of oxygen bonded In and P at the interface. Additionally, preferential sputtering of phosphorus occurs. The understanding of these effects which complicate the interpretation of SIMS and AES depth profile measurements of the system SiO₂/InP allows us to investigate the silicon dioxide layers and the interface region in order to optimize the SiO₂ deposition process, e.g. for surface passivation or MIS structures.     

Installation of a Shielded SIMS for the Analysis of Irradiated Nuclear Fuels

A CAMECA IMS 6F secondary ion mass spectrometer (SIMS) for the analysis of irradiated nuclear fuel has been installed in the Microbeam Analysis Laboratory of the Institute for Transuranium Elements (ITU). This device is specially equipped with heavy metal shielding to enable the safe examination of irradiated nuclear fuel samples with activities up to 75 GBq. At ITU the shielded SIMS will be used in conjunction with EPMA taking advantage of the complementary nature of the two techniques and will make important contributions to ongoing research programmes such as the safety of nuclear fuels, the partitioning and transmutation programme and the characterisation of spent fuels. The paper describes the shielded SIMS installation and presents a selection of results from the commissioning tests.     

Characterization of oxygen precipitates in Czochralski silicon by imaging SIMS

This paper presents a three-dimensional characterization of oxygen defects in Czochralski-silicon (CZ) by 3D-SIMS using a camera based imaging system. Different manufacturing processes yielding a variation in size and distribution of oxygen precipitates are monitored by imaging SIMS and conventional depth profiling. Emphasis is laid on the characterization of the precipitation behavior governed by different annealing processes. The limitations of 3D SIMS for oxygen defect imaging are studied. Sputter induced microroughening of the crater bottom, investigated by SEM, is shown to be strongly correlated with defect densities caused by oxygen precipitates.     

The detection of oxygen in magneto-optical layers with SIMS

The detection of oxygen in magneto-optical layers is of fundamental importance for the characterization of the stability of RE-TM material. The magnetic properties are directly influenced by oxide formation. Oxygen depth profiles are carried out by using the SIMS technique. A comparison with magnetic measurements showed a clear conformity. We were able to study the oxidation behaviour of various layers at room temperature and at higher values up to 250° C for several hours. It could be shown that aluminum is a successful material for the protection of RE-films against oxidation. The difficulties of translating SIMS counting rates into concentration values were overcome by using EPMA. Specially prepared reference samples were measured by this technique and could then be used as standard samples for SIMS.     

Structural Characterization by SIMS of Alumina Coatings on Stainless Steel

Al₂O₃ coatings were obtained by the alkoxide route and deposited on stainless steel using the dip coating technique. The starting precursor was aluminum sec-butoxide modified by acrylic acid in order to prevent its precipitation in the presence of water.Useful information for the structural organization of alumina coatings on stainless steel is deduced from SIMS analysis. SIMS data reveal that the coating structure brings into play two different layers: an outer alumina layer that is more or less doped, mainly by iron, and an internal layer corresponding to the alumina/steel interphase. Beneath the interphase, the presence of an oxidized steel layer on the substrate surface is detected.Whatever the coating, the alumina/steel interphase exhibits a nearly constant thickness. On the other hand, a thickness variation of the oxidized steel layer is observed between samples under study: this thickness increases with the curing time of the coating.     

A comparison of the static SIMS and G‐SIMS spectra of biodegradable homo‐polyesters

Static SIMS (SSIMS) is a surface analytical technique capable of providing molecular chemical information from solids. A major barrier to the wider take‐up of the technique is the complexity associated with the interpretation of SSIMS spectra. Quality of the interpretation depends on the expertise of analysts and making references to the limited mass spectral libraries. For many materials, there are no SSIMS library spectra. A new library‐independent method, G‐SIMS, is capable of facilitating the interpretation of SSIMS data. G‐SIMS spectra contain parent fragments, which are formed without substantial degradation or rearrangements, and highlight molecular fragments, which are directly related to the surface. In our study, G‐SIMS has been tested on medically relevant biodegradable polyester series, including poly (glycolic acid) (PGA), poly‐l‐(lactic acid) (PLA), poly‐β‐(hydroxybutyrate) (PHB) and poly‐ε‐(caprolactone) (PCL). The polyester series chosen here have closely related structures, which allow us to explore the capabilities of G‐SIMS. The G‐SIMS spectra have facilitated the identification of different polyesters by exhibiting mainly characteristic ions, representative of the polymers' molecular structures. The results also indicated that for the chosen polyester series, the larger the repeating monomer structures, the smaller the maximum number of repeat units were seen in the G‐SIMS spectra. The G‐SIMS spectra for the homologous polyester series have provided an insight into the fragmentation mechanisms as a function of repeating monomer molecular weights and structures. Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization of Two-Component Metal Coatings (Al/Sn) with SIMS

 Vacuum deposited films of immiscible metal–metal systems can be applied as tribological coatings for plain bearings in high performance diesel engines. These industrially manufactured coatings show higher lifetimes than conventional electroplated coatings. For our investigations we used aluminum-tin coatings of 1 μm thickness on a glass substrate produced by sequential deposition from two separate targets under working gas pressure of 0.4 Pa. The tough Al matrix takes high mechanical loads and the soft inclusions of Sn act as solid lubricant. While Sn is deposited it migrates on the Al surface and grows as islands. We characterized the conformation and the distribution of the Sn islands on the surface and to the interstitial area between the islands with 3-D secondary ion mass spectroscopy (SIMS). The existence of a Sn layer between the islands (“wetting layer”) has been detected by SIMS and verified by measurements with Auger electron spectroscopy (AES).     

Reduction of matrix effects in TOF‐SIMS analysis by metal‐assisted SIMS (MetA‐SIMS)

We investigated reduction of the matrix effect in time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analysis by the deposition of a small amount of metal on the sample surfaces (metal‐assisted SIMS or MetA‐SIMS). The metal used was silver, and the substrates used were silicon wafers as electroconductive substrates and polypropylene (PP) plates as nonelectroconductive substrates. Irganox 1010 and silicone oil on these substrates were analyzed by TOF‐SIMS before and after silver deposition. Before silver deposition, the secondary ion yields from the substances on the silicon wafer and PP plate were quite different due to the matrix effect from each substrate. After silver deposition, however, both ion yields were enhanced, particularly the sample on the PP plate, and little difference was seen between the two substrates. It was therefore found that the deposition of a small amount of metal on the sample surface is useful for reduction of the matrix effect. By reducing the matrix effect using this technique, it is possible to evaluate from the ion intensities the order of magnitude of the quantities of organic materials on different substrates. In addition, this reduction technique has clear utility for the imaging of organic materials on nonuniform substrates such as metals and polymers. MetA‐SIMS is thus a useful analysis tool for solving problems with real‐world samples. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of the sintering atmosphere on the densification of B4C ceramics

Densification of boron carbide during sintering may be improved by a two-stage process, namely heating to 2000°C under vacuum and sintering at 2190°C under argon. This sintering regime allows achieving a relative density of the ceramic bodies fabricated from a fine powder higher than 95%. The nitrogen treatment of the boron carbide phase at 1900°C leads to the formation of the BN phase and precipitation of graphite. Vacuum treatment of these samples at 2000°C leads to decomposition of the boron nitride phase. The liberated free boron may again react with graphite to form in situ boron carbide particles. The experimental investigations of the sintering behavior of the boron carbide phase under various atmospheres supported the thermodynamic predictions regarding the phase transformation. No evidence, however, was found for enhanced sintering under a nitrogen atmosphere.     

Direct phase identification with SIMS by evaluation of atomic and cluster ion intensities: A Study of calcium sulfide formation in hard metals during sintering

A SIMS method for the direct identification of micro and nanophases based on the quantitative evaluation of atomic and cluster ion intensities is described and applied to the study of the formation of CaS phases in hard metals.     

Experimental shift allowance in the deconvolution of SIMS depth profiles

We study the deconvolution of the secondary ion mass spectrometry (SIMS) depth profiles of silicon and gallium arsenide structures with doped thin layers. Special attention is paid to allowance for the instrumental shift of experimental SIMS depth profiles. This effect is taken into account by using Hofmann's mixing‐roughness‐information depth model to determine the depth resolution function. The ill‐posed inverse problem is solved in the Fourier space using the Tikhonov regularization method. The proposed deconvolution algorithm has been tested on various simulated and real structures. It is shown that the algorithm can improve the SIMS depth profiling relevancy and depth resolution. The implemented shift allowance method avoids significant systematic errors of determination of the near‐surface delta‐doped layer position. Copyright © 2013 John Wiley & Sons, Ltd.     

On the generation of MCs+ ions in SIMS with Cs+ primary beams

The formation of MCs⁺ secondary ions in SIMS operated with Cs⁺ ion beams is discussed on the basis of a well-confirmed quadratic dependence of MCs⁺ yields on the atomic polarizabilities of elements M contained in semiconductor samples. This behavior is understood by the generation of a dipole induced in M by the positive charge of a neighboring Cs⁺ projectile and the mutual induction of a dipole in Cs⁺, both dipoles depending on the atomic polarizability of M. An evaluation of the dipole–dipole interaction energy indicates that MCs⁺ ions generated at the target are emitted according to the direct emission model (DEM). This mechanism is in contrast with an association model where constituents of MCs⁺ are assumed to combine after their independent sputter emission.     

Static TOF‐SIMS. A VAMAS interlaboratory study. Part II — accuracy of the mass scale and G‐SIMS compatibility

An interlaboratory study involving 32 time‐of‐flight static SIMS instruments from 13 countries has been conducted. In Part I of the analysis of data, we showed that 84% of instruments have excellent repeatabilities of better than 1.9% and that a relative instrument spectral response (RISR) can be used to evaluate variations between different generic types of instrument. Use of the RISR improves comparability between instruments by a factor of 33. Here, in Part II, we study the accuracy of the mass scale calibration in TOF‐SIMS and evaluate instrument compatibility with G‐SIMS. We show that the accuracy of calibration of the mass scale is much poorer than generally expected (?60 ppm for peaks <200 u and ?150 ppm for a large molecular peak at 647 u). This is a major issue for analysts. Elsewhere, we have developed a detailed study of the factors affecting the mass calibration and have developed a generic protocol that improves accuracy by a factor of 5. Here, this framework of understanding is used to interpret the results presented. Furthermore, we show that eight out of the ten participants submitting data for G‐SIMS could use operating conditions that generated G‐SIMS spectra of the PC reference material. This demonstrates that G‐SIMS may be conducted with a wide variety of instrument designs. © Crown Copyright 2007. Reproduced by permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd.     

Static SIMS studies of the oxides and hydroxides of aluminium

The degree of hydroxylation or hydration of aluminium surfaces has been examined by static secondary ion mass spectroscopy (SSIMS). The SSIMS spectra of a series of aluminium oxide, oxyhydroxide and hydroxide surfaces have been obtained using instruments in three configurations. Similarities were observed in both negative and positive secondary ions spectra. Even though a direct comparison of the relative intensities cannot be made from one instrument to the other, a similar ranking of the various aluminium hydroxylation states was observed. Several ranking methods are discussed, as well as the similarities and differences observed while using the three instruments. Similar secondary ions were detected whatever the degree of hydroxylation of the aluminium oxide. This argues in favour of the formation of fragments by the combination of individually sputtered atoms or clusters to form the more stable secondaries, rather than the kick-off of 'structure-related' clusters originating directly from the upper surface layer.     

Extracting information on the surface monomer unit distribution of PLGA by ToF‐SIMS

The surface chemistry of a range of random poly l‐lactide‐co‐glycolide (PLGA) materials has been investigated using XPS, static secondary ion mass spectrometry (SSIMS) and gentle secondary ion mass spectrometry (G‐SIMS). The estimated mole fraction of lactide units provided by SSIMS was in good agreement with bulk composition and appeared not to have been affected by contamination. Conversely, XPS assessment of lactide compositions was unreliable due to hydrocarbon contamination contributions. In this study, we propose a novel model to demonstrate that by using SSIMS it is possible to infer the degree of trans‐esterification for PLGA co‐polymers synthesised from a mixture of lactide and glycolide homo‐dimers. This was determined by introducing two independent parameters, the ratio of trans‐esterified bonds to the total number of ester bonds, P_T, and the lactide composition. The model has indicated that, for this set of polymers, P_T was approximately 0.25. Furthermore, we have demonstrated that G‐SIMS successfully identified the structurally important key fragments leading to direct identification. Analysis by G‐SIMS showed that the glycolic acid units from all PLGA compositions are emitted in a lower energy‐fragmentation process than lactic acid units. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative SIMS depth profiling of Al in AlGaN/AlN/GaN HEMT structures with nanometer‐thin layers

The possibilities of quantitative secondary ion mass spectrometry (SIMS) depth profiling of Al in AlxGa1 ? xN/AlN/GaN transistor heterostructures are shown. Using a series of test structures for a TOF.SIMS‐5 time‐of‐flight mass spectrometer, we obtained a refined linear calibration dependence of the secondary‐ion yield on the composition ×, namely, Y(CsAl+)/Y(CsGa+) = K × x/(1 ? x), with a high linear correlation coefficient, Rl = 0.9996, which permits quantitative SIMS analysis of relatively thick AlGaN barrier layers. The method of profile reconstruction with allowance for the main artifacts of ion sputtering has been first applied for the analysis of GaN/AlGaN/AlN/GaN high electron mobility transistor structure. This method permits to perform quantitative analysis of the thickness and composition of a nanometer‐thin AlN sublayer and to estimate the measurement error. For the structure being studied, the AlN sublayer is 1.2 ± 0.2 nm thick. Copyright © 2016 John Wiley & Sons, Ltd.     

沉积碳氟磷灰石中痕量碘的SIMS定量分析

采用合成的标样对微细碳氟磷灰石中痕量碘进行了离子探针（ＳＩＭＳ）定量分析，给出了碘浓度与其二次离子相对强度的线性方程，对不同组构类型的沉积磷灰石进行的ＳＩＭＳ微区显微分析表明：针柱状结晶良好的微细磷灰石含碘很低，碘主要富集于生物成因的超微莓球磷灰石中。碘在磷块岩中分布不均匀性是受其超微组构制约的，ＳＩＭＳ微区分析深入地揭示了富碘磷块岩中碘的赋存特征。该法也可应用于生物骨骼、化石等磷酸盐样品中卤素的