SIMS Characterisation of Aluminum-Alloyed Hot Isostatic Pressed Steel

 Recently, interest in steel alloyed with∼1% Al increased. These materials are expected to show a higher resistance against oxidation at high temperatures which will improve their performance when used as high-speed-steels. Furthermore, efforts have been made to combine the advantages of Al-steels with those of powder-metallurgic methods like hotisostatic-pressing (hip). This should result in a better macro- and microscopic homogeneity of the distribution of all compounds, yielding less waste-production and a longer life-time of products. In order to gain deeper insights in the process of “hipping” of the considered material and to see the distribution of both main as well as trace components, 2D and 3D-SIMS measurements of the material were performed before and after having undergone the hip process. The measurements showed enrichments of Na, K, Mg, Ca, and S at the particle boundaries before as well as after the hip-process. In the hipped material, the enrichments are significantly stronger in the spatial domains in-between larger particles. They also reveal, that the concentration of C is not equal in all particles and that the particles are covered with an Al₂O₃-layer which is not dispersed by the hip-process. There were also found small (∼50–100 nm) nitride-precipitates before as well as after the hip-process.     

Surface Characterisation of Water-Atomised Al–Zn–Mg–Cu Alloy Powders by SIMS and AES

 The present paper focuses on the characterisation of surface composition and alloying element in-depth distribution of water-atomised Al–Zn–Mg–Cu alloy powders by secondary ion mass-spectrometry and Auger electron spectroscopy. A pronounced segregation of Mg and some impurities (Fe, Ca, S) concurrently with some Zn depletion are observed on the powder surface. The oxide film formed on the powder surface mainly consists of Al and Mg oxides. The film is non-uniform in thickness: rather coarse surface oxide islands coexist with surface areas covered by a thin (<1.8 nm) oxide layer. The extent of surface oxidation is strongly affected by solidification conditions: The average thickness of the surface oxides increases with increasing particle size or with decreasing cooling rate. All alloying elements are homogeneously distributed in the bulk of individual particles. No significant differences in chemical composition between different particles of a given powder are observed. Received November 26, 1999. Revision September 25, 2001.     

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.     

Comparative Analysis of a Solar Control Coating on Glass by AES, EPMA, SNMS and SIMS

 A solar control coating was analysed by different methods of surface analysis with respect to the layer sequence and the composition and thickness of each sublayer. The methods used for depth profiling were Auger electron spectroscopy, electron probe microanalysis, secondary neutral mass spectroscopy and secondary ion mass spectroscopy based on MCs⁺. The structure of the coating was unknown at first. All methods found a system of two metallic Ag layers, embedded between dielectric SnO_X layers. Additionally, thin Ni-Cr layers of 1–2 nm were detected on top of the Ag layers. Thus the detected layer sequence is SnO_X/Ni-Cr/Ag/SnO_X/Ni-Cr/Ag/SnO_X/glass. The Ni:Cr ratio in the nm-thin layers could be quantified by every method, the Cr fraction corresponding to less than one monolayer. We compare the capabilities and limitations of each method in routinely investigating this solar control coating. Importance was attached to an effective investigation. Nevertheless, by combining all methods, measuring artefacts could be uncovered and a comprehensive characterisation of the system was obtained.     

Development of a SIMS Method for Isotopic Measurements in Nuclear Forensic Applications

 Methodologies based on secondary ion mass spectrometry (SIMS) for isotopic measurements in nuclear forensic applications relevant to the age determination of Pu particles and isotopic composition of oxygen for geolocation assignment are described. For the age determination of Pu particles, a relative sensitivity factor (RSF) to correct for the different ionisation efficiencies of U and Pu, was obtained by analysing standard Pu materials with known ages. An RSF of 2.41±0.05 was obtained for PuO₂ from measurements on samples with different Pu/U ratios. In a sample of known origin, using this RSF value, the age calculated from the ²³⁸Pu/²³⁴U and ²⁴⁰Pu/²³⁶U ratios agreed well with the reported age of 2.3 years. For geolocation assignment, a new approach based on the measurement of differences in the natural abundance of ¹⁸O and ¹⁶O isotopes and their ratio was developed. The instrumental mass discrimination of the ¹⁸O/¹⁶O ratio was determined using three O-isotope samples of different chemical composition. The measured precision (the standard error of 100 cycles/analysis) obtained for the oxygen isotopic measurement on the samples was typically ±1.1‰.     

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).     

SIMS Profiling and TEM of CVD Films on Multi-Filament Samples

 A suitable fibre coating is essential to obtain optimal fibre-matrix interaction in fibre-strengthened composite materials. Thin films (∼100 nm) of silicon carbide, turbostratic carbon, and boron nitride were deposited by CVD as single or double layers on commercial multi-filament fibres in a continuous process. The fibre material itself may be carbon, alumina, silicon carbide, or a quaternary ceramic of SiCBN. The application of MCs⁺-SIMS enables one to determine the composition (including impurities of H and O) of various fibre coating materials with an accuracy of at least 20% relative. Due to the special geometry of the multi-filament samples the depth resolution of the SIMS depth profiles is limited, nevertheless, layered structures and some details of the interface between coating and fibre can be studied. The depth calibration of the SIMS depth profiles is derived from sputter rates established on flat samples with a composition similar to that of the fibre coating material. However, the obtained film thicknesses are not extremely different from the values derived from TEM on cross sections of coated fibres.     

Quantification of H, B and F in Kornerupine: Accuracy of SIMS and SREF (X-Ray Single-Crystal Structure-Refinement) Data

 We use a multiple-analytical approach based on secondary-ion mass-spectrometry (SIMS), X-ray single-crystal structure refinement (SREF) and electron-probe micro-analysis (EPMA) to derive the complete crystal-chemical formula of a B-rich kornerupine-group mineral, prismatine, from Hrarigahy, Madagascar: (Ca_0.01Li_0.02Mg_0.20Fe²⁺ _0.10) (Mg_3.57Fe²⁺ _0.06 Al_5.37) (Si_3.84B_0.91Al_0.26)O₂₁ (OH_1.08F_0.07). SIMS matrix effects related to crystal structure were investigated by analyzing two grains with a known crystallographic orientation relative to the ion beam. Boron orders at the T3 site. The refined site-scattering for T3, 6.33 eps (electrons per site) agrees well with the mean bond-length for this site (1.512 ?), which indicates nearly complete occupancy by B (85% rel.). B₂O₃ (∼ 4 wt%), derived by SREF, agrees with the SIMS data within analytical uncertainty using Si as the inner reference for the matrix. The occupancy of the X site obtained by combining the SIMS and EPMA data (5.30 eps; electrons per site) agrees with the refined site-scattering value (5.75 eps). Trace quantities of Li and Ca are ordered at this site. SIMS data for H₂O is in accord with the stoichiometric value, indicating complete occupancy at O10 by OH. Fluorine (∼ 0.17 wt%) orders at O10: it corresponds to ∼ 0.07 atoms per formula unit (apfu) vs. 0.15 apfu (atoms per formula unit) by SREF, indicating a slight overestimation of F with SREF, as previously observed in fluoborite. Our data show that SIMS chemical matrix effects are well-calibrated, and emphasize the usefulness of independent micro-analytical techniques in testing the mutual accuracy and consistency of experimental data.     

Fusion of 2-D SIMS Images Using the Wavelet Transform

 Secondary ion mass spectroscopy (SIMS) is a powerful method for element distribution examination of conducting and semi-conducting surfaces at high spatial resolution and with a high sensitivity. Routine surface analysis produces about 8 to 15 images in a short time, each of which displays the intensity distribution of one mass, thus generating a multispectral SIMS image. Formation of occlusions, segregations, and the overall location of the elements relative to each other, are difficult to recognise when looking at n separate 2-D images. Image fusion is a process whereby images obtained from various sensors, or at different moments of time, or under different conditions, are combined together to provide a more complete picture of the object under investigation. The process of combining SIMS images may be viewed as an attempt to compensate for the inherent effect of SIMS to channel the information obtained from the sample into different images, corresponding to different element phases. The wavelet transform is a powerful method for fusion of images. This work covers the use of wavelet based fusion algorithms on multispectral SIMS images, evaluating the performance of different wavelet based fusion rules on different type of image systems and comparing the results to conventional fusion techniques. An aim of this study is to increase the information, i.e. the number of masses, which can be merged into one image in order to enhance the perception and interpretation of the SIMS surface images.     

Application of SIMS in Re-Technology Studies: Characterization of Trace-Element Distributions and Quantitative of Carbon-Determination

 The content and the three dimensional distribution of impurities play an important role in the production process of high purity rhenium powder (99.99% purity grade) and for its further use as alloying and coating agent in high temperature applications. In this paper the characterization of raw Re granulate, Re powder, cleaned by heat treatment, Re coatings, produced by most common preparation methods (PVD and VPS) and PM Re by means of SIMS is presented. The analysis of the three dimensional distribution of trace elements is performed by 3D SIMS. The quantification of carbon, which was not possible with other analytical techniques as a result of the high volatility of Re₂O₇ until now, has been carried out by SIMS depth profile analysis. It is discussed if internal standards, produced by introduction of defined amounts of carbon soot to the Re powder lead to useful results.     

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.     

SIMS Analysis of Uranium and Actinides in Microparticles of Different Origin

In the framework of the projects Environmental Sampling and High Performance Trace Analysis in support to the International Atomic Energy Agency (IAEA) and the Euratom Safeguards Office (ESO), the research has been focused on the identification and characterisation of particles of interest containing mainly U and other actinides.Multiple analyses, elemental and isotopic, of single radioactive particles in the µm-size range are key-tools in environmental research and in nuclear forensics. The main purpose in the analysis of single particles by SIMS is the determination of their isotopic composition that has been demonstrated successfully for uranium and plutonium particles. From these results, the enrichment of the material produced, the process used for the enrichment as well as the starting material employed (natural or reprocessed uranium) can be identified.     

Fission Gas Bubbles Characterisation in Irradiated UO2 Fuel by SEM, EPMA and SIMS

The behaviour of gases produced by fission is of great importance for nuclear fuel operation. Within this context, an experimental method for the characterisation of the fission gas including gas bubbles in an irradiated UO₂ nuclear fuel was developed in our laboratory using SIMS, EPMA and SEM results. SIMS and EPMA have been used to measure the radial distribution of xenon and SEM gives information on bubble formation across the fuel pellet radius. Using SIMS, xenon concentration can be determined in the matrix and in the bubbles. A quantification method, allowing the determination of the total inventory of xenon, is proposed and qualified with EPMA results. It is concluded that the complementary micro-analytical techniques SIMS, EPMA and SEM are very powerful tools for the characterisation of the fission gas bubbles in irradiated nuclear fuel.     

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.     

Detection of Gas Bubble by SIMS in Irradiated Nuclear Fuel

The formation of gas bubbles is a key issue for nuclear fuel behaviour. The first measurements of xenon during a depth profile in irradiated nuclear fuel evidenced some peaks over a non-zero baseline. In comparison with EPMA mappings of xenon and SEM image of the sputtered surface, it is proven that the peaks correspond to bubbles while the baseline corresponds to xenon included in the UO₂ matrix.     

The Legacy of Raimond Castaing

 In April 1998 Raimond Castaing left the world of electrons, of ions and others particles, his wife and his family, his numerous students, for the world of stars. Raimond Castaing (Fig. 1) had a very strong personality. No one will forget their first meeting with him and all his students remember how brilliant he was as a teacher. A lot of anecdotes about his famous hot temper are still circulating among his friends and his former students. But in this paper, we would like to evoke Castaing’s memory through his achievements in Instrumental Physics, from the time of his doctoral thesis to later developments with his students, which were all centred on the imaging of the microstructures of materials and their quantitative chemical analysis.     

Characterisation of Screen-Printed Electrodes for Detection of Heavy Metals

 The characterisation of disposable screen-printed electrodes for stripping analysis is described. The graphite surface of the working electrode is used as substrate for plating a thin mercury film, which allows the electrochemical preconcentration of heavy metals. Optimisation procedures and experimental results are presented. Detection limits around the ppb level were obtained for different metals [Pb(II), Cd(II), Cu(II)]. Received June 6, 1998. Revision November 10, 1988.     

Determination of Selenium Species in Environmental Samples

 The essential nature of selenium as well as its toxicity depend on the concentration and the chemical forms in which this element is present in a given sample. Dissolved inorganic selenium can be found in natural water and soil as selenides, selenite and selenate. Organoselenium compounds present in air, soil and plants are volatile methylselenides, trimethylselenonium ion and several selenoamino acids. This review is a summary of recent research on the determination of selenium species in environmental samples such as water, air, soil and plants. Stability of selenium species in solutions and their storage is also discussed. In the metabolic pathway in the body selenide could act as the common intermediate for inorganic and organic Se sources as well as the checkpoint between further utilisation and excretion of selenium. Received May 30, 2001; accepted October 19, 2001; published online July 15, 2002     

Determination of Thiosemicarbazones by Means of the Induced Iodine-Azide Reaction

 The iodine-azide reaction induced by eight thiosemicarbazones was investigated. Inducing properties of thiosemicarbazones are different and depend on the parent carbonyl compound used for synthesis. The inductor coefficients of the examined thiosemicarbazones vary from 61 to 176. Optimum conditions for the determination of microamounts of thiosemicarbazones are given. The detection limit for the determination by the back-titration method depends on the inducing activity and is 0.9 μg for phenyl-thiosemicarbazones and 2 μg for diethyl-thiosemicarbazone in a 5-mL sample, and this corresponds to a concentration of 0.9 × 10⁻⁶ mol/L and , respectively. The automatic titration with the diluted iodine solution decreases the detection limit to about 50 ng in a 10-mL sample. Received October 28, 1998. Revision April 9, 1999.     

Determination of Amitraz Pesticide by Adsorptive Stripping Voltammetry on the Hanging Mercury Drop Electrode

 A sensitive method for the determination of amitraz pesticide at nanomolar level by adsorptive stripping voltammetry at a hanging mercury drop electrode is described. The cyclic voltammograms demonstrate the adsorption of this compound on the mercury electrode. A systematic study of the various experimental parameters, that affect the stripping response, was carried out by differential pulse voltammetry. Using an accumulation potential of −0.50 V, and 30 s accumulation time, the limit of detection was found to be 2.3 × 10⁻⁹ mol L⁻¹ and the relative standard deviations (n = 5) was 2.2% at concentration level of 5.0 × 10⁻⁸ mol L⁻¹ of amitraz. The influence of diverse ions and some other pesticides was investigated. Finally, the method was applied to the determination of amitraz in spiked soil and water. The relative standard deviation is 4.5% for 5 determinations of amitraz in water and 3.2% for 5 determinations in soil. Received December 6, 2000. Revision March 1, 2001.