Characteristic X-ray Analysis Research Articles

Characteristic X-ray study over a hoard of bracelets from Vânători

The article is dedicated to the characteristic X-ray analysis of a hoard composed of eight bracelets discovered in an Early Iron Age context at the Vânători site. In order to obtain a complete view over the bracelets, Particle Induced X-ray Emission and Energy Dispersive X-Ray Fluorescence tests were performed. The goal was to obtain the main composing elements as well as trace elements in an effort to identify the type of alloy.

Non-destructive elemental analysis of a carbonaceous chondrite with direct current Muon beam at MuSIC

Electron- or X-ray-induced characteristic X-ray analysis has been widely used to determine chemical compositions of materials in vast research fields. In recent years, analysis of characteristic X-rays from muonic atoms, in which a muon is captured, has attracted attention because both a muon beam and a muon-induced characteristic X-ray have high transmission abilities. Here we report the first non-destructive elemental analysis of a carbonaceous chondrite using one of the world-leading intense direct current muon beam source (MuSIC; MUon Science Innovative Channel). We successfully detected characteristic muonic X-rays of Mg, Si, Fe, O, S and C from Jbilet Winselwan CM chondrite, of which carbon content is about 2 wt%, and the obtained elemental abundance pattern was consistent with that of CM chondrites. Because of its high sensitivity to carbon, non-destructive elemental analysis with a muon beam can be a novel powerful tool to characterize future retuned samples from carbonaceous asteroids.

Quantitative Characteristic X-Ray Analysis for Different Compound Samples by Using Monte Carlo Method

Quantitative Characteristic X-Ray Analysis for Different Compound Samples by Using Monte Carlo Method

Quantitative Characteristic X-Ray Analysis for Different Compound Samples by Using Monte Carlo Method

Quantitative Characteristic X-Ray Analysis for Different Compound Samples by Using Monte Carlo Method

Uranium aerosols at a nuclear fuel fabrication plant: Characterization using scanning electron microscopy and energy dispersive X-ray spectroscopy

Detailed aerosol knowledge is essential in numerous applications, including risk assessment in nuclear industry. Cascade impactor sampling of uranium aerosols in the breathing zone of nuclear operators was carried out at a nuclear fuel fabrication plant. Collected aerosols were evaluated using scanning electron microscopy and energy dispersive X-ray spectroscopy. Imaging revealed remarkable variations in aerosol morphology at the different workshops, and a presence of very large particles (up to≅100×50μm2) in the operator breathing zone. Characteristic X-ray analysis showed varying uranium weight percentages of aerosols and, frequently, traces of nitrogen, fluorine and iron. The analysis method, in combination with cascade impactor sampling, can be a powerful tool for characterization of aerosols. The uranium aerosol source term for risk assessment in nuclear fuel fabrication appears to be highly complex.

Formation of periodic patterns in the (Ni,W)/Al diffusion couples

Formation of periodic patterns was observed in the (Ni,W)/Al finite diffusion couples after annealing at 600 °C. The individual layers in the patterns grew parallel to the original interface between the counterparts of the diffusion couples. A combination of the scanning electron microscopy, energy dispersive analysis of characteristic X-rays and X-ray diffraction revealed that the periodic patterns consisted of Al 4W/Al 5W layers, which were embedded either in the Al 3Ni or in the Al 3Ni 2 matrix depending on the local Al concentration. The Al 3Ni matrix developed in the Al-rich part of the sample, the Al 3Ni 2 matrix in the (Ni,W)-rich part of the sample. The microstructure analysis was accompanied by nanoindentation experiments that were performed in selected phases, which developed in the samples. The kinetic of the formation of the periodic patterns was investigated with the aid of diffusion couples that were annealed for 1, 3, 6 and 24 h. It was confirmed that the formation of the periodic patterns in the (Ni,W)/Al diffusion couples at 600 °C is a diffusion-controlled process. A model was suggested to describe this process and compared with existing models from literature.

Electrochemical oxidation of WC in acidic sulphate solution

The electrochemical oxidation of WC in aqueous solutions is critical for the functional stability of hardmetals in aggressive environments. The oxidation of WC and the nature of the oxides formed in 0.1 M sulphuric acid under electrochemical polarisation have been studied by electrochemical methods (cyclic voltammetry, chronoamperometry). The structure and composition of the electrochemically treated surfaces has been analysed by X-ray diffraction, surface Raman spectroscopy and energy dispersive analysis of characteristic X-rays. The morphology of the attacked surfaces was investigated by scanning electron microscopy. Anodic attack gives rise to hydrous WO 3 forming a continuous film which tends to develop pits. Alternated anodic and cathodic polarisation yields a very similar composition, but with a lower degree of hydration. The morphology is characterised by micrometric loose grains forming by disruption of the larger grains of the pristine sintered WC surface. The electrochemical conditions giving rise to the inception of WO 3 formation by WC oxidation could be accurately identified by monitoring the inception of the development of the cathodic loop corresponding to the electrochemical behaviour of the electrochromic material.

X-ray spectral simulation and experimental detection of phosphorus segregation to grain boundaries in the presence of molybdenum

A fundamental limitation of X-ray energy-dispersive (EDS) spectrometry is the detection and quantitative analysis of characteristic X-rays from one element, in the presence of an overlapping peak from another element. This problem is particularly acute when the unambiguous detection of one element is crucial to ensuring the mechanical performance of the material, such as the presence of an embrittling species. This paper addresses the specific problem of defining the conditions of specimen composition and thickness under which phosphorus can be detected in the presence of molybdenum, since the Mo L l and the P K α elemental peaks are separated by 2 eV. This separation is significantly below the resolution limit of X-ray spectrometry in the electron microscope. Simulations of the X-ray spectra from low-alloy steels have been performed via Desk-Top Spectrum Analyzer and compared with experimental measurements on a field-emission gun VG HB 603 dedicated scanning transmission electron microscope.

Application of the electron-counting method to low-Z elemental analysis

We applied the electron counting method, in low-density gas, for ultra-soft X-ray spectroscopy. The method is based on the spatial expansion of photon-induced ionization electron clusters, and the recording of pulse trails formed by individual electron avalanches in a fast multiplication element. A detector, operating at room temperature with low gas pressure, was characterized with Particle-Induced X-ray Emission (PIXE) and with electron-induced X-ray emission in a Scanning Electron Microscope (SEM). High detection efficiency for soft X-rays is obtained due to the very thin polymer window between the detector and the radiation source. The low-density detector is blind to Bremsstrahlung and charged-particle background. We present the results of the spectral analysis of characteristic X-rays emitted from low-Z elements, in the energy range 100–1500 eV. The recorded X-ray spectra, using both the information of the number of counted electrons and the length of the electron pulse trail, are unfolded with the help of a computer simulation of the detector response to X-ray photons. This detailed simulation of the electron detection and counting process provides an efficient means for a quantitative spectral analysis and permits the precise reconstruction of complex energy spectra.

Fabrication of a Beryllium Window Sealed with an Au Gasket for Analysis of Characteristic X-Rays from Surface

A window through which X-rays exit from a vacuum chamber into the atmosphere was fabricated from thin Be foil, using a ring of thin Au wire as a gasket for sealing.

Kinetics of the Oxidation and Reduction of Synthetic Ilmenite.

The kinetics of the oxidation and reduction of synthetic ilmenite was studied thermogravimetrically in the light of kinetic theory for heterogeneous noncatalytic reactions. It was found that the oxidation and reduction proceeded topochemically and their kinetic parameters were determined according to the unreacted core shrinking model. The mineral composition of the partially oxidized and/or reduced ilmenite was examined by means of characteristic X-ray analysis, the results of which showed that there were two phases in the oxidized ilmenite which separated each other. One of them was rich in titanium and the other was rich in iron. There were two phases too separating completely in the reduced ilmenite, one of which was the metallic phase consisting of almost pure iron and the other was an oxide phase mainly composed of titanium dioxides. The composition of the titanium-rich phase in the oxidized ilmenite was between the composition of Fe2O3·TiO2 and that of Fe2O3·3TiO2.

Multiple collision analysis of characteristic X-rays from 50 to 600 keV argon stopping in Mg, Al, and Si

Target K-shell ionization and Ar-ion L X-ray production cross sections were measured in order to determine the Ar L-vacancy lifetime and fluorescence yield in solid Mg, Al, and Si. The analysis is based on steady-state equilibrium of the L vacancies produced by Sdδ +−3dπ +−3dσ rotational coupling in the collision quasimolecule, followed by transfer of the vacancy to a target-atom K shell via 2pπ +−2pσ rotational coupling in a second collision. The results are compared with model expectations.

The observation of cristobalite formed on the oxidized layer of silicon nitride by EPMA

Hot-pressed silicon nitride test bars were oxidized in air flow at 1200°C for 480h. The observations by composition and topography image of SEM indicate that cristobalite crystals of 1-4μm are formed (appears as black spots) and cracks run in all directions all over the oxidized surface, and Y2O3⋅2SiO2 crystals are clearly convex and the SEM image of cristobalites indicate that they are concave to the surface and this aspect is correspond to the COMPO image. The concentration of Al in the glass phase on the grain boundary is presumed to be high from the characteristic X-ray analysis. EDS analysis showed that a large amount of SiO2 and a small amount of alkali were found in the cristobalite phase and a large amount of Fe2O3, CaO and K2O are dissolved in the glass phase.

The Observation of Cristobalite Formed on the Oxidized Layer of Silicon Nitride by EPMA

Hot-pressed silicon nitride test bars were oxidized in air flow at 1200°C for 480h. The observations by composition and topography image of SEM indicate that cristobalite crystals of 1-4μm are formed (appears as black spots) and cracks run in all directions all over the oxidized surface, and Y2O3⋅2SiO2 crystals are clearly convex and the SEM image of cristobalites indicate that they are concave to the surface and this aspect is correspond to the COMPO image. The concentration of Al in the glass phase on the grain boundary is presumed to be high from the characteristic X-ray analysis. EDS analysis showed that a large amount of SiO2 and a small amount of alkali were found in the cristobalite phase and a large amount of Fe2O3, CaO and K2O are dissolved in the glass phase.

Analytical and structural analysis of the lanthanum-deficient lanthanum hexaboride

The blue lanthanum boride LaB/sub 6+delta/ previously reported as LaB/sub 9/, was investigated in arc-melted samples of LaB/sub 9/ bulk stoichiometry. The samples were structurally analyzed by high-resolution transmission electron microscopy including comparative computer imaging and analytically studied by using backscattered electron imaging, quantitative characteristic x-ray analysis, nuclear magnetic resonance, and other techniques. The blue boride observed has a composition of LaB/sub 6.13 +- 0.03/ due to random La vacancies in the LaB/sub 6/ structure and is interpreted as belonging to the nonstoichiometric LaB/sub 6/ phase region. The color change from purple to blue occurs for decreasing lanthanum content roughly at a composition LaB/sub 6/ /sub 07/. A modification of the La-B phase diagram is proposed.

Multiple-collision analysis of characteristic X-rays from low-energy Ar 2+ travelling in solid targets

The density of atoms in a solid target fosters a multiple-collision mechanism that leads to the production of an equilibrium fraction of L-shell vacancies in an incident heavy ion. It is then possiblein a subsequent ion-atom collision in the solid for an L-vacancy to be transferred to the K-shell of a target atom via rotational coupling of the 2p π−2p σ molecular orbitals formed in the ion-atom quasimolecule. The vacancy-transfer cross section and the equilibrium fraction and lifetime of the vacancies can be found by using an appropriate multiple-collision analysis of the characteristic target and projectile X-rays. Results will be presented for 160–380 keV Ar 2+ incident of targets of Mg, Al, and Si.

Out-reactor nodular corrosion behaviour of zircaloys

The effect of sputtered films of Nichrome, stainless steels and platinum on the oxidation behaviour of Zircaloy-2 and Zircaloy-4 in steam at 773 K and 10.5 MPa was investigated. The occurrence of nodular type accelerated oxidation, normally observed with regular uncoated samples, was reduced drastically in the case of sputter coated samples. The effect of sputtered films was similar to pre-oxidizing the alloy at < 773 K to form a black adherent oxide 2 to 3 μm in thickness. The formation of nodules is, however, not completely eliminated by either the sputtered films or the pre-oxidation. Characteristic X-ray analysis of nodules on uncoated samples revealed that the second phase intermetallic precipitates in the bulk of the growing oxide are sites of nodule nucleation. It is proposed that hydrogen produced at these sites leads to stress generation and cracking of the protective oxide. The localized rapid oxidation accompanying the cracking forms the nodules.

Proton-induced characteristic x-ray analysis of Na and Cl impurity atoms in SiO2 thin films

Analysis of SiO2:Si and Au:SiO2:Si thin-film systems using proton-induced characteristic x rays (PIX) indicates that small quantities (≥1014/cm2) of Na and Cl atoms may be detected in SiO2 films even in the presence of strong O(K), Si(K), and/or Au(M) x-ray outputs. Distributions of implanted Na and contaminant Cl atoms were found to be stable during PIX analysis and for very high proton fluences. In contrast, heavy-ion Ne+ bombardment caused movement of Na and Cl within the oxide. Finally, PIX analysis of 50-keV Ar+ sputtering in Au:SiO2:Si shows that sputter profiling is complicated by strong ion-beam-induced intermixing of Au with SiO2 and of Au with Si.

An ultrahigh vacuum system for ion-induced characteristic X-ray analysis

Abstract This paper describes a new ultrahigh vacuum system designed and constructed primarily for ion-induced characteristic X-ray studies. Details of the following four special features of interest are described: (1) an ultrahigh vacuum beam line system; (2) a multi-purpose scattering chamber; (3) a windowless Si(Li) X-ray detector scheme; and (4) a target manipulator for ion beam experiments with in situ heating and cooling over the range from approximately 1200°C down to 110 K.

Electron Microscopy in Materials Science

The materials scientist is concerned with relating microstructure and properties. In crystals, most of the important imperfections can only be observed by transmission through thin foils (T.E.M.), first accomplished by Heidenreich in 1949. The truly amazing growth of T.E.M. is due mainly to three factors: a) improvements in microscopes, b) techniques for foil preparation, c) interpretation of images using electron diffraction contrast theory. Almost all of T.E.M. has developed since 1955 as a result of the above factors.The following is a listing of some of the applications of Electron Microscopy.a) Observation and identification of lattice defects (dislocations, faults, small defect clusters, etc.).b) Crystallographic data from electron diffraction.c) Surface investigations, replication, reflection and scanning microscopy; fractography.d) Qualitative chemical analysis of characteristic x-rays emitted by the foil.e) Energy analyses for contrast and for identifying elements (by scanning microscopy also).f) In situ investigations of crystal growth, epitaxy.g) Examination of specimens at different temperatures; deformation, bombardment in situ.