XRF induced by PIXE: Comparison with PIXE

Two different modes of sample excitation have been used for elemental analysis of thin standard reference materials and of chemical standards with known composition. PIXE /2.5 MeV protons/ and XRF induced by PIXE, will be called XRF-PIXE /2.5 MeV protons on Mo primary target/. The same samples were alternatively exposed to protons and X-ray beams. The sensitivities under standard running conditions are determined for both an XRF-PIXE and a PIXE analysis system. It is shown that the sensitivity of the PIXE spectrometer depends strongly on the sample matrix, whereas the XRF-PIXE sensitivity is rather constant with respect to different kinds of samples. In addition, the advantages of one mode of excitation on the other are discussed. It is shown that XRF-PIXE can be a useful complement to PIXE analysis.     

Zeolite analysis: PIXE,XRF or neutron activation

The determination of aluminium-to-silicon ratios in zeolites is of great benefit to catalyst technology and of general interest to mineralogists. However, such determinations tend to be open to error because of interferences that are due mainly to the juxtaposition of these elements in the Periodic Table. The capabilities of neutron activation, both with isotopic sources and accelerator based, of PIXE and of XRF were evaluated to establish which of these instrumental methods was best suited especially for routine on-line usage.     

PIXE and XRF elemental analysis of breakfast cereals consumed in Mexico

Elemental concentrations in breakfast cereals consumed in Mexico were measured using Particle induced X-ray emission with 1.7 MeV protons and X-ray fluorescence with a Rh X-ray tube operating at 35 kV. The specimens, obtained from packages purchased in markets, were freeze dried, ground and pelletized. Standardization was done with tomato, spinach, peach, and orchid leaves NIST standard reference materials, and analytical accuracy verified with NIST 3233 standard reference material (fortified cereal). The concentrations of nine elements did not agree with values quoted in the packages. Therefore, there may be inaccurate official estimations of Mexican population nutrient intakes.     

Etching of metallic glasses for destructive determination of depth concentration profile by the PIXE method

The destructive technique for the determination of the depth concentration profile in metallic glasses of composition B₂₀Fe_xNi_80–x (for x from 40 to 70) is presented. The etching technique with HNO₃ has been proposed for removing surface layers of the thickness from 1 to 12 m. In the residual surfaces the concentration of Fe and Ni has been determined by the PIXE method with 1.4 MeV⁴He⁺ ions of the JINR Van de Graaff accelerator. With an emphasis on the solution of matrix effects in Fe–Ni systems, empirical correction methods have been applied.     

Analysis of archaeological artefacts: PIXE, XRF or ICP-MS?

Elemental analysis of ancient artefacts is of considerable benefit to the field of Archaeology and of general interest to earth scientists. Several techniques are currently available for this purpose, and in this paper the capabilities of PIXE (Particle Induced X-ray Emission), XRF (X-ray Fluorescence) and ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) were evaluated to establish which of these instrumental methods was best suited especially for routine on-line usage. The elements of interest discussed in this paper are useful in archaeological provenance studies.     

Crystallization kinetics of metallic glasses

In this study, the temperature-heating rate diagram of the main crystallization process of two metallic glasses, Fe₇₄Ni_3.5Mo₃B₁₆Si_3.5 and Fe₄₁Ni₃₈Mo₃B_18, was obtained from one experimental differential scanning calorimetry (DSC) scan and the knowledge of their activation energy as determined by an isoconversional method. A good concordance was observed between the diagram curves obtained by calculation (isoconversional approach) and the experimental data, which verifies the reliability of the method and the validity of the kinetic approach in these alloys.     

ED XRF analysis of precious metallic alloys with the use of combined FP method

The “combined” FP method, which combines standardless FP method with empirical calibration, was applied to the analysis of Ir-Pt, Rh-Pt, Rh-Pd-Pt and Rh-Ir-Pt disk samples and Pt-Rh thermocouple wire. Four reference materials of binary Pt-Ir system, eight Pt-Rh systems, eight reference materials of ternary Pt-Ir-Rh system and 10 Pt-Rh-Pd systems were used for calibration of “combined” FP XRF method. Results of mentioned method agreed well with certified values, or ICP OES results respectively. For determination of elements, which were not present or certified in calibration standards (Ru in Rh-Pt-Pd disc and Fe in Pt-Rh thermocouple wire) the standardless FP method was used. This approach provides good results as well.     

PIXE analysis of allanites

Allanites from Telixtlahuaca (Oaxaca, Mexico) were analyzed using the PIXE technique. The concentrations of 12 elements, mainly rare earths, were determined.     

Structural instability of metallic glasses under radio-frequency-ultrasonic perturbation and its correlation with glass-to-crystal transition of less-stable metallic glasses

It has been reported that the structural stability is significantly deteriorated under radio-frequency-ultrasonic perturbation at relatively low temperatures, e.g., near/below the glass transition temperature T(g), even for thermally stable metallic glasses. Here, we consider an underlying mechanism of the ultrasound-induced instability, i.e., crystallization, of a glass structure to grasp the nature of the glass-to-liquid transition of metallic glasses. Mechanical spectroscopy analysis indicates that the instability is caused by atomic motions resonant with the dynamic ultrasonic-strain field, i.e., atomic jumps associated with the beta relaxation that is usually observed for low frequencies of the order of 1 Hz at temperatures far below T(g). Such atomic motions at temperatures lower than the so-called kinetic freezing temperature T(g) originate from relatively weakly bonded (and/or low-density) regions in a nanoscale inhomogeneous microstructure of glass, which can be straightforwardly inferred from a partially crystallized microstructure obtained by annealing of a Pd-based metallic glass just below T(g) under ultrasonic perturbation. According to this nanoscale inhomogeneity concept, we can reasonably understand an intriguing characteristic feature of less-stable metallic glasses (fabricated only by rapid melt quenching) that the crystallization precedes the glass transition upon standard heating but the glass transition is observable at extremely high rates. Namely, in such less-stable metallic glasses, atomic motions are considerably active at some local regions even below the kinetic freezing temperature. Thus, the glass-to-crystal transition of less-stable metallic glasses is, in part, explained with the present nanoscale inhomogeneity concept.     

Thermal evolution of ferromagnetic metallic glasses

A traditional TG apparatus was modified by placing two permanent magnets producing a controlled magnetic field (TG(M): Magneto Thermogravimetry). This technique proved to be useful to study both structural relaxation and crystallisation of ferromagnetic metallic glasses. Results obtained for the amorphous alloys Fe₄₀Ni₄₀P₁₄B₆ and Fe_62.5Co₆Ni_7.5Zr₆Nb₂Cu₁B₁₅, are reported in this paper. Structural relaxation can be evaluated by measuring changes in Curie temperature induced by thermal treatments. Crystallisation in TG(M) is detected through a change in the measured apparent mass (difference between the sample mass and magnetic force driving it upward). These results were confirmed by DSC analysis. Whether the obtained crystalline phase is ferromagnetic, it can be identified through its Curie temperature, measured by TG(M). In fact the value of 770°C measured as Curie temperature of crystallised Fe_62.5Co₆Ni_7.5Zr₆Nb₂Cu₁B₁₅led to conclude that the only ferromagnetic crystalline phase is a-Fe. These hypothesis was confirmed by XRD analysis, showing that the first crystallisation yields to a-Fe nanocrystals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Application of XRF and field portable XRF for environmental analysis

The aim of the present review is to evaluate, on the basis of published papers, the real potential of XRF technique for environmental analysis. Special attention is given for the determination of heavy metal pollution in water. Results of numerous papers for various samples are presented. Some details of the technique and preconcentration methods employed are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Use of INAA, PIXE and XRF in Homogeneity Testing of New IAEA Reference Air Filters

About 250 sets of polycarbonate (Nuclepore, Costar) membrane filters loaded with two urban air particulate matter (APM) obtained in Vienna and Prague were prepared by filtration of a watter suspension of the above APM materials. The homogeneity of both bulk APM materials and the loaded filters was tested by determining a number of elements by instrumental neutron activation analysis (INAA), proton induced X-ray emission (PIXE) and micro-X-ray fluorescence (-XRF). Relative standard deviations due to inhomogeneity (s _inh ) were below 3% for many elements in the bulk APM materials. In the loaded filters, the s _inh values increased significantly. Nevertheless, for up to 20 elements important in air pollution studies the s _inh values were below 15%, allowing target values with a reasonably low uncertainties (up to 20%) to be derived for the future use of the filters in proficiency testing of laboratories involved in air pollution monitoring.     

Flow and fracture in Zr-based bulk metallic glasses

Effects of atomic-scale open-volume regions in metallic glass structure on the flow and fracture behavior of a Zr-Ti-Ni-Cu-Be bulk metallic glass were examined. Metallic glass structure was changed by annealing at 300 °C. Studies of relaxation time scales showed that atomic arrangement processes for viscous flow were significantly retarded with annealing. Plane strain fracture toughness was significantly decreased and fatigue crack-growth rates were dramatically increased, indicating degradation of resistance to crack extension as a result of annealing. Fracture morphology completely changed from vein patterns to cleavage-like features with little evidence of plasticity with annealing. The positron lifetime and Doppler broadening experiments revealed decreased open-volume regions as a result of annealing. The observed variation of the viscoelastic relaxation time scales with annealing was well described in terms of the anneal-out of open-volume regions. The current metallic glass was found to posses a low fractional free volume of the order of 0.1% indicating dense-packed structure which contributes to the excellent glass forming ability. The loss of stress relief ability by retarded crack tip viscous flow as a result of the anneal-out of open-volume regions is believed to contribute to subsequent embrittlement.     

The role of trace metallic elements in neurodegenerative disorders: quantitative analysis using XRF and XANES spectroscopy.

The present paper focuses on the analysis of trace metallic elements and their role in neurodegenerative disorders. The use of synchrotron radiation microbeams allows investigation of pathological tissues from Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis cases in a nondestructive manner and at cellular level. By employing X-ray absorption near edge structure (XANES) technique, the chemical state of the investigated elements can be determined, while energy-selective X-ray fluorescence spectroscopy provides the spatial distribution of each element in each oxidative state selectively. The investigated tissues (derived from human, monkey and mouse specimens) show distinct imbalances of metallic elements such as Zn and Cu as well as Fe(2+)/Fe(3+) redox pair, which point to oxidative stress as a crucial factor in the development or progress of these neurodegenerative diseases.     

Calorimetric measurement of structural relaxation in chalcogenide and metallic glasses

Some special characteristics of the structural relaxation (SR) in chalcogenide and metallic glasses are presented and the current theories dealing with the physical nature of the SR are recalled. The type of experiments used to measure SR by differential scanning calorimetry are reviewed and some rules to be taken into account when measuring calorimetrically the SR are stressed.

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Zusammenfassung Es werden einige spezielle Charakteristiken der Strukturrelaxation (SR) von Chalkogeniden und Metallgläsern vorgestellt und die gegenwärtigen Theorien über die physikalische Natur der SR zitiert. Die Art von Experimenten zur Messung von SR mittels DSC wurden kritisch besprochen und einige inbetrachtzuziehende Regeln für die kalorimetrische Bestimmung der SR hervorgehoben.

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This work was supported by the Comisión Interministerial de Ciencia y Tecnología (CICYT) project MAT88-0439.     

Study of kinetics of glass transition of metallic glasses

In this study, the kinetics of glass transitions of Ti₅₀Cu₂₀Ni₃₀ and Fe₆₇Co₁₈B₁₄Si₁ metallic glasses are studied using thermal analysis technique, i.e., differential scanning calorimetry, by means of continuous heating of the sample at various heating rates. In the present study, based on the heating rate dependence of glass transition temperature (T _g), the activation energy (E) of the glass transition region is determined by two most frequently used approaches, i.e., Moynihan's method and Kissinger's equation. The fragility index, m, is also calculated using T _g, which is a measure of glass-forming ability of the given system. The result shows that the fragility index, m, of the given systems is <16. This indicates that the given systems are strong liquids with excellent glass-forming ability.     

Evaluation of the elastic properties of bulk metallic glasses

The development of bulk metallic glasses as a prominent class of functional and structural materials has attracted considerable interest in the last years. One of the fundamental physical quantities necessary to describe the mechanical properties of the materials is the bulk modulus. In the present article, a simple method to estimate the bulk modulus and its pressure derivative is proposed. It is shown that these quantities can be estimated from the values of the constituent elements and their compositions. Comparison with measured data shows good agreement. The physical background of the method is discussed based on the jellium model of metals.     

Trace analysis of lithium metal by PIXE

A rapid method is described for simultaneous trace determination of metallic impurities in lithium metal by Particle Induced X-ray Emission (PIXE) technique. The impurities were preconcentrated by ion-exchange separation using a weak cation exchanger, Bio Rex-70 and analyzed by 2.34 MeV protons. The reliability of the method was tested by analyzing synthetic samples having several metallic impurities at 1–5 ppm range.