共查询到20条相似文献,搜索用时 15 毫秒
1.
A homogeneous (phosphate glass) and a heterogeneous (glass ceramic) material were chosen to develop a method for electron
microprobe analysis of nitrogen in glasses and glass ceramics. The metaphosphate (50 mole-% P2O5, 25 mole-% BaO, 25 mole-% Rb2O) base glass and the silicate glass (composition of the base glass: 6.9 mole-% Al2O3, 21.3 mole-% MgO, 47.3 mole-% SiO2, 5.1 mole-% CaO, 19.4 mole-% AlN) were melted and cooled down to room temperature. In a second step, the two materials were
nitrided by applying dry NH3 in a special tube furnace. Up to 5 wt.-% of nitrogen could be introduced. The ability of energy dispersive (EDX) as well
as wavelength dispersive (WDX) electron probe microanalysis to analyze low contents of light elements in combination with
highly concentrated heavy elements was tested both for glasses and for glass ceramics. Measuring conditions had to be optimized
to get reliable analytical results as well as to avoid radiation damage of the glasses which may occur especially in the case
of wavelength dispersive X-ray analysis.
The results were compared with two different analytical methods: inductive coupled plasma analysis and a commercial nitrogen-oxygen-analyzer
(the specimen is decomposed by heating and the released gases are analyzed spectroscopically (O) and electrically (N)). 相似文献
2.
B. Raeymaekers M. Demuynck W. Dorrine F. Adams 《International journal of environmental analytical chemistry》2013,93(3-4):291-312
Abstract An automated electron microprobe was used to characterize more than 25000 fly ash particles with diameters between 1μm and 200μm, which were collected in two fractions from the stack of an oil fired power plant under two different burning conditions. Sample preparation procedures were developed to insure a quantitative particle transfer from the collection container to a Nuclepore filter and the automated localization of the carbonaceous particles in the backscattered electron image was optimized. Size distributions were measured and the results were interpreted in terms of the burning conditions of the power plant. 相似文献
3.
A set of procedures was developed for the electron probe X-ray microanalysis (EPMA) of fish and animal bone tissues, solid snow sediments, and coal ashes. Various sample-preparation procedures and two variants of the optimum conditions for analytical measurements were considered. In calculating analyte concentrations, matrix effects were taken into account using ZAF methods and the function of generated X-ray distribution with depth, namely, by the PAP method and by adding a joint correction for absorption and atomic number within a biexponential (z) model. For EPMA of small fractions 1–5 m in size, an approach was proposed that takes into account the test sample size using an analytical expression. In calculations of concentrations for micron-sized particles, this approach can lower the relative deviation from the stoichiometric composition from 36.8% to 22.2%. In developing the procedures, the potentialities of the proposed technique were assessed and its metrological characteristics were determined. 相似文献
4.
采用特制的Fe-Si、Fe-Mn合金系列标样,用电子探针测定了钢或铁基合金中低含量的Si和Mn元素、与用纯元素作标样、经ZAF修正的结果相比较,提高了分析准确度. 相似文献
5.
Francesc Salvat Xavier Llovet José M. Fernández-Varea Josep Sempau 《Mikrochimica acta》2006,155(1-2):67-74
Practical aspects of Monte Carlo simulation of EPMA experiments are considered. Simulations are performed using the general-purpose
Monte Carlo code system Penelope, which is briefly described. This code includes geometry tools and variance reduction methods that allow the practical simulation
of x-ray spectra from samples with complex geometries in moderate computing times. The reliability of simple interaction models
and approximations, which have been frequently used in EPMA studies, is analyzed by studying their effects on the simulated
x-ray spectra. 相似文献
6.
Four methods of correction and three methods of calculation of absorption coefficients are tested in electron probe microanalysis of rock-forming minerals. Experimental data by Pouchou and Pichoir, Sewell–Love–Scott, and Armstrong are attracted in tests. It is shown that the correction factor can be calculated with the error no more than 1 rel. % if a short-wave line (matrix effect is determined mainly by the effect of atomic number) is used as an analytical line or the analytical line belongs to the absorption K-edge of elements present in the sample. In the presence of binary matrix effect, when the analytical line absorbs in the K–L1 region, the situation is more complex and additional studies are required. 相似文献
7.
Experimental data on the generation and detection of characteristic X-radiation of elements in electron probe microanalysis of dielectric samples in the low vacuum mode without the deposition of conducting coatings are discussed. The main advantage of the considered method of analysis is the stability of the intensity ratio between diagnostic analyte lines in the wide range of currents of the electron probe and gas phase pressure in the chamber in the range 60–130 Pa, sufficient for obtaining undistorted images of the surface of dielectrics. The stability of the intensity ratio ensures obtaining correct data of the quantitative analysis of nonconducting samples without the deposition of conducting coatings. The main features of low-vacuum microanalysis for the range of gas phase pressures used are discussed, which can create additional difficulties in the study. Among such features is a possibility of the manifestation of reflexes of gas-phase elements, significant underestimation of the relative emission intensity from lighter elements in the composition of the studied samples, loss of scanning locality in the analysis of small sites on the sample surface. An example of the correct quantitative elemental analysis of a dielectric surface without the deposition of an electroconductive coating for a number of aluminosilicates is presented. 相似文献
8.
Frank Eggert 《Mikrochimica acta》2006,155(1-2):129-136
Standardless determination of absolutely calculated concentrations (P/B based) has been successfully applied for over a decade.
The PUzaf-method [1, 2] works without normalization to 100 per cent and without any information in addition to the spectrum,
apart from excitation conditions (E
0, geometry) and detector parameters. The simulation of EPMA spectra is simply the inverse procedure of this real standardless
spectra evaluation. The absolute calculation of P/B-ratios based on a fundamental parameter method and a reliable computation
of bremsstrahlung over the entire distribution of energies are the basis for the simulation. The accuracy of the data base
is crucial for the quality of a simulation [4]. The addition of detector effects and count-statistics are necessary to compute
the artificial spectra close to a real EDX data acquisition. 相似文献
9.
Marina Lulla Jelena Asari Jaan Aarik Kaupo Kukli Raul Rammula Unto Tapper Eero Kauppinen Väino Sammelselg 《Mikrochimica acta》2006,155(1-2):195-198
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating
samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage
and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed.
For comparison, Al2O3, Ta2O5 and TiO2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized
by atomic layer deposition method. 相似文献
10.
Theoretical models for Monte Carlo simulation of radiative processes, i.e. bremsstrahlung and characteristic x-ray emission, are presented. Possible strategies for simulating electron transport are briefly described. For mechanisms involving energy loss and angular deflections, difficulties for strict implementation of accurate numerical differential cross sections still remain due to the strong correlations between these variables. Practical solutions for the case of inelastic collisions and bremsstrahlung emission are described. Comparisons of simulation results with experimental data for several problems of interest in electron probe microanalysis are presented. 相似文献
11.
Ian Barkshire Peter Karduck Werner P. Rehbach Silvia Richter 《Mikrochimica acta》2000,132(2-4):113-128
Performing X-ray microanalysis at beam energies lower than those conventionally used (< 10 keV) is known to significantly
improve the spatial resolution for compositional analysis. However, the reduction in the beam energy which reduces the X-ray
interaction diameter also introduces analytical difficulties and constraints which can diminish the overall analytical performance.
This paper critically assesses the capabilities and limitations of performing low beam energy, high spatial resolution X-ray
microanalysis. The actual improvement in the spatial resolution and the reduction in the X-ray yield are explored as the beam
energy is reduced. The consequences for spectral interpretation, quantitative analysis and imaging due to the lower X-ray
yield and the increased occurrence of X-ray line overlaps are discussed in the context of currently available instrumentation. 相似文献
12.
The review is concerned with the present-day correction models used in electron probe x-ray microanalysis (EPXMA). A general approach to constructing models of the excitation distribution function along the target depth is described. Specific correction methods are considered in detail. 相似文献
13.
Bradley L. Thiel 《Mikrochimica acta》2006,155(1-2):39-44
A variety of gas cascade amplification and signal detection strategies have evolved for use in low vacuum and environmental
scanning electron microscopy on poorly conducting specimens. These detectors have been optimized to perform well under various
limitations on the range of gas pressure and working distance which may be imposed by experimental requirements. All of the
detectors must produce high gains, low backgrounds, and generate a sufficient positive ion flux to the specimen to enable
charge neutralization. The underlying principles of operation of each detector type are discussed, along with the range of
experimental conditions appropriate to each. 相似文献
14.
H. Schildknecht F. Enzmann K. Gessner K. Penzien F. Rmer O. Volkert 《Angewandte Chemie (International ed. in English)》1966,5(9):751-759
Organic compounds incubated with tritiated water of specific activity 5 Ci/ml are specifically fragmented. The β-active fragments can be detected in very small quantities by chromatographic separation. Chemical identification of these fragments provides information about the original compounds, as has been shown by experiments with amino acids, esters, lactones, amides, quinones, terpenes, nitrogen-sulfur heterocycles, and natural products. 相似文献
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17.
Scanning electron microscopy (SEM) is a powerful imaging technique able to obtain astonishing images of the micro- and the nano-world. Unfortunately, the technique has been limited to vacuum conditions for many years. In the last decades, the ability to introduce water vapor into the SEM chamber and still collect the electrons by the detector, combined with the temperature control of the sample, has enabled the study of ice at nanoscale. Astounding images of hexagonal ice crystals suddenly became real. Since these first images were produced, several studies have been focusing their interest on using SEM to study ice nucleation, morphology, thaw, etc. In this paper, we want to review the different investigations devoted to this goal that have been conducted in recent years in the literature and the kind of information, beyond images, that was obtained. We focus our attention on studies trying to clarify the mechanisms of ice nucleation and those devoted to the study of ice dynamics. We also discuss these findings to elucidate the present and future of SEM applied to this field. 相似文献
18.
Silvia Richter Matthias Bückins Anke Aretz Stepan Kyrsta Michael Spähn Joachim Mayer 《Mikrochimica acta》2004,145(1-4):187-192
Electron probe microanalysis (EPMA) offers high sensitivity and high accuracy in quantitative measurements of chemical compositions and mass coverages. Owing to the low detection limits of the wavelength-dispersive technique, monolayers with mass coverages of about 0.05µgcm–2 can be detected. Assuming a density of 5gcm–3 this corresponds to a thickness of 0.1nm. With these advantages in mind, EPMA was extended to depth profile analysis in the sub-micron range using a surface removal technique.The present paper shows how depth profile analysis can be improved by combining EPMA and the focused ion beam (FIB) technique. The focused ion beam system uses a Ga+ ion beam. The ion beam allows the milling of defined geometries on the nanometer scale, so that very shallow bevels with exactly defined angles in relation to the surface can be obtained. Low surface damage is expected due to low sputtering effects. Calibrated WDX measurements along the bevel deliver quantitative concentration depth profiles. First results obtained with this new combination of methods will be presented for a multilayered sample used in optical data storage. 相似文献
19.
A peak/ratio in pyrene-fluorescence spectrum was employed to measure the polarity of micro-environment of chitosan adsorb-ing py--rene molecules. The authors have in the first time detect-ed the pyrene-fluorescence spectrum of chitosan with different degrees of deacetylation (D. D. ), and found the relationship between the flocculaflon of bentonite colloid by chitosan and the peak/ratio values of different molecular weight (M. W. ) and D .D. of chitosan. We find that M.W. plays a key role in the flocculatlon, but D.D. has limited effect on it. From micro-en-vironmental structure of view, it can be proved that the inter-particle bridging rather than charge neutralization dominates the flocculatlon with chitosan. 相似文献