共查询到20条相似文献,搜索用时 15 毫秒
1.
Frank Scholze Burkhard Beckhoff Michael Kolbe Michael Krumrey Matthias Müller Gerhard Ulm 《Mikrochimica acta》2006,155(1-2):275-278
Energy-dispersive X-ray spectrometry offers the opportunity for a fast and reliable determination of the composition of a
specimen. For fundamental parameter based quantification, detailed knowledge of the X-ray generation cross sections and of
the detection system’s efficiency is required. The detection efficiency is determined comparing the measured and calculated
spectrum of undispersed synchrotron radiation (SR) from the electron storage ring BESSY II in the spectral range from 0.1 keV
to 100 keV. Alternatively, monochromatized SR in the spectral range from 0.1 keV to 60 keV is used to determine the detection
efficiency with a typical relative uncertainty of 1% to 2% by direct comparison with a reference detector. Employing well-calibrated
detectors and monochromatized SR of well-known radiant power and high spectral purity, fluorescence yields have been investigated
and resonant Raman scattering was studied as an example of a basic effect creating spectral background. 相似文献
2.
β-sialon ceramics sintered with yttria additives have been studied with the use of an electron probe X-ray analysis (EPMA).
Sialon ceramics were prepared from a carbothermally derived β-sialon powder and then sintered in a nitrogen atmosphere with
yttria admixture. The above process was followed by annealing in flowing nitrogen. Scanning electron microscope (SEM) observations
have shown that the sintered material contains a glassy phase (Y-Si-Al-O-N) on the grain boundaries. X-ray diffraction (XRD)
after annealing in nitrogen revealed the presence of a considerable amount of yttrium aluminium garnet (YAG). The higher voltage
of 30 kV was used in order to excite the yttrium Kα radiation (14.96 keV) at an appropriate overvoltage ratio because in some phases of the material, the disappearance of the
yttrium Lα line has been observed during EPMA examination at an accelerating voltage of 15 kV in energy dispersive spectra (EDS). The
intensity of the yttrium Kα line was sufficiently high, while the Y Lα line was not seen in the ED spectrum. Because the position of the yttrium Lα line (1.922 keV) is very close to the Si (K) absorption edge (1.84 keV), the strong absorption at this edge is probably responsible
for the effect. This result should be considered as a serious warning in the case of EPMA (EDS) studies on compounds or mixtures
suspected to contain both silicon and yttrium, because at electrons energies lower than 15 keV, the presence of yttrium in
materials can go unnoticed. In wavelength dispersive spectra (WDS) obtained at 15 keV the intensity of the yttrium Lα line was also very low but measurable. 相似文献
3.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
4.
Various K-, L- and M-shell X-ray production cross sections are measured for heavy ion impact on elements in the range Z
2 = 13 to 83. The ion species range from Z
1 = 10 to 36, and ion energies from 1 to 16 MeV are used. Enhanced cross sections are observed when the projectile K- or L-
binding energy is similar to the energy of the target K-, L- or M-shell. This effect is used to improve the analysis sensitivity
for selected elements. As an example trace analysis of Fe in glass with V, Mn, Co and Ni ions is investigated. Results are
compared with proton induced X-ray emission analysis on the same samples. In these samples Fe-Kα X-ray production is similar for irradiation with 3 MeV protons and 14 MeV Ni ions. However the signal to background ratio
is four times higher for the irradiation with Ni ions as compared to irradiation with protons. Advantages and drawbacks of
heavy ion induced X-ray emission for quantitative analysis compared to proton induced X-ray emission analysis are discussed. 相似文献
5.
Gloria Vaggelli Alessandro Borghi Roberto Cossio Mariaelena Fedi Lorenzo Giuntini Bruno Lombardo Aldo Marino Mirko Massi Filippo Olmi Maurizio Petrelli 《Mikrochimica acta》2006,155(1-2):305-311
Quantitative micro-PIXE and electron microprobe analyses, as well as micro-PIXE compositional mapping of trace elements were
performed on monazite [(Ce, La, Nd, Th)PO4] inclusions in pyrope megablasts from Dora Maira Massif, Western Italian Alps for petrological and geochronological purposes.
Monazite was studied by SEM-BSE imaging and by X-ray qualitative compositional maps of major elements; further WDS electron
microprobe analyses were carried out in areas showing different BSE intensity in order to quantify chemical zoning. Finally,
micro-PIXE compositional maps and quantitative analyses were performed on selected spots and areas. EPMA data indicate that
the Dora Maira monazite is Ce- and Th-rich with homogeneous concentrations of LREE, but with a significantly heterogeneous
distribution of Th, as well as of Y, Sr, U and Pb as displayed by micro-PIXE compositional mapping. HREE mostly occur in concentrations
below the detection limit for standard quantitative EPMA. Th–U–Pb zoning suggests two monazite growth events, dated at 35
(±7 Ma) and 60 Ma (±10 Ma), respectively. While the younger age of 35 Ma found in high-Th monazite areas corresponds to the
thermal and baric peak of the UHP metamorphism in the Dora Maira Massif, in agreement with previous literature data, the older
ages of 60 Ma found in low-Th areas have to be confirmed by U–Th–Pb isotopic data. 相似文献
6.
The 24Mg(α, p)27 Al nuclear reaction was applied for the determination of the magnesium distribution in near-surface layers of materials.
The cross sections of this reaction were determined in the energy region between 4.5 and 5.5 MeV in steps of 5 to 10 KeV (θlab : 158°) using thin magnesium films. The investigated projectile energy region included five main resonances allowing the
determination of magnesium. The uncertainty of the cross-section determination was of the order of 7%. The applicability of
the technique was tested using Mg-implanted AISI 321 steel samples. Depth resolution of 100 nm and detection limits of the
order of 0.1 ppm were achieved for the determination of magnesium in steel samples using the 4805 keV resonance of the 24Mg(α, p)27 Al nuclear reaction. The shape and height of the magnesium depth-profile in the Mg-implanted steel samples were compared
with corresponding values obtained by X-ray photoelectron spectroscopy.
Received July 15, 1999. Revision March 30, 2000. 相似文献
7.
Cabal Rodríguez AE Leyva Pernía D Schalm O Van Espen PJ 《Analytical and bioanalytical chemistry》2012,402(4):1471-1480
X-ray radiographic images of paintings often show little or no contrast. In order to increase the contrast in radiographic
images we measured the X-ray spectrum of a low power X-ray tube, after passing through the painting, with a high energy-resolution
SDD detector. To obtain images, the detector is collimated with a 400 μm diameter pinhole and the painting was moved through
the beam in the x and y-direction using a dwell time of a few seconds per pixel. The data obtained consists of a data cube of, typically, 200 × 200
pixels and a 512-channel X-ray spectrum for each pixel, spanning the energy range from 0 to 40 keV. Having the absorbance
spectrum available for each pixel, we are able, a posteriori, to produce images by edge subtraction for any given element.
In this way high contrast, element-specific, images can be obtained. Because of the high energy-resolution a much simpler
edge subtraction algorithm can be applied. We also used principal-component imaging to obtain, in a more automated way, images
with high contrast. Some of these images can easily be attributed to specific elements. It turns out that preprocessing of
the spectral data is crucial for the success of the multivariate image processing. 相似文献
8.
There are particular benefits in spectrum simulation for the interpretation of characteristic X-ray peaks below about 2 keV
in energy, where peak overlaps, a sloping background and changing detector efficiency make it difficult to measure true peak
intensities. Despite these difficulties, we have shown that a useful accuracy of simulation is possible without major revision
of the existing theory, allowing the electron microprobe user to compare on-line a measured spectrum with one synthesised
from an assumed sample composition.
As part of a wider study, we have used a database of X-ray spectra from 150 samples of known composition to confirm the accuracy
of simulation over the energy range from 0.28–1.9 keV, finding an RMS error of better than 8%. The database included 181 Kα,
Lα and Mα peaks from elements of atomic number 6–77, excited by beam voltages from 5–30 kV. Central to the method is the use
of the ratio of (Peak Intensity)/(Total Background Intensity), which allows spectra to be compared from instruments of differing
collection efficiency, thereby easing the collection of data over a wide range of conditions.
Examples are given to illustrate the use of the simulator in helping to choose the best conditions for analysis, and as an
aid in interpreting the spectra so obtained. Both modes of operation are iterative in nature and require a fast and accurate
simulator that is easy to use. Further development will be guided by experience in its use. 相似文献
9.
Guan-Ping Jin Li-Li Chen Guo-Pei Hang Shan-Zhong Yang Xiao-Jing Wu 《Journal of Solid State Electrochemistry》2010,14(7):1163-1169
Silver nanoparticles coat polyquercetin (Qu) and multi-walled carbon nanotube (MWCNT) complex films were prepared using an
electrochemical coupling strategy on platinum electrode (Ag/Qu/MWCNT/Ch/Pt). The new composite material was characterized
by means of field emission scanning electron microscopy, X-ray photoelectron spectroscopy spectra, X-ray diffraction, and
electrochemical techniques, which confirmed that polyquercetin plays an important role to obtain a great deal of uniformly
dispersed silver nanoparticles and MWCNT complex film with a diameter of 10 ± 6 nm. The resulting Ag/Qu/MWCNT/Ch/Pt electrode
shows a significant electrocatalysis for the redox of cysteine (CysH). The stripping chronopotentiometric analysis of CysH
has been successfully used with a satisfying effect. A linear range of 1 × 10−10 to 9 × 10−8 M was obtained with a detection limit of 3 × 10−11 M (3σ) and sensitivity of 35 μA/nM. The films were also robust, surviving up to 100 consecutive cyclic voltammograms and
sonication. 相似文献
10.
Tadeusz Błaszczyk Danuta Kaźmierczak Pawel Krzyczmonik Henryk Scholl Krzysztof Polański 《Journal of Solid State Electrochemistry》2000,4(2):95-106
The oxidation of cobalt electrodes has been carried out by means of cyclic voltammetry and coulometry under controlled potential
in sulfuric acid solutions of different concentrations. The electrochemical scanning tunneling microscope/scanning tunneling
microscope (ECSTM/STM) systems constructed by the authors and scanning electron microscopy (SEM) with the SEM-EDX system of
surface analysis of the elements have been used. The procedure applied in this work made it possible to observe the fragments
of the same surface by means of SEM and ECSTM/STM. The most typical images for a polycrystalline Co electrode with a ±10%
accuracy at the scales of 4800 nm × 4800 nm and 100 nm × 100 nm are presented and the results are discussed. In a diluted
electrolyte (0.1 M), irregular forms of a stable cobalt oxide with Co:O ratio ∼1:1 appear. Unreproducible results have been
obtained in a 1.0 M H2SO4 solution. Compact and relatively regular layers of cobalt oxide of the same ratio have been obtained in 0.1 M H2SO4, as well as in 10.0 M sulfuric acid solution, under controlled oxidation potential at the passivation range.
Received: 6 January 1999 / Accepted: 5 May 1999 相似文献
11.
Aigars Vītiņš Ģirts Vītiņš Jānis Krastiņš Ints Šteins Ilmārs Zālīte Andrejs Lūsis 《Journal of Solid State Electrochemistry》1998,2(5):299-307
Ceramic specimens have been obtained from the powder of ZrO2-7.5 mol% Y2O3 having a specific surface area of 30 m2/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare
so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties.
The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm3. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency
range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the temperature
range 200–850 °C in heating and cooling cycles. The intragrain, the grain boundary and the total bulk conductivities, the
electrode polarization resistance and their activation energies were determined. The thermal stability of the studied system
was proved in three measurement series up to 600–850 °C in heating and cooling cycles. The results obtained have shown that
the conductivity of ZrO2-7.5 mol% Y2O3 ceramics is not solely a function of temperature, but also depends on the previous thermal state of the ceramics.
Received: 16 October 1997 / Accepted: 19 January 1998 相似文献
12.
Soft X-ray spectromicroscopy on solid-stabilized emulsions 总被引:2,自引:0,他引:2
Oil–water emulsions stabilized by solids have been imaged with sub-100 nm spatial resolution and analyzed spectroscopically
using a scanning transmission X-ray microscope. The emulsions are stabilized by particle heterocoagulate cages surrounding
the oil droplets. These cages form due to the interaction of negatively charged clay mineral particles (sodium montmorillonite,
Wyoming) and positively charged particles of calcium/aluminum layered double hydroxide (LDH). The emulsions were studied at
atmospheric pressure, without any pretreatment using carbon K and calcium L X-ray absorption edges. Oil- and calcium-rich LDH were separately mapped, and the clay mineral dispersions were also imaged.
Applying X-ray absorption-edge contrast, oil could be distinguished from water in the emulsion near the carbon K absorption edge (284 eV, 4.4 nm). Spectromicroscopy near the calcium L absorption edge (346 eV, 3.6 nm) allowed the structural details of heterocoagulate formation to be revealed.
Received: 11 December 1998 Accepted in revised form: 10 January 1999 相似文献
13.
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
14.
Soledad García Concepción Sánchez-Pedreño Isabel Albero Concepción García 《Mikrochimica acta》2001,136(1-2):67-71
Two flow injection (FI) spectrophotometric methods are proposed for the determination of diclofenac (DCF) or mefenamic acid
(MF) in bulk samples and pharmaceuticals. Both methods are based on the reaction of DCF or MF with potassium ferricyanide
in a sodium hydroxide medium. The absorbance of the orange products obtained is measured at 455 nm for DCF and 465 nm for
MF. The corresponding calibration graphs are linear over the range 0.20–20.0 mg L−1 for DCF and 1.00–100 mg L−1 for MF, while the limits of detection were 0.05 and 0.18 mg L−1, respectively.
Received March 27, 2000. Revision November 15, 2000. 相似文献
15.
Michael Wendt 《Mikrochimica acta》2002,139(1-4):195-200
Elements in the range 39 ≤ Z ≤ 56 were excited by electrons of an energy between 3 and 15 keV. The X-rays were detected by
means of an energy dispersive Si(Li) spectrometer with an ultra-thin polymer entrance window. In all cases Mζ = M5N3 was found to be the most intense M line. Thus, the relative intensity of this line is by definition 100%. For the heavier
of the investigated elements some other M lines were observed: M5O3, Mγ and M2N4. Mγ was detectable for Z ≥ 47, starting with a relative intensity of about 5%, which increased rapidly with Z to approximately
10%. M5O3 was first observed for 49-In, with a relative intensity of less than 10%, which increased up to approximately 50% for 56-Ba.
Also, M2N4 was observed for Z ≥ 49. The relative intensity of that line is approximately one half of that of Mγ. 相似文献
16.
Synthesis of large-pore SBA-15 silica using poly(ethylene oxide)-poly(methyl acrylate) diblock copolymers 总被引:1,自引:0,他引:1
Liang Cao Hongchen Dong Liang Huang Krzysztof Matyjaszewski Michal Kruk 《Adsorption》2009,15(2):156-166
Poly(ethylene oxide)-poly(methyl acrylate) diblock copolymers with narrow molecular weight distributions were synthesized
using atom transfer radical polymerization. The copolymers were used as micellar templates for the synthesis of mesoporous
silicas. The products were characterized using small-angle X-ray scattering, transmission electron microscopy (TEM) and nitrogen
adsorption. The obtained silicas exhibited two-dimensional hexagonal structures of cylindrical mesopores, and thus can be
classified as SBA-15 silicas. In some cases, the size of ordered domains was very small. The (100) interplanar spacings were
13–17 nm, depending on the size of the diblock copolymer used and on the synthesis conditions. Nitrogen adsorption showed
that the silicas exhibited specific surface areas of 350–800 m2 g−1, pore volumes ∼1 cm3 g−1, and narrow pore size distributions. The BJH (nominal) pore diameters were up to ∼20 nm, but actual diameters of cylindrical
pores are expected to be somewhat smaller. In many cases, the mesopores exhibited constrictions. 相似文献
17.
In this work, a new ligand, 2,9-bis[N,N-bis(carboxymethyl)-aminomethyl]-1,10-phenanthroline (BBCAP), was synthesized and
used to establish a novel fluorimetric method for the determination of trace amounts of terbium in a binary system. Its luminescence
mechanism was studied. The excitation and emission wavelengths are 284 nm and 547 nm, respectively. Other rare-earth metal
ions in 100-fold excess caused no interference. The fluorescence intensity was a linear function of the concentration of terbium
in the range of 5.0 × 10−10–1.0 × 10−6 mol/L. The detection limit was 2.0 × 10−11 mol/L (n = 12). The standard addition method was used to determine the terbium in a synthetic rare-earth sample with satisfactory
results. This method represents a direct, rapid, selective and sensitive analytical procedure with a widely linear range.
Received November 29, 2001 Revision February 9, 2002 相似文献
18.
Jürgen Vogt Rolf-Horst Flagmeyer Johannes Heitmann Dietmar Lehmann Tilo Reinert Steffen Jankuhn Daniel Spemann Wolfgang Tröger Tilman Butz 《Mikrochimica acta》2000,133(1-4):105-111
The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. The ultrastable
single ended 3.5 MV SINLETRONTM accelerator supplies the H+ or He+ ion beam. A magnetic scanning system moves the focused beam across the sample. At present, a resolution of 150 nm in the
low current mode and 300 nm at 5 pA could be achieved.
The UHV grade experimental chamber is equipped with electron-, energy dispersive X-ray-, and particle detectors. They can
be used simultaneously to analyse the sample by means of PIXE (particle induced X-ray emission), RBS (Rutherford backscattering)
and in the case of thin samples STIM (scanning transmission ion microscopy).
A goniometer allows the application of channeling measurements in single crystals in combination with these methods.
The detection limits depend on the elements to be analysed and range from (1000⋯1) μg/g relative and (1⋯0.01) pg absolute.
The analysis is nondestructive, but the sample has to be vacuum resistant. Applications of the nanoprobe in the field of semiconductor
research, biomedicine, and archaeology will be described. 相似文献
19.
Suspensions of triglyceride nanoparticles have been proposed as carrier systems for intravenous administration of poorly
water soluble drugs. Such nanosuspensions can easily be produced by homogenization of the melted triglyceride in an aqueous
phase. Using special emulsifier blends it is possible to obtain suspensions with an average size of the recrystallized particles
below 100 nm (photon correlation spectroscopy z-average). As can be observed by transmission electron microscopy the particles are very thin platelets with thicknesses in
the range of only a few molecular layers. Nanoparticles of saturated monoacid triglycerides (smaller than 200 nm) exhibit
uncommon melting behaviour, which is expressed in their differential scanning calorimetry curve by multiple endothermal peaks
over a temperature range of about 10 °C. This effect was attributed earlier to the particle thickness distribution in the
suspension rather than to polymorphic transitions since all the material exists in the stable β modification. Here we present
experimental investigations on the correlation between the melting behaviour of trilaurin nanosuspensions and the particle
thickness distribution determined by analysis of difference X-ray diffraction patterns recorded at progressively higher temperatures
in the melting range of the particles. Because of the weak X-ray scattering of the systems investigated synchrotron radiation
was used besides conventional sources. The Fourier analysis of the difference diffraction patterns is described in detail
and the advantages and difficulties in using this method are discussed. It was observed that the melting temperatures of the
nanoparticles increase with increasing particle thicknesses. Simultaneously a decrease in the interplanar (001) spacing with
increasing particle thickness was found.
Received: 27 July 1999 Accepted: 5 October 2000 相似文献