Analytical Methods Based upon X-Ray Absorption

1953 ◽  
Vol 25 (5) ◽  
pp. 689-692 ◽  
Author(s):  
H. A. Liebhafsky
Keyword(s):  
Analytical Methods ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Emerging surface characterization techniques for carbon steel corrosion: a critical brief review

2017 ◽  
Vol 473 (2199) ◽  
pp. 20160852 ◽  
Author(s):  
D. Dwivedi ◽  
K. Lepkova ◽  
T. Becker
Keyword(s):  
Carbon Steel ◽  
Analytical Methods ◽  
Surface Characterization ◽  
Construction Material ◽  
Film Surface ◽  
Surface Films ◽  
Corrosive Media ◽  
Metallic Substrates ◽  
X Ray ◽  
X Ray Absorption

Carbon steel is a preferred construction material in many industrial and domestic applications, including oil and gas pipelines, where corrosion mitigation using film-forming corrosion inhibitor formulations is a widely accepted method. This review identifies surface analytical techniques that are considered suitable for analysis of thin films at metallic substrates, but are yet to be applied to analysis of carbon steel surfaces in corrosive media or treated with corrosion inhibitors. The reviewed methods include time of flight-secondary ion mass spectrometry, X-ray absorption spectroscopy methods, particle-induced X-ray emission, Rutherford backscatter spectroscopy, Auger electron spectroscopy, electron probe microanalysis, near-edge X-ray absorption fine structure spectroscopy, X-ray photoemission electron microscopy, low-energy electron diffraction, small-angle neutron scattering and neutron reflectometry, and conversion electron Moessbauer spectrometry. Advantages and limitations of the analytical methods in thin-film surface investigations are discussed. Technical parameters of nominated analytical methods are provided to assist in the selection of suitable methods for analysis of metallic substrates deposited with surface films. The challenges associated with the applications of the emerging analytical methods in corrosion science are also addressed.

scholarly journals Aplicação de técnicas de análise síncrotron em arqueologia

2018 ◽  
Vol 15 (30) ◽  
pp. 277
Author(s):  
Douglas Galante ◽  
Fabio Rodrigues ◽  
Lara Maldanis ◽  
Tamires Gallo
Keyword(s):  
Cultural Heritage ◽  
Light Source ◽  
Analytical Methods ◽  
Chemical Speciation ◽  
Special Focus ◽  
Chemical Mapping ◽  
X Ray ◽  
Synchrotron Light ◽  
X Ray Absorption

Este artigo apresenta uma revisão sobre os principais métodos analíticos atualmente empregados no estudo de bens culturais e arqueológicos, com especial foco em técnicas baseadas em sincrotron, explorando suas vantagens e limitações dentro das demandas desse campo. As técnicas abordadas são a tomografia de raios X para análises de imagem do interior de objetos, a fluorescência de raios X para o mapeamento químico da superfície dos objetos de interesse, e a absorção de raios X para a especiação química de determinados elementos. Tais técnicas encontram-se disponíveis na fonte de luz sincrotron brasileira do Laboratório Nacional de Luz Síncrotron, o qual atualmente constrói Sirius, uma fonte de 4a geração que irá levar o Brasil a novas fronteiras tecnológicas para estudos de materiais, tal qual na área arqueometria. Abstract: This article presents a review about the main analytical methods currently applied in the study of cultural heritage and archeology, with a special focus on synchrotron-based techniques, exploring the advantages and limitations within the requirements of the field. The techniques presented are X-ray tomography for imaging the interior of objects, X- ray fluorescence for chemical mapping of the surface of objects of interest and X-ray absorption for chemical speciation of elements. These techniques are available in the Brazilian synchrotron light source of the Brazilian Synchrotron Light Laboratory, which currently builds Sirius, a 4th generation source that will take Brazil to new technological frontiers for the study of materials, as in the field of archeometry. 

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

point-Analysis Using the Extrapolation Method in the Analytical Electron microscope

1990 ◽  
Vol 48 (2) ◽  
pp. 430-431
Author(s):  
Zenji Horita ◽  
Ryuzo Nishimachi ◽  
Takeshi Sano ◽  
Minoru Nemoto
Keyword(s):  
Electron Microscope ◽  
Extrapolation Method ◽  
X Ray ◽  
Absorption Correction ◽  
Point Analysis ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Data Points ◽  
Identical Composition ◽  
X Ray Absorption

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.

EXELFS Studies of Carbon Fibers

1990 ◽  
Vol 48 (2) ◽  
pp. 72-73
Author(s):  
V. Serin ◽  
K. Hssein ◽  
G. Zanchi ◽  
J. Sévely
Keyword(s):  
Carbon Fibers ◽  
Energy Analysis ◽  
Electron Excitation ◽  
Complex Structures ◽  
High Modulus ◽  
Promising Technique ◽  
X Ray ◽  
Fine Structures ◽  
X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

Improving soil remediation through characterization

1995 ◽  
Vol 53 ◽  
pp. 386-387
Author(s):  
E. C. Buck ◽  
N. L. Dietz ◽  
J. K. Bates
Keyword(s):  
Dust Particles ◽  
Radiochemical Analysis ◽  
Solid Product ◽  
Uranium Contamination ◽  
Physical Separation ◽  
X Ray ◽  
Rocky Flats ◽  
Remediation Strategies ◽  
Bearing Materials ◽  
X Ray Absorption

Operations at former weapons processing facilities in the U. S. have resulted in a large volume of radionuclidecontaminated soils and residues. In an effort to improve remediation strategies and meet environmental regulations, radionuclide-bearing particles in contaminant soils from Fernald in Ohio and the Rocky Flats Plant (RFP) in Colorado have been characterized by electron microscopy. The object of these studies was to determine the form of the contaminant radionuclide, so that it properties could be established [1]. Physical separation and radiochemical analysis determined that uranium contamination at Fernald was not present exclusively in any one size/density fraction [2]. The uranium-contamination resulted from aqueous and solid product spills, air-borne dust particles, and from the operation of an incinerator on site. At RFP the contamination was from the incineration of Pu-bearing materials. Further analysis by x-ray absorption spectroscopy indicated that the majority of the uranium was in the 6+ oxidation state [3].

Chemical and orientational imaging of polymeric samples

1994 ◽  
Vol 52 ◽  
pp. 68-69
Author(s):  
H. Ade ◽  
B. Hsiao ◽  
G. Mitchell ◽  
E. Rightor ◽  
A. P. Smith ◽  
...  
Keyword(s):  
Ethylene Terephthalate ◽  
National Laboratory ◽  
Brookhaven National Laboratory ◽  
Carbonyl Groups ◽  
Aromatic Rings ◽  
Edge Structure ◽  
X Ray ◽  
Scanning Transmission ◽  
Polymeric Samples ◽  
X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

Quantitative x-ray microanalysis and thickness determination using ζ factor

1996 ◽  
Vol 54 ◽  
pp. 580-581
Author(s):  
M. Watanabe ◽  
Z. Horita ◽  
M. Nemoto
Keyword(s):  
Diffusion Couple ◽  
Extrapolation Method ◽  
Thin Specimen ◽  
Beam Position ◽  
X Ray ◽  
Thickness Determination ◽  
Experimental Limitation ◽  
X Ray Absorption

X-ray absorption in quantitative x-ray microanalysis of thin specimens may be corrected without knowledge of thickness when the extrapolation method or the differential x-ray absorption (DXA) method is used. However, there is an experimental limitation involved in each method. In this study, a method is proposed to overcome such a limitation. The method is developed by introducing the ζ factor and by combining the extrapolation method and DXA method. The method using the ζ factor, which is called the ζ-DXA method in this study, is applied to diffusion-couple experiments in the Ni-Al system.For a thin specimen where incident electrons are fully transparent, the characteristic x-ray intensity generated from a beam position, I, may be represented as I = (NρW/A)Qωaist.

X-Ray absorption edge elemental imaging of B. thuringienis

1989 ◽  
Vol 47 ◽  
pp. 212-213
Author(s):  
R. L. Stears
Keyword(s):  
Absorption Edge ◽  
Elemental Distribution ◽  
X Rays ◽  
Differential Absorption ◽  
Synchrotron Source ◽  
High Brightness ◽  
X Ray ◽  
Elemental Imaging ◽  
Cellular Integrity ◽  
X Ray Absorption

Because of the nature of the bacterial endospore, little work has been done on analyzing their elemental distribution and composition in the intact, living, hydrated state. The majority of the qualitative analysis entailed intensive disruption and processing of the endospores, which effects their cellular integrity and composition.Absorption edge imaging permits elemental analysis of hydrated, unstained specimens at high resolution. By taking advantage of differential absorption of x-ray photons in regions of varying elemental composition, and using a high brightness, tuneable synchrotron source to obtain monochromatic x-rays, contact x-ray micrographs can be made of unfixed, intact endospores that reveal sites of elemental localization. This study presents new data demonstrating the application of x-ray absorption edge imaging to produce elemental information about nitrogen (N) and calcium (Ca) localization using Bacillus thuringiensis as the test specimen.

Sign in / Sign up

Export Citation Format

Share Document