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Non-dispersive soft x-ray fluorescence analyses

Description: In a nondispersive x-ray fluorescence analysis system, all x-rays incident on the detector are analyzed according to energy in a time sharing manner. The spectrometer and techniques described were designed to take advantage of the features of a nondispersive detector. These include sensitivity, relatively short geometry, and the ability to detect oxygen and sodium x-rays at the low energy end of the elemental scale. Results are given for analyses of Sirof pottery samples and standard USGS rocks. (LK)
Date: May 1, 1975
Creator: Herbert, A. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

AUTOMATED ELEMENTAL ANALYSIS USING ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYSIS

Description: The application of energy dispersive x-ray fluorescence analysis to the measurements of air particulate samples has been described in several recent publications. Among its many advantages, the possibility of automatic analysis for large scale monitoring programs has not been widely discussed. We describe the completion of a program in which a total of 34,000 air particulate samples have been collected and analyzed over the past two years. An automatic photon-excited energy dispersive spectrometer was used to obtain elemental concentrations for 27 elements on each sample. The sensitivity of the system is adequate to detect quantities of 10 ngm/cm{sup 2} or less in a measurement time of approximately six minutes per sample. The precision and accuracy of the results will be compared to statistical analyses of the data set. Summaries of the results are presented and the implications for air particulate monitoring discussed.
Date: November 1, 1977
Creator: Jaklevic, J.M.; Gatti, R.C.; Goulding, F.S.; Loo, B.W. & Thompson, A.
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Partner: UNT Libraries Government Documents Department

X-Ray Fluorescence Analysis Applied to Small Samples

Description: We describe an adaptation of photon excited x-ray fluorescence analysis which is optimized for the analysis of small samples. A fine focus x-ray tube is used in conjunction with small diameter detector collimators in order to focus on a small sample volume with as high sensitivity as possible. Sample areas of less than 1 mm diameter can be analyzed with ppm detectability. In applications involving the analysis of human hair samples, a minimum detectable limit of 10 ppm Hg can be realized in a 1 mm long segment of a single hair in a counting time of 200 seconds. Simultaneous measurements of the sample mass can be obtained from the intensity of the incoherent scattering. An automated x-ray fluorescence analysis system using the technique for the scanning of elemental profiles in such hair samples will be described.
Date: August 1, 1977
Creator: Jaklevic, J. M.; French, W. R.; Clarkson, T. W. & Greenwood, M. R.
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Partner: UNT Libraries Government Documents Department

Material verification of quadralatch ringers by x-ray flourescence

Description: A sample of cast quadralatch fingers were measured with an X-ray fluorescence spectrometer. The results are compared with measurements of standard 300-series and 400-series stainless steel billets. Use of this measuring technique for material verification of fingers is described.
Date: February 24, 1997
Creator: Deichelbohrer, P. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

High resolution x-ray fluorescence spectroscopy - a new technique for site- and spin-selectivity

Description: X-ray spectroscopy has long been used to elucidate electronic and structural information of molecules. One of the weaknesses of x-ray absorption is its sensitivity to all of the atoms of a particular element in a sample. Through out this thesis, a new technique for enhancing the site- and spin-selectivity of the x-ray absorption has been developed. By high resolution fluorescence detection, the chemical sensitivity of K emission spectra can be used to identify oxidation and spin states; it can also be used to facilitate site-selective X-ray Absorption Near Edge Structure (XANES) and site-selective Extended X-ray Absorption Fine Structure (EXAFS). The spin polarization in K fluorescence could be used to generate spin selective XANES or spin-polarized EXAFS, which provides a new measure of the spin density, or the nature of magnetic neighboring atoms. Finally, dramatic line-sharpening effects by the combination of absorption and emission processes allow observation of structure that is normally unobservable. All these unique characters can enormously simplify a complex x-ray spectrum. Applications of this novel technique have generated information from various transition-metal model compounds to metalloproteins. The absorption and emission spectra by high resolution fluorescence detection are interdependent. The ligand field multiplet model has been used for the analysis of K{alpha} and K{beta} emission spectra. First demonstration on different chemical states of Fe compounds has shown the applicability of site selectivity and spin polarization. Different interatomic distances of the same element in different chemical forms have been detected using site-selective EXAFS.
Date: December 1, 1996
Creator: Wang, Xin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department

Quantitative XRFA of carbon in a special matrix by the fundamental parameter method

Description: We report on results obtained from experiments using specially prepared carbon substrates and treatment of the data by means of recently introduced theory. Medium Z grids with known parameters have been coated on top of pyrolytic carbon substrates to achieve well defined absorption geometries. The various copper grids exhibit satisfactory performance in terms of mechanical stability, homogeneity and uniformity of the coating. A detailed study of the measurement results shows that there is a more rapid increase of the associated C-K{alpha} countrate from the coated samples compared to the pure elements and is attributed to the contribution of secondary enhancement effects, including those resulting from photoelectrons generated after the primary ionization. A variety of multilayer analyzers has also been evaluated during these experiments. Only a certain combination of muitilayer component materials have been found to be appropriate for use as dispersing elements due to the reflectivity and spatial resolution requirements of our long wavelength spectrometer. Another experimental factor is the low intensity of available tube photons which is due to the selection of the target material and absorption effects in the target as well as the tube window. 12 refs., 7 figs., 2 tabs.
Date: May 1, 1996
Creator: Weber, F.A.; Da Silva, L.B.; Barbee, T.W. Jr.; Ciarlo, D. & Mantler, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Inorganic profile of some Brazilian medicinal plants obtained from ethanolic extract and ''in natura'' samples

Description: The Anadenathera macrocarpa, Schinus molle, Hymenaea courbaril, Cariniana legalis, Solidago microglossa and Stryphnodendron barbatiman, were collected ''in natura'' samples (leaves, flowers, barks and seeds) from different commercial suppliers. The pharmaco-active compounds in ethanolic extracts had been made by the Mato Grosso Federal University (UFMT). The energy-dispersive x-ray fluorescence (ED-XRF) spectrometry was used for the elemental analysis in different parts of the plants and respective ethanolic extracts. The Ca, Cl, Cu, Fe, K, Mg, Mn, Na, Ni, P, Rb, S, Sr and Zn concentrations were determined by the fundamental parameters method. Some specimens showed a similar inorganic profile for ''in natura'' and ethanolic extract samples and some ones showed a distinct inorganic profile. For example, the Anadenathera macrocarpa showed a similar concentration in Mg, P, Cu, Zn and Rb elements in ''in natura'' and ethanolic extract samples; however very different concentration in Na, S, Cl, K , Ca, Mn, Fe and Sr was observed in distinctive samples. The Solidago microglossa showed the K, Ca, Cl, S, Mg, P and Fe elements as major constituents in both samples, suggesting that the extraction process did not affect in a considerable way the ''in natura'' inorganic composition. The elemental composition of the different parts of the plants (leaves, flowers, barks and seeds) has been also determined. For example, the Schinus molle specimen showed P, K, Cl and Ca elements as major constituents in the seeds, Mg, K and Sr in the barks and Mg, S, Cl and Mn in the leaves, demonstrating a differentiated elementary distribution. These inorganic profiles will contribute to evaluate the quality control of the Brazilian herbaceous trade and also will assist to identify which parts of the medicinal plants has greater therapeutic effect.
Date: October 3, 2004
Creator: Ferreira, M.O.M.; de Sousa, P.T.; Salvador, V.L.R. & Sato, I.M.
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Partner: UNT Libraries Government Documents Department

Development of total uranium analytical method by L x-ray fluorescence

Description: This paper describes development of an L x-ray fluorescence technique to perform total uranium analysis using an internal excitation source which is added directly to the sample. The method has been demonstrated with synthetic U samples in the limited concentration range of 1g/l to 15g/l, and provides the advantages of simplicity, involving no mechanical parts which would normally be found in an external excitation source. Total uranium is determined by counting L x-rays fluoresced by a microCurie level spike of Cd-109 added directly to the sample and without shielding the excitation source from the detector. A method for correction of sample self-absorption is included in the analysis.
Date: September 18, 1996
Creator: Dewberry, R.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Evaluation of field-portable X-ray fluorescence spectrometry for the determination of lead contamination on small-arms firing ranges

Description: Field analytical methods for the characterization of lead contamination in soil are being developed. In this study, the usefulness of a commercially available, field-portable energy-dispersive X-ray fluorescence spectrometer (XRF) is evaluated for determining the extent of lead contamination in soils on small-arms firing ranges at a military installation. This field screening technique provides significant time and cost savings for the study of sites with lead-contaminated soil. Data obtained with the XRF unit in the field are compared with data obtained from soil samples analyzed in an analytical laboratory by inductively coupled plasma atomic emission spectroscopy. Results indicate that the field-portable XRF unit evaluated in this study provides data that are useful in determining the extent and relative magnitude of lead contamination. For the commercial unit used in this study, improvements in the spectral resolution and in the limit of detection would be required to make the unit more than just a screening tool.
Date: February 1, 1995
Creator: Schneider, J.F.; Taylor, J.D.; Bass, D.A.; Zellmer, D. & Rieck, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Refracted x-ray fluorescence (RXF) applied to the study of thermally grown oxide scales

Description: RXF is a new technique for studying thin films. Here, it is applied to study of thermally grown oxide scales. Evolution of chromia scales on Fe-25Cr-20Ni-0.3Y alloys and the evolution of alumina scales on {beta}-NiAl are investigated. The technique provides scale composition and depth profile information, scale thicknesses and growth rates, and information about transient phase evolution.
Date: October 1996
Creator: Koshelev, I.; Paulikas, A. P. & Veal, B. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Industrial x-ray fluorescence analysis new applications and challenges for cryogenic detectors

Description: Cryogenic, high-resolution X-ray detectors have potential applications in industrial X-ray fluorescence (XRF) analysis. We discuss various XRF analysis techniques currently used in the semiconductor industry, problems encountered due to limitations of current detectors and the potential benefits of using cryogenic detectors in these applications. We give examples of demonstration experiments, compare the performance of current conventional and cryogenic X-ray spectrometers and present an outlook.
Date: August 1, 1997
Creator: Frank, M.
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Partner: UNT Libraries Government Documents Department

Development of improved x-ray optics for analytical x-ray microbeams. CRADA final report for CRADA Number Y-1294-0283

Description: The purpose of this CRADA was to develop improved glass capillary, x-ray optics for analytical x-ray microbeam applications. X-Ray Optical Systems, Inc. (XOS) designed and fabricated capillary optics and LMES tested those optics for x-ray microanalytical applications using its unique X-Ray Microprobe. Tapered capillaries with 3-{micro}m and 8-{micro}m output openings were fabricated and tested. The tapered capillaries had better spectral quality for x-ray microfluorescence (XRMF) analysis, than non-tapered, straight capillaries that are currently used in the system. X-ray beam count-rates for the tapered capillaries were also greater than the straight capillaries. Two monolithic, polycapillary optics were fabricated and tested. The polycapillary optics produced focal spots of 40 and 100 {micro}m. Beam intensities for the polycapillaries were, respective, 44 and 18 times the intensities found in straight 50-{micro}m and 100-{micro}m capillaries. High-sensitivity scanning will be possible because of the enhanced intensity of the polycapillary optic. LMES and the DP program will benefit from improved capabilities for nondestructive x-ray microanalysis, while XOS will benefit from test results that will enhance the marketability of their products.
Date: March 18, 1996
Creator: Carpenter, D.A.; Gao, N.; Xiao, Q.F. & Ponomarev, I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

High-resolution x-ray imaging for microbiology at the Advanced Photon Source

Description: Exciting new applications of high-resolution x-ray imaging have emerged recently due to major advances in high-brilliance synchrotrons sources and high-performance zone plate optics. Imaging with submicron resolution is now routine with hard x-rays: the authors have demonstrated 150 run in the 6--10 keV range with x-ray microscopes at the Advanced Photon Source (APS), a third-generation synchrotrons radiation facility. This has fueled interest in using x-ray imaging in applications ranging from the biomedical, environmental, and materials science fields to the microelectronics industry. One important application they have pursued at the APS is a study of the microbiology of bacteria and their associated extracellular material (biofilms) using fluorescence microanalysis. No microscopy techniques were previously available with sufficient resolution to study live bacteria ({approx}1 {micro}m x 4 {micro}m in size) and biofilms in their natural hydrated state with better than part-per-million elemental sensitivity and the capability of determining g chemical speciation. In vivo x-ray imaging minimizes artifacts due to sample fixation, drying, and staining. This provides key insights into the transport of metal contaminants by bacteria in the environment and potential new designs for remediation and sequestration strategies.
Date: November 2, 1999
Creator: Lai, B.; Kemner, K. M.; Maser, J.; Schneegurt, M. A.; Cai, Z.; Ilinski, P. P. et al.
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Partner: UNT Libraries Government Documents Department

CHARACTERIZATION OF SALT PARTICLE INDUCED CORROSION PROCESSES BY SYNCHROTRON GENERATED X-RAY FLUORESCENCE AND COMPLEMENTARY SURFACE ANALYSIS TOOLS.

Description: The benefits of using synchrotron-generated X-rays and X-ray fluorescence analysis in combination with other surface analysis techniques have been demonstrated. In studies of salt-induced corrosion, for example, the detection of Rb ions in the area of secondary spreading when salt-containing micro-droplets are placed on zinc surfaces, further supports a mechanism involving cation transport during the corrosion and spreading of corrosive salt on exposed metal surfaces. Specifically, the new analytical data shows that: (a) cations are transported radially from a primary drop formed from a salt deposit in a thin film of secondary spreading around the drop; (b) subsequently, micro-pools are formed in the area of secondary spreading, and it is likely that cations transported within the thin film accumulate in these micro-pools until the area is dehydrated; (c) the mechanism of cation transport into the area of secondary spreading does not include transport of the anions; and (d) hydroxide is the counter ion formed from oxygen reduction at the metal surface within the spreading layer. Data relevant to iron corrosion is also presented and the distinct differences relative to the zinc situation are discussed.
Date: March 25, 2001
Creator: NEUFELD, A.K.; COLE, I.S.; BOND, A.M.; ISAACS, H.S. & FURMAN, S.A.
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Partner: UNT Libraries Government Documents Department

X-ray Raman scattering in H-BN observed by soft x-ray fluorescence spectroscopy

Description: Raman scattering of soft x-rays is observed in h-BN using monochromatic soft x-rays just below the B K absorption edge. The inelastic features are visible below threshold, track with the excitation energy, go through a resonance as the excitation is tuned to the B ls core exciton energy, and finally evolve into normal fluorescence as the excitation is raised above the energy needed to excite the B ls electron into the conduction band. The inelastic energy loss is identified as an excitation of valence {sigma} electrons into the {pi}* valence exciton state; at resonance and above, {pi} {minus} {pi}* transitions are also observed. At resonance, a sideband on the elastic peak Ls observed, which gives evidence of additional electronic and phonon loss processes. Very similar results have also been observed for B{sub 2}O{sub 3}.
Date: March 1, 1995
Creator: Jia, J.J.; Callcott, T.A.; Carlisle, J.A.; Terminello, L.J.; Asfaw, A.; Ederer, D.L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Preliminary uranium enrichment analysis results using cadmium zinc telluride detectors

Description: Lawrence Livermore National Laboratory (LLNL) and EG&G ORTEC have jointly developed a portable ambient-temperature detection system that can be used in a number of application scenarios. The detection system uses a planar cadmium zinc telluride (CZT) detector with custom-designed detector support electronics developed at LLNL and is based on the recently released MicroNOMAD multichannel analyzer (MCA) produced by ORTEC. Spectral analysis is performed using software developed at LLNL that was originally designed for use with high-purity germanium (HPGe) detector systems. In one application, the CZT detection system determines uranium enrichments ranging from less than 3% to over 75% to within accuracies of 20%. The analysis was performed using sample sizes of 200 g or larger and acquisition times of 30 min. The authors have demonstrated the capabilities of this system by analyzing the spectra gathered by the CZT detection system from uranium sources of several enrichments. These experiments demonstrate that current CZT detectors can, in some cases, approach performance criteria that were previously the exclusive domain of larger HPGe detector systems.
Date: September 8, 1995
Creator: Lavietes, A.D.; McQuaid, J.H. & Paulus, T.J.
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Partner: UNT Libraries Government Documents Department