Correction factors for the effect of shape and thickness of SEM-EDS microanalysis of asbestos fibres by Monte Carlo simulation

Giovanni Valdrè, Daniele Moro, Gianfranco Ulian

Abstract


SEM-EDS quantitative microanalysis of asbestos mineral fibres still represents a complex analytical issue because of the variable fibre shape and small thickness (< 5 µm) compared with the penetration distance of the incident electron beam. Size and shape of micro- and sub-micrometric particles may cause large errors in the quantification due to particle effects on the generation and measurement of X-rays from the sample. These effects are related to the elastic scattering of electrons in the finite size (mass) of the fibre, which is strongly influenced by the average atomic number. The thickness of the particle is key, for a given mean atomic number, with a shape component affecting the absorption and fluorescence contributions to the correction routine. To overcome these issues empirical methods were developed, however they are cumbersome and need characterized standards for thickness, geometry and composition. Here we present correction factors obtained by Monte Carlo analysis for the thickness and shape effect of SEM-EDS and microprobe analysis of chrysotile, crocidolite, amosite, anthophyllite, tremolite and actinolite asbestos. Monte Carlo simulation was used to investigate electron transport, X-ray generation and detection in asbestos bundles and fibres of variable thickness and shape on a pure carbon holder. We report the results obtained on 100 µm long fibres and bundles of circular and square section and thicknesses from to 0.1 µm to 10 µm. Realistic experimental conditions, such as sample geometry, SEM set-up and detector physics were taken into account. An electron probe of 40 nm in diameter was simulated, focussed in parallel illumination onto the surface of the fibre or bundle, in a mid position with respect to the edges. The modelled EDS detector has a resolution of 130 eV measured at Mn Kα, an elevation angle of 40°, and an azimuthal angle of 0°. The influence of thickness and shape on the simulated spectrum was investigated for electron beam energies of 5, 15 and 25 keV. A strong influence of the asbestos fibres and bundles thickness and shape was observed. In general, the X-ray intensities as a function of fibre thickness showed a considerable reduction below about 0.5 µm at 5 keV, 2 µm at 15 keV, and 5 µm at 25 keV, with a non-linear dependence. Specific correction parameters, k-ratio, for the asbestos fibre thickness effect are here presented.

Keywords


asbestos; SEM-EDS microanalysis; Monte Carlo simulations; correction factors;

Full Text:

PDF

References


Aparicio, P., Galan, E., Valdrè, G., and Moro, D. (2009) Effect of pressure on kaolinite nanomorphology under wet and dry conditions Correlation with other kaolinite properties. Applied Clay Science, 46(2), 202-208.

Armstrong, J.T. (1991) Quantitative Elemental Analysis of Individual Microparticles with Electron-Beam Instruments. Electron Probe Quantitation, 261-315.

Bambynek, W., Crasemann, B., Fink, R.W., Freund, H.U., Mark, H., Swift, C.D., Price, R.E., and Venugopala Rao, P. (1972) X-Ray fluorescence yields, Auger, and Coster-Kronig transition probabilities Reviews of Modern Physics, 44, 716-813.

Bernstein, D.M. (2014) The health risk of chrysotile asbestos. Current Opinion in Pulmonary Medicine, 20(4), 366-370.

Bernstein, D.M., and Hoskins, J.A. (2006) The health effects of chrysotile: Current perspective based upon recent data. Regulatory Toxicology and Pharmacology, 45(3), 252-264.

Bethe, H.A., and Ashkin, J. (1953) Passage of radiation through matter. In E. Segre, Ed. Experimental Nuclear Physics, 1. John Wiley & Sons, New York, N.Y.

Bocchi, G., and Valdre, G. (1993) Physical, Chemical, and Mineralogical Characterization of Carbonate-Hydroxyapatite Concretions of the Human Pineal-Gland. Journal of Inorganic Biochemistry, 49(3), 209-220.

Borgia, G.C., Brown, R.J.S., Fantazzini, P., Mesini, E., and Valdre, G. (1992) Diffusion-Weighted Spatial Information from H-1 Relaxation in Restricted Geometries. Nuovo Cimento Della Societa Italiana Di Fisica D-Condensed Matter Atomic Molecular and Chemical Physics Fluids Plasmas Biophysics, 14(7), 745-759.

Bote, D., and Salvat, F. (2008) Calculations of inner-shell ionization by electron impact with the distorted-wave and plane-wave Born approximations. Physical Review A, 77(4).

Catherine, H., and Skinner, W. (2003) Mineralogy of asbestos minerals. Indoor and Built Environment, 12(6), 385-389.

Chantler, C.T., Olsen, K., Dragoset, R.A., Chang, J., Kishore, A.R., Kotochigova, S.A., and Zucker, D.S. (2005) NIST Standard Reference Database version 2.1. National Institute of Standards and Technology, Available at http://physics.nist.gov/ffast.

Czyzewski, Z., Maccallum, D.O., Romig, A., and Joy, D.C. (1990) Calculations of Mott Scattering Cross-Section. Journal of Applied Physics, 68(7), 3066-3072.

Gatti, A.M., Valdre, G., and Tombesi, A. (1996) Importance of microanalysis in understanding mechanism of transformation in active glassy biomaterials. Journal of Biomedical Materials Research, 31(4), 475-480.

Gazzano, E., Turci, F., Foresti, E., Putzu, M.G., Aldieri, E., Silvagno, F., Lesci, I.G., Tomatis, M., Riganti, C., Romano, C., Fubini, B., Roveri, N., and Ghigo, D. (2007) Iron-loaded synthetic chrysotile: A new model solid for studying the role of iron in asbestos toxicity. Chemical Research in Toxicology, 20(3), 380-387.

Gunter, M.E., Belluso, E., and Mottana, A. (2007) Amphiboles: Environmental and health concerns. Amphiboles: Crystal Chemistry, Occurrence, and Health Issues, 67, 453-516.

Hardy, J.A., and Aust, A.E. (1995) Iron in Asbestos Chemistry and Carcinogenicity. Chemical Reviews, 95(1), 97-118.

Hawthorne, F.C., and Oberti, R. (2007a) Amphiboles: Crystal chemistry. Amphiboles: Crystal Chemistry, Occurrence, and Health Issues, 67, 1-54.

-. (2007b) Classification of the amphiboles. Amphiboles: Crystal Chemistry, Occurrence, and Health Issues, 67, 55-88.

Hawthorne, F.C., Oberti, R., Harlow, G.E., Maresch, W.V., Martin, R.F., Schumacher, J.C., and Welch, M.D. (2012) Nomenclature of the amphibole supergroup. American Mineralogist, 97(11-12), 2031-2048.

Jablonski, A., Salvat, F., and Powell, C.J. (2010) NIST electron elastic-scattering cross-section database. National Institute of Standards and Technology, Gaithersburg, MD.

Joy, D.C., and Luo, S. (1989) An Empirical Stopping Power Relationship for Low-Energy Electrons. Scanning, 11(4), 176-180.

Merlet, C., and Llovet, X. (2011) New measurements of the surface ionization for quantitative electron probe microanalysis. X-Ray Spectrometry, 40(1), 47-54.

-. (2012) Uncertainty and capability of quantitative EPMA at low voltage - A review. Emas 2011: 12th European Workshop on Modern Developments in Microbeam Analysis, 32.

Moro, D., Ulian, G., and Valdrè, G. (2015) Single molecule investigation of glycine-chlorite interaction by cross-correlated scanning probe microscopy and quantum mechanics simulations. Langmuir : the ACS journal of surfaces and colloids, 31(15), 4453-63.

Myklebust, R., Newbury, D., and Yakowitz, H. (1976) NBS Monte Carlo Electron Trajectory Calculation Program. In K. Heinrich, H. Yakowitz, and D. Newbury, Eds. NBS Special Publication, 460, p. 105. National Bureau of Standards, Washington, DC.

Paoletti, L., Bruni, B.M., Arrizza, L., Mazziotti-Tagliani, S., and Pacella, A. (2008) A micro-analytical SEM-EDS method applied to the quantitative chemical compositions of fibrous amphiboles. Periodico Di Mineralogia, 77(2), 63-73.

Paoletti, L., Bruni, B.M., Gianfagna, A., Mazziotti-Tagliani, S., and Pacella, A. (2011) Quantitative Energy Dispersive X-Ray Analysis of Submicrometric Particles Using a Scanning Electron Microscope. Microscopy and Microanalysis, 17(5), 710-717.

Ritchie, N.W.M. (2009) Spectrum Simulation in DTSA-II. Microscopy and Microanalysis, 15(5), 454-468.

-. (2010) Using DTSA-II to Simulate and Interpret Energy Dispersive Spectra from Particles. Microscopy and Microanalysis, 16(3), 248-258.

Salvat, F., Llovet, X., Fernandez-Varea, J.M., and Sempau, J. (2006) Monte Carlo simulation in electron probe microanalysis. Comparison of different simulation algorithms. Microchimica Acta, 155(1-2), 67-74.

Small, J.A. (2002) The analysis of particles at low accelerating voltages (<= 10 kV) with energy dispersive x-ray spectroscopy (EDS). Journal of Research of the National Institute of Standards and Technology, 107(6), 555-566.

Valdre, G., Botton, G.A., and Brown, L.M. (1999) High spatial resolution peels characterization of FeAl nanograins prepared by mechanical alloying. Acta Materialia, 47(7), 2303-2311.

Wiewiora, A. (1990) Crystallochemical Classifications of Phyllosilicates Based on the Unified System of Projection of Chemical-Composition .3. The Serpentine-Kaolin Group. Clay Minerals, 25(1), 93-98.

Yao, S.D., Della Ventura, G., and Petibois, C. (2010) Analytical characterization of cell-asbestos fiber interactions in lung pathogenesis. Analytical and Bioanalytical Chemistry, 397(6), 2079-2089.


Refbacks

  • There are currently no refbacks.




Copyright (c) 2018 Journal of Mediterranean Earth Sciences

ISSN Online: 2280-6148
ISSN Print: 2037-2272