EBSD Challenges Conventional Asbestos Identification Methods

EBSD Challenges Conventional Asbestos Identification Methods

Post by:
  • 12:05PM Aug 05, 2015
  • Comments off

RJ Lee Group has a long history of providing high-quality asbestos analysis and litigation expertise, supported by the research of our subject matter experts.  Brian Bandli, Ph.D., a Principal Investigator with our materials group, presented a paper (Microscopy & Microanalysis, Vol. 20, pp. 1805-1816) that outlines how electron backscatter diffraction (EBSD) can successfully identify asbestos reference materials and particles of varying morphology for sizes from asbestiform to massive, plus identify minerals from real world samples. 

The ability to correctly identify asbestos particles is critical to protecting public health. This task has become more difficult in recent years.  The challenges posed by newly identified materials and environments where asbestos-like particles may be found require different analytical approaches than have been employed in the past.  However, the tools used in this field have changed little over the last four decades. Recent research employing EBSD for phase identification of amphibole asbestos minerals may help streamline analysis of challenging samples. The purpose of the paper was to determine if EBSD can successfully be used to collect crystallographic information that would be useful for the identification of asbestos fibers.

The first test was to examine reference samples of known asbestos materials. This test indicated that while the quality of diffraction patterns varied among the different asbestos types, most particles analyzed were successfully identified using EBSD. Compositional information was also collected with energy dispersive x-ray spectroscopy (EDS). The second test was to determine if EBSD could measure shape-preferred orientation in samples of varying morphology. Morphology of particles is important because the size and shape of a particle can influence how it behaves in the environment.

The final test examined a real-world sample to determine if particles from a talc ore could be identified. This result was mixed, as some particles were able to produce high quality diffraction patterns. However, many were not. Particularly, the asbestiform particles that had caused specific health concerns could not produce usable patterns.

EDS Spectrum
Figure 1: Energy dispersive x-ray spectroscopy (EDS) spectrum and secondary electron micrograph (inset, cross designates point of analysis) of representative anthophyllite particle from sample TV_plates. b: Transmission electron backscatter diffraction (tEBSD) pattern collected from particle in a. c: tEBSD pattern from b with blue lines showing position of simulated anthophyllite EBSD pattern diffraction bands with orientation of unit cell inset. Blue line on unit cell orientation corresponds to [001], which is parallel to particle elongation.

EBSD has been a powerful tool for phase discrimination since its advent. Accurate phase discrimination for the analysis of asbestos is critically important, as inaccurate results lead to confusion when searching for the source of potentially harmful fibers. The research conducted for this paper determined that using the EBSD and/or transmission electron backscatter diffraction (tEBSD), in conjunction with existing microanalytical platforms used for asbestos fiber testing, demonstrated significant gains in speed and accuracy.

From the editor: This paper is the first published work demonstrating that EBSD can be successfully used for asbestos identification. Dr. Bandli will be receiving an award for this paper from the editors of Microscopy and Microanalysis. The paper, which has been named the “Best Materials Application Paper” was published in Microscopy and Microanalysis in 2014 for research he has done on investigating the utility of EBSD for asbestos analysis.  The award is chosen by the journal editors based on the technical merit and number of downloads of the paper, and represents the significance of this work to the greater microscopy community. To read the whole paper, please click here.