Boron Substrates for Particulate X-Ray Microanalysis

Abstract

<jats:p>Sample substrates for x-ray microanalysis of particles should be chemically simple and composed of low atomic number elements. Substrates meeting these requirements will generate a minimum number of low energy x-ray peaks that should not interfere with spectra generated by the particles of interest. Elemental carbon fulfills these requirements and carbon planchets are used for the majority of work involving x-ray microanalysis of particles. When particles of interest are carbonaceous, alternate substrates must be sought. Beryllium planchets have traditionally been used for the analysis of carboncontaining particles. However, concerns about beryllium toxicity along with regulations from the Occupational Safety and Health Administration (OSHA) have resulted in diminished use of beryllium as a substrate material. These toxicity issues prompted us to explore the possibility of using elemental boron as a substrate for microanalysis of carbon-containing particles.</jats:p><jats:p>Elemental boron is available from chemical supply houses and the material we purchased was in the form of irregularly shaped pieces, approximately 3 cm in the longest dimension.</jats:p>

X-ray microanalyses in the variable pressure (environmental) scanning electron microscope

“…As an alternative, elemental boron and its oxide are not significantly toxic, although its x-ray peak at 185 eV is detectable with high performance EDS systems. Boron is extremely hard, and a highly polished surface can be produced with an appropriate polishing protocol [ 16 ].…”

Direct preparation of particles from liquid suspension for ESEM or SEM analysis

“…It is of sufficient purity that it does not produce any interfering peaks in the EDS spectrum outside of carbon K. As many specimens are carbon coated for conventional SEM and EDS to reduce charging, the contribution of carbon to the EDS spectrum is often ignored. In cases where carbon was of interest by EDS, these substrates would be unsuitable and beryllium or boron substrates (Windsor et al ., 1999) would be more appropriate.…”