Pushing the detection limit of light elements

Spatially resolved detection and quantification of light alloying elements in steel remain a challenge.

With recent progress of X-ray sensitive spectrometers, collection of low energy X-rays – so called “soft” X-rays – is now possible with energy resolution of 0.3 eV using the Soft X-ray Emission Spectrometer (SXES). Owing to the varied line spacing grating, soft X-rays in the range of  50 eV to 210 eV can be detected for light elements with concentrations below 0.01% in mass.

By replacing the old tungsten EPMA by a new FEG-EPMA, OCAS improves its micro-area analysis capability. The new FEG-EPMA is additionally equipped with a soft X-ray emission spectrometer for even better detection limits. The field emission gun (FEG) is capable of achieving a much smaller probe size at lower accelerating voltages and high probe currents over the traditional EPMA with tungsten source.

Identification and detection limit of boron based precipitates in steel

Soft X-rays probed over large a area were used to determine the average boron concentration. A detection limit of < 10 ppm was calculated. In addition, localised spots were analysed in detail for individual phase identification of particles. Boron based precipitates were unambiguously identified as BN.

 

B in steel OCAS FEG-EPMA SXES_cropped

“Results achieved by using the new FEG-EPMA with SXES detector are excellent.  In the near future we are working to determine the quantitative distribution of more light elements. We will also be able to identify the chemical state of an element, a great asset for our customers’ research.”

Ann De Vyt, team leader Structural Material Characterisation, OCAS and Mélanie Gauvin, research engineer Materials Characterisation and Testing, OCAS