Sensitive determination of silicon contents in low-alloy steels using micro laser-induced breakdown spectroscopy assisted with laser-induced fluorescence.

Silicon element plays an important role in strength and hardness improvement in steels, but is harmful for ductility, tenacity, and anti-corrosion. Therefore, silicon content should be fast determined in steel manufacture to keep silicon in moderation. In this work, micro laser-induced breakdown spectroscopy assisted with laser-induced fluorescence (μLIBS-LIF) was proposed to sensitively determine silicon in low-alloy steels. The mechanism and excitation selection of laser-induced silicon atomic fluorescence in laser-induced plasma were discussed. Under 10 µm laser-ablated scatters, the results showed that μLIBS-LIF had analytical performance with R2 of 0.9998, LoD of 2.8 μg g-1, and RMSECV of 63 μg g-1, significantly better than μLIBS under their respective optimal conditions. The analytical sensitivity in μLIBS-LIF was even better than macro LIBS in others' works. As our best knowledge, the silicon LoD in LIBS technique was improved to better than 10 μg g-1 in steel matrix for the first time. This work demonstrates μLIBS-LIF as a capable and potential approach for fast determining silicon element in steel industries.