Microwave-assisted laser-induced breakdown spectroscopy on aluminum alloy for improved quantitation

Abstract

This study employed microwave-assisted laser-induced breakdown spectroscopy (MW-LIBS) to investigate the sensitivity and reproducibility of emission line intensity, plasma parameters, and analytical measurements. Standard Al-alloys (Xiamen Yichen Technology Co., China) were used due to its wide applications and excellent physical and mechanical properties. The plasmas of these alloys were produced using a fundamental harmonic (1064 nm) of Nd: YAG laser. The plasma emissions were recorded at laser energies (40–260 mJ) and microwave power 400, 800, and 1200 W. The MW setup consists of air-cooled 2.45 GHz microwave source (magnetron), a WR340 waveguide, a 3-stub impedance tuner, and a waveguide-to-coaxial adaptor. A one-meter coaxial cable with a sharpened end served as a near-field antenna. The experimental parameters, such as laser energy, microwave power, and detector gate delay, were optimized for sensitivity and repeatability. At an optimized laser energy of 140 mJ and a microwave peak power of 1200 W, signal enhancement was observed to increase six-fold, the signal-to-noise ratio (SNR) improved five-fold, and the limit of detection (LOD) decreased seven-fold compared to conventional LIBS. The repeatability in emission line intensity, measured in terms of relative standard deviation (RSD), was significantly improved from 36 % to 6 %, 46–18 %, and 27–13 % for Mg, Si, and Cu emission lines, respectively. The improvement in repeatability of emission line intensities led to improved accuracy in predicted concentration measurements based on calibration curves, with percentage deviations of 18–3 % for Mg and 35–11 % for Si.