Elemental analysis of aluminum alloys by Laser Induced Breakdown Spectroscopy based on TEA CO2 laser

Abstract

The applicability of nanosecond infrared Transversely Excited Atmospheric (TEA) CO2 laser induced plasma for spectrochemical analysis of aluminum alloys was investigated. The plasma was generated by focusing a pulsed TEA CO2 laser that emits at 10.6 μm on the Al target in ambient air at atmospheric pressure. The temporal profile of the laser pulse is composed of a 100 ns peak followed by a slowly decaying tail of about 2 μs. The output pulse energy was approximately 160 mJ, thus the peak output power was estimated to be around 1.6 MW. Time-Integrated Space-Resolved Laser Induced Breakdown Spectroscopy (TISR-LIBS) was employed to obtain the emission spectra. The maximum intensity of emission, with sharp and well resolved spectral lines that were almost free of the background continuum, was obtained from plasma region 2 mm from the target surface. Linear calibration curves for Mg, Cr, Cu and Fe were obtained using aluminum alloy spectrochemical standards. The limits of detection for the investigated elements were in the 2–73 ppm range. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used as a reference technique to estimate the accuracy of LIBS determination by use of control samples with known compositions. Comparison of the obtained results with those available in the literature confirms that LIBS system based on TEA CO2 laser, in combination with TISR spectral measurements, can be successfully applied to qualitative and quantitative determinations of minor elements in aluminum based alloys.