Applications of laser-induced emission spectral analysis for industrial process and quality control

Abstract

Laser-induced emission spectral analysis (LIESA, a registered trademark of instruments developed by Krupp), better known in the literature as laser microanalysis or laser-induced breakdown spectroscopy, is a suitable method for the direct in-process measurement of elemental concentrations in various solid and liquid materials. This method has been developed recently by Krupp for in-process quality assurance and process control in different industrial branches such as steel production ahd plant making. As a result several LIESA instruments have already been developed or are under development for marketing. In all cases on-line and in-process elemental analysis of materials at various stages of production yield information on the quality of the material and the fabrication process. The beam of a pulsed high-power laser (irradiance: 1 x 108-5 x lo9 W cm-2), focused onto the solid or liquid sample surface in an ambient gas atmosphere of normal pressure (focus areazablation area, 0.1 -6 mm2), produces a hot bright plasma (early electron temperatures, 20 000-30 000 K). The emitted plasma light is observed end-on and passes by way of an optical fibre bundle to a spectrometer, where it is detected in the focal plane by means of an optical multichannel analyser with high time resolution (on the microsecond scale). A fast computer evaluates the measured spectra and calculates the element concentrations via calibration procedures. Relative detection limits of between 10 and 100 ppm can be achieved for most of the detectable elements in various matrices (steel, rubber, rock and glass). Procedures are available to convert relative measurements with relative standard deviations of between 1 and 2% into absolute concentration values with relative accuracies of about 3%.

Time-resolved laser-induced plasma spectrometry for determination of minor elements in steelmaking process samples

“…Davies et al [9] used a 100-m fiber optic pair to perform remote LIPS on ferrous targets in an operating nuclear reactor. Detection limits of 200 µg g -1 or less were found for Cr, Cu, Mn, Mo, Ni, Si and V. Lorenzen et al [10] developed an industrial device for online analysis of liquid steel using optical fiber, time-resolved optical multichannel analyzer and a fast computer. Recently, LIPS has been evaluated for stainless steel samples at high temperatures [11].…”

Space and time-resolved laser-induced breakdown spectroscopy using charge-coupled device detection

“…Recent analytical applications include the detection of contaminants on electronic microcircuits [6], control of on-line processes [7], and particulates in combustion environments [8]. The technique has also been evaluated in air at atmospheric pressure [9], in inert or reactive atmospheres [10] and under high-vacuum conditions [11].…”

Characterisation of Inclusions in Clean Steels via Laser Ablation-ICP Mass Spectrometry

“…LIBS has yet to be fully exploited for characterisation of inclusions in clean steels but the potential is considerable given its success as a microanalytical tool [8][9][10][11] for spatially resolved measurement and depth profiling. 10,[12][13][14] Progress in the use of LIBS for inclusion measurement has recently been elaborated by Noll et al 15) and Laserna et al 16) Laser ablation in combination with ICP emission or ICP mass spectrometry constitutes an important bulk and microanalysis tool as evidenced by an extensive literature. [17][18][19] Relative to the LIBS approach a major advantage of the laser-ICP combination is the improved measurement sensitivity particularly for ICP-MS detection where the current state of the art is at the ng/g level.…”

“…LIBS has yet to be fully exploited for characterisation of inclusions in clean steels but the potential is considerable given its success as a microanalytical tool [8][9][10][11] for spatially resolved measurement and depth profiling. 10,[12][13][14] Progress in the use of LIBS for inclusion measurement has recently been elaborated by Noll et al 15) and Laserna et al …”