Analysis of Lithium and other Critical Elements in Aluminum Alloys Using Handheld LIBS

Handheld LIBS analysis offers an alternative to both handheld XRF and spark OES for analyzing a broad range of sample types and elements. In the LIBS process, plasma is created at the material surface, as in spark optical emission spectroscopy (OES), and the measurement of spectral lines from the various elements present is taken as the plasma cools. The elements present are revealed by the wavelength of specific lines and the light intensity at a given wavelength is related to the element concentration.

Recently SciAps has introduced the Z, a handheld analyzer featuring LIBS technology. The Z, as shown in Figure 1, delivers the low atomic number performance of mobile OES, while maintaining the portability of handheld XRF.

The key features of the Z are:

  • A pulsed, 5 mJ eye-safe, Class 1 rated laser
  • A high resolution (< 80 pm) spectrometer (Patent Pending)
  • Opti-Purge™ (Patent Pending) for measurements in the deep UV (< 200 nm) and overall improved limits of detection (LODs)

Figure 1. The Z: Handheld LIBS Analysis for Lithium and other Critical Elements in Aluminum Alloys

Aluminum Alloy Analysis

A rapid, precise and highly portable technique for aluminum alloy ID and chemistry is offered by the Z. Critical elements to identify in many common grades include Mg, Si, Cr, Mn and Cu. For instance, the ability to analyze low concentrations of Mg, Cr and Cu is critical to confidently identify several common wrought grades such as 6063, 1100, 5083/5086, and 2014, 2018 and 2024.

The latter three grades are different in magnesium concentration and require accurate analysis to 0.2% magnesium or lower.

Another example concerns common alloys 1100, 6061 and 6063. 1100 and 6061 are uniquely identified by measuring > 0.04% Cr and 0.8 – 1.2% Mg. Differentiating 6063 and 1100 requires measuring 0.4%Mg. 356 and 357 is an example with foundry alloys, which can only be identified by the difference in magnesium concentrations, 0.2%-0.45% for 356, and 0.45%-0.6% for 357. All of these analysis can be made with the Z in a few seconds.

Table 1. shows the speed and performance of the Z LIBS system. Detection limits for 2, 5 and 10s test times, for Mg, Si, Cr, Mn and Cu are shown in Table 1. A LIBS spectra from a high-purity 1050 certified reference material (CRM) containing 0.027% Mg is shown in Figure 2.

In a two second test, two prominent Mg lines at 279.57 and 285.23nm are measurable in excess of a 99.7% confidence level, the criteria for detection. The visible lines even at 0.027% Mg concentration after 2s, demonstrates that LIBS technology offers the performance needed for confident aluminum alloy analysis.

Table 1. Limits of detection (%) for 2, 5 and 10 s tests of several key alloying elements in Al grades. The analyzer measures more elements than shown in the table.

Element 2 sec 5 sec 10 sec
Mg 0.025 0.02 0.015
Cr 0.04 0.03 0.02
Mn 0.11 0.08 0.08
Cu 0.02 0.015 0.015
Si 0.25 0.10 0.08

A key advantage of the SciAps LIBS technology is that it analyzes all elements in Aluminum alloys with low detection limits, including the low atomic number elements such as Mg, Li, Be and Si. This implies that the above alloys can be separated in just a few seconds as opposed to the 30+ seconds needed by many handheld XRF units.

Lithium in Aluminum Alloys

The analysis of lithium in aluminium alloys, especially in the aluminium re-melting industries, is a growing need. Several aluminium grades manufactured contain between 0.1% and 1.5% lithium. If this scrap is mixed with others alloys for re-melting there is a chance of an explosion. Figure 3 shows a spectrum from an aluminum alloy with 1.83% Li. The large peaks at 610.3 and 670.7 nm represent the Li in the sample.

The 610nm line is used for quantifying Li down to a lower limit of about 0.05%. The stronger line at 670.7nm may be used for lower concentrations. The advanced spectrometer technology inherent in the Z is also highlighted in this application. The analyzer measures lines as low as 185nm including carbon at 193nm, and extends up to 675nm in order to measure major Li lines at 610.2nm and 670.7nm.

Figure 2. Spectrum for a 2 second test of a 1050 grade aluminum alloy containing 0.027% Mg.

Figure 3. Spectrum from a 2 second test on a aluminum alloy containing 1.86% lithium.

Conclusion

The Z offers a high performing alternative to HHXRF for transition and heavy metals, as well as low-atomic number elements and aluminum alloys.

About SciAps, Inc

SciAps, Inc., is a Boston-based instrumentation company specializing in portable analytical instruments. Our mission is to provide durable, field-tested, portable instruments to identify any compound, any mineral, any element — any place on the planet. Manufacturing, service and customer support is operated out of our fully ISO-certified facility located in Laramie, WY.

This information has been sourced, reviewed and adapted from materials provided by SciAps, Inc.

For more information on this source, please visit SciAps, Inc.

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