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Time resolved and time integrated VUV LIBS for the detection of carbon in steel

Zehra, Syedah Sadaf (2022) Time resolved and time integrated VUV LIBS for the detection of carbon in steel. PhD thesis, Dublin City University and University of Padua.

Abstract
Laser Induced Breakdown Spectroscopy (LIBS) is an analytical technique used to classify and potentially quantify elements in complex hosts (or matrices). Vacuum Ultraviolet Laser Induced Breakdown Spectroscopy (VUV LIBS) offers measurable improvements over traditional visible region LIBS, due to the presence of strong resonance and well spectrally isolated transitions at these shorter wavelengths. This extends the ability of LIBS to discriminate between emission lines from different elements, particularly light elements such as carbon, nitrogen, oxygen, sulphur, etc. In addition, as with visible LIBS, the precision obtainable can be limited by the continuum emission at the early stage of the plasma lifetime and greater performance can be achieved by moving to a time resolved detection system, reducing the contribution from the continuum. Hence, a (single channel) time resolved VUV LIBS system has been designed by replacing a back illuminated CCD with a combination of a plastic scintillator and a photomultiplier tube on an existing LIBS system. In this research, the performance of time integrated and time resolved VUV LIBS for the determination of the carbon content in steel samples is compared. The results demonstrated an improved limit of detection (LOD) for time resolved VUV LIBS over time integrated VUV LIBS for traditional point plasmas. In addition, VUV emission from plasma plumes created at a line (laser) focus was also studied for the same steel samples and the limit of detection was optimised and compared the limit for conventional point plasmas. The results demonstrate that the line focused plasma source in multichannel time integrated space resolved (TISR) mode and the single channel time resolved VUV mode yield comparable LoD values of 50 and 56 ppm respectively. It also showed that both were significantly better than TISR VUV LIBS with point plasma VUV sources which exhibited a poorer LoD of 316 ppm. In addition, two ultraviolet-visible (UV-Vis) LIBS studies were carried out in University of Padova. One of these focused on exploring the potential of conventional LIBS for depth profiling of thin films. The other focused on the classification and sorting of scrap metal samples using multivariate analysis, in particular using principal component analysis (PCA).
Metadata
Item Type:Thesis (PhD)
Date of Award:February 2022
Refereed:No
Supervisor(s):Costello, John T., Nicolosi, Piergiorgio and Hayden, Patrick
Uncontrolled Keywords:Principal Component Analysis
Subjects:Physical Sciences > Analytical chemistry
Physical Sciences > Laser plasmas
Physical Sciences > Physics
Physical Sciences > Spectrum analysis
Physical Sciences > Photochemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Physical Sciences
Research Institutes and Centres > National Centre for Plasma Science and Technology (NCPST)
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
Funders:Erasmus Mundus Joint Doctorate Programme Project No. 2012 – 0033, Sustainable Energy Authority of Ireland
ID Code:26581
Deposited On:18 Feb 2022 12:36 by John Costello . Last Modified 30 Sep 2022 10:30
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