Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Henk F. Arnoldus

Committee Member

Henk F. Arnoldus

Committee Member

Jagdish P. Singh

Committee Member

David Monts

Committee Member

Mark A. Novo

Other Advisors or Committee Members

Neeraj Rai

Date of Degree

8-6-2021

Original embargo terms

Visible to MSU only for 1 year

Document Type

Dissertation - Open Access

Major

Physics

Degree Name

Doctor of Philosophy

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Arts and Sciences

College

College of Arts and Sciences

Department

Department of Physics and Astronomy

Department

Department of Physics and Astronomy

Abstract

Laser-induced breakdown spectroscopy (LIBS) is a technique that allows quantitative and qualitative analysis of many materials. In this study, the LIBS analysis options for strontium mixture powders is expanded by increasing the number of usable strontium atomic transitions to avoid incorrect results due to spectral congestion or high strontium concentrations. The research employs double-sided tape affixed to a glass slide to hold the sample where the powder is poured onto one surface of the tape and excess dust that has not adhered is removed. This method minimizes the sample quantity needed and keeps the sample on the slide during experimentation, which also reduces costs. Herein, LIBS was used to detect and quantify the level of metal concentrations in used engine oil samples to provide valuable information about the composition of the selected material in a liquid sample. Data were obtained using multivariate analysis to develop calibration curves using LIBS spectra, which was employed for the quantification of the elements Al, Ca, Fe, Mg, and Mn. The relationship between the peak intensity of the metals in new engine oil samples and the metal concentrations in used engine oil samples were analyzed to minimize the matrix effect and the interference of element lines after which the atomic emission observed in LIBS spectra of used engine oil and new engine oil were compared. C2 molecular band emissions were also used to determine the degree of the engine oil degradation. Next, calibration models were developed for samples with high species concentrations. A partial least squares regression model was developed for calibration models to overcome matrix effect problems of some lines of each metal. This research successfully used the LIBS technique to determine the degree of engine oil degradation. This study established that used engine oil analysis using the LIBS technique can be utilized to maintain engines in good condition and to prevent engine failure. This paper presents the key findings and conclusions regarding the application of LIBS. Finally, although this technique shows many benefits and reliable results, challenges remain in terms of matrix effects, spectral pre-processing, model calibration, and instrumentation.

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