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Depth profiling using laser-induced breakdown spectroscopy method
Průcha, Lukáš ; Novotný,, Karel (referee) ; Pořízka, Pavel (advisor)
The diploma thesis deals with the use of Laser-Induced Breakdown Spectroscopy (LIBS) for depth profiling and 3D mapping of the zinc-coated steel used in the automotive industry. Before creating depth maps and depth profiles, optimization of the experiment was performed. It was shown that the LIBS technique is suited for making depth profiles and depth maps. The theoretical part deals with the description of the LIBS instrumentation, characteristics of plasma, and assembling of scientific papers which reflect the up to date knowledge about depth profiling and mapping with the use of the LIBS technique. The experimental part describes the optimization of the experiment. Gate delay, the depth and the diameter of craters using the profilometer, the position of the focal plane relative to the sample surface, and selection of spectral lines with the smallest residual signal and small scattering of data were optimized. Depth profiles of zinc, iron, chromium and manganese with the depth map of zinc and iron were made, and also the depth resolution for both elements was calculated.
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Korelace charakteristických signálů laserem buzeného plazmatu
Terschová, Vanda ; Novotný, Karel (referee) ; Pořízka, Pavel (advisor)
Laser-induced breakdown spectroscopy (LIBS) is a fast analytical method, but can also be complicated. This spectroscopic method is used to provide a qualitative and quantitative analysis of a sample. The analysis is carried out by capturing the emission radiation of the generated plasma. The accuracy and stability of the measurement is affected by several parameters, such as stability of the laser, physical and chemical properties of the sample, its homogeneity and others, that can not always be eliminated. For this reason other methods are being added to the LIBS experiment that could improve the quality of this analysis. This diploma thesis is focused on a research of the literature on the standardization of laser-induced plasma signal and the possibility of using an acoustic signal for this purpose. For this reason , it is necessary to perform basic experiments and to verify if the acoustic signal correlates with the emission signal. If these signals correlate together, it would be possible to use the acoustic signal for standardization og the LIBS data, which would improve the accuracy of the analysis. In the theoretical part at the beginning other spectroscopic methods are summarised. Then the work is focused on the description of the LIBS method, possible ways of the analysis, standardization of emission signals and its review in the literature. The experimental part is aimed at the study of the acoustic signal that was performed in the framework of this study. At the beginning, there are introduced results of the basic measurements on steel and brass samples. These results were important for an optimization of the experiment. The following section shows the results obtained from the measurements of the acoustic signal on the samples with the same chemical composition but different hardness. At the end the correlation between the acoustic and emission signals is discussed.
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Visualization of spectroscopic data using Principal Component Analysis
Šrenk, David ; Žák, Libor (referee) ; Pořízka, Pavel (advisor)
This diploma thesis deals with using laser-induced breakdown plasma spectroscopy for determining the elemental structure of unknown samples. It was necessary to design an appropriate method to qualify material by laser-induced emission spectrum. Pretreatment of data and using a variety of chemometrics methods had to be done in order to qualify the structure of elements. We achieved a required solution by projecting the data to a new PCA space, creating clusters and computing the Euclidean distance between each cluster. The experiment in the practical part was set to detect an interface of two elements. We created a data file simulating the ablation on the interface. This data set was gradually processed applying a mathematical-chemical-physical view. Several data procedures have been compiled: approximation by Lorenz, Gauss and Voigt function and also a pretreatment method such as the detection of outliers, standardization by several procedures and subsequent use of principal components analysis. A summarization of processes for input data is fully described in the thesis.
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Combination of laser spectroscopy methods for chemical analysis
Holub, Daniel ; Novotný, Karel (referee) ; Pořízka, Pavel (advisor)
The topic of this Master’s thesis is combination of laser spectroscopic methods. LIBS and Raman spectroscopy were chosen for the combination. This combination is applied to plastic identification and separation as a mean to automate sorting of plastic waste. Data handling was done via different methods of computer learning algorithms scripted in R language. Plastic sorting accuracy over 90 % was reached thanks to the combination of chosen methods. This work also addresses some issues implied by combination of two different methods.
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Development and optimization of laser assisted spark discharge optical emission spectroscopy
Kleštinec, Róbert ; Samek, Ota (referee) ; Pořízka, Pavel (advisor)
This master's thesis addresses the improvement of the detection capability and sensitivity of the LIBS method through the utilization of a secondary energy source in the form of spark discharge. The use of spark discharge for plasma excitation significantly extends its lifetime and provides an opportunity to enhance the analytical properties of the existing LIBS system. In the experimental part, both conductive and non-conductive samples were analyzed. In cement paste samples, chlorine was successfully detected without the need for additional rare gas atmosphere.
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Optimizing experimental parameters for LIBS analysis of hard tissues
Fazlić, Aida ; Kuchynka,, Michaela (referee) ; Pořízka, Pavel (advisor)
Tato diplomová práce se zaměřuje na detekci a analýzu těžkých kovů, zejména olova (Pb), v tvrdých tkáních pomocí hydroxyapatitových standardů a spektroskopie laserem buzeného plazmatu (LIBS). Studie využívala různé vlnové délky laseru 1064 nm, 532 nm a 266 nm, stejně jako různé konfigurace laseru, včetně jednopulzní (SP, z angl. single-pulse) LIBS a dvojpulzní (DP, z angl. double-pulse) LIBS v ortogonálním a kolineárním uspořádání. Byla provedena optimalizace parametrů laseru, jako jsou vlnová délka, defokus, doba zpoždění, mezipulzní doba zpoždění a energie. Poměr signál-ke-šumu (SBR), limit detekce a rozlišení odpovídající průměru ablačního kráteru sloužily jako základní parametry pro určení optimální kombinace parametrů. Výsledky této studie poskytují důležité poznatky o optimálních parametrech LIBS pro detekci a analýzu těžkých kovů v tvrdých tkáních, což může mít potenciálně významné dopady pro lékařský výzkum.
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LIBS analysis of heavy metals in plant matrice
Opluštil, Marek ; Pořízka, Pavel (referee) ; Krčma, František (advisor)
This bachelor thesis deals with the analysis of cadmium distribution in the plant matrix using laser - induced breakdown spectroscopy (LIBS). Technical hemp plants grown in soil with different cadmium concentrations were used as samples. The theoretical part focuses on LIBS methods in terms of basic principles, description of accompanying phenomena during measurements and instrumentation. Advantages and disadvantages over other analytical techniques as well as practical applications are also described. In addition, the issue of cadmium in the environment, its occurrence and use in human activities is described. In the experimental part, the methodology for sample preparation for LIBS and ICP-OES analysis is described. The aim of this work is to observe the effect of cadmium on the growth of plants that were successively harvested weekly until the fourth week. Subsequently, plant and soil samples were prepared for LIBS and ICP-OES measurements and the results were evaluated. ICP-OES analysis led to the determination of each element content. The LIBS method provided information on the areal distribution of the elements (spectral maps), allowing to see in which plants part the determined element is located. It is clear from the results of the experimental part that the LIBS method is very advantageous and efficient in the analysis of elements in biological matrices, both biogenic and toxic.
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Optimization of laser ablation of soft tissues
Bischofová, Hana ; Kuchyňka,, Michaela (referee) ; Pořízka, Pavel (advisor)
Laser-induced breakdown spectroscopy (LIBS) is an analytical method which is used in many fields and also for elemental analysis of soft tissues. It is necessary to optimize the soft tissue laser ablation to achieve the highest possible intensity of the wavelength spectrum. Mouse kidneys were ablated in the experimental part of this master thesis. The samples of the kidneys were prepared in two different ways, by embedding in paraffin and by preparing cryo-sections. The femto- and the nano- second lasers with different wavelengths, energies and pulse counts were used for ablation.
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Automatic sample tilt compensation for chemical mapping by LIBS
Stříbrná, Klára ; Pořízka, Pavel (referee) ; Prochazka, David (advisor)
This thesis deals with designing an algorithm for slope compensation of a sample examined using the LIBS (Laser-induced breakdown spectroscopy) method. It mainly fucuses on the purpose of elemental mapping. The sample slope noticeably affects the result quality and therefore a demand for a simple and inexpensive solution to this problem appeared that would also be applicable for commercial uses of LIBS.
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