Laser-Induced Breakdown Spectroscopy (LIBS) is a powerful tool for performing chemical analysis measurements of materials, such as slurries, soils, plastics and powder samples. The LIBS technique has proven to be sensitive, selective and robust for rapid, in situ analysis. The focus of this dissertation is the optimization of laser spectroscopic sensing methodologies for material characterization. The applications of the LIBS technique to slurry samples is very challenging due to the water content (~80%). A new sample preparation method called “spin-on-glass” was adopted to reduce the water content in slurry samples and improve the LIBS signal. The feasibility of using the new sampling method with a LIBS system was tested by applying multivariate analysis to the LIBS spectral data. The calibration results demonstrated that the LIBS technique with the new sampling method could successfully predict the elemental concentrations of slurry samples qualitatively and quantitatively. The possibility of developing a LIBS-based sensor system for total carbon quantification in soil samples was studied. The soil samples were studied in pellet form and the calibration models were developed by using simple linear regression (SLR) and multiple linear regression (MLR) analysis. It was found that both SLR- and MLR-based calibrations successfully predicted the carbon concentration in an unknown sample with relative accuracy (RA) within 8%. The LIBS experimental setup was designed, developed and tested for the determination of elemental impurities in plastic calibration standards that are used in dual-energy computed tomography (CT) scanning for petrophysical applications. Univariate calibration (UC) and multiple linear regression (MLR) analysis were used to develop calibration models. From this study, it was concluded that MLR improved the calibration results and data derived from the LIBS analysis enhanced the predictive capabilities of dual-energy CT scanning in general. A comparative study was performed for quantification of strontium (Sr) in an aluminum (Al) batch with both the atomic and molecular LIBS emissions. The calibration models were developed using SLR analysis and the limits of detection (LOD) were obtained. The study confirmed that molecular LIBS could be used for quantification of Sr in a binary mixture.

Laser induced breakdown spectroscopy (LIBS) was tested to examine its applicability to remote and in suit analysis in inaccessible situation. Two types of liquid sample (slurry) prepared for simulating vitrification of liquid hazardous wastes was tested. In situ analysis ability makes the LIBS technique practical for analysis of the slurry samples during vitrification, which is in inaccessible situation. For the first slurry sample, two slurry circulation systems were devised to overcome major technical problems associated with LIBS measurements of slurry samples - namely sedimentation and change in the lens-to-sample distance (L.T.S.D) during measurement. The second slurry sample contained less water and is able to be managed in a small glass container during test. We applied direct analysis of slurry sample filled in glass container. Spectroscopic analysis was performed using two different detection systems: Czerny-Turner and Echelle spectrometer systems. In particular, spectroscopic analysis of data from an echelle spectrometer shows the high efficiency for simultaneously determining physical quantities of all elements of interest. We also evaluate LIBS technique to tin alloy samples for the purpose of quantitative analysis by using Echelle spectrometer system. Unknown samples without information of elemental composition were tested to estimate several sample compositions simultaneously. An artificial neural network, calibration method, and chemical analysis were applied to estimate the elemental concentrations of impurities in tin (Sn) alloy.

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Due to their scientific significance and practical applications, turbulent flows and flames have been under extensive and intensive research for a long time. Turbulent flows and flames of interests to practice inherently have three-dimensional (3D) spatial structures, and therefore diagnostic techniques that can instantaneously resolve their 3D spatial features have long been desired and probably are needed to ultimately answer some of the open research questions. The goal of this dissertation thus is to investigate such diagnostics and demonstrate their capability and limitations in a range of turbulent flows/flames. To accomplish this goal, this dissertation developed and evaluated the following three diagnostic methods: tomographic chemiluminescence (TC), volumetric laser induced fluorescence (VLIF), and super-resolution planar laser induced fluorescence (SR-PLIF). First, 3D flame topography of well-controlled laboratory flames was measured with TC method and validated by a simultaneous 2D Mie scattering measurement. The results showed that the flame topography obtained from TC and the Mie scattering agreed qualitatively, but quantitative difference on the order of millimeter was observed between these two methods. Such difference was caused by the limitations of the TC method. The first limitation involves TC's reliance on chemiluminescence of nascent radicals (mainly CH*) in reacting flows, causing ambiguity in the definition of flame front and limiting its applications to certain types of reactive flow only. The second limitation involves TC's inability to study an isolated region of interest because the chemiluminescence is emitted everywhere in the flame. Based on the above understanding of the TC technique, the second part of this dissertation studied a VLIF method to overcome the above limitations of the TC technique. Compared with the TC technique, the VLIF method can be used in either reacting or non-reacting flow and on any particular region of interest. In the VLIF technique, the fluorescence signal was generated by exciting a target species with a laser slab of certain thickness. The signal was recorded by cameras from different perspectives, and then a VLIF tomographic algorithm was applied to resolve the spatial distribution of the concentration of the target species. An innovative 3D VLIF algorithm was proposed and validated by well-designed experiment. This model enables analysis of VLIF performance in terms of signal level, size of the field of view in 3D, and accuracy. However, due to the limited number of views and the tomographic reconstruction itself, the spatial resolution of VLIF methods is limited. Hence, the third part of this dissertation investigated a SR-PLIF method to provide a strategy to improve the spatial resolution in two spatial directions, and also to extend the measurement range of scanning 3D imaging strategies. The SR-PLIF method used planar images captured simultaneously from two (or more) orientations to reconstruct a final image with resolution enhanced or blurring removed. Both the development of SR algorithm, and the experimental demonstration of the SR-PLIF method were reported. / Ph. D. / Optical diagnostics have become indispensable tools for the study of the turbulent flows and flames. Due to the inherently 3D structure of turbulent flows and flames, diagnostic techniques which can provide 3D measurements have been long desired. Therefore, this dissertation reports the development of three optics diagnostic methods that can provide such measurement capability, with a detailed discussion of their capabilities and limitations. The methods studied are tomographic chemiluminescence (TC), volumetric laser-induced fluorescence (VLIF), and super-resolution planar laser induced fluorescence (SR-PLIF). For the TC technique, the emission of light from combustion radicals (CH* and OH*) was recorded by multiple cameras placed at different orientations. A numerical algorithm was then applied to reconstruct the 3D flame structure. For the VLIF technique, a laser slab was used to excite a specific chemical species in the flame, which were captured from different perspectives to reconstruct the flow or flame structure in 3D. For the SR-PLIF technique, a series of planar images were recorded from multiple orientations to reconstruct a target image with higher resolution or to extend the measurement volume of scanning 3D diagnostics. It is expected that the results obtained in this dissertation lay the groundwork for further development and expanded application of 3D diagnostics for the study of turbulent flows and combustion processes.

Optical diagnostics have become indispensable tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited to measurements at a point, along a line, or across a two-dimensional (2D) plane; while turbulent flows and flames are inherently four-dimensional (three-dimensional in space and transient in time). As a result, diagnostic techniques which can provide 4D measurement have been long desired. The purpose of this dissertation is to investigate two of such 4D diagnostics both for the fundamental study of turbulent flow and combustion processes and also for the applied research of practical devices. These two diagnostics are respectively code named tomographic chemiluminescence (TC) and volumetric laser induced fluorescence (VLIF). For the TC technique, the emission of light as the result of combustion (i.e. chemiluminescence) is firstly recorded by multiple cameras placed at different orientations. A numerical algorithm is then applied on the data recorded to reconstruct the 4D flame structure. For the VLIF technique, a laser is used to excite a specific species in the flow or flame. The excited species then de-excite to emit light at a wavelength longer than the laser wavelength. The emitted light is then captured by optical sensors and again, the numerical algorithm is applied to reconstruct the flow or flame structure. This dissertation describes the numerical and experimental validation of these two techniques, and explores their capabilities and limitations. It is expected that the results obtained in this dissertation lay the groundwork for further development and expanded application of 4D diagnostics for the study of turbulent flows and combustion processes. / Ph. D. / Optical diagnostics have become indispensable tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited to measurements at a point, along a line, or across a two-dimensional (2D) plane; while turbulent flows and flames are inherently four-dimensional (three-dimensional in space and transient in time). As a result, diagnostic techniques which can provide 4D measurement have been long desired. The purpose of this dissertation is to investigate two of such 4D diagnostics both for the fundamental study of turbulent flow and combustion processes and also for the applied research of practical devices. These two diagnostics are respectively code named tomographic chemiluminescence (TC) and volumetric laser induced fluorescence (VLIF). For the TC technique, the emission of light as the result of combustion (i.e. chemiluminescence) is firstly recorded by multiple cameras placed at different orientations. A numerical algorithm is then applied on the data recorded to reconstruct the 4D flame structure. For the VLIF technique, a laser is used to excite a specific species in the flow or flame. The excited species then de-excite to emit light at a wavelength longer than the laser wavelength. The emitted light is then captured by optical sensors and again, the numerical algorithm is applied to reconstruct the flow or flame structure. This dissertation describes the numerical and experimental validation of these two techniques, and explores their capabilities and limitations. It is expected that the results obtained in this dissertation lay the groundwork for further development and expanded application of 4D diagnostics for the study of turbulent flows and combustion processes.

No / We demonstrate that nanofiltration of aqueous glycine solutions has a pronounced effect on laser-induced nucleation. Two nucleation regimes were observed in nonfiltered, irradiated solutions under isothermal conditions: a rapid initial regime associated with laser-induced nucleation and a second much slower spontaneous nucleation regime. Filtration of the solutions prior to irradiation greatly suppressed the rapid regime, while the slow regime was similar regardless of filtration or irradiation, for all supersaturations studied. A clear effect of filtration on crystal polymorphism was also observed. Nonfiltered irradiated solutions at a lower supersaturation almost exclusively yielded the α-polymorph, while at higher supersaturations there was significant presence (∼40%) of the γ-polymorph. On the other hand, filtered solutions almost exclusively yielded the α-polymorph of glycine at all supersaturations studied. These surprising results challenge some established ideas about laser-induced nucleation, showing that previously reported laser-induced nucleation phenomena in glycine aqueous solutions can be effectively suppressed by filtration, so that the underlying mechanism is unlikely to be based on molecular scale interactions involving just the solute and the solvent alone. Instead, laser-induced nucleation in this system appears to be related to either colloidal scale solution clusters or foreign solid or molecular impurities that can be removed by nanofiltration.

The development of Laser-Induced Thermal Grating Spectroscopy (LITGS) for diagnostics of combusting and non-combusting flows is described. The first use of LITGS to provide in situ calibration of 2-Dimensional temperature distributions generated using Two-Colour Planar Laser-Induced Fluorescence (TC-PLIF) is reported. Time-resolved measurements of temperature distributions in a firing GDI optical engine obtained by TC-PLIF were made during the compression stroke and calibrated to the absolute temperature scale by simultaneous LITGS measurements. The accuracy and precision of the temperatures derived from LITGS data are evaluated using alternative methods of data analysis - Fast Fourier Transform and Fitting to theoretical models of the experimental data. The relative merits of the two methods are examined for analysis of weak LITGS signals obtained under engine conditions of low pressure and high temperature. The combined TC-PLIF and LITGS system was demonstrated by performing repeated single-shot measurements for 1 in every 10 four-stroke cycles showing excellent correlation of the temperatures derived from both techniques. Direct measurement of the effect of 'charge cooling', of order 5 K, for operation with direct injection is reported. Inhomogeneous temperature distributions were observed during the compression stroke for fired operation with Port Fuel Injection (PFI) and also with Gasoline Direct Injection (GDI). The effects of varying the relative concentrations of toluene and iso-octane in the two-component fuel were investigated. Extension of the LITGS technique to multi-point measurements along a 1-D line is described. By recording signals from 4 points on separate detectors using a fibre-coupled photodiode array the limitations of Streak Cameras used previously for 1-D LITGS measurements were overcome. Demonstration of principle experiments are reported in which simultaneous 4-point measurements were made with 1 mm spatial resolution and a precision of 0.7 % in temperature gradients in gas flows and in boundary layers at surfaces.

Laser Induced Breakdown Spectroscopy (LIBS) which is used to determine the elemental content of various samples, inspects the emission spectroscopy of samples of interest for searching certain elements or identifying the unknown content. In this study, spectroscopic analyses of various kinds of metals, namely, Cu, Fe, Mo, Ti, W, some compounds such as CuBe, ZnSe, ZnS, GaSe, some semimetals like Si, Ge and even gases were investigated by means of a compact-commercial portable LIBS system and an independently constructed experimental set-up consisting of a single pulse system and various kinds of double pulse configurations using Nd:YAG lasers. The contributions of this thesis to the LIBS community can be classified into two main groups- which are experimental and code development. One of the experimental contributions was the investigation of the different crystal surfaces of silicon in which dangling bond density were taken into account for a more precise comparison of atomic emissions. The second experimental contribution was the polarization experiments by which polarization dependency, to some extent, was demonstrated. The third and final one was the orthogonal double pulse configuration with a 45 o incidence angle for both lasers in opposite directions by which it was shown that the positioning becomes straightforward yielding the desired reproducible results. The second major contribution was to develop a basic code for analyzing the experimental data more accurately. In conclusion, by means of the different experimental approaches, factors relating to the enhancement in intensity were investigated and as a result of developing the code, flexibility in upgrading the constraints of element searching was obtained and the updating of the database was accomplished.

A new technique is developed that uses planar laser-induced fluorescence (PLIF) imaging of sublimated naphthalene to image the transport of ablation products in a hypersonic boundary layer. The primary motivation for this work is to understand scalar transport in hypersonic boundary layers and to develop a database for validation of computational models. The naphthalene is molded into a rectangular insert that is mounted flush with the floor of a Mach 5 wind tunnel. The distribution of naphthalene in the boundary layer is imaged by using PLIF, where the laser excitation is at 266 nm and the fluorescence is collected in the range of 320 to 380 nm. To investigate the use of naphthalene PLIF as a quantitative diagnostic technique, a series of experiments is conducted to determine the linearity of the fluorescence signal with laser fluence, as well as the temperature and pressure dependencies of the signal. The naphthalene fluorescence at 297 K is determined to be linear for laser fluence that is less than about 200 J/m². The temperature dependence of the naphthalene fluorescence signal is found at atmospheric pressure over the temperature range of 297K to 525K. A monotonic increase in the fluorescence is observed with increasing temperature. Naphthalene fluorescence lifetime measurements were also made in pure-air and nitrogen environments at 300 K over the range 1 kPa to 40 kPa. The results in air show the expected Stern-Volmer behavior with decreasing lifetimes at increasing pressure, whereas nitrogen exhibits the opposite trend. Preliminary PLIF images of the sublimated naphthalene are acquired in a Mach 5 turbulent boundary layer. Relatively low signal-to-noise-ratio images were obtained at a stagnation temperature of 345 K, but much higher quality images were obtained at a stagnation temperature of 380 K. The initial results indicate that PLIF of sublimating naphthalene may be an effective tool for studying scalar transport in hypersonic flows. / text