Materials Science

Petroleum coke (petcoke) is a waste by-product of the upgrading process in the oil refining industry. It has limited utility in other areas of application.1 High carbon content (over 85 wt.%), low ash content, and softness make petcoke a potentially valuable precursor for graphitization, where amorphous carbon can be transformed into graphitic carbon. The synthetic production of graphite is gaining more interest due to the increasing demand for battery materials.2,3 Without metal moderators, achieving graphitization requires significantly high temperatures (> 2500 °C). Magnesium (Mg) has been identified as a promising reactant because of its efficacy in promoting graphitization and its relatively simple removal from the final product.3–5 The optimized conditions of magnesium-assisted graphitization showed an electrical conductivity of (3552.0 ± 78.5) S/m at 10 mA. Furthermore, bimetallic metal mediators can exhibit improved catalytic activity in graphitization due to the synergistic effect.3,6,7 Raney nickel alloy (Ni-Al alloy) contains 50 wt.% nickel and 50 wt.% aluminum. Individually, nickel and aluminum have shown efficacy in graphitization.8 However, no research has been conducted on the efficacy of Raney nickel alloy as a metal mediator in petcoke graphitization. We present our work on the graphitization of petcoke and its derived activated carbon using magnesium and Ni-Al alloy at 1000 °C and 1500 °C, respectively. This study assesses the effects of heating time, temperature, and precursor particle size on the degree of graphitization. Additionally, magnesium was completely removed after the graphitization process, and the residual Raney nickel alloy percentage was minimal.

Author Keywords: activated carbon, magnesium, Petroleum coke, Raney nickel alloy, synthetic graphitization

In electron-doped ferroelectrics, the free electrons can become concentrated along the domain walls which act like a conducting surface. We consider the impact of free electrons occupying the t2g orbitals on the domain walls of an electron-doped perovskite ferroelectric. We build an analytical model based on Landau-Ginzburg-Devonshire theory, and a trio of tight-binding Hamiltonians for free electrons. We self-consistently solve for the polarization, potential, and electron density using a finite-difference approximation. We find that the ferroelectric is effectively charge neutral. The free electrons are attracted to the positively-charged domain wall, leaving it with a small residual charge. As the electron density increases, the domain walls tilt to form zig-zag domain walls. Orbital selectivity of the t2g orbitals depends on the relative orientations of the orbital plane and the domain wall. This property influences the rate at which the domain wall tilts as a function of the electron density.

Author Keywords: Charged Domain Wall, Domain Wall, Ferroelectric, Landau-Ginzburg, Perovskite, Strontium Titanate

There is a `universal' picture of a charged domain wall (CDW) in theoretical work, often depicted as residing in an infinite thickness film, charge neutral, and with no bias voltage applied. However, in experiment CDWs are shown with none of these assumptions. CDWs are produced in thin or ultra-thin films, the CDW is not charge neutral, and a bias voltage is being applied. We look to go beyond these assumptions. It was shown that a positively charged domain wall (DW) moves against an external electric field which is not expected. The free electron density was also shown to determine the DW displacement amount. When the film thickness is lowered (ultra-thin film) we get a negatively charged DW which still moves against an external electric field, which agrees with experiment of a CDW in a ultra-thin film. This suggests the charge on the DW does not determine displacement direction.

Author Keywords: charged domain wall, displacement

This thesis presents the design, synthesis, and evaluation of activated carbon polyacrylamide (AC-PAM) composites for oil sands tailings remediation, integrating flocculation and adsorption functionalities. Surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to graft high molecular weight PAM brushes onto petroleum coke and commercial activated carbon, with SARA-ATRP yielding the most uniform architecture (Mn ≈ 5.2 kg/mol, Đ ≈ 1.25). Flocculation tests using mature fine tailings (MFT) revealed superior sedimentation and dewatering with SARA-ATRP composites, outperforming conventional PAM at lower dosages. Adsorption studies using benzoic acid and model naphthenic acids showed selective uptake governed by polymer brush morphology and molecular structure, with Dubinin–Radushkevich isotherms best capturing the behavior of ARGET-ATRP composites. Post-flocculation assays confirmed reduced metal and polymer contamination, validating dual-function efficacy. These findings underscore petcoke's viability as a sustainable substrate and highlight controlled polymerization as a critical driver for tuning composite performance in industrial water treatment.

Author Keywords: Activated Carbon, Adsorption, Atom Transfer Radical Polymerization, Dubinin–Radushkevich, Isotherm, Polyacrylamide

The synthesis of biaryls through transition metal catalyzed cross-coupling reactions has been instrumental for synthetic organic chemists. The Hiyama reaction, which features organosilicon derived cross-coupling partners with aryl chlorides, remains relatively underdeveloped compared to other cross-coupling reactions. In this thesis, it is demonstrated that bench stable Palladium N-Heterocyclic Carbene (NHC) precatalysts of the general type [(NHC)Pd(allyl)Cl] are highly active in the Hiyama cross-coupling of activated aryl chlorides with low catalyst loading. Notably, this research demonstrates that catalysts featuring sterically less demanding NHCs display higher activity in this reaction, which contrasts with other cross-coupling reactions. Preliminary mechanistic investigations including in situ reaction monitoring by 19F NMR spectroscopy have uncovered side reactions. These side reactions may explain the low catalytic performance observed with unactivated substrates. These studies could help to further develop this reaction and improve catalytic performance. Additional investigations have also been made into ligand development by altering the electronics of sterically hindered NHC ligands for use in other cross-coupling reactions.

Author Keywords: Catalysis, Cross-coupling, Organic Chemistry, Organometallics, Side Reactions, Synthesis

The generation of polymer brushes by surface-initiated polymerization techniques has become a powerful tool for the creation of hybrid materials. Governed by the type and amount of polymer used in the modification, the chemical and physical properties of a surface can be tailored by polymer grafting. In this study, a commonly used polymer flocculant, polyacrylamide (PAM), was grafted onto the surface of activated carbon (AC). This hybrid material was designed with the intent of combining the functionalities of both the activated carbon and the polymer flocculant, potentially acting in a synergistic manner. The PAM grafted AC (AC-PAM) was examined as a flocculant in the treatment of mature fine tailings (MFT). AC-PAM was synthesized by surface-initiated activators generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). This was accomplished by pre-functionalizing the surface of activated carbon by oxidation, followed by the attachment of an ATRP initiator. From this surface, SI-AGET ATRP of acrylamide monomers was performed. The resulting AC-PAM was characterized by FTIR, XPS, TGA, SEC, and BET analysis. Characterization results indicated the successful grafting of polyacrylamide from the surface of activated carbon. The AC-PAM was measured to contain approximately 10.6% PAM by weight, and the average-number molecular weight of the grafted polymer was 176,100 g/mol. The flocculation performance of AC-PAM and PAM were compared by performing settling tests with 5 wt% MFT. The optimal polymer dosage for PAM was found to be 10,000 ppm, producing an initial settling rate of 3.51 m/hr and a supernatant turbidity of 430 NTU. Comparatively, the optimal dosage for AC-PAM was found to be 20,000 ppm, producing a supernatant turbidity of 114 NTU and a fast initial settling rate of 27.54 m/hr. The improved flocculation performance is hypothesized to occur due to the effective increase in the molecular weight of PAM when grafted from the surface of activated carbon. In all, our work demonstrates the successful grafting of PAM from AC, as well as potential wastewater treatment applications for these types of hybrid materials.

Author Keywords: Activated carbon, Atom transfer radical polymerization, Flocculation, Grafting, Polyacrylamide, Surface-initiated polymerization

Coherent anti-Stokes Raman scattering (CARS) microscopy is a label-free chemical imaging modality that uses CARS as a contrast mechanism to spatially resolve materials based on their molecular vibrational spectra. Due to the presence of a non resonant background that obfuscates the chemical information contained in CARS spectra, CARS images suffer from poor contrast and cannot be readily used for quantitative chemical analysis. Over the past two decades, spectral retrieval methods have been developed to obtain Raman-like spectra from CARS spectra. These methods promise to improve image contrast and enable reliable quantitative analysis. In this work I systematically evaluate a selection of the forefront spectral retrieval methods, including both analytical and machine learning approaches, to determine how well they perform at the task of non resonant background removal. The more recent machine learning methods demonstrate remarkable performance on spectra resembling the training dataset but are not as suitable as the analytical methods in general. The analytical methods based on the discrete Hilbert transform thus remain preferable due to their ease-of-use and general applicability.

Author Keywords: chemical imaging, coherent anti-stokes raman scattering, kramers-kronig analysis, machine learning, non-resonant background, spectral phase retrieval

This thesis comprises two parts:Part I describes a method to improve the accuracy with which the polarization state of light can be characterized by the rotating quarter-wave plate technique. Through detailed analysis, verified by experiment, we determine the positions of the optic axes of the retarder and linear polarizer, and the wave plate retardance, to better than 1° for typical signal-to-noise ratios. Accurate determination of the Stokes parameters can be achieved using this technique to determine the precise retardance at each of the wavelengths of interest. In Part II, a theoretical analysis of the Fabry-Perot interferometer and its application to quantitative absorption spectroscopy is presented. Specifically the effects of broadening due to non-monochromatic light sources and examples of non-ideal etalon surfaces on the visibility of absorption features are investigated. The potential of this type of spectrometer for ethanol detection in a portable breath analysis application is discussed.

Author Keywords: ABSORPTION SPECTROSCOPY, CALIBRATION, FABRY-PEROT INTERFEROMETER, OPTICS, POLARIMETRY

Microwave resonances in isolated water-based spheres, dimers, and trimers are explored using simulations conducted with COMSOL Multiphysics. The study centers on morphology-dependent resonances (MDRs) and hotspot characteristics in cm-sized objects at microwave frequencies. Monomers subjected to microwave radiation exhibit four distinct resonant modes at specific sizes characterized by electric and magnetic field distributions which correspond to magnetic-dipolar, electric-dipolar, magnetic quadrupolar, and electric quadrupolar resonances, respectively. Dimer configurations reveal intriguing hotspot features, with axial hotspots emerging as a key resonant characteristic. The three fundamental dimer orientations dictate unique resonant behaviors, highlighting the sensitivity of hotspot intensity to orientation changes, but smooth and consistent trends during transitions between them. Investigations into trimer structures, as a more intricate geometry formed by interconnected dimers, reveal the subtle interactions of spheres in a trimer structure. Trimer hotspots largely reflect the sum of isolated dimer hotspot contributions, showcasing the energy conservation with no evidence of a newly formed hotpot. Our results, while arising as a consequence of the particularly high index of refraction of water at GHz frequencies, are generalizable to other length scales (such as nano-photonics), were materials with sufficiently high refractive index and transparency to be found.

Author Keywords: COMSOL simulations, Electromagnetic physics, Microwave frequencies, Morphology-dependent resonance, water-based objects

This thesis describes the preparation, optimization, functionalization, and characterization of activated carbon materials sourced from a petroleum coke feedstock for the tailored removal of heavy metal species in contaminated waters. The goal of this work is to develop an understanding of the mechanisms that drive adsorption of heavy metals onto activated carbon surfaces. By determining the mechanisms that drive adsorption, activated carbon materials can be modified to increase the efficiency of the adsorption process. The novelty of this work comes from the use, modification, and functionalization of activated carbon derived from petroleum coke, a waste by-product of the oil-sands extraction process, a source not prevalent in current literature. The novelty also comes from the determination of the methods by which heavy metals are adsorbed onto the given adsorbate as literature does not focus on the mechanisms themselves. The work presented sheds light on the specific adsorption mechanisms, with the aim of elucidating how a given material's surface can be enhanced to target a specific analyte. This work focused on the use of microwave plasma atomic emission spectroscopy (MP-AES), x-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller theory (BET) to obtain the necessary data required for the determination of adsorption mechanisms, adsorption capacities, and surface characterization of the materials. MP-AES is used for the determination of the adsorption capacity of the materials produced. Surface characterization of the materials was done using XPS, and surface area and pore size distributions were determined using BET for surface area determination and nitrogen adsorption measurements following density functional theory for pore size distribution determination. XPS of the activated carbon post-chromium and post-arsenic adsorption show a reduction of the metals from chromium (VI) to chromium (III) and from arsenic (V) to arsenic (III). By increasing the amount of hydroxyl functional groups on the AC surface through a simple thermal-treatment, the chromium adsorption was increased from 17.0 mg/g to 22.4 mg/g. By loading a reducing agent onto the activated carbon surface, an increased number of potential binding sites for the arsenic are loaded onto the AC surface and the adsorption of arsenic increased from 8.1% to 51%.

Author Keywords: Activated Carbon, Adsorption, Adsorption Mechanisms, Arsenic, Chromium, Petroleum Coke