Titanium dioxide and aluminum oxide are conventional materials used in heterogeneous catalysis as catalyst support. The widely used crystalline phase of both supports is the metastable phase (anatase and γ-Al$_2$O$_3$) in which they possess a higher specific surface area compared to the thermodynamically stable phase (rutile and α-Al$_2$O$_3$). However, these phases have better thermal and mechanical stability than anatase and γ-Al$_2$O$_3$. A novel method to induce phase transformation and structural modification of crystalline materials is by applying shock waves. This study aims to experimentally investigate the effects of shock wave treatment on titania and alumina. A pressure-driven shock tube was used in this work to generate the shock waves. Two sets of experiments were carried out for TiO$_2$ and one for Al$_2$O$_3$. Titania samples were prepared in the form of pellets for the first set. Titania and alumina samples were maintained as powder for the second set of experiments. For titania, twenty shocks were applied at nominal temperature and pressure of ~ 1772 K and 23.3 bar in the first set of experiments, while thirty shocks of ~ 1572 K and 66 bar were applied in the second set of experiments. For alumina, twenty shock loadings were applied at the same conditions used for the second set of titania. Characterization techniques, such as XRD, Raman spectroscopy, TEM, SEM, XPS, and N$_2$ physisorption were employed on treated samples in order to understand the effects of shock wave treatment. Partial phase transformation was observed in shock treated TiO2 from Raman spectra and TEM images. Crystallite size reduction was observed in the first set of experiments, while increase in defects was observed by the enhanced Ti$^{+3}$ in XPS spectra in both sets of experiments. Partial phase transformation was also observed in shock treated Al$_2$O$_3$, when mixed with CNF (carbon nanofibers), from XRD patterns and confirmed with XPS. For alumina, TEM and SEM images showed the smallest particles in contact with carbon fibers, while the biggest particles exhibited agglomeration. Physisorption experiments showed a decrease of 40% in surface area and pore collapse.

Yttria stabilized zirconia (YSZ) is a polymorph with possible phase transformation toughening occurring during impact. The fractography and mechanical properties of laminated alumina and YSZ were studied in this thesis. Five sample types were studied in this thesis: (5:5) Al2O3/YSZ (a sequence of 5 alumina tapes stacked on 5 YSZ tapes), (5:5) Al2O3/YSZ (1 wt.% Pure ZrO2), (7:3) Al2O3/YSZ, Al2O3, and YSZ. Scanning electron microscopy (SEM) and X-ray microscopy (XRM) were used to study morphology and crack propagation with three-point tests performed to study the flexural strength. X-ray diffraction (XRD) spectra of all samples pre and post three-point tests were examined to determine if a change in monoclinic zirconia occurred. The combination of SEM and XRM data found microcracks in the YSZ layers of Al2O3/YSZ laminates with none present on YSZ laminates, leading to the conclusion tensile stress was performed on YSZ during sintering with Al2O3. Fracture patterns show a curving of cracks in Al2O3 layers and abrupt, jagged breaks in YSZ layers with crack forking at major YSZ microcrack regions. YSZ laminates were found to have the highest average flexural strength, but a very high standard deviation and low sample count and Al2O3 laminates having the second highest flexural strength. The (7:3) Al2O3/YSZ laminates had a significant increase in flexural strength compared to both types of (5:5) Al2O3/YSZ laminates. Significant change in monoclinic presence was not found except for the (5:5) Al2O3/YSZ (1 wt.% Pure ZrO2) laminates.

An adsorbent for Cs removal from contaminated water based on phosphotungstic acid (PTA) embedded in SiO 2 network was synthesized and granulated with γ-Al 2 O 3 . PTA/SiO 2 had a high adsorption capacity towards Cs while the binder provided excellent mechanical characteristics of the material. It was shown that small particles of PTA/SiO 2 with the sizes of 0.1–1 µm occupied space between larger particles of the binder (up to 5 µm). Chemical interaction between PTA and γ-Al 2 O 3 during the adsorbent preparation also took place. The obtained porous material with the specific surface area of 286.9 m 2 /g contained 4.73% of PTA. Presence of Keggin units in the structure was confirmed by solid state NMR spectroscopy. Study of the adsorbent in Cs + adsorption from solutions demonstrated its high adsorption capacity. The concentrations of Cs + in the solutions after the column tests decreased by 3.3–5.2 times. The presence of Na + and K + as competing ions did not affect the adsorption. The material was tested in clean-up of radioactive water from the shelter of Chernobyl nuclear power plant (Ukraine). A significant decrease of 137 Cs radioactivity was detected in all samples of radioactive water, especially in acidic solutions. Thus the adsorbent can be used for water treatment after incidents resulting in release of radioactive isotopes 134 Cs and 137 Cs.

The adsorption of cesium on mesoporous silica materials containing embedded phosphotungstic acid (PTA) was studied. The materials contained active adsorbent and binders: γ-Al2O3, kaolin, or charcoal. The presence of Keggin units of PTA in the bound materials was confirmed by FT-IR spectroscopy. Among all materials, the formulation with γ-Al2O3 demonstrated the highest porosity and effectiveness in adsorption. Pure PTA/SiO2 contained a significant fraction of small particles between 100 and 300 nm. However, in the alumina-bound material, they were not detected. SEM imaging showed that these particles occupied interparticle space between larger γ-Al2O3 particles. The material was stable up to 540 °C. In most materials, the adsorption of cesium decreased with increase of the binder contents but not proportionally. The adsorption capacity of all materials depended on the concentration of cesium in the solutions. Maximum adsorption was achieved after 1 h. The adsorption of cesium is controlled by intraparticle diffusion while its rate can be described by the pseudo-second-order model.

A method was found for creating ordered nanoparticles whose size and theoretical order-disorder temperature are ideal for study in the TEM. Specifically FePt, NiPt, FeNiPt and AuCu nanoparticles were studied. We were able to show how a nanoparticle's size affects its order-disorder temperature (Tod). When the particles were around 6 nm in diameter there was a shift downward of the Tod of 10-15 percent compared to the bulk. While particles around 10 nm in diameter experienced a downward shift of 0-6 percent compared to the bulk. One can approximate that particles less than 10-15 nm in diameter would show significant decreases in order-disorder temperature. We confirmed that alumina prevents copper losses, compositions were well within percent error. In addition we showed that when the alumina used is thin enough the images are not adversely affected and charging is not an issue.

Aluminum-alumina nanocomposites were synthesized using mechanical alloying of blended component powders of pure constituents. This study was performed on various powder mixtures with aluminum as the matrix and alumina as the reinforcement with volume fractions of 20, 30, and 50 % and Al2O3 particle sizes of 50 nm, 150 nm, and 5 µm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used for the crystal structure and microstructural characterization of the powders at different stages of milling. Al2O3 powders with 50 nm and 150 nm particle size were predominantly of γ-type, while Al2O3 of 5 µm size was of α-type. The main goal was to achieve uniform distribution of the Al2O3 ceramic particles in the Al matrix, which was achieved on milling for 24 h in a SPEX mill or 100 h in a Fritsch Pulverisette planetary ball mill. The powders were consolidated in two stages: pre-compaction at room temperature followed by vacuum hot pressing (VHP) or hot isostatic pressing (HIP) techniques to a fully dense condition. The effect of reinforcement particle size and volume fraction on the stress-strain response, elastic modulus and yield strength of the composites was investigated. Nanoindentation and compression tests were performed to characterize the composite material. Yield strength of 515 MPa, compressive strength of 685 MPa and elastic modulus of 36 GPa were obtained from compression tests. Nanoindentation results gave the yield strength of 336 MPa, maximum shear stress of 194 MPa and an elastic modulus of 42 GPa. The low elastic modulus values obtained from the above tests might be because of localized yielding possibly due to residual stresses.

Particulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particlematrix bonding and therefore improved stiffness and load transfer in the composite. Photo-luminescent α-alumina nanoparticles when embedded in an epoxy matrix allow for the added benefit of in situ measurements at low strain rates to provide stress-sensitive information using the particle piezospectroscopic (PS) property. To investigate the low strain rate behavior, cylindrical specimens of alumina-epoxy composites with varying volume fractions of alumina were fabricated using a casting process to ensure minimal surface finishing and reduced manufacturing time. The results illustrate the capability of alumina nanoparticles to act as diagnostic sensors to measure the stress-induced shifts of the spectral R-line peaks resulting from low compressive strain rates. The range of PS coefficients measured, -3.15 to -5.37 cm−1/GP a for R1 and -2.62 to -5.39 cm−1/GP a for R2, correlate well with static test results of similar volume fractions. Results reveal a general trend of increasing sensitivity of the PS coefficients with increasing strain rate when compared to similar materials under static conditions. In contrast to static results, at a given strain rate, the PS coefficients show varying degrees of sensitivity for each iii volume fraction. This information can be used to determine the time-dependent microscale stresses the nanoparticles sustain during composite loading. Additionally, this work facilitates failure prediction by monitoring upshifts in the PS information. Calibration of the in situ diagnostic stress sensing capabilities of varying volume fractions of alumina nanocomposites under quasi-static strain rates in this work sets the precedent for future studies at high strain rates.

The work disclosed in this dissertation outlines a newly discovered acidic alumina-mediated orthoallylation of unprotected phenols and the application of this method to the synthesis of prenylated phenolic natural products including dorsmanin A and hyperbeanol Q. Chapter 1 consists of a literature review of prenylated phenolic compounds and includes a discussion of their biological significance followed by an extensive review of the various synthetic strategies that have been used to prepare them. It is our intention to publish the content of this chapter as a review article for the synthetic chemistry community. Showcased in Chapter 2 is the optimization of a novel prenylation method via acidic alumina as the promoter. Phenols and allyl alcohols are combined with acidic alumina in 1,2-dichloroethane or acetonitrile to induce a proposed coordination of the substrates to the alumina surface via hydrogen bonding which facilitates the regioselective ortho-prenylation of phenols. The extensive substrate scope of this chemistry is discussed. In Chapter 3, this alumina-mediated prenylation is applied to the syntheses of several acylphloroglucinol natural products and unnatural structural analogues which are evaluated for their antimicrobial and anthelmintic (anti-parasitic) activity. Some of these compounds exhibited antimicrobial activity and some exhibited anthelmintic potential. In Chapter 4, this prenylation strategy is further extended to the syntheses of additional prenylated phenolic natural products: (±)-sanjuanolide and dorsmanin A. Investigations towards the synthesis of HP1 are also reported. Development of the syntheses of these natural product targets provides a useful venue to investigate the scope of our alumina-mediated phenol prenylation chemistry and to identify its scope and limitations. / Thesis / Doctor of Philosophy (PhD)

Ceramic composites for high temperature applications must be designed with crack arrest capability to improve the resistance to flaws produced in service, such as by thermal shock. Laminated composites containing Al2O3 layers in 3mol%Y2O3-ZrO2 (TZ3Y) were fabricated by electrophoretic deposition (EPD) and pressureless sintering. The layering design (Al2O3 layer thickness and volume fraction) was varied to determine the influence on fracture behaviour. The residual stress in Al2O3 layers was measured using a fluorescence spectroscopy technique. The fracture strength of 15 different laminates, and monolithic Al2O3 and TZ3Y, was tested in 4-point bending at room temperature. Vickers indentation (10 kg load) was used to simulate natural flaws at the sample surface before testing as a measure of flaw tolerance. Fracture ranged from catastrophic failure, to multi-stage failure and complete delamination (in processing). Transitions in behaviour were found related to a geometrical parameter derived from the strain energy release rate for edge cracks. The strength of three Al2O/TZ3Y composites was compared with monolithic Al2O3 and TZ3Y for a range of indentation loads (up to 20 kg). The strength of the composites was similar to monolithic TZ3Y but the flaw tolerance was improved due to multi-stage fracture. The strength and flaw tolerance (using 10 kg indentation) of two Al2O3/TZ3Y composites and monolithic TZ3Y was measured < 1300°C. The multi-stage fracture behaviour disappeared > 25 °C, and there was no beneficial effect of the Al2O3 layers on the strength. Superplastic deformation of the TZ3Y layers at 1300°C was prevented by the constraint of the Al2O3 layers. Recommendations are made about the design of flaw tolerant ceramic laminates for high temperature use. / Thesis / Master of Engineering (ME)

Anodic aluminum oxide (AAO) nanopores are excellent templates to fabricate different nanostructures. However, the pores are limited to a hexagonal arrangement with a domain size of a few micrometers.  In this dissertation, focused ion beam (FIB) is used to create pre-patterned concaves to guide the anodization. Due to the advantage of FIB lithography, highly ordered AAO arrays with different arrangements, alternating diameters, and periodic pore densities are successfully achieved. Anodization window to fabricate ordered AAO is enlarged due to the FIB pre-pattern guidance. AAO has also been successfully used as a template to nanoimprint prepolymer to synthesize vertically aligned and high aspect ratio h-PDMS nanorod arrays with Moiré pattern arrangements. The formation mechanism of anodic TiO2 nanotubes is proposed in this dissertation. Moreover, FIB pre-pattern guided anodization is introduced to synthesize highly ordered TiO₂ nanotubes with different morphologies. The effects of inter-tube distance and arrangement to the structure of TiO₂ nanotubes are investigated. TiO2 nanotubes with branched and bamboo-type structures are achieved by adjusting anodization voltage. The influence of patterned concave depth and surface curvature on the growth of TiO₂ nanotubes and AAO are studied. The efficiency of TiO₂ nanotubes in supercapacitors and photoelectrochemical water splitting are optimized by enlarging surface area and increasing electrical conductivity. Focused ion beam can not only create concave arrays to guide the electrochemical anodization, but also be used for nanoscale sculpting and 3D analysis. When the TiO₂ nanotube surface is bombarded by FIB, there is a mass transfers due to ion-induced viscous flow and sputter milling, thus the TiO₂ nanotubes are selectively closed and opened. By combining FIB cutting and SEM imaging to create a series of 2D cross section SEM images, 3D reconstruction can be obtained by stacking SEM images together. This 3D reconstruction offers an opportunity to directly and quantitatively observe the pore evolution to understand the sintering process. / Ph. D.