The technological development and application of waste-to-resource strategy is significantly critical and crucial in both environmental and manufacturing industries, via which we do not only provide practical treatments to toxic waste materials but also translate them into usable products. It has been considered as a preferred method which should be applied in future wastewater treatment strategies. In this study, we investigated the process of incorporating cadmium oxide and nickel oxide into ceramic-based materials with the phases of CdAl4O7, and CdFe2O4. Such products are of less harmful effect to the natural environment and can also be of beneficial use with their good mechanical properties identified by nano-indentation. We proved the possibility and provided an opportunity to convert the waste from wastewater treatment process to a new material resource. XRD is preferred for characterizing solid mixtures to determine the relative abundances of crystalline phases during the reaction process. As a result, we can obtain the relative abundance information on the growth of the crystalline products, such as CdAl4O7, and CdFe2O4 according to the change of fabrication temperatures. In that case, the starting reaction temperature and the optimized temperature (at which the completed reaction could be achieved) could be revealed. In Cd-Al system, the starting temperature for CdAl4O7 formation is 900 °C, and the optimized formation temperature is around 1020 °C. On the other hand, for Cd-Fe system, such temperatures are of 700 °C and 850 °C correspondingly. In our research, it is shown that the ceramic-process is an effective strategy to stabilize the waste hazardous metals (cadmium and nickel) by materials such as aluminate, ferrite, and kaolin commonly used in ceramic industry. Through this method, the difficult-to-treat wasted metals would become reusable and applied in building and infrastructure projects. Products containing CdAl4O7, CdFe2O4 and NiAl2O4 have shown higher resistance to acidic leaching, comparing to CdO and NiO used as the starting materials to simulate the waste metal forms discharged from the industrial stream. Furthermore, similar measurements by alkaline attack on the sintered products (NiAl2O4 containing samples) were also studied. Besides the investigation to leaching behavior, the mechanical properties are also measured by nano-indentation in our work. The incorporation of metal waste into the fabrication of ceramic products is valuable due to the preferred stabilization mechanisms of crystal structures and the large volume of ceramic products needed by the construction industry. Furthermore, because the product safety and functionality should not be compromised, a fundamental understanding of the surface properties of metal containing phases should be further established, rather than relying solely on data from regulatory tests on bulk samples. Therefore, the results of this study demonstrate the superior mechanical properties of nickel spinel containing products, comparing to the cristobalite silica matrix, under severe acid attack. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

This work addresses fundamental aspects of designing templates and curing conditions for the synthesis of mesoporous metal oxide thin films. The first section addresses selection of cationic-carbohydrate surfactant mixtures to synthesize templated silica thin films for selective adsorption of simple carbohydrates based on molecular imprinting. Nuclear magnetic resonance and fluorescence spectroscopy results suggest a novel structure for mixtures of alkyl glucopyranosides or xylopyranosides with cationic (trimethylammonium) surfactants. Despite thermodynamically favorable mixing, the carbohydrate headgroups in the mixed micelle adopt an inverted configuration with their headgroups in the micelle core, and therefore are inaccessible for molecular imprinting. This orientation occurs even when the alkyl tail length of the carbohydrate surfactant is greater than that of the cationic surfactant, but this limitation can be overcome by introducing a triazole linker to the carbohydrate surfactant. The next section addresses the effects of aging conditions on the structural and chemical evolution of surfactant templated silica thin films. The third section describes the synthesis of carbohydrate/cationic surfactant imprinted silica thin films with orthogonally oriented cylindrical pores by modifying the glass surface with a random copolymer. The last part of the dissertation addresses the effect of pore orientation on the transformation mechanism of block copolymer templated titania thin films during high temperature curing. Mesoporous titania thin films can be used for photochemical and solar cell applications, but doing so requires addressing the tradeoff between loss of mesostructural order and growth of crystallinity during thermal treatment. By using advanced x-ray scattering techniques it has been shown that the titania films with vertically oriented pores can better withstand the anisotropic stress that develops during thermal treatment compare to titania films with mixed pore orientation. For instance, films with parallel or mixed pores can only be heated at 400 °C for a brief time (~10 min) without loss of order, while orthogonally oriented films can be heated at 550 °C or greater for extended time periods (on the order of hours) without significant loss of long-range mesopore structure. Detailed kinetic modeling was applied to enable the comparison of activation energy for mesostructure loss in films as a function of pore orientation and thickness.

Health monitoring of aeronautic structures and human beings is becoming crucial because of the human safety issues. In this thesis integrated (IUTs) and flexible ultrasonic transducers (FUTs) have been developed using a sol-gel spray piezoelectric film fabrication technology. IUTs can be fabricated directly onto the structures with curved surfaces even on-site. FUTs were made using membrane substrates of thickness less than 75 mum. In-situ monitoring of AI airframe thickness was carried out and the thickness measurement accuracy was better than 36 mum and 41 mum for IUT and FUT, respectively. The thickness of the ice on top of the AI airframe was also measured. Two crucial piezoelectric constants d33 and d31 of the composite film were measured with laser interferometer and optical coherence tomography system, respectively. Pulse and breath of a human being were also monitored using flexible piezoelectric membrane sensors. In addition, bones in human body were observed using FUTs as well and their performance is comparable to that of commercial ultrasonic transducers.

High fuel utilization SOFCs could eliminate emissions from systems that include afterburners and potentially be suitable for carbon sequestration, while producing electricity more efficiently. Current fuel utilization operating points are typically chosen at approximately 85% for Ni-cermet anodes because higher fuel utilization frequently results in the formation of nickel oxide and reduces drastically the performance of the SOFC. In this work the feasibility of an in-plane graded anode architecture with a transition from a material with high catalytic activity to materials more stable under high fuel utilization conditions was evaluated through a steady-state SOFC finite element model. Thereafter, plasma spraying of solution precursor feedstock (SPPS) and suspension feedstock (SPS) was used to fabricate ceramic coatings that could potentially be used as SOFC anodes for high fuel utilization conditions. Microstructural, electrical and electrochemical properties of LST, LSBT and LSFCr coatings with additions of carbon black pore former were investigated.

High fuel utilization SOFCs could eliminate emissions from systems that include afterburners and potentially be suitable for carbon sequestration, while producing electricity more efficiently. Current fuel utilization operating points are typically chosen at approximately 85% for Ni-cermet anodes because higher fuel utilization frequently results in the formation of nickel oxide and reduces drastically the performance of the SOFC. In this work the feasibility of an in-plane graded anode architecture with a transition from a material with high catalytic activity to materials more stable under high fuel utilization conditions was evaluated through a steady-state SOFC finite element model. Thereafter, plasma spraying of solution precursor feedstock (SPPS) and suspension feedstock (SPS) was used to fabricate ceramic coatings that could potentially be used as SOFC anodes for high fuel utilization conditions. Microstructural, electrical and electrochemical properties of LST, LSBT and LSFCr coatings with additions of carbon black pore former were investigated.

No description available.

No description available.

Low temperature co-fired ceramic (LTCC) electronic packaging materials are applied for their electrical and mechanical properties, high reliability, chemical stability and ease of fabrication. Three dimensional features can also be prepared allowing integration of microfluidic channels and cavities inside LTCC modules. Mechanical, optical, electrical, microfluidic functions have been realized in single LTCC modules. For these reasons LTCC is attractive for biomedical microfluidics and Lab-on-a-Chip systems. However, commercial LTCC systems, optimized for microelectrics applications, have unknown cytocompatibility, and are not compatible with common surface functionalization chemistries. The first goal of this work is to develop biocompatible LTCC materials for biomedical applications. In the current work, two different biocompatible LTCC substrate materials are conceived, formulated and evaluated. Both materials are based from well-known and widely utilized biocompatible materials. The biocompatibilities of the developed LTCC materials for in-vitro applications are studied by cytotoxicity assays, including culturing endothelial cells (EC) both in LTCC leachate and directly on the LTCC substrates. The results demonstrate the developed LTCC materials are biocompatible for in-vitro biological applications involving EC. The second goal of this work is to develop functional capabilities in LTCC microfluidic systems suitable for in-vitro and biomedical applications. One proposed application is the evaluation of oxygen tension and oxidative stress in perfusion cell culture and bioreactors. A Clark-type oxygen sensor is successfully integrated with LTCC technique in this work. In the current work, a solid state proton conductive electrolyte is used to integrate an oxygen sensor into the LTCC. The measurement of oxygen concentration in Clark-type oxygen sensor is based on the electrochemical reaction between working electrode and counter electrode. Cyclic voltammetry and chronoamperometry are measured to determine the electrochemical properties of oxygen reduction in the LTCC based oxygen sensor. The reduction current showed a linear relationship with oxygen concentration. In addition, LTCC sensor exhibits rapid response and sensitivity in the physiological range 1─9 mg/L. The fabricated devices have the capabilities to regulate oxygen supply and determination of local dissolved oxygen concentration in the proposed applications including perfusion cell culture and biological assays.

Specimens of ZrB2 containing various concentrations of B4C, SiC, TaB2, and TaSi2 were pressureless-sintered and post-hot isostatic pressed to their theoretical densities. Oxidation resistances were studied by scanning thermogravimetry over the range 1150 - 1550 degree C. SiC additions improved oxidation resistance over a broadening range of temperatures with increasing SiC content. Tantalum additions to ZrB2-B4C-SiC in the form of TaB2 and/or TaSi2 increased oxidation resistance over the entire evaluated spectrum of temperatures. TaSi2 proved to be a more effective additive than TaB2. Silicon-containing compositions formed a glassy surface layer, covering an interior oxide layer. This interior layer was less porous in tantalum-containing compositions. The oxidation resistances of ZrB2 containing SiC, TaB2, and TaSi2 additions of various concentrations was studied using isothermal thermogravimetry at 1200, 1400, and 1500 degree C, and specimens were further characterized using x-ray diffraction and electron microscopy. Increasing SiC concentration resulted in thinner glassy surface layers as well as thinner ZrO2 underlayers deficient in silica. This silica deficiency was argued to occur by a wicking process of interior-formed borosilicate liquid to the initially-formed borosilicate liquid at the surface. Small (3.32 mol%) concentrations of TaB2 additions were more effective at increasing oxidation resistance than equal additions of TaSi2. The benefit of these additives was related to the formation of zirconium-tantalum boride solid solution during sintering, which during oxidation, fragmented into fine particles of ZrO2 and TaC. These particles resisted wicking of their liquid/glassy borosilicate encapsulation, which increased overall oxidation resistance. With increasing TaB2 or TaSi2 concentration, oxidation resistance degraded, most egregiously with TaB2 additions. In these cases, zirconia dendrites appeared to grow through the glassy layers, providing conduits for oxygen migration.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.