Aerogel materials have had limited utility due to their fragility, geometrical limitations, fabrication costs and protracted fabrication times. The objective of this project was to eliminate these limitations. Native, cross-linked and hybrid aerogel monoliths have been fabricated using a newly developed one-pot method without the need for solvent exchange. The key to this technique is the use of an ethanol–water azeotrope mixture, which contains 4.4% water by volume, as both a gelation and supercritical drying solvent. The small water content allows for drying at temperatures close to the supercritical temperature of the dry solvent, where reactions such as silica dissolution and polymer degradation are negligible. This improvement on conventional fabrication processes is of particular importance since it decreases the total duration of aerogel fabrication from five days to one day. Cross-linked silica aerogel monoliths were fabricated using one-pot hydrolysis-condensation wet chemistry methods as well as a rapid photogelation method. Both native silica and cross-linked aerogel components were made with a minimum dimension of up to 3.6 cm and in customizable shapes. Fabrication of homogeneous aerogels using these methods required a maximum of one day, as demonstrated in this work. Finally, LEDs and Laser irradiation were both used to selectively embed cross-linked aerogel into a larger native silica component to provide reinforcement and/or a surface which can be used for labeling or affixing the aerogel component to another surface.

Selective Serotonin Reuptake Inhibitors (SSRIs) are the most frequently prescribed class of drugs worldwide and are implemented in the treatment of depression and other psychiatric disorders. SSRIs relieve depressive symptoms by modulating levels of the neurotransmitter serotonin in the brain. SSRIs block the function of the serotonin transporter, thereby increasing concentrations of extracellular serotonin. However, serotonin levels in the neurons of the brain only account for 5% while the remaining 95% is present outside the brain. Serotonin receptors and transporter are located on bone resident cells (mesenchymal stem cells (MSCs)), osteoblasts and osteoclasts, and serotonergic activity is believed to affect bone homeostasis. Consequently, alterations in serotonin levels by SSRI treatment have the potential to alter bone formation and remodeling. Clinical reports correlate increase risk of bone fractures and delayed bone healing with SSRI use. Metallic implants are commonly used as orthopedic and dental implants to fix bony defects. Surface modifications have been used to increase the level of bone to implant contact by controlling the differentiation of MSCs into an osteoblastic linage and facilitate bone production. However, it is not known if SSRIs can affect MSCs osteoblastic differentiation and bone remodeling signaling in response to microstructured biomaterials. The aims of this study were: 1) Investigate the effects of SSRIs on MSCs differentiation on microstructured titanium (Ti), 2) Determine the effects of SSRIs on bone remodeling signaling and osteoclast activation, and 3) Elucidate the effects of SSRIs on serotonin receptors and their effect on bone remodeling. To investigate this, human MSCs were grown on tissue culture polystyrene (TCPS), smooth Ti (PT) or microstructured Ti (SLA) surfaces under exposure to therapeutic concentrations of commonly prescribed antidepressants (SSRIs (fluoxetine, sertraline, paroxetine), Selective Norepinephrine Reuptake Inhibitor (SNRI) (duloxetine) and other regularly prescribed antidepressants (bupropion)) during differentiation toward osteoblasts. Osteoblastic differentiation was assessed in MSCs after treatment with the drugs (0.1μM, 1μM, 10μM) by alkaline phosphatase activity and osteocalcin levels. Antidepressant treatment decreased levels of MSC differentiation markers on microstructured Ti surfaces. Furthermore, treatment dose-dependently decreased protein levels secreted by MSCs which are important for bone formation (BMP2, VEGF, Osteoprotegerin), and increased those involved in bone resorption (RANKL). To determine the effect of SSRIs on bone remodeling signaling and osteoclast activation, human osteoclasts were either directly exposed to antidepressants or conditioned media obtained from MSCs treated with antidepressants on Ti surfaces, after which, enzymatic tartrate-resistant acid phosphatase (TRAP) activity was assessed. Antidepressants increased TRAP activity both directly and through treated MSCs, with the highest levels evident after treatment with conditioned media from MSCs on microstructured Ti surfaces. To elucidate the effects of serotonin receptors and their effect on bone remodeling, receptors were pharmacologically inhibited. Surface roughness decreased gene expression of HTR2A, HTR1B, and HTR2B, and antidepressant treatment increased their expression. Inhibition of HTR2A decreased RANKL protein levels, while inhibition of other serotonin receptors had no effect on RANKL or OPG levels. These studies suggest that antidepressants inhibit MSCs differentiation on microstructured Ti surfaces and increase levels of proteins associated with bone resorption. Additionally, our results showed that RANKL is regulated by serotonin receptor HTR2A. Taken together, our results suggest that antidepressants have a negative effect on osteoblastic differentiation, compromising bone formation and enhancing bone resorption, which can be detrimental to patients under orthopedic and dental treatment.

This thesis addresses the problem healthcare facilities are having in maintaining proper food temperatures while transporting meals to patients after food has left the kitchen area. Induction heat has been a known method for generating heat for many years. The commercial food industry currently uses this technology, which is beginning to appear in the residential sector as well because of developments made by manufacturers. This study focuses on the top commercial brand models of induction heaters and the supporting materials currently used to create heat sources to maintain food temperatures in hospitals and long term care facilities. The research in this thesis includes data recorded from 6,000 total induction cycles from the 3 leading induction heating models. The focus of the research was to gather data concerning the models’ reliability to consistently create the intended inducement of radio frequency waves as well as deliver consistent temperature reactions from the recorded induction cycles. There were 18,000 temperature data points recorded during different time intervals for each of the induction cycles for the entire study. The results indicate the current technology not only is reliable in creating inductions fields but also in delivering consistent temperatures in the supporting materials being heated. Induction has been used historically as a fast heating process to treat large metal products and requires no direct contact to create or transfer heat to a surface (Rudnev et al., 2003). The speed and consistent application of heat transfer that has been derived by modern manufacturing induction practices makes it a logical use of existing technology to be applied in maintaining temperatures of food in the healthcare market. However, the focus for commercial equipment manufacturers has been to market products that can consistently maintain desired food temperatures, particularly in the healthcare industry. Traditionally, heating foods was accomplished by physically applying heat to areas where food is stored, in order to reach a certain temperature, and then working to deliver that food to the patient in a timely manner or before it cooled to temperatures that would be deemed too cold for consumption. If the food was too cold, before it was served to the patient, then it was typically micro waved in order to reheat the food. However, reheating food in the microwave is not only detrimental, but it also degrades food quality, texture, and visual presentation (Harvard Health, 2015). As a result, the effort demanded to deliver all foods to all patients, while the food is still at an ideal temperature, has resulted in an increased cost of labor. This is because healthcare facilities have had to hire additional workers to meet the demands placed on the nutrition department related to safe temperatures and speed of food delivery (Aladdin, 2013).

Previous work done at Cal Poly has shown that thin-film nickel-titanium (NiTi) can be easily sputtered onto silicon wafers and annealed to create a crystallized shape memory alloy (SMA) film. Initial work on creating devices yielded cantilevers that were highly warped due to thin-film stress created during the sputtering process. The objective of this work was to create a thin-film NiTi SMA device that could be better characterized. A membrane was selected due to the simplicity of fabrication and testing which would also oppose the thin-film stress due to the increase in attachment points to the substrate. Silicon wafers were etched through the majority of the thickness (~75%) creating square etch pits of varying sizes varying from 1294 µm to 4394 µm. The wafers were then sputtered with an approximate NiTi film of 5 µm followed by a thin chromium film. The chromium film would act as a diffusion barrier and prevent oxygen from diffusing into the NiTi and reacting with the titanium and forming titanium dioxide. These wafers were then annealed in a custom built vacuum annealing chamber at 550 °C for 1 hour with a pressure around 77 kPa. The chromium was then etched away followed by the remaining silicon. This left a thin membrane of shape memory NiTi which was packaged in order for characterization. The devices were glued to an aluminum substrate using polydimethylsiloxane (PDMS) and sealed with a small Tygon tube leading to the sealed chamber. This packaged device was then able to be pressurized using a nitrogen tank and the resulting NiTi membrane deflection was measured using a profilometer. Due to the differences in elastic moduli of the room temperature phase (martensite) and the high temperature phase (austenite) a difference of deflection was expected. The austenite finish (Af) temperature of bulk NiTi films was found to be around 60 °C so the devices were tested at both room temperature and at 60 °C. After testing seven separate devices of varying sizes, a regression model was used to analyze the final data. It was found that pressure, membrane size and theoretical versus actual deflection all affected the maximum deflection, but temperature did not. Higher pressures and larger membranes led to higher deflections as membrane deflection models from fundamental principles indicated. Some devices showed inferior performance when compared to the model due to incomplete silicon etching which caused lower deflection due to the much higher modulus of the remaining silicon. Thickness could also limit the amount of deflection measured with a thicker film leading to less deflection, but this is likely not the case due to the high uniformity of the sputtering system. Other devices showed superior performance over the model most likely due to either local delamination or lateral silicon etching. Both these would create a membrane that was larger than expected leading to a higher deflection. Unforutnaly, differential scanning calorimetry (DSC) analysis showed no shape memory behavior on a test wafer which was anneald at 550 ˚C for 1 hour. A design of experiments was conducted in order to find a heat treatment that would anneal the NiTi film and ensure that shape memory behavior could be obtained. An annealing at 650 °C for 1 hour showed a sharper and clearer Af phase transformation at around the target temperature of 60 °C. Annealing a full wafer at this temperature and time also showed that no delamination would occur which has also been linked to nonideal behavior of the NiTi membranes which has also been linked to meaningful behavior of the NiTi membranes.

Fundamental thermodynamic investigations have been carried out regarding the phase equilibria of La0.8Sr0.2MnO3±δ (LSM), a cathode of a solid oxide fuel cell (SOFC), utilizing the CALculation of PHAse Diagram (CALPHAD) approach. The assessed thermodynamic databases developed for LSM perovskite in contact with YSZ fluorite and the other species have been discussed. The application of computational thermodynamics to the cathode is comprehensively explained in detail, including the defect chemistry analysis as well as the quantitative Brouwer diagrams, electronic conductivity, cathode/electrolyte interface stability, thermomechanical properties of the cathode and the impact of gas impurities, such as CO2 as well as humidity, on the phase stability of the cathode. The quantitative Brouwer diagrams for LSM at different temperatures are developed and the detailed analysis of the Mn3+ charge disproportionation behavior and the electronic conductivity in the temperature range of 1000-1200°C revealed a good agreement with the available experimental observations. The effects of temperature, CO2 partial pressure, O2 partial pressure, humidity level and the cathode composition on the formation of secondary phases have been investigated and correlated with the available experimental results found in the literature. It has been indicated that the CO2 exposure does not change the electronic/ionic carriers’ concentration in the perovskite phase. The observed electrical conductivity drop is predicted to occur due to the formation of secondary phases such as LaZr2O7, SrZrO3, SrCO3 and Mn oxides at the LSM/YSZ interface, resulting in the blocking of the electron/ion transfer paths. For the thermo-mechanical properties of LSM, a new weight loss Mechanism for (La0.8Sr0.2)0.98MnO3±δ using the La-Sr-Mn-O thermodynamic database is modeled with respect to the compound energy formalism model. This newly proposed mechanism comprehensively explains the defect formation as a result of volume/weight change during the thermal cycles. According to the proposed mechanism the impact of cation vacancies regarding the volume change of cathode was explained.

This work focuses on discovery and development of novel binary halide scintillation materials for radiation detection applications. A complete laboratory for raw materials handling, ampoule preparation, material rapid synthesis screening, single crystal growth, sample cutting, polishing and packaging of hygroscopic halide scintillation materials has been established. Ce3+ and Eu2+ activated scintillators in three binary systems: Alkali Halide – Rare Earth Halide (AX–REX3), Alkali Halide – Alkaline Earth Halide (AX–AEX2) and Alkalin Earth Halide – Rare Earth Halide (AEX2–REX3) were systematically studied. Candidates for new scintillation materials in the three systems were selected based on a set of selection rules. A total of 42 Ce3+ or Eu2+ activated binary halide scintillation material candidates were synthesized and characterized. Among all synthesized candidates, 10 - 15 candidate materials were found to be highly promising in terms of high scintillation light output, fast scintillation decay or desirable emission wavelength. Three most promising candidates, Cs3EuI5, CsGd2Cl7:Ce3+ and CsSrI3:Eu2+ were selected for single crystal growth and further evaluation. Technologies for single crystal growth of hygroscopic halide scintillation materials were developed. Detailed design of experimental apparatuses was discussed. Single crystals were successfully grown via Bridgman or Vertical Gradient Freeze techniques. Study on optical and scintillation properties was performed. Possibility of using CsGd2Cl7:Ce3+ as a neutron detector was confirmed. CsSrI3:Eu2+ shows extraordinary scintillation light output (73,000 ph/MeV), excellent energy resolution (3.9%) and ease for crystal growth. A scaled-up crystal growth was carried out. A bulk crystal of 1” diameter CsSrI3:Eu2+ was successfully grown. Energy level structure and charge carrier traps in CsSrI3:Eu2+ were investigated. Potential of CsSrI3:Eu2+ in various radiation detection applications were evaluated.

The interaction at the surfaces of load bearing implant biomaterials with tissues and physiological fluids is an area of crucial importance to all kinds of medical technologies. To achieve the best clinical outcome and restore the function of the diseased tissue, several surface engineering strategies have been discussed by scientific community throughout the world. In the current work, we are focusing on one such technique based on laser surface engineering to achieve the appropriate surface morphology and surface chemistry. Here by using a pulsed and continuous wave laser direct melting techniques we synthesize three dimensional textured surfaces of calcium phosphate (Ca-P) based surface chemistry on Ti-6Al-4V. The influence of each processing type on the micro texture and phase evolution and thereby its associated effect on wettability, in vitro bioactivity, and in vitro biocompatibility are systematically discussed. For samples processed using the pulsed laser, it was realized that with increasing laser scan speed and laser pulse frequency there was a transition from surface textures with sharp circular grooves to surface textures with radial grooves and thereby improved hydrophilicity. For CW laser processing the results demonstrated improved hydrophilicity for the samples processed at 100 μm line spacing as compared to the samples processed at 200 μm line spacing. Owing to the importance of Si for cartilage and hard tissue repair, a preliminary effort for synthesizing Ca-P-SiO2 composite coating on Ti-6Al-4V surface were also conducted. As a future potential technique we also explored the Laser Interference Patterning (LIP) technique to achieve the textured surfaces and developed understanding on their wetting behavior. In the current work, by adjusting the laser processing parameters we were able to synthesize textured coatings with biocompatible phases. The in vitro bioactivity and in vitro vi biocompatibility of the coatings were proved by the precipitation of an apatite like phase following immersion in simulated body fluid (SBF), and increased proliferation and spreading of the MC3T3-E1 like cells. The results and understanding of the current research is encouraging in terms of looking at other bio-ceramic precursor compositions and laser process parameter window for synthesizing better textured biocompatible coatings.

The development and application of a combinatorial sputtering thin film technique to screen potential scintillation material systems was investigated. The technique was first benchmarked by exploring the binary lutetium oxide-silicon oxide material system, which successfully identified the luminescence phases of the system, Lu2SiO5 (LSO) and Lu2Si2O7 (LPS). The second application was to optimize the activator concentration in cerium doped LSO. The successfully optimized cerium concentration in the thin film LSO of 0.34 atomic percent was much greater than the standard cerium concentration in single crystal LSO. This lead to an intensive study based on temperature dependent steady-state and lifetime photoluminescence spectroscopy to understand the different concentration quenching mechanisms involved in the bulk single crystal versus the thin film LSO. The results were used to develop configuration coordinate models which were employed to explain the observed concentration dependent behavior. The nature of single crystal LSO:Ce concentration quenching was determined to be due to radiative energy transfer, and ultimately self-absorption. For the thin films it was found self-absorption was not a dominant factor due to the thin dimension of the film and also its nano-crystalline nature. Instead, the photoluminescence excitation and emission spectra as a function of concentration demonstrated the concentration quenching behavior was due to an increase in defect-mediated non-radiative transitions with increasing cerium. The final application of the thin film screening technique was the exploration of the ternary Lu2O3-SiO2-Al2O3 material system doped with cerium. It was found that the presence of aluminum and silicon hindered LSO and Al5Lu3O12 (LuAG) emission, respectively. However, the presence of aluminum was found to increase LPS emission intensity. The percent of aluminum in the LPS phase was estimated at 2.5 atomic percent.

The objective of this work was to use LEFM in order to assess the detrimental influence of surrounding chloride-containing environments for stainless steels, hardened steel as well as for a cast aluminium alloy. An additional aim was also to use LEFM to assess the influence of porosity on the fatigue properties for different commercial cast aluminium alloys and manufacturing methods. The environmental influence on fatigue performance was mainly evaluated from fatigue crack growth measurements using compact tension (CT) specimens. In addition, fatigue performance in the high cycle regime was studied using spot welded specimens and smooth specimens. Corrosion fatigue tests for stainless steels were performed in different chloride-containing aqueous solutions and compared to the behaviour in air. Variables, which have been investigated, included temperature, redox potential and fatigue test frequency. The environmental influence on fatigue performance has also been compared to localised corrosion properties. Fatigue crack propagation rates were found to be higher in 3% NaCl than in air for all stainless steels investigated. The highest alloyed austenitic steel, 654SMO, showed the least influence of the environment. For duplex stainless steels the environment enhanced fatigue crack propagation rate to a higher degree than for austenitic stainless steels. This is explained by a material-dependent corrosion fatigue mechanism. In the high cycle regime, fatigue properties for spot welded stainless steels specimens were found to be decreased between 30%-40% due to the presence of 3% NaCl. For the hardened steel 100CrMnMo8 a fracture mechanics approach was employed for prediction of corrosion fatigue properties. In this model corrosion pit growth rate and the threshold stress intensity factor for fatigue crack propagation are needed as input parameters. For the high pressure die cast aluminium alloy the environmental influence of fatigue initiation through pre-exposure of smooth specimens was studied. Depending on environment used for pre-exposure, fatigue strength was found to be reduced by up to 50 % compared to the fatigue strength in air. Fatigue strength reduction was clearly associated to corrosion pits in the aluminium material. A fracture mechanics model was further successfully used to predict the environmental influence. The influence of porosity on the fatigue strength for the cast aluminium alloys tested has been described by a Kitagawa diagram. In design, the Kitagawa diagram can be used to predict the largest allowable pore size if the load situation in the component is known. The size of the porosity could either be evaluated directly from x-ray images or from metallographic prepared cross-sections using a method of extreme value analysis / QC 20100907

This thesis concerns computer simulation of diffusional processes in alloys. The main focus is on the development of simulation techniques for diffusion in single-phase domains, but also diffusion controlled phase-transformations and interfacial processes are discussed. Different one-dimensional simulation techniques for studying the Kirkendall effect are developed and analyzed. Comparisons with experimentally observed marker migration show good agreement for small shifts and comparisons with observed Kirkendall porosity show reasonable agreement under the assumption that a certain supersaturation is needed before the vacancies coalesce into pores. A convenient approach in simulations of kinetics is to use thermodynamic software, e.g. Thermo-Calc, to calculate thermodynamic quantities, e.g. chemical potentials, required in the simulation. The main drawback with such an approach is that it will generate a large amount of additional computational work. To overcome this problem a method that decreases the amount of computational work has been developed. The new method is based on artificial neural networks (ANN). By training the ANN to estimate thermodynamic quantities a significant increase in computational speed was obtained. By calculating the dissipation of available driving force due to diffusion inside migrating interfaces an approach for including the effect of solute drag in computer simulations of grain growth and phase transformations has been developed. The new method is based on an effective interfacial mobility and simulations of grain growth have been performed in binary and ternary systems using experimentally assessed model parameters. / QC 20100930