Recently, there has been growing interest in the green synthesis of zeolite (aluminosilicate) materials using solvent-free synthesis methods. Solid starting materials are typically ground for a period of time followed by thermal heating to synthesize crystalline ZSM-5 zeolite. These studies generally have focused on products formed after the thermal heating. However, very little is known about the reaction intermediates formed during the mechanochemical pre-reaction grinding step and how the pre-reaction impacts the subsequent synthetic success. In this study, the mechanochemical approach used to synthesize ZSM-5 and mordenite zeolite was investigated. Two types of solvent-free synthesis methods were investigated; templated solvent-free synthesis, and template-free and solvent-free synthesis. The effect of grinding time was investigated first to find the optimal grinding time that initiates pre-reactions between the starting materials. Controlled experiments were used to monitor chemical and physical changes occuring during the grinding step. Subsequently, the effect of different synthesis conditions such as time, temperature, template, SiO2/Al2O3, and Na2O/Al2O3 ratios, and different precursors were studied using the optimal grinding time. Both manual (mortar and pestle) and ball mill (FTS 1000) grinding were used in this study. The synthesized products were characterized using XRD, BET nitrogen adsorption, SEM, and ICP-OES. Finally, selected single-phase synthesized zeolite materials were evaluated for their catalytic performance in biomass conversion process of cellulose and glucose to useful chemicals such as hydroxymethylfurfural (HMF).

This study documents the evolution of a unique body of ceramic work which straddles the areas of science and art. The author establishes the framework and context for the development of a range of ceramics incorporating crystalline glazes and forms. A personal aesthetic sensibility for the work is defined with reference to ceramics in general and specifically to the historical and contemporary development of glazes within this genre. The study articulates the stages of contemplation, design and development in the creation of a unique body of work which is cognisant of the decorative qualities of crystalline glazes. The forms are simple and uncomplicated, and the work is concerned with the pinnacle of the craft of ceramics at every level. / Doctor of Creative Arts (DCA)

This paper reports the surface morphologies and ablation of crystalline silicon wafers irradiated by infra-red 775 nm Ti:sapphire femtosecond laser. The effects of energy fluences (below and above single-pulse modification) with different number of pulses were studied. New morphological features such as pits, cracks formation, Laser-Induced Periodic Surface Structures (LIPSS) and ablation were observed. The investigation indicated that there are two distinct mechanisms under femtosecond laser irradiation: low fluence regime with different morphological features and high fluence regime with high material removal and without complex morphological features. / Singapore-MIT Alliance (SMA)

Cast multi-crystalline silicon substrates are used in more than 50% of the photovoltaic modules produced today. The random grain orientations of multi-crystalline silicon wafers inhibit the formation of an effective surface texturing using conventional techniques. The other main substrate used is single crystalline Czochralski wafers (~30% of the market share). Czochralski silicon material is known to suffer from the formation of a metastable defect under carrier injection, sometimes referred to as light induced degradation (LID). Light induced degradation in low-cost photovoltaic grade silicon is studied. Trap formation is shown to occur at temperatures above 200oC. Efficiency degradation reduced from 0.75% to 0.24% when the cell thickness was reduced from 378 to 157m. The presence of light induced degradation in ribbon silicon solar cells is documented for the first time in this thesis. Trap generation and annihilation are observed in high lifetime regions of multi-crystalline silicon samples. No degradation was observed over a 24-hour period at 25oC in high efficiency ribbon solar cells (>16%), but at an elevated temperature of ~75oC, appreciable efficiency degradation was observed. Czochralski silicon solar cells showed full degradation within 24 hours at 25o C. Part two of this thesis involves the development of a surface texturing suitable for all crystalline silicon. Only 6 to 10 seconds in a 200:1 HF to HNO3 solution at room temperature allows for the formation of an effective porous silicon anti-reflection coating. This resulted in a porous silicon anti-reflection coated solar cell efficiency of 15.3% on a float zone Si sample with an excellent fill factor (78.7%). The typical process used in the literature involves porous silicon etching as the final step in the solar cell fabrication sequence. The major problem associated with this process sequence is fill factor degradation. This problem was overcome in this research by porous silicon etching prior to cell processing. It is shown that incorporating an acid texture prior to porous silicon etching can improve the surface reflectance for cast multi-crystalline and Czochralski silicon samples. Solar cell efficiencies of 14.8% for Cz Si and 13.6% for cast mc-Si were achieved.

Double crystalline block copolymers (BCPs), syndiotactic poly(4-methyl-1-pentene)-b-poly(L-lactide) (sPMP-PLLA) and syndiotactic poly(4-methylstyrene)-b-poly(L-lactide) (sPMS-PLLA), were synthesized to examine crystallization effect on the self-assembled morphologies in the double crystalline BCPs. Because of the stainable chemical structures, morphological observation can be carried out in these double crystalline BCPs. Also, different microphase-separated structures including lamellae and hexagonally packed cylinders were explored to study the shape effect for double crystallization. Based on differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results, both sPMP and PLLA blocks are able to crystallize in the sPMP-PLLA BCP (fsPMPv=0.52) at the crystallization temperature (Tc) from 80¢XC to 120¢XC. Notably, temperature-dependent phase transitions between the PLLA polymorphisms are obtained by WAXD. By using small-angle X-ray scattering (SAXS) and transmission electron microscope (TEM), the microphase-separated lamellar structures can be observed in the sPMP-PLLA BCP (fsPMPv=0.52). Also, the preservation of the lamellar morphology at all Tcs (80¢XC~120¢XC) indicates that the sPMP and PLLA crystallization can be strongly confined within the lamellar microstructures due to the strong segregation strength of the sPMP-PLLA (fsPMPv=0.52) BCP. This can be further demonstrated by the ambiguous birefringence under polarized light microscope (PLM). According to the time-resolved SAXS and WAXD profiles at 90oC and 110oC, the sPMP block crystallizes first and induces the enlargement of the BCP long period. Also, the leading sPMP crystallization gives rise to the robust lamellar microstructural template and result in strong confinement for the subsequent PLLA crystallization. In the sPMS-PLLA BCP (fsPMSv=0.58), the microphase-separated lamellar nanostructures can be found by SAXS and TEM. DSC analysis shows that PLLA block is able to crystallize as Tc=90¢XC~100¢XC; the sPMS block is able to crystallize as Tc ≥120oC. By self-nucleation processes, both sPMS and PLLA blocks are able to crystallize. Therefore, by the manipulation of the respective crystallization, two-stage crystallization and coincident crystallization, systematic studies in the semi-crystallization, double crystallization and coincident double crystallization with the accompanying environmental Tg effect and BCP segregation strength can be carried out in the lamella-forming sPMS-PLLA (fsPMSv=0.58) BCP. By SAXS and TEM, the microphase-separated lamellar microstructures can be preserved in the self-assembly of the sPMS-PLLA (fsPMSv=0.58) BCP whatever the PLLA crystallization occurs under hard confinement (Tc,PLLA<Tg,sPMS) or soft confinement(Tc,PLLA˃Tg,sPMS). For the sPMS crystallization under soft confinement, the lamellar microstructures can be preserved as Tc,sPMS ≤140oC, whereas the breakout morphology by the sPMS crystallization is found as Tc,sPMS ≥150oC. As a result, the final morphologies is strongly dependent on the BCP segregation strength in the lamella-forming sPMS-PLLA (fsPMSv=0.58) BCP. In sPMS-PLLA BCP (fsPMSv=0.7), hexagonally-packed PLLA cylinders in the sPMS matrix are obtained by SAXS and TEM. DSC analysis shows that the sPMS block is able to crystallize as Tc=130¢XC~180¢XC, whereas no PLLA crystallization can be found in the cylinder-forming sPMS-PLLA BCP (fsPMSv=0.7). This indicates that the 2-D cylindrical shape might give rise to the strong confined effect and result in non-crystallizable PLLA. According SAXS and TEM results, the intrinsic hexagonally-packed cylinders can be preserved after the sPMS crystallization at 130oC due to the strong BCP segregation strength. By contrast, the crystallization driving force may overwhelm the microphase separation so as to form breakout morphology in the sPMS-PLLA (fsPMSv=0.7) BCP as Tc≥150¢XC.

Two feeding trials were conducted to study the requirements of juvenile cobia for dietary methionine and lysine. Experiment I compared both fishmeal-based (fish meal and soybean meal as protein sources) and casein-based (casein and gelatin as protein sources) diets. All diets were isonitrogenous and isoenergetic. Crystalline amino acids was pre-coated with carboxymethylcellulose (CMC) and supplemented to simulate the amino acid pattern of juvenile cobia muscle protein except methionine. Five methionine levels of 0.45, 0.70, 0.95, 1.20 and 1.45% (1.07, 1.66, 2.26, 2.86 and 3.45% of protein) were studied. The test diets contained 0.16% cystine. Juvenile cobia (initial weight 35g) were fed test diets for 8 weeks. The results showed that the cobia used fish meal more effectively than casein. Final weight, percent weight gain (PWG), feed conversion ratio(FCR), hepatosomatic index (HSI), condition factor (CF), protein efficiency ratio (PER), protein retention (PR), carcass proximate composition and free methionine concentration in the serum were significantly enhanced (p<0.05) by increasing dietary methionine level. But profile of essential amino acids in the muscle and serum superoxidase and lysozyme activity were not significantly affected. Weight gain of the cobia fed the fishmeal-based diet containing 1.2% methionine was significantly higher than the other dietary groups. Methionine content of 0.45% resulted in reduced growth. No significant difference in weight gain was found in the casein-containing diets when methionine was 0.7% and over. The cobia fed diet containing 0.45% methionine started show apparent skin lesions in their heads on the sixth week of the growth trial and significant mortalities were observed since the seventh week (p<0.05). The optimum dietary level of methionine for cobia, estimated by the broken-line regression analysis on weight gain, was 1.10% (2.62% of protein) based on the fishmeal-based diet results and was 0.70% (1.67% of protein) based on the casein-based diet results. Experiment II used fish meal and wheat gluten as the protein sources. Pre-coated crystalline amino acids were supplemented to simulate the amino acid pattern of juvenile cobia muscle protein except lysine. Lysine levels including 1.49, 1.75, 2.00, 2.25, 2.50 and 2.75% (3.54, 4.16, 4.76, 5.35, 5.95 and 6.54%) were studied. Juvenile cobia (initially 12g) were fed test diets for 8 weeks. The results showed that the final weight, PWG, FCR, CF, PER, PR, carcass proximate composition and free lysine concentration in the serum were significantly enhanced (p<0.05) by increasing lysine levels. But HSI and essential amino acid profile of fish in the muscle were not significantly affected. Final weight and percent weight gain of the cobia fed diets containing 1.75% lysine or over were significantly higher than fish fed diet contained 1.49% lysine. FCR was lower for cobia fed diets containing 1.75% lysine or over than the 1.49% lysine group. The optimum dietary level of lysine, estimated by the broken-line regression analysis on weight gain was 1.76% (4.19% of protein), and was 1.95% (4.64% of protein) on serum free lysine concentration. There was no overt deficiency symptom, such as caudal fin rot in rainbow trout, in the cobia during the growth trial.

The polyglutamate which grafts with flexible alkyl side-chain by ester exchange reaction is like rod-hairy molecule. The numbers of methylene group of side-chain and the graft-density affect the molecular packing of poly(gama-alkyl-L-glutamate)s. To be sure the correct chemical structure of poly(gama-alkyl-L-glutamate)s by Fourier transform infrared spectrometer (FTIR), and find out the graft-density of each sample by proton nuclear resonance spectrometer (1H-NMR). Phase behavior of poly(gama-alkyl-L-glutamate)s were studied via differential scanning calorimetry (DSC) and variable temperature x-ray diffraction (XRD).We combine the results from C. C. Hsu(24). When the side-chain length is long enough (m>10), side-chains will crystallize into a 3D hexagonal lattice. The results of DSC and XRD analyses show that the side-chain crystalline phase will melt at Tm1, where as a liquid crystalline (LC) phase transition exists at Tm2. Poly(gama-alkyl-L-glutamate)s with shorter side-chain (m<8) tend to form 2D hexagonal LC structure. On the other hand, longer side-chains (m>10) tend to give lamellar structure. The critical number of methylene group of side-chain between hexagonal and lamellar structure is between 8 and 10.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 104-115). Also available in print.

Inside your microelectronic devices there are up to a billion transistors working in flawless operation. Silicon has been the workhorse semiconductor used for the transistor; however, there must be a transition to materials other than silicon, such as germanium, with future device sizes. In addition, new dielectric oxide materials are needed. My research has examined a type of crystalline oxide, known as a perovskite, which is selected for its ability to bond chemically to Si and Ge, and eliminate the electrical defects that affect performance. Many perovskite oxides are lattice-matched to the Si (001) and Ge (001) surface spacing, enabling heteroepitaxy. To date, the majority of research on crystalline oxides integrated with semiconductors has been based on strontium titanate, SrTiO3, epitaxially grown on Si (001) by molecular beam epitaxy. Alternative low-temperature growth methods, such as atomic layer deposition (ALD), offer both practical and economic benefits for the integration of crystalline oxides on semiconductors. My initial research informed the broader community that four unit cells (~1.5 nm) of SrTiO3 are required to enable heteroepitaxy on Si. The research has also shown that heteroepitaxial layers can be monolithically integrated with Si (001) without the formation of a SiOx interlayer between the Si (001) surface and the SrTiO3 layer because ALD is performed at lower temperatures than are typical for MBE. Thus, a combined MBE-ALD growth technique creates possible advantages in device designs that require the crystalline oxide to be in contact with the Si (001) surface. In recent work, I have demonstrated a method for integrating crystalline oxides directly on Ge by ALD. Germanium is being explored as an alternative channel material due to its higher hole and electron mobilities than Si, potentially enabling device operation at higher speed. This all-chemical growth process is expected to be scalable, is inherently less costly from a manufacturing cost of ownership, and is based on current manufacturing tool infrastructure. The impact of my research will be in continued scaling of device dimensions with novel materials that will provide faster speed and lower power consumption for microelectronic devices. / text

Through collaborative efforts at Texas A&M University and Sandia National Laboratories, a crystalline silicotitanate (CST), which shows extremely high selectivity for radioactive cesium removal in highly concentrated sodium solutions, was synthesized. The effect of hydrogen peroxide on a CST under cesium ion exchange conditions has been investigated. The experimental results with hydrogen peroxide showed that the distribution coefficient of cesium decreased and the tetragonal phase, the major component of CST, slowly dissolved at hydrogen peroxide concentrations greater than 1 M. A simple and novel experimental apparatus for a single-layer ion exchange column was developed to generate experimental data for estimation of the intraparticle effective diffusivity. A mathematical model is presented for estimation of effective diffusivities for a single-layer column of CST granules. The intraparticle effective diffusivity for Cs was estimated as a parameter in the analytical solution. By using the least square method, the effective diffusivities of 1.56 ± 0.14 x 10-11 m2/s and 0.68 ± 0.09x 10-11 m2/s, respectively, were obtained. The difference in the two values was due to the different viscosities of the solutions. A good fit of the experimental data was obtained which supports the use of the homogeneous model for this system. A counter-current ion exchange (CCIX) process was designed to treat nuclear waste at the Savannah River Site. A numerical method based on the orthogonal collocation method was used to simulate the concentration profile of cesium in the CCIX loaded with CST granules. To maximize cesium loading onto the CST and minimize the volume of CST, two design cases of a moving bed, where the fresh CST is pulsed into the column at certain periods or at certain concentration of cesium, were investigated. Simulation results showed that cesium removal behavior in the pilot-scale test of CCIX experiment, where the column length is 22 ft and the CST is pulsed 1 ft in every 24 hours, was well predicted by using the values of the effective diffusivities of 1.0 to 6.0 × 10-11 m2/s.