The structure of Fe[x] - Pd[1-x] (0.85 > x > 0.5) and Fe[x] - Pt[1-x] (0.85 > x > 0.3) thin film alloys co-deposited from the vapour phase over substrate temperatures (T[s]) ranging over 200-700°C have been examined at room temperature, using X-Ray, Microprobe, TEM and SEM techniques. The sequence of phases developed as T[s] is changed have been explained in terms of three factors: a) The structure of the initial phase, which in turn is a function of the T[o] temperature where DeltaG[bcc-fcc]=0 b) Diffusion at the designated temperature, which depends on both T[s] and the rate of deposition. c) Further transformations which occur on cooling through critical ordering or martensite start temperatures. Based on the co-deposited thin film results, a model is proposed which facilitates the determination of alloy phase diagrams. A direct determination of T[o] temperature in certain composition ranges is also possible through vapour deposition techniques. Preliminary calculation of T[o] confirms the experimental results and the role played by magnetic contributions. The combined experimental data for Fe-Pt alloys confirm the earlier assumption of a eutectoid transformation at about 17at% Pt at around 600°C and provides evidence of the efficacy of thin films for the rapid assessment of low temperature equilibria.

The problems associated with the use of ion implantation during the preparation of compound semiconductors have been examined. In particular, the use of an encapsulant as protection during annealing was considered and the properties and ease of preparation of the ideal encapsulant were studied. Among the experimental techniques used to study the surface of thin film coatings on the semiconductors materials, reflection high energy electron diffraction (RHEED) was extremely useful in allowing the study of thin layers. Other techniques used in the work included scanning electron microscopy (SEM), Rutherford backscattering (RBS), rapid thermal annealing using a graphite strip heater and thin film deposition by evaporation and sputtering. Among the encapsulants studied were aluminium nitride and the zirconium nitride the former being the most important. A study was also made of the chemical reactivity of aluminium nitride to oxidation and hydration. It was found that AlN was resistant to oxidation in air up to about 1000°C and in an inert atmosphere up to at least 1400°C. It was shown that aluminium nitride reacts readily with water to form AlOOH. The reproducibility of a good quality evaporated AlN film as an encapusulant was found to be difficult to control, but a combination of AlN and Si[3]N[4] in a "sandwich" proved to be more successful. Zirconium nitride was found to be useful as a passivation layer up to 700°C. Sputtered AlN coatings seemed to offer the best hope of success but further work is needed to improve the sputtering techniques so that free Al, or Al[2]O[3] is not present in the AlN layers.

In this thesis, the growth of c-axis oriented Sr2RuO4 thin films using pulsed laser deposition and their electrical transport properties are systematically discussed. The deposition and optimization process involved several progressive steps. Specifically, the first focus was on the Sr2RuO4 phase optimization in films grown on lattice-matched (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates. Film composition was found to be greatly influenced by changes in oxygen pressure, substrate temperature, target to substrate distance, and laser fluence. High oxygen pressure, low substrate temperature, large target to substrate distance, and high laser fluence increased the tendency to form the Ru-rich SrRuO3 phase in the film. The second focus was on improving the electrical transport properties of Sr2RuO4 from metal-insulating to fully metallic and eventually to superconducting behavior. It was observed that the full width at half maximum (FWHM) of the Sr2RuO4 (006) rocking curves in x-ray diffraction (XRD) scan was related to the quality of the electrical transport response. By fine tuning the deposition parameters to obtain low FWHM values, the electrical transport behavior of the Sr2RuO4 thin films was consistently improved from metal-insulating to fully metallic. In addition, localized superconductivity with enhanced superconducting transition temperature Tc onset was also observed among the fully metallic film. An in-depth study of the XRD results in fully metallic films indicated the existence of defects (intergrowths) along the c-axis direction, which caused localized c-axis tensile strain. The existence of structural defects within the film was likely to be responsible for the fact that only localized superconductivity was observed in the films. Furthermore, the enhanced superconducting transition temperature (Tc) relative to bulk single crystals is likely to be associated to localized strain in the film. Finally, Nb doped SrTiO3 substrates were used to achieve better quality growth of partial superconducting Sr2RuO4 thin films. Sr2RuO4 films grown on Nb doped SrTiO3 substrates had smaller FWHM values and lower level of c-axis tensile strain compared to those on LSAT substrates. Various partially superconducting films with different thicknesses and different superconducting Tc values are presented, and correlations between fabrication process, film crystalline quality as well as transport properties are discussed. This work provides better understanding of the importance of maximizing crystalline quality by delicate fine tuning of PLD deposition parameters to achieve high quality superconducting films.

No description available.

In this study, two kinds of mesoporous materials were prepared. The first was a silica mesostructure grown within a porous aluminium oxide membrane columnar material (hybrid-AOM). This was prepared using a sol-gel technique with Pluronic P123 triblock copolymer as the structure-directing agent and tetraethyl orthosilicate as the inorganic source. The hybrid-AOM had a similar pore size distribution to that of as-prepared SBA-15 but showed an amorphous character, as demonstrated by nitrogen adsorption and SAXRD. The second type of material was a continuous mesoporous silica thin film, prepared by the dip-coating technique using Pluronic F127 triblock copolymer as the structure-directing agent and the same silica source as hybrid-AOM. The film, which was self-assembled on substrates such as indium tin oxide (ITO), glass and gold, exhibited long-range ordered mesostructures after several treatments and aging. Grazing incidence small-angle X-ray scattering method (GISAXS) showed that the thin film contracted in a direction perpendicular to the substrate after drying and surfactant removal.Removal of the surfactant template from both materials in order to create porous silica was achieved by calcination, ethanol extraction and peroxide-Fe treatments. Calcination was found to be the best method to remove surfactant from both mesostructures (hybrid-AOM and thin film). However, this was found to cause cracking and crumpling of the hybrid-AOM with the evaporated gold being easily peeled off after calcination. Ethanol extraction was thus applied where calcination was not suitable. The surfactant removal was confirmed using an infrared spectroscopy and the structure was confirmed after extraction using 1D X-ray diffraction (XRD). The surface morphology, porosity and crystallinity of the mesostructures prepared were characterized by nitrogen adsorption, scanning electron microscopy and small angle XRD. To form modified electrodes, the hybrid-AOM template was coated by evaporation with pure gold on one side, whilst the mesostructured thin film was grown on either gold or ITO. The permeability of the void space for both hybrid and thin film samples was calculated from the cyclic voltammetry response of a neutral probe (FcMeOH). Cationic ([Ru(bpy)3]2+) and anionic (I-) electroactive species were used to observe the electrochemical response under different pH regimes. FcMeOH was also used to study the effect of KCl concentration on the silica surface charge. Gold and platinum were electrochemically deposited using mesoporous silica as a template.

Billions of people rely solely on groundwater for drinking and daily use. In the last few decades, groundwater was shown to be contaminated with arsenic in high concentrations, especially in Asian countries such as Bangladesh. Arsenic (As) is ranked the first among 20 toxic substances by the Agency for Toxic Substances and Disease Registry (ATSDR) and United States Environmental Protection Agency (USEPA). Because many diseases and deaths were linked to consumption of arsenic-contaminated groundwater, the world health organization (WHO) reduced the arsenic standard level for drinking water from 50 to 10 µg L-1. Urgent demands for safe drinking water lead to developing potential technologies for removal of arsenic from groundwater. Arsenic is mainly present as uncharged As(III) in groundwater, which makes it difficult to be efficiently removed by conventional treatment methods. Therefore, membrane technology could be a promising potential solution. Because membrane technology has not been widely tested for arsenic removal, a novel in-house defect-free interfacially-polymerized (IP) cross-linked polyamide thin-film composite (TFC) nanofiltration membrane, namely, PIP-KRO1, was tested in this research. Two commercial TFC membranes, namely Dow NF270 and Sepro RO4, were also tested and compared to PIP-KRO1. The membranes were tested at four different pH conditions (4, 6, 8, and 10) in a cross-flow flat sheet membrane unit. The experiments were divided into two parts: (i) the membranes were tested for water permeance and salt (NaCl) removal and (ii) tested for As(III) removal in the presence of 250 ppm NaCl. The results in this study showed strong size sieving rejection for RO4 and a combination of size sieving and charge exclusion mechanisms for PIP-KRO1 and NF270. In general, the rejection trend was RO4 > PIP-KRO1 > NF270 for both NaCl and As(III). In contrast, the trend for water permeance was NF270 > PIP-KRO1 > RO4. The minimum and maximum salt rejection at pH 4 and pH 10, respectively, were 85 and 98.8% for RO4, 57 and 89% for PIP-KRO1, and 34 and 76.8% for NF270. In addition, the TFC membranes demonstrated a maximum As(III) rejection of 98.7, 69.5, and 46.3% for RO4, PIP-KRO1, and NF270, respectively. Based on the characterizations of the membranes, PIP-KRO1 had the highest cross-linking (N/O ratio) followed by RO4 and NF270, respectively. The same trend was observed for the thickness of the polyamide selective layer (PIP-KRO1 > RO4 > NF270). The zeta potential for NF270 was slightly higher than that for PIP-KRO1; RO4 had much lower membrane surface charge. In terms of surface roughness, the following trend was observed: RO4 > PIP-KRO1 > NF270.

No description available.

The main purpose of this work is the physical understanding and the numerical description of the reaction of the dense metastable intermolecular composition (MIC). Energy density of MIC is much higher than conventional energetic material; therefore, MIC finds more applications in the propellant and explosive system. The physical model includes the speed of propagation and rate of reaction, and the relationship between the layer thickness, heat rate, and length of the flame based on physical model. In Part I of this thesis, a one-dimensional model based on Weihs was developed for 20 pairs of a multi-layer of aluminum and copper oxide. This problem was solved using an assumed value of constant atomic diffusion in Arrhenius' equation to obtain the velocity of self- propagation. Using the maximum and minimum measured velocities in a similar configuration, the activation energy was computed and was found to be significantly different. When the velocity was used to obtain a linear temperature profile, the margin of error was significant as well. Therefore, this method was seen to have severe shortcomings. In Part II of this thesis, adiabatic unit cell of one layer of aluminum and copper oxide in an ideal reaction was considered. Temperature profile based on chemical heat generation and phase transformation of reactants has been calculated. This model confirmed the highest possible temperature during reaction of 2920 C ± 5% obtained in the literature, however, the model was unable to provide other important flame characteristics. In Part III, a two-dimensional model was developed introducing the flame at the interface. A black box theory has been used to simplify some of the characteristics of the flame, ignoring diffusion characteristics. Using this model, the length of flame was calculated using the measured value of the speed of propagation of the flame. Measuring some of the characteristics of the flame was the main goal of Part III of this thesis. Controllable environment was created for the multilayer thin film of aluminum and copper oxide to eliminate the number of effective variables that affect the speed of propagation. Transformable heat of reaction was used to control the speed of propagation. In addition, a MIC sample was designed and fabricated to measure the speed of propagation with an accuracy of 0.1 m/s. This measurement technique was used to measure the speed of propagation on variable substrate up to 65 m/s. The flame length was also calculated for different speeds of propagation over different substrates. The temperature distribution on the substrate was calculated numerically. Significant improvements have been made in Part III; however, this model does not provide concentration profiles. For future work, a more complete two-dimensional physical model will be developed for self-propagation reaction of multilayer thin film of aluminum and copper oxide based on thermal transport and atomic diffusion. This two-dimensional model includes the reaction rate, speed of propagation and the temperature profile. Since this model relies on a number of physical variables that are as yet unknown, further work is warranted in this area to carry out a thorough computational study.

No description available.

Electro-optical properties of thin film are of great interest owing to the perpetual demand for miniaturization and higher speed devices for communication, electronic, and biomedical applications. The thickness of polymer films developed for these applications has decreased dramatically making interfacial effects significant. It is well documented that, in submicron thickness range, both film/substrate & film/air interface are critical. In this study, we probe the dynamics of electro-optical polymer thin films in the sub-micron thickness regime to understand interfacial effects. The polymer chain dynamics of Polypropylene oxide (PPO) under electric field are investigated in this study. The effects of electric field strength, frequency, and polymer molecular weight on the polymer chain dynamics under electric field are studied. Experimental results show that PPO exhibits both piezoelectric and electrorestrictive effects at significantly high frequencies (101kHz range). Conventional organic materials are responsive only at frequencies in <1kHz range. A high signal-to-noise ratio differential interferometry is designed to quantitatively study the effects of film thickness, electric field frequency and amplitude on the dynamic properties of PPO thin films ranging from 30 nm to 400 nm. The interferometer can concurrently monitor the index of refraction, thickness change of polymer films, and birefringence due to the applied electrical field. / Master of Science