<p>This work considers the transport and attachment of nanoscale particles to surfaces and the associated phenomena that dictate particle-surface interactions. A consideration of the deposition of nano-scale particles on surfaces is a natural outgrowth of more than a century of research in the area of colloid science, and has taken on new pertinence in the context of understanding the fate and transport of engineered nanoparticles in aqueous environments. More specifically, the goal of this work is to better understand the effects of particle size, surface polymer coatings, and aggregation state on the kinetics of nanoparticle deposition. Theoretical tools such as those developed by Derjaguin-Landau-Verwey-Overbeek (DLVO) and Flory-Krigbaum , as well as the soft particle theory and surface element integration scaling methods are employed to address certain problems that were not considered with the existing theoretical frameworks for the conventional colloidal problems. Consequences of theoretical predictions are evaluated experimentally using column experiments or the quartz crystal microbalance techniques to monitor deposition kinetics. One of the key findings of this work is the observation that polymer coatings may stabilize nanoparticles against deposition or increase deposition, depending on whether the polymer coatings exist on both of the interacting surfaces and the interaction between the polymer and the collector surface. Both steric and bridging mechanisms are possible depending on whether contact between the polymer and collector surface can result in successful attachment. In addition, limitations in the use of conventional, equilibrium-based DLVO theory to describe the deposition of nano-scale particles at very low ionic strength are also identified and discussed. Moreover, it is demonstrated that the interaction between the aggregated nano-scale particles and environmental surfaces is controlled by the characteristic size of the primary particles rather than that of the aggregates. Thus despite an increase in hydrodynamic diameter, aggregation is predicted to reduce deposition only from the hydrodynamic aspects, but not from the colloidal interaction aspect. The affinity between aggregated nanoparticles and a surface may be increased at the initial stage of deposition while being unaffected by aggregation state during later stages of deposition. The results of this study lead to better understandings, at least on a qualitative level, of the factors that controlling the kinetics of deposition and, in a broader sense, the fate and transport of nanoscale particles in the aqueous environment.</p> / Dissertation

In this study,The bottom electrode(TiN),middle insulator(Hf:SiOx),and top electrode(Pt) were deposited respectively by sputtering technique for fabricating the RRAM with MIM structure.The mole fraction of hafnium were about 5%.Instead of non-doped SiO2 base device has no switching characteristic,the Hf-doped SiO2 RRAM could be operator over 100 times and resistive state was kept stable over 104 second. In this researches,the double layer structure(Pt/Hf:SiO2/Hf:SiO2(doped N2 and NH3)).The Resistance switching characteristics of double layer structure device has particular I-V characteristics due to the doping of N.The doping of NH3 cause hydrogen plasma treatment on double layer device also bring about particular I-V characteristics. The physical mechanism we had proposed were proof by the Current-Voltage fitting and the material analysis.By control stop-voltage,the double layer structure device can operation by multi-bit. The detail physical mechanism is studied by the stable RRAM device(Ti/HfO2/TiN).In this study,the model of reset process we had proposed were proof by the special measurement methods(Constant-voltage sampling) and the principle of chemical reaction mechanism.

Double-layer grid systems are three-dimensional pin-jointed structures, which are generally used for covering roofs having large spans. In this study, evolution strategies method is used to optimize space trusses. Evolution strategies method is a type of evolutionary algorithms, which simulate biological evolution and natural selection phenomenon to find the best solution for an optimization problem. In this method, an initial population is formed by various solutions of design problem. Then this initial population starts to evolve by using recombination, mutation, and selection operators, which are adopted for optimization of space trusses by modifying some parameters. Optimization routine continues for a certain number of generations, and best design obtained in this process is accepted as optimum solution. OFES, a design and optimization software developed for optimum design of steel frames, is modified in this study to handle space truss systems. By using this v software, six design examples taken from real-life industrial applications with element numbers changing between 792 and 4412 are studied. The structural systems defined in examples are optimized for minimum weight in accordance with design provisions imposed by Turkish Specification, TS648. The optimization is performed based on selecting member sizes and/or determining the elevation of the structure and/or setting the support conditions of the system. The results obtained are compared with those of FrameCAD, a software which is predominantly used for design of such systems in national current design practice.

The main goal of this research was to develop a mechanism-based model for photocatalytic disinfection of bacteria in water using suspended catalyst pthesiss in batch reactors. The photocatalytic disinfection process occurs as a semiconductor photocatalyst, most commonly titanium dioxide (TiO2), is irradiated with light of wavelength less than 380 nm to produce hydroxyl radicals and other highly reactive oxidants which can inactivate microorganisms. Photocatalytic disinfection involves a complex interaction of many fundamental mechanisms such as light absorption and scattering by semiconductor pthesiss, electrochemical surface reactions, and heterogeneous colloidal stability. Current models, based largely on chemical reacting systems, do not adequately account for these fundamental mechanisms. Even the Langmuir model developed for heterogeneous systems cannot describe the interactions of such large colloidal pthesiss. As a result, it is difficult to assess the combined effects of many important factors which go into the design of a photocatalytic disinfection system. A mechanistic modeling approach is desirable because it provides a framework to understand the influence of many important parameters on the disinfection process. It requires a description of the physical properties of the catalyst, the nature of the suspending electrolyte solution, the physical and chemical properties of the cell surface, and the energetic aspects that influence the interaction of the pthesiss. All these aspects are interrelated. While it is customary to envision the adsorption of reactants unto a catalyst surface, for photocatalytic disinfection involving suspended catalyst pthesiss, multiple catalyst pthesiss adhere to the bacterial surface. In this work a mechanistic model has been developed that simulates the effect of light intensity and catalyst concentration on the disinfection process. The simulations show good agreement with the experimental data for stable colloidal suspensions, that is, suspensions in which rapid aggregation of cells and TiO2 do not occur. Increased disinfection rates and high levels of inactivation can be achieved by maintaining a relatively low catalyst-to-microbe ratio while maximizing the light intensity. The influence of pH and ionic strength on the disinfection process have been included in the model, but these are only expected to be accurately predicted when the solution remains stable.

No description available.

Surgical correction of scoliosis is a complicated mechanical process. Understanding the loads applied to the spine and providing immediate feedback to surgeons during scoliosis surgery will prevent overloading, improve surgical outcome and patient safety. Long-term development of residual forces in the spinal instrument after surgery with the continual curvature changes over time has been unknown. The goal of this research work was to develop a wireless implantable sensor platform to investigate the loads during and after surgery. This thesis describes research leading to the design of a sensor platform that uses both 403 MHz and 2.45 GHz for wireless communication, and reports the resolution and accuracy of the built-in temperature sensor, the A/D accuracy of the sensing platform, the power consumption at different operation modes, the range of the wireless communication and the discharge characteristics of a potential capacitive power module. / Biomedical Engineering

Hydrogen is considered one of the best alternatives to fossil-fuels for the transportation sector because hydrogen can be burnt cleanly and efficiently in a fuel cell to drive an electric motor. However, due to the low density of H2 at ambient conditions the conventional H2 storage technologies (cryogenic liquid and compressed gas) cannot achieve energy densities comparable to to gasoline and diesel. A second energy storage challenge onboard electric fuel cell vehicles is fuel cell power management at peak current loads, which requires an auxiliary power source like a battery or supercapacitor. The development of efficient onboard energy storage systems for H2 and auxiliary power is critical to realisation of a hydrogen economy. Mesoporous carbons were investigated as H2 storage materials in composites with magnesium hydride (MgH2),and as electrode materials for electrochemical double-later capacitors. The mesoporous carbons were prepared by two methods: (1) from porous silica and alumina templates, and (2) by chemical activation of a waste carbon source (waste coffee grounds). The experimental approach targeted reducing the cost of mesoporous carbon preparation by using a cheaper template, where the cost of alumina template was one-fifth the cost of the silica template (at the laboratory scale), or by using a waste material as a carbon source. The alumina template was found to be suitable to produce a mesoporous carbon with an average pore size of 4.8 nm. Chemical activation of coffee grounds with ZnCl2 produced activated carbons with BET surface areas up to 1280 m2/g. Mesopore volume increased with ZnCl2 impregnation ratio, with mesopore size distributions in the range 2 - 20 nm. The theoretical H2 capacity of MgH2 is 7.6 % but MgH2 application in fuel cell vehicles is limited by slow hydrogenation kinetics and high temperatures (> 573 K) for H2 release. Magnesium was impregnated on activated carbon fibres (ACF) and mesoporous carbon (prepared from silica and alumina templates) to improve H2 storage kinetics and thermodynamics by reducing the magnesium hydride particle size. Thermal gravimetric analysis (TGA) and temperature programmed desorption (TPD) studies showed that thermal decomposition of MgCl2 supported on ACF at 1173 K in N2 and H2 can produce a Mg-ACF composite. At 573 K and 2 MPa H2 pressure a Mg-ACF composite, containing 11.2 %wt Mg, showed improved H2 adsorption kinetics compared to bulk Mg powder, but the total capacity of the Mg-ACF composite was only 0.4 % wt H2. To achieve a target of 6 %wt for onboard H2 storage higher Mg loadings are required. Attempts to impregnate Mg in mesoporous carbon via the MgCl2 thermal decomposition process highlighted the difficulties of avoiding MgO formation, and show that MgH2 loaded carbon is unlikely to be a practical high density onboard H2 storage technology. Activated carbons from waste coffee grounds (CGCs) were used as electrode materials in electrochemical double-layer capacitors. The specific capacitance of CGCs was as high as 368 F/g in 1 mol/L H2SO4, with good capacitance retention at fast charge rates and stable cycling performance. The good electrochemical performance of CGCs is attributed to a porous structure featuring both micropores 0.5 - 1.0 nm wide, which are effective for double-layer formation, and small mesopores, which facilitate electrolyte transport at fast charge rates. The capacitance of CGCs is enhanced by pseudo-Faradaic reactions involving nitrogen and oxygen functional groups. At fast charge-discharge rates the CGCs had higher energy density and better stability than a commercial benchmark activated carbon (Maxsorb). The ZnCl2 activation process can be optimised to develop mesopores for improved capacitance at fast charge rates and capacitance in organic electrolytes. In 1 mol/L tetra ethyl ammonium tetrafluoroborate (TEABF4) / acetonitrile the CGC with the most mesopores, which was prepared with a ZnCl2 to coffee ratio of 5:1, has the highest capacitance at high power density. CGCs with greater mesopore content retained higher specific capacitance at fast charge-discharge rates as the mesopores acts as channels or reservoirs for electrolyte transport. An improved model for evaluation of contributions to capacitance from micropore surfaces and mesopore surfaces is proposed. From this model the double-layer capacitance of mesopores surface area was found to be about 14 μF/cm2 and did not change considerably with increasing current load. The contribution of micropores to capacitance is dependent on the accessibility of ions to the micropores, and this accessibility is proportional to the mesopore surface area. An exponential function was found to describe the contribution of mesopores and micropore surfaces to capacitance. The effective double-layer capacitance of the micropore surface area drops at fast charge-discharge rates as a result of restricted ion transport, and this result highlights the importance of mesopores to retain energy density for high power supercapacitor applications.

Bibliography : leaves 154-163 / ix, 163 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, and Mathematical Physics, 1993

Energy storage devices are generally evaluated on two main requirements; power and energy. In supercapacitors these two performance criteria are altered by the capacitance, resistance and voltage. (For complete abstract open document)

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2005. / Ready, Jud, Committee Co-Chair ; Carter, Brent, Committee Co-Chair ; Snyder, Bob, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.