Traditional dissolution models are based in the analyses of bulk solution compositions and ignore the fact that different sites of a surface dissolve at different rates. Consequently, the variation of surface area and surface reactivity during dissolution are not considered for the calculation of the overall dissolution rate, which is expected to remain constant with time. The results presented here show the limitations of this approach suggesting that dissolution rates should be calculated as a function of an overall surface reactivity term that accounts for the reactivity of each of the sites that constitute the surface. In contrast to previous studies, here the focus is put on studying the surface at different dissolution times. Significant changes in surface topography of CaF2 were observed during the initial seconds and up to 3200 hours of dissolution. The observed changes include the increase of surface area and progressive exposure of the most stable planes, with consequent decrease in overall reactivity of the surface. The novelty of a proposed dissolution model for fluorite surfaces, when compared with traditional dissolution models, is that it differentiates the reactivity of each characteristic site on a surface, e.g. plane or step edge, and considers the time dynamics. The time dependency of dissolution rates is a major factor of uncertainty when calculating long term dissolution rates using equations derived from dissolution experiments running for short periods of time and using materials with different surface properties. An additional factor of uncertainty is that the initial dissolution times are the most dynamic periods of dissolution, when significant variations of surface area and reactivity occur. The results are expected to have impact in the field of nuclear waste management and to the larger geological and material science community. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.</p>

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Probing Defects and Electronic Processes on Gadolinia-doped Ceria Surfaces Using Electron Stimulated Desorption Haiyan Chen 133 Pages Directed by Professor Thomas M. Orlando Polycrystalline gadolinia-doped ceria (GDC) has been widely investigated as a promising low temperature solid oxide fuel cell (SOFC) electrolyte and as part of composite electrodes. In this thesis, electron stimulated desorption (ESD) has been used to probe the defect related electronic properties of GDC surfaces and the interactions of water and molecular oxygen with these surfaces. In particular, the electron irradiation induced surface charging of GDC has been found to be dependent on the incident electron energy: negative at lower energy and positive at higher energy. Trapping of electrons and holes by the gadolinium aggregated, oxygen vacancy rich grain boundaries has been considered as the origin of surface charging. Depending on the sample treatment, there can be various defects, hydroxyl groups, chemically adsorbed water molecules, or water dimers on GDC surfaces. Water and molecular oxygen interact primarily with defect sites. Systematic investigations of electron stimulated O+ desorption have yielded activation energies relevant to oxygen vacancy production on ceria surfaces, and to surface positive charge dissipation related to ionic conduction of GDC. Highly efficient electron stimulated O+ desorption from GDC surfaces has been attributed to the lowered charge density on oxygen ions coordinated with oxygen vacancy clusters and thus may be used as a probe for surface defect types. Electron stimulated desorption of O2+ from GDC surfaces during molecular oxygen adsorption has shown the ability of ESD to detect chemically adsorbed O2. The velocity distributions of O2+ can be used to probe intermediate adsorption species such as O2, as well as the positive charge of the surface. Overall, this thesis has demonstrated that ESD can provide important information on the kinetics and dynamics of surface charging, charge transport, adsorption and reactions occurring at defective insulating metal oxides materials. The abilities to probe the defects and their roles in surface processes make ESD a valuable technique for surface chemistry and catalysis studies.

The study uses the Phase-field method to simulate the bubble behavior of liquid-solid interface in the solidification.The flow use the mass equation,momentum equation,and energy equation for simulating the variation of bubble. This pattern considers that three-phase of solid, liquid,and gas coexist with the different density and viscosity coefficient,and the external force considers surface tension and the gravity force. In addition,the mass transfer also can¡¦t neglect around interface. The result discuss the production of pore when the velocity of solidification is fast,but bubble leaves when the velocity of solidification is slow.

Layer-by-layer assembly has received much attention over the last fifteen years. This assembly process can be carried out using different methods including hydrogen-bonding, electrostatic, and to a lesser extent, covalent interactions. However, these assemblies are rarely seen on polyolefin substrates due to the lack of functionality on the surface. “Click” chemistry has become very popular in recent years as a means to join modular compounds together. This thesis is the first published report to use “click” chemistry as a means for layer-by-layer assembly on a polymeric substrate. By designing polymers that contain alkyne or azide groups, it is possible to assemble them layer-by-layer on a polyethylene substrate. Polymers based on tert-butyl acrylate were initially designed for use in organic solvents such as tetrahydrofuran. The copper catalyst that facilitated the 1,3-dipolar cycloaddition was air sensitive and expensive. To capture the true essence of “click” chemistry, a new system was designed based on N-isopropyl acrylamide (NIPAM)-based polymers. These polymers were water soluble and allowed for “click” chemistry to be performed in water and open to air in benign conditions. With the development of a water soluble polymer system that could be modified to contain either azide groups or alkyne groups, layer-by-layer assembly was carried out in water. A polyethylene film was modified in a series of reactions to have an alkyne-functionalized surface. The poly(N-isopropyl acrylamide)-based polymers were layered in an alternating fashion to form multilayer assemblies. A series of control reactions were also performed, showing that these layers were interconnected via triazole linkages. These assemblies were monitored by attenuated total reflectance spectroscopy. Once the layers were assembled, the polyvalent nature of the polymers allowed for further functionalization. Various surface functionalizations were established using fluorescence microscopy and contact angle analysis. By using spectroscopic and chemical means, layer-by-layer assembly on polyethylene films was proven. Control reactions showed the necessity of components for triazole formation. Therefore, layer-by-layer assembly using “click” chemistry was achieved.

ABSTRACT Electrostatic discharge (ESD) influences a lot in the industries of petrochemistry, semiconductor, and electronics. ESD is one of the reasons for the deterioration of the lubricant in the lubrication system. In this study, to understand the performance of the frictional electrification of the lubricant, the circumrotating frictional electrification tester with the measurement systems is employed to investigate the friction electrification under the dry and lubricated conditions. The materials of the specimens are made of Fe and PTFE, and the paraffin base oil is used as the lubricant. Furthermore, the effects of the load, the sliding speed, and the sliding distance on the friction electrification are investigated. Results show that the electrification voltage and the surface voltage in the lubricated condition is much lower than in the dry condition for the pair of Fe/PTFE. Because the capacitance effect is almost disappears in the lubricated condition for the pair of Fe/PTFE. When two conductors become a capacitor by inserting an insulator, such as Fe/PTFE in the dry condition, the surface voltage is about 3~4 times higher than in the lubricated condition, and the frictional voltage is about 10 times higher than in the lubricated condition because of the isolator capacitance. Moreover, the oil, the PTFE and the Fe have different polarities. The surface voltage of PTFE and output voltages of Fe are negative, and surface voltage of oil are positive. The normal load, the sliding speed, and the sliding distance also affect the surface voltage of PTFE and output voltage of Fe. Among them, the load is the most significant parameter for surface voltage of PTFE, the sliding speed is the most significant parameter for output voltage of Fe.

Surface plasmons¡]SPs¡^have been extensive applied to various kinds of detector and devices. There are very great relations of physical quantity, such as resonant angle, damping rate, halfwidth of resonance and reflection rate, etc. of resonating in the exciting of SPs. In this study, we derived some approximate formulas of these physical quantities from fresnel¡¦s formulas and pole approximate expansion, such as, the damping rate of SPs, the resonant angle, the optimum metallic thickness of these structure. In addition, we have also proceeding to some numerical simulations. Surface plasmons can also apply to near-field optics, using the super-resolution near-field structure¡]Super-RENS¡^ , the data densities can be promoted, and the diffraction limit can be overcome. SPs are excited at the Sb/SiN interface may concentrate light spot and enhance the field intensity. In this study, we have also expounded the fact that its antimony film in a Super-RENS of propagation, function and simulation of the SPs. As a result of calculations and simulations, we conclude that the enhanced filed intensity is larger for a system using a metal with a smaller imaginary part of the dielectric constant. The resonant angle decreases when the dielectric constant of the prism increases and the dielectric constant of the intermediate layer decreases. In addition, the optimum resonant condition in Super-RENS can be made by proper selection of parameters.

ABSTRACT The ceramic ball bearing has been used to exact machine for its good properties such as heat-resistant, corrosion-resisting, and wear-resisting. Now, the produced expense of ceramic ball is hundred of steel ball because the grinding process must spend much time and money. This study research the effects of eccentricity (e: the distance is between the center of the ball circulation and the center of the spindle), spindle speed, and load on grinding characteristics of ball by using eccentric ultra-precision ball grinding machine which developed by our lab, under saving cost and time, search the optimum operating conditions of this machine, it¡¦s good for industrial circles in the future. Experimental results show that the converged rate of the saturated value for the sphericity is increased with increasing eccentricity. Saturated value of sphericity is sphericity reduced to a steady state. The saturated value of the sphericity is not fully proportional to eccentricity. The relation between eccentricity and saturated value of sphericity are divided two region by one rb, the first region is that sphericity is proportional to eccentricity when eccentricity is 0~rb, and the second region is that sphericity is inverse proportional to eccentricity when eccentricity is rb~2rb. The converged rate of surface roughness (Ra) are negative with increasing eccentricity and the saturated value of the surface roughness (Ra) is higher. The volume removal rate is increased with increasing eccentricity. The converged rate of the saturated value for the sphericity and surface roughness (Ra) are increased with increasing spindle speed and load, and the saturated value are higher. The volume removal rate is also increased with increasing spindle speed and load.

The attenuated total reflection (ATR) method and the scattering spectrum analysis are used to study the effects due to the surface plasma of Ag nanoparticles. A slide is coated with a thin Ag film of thickness about 40nm and anneals the sample few minutes at 197¢XC. The Ag film is thus congregated to be a rough surface. By ATR(with the slide attached to the back of the prism), the intensity of the total refection light and the reflective angle are measured. Then we can determine the dielectric coefficient of the rough Ag surface. We also coat a thin Ag film about 8nm on the ITO glass and anneal the sample. The thin Ag film is thus congregated to be nanoparticles. We discuss the effects due to the surface plasma excited on the Ag nanoparticles by analyzing the absorbance and scattering spectrums from Ag nanoparticles in liquid crystals environment.

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