No description available.

No description available.

The surface force apparatus (SFA) has been an important technique for making direct force measurements and has contributed enormously to our understanding of colloidal interactions. The conventional SFA has been limited to measuring forces between solid surfaces, until recently when a modified SFA was developed at the Ian Wark Research Institute [1]. A fluid drop (mercury) is introduced into the apparatus which allows a range of deformable surfaces to be studied in the SFA. This project is an extension of this technique. Interactions between a mica sheet and a mercury drop are studied, including the modification of mercury with self-assembled monolayers (SAMs) of thiol surfactants, and the drop deformation due to non-equilibrium adsorption effects and hydrodynamic forces. / SAMs can form spontaneously onto a surface by immersing the substrate into an appropriate surfactant solution. They have been used, generally formed on gold surfaces, for biosensors, chemical sensors, micro-electronics and detection of DNA and protein adsorption. In our study, mercury was chosen as the substrate, for its defect-free, renewable and molecularly smooth surface. The additional advantage of being an ideal polarisable electrode allows a potential to be applied to the mercury, and hence control of the surface forces. The charging behaviour of the mercury is changed by introducing a SAM onto the surface. An uncharged SAM (11-mercapto-1-undecanol or 11-mercaptoundecane) modifies the dipole potential of the mercury by replacing the water molecules oriented on the surface, whereas a charge SAM (11-mecapto-1-undecanoic acid) brings additional charges to the surface. / Drop deformation is an important factor when deformable surfaces are involved in colloidal systems, e.g. emulsions, foams, in mineral flotation and in biological systems. Drop profiles of a mercury surface which is already close ( ̃50 nm) to a flat mica sheet, with or without a SAM, were measured using the SFA technique. For the SAM-modified mercury, the negatively charged functional group (-COO⁻) yields a repulsion against mica, and a thin film is formed between the surfaces. When the applied potential was scanned negatively, desorption of thiols occurred at certain potentials, increasing the local solute concentration in the solution. The restricted flow of the solute within the small gap creates an excess osmotic pressure in the thin film compared to the bulk solution. As a result, the film pressure exceeds the internal pressure of the drop, inverting the drop curvature and forming a dimple. We propose that the drainage of the dimple is a diffusion-controlled process, which is supported by the comparison of the data with a simple model calculation. / For the bare mercury drop, a negative potential was applied to the mercury to provide a repulsion to form a thin film. Mica was then driven towards the mercury with an abrupt step. Beyond certain step sizes, a rippled shape - which we dub a “wimple” - was observed before it evolved into a classical hydrodynamic dimple. At small step sizes, no wimple was observed, but curiously the film in the central part thickens before eventually thinning out. This shows that fluid first flows towards the central axis before reversing its flow direction and flowing radially outwards. / Thesis ([PhDApSc(MineralsandMaterials)])--University of South Australia, 2005.

Thesis (PhD)--University of South Australia, 2001

Two thin film materials - intermetallic and porous silicon thin films, have been studied in this thesis. The first part focuses on the hydrogen storage and electrochemical properties of single layer LaNi5-based thin films fabricated by magnetron sputtering. The aim is to enhance their performance in mini hydrogen storage systems, and their application as electrodes in thin film Ni-MH micro-batteries. Such LaNi5-based thin films were fabricated by magnetron puttering. Using X-ray diffraction (XRD), these thin films revealed a crystalline structure with uniform chemical composition. Using AFM, SEM and TEM, they were found to have a unique microstructure: (1) Nanopores of approximately 15-40 nm which could possibly act as hydrogen reservoir (2) A dense, defect free cross sectional region which would ultimately improve the efficiency and lifetime of the thin film electrodes used in thin film battery. The hydrogen absorption/desorption behaviour of these thin films were determined by volumetric method. The maximum hydrogen content of the La-Ni-A1 film was found to be 1.45 wt% at 333 K which was very close to the theoretical capacity of 1.47 wt%; and higher than that of the La-Ni-AI powder materials (1.2 wt%). Electrochemical properties of the films were measured by simulated battery tests. When discharged at low current, the discharge capacity of the film was similar to that of powder materials - about 220 mAh/g for the first 30 cycles. When the thin film electrode was discharged at a high rate, 4C (current density of 100 mA/g), it could reach the maximum specific capacity of 200 mAh/g and maintained this capacity for 200 cycles; the value was not attainable for La-Ni-AI powder electrode. The presence of crack propagation in film during charge/discharge cycles would improve the electrochemical performance which was different to that of powder materials. Cyclic voltammetry reported that the efficiency of the film could maintain at 80% for the first 200 cycles and gradually decreased due to the formation of corrosion products on surface, which is consistent with the galvanostatic results. XPS (X-ray Photoelectron Spectroscopy) revealed that the corrosion products ??? A1203, La203 and La(OH)3 formed on the film surface after cyclic voltammetry. The second part reported the hydrogen absorption/desorption behaviour of porous silicon thin films. The hydrogen content was determined quantitatively by both volumetric method and thermogravimetric analysis (TGA) and found to be 15 wt% at 423 K under 15 atm of hydrogen pressure. This is an extraordinary amount of hydrogen absorption which supersedes the US Department of Energy's 2007 target of 6.5 wt%. Hydrogen depth profiles of the film after hydrogenation performed by Secondary Ion Mass Spectroscopy confirmed there was hydrogen within the film structure, this was an indication that hydrogen was not just physisorbed on the film surface, but chemisorbed into the porous Si lattice. X-ray diffraction found that there was a lattice contraction upon hydrogen insertion, again suggesting the hydrogen entered into the film structure by chemisorption.

Thesis (PhD)--University of South Australia, 2001

Thesis (Ph.D.) in Chemical Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 92-107).

Thesis (M.S.)--Ohio University, November, 1999. / Title from PDF t.p.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 161-180). Also available in electronic version.

Thesis (M.S.)--Rochester Institute of Technology, 1994. / Typescript. Includes bibliographical references (leaves 134-137).