Drop impacts are ubiquitous in nature forming a vital pathway for the transport of liquids, primarily water, and any dissolved substances. The axisymmetric impact of drops has been heavily studied but less work has been done on droplet impacts in which axial symmetry is broken. To analyse such impacts we used a two phase lattice Boltzmann code capable of simulating high density differences. We studied the impact of droplets on cylindrical surfaces, with radius of curvature similar to that of the drop. We found that the symmetry breaking nature of these surfaces leads to droplets bouncing faster and in elongated shapes. The origin of this effect is a positive feedback mechanism through which the momentum asymmetry resulting from the impact grows during retraction. We next looked at how varying the size of the cylinder affected this phenomenon. We found that smaller cylinders increased the contact time reduction, as long as they were still bigger than the droplet, but that below this limit the drop contacted the flat surface and entered a new regime. The work was expanded to look at other types of bouncing asymmetry, using a simple, exactly solvable Lagrangian model. We found that contact time reduction can result from an asymmetric droplet shape, an initially asymmetric velocity or if the surface has an asymmetric drag. A study of the impact of liquid drops containing embedded air bubbles was also undertaken. This was found to lead to jet formation from the bottom of the bubble. We showed how the jet velocity depended on the physical parameters of the drop and impact. In particular the jet formation was very sensitive to the position of the air bubble inside the drop.

No description available.

No description available.

Biomedical research has shown that one-dimensional nanostructures present many potential advantages as delivery vehicles for drugs and biologics. These elongated structures have high aspect ratios that enable increased drug loading capacities and have been shown to have longer in vivo circulation times than other spherical nanoparticles. The increasing interest in these one-dimensional structures has necessitated the developments of fabrication methods for the precise control of the final morphology. A simple, cost effective means of producing nanotubes and nanorods is known as solution template wetting. While this technique has been used to fabricate many different types of elongated nanostructures, the parameters governing the final morphology remain ambiguous. The objectives of this research are to investigate these critical parameters, and furthermore to develop an understanding of the physical mechanism of nanostructure formation. The effects of the infiltration technique, dipping time, polymer molecular weight and template pore size on the morphology of the resulting nanostructure have been evaluated. Key results have established that the infiltration technique is a critical parameter that can enable the formation of stable nanotubes at very low polymer concentrations. Additionally, a tube to rod transition occurs as the infiltration time is increased over 18 hr. An investigation of the rheological properties of high and low molecular weight solutions also indicates that the capillary flow and infiltration of polymer occurs differently. Finally, the pore size was also shown to affect the ability to form hollow, stable structures, and that relatively large pore sizes are necessary for nanotube formation. The culmination of these results is an understanding of the physical layering mechanism of structure formation, and the tube to rod transition can thus be predicted by researchers investigating the use of elongated nanostructures for biomedical applications.

Understanding high temperature interfacial phenomena with Al-alloys is essential for improving corrosion performance of refractories in melting/holding furnaces. Both physical and chemical properties are known to influence wetting and corrosion behaviour. However, uncertainties exist regarding the influence of SiO2 in refractory compositions on interfacial reactions/mechanisms, particularly when present along with non-wetting chemical additives like BaSO4, CaF2 and AlF3. An experimental study was conducted to clarify the interfacial phenomena of Al-alloy7075 with high-alumina refractories at extreme furnace temperatures of 1250??C and 815??C, using classical sessile drop approach and industrial cup tests respectively. At 1250??C, Al-alloy reacted more intensely with SiO2 compared to Al2O3. The interfacial behaviour of SiO2-Al2O3 system with Al-alloy was strongly dependent on SiO2 percentage, such that when upto 25% silica was present, wetting was reduced due to the presence of both original and newly formed corundum. Formation of mullite and originally present silica, along with decreasing corundum contents increased wetting in systems where silica varied from 25-45wt% and more than 45wt% respectively. Moreover, the nature of silica did not influence wetting when present in concentrations less than 20wt%. Different additives produced varying interfacial reactions in the Al-alloy/high-alumina refractory system. AlF3 did not improve the wetting resistance, except when present in high concentrations (>10wt%) in the refractory; this improvement attributed to corundum-rich matrix formation resulting from silica loss as gaseous fluorides. Low CaF2 amounts (<3wt%) improved the wetting resistance due to corundum presence and anorthite formation in the refractory. As CaF2 content exceeded 5wt%, proportion of glassy phases increased, hence enhancing interfacial reactions. However unlike CaF2, low BaSO4 levels (<5wt%) decreased the wetting resistance due to barium silicate formation, while high BaSO4 concentrations (≥10wt%) increased the wetting resistance due to celsian formation. Also, CaF2 dominated interfacial mechanisms when present along with BaSO4 in the refractory. The effect of additives on modifying wetting resistance was found to strongly vary with SiO2 levels of the refractory. The study demonstrated that additive effect is also influenced by treatment temperatures such that generally higher additive amounts are required at lower temperatures for improving the wetting resistance of high-alumina refractories.

No description available.

The broad aim of this research study was to investigate the influence of adsorbing polymers on surface wettability. In particular, the relationship between the properties of the adsorbed polymer layer (the adsorbed amount, layer thickness and morphology) and the surface wettability was elucidated. / Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2005.

Thesis (PhD)--University of South Australia, 2003.

Understanding high temperature interfacial phenomena with Al-alloys is essential for improving corrosion performance of refractories in melting/holding furnaces. Both physical and chemical properties are known to influence wetting and corrosion behaviour. However, uncertainties exist regarding the influence of SiO2 in refractory compositions on interfacial reactions/mechanisms, particularly when present along with non-wetting chemical additives like BaSO4, CaF2 and AlF3. An experimental study was conducted to clarify the interfacial phenomena of Al-alloy7075 with high-alumina refractories at extreme furnace temperatures of 1250??C and 815??C, using classical sessile drop approach and industrial cup tests respectively. At 1250??C, Al-alloy reacted more intensely with SiO2 compared to Al2O3. The interfacial behaviour of SiO2-Al2O3 system with Al-alloy was strongly dependent on SiO2 percentage, such that when upto 25% silica was present, wetting was reduced due to the presence of both original and newly formed corundum. Formation of mullite and originally present silica, along with decreasing corundum contents increased wetting in systems where silica varied from 25-45wt% and more than 45wt% respectively. Moreover, the nature of silica did not influence wetting when present in concentrations less than 20wt%. Different additives produced varying interfacial reactions in the Al-alloy/high-alumina refractory system. AlF3 did not improve the wetting resistance, except when present in high concentrations (>10wt%) in the refractory; this improvement attributed to corundum-rich matrix formation resulting from silica loss as gaseous fluorides. Low CaF2 amounts (<3wt%) improved the wetting resistance due to corundum presence and anorthite formation in the refractory. As CaF2 content exceeded 5wt%, proportion of glassy phases increased, hence enhancing interfacial reactions. However unlike CaF2, low BaSO4 levels (<5wt%) decreased the wetting resistance due to barium silicate formation, while high BaSO4 concentrations (≥10wt%) increased the wetting resistance due to celsian formation. Also, CaF2 dominated interfacial mechanisms when present along with BaSO4 in the refractory. The effect of additives on modifying wetting resistance was found to strongly vary with SiO2 levels of the refractory. The study demonstrated that additive effect is also influenced by treatment temperatures such that generally higher additive amounts are required at lower temperatures for improving the wetting resistance of high-alumina refractories.

Thesis (M.S.)--University of North Texas, Dec., 2009. / Title from title page display. Includes bibliographical references.