The phase behaviour, rheological effects and interfacial properties of binary and ternary liquid mixtures have been studied near critical points. In particular, measurements have been made of the viscosity-at the bulk macroscopic level by capillary viscometry and at the microscopic level by fluorescence depolarisatiorr-and of critical-point wetting and adsorptiorr-at the solid-liquid interface using evanescent-wave-generated fluorescence spectroscopy and at the liquid-vapour interface using specular neutron reflection. The systems investigated have been mostly alkane + perfluoroalkane mixtures or 2-butoxyethanol + H20 or D20 mixtures, although in some cases hexamethyldisiloxane, propanenitrile and perfluorooctyloctane have also been the components of mixtures. The main outcomes of this study are: • Macroscopic viscosity: The divergence to infinity in the shear viscosity of hexane + perfluorohexane at the critical endpoint for approach along the path of constant critical composition both from the single phase and along both limbs of the coexistence curve is described well using the Renormalisation Group Theory critical exponent y = 0.04. The correlation length amplitude obtained by fitting the sheargradient dependence of the viscosity is ~o = (S.S±l.S) A. • Microscopic viscosity: The product of the rotational correlation time and the temperature 'tR"T, often taken as a measure of the microscopic viscosity, exhibits an anomaly as the critical point is approached as a function of temperature. This anomaly mirrors that in the macroscopic viscosity for some fluorescent dye probes, but for others the anomaly is in the opposite sense indicating that other effects such as solvent structure must playa part in the near-critical behaviour of'tR·T. • Critical-point wetting at the solid-liquid interface: The wetting transition temperature has been identified for heptane + perfluorohexane at the quartz-liquid interface from fluorescence lifetime measurements of a probe. The wetting layer is of the same composition as the bulk heptane-rich phase and the transition is tentatively identified as first-order. • Adsorption and wetting at the liquid-vapour interface: The surface structure of several mixtures has been determined by neutron reflection. The results are in general agreement with the expectations of critical-point wetting and adsorption. The surface is complex and in some mixtures an oscillatory scattering length density profile through the interface is required to model the reflectivity data. • Ternary mixtures: The phase behaviour of three mixtures exhibiting tunnel phase behaviour has been studied experimentally and various characteristics of the shape of the twmel identified. A theoretical study on one of the mixtures predicts the drop in temperature for the locus of maximum phase separation temperatures which is observed experimentally.

The drained residual shear strength at the interface between soils and solid materials can be of importance in evaluating the stability of geotechnical structures. Drained residual shear tests have been performed at relatively high effective normal stress levels, over 50 kPa. These effective normal stresses are relevant for many field applications and manageable in typical laboratory shear testing. However, there are field applications, such as offshore pipelines where the effective normal stresses can be below 50 kPa. There are two significant challenges in measuring the drained shear strength at low effective normal stresses: (1) a small amount of friction in a test device can affect the results; (2) small shear rates may be required to achieve drained conditions at the soils. A tilt table test method has been developed to overcome these challenges. The objective of this work is to measure the drained residual shear and interface strength of soils at low effective normal stresses so as to provide logical explanations of the effect of various parameters. These parameters include soil index properties, clay content, clay mineralogy, stress history, and loading rate together with the effective normal stress levels. The total 74 tilt table tests are performed to measure the drained residual shear and interface strength of marine clays and sand-kaolinite mixtures. The following conclusions can be drawn based on the test results. 1. The drained residual shear strength both for the interface and for the soils is not affected by the over-consolidation ratio. 2. The drained residual shear strengths for the interfaces are all less than the drained residual shear strengths of soils. The drained residual strength of interface depends on the roughness of interface, clay mineralogy. 3. The empirical correlations and shear test results at higher effective normal stresses cannot be extrapolated to lower effective normal stresses. 4. Clay mineralogy and clay contents together with the magnitude of effective normal stress are the most important factors to estimate the drained residual shear strength of cohesive soils. 5. Cohesionless soils exhibit a constant residual secant friction angle regardless of effective normal stress levels. / text

No description available.

No description available.

The use of Raman spectroscopy in ultra high vacuum to assess structure and reactivity at the interface of tris-(8-hydroxyquinoline) aluminum (Alq3) with vapordeposited metals is presented. Understanding the structure of the interface between electron transport layer materials such as Alq3 and low work function metals such as Al, Mg and Ca is vital for engineering organic light emitting diodes with high efficiency and low driving voltage. Reactivity at the interface of Al, Mg and Ca with Alq₃ thin films is examined with Raman spectroscopy along with the non-reactive Ag/Alq₃ interface for comparison. Additionally, the effect of a thin LiF barrier layer on reactivity at the Al/Alq₃ and Mg/Alq₃ interfaces is also examined. Raman spectroscopy of post-deposited Ag on Alq3 films confirms preservation of the Alq₃ structure along with evolution of simple surface enhancement of Alq₃ spectral intensities. Changes in key vibrational modes of Alq₃ upon Ag deposition are consistent with weak interaction of Ag with the conjugated ring of the ligand. In contrast, vapor deposition of Al onto Alq₃ films results in the appearance of new Raman modes linked to the formation of an Al-Alq₃ adduct. Additionally, Raman modes associated with graphitic carbon are also noted for the Al/Alq₃ interface and are attributed to partial degradation of the organic film. The Raman spectral results for deposition of Mg onto Alq3 films also indicate formation of a complex interfacial region composed primarily of Mg-Alq₃ adducts and small-grained amorphous or nanocrystalline graphite. Raman spectroscopy of the Ca/Alq₃ interface is also indicative of formation of a Ca-Alq₃ complex; however, the graphitic carbon in this system is noted to be more disordered, sp³-type carbon compared to that observed for Al/Alq₃ and Mg/Alq₃. Examination of the Al/LiF/Alq₃ and Mg/LiF/Alq₃ interfaces illustrates that 5 Å-thick LiF layers partially block reaction chemistry between the metal and organic, while 10 Å thick LiF films completely eliminates reactivity at these interfaces. Implications of the presence of chemical species observed at these metal/organic interfaces on charge transport in devices are also discussed.

No description available.

No description available.

No description available.

No description available.

No description available.