Thesis (B. S.)--University of Wisconsin -- La Crosse, 2008. / Also available online. Includes bibliographical references (leaves 33-36).

Thesis (PH. D.)--Duke University, 1963. / Without thesis note. Map on lining-papers. Bibliography: p. 201-223.

Thesis (doctoral)--Friedrich-Alexanders-Universität Erlangen, 1909. / Vita. Includes bibliographical references (p. [143]-144).

Inaug.-Diss.--Frankfurt a. M. / "Literaturverzeichnis": p. [192]-198.

Thesis (Ph. D.)--Columbia University, 1915. / Vita.

Amorphous hydrogenated carbon (a-C:H), diamond & diamond-like (DLC) thin films are some of the many terms used when referring to the generic group of coatings based on hard carbon. They are an emerging technological area within the surface coating discipline and are being increasingly used to improve the efficiency of a wide range of engineering components. In addition, the unique and extreme characteristics of these films result in unequalled material properties, such that in many cases a wide range of new and superior performance devices have only recently begun to be realised. This study focuses on hydrogenated & non-hydrogenated diamond-like thin films deposited by various plasma based, hybrid and beam deposition techniques. The wear resistant and low friction properties of these films are of great importance in many of the potential application areas and has attracted particular interest in recent years. Therefore the major thrust of this research has been on the tribological aspect, particularly in relation to other advanced ceramic coatings, and to highlight the applicability of endurance wear tests used to evaluate diamond-like films. The main findings have been:- a} That carbon can be deposited by several techniques in a hard amorphous phase, the properties of which depend heavily upon the conditions, substrate choice and method of deposition. For a particular technique, material properties can be made to be repeatable by a good understanding of deposition process control. b} The use of plasma based hybrid PVD and beam methods have resulted in a considerably improved structural performance of the films over those produced by the direct evaporation of graphite. The introduction of a hydrocarbon gas into the plasma at the synthesis stage has also been shown to provide further improvements in the physical properties which has correspondingly led to an enhancement in the tribological behaviour. The levels of hydrogen, whether in an unbonded or bonded form, included in the film after deposition has been demonstrated to affect the mechanical and optical properties of the considerably. c) The wear resistant and frictional performance of these coatings has been shown to be variable, depending upon the method and conditions of deposition as well as test parameters such as humidity, surface roughness, film structure, adhesive strength and oxide/impurity formation. In some cases the tribological performance was found to be excellent. The presence of the diamond-like carbon coating has been shown to be beneficial in reducing wear between contacting bodies experiencing relative movement by encouraging the formation of a carbon transfer layer on the surface of the counterface material which acts as a zone of low shear and provides a physical barrier to tribo-chemical interactions. Under certain conditions, such tribo-chemical interactions can occur readily at the interface, facilitating the formation of strong interfacial bonding and increased wear. d) The inclusion of metallic elements into the carbon matrix has been shown to enhance the wear resistant properties of the film to only a small extent, although at the expense of a deterioration in the friction coefficient. The most beneficial effect of doping carbon films with metal species has been the improved resistance to thermal degradation. e) Thin intermediate layers of titanium nitride have also been shown to produce a remarkable improvement in both wear resistance and frictional performance of the diamond-like carbon films to an extent which appears to be related to the level of stoichiometry of the titanium nitride. The main mechanism behind this increased performance appears to be due largely to an enhancement in adhesive strength at the diamond-like carbon/titanium nitride junction, with an increase in load support being provided as a secondary benefit. f) A critical assessment of the available techniques and methodology available for testing hard carbon films has been made and in some cases methods have been found to be either entirely inappropriate or appropriate only when suitable precautionary measures have been taken. These difficulties largely stem from the exacting demands of thin, hard layers of diamond-like carbon due to its unique and extreme mechanical, electrical and optical properties.

Commercial polymers are typically classified according to their melt flow indices, measures of their viscosities. These properties are known to depend on a material’s molar mass distribution, on its averages and its degree of polydispersity. In determining a polymer’s performance, both the molar mass distribution and the process employed to produce the part are highly relevant, since the balance in the mass fractions from its distribution will determine the flow characteristics in the mould, and influence the material’s performance. The compromise polymer manufacturers have to make is to maintain the mechanical properties known to improve with increased molar mass at the same time as a sufficiently low viscosity, known to reduce with decreasing molar mass, to enable part production. This is often achieved by judicious blending of homopolymers. This thesis examines how varying molar mass and distribution in blends leads to changes in the thermal, rheological, and mechanical properties in polystyrene, and discusses and develops physical models to capturing the observed experimental responses. Chromatographic and calorimetric studies were carried out on monodisperse, bimodal blends of monodisperse, polydisperse, and blends of polydisperse polystyrenes. They revealed that changes in molar mass distributions and glass transition temperatures, Tg, could be directly attributed to the blending procedure of choice. In polydisperse blends, higher contents of low molar mass fractions, and corresponding lower Tgs were observed in the blends produced using a melt mixing method compared with solution-blended equivalents. Thermal degradation, accelerated by the large number of chain ends, was suggested as the cause for the increase in low molar mass fractions in the melt-mixed blends. The filtration and precipitation stages characteristic of solution blending instead promoted oligomer loss and evaporation, resulting in reductions in the low molar mass tails of the distributions. Craze initiation stress was measured in 3-point bending isochronal creep tests on the same polymers and blends, and was found to in-crease rapidly with additions of a higher molar mass component, reaching a plateau at 20 wt%. A simple model based on a weighted addition of the crazing stress contributions of individual weight fractions was developed from an established piecewise linear crazing law in order to enable predictions of the crazing stress in the blends, using a power law exponent of 2.59 (90% CI [1.75 17.34]). In highly poly-disperse systems, where short unentangled chains dilute the polymer, it was necessary to include dynamic tube dilution theory. Dilution leads to a change in the entanglement length and hence in the molar mass at which transitions in the crazing mechanisms (disentanglement and chain scission) occur. With the improved model, crazing stress could be predicted even for highly polydisperse blends with wide and bimodal distributions. Linear and non-linear rheological measurements were carried out in shear and extensions on the same materials. Existing rheological models for linear viscoelasticity including Likhtman-McLeish (L-M), Rubinstein-Colby (R-C) and polydisperse double reptation (pDR) theory were applied to the linear experimental data, exposing some of the fundamental difficulties of modelling the structure of systems where multiple chain-lengths interact. R-C was found applicable to bi-modal blends of monodisperse, whereas pDR was better able to model broad polydisperse blends. New non-linear shear and extensional rheology was recorded experimentally on all polymers and blends, and should enable future non-linear theories to be compared to experiment.

Acoustic arrays have been widely studied and can be used for a variety of applications. Existing acoustic array systems have mainly utilised linear and planar geometries. Such geometries have limited scan angles and can suffer from beam broadening and large grating lobes. This thesis presents a new acoustic array topology, the random spherical volumetric array. The system developed consists of 64 omni-directional microphones arranged at pseudo random locations within a spherical volume. The spherical array geometry provides the potential for full elevation and azimuth scan coverage. The projected aperture of a spherical array is direction independent, with the beamwidth and gain of the direction response being constant for all scan angles. The non-periodic element arrangement eliminates the possibility of large grating lobes and results in an array pattern with an average sidelobe level that is inversely proportional to the number of array elements. These properties enable wide-angle beam steering over a very large frequency bandwidth. The potential of acoustic volumetric arrays is examined and the results of theoretical and experimental investigations are presented. Holographic techniques have been implemented on the experimental system to produce images of sound sources and of reflections in the test environment. The concept of a synthetic volumetric array is introduced in which original synthetic aperture and multiple frequency techniques can be successfully used to reduce the average sidelobe level of the random spherical volumetric array. Initially, the acoustic random spherical volumetric array was envisaged as an inexpensive test-bed for microwave and radar system algorithm development. Since that time it has been found that application areas for the random spherical volumetric array also include covert surveillance operations, acoustic imaging and auditorium characterisation. Development of the system could allow security forces to monitor large crowds and riot situations; help in the detection of sniper location; and assist designers to build better auditoriums by highlighting areas of high reflection and reverberation.

M.Tech. (Chemical Engineering) / Laboratory and pilot plant trials were carried out on a modified carbonatation process to reduce overall refining costs. Sulphur dioxide dosages of less than 250ppm on brix were added to carbonatated liquors. The resultant filtered liquor had an additional 4,6% colour removal and a 10% ash gain relative to factory liquors. Reducing sugars and filterability were not affected. Additional colour removal of 14% was noted in the affinated crystal colour of crystals grown from the resultant brown liquors in the SMRI pilot pan. The failure of the combined carbonatation - sulphitationLaboratory and pilot plant trials were carried out on a modified carbonatation process to reduce overall refining costs. Sulphur dioxide dosages of less than 250ppm on brix were added to carbonatated liquors. The resultant filtered liquor had an additional 4,6% colour removal and a 10% ash gain relative to factory liquors. Reducing sugars and filterability were not affected. Additional colour removal of 14% was noted in the affinated crystal colour of crystals grown from the resultant brown liquors in the SMRI pilot pan. The failure of the combined carbonatation - sulphitation process to remove the ash that the carbonatation process does, negates the cost benefits of the additional colour removals. The reason for the ash "gain" is that the sulphur dioxide partially dissolves the calcium carbonate, releasing the adsorbed ash and colour. The colour is then adsorbed onto the calcium sulphite. process to remove the ash that the carbonatation process does, negates the cost benefits of the additional colour removals.

Knowledge of the mechanism of detergency under various conditions has thus far been built up from laboratory studies. It is well known that the laboratory methods for determing detergency are on the whole not able to give results which agree with those obtained in practice, probably because the actual scouring conditions cannot be duplicated exactly in the laboratory. Detergency testing on a full industrial scale is virtually impossible in view of the high cost and the production losses involved. In commercial raw wool scouring, which is an extremely complex system, it would be very difficult to exercise proper and complete control. The study described here was carried out on a specially constructed pilot plant which is similar to a fullscale plant in that the lengths of the bowls are of the same order as those of industrial plants, but they are considerably narrower. The trials were carried out under strictly controlled conditions in which the effects to be studied were created by the necessary changes while all other factors were kept constant, The pilot plant experiments were planned from indications of laboratory studies and the results were expected to be more comparable with those obtained in industrial practice, The effect of several factors on the scouring of raw wool was studied from the detergent efficiency aspect. The factors investigated were: mechanical action, backflow, temperature and detergency builders. A number of detergents which were selected from the large range which is available were compared with regard to efficiency and economy of scouring. A difficulty which hinders quantitative laboratory work on nonionic detergents is the fact that there is no rapid, accurate method for the estimation of nonionic detergents. The analytical methods which are employed at present are interfered with by virtually all the impurities which are normally present in scouring liquors. Some of the existing methods have been investigated and tested for precision and reproducibility and an attempt was made at establishing a new method. The sorption of nonionic detergents by various substrates has not been fully investigated because of the above reason and also because the amounts of detergent sorbed by most substrates are very small and difficult to determine. Attempts were made at determining the sorption of nonionic detergents onto wool and impurities which are normally found in scouring liquors. A new method for the investigation of "inactivation" of detergent by contaminants present in scouring liquors, which may be regarded as an indirect indication of detergent sorption, was investigated.