Thesis (Diploma)--University of the Witwatersrand.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Okenwa Okoli, Florida State University, College of Engineering, Dept. of Industrial Engineering. Title and description from dissertation home page (viewed Oct. 27, 2004). Includes bibliographical references.

Thesis (Ph. D)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xv, 203 p.: ill. Includes abstract and vita. Advisor: Rudolph G. Buchheit, Dept. of Materials Science and Engineering. Includes bibliographical references (p. 192-203).

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiii, 137 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 101-103).

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xi, 106 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 71-73).

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph. D.)--University of Iowa, 2007. / Supervisors: Alec B. Scranton, Chris N. Coretsopoulos. Includes bibliographical references (leaves 132-138).

This thesis reports investigations into laser ablation inductively coupled plasma emission spectrometry for rapid elemental analysis of a diverse range of samples: glasses, aqueous solutions, oils, coated steels and glasses, and biological samples. Bulk analysis of glasses for major, minor and trace elements is reported. Results showed that element emission responses are dependent upon laser operating conditions. With optimised operating conditions of a Q switched laser operating at 60 J for 5 s ablation time with the laser defocused by 5 mm above the sample surface. The limits of detection are in the sub ug g -1 level with precision ranging from 6.6 %RSD for a non volatile element such as boron to 23 %RSD for a volatile element silver. Although the principal aim of using aqueous multielement solutions as novel calibration standards for quantitative analysis of other liquids was not achieved, optimised laser operating parameters needed for microsampling of aqueous solutions and analytical performance data were obtained. The optimum laser operating conditions for a 20 ul sample were found to be the same as for glasses and were as follows: a Q switched laser operating at 60 J for a 5 s ablation time with the laser defocused by 5 mm above the sample surface. Transport efficiencies of approximately 30 % can be achieved, compared to < 1% by pneumatic nebulisation. Also there was no differential loss of elements by laser ablation which may occur with electrothermal vaporisation. Limits of detection were found to be in the sub ug ml -1 level. Precisions were typically between 6.6 and 12 %RSD. The main cause for lack of precision was spattering of the sample. Microsampling of oils by laser ablation proved to be an effective and accurate technique for rapid determination of element concentration without the need for sample filtration or digestion. Precision proved to be better than for aqueous solutions, typically from 3 to 7 %RSD, because of a reduction in spattering. The same optimum laser operating conditions used for aqueous solutions were identical for oils. This thesis reports the first experiments to fully utilise laser ablation as a routine method for quantitative measurement of coating depth for coated steels and glasses. It was found that the peak width at half the maximum height was proportional to the coating thickness (over a range of 1 to 10 um). With optimised laser operating conditions a depth resolution of less than 1 um was achieved. The optimum laser operating conditions were as follows: a Q switched laser ran continuously with a laser lamp energy of 60 J at 10 Hz pulse repetition rate. Finally experiments show the great potential for the use of laser ablation as a microsampling technique for microtome tissue samples. Micro depth analysis of nickel distribution in skin shows that the technique could differentiate between two skin samples with different nickel concentrations. The use of gel multielement standards as a novel calibration technique for analysis of microtome tissue samples has also been demonstrated. Optimum laser operating condition were to use a moderate laser energy of 750 V with the laser defocused 5 mm above the sample surface.

Industrial recognition of the importance of optimising engineering component performance has recently led to a significant increase in the use of surface coating technologies. An important process for the production of such coatings is Physical Vapour Deposition (PVD) which has proved to be a consistent, reliable and improving technique for industry. In the area of advanced wear resistant coatings however, fundamental research to improve deposition efficiency and enhance coating performance has been required. This thesis describes research investigating the following three areas: A series of experiments was carried out to study the design, metallurgy and performance of TiZr, ZrMo and TiMo segmented targets for use in steered cathodic arc evaporation and unbalanced magnetron sputter PVD techniques. A hot isostatic pressing technique was used to manufacture a range of prototype targets by diffusion bonding of appropriate metallic segments to controllable depths. In steered arc evaporation trials, a deleterious evaporation phenomenon occurred at segment interfaces when the cathode spot traversed from high vapour pressure to low vapour pressure materials. Analysis of the spot motion has led to the proposal of a simple model. Reactive unbalanced magnetron sputtering trials successfully produced a range of TiZrN, TiMoN and ZrMoN coatings of compositions in good agreement with Monte-Carlo simulation predictions. However, preferential poisoning of the high reactivity metal segments on TiMo and ZrMo targets was found to occur during high N[2] partial pressure processes. A comparative study of unbalanced magnetron sputtering, steered arc evaporation and the hybrid arc-bond sputter technique has been made during deposition trials on the ternary TiZrN hard coating system. Examination of the influence of two process parameters, substrate bias voltage and nitrogen partial pressure, on the mechanical and physical properties of TiZrN coatings is also reported. Stoichiometric TiZrN films were generally found to exhibit a single phase, face centred cubic structure with lattice parameters which followed Vegard's law. Alteration of the elemental composition of the alloy could be achieved by altering the power to individual magnetron cathodes or varying the current of the arc discharge during co-deposition. Solid solution strengthening mechanisms produced high hardness values (2500-3600H[k]) which maximised as the alloy composition approached Ti[0.6]Zr[0.4]. Further studies have been undertaken where Al was partially substituted for Zr within the lattice to enhance oxidation resistance properties and a range of fully adherent TiAlZrN quaternary films on high speed steel substrates were produced. The development of an original technique for industrial scale fabrication of a range of hard, low period (< 150A) multi-layer PVD thin films is outlined and the effects of substrate rotation velocity, type of rotation (1-fold or 3-fold) and deposition rate have been investigated. The high level of lattice mis-match and substantial differences in dislocation line energy and shear modulus has given rise to TiAlN-ZrN films exhibiting Knoop micro-hardness in excess of 4000H[k]. Bulk and micro-analysis techniques have indicated a reproducible lamella coating structure can be formed, with accurate control of the layer period. Excellent levels of coating adhesion were implemented by a metal ion etch substrate pre-treatment and the deposition of a sputtered base layer and films exhibited relatively low surface roughness and high density. A coating strategy, based upon the reactivity of the individual target materials and the characteristics of arc evaporated and magnetron sputtered vapour fluxes, has been determined which provides high flexibility in the coating elemental composition. The investigations clearly indicate that the multi-layer coating methods utilised allow the deposition of 3rd generation films without a productivity loss in comparison to 1st generation and 2nd generation hard coatings.

In recent years demand from production industry for high performance cutting tools, aero and automobile engine parts has prompted research into both existing and novel methods of laying down hard, low friction coatings . A key process for the production of such coatings has been Physical Vapour Deposition (PVD) which has proved to be a consistent and reliable tool for industry. For this technique to continue to be improved and more advanced coatings to be produced, research at the fundamental level is required. This thesis describes research investigating the behaviour of the steered arc cathode spot and methods of improving existing steered arc coating technology. The majority of existing steered arc systems use either permanent magnets or a combination of permanent and electromagnets to steer the arc. Described here is a novel system which employs a pair of electromagnetic coils of cylindrical geometry which enable the arc to be positioned on a circular orbit through a range of continuously variable radii. In addition to this the coils are capable of controlling the transverse and normal magnetic field profiles independently of the steering radius selected. This enables the behaviour of the arc spot to be investigated under a range of magnetic field conditions thus allowing the comparison of measured arc behaviour with a new model of arc motion. Care has described the motion of the arc spot as a biased random walk and has derived an analytical solution to describe the time dependent, probability density function for the arc position in two dimensions. Two distributions are proposed (one in each dimension); the first describes the probability density for the arc position in the direction of driven motion, the second the probability density in the direction of arc confinement. The shape of these distributions is dependent upon the transverse and normal components of the applied magnetic field. A series of experiments are described here that measure the shape of these distributions as a function of either magnetic field, cathode material or both. In the case of the distribution of the arc position in the direction of confinement the width of the distribution is measured as a function of normal and transverse field components. In the direction of steered motion, distributions of arc orbital transit times are measured for a number of cathode materials: analysis of these distributions allow the determination of a mean macroscopic spot velocity and the spot diffusion coefficient. In both cases comparison with Care's model reveals good agreement between experiment and theory to the limits of the experimental apparatus. A further experiment was also conducted to test the prediction that the diffusion coefficient (measured in the direction of steered motion) is independent of the applied field. In this case results are inconclusive and further work is recommended. The mean spot velocity and diffusion coefficients for four materials were measured; titanium, zirconium, aluminium and 316 stainless steel. The results for aluminium and stainless steel compared favourably with some measurements performed by other workers, whilst those for titanium and zirconium are new results with no data available for comparison.