Thermal barrier coatings (TBCs) of ZrO2-7wt% Y2O3 were deposited by electron beam physical vapor deposition (EB-PVD) onto stationary flat plates and cylindrical surfaces in a multiple ingot coater. Crystallographic texture, microstructure, and deposition rate were investigated in this thesis. The crystallographic texture of EB-PVD TBCs deposited on stationary flat surfaces has been experimentally determined by comparing pole figure analysis data with actual column growth angle data. It was found that the TBC coating deposited directly above an ingot exhibits <220> single crystal type crystallographic texture. Coatings deposited between and off the centerline of the ingots the exhibited a <311>-type single crystal texture. For coatings deposited in the far corners of the coating chamber either a <111> fiber texture or a <311> single crystal type texture existed. The crystallographic texture of EB-PVD TBCs deposited on cylindrical surfaces was characterized using x-ray diffraction (XRD) at different angular positions on the cylinder substrate. XRD results revealed that crystallographic texture changes with angular position. Changes in crystallographic texture are attributed to the growth direction of the columns and substrate temperature. Growth direction is controlled by the direction of the incoming vapor flux (i.e. vapor incidence angle), in which competition occurs between crystallites growing at different rates. The fastest growing orientation takes over and dominates the texture. Substrate temperature variations throughout the coating chamber resulted in different growth rates and morphology. Morphology differences existed between cylindrical and flat plate surfaces. Flat cross sectional surfaces of the coatings exhibited a dense columnar structure in which the columns grew towards the closest vapor source. Surface features were found to be larger for coatings deposited directly above an ingot than coatings deposited away from the ingots. Morphological differences result from substrate temperature changes within the coating chamber, which influences growth kinetics of the coating. Cylindrical surfaces revealed a columnar structure in which columns grew towards the closest vapor. Porosity of the coating was found to increase when the angular position changed from the bottom of the cylinder. Change in angular position also caused the column diameter to decreases. Morphology changes are attributed to self-shadow effects caused by the surface curvature of the cylinder and vapor incidence angle changes. Overall, the microstructure and crystallographic texture of EB-PVD coatings was found to depend on the position in the coating chamber which was found to influence substrate temperature, growth directions, and shadowing effects. The coating thickness profiles for EB-PVD TBCs deposited on stationary cylinders have been experimentally measured and theoretically modeled using Knudsen's cosine law of emissions. A comparison of the experimental results with the model reveals that the model must to be modified to account for the sticking coefficient as well as a ricochet factor. These results are also discussed in terms of the effects of substrate temperature on the sticking coefficient, the ricochet factor, and coating density.

by Peng Qicai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / includes bibliographical references (p. 187-206). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

Neste trabalho, é apresentado um estudo sobre a influência de aditivos em banhos de eletrodeposição de Au, análise da morfologia dos depósitos de Au e o crescimento de multicamadas da liga AuxSny por deposição eletroquímica. Os banhos de eletrodeposição estudados são baseados em uma composição, comum na literatura, formada por tetraclorourato(III) de potássio (KAuCl4), cloreto de estanho(II) (SnCl2), sulfito de sódio (Na2SO3), e citrato de amônio [(NH4)HC6H5O7]. Os contatos de solda da liga AuxSny, aplicáveis em diversos dispositivos microeletrônicos, podem ser formadas de maneira mais econômica a partir de banhos eletroquímicos. Banhos ácidos e reagentes de baixa toxicidade são exigências comuns dos novos banhos de eletrodeposição. A formação de multicamadas permite, ainda, ampliar o uso do metal de solda em dispositivos sensíveis a altas temperaturas, devido ao baixo ponto de fusão da liga. A obtenção das ligas AuxSny utilizando deposição eletroquímica, foi feita com base no estudo sobre banho de eletrodeposição e seus depósitos, a partir de um banho para deposição da liga AuxSny já conhecido. O aprimoramento do banho de eletrodeposição foi focado no banho de eletrodeposição de Au, com três opções de aditivos, buscando avaliar as características dos depósitos e o tempo de estabilidade do banho. Os aditivos utilizados foram hipofosfito de sódio (NaH2PO2), metanal (HCHO) e tiossulfato de sódio (Na2S2O3), separadamente. Esses banhos foram analisados por voltametria cíclica, e os depósitos obtidos a partir de eletrodeposições foram caracterizados por Espectrometria por Retroespalhamento de Rutherford (RBS), Microscopia Eletrônica de Varredura (SEM) e, em alguns casos, por Espectrometria de Energia Dispersiva de Raios X (EDS). Análises de dimensão fractal e de escalamento dinâmico da rugosidade forneceram detalhes importantes sobre a morfologia superficial dos depósitos. .A adição de Na2S2O3 ao banho permitiu o desenvolvimento de um novo banho de eletrodeposição para a co-deposição de Au AuxSny. O Na2S2O3 atua como um complexante dos íons de Au(I) juntamente com o sulfito de sódio. O emprego de 3 g L-1 de Na2S2O3 evita a degradação do banho durante as eletrodeposições. Finalmente, o estudo da eletrodeposição de multicamadas foi feito por controle do potencial aplicado e por controle da corrente aplicada. As multicamadas obtidas apresentaram camadas da liga AuxSny com a concentração de Sn incorporado, variando entre 6 % e 49 % (em porcentagem atômica). / It is shown in this work a study about the influence of additives in baths for electrodeposition of Au, analysis of morphology of gold deposits and the growth of multilayered AuxSny alloys from improved electrodeposition baths based on a common composition of the literature containing potassium gold(III) chloride (KAuCl4), tin(II) chloride (SnCl2), sodium sulfite (Na2SO3) and ammonium citrate dibasic [(NH4)HC6H5O7]. The AuxSny solders are commonly used in microelectronic devices. These solders can be applied in a number of ways, and electrochemical deposition is an attractive alternative due to the low cost process. Acidic baths and low toxicity reagents are common requirements of new electrochemical baths. The multilayered AuxSny alloys are applicable to temperature sensitive materials due to its reduced melting point temperature. Therefore, the study of electrodeposition of AuxSny alloys began with an already known bath and aiming its improvement. The focus of interest was the gold bath, which received additives to improve control of the deposits and their stability. The additives used were sodium hypophosphite (NaH2PO2), methanal (HCHO) and sodium thiosulfate (Na2S2O3), one of each time. These baths were analyzed by cyclic voltammetry and the deposits obtained from these baths were analyzed by Rutherford Backscattering Spectrometry (RBS), Scanning Electron Microscopy (SEM) and, in some cases, Energy Dispersive Spectrometry (EDS). Fractal dimension and dynamic scaling of the surface width analysis allowed one to quantify the surface morphology details. The addition of Na2S2O3 to the bath allowed the development of a new electrodeposition bath for co-deposition of AuxSny. The Na2S2O3 acts as complexing agent of Au(I) ions together with sodium sulfite. The use of 3 g L-1 of Na2S2O3 avoids bath degradation during the electrodepositions. Potential-controlled and current-controlled electrodepositions were employed to obtain multilayers of AuxSny alloys. The multilayer deposits obtained presented between 6 atomic % and 49 atomic % of tin.

This work places itself in the field of textile design, knitting and three-dimensional objects. The primary motive is to investigate flat knitting as a technique to design form. The aim is to explore the possibilities within flat knitting in order to explore the relationship between knit and non-textile components to achieve three-dimensional forms for sitting. The design process consisted of experimental sketching on a flat knitting machine and small prototypes were produced. Rib, plain knit and mesh structures were tested in combination with partial knit, intarsia and plating. These bindings and techniques were combined with steel constructions to explore possibilities for shaping and function. By integrating a non-textile component as support in the knitted samples three-dimensional objects are created. The outcome of the study is a collection of knitted objects. Common for these is that they all suggest a function in relation to seating. The textile in the construction serves a function, an aesthetic expression and as the connection material in the construction. For further development, the possibility of creating textiles for furniture with capabilities for changes in expression and function can be explored.

The deformation mechanisms and contact response of TiN-based thin films deposited onto a soft substrate using a physical vapour deposition (PVD) technique is still an area of both technological importance and considerable discussion. These coatings are commonly applied to various kinds of steel cutting tools, creating surfaces with enhanced tribological properties. However, no extensive systematic study of the deformation mechanisms in these thin film systems has been performed to date. In the present study, the effect of the coating microstructure, indenter geometry, coating thickness and substrate hardness on the deformation mechanisms in both TiN and TiAlN coatings of varying thickness deposited onto ductile steel substrates has been investigated using a combination of nanoindentation and microstructural analysis, including focused ion beam (FIB) milling and transmission electron microscopy (TEM). Different modes of cracking, such as columnar and transverse cracking, as well as shear steps at the coating/substrate interface, were observed. The microstructure of the TiN coatings was found to be very important in controlling their modes of deformation. Thicker coatings were seen to contain more equiaxed grains, so less columnar shearing occurred and inclined cracks were found to be a more dominant fracture type in the thicker coating. Also, it was found that soft substrates absorbed most of the energy from indentation by plastic deformation. It was found that both the TiN and TiAlN/TiN dual-layer coatings exhibited broadly similar mechanisms of deformation. The epitaxial interface between the TiAlN and TiN in the dual-layer coating did not appear to affect the deformation behaviour. As a further investigation of the overall deformation behaviour for the coating/substrate systems studied, a DualBeam FIB was used to generate three dimensional images of the indented regions which provided additional information on the crack morphology. For the first time, a systematic study of the deformation behaviour of TiN and TiAlN coatings upon indentation has been carried out. FIB milling was demonstrated to be a highly appropriate technique for characterization of the deformation behaviour of these coatings, allowing detailed, high resolution microstructural investigations to be performed in both two and three dimensions.

<p>South Africa s coal and platinum mineral resources are crucial resources towards creating an alternative and environmentally sustainable energy system. The beneficiation of these natural resources can help to enhance a sustainable and effective clean energy base infrastructure and further promote their exploration and exportation for economics gains. By diversification of these resources, coal and the platinum group metals (PGMs) especially palladium market can be further harnessed in the foreseeable future hence SA energy security can be guaranteed from the technological point of view. The South Africa power industry is a critical sector, and has served as a major platform in the South African socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. The South Africa power industry is a critical sector, and has served as a major platform in the SA&rsquo / s socio-economic development. This sector has also been identified as a route towards an independent energy base, with global relevance through the development of membrane technologies to effectively and economically separate and purify hydrogen from the gas mixtures released during coal gasification. Coal gasification is considered as a source of hydrogen gas and the effluent gases released during this process include hydrogen sulphide, oxides of carbon and nitrogen, hydrogen and other particulates. In developing an alternative hydrogen gas separating method, composite membrane based on organic-inorganic system is being considered since the other available methods of hydrogen separation are relatively expensive.<br /> &nbsp / </p>

The present thesis was mainly to study the preparation of nickel composite materials by chemical plating process. Nickel coated boron nitride particles, nickel coated spherical silica particles and nickel viscose composite fibres were prepared. Both experiment and model development were carried out to study the kinetics of the processes. Preparation of hollow nickel fibres was also investigated. NiSO4-(NH4)2SO4-NH3·H2O-N2H4·H2O was found a suitable system for nickel plating. This system could be employed in preparing nickel coating layer on surface of boron nitride particles, spherical silica powder and viscose fibres. The main factors which could affect the plating process were investigated. The optimum conditions were suggested for different substrate materials based on the experimental results. It was found that Pd on the surface of substrate materials acted as an active center for nickel deposition at the initial stage of the process. Thereafter, Ni itself would act as an active center to catch Ni from the solution through the reaction: Ni2+ + 2H* ad ⇒ Ni + 2H+. The rate of the process was found to be controlled by the reaction at the interface under the present experimental conditions. A kinetic model was developed on the basis of the mechanism study. The model predictions were found to be in agreement with the experimental data for different substrate materials. Since the kinetic model does not have any parameters related to the shape and surface area of the substrate, it could be used as a general model to describe the processes controlled by interface reaction with growing interface area. Hollow nickel fibers were prepared by thermal decomposition method from nickel viscose composite. The experiments showed that viscose filling could be removed by heat treatment in air atmosphere. Experiments showed that hollow nickel fiber could be prepared by direct thermal decomposition in air flow at low temperature, e.g. 573 K. But slight surface oxide is inevitable. Decomposition of the viscose filling could also be carried at higher temperature. However, serious oxidation of nickel would also take place during the decomposition. To remove nickel oxide, reduction by hydrogen gas could be applied. Preliminary effort was made to extend the application of the present method to prepare copper viscose composite fibres. Promising result was obtained. More detailed study is required to confirm the applicability of the technique. / QC 20100804

In past years, legislative pressures (particularly in Japan and Europe) had forced the electronics industry to eliminate Pb from their end products and manufacturing processes. With respect to factors such as ease of converting existing tin-lead plating systems, ease of manufacture and compatibility with existing assembly methods, pure tin plating is seen by many in the industry as a potentially simple and cost effective alternative to SnPb-based systems. The problem of spontaneous tin whisker formation, a characteristic of pure tin, still needs to be addressed, as it can lead to device failure by shorting two terminals on electronic devices. This possibility gives rise to major reliability concerns. The study relates to an electronic component with pure tin deposit layer on the part for electric connection, wherein pure tin deposit layer is a fine grained tin deposit layer composed of grains with smaller size in the direction perpendicular to the deposit surface than in the direction parallel to the deposit surface. It is called irregular tin grain structure. It applies a process for plating an electronic component, so as to form a pure tin deposit layer on the part for electric connection, comprising the steps of: adjusting the composition of tin plating solution in which starter additive and brighter additive are included; moving the electronic component through the tin plating solution, so as to form a fine grained tin deposit layer on the part for electric connection. We performed a DoE by depositing different tin grain structures with variant thickness. After whisker test in high temperature/high humidity and room condition, we confirmed corrosion mechanism, intermetallic morphology, and different behaviour of tin atoms. To summarize the studies, as compared with the prior arts, irregular grain structure can validly inhibit the whisker growth.

New environmental regulations enforce the electronic industry to replace Pb-Sn solder due to Pb could contaminate our environment. Pure Sn has good material properties such as solderability, conductivity and anti-corrosion. Pure Sn is a good candidate to replace Pb-Sn solder. One of the disadvantages of pure Sn is the whisker growth phenomenon. Whisker problem has become a major concern in electronic industry due to the trend toward component miniaturization and pitch reduction. It is well understood that the root cause for tin whisker growth is the compressive stress within the tin layer. In the literature, the main stress sources are, (1) the intermetallic layer induced interface stress, (2) the difference of thermal expansion coefficient between Sn layer and substrate and (3) the mechanical residual stress from trim-form operation after tin plating. In our study, we used the electrochemical electrolysis method and Cross-section Polisher (CP) to examine the tin whisker growth mechanism. In the result, we can clearly show the Cu6Sn5 phase grow up in the tin grain boundary regions and demonstrate that the Cu6Sn5 phase formation is the main cause of the tin whisker growth. We also discuss the relationship of tin whisker growth and tin-plating process parameters that include the temperature effect; Ni underlay effect and tin-plating bath effect. For the temperature effect, the Cu6Sn5 is the major phase at 150¢XC aging. The mechanism behind its growth mechanism was grain boundary diffusion at the earlier stage and then the bulk diffusion in the later stage. The application of 150¢XC post-heat treatment could drive the bulk diffusion and form a layer type Cu6Sn5 phase to eliminate the whisker growth. For the Ni underlay effect, the Ni underlay can block the Cu atom diffusion to the tin layer and changed the tin layer stress state from compressive to tensile. Therefore, the tin whisker can be eliminated. For the tin-plating bath effect, in the sulfuric acid base and uses Triton X-100 as the surface active agent, may transform the whisker type to particular tin grain type. Thus, this tin-plating solution can restrain the tin whisker growth.

Avatrel 8000P's excellent photo-definition properties and mechanical strength make it an ideal polymer collar material. Avatrel 8000P is a high contrast, I-line sensitive mixture that can be developed in traditional aqueous-base developers. The great photolithographical performance of this photopolymer can be partly contributed to the minimal amount of light absorbed by the base norbornene polymer. The processing conditions noted in this work are an optimized version, which have been shown to give superior photolithographical performance. The simple baking procedures make Avatrel 8000P easier to process than SU-8. The ability to develop Avatrel 8000P in aqueous base can reduce chemical waste. As shown by SEM images, high fidelity structures with aspect ratios of 7:1 can be fabricated in thick films with vertical sidewalls. Bonding between two copper surfaces over various gap sizes was achieved by electroless deposition without the addition of surfactants or inhibitors in the bath. The effect of anneal temperature on the electroless bond formed was analyzed. The electroless bond strength increased with anneal temperature. However, the bond strength estimation for samples annealed at 80°C to 120°C is a minimum value due to the failure location of most of the pillars and the resulting area used in the calculation of bond strength. Grain growth from copper recrystallization and removal of small defects improve the bond strength. Large voids at the interface of the two pillars were related to rough starting surfaces for the electroplated pillars.