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Functionalization of particles and selective functionalization of surfaces for the electroless metal plating processMondin, Giovanni 28 November 2014 (has links)
Electroless plating is a metal deposition technique widely used in the coating industry. It is the method of choice to plate substrates with complex geometries and nonconductive surfaces, such as polymers and ceramics, since it is based on a chemical reduction in solution rather than on an external electrical energy source like the electroplating method. Among others, examples of well-established applications are the electroless deposition of decorative metal coatings such as gold and silver, wear and corrosion resistant nickel coatings, particularly to coat drive shafts, rotors, and bathroom fixtures, as well as the electroless deposition of copper in electronic devices as diffusion barriers and conductive circuit elements.
In the academic research, electroless plating is extensively used thanks to its low cost, simple equipment and versatility that allow rapid prototyping. Two common applications are the coating of small particles and the selective plating of flat surfaces. Metal coated ceramic particles are of enormous interest in many scientific fields, e.g. fluorescent diagnostics in biochemistry, catalysis, and fabrication of photonic crystals. Metal coated ceramic nanoparticles and microparticles are also gaining attention as potential candidates in the fabrication of higher quality metal matrix Composites, which is one of the applications addressed by this work. Metal coated ceramic particles are easier to integrate in metal matrix composites, avoiding aggregation caused by the low wettability of the particles by the matrix metal, and are potentially shielded from oxidation and undesired chemical reactions that take place at the interface between the particles and the metal Matrix.
Electroless plating is an autocatalytic process, meaning that the deposited metal atoms catalyze the deposition of further metal. In order to achieve the first stable metal seeds on a surface, the latter has to be functionalized. Without this functionalization the metal ions in the electroless plating bath are not reduced or are simply reduced to metal nanoparticles in solution. The traditional activation step for nonconductive surfaces is performed by immersion of the substrate in palladium based solutions, which is very time-consuming and extremely expensive. In particular for nanoparticles, previous work showed that at least 1015 Pd atoms/cm2 are required for a uniform activation of a surface, meaning that in the case of nanoparticles with a surface area of about 100 m2/g are necessary 6.4 g of palladium for each gram of substrate. Assuming a price of about 150 €/g (laboratory scale) for palladium nanoparticles and palladium precursors used for surface activation, it results that the activation of 1 g of nanoparticles costs around 1000 €.
Such costs are suboptimal considering the typical production scale, and therefore alternative functionalization methods are desired. In this work, new organic-based functionalization methods based on (3-mercaptopropyl)triethoxysilane to functionalize oxide particles, 3-aminopropylphosphonic acid to activate carbide particles and a substrate-independent method based on the bioinspired polydopamine are developed and investigated in detail, together with the respective electroless plating baths, which often have to be specifically tailored regarding the different reactivity of the different molecules and substrates. Furthermore, in the fabrication of metallic patterns on substrates by electroless plating, new, simple, and cost-effective activation and metal deposition processes are desired. In this work, two new methods are presented, one based on the printing of (3-mercaptopropyl)triethoxysilane by microcontact printing, the other based on the capillary force lithography of polymethylmethacrylate.
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Nanášení kovové vrstvy na keramické substráty pro úpravu povrchových vlastností / Tailoring of physical properties of ceramic surface by the metallic layer depositionDvorský, Vojtěch January 2019 (has links)
The master thesis focuses on the preparation of nickel coating on ceramic (Al2O3) substrate. The deposition of nickel was carried out by the electroless plating method in bath at various kinetic conditions. An impact of varied size, shape and roughness on the quality of the coated surface was investigated. The main goal was to find optimized conditions of the plating process of the thin metal coatings. Prepared nickel coatings were analysed by SEM, EDX analysis, mechanical profilometry and the plating bath was analysed by UV-VIS spectrophotometry. The continuous nickel coatings were achieved by modifying the deposition process, and the kinetic mechanism of experimental conditions was described.
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Optimalizace výroby tlakového odlitku. / Optimisation of a die casting part production.Vencálek, Jaroslav January 2009 (has links)
The project aim is an optimalization of production of pressure die casting, which serves as a one part of handle in office furniture area. The main emphasis was for mass finishing operation, which serves for rounding of very sharp part edges after die casting operation. A few tests of single mass finishing parameter was carried out and as result was a few partial recommendations for an increasing of production efficiency and improving of manufacturing process, namely an adjustment of separation cycle, proposal of optimum amount of pieces in each single batch and an innovation of chips type and dimensions. The project includes a proposal of a new and more efficiency layout of pieces on the transport pallet.
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