This master’s thesis deals with ways of lamination of ceramic tapes prepared by gel–tape casting method. The thesis is divided into two parts. The first part, a literary recherche, describes methods of production of thin ceramic layers. The main focus is on the tape casting method. The second, experimental, part of the thesis describes the preparation of ceramic suspensions, the fabrication of thin ceramic layers by gel–tape casting method, the preparation of laminated bodies from thick-walled discs and laminated tapes and it also shows a possibility of creating of ceramic layers by the spin coating method used on polycrystalline ceramic substrate.

The global demand for potable water has increase the use of chemicals to clean or prevent undesirable biofouling in reverse osmosis membranes. Biofouling is the growth and accumulation of biomass that generates an unacceptable performance decline. To date, a thoroughly efficient and green method to remove, prevent or treat biofouling in water treatment systems has not been developed. The studies carried out during my Ph.D. aim to develop greener and more efficient biofuling prevention/cleaning methods. The first two studies introduce a polyelectrolyte coating with the atypical characteristic of being removed and reapplied under operating conditions. After the biofilm develops on the coating, both biomass and coating can be removed with brine. The application of the coating can be done in-situ without hindering membrane performance. Using this procedure, both biofilm and coating could be simultaneously removed, leaving a clean surface. The biofouled coated membrane had two-fold higher permeate flux recovery compare to the non-coated. The sacrificial polyelectrolyte coating offers a greener solution for biofouling treatment in membrane systems. As an alternative to harsh chemicals, natural deep eutectic solvents (NADES) are presented as an alternative for biofilm treatment. Our results indicate that the NADES could solubilize up to ≈70% of the main components of the biofilm. The biofilm is weakened by the biomolecule’s solubilization, which could enhance biofilm removal. NADES have a great potential to be used for biofilm and avoid the currently used solvents. The last chapter is focused on understanding the structural characteristics and stability of NADES composed of betaine, urea, and water. The NADES composition and the water content is of significant relevance for its stability and supramolecular structure. Our experimental and computational results show that water is of crucial importance to the NADES supramolecular structure and stability. Understanding the NADES characteristics leads to finding better applications and giving insights into the interaction that these solvents have with other molecules, such as biopolymers or proteins. Even though there is still further research to be done, the studies presented on this thesis are a step forward towards finding and understanding greener solutions for biofilm treatment in water treatment systems.

Characteristics of coating methods PVD, CVD, PACVD, MTCVD. The parting of the PVD methods. Advance operations before coating of round tools and hobs. Chemical stripping of HSS. Electrochemical stripping of AlCrN coats. Differently experimental methods of stripping of the cemented carbides. Finding of the most favour stripping method with help of the electron microscope. The history of the coating. Types of coats, their usage, properies and testing. Coating machine, description and characteristics data. Preparation of tools on the coating. Behaviour of the coating process. Signification of the geometry, cutting material and coating in relation to tool life. Test evaluation of the hobs.

This dissertation treats of the influence of PVD coats to a change of tool lifetime. The theoretical part of the dissertation describes the adjustment of tools before the process of coating. Following part describes the specific properties of deposited layers of the coating and its measuring. There is also the enumeration and specification of selected ways of depositing PVD coats and brief description of its advantages and disadvantages. Second part of the dissertation is focused on an experiment with measuring of the tool force loading and its change depending to the tool wear. There are compared four short four-edged milling cutters with a coat and as well without it. Those tools were made of high speed steel by the conventional way and also by the powder metallurgy. Milling operation was done by down and up milling technique. The evaluation of the experimental results for powder metallurgy tools confirmed that these tools are advantageous compared to the standard high speed steel tools.

Works created within the engineering studies in collaboration with IDEAL-Trade service discusses the influence of pickling acids on steel material and on the same material with powder coated . Based on the literature study and consultations with employees of the company were designed each experiment, investigators removal and acid corrosion attack , another verify adhesiveness powder coatings for various periods of exposure pickled material. Experiments and tests were carried out in companies ECOS , ITS and faculty FSI.

Electrically conductive smart textiles are a very interesting area that could be important for the development of smart textiles. Today, conductive yarns and threads are often produced from coveted metals such as silver, copper and gold. These metals require large resources to be extracted and processed into yarns and threads and have a major impact on humans and the environment. One way to reduce the consumption of metals and save resources is to coat yarns of textile materials with electrically conductive polymers. In this study, we will investigate coating yarns with the conductive polymer blend PEDOT-PSS. PEDOT-PSS is extracted from oil, which is a non-renewable raw material, but coating with this polymer dispersion has many other advantages over metals and its production chain. Like coating yarn through a chemical bath produces very little waste, the yarn has a smaller mass, the yarn becomes more flexible, and it is easy to scale up production. However, previous studies have shown that there are some difficulties when it comes to coating yarns with PEDOT-PSS. The coating becomes fragile and brittle and to some extent affects the yarn that is coated in terms of mechanical properties. In this study, its investigated how the yarn is affected by various parameters in the production line, such as drying temperature, the viscosity of the PEDOT-PSS dispersion and the speed of the thread traveling through the production line, to find optimal production parameters that provide a balance between conductive and mechanical properties. We have produced a number of samples, all with different variations of parameters, and investigated how its conductive and mechanical properties are affected to see if there is a pattern and connection between parameters and conductive and mechanical properties on the yarn. The results show that yarn samples made with high viscosity of the PEDOT-PSS dispersion are among the lower range of resistance (with some exceptions), with average values of about 2990 O up to 10300 O, while lower viscosity shows uneven results with average values of about 92,000 O and all the way up to about 6,500,000 O. Most samples with lower measured O values are made with a high drying temperature, but no clear connection could be detected between temperature and end result, nor did the different speeds show any clear connection to the result. For the mechanical properties, it turns out that there is a relationship between result and viscosity as well as result and drying temperature. Samples made with low viscosity and low drying temperature perform best in the mechanical tests, 59.7% to 52.9% elongation and 25 cN / tex to 21 cN / tex. While speeds in this category could not show any connection between the results either. Overall, the results can be summarized as the results of tests show that there are some correlations between the parameters and the properties of the yarn samples and that the viscosity of the PEDOT-PSS dispersion and drying temperature are the most influential parameters. For conductive properties, viscosity has the greatest effect and for mechanical properties, viscosity and temperature have the greatest effect. For conductive properties, high viscosity is good, and for mechanical properties, low temperature and low viscosity are best. The sample with the best combination of test results was tested in a knitting machine but the variant chosen for knitting did not have good enough mechanical properties for the knitting machine used and broke when exposed to the stress from the knitting process. Therefore, the knitting test was not successful, but it was possible to sift out what parameter of the production line that had the greatest impact on the coated yarn properties.

Möjligheten att syntetisera UV-härdande bindemedel från enbart förnyelsebara startmaterial (syra A och alkohol A) eller från kombinationer av dessa med konventionella monomerer (syra B, C och D; alkohol B, C, D, E samt cyklisk ester A) utvärderades. Effekten av två katalysatorer, tenn(II)oktanoat och butyltenn, på direkt förestring och på ringöppning utvärderades. Totalt framställdes 22 polyestrar som analyserades med avseende på syratal, medelmolekylvikt (SEC), kulörindex (Gardner), och strukturell sammansättning (NMR). Bindemedlen formulerades med UV-initiator och härdades med UV-ljus. De torra filmerna utvärderades med avseende på hårdhet (pendelhårdhet), flexibilitet och kemisk resistens.   Det var möjligt att framställa polyestrar baserade på ovan nämnda monomerer. Några monomer gav bäst egenskaper med avseende på pendelhårdhet och flexibilitet medan andra byggstenar resulterade i bättre kemisk resistens.

To minimize global carbon emissions, having efficient jet engines and internal combustion engines necessitates utilizing lightweight alloys such as Al, Ti, and Mg-based alloys. Because of their remarkable strength/weight ratio, these alloys have received a lot of attention. Nonetheless, they have very poor tribological behavior, particularly at elevated temperatures beyond 200 °C, when most liquid lubricants begin to fail in lubrication. Over the last two decades, there has been a lot of interest in protecting Al, and Ti-based alloys by developing multiphase solid lubricants with a hard sublayer that provide mechanical strength and maintain the part's integrity while providing lubricity. The development of novel coatings with superior lubricity, high toughness, and high-temperature tolerance remains a challenging and hot topic to research and provide new engineered solutions for. To address and provide solutions to protect light-weight, i.e., Al, and Ti alloys at high-temperature and bestow superior tribological properties to such alloys, three types of adaptive lubricious coatings have been studied in this thesis: Nb-Ag-O self-healing lubricious ternary oxide, PEO-chameleon a self-adaptive multi-phase coating, and Sb2O3-MSH-C lubricious adaptive coatings to address this challenge. The development of the Nb-Ag-O ternary resulted in a coefficient of friction as low as 0.2 at 600 °C and crack healing at 900 °C. PEO-chameleon coatings demonstrated a remarkably low COF, as low as 0.07 at 300 °C and 1.4 GPa applied pressure. Finally, the Sb2O3-MSH-C multi-phase lubricious solid lubricant revealed superlubricity, with a CoF of 0.008 at 300 °C, providing a potentially promising contender for high-temperature, high-load applications.

The objective of this research was the development of a novel synthetic method for preparation of silver/polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by amino groups, which then reacted with end acidic groups of polylactide (PLA) and its co-polymer with polyglycolide (PLGA). The condensation reaction was conducted in the presence of diisopropylcarbodiimide. Nanosilver coating with the polymers was confirmed by FT-IR and UV-vis spectroscopy. It was found that not only acid-terminated but also ester-terminated polymers can react with functionalized nanosilver. However, high dispersibility of the nanoparticles was achieved with acid-terminated polymers only. Obtained materials demonstrated X-ray contrast and bactericidal properties that makes possible their prospective application in biology and medicine.

This research aims to contribute to the safe methodology for additive manufacturing (AM) of energetic materials. Coating formulation processes were investigated to find a suitable method that may enable selective laser sintering (SLS) as the safe method for fabrication of high explosive (HE) compositions. For safety and convenience reasons, the concept demonstration was conducted using inert explosive simulants with properties quasi-similar to the real HE. Coating processes for simulant RDX-based microparticles by means of PCL and 3,4,5- trimethoxybenzaldehyde (as TNT simulant) are reported. These processes were evaluated for uniformity of coating the HE inert simulant particles with binder materials to facilitate the SLS as the adequate binding and fabrication method. The critical constraints being the coating effectiveness required, spherical particle morphology, micron size range (>20 μm) and a good powder deposition and flow, and performance under SLS to make the method applicable for HEs. Of the coating processes investigated, suspension system and single emulsion methods gave required particle near spherical morphology, size and uniform coating. The suspension process appears to be suitable for the SLS of HE mocks and potential formulation methods for active HE composites. The density was estimated to be comparable with the current HE compositions and plastic bonded explosives (PBXs) such as C4 and PE4, produced from traditional methods. The formulation method developed and the understanding of the science behind the processes paves the way toward safe SLS of the active HE compositions and may open avenues for further research and development of munitions of the future. / Dissertation (MSc (Applied Science:Chemical Technology))--University of Pretoria, 2019. / Chemical Engineering / MSc (Applied Science:Chemical Technology) / Unrestricted