Magnesium (Mg) and its alloys offer potential as a new class of degradable metallic orthopaedic biomaterials. In comparison with current metallic orthopaedic implant materials, Mg offers advantages such as, high specific strength, closer-to-bone stiffness and biodegradability, thereby eliminating the need for a second surgery to remove hardware. The use of porous metal foams as biomaterial scaffolds has been widely adopted, however, many of these porous structures are manufactured with pore architectures that are inherently random. This makes structural optimisation for a specific purpose challenging. Scaffolds containing ordered pore architectures can be fabricated to meet design criteria, such as porosity, stiffness, and volume fraction. Currently there are few methods described in the literature to manufacture ordered porous Mg. The main aim of this thesis was to determine the resolution of a novel indirect solid free-form fabrication (SFF) process for producing topologically-ordered porous Mg (TOPM) structures from pure Mg and commercial Mg alloys. The produced structures were examined for properties such as dimensional accuracy, microstructure, surface properties, mechanical properties and corrosion behaviour. The capability of the process was further examined in manufacturing structures with complex architecture for potential application as degradable metallic orthopaedic devices, namely a spinal fusion device (SFD) and screw. With the produced structures aimed at load-bearing applications in bone, the mechanical properties and behaviour of the TOPM and SFD made from Mg alloys were investigated using finite element analysis (FEA) and compression testing. The relationship between surface roughness and degradation behaviour in Mg biomaterials has received limited interest and is still a controversial issue. Therefore, it was necessary to accurately determine the effect of surface roughness on corrosion rate of Mg, especially samples manufactured from SFF and casting of molten Mg. Given the well-established need for improved corrosion resistance of Mg, two coating techniques, including biomimetic calcium phosphates and electrochemically-assisted deposition coating, were applied on Mg substrates cast via the SFF process. Corrosion testing was employed to investigate the effectiveness of the coating layers in improving corrosion resistance. In this thesis, the capability of the SFF manufacturing process and properties of the produced structures were thoroughly investigated. Results and findings contribute to the development of topology optimised, degradable Mg devices for biomedical applications.

No description available.

No description available.

No description available.

No description available.

Unsustainable energy sources are running out and global warming is getting worse. Therefore the need for renewable energy sources is growing. Solar cells are a popular options used as an energy source. Most popular are the inorganic photovoltaic cells. With their high efficiency and long lifetime, they make a very good energy source. Unfortunately the costs for inorganic solar cells are rather high. Organic solar cells can make a good replacement for inorganic photovoltaic. They are easy to make, light and rather cheap. In this thesis, the morphology of a model system of the active layer of organic solar cells will be discussed, using dip coating as well as spin coating as a technique to prepare the films. The films consist of a blend of poly(9,9-dioctylfluorenyl-2,7-diyl) and [6,6]-phenyl C61-butyric acid methyl ester in different ratios and different solvents. The films that were made were prepared by spin coating or dip coating a glass substrate. After analysing the samples using atomic force microscopy, fluorescence spectroscopy and absorption spectroscopy it was clear that the morphology, as well as the position of the polymer chains can be influenced by using different dipping speeds, ratios or solvents.

For the induction heating process of bi-metallic tubes, the inner tube of alloy-layer is much easier to cause a lot of defects of cavities due to the fact that heating power, maximum temperature value and the time frame of temperature retention were chosen improperly. This research focuses on the effect of maximum temperature value and the time frame of temperature retention on the micro-structure and defects of cavities of the Nickel-based alloy-layer. The experiments of this study are divided into two parts. In the domain of the experiment in simulation fashion, Nickel-based alloy powders were put into the specimens of AISI 4140 steel. Radio Frequency (RF) oven were used to smelt Nickel-based alloy powders in the vacuum conditions over the maximum temperature range of 920~1180¢Jrespectively. After that, the time frame of temperature retention was conducted from 0 to 10 minutes. Then, the furnace-cooling went down to 700¢J then air-cooling down to the room temperature. Nickel-based alloy-layer, microstructure, component analysis, defects of cavities of the interface between Nickel-based alloy-layer and steels, and diffusion of interfaces were analyzed using optical microscopes (OM) and scanning electron microscopes (SEM). From the experiments, it was found that Nickel-based alloy-layer consisted of £^-Ni¡BCrB¡BCr7C3 over the maximum temperature range of 920~1050¢Jwhether temperature retention is performed or not. According to the findings of metallographic observation, the increase of coarsening and the reduction of the capacity of CrB and Cr7C3 become more obvious as maximum temperature value and the time frame of temperature retention become large. In addition, the whitening layer (diffusion zone) formed between the interface of alloy-layer and steels become much wider as maximum temperature value and the time frame of temperature retention become large. Secondly, the field experiment method was also applied in this paper. The tube rich in Nickel-based alloy powders was heating to analyze induction coil in various conditions: heating power (200~285KW), maximum temperature value (1020~1040¢J), the time frame of temperature retention (10, 30, 50sec), and the rotating speed (1000~1300rpm). The results of the experiments indicated that the surface of the alloy-layer cause defects of vermicular cavities since the volume of liquid cannot fill out the crack of cavities completely due to lower temperature when there is insufficient time; too long periods of the time frame of temperature retention lead to the tough and huge dendrites to obstacle the flowing of liquid and the solidification of shrinkage cavity. According to the observation of the microstructure, the larger the maximum temperature value and the time frame of temperature retention were, the more the dendrites formed. The formation of dendrites causes not only the uneven distribution of hardening phase of CrB and Cr7C3 of the alloy-layer but also the reduction of hardness of the alloy-layer. The dendrites are typically formed from the interface to the surface of the alloy-layer. Besides that, the alloy-layer mainly consists of £^-Ni, Ni3B, Ni3Si, CrB, and Cr7C3 via X-ray Diffraction (XRD). Among them, the main hardening phases are CrB and Cr7C3 which is the main reason that the alloy-layer has high-level hardness. As maximum temperature value and the time frame of temperature retention become large, the whitening layer (diffusion zone) was formed between the interface of alloy-layer become much wider because the faster the elements of the based materials (tube) diffused and the wider the intermetallic compound formed among the interfaces. After heated for 800 seconds over the temperature range of 750~1030¢J, iron element was diffused all over the alloy-layer. The increase of coarsening and the reduction of the capacity near interface and interface become more obvious as maximum temperature value and the time frame of temperature retention become large.

Wood service life is significantly prolonged by the use of preservatives. Unfortunately, preservative treated wood is still susceptible to weathering degradation (UV and moisture) and subsequent leaching of preserving components. These negative impacts of weathering can be reduced by the application of a coating; however, the effectiveness of the coating depends on its characteristics, especially its compatibility with preservative treated wood. In this project, the performance characteristics of semitransparent deck stains were evaluated for untreated wood samples and for samples treated with chromated copper arsenate (CCA), alkaline copper quat (ACQ) and copper azole (CA) over three years of natural and three months of accelerated weathering conditions. The parameters measured were water permeability, colour change, general appearance, checking of wood, and the coating‟s ability to reduce preservative leaching. Coatings were characterized in terms of glass transition temperature (Tg), solid content, viscosity, density, contact angle, surface tension, and film thickness. Also penetration depth of a polyurethane (PU) coating was examined using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). iii All the stains evaluated effectively reduced cumulative leaching of preservative components by about 60% on average. An analysis of the preservative gradients and residual soluble components in the ACQ-samples after weathering indicated that preferential leaching of monoethanolamine (Mea) is most likely responsible for the reduced amounts of available copper in coated treated wood samples. Also, a two-week screening test was able to provide accurate predictions of the long-term leaching performance of different coatings. There was a significant interaction effect between coatings and preservatives: solvent-based coatings showed better water repellency for CCA and untreated wood, but there was no significant difference in water repellent effectiveness between water-based and solvent-based coatings for ACQ or CA-treated wood. Overall, preservative treatments greatly enhanced coating performance. Image analysis of the samples subjected to 3 years weathering showed that coatings reduced surface checking by 30-40%. Partial least squares regression (PLS-R) modeling was used to correlate measured coating properties with their weathering performance characteristics. The modeling results showed that coatings with low Tg and high viscosity effectively reduce the leaching of preservative components and improved water repellency and visual ratings

Wood service life is significantly prolonged by the use of preservatives. Unfortunately, preservative treated wood is still susceptible to weathering degradation (UV and moisture) and subsequent leaching of preserving components. These negative impacts of weathering can be reduced by the application of a coating; however, the effectiveness of the coating depends on its characteristics, especially its compatibility with preservative treated wood. In this project, the performance characteristics of semitransparent deck stains were evaluated for untreated wood samples and for samples treated with chromated copper arsenate (CCA), alkaline copper quat (ACQ) and copper azole (CA) over three years of natural and three months of accelerated weathering conditions. The parameters measured were water permeability, colour change, general appearance, checking of wood, and the coating‟s ability to reduce preservative leaching. Coatings were characterized in terms of glass transition temperature (Tg), solid content, viscosity, density, contact angle, surface tension, and film thickness. Also penetration depth of a polyurethane (PU) coating was examined using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). iii All the stains evaluated effectively reduced cumulative leaching of preservative components by about 60% on average. An analysis of the preservative gradients and residual soluble components in the ACQ-samples after weathering indicated that preferential leaching of monoethanolamine (Mea) is most likely responsible for the reduced amounts of available copper in coated treated wood samples. Also, a two-week screening test was able to provide accurate predictions of the long-term leaching performance of different coatings. There was a significant interaction effect between coatings and preservatives: solvent-based coatings showed better water repellency for CCA and untreated wood, but there was no significant difference in water repellent effectiveness between water-based and solvent-based coatings for ACQ or CA-treated wood. Overall, preservative treatments greatly enhanced coating performance. Image analysis of the samples subjected to 3 years weathering showed that coatings reduced surface checking by 30-40%. Partial least squares regression (PLS-R) modeling was used to correlate measured coating properties with their weathering performance characteristics. The modeling results showed that coatings with low Tg and high viscosity effectively reduce the leaching of preservative components and improved water repellency and visual ratings

Pool boiling process is frequently encountered in a number of engineering applications. It is difficult to exactly predict the heat transfer coefficient. This is because the boiling phenomenon is rather complex and influenced by many factors, such as surface condition, heater size, geometry, material, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure diameter, frequency, velocity and nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. Furthermore, more fundamental of the physical phenomenon can be obtained. This study was performed experimentally. R-134a and R-600a were used as refrigerants. The surface condition will be changed with plasma spray coating. It is expected that the surface condition can affect the nucleate boiling heat transfer in certain degree. In addition, using the high speed digital vide camera and LDV to measure the bubble diameter and dynamics of R-600a and R-134a while growing. According of the results of experiments. The boiling curves in different situation were drawn and the influences of heat transfer coefficients by bubble velocity was also examinate. Finally, to broaden our basic understanding of different characteristics of refrigeration surface condition and heat transfer coefficient, thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.