Papers by Keyword: Shaping

Abstract: Urban waterfront is a specific space district in the city which denotes the land or construction adjoining rivers, lakes and oceans in the city. With the rising of economic development and people’s higher requirements for the quality of life, urban waterfront has become a distinctive district of city landscape and the window of city’s charm. This paper discusses the excavation and shaping of distinctive elements in landscape planning of modern urban waterfront.

Abstract: In this paper, ultra-precision shaping and polishing experiments have been done to research the shaping and polishing characters of nanoparticle colloid jet machining. A high-purity quartz glass sample with aspheric surface profile was employed as workpiece and polished by nanoparticle colloid jet machining. We utilized surface profilometer to measure the surface profiles of workpiece before and after shaping by nanoparticle colloid jet machining. The measurement results indicate that the nanoparticle colloid jet machining has good shaping ability to satisfy the demands for surface shape correction in ultra-precision machining. Atomic force microscopy (AFM) was utilized to observe the surface microscopic morphological characteristics of the workpiece surface polished by nanoparticle colloid jet machining. The observation results show that the roughness of the workpiece surface has been reduced from 1.919 nm RMS to 0.784 nm RMS by nanoparticle colloid jet machining. Based on the atomic force microscopy observation results, power spectral density analyses have been done to evaluate the polishing performance of the nanoparticle colloid jet machining.

Abstract: Saccharides, particularly monosaccharides, as well as their derivatives, were found to be a group of effectively working processing agents in case of alumina which has been used as a solid phase of highly loaded suspensions. The synthesis of new low-toxic monomers obtained from saccharides is reported and their application in gelcasting process is presented. The synthesized monomer named 3-O-acrylic-D-glucose is an interesting alternative for the commercially available acrylic monomers. The present paper describes the properties of ceramic slurries obtained from two alumina powders of different grain size (47nm and 0.70mm) with the use of the new monomer 3-O-acrylic-D-glucose. The rheological measurements showed that new monomer can be applied not only as monomer able to polymerize in situ but also as dispersing agent for nanoalumina powders.

Abstract: The paper presented a computer aided design and engineering (CAD/CAE) system that can be used to simulate and analyse three-dimensional complicated workpiece’s shaping process in electrochemical mahining. In the CAE model the finite element method was applied to analysis the electric-field distribution in inter-electrode gap. Factors affecting the electric-field distribution, such as flow factors and passivating electrolyte, are also taken into account by using database technology. The results of simulation and experiments showed that the system was of high precision.

Abstract: Gelcasting was used to form large and thin walled shapes of fused silica. Large square crucibles of 720x720x420 with a thickness of 14mm for polycrystalline silicon melting and fused silica radoms of up to 500mm in diameter and 1000mm in height with a thickness of 10 to 12 mm have been formed and sintered with excellent homogeneity. Process parameters have been discussed such as dispersion of the ceramic particles in the casting slurry and design of the casting moulds. Simultaneous vibration treatment was applied during the casting process for more homogeneous structure of the formed bodies for some of the casting shapes.

Abstract: Up to now, Solid Oxide Fuel Cell (SOFC) materials and processing does not meet the cost goals for commercialization. This resulted in a worldwide increase in R&D activities dealing with advanced materials and effective manufacturing methods. The present paper describes efforts to process novel SOFC materials as well as optimization of well known ones. The R&D trends are explained for key components such as anode, electrolyte, cathode, contact- and protective layers. Typical SOFC manufacturing methods include tape casting, extrusion, calendaring and axial pressing. Each of these techniques has advantages and limitations. Examples for the highly efficient use of these methods are given for electrolyte supported cells as well as anode and cathode supported designs. An evaluation in reference to automation, process complexity and costs is given under the present limiting factors. Exemplary the processing by tape casting and the micro structural fine tuning of an advanced anode-supported system is discussed in detail. To produce the layered components of an SOFC, techniques like screen printing, wet powder spraying, PVD and CVD are under development. While the layer properties are excellent, PVD and CVD are nowadays too expensive in some cases, due to the low deposition rates. If thin layers are required, these techniques become interesting under cost considerations. The effectiveness of a PVD interlayer between electrolyte and high power density cathodes is shown in comparison to a sintered layer. In thin electrolyte concepts, the cathode becomes the power limiting component at operating temperatures below around 750°C. Thus new cathode materials and adjusted processing parameters are under development. The possibilities to manufacture advanced cathode layers by screen printing, wet powder spraying and other wet chemical methods are discussed. As an example screen printing of LSCF is described which results in a high power density cathode layer for low temperature SOFC operation. Finally, future needs to achieve the technical and economic goals are summarized.

Abstract: Multilayered materials and coating are complex structures proposed among others to face the structural requirements of ceramics. The development of reinforcement mechanism by laminated structures can be due to deflection criteria or to the presence of residual stresses and requires of tailored laminates. These designs are characterized by the phases, thickness and distribution of the layers as well as the joining strength between them. In this sense water based colloidal processing techniques are used to fabricate layered structures by consolidating the layers from fluid dispersions of the powders in water. In these processing methods the phases presented in the final laminate are mainly given by the composition of the starting slurries while the changes in thickness and sharpness of the layers are controlled by acting on the processing parameters. The achievement of stable slurries is a shared step for all the colloidal processing techniques. In the water based slurries the stability will be dominated by the polar media, the surface behavior of the particles and the presence of dispersant additives to increase the repulsion between particles. The stable slurry ensures an effective milling and dispersion of the phases as well as high solid loadings, if required. Further processes associated to shaping and consolidation of the layers requires the incorporation of additives and-or water removal. The shaping methods based on aqueous slurries can be classified taking into account the process of solid-water separation. For each of those shaping methods, the nature and amount of the additives is different in order to get the optimum rheological behavior and green strength after drying. Depending on the thickness of layers and coatings as well as the shape and dimensions of the samples, the shaping method can be selected alone and combined with others.