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M. Pastrama:
"Computer Tomography of aluminum oxide parts fabricated by Additive Manufacturing Technology";
Supervisor: J. Stampfl, Ch. Hellmich; Institut für Werkstoffwissenschaft und Werkstofftechnologie, 2013; final examination: 04-08-2013.

Additive Manufacturing Technology (AMT) offers the advantage of fabricating cost-effectively and rapidly parts that may otherwise be difficult to obtain by machining. Especially very small, detailed parts, such as scaffolds for bone cells used in tissue engineering can be easily produced by this layer-by-layer technique. Alumina (aluminum oxide, Al2O3) is a hard material, with high resistance to corrosion and fracture and a low friction coefficient. These properties recommend it as a highly useful material in many fields, for instance in the textile industry where parts that can resist to abrasive wear are needed. Additionally, due its linear wear rate, aluminum oxide also finds its applications in biomedical engineering, in the fabrication of hip prosthesis. The current research assesses the quality of alumina parts built using the "Blueprinter" - the AMT machine in the Institute for Material Science at the Vienna University of Technology. The quality analysis was made with the help of Computer Tomography (CT) scans. The aim of the work is to determine which machine parameters result in the best quality of the fabricated parts, translated in the lowest number of flaws (air pores) in a given control area. The first three chapters of the work focus on the theoretical aspects of the research, presenting basic notions of Additive Manufacturing Technology, ceramics in general and Al2O3 in particular, as well as Computer Tomography. The experimental part of the work (chapter 4) presents all the steps followed for manufacturing the parts. After the presentation of the used sample geometries designed in a CAD program, the fabrication process with the Blueprinter is described, from preparation of the slurry to the final sintering step. Additionally, the different combinations of the printing parameters used for obtaining the samples are presented. Chapter 5, "Results and interpretation", deals with three methods that were used for analyzing the alumina parts: light microscopy for the assessment of the surface quality, density measurements and CT scans. The latter are the most relevant for the present work, since structural flaws influence the overall quality and usability of ceramic parts the most. Therefore, the analysis of these flaws with focus on the large ones (size bigger than 0.1 mm) is presented. Finally, a discussion of the obtained results shows the possible connections between machine parameters and quality of the parts and delivers a conclusion on the optimal parameter combinations.