| Summary: | 碩士 === 國立臺北科技大學 === 製造科技研究所 === 96 === The aim of this study is to improve the mechanical strength and to develop the methods of green portion removal for the slurry contained clay and PVA as binders. In order to achieve the goal, the modification has to be started from the very beginning. By changing the formulation of the slurry, establishing the laser scanning parameters, and executing a post-process, the density and mechanical strength of the alumina part can be elevated. The method of the green portion removal is adapted to the characteristics of each binder.
Firstly, the formulation of the slurry was modified. The slurry included alumina powder (the average particle size of alumina is 0.5μm) and organic polyvinyl alcohol binder. The formulation, rheological properties and the homogeneity of the slurry were investigated; a well-dispended alumina powder was obtained. The laser scanning parameters were built to fabricate ceramic part by selective scanning the thin layers. Alumina ceramic parts were obtained by burning out binder at 600℃ and sintering the green parts at 1600℃. Finally, the theoretical density of alumina ceramic parts was 93% and the average bending strength was 232.5MPa.
Secondly, removing green portion of a hollow part fabricated with the slurry contained silica powder and clay, using a nozzle and fixtures can effectively remove green portion without damaging the hollow part. The experiment of removing green portion was conducted for the slurry which contained PVA and alumina powders which have different surface properties. Eventually, the green portion can be effectively removed by immersing it in the H2O2 solution and vibrating with an ultrasonic vibrator for a period of time.
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