engleski

Spark plasma sintering of alumina ceramics with addition of waste alumina powder

During industrial production of ceramic materials are observed process losses such as broken ware from shaping, drying, firing and refractory material, different kinds of sludge, dust, and used plaster molds. Some of the accumulated process losses mentioned above can be recycled and reused within the plant due to product specifications or process requirements ; otherwise, remaining materials are considered as waste and are supplied to external recycling or disposal facilities. European Commission recently adopted an ambitious Circular Economy Action Plan, which proposes actions that should help to “close the loop” of a product lifecycle by reducing the generated waste, reusing the waste, and recycling where possible. The aim of this research was to investigate the possibility of recycling waste alumina powder. In this study, the high-purity alumina powder and waste alumina powder obtained after the green machining were used as raw materials. The powder mixture was suspended in ethanol and then subjected to the ball milling process. The resulting slurry was dried and densified by Spark Plasma Sintering according to Box-Behnken design in order to determine the optimal sintering regime based on the obtained densities of sintered samples. The corresponding response density of each sintered sample was measured in distilled water using Archimede’s principle. Then, the Response Surface Method was applied to find the optimal value of each factor to obtain maximum density. After the determination of the optimal sintering regime, the sample prepared with commercial alumina powder was sintered at optimal conditions and compared to the alumina/waste alumina sample. Additionally, the morphology of the sintered samples was examined by Scanning Electron Microscopy (SEM). The polished samples were submitted to the hardness and fracture toughness measurement by the Vickers indentation method. According to obtained data the waste alumina powder could be used as secondary raw material to produce high quality advanced ceramics.

alumina, recycling, spark plasma sintering, mechanical properties

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