Optimization of the sintering process of pure and waste alumina powder

U ovom radu istražena su svojstva izratka od aluminijevog oksida (Al2O3) dobivenog korištenjem primarnog i sekundarnog (otpadnog) keramičkog praha. Metodom odzivnih površina analiziran je utjecaj parametara sinteriranja keramičkog uzorka s različitim udjelom sekundarnog praha, vremenom zadržavanja na temperaturi sinteriranja i temperaturom sinteriranja na gustoću i tvrdoću dobivenih keramičkih uzoraka. Sekundarni, tj. otpadni keramički prah nastaje strojnom obradom sirovca kod tvorničke proizvodnje keramike. Navedeni se otpad zbog svoje kemijske inertnosti smije odlagati na odlagalištu otpada jer ne zagađuje okoliš, no problem leži u nerazgradivosti. Problem recikliranja i oporabe otpadnog aluminijevog oksidnog praha je u visokoj termostabilnosti, te neorganskom podrijetlu samog praha. U ovom radu će se ispitati može li se recikliranjem otpadnog aluminijevog oksidnog praha smanjiti količina otpada, te općenito sniziti troškovi proizvodnje keramike, a da pri tome ne narušavamo svojstva konačnog proizvoda aluminijeve oksidne keramike. Vodena Al2O3 suspenzija je homogenizirana mljevenjem u planetarnom kugličnom mlinu. Stabilna suspenzija je dobivena uz dodatak aditiva trgovačkog naziva Tiron, kako bi se dobila optimalna viskoznost prilikom lijevanjem u gipsane kalupe, te kako bi se smanjila mogućnost nepravilnosti u mikrostrukturi prilikom sinteriranja.In this thesis the procedure of preparing aluminium oxide ceramics samples by using pure and waste alumina powder is described. The analysis of the effect of different waste alumina percentage, sintering temperature and sintering duration on the density and hardness of alumina ceramics was performed by the Response Surface Methodology. Alumina powder waste is produced as a result of the green machining during factory manufacturing of alumina ceramics. This waste is chemically inactive and can be disposed on landfills. Alumina powder does not pollute the environment, but the problem is that it is not non-biodegradable. The high thermal stability and non-organic origin of the waste is also a problem for recycling or recovery. In this thesis the possibility of recycling waste alumina powder, in order to decrease the generated waste and manufacturing costs, while saving the final properties of the product will be examined. The water suspension of alumina oxide is homogenised in the planetary ball mill. The stable suspension is obtained by slip casting, using Tiron as a commercially available dispersant. This way, an optimal apparent viscosity is obtained for the slip casting method, in order to decrease the imperfections in the microstructure after sintering