| Sažetak | U ovom radu pripravljena je porozna aluminijeva oksidna keramika s različitim udjelima otpadnog grafita. Sirovci su oblikovani postupkom lijevanja suspenzije u gipsani kalup. U tu svrhu pripravljene su 60 %-tne vodene Al2O3 suspenzije s različitim masenim udjelima (0, 1, 5 i 10 %) otpadnog grafita te uz dodatke disperzanta Dolapix PC 75 (0,4 %) i veziva PVA (0, 5 %).
Suspenzije su homogenizirane u planetarnom kugličnom mlinu nakon čega slijedi lijevanje u gipsane kalupe za dobivanje sirovaca. Prije samog lijevanja suspenzijama su određena reološka svojstva na rotacijskom viskozimetru. Lijevanjem u gipsani kalup su dobiveni sirovci Al2O3 keramike s masenim udjelom 0, 1, 5 i 10 % otpadnog grafita koji su sinterirani (konvencionalnim postupkom) u električnoj peći. Režim sinteriranja se sastojao od zagrijavanja na temperaturu od 800 °C pri brzini zagrijavanja od 5 °C min-1, izotermnog držanja na toj temperaturi u trajanju od 2 sata da izgori sav otpadni grafit, zatim zagrijavanje do 1600 °C pri brzini zagrijavanja od 5 °C min-1 te ponovno držanje od 2 sata da se završi proces sinteriranja keramike. Poslije toga je uslijedilo hlađenje u peći na sobnoj temperaturi. Dobivenim keramičkim proizvodima je analizirana mikrostruktura pretražnim elektronskim mikroskopom (SEM) te je određen gubitak mase, gustoća, poroznost i skupljanje.
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| Sažetak (engleski) | In this study, porous alumina ceramic with varying proportions of waste graphite was prepared. Green bodies were formed by pouring the suspension in plaster mold. For this purpose, 60 % aqueous Al2O3 suspension with different mass fractions (0, 1, 5 and 10 %) of waste graphite, along with addition of dispersant Dolapix PC 75 (0,4 %) and a binder PVA (0, 5 %) were prepared.
The suspensions were homogenized in a planetary ball mill, followed by pouring into a plaster mold to obtain green bodies. Prior to pouring of the suspensions, the rheological properties were determined using a rotational viscometer. Casting into plaster mold yielded green boodies of Al2O3 ceramic with mass fractions of 0, 1, 5 and 10 % of waste graphite, which were then sintered (by conventional technique) in an electric furnace. The sintering regime involved heating to a temperature of 800 °C at a heating rate of 5 °C min-1 , isotermic holding at that temperature for 2 hours to burn off all the waste graphite, followed by heating to 1600 °C at a heating rate of 5 °C min-1 and another 2-hour hold to complete the ceramic sintering process. Subsequently, cooling was performed in the furnace at room temperature. The obtained ceramic products microstructure was analyzed using a scanning electronic microscope (SEM), and the mass loss, density, porosity and shrinkage were determined.
The results were discussed at the end of the study, and a conclusion was reached. |
