Low-Temperature Synthesis of Corundum Ceramics. Study of the Influ-Ence of Specially Introduced Nano-Additives on the Sintering Process

The present paper reports for the synthesis of fine-grained corundum ceramics by the method of diffusion dominated solid state sintering at temperature relatively low for corundum materials - 1300 °C, 1450 °C and 1500 °C, using specially introduced additives as follows: 3.0 wt. % T i O 2 , graphene nanostructures - 2.0 wt. % GnP or 20.0 wt. % G3 and nanosized A l 2 O 3 . The initial powders and the ceramics synthesized from them were characterized mainly by the methods of Infrared spectroscopy (FT-IR), X-ray phase analysis (XRD), Scanning electron microscopy (SEM). The results obtained from the conducted research show that the introduction of special additives in a certain amount has an impact on the sintering temperature and recrystallization processes in ceramics. The X-ray phase analysis proved that the main crystalline phase in the ceramics synthesized from blends G1, A1 and C0 was corundum. The main functional groups present in the compositions of the ceramic samples synthesized were determined by FT-IR spectroscopy. Using SEM, it was proved that the introduced nano-additives initiated the formation of fine-grain and fine-pore structure with corundum grain sizes ranging from 0.2 to 2.0 μm. The decreased ceramics synthesis temperature, in this case, was mainly due to the additive T i O 2 (3.0 wt. %) included in the initial blends and the high dispersity of the initial materials. The specific additives introduced into the resulting ceramic ( T i O 2 , G3, GnP, nano- A l 2 O 3 ) lead to a significant reduction in the synthesis temperature. The corundum-based samples containing additives were studied to determine the more important physical-mechanical properties, e.g. water absorption ( W A , % ), apparent density ( ρ a p p , g / c m 3 ) and apparent porosity ( P a p p , % ). Given the characteristics of the synthesized corundum samples, they can be studied and applied as filtering elements and adsorbents in the purification of wastewater from various pollutants, such as dyes and some heavy metals.