Spontaneous infiltrations of compound systems of Y_2O_3, Sm_2O_3, RE_2O_3, Al_2O_3 and AIN in SiC ceramics

摘要

Silicon carbide ceramics (SiC) are used in different applications in the engineering area due to the excellent properties, mainly in high temperatures. They are usually obtained by liquid-phase sintering enabling to form volatile products and, consequently, defects. The present work aims at studying the obtention of SiC ceramics by spontaneous infiltration using a eutectic composition of the Al_2O_3/Y_2O_3, AlN/Y_2O_3, Al_2O_3/ Sm_2O_3, AlN/Sm_2O_3, Al_2O_3/RE_2O_3 and AlN/RE_2O_3 systems. RE_2O_3 is the concentrate of the rare-earth oxide obtained from Xenotime ore. Infiltration tests were carried out in argon atmosphere, graphite crucibles, in several temperatures near the melting point of each system, varying from 2.5 to 60 min. It was observed that Al_2O_3/Y_2O_3, Al_2O_3/Sm_2O_3, A1N/Sm_2O_3 and Al_2O_3/RE_2O_3 systems do not infiltrate appropriately and the AlN/Y_2O_3 and AlN/RE_2O_3 systems infiltrated spontaneously more than 20 mm; however, the first one presented a higher degree of infiltration, approximately 97%.