Solid-Gas Reaction during Sintering of Si_3N_4 Ceramics (Part 3) –Mass Losses in a Carbon Heater Furnace-

摘要

Solid-gas reactions of Si_3N_4 ceramics wereinvestigated with emphasis on the mass loss during sinteringunder various sagger conditions. A Si_3N_4 powder compactwithout sintering aids was heat-treated at 2023 K for 0 to 8 hunder 0.1 and 1 MPa N_2 adopting three sagger conditions: aSi_3N_4 powder bed, without a powder bed in BN sagger, andwithout a powder bed in C sagger, and Si_3N_4 with addition of5 mass percent Y_2O_3 and 3 mass percent Al_2O_3 wassintered at 2023 K for 0 to 16 h under 0.1 to 100 MPa N_2adopting four sagger conditions: a 50 mass percent Si_3N_4/50mass percent BN powder bed, without a powder bed in BNsagger, a C powder bed, and without a powder bed in C sagger.In C sagger, the principal mass loss reaction was that ofSi_3N_4 (S) with CO (g): 2Si_3N_4 (S) + 3CO (g)->6SiO(g)+4N_2 (g). In BN sagger, the principal mass lossreaction was that of Si_3N_4 (s) with SiO_2 (1): Si_3N_4(S)+3SiO_2 (1)->6SiO(g)+N_2 (g). When SiO(g) generatedfrom the sample and the powder bed (based on the abovereaction between Si_3N_4 (S) and SiO_2 (1)) was exhausted, themass loss reaction of Si_3N_4 (S) with CO(g) occurred even inBN sagger, which diffused in through a gap of the sagger.