Premium
Accelerated Reaction Bonding of Mullite
Author(s) -
Mechnich Peter,
Schneider Hartmut,
Schmücker Martin,
Saruhan Bilge
Publication year - 1998
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1998.tb02569.x
Subject(s) - mullite , materials science , sintering , corundum , ceramic , silicon , chemical engineering , composite material , oxide , mineralogy , metallurgy , chemistry , engineering
A suitable way to process mullite ceramics and mullite‐matrix composites with low dimensional changes (“near‐net‐shape processing”) is reaction bonding, using silicon metal and corundum (α‐Al 2 O 3 ) as starting materials, be‐cause sintering‐induced shrinkage is compensated by vol‐ume expansion caused by the silicon‐oxidation‐induced vol‐ume expansion. This work describes a new reaction‐bonded mullite (RBM) processing route that proceeds at much lower temperatures (≤1350°C) than in “normal” RBM systems (≥1550°C). Accelerated silicon oxidation and mullite formation are effected by adding low amounts of yttria (Y 2 O 3 ) or ceria (CeO 2 ) to the green powder mixtures, which causes the formation of transient, metastable, and low‐viscosity Y‐Al‐Si‐O and Ce‐Al‐Si‐O partial melts. After long‐term heat treatments at ≤1350°C, however, the intermediate liquids recrystallize and leave behind RBM ceramics that are homogeneous, substantially glass‐free, and relatively dense. These two RBM materials consist of mullite, α‐Al 2 O 3 , and Y 2 Si 2 O 7 or CeO 2 , respectively.