ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
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-Al2O3) 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 (Y2O3) or ceria (CeO2) 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-Al2O3, and Y2Si2O7 or CeO2, respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.1998.tb02569.x
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