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Densification of Sol‐Gel‐Derived Mullite Ceramics after Cold Isostatic Pressing up to 1 GPa
Author(s) -
Kamiya Hidehiro,
Suzuki Hisao,
Ichikawa Takahiro,
Cho Yong Ick,
Horio Masayuki
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.tb02310.x
Subject(s) - mullite , materials science , ceramic , sintering , calcination , hot isostatic pressing , microstructure , grain size , stoichiometry , pressing , metallurgy , composite material , mineralogy , catalysis , geology , chemistry , biochemistry , organic chemistry
Molecular‐designed ultrafine mullite precursor powders with a stoichiometric composition were prepared by copolymerization of alkoxides. The precursor powders were calcined in the range from 800° to 1200°C and consolidated by ultra‐high‐pressure cold isostatic pressing up to 1 GPa. Ultrahigh isostatic pressure of 1 GPa led to a closed packing structure in the green compacts. Interaggregate pores in the green compacts were collapsed by the ultrahigh cold isostatic pressure to reduce the pore size below 6 nm. As a result, the maximum density of the green compacts reached 70% of theoretical. These closely packed green compacts of precursor powders with a stoichiometric composition and calcined at relatively low temperatures could be sintered to >95% of theoretical at 1500°C. Relatively low‐temperature sintering below the liquid formation temperature resulted in fine microstructure of the resultant mullite ceramic with a grain size below 300 nm.