Silicon nitride –
Improving the properties of one of the world's most important
structural materials
Tape-cast silicon nitride for high temperature
applications.
With excellent high temperature strength, good
resistance to oxidation and low coefficient of thermal expansion Si3N4
ceramic is one of the most important structural materials. However,
the pure silicon nitride ceramics are difficult to densify and the
addition of various oxides is used to improve sinterability.
Previous work has shown Lu2O3-SiO2
additives are useful in improving the bending strength of Si3N4
at elevated temperature. The bending strength of the tape-cast Si3N4
with rod-like ß-Si3N4 seed can be further
improved because the elongated grains from seeds were preferentially
oriented parallel to the casting direction. In this study from the
National Institute of Advanced Industrial Science and Technology (AIST)
and published in AZojomo *), Lu2O3-SiO2
additives were selected as sintering additives, and tape casting was
used to prepare the unidirectional aligned ß-Si3N4
elongated grain Si3N4 ceramics.
The researchers Yu-Ping Zeng, Jian-Feng Yang, Naoki
Kondo, Kiyoshi Hirao, Tatsuki Ohji, Hideki Kita and Shuzo Kanzaki
found that the seeded and tape-cast Si3N4
materials showed anisotropic microstructures and bending strength with
the thickness of green tape having some effect on the bending strength.
Due to the formation of a high melting point grain boundary phase Lu2Si2O7N2
and the unidirectionally aligned ß-Si3N4
elongated grains, the seeded and tape-cast Si3N4
shows good bending strength at elevated temperature.
*) AZojomo (ISSN 1833-122X) publishes high quality articles and
papers on all aspects of materials science and related
technologies. All the contributions are reviewed by a world class
panel of editors who are experts in a wide spectrum of
materials science.
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AZojomo
is based on the patented
OARS (Open
Access Rewards System) publishing protocol. The OARS protocol
represents a unique development in the field of scientific
publishing – the distribution of online scientific journal revenue
between the authors, peer reviewers and site operators with no
publication charges, just totally free to access high quality,
peer reviewed materials science.
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