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Shock‐Compacted Si 3 N 4 Nanocrystalline Ceramics: Mechanisms of Consolidation and of Transition from α‐ to β‐form
Author(s) -
Hirai Hisako,
Kondo Kenichi
Publication year - 1994
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.1151-2916.1994.tb07018.x
Subject(s) - materials science , nanocrystalline material , transmission electron microscopy , consolidation (business) , compaction , indentation hardness , nanometre , ceramic , sintering , mineralogy , composite material , crystallography , microstructure , nanotechnology , chemistry , accounting , business
Ultrafine powder of α‐Si 3 N 4 several tens of nanometers in size was successfully consolidated using a shock‐compaction technique under 40 GPa. The bulk density of the most dense portion attained 99% of the theoretical value, and the Vick‐ers microhardness was 2300 kg/mm. Consolidation was achieved through both densificarion by plastic deformation of constituent grains and interparticle bonding by surface melting. A transition process to β‐Si 3 N 4 was observed by transmission electron microscopy: Surface melting of the individual grains propagated into the center as temperature increased, and a large mass formed. A precursor of β–Si3N4 then emerged from the mass and finally grew into a β‐Si 3 N 4 crystal.