Silicon nitride based ceramics and method
A method is described of preparing fully dense silicon nitride base ceramic articles comprising the steps of blending form about 1 to about 25 mole percent of a metal oxide selected from the group consisting of magnesium oxide, aluminum oxide, silicon dioxide, yttrium oxide, the lanthanide rare earth oxides, and mixtures thereof with the balance consisting essentially of silicon nitride including acicular crystals of the silicon nitride; the acicular crystals having an average aspect ratio greater than 3; the acicular crystals being present in sufficient quantity to yield compact having a green density less than 60% of theoretical; comminuting the blend of metal oxide and silicon nitride to form a powder mixture; monitoring the comminuting to determine the degree of acicularity of the acicular crystals of the silicon nitride, the monitoring comprising removing a sample of the powder mixture being comminuted and pressing the sample into a pill, fracturing the pill forming a fractured surface, examining the fractured surface to determine the degree of acicularity of the acicular crystals; controlling the comminuting to obtain an average aspect ratio of the acicular crystals of the silicon nitride equal to or less than about 3; compacting the comminuted powder mixture to form a green compact having a density of at least 60% of theoretical; and pressureless sintering the compact to form an article having a density of at least 98% of theoretical.
- Assignee:
- GTE Labs., Inc., Waltham, MA
- Patent Number(s):
- US 4603116
- OSTI ID:
- 5474073
- Resource Relation:
- Patent File Date: Filed date 27 Sep 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CERAMICS
CHEMICAL PREPARATION
SILICON NITRIDES
ALUMINIUM OXIDES
ASPECT RATIO
COMPACTING
CRYSTAL STRUCTURE
CRYSTALS
DENSITY
FRACTURING
MAGNESIUM OXIDES
MIXTURES
MONITORING
POWDERS
QUANTITY RATIO
RARE EARTH COMPOUNDS
SILICON OXIDES
SINTERING
YTTRIUM OXIDES
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
COMMINUTION
DISPERSIONS
FABRICATION
MAGNESIUM COMPOUNDS
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
SILICON COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication