Silicon nitride based ceramics and method

Patent · Tue Jul 29 04:00:00 EDT 1986

OSTI ID:5474073

Smith, J T; Quakenbush, C L.W.; Moschetti, A P; Lingertat, H

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
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ASPECT RATIO
CERAMICS
CHALCOGENIDES
CHEMICAL PREPARATION
COMMINUTION
COMPACTING
CRYSTAL STRUCTURE
CRYSTALS
DENSITY
DISPERSIONS
FABRICATION
FRACTURING
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MIXTURES
MONITORING
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
POWDERS
QUANTITY RATIO
RARE EARTH COMPOUNDS
SILICON COMPOUNDS
SILICON NITRIDES
SILICON OXIDES
SINTERING
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES