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US 5,665,279 AGranted
Low density silicon nitride-containing beads, aggregates thereof, and method for preparing same
AssigneeMinnesota Mining and Manufacturing Company
InventorRoss H. Plovnick
Life of this patent
Estimating the term…
Abstract
A sintered bead that includes at least 95% by weight silicon nitride, based on the total weight of the bead, and has a bulk density no greater than about 60% of theoretical density. The invention further features aggregates prepared from a plurality of such beads, as well as methods for preparing the beads and aggregates.
Claims14
A method for preparing beads comprising silicon nitride comprising the steps of:
- (a) providing a sufficient amount of a mixture comprising (i) an aqueous solution of a water-soluble organic polymer and (ii) a powder comprising silicon, silicon nitride, or a combination thereof, to provide after steps (b), (c), and (d) a plurality of free flowing, sintered silicon nitride beads in which each of the beads comprises at least 95% by weight silicon nitride, based on the total weight of the bead, and in which each of the beads has a bulk density no greater than about 60% of theoretical density;
- (b) injecting said mixture into an aqueous coagulating solution to form a plurality of beads;
- (c) removing volatiles from said beads;
- and
- (d) sintering said beads of step (c) in the presence of nitrogen to form a plurality of free flowing, sintered silicon nitride beads in which each of said beads comprises at least 95% by weight silicon nitride, based on the total weight of the bead, and in which each of said beads has a bulk density no greater than about 60% of theoretical density.
2 more elements
A method for preparing an aggregate comprising the steps of:
- (a) providing a mixture comprising a sufficient amount of (i) an aqueous solution of a water-soluble organic polymer and (ii) a powder comprising silicon, silicon nitride, or a combination thereof, to provide after steps (b), (c), (d), and (e) an aggregate comprising a plurality of sintered silicon nitride beads bonded together in which each of the beads comprises at least 95% by weight silicon nitride, based on the total weight of the bead, and each of the beads has a bulk density no greater than about 60% of theoretical density;
- (b) injecting said mixture into an aqueous coagulating solution to form a plurality of beads;
- (c) contacting said beads with an aqueous solution comprising a fugitive bonding agent to form a precursor aggregate in which said beads of step (b) are held together;
- (d) removing volatiles from said precursor aggregate;
- and
- (e) sintering the precursor aggregate of step (d) in the presence of nitrogen to form said aggregate comprising a plurality of sintered silicon nitride beads bonded together in which each of said beads comprises at least 95% by weight silicon nitride, based on the total weight of said bead, and each of said beads has a bulk density no greater than about 60% of theoretical density.
3 more elements
Dependencies are inferred from the claim text.