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Patent US5665279A successfully refreshed from Google Patents.
US5665279A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low density silicon nitride-containing beads, aggregates thereof, and method for preparing same
Assignee: 3M Co
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Filing: 1996-11-04
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Granted: 1997-09-09
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Expires: 2016-11-04
Abstract
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.
Inventors
- 👤 Ross H. Plovnick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:06
CPC Classifications
B; B01; B01J; B01J2/00; B01J2/02; B01J2/06
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
186 words
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.
Claim 2
Independent Claim
186 words
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.
Claim 3
Dependent Claim
19 words
A method according to claim 1 in which said water soluble organic polymer comprises a salt of alginic acid.
Claim 4
Dependent Claim
13 words
A method according to claim 2 comprising the sodium salt of alginic acid.
Claim 5
Dependent Claim
14 words
A method according to claim 1 in which said coagulating solution comprises calcium chloride.
Claim 6
Dependent Claim
13 words
A method according to claim 1 in which said powder is silicon powder.
Claim 7
Dependent Claim
14 words
A method according to claim 1 in which said powder is silicon nitride powder.
Claim 8
Independent Claim
217 words
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.
Claim 9
Independent Claim
217 words
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.
Claim 10
Dependent Claim
16 words
A method according to claim 7 in which said fugitive bonding agent comprises a chelating agent.
Claim 11
Dependent Claim
19 words
A method according to claim 8 in which said chelating agent comprises a salt of ethylene diamine tetraacetic acid.
Claim 12
Dependent Claim
19 words
A method according to claim 7 in which said water soluble organic polymer comprises a salt of alginic acid.
Claim 13
Dependent Claim
13 words
A method according to claim 10 comprising the sodium salt of alginic acid.
Claim 14
Dependent Claim
14 words
A method according to claim 7 in which said coagulating solution comprises calcium chloride.
Claim 15
Dependent Claim
13 words
A method according to claim 7 in which said powder is silicon powder.
Claim 16
Dependent Claim
14 words
A method according to claim 7 in which said powder is silicon nitride powder.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2000-09-08 | 2001-03-10 | 2001-09-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-09-08 | 2005-03-10 | 2005-09-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-09-08 | 2009-03-10 | 2009-09-09 | $7700.00 | Window Closed / Lapsed |