Patent US5204300A successfully refreshed from Google Patents.
US5204300A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Methods of seeding sintered objects
Assignee: JFE Steel Corp
•
Filing: 1989-06-12
•
Granted: 1993-04-20
•
Expires: 2009-06-12
Abstract
Abstract A ceramic sintered body and a method for manufacturing the same in which the body includes a first material having at least one of a precursor and a metastable material of the final sintered body and a second material morphologically related to the first material and added to the first material to affect transformation of said first material into the desired crystalline form of the ceramic sintered body, in which method transformation of a metal oxide compound from one phase to another, where the compound has a high activation energy and is confronted with a high nucleation energy barrier to the transformation, produces the body and includes the steps of making a mixture by bringing a multiplicity of particles of the compound into intimate contact with the multiplicity of nucleation particles having crystallographically related structure to act as nuclei for the transformation and sintering the resulting mixture to transform the compound from one phase to another by nucleation and growth, independently of growth of the nucleation particles.
Inventors
- 👤 Masato Kumagai
- 👤 Gary Messing
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 19:58
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/626; C04B35/01; C04B35/10; C04B35/111; C04B35/46; C04B35/624
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
188 words
A method for solid-state transformation of a metastable aluminum oxide compound from one crystalline form to another, said compound having a high activation energy and being confronted with a high activation nucleation energy barrier to such transformation, comprising: (a) preparing an aqueous colloidal dispersion of a multiplicity of solid particles of said oxide compound; (b) preparing an aqueous colloidal dispersion of 0.1% up to 10% of a multiplicity of solid-state nucleation particles, based on the number of particles of said oxide, said nucleation particles having crystallographically similar structure to act as nuclei for the transformation; (c) intimately contacting and mixing said dispersions into a homogeneous mixture; (d) causing said mixture to gel by dehydration; and (e) sintering the gelled and dried mixture in the solid-state between about 1050° C. and about 1150° C. to transform said compound from one crystalline form to another by initiation of grain nucleation and growth, said transformed compound reaching between about 65 and 97% of theoretical density and said transformation being effected independently of growth of the nucleation particles, said transformed compound having submicron sized grains and a substantially evenly distributed pore phase.
Claim 2
Independent Claim
188 words
A method for solid-state transformation of a metastable aluminum oxide compound from one crystalline form to another, said compound having a high activation energy and being confronted with a high activation nucleation energy barrier to such transformation, comprising: (a) preparing an aqueous colloidal dispersion of a multiplicity of solid particles of said oxide compound; (b) preparing an aqueous colloidal dispersion of 0.1% up to 10% of a multiplicity of solid-state nucleation particles, based on the number of particles of said oxide, said nucleation particles having crystallographically similar structure to act as nuclei for the transformation; (c) intimately contacting and mixing said dispersions into a homogeneous mixture; (d) causing said mixture to gel by dehydration; and (e) sintering the gelled and dried mixture in the solid-state between about 1050° C. and about 1150° C. to transform said compound from one crystalline form to another by initiation of grain nucleation and growth, said transformed compound reaching between about 65 and 97% of theoretical density and said transformation being effected independently of growth of the nucleation particles, said transformed compound having submicron sized grains and a substantially evenly distributed pore phase.
Claim 3
Independent Claim
203 words
A method for solid-state transformation of a metastable aluminum oxide compound from one crystalline form to another, said compound having a high activation energy and being confronted with a high activation nucleation energy barrier to such transformation, comprising: (a) preparing an aqueous colloidal dispersion of a multiplicity of solid particles of said oxide compound by adjusting the pH thereof; (b) preparing an aqueous colloidal dispersion of 0.1% up to 10% of a multiplicity of solid-state alumina nucleation particles, based on the number of particles of said oxide, said nucleation particles having crystallographically similar structure to act as nuclei for the transformation; (c) intimately contacting and mixing said dispersions into a homogeneous mixture; (d) causing said mixture to gel by dehydration; and (e) sintering the gelled and dried mixture in the solid-state, between about 1050° C. and about 1150° C. to transform at least about 95% of said compound from one crystalline form to another at about 1025° C. by initiation of grain nucleation and growth, said transformed compound reaching between about 65 and 97% of theoretical density and said transformation being effected independently of growth of the nucleation particles, said transformed compound having submicron sized grains and a substantially evenly distributed pore phase.
Claim 4
Independent Claim
203 words
A method for solid-state transformation of a metastable aluminum oxide compound from one crystalline form to another, said compound having a high activation energy and being confronted with a high activation nucleation energy barrier to such transformation, comprising: (a) preparing an aqueous colloidal dispersion of a multiplicity of solid particles of said oxide compound by adjusting the pH thereof; (b) preparing an aqueous colloidal dispersion of 0.1% up to 10% of a multiplicity of solid-state alumina nucleation particles, based on the number of particles of said oxide, said nucleation particles having crystallographically similar structure to act as nuclei for the transformation; (c) intimately contacting and mixing said dispersions into a homogeneous mixture; (d) causing said mixture to gel by dehydration; and (e) sintering the gelled and dried mixture in the solid-state, between about 1050° C. and about 1150° C. to transform at least about 95% of said compound from one crystalline form to another at about 1025° C. by initiation of grain nucleation and growth, said transformed compound reaching between about 65 and 97% of theoretical density and said transformation being effected independently of growth of the nucleation particles, said transformed compound having submicron sized grains and a substantially evenly distributed pore phase.
Claim 5
Dependent Claim
21 words
The method as set forth in claim 1 which further comprises a step for adjusting the pH of said colloidal dispersions.
Claim 6
Dependent Claim
16 words
The method as set forth in claim 3, wherein said pH is adjusted to about 3.
Claim 7
Dependent Claim
18 words
The method as set forth in claim 3, wherein said pH is adjusted by addition of nitric acid.
Claim 8
Independent Claim
22 words
The method as set forth in claims 1 and 2, wherein said oxide compound is boehmite and said nucleation particles are alpha-alumina.
Claim 9
Dependent Claim
31 words
The process as set forth in claim 6, wherein the number of particles of said alpha-alumina added to said boehmite is approximately 3% of the number of particles of said boehmite.
References Cited (Backward Citations)
US3141786A
Cited
US2982614A
Cited
US2944914A
Cited
US3377176A
Cited
US3862297A
Cited
US3945945A
Cited
JPS4965392A
Cited
US4101615A
Cited
US4166147A
Cited
US4019914A
Cited
US4196769A
Cited
JPS5788075A
Cited
US4505886A
Cited
US4623364A
Cited
US4555394A
Cited
US4562059A
Cited
EP0168606A2
Cited
US4543107A
Cited
USH189H
Cited
US4835124A
Cited
US4615875A
Cited
US4829031A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-04-19 | 1996-10-19 | 1997-04-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-04-19 | 2000-10-19 | 2001-04-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-04-19 | 2004-10-19 | 2005-04-20 | $7700.00 | Window Closed / Lapsed |