Porous mullite
Abstract
Abstract Clay, preferably kaolin, is calcined through its exotherm, but without substantial mullite formation (e.g., 1 hour at 1000° C.). The calcined clay is leached with an alkaline aqueous solution to remove (i.e., leach) silica. The severity of leaching, i.e., amount of silica removed, determines whether the final product will comprise mullite plus excess Al 2 O 3 . If the molar Al 2 O 3 /SiO 2 ratio is <3/2 the final product will contain mullite plus excess SiO 2 and if the Al 2 O 3 /SiO 2 ratio is >3/2, the final product will contain excess Al 2 O 3 . The leached clay is washed, preferably under acid conditions at about pH 3-5, to remove excess alkali ions; and then dried. The washed clay is then calcined at conditions to produce mullite (e.g., 3 hours at 1250° F.). Materials made in this manner exhibit high pore volume despite the final high temperature heat treatment.
Inventors
- 👤 Barry K. Speronello
Bibliographic Details
Claims Analysis
Total Claims: 12References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-07-21 | 1990-01-20 | 1990-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-07-21 | 1994-01-20 | 1994-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-07-21 | 1998-01-20 | 1998-07-22 | $7700.00 | Window Closed / Lapsed |