 |
|
|
|
|
|
 Title: |
US4837069:
Transparent alumina microspheres
[ Derwent Title ]
|
| Country: |
US United States of America
|
| |
| Inventor: |
Bescup, Terrance L.; Woodbury, MN
Fellows, Benjamin T.; Oakdale, MN
Leedecke, Charles J.; Northford, CT
|
| Assignee: |
Minnesota Mining and Manufacturing Company, St. Paul, MN
other patents from MINNESOTA MINING AND MANUFACTURING COMPANY (377880) (approx. 9,335)
News, Profiles, Stocks and More about this company
|
| Published / Filed: |
1989-06-06
/ 1987-01-07
|
| Application Number: |
US1987000001173
|
| IPC Code: |
Advanced:
C01F 7/02;
C01F 7/36;
E01F 9/00;
E01F 9/04;
G02B 5/128;
Core:
C01F 7/00;
more...
IPC-7:
B32B 9/03;
C01F 7/02;
F21D 7/22;
|
| U.S. Class: |
Current:
428/148;
106/401;
106/442;
359/536;
404/014;
423/600;
423/625;
423/628;
428/141;
428/329;
428/402;
428/457;
501/127;
523/172;
Original:
428/148;
106/442;
106/401;
350/105;
404/014;
423/600;
423/625;
423/628;
428/141;
428/329;
428/402;
428/457;
501/127;
523/172;
|
| Field of Search: |
264/015
501/127
423/625,628,600
350/105
404/014
428/329,402,402.24,141,148,457
252/315.7,589
106/288 B
523/172
|
| Priority Number: |
| 1987-01-07 |
US1987000001173 |
|
| Abstract: |
Procedure for making Al2 O3 spheroids, 600 micrometers in diameter or less, utilizes an AlOOH sol containing 0.25% weight percent MgO (in the form of Mg(NO3)2 .multidot.6H2 O) and HNO3. The sol is dispersed into droplets in a particle forming fluid (e.g., 2-ethylhexanol) where gelling occurs. The gelled spheroids are collected, dried and pre-fired in air at temperatures less than 1,200° C. for up to about 12 hours. The dried and prefired beads are fired in a 2-step process at temperatures of about 1,850-1,950° C. in the following sequence:
- a first dry oxygen firing for about ten minutes, followed by a wet hydrogen firing for up to 350 minutes. Reasonably transparent microspheres having crystallites in the range of 5-100 micrometers are obtained with little intergranular porosity, and their density is estimated to be near theoretical.
|
| Attorney, Agent or Firm: |
Sell, Donald M. ;
Kirn, Walter N. ;
Little, Douglas B. ;
|
| Primary / Asst. Examiners: |
Lesmes, George F.; Monroe, James B.
|
| Maintenance Status: |
CC Certificate of Correction issued
|
| INPADOC Legal Status: |
Show legal status actions
Family Legal Status Report
|
| Designated Country: |
AT DE FR GB IT SE
|
| Family: |
Show 10 known family members
|
First Claim:
Show all 10 claims |
What is claimed is:
1. A solid, transparent, polycrystalline spheroid useful as a retroreflective lens element and having a diameter less than about 500 micrometers, consisting essentially of alpha alumina having crystallites of about 5 to 200 micrometers in largest dimension.
|
| Background / Summary: |
Show background / summary
|
| Drawing Descriptions: |
Show drawing descriptions
|
| Description: |
Show description
|
| Forward References: |
Show 19 U.S. patent(s) that reference this one
|
|
