US3608050A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Production of single crystal sapphire by carefully controlled cooling from a melt of alumina
Assignee: Union Carbide Corp
•
Filing: 1969-09-12
•
Granted: 1971-09-21
•
Expires: 1989-09-12
Abstract
Abstract A charge of alumina is placed in a mold and heated in a vacuum or an inert gas atmosphere to melt the charge. The melt is then cooled in a generally upward direction to solidify and crystallize the melt at a rate that the generally vertical, downward temperature gradient in the crystallizing zone is less than 25* C. per millimeter. After all of the melt has crystallized the single crystal is uniformly cooled and removed from the mold. Special methods of making the mold and removing the mold are also disclosed.
Inventors
- 👤 Justice N Carman
- 👤 Herman G Mcknight
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 22:34
CPC Classifications
C; C30; C30B; C30B11/00; C30B29/00; C30B29/10; C30B29/16; C30B29/20; Y; Y10; Y10S; Y10S117/00; Y10S117/90; Y10T; Y10T117/00; Y10T117/10; Y10T117/1024; Y10T117/1092
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
24 words
The method of claim 1 wherein said heating step and said directional crystallizing step are conducted in a vacuum of less than one torr.
Claim 2
Dependent Claim
29 words
The method of claim 1 wherein said heating step and said directional crystallizing step are conducted in an inert gas selected from the group consisting of helium and argon.
Claim 3
Dependent Claim
46 words
The method of claim 1 wherein said directional crystallizing step include cooling said mold and said molten sapphire therein at such a rate that the generally vertical, downward temperature gradient of said sapphire in said transition zone is between -1* C. and -10* C. per millimeter.
Claim 4
Dependent Claim
33 words
The method of claim 1 wherein said directional crystallizing step includes cooling at a rate between 1 and 10 mm. per hour along the generally vertical axis of said mold and molten sapphire
Claim 5
Dependent Claim
31 words
The method of claim 1 wherein said charging step includes at least partially filling said mold with molten sapphire while maintaining said mold at a temperature of at least 2,030* C.
Claim 6
Dependent Claim
26 words
The method of claim 1 including the step of preparing said mold by depositing said metal on a pattern of the desired form by electro deposition.
Claim 7
Dependent Claim
25 words
The method of claim 1 including the step of preparing said mold by depositing said metal on a pattern of desired form by vapor deposition.
Claim 8
Dependent Claim
36 words
The method of claim 1 including the step of preparing said mold by forming said mold with a thin inner layer of one of said metals and a thicker outer layer of another of said metals.
Claim 9
Dependent Claim
41 words
The method of claim 1 wherein the charging step comprises: heating said mold, melting a quantity of alumina or sapphire to form molten sapphire, and pouring said molten sapphire into said mold heated to a temperature of at least 2,030* C.
Claim 10
Dependent Claim
20 words
The method of claim 1 wheRein said charging step includes placing pieces of solid alumina or sapphire in said mold.
Claim 11
Dependent Claim
57 words
The method of claim 1 wherein said heating step includes heating said mold and said charge therein by directing radiant heat laterally thereon; and wherein said directional crystallizing step includes cooling said mold and said molten sapphire in a generally upward direction by moving a heat shield upwardly adjacent said mold to progressively block said radiant heat.
Claim 12
Dependent Claim
67 words
The method of claim 1 wherein said heating step includes heating said mold and said charge therein in a first heating zone to a substantially uniform temperature of at least 2,030* C.; and wherein said directional crystallizing step includes cooling said mold and said sapphire in a generally upward direction by lowering the mold into a second heating zone where the temperature is less than 2,030* C.
Claim 13
Dependent Claim
81 words
The method according to claim 1 wherein a sapphire seed crystal is placed in the bottom inside of said mold to act as a nucleus for crystal growth in said directional cooling step, and including maintaining the bottom of said mold and the bottom portion of said sapphire seed crystal during said heating step at a lower temperature than the remainder of said mold and said crystal so as to prevent the bottom portion of said sapphire seed crystal from melting.
Claim 14
Independent Claim
196 words
A method of casting a sapphire crystal article having substantially no thermal tension which includes the steps of: heating an alumina or sapphire charge in a mold made of a metal from the group consisting of tungsten, molybdenum, iridium and rhenium in a first heating zone having a substantially uniform temperature of at least 2,030* C. to form a sapphire melt; directionally solidifying the sapphire melt in the mold in an upward direction from the bottom end to the top end along the mold by moving the mold into a second heating zone having a minimum temperature of less than 2,030* C. at such a rate that the generally vertical, downward temperature gradient of the sapphire in a transition zone between said first and said second heating zones is less than -25* C. per millimeter; directionally cooling the cast solidified sapphire, in the mold in an upward direction from the bottom end to the top end along the mold by moving the mold into a third heating zone having a substantially uniform temperature which is below 2,030* c. wherein the heating and the directional solidifying steps are conducted in a vacuum or an inert gas atmosphere.
Claim 15
Dependent Claim
24 words
The method of claim 15 wherein the second heating zone has a generally vertical, downward temperature gradient of less than -25* C. per millimeter
Claim 16
Dependent Claim
22 words
The method of claim 15 wherein said second heating zone has a minimum temperature between about 2,000* C. and about 1,500* C.
Claim 17
Dependent Claim
18 words
The method of claim 15 wherein said second heating zone has a minimum temperature of about 1,800* C.
Claim 18
Dependent Claim
28 words
The method of claim 15 wherein said heating step, said directional solidifying step, and said directional cooling step are conducted in a vacuum of less than one torr.
Claim 19
Dependent Claim
33 words
The method of claim 15 wherein said heating step, said directional solidifying step, and said directional cooling step are conducted in an inert gas selected from the group consisting of helium and argon.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-20 | 1975-03-22 | 1975-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-20 | 1979-03-22 | 1979-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-20 | 1983-03-22 | 1983-09-21 | $7700.00 | Window Closed / Lapsed |