US4686070A
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Method of producing aluminum oxynitride having improved optical characteristics
Assignee: Halliburton Co
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Filing: 1984-10-29
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Granted: 1987-08-11
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Expires: 2004-10-29
Abstract
Abstract A method of preparing substantially homogeneous aluminum oxynitride powder is provided comprising the steps of reacting gamma aluminum oxide with carbon in the presence of nitrogen, and breaking down the resulting powder into particles in a predetermined size range. A method of preparing a durable optically transparent body from this powder is also provided comprising the steps of forming a green body of substantially homogeneous cubic aluminum oxynitride powder and sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred additives are boron, in elemental or compound form, and at least one additional element selected from the group of yttrium and lanthanum or compounds thereof. The sintered polycrystalline cubic aluminum oxynitride has a density greater than 99% of theoretical density, an in-line transmission of at least 50% in the 0.3-5 micron range, and a resolving angle of 1 mrad or less.
Inventors
- 👤 Edward A. Maguire
- 👤 Thomas M. Hartnett
- 👤 Richard L. Gentilman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 22:03
CPC Classifications
C; C09; C09J; C09J161/00; C09J161/04; C09J161/06; C01; C01B; C01B21/00; C01B21/082; C01B21/0821; C01B21/0825; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/581; Y; Y10; Y10S; Y10S501/00; Y10S501/90; Y10S501/904
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
73 words
A method of preparing homogeneous aluminum oxynitride comprising the steps of: introducing aluminum oxide powder and carbon black into a reaction chamber with the carbon black content being in the range of 5.4 to 7.1 weight percent; providing nitrogen in said chamber; and heating said chamber at a temperature in the range of about 1550° to 2140° C. to react said powders and gas to produce a reacted powder substantially comprising aluminum oxynitride.
Claim 2
Independent Claim
73 words
A method of preparing homogeneous aluminum oxynitride comprising the steps of: introducing aluminum oxide powder and carbon black into a reaction chamber with the carbon black content being in the range of 5.4 to 7.1 weight percent; providing nitrogen in said chamber; and heating said chamber at a temperature in the range of about 1550° to 2140° C. to react said powders and gas to produce a reacted powder substantially comprising aluminum oxynitride.
Claim 3
Dependent Claim
41 words
The method of claim 1 wherein: said reacted powder may comprise up to 15 weight percent of aluminum oxide and aluminum nitride such that the ratio of aluminum oxide to aluminum nitride is within the composition range of cubic aluminum oxynitride.
Claim 4
Dependent Claim
22 words
The method of claim 2 wherein: said heating step occurs at a temperature in the range of 1550° C. to 1850° C.
Claim 5
Dependent Claim
99 words
The method of claim 1 wherein said heating step further comprises the steps of: heating said aluminum oxide powder, carbon black, and nitrogen to a temperature in the range of about 1550° C. to 1620° C. for a first predetermined period of time to convert said aluminum oxide carbon black and nitrogen into aluminum oxide and aluminum nitride; and heating said aluminum oxide and aluminum nitride to a temperature in the range of about 1750° C. to 2140° C. for a second predetermined period of time to convert said aluminum oxide and aluminum nitride into the homogeneous aluminum oxynitride.
Claim 6
Dependent Claim
41 words
The method of claim 4 wherein: said aluminum oxide has a purity of 99.98% and an average particle size of approximately 0.06 microns, and said carbon black has a purity of 97.6% and an average particle size of approximately 0.027 microns.
Claim 7
Dependent Claim
27 words
The method of claim 4 wherein during said second heating step said chamber is heated to a temperature in the range of 1750° C. to 1820° C..
Claim 8
Dependent Claim
39 words
The method of claim 5 wherein said first heating step occurs at a temperature of approximately 1550° C. for approximately an hour and said second heating step occurs at a temperature of approximately 1750° C. for approximately 40 minutes.
Claim 9
Dependent Claim
38 words
The method of claim 5 wherein: said first heating step occurs at a temperature of approximately 1620° C. for approximately one hour and said second heating step occurs at a temperature of 1820° C. for approximately 40 minutes.
Claim 10
Dependent Claim
53 words
The method of claim 6 wherein said first heating step further comprises the step of: converting temperature unstable gamma aluminum oxide present in the mixture into a temperature stable alpha aluminum oxide; and the second heating step comprises: reacting said converted mixture of alpha aluminum oxide and aluminum nitride to produce aluminum oxynitride.
Claim 11
Dependent Claim
27 words
The method of claim 2 further comprising the step of: milling said reacted powder to produce particles of size in the range of 0.5 to 5 microns.
Claim 12
Dependent Claim
34 words
The method of claim 10 further comprising the step of: heating said powder in air to a temperature less than about 600° C. until any organic contaminants present in the mixture are substantially removed.
Claim 13
Independent Claim
90 words
A method of preparing homogeneous aluminum oxynitride comprising the steps of: preparing a mixture of aluminum oxide and carbon black, the carbon content of said mixture being in the range of 5.4-7.1 weight percent; reacting in a flowing nitrogen atmosphere said mixture first at a temperature of approximately 1550° C. for one hour, and then at a temperature of at least 1750° C. for 40 minutes; and ball milling the reacted mixture to provide a powder having a particle size in the range of about 0.5 microns to 5 microns.
Claim 14
Independent Claim
90 words
A method of preparing homogeneous aluminum oxynitride comprising the steps of: preparing a mixture of aluminum oxide and carbon black, the carbon content of said mixture being in the range of 5.4-7.1 weight percent; reacting in a flowing nitrogen atmosphere said mixture first at a temperature of approximately 1550° C. for one hour, and then at a temperature of at least 1750° C. for 40 minutes; and ball milling the reacted mixture to provide a powder having a particle size in the range of about 0.5 microns to 5 microns.
Claim 15
Dependent Claim
35 words
The method of claim 12 further comprising the steps of: drying said powder; and heating said powder in air at a temperature of about 600° C. to remove any organic contaminants that might be present.
Claim 16
Independent Claim
122 words
A method of producing transparent sintered aluminum oxynitride bodies comprising the steps of: preparing a mixture of aluminum oxide and carbon black, the carbon black content of said mixture being in the range of 5.4 to 7.1 weight percent; reacting said mixture in the presence of nitrogen and at a temperature in the range of 1550°-1850° C.; forming a pressed green body of predetermined shape from said mixture; placing said green body in a sintering chamber; providing at least one dopant in said chamber, said dopant selected from the group consisting of yttrium, lanthanum, and compounds thereof; and sintering said green body in a nitrogen atmosphere at a temperature higher than 1900° C. but lower than the solidus temperature of aluminum oxynitride.
Claim 17
Independent Claim
122 words
A method of producing transparent sintered aluminum oxynitride bodies comprising the steps of: preparing a mixture of aluminum oxide and carbon black, the carbon black content of said mixture being in the range of 5.4 to 7.1 weight percent; reacting said mixture in the presence of nitrogen and at a temperature in the range of 1550°-1850° C.; forming a pressed green body of predetermined shape from said mixture; placing said green body in a sintering chamber; providing at least one dopant in said chamber, said dopant selected from the group consisting of yttrium, lanthanum, and compounds thereof; and sintering said green body in a nitrogen atmosphere at a temperature higher than 1900° C. but lower than the solidus temperature of aluminum oxynitride.
Claim 18
Dependent Claim
72 words
The method of claim 14 wherein said reacting step includes the steps of: reacting said mixture for a first predetermined time interval to convert said mixture into a second mixture comprising alpha-phase aluminum oxide and aluminum nitride and then reacting said second mixture at a temperature in the range of 1750° C. to 2140° C. for a second predetermined time interval to convert said second mixture into substantially single phase aluminum oxynitride.
Claim 19
Dependent Claim
20 words
The method of claim 14 wherein: said dopants are in a vapor phase during a portion of said sintering step.
Claim 20
Dependent Claim
19 words
The method of claim 14 wherein: in said sintering step, the dopants transport to and diffuse throughout said body.
Claim 21
Dependent Claim
19 words
The method of claim 17 wherein: said dopants produce a liquid phase at grain boundaries during said sintering step.
Claim 22
Dependent Claim
15 words
The method of claim 15 wherein: said doping additives are mixed in with said mixture.
Claim 23
Dependent Claim
19 words
The method of claim 19 wherein: said doping additives comprise not more than 0.5 weight percent of said mixture.
Claim 24
Dependent Claim
36 words
The method of claim 14 further comprising the steps of: breaking up the reacted mixture in particles of size in the range of 0.5 to 5 microns; and heating said reacted mixture to remove organic contaminants.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1990-08-10 | 1991-02-09 | 1991-08-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-10 | 1995-02-09 | 1995-08-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-10 | 1999-02-09 | 1999-08-11 | $7700.00 | Window Closed / Lapsed |