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US4414176A
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First wall and limiter surfaces for plasma devices
Assignee: United States Department of Energy
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Filing: 1981-06-01
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Granted: 1983-11-08
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Expires: 2001-06-01
Abstract
Abstract For a plasma device, a surface of a first wall or limiter with reduced loss of metal by erosion is provided by forming a monolayer of an alkali or alkaline earth metal on a substrate of a more negative metal. The surface exhibits a reduced loss of metal by erosion and particularly by sputtering and an increased secondary ion/neutral ratio resulting in a greater return of atoms escaping from the surface. In another aspect of the invention, the substrate includes a portion of the second metal and serves to replenish the surface layer with atoms of the second metal. In one process associated with self-generating desired surface, the metals as an alloy are selected to provide a first layer having a high concentration of the second metal in contrast to a very low concentration in the second layer and bulk to result in a surface with a monolayer of the second metal. When the combination of metals results in an intermetallic compound, selective removal of the first metal during an initial bombardment stage provides the surface layer with a predominance of the second metal.
Inventors
- 👤 Alan R. Krauss
- 👤 Dieter M. Gruen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 23:17
CPC Classifications
G; G21; G21B; G21B1/00; G21B1/11; G21B1/13; Y; Y02; Y02E; Y02E30/00; Y02E30/10
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
156 words
In a plasma device, a metallic member exhibiting reduced erosion when exposed to plasma at an elevated temperature, the member comprising: a metallic substrate composed of a first metal and a protective thin surface layer on the substrate, the surface layer comprising at least about 90 atomic percent of a second metal selected from the group consisting of alkali and alkaline earth metals, the first metal being more electronegative than the second metal, the surface layer being characterized by atoms of the second metal having ionic bonds to atoms of the first metal in the substrate and forming a higher ratio of secondary ions to neutrals than atoms of the second metal in bulk form when exposed to said plasma, and the binding energy between atoms of the first and second metal being below the binding energy between like atoms of the first metal and above the binding energy between like atoms of the second metal.
Claim 2
Dependent Claim
156 words
In a plasma device, a metallic member exhibiting reduced erosion when exposed to plasma at an elevated temperature, the member comprising: a metallic substrate composed of a first metal and a protective thin surface layer on the substrate, the surface layer comprising at least about 90 atomic percent of a second metal selected from the group consisting of alkali and alkaline earth metals, the first metal being more electronegative than the second metal, the surface layer being characterized by atoms of the second metal having ionic bonds to atoms of the first metal in the substrate and forming a higher ratio of secondary ions to neutrals than atoms of the second metal in bulk form when exposed to said plasma, and the binding energy between atoms of the first and second metal being below the binding energy between like atoms of the first metal and above the binding energy between like atoms of the second metal.
Claim 3
Dependent Claim
15 words
In a plasma device, the member of claim 1 wherein surface layer is a monolayer.
Claim 4
Dependent Claim
17 words
In a plasma device, the member of claim 1 wherein the second metal is an alkali metal.
Claim 5
Dependent Claim
15 words
In a plasma device, the member of claim 3 wherein the second metal is lithium.
Claim 6
Dependent Claim
15 words
In a plasma device, the member of claim 3 wherein the second metal is potassium.
Claim 7
Dependent Claim
15 words
In a plasma device, the member of claim 3 wherein the second metal is cesium.
Claim 8
Dependent Claim
18 words
In a plasma device, the member of claim 1 wherein the second metal is an alkaline earth metal.
Claim 9
Dependent Claim
15 words
In a plasma device, the member of claim 7 wherein the second metal is barium.
Claim 10
Dependent Claim
15 words
In a plasma device, the member of claim 1 wherein the first metal is aluminum.
Claim 11
Dependent Claim
15 words
In a plasma device, the member of claim 3 wherein the first metal is gold.
Claim 12
Dependent Claim
52 words
In a plasma device, the member of claim 1 wherein the substrate is composed of the first metal in a major amount and the second metal in a minor amount, the second metal migrating to the surface during exposure of the surface to said plasma to replenish second metal lost by erosion.
Claim 13
Dependent Claim
21 words
In a plasma device, the member of claim 11 wherein a portion of the second metal is adjacent the surface layer.
Claim 14
Dependent Claim
24 words
In a plasma device, the member of claim 11 wherein the minor amount ranges from a small yet effective amount to about 20 at.%.
Claim 15
Dependent Claim
70 words
In a plasma device, a metallic member exhibiting reduced erosion when exposed to plasma at an elevated temperature, the member comprising a bulk portion composed of first and second metals, and a surface layer composed of a second metal, a portion of the second metal on the surface being lost during exposure to said plasma, and the bulk portion providing second metal at said surface to reform said surface layer.
Claim 16
Dependent Claim
70 words
In a plasma device, a metallic member exhibiting reduced erosion when exposed to plasma at an elevated temperature, the member comprising a bulk portion composed of first and second metals, and a surface layer composed of a second metal, a portion of the second metal on the surface being lost during exposure to said plasma, and the bulk portion providing second metal at said surface to reform said surface layer.
Claim 17
Dependent Claim
41 words
In a plasma device, the metallic member of claim 14 wherein said second metal is selected from the group consisting of an alkali metal and barium and is capable of producing a high secondary ion yield when exposed to particle radiation.
Claim 18
Dependent Claim
31 words
In a plasma device, the metallic member of claim 14 wherein said second metal has a low atomic number and is selected from the group consisting of lithium, sodium, and potassium.
Claim 19
Independent Claim
122 words
A method of providing a self-sustaining surface of a metallic member in a plasma device, comprising the steps of: providing a structural member composed of an alloy of first and second metals, the first metal being more electronegative than the second metal with the second metal being selected from the group consisting of alkali and alkaline earth metals, the first and second metals having a binding energy between different atoms above the energy for like atoms of the second metal and below the energy for like atoms of the first metal, and applying energy to the structural member sufficiently to cause atoms of the second metal to migrate to form a surface layer predominantly of the second metal and an underlying substrate.
Claim 20
Independent Claim
122 words
A method of providing a self-sustaining surface of a metallic member in a plasma device, comprising the steps of: providing a structural member composed of an alloy of first and second metals, the first metal being more electronegative than the second metal with the second metal being selected from the group consisting of alkali and alkaline earth metals, the first and second metals having a binding energy between different atoms above the energy for like atoms of the second metal and below the energy for like atoms of the first metal, and applying energy to the structural member sufficiently to cause atoms of the second metal to migrate to form a surface layer predominantly of the second metal and an underlying substrate.
Claim 21
Dependent Claim
24 words
The method of claim 17 wherein the step of applying energy is carried by applying heat to heat the substrate to an elevated temperature.
Claim 22
Dependent Claim
40 words
The method of claim 18 wherein the first and second metals satisfy the equation H.sub.1,2 =Ω+1/2(H.sub.1,1 +H.sub.2,2) where Ω≦0 and H is the enthalpy associated with the heat of sublimation of the alloy and of the first and second metals.
Claim 23
Dependent Claim
52 words
The method of claim 19 which includes the steps of exposing the first layer to plasma during which atoms of the second metal escape from the first layer, and continuing to apply energy to the substrate to cause atoms of the second metal in the substrate to migrate to the first layer.
Claim 24
Dependent Claim
30 words
The method of claim 20 which includes the step of providing an electromagnetic field to return a portion of the escaping atoms of the second metal to the surface layer.
Claim 25
Independent Claim
96 words
A method of providing a self-sustaining surface of a metallic member in a plasma device, comprising the steps of: providing a structural member composed of an intermetallic compound of a first metal and a second metal, the first metal being more electronegative than the second metal with the second metal being present in an amount not greater than about 70 at.%, and exposing the surface to plasma to selectively sputter atoms of the first metal to escape the surface thereby leaving a layer of the second metal and an underlying substrate collectively forming the metallic member.
Claim 26
Independent Claim
96 words
A method of providing a self-sustaining surface of a metallic member in a plasma device, comprising the steps of: providing a structural member composed of an intermetallic compound of a first metal and a second metal, the first metal being more electronegative than the second metal with the second metal being present in an amount not greater than about 70 at.%, and exposing the surface to plasma to selectively sputter atoms of the first metal to escape the surface thereby leaving a layer of the second metal and an underlying substrate collectively forming the metallic member.
References Cited (Backward Citations)
US3677326A
Cited
US4260455A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-07 | 1987-05-09 | 1987-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-07 | 1991-05-09 | 1991-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-07 | 1995-05-09 | 1995-11-08 | $7700.00 | Window Closed / Lapsed |