US4155758A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Lamps and discharge devices and materials therefor
Assignee: EMI Group Ltd
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Filing: 1976-12-08
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Granted: 1979-05-22
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Expires: 1996-12-08
Abstract
Abstract Conducting cermets with volume fractions of nickel down to 0.045 are produced by coating relatively coarse refractory oxide granules with fine metal powder particles and compacting and sintering the coated granules. Using oxide granules in the size range 400 to 800 microns it is possible to make conducting cermets having the same volume fraction of metal and thus the same thermal expansion coefficients as insulating cermets prepared from finer granules of the same oxide. The cermets can be used to fabricate tubes and components for electric lamps and may include integrally formed conducting and insulating regions.
Inventors
- 👤 David T. Evans
- 👤 Peter Hing
- 👤 Raymond Marshall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:45
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/71; H; H01; H01B; H01B1/00; H01J; H01J61/00; H01J61/02; H01J61/36
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
91 words
An electrically conducting cermet comprising refractory oxide granules having a mean diameter of about 800 microns or less and being formed as agglomerates of refractory oxide particles having diameters less than said mean diameter, said granules being surrounded by a thin layer of a B group metal of Group 4B to 7B or a metal of Group 8 of the Periodic System, which layer comprises particles of said metal having mean diameters which are substantially less than those of said granules, said layer constituting a conducting network extending through the cermet.
Claim 2
Dependent Claim
91 words
An electrically conducting cermet comprising refractory oxide granules having a mean diameter of about 800 microns or less and being formed as agglomerates of refractory oxide particles having diameters less than said mean diameter, said granules being surrounded by a thin layer of a B group metal of Group 4B to 7B or a metal of Group 8 of the Periodic System, which layer comprises particles of said metal having mean diameters which are substantially less than those of said granules, said layer constituting a conducting network extending through the cermet.
Claim 3
Dependent Claim
17 words
A cermet according to claim 1 wherein the volume fraction of metal is from 0.067 to 0.2.
Claim 4
Dependent Claim
19 words
A cermet according to claim 1 wherein the refractory oxide comprises alumina and the metal comprises tungsten or molybdenum.
Claim 5
Dependent Claim
17 words
A cermet according to claim 1 formed integrally with an insulating body comprising the same refractory oxide.
Claim 6
Dependent Claim
16 words
A cermat according to claim 1 formed as an end cap for an electric lamp envelope.
Claim 7
Dependent Claim
33 words
A cermet according to claim 1 wherein the mean diameter of the oxide granules is from 50 to 200 microns and the diameters of the oxide particles are about 50 microns or less.
Claim 8
Dependent Claim
38 words
A cermet according to claim 5 constituting a portion of an end cap for an electric lamp envelope, the remainder of said envelope being composed of an insulating cermet comprising the same refractory oxide and formed integrally therewith.
Claim 9
Dependent Claim
32 words
A cermet according to claim 4 formed as an end or longitudinal strip in an arc tube the remainder of said tube being composed of a ceramic comprising the same refractory oxide.
Claim 10
Independent Claim
76 words
A method of making a conducting cermet having thermal expansion characteristics closely matching those of an insulating ceramic or cermet comprising a refractory oxide, said method comprising the steps of: rolling together granules of said refractory oxide with fine particles of metal powder such that the metal particles coat the oxide granules; compacting said rolled granules; and sintering the resulting compact to form a cermet in which the metal coating constitutes a conducting network extending therethrough.
Claim 11
Independent Claim
76 words
A method of making a conducting cermet having thermal expansion characteristics closely matching those of an insulating ceramic or cermet comprising a refractory oxide, said method comprising the steps of: rolling together granules of said refractory oxide with fine particles of metal powder such that the metal particles coat the oxide granules; compacting said rolled granules; and sintering the resulting compact to form a cermet in which the metal coating constitutes a conducting network extending therethrough.
Claim 12
Dependent Claim
30 words
A method according to claim 9 wherein the oxide granules have a mean diameter of more than 50 microns and the metal particles are of at most 12 microns diameter.
Claim 13
Dependent Claim
30 words
A method according to claim 9 wherein the refractory oxide has a mean particle size of about 200 microns and the metal particles are of the order of 1 micron.
Claim 14
Dependent Claim
18 words
A method according to claim 11 wherein the volume fraction of the metal is not less than 0.067.
Claim 15
Dependent Claim
39 words
A method according to claim 11 including the step of compacting a body of particles of the same refractory oxide with said body of rolled particles, whereby on sintering a composite body is obtained having conducting and insulating regions.
Claim 16
Dependent Claim
30 words
A method according to claim 11 wherein said rolled granules are compacted under a pressure of 10,000 to 20,000 p.s.i. and sintered at a temperature of 1600° to 1800° C.
Claim 17
Dependent Claim
11 words
An electrically conducting cermet made by the method of claim 9.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-05-21 | 1982-11-20 | 1983-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-21 | 1986-11-20 | 1987-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-21 | 1990-11-20 | 1991-05-22 | $7700.00 | Window Closed / Lapsed |