US4279657A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light-transmitting silicon nitride
Assignee: Lockheed Martin Corp
•
Filing: 1980-01-30
•
Granted: 1981-07-21
•
Expires: 2000-01-30
Abstract
Abstract A polycrystalline silicon nitride body having a density of at least 99.5% of the theoretical density of silicon nitride, a thickness ranging from about 0.15 mm up to but less than 0.4 mm, a minimum in-line transmission of about 1% of radiant energy at wavelengths ranging from about 1.6 microns to about 5.0 microns.
Inventors
- 👤 Charles D. Greskovich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 03:56
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
168 words
A light-transmitting polycrystalline silicon nitride body having a density of at least 99.5% of the theoretical density of silicon nitride and consisting essentially of silicon nitride, magnesium and oxygen, said silicon nitride ranging from the β-form to a mixture of the α- and β-forms wherein the β-form is present in excess of 50% by weight of the total amount of said silicon nitride, said magnesium being present in an amount ranging from about 0.4% by weight to less than about 2.0% by weight of said body, said oxygen being present in an amount ranging from about 2.5% up to about 5% by weight of said body, said polycrystalline body consisting of a primary phase and up to about 5% by volume of said body of a secondary phase, said body having a thickness ranging from about 0.15 millimeter up to but less than about 0.4 millimeter, and a minimum in-line transmission of about 1% of radiant energy at wavelengths ranging from about 1.6 microns to about 5.0 microns.
Claim 2
Dependent Claim
168 words
A light-transmitting polycrystalline silicon nitride body having a density of at least 99.5% of the theoretical density of silicon nitride and consisting essentially of silicon nitride, magnesium and oxygen, said silicon nitride ranging from the β-form to a mixture of the α- and β-forms wherein the β-form is present in excess of 50% by weight of the total amount of said silicon nitride, said magnesium being present in an amount ranging from about 0.4% by weight to less than about 2.0% by weight of said body, said oxygen being present in an amount ranging from about 2.5% up to about 5% by weight of said body, said polycrystalline body consisting of a primary phase and up to about 5% by volume of said body of a secondary phase, said body having a thickness ranging from about 0.15 millimeter up to but less than about 0.4 millimeter, and a minimum in-line transmission of about 1% of radiant energy at wavelengths ranging from about 1.6 microns to about 5.0 microns.
Claim 3
Dependent Claim
16 words
A light-transmitting polycrystalline silicon nitride body according to claim 1 in the form of a plate.
Claim 4
Dependent Claim
17 words
A light-transmitting polycrystalline silicon nitride body according to claim 1 wherein said thickness is about 0.2 millimeter.
Claim 5
Dependent Claim
30 words
A light-transmitting polycrystalline silicon nitride body according to claim 1 wherein said magnesium is present in an amount ranging from about 0.5% by weight up to about 1.2% by weight.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-07-20 | 1985-01-19 | 1985-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-07-20 | 1989-01-19 | 1989-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-07-20 | 1993-01-19 | 1993-07-21 | $7700.00 | Window Closed / Lapsed |