USH1002H - Microwave absorbing material - Google Patents
Microwave absorbing material Download PDFInfo
- Publication number
- USH1002H USH1002H US07/509,670 US50967090A USH1002H US H1002 H USH1002 H US H1002H US 50967090 A US50967090 A US 50967090A US H1002 H USH1002 H US H1002H
- Authority
- US
- United States
- Prior art keywords
- absorbing material
- percent
- weight
- microspheres
- range
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000011358 absorbing material Substances 0.000 title claims abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 12
- 239000004005 microsphere Substances 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 10
- 239000011159 matrix material Substances 0.000 claims abstract description 7
- 229920001296 polysiloxane Polymers 0.000 claims abstract description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 6
- 229910052742 iron Inorganic materials 0.000 abstract description 3
- 230000035939 shock Effects 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 4
- 230000005855 radiation Effects 0.000 description 3
- 239000004593 Epoxy Substances 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
Definitions
- This invention pertains to a material for absorbing microwave radiation.
- Microwave absorbing materials are known in the prior art, but these are generally iron-filled and thus dense. Prior art material also tend to be unstable in a high radiation environment.
- hollow carbon microspheres in the range of sizes between 90 and 350 microns outside diameter are mixed uniformly in a matrix of flexible silicone such that the microspheres are 27 to 34 percent by weight of the absorbing material.
- the material is strongly absorbent in the range of frequencies 2500 to 6000 MHz.
- An important advantage of the present invention is the material is stock resistant, flexible and stable in thickness of 0.2 inches or greater.
- FIG. 1 shows plots of standing wave ratios as a function of frequency for varying thicknesses of the preferred embodiment of the material of the invention.
- the material according to the invention is formed by embedding hollow carbon microspheres in a suitable matrix material, such as a flexible silicone or an inflexible epoxy.
- a suitable matrix material such as a flexible silicone or an inflexible epoxy.
- the carbon microspheres have a preferable diameter between 90 and 350 microns.
- Carbon microspheres are available from Kureha Chemical Industries Co., Ltd., Tokyo, Japan and Versar, Inc., Springfield, Va.
- Suitable flexible silicone matrix materials include Dow-Coming RTV 3112, Dow-Coming Sylgard 184, and General Electric Silicone 566A.
- Sylgard 184 is preferred because it (a) has a good radiation resistance, (b) has low shrinkage during curing, (c) bonds well to a substrate, and (d) needs no post-cure before use.
- compositions containing from 27 weight percent microspheres to 34 percent by weight microspheres are best. Although compositions over this range have been tested and found satisfactory, the composition containing 30.0 percent by weight carbon spheres in Sylgard 184 is preferred. This composition has a satisfactory mechanical integrity and flexibility in thicknesses of 0.2 inches and greater.
- the density of the preferred embodiment is 0.48 g/cm 3 . In a thickness of 0.22 inches, this corresponds to 0.55 pounds per square foot.
Landscapes
- Compositions Of Macromolecular Compounds (AREA)
Abstract
A microwave absorbing material for the range 2500-6000 MHz is formed by using hollow carbon microspheres in the range of sizes between 90 and 350 microns outside diameter mixed unformly in a matrix of flexible silicone such that the microspheres are 27 to 34 percent by weight of the absorbing material. An important advantage of the present invention is the material contains no iron, is shock resistant, flexible and stable in thicknesses of 0.2 inches or greater.
Description
This invention pertains to a material for absorbing microwave radiation.
Microwave absorbing materials are known in the prior art, but these are generally iron-filled and thus dense. Prior art material also tend to be unstable in a high radiation environment.
It is therefore a primary objective of the present invention to provide a stable low-density material for absorbing microwave energy in the 2500 to 6000 MHz band.
These objects of the invention and other objects, features and advantages to become apparent as the specification progresses are accomplished by the invention according to which, briefly stated, hollow carbon microspheres in the range of sizes between 90 and 350 microns outside diameter are mixed uniformly in a matrix of flexible silicone such that the microspheres are 27 to 34 percent by weight of the absorbing material.
The material is strongly absorbent in the range of frequencies 2500 to 6000 MHz.
An important advantage of the present invention is the material is stock resistant, flexible and stable in thickness of 0.2 inches or greater.
For many applications, the most important advantage is its low density compared to iron-loaded composites.
These and further objectives, constructional and operational characteristics, and advantages of the invention will no doubt be more evident to those skilled in the art from the detailed description given hereinafter which illustrates a preferred embodiment by way of non-limiting example.
FIG. 1 shows plots of standing wave ratios as a function of frequency for varying thicknesses of the preferred embodiment of the material of the invention.
The material according to the invention is formed by embedding hollow carbon microspheres in a suitable matrix material, such as a flexible silicone or an inflexible epoxy. The carbon microspheres have a preferable diameter between 90 and 350 microns. Carbon microspheres are available from Kureha Chemical Industries Co., Ltd., Tokyo, Japan and Versar, Inc., Springfield, Va. Suitable flexible silicone matrix materials include Dow-Coming RTV 3112, Dow-Coming Sylgard 184, and General Electric Silicone 566A. Sylgard 184 is preferred because it (a) has a good radiation resistance, (b) has low shrinkage during curing, (c) bonds well to a substrate, and (d) needs no post-cure before use. Compositions containing from 27 weight percent microspheres to 34 percent by weight microspheres are best. Although compositions over this range have been tested and found satisfactory, the composition containing 30.0 percent by weight carbon spheres in Sylgard 184 is preferred. This composition has a satisfactory mechanical integrity and flexibility in thicknesses of 0.2 inches and greater.
When backed by a metal plate, i.e., shorted, 0.026 inches thick material of the preferred embodiment displayed the followings standing wave ratios (SWR):
______________________________________
MHz SWR
______________________________________
2600 3.84
3000 2.03
3400 1.39
3800 1.67
4200 2.18
4600 2.70
5000 3.28
5400 3.82
6000 4.30
______________________________________
The density of the preferred embodiment is 0.48 g/cm3. In a thickness of 0.22 inches, this corresponds to 0.55 pounds per square foot.
Another embodiment containing 33.1 percent by weight carbon spheres in RTV 3112 with a thickness of 0.267 inches provided the following standing wave ratios:
______________________________________
MHz SWR
______________________________________
2400 2.25
2600 1.52
2800 1.31
3000 1.61
3200 2.02
3400 1.98
3600 1.88
3800 1.98
4000 2.10
5000 3.65
______________________________________
Another embodiment containing 32.9 percent by weight carbon sphere in Silicone 566A with a thickness of 0.263 inches yielded the following standing wave ratios:
______________________________________
MHz SWR
______________________________________
2400 2.24
2600 1.61
2800 1.42
3000 1.60
3200 1.90
3400 2.25
3600 2.60
3800 2.93
4000 3.29
______________________________________
This invention is not limited to the preferred embodiment and alternatives heretofore described, to which variations and improvements may be made, without departing from the scope of protection of the present patent and true spirit of the invention, the characteristics of which are summarized in the following claims.
Claims (3)
1. A microwave absorbing material for the range 2500 to 6000 MHz, comprising:
a matrix of flexible silicone, forming 66 to 73 percent by weight of the absorbing material,
hollow carbon microspheres having a range of sizes between 90 and 350 microns outside diameter, said microspheres being mixed uniformly into said matrix to form 27 to 34 percent by weight of the absorbing material.
2. The material of claim 1 wherein said matrix material comprises approximately 70 percent by weight of the absorbing material and said hollow carbon microspheres comprise approximately 30 percent by weight of the absorbing material.
3. The material of claim 2 wherein said material is formed into sheets of thickness 0.2 inches or greater.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/509,670 USH1002H (en) | 1990-04-16 | 1990-04-16 | Microwave absorbing material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/509,670 USH1002H (en) | 1990-04-16 | 1990-04-16 | Microwave absorbing material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USH1002H true USH1002H (en) | 1991-12-03 |
Family
ID=24027618
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/509,670 Abandoned USH1002H (en) | 1990-04-16 | 1990-04-16 | Microwave absorbing material |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | USH1002H (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030062641A1 (en) * | 2001-08-16 | 2003-04-03 | Niraj Vasishtha | Microencapsulation using electromagnetic energy and core and shell materials with different dielectric constants and dissipation factors |
| US20030062722A1 (en) * | 2001-08-21 | 2003-04-03 | Linhart Georg Peter | Hose line with a connection sleeve |
| US7869216B2 (en) | 2008-08-25 | 2011-01-11 | Honeywell International Inc. | Composite avionics chassis |
| CN117353046A (en) * | 2023-12-05 | 2024-01-05 | 南昌大学 | A hollow multi-layer composite electromagnetic wave-absorbing material and its preparation method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2877286A (en) | 1955-06-13 | 1959-03-10 | Cs 13 Corp | Radiant energy shielding device |
| US2996710A (en) | 1945-09-20 | 1961-08-15 | Du Pont | Electromagnetic radiation absorptive article |
| US3951904A (en) | 1973-03-07 | 1976-04-20 | Kureha Kagaku Kogyo Kabushiki Kaisha | Electromagnetic wave absorbing material containing carbon microspheres |
| US4003840A (en) | 1974-06-05 | 1977-01-18 | Tdk Electronics Company, Limited | Microwave absorber |
| US4112179A (en) | 1975-12-10 | 1978-09-05 | Maccalous Joseph W | Method of coating with ablative heat shield materials |
| US4116906A (en) | 1976-06-09 | 1978-09-26 | Tdk Electronics Co., Ltd. | Coatings for preventing reflection of electromagnetic wave and coating material for forming said coatings |
-
1990
- 1990-04-16 US US07/509,670 patent/USH1002H/en not_active Abandoned
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2996710A (en) | 1945-09-20 | 1961-08-15 | Du Pont | Electromagnetic radiation absorptive article |
| US2877286A (en) | 1955-06-13 | 1959-03-10 | Cs 13 Corp | Radiant energy shielding device |
| US3951904A (en) | 1973-03-07 | 1976-04-20 | Kureha Kagaku Kogyo Kabushiki Kaisha | Electromagnetic wave absorbing material containing carbon microspheres |
| US4003840A (en) | 1974-06-05 | 1977-01-18 | Tdk Electronics Company, Limited | Microwave absorber |
| US4112179A (en) | 1975-12-10 | 1978-09-05 | Maccalous Joseph W | Method of coating with ablative heat shield materials |
| US4116906A (en) | 1976-06-09 | 1978-09-26 | Tdk Electronics Co., Ltd. | Coatings for preventing reflection of electromagnetic wave and coating material for forming said coatings |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030062641A1 (en) * | 2001-08-16 | 2003-04-03 | Niraj Vasishtha | Microencapsulation using electromagnetic energy and core and shell materials with different dielectric constants and dissipation factors |
| US6881482B2 (en) | 2001-08-16 | 2005-04-19 | Southwest Research Institute | Microencapsulation using electromagnetic energy and core and shell materials with different dielectric constants and dissipation factors |
| US20030062722A1 (en) * | 2001-08-21 | 2003-04-03 | Linhart Georg Peter | Hose line with a connection sleeve |
| US7869216B2 (en) | 2008-08-25 | 2011-01-11 | Honeywell International Inc. | Composite avionics chassis |
| CN117353046A (en) * | 2023-12-05 | 2024-01-05 | 南昌大学 | A hollow multi-layer composite electromagnetic wave-absorbing material and its preparation method |
| CN117353046B (en) * | 2023-12-05 | 2024-06-04 | 南昌大学 | A hollow multilayer composite electromagnetic absorbing material and preparation method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AS | Assignment |
Owner name: UNITED STATES OF AMERICA, THE, AS REPRESENTED BY T Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. SUBJECT TO LICENSE RECITED;ASSIGNOR:HAHN, HAROLD T.;REEL/FRAME:005279/0803 Effective date: 19900412 |
|
| STCF | Information on status: patent grant |
Free format text: PATENTED CASE |