|
|
Library > Fact Sheets > Program Yields Lightweight, Highly Conductive Electromagnetic Shielding Coatings
PROGRAM YIELDS LIGHTWEIGHT, HIGHLY CONDUCTIVE ELECTROMAGNETIC SHIELDING COATINGS
Posted 3/23/2011
Printable Fact Sheet
Accomplishment: The Air Force Research Laboratory's Materials and Manufacturing Directorate completed a Small Business Innovation Research (SBIR) initiative with Conductive Composites Company that developed a suite of conductive nanostructured materials and coatings. These materials will help control the electromagnetic properties of materials and are especially critical in the development of High-Power Microwave and Directed Energy survivable structures.
Background: The most effective shielding material developed during the execution of this program is a NiCVD coated nonwoven carbon fiber broad good (such as a paper or cloth). This product is made by taking a continuous roll of carbon fiber broad good and coating it continuously by a nickel chemical vapor deposition reactor. Using this method, the outer surfaces of the fibers and the binders can be coated with a thin, uniform film of pure, ductile nickel. The film may be as thin as 50 nanometers, or as thick as a micron or two. A film of about 200 nanometers provides the most effective return for shielding applications. This process is performed on a reel-to-reel basis, with very high throughput capabilities. In addition, coating application for Kevlar, felts, foams and woven cloths is possible using this method. This NiCVD nonwoven material may be co-cured directly into laminate structures, or applied as a secondary operation.
Base carbon nonwoven materials are typically eight grams per square meter (gsm), and the nickel coating can be added in any range from two gsm to one hundred gsm. At a nickel weight of seven gsm (15 gsm total), the material affords approximately 55 decibels of broadband shielding effectiveness. These sheets can also be stacked, providing an additional 20 dB of shielding per layer. The nickel coated nonwoven is the thinnest, lightest and most effective shielding material that is currently commercially available, and matches the per-gram shielding efficiency of carbon nanotube sheets. For other applications, such as lightning strike protective material, nickel CVD coated materials present advantages over conventional materials.
Nickel CVD coated nonwoven material is available on a continuous roll basis. Rolls of a 28-inch width and several hundred feet in length are regularly produced on a pilot scale coater. The small pilot process is capable of producing 25 square feet an hour. These rates have resulted in product prices of dollars per square foot. The process is readily scalable to any width of reactor and any size of feed roll. Nickel CVD coated nonwovens provide a high performance lightweight conductivity and shielding solution for a wide range of composites applications. These materials are continuously available in a wide range of specifications.
Payoff: This SBIR program resulted in the fabrication of very lightweight, highly conductive carbon fiber composites. Materials developed were used to tailor the electromagnetic properties of polymer materials such as coatings, resins, adhesives, and elastomers. The ability to incorporate these conductive materials directly into a composite offers weight advantages, labor savings, fabrication time reduction, and also solves several challenges associated with previous methods that required foils and appliqués. Of the suite of materials made by Conductive Composite Company, nickel chemical vapor deposition (NiCVD) coated nonwoven materials are the first to reach continuous manufacturability. This combination of technological success and manufacturability has poised this product to become a standard material in the electromagnetic material designer's toolbox.
| |
|
|
|
|
