N141-038 TITLE: Coating for Electromagnetic / Radio Frequency Interference (EMI/RFI) Attenuation

TECHNOLOGY AREAS: Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: PMS500, DDG-1000 Zumwalt Class Destroyer Program Office.

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop innovative coating to attenuate Electromagnetic Interference/Radio Frequency Interference (EMI/RFI) without compromising required optical characteristics.

DESCRIPTION: Electronic signature control (REF #1) is one self-defense technique employed by the Navy. If the enemy can’t pick up the ships electronic signal, then they can’t target it. Therefore, the Navy needs to be able to attenuate EMI/RFI to control the ships electronic signature. The Navy also needs to be able to effectively use its own passive sensors to detect any threats. Metallic grids that are typically used to attenuate EMI/RFI diminish the ability of passive EO/IR sensors to detect potential threats. Sensors used for surveillance and fire-control need to be able to pass through windows unobstructed. For ships with stringent radar cross section (RCS) requirements, these EO/IR sensors need to be mounted behind RCS-compliant windows. Therefore, the Navy needs windows that will meet EMI/RFI requirements, while maintaining the ability to pass both visible and IR wavelengths for its own sensors.

New naval shipboard electro-optical sensor systems require large, strong, high optical quality windows that are transparent from 0.4 to 5 µm wavelengths (REF #2) and provide electromagnetic interference/radio frequency interference shielding of the sensor electronics.

The focus of this effort will be on shipboard Spinel windows. Current state of the art shielding accomplished by using metal grids produces undesirable optical attenuation, diffraction, and reflections and as such is unsuitable for this planned application.

A continuous, conductive coating that is transparent from 0.4 to 5 µm and has an electrical sheet resistance of <10 ohms/square could provide the needed shielding. The conductive coating must be part of a coating stack of layers that includes an antireflection coating that provides at least 68% transmission at incident angles up to 60° in selected bands from 0.4 to 5 µm for a fully coated window. No currently existing coating provides both the electrical and optical properties required (REF #3).

If the conductive coating is on the outer surface of the sensor window coating stack, it must survive shipboard salt spray and salt fog, abrasion by blowing and wave-borne particles, hail impact, and solar irradiation.

Coatings demonstrated in this effort must be scalable to deposition on 19" x 27" spinel windows. Proposals to use graphene, carbon nanotubes, or metal nanowires must provide experimental evidence that these materials can meet the optical and electrical requirements simultaneously. Previous attempts to use these materials have failed to meet all requirements simultaneously.

PHASE I: The company will develop a concept for a coating to attenuate Electromagnetic Interference/Radio Frequency Interference (EMI/RFI) that meets the requirements described above. The company will demonstrate the feasibility of the concept in meeting Navy needs and will establish that the concept can be feasibly developed into a useful product for the Navy. Feasibility will be established by material testing and analytical modeling. The small business will provide a Phase II development plan that addresses technical risk reduction and provides performance goals and key technical milestones.

PHASE II: Based on the results of Phase I and the Phase II development plan, the small business will develop a prototype for evaluation. The prototype will be evaluated to determine its capability in meeting the performance goals defined in Phase II development plan and the Navy requirements for the coating to attenuate Electromagnetic Interference/Radio Frequency Interference (EMI/RFI). System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters including numerous deployment cycles. Evaluation results will be used to refine the prototype into an initial design that will meet Navy requirements. The company will prepare a Phase III development plan to transition the technology to Navy use.

PHASE III: The company will be expected to support the Navy in transitioning the technology for Navy use. The company will coat spinel windows provided by the government. These windows will then be evaluated to determine their effectiveness in the operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the coated spinel windows for Navy use.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: In addition to the need for the DDG 1000 program, spinel windows can be used in a number of other applications, such as missile and aircraft EO/IR apertures, submarine periscopes, and directed energy weapon apertures. EMI/RFI coatings such as those developed under this topic would have applicability to all of those applications. In addition, optically transparent, electrically conductive coatings could become components of photovoltaic cells.

REFERENCES:
1. Chief of Naval Operations, OPNAV INSTRUCTION 9070.2A, September, 12, 2012, <http://www.scribd.com/doc/106520314/Navy-Signature-Control-of-Ships-and-Craft-Opnav-9070-2a> Retrieved May 13, 2013

2. R. G. Gordon, "Criteria for Choosing Transparent Conductors," MRS Bulletin, 2000, Volume 25[8], p. 52. <http://www-chem.harvard.edu/groups/gordon/papers/Gordon_MRS_Bull.pdf> Retrieved May 13, 2013

3. L. Castañeda, "Present Status of the Development and Application of Transparent Conductors Oxide Thin Solid Films," Materials Sciences and Applications, Vol. 2 No. 9, 2011, pp. 1233-1242. doi: 10.4236/msa.2011.29167. Published Online September 2011. <https://www.google.com/#q=G.+Haacke,+%E2%80%9CTransparent+Conducting+Coatings,%E2%80%9D+Annual+Review+of+Materials+Science,+Vol.+7,+August+1977,+pp.+73-93.+doi:10.1146/annurev.med.07.080177.000445&spell=1&sa=X&ei=9uCQUeKYIIrY9ASLzIGIBw&ved=0CC0QBSgA&bav=on.2,or.r_qf.&bvm=bv.46340616,d.eWU&fp=b749a25a4369e81d&biw=1093&bih=460> Retrieved May 13, 2013

4. A. J. Freeman, K. R. Poeppelmeier, T. O. Mason, R. P. H. Chang, and T. J. Marks, "Chemical and Thin-Film Strategies for New Transparent Conducting Oxides," MRS Bulletin, 2000, Volume 25[8], p. 45. <http://chemgroups.northwestern.edu/poeppelmeier/pubs/TCO/chemical_and_thin_film.pdf> Retrieved May 13, 2013

KEYWORDS: EMI/RFI attenuation; conductive coating; optical coating; electrically conductive coating; electromagnetic shielding; transparent conductive coating; electronic signature

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