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Highly conductive brominated graphitic fibers for infrared and centimeter-wave electromagnetic attenuation


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 3.5 of the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: To develop a high performing infrared and centimeter-wave attenuating graphitic fiber with improved conductivity through heat treatment and bromination. DESCRIPTION: To maintain operational overmatch of our near-peers, signature management needs to be exploited to the greatest limits of science. Obscuration leverages our resources by protecting multi-million dollar assets with cost-effect aerosol materials. Recent discoveries have illustrated the ability to vastly increase the performance of these obscurants in the infrared and centimeter-wave regions of the electromagnetic spectrum– both areas in which our enemies use imagers to identify our warfighter’s locations. This topic focuses on these developments of carbonaceous-based obscurant materials in the form of fibers, either fractal-quasilinear or linear. Due to the recent improved understanding of the significant impact heat treatment and bromination make on conductivity, and thereby efficiency, STTR is the preferred pathway to ensure success among small business and university partnerships (references 5-7). Graphitic particles have long been recognized as obscurants. Such particles can be produced by graphitization of polymers, for example, or from fibrous forms, already nominally graphitic. One cost-effect, scalable approach may be through electrospinning and subsequent heat-treating of these particles. Further bromination of these particles has been illustrated to improve the conductivity above 10^5 mho/cm—a factor that vastly improves obscuration performance. Produced in this way, a low-cost, high performing, high strength material that will not fuse or agglomerate upon compression can be realized. PHASE I: Demonstrate with 50 milligram or greater quantities, an ability to produce graphitized fibers using high heat treatments in the range of 2800-3000oC on nominal graphite or polymeric material. For IR fibers optical measurements and/or electrical conductivity will be used to determine the success of the heat treatments while for CMW fibers, both optical and electrical measurements (equivalents) will be used. Following successful heat treatments, the graphite fibers should be brominated and additional enhancement of conductivity remeasured for both wavelengths. PHASE II: Demonstrate that the process is scalable by providing 1 kilogram of samples with no loss in performance from that achieved with the small samples. During Phase II, idealized particle lengths and widths should be achieved for infrared (3-5 µm in lengths, 50-100 nm diameters) and centimeter-wave (one cm or greater in length, 4-10 µm diameters) attenuation. In Phase II, a design of a manufacturing process to commercialize the concept should be developed. PHASE III DUAL USE APPLICATIONS: The techniques developed in this program can be integrated into current and future military obscurant applications. Improved grenades and other munitions are needed to reduce the current logistics burden of countermeasures to protect the soldier and associated equipment. This technology could have application in other Department of Defense interest areas including high explosives, fuel/air explosives and decontamination. Improved separation techniques can be beneficial for all powdered materials in the metallurgy, ceramic, pharmaceutical and fuel industries. Industrial applications could include electronics, fuel cells/batteries, furnaces and others. REFERENCES: 1. Jelinek Al V., Charles W. Bruce and Sharhabeel Alyones, “Absorption Coefficient of Moderately Conductive Fibrous Aerosols at 35 GHz,” Applied Physics, 2021. 2. S. Alyones, C. W. Bruce and A. Buin, “Numerical Methods for Solving the Problem of Electromagnetic Scattering by a Thin Finite Conducting Wire,” IEEE Trans. Antennas and Propagation,” 55, (June 2007). 3. C. W. Bruce, Al V. Jelinek, Sheng Wu, Sharhabeel Alyones and Qingsong Wang, "Millimeter Wavelength Investigation of Fibrous Aerosol Absorption and Scattering Properties,” Appl. Opt., 43, (20 Dec. 2004). 4. Chen, Y., Zhang, X., Liu, E., He, C., Shi, C., Li, J., Nash, P., Zhao, N., “Fabrication of in-situ grown graphene reinforced Cu matrix composites”, Scientific Reports 6, 19363, 2016. 5. Ping Wang; Dandan Liu; Jingyun Zou; Yuanhang Ye; Ligan Hou; Jingna Zhao; Chuanling Men; Xiaohu Zhang; Qingwen Li, “Gas infiltration of bromine to enhance the electrical conductivity of carbon nanotube fibers,” Materials & Design, Volume 159, p138-144; 2018. 6. Wonsik Eom, Sang Hoon Lee, Hwansoo Shin, Woojae Jeong, Ki Hwan Koh, and Tae Hee Han*, “Microstructure-Controlled Polyacrylonitrile/Graphene Fibers over 1 Gigapascal Strength.” ACS Nano 2021, 15, 8, 13055–13064, 2021. 7. Fogg,J.L., Putman, K.J.,Zhang, T., Lei, Y.,Terrones, M., Harris, P.J.Marks, N.A., Suarez-Martinez, I. Catalysis-free transformation of non-graphitising carbons into highly crystalline graphite.” Communications Materials, 1,47, 2020. KEYWORDS: High conductivity, graphene, infrared obscuration, bromination
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