Development of Pyrophoric Foam Materials for Environmentally-Benign Pyrotechnics

Dr. Zhaohua Luan | U.S. Army RDECOM-Army Research, Development and Engineering Center (ARDEC)

WP19-1105

Objective

Pyrophoric iron materials have long been used as the primary charge in pyrotechnic devices, such as pyrophoric penetrators, ammunition training round markers, and aerial decoy devices against heat-seeking missiles [1, 2]. For example, a known type of decoy device is reportedly constructed with steel foils coated with nanosized iron particles [3]. The process to produce the foil materials and fabricate the finished items, however, is considered too corrosive and cost-prohibitive with serious reproducibility issues. Furthermore, the residue left on the test ranges is notoriously difficult to collect and often becomes an environmental hazard. To address these environmental problems, pyrophoric foam materials have been developed at the US Army Combat Capabilities Development Command Armaments Center as a viable replacement for these energetic materials [4, 5]. The foams are produced via a patented “one-pot” synthesis process from wheat flour and iron oxalate hydrate, both of which are environmentally benign, and the end products upon exposure to air are merely iron oxide and carbon dioxide, which are natural to the environment. The primary focus of this effort has been the optimization of the synthesis process and the scale-up production of the pyrophoric foam materials to facilitate the development of viable decoy prototypes. The environmental impact of both the precursor chemicals and life-cycle end products from those prototypes were also examined.

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Technical Approach

The effort was carried out as three separate but parallel tasks to address a number of technical challenges. These include (1) synthesis optimization and scale-up production of the pyrophoric foam materials at a meaningful scale without employment of any hazardous chemicals or processes; (2) development of new prototypes and loading techniques for the pyrophoric foam materials while still conforming to the existing requirements/configurations for deployment; (3) preliminary assessment of environmental impact of the precursor materials and/or the end products.

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Interim Results

Among many material characterization techniques, a novel in-situ flow calorimeter has been developed in-house to examine the time-resolved energetic properties of the pyrophoric foam material as functions of composition, dimension, activation temperature and duration, as well as of flow dynamics in the air. This led to the establishment of a quantitative baseline for the synthesis process, and the characteristically defined pyrophoric foam materials were thus produced in large quantities to support the prototyping of new decoy devices. In addition, two more patent-pending technologies were developed to address issues associated with the granulation of the foam materials into desirable sizes and shapes, and with the loading techniques to maintain the proper mechanical and pyrophoric properties. The new decoy prototypes have been subjected to a series of proof-of-concept, designs of experiment, setback, and flight tests with satisfactory results. A preliminary sustainability analysis concluded that both the precursor chemicals and end products were environmentally benign.

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Benefits

The Army is currently seeking novel or improved materials solutions to deal with increasing and emerging aerial threats while also addressing the significant environmental concern associated with the conventional magnesium/Teflon, or MTV based formulations. The newly-discovered pyrophoric foam material possesses advantageous physiochemical properties and is environmentally-benign throughout its life-cycle. As such, this material could be used to fabricate improved pyrotechnic systems.

References:

[1]    Huber, D. L. Small, 2005, 1(5), 482-501.

[2]    Koch, E. -C. Propellants, Explos., Pyrotech. 2006, 31(1), 3-19.

[3]    Gash, A. E.; Satcher, J. H. JR.; Simpson, R. L. US Pat. Appl. 0139823 A1, 2010.

[4]    Luan Z.; Mills, K.C.; Morris, L.A.; Haines, C. D. US Pat. 10 059 637, 2018.

[5]    Luan, Z.; Zimmer, A.; Latalladi, E.; Chu, P.; Motyka, M. D.; Chen, G.; Broad, R. Development of Low Visibility First Fire Compositions for M206 Aircraft Countermeasure Flares (ARMET-TR-12061); U.S. Army CDCC - Armaments Center: Picatinny Arsenal, NJ, 2014.

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Points of Contact

Principal Investigator

Dr. Zhaohua Luan

U.S. Army RDECOM-Army Research, Development and Engineering Center (ARDEC)

Phone: 973-724-8041

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