N141-072 TITLE: Deflagration Efficiencies in Metals

TECHNOLOGY AREAS: Materials/Processes, Weapons

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: The objective is to develop and define the properties affecting impact driven oxidative combustion of Aluminum (Al) and Tungsten (W) powder neat and as composites.

DESCRIPTION: Today�s ordnance fills often contain substantial quantities of Al and W micron size powders to enhance blast and momentum effects. These metal powders demonstrate high efficiencies in propulsion compositions, but do not provide similar combustion efficiencies during detonation or impact driven events. Innovative processing technology is sought to better define the scope and limitations of metal particle combustion efficiencies and to identify the material properties that can be manipulated to enhance measured energy release. Methodologies that provide Al or W metal composites resulting in high combustion (50-80%) efficiency within a 0.5-15 ms time frame are of interest. The improvements in combustion efficiency of micron sized metal composites should be stable with time and environmental exposure. Any processes must be fully described and should be sufficiently adaptable and scalable for production of well characterized materials.

During deflagration, Al contributes only 10 to 25% of its potential energy output, and W provides no measured enhancements. Recent Army Research Lab publications indicate shear phenomena in nanostructured W may provide a pathway to higher combustion efficiencies. Doping Al with various metals results in lowered ignition temperatures, a potential route to enhanced energy release mechanisms. Other combinations of work�harden technologies (mechanochemistry) may provide insight into the ignition and growth process for these metals.

PHASE I: This topic in Phase I strives to: (1) Identify properties and mechanisms that increase energy release rates and combustion efficiencies of shock/impact initiated of aluminum and tungsten; (2) Develop and define concepts which will increase combustion efficiencies of aluminum and tungsten; (3) Provide experimental and test data supporting hypotheses.

PHASE II: Based on the Phase I effort, demonstrate and validate the concept identified for improving the impact initiated combustion efficiency of aluminum and tungsten both neat and in formulations to be identified. Deliver samples of the prototype solutions to the government for test and evaluation in a government laboratory. Work under Phase II might be classified.

PHASE III: Utilizing the concept successfully demonstrated in Phase II, warhead components (cases or preformed fragments) will be manufactured and delivered to government laboratories and/or system integrators for evaluation in weapon applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Pressed metallic powder formulations have a range of uses beyond those relevant to the military. The ability to more readily combust Aluminum or Tungsten in commercial pyrotechnic devices could lead to their use in place of more expensive or more sensitive materials.

REFERENCES:
1. Ames, R.G., "Vented Chamber Calorimetry for Impact-Initiated Energetic Materials", AIAA Aerospace Sciences Meeting, Reno, NV, January, 2005.

2. Graham,R.A., Anderson,M.U., Holman,G.T. and Baer,M.R., "Prediction of Violent Mechanochemical Processes", SAND97-0038, January, 1997.

3. Jennrich, A., Delaney,C., Clemenson,M., Krier,H., and Glumac,N., "Rapid combustion of Tungsten in W/Zr Mechanical Alloys", Spring Technical Meeting of the Central States Section of the Combustion Institute, April, 2012.

4. Tucker, M., "Characterization of Impact Initiation of Aluminum-Based Intermetallic-Forming Reactive Materials", MSc Thesis Georgia Institute of Technology, December, 2011.

5. Dreizin,E.L., Schoenitz,M., Mohan,S., Santhanam.P., and Gill,R., "Mechanisms of Aluminum Ignition and Combustion in Different Environments", National Capital Region Energetics Symposium, April, 2009.

6. Hooper, J., "Impact fragmentation of aluminum reactive materials", J. Appl. Phys. 112, 043508 (2012);

7. Nesterenko,V.F, Po-Hsun Chiu, Braithwaite,C., Collins,A., Williamson,D., Olney,K.L., Benson,D.B. and McKenzie,F., "Dynamic Behavior of Particulate/Porous Energetic Materials", Shock Compression of Condensed Matter � 2011, AIP Conf. Proc. 1426, 533-538 (2012)

KEYWORDS: Reactive Materials; Energy Release Mechanisms; Impact Initiated Combustion;Metal Composites; Tungsten; Aluminum

** TOPIC AUTHOR (TPOC) **

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