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Symposium : D

Nano-scale energetic materials: fabrication, characterization and molecular modeling

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 nanoenergetic systems and application : new opportunities : to be defined
09:00A new area in MEMS and nanotechnology through integration of nanoenergetics
Authors : Dr. John M. Pellegrino Sensors & Electron Devices Directorate AMSRD-ARL-SE US Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783
Resume : (Modify) Dr. Pellegrino Resume : Dr. John M. Pellegrino is the Director of the Sensors & Electron Devices Directorate (SEDD) of the Army Research Laboratory (ARL). Dr. Pellegrino holds a bachelor’s degree in Physics from Gordon College, Boston, MA and Master’s and a Doctoral degree in Physics from the University of Wisconsin Madison. Prior to his appointment in September 1998 to the Director, SEDD, Dr. Pellegrino was the Chief, Electro-Optics and Acoustics Division and Associate Director for Sensors Research. He also served as Chief, ARL Signal and Information Processing Division, and Chief, Optical Processing Branch, Harry Diamond Laboratories. He began his professional career as a Physicist in September 1981 at the Harry Diamond Laboratories. Dr. Pellegrino regularly serves by invitation as conference chair, technical consultant for various programs, and as a member of various advisory boards and committees. These include serving as a member of the SPIE Board of Directors, Chair of the SPIE Symposia Committee, Chair of the Office of Secretary of Defense Energy and Power Technologies Initiatives, Army member of the Defense Department Advisory Group on Electron Devices, and conferences and studies on sensors and sensor networking. Dr. Pellegrino is a fellow of the International Optical Engineering Society (SPIE), and a Senior Member of the IEEE; he also a member of AAAS, Sigma Xi, and the Optical Society of America. He is twice recipient of the U.S. Army Research and Development Achievement Award (1994 & 1997), and a recipient of the Harry Diamond Laboratories Hinman Award for Technical Achievement (1986). He has authored and co-authored more than two dozen technical papers and reports, and is co-editor of the book “Acousto-Optic Signal Processing.”
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09:45Les nanomatériaux et les besoins futures pour les matériaux énergétiques
Resume : Les nanomatériaux et les besoins futures pour les matériaux énergétiques
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10:10Fabrication, assembly and tests of a MEMS based safe, arm and fire device
Authors : H. Pezous, M. Sanchez, F. Mathieu, X. Dollat, S. Charlot, G.A. Ardila, C. Rossi, D. Estève
Resume : The french military agency DGA in collaboration with NEXTER MUNITIONS is applying MEMS technology to fabricate smaller, safer arm and fire system. The main functions of a safe arm and fire device (SAF) are to keep the device safe, to arm it and to contain one energetic material necessary for initiating the munition. We propose a SAF device that could constitutes a really breakthrough for safe miniature fuzing device. On the one hand, it takes all the functions embodied in a conventional mechanical arm and fire system and implements them in a single 1cc package. On the other hand, for the first time, it combines mechanical arming unit with electrical safety functionalities on the same chip of the pyrotechnical initiator, making it respecting the STANAG 4187 (1A/W during 5 minutes of not fire) norm while consuming less than 200mW for ignition. In this paper, we present the design, fabrication, assembly and test of the SAF MEMS device. The architecture is a multilayer stacked –wafers. The top layer contains the electronic circuitry and power supply device. The middle layer is a Si-based safe initiator layer. The bottom layer constitutes the arming function. 3.5mJ (500mW during 7ms) and 130mJ (400mW during 320ms) are required to commute the ON-OFF and OFF-ON bistable switches, respectively. Switching current is between 10 and 20mA for ON-OFF and between 50-70mA for OFF-ON concept. Experimentations show that the shutter requires 3bar to be actuated and moved along 1.43cm.
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10:45Silicon as an Energetic Material
Authors : Luke J. Currano , Wayne Churaman, and Collin Becker
Resume : Silicon based devices have included electrical, mechanical, thermal, optical, and fluidic physics on chip. Energetics is one remaining area of physics that has not widely been considered for integration on chip, although there are some unique benefits that cannot be replicated by the existing devices. Foremost among these is power density, with energetic materials boasting power densities 6 orders of magnitude above the best batteries or capacitors. Nanoporous silicon is one energetic material system that lends itself to on-chip integration, since the chip material itself is generally silicon. By using the substrate instead of deposited films as the energetic material, the quantity of the energetic material can be greatly increased. Nanoporous silicon is created via electrochemical etching in HF. The pores are filled with a solid oxidizer by applying as a liquid solution and allowing the solvent to evaporate away. The tremendous surface area inside the pores (up to 1000m2/cm2) allows for very fast propagation of oxidation reactions. The chemical energy is released in a matter of milliseconds, for an unprecedented on-chip power density of megawatts per gram. We have made significant progress in integrating nanoporous energetic silicon with MEMS and electronic devices on-chip. We have demonstrated integration with a microfabricated hotwire initiator, and with a MEMS acceleration switch. Other electronic and MEMS devices can be integrated using the same techniques.
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11:10Coated Magnesium Powder for Pyrotechnic Decoy Flares for the Protection of Aircraft.
Authors : Nigel Davies*, James Callaway** and P Smith*** * Cranfield University, Defence College of Management and Technology, Shrivenham, Swindon, Wiltshire,SN6 8LA, UK ** Dstl, Fort Halstead, Sevenoaks, Kent, TN14 7BP, UK *** Advanced Powder Technology Ltd., Water Orten, Birmingham B46 1SA, UK
Resume : Pyrotechnic compositions containing fine magnesium powder and polytetrafluoroethane have been used for over fifty years to protect aircraft from heat seeking missiles. Such compositions contain a fluorinated binder to make the compositions safer to handle and to allow a structurally robust pellet to be pressed. It is now apparent that there is a chemical incompatibility between the commonly used binder – a copolymer of vinylidene fluoride and hexafluoropropylene – which leads to the evolution of gas, to mechanical deterioration of the flare pellet, and to a reduction in the performance characteristics. This paper discusses the use of such flares, and methods that may be used to reduce the extent of the ageing problem.
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11:35Nanoenergetic Materials for Energy Conversion Applications
Authors : Christopher J. Morris, Luke Currano, Wayne Churaman, Eugene Zakar
Resume : The development of new energetic materials with nanoscale particle sizes and/or reaction paths holds great promise for many new application areas. One area is the conversion of energetic material chemical energy other forms of usable energy. In this presentation we present our progress toward the development of two MEMS-scale energy conversion devices. The first device investigates the conversion of chemical energy to kinetic energy in conjunction with large electrical pulses to eject a small plate or flyer material. We are incorporating a Ni/Al nanolayer film into conducting bridges designed to create intense local heating upon application of a large electrical current. The Ni-Al intermetallic reaction normally proceeds at rates lower than 10 m/s along the length of a film, but models indicate that uniform heating of the film leads to much more rapid reactions. We will report on kinetic energy enhancements resulting from this intermetallic reaction energy. The second device concerns the transduction of chemical to electrical energy, representing a potential microscale power source. A model of the electrical power pulse induced by a microscale magnetic projectile suggests that a several orders of magnitude increase in power density over conventional battery technology is possible, assuming an energetic material which accelerates the projectile to sufficient velocity. We will report on preliminary results using a porous silicon-based nanoenergetic chemical energy source.
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12:00Investigations into MEMS Scale Detonators
Authors : R. P. Claridge, T. A. Vine QinetiQ Plc, Fort Halstead; Sevenoaks; Kent, TN14 7BP, United Kingdom
Resume : Initiators and explosive trains are found in virtually all weapons and munitions. One way of improving Insensitive Munitions compliance is through the miniaturisation of these systems. Miniaturisation reduces the amount of sensitive energetic material present and makes the systems easier to protect with mitigation techniques. For some munitions, for example fuzes, there is also a requirement to develop miniature and Micro Electro Mechanical System (MEMS) detonators so that reductions in both the weight and volume of the initiator and explosive train can be achieved. The space saved can be utilised for improved ‘on-board’ guidance and control systems. An additional advantage is that MEMS detonators can be integrated directly with an electronic safety and arming unit. Although research on MEMS containing energetic materials is still at a very early stage, a range of MEMS detonators were successfully filled with an initiatory material using a specially designed press and tooling. A range of explosive loadings was examined. The detonators were functioned and the power output determined by the degree of damage to the witness plates. Several of the systems examined gave sufficient output to reliably initiate further components of an explosive train. Further research to improve the solids loading, density and consistency of MEMS filling is required along with work on shutter design, alternative measurement techniques and modelling of detonation transfer in MEMS.
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 Advanced synthesis technique of nanoscale energetic materials : to be defined
14:00Nano Reactives in Weapons; Reactions and Sintering
Authors : Suhithi M. Peiris, Ph.D. Basic Research Sciences Team Lead Defense Threat Reduction Agency RD-BAS, Cube 3680D 8725 Kingman Road Fort Belvoir, VA 22060-6201
Resume : The utility of nano materials in explosives and weapons has been considered for nearly a decade. Early studies of simply substituting a nano material where a macro (micron to millimeter size) material was being used yielded disappointing results. We now understand that we need to consider many aspects, such as the kinetics of the nano-material reaction, the ignition temperature, the effect of the inert oxide shell, the loading/mixing of the nano particles with other materials, the dispersion/turbulence effects of nano particles during explosion, etc., when using them in explosives. In addition, when using them as weapon casings or structural materials, we also have to consider many other constraints like density, structural strength, tensile strength, etc. This presentation will address these considerations. Some experimental results of the reaction kinetics of a few thermites and results of the high-pressure sintering of nano materials will also be presented.
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14:25Synthesis and atomic level structural characterization of Nanoenergetic Materials : Surprises in New and More Familiar Systems
Authors : Ralph Nuzzo, Department of Chemistry University of Illinois A128 Chemical & Life Sciences Lab 600 South Mathews Avenue Urbana, IL 61801
Resume : This talk will explore the chemical synthesis of high energy density materials in useful nanoscale forms. The development of new approaches to the synthesis of useful nanoscale materials, including Al, B, and a variety of binary compositions, will be highlighted along with their structural and physical characterization. We will highlight specific approaches that can be used modify the surfaces of these highly reactive materials, doing so in ways that serve to modify the nature of their reactivity in useful ways that preserve their energy content, along with insights coming from the characterization of the atomic level structures that provide these benefits. We will explore as well new designs for binary (and higher) compositions that provide competencies for controlling energy release properties via control of structure.
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14:50Generation of Al nanoparticles via short pulse laser ablation of Al in liquids
Authors : E. Stratakis(1,2), M. Barbeoroglou(1,3), C. Fotakis(1,3), G. Viau(4), C. Garcia (4), G.A. Shafeev(5) 1Institute of Electronic Structure and Laser, Foundation for Research & Technology—Hellas, (IESL-FORTH), P.O. Box 1527, Heraklion 711 10, Greece. 2 Materials Science and Technology Department, University of Crete, Heraklion 710 03, Greece. 3 Physics Department, University of Crete, Heraklion 714 09, Greece. 4 Laboratoire de Physique et Chimie des Nano-Objets, INSA de Toulouse, UMR CNRS 5215, 135 av. de Rangueil, 31077 Toulouse Cedex. 5 Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov Street, 119991 Moscow, Russian Federation.
Resume : Al nanoparticles (NPs) have attracted considerable interest as a candidate material in advanced energetic material and optoelectronic applications. One of the major impediments to their use is that bare Al is highly reactive, while oxide coated Al significantly decreases overall performance. Ablation of Al in liquid using short laser pulses may help towards faster quenching of the nanostructured Al and thus preservation of its metallic nature. Highly stable Al NPs are generated via ablation of bulk Al in ethanol using either femtosecond (fs) or picosecond (ps) laser sources. The colloidal NP solutions obtained with fs pulses exhibit a yellow coloration and show an increased optical absorption between 300 and 400 nm, tentatively assigned to the plasmon resonance of nanosized Al. The corresponding solutions after ps ablation are gray coloured and opalescent. The average size of the NPs formed ranges from 20nm for the fs case to 60 nm for the ps case, while a narrower distribution is obtained using the shorter pulses. High Resolution TEM studies indicate that the NPs are mostly amorphous with single crystalline inclusions.
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15:10Preparation and Performance of Nano-thermite and Its Composites With Superfine RDX
Authors : Zhiqiang Qiao, Fude Nie, Lan liu, Juan Zhang Institute of Chemical Materials, China Academy of Engineering Physics
Resume : Nano-thermite (nano-Fe2O3-Al) was prepared by sol-gel method, and the composite of nano-thermite and superfine RDX ( nano-Fe2O3-Al/SFRDX ) was obtained. The nanostructure of nano-thermite was characterized by BET, and SEM methods. Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) analysis of nano-Fe2O3-Al was performed in N2 ambience, two exothermic peaks appear in the DSC trace, and mass increase appears in the DSC trace. The combustion behavior of nano-Fe2O3-Al and nano-Fe2O3-Al/SFRDX without confinement was perfomed by high-speed camera method, and the combustion velocity of nano-Fe2O3-Al reach 300m/s, and the nano-Fe2O3-Al/SFRDX composite has the tendency of deflagration to detonation transition (DDT) without confinement. But in the closed combustion bomb test, the combustion velocity of nano-Fe2O3-Al/SFRDX increases markedly while the nano-Fe2O3-Al content increases, and the time of pressure increasing decreased to100μs from 500μs.
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15:45Aspects of Metal Combustion and Nanotechnology
Authors : Richard A. Yetter The Pennsylvania State University University Park, PA
Resume : Metal combustion has received renewed interest largely as a result of the ability to produce and characterize metallic nanoparticles. Nanosized powders are known to display increased catalytic activity, superparamagnetic behavior, superplasticity, lower melting temperatures, lower sintering temperatures, and higher theoretical densities compared to micron and larger sized materials. Much of the highly desirable traits of nanosized metal powders in combustion systems have been attributed to their high specific surface area (high reactivity) and potential ability to store energy in surfaces. The lower melting temperatures can result in lower ignition temperatures of metals. The combustion rates of materials with nanopowders have been observed to increase significantly over similar materials with micron sized particles. A lower limit in size of nanoenergetic metallic powders in some cases may result from the presence of their passivating oxide coating. Consequently, coatings, self-assembled monolayers (SAMs), and the development of composite materials that limit the volume of non-energetic material in the powders have been under development in recent years. After a review of the classifications of metal combustion based on thermodynamic considerations and the different types of combustion regimes of metal particles, recent results of the combustion of nano-sized materials, their applications, and their synthesis and assembly is presented.
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16:10Synthesis and Characterization of Novel Highly Energetic Polyazides
Authors : Ralf Haiges and Karl Christe, Loker Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089, Fax: 213-740-6679,
Resume : Reactions of covalent fluorides or oxofluorides of B, Al, Ga, In, Tl, P, As, Sb, S, Se, Te, Ti, V, Nb, Ta, Mo, W, Mn, Re, and U with (CH3)3SiN3 in either SO2 or CH3CN solution provide ready access to covalent polyazides. The compounds were characterized by low-temperature vibrational and multinuclear NMR spectroscopy and, whenever possible, x-ray crystallography. Most of these polyazides are extremely sensitive and explode with great violence. The previously known P(N3)6- and B(N3)4- anions were successfully combined with the N5+ cation in the form of N5+B(N3)4- and N5+P(N3)6-. The salts are extremely energetic, with N5+B(N3)4- containing 96 weight % of energetic nitrogen. The possibility of incorporating azido groups into nano-materials will be discussed.
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16:35Synthesis of nano-sized RDX using the RESS (Rapid Expansion of a supercritical Solution) Technique
Authors : Kenneth K. Kuo, Department of Mechanical and Nuclear Engineering College of Engineering The Pennsylvania State University 140 Research Building East, Bigler Road University Park, PA 16802
Resume : Synthesis of nano-sized RDX using the RESS (Rapid Expansion of a supercritical Solution) Technique
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17:00First-principles Study of Small Aluminum Clusters: Oxygen Adsorption, Oxidation and Phase Stability
Authors : Ligen Wang and Maija Kuklja Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
Resume : Adding small Al clusters to high explosive materials (such as HMX and RDX) is expected to lower sensitivity of explosives to detonation initiation and increase their performance; in other words, aluminized energetic materials are predicted to significantly improve two the most desirable qualities of these materials. However, details and mechanisms of the aluminum-induced effect on organic energetic materials are far from being understood. More so, experimental attempts did not achieve much success so far. Small Al clusters display unusual behaviors arisen from the quantum size confinement and boundary effects, which are significantly different from individual atoms or bulk materials. Clusters with a magic number of atoms corresponding to closed electronic shells (such as Al7, Al13, and Al23 etc) are especially interesting and exhibit a pronounced stability over their neighboring clusters. As a first step towards understanding how small Al clusters affect the sensitivity to initiation of detonation and performance of high explosive materials, we need to determine whether the small Al clusters are oxidized under experimental conditions. In the present paper, we have investigated properties of oxygen adsorption, oxidation and phase stability of Al13 by the first-principles method with the generalized gradient approximation (GGA). Since we optimize the Al13 structure without any symmetry constraint there are total 62 nonequivalent adsorption sites (i.e. 12 atop sites, 20 hollow sites and 30 bridge sites) on the Al13 cluster surface. We find that O adsorptions at the bridge sites are most stable, whereas adsorptions at the hollow sites are slightly unfavorable. Oxygen adsorptions at the atop sites are much weaker. This is in contrast to adsorptions on Al(111) where O atoms prefer to adsorb at the hollow sites. Compared to O adsorptions on Al(111) surface, the corresponding oxygen adsorption processes on the Al13 cluster have smaller adsorption energies and therefore are relatively weaker. This can be explained by the enhanced stability of Al13 and a smaller probability of an electron transfer from Al13 to the adsorbed O atom. For various oxygen adsorption layers, we determine the adsorption configurations/patterns by performing Monte Carlo calculations. We assume that the metal cluster gets completely oxidized and calculate the formation enthalpies of the oxidized metal clusters. Based on these calculated results, we are able to construct the (p, T) phase diagram by taking into account the temperature and pressure via the oxygen chemical potential. Our results show that clean Al13 cluster is stable at the low O chemical potential range and the completely oxidized metal cluster is stable at the high O chemical potential range. However, the O adsorption phases are thermodynamically unstable. This study sheds some light on basic behavior of small aluminum clusters in the presence of oxygen. The performed analysis will be instrumental in extension of the calculations to aluminum-explosive composite materials and systems and in providing important information regarding potential enhancement of their properties.
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