ICMCTF 2012! - CD-Lab Application Oriented Coating Development

Energetic Materials and Micro-Structures for
Nanomanufacturing
Room: Sunset - Session TS3-1
Energetic Materials and Micro-Structures for
Nanomanufacturing
Moderator: C. Rebholz, University of Cyprus, Cyprus, C.
Doumanidis, University of Cyprus, Cyprus, T. Ando,
Northeastern University, US
8:00am TS3-1-1 Recent ADvances in Nanolaminate Energetic
Materials, C. Rossi (rossi@laas.fr), 1CNRS; LAAS, France INVITED
Since more than a decade, nanostructured thermite materials, which
classically consist of a mixture of oxidizer and fuel nanoparticles, have
drawn considerable interest due to enhanced energy release rates in
comparison to their macro-scale counterparts which arises from an
increased fuel and oxidizer interfacial contact area. In comparison with
other energy sources such as batteries, capacitors, fuel cells, nanothermites
energy and power density is orders of magnitude higher, making them ideal
candidates to provide high energy density local source of heat or pressure
for mechanical and/or electrical power. Since 2005, progress in
nanotechnologies paved the way to engineering nanothermites on a chip.
Typically, magnetron sputtering method permit to stack alternatively metal
and metal oxide nanofoils, typically Al and CuO, each foil being accurately
controlled in thickness (from 25nm‐100nm with a precision of 5nm) and
high purity. This deposition technique places the reactants in intimate
contact reducing notably the diffusion distance between reactants compared
to the same material prepared by powder mixing.
Al-CuO nanolaminates are magnetron sputter deposited from Al and Cu
targets using DC power supplied, on oxidized silicon wafer. Copper Oxide
thin films are deposited by dc reactive magnetron sputtering method under
argon and oxygen plasma from a Cu target.
We compared the ignition characteristics and combustion rate of Al/CuO
nanolaminate for different Fuel (Al) to Oxidizer (CuO) ratio
(stoichiometric, fuel rich and fuel poor) and for different Al and CuO
individual reactive layer thickness. Results show that Al/CuO
nanolaminates provide unparalleled selectivity to tailor their energetic
response to satisfy desired application based on material composition,
structure and stochiometry.
Second point discussed in this paper is the formation and role of the
intermixing zone at the interface of Al and CuO reactive layers. We find
that an interface layer formed during sputter deposition of alumimum on
CuO is composed of a mixture of Cu, O and Al through Al penetration into
CuO, and constitutes a poor diffusion barrier (low ignition temperature);
and in contrast atomic layer deposition (ALD) of Al2O3 using
trimethylaluminum (TMA) produces a conformal coating that effectively
prevents Al diffusion (higher ignition temperature) even for ultra-thin layer
thicknesses (~ 0.5 nm). These findings evidence that interface layers plays a
crucial role in the characteristics and performances of energetic
nanolaminates. We have combined in-situ FTIR and ex-situ X-ray, DSC and
HRTEM to identify the stable configurations that can occur at the interface.
8:40am TS3-1-3 Comparison of engineered nanocoatings on the
combustion of aluminum and copper oxide nanothermites, E. Collins,
M. Pantoya (michelle.pantoya@ttu.edu), A. Vijayasai, T. Dallas, Texas
Tech University, US
Water-repellent nanocoatings for submerged combustion of nanoenergetic
composite materials were developed. Some of the possible applications of
submerged combustion are - oceanic power generation, underwater
ordnance, propulsion, metal cutting, and torch technologies. Nanocoatings
were deposited on thermite pellets by a vapor-phase technique. Two types
of deposition techniques, namely chemical vapor deposition (CVD) and
atomic layer deposition (ALD) were studied. A total of six types of
nanocoatings were applied on the thermite pellets. Various process
parameters to produce the coatings were explored. Characterization of the
nanocoatings was carried out using FTIR, SEM, AFM and contact angle
goniometry. Submerged combustion tests of the nanocoated thermite pellets
were performed as a function of submerged time. The pellets were
submerged in deionized water for 3, 5 and 10 days. The bubble energy
produced was analyzed and compared to other types of nanocoated pellets.
Initial results were analyzed using a fluorocarbon (FSAM) based monolayer
coating (type 1 – thickness ~1.8nm) and compared with a.
nanoparticle+FSAM coating (type 2 – thickness ~300nm).
Results suggest that with increasing submerged time, there is a decrease in
the ratio of bubble energy to total energy of combustion
(Kc=Kbubble/Kcombustion). The bubble energy of the pellets with type 1 and type
2 coating was 532.6 and 528.6 (KJ/Kg) respectively, with immediate
ignition after submersion and 27.6 and 48.2 (KJ/Kg) respectively, after 10
days. The value of Kc for Type 1 coating decreased by a factor of 19.3
whereas the Type 2 coating decreased by a factor of 11.0. The hydrophobic
coating is critical for energy generation because without it, the pellets do
not ignite, resulting in 100% loss of energy. Other coatings are being
explored to improve durability of submerged pellets.
9:00am TS3-1-4 Study of the reactive dynamics of nanometric metallic
multilayers using molecular dynamics : the Al-Ni system., O. Politano
(politano@u-bourgogne.fr), F. BARAS, Université de Bourgogne - CNRS,
France
A molecular dynamics study of a layered Ni-Al-Ni system is developed
using an embedded atom method type potential. The specific geometry is
designed to model a Ni-Al nanometric metallic multilayer. By means of this
microscopic approach, we are able to detect the very first steps of the
spontaneous dynamics at nanoscale. The system made of an Al-slice
embedded in Ni, is initially thermalized at the fixed temperature of 600 K.
Both pure metals are in FCC configurations. We first observe the
interdiffusion of Ni and Al at interfaces which is followed by the
spontaneous phase formation of NiAl (B2) in the Al layer. The solid-state
reaction is associated with a rapid system's heating which further enhances
the diffusion processes. NiAl phase is organized in small regions separated
by grain boundaries. Such crystallites are larger in the direction parallel to
the interface than in the perpendicular one. This study confirms the
hypothesis of a layer by layer development of the new phase. For longer
times, the temperature is notably higher (> 1000 K) and the system may
partly lose some its B2 NiAl microstructure in favor of the formation of
Ni3Al in L12 configuration. This work shows the spontaneous development
of a real exothermic solid-state reaction in metallic nanosystems mostly
constituted by interfaces. It allows to explain the extreme reactivity of such
systems and gives the basic mechanisms at its origin.
9:20am TS3-1-5 Exothermic metal-metal multilayers: Pulsed laser
ignition thresholds, reaction modes and effects of environment, D.
Adams (dpadams@sandia.gov), R. Reeves, P. McDonald, D. Jones, Jr., M.
Rodriguez, Sandia National Laboratories, US INVITED
Vapor-deposited, metal-metal multilayers are an ideal class of materials for
systematic, detailed investigations of reactive material properties. Created
in a pristine vacuum environment by sputter deposition, these high purity
materials have well-defined reactant layer thicknesses between 1 and 1000
nm, minimal void density and intimate contact between layers. With this
presentation, we describe the ignition characteristics, reaction behaviors and
final phase formation of multiple exothermic metal-metal pairs. This
includes equiatomic Al/Pt, Co/Al and Ni/Ti. Regarding initiation, we show
how pulsed laser ignition thresholds vary with material system. For a given
reactive material system, the thresholds for ignition are also shown to
depend on (i) pulse duration (evaluated from decisecond to femtosecond
time scales) and (ii) nanolaminate periodicity. With regards to steady-state
propagation, we show that some nanolaminate systems (Al/Pt) exhibit
stable propagation modes characterized by rapid reaction rates and
microscopically-smooth reaction front morphologies. Other kineticallyconstrained
systems (Co/Al, Ni/Ti) exhibit an in-plane spin-like (unstable)
propagation mode characterized by transverse propagation bands and
colliding wavefronts. Regarding phase formation, we describe how reaction
environment can affect final phase.
Sandia is a multi-program laboratory managed and operated by Sandia
Corporation, a wholly owned subsidiary of Lockheed Martin Company, for
the United States Department of Energy’s National Nuclear Security
Administration under Contract DE-AC04-94AL85000.
10:00am TS3-1-7 Time-Resolved Emission Spectroscopy Of
Electrically Heated Energetic Ni/Al Laminates, C. Morris
(christopher.j.morris58.civ@mail.mil), U.S. Army Research Laboratory,
US, P. Wilkins, C. May, Lawrence Livermore National Laboratory, US, T.
Weihs, Johns Hopkins University, US
The nickel-aluminum (Ni/Al) intermetallic system is useful for a variety of
reactive material applications, and reaction characteristics are well studied
at the normal self-heating rates of 10 3 –10 6 K/s. Our experiments at 10 11 –
10 12 K/s have measured the kinetic energy of material ejected from the
reaction zone relative to input electrical energy, indicating an exothermic
effect from Ni and Al laminates despite the extremely high heating rate.
In order to better probe reaction phenomena at these time scales, we
reported at the 2010 ICMCTF meeting on emission spectroscopy of
electrically heated, patterned Ni/Al bridge wires, time resolved over 350 ns
through the use of a streak camera. We conducted these experiments in
rough vacuum, but found the emission to be dominated by argon (Ar) and
nitrogen (N) lines in addition to the expected emission of Al and Ni. Using
spectral information from this Ar, we analyzed expected Boltzmann
81 Thursday Morning, April 26, 2012