Note: Descriptions are shown in the official language in which they were submitted.
CA 02434859 2003-07-09
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a light ignitable, energetic materials. More
specifically, the invention relates to light ignitable, energetic materials
containing
carbon nanotubes or activated carbon containing a metal.
DISCUSSION OF THE PRIOR ART
A carbon nanotube (CNT) is a hollow nanostructure consisting essentially of a
graphitic plane rolled into a thin tube, both ends of which can be closed by a
fullerene-type dome structure. The existence of CNT°s was originally
discovered by
S. lijima [see Nature 354, 56 (1991 )]. The material exhibits various
interesting
mechanical and electrical properties. There exists two forms of carbon
nanotubes,
namely single walled nanotubes (SWNT) and multiwalled nanotubes (MWNT).
It has recently been reported by P.M. Ajayan et al in Science, Vol. 296, 705
(2002) that carbon nanotubes release a large photoacoustic effect when
subjected
to a flash of light caused by the absorption of the light. It seems that the
phenomenon is predominantly present in SWNT's and that the temperature of the
process can reach 1500°C. The inventors have also determined that
activated
carbon containing a metal such as palladium also possesses the property of
releasing a photoacoustic effect when subjected to a flash of light.
GENERAL DESCRIPTION OF THE INVENTION
The object of the present invention is to exploit the above described property
of carbon nanotubes and activated carbon containing a metal to produce a light
ignitable, energetic material.
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Accordingly, the present invention relates to a light ignitable, energetic
composition comprising an intimate mixture of an energetic material and one of
carbon nanotubes and activated carbon containing a metal selected from the
group
consisting of palladium, iron, nickel, cobalt, aluminum, copper, zinc,
potassium,
sodium and titanium.
The invention also relates to a method of preparing a sight ignitable,
energetic
composition comprising intimately mixing an energetic material and one of
carbon
nanotubes and activated carbon containing a metal selected from the group
consisting of palladium, iron, nickel, cobalt, aluminum, copper, zinc,
potassium,
sodium and titanium.
A variety of energetic materials can be used in the method of the present
invention. Such energetic materials include carbon black powder, ammonium
perchlorate (AP), hexogen (RDX), octogen (HMX), pentaerythritol tetranitrate,
(PETN), trinitrotoluene (TNT), nitroglycerine, nitrocellulose, ammonium
nitrate, lead
azide, lead styphnate, vitro plasticizers and picric acid. While the carbon
nanotubes
can be SWNT or MWNT, the single walled nanotubes are preferred.
DESCRIPTION OF THE PREFERRED EMBODIMENT
!n general terms, the invention takes advantage of the photoacoustic effect of
carbon nanotubes when subjected to a burst of light, e.g. a camera flash to
ignite an
energetic material. !n order to test the theory, different carbon nanotubes
were
used, the most common one being a SWNT commercial available from Carbon
Nanotechnologies, Inc., Houston, Texas. Different percentages of carbon
nanotubes (1 - 90 weight percent) were manually mixed (gently) with carbon
black
powder. Initially, the most efficient composition contained 5 weight percent
SWNT
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mixed with 95 weight percent Grade 7 carbon black powder. The composition
exploded instantaneously after being subjected to a camera flash. It was found
that
carbon black powder with the smallest particle size was the most effective.
The
same effect was observed when activated carbon containing a metal, e.g.
palladium
was mixed with carbon black powder, and the resulting mixture was exposed to a
camera flash.
The invention will be better understood from the following examples.
Example 1
3 weight percent of crude carbon nanotubes were mixed with 97 weight
percent ground ammonium perchlorate. The mixture was homogenized using ball
milling equipment for 15 minutes. The bails used in the mill were made of
glass.
The resulting composition was then exposed to an intense flash using a
commercially available Vivitar (firademark) flash. The power of the flash was
200W1cm2 at a distance of 4.5 cm.
Example 2
The procedure of Example 1 was repeated using 3%, 5°/~, 10% and 20%
carbon nanotubes. At a concentration in excess of 20% nanotubes, the ignition
phenomenon was less efficient, i.e. the combustion process (explosion) appears
to
be incomplete.
Example 3
Energetic formulations containing carbon nanotubes and RDX; TNT, black
powder or AP were ignited at distances from 3 to 7 cm using the Vivitar flash.
In a
few cases, ignition was possible from a distance as great as 14 cm.
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Example 4
The method of Example 1 was repeated using 5 weight percent activated
carbon containing palladium (97% carbon and 3% palladium) with 95 weight
percent
ground ammonium perchlorate. The mixture was homogenized using the same ball
milling equipment as in Example 1. The composition was ignited using a flashy
however, the process was less efficient than when using carbon nanotubes.
Example 5
The ignition effect was observed for a variety of mixtures of activated carbon
containing 3 - 30% palladium catalyst and a variety of energetic materials.
The
ignition effect was similar to that observed when using carbon nanotubes, but
seemed to be less efficient after 3 to 5 days. It is believed that the
activated carbon
was absorbing water which reduced the efficiency of the ignition phenomenon.
Compositions in accordance with the present invention can be used for light
ignited pyrotechnic effects and as light ignited triggers for detonators, gas
generators
and air bags.
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