U.S. patent application number 12/473274 was filed with the patent office on 2010-12-02 for stimulated emission release of chemical energy stored in stone-wales defect pairs in carbon nanostructures.
This patent application is currently assigned to Raytheon Company. Invention is credited to Delmar L. Barker, William R. Owens.
Application Number | 20100304218 12/473274 |
Document ID | / |
Family ID | 43087243 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100304218 |
Kind Code |
A1 |
Barker; Delmar L. ; et
al. |
December 2, 2010 |
STIMULATED EMISSION RELEASE OF CHEMICAL ENERGY STORED IN
STONE-WALES DEFECT PAIRS IN CARBON NANOSTRUCTURES
Abstract
Stone Wales defect pairs in a carbon nanostructure are used to
store energy. Energy is released by a chain reaction of phonons
disrupting the defect pairs to generate more phonons until the
lattice returns to its original hexagonal form and the energy is
released in the form of lattice vibrations. Devices may be
configured as a battery to release electrical energy in a
controlled manner or as an explosive to release energy in an
uncontrolled manner.
Inventors: |
Barker; Delmar L.; (Tucson,
AZ) ; Owens; William R.; (Tucson, AZ) |
Correspondence
Address: |
Eric A. Gifford (Raytheon Company)
11770 E. Calle del Valle
Tucson
AZ
85749
US
|
Assignee: |
Raytheon Company
|
Family ID: |
43087243 |
Appl. No.: |
12/473274 |
Filed: |
May 28, 2009 |
Current U.S.
Class: |
429/231.8 ;
977/742; 977/932 |
Current CPC
Class: |
C06B 45/00 20130101;
H01M 6/36 20130101 |
Class at
Publication: |
429/231.8 ;
977/742; 977/932 |
International
Class: |
H01M 4/58 20060101
H01M004/58 |
Claims
1. (canceled)
2. The device of claim 28, wherein said carbon nanostructures
comprise carbon nanotubes (CNTs).
3. The device of claim 28, wherein said carbon nanostructures
comprise graphene sheets.
4. The device of claim 28, wherein the density of Stone-Wales
defect pairs is at least 25%.
5. The device of claim 28, wherein the density of Stone-Wales
defect pairs is at least 75%.
6. The device of claim 28, wherein the means for stimulating the
excited medium comprises a laser, a heater or means of physically
deforming the carbon nanostructure.
7. The device of claim 28, wherein the mass of carbon
nanostructures are within a resonant cavity.
8. A chemical energy storage device comprising; a carbon
nanostructure including a density of Stone-Wales defect pairs that
define an excited medium within a cavity that exhibits cavity
losses; first and second isotope junctions at opposite ends of the
cavity to create the resonant cavity; and means for coherently
stimulating the excited medium to annihilate Stone-Wales defect
pairs to emit phonons, said density of Stone-Wales defect pairs
being greater than a threshold required to overcome cavity losses
and initiate a chain reaction to annihilate substantially all of
the defect pairs to release chemical energy.
9. The device of claim 7, wherein the annihilation of the
Stone-Wales defect pairs in the chain reaction inside the resonant
cavity releases sufficient energy to break the carbon-carbon bonds
in the nanostructure to produce an explosive detonation.
10. The device of claim 9, further comprising a plurality of said
carbon nanostructures that are coherently stimulating to produce
the explosive detonation.
11. A chemical energy storage device comprising: a resonant cavity
that exhibits cavity losses; an explosive medium in the resonant
cavity; a plurality of carbon nanostructures embedded in said
explosive medium, said carbon nanostructures including a density of
Stone-Wales defect pairs; and means for coherently stimulating the
excited medium to annihilate Stone-Wales defect pairs to emit
phonons, said density of Stone-Wales defect pairs being greater
than a threshold required to overcome cavity losses and initiate a
chain reaction to annihilate substantially all of the defect pairs
to release sufficient chemical energy to break the carbon-carbon
bonds in the nanostructure to produce an explosive detonation that
detonates the explosive medium.
12. A chemical energy storage device, comprising: a carbon
nanostructure including a density of Stone-Wales defect pairs that
define an excited medium within a cavity that exhibits cavity
losses; a reflector at a first end of the cavity; an absorber at a
second end of the cavity; means for coherently stimulating the
excited medium to annihilate Stone-Wales defect pairs to emit
phonons, said density of Stone-Wales defect pairs being greater
than a threshold required to overcome cavity losses and initiate a
chain reaction to annihilate substantially all of the defect pairs
to release chemical energy; whereby annihilation of the Stone-Wales
defect pairs causes phonons to be reflected by the reflector at the
first end of the cavity and absorbed by the absorber at the second
end of the cavity to establish a thermal gradient across the
cavity; and means for converting the thermal gradient across the
cavity into electrical energy.
13. The device of claim 12, wherein the reflector comprises an
isotope junction.
14. The device of claim 12, wherein the means includes first and
second metals at opposite ends of the cavity that exhibit different
Seebeck coefficients.
15. The device of claim 14, wherein a plurality of carbon
nanostructures are arranged in a parallel configuration between
said first and second metals.
16. The device of claim 28, wherein the mass of carbon
nanostructures is stable at temperatures of no less than 300
degrees C. until stimulated.
17. (canceled)
18. (canceled)
19. A chemical energy storage device, comprising: a plurality of
carbon nanostructures, each nanostructure including a density of
Stone-Wales defect pairs of at least 25% that define an excited
medium within a cavity that exhibits cavity losses; a reflector at
a first end of the cavity and an absorber at a second end of the
cavity; stimulation means for coherently stimulating the excited
medium to annihilate Stone-Wales defect pairs to emit phonons, said
density of Stone-Wales defect pairs being greater than a threshold
required to overcome cavity losses and initiate a chain reaction to
annihilate substantially all of the defect pairs to release
chemical energy, said emitted phonons reflected by the reflector at
the first end of the cavity and absorbed by the absorber at the
second end of the cavity to establish a thermal gradient across the
cavity; and means for converting the thermal gradient across the
parallel configured carbon nanostructures into electrical
energy.
20. The device of claim 19, wherein the means comprises two
different metals thermally coupled to the reflector and absorber at
opposite ends of the cavity that exhibit different Seebeck
coefficients.
21. The device of claim 20, wherein the second metal provides the
absorber at the second end of the cavity for each said
nanostructure and wherein each nanostructure has its own reflector
at the first end of the cavity in thermal contact with the first
metal.
22. The device of claim 19, wherein the density of Stone-Wales
defect pairs is at least 75%.
23. The device of claim 19, further comprising a plurality of
cells, each cell including a cavity with a reflector and an
absorber at opposite ends with a plurality of carbon nanostructures
including a density of Stone-Wales defects there between, said
stimulation means adapted to stimulate each said cell
independently.
24. The device of claim 19, wherein said means for stimulating the
excited medium comprises a laser, a heater or means of physically
deforming the carbon nanostructure.
25. (canceled)
26. A chemical energy storage device, where comprising: a solid
medium comprising an explosive; a mass of carbon nanostructures
embedded in said solid explosive medium, each said nanostructure
including a density of Stone-Wales defect pairs of at least 25%
within a resonant cavity; and means for stimulating the Stone-Wales
defect pairs to detonate the carbon nanostructures to detonate the
explosive.
27. A chemical energy storage device, comprising: a plurality of
carbon nanostructures, each nanostructure including a density of
Stone-Wales defect pairs that define an excited medium within a
cavity that exhibits cavity losses; a reflector at a first end of
the cavity; an absorber at a second end of the cavity; stimulation
means for coherently stimulating the excited medium to annihilate
Stone-Wales defect pairs to emit phonons that are reflected by the
reflector at the first end of the cavity and absorbed by the
absorber at the second end of the cavity to establish a thermal
gradient across the cavity; and means for converting the thermal
gradient into electrical energy.
28. A chemical energy storage device, comprising: a solid
explosive; a mass of carbon nanostructures embedded in said solid
explosive, each said nanostructure including a density of
Stone-Wales defect pairs; and means for stimulating the Stone-Wales
defect pairs to detonate the carbon nanostructures to detonate the
solid explosive.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to chemical energy storage devices
such as batteries or explosives.
[0003] 2. Description of the Related Art
[0004] Higher density chemical energy storage devices present an
ongoing technological challenge. Chemical energy is the energy
that's stored in the bonds and between atoms that make up
molecules.
[0005] Batteries store chemical energy in cells. The energy is
converted by allowing two different chemical compounds in different
cells to slowly interact thereby producing a controlled release of
electrical energy. Normal chemical batteries start to degrade at
temperatures of about 55 C and more rapidly at about 100 C because
the chemical reaction barrier between the two chemical components
breaks down and direct path leakage current flows and drains the
battery of all the stored chemical potential energy. Battery
technology and particularly high-temperature battery technology is
a critical component to reducing the use and dependence on fossil
fuels.
[0006] An explosive material may be a single unstable chemical
compound or mixture of two or more stable chemical compounds, which
upon the application of heat or shock, decomposes or rearranges the
molecules to produce a violent detonation producing a shockwave.
The release of energy is generally too fast for controlled
electrical energy production. Explosives tend to become unstable at
elevated temperatures. For example, TNT may detonate around
temperatures of 250 C. Higher density stable explosives have
applicability in both defense and commercial applications.
[0007] The efforts to improve existing battery and explosive
technologies and to develop alternative technologies that hold the
promise for higher density storage are ongoing. Such efforts must
also address the stability, shelf life and environmental impact of
the technologies.
SUMMARY OF THE INVENTION
[0008] The present invention provides a chemical energy storage
device and means for releasing the energy. The device is capable of
storing and releasing energy densities comparable to conventional
explosives, exhibits high temperature stability, long shelf life
and is environmentally friendly. The device may release the stored
energy fast (explosive) or slow (battery) based on the same storage
mechanism.
[0009] This is accomplished by manufacturing carbon nanostructures
such as carbon nanotubes (CNTs) or graphene sheets with a high
density of Stone-Wales defect pairs. Stone-Wales defect pairs store
chemical energy and arc stable in the carbon lattice at and well
above typical operating temperatures. The manufactured densities of
Stone-Wales defect pairs may exceed 25% and may preferably exceed
75%. The high concentration of Stone-Wales defect pairs creates an
excited medium inside a nano cavity foined on the surface of the
nanostructure. Stimulation means (e.g. laser pulse, heat or
stretching) stimulate enough Stone-Wales defect pairs to overcome
cavity losses to produce stimulated coherent emissions. As each
defect pair is annihilated, it generates two opposite traveling
phonons (lattice vibrations) thereby releasing the stored chemical
energy as heat. The traveling phonons in turn annihilate other
defect pairs producing a chain reaction. In a first mode a mass of
carbon nanostructures are configured as an explosive material in
which the chain reaction builds up rapidly in a resonant cavity to
produce a violent shockwave. In a second mode a mass of carbon
nanostructures are configured as a battery in which a reflector and
an absorber are positioned at opposite ends of the cavity to
produce a large temperature differential. This temperature
differential is converted to electrical energy. A battery may
include multiple independent carbon nanostructure "cells" to
generate electrical energy.
[0010] These and other features and advantages of the invention
will be apparent to those skilled in the art from the following
detailed description of preferred embodiments, taken together with
the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram of a carbon nanotube (CNT).
[0012] FIG. 2 is a diagram illustrating the transformation of a 6:6
carbon lattice to a pair of 5:3 Stone-Wale (SW) defects,
[0013] FIGS. 3a and 3b are diagrams of a graphene sheet with SW
defects and the corresponding single-walled nanotube (SWNT);
[0014] FIG. 4 is a diagram of a SWNT manufactured with a high
density of SW defect pairs;
[0015] FIGS. 5a through 5c are diagrams illustrating the
stimulation and annihilation of the SW defects to release energy in
the form of lattice vibrations;
[0016] FIG. 6 is a diagram of an explosive nano-device;
[0017] FIG. 7 is an embodiment of an isotope-junction for providing
a reflector;
[0018] FIG. 8 is a diagram of an explosive device;
[0019] FIG. 9 is a diagram of a nano-battery; and
[0020] FIG. 10 is a diagram of a battery cell.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention provides a nano-scale device capable
of storing and releasing energy densities comparable to
conventional explosives, exhibits high temperature stability, long
shelf life and is environmentally friendly. The device may release
the stored energy fast (explosive) or slow (battery) based on the
same storage mechanism.
Carbon Nanostructures
[0022] Carbon nanostructures have stimulated a great deal of
interest in the materials, microelectronic and other industries
because of their unique properties including tensile strengths
above 35 GPA, elastic modulus reaching 1 TPa, higher thermal
conductivity than diamond, ability to carry 1000.times. the current
of copper, densities below 1.3 g/cm.sup.3 and high chemical,
thermal and radiation stability. CNTs have great promise for
composite and fiber materials and devices such as field effect
transistors, field emission displays, single electron transistors
in the microelectronic industry, and uses in other industries.
Commercialization of CNTs will depend in large part on the ability
to grow and network CNTs on a large cost-effective scale without
compromising these properties.
[0023] As used herein, "nanostructures" are carbon-based materials
that have at least one dimension in the nanometer scale (i.e. less
than 1 micrometer). All three dimensions may be less than 1
micrometer. Most nanostructures are electrically conductive
although they may be insulating or semiconducting. This definition
of nanostructures encompasses carbon nanotubes (CNTs), graphene
sheets and fullerenes. Fullerenes are spheroidal, closed-cage
molecules consisting essentially of sp.sup.2-hybridized carbons
typically arranged in hexagons and pentagons. Fullerenes, such as
C.sub.60, also known as Buckminsterfullerenes, more commonly,
"buckyballs," and C.sub.70, have been produced from vaporized
carbon at high temperature. a CNT 10 is a hollow cylindrical shaped
carbon molecule. The cylindrical structure is built from a
hexagonal lattice of sp.sup.2 bonded carbon atoms 12 with no
dangling bonds. The properties of single-walled nanotubes (SWNTs)
are determined by the graphene structure in which the carbon atoms
are arranged to form the cylinder. Multi-walled nanotubes (MWNTs)
are made of concentric cylinders around a common central
hollow.
[0024] The nanostructures may be prepared by any known method, and
some are commercially available. A wide variety of methods have
been devised for producing CNTs since the early disclosures by
Iijima et al., including "Helical microtubules of graphitic
carbon", NATURE, 354, 56 (1991) and "Single-shell carbon nanotubes
of 1-nm diameter", NATURE, 363, 605-606 (1993). For example, a
number of methods are mentioned in U.S. Pat. No. 7,052,668, the
disclosure of which relating to preparation of SWCNTs is
incorporated herein by reference. SWCNTs are commercially available
presently in small commercial quantities. Various methods are known
for synthesis of carbon nanotubes, and presently there are three
main approaches. These include the laser ablation of carbon (Thess,
A. et al., SCIENCE 273, 483 (1996)), the electric arc discharge of
graphite rod (Journet, C. et al., NATURE 388, 756 (1997)), and the
chemical vapor deposition of hydrocarbons (Ivanov, V. et al., CHEM.
PHYS. LETT. 223, 329 (1994); Li A. et al., SCIENCE 274, 1701
(1996)). The production of multi-walled carbon nanotubes by
catalytic hydrocarbon cracking is conducted on a commercial scale
(U.S. Pat. No. 5,578,543), while the production of single-walled
carbon nanotubes was still in a gram scale (as of 1998) by laser
(Rinzler, A. G. et al., APPL. PHYS. A. 67, 29 (1998)) and arc
(Haffner, J. H. et al., CHEM. PHYS. LETT. 296, 195 (1998))
techniques.
[0025] The manufacture of carbon nanostructures will yield a
certain number of "defects" in the hexagonal carbon lattice. The
manufacturing process is controlled to minimize the number of
defects but some always remain. A "Stone-Wales" defect is the
simplest possible point defect, which consists in a 90 degree
rotation of a pair 20 or C atoms, with some rearrangement of the
C--C bonds. The net result is the transformation of four hexagons
22 into two heptagons 24 and two pentagons 26 to form a
"Stone-Wales defect pair" 28 (shown as a simplified iconic
representation). A graphene sheet 30 having six SW defect pairs 32
and its corresponding CNT are shown in FIGS. 3a and 3b. The SW
defect pairs lie within the 2-D cylindrical surface cavity of the
CNT, one atom layer thick. For known manufacturing processes the
maximum density of SW defects is approximately 5% e.g. at most 5%
of the total carbon atoms reside in a SW defect pair.
[0026] The deleterious effects of SW defects in nanostructures is
well known (see (1) Felip Valencia "Large-amplitude coherent
phonons and inverse Stone-Wales transitions in graphitic systems
with defects interacting with ultrashort laser pulses" Physical
review B 74, 075409 (2006), (2) F. Beuneu "Nucleation and growth of
single wall carbon nanotubes" Cond. Mat. Mtrl. Sci. 15 Sep. 2005,
(3) C. Shet "Defect annihilations in carbon nanotubes under
thermo-mechanical loading" Journal of Materials Science 40 (2005)
27-36 and (4) Hua-Tong Yang "Antiresonance effect due to
Stone-Wales defect in carbon nanotubes" Physics Letters A 325
(2004) 287-293). SW defects can weaken the mechanical properties of
materials such as composites and fibers. SW defects cause electron
scattering and degrade other electrical properties of electronic
devices. SW defects may make it easier for contaminate atoms such
as oxygen to attach to the carbon when exposed to air which may
inhibit functionalization. SW defects are stable at and well above
normal operating temperatures but may be removed by
thermo-mechanical loading (see Shet) or laser irradiation (see
Valencia). A more pristine carbon nanostructure will exhibit better
mechanical and electrical properties.
Energy Storage Device
[0027] The present invention turns a defect to advantage by the
realization that each Stone-Wales defect pair is a stable energy
storage mechanism albeit only approximately 10 eV per pair.
Annihilation of each defect pair releases two phonons of 5 eV each
and returns the 5:7:5:7 structures in a local energy minimum to the
ground state in the hexagonal topology. The defect pair is stable
up to temperatures of at least 300 C well above normal operating
temperatures for long periods of time. Furthermore, the device is
environmentally friendly, the only byproduct being carbon atoms
which are not converted to CO or CO.sub.2.
[0028] The path to a viable energy storage device does not end with
this realization. In addition we had to determine whether the
energy density stored in the carbon nanostructures was or could be
made high enough for practical application. And if theoretically
possible, how to introduce SW defect pairs to achieve high energy
storage density. Furthermore, once energy is stored in the
Stone-Wales defect pairs we had to determine how to release the
energy in a useful manner. Could the energy be released as
electrical energy in a controlled manner for use as a battery?
Could the energy be released in an uncontrolled manner for use as
an explosive?
[0029] A SW defect density of 5% or less that naturally occurs in
known manufacturing processes is insufficient in that both the
energy density is too low to be useful and the defect density is
too low to support stimulated annihilation of the defects to
extract the stored energy. Therefore instead of treating the
nanostructures to remove the SW defect pairs, we modify the initial
manufacturing process or provide additional processing for carbon
nanostructures 40 to increase the density of SW defect pairs 42 to
at least a threshold of 25% and preferably at least 75% as shown in
FIG. 4. A maximum packing of SW defect pairs requires a single atom
separating pairs, which corresponds to a density of approximately
90%.
[0030] Calculations of energy density revealed surprisingly high
energy concentrations considering each defect contributes only 10
eV. A density of approximately 25% provides an energy density
comparable to that of a Lithium ion battery (.apprxeq.0.5 Meg
Joules/Kg). A density of approximately 75% provides an energy
density comparable to that of TNT (.apprxeq.4 Meg Joules/Kg). Other
materials than carbon and other defects than Stone-Wales could in
theory work but (a) other defects are not as stable as the
Stone-Wales defect and (b) other materials provide much less energy
in the bonds.
[0031] SW defect pairs are also unique because they can be
generated by a carbon atom conserving topological transformation as
shown in FIG. 2 that simply rotates a bond that links two carbon
atoms in the graphene lattice, while holding the two atoms along
the line that is being rotated. SW defect pairs may be created by,
for example, physical deformation of the carbon nanotubes (e.g.
stretching or bending) or by irradiation with electrons, ions or
even neutrons. Stretching carbon nanostructures at elevated
temperatures, say 700 C.+-.300 C, will introduce SW defect pairs.
The structures are then cooled to lock-in the defects. Bending a
nanostructure (CNT or graphene sheet) forms a line of SW defects
pairs along the bend. Irradiation of the nanostructure with an
electron, ion or neutron beam (including carbon or other atoms) may
create SW defect pairs directly or produce simple hole defects that
can be "annealed" to form SW defect pairs. Conventional electron
and ion beams may be used to irradiate the structures. The
structures may be placed in a nuclear reactor and used in place of
the graphite moderate to slow down the neutron beam. As such, the
creation of masses of carbon nanostructures with high-density
Stone-Wales defect pairs is a by product of a conventional nuclear
reactor. These procedures can be performed during the initial
manufacturing process of the nanostructures or during subsequent
process of nanostructures initial manufactured using convention
techniques that produce SW defect densities of <5%.
[0032] The mechanism for releasing the chemical energy in the form
of lattice vibrations is illustrated in FIGS. 5a through 5c. The
high concentration of Stone-Wales defect pairs 50 in a carbon
nanostructure 52 creates an excited medium inside a nano-cavity 54
formed by the 2-D outer surface of the nanostructure. Stimulation
means 56 (e.g. laser pulse, heat or stretching) stimulate enough
Stone-Wales defect pairs 50 to overcome cavity losses to produce
stimulated coherent emissions. Any mode of excitation that couples
a little to the lattice vibration (phonon) will drain energy (loss)
such as plasmon modes (coherent electron gas motion) or photon
radiation modes in form of cavity losses. As each defect pair is
annihilated, it generates two opposite traveling phonons, phonon 1
and phonon 2 due to lattice vibrations, thereby releasing the
stored chemical energy as heat. The traveling phonons in turn
annihilate other defect pairs producing a chain reaction. About 3
eV of energy is required to stimulate each SW defect pair to
release about 10 eV of energy. The density (<5%) or SW defect
pairs that naturally occurs in conventional manufacturing processes
may be too low to provide an excited medium to sustain the chain
reaction. Increasing the density is thus not only important to
increase the energy density but also to release the stored
energy.
[0033] Stimulation means 56 can be any mechanism that can stimulate
the excited medium to annihilate enough Stone-Wales defect pairs to
overcome cavity losses to produce stimulated coherent emissions. In
an embodiment, the stimulation means includes a laser source that
emits phonons at least some of which are of the correct frequency
to stimulate the SW defect pairs. The quantum of lattice vibrations
of the SW defect pair will determine the correct frequency. For
example, a pulse laser will generate a lot of phonons at different
frequencies at least some of which will stimulate a number of the
Stone-Wales defect pairs. In another embodiment, a heat source
heats the carbon nanostructures to a sufficiently high temperature
that the Stone-Wales defect pairs return to the "ground state" of
the hexagonal topology. In another embodiment, a mechanical source
stretches or otherwise physical deforms the nanostructures in such
a manner that the defects return to the ground state.
[0034] In most applications a mass of carbon nanostructures with
Stone-Wales defect pairs will be used to release a useful amount of
energy. Since the annihilation of each defect pair releases only 10
eV the total energy released for a single nanostructure is quite
small. The mass may include millions to billions or more carbon
nanostructures in a confined volume. A single means may be provided
to stimulate all of the structures or multiple means provided to
stimulate the structures at the same time or in accordance with a
desired timing schedule.
Explosive
[0035] As shown in FIG. 6, an explosive 59 includes a carbon
nanostructure 60 including a high density of Stone-Wales defect
pairs 62. Reflectors 64 and 66 at opposite ends of the
nanostructure form a resonant cavity 68. Each reflector may be
formed simply by the interface of the end of the carbon
nanostructure 60 with the external environment that provides an
impedance mismatch. Alternately, the growth of the carbon
nanostructure may be controlled to form isotope junctions 70 (e.g.
C12:C13:C12:C13) in-situ that provide higher quality reflectors as
shown in FIG. 7. A laser source 71 generates phonons 72 that
stimulate some of the Stone-Wales defect pairs 62, which in turn
release a pair of phonons 73 in opposite directions. These phonons
reflect back-and-forth in the cavity. The chain reaction builds up
rapidly in the resonant cavity to release all of the stored energy
at one in a violent shockwave that breaks the stable carbon bonds
to detonate.
[0036] As shown in FIG. 8, an explosive 74 includes a mass of
carbon nanostructures 60 including a high density of Stone-Wales
defect pairs 62 in a resonant cavity. The structures are embedded
in another medium 75 such as another high explosive or an inactive
material. A detonator 76 such as a laser or conventional primary
detonator stimulates the nanostructures 60 to cause them to
detonate. If the medium is another explosive, the detonation of the
nanostructures in turn causes that explosive to detonate.
[0037] This explosive may provide comparable energy densities of
more traditional explosives while providing much improved
temperature stability. The high temperature stability is also a
measure of its stability against other perturbations such as
mechanical shock, electrical discharge, and even explosions near
by. Explosives that are more stable, less prone to accidental
detonation, are always of interest.
[0038] Battery
[0039] As shown in FIG. 9, a battery 80 includes a carbon
nanostructure 82 including a high density of Stone-Wales defect
pairs 84. A heat reflector 86 and a heat absorber 88 are positioned
at opposite ends of the cavity. Again, heat reflector 86 may be an
isotope junction as shown. A laser source 89 generates phonons 90
that stimulate some of the Stone-Wales defect pairs 84, which in
turn release a pair of phonons 92 in opposite directions. Phonons
travelling towards heat absorber 88 are absorbed. Phonons
travelling towards the heat reflector 86 are reflected and then
absorbed. This produces a larger temperature differential at
opposite ends of the cavity.
[0040] The Seebeck effect is used to convert the temperature
differential across the cavity directly into electricity. The
effect is that a voltage, the thermoelectric EMF, is created in the
presence of a temperature difference between two different metals
or semiconductors. A first metal "A" 94 is placed at the reflecting
end of the cavity. The isotope junction could be removed and metal
94 could also act as the reflector. A second metal "B", which in
this embodiment doubles as the heat absorber 88, is at the
absorbing end of the cavity. This causes a continuous current to
now through the carbon nanostructures if they form a complete loop.
A complete loop may be formed by connecting the battery across a
load 96.
[0041] The voltage created by the battery across the load is of the
order of several microvolts per Kelvin difference. In the circuit
the voltage V developed is
V=.intg.(SB(T)-SA(T)) dT for T=T1 to T2
where SA and SB are the Seebeck coefficients (also called
thermoelectric power or thermopower) of the metals A and B as a
function of temperature, and T1 and T2 are the temperatures of the
two junctions. The Seebeck coefficients are non-linear as a
function of temperature, and depend on the conductors' absolute
temperature, material, and molecular structure. If the Seebeck
coefficients arc effectively constant for the measured temperature
range, the above formula can be approximated as:
V=(SB-SA).times.(T2-T1).
[0042] As shown in FIG. 10, a battery cell 100 includes a 2-D array
of carbon nanostructures 102 including a high density of SW defect
pairs arranged in parallel between a common metal electrode 104 at
the reflecting end of the structure and a common metal electrode
106 at the absorbing end of the structure. The connection of many
nanostructures in parallel increases the heat capacity to produce a
voltage V across a load 108. In this embodiment, each nanostructure
has its own isotope junction 110 that functions as the reflector.
These junctions are in thermal contact with common metal electrode
104. Alternately, the common metal electrode could also function as
a common reflector for all the structures. In this embodiment,
common metal electrode 106 also functions as a common absorber for
all of the structures. Alternately, each structure could have its
own absorber, which would be in thermal contact with electrode 106.
In the field of carbon nanotube growth, techniques are known for
growing large numbers of CNTs between two parallel plates. This
process can be modified to accommodate the present invention by
forming one plate as a reflector and one plate as an absorber and
either modifying the growth process to increase the density of SW
defect pairs and/or post-processing the structures to increase the
density.
[0043] A battery may include one or more independent "cells" each
containing a single carbon nanostructure or a mass of carbon
nanostructures with a high density of SW defects to generate
electrical energy. The stimulation of each cell will produce a
temperature differential and a pulse of electrical energy. Once all
of the SW defect pairs are annihilated the temperature differential
will subside. To produce a sequence of energy pulses or an
approximately continuous energy source for some period of time,
multiple cells can be stimulated in a time sequence. To produce a
larger voltage, multiple cells may be connected in series. To
source a larger current at a given voltage, multiple cells may be
connected in parallel. A notable difference of the carbon
nanostructure battery as compared to conventional chemical
batteries is that the release of electrical energy is controlled by
the source and stimulation of the SW defect pairs, not the
connection of the load across the battery.
[0044] This battery provides high temperature stability not found
in standard chemical batteries. Furthermore, the battery may be
configured to provide energy storage densities several times that
of standard chemical batteries.
Thermocouple
[0045] The Seebeck Effect forms the basis for thermocouples. A
conductor generates a voltage when subjected to a temperature
gradient. To measure this voltage, one must use a second conductor
material which generates a different voltage under the same
temperature gradient. Otherwise, if the same material was used for
the measurement, the voltage generated by the measuring conductor
would simply cancel that of the first conductor. The voltage
difference generated by the two materials can then be measured and
related to the corresponding temperature gradient. It is thus clear
that, based on Seebeck's principle; thermocouples can only measure
temperature differences and need a known reference temperature to
yield the absolute readings. There are three major effects involved
in a thermocouple circuit: the Seebeck, Peltier, and Thomson
effects. The Seebeck effect describes the voltage or electromotive
force (EMF) induced by the temperature difference (gradient) along
the wire. The change in material EMF with respect to a change in
temperature is called the Seebeck coefficient or thermoelectric
sensitivity. This coefficient is usually a nonlinear function of
temperature. Peltier effect describes the temperature difference
generated by EMF and is the reverse of Seebeck effect. Finally, the
Thomson effect relates the reversible thermal gradient and EMF in a
homogeneous conductor.
[0046] While several illustrative embodiments of the invention have
been shown and described, numerous variations and alternate
embodiments will occur to those skilled in the art. Such variations
and alternate embodiments are contemplated, and can be made without
departing from the spirit and scope of the invention as defined in
the appended claims.
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