U.S. patent application number 10/016758 was filed with the patent office on 2003-05-01 for carbon nanoloop.
Invention is credited to Nettleton, Nyles I..
Application Number | 20030082092 10/016758 |
Document ID | / |
Family ID | 21778806 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030082092 |
Kind Code |
A1 |
Nettleton, Nyles I. |
May 1, 2003 |
Carbon nanoloop
Abstract
The present invention relates to the field of carbon, and in
particular to making a carbon nanoloop. According to one
embodiment, this nanoloop is made using nanomanipulators or some
exotic chemistry. According to another embodiment, depending upon
the cross-sectional structure of the nanoloop, it can be a
conductor, an insulator, or a semi-conductor, such that two
nanoloops with the same chirality exhibit the same mechanical,
electrical, and magnetic properties.
Inventors: |
Nettleton, Nyles I.;
(Campbell, CA) |
Correspondence
Address: |
ROSENTHAL & OSHA L.L.P. / SUN
1221 MCKINNEY, SUITE 2800
HOUSTON
TX
77010
US
|
Family ID: |
21778806 |
Appl. No.: |
10/016758 |
Filed: |
October 30, 2001 |
Current U.S.
Class: |
423/447.2 |
Current CPC
Class: |
D01F 9/12 20130101; B82Y
30/00 20130101 |
Class at
Publication: |
423/447.2 |
International
Class: |
D01F 009/12 |
Claims
We claim:
1. A new shape to the existing carbon nanotube shape comprising:
constructing a toroidal structure from said carbon nanotube.
2. Said toroidal structure of claim 1 is either single or
multi-walled.
3. Said toroidal structure of claim 1 is an electrical conductor,
an electrical resistor, or an electrical insulator depending on the
way the loop is rolled.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the field of carbon and in
particular to making a carbon nanoloop.
[0003] Portions of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure as it appears in the
Patent and Trademark Office file or records, but otherwise reserves
all rights whatsoever.
[0004] 2. Background Art
[0005] Carbon
[0006] Carbon is a non-metallic chemical that is known by several
names depending on its purity, and its interaction with other
chemicals. Elemental carbon is one such form that has three
profiles, viz.: diamond, graphite, and carbon black which includes
charcoal, coal, lampblack, and coke. Each of the three profiles
have their own physical characteristics. While diamond and
graphite, on one hand, are crystalline in structure (yet differ in
physical properties because the arrangements of the carbon atoms in
their structures are dissimilar), carbon black, on the other hand,
is amorphous. While pure diamond is the hardest naturally occurring
substance known, it is a poor conductor of electricity. Graphite,
on the other hand, is a soft, slippery solid that is a good
conductor of both heat and electricity. Each of the amorphous forms
of black carbon have their own characteristics, and hence, each has
its own particular applications.
[0007] Carbon also comes in an aromatic compound form. In this form
there are three known profiles, viz.: diamond, graphite, and
fullerene. Fullerenes is a class by itself and contains such
elements as buckyball or C.sub.60, and buckytube or nanotube.
Essentially, they are any class of closed, hollow, aromatic carbon
compounds made up of 12 pentagonal and differing numbers of
hexagonal faces consisting of an even number of carbon atoms
ranging from 32 to as many as 600 atoms.
[0008] Buckyball (C.sub.60)
[0009] Found only as early as 1985, a buckyball contains 60 carbon
atoms (C.sub.60) joined together by single or double bonds to form
a hollow sphere with 12 pentagonal and 20 hexagonal faces
resembling a soccer ball. FIG. 1 shows the molecular structure of a
buckyball, which is also known by its more celebrated name of
Buckminsterfullerene after the American architect R. Buckminster
Fuller. C.sub.60 is an extremely stable compound since every carbon
vertex (the junction of one pentagon and two hexagon) is identical,
resulting in an equal distribution of bonding strains which makes
it withstand very high temperatures and pressures. Even though
C.sub.60 can react with a wide variety of elements, its spherical
structure is left intact. This means that C.sub.60 can not only
withstand high temperatures and pressures, but also withstand
external forces like stresses caused when it reacts with other
elements. The unique structure as well as properties of C.sub.60
suggests potential uses as superconductors, lubricants, industrial
catalysts, and drug-delivery systems ( e.g., targeted cancer
therapy).
[0010] Buckytube (Nanotube)
[0011] The buckytube was accidentally discovered in the resultant
soot left behind from an electrical discharge between two carbon
electrodes. A buckytube is a single-molecule structure similar in
construction to a buckyball, but tubular and of variable length.
Currently, a nanotube comes in two forms, viz.: single and
multi-walled carbon nanotube. A multi-walled nanotube is several
concentric tubes of carbon (or graphite sheets) nested within each
other, while a single walled nanotube is a single sheet of graphite
rolled up into just one tube. A nanotube ends in a cap section,
which is usually hemispherical in shape. While the thickness of a
multi-walled nanotube ranges in the tens of nanometers, the typical
diameter of a single-walled nanotube is a couple of nanometers
across. In spite of the microscopic size, a nanotube has
exceptional strength due to the strong bond that connects every
carbon atom to its neighbors. Depending on the manner in which this
tube is cultivated and the substrate on which it is grown, novel
structures, such as "nanobrushes" 200 can be observed and are shown
in FIG. 2. A nanotube has unique electrical, mechanical, and
magnetic properties depending on the way it is rolled and due to
the characteristics of carbon itself.
[0012] Electrical Properties
[0013] Depending on the way the tube is rolled, a nanotube can be a
semi-conductor or a resistor of electric current, and has
commercial applications in nanoscale wires, resistors, transistors,
and sensors. Since a carbon nanotube conducts electric current via
the ballistic transport mechanism rather than via conductance,
every electron that enters one end of the nanotube leaves out the
other end. This means that a nanotube can function as a
superconductor, or a semi-conductor. The basic resistance between a
nanotube and a conductive metal attached to its end is constant at
12.7 K ohms. This characteristic of the nanotube can be used to
measure a precise resistance of 12.7 K ohms in an electric circuit
by using it as a resistor in series or in parallel to other
resistors made of carbon nanotubes with conductive metals on the
ends. A complete description of using a carbon nanotube as an
electrical resistor is contained in co-pending U.S. patent
application "Use Of Carbon Nanotubes As Electrical Resistors", Ser.
No. ______ filed on ______, and assigned to the assignee of this
patent. A small diameter of carbon nanotube is also very favorable
for field emission, the process by which a device emits electrons
when an electric field or voltage is applied to it. The use of
nanotubes as field emitters is important in several industries,
including lighting and displays, and electron microscopy.
[0014] Mechanical Properties
[0015] Since each carbon atom is strongly bonded to three other
atoms in each graphite sheet, the sheet is very strong in certain
directions. In numerous experiments where a rod of graphite is
compressed along its length, the rod remains straight as the
compression increases, before flipping into a curve at the Euler
limit. This means that a carbon nanotube will bend over to
surprisingly large angles, before it starts to ripple and buckle,
and then finally develop kinks as well. The amazing thing about a
carbon nanotube is that these deformations are elastic (as opposed
to plastic) which disappear completely when the load or stress is
removed. This mechanical property of the carbon nanotube allows it
to be used as a strain gauge to measure a precise strain in another
material when attached firmly to the other material. A complete
description of using a carbon nanotube as a strain gauge by
altering its physical shape is contained in co-pending U.S. patent
application "Carbon Nanotubes As A Strain Gauge", Ser. No. ______
filed on ______, and assigned to the assignee of this patent.
[0016] Magnetic Properties
[0017] A carbon nanotube is used to demonstrate the AharonovBohm
effect which is a fundamental actuality in quantum physics. In the
AharonovBohm effect a beam of quantum particles like electrons are
split in two partial beams that pass on either side of a region
containing a magnetic field. These partial beams are then
recombined to form an interference pattern. This pattern can be
changed by altering the magnetic field in between it, even though
the pattern does not actually come in contact with the magnetic
field. By observing the interference pattern, one can demonstrate
that a single electron does not choose a particular path but
behaves as an extended wave that follows both paths simultaneously.
This pattern shifts as the magnetic field changes, returning to the
original pattern when the magnetic flux has changed by the quantum
of magnetic flux, .PHI..sub.0=h/e, where h is the Planck constant
and e is the charge on the electron. Since a nanotube is a
cylindrical conductor when it is placed in a magnetic field with
its axis parallel to the field, the electrons can propagate in
either clockwise or anti-clockwise directions. These "two" paths
interfere resulting in a periodic modulation of the electrical
resistance as the magnetic flux through the tube is changed. This
effect is quite robust and can be observed even if the electron
transport in the nanotube is diffusive.
SUMMARY OF THE INVENTION
[0018] The present invention relates to the field of carbon, and in
particular to making a carbon nanoloop. According to one
embodiment, this nanoloop is made using nanomanipulators or some
exotic chemistry. According to another embodiment, depending upon
the cross-sectional structure of the nanoloop, it can be a
conductor, an insulator, or a semi-conductor, such that two
nanoloops with the same chirality exhibit the same mechanical,
electrical, and magnetic properties.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other features, aspects and advantages of the
present invention will become better understood with regard to the
following description, appended claims and accompanying drawings
where:
[0020] FIG. 1 is an illustration of a buckyball.
[0021] FIG. 2 is an illustration of "nanobrushes".
[0022] FIG. 3A is an illustration of a nanoloop according to the
present invention.
[0023] FIG. 3B shows different illustrations of a nanoloop.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The invention relates to the field of carbon, and in
particular to making a carbon nanoloop. In the following
description, numerous specific details are set forth to provide a
more thorough description of embodiments of the invention. It is
apparent, however, to one skilled in the art, that the invention
may be practiced without these specific details. In other
instances, well known features have not been described in detail so
as not to obscure the invention.
[0025] A carbon nanoloop is a variation of a carbon nanotube, where
instead of the ends of the tube terminating in a cap section, the
end caps are joined together forming a continuous loop. FIG. 3A is
one illustration of a nanoloop which is a toroidal shaped structure
similar to a nanotube in cross section. Having a continuous closed
looped form, this shape can be changed to other interesting closed
looped shapes, some of which are shown in FIG. 3B. Further, since a
nanotube can be either single or multi-walled, a nanoloop can also
be either single or multi-walled. A complete description of single
and multi-walled nanotubes is contained in co-pending U.S. patent
application "Carbon Nanotubes As A Strain Gauge", Ser. No. ______
filed on ______, and assigned to the assignee of this patent. A
carbon nanoloop displays characteristics similar to a carbon
nanotube, and include electrical, mechanical, and magnetic
properties that may be used commercially. These properties as well
as their commercial applications have been discussed in the
background section.
[0026] Growth of Carbon Nanoloops
[0027] Since carbon nanoloops are made out of carbon nanotubes
whose ends touch each other, one possibility is to take carbon
nanotubes and mechanically join its ends to form loops. Another
possibility is to use a chemical process whereby the two ends of a
carbon nanotube can be made to join without altering the chemical
form of the carbon nanotube.
[0028] Thus, a new shape to a carbon nanotube namely a carbon
nanoloop is described in conjunction with one or more specific
embodiments. The invention is defined by the following claims and
their full scope of equivalents.
* * * * *