U.S. patent application number 15/915112 was filed with the patent office on 2018-07-12 for carbon nanotube fibers/filaments formulated from metal nanoparticle catalyst and carbon source.
This patent application is currently assigned to The Government of the United States of America, as represented by the Secretary of the Navy. The applicant listed for this patent is The Government of the United States of America, as represented by the Secretary of the Navy, The Government of the United States of America, as represented by the Secretary of the Navy. Invention is credited to Teddy M. Keller, Matthew Laskoski.
Application Number | 20180195209 15/915112 |
Document ID | / |
Family ID | 44911957 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180195209 |
Kind Code |
A1 |
Keller; Teddy M. ; et
al. |
July 12, 2018 |
CARBON NANOTUBE FIBERS/FILAMENTS FORMULATED FROM METAL NANOPARTICLE
CATALYST AND CARBON SOURCE
Abstract
Disclosed is a method of: providing a mixture of a polymer or a
resin and a transition metal compound, producing a fiber from the
mixture, and heating the fiber under conditions effective to form a
carbon nanotube-containing carbonaceous fiber. The polymer or resin
is an aromatic polymer or a precursor thereof and the mixture is a
neat mixture or is combined with a solvent. Also disclosed are a
carbonaceous fiber or carbonaceous nanofiber sheet having at least
15 wt. % carbon nanotubes, a fiber or nanofiber sheet having the a
polymer or a resin and the transition metal compound, and a fiber
or nanofiber sheet having an aromatic polymer and metal
nanoparticles.
Inventors: |
Keller; Teddy M.; (Fairfax
Station, VA) ; Laskoski; Matthew; (Springfield,
VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Government of the United States of America, as represented by
the Secretary of the Navy |
Arlington |
VA |
US |
|
|
Assignee: |
The Government of the United States
of America, as represented by the Secretary of the Navy
Arlington
VA
|
Family ID: |
44911957 |
Appl. No.: |
15/915112 |
Filed: |
March 8, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15000406 |
Jan 19, 2016 |
9926649 |
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15915112 |
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13525620 |
Jun 18, 2012 |
9255003 |
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15000406 |
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13188720 |
Jul 22, 2011 |
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13525620 |
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13020887 |
Feb 4, 2011 |
8277534 |
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13188720 |
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61301279 |
Feb 4, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01F 9/127 20130101;
D01D 5/003 20130101; D01F 1/02 20130101; D01F 9/12 20130101; D01F
9/14 20130101; Y10T 442/658 20150401; B82Y 40/00 20130101; C01B
32/16 20170801; D04H 1/4242 20130101; Y10T 442/60 20150401 |
International
Class: |
D01F 9/12 20060101
D01F009/12; D01F 9/127 20060101 D01F009/127; C01B 32/16 20170101
C01B032/16; D01F 9/14 20060101 D01F009/14; D01F 1/02 20060101
D01F001/02; D04H 1/4242 20120101 D04H001/4242 |
Claims
1. A nanofiber sheet comprising at least 15 wt. % carbon
nanotubes.
2. The nanofiber sheet of claim 1, wherein nanofiber sheet further
comprises metal nanoparticles.
3. A nanofiber sheet comprising a mixture of: a polymer or a resin;
and a transition metal compound; wherein the polymer or resin is an
aromatic polymer or a precursor thereof.
4. The nanofiber sheet of claim 3, wherein the polymer or resin is
a phthalonitrile polymer, polyacrylonitrile, coal pitches,
petroleum pitches, or pitch resins.
5. The nanofiber sheet of claim 3, wherein the transition metal
compound is octacarbonyldicobalt,
1-(ferrocenylethynyl)-3-(phenylethynyl)benzene, diironnonacarbonyl,
or bis(1,5-cyclooctodiene)nickel(0).
6. A nanofiber sheet comprising: an aromatic polymer; and metal
nanoparticles.
7. The nanofiber sheet of claim 6, wherein the aromatic polymer is
a phthalonitrile polymer or a thermo-oxidative stabilized
polyacrylonitrile, coal pitches, petroleum pitches, or pitch
resins.
Description
[0001] This application is a divisional application of U.S. Pat.
No. 9,926,649, issued on Mar. 27, 2018, which is a divisional
application of U.S. Pat. No. 9,255,003, issued on Feb. 9, 2016,
which is a continuation application of U.S. patent application Ser.
No. 13/188,720, filed on Jul. 22, 2011, which is a
continuation-in-part application of U.S. Pat. No. 8,277,534, issued
on Oct. 2, 2012, which claims the benefit of U.S. Provisional
Application No. 61/301,279, filed on Feb. 4, 2010. These
applications and all other publications and patent documents
referred to throughout this nonprovisional application are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure is generally related to fibers
containing carbon nanotubes.
DESCRIPTION OF RELATED ART
[0003] High-performance synthetic fibers have been under
development for the past half century, motivated in particular by
the high strength and stiffness of the covalent carbon-carbon bond
and by the ability to achieve alignment with the fiber axis where
they are in the form of polymer molecules or graphene sheets.
Optimally, one may maximize the number of covalently bonded carbon
atoms per unit volume or mass (high average molecular weight) and
thus other types of atoms or groups attached to polymer chains will
tend to reduce ultimate properties. An advantage of pure carbon
fibers is that the mechanical properties are derived from the
in-plane stiffness and strength of graphene sheets, without the
adulterating effect of additional atoms to satisfy available carbon
bonds. However, the route to carbon fibers involves the alignment
of precursor structures, which are then covalently bonded to each
other to create the final structure. Carbon fibers are thus
comparatively brittle, especially when they are heat treated above
1500.degree. C. to maximize stiffness. The very high axial strength
and stiffness of individual carbon nanotubes opens up the
possibility of processing them directly into continuous fibers.
Thus, the benefits of high-performance polymeric fibers, especially
directness of processing and fiber toughness, can be combined with
the advantages of nanofibers consisting of carbon atoms. The
processing routes developed so far to incorporate CNTs into
polymeric fibers borrow concepts from polymer fiber processing
technologies.
[0004] Polyacrylonitrile (PAN), petroleum pitch, and cellulosic
fibers are typically used as carbon fiber precursors. Other high
temperature polymers have also been used. Currently, PAN is the
precursor of choice. For converting PAN to carbon and carbon
nanotube fibers, thermo-oxidative stabilization typically in the
200-300.degree. C. range is a key step. The PAN fibers are fed
through a series of specialized ovens during the time-consuming
oxidative stage. The process combines oxygen molecules from the air
with the PAN fibers in the warp and causes the polymer chains to
start crosslinking. The crosslinked fibers then have a definite
shaped (will not soften) and are then carbonized under inert
conditions typically between 700 and ends in a high temperature
furnace at 1200.degree. C. to 1500.degree. C. While dwell times are
sometimes proprietary, oxidative dwell time is measured in hours,
while carbonization is an order of magnitude shorter, measured in
minutes. As the fiber is carbonized, it loses weight and volume,
contracts by 5 to 10 percent in length and shrinks in diameter.
[0005] There are two main methods for fiber production, namely,
liquid and solid state spinning. Both methods have been developed
for CNT-based fibers. Increased thermal stability, glass transition
temperature, and storage modulus have been reported with the
incorporation of carbon nanotubes in various polymer matrices.
Poly(p-phenylene benzobisoxazole)(PBO)/CNT composite fibers
containing 10 wt-% CNTs exhibited 50% higher tensile strength
compared to the controlled PBO fiber. Polyacrylonitrile (PAN)
copolymers are commercially important and are used as carbon fiber
precursors as well as for the development of porous and activated
carbon for a variety of applications. Films have been made from
PAN/MWNT homogeneous dispersions. The CNTs can be dispersed in
solvents such as dimethylformamide (DMF) and dimethylacetamide
(DMAC). Carbonized and activated PAN/CNT films are very promising
for supercapacitor electrode applications. Solution spun PAN/CNT
fibers containing 10 wt-% nanotubes exhibit a 100 percent increase
in tensile modulus at room temperature, a significant reduction in
thermal shrinkage, and a 40.degree. C. increase in the glass
transition temperature. These observations provide evidence of the
interaction between PAN and the CNTs.
[0006] One parameter in making high-strength fibers from carbon
nanotubes is the availability of nanotubes which are as long and as
structurally perfect as possible. Another parameter is to align all
nanotubes as perfectly as possible with the fiber axis, so as to
maximize the translation of their axial properties to those of the
fiber. The bonding between adjacent nanotubes is weak in shear
(graphite is a lubricant) and thus as great a contact length as
possible is necessary to transfer the load into any given nanotube.
Another advantage of thin walled nanotubes (single or double) is
that they tend to facet or flatten so to maximize their contact
area. Alignment is typically achieved through mechanical forces
whether applied to a partly linked array of fibers or through
fluid-flow forces on a lyotropic suspension.
[0007] Today, there is currently an intense effort throughout the
scientific community to efficiently disperse MWNTs into polymeric
fibers to take advantage of the exceptional mechanical properties
of carbon nanotubes. Moreover, various research groups have used
aerogels and fuming sulfuric acid to utilize the CNTs grown by
chemical vapor deposition (CVD) in the formation of CNT containing
fibers. Carbon fibers derived from polyacrylonitrile (PAN) have
been the dominant reinforcement in advanced composites since their
commercialization in the late 1960s. By using a resin such as PAN,
which can be spun into a fiber, cured, and then carbonized, the
formation of CNT fibers can be exploited using the NRL breakthrough
method for the formation of CNTs by heating the PAN or other carbon
sources in the presence of small metal nanoparticles that may be
magnetic in nature.
BRIEF SUMMARY
[0008] Disclosed herein is a method comprising: providing a mixture
of a polymer or a resin and a transition metal compound, producing
a fiber from the mixture, and heating the fiber under conditions
effective to form a carbon nanotube-containing fiber. The polymer
or resin is an aromatic polymer or a precursor thereof and the
mixture is a neat mixture or is combined with a solvent.
[0009] Also disclosed herein is a fiber or nanofiber sheet
comprising at least 15 wt. % carbon nanotubes.
[0010] Also disclosed herein is a fiber or nanofiber sheet
comprising a mixture of: a polymer or a resin, as described above,
and a transition metal compound.
[0011] Also disclosed herein is a fiber or nanofiber sheet
comprising: an aromatic polymer and metal nanoparticles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete appreciation of the disclosure will be
readily obtained by reference to the following Description of the
Example Embodiments and the accompanying drawings.
[0013] FIG. 1 shows photographs of large CNT-containing fibers and
rods formulated from PAN and phthalonitrile, respectively.
[0014] FIGS. 2 and 3 show SEM images showing the crude fibers and
the CNTs appearing somewhat aligned within the fibers.
[0015] FIG. 4 shows a synthetic scheme for an embodiment of the
method.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0016] In the following description, for purposes of explanation
and not limitation, specific details are set forth in order to
provide a thorough understanding of the present disclosure.
However, it will be apparent to one skilled in the art that the
present subject matter may be practiced in other embodiments that
depart from these specific details. In other instances, detailed
descriptions of well-known methods and devices are omitted so as to
not obscure the present disclosure with unnecessary detail.
[0017] A high-yield method has been developed for the production of
carbon nanotubes (CNTs) and carbon nanotube-magnetic metal
nanoparticle compositions in a bulk carbonaceous solid. The yield
of CNT formation can be controlled as a function of the
carbonization temperature and exposure time at elevated
temperatures. With this method, CNTs are formed in a bulk
carbonaceous solid from thermal decomposition of various amounts of
an organometallic compound and/or metal salts in the presence of an
excess amount of a carbon source such as selected highly aromatic
compounds. Only a small amount of the organometallic compound or
metal salt is needed to achieve the formation of CNTs in high
yield, but larger quantities of the metal source can also be
incorporated, if desired.
[0018] The disclosed process is concerned with the formation of
neat aligned CNT fibers from precursor compositions formulated from
(1) a carbon source such as polyacrylonitrile (PAN) or copolymers
thereof, pitch-based compounds, high temperature compounds or
resins that char and (2) a metal salt(s) and/or organometallic
compound(s). The spinning of fibers occurs from the precursor
compositions either melted or dissolved or dispersed in a dipolar
aprotic solvent, and thermal treatment of the precursor composition
resulting in the decomposition of the metal salt and/or
organometallic compounds into metal nanoparticles that behave as
the catalyst for the formation of the CNTs. Heat treatment at, for
example, 200-400.degree. C. is important to convert the polymeric
fibers to a form with retention of structural integrity for heating
to elevated temperatures and for conversion of the fibers above,
for example, 500.degree. C. to metal nanoparticle/carbon nanotube
fibers during a carbonization process. The carbonization process to
form the carbon nanotube fibers occurs in temperature steps from,
for example, about 600.degree. C. to 1500.degree. C. The property
of the carbon nanotube fibers will depend on the heat
treatment.
[0019] The process may result in the high-yield formation of
multi-walled carbon nanotubes (MWNTs) in the solid carbonaceous
domain upon heat treatment to elevated temperatures under ambient
pressure. The method permits the large-scale inexpensive production
of MWNTs in a shaped, solid configuration. The MWNTs are formed
under atmospheric pressure during the carbonization process above
500.degree. C. in the carbonaceous solid. The catalytic metal
atoms, nanoclusters, and/or nanoparticles formed from the
decomposition of the organometallic compound or metal salt are the
key to the formation of the carbon nanotubes in the developing
carbonaceous nanomaterial by reacting with the developing
polycondensed aromatic ring system. To date, the average size as
determined by X-ray diffraction studies are 5-30 nm. Small metal
nanoparticles (1-3 nm) could produce single-walled carbon
nanotubes. The composition can be tailored to have mainly CNTs or
varying amounts of CNTs and magnetic metal nanoparticles, as
formed. Shaped solid forms, films, and fibers/rods can be readily
formulated from the precursor mixtures. If desired, CNT-containing
powders can be obtained by milling of the carbonaceous solid. The
CNT content of the bulk solid can be controlled by the final
pyrolysis temperature. For example, a final pyrolysis temperature
of 800.degree. C. and 1300.degree. C. may afford a CNT content of
approximately 20 and 70 wt. %, respectively. A suitable range of
pyrolysis temperatures includes, but is not limited to,
600-2700.degree. C.
[0020] The initial fiber form of the initial materials may be made
by a variety of methods that are known in the art including, but
not limited to, spinning with a spinneret, electrospinning, solvent
precipitation, and physically pulling a fiber from a mixture of the
materials. A variety of such methods are described in U.S.
Provisional Application No. 61/301,279. The materials may be mixed
neat in the melt or liquid state, or mixed or dissolved in a
solvent. When the precursor composition is completely dissolved in
a solvent, it can help to ensure that metal salt(s)
and/organometallic compounds are deposited within the spun
polymeric fibers. The fiber is a threadlike material and may have
the same dimensions as is typical for other carbon fibers.
[0021] The polymer or resin may be dissolved in a solution
simultaneously, before, or after dissolving the transition metal
compound. The transition metal compound may be dissolved close in
time to the production of the fiber from the same solution. This
may be done to avoid decomposition of certain transition metal
compounds, such as Co.sub.2(CO).sub.8. Such decomposition may occur
gradually over time, particularly if exposed to air or elevated
temperatures. The fibers may be produced when at least 50%, 70%, or
90% of the original amount of the transition metal compound still
remains in the solution without having decomposed. For example, the
solution may be spun into fibers within 30 days of dissolving the
transition metal compound in the solution. A polar aprotic solvent
may be used for dissolving both components. Such solvents are known
in the art and include, but are not limited to, dimethylacetamide,
dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone. Any
concentration of transition metal compound that results in the
formation of carbon nanotubes may be used, including concentrations
higher and lower than used in the examples below.
[0022] Suitable carbon sources include aromatic polymers and
precursors thereof. The polymer may be a crosslinked or thermoset
polymer, with the crosslinking occuring during or after formation
of the fiber. The aromatic polymer may be an aromatic
phthalonitrile polymer or oligomer, or a thermoset thereof, such as
a phthalonitrile oligomer made from bisphenol A and benzophenone. A
precursor is a compound or material that can be converted to an
aromatic polymer or material by heating before forming the CNTs.
Such heating may be in oxygen, including atmospheric air. The
heating may be, for example, from 200-300.degree. C. When heated in
this way, PAN converts to an aromatic polymer as the side groups
form rings. Pitch resins such as coal pitch (coal tar pitch),
petroleum pitch, or synthetic pitches also form aromatic materials.
Other suitable carbon sources include any aromatic material, or
material that converts to an aromatic, that forms a char when
heated in an inert atmosphere. Such materials and their products
are disclosed in U.S. Pat. Nos. 6,673,953; 6,770,583; 6,846,345;
6,884,861; and 7,819,938.
[0023] The transition metal compound may be, for example, a metal
salt or an organometallic compound. Such compounds can decompose at
elevated temperatures to form metal nanoparticles. Such suitable
compounds include, but are not limited to, octacarbonyldicobalt,
1-(ferrocenylethynyl)-3-(phenylethynyl)benzene, diironnonacarbonyl,
and bis(1,5-cyclooctodiene)nickel(0).
[0024] The small metal nanoparticles, formed by thermal
degradation/decomposition of the metal salt(s) and/or
organometallic compounds, are responsible for the formation of the
CNTs within the carbonized fiber upon heat treatment to elevated
temperatures. The precursor polymeric fibers (carbon source and
metal salt) may be carbonized by the simple carbonization process
already used to produce carbon and graphitic fibers.
[0025] The precursor compositions such as polyacrylonitrile,
phthalonitriles, petroleum pitches, etc. and metal salts and/or
organometallic compound are mixed and heated to cause the
decomposition of the metal component into metal atoms, clusters,
and/or metal nanoparticles (controlling the metal particle size to
less than 25 nm). The small metal nanoparticles are responsible for
and catalyze the formation of the CNTs. Large metal nanoparticles
larger than 40 nm in size may afford graphite; thus it may be
important to keep the metal catalyst at much smaller sizes.
Stretching may help to align the molecules within the small
diameter sized fibers and provides the basis for the formation of
the tightly bonded carbon crystals after carbonization and the
means for aligning the CNTs within the fibers.
[0026] Carbon nanotube fibers may be fabricated by injecting a
solution of a precursor composition formulated from a carbon
source-metal salt and/organometallic compound into a protic solvent
such as water, by drawing from the melt of a B-staged thermoset
resin at elevated temperatures or by conventional spinning
techniques of a carbon precursor followed by carbonization of the
polymeric fibers formed by the listed methods of preparation. In an
effort to develop a method for the fabrication of CNT fibers
formulated directly from the precursor carbon material, experiments
have been conducted whereby fibers were drawn from the melt of a
Fe.sub.2(CO).sub.9/phthalonitrile precursor composition and by the
deposition of a fiber into water from a solution of
Fe.sub.2(CO).sub.9/polyacrylonitrile (PAN) and a dipolar aprotic
solvent. The polymeric fibers were used in the direct formation of
the carbon nanotube (MWNT) fibers by slowly heating to 1000.degree.
C. under inert conditions. Studies show that any CNT precursor
composition formulation from a carbon source and a metal salt(s)
and/or organometallic compound that can be spun or drawn into a
fiber and carbonized by the method can be converted into carbon
nanotube fibers. There are no known prior reports of the ability to
achieve the direct formation of CNT fibers using a simple
carbonization process from precursor materials such as PAN and
petroleum pitches that are currently used to form carbon and
graphitic fibers. To show the feasibility of forming CNT fibers,
large diameter fibers and rods were formed from a phthalonitrile
oligomer and PAN and converted into CNT large fibers and rods (see
FIG. 1).
[0027] Since the formation of CNTs can occur directly from a
mixture of a metal salt such as Fe.sub.2(CO).sub.9,
Co.sub.2(CO).sub.8, and nickel(cyclooctadiene) and carbon sources
such as PAN or phthalonitriles in a shaped composition including
large diameter fibers and rods, these precursor compositions are
suitable candidates to spin polymeric fibers that can be directly
converted into MWNT-fibers during the carbonization process. The
fibers may also contain various quantities of magnetic metal
[0028] nanoparticles depending upon the initial concentration of
the metal salt(s) or organometallic compound(s) in the precursor
composition. The photographs (see FIG. 1) show carbon nanotube
fibers obtained from PAN (top) and phthalonitrile (bottom). Upon
cure and carbonization of the polymeric fibers, x-ray diffraction
(XRD) and transmission electron microscopy (TEM) studies confirmed
the presence of copious amounts of MWNTs in the carbonized fibers.
Scanning electron microscopy (SEM) images (see FIGS. 2 and 3) show
that the CNTs can be potentially aligned within small diameter
sized fibers (micron-and nanometer-sized fibers). No stretching of
the fibers/rod was performed during these experiments.
[0029] The formation and heat treatment of the fibers may be
similar to method known in the art for that of the same materials
in the absence of the transition metal compound. A variety of such
methods are described in U.S. Provisional Application No.
61/301,279.
[0030] The resulting fiber may have at least 5, 10, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 wt. % CNTs. The CNTs may
be generally aligned parallel with each other and the length of the
fiber. The fiber may also contain metal nanoparticles. However, if
heated to a high enough temperature the metal nanoparticles may be
removed. These properties also apply to nanofiber sheets.
[0031] Many potential applications have been proposed for carbon
nanotubes, including conductive and high-strength composites;
energy storage and energy conversion devices; sensors; field
emission displays and radiation sources; hydrogen storage media;
and nanometer-sized semiconductor devices, probes, high electrical
current flow, and interconnects. Some of these applications are now
realized in products. Another potential application is use is in
garments, such as anti-ballistic and decontamination garments. The
small diameter sized, high surface area CNT fibers would be
expected to exhibit superior mechanical, electrical, magnetic,
catalytic, and optical properties. Potential payoffs and impact
areas of the CNT fibers include structural, motor/generator, energy
(fuel cell electrodes, Li-batteries, hydrogen storage, and
electricity carrier--electrically conductive carbon nanotubes),
membrane for water purification, air filtration (toxin removal),
and various catalytic applications. Metal nanoparticles also
present in the fibers could be of importance for many of these
applications.
[0032] The following examples are given to illustrate specific
applications. These specific examples are not intended to limit the
scope of the disclosure in this application.
EXAMPLE 1
[0033] Synthesis of 1/20 by weight
octacarbonyldicobalt/polyacrylonitrile
mixture--Co.sub.2(CO).sub.8(50 mg, 0.146 mmol), polyacrylonitrile
("PAN") (1.00 g) and 10 mL of methylene chloride were added to a 50
mL round bottomed flask. The Co.sub.2(CO).sub.8 readily dissolved
in the methylene chloride. The PAN did not dissolve. The slurry was
allowed to stir for 5 min before the solvent was removed under
reduced pressure. The mixture was vacuum dried and isolated as an
off-white solid.
EXAMPLE 2
[0034] Thermal conversion of 1/20 by weight Co.sub.2(CO).sub.8/PAN
mixture to carbon nanotube-cobalt nanoparticle composition by
heating to 1000.degree. C.--A sample of the mixture from Example 1
(22.8 mg) was heated in a TGA chamber under nitrogen at 10.degree.
C./min to 1000.degree. C. resulting in a shaped composition and a
char yield of 36%. The DTA curve showed an exotherm at 308.degree.
C. X-ray studies confirmed the presence of carbon nanotubes-cobalt
nanoparticles in the carbon composition. The x-ray diffraction
study showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
fcc-cobalt nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 3
[0035] Thermal conversion of 1/20 by weight Co.sub.2(CO).sub.8/PAN
mixture to carbon nanotube-cobalt nanoparticle composition by
heating to 1500.degree. C.--A sample of the mixture from Example 1
(21.5 mg) was heated in a TGA chamber under nitrogen at 10.degree.
C./min to 1500.degree. C. resulting in a shaped composition and a
char yield of 32%. The DTA curve showed an exotherm at 310.degree.
C. X-ray studies confirmed the presence of carbon nanotubes-cobalt
nanoparticles in the carbon composition. The x-ray diffraction
study showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
fcc-cobalt nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 4
[0036] Pre-oxidation and thermal conversion of 1/20 by weight
Co.sub.2(CO).sub.8/PAN mixture to carbon nanotube-cobalt
nanoparticle composition--A sample of the mixture prepared as in
Example 1 (25.52 mg) was heated in a TGA chamber at 10.degree.
C./min to 280.degree. C. under air and isothermed for 1.5 hr. The
resulting air stabilized solid was further heated at 10.degree.
C./min to 1000.degree. C. under nitrogen resulting in a shaped
composition and an overall char yield of 45%. X-ray studies
confirmed the presence of carbon nanotubes-cobalt nanoparticles in
the carbon composition. The x-ray diffraction study showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt nanoparticles.
The x-ray (002) reflection for carbon nanotubes was readily
apparent.
EXAMPLE 5
[0037] Synthesis of 1/40 by weight Co.sub.2(CO).sub.8/PAN
mixture--Co.sub.2(CO).sub.8 (20 mg, 0.0584 mmol), PAN (1.00 g) and
10 mL of methylene chloride were added to a 50 mL round bottomed
flask. The Co.sub.2(CO).sub.8 readily dissolved in the methylene
chloride. The PAN did not dissolve. The slurry was allowed to stir
for 5 min before the solvent was removed under reduced pressure.
The mixture was vacuum dried and isolated as an off-white
solid.
EXAMPLE 6
[0038] Thermal conversion of 1/40 by weight Co.sub.2(CO).sub.8/PAN
mixture to carbon nanotube-cobalt nanoparticle composition by
heating to 1000.degree. C. and 1400.degree. C.--Sample of the
mixture from Example 5 (25.04 mg and 30.26 mg) were heated in a TGA
chamber under nitrogen at 10.degree. C./min to 1000.degree. C. and
1400.degree. C. resulting in a shaped composition and char yields
of 37% and 34%, respectively. The DTA curve showed an exotherm at
304.degree. C. X-ray studies confirmed the presence of carbon
nanotubes-cobalt nanoparticles in the carbon composition. The x-ray
diffraction studies showed the four characteristic reflection
values [(002), (100), (004), and (110)] for carbon nanotubes and
the pattern for fcc-cobalt nanoparticles. The x-ray (002)
reflection for carbon nanotubes was readily apparent.
EXAMPLE 7
[0039] Pre-oxidation and thermal conversion of 1/40 by weight
Co.sub.2(CO).sub.8/PAN mixture to carbon nanotube-cobalt
nanoparticle composition--A sample of the mixture prepared as in
Example 5 (26.75 mg) was heated in a TGA chamber at 10.degree.
C./min to 280.degree. C. under air and isothermed for 1.5 hr. The
resulting air stabilized solid was further heated at 10.degree.
C./min to 1000.degree. C. under nitrogen resulting in a shaped
composition and an overall char yield of 47%. X-ray studies
confirmed the presence of carbon nanotubes-cobalt nanoparticles in
the carbon composition. The x-ray diffraction study showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt nanoparticles.
The x-ray (002) reflection for carbon nanotubes was readily
apparent.
EXAMPLE 8
[0040] Synthesis of 1/100 by weight Co.sub.2(CO).sub.8/PAN
mixture--Co.sub.2(CO).sub.8 (10 mg, 0.0292 mmol), PAN (1.00 g) and
10 mL of methylene chloride were added to a 50 mL round bottomed
flask. The Co.sub.2(CO).sub.8 readily dissolved in the methylene
chloride. The PAN did not dissolve. The slurry was allowed to stir
for 5 min before the solvent was removed under reduced pressure.
The mixture was vacuum dried and isolated as an off-white
solid.
EXAMPLE 9
[0041] Thermal conversion of 1/100 by weight Co.sub.2(CO).sub.8/PAN
mixture to carbon nanotube-cobalt nanoparticle composition by
heating to 1000.degree. C.--A sample of the mixture from Example 8
(25.32 mg) was heated in a TGA chamber under nitrogen at 10.degree.
C./min to 1000.degree. C. resulting in a shaped composition and a
char yield of 35%. The DTA curve showed an exotherm at 295.degree.
C. X-ray studies confirmed the presence of carbon nanotubes-cobalt
nanoparticles in the carbon composition. The x-ray diffraction
studies showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern
(small intensity) for fcc-cobalt nanoparticles. The x-ray (002)
reflection for carbon nanotubes was readily apparent.
EXAMPLE 10
[0042] Synthesis of 1/20 by weight
1-(ferrocenylethynyl)-3-(phenylethynyl)benzene/PAN
mixture--1-(Ferrocenylethynyl)-3-(phenylethynyl) benzene (10 mg,
0.0259 mmol), PAN (500 mg) and 10 mL of methylene chloride were
added to a 50 mL round bottomed flask. The
1-(ferrocenylethynyl)-3-(phenylethynyl) benzene readily dissolved
in the methylene chloride. The PAN did not dissolve. The slurry was
allowed to stir for 10 min before the solvent was removed under
reduced pressure. The mixture was vacuum dried and isolated as an
orange solid.
EXAMPLE 11
[0043] Thermal conversion of 1/20 by weight
1-(ferrocenylethynyl)-3-(phenylethynyl)-benzene/PAN mixture to
carbon nanotube-iron nanoparticle composition by heating to
1000.degree. C. and 1500.degree. C.--Samples of the mixture from
Example 10 (30.26 mg and 32.56 mg) were heated in a TGA chamber
under nitrogen at 10.degree. C./min to 1000.degree. C. and to
1500.degree. C. resulting in a shaped composition and char yields
of 33% and 30%, respectively. The DTA curves showed an exotherm at
297.degree. C. X-ray studies confirmed the presence of carbon
nanotubes-iron nanoparticles in the carbon compositions. The x-ray
diffraction studies showed the four characteristic reflection
values [(002), (100), (004), and (110)] for carbon nanotubes and
the pattern for bcc-iron nanoparticles. The x-ray (002) reflection
for carbon nanotubes was readily apparent.
EXAMPLE 12
[0044] Pre-oxidation and thermal conversion of 1/20 by weight
1-(ferrocenylethynyl)-3-(phenylethynyl)-benzene/PAN mixture to
carbon nanotube-iron nanoparticle composition by heating to
1000.degree. C. and 1500.degree. C.--Samples of the mixture from
Example 10 (35.46 mg and 38.87 mg) were heated in a TGA chamber at
10.degree. C./min to 280.degree. C. under air and isothermed for
3.5 hr. The air stabilized samples were then heated under nitrogen
at 10.degree. C./min to 1000.degree. C. and to 1500.degree. C.
resulting in a shaped composition and char yields of 48% and 45%,
respectively. X-ray studies confirmed the presence of carbon
nanotubes-iron nanoparticles in the carbon compositions. The x-ray
diffraction studies showed the four characteristic reflection
values [(002), (100), (004), and (110)] for carbon nanotubes and
the pattern for bcc-iron nanoparticles. The x-ray (002) reflection
for carbon nanotubes was readily apparent.
EXAMPLE 13
[0045] Synthesis of 1/20 by weight diironnonacarbonyl/PAN
mixture--Fe.sub.2(CO).sub.9 (250 mg, 0.688 mmol), PAN (5.00 g) and
10 mL of methylene chloride or acetone were added to a 50 mL round
bottomed flask. The Fe.sub.2(CO).sub.9 readily dissolved in the
methylene chloride or acetone. The PAN did not dissolve. The slurry
was allowed to stir for 15 min before the solvent was removed under
reduced pressure. The mixture was vacuum dried and isolated as an
orange solid.
EXAMPLE 14
[0046] Thermal conversion of 1/20 by weight Fe.sub.2(CO).sub.9/PAN
mixture to carbon nanotube-iron nanoparticle composition by heating
to 1000.degree. C.--A sample of the mixture from Example 13 (25.11
mg) was heated in a TGA chamber under nitrogen at 10.degree. C./min
to 1000.degree. C. resulting in a shaped composition and a char
yield of 36%. The DTA curve showed an exotherm at 308.degree. C.
X-ray studies confirmed the presence of carbon nanotubes-iron
nanoparticles in the carbon composition. The x-ray diffraction
studies showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
bcc-iron nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 15
[0047] Thermal conversion of 1/20 by weight Fe.sub.2(CO).sub.9/PAN
mixture to carbon nanotube-iron nanoparticle composition by heating
to 1500.degree. C.--A sample of the mixture from Example 13 (21.8
mg) was heated in a TGA chamber under nitrogen at 10.degree. C./min
to 1500.degree. C. resulting in a shaped composition and a char
yield of 32%. The DTA curve showed an exotherm at 310.degree. C.
X-ray studies confirmed the presence of carbon nanotubes-iron
nanoparticles in the carbon composition. The x-ray diffraction
studies showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
bcc-iron nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 16
[0048] Pre-oxidation and thermal conversion of 1/20 by weight
Fe.sub.2(CO).sub.9/PAN mixture to carbon nanotube-iron nanoparticle
composition--A sample of the mixture from Example 13 (50 mg) was
heated in a TGA chamber at 10.degree. C./min to 280.degree. C.
under air and isothermed for 2 hr. The resulting solid was further
heated at 10.degree. C./min to 1000.degree. C. under nitrogen
resulting in a shaped composition and an overall char yield of 40%.
X-ray studies confirm the presence of carbon nanotubes-iron
nanoparticles in the carbon composition. The x-ray diffraction
studies showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
bcc-iron nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 17
[0049] Synthesis of 1/20 by weight Fe.sub.2(CO).sub.9/PAN mixture
by adding Fe.sub.2(CO).sub.9 dropwise--Fe.sub.2(CO).sub.9 (750 mg,
2.06 mmol) in 10 mL of methylene chloride was added dropwise to a
mixture of PAN (15.00 g) and 20 mL of methylene chloride in a 50 mL
round bottomed flask. The Fe.sub.2(CO).sub.9 readily dissolved in
the methylene chloride. The PAN did not dissolve. The slurry was
allowed to stir for 5 min before the solvent was removed under
reduced pressure. The mixture was vacuum dried and isolated as an
orange solid.
EXAMPLE 18
[0050] Thermal conversion of 1/20 by weight Fe.sub.2(CO).sub.9/PAN
mixture (dropwise addition of Fe.sub.2(CO).sub.9) to carbon
nanotube-iron nanoparticle composition by heating to 1500.degree.
C.--A sample of the mixture from Example 17 (75.6 mg) was heated in
a TGA chamber under nitrogen at 10.degree. C./min to 1500.degree.
C. resulting in a shaped composition and a char yield of 37%. The
DTA curve showed an exotherm at 310.degree. C. X-ray studies
confirmed the presence of carbon nanotubes-iron nanoparticles in
the carbon composition. The x-ray diffraction studies showed the
four characteristic reflection values [(002), (100), (004), and
(110)] for carbon nanotubes and the pattern for bcc-iron
nanoparticles. The x-ray (002) reflection for carbon nanotubes was
readily apparent.
EXAMPLE 19
[0051] Synthesis of 1/20 molar Co.sub.2(CO).sub.8/phthalonitrile
mixture--The phthalonitrile resin (a 2:1 oligomer of bisphenol A
and benzophenone capped with phthalonitrile units, hereinafter
"phthalonitrile") (200 mg, 0.225 mmol) was dissolved in 10 mL of
methylene chloride in a 25 mL round bottomed flask.
Co.sub.2(CO).sub.8 (10 mg, 0.0292 mmol) dissolved in 2 mL of
hexanes was added and a brown precipitate formed. The solvent was
removed under reduced pressure, the mixture vacuum was dried, and
the product was isolated as a dark brown solid.
EXAMPLE 20
[0052] Thermal conversion of 1/20 molar
Co.sub.2(CO).sub.8/phthalonitrile mixture to carbon nanotube-cobalt
nanoparticle composition by heating to 1000.degree. C. and to
1500.degree. C.--Samples of the mixture from Example 19 (38.01 mg
and 33.75 mg) were heated in a TGA chamber under nitrogen at
10.degree. C./min to 1000.degree. C. resulting in a shaped
composition and a char yield of 47%. The DTA curve showed exotherms
at 163, 276, 514, and 868.degree. C. X-ray studies confirmed the
presence of carbon nanotubes-cobalt nanoparticles in the carbon
composition. The x-ray diffraction studies showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt nanoparticles.
The x-ray (002) reflection for carbon nanotubes was readily
apparent.
EXAMPLE 21
[0053] Direct formation of fibers from melt of 1/20 molar
Co.sub.2(CO).sub.8/phthalonitrile mixture to carbon nanotube-cobalt
nanoparticle composition and heating of stabilized fiber to
1000.degree. C.--A sample (0.25 g) of the mixture from Example 19
was melted on a hot plate and heated at 330.degree. C. to a viscous
melt followed by the insertion of a glass rod into the sample and
the upward drawing of fibers. The diameter of the fibers was
controlled as a function of the rate of drawing of the fibers. The
drawn fibers were cured or solidified by heating at 280.degree. C.
for 12 hr, 300.degree. C. for 2 hr, 350.degree. C. for 3 hr, and
375.degree. C. to form a thermoset fiber, which was carbonized by
heating at 2.degree. C./min in a flow of nitrogen. Drawing the
fibers at 325.degree. C. permitted the retention of shape during
the curing process. The x-ray diffraction and transmission electron
microscopy (TEM) studies showed the presence of carbon nanotubes
within the fibers.
EXAMPLE 22
[0054] Thermal conversion of 1/20 molar
Co.sub.2(CO).sub.8/phthalonitrile/bis[4-(3-aminophenoxy)phenyl]sulfone
mixture to carbon nanotube-cobalt nanoparticle composition by
heating to 1000.degree. C.--A samples of the mixture prepared as in
Example 19 (100 mg) was mixed and melted with
bis[4-(3-aminophenoxy)phenyl]sulfone (p-BAPS) (2 mg) at 180.degree.
C. The resulting mixture was cooled and a sample (61.75 mg) was
cured under nitrogen in a TGA chamber by heating at 250.degree. C.
for 1 hr, 300.degree. C. for 2 hr, 350.degree. C. for 6 hr, and
375.degree. C. for 4 hr. The shaped composition was cooled and a
sample (84.65 mg) was heated under nitrogen at 10.degree. C./min to
1000.degree. C. resulting in a char yield of 67%. The DTA curve
showed exotherms at 530 and 751.degree. C. X-ray studies confirmed
the presence of carbon nanotubes-cobalt nanoparticles in the carbon
composition. The x-ray diffraction studies showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt nanoparticles.
The x-ray (002) reflection for carbon nanotubes was readily
apparent.
EXAMPLE 23
[0055] Thermal conversion of 1/20 molar
Co.sub.2(CO).sub.8/phthalonitrile/p-BAPS mixture to carbon
nanotube-cobalt nanoparticle composition by heating to 1500.degree.
C.--A samples of the mixture prepared as in Example 19 (150 mg) was
mixed and melted with p-BAPS (3 mg) at 180.degree. C. The resulting
mixture was cooled and a sample (75.23 mg) was cured under nitrogen
in a TGA chamber by heating at 250.degree. C. for 1 hr, 300.degree.
C. for 2 hr, 350.degree. C. for 6 hr, and 375.degree. C. for 4 hr.
The shaped composition was cooled and a sample (65.24 mg) was
heated under nitrogen at 10.degree. C./min to 1000.degree. C.
resulting in a char yield of 67%. The DTA curve showed exotherms at
530 and 751.degree. C. X-ray studies confirmed the presence of
carbon nanotubes-cobalt nanoparticles in the carbon composition.
The x-ray diffraction studies showed the four characteristic
reflection values [(002), (100), (004), and (110)] for carbon
nanotubes and the pattern for fcc-cobalt nanoparticles. The x-ray
(002) reflection for carbon nanotubes was readily apparent.
EXAMPLE 24
[0056] Thermal conversion of 1/20 molar
Co.sub.2(CO).sub.8/phthalonitrile/p-BAPS mixture to carbon
nanotube-cobalt nanoparticle fibers by heating to 1500.degree.
C.--A samples of the mixture prepared as in Example 19 (500 mg) was
mixed and melted with p-BAPS (10 mg) at 180.degree. C. The
resulting sample was placed on a hot plate and heated at
330.degree. C. to a viscous melt followed by the insertion of a
glass rod into the sample and the upward drawing of fibers. The
diameter of the fibers was controlled as a function of the rate of
drawing of the fibers. The drawn fibers were cured or solidified by
heating at 280.degree. C. for 12 hr, 300.degree. C. for 2 hr,
350.degree. C. for 3 hr, and 375.degree. C. for 4 hr to form a
thermoset fiber, which was carbonized by heating at 2.degree.
C./min in a flow of nitrogen. Drawing the fibers at 325.degree. C.
permitted the retention of shape during the curing process, which
was initiated at a lower temperature (270.degree. C.) so that the
fiber would retain its solid shape while curing to a thermoset
fiber. The x-ray diffraction and transmission electron microscopy
(TEM) studies showed the presence of carbon nanotubes within the
fibers. X-ray studies confirmed the presence of carbon
nanotubes-cobalt nanoparticles in the carbonized fibers/rods. The
x-ray diffraction studies showed the four characteristic reflection
values [(002), (100), (004), and (110)] for carbon nanotubes and
the pattern for fcc-cobalt nanoparticles. The x-ray (002)
reflection for carbon nanotubes was readily apparent.
EXAMPLE 25
[0057] Synthesis of 1/20 molar Fe.sub.2(CO).sub.9/phthalonitrile
mixture--The phthalonitrile (200 mg, 0.225 mmol) was dissolved in
10 mL of methylene chloride in a 25 mL round bottomed flask.
Fe.sub.2(CO).sub.9 (8.2 mg, 0.0225 mmol) dissolved in 2 mL of
hexanes was slowly added and a brown precipitate formed. The
solvent was removed under reduced pressure, the mixture vacuum was
dried, and the Fe.sub.2(CO).sub.9/phthalonitrile mixture was
isolated as a solid.
EXAMPLE 26
[0058] Thermal conversion of 1/20 molar
Fe.sub.2(CO).sub.9/phthalonitrile mixture to carbon nanotube-cobalt
nanoparticle composition by heating to 1000.degree. C. and
1500.degree. C.--Samples of the mixture from Example 25 (38.01 mg
and 50.26 mg) were heated in a TGA chamber under nitrogen at
10.degree. C./min to 1000.degree. C. and to 1500.degree. C.
resulting in a shaped composition and char yields of 47% and 43%,
respectively. The DTA curve showed exotherms at 163, 276, 514, and
868.degree. C. during the heat treatment to 1000.degree. C. and to
1500.degree. C. X-ray studies confirmed the presence of carbon
nanotubes-iron nanoparticles in the carbon composition. The x-ray
diffraction studies showed the four characteristic reflection
values [(002), (100), (004), and (110)] for carbon nanotubes and
the pattern for fcc-Co nanoparticles. The x-ray (002) reflection
for carbon nanotubes was readily apparent.
EXAMPLE 27
[0059] Synthesis of 1/20 molar bis(1,5-cyclooctodiene)nickel
(0)/phthalonitrile mixture--The phthalonitrile (1.00 g, 1.12 mmol)
was dissolved in 25 mL of methylene chloride in a 50 mL round
bottomed flask. Ni[COD].sub.2 (27.5 mg, 0.100 mmol) dissolved in 2
mL of methylene chloride was added dropwise and a brown precipitate
formed. The solvent was removed under reduced pressure, the mixture
vacuum was dried, and the mixture was isolated as a dark brown
solid.
EXAMPLE 28
[0060] Thermal conversion of 1/20 molar
Ni[COD].sub.2/phthalonitrile mixture to carbon nanotube-nickel
nanoparticle composition by heating to 1000.degree. C.--A sample of
the mixture from Example 27 (46.2 mg) was heated in a TGA chamber
under nitrogen at 10.degree. C./min to 1000.degree. C. resulting in
a shaped composition and a char yield of 50%. X-ray studies confirm
the presence of carbon nanotubes-nickel nanoparticles in the carbon
composition. The x-ray diffraction studies showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for nickel nanoparticles. The
x-ray (002) reflection for carbon nanotubes was readily
apparent.
EXAMPLE 29
[0061] Synthesis of 1/20 by weight Co.sub.2(CO).sub.8/coal pitch
mixture--A coal tar pitch (1.18 g) and Co.sub.2(CO).sub.8 (59 mg,
0.172 mmol) were mixed together in 5 mL of methylene chloride. The
mixture was stirred for 5 min and the solvent was removed under
reduced pressure. The mixture was vacuum dried and the product
isolated as a black oil.
EXAMPLE 30
[0062] Heating of 1/20 by weight Co.sub.2(CO).sub.8/coal pitch
mixture to 1100.degree. C. and 1400.degree. C.--Samples of the
mixture from Example 29 (45.92 mg and 35.43 mg) were heated at
10.degree. C./min to 1100.degree. C. and to 1400.degree. C. in a
TGA chamber under nitrogen resulting in shaped components to afford
char yields of 30% and 27%, respectively. X-ray studies confirmed
the presence of carbon nanotubes-cobalt nanoparticles in the carbon
compositions. The x-ray diffraction studies showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt and cobalt
oxide nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 31
[0063] Synthesis of 1/20 by weight Co.sub.2(CO).sub.8/petroleum
pitch mixture--The petroleum pitch (1.05 g) and Co.sub.2(CO).sub.8
(53 mg, 0.154 mmol) were mixed together in 5 mL of methylene
chloride. The mixture was stirred for 5 min and the solvent was
removed under reduced pressure. The mixture was vacuum dried and
the product was isolated as a black oil.
EXAMPLE 32
[0064] Heating of 1/20 by weight Co.sub.2(CO).sub.8/petroleum pitch
mixture to 1000.degree. C. and 1500.degree. C.--Samples of the
mixture from Example 31 (52.22 mg and 55.66 mg) were heated at
10.degree. C./min to 1000.degree. C. and to 1500.degree. C. under
nitrogen resulting in a shaped component to afford char yields of
29% and 26%, respectively. X-ray studies confirmed the presence of
carbon nanotubes-cobalt nanoparticles in the carbon composition.
The x-ray diffraction studies showed the four characteristic
reflection values [(002), (100), (004), and (110)] for carbon
nanotubes and the pattern for fcc-cobalt and cobalt oxide
nanoparticles. The x-ray (002) reflection for carbon nanotubes was
readily apparent.
EXAMPLE 33
[0065] Synthesis of 1/20 by weight
Co.sub.2(CO).sub.8/naphthalene-derived mesophase pitch (AR pitch
resin by Mitsubishi) mixture--The AR pitch resin (1.05 g) and
Co.sub.2(CO).sub.8 (53 mg, 0.154 mmol) were mixed together in
powdered form and heated to 270.degree. C. with stirring by
mechanical means under inert condition. The sample was then cooled
to room temperature.
EXAMPLE 34
[0066] Conversion of 1/20 by weight
Co.sub.2(CO).sub.8/naphthalene-derived mesophase pitch (AR pitch
resin by Mitsubishi) mixture to carbon nanotubes--A Sample (50 mg)
of the mixture from Example 33 was oxidatively stabilized in a flow
(50 cc/min) of air at 290.degree. C. for 1 hr, cooled and then
heated at 10.degree. C./min to 1500.degree. C. under nitrogen. The
air stabilization converted the melt to a solid so that the
resulting composition retained its structure upon further heating
to elevated temperatures. The x-ray diffraction studies showed the
four characteristic reflection values [(002), (100), (004), and
(110)] for carbon nanotubes and the pattern for fcc-cobalt and
cobalt oxide nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 35
[0067] Direct formation of fibers from melt of 1/20 by weight
Co.sub.2(CO).sub.8/naphthalene-derived mesophase pitch (AR pitch
resin by Mitsubishi) mixture--A sample (0.2 g) of the mixture
prepared in Example 33 was melted at 290.degree. C. under inert
condition and a glass rod was inserted and a fiber was pulled out.
This procedure was repeated several times. The fibers were air
stabilized by heating under a flow of air at 1.degree. C./min to
290.degree. C. and holding for 1 hr. After cooling, the stabilized
fibers were heated and carbonized at 5.degree. C./min to
1500.degree. C. and held at this temperature for 1 hr; the fibers
retained their shape. X-ray diffraction studies showed the four
characteristic reflection values [(002), (100), (004), and (110)]
for carbon nanotubes and the pattern for fcc-cobalt and cobalt
oxide nanoparticles. The x-ray (002) reflection for carbon
nanotubes is readily apparent. TEM studies also showed the presence
of carbon nanotubes. Thus, this experiment showed that fibers can
be spun from the melt of such a mixture as Example 33, air
stabilized, and converted in situ into carbon nanotube containing
fibers. The yields in such fibers would depend on the optimization
of the carbonization/graphitization conditions.
EXAMPLE 36
[0068] Fabrication of CNT fibers from the
Co.sub.2(CO).sub.8/phthalonitrile/p-BAPS sample--A sample of the
Co.sub.2(CO).sub.8/phthalonitrile mixture from Example 19 (250 mg)
and p-BAPS (12.5 mg) were placed in an aluminum pan. The mixture
was heated at 350.degree. C. with stirring and held at that
temperature until the mixture became too viscous to stir easily. A
glass rod was inserted into the mixture and pulled out resulting in
the formation of fibers from the surface of the mixture and
attached to the glass rod. The diameter of the fibers was
controlled by the rate that the fibers were drawn. The polymeric
fibers were heat treated at 200.degree. C. for 2 hr, 250.degree. C.
for 12 hr in air and 300.degree. C. for 4 hr, 350.degree. C. for 2
hr and 375.degree. C. for 4 hr under argon. Different fibers were
then carbonized by heating under nitrogen to 1000.degree. C. and to
1500.degree. C. at 0.3.degree. C./min and holding for 1 hour to
produce CNT-containing fibers. Higher yield of CNTs were obtained
for the higher temperature treated fibers. It was important that
the fibers be initially heated at a temperature below the
temperature of the melt so as to convert to a solid thermoset
before heat treatment to higher temperatures.
EXAMPLE 37
[0069] Fabrication of CNT fibers from the 1:20 by weight
Co.sub.2(CO).sub.8/PAN mixture--A sample of the mixture prepared as
in Example 1 (200 mg) was dissolved in DMF (2 mL) by heating at
100.degree. C. until a homogeneous solution was obtained. The
mixture was then drawn into a 1 mL syringe and slowly precipitated
into water yielding PAN polymeric fibers. The fiber shaped
structures obtained were isolated and dried. The shaped solid
fibers were oxidatively stabilized by heating at 280.degree. C. for
3 hr so that the fibers would retain their shape and not melt upon
further heat treatment at elevated temperatures. Different
stabilized fibers were then carbonized by heating under nitrogen to
1000.degree. C. and to 1500.degree. C., respectively, at
0.3.degree. C./min and holding for 1 hour to produce CNT-containing
fibers. Higher yield of CNTs were obtained for the higher
temperature treated fibers.
EXAMPLE 38
[0070] Fabrication of CNT fibers from the 1:20 by weight
Fe.sub.2(CO).sub.9/PAN sample--A sample of the
Fe.sub.2(CO).sub.9/PAN mixture prepared as in Example 13 (250 mg)
was dissolved in DMF (2 mL) with heating (100.degree. C.) until a
homogeneous solution was obtained. The mixture was drawn into a 1
mL syringe and slowly precipitated into water yielding fibers. The
fiber shaped structures obtained were isolated, washed several
times with distilled water, and dried. The shaped solid fibers were
oxidatively stabilized by heating at 280.degree. C. for 2-3 hr so
that the fibers would retain their shape and not melt upon further
heat treatment at elevated temperatures. Different polymeric fibers
were then carbonized by heating under nitrogen to 1000.degree. C.
and to 1500.degree. C., respectively at 0.3.degree. C./min, and
holding for 1 hour to produce in situ CNT-containing fibers. Higher
yield of CNTs were obtained for the higher temperature treated
fibers.
EXAMPLE 39
[0071] Synthesis of 1/20 by weight Ni[COD].sub.2/PAN
mixture--Ni[COD].sub.2(50 mg, 0.181 mmol) dissolved in 1 mL of
methylene chloride was added dropwise to a mixture of PAN (1.00 g)
and 30 mL of methylene chloride in a 50 mL round bottomed flask.
The PAN did not dissolve. The slurry was allowed to stir for 15 min
before the solvent was removed under reduced pressure. The mixture
was vacuum dried and isolated as an off-white solid.
EXAMPLE 40
[0072] Thermal conversion of 1/20 by weight Ni[COD].sub.2/PAN
mixture to carbon nanotube-nickel nanoparticle composition by
heating to 1000.degree. C.--A sample of the mixture from Example 39
(25.23 mg) was heated in a TGA chamber under nitrogen at 10.degree.
C./min to 1000.degree. C. resulting in a shaped composition and a
char yield of 36%. The DTA curve showed an exotherm at 308.degree.
C. X-ray studies confirmed the presence of carbon nanotubes-cobalt
nanoparticles in the carbon composition. The x-ray diffraction
studies showed the four characteristic reflection values [(002),
(100), (004), and (110)] for carbon nanotubes and the pattern for
nickel nanoparticles. The x-ray (002) reflection for carbon
nanotubes was readily apparent.
EXAMPLE 41
[0073] Large scale synthesis of 1/20 by weight
Fe.sub.2(CO).sub.9/PAN mixture--PAN (250 g) and 1500 mL of
methylene chloride were added to a 3000 mL three-necked flask with
a mechanical stirrer. The mixture was degassed with nitrogen for 30
min. Fe.sub.2(CO).sub.9 (12.5 g) was then added which readily
dissolved in the methylene chloride forming an orange colored
suspension since the PAN did not dissolve. The slurry was allowed
to stir for 1 hr before the solvent was removed under reduced
pressure. The solid was vacuum dried.
EXAMPLE 42
[0074] Large scale synthesis of 1/20 by weight
Co.sub.2(CO).sub.8/PAN mixture--PAN (250 g) and 1500 mL of
methylene chloride were added to a 3000 mL three-neck flask with a
mechanical stirrer. The mixture was degassed with nitrogen for 30
min. Co.sub.2(CO).sub.8 (12.5 g) was then added which readily
dissolved in the methylene chloride forming a dark red colored
suspension since the PAN did not dissolve. The slurry was allowed
to stir for 1 hr before the solvent was removed under reduced
pressure. The solid was vacuum dried.
EXAMPLE 43
[0075] Conversion of 1/20 by weight Fe.sub.2(CO).sub.9/PAN mixture
to polymeric nanofiber sheets--Samples of the mixture from Example
41 were dissolved in DMF at 80.degree. C. to a desired viscosity
and used in electrospinning to obtain random and aligned polymeric
(PAN) nanofiber-containing sheets. Various thicknesses (50, 100,
and 200 .mu.m) of the sheets (9''.times.18'') were formulated and
used for further studies.
EXAMPLE 44
[0076] Oxidative stabilization of polymeric (PAN) nanofiber sheets
formulated from 1/20 by weight Fe.sub.2(CO).sub.9/PAN mixture--The
polymeric nanofiber sheets of Example 43 were oxidatively
stabilized by heating at 1.5.degree. C./min to 260.degree. C. and
holding at this temperature for 3-5 hr in a flow of air followed by
rapid heating (5.degree. C./min) to 300.degree. C. followed by
cooling. The color of the sheets changed from off white to a dark
tan color.
EXAMPLE 45
[0077] Conversion of the oxidatively stabilized polymeric (PAN)
nanofiber sheets formulated from 1/20 by weight
Fe.sub.2(CO).sub.9/PAN mixture to carbon nanotube-containing
nanofiber carbon sheets--The air stabilized polymeric sheets of
Example 44 were heated at 5.degree. C./min to 1000.degree. C. under
a flow of nitrogen and held at 1000.degree. C. for 2 hr. During the
heat treatment, the polymeric sheet shrunk to about 1/3 of the
original size. X-ray diffraction showed that carbon nanotubes were
being formed in situ within the nanofibers of the carbon sheets
along with some amorphous carbon and iron oxide nanoparticles.
EXAMPLE 46
[0078] Heat treatment of carbon nanotube-containing nanofiber
carbon sheets formulated from the oxidatively stabilized polymeric
(PAN) nanofiber sheets to 1500.degree. C.--Samples of the carbon
nanotube-nanofiber carbon sheets of Example 45 were further heated
at 5.degree. C./min to 1500.degree. C. and held at this temperature
for 2 hr under a flow of nitrogen. X-ray diffraction studies showed
a large 002 peak at about 25.83 and the peak attributed to the
amorphous carbon had been greatly diminished. This study showed
that the amount of carbon nanotubes within the nanofibers can be
controlled as a function of the heat treatment temperature.
EXAMPLE 47
[0079] Conversion of sample formulated from the large scale
synthesis of 1/20 by weight Co.sub.2(CO).sub.8/PAN mixture into
films--A sample (0.5 g) of the mixture of Example 42 was dissolved
in 25 mL of DMF at 80.degree. C. Upon cooling to ambient
conditions, aliquots were poured into distilled water forming solid
films. The off white colored films were washed several times with
distilled water, collected, and dried.
EXAMPLE 48
[0080] Oxidative stabilization of sample (film) formulated from
1/20 by weight Co.sub.2(CO).sub.8/PAN mixture--A sample (10 mg) of
the off white colored film from Example 47 was heated in a flow of
air at 2.degree. C./min to 225.degree. C. and held at this
temperature for 4 hr. The oxidatively heat treatment converted the
PAN into an unsaturated conjugated black material; sample lost
about 5% weight during the heat treatment.
EXAMPLE 49
[0081] Conversion of oxidatively stabilized PAN film to Co metal
nanoparticle-carbon nanotube containing film--A sample of the
stabilized film from Example 48 (45 mg) was heated in a TGA chamber
under flow of nitrogen at 10.degree. C./min to 1300.degree. C.
resulting in a shaped composition and a char yield of 50%. At 1000,
1100, and 1300.degree. C., the sample retained about 58, 53, and
59% weight. X-ray studies confirmed the presence of carbon
nanotubes-cobalt nanoparticles in the carbon composition of the
film. The x-ray diffraction studies showed the four characteristic
reflection values [(002), (100), (004), and (110)] for carbon
nanotubes and the pattern for fcc-cobalt nanoparticles. The x-ray
(002) reflection at about 25.65 for carbon nanotubes is intense and
readily apparent. This composition may be suitable for the spinning
of fibers, oxidative stabilization, and conversion to carbon and
graphite fibers.
EXAMPLE 50
[0082] Conversion of 1/20 by weight Co.sub.2(CO).sub.8/PAN
mixture--Samples of a mixture as formed in Example 42 are dissolved
in DMF to a desired viscosity and used in electrospinning to obtain
random and aligned polymeric (PAN) nanofiber-containing sheets.
Various thickness (50, 100, and 200 .mu.m) of the sheets
(9''.times.18'') and nanofiber diameter sizes are formulated and
used for further studies and conversion to carbon nanotubes in situ
within the nanofibers of carbon sheets.
EXAMPLE 51
[0083] Oxidative stabilization of polymeric (PAN) nanofiber sheets
formulated from 1/20 by weight Co.sub.2(CO).sub.8/PAN mixture--The
polymeric nanofiber sheets of Example 50 are oxidatively stabilized
by heating at 1.5.degree. C./min to 230-260.degree. C. and holding
at the temperature for 3-5 hr in a flow of air followed by rapid
heating (5.degree. C./min) to 300.degree. C. followed by cooling.
The color of the sheets is expected to change from off white to a
dark color.
EXAMPLE 52
[0084] Conversion of the oxidatively stabilized polymeric (PAN)
nanofiber sheets formulated from 1/20 by weight
Co.sub.2(CO).sub.8/PAN mixture to carbon nanotube-containing
nanofiber carbon sheets--The air stabilized polymeric sheets of
Example 51 are heated at 5.degree. C./min to 1000.degree. C. under
flow of nitrogen and held at 1000-1200.degree. C. for 2 hr. During
the heat treatment, the polymeric sheet is expected to shrink in
size. X-ray diffraction studies are expected to show that Co
nanoparticle-carbon nanotubes are formed in situ within the
nanofibers of the carbon sheets along with some amorphous carbon
and Co oxide nanoparticles.
EXAMPLE 53
[0085] Heat treatment of carbon nanotube-containing nanofiber
carbon sheets formulated from the oxidatively stabilized polymeric
(PAN) nanofiber sheets to 1500.degree. C.--Samples of the carbon
nanotube-nanofiber carbon sheets of Example 52 are further heated
at 5.degree. C./min to 1500.degree. C. and held at this temperature
for 2 hr under a flow of nitrogen. X-ray diffraction studies are
expected to show a large 002 peak at about 25.83 and the peak
attributed to the amorphous carbon is expected to be greatly
diminished. This study is expected to show that the amount of
carbon nanotubes within the nanofibers can be controlled as a
function of the heat treatment temperature.
EXAMPLE 54
[0086] Formulation of wt. % solutions in DMAC from 1/20 by weight
Fe.sub.2(CO).sub.9/PAN mixture--Varying wt. % polymeric solutions
in DMAC were prepared using the Fe.sub.2(CO).sub.9/PAN mixture of
Example 41 and thoroughly mixed by heating at 120.degree. C. for 1
hr. It was found that an 18 wt. % solution had the most desirable
viscosity value for spinning fibers.
EXAMPLE 55
[0087] Spinning of fibers from 1/20 by weight
Fe.sub.2(CO).sub.9/PAN in solution--Polymeric fibers (100 filament
tow) were spun using a spinneret from the mixture of Example 54,
passed into water, and dried. The color of the fibers/tows was a
bit yellow-brown compared to homopolymer PAN, which was white. But
this was expected as the Fe.sub.2(CO).sub.9/PAN powder had a darker
color relative to pure PAN attributed to the presence of the
Fe.sub.2(CO).sub.9.
EXAMPLE 56
[0088] Oxidative stabilization of the fibers spun from a solution
of 1/20 by weight Fe.sub.2(CO).sub.9/PAN mixture--To oxidatively
stabilize the PAN-based fibers formulated in Example 55, the
fibers/tows were heated from room temperature to 250.degree. C. at
1.degree. C./min in a flow of air; dwell time at 250.degree. C. was
for 5 hr followed by heating at 1.degree. C./min to 300.degree. C.
and then cooling back to room temperature. During the heat
treatment, the fibers changed in color from light yellow-brown to
amber to dark brown to black.
EXAMPLE 57
[0089] Carbonization of the oxidatively stabilized Fe-Pan fibers at
1300.degree. C.--Oxidatively stabilized fibers of Example 56 were
mounted onto a graphite rack system and carbonized in a graphitic
furnace in inert gas (helium). The stabilized fibers were heated
under a constant tension from room temperature to 1300.degree. C.
at 10.degree. C./min and allowed to dwell at 1300.degree. C. for 1
hr followed by cooling back to room temperature at 50.degree.
C./min. The fibers had weight retention of 49.39%. Scanning
electron microscopy studies of the black fibers showed the presence
of carbon nanotubes within the fibers that had been formed in situ
within the fibers during the carbonization process; the carbon
nanotubes were mostly aligned along the direction of the fibers.
Transmission electron microscopy studies showed the presence of
carbon nanotubes and Fe nanoparticles within the fibers.
EXAMPLE 58
[0090] Graphitization of the oxidatively stabilized Fe-Pan fibers
at 2700.degree. C.--Oxidatively stabilized fibers of Example 56
were mounted onto a graphite rack system and graphitized in a
graphitic furnace in inert gas (helium). The stabilized fibers were
heated under a constant tension from room temperature to
1300.degree. C. at 10.degree. C./min and allowed to dwell at
1300.degree. C. for 1 hr followed by heating at 50.degree. C./min
to 2700.degree. C. and dwelling at 2700.degree. C. for 1 hr and
cooling back to room temperature at 50.degree. C./min. The fibers
had weight retention of 47.77%. Scanning electron microscopy
studies of the black fibers showed the presence of carbon nanotube
within the fibers that had been formed in situ within the fibers
during the carbonization and graphitization processes; the carbon
nanotubes were mostly aligned along the direction of the fibers.
Transmission electron microscopy studies showed the presence of
carbon nanotubes within the fibers.
EXAMPLE 59
[0091] Formulation of wt. % solutions in DMAC from 1/20 by weight
Co.sub.2(CO).sub.8/PAN mixture--Varying wt. % polymeric solutions
in DMAC were prepared using the Co.sub.2(CO).sub.8/PAN mixture of
Example 42 and thoroughly mixed by heating at 120.degree. C. for 1
hr.
EXAMPLE 60
[0092] Spinning of fibers from 1/20 by weight
Co.sub.2(CO).sub.8/PAN mixture--Polymeric fibers (100 filament tow)
are spun using a spinneret from the mixture of Example 59, passed
into water, and dried. The color of the fibers/tows is expected to
be white based on the formation of films of Example 47 from the
deposition of the solution in water and drying of the films
resulting in white film. The white fibers/tows are stabilized in
air to convert the polymer into a conjugated system that is
expected to retain its structural integrity during carbonization
and graphitization.
EXAMPLE 61
[0093] Oxidative stabilization of the fibers spun from a solution
of 1/20 by weight Co.sub.2(CO).sub.8/PAN mixture--To oxidatively
stabilize the PAN-based fibers/tows formulated in Example 60, the
fibers/tows are heated from room temperature to 250.degree. C. at
1.degree. C./min in a flow of air; dwell time at 250.degree. C. is
for 5 hr followed by heating at 1.degree. C./min to 300.degree. C.
and then cooling back to room temperature. During the heat
treatment, the fibers/tows are expected to change in color from
off-white to amber to dark brown to black.
EXAMPLE 62
[0094] Carbonization of the oxidatively stabilized Co-Pan fibers at
1300.degree. C.--Oxidatively stabilized fibers/tows of Example 61
are mounted onto a graphite rack system and carbonized in a
graphitic furnace in inert gas (helium). The stabilized fibers/tows
are heated under a constant tension from room temperature to
1300.degree. C. at 10.degree. C./min and allowed to dwell at
1300.degree. C. for 1 hr followed by cooling back to room
temperature at 50.degree. C./min. Scanning electron microscopy
studies of the black fibers are expected to show the presence of
carbon nanotube within the fibers formed in situ within the fibers
during the carbonization process with the carbon nanotubes mostly
aligned along the direction of the fibers based on the results of
Example 49. Transmission electron microscopy studies should show
the presence of carbon nanotubes and Co nanoparticles within the
fibers as in Example 57.
EXAMPLE 63
[0095] Graphitization of the oxidatively stabilized Co-Pan fibers
at 2700.degree. C.--Oxidatively stabilized fibers of Example 61 are
mounted onto a graphite rack system and graphitized in a graphitic
furnace in inert gas (helium). The stabilized fibers are heated
under a constant tension from room temperature to 1300.degree. C.
at 10.degree. C./min and allowed to dwell at 1300.degree. C. for 1
hr followed by heating at 50.degree. C./min to 2700.degree. C. and
dwelling at 2700.degree. C. for 1 hr and cooling back to room
temperature at 50.degree. C./min. Scanning electron microscopy
studies of the black fibers should show the presence of carbon
nanotube within the fibers formed in situ within the fibers during
the carbonization and graphitization processes with the carbon
nanotubes aligned along the direction of the fibers. Transmission
electron microscopy studies are expected to show the presence of
carbon nanotubes within the fibers as in Example 58.
EXAMPLE 64
[0096] Synthesis of metal salt/naphthalene-derived mesophase pitch
(AR pitch resin by Mitsubishi) mixture--Various concentrations of
metal salts and/or organometallic compounds/resins such as
octacarbonyldicobalt, diironnonacarbonyl, and ferrocene-based
materials are mixed with AR pitch resin. The metal salt-AR pitch
resin composition are thoroughly mixed in powdered form and heated
at an elevated temperature above where the AR pitch resin flows
with stirring by mechanical means under inert condition to
homogeneously mix. These samples are then cooled to room
temperature.
EXAMPLE 65
[0097] Spinning of fibers from 1/20 by weight Co.sub.2(CO).sub.8/AR
pitch resin mixture--A sample of 1/20 by weight
Co.sub.2(CO).sub.8/AR pitch resin mixture of Examples 33 and 64 is
used to spin fiber at 300-370.degree. C. through a spinneret. The
fibers/filament passes through a nitrogen atmosphere as they leave
the spinneret and before being taken up by a reel.
EXAMPLE 66
[0098] Stabilization of the mesophase AR pitch fibers produced from
1/20 by weight Co.sub.2(CO).sub.8/AR pitch resin mixture--AR pitch
fibers produced by Example 65 are stabilized to a thermoset by
heating between 250-350.degree. C. in an air atmosphere for 5-60
min. The fibers are oxidatively heated so that they will not soften
when heated to carbonization and the fibers should be totally
infusible so they will not sag during carbonization.
EXAMPLE 67
[0099] Carbonization of the mesophase AR pitch fibers derived from
Co.sub.2(CO).sub.8/AR pitch resin mixture--AR pitch thermosetting
fibers produced by Example 66 are carbonized by heating up to
2000.degree. C. in an inert (helium) atmosphere and holding from
5-30 min. Carbon nanotubes are expected to grow in situ within the
fibers along with other carbonaceous materials. As carbon nanotubes
were observed in Examples 34 and 35 on solid sample and fibers
pulled from the melt and carbonized under similar conditions,
fibers formed by this procedure using a spinneret (Example 65)
should contain carbon nanotubes with the yield dependent on the
carbonization temperature. X-ray diffraction, scanning electron
microscopy, and transmission electron microscopy studies are used
to analyze the fibers for the carbon nanotubes.
EXAMPLE 68
[0100] Spinning of fibers from 1/20 by weight Fe.sub.2(CO).sub.9/AR
pitch resin mixture--A sample of 1/20 by weight
Fe.sub.2(CO).sub.9/AR pitch resin mixture of Example 64 is used to
spin fibers at 300-370.degree. C. through a spinneret. The
fibers/filaments pass through a nitrogen atmosphere as they leave
the spinneret and before being taken up by a reel.
EXAMPLE 69
[0101] Stabilization of the mesophase AR pitch fibers produced from
1/20 by weight Fe.sub.2(CO).sub.9/AR pitch resin mixture--AR pitch
fibers produced by Example 68 are stabilized to a thermoset by
heating between 250-350.degree. C. in an air atmosphere for 5-60
min. The fibers are oxidatively heated so that they will not soften
when heated to carbonization and the fibers should be totally
infusible so they will not sag during carbonization.
EXAMPLE 70
[0102] Carbonization of the mesophase AR pitch fibers derived from
Fe.sub.2(CO).sub.9/AR pitch resin mixture--AR pitch thermosetting
fibers produced by Example 69 are carbonized by heating up to
2000.degree. C. in an inert (helium) atmosphere and holding from
5-30 min. Carbon nanotubes are expected to grow in situ within the
fibers along with other carbonaceous materials. As carbon nanotubes
were observed in Examples 34 and 35 on solid sample and fibers
pulled from melt and carbonized under similar conditions, small
diameter fiber formed by this procedure should also have carbon
nanotubes with the yield dependent on the carbonization
temperature. X-ray diffraction, scanning electron microscopy, and
transmission electron microscopy studies are used to analyze the
fibers for the carbon nanotubes.
EXAMPLE 71
[0103] Synthesis of 1/20 by weight
octacarbonyldicobalt/polyacrylonitrile DMAC
mixture--Polyacrylonitrile (2.68 g) was dissolved over 2 h in 20 mL
of heated dimethylacetamide (DMAC). The mixture was cooled to
ambient temperature and Co.sub.2(CO).sub.8 (134 mg, 0.332 mmol) was
added. Gentle heating to around 50.degree. C. with stirring
dissolved the Co.sub.2(CO).sub.8 resulting in a reddish-brown
solution The mixture was used as prepared.
EXAMPLE 72
[0104] Thermal conversion of 1/20 by weight
octacarbonyldicobalt/polyacrylonitrile mixture to carbon
nanotube-cobalt nanoparticle composition to 1000.degree. C.--A
sample of the mixture from Example 70 was added to distilled water
resulting in the deposition of an oft-white solid. The solid was
washed several times to remove the solvent and then dried. A sample
(50 mg) of the dried sample was heated in a TGA chamber under
nitrogen at 10.degree. C./min to 1000.degree. C. resulting in a
shaped composition and a char yield of 50%. The DTA curve showed an
exotherm at 308.degree. C. X-ray studies confirmed the presence of
carbon nanotubes-cobalt nanoparticles in the carbon composition.
The x-ray diffraction study showed the four characteristic
reflections [(002), (100), (004), and (110)] values for carbon
nanotubes and the pattern for cobalt nanoparticles. The x-ray (002)
reflection for carbon nanotubes is readily apparent.
EXAMPLE 73
[0105] Fabrication of CNT fibers from the 1:20 by weight
octacarbonyldicobalt/polyacrylonitrile DMAC mixture--The solution
from Example 70 (200 mg) was drawn into a 1 mL syringe and slowly
precipitated into water. Fiber shaped structures were obtained. The
fibers were washed several times with distilled water to remove the
solvent and then dried. The shaped solid fibers were oxidatively
stabilized by heating in air at 280.degree. C. for 2 h. The fibers
were then carbonized by heating under argon to 1000.degree. C. at
0.3.degree. C./min.
EXAMPLE 74
[0106] Synthesis of 1/20 by weight
diironnonacarbonyl/polyacrylonitrile DMAC
mixture--Polyacrylonitrile (2.68 g) was dissolved over 2 h in 20 mL
of heated dimethylacetamide (DMAC). The mixture was cooled to
ambient temperature and Fe.sub.2(CO).sub.9 (134 mg, 0.368 mmol) was
added. Gentle heating to around 50.degree. C. with stirring
dissolved the Fe.sub.2(CO).sub.9 resulting in an orange-red
solution. The mixture was used as prepared.
EXAMPLE 75
[0107] Thermal conversion of 1/20 by weight diironnonacarbonyl
/polyacrylonitrile mixture to carbon nanotube-iron nanoparticle
composition--A sample of the mixture from Example 73 was added to
distilled water resulting in the deposition of an oft-white solid.
The solid was washed several times to remove the solvent and then
dried. A sample (43.5 mg) of the dried sample was heated in a TGA
chamber under nitrogen at 10.degree. C./min to 1000.degree. C.
resulting in a shaped composition and a char yield of 48%. The DTA
curve showed an exotherm at 310.degree. C. X-ray studies confirmed
the presence of carbon nanotubes-iron nanoparticles in the carbon
composition. The x-ray diffraction study showed the four
characteristic reflections [(002), (100), (004), and (110)] values
for carbon nanotubes and the pattern for iron nanoparticles. The
x-ray (002) reflection for carbon nanotubes is readily
apparent.
EXAMPLE 76
[0108] Fabrication of CNT fibers from the 1:20 by weight
diironnonacarbonyl/polyacrylonitrile DMAC mixture--The solution
from Example 73 (500 mg) was drawn into a 1 mL syringe and slowly
precipitated into water. Fiber shaped structures were obtained. The
fibers were washed several times with distilled water to remove the
solvent and then dried. The shaped solid fibers were oxidatively
stabilized by heating in air at 280.degree. C. for 2 h. The fibers
were then carbonized by heating under argon to 1000.degree. C. at
0.3.degree. C./min.
[0109] Obviously, many modifications and variations are possible in
light of the above teachings. It is therefore to be understood that
the claimed subject matter may be practiced otherwise than as
specifically described. Any reference to claim elements in the
singular, e.g., using the articles "a," "an," "the," or "said" is
not construed as limiting the element to the singular.
* * * * *