U.S. patent application number 10/097393 was filed with the patent office on 2003-05-22 for carbon nanotube complex molded body and the method of making the same.
This patent application is currently assigned to Polymatech Co., Ltd.. Invention is credited to Ago, Hiroki, Kakudate, Yozo, Kimura, Toru, Ohshima, Satoshi, Tobita, Masayuki, Uchida, Kunio, Yokoi, Hiroyuki, Yumura, Motoo.
Application Number | 20030096104 10/097393 |
Document ID | / |
Family ID | 18931545 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030096104 |
Kind Code |
A1 |
Tobita, Masayuki ; et
al. |
May 22, 2003 |
Carbon nanotube complex molded body and the method of making the
same
Abstract
A complex molded body of carbon nanotubes includes a matrix and
carbon nanotubes arranged in a given direction in the matrix. The
matrix is at least one organic polymer selected from the group
consisting of thermoplastic resin, thermosetting resin, rubber, and
thermoplastic elastomer. The complex molded body is produced by a
method comprising the step of: providing a composition that
includes a matrix and carbon nanotubes; applying a magnetic field
to the composition to arrange the carbon nanotubes in a given
direction; and hardening the composition to produce a complex
molded body. The complex molded body has excellent anisotropy in
terms of electrical property, thermal property, and mechanical
property.
Inventors: |
Tobita, Masayuki; (Tokyo,
JP) ; Kimura, Toru; (Tokyo, JP) ; Yumura,
Motoo; (Ibaraki-ken, JP) ; Ohshima, Satoshi;
(Ibaraki-ken, JP) ; Ago, Hiroki; (Ibaraki-ken,
JP) ; Uchida, Kunio; (Ibaraki-ken, JP) ;
Kakudate, Yozo; (Ibaraki-ken, JP) ; Yokoi,
Hiroyuki; (Ibaraki-ken, JP) |
Correspondence
Address: |
STOUT, UXA, BUYAN & MULLINS LLP
4 VENTURE, SUITE 300
IRVINE
CA
92618
US
|
Assignee: |
Polymatech Co., Ltd.
Senjyo Bldg., 4-8-16, Nihonbashi-honcho, Chuo-ku
Tokyo
JP
103-8424
|
Family ID: |
18931545 |
Appl. No.: |
10/097393 |
Filed: |
March 14, 2002 |
Current U.S.
Class: |
428/332 ;
204/155; 428/336 |
Current CPC
Class: |
Y10T 428/265 20150115;
C04B 2235/605 20130101; C04B 2235/5288 20130101; C04B 2235/787
20130101; C04B 35/524 20130101; B82Y 30/00 20130101; C04B 2235/5264
20130101; C08K 7/24 20130101; C08K 3/041 20170501; C04B 2235/48
20130101; C04B 2235/526 20130101; C04B 35/522 20130101; Y10T 428/26
20150115; C08K 3/04 20130101; C08K 3/041 20170501; C08L 67/04
20130101; C08K 3/041 20170501; C08L 63/00 20130101; C08K 3/041
20170501; C08L 69/00 20130101 |
Class at
Publication: |
428/332 ;
428/336; 204/155 |
International
Class: |
C25B 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2001 |
JP |
2001-74244 |
Claims
1. A complex molded body of carbon nanotubes comprising: a matrix;
and carbon nanotubes arranged in a given direction in the
matrix.
2. A complex molded body of claim 1, wherein the matrix is at least
one organic polymer selected from the group consisting of
thermoplastic resin, thermosetting resin, rubber, and thermoplastic
elastomer.
3. A complex molded body of claim 1, wherein the matrix is metal,
ceramic, other inorganic material, or a precursor thereof.
4. A complex molded body of claim 1, wherein the carbon nanotubes
have a diameter of 1 to 20 nm and a length of 50 nm to 100
.mu.m.
5. A complex molded body of claim 1, wherein the amount of the
carbon nanotubes is 0.1 to 20 parts by weight relative to 100 parts
by weight matrix.
6. A complex molded body of claim 1, further comprising graphitized
carbon fibers.
7. A complex molded body of claim 1, wherein the carbon nanotubes
have a ferromagnetic coating on their surface.
8. A method of making a complex molded body of carbon nanotubes
comprising the steps of: providing a composition that includes a
matrix and carbon nanotubes; applying a magnetic field to the
composition to arrange the carbon nanotubes in a given direction;
and hardening the composition to produce a complex molded body.
9. A method of claim 8, wherein the matrix is at least one organic
polymer selected from the group consisting of thermoplastic resin,
thermosetting resin, rubber, and thermoplastic elastomer.
10. A method of claim 8, wherein the matrix is metal, ceramic,
other inorganic material, or a precursor thereof.
11. A method of claim 8, wherein the carbon nanotubes have a
diameter of 1 to 20 nm and a length of 50 nm to 100 .mu.m.
12. A method of claim 8, wherein the amount of the carbon nanotubes
in said composition is 0.1 to 20 parts by weight relative to 100
parts by weight matrix.
13. A method of claim 8, wherein said composition further includes
graphitized carbon fibers.
14. A method of claim 8, wherein the carbon nanotubes have a
ferromagnetic coating on their surface.
15. A method of claim 8, wherein the magnetic field has a magnetic
flux density from 5 to 20 tesla.
16. A method of claim 8, wherein the step of providing a
composition includes injecting the composition into a recess of a
forming mold.
17. A method of claim 10, wherein the step of hardening the
composition includes cooling the composition.
18. A method of claim 8, wherein the step of hardening the
composition includes drying and sintering the composition to
carbonize or graphitize the matrix.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a complex molded body where
carbon nanotubes are arranged in a given direction in a matrix and
a method of making the complex molded body. The molded body
functions anisotropically in terms of electrical property, thermal
property, mechanical property and may be used as electronic parts,
thermally conductive material, and high-strength material.
[0002] Japanese Laid-Open Patent Publication No.5-125619 and
Japanese Laid-Open Patent Publication No.7-216660 disclose a carbon
nanotube and a method of making it. According the publications,
development of many interesting applications, which use specific
functions of carbon nanotube, such as an electron-emitting element,
a hydrogen storage, a thin-film cell, a probe, a micromachine,
semiconductor ultra large-scale integrated circuit, electrically
conductive material, thermally conductive material, high-strength
and high-elasticity material are actively examined.
[0003] A conventional complex molded body of carbon nanotube is
obtained by blending carbon nanotubes in a matrix such as resin,
rubber, metal, or ceramic and hardening the composition. In such a
complex molded body, carbon nanotubes are basically dispersed at
random in the matrix. Accordingly, resultant properties such as
mechanical property, electrical property, electron-emitting
property are randomly or equally provided. In other words, the
conventional complex molded body is an isotropic material.
[0004] Carbon nanotubes in the matrix can be oriented in a flowing
direction by molding the composition in a flowing field or shearing
fields or by extending the composition. However, in these methods,
carbon nanotubes can not be arranged in a thickness direction of
the plate-like molded body. The direction of nanotubes can not be
controlled in a desired direction.
[0005] Japanese Laid-Open Patent Publication No.11-194134 and
Japanese Laid-Open Patent Publication No.10-265208 propose a carbon
nanotube device and a method of carbon nanotube film respectively
where carbon nanotubes are grown in a given direction in vapor on
the catalytic molecules (such as iron, cobalt, nickel) arranged on
the substrate. However, when the carbon nanotubes are arranged on
the planar substrate by using these methods, only a device in which
carbon nanotubes are arranged perpendicular to the substrate can be
obtained. Therefore, to fabricate a device that has a desired form
is difficult.
[0006] The object of the present invention is to provide a complex
molded body of carbon nanotubes that has excellent anisotropic
functions in terms of electrical property, thermal property, and
mechanical property, and a method of making the complex molded
body.
BRIEF SUMMARY OF THE INVENTION
[0007] The complex molded body of carbon nanotubes includes a
matrix and carbon nanotubes that are arranged in the matrix in a
given direction.
[0008] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0010] FIG. 1 is a schematic view of a complex molded body of
carbon nanotubes of Example 1;
[0011] FIG. 2 is a cross-sectional view of forming molds in an
opened position;
[0012] FIG. 3 is a cross-sectional view of forming molds where the
composition is injected in a recess of a mold and two molds are
closed together;
[0013] FIG. 4 is a cross-sectional view showing that, following
FIG. 3, a pair of magnets are placed on both sides of the forming
mold and a magnetic field is applied to the composition in the
recess;
[0014] FIG. 5 is a schematic view of a complex molded body of
carbon nanotubes of Example 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Embodiments of the present invention are described in detail
below.
[0016] A complex molded body of carbon nanotubes is formed such
that the carbon nanotubes are arranged in a matrix in a given
direction. The complex molded body may be formed into a desired
shape such as a plate, a tube, and a block to be used.
[0017] A type and a manufacturing method of the carbon nanotube for
use in the present invention are not particularly limited so long
as the carbon nanotube is made of carbon, it takes a tubular shape,
and it has a diameter on the order of nanometer. For example, the
carbon nanotubes manufactured by the methods disclosed in Japanese
Laid-Open Patent Publication No.6-157016, Japanese Laid-Open Patent
Publication No.6-280116, Japanese Laid-Open Patent Publication
No.10-203810, and Japanese Laid-Open Patent Publication No.11-11917
may be used. An arc discharge process has become generally used for
synthesis of carbon nanotubes. However, the use of a laser
vaporization process, a thermal cracking process, and a plasma
discharge process have recently been studied and carbon nanotubes
produced by such processes.
[0018] A carbon nanotube has a structure of hexagonal networks of
carbon atoms extending in tubular form. The nanotube that has one
tubular layer is called single-wall nanotube (called SWNT
hereinafter) while the nanotube that has a multiple of tubular
layers is called multi-wall nanotube (called MWNT hereinafter).
Structure of carbon nanotube is determined by a kind of synthesis
process or various conditions during the process.
[0019] By-products, such as amorphous carbon nanoparticles,
fullerenes, and metal nanoparticles, are produced together with
carbon nanotubes, and such by-products may remain in the product.
However, since fullerenes are soluble in organic solvents, such as
toluene, carbon disulfide, benzene, and chlorobenzene, they can be
extracted. Also, carbon nanoparticles and graphite pieces can be
removed by forming selective inter-layer compounds of carbon
nanoparticles and graphite pieces and sintering them at low
temperature, based on the fact that interlayer distances between
layers of carbon nanotubes are shorter than those of carbon
nanoparticles and graphite pieces. The decrease in temperature
inhibits decrement of carbon nanotubes due to combustion and thus
improves a yield of the nanotubes.
[0020] Further, the carbon nanotubes are materials of high aspect
ratio. Thus the product often has a complex intertwined structure,
depending on the manufacturing process. In such cases, the carbon
nanotubes may be dispersed by ultrasonic dispersion. Preferably,
carbon nanotubes are pulverized under a predetermined condition and
processed to yield shorter carbon nanotubes. The pulverization
process may include, but is not limited to, dry pulverization
processes such as shearing and grinding, and ball milling and a
homogenizer that use a surfactant-containing water or an organic
solvent.
[0021] The carbon nanotube for use in the present invention is not
limited to SWNT or MWNT. Carbon nanotubes such as those containing
metal or other inorganic or organic materials; those filled with
carbon or other materials; coiled, spired, or fibrillary carbon
nanotubes; or so-called nanofibers may also be used. Neither the
diameters nor the lengths of the carbon nanotubes are limited.
However, with regard to manufacturing facility and realization of
anisotropic function, the carbon nanotubes preferably have a
diameter from 1 to 20 nm and a length from 50 nm to 100 .mu.m.
[0022] The matrix is a base material in which carbon nanotubes are
blended. Examples of the matrix may include resin, rubber,
thermoplastic elastomer, adhesive, paint, ink, metal, alloy,
ceramic, cement, gel, paper, fiber, web, and nonwoven fabric. The
matrix may be selected according to intended required
characteristics of the complex molded body, such as hardness,
mechanical strength, heat resistance, electrical properties,
durability, and reliability. In particular, the matrix is
preferably at least one organic polymer selected from the group
consisting of thermoplastic resin, thermosetting resin, rubber, and
thermoplastic elastomer, due to their molding capability.
[0023] Thermoplastic resin includes polyethylene, polypropylene,
ethylene-.alpha.-olefin copolymer such as ethylene-propylene
copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene
chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer,
polyvinyl alcohol, polyvinyl acetal, fluoropolymers such as
polyvinylidene fluoride and polytetrafluoroethylene, polyethylene
terephthalate, polybutylene terephthalate, polyethylene
naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile
copolymer, ABS resin, polyphenylene ether (PPE) resin and modified
PPE resin, aliphatic and aromatic polyamide, polyimide, polyamide
imide, polymethacrylic acid and polymethacrylates such as
polymethyl methacrylate, polyacrylic acids, polycarbonate,
polyphenylene sulfide, polysulfone, polyether sulfone, polyether
nitrile, polyether ketone, polyketone, liquid crystal polymer,
silicone resin, and ionomer.
[0024] The thermosetting resin includes epoxy resin, phenol resin,
acrylic resin, urethane resin, polyimide resin, unsaturated
polyester resin, diallyl phthalate resin, dicycropentadiene resin,
and benzocyclobutene diene. The methods of hardening the
thermosetting resin are not limited to thermosetting but include
ordinary hardening methods, such as light setting and moisture
setting.
[0025] The rubber may be natural rubber or synthetic rubber.
Synthetic rubbers may include butadiene rubber, isoprene rubber,
styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated
nitrile rubber, chloroprene rubber, ethylene-propylene rubber,
chlorinated polyethylene, chlorosulfonated polyethylene, butyl
rubber and butyl rubber halide, fluorine rubber, urethane rubber,
and silicone rubber.
[0026] The thermoplastic elastomer includes styrene-butadiene or
styrene-isoprene block copolymers and hydrogenated polymer thereof,
styrene thermoplastic elastomer, olefin thermoplastic elastomer,
vinyl chloride thermoplastic elastomer, polyester thermoplastic
elastomer, polyurethane thermoplastic elastomer, and polyamide
thermoplastic elastomer. Thermoplastic resin and thermoplastic
elastomer are particularly preferred since they are recyclable.
[0027] The matrix preferably contains at least one material
selected from the group consisting of silicone rubber, epoxy resin,
polyimide resin, bis-maleimide resin, benzocyclobutene resin,
fluororesin, and polyphenylene ether resin. More preferably, the
matrix contains at least one material selected from the group
consisting of silicone rubber, epoxy resin, and polyimide resin in
terms of reliability.
[0028] A polymer alloy of the above-mentioned organic polymers, as
well as additives including a known plasticizer, a filler, a
hardener, organic fiber such as carbon fiber, glass fiber, and
aramid fiber, a stabilizer, a colorant may also be mixed in the
matrix.
[0029] To facilitate mixing of carbon nanotubes with the matrix or
arrangement of carbon nanotubes in the matrix, an organic solvent
such as methylene chloride or water may be added to decrease the
viscosity of the composition. Further, a dispersion and
stabilization agent such as a surfactant may be used to improve
dispersion.
[0030] The amount of carbon nanotubes mixed in the matrix is
preferably 0.01 to 100 parts by weight relative to 100 parts by
weight matrix. When the amount is less than 0.01 parts by weight,
the composition has inadequate anisotropic function. When the
amount is more than 100 parts by weight, dispersion of carbon
nanotubes in the matrix is worsen. The amount of carbon nanotubes
mixed in the matrix in which the nanotubes can be arranged by a
magnetic field and the composition exhibit achieves the effective
anisotropic function is conveniently 0.1 to 20 parts by weight,
although the amount may vary depending on a kind of matrix
material, other additives, or strength of magnetic field used.
[0031] Further, to improve wettability or adhesion of the carbon
nanotubes to the matrix, the surface of the carbon nanotubes is
preferably pretreated with degreasing, washing, or activation
process such as UV-radiation, corona discharge, plasma treatment,
flaming treatment, and ion implation. In addition, after these
surface treatments, the surface can be treated with a coupling
agent such as a silane-containing agent, a titanium-containing
agent, and an alminum-containing agent. This facilitates the
filling of more carbon nanotubes, so that the resultant complex
molded body functions more effectively.
[0032] A dispersing method of carbon nanotubes in the matrix is not
particularly limited. For example, when the matrix is a liquid
polymer, carbon nanotubes may be mixed in the matrix at a certain
amount with a usual mixer or a usual blender. Ultrasonic or
vibration may further be applied to improve dispersion of carbon
nanotubes. Preferably, degas process is conducted to remove
entrained air under vacuum or with pressure.
[0033] When the matrix is a solid polymer in the form of pellet or
powders, carbon nanotubes may be mixed in the matrix at a certain
amount with a usual mixing machine, such as an extruder, a kneader,
or a roller.
[0034] The strength of the magnetic field applied to the carbon
nanotubes sufficient to arrange them in a given direction is a
magnetic flux density from 0.05 to 30 tesla. When the magnetic flux
density is less than 0.05 tesla, carbon nanotubes can not be
arranged in a given direction sufficiently. When the density is
more than 30 tesla, the magnetic field is too strong to improve the
arrangement further. Although the magnetic flux density is
experimentally determined from types or amount of the matrix and
the carbon nanotubes, an intended shape of complex molded body, and
required characteristics of end products, the practical range of
magnetic flux density for arranging carbon nanotubes effectively is
from 5 to 20 tesla.
[0035] A device for producing an external magnetic field is, for
example, a permanent magnet, an electromagnet, and a coil. In the
present invention, carbon nanotubes have diamagnetism and they can
be arranged in the direction parallel to magnetic lines of force.
Therefore, to apply the magnetic field properly, a north pole and a
south pole of magnets may be placed corresponding to a desired
arrangement direction of tubes. Alternatively, a north pole and a
north pole of magnets may be placed so as to face to each other. Or
a magnet may be placed only one side of the composition. Further,
magnets may be placed such that magnetic lines of force are curved.
That is, a magnetic field may be applied in any way so long as the
magnetic lines of force are adjusted to achieve the aimed
anisotropic function.
[0036] The composition may then be molded into a desired shape,
such as a plate, a tube, or a block by press molding, extrusion
molding, transfer molding, calendering molding, to form a complex
molded body. The composition may be further processed into a thin
film by processes such as painting and printing. Thus, the
resultant carbon nanotube complex molded body includes carbon
nanotubes that are arranged in a given direction. This can be
confirmed in an enlarged picture with an electron microscope.
[0037] The complex molded body of the present invention is
anisotropic in terms of carbon nanotube-specific properties, such
as electrical property, thermal property, and mechanical property.
In other words, the complex molded body has different degrees of
such properties at different directions.
[0038] For electrical property, the complex molded body of the
present invention has high electrical conductivity in a certain
direction. In addition, this molded body exhibits higher
conductivity with a smaller amount of carbon nanotubes compared
with a molded body in which carbon nanotubes are not arranged in a
given direction. The electron emission of carbon nanotubes is
believed to be most efficient at the end of nanotubes. According to
the invention, carbon nanotubes may be placed so that a larger
number of ends of carbon nanotubes are placed at the edge of the
complex molded body.
[0039] For thermal property, when the carbon nanotubes are arranged
in a thickness direction of a plate-like molded body, thermal
conductivity in a direction parallel to the arrangement direction
of the nanotubes is different from that in a direction
perpendicular to the same. Since the carbon nanotubes have greater
thermal conductivity in their axial direction than that in a
direction perpendicular to the axial direction, the above
plate-like molded body has greater thermal conductivity in a
thickness direction, which allows the molded body to be
anisotropic. In this case, the carbon nanotubes are preferably
graphitized to improve thermal conductivity.
[0040] For mechanical property, when the carbon nanotubes are
arranged in a thickness direction of a plate-like molded body,
anisotropic elasticity is obtained. The tensile strength and
bending strength in the thickness direction are improved.
[0041] Besides, the complex molded body of the present invention
may be anisotropic in terms of magnetic property, electromagnetic
property, linear expansion coefficient, dielectric property, and
wave-absorbing property. Thus, the molded body may be used for
various applications such as a damping material and a
wave-absorber.
[0042] The advantages of the above embodiments are described
below.
[0043] In the embodiments, carbon nanotubes are arranged in a given
direction. Thus, properties (such as electrical property, thermal
property, and mechanical property) of the molded body in a
direction in which the carbon nanotubes extend is different from
those in other directions. This allows the complex molded body to
have excellent anisotropic functions that have never been achieved.
Moreover, since microscopic carbon nanotube is a minute material,
such anisotropic functions can be achieved in a minute complex
molded body.
[0044] In addition, the complex molded body may be anisotropic in
terms of magnetic property, electromagnetic property, linear
expansion coefficient, dielectric property, and wave-absorbing
property. Accordingly, the complex molded body may be used for
various applications such as a pressure sensor, a sensing switch, a
magnetic shield material, magnetic recording material, and a
magnetic filter.
[0045] With respect to the above embodiments, a magnetic field may
be applied to the composition that includes carbon nanotubes. Thus,
the carbon nanotubes may be arranged in a given direction in the
matrix effectively.
EXAMPLE
[0046] The above embodiments will be described by way of examples.
Although the description is made on a plate-like complex molded
body in Examples and Comparative examples, the invention is not
limited in any way by the examples.
[0047] In each example, carbon nanotubes were synthesized by a
thermal cracking process using a catalyst, which is an example of
synthetic method of carbon nanotubes. The cracking process is
almost equal to carbon fiber vapor phase epitaxy and will be
described below.
[0048] Firstly, ethylene or propane as a source gas is introduced
into a thermostat together with hydrogen. A source gas may be
saturated hydrocarbons such as methane, ethane, butane, hexane, and
cyclohexanone; unsaturated hydrocarbons such as propylene, benzene,
toluene; and oxygen-containing material such as acetone, methanol,
and carbon monoxide.
[0049] Next, the source gas introduced into a thermostat is heated
or cooled to control a vapor pressure. Then the gas is further
introduced with hydrogen gas into a thermal cracking reactor, where
ethylene or propane as a source gas is cracked to yield carbon
nanotubes.
Example 1
[0050] A manufacturing device and a manufacturing method for making
a plate-like complex molded body are described with reference to
FIGS. 1 to 4.
[0051] As shown in FIG. 2, a pair of forming molds 1a, 1b is placed
to oppose to each other. A forming recess 2 is provided in the
opposing surface of the forming mold 1a. The recess 2 matches to a
intended plate-like complex molded body. Both of the mold 1a, 1b
are formed of aluminum. The surface of the recess 2 is coated with
fluororesin.
[0052] A composition 3 was prepared by adding 1 part by weight of
carbon nanotubes to 100 parts by weight of thermosetting
unsaturated polyester resin (NIPPON SHOKUBAI CO., Ltd., a trade
name of EPOLAC.TM. G-157 MB) and stirring. The composition 3 was
filled in the recess 2.
[0053] As shown in FIG. 3, the molds 1a, 1b were closed together at
a certain pressure to seal the recess 2. Then, as shown in FIG. 4,
a pair of magnets 4a, 4b was placed on either side of the molding
1a, 1b. A north pole N of the magnet 4a and a south pole S of the
magnet 4b were opposed to each other. A magnetic field of 10 tesla
was applied in a direction parallel to an inner bottom face of the
recess 2. Then the composition 3 was left for 30 minutes at room
temperature to be hardened. After that, the mold 1a, 1b were opened
to remove a plate-like complex molded body 5 of carbon nanotubes
from the recess 2.
[0054] As seen in FIG. 1, the carbon nanotubes 6 in the resultant
complex molded body 5 were arranged in a direction parallel to
upper and lower faces of the mold 1a, 1b.
Example 2
[0055] A complex molded body 5 was obtained as in Example 1, except
that a magnetic field of 10 tesla was applied in a direction
perpendicular to an inner bottom face of the recess 2. As seen in
FIG. 5, The carbon nanotube 6 in the resultant complex molded body
5 were arranged in a direction perpendicular to upper and lower
faces of the complex molded body 5.
Example 3
[0056] A composition 3 was prepared by adding 1 part by weight of
carbon nanotubes to 100 parts by weight of thermosetting epoxy
resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and
stirring. The composition 3 was filled in the recess 2 of the mold
1a shown in FIG. 2. Following the procedures as in Example 1, a
complex molded body 5 was obtained.
Example 4
[0057] A composition 3 was prepared by adding 2 parts by weight of
carbon nanotubes to 100 parts by weight of thermosetting epoxy
resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and
stirring. The composition 3 was filled in the recess 2 of the mold
1a shown in FIG. 2. Following the procedures as in Example 1, a
complex molded body 5 was obtained.
Example 5
[0058] A composition was prepared by adding 1 part by weight of
carbon nanotubes to 100 parts by weight of thermoplastic
polycarbonate resin (MITSUBISHI ENGINEERING-PLASTICS CORPORATION, a
trade name of Iupilon.TM. S-2000) and mixing with a screw extruder.
Then methylene chloride was added to the composition and the
mixture was stirred until the mixture became a uniform liquid. The
resultant liquid was filled in the recess 2 of the mold 1a shown in
FIG. 2. While a magnetic field of 10 tesla was applied in a
direction parallel to an inner bottom face of the recess 2, the
liquid was thermally hardened at 120 degrees C. for an hour to
obtain a complex molded body 5.
Example 6
[0059] A complex molded body 5 was obtained as in Example 5, except
that a magnetic field of 10 tesla was applied in a direction
perpendicular to an inner bottom face of the recess 2.
Comparative Example 1
[0060] A composition was prepared by adding 1 part by weight of
carbon nanotubes to 100 parts by weight of thermosetting
unsaturated polyester resin (NIPPON SHOKUBAI CO., Ltd., a trade
name of EPOLAC.TM. G-157 MB) and stirring. The composition was
filled in the recess 2. Then, without a magnetic field applied, the
composition was left for 30 minutes at room temperature to be
hardened to form a complex molded body. The carbon nanotubes were
randomly dispersed in the complex molded body.
Comparative Example 2
[0061] A composition was prepared by adding 1 part by weight of
carbon nanotubes to 100 parts by weight of thermosetting epoxy
resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and
stirring. The composition was filled in the recess 2 of the mold 1a
shown in FIG. 2. Then, without a magnetic field applied, the
composition was left for 30 minutes at room temperature to be
hardened to form a complex molded body.
Comparative Example 3
[0062] A composition was prepared by adding 2 parts by weight of
carbon nanotubes to 100 parts by weight of thermosetting epoxy
resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and
stirring. The composition was filled in the recess 2 of the mold 1a
shown in FIG. 2. Then, without a magnetic field applied, the
composition was left for 30 minutes at room temperature to be
hardened to form a complex molded body.
Comparative Example 4
[0063] A pellet was prepared by adding 1 part by weight of carbon
nanotubes to 100 parts by weight of thermoplastic polycarbonate
resin (MITSUBISHI ENGINEERING-PLASTICS CORPORATION, a trade name of
Iupilon.TM. S-2000) and mixing with a screw extruder. Then 70 parts
by weight of methylene chloride was added to 100 parts by weight of
the pellet and the mixture was stirred until the pellet was
completely dissolved. The resultant liquid was filled in the recess
2 of the mold 1a shown in FIG. 2. Then, without a magnetic field
applied, the liquid was thermally hardened at 120 degrees C. for an
hour to obtain a complex molded body.
[0064] For complex molded bodies obtained in Examples 1, 2, 5, and
6 and Comparative examples 1 and 4, storage modulus E', loss
modulus E", loss tangent tan .delta. at a frequency of 11 Hz were
measured using a dynamic viscoelasticity measuring system
(ORIENTECH CO., Ltd., a trade name of RHEOVIBRON DDV-III). The
results were shown in Table 1.
1 TABLE 1 amount E' E" (part by wt) direction (N/m.sup.2)
(N/m.sup.2) tan .delta. Ex. 1 1 parallel 1.8 .times. 10.sup.5 2.4
.times. 10.sup.4 0.13 Ex. 2 1 perpendicular 1.2 .times. 10.sup.5
0.89 .times. 10.sup.4 0.074 Ex. 5 1 parallel 1.5 .times. 10.sup.6
2.2 .times. 10.sup.4 0.14 Ex. 6 1 perpendicular 0.92 .times.
10.sup.6 0.78 .times. 10.sup.4 0.085 Comp. 1 1 no 1.1 .times.
10.sup.5 0.87 .times. 10.sup.4 0.078 Comp. 2 1 no 0.95 .times.
10.sup.6 0.80 .times. 10.sup.4 0.084
[0065] Aside from the above measurement, for complex molded bodies
obtained in Examples 3, 4 and Comparative examples 2, 3, magnetic
susceptibility .chi. from 0 to 5 T was measured using a SQUID
susceptibility measurement system (Quantum Design, Model MPMS-7).
The results were shown in Table 2. In Tables 2 to 4 below,
measurement direction means the following:
[0066] Parallel: sample was measured in a direction parallel to the
direction in which the carbon nanotubes extend.
[0067] Perpendicular: sample was measured in a direction
perpendicular to the direction in which the carbon nanotubes
extend.
[0068] No: sample in which the carbon nanotubes were randomly
dispersed were measured.
2 TABLE 2 amount measurement (part by wt) direction .chi. (/g)
.vertline..DELTA..chi..vertline. (/g) Ex. 3 1 parallel -6.4 .times.
10.sup.-5 1.2 .times. 10.sup.-5 perpendicular -7.5 .times.
10.sup.-5 Ex. 4 2 parallel -8.2 .times. 10.sup.-5 1.0 .times.
10.sup.-6 perpendicular -8.3 .times. 10.sup.-5 Comp. 2 1 no -7.0
.times. 10.sup.-5 -- Comp. 3 2 no -8.2 .times. 10.sup.-5 --
[0069] Further, for complex molded bodies obtained in Example 3 and
Comparative example 2, electric resistance was measured. The
results were shown in Table 3. Electric resistance is a measured
voltage across the two terminals, when a direct current of 1 mA is
passed through and the distance between the terminals is 1 mm.
3 TABLE 3 amount measurement (part by wt) direction resistance
(.OMEGA.) Ex. 3 1 parallel 17.8 .times. 10.sup.3 perpendicular 1.14
.times. 10.sup.3 Comp. 2 1 no 6.06 .times. 10.sup.3
[0070] For complex molded bodies obtained in Example 1 and
Comparative example 2, linear expansion coefficient at from 30 to
200 degree C. was measured using a thermomechanical analyzer
(Mettler, TMA-40, TA-3000). The results were shown in Table 4.
4 TABLE 4 amount measurement linear expansion (part by wt)
direction coefficient (/degree C.) Ex. 1 1 parallel 1.45 .times.
10.sup.-4 perpendicular 1.70 .times. 10.sup.-4 Comp. 2 1 no 1.57
.times. 10.sup.-4
[0071] Particularly, variations in magnetic susceptibility .chi.,
or the absolute value of the difference between the magnetic
susceptibility in a parallel direction and that in a perpendicular
direction .vertline..DELTA..chi..vertline., of Table 2 show that
Example 3 has magnetic anisotropy. Variations in electric
resistance of Table 3 show that Example 3 has anisotropy of
electric resistance. Variations in linear expansion coefficient
show that Example 1 has anisotropy of linear expansion coefficient.
In addition, Table 1 showed that the molded body of Example 1 has
greater storage modulus E' and loss modulus E" in a parallel
direction than in a perpendicular direction, indicating that the
molded body of Example 1 has an excellent elasticities in a
direction parallel to the upper and lower faces of the molded
body.
[0072] It should be apparent to those skilled in the art that the
present invention may be embodied in many other specific forms
without departing from the spirit or scope of the invention.
Particularly, it should be understood that the invention may be
embodied in the following forms.
[0073] The magnetic field applied to the composition 3 may be
oriented in an oblique direction relative to the inner bottom face
of the recess 2 of the mold 1a.
[0074] A coating of ferromagnetic material may be formed on the
surface of the carbon nanotubes to arrange them effectively. This
facilitates the anisotropic functions of the molded body.
[0075] Carbon fibers, such as graphitized carbon fibers, may be
mixed with the carbon nanotubes. This facilitates the anisotropy
functions in terms of thermal conductivity and electro-isolative
property.
[0076] Metals, ceramics, other inorganic materials, or precursors
thereof may be used as a matrix. In such cases, a magnetic field is
applied to the matrix that is melted or dispersed in a solvent. The
matrix is then cooled to be hardened or dried or sintered to be
hardened to form a complex molded body. For example, an
aluminum-alloy composition including carbon nanotubes is melted in
a container that has a predetermined shape. Then a magnetic field
is applied to the composition to arrange the carbon nanotubes in a
given direction. The composition is then cooled and hardened to
form a complex molded body. This manufacturing method provides a
resultant molded body with required characteristics such as
hardness and anisotropy in terms of mechanical strength, heat
resistance, electrical properties, and durability.
[0077] The matrix may be carbonized or graphitized. For example,
the composition including phenol resin or epoxy resin as a matrix
and carbon nanotubes is melted in a container that has a
predetermined shape. Then a magnetic field is applied to the
composition to arrange the carbon nanotubes in a given direction.
The composition is then dried and sintered to carbonize or
graphitize the matrix, thereby forming a complex molded body. This
manufacturing method provides a resultant molded body with required
characteristics such as hardness and anisotropy in terms of
mechanical strength, heat resistance, electrical properties, and
durability.
[0078] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive and the invention is
not to be limited to the details given herein, but may be modified
within the scope and equivalence of the appended claims.
* * * * *