U.S. patent application number 12/482040 was filed with the patent office on 2013-01-31 for electrostrictive composite and method for making the same.
This patent application is currently assigned to HON HAI PRECISION INDUSTRY CO., LTD.. The applicant listed for this patent is LU-ZHUO CHEN, SHOU-SHAN FAN, CHANG-HONG LIU. Invention is credited to LU-ZHUO CHEN, SHOU-SHAN FAN, CHANG-HONG LIU.
Application Number | 20130026410 12/482040 |
Document ID | / |
Family ID | 41470351 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130026410 |
Kind Code |
A1 |
CHEN; LU-ZHUO ; et
al. |
January 31, 2013 |
ELECTROSTRICTIVE COMPOSITE AND METHOD FOR MAKING THE SAME
Abstract
An electrostrictive composite includes a flexible polymer
matrix, a plurality of carbon nanotubes and a plurality of
reinforcing particles dispersed in the flexible polymer matrix. The
carbon nanotubes cooperatively form an electrically conductive
network in the flexible polymer matrix.
Inventors: |
CHEN; LU-ZHUO; (Beijing,
CN) ; LIU; CHANG-HONG; (Beijing, CN) ; FAN;
SHOU-SHAN; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHEN; LU-ZHUO
LIU; CHANG-HONG
FAN; SHOU-SHAN |
Beijing
Beijing
Beijing |
|
CN
CN
CN |
|
|
Assignee: |
HON HAI PRECISION INDUSTRY CO.,
LTD.
Tu-Cheng
TW
TSINGHUA UNIVERSITY
Beijing
CN
|
Family ID: |
41470351 |
Appl. No.: |
12/482040 |
Filed: |
June 10, 2009 |
Current U.S.
Class: |
252/62.9R ;
977/742; 977/750; 977/752 |
Current CPC
Class: |
H01L 41/45 20130101;
H01L 41/183 20130101; H01L 41/37 20130101; B29B 7/00 20130101 |
Class at
Publication: |
252/62.9R ;
977/742; 977/750; 977/752 |
International
Class: |
H01L 41/193 20060101
H01L041/193 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2008 |
CN |
200810067725.7 |
Claims
1. An electrostrictive composite comprising: a flexible polymer
matrix; and a plurality of carbon nanotubes and a plurality of
reinforcing particles dispersed in the flexible polymer matrix, the
carbon nanotubes cooperatively forming an electrically conductive
network in the flexible polymer matrix, wherein a weight percentage
of the sum of the carbon nanotubes and reinforcing particles in the
electrostrictive composite is less than 20%.
2. (canceled)
3. The electrostrictive composite of claim 1, wherein a weight
ratio of the carbon nanotubes to the reinforcing particles is
greater than or equal to 1:1.
4. The electrostrictive composite of claim 1, wherein a weight
percentage of the reinforcing particles in the electrostrictive
composite ranges from about 1% to about 10%.
5. The electrostrictive composite of claim 1, wherein the
reinforcing particles are made of material selected from a group
consisting of ceramic, metal, metal oxide, metal nitride, glass and
combinations thereof.
6. The electrostrictive composite of claim 1, wherein an effective
diameter of the reinforcing particles ranges from about 1 nanometer
to about 10 micrometers.
7. The electrostrictive composite of claim 1, wherein a weight
percentage of the carbon nanotubes in the electrostrictive
composite ranges from about 0.1% to about 10%.
8. The electrostrictive composite of claim 1, wherein the carbon
nanotubes are selected from a group consisting of single-walled
carbon nanotubes, double-walled carbon nanotubes, multi-walled
carbon nanotubes, and combinations thereof.
9. The electrostrictive composite of claim 1, wherein the flexible
polymer matrix comprises a material selected from a group
consisting of silicone elastomer, polyester, polyurethane, epoxy
resin, polymethyl methacrylate and combinations thereof.
10. The electrostrictive composite of claim 1, further comprising
at least one flexible polymer layer located on one surface of the
flexible polymer matrix.
11. The electrostrictive composite of claim 10, wherein the
flexible polymer matrix is located between two flexible polymer
layers.
12-19. (canceled)
20. An electrostrictive composite comprising: a flexible polymer
matrix; and a plurality of carbon nanotubes and a plurality of
reinforcing particles dispersed in the flexible polymer matrix, and
the carbon nanotubes cooperatively forming an electrically
conductive network in the flexible polymer matrix, wherein the
reinforcing particles are made of material selected from a group
consisting of ceramic, metal, metal oxide, metal nitride, glass and
combinations thereof.
21. An electrostrictive composite comprising: a flexible polymer
matrix; and a plurality of carbon nanotubes and a plurality of
reinforcing particles dispersed in the flexible polymer matrix, and
the carbon nanotubes cooperatively forming an electrically
conductive network in the flexible polymer matrix, wherein an
effective diameter of the reinforcing particles ranges from about 1
nanometer to about 10 micrometers.
Description
RELATED APPLICATIONS
[0001] This application is related to copending applications
entitled "ELECTROSTRICTIVE COMPOSITE AND METHOD FOR MAKING THE
SAME", filed ______ (Atty. Docket No. US22230); and
"ELECTROSTRICTIVE MATERIAL METHOD FOR MAKING THE SAME AND
ELECTROTHERMIC TYPE ACTUATOR", filed ______ (Atty. Docket No.
US22892). The disclosures of the above-identified applications are
incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] One disclosure relates to a carbon nanotube based
electrostrictive composite and method for making the same.
[0004] 2. Description of Related Art
[0005] Electrostrictive composites are materials that can convert
electrical energy to mechanical energy, thus imparting a force,
while a current or voltage is applied. Electrostrictive composites
have been called artificial muscles due to their similar motion
properties.
[0006] Referring to FIG. 6, a flexible electrothermal composite 10
according to a prior art is shown. The flexible electrothermal
composite 10 includes a flexible polymer matrix 14 and a plurality
of carbon nanotubes 12 dispersed therein. The carbon nanotubes 12
cooperatively form a conductive network in the flexible polymer
matrix 14. The flexible electrothermal composite 10 is made by the
following steps of: (a) preparing a solution of a polymer
precursor; (b) immersing carbon nanotubes in the solution and
ultrasonically cleaning the solution; and (c) polymerizing and
curing the polymer precursor.
[0007] However, the Young's modulus of the flexible electrothermal
composite 10 is relatively small.
[0008] What is needed, therefore, is to provide an electrostrictive
composite having a relatively larger Young's modulus and method for
making the same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Many aspects of one electrostrictive composite and method
for making the same can be better understood with reference to the
following drawings. The components in the drawings are not
necessarily drawn to scale, the emphasis instead being placed upon
clearly illustrating the principles of one electrostrictive
composite and method for making the same.
[0010] FIG. 1 is a schematic view of an electrostrictive
composite.
[0011] FIG. 2 is a schematic view of the electrostrictive composite
of FIG. 1 before and after expansion.
[0012] FIG. 3 is a schematic view of an electrostrictive composite
having a sandwich structure.
[0013] FIG. 4 is a schematic view of an electrostrictive composite
having a multi-layer structure.
[0014] FIG. 5 is a flow chart of a method for making the
electrostrictive composite of FIG. 1.
[0015] FIG. 6 is a schematic view of a flexible electrothermal
composite according to the prior art.
[0016] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate at least one embodiment of one electrostrictive
composite and method for making the same, in at least one form, and
such exemplifications are not to be construed as limiting the scope
of the disclosure in any manner.
DETAILED DESCRIPTION
[0017] References will now be made to the drawings to describe, in
detail, various embodiments of one electrostrictive composite and
method for making the same.
[0018] Referring to FIG. 1, an electrostrictive composite 20
according to one embodiment is shown. The electrostrictive
composite 20 includes a flexible polymer matrix 22, a plurality of
carbon nanotubes 24, and a plurality of reinforcing particles 26.
The carbon nanotubes 24 and reinforcing particles 26 are dispersed
in the flexible polymer matrix 22. Shape and size of the
electrostrictive composite 20 are arbitrary. In one embodiment, the
electrostrictive composite 20 is rectangular, and the carbon
nanotubes 24 and the reinforcing particles 26 are uniformly
dispersed in the flexible polymer matrix 22.
[0019] A weight percentage of the flexible polymer matrix 22 in the
electrostrictive composite 20 ranges from about 80% to about 98.9%.
The flexible polymer matrix 22 includes a material selected from a
group consisting of silicone elastomer, polyester, polyurethane,
epoxy resin, polymethyl methacrylate (PMMA) and combinations
thereof. In one embodiment, the flexible polymer matrix 22 is
silicone elastomer.
[0020] A weight percentage of the sum of the carbon nanotubes 24
and reinforcing particles 26 in the electrostrictive composite 20
is less than 20%. A weight ratio of the carbon nanotubes 24 to the
reinforcing particles 26 is greater than or equal to 1:1. A weight
percentage of the reinforcing particles 26 in the electrostrictive
composite 20 can range from about 1% to about 10% and a weight
percentage of the carbon nanotubes 24 in the electrostrictive
composite 20 can range from about 0.1% to about 10%. In one
embodiment, a weight percentage of the reinforcing particles 26 in
the electrostrictive composite 20 ranges from about 1% to about 5%
and a weight percentage of the carbon nanotubes 24 in the
electrostrictive composite 20 ranges from about 0.1% to about
5%.
[0021] The carbon nanotubes 24 can be selected from a group
consisting of single-walled carbon nanotubes, double-walled carbon
nanotubes, multi-walled carbon nanotubes, and combinations thereof.
A length of the carbon nanotubes 24 can be greater than about 1
micrometer. The length of the carbon nanotubes 24 can range from
about 50 micrometers to about 900 micrometers in one embodiment.
The carbon nanotubes 24 are flexible and have excellent electricity
to heat conversion efficiency. The carbon nanotubes 24 are in
contact with each other to form a conductive network in the
flexible polymer matrix 22, thus the electrostrictive composite 20
is conductive. While a voltage is applied to the electrostrictive
composite 20, the carbon nanotubes conductive network will rapidly
heat and expand the flexible polymer matrix 22.
[0022] The reinforcing particles 26 can be made of material
selected from a group consisting of ceramic, metal, metal oxide,
metal nitride, glass and combinations thereof. An effective
diameter of the reinforcing particles 26 can range from about 1
nanometer to about 10 micrometers. The reinforcing particles 26 can
reduce the thermal response time of the electrostrictive composite
20 due to its high thermal conductivity. The reinforcing particles
26 can enhance the Young's modulus of the electrostrictive
composite 20 and raise its propelling power capability during
expansion.
[0023] Testing was performed on the electrostrictive composite 20
wherein the flexible polymer matrix 22 was silicone elastomer with
a weight ratio of 94 wt %, the carbon nanotubes 24 were
multi-walled carbon nanotube with a weight ratio of 4 wt %, and the
reinforcing particles 26 were boron nitride (BN) particles with a
weight ratio of 2 wt %. The Young's modulus of the electrostrictive
composite 20 was 1.92 MPa. In another test, the flexible polymer
matrix 22 was silicone elastomer with a weight ratio of 94 wt %,
the carbon nanotubes 24 were multi-walled carbon nanotube with a
weight ratio of 4 wt %, and the reinforcing particles 26 were
aluminum oxide (Al.sub.2O.sub.3) particles with a weight ratio of 2
wt %. The Young's modulus of the electrostrictive composite 20 was
1.57 MPa. Another test found that the Young's modulus of a
composite consisting of silicone elastomer of 96 wt % and carbon
nanotubes of 4 wt % was 1.2 MPa.
[0024] The work principle of the electrostrictive composite 20 is
described as follows. When a voltage is applied to the
electrostrictive composite 20, a current flows through the carbon
nanotube conductive network. The electrical energy absorbed by the
carbon nanotubes 24 results in local thermal confinement, which
breaks the thermodynamic equilibrium therearound. The current and
temperature increase simultaneously and rapidly until another
thermodynamic equilibrium is achieved. The temperature of the
carbon nanotubes 24 rises by absorbing electrical energy, resulting
in a temperature increase of the flexible polymer matrix 22 due to
the high thermal conductance of the carbon nanotubes. That can lead
to an expansion of the electrostrictive composite 20 along its
length and width.
[0025] The expansion coefficient of the electrostrictive composite
20 ranges from about 0.66.times.10.sup.-4K.sup.-1 to about
5.28.times.10.sup.-4K.sup.-1. Referring to FIG. 2, in one
embodiment, the expansion coefficient of the electrostrictive
composite 20 is tested. In the tested electrostrictive composite
20, the flexible polymer matrix 22 is silicone elastomer of 91 wt
%, the carbon nanotubes 24 are multi-walled carbon nanotube of 5 wt
%, and the reinforcing particles 26 are Al.sub.2O.sub.3 particle of
4 wt %. An effective diameter of the reinforcing particles 26
ranges from about 10 nanometers to about 100 nanometers. The
expansion coefficient .alpha. of the electrostrictive composite 20
is calculated according to
.alpha. = L 2 - L 1 L 1 .times. 1 .DELTA. T = .DELTA. T
##EQU00001##
[0026] where L1 is the original length of the electrostrictive
composite 20, L2 is the length of the electrostrictive composite 20
after expansion, .DELTA.T is the increase of the temperature of the
electrostrictive composite 20, .epsilon. is the strain. In one
embodiment, the L1 is 4 millimeters. The L2 increases to 4.2
millimeters after a voltage of 40 V is supplied for about 2
minutes. The increase of the length .DELTA.L is 0.2 millimeters.
The increase of the temperature .DELTA.T is 150K. The strain
.epsilon. of the electrostrictive composite 20 is calculated to be
is the 5%. The expansion coefficient .alpha. of the
electrostrictive composite 20 is calculated to be
3.3.times.10.sup.-4K.sup.-1.
[0027] In other embodiments, the electrostrictive composite 20 can
further include at least one flexible polymer layer 28 located on
at least one surface of the flexible polymer matrix 22. The
electrostrictive composite 20 with the flexible polymer layer 28 on
at least one surface of the flexible polymer matrix 22 can be an
insulator. A thickness ratio of the flexible polymer layer to the
flexible polymer matrix 22 can range from about 1% to about 10%. In
one embodiment, the flexible polymer matrix 22 can be sandwiched
between two silicone elastomer layers serving as the flexible
polymer layers 28 as shown in FIG. 3. Alternatively, the
electrostrictive composite 20 can be a multi-layer structure as
shown in FIG. 4.
[0028] Referring to FIG. 6, a method of making the electrostrictive
composite 20 includes the following steps of: (a) providing a
plurality of carbon nanotubes, a plurality of reinforcing particles
and a polymer precursor; (b) mixing the carbon nanotubes,
reinforcing particles and the polymer precursor to obtain a
mixture; and (c) polymerizing and curing the polymer precursor in
the mixture.
[0029] In step (a), the carbon nanotubes can be obtained by a
conventional method selected from a group consisting of chemical
vapor deposition (CVD), arc discharging, and laser ablation. In one
embodiment, the carbon nanotubes are obtained by the following
substeps of: providing a substrate; forming a carbon nanotube array
on the substrate by a chemical vapor deposition method; peeling the
carbon nanotube array off the substrate by a mechanical method,
thereby achieving a plurality of carbon nanotubes. The carbon
nanotubes in the carbon nanotube array can be substantially
parallel to each other.
[0030] The reinforcing particles can be made by a sol-gel or ball
milling process. The polymer precursor can be selected according to
the flexible polymer. The polymer precursor generally includes a
prepolymer or a monomer. The prepolymer can be selected from the
group consisting of silicone elastomer prepolymer, polyester
prepolymer, polyurethane prepolymer, epoxy resin prepolymer, PMMA
prepolymer and combination thereof. In one embodiment, the flexible
polymer is silicone elastomer, and the prepolymer is silicone
elastomer prepolymer.
[0031] In step (b), when the polymer precursor is liquid, the
carbon nanotubes and reinforcing particles can be added into the
polymer precursor directly to obtain a liquid mixture. When the
polymer precursor is solid or glue-like, step (b) can include the
substeps of: (b1) dissolving the polymer precursor into a
volatilizable solvent to obtain a solution of polymer precursor;
and (b2) adding the carbon nanotubes and the reinforcing particles
into the solution to obtain a liquid mixture. In one embodiment,
the component A of the silicone elastomer is dissolved into ethyl
acetate. The component A can be hydroxyl terminated
polydimethylsiloxane.
[0032] After step (b), an optional step (d) of ultrasonically
treating the liquid mixture can be carried out. In step (d),
ultrasonically treatment of the liquid mixture is performed in an
ultrasonic processor for about 10 minutes to reduce the size of the
carbon nanotubes and reinforcing particles. In order to avoid the
carbon nanotubes conglomerating with each other in the solution,
step (d) further includes the following steps of: ultrasonically
agitating the solution for a few minutes to uniformly disperse the
carbon nanotubes therein. In one embodiment, ultrasonic agitation
is performed in an ultrasonic cleaner for about 3 hours.
[0033] When the polymer precursor is dissolved into a volatilizable
solvent, an optional step (e) of removing the volatilizable solvent
can be performed before the step (c). In one embodiment, the liquid
mixture is heated in an oven at a temperature ranging from about
80.degree. C. to about 120.degree. C. until all the ethyl acetate
is volatilized.
[0034] In step (c), the polymer precursor is polymerized with an
initiator to obtain a flexible polymer matrix having carbon
nanotubes and reinforcing particles dispersed therein. In one
embodiment, the initiator includes a solution of ethanol or
deionized water having component B of the silicone elastomer
dispersed therein. The initiator is added in the solution of the
prepolymer having component A of the silicone elastomer to obtain a
mixture solution, in order to polymerize the prepolymer. A weight
ratio of the initiator and the prepolymer can be about 6:100. In
one embodiment, the component A can be hydroxyl terminated
polydimethylsiloxane and the component B can be tetraethoxysilane.
Then, after ultrasonically agitating the mixture solution, sediment
is collected. The sediment (a glue-like material) having the carbon
nanotubes and the reinforcing particles uniformly dispersed therein
is the electrostrictive composite.
[0035] An optional step (f) of keeping the electrostrictive
composite in a vacuum for a period of time to remove bubbles
therein can be carried out after step (c). An optional step (g) of
pressing the electrostrictive composite can be carried out to
obtain a smooth electrostrictive composite after step (f). In one
embodiment, the electrostrictive composite is pressed by a smooth
presser for about 12 hours to about 18 hours to obtain a planar
electrostrictive composite. Furthermore, the planar
electrostrictive composite can be cut to have a rectangular
shape.
[0036] In addition, a step (h) of forming a flexible polymer layer
on at least one surface of the flexible polymer matrix can be
carried out after step (g). Step (h) can include the substeps of:
(h1) providing a liquid prepolymer; (h2) adding initiator into the
liquid prepolymer to obtain a liquid mixture; and (h3) immersing
the electrostrictive composite into the liquid mixture.
[0037] It is also to be understood that the above description and
the claims drawn to a method may include some indication in
reference to certain steps. However, the indication used is only to
be viewed for identification purposes and not as a suggestion as to
an order for the steps.
[0038] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
disclosure. Variations may be made to the embodiments without
departing from the spirit of the disclosure as claimed. The
above-described embodiments illustrate the scope of the disclosure
but do not restrict the scope of the disclosure.
* * * * *