U.S. patent application number 10/329333 was filed with the patent office on 2005-03-17 for preparation of magnetic metal-filled carbon nanocapsules.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Hwang, Gan-Lin.
Application Number | 20050056119 10/329333 |
Document ID | / |
Family ID | 32028382 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050056119 |
Kind Code |
A1 |
Hwang, Gan-Lin |
March 17, 2005 |
PREPARATION OF MAGNETIC METAL-FILLED CARBON NANOCAPSULES
Abstract
A method of producing magnetic metal-filled carbon nanocapsules.
An arc chamber comprising a graphitic anode and a composite
graphitic cathode containing at least one kind of magnetic metal or
its derivatives is provided, before introducing an inert gas into
the arc chamber, applying a voltage across the cathode and the
anode by a pulse current, the voltage sufficient to generate a
carbon arc reaction between the cathode and the anode, and finally
collecting a deposit formed on the cathode.
Inventors: |
Hwang, Gan-Lin; (Tainan,
TW) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
|
Family ID: |
32028382 |
Appl. No.: |
10/329333 |
Filed: |
December 27, 2002 |
Current U.S.
Class: |
75/347 ; 205/478;
205/555 |
Current CPC
Class: |
H01F 1/0045 20130101;
C01B 32/162 20170801; Y10S 977/844 20130101; Y10S 977/846 20130101;
B82Y 30/00 20130101; C22C 2026/001 20130101; B82Y 25/00 20130101;
B82Y 40/00 20130101; C30B 23/00 20130101; C30B 29/605 20130101 |
Class at
Publication: |
075/347 ;
205/478; 205/555 |
International
Class: |
B22F 009/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2002 |
TW |
91117435 |
Claims
1. A method of producing magnetic metal-filled carbon nanocapsules,
comprising: providing an arc chamber comprising a graphitic anode
and a composite graphitic cathode containing at least one kind of
magnetic metal or its derivatives, wherein the derivatives are
alloys of the magnetic metal and another element, oxide and/or
carbide of the magnetic metal, and introducing an inert gas into
the arc chamber, wherein the arc chamber has a pressure of 1-2 atm;
applying a voltage across the cathode and the anode by a pulse
current, the voltage being sufficient to generate a carbon arc
reaction between the cathode and the anode; and collecting a
deposit comprising the nanocapsules formed on the cathode.
2. The method as claimed in claim 1, wherein the graphitic anode is
in the form of a graphite rod.
3. The method as claimed in claim 1, wherein the composite
graphitic cathode is formed from a mixture of carbon powders and
powders of at least one kind of magnetic metal or its
derivatives.
4. The method as claimed in claim 3, wherein the mixture further
comprises a graphitizable resin.
5. The method as claimed in claim 1, wherein the magnetic metal is
Sc, V, Cr, Fe, Co, Ni, Y, Zr, Mo, Ru, Pd, La, Ce, Pr, Nd, Gd, Tb,
Dy, Ho, Er, Tm, Lu, Ta, Os, Ir, Pt, Au, Th, U or a combination
thereof.
6. (canceled).
7. The method as claimed in claim 3, wherein the molar mixing ratio
of carbon powders and powders of at least one kind of magnetic
metal or its derivatives is between 100:1 and 5:1.
8. The method as claimed in claim 4, wherein the graphitizable
resin is melamine resin, epoxy resin or phenolic resin.
9. The method as claimed in claim 4, wherein the weight ratio of
graphitizable resin to carbon powders and powders of at least one
kind of magnetic metal or its derivatives is between 1:10 to
3:10.
10. The method as claimed in claim 1, wherein the inert gas has a
flow rate of 10 to 200 mm3/min.
11. (canceled).
12. The method as claimed in claim 1, wherein the pulse current has
a frequency of 0.01 to 1000 Hz.
13. The method as claimed in claim 1, wherein the arc reaction is
conducted at a pulse frequency of 0.01 to 1000 Hz, at a voltage of
10 to 30 V, and at a current of 50 to 800 A.
14. The method as claimed in claim 1, wherein collection of the
deposit further comprises collecting a core portion of the deposit
formed on the cathode.
15. The method as claimed in claim 14, wherein the deposit includes
a magnetic metal-filled carbon nanocapsule main product, a hollow
carbon nanocapsule and carbon nanotube byproducts.
16. A method of producing magnetic metal-filled carbon
nanocapsules, comprising: providing an arc chamber comprising a
graphitic anode and a composite graphitic cathode comprising a
mixture of carbon powders, powders of at least one kind of magnetic
metal or its derivatives, and a graphitizable resin, wherein the
derivatives are alloys of the magnetic metal and another element,
oxide and/or carbide of the magnetic metal, and introducing an
inert gas into the arc chamber; applying a voltage across the
cathode and the anode by a pulse current, the voltage sufficient to
generate an carbon arc reaction between the cathode and the anode;
collecting a deposit formed on the cathode, the deposit comprising
a magnetic metal-filled carbon nanocapsule main product, a hollow
carbon nanocapsule and carbon nanotube byproducts; and separating
and purifying the deposit to obtain the magnetic metal-filled
carbon nanocapsules.
17. The method as claimed in claim 16, wherein the magnetic metal
is Sc, V, Cr, Fe, Co, Ni, Y, Zr, Mo, Ru, Pd, La, Ce, Pr, Nd, Gd,
Tb, Dy, Ho, Er, Tm, Lu, Ta, Os, Ir, Pt, Au, Th, U or a combination
thereof.
18. (canceled).
19. The method as claimed in claim 16, wherein the molar mixing
ratio of carbon powders and powders of at least one kind of
magnetic metal or its derivatives is between 100:1 and 5:1.
20. The method as claimed in claim 16, wherein the graphitizable
resin is melamine resin, epoxy resin or phenolic resin.
21. The method as claimed in claim 16, wherein the weight ratio, of
graphitizable resin to carbon powders and powders of at least one
kind of magnetic metal or its derivatives is between 1:10 to
3:10.
22. The method as claimed in claim 16, wherein the inert gas has
flow rate of 10 to 200 mm3/min.
23. The method as claimed in claim 16, wherein the arc chamber has
a pressure of 0.1 to 5 atm.
24. The method as claimed in claim 16, wherein the pulse current
has a frequency of 0.01 to 1000 Hz.
25. The method as claimed in claim 16, wherein the arc reaction is
conducted at a pulse frequency of 0.01 to 1000 Hz, at a voltage of
10 to 30 V, and at a current of 50 to 800 A.
26. The method as claimed in claim 16, wherein collection further
comprises collecting a core portion of the deposit formed on the
cathode.
27. The method as claimed in claim 16, wherein separation and
purification further comprise: dispersing the deposit in a solution
using a surfactant; separating the magnetic metal-filled carbon
nanocapsules main product and the carbon nanotube byproduct using
column chromatography; and extracting the magnetic metal-filled
carbon nanocapsules by magnetic attraction and cleaning the
magnetic metal-filled carbon nanocapsules by acidic or basic
solution and alcohol.
28. The method as claimed in claim 27, wherein the surfactant is a
cation surfactant, anion surfactant, zwitterion surfactant, or
non-ionic surfactant.
29. The method as claimed in claim 27, wherein the surfactant is
cetyltrimethyl ammonium bromide or sodium dodecyl sulfate.
30. The method as claimed in claim 27, wherein separation of the
magnetic metal-filled carbon nanocapsules main product and the
carbon nanotube byproduct uses a column having a filter film at the
front.
31. The method as claimed in claim 30, wherein the filter film has
a pore size of about 0.2 .mu.m.
32. The method as claimed in claim 27, wherein the magnetic
metal-filled carbon nanocapsules obtained extraction have a purity
between 80% to 99.9%.
33. The method as claimed in claim 27, wherein the magnetic
metal-filled carbon nanocapsules obtained by extraction have a
purity higher than 95%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for producing
magnetic metal-filled carbon nanocapsules, and more particularly to
a method for producing high purity magnetic metal-filled carbon
nanocapsules.
[0003] 2. Background of the Invention
[0004] A magnetic metal-filled carbon nanocapsule is a polyhedral
carbon cluster constituting multiple graphite layers having a
balls-within-a ball structure with magnetic metals, metal
compounds, metal, carbides or alloys therein. The diameter of a
magnetic metal-filled carbon nanocapsule is about 3-100 nm.
Magnetic metal-tilled carbon nanocapsules have special fullerene
structure and optoelectronic properties. The magnetic metal
nanoparticles therein is well-protected by the outer graphite
layers from oxidation and acidic etching. Magnetic metal-tilled
carbon nanocapsules can be utilized in various fields such as
medicine (medical grade active carbon), light and heat absorption,
magnetic recording, magnetic fluids, catalysts, sensors, and
nanoscale composite materials with thermal conductivity, special
magnetic and electrical properties.
[0005] However, conventional methods for producing magnetic
metal-filled carbon nanocapoules produce mainly single layer carbon
nanotubes, but few carbon nanocapaules. Owing to the strong van der
Waals force between carbon nanocapaules and nanotubes, it is not
easy to separate the products. In addition, single layer carbon
nanotubes have an end capped with metal particles of catalyst
having magnetism as the magnetic metal-filled carbon nanocapsules,
therefore magnetic attraction cannot be used for product
separation. Conventional methods are not able to produce high
purity magnetic metal-filled carbon nanocapsules, huge amounts of
carbon ash impurities and single layer carbon nanotubes exist and
lower the purity of products, increasing the cost. The related
application on magnetic metal-filled carbon nanocapsules is limited
and insufficient.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to provide a method
for producing high purity magnetic metal-filled carbon
nanocapsules.
[0007] To achieve the above-mentioned object, the inventive method
for producing high purity magnetic metal-filled carbon nanocapsules
includes the following steps. An arc chamber comprising a graphitic
anode and a composite graphitic cathode containing at least one
kind of magnetic metal or its derivatives is provided; an inert gas
is introduced into the arc chamber. A voltage is applied across the
cathode and the anode by a pulse current, the voltage sufficient to
generate an carbon arc reaction between the cathode and the anode.
Finally, the deposit formed on the cathode is collected. Moreover,
after the collection step, the method of the present invention can
further include the following purification steps. The deposit is
dispersed in a solution using a surfactant. Next, the magnetic
metal-filled carbon nanocapsule main product and the carbon
nanotube byproduct are separated using column chromatography or
filter film. Finally, the magnetic metal-filled carbon nanocapsules
are extracted by magnetic attraction and cleaned by acidic or basic
solution and alcohol.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings, given by way of illustration only and thus not intended
to be limitative of the present invention.
[0009] FIG. 1 shows a schematic diagram of an arc chamber according
to the present invention.
[0010] FIG. 2 is a TEM photograph of the purified magnetic
metal-filled carbon nanocapaules of the present invention.
[0011] FIG. 3 is a high resolution TEM photograph of the purified
magnetic metal-filled carbon nanocapaules of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention uses pulse current under high pressure
(above 1 atm) of an inert gas to undergo a carbon arc reaction.
During the carbon arc reaction, the temperature at the electrode
surface and the density of the carbon vapor are changed. Thus, the
magnetic metal-filled carbon nanocapsules obtained will have an
improved yield.
[0013] FIG. 1 shows a schematic diagram of an arc chamber according
to the present invention. Referring to FIG. 1, the arc chamber 1
includes at least one pair of electrodes 10 and 12 for carbon arc
reaction. Inert gas is introduced into the arc chamber 1 via an
inlet 14 and is expelled via an outlet 16. The arc chamber 1 is
surrounded by flowing cooling water. Symbol 18 indicates a cooling
water inlet, and symbol 20 a cooling water outlet.
[0014] In the present invention, the arc reaction is conducted
under a flowing inert gas. The flow rate of the inert gas can be
controlled to 10 to 200 mm.sup.3/min, preferably 30 to 120
mm.sup.3/min. Inert gas suitable for use in the present invention
includes but is not limited to helium, argon, and nitrogen. The
pressure of the arc chamber can be controlled to 0.1 to 5 arm,
preferably 1 to 2 atm.
[0015] The electrode 10 can be graphite. Generally, the electrode
10 is in the form of a graphite rod. The electrode 12 is a
composite graphitic electrode containing at least one kind of
magnetic metal or its derivatives. Generally, the electrode 12 is a
mixture of carbon powders and powders of at least one kind of
magnetic metal or its derivatives. The molar mixing ratio of carbon
powders and powders of at least one kind of magnetic metal or its
derivatives is 100:1 to 5:1. The composite graphite electrode can
further comprise graphitizable resin. The resin is mixed with the
powders and pressed, and molded after graphitization via annealing
without oxygen under high temperature between 400 to 1500.degree.
C. The weight ratio of resin to powders is between 1:10 and 3:10.
The resin can be melamine resin, epoxy resin, phenolic resin or
other graphitizable resins. The magnetic metal can be Sc, V, Cr,
Fe, Co, Ni, Y, Zr, Mo, Ru, Pd, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er,
Tm, Lu, Ta, Os, Ir, Pt, Au, Th, U or a combination thereof,
preferably Co, Fe, Ni, La, Y or a combination thereof. The
derivatives of magnetic metals can be alloy of the magnetic metal
and another element, oxide and/or carbide of the magnetic
metal.
[0016] In the process of producing magnetic metal-filled carbon
nanocapsules, electrical energy is applied from a power supply 2 to
the graphitic anode 10 and composite graphitic cathod 12. The
electric energy applied has a voltage sufficient to generate a
carbon arc reaction between the anode 10 and the cathode 12 and to
form deposit on the graphitic anode 10.
[0017] According to the main feature of the present invention, when
performing the carbon arc reaction, a pulse current with a
predetermined frequency applies a voltage across the cathode and
anode. However, in the conventional techiques, DC (direct current)
or AC (alternating current), rather than pulse current, is used to
apply voltage. According to the present invention, the pulse
current can have a frequency of 0.01 to 1000 Hz, and can be
controlled to 50 to 800 A, and the voltage between electrodes can
be controlled to 10 to 30 V.
[0018] After the carbon arc reaction is conducted according to the
above conditions, a deposit is formed on the anode 10. According to
the present invention, most of the obtained magnetic metal-filled
carbon nanocapsules are present in the core portion of the deposit.
Therefore, preferably, the core portion of the deposite on the
anode 10 is collected. The core portion of the deposite is black
powder and is referred to as "crude product" in the following
descriptions. The crude product includes magnetic metal-filled
carbon nanocapsules main product (40% to 90%), hollow carbon
nanocapsules and short carbon nanotube byproduct (10% to 50%), and
few (under 10%) metal particles not surrounded by carbon layers.
After further purification of the crude product, high purity
magnetic metal-filled carbon nanocapsules are obtained. The
purification process is described below. First, the crude product
is dispersed in a solution using a surfactant. Then, the magnetic
metal-filled carbon nanocapsules main product and the hollow carbon
nanocapsules are separated from the short carbon nanotube byproduct
in the solution using column chromatography or a filter film.
Furthermore, the magnetic metal-filled carbon nanocapsules are
extracted by magnetic attraction. Finally, the surfactant and the
residue metal particles are washed away from the magnetic
metal-filled carbon nanocapaules using acidic or basic solution and
alcohol. Magnetic metal-filled carbon nanocapaules having a purity
higher than 80%, generally 95%, are obtained.
[0019] Surfactant suitable for use in the present invention can be
a cation surfactant such as cetyltrimethyl ammonium bromide, an
anion surfactant such as sodium dedecyl sulfate, a zwitterion
surfactant such as alkyl betaine, or a non-ionic surfactant such as
lauryl alcohol ether. Preferable examples are certyltrimethyl
ammonium bromide and sodium dedecyl sulfate. For column
chromatography, the suitable column can have size exclusion
function. For example, the column can preferably have a filter film
at the front, and the pore size of the filter film can be about 0.2
.mu.m. In addition, rather than using column chromatography, a
filter film can be singly used to perform separation. When a filter
film is used for separation, several filterings can be performed to
achieve better separation.
[0020] Compared with conventional techniques, the present invention
is the only currently available way to obtain high purity magnetic
metal-filled carbon nanocapsules.
[0021] The following example is intended to illustrate the process
and the advantages of the present invention more fully without
limiting its scope, since numerous modifications and variations
will be apparent to those skilled in the art.
EXAMPLE
[0022] This example uses the arc chamber shown in FIG. 1 to prepare
magnetic metal-filled carbon nanocapsules. One graphite rod was
used as a anode, and one composite graphite rod was used as a
cathode. Both electrodes had a diameter of 0.24 inches and the
anode had a rather short length of about 8-10 cm. The composite
graphite electrode was made by mixing the powders of carbon and Co
at a molar ratio of 100:5 with melamine resin having a weight
percent of 20 of total powders weight. The mixture was then molded
into an electrode by a hot-press machine under 170.degree. C. The
composite electrode was heated to 700.degree. C. without exposure
to oxygen to graphitize the resin.
[0023] Argon was introduced into the arc chamber at 60-90
cm.sup.3/min. The pressure of the arc chamber was controlled to 1.2
atm. The arc chamber was surrounded by flowing cooling water.
[0024] A carbon arc reaction was performed under the following
conditions: a pulse current of about 60 Hz, voltage of about 20 V,
and electric current of about 100 A. The carbon arc reaction
proceeded for about 30 minutes and then stopped. A deposit was
formed on the anode. The deposit was about 3-4 cm long and had the
same diameter as the graphitic anode. The deposit was cut and a
black powdery crude product was obtained in the core portion of the
deposit. The crude product contained about 70% Co-tilled carbon
nanocapsules, 30% hollow nanocapsules and short carbon nanotubes,
and a trace of Co particles not surrounded by carbon layers.
[0025] The crude product was dispersed in a solution using a
surfactant. Then, the dispersion solution was subjected to column
chromatography to separate the Co-filled carbon nanocapsules and
carbon nanotubes. Finally, the co-tilled carbon nanocapsules were
extracted by magnetic attraction, and the surfactant and residue Co
particles were washed away from the Co-filled carbon nanocapsules
by acidic or basic solution and alcohol. The Co-filled carbon
nanocapsules obtained had higher than 95% purity. FIG. 2 is a TEM
(transmission electron microscopy) photograph of the purified
Co-filled nanocapsule product. FIG. 3 is a high resolution TEM
photograph of the purified Co-tilled carbon nanocapsules.
[0026] The foregoing description of the preferred embodiments of
this invention has been presented for purposes of illustration and
description. Obvious modifications or variations are possible in
light of the above teaching. The embodiments chosen and described
provide an excellent illustration of the principles of this
invention and its practical application to thereby enable those
skilled in the art to utilize the invention in various embodiments
and with various modifications as are suited to the particular use
contemplated. All such modifications and variations are within the
scope of the present invention as determined by the appended claims
when interpreted in accordance with the breadth to which they are
fairly, legally, and equitably entitled.
* * * * *