U.S. patent application number 12/064378 was filed with the patent office on 2008-09-11 for method for manufacturing nanostructured powder by wire explosion in liquid and device for manufacturing the same.
Invention is credited to Chu Hyun Cho, Byung Geol Kim, Hong Sik Lee, Geun Hie Rim.
Application Number | 20080216604 12/064378 |
Document ID | / |
Family ID | 37771785 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080216604 |
Kind Code |
A1 |
Cho; Chu Hyun ; et
al. |
September 11, 2008 |
Method for Manufacturing Nanostructured Powder by Wire Explosion in
Liquid and Device for Manufacturing the Same
Abstract
The present invention relates to a method for manufacturing the
nanostructured powder by a wire explosion in liquid and a device
for manufacturing the same. To be more specific, the object of the
invention is to provide a method for manufacturing the
nanostructured powder by a wire explosion in liquid and a device
for manufacturing the same, in which, a metal wire (18) is
vaporized in liquid (14) by generating an electrical explosion
using the same principle al in gas, with the characteristic of
pulsed power, even though the liquid (14) with a low conductivity
is used, and the nanostructured powder of a metal wire (18) is
produced in the space made by the volume expansion of vaporized
vapour, all of which was performed with an understanding that
electrical explosion is not so different in principle weather in
gas or in liquid. By achieving this object, the present invention
can provide an advantage of natural disperse of the nanostructured
powder into a liquid, hence either the agglomeration between powder
particles or the surface oxidation of the nanostructured powder is
not generated, as the powder is not in contact with oxygen in
liquid. Moreover, the classification according to size becomes
possible with the reduction of the number of processes, hence
providing an advantage of an effective application of the
nanostructured powder an the economic ripple effect thereto.
Inventors: |
Cho; Chu Hyun;
(Gyeongsangnam-do, KR) ; Kim; Byung Geol; (Seoul,
KR) ; Rim; Geun Hie; (Gyeongsangnam-do, KR) ;
Lee; Hong Sik; (Gyeongsangnam-do, KR) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Family ID: |
37771785 |
Appl. No.: |
12/064378 |
Filed: |
August 16, 2006 |
PCT Filed: |
August 16, 2006 |
PCT NO: |
PCT/KR2006/003195 |
371 Date: |
February 21, 2008 |
Current U.S.
Class: |
75/345 ;
266/137 |
Current CPC
Class: |
B22F 1/0018 20130101;
B22F 9/14 20130101; B22F 9/12 20130101; B22F 9/14 20130101; B82Y
30/00 20130101; B22F 2998/10 20130101; B22F 2998/10 20130101 |
Class at
Publication: |
75/345 ;
266/137 |
International
Class: |
B22F 9/14 20060101
B22F009/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2005 |
KR |
10-2005-0078518 |
Claims
1. A method for manufacturing nanostructured powder by a wire
explosion in liquid, comprising: exploding a metal wire
electrically using pulsed power in the chamber filled with a liquid
(dispersing solvent) selected from the group consisting of oil,
distilled water, insulating oil, solvent, acetone, ethanol and
gasoline; vaporizing the metal wire in liquid; and concentrating or
collecting the produced nanostructured powder.
2. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 1, wherein the first process
is progressed by including a step of providing the chamber filled
with a liquid; a step of continuously feeding a metal wire into the
liquid from an upper side of the chamber; and a step of flowing
0.1-100 kJ pulsed power into the metal wire in the liquid to
generate an electrical explosion.
3. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 1, wherein the second
process includes a step of vaporizing the metal wire in liquid due
to an electrical explosion; and a step of producing nanostructured
powder of the metal wire in the space made by the volume expansion
of vaporized vapour.
4. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 1, wherein the third process
includes a step of discharging the liquid dispersed (suspended)
with nanostructured powder from the chamber; a step of uniformly
injecting the discharged liquid into a collecting filter using a
spray; and a step of picking up nanostructured powder filtered by
the collecting filter.
5. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 1, wherein the third process
includes a step of discharging the liquid dispersed (suspended)
with nanostructured powder from the chamber; and a step of
evaporating the discharged liquid by an evaporation classification
method to retrieve or concentrate nanostructured powder for
pickup.
6. (canceled)
7. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 4, wherein a plurality of
collecting filters having different sizes of mesh (hole diameter)
are vertically arranged to collect nano-structured powder through
classification according to size.
8. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 4, wherein when
nanostructured powder filtered by the collecting filter is picked
up, it is picked up in a state that the nanostructured powder is
covered with the liquid (dispersing solvent) to prevent an
oxidation.
9. The method for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 4, wherein a step of
reflowing the liquid passing through the collecting filter into the
chamber is further progressed by a liquid circulating motor.
10. A device for manufacturing nanostructured powder by a wire
explosion in liquid, comprising: a chamber having a structure
divided into an upper space and a lower space by an insulator; a
liquid (dispersing solvent) selected from the group consisting of
oil, distilled water, insulating oil, solvent, acetone ethanol and
gasoline filled in the lower space; a wire feeding device as a
configuration provided in the upper space, including a wire roll
wound with a metal wire, a pair of feeding rollers for feeding the
wire being unfolded from the wire roll into the lower space through
a wire guide, and an electric motor connected with the wire roll
and the rotational axis of a pair of the feeding rollers; a wire
explosion device as a configuration provided in the lower space,
including a high voltage electrode mounted on a bottom surface of
the lower space in the chamber, a trigger switch connected with the
high voltage electrode, a capacitor connected with the switch, a
charging device for charging the capacitor with high voltage, a
controller for sensing the rotation angle of the feeding motor to
generate a trigger signal in the switch; a nanostructured powder
collecting device as a configuration arranged for communicating
with a bottom corner location of the lower space, including a
cistern tank having a predetermined volume, a valve imbedded pipe
connected for communicating the lower space of the chamber with an
upper space of the cistern tank, a spray mounted integrally at the
end of the pipe for being arranged in an upper end space of the
cistern tank, and a number of collecting filters vertically mounted
at equal intervals under the spray in the interior space of the
cistern tank; and a recirculation device as a configuration for
recirculating the liquid from the nanostructured powder collecting
device to the lower space, including a circulation pipe connected
for communicating between a lower end of the cistern tank and an
upper end of the lower space in the chamber, an on-off valve
mounted on the circulation pipe, and a liquid circulating pump.
11. The device for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 10, wherein a hollow wire
guide for feeding the wire is mounted in the insulator of the
chamber, and a grounding electrode is further mounted in the lower
space filled with the liquid.
12. The device for manufacturing nanostructured powder by a wire
explosion in liquid according to claim 10, wherein among a number
of the collecting filters, the filter with a large mesh size (hole
diameter) is located at upper level, while the filter with a small
mesh size is located at the lower level.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for manufacturing
nanostructured powder by a wire explosion in liquid and a device
for manufacturing the same, and more particularly, to a method for
manufacturing nanostructured powder by a wire explosion in liquid
and a device for manufacturing the same, which can prevent the
problems caused when manufacturing nanostructured powder by a wire
explosion in gas in the related art, such as a phenomenon of
agglomeration among nanostructured powder particles, a phenomenon
of oxidation on the surface of nanostructured powder, etc., and
also enable the classification of nanostructured powder by size due
to its excellent dispersibility, and as a result, enabling an
effective application of nanostructured powder and its great
economic ripple effect.
BACKGROUND ART
[0002] In recent years, the technological development of
nanostructured powder as a new material has been recognized as
being very important as it can be applied to base technology of new
fields, including the nano-devices.
[0003] A nanostructured powder material can display an unique
electromagnetic, mechanical and catalytic property which cannot be
obtained through existing materials due to their minute material
structure (100 nm or less) and the increased surface thereupon, and
therefore there is no doubt that there will be a new demand over
the whole industry as the post-generation functional material for
super-high strength part, magnetic part, thermocouple, sensor,
filter, catalyst, etc.
[0004] According to the advancement of the high-tech industry,
parts and systems move toward higher performance and
miniaturization, and the structural particle with the
phenomenological length of micron or sub-micron is currently used
for determining physical/chemical/biological properties.
[0005] Accordingly, the significance of nano technology that it is
a technology to overcome the limits of the existing technologies in
terms of higher performance and miniaturization of parts and
systems, while it is recognized as the model for the future
technology as well as an essential element for the development of
high-tech products as a new performance may be revealed with the
reduction of the phenomenological length.
[0006] At the present, various methods for manufacturing
nanostructured powder from certain materials are known to us;
however, among them is a widely known technology for manufacturing
nanostructured metal powder by a wire explosion using pulsed power
and is still actively studied today.
[0007] The method for manufacturing nanostructured powder using
pulsed power has much significance in the aspect of industrial
application, while also having much economic advantage, compared to
other methods for manufacturing nanostructured powder.
[0008] The conventional method for manufacturing nanostructured
metal powder by wire explosion using pulsed power is described as
in the following:
[0009] A wire explosion in gas is used in the conventional method
for manufacturing nanostructured metal powder, and it is conducted
by including the steps of providing a predetermined chamber filled
with air or inert gas, feeding a metal wire into the chamber,
electrically exploding and vaporizing the metal wire inside the
chamber using pulsed power, and collecting the nanostructured metal
powder produced that is cooled and condensed by inert gas using an
air filter.
[0010] However, the conventional method for manufacturing
nanostructured powder using wire explosion in gas aforementioned
has the following problems:
[0011] First of all, it has a disadvantage that most of
nanostructured metal powder is exposed to the air and hence easily
oxidized, and has a difficulty in its handling as the risk of dust
explosion is inherent during the process.
[0012] Second, there is an inconvenience of periodical cleaning of
the deposited powder due to frequent dielectric breakdown caused by
the powder deposited in the chamber during the process of
manufacturing nanostructured powder, and accordingly, there is a
disadvantage of exceptionally low productivity and workability.
[0013] Third, the nanostructured powder collected in air tends to
agglomerate in its characteristic, and as a result, there is a
difficulty in classification according to the size.
[0014] Fourth, there is an aspect of being inefficient and
uneconomical in the process, since an essential process of
dispersing nanostructured powder into a dispersing agent is further
required in order to use the agglomerated powder.
[0015] The present invention has been studied and developed in
consideration of the above issues, and considering that electrical
explosion is not so different in principle between the one in gas
and in liquid, the object of the invention is to provide a method
for manufacturing nanostructured powder by a wire explosion in
liquid, as well as a device for manufacturing the same, in which as
a feature of pulsed power a metal wire is vaporized in liquid by
generating an electrical explosion using the same principle as in
gas despite the low conductivity of the liquid and nanostructured
powder of a metal wire is produced in the space made through the
volume expansion of vaporized vapour.
[0016] The nanostructured powder, produced by such a method of the
present invention, can provide an advantage that it is naturally
dispersed into liquid so that the agglomeration between powder
particles does not occur at all, and also the surface oxidation of
powder is not generated as it is not contacted with oxygen in
liquid.
DISCLOSURE
[0017] In order to accomplish the aforementioned object, a method
for manufacturing nanostructured powder by wire explosion in
liquid, comprising: the first process of electrically exploding a
metal wire using pulsed power in the chamber filled with a liquid
(dispersing solvent); the second process of producing
nanostructured powder by vaporizing the metal wire in liquid; and
the third process of concentrating or collecting the produced
nanostructured powder.
[0018] As an appropriate embodiment, the aforementioned first
process is characterized with a progress including a step to
provide a chamber filled with a liquid; a step to continuously feed
a metal wire into the liquid from an upper side of the chamber; and
a step to flow in 0.1-100 kJ pulsed power into the metal wire in
liquid to generate an electrical explosion.
[0019] As another preferred embodiment, the aforementioned second
process is characterized by including a step to vaporize the metal
wire in liquid due to an electrical explosion; and a step to
produce nanostructured powder of the metal wire in the space made
by the volume expansion of vaporized steam.
[0020] As still yet another preferred embodiment, the
aforementioned third process is characterized by including a step
to discharge the liquid dispersed (suspended) with nanostructured
powder from the chamber; a step to uniformly inject the discharged
liquid into a collecting filter with a spray; and a step to pick up
nanostructured powder filtered by the collecting filter.
[0021] Or, the aforementioned third process is characterized by
including a step to discharge the liquid dispersed (suspended) with
nanostructured powder from the chamber; and a step to evaporate the
discharged liquid by an evaporation classification method to
collect or to condense the nanostructured powder for pickup.
[0022] At this time, the main characteristic lies in that the
liquid (dispersing solvent) was any one selected from oil,
distilled water, insulating oil, solvent, acetone, ethanol, or
gasoline.
[0023] In particular, one of the main characteristics is the fact
that a number of collecting filters with different sizes of mesh
(hole diameter) are vertically arranged to collect nanostructured
powder in classification according to size.
[0024] Also, another characteristic is the fact that when
nanostructured powder filtered by the collecting filter is picked
up, it is picked up in a state where the nanostructured powder is
covered with the liquid (dispersing solvent).
[0025] Furthermore, another characteristic lies in a step of
reflowing the liquid passing through the collecting filter into the
chamber is further progressed by a liquid circulating motor.
[0026] In order to accomplish the above-mentioned object, a device
is provided for manufacturing nanostructured powder by a wire
explosion in liquid, comprising a chamber having a structure
divided into an upper space and a lower space by an insulator; a
liquid (dispersing solvent) filled in the lower space; a wire
feeding device provided in the upper space; a wire explosion device
provided in the lower space; a nanostructured powder collecting
device arranged for connection with a bottom corner location of the
lower space; and a recirculation device for recirculating the
liquid from the nanostructured powder collecting device to the
lower space.
[0027] As an appropriate embodiment, the aforementioned insulator
of the chamber is characterized in that a hollow wire guide for
feeding the wire is mounted in the insulator of the chamber, while
a grounding electrode is further mounted in the lower space filled
with the liquid.
[0028] As another preferred embodiment, the aforementioned wire
feeding device is characterized with an inclusion of a wire feeding
device includes a wire roll wound with a metal wire, a pair of
feeding rollers for feeding the wire being unfolded from the wire
roll into the lower space through a wire guide, and an electric
motor connected with the wire roll and the rotational axis of a
pair of the feeding rollers.
[0029] As still yet another preferred embodiment, the
aforementioned wire explosion device is characterized with an
inclusion of a high voltage electrode mounted on a bottom surface
of the lower space in the chamber, a trigger switch connected with
the high voltage electrode, a capacitor connected with the switch,
a charging device for charging the capacitor with high voltage, a
controller for sensing the rotation angle of the feeding motor to
generate a trigger signal in the switch.
[0030] Furthermore, the aforementioned nanostructured powder
collecting device is characterized with an inclusion of a cistern
tank having a predetermined volume, a valve imbedded pipe connected
for communicating the lower space of the chamber with an upper
space of the cistern tank, a spray mounted integrally at the end of
the pipe to be arranged in an upper end space of the cistern tank,
and a number of collecting filters vertically mounted at equal
intervals under the spray in the interior space of the cistern
tank.
[0031] At this time, the number of the collecting filters
aforementioned is characterized with an arrangement of the one
having a large mesh size (hole diameter) located at higher level,
while the one having a small mesh size is located at lower
level.
[0032] Furthermore, the aforementioned recirculation device is
characterized with an inclusion of a circulation pipe linked for a
connection between a lower end of the cistern tank and an upper end
of the lower space in the chamber, an on-off valve mounted on the
circulation pipe, and a liquid circulating pump.
[0033] A preferred embodiment of the present invention will be
described in detail with reference to the accompanying drawings
hereinafter.
[0034] As illustrated herein, the attached FIG. 1 is a
configuration view illustrating a device for manufacturing
nanostructured powder by a wire explosion in liquid according to
the present invention, while FIG. 2 is a flow chart illustrating a
method for manufacturing nanostructured powder by a wire explosion
in liquid according to the present invention.
[0035] As described above, the main object of the present invention
is to provide an advantage of naturally dispersing the
nanostructured powder of a metal wire into liquid and hence not
resulting in the phenomenon of agglomeration between powder
particles or in the generation of surface oxidation of powder as
the powder is not in contact with oxygen in liquid, by applying
pulsed power to a metal wire to generate an electrical wire
explosion in liquid.
[0036] The method for manufacturing nanostructured powder, as well
as a detailed explanation for each element of a device for
manufacturing nanostructured powder according to the present
invention, will be described in detail.
[0037] As the site where an electrical explosion takes place in a
device for manufacturing nanostructured powder according to the
present invention, a chamber (10) with a pre-determined volume is
provided, and the interior of this chamber (10) is divided into an
upper space (12) and a lower space (14) by a plate-shaped insulator
(16).
[0038] The lower space (14) is filled with a liquid (dispersing
solvent), and any one selected from oil, distilled water,
insulating oil, solvent, acetone, ethanol, or gasoline can be used
as this liquid.
[0039] The upper space (12) is provided with a wire feeding device,
and the wire feeding device includes a wire roll (20) stored with a
winding of a metal wire (18), and a pair of feeding rollers (22)
for feeding downward the metal wire (18) unfolded from the wire
roll (20).
[0040] Furthermore, an electric motor (not shown) is connected with
the wire roll (20) and the rotational axis of a pair of the feeding
rollers (22).
[0041] On the other hand, as the path for providing the metal wire
(18) that is fed downward by a pair of the feeding rollers (22) to
the lower space (14), a hollow wire guide (24) is mounted on the
insulator (16) of the chamber (10) to vertically pass through.
[0042] Furthermore, a grounding electrode (26) is attached to the
lower space (14) while being immersed in liquid, and this will act
as a grounding means for electrical explosion, which will be
described later.
[0043] Here, a wire explosion device is installed at the bottom
side of the lower space (14).
[0044] As a configuration of the wire explosion device, a high
voltage electrode (28) is mounted at the bottom of the lower space
(14) in the chamber (10), and a spark gap switch (30) connected
with the aforementioned high voltage electrode (28) is arranged at
the outside of the lower space (14).
[0045] Furthermore, a capacitor (32) charged with high voltage is
connected to the switch (30), and a charging device (34) for
charging high voltage is connected to this capacitor (32).
[0046] In particular, a controller (36) is connected to the
aforementioned switch (30), and this controller (36) senses either
the rotation angle of an electric motor (not shown) that provides a
rotational driving force to a pair of feeding rollers (22) or the
reduction of resistance generated through contacting a wire with
the electrode, thereby taking control of generating a trigger
signal to the switch (30).
[0047] Here, the process of producing nanostructured powder of a
metal wire (18) in the lower space (14) of the aforementioned
chamber (10) by the aforementioned wire feeding device and the wire
explosion device may be described as in the following:
[0048] As a wire roll (20) of the aforementioned wire feeding
device rotates in one direction, this unfolded metal wire (18) is
fed to the lower space (14) of the chamber (10) by a pair of
feeding rollers (22).
[0049] In other words, a metal wire (18) that is fed downward by a
pair of feeding rollers (22) is continuously provided to the high
voltage electrode (28) of the lower space (14) through the wire
guide (24).
[0050] Subsequently, when the controller (36) transmits a trigger
signal to the switch (30) as it senses the rotation angle of an
electric motor (not shown) for rotating a pair of the feeding
rollers (22) or the reduction of resistance that is generated by
contacting a wire with the electrode, the pulsed power provided
from the capacitor (32) flows to the metal wire through the high
voltage electrode (28) with a switch on, thereby generating an
electrical wire explosion.
[0051] At this time, a wire explosion is generated with 0.1-100 kJ
pulsed power flows into the metal wire in liquid.
[0052] The metal wire (18) is vaporized in liquid with such
electrical explosion, and nanostructured powder of the metal wire
(18) is produced in the space made by the volume expansion of
vaporized vapour.
[0053] Here, a device for collecting nanostructured powder produced
as described above and the process thereto may be described as in
the following:
[0054] As a configuration of the aforementioned nanostructured
powder collecting device, a cistern tank (40) with a predetermined
volume is provided, and an upper side of the interior space in the
aforementioned cistern tank (40) is linked by a connection with a
corner location of the lower space (14) in the chamber (10) through
a valve imbedded pipe (42).
[0055] Furthermore, a spray (44) having a shape that widens
downward is adhered to the end of the aforementioned pipe (42)
inside the aforementioned cistern tank (40), and a number of
collecting filters (46) are vertically adhered at equal intervals
in the interior space of the cistern tank (40) under the spray.
[0056] At this time, among a number of the aforementioned
collecting filters (46), the filter with a large mesh size (hole
diameter) is mounted at higher level, while the filter with a small
mesh size is mounted at lower level, thereby allowing
nanostructured powder to be selectively collected by sizes.
[0057] Here, a state in which nanostructured powder is collected by
a nanostructured powder collecting device as configured in the
above may be described as in the following:
[0058] As described above, the liquid dispersed (suspended) with
nanostructured powder of a metal wire (18) in liquid is discharged
from the aforementioned chamber (10) by an electrical explosion,
and the discharged liquid is provided to the spray (44) through the
aforementioned valve imbedded pipe (42) and is uniformly injected
into the aforementioned collecting filters (46) through this spray
(44).
[0059] Accordingly, the nanostructured powder with the largest size
is filtered in the uppermost collecting filter (46), while the
nanostructured powder with the smallest size is filtered in the
lower-most collecting filter (46), thereby allowing nanostructured
powder to be collected while being classified according to
size.
[0060] At this time, while the nanostructured powder filtered by
the collecting filter (46) is being picked up, it is more
appropriate to collect the nanostructured powder in a state of
being covered (immersed) with the liquid (dispersing solvent), in
order to prevent an oxidation of the nanostructured powder through
contact with air.
[0061] On the other hand, the device for manufacturing
nanostructured powder in the present invention further includes a
recirculation device that recirculates the discharged liquid to the
lower space (14) of the chamber (10).
[0062] The aforementioned recirculation device includes a
circulation pipe (48) that connects the lower end of the cistern
tank (40) with the lower space (14) of the chamber (10), an on-off
valve (50) mounted on the circulation pipe (48), and a liquid
circulating pump (52).
[0063] Accordingly, the liquid in a state where the nanostructured
powder is filtered by passing through the collecting filters (46)
is pumped by the aforementioned circulating pump (52) and reflowed
into the lower space (14) of the chamber (10).
[0064] As described above, by inducing an electrical explosion
through applying pulsed power to the metal wire in liquid, the
nanostructured powder of the metal wire is produced and dispersed,
thereby preventing agglomeration among nanostructured powder
particles. In particular, contact with air is blocked off since
nanostructured powder is produced in liquid, thereby effectively
preventing the oxidation. Furthermore, the nanostructured powder in
liquid may be selectively collected by size, thereby allowing its
classification according to size.
DESCRIPTION OF DRAWINGS
[0065] The above and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following description of the exemplary embodiments, taken in
conjunction with the accompany drawings, which include:
[0066] FIG. 1 is a configuration view illustrating a device for
manufacturing the nanostructured powder by a wire explosion in
liquid according to the present invention;
[0067] FIG. 2 is a flow chart illustrating a method for
manufacturing the nanostructured powder by a wire explosion in
liquid according to the present invention;
[0068] FIG. 3 is a photograph taken at high speed, illustrating a
state in which the nanostructured silver powder is manufactured by
a wire explosion in liquid according to the present invention;
[0069] FIG. 4 is a view illustrating a voltage and current waveform
of a wire explosion in liquid;
[0070] FIG. 5 is a microphotograph illustrating the nanostructured
silver powder that is manufactured according to the method for
manufacturing the nanostructured powder by a wire explosion in
liquid according to the present invention;
[0071] FIG. 6 is an analytical graph by an X-ray diffraction method
for confirming that the nanostructured powder of the invention is
pure nanostructured silver powder;
[0072] FIG. 7 is a photograph illustrating the experimental results
of sedimentation for the nanostructured silver powder manufactured
in liquid according to the present invention, and the
nanostructured silver powder manufactured in gas in the related
art;
[0073] FIG. 8 is a SEM photograph illustrating the nanostructured
copper powder in the embodiment 5, manufactured in liquid according
to the present invention; and
[0074] FIG. 9 is a graph by an XRD analytic result illustrating the
nanostructured copper powder in the embodiment 5, manufactured in
liquid according to the present invention.
BEST MODE
[0075] Reference will now be made in detail to the preferred
embodiment of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout. The embodiments are
described below so as to explain the present invention by referring
to the figures.
EMBODIMENTS 1-4
[0076] As an embodiment of a method for manufacturing the
nanostructured powder according to the present invention, a
predetermined chamber was filled with liquid (distilled water),
into which a silver (Ag) wire was provided and the pulsed power was
flowed into at 1, 2, 3 and 4 kJ, respectively, to generate an
electrical explosion, and due to this electrical explosion, the
nanostructured powder of the metal wire was produced in a dispersed
state in liquid.
[0077] More specifically, as seen in the high-speed photograph of
FIG. 3, as an electrical explosion was generated by flowing pulsed
power at 1, 2, 3 and 4 kJ, respectively, where a silver wire of 0.3
mm in diameter and 25 mm in length was immersed in distilled water,
a metallic vapour plasma was generated in the space produced in
liquid by an impulse wave, and simultaneously, the metal (silver)
vapour was condensated to produce the nanostructured powder,
ultimately producing the nanostructured silver powder dispersed in
liquid.
[0078] Subsequently, the nanostructured aluminum powder in liquid
was selectively collected according to sizes using a number of
collecting filters.
EMBODIMENTS 5
[0079] As an embodiment of a method for manufacturing the
nanostructured powder according to the present invention, a
predetermined chamber was filled with liquid (acetone), and then a
copper wire of 0.3 mm in diameter and 40 mm in length was
discharged 200 times in acetone solvent to produce the
nanostructured powder, and the nanostructured powder was collected
using a rotary evaporator for observation.
COMPARATIVE EXAMPLE 1
[0080] According to the conventional method for manufacturing the
nanostructured powder, an electrical explosion was generated by
flowing pulsed power at 2 kJ into a silver wire in the chamber (in
gas), and due to this electrical explosion, the nanostructured
powder of the aluminum metal wire was cooled/condensated and
produced in gas.
COMPARATIVE EXAMPLE 2
[0081] According to the conventional method for the manufacturing
nanostructured powder, an electrical explosion was generated by
flowing pulsed power at 2 kJ into a silver wire in the chamber (in
gas), and due to this electrical explosion, the nanostructured
powder of the copper metal wire was cooled/condensated and produced
in gas.
EXPERIMENTAL EXAMPLE 1
Experiment of Voltage and Current Waveform
[0082] As illustrated herein, FIG. 4 displays a voltage and current
waveform of a wire explosion in liquid.
[0083] A current curve properly represents a feature shown by an
electrical explosion. In other words, it shows the loss of
conductivity due to vaporization and the abrupt current reduction
thereto.
[0084] Furthermore, it properly represents a process of resolving
the abrupt current reduction then converting to a damped vibration
mode, with the resumption of conducting a current by the plasma,
generated at the moment of an explosion. Moreover, a voltage curve
represents a feature of decreasing at the beginning of discharge
then slightly increasing at the moment when the wire explodes.
[0085] As illustrated herein, FIG. 5 is a SEM (Scanning Electron
Microscope) photograph showing the nanostructured silver powder
manufactured by a wire explosion in liquid. It can be seen that the
nanostructured powder is composed of spherical nanoparticles of
about 100 nm, and it was confirmed that the manufactured
nanostructured powder was pure nanostructured silver powder through
an analysis by an X-ray diffraction method as in FIG. 6. Here, an
XRD analysis is an analysis method for irradiating the crystalline
structure of a material to find out the type of material, and the
position and the size of peaks as illustrated in FIG. 6 is compared
with an already known database in order to assume what material it
is. The graph in FIG. 6 has the peaks of silver material as a
whole.
[0086] In this manner, according to the embodiments 1-4 of the
present invention, the nanostructured silver powder was produced
and dispersed in liquid by an electrical explosion, and it could be
confirmed that uniformly spherical nanoparticles of about 100 nm
could be obtained, in comparison to the nanostructured powder
produced in gas, according to the comparative example.
EXPERIMENTAL EXAMPLE 2
[0087] According to the embodiments 1-4 of the present invention,
an experiment on the sedimentation state was conducted for the
nanostructured silver powder manufactured in liquid and the
nanostructured silver powder manufactured in gas according to the
comparative example, and the results are as illustrated herein in
photographs of FIG. 7.
[0088] The Nanostructured silver powder contained in the two
bottles on the left side in photographs (a) and (b) of FIG. 7 is
the nanostructured powder manufactured in gas, and the change of
color to transparent by sedimentation could be observed after 4
days, and the nanoparticles cohered with each other.
[0089] On the other hand, the nanostructured silver powder
manufactured in liquid according to the present invention
(contained in a bottle on the most right side in photographs (a)
and (b) of FIG. 7 as illustrated herein) was uniformly dispersed
and not precipitated in liquid even after 4 days, neither did the
powder particles cohere with each other.
[0090] As described above, in order to manufacture the
nanostructured powder with good quality, a method for manufacturing
nanostructured powder in liquid according to the present invention
is much more excellent, economical, and effective than the
conventional method for manufacturing nanostructured powder in
gas.
EXPERIMENTAL EXAMPLE 3
[0091] The copper powder manufactured according to the embodiment 5
was collected and a photograph was taken by an electron microscope,
as seen in the SEM photograph illustrated in FIG. 8. It was
confirmed that the specific surface area measured by BET was 40.84
m.sup.2/g, and the average granularity when converted into diameter
was 17 nm.
[0092] Furthermore, the copper powder manufactured according to the
embodiment 5 was analyzed by an XRD method, and the result showed
that each peak represents the peaks of copper metal as a whole, and
also that this copper powder was pure non-oxidized nanostructured
metal powder, as seen under the graph of FIG. 9.
INDUSTRIAL APPLICABILITY
[0093] As described above, a method of manufacturing the
nanostructured powder by a wire explosion in liquid and a device
for manufacturing the same has the following advantages.
[0094] 1) It has an advantage that the nanostructured powder of a
metal wire is produced and dispersed in liquid by feeding the metal
wire in liquid in the chamber while flowing a pulsed power to
generate an electrical explosion, thereby completely preventing a
agglomeration of the nanostructured powder, and remarkably reducing
the oxidation in nanostructured powder, by blocking off the contact
with air by the liquid.
[0095] 2) By excluding a process of eliminating oxygen on the
surface of the nanostructured powder and a process required for
dispersing agglomerated powder in a dispersing agent in the related
art, cost reduction and more efficient process for manufacturing
nanostructured powder can be achieved.
[0096] 3) According to the present invention, the nanostructured
powder is produced in a dispersed (suspended) state, which prevents
the deposit in the chamber, as well as the dielectric breakdown due
to deposited powder, thereby improving the productivity of
manufacturing nanostructured powder.
[0097] 4) According to the present invention, the nanostructured
powder is dispersed but not agglomerated in liquid, and hence
enabling its classification through selective collection by size,
thereby enhancing the added value.
[0098] Although a few exemplary embodiments of the present
invention have been shown and described, it will be appreciated by
those skilled in the art, that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the appended claims and
their equivalents.
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