U.S. patent application number 15/589151 was filed with the patent office on 2017-08-24 for single mode microwave device for producing exfoliated graphite.
The applicant listed for this patent is MICHAEL R. KNOX, Scott L. Murray, Jeffri J. Narendra. Invention is credited to MICHAEL R. KNOX, Scott L. Murray, Jeffri J. Narendra.
Application Number | 20170240427 15/589151 |
Document ID | / |
Family ID | 48465878 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170240427 |
Kind Code |
A1 |
KNOX; MICHAEL R. ; et
al. |
August 24, 2017 |
SINGLE MODE MICROWAVE DEVICE FOR PRODUCING EXFOLIATED GRAPHITE
Abstract
A device for producing exfoliated graphite from graphite flakes,
intercalated graphite, or expanded graphite by means of microwave
heating using single mode microwave cavities, a method of producing
such materials and products from such methods.
Inventors: |
KNOX; MICHAEL R.; (East
Lansing, MI) ; Murray; Scott L.; (East Lansing,
MI) ; Narendra; Jeffri J.; (Okemos, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KNOX; MICHAEL R.
Murray; Scott L.
Narendra; Jeffri J. |
East Lansing
East Lansing
Okemos |
MI
MI
MI |
US
US
US |
|
|
Family ID: |
48465878 |
Appl. No.: |
15/589151 |
Filed: |
May 8, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13686961 |
Nov 28, 2012 |
|
|
|
15589151 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B 6/642 20130101;
Y10S 977/842 20130101; H05B 6/701 20130101; H05B 6/707 20130101;
H05B 6/80 20130101; C01B 32/19 20170801; B82Y 30/00 20130101; B82Y
40/00 20130101; C01B 32/225 20170801; Y10S 977/734 20130101; H05B
6/6402 20130101; H05B 6/78 20130101 |
International
Class: |
F24C 7/02 20060101
F24C007/02; H05B 6/70 20060101 H05B006/70; H05B 6/64 20060101
H05B006/64; H05B 6/80 20060101 H05B006/80; C01B 31/04 20060101
C01B031/04 |
Claims
1. A single mode microwave device, said single mode microwave
device comprising: a stainless steel housing comprised of a top, a
bottom, two side walls, a front, and a moveable back wall, all
forming a hollow cavity; said moveable wall having a back surface,
and fixedly attached to said back surface, a control rod; contained
within said housing, an exfoliation tray, said exfoliation try
supported by at least two support rods which rods are supported at
predetermined levels by the side walls, said exfoliation tray being
electrically non-conducting; said bottom, front wall, and side
walls having a cooling jacket mounted on outside surfaces; an
adapter surmounting the top of the housing; said moveable back wall
having at least one gas inlet port therethrough; said bottom, of
said housing containing therein, an exhaust port; fingerstock
gaskets attached to the edges of the moveable back wall, to retain
electrical contact between the moveable back wall and the housing;
a microwave generator to deliver microwave energy to the hollow
cavity using a rectangular waveguide that is connected to said
adapter.
2. A single mode microwave device as claimed in claim 1 wherein, in
addition, there is a viewing window in a side wall.
3. A method of exfoliating a nanomaterial said method comprising:
providing a nanomaterial; placing the nanomaterial in the hollow
cavity of a device as claimed in claim 1; moving the moveable back
wall of the device such that the nanomaterial is in resonance with
the microwave frequency inside the cavity; heating the cavity until
the nanomaterial is exfoliated; removing the exfoliated
nanomaterial from the hollow cavity.
4. A method for preparing exfoliated graphene, said method
comprising: using a single mode microwave device as claimed in
claim 1; while the single mode microwave device is operating,
delivering intercalated graphite at a controlled rate to the
exfoliation tray through the delivery chute while controlling the
microwave frequencies at a frequency selected from the group
consisting of: a. 915 MHz and, b. 2.45 GHz.
5. A product prepared by the method as claimed in claim 2.
6.-10. (canceled)
11. A single mode microwave device of claim 1 having power ranging
from 2 to 15 kW.
12. (canceled)
13. A single mode microwave device as claimed in claim 1 wherein
the microwave power density to exfoliate intercalated graphite or
expanded graphite ranges from 100 to 300 W/cm.sup.3.
14. (canceled)
Description
[0001] This application claims priority from U.S. Utility patent
application Ser. No. 13/686,961, filed Nov. 28, 2012, currently
pending, which is a U.S. Utility patent application from U.S.
Provisional application Ser. No. 61/629,871, filed Nov. 30, 2011
from which priority is claimed.
BACKGROUND OF THE INVENTION
[0002] The present invention is in the technical field of
nanotechnology. More particularly, the present invention is in the
technical field of nanomaterial manufacturing. More specifically,
the present invention is in the technical field of graphite
exfoliation.
[0003] Graphite is a well known material occurring in natural and
synthetic forms. Graphite is made up of layered sheets of hexagonal
arrays or network of sp2-carbon atoms, called graphene. A useful
form of graphite is exfoliated graphite. Exfoliated graphite
generally is exfoliated or partially delaminated graphite having a
Braunauer-Ernmett-Teller (BET) surface area greater than BET
surface area of graphite but less than BET theoretical surface area
of single graphene sheet.
[0004] Exfoliation of graphite can be performed by applying heat to
graphite by a variety of means. Heating by direct application of
heat generally requires a significant amount of energy, especially
in the case of large-scale production. Radiofrequency (RF) or
microwave expansion methods can heat more material in less time at
lower cost.
THE INVENTION
[0005] In one embodiment, the present invention relates to a
microwave device for the production of exfoliated graphite and to
products produced by such a device, thus, there is a single mode
microwave device, the single mode microwave device comprising a
stainless steel housing comprised of a top, a bottom, two side
walls, a front, and a moveable back wall, all forming a hollow
cavity. The moveable wall has a back surface, and fixedly attached
to the back surface is a control rod.
[0006] There is contained in the housing an exfoliation tray, the
exfoliation tray being supported by at least two support rods which
rods are supported at predetermined levels by the side walls. The
exfoliation trays are electrically non-conducting.
[0007] The bottom, front wall and side walls have a cooling jacket
mounted on the outside surfaces and there is an adapter surmounting
the top of the housing. The moveable back wall has at least one gas
inlet port through it and the bottom of the housing contains an
exhaust port.
[0008] Fingerstock gaskets or conductive brushes are attached to
the edges of the moveable back wall to retain electrical contact
between the moveable back wall and the housing and there is a
microwave generator to deliver microwave energy to the hollow
cavity using a rectangular waveguide that is connected to said
adapter. For purposes of this invention, "fingerstock gaskets" and
"conductive brushes" are interchangeable.
[0009] Fingerstock gaskets are purchasable from
www.surplussales.com. A gasket that works particularly well in this
invention is 97-440-02M Fingerstock, Cu--Be.
[0010] In another embodiment, there is a method of exfoliating
graphite, said method comprising providing a nanomaterial and
placing the nanomaterial in the hollow cavity of a device as set
forth Supra.
[0011] Thereafter, moving the moveable back wall of the device such
that the nanomaterial is in resonance with the microwave frequency
inside the cavity, and heating the cavity until the nanomaterial is
exfoliated and thereafter, removing the exfoliated nanomaterial
from the hollow cavity.
[0012] An additional embodiment is a method for preparing
exfoliated graphene, the method comprising using a single mode
microwave device as set forth Supra while the single mode microwave
device is operating, delivering intercalated graphite at a
controlled rate to the exfoliation tray through the delivery chute
while controlling the microwave frequencies at a frequency selected
from 915 MHz and 2.45 GHz.
[0013] Other, additional embodiments are products prepared by the
methods as set forth just Supra.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a full view in perspective of a microwave device
of the present invention.
[0015] FIG. 2 is a full cross sectional view of the microwave
device of FIG. 1 through line A-A.
[0016] FIG. 3 is a full side view of a microwave device of FIG.
1.
[0017] FIG. 4 is a full cross sectional view of the microwave
device of FIG. 3 through line B-B.
DETAILED DESCRIPTION Of THE INVENTION
[0018] The instant invention provides a device for exfoliating
intercalated graphite, or expanded graphite by applying microwave
energy to the intercalated graphite, or expanded graphite inside a
microwave cavity. Such a device is a single mode microwave 1 as
shown in FIG. 1.
[0019] In FIGS. 1 and 2, the microwave housing 3 is made of
stainless steel or of any other metals that exhibit electrical
conductivity. The dimensions of the microwave cavity 2 formed by
the housing 3 are calculated based on the resonance dimension of
the operating frequency of the microwave inside the rectangular
cavity. In general, the microwave frequencies used for industrial
application in the U.S. are 915 MHz and 2.45 GHz.
[0020] To adjust the cavity 2 dimensions, a movable wall 4 is used.
This movable wall 4 can be set so that the microwave cavity 2,
along with the material inside the microwave cavity 2, is in
resonance condition with the microwave frequency. A rod 5 is
connected to the movable wall 4 so that the adjustment of the
wall's position relative to the dimension of the cavity 2 can be
performed outside of the microwave cavity 2. The rod 5 may be
either solid or hollow. With this sliding wall feature the
dimension of the microwave cavity 2 can be adjusted to allow
resonance condition and to produce a specific resonance mode of
which its location is at the intercalated graphite load 6 (See FIG.
2), Fingerstock gaskets 7 are attached to the edges 8 of the
movable wall 4 to ensure that the wall 4 can be moved white it
still electrically connected to the rest of the microwave cavity
wait.
[0021] Microwave energy is delivered from a microwave generator
(not shown) to the microwave cavity 2 using a rectangular waveguide
that is connected to an adapter 10 on the top side 11 of the
microwave cavity 2. To improve the coupling of the microwave into
the cavity, an iris structure may be used.
[0022] The intercalated graphite or the expanded graphite is
dropped at controlled rates to an exfoliation tray 12 inside the
microwave cavity 2 using the chute 13 that is located on the top
side 11 of the microwave cavity 2. The exfoliation tray 12 is made
of non-conductive materials that can withstand high temperature
environment. Examples of such materials are fused quartz and
alumina. The exfoliation tray 12 is sitting on top two support rods
14 made of similar materials. These rods 14 extend along the width
of the microwave cavity 2 and are fastened by outside nipples 15
protruded on the sidewalls 16 of the microwave cavity 2. This
configuration of the exfoliation tray 12 and the support rods can
be best observed in FIG. 4 which is a full cross sectional side
view of the device of FIG. 3 through line B-B.
[0023] The exfoliated graphite has a much lower bulk density
compared to the intercalated graphite or the expanded graphite.
Thus, extracting the exfoliated graphite from the microwave cavity
2 can be done by suspending the exfoliated graphite in air or
nitrogen. The microwave cavity exhaust 17, which is connected to a
cyclone (not shown), extracts the exfoliated graphite from the
microwave cavity 2. To control the suspension velocity of the
exfoliated graphite and the gas flow within the cavity 2,
compressed air or nitrogen is flown into the microwave cavity 2
from the inlets 18, which are found in the bottom part of the
movable wall 4. By flowing compressed air or nitrogen on the bottom
part of the microwave cavity 2, the pressure within that region of
the microwave cavity 2 drops. The introduction of pressure
differential creates a macroscopic drift of air from the top part
of the microwave cavity 2 into the bottom part of the microwave
cavity 2. Thus, the suspended exfoliated graphite flows downward.
The microwave cavity 2 is tilted at an angle to minimize the
exfoliated graphite depositing on the microwave cavity 2 bottom
wall 19 and to maximize the extraction of the exfoliated graphite
using the microwave cavity exhaust 17.
[0024] The waveguide is pressurized to prevent the exfoliated
graphite from flowing into the waveguide transmission line. The
back area of the movable wall 4 is also pressurized to prevent the
exfoliated graphite from obstructing the fingerstock gaskets 7.
[0025] The chute 13 and the exhaust 17 of the microwave cavity 2
have a grid like structure as seen in FIGS. 2, and 4, This
structure is built to prevent microwave radiation. Essentially, the
grid can be seen as a group of small waveguides of which their
dimensions are small enough that their cutoff frequency is much
higher than the operating frequency. Thus, the microwave is
attenuated through these waveguides or grids.
[0026] The bottom 19, front 20, and part of the sides 16 of the
microwave cavity 2 are enclosed with cooling jacket 21 to maintain
the microwave cavity wall temperature low, such as below 120 F. The
cooling agent is in liquid form such as water or ethylene
glycol.
[0027] Viewing windows 22 can be built on the side of the microwave
cavity 2 to enable one to observe the exfoliation process. The view
of the viewing windows 22 can best be observed in FIG. 3, which is
a full side view of the device 1 of this invention. The viewing
windows 22 are made of perforated metal with holes diameter much
less than 1/10 of the wavelength of the operating microwave
frequency. The perforated metals are covered with glass or any
other optically transparent medium.
* * * * *
References