U.S. patent application number 14/624708 was filed with the patent office on 2015-06-18 for microspheres and their methods of preparation.
The applicant listed for this patent is Ohio University. Invention is credited to ANIMA B. BOSE, Junbing Yang.
Application Number | 20150170782 14/624708 |
Document ID | / |
Family ID | 42736708 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150170782 |
Kind Code |
A1 |
BOSE; ANIMA B. ; et
al. |
June 18, 2015 |
MICROSPHERES AND THEIR METHODS OF PREPARATION
Abstract
Carbon microspheres are doped with boron to enhance the
electrical and physical properties of the microspheres. The
boron-doped carbon microspheres are formed by a CVD process in
which a catalyst, carbon source and boron source are evaporated,
heated and deposited onto an inert substrate.
Inventors: |
BOSE; ANIMA B.; (Athens,
OH) ; Yang; Junbing; (Westmont, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ohio University |
Athens |
OH |
US |
|
|
Family ID: |
42736708 |
Appl. No.: |
14/624708 |
Filed: |
February 18, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12720102 |
Mar 9, 2010 |
8986836 |
|
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14624708 |
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Current U.S.
Class: |
424/490 ;
210/502.1; 252/502; 252/511; 423/648.1; 502/182 |
Current CPC
Class: |
B01J 35/0033 20130101;
B01J 20/20 20130101; Y10S 977/962 20130101; Y10S 977/932 20130101;
A61K 9/1611 20130101; B01J 21/02 20130101; Y10S 977/773 20130101;
C01B 32/05 20170801; A61M 1/3679 20130101; Y02E 60/32 20130101;
H01B 1/04 20130101; C01B 3/0021 20130101; B01J 35/08 20130101; Y10S
977/948 20130101; B82Y 30/00 20130101; H01B 1/24 20130101; Y10T
428/2982 20150115; A61K 47/02 20130101; B01J 21/18 20130101; C01B
3/0084 20130101; C01B 32/336 20170801; Y02E 60/325 20130101; Y10S
977/775 20130101; Y10T 428/2989 20150115 |
International
Class: |
H01B 1/04 20060101
H01B001/04; B01J 35/00 20060101 B01J035/00; C01B 3/00 20060101
C01B003/00; A61K 9/16 20060101 A61K009/16; B01J 21/18 20060101
B01J021/18; B01J 21/02 20060101 B01J021/02; B01J 35/08 20060101
B01J035/08; A61K 47/02 20060101 A61K047/02; H01B 1/24 20060101
H01B001/24; B01J 20/20 20060101 B01J020/20 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with Government support under
Contract No. DE-AC02-06CH11357, awarded by the US Department of
Energy, and Contract IL-26-7006-01 05P 08-282 awarded by the
Department of Transportation. The Government has certain rights in
this invention.
Claims
1-6. (canceled)
7. A method of forming boron-doped carbon microspheres comprising
heating a carbon source and a boron source and a catalyst in a gas
stream to a temperature effective to vaporize said sources and said
catalyst thereby forming a reactant vapor mixture; and further
heating said vapor mixture to a second temperature effective to
cause said boron source and said carbon source to react and
depositing boron-doped microspheres onto a substrate.
8. The method claimed in claim 7 wherein said gas stream comprises
one of H2, N2, Ar, and mixtures thereof.
9. The method claimed in claim 7 wherein said gas stream further
includes NH3.
10. The method claimed in claim 7 further comprising contacting
said microspheres with steam to activate said microspheres.
11. (canceled)
12. (canceled)
13. A fuel cell including a membrane; said membrane comprising an
electron conducting resin in combination with boron-doped carbon
microspheres.
14. A catalyst structure comprising a layer of boron-doped carbon
microspheres coated with a catalyst.
15. The catalyst structure claimed in claim 13 wherein said
catalyst is a metal.
16. The catalyst structure claimed in claim 14 wherein said
structure is an electrode in an electrolytic cell.
17. A method of storing H2 with boron-doped carbon microspheres at
superatmospheric pressure and at subambient temperatures, thereby
causing said H2 to be absorbed into said microspheres.
18. A hemoperfusion device having a filter; said filter comprising
a layer of boron-doped carbon microspheres supported on a porous
substrate.
19. A delayed release composition comprising an active
pharmaceutical composition adsorbed onto a boron-doped carbon
microsphere.
20. A photovoltaic device comprising a layer comprising a
photoactive composition adsorbed onto boron-doped carbon
microspheres.
21. An electrical conductor formed from carbon microspheres claimed
in claim 1.
22. The electrical conductor claimed in claim 21 wherein said
conductor is in a battery.
23. The electrical conductor claimed in claim 22 wherein said
conductor is an electrode.
24. The electrical conductor claimed in claim 21 wherein said
conductor comprises nano wiring.
Description
RELATED APPLICATION
[0001] This application is related to and claims the benefit of
U.S. Provisional Patent Application Ser. No. 61/161,580, filed Mar.
19, 2009, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0003] Carbon microspheres, which generally have a particle size
less than about 700 nanometers, have a wide variety of potential
applications. These microspheres can be used as catalyst supports,
as a medium for storing hydrogen, and as adsorbants, such as in the
case of hemoperfusion and ultrafiltration membranes. These
microspheres are nanoporous particles which are prepared by
chemical vapor deposition. However, their use is somewhat limited
by a lack of activity, in particular, electrical conductivity.
SUMMARY OF THE INVENTION
[0004] The present invention is premised on the realization that
boron-doped carbon microspheres can be prepared, and can be used in
a wide variety of applications including nano wiring and integrated
circuits, and have superior physical properties relative to carbon
microspheres.
[0005] The objects and advantages of the present invention will be
further appreciated in light of the following detailed description
and drawing in which:
BRIEF DESCRIPTION OF DRAWING
[0006] FIG. 1 is a graph of the BJH desorption differential pore
volume distribution of boron-doped carbon microspheres (BCMS).
[0007] FIG. 2 is a diagrammatic depiction of a catalyst
support.
[0008] FIG. 3 is a diagrammatic depiction of a hemoperfusion
filter.
DETAILED DESCRIPTION
[0009] The boron-doped carbon microspheres of the present invention
are microspheres having a diameter of less than about 700 nm and
generally less than 500 nm, or less than 100 nm down to about 50
nm. The microspheres are further considered to be nanoporous
wherein the spheres include pores having a diameter generally in
the range of 0.6 nm to about 2 nm
[0010] These microspheres are formed from a combination of carbon
and boron. The major component of the microspheres is carbon. The
boron-doped carbon microspheres of the present invention are formed
by chemical vapor deposition. In the chemical vapor deposition
process, the reactants are injected into a flowing gas stream and
are vaporized. The flowing gas stream, including the reactants, is
heated further and impacted against a substrate and the carbon
microspheres deposit on the substrate.
[0011] The reactants include a carbon source gas, a boron source,
as well as a catalyst. Generally, any typical catalyst suitable for
use in forming carbon microspheres can be employed. Iron, nickel
and cobalt catalysts can be used. One typical catalyst is
ferrocene.
[0012] The carbon source can be any hydrocarbon, either saturated
or unsaturated and may be aromatic. In particular, compounds such
as benzene and xylene are particularly suitable for use in the
present invention as a carbon source.
[0013] The boron source must be a compound that can be formed into
a vapor at reaction temperatures without decomposing. Generally, a
vapor is formed by dissolving a boron containing compound into an
appropriate solvent, preferably a hydrocarbon solvent, and then
injecting this into the chemical vapor deposition reactor. As is
described below, it is convenient to dissolve the boron source into
the carbon source.
[0014] Suitable boron containing compounds include the halides,
such as boron triflouride and boron trichloride, as well as other
compounds that can be dissolved in an appropriate solvent such as
nitrates, and the like. Generally, the stoichiometric ratio of
boron to carbon will be 1 to 20 to 1.5 to 10 generally 1 to 9 to 1
to 10.
[0015] The reaction is conducted in a chemical vapor deposition
reactor with a suitable deposition substrate. The deposition
substrate must be inert under reaction conditions. Suitable
substrates include magnesium oxide, aluminum oxide, indium tin
oxide, as well as quartz.
[0016] Chemical vapor deposition reactors include a heating zone
and a reaction zone. To form the microspheres, the heating zone is
maintained at a temperature sufficient to vaporize the reactants,
typically about 200.degree. C. The reaction zone is maintained at a
much higher temperature, generally above 650.degree. C. for this
reaction, typically about 850-1000.degree. C. The reaction is
conducted by forming a solution of the reactants, including the
catalyst, carbon source and boron source, in the desired
stoichiometric relation. This is injected into the heating zone
into a flowing gas stream.
[0017] The flowing gas stream can be a variety of inert gases, but
typically are nitrogen or argon, or mixtures thereof. Hydrogen may
also be included to avoid soot formation, if needed. Further, a
nitrogen source gas such as ammonia may be added to facilitate
boron inclusion into the microspheres.
[0018] If ammonia is added, it will generally comprise about 10% of
the partial pressure of the gas stream. Hydrogen will comprise
0-20% of the partial pressure of the gas stream. Generally, the
ratio of ammonia to hydrogen to inert gas (Ar) will vary from
1:1:1: to 1:4:4 by volume. The flowing gas stream draws the
reactants from the heating zone where they are vaporized into the
reaction zone where they form the boron-doped carbon microspheres
on the selected substrate, typically quartz.
[0019] When the nitrogen source gas, ammonia, is added, it is
believed that the nitrogen bonds to carbon and bonds to the boron.
If ammonia is not present, the boron bonds directly to the carbon.
This latter reaction is not as thermodynamically favored as the
nitrogen carbide formation. Thus, the addition of ammonia increases
the incorporation of boron into the microspheres.
[0020] Typically, the reactor is purged with an inert gas to remove
all oxygen from the system prior to the reaction. After purging,
the flow of gas is started. The reactants are then introduced in
the desired ratio into the flowing gas stream. After an appropriate
period of time, generally 5 minutes to 1 hour, the injection of the
reactants is discontinued and the furnace cooled down to room
temperature under argon and hydrogen.
[0021] The formed microspheres can be subjected to a mild oxidation
in order to open the porous structure. In order to do so, the
preheating zone is heated to a temperature of about 500.degree. C.,
and the reaction zone to about 850.degree. C. Deionized water is
simply injected into the preheating zone and evaporated and
transported into the reaction zone in flowing argon. This is
continued again for about 30 minutes. The furnace is then cooled
down to room temperature under flowing argon.
[0022] The invention will be further appreciated in light of the
following detailed examples.
EXAMPLE 1
Synthesis of BCMS
[0023] Boron-doped carbon microspheres (BCMS) were prepared by a
chemical vapor deposition process inside a quartz tube inserted
through a low-temperature heating section (Zone I, 200.degree. C.)
and a high-temperature heating section (Zone II, 950.degree.
C.).
[0024] 0.34 g Ferrocene was dissolved in 23.63 g boron trichloride
solution 1.0 M in p-xylene (both from Sigma-Aldrich) and used as
precursor for BCMS synthesis. The solution was injected and
vaporized in Zone I. A hydrogen and argon mixture (60 ml/min and 90
ml/min, respectively) was used to transport the vapor from Zone Ito
Zone II. The BCMS were formed over a polished quartz plate inside
Zone II. After 30 minutes, the solution injection was stopped and
the furnaces were cooled down to room temperature with the argon
and hydrogen flowing.
EXAMPLE 2
Activation of BCMS
[0025] The boron-doped carbon microspheres (BCMS) formed in Example
1 were activated in steam to open the pore structure. For this
purpose, Zone I and Zone II were heated and kept at 500.degree. C.
and 850.degree. C., respectively. Deionized water was injected into
and evaporated inside the quartz tube in the middle of Zone I at
the rate of 0.225 ml/min. Flowing argon (140 ml/min) was used to
carry the steam to Zone II and react with BCMS, which were
synthesized as disclosed in Example 1. The injection of water
lasted for 30 minutes. After stopping the injection of water and
turning off the temperature controller, the furnace was cooled down
to room temperature with flowing argon.
[0026] The boron-doped carbon microspheres formed from the above
examples were spherical particles with uniform particle size. TEM
images reveal that the microspheres have an onion structure, and
x-ray photon electron spectrum indicated they are comprised of
carbon, boron and oxygen an impurity. Generally, the boron to
carbon ratio is approximately from 1:4-1:12.
[0027] The microspheres are high purity uniform spheres of about
700 nanometers or less in diameter, and reasonably high surface
area of about 220 m.sup.2/g measured via nitrogen absorption.
[0028] Further, thermogravimetric analysis demonstrates that the
oxidation stability is comparable to pure multiwall nanotubes. The
activated microspheres contain a large number of mesopores and the
BET surface area is about 213 m.sup.2/g, which is the same range as
standard carbon black, but higher than multiwall carbon nanotubes.
The sheet resistance of the microspheres is lower than that formed
from multiwalled carbon nanotubes. The micropore surface area was
107 m.sup.2/g and the total pore volume was 0.163 cm.sup.3/g. The
micropore volume was 0.054 cm.sup.3/g and the median micropore
diameter was 0.62 nm. FIG. 1 shows the pore size distribution of
the activated mircospheres. The activated microspheres clearly
contain a large number of mesospheres.
EXAMPLE 3
Incorporation of Nitrogen
[0029] 0.5 g Ferrocene was dissolved in 28.0 g boron trichloride
solution in 1.0 M p-xylene (both from Sigma-Aldrich) and used as
precursor for BCMS synthesis. The solution was injected into the
same reactor as in Example 1 and fully vaporized in the
low-temperature zone I (200.degree. C.). A carrier gas mixture
containing ammonia, hydrogen and argon with pre-set volume ratio
(volume ratio NH.sub.3/H.sub.2/Ar=1/1.33/4 and total flow rate of
190 ml/min) was added through upstream of zone I. BCMS formed on
the surface of a quartz substrate positioned in the
high-temperature zone at 900.degree. C. The growth process lasted
for 30 minutes until the liquid precursor injection stopped. The
carrier gas continued to flow for another 20 minutes before the
reactor was cooled down.
[0030] The boron-doped carbon microspheres of the present invention
can be used in a variety of different applications. In particular,
these can be used in fuel cells, which are devices that convert
chemical energy of fuels, such as hydrogen, directly into
electrical energy. The proton exchange membrane fuel cell is one
type of fuel cell that can utilize the boron-doped carbon
microspheres of the present invention. The boron-doped carbon
microspheres can be used in any fuel cell operating at less than
500.degree. C. These can be combined with an electron conducting
resin or used on other supports.
[0031] Also, the boron-doped carbon microspheres of the present
invention can provide a durable catalyst support. The uniform pore
size of the microspheres allow the microspheres to carry gases
through their porous structure. In particular, the unique spherical
structure and high thermal stability and oxidation resistance of
the boron-doped carbon microspheres compared to carbon black,
carbon fibers or carbon nanotubes, enable this product to be used
as a catalyst support in which its uniform rate of gas transport
does not degrade. Thus, the microspheres can be used as supports
for electrolytic cell cathodes or anodes. These would be used in
the electrolysis of water, ammonia or dissolved organic
material.
[0032] The catalyst support can take the configuration shown in
FIG. 2 in which a porous conductive support layer 11 is coated with
a layer 12 of the boron-doped carbon nanospheres. This layer is in
turn coated with a catalyst 13 such as a noble metal. The catalyst
can be deposited by well known methods such as vapor deposition,
electrochemical deposition and chemical deposition. Exemplary
catalysts include platinum, iridium, ruthenium, rhenium, palladium,
gold, silver, nickel, iron, lanthanides and alloys of these.
Basically, any catalyst can be supported by these microspheres,
including nonmetallic catalysts as well as metallic catalysts.
[0033] The boron-doped carbon microspheres of the present invention
can also be used as an adsorbant to store gases such as hydrogen.
In this application, hydrogen is typically stored under elevated
pressure, and frequently at reduced temperatures, causing the
hydrogen to migrate into the boron-doped carbon microspheres. The
boron, in particular, enhances the hydrogen absorption via a
non-classical chemical binding mechanism in which the two
undissociated H atoms in the molecule and the B form a 3-body
center sharing two common electrons. Further the high surface area
increase H.sub.2 absorption.
[0034] Also, due to the ability of the microspheres to absorb
organic compounds, the microspheres of the present invention can be
used as a drug delivery system, absorbing pharmacologically active
organic compounds, and gradually releasing them subsequent to
administration.
[0035] In another application, the boron-doped carbon microspheres
of the present invention can be used as adsorbants in a wide
variety of different applications, and, in particular, in
hemoperfusion applications. The uniform size of these spheres,
along with their porous structure, both facilitate in use in
hemoperfusion in place of activated carbon.
[0036] As shown in FIG. 2, the hemoperfusion filter 20 would
include a porous support layer 22 coated with a layer of the
boron-doped carbon microspheres 24. Blood or other fluid would flow
through the filter 20 in the direction of arrow 26. Organic
molecules will tend to bond to the microspheres thereby filtering
the fluid.
[0037] The boron-doped carbon microspheres possess a much higher
electrical conductivity than carbon nanotubes while being stable at
higher temperatures. For that reason, the microspheres can be used
in a variety of different applications.
[0038] These microspheres are particularly useful in batteries as a
conductive surface and/or support. The microspheres can form
conductive surfaces in metal ion batteries as well as metal hydride
batteries and other batteries such as metal/air batteries. These
microspheres can also replace carbon in the cathodes and anodes in
batteries, fuel cells and electrolytic cells. They can also
comprise nonometer size conductors or nano wiring for micro
circuits.
[0039] The boron-doped carbon microspheres can be used in any
application requiring electrical conductivity, and, in particular
can be used to replace indium tin oxide in a variety of different
applications, including solar panels, and the like. In particular,
the boron-doped carbon microspheres can be added to photoactive
compositions and used to form thin layer solar panels.
[0040] Thus, the boron-doped carbon microspheres of the present
invention can be used in a wide variety of different applications
because of their enhanced support stability through boron doping,
enhanced catalyst support interaction providing improved stability,
high electronic conductivity, spherical particle shape permitting
uniform packing density.
[0041] This has been a description of the present invention along
with the preferred method of practicing the present invention.
However, the invention itself should only be defined by the
appended claims.
* * * * *