U.S. patent application number 14/846497 was filed with the patent office on 2015-12-31 for nanomaterials and process for making the same.
The applicant listed for this patent is Graphene Technologies, Inc.. Invention is credited to Robert Wayne Dickinson, Douglas Paul DuFaux, Lawrence Joseph Musetti, Oliver Douglas Ousterhout.
Application Number | 20150376012 14/846497 |
Document ID | / |
Family ID | 49512664 |
Filed Date | 2015-12-31 |
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United States Patent
Application |
20150376012 |
Kind Code |
A1 |
Dickinson; Robert Wayne ; et
al. |
December 31, 2015 |
Nanomaterials and Process for Making the Same
Abstract
Process for producing nanomaterials such as graphenes, graphene
composites, magnesium oxide, magnesium hydroxides and other
nanomaterials by high heat vaporization and rapid cooling. In some
of the preferred embodiments, the high heat is produced by an
oxidation-reduction reaction of carbon dioxide and magnesium as the
primary reactants, although additional materials such as reaction
catalysts, control agents, or composite materials can be included
in the reaction, if desired. The reaction also produces
nanomaterials from a variety of other input materials, and by
varying the process parameters, the type and morphology of the
carbon nanoproducts and other nanoproducts can be controlled. The
reaction products include novel nanocrystals of MgO (percilase) and
MgAl.sub.2O.sub.4 (spinels) as well as composites of these
nanocrystals with multiple layers of graphene deposited on or
intercalated with them.
Inventors: |
Dickinson; Robert Wayne;
(San Rafael, CA) ; Ousterhout; Oliver Douglas;
(Belvedere, CA) ; Musetti; Lawrence Joseph; (San
Rafael, CA) ; DuFaux; Douglas Paul; (Orchard Park,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Graphene Technologies, Inc. |
Novato |
CA |
US |
|
|
Family ID: |
49512664 |
Appl. No.: |
14/846497 |
Filed: |
September 4, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13864080 |
Apr 16, 2013 |
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14846497 |
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13237766 |
Sep 20, 2011 |
8420042 |
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13864080 |
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13090053 |
Apr 19, 2011 |
8377408 |
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13237766 |
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Current U.S.
Class: |
423/448 |
Current CPC
Class: |
C01F 5/02 20130101; C01G
9/03 20130101; C01F 7/162 20130101; C01P 2004/38 20130101; C01B
32/184 20170801; C01G 23/07 20130101; C01P 2004/64 20130101; C01G
23/04 20130101; C01G 9/02 20130101; B82Y 40/00 20130101; B82Y 30/00
20130101; C01P 2004/04 20130101 |
International
Class: |
C01B 31/04 20060101
C01B031/04 |
Claims
1. A composition of matter comprising a plurality of graphene
platelets that adhere to each other and form the faces of a hollow
body.
2. The composition of claim 1 wherein the hollow body is a
cube.
3. A process for creating a composition of matter, comprising the
steps of forming graphene platelets on the faces of a magnesium
oxide (MgO) crystal, and thereafter removing the MgO crystal, with
the graphene platelets adhering to each other and forming the faces
of a hollow body having a shape corresponding to the shape of the
MgO crystal.
4. The process of claim 3 wherein the MgO crystal is removed
chemically.
5. The process of claim 3 wherein the MgO crystal is dissolved in
hydrochloric acid.
6. The process of claim 3 wherein the MgO crystal is a cubic
crystal, and the graphene platelets form the faces of a hollow
cube.
7. The process of claim 3 wherein the graphene platelets and the
MgO crystal are formed by combusting carbon dioxide (CO.sub.2) and
magnesium (Mg) together in a highly exothermic oxidation-reduction
reaction that produces a reaction product containing carbon and
magnesium oxide (MgO), and rapidly cooling the reaction product to
form carbon graphenes and MgO nanoparticles.
Description
RELATED APPLICATIONS
[0001] This is a division of application Ser. No. 13/864,080, filed
Apr. 16, 2013, which is a continuation-in-Part of application Ser.
No. 13/237,766, filed Sep. 20, 2011, now U.S. Pat. No. 8,420,042,
which is a continuation-in-part of application Ser. No. 13/090,053,
filed Apr. 19, 2011, now U.S. Pat. No. 8,377,408.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] This invention pertains generally to carbon graphenes and
other nanomaterials and to a process for making the same.
[0004] 2. Related Art
[0005] Nanomaterials is an emerging new field to which major
efforts in research and development are being applied. The
characteristics of nanomaterials can differ significantly from
those of conventional materials in a number of respects that may be
important to applications in many fields, including the medical
field, semiconductors, energy storage, advanced composites,
electronics, and catalytics. Many nanomaterials can be used in ways
that exploit their quantum-mechanical properties.
[0006] Recently, significant research and interest have been
focused on graphenes. Graphenes are allotropes of carbon in the
form of one atom thick sheets of carbon atoms densely packed in a
hexagonal honeycomb crystal lattice. Graphenes have a number of
unique and desirable qualities, including extraordinary surface
area, electrical conductivity and capacitance, thermal and mass
transfer capability, magnetic properties, and extraordinary values
of tensile strength and modulus of elasticity. These attributes,
individually or in combination, are projected to make carbon
graphene structures applicable to a number of important
technologies and markets, including electrolytic storage media for
lithium ion batteries and ultra capacitors, facilitated transport
membranes for micro filtration, catalysis as substrate material,
heat transfer for light-emitting diodes (LEDs) and other
applications, high frequency semiconductors for computing, hydrogen
storage, conductive materials for flatscreen and liquid crystal
displays (LCDs), and strengthening agents for advanced materials in
wind turbines and automobiles. IBM has demonstrated a 100 gigahertz
graphene transistor and stated that a 1 terahertz transistor
graphene is conceivable.
[0007] There are a number of known methods for producing graphenes,
including chemical vapor deposition, epitaxial growth,
micro-mechanical exfoliation of graphite, epitaxial growth on an
electrically insulating surface, colloidal suspension, graphite
oxide reduction, growth from metal-carbon melts, pyrolysis of
sodium ethoxide, and from nanotubes. Each of these methods has well
documented advantages and disadvantages. A general advantage of
many of the processes is the ability to produce relatively pure
graphene materials and, in some cases, large continuous surface
graphene materials. Processes such as epitaxial growth and
colloidal suspension may lead to the customization of graphene
materials to suit very specific requirements.
[0008] There are also a number of known methods for producing other
forms of carbon nanomaterials such as nanospheres, fullerenes,
scrolls and nanotubes, including, for example, the use of carbon
arc and laser technologies.
[0009] To date, however, no process for the production of carbon
nanomaterials has been successfully commercialized, despite many
serious efforts to do so, particularly with respect to carbon
nanotubes. Therefore, there is justified concern that commercial
production of graphenes may also be difficult to realize. All the
known graphene formation processes have significant limitations and
disadvantages, including the dependency on relatively scarce highly
crystalline graphite as feedstock, high cost, and limited
scalability. Because of these limitations, the known methods may
not be capable of providing a dependable supply of low cost
graphenes with high volumes of production.
[0010] The invention is based upon an extremely robust and scalable
reaction in which the preferred reagents or feedstock are carbon
dioxide (CO.sub.2) and magnesium (Mg).
[0011] When carbon-based fuels such as coal, oil, and natural gas
are variously combusted to generate heat, substantial amounts of
CO.sub.2 and other combustion products are produced, and there is
widespread concern about the historically high and increasing
amounts of CO.sub.2 in the atmosphere. Scientists believe the
unusually high levels of CO.sub.2 in the atmosphere could cause or
are already causing adverse global climate effects and
acidification of the oceans. While a number of solutions have been
proposed for the reduction of CO.sub.2 emissions, the dominant
model in publications and public policy debate involves capture of
the CO.sub.2 by one or another of several chemical mechanisms,
followed by compression of the captured CO.sub.2 and, finally,
disposition of the CO.sub.2 as a waste product by injection
(sequestration) into the earth. Since the capture of CO.sub.2 from
fossil fuel emissions is costly and energy intensive, it would be
desirable if at least some of the captured CO.sub.2 be put to
productive use rather than be treated as a waste product. An
economically feasible, large scale, and profitable process for
reduction of CO.sub.2 to carbon products would create demand for
captured CO.sub.2 and reduce the requirement for sequestration of
CO.sub.2.
[0012] There are a number of known methods for the reduction of
CO.sub.2. One such process is photosynthesis, which is a widely
appreciated and prolific CO.sub.2 reduction mechanism that reduces
CO.sub.2 to carbon that is then used by the living system to
produce complex organic molecules which are necessary for life.
However, photosynthesis has the disadvantage of being difficult to
replicate in technical or man-made biologic systems.
[0013] Ferrous Oxides, including magnetite and several other
similar mineral compounds, have also been found to beneficially
reduce CO.sub.2 to an amorphous form of carbon. Likewise, liquid
potassium has been found to beneficially reduce CO.sub.2 to
amorphous carbon. In addition, there are a number of partial
reduction (mineralization) processes in which CO.sub.2 is converted
to carbonates. Partial reduction approaches are currently
considered more likely than full reduction of CO.sub.2 to carbon to
be feasible alternatives to sequestration because full reduction of
CO.sub.2 is generally believed to be steeply endothermic and,
therefore, economically challenging. However, partial reduction
approaches have the disadvantage of producing materials for which
the market prices are relatively low.
[0014] In sum, previously known CO.sub.2 reduction methods are
limited practically and economically by one or more factors,
including cumbersome mass flow requirements, significant energy
requirements, high cost of reactants, difficult or risky materials
management, and/or low value of the end products, with the value of
the products often being less than the cost of producing them.
[0015] Magnesium is not presently found in nature in pure form and
must be produced by one or more well-known methods from one or more
of its natural existing forms, which include magnesium chloride and
magnesium oxide. Magnesium is frequently produced from seawater
where it resides naturally as the second most abundant cation. In
this production process, the Mg is precipitated with calcium
hydroxide, and the precipitant is reacted with HCl and finally
reduced to magnesium by electrolysis. Other processes, including
the Pidgeon process, which utilize heat to reduce mined magnesium
rich ore, are employed to produce relatively pure magnesium.
However, these processes are relatively expensive and do not always
produce the level of purity desired.
OBJECTS AND SUMMARY OF THE INVENTION
[0016] It is, in general, an object of the invention to provide new
and improved carbon graphenes and other nanomaterials and a new and
improved process for making the same.
[0017] Another object of the invention is to provide nanomaterials
and a process of the above character which overcome the limitations
and disadvantages of the prior art.
[0018] These and other objects are achieved in accordance with the
invention by combusting reactants together in a highly exothermic
oxidation-reduction reaction which produces high energy and heat at
a temperature of approximately 5610.degree. F., or higher, then
rapidly cooling products of the reaction to form nanoparticles, and
then separating nanoparticles of different materials from each
other.
[0019] In some of the preferred embodiments, the high heat is
produced by an oxidation-reduction reaction of carbon dioxide and
magnesium as the primary reactants. Additional materials such as
reaction catalysts, control agents, or composite materials can be
included in the reaction, as desired. The reaction is capable of
producing nanomaterials from a variety of input materials. The
carbon dioxide and magnesium are combusted together in a reactor to
produce nano-magnesium oxide, graphenes, graphene composites, and,
if desired, other nanoproducts which are then separated or excluded
by suitable processes or reactions to provide the individual
reaction products.
[0020] By varying the process parameters, such as reaction
temperature and pressure, the type and morphology of the carbon
nanoproducts and other nanoproducts can be controlled.
[0021] The Mg--CO.sub.2 reaction is highly energetic, producing
very high temperature on the order of 5610.degree. F. (3098.degree.
C.), or higher, and also produces large amounts of useful energy in
the form of heat and light, including infrared and ultraviolet
radiation, all of which can be captured and reused in the invention
or utilized in other applications. The products of combustion,
particularly the magnesium oxide, can be recycled to provide
additional oxidizing agents for combustion with the carbon
dioxide.
[0022] The reaction products include novel nanocrystals of MgO
(periclase) and MgAl.sub.2O.sub.4 (spinels) as well as composites
of these nanocrystals with multiple layers of graphene deposited on
or intercalated with them.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a flow diagram of one embodiment of a process for
the production of carbon graphenes and other nanomaterials in
accordance with the invention.
[0024] FIG. 2 is a flow diagram of another embodiment of a process
for the production of carbon graphenes and other nanomaterials in
accordance with the invention.
[0025] FIG. 3 is a vertical sectional view of one embodiment of a
reactor for carrying out the process of the invention.
[0026] FIG. 4 is a vertical sectional view of the reaction chamber
in the embodiment of FIG. 3 operating as a continuous annular flow
combustor.
[0027] FIG. 5 is a vertical sectional view of the reaction chamber
in the embodiment of FIG. 3 operating as a centrifugal
separator.
[0028] FIG. 6 is a block diagram of one embodiment of a system for
carrying out the process of the invention.
[0029] FIG. 7 is a block diagram of another embodiment of a system
for carrying out the process of the invention.
[0030] FIG. 8 is an exploded vertical sectional view of one
embodiment of a high pressure CO2 reactor or furnace suitable for
use in the embodiment of FIG. 7.
[0031] FIG. 9 is a bottom plan view of the upper end cap of the
reactor in the embodiment of FIG. 8.
[0032] FIG. 10 is a top plan view of the lower end cap of the
reactor in the embodiment of FIG. 8.
[0033] FIG. 11 is a block diagram of another embodiment of a system
for carrying out the process of the invention.
[0034] FIG. 12 is a vertical sectional view, partly schematic, of
another embodiment of a reactor for use in carrying out the process
of the invention.
[0035] FIG. 13 is an enlarged bottom plan view of the lower wall of
the reaction chamber in the embodiment of FIG. 12.
[0036] FIG. 14 is a vertical sectional view, partly schematic, of
another embodiment of a reactor for use in carrying out the process
of the invention.
[0037] FIG. 15 is a vertical sectional view, partly schematic, of
another embodiment of a reactor for use in carrying out the process
of the invention.
[0038] FIG. 16 is a cross-sectional view taken along line 16-16 in
FIG. 15.
[0039] FIG. 17 is a flow chart showing the conversion of MgO to Mg
by electrolytic reduction in one embodiment of the invention.
[0040] FIG. 18 is a transmission electron microscopy (TEM) bright
field image of a material having graphene platelets and
graphene-MgO composites produced in accordance with the
invention.
[0041] FIG. 19 is a TEM image of graphene-MgO crystal with layers
of graphene produced in accordance with the invention.
[0042] FIG. 20 is a TEM image of crystals of magnesium oxide
(periclase) produced by the process of the invention.
[0043] FIG. 21 is a scanning electron microscopy (SEM) image of
magnesium oxide (periclase) cubic nanocrystals produced by the
process of the invention.
[0044] FIG. 22a is a TEM image of a graphene sample generated with
solid CO2 (dry ice) on a 20 nanometer scale.
[0045] FIG. 22b is a TEM image of a graphene sample generated with
solid CO2 (dry ice) on a 10 nanometer scale.
[0046] FIG. 22c is a TEM image of a graphene sample generated with
gaseous CO2 on a 20 nanometer scale.
[0047] FIG. 23a is a TEM image of graphene platelets formed on an
MgO substrate on a 100 nanometer scale.
[0048] FIG. 23b is a TEM image of a portion of the graphene
platelets of FIG. 23a on an enlarged (20 nanometer) scale.
DETAILED DESCRIPTION
[0049] Overview
[0050] In the invention, an oxidizing agent such as CO.sub.2 is
combusted with a reducing agent such as magnesium in a high
temperature reactor to form various nanoscale products such as
graphenes, graphene composites, MgO, and other nanomaterials. Thus,
as illustrated in FIG. 1, the CO.sub.2 and magnesium are introduced
into a reactor where a combustion reaction occurs, producing a
heterogeneous mixture of nanoscale materials consisting primarily
of carbon and MgO nanoparticles. The reaction produces intense
amounts of energy including heat at a temperature of 5610.degree.
F. (3098.degree. C.), or higher, infrared radiation, visible light,
and ultraviolet electromagnetic radiation, all of which can be
captured and utilized. The carbon and magnesium oxide are then
separated from each other and from any other reaction products that
may be present in an integrated set of process steps such as
annular flow separation, cyclone separation, gravity cell
separation, flotation separation, centrifugal separation, acid
washing, deionized water washing, ultrasonic processing, elevated
temperature treatment in a vacuum, and/or other suitable separation
processes. The heat produced by the reaction is recovered for use
in the separation steps and in purifying the reaction products, and
the UV radiation and other energy produced by the reaction can be
recovered for other uses. The chemistry, temperature of reaction,
rate of cooling, pressure, input materials and gases and other
parameters are controlled to determine the quality, character and
morphology of the reaction products. All or part of the MgO product
is recycled to provide highly purified magnesium for use in the
reaction.
[0051] The products produced by the invention are determined by the
control of variables in all phases of the process, i.e.
pre-reaction, during the reaction, and post reaction. For example,
the introduction of additional materials to the reaction has been
found to result in the production of nano-forms and composites of
the added materials, varying the reaction temperature and gradient
has been found to influence the morphology of the reaction
products, and varying the separation and purification treatment has
been demonstrated to significantly alter the constituency of the
products.
[0052] The invention has been found to produce a novel intercalated
or multilayered graphene-magnesium oxide composite as well as
nanoscale MgO particles in various forms, including periclase, or
crystalline MgO. Other materials present in the reaction can also
be converted to nanomaterials or composites. For example, when
aluminum is present as an alloy material in the magnesium, the
invention produces nano-spinels (crystalline MgAl.sub.2O.sub.4).
Other oxidizing agents can be introduced to the reaction as inputs
with the feedstock to produce new composite or single-component
nanostructures. In addition, non-reactant materials such as
silicon, silver, gold, copper, and iron can be introduced into the
reaction to produce nano forms of those materials, graphenes
decorated with those materials, and graphene composites and other
nano composites of them.
[0053] The magnesium-CO.sub.2 reaction is highly exothermic and
produces a high energy flux across the electromagnetic spectrum,
including very high temperature in the range of 5610.degree. F.
(3098.degree. C.). The invention includes process controls and
systems for preserving the intense energy of the reaction,
including management, capture, and reuse that energy to improve the
operational and economic efficiency of the process. The heat from
reaction can be used for product separation and purification and in
converting the MgO to magnesium for recycling in the process, or
for sale for use in the production of electricity or for other
uses. Ultraviolet energy produced by the reaction is also captured
and used.
[0054] Recycling most or all of the MgO product for use in the
reaction not only keeps the cost of the feedstock down, but also
minimizes impact on the market for magnesium, particularly when the
invention is operated at large scale. It is also significant in
view of the limited capacity to produce magnesium from mined
sources. In one presently preferred embodiment, for example, the
MgO product is reduced to magnesium by electrolysis, which is a
relatively low-cost, energy efficient process compared to
conventional techniques for producing magnesium.
[0055] The products of the invention include nanoscale materials
such as carbon graphenes and MgO nanoparticles and, if desired,
novel graphene composites and other nanomaterials. The invention
can also produce non-carbon nanomaterials such as spinels and novel
intercalated or layered graphene-periclase and graphene-spinel
composite materials, and it is believed to be capable of producing
many other forms of nanomaterial as well. In addition, as noted
above, non-reactive substances such as silver or silicon can be
introduced to the reaction to produce nano-silver, nano-silicon,
silver or silicon decorated graphenes, silver- or silicon-graphene
composites, and other silver or silicon nano composites. Two forms
of nanocrystals produced by the invention are spinels (crystalline
MgAl.sub.2O.sub.4) and periclase (crystalline MgO). In addition,
composites of these nanocrystals with multiple layers of graphene
deposited on them or intercalated with them have also been
produced. In such composites, the layers are in the range of one
nanometer or less apart and are held together by Van der Waals
forces. The graphene-periclase and graphene-spinel nano-composites
are believed to be novel materials.
[0056] While the exothermic reaction of CO.sub.2 and magnesium is
utilized in the preferred embodiment, the heat can be supplied by
other sources such as other exothermic chemical reactions, a high
temperature nuclear reactor, a solar furnace, an electric arc,
magneto hydrodynamic heating of plasma, combustion of hydrogen or
other fuel, or by other suitable means. Likewise, the initial
reactant for producing graphenes can be any carbon containing
molecule such as carbon dioxide, carbon monoxide, phosgene
(COCl.sub.2), methane, ethylene, acetylene, other carbon containing
material, and combinations thereof. Similarly, other earth metals
such as aluminum, titanium, zinc, sodium, lithium, calcium, and
combinations thereof can be used as the reducing agent.
Preferred Embodiments
[0057] In the embodiment illustrated in FIG. 2, CO.sub.2 and
magnesium are introduced into a high temperature reactor 21 where
they are combusted together in a highly exothermic
oxidation-reduction reaction which produces high energy and heat at
a temperature on the order of 5610.degree. F. (3098.degree. C.), or
higher, while producing a homogeneous reaction product consisting
of magnesium oxide (MgO) and carbon in accordance with the
relationship:
2Mg(s)+CO.sub.2(g).fwdarw.2MgO(s)+C(s).
[0058] The homogeneous reaction product is cooled rapidly by
beneficial expansion of the superheated reaction products or by
additional active cooling to quench and retain the nanoparticle
structure and then wetted in a bath of deionized water 22. This
results in the wetting of the nanocarbon graphene and nano MgO
reaction products, with some of the MgO reacting with the water to
form magnesium hydroxide (Mg(OH.sub.2)):
MgO(s)+H.sub.2O(I).fwdarw.Mg(OH).sub.2.
[0059] The mixture is then treated with an ultrasonic probe 23,
operating, for example, at a frequency of 20 kilohertz and a power
level of 500 watts, to break up the heterogeneous reaction product
into smaller particles, exposing more surface area for subsequent
treatment or processing.
[0060] Hydrochloric acid (HCl) 24 is added to the ultrasonically
treated mixture. The carbon graphenes are inert to HCl, but the HCl
reacts with unreacted magnesium in the mixture as well as the
dissolved MgO and Mg(OH.sub.2) to form magnesium chloride
(MgCl.sub.2) and water (H.sub.2O):
Mg(OH).sub.2(s)+2HCl(I).fwdarw.MgCl.sub.2(s)+2H.sub.2O(I).
[0061] After the reaction products have been treated with HCl, the
solution is filtered using a Buchner vacuum funnel 26 with 2.5
micron filter paper, with the graphenes being deposited onto the
filter paper and the MgCl.sub.2 passing through. The filter paper
and graphenes are then heated, in a first heating stage 27, to a
temperature of 93.degree. C. to dry the graphenes and facilitate
their removal from the filter paper.
[0062] In order to fully remove any oxide attached to or co-mingled
with the graphenes, the graphenes are placed in a seasoned quartz
boat and heated in a seasoned quartz tube oven 28 under vacuum at a
temperature of 1150.degree. C. for a predetermined time. This step
is repeated until the graphenes have reached a desired level of
purity, with successive repetitions providing a linear reduction in
the magnesium contamination of the graphene product.
[0063] The MgCl.sub.2 from filter 26 is processed by electrolysis
in a cell 29 to separate the magnesium from the chlorine:
MgCl.sub.2(s)+Energy.fwdarw.Mg(s)+Cl.sub.2(g).
[0064] The magnesium is recycled to reactor 21 for use in the
Mg--CO.sub.2 reaction, and the chlorine can be recycled or
sold.
[0065] Magnesium oxide vented from the reactor is captured and
processed by filtration 30 to recover MgO nanoparticles.
[0066] The reaction is preferably carried out in a heavily
insulated, externally cooled reactor, one embodiment of which is
shown in FIG. 3. This reactor has an upright, open-ended reaction
chamber 31 with an inner cylindrical side wall 32, an outer side
wall 33, insulation 34 between the walls, and a floor 36. The inner
wall is a double wall structure with an inner layer or section 32a
fabricated of a material that will withstand reaction temperatures
on the order of 5610.degree. F. (3098.degree. C.) or higher and not
introduce impurities into the reaction and an outer layer or
section 32b fabricated of an insulative material that can also
withstand the high temperatures produced by the reaction. The inner
layer or section can, for example, be fabricated of a mixture of
zirconia and rare earth oxides, graphite, or another suitable
material that is compatible with high temperatures. Outer wall 33
is fabricated of metal and is liquid-cooled to lower the local
temperature and collect waste heat. Ports such as inlet ports 37,
37 provide communication with the interior of the reaction chamber
and permit a controlled introduction of feedstock or reagents,
inert gases, other materials and gases, and sensors into the
reaction chamber. Other ports (not shown) provide a controlled
withdrawal of a reaction product from the chamber.
[0067] The CO.sub.2 atmosphere in the reactor provides an
oxygen-free environment that prevents combustion of the graphene,
other reaction products, and the graphite reactor walls. At the
outlet end of the open-ended reactor, the CO.sub.2 gas zone allows
the carbon products additional time to cool below ignition
temperature. Magnesium metal particles for the reaction can be
injected into the reactor in an argon gas stream, and the argon can
also be used to provide a barrier to keep other potentially
reactive gasses such as oxygen or nitrogen out of the combustion
reaction.
[0068] The reactor can be operated either in a batch mode or in a
continuous mode. Batch processing has been found to allow for
significant control of reaction parameters including, for example,
time of reaction, and may be preferable for certain end product
objectives. However, a continuous process generally provides a
larger product yield in a shorter period of time and may,
therefore, be the preferred mode in many applications.
[0069] In the batch mode, gaseous MgO is beneficially ejected from
the reaction chamber, and the other reaction products are separated
outside the chamber, with the reaction product entering the
separation process as a heterogeneous mix, as in the embodiment of
FIG. 2.
[0070] In the continuous mode, initial separation of the reaction
products occurs in the reaction chamber, as seen, for example, in
FIG. 4. Here, the reactor is shown as operating as a continuous
annular flow combustor, with initial separation of the carbon and
magnesium oxide reaction products occurring in an annular flow
process. In this embodiment, CO.sub.2 gas and solid magnesium
particles are fed into the lower portion of the chamber and ignited
with an electric arc or a hydrogen-oxygen flame to produce an
upwardly directed annular flow of fluidized CO.sub.2, magnesium
oxide, and reaction particles, with a high density annular flow
component 39 in the outer portion of the chamber and a lower
density annular flow component 41 in the inner region. As the flow
progresses upwardly, the inner region and the boundary between the
two regions expand outwardly, with the particles of greater density
being concentrated near the side wall of the chamber toward the top
of the reaction zone. Although the reactor is shown with a vertical
orientation and an upward flow, the reactor can be inverted and
have the flow in a downward direction, or it can be oriented
horizontally and have a horizontal flow, if desired.
[0071] Ignition of the CO.sub.2 and Mg is initiated by the electric
arc or flame at the base of the reaction chamber, and the conical
shape of the inner flow zone results from the action of the
particles in the Mg--CO.sub.2 reaction. Thus, as noted above, there
is an upward flow of high density, heated nanocarbon and magnesium
oxide particles in the outer portion of the chamber and an upward
flow of low density, heated nano-carbon and magnesium oxide
particles in the inner region, with the inner region expanding
outwardly as the flows progress upwardly. As the reaction products
travel upward through the annular flow zone, they also may acquire
a rotational component of velocity either naturally or from fixed
vanes that further aid in the separation process. Thus, as
illustrated, the upward flow of high density, low rotational
velocity, lower temperature nano-carbon particles and magnesium
oxide particles occurs in the outer portion of the chamber, while
the upward flow of high rotational velocity, low density, very hot
nano carbon particles and magnesium oxide particles occurs in the
innermost region. The length or height of the reaction chamber is
sufficient to allow cooling of the C/Mg material before it leaves
the reactor.
[0072] The result is an initial stage separation process integrated
within the reactor that aids in separation of fluids or slurries as
a function of fluid density. The MgO vapor beneficially rises to
the top of the chamber and can be collected, for example, with a
partial vacuum, a cooling system, and a receptacle. Vent ports at
the top of the reaction chamber can be utilized to further
facilitate the beneficial collection of pure MgO. After leaving the
reaction chamber, the reaction products are further separated and
treated to further prepare them for sale and recycling. Management
and control of the temperature, locus and duration of the reaction
will determine the final composition of the materials produced by
the reactor combustion process.
[0073] Rotating the reaction chamber about its central axis 42, as
illustrated in FIG. 5, provides centrifugal separation of the
reaction products as they flow upwardly through the reaction zone.
In the lower region 43 of the zone, there is an upward flow and
flux of carbon nanoparticles, MgO, and other reaction products at
relatively low rotational velocity and temperature, with higher and
lower density particles interspersed both in the inner portion 41
and in the outer portion 39 of the region. By the time the
particles reach upper region 44 of the chamber, they have acquired
a much higher rotational velocity, and they are very hot, with the
particles of higher density being concentrated in the outer region
near side wall 32 and the particles of lower density in the inner
region.
[0074] In the batch process illustrated in FIG. 6, CO.sub.2 and
magnesium are introduced into a reactor furnace 46 where they are
combusted together in a highly exothermic oxidation-reduction
reaction, as discussed above, producing a mixture of carbon and
magnesium oxide (MgO) products which are delivered to a preparation
stage 47 where they are ground into finer particles and prepared
for further processing. These particles are processed
ultrasonically in deionized water in a sonifier 48, then washed in
hydrochloric acid (HCl). The carbon graphenes are inert to HCl, but
the HCl reacts with unreacted magnesium in the mixture as well as
the dissolved MgO and Mg(OH.sub.2) to form magnesium chloride
(MgCl.sub.2) and water (H.sub.2O).
[0075] The aqueous solution of carbon graphenes and MgCl.sub.2 is
filtered in a vacuum filter 49 to separate the graphenes from the
MgCl.sub.2. The graphenes are dried in a dryer 51 and recycled back
through the sonification, filter, dryer, and heating stages to
further purify them. The number of times the graphenes are recycled
is determined by the level of purity desired, and is typically on
the order of three or four times per cycle batch. When the
purification process is completed, the graphenes are discharged
through a product line 52.
[0076] Magnesium oxide (MgO) produced by the Mg--CO.sub.2 reaction
is collected and converted to magnesium which is recycled for use
in the reaction. Thus, gaseous MgO from the reactor is collected
and solidified in a collector 53, then washed with HCl and
converted to MgCl.sub.2 in a dissolver 54. This MgCl.sub.2 is dried
in a dryer 55 along with the MgCl.sub.2 that was separated from the
carbon graphenes in filter 49. The dried MgCl.sub.2 is then
separated into magnesium and chlorine by electrolysis in a cell 56.
The magnesium is cooled in a cooler 57, then collected and ground
into finer particles, e.g. 400 Mesh, in a collector and grinder 58.
The magnesium particles from the grinder are fed back to reactor 46
and used in the combustion process. Although grinding is used in
this particular embodiment, the magnesium can also be reduced to
finer particles by other means such as cutting or cooling small
droplets from a melt.
[0077] In addition to the reaction products, the combustion of
CO.sub.2 and magnesium also produces substantial amounts of heat
and energy which are captured and utilized in other steps of the
process, such as sonification and drying, or otherwise. Chlorine,
hydrogen, and HCl utilized in the process are provided by a cell 59
to which hydrogen (H.sub.2) and methane (CH.sub.4) are supplied
along with the chlorine from electrolysis cell 56.
[0078] FIG. 7 illustrates another embodiment of a batch process in
which ignition of the CO.sub.2 and magnesium is initiated by a
hydrogen-oxygen flame. The hydrogen and oxygen are supplied to a
reactor 61 through branches 62, 63, each of which includes a
shut-off valve 64, a pressure reducing valve 66, a check valve 67,
and an electrically operated control valve 68, designated prime in
branch 62 and double prime in branch 63. Pressure in the branch
lines is monitored by pressure transducers 69', 69''. Hydrogen and
oxygen from the branches are mixed together in and delivered to the
reactor by a feed line 71 with a check valve 72 in the feed line to
prevent backflow from the reactor to the branches. A high voltage
spark igniter 73 for the hydrogen-oxygen mixture is located at the
base of the reactor.
[0079] Means is provided for supplying CO.sub.2 to the reactor at a
reduced pressure level until ignition occurs and thereafter at
higher pressure. This means includes a low pressure branch 76 and a
high pressure branch 77. The low pressure branch has a pressure
reducing valve 78, a flow control valve 79, and a check valve 81,
with a flowmeter 82 and a pressure transducer 83 for monitoring
flow and pressure in the branch. The high pressure branch has a
control valve 84. CO.sub.2 is supplied to the two branches through
a supply line 85 with a shut-off valve 86 and a pressure transducer
87. CO.sub.2 from the branches is supplied to the reactor through a
feed line 88, with a pressure transducer 89 for monitoring the
pressure of the CO.sub.2 in that line.
[0080] Reactor 61 has a removable cap or lid 61a, and the magnesium
particles to be combusted are poured directly into the reactor when
the lid is off and the reactor is not operating.
[0081] A discharge line 91 is connected to the reactor for
collecting the products of the reaction, with a control valve 92
for controlling product discharge and a pressure relief valve 93
through which gaseous products of combustion can escape in the
event that the pressure in the reactor becomes too high.
[0082] A vacuum system 94 is also connected to the reactor for
collecting MgO particles produced by the combustion of CO.sub.2 and
magnesium. A control valve 96 is included in the line 97 between
the reactor and the collector, and a pressure transducer 98
monitors the pressure in the line.
[0083] Data from the pressure transducers and flowmeter is
delivered to a data acquisition and control system 99 which
processes the data and controls the operation of the control valves
and the igniter.
[0084] To begin the process, the lid is removed from the reactor,
and the Mg particles are poured into the chamber. The lid is
replaced, and control valve 79 is opened to allow CO.sub.2 to flow
into the reactor at the reduced pressure set by regulator valve 78.
Control valves 68', 68'' are also opened to allow hydrogen and
oxygen to flow into the reactor, and igniter 73 is turned on to
ignite those gases. The hydrogen-oxygen flame ignites the Mg
particles and the CO.sub.2, and when they begin to burn vigorously,
control valves 68', 68'' are closed to shut off the flow of
hydrogen and oxygen. At the same time, control valve 84 is opened
to deliver the high pressure CO.sub.2 to the reaction chamber, and
valve 79 is closed to shut off the low pressure flow. As the
reaction progresses, control valve 92 is opened to allow the
discharge and collection of the reaction products through discharge
line 91, and control valve 97 is opened to allow vacuum system 96
to draw gaseous MgO into the vacuum collector where the MgO
particles are collected.
[0085] One embodiment of a high pressure CO.sub.2 reactor or
furnace suitable for use in the process of FIG. 7 is illustrated in
FIGS. 8-10. This reactor has a cylindrical side wall 101 with end
caps 102, 103 threadedly attached to the upper and lower end
portions of the side wall to form a closed chamber 104. They are
fabricated of a material that can withstand the extremely high
temperatures of the reaction, and in the embodiment illustrated,
they consist of a carbon steel pipe nipple and a pair of carbon
steel pipe caps, with the length of the nipple and the outer
diameter of the caps both being on the order of 5 inches.
[0086] A reactor bed 106 is provided in the bottom wall 103a of
lower end cap 103. This bed consists of a inch deep pocket 107
formed in one half of the bottom wall filled with a material 108
such as zirconium dioxide (ZrO.sub.2) or zirconia which can
withstand the high temperatures and not introduce impurities into
the reaction.
[0087] Ports are formed in the end caps to provide communication
with the reactor chamber when the reactor is in use. The ports
include an H.sub.2/O.sub.2 inlet port 109 and an ignition port 111
in the side wall 103b of the lower end cap, a CO.sub.2 inlet port
112 in the upper wall 102a of the top cap, a product outlet port
113 in upper wall 102a for the carbon and magnesium reaction
products, and another outlet port 114 in the upper wall for the
gaseous MgO. These ports are threaded for connection to the lines
that carry the incoming gases, the ignition conductor, and the
reaction products. Clearance holes 116, 117 are formed in side wall
101 in registration with inlet port 109 and ignition port 111 in
the side wall of the lower cap. In this particular embodiment,
there is no port for the magnesium since it is introduced by
removing the top cap and pouring the magnesium particles onto the
reactor bed.
[0088] FIG. 11 illustrates an embodiment in which ignition of the
CO.sub.2 and magnesium is initiated by an electric arc. In this
embodiment, CO.sub.2 is supplied to reactor 118 at ambient pressure
through a supply line 119 which includes a shut-off valve 121, a
pressure reducing valve 122, a control valve 123, and a check valve
124, with pressure transducers 125, 126 and a flowmeter 127 for
monitoring pressure and flow in the line. The reactor walls and lid
are fabricated of a material, such as carbon steel, that is capable
of withstanding the high temperatures produced by the reaction, and
a graphite crucible 128 is disposed within the reaction chamber for
holding the magnesium particles for combustion. Those particles are
introduced by removing the lid and pouring them into the crucible.
Temperature and pressure within the reactor are monitored by a
thermocouple 129 and a pressure transducer 131.
[0089] The arc for initiating ignition of the CO.sub.2 and
magnesium is provided by an electric arc generator 132 which can,
for example, be similar to that employed in an arc welder and have
a rating on the order of 90 amperes at 40 volts AC.
[0090] As in the embodiment of FIG. 6, the reaction products are
collected through a discharge line 133 which includes a control
valve 134 and a pressure relief valve 136, and MgO particles are
collected in a vacuum collector 137 which is connected to the
reactor by an output line 138 which includes a control valve 139
and a pressure transducer 141.
[0091] Data from the pressure transducers, flowmeter, and
thermocouple is delivered to a data acquisition and control system
142 which processes the data and controls the operation of the
control valves and the arc generator.
[0092] Care is taken to ensure the ejected reaction products,
particularly the graphenes, are not combusted post reaction by
interaction of the carbon with oxygen and high heat. The presence
of a CO.sub.2 or similarly inert gas at the reaction exit point is
maintained and high heat is drawn away from the exit point by an
integrated cooling system.
[0093] The nanocarbon graphene and nano MgO reaction products have
been found to be extremely consistent from batch to batch in the
embodiment of FIG. 11. Also, with the gaseous CO.sub.2 feedstock,
this process has produced measurably and significantly less
intercalated material, specifically MgO encapsulated in graphene
layers, than batch processes employing solid CO.sub.2 feedstock.
Gaseous carbon monoxide (CO) was also investigated as an
alternative feedstock in this embodiment, but the CO--Mg reaction
was much less vigorous than the Mg--CO.sub.2 reaction, probably due
to the lesser amount of oxygen available to the reaction. CO may be
useful in regulating the rate of the Mg--CO.sub.2 reaction.
[0094] In the embodiment of FIG. 12, low pressure CO.sub.2 gas is
utilized in the reaction process. This embodiment includes a
reaction chamber 143 with a cylindrical side wall 144 and a bottom
wall 146 fabricated of a material, such as carbon steel, which will
withstand the high temperatures of the reaction. The chamber is
open at the top, and a graphite crucible 147 is disposed within the
chamber for holding magnesium particles 148. CO.sub.2 gas is
introduced into the chamber at atmospheric pressure through ports
in the chamber walls and passes through slotted openings 149, 151
in the bottom and side walls 147a, 147b of the crucible.
[0095] A hood 152 is mounted on the upper portion of side wall 144
for collecting magnesium oxide (MgO) produced by combustion of the
CO.sub.2 and magnesium in the reaction chamber. The MgO is drawn
into and through the hood by a vacuum-operated collector 153
connected to the discharge end of the hood, with a valve 154 at the
discharge end for controlling when the vacuum system can draw the
MgO into the collector. The hood can be removed from the chamber to
allow the magnesium particles to be poured into the crucible.
[0096] The embodiment shown in FIG. 14 is generally similar to the
embodiment of FIG. 12, and like reference numerals designate
corresponding elements in the two. In the embodiment of FIG. 13,
hood 152 is fabricated of stainless steel and includes a cooling
chamber 156 with a screw conveyor 157 for cooling the MgO and
facilitating the recovery of MgO particles from the reactor. In the
embodiment illustrated, fluid coolant is circulated through the
cooler to cool the MgO passing through it. If desired, additional
cooling can be provided by using an internally cooled feed screw in
the conveyor.
[0097] FIG. 15 illustrates a continuous flow embodiment utilizing a
horizontally extending reactor 158 having a conical side wall 159,
with the axis of the reaction chamber 161 being inclined downwardly
at an angle on the order of 10 degrees relative to the horizontal.
The reactor has an end wall 162 at the small end of the cone and is
open at the large end. An input manifold or chamber 163 is formed
between the end wall and a baffle plate 164. This plate is spaced
inwardly from and generally parallel to the end wall and is
peripherally attached to the conical side wall. The reactor walls
and the baffle plate are all made of graphite.
[0098] A generally U-shaped trough 166 extends in a downwardly
inclined manner between the baffle plate and the open or outer end
of the reaction chamber on the inner side of the lower portion of
side wall 159. An opening 167 in the baffle plate at the upper or
inner end of the trough provides communication between the input
manifold and the reaction chamber.
[0099] Magnesium particles and CO.sub.2 gas are introduced into the
input manifold where they mix together before flowing through the
opening in the baffle plate to the upper portion of the trough.
Means such as a gas flame or an electric arc is provided for
initiating ignition of the CO.sub.2 and magnesium in the upper
portion of the trough, and an inert gas such as argon is introduced
into the intake manifold to prevent backflow from the reaction
chamber to the manifold.
[0100] A feed screw or auger 169 extends longitudinally within the
trough for carrying solid reaction products to the outer end of the
reaction chamber. The lower or outer end portion of the feed screw
is internally cooled to provide cooling for the carbon and other
solid reaction products before they are discharged at the lower end
of the trough.
[0101] A significant portion of the magnesium oxide (MgO) gas and
nanomaterial produced by the Mg--CO.sub.2 reaction beneficially
rises to the top of the reaction chamber and passes through a
cooling chamber 171 at the outer end of the upper portion of side
wall 159 before being collected.
[0102] The system is maintained in an inert atmosphere to prevent
post reaction combustion of the carbon and other reaction
products.
[0103] Another embodiment is a small to medium scale,
self-contained, continuous flow system, referred to herein as the
modular embodiment. The primary features of this embodiment include
capture of CO.sub.2 directly from emissions, reduction of the
CO.sub.2 to carbon, production of reusable nanomaterials, and
destruction, by heat of reaction, of harmful fossil fuel combustion
products such as soot. The resultant nanocarbon, MgO, and other
materials can be captured in a holding tank and separated in batch
mode on a regular basis. The modular embodiment can, for example,
be utilized in the production of graphenes or other nanomaterials
for industrial purposes, and it may also be useful as a stationary
emissions control system on a ship or in conjunction with a
stationary diesel generator. A smaller version may be useful in
mobile vehicular applications.
[0104] Subprocesses
[0105] A number of subprocesses are included in the preferred
embodiments in order to provide a complete system and process for
the production of nanomaterials. These subprocesses include
management of reaction input materials and ignition systems,
reaction process controls, reaction product separation and
purification treatment, integrated product functionalization,
recycling of product materials, and energy management. These
processes are an important part of the invention, enabling it to
operate as an industrial system.
[0106] Materials Management
[0107] There are two primary inputs or feedstocks for the preferred
reaction--CO.sub.2 and magnesium. In the preferred embodiment, pure
(99+%) or relatively pure (commercial grade) gaseous CO.sub.2 is
utilized. If the CO.sub.2 gas contains or is seeded with other
gases, these gases will, subject to their inherent phase
attributes, become an additional reaction product with the MgO and
graphenes. The CO.sub.2 feedstock can be obtained in large volumes
from fossil fuel emissions, industrial sources such as breweries
and refineries, natural earth deposits and other sources. In the
preferred embodiments, the pressure of the CO.sub.2 can be
controlled to influence the performance of the reaction and the
morphologies of the products, with CO.sub.2 at a pressure in the
range on the order of 200 to 800 psi being preferred. The gaseous
CO.sub.2 is injected into the reactor at a pressure determined to
optimize the reaction performance and desired products.
[0108] Magnesium can be obtained from third parties in various
alloyed forms or in very pure form. In the preferred embodiments,
pure (99+%) magnesium feedstock is utilized, and it is introduced
in the form of small particles. The size of the particles has been
found to have a significant impact on the reaction and reaction
products, and it is generally selected to achieve optimal reaction
combustion and reaction products. The magnesium can, for example,
be obtained in the form of bar stock and machined to the desired
particle size. Thin gauge magnesium wire segments can also be used,
if desired.
[0109] As discussed above, in the invention, a significant portion
of the magnesium feedstock is obtained by recycling the very pure
MgO product of the reaction in a low-cost electrolytic process.
This method of obtaining magnesium has several advantages, the
first being that the cost of recycled magnesium will be much lower
than the cost of magnesium manufactured by third parties. A second
advantage is that world magnesium production is relatively
inelastic and, thus, magnesium could become more expensive should
operators of the invention require significant amounts of fresh
magnesium feedstock. Presently, more than 80% of the world's
magnesium supply is produced in China, which subsidizes the
industry. Thus, the cost of magnesium may be artificially low,
making recycling even more attractive. A third advantage of
recycling is the high purity (more than 99%) of the recycled
magnesium, which is important to the Mg--CO.sub.2 reaction.
[0110] If desired, other oxidizing and/or reducing agents can be
utilized in place of or in addition to CO.sub.2 and magnesium to
produce other reaction products. The initial reactant for producing
graphenes can be any carbon containing molecule such as carbon
dioxide, carbon monoxide, phosgene (COCl.sub.2), methane, ethylene,
acetylene, other carbon containing material, and combinations
thereof. The reducing agent can be another earth metal such as
aluminum, titanium, zinc, sodium, lithium, calcium, and
combinations thereof.
[0111] Ignition
[0112] High heat input is required for ignition of the Mg--CO.sub.2
reaction. To maintain purity of the reaction products, it is
preferable that an ignition source not introduce foreign
contaminants into the reaction chamber. The Mg--CO.sub.2 mixture
can, for example, be ignited with an electric arc, an electric
spark, a hydrogen-oxygen flame or a xenon lamp. An electric arc
ignition with carbon electrodes is preferred due to its ease of
operation, ability to function continuously, ability to function in
high temperature environments, and because it does not introduce
foreign material or gas to the reaction. Other ignition sources may
also be used as long as they impart no impurities into the reaction
product.
[0113] Process Controls
[0114] Significant control of the reaction and reaction products is
also provided by manipulation of parameters such as regulation of
the temperature gradient, the contact and saturation of CO.sub.2,
and the nature and flow of the magnesium particles. In the
preferred embodiments, a number of process controls are implemented
to optimize costs, safety, conservation of energy and materials,
and production of desired products. These controls include, but are
not limited to, varying the attributes of or type of input
materials and gases, controlling the heat of reaction, controlling
speed of reaction, controlling the post-reaction temperature
gradient, controlling pressure within the reaction chamber,
controlling the atmosphere into which the reaction product emerges
to prevent combustion of the carbon, capturing the energy released
by the reaction, and controlling the post reaction product
separation and treatment processes.
[0115] In the preferred embodiments, the feedstock is managed
before introduction to the reactor, and provisions are made in the
reactor design for the introduction of additional materials and
gases. The supply, purity and pressure of CO.sub.2 feedstock are
managed, as are the supply, purity and form of magnesium feedstock,
with the size of the magnesium particles, and hence the volume to
surface area ratio of the magnesium, directly impacting the
production of and morphology of the reaction products. It has also
been found that the amount of CO.sub.2 available to the reaction
has a significant impact on the reaction products, and the CO.sub.2
can be introduced at precisely controlled pressures and rates to
control the reaction process and products. A non-oxygen, CO.sub.2,
or inert gas environment is maintained post reaction and prior to
heat dissipation to prevent combustion of the carbon graphenes.
Solid particles of CO.sub.2 may also be input into the reactor,
depending on requirements, and will sublimate to large volumes of
gas at high pressures. In this manner, CO.sub.2 can either be
flooded at high pressure in the reactor, or it can be introduced in
restrictive quantities which allow the operator to `throttle` the
reaction with the Mg or Mg alloy or additional mixtures of input
materials.
[0116] The reaction and reaction products can also be controlled by
varying the pressure and presence of the gaseous and solid material
inputs. Reactors in which the invention is carried out are designed
to accommodate the regulated introduction of a range of gaseous and
solid material inputs other than the feedstock at all three stages
of the reaction, i.e. pre-reaction, during the reaction, and
post-reaction. Other reactive gases or inert gases, such as argon,
can be introduced to further control and optimize the reaction
process and products. Other reactive materials such as aluminum,
catalysts such as platinum, or non-reactive materials such as
silver or silicon can be introduced either with the feedstock or
directly into the reaction or at a point after the reaction. Also,
the addition of non-reactant material with desirable attributes
such as silver or silicon can result in the formation of a
composite or decorated graphene material with potentially
advantageous characteristics.
[0117] It has also been found that controlling the temperature
gradient to which the vaporized reaction product and any additional
materials are exposed immediately following the reaction affects
formation of the products and the resultant morphologies and
characteristics of those products. This gradient can be controlled
in several ways. The reactor can, for example, have an open
configuration, or the reaction can be confined to a limited space
within the reactor. The use of an expander and the presence of an
inert or non-reactive gas between the reaction site and the product
outlet can also affect the temperature gradient, with the expander
facilitating the natural tendency of hot vapor from the reaction to
expand, cool, and nucleate or form the reaction product. A liquid
or gaseous cooling agent can also be utilized to further control
the temperature gradient in the reaction process. The cooling agent
can, for example, be injected directly into the reaction chamber,
the discharge region, or the expander, or it can be circulated in a
cooling jacket surrounding portions of the reactor.
[0118] Materials Separation
[0119] In both continuous flow and batch reactions, an initial
separation of reaction products occurs when gaseous MgO is vented
beneficially away from the other reaction products and/or when an
upwardly directed annular flow process provides initial gravity
separation of magnesium oxide nanoparticles and carbon
nanoparticles. The reaction products are then further separated and
purified in a post reaction separation process which is optimized
for the production of the desired products.
[0120] In the preferred embodiments, the post reaction materials
separation process consists of a substantially automated sequence
of treatment, separation and purification steps which are applied
to the unseparated post reaction product that emerges or is
withdrawn from the reactor. In the production of graphenes and nano
MgO, for example, the heterogeneous reaction product undergoes
repeated cycles of treatment with deionized water, hydrochloric
acid, and ultrasound, filtration to isolate graphenes, graphene
drying, and heat treatment of the graphenes. This cycle is repeated
as many times as needed to achieve the desired purity of
graphenes.
[0121] Fluids are useful in separating materials that are resistant
to dissolution and have different specific gravities, and are
required in ultrasonic processing. In gravity separation and
flotation, the density of the solution within the cell is
manipulated to a specific value whereby the particles sink or float
to occupy distinct layers within the vessel. The fluid can be water
or other substances such as acids or fluids with other densities,
depending on the solubility and reactivity of the materials to be
separated.
[0122] Magnesium Recycling
[0123] The recycling of magnesium is an important part of the
invention because of the cost and difficulty of obtaining magnesium
of high enough purity for use in the Mg--CO.sub.2 reaction,
particularly in large scale operations. The crystalline nano MgO
produced by the invention has been found to be extremely pure, and
this unusually high purity makes recycling the MgO to Mg very
practical and cost effective. Given the high cost of magnesium and
MgO in the marketplace and the limited availability of pure,
non-alloyed magnesium, the ability to recover and recycle highly
pure magnesium is an important element and advantage of the
invention.
[0124] The preferred process for recycling magnesium in the
invention is electrolytic reduction from MgCl.sub.2. The chemical
and electrolytic steps in the reduction of MgO to Mg by this
process are shown in FIG. 17. As illustrated, the MgO reaction
product is converted to Mg(OH).sub.2 by treatment with H.sub.2O,
and the Mg(OH).sub.2 is converted to MgCl.sub.2 and H.sub.2O by
treatment with HCl, with the differential thermal expansion between
MgO and carbon opening up cracks in the carbon, allowing the HCl to
attach to the carbon. In the electrolysis step, the MgCl.sub.2 is
separated into magnesium nanoparticles and chlorine gas.
[0125] Energy Management and Reuse.
[0126] The invention is designed to preserve, capture and utilize
as much of the exothermic energy of reaction as possible. The
reaction temperature of approximately 5610.degree. F. (3098.degree.
C.) is unusually high and is in a range that can generally be
achieved at larger scales only with solar furnaces or via nuclear
reaction. In the preferred embodiments, waste heat from the
reaction is captured and utilized in post reaction product
separation and treatment, including production of electricity for
use in the recycling of magnesium. Heat and light energy from the
reaction can also be captured and utilized in other
applications.
[0127] Thermodynamic Analysis
[0128] A thermodynamic analysis of the Mg--CO.sub.2 reaction and
the recycling of the MgO reaction product is summarized in Table 1
below.
TABLE-US-00001 TABLE 1 Production of Solid Carbon through Reduction
Of Gaseous Carbon Dioxide with Magnesium Heat Heat (MJ/kg) (MJ/kg)
Step Reaction Thermicity Mg C. A Mg (s) + 0.5 CO.sub.2 (g) .fwdarw.
1 MgO (s) + 0.5 C (s) Exothermic -16.8 -67.507 Production B MgO (s)
+ H.sub.2O (l) .fwdarw. Mg(OH).sub.2 Exothermic -3.37 -13.507 Mg
Recycle C Mg(OH).sub.2 (s) + 2HCl (l) .fwdarw. MgCl.sub.2 (s) +
2H2O (l) Endothermic 5.74 22.993 Mg Recycle D MgCl.sub.2 (s) +
Energy .fwdarw. Mg (s) + Cl.sub.2 (g) Endothermic 22.4 89.667 Mg
Recycle Total Endothermic 7.91 31.647
[0129] As this table shows, one cycle of the process requires
approximately 8 MJ of energy for each kilogram of magnesium
produced and approximately 32 MJ for each kilogram of carbon. Each
cycle generates 0.25 kg of carbon by reducing 0.92 kg of CO.sub.2,
and produces 1.45 kg of chlorine (Cl.sub.2). On a molar basis, this
can be expressed as:
Mg(s)+H.sub.2O(I).fwdarw.Mg(OH).sub.2(s)+0.5C(s)+Cl.sub.2,
and on a mass basis as:
1kg Mg(s)+0.92kg CO.sub.2+0.75H.sub.2O(I)+7.91MJ.fwdarw.0.25kg
C(s)+1.45kg Cl.sub.2
[0130] The reactions were evaluated using a Gibbs free energy
analysis that provides a theoretical maximum energy (heat)
available for work in each step of the reactions. Steps A and B are
exothermic, releasing approximately 20 MJ of heat per kilogram of
magnesium while recycling Steps C and D are endothermic, requiring
an energy input of approximately 28 MJ to proceed.
Example 1
[0131] A reactor was constructed using two blocks of solid
CO.sub.2, more commonly known as dry ice. A cavity was drilled in
one of the dry ice blocks to serve as a reactor vessel, and the
other block was used as a cover. Magnesium bar stock was machined
into chips which were placed in the cavity and ignited with a
propane torch, following which the cover block was immediately
placed on top of the first block. The reaction product, a mixture
of white and black crusty powder, was collected and sent out for
analytical testing. A second sample was prepared in a similar
manner and treated with deionized water and hydrochloric acid (HCl)
before being sent out for testing.
[0132] The test results showed that the reaction product consisted
of nanomaterial and that the nanomaterial consisted of two dominant
morphologies as well as some less frequently observed morphologies.
The two dominant morphologies were a clear, irregularly shaped,
flat particle showing classic evidence of graphitic (carbon)
composition and a clear square, crystalline particle deduced to be
MgO in nano-crystalline (periclase) form. The untreated reaction
product showed considerably more nano MgO than the sample that had
been treated with deionized water and HCl. The appearance of the
carbon particles in each sample was substantially the same.
[0133] This example shows that the Mg--CO.sub.2 reaction, and most
likely the energy from the reaction, causes the feedstock to
vaporize and reform by nucleation as nanometerial. The extreme
temperature gradient between the reaction site or locus, where the
temperature is approximately 5610.degree. F. (3098.degree. C.), and
other locations within the reactor, where the temperature is near
ambient, is believed to cause very rapid reformation of solid
material from the vaporous reaction product. Moreover, the
extremely short time lapse from formation of the vaporous reaction
product to ejection of the vapor from the reaction site and
interaction with the extreme temperature gradient surrounding the
reaction site limits the operational timeframe for nucleation and
results in the formation of very small, nanoscale particles. The
reaction product vapor nucleates and self-assembles as homogeneous
bonded carbon and MgO.
[0134] The process described in this example is believed to be not
just a process for producing carbon and magnesium nanomaterials,
but rather a more general process and enabling oxidation-reduction
reaction for beneficial formation of nanomaterial in a
vapor-nucleation process. The process has been found to be a
repeatable process for production of nanomaterial including, but
not limited to, the reaction products. Moreover, the absence of MgO
in the reaction product that was treated with deionized water and
HCl shows that the carbon nanoproduct can be effectively separated
from the MgO nanoproduct by means of a relatively simple water and
acid treatment.
[0135] When supplemental, low-pressure, gaseous CO.sub.2 was
injected into the cavity in the dry ice to enhance the reaction,
there was a significant increase in the percentage of carbon
produced relative to the percentage of MgO. Chemical analysis has
shown the reaction products to be extremely consistent from batch
to batch even when conditions are varied as discussed above and to
consist of nanocarbon graphenes, nano MgO, and composites
consisting of intercalated layers of graphene and MgO.
Example 2
[0136] A reactor was constructed from blocks of solid CO.sub.2, or
dry ice, which were approximately 12 inches square and 13/4 inches
square. A cavity having a diameter of approximately 15/8'' was
drilled into one of the blocks to serve as the reactor chamber.
Exhaust pressure release vents having a diameter on the order of
1/4 inch were drilled laterally from the outer edges of the block
to the cavity. The second block was used as a lid for the
reactor.
[0137] Magnesium bar stock believed to have a purity of 99% was
machined into several batches of various sized flakes.
Approximately 10 grams of magnesium chips of between number 5 and
number 10 sieve mesh (2.00-4.00 mm) were placed in the cavity. The
flakes were ignited with an oxygen-hydrogen torch and the dry ice
lid was immediately place on the lower block. The reaction was
observed to be extremely vigorous producing a sizable amount of
light and resulting in some ejection of white smoky (MgO) material
from the edges of the two blocks. The reaction took less than 30
seconds. A residue of agglomerated powdery black (C) and white
(MgO) reaction product material was left in the reactor cavity. The
reaction product material was removed by inverting the dry ice slab
and dropping the reaction product into a clean container.
[0138] The reaction product was then processed to isolate the
carbon material and provide samples for analysis. The material was
separated using 4M (4 moles per liter) HCl, which caused the MgO to
go into solution as MgCl.sub.2. A black material (carbon) remained
and was isolated and removed by washing the material through a 1
micron filter with alternating applications of ethanol and
distilled water. The cleaned sample was spattered onto a plastic
sheet, left to dry overnight, then placed in a clean container. A
second sample was prepared in a similar manner.
[0139] During this study, it was observed that certain sized
magnesium chips were more readily combustible than others and that
the reaction product differed dramatically in appearance depending
on the size of magnesium chips. Magnesium flakes having a sieve
mesh size between number 5 (4 mm) and number 10 (2 mm) resulted in
the most complete combustion. These particles were large enough to
combust, yet small enough to allow a reasonable mass quantity in
the reaction.
[0140] The samples were analyzed by a number of tests, including
Transmission Electron Microscopy (TEM), Scanning Electron
Microscopy (SEM), Glow Discharge Mass Spectrometry (GDMS) and X-Ray
Diffraction (XRD).
[0141] The TEM and SEM analyses showed that particles from the
samples set appeared to be agglomerated, plate-like particles of
approximately 10 to 60 nanometer scale and had very large surface
area. Graphitic carbon was identified in the samples by the
presence of lattice fringes as well as electron diffraction
(graphitic ribboning). This material appeared to be unique.
Crystalline MgO (Periclase) having a particle size in the range of
40 to 60 nanometers was clearly observable, and the TEM imagery
showed the presence of MgAl.sub.2O.sub.4 spinels in the form of 40
nanometer pill-like structures.
[0142] The GDMS analysis was performed to examine the purity of the
samples. It showed that the sample material contained 15% magnesium
by weight and, somewhat surprisingly, that it also contained 5.1%
aluminum by weight. The aluminum was clearly present in the
nanospinels and may have been in the samples in uncombusted form.
The only potential source of aluminum was the magnesium bar stock
that was thought to be pure.
[0143] The XRD test showed a strong presence of three types of
crystalline structures, with spinels (MgAl.sub.2O.sub.4
nanocrystals) being the dominant form.
[0144] From this example, it was determined that the Mg--CO.sub.2
reaction reliably produces nanomaterial of carbon and non-carbon
types, and that essentially pure MgO is ejected by the reaction
when vents are provided in the reaction vessel. It also
demonstrated that the process will form nanomaterial from other
reactive feedstock such as aluminum, and that the reaction and the
vapor-nucleation cycle is likely to convert most, if not virtually
all, materials present to nanomaterial form.
[0145] This example also demonstrated that the reaction can be
controlled, e.g. by altering the magnesium feedstock to affect the
efficiency of combustion and the composition of the reaction
product. This strongly suggested that the morphology and
characteristics of the reaction products are controllable.
[0146] It also confirmed that significant separation of the
reaction products is feasible. The carbon reaction product was
separated by means of simple deionized water, alcohol and acid
washing, and these steps were found to be highly effective in
reducing the presence of magnesium oxide in the carbon reaction
product from its theoretical output ratio of approximately 85% MgO
and 15% C to approximately 25% MgO and 75% C.
Example 3
[0147] Magnesium barstock was machined into chips ranging in size
between about 2.0 and 4.0 mm (sieve mesh sizes #5-#10). These chips
combusted with CO.sub.2 in a manner similar to that in Example 2,
and two samples were prepared for separation processing.
[0148] As an initial step in the post reaction separation
processing, the heterogeneous product samples were ground to a 140
mesh size to reduce agglomeration and provide more uniform samples
with greater surface area for fluid treatment. The ground up
samples were introduced into a vessel containing deionized water
and were processed ultrasonically at 20 kHz and 500 Watts for a
defined period of time to further reduce particle size and increase
surface area. Thereafter, 12M (moles per liter) HCl was added to
dissolve the MgO reaction product as well as any remaining
uncombusted Mg. The HCl reacted with MgO and Mg to form MgCl.sub.2
in an exothermic reaction. The vessel was allowed to cool,
following which the sample was treated with HCl again and then once
again treated ultrasonically for an identical period of time.
Following the second ultrasound treatment, the sample was once
again treated with deionized water. After these steps, the carbon
product was removed by filtration (1 micron) as in Example 2. Two
separate batches were prepared in this manner.
[0149] GDMS analysis of the samples showed a substantially lower
magnesium content than in Example 2, with 12% by weight in the
first sample and 11% in the second. It also revealed the presence
of 5.5% aluminum by weight in the first sample and 3.1% in the
second. The magnesium barstock used as the feedstock was then
analyzed and found to contain 2.5% aluminum by weight.
[0150] TEM and SEM analysis showed that the two product samples
were identical in physical form and that both samples contained
graphitic carbon, which was identified by the presence of lattice
fringes and electron diffraction consistent with graphitic
material. The size of the carbon particles was predominantly on the
order of 10 to 20 nanometers, substantially smaller than the
particles produced in Example 2. These particles were also
significantly less agglomerated than the particles in Example 2.
The morphology of the nanocarbon was flat, with irregular edges,
and the particles appeared to consist of one to several layers.
[0151] XRD analysis showed strong evidence of thin layers of
graphitic graphene material in both samples, and both samples had
two non-graphitic dominant phases: MgAl.sub.2O.sub.4 (spinel) and
MgO (periclase). This analysis also suggested the presence of
composited material in addition to the spinel and periclase
structures. It also revealed the presence of traces of pyrolitic
carbon, probably from the ignition source. The carbon material in
the samples was determined to be hydrophobic.
[0152] Porosity tests showed the carbon product sample material to
be mesoporous (pores in the range of 1 to 50 nanometers), with a
majority of the pores in the range of 1 to nanometers. Surface area
tests showed surface areas between 230 and 460 square meters per
gram. It is believed that some pores may be blocked by the Mg--Al
oxides (spinels) that were found in the samples.
[0153] These tests show that the invention produces one to a few
layers of a nanocarbon material having a surface area, pore size,
pore volume and order characteristics consistent with high quality
graphenes. The product samples were consistent in appearance and
test results from batch to batch.
[0154] The GDMS tests indicated that magnesium oxide remained
present in the samples in significant quantities, and the XRD tests
provided a strong indication that the magnesium oxide is present as
crystalline nano-periclase. Analysis of the TEM images and other
tests suggests that the remaining MgO is intercalated with the
carbon graphene layers. This is consistent with the evidence of
composite material indicated by the XRD tests. The MgO intercalated
with graphene may be an important and novel material.
[0155] The presence of composites consisting of graphenes and MgO
in the product samples suggests that the production of composites
of graphene or MgO with other non-feedstock materials is also
feasible.
Example 4
[0156] Laboratory grade, 99.9% pure, magnesium bar stock was
machined to the established chip size, and an airtight reaction
chamber was constructed. Several samples were prepared and
tested.
[0157] A first sample was prepared by reacting the 99.9% pure
magnesium with CO.sub.2 in an argon environment. The reaction
product was separated and stored in an argon environment, with the
separation process including HCl, deionized H.sub.2O, and
ultrasonic treatment as in Example 3.
[0158] A second sample was prepared in a similar manner by reacting
the 99.9% pure magnesium with CO.sub.2 in an argon environment, but
then a reflux/leach process was used to separate the reaction
product. The sample was refluxed with nitric acid by boiling the
sample in the acid and re-condensing vapors in a confined
environment. The sample was then extracted from the solution,
cleaned with deionized water, and dried overnight in an oven.
[0159] A third sample was prepared by reacting 95% pure magnesium
(similar to AZ31) with CO.sub.2 in an argon environment. This
sample was not processed for separation or tested, but instead was
stored in an argon environment for reference purposes.
[0160] A sample of the unreacted laboratory grade (99.9% pure)
magnesium feedstock was kept in an air environment for the purpose
of verification of the purity of the magnesium input.
[0161] In addition, samples of ejected MgO were collected in a
vacuum system attached to the reactor.
[0162] The samples were analyzed in a number of tests, including
TEM and SEM, GDMS, XRD, pore size, pore volume, surface area, BET,
gas sorption, and thermal and oxidation stability.
[0163] The GDMS analysis showed that the sample separated by HCl,
deionized H.sub.2O, and ultrasonic processing contained 20%
magnesium by weight, whereas the sample separated by the nitric
acid reflux/leach process contained 40% magnesium by weight. It
also confirmed the high purity (99.9%) of the magnesium reactant
and determined that the MgO sample was of unusually high purity
(above 99%), with none of the contaminants commonly found in MgO
samples.
[0164] The XRD tests showed that the sample separated by HCl,
deionized H.sub.2O, and ultrasonic processing had only two phases,
a dominant crystalline MgO phase and a crystalline carbon phase
consistent with graphenes.
[0165] The TEM images were very similar in Examples 3 and 4. As can
be seen in the TEM image in FIG. 18, the product contains graphene
platelets 173, cubic MgO crystals (periclase) 174, and graphene-MgO
composites 176. The graphene platelets appear as clear, irregular
bodies and include single layer graphenes as well as graphenes
having several layers. The MgO crystals are darker, indicating
denser or layered material, and have a length of approximately 20
nanometers on each side. The graphene-MgO composites have one or
more layers of graphene platelets formed on the faces of the cubic
MgO crystals. A single MgO crystal 177 with graphene layers 178
produced in accordance with the invention can be seen in the TEM
image of FIG. 19.
[0166] Cubic crystals of MgO, or periclase, produced by the
invention can be seen in the TEM image of FIG. 20, where crystals
179, 181, 182 have a length of approximately 30-50 nanometers on
each side and crystals have a length of approximately 20 nanometers
per side.
[0167] The SEM images were also similar to the ones in Example 3 in
showing agglomerated material. As can be seen in the SEM image of
the sample material shown in FIG. 21, the graphene platelets have
short-range order and are on the order of 10 to 20 nanometers in
length. The graphene-MgO composite material seen in this image has
both short- and long-range order, 6 or more layers, and is
consistently in the range of 40 to 60 nanometers.
[0168] In the gas sorption tests, the sample separated by HCl,
deionized H.sub.2O, and ultrasonic processing was found to have
both a significantly larger surface area and significantly more
pore volume than the sample separated by the nitric acid
reflux/leach process.
[0169] In the thermal testing, no melting point of the product was
found in the temperature range tested, and very high thermal
transference was indicated.
[0170] The pore testing showed that the majority of the pores have
size of 5 nanometers, similar to that of the product samples in
Example 3. They also showed that they were mesoporous, with pores
in the range of 2 to 50 nanometers.
[0171] The results of the surface area, pore volume, pore size test
are summarized in the table below.
TABLE-US-00002 TABLE 2 SURFACE AREA DATA Multipoint BET 2.048E+01
m.sup.2/g BJH Method Cumulative Adsorption Surface Area 5.659E+01
m.sup.2/g DH Method Cumulative Adsorption Surface Area 5.786E+01
m.sup.2/g DR Method Micro Pore Area 2.441E+01 m.sup.2/g PORE VOLUME
DATA BJH Method Cumulative Adsorption Pore Volume 5.141E-02 cc/g
BJH Interpolated Cumulative Adsorption Pore 5.141E-02 cc/g Volume
for pores in the range of 5000.0 to 0.0 .ANG. Diameter DH Method
Cumulative Adsorption Pore Volume 5.024E-02 cc/g DR Method Micro
Pore Volume 8.695E-03 cc/g PORE SIZE DATA BJH Method Adsorption
Pore Diameter (Mode) 7.005E+00 .ANG. DH Method Adsorption Pore
Diameter (Mode) 7.005E+00 .ANG. DR Method Micro Pore Width
2.151E+01 .ANG.
[0172] The MgO sample was reacted and functionalized with deionized
water to form magnesium hydroxide (Mg(OH).sub.2), a so-called green
plastics fire retardant well known to those skilled in the art. The
Mg(OH).sub.2 functions as a fire retardant by converting back to
MgO and H.sub.2O when exposed to temperatures in excess of
332.degree. C., at which temperature it undergoes an endothermic
decomposition. The formation and decomposition of the
functionalized MgO was verified in a series of successful
tests.
[0173] This testing confirms that the invention consistently
produces graphenes and indicates that graphene is the dominant
nanostructure in the product samples. The thermal test results show
very high thermal transference consistent with graphenes, and
comparative analysis with available TEM graphene images shows that
the carbon nanostructures are graphenes. Moreover, TEM images from
Examples 2-4 showing both lattice fringes and electron diffraction
indicate that the process of the invention produces graphenes and
is extremely consistent over time.
[0174] The graphene-MgO composites produced by the invention are
believed to be novel, with the graphenes encapsulating the MgO in
such a way that the composite is inert to acid treatments.
[0175] The presence of novel nano-structures, composites, spinels,
peridases and graphenes in the reaction product indicates that the
invention can produce novel materials and composites, depending on
feedstock.
[0176] This testing also confirms that the invention is
controllable such that the products can be determined, separated
and purified, and the morphologies and attributes of the products
can be controlled. The combination of XRD and GDMS data indicates
that, when the inputs are pure Mg and CO.sub.2, the reaction
produces a pure material consisting of MgO and carbon and that all
other components were insubstantial. Varying the separation
protocol has been found to have a significant influence on the
purity and character of the product materials. The use of HCl and
ultrasonification proved to be superior to the use of a nitric acid
reflux/leach process for separation of magnesium products from the
sample batch. The absence of aluminum in the product samples
produced from 99.9% pure magnesium confirms that different
nanoscale materials can be produced with different feedstock.
[0177] The TEM image of FIG. 18 shows the broad range of
capabilities of the invention.
[0178] As noted above, it shows graphene platelets 173, cubic MgO
crystals (periclase) 174, and graphene-MgO composites 176. It also
appears to show some amorphous carbon that could have formed if
local conditions in the reactor did not produce adequate reaction
heat to fully vaporize the carbon and produce graphenes. This,
however, is the only image of amorphous material obtained in the
three phases of testing to date.
[0179] Both the sample prepared by HCl and ultrasonic separation
and the sample prepared by the nitric acid reflux/leaching had a
larger surface area and more pore volume than the samples in
Examples 2 and 3, possibly due to the elimination of spinel
structures that may have clogged the pore space of the material.
This finding is further indication that the reaction process can be
manipulated to produce nanomaterials having significantly different
characteristics.
[0180] The argon environment in the reactor and storing the product
samples in argon had no discernable impact on either the reaction
process or the reaction products of using inert gas to isolate the
reaction was detected.
Example 5
[0181] Two samples were prepared from gaseous CO.sub.2 in a carbon
steel reaction vessel. The first was prepared in a high pressure,
pure CO.sub.2 environment, and the second was prepared in a pure
CO.sub.2 environment at standard atmospheric pressure. The carbon
steel reaction vessel had ports for ignition, feedstock injection,
and MgO ejection, and Ignition was provided by electric arc. Both
samples were prepared from magnesium chips having a size on the
order of 2.0-4.0 mm (#5-#10 sieve mesh). Post reaction separation
was done with HCl and ultrasound, and the samples were dried to
create a graphene powder.
[0182] Additional samples were prepared in a similar manner but
with high pressure gaseous carbon monoxide (CO) in a carbon steel
vessel.
[0183] The sample prepared from the gaseous CO.sub.2 reaction at
high pressure was examined with GDMS, TEM, SEM, and XRD testing.
The GDMS testing showed that the percentage of magnesium in the
sample was only 10% by weight, whereas the samples prepared with
solid CO.sub.2 in the previous examples contained 20%-25% Mg by
weight. The TEM and SEM images both revealed that the morphology of
the materials produced in the reaction was similar to that produced
from solid (dry ice) CO.sub.2, and the XRD images revealed only one
dominant phase--a carbon phase.
[0184] The material produced from gaseous CO.sub.2 at atmospheric
pressure was examined with GDMS and Instrumental Gas Analysis
(IGA). The GDMS testing indicated that the mass percentage of
magnesium in the samples was 14% by weight, and IGA testing found
concentrations of the following elements by weight percent:
nitrogen 0.64%, hydrogen 0.77%, and oxygen 8.6%. In comparison,
samples prepared with solid CO.sub.2 (dry ice) in the previous
examples contained 11.7% oxygen after processing in fluid with no
heat processing and only one processing cycle. TEM analysis showed
the presence of graphene material substantially similar in
character and appearance to that shown in the TEM results in
Example 4 and the prior examples.
[0185] In preparing the samples with CO, it was found that ignition
of the reaction with high pressure CO was extremely difficult and,
when successful, resulted in only partial combustion of the
magnesium.
[0186] Gaseous CO.sub.2 was found to be highly effective as a
feedstock in the Mg--CO.sub.2 reaction. Virtually all MgO remaining
in the samples was intercalated MgO encapsulated in graphenes that
are recalcitrant to HCl and ultrasonic purification treatment, and
gaseous CO.sub.2 was found to produce significantly less
recalcitrant intercalated MgO than solid CO.sub.2 feedstock. The Mg
in reaction product is predominately in the form of MgO. The MgO
weight of the sample prepared with high pressure CO.sub.2 gas was
approximately 14% versus approximately 35% for the samples prepared
with dry ice in the earlier examples.
[0187] Gaseous CO.sub.2 at higher pressure also results in
significantly lower recalcitrant intercalated MgO-C composites in
the reaction product than products prepared with gaseous CO.sub.2
at atmospheric pressure. The MgO weight in the high pressure sample
was approximately 14% compared with approximately 20% in the sample
prepared at atmospheric pressure.
[0188] Highly pure MgO was ejected very vigorously from the
reaction chamber, whereas virtually all the graphenes remained
within the chamber. The degree of such separation can be controlled
in a number of ways, including the use of vents and vacuum to
recover the MgO and varying the initial phase and pressure of the
CO.sub.2 input.
[0189] Carbon monoxide (CO) has been found to be considerably more
difficult to react with magnesium and may not be an attractive
alternative to CO.sub.2 in the reaction. The difficulty in reacting
is believed to be due to the lesser amount of oxygen in CO than in
CO.sub.2 at similar pressures. CO is, however, believed to be very
likely to be very effective in modulating the vigor of the
Mg--CO.sub.2 reaction.
[0190] The invention has been found to be extremely consistent in
producing reaction nanoproduct when the CO.sub.2 feedstock is
changed from solid CO.sub.2 (dry ice) to gaseous CO.sub.2, both at
atmospheric pressure and at high pressure. The amount of
intercalated MgO-graphene composites has been found to be highly
controllable by adjustment of the CO.sub.2 feedstock, with gaseous
CO.sub.2 at high pressure producing the least intercalated material
and solid CO.sub.2 (dry ice) producing more than 100% more by
weight.
[0191] It is believed that two operational parameters are
responsible for the reduction in the amount of intercalated
MgO-graphene composites. First, the saturation of CO.sub.2 at the
reaction site is the highest with high pressure gaseous CO.sub.2
and the lowest with solid CO.sub.2 (dry ice), which suggests that
CO.sub.2 saturation is a critical factor in controlling the degree
of formation of intercalated material. Second, the open space
surrounding the magnesium in the carbon steel vessels is
approximately ten times the open space in the dry ice blocks. The
additional space provides the vaporous reaction product
substantially more opportunity to nucleate and form homogenous
carbon and MgO nanoparticles. Thus, it is believed that a
continuous flow system in which the reaction products are ejected
from the reaction site and have the maximum opportunity to nucleate
and form homogenous carbon and magnesium oxide nanoparticles will
result in a very low amount of intercalated MgO-graphene
composites.
Example 6
[0192] Samples were prepared in the airtight reaction chamber of
Example 4, with a CO.sub.2 flood being used instead of argon to
prevent post-reaction carbon combustion. A partial vacuum and
collection receptacle was attached to the reaction chamber for
collecting vented MgO, and solid CO.sub.2 (dry ice) was used as the
feedstock in order to provide the maximum amount of intercalated
MgO-graphene composite for testing purposes.
[0193] A first sample underwent standard fluid and ultrasound
processing followed by heat treatment at 1200.degree. C. for a
period of 2 hours. This cycle was repeated twice. Heating was
performed in a quartz tube at vacuum, with the material in an
alumina boat.
[0194] GDMS testing showed the following weight concentrations of
elements in the sample:
TABLE-US-00003 Mg 6% Al 4% Si 7% Ti 0.1%
[0195] And IGA testing showed the presence of 6.2% oxygen. Thus,
the heat treatment significantly reduced the mass quantity of both
magnesium and oxygen in the product. The aluminum in the sample is
believed to have come from the alumina boat that held the sample
during the heating process.
[0196] A second sample was prepared in a similar manner except the
material was placed in a seasoned quartz boat, the heating was done
in a seasoned quartz tube at vacuum, and the heating cycle was
repeated three times. GDMS testing showed this sample contained 3%
magnesium and 5% silicon by weight, with negligible aluminum and
titanium. IGA testing showed the presence of 3.6% oxygen. Thus,
using a quartz boat instead of an alumina boat at high temperatures
was found to eliminate the diffusion of aluminum into the sample,
and it was concluded that the high temperature of the heating
process caused silicon to diffuse from the quartz into the
sample.
[0197] The next sample was also prepared in a similar manner, with
fluid and ultrasonic processing followed by heating in a seasoned
quartz boat in a seasoned quartz oven at vacuum at 1200.degree. C.
for a period of 2 hours. This complete cycle was repeated three
times, then the sample was heated at 1000.degree. C. for a period
of 2 hours. GDMS testing showed that the sample contained 2%
magnesium and 6% silicon by weight, and IGA testing showed the
presence of 3.4% oxygen and 0.57% nitrogen. TEM images showed that
the morphology of the graphene material produced in the process was
similar to that of material produced without heat treatment,
although no nano MgO or MgO-graphene composites were observed. SEM
images showed that the morphology of the materials produced in the
process was similar to that of materials produced without heat
treatment, and XRD images showed the presence of only one dominant
phase--a carbon phase. These tests seem to confirm that the silicon
material was infused from the quartz boat and possibly also the
quartz vacuum apparatus, and it was concluded that 1200.degree. C.
is an upper boundary for the heating if a silicon-free material is
desired.
[0198] Another sample was then prepared in a similar manner, with
heating in a seasoned quartz boat in a seasoned quartz tube at
vacuum at 1000.degree. C. for a period of 4 hours. This cycle was
repeated four times. GDMS testing showed that this sample contained
8.5% magnesium and 0.15% silicon by weight, and IGA testing showed
the presence of 4.6% oxygen. Thus, lowering the heating temperature
from 1200.degree. C. to 1000.degree. C. significantly reduced and
essentially eliminated the mass quantity of silicon that diffused
into the sample, notwithstanding the doubling of the heating time
for all heat cycles. However, the lower heating temperature was
considerably less effective in removing oxygen from the sample even
with the increased heating time. Therefore, it was concluded that
1000.degree. C. is a lower boundary for the heating process.
[0199] The next sample was prepared in a similar manner, with
heating in a seasoned quartz boat in a seasoned quartz tube at
vacuum at 1000.degree. C. for a period of 4 hours. This cycle was
repeated four times. The sample was then heated at 1150.degree. C.
for a period of 2 hours, followed by with heating at 1125.degree.
C. for a period of 2 hours. GDMS testing showed that this sample
contained 5% magnesium and 0.1% silicon by weight, and IGA testing
showed the presence of 4.6% oxygen by weight. Thus, with the
additional heating cycle, the quantity of both magnesium and oxygen
was reduced, and the quantity of silicon remained substantially the
same.
[0200] Another sample was prepared in a similar manner, with a
first heating cycle of 2 hours at 1125.degree. C. followed by four
successive cycles of heating at 1150.degree. C. for 2 hours. The
heating was done in a seasoned quartz tube at vacuum, with the
material in a seasoned quartz boat. GDMS testing showed that this
sample contained 3.5% magnesium and 0.3% silicon by weight, and IGA
testing showed the presence of 2.2% oxygen.
[0201] A final sample was prepared using five heating cycles at
1150.degree. C. for 2 hours each. The heating was done in a
seasoned quartz tube at vacuum, with the material in a seasoned
quartz boat. GDMS testing showed that this sample contained 3.2%
magnesium by weight and negligible silicon, and IGA testing showed
the presence of 2.1% oxygen. From this, it was concluded that
1150.degree. C. is an optimal temperature both for reduction of the
mass concentration of oxygen and Mg in the sample and for
preventing diffusion of silicon into the graphene sample from
quartz equipment.
[0202] Although an Ellington diagram showing the relationship
between temperature and standard free energies in the formation of
oxides suggests a somewhat higher temperature (1850.degree. C.), by
doing the heat processing under vacuum and for a longer period of
time, the inventors have avoided the need for the higher
temperature. However, the higher temperature can be utilized, if
desired, with corresponding adjustments in pressure and/or
processing time, and since reaction rates for many reactions double
with each 10.degree. C. rise in temperature, higher temperatures
can have a dramatic effect on the reactions.
[0203] Graphene Production
[0204] In one presently preferred embodiment of a batch process for
producing graphenes which roughly parallels the embodiment of FIG.
2, the Mg--CO.sub.2 reaction is carried out in graphite crucibles
placed in a steel vessel. The steel vessel has an internal CO.sub.2
atmosphere around the graphite crucible to prevent combustion of
the graphite and contamination by other gases such as air. The
CO.sub.2 is introduced into the vessel at low pressure and enters
the graphite crucible through openings in the bottom, top and sides
of the crucible. Magnesium metal chips are placed in the crucible
and ignited by an electric arc (40 VAC, 90 .ANG.).
[0205] The system can have a negative pressure MgO collection
system with a 1 micron filter attached to the top of the steel
vessel, or the MgO can be collected in a low pressure, cooled
cylindrical axial collector that has an auger system to constantly
remove the MgO powder that is produced when the MgO gas nucleates
inside the MgO collector. The MgO is collected at the exit of the
collector and stored for recycling back into Mg metal or for use in
other applications.
[0206] The combustion products formed in the graphite crucibles are
ground to a 140 mesh size (0.104.times.0.104 mm) to make the
material easier to process in subsequent fluid purification
processing steps.
[0207] The ground material is ultrasonically processed in deionized
water. The processing time is dependent on the level of the
ultrasonic energy input, with lower energy requiring longer
processing times and higher energy requiring shorter processing
times. The processing can be done, for example, in 2 hour cycles in
a 500 watt ultrasonic unit. Since energy is the product of time and
power, either time or power can be adjusted as needed. For
industrial scale production, large ultrasonic processors will be
utilized.
[0208] Hydrochloric acid (HCL) having a density of 20.degree. Baume
is added to the material from the ultrasonic processor to dissolve
any free Mg metal and MgO present in the solution, and this new
solution is also processed ultrasonically for a suitable time at a
suitable energy level, e.g. 2 hours at 500 watts.
[0209] The solution is then filtered in a Buchner vacuum funnel 26
with 2.5 micron filter paper, with the graphenes being deposited
onto the filter paper and the MgCl.sub.2 passing through. The
filter paper and graphenes are then heated, in a low temperature
oven (less than 100.degree. C.) to dry the graphenes and facilitate
their removal from the filter paper.
[0210] The dried material is placed in a seasoned quartz boat in a
high temperature seasoned quartz oven and heated to 1150.degree. C.
for a preset period of time which can range from less than 2 hours
to more than 6 hours, depending upon the result desired. The oven
is regulated by a PID controller that provides a low temperature
ramp up, operation at the processing temperature for the preset
period of time, and then a ramp down in temperature. The low
temperature ramp up stabilizes the combusted material and drives
off any water that may be present in it in order to avoid any loss
of material due to violent evaporation of water in the material and
eruption of the material out of the boat by the water evaporation
energy.
[0211] The material is removed from the oven, and a GDMS analysis
is made to determine whether additional processing is required to
achieve the desired level of purity. If so, some or all of the
steps in the process can be repeated until the desired purity is
achieved.
[0212] This process has been found to be fully reproducible and
quite robust in that unintended or unplanned events in the
procedure had no effect on the final graphene product. For example,
prior to the use of the PID controllers, the heating cycles were
not exact and varied by as much as +/-30 minutes, and the
thermocouples for the temperature controllers were not certified by
a standards laboratory. The procedure is very forgiving.
[0213] If desired, other techniques can be employed to purify the
material before the treatment with acid and ultrasound. Ore
beneficiation using density separation is effective since there is
a significant difference in density between Mg and MgO. Separation
can likewise be done by centrifugal action in a cyclone type of
separator.
[0214] Ignition Systems
[0215] The Mg--CO.sub.2 reaction must be ignited by an external
source of heat, preferably one that avoids contamination of the
graphene reaction product. Many ignition systems have been tested.
An H.sub.2O.sub.2 torch, for example, has been found to be
effective in an open cavity in a sheet of solid CO.sub.2 (dry ice),
and an H.sub.2/O.sub.2 torch ignited by an electric spark (15,000
volts) has been found to be effective in a gaseous CO.sub.2 vessel
operating in the batch mode. When the reaction is conducted with
CO.sub.2 at atmospheric pressure, it was found to be preferable to
use an AC or DC electric arc, with a ground connection to the
graphite crucible and the arc being struck with a magnesium rod or
carbon electrode in very close proximity to the magnesium chips.
With the electrode and the ground in a Siamese parallel
configuration and the two simultaneously coming very close to, but
not touching the magnesium chips, the system has the potential to
ignite the Mg/CO.sub.2 mixture in an aerosol environment.
[0216] If desired, a high intensity lamp, a glow plug, or an
H.sub.2/O.sub.2 torch can be used in place of the electric arc to
ignite the Mg/CO.sub.2 mixture. However, an electric arc can be
left on continuously to insure continuous combustion of the
Mg/CO.sub.2 mixture, and multiple carbon arc units can also be used
to insure complete and total combustion of the Mg/mixture.
[0217] Reactor Design
[0218] Different materials have been tested for use in the
construction of a reactor for carrying out the invention. A carbon
steel reactor performed well initially but degraded from repeated
exposure to high temperature. The reactor shown in FIG. 8, with a
pocket of high temperature zirconia oxide (ZrO.sub.2) in the base,
worked well thermally, but contaminated the reaction products with
ZrO.sub.2. A graphite reactor with a graphite crucible performed
very well over extended testing, and graphite is currently the
preferred material for reaction containment. Graphite has good high
temperature properties, and any contamination carbon from the
graphite will just go into the graphenes. Also, graphite is readily
machined to desired shape and dimensions.
[0219] Heat Cycle Containment
[0220] Heating the carbon reaction products to the temperatures
employed in the separation and purification stages requires that
the samples be treated under vacuum to prevent combustion of the
carbon, and it also requires that the oven be made of materials
that are capable of maintaining their structure over repeated
exposure to the processing temperatures without contaminating the
products being treated. Quartz tubes and mullite or porcelainite
tubes (3Al.sub.2O.sub.32SiO.sub.2 or 2A.sub.2O.sub.3SiO.sub.2) have
been used successfully for this purpose. Other materials, such as
titanium, have been found to fail structurally and to contaminate
the product.
[0221] Observations and Conclusions
[0222] The invention produces materials that are remarkably
consistent over time and with different embodiments. TEM and XRD
results demonstrate consistent production of graphenes of a highly
crystalline nature. Pore size and volume measurements also remain
consistent, with graphenes from which MgO-graphene composites are
removed having significantly higher surface area than graphenes
from which the composites are not removed.
[0223] The reaction products can be controlled and managed at
various stages of the process. The addition of heat treatment to
the fluid and ultrasound steps results in a substantial reduction
of recalcitrant intercalated MgO-graphene composites due to the
release of oxygen from the MgO bond or by sublimation of the MgO in
the graphene composite. The temperature and duration of the heat
treatment can be determined empirically, or it can be calculated
through the use of Ellinghams Diagram. The reduction of
MgO-graphene composites takes place in a linear manner where each
heat cycle reduces the remaining composites by a constant
percentage, and it is believed that the reaction product graphenes
can be purified commercially to a purity level of 99% or higher. In
order to have the least amount of intercalated MgO-graphene
composites to start with, it is preferable to use gaseous CO.sub.2
feedstock, even more preferably pressurized gaseous CO.sub.2
feedstock, rather than solid CO.sub.2 (dry ice) feedstock.
[0224] The examples show that the beneficial vapor-nucleation cycle
and the beneficial exothermic oxidation-reduction reaction of
CO.sub.2 and Mg are parts of a broader, more general process that
can produce nanomaterials other than graphenes and other carbon
nanoproducts. The process creates a vaporized homogeneous material
that "self-reorganizes" as pure materials to a significant
degree.
[0225] Highly pure MgO reaction product is beneficially ejected
from the reaction site, e.g. through vents in the reaction chamber
and can, for example, be collected in a vacuum particle collector.
The MgO ejection can also be utilized as a preliminary step in
separating the reaction products.
[0226] Batch processing of magnesium metal and solid CO.sub.2 (dry
ice) in the production of graphenes results in a product with a
relatively high initial concentration of MgO, which is believed to
be the result of incomplete combustion due to insufficient CO.sub.2
to combine with the magnesium. When gaseous CO.sub.2 is added to
the reaction, there is a significant decrease in the amount of MgO
in the product, thus demonstrating that the composition of the
reaction product can be controlled by controlling the amount of
CO.sub.2 available to the reaction.
[0227] Although the Mg--CO.sub.2 reaction is the preferred method
of generating the high temperatures required in the production of
graphenes and other nanoproducts, it is possible to use other
materials in the reaction, if desired. Thus, for example, aluminum
can be used instead of magnesium as a primary feedstock to make
graphenes and/or graphene composites with different chemical and
physical compositions. There are other elements that could also be
considered for use as reactants in the process, and there likewise
are other carbon compounds, such as CH.sub.4 and other hydrocarbons
that could be used instead of CO.sub.2 to provide the carbon source
for the reactions.
[0228] The purity and composition of the reaction feedstock can
also affect the purity of the reaction products and the composition
of the final product. Thus, for example, if the magnesium feedstock
has even a small percentage of aluminum in it, the reaction will
produce aluminum and spinel contamination in the graphene produce.
Likewise, CO.sub.2 purity will affect the final chemical
composition of the reaction products. The high temperature
reactions and use of various reactants, additives, or components
may make it possible for many chemical applications to be done on a
continuous industrial scale when heretofore they could only be done
on that scale with a solar furnace.
[0229] By including other gases in the CO.sub.2 mixture, the
addition of other elements to the graphene can be easily
accomplished. For example, the addition of borane (BH.sub.3 or
B.sub.2H.sub.6) to the CO.sub.2 results in a p-doped graphene
semiconductor when a semiconductor material is doped with the
reaction product, and the addition of ammonia (NH.sub.3) to the
CO.sub.2 results in an n-doped graphene semiconductor when a
semiconductor material is doped with the reaction product. In view
of the desirable electronic properties of graphene, p-doped and
n-doped graphene semiconductors could have wide use and substantial
value.
[0230] It should be noted that even though the measured reaction
temperature of 5610.degree. F. (3098.degree. C.) is below the vapor
point of MgO (6512.degree. F./3600.degree. C.), MgO nanoparticles
are nevertheless formed by the reaction. The inventors believe this
may be due to the temperature deep in the reaction zone being
substantially higher than the temperature that is measured outside
that zone.
[0231] It also appears that the reaction temperatures at which the
nanomaterials are formed may range from about 1000.degree. F.
(537.degree. C.) to about 7000.degree. F. (3871.degree. C.).
[0232] The nanomaterials produced by the invention have shown a
strong tendency to form as separate homogeneous particles, with the
MgO tending to beneficially vent and the carbon graphenes tending
to remain in the reactor vessel.
[0233] The high temperature of the reaction may have industrial
application beyond the production of graphenes, nano-periclase or
composites thereof. For example, the energy and temperature of the
reaction may be useful in alloying fine powders of metals such as
aluminum, steel, or iron with magnesium and/or in infusing such
metals with graphenes to produce products such as light weight,
super strong graphene-steel, a magnetic or field weldable
magnesium-iron alloy, or a new family of iron, aluminum, or steel
materials.
[0234] The invention has a number of important features and
advantages. It provides a process for the production of graphenes
and other nanomaterials, utilizing a beneficial vapor-nucleation
cycle enabled by the high energy and heat of a highly exothermic
oxidation-reduction reaction of magnesium and carbon dioxide,
together with integrated feedstock management, cooling of the
reaction products, capture of heat from the reaction, recycling of
energy and materials produced by the reaction, capture of reaction
product, separation and purification of reactor product, and
product functionalization.
[0235] The reaction produces extreme temperatures that cause an
extraordinary breakdown of material bonds, most likely in a vapor
state, followed by a rapid cooling of the vaporized material as it
is forced away from the reaction. This results in the vapor
contacting an extreme declining temperature gradient which causes
the material to beneficially nucleate and coalesce into
predominantly homogeneous nanomaterial forms.
[0236] If desired, other sources of very high temperature,
including other oxidation-reduction reactions involving earth
metals and oxygen bearing molecules, can be utilized instead of the
reaction of magnesium and carbon dioxide to generate the conditions
for the process to produce nanomaterials.
[0237] The invention produces nanomaterials from virtually any
material present in the reaction and exposed to the high energy and
temperature of the reaction, and beneficially produces nanocarbon
and nano-MgO. In the preferred mode, these beneficially formed
nanomaterials are predominantly in the form of homogeneous,
nanoscale, crystalline forms of carbon known as graphenes and MgO
known as periclase.
[0238] The invention consistently produces nanomaterials of similar
morphology and character over time, from batch to batch, with
different embodiments of the process, and when the feedstock is
altered in form and/or pressure, as can be seen in the TEM images
of FIGS. 22a-22c. FIGS. 22a and 22b show samples generated by solid
CO2 (dry ice) on 10 and 20 nanometer scales, and FIG. 22c shows a
sample generated with gaseous CO2 on a 20 nanometer scale. The
samples were produced in batch processes over a period of 18 months
and treated only with hydrochloric acid (HCl). These images show
the remarkable consistency of the graphene morphology over the 18
month period and among the different embodiments of the
process.
[0239] FIGS. 23a and 23b show groups of individual graphene
platelets 186, 187 which were formed on cubical MgO crystalline
substrates, as seen, for example, in FIG. 20. After the graphene
platelets were formed, the MgO crystals were removed chemically,
e.g. by dissolution in hydrochloric acid (HCl), leaving the
graphene platelets adhering to each other on the six sides of a
hollow cube.
[0240] The invention produces single layer graphenes and graphenes
having just a few layers, a valuable nanomaterial with
characteristics that are considered promising for a significant
number of present and future applications. The presence and the
morphology of graphenes have been confirmed by both measured and
observed attributes of the material, including appearance, surface
area, x-ray reflectivity and porosity are consistent with
graphenes.
[0241] The invention also produces nanoscale magnesium oxide
crystals, or pericase. A significant amount of MgO produced by the
reaction can be beneficially vented and captured. The measured
purity of captured MgO produced by the invention is 99.2%, which is
among the highest levels of purity produced. Such very pure nano
MgO may have significant applications in a number of fields,
including medicine, electronics and computing, food, and fire
safety. This MgO is highly suitable to be used for recycling to
magnesium for reuse in the reaction of the invention. The MgO can
be functionalized as a fire retardant for plastics by simple
reaction with water to form Mg(OH).sub.2.
[0242] The invention can also produce unique and potentially
valuable combinations of nanomaterials such as intercalated
graphene-MgO composites and nano spinels. The graphene-MgO
composite materials are believed to be novel materials, and nano
spinels are relatively uncommon. Any material present in the
reaction is likely to be reduced to nanomaterial form as long as it
is a solid at ambient temperature.
[0243] The invention has been found to be highly controllable and
scalable. The feedstock and other material and gaseous inputs can
be varied in size, pressure and chemical composition. This will
produce varied and controllable results, including novel materials,
composites, and non-carbon, non-magnesium nanomaterials.
[0244] The reaction itself can be regulated or controlled by means
such as alteration in the type, nature, morphology, amount, or
pressure of the feedstock, injection of inert gases, cooling or
pre-heating of the injected materials, type of ignition, and type
and size of vessel. This will produce varied and controllable
results.
[0245] The reaction products can also be controlled. The inputs to
the reaction, the energy and temperature of reaction, and other
parameters can be manipulated to control the nature, constituency
and type of reaction products. Due to the high energy and
temperature of the reaction, the reaction may provide way to alter
the quantum mechanical attributes of the graphenes and other
reaction products, including low electrical resistivity, high
electrical conductivity, and/or the magnetic fields issued from the
material. The post-reaction processes for treatment, separation,
and purification of the material can be managed and controlled to
produce varied and controllable products, and intercalated
MgO-graphene composites can be reduced or eliminated by the
addition of a heat cycle to the purification and separation
process.
[0246] The invention is scalable and adaptable. The reaction is
simple and inherently energetic, producing the energy and
temperature required to produce the desired nanomaterials. The
feedstock is common and readily available, and the reaction can be
contained with known materials and methods. Energy and materials
capture and reuse can also be done with known materials and
methods. A number of standard, well-known separation processes and
methods can be employed and optimized, and the invention provides a
novel separation process involving beneficial ejection of MgO. The
reaction products are consistent, controllable, and predictable,
and the invention can be implemented at different scales and in
different forms, ranging from large-scale nanomaterials production
to mobile emissions capture. The MgO reaction product can be
beneficially captured and efficiently recycled for reuse as
magnesium feedstock for the reaction process, thereby avoiding the
impact of large-scale operation of the invention on global demand,
supply, and price of magnesium.
[0247] The invention provides a novel, unique, general, complete
and scalable process for production of nanomaterials, including
graphenes, which overcomes obstacles that have heretofore prevented
the production of carbon nanomaterials from reaching commercial
scale and price points suitable for the many industries interested
in using such materials to improve their products and
solutions.
[0248] Previously known methods and strategies for the production
of graphenes are not amenable to scaling and cost reduction. Known
nanocarbon production processes are energy, materials and labor
intensive. They are reliant on mineral or synthetic graphite
feedstock. However, the supply of graphite is not elastic, and high
quality crystalline graphite, the preferred source material for
graphene production, is in limited supply. The energy required for
many nanomaterials production processes are significant, with known
processes using large amounts of mechanical and/or electrical
energy.
[0249] Known nanocarbon production processes are difficult to
scale. Many of them are difficult to automate and require costly
specialized equipment that would be challenging to scale. While
processes for producing carbon nanotubes have been widely known for
more than ten years and promises to scale and lower price points to
reasonable levels have been made, the production of carbon
nanoproducts is no closer to industrial scale and price than it was
ten years ago.
[0250] The invention does not rely on graphite or relatively scarce
highly crystalline graphite feedstock, but rather on carbon
dioxide, a widely available, low cost gas for the production of
carbon nanomaterial or graphenes. It utilizes a highly exothermic
and beneficial reaction that does not require energy to produce
carbon nanomaterial or graphenes. While some energy is used in
separating and purifying the reaction products, substantially less
energy is used overall by the invention than by other processes,
and the energy footprint of the invention could even approach zero.
The invention recycles important materials, including the magnesium
feedstock and hydrochloric acid used in separation and purification
of the reaction products. The simplicity and vigor of the reaction
enable the invention to be scaled to produce very large volumes of
graphenes. The low cost of carbon dioxide feedstock, the ability to
recycle magnesium feedstock, and the relatively simple separation
and purification protocol make it possible to produce graphenes at
exceptionally low cost, well below the most optimistic estimates
for known processes and roughly equivalent to market prices for
high quality micron-scale graphite powders of comparable
purity.
[0251] The invention can be implemented in various embodiments,
each of which benefits from the unique integrated features and
function of the invention and can be utilized to achieve specific
objectives. Continuous flow embodiments generally will produce
substantially greater volumes of graphenes and other nanomaterials
than batch processes, but batch process can be utilized if more
precise control and manipulation of the graphene product or
customized composite materials are desired. A batch process with
gaseous CO.sub.2 is the most controllable process for determination
of processing variables and allows the graphene material
characteristics to be altered readily. The batch process is similar
to the "pot lines" used in electrolytic aluminum reduction and in
the electric furnace production in steel production. The batch
process is also valuable at the development stage for determining
system operational parameters.
[0252] The modular embodiment can be utilized in the capture and
destruction of CO.sub.2 and particulates in fixed base or large
mobile fossil fuel combustion systems. Also, since MgO is known to
perform as a CO.sub.2 capture agent, the nano MgO reaction product
may be useful in enhancing the performance of an MgO-based CO.sub.2
capture system.
[0253] The invention has significant advantages for the industrial
production of nanomaterials, including scalability, cost, and
product quality, e.g. consistency, reliability, and purity. The
products of the invention have significant applicability to
advanced industrial products, solutions and applications. Graphenes
have unique and proven capabilities in electrochemistry and other
applications, including catalytics, magnetics, heat and mass
transfer, semiconductors, hydrogen storage and advanced materials
construction. The ultra pure nano MgO produced by the invention has
numerous potential applications in many industries, including the
plastics industry, in addition to its use as feedstock for recycled
Mg for reuse in the invention. Other nanomaterials that can be
readily produced by the invention may also be valuable. Nano
Spinels, for example, have application in lithium ion battery
cathodes, and nano MgO may be important as a base constituent in
CO.sub.2 capture.
[0254] The invention provides significant control of the inputs as
well as the reaction and separation processes. By varying the
inputs, temperature, speed, constituents, and other parameters of
the reaction and the post-reaction separation process, the
morphology, constituency and quantum mechanical attributes of the
nano-carbon and other nanoproducts can be controlled.
[0255] It is apparent from the foregoing that a new and improved
process for the production of graphenes and other nanomaterials has
been provided. While only certain presently preferred embodiments
have been described in detail, as will be apparent to those
familiar with the art, certain changes and modifications can be
made without departing from the scope of the invention as defined
by the following claims.
* * * * *