Note: Descriptions are shown in the official language in which they were submitted.
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FIBROUS SOLID CARBON MANIFOLD ASSEMBLY AND
METHOD FOR PRODUCING THE SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fibrous solid carbon
manifold assembly which can be applied to a wide technical field
such as field-emission electron sources ( specifically, needles
of electron guns), various gas adsorbing materials, electrode
materials for batteries, superfine cushioning materials,
superfine elastic materials, and so on, and a method for
producing the fibrous solid carbon manifold assembly.
2. Description of the Related Art
A conventional needle of a field-emission electron gun
or the like was provided as one piece. For this reason, the
needle of the electron gun was obliged to be exchanged for a
new one when the needle was damaged in use.
JP-A-2001-2290806 has proposed a material used as a
field-emission electron source and including: a metallic
substrate containing a metal such as iron as a main component
serving as a core on which nanotube-like fiber of carbon will
be produced; a large number of through-holes formed in the
metallic substrate; and a film of carbon nanotube-like fiber
formed on surfaces of the metal substrate and on circumferential
walls of the through-holes . Methods for producing such carbon
nanotube-like fiber have been proposed in JP-A-2000-203820,
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JP-A-2000-327317, JP-A-2001-48510, etc.
The aforementioned material having carbon nanotube-like
fiber grown on surfaces of a metallic substrate has various
excellent properties.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fibrous
solid carbon manifold assembly in which the number of superfine
graphite filaments such as carbon nanotube-like fiber filaments
is increased more greatly, and a method for producing the fibrous
solid carbon manifold assembly.
In order to achieve the above object , according to first
means of the present invention, there is provided a fibrous
solid carbon manifold assembly including: fibrous bodies
carbonized; and a limitless number of superfine graphite
filaments grown on surfaces of the fibrous bodies, in the inside
of each of the fibrous bodies and in a gap between adjacent
ones of the fibrous bodies.
According to second means of the present invention, there
is provided a fibrous solid carbon manifold assembly including:
fibrous bodies carbonized; a limitless number of superfine
graphite filaments grown and carried on surfaces of the fibrous
bodies , in the inside of each of the fibrous bodies and in a
gap between adjacent ones of the fibrous bodies; and chaff
charcoal powder or marine algae/bacteria containing a
micro-crystal structure of cellulose, and carried on the
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surfaces of the fibrous bodies, in the inside of each of the
fibrous bodies and in the gap between adjacent ones of the fibrous
bodies.
According to third means of the present invention, there
is provided a fibrous solid carbon manifold assembly defined
in the first or second means, wherein the superfine graphite
filaments are hollow filaments.
According to fourth means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly, including the steps of: depositing fine particles
of a catalyst on surfaces of fibrous bodies, in the inside of
each of the fibrous bodies and in a gap between adjacent ones
of the fibrous bodies, for example, by an impregnation method
or an ion exchange method; and bringing the catalyst fine
particle-deposited fibrous bodies into contact with a
hydrocarbon gas such as a methane gas at a high temperature
in an anaerobic condition to thereby carbonize the fibrous bodies
and generate and grow a limitless number of superfine graphite
filaments on the surfaces of the fibrous bodies, in the inside
of each of the fibrous bodies and in the gap between adjacent
ones of the fibrous bodies.
According to fifth means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly, including the steps of : carbonizing fibrous bodies
in another place or as a pre-treatment process in the same
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reaction furnace; depositing fine particles of a catalyst on
surfaces of the carbonized fibrous bodies, in the inside of
each of the f fibrous bodies and in a gap between ad j acent ones
of the fibrous bodies; and bringing the catalyst fine
particle-deposited fibrous bodies into contact with a
hydrocarbon gas at a high temperature to thereby generate and
grow a limitless number of superfine graphite filaments in the
inside of each of the carbonized fibrous bodies and in the gap
between adjacent ones of the fibrous bodies.
According to six means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly defined in the fourth or fifth means, wherein: the
catalyst is constituted by metallic fine particles such as nickel
fine particles; and the step of bringing the catalyst fine
particle-deposited fibrous bodies into contact with a
hydrocarbon gas to generate and grow superfine graphite
filaments is carried out while a magnetic field is applied to
the fibrous bodies.
According to seventh means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly defined in the fourth or fifth means , further including
the step of removing (for example, polishing) the catalyst fine
particles deposited on head portions of the graphite filaments .
According eighth means of the present invention, there
is provided a method of producing a f fibrous solid carbon manifold
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assembly defined in the fourth or fifth means , further including
the steps of : forming a filament set layer by using a mixture
of each of the grown graphite filament-containing fibrous bodies
and a binder such as a high-molecular binder; and polishing
a surface of the filament set layer to thereby reveal the graphite
filaments.
According to ninth means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly defined in the eighth means, wherein: the step of
forming the filament set layer is carried out by applying or
bonding the mixture of each of the fibrous bodies and the binder
onto a support member such as a metal plate; and the method
further includes the step of releasing the support member from
the filament set layer after a surface of the filament set layer
is polished.
According to tenth means of the present invention, there
is provided a method of producing a fibrous solid carbon manifold
assembly defined in the ninth means , wherein : the step of forming
the filament set layer is carried out by forming a water-soluble
adhesive layer such as a polyvinyl alcohol layer on the support
member and applying or bonding the mixture of each of the fibrous
bodies and the binder onto the water-soluble adhesive layer;
and the step of releasing the support member from the filament
set layer is carried out by dissolving the water-soluble adhesive
layer in water.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a sectional view of an apparatus for producing
a fibrous solid carbon manifold assembly according to an
embodiment of the invention;
Fig. 2 is a view for explaining an example of the form
of the fiber base material used in the invention;
Fig. 3 is a view for explaining another example of the
form of the fiber base material used in the invention;
Fig. 4 is a view for explaining a further example of the
form of the fiber base material used in the invention;
Fig. 5 is a typical view for explaining a process of growth
of a graphite filament;
Fig. 6 is a typical view showing a state in which graphite
filaments are grown on a surface of a fibrous body;
Fig. 7 is a typical view showing a state in which graphite
filaments are grown in the inside of a fibrous body;
Fig . 8 is a typical view showing a state in which graphite
filaments are grown in a gap between two fibrous bodies;
Fig. 9 is a sectional.view of an intermediate product
having a filament set layer formed therein;
Fig. 10 is a sectional view of a display device formed
by using the fibrous solid carbon manifold assembly;
Fig. 11 is a top view of a substrate printed with catalytic
ink according to another embodiment of the invention;
Fig. 12 is a sectional view of the substrate printed with
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the catalytic ink; and
Fig. 13 is a sectional view showing a state in which
graphite filaments are grown on the substrate.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention will be described below
with reference to the drawings. Fig. 1 is a sectional view
of an apparatus for producing a fibrous solid carbon manifold
assembly according to an embodiment of the invention . Figs .
2 to 4 are views for explaining the form of a fiber base material
used in the invention. Fig. 5 is a typical view for explaining
a process of growth of a graphite filament. Fig. 6 is a typical
view showing a state in which graphite filaments are grown on
a surface of a fibrous body. Fig. 7 is a typical view showing
a state in which graphite filaments are grown in the inside
of a fibrous body. Fig. 8 is a typical view showing a state
in which graphite filaments are grown in a gap between two fibrous
bodies. Fig. 9 is a sectional view of an intermediate product
having a filament set layer formed therein. Fig. 10 is a
sectional view of a display device formed by using the fibrous
solid carbon manifold assembly.
A material prepared by winding a wide sheet spirally into
a roll and pressing the roll vertically into a flat plate shape
as a whole as shown in Fig. 2 may be used as the fiber base
material 1 which serves as a graphite filament carrier as will
be described later . Or a material prepared by piling a large
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number of cut sheets having a predetermined width and pressing
the pile vertically into a flat plate shape as a whole as shown
in Fig. 3 may be used as the fiber base material 1. Or a material
prepared by folding a wide sheet alternately and pressing the
folded sheet vertically into a flat plate shape as a whole as
shown in Fig. 4 may be used as the fiber base material 1.
The fiber base material 1 is made of fabric or nonwoven
fabric of synthetic fiber, natural fiber or inorganic fiber,
paper, felt, implanted matter, corrugated board matter, etc.
For example, polyamide, polyester, polyethylene
terephthalate, acrylonitrile, polyvinyl alcohol, etc. can be
used as the material of the synthetic fiber. For example, cotton,
hemp, silk, wool, etc. can be used as the material of the natural
fiber. For example,glassfiber,aluminafiber,silica-alumina
f fiber , carbon f fiber , etc . can be used as the inorganic f fiber .
The fiber base material 1 may be hybridized with marine
algae, bacteria, etc. containing chaff charcoal powder of
carbonized and pulverized chaff or cellulose microfibril (fine
cellulose molecular crystal structure).
A catalyst which serves as a core on which graphite
filaments will be produced is carried on a surface of the fiber
base material 1 and in the inside of the fiber base material
1. Examples of the catalyst used include : ametal such as nickel,
cobalt, iron, copper or molybdenum; an alloy of at least two
selected from these metals ( such as Ni-Co, Ni-Fe-Co, Ni-Mo or
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Fe-Ni-Mo ) : and a mixture of the metal or alloy and a precious
metal such as platinum, rhodium or silver.
Specifically, for example, a mixture solution of lower
alcohol and nickel acetate can be used. When the fiber base
material 1 is immersed into this solution and dried, the fine
particle-like catalytic metal is carried on the nearly whole
surface of the fiber base material 1 and in the nearly whole
inside of the fiber base material 1 by an impregnation method
or an ion exchange method.
The fiber base material 1 with the catalyst is set in
a reaction chamber 2 shown in Fig. 1. A plurality of stages
each having a frame member 3 and a gas-permeable bearing member
4 placed on the frame member 3 and made of a metallic net, an
expanded metal, or the like, are provided in the reaction chamber
2. The fiber base material 1 with the catalyst is placed on
each of the stages.
A gas inlet 9 is provided at a lower portion of the reaction
chamber 2. A gas outlet 10 is provided at an upper portion
of the reaction chamber 2. Magnetic field generating means
made of a single or laminated magnet or the like is provided
on the top of the reaction chamber 2 . Magnetic field and magnetic
flux are generated vertically in the reaction chamber 2 by the
magnetic field generating means 5. The inside of the reaction
chamber 2 is kept in a high-temperature state by a heater (not
shown). The reaction temperature is preferably selected to
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be in a range of from 500° C to 900° C, particularly not lower
than 6 50° C .
Gas-like hydrocarbon or a mixture containing hydrocarbon
is introduced into the reaction chamber 2 through the gas inlet
9. For example, chain hydrocarbon such as alkane, alkene or
alkyne, alicyclic hydrocarbon or aromatic hydrocarbon can be
used as the hydrocarbon . For example , natural gas or petroleum
gas can be used as the hydrocarbon-containing mixture. As
occasion demands , inert gas such as argon or nitrogen may be
mixed with the hydrocarbon or the hydrocarbon-containing
mixture.
When methane gas is used as the hydrocarbon,
monocrystalline, polycrystalline or sooty graphite filaments
having a multilayer structure of six-membered rings (graphene)
are generated and grown by the following chemical reaction under
the presence of the aforementioned catalyst. The chemical
reaction serves as a reaction for directly discomposing methane
and also as a reaction for producing by-product pure hydrogen
simultaneously.
CH4 C + 2H2
Fig. 5 is a view typically showing a state in which a
graphite filament is generated and grown. First, the fine
particle-like catalytic metal serves as a core on which a
graphite filament will be produced. Carbon atoms are trapped
in the catalyst 7 which gets into a substantially molten state
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because of the high temperature. Then, the carbon atoms are
extruded into a tube shape from the catalyst 7 to start the
production of a hollow graphite filament 6. When entrapment
and extrusion of carbon atoms through the catalyst 7 is repeated
in the aforementioned manner, the hollow graphite filament 6
grows gradually. Also when the graphite filament has another
shape, the graphite filament can grow.
When a magnetic material such as Ni, Co, Fe, Ni-Co,
Ni-Fe-Co, Ni-Mo or Fe-Ni-Mo as described above is used as the
catalyst 7 in the condition that magnetic field is formed in
a predetermined direction by the magnetic field generating means
as shown in Fig. 1, graphite filaments 6 grow in the
predetermined direction (magnetic field direction) because of
the influence of the magnetic field. Accordingly, the
directions of growth of the graphite filaments 6 can be made
uniform as well as the growth of the graphite filaments 6 can
be accelerated.
Incidentally, it is generally said that there is a
possibility that ametalmaybe demagnetized when the temperature
of the metal reaches its Curie point ( a . g . , Fe : 800° C , Ni :
350° C ) .
A magnetic resonance phenomenon or the like however occurs
because a substance vibrates finely atomistically. For this
reason, it is conceived that each graphite filament 6 grows
in a predetermined direction because the catalyst 7 made of
metallic fine particles is influenced by the magnetic field
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under the aforementioned high-temperature condition.
Each graphite filament 6 can be grown substantially
linearly or can be grown non-linearly into a coiled spring shape,
a "U" shape , an " S " shape , a "W" shape , a " 9 " shape , a circular
arc shape or the like , in accordance with the way of applying
the magnetic field. A set of graphite filaments 6 each grown
nonlinearly into a coiled spring shape or the like can be used
as a micro cushioning or elastic material such as a micro spring
because the graphite filament set has micro elasticity.
Figs . 6 to 8 are views typically showing states in which
the graphite filaments 6 are generated and grown. The fiber
base material 1 used as a carrier for carrying the graphite
filaments 6 has been already carbonized because of the
high-temperature and oxygen-free condition in the reaction
chamber 2. A limitless number of graphite filaments 6 are
generated and grown on a surface of each of carbonized fibrous
bodies 8 constituting the fiber base material 1 as shown in
Fig. 6, in the inside of each of the fibrous bodies 8 as shown
in Fig. 7 and in a gap between adjacent ones of the fibrous
bodies 8 as shown in Fig. 8.
Although Figs. 6 to 8 show graphite filaments 6 grown
substantially linearly, the graphite filaments 6 may be
constituted by a mixture of non-linearly grown graphite
filaments 6 and linearly grown graphite filaments 6 or by
non-linearly grown graphite filaments 6 as a main component
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in accordance with contrivance of the way of applying the
magnetic field.
Although Figs. 6 to 8 show the case where states of a
surf ace of a f fibrous body 8 , an ins fide of a f fibrous body 8 and
a gap between two fibrous bodies 8 are drawn separately, a
limitless number of graphite filaments 6 are actually grown
in every place of one fiber base material 1 so that the states
as shown in Figs. 6 to 8 are mixed together.
Each graphite filament 6 has a length ranging from about
1 im to about 100 im and a thickness ranging from about 10 nm,
inclusively, to about 1 im, exclusively.
Although this embodiment has shown the case where the
fiber base material 1 is carbonized in the reaction chamber
2, the invention may be also applied to the case where the fiber
base material 1 is carbonized at a high temperature in an
anaerobic condition by another process or by a pre-treatment
process in the same reaction furnace before the fiber base
material 1 is set in the reaction chamber 2.
After the first reaction, the same catalytic treatment
as described above is applied to perform a second growth reaction .
While grown in the lengthwise direction, the graphite filaments
6 are grown fat as a whole simultaneously. If such growth is
required, the aforementioned catalytic treatment and the
reaction for generating the graphite filaments 6 can be repeated
so many times. The number of reactions depends on the final
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state of each of the graphite filaments 6. It is generally
preferable that the number of reactions is 1 or 2.
Hydrogen gas produced by the reaction of generating the
graphite filaments 6 is taken out through the gas outlet 10
shown in Fig. 1. To prevent explosion due to the hydrogen gas,
an adequate amount of inert gas (such as Ar, N2, etc. ) may be
mixed with the hydrocarbon gas supplied as a raw material in
advance.
A method for producing needles of an electron gun for
display device by using the fiber base material having a
limitless number of graphite filaments grown and carried thereon
in the aforementioned manner will be described below.
The fiber base material having the graphite filaments
grown and carried thereon in the aforementioned manner is
mechanically squashed and pulverized to form fine particles.
A high-molecular material (such as an epoxy resin or an
ultraviolet-setting resin) or a glass material used as a binder
is immersed in or kneaded with the fine particles . A plate-like
support member constituted by a metal plate, a ceramic plate,
or the like, is used and the aforementioned kneaded mixture
is expanded like a sheet on the support member and solidified
so that a filament set layer endurable in the polishing step
(which will be described later) is formed. On this occasion,
a water-soluble adhesive agent such as polyvinyl alcohol (PVA)
or carboxymethyl cellulose ( CMC ) is applied onto a surf ace of
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the support member and dried in advance so that the filament
set layer is applied onto the water-soluble adhesive' layer and
dried.
Fig . 9 is a sectional view showing an intermediate product
having the filament set layer formed thereon. As shown in Fig.
9 , the filament set layer 13 having a predetermined thickness
is formed on a support member 11 through a water-soluble adhesive
layer 12.
In this example, a fiber base material having graphite
filaments grown and carried thereon is pulverized in use.
Alternatively, after a fiber base material having graphite
filaments grown and carried thereon is mechanically squashed
into a predetermined shape such as a plate shape, the inside
and surface of the fiber base material may be impregnated or
kneaded with a high-molecular material or a glass material as
a binder and then the fiber base material may be fixed onto
a surface of the support member.
The water-soluble adhesive layer 12 may be replaced by
a double-sided pressure-sensitive adhesive tape.
Then, the surface of the filament set layer 13 is polished
with a grindstone so that graphite filaments not covered with
the binder are revealed on the surface. The limitless number
of graphite filaments revealed in the aforementioned manner
form needles of an electron gun. On this occasion, low accuracy
of the order of tens of im will do for the surface roughness .
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This is because the thickness of a vacuum layer enough to receive
tip portions of the needles of the electron gun (revealed
graphite filaments) is about 100 im. The reason why the vacuum
layer is made relatively thick in the aforementioned manner
is that reduction in the cost of ceramic balls (e. g., glass
hollow balls ) interposed as spacers for forming the vacuum layer
can be attained.
Although this embodiment has shown the case where the
filament set layer 13 is polished with a grindstone, another
means such as a dicing saw may be used. In addition, in order
to polish the filament set layer 13 , a superfine polishing method
such as CMP ( Chemical Mechanical Polishing ) which is a polishing
technique used in the semiconductor-related field may be used
for performing high-precision processing to make the
aforementioned vacuum layer thinner.
The filament set layer 13 needs to come into contact with
an electrode. Therefore, the support member 11 of the
intermediate product shown in Fig. 9 is released. Then, the
rear surface of the filament set layer 13 is slightly polished
so that the graphite filaments are revealed also on the rear
surface . Because the support member 11 is integrated with the
filament set layer 13 by the water-soluble adhesive layer 12
in the aforementioned manner, the support member 11 can be
released easily when the water-soluble adhesive layer 12 is
dissolved in water.
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Fig. 10 is a sectional view of a display device using
the electron gun. In Fig. 10, the reference numeral 14
designates an electrode patterned into a predetermined shape;
and 13, a filament set layer placed on the electrode 14. A
limitless number of graphite filaments 6 exposed on the front
surface of the filament set layer 13 serve as needles of an
electron gun. The graphite filaments 6 are brought into contact
with each other or electrically connected to one another through
the carbonized fibrous bodies 8.
The reference numeral 15 designates a vacuum layer; 16 ,
a fluorescent substance layer; and 17, a glass layer. Ceramic
balls ( not shown ) which serve as spacers are interposed between
the filament set layer 13 and the fluorescent substance layer
16 to thereby secure the thickness of the vacuum layer 15.
Figs. 11 to 13 axe views showing another embodiment of
the invention. In thisembodiment,desired patternsor designs
are drawn on a substrate 18 such as a ceramic substrate or a
metal substrate with catalytic ink 19 by printing as shown in
Figs. 11 and 12. For example, the catalytic ink 19 is a solution
composed of a solvent of organic liquid such as alcohol or/and
water, and a compound containing a catalytic component such
as nickel acetate and dissolved in the solvent . The catalytic
content of the solution is preferably in a range of from about
~ by weight to about 30 ~ by weight.
The substrate 18 on which the catalytic ink 19 is deposited
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is placed on a bearing member 4 shown in Fig. 1 and brought
into contact with hydrocarbon gas in a high-temperature
condition to grow graphite filaments 6 on the substrate 18 to
thereby form a filament set layer 13 as shown in Fig. 13. The
grown graphite filaments 6 are influenced by the magnetic field
formed by the magnetic field generating means 5 so that the
direction of growth thereof is substantially uniform. The
planar shape of the formed filament set layer 13 is the same
as that of the printed pattern of the catalytic ink 19.
Although this embodiment has shown the case where a fiber
base material having graphite filaments grown and carried
thereon is pulverized into fine particles so that a mixture
of the fine particles and a binder is molded, the invention
may be also applied to the case where the aforementioned fiber
base material having graphite filaments grown and carried
thereon is used directly without pulverization in accordance
with use purpose.
The fibrous solid carbon manifold assembly according to
the invention can be applied not only to the field-emission
electron source but also to various industrial fields, for
example, materials for adsorbing/occluding various kinds of
gases such as hydrogen gas, deodorants, filters, electrodes
for batteries such as fuel batteries or solar cells,
electromagnetic absorbing (or shielding] materials, probes,
micro cushioning materials, micro elastic materials, etc.
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As described above, in accordance with the invention,
a limitless number of superfine graphite filaments are grown
on surfaces of fibrous bodies, in the inside of each of the
fibrous bodies and in a gap between adjacent ones of the fibrous
bodies . The fibrous bodies can carry catalytic fine particles
in every place such as the surfaces of the fibrous bodies, the
inside of each of the fibrous bodies and the gap between adjacent
ones of the fibrous bodies . Accordingly, the number of graphite
filaments can be increased limitlessly.
With the increase in the number of graphite filaments
in the aforementioned manner, functional improvement of the
graphite filaments, e.g. , uniform emission of field electrons,
increase in the quantity of adsorbed/occluded gas and
improvement of the electromagnetic absorbing (or shielding)
function, or achievement of a micro cushioning material or a
micro elastic material can be attained.
In addition, when a magnetic field is applied, the shape
of each of the graphite filaments can be controlled to any shape
such as a linear shape or a non-linear shape.
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