JP3417869B2 - Method of forming carbon bonded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a joined body of carbon fibers such as carbon tubes and carbon fibers.

[0002]

2. Description of the Related Art Carbon fibers typified by carbon nanotubes and carbon nanofibers are made of hydrogen storage materials,
In the field of recording materials and the like, it has recently received a great deal of attention as a new high-performance material.

[0003] These materials are mainly produced by vacuum deposition, CV
It is synthesized by a catalytic reaction with a transition metal such as Fe, Co, or Ni using an evaporation method from a gas phase such as the D method. However, the carbon nanofibers synthesized in this manner are basically grown randomly, and those having various lengths, thicknesses, and directions are collected in a cotton-like state. For this reason, there is a problem that the handleability is poor, and especially when used as a hydrogen storage material, there is no method of holding the container other than collecting and filling the container or the like.

[0004] Further, there is a problem that controllability is extremely difficult in a state where control of an amount per unit area is required. Furthermore, in the case of a hydrogen storage material typified by carbon nanotubes, the catalyst layer used during the synthesis mainly remains at the end of the tube even after the synthesis, so that hydrogen is efficiently stored in the tube during the storage of hydrogen. There was a problem that it was not possible to occlude.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. That is, a method of stably holding a certain amount of carbon fibers,
The present invention proposes a method for efficiently storing hydrogen in carbon fibers.

[0006]

According to the present invention, there is provided a method for forming a carbon bonded body, comprising the steps of: depositing nickel oxide particles on a substrate by sputtering; reducing the nickel oxide particles to form a nickel catalyst; On the substrate on which the catalyst has been deposited, heat C
A step of producing carbon nanotubes or carbon fibers by the VD method so that the nickel catalyst remains at the tip, and adding a 4a transition metal and a run to the tip of the carbon nanotube or carbon fiber.
At least one metal element selected from tanoid metals
Reaction between the contained metal brazing material and the nickel catalyst
Ri, is characterized in that a step of bonding the substrates.

In the method for forming a carbon bonded body according to the present invention, the bonding of the base material may be performed before the carbon tube is wetted by capillary action in the distal end tube of the carbon tube.
It is characterized by being joined via the metal brazing material layer.

Further, in the method for forming a carbon joined body according to the present invention, the 4a transition metal or the lanthanoid gold may be used.
A eutectic alloy of a metal and a 3d transition metal .

[0009]

Further, in the method for forming a carbon bonded body according to the present invention, the bonding step of the base material may include:
Ceramics such as alumina, magnesia, zirconia,
It is characterized by using pure metals or alloys such as aluminum and its alloys, stainless steel and hydrogen storage alloys.

In general, carbon fibers having a submicron diameter, such as carbon nanotubes and carbon nanofibers, have a low density at the center of the fiber and have a narrow space along the longitudinal direction at the center. According to the present invention, a low-density phase or a narrow space portion is used to join a metal or ceramic base material with a brazing material. At this time, the brazing material is present in a form of penetrating into the center of the carbon tube or carbon fiber due to the capillary phenomenon and is joined.

[0012] The brazing material layer used in the joining of the present invention has four layers.
a Fe containing a transition metal or a lanthanoid metal,
It is a eutectic alloy system of Ni, Co and other 3d transition metals. As a method of supplying the brazing material layer, one or more of 4a transition metal or lanthanoid metal and Fe, Ni, C
An eutectic alloy with a 3d transition metal such as o may be supplied to the joint between the base material and the carbon fiber.

As another method, there is a method in which a 4a transition metal or a lanthanoid metal is bonded to a catalyst layer by a solid phase reaction or a liquid phase reaction using a carbon fiber synthetic catalyst layer.

The eutectic alloy system of at least one of the 4a transition metal or the lanthanoid metal and the 3d transition metal containing Fe, Ni, and Co is not only known as a brazing filler metal layer for joining, Also known as hydrogen storage alloy.
When a carbon fiber typified by a carbon tube is used as a hydrogen storage material, the remaining catalyst layer hinders the hydrogen storage efficiency in the tube. In the present invention, the remaining catalyst layer is made of a hydrogen storage alloy to increase the efficiency of storing hydrogen in the tube.

Further, instead of the 4a transition metal, Pd, Pt
May be alloyed with Fe, Co, and Ni, and used as a brazing material layer.

By forming these composites of carbon fibers and a hydrogen storage alloy or a composite of the composite of carbon fibers and a hydrogen storage alloy and a metal or ceramic substrate, the filling rate of the carbon fibers can be reduced. In addition to improving the hydrogen storage capacity, the hydrogen storage capacity for carbon fibers is also improved.

The procedure of the method for forming a carbon bonded article according to the present invention will be further described below.

Carbon fibers such as nanotubes and nanofibers are synthesized in a pipe-shaped or filter-shaped container or the like in view of the ease of bundling after synthesis. At this time, the catalyst is arranged at the closed end of the pipe or the filter, and is grown in the longitudinal direction of the pipe. An example of the synthesis of carbon fiber is illustrated in FIG.

After the synthesis, the end side where the catalyst is present is joined to the base material via the brazing material layer. At this time, it is preferable to perform a heat treatment by arranging a metal that causes a eutectic reaction with the catalyst between the substrate and the catalyst. FIG. 2 shows an example of the joining process.

As a system that causes a eutectic reaction with a catalyst, 4a
Transition metals, lanthanoid metals, and the like can be given.
These 4a transition metals and lanthanoid metals are formed by physical and chemical vapor deposition such as sputtering and CVD.
It can also be coated on a catalyst containing carbon fibers.

4a Joining performed after coating a brazing material layer such as a transition metal or a lanthanoid metal can be performed in a vacuum or in an inert atmosphere.

In the form after the joining, the brazing material alloyed with the catalyst has penetrated into the tube at the center of the carbon fiber by the capillary phenomenon, and has been chemically and physically joined to the base material side. I have.

The base material as the joining partner material includes ceramics such as alumina, magnesia, and zirconia; aluminum and its alloys; and pure metals or alloys such as stainless steel and hydrogen storage alloys.

By forming a carbon bonded body by such a method, it is possible to obtain a carbon fiber which has a constant filling rate per unit area and volume, has high adhesion to a substrate, and is easy to handle. it can.

Further, by adopting a structure in which an alloy layer containing a 4a transition metal or a lanthanoid metal is joined to the end of a carbon tube or a carbon fiber, when used as a hydrogen storage, a high capacity is required. A hydrogen storage body can be obtained.

[0026]

Embodiments of the present invention will be described below.

Example 1 Nickel oxide particles having a particle size of 20 nm were formed on an alumina disk by sputtering, and then the disk was placed on the bottom of a cylindrical container made of quartz and placed in an electric furnace. It was introduced and reduced at 600 ° C. in a hydrogen atmosphere to produce a nickel catalyst.

Subsequently, a mixed gas of ethylene and hydrogen at a ratio of 1: 4 was introduced into the same furnace, and carbon nanotubes were synthesized by a thermal CVD method. At this time, the carbon nanotubes grew at the end opposite to the bottom where the alumina disk was placed in the cylindrical container, and the nickel catalyst was present at the tip.

After the synthesis of the fiber, the carbon tube was taken out together with the quartz cylindrical container, and heated in a vacuum furnace at 960 ° C. for 5 minutes while keeping the nickel disk in contact with the alumina disk on which the titanium film was formed. .

After being heated and taken out of the furnace, the carbon nanotubes were bonded to the alumina disk via the alloy layer formed by the eutectic reaction between titanium and nickel. In more detail, the joint was observed, and it was found that a eutectic alloy brazing material layer of nickel and titanium had penetrated into a narrow space near the center of the carbon nanotube by capillary action.

After the synthesis of the carbon tube, the joined body is
In a stainless steel container, the volume ratio of the carbon tube is 3
As a result of filling up to 0% and performing hydrogen storage evaluation, 1
It was found that 5 t% of hydrogen was absorbed per carbon under the conditions of 0 atm and 80K.

On the other hand, synthesis was performed using the same catalyst as in Example 1 at the same synthesis temperature, synthesis time, and synthesis gas type, and hydrogen storage evaluation was performed using a carbon tube that was not synthesized. Under the condition of 10 atm-80K, only 3 wt% of hydrogen was absorbed per carbon.

When an attempt was made to fill a stainless steel container having the same shape, it was possible to fill only up to 10% by volume.

Example 2 Iron oxide particles having a particle size of 30 nm were precipitated from a liquid phase on a quartz disk. Thereafter, the disk was introduced into an electric furnace and reduced at 600 ° C. in a hydrogen atmosphere to produce an iron catalyst.

Subsequently, a 1: 1 mixed gas of ethylene and hydrogen was introduced into the same furnace, and carbon nanofibers were synthesized by a thermal CVD method. At this time, the carbon nanofibers grew on the opposite end from the bottom where the quartz disk was arranged in the cylindrical container, and the tip thereof had an iron catalyst.

After the synthesis of the tube, the carbon nanofibers were taken out together with the quartz cylindrical container, and transferred into a vacuum furnace while keeping the zirconium thin film and the iron catalyst portion in contact with each other.
From the back surface of the zirconium thin film, local condensing heating was performed by a lamp, and the iron catalyst and the zirconium thin film were bonded by reacting in a solid phase.

After joining, when the iron catalyst and the zirconium were taken out of the furnace, they were alloyed, and through the alloy layer,
The zirconium thin film and the carbon nanofiber were joined.

After synthesizing the carbon nanofiber, the above-mentioned bonded body was filled in a stainless steel container until the volume ratio of the carbon nanotube was 35%, and the hydrogen absorption was evaluated. It was found that 2 wt% of hydrogen was absorbed per carbon.

On the other hand, the hydrogen absorption of carbon nanofibers that were not synthesized and bonded were evaluated using the same catalyst as in Example 1 and using the same catalyst at the same synthesis temperature, synthesis time, and synthesis gas type. Under the condition of 10 atm-80K, only 0.5 wt% of hydrogen was absorbed per carbon.

When an attempt was made to fill a stainless steel container having the same shape, the filling could be performed only up to 15% by volume.

[0041]

As described above, it is possible to form an aggregate of carbon fibers having a high bondability to a substrate with a constant length and a constant area density.

By interposing a hydrogen storage alloy at the joint, a composite of carbon fiber and a substrate having particularly high hydrogen storage efficiency can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a carbon fiber synthesis process.

FIG. 2 is a diagram illustrating an example of a bonding process of carbon fibers.

────────────────────────────────────────────────── (5) References JP-A-11-139815 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 31/02 D01F 9/08-9 / 32 C04B 37/00-37/04

Claims (4)

(57) [Claims] (1) Sputtering nickel oxide particles on a substrate
And then reduce it to form a nickel catalyst.
That the step, on the substrate the nickel catalyst is deposited, heat C
By the VD method , the nickel catalyst is left at the tip.
Carbon nanotubes or carbon fibers
Process and the carbon nanotube or carbon
4a transition metal and run
At least one metal element selected from tanoid metals
Reaction between the contained metal brazing material and the nickel catalyst
Ri, mosquitoes, characterized in that a step of bonding the substrate
A method for forming a carbon bonded body. 2. The method according to claim 2 , wherein the step of bonding the base material comprises:
Wet in the tube at the tip of the tube by capillary action
Characterized by being joined via the metal brazing material
A method for forming a carbon joined body according to claim 1. 3. The metal brazing material according to claim 1, wherein the metal is a 4a transition metal.
Or a eutectic alloy of a lanthanoid metal and a 3d transition metal
3. The shape of the carbon joined body according to claim 2, wherein
Method. 4. The bonding step of the base material , wherein the base material includes:
Ceramics such as alumina, magnesia, zirconia,
Aluminum and its alloys, stainless steel, hydrogen storage alloy, etc.
4. A pure metal or an alloy according to claim 3 is used.
A method for forming a carbon joined body according to the above.