JPH0477307A - Fine graphite powder and its production - Google Patents

Abstract

PURPOSE:To obtain fine graphite powder of the submicron order with the height of the laminated carbon network faces, interfacial distance and cross-sectional area in the specified direction specified by disintegrating a carbon material having the structure in which fine graphite network faces are originally collected. CONSTITUTION:Although any starting carbon material having the above- mentioned structure can be used, a microstructure in which graphite network faces are laminated in the one-dimensional direction is preferably used. The fine fibrous carbon formed from CO under the catalysis of fine metallic particles, in which carbon network faces are uniformly laminated perpendicularly to the fiber axis and having a high degree of graphitization is exemplified as the carbon material, and the material is disintegrated. Consequently, a fine graphite powder having <=0.5mu height of the laminated carbon network faces, 3.354-3.470Angstrom interfacial distance and <=1mu<2> cross-sectional area perpendicular to the laminating direction of the fine graphite powder, having a reactangular or flat elliptic cross section and with the major axis being >=2 times the minor axis is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to fine graphite powder, and more particularly to fine graphite powder in which carbon mesh surfaces are aligned in one direction, and a method for producing the same.

[Conventional technology 1 Graphite fine powder has electrical conductivity, thermal conductivity, mobility, heat resistance,
It has excellent chemical stability and is widely used as conductive coatings, industrial lubricants, antistatic agents, battery materials, heat dissipation materials, and additives for various composite materials.

For these applications, it is often required that the graphite fine powder has a size of 1 μm or less.

The conventional method for producing fine graphite powder is to mechanically crush and classify lumps of natural graphite or artificial graphite, but graphite is a highly anisotropic material made of laminated layers of developed carbon networks. Therefore, the carbon mesh surface itself is difficult to break, but on the other hand, the layered direction of the mesh surface is soft and slippery, and such materials can be crushed to 1 μm or less in any three-dimensional direction. That is difficult.

In addition, although it is possible to reduce the particle size to 1 μm or less by mechanical crushing in this way, it is extremely difficult to reduce the total size to 1 μm or less. In order to obtain fine powder, an extremely large amount of crushing energy is required.

As a means to solve this problem, there are known methods such as graphitizing carbon powder that is easy to crush, such as coke, and heat treating carbon black, which is originally a fine carbon powder with a particle size of 1 μm or less. It is being

[Problems to be Solved by the Invention] However, in the method using coke or the like, it is difficult to obtain submicron-order fine graphite powder, which is the intended purpose, because it aggregates and coalesces during the graphitization process.

On the other hand, even in the method of graphitizing carbon black, increasing the degree of graphitization itself has its own problems - and, like the coke crushing method, there is also the problem of agglomeration and coalescence during the graphitization process.

In both cases, when we focus on the microstructure of the fine graphite powder, we find that it is not a graphite structure in which the carbon network surfaces are neatly layered, but a disordered structure, which is different from the structure that is imagined when we call it graphite. Many have different structures.

Furthermore, in both cases, 2000
It is necessary to process at a high temperature of .degree. C. or higher, which poses difficulties in terms of production costs as well as limitations in terms of equipment, including handling.

[Means for Solving the Problem] As a result of intensive study, the inventors of the present invention found that if they selected a starting carbon material with a structure in which fine graphite networks were originally gathered together and crushed it, the above-mentioned results could be achieved. Not only can we solve problems that were difficult to solve with conventional technology, but we are also able to produce graphite fine powder with an almost ideal morphology and microstructure, which was previously thought to be impossible. As a result, the present invention was completed.

That is, an object of the present invention is to provide an unprecedented graphite fine powder having a particle size on the order of submicrons and a controlled microstructure in which the graphite network surface is oriented in one direction, and a method for producing the same. It is in.

This purpose is to provide a fine graphite powder in which carbon mesh surfaces are substantially stacked in one direction, the stacking height of the carbon mesh surfaces of the graphite fine powder is 0.5 μm or less, and the distance between the surfaces (d002) is 3.354 to 3.470 people, and the area of the cross section perpendicular to the stacking direction of the graphite fine powder is 1 μm or less,
Graphite fine powder is characterized in that the cross-sectional shape is rectangular or flat elliptical, and the major axis is at least twice as long as the minor axis, and the carbon network surface is substantially in the longitudinal direction of the fiber. Graphite fine powder is obtained by crushing vertically stacked fibrous carbon along the carbon network plane, so that the carbon network planes are substantially stacked in one direction, and the carbon network planes of the graphite fine powder are stacked. Height is 0
．． 5 μm or less, and the distance between the surfaces (d002) is 3.
354 to 3.470 people, and the area of the cross section perpendicular to the stacking direction of the graphite fine powder is 1 μm2 or less, the shape of the cross section is rectangular or flat elliptical, and the long axis is short. This can be easily achieved by a method for producing graphite fine powder characterized in that the particle size is at least twice that of the shaft.

The present invention will be explained in detail below.

The starting carbon material used in the present invention is not particularly limited as long as it has a structure in which fine graphite network surfaces are assembled, but it has a microstructure in which graphite network surfaces are stacked in a one-dimensional direction. Something is desirable.

Examples of such carbon materials include ribbon-shaped carbon fibers (patent application No. 1-286673) for which the present inventors have applied for a patent.
) can be mentioned.

The carbon fibers are fine fibrous carbon produced by the catalytic action of ultrafine metal particles using carbon oxide as a raw material, and have a fiber width of 0.05 to 0.7 μm and a length of several to several tens of μm,
It has a very characteristic microstructure in which the carbon network planes are uniformly stacked perpendicular to the fiber axis, and has a high degree of graphitization even though it is produced at a relatively low temperature.

For example, the d002 (distance between carbon network planes) of the fiber obtained by the reaction at 700°C is 3.366, which is very close to the value of 3.354 for graphite single crystal, and the value of Mering and Me
The degree of graphitization is estimated to be 86% when calculated from the ire formula.

To obtain such highly graphitized carbon, it is usually 2500~
Considering that heat treatment at 3000°C is required, fibers with a high degree of direct graphitization were obtained at an unusually low temperature.

The fibrous carbon is used together with a mixed gas of carbon oxide and hydrogen (mixing ratio 1:1) as a catalyst raw material for fiber growth. Iron pentacarbonyl is added so that the total carbon atom weight is 100 and the iron weight is 1 to 20. 550 to 800
60e/in a reaction tube placed in an electric furnace set at °C
It can be obtained by continuous insertion at a rate of around hr. (
Patent application No. 1-286673).

Fibrous carbon, which has an ideal microstructure and morphology as a starting material for obtaining fine graphite powder, in which submicron-order graphite obtained in this manner is laminated in a one-dimensional direction to form a fiber, is first By crushing as shown in the figure, fine graphite powder with a controlled microstructure is obtained.

As a method of crushing the fibrous carbon, after various studies, it was found that mechanical crushing methods such as using a jet mill or using ultrasonic waves may be used. It is particularly preferable to disintegrate by intercalating an alkali metal between the layers and heat treating.

The alkali metal used is not particularly limited, but
Considering that the fibrous carbon is crushed by expanding and penetrating between the carbon layers, it is preferable to use a material that is inserted between the graphite layers and has as large an atomic radius as possible, such as potassium.

In addition, when crushing the fibrous carbon, it is possible to expose the fibrous carbon to alkali metal vapor to insert the alkali metal between the layers, and then rapidly heat it to destroy it, but it is easier. Another method is to heat a mixture of an alkali metal or an alkali metal compound and the fibrous carbon.

In the latter method, it has recently been known that activated carbon with a high surface area can be obtained by heating and carbonizing lignin and carbonaceous materials such as coconut shell char, petroleum coke, and coal together with KOH (for example, Tatsuaki Yamaguchi; Journal of the Chemical Society of Japan; 1988 (2)
, p217-220, H, Marsh and D.

Crawford, Carbon 20.419 (
(1982)), which is a commonly used method.

The latter method is preferable because it is not only simpler, but also requires less time and a simpler device.

In addition to hydroxide, alkali metal compounds include chloride,
Halides and oxides such as bromide, or nitrates,
Inorganic salts such as sulfates and carbonates, or acetic acid, oxalic acid,
Organic acid salts such as carbolic acid or compounds such as alkoxides can be used.

Regarding the blending of the fibrous carbon and the alkali metal compound, the amount of the alkali metal is 0.01 to 100 per mole of carbon.
It is desirable to add the alkali metal or alkali metal compound in an amount of mol, more preferably 0.1 to 10 mol.

In mixing the fibrous carbon and the alkali metal compound,
Although it is possible to mix the alkali metal compound in a solid state, it is more efficient to mix the alkali metal compound with the fibrous carbonic acid as an aqueous solution, alcoholic solution, etc., and then dry it.

Next, this mixture of fibrous carbon and alkali metal compound is heat treated at a predetermined temperature. Heat treatment temperature is 500-1200
The temperature is preferably 600 to 1000°C rather than 1°C.

Further, it is also desirable to temporarily maintain the temperature at a predetermined temperature during the heating process and perform dehydration treatment. This dehydration treatment temperature is 100 to 60
The temperature is more preferably 200 to 500°C than 0°C.

This heat-treated mixture is thoroughly washed with water and dried to obtain fine graphite powder.

According to this method, the stacked carbon layers of the fibrous carbon can be crushed to a thickness of several tens to hundreds of layers, and since the width of the fibers is 1 μm or less, the graphite lump can be crushed. There may be problems with refinement in the direction of the carbon network, or if the overall
There is no problem of difficulty in reducing the powder to micrometers or less, and it is possible to reliably produce a fine powder on the submicron order.

In addition, since the fibrous carbon is generated by utilizing the unique catalytic effect of transition metals, it can be obtained at several hundred degrees Celsius, and there is no need for the graphitization process at 2000 degrees Celsius or higher, which has been necessary in the past. By performing the crushing at a temperature of 1000°C or less, the entire process can be kept at 1000°C or less, making it a very advantageous method in terms of energy and equipment.

Furthermore, this method makes it possible to obtain fine graphite powder having a microstructure in which graphite network surfaces are properly oriented in one direction, which has not been possible until now.

The particle structure of the graphite fine powder thus obtained is shown in FIG. 2, and the particle structure of the carbon mesh surface of the graphite fine powder is shown in FIG.

[Example] Example 1 Ribbon-shaped carbon fibers (fiber growth catalyst iron compound removed by boiling in concentrated hydrochloric acid) were mixed with potassium hydroxide (fibrous carbon in weight ratio) dissolved in water/ethanol mixed solution (50150). ), stir well, and heat to 115°.
It was dried at C.

This mixture was placed in a magnetic crucible at 20°C under a nitrogen stream.
After heating at 400°C for 30 minutes, the temperature was increased at 20°C.
The temperature was increased to 800°C at a rate of C/min and maintained for 1 hour. The contents of the reaction solution were taken out, thoroughly washed with water repeatedly to elute the alkaline content, and then dried at 115°C.

Example 2 The same procedure as Example 1 was carried out except that the holding time at 800°C was changed to 3 hours.

Example 3 The same procedure as Example 1 was carried out except that the heat treatment temperature was 900°C.

Example 4 The same procedure as in Example 1 was carried out except that the temperature increase rate was 1°C/min.

Table 1 shows the physical properties of the graphite fine powder obtained in Examples 1 to 4.

The specific surface area was determined by the nitrogen adsorption method.

X-ray diffraction was measured by the stainless steel scanning method based on the Jakushin method using silicon single crystal powder as an internal standard.

5 BET of ribbon carbon fiber which is the starting material is 110m
2/g, d002 of 3.37 people, and Lc of 230 people, the graphite fine powder produced had an increased specific surface area (5BET) compared to the fiber, and the dooz value was kept relatively small. It can be seen that the thickness (Lc) of the stacked graphite layers is significantly reduced while maintaining the orientation of the microstructure.

Table 1 [Effect of the Invention 1 According to the present invention, fibrous carbon in which highly graphitized carbon network surfaces are laminated substantially perpendicularly to the longitudinal direction of the fibers is preferably dissolved using an alkali metal compound. By crushing, we can reliably produce graphite fine powder, which is unprecedented in that its particle size is on the order of submicrons and has a controlled microstructure in which the carbon network surface is oriented in one direction, and it is easy to use at relatively low temperatures. can be manufactured.

The obtained graphite fine powder of the present invention is widely used as a conductive coating agent, an industrial lubricant, an antistatic agent, a battery material, a heat dissipating material, an additive for various composite materials, and the like.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the method for producing graphite fine powder in the present invention,

Claims (3)

[Claims] (1) Graphite fine powder in which carbon mesh surfaces are substantially stacked in one direction, and the stacking height of the carbon mesh surfaces of the graphite fine powder is 0.5
μm or less, and the distance between the surfaces (d_0_0_2) is 3
．． 354 to 3.470 Å, and the area of the cross section perpendicular to the stacking direction of the graphite fine powder is 1 μm^2 or less,
Graphite fine powder characterized in that the cross-sectional shape is rectangular or flat elliptical, and the major axis is at least twice as long as the minor axis. (2) By crushing fibrous carbon in which the carbon mesh surfaces are stacked substantially perpendicularly to the length direction of the fibers, the carbon mesh surfaces are stacked substantially in one direction. A fine graphite powder made of
．． 5 μm or less, and the distance between the surfaces (d_0_0_2)
is 3.354 to 3.470 Å, and the area of the cross section perpendicular to the stacking direction of the graphite fine powder is 1 μm^2 or less, and the cross section has a rectangular or flat elliptical shape,
A method for producing fine graphite powder, characterized in that its long axis is at least twice as long as its short axis. (3) The method for producing graphite fine powder according to claim 2, wherein the crushing treatment includes adding an alkali metal compound and heat-treating.