JPH0280398A - Whisker-shaped carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the title whisker-shaped carbon fiber having a large diameter and high crystallinity almost without need for oxidation by specifying the aspect ratio, density, spacing of the carbon hexagonal net planes by X-ray analysis, size of the crystallite in the c-axis direction, and R value, and fuzzing the surface. CONSTITUTION:The carbon fiber has 0.1-50mum diameter, 50-10,000 aspect ratio, >=1.9g/cm<3> density, 3.36-3.49Angstrom above mentioned spacing, and >=50Angstrom size of the crystallite in the c-axis direction. In addition, the ratio (R value) I 1360/I 1580 of the peak height of the Raman scattering spectrum at the 1360cm<-1> band to the peak height at the 1580cm<-1> band is controlled to >=0.5 in the carbon fiber. The carbon fiber surface is fuzzed in about 300Angstrom thickness. When a fiber-reinforced composite material is made from the carbon fiber, a sufficient reinforcing effect as the reinforcing fiber is produced, and the surface treatment requiring effort is simplified. Consequently, the time, cost, and labor spent in the surface treatment can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to whisker-like carbon fibers produced by a vapor phase growth method, and in particular whisker-like carbon fibers with a rough surface, high crystallinity, and easy graphitization. Regarding carbon fiber.

[Prior Art] Carbon fiber has excellent properties such as high strength and high modulus of elasticity, and is attracting attention as a variety of composite materials.

Conventionally, carbon fibers have been mainly produced by carbonizing organic fibers such as PAN1 pitch and cellulose. When making fiber-reinforced composite materials using these carbon fibers, it is desired to increase the contact area with the base material, reduce the diameter, and increase the length to increase the reinforcing effect. Furthermore, surface treatments such as oxidation and coating are performed to improve adhesion to the base material. Graphitization treatment is also performed to improve crystallinity, electrical conductivity, etc.

However, conventionally, when carbonized carbon fibers are made from organic fibers, spinning is difficult and the diameter of the fibers is small (but at most
It is about 10 μm. Therefore, a time-consuming and time-consuming oxidation treatment step is required under severe conditions. Moreover, even if graphitization treatment is performed, this carbon GnH (k is difficult to graphitize and cannot form a sufficient graphite structure. For example, P
The AN-based carbon fiber has a plane spacing d00 of carbon hexagonal network planes (002) determined by X-ray diffraction of yarn graphitized at 3000°C.
2 is about 3.42 people, and the density is 1.8g/cm3
(The value is . Even when carbon fiber made from mesophase pitch, which has a higher degree of graphitization than PAN-based or pitch-based carbon fibers, is graphitized at 3000°C, the interplanar spacing d002 is approximately 3.38 The crystallite size L c (002) is about 180 people, and the density is 2.
It is a little less than -0 g/cm3.

On the other hand, it is also known to produce carbon fibers by thermally decomposing hydrocarbons and using a vapor phase growth method. This vapor-grown carbon fiber has extremely few crystal defects and has excellent crystal r orientation. For this reason, it is a material with higher strength and higher modulus of elasticity compared to carbonized carbon fiber, and is expected to be used in many directions as a fiber-reinforced composite material. However, although conventionally known vapor-grown carbon fibers are easily graphitized, the density of carbon fibers immediately after carbon fiber production is around 1.85 g/am3 at most, and they still do not have sufficient graphite structure. I haven't gotten around to taking it yet. Therefore, graphitization treatment is required to achieve high orientation. Also, JP-A-61-
No. 225325 discloses carbon fiber, but this carbon fiber has a Raman scattering spectrum of 1360 cm''l.
The ratio of the peak height of the band to the peak height of the 1.580 cm-1 band, 11300/11580, is 1.0 or less, and the surface is smooth. Similarly, JP-A-61-7
The carbon fiber disclosed in No. 0014 has a smooth surface. For this reason, these carbon fibers have poor chemical reactivity,
When used as a composite material, it is necessary to sufficiently oxidize the surface.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the prior art. The object of the present invention is to provide whisker-like carbon fibers with a rough surface and easy graphitization properties that can be processed easily.

[Means for solving the problem] The carbon fiber of the present invention has a fiber diameter of 01 μm to 50 μm.
1 Preferably, it is 0.5 μm to 5 μm. The fiber length/fiber diameter (aspect ratio) is 50 to 10,000, preferably 100 to 10,000. Density is 1.9g
/cm3 or more, preferably '), Q g /
cm3 or more.

In addition, the interplanar spacing do O2 force of carbon hexagonal network plane (002) by X-ray diffraction method is <3.36 Å to 3.49 Å, the crystallite size Lc (002) in the C-axis direction is 50 Å or more, and the Raman scattering spectrum is 1360 cm. -1 band peak height to 1580 cm-' band peak height ratio (R value) I 1360/I 1580 is 1.05 or more,
Preferably it is 1.1 or more. It is a whisker-like carbon fiber that is easily graphitized and has a fluffy appearance on the surface of about 300 layers from the surface of the iron cone.

In the present invention, the reason why the aspect ratio is limited to the above range is as follows.
If it is less than 50, the strength reinforcement effect of the composite material cannot be obtained when a composite material of carbon fiber, resin, metal, dense cement, ceramic, etc. is produced. Moreover, if it is less than 50, there will be little bonding between fibers, making it difficult to make paper.

In addition, the density, the interplanar spacing of the carbon hexagonal network plane (002) do0
2. The reason why the crystallite size Lc (002) in the C-axis direction is limited to the above range is that carbon fibers in this range are heated to 2000°C.
When graphitized at a temperature above, it easily becomes graphitized fiber with a density of 2.1 g/cm3 or more, cto O2
This is because Lc (002) is 3.45 Å or less and Lc (002) is 150 Å or more. Note that the upper limits of these values were set in consideration of economic efficiency during manufacturing.

The carbon fiber of the present invention has a fluffy surface and has a Raman scattering spectrum R value of 1.05 or more.However, since the carbon fiber has a highly crystalline graphite structure inside the fiber, The density of is 0 people. Because of this surface structure, it is possible to mix easily without oxidation treatment or by applying mild oxidation treatment, for example, due to good wettability with resin, and sufficient reinforcement. effect can be obtained.

As described above, the carbon fiber according to the present invention can be obtained as a whisker-like carbon fiber having excellent adhesiveness to a base material without undergoing any surface treatment or only by being subjected to a mild oxidation treatment.

The whisker-like carbon fiber according to the present invention is produced by introducing a hydrocarbon (raw carbon source) and an organometallic compound into a reaction system, and converting the carbon obtained by thermal decomposition of the hydrocarbon into the carbon produced by the thermal decomposition of the organometallic compound. This can be achieved by using a gas containing predetermined amounts of -carbon oxide, carbon dioxide, and hydrogen as a carrier gas when growing on fine particles.

Hydrocarbons used in the present invention include aliphatic hydrocarbons such as methane, ethane, propane, ethylene, propylene, and butadiene, monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene, and naphthalene and anthracene. Polycyclic aromatic hydrocarbons or mixtures thereof can be applied, but crude light oils, absorption oils, Kalpolura oil, anthracene oil, heavy oil, pitch, and mixtures thereof, which are by-products from coke ovens, are cheap and available in large quantities. In particular, sulfur-containing thiophenes, thiols, and thiophenols are useful because they increase the rate of carbon fiber production.

Any known metal compound can be used as long as it has a carbon-metal bond, but when used by dissolving it in the raw material hydrocarbon, it should be soluble or in gaseous form. In this case, it is preferable to use a material with sublimation properties. Specifically, organic transition metal compounds containing titanium, vanadium, chromium, manganese, iron, cobalt, nickel, rubidium 1, rhodium, tungsten, palladium, or platinum are suitable, and organic transition metal compounds containing iron are particularly suitable. The compounds are most preferred. In particular, metallocenes having a cyclopentadienyl group as a ligand are useful because they form dinuclear complexes with many high-valent metal salts and are inexpensive and active.

The metal compound that is a decomposition catalyst for the organometallic compound is preferably added in an amount of about 0.01 to 50 mol per 1 mol of the organometallic compound used. Moreover, any metal compound can be used as long as it has the same type of metal atom or a different type of metal atom with respect to the organometallic compound used. The metal is preferably titanium, vanadium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, ruthenium, rhodium, osmium, or iridium, and particularly preferably manganese, iron, cobalt, or nickel. The compound may be in any form, including inorganic compounds such as sulfates, nitrates, acetates, chlorides, sulfides, oxides, carbides, nitrides, acetylacetonate salts, and organic transition metal complexes such as carbonyl compounds. is used.

Charcoal X related to the present invention! : The carrier gas for obtaining fibers contains at least 50-80% carbon monoxide and 5% carbon dioxide.
A gas containing ~30% is used as the atmospheric gas, and a composition of -50 to 80% carbon oxide, 5 to 30% carbon dioxide, 0.1 to 10% hydrogen, and 20% or less nitrogen is particularly preferred. Specifically, it is a mixed gas of converter gas, blast furnace gas, or a gas obtained by mixing these gases with a hydrogen-containing gas such as coke oven gas. In particular, converter gas is effective because it alone has this composition.

[Effects of the Invention] Therefore, the carbon fiber of the present invention obtained by the above method has a large fiber diameter, a large fiber length/fiber diameter, a high density, and a highly crystalline graphite structure inside the fiber. However, the fiber surface is a whisker-like carbon fiber that is easily graphitized.

Therefore, when a fiber-reinforced composite material is produced using this carbon fiber, not only does it have a sufficient reinforcing effect as a reinforcing fiber, but also the time-consuming surface treatment described in (1) can be easily completed. Therefore, the time, cost, and labor required for surface treatment can be reduced.

The present invention will be explained below with reference to Examples.

Example 1 Carbon fibers were manufactured using the apparatus shown in FIG. In the figure, reference numeral 11 is a gas cylinder filled with argon gas. 12 is a gas cylinder filled with converter gas,
This converter gas contains carbon monoxide gas 0% by volume, carbon dioxide gas 15% by volume, hydrogen gas 1.18%, and nitrogen gas 15% by volume.
This gas has a composition of % by volume, and is introduced into the reaction system as an atmospheric gas. Each cylinder 11.12 has a flow meter 13
E and 15 are raw material tanks, in which benzene was charged as a raw material. This benzene contains ferrocene, thiophene, and Mn (I
I) Acetylacetonate salt is dissolved, and its weight composition ratio is 0.4.0.2. The ratio is 0.1. These cylinders 11 and 12 are connected to the reaction tube 20 via a stainless steel pipe 16, and the raw material tank 15 is
It is connected to a reaction tube 20 via a stainless steel pipe 17. The reaction tube 20 has an inner diameter of 90 mm and a length of 1
000mm alumina tube, its length is 800m
An electric furnace 23 is installed on the outer periphery over m. The temperature of this electric furnace 23 is detected by a thermocouple 24, and the temperature controller 2
5 to control the temperature to a constant temperature. In this example, the temperature during operation of the electric furnace 23 was set to 1150°C.

During operation, argon gas is first supplied from the cylinder 11 into the reaction tube to replace the inside of the reaction tube with argon gas. Subsequently, the converter gas contained in the cylinder 12 was flowed into the reaction tube 20 at a rate of 300 m1/min. Furthermore, the raw material surface with the above composition is pumped into the reaction tube 2 at a rate of 20+1/min using the chemical pump 22.
Supplied within 0.

As a result, thermal decomposition and catalytic reaction occurred on the surface of the raw material in the reaction tube, thereby continuously producing whisker-like carbon fibers, which were collected by the fruit collector 21.

1. The average diameter of the polished carbon Gll is 1 μm, the average length is 2000 l1m, and the yield is χ, J to benzene.
It was 6896. Also, the density is 2.05g/cm3
Surface spacing d of carbon hexagonal network plane (002) 11°2 is 3
．． 48 Å, and the crystallite size Lc ([J O2) was 70. Also, the R value of the Raman scattering spectrum is 1.10
It is. As a result of observation using a carbon ``a-pyramid back surface'' transmission electron microscope, the fiber surface exhibited a fluffy appearance at a depth of m < 300 mm. This micrograph is shown in FIG.

Furthermore, this fiber was mixed with epoxy resin (trade name: Epicoat 828) at a ratio of 5 and 20% by volume without oxidation treatment.
, curing agent B F 3 M EA ) and PP at a ratio of 30% by volume to produce FRP (sample numbers: 5 and 6.2, respectively). In addition, FRP was prepared by mixing fibers boiled in concentrated nitric acid for 0.5 hours with epoxy resin at a ratio of 20% by volume and PP at a ratio of 30% by volume (sample numbers: ?, 3.). Width 1 from this FRP
0mm.

A three-point bending test was conducted using a test piece with a thickness of 4 mm and a distance between fulcrums of 64 mm. The results are shown in Table 1 along with the bending strengths of the epoxy resin matrix alone (sample number: 1) and the polypropylene matrix alone (sample number: 4). In any case, the carbon fiber of the present invention has a strength of 1.3 to 1.
Reinforcement hardening of 2.1 times was observed. Also, in terms of wettability with resin, it is better than pitch-based carbon fiber whose surface has been oxidized with nitric acid.

Example 2 2 (10
Graphitization treatment was performed at 0°C. The density of this graphitized thread is 2.15 g/cm3, the interplanar spacing do O2 of the carbon hexagonal network plane (002) is 3.43 Å, and the crystallite size L c
(002) was 200 people. Furthermore, when this whisker-like carbon fiber was graphitized at 2800°C,
The density of this graphitized thread was 2.21 g/cm3, the interplanar spacing d002 of carbon hexagonal network planes (002) was 3.37 Å, and the crystallite size L c (002) was 660.

Thus, it can be seen that this whisker-like carbon fiber is easily graphitized.

Comparative Example 1 Whisker-like carbon fibers were produced using the apparatus used in Example 1, using hydrogen as a carrier gas, and under the same conditions as in Example 1 except for the same conditions. The obtained carbon fiber has an average diameter of 0
．． 5 μm 1 average length is 2000 μm, density is 1
．． 80 g/cm' (planar spacing d Ll t+ 2 of carbon hexagonal network plane (002) is 3.53 Å, crystallite size Lc
(IJ O2) was 35 people. Further, the R value of the Raman scattering spectrum was 0.89, and as a result of observation with a transmission microscope, the carbon fiber surface was smooth. A transmission micrograph of the surface of the carbon fiber is shown in Figure '3. Furthermore, when this whisker-like carbon fiber was graphitized at 2000° C., the density increased only to 1.90 g/cm 3 .

Using this fiber, FR
P was prepared and subjected to a bending strength test.

The results are shown in Table 2. From Table 2, it can be seen that the carbon fibers of the comparative example have inferior bending strength compared to those of the present invention.

Example 3 The apparatus used in Example 1 was changed to a horizontal type, and commercially available ultrafine iron powder (
A magnetic plate with dispersed powder (manufactured by Vacuum Metallurgy) was placed in the furnace, and the inside of the furnace was replaced with argon. Wire the electric furnace to 600℃
When the temperature reached 300 sec cm, converter gas was flowed into the reaction tube for 30 minutes. After that, we installed a '1' electric furnace at 1,150 yen.
The temperature was maintained at °C, and benzene was supplied at a flow rate of 0.1 ml/min. The carbon fibers obtained by the operation for -1 hour had an average diameter of 30 μm and an average length of 60 mm. Each time 2.03g/Cl113, carbon hexagonal mesh plane (002)
The interplanar spacing do02 is 3.49 Å, and the crystallite size L
c (002) or 55 people. Further, the R value of the Raman scattering spectrum was 1.05, and when observed with a transmission electron microscope, the fiber surface had a fluffy appearance over about 500 layers.

Table 1 Bending strength of FRP Bending strength (kg/mm2) 3.82 7.65 8.1O No, FRP I PP 2 PP+30vo1%CP 3 PP+3 (IVOI% Surface treatment CF* POX I IEPOXl+5vo1%CF EPOXl+ 20vo1%CP IEPOX I+ 20vo1% Surface treatment CP book * Boiling treated with concentrated nitric acid for 0.5 hours 10.78 15.10 1g, 72 20.45 Table 2 FRP bending strength (comparative example) No. FRP bending strength (kg/mm2 )I
PP+30vo1%CP 3.8
22 PP+30vo1% 7.13 Surface treatment cp** 3 PP0XI+ 20vo1%CF 8.37
4 1EPOXI+ 20vo1%CI' 18.2
0 Surface treatment CF** Zero *Boiling treated with concentrated nitric acid for 2 hours

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the outline of an apparatus for implementing the method of the present invention, Fig. 2 is a micrograph showing the surface shape of carbon fibers obtained by the method of the present invention, and Fig. 3 is a photomicrograph showing the surface shape of carbon fibers obtained by the method of the present invention. 1 is a micrograph showing the surface shape of carbon fibers obtained by 11... Argon gas cylinder, 12... Carrier gas cylinder, 13.14... Flow meter, 15... Raw material tank, 16.17... Stainless steel pipe, 20...
...Reaction tube, 21...Collector, 22...Chemical pump, 23...Electric furnace, 24...Thermocouple, 25...
・Temperature controller.

Claims (2)

[Claims] (1) Fiber diameter is 0.1 μm to 50 μm, fiber length/fiber diameter is 50 to 10,000, and density is 1.9 g/cm
^3 or more, carbon hexagonal network plane (002) by X-ray diffraction method
The interplanar spacing d_0_0_2 is 3.36 Å to 3.49 Å, the crystallite size Lc(002) is 50 Å or more, and the peak height of the 1360 cm^-^1 band and the peak height of the 1580 cm^-^1 band in the Raman scattering spectrum. The ratio of I13
60/I1580 is 1.05 or more, and an easily graphitized whisker-like carbon fiber exhibiting a fluffy appearance with a fiber surface depth of about 0.001 to 0.1 per fiber diameter 1. (2) Fiber diameter is 0.5 μm to 5 μm, fiber length/
Fiber diameter is 100-10,000, density is 2.0g/cm
^3 or more, carbon hexagonal network plane (002) by X-ray diffraction method
The interplanar spacing d_0_0_2 is 3.36 Å to 3.49 Å, the crystallite size Lc(002) is 50 Å or more, and the peak height of the 1360 cm^-^1 band and the peak height of the 1580 cm^-^1 band in the Raman scattering spectrum. The ratio of I13
60/I1580 is 1.1 or more, and the fiber surface is about 300
A whisker-like carbon fiber that is easily graphitized and has a fluffy appearance at a depth of about 100 Å.