JPH01192824A - Carbon fiber produced by vapor phase process - Google Patents

Abstract

PURPOSE:To obtain a carbon fiber produced by vapor-phase process, exhibiting a specific X-ray diffraction pattern, rich in graphite structure and having excellent properties, by thermally decomposing an organic compound in the presence of a transition metal element or transition metal compound. CONSTITUTION:The raw material of the carbon fiber is produced by dissolving 2wt.% of iron pentacarbonyl [Fe(CO)5] in benzene and further dissolving 0.5wt.% of thiophene in the solution. The raw material is mixed into a carrier gas consisting of hydrogen and carbon dioxide gas and the mixture is introduced into an externally heated vertical furnace 1 to effect the thermal decomposition of the raw material. Vapor-phase carbon fiber having a diameter of 0.1-0.3mum and a length of >=50mum can be produced by this process. The X-ray diffraction pattern of the fiber has asymmetrical (002) diffraction line of carbon and has at least one peak having an area accounting for >=5% of the total area of peaks at a position beyond 26.0 deg. when resolved into each peak after removing the back-ground of amorphous halo.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to vapor grown carbon fiber (hereinafter referred to as VGCF), and in particular, it combines the properties unique to graphite, such as strength, elastic modulus, and excellent crystallinity. Concerning the included VGCF.

[Prior Art] Carbon fiber is used in many fields because it not only has high mechanical properties but also excellent corrosion resistance, heat resistance, and electrical conductivity.

PAN type carbon fibers, pitch type carbon fibers, etc. are well known and are used in a wide range of fields such as aviation parts, sports goods, leisure goods, and industrial parts.

Furthermore, VGCF is one that has attracted attention in recent years, and is said to grow by thermal decomposition of organic compounds mediated by fine particles of Fe, Nj, etc. VGC
Conventional manufacturing methods for F include a method in which fine particles are scattered on a substrate placed in a pyrolysis zone and fibers are grown therefrom (for example, Japanese Patent Publication No. 58-22571), and a method in which fine particles are suspended and fibers are grown while suspended. (for example, JP-A-58-1)
No. 8061.5 and JP-A-Sho [io-54998].

[Problems to be Solved by the Invention] It is known that VGCF undergoes high-temperature treatment (approximately 2000° C. or higher) to develop selective orientation of carbon network planes to a high degree, resulting in a structure similar to that of graphite Rice Car.

For example, R, Bacon (1, Appl, Phys,
31. According to p283 (1980), tensile strength 2
000 kg/- or more, and an elastic modulus of 71.5 T/-, which shows extremely high performance, and great expectations are placed on VGCF due to the similarity in its structure.

Also, G, G, Tjbbetts (SAMPE J
, 5ept, / Oct.

(1,98[i) p30) According to 2, vGCF treated at 2800°C has a tensile strength of 300 to 700 kg/mj and an elastic modulus of 36 to 60 T/mj, and the tensile strength is the same as that of commercially available PAN.
carbonized fiber (processed at 1400℃), the elastic modulus is comparable to meso-fused pitch graphite fiber (processed at 2500℃ or higher),
Data are shown that reach the top level of each property obtained with conventional carbon fibers. Also, the electrical conductivity is 6×10-
At 5Ω・am, it exhibits properties that far exceed those of conventional carbon fibers, indicating that its structure is superior.

On the other hand, VGCF (hereinafter referred to as generated VGC) remains as generated in the reactor.
According to a previous report by G, G, and Tjbbetts, the tensile strength is 220 to 270 kg/nuR1, and the modulus of elasticity is 2.
3 to 40T/IIIi, which is almost comparable to meso-fused pitch carbonized fiber (treated at 1000 to 1200°C), but considering the possibilities of its structure, it must be said that it is still insufficient. One of the reasons for this is that the orientation of carbon network planes in the fiber axis direction and the carbon network spacing are poorly achieved in graphite crystals. This is a transmission electron microscope (T
It can be confirmed by means such as an electron beam diffraction image and a lattice image using EM) or a structural parameter d (002) using X-rays.

In addition, various studies have been conducted on floating methods that can obtain VGCF efficiently at low cost, but according to TEM analysis structural parameters, etc., the VGCF produced by this method is equivalent to or even inferior to the seeding method. It has only gone so far.

An object of the present invention is to provide a generated VGCF with excellent characteristics.

[Means for Solving the Problems] As a result of intensive research in order to obtain VGCF with excellent characteristics even in the above produced VGCF, the present inventor found that at least a part of its crystal structure is substantially graphitic. This can be achieved by producing a VGCF having excellent properties, and the present invention was completed by discovering that this product exhibits a new X-ray diffraction pattern that has never existed before.

That is, the gist of the present invention is a vapor grown carbon fiber obtained by thermal decomposition of an organic compound in the presence of a transition metal element or a transition metal compound, which
002) The diffraction line is asymmetric, and after removing the amorphous halo in the X-ray diffraction pattern as a background and separating the peaks, at least one peak position determined by correcting with the peak position of standard silicon powder is determined. The temperature is 26.0 degrees or more, and the area of the peak is 5% or more of the total area of all the peaks.

The present invention is characterized by VGCF having at least a portion of its crystal structure with excellent graphitic properties.

This confirmation can be performed using X-ray diffraction, which is the most common structural analysis method for carbon materials. (related), Michio Inagaki, "Carbon Materials Experimental Techniques 1" edited by the Carbon Materials Society, published by Science and Technology Company (1978), p55).

When using X-ray diffraction (002 diffraction line), the simplest method, although qualitative, is to determine whether or not the diffraction pattern is asymmetric. For further quantitative determination, remove the amorphous halo as a background, separate the peaks by curve fitting, and correct at least one of the peak positions determined by the peak position of standard silicon powder with a diffraction angle. The temperature is preferably 26.0 degrees or more, more preferably 26.3 degrees or more. Also, the diffraction angle is 25.
If only the peak is 8 degrees or less, it is substantially a turbostratic structure, which is not the graphitic structure of the present application, and therefore no effect can be expected. The most ideal case would be for the produced VGCF to consist only of a graphitic structure, and in this case it would be symmetrical, but its peak position would be within the above diffraction angle range, which is the case in the present application. This is the ultimate VGCF.

Furthermore, the effect of the produced VGCF of the present application is clearly seen when the area of the peak-separated graphitic peak portion defined by the above-mentioned diffraction angle is 1% or more of the total area of all the peaks, which is particularly preferable. is 5% or more. When the area of the graphitic peak portion is 1% or less, no significant difference is observed from the conventional VGCF which has a crystal structure of substantially only a turbostratic structure.

As stated in the heading of [Problems to be Solved by the Invention] above, the properties of the produced VGCF are improved by high-temperature treatment, and this is largely due to the development of the graphite structure.

Literature cited in that section (SAMPE J, 5ept,
/ Oct.

(198Ei) p30) contains VG with iron as the production core.
A description of CF is made, and an X-ray diffraction pattern is shown corresponding to the significant improvement in properties due to high-temperature treatment.

In other words, the X-ray diffraction pattern of the produced VGCF alone shows only a relatively broad symmetrical peak at d (002) = 0.348 nm (corresponding to a diffraction angle peak of 25.6 degrees). , d(002)=0.33Gnm (
The peak of the diffraction angle corresponds to 265 degrees, which is approximately the same mesh spacing as d (002) = OJ 354 nm of an ideal graphite crystal). It shows. As described above, there is a strong correlation between the development of the graphite crystal structure and the improvement of properties due to high-temperature treatment, so the produced VGCF having at least a part of the graphite structure in the present application is different from the conventional produced VGCF.
It has superior characteristics compared to .

The produced VGCF of the present application can be suitably used alone as a functional material or its raw material, or as a composite material with fillers of various matrices, and can also be used after further high-temperature treatment.

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

[Example] Iron pentacarbonyl (Fe(CO) 5) in benzene
was dissolved in an amount of 2% by weight, and further 0.5% by weight of thiophene was dissolved therein to obtain a raw material.

As the VGCF reactor, an external heating type vertical furnace shown in FIG. 1 was used. In Figure 1, 1 is a reactor, 2 is a heater, 3 is a sprayer, 4 is a collection chamber, 5 is a filter, 6 is a duct, 7 is a flow rate regulator for CO2, 8 is a flow rate regulator for H2, and 9 is a A raw material metering pump, 10 is a raw material container, and 11 is a raw material. or,
The reactor uses a mullite tube with a furnace length of 1500 mm and an inner diameter of 80 mm, a soaking zone of 300 m + n, and a temperature of 12 mm.
The temperature was adjusted to 00°C.

Hydrogen was used as a carrier gas and the flow rate was adjusted to 20 g/min, and 0.1 g/min of carbon dioxide was mixed with the hydrogen and flowed at the same time. Then, a metering pump pumps the raw material at a rate of 1.
It was supplied into the furnace at a rate of 7 g.

After injecting 25.9 g of raw material, the reactor was cooled and the weight of carbonaceous matter deposited in the collection chamber was measured. Carbonaceous weight is 2.59
g, and the yield (ratio to benzene) was 10.0%.

The obtained carbonaceous product was a very good VGCF with a diameter of 0.1 to 0.3 mm and a length of 50 μs or more, as shown in the scanning electron micrograph shown in Figure 2, and no soot-like substances were observed. Ta.

This VGCF was ground into powder in an agate mortar and then subjected to X-ray diffraction using silicon powder as an internal standard in accordance with the Gakushin method. The apparatus used was Rigaku Denki RU-200 model, and the Rigaku Denki C-system was used for peak separation. The results of peak separation are shown in Figure 3.

In Figure 3, the A line is the amorphous halo, the B line is the turbostratic structure peak obtained by peak separation, the C line is the graphite structure peak obtained by peak separation, and the D line is the peak separation. The peak of the obtained standard silicon powder, the E line, shows the sum of the A-D lines. The peak after correction based on the peak position of silicon powder is 26.3
A sharp graphitic peak with a half-width of 0.7 degrees,
It was possible to separate a broad carbon turbostratic structure peak with a peak position of 25.3 degrees and a half width of 5.3 degrees. Area ratio=(graphitic peak area)/(graphitic peak area+turbostratic structure peak area)=0.1.4.

[Effects of the Invention] The vapor-grown carbon fiber according to the present invention contains a graphite structure with excellent crystallinity even in the produced VGCF, so it has a strength of 9 and a modulus of elasticity of 9.
Since it can be expected to improve properties such as electrical conductivity and thermal conductivity, it can be used as a variety of materials.

[Brief explanation of the drawing]

FIG. 1 shows a flow diagram of an apparatus for manufacturing vapor-grown carbon fiber of the example, FIG. 2 shows a scanning electron micrograph of the vapor-washed carbon fiber of the example, and FIG. 1 shows a peak-separated X-ray diffraction pattern of phase-grown carbon fiber.

Claims (1)

[Claims] A vapor-grown carbon fiber obtained by thermal decomposition of an organic compound in the presence of a transition metal element or a transition metal compound, wherein the (002) diffraction line of carbon is asymmetric in the X-ray diffraction pattern,
After removing the amorphous halo in the X-ray diffraction pattern as a background and separating the peaks, at least one peak position determined by correcting with the peak position of standard silicon powder is 2.
6.0 degrees or more, and the area of the peak is 5% or more of the total area of all the peaks.