Carbon fiber composition including graphene nano-powder and fabrication method for carbon fiber using the same

Abstract

The present disclosure relates to a carbon fiber composition and a fabrication method for high-performance carbon fiber using the same. The method can fabricate high-performance carbon fiber (or graphite fiber) with lowering a graphitization temperature by using graphene carbon fiber composition including nano-sized graphene.

Claims

1. A method for fabricating high-performance carbon fiber, the method comprising steps of: a mixing step to make a graphene carbon fiber composition by mixing a composition for fabricating carbon fiber, and graphene powder, wherein the composition for fabricating carbon fiber includes one selected from the group consisting of, pitch, rayon and combinations thereof; and a heat treatment step of the graphene carbon fiber composition, and wherein the graphene powder serves as a seed of nanoribbon-shaped graphite to be formed during carbon fiber fabricating processes.

2. The method of claim 1, wherein the graphene powder is fabricated by decomposing crystalline graphite, and has a particle size of 20 nm or less.

3. The method of claim 2, wherein the crystalline graphite is a graphite structure grown in a helix shape.

4. The method of claim 1, wherein a content of the graphene powder is more than 0.1 wt % based on 100 wt % of the sum of the composition for fabricating carbon fiber and the graphene powder.

5. The method of claim 1, the mixing step further comprising a solvent, wherein the solvent is selected from the group consisting of alcohol, acetone, dimethylformamide (DMF), tetrahydrofuran (THF) and combinations thereof.

6. The method of claim 1, wherein the composition for fabricating carbon fiber further includes polyacrylonitrile (PAN).

7. A method for fabricating high-performance carbon fiber, the method comprising steps of: a mixing step to fabricate a graphene suspension by mixing a composition for fabricating carbon fiber with graphene powder to form a graphene carbon fiber composition, and dispersing the graphene carbon fiber composition in a solvent, wherein the composition for fabricating carbon fiber includes one selected from the group consisting of, pitch, rayon and combinations thereof; a fabrication step to fabricate mixed-fiber by controlling a viscosity of the graphene suspension and performing a fiberization process of the graphene suspension; a stabilization step to stabilize the fibers by heating at 200400 C. under atmosphere; and a heat treatment step of fabricating nano ribbon-shaped graphite by graphitization of the stabilized fibers at a temperature less than 2,500 C., wherein the graphene powder included in the graphene carbon fiber composition serves as a seed of graphite to be formed during high-performance carbon fiber fabricating processes.

8. The method of claim 7, wherein the graphitization of the heat treatment step is performed at a temperature in the range of 1,500 C. and greater to less than 2,500 C.

9. The method of claim 7, wherein the composition for fabricating carbon fiber further includes polyacrylonitrile (PAN).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the disclosure.

(2) In the drawings:

(3) FIG. 1 is a conceptual view illustrating a graphene carbon fiber composition according to an embodiment of the present invention, and nano ribbon-shaped graphite obtained by heat-treatment (graphitization) the graphene carbon fiber composition;

(4) FIG. 2 illustrates a high-resolution transmission electron microscopy (HRTEM) image (upper side on the right) of graphene powder fabricated in Example 1-1), an X-ray diffraction (XRD) pattern of graphene powder, and an XRD pattern of nano ribbon-shaped graphite after a graphitization process, in which full with half maximum (FWHM) of the (002) peak which near 26 (2) are 7.9 and 2.6, respectively;

(5) FIG. 3(A) (left) is an image illustrating a graphene suspension, a liquid-phase PAN-based graphene carbon fiber composition fabricated according to Example 1 (weight of graphene based on the sum of PAN and graphene powder: 10 wt %), and FIG. 3 (B) (right) is an image illustrating the graphene suspension according to Example 1 in the form of powder through a drying process and a granulation process;

(6) FIG. 4(A) (left) is a transmission electron microscopy (TEM) image illustrating nano ribbon-shaped graphite fabricated according to Example 1, and FIG. 4(B) (right) illustrates a TEM analysis result on nano ribbon-shaped graphite fabricated according to Example 3;

(7) FIG. 5(A) (left) is a transmission electron microscopy (TEM) image illustrating nano ribbon-shaped graphite fabricated according to Example 1, and FIG. 5(B) (right) illustrates a TEM analysis result on nano ribbon-shaped graphite fabricated according to Example 3; and

(8) FIG. 6 illustrates that a sample not including graphene powder has been thermally-treated, in which full with half maximum (FWHM) of (002) peak shown near 26 (2) is 4.8.

DETAILED DESCRIPTION OF THE DISCLOSURE

(9) Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated.

Example 1

(10) 1-1) Fabrication of Graphene Nanopowder

(11) Nano-sized graphene powder was fabricated by mechanical milling (decomposing) helical crystalline graphite structure (diameter: several tens of nm, length: several m).

(12) An XRD analysis result on the graphene powder was shown in FIG. 2, and an HRTEM image of the graphene powder was shown on the upper right corner of FIG. 2.

(13) Referring to FIG. 2, (002) peak of an XRD pattern appears to be broadened, and an HRTEM image reveals disordered graphene layers although some of them are stacked in parallel. Graphene sheets have a length of 10 nm or less than and a thickness of 0.4 nm or less than The data prove that the sample was graphene in the form of a nanopowder.

(14) 1-2) Fabrication of Graphene Carbon Fiber Composition

(15) 0.2 g of the graphene powder fabricated according to Example 1-1) was put in 10 cc of dimethylformamide (DMF), and the mixture underwent an ultrasoncation, thereby fabricating a graphene suspension formed as the graphene was dispersed into the DMF.

(16) 1.8 g of polyacrylonitrile (PAN, manufactured by Aldrich Co., Ltd., weightaverage molecular weight: 150, 000) and 100 cc of DMF were mixed to each other, thereby fabricating a PAN solution (composition for fabricating carbon fiber). The graphene suspension and the PAN solution were mixed to each other, and the mixture underwent ultrasonication, thereby fabricating a graphene suspension, a liquid-phase PAN-based graphene carbon fiber composition (the amount of graphene powder was 10 wt % based on the sum (PAN+graphene powder)). The graphene carbon fiber composition of the present invention may be prepared in the form of the graphene suspension, or a material formed as the graphene suspension has a prescribed viscosity, or particles formed after the graphene suspension is dried, etc.

(17) FIG. 3(A) (left) is an image illustrating a graphene suspension, a liquid-phase PAN-based graphene carbon fiber composition according to Example 1 (weight of graphene based on the sum of PAN and graphene powder: 10 wt %). Referring to FIG. 3(A), the graphene suspension exhibited a uniform black color differently from a transparent PAN solution. From this, it was proved that the graphene powder was uniformly dispersed in the PAN solution.

(18) 1-3) Heat Treatment of Graphene Carbon Fiber Composition

(19) For heat treatment of a graphene carbon fiber composition, the graphene suspension was dried in an oven to be granulated. As a result, fabricated was a powder-type graphene carbon fiber composition shown in FIG. 3(B). In case of fabricating graphene carbon fiber, such process is not required, but a suspension viscosity controlling process and a fiberization process are required. Prior to the heat treatment, the graphene carbon fiber composition was stabilized at 300 C. for 3 hours.

(20) The stabilized sample was put into a vacuum furnace, and then was heated (graphitization process) at a temperature of 2,000 C.

(21) An XRD analysis result on the thermally-treated sample was shown in the lower graph of FIG. 2. Referring to FIG. 2, (002) peak was clearly observed near 26 (2). From this, it was proved that the graphene carbon fiber composition was graphitized.

(22) The graphitized sample was analyzed using high-resolution transmission electron microscopy (HRTEM), and an image thereof was shown in FIGS. 4(A) and 5(A). Referring to FIGS. 4(A) and 5(A), nano ribbon-shaped graphite having a thickness of several nm or less than, and a length of several tens of nm is observed.

Comparative Example 1

(23) A PAN carbon fiber composition fabricated in the same manner as in Example 1, except that graphene powder was not included, was stabilized at 300 C. for 3 hours. Then, the PAN carbon fiber composition underwent a graphitization process at a temperature of 2,000 C. for 1 minute.

(24) As shown in FIG. 6, full with half maximum (FWHM) of (002) peak was 4.8, which was much greater than 2.8 shown in FIG. 2 where the PAN-based carbon fiber composition includes graphene powder. This means that graphite is not well formed in a case where the PAN-based carbon fiber composition does not include graphene nano powder. From this, it can be proved that the graphene powder of the present invention serves as a seed in a process of fabricating graphene carbon fiber.

Example 2

(25) In Example 1, experiments were conducted on a change of formation behavior of nano ribbon-shaped graphite, according to a change of the amount of graphene with respect to PAN, when fabricating the graphene carbon fiber composition of Example 1-2) using the graphene nano powder of Example 1-1). The content of the graphene powder was lowered to 0.1 wt % from 10 wt %, and the result was shown in the following Table 1.

(26) When the content of graphene powder based on the sum of PAN and graphene in the graphene suspension is 0.5 wt % or more than, the sample exhibited an entirely opaque black color. However, the sample was gradually diluted when the content of graphene powder is 0.4 wt % or less than. Then, the sample exhibited a semi-transparent black color when the content of graphene powder is 0.1 wt %.

(27) Each graphene suspension was dried, and underwent the same process as in Example 1-3). The resulting materials were analyzed using XRD and TEM, and the degree of graphitization with respect to each sample was shown in Table 1. In a case where the nano ribbon-shaped graphite was well formed (FWHM of (002) peak using XRD was 4.5 or less), it was expressed as Excellent. On the other hand, in a case where the nano ribbon-shaped graphite was not well formed (FWHM of (002) peak using XRD was 4.5 or more), it was expressed as Inferior.

(28) TABLE-US-00001 TABLE 1 Degree of Content of Formation of Nano Graphene Powder Content of PAN Ribbon-Shaped (wt %) (wt %) Graphite Example 2-1 10 90 Excellent Example 2-2 1.0 99.0 Excellent Example 2-3 0.5 99.5 Excellent Example 2-4 0.1 99.9 Inferior

(29) Referring to the above Table 1, in a case where each sample was dried to undergo a graphitization process at 2,000 C., graphitization was performed when the amount of graphene powder is more than 0.1 wt %. Also, graphitization was excellently performed when the amount of graphene powder is 0.5 wt % or more than. On the other hand, the seed effect of the present invention was not observed when the amount of graphene powder is 0.1 wt % or less than.

(30) From the above experiments, it could be proved that the content of graphene powder added to a graphene carbon fiber composition should be more than 0.1 wt %, preferably 0.5 wt % or more than, for fabrication of nano ribbon-shaped graphite when a graphitization temperature is 2,000 C. This means that the content of graphene powder added to a graphene carbon fiber composition is preferably about 0.5 wt % or more than. However, the lower limit may be much lower than 0.1 wt %, according to an experimental method, an optimization of experimental conditions, etc.

Example 3

(31) A pitch-based graphene carbon fiber composition was fabricated using the nano-sized graphene powder fabricated in Example 1-1), and using anisotropy pitch (manufactured by Donga Carbon Fiber Co., Ltd.) rather than the PAN of Example 1-2). Suspension was mixed with the anisotropy pitch. The content of the graphene powder was 10 wt % based on the sum of the anisotropy pitch and the graphene powder, in the same manner as in Example 1.

(32) The pitch-based graphene carbon fiber composition underwent a stabilization process and a graphitization process, in the same manner as in Example 1.

(33) The experimental results obtained in Example 3 were similar to those in Example 1. As shown in the TEM images of FIGS. 4(B) and 5(B), observed was nano ribbon-shaped graphite having a thickness of several nm or less than, and a length of several tens of nm. Further, as an XRD analysis result at (002) peak (FWHM: 3 or less than) was clearly observed near 26 C. (2) in the same manner as in Example 1. This means that high-performance carbon fiber can be fabricated at 2,000 C. if nano-sized graphene is added to a graphene carbon fiber composition, in case of pitch-based carbon fiber.

(34) Referring to the results obtained in Examples and Comparative Example, in the examples where graphene powder was added to a graphene carbon fiber composition, a graphitization process was excellently performed even at a temperature of 2,000 C. This means that high-performance carbon fiber can be fabricated at a temperature of 2,000 C. lower than the conventional 2,500 C. or more than by about 500 C.

(35) The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.

(36) As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.