KR20100137621A - Producing method of low-dimensional carbon-contained composits and carbon block - Google Patents

Abstract

PURPOSE: A method for producing a low-dimensional carbon-contained composite and a method for producing a carbon block are provided to add a carbon nano tube with point/line contact properties and grapheme with surface contact properties, thereby increasing electric conductivity of a carbon composite. CONSTITUTION: Graphene and a low-dimensional carbon material are added to pitch. The grapheme, the low-dimensional carbon material, and the pitch are uniformly distributed through a post-processing process. Pressing molding of a carbon composite is performed by a press device. A molded product is thermally processed at 150~350 degrees for 2~6 hours. The molded product is carbonized at 1000~1500 degrees after oxidation stabilization. The oxidation stabilization of the molded product is performed under a low temperature for a long time. Therefore, a carbon block with high electric conductivity is manufactured.

Description

Producing method of low-dimensional carbon-contained composits and carbon block

The present invention relates to a carbon composite material in which pitch and graphene and low dimensional carbon materials are uniformly dispersed, and a technology for producing a carbon block having excellent electrical conductivity by pressure molding the carbon composite material and heat treatment (carbonization process).

Graphene refers to a two-dimensional plate-shaped nanostructure in which graphite is formed in one layer or several layers. Such graphene is generally produced through vapor deposition, chemical carbon layer separation, or the like (Mater. Today 10, 2026 (2007)). The structure of the graphene is based on a planar honeycomb shape having sp2 bonds, and three of the four sp-hybridized bonding electrons are used, and one of the remaining electrons is present in the form of a pie bond on the upper and lower surfaces of the two-dimensional plane. Plays an important role in conductive properties. Theoretical findings indicate that the electrons on the graphene surface are ballistic conduction and move in any length. The allowable current density is 109 A / cm 2, which is about 1,000 times that of copper. Graphene's high density electrical conductivity is similar to that of metallic CNTs.

Such graphene is easily induced between the surface contact when pressed, and thus can play a big role in improving the electrical conductivity of the carbon composite when used as an additive of the carbon composite. This is comparable to the linear contact of carbon nanotubes.

Pitch can be largely classified into coal-based, petroleum-based, pure-material-based (PVC pitch, Pz pitch, naphthalene pitch, acenaphthalene pitch) and the like. Representative raw material pitches include petroleum and coal. The petroleum pitch is mainly composed of aromatic hydrocarbons in which alkyl chains are bonded to polycyclic aromatic ring compounds, and the coal pitch is composed of approximately two-thirds of aromatic ring compounds and two-membered ring. In particular, a mixture of 3 to 6 cyclic compounds (bp: 340-550 ℃) is mainly used, and has a low softening point, low melt viscosity, high carbon yield, and excellent graphitization property, so it is widely used as a starting material for carbon materials. . However, it has an amorphous shape even in heat treatment at 1000 ~ 1500 ℃ and shows very low physical properties with crystalline graphite. However, since pitch is a very inexpensive raw material, attempts have been made to obtain high conductivity carbon blocks through simple heat treatment.

In the existing research, an attempt has been made to produce a highly conductive pitch-based carbon block by combining graphite powder with pitch. This is because the pitch-based sintered body (carbonized at 1000 to 1500 ° C) is female amorphous, whereas each graphite powder has high electroconductivity. This is a concept that complements the disadvantages of the non-sintering and pitch-low electrical conductivity of the graphite powder itself. However, the point contact property of graphite powder has a limit in improving the electrical conductivity of pitch sintered compacts.

An object of the present invention is to obtain a carbon composite and a carbon block having improved electrical conductivity compared to a sintered body of the conventional pitch by combining graphene with a low-cost pitch.

The present invention (a) adding the graphene and low-dimensional carbon material to the pitch; (b) post-processing the graphene, pitch and low dimensional carbon material to be evenly dispersed; It provides a graphene-pitch composite manufacturing method comprising a. As the low dimensional carbon material, graphite powder or carbon nanotubes may be applied, or a mixture of the graphite powder and carbon nanotubes may be applied.

In addition, the present invention provides a low-dimensional carbon-containing carbon composite manufacturing method characterized in that the pitch of step (a) is to remove the volatiles by heat treatment at 400 ~ 600 ℃. In this case, the pitch may be applied to the pitch on the meso face formed through the heat treatment, and may be applied to the coke state by adding heat to the pitch on the meso face.

In addition, the present invention provides a method for producing a low-dimensional carbon-containing carbon composite, characterized in that the post-processing by ball milling in the step (b). Thereafter, the step (b) may further include a step of oxidatively stabilizing the pitch by applying heat of 200 ~ 400 ℃. For the oxidation stabilization of the pitch, a low temperature heat treatment may be performed to increase the temperature at a rate of 5 ° C./min and maintain it at 1000 to 1500 ° C. for 50 to 70 minutes.

In addition, the present invention is a carbon composite produced by the above-described low-dimensional carbon-containing carbon composite manufacturing method (a) a step of producing a molded body by pressing the carbon composite; And (b) heat treating the molded body to carbonize it; It also provides a method for producing a carbon block to be processed with.

In addition, the present invention provides a method for producing a carbon block, characterized in that the (b) carbonized the molded body at 1000 ~ 1500 ℃ in the step, wherein the molded body is maintained for 2 to 6 hours at 150 ~ 350 ℃ After the oxidation and stabilization by heat treatment, it provides a carbon block manufacturing method characterized in that the carbonization at 1000 ~ 1500 ℃.

In addition, the present invention provides a method for producing a carbon block, characterized in that the (b) the carbonized the molded body at 1700 ~ 2500 ℃ in the step.

In the present invention, not only the conventional point contact graphite powder (zero-dimensional carbon material) is added but also point / line contact carbon nanotubes (one-dimensional carbon material) and surface contact graphene (two-dimensional carbon material) are added. This greatly improves the electrical conductivity of the carbon composite material. Main components of the low dimensional carbon-containing carbon composites provided by the present invention include 1) "graphene-graphite powder-pitch", 2) "graphene-carbon nanotube-pitch", and 3) "graphene-graphite powder- Carbon nanotube-pitch ”.

In addition, the low-dimensional carbon-containing carbon composite may be press-molded, followed by heat treatment to obtain a highly conductive carbon block.

As a result, the conductivity of carbon blocks containing `` graphene-graphite powder-pitch '' is improved by 20-50% compared to the pitch-graphite powder carbon block, and `` graphene-graphite powder-carbon nanotube-pitch '' is contained. In the case of a carbon block, it is improved by 30 to 70%.

Ⅰ. Low Dimensional Carbon-Containing Carbon Composite

The present invention (a) adding the graphene and low-dimensional carbon material to the pitch; (b) post-processing the graphene, pitch and low dimensional carbon material to be evenly dispersed; It provides a graphene-pitch complex manufacturing method comprising a (see Fig. 1).

Step (a) is a step of adding the graphene and low-dimensional carbon material to the pitch.

Pitch used in the present invention may be applied to all of the coal-based, petroleum-based, pure material-based pitch. The pitch may be heat treated to remove some of the volatiles or cause some crosslinking reaction.

When the pitch is heat-treated at 400 to 600 ° C., some of the volatiles in the pitch are removed, and when polycondensation occurs between pitches, the pitches become spherical bodies having a diameter of about 0.1 μm. It has the same property as the anisotropic liquid crystal which has a flow phase as a whole. This state is a mesophase state as a previous stage of cokes. These mesophase pitches form a dense graphite structure during sintering, since the liquid crystals having a proper phase of volatiles and a flow phase are easily arranged during carbonization and graphite softening. When heat is continuously applied to the pitch of the mesophase state and heat treated at about 1000 ° C., some of the hydrogen residues and hetero atoms are evaporated and removed to form coke. The final product through this step is an amorphous carbon material, and atoms such as nitrogen and sulfur contain a significant amount in the form of a safe heterocyclic compound.

The graphene may be prepared by making graphene oxide through chemical treatment from graphite powder using a human method and chemically reducing the graphene oxide. Graphene thus produced is usually formed of 1 to 10 layers. Referring to the specific method performed by the inventor of the present invention to produce the graphene oxide and graphene is as follows.

50 g of graphite powder having a size of several tens of microparticles and 40 g of NaNO ₃ were added to a solution containing 200 ml of H ₂ SO ₄ , and 250 g of KMnO ₄ was slowly added over 1 hour while cooling. After that, slowly add 5ℓ of solution dissolved in H ₂ SO ₄ to 4 ~ 7vol% over 1 hour and add H ₂ O ₂ . The solution is then centrifuged to wash the precipitate with 3% H ₂ SO ₄ -0.5% H ₂ O ₂ and distilled water to give a tan graphene oxide. The graphene oxide thus prepared is dispersed in 2 g of distilled water in 40 g of a 3% graphene aqueous solution, and then dispersed 20 ml of hydrazine hydrate and reduced at 100 ° C. for 24 hours. The prepared graphene is filtered with a filter paper and washed with water and methanol.

On the other hand, the low-dimensional carbon material may be applied to the graphite powder or carbon nanotubes, a mixture of the graphite powder and carbon nanotubes may be applied.

Step (b) is a step of post-processing so that the graphene, pitch and low dimensional carbon materials are evenly dispersed. The process of dispersing the graphene and the low-dimensional carbon material by adding it to the pitch may be a physical dispersion method or a chemical dispersion method, and in particular, a ball milling method may be applied. In some cases, wet milling may be performed by adding a small amount of a solvent of hexanes.

On the other hand, in the step (b) it can be additionally carried out a process of oxidative stabilization by heat treatment (relatively low temperature heat treatment) to 200 ~ 400 ℃ the pitch. This is to control the viscosity and crosslinkability of the pitch, and the viscosity of the pitch is increased by this low temperature heat treatment, and the polycondensation is disturbed.

Separately, for the oxidation stabilization of the pitch, the temperature may be elevated at a rate of 5 ° C./min and low temperature heat treatment may be performed at 300 to 550 ° C. for 50 to 70 minutes.

II. Carbon block manufacturing method

The carbon composite produced through the above-described process is transformed into a carbon block through a press molding process and a carbonization process.

Thus, the present invention is a carbon composite prepared by performing the low-dimensional carbon-containing carbon composite manufacturing method (a) a step of producing a molded body by pressing the graphene-carbon composite; And (b) heat treating the molded body to carbonize it; It also provides a carbon block manufacturing method for processing with (see FIG. 2).

The step (a) can be carried out by press molding the carbon composite.

The step (b) is a step for obtaining a carbon block having high conductivity, and may be carried out by carbonization after heat treatment to oxidatively stabilize the molded body or carbonization immediately without an oxidation stabilization process.

In the step (b), the molded body may be carbonized at 1000 to 1500 ° C. As described above, before the carbonized product is carbonized, oxidation stabilization may be performed by low temperature heat treatment, and the carbonized product may be carbonized at 1000 ° C to 1500 ° C after oxidation stabilization by heat treatment for 2 to 6 hours at 150 to 350 ° C. have.

The molded body is subjected to oxidation stabilization process and secures dimensional stability in the process of carbonization, so that the structure is densified by cross-linking reaction by oxygen, thereby improving mechanical properties, thus, warping and deformation of the molded body containing pitch during high temperature sintering Etc. is minimized. It is preferable to perform oxidation stabilization of the molded body for a long time at low temperature because the rapid oxidation reaction of the molded product occurring at a high temperature may cause cracking of the molded body or cause decomposition of the pitch component.

When the inventor of this invention demonstrates the specific example which carried out the specific oxidation stabilization process of the said molded object, it is as follows. The coal-based pitch is placed in a chemical resistance reaction vessel (SUS), and the temperature is raised to 5 ° C / min and maintained at 300 to 550 ° C for 50 to 70 minutes. The heat treated pitch was ball milled for 12 hours or longer at 250 rpm. After the ball milling, a molded article was prepared by mixing and pressing with graphene using only a powder having a particle size of 325 mesh (about 44 μm) or less. The molded product thus prepared was heat treated for 2 to 6 hours while maintaining a temperature in the range of 150 to 350 ° C. using a hot air dryer to circulate air. The oxidatively stabilized graphene-pitch composite molded article may be carbonized at 1000 to 1500 ° C. to produce a highly conductive carbon block.

On the other hand, the step (b) can be carried out as a step of carbonizing the molded body at 1700 ~ 2500 ℃. Heat treatment at 1000 ~ 1500 ℃ is close to female mold type even if pitch is carbonized. However, when the heat treatment of 1700 ~ 2500 ℃ or more induction of the crystallization of carbon can be produced a more excellent high conductivity carbon block. At this time, the added two-dimensional nano-graph graphene made a pass of the high conductivity, showing an electrical conductivity improvement of 20 ~ 100% increased than when using only the pitch. For example, the pitch and graphene-carbon composites heat-treated at 1000 ° C., 1300 ° C., and 1500 ° C. were significantly improved from 20 Siemens to 30 Siemens, 32 Siemens to 55 Siemens, and 50 Siemens to 90 Siemens, respectively. For reference, the electrical conductivity of the pitch before sintering showed the physical properties of the insulator, but showed about 35KΩ / sq when 5% of graphene was added.

Figure 3 shows a photograph of the graphene oxide and SEM (scanning electron microscope) photograph. In the SEM photographs, the wide plate shapes overlap and show wrinkles.

4 is a SEM photograph of the graphene powder prepared by treating the graphene oxide of FIG.

5 is a SEM photograph of the pitch heat-treated at 450 ~ 470 ℃.

6 is a SEM photograph of the graphene-carbon composite powder coated with graphene on the pitch surface after ball milling for 24 hours by adding 5% graphene to the pitch of FIG. 4.

7 is a schematic view showing a carbon block structure in the case of sintering a molded article pressurized with a carbon composite material.

1 is a flow chart of a low-dimensional carbon-containing carbon composite manufacturing method according to the present invention.

2 is a flowchart of a carbon block manufacturing method according to the present invention.

3 is a SEM photograph of the graphene oxide.

4 is an SEM photograph of graphene powder.

5 is a SEM photograph of the pitch.

6 is an SEM photograph of graphene-carbon composite powder.

7 is a schematic diagram of a carbon block structure containing a low dimensional carbon material.

<Explanation of symbols for the main parts of the drawings>

S11: Step (a) (Method for producing low dimensional carbon-containing carbon composite material)

S12: step (b) (method of preparing a low dimensional carbon-containing carbon composite)

S21: (a) process (carbon block manufacturing method)

S22: (b) process (carbon block manufacturing method)

Claims (14)

(a) adding graphene and a low dimensional carbon material to the pitch; (b) post-processing the graphene, pitch and low dimensional carbon material to be evenly dispersed; Graphene-pitch composite manufacturing method comprising a. According to claim 1, wherein the low-dimensional carbon material of step (a) is a low-dimensional carbon-containing carbon composite manufacturing method, characterized in that the graphite powder. The method of claim 1, wherein the low dimensional carbon material of step (a) is a carbon nanotube manufacturing method of the low dimensional carbon containing carbon composite. The method of claim 1, wherein the low dimensional carbon material of step (a) is a low dimensional carbon-containing carbon composite manufacturing method, characterized in that the mixture of graphite powder and carbon nanotubes. The method of claim 1, wherein the pitch of step (a) is a low-dimensional carbon-containing carbon composites manufacturing method, characterized in that the volatiles are removed by heat treatment at 400 ~ 600 ℃. The method of claim 5, wherein the pitch of step (a) is a low-dimensional carbon-containing carbon composite manufacturing method, characterized in that the pitch of the mesophase formed through the heat treatment. 7. The method of claim 6, wherein the pitch of step (a) is converted to a coke state by adding heat to the pitch on the mesophase. The method of claim 1, wherein step (b) is a low-dimensional carbon-containing carbon composites manufacturing method, characterized in that the post-treatment process by ball milling. The method of claim 8, wherein step (b) further comprises the step of oxidatively stabilizing the pitch by applying heat of 200 ~ 400 ℃ low dimensional carbon-containing carbon composites manufacturing method. The method of claim 8, wherein the step (b) further comprises the step of oxidatively stabilizing the pitch by low temperature heat treatment to maintain the temperature at a rate of 5 ℃ / min at 300 ~ 550 ℃ 50 ~ 70 minutes Method of producing carbon-containing carbon composites. The carbon block manufacturing method which processes the carbon composite manufactured by implementing the low-dimensional carbon containing carbon composite manufacturing method of any one of Claims 1-10 by the following process. (a) pressurizing the carbon composite to produce a molded article; And (b) heat-treating the molded body to carbonize it; 12. The method of claim 11, wherein the step (b) carbonizes the molded body at 1000 to 1500 ° C. The method according to claim 12, wherein the step (b) is a carbon block manufacturing method characterized in that the carbonized at 1000 ~ 1500 ℃ after the oxidation is stabilized by heat treatment to maintain the molded body at 150 ~ 350 ℃ 2 to 6 hours. 12. The method of claim 11, wherein the step (b) carbonizes the molded body at 1700 to 2500 ° C.

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