KR20180000915A - Manufacturing method for isotropic graphte article and high density isotropic graphte article manufactured by the method - Google Patents

Abstract

The present invention relates to a manufacturing method of an isotropic graphite molded body. The manufacturing method of the present invention comprises: a step (S100) of preparing a raw material powder; a step (S200) of pressurizing and molding the raw material powder at an isostatic pressure; a step (S300) of sintering a molded body obtained by molding the raw material powder; and a step (S400) of graphitizing a sintered body obtained by sintering the molded body. The raw material powder is a carbon powder in which interplanar spacing d (002) between (002) faces is in a range of 0.370.01 (nm) and an Lc value, a crystallite size in a c-axis direction, is in a range of 0.640.01 (nm), and the step (S200) is performed without mixing a binder with the raw material powder. Therefore, the manufacturing method according to the present invention has an effect that an isotropic graphite molded body is capable of being manufactured within a short time without a lack problem of isotropization due to heterogeneity of binder components generated in sintering and graphitization processes by manufacturing the isotropic graphite molded body without using binder materials. Furthermore, the isotropic graphite molded body according to the present invention has an effect of providing a high density isotropic graphite molded body having a high density of 1.90 g/cm^3 or more and a shore hardness of 80 or more since the isotropic graphite molded body has excellent homogeneity by manufacturing the isotropic graphite molded body by using carbon powder only without using the binder materials.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing an isotropic graphite molded body and a high density isotropic graphite formed body produced therefrom,

The present invention relates to a process for producing an isotropic graphite compact and a high density isotropic graphite compact produced thereby.

In general, carbon is a chemically stable element that plays an important role in the mechanical and chemical industries. It has both physical and ceramic properties, has van der Waals bonds in the c-axis direction, It has covalent bonds on the surfaces a and b, and exhibits high anisotropy. In particular, it is considered to be a material excellent in lubricity, heat resistance, thermal shock resistance, thermal conductivity, and corrosion resistance that can not be found in metals and ceramics.

One of the materials that can be used as carbon materials is graphite, which is superior in heat resistance, corrosion resistance, electrical conductivity, high temperature strength and lubricity to other materials. Therefore, carbon is used in various fields such as high-temperature structural materials such as electrodes, carbon brushes, and mechanical seals, and special mechanical parts. Since graphite exhibits anisotropy in its crystal structure, isotropic cokes having isotropy are mixed with binder pitch or the like to form an isotropic graphite material, and after the isotropic coke is brought into close contact with isotropic pressure (hydrostatic pressure) And additional process such as re-impregnation with impregnation pitch in carbonization process is required.

In order to solve such inconvenience and increase the isotropy and physical properties of the graphite material, a technique of using a large amount of binder pitch in spherical natural graphite (Korean Patent Registration No. 10-1618736), using a pitch of graphite as a binder, (Korean Patent No. 10-1249647). However, in all the techniques, pitch or resin component is still used as the binder material, and since the filler and binder are mixed and used, there is a problem that the anisotropic texture of the binder in the firing process shows the shape of the filler and other textures in the firing process. It is disadvantageous in that density and strength are lowered as a result of difficulty in developing uniform physical properties.

Korean Patent No. 10-1618736 Korean Patent No. 10-1249647

It is an object of the present invention to provide a method for producing an isotropic graphite molded body without using a binder, and an isotropic graphite molded body produced by the method and having improved density and strength.

According to an aspect of the present invention, there is provided a process for producing an isotropic graphite compact, comprising the steps of: preparing a raw material powder; Pressurizing the raw material powder by iso-pressure to form (S200); A step (S300) of firing the molded body from which the raw material powder is molded; (002) of 0.37 + - 0.01 (nm), which is an interplanar spacing of the (002) plane of the raw powder, and graphitizing the calcined sintered body by Lc Value is 0.64 占 0.01 (nm), and the step S200 is performed without mixing the binder in the raw material powder.

The present invention provides a method for producing a high density isotropic graphite molded body by molding at a uniform pressure using only a raw powder composed of only carbon powder without any mixing of other materials such as a binder, sintering and graphitizing, and as a raw material powder A carbon powder having an interplanar spacing d (002) of 0.37 ± 0.01 (nm) and an Lc value of 0.64 ± 0.01 (nm) as a crystallite size in the c-axis direction is used.

At this time, it is preferable that the average particle diameter of the raw material powder is 0.5 to 10 mu m. Further, after step S100, it is preferable to further carry out the step of removing the raw material powder having a diameter exceeding 10 mu m.

It is preferable that the iso-pressure applied to the raw material powder in the step S200 is in the range of 50 to 200 MPa.

In step S300, it is preferable that the sintering process is performed at a heating rate in the range of 50 to 500 ° C per hour and at a temperature range of 1,100 to 1,300 ° C for at least 5 hours, and the total sintering time is within 75 hours.

The step S400 is preferably performed in a temperature range of 2,600 to 3,000 DEG C. [

Density isotropic graphite molded article according to another embodiment of the present invention is characterized in that the interplanar spacing d 002 of the (002) plane is in the range of 0.37 0.01 (nm) and the crystallite size in the c-axis direction is 0.64 0.01 (nm) In the sintering process. In the sintering process, only the carbon powder is used and the binder is not used.

Although the high density isotropic graphite molded body of the present invention is specified in terms of the production method, it is manufactured by sintering and graphitizing only carbon powder without using a binder and the like, and its characteristics are different from those of a conventional graphite molded body. It is specific by the manufacturing method because it is difficult to specify by the physical properties of the final product. By this specification, one skilled in the art can clearly recognize that the high-density isotropic graphite molded body of the present invention differs in physical properties from graphite molded bodies conventionally produced using a binder.

The isotropic graphite compact of the present invention has a density of 1.9 g / cm 3 or more and a Shore hardness of 80 (Hs) or more.

According to the present invention configured as described above, an isotropic graphite compact can be produced in a short time without problems of isotropy due to heterogeneity of binder components generated during firing and graphitization, by using an isotropic graphite compact without using a binder material There is an effect that can be.

Since the isotropic graphite compact of the present invention is made only of carbon powder without using a binder material and is excellent in homogeneity, the effect of providing a high density isotropic graphite compact having a high density of 1,9 g / cm 3 or more and a Shore hardness of 80 or more have.

1 is a flow chart for explaining a method for producing an isotropic graphite molded article according to the present invention.
Fig. 2 is a photograph of the appearance of raw material powder prepared for use in the production of a high density isotropic graphite molded article according to this embodiment.
3 is a photograph of a fracture surface of a press-molded formed article during the manufacturing process according to the present invention.
Fig. 4 shows the crystal structure of the high-density isotropic graphite molded body produced according to the embodiment of the present invention.
FIG. 5 shows XRD analysis results of the high density isotropic graphite formed according to the embodiment of the present invention.
Fig. 6 is an external view of a high-density isotropic graphite molded article produced according to the present invention.

A method for producing an isotropic graphite formed body according to the present invention, a high density isotropic graphite formed body produced by the method, and an embodiment according to the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

1 is a flow chart for explaining a method for producing an isotropic graphite molded article according to the present invention.

As shown in the drawing, the method of manufacturing a high density isotropic graphite molded body according to the present invention includes the steps of preparing a raw material powder (S100), pressing the prepared raw material powder by cold isostatic pressing (CIP) (S200) (S300), and graphitizing the sintered body (S400).

The step (S100) of preparing the raw material powder is a step of preparing a raw material powder for producing a graphite compact, wherein the (002) plane spacing (002) of the (002) plane is in the range of 0.37 + - 0.01 And the Lc value of the crystallite size of 0.64 ± 0.01 (nm) is prepared. The carbon powder having such physical properties can be prepared by heat treating a pitch in a solid state. The raw material pitch in the solid phase is charged into an agitated reactor capable of controlling the atmosphere, and then heated so that the temperature can be raised at a rate of 30 ° C or higher per minute. The carbon powder having a d (002) in the range of 0.37 ± 0.01 (nm) and an Lc value in the range of 0.64 ± 0.01 (nm) can be prepared by heat treatment at ~ 600 ° C. for 3 to 5 hours. In this case, the raw material powder preferably has an average particle diameter in the range of 0.5 to 10 mu m, and when the average particle size is larger, the density is lowered. Particularly, when the raw material powder contains a raw material powder having a particle size larger than 10 mu m, the physical properties of the graphite formed body deteriorate. Therefore, it is preferable to perform a process of removing the raw material powder having a size of 10 mu m or more.

In the step S200 of pressurizing the raw material powder, the prepared raw material powder is molded into a desired shape by using a cold isostatic pressing device. At this time, in the conventional isotropic graphite formed body manufacturing methods, a pitch or a binder made of a resin material is mixed with a raw material which is a filler, and the forming process is carried out. In contrast, in the present invention, only a raw powder is mixed with a cold isostatic pressing The isotropy of the raw material can be ensured even if a molded article is produced. The molding process using a cold isostatic device is carried out in a pressure range of 50 MPa to 200 MPa.

The step of firing the molded body (S300) is a step of firing and sintering the formed body composed only of the raw powder to produce a densified fired body. The firing process is carried out at a heating rate in the range of 50 to 500 ° C. per hour and the firing process is performed for a time period of 5 hours or more at a temperature range of 1,100 to 1,300 ° C. The total firing time is performed for 75 hours or less, Lt; / RTI > The initial compact has a 3% to 10% pre-shrinkage and a 8% to 25% volume shrinkage during the firing process.

In the step of graphitizing the sintered body (S400), a sintered and densified sintered body is heat-treated to manufacture a graphite compact of graphite material. The graphitization heat treatment is carried out in an inert atmosphere at a temperature range of 2,600 ~ 3,000 ℃, and the time required may vary depending on the characteristics of the heat treatment apparatus. When the induction heating method is applied, graphitization can be performed within 48 hours. When the Acheson type heating method is applied, it can take more than 72 hours. The sintered body undergoes a linear shrinkage of 1% to 5% and a volume shrinkage of 5% to 12% during the graphitization process.

Hereinafter, the method for producing an isotropic graphite molded body of the present invention and the high density isotropic graphite formed body produced therefrom will be described with reference to specific examples.

Example 1

First, the solid state pitch was heated in an agitated reactor capable of controlling the atmosphere at a heating rate of 30 ° C or higher per minute, and heat treatment was performed at 500 to 600 ° C for 3 to 5 hours to obtain d (002) Of 0.37 + - 0.01 (nm) and an Lc value in the range of 0.64 + - 0.01 (nm) were prepared and prepared as raw material powders. (S100)

Fig. 2 is a photograph of the appearance of raw material powder prepared for use in the production of a high density isotropic graphite molded article according to this embodiment.

(002) plane interval (d002) is in the range of 0.37 ± 0.01 (nm), and the Lc value, which is the crystallite size in the c-axis direction, is 0.64 ± 0.01 (nm).

Then, a raw material powder having a size of 10 탆 or more was removed from the prepared raw material powder.

Next, the prepared raw material powder was charged in a molding mold, charged into a cold isotropic device, and subjected to iso-pressure molding at a level of 100 MPa to produce a molded article (S200)

The molded body was sintered in a neutral atmosphere at a temperature of 1300 DEG C for 6 hours and sintered to produce a sintered body (S300)

Finally, the sintered body was graphitized in an inert atmosphere at a temperature of 2,600 DEG C to prepare a high density isotropic graphite compact (S400).

Example 2

Isotropic compression molding was performed at a pressure of 130 MPa in step S200. Finally, a high density isotropic graphite molded body was produced in the same manner as in Example 1, except that the sintered body was graphitized at a temperature of 2,800 DEG C in an inert atmosphere.

Example 3

Isotropic compression molding was performed at a pressure of 150 MPa in step S200, and finally, a high density isotropic graphite molded body was produced in the same manner as in Example 1, except that the sintered body was graphitized at a temperature of 2,900 DEG C in an inert atmosphere.

Example 4

Isotropic compression molding was performed at a pressure of 170 MPa in step S200. Finally, a high density isotropic graphite molded body was produced in the same manner as in Example 1, except that the calcined body was graphitized at an operating temperature of 3,000 DEG C in an inert atmosphere.

Example 5

Density isotropic graphite molded body was manufactured in the same manner as in Example 1, except that isotropic pressing was performed at a pressure of 200 MPa in step S200, and finally, the graphite body was subjected to graphitization at an operating temperature of 3,000 DEG C in an inert atmosphere. Respectively.

Comparative Example 1

For comparison with the above-mentioned examples according to the present invention, a carbon powder having a d002 of 0.35 (nm) and an Lc value of 0.78 ± 0.01 (nm) is used as the raw material powder, The graphite molded body was produced in the same manner as in the above examples, except that the isotropic pressing was performed under pressure and the graphitization step was performed at 3000 占 폚 in step S400.

The process conditions of the examples and comparative examples are shown in Table 1 below.

(d200) (nm) Lc (nm) Molding pressure (MPa) Graphitization temperature (캜) Example 1 0.37 ± 0.01 0.64 ± 0.01 100 2,600 Example 2 0.37 ± 0.01 0.64 ± 0.01 130 2,800 Example 3 0.37 ± 0.01 0.64 ± 0.01 150 2,900 Example 4 0.37 ± 0.01 0.64 ± 0.01 170 3,000 Example 5 0.37 ± 0.01 0.64 ± 0.01 200 3,000 Comparative Example 1 0.35 0.78 ± 0.01 200 3,000

The density and the hardness of the graphite moldings produced by the methods according to Examples 1 to 5 and Comparative Example 1 were measured, and the results are shown in Table 2.

Density (g / cm3) Shore Hardness (Hs) Example 1 1.93 100 Example 2 1.95 95 Example 3 1.97 96 Example 4 1.99 85 Example 5 2.01 80 Comparative Example 1 Cracking Cracking

According to the present invention, the graphite compacts produced by the methods of Examples 1 to 5 using only carbon powder having a (d002) in the range of 0.37 占 0.01 (nm) and an Lc value in the range of 0.64 占 0.01 (nm) Or more and a Shore hardness of 80 Hs or more, confirming that a high density isotropic graphite formed body was produced. In addition, the density of the high density isotropic graphite formed according to Examples 1 to 5 was slightly decreased as the pressure was increased in the isostatic pressing, but the density was increased.

On the other hand, in Comparative Example 1, although the isotropic compression molding was performed at a higher pressure than the Examples in S200, the graphite compact could not be produced due to cracking. This is because the nature of the carbon powder used as the raw material powder of Comparative Example 1 does not allow the intergranular sintering to occur without using a binder and thus it is judged that an appropriate graphite molded body can not be manufactured. Consequently, the carbon powder according to the present invention is used as a raw material powder It can be understood that a high-density graphite molded body can be produced without a binder.

3 is a photograph of a fracture surface of a press-formed molded article during the manufacturing process of Example 3 according to the present invention.

As shown in the figure, it can be seen that the formed body obtained by isostatic pressing of the carbon powder used in the manufacturing process according to the present invention is well integrated with each other even though no binder is added.

FIG. 4 shows the crystal structure of the high density isotropic graphite molded body manufactured according to Example 4 of the present invention, and FIG. 5 shows the XRD analysis result of the high density isotropic graphite molded body manufactured according to Example 2 of the present invention. Fig. 6 is an external view of a high-density isotropic graphite molded article produced according to the present invention.

From FIG. 4 and FIG. 5, it can be confirmed that the formed body manufactured by the manufacturing method according to the present embodiment is an isotropic graphite body in which the graphitization is fully advanced. In addition, when graphitization was performed at a temperature of 2,800 ° C., it can be confirmed that a high-density graphite molded body having a d (002) of 0.345 (nm) or less and an Lc value of 10.0 ± 0.1 (nm) or more was produced. Further, the apparent density of the graphite molded body produced at a temperature of 2,800 ° C in the graphitization step is 1.99 g / cm 3 or more.

The bending strength, compressive strength and electrical conductivity of the high density isotropic graphite molded body produced by the method according to Examples 1 to 5 were measured, and the results are shown in Table 3.

Flexural strength (MPa) Compressive strength (MPa) Electrical resistance (μΩcm) Example 1 64 172 40 Example 2 54 148 13 Example 3 53 149 12 Example 4 52 151 12 Example 5 52 153 11

The specimen according to Example 1 having a graphitization temperature as low as 2,600 ° C had a high mechanical strength but a high electric resistance value. From Examples 2 to 5, the molding pressure was increased and the graphitization temperature was 2,800 ° C. Although the bending strength slightly decreased as the temperature increased to 3,000 ℃, the compressive strength tended to increase slightly, and the electrical resistance value decreased significantly.

From the above results, it can be confirmed that the high density isotropic graphite molded article according to the present invention is produced without using a binder and has excellent characteristics showing a density of 1.90 g / cm 3 or more and a Shore hardness of 80 (Hs) or more.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Those skilled in the art will understand. Therefore, the scope of protection of the present invention should be construed not only in the specific embodiments but also in the scope of claims, and all technical ideas within the scope of the same shall be construed as being included in the scope of the present invention.

Claims (10)

Preparing a raw material powder (S100);
Pressurizing the raw material powder by iso-pressure to form (S200);
A step (S300) of firing the molded body from which the raw material powder is molded; And
And graphitizing the fired sintered body (S400)
(002) of the (002) plane of the raw material powder is in the range of 0.37 + - 0.01 (nm) and the crystallite size in the c-axis direction is in the range of 0.64 + - 0.01 (nm)
Wherein the step S200 is carried out without mixing the binder in the raw material powder.
The method according to claim 1,
Wherein the raw material powder has an average particle diameter of 0.5 to 10 占 퐉.
The method according to claim 1,
Further comprising the step of removing the raw material powder having a diameter exceeding 10 mu m after the step S100.
The method according to claim 1,
Wherein in step S200, the applied pressure is in the range of 50 to 200 MPa.
The method according to claim 1,
Wherein the step of heating is performed at a temperature raising rate in a range of 50 to 500 占 폚 per hour in the step S300.
The method according to claim 1,
Wherein the calcination step is performed at a temperature ranging from 1,000 to 1,300 DEG C for not less than 5 hours but not more than 75 hours.
The method according to claim 1,
Wherein the step S400 is performed in a temperature range of 2,600 to 3,000 DEG C.
(002) of 0.37 ± 0.01 (nm), which is the interplanar spacing of the (002) plane, and the Lc value of the crystallite size in the c-axis direction of 0.64 ± 0.01 ,
Wherein the carbon powder is used only in the sintering process without using a binder.
The method of claim 8,
Wherein the isotropic graphite compact has a density of 1.90 g / cm < 3 > or more.
The method of claim 8,
Wherein the isotropic graphite compact has a Shore hardness of 80 (Hs) or higher.

Images