KR101618736B1 - Isotropic graphite article and and method of manufacturing the same - Google Patents

Abstract

The method of manufacturing an isotropic graphite molded body according to the present invention comprises the steps of preparing spherical natural graphite, preparing graphite-pitch mixed powder by mixing the spherical natural graphite and binder pitch, forming the graphite- , Carbonizing the green compact, and graphitizing the green compact.

Description

TECHNICAL FIELD [0001] The present invention relates to an isotropic graphite formed body and an isotropic graphite formed body,

TECHNICAL FIELD The present invention relates to an isotropic graphite compact and a manufacturing method thereof.

The present invention relates to a method for producing a graphite compact having a high density of isotropic structure and properties and a low coefficient of thermal expansion (CTE). The present invention relates to the production of an isotropic graphite molded body formed from natrual graphite having a high anisotropic structure as a raw material.

In order to have a low CTE, conventional isotropic graphite is subjected to a kneading process using an isotropic coke having an isotropic microstructure as a raw material and an appropriate binder pitch, followed by a CIP (cold isostatic pressing) process to produce a molded article. Thereafter, it is produced by applying a complicated process which carries out carbonization and graphitization again after carbonization process and impregnation pitch reinfusion process.

In such a complicated process, when a coke-binder pitch kneading powder is formed, a separate pitch impregnation process is applied because the gap between particles and particles can not be sufficiently reduced by the CIP process alone. Also, in the case of isotropic graphite used as a raw material, the growth of graphite crystals is limited compared to raw materials having anisotropic structure due to the characteristics of raw coke.

Commercial graphite production methods were capable of producing isotropic graphite compacts having an isotropic ratio close to 1.0, but could not produce graphitic articles having a high degree of graphitization with a CTE of less than 2.0 ppm / ° C over a temperature range of 30 to 100 ° C . To date, highly isotropic graphite articles having thermal shock resistance parameters of more than 150 x 10 < ³ > W / m in both directions have not been marketed. To be useful in applications where thermal shock resistance or high temperature dimensional stability is desired, or useful as a substrate for low thermal expansion coatings, an isotropic ratio of less than about 1.5, a temperature of less than 2.0 ppm / A method for producing graphite having a CTE and having thermal shock resistance parameters in both directions in excess of about 150 x 10 ³ W / m is desired.

U.S. Patent No. 2009-7007196 (Graphtech) discloses a technique for applying an anisotropic coke as a raw material to solve the above problems. However, in the above-described technique, it is essential to apply a re-impregnation process using impregnation pitch in order to obtain a high-density molded article. Through the application of this re-impregnation process, there is a limit to the manufacturing process cost reduction.

Therefore, it is necessary to develop a relatively simple process for producing a high-density molded body having a low CTE value.

Accordingly, the present invention provides a method of producing a molded article by using a large amount of binder pitch and impregnation pitch based on isotropic or needle-shaped coke in the conventional isotropic graphite manufacturing technology, and thus has a high CTE value due to limited graphitization degree, And solve the disadvantages of the process.

According to an embodiment of the present invention, there is provided a method of manufacturing a graphite-pitch mixture powder, comprising the steps of: preparing spherical natural graphite; mixing the spherical natural graphite and a binder pitch to prepare a graphite- A step of carbonizing the green compact, and a step of graphitizing the green compact. The present invention also provides a method of manufacturing an isotropic graphite compact.

The step of preparing the graphite-pitch mixed powder may include adding the binder pitch in an amount of 5 to 15% by weight based on the total weight of the spherical natural graphite.

The step of preparing the graphite-pitch mixed powder may include adding the binder pitch in an amount of 5 to 10 wt% based on the total weight of the spherical natural graphite.

The graphitization step may include a heat treatment step performed at a temperature of 2400 DEG C or higher and 2800 DEG C or lower.

The graphitization step may include a step of raising the temperature within the above temperature range at a rate of 2 DEG C / min or less.

The graphitization step can maintain the elevated maximum temperature for 4 to 6 hours.

The graphitization step may include a heat treatment step performed at a temperature of 2500 DEG C or more and 2700 DEG C or less.

The step of preparing the graphite-pitch mixed powder may include crushing the mixture of the spherical natural graphite and the binder pitch to a particle size of 14 to 18 탆.

The forming step may include molding the graphite-pitch mixed powder.

The molding may be carried out under a pressure condition of 150 MPa or more.

The forming step may be performed according to a cold isostatic press (CIP).

The carbonization step may include a heat treatment step performed at a temperature of 900 ° C to 1300 ° C.

The heat treatment in the carbonization step may be performed in a nitrogen (N ₂ ) atmosphere.

The heat treatment in the carbonization step may include a step of raising the temperature to 2 [deg.] C / min within the temperature range.

The heat treatment in the carbonization step may be carried out for 4 to 6 hours.

The spherical natural graphite may have a tap density of 0.87 g / cm ³ , a Raman peak intensity ratio (I _G / I _D ) of 20, a BET specific surface area of 5.5 m ² / g, and a particle size of 16.7 탆 .

According to another embodiment of the present invention, there is provided an isotropic graphite molded body produced by the above-described methods.

The isotropic graphite compact may have a density of 1.7 g / cc or more.

The isotropic graphite compact may have a coefficient of thermal expansion (CTE) of 0.8 ppm / DEG C or less.

The isotropic graphite compact may have a coefficient of thermal expansion (CTE) of 0.8 ppm / DEG C or less.

According to the present invention, it is possible to produce an isotropic graphite compact having high density and low thermal shock even at a relatively low temperature.

1 is a flow chart for explaining a method for producing an isotropic graphite molded body according to the present invention.
Fig. 2 is a microscope photograph showing the appearance of spherical natural graphite used for producing the isotropic graphite molded article of the present invention.
3 is a photomicrograph showing a cross section of spherical natural graphite used for producing the isotropic graphite compact of the present invention.
4 is a photograph showing the size of the isotropic graphite molded body manufactured according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of 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.

Hereinafter, the isotropic graphite formed body and the manufacturing method thereof according to the present invention will be described with reference to the drawings.

FIG. 1 is a flow chart for explaining a method of producing an isotropic graphite molded body according to the present invention, FIG. 2 is a photograph of a microscope showing the appearance of spherical natural graphite used for producing the isotropic graphite molded body of the present invention, Is a micrograph showing a cross section of spherical natural graphite used in the production of an isotropic graphite compact of the invention.

As shown in FIG. 1, the method for producing an isotropic graphite molded body according to the present invention comprises the steps of preparing spherical natural graphite (S100), mixing the spherical natural graphite and binder pitch to prepare a graphite- S102), forming the graphite-pitch mixed powder into a green compact (S104), carbonizing the green compact (S106), and graphitizing the green compact (S108).

The step (S100) of preparing the spherical natural graphite includes a step of producing natural graphite in the form of spherical particles by crushing the natural graphite with a strong rotational force.

The natural graphite thus formed has a spherical particle shape as shown in Fig. 2, and its cross section is as shown in Fig.

The spherical natural graphite may have a tap density of 0.87 g / cm ³ , a Raman peak intensity ratio (I _G / I _D ) of 20, a BET specific surface area of 5.5 m ² / g, and a particle size of 16.7 탆 .

Next, the spherical natural graphite and the binder pitch are mixed to prepare a graphite-pitch mixed powder (S102).

The binder pitch may have a quinoline-insoluble content of less than 5% and a softening point of about 250 ° C, but is not limited thereto. The carbonization yield in the N ₂ atmosphere up to 1000 ° C with respect to the binder pitch may be about 67%.

The step (S102) of preparing the graphite-pitch mixed powder includes mixing the binder pitch and the spherical natural graphite, and coating the binder pitch on the surface of the spherical natural graphite.

At this time, the binder pitch may be added in an amount of 5 to 15% by weight based on the total weight of the spherical natural graphite. When the binder pitch is added in excess of 15 wt%, carbon and artificial graphite components formed during the process increase as the coating layer of the binder pitch becomes thicker, resulting in a decrease in the compression ratio, which is disadvantageous for high density formation . When the binder pitch is less than 5 wt%, it is impossible to obtain a desired level of pitch coating effect. The binder pitch is more preferably 5 to 10 wt% based on the total weight of the spherical natural graphite.

The step of producing the graphite-pitch mixed powder (S102) may include a step of crushing the mixture of the spherical natural graphite and the binder pitch. The crushing can be performed using a pin-mill and / or a jet-mill to crush the mixture to a particle size of about 14 to 18 μm. When the isotropic graphite compact is shredded to the above-mentioned range, the isotropic graphite compact which is produced can secure a desired level of density. It is most preferable that the graphite-pitch mixed powder has a particle size of about 16 mu m.

When the graphite-pitch powder is produced, it is molded (S104) into a green compact.

The forming step may include molding the graphite-pitch mixed powder. After the graphite-pitch powder is filled in a molding mold, a molded body can be formed through a press process. At this time, the molding preferably proceeds under a pressure of 150 MPa or more. When the molding progresses at less than 150 MPa, it is difficult to ensure a desired level of density of the isotropic graphite molded body.

The molding step may be performed according to a cold isostatic press (CIP).

After the molding step is completed, the step of carbonizing the green compact (S106) is performed.

In the carbonization step, the green compact may be subjected to a carbonization process of coke through heat treatment in an N ₂ atmosphere at 900 to 1300 ° C or less for 5 hours. When carbonized at a temperature of 900 ° C or less, sublimation components are generated during the graphitization process due to components which are not sufficiently carbonized in the carbonaceous material, which adversely affects the graphitization equipment. On the other hand, in the heat treatment of 1300 ° C or more, it is necessary to use a separate heating element, which results in restriction of the carbonization process. The rate of temperature rise in the carbonization step can be set at 2 DEG C / min.

When the carbonization step is completed, a graphitization step (S108) is performed.

The graphitization step may be performed at a temperature of 2400 DEG C or higher and 2800 DEG C or lower. Within the above range, a sufficient graphitizing effect can be achieved. It is more preferable that the temperature is in the range of 2500 ° C to 2700 ° C, and may be, for example, 2600 ° C.

The graphitization step may raise the temperature at a rate of 2 DEG C / min or less within the above temperature range. When the rate of temperature rise exceeds 2 DEG C / min, cracking of the formed body may proceed, so that the maximum rate of temperature rise is preferably limited to 2 DEG C / min or less. The graphitization step can maintain the elevated maximum temperature for 4 to 6 hours, for example, maintain the maximum elevated temperature for about 5 hours.

According to another embodiment of the present invention, an isotropic graphite molded body manufactured according to the above method can be provided.

The isotropic graphite compact may have a density of 1.7 g / cc or more.

The isotropic graphite compact may have a coefficient of thermal expansion (CTE) of 0.8 ppm / ° C or less and a coefficient of thermal expansion (CTE) of 0.8 ppm / ° C or less.

The isotropic graphite compact according to the present invention is produced by using spherical granulated powder of natural graphite having high crystallinity and high compressibility as raw materials and coating the surface of each spherical graphite particle with binder pitch and then performing CIP process and carbonization / . At this time, the pores in the graphite particles having a high compression ratio are reduced through the CIP process, so that an isotropic graphite compact having a high molding density can be produced.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

Example  One

(1) Preparation of spherical natural graphite and binder pitch

A natural graphite having a tap density of 0.87 g / cm ³ , a Raman peak intensity ratio (I _G / I _D ) of 20, a BET specific surface area of 5.5 m ² / g, and a particle size of 16.7 μm was prepared.

Subsequently, a binder pitch having a quinoline-insoluble content of less than 5% and a softening point of 250 DEG C was prepared. The yield of carbonization in the N ₂ atmosphere up to 1000 ° C with respect to the binder pitch was about 67%.

(2) Pretreatment process (graphite-pitch mixing)

Then, the mixed powder of the spherical natural graphite and the binder pitch was put into a 1 kg stirrer and 1 L of THF was added, and then the pitch component was dissolved and mixed with the graphite powder. THF was distilled by heating at 70 DEG C while maintaining the liquid stirring for 1 hour. The aggregates of pitch-graphite mixed powders prepared through this process were pulverized to a particle size of 16 탆 which is the particle size of the natural graphite powder through a finishing process using a pin mill and a jet mill.

At this time, the mixing ratio of the binder pitch of the spherical natural graphite was set to graphite: pitch = 100: 5 (weight ratio).

(3) Molding process ( CIP )

The mixed powder thus prepared was filled in a molding mold, and then a molded body was produced through a pressing process. In this case, the applied molding pressure was fixed at 150 MPa. In the molding step, cold isostatic pressing was applied.

(4) Graphitization  fair

The graphitized green body was subjected to graphitization at 2600 ° C to prepare an isotropic graphite body. At this time, the graphitization was performed at a heating rate of 2 ° C / min and continued at 2600 ° C for about 5 hours.

Example  2

An isotropic graphite molded body was produced in the same manner as in Example 1 except that the mixing ratio of the binder pitch of the spherical natural graphite was changed to graphite: pitch = 100: 10 (weight ratio).

Example  3

The isotropic graphite molded body was produced in the same manner as in Example 1, except that the mixing ratio of the binder pitch of the spherical natural graphite was changed to graphite: pitch = 100: 15 (weight ratio).

Example  4

The isotropic graphite molded body was produced in the same manner as in Example 1, except that the mixing ratio of the binder pitch of the spherical natural graphite was changed to graphite: pitch = 100: 20 (weight ratio).

Comparative Example  One

The isotropic coke was used instead of the spherical natural graphite, and the binder pitch was added to the isotope coke at 20 wt% based on the total weight of the isotropic coke, and the particle size of the mixed powder was pulverized to a level of 5 탆. Graphitization was performed at a temperature of 3000 캜 . The other conditions were the same as in Example 1 to prepare a graphite compact (isotropic coke: pitch = 100: 20 (weight ratio)).

The composition and graphitization temperature applied in Examples 1 to 4 and Comparative Example 1 are as follows.

Weight ratio Graphitization temperature (캜) Example 1 Graphite: pitch = 100: 5 2600 Example 2 Graphite: pitch = 100: 10 2600 Example 3 Graphite: pitch = 100: 15 2600 Example 4 Graphite: pitch = 100: 20 2600 Comparative Example 1 Isotropic coke: Pitch = 100: 20 3000

Rating 1: XRD  analysis

XRD analysis was carried out on the graphite formed bodies according to Examples 1 to 4 and Comparative Example 1, and the degree of progress of graphitization of the formed bodies was compared.

The results are shown in Table 2 below.

division d002 (A) Lc (A) La (A) Example 1 3.355 400 680 Example 2 3.357 395 667 Example 3 3.360 380 653 Example 4 3.365 330 600 Comparative Example 1 3.366 343 612

Referring to the above Table 2, it was confirmed that Example 2, in which the amount of pitch used was 20% by weight, had excellent crystallinity as compared with Comparative Example 1 in which isotropic coke was applied in the same amount in spite of graphitization at 2600 ° C there was.

On the other hand, it was confirmed that as the content of pitch increases in Examples 1 to 4, the crystallinity tends to decrease due to the isotropy of graphite produced by graphitization of pitch.

Evaluation 2: Comparison of physical properties

The density, horizontal bending strength, vertical bending strength, strength anisotropy ratio, horizontal CTE, vertical CTE and CTE anisotropy of the graphite moldings according to Examples 1 to 4 and Comparative Example 1 were evaluated, and the results are shown in Table 3 below.

density
(g / cc) level
Flexural strength
(MPa) Perpendicular
Flexural strength
(MPa) burglar
Anger
(Vertical / horizontal) level
CTE
(ppm / DEG C) Perpendicular
CTE
(ppm / DEG C) CTE
Anger Example 1 1.80 31 32 1.03 0.76 0.78 1.03 Example 2 1.77 30 31 1.03 0.65 0.68 1.05 Example 3 1.72 28 30 1.07 0.56 0.57 1.02 Example 4 1.71 23 25 1.08 0.53 0.54 1.02 Comparative Example 1 1.65 28 29 1.03 2.5 2.7 1.08

Referring to Table 3, it can be seen that as the content of pitch increases in Examples 1 to 4, the density of the graphite compact tends to decrease. It is understood that the larger the content of the pitch is, the thicker the coating layer on the natural graphite surface, the more carbon and artificial graphite components formed in the process are increased and the compression ratio is decreased, resulting in a higher density formation.

In addition, it can be confirmed that the molded bodies according to Examples 1 to 4 are superior in density as compared with the molded bodies according to Comparative Example 1, and have a low CTE value, which is also excellent in thermal shock resistance.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the following claims. Those who are engaged in the technology field will understand easily.

Claims (20)

Preparing spherical natural graphite,
Mixing the spherical natural graphite and the binder pitch to prepare a graphite-pitch mixed powder,
Molding the graphite-pitch mixed powder into an unformed body,
Carbonizing the green compact; and
And graphitizing the green compact, the method comprising the steps of:
The isotropic graphite compact produced according to the above method has a density of 1.7 g / cc or more and a coefficient of thermal expansion (CTE) of 0.8 ppm /
Method of manufacturing isotropic graphite compact
Preparing spherical natural graphite,
Mixing the spherical natural graphite and the binder pitch to prepare a graphite-pitch mixed powder,
Molding the graphite-pitch mixed powder into an unformed body,
Carbonizing the green compact; and
And graphitizing the green compact, the method comprising the steps of:
The isotropic graphite compact produced according to the above method has a density of 1.7 g / cc or more and a coefficient of thermal expansion (CTE) of 0.8 ppm /
Method of manufacturing isotropic graphite compact
3. The method according to claim 1 or 2,
Wherein the step of preparing the graphite-pitch mixed powder comprises the step of adding the binder pitch in an amount of 5 to 15% by weight based on the total weight of the spherical natural graphite. 4. The method of claim 3,
Wherein the step of preparing the graphite-pitch mixed powder comprises the step of adding the binder pitch in an amount of 5 to 10% by weight based on the total weight of the spherical natural graphite. 3. The method according to claim 1 or 2,
Wherein the graphitization step comprises a heat treatment step carried out at a temperature of 2400 DEG C or higher and 2800 DEG C or lower. The method of claim 5,
Wherein the graphitization step includes a step of raising the temperature at a rate of 2 DEG C / min or less within the temperature range. The method of claim 6,
Wherein the graphitization step comprises maintaining the elevated maximum temperature for 4 hours to 6 hours. The method of claim 5,
Wherein the graphitization step comprises a heat treatment step carried out at a temperature of 2500 DEG C or more and 2700 DEG C or less. 3. The method according to claim 1 or 2,
Wherein the step of preparing the graphite-pitch mixed powder includes a step of crushing the mixture of the spherical natural graphite and the binder pitch to a particle size of 14 to 18 占 퐉. 3. The method according to claim 1 or 2,
Wherein the forming step comprises molding the graphite-pitch mixed powder. 11. The method of claim 10,
Wherein the molding is performed under a pressure of 150 MPa or more. 3. The method according to claim 1 or 2,
Wherein the forming step is performed according to a cold isostatic press (CIP). 3. The method according to claim 1 or 2,
Wherein the carbonization step comprises a heat treatment step carried out at a temperature of 900 ° C or higher and 1300 ° C or lower. The method of claim 13,
Wherein the heat treatment in the carbonization step proceeds in an atmosphere of nitrogen (N ₂ ). The method of claim 13,
Wherein the heat treatment in the carbonization step includes a step of raising the temperature to 2 占 폚 / min within the temperature range. The method of claim 13,
Wherein the heat treatment in the carbonization step is performed for 4 hours to 6 hours. 3. The method according to claim 1 or 2,
The spherical natural graphite had isotropic graphite with a tap density of 0.87 g / cm ³ , a Raman peak intensity ratio (I _G / I _D ) of 20, a BET specific surface area of 5.5 m ² / g and a particle size of 16.7 μm A method of manufacturing a molded article.
delete delete delete

Images