KR101859818B1 - Preparation method of sintered SiC ceramic by using plasma treated Si-SiC nanoparticle - Google Patents

Abstract

The present invention relates to a method for producing a SiC sintered body using plasma-treated Si / SiC nanocomposite powder, comprising the steps of mixing a micron-sized SiC fine powder and a plasma-treated Si / SiC nanocomposite powder sintering aid to obtain a mixed powder, ; And sintering the mixed powder to obtain a SiC sintered body.

Description

[0001] The present invention relates to a method for producing a SiC sintered body using a plasma-treated Si-SiC nanocomposite powder,

The present invention relates to a method for producing a SiC sintered body using a plasma-treated Si-SiC nanocomposite powder.

 SiC (silicon carbide) is generally physically / chemically stable and has high heat stability and high temperature strength because it has high heat resistance and thermal conductivity. It has high abrasion resistance and is used as a high temperature material for gas turbine structural materials, It can be used mainly for manufacturing semiconductor fixtures, wear resistant materials, automobile parts, corrosion resistance or chemical resistance parts and electronic parts of chemical plants.

SiC based products are manufactured by the sintering method because of the high melting point of SiC (over 2400 ℃) and sintering additives are used to lower the sintering temperature. When the sintering additive is added, the sintering temperature can be lowered to around 2000 ℃. As the sintering aid for the SiC powder, B (boron), Al ₂ O ₃ (alumina), C (carbon) and the like are used. On the other hand, in order to use the SiC sintered product for the semiconductor wafer manufacturing process and the facing material of the fusion reactor, high purity is essential. However, sintering aids used in the sintering of SiC powders may act as impurities.

In order to solve this problem, nano-sized SiC can be used as a sintering auxiliary agent. The effect of nano-sized SiC powder on the sintering of micron-sized SiC powder is as follows. As the particle size becomes smaller, the surface energy is increased. As a result, the melting point of the nano-sized SiC powder is lowered and the sintering phenomenon occurs. . That is, the sintering method using nano powder can be called solid phase sintering or partial liquid sintering method. In this case, since a homogeneous material is used as the sintering aid, there is an advantage that the concern about a decrease in the purity of the sintered body of SiC, which occurs when the hetero-oxide is used as a sintering aid, can be minimized. However, even if a nano-sized SiC powder is used as a sintering aid, a high sintering temperature of 2000 ° C or more is required. Therefore, in order to lower the sintering temperature and the impurity concentration of the SiC sintered body simultaneously, it is required to develop a new sintering auxiliary agent.

On the other hand, there is a liquid reaction sintering method for producing a SiC sintered body at a relatively low sintering temperature. In this method, SiC powder and C (carbon) powder are mixed with an organic binder (10-20 wt% The Si is evaporated or infiltrated into the SiC compact in a high-temperature vacuum of 1500-1700 ° C to react with carbon in the SiC compact to obtain a sintered compact. However, in this method, there is a problem that unreacted Si remains in the SiC sintered body because the silicon metal infiltrates into the SiC molded body after melting or requires infiltration after evaporation.

Therefore, it is necessary to develop a sintering additive capable of simultaneously exhibiting the effect of sintering assistant nanoparticles and the sintering of liquid phase reaction in order to reduce the mixing of impurities by the sintering aid in the production of high-purity SiC sintered body and at the same time lower the sintering temperature. The Si-SiC nanocomposite powder is a sintering aid material suitable for this demand.

(0001) KR2010-0128437A (2010.12.08)

An object of the present invention is to provide a method of manufacturing a SiC sintered body capable of producing a high-density SiC sintered body at a relatively low temperature of 2000 ° C or less.

According to an aspect of the present invention,

Mixing a micron sized SiC fine powder and a plasma treated Si / SiC nanocomposite powder sintering aid to obtain a mixed powder;

And sintering the mixed powder to obtain a SiC sintered body. The present invention also provides a method of manufacturing a SiC sintered body.

Particularly, it is preferable to mix the SiC fine powder and the sintering auxiliary at a weight ratio of 9: 1, and more preferably, the mixed powder is further mixed with activated carbon.

It is preferable that 1 to 3 parts by weight of the activated carbon is mixed with 100 parts by weight of the sintering auxiliary.

It is also preferable that the mixed powder is sintered by a discharge plasma sintering method at 1700 to 1800 ° C, and particularly, the sintered powder is sintered by a discharge plasma sintering method while being maintained at 1700 to 1800 ° C for 1 to 2 minutes.

The plasma-treated Si / SiC nanocomposite powder sintering assistant is prepared by mixing a solid raw material of silicon and carbon and then firing to synthesize SiC fine powder and thermally decomposing the synthesized SiC fine powder by thermal plasma treatment It is good to use.

Particularly, it is preferable that the silicon and carbon have a particle diameter of 100 mu m or less and the mixing ratio of silicon to carbon is 1: 1.1 to 2.0.

It is preferable to synthesize the SiC fine powder by firing the mixed powder of silicon and carbon at 1200 to 1400 ° C for 2 to 10 hours.

The SiC sintered body produced by using the plasma-treated Si / SiC nanocomposite powder sintering aid according to the present invention exhibited a sintering temperature of micron-sized SiC powder due to the effect of nanoization of Si-SiC composite powder and partial sintering reaction with activated carbon Density SiC sintered body having a relative density of 99% or more and a Vickers hardness of 30 GPa or more can be produced.

1 is a flowchart schematically showing a method for producing a plasma-treated Si / SiC nanocomposite powder sintering aid of the present invention.
2 is a flow chart schematically showing a method for producing a SiC sintered body.
Figs. 3 and 4 are FESEM photographs and X-ray diffraction lines of synthesized micron-sized SiC powder.
5 and 6 are TEM photographs and X-ray diffraction lines of the Si-SiC nanocomposite powder.

Hereinafter, a method for manufacturing a SiC sintered body using the plasma-treated Si / SiC nanocomposite powder of the present invention will be described in detail.

1 is a flowchart schematically showing a method for producing a plasma-treated Si / SiC nanocomposite powder sintering auxiliary agent.

The plasma-treated Si / SiC nanocomposite powder sintering aids of the present invention largely include a SiC fine powder synthesis step and a Si / SiC nanocomposite powder manufacturing step.

First, in the step of synthesizing the SiC fine powder, a solid phase raw material of silicon and carbon is mixed and then fired to synthesize SiC fine powder.

The kind and the particle diameter of the silicon and the carbon are not limited, but it is preferable to use the powder with a particle size of 100 탆 or less for the activation of the solid-phase reaction. As the carbon, activated carbon, carbon black, graphite and the like can be used.

It is preferable that the silicon powder and the carbon powder are accommodated using a ball mill to uniformly mix the silicon powder and the carbon powder.

The mixed powder obtained by mixing the silcone powder and the carbon powder is fired at a temperature and for a time sufficient to produce silicon carbide.

In particular, for the synthesis of micron-sized SiC powder, it is preferable to sinter at 1200 to 1300 ° C for 2 to 10 hours at a Si: C mixing molar ratio of 1: 1.1 to 2.0.

In order to prevent the oxidation of silicon during the firing process, firing is performed while introducing a predetermined amount of argon gas or the like.

In the step of manufacturing the Si / SiC nanocomposite powder, the SiC fine powder is subjected to a thermal plasma treatment to produce a Si / SiC nanocomposite powder through a thermal decomposition reaction.

The thermal plasma treatment converts the micron-sized SiC fine powder into a Si-SiC nanocomposite powder by applying a non-transferred plasma.

When the SiC fine powder is injected into the flame of the non-transferring arc thermal plasma through the quantitative feeder, the micron size SiC powder is temporarily melted in the plasma space. At this time, the argon and hydrogen gas ejected at high speed melt SiC powders are dispersed into nano-size and partially pyrolyzed. SiC nano powder is separated into Si and C, and Si is adhered to other SiC nano powder to form Si / SiC nanocomposite powder.

2 is a flow chart schematically showing a method for producing a SiC sintered body.

Next, a SiC sintered body was manufactured using the thus prepared Si / SiC nanocomposite powder as a sintering auxiliary agent.

The SiC sintered body is produced by mixing Si / SiC nanocomposite powder sintering aids and micron sized SiC fine powder to obtain a mixed powder; And sintering the mixed powder by a discharge plasma sintering (SPS) method to obtain a SiC sintered body.

Particularly, the mixed powder is preferably formed by mixing the SiC fine powder and the sintering auxiliary at a weight ratio of 9: 1. When the sintering aids are mixed in a small amount, sufficient binding force can not be exhibited and the relative density and hardness value are lowered. When the sintering aids are mixed in a large amount, there is a problem that the relative density and hardness value are lowered due to agglomeration of the sintering assistant.

The mixed powder may be further mixed with activated carbon. As the activated carbon is further mixed, the sintering temperature of the micron-sized SiC powder can be lowered to 2,000 DEG C or lower owing to the partial liquid reaction sintering effect with the activated carbon.

The activated carbon is preferably mixed with 1 to 3 parts by weight per 100 parts by weight of the sintering auxiliary. When the activated carbon is mixed in an amount of less than 1 part by weight, the liquid reaction sintering does not sufficiently take place and the relative density is lowered. When the activated carbon is mixed in an amount of more than 3 parts by weight, the relative density and the hardness value are simultaneously lowered due to excess carbon .

Next, the mixed powder is sintered by a discharge plasma sintering method at 1700 to 1800 ° C. In particular, in order to improve the relative density and Vickers hardness of the SiC sintered body, the mixed powder is preferably sintered by a discharge plasma sintering method while being maintained at 1700 to 1800 ° C for 1 to 2 minutes.

Hereinafter, a method of manufacturing a Si / SiC nanocomposite powder sintering assistant of the present invention and a method of manufacturing a SiC sintered body using the same will be described in detail with reference to the following examples.

[Example 1] Manufacturing method of Si / SiC nanocomposite powder sintering aids

Silicon powder having a particle diameter of 10 to 50 탆 and activated carbon powder having a particle diameter of 5 to 50 탆 were mixed at a mixing ratio of 1: 1.5. The mixed powders were sintered at 1,300 ℃ for 2 hours to synthesize micron sized SiC powders. Argan gas was flown to prevent oxidation of silicon during firing.

The FESEM photograph and the X-ray diffraction line of the synthesized micron-sized SiC powder are shown in FIGS. 3 and 4. FIG. The size of the micron - size SiC powder was 2 ~ 5 ㎛, and the crystal structure mostly showed β - phase SiC and very small amount of α - phase SiC was present.

Next, the synthesized SiC powder of micron size was put into a non-transferring arc thermal plasma through a quantitative feeder and subjected to thermal plasma treatment to produce Si-SiC nanocomposite powder. TEM photographs and X-ray diffraction lines of the Si-SiC nanocomposite powder thus produced are shown in FIG. 5 and FIG.

From the results of X-ray diffraction analysis, most of the crystal structures showed β-phase SiC, and very small amount of α-phase SiC and free Si phase were present in the prepared Si-SiC nanocomposite powder. The Si content in the nano-sized Si-SiC composite powder was analyzed to be 4 to 5 wt%.

[Examples 2 to 4] Preparation of SiC sintered bodies by sintering temperature

In order to prepare a mixed sample in which the weight ratio of the micron-size SiC fine powder to the nano-sized Si-SiC composite powder prepared in Example 1 was 90:10, mL plastic container and mixed for 12 hours. About 3 g of the mixed sample was filled in a graphite mold having a diameter of 20 mm and charged into an SPS sintering apparatus. SiC sintering was carried out under vacuum, the rate of temperature increase was 600 ° C / min and the applied pressure was 80 MPa. The sintering temperature was set to 1600 ℃, 1700 ℃ and 1800 ℃. When the sintering temperature was reached, the sintering process was stopped without holding time. After the sintering, the SiC specimen was removed from the graphite mold and polished with a diamond paste. Relative density was measured by the Archimedes method and the beaker hardness was also examined. Table 1 shows the relative density and hardness changes with sintering temperature. The highest relative density (87.4%) and Vickers hardness (18.6 GPa) were obtained at 1800 ℃.

Sintering temperature
(° C) Relative density
(%) Vickers hardness
(GPa) Example 2 1600 78.7 9.8 Example 3 1700 86.1 14.8 Example 4 1800 87.4 18.6

[Examples 5 to 6] Production of SiC sintered body by sintering temperature holding time

In Example 4, the sintering was completed without a holding time when the sintering temperature was reached. In this example, the other experimental conditions were the same as in Example 4, and the sintering temperature was maintained at 1800 ° C. for 1 minute and 2 minutes, and sintering was performed. The results are shown in Table 2. As shown in Table 2, relative density and hardness values were 88.2% and 21.2 GPa, respectively, when the retention time at 1800 ° C. was 1 minute, and the hardness values were the highest values. When the holding time is 2 minutes, the relative density increases but the hardness value tends to decrease. This is because the heating time of the SiC sintered body becomes long and the SiC specimen is in a molten state, thereby increasing the relative density. However, The hardness value is judged to decrease.

Sintering temperature holding time
(at 1800 DEG C) (min) Relative density
(%) Vickers hardness
(GPa) Example 4 0 87.4 18.6 Example 5 One 88.2 21.2 Example 6 2 89.5 17.6

[Examples 7 and 8] Production of SiC sintered body with addition of nano-sized Si-SiC composite powder sintering additive

The other experimental conditions were the same as in Example 5, and the addition amounts of the nano-sized Si-SiC composite powder used as the sintering aid were adjusted to 5 wt%, 10 wt% and 15 wt%. At this time, sintering was carried out at a sintering temperature of 1800 ° C and a holding time of 1 minute. Table 3 shows the relative density and hardness values of the SiC sintered bodies by the addition amounts of the nano-sized SiC composite powder. The highest relative density and Vickers hardness were obtained when the addition amount of nano-sized Si-SiC composite powder was 10 wt%. It is considered that the hardness value decreases sharply when the addition amount of the nano-sized Si-SiC composite powder is 15 wt% because the pore increases in the SiC sintered body due to the excessive addition of the nano-sized Si-SiC composite powder.

Micron size SiC (wt%) Nano size
Si-SiC (wt%) Relative density (%) Vickers hardness (GPa) Example 5 90 10 88.2 21.2 Example 7 95 5 85.9 20.1 Example 8 85 15 85.6 16.6

[Examples 9 to 12] Production of SiC sintered bodies by the amount of activated carbon added

The other experimental conditions were the same as in Example 5 except that activated carbon was added in addition to nano-sized Si-SiC composite powder as a sintering aid. The addition amount of nano-sized Si-SiC composite powder was fixed to 10 wt%, and the addition amount of activated carbon was changed to 0.1 wt%, 0.2 wt%, 0.25 wt% and 0.3 wt% by controlling the addition amount of micron size SiC powder. Table 4 shows changes in relative density and hardness of SiC sintered body depending on the amount of activated carbon added. Relative density and Vickers hardness value tended to increase with increasing amount of activated carbon. At 0.25g, maximum density was 99.2% and hardness was 32.5 GPa. When the addition amount was 0.3 g, both the relative density and the hardness were slightly reduced, but still maintained a relative density of 98% or more.

Micron size SiC (wt%) Nano size
Si-SiC (wt%) Activated carbon (wt%) Relative density (%) Vickers hardness (GPa) Example 9 89.9 10 0.1 93.1 25.2 Example 10 89.8 10 0.2 97.1 31.4 Example 11 89.75 10 0.25 99.2 32.5 Example 12 89.7 10 0.3 98.1 30.4

Claims (10)

Mixing a micron-sized SiC fine powder and a plasma-treated Si-SiC nanocomposite powder sintering aid to obtain a mixed powder;
And sintering the mixed powder to obtain a SiC sintered body. The method of producing a SiC sintered body using the plasma-treated Si-SiC nanocomposite powder.
The method according to claim 1,
Wherein the SiC fine powder and the Si-SiC nanocomposite powder sintering aid are mixed at a weight ratio of 9: 1.
3. The method of claim 2,
Wherein the mixed powder is further mixed with activated carbon. The method for producing a SiC sintered body using the plasma-treated Si-SiC nanocomposite powder.
The method of claim 3,
Wherein the activated carbon is mixed with 1 to 3 parts by weight per 100 parts by weight of the sintering auxiliary.
The method according to claim 1,
Wherein the mixed powder is sintered at 1700 to 1800 ° C by a discharge plasma sintering method.
6. The method of claim 5,
Wherein the mixed powder is sintered by a discharge plasma sintering method while being maintained at 1700 to 1800 캜 for 1 to 2 minutes. The method for producing a SiC sintered body using the plasma-treated Si-SiC nanocomposite powder according to claim 1,
The method according to claim 1,
The Si-SiC nanocomposite powder sintering aids are prepared by mixing a solid raw material of silicon and carbon and then firing to synthesize SiC fine powder, and thermally decomposing the synthesized SiC fine powder by thermal plasma treatment Method of manufacturing SiC sintered body using plasma-treated Si-SiC nanocomposite powder.
8. The method of claim 7,
Wherein the silicon-carbon nanocomposite powder has a particle diameter of 100 mu m or less and a mixing molar ratio of 1: 1.1 to 2.0.
9. The method of claim 8,
Wherein the mixed powder of silicon and carbon is fired at 1200 to 1400 ° C for 2 to 10 hours to synthesize a SiC fine powder. 2. The method for producing a SiC sintered body according to claim 1,
delete

Images