KR102685290B1 - MAX phase with low oxygen synthesis method - Google Patents

Abstract

The present invention relates to a low-oxygen max phase synthesis method, which includes a raw material preparation step of preparing titanium (Ti) powder, aluminum (Al) powder, and carbon (C) powder; A mixing step of mixing the titanium powder, the aluminum powder, and the carbon powder to form a powder mixture; A compression step of compressing the powder mixture to form a green compact; and a sintering step of sintering the green compact to form a max phase. In the raw material preparation step, the titanium powder is prepared to have an oxygen content of 1,000 ppm or less.
Accordingly, it is possible to effectively produce the Max phase in a hypoxic state.

Description

Low oxygen MAX phase synthesis method {MAX phase with low oxygen synthesis method}

The present invention relates to a hypoxic Max phase synthesis method, and more specifically, to a hypoxic Max phase synthesis method for increasing the production yield of MXene films and improving electrical properties.

MXene shows excellent potential in areas such as electromagnetic interference shielding, energy storage, and wearable electronics due to its high electrical conductivity and chemical stability. And among MXenes, titanium-based Ti ₃ C ₂ T _x (T _x is a surface terminator) is known to have the highest electrical conductivity.

MXene is manufactured from the MAX phase (Ti ₃ AlC ₂ and Ti ₃ SiC ₂ etc.). The chemical form of the Max phase is M _n+1 AX _n , where M is a transition metal, A is an element of groups 3A and 4A on the periodic table, and X is a C and N element. After removing the A (Al, Si, etc.) element from the MAX by selective etching to manufacture multilayered MXene, the multilayer MXene can be physically separated to produce single-layered MXene. .

However, when the oxygen content of the Max phase is high _, Al ₂ O ₃ oxide increases in the Max phase _{and aluminum (Al) in the Ti x AlC x} phase escapes, resulting in the formation of TiC from Ti There is a problem in that the recovery rate of single-layer MXene from multi-layer MXene is reduced due to the remaining ₂ O ₃ oxide and TiC carbide. Additionally, when MXene is prepared from a commercial MXene phase with high oxygen content (oxygen content greater than 20,000 ppm), the electrical properties of MXene may be reduced.

In particular, since titanium has a high affinity for oxygen, it is necessary to lower the oxygen content of the titanium-containing MXene phase in order to increase the recovery rate of titanium-containing single-layer MXene.

KR 10-2014-0090754 A

Therefore, the purpose of the present invention is to solve such conventional problems, and to provide a hypoxic Max phase synthesis method that allows the production of the Max phase, which is a raw material for the production of single-layer MXene, in a hypoxic state in order to increase the production efficiency and electrical properties of single-layer MXene. In providing.

The problem to be solved by the present invention is not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

The above object is, according to the present invention, a raw material preparation step of preparing titanium (Ti) powder, aluminum (Al) powder, and carbon (C) powder; A mixing step of mixing the titanium powder, the aluminum powder, and the carbon powder to form a powder mixture; A compression step of compressing the powder mixture to form a green compact; and a sintering step of sintering the green compact to form a max phase, wherein in the raw material preparation step, the titanium powder is prepared with an oxygen content of 1,000 ppm or less. This is achieved by a low-oxygen max phase synthesis method. .

The raw material preparation step may include a deoxidation step to remove oxygen from the titanium powder.

The deoxidation step may be performed at 700 to 1,000°C for 1 to 6 hours by charging titanium powder and calcium deoxidizer into a heat treatment furnace in an inert gas atmosphere or vacuum atmosphere at 0.1 to 2 atmospheres.

The raw material preparation step may include a sieving step of sieving the titanium powder, aluminum powder, and carbon powder using a sieve of 50 μm or less.

The titanium powder, aluminum powder, and carbon powder can be mixed using ultrasonic waves.

In the sintering step, the green compact is charged into a crucible, then the crucible is charged into a heat treatment furnace, the heat treatment furnace is created in an inert gas atmosphere of 0.1 to 2 atmospheres, and the temperature is maintained at 1,300 to 1,450°C for 1 to 5 hours. The green compact can be sintered.

In the sintering step, the heat treatment furnace is created in an inert gas atmosphere using argon (Ar), and the purity of the argon may be 3N or higher.

The argon may be supplied to the heat treatment furnace through a purifier that removes moisture.

The heat treatment furnace is provided with an oxygen eliminator that removes oxygen in the argon, and the argon may be supplied to the crucible through the oxygen eliminator.

According to the hypoxic Max phase synthesis method of the present invention, the Max phase is synthesized using titanium powder with an oxygen content of 1,000 ppm or less, so it is possible to produce a Max phase with a low oxygen content.

By using this MAX phase, it is possible to increase the manufacturing yield and electrical properties of multilayer MXene and single-layer MXene.

When performing a sieving step in the raw material preparation stage or mixing raw material powders using ultrasonic waves in the mixing stage, the raw material powders can be mixed more evenly, making it possible to synthesize a uniform max phase.

If the residual oxygen and moisture in argon, which creates an inert gas atmosphere inside, is removed through heat treatment in the sintering step, the oxygen content of the synthesized Max can be lowered.

1 is a flow chart of the hypoxic Max phase synthesis method according to the present invention;
Figure 2 is a schematic diagram of the device used in the mixing step of the hypoxic max phase synthesis method according to the present invention;
Figure 3 is an explanatory diagram of how the sintering step constituting the hypoxic max phase synthesis method according to the present invention proceeds;
Figure 4 is a graph of the XRD analysis results of the Max phase produced by Example 1 of the hypoxic Max phase synthesis method according to the present invention;
Figure 5 is an SEM image of the Max phase synthesized by Example 1 of the hypoxic Max phase synthesis method according to the present invention;
Figure 6 is a graph of the XRD analysis results of the Max phase synthesized by Example 2 of the hypoxic Max phase synthesis method according to the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

The method for synthesizing the hypoxic MAX phase according to the present invention relates to a method of producing Ti ₃ AlC ₂ among the MAX phases. For reference, it is possible to manufacture Ti ₃ C ₂ T _x , which is known to have the highest conductivity among Mxenes, using Ti ₃ AlC ₂ .

The hypoxic Max phase synthesis method according to the present invention includes a raw material preparation step (S10), a mixing step (S20), a compression step (S30), and a sintering step (S40).

Figure 1 shows a flow chart of the hypoxic max phase synthesis method according to the present invention.

In the raw material preparation step (S10), titanium (Ti) powder, aluminum (Al) powder, and carbon (C) powder, which are raw materials for Ti ₃ AlC _2, are prepared.

Titanium powder, aluminum powder, and carbon powder can be prepared stoichiometrically in a ratio of 3:1:2, but considering that aluminum is lost through evaporation during synthesis of each powder, the aluminum ratio can be slightly increased. And the proportion of carbon can be slightly lowered to minimize the formation of TiC carbide.

Titanium powder with an oxygen content of 1,000 ppm or less can be prepared. For reference, the oxygen content of commercially available titanium powder 45㎛ or smaller is over 4,000ppm.

Aluminum powder can be prepared with a purity of 99%, and graphite powder as a carbon powder can be prepared with a purity of 99.9995%.

In the mixing step (S20), titanium powder, aluminum powder, and carbon powder are mixed to form a powder mixture. In the mixing step (S20), each powder can be mixed so that it is distributed as evenly as possible without clumping.

In the compression step (S30), the powder mixture prepared in the mixing step (S20) is compressed to form a green compact. The powder mixture can be compressed, for example by a hydraulic press. It is possible for each raw material powder that is compressed and brought into close contact with each other to be smoothly sintered in the subsequent sintering step (S40).

In the sintering step (S40), the green compact is sintered to form the Max phase. The sintering step (S40) is performed within the heat treatment furnace 20 so that the raw material powders constituting the green compact can be sintered.

According to the low-oxygen Max phase synthesis method of the present invention, the Max phase is synthesized using titanium powder with an oxygen content of 1,000 ppm or less, so it is possible to produce a Max phase with a low oxygen content.

Since this MXene hardly contains oxides such as Al ₂ O ₃ or SiO ₂ , it can be prevented from reducing the production yield of multilayered MXene or single layered MXene by oxides during MXene production. .

In addition, MXene produced using a MAX phase with a low oxygen content has excellent electrical properties.

In summary, it is possible to increase the production yield and electrical properties of multilayer MXene and single-layer MXene by using the Max phase produced by the Max phase synthesis method of the present invention.

The raw material preparation step (S10) may include a deoxidation step (S11).

In the deoxidation step (S11), oxygen is removed from commercial titanium powder to form titanium powder with an oxygen content of 1,000 ppm or less. Titanium powder with a particle size of 45㎛ or less can be used.

More specifically, the deoxidation step (S11) can be performed at 700 to 1,000°C for 1 to 6 hours by charging titanium powder and calcium deoxidizer into a heat treatment furnace (not shown) in an inert gas atmosphere or vacuum atmosphere at 0.1 to 2 atm. .

When titanium powder and calcium deoxidizer are heated together at 700 to 1,000°C, the calcium deoxidizer removes oxygen from titanium. If this process is performed in an inert gas atmosphere or a vacuum atmosphere, it is possible to prevent oxygen from entering from the outside through heat treatment, thereby allowing deoxidation to proceed more effectively.

The efficiency of deoxidation can be increased by deoxidizing titanium powder and calcium deoxidizing agent in contact with each other.

After deoxidation, the titanium powder and calcium deoxidizer can be separated from each other using a sieve, and the titanium powder separated from the calcium deoxidizer can be washed with water and acid to remove surface impurities. Then, the cleaned titanium powder can be dried to remove surface moisture.

The raw material preparation step (S10) may further include a sieving step (S12).

In the sieving step (S12), titanium powder, aluminum powder, and oxygen powder are sieved using a sieve of 50 μm or less. For example, in the sieving step (S12), powders can be sieved using a 45㎛ sieve, and thus the Max phase can be synthesized using powder with a particle size of 25 to 45㎛.

When synthesizing the Max phase using raw material powders having a uniformly small particle size, it is possible to evenly mix the raw material powders in the mixing step (S20), and therefore, the Max phase with a constant composition can be effectively formed in the sintering step (S40). can be made

On the other hand, when powders that have not been separately processed are pulverized and mixed by a mechanical activation method, as in the method of making a composition by a general sintering method, the oxygen content of the powder increases due to the mechanical activation process. A problem may arise in which the oxygen content of the manufactured product also increases.

In other words, in the present invention, there is no need to undergo a mechanical activation process in the sieving step (S12), so it is possible to synthesize a hypoxic Max phase.

In the mixing step (S20), titanium powder, aluminum powder, and carbon powder can be mixed using ultrasonic waves. Figure 2 shows a schematic configuration diagram of a device used in the mixing step (S20) using ultrasonic waves.

When mixing powders using ultrasonic waves, the powders can be mixed very uniformly. Additionally, unlike when using a mechanical activation method, the oxygen content of the powder does not increase during the process of mixing the powders.

More specifically, in the mixing step (S20) using ultrasonic waves, titanium powder, aluminum powder, and carbon powder are added in proportions (e.g., 3:1:2 or 3:1.1:2, etc.) and mixed with alcohol in a container. After charging into a glass bottle or beaker, etc., the mixing container is placed in an ultrasonic generator to mix the powders in the alcohol solution. The frequency of ultrasonic waves used during mixing can be 40kHz. After mixing the powders with an ultrasonic generator, the mixed powder and alcohol solution are removed using a vacuum filtration device, and then dried at about 70°C for about 1 hour using a vacuum oven.

In the sintering step (S40), the green compact is charged into the crucible 10, the crucible 10 is charged into the heat treatment furnace 20, and the heat treatment furnace 20 is created in an inert gas atmosphere of 0.1 to 2 atm to prepare the green compact. It can be sintered.

Figure 3 shows an explanatory diagram of how the sintering step (S40) proceeds.

The device in which the sintering step (S40) is performed includes a heat treatment furnace 20, a crucible 10 located in the heat treatment furnace 20 and into which the green compact is charged, and an inert gas for supplying an inert gas to the heat treatment furnace 20. It includes a gas supplier 30, and may further include a purifier 40 that removes moisture in the inert gas and an oxygen remover 50 that removes oxygen in the inert gas.

The green compact heated within the heat treatment furnace 20 while being charged into the crucible 10 can be easily loaded into the heat treatment furnace 20 and can be easily removed from the heat treatment furnace 20 after being made into a max phase. The crucible 10 may be made of, for example, alumina.

When the heat treatment furnace 20 is maintained in an inert gas atmosphere in the sintering step (S40), oxygen is prevented from flowing into the heat treatment furnace 20, making it possible to effectively synthesize a low-oxygen Max phase.

In the sintering step (S40), the heat treatment furnace 20 is maintained at 1,300 to 1,450°C, and the sintering step (S40) may proceed for 1 to 5 hours.

It is possible to synthesize the Ti ₃ AlC ₂ Max phase only when the heat treatment furnace 20 is maintained at the above temperature.

Under the above conditions, the powders constituting the green compact can be sufficiently synthesized to create a max phase with almost no impurities.

For example, argon (Ar) may be used as an inert gas that creates an inert gas atmosphere in the heat treatment furnace 20, and argon with a purity of 3N (99.9%) or higher may be used.

When argon having a purity of 3N or higher is used, it is possible to prevent the purity of the Max phase synthesized in the heat treatment furnace 20 from decreasing due to moisture or oxygen contained in argon.

The purifier 40 is disposed between the heat treatment furnace 20 and the inert gas supplier 30 and can remove moisture from argon supplied from the inert gas supplier 30 to the heat treatment furnace 20. The purifier 40 contains CaSO ₄ and P ₂ O ₅ and can remove moisture in argon as shown below.

CaSO ₄ + H ₂ O -> CaSO ₄ ·2H ₂ O

P ₂ O ₅ + 3H ₂ O -> 2H ₃ PO ₄

Additionally, the oxygen remover 50 is disposed before the crucible 10 in the heat treatment furnace 20 and can remove oxygen in argon supplied into the heat treatment furnace 20. Argon is supplied to the crucible (10) through the oxygen remover (50). The oxygen eliminator 50 may be formed by embedding a titanium sponge or deoxidized titanium powder in the second crucible 60.

The bulk Max phase created in the sintering step (S40) can be pulverized and made into powder form.

Hereinafter, an example of the hypoxic max phase synthesis method according to the present invention will be described.

Example 1

The hypoxic Max phase was synthesized through the raw material preparation step (S10), mixing step (S20), compression step (S30), and sintering step (S40).

In the raw material preparation step (S10), titanium powder was prepared by deoxidizing the oxygen content to 950ppm, and the raw material particle size of 25 to 45㎛ was used. Synthesis was performed while changing the temperature in the heat treatment furnace 20 in the sintering step (S40) to 1,350°C, 1,400°C, and 1,450°C, and changing the sintering step (S40) progress time to 1, 3, and 5 hours.

Experimental Example 1

XRD analysis was performed on the Max phase manufactured by performing synthesis while changing the temperature in the heat treatment furnace (20) and the progress time of the sintering step (S40).

XRD analysis was also performed on commercial Chinese Max powder and Ukrainian powder.

[Table 1] and Figure 4 show the XRD analysis results of the Max phase made in Example 1, and the XRD analysis results of commercial Chinese Max powder and Ukrainian powder. Figure 4 (a) is the result of XRD analysis of Max powder from China, Figure 4 (b) is the XRD analysis result of Max powder from Ukraine, and Figure 4 (c) is the result of XRD analysis of Max powder from Ukraine. This is the XRD analysis result of the Max phase made at a temperature of 1,450°C and a sintering time of 5 hours.

Looking at [Table 1] and FIG. 4, commercial Max powder contains impurities such as Al ₂ O ₃ , TiC, and SiO ₂ , but according to the present invention, the temperature in the heat treatment furnace 20 in the sintering step (S40) is 1,450. When sintering was carried out at ℃ for 5 hours, it can be confirmed that Max single phase (Ti ₃ AlC ₂ ), excluding some TiC, was successfully synthesized.

Therefore, it can be confirmed that the sintering step (S40) is preferably performed with the temperature in the heat treatment furnace 20 set to 1,450°C or higher and the sintering time set to 5 hours or longer.

Experimental Example 2

SEM images were taken of the Max phase synthesized by Example 1. Figure 4 shows an SEM image of the Max phase synthesized in Example 1.

Looking at Figure 5, it can be seen that the surface of the Max phase was uniformly synthesized and that the layered structure, which is a characteristic of the Max phase, is clearly visible.

Comparative Example 1

The Max phase was synthesized through the raw material preparation step (S10), mixing step (S20), compression step (S30), and sintering step (S40).

In the raw material preparation step (S10), titanium powder that was not deoxidized was prepared, and the raw material with a particle size of 25 to 45 ㎛ was used. The temperature in the heat treatment furnace 20 in the sintering step (S40) was set to 1,450°C, and the sintering step (S40) progressed for 5 hours to perform synthesis.

Experimental Example 4

The oxygen content of Max synthesized by Example 1 and Comparative Example 1 was analyzed. Additionally, the oxygen content of commercial Chinese Max powder and Ukrainian powder was analyzed. Oxygen content analysis of the Max phase according to Example 1 and Comparative Example 1 was performed on the bulk composite formed immediately after the sintering step (S40) and the powder made after pulverization, respectively.

[Table 2] shows the results of the oxygen content analysis of the Max powder made in Example 1 and Comparative Example 1, as well as the oxygen content analysis results of commercially available Chinese Max powder and Ukrainian powder.

Looking at [Table 2], the Max phase synthesized by Example 1 has a very low oxygen content of 3,200 ppm and the oxygen content of the powder is 3,900 ppm, while the Max phase synthesized by Comparative Example 1 has a very low oxygen content of 3,200 ppm and 3,900 ppm, respectively. It can be seen that the content is relatively high at 5,000ppm and the oxygen content of the powder is 6,300ppm.

Therefore, it can be seen that preparing deoxidized titanium powder in the raw material preparation step (S10) is much more advantageous in synthesizing the low-oxygen Max phase.

Example 2

The hypoxic Max phase was synthesized through the raw material preparation step (S10), mixing step (S20), compression step (S30), and sintering step (S40).

In the raw material preparation step (S10), deoxidized titanium powder was prepared, and the raw material with a particle size of 25 to 45㎛ was used. In the mixing step (S20), the powders were mixed using ultrasonic waves. The temperature in the heat treatment furnace 20 in the sintering step (S40) was set to 1,450°C, and the sintering step (S40) progressed for 5 hours to perform synthesis.

Comparative Example 2

The Max phase was synthesized under the same conditions as in Example 2, but in the mixing step (S20), the raw material powders were charged into the container and the powders were simply mixed by shaking the container.

Experimental Example 5

XRD analysis was performed on the Max phase synthesized by Example 2 and the Max phase synthesized by Comparative Example 2.

Figure 6 shows the XRD analysis results for the Max phase synthesized by Example 2 and the Max phase synthesized by Comparative Example 2.

Looking at (a) of FIG. 6, it can be seen that the Max phase synthesized in Example 2 is a single Max phase of Ti ₃ AlC ₂ composition. On the other hand, it can be confirmed that the Max phase synthesized by Comparative Example 2 was incompletely synthesized, including Ti ₂ AlC in addition to Ti ₃ AlC _2, as shown in (b) of FIG.

That is, it can be confirmed that when the raw material powders are mixed ultrasonically in the mixing step (S20), it is possible to completely synthesize a single Max phase.

Example 3

The hypoxic Max phase was synthesized through the raw material preparation step (S10), mixing step (S20), compression step (S30), and sintering step (S40).

In the raw material preparation step (S10), deoxidized titanium powder was prepared, and the raw material with a particle size of 25 to 45㎛ was used. In the mixing step (S20), the powders were mixed using ultrasonic waves. The temperature in the heat treatment furnace 20 in the sintering step (S40) was set to 1,450°C, and the synthesis was performed with the sintering step (S40) progressing for 5 hours, with purity of 3N (99.9%) and purity of 5N (99.999%). Argon was used to create an inert gas atmosphere inside the heat treatment furnace (20). In the sintering step (S40), the Max phase was synthesized by changing whether or not the purifier (40) and oxygen remover (50) were used.

Experimental Example 6

The oxygen content of Max synthesized by Example 3 was analyzed. [Table 3] shows the results of oxygen content analysis of the Max phase synthesized in Example 3.

Looking at [Table 3], in the sintering step (S40), if the inside of the heat treatment furnace (20) is created in an inert gas atmosphere with argon of purity 3N, but the purifier (40) and oxygen remover (50) are not used, the synthesized Max Although the oxygen content of the phase is high at 4,620 ppm, it can be seen that when the purifier 40 and the oxygen remover 50 are used, the oxygen content of the synthesized Max phase drops to 2,610 ppm, below 3,000 ppm.

Even when the inside of the heat treatment furnace (20) is made into an inert gas atmosphere with argon of purity 5N and the purifier (40) and oxygen remover (50) are used, the synthesis rate is higher than when the purifier (40) and oxygen remover (50) are not used. It can be seen that the oxygen content on the max is lowered.

Through this, when using the purifier 40 and oxygen remover 50 in the sintering step (S40), even if the inside of the heat treatment furnace 20 is created in an inert gas atmosphere with argon with a purity of 3N, the oxygen content is maxed at 3,000 ppm or less. Since it is possible to synthesize the phase, it can be confirmed that it is possible to economically synthesize the low-oxygen Max phase without using expensive high-purity argon.

The scope of the present invention is not limited to the above-described embodiments, but may be implemented in various forms of embodiments within the scope of the appended claims. It is considered to be within the scope of the claims of the present invention to the extent that anyone skilled in the art can make modifications without departing from the gist of the invention as claimed in the claims.

10: Crucible
20: Heat treatment furnace
30: Inert gas supplier
40: Purifier
50: oxygen eliminator
60: Second crucible

Claims (9)

Raw material preparation step of preparing titanium (Ti) powder, aluminum (Al) powder, and carbon (C) powder;
A mixing step of mixing the titanium powder, the aluminum powder, and the carbon powder to form a powder mixture;
A compression step of compressing the powder mixture to form a green compact; and
It includes a sintering step of sintering the green compact to form a max phase,
In the raw material preparation step, the titanium powder is prepared with an oxygen content of 1,000 ppm or less,
In the sintering step,
After charging the green compact into a crucible, the crucible is charged into a heat treatment furnace, the heat treatment furnace is created in an inert gas atmosphere of 0.1 to 2 atm, and the green compact is sintered for 1 to 5 hours while maintaining the temperature at 1,300 to 1,450°C. ,
The heat treatment furnace is created in an inert gas atmosphere using argon (Ar) with a purity of 3N or higher,
The argon is supplied to the heat treatment furnace through a purifier that removes moisture.
According to paragraph 1,
The raw material preparation step is,
A low-oxygen max phase synthesis method comprising a deoxidation step of removing oxygen from the titanium powder.
According to paragraph 2,
The deoxidation step is,
A low-oxygen max phase synthesis method characterized by charging titanium powder and calcium deoxidizer into a heat treatment furnace in an inert gas atmosphere or vacuum atmosphere at 0.1 to 2 atmospheres and proceeding at 700 to 1,000°C for 1 to 6 hours.
According to paragraph 1,
The raw material preparation step is,
A hypoxic max phase synthesis method comprising a sieving step of sieving the titanium powder, the aluminum powder, and the carbon powder using a sieve of 50 μm or less.
According to paragraph 1,
In the mixing step,
A low-oxygen max phase synthesis method characterized by mixing the titanium powder, the aluminum powder, and the carbon powder using ultrasonic waves.
delete delete delete According to paragraph 1,
An oxygen remover is provided in the heat treatment furnace to remove oxygen in the argon,
The argon is supplied to the crucible through the oxygen remover.

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