KR20200060677A - Layered compound, nanosheet and preparing method thereof - Google Patents

Abstract

The present invention relates to layered compounds, nanosheets, and a manufacturing method thereof. According to the present invention, MnAs and ZnAs having a two-dimensional layer structure different from an existing three-dimensional bulk can be efficiently peeled to form MnAs nanosheets and ZnAs nanosheets. High-quality layered ZnSb nanosheets manufactured by the above process can be mass-produced, enabling application and use of flexible magnetic materials or flexible semiconductor materials. The present invention provides a method for synthesizing the nanosheets, which comprises the following steps of: (a) inserting a synthetic raw material into a reaction vessel; (b) manufacturing a crystalline product; (c) manufacturing the layered compounds; and (d) manufacturing the nanosheets.

Description

Layered compounds, nanosheets and their manufacturing methods {LAYERED COMPOUND, NANOSHEET AND PREPARING METHOD THEREOF}

The present invention relates to a layered compound, a nanosheet, and a method of manufacturing the same, and more particularly, to a layered compound, nanosheet, and a method of manufacturing the same, having excellent ferromagnetic properties or semiconductor properties.

Various ultra-thin two-dimensional (2D) materials including graphene have been actively researched in various fields based on new physical, chemical, mechanical and optical properties.

Manganesearsenide is a material having ferromagnetic properties at room temperature, and because it is inexpensive, non-toxic, and rich, it can be widely used as a room temperature magnetic material, and thus has received considerable attention.

The existing three-dimensional structure MnAs shows considerable ferromagnetic properties, but it is difficult to develop and apply a low-dimensional thin film material due to the structure of the matrix. The layered structure MnAs produced by the present inventors and the exfoliated MnAs nanosheet are existing 3 By overcoming the limitations of dimensional structure MnAs, it can be a promising candidate for the development of flexible magnetic materials and thin-film magnetic materials.

The existing three-dimensional structure ZnAs is a material having the same structure as ZnSb, and exhibits significant electrical properties, but has poor thermoelectric efficiency due to its high thermal conductivity. The layered ZnAs structure and the exfoliated ZnSb nanosheets, which are manufactured such that thermal movement is significantly impeded by phonon grain boundary scattering, may be promising candidates for thermoelectric applications and thin film thermoelectric materials development.

The inventors of the present invention have a high-quality mass single crystal growth of a layered AMnSb in which alkali ions A are intercalated and inserted through a flux method, and a layered square symmetric structure MnSb layered structure through alkali ion deintercalation (etch). A study was conducted on nanosheeting of a layered square symmetrical structure through fabrication and peeling. The inventors of the present invention successfully confirmed that AMnAs was synthesized by an X-ray diffraction analyzer (XRD), and confirmed that AMnAs has ferromagnetic semiconductor properties through a physical property meter (PPMS). In addition, the AMnAs material is expected to be capable of nanosheeting through the synthesis and exfoliation of the layered MnAs material through the removal of A ions.

In addition, the inventors of the present invention have succeeded in high-quality bulk single crystal growth of layered AZnAs in which alkali ions A have been intercalated through the flux method, and high-quality layered AZnAs synthesized by the present inventors have deintercalation of alkali ions. , etch) is expected to be possible to produce ZnAs in a layered structure and nanosheeting through exfoliation.

The problem to be solved by the present invention is to provide a method to form MnAs nanosheets and ZnAs nanosheets by preparing the existing three-dimensional materials MnAs and ZnAs in a layered structure, and peeling the prepared layered MnAs and layered ZnAs. To have.

The present invention provides a layered compound represented by any one of the following formulas 1 to 4.

<Formula 1>

AMnAs (where A is one of Li, Na and K)

<Formula 2>

MnAs

<Formula 3>

BZnAs, where B is Na or K

<Formula 4>

ZnAs

The layered compound represented by any one of Formula 1 to Formula 4 may have a structure of P4 / nmms, P6 ₃ / mmc or P6 ₃ mc.

The layered compound represented by Chemical Formula 1 or Chemical Formula 2 may have ferromagnetic properties.

The layered compound represented by any one of Chemical Formulas 1 to 4 may have semiconductor properties.

The present invention comprises the steps of (a) inserting a synthetic raw material comprising A, Mn and As or a synthetic raw material comprising B, Zn and As into a reaction vessel (where A is any one of Li, Na and K, B Is Na or K); And (b) crystallizing the synthetic raw material inserted in the reaction vessel through melt-cooling to prepare a crystallization method.

After step (a), Sn may be additionally inserted into the reaction vessel.

The melting may be performed at a temperature of 650 ~ 800 ℃.

The cooling may be performed by quenching or slow cooling the molten synthetic raw material.

The slow cooling is a step of forming a single crystal by growing crystals by cooling at a rate of 0.5-3 ° C per hour to a temperature of 300-500 ° C, and the rapid cooling may be a step of rapidly cooling than the rate of slow cooling to form a polycrystal. have.

After step (b), (c) using an organic solvent, water or a mixture thereof may further include the step of removing ions from the crystallization to prepare a layered compound.

The ion may be one or more selected from Li, Na and K.

The organic solvent may be a cyclic carbonate solvent, a chain carbonate solvent, an ester solvent, an ether solvent, a nitrile solvent, an amide solvent or a mixture thereof.

The present invention provides a nanosheet represented by any one of the following formula 1 to formula 4.

<Formula 1>

AMnAs (where A is one of Li, Na and K)

<Formula 2>

MnAs

<Formula 3>

BZnAs, where B is Na or K

<Formula 4>

ZnAs

The present invention comprises the steps of (a) inserting a synthetic raw material comprising A, Mn and As or a synthetic raw material comprising B, Zn and As into a reaction vessel (where A is any one of Li, Na and K, B Is Na or K); (b) preparing a crystallized product by crystallizing the synthetic raw material inserted in the reaction vessel through melt-cooling; (c) preparing a layered compound by removing ions from the crystallization using an organic solvent, water or a mixture thereof; And (d) peeling the layered compound to prepare a nanosheet.

The peeling is selected from the group consisting of peeling with energy by ultrasonic waves, peeling by invasion of solvents, peeling with salts and reactive gases formed by solvents and ions, peeling with tape, and peeling with a material having an adhesive surface. It may be made using one or two or more processes.

The compound of the present invention, such as layered MnAs and layered ZnAs, and MnAs nanosheets and ZnAs nanosheets have excellent ferromagnetic properties or semiconductor properties, and thus can be effectively utilized as flexible magnetic materials or flexible semiconductor materials.

1 schematically shows the synthesis process of AMnAs (where A is any one of Li, Na, and K).
2 is an X-ray diffraction analysis result of AMnAs synthesized according to Examples 1 to 3.
3 is a result of measuring the electrical conductivity of the AMnAs synthesized according to Examples 1 to 3.
4 is a result of measuring the magnetic properties of MnAs synthesized according to Examples 1 to 3.
5 is a two-dimensional MnAs structure and a schematic diagram obtained from AMnAs.
Figure 6 schematically shows the synthesis process of BZnAs (where B is Na or K).
7 is an X-ray diffraction analysis result of BZnAs synthesized according to Examples 5 and 6.
8 is a result of measuring the electrical conductivity of BZnAs synthesized according to Examples 5 and 6.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms.

The examples herein are provided to make the disclosure of the present invention complete, and to provide those who have ordinary knowledge in the art to which the present invention pertains, to fully disclose the scope of the invention, and the present invention is defined by the scope of the claims. It just works.

Thus, in some embodiments, well-known components, well-known operations, and well-known techniques may be omitted from the detailed description to avoid ambiguous interpretation of the present invention.

In the present specification, the singular form also includes the plural form unless specifically stated in the phrase, and the components and operations referred to as 'comprising (or, provided)' do not exclude the presence or addition of one or more other components and operations. .

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains.

Hereinafter, the present invention will be described in detail.

The present invention provides a layered compound represented by any one of the following formulas 1 to 4.

<Formula 1>

AMnAs (where A is one of Li, Na and K)

<Formula 2>

MnAs

<Formula 3>

BZnAs, where B is Na or K

<Formula 4>

ZnAs

The layered compound represented by any one of Formula 1 to Formula 4 may have a structure of P4 / nmms, P6 ₃ / mmc or P6 ₃ mc, and may be polymorphs.

The layered compound represented by Chemical Formula 1 or Chemical Formula 2 may have ferromagnetic properties.

The layered compound represented by any one of Chemical Formulas 1 to 4 may have semiconductor properties.

Hereinafter, a method for synthesizing the layered compound of the present invention will be described in detail.

First, a synthetic raw material containing A, Mn and As or a synthetic raw material containing B, Zn and As is inserted into the reaction vessel (step a).

Here, A is any one of Li, Na and K, and B is Na or K.

It is suitable that the reaction vessel does not react with the sample and does not break at high temperatures. Typical examples include alumina crucibles, molybdenum crucibles, and tungsten crucibles.

Sn may be additionally inserted into the reaction vessel. The Sn inhibits the vaporization of the synthetic raw material, and serves as a flux that facilitates compound growth.

Next, crystallization is prepared by crystallizing the synthetic raw material inserted in the reaction vessel through melt-cooling (step b).

The melting is preferably performed at a temperature of 650 ~ 800 ℃.

If the upper limit of the temperature range is exceeded, the vapor pressure in the quartz tube encapsulated by the vaporization of the alkali ion may increase and burst, and if it is less than the lower limit of the temperature range, the raw material that has not been reacted because the sintering reaction of the material is not completed It is undesirable because it may remain.

The cooling may be achieved by quenching or slow cooling the mixture.

The slow cooling is a step of growing crystals to form a single crystal by cooling at a rate of 0.5-3 ° C. per hour to a temperature of 300-500 ° C., and the rapid cooling is a step of rapidly cooling than the rate of slow cooling to form a polycrystal.

When the slow cooling exceeds the upper limit of the temperature range, it is difficult to secure the size of a single crystal (polycrystallization), and if it is less than the lower limit, it is not preferable because a composition change may occur due to evaporation of alkali ions.

The quenching may be performed using various methods such as quenching the temperature by putting a sample enclosed in a low-temperature solvent such as water or oil (quenching), or quenching to room temperature by removing a heat source.

Next, a layered compound is prepared by removing ions from the crystallization using an organic solvent, water, or a mixture thereof (step c).

The ions may be alkali ions such as Li, Na, and K.

The organic solvent may be a cyclic carbonate solvent, a chain carbonate solvent, an ester solvent, an ether solvent, a nitrile solvent, an amide solvent or a mixture thereof.

By peeling the layered compound, a nanosheet represented by any one of the following Chemical Formulas 1 to 4 may be prepared.

<Formula 1>

AMnAs (where A is one of Li, Na and K)

<Formula 2>

MnAs

<Formula 3>

BZnAs, where B is Na or K

<Formula 4>

ZnAs

The peeling is selected from the group consisting of peeling with energy by ultrasonic waves, peeling by invasion of solvents, peeling with salts and reactive gases formed by solvents and ions, peeling with tape, and peeling with a material having an adhesive surface. It can be made using one or two or more processes.

Hereinafter, the present invention will be described in more detail through examples and experimental examples. These examples and experimental examples are only intended to describe the present invention in more detail, and according to the gist of the present invention, the scope of the present invention is not limited by these examples and experimental examples. It is self-evident.

[Example]

Example 1: Preparation of LiMnAs single crystal

A well mixed quantity of Mn and As powder and a quantity of Li and Sn are inserted into the reaction vessel. At this time, Sn inhibits the vaporization of the Li, Mn, and As materials, and serves as a metal flux that facilitates the growth of the compound LiMnAs. The sample inserted into the reaction vessel is sealed in a quartz tube. At this time, the inside of the quartz tube maintains an inert gas atmosphere, such as Ar, or creates a vacuum to prevent oxidation or deterioration of the sample. The present inventor used a vacuum-encapsulated quartz due to fear of quartz damage due to volume expansion of the inert gas at high temperature. . The quartz tube containing the sample was reacted in an electric furnace, and the sample was melted at a temperature of 650-800 ° C for 12 hours, and then slowly cooled at a rate of 0.5-3 ° C per hour for recrystallization. After reaching 500 ° C, cut off the power to the electric furnace and reverse the direction of the reaction vessel. The reason for inverting the container is to remove the Sn flux after the reaction to facilitate separation of the single crystal sample. Through this, a high purity LiMnAs single crystal was obtained. The manufacturing process described above is schematically illustrated in FIG. 1.

The synthesized LiMnAs sample confirmed the phase by the X-ray diffraction pattern of FIG. 2, and confirmed that the high purity single crystal was synthesized.

Example 2: Preparation of NaMnAs single crystal

NaMnAs single crystals were prepared in the same manner as in Example 1, except that Na was used instead of Li, and it was confirmed that high-purity single crystals were synthesized by the X-ray diffraction pattern of FIG. 2.

Example 3: Preparation of KMnAs single crystal

KMnAs single crystals were prepared in the same manner as in Example 1, except that K was used instead of Li, and it was confirmed that high-purity single crystals were synthesized by the X-ray diffraction pattern of FIG. 2.

Example 4: Preparation of layered MnAs nanosheets

Various solvents can be used to remove Li ions from the synthesized high purity LiMnAs samples. Among them, the present inventor used Deionized water (H ₂ O), and a layered MnAs structure can be obtained at a faster reaction time than other solvents, so that the corresponding solvent was selected. The structure of the produced layered MnAs can be easily peeled by a method used for peeling existing two-dimensional materials. To obtain a MnAs nanosheet, tip sonication may be performed using a solvent in which a layered MnAs or LiMnAs material is mixed in a DI / IPA 1: 4 ratio. At this time, the power is 400W, the time is suitable for 40 minutes, and the peeled nanosheet can be taken from the supernatant by rotating the centrifuge at 3600 rpm for 10 minutes. The peeled MnAs nanosheet can be predicted to have a square symmetry structure, and a schematic diagram for this is shown in FIG. 5.

Example 5: Preparation of NaZnAs single crystal

A well mixed quantity of Zn and As powder and a quantity of Na and Sn are inserted into the reaction vessel. The sample inserted into the reaction vessel is sealed in a quartz tube. At this time, Sn inhibits the vaporization of the Na, Zn, As materials, and serves as a metal flux that facilitates the growth of the compound NaZnAs. At this time, the inside of the quartz tube maintains an inert gas atmosphere, such as Ar, or creates a vacuum to prevent oxidation or deterioration of the sample. The present inventor used a vacuum-encapsulated quartz due to fear of quartz damage due to volume expansion of the inert gas at high temperature. . The quartz tube containing the sample reacted in an electric furnace, and the sample was melted at a temperature of 650-800 ° C for 12 hours, and then slowly cooled at a rate of 0.5-3 ° C per hour for recrystallization. After reaching 500 ° C, cut off the power to the electric furnace and reverse the direction of the reaction vessel. The reason why the container is turned over is to remove the Sn flux after the reaction to facilitate separation of the single crystal sample. Through this, high-purity NaZnAs single crystals were obtained. The above-described manufacturing process is schematically illustrated in FIG. 6.

The synthesized NaZnAs sample confirmed the phase by the X-ray diffraction pattern of FIG. 7 and confirmed that it was high purity single crystal synthesis.

Example 6: Preparation of KZnAs single crystal

KZnAs single crystals were prepared in the same manner as in Example 5, except that K was used instead of Na, and it was confirmed that high-purity single crystals were synthesized by the X-ray diffraction pattern of FIG. 7.

Example 7: Preparation of layered ZnAs nanosheets

Various solvents can be used to remove Na ions from the synthesized high purity NaZnAs samples. Among them, the present inventor used Deionized water (H ₂ O), and the corresponding solvent was selected because a layered ZnAs structure can be obtained at a faster reaction time than other solvents. The structure of the produced layered ZnAs can be easily peeled using a method used for peeling existing two-dimensional materials. To obtain ZnAs nanosheets, layered ZnAs or NaZnAs materials can be run through tip sonication using a solvent mixed in a DI / IPA 1: 4 ratio. At this time, the power is 400W, the time is suitable for 40 minutes, and the peeled nanosheet can be taken from the supernatant by rotating for 10 minutes at 3,600 rpm with a centrifuge.

[Test Example]

Test Example 1: Measurement of physical properties of layered AMnAs

3 and 4, AMnAs (LiMnAs, NaMnAs, KMnAs) prepared according to Examples 1 to 3 show semiconductor properties with increasing resistance as temperature decreases, and improvement of graph hysteresis curves of MT and MH measurements It shows ferromagnetic properties when viewed. Therefore, AMnAs may be used as a ferromagnetic semiconductor material, and MnAs from which A (Li, Na, and K) is removed may also be used as a ferromagnetic semiconductor material.

Test Example 2: Measurement of physical properties of layered BZnAs

Referring to FIG. 8, BZnAs (NaZnAs, KZnAs) prepared according to Examples 5 and 6 exhibits a semiconductor property in which resistance increases with decreasing temperature. B etched ZnAs is also expected to be a semiconductor material.

Claims (15)

A layered compound represented by any one of the following Chemical Formulas 1 to 4.
<Formula 1>
AMnAs, where A is one of Li, Na and K
<Formula 2>
MnAs
<Formula 3>
BZnAs, where B is Na or K
<Formula 4>
ZnAs According to claim 1,
The layered compound represented by any one of Formulas 1 to 4 is a layered compound characterized in that it has a structure of P4 / nmms, P6 ₃ / mmc or P6 ₃ mc. The method of claim 1.
The layered compound represented by Formula 1 or Formula 2 has a ferromagnetic property. The method of claim 1
The layered compound represented by any one of Formulas 1 to 4 has a layered compound, characterized in that it has semiconductor properties. (a) inserting a synthetic raw material comprising A, Mn and As or a synthetic raw material containing B, Zn and As into the reaction vessel, wherein A is any one of Li, Na and K, and B is Na or K); And
(B) a method of synthesizing a layered compound comprising; preparing a crystallization by crystallization through melt-cooling the synthetic raw material inserted into the reaction vessel. The method of claim 5, after step (a),
A method for synthesizing a layered compound, characterized in that Sn is further inserted into the reaction vessel. The method of claim 5,
The melting method of synthesizing a layered compound, characterized in that is performed at a temperature of 650 ~ 800 ℃. The method of claim 5,
The cooling is a method of synthesizing the layered compound, characterized in that the rapid or slow cooling of the molten synthetic raw material. The method of claim 8,
The slow cooling is a step of forming a single crystal by growing crystals by cooling at a rate of 0.5-3 ° C per hour to a temperature of 300-500 ° C, and the rapid cooling is a step of rapidly cooling than the rate of slow cooling to form a polycrystal. Method for synthesizing layered compound characterized by The method of claim 5, after step (b),
(c) A method for synthesizing a layered compound, further comprising the step of preparing an layered compound by removing ions from the crystallization using an organic solvent, water or a mixture thereof. The method of claim 10,
The ion is a method of synthesizing a layered compound, characterized in that at least one selected from Li, Na and K. The method of claim 10,
The organic solvent is a cyclic carbonate-based solvent, a chain carbonate-based solvent, an ester-based solvent, an ether-based solvent, a nitrile-based solvent, a method for synthesizing a layered compound, characterized in that a amide-based solvent or a mixture thereof. Nanosheets represented by any one of the following formula 1 to formula 4.
<Formula 1>
AMnAs, where A is one of Li, Na and K
<Formula 2>
MnAs
<Formula 3>
BZnAs, where B is Na or K
<Formula 4>
ZnAs (a) inserting a synthetic raw material comprising A, Mn and As or a synthetic raw material containing B, Zn and As into the reaction vessel, wherein A is any one of Li, Na and K, and B is Na or K);
(b) preparing a crystallized product by crystallizing the synthetic raw material inserted in the reaction vessel through melt-cooling;
(c) preparing a layered compound by removing ions from the crystallization using an organic solvent, water or a mixture thereof; And
(d) peeling the layered compound to prepare a nanosheet; a method for synthesizing a nanosheet comprising a. The method of claim 14,
The peeling is selected from the group consisting of peeling with energy by ultrasonic waves, peeling by invasion of solvents, peeling with salts and reaction gases formed by solvents and ions, peeling with tape, and peeling with a material having an adhesive surface. Method of synthesizing a nanosheet characterized in that it is made using one or two or more processes.

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