WO2018101739A1 - Method for manufacturing thermally refined high-purity nanodiamond having improved dispersibility - Google Patents

Abstract

The present invention relates to a method for manufacturing a high-purity nanodiamond (nD) having improved dispersibility, comprising a step of thermally treating a nanodiamond, and according to the present invention, the method for manufacturing a high-purity nanodiamond having improved dispersibility is capable of: obtaining a high-crystalline nanodiamond which is completely individually dispersed within a liquid, through a simple heat treatment process in a specific temperature range under the atmosphere; allowing particles of the thermally refined high-crystalline nanodiamond to be easily dispersed in the liquid without coagulation, through an ultrasonic or electrostatic dispersion method even without using a separate dispersant, so as to be applicable as material components in various fields such as machinery, automobiles, trains, vessels, and space aviation, and specifically, to be immediately modularized to bushings and the like which require strength and wear resistance; being expected to be applied as a basic material for various display materials and quantum computers since a quantum dot effect can be implemented; and being useful as heat dissipating materials for artificial satellites and electronic devices due to excellent heat dissipating properties.

Description

Process for preparing passion-purified high-purity nanodiamonds with improved dispersibility

The present invention relates to a method for producing high purity nanodiamonds having improved dispersibility in a liquid phase.

Nanodiamond (nanodiamond, nD) refers to diamond single crystal nanoparticles having a structure in which a carbon atom is bonded to a hetero atom on the surface, the particle size of 5 ~ 100 nm.

Nanodiamond, a kind of nanocarbon, is a high-tech material that is specialized in wear resistance, biocompatibility, lubricity, heat conduction, and non-conductivity unlike other carbon materials, and is a high-tech, high-value-added, high-spec high-tech product. It is a new material that can be applied.

Specifically, nanodiamonds have high hardness (Mohs hardness 15), wear resistance (10 times durability), high refractive index (2.43), friction resistance (lowest coefficient of friction (0.03)), corrosion resistance (4 times higher), insulation, optical (Quantum dots, IR / UV absorption), biocompatibility, high specific surface area (200 ~ 450m ² / cm ² ), high thermal conductivity (2000W / mk), lowest thermal window coefficient, etc. BACKGROUND OF THE INVENTION There are many spotlights in the art as additives for optimizing mechanical and thermal performance.

However, nanodiamonds have surface characteristics of amphiphilic form, so that even when dispersed in a liquid phase to perform a post-treatment process for use in various applications, there is a technical difficulty that is difficult to maintain the desired size.

Therefore, in order to actually utilize nanodiamonds in the above-described various technical fields, development of a technique capable of individually dispersing by increasing the dispersibility of nanodiamonds should be preceded.

(Patent Document 1) Korean Patent Publication No. 10-2015-0015245 (Published Date: 2015.02.10)

(Patent Document 2) Korean Patent Publication No. 10-2013-0074206 (Published Date: 2013.07.04)

(Patent Document 3) Korean Patent Publication No. 10-2013-0041573 (Published Date: 2013.04.25)

The present invention has been made to solve the problems of the prior art as described above, the dispersibility in the liquid phase is significantly improved compared to the prior art, and furthermore, to provide a method for producing a nanodiamond having a high crystallinity for that purpose. do.

In order to achieve the technical problem as described above, the present invention provides a method for producing high purity nanodiamonds having improved dispersibility comprising the step of heat-treating nanodiamond (nD).

In addition, the step of heat treatment provides a method for producing high purity nanodiamonds having improved dispersibility, characterized in that carried out at a temperature of 450 ℃ to 800 ℃ under an air atmosphere (air atmosphere).

In addition, the heat treatment step provides a method for producing high-purity nanodiamonds having improved dispersibility, which is performed at an air temperature of 600 ° C. for 300 minutes.

In addition, the present invention provides a method for producing high purity nanodiamonds having improved dispersibility, characterized in that heat treatment of nanodiamonds produced by a detonation technique or a high-pressure high-temperature (HPHT) method. .

In addition, the manufacture of having improved dispersibility, characterized in that the conversion in the step of the heat treatment is performed at the sp ³ bonded carbon (sp ³ -bonded carbon) sp ² carbon bond (sp ² -bonded carbon) of high purity NCD NCD Provide a method.

In another aspect of the present invention, the present invention provides nanodiamonds prepared by the above method.

Furthermore, in another aspect of the present invention, it provides a nanodiamond dispersion in which the nanodiamond is dispersed.

In addition, the dispersion medium provides a nanodiamond dispersion, characterized in that the distilled water (distilled water).

In addition, it provides a nanodiamond dispersion, characterized in that dispersed by ultrasonic or electrostatic dispersion method.

According to the method for preparing high-purity nanodiamonds having improved dispersibility according to the present invention, highly crystalline nanodiamonds which are individually dispersed in a liquid phase through a simple process of heat treatment to a specific temperature range in an atmospheric atmosphere. You can get it.

In addition, the zeolite high crystalline nanodiamond particles are easily dispersed without agglomeration in the liquid phase through ultrasonic or electrostatic dispersion method without using a separate dispersant, so that various fields such as machinery, automobiles, trains, ships, aerospace, etc. It can be applied as a material part, and in particular, it can be immediately parted into bushings requiring strength and abrasion resistance, and it is also possible to implement a quantum dot effect, and thus it is expected to be applied as a basic material for various display materials and quantum computers. Due to its excellent heat dissipation, it can be usefully used as a heat dissipating material for satellites and electronic devices.

1 is a diagram schematically showing an apparatus for synthesizing nanodiamonds by the HPHT method.

FIG. 2 (a) is a scanning electron microscope (SEM) photograph of monocrystalline nanodiamonds (D90 = 125 nm) synthesized in the Examples of the present application, and FIG. 2 (b) is an enlarged view of FIG. 2 (a) and It is the result of elemental analysis by energy dispersive X-ray spectroscopy (EDS).

Figure 3 (a) is a graph of the thermogravimetric analysis (TGA) results according to the temperature change, Figure 3 (b) is a graph of the thermogravimetric analysis (TGA) results when maintained for 300 minutes at a specific temperature.

FIG. 4 shows unannealed nanodiamonds (125 nm SYN raw), nanodiamonds thermally treated at 500 ° C. for 300 minutes (500 ° C., 300 min), nanodiamonds thermally treated at 600 ° C. for 300 minutes (600 ° C., 300 min), and 800 ° C. Raman spectroscopic analysis results of nanodiamond (800 ℃ 300 min) heat-treated for 300 minutes.

5 (a) and 5 (b) are optical photographs of the nanodiamond powder before and after the heat treatment for 420 minutes at 600 ° C in the air, respectively, Figures 5 (c) to 5 (f) Scanning electron microscope (SEM) image showing the shape of the nanodiamonds.

Figure 6 (a) is a photograph showing the ultrasonic dispersion device, Figure 6 (b) and Figure 6 (c) is a scanning electron microscope (SEM) picture of the ultrasonic nano-dispersed passion nanodiamond particles, Figure 6 (d) 6 is a photograph showing an electrostatic dispersing device, and FIGS. 6 (e) and 6 (f) are scanning electron microscope (SEM) photographs of electrostatically dispersed passion nanodiamond particles.

7 is a result of analyzing the particle size distribution of the ultrasonically dispersed passion nanodiamond using a PowderShape device. 8 is a result of analyzing the particle size distribution of the electrostatically dispersed passion nanodiamond using a PowderShape device.

9 is a result of analyzing the particle size distribution of the passion nanodiamond by dynamic light scattering (DLS).

In describing the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Embodiments according to the concept of the present invention can be variously modified and can have various forms, and specific embodiments will be illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiments in accordance with the concept of the present invention to a particular disclosed form, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise" or "having" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof that is described, and that one or more other features or numbers are present. It should be understood that it does not exclude in advance the possibility of the presence or addition of steps, actions, components, parts or combinations thereof.

Hereinafter, the present invention will be described in detail.

The method for improving dispersibility of nanodiamonds according to the present invention includes the step of heat-treating the nanodiamonds.

At this time, the step of heat treatment is preferably carried out at a temperature of 550 ℃ to 750 ℃ in an air atmosphere (air atmosphere), which is when sp ² -bonded carbon (sp ² -bonded carbon) when the heat treatment at a temperature of less than 550 ℃ sp ³ bonded carbon (sp ³ -bonded carbon) not it is effectively made the transition to difficult formation of a high-purity nano-diamond, if a heat treatment at a temperature exceeding 750 ℃ has as an oxide by heating (overheating) (oxide) This is because impurities such as these are formed to lower the purity of the nanodiamond.

As it mentioned above, in the sp ³ bonded carbon (sp ³ -bonded carbon) the sp ² carbon bond (sp ² -bonded carbon) of the raw nano diamond by performing the heat treatment at a temperature of 450 ℃ to 800 ℃ the invention By converting, highly crystalline nanodiamonds with greatly improved powder separation in the liquid phase can be produced.

On the other hand, the raw nanodiamonds provided in the heat treatment can be prepared by a known synthesis method, for example, detonation technique (detonation technique), high-pressure high-temperature (HPHT) method, other chemicals It may be produced by a synthetic method or the like.

For example, the explosive synthesis method mainly used in the synthesis method, the carbon component of the gunpowder at the high temperature and high pressure generated by detonating the high explosives in an airtight container is a form in which ~ 5 nm single crystal diamond nanoparticles are agglomerated to 50 to 500 nm in the carbonization process. Nanodiamonds are synthesized.

The high-purity nanodiamonds obtained by the manufacturing method according to the present invention are greatly improved in dispersibility in a liquid, in particular, in water, through a thermal purification through heat treatment, in the form of a dispersion dispersed in distilled water. After processing, it may be utilized in various fields such as nanocomposite, quantum dot, and biomedical material through subsequent processes (surface treatment, commercialization, etc.).

According to the method for preparing high-purity nanodiamonds having improved dispersibility according to the present invention described above in detail, through a simple process of heat treatment to a specific temperature range in an air atmosphere, the highly crystalline highly dispersed individually in the liquid phase (individually dispersed) Nanodiamonds can be obtained.

In addition, the zeolite high crystalline nanodiamond particles are easily dispersed without agglomeration in the liquid phase through ultrasonic or electrostatic dispersion method without using a separate dispersant, so that various fields such as machinery, automobiles, trains, ships, aerospace, etc. It can be applied as a material part, and in particular, it can be immediately parted into bushings requiring strength and abrasion resistance, and it is also possible to implement a quantum dot effect, and thus it is expected to be applied as a basic material for various display materials and quantum computers. Due to its excellent heat dissipation, it can be usefully used as a heat dissipating material for satellites and electronic devices.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present disclosure may be modified in various other forms, and the scope of the present disclosure is not interpreted to be limited to the embodiments described below. The embodiments of the present specification are provided to more fully describe the present specification to those skilled in the art.

<Example>

First, as shown in FIG. 1, single crystal nanodiamond particles (average particle size: 125 nm) were synthesized by a high pressure and high temperature (HPHT) method.

As shown in FIG. 2, as a result of SEM-EDS analysis, the synthesized single crystal nanodiamonds were heavily aggregated and had an irregular shape before the heat treatment, and included oxide components. Specifically, according to the results of EDS analysis, a relatively high content of carbon was found to be included in the nanodiamond, but it was confirmed that it contained about 8.5 wt% oxygen.

To examine the thermal behavior of the synthesized nanodiamond particles, a thermogravimetric analyzer (model: TGA7 Thermogravimetric Analyzer, Perkin Elmer, USA) was used. Thermogravimetric Analysis (TGA) was performed at various temperatures (up to 800 ° C) and holding time in the atmosphere at a heating rate of ˚C / min.

According to the TGA analysis, the weight loss of the nanodiamond particles showed a different value depending on the treatment temperature. That is, weight loss of about 4, 10, 16, and 48% occurred at treatment temperatures 500, 550, 600, and 800 ° C, respectively (see FIG. 3 (a)). Except for the case of 500 ℃, after 300 minutes of holding time, the weight loss ratio (weight loss ratio) was significantly changed (see Fig. 3 (b)). In particular, at 800 ° C., at the point where the holding time was about 220 minutes, the residual nanodiamonds reached 3% by weight (97% by weight of nanodiamond combustion) and reached a weight loss saturation state. At 600 ° C. for 300 minutes, it was nearly saturated, but still a relatively large amount of nanodiamonds (about 16 wt%) remained. The results indicate that the heat treatment temperature plays an important role in the purification of nanodiamonds.

On the other hand, when the heat treatment for 300 minutes at 800 ℃ brownish white (brownish white) nanodiamond powder was obtained. And, when maintained at 600 ° C. for 300 minutes, a greyish white nanodiamond powder was obtained. In general, the purity of the nanodiamonds of sp ³ bond can be easily confirmed by the color, the color of the nanodiamond powder obtained when maintained at 800 ℃ 300 minutes is due to the inclusion of a large amount of oxide overheating (overheating).

In order to evaluate the quality of the nanodiamonds, Raman spectroscopy was performed using a red He-Ne ion laser (Leica, Switzerland) having a wavelength of 633 nm. The microstructure of nanodiamonds was examined using high resolution cold field emission scanning electron microscopy (Hitachi, HRCFE-SEM S-4800).

Raman spectroscopy is a very useful method for determining the quality of nanodiamonds. Referring to FIG. 4, single crystal nanodiamonds which were not heat-treated after synthesis were found to have relatively high D-bands due to defects in crystals in the Raman spectrum. Diamond (sp ³ ) peaks were observed in the Raman spectrum of both the heat treated nanodiamonds as well as the heat treated nanodiamond specimens. On the other hand, the Raman spectra of the nanodiamond specimens heat-treated at 600 ° C. for 300 minutes did not show G-bands, which are commonly observed in sp ² -bonded carbon materials. This means that sp ² bonded carbon has been effectively converted to sp ³ bonded carbon. On the other hand, the Raman spectrum of the specimen heat-treated at 600 ° C. for 300 minutes shows a very unstable peak, even though only a diamond peak appears in the Raman spectrum of the specimen, which is still in a transient state. As described above, although the unstable peak exists in the Raman spectrum of the nanodiamond, which has been enthusiastically limited at 600 ° C. for 300 minutes, it exhibits a high intensity diamond peak without a G band. It has been found that it can be formed in large quantities.

Next, the synthesized nanodiamond was 600 at a temperature increase rate of 5˚C / min in a muffle furnace (model: L5 / 12, Nabertherm Gmbh, Germany). After heating to ˚C it was carried out heat treatment to hold for 300 minutes.

5 (a) and 5 (b), the color of the nanodiamonds which were not heat treated was changed from black to grayish white by heat treatment. The weight loss rate (85%) of the nanodiamond after the heat treatment was similar to the TGA analysis result. According to Figs. 5 (d) and 5 (e), some very fine particles were observed, which were formed by thermal decomposition of nanodiamonds during the heat treatment. However, most of the particle size and shape of the heat treated nanodiamonds were similar to the particle size and shape of the nanodiamonds which were not heat treated (see FIG. 2). Therefore, it was confirmed that the enthusiastic agent by the heat treatment did not significantly affect the grain growth. On the other hand, the nanodiamonds obtained after the heat treatment showed high crystalline high quality, while the collection ratio was still very low.

The heat treated nanodiamond particles were dispersed for 5 minutes in a volume of 10 ml of water using an ultrasonic device (model: UP50H, Hielscher Ultrasonic Gmbh, Germany). The ultrasonically dispersed solution was then dropped directly onto the polished silicon wafer using a pipette. Heat-treated nanodiamonds were also dispersed directly on the polished silicon wafer using an electrostatic dispersion device (model: TSI nanometer aerosol sampler 3089, TSI Incorporated, USA). The dispersibility of nanodiamonds dispersed in the two methods was examined using a scanning electron microscope (SEM). Next, the average particle size of the individually dispersed nanodiamonds was measured by a PowderShape system (model: PowderShape MF, IST-AG-Innovative Sintering Technologies, Switzerland) based on SEM images. The average particle size distribution of the heat treated nanodiamonds was also analyzed by a dynamic light scattering (DLS) device (model: StabiSizer PMX200C, Microtrac Europe Gmbh, Germany).

The heat treated grayish white nanodiamond particles were well dispersed on the silicon (Si) wafer by the ultrasonic dispersion method and the electrostatic dispersion method. As shown in FIG. 6, the two dispersion methods showed the same aspect.

In general, agglomeration of particles caused by large surface areas causing strong agglomeration in the dispersion of nanoparticle materials is a challenge to be solved. However, the nanodiamonds entrapped according to the present invention were easily sprayed into the distilled water by ultrasonic or electrostatic dispersion method, which means that the distilled water is an excellent dispersant for the nanodiamond particles.

The size distribution of the nanodiamond particles dispersed by the two methods described above was measured using two kinds of particle analysis equipment (Powdershape and Stabisizer). For reference, Powdershape is a characterization system developed for quality investigation of powder and all kinds of particles, and Stabisizer is a colloid characterization system through dynamic light scattering (DLS). According to the Powdershape results of FIGS. 7 and 8, the particles dispersed by the two methods described above were similarly shown to have a D50 value of 80 to 90 nm. The particle size distribution ranged from 2 nm to 180 nm, and the smallest nanodiamond particles were found in electrostatically dispersed specimens. Electrostatically dispersed particles, however, were found to be more dispersible, exhibiting narrower and more continuously distributed histograms than ultrasonically dispersed particles. However, the particles dispersed in both methods within the acceptable error range (10%) showed similar dispersibility.

9 shows that the D50 value (88 nm) of the heat treated nanodiamonds obtained from DLS is very similar to the Powdershape results. In particular, up to 10% of the size distribution showed good agreement (Powdershape: 50 nm, DLS: 53 nm). It is noteworthy that the size distribution of nanodiamonds of about 100 nm size was measured (see Table 1) by Powdershape and DLS with or without heat treatment. Individually dispersed nanodiamonds by ultrasonic and electrostatic dispersion methods can be further processed to be used as nanocomposites, quantum dots, and biomedical materials. Has

In the manufacturing method of the high purity nanodiamond having the improved dispersibility of the present invention, since the passionate highly crystalline nanodiamond particles are easily dispersed without agglomeration in the liquid phase through ultrasonic or electrostatic dispersing without using a separate dispersant, It can be applied as material parts in various fields such as automobiles, trains, ships and aerospace.

Particularly, it can be directly made into parts such as bushings requiring strength and wear resistance, and it is also possible to realize quantum dot effect, so it is expected to be applied to various display materials and basic materials of quantum computer. It can be usefully used as a heat radiation material.

Claims (9)

1. A method of manufacturing high-purity nanodiamonds having improved dispersibility, comprising the step of heat-treating nanodiamonds (nD).
2. The method of claim 1,

   The heat treatment is a method for producing high purity nanodiamonds having improved dispersibility, characterized in that carried out at a temperature of 450 ℃ to 800 ℃ under an air atmosphere (air atmosphere).
3. The method of claim 2,

   The heat treatment step is a method for producing high purity nanodiamonds having improved dispersibility, characterized in that carried out for 300 minutes at a temperature of 600 ℃ under an atmospheric atmosphere.
4. The method of claim 1,

   A method for producing high purity nanodiamonds having improved dispersibility, characterized in that heat treatment of nanodiamonds produced by a detonation technique or a high-pressure high-temperature (HPHT) method.
5. The method of claim 1,

   The sp ² bond of nanodiamonds in the step of heat treatment of carbon (sp ² -bonded carbon) is sp ³ carbon bonding process for producing a high-purity nano-diamond having improved dispersibility, characterized in that is converted to (sp ³ -bonded carbon).
6. Nanodiamond produced by the method of any one of claims 1 to 5.
7. The nanodiamond dispersion liquid which disperse | distributed the nanodiamond of Claim 6.
8. The method of claim 7, wherein

   The dispersion medium is nanodiamond dispersion, characterized in that the distilled water (distilled water).
9. The method of claim 7, wherein

   Nanodiamond dispersion, characterized in that dispersed by ultrasonic or electrostatic dispersion method.

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