KR102062362B1 - Detonation nanodiamond chemical purification and recycling methods based on potassium permanganate - Google Patents

Abstract

A detonation nanodiamond (DND) chemical purification and recycling process method based on potassium permanganate (KMnO_4) according to an embodiment of the present invention comprises steps of: preparing a DND powder; stirring a first solution containing the DND powder and a first strong acid; stirring a second solution containing KMnO_4 and a second strong acid; mixing the first solution and the second solution, and then heating the same for a predetermined reaction time to purify DND; and recovering a third strong acid containing the first strong acid and the second strong acid, followed by reusing the same for purification of DND. According to the present invention, it is possible to minimize the generation of waste strong acid used in purification and improve the process efficiency.

Description

DND chemical purification and recycling process method based on potassium permanganate (KMnO4) {DETONATION NANODIAMOND CHEMICAL PURIFICATION AND RECYCLING METHODS BASED ON POTASSIUM PERMANGANATE}

A potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process method is provided.

Detonation Nano Diamond (DND) by explosion reaction has a few nanometer size and specific surface area with very small particle diameter, which is usually about tens to hundreds of times larger than diamond.

In addition, DND is almost non-toxic in vivo, has biocompatibility due to the stability of the structure, and the surface of the DND has a feature that contains a number of hydrophilic functional groups. Thus, the importance of DND materials with unique electrical, chemical and optical characteristics is growing.

On the other hand, DND is very difficult to separate into single or several particle clusters due to the strong aggregation of single diamond particles, because the explosion process is very short and shrinkage occurs simultaneously with the explosion. It is also difficult to purify.

Previous studies have shown that the purification method using sulfuric acid (H ₂ SO ₄ ) and KMnO ₄ is about 50% cheaper than the method using HClO ₄ . However, in the case of waste sulfuric acid used for DND purification, sulfuric acid itself acts as a major water pollutant and incurs high disposal costs.

In addition, the refining process is known to play an important role in affecting the quality of the product, and in the industrial aspect, lowering the production cost is an important factor to increase the productivity and competitiveness of the product.

However, the conventional purification process is difficult to control the purity of the DND purification, and due to the problem of processing cost due to excessive generation of waste strong acid, the utilization rate as a substantial DND purification process may be low.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to reduce the occurrence of explosion.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to minimize the generation of by-products.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to improve the purification efficiency at low temperatures.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to an embodiment of the present invention by adjusting the amount, temperature and time of KMnO ₄ to adjust the sp ³ / sp ² carbon content, I _Dia / I _G ratio It is to.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to control the purification purity of DND.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to minimize the generation of waste strong acid used in the purification.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to one embodiment of the present invention is to improve the utilization of waste strong acid.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to an embodiment of the present invention is to improve the process efficiency.

In addition to the above object, embodiments according to the present invention can be used to achieve other objects not specifically mentioned.

Potassium permanganate (KMnO ₄ ) -based DND chemical purification and recycling process according to an embodiment of the present invention comprises the steps of preparing a detonation nano diamond (DND) powder, stirring the first solution comprising the DND powder and the first strong acid Purifying the DND by stirring a second solution comprising potassium permanganate (KMnO ₄ ) and a second strong acid, mixing the first solution and the second solution and heating for a predetermined reaction time, and the first strong acid And a recycling step of recovering the third strong acid including the second strong acid and reusing the purified DND.

In the recycling process step, the third strong acid and the unused strong acid may be mixed.

The strong acid may include at least one of sulfuric acid (H ₂ SO ₄ ), hydrogen fluoride (HF), hypochlorous acid (HClO), chloric acid (HClO ₃ ), and perchloric acid (HClO ₄ ).

The amount of DND powder and potassium permanganate (KMnO ₄ ) may be in a ratio of 1: 2 to 1: 6.

Depending on the amount of potassium permanganate (KMnO ₄ ), the sp ³ / sp ² carbon ratio of the purified DND can be adjusted.

In the step of purifying the DND by mixing the first solution and the second solution and heating for a predetermined reaction time, the reaction time may be 1 hour to 24 hours.

In the step of purifying the DND by mixing the first solution and the second solution and heating for a predetermined reaction time, the heating temperature may be 100 ° C to 400 ° C.

Here, the heating temperature can be heated by the method of step function.

Potassium permanganate (KMnO ₄ ) based DND chemical purification and recycling process according to an embodiment of the present invention can reduce the occurrence of explosion, minimize the generation of by-products, can improve the purification efficiency at low temperature The amount, temperature and time of KMnO ₄ can be adjusted to adjust the sp ³ / sp ² carbon content, I _Dia / I _G ratio, the purification purity of DND, and the generation of waste strong acid used for purification. It can minimize, improve the utilization of the waste strong acid, and improve the process efficiency.

1 is a view illustrating a circulation process of a DND purification and recycling process according to an embodiment.
2 is a diagram illustrating a DND purification process according to an embodiment.
3 is a graph showing a heating temperature curve over time in a DND purification process according to an embodiment.
4A is a view illustrating UV-Raman spectra with respect to temperature according to Example 1. FIG.
4B is a diagram illustrating I _Dia / I _G ratios according to temperature according to Example 1. FIG.
5A to 5C are diagrams showing each layer of the purified DND according to Example 1. FIG.
6A to 6F are diagrams showing UV-Raman spectra and I _Dia / I _G ratios for each layer of the purified DND according to Example 1. FIG.
7 is a diagram showing an XRD analysis of DND according to Example 1. FIG.
8A is a view showing UV-Raman spectra of purified DND according to the amount of KMnO ₄ according to Example 2. FIG.
8B is a graph showing I _Dia / I _G ratios of purified DND according to the amount of KMnO ₄ according to Example 2. FIG.
9 is a diagram showing an XRD analysis of DND according to Example 2. FIG.
FIG. 10A is a view illustrating UV-Raman spectra with respect to temperature according to Example 3. FIG.
FIG. 10B is a diagram illustrating I _Dia / I _G ratios according to temperature according to Example 3. FIG.
11A is a view showing UV-Raman spectra according to the amount of KMnO ₄ according to Example 4. FIG.
FIG. 11B is a diagram showing I _Dia / I _G ratios depending on the amount of KMnO ₄ according to Example 4. FIG.
12A is a view illustrating UV-Raman spectrum according to reaction time according to Example 5. FIG.
12B is a view showing I _Dia / I _G ratios according to reaction time according to Example 5. FIG.
13A is an ICP-OES analysis graph according to the number of reuse of H ₂ SO ₄ in the purification of DND using 0.5 g of potassium permanganate (KMnO ₄ ) according to Example 6. FIG.
13B is an ICP-OES analysis graph according to the number of reuse of H ₂ SO ₄ in the purification of DND using 3 g of potassium permanganate (KMnO ₄ ) according to Example 6. FIG.
14A is a view illustrating UV-Raman spectra of purified DND (KMnO ₄ 0.5 g) according to the number of recycling cycles according to Example 6. FIG.
14B is a view showing UV-Raman spectra of purified DND (KMnO ₄ 3 g) according to the number of recycling according to Example 6. FIG.
FIG. 14C is a graph illustrating I _Dia / I _G ratios of (KMnO ₄ 0.5 g and KMnO ₄ 3 g) according to the number of recycling cycles according to Example 6. FIG.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily practice the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. In addition, in the case of well-known technology, a detailed description thereof will be omitted.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise.

1 is a view showing a cyclic process of the DND purification and recycling process, Figure 2 is a view showing a DND purification process.

1 and 2, according to the embodiment of the potassium permanganate (KMnO4) -based DND chemical purification and recycling process method, preparing a DND powder, stirring the first solution containing the DND powder and the first strong acid Stirring the second solution comprising potassium permanganate and the second strong acid, mixing the first solution and the second solution, and heating for a predetermined reaction time to purify the DND, recovering the third strong acid to recover the DND. A recycling step for reuse in purification.

First, a step of preparing the DND powder is performed.

The detonation nanodiamond (DND) may be in the form of a black powder, and may be a nanodiamond synthesized using an explosion method. In this case, the nanodiamond may be synthesized by a plasma method or a laser method, in addition to the explosion method.

Subsequently, the step of stirring the first solution comprising the DND powder and the first strong acid may be performed.

The first strong acid refers to a strong acid mixed with the DND powder. The first strong acid may include, for example, at least one of sulfuric acid (H ₂ SO ₄ ), hydrogen fluoride (HF), hypochlorous acid (HClO), chloric acid (HClO ₃ ), and perchloric acid (HClO ₄ ). However, the present invention is not limited thereto.

The first solution refers to a solution containing the DND powder and the first strong acid. For example, the first solution may be obtained by adding the first sulfuric acid and the DND powder to a reactor and stirring the dispersion for about 3 hours or more, but is not limited thereto. In this case, about 40 mL of the first sulfuric acid and about 1 g of DND powder may be included, but is not limited thereto. In this step, the DND powder may be sufficiently stirred in the first strong acid to be completely dispersed. When mixed with the fully dispersed DND powder and the second solution, the generation of sparks and sparks can be reduced, and the occurrence of dangerous situations such as explosions can be reduced.

Next, a step of agitating the second solution comprising potassium permanganate and a second strong acid is performed.

The second solution refers to a solution containing potassium permanganate and a second strong acid. For example, the second solution may be obtained by mixing about 40 mL of the second sulfuric acid with potassium permanganate, and then stirring the mixture for about 1 hour or more, but is not limited thereto. At this time, the second solution may be performed by adding potassium permanganate little by little to a container containing the second strong acid while cooling to room temperature or less. The cooling method may be, but is not limited to, the second solution prepared in a water bath containing ice.

The second strong acid refers to a strong acid mixed with potassium permanganate. The second strong acid may include at least one of sulfuric acid (H ₂ SO ₄ ), hydrogen fluoride (HF), hypochlorous acid (HClO), chloric acid (HClO ₃ ), and perchloric acid (HClO ₄ ), but is not limited thereto. It doesn't work.

Potassium permanganate is an oxidizing agent, and the weight ratio of DND powder and potassium permanganate may be 1: 2 to 1: 6. For example, the amount of potassium permanganate may be 2 g to 6 g, but is not limited thereto. In this case, when the DND is purified according to the amount of potassium permanganate at about 340 ° C. for about 3 hours, I _Dia / I _G of the DND may increase as the amount of potassium permanganate increases. This may be due to an increase in the diamond peak of 1325 cm ⁻¹ and an upshift of the G-band peak.

The sp ³ / sp ² carbon ratio is closely related to the I _Dia / I _G ratio. At this time, sp ³ carbon may be a diamond, sp ² carbon may include graphene, graphite (graphite), nanotubes (nanotube) and the like. The I _Dia / I _G ratio is the intensity ratio of a 1325 cm ^-1 diamond peak and a 1590 cm ^-1 G-band peak using an UV-Raman spectroscopy. Accordingly, the diamond content of the purified DND can be determined by the I _Dia / I _G and sp ³ content.

As the amount of potassium permanganate increases, the sp ³ / sp ² carbon content may increase, the I _Dia / I _G ratio may increase, and the purification efficiency may increase. The increase in the sp ³ / sp ² carbon ratio and the I _Dia / I _G ratio may be due to a phenomenon in which the amount of non-diamond carbon is selectively removed as the amount of the oxidant increases.

Therefore, by adjusting the amount of the oxidizing agent, it is possible to adjust the sp ³ / sp ² carbon content of the purified DND, to adjust the I _Dia / I _G ratio, it is possible to control the purification efficiency.

Subsequently, a step of purifying the DND by mixing the first solution and the second solution and heating for a predetermined reaction time is performed.

The tablet of the DND can be visually confirmed through the color change, and it can be confirmed that the black powder is purified as it turns gray. For example, when purified under the conditions of 6 g of potassium permanganate, 1 g of DND powder, and a heating temperature of about 330 ° C., the purified DND may appear gray and no impurities may be present. If impurities are included in the purified DND, the DND may appear dark brown.

Impurities may be generated when an excessive amount of oxidant is included relative to the heating temperature, and may be K _{1. 33} Mn ₈ O ₁₆ or MnO ₂ which is a byproduct of potassium permanganate, but is not limited thereto. In the prior perchloric acid (HClO _4), compared to that shown for base DND purified study I _Dia / I _G is close to gray in the original black or black, depending on the purification degree in the case of low DND in the purification of DND using potassium permanganate I _Dia / I _It can be seen that the DND having a low _G shows dark brown color, and thus the impurities contained in the DND.

The DND may be purified through a process of slowly adding and mixing a second solution to the first solution. In this case, the mixing speed may be about 100 mL / sec or less. When the mixing rate is about 100 mL / sec or more, the first solution and the second solution may exothermicly react, causing the temperature to rise sharply and explode. In this step, about 20 mL of the second strong acid may be further added to the reaction vessel of the second solution. Using the added second strong acid, the remaining solution in the reaction vessel of the second solution may be rinsed and cleanly added to the reaction vessel of the first solution. In this case, the first strong acid and the second strong acid may be about 100 mL in total, but are not limited thereto. Explosion may occur by mixing KMnO ₄ and H ₂ SO ₄ , which is an oxidative solid, to generate Mn ₂ O ₇ , but is not limited thereto.

The preset reaction time may include 1 hour to 24 hours. For example, the purification experiment may be performed while increasing the reaction time to 3, 6, 12, or 24 hours, but is not limited thereto. At this time, when the reaction time was increased by using about 3 g of KMnO ₄ at about 330 ° C., and the DND was purified, the I _Dia / I _G of the purified DND was about 1.11 ± 0.03, and the I was reacted for about 6 hours. _Dia / I _G is about 1.15, I _Dia / I _G of DND reacted for about 12 hours may be about 1.24 ± 0.02460, and I _Dia / I _G of DND reacted for about 24 hours may be about 1.24 ± 0.02190. (See Table 2).

Therefore, as the reaction time increases, I _Dia / I _G may increase to a certain level, sp ³ / sp ² carbon ratio may increase to a certain level, and purification efficiency may increase. This may be due to the phenomenon that the amount of non-diamond carbon is selectively removed as the reaction time increases.

The heating temperature may include a range from about 100 ° C to about 400 ° C. The heating temperature refers to the reaction temperature at which the DND is purified. At this time, the increasing method of the heating temperature may follow the step function. The heating temperature of the mixed solution can be below the boiling point of the strong acid. For example, the mixed solution may begin to boil around about 320 ° C. and maintain a temperature up to about 330 ° C. At this stage, about 330 ° C. is the set temperature value of the thermostat and is consistent with the boiling point of sulfuric acid (H ₂ SO ₄ ).

As the heating temperature increases, the sp ³ / sp ² carbon content may increase and the I _Dia / I _G ratio may increase. For example, when purified at heating temperatures of about 190 ° C., about 230 ° C., about 255 ° C., and about 330 ° C., under conditions including 6 g of potassium permanganate and 1 g of DND powder, I _Dia / I with temperature rise _G may be increased.

However, when 3 g of potassium permanganate and 1 g of DND powder are included, the change in I _Dia / I _G may not appear due to an increase in temperature. Accordingly, it can be seen that the optimal weight ratio of potassium permanganate and DND powder is 3: 1. When the weight ratio of potassium permanganate and DND powder is 3: 1, it can be inferred that the optimized sp ³ / sp ² carbon ratio appears.

Therefore, as the temperature increases, the sp ³ / sp ² carbon content of the purified DND may increase, the I _Dia / I _G ratio may increase, and the purification efficiency may increase. This may be due to the phenomenon that the amount of non-diamond carbon is selectively removed as the reaction time increases.

Next, a recycling process step of recovering the third strong acid and reusing the purified DND may be performed.

The third strong acid refers to a strong acid in which the first strong acid and the second strong acid are mixed. At this time, the third strong acid may be a strong acid already used for purification of the DND, and may be recovered and reused for purification of the DND.

The recycling process may be a process of repeatedly recovering the third strong acid used in the DND chemical purification process and repeating the previous DND chemical purification process based on potassium permanganate (KMnO ₄ ). At this time, in the process of purifying the DND using the third strong acid, the DND may be purified without impurities. The number of times the third strong acid is reused may be at least three times, but is not limited thereto.

3 is a graph showing a heating temperature curve over time.

Referring to FIG. 3, in the step of purifying the DND by mixing the first solution and the second solution and heating for a predetermined reaction time, the heating method will be described in more detail. In this case, the heating method may follow a step function.

Referring to FIG. 3, the solution in which the first solution and the second solution are mixed may be heated by a step function method of heating a reaction temperature by alternately repeating a temperature rising section and a temperature maintaining section.

The rate of temperature rise in the temperature increase section may be about 10 ° C./minute or less. If the rate of rise is about 10 ° C./minute, the temperature and pressure can rise rapidly during the purification process, causing an explosion during the reaction.

The length of the temperature maintaining section may be at least 0.01 times the length of the temperature rising section. For example, the length of the temperature maintenance section may be at least 0.1 times the length of the temperature rising section, but is not limited thereto. If the length of the temperature holding section is shorter than 0.01 times the length of the temperature rising section, the reaction solution may not be sufficiently stabilized during the reaction, and an explosion may occur in the temperature rising section.

In this step, the reaction temperature is preferably 25 ° C. or higher and below the boiling point of the strong acid used. The boiling point of the strong acid may be, for example, about 330 ° C. or less, which is the boiling point of sulfuric acid, but is not limited thereto.

The reaction temperature may vary depending on the type of strong acid or oxidizing agent used and should be in a range that does not affect the oxidizing power of the strong acid or oxidizing agent. If the reaction temperature is lower than the above range, the rate at which the purification proceeds after reaching the reaction temperature may be slow. If the reaction temperature is higher than the boiling point or melting point of the strong acid or oxidizing agent, the strong acid or oxidizing agent is vaporized to facilitate oxidation. And much energy can be consumed for heating.

In summary, the potassium permanganate (KMnO4) -based DND chemical purification process according to the embodiment, after preparing a first solution containing the DND powder and the first strong acid, a second solution containing potassium permanganate and the second strong acid, respectively And slowly mixing the two solutions at a rate of about 100 mL / sec or less. This process can reduce the occurrence of explosions during the purification process and control the rapid rise in temperature.

In the potassium permanganate (KMnO ₄ ) -based DND chemical purification process according to the embodiment, the amount, temperature and time of KMnO ₄ may be adjusted to adjust the sp ³ / sp ² carbon content, the I _Dia / I _G ratio, and the purity of the DND. And it is possible to control the purification efficiency, it is possible to minimize the impurities of the DND even at a low purification reaction temperature.

In addition, the recycling process according to the embodiment is a process for reuse in the DND chemical purification process with a third strong acid containing the first and second strong acids used in the DND chemical purification process, the third strong acid does not generate impurities and at least 3 It can be reused in the purification process more than once, thereby minimizing the generation of waste strong acids used in the purification and can be economical, and thus may be applicable to various industries.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are merely examples of the present invention and the present invention is not limited to the following Examples.

In embodiments, less than 1% metal impurities are used as DND black powder (purity = 54.50%) of Nabond Technologies Co., Ltd. (Hong Kong). Sulfuric acid (JTBaker, 95-98%, H ₂ SO ₄ ) and potassium permanganate (sigma-aldrich, 99.9%, KMnO ₄ ) are used for DND purification. A reflux cooler (Graham type) and a temperature sensor are connected to a 100 mL round bottom three neck flask, and the temperature of the purification reaction is controlled by a temperature controller and a heating mantle. All reaction spaces are made of glass to prevent the occurrence of secondary metal contamination, and the temperature control program of the thermostat is designed to automatically adjust the target reaction temperature and time. Also, for safety, when making KMnO ₄ / H ₂ SO ₄ solution, mix KMnO ₄ little by little with H ₂ SO ₄ while cooling below room temperature in an ice bath or other method, and separate the DND / H ₂ SO ₄ solution separately. Each must be prepared and thoroughly stirred. H ₂ SO ₄ solution DND with KMnO ₄ / H ₂ SO ₄ are not dispersed in this, and to avoid direct encounter situation, since an exothermic reaction occurs when mixing the two solutions the reaction equipment are required to maintain the stirring and determine the temperature of the solution The KMnO ₄ solution should be slowly poured into the DND solution. UV-Raman spectroscopy (InVia Raman Microscope, Renishaw) performed an analysis using excitation frequency of 325 nm (He-Cd laser) in the back-scattering geometry. A 100X lens was used and the exposure time was fixed at 180 seconds. The laser output is kept within 10%. Background removal uses fixed point subtraction in the range 900–2000 cm ⁻¹ . DND of purity is estimated to 1325cm ^-1 of the diamond peak and the G-band peak of 1590cm ^-1 _{Intensity ratio (I Dia / I G} ) after removing the background. DND samples for UV-Raman analysis are prepared by dispersing in deionized water for 5 minutes with a vortex-mixer and drying at room temperature by drop-casting the solution onto a SiO ₂ wafer. Scanning electron microscope energy dispersive spectroscopy (SEM-EDS) analysis was performed by Carl Zeiss Co., Ltd. SIGMA is used to analyze the composition under 15 keV energy beam conditions. X-ray diffraction (XRD) spectra are obtained using Empyrean (PANalytical, Netherlands) using a Cu-Kα line (λ = 0.1540598 nm) at a scan rate of 0.026 ° / s. Inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis uses iCAP7400DUO (Thermo Scientific) from a joint laboratory at Kunsan National University. For direct ICP-OES analysis of DND, 0.02 g of DND was dispersed in 20 mL of deionized water for 5 minutes (amplitude 100%) using EpiShear ™ Probe Sonicator (120 W, 20 kHz, Active Motif Corporation) Dilute ionized water in 50:50 ratio. The DND-dispersed solution is introduced into ICP-OES to directly analyze the metal impurities of the DND.

Example  One - DND  Chemical purification

Prepare 1 g of DND black powder, 6 g of potassium permanganate and 100 mL of sulfuric acid.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, 40 mL of sulfuric acid and 6 g of potassium permanganate (KMnO ₄ ) were mixed in another beaker in an ice bath, followed by stirring for at least 1 hour.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. When the two solutions are mixed, an exothermic reaction occurs, and if a large amount is mixed at a time, the temperature may increase rapidly, so be careful.

Subsequently, KMnO ₄ / H ₂ SO ₄ solution and DND / H ₂ SO ₄ solution were mixed at 190 ° C, 230 ° C, 255 ° C, and 330 ° C to proceed with purification for 3 hours. The solution began to boil around 320 ° C. and maintained at a temperature between 330 ° C. 330 ° C. is the set temperature value of the thermostat, which is consistent with the boiling point of H ₂ SO ₄ .

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

At this time, by adjusting the temperature, time, the amount of the oxidizing agent (KMnO4) differently, the purification experiment can be carried out in the same manner as described above.

Experimental Example  One - Example  According to 1 Of DND  UV-Raman Spectrum and I _Dia / I _G  Ratio analysis

Purified DND at 190 ° C., 230 ° C., 255 ° C. and 330 ° C. according to Example 1 were prepared, respectively, and UV-Raman spectra and I _Dia / I _G ratios were analyzed according to the temperatures. Shown in 4b.

4A represents the Raman shift (cm ⁻¹ ), and the vertical axis represents the intensity of the UV-Raman spectrum with temperature.

The horizontal axis of Figure 4b represents the temperature (temperature, ℃), the vertical axis _Dia I / I intensity ratio _G ^- represents a ^{(intensity ratio, ~ 1325 cm -1} / ~ 1590 cm 1).

Referring to FIGS. 4A and 4B, I _Dia / I _G was calculated from UV-Raman spectra of DND purified at reaction temperatures of 190 ° C. and 230 ° C., and 0.70 ± 0.095 at 190 ° C. and 1.16 ± 0.071 at 230 ° C. The DND purified at a reaction temperature of 255 ° C. or higher showed gray color, and it was confirmed that the DND was purified through color change.

Referring to Figure 4b, compared with the results of the conventional perchloric acid (HClO ₄ ) based chemical purification research, it was found that the DND purified at 190 ℃ and 230 ℃ is also an IDia / IG ratio that should show a gray but specifically blackish brown.

Therefore, it can be seen that the I _Dia / I _G value of the DND increases with temperature.

Experimental Example  2-UV-Raman spectrum and I _Dia / I _G  Ratio analysis

Purified DND at 190 ° C., 255 ° C. and 330 ° C. according to Example 1 were prepared, and the UV-Raman spectrum and the I _Dia / I _G ratio of each layer of the solutions divided into three layers were analyzed. The results are shown in Figs. 5A to 5C and 6A to 6F.

At this time, the black-brown material was separated and analyzed, and in order to confirm the purification of the DND, the DND purification experiment was carried out again at the reaction temperatures of 190 ° C, 255 ° C, and 330 ° C. The state may have been observed.

5A to 5C show the (i) layer, (ii) layer, and (iii) layer of each of the DND solutions purified at 190 ° C, 255 ° C, and 330 ° C.

Figure 6a is a UV-Raman spectrum graph of each layer of DND purified at 190 ℃.

Figure 6b is a UV-Raman spectral graph of each layer of DND purified at 255 ℃.

6c is a UV-Raman spectrum graph of each layer of DND purified at 330 ° C.

6D is a graph of I _Dia / I _G ratios for each layer of DND purified at 190 ° C.

6E is a graph of I _Dia / I _G ratios for each layer of DND purified at 255 ° C.

Figure 6f is a graph of the I _Dia / I _G ratio of each layer of DND purified at 330 ℃.

6A to 6C represent the Raman shift (cm ⁻¹ ), and the vertical axis represents the intensity of the UV-Raman spectrum of each layer.

6D to 6F show the (i) layer, the (ii) layer, and the (iii) layer, and the vertical axis represents the I _Dia / I _G ratio.

5A to 5C and 6A to 6F, all solutions were divided into three layers ((i) layer, (ii) layer, and (iii) layer), and only the solution experimented at 190 ° C. Gray material was observed which was not visible during the stirring.

As a result, a diamond-enhanced peak of 1325 cm ^{-1 and} a 1590 cm ^-1 G-band characterizing the UV-Raman spectrum of DND purified from the material of each layer except for the material at the bottom of the 190 ° C. solution ((iii) of FIG. 5A). The peak was confirmed. The lower level of material 190 ℃ solution may be inferred that not to be viewed as DND diamond peak of 1325cm ^-1 is also G-band peak of 1590cm ^-1 also appear.

In addition, it can be confirmed that I _Dia / I _G increased as the reaction temperature increased.

Experimental Example  3- XRD  Analysis and EDS Composition Analysis

DND purified at 190 ° C., 230 ° C., 255 ° C. and 330 ° C. according to Example 1 was prepared, and their XRD analysis and EDS composition analysis were performed, which are shown in FIG. 7 and Table 1.

(degree)를 나타내고, 세로축은 세기(intensity)를 나타낸다.7 is 2

(degree), and the vertical axis represents intensity.

The horizontal axis of Table 1 shows EDS compositions, such as C-K, O-K, Si-K, S-K, K-K, Mn-K, and a vertical axis | shaft shows 190 degreeC, 230 degreeC, 255 degreeC, and 330 degreeC.

Referring to FIG. 7, the XRD pattern of the purified DND showed a diamond cubic diffraction pattern (2θ = 43.8 ° (111), 75.2 ° (220)), and the DND purified at a reaction temperature of 190 ° C. and 230 ° C. a number of peaks of DND is a by-product of KMnO ₄ tablets at a reaction temperature of 190 ℃ through ICSD (inorganic crystal structure database) Standard patterns (standard pattern) analysis shown in K _{1. 33} Mn ₈ O ₁₆ is left, and a reaction temperature 230 It was confirmed that MnO ₂ was present as a by-product in DND purified at ℃.

Referring to Table 1, as confirmed through XRD analysis, the purified DND at 190 ° C. and 230 ° C. showed a high content of K, Mn, and O, indicating that KMnO ₄ residues remained at 255 ° C. Purified DND was detected by a small amount of Mn but was not confirmed by XRD analysis, but it was assumed that a very small amount of Mn compound was present. K and Mn were not detected in DND purified at 330 ° C. As a result, when purifying DND using 6 g of KMnO ₄ and 1 g of DND, it was confirmed that KMnO _{4 by-} products did not remain in the purified DND. At this time, the reason that the by-products are present in the DND purified at 190 ℃, it can be inferred that a large amount of KMnO ₄ is included to react at all the 190 ℃ reaction temperature.

Therefore, it was confirmed that DND was purified through KMnO ₄ based chemical purification, and it was confirmed that I _Dia / I _G was increased as the temperature was increased. In addition, it was confirmed that the oxidizing agent (KMnO ₄ ) by-products did not exist in the DND when reacting at the temperature of 330 ° C. under the same conditions.

C-K O-K Si-K S-K K-K Mn-K 190 ℃ 36.28 40.04 0.29 0.56 0.73 22.09 230 ℃ 76.32 16.05 0.46 0.11 0.07 6.99 255 ℃ 91.21 8.08 0.64 0.01 0.00 0.07 330 ℃ 84.89 14.75 0.34 0.01 0.00 0.00

Example  2 - At 190 ℃ KMnO ₄  According to quantity DND  Chemical purification

Prepare 1 g of DND black powder, 1 g to 5 g of potassium permanganate and 100 mL of sulfuric acid.

Purification reaction was carried out for 3 hours while increasing the amount of KMnO ₄ from 1 g to 5 g at a reaction temperature of 190 ° C. This, in Example 1 KMnO ₄ 6 g, DND 1 g, DND reacted for 3 hours at a reaction temperature of 190 ℃ it was confirmed that the by-products of KMnO ₄ remained, because the reason is many to react at 190 ℃ It was inferred that the amount of KMnO ₄ was used to control the amount of KMnO ₄ to check the residue of the by-product.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, a solution containing 40 mL of sulfuric acid and 1 g, 2 g, 3 g, 4 g, and 5 g of potassium permanganate (KMnO ₄ ) was prepared in another beaker in an ice bath containing water, and stirred for at least 1 hour. It was.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. When the two solutions are mixed, an exothermic reaction occurs, and if a large amount is mixed at a time, the temperature may increase rapidly, so be careful.

Subsequently, a KMnO ₄ / H ₂ SO ₄ solution and a DND / H ₂ SO ₄ solution were mixed to proceed with purification at 190 ° C. for 3 hours.

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

As a result, the purified DND was gray only in the experiment with 3 g of KMnO ₄ . DND purified using 1 g and 2 g of KMnO ₄ was close to black and DND purified using 4 g was dark brown as in the above experiment (see vial bottle photo of FIG. 7a).

Experimental Example  4 - Of DND  UV-Raman Spectrum and I _Dia / I _G  Ratio analysis

The DND according to Example 2 was prepared, UV-Raman spectra were analyzed to determine the sp ³ / sp ² carbon ratio of the purified DND, the I _Dia / I _G ratio was calculated, and the results 8A and 8B.

8A represents the Raman shift (cm ⁻¹ ), and the vertical axis represents the intensity of the UV-Raman spectrum according to the amount of KMnO ₄ .

The horizontal axis of Figure 8b represents the amount (g) of KMnO _4, the vertical axis _Dia I / I intensity ratio _G ^- represents a ^{(intensity ratio, ~ 1325 cm -1} / ~ 1590 cm 1).

8A and 8B, DND purified using 1 g and 2 g of KMnO ₄ had no enhancement of diamond peaks of 1325 cm ⁻¹ , and DND purified using 3 g, 4 g, and 5 g. The spectrum was confirmed to have an augmentation of a diamond peak of 1325 cm ⁻¹ and an upshift of a G-band peak, but when 6 g was used, a spectrum of a down-shift of a G-band peak was found. I _Dia / I _{G was} also found to have similar or lower values than DND using 4 g.

Experimental Example  5- XRD  analysis

DND according to Example 2 was prepared, XRD analysis was performed, and the results are shown in FIG. 9.

(degree)를 나타내고, 세로축은 KMnO₄ 양에 따른 세기(intensity)를 나타낸다.The horizontal axis of FIG. 9 is 2

(degree), and the vertical axis represents intensity according to the amount of KMnO ₄ .

Referring to Figure 9, the explosion soot of the DND shows a peak at about 2θ = 26 °, which is reported to correspond to graphite.

XRD analysis showed that DND purified using KMnO ₄ 1 g and 2 g showed a broad peak near 2θ = 25 ° and the presence of unrefined graphite. In the DND purified using 4 g of KMnO ₄ , the MnO ₂ peak was confirmed as expected and it was confirmed that MnO ₂ was present in the purified DND. Specifically, no peaks related to residues were observed only in DND purified using KMnO ₄ 3 g, and the graphite peak near 2θ = 25 ° showed a reduced diffraction pattern.

Therefore, it was confirmed that DND can be purified without residues of by-products at 190 ° C. without using a high temperature reaction temperature, and the optimized ratio of DND and KMnO ₄ oxidizer was 1: 3.

Example  3-depending on temperature DND  Chemical purification

Prepare 1 g of DND black powder, 3 g of potassium permanganate and 100 mL of sulfuric acid.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, 40 mL of sulfuric acid and 3 g of potassium permanganate (KMnO ₄ ) were mixed in another beaker in an ice bath containing water, followed by stirring for at least 1 hour.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. When the two solutions are mixed, an exothermic reaction occurs, and if a large amount is mixed at a time, the temperature may increase rapidly, so be careful.

Subsequently, the KMnO ₄ / H ₂ SO ₄ solution and the DND / H ₂ SO ₄ solution were mixed at 190 ° C, 230 ° C, 255 ° C, 310 ° C and 330 ° C for 3 hours to proceed with purification. The solution began to boil around 320 ° C. and maintained at a temperature between 330 ° C. 330 ° C. is the set temperature value of the thermostat, which is consistent with the boiling point of H ₂ SO ₄ .

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

Experimental Example  6-depending on temperature Of DND  UV-Raman Spectrum and I _Dia / I _G  Ratio analysis

Purified DND was prepared at 190 ° C., 230 ° C., 255 ° C., 310 ° C. and 330 ° C. according to Example 3, and the UV-Raman spectrum and I _Dia / I _G ratio were analyzed according to the temperature. 10A and 10B.

In FIG. 10A, the horizontal axis represents Raman shift (cm ⁻¹ ), and the vertical axis represents intensity of the UV-Raman spectrum with temperature.

Figure 10b of the horizontal axis represents the processing temperature (process temperature, ℃), the vertical axis _Dia I / I intensity ratio _G ^- represents a ^{(intensity ratio, ~ 1325 cm -1} / ~ 1590 cm 1).

Referring to Figures 10a and 10b, the diamond peak and 1590cm ^-1 G-band intensity ratio of _{^{1325cm -1 (I Dia / I G}} ) is related to the sp ³ / sp ² carbon ratio of DND directly. In addition, the diamond content was determined by I _Dia / I _G and sp ³ determined by the X-ray absorption near-edge structure (XANES) spectrum. Based on the content.

As a result of the analysis, contrary to the expectation that I _Dia / I _G will also increase with the temperature rise, the change of I _Dia / I _G did not occur in the chemical purification reaction using KMnO ₄ 3 g.

Example  4 - At 340 ℃ KMnO ₄  According to quantity DND  Chemical purification

Prepare 1 g of DND black powder, 0.1 g to 6 g of potassium permanganate and 100 mL of sulfuric acid.

Purification reaction was performed for 3 hours while adjusting the amount of KMnO ₄ to 0.1 g, 0.5 g, 1 g, 2 g, 3 g, 5 g, 6 g at a reaction temperature of 340 ° C. In the UV-Raman spectral analysis according to Example 3, when using 3 g of KMnO ₄ , there is no change in I _Dia / I _{G with} temperature rise, whereas in the UV-Raman spectral analysis according to Example 1, KMnO _{When 4} 6 g was used, I _Dia / I _G increased with increasing reaction temperature. Accordingly, it is intended to by analogy to the reason is due to the amount of KMnO ₄ would make the _Dia I / I _G according to the amount of KMnO _4.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, each of preparing a solution containing the ice by containing tank potassium permanganate, 40 mL of sulfuric acid and in another beaker in the _{(KMnO 4) 0.1 g, 0.5} g, 1 g, 2 g, 3 g, 5 g, 6 g And stirred for at least 1 hour.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. When the two solutions are mixed, an exothermic reaction occurs, and if a large amount is mixed at a time, the temperature may increase rapidly, so be careful.

Subsequently, a KMnO ₄ / H ₂ SO ₄ solution and a DND / H ₂ SO ₄ solution were mixed, and the purification reaction was performed at 340 ° C. for 3 hours.

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

Experimental Example  7- Of DND  UV-Raman Spectrum and I _Dia / I _G  Ratio analysis

DND according to Example 4 was prepared, the spectrum was confirmed by UV-Raman analysis, and the I _Dia / I _G ratio was calculated, and the results are shown in FIGS. 11A and 11B.

11A represents the Raman shift (cm ⁻¹ ), and the vertical axis represents the intensity of the UV-Raman spectrum according to the amount of KMnO ₄ .

The horizontal axis of FIG. 11b represents the amount (g) of KMnO _4, the vertical axis _Dia I / I intensity ratio _G ^- represents a ^{(intensity ratio, ~ 1325 cm -1} / ~ 1590 cm 1).

11A and 11B, the amount of KMnO ₄ increased from 0.1 g to 6 g and the diamond peak of 1325 cm ⁻¹ was significantly increased, and the upshift of the G-band peak was also confirmed.

Therefore, as the amount of KMnO ₄ increases, I _Dia / I _G of the purified DND also increased. Accordingly, by using the amount of oxidant as a control variable in the chemical purification of KMnO ₄ based DND, the sp ³ / sp ² carbon ratio can be controlled by selectively removing the amount of non-diamond carbon of DND. You can check it.

Example  5-depending on the reaction time DND  Chemical purification

Prepare 1 g of DND black powder, 3 g of potassium permanganate and 100 mL of sulfuric acid.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, 40 mL of sulfuric acid and 3 g of potassium permanganate (KMnO ₄ ) were mixed in another beaker in an ice bath containing water, followed by stirring for at least 1 hour.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. When the two solutions are mixed, an exothermic reaction occurs, and if a large amount is mixed at a time, the temperature may increase rapidly, so be careful.

Subsequently, the reaction time was increased to 3 hours, 6 hours, 12 hours, and 24 hours by mixing the KMnO ₄ / H ₂ SO ₄ solution and the DND / H ₂ SO ₄ solution at the reaction temperature of 330 ° C. .

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

Experimental Example  8 - sp ³ Of sp ²  Carbon ratio analysis

Embodiment, each ready for 3 hours, 6 hours, 12 hours, DND purified with reaction time of 24 hours according to Example 5, confirmed the spectrum of the purified DND subjected to these UV-Raman analysis, and I _Dia / I _G Was calculated and the results are shown in FIGS. 12A, 12B and Table 2.

12A represents the Raman shift (cm ⁻¹ ), and the vertical axis represents the intensity of the UV-Raman spectrum with respect to the reaction time.

Figure 12b of the horizontal axis indicates the reaction time (process time, hours), vertical axis _Dia I / I intensity ratio _G ^- represents a ^{(intensity ratio, ~ 1325 cm -1} / ~ 1590 cm 1).

Table 2 shows I _Dia / I _G and standard deviation of DND with increasing reaction time.

12A, 12B and Table 2, as a result of confirming the change in the sp ³ / sp ² carbon ratio with the reaction time, I _Dia / I _G of DND purified as a reference reaction time of 3 hours was about 1.11 ± 0.03, 6 I _Dia / I _G of time-reacted DND was 1.15 ± 0.07, and I _Dia / I _G of DND-reacted 12 hours was 1.24 ± 0.02460.

In addition, the DND reacted for 24 hours was 1.24 ± 0.02190 even after a longer reaction, showing a similar result to the DND reacted for 12 hours. The increase in I _Dia / I _G with the increase of reaction time increased from about 1.1 (3 hours) to about 1.24 (12 hours), and the subsequent reaction time converged to the level similar to DND reacted for 12 hours. .

Therefore, increasing the reaction time in the chemical purification of KMnO ₄ based DND, it can be confirmed that the sp ³ / sp ² carbon ratio up to a certain level.

Time (hours) I _Dia / I _G (average) I _Dia / I _G (STDV) 3 1.109 0.034 6 1.151 0.073 12 1.238 0.025 24 1.242 0.022

Example  6- Recycling  fair

The sulfuric acid used for purification of the DND is recovered and prepared, and 1 g of DND black powder, 0.5 g of KMnO ₄ and 3 g are prepared.

First, 40 mL of sulfuric acid (H ₂ SO ₄ ) and 1 g of DND black powder were placed in a reactor and stirred for at least 3 hours for dispersion.

Next, 40 mL of sulfuric acid, 0.5 g of potassium permanganate (KMnO ₄ ), and 3 g were mixed in a beaker in an ice bath containing water, and then stirred for at least 1 hour.

Then, the two solutions were slowly mixed while checking the temperature inside the reactor where DND and sulfuric acid were mixed. At this time, KMnO ₄ / H ₂ SO ₄ solution is slowly flowed into the DND / H ₂ SO ₄ solution. 20 mL of sulfuric acid remaining in 100 mL of sulfuric acid was used to cleanly add the remaining solution in the KMnO ₄ / H ₂ SO ₄ beaker to the DND / H ₂ SO ₄ solution. Note that exothermic reactions occur when the two solutions are mixed, and if a large amount is mixed at one time, the temperature may rise rapidly.

Subsequently, at a reaction temperature of 340 ° C., a KMnO ₄ / H ₂ SO ₄ solution and a DND / H ₂ SO ₄ solution were mixed and purified for 3 hours.

After the reaction was completed, the solution was cooled to room temperature, centrifuged at about 8,000 rpm for about 20 minutes, washed five times with DI water, and dried in a vacuum oven at about 60 ° C.

After completion of the purification reaction, the DND solution was divided into three conical tubes and centrifuged at 8,000 rpm for 1 hour. The centrifuged H ₂ SO ₄ is recovered and the amount less than 100 mL can be used again for the purification of DND by adding unused sulfuric acid. This recycling process was repeated three times each.

After completion of the purification reaction, the DND solution was divided into three conical tubes and centrifuged for 1 hour at 8,000 rpm.

Experimental Example  9-ICP- OES  analysis

H ₂ SO ₄ was prepared according to the number of times reused according to Example 6, and the concentration change of K and Mn was analyzed by ICP-OES analysis, and the reusability of H ₂ SO ₄ was confirmed. 13a, 13b, and Table 3 are shown.

FIG. 13a shows the results of analysis of K and Mn ICP-OES in H ₂ SO ₄ reused when 0.5 g of potassium permanganate (KMnO ₄ ) was used.

Figure 13b shows the results of K and Mn ICP-OES in H2SO4 reused when using 3 g of potassium permanganate (KMnO ₄ ).

13A and 13B, the horizontal axis represents recycling times of H ₂ SO ₄ , and the vertical axis represents changes in concentrations of K and Mn metals.

Table 3 shows the results of ICP-OES analysis of DND purified using unrefined DND black powder, 0.5 g, 3 g of KMnO ₄ and reused H ₂ SO ₄ in terms of DND 1 g. Table is in mg.

Referring to FIGS. 13A, 13B and Table 4, regardless of the amount of KMnO ₄ used, Mn was maintained at a very low concentration and K was accumulated and increased in H ₂ SO ₄ reused after purification.

In order to confirm the effect on the metal impurity content of the purified DND as K content was increased in the reused H ₂ SO ₄ , it was directly analyzed by ICP-OES.

Referring to Table 3, the contents of the total metal impurities were found to contain about 15.683 mg of the metal impurities in 1 g of DND Black powder before purification, and DND contained less than 10 mg of metal impurities in the DND after purification. KMnO ₄ -based chemical purification showed that the total metal impurities were reduced 5.053 ~ 9.574 mg. In the reused H ₂ SO ₄ , the concentration of K increased with the number of reuse, but the DND black powder before purification and the D content after purification were 0.1 by direct ICP-OES analysis of DND. It can be seen that the difference in the mg level appeared, Mn, which showed a low content according to the number of reuse in H ₂ SO _{4 It} was also confirmed that the content difference of 0.1 mg level occurred. KMnO ₄ is purified before the amount and change of the K content of up to 0.158 mg though using re a H ₂ SO ₄ the K concentration is increased equal to 50% of DND weight and 300%, used at the time of purification is to re-H ₂ SO ₄ It was confirmed that even if used, it has little effect on the metal impurity content of the purified DND to be confirmed in the study.

Therefore, the increase in K, Mn or metal impurities of DND did not occur even if the used H ₂ SO ₄ was used again in the purification reaction, but the amount of total metal impurities was reduced, and thus the KMnO ₄ based chemical purification of DND was reduced. In this regard, it is determined that the proposed reuse process can reuse H ₂ SO ₄ at least three times.

DND
Black powder 0.5 g of KMnO ₄ KMnO ₄ 3 g Recycling
(One) Recycling
(2) Recycling
(3) Recycling
(One) Recycling
(2) Recycling
(3) Na 1.692 1.868 2.042 1.585 1.532 1.405 1.615 K 0.112 0.096 0.194 0.046 0.215 0.229 0.270 Mg 0.634 0.129 0.119 0.057 0.080 0.091 0.144 Ca 2.387 0.514 0.518 0.404 0.423 0.371 0.398 Cr 0.010 0.002 0.002 0.002 0.003 0.004 0.004 Mn 0.027 0.012 0.021 0.059 0.332 0.107 0.270 Fe 2.149 2.690 0.197 1.633 0.295 3.001 0.494 Co 0.001 0.001 0.001 0.000 0.001 0.001 0.001 Ni 0.005 0.002 0.001 0.000 0.001 0.003 0.002 Cu 0.022 0.000 0.000 0.000 0.000 0.000 0.000 Zn 0.161 0.010 0.005 0.003 0.006 0.004 0.003 Al 5.545 0.874 0.644 2.481 0.620 0.800 0.812 Si 2.931 4.430 4.018 2.084 2.600 3.158 3.354 Pb 0.008 0.002 0.001 0.000 0.000 0.000 0.000 system 15.683 10.630 7.764 8.354 6.109 9.175 7.369

Experimental Example  10- Recycling  Refined by Count Of DND  UV-Raman Spectrum and I _Dia / I _G

Purified DND according to the recycling number according to Example 6 was prepared, their UV-Raman analysis and I _Dia / I _G was calculated to determine the sp ³ / sp ² carbon ratio of the purified DND by H ₂ SO ₄ reuse process And the results are shown in FIGS. 14A to 14C.

14A is a UV-Raman spectrum of purified DND by the number of recycling using 0.5 g of KMnO ₄ .

14B is a UV-Raman spectrum of purified DND by the number of recycling when KMnO ₄ 3 g is used.

Figure 14c is a graph of the I _Dia / I _G ratio of purified DND by the number of recycling when using 0.5 g and 3 g KMnO ₄ .

14A and 14B, the horizontal axis represents Raman shift (cm ⁻¹ ), and the vertical axis represents intensity of the UV-Raman spectrum according to the number of sulfuric acid reuse.

The horizontal axis of FIG. 14C represents the number of recycling cycles, and the vertical axis represents the intensity of the UV-Raman spectrum.

Referring to Figures 14a to 14b, the reinforcement of the diamond peak of 1325cm ^-1 was clearly confirmed, and purified DND was able to obtain a similar spectrum for each experiment.

Referring to FIG. 14c, even if the H ₂ SO ₄ used in the purification reaction is recovered and reused three times, the I _Dia / I _G value of the purified DND is maintained without significant change, and thus, the proposed H ₂ SO ₄ reuse process is used for DND. Purification does not affect the sp ³ / sp ² carbon ratio.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (8)

Preparing a detonation nano diamond (DND) powder,
Stirring the first solution comprising the DND powder and the first strong acid,
Stirring the second solution comprising potassium permanganate (KMnO ₄ ) and a second strong acid,
Mixing the first solution and the second solution and heating for a preset reaction time to purify the DND, and
Recycling process for recovering a third strong acid containing the first strong acid and the second strong acid and reused in the purification of DND
Including,
In the step of purifying the DND, the heating temperature is 190 ℃ to 330 ℃, the weight ratio of the DND powder and the potassium permanganate (KMnO ₄ ) is 1: 2.5 to 1: 3.5, the first solution and the second solution Mixing at a mixing rate of less than 100 mL / sec
DND Purification Method.
In claim 1,
In the recycling step, DND purification method comprising the mixture of the third strong acid and the unused strong acid.
In claim 1,
The first strong acid or the second strong acid includes at least one of sulfuric acid (H ₂ SO ₄ ), hydrogen fluoride (HF), hypochlorous acid (HClO), chloric acid (HClO ₃ ), and perchloric acid (HClO ₄ ). Purification method.
delete In claim 1,
DND purification method of adjusting the sp ³ / sp ² carbon ratio of the purified DND according to the amount of potassium permanganate (KMnO ₄ ).
In claim 1,
In the step of purifying the DND by mixing the first solution and the second solution and heating for a predetermined reaction time, the reaction time is 1 hour to 24 hours DND purification method.
delete In claim 1,
And said heating temperature is heated by a step function.

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