Method and device for purifying boron nitride nanotubes

Abstract

One embodiment of the present invention discloses an apparatus for purifying boron nitride nanotubes, comprising: a disperser for stirring and dispersing a mixed solution in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive containing a polyphenol group is dissolved, and extracting a supernatant from the mixed solution; and a centrifugal filter having one end connected to the disperser and obtaining filtered boron nitride nanotubes from the extracted supernatant, in which the centrifugal filter includes a sheet on the inner side, the sheet extending in the height direction of the centrifugal filter and obtaining the filtered boron nitride nanotubes.

Description

Technical Field

[0001] This invention relates to a purification apparatus and method for boron nitride nanotubes. Background Technology

[0002] Boron nitride nanotubes (BNNTs) are one-dimensional nanotube particles whose walls are formed by a hexagonal lattice of intersecting boron (B) and nitrogen (N). As a novel material, BNNTs have recently attracted significant attention due to their exceptional electrical, chemical, thermal, and mechanical properties, such as high insulation, excellent thermal conductivity and stability, and high neutron absorption. Based on these properties, BNNTs are applied in various fields, including electronic components, composite fillers, and aerospace materials. However, impurities are inevitably introduced during the synthesis of BNNTs, which degrade their physical and chemical properties. Therefore, a purification method for industrially applicable BNNTs is needed.

[0003] The information disclosed in the background section of this invention is only for enhancing the understanding of the background of this invention, and therefore may include information that does not constitute prior art. Summary of the Invention

[0004] The problem the invention aims to solve Embodiments of the present invention provide highly purified boron nitride nanotubes.

[0005] However, the technical problems to be solved by the present invention are not limited to the above-mentioned problems. Those skilled in the art can clearly understand other problems not mentioned from the following description of the invention.

[0006] means for solving problems One embodiment of the present invention discloses a purification apparatus for boron nitride nanotubes, comprising: a disperser for stirring and dispersing a mixture and extracting a supernatant from the mixture, wherein the mixture disperses the boron nitride nanotubes in an aqueous solution containing an additive comprising polyphenol groups; and a centrifugal filter, one end of which is connected to the disperser and obtains filtered boron nitride nanotubes from the extracted supernatant, wherein the centrifugal filter includes a sheet on its inner side that extends along the height direction of the centrifugal filter and obtains the filtered boron nitride nanotubes.

[0007] Invention Effects According to embodiments of the present invention, impurities in boron nitride nanotubes can be largely removed, thus enabling the present invention to be applied industrially.

[0008] Furthermore, using water as a solvent when removing impurities from boron nitride nanotubes can avoid environmental pollution during the process. Attached Figure Description

[0009] The following figures accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention below, serve to further understand the technical concept of the invention. Therefore, the invention should not be construed as being limited to what is described in such figures.

[0010] Figure 1 This is a schematic diagram illustrating an example of a purification apparatus for boron nitride nanotubes according to an embodiment of the present invention.

[0011] Figure 2 This is a schematic flowchart of a method for purifying boron nitride nanotubes according to an embodiment of the present invention.

[0012] Figure 3 To capture images of boron nitride nanotubes obtained from thin films.

[0013] Figure 4 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from a thin sheet when the centrifugal filter is running at 3000 rpm.

[0014] Figure 5 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from a thin sheet when the centrifugal filter is running at 19,000 rpm.

[0015] Figure 6 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from the harvest container when the centrifuge filter is running at 3000 rpm.

[0016] Figure 7 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from the harvest container when the centrifuge filter is running at 19,000 rpm.

[0017] Figure 8 Scanning electron microscope image of the substance precipitated in the precipitation container. Detailed Implementation

[0018] One embodiment of the present invention discloses a purification apparatus for boron nitride nanotubes, comprising: a disperser for stirring and dispersing a mixture and extracting a supernatant from the mixture, wherein the mixture disperses the boron nitride nanotubes in an aqueous solution containing an additive comprising polyphenol groups; and a centrifugal filter, one end of which is connected to the disperser and obtains filtered boron nitride nanotubes from the extracted supernatant, wherein the centrifugal filter includes a sheet on its inner side that extends along the height direction of the centrifugal filter and obtains the filtered boron nitride nanotubes.

[0019] In this embodiment, the purity of the filtered boron nitride nanotubes can be increased along the height direction of the sheet.

[0020] In this embodiment, the purification device for the boron nitride nanotubes may further include a harvesting container connected to the other end of the centrifugal filter for obtaining the boron nitride nanotubes after passing through the centrifugal filter.

[0021] In this embodiment, the additive may include at least one of tannic acid, gallic acid, catechol, epigallocatechin, pyrogallol, hexahydroxydiphenic acid, ellagic acid, or chlorogenic acid.

[0022] In this embodiment, the disperser may include a precipitation container in which the precipitate of the dispersed boron nitride nanotube solution is precipitated.

[0023] In this embodiment, the supernatant can rise in a spiral shape along the height direction of the centrifugal filter to be filtered.

[0024] In this embodiment, based on the entire aqueous solution, the content of the additive in the aqueous solution can be from 0.01 wt% to 1 wt%.

[0025] Another embodiment of the present invention discloses a method for purifying boron nitride nanotubes, comprising: preparing a mixture in which boron nitride nanotubes are dispersed in an aqueous solution containing an additive comprising polyphenol groups; extracting a supernatant containing the boron nitride nanotubes from the mixture; and filtering the extracted supernatant using a centrifugal filter to obtain the boron nitride nanotubes according to purity, wherein the boron nitride nanotubes are attached to a thin sheet disposed on the inner surface of the centrifugal filter for obtaining.

[0026] In this embodiment, based on the entire aqueous solution, the content of the additive in the aqueous solution can be from 0.01 wt% to 1 wt%.

[0027] In this embodiment, the step of acid washing the obtained boron nitride nanotubes may also be included.

[0028] In this embodiment, a step of heat-treating the acid-washed boron nitride nanotubes to decarburize them may also be included.

[0029] In this embodiment, the step may also include dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide.

[0030] In this embodiment, when obtaining the boron nitride nanotubes, the more the dissolved boron nitride nanotubes adhere to the top of the sheet, the higher their purity can be.

[0031] In this embodiment, the step of collecting the precipitate that has settled from the mixture may also be included.

[0032] In this embodiment, a harvesting container may also be included for obtaining the boron nitride nanotubes after passing through the centrifugal filter. Specific Implementation Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be limited to their ordinary or dictionary meanings, but should be interpreted as conforming to the technical concept of the present invention, based on the principle that the inventor is able to appropriately define the concepts of the terms in order to best interpret their invention. Therefore, the embodiments described in this specification and the configurations shown in the accompanying drawings are only some of the most preferred embodiments of the present invention and do not represent all the technical concepts of the present invention. It should be understood that various equivalents and modifications may exist at the time of filing this application.

[0034] Furthermore, when used herein, the words “comprise, include” and / or “comprising, including” specify the presence of the shape, number, step, operation, component, element and / or group thereof, but do not exclude the presence or addition of one or more other shapes, numbers, operations, components, elements and / or groups thereof.

[0035] Furthermore, to aid in understanding the invention, the accompanying drawings are not drawn to scale, and the dimensions of some components may be exaggerated. Additionally, the same reference numerals may be assigned to the same components in different embodiments.

[0036] Although terms such as "first," "second," etc., are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another, and unless otherwise explicitly stated, a first component may also be a second component.

[0037] Throughout this specification, unless otherwise expressly stated, each component may be singular or plural.

[0038] The placement of any configuration "above (or below)" or "on (or under)" a component not only means that any configuration is placed in contact with the upper (or lower) surface of the component, but also means that other configurations can be placed between the component and any configuration placed on (or under) the component.

[0039] Furthermore, when describing a component as "connected," "coupled," or "connected" to another component, it should be understood that these components can be directly connected or connected to each other, while other components can also "intervene" between the components, or the components can be "connected," "coupled," or "connected" through other components. Additionally, when we say that one part is electrically coupled to another part, this includes not only the case where they are directly connected, but also the case where they are connected through another element.

[0040] Figure 1 This is a schematic diagram illustrating an example of a purification apparatus for boron nitride nanotubes according to an embodiment of the present invention. Figure 2 This is a schematic flowchart illustrating a method for purifying boron nitride nanotubes according to an embodiment of the present invention. Figure 3 To capture images of boron nitride nanotubes obtained from thin films.

[0041] First, see Figure 1 and Figure 2 According to an embodiment of the present invention, a boron nitride nanotube purification apparatus 1000 may include: a mixture preparer 100 for preparing a mixture; a disperser 200, one end of which is connected to the mixture preparer 100 via a first flow path f1 for stirring and dispersing the mixture and extracting a supernatant from the mixture; and a centrifugal filter 300, one end of which is connected to the disperser 200 via a second flow path f2 for obtaining filtered boron nitride nanotubes from the extracted supernatant, wherein a pump P is disposed between them for automatically moving the boron nitride nanotube solution according to the sequence of the boron nitride nanotube purification method.

[0042] Additionally, a purification method S100 for boron nitride nanotubes according to an embodiment of the present invention may include: preparing a mixture S110 in which boron nitride nanotubes are dispersed in an aqueous solution containing an additive comprising polyphenol groups; extracting a supernatant containing boron nitride nanotubes from the mixture S120; filtering the extracted supernatant in a centrifugal filter 300 S130; obtaining boron nitride nanotubes from a sheet 320 disposed inside the centrifugal filter 300 S140; acid washing the obtained boron nitride nanotubes S150; heat-treating the acid-washed boron nitride nanotubes to decarbonize S160; and dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide S170.

[0043] The mixture preparation apparatus 100 may include a preparation container 110 containing a boron nitride nanotube mixture 130 and a homogenizer 120 for mixing water containing additives with boron nitride nanotube synthetic powder.

[0044] In step S110 of preparing the boron nitride nanotube mixture 130, water mixed with additives and boron nitride nanotube synthetic powder are added to the mixture preparer 100 in a certain proportion. Then, the water mixed with additives and the boron nitride nanotube synthetic powder are mixed using a homogenizer 120 to prepare the boron nitride nanotube mixture 130.

[0045] At this point, the homogenizer 120 can disperse the water mixed with additives and boron nitride nanotube powder at a speed of 3000 rpm to 7000 rpm for 10 to 40 minutes to prepare boron nitride nanotube mixture 130.

[0046] On the other hand, boron nitride nanotubes are hexagonal nanotubes with alternating nitrogen (N) and boron (B) elements, exhibiting excellent thermal conductivity and a wide band gap, thus possessing electrical insulation properties similar to ceramics. Therefore, boron nitride nanotubes can serve as a composite material that is electrically insulating yet possesses high thermal conductivity.

[0047] Furthermore, boron nitride nanotubes are known to possess excellent mechanical properties, chemical resistance, and antioxidant properties. They can absorb thermal neutrons and are harmless to the human body, thus making them applicable to various industrial fields such as electronics, energy, aerospace, nuclear energy, and biomedicine.

[0048] However, since these boron nitride nanotubes generally cannot be dispersed in organic and aqueous solvents, in order to practically apply boron nitride nanotubes in industry, they must be dispersed in an aqueous solution containing additives containing polyphenol groups.

[0049] Therefore, in one embodiment of the present invention, boron nitride nanotube powder is dispersed in an aqueous solution containing an additive containing polyphenol groups, so that the boron nitride nanotube powder can be well dispersed even in polar solvents.

[0050] Based on the entire aqueous solution, the content of the additive in the aqueous solution can be from 0.01 wt% to 1 wt%. In addition, the additive may include at least one of tannic acid, gallic acid, catechol, epigallocatechin, pyrogallol, hexahydroxydiphenic acid, ellagic acid, or chlorogenic acid.

[0051] On the other hand, the additives such as tannic acid are all environmentally friendly substances derived from nature, so the dispersed boron nitride nanotube solution will not cause environmental pollution.

[0052] On the other hand, the boron nitride nanotube mixture 130 prepared in step S110 can be discharged from the mixture preparer 100 through the mixture discharge channel 140, and then move to the disperser 200 through the first flow path f1. At this time, the boron nitride nanotube mixture 130 can be supplied to the adjacent disperser 200 through the pump P included in the first flow path f1.

[0053] In another embodiment of the present invention, the boron nitride nanotube purification device 1000 may omit the mixture preparer 100 for preparing the mixture. If the boron nitride nanotube purification device 1000 omits the mixture preparer 100, water mixed with additives and boron nitride nanotube synthetic powder may be added to the disperser 200 in a certain proportion and then mixed in the disperser 200.

[0054] The disperser 200 may include: a dispersion container 210 for containing a boron nitride nanotube mixture 130; an inlet 250 connected to a first flow path f1; a stirrer 220 for stirring the boron nitride nanotube mixture 130 added to the dispersion container 210; an ultrasonic generator 230 for dispersing the boron nitride nanotube mixture 130; a precipitate discharge channel 240 for discharging the precipitate 280 of the extracted supernatant; and a sedimentation container 270 in which the precipitate 280 is settled.

[0055] In step S120, which involves extracting a supernatant containing boron nitride nanotubes from the boron nitride nanotube mixture 130, a stirrer 220 and an ultrasonic mixer 230 can be used to uniformly stir and disperse the boron nitride nanotube mixture 130. Specifically, the stirrer 220 can stir the boron nitride nanotube mixture 130 at a speed of 200 rpm to 500 rpm for 5 to 15 minutes. Additionally, the ultrasonic mixer 230 can disperse the boron nitride nanotube mixture 130 at a frequency of 10 kHz to 20 kHz for 5 to 15 minutes.

[0056] Next, the dispersed boron nitride nanotube mixture 130 can be left to stand for a period of time. As a result, the uniformly dispersed supernatant in the dispersed boron nitride nanotube mixture 130 can be extracted to the upper layer of the dispersion container 210, while the precipitate 280 settles to the lower layer. Subsequently, the precipitate 280 can be discharged into the sedimentation container 270 through the precipitate discharge channel 240, and the extracted supernatant can be supplied to the centrifugal filter 300 through the supernatant discharge channel 260 and the second flow path f2. At this time, the pump P included in the second flow path f2 can supply the supernatant to the adjacent centrifugal filter 300.

[0057] On the other hand, the purification method S100 for boron nitride nanotubes may further include the step of collecting the precipitate 280 precipitated from the mixture 130 into a precipitation container 270. The precipitate 280 as described above is as follows: Figure 8 As described herein, it may include catalysts and boron added during the synthesis of boron nitride nanotubes.

[0058] The centrifugal filter 300 may include a filter container 310 containing boron nitride nanotube supernatant, a sheet 320 attached to the inner wall of the filter container 310, and a supernatant inflow channel 330 connected to the second flow path f2.

[0059] At this time, the supernatant inflow channel 330, which is connected to the second flow path f2, can be set at one end of the centrifugal filter 300. Specifically, the supernatant inflow channel 330 can be set at the bottom of the centrifugal filter 300.

[0060] Centrifugal filter 300 can centrifuge the boron nitride nanotube supernatant at speeds ranging from 1000 rpm to 23000 rpm. Thus, the boron nitride nanotube supernatant can rise along the height of centrifugal filter 300 while rotating at the bottom using centrifugal force, and move to the top of centrifugal filter 300. For example, the boron nitride nanotube supernatant can rise in a spiral shape along the height of centrifugal filter 300. During this process, the boron nitride nanotubes can adhere to the sheet 320 attached to the inner wall of the filter container 310.

[0061] See Figure 3 Boron nitride nanotubes can be attached to sheet 320.

[0062] As an example, the sheet 320 may include a first region a1 corresponding to the top of the centrifugal filter 300, a third region a3 corresponding to the bottom of the centrifugal filter 300, and a second region a2 located between the first region a1 and the third region a3. However, it is not limited to this, and as will be described later, the regions of the sheet 320 may be divided into sections according to the purity of the boron nitride nanotubes collected from the sheet 320.

[0063] The supernatant supplied from the disperser 200 is filtered as it moves from the bottom to the top of the centrifugal filter 300, allowing the relatively high-impurity boron nitride nanotubes to adhere to the sheet 320 first. That is, the purity of the boron nitride nanotubes attached to the sheet 320 is highest in the first region a1, and decreases sequentially in the second region a2 and the third region a3. The purity of the boron nitride nanotubes attached to the sheet 320 can continuously increase along the height of the sheet 320.

[0064] The amount of boron nitride nanotubes attached to each region of the sheet 320 can be adjusted according to the rotational speed of the centrifugal filter 300. For example, as the rotational speed of the centrifugal filter 300 increases, the amount of boron nitride nanotubes attached to the sheet 320 increases, while as the rotational speed of the centrifugal filter 300 decreases, the amount of boron nitride nanotubes contained in the effluent, described later, increases. In other words, by adjusting the rotational speed of the centrifugal filter 300, the amount of boron nitride nanotubes collected from the sheet 320 and the purity of the collected boron nitride nanotubes can be controlled. For example, when the rotational speed of the centrifugal filter 300 increases, boron nitride nanotubes with more impurities are preferentially collected in the third region a3, thus the purity of the boron nitride nanotubes attached to the same first region a1 and second region a2 can be improved.

[0065] On the other hand, boron nitride nanotubes attached to the sheet 320 can be obtained, for example, by using a brush or scraper, or, as another example, by washing with a suitable solvent followed by filtration. However, this is not a limitation; various methods are feasible as long as boron nitride nanotubes attached to the sheet 320 can be obtained without damage.

[0066] Boron nitride nanotubes obtained from sheet 320 can be acid-washed S150. Acid washing S150 can be carried out by heating the obtained boron nitride nanotubes to 60°C to 100°C while stirring with an acid such as hydrochloric acid for 3 to 5 hours.

[0067] The acid-washed boron nitride nanotubes can then be filtered. An example of such a solvent could be deionized water (DI water).

[0068] In step S150, acid washing of boron nitride nanotubes removes the catalyst used in the synthesis of boron nitride nanotube powder, thereby further improving the purity of the boron nitride nanotubes. The catalyst used in the synthesis of boron nitride nanotube powder may include at least one of, for example, Fe, Mg, Ni, Cr, Co, Zr, Mo, W and / or Ti and their oxides.

[0069] Next, the acid-washed boron nitride nanotubes can be subjected to heat treatment S160. The heat treatment can be carried out as follows: after crushing the boron nitride nanotubes, they are placed in an electric furnace and heated at a rate of 7°C / min to 15°C / min, while being heat-treated at a maximum temperature of 700°C to 900°C for 1 to 3 hours.

[0070] Furthermore, the heat treatment step S160 can be carried out by supplying oxygen-containing gas at a temperature of 800 sccm to 1200 sccm. Therefore, in the heat treatment step S160, unreacted boron during the synthesis of boron nitride nanotubes can be converted into solid boron oxide (B₂O₃). Subsequently, in the dissolution step S170, the solid boron oxide can be dissolved in deionized water and then removed by filtration. Additionally, carbon, another impurity, can be removed after being oxidized to carbon dioxide in the heat treatment step S160.

[0071] The dissolution step S170 may include the following steps: adding heat-treated boron nitride nanotubes to heated deionized water, dispersing and stirring with an ultrasonic machine and a stirrer, and then filtering the boron nitride nanotubes.

[0072] At this point, boron oxide can be dissolved in deionized water and then filtered. That is, the boron nitride nanotubes remain on the filter paper, while the boron oxide dissolved in the deionized water can be removed by filtration. Thus, by using deionized water as a solvent to dissolve boron oxide, it is possible to remove boron oxide without using environmentally polluting solvents.

[0073] In other words, boron and carbon, which are impurities contained in boron nitride nanotubes, can be removed in the form of boron oxide and carbon dioxide during the heat treatment step S160 and the dissolution step S170. As a result, the purity of boron nitride nanotubes can be further improved.

[0074] The purity of the dissolved boron nitride nanotubes can reach 90% or higher. Furthermore, as mentioned above, when obtaining boron nitride nanotubes, the more the dissolved boron nitride nanotubes adhere to the top of the sheet 320, the higher their purity can be. That is, the purity of the dissolved boron nitride nanotubes increases in the order of the third region a3, the second region a2, and the first region a1 of the sheet 320, allowing embodiments of the present invention to obtain purified boron nitride nanotubes based on purity.

[0075] Simultaneously, the centrifugal filter 300 may also include a filter discharge channel 340 through which effluent containing the filtered boron nitride nanotubes is discharged. The filter discharge channel 340 may be connected to a harvest container 400 for obtaining the filtered boron nitride nanotubes.

[0076] The filter discharge channel 340 connected to the harvest container 400 can be located at the other end of the centrifugal filter 300. Specifically, the supernatant inflow channel 330 can be located at the bottom of the centrifugal filter 300, and the filter discharge channel 340 can be located at the top of the centrifugal filter 300.

[0077] As described above, the centrifugal filter 300 can centrifuge the boron nitride nanotube supernatant at speeds ranging from 1000 rpm to 23000 rpm. Therefore, the boron nitride nanotube supernatant can rise along the height of the centrifugal filter 300 while rotating at the bottom using centrifugal force, and move to the top of the centrifugal filter 300. For example, the boron nitride nanotube supernatant can rise in a spiral shape along the height of the centrifugal filter 300. During this process, the boron nitride nanotubes can adhere to the sheet 320 attached to the inner wall of the filter container 310, while the wastewater containing boron nitride nanotubes that is not attached to the sheet 320 can be discharged into the harvest container 400 through the filter discharge channel 340.

[0078] On the other hand, the supernatant supplied from the disperser 200 is filtered as it moves from the bottom to the top of the centrifugal filter 300, such that the purity of the boron nitride nanotubes contained in the effluent discharged from the top of the centrifugal filter 300 can be higher than the purity of the boron nitride nanotubes attached to the sheet 320.

[0079] Boron nitride nanotubes contained in the effluent are obtained by filtering them. Then, the nanotubes undergo an acid washing process (S150), followed by a heat treatment process (S160) to decarbonize the acid-washed nanotubes, and a dissolution process (S170) to remove boron from the heat-treated nanotubes. This process yields boron nitride nanotubes with impurities removed. At this point, the purity of the impurity-removed boron nitride nanotubes can reach 95% or higher.

[0080] The present invention will now be described in more detail through specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto.

[0081] Example 1 1. Preparation of boron nitride nanotube mixture Mix 0.5 g of tannic acid as an additive in 0.5 wt% aqueous solution with 20 g of boron nitride nanotube synthesis powder in 1000 mL of water and homogenize at 5000 rpm for 20 minutes to obtain 1000 mL of boron nitride nanotube mixture.

[0082] 2. Disperse the boron nitride nanotube solution 16 L of water was added to the prepared boron nitride nanotube mixture, which was then placed in a stirrer and stirred at 300 rpm. Simultaneously, the mixture was stirred and dispersed in an ultrasonic machine at a frequency of 20 kHz for 7 minutes. The dispersed boron nitride nanotube mixture was then allowed to stand for 2 minutes.

[0083] As a result, a uniformly dispersed boron nitride nanotube supernatant was formed in the upper layer of the disperser, while a precipitate was formed in the lower layer.

[0084] The supernatant of boron nitride nanotubes was fed to a centrifugal filter, and the precipitate containing the catalyst was collected in a precipitation container.

[0085] 3. Centrifuge and filter the supernatant. The boron nitride nanotube supernatant was filtered using a centrifugal filter running at 3000 rpm. As a result, the effluent containing boron nitride nanotubes was discharged from the top of the centrifugal filter into the harvest container, and the boron nitride nanotubes adhered to a sheet located on the inner wall of the centrifugal filter.

[0086] 4. Obtaining boron nitride nanotubes Boron nitride nanotubes are obtained by filtering them using a filter in a harvesting container. Alternatively, boron nitride nanotubes can be obtained by scraping thin sheets using a brush or scraper.

[0087] 5. Pickling The obtained boron nitride nanotubes were heated to 80°C while being stirred with 2M hydrochloric acid (HCl) for 4 hours to acid treat the boron nitride nanotubes.

[0088] Subsequently, the acid-treated boron nitride nanotubes were dissolved in deionized water and filtered to remove the catalysts (Fe, Mg, etc.) used in the synthesis of boron nitride nanotube powder.

[0089] 6. Heat treatment After being acid-washed, boron nitride nanotubes were pulverized and placed in an electric furnace. They were heated at a rate of 10°C / min and then heat-treated at a maximum temperature of 800°C for 2 hours. During this process, an oxygen-containing mixed gas was supplied to the furnace at 1000 sccm to oxidize the boron and carbon. As a result, the carbon in the boron nitride nanotubes was oxidized to carbon dioxide and removed, while the boron was oxidized to solid boron oxide.

[0090] 7. Dissolve The heat-treated boron nitride nanotubes were added to deionized water heated to 80°C, and then the nanotubes were dispersed by oscillating at a frequency of 20 kHz for 5 minutes using an ultrasonic machine.

[0091] Then, the boron nitride nanotubes were stirred on a hot plate at 80°C for 30 minutes, and then filtered to obtain high-purity boron nitride nanotubes with boron oxide removed.

[0092] Example 2 Example 2 uses the same method as Example 1 to purify boron nitride nanotubes, while the centrifuge filter is operated at a speed of 19,000 rpm.

[0093] Figure 4 Scanning electron microscope (SEM) images of boron nitride nanotubes obtained from a thin sheet when the centrifuge filter is running at 3000 rpm. Figure 5 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from a thin sheet when the centrifugal filter is running at 19,000 rpm.

[0094] Right now, Figure 4 The images shown are scanning electron microscope (SEM) images of boron nitride nanotubes according to Example 1. Figure 5 This is a scanning electron microscope image of boron nitride nanotubes according to Example 2.

[0095] 320 is a scanning electron microscope image of boron nitride nanotubes obtained from a thin sheet. Specifically, a1 is from the first region of the thin sheet (see...). Figure 3 Scanning electron microscope image of boron nitride nanotubes obtained from the second region of the sheet (see [reference]). Figure 3 Scanning electron microscopy image of boron nitride nanotubes obtained from the third region of the sheet (see [reference]). Figure 3 Scanning electron microscope (SEM) images of boron nitride nanotubes obtained.

[0096] See Figure 4 and Figure 5It can be confirmed that the boron nitride nanotubes a1 in the first region are formed more uniformly and densely than those a2 in the second region, and the boron nitride nanotubes a2 in the second region are formed more uniformly and densely than those a3 in the third region. In other words, it can be seen that the purity of the boron nitride nanotubes (a1, a2, a3) attached to the sheet increases along the height direction of the sheet.

[0097] In addition, comparison Figure 4 and Figure 5 It can be confirmed that Figure 5 Boron nitride nanotubes (a1, a2, a3) are more than Figure 4 The boron nitride nanotubes (a1, a2, a3) formed more uniformly and densely. Therefore, it can be seen that in the centrifugal filtration step, the purity of the purified boron nitride nanotubes (a1, a2, a3) also increases with the increase of the centrifugal filter speed.

[0098] Figure 6 Scanning electron microscope (SEM) images of boron nitride nanotubes obtained from the harvest container when the centrifuge filter was running at 3000 rpm. Figure 7 Scanning electron microscope (SEM) image of boron nitride nanotubes obtained from the harvest container when the centrifuge filter is running at 19,000 rpm.

[0099] Figure 6 The images shown are scanning electron microscope (SEM) images of boron nitride nanotubes according to Example 1. Figure 7 This is a scanning electron microscope image of boron nitride nanotubes according to Example 2.

[0100] Compare Figure 6 and Figure 7 It can be confirmed that the boron nitride nanotubes obtained from the harvesting container 400 of Example 2 are formed more uniformly and densely than those obtained from the harvesting container 400 of Example 1. Therefore, it can be seen that in the centrifugal filtration step, the purity of the purified boron nitride nanotubes 410 increases with the increase of the centrifugal filter speed.

[0101] In addition, Figure 6 and Figure 7 respectively with Figure 4 and Figure 5 Comparison confirms that the boron nitride nanotubes obtained from the harvesting container 400 are formed more uniformly and densely than those obtained from the sheet (a1, a2, a3). That is, it can be confirmed that the purity of the boron nitride nanotubes obtained from the harvesting container 400 is higher than that of the boron nitride nanotubes (a1, a2, a3) obtained from the sheet.

[0102] Specifically, in Example 1, the boron nitride nanotubes obtained from the harvesting container 400 have a purity of 83% to 87%, the boron nitride nanotubes a1 obtained from the first region of the sheet have a purity of 63% to 67%, the boron nitride nanotubes a2 obtained from the second region of the sheet have a purity of 41% to 45%, and the boron nitride nanotubes a3 obtained from the third region of the sheet have a purity of 21% to 25%.

[0103] In addition, in Example 2, the boron nitride nanotubes obtained from the harvesting container 400 have a purity of 95% to 99%, the boron nitride nanotubes a1 obtained from the first region of the sheet have a purity of 88% to 92%, the boron nitride nanotubes a2 obtained from the second region of the sheet have a purity of 78% to 82%, and the boron nitride nanotubes a3 obtained from the third region of the sheet have a purity of 26% to 30%.

[0104] As described above, the boron nitride nanotube purification apparatus according to the present invention can efficiently remove impurities from boron nitride nanotubes, thereby producing high-purity boron nitride nanotubes in large quantities.

[0105] Figure 8 Scanning electron microscope image of the substance precipitated in the precipitation container.

[0106] See Figure 8 In the step of extracting a supernatant containing boron nitride nanotubes from a boron nitride nanotube mixture, the boron nitride nanotube supernatant may be located in the upper layer of the disperser, while the precipitate formed from the boron nitride nanotube mixture may be located in the lower layer of the disperser.

[0107] As described above, the precipitate can be discharged into the sedimentation container through the precipitate discharge channel. For example... Figure 8 As shown, boron nitride nanotubes are barely observable in the precipitate, but the presence of many large particles of 100 μm or larger can be confirmed.

[0108] Specifically, the precipitate may include the catalyst and boron added during the synthesis of boron nitride nanotubes. The catalyst used in the synthesis of boron nitride nanotube powder may include, for example, Fe, Mg, Ni, Cr, Co, Zr, Mo, W and / or Ti and their oxides.

[0109] The precipitate can be collected from the precipitation vessel, and the collected catalyst and boron can be recycled during the synthesis and / or purification of boron nitride nanotubes. Therefore, the synthesis and / or purification costs of boron nitride nanotubes can be reduced.

[0110] Although the invention has been described above with reference to limited embodiments and accompanying drawings, the invention is not limited thereto, and it will be apparent to those skilled in the art that various modifications and variations can be made within the scope of the technical concept of the invention and the following claims.

Claims

1. A device for purifying boron nitride nanotubes, comprising: A disperser for stirring and dispersing a mixed solution in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive containing a polyphenol group is dissolved, and extracting a supernatant from the mixed solution, and a centrifugal filter connected to one end of the disperser and obtaining filtered boron nitride nanotubes from the extracted supernatant, wherein the centrifugal filter includes a sheet on the inside thereof, the sheet extending in a height direction of the centrifugal filter and obtaining the filtered boron nitride nanotubes. 2.The purification apparatus of boron nitride nanotubes according to claim 1, wherein a purity of the filtered boron nitride nanotubes is improved in the height direction of the sheet. 3.The purification apparatus of boron nitride nanotubes according to claim 1, further comprising: a harvesting container communicating to the other end of the centrifugal filter for obtaining the boron nitride nanotubes after passing through the centrifugal filter. 4.The purification apparatus of boron nitride nanotubes according to claim 1, wherein the additive includes at least any one of tannic acid, gallic acid, catechol, epicatechin, pyrogallic acid, hexahydroxydiphenic acid, ellagic acid, or chlorogenic acid. 5.The purification apparatus of boron nitride nanotubes according to claim 1, wherein the disperser includes a precipitate container in which a precipitate of the dispersed boron nitride nanotube solution is precipitated. 6.The purification apparatus of boron nitride nanotubes according to claim 1, wherein the supernatant is filtered by spirally ascending in the height direction of the centrifugal filter. 7.The purification apparatus of boron nitride nanotubes according to claim 1, wherein the additive is contained in the aqueous solution in an amount of 0.01 wt% to 1 wt% based on the entire aqueous solution. 8.A method of purifying boron nitride nanotubes, the method comprising: preparing a mixed solution in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive containing a polyphenol group is dissolved; extracting a supernatant containing the boron nitride nanotubes from the mixed solution; and filtering the extracted supernatant using a centrifugal filter to obtain the boron nitride nanotubes according to purity, wherein the boron nitride nanotubes are attached to a sheet provided on an inner side surface of the centrifugal filter to be obtained. 9.The method of purifying boron nitride nanotubes according to claim 8, wherein the additive is contained in the aqueous solution in an amount of 0.01 wt% to 1 wt% based on the entire aqueous solution. 10.The method of purifying boron nitride nanotubes according to claim 8, further comprising: pickling the obtained boron nitride nanotubes. 11.The method of purifying boron nitride nanotubes according to claim 10, further comprising: heat-treating the pickled boron nitride nanotubes to decarburize.

8. A method of purifying boron nitride nanotubes comprising: 12.The method of purifying boron nitride nanotubes according to claim 11, further comprising: dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide. 13.The method of purifying boron nitride nanotubes according to claim 12, wherein the additive includes at least any one of tannic acid, gallic acid, catechol, epicatechin, pyrogallic acid, hexahydroxydiphenic acid, ellagic acid, or chlorogenic acid. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The more the dissolved boron nitride nanotubes adhere to the top of the sheet, the higher the purity of the boron nitride nanotubes is improved when the boron nitride nanotubes are obtained.

14. The method of purifying boron nitride nanotubes of claim 8, further comprising: collecting a precipitate precipitated out of the mixed solution.

15. The method of purifying boron nitride nanotubes of claim 8, further comprising: a harvest container for obtaining the boron nitride nanotubes after the centrifugal filter.

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