Method and apparatus for purifying boron nitride nanotubes

Abstract

Disclosed according to an embodiment of the present invention is an apparatus for purifying boron nitride nanotubes, the apparatus comprising: a disperser for stirring and dispersing a liquid mixture having boron nitride nanotubes dispersed in an aqueous solution in which an additive including a polyphenol group has been dissolved, and extracting a supernatant from the liquid mixture; and a centrifugal filter, one side of which is connected to the disperser, for obtaining filtered boron nitride nanotubes from the extracted supernatant, wherein the centrifugal filter includes, on the inner side thereof, a sheet that extends along the height direction of the centrifugal filter and collects the filtered boron nitride nanotubes.

Description

Boron nitride nanotube purification method and purification device

[0001] The present invention relates to a device and method for purifying boron nitride nanotubes.

[0002] Boron nitride nanotubes (BNNTs) are one-dimensional nanotube particles with a hexagonal lattice of alternating boron (B) and nitrogen (N) atoms as their walls. BNNTs are a novel material that has recently attracted considerable attention due to their excellent electrical, chemical, thermal, and mechanical properties, including high dielectric properties, excellent thermal conductivity and thermal stability, and high neutron absorption. Based on these properties, BNNTs are utilized in various fields such as electronic device materials, composite fillers, and aerospace materials. However, the synthesis of BNNTs inevitably includes impurities, and these impurities can degrade the physical and chemical properties of BNNTs. Therefore, a method for purifying BNNTs that can be used industrially is needed.

[0003] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0004] Embodiments of the present invention provide boron nitride nanotubes purified to high purity.

[0005] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0006] One embodiment of the present invention discloses a boron nitride nanotube purification device, comprising: a disperser for stirring and dispersing a mixture in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive including a polyphenol group is dissolved, and extracting a supernatant from the mixture; and a centrifugal filter connected at one end to the disperser and obtaining filtered boron nitride nanotubes from the extracted supernatant; wherein the centrifugal filter includes a sheet extending on the inside along the height direction of the centrifugal filter and obtaining the filtered boron nitride nanotubes.

[0007] According to embodiments of the present invention, impurities in boron nitride nanotubes can be removed in large quantities, and thus, they can be used industrially.

[0008] In addition, by using water as a solvent when removing impurities from boron nitride nanotubes, environmental pollution can be avoided during the process of removing impurities from boron nitride nanotubes.

[0009] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

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

[0011] FIG. 2 is a flowchart schematically illustrating a method for purifying boron nitride nanotubes according to one embodiment of the present invention.

[0012] Figure 3 is an image of boron nitride nanotubes obtained from a sheet.

[0013] Figure 4 is a SEM image of boron nitride nanotubes obtained from a sheet when the operating speed of the centrifugal filter is 3000 rpm.

[0014] Figure 5 is a SEM image of boron nitride nanotubes obtained from a sheet when the operating speed of the centrifugal filter is 19,000 rpm.

[0015] Figure 6 is a SEM image of boron nitride nanotubes obtained from a collection vessel when the operating speed of the centrifugal filter is 3000 rpm.

[0016] Figure 7 is a SEM image of boron nitride nanotubes obtained from a harvesting vessel when the operating speed of the centrifugal filter is 19,000 rpm.

[0017] Figure 8 is an SEM image of the material deposited in the sedimentation vessel.

[0018] One embodiment of the present invention discloses a boron nitride nanotube purification device, comprising: a disperser for stirring and dispersing a mixture in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive including a polyphenol group is dissolved, and extracting a supernatant from the mixture; and a centrifugal filter connected at one end to the disperser and obtaining filtered boron nitride nanotubes from the extracted supernatant; wherein the centrifugal filter includes a sheet extending on the inside along the height direction of the centrifugal filter and obtaining the filtered boron nitride nanotubes.

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

[0020] In the present embodiment, a obtaining vessel may further be included that is connected to the other side of the centrifugal filter and obtains the boron nitride nanotubes that have passed through the centrifugal filter.

[0021] In the present 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 the present embodiment, the disperser may include a sedimentation vessel in which a sediment of the dispersed boron nitride nanotube solution is sedimented.

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

[0024] In this embodiment, the additive may be included in the aqueous solution in an amount of 0.01 wt% to 1 wt% based on the entire aqueous solution.

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

[0026] In this embodiment, the additive may be included in the aqueous solution in an amount of 0.01 wt% to 1 wt% based on the entire aqueous solution.

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

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

[0029] In this embodiment, a step of dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide may be further included.

[0030] In this embodiment, the purity of the dissolved boron nitride nanotubes may increase as they are attached to the upper portion of the sheet when the boron nitride nanotubes are obtained.

[0031] In this embodiment, a step of collecting a sediment precipitated from the mixed solution may be further included.

[0032] In the present embodiment, a obtaining vessel for obtaining the boron nitride nanotubes that have passed through the centrifugal filter may be further included.

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0034] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0035] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0036] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0037] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0038] Any configuration being placed "on (or under)" or "above (or below)" a component may mean not only that any configuration is placed in contact with the upper surface (or lower surface) of said component, but also that other configurations may intervene between said component and any configuration placed on (or below) said component.

[0039] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component. Furthermore, when it is said that a part is electrically coupled to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another element in between.

[0040] FIG. 1 is a schematic diagram illustrating an example of a purification device for boron nitride nanotubes according to an embodiment of the present invention, FIG. 2 is a flowchart schematically illustrating a method for purifying boron nitride nanotubes according to an embodiment of the present invention, and FIG. 3 is an image of boron nitride nanotubes obtained from a sheet.

[0041] First, referring to FIGS. 1 and 2, a purification device (1000) of boron nitride nanotubes according to one embodiment of the present invention may include a mixture preparation device (100) for preparing a mixture, a disperser (200) connected at one end to the mixture preparation device (100) through a first flow path (f1) for stirring and dispersing the mixture and extracting a supernatant from the mixture, and a centrifugal filter (300) connected at one end to the disperser (200) through a second flow path (f2) for obtaining filtered boron nitride nanotubes from the extracted supernatant, and a pump (P) may be arranged between these to automatically move the boron nitride nanotube solution according to the order of the purification method of boron nitride nanotubes.

[0042] In addition, a method for purifying boron nitride nanotubes according to an embodiment of the present invention (S100) may include a step of preparing a mixture in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive including a polyphenol group is dissolved (S110), a step of extracting a supernatant containing boron nitride nanotubes from the mixture (S120), a step of filtering the extracted supernatant in a centrifugal filter (300) (S130), a step of obtaining boron nitride nanotubes from a sheet (320) disposed inside the centrifugal filter (300) (S140), a step of acid-cleaning the obtained boron nitride nanotubes (S150), a step of heat-treating the acid-cleaned boron nitride nanotubes to remove carbon (S160), and a step of dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide (S170).

[0043] The mixture manufacturing device (100) may include a manufacturing vessel (110) that accommodates a boron nitride nanotube mixture (130) and a homogenizer (120) that mixes water mixed with an additive and boron nitride nanotube synthetic powder.

[0044] In the step (S110) of manufacturing a boron nitride nanotube mixture (130), water mixed with an additive and boron nitride nanotube synthesis powder can be fed into a mixture manufacturing device (100) at a certain ratio. Thereafter, the water mixed with an additive and the boron nitride nanotube synthesis powder can be mixed through a homogenizer (120) to manufacture a boron nitride nanotube mixture (130).

[0045] At this time, the homogenizer (120) can disperse the boron nitride nanotube powder and water containing additives at 3000 rpm to 7000 rpm for 10 to 40 minutes to produce a boron nitride nanotube mixture (130).

[0046] Meanwhile, boron nitride nanotubes, hexagonal nanotubes with alternating nitrogen (N) and boron (B) atoms, possess excellent thermal conductivity, but also possess a wide band gap, resulting in electrical insulation properties similar to ceramics. Therefore, while boron nitride nanotubes are electrically insulating, they can be applied as high-thermal-conductivity composites.

[0047] In addition, boron nitride nanotubes have excellent mechanical properties, chemical resistance and oxidation resistance, absorb thermal neutrons, and are known to be harmless to the human body, so they can be applied to various industrial fields such as electronics, energy, space, nuclear power, and bio-medical.

[0048] However, since these boron nitride nanotubes are generally not dispersed in organic and aqueous solvents, in order to actually apply boron nitride nanotubes industrially, it is necessary to disperse the boron nitride nanotubes in an aqueous solution to which an additive containing a polyphenol group has been added.

[0049] To this end, one embodiment of the present invention can disperse boron nitride nanotube powder in an aqueous solution in which an additive including a polyphenol group is dissolved, so that the boron nitride nanotube powder can be well dispersed even in a polar solvent.

[0050] The additive may be included in the aqueous solution in an amount of 0.01 to 1 wt% based on the total aqueous solution. 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] Meanwhile, tannic acid and other substances contained in the additive are environmentally friendly substances derived from nature, so the dispersed boron nitride nanotube solution may not cause environmental pollution.

[0052] Meanwhile, the boron nitride nanotube mixture (130) manufactured in the step (S110) of manufacturing the mixture (130) can be discharged from the mixture manufacturing device (100) through the mixture discharge path (140) and then moved 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] As another embodiment of the present invention, the purification device (1000) for boron nitride nanotubes may omit the mixture solution generator (100) for producing the mixture solution. When the purification device (1000) for boron nitride nanotubes omit the mixture solution generator (100), water mixed with additives and boron nitride nanotube synthetic powder may be introduced into the disperser (200) at a certain ratio and then mixed in the disperser (200).

[0054] The disperser (200) may include a dispersion vessel (210) that receives a boron nitride nanotube mixture (130), an inlet (250) connected to the first flow path (f1), a stirrer (220) that stirs the boron nitride nanotube mixture (130) introduced into the dispersion vessel (210), an ultrasonicator (230) that disperses the boron nitride nanotube mixture (130), a sediment discharge path (240) that discharges the sediment (280) of the extracted supernatant, and a sedimentation vessel (270) in which the sediment (280) is sedimented.

[0055] In the step (S120) of extracting a supernatant containing boron nitride nanotubes from a boron nitride nanotube mixture (130), the boron nitride nanotube mixture (130) can be uniformly stirred and dispersed using a stirrer (220) and an ultrasonicator (230). Specifically, the stirrer (220) can stir the boron nitride nanotube mixture (130) at 200 rpm to 500 rpm for 5 to 15 minutes. In addition, the ultrasonicator (230) can disperse the boron nitride nanotube mixture (130) at 10 KHz to 20 KHz for 5 to 15 minutes.

[0056] Next, the dispersed boron nitride nanotube mixture (130) can be left in a resting state for a certain period of time. As a result, the dispersed boron nitride nanotube mixture (130) can be extracted as a uniformly dispersed supernatant in the upper layer of the dispersion vessel (210) with the sediment (280) settling to the lower layer. Thereafter, the sediment (280) can be discharged to the sedimentation vessel (270) through the sediment 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] [Revised 16.06.2025 under Rule 91] Meanwhile, the method for purifying boron nitride nanotubes (S100) may further include a step of collecting a precipitate (280) precipitated from a mixture (130) in a precipitation vessel (270). Such a precipitate (280) may include a catalyst and boron added during the synthesis of boron nitride nanotubes, as described later in FIG. 8.

[0058] A centrifugal filter (300) may include a filter vessel (310) for receiving a boron nitride nanotube supernatant, a sheet (320) attached to the inner wall of the filter vessel (310), and a supernatant inlet (330) connected to a second flow path (f2).

[0059] At this time, the supernatant inflow path (330) connected to the second flow path (f2) may be arranged on one side of the centrifugal filter (300). Specifically, the supernatant inflow path (330) may be arranged at the bottom of the centrifugal filter (300).

[0060] The centrifugal filter (300) can centrifuge the boron nitride nanotube supernatant at 1000 rpm to 23000 rpm. Accordingly, the boron nitride nanotube supernatant can rotate using centrifugal force at the bottom of the centrifugal filter (300) and rise along the height direction of the centrifugal filter (300) to 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 direction of the centrifugal filter (300). In this process, the boron nitride nanotubes can be attached to the sheet (320) attached to the inner wall of the filter container (310).

[0061] Referring to FIG. 3, boron nitride nanotubes may be attached to the sheet (320).

[0062] For example, the sheet (320) may include a first region (a1) corresponding to the upper portion of the centrifugal filter (300), a third region (a3) ​​corresponding to the lower portion of the centrifugal filter (300), and a second region (a2) positioned between the first region (a1) and the third region (a3). However, the present invention is not limited thereto, and the regions of the sheet (320) may be variously divided depending on the purity of the boron nitride nanotubes collected from the sheet (320), as described below.

[0063] The supernatant supplied from the disperser (200) moves while being filtered from the bottom of the centrifugal filter (300) to the top of the centrifugal filter (300), so that boron nitride nanotubes with a relatively high content of impurities can be attached to the sheet (320) first. That is, the purity of the boron nitride nanotubes attached to the sheet (320) may be the highest in the first region (a1) and may decrease in the order of the second region (a2) and the third region (a3). The purity of the boron nitride nanotubes attached to the sheet (320) may continuously increase along the height direction of the sheet (320).

[0064] The amount of boron nitride nanotubes attached to each region of the sheet (320) can be controlled depending on the rotation speed of the centrifugal filter (300). For example, as the rotation speed of the centrifugal filter (300) increases, the amount of boron nitride nanotubes attached to the sheet (320) can increase, and as the rotation speed of the centrifugal filter (300) decreases, the amount of boron nitride nanotubes included in the discharged water described later can increase. That is, by controlling the rotation 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 rotation speed of the centrifugal filter (300) increases, boron nitride nanotubes with many impurities are preferentially collected in the third region (a3), so the purity of boron nitride nanotubes attached to the same first region (a1) and second region (a2) can increase.

[0065] Meanwhile, the 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 and then filtering. However, the present invention is not limited thereto, and various methods are possible as long as the boron nitride nanotubes attached to the sheet (320) can be obtained without damage.

[0066] The boron nitride nanotubes obtained from the sheet (320) can be acid-washed (S150). Acid-washing (S150) can be performed by applying heat of 60°C to 100°C to the obtained boron nitride nanotubes and stirring them for 3 to 5 hours using an acid such as hydrochloric acid.

[0067] Afterwards, the acid-washed boron nitride nanotubes can be filtered. The solvent may be, for example, DI water (deionized water).

[0068] In the step of acid-cleaning the boron nitride nanotubes (S150), the catalyst used in synthesizing the above-described boron nitride nanotube powder can be removed, and thus, the purity of the boron nitride nanotubes can be further increased. The catalyst used in synthesizing the boron nitride nanotube powder can include, for example, at least one of Fe, Mg, Ni, Cr, Co, Zr, Mo, W, and / or Ti and oxides thereof.

[0069] Next, the acid-washed boron nitride nanotubes can be heat-treated (S160). The heat treatment can be performed by pulverizing the boron nitride nanotubes, placing them in an electric furnace, and heating them at a rate of 7°C / min to 15°C / min, at a maximum temperature of 700°C to 900°C for 1 to 3 hours.

[0070] Additionally, the heat treatment step (S160) may be performed by supplying a gas containing oxygen at 800 sccm to 1200 sccm. Accordingly, in the heat treatment step (S160), unreacted boron during the synthesis of boron nitride nanotubes may become solid boron oxide (B2O3). Subsequently, in the dissolving step (S170), the solid boron oxide may be dissolved in deionized water and then filtered to be removed. In addition, carbon, another impurity, may be oxidized to carbon dioxide and then removed in the heat treatment step (S160).

[0071] The dissolving step (S170) may include adding heat-treated boron nitride nanotubes to heated DI water, dispersing and stirring with an ultrasonicator and a stirrer, and then filtering the boron nitride nanotubes.

[0072] At this time, boron nitride nanotubes can be dissolved in deionized water and filtered. This means that boron nitride nanotubes can remain on the filter, and the boron oxide dissolved in the deionized water can be filtered out. By using deionized water as a solvent to dissolve the boron oxide, the boron oxide can be removed without using a solvent that causes environmental pollution.

[0073] That is, boron and carbon, which are impurities contained in boron nitride nanotubes, can be removed in the form of boron oxide and carbon dioxide in the heat treatment step (S160) and dissolving step (S170). As a result, the purity of boron nitride nanotubes can be further increased.

[0074] The purity of the dissolved boron nitride nanotubes can be up to 90% or more. In addition, as described above, the purity of the dissolved boron nitride nanotubes can increase as they are attached to the upper portion of the sheet (320) when the boron nitride nanotubes are obtained. 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), so that the embodiments of the present invention can obtain purified boron nitride nanotubes according to their purity.

[0075] Meanwhile, the centrifugal filter (300) may further include a filter discharge path (340) through which discharge water containing filtered boron nitride nanotubes is discharged. The filter discharge path (340) may be connected to a harvesting vessel (400) for obtaining the filtered boron nitride nanotubes.

[0076] The filter discharge path (340) connected to the harvesting vessel (400) may be arranged on the other side of the centrifugal filter (300). Specifically, the supernatant inlet path (330) may be arranged at the bottom of the centrifugal filter (300), and the filter discharge path (340) may be arranged at the top of the centrifugal filter (300).

[0077] As described above, the centrifugal filter (300) can centrifuge the boron nitride nanotube supernatant at 1000 rpm to 23000 rpm. Accordingly, the boron nitride nanotube supernatant can rise along the height direction of the centrifugal filter (300) while rotating using centrifugal force at the bottom of the centrifugal filter (300) 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 direction of the centrifugal filter (300). In this process, boron nitride nanotubes can be attached to the sheet (320) attached to the inner wall of the filter container (310), and the discharged water including boron nitride nanotubes that are not attached to the sheet (320) can be discharged to the harvest container (400) through the filtration discharge path (340).

[0078] Meanwhile, the supernatant supplied from the disperser (200) moves while being filtered from the bottom of the centrifugal filter (300) to the top of the centrifugal filter (300), so that the purity of the boron nitride nanotubes included in the discharged water discharged from the top of the centrifugal filter (300) may be greater than the purity of the boron nitride nanotubes attached to the sheet (320).

[0079] Boron nitride nanotubes contained in the effluent are filtered and obtained, and then a step of acid-cleaning the boron nitride nanotubes (S150), a step of heat-treating the acid-cleaned boron nitride nanotubes to remove carbon (S160), and a step of dissolving the heat-treated boron nitride nanotubes to remove boron (S170) are performed to obtain boron nitride nanotubes from which impurities have been removed. At this time, the purity of the boron nitride nanotubes from which impurities have been removed can be at most 95% or more.

[0080] Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely illustrative examples to aid understanding of the present invention and are not intended to limit the scope of the present invention.

[0081] Example 1

[0082] 1. Preparation of boron nitride nanotube mixture

[0083] A 0.5 wt% aqueous solution containing 0.5 g of tannic acid in 1000 mL of water as an additive and 20 g of boron nitride nanotube synthetic powder were mixed with a homogenizer at 5000 rpm for 20 minutes to prepare 1000 mL of boron nitride nanotube mixture.

[0084]

[0085] 2. Dispersion of boron nitride nanotube solution

[0086] 16 L of water was added to the prepared boron nitride nanotube mixture, which was then stirred at 300 rpm in a stirrer and stirred and dispersed for 7 minutes using an ultrasonicator at a frequency of 20 KHz. The dispersed boron nitride nanotube mixture was then allowed to rest for 2 minutes.

[0087] As a result, a uniformly dispersed boron nitride nanotube supernatant was formed in the upper layer of the disperser, and a sediment was formed in the lower layer of the disperser.

[0088] The boron nitride nanotube supernatant was fed to a centrifugal filter, and the precipitate containing the catalyst was collected in a sedimentation vessel.

[0089]

[0090] 3. Centrifugal filtration of the supernatant

[0091] A centrifugal filter was operated at 3000 rpm to filter the boron nitride nanotube supernatant. As a result, the discharged water containing boron nitride nanotubes was discharged from the upper part of the centrifugal filter into a collection vessel, and the boron nitride nanotubes were attached to the sheet located on the inner wall of the centrifugal filter.

[0092]

[0093] 4. Obtaining boron nitride nanotubes

[0094] Boron nitride nanotubes were obtained by filtering using a filter in a collection vessel. In addition, boron nitride nanotubes were obtained by scraping the sheet using a brush or scraper.

[0095]

[0096] 5. Mountain washing

[0097] The obtained boron nitride nanotubes were subjected to acid treatment with 2 M hydrochloric acid (HCl) while applying heat of 80°C and stirring for 4 hours.

[0098] After that, the acid-treated boron nitride nanotubes were dissolved in DI water and filtered to remove the catalyst (Fe, Mg, etc.) used in synthesizing the boron nitride nanotube powder.

[0099]

[0100] 6. Heat treatment

[0101] Acid-washed boron nitride nanotubes were pulverized and placed in an electric furnace, where they were heat-treated at a maximum temperature of 800°C for 2 hours while heating at a rate of 10°C / min. During this process, a mixed gas containing oxygen was supplied to the furnace at 1000 sccm to oxidize boron and carbon. As a result, the carbon in the boron nitride nanotubes was removed by oxidation to carbon dioxide, and the boron was oxidized to solid boron oxide.

[0102]

[0103] 7. Dissolving

[0104] After adding heat-treated boron nitride nanotubes to DI water heated to 80℃, the heat-treated boron nitride nanotubes were dispersed by operating the ultrasonicator at 20 KHz for 5 minutes.

[0105] After that, the boron nitride nanotubes were stirred on a hot plate at 80°C for 30 minutes, and then the boron nitride nanotubes were filtered to obtain high-purity boron nitride nanotubes from which boron oxide was removed.

[0106]

[0107] Example 2

[0108] Example 2 purified boron nitride nanotubes in the same manner as Example 1, but the operating speed of the centrifugal filter was 19,000 rpm.

[0109]

[0110] Fig. 4 is an SEM image of boron nitride nanotubes obtained from a sheet when the operating speed of the centrifugal filter is 3000 rpm, and Fig. 5 is an SEM image of boron nitride nanotubes obtained from a sheet when the operating speed of the centrifugal filter is 19000 rpm.

[0111] That is, FIG. 4 is an SEM image of boron nitride nanotubes according to Example 1, and FIG. 5 is an SEM image of boron nitride nanotubes according to Example 2.

[0112] 320 is an SEM image of boron nitride nanotubes obtained from the sheet. Specifically, a1 is an SEM image of boron nitride nanotubes obtained from a first region of the sheet (see FIG. 3), a2 is an SEM image of boron nitride nanotubes obtained from a second region of the sheet (see FIG. 3), and a3 is an SEM image of boron nitride nanotubes obtained from a third region of the sheet (see FIG. 3).

[0113] Referring to FIGS. 4 and 5, it can be confirmed that the boron nitride nanotubes (a1) in the first region are formed more evenly and densely than the boron nitride nanotubes (a2) in the second region, and that the boron nitride nanotubes (a2) in the second region are formed more evenly and densely than the boron nitride nanotubes (a3) ​​in the third region. That is, 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.

[0114] In addition, when comparing FIGS. 4 and 5, it can be confirmed that the boron nitride nanotubes (a1, a2, a3) of FIG. 5 are formed more evenly and densely than the boron nitride nanotubes (a1, a2, a3) of FIG. 4. Therefore, it can be seen that as the rotation speed of the centrifugal filter increases in the centrifugal filtration step, the purity of the purified boron nitride nanotubes (a1, a2, a3) increases.

[0115] Fig. 6 is an SEM image of boron nitride nanotubes obtained from a harvesting vessel when the operating speed of the centrifugal filter is 3000 rpm, and Fig. 7 is an SEM image of boron nitride nanotubes obtained from a harvesting vessel when the operating speed of the centrifugal filter is 19000 rpm.

[0116] FIG. 6 is an SEM image of boron nitride nanotubes according to Example 1, and FIG. 7 is an SEM image of boron nitride nanotubes according to Example 2.

[0117] Comparing FIGS. 6 and 7, it can be seen that the boron nitride nanotubes (400) obtained from the harvesting vessel of Example 2 are formed more evenly and densely than the boron nitride nanotubes (400) obtained from the harvesting vessel of Example 1. Accordingly, it can be seen that as the rotation speed of the centrifugal filter increases in the centrifugal filtration step, the purity of the purified boron nitride nanotubes (410) increases.

[0118] In addition, when FIGS. 6 and 7 are compared with FIGS. 4 and 5, respectively, it can be confirmed that the boron nitride nanotubes (400) obtained in the obtaining vessel are formed more evenly and densely than the boron nitride nanotubes (a1, a2, a3) obtained in the sheet. That is, it can be confirmed that the purity of the boron nitride nanotubes (400) obtained in the obtaining vessel is higher than that of the boron nitride nanotubes (a1, a2, a3) obtained in the sheet.

[0119] Specifically, in Example 1, the purity of the boron nitride nanotubes (400) obtained from the obtaining vessel was 83 to 87%, the purity of the boron nitride nanotubes (a1) obtained from the first region of the sheet was 63 to 67%, the purity of the boron nitride nanotubes (a2) obtained from the second region of the sheet was 41 to 45%, and the purity of the boron nitride nanotubes (a3) ​​obtained from the third region of the sheet was 21 to 25%.

[0120] In addition, in Example 2, the purity of the boron nitride nanotubes (400) obtained in the obtaining vessel was 95 to 99%, the purity of the boron nitride nanotubes (a1) obtained in the first region of the sheet was 88 to 92%, the purity of the boron nitride nanotubes (a2) obtained in the second region of the sheet was 78 to 82%, and the purity of the boron nitride nanotubes (a3) ​​obtained in the third region of the sheet was 26 to 30%.

[0121] In this way, the purification device for boron nitride nanotubes according to the present invention can efficiently remove impurities from boron nitride nanotubes and produce high-purity boron nitride nanotubes purified in large quantities.

[0122] Figure 8 is an SEM image of the material deposited in the sedimentation vessel.

[0123] Referring to FIG. 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 positioned in the upper layer of the disperser, and a precipitate precipitated from the boron nitride nanotube mixture may be positioned in the lower layer of the disperser.

[0124] As described above, the sediment can be discharged into a sedimentation vessel through a sediment discharge channel. As illustrated in Fig. 8, boron nitride nanotubes are rarely observed in the sediment, and numerous large particles larger than 100 μm are observed.

[0125] Specifically, the precipitate may include a catalyst and boron added during the synthesis of boron nitride nanotubes. The catalyst used during the synthesis of the boron nitride nanotube powder may include, for example, Fe, Mg, Ni, Cr, Co, Zr, Mo, W, and / or Ti and oxides thereof.

[0126] The sediment can be collected from the sedimentation vessel, and the collected catalyst and boron can be recycled during the synthesis and / or purification of boron nitride nanotubes. Accordingly, the cost of the synthesis and / or purification of boron nitride nanotubes can be reduced.

[0127] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. A disperser that stirs and disperses a mixture in which boron nitride nanotubes are dispersed in an aqueous solution in which an additive containing a polyphenol group is dissolved, and extracts a supernatant from the mixture; and A centrifugal filter having one side connected to the above disperser and obtaining filtered boron nitride nanotubes from the extracted supernatant; A boron nitride nanotube purification device, wherein the centrifugal filter comprises a sheet extending along the height direction of the centrifugal filter on the inside and obtaining the filtered boron nitride nanotube.

2. In paragraph 1, A boron nitride nanotube purification device wherein the purity of the filtered boron nitride nanotube increases along the height direction of the sheet.

3. In paragraph 1, A boron nitride nanotube purification device further comprising a obtaining vessel that is connected to the other side of the centrifugal filter and obtains the boron nitride nanotubes that have passed through the centrifugal filter.

4. In paragraph 1, A boron nitride nanotube purification device, wherein the additive comprises at least one of tannic acid, gallic acid, catechol, epigallocatechin, pyrogallol, hexahydroxydiphenic acid, ellagic acid, and chlorogenic acid.

5. In paragraph 1, A boron nitride nanotube purification device including a precipitation vessel in which a precipitate of the dispersed boron nitride nanotube solution is precipitated.

6. In paragraph 1, A boron nitride nanotube purification device in which the supernatant is filtered by rising in a spiral shape along the height direction of the centrifugal filter.

7. In paragraph 1, A boron nitride nanotube purification device in which 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 step of 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; A step of extracting a supernatant containing the boron nitride nanotubes from the above mixture; and A step of filtering the extracted supernatant using a centrifugal filter to obtain the boron nitride nanotubes according to purity; A method for purifying boron nitride nanotubes, wherein the boron nitride nanotubes are attached to a sheet disposed on the inner surface of the centrifugal filter.

9. In paragraph 8, A method for purifying boron nitride nanotubes, 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. In paragraph 8, A method for purifying boron nitride nanotubes, further comprising a step of acid-washing the obtained boron nitride nanotubes.

11. In paragraph 10, A method for purifying boron nitride nanotubes, further comprising a step of heat-treating the acid-washed boron nitride nanotubes to remove carbon.

12. In paragraph 11, A method for purifying boron nitride nanotubes, further comprising a step of dissolving the heat-treated boron nitride nanotubes to remove residual boron oxide.

13. In paragraph 12, A method for purifying boron nitride nanotubes, wherein the purity of the dissolved boron nitride nanotubes increases as they are attached to the upper part of the sheet when the boron nitride nanotubes are obtained.

14. In paragraph 8, A method for purifying boron nitride nanotubes, further comprising a step of collecting a precipitate precipitated from the above mixture.

15. In paragraph 8, A method for purifying boron nitride nanotubes, further comprising a obtaining vessel for obtaining the boron nitride nanotubes that have passed through the centrifugal filter.

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