METHOD FOR PREPARING BORON NITRIDE NANOTUBES BY HEAT TREATING BORON PRECURSOR AND APPARATUS THEREOF

The present disclosure provides a method for producing a boron nitride nanotube by heating a boron precursor, and an apparatus therefor. According to an embodiment, a method of producing a boron nitride nanotube includes: inserting several reaction modules each accommodating a holding rod disposed through at least one precursor block into a supply chamber disposed at a front end of a reaction chamber; conveying N reaction modules of the several reaction modules inserted in the supply chamber to a reaction zone of the reaction chamber; growing a boron nitride nanotube in the precursor block by operating the reaction zone for a predetermined time, in the reaction chamber; and conveying the N reaction modules from the reaction chamber to a discharge chamber disposed at a rear end of the reaction chamber after the predetermined time passes. Accordingly, it is possible to maximize the yield and productivity of BNNTs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No. 10-2020-0061350 filed on May 22, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a boron nitride nanotube. More particularly, the present disclosure relates to a method of producing a boron nitride nanotube by heating a boron precursor, and an apparatus therefor.

2. Description of the Related Art

Boron Nitride Nano-Tubes (BNNT) are similar in mechanical properties and thermal conduction to Carbon Nano-Tubes (CNT) well known in the art. However, a CNT has low thermal and chemical stability because it has conductors and semiconductors electrically mixed therein and oxidizes at about 400° C., but a BNNT has electrical insulation and is thermally stable even at high temperatures over about 800° C. even in the air because it has a wide band gap of about 5 eV. Further, boron in a BNNT has a thermal neutron absorption ability about 200 thousand times higher than carbon in a CNT, so it is a substance useful for blocking neutrons.

However, a BNNT requires a high-temperature synthesis process of 1000° C. or higher and has a limit in that it is difficult to increase the reaction yield due to impurities and/or remains that are produced in producing, and an expensive refining process is required to remove the impurities, so it is difficult to develop a technology that produces high-quality BNNTs in large quantities.

A technology about a method and apparatus for producing a BNNT that solve the problems described above has been recently developed (Korean Patent No. 10-1964432).

A technology that remarkably reduces the production time and the process energy and further increases the production yield of BNNTs has been required in relation to the method and apparatus for producing BNNTs in the industrial field with an increase in demand for BNNTs.

SUMMARY

The present disclosure provides a method of producing a boron nitride nanotube by heating a boron precursor, and an apparatus therefor.

Firstly, it is to provide an apparatus and method of continuously supplying reaction modules to a reaction chamber through a continuous organic operation of a supply chamber, a reaction chamber, and a discharge chamber in relation to an apparatus and method of producing a boron nitride nanotube.

Secondly, it is to provide an apparatus and method being able to uniformly compound, mix, and supply a reaction gas through arrangement of reaction gas supply pipes and supply holes.

A method of producing a boron nitride nanotube according to an embodiment of the present disclosure includes steps of: inserting several reaction modules each accommodating a holding rod disposed through at least one precursor block into a supply chamber disposed at a front end of a reaction chamber; conveying a first set of N reaction modules of the several reaction modules inserted in the supply chamber to a reaction zone of the reaction chamber; growing a boron nitride nanotube in the precursor block by operating the reaction zone for a predetermined time, in the reaction chamber; and conveying the first set of N reaction modules from the reaction chamber to a discharge chamber disposed at a rear end of the reaction chamber after the predetermined time passes, in which the conveying of the first set of N reaction modules of the several reaction modules inserted in the supply chamber to a reaction zone of the reaction chamber conveys a second set of N reaction modules of the several reaction modules from the supply chamber to the reaction chamber when conveying the first set of N reaction modules from the reaction chamber to the discharge chamber, and a conveying operation of the supply chamber may be ended when all the several reaction modules are conveyed to the reaction chamber.

The conveying the first set of N reaction modules of the several reaction modules inserted in the supply chamber to a reaction zone of the reaction chamber may be accomplished by moving up the several reaction modules, which are vertically arranged, in the supply chamber in a longitudinal direction of the supply chamber.

The conveying the first set of N reaction modules of the several reaction modules inserted in the supply chamber to the reaction zone of the reaction chamber may be accomplished by circulating several reaction modules arranged on a circulation track along the circulation track in the supply chamber.

A method of producing a boron nitride nanotube according to an embodiment of the present disclosure includes steps of: conveying a reaction module accommodating a holding rod disposed through at least one precursor block to a reaction zone of a reaction chamber; and growing a boron nitride nanotube by reacting a nitrogen-containing reaction gas supplied from two or more gas supply pipes disposed in the reaction chamber with the precursor block, in which a gas supply hole that is diagonally open may be formed on a surface of each of the gas supply pipes.

An even number of gas supply pipes maybe disposed in a pair at positions facing each other in the diameter direction of the reaction chamber, and the gas supply holes of a pair of the gas supply pipes may be open in opposite directions.

The gas supply holes may be formed to be alternate to each other on the gas supply pipes.

Each of the gas supply holes may be formed on each of the gas supply pipes and may be disposed with regular intervals in a longitudinal direction of the gas supply pipes in the reaction zone.

An apparatus for producing a boron nitride nanotube according to another embodiment of the present disclosure includes: a reaction module accommodating a holding rod disposed through at least one precursor block; a reaction chamber having a conveying path for conveying the reaction module and a reaction zone in which a nitrogen-containing reaction gas is provided to the precursor block on the conveying path; a supply chamber disposed at a front end of the reaction chamber, accommodating several reaction modules, and conveying a first set of N reaction modules of the several reaction modules to the reaction chamber; and a discharge chamber disposed at a rear end of the reaction chamber, in which the reaction chamber conveys the first set of N reaction modules to the discharge chamber, and the supply chamber conveys a second set of N reaction modules of the several reaction modules to the reaction chamber when the first set of N reaction modules are conveyed from the reaction chamber to the discharge chamber, and a conveying operation of the supply chamber may be ended when all the several reaction modules are conveyed to the reaction chamber.

The supply chamber may include a lift having a plurality of reaction module holding units vertically arranged to mount the several reaction modules, and moving up the plurality of reaction module holding units in a longitudinal direction of the supply chamber.

The supply chamber may include a lift having a plurality of reaction module holding units arranged on a circulation track to mount the several reaction modules, and circulating the plurality of reaction module holding units along the circulation track.

An apparatus for producing a boron nitride nanotube according to another embodiment of the present disclosure includes: a reaction module accommodating a holding rod disposed through at least one precursor block; a reaction chamber having a conveying path for conveying one or more of the reaction modules and a reaction zone in which a nitrogen-containing reaction gas is provided to the precursor block on the conveying path; and at least two gas supply pipes disposed along the conveying path, in which one or more gas supply holes that are diagonally open are formed on a surface of each of the gas supply pipes.

The several reaction modules each may include: a pair of supports separably combined with the holding rod, having holders formed at positions respectively corresponding to the gas supply pipes, and facing each other; and a housing formed between the pair of supports to accommodate the holding rod.

An even number of gas supply pipes may be disposed in a pair at positions facing each other in the diameter direction of the reaction chamber, and the gas supply holes of the pair of gas supply pipes may be open in opposite directions.

The gas supply holes may be formed to be alternate to each other on the gas supply pipes.

Each of the gas supply holes may be formed on each of the gas supply pipes and may be disposed with regular intervals in a longitudinal direction of the gas supply pipes in the reaction zone.

According to the present disclosure, there are the following effects.

First, in an organic continuous process continuing through the supply chamber, the reaction chamber, and the discharge chamber, reaction modules are continuously supplied to the reaction chamber, thereby being able to maximize the yield and productivity of BNNTs.

Second, since the reaction gas supply pipes and supply holes are disposed, a reaction gas supplied to the reaction chamber may be compounded by a vortex generated by turning of the reaction gas, thereby being able to maximize the yield and productivity of BNNTs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Example embodiments of the present disclosure will be described in detail but technological configurations well known in the art are omitted or compressed for brief description.

Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings, and in the following description of the accompanying drawings, like reference numerals are given to like components and repetitive description is omitted.

In the following embodiments, terms such as “first” and “second” are used to discriminate a component from another component without limiting the components.

When an embodiment can be implemented in another way, specific processes may be performed in order different from the description. For example, two sequentially described processes may be substantially simultaneously performed or may be performed in the reverse order of the described order.

Description of Precursor Block for Producing Boron Nitride Nanotube

A precursor block for producing a boron nitride nanotube of the present disclosure is manufactured by an apparatus for manufacturing a precursor block.

The apparatus for manufacturing a precursor block forms a precursor block by mixing a binder in powder including boron.

Firstly, the powder may include first powder and second powder.

The first powder may include boron.

The boron may be in a powder state.

The boron may be amorphous and/or crystalline boron.

Since amorphous boron has low hardness, the amorphous boron efficiently contributes to nano-sizing of the particles of catalytic metal and a metal oxide that are additionally mixed in a nano-sizing step, in detail, a nano-sizing process of boron powder using vortexes of air. Further, nano-sized boron is coated on or embedded in the surfaces of the nanoparticles of the catalytic metal and the metal oxide, whereby seed precursor nanoparticles with high efficiency may be obtained. On the other hand, when crystalline boron is used, nano-sizing may be difficult and may take a long time due to high hardness, so a composition yield may be deteriorated or the entire process may take a long time when producing a BNNT, which may reduce productivity. Using crystalline born consequently causes deterioration of the purity of a BNNT, and an additional precise refining process is also required to reduce impurities, which may cause an increase in the producing cost.

Therefore, according to an embodiment of the present disclosure, the boron may be amorphous boron rather than crystalline boron. When amorphous boron is used, it is possible to obtain boron nanopowders even through a short nano-sizing process. Further, it is possible to form a BNNT at a high yield.

The first powder may further include a catalyst and the catalyst may be provided in a powder state. The catalyst is more effective for amorphous boron. This is because it is possible to produce a large amount of boron nanopowders within a very short time when using amorphous boron unlike using crystalline boron in a nano-sizing process that uses air jets and/or vortexes of air. The catalyst is mixed with boron particles in a nano-sizing process of the first powder, thereby producing precursor nanoparticles. The precursor nanoparticles function as seeds and react with nitrogen in producing of a BNNT, thereby being able to contribute to composition of a BNNT. The catalyst particles are not specifically limited, and for example, may be Fe, Mg, Ni, Cr, Co, Zr, Mo, W, and/or Ti, and oxides thereof.

Forming a precursor block2is described in detail.

According to an embodiment of the present disclosure, second powder including a boron precursor is produced through nano-sizing of first powder in which precursor boron powder and catalyst powder are mixed.

In nano-sizing of the first powder, first air may be provided at an angle to a normal direction of a circular nano-sizing area and the first powder may be provided at an acute angle to the flow direction of the first air.

The nano-sizing area, which is positioned inside a container that is a component of a first-powder nano-sizing apparatus, may be an area where second powder is produced through nano-sizing of the first powder.

The container may have a nano-sizing area, a first inlet, a second inlet, and an outlet.

The nano-sizing area may be defined as a circle, and accordingly, the first air flowing inside through the second inlet of the first-powder nano-sizing apparatus may generate a vortex in the nano-sizing area.

The first powder may be made into a nano-size by the first air rotating at a highspeed in the nano-sizing area. Boron powder and catalyst powder may be mixed in the first powder, as described above, and the boron powder may be embedded with an optimal amount of catalyst powder by nano-sizing in the nano-sizing area, whereby an optimal condition and/or particle size for composition and growth of a BNNT to be described above may be provided.

As described above, second powder may be produced by the first air in the nano-sizing area.

Thereafter, second air is sent through a first membrane connected with the nano-sizing area such that the second air collects in a first collection container accommodating the first membrane.

The second air is sent through a second membrane from the first collection container and the second powder is put into a receiver connected with the second membrane, thereby being able to collect the second powder included in the second air.

A binder including at least one of sucrose, syrup, glutinous starch syrup, polypropylene carbonate, polyvinyl alcohol, polyvinyl butyral, and ethyl cellulose, which may be sublimated and removed in a gas state in a high-temperature heat treatment BNNT composition process to be described below, with precursor powder in the collected second powder, thereby forming the precursor block2. However, the binder may be removed in a sublimation process and may leave a smallest amount of remains in the precursor block, and any substance may be used as the binder as long as it may form pores in the block.

Meanwhile, the second powder may include large-granularity catalyst particles not made into a nano-size in the nano-sizing process and/or not filtered in the collecting process.

The large-granularity catalyst particles may act as an impurity in a finally obtained BNNT and may decrease the purity. Accordingly, it is preferable to remove particles having a diameter over 1000 nm and a refining process of removing such large-granularity catalyst particles may be included.

The precursor block2maybe formed in a removable film shape such as a release film. It is possible to manufacture a precursor block2having a predetermined shape, for example, by putting a release film into a mold, uniformly spreading a powder mixture of precursor powder and binder powder on the release film, and then pressing the powder mixture. Preferably, it is possible to put the precursor block2into a heat treatment reaction chamber after removing the release film.

In this case, the binder may be used not only in a powder state, but also in a liquid state.

When the binder is used in a powder state, the precursor block2is manufactured by producing a powder mixture by mixing the precursor powder and the binder powder and then uniformly spreading and heating the powder mixture at an appropriate temperature. Alternatively, the precursor block2may be manufactured by uniformly spreading the powder mixture in a mold, which may manufacture a block having a predetermined shape, and pressing the powder mixture with a hot-press at a predetermined temperature such that the viscosity of the binder powder increases and accordingly the precursor powder is bonded to each other.

When the binder is in a liquid state, it is possible to simply form a block by mixing precursor powder in the liquid binder, uniformly spreading the mixture on a release film, and then heating and drying the mixture at an appropriate temperature.

In this case, any binders such as sucrose, syrup, glutinous starch syrup, or polyvinyl alcohol (PVA) may be used as the liquid binder by mixing them in water.

Further, binders such as polypropylene carbonate (PPC), polyvinyl butyral (PVB), or ethyl cellulose (EC) may be used as liquid binders by using a solvent. In this case, the solvent may be appropriately selected, depending on the kinds of binders. For example, ketone or ethyl acetate may be used for polypropylene carbonate (PPC), methanol or ethanol may be used for polyvinyl butyral (PVB), and terpinol may be used for ethyl cellulose (EC).

According to another embodiment, it is possible to form a precursor block2by applying and spreading a mixture of precursor powder and a binder on a predetermined substrate and then pressing or heating the mixture, and it is possible to put the substrate with the precursor block2formed thereon into a reaction chamber. In this case, the precursor block2may be formed not only on a surface, but also both surfaces of the substrate. When a block is formed by applying a mixture on a substrate, the above-mentioned method of forming a block on a release film may be applied as it is.

In this case, it is preferable to use a substrate made of a material that may resist heat treatment at a high temperature because the mixture may be put into a reaction chamber31together with the substrate. Accordingly, the substrate may be made of metal such as stainless steel (STS), tungsten (W), and titanium (Ti), an oxide of the metal, and ceramic such as silicon carbide (SiC) and alumina.

Considering reaction efficiency with nitrogen in the reaction chamber, it is preferable that the precursor block2is thin, but it may be thick in consideration of shape stability that maintains the shape of the block in the reaction chamber. In particular, the binder used for manufacturing the precursor block2is sublimated in the heat treatment process, thereby forming a plurality of pores in the precursor block2during the heat treatment.

For example, when sucrose is used as the binder, the pores may be formed through a thermal decomposition process expressed as the following chemical formula (Formula 1), and carbon that is produced as a remain may maintain the soundness of the precursor block throughout the BNNT composition process by functioning as a support for the porous precursor block.

A BNNT is produced by applying heat treatment to the precursor block2formed in this way. A method of producing a BNNT is described hereafter.

Description of Method of Producing BNNT

FIG. 1is a flowchart schematically showing a method of producing a boron nitride nanotube according to an embodiment of the present disclosure.

In briefly, a BNNT may be grown by providing a reaction gas to a heated reaction zone while moving the precursor block2to the reaction zone in a reaction chamber.

Referring toFIG. 1, a method of producing a boron nitride nanotube (BNNT) according to an embodiment of the present disclosure includes inserting several reaction modules each accommodating a holding rod37disposed through at least one precursor block2into a supply chamber321disposed at the front end of a reaction chamber31(S1); conveying N reaction modules of the several reaction modules inserted in the supply chamber321to a reaction zone311of the reaction chamber31(S2); growing a BNNT in the precursor block2by operating the reaction zone311for a predetermined time (S3), in the reaction chamber31; and conveying the N reaction modules from the reaction chamber31to a discharge chamber322disposed at the rear end of the reaction chamber31after the predetermined time passes (S4).

FIG. 2is a flowchart schematically showing a method of producing a boron nitride nanotube (BNNT) according to another embodiment of the present disclosure.

As shown inFIG. 2, a method of producing a BNNT according to another embodiment includes conveying a reaction module38accommodating a holding rod37disposed through at least one precursor block2to a reaction zone311of a reaction chamber31(S1′); and growing a BNNT by reacting a nitrogen-containing reaction gas discharged from two or more gas supply pipes33disposed in the reaction chamber31with the precursor block2(S2′).

An embodiment of a method of producing a boron nitride nanotube is described in detail hereafter.

As shown inFIGS. 3, 4A, 4B, and 6, an apparatus3for producing a boron nitride nanotube that performs the method of producing a boron nitride nanotube according to an embodiment of the present disclosure includes a reaction chamber31, a supply chamber321, a discharge chamber322, and a reaction module38.

The reaction chamber31is used to accommodate the precursor block2described above, a conveying path for conveying the reaction module38is formed in the reaction chamber31, and a reaction zone in which a BNNT is grown by providing a nitrogen-containing reaction gas to the precursor block2is included in a part of the conveying path.

The reaction zone311is an area in which an appropriate temperature for reaction is maintained and a reaction gas is provided through the gas supply pipes33.

The reaction gas for producing a BNNT from the precursor block2disposed in the reaction chamber31may be a nitrogen-containing reaction gas. In detail, the reaction gas that is supplied into the reaction chamber31is not specifically limited, nitrogen (N2) or ammonia (NH3) may be used, and these gases may be mixed and supplied into the reaction chamber31as a gas mixture. Alternatively, hydrogen (H2) may be additionally mixed and used.

The reaction gas may be supplied at a speed of 20 to 500 sccm into the reaction chamber31. When the reaction gas is supplied at a speed less than 20 sccm, the supply amount of the nitrogen element is small, so the nitrification reaction efficiency of boron is deteriorated and reaction needs to be performed for a long time. When the speed exceeds 500 sccm, the boron powder in the solid precursor block2is ablated due to the high movement speed of the reaction gas, so the yield of BNNTs may decrease.

A BNNT may be obtained by performing heat treatment in the temperature range of about 1100 to about 1400° C. for approximately 0.5 to 6 hours in the reaction chamber31.

The reaction chamber31may be an alumina pipe, but is not necessarily limited thereto and may be made of a material that may resist a temperature of up to about 1500° C.

As depicted inFIG. 4A, the supply chamber321and the discharge chamber322may be connected to a front end and a rear end of the reaction chamber31respectively, and a front gate323and a rear gate323′ may be disposed between the reaction chamber31and the supply chamber321and between the reaction chamber31and the discharge chamber322respectively, whereby it is possible to separate the environments inside of the chambers.

A vacuum device (not shown) is connected with the reaction chamber31and may adjust the degree of a vacuum in the reaction chamber31, and to this end, the vacuum device may include a vacuum pump and a controller. However, the present disclosure is not necessarily limited thereto. For example, the vacuum device may be connected to the supply chamber321, or the vacuum device may be connected to the discharge chamber322.

A temperature adjuster (not shown) may be connected to the reaction chamber31. The temperature adjuster (not shown) may include a heater directly adjusting the temperature in the reaction chamber31and a controller controlling the heater.

The supply chamber321is disposed at the front end of the reaction chamber31. The supply chamber321accommodates several reaction modules and N reaction modules of the several reaction modules are conveyed to the reaction chamber31. A pusher for pushing the reaction modules38maybe disposed in the supply chamber321. The reaction modules in the supply chamber321may be pushed into the reaction chamber31.

The discharge chamber322is disposed at the rear end of the reaction chamber31. The discharge chamber322receives the N reaction module from the reaction chamber31.

The supply chamber321, the reaction chamber31, and the discharge chamber322may be organically operated to continuously put the reaction modules38into the reaction chamber31.

In detail, when N reaction modules are conveyed to the discharge chamber322from the reaction chamber31to continuously supply N reaction modules to the reaction chamber31, the supply chamber321conveys N new reaction modules of the several reaction modules to the reaction chamber31.

When the several reaction modules accommodated in the supply chamber321are all conveyed into the reaction chamber31through this process, the supply chamber321stops operating without conveying a reaction module38to the reaction chamber31.

As shown inFIGS. 4A and 4B, the supply chamber321may have various types of lifts for continuously supplying several reaction modules to the reaction chamber31.

For example, as shown inFIG. 4A, when several reaction modules are vertically accommodated in the supply chamber321, a plurality of reaction module holding units for mounting the several reaction modules may be vertically arranged in the supply chamber321. A reaction module38is mounted on each of the plurality of reaction module holding units and the several reaction modules may be moved up in the longitudinal direction of the supply chamber321in the supply chamber321by the lift.

Alternatively, as shown inFIG. 4B, several reaction modules maybe arranged on a circulation track in the supply chamber321. In this case, a plurality of reaction module holding units for mounting the several reaction modules may be arranged on the circulation track in the supply chamber321, and the reaction modules38mounted on each of the plurality of reaction module holding units may be circulated along the circulation track by a lift.

A controller for controlling the organic operation of the supply chamber321, the reaction chamber31, and the discharge chamber322may be provided.

Hereafter, a process of continuously putting reaction modules38into the reaction chamber31is described.

Firstly, the temperature and the gas atmosphere in the reaction chamber31are optimized, and then a reaction module38having a precursor block is put into the reaction chamber31through the supply chamber321. Since the front gate323is disposed between the supply chamber321and the reaction chamber31, it is possible to put the reaction module38into the reaction chamber31while maximally maintaining the atmosphere in the reaction chamber31.

A front gate323and a vacuum pump may be additionally disposed in the supply chamber321together with the above-mentioned lift that may convey reaction modules38toward the reaction chamber31. Accordingly, when the front gate323of the reaction chamber31is opened, the reaction gas atmospheres and pressures of the supply chamber321and the reaction chamber31may become equilibrium respectively, and a reaction module38is conveyed to the reaction chamber31from the supply chamber321. Further, the gate front323is closed after the reaction module38is conveyed.

When the front gate323is closed, an auxiliary gate of the supply chamber321is opened again, a new reaction module38is put into the supply chamber321, the gate is closed, and then the reaction module38is conveyed into the reaction chamber31through the process described above. In this operation, the auxiliary gate and the vacuum pump prevent the block precursor of a reaction module in the supply chamber321from being contaminated and make the inside of the supply chamber321similar to the atmosphere of the reaction chamber31.

Reaction modules38are sequentially conveyed toward the discharge chamber322in this way, so the reaction modules38may be horizontally sequentially arranged in the reaction chamber31.

The reaction chamber31performs a process of growing a BNNT in a precursor block by providing a reaction gas to the reaction module disposed in a reaction zone311by operating the reaction zone311for a predetermined time.

The supply amount of the reaction gas may be adjusted in this process to maintain maximum reaction with the reaction gas when a reaction module38is positioned at the center of the reaction zone311.

Such a sequential operation may be applied as follows when there is a storage space for storing one or more reaction modules in the supply chamber321.

A conveyer that may continuously convey reaction modules38toward the reaction chamber31from the storage space of the supply chamber321may convey reaction modules38in the supply chamber321toward the front end of the reaction chamber31in the longitudinal direction of the supply chamber321while supporting the reaction modules38.

Accordingly, since one or more reaction modules38may be stored in the supply chamber321, it is not required to individually put a new reaction module38into the auxiliary gate of the supply chamber321every time a reaction module38is conveyed into the reaction chamber31.

Thereafter, the front gate323disposed between the supply chamber321and the reaction chamber31is opened when a reaction module38is conveyed toward the front end of the reaction chamber31by the conveyer3211.

The front gate323disposed between the supply chamber321and the reaction chamber31is closed when the reaction module38is conveyed into the reaction chamber31by the conveyer.

However, preferably, the front gate323disposed between the supply chamber321and the reaction chamber31is closed after a predetermined number of reaction modules38that the reaction chamber31may accommodate are continuously conveyed into the reaction chamber31from the supply chamber321.

Accordingly, one or more reaction modules38may be put into the reaction chamber31and may react with the reaction gas therein.

Meanwhile, the discharge chamber322may discharge reaction modules38from the reaction chamber31by reversely performing the operation of conveying reaction modules38from the supply chamber321to the reaction chamber31.

Though not shown in the figures, the rear gate323′ and the vacuum pump may be additionally disposed in the discharge chamber322together with a separate conveyer that may discharge reaction modules38from the reaction chamber31. Accordingly, when the rear gate323′ between the reaction chamber31and the discharge chamber322is opened, the reaction gas atmospheres and pressures of the discharge chamber322and the reaction chamber31may become equilibrium respectively, and a reaction module38is conveyed into the discharge chamber322. Further, the rear gate323′ is closed after the reaction module38is conveyed.

When the rear gate323′ is closed, an auxiliary gate of the discharge chamber322is opened, a reaction module38that has finished reacting is taken out, and then the auxiliary gate is closed. Reaction modules38that have finished reacting are discharged from the reaction chamber31through this process. In this operation, the discharge chamber322changes into a nitrogen atmosphere similar to the atmosphere using the vacuum pump before the auxiliary gate is opened. Accordingly, after a reaction module38is discharged, precursor blocks in the reaction chamber31are prevented from being contaminated before the rear gate323′ is opened, and the inside of the discharge chamber322is made similar to the atmosphere of the reaction chamber31.

Reaction modules38that have finished reacting may be sequentially discharged outside in this way.

Thereafter, the rear gate323′ is opened and a reaction module38is moved to the discharge chamber322. The reaction module38may be discharged from the discharge chamber322after the rear gate323is closed.

Such a sequential operation may be applied as follows when there is a storage space for storing one or more reaction modules in the discharge chamber322.

A conveyer that may continuously convey reaction modules38that have finished reacting from the reaction chamber31toward a storage space of the discharge chamber322may convey reaction modules38in the discharge chamber322toward the auxiliary gate of the discharge chamber322in the longitudinal direction of the discharge chamber322while supporting the reaction modules38.

Accordingly, since one or more reaction modules38may be stored in the discharge chamber322, it is not required to individually take out the reaction modules38that have finished reaction through the auxiliary gate of the discharge chamber322every time a reaction module38is conveyed into the reaction chamber31.

Thereafter, the rear gate323′ disposed between the discharge chamber322and the reaction chamber31is opened when a reaction module38is conveyed toward the rear end of the reaction chamber31by the conveyer.

Thereafter, the rear gate323′ disposed between the discharge chamber322and the reaction chamber31is closed when a reaction module38is conveyed into the reaction chamber31.

However, preferably, the rear gate323′ disposed between the discharge chamber322and the reaction chamber31may be closed after a predetermined number of reaction modules38such that the reaction chamber31may accommodate are continuously conveyed into the reaction chamber31from the supply chamber321.

When a BNNT is grown by applying heat treatment to powder in accordance with a conventional method, a process of temperature increase, maintaining temperature maintenance, BN composition, BNNT growth, temperature decrease, room temperature cooling, and reactant collection has to be undergone. Thus, there is a limit in one-time output, and it is difficult to minimize cost due to an increase in energy and time.

However, according to an embodiment of the present disclosure, since BNNTs are continuously produced in a line by the method described above, it is possible to maximize the yield and productivity of BNNTs.

The above-described precursor blocks2may be arranged in the reaction chamber31, that is, as shown inFIGS. 5 and 6, a holding rod37is disposed through at least one precursor block2and then puts into at least the reaction zone311in the reaction chamber31. The holding rod37may be disposed in parallel with the longitudinal direction of the reaction chamber31.

According to an embodiment of the present disclosure, a reaction module38may be provided to accommodate the precursor blocks2.

The holding rod37disposed through at least one precursor block2is accommodated in the reaction module38.

That is, as shown inFIGS. 5 and 6, precursor blocks2may be accommodated in a reaction module38and such reaction modules38may be continuously supplied into the reaction chamber31, as shown inFIGS. 3, 4A, and 4B.

As shown inFIGS. 5 and 6, the reaction module38has a pair of supports381facing each other and a housing382having a storage space, in which the holding rod37is disposed, between the supports381. The holding rod37maybe coupled to the supports381. The holding rod37may be disposed through holes formed in the supports381so that the support381and the holding rod37may be separately combined, and precursor blocks2maybe arranged on the holding rod37, as described above. The supports381may be made of alumina that is a heat-proof material but is not necessarily limited thereto.

Though not shown in the figures, one or more holes may be formed in the supports381. The pressure of a reaction gas in the reaction module38may be prevented from being maintained at an excessive level due to the supports381and the pressure of a reaction gas in the reaction chamber31may be appropriately maintained by the holes. The holes are formed in the pair of supports381to correspond each other, whereby a reaction gas may uniformly and smoothly flow to both sides.

According to an embodiment of the present disclosure, as described above, since at least one precursor block2is disposed on the holding rod37, it is possible to compose and grow a BNNT using the at least one precursor block2. Accordingly, the reaction space in the reaction chamber31may be maximally used, productivity and/or mass productivity may be maximized.

Precursor blocks2may be disposed with predetermined gaps on the holding rod37and it is possible to adjust the number of blocks that is put into the reaction chamber31by adjusting the gaps of the precursor blocks2.

At least one notch (not shown) may be formed on the holding rod37so that a precursor block2may be fixed on the holding rod37by the notch (not shown). Accordingly, it is possible to adjust the gaps and/or the number of precursor blocks to be mounted by adjusting gaps of the notches (not shown).

Meanwhile, the precursor block2may be formed to corresponding to the shape of the space in the reaction chamber31. That is, when the inside of the reaction chamber31is a circle, a circular block body21may be provided as shown inFIG. 7A. A holding hole22is formed at the center of the block body21so that the holding rod37may be disposed through the holding hole22.

In the meantime, the diameter of the block body21of the precursor block2may be formed smaller than the inner diameter of the reaction chamber31.

A precursor block2′ according to another embodiment shown inFIG. 7Bmay further have a groove23formed on a side of the block body21. When a gas supply pipe33(illustrated inFIG. 8A) is disposed at a side in the reaction chamber31, interference between the block body21and the gas supply pipe33may be prevented by the groove23.

As shown inFIG. 7A, precursor block2may be disposed in the reaction chamber such that a reaction gas comes in contact with the precursor block2as much as possible. For example, the precursor block2may be disposed vertically in a horizontal cylindrical reaction chamber, that is, perpendicular to the bottom of the reaction chamber. Since the precursor block2is vertically disposed, a plurality of precursor block2may be arranged in the reaction chamber, which is preferable because BNNTs may be manufactured in large quantities through one-time heat treatment process. Further, since the precursor block2is formed in a thin film shape, a nitrogen-containing reaction gas may come in contact with both sides of the precursor block2. Accordingly, the reaction area increases, and the yield of BNNTs may be improved.

Vertically disposing the precursor block2in the horizontal cylindrical reaction chamber31may be appropriately selected in consideration of the shape inside the reaction chamber31, that is, reaction efficiency and efficiency of using the space inside the reaction chamber31, and the present disclosure is not specifically limited thereto.

The reaction chamber31is not specifically limited as long as it is generally used for composition of a BNNT, and may include a facility in which precursor blocks2may be arranged in an erect position in a line.

A gas supply pipe33(illustrated inFIG. 8A and 8B) may extend into the reaction chamber31and a reaction gas may be provided to at least a reaction zone in the reaction chamber31through the gas supply pipe33. Accordingly, the gas supply pipe33may be longer than the reaction zone and may be disposed across the reaction zone in the reaction chamber31.

In this case, a gas supply hole331that is diagonally open is formed on the surface of the gas supply pipe33, so gas maybe supplied into the reaction chamber31through the gas supply pipe33.

One or more gas supply holes331formed on the gas supply pipe33may be positioned in the reaction zone311. Preferably, a plurality of gas supply holes331may be arranged with regular intervals in the longitudinal direction of the gas supply pipe33in the reaction zone311.

The gas supply pipe33may extend in the longitudinal direction of the reaction chamber31.

A reaction gas that is supplied into the reaction chamber31may be a mixture of nitrogen (N2), ammonia (NH3), hydrogen (H2), etc., as described above. Further, since the molecular weights of nitrogen, ammonia, and hydrogen are respectively 28, 17, and 2 which are different, layer separation phenomenon in which the layers of the gases composing the reaction gas are separated may be generated.

When a reaction gas with separated layers is supplied, it influences the supply amount of the nitrogen element that is supplied to the precursor block so that the reaction gas may not be uniformly supplied, which may reduce the nitrification reaction efficiency of boron. Accordingly, it is required to prevent the layer separation phenomenon in the reaction gas, for example, by increasing the time of a heat treatment process in the reaction chamber31in order to provide a sufficient nitrogen element to the precursor block.

The gas supply pipe33supplies a reaction gas diagonally to the direction facing the holding rod37, thereby being able to prevent the layer separation phenomenon.

In detail, the gas supply pipe33provides a reaction gas diagonally not providing the reaction gas directly to a holding rod holding precursor blocks2. To this end, the gas supply pipe33has a gas supply hole331that is diagonally open. Since a reaction gas is provided through the gas supply hole331that is open at a predetermined angle, the reaction gas may generate a vortex while flowing along the inner wall of the reaction chamber31. In this process, the reaction gas is rotated, mixed, and compounded, whereby it is possible to prevent layer separation phenomenon in the reaction gas.

As shown inFIGS. 8A and 8B, a gas supply hole331of a gas supply pipe33disposed in the reaction zone311of the reaction chamber31may provide a reaction gas at 45° diagonally from the straight line connecting the surface of the gas supply pipe33and the holding rod37as shown inFIG. 3.

As shown inFIGS. 8A, 8B, 9A, 9B, 10A, and 10B, two or more gas supply pipes33may be disposed in the reaction chamber31. In this case, the gas supply pipes33may be disposed on the inner side of the reaction chamber31and arranged with regular intervals in the reaction chamber31, respectively, so that a reaction gas discharged from their gas supply holes331may flow in one direction along the inner wall of the reaction chamber31. Accordingly, the flow speed of a vortex generated by the discharged reaction gas turning around the inner side of the reaction chamber31may be relatively improved as compared with when one gas supply pipe33is provided.

Alternatively, when an even number of gas supply pipes33are disposed, they may be arranged in a pair at positions facing each other in the diameter direction of the reaction chamber31. The gas supply holes331of the pair of gas supply pipes may be open in opposite directions so that a reaction gas discharged from the gas supply holes331may flow in one direction along the inner wall of the reaction chamber31.

In this case, it is preferable that a plurality of gas supply holes331of the gas supply pipe33has the angle (hereafter, referred to as a “diagonal angle”) between the direction facing the holding rod and the diagonal opening directions of the gas supply holes331so that the reaction gas generates a stable vortex.

It is preferable that even though a plurality of gas supply pipes33is provided, the gas supply holes331of the gas supply pipes33have the same diagonal angle.

The nitrogen-containing reaction gas is mixed and compounded by the vortex in the reaction zone311, and gases having different specific weights in the reaction gas may be mixed without layer separation. Accordingly, the supply amount of a nitrogen element that is supplied to the precursor block2becomes uniform, so the nitrification reaction efficiency of boron may be improved. That is, according to an embodiment of the present disclosure, the yield and productivity of BNNTs may be maximized.

As shown inFIG. 10A, gas supply holes331formed on at least two gas supply pipes33may be positioned to face each other. Alternatively, as shown inFIG. 10B, gas supply holes331may be formed to be alternate to each other on gas supply pipes33.

The gas supply pipe33may be connected to a gas supplier disposed outside the reaction chamber31, and though not shown in the figures, the gas supplier may include a reaction gas storage tank and a gas supply pump.

According to another embodiment of the present disclosure, an exhaust pipe may extend into the reaction chamber31. The exhaust pipe may be positioned at least out of the reaction zone of the reaction chamber31. Accordingly, a reaction gas that has finished reacting may be discharged out of the reaction chamber31, and an excessive increase of the internal pressure of the reaction chamber31may be prevented.

The exhaust pipe may be connected with a gas discharger disposed outside the reaction chamber31, and though not shown in the figures, the gas discharge may include a valve for controlling the internal pressure of the reaction chamber31, and an exhaust pump.

The reaction zone311, as shown inFIGS. 3, 4A, and 4B, may be positioned substantially at the center of the reaction chamber31and the length of the reaction zone311may be adjusted in accordance with the capacity of the temperature adjuster of the reaction chamber31.

According to an embodiment, it is possible to change the supply density of the reaction gas that is provided to the reaction zone311. That is, it is possible to supply the reaction gas most to the middle portion, in which reaction is most actively generated, in the reaction zone311, and it is possible to reduce the supply amount of the reaction gas that is supplied to the front and rear of the middle portion.

According to an embodiment of the present disclosure, a reaction module38may be moved in the longitudinal directions of the gas supply pipe33and the reaction chamber31to the heating zone311in the reaction chamber31.

In this case, the gas supply pipe33may be disposed close to the supports381of the reaction module38to be able to provide a reaction gas close to the precursor block2.

That is, as shown inFIG. 9A, the gas supply pipe33may be disposed between the supports381of the reaction module38.

As shown inFIGS. 5 and 6, the supports381may have holders383to be disposed without interference with the gas supply pipe33.

It is preferable that the holders383are formed to face each other at the supports381facing each other to pass the gas supply pipe33.

The holders383may be grooves formed on the supports381or may be holes formed through the supports381, but are not limited thereto.

The holders383may be positioned such that the gas supply pipe33and the supports381do not interfere with each other while the reaction module38is conveyed through a conveying path in the reaction chamber31.

Although embodiments of the present disclosure were described above in detail, the right range of the present disclosure is not limited thereto, and various changes, equivalents, and modifications by those skilled in the art using the fundamental concept of the present disclosure defined in claims are also included in the right range of the present disclosure.