WO2021157756A1 - Method for preparing carbon nanotube-carbon nanofiber composite, and carbon nanotube-carbon nanofiber composite prepared thereby - Google Patents

Method for preparing carbon nanotube-carbon nanofiber composite, and carbon nanotube-carbon nanofiber composite prepared thereby Download PDF

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WO2021157756A1
WO2021157756A1 PCT/KR2020/001664 KR2020001664W WO2021157756A1 WO 2021157756 A1 WO2021157756 A1 WO 2021157756A1 KR 2020001664 W KR2020001664 W KR 2020001664W WO 2021157756 A1 WO2021157756 A1 WO 2021157756A1
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carbon
alkali metal
nanofibers
metal precursor
containing polymer
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French (fr)
Korean (ko)
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강준
고정혁
김대영
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한국해양대학교 산학협력단
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    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
    • D06M13/10—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with compounds containing oxygen
    • D06M13/144—Alcohols; Metal alcoholates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D10/00—Physical treatment of artificial filaments or the like during manufacture, i.e. during a continuous production process before the filaments have been collected
    • D01D10/02—Heat treatment
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/0007—Electro-spinning
    • D01D5/0015—Electro-spinning characterised by the initial state of the material
    • D01D5/003—Electro-spinning characterised by the initial state of the material the material being a polymer solution or dispersion
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • D01F1/10—Other agents for modifying properties
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
    • D06M13/02—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with hydrocarbons
    • D06M13/03—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with hydrocarbons with unsaturated hydrocarbons, e.g. alkenes, or alkynes
    • D06M13/07—Aromatic hydrocarbons

Definitions

  • the present invention relates to a method for producing a carbon nanotube-carbon nanofiber composite and a carbon nanotube-carbon nanofiber composite prepared thereby.
  • Carbon is a substance that exists in various forms, and the structure and physical properties of the substance change depending on the bonding method between carbon atoms.
  • a carbon atom has four valences composed of two 2s orbitals and two other 2p orbitals, and various allotropes exist because electrons are bonded to adjacent carbon atoms in various covalent bonds. That is, when a carbon atom is covalently bonded to another atom, the four electrons in the outermost shell form sp 3 , sp 2 and sp hybrid orbital by hybridization of s orbital and p orbital.
  • Representative carbon allotropes of each hybrid orbital include diamond composed of sp 3 hybrid orbitals, graphite composed of sp 2 hybrid orbitals, and carbine composed of sp hybrid orbitals.
  • carbon nanofiber (CNF), carbon nanotube (CNT), and fullerene which are recently spotlighted as carbon nanomaterials, are composed of sp 2 hybrid orbitals, but structural forms are different. Because they are different, there is a difference in the properties of substances.
  • carbon nanofibers are in the spotlight as a reinforcing component of fiber-reinforced materials because of their excellent mechanical strength and conductivity.
  • Carbon nanotubes are attracting attention as high-performance materials because they have superior mechanical strength, excellent elasticity, thermal and electrical properties, and low density compared to carbon nanofibers. Although many efforts have been made on carbon nanotubes so far, they have a pre-emptive problem that they must be manufactured for a much longer time and at a lower cost in order to be used in more diverse fields. Although research on composite materials using carbon nanotubes and polymers has been made only recently, carbon nanotubes have a large specific surface area. There is a problem in that it is difficult to realize high thermal conductivity, which is the intrinsic property of the tube, so it is difficult to disperse the carbon nanotubes in the polymer, making practical applications difficult. Much more research is still needed before development.
  • the composite material in which carbon nanotubes are formed on carbon nanofibers can combine the advantages of both, and excellent electrical and mechanical properties can be extended not only in the longitudinal direction of the carbon nanofiber but also in the direction perpendicular to it. It can serve as an ideal two-dimensional fiber-reinforced component. Furthermore, since these composite materials can utilize the relatively large surface area of carbon nanotubes, the adhesion area can be substantially expanded, and functional groups can be introduced into the carbon nanotubes, so that the compatibility of the fiber-reinforced material with the polymer can be improved.
  • Composite materials of carbon nanotubes and carbon nanofibers to date have suggested a solution to the problem of dispersing carbon nanotubes in a polymer, but the bonding force between carbon nanotubes and carbon nanofibers is weak, and the carbon nanotubes are not aligned. When it is made of a composite material, there is a problem that the mechanical strength is rather weak.
  • FIG. 1 showing the TEM photograph of the defects occurring in the conventional composite material of carbon nanotubes and carbon nanofibers, and the defective part caused by the non-alkali metal catalyst particles in the part indicated by the arrow in FIG. This is confirmed.
  • the present invention was invented to solve the above problems, and a method for producing a carbon nanotube-carbon nanofiber composite that enables carbon nanotubes to grow from the surface of carbon nanofibers, and a carbon nanotube-carbon produced thereby It is a technical solution to provide a nanofiber composite.
  • the present invention provides a first step of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution; a second step of preparing a spinning solution by dissolving a carbon-containing polymer in the alkali metal precursor solution; a third step of electrospinning the spinning solution to produce carbon-containing polymer nanofibers to which the alkali metal precursor is bonded to a surface; a fourth step of heat-treating the carbon-containing polymer nanofibers to prepare carbon nanofibers in which the alkali metal precursor is bonded to the surface; and heat treatment while supplying a carbon source to the carbon nanofibers so that the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bonded to the surface of the carbon nanofibers by the nanocatalyst as carbon nanotubes. It provides a method for producing a carbon nanotube-carbon nanofiber composite comprising; a fifth step of crystallizing and growing to produce carbon nanofibers
  • the alkali metal precursor is characterized in that it is selected from the group consisting of a lithium precursor (Li precursor), a sodium precursor (Na precursor), a potassium precursor (K precursor), and mixtures thereof.
  • the carbon-containing polymer is polyacrylonitrile (polyacrylonitrile, PAN), polyvinyl acetate (polyvinyl acetate, PVA), polyvinyl pyrrolidone (polyvinyl pyrrolidone, PVP), polycarbonate (polycarbonate, PC) , characterized in that it is selected from the group consisting of polyvinyl chloride (PVC), cellulose (cellulose), cellulose acetate (cellulose acetate), and mixtures thereof.
  • PAN polyacrylonitrile
  • PVA polyvinyl acetate
  • PVP polyvinyl pyrrolidone
  • PC polycarbonate
  • the carbon source is a liquid, gaseous or solid carbon source
  • the liquid carbon source is ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ) ) and mixtures thereof
  • the gaseous carbon source is methane (CH 4 ), propylene (C 3 H 6 ), propine (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 ) H 10 ), butylene (C 4 H 8 ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ), and selected from the group consisting of mixtures thereof
  • the solid carbon source is camphor (C 10 H 16 O) characterized by being.
  • the carbon-containing polymer nanofiber is characterized in that the preliminary heat treatment at a temperature in the range of 100 to 300 °C.
  • the carbon-containing polymer is carbonized by heat treatment at a temperature in the range of 800 to 1,200° C. under an inert gas atmosphere.
  • the present invention provides a carbon nanotube-carbon nanofiber composite, characterized in that produced by the above method.
  • the carbon nanotube-carbon nanofiber composite of the present invention by means of solving the above problems, and the carbon nanotube-carbon nanofiber composite prepared by the method have the following effects.
  • lithium (Li), potassium (K) without using a catalyst based on transition metals, that is, non-alkali metals of Groups 8, 9, and 10 such as iron (Fe), cobalt (Co), and nickel (Ni)
  • transition metals that is, non-alkali metals of Groups 8, 9, and 10
  • iron (Fe), cobalt (Co), and nickel (Ni) since an alkali metal-based catalyst such as sodium (Na) is used, catalyst particles such as sodium are simply dissolved in water and can be easily removed, making the synthesis of metal-free carbon nanotube-carbon nanofiber composites easier. After completion, there is no need to go through a cleaning process such as acid treatment, which has the effect of reducing environmental costs.
  • carbon nanotubes can be easily grown from the surface of carbon nanofibers only by manufacturing carbon-containing polymer nanofibers having an alkali metal precursor bonded to their surface through electrospinning, carbonizing them, and then heat-treating them while supplying a carbon source. , carbon nanotube-carbon nanofiber composites can be mass-produced.
  • the carbon nanotube-carbon nanofiber composite produced through the present invention is an emission source of various devices, a vacuum fluorescent display (VFD), a white light source, a field emission display (FED), an electrode for a lithium ion battery, a hydrogen storage fuel cell, There is an effect that can be widely used in various energy application fields such as nanowires, gas sensors, micro-parts for biomedical engineering, and high-functional composites.
  • VFD vacuum fluorescent display
  • FED field emission display
  • an electrode for a lithium ion battery a hydrogen storage fuel cell
  • 1 is a TEM photograph showing defects occurring in a conventional composite material of carbon nanotubes and carbon nanofibers.
  • Figure 2 is a flow chart showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention.
  • Figure 3 is a schematic diagram showing a manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention.
  • 5 is a conceptual diagram of electrospinning according to the present invention.
  • FIG. 6 is a photograph of a carbonization heat treatment furnace.
  • FIG. 7 is a photograph of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers.
  • Example 8 is a SEM photograph of the carbon nanotube-carbon nanofiber composite prepared according to Example 1 of the present invention.
  • 10 is a SEM photograph showing the length of carbon nanotubes grown on carbon nanofibers.
  • 11 is a SEM photograph showing the density of carbon nanotubes grown on carbon nanofibers.
  • FIG. 2 is a flowchart showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention
  • FIG. 3 is a schematic diagram showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention, see this
  • the carbon nanotube-carbon nanofiber composite of the present invention is a first step (S10) of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution
  • a carbon-containing polymer is dissolved in an alkali metal precursor solution to prepare a spinning solution
  • the fourth step (S40) of manufacturing the bonded carbon nanofibers and heat treatment while supplying a carbon source to the carbon nanofibers the alkali metal precursor is activated as an alkali metal nanocatalyst, and
  • an alkali metal precursor is dissolved in a solvent to prepare an alkali metal precursor solution (S10).
  • non-alkali metals of Groups 8, 9, and 10 such as iron (Fe), cobalt (Co), and nickel (Ni), that is, transition metal-based catalysts are mainly used.
  • an additional process such as acid treatment is required to remove the nanoparticles remaining in the metallic state of the non-alkali metal catalyst, and acid treatment In order to do this, washing water is required, so there has been a burden due to the increase in environmental costs.
  • an alkali metal precursor solution based on a Group 1 element other than hydrogen is dissolved in a solvent to prepare an alkali metal precursor solution. It allows the carbon nanotubes to grow from the surface of the nanofibers and is easily dissolved in water and removed without removing the nanocatalyst through a separate process such as acid treatment later, so that the synthesis of high-purity carbon nanotube-carbon nanofiber composites is possible. possible.
  • the alkali metal precursor is selected from the group consisting of a lithium precursor (Li precursor), a sodium precursor (Na precursor), a potassium precursor (K precursor), and a mixture thereof. That is, the alkali metal precursor is one or more alkali metal salts selected from the group consisting of lithium (Li), sodium (Na) and potassium (K), alkali metal organic compounds, or alkali metal inorganic compounds. It can be said that it is composed of alkali metal inorganic compounds.
  • lithium precursor which is a compound containing lithium
  • the sodium precursor is a compound containing sodium
  • sodium benzoate sodium benzoate
  • sodium chloride sodium chloride, NaOH
  • sodium bicarbonate sodium bicarbonate
  • potassium precursor which is a compound containing potassium, potassium benzoate
  • ate Potassium benzoate
  • potassium chloride Potassium chloride
  • potassium hydroxide Potassium hydroxide
  • the solvent consists of a polar solvent or a non-polar solvent, and is a polar solvent selected from the group consisting of water, dimethylformamide (DMF), lower alcohols having 1 to 5 carbon atoms, and mixtures thereof, or xylene, benzene ( A non-polar solvent selected from the group consisting of benzene), toluene, and mixtures thereof may be selected and used.
  • a polar solvent selected from the group consisting of water, dimethylformamide (DMF), lower alcohols having 1 to 5 carbon atoms, and mixtures thereof, or xylene, benzene ( A non-polar solvent selected from the group consisting of benzene), toluene, and mixtures thereof may be selected and used.
  • an alkali metal precursor solution in which an alkali metal precursor is mixed in a solvent is prepared in the following two ways.
  • an alkali metal precursor solution is prepared by dissolving an alkali metal precursor in a polar solvent such as dimethylformamide.
  • the amount of the alkali metal precursor used is not particularly limited, but when mixed at less than 0.01 mol per 1 liter of solvent, the alkali metal precursor cannot be activated or functionalized with the alkali metal nano catalyst when the fifth step heat treatment is performed. Not only does it take a lot of time until the point at which carbon nanotubes can be grown from the surface, but there are also cases where the carbon source supplied in the fifth step cannot be grown into carbon nanotubes, so it is limited in application to energy application fields. In particular, when the alkali metal precursor is added in an excessively small amount, the reaction rate cannot be increased, which is not preferable in terms of production efficiency.
  • the alkali metal precursor per 1 liter of solvent exceeds 0.05 mol
  • the alkali metal precursor is activated or functionalized with the alkali metal nanocatalyst during the heat treatment in the fifth step, and then the nanocatalysts remain partially attached to the carbon nanotubes.
  • the purity of the carbon nanotubes grown on the carbon nanofibers is reduced.
  • the alkali metal precursor in the range of 0.01 to 0.05 mol per 1 liter of solvent, and 0.02 mol is most preferable in consideration of the optimal activity as a nanocatalyst.
  • the alkali metal cation of the alkali metal precursor is coordinated to the cavity of the crown ether to form a complex, thereby solvating the alkali metal cation to prepare an alkali metal precursor solution.
  • Crown ether (x-Crown ether-y; x is the number of all atoms in the ring, y is the number of oxygen atoms) is an oligomer of ethylene oxide in which ethyleneoxy (-CH 2 CH 2 O-) units are repeated ( oligomer), which forms a stable structure with alkali metal cations as the alkali metal cations in the alkali metal precursor solution are put into the cavity at the center of the crown ether, so that the alkali metal cations are solvated and dissolved, especially in non-polar solvents.
  • the solubility of the phosphorus alkali metal precursor is increased.
  • crown ether forms a stable complex with metal ions, that is, alkali metal cations such as Li + , Na + , K + It will be able to bloom.
  • the alkali metal precursor When the alkali metal precursor is dissolved in the solvent through the crown ether, it is converted into a transparent alkali metal precursor solution.
  • the weight ratio of the crown ether may be 1:0.1-100.), it is also possible to control the solubility of the alkali metal precursor solution by adjusting the amount of the crown ether.
  • the amount in which the alkali metal precursor and the crown ether can be mixed is not limited.
  • crown ether it can be used by selecting from the group consisting of 12-Crown-4, 15-Crown-5, 18-Crown-6, and mixtures thereof. It can be confirmed through FIG. 4 shown.
  • Figure 4 (a) is an illustrative example of 12-Crown-4 forming a complex with Li +
  • Figure 4 (b) is an illustrative example of 15-Crown-5 forming a complex with Na +
  • FIG. 4( c ) exemplarily shows 18-Crown-6 forming a complex with K + .
  • the crown ether helps the oxygen atoms constituting the crown to coordinate alkali metal cations to the cavity in the crown, and the types of ions that form a stable complex depend on the size of the crown. That is, Li + forms the most stable complex with 12-Crown-4, Na + forms the most stable complex with 15-Crown-5, and K + forms the most stable complex with 18-Crown-6. can be checked
  • the solvents such as water or dimethylformamide presented in the first method are polar, so alkali metal precursors are easily dissolved, but in polar solvents and other non-polar solvents (eg, xylene), the alkali metal precursor does not dissolve, so crown ether is the solute. It solvates and plays an important role in increasing solubility.
  • a carbon-containing polymer is dissolved in an alkali metal precursor solution to prepare a spinning solution (S20).
  • 1 to 15 wt% of a polymer containing carbon is added to 85 to 99 wt% of the alkali metal precursor solution and dissolved while stirring to prepare a spinning solution capable of electrospinning.
  • the alkali metal precursor solution is relatively small.
  • the amount of the activated nanocatalyst is also relatively reduced, so that the amount of carbon nanotubes that can be grown from the surface of the carbon nanofibers is also reduced.
  • the alkali metal precursor solution is less than 85wt%, the amount of activated nanocatalyst is reduced, so the amount of carbon nanotubes that can be grown is also reduced.
  • the growth of carbon nanotubes cannot be stably performed due to insufficient space in which the nanocatalyst can be formed in the fiber.
  • the carbon-containing polymer be contained in an amount of 9wt% in consideration of solvent volatilization in the alkali metal precursor solution.
  • Carbon-containing polymers can be called carbon nanofiber precursors, polyacrylonitrile (PAN), polyvinyl acetate (PVA), polyvinyl pyrrolidone (PVP), polycarbonate (polycarbonate, PC), polyvinyl chloride (PVC), cellulose, cellulose acetate, and mixtures thereof may be selected from the group consisting of, and in the present invention, polyacrylonitrile is applied, but carbon It is not particularly limited as long as it is a carbon-containing polymer that can be formed into nanofibers.
  • This step is for producing a carbon-containing polymer nanofiber in the form of a fiber with a spinning solution.
  • FIG. 5 showing a conceptual diagram of electrospinning according to the present invention
  • a high voltage terminal is connected and a sufficiently high voltage is applied with the conductor connected to the ground
  • an electromagnetic field is formed between the nozzle and the conductor, and the spinning solution inside the nozzle is affected, and the electromagnetic force changes the surface tension and viscosity of the spinning solution.
  • a taylor cone is formed and stretched at the tip to form composite nanofibers, which are nano-sized composite fibers.
  • 'composite nanofibers' and 'nano-sized composite fibers' referred to in the present invention mean 'carbon-containing polymer nanofibers having an alkali metal precursor bonded to the surface'.
  • the molecular weight of the carbon-containing polymer For the production of nano-sized composite fibers through electrospinning, the molecular weight of the carbon-containing polymer, the characteristics of the spinning solution, the voltage, the distance between the nozzle and the conductor, the amount and concentration of the carbon-containing polymer, the parameters, the movement of the nozzle, the conductor It is desirable to satisfy the size and nozzle size conditions of , and each condition will be described in detail below.
  • the molecular weight conditions of the carbon-containing polymer are as follows. That is, if the molecular weight (M w ) of the polymer containing carbon is less than 45,000 or exceeds 1,000,000, it is difficult to form a composite nanofiber uniformly, so it is preferable to make it in the range of 45,000 to 1,000,000.
  • the characteristic conditions of the spinning solution are as follows. Regarding the viscosity of the spinning solution, if it is less than 1 Pa ⁇ s, the viscosity is too low and the spinning solution breaks before it is formed into nano-sized composite fibers in the process of electrospinning. If it exceeds s, the viscosity becomes too high and more electromagnetic force is required to elution from the nozzle, which causes overcurrent and burns the experimental equipment. desirable. With respect to the conductivity of the spinning solution, if it exceeds 53 ⁇ s/cm, it is not suitable for carbon nanofiber formation, so it is preferable that the spinning solution has a conductivity of 53 ⁇ s/cm or less.
  • the electromagnetic force With respect to the surface tension of the spinning solution, if it exceeds 450 dyn/cm, the electromagnetic force becomes smaller than the surface tension of the spinning solution, and Taylor cone formation does not occur, making it difficult to form a composite nanofiber. It is preferably made of 450 dyn/cm or less.
  • Voltage conditions are as follows. When a voltage of 30 kV or less is applied for electrospinning of the spinning solution, an electromagnetic field is formed between the nozzle and the conductor, so there is no need to apply a voltage exceeding 30 kV.
  • the distance condition between the nozzle and the conductor is as follows. That is, when the distance between the nozzle in which the spinning solution is accommodated and the conductor is less than 30 cm, the nano-sized composite fiber is formed. If the distance between the nozzle and the conductor exceeds 30 cm, the distance between the nozzle and the conductor is too far and the electromagnetic force is small, making it difficult to make the nano-size of the composite fiber uniform, as well as the disadvantage that the form of droplets rather than nanofibers can be seen. there is.
  • the fluid amount and concentration conditions of the carbon-containing polymer are as follows. When the amount of fluid is 25ml/min or less, the spinning solution is formed into a Taylor cone so that the nanofibers can be stretched well. The higher the probability, the higher the defect rate. In the case of concentration, 30 wt% is sufficient to be manufactured into nano-sized composite fibers.
  • the parameter conditions are as follows.
  • the parameters relate to basic environmental aspects such as temperature, humidity, and airflow.
  • a temperature of 35°C or less a humidity of 60% or less, and an airflow environment of 1 or less
  • the alkali metal precursor is bonded to the surface through electrospinning. It can be manufactured from carbon-containing polymer nanofibers.
  • the nozzle movement and conductor size conditions are as follows. First of all, the spinning solution is stably stretched to the conductor through electrospinning only when the movement of the nozzle is 0.1mm/min or less, and even if the size of the conductor is 10cm2 or more, the composite nanofibers electrospun from the nozzle are stably captured by the conductor. can be done However, if the size of the conductor is less than 10 cm 2 , the area is too small to secure a space to sufficiently collect the composite nanofibers.
  • the nozzle size conditions are as follows. If the nozzle size is less than 0.01 mm or exceeds 1.7 mm, it does not help the formation of carbon-containing polymer nanofibers bonded to the surface of the alkali metal precursor, so the nozzle size is preferably in the range of 0.01 to 1.7 mm.
  • the carbon-containing polymer nanofibers are heat-treated to prepare carbon nanofibers having an alkali metal precursor bonded to the surface (S40).
  • the carbon-containing polymer nanofibers having an alkali metal precursor bonded to the surface are heated to 100 to 300° C. at a temperature increase rate of 8 to 12° C./min in the atmosphere for 20 minutes to The carbon-containing polymer is stabilized through preliminary heat treatment for 1 hour. At this time, if the preliminary heat treatment is less than 100 °C, it is difficult to stabilize the carbon-containing polymer nanofibers, and if the preliminary heat treatment is made above 300 °C, the temperature is higher than necessary, which may cause deterioration of the shape or physical properties of the carbon-containing polymer nanofibers. .
  • a temperature increase rate it may be 8 to 12° C./min, and 10° C./min is most preferred.
  • the preliminary heat treatment is performed in less than 20 minutes, it is difficult to stabilize the carbon-containing polymer of the carbon-containing polymer nanofibers as in the temperature condition. There is no effect. In particular, it has the advantage of being able to rapidly form carbon-containing polymer nanofibers because oxygen supply is smooth only when preliminary heat treatment is performed in an oxygen environment in the atmosphere.
  • Carbonization herein refers to a heat treatment process for increasing the carbon/hydrogen ratio of the carbon-containing polymer constituting the carbon-containing polymer nanofiber, and refers to a process for converting carbon-containing components into carbon.
  • the heat treatment temperature for carbonization if the heat treatment is less than 800° C., it takes a lot of time to complete carbonization of the carbon-containing polymer due to incomplete carbonization, so that complete carbonization cannot be expected, so the surface of carbon nanofibers are damaged. On the other hand, if the temperature exceeds 1,200° C., the temperature is rather high, so that the carbon-containing polymer is not sufficiently converted to carbon or the degree of improvement in the properties of carbon nanofibers is reduced due to excessive heat treatment. The alkali metal precursor contained in the vaporized and disappeared, resulting in difficulties in the formation of the nano-catalyst in the future. For complete carbonization, it is most preferable to heat treatment at 1,000°C.
  • the reason why the temperature increase rate is relatively slow compared to when the preliminary heat treatment for stabilizing the carbon-containing polymer nanofibers is 3 to 7 °C/min is during the carbonization process while the temperature is increasing. This is to check whether there is any problem in the formation of carbon nanofibers and at the same time to prevent deterioration of the physical properties of carbon nanofibers. It is most preferably carried out at 5° C./min for stable carbon nanofiber production.
  • the target carbonization effect is insignificant, and if it exceeds 1 hour and 30 minutes, the inefficient aspect in the process is highlighted due to too long time.
  • process efficiency most preferably, it is good to heat-treat for 60 minutes to carbonize it.
  • the inert gas atmosphere may be, for example, a gas such as helium, nitrogen, argon, or carbon dioxide, more specifically, a nitrogen (N 2 ) gas. That is, the carbon-containing polymer of the carbon-containing polymer nanofiber can be converted to carbon nanofiber by being carbonized by heat treatment in an inert atmosphere.
  • the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bonded to the surface of the carbon nanofiber by the nanocatalyst to crystallize and grow into carbon nanotubes.
  • carbon nanofibers to which carbon nanotubes are bonded to the surface are prepared (S50).
  • carbon nanofibers are coated with a non-alkali metal catalyst such as iron (Fe), and carbon atoms start to dissolve in iron particles while passing carbon dioxide and other carbon-containing gases.
  • Fe iron
  • the process of forming a vertical tube of carbon atoms around carbon nanofibers was mainly based on the method in which carbon nanotubes were grown.
  • the iron particles remain in the carbon nanotubes, and eventually, there is a disadvantage that the acid treatment to remove the iron particles must be repeated several times.
  • the alkali metal of the alkali metal precursor is activated as a nanocatalyst, and the carbon source is crystallized into carbon nanotubes through this nanocatalyst so that it can be grown from the surface of the carbon nanofibers.
  • alkali metals of the alkali metal precursor cannot be activated or functionalized as a nano catalyst, and rather remain as impurities in some grown carbon nanotubes. As a result, the activity of the nanocatalyst is not stabilized, thereby hindering the growth of carbon nanotubes.
  • the heat treatment time condition if it is less than 15 minutes, it is insufficient time to induce the activation of the nanocatalyst, so it does not secure sufficient time for the carbon nanotubes to grow, and if it exceeds 30 minutes, the length of the grown carbon nanotubes It is preferable to heat treatment within 30 minutes because it becomes too long and it is difficult to achieve optimal physical properties and unnecessary side reactions may be generated.
  • the nanocatalyst is an alkali metal, in particular, sodium, which is an alkali metal of the alkali metal precursor applied in the present invention, is soluble in water, so there is no need to remove it using a separate acid, so metal-free carbon It is important to synthesize the nanotube-carbon nanofiber composite. That is, even if a part of the nanocatalyst remains in the carbon nanotube, there is an effect that it can be removed by dissolving it in general water rather than an acid treatment due to the high reactivity of the alkali metal cation.
  • the nanocatalyst can be simply vaporized or evaporated and removed by the heat treatment temperature of the fifth step, only pure carbon nanotubes can be grown from the surface of the carbon nanofibers.
  • high binding force between carbon nanofibers and carbon nanotubes is generated, and carbon nanofibers and carbon nanotubes are not separated, thereby binding carbon nanofibers and carbon nanotubes to each other. There is no need for a separate means to do this.
  • any one of a liquid type carbon source, a gaseous gas phase carbon source, and a solid type carbon source choose one or more to use.
  • the liquid phase carbon source is selected from the group consisting of ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ), and mixtures thereof.
  • Gas phase carbon sources include methane (CH4), propylene (C3H6), propane (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ), butylene (C 4 H 8 ) ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ) and mixtures thereof.
  • camphor C 10 H 16 O
  • monoterpene ketones may be used as a solid carbon source.
  • alkali metal precursors are activated as alkali metal nanocatalysts simply by heat treatment in the presence of a carbon source that helps the growth of carbon nanotubes without the need to separately prepare Group 1 elements other than hydrogen, especially sodium, as a catalyst in the form of particles,
  • the carbon source is crystallized into carbon nanotubes by the nanocatalyst, it can be grown from the surface of the carbon nanofibers, and eventually a carbon nanotube-carbon nanofiber composite in which the carbon nanotubes are bonded to the surface of the carbon nanofiber is manufactured.
  • the nanocatalyst may be vaporized and removed, so that the nanocatalyst is not attached or attached to the carbon nanotube grown on the carbon nanofiber. Therefore, there is no need to remove the nano-catalyst by performing a post-treatment process such as additional heat treatment or acid treatment. Even if a part of the nanocatalyst remains in the carbon nanotube, the advantages of the process are maintained because the alkali metal ion needs to be removed by dissolving it in general water rather than acid treatment due to the high reactivity to water.
  • Carbon-containing polymer nanofibers were heat-treated at 200°C for 40 minutes at a temperature increase rate of 10°C/min in the atmosphere, then heat-treated at 1,000°C for 60 minutes at a temperature increase rate of 5°C/min in an N 2 atmosphere, and then naturally cooled to carbonize Carbon nanofibers were prepared. This carbonization process was carried out using a heat treatment furnace as shown in the photo of the carbonization heat treatment furnace of FIG. 6 .
  • FIG. 7 showing a photo of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers
  • a SUS pipe (diameter 5cm, length 20cm), which is a tube, was placed in the center of the furnace, and the temperature inside the SUS pipe was 700 It was maintained at °C, and the ethanol vapor generated while heating the ethanol using a heater was supplied to the inside of the SUS pipe through N 2 bubbling for 15 minutes so that carbon nanotubes were grown on the surface of the carbon nanofibers.
  • a carbon nanotube-carbon nanofiber composite was prepared.
  • Example 2 a spinning solution was prepared using sodium benzoate and other sodium bicarbonate of Example 1 as alkali metal precursors. That is, after dissolving sodium bicarbonate (Sigma Aldrich, BioXtra, > 99.5%) in DMF (Sigma Aldrich, for molecular biology, > 99%) solution at 0.02 mol/L, PAN (Sigma Aldrich, Mw 150,000 Typical) was added with 9 wt % ratio was dissolved again to prepare a spinning solution.
  • sodium bicarbonate Sigma Aldrich, BioXtra, > 99.5%
  • DMF Sigma Aldrich, for molecular biology, > 99%
  • PAN Sigma Aldrich, Mw 150,000 Typical
  • Carbon-containing polymer nanofibers were heat-treated at 200°C for 40 minutes at a temperature increase rate of 10°C/min in the atmosphere, then heat-treated at 1,000°C for 60 minutes at a temperature increase rate of 5°C/min in an N 2 atmosphere, and then naturally cooled to carbonize Carbon nanofibers were prepared. This carbonization process was carried out using the same heat treatment furnace shown in the photo of the carbonization heat treatment furnace of FIG. 6 mentioned in Example 1.
  • FIG. 7 showing a photo of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers
  • a SUS pipe (diameter 5cm, length 20cm), which is a tube, was placed in the center of the furnace, and the temperature inside the SUS pipe was 700 It was maintained at °C, and the ethanol vapor generated while heating the ethanol using a heater was supplied to the inside of the SUS pipe through N 2 bubbling for 15 minutes so that carbon nanotubes were grown on the surface of the carbon nanofibers.
  • a carbon nanotube-carbon nanofiber composite was prepared.
  • FIGS. 8(a), 8(b) and 8(c) it is possible to confirm the crystallization and growth of carbon nanotubes on carbon nanofibers.
  • 9 is an SEM photograph of a carbon nanotube-carbon nanofiber composite prepared according to Example 2 of the present invention. It is possible to confirm the growth of the tube as it is combined.
  • 10 is an SEM photograph showing the length of carbon nanotubes grown on carbon nanofibers.
  • 10 (a) is a carbon nanotube-carbon nanofiber composite prepared when all the conditions in Example 1 are set the same, but heat-treated with only the carbon nanotube growth time of less than 5 minutes as an SEM photograph
  • Figure 10 (b) is a further enlarged SEM photograph of Figure 10 (a)
  • Figure 10 (c) is a further enlarged SEM photograph of Figure 10 (b)
  • the heat treatment time is less than 5 minutes carbon
  • 11 is a SEM photograph showing the density of carbon nanotubes grown on carbon nanofibers.
  • 11 (a) is a carbon nanotube-carbon nanofiber composite prepared when the concentration of sodium benzoate, which is an alkali metal precursor dissolved in DMF, is reduced to 1/5, except that all conditions in Example 1 are the same, SEM It is shown as a photograph, FIG. 11 (b) is an SEM photograph by further expanding FIG. 11 (a), and FIG. 11 (c) is an SEM photograph by further expanding FIG. It can be seen that it is possible to control the density of the carbon nanotubes grown from the surface of the carbon nanofibers according to the concentration of the alkali metal precursor.
  • the present invention relates to a method for producing a carbon nanotube-carbon nanofiber composite and a carbon nanotube-carbon nanofiber composite prepared thereby, by electrospinning a spinning solution in which a carbon-containing polymer is dissolved in an alkali metal precursor solution.
  • carbon nanofibers in which carbon-containing polymer nanofibers are carbonized through heat treatment are produced, and then heat-treated while supplying a carbon source to the carbon nanofibers to obtain alkali metal
  • the precursor is activated with an alkali metal nanocatalyst, and a carbon source is bonded to the surface of the carbon nanofiber by the nanocatalyst, and can be crystallized and grown into carbon nanotubes.
  • the present invention does not use a catalyst based on a non-alkali metal such as iron (Fe), cobalt (Co), or nickel (Ni), that is, a transition metal-based catalyst such as lithium (Li), potassium (K), especially sodium (Na). Since the alkali metal-based catalyst is used, catalyst particles such as sodium are simply dissolved in water and easily removed, so it is meaningful in that a metal-free carbon nanotube-carbon nanofiber composite can be synthesized. .
  • a non-alkali metal such as iron (Fe), cobalt (Co), or nickel (Ni)
  • a transition metal-based catalyst such as lithium (Li), potassium (K), especially sodium (Na). Since the alkali metal-based catalyst is used, catalyst particles such as sodium are simply dissolved in water and easily removed, so it is meaningful in that a metal-free carbon nanotube-carbon nanofiber composite can be synthesized. .
  • the present invention since there is no need for a cleaning process such as acid treatment to remove catalyst particles, washing water is unnecessary, thereby reducing environmental costs, and it is possible to easily grow carbon nanotubes from the surface of carbon nanofibers. , the carbon nanotube-carbon nanofiber composite can be mass-produced, so it is expected to be widely used in various energy application fields.

Abstract

The present invention relates to a method for preparing a carbon nanotube-carbon nanofiber composite, and a carbon nanotube-carbon nanofiber composite prepared thereby. The subject matters of the present invention are a method for preparing a carbon nanotube-carbon nanofiber composite, and a carbon nanotube-carbon nanofiber composite prepared thereby, the method comprising: a first step of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution; a second step of dissolving a carbon-containing polymer in the alkali metal precursor solution to prepare a spinning solution; a third step of electrospinning the spinning solution to prepare carbon-containing polymer nanofibers having surfaces to which the alkali metal precursor is bound; a fourth step of heat-treating the carbon-containing polymer nanofibers to prepare carbon nanofibers having surfaces to which the alkali metal precursor is bound; and a fifth step of heat-treating the carbon nanofibers while a carbon source is supplied, so that the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bound to the surfaces of the carbon nanofibers by the nanocatalyst, and crystallizes and grows into carbon nanotubes, thereby preparing carbon nanofibers having surfaces to which the carbon nanotubes are bound.

Description

탄소나노튜브-탄소나노섬유 복합체의 제조방법 및 이에 의해 제조되는 탄소나노튜브-탄소나노섬유 복합체Method for producing carbon nanotube-carbon nanofiber composite and carbon nanotube-carbon nanofiber composite prepared thereby
본 발명은 탄소나노튜브-탄소나노섬유 복합체의 제조방법 및 이에 의해 제조되는 탄소나노튜브-탄소나노섬유 복합체에 관한 것이다.The present invention relates to a method for producing a carbon nanotube-carbon nanofiber composite and a carbon nanotube-carbon nanofiber composite prepared thereby.
탄소는 여러가지 형태로 존재하는 물질로, 탄소원자들 사이의 결합 방법에 의해 물질의 구조와 물리적 성질이 달라진다. 탄소원자는 2개의 2s 오비탈과 다른 2개의 2p 오비탈로 구성된 4개의 가전자를 가지고 있고 근접한 탄소원자들과 여러가지 공유결합 형태로 전자들이 결합되어 다양한 동소체가 존재한다. 즉, 탄소원자가 다른 원자와 공유결합한 경우에는 최외각에 존재하는 4개의 전자가 s오비탈과 p오비탈의 혼성에 의해서 sp3, sp2 및 sp 혼성오비탈을 형성한다.Carbon is a substance that exists in various forms, and the structure and physical properties of the substance change depending on the bonding method between carbon atoms. A carbon atom has four valences composed of two 2s orbitals and two other 2p orbitals, and various allotropes exist because electrons are bonded to adjacent carbon atoms in various covalent bonds. That is, when a carbon atom is covalently bonded to another atom, the four electrons in the outermost shell form sp 3 , sp 2 and sp hybrid orbital by hybridization of s orbital and p orbital.
각 혼성오비탈의 대표적인 탄소동소체는 sp3 혼성오비탈로 구성된 다이아몬드, sp2 혼성오비탈로 구성된 흑연(graphite), sp 혼성오비탈로 구성된 카빈(carbin)이 있다. 이외에도 최근 각광받고 있는 탄소나노소재로 탄소나노섬유(carbon nanofiber, CNF), 탄소나노튜브(carbon nanotube, CNT) 그리고 풀러렌(fullerene)이 있으며, 이 물질들은 sp2 혼성오비탈로 구성되나 구조적인 형태가 다르기 때문에 물질의 성질에서 차이가 있다.Representative carbon allotropes of each hybrid orbital include diamond composed of sp 3 hybrid orbitals, graphite composed of sp 2 hybrid orbitals, and carbine composed of sp hybrid orbitals. In addition, carbon nanofiber (CNF), carbon nanotube (CNT), and fullerene, which are recently spotlighted as carbon nanomaterials, are composed of sp 2 hybrid orbitals, but structural forms are different. Because they are different, there is a difference in the properties of substances.
그중 탄소나노섬유는 기계적 강도, 전도성 등에서 우수하여 섬유 강화 재료의 강화 성분으로 각광을 받고 있다.Among them, carbon nanofibers are in the spotlight as a reinforcing component of fiber-reinforced materials because of their excellent mechanical strength and conductivity.
탄소나노튜브는 탄소나노섬유보다 우수한 기계적 강도, 뛰어난 탄력성과 열적, 전기적 특성을 갖추고 있으면서 밀도까지 낮은 장점이 있기 때문에 고성능 재료로 주목받고 있다. 탄소나노튜브에 대해 현재까지 많은 노력이 있어 왔지만 더 다양한 분야에 사용되려면 지금보다 훨씬 더 길게 더 염가로 제조할 수 있어야 한다는 선결문제를 안고 있다. 최근들어서야 탄소나노튜브와 고분자를 이용한 복합재료 연구가 이루어졌지만, 탄소나노튜브는 비표면적이 크기 때문에 고분자와 복합재료로 제조하는 경우 고분자와의 접촉 계면이 커지게 되어 완벽한 분산이 이루어지지 않으면 탄소나노튜브 고유의 물성인 높은 열전도도의 구현이 어려운 문제점이 있으므로, 고분자 내에서 탄소나노튜브의 분산이 쉽지 않아 실질적인 응용에 어려움이 있음에 따라 탄소나노튜브를 단독 강화 성분으로 사용하는 고분자 섬유 강화 재료의 개발까지는 아직 많은 연구가 더 필요하다.Carbon nanotubes are attracting attention as high-performance materials because they have superior mechanical strength, excellent elasticity, thermal and electrical properties, and low density compared to carbon nanofibers. Although many efforts have been made on carbon nanotubes so far, they have a pre-emptive problem that they must be manufactured for a much longer time and at a lower cost in order to be used in more diverse fields. Although research on composite materials using carbon nanotubes and polymers has been made only recently, carbon nanotubes have a large specific surface area. There is a problem in that it is difficult to realize high thermal conductivity, which is the intrinsic property of the tube, so it is difficult to disperse the carbon nanotubes in the polymer, making practical applications difficult. Much more research is still needed before development.
이러한 사정 때문에 탄소나노튜브를 탄소나노섬유 상에 형성한 복합재료는 양자의 장점을 결합할 수 있고, 탄소나노섬유의 길이방향 뿐 아니라 그에 수직한 방향까지 우수한 전기적·기계적 특성을 확장시킬 수 있어 매우 이상적인 2차원 섬유 강화 성분의 구실을 할 수 있다. 나아가 이러한 복합재료는 탄소나노튜브의 상대적으로 넓은 표면적을 활용할 수 있으므로 접착 면적의 실질적 확장이 가능하고, 탄소나노튜브에 작용기를 도입할 수도 있으므로 섬유 강화 재료의 고분자와의 상용성도 향상시킬 수 있을 것으로 기대되어 기계적 강도 또한 월등한 물질이 예상되기 때문에, 고성능 복합재료가 필요한 산업 분야에 크게 기여할 것으로 기대됨에도 불구하고, 탄소나노튜브와 탄소나노섬유의 복합재료가 제 기능을 발휘하려면 양자 사이의 결합력이 우수하여야 하나 그렇지 못한 문제점이 있다.Due to these circumstances, the composite material in which carbon nanotubes are formed on carbon nanofibers can combine the advantages of both, and excellent electrical and mechanical properties can be extended not only in the longitudinal direction of the carbon nanofiber but also in the direction perpendicular to it. It can serve as an ideal two-dimensional fiber-reinforced component. Furthermore, since these composite materials can utilize the relatively large surface area of carbon nanotubes, the adhesion area can be substantially expanded, and functional groups can be introduced into the carbon nanotubes, so that the compatibility of the fiber-reinforced material with the polymer can be improved. Because it is expected that a material with superior mechanical strength is expected, even though it is expected to greatly contribute to industrial fields that require high-performance composite materials, for the composite material of carbon nanotubes and carbon nanofibers to function properly, the bonding force between the two is required. It should be excellent, but there are problems.
현재까지의 탄소나노튜브와 탄소나노섬유의 복합재료는 고분자 내에 탄소나노튜브를 분산하는 문제점에 대한 해결책을 제시하였지만 탄소나노튜브와 탄소나노섬유 사이의 결합력이 약하고, 또한 정렬된 탄소나노튜브가 아니라서 복합재료로 제작하였을 때 오히려 기계적 강도가 약한 문제점이 있다.Composite materials of carbon nanotubes and carbon nanofibers to date have suggested a solution to the problem of dispersing carbon nanotubes in a polymer, but the bonding force between carbon nanotubes and carbon nanofibers is weak, and the carbon nanotubes are not aligned. When it is made of a composite material, there is a problem that the mechanical strength is rather weak.
특히 철(Fe), 니켈(Ni), 코발트(Co) 및 팔라듐(Pd)과 같은 비알칼리금속촉매를 대부분 사용하기 때문에 복합재료로 합성된 후 탄소나노튜브에 수많은 비알칼리금속촉매 입자들이 불순물로 잔존하게 된다. 이는 종래 탄소나노튜브와 탄소나노섬유의 복합재료에 발생된 불량을 TEM 사진으로 나타낸 도 1을 통해 확인 가능하며, 도 1의 화살표로 표시한 부분에서 비알칼리금속촉매 입자들로 인해 발생된 불량한 부분이 확인된다.In particular, since non-alkali metal catalysts such as iron (Fe), nickel (Ni), cobalt (Co) and palladium (Pd) are mostly used, numerous non-alkali metal catalyst particles are found in carbon nanotubes as impurities after being synthesized as a composite material. will remain This can be confirmed through FIG. 1 showing the TEM photograph of the defects occurring in the conventional composite material of carbon nanotubes and carbon nanofibers, and the defective part caused by the non-alkali metal catalyst particles in the part indicated by the arrow in FIG. This is confirmed.
이런 이유로 비알칼리금속촉매 입자들을 제거하기 위해 고농도의 산처리가 요구되나, 한번의 산처리로 비알칼리금속촉매 입자들이 완전히 제거되지 않아 복수 회 연속적으로 진행해야하는 번거로움이 있으며, 산처리를 할 때마다 세정수가 필요하여 환경비용이 추가되는 문제점과, 이로 인해 탄소나노튜브와 탄소나노섬유의 복합재료를 대량 생산하기 어려운 문제점이 있다.For this reason, a high-concentration acid treatment is required to remove the non-alkali metal catalyst particles, but the non-alkali metal catalyst particles are not completely removed by one acid treatment, so it is inconvenient to proceed continuously several times. There is a problem in that environmental costs are added because washing water is required every time, and thus it is difficult to mass-produce a composite material of carbon nanotubes and carbon nanofibers.
따라서 기존 탄소나노튜브와 탄소나노섬유의 복합재료로부터 탈피하여 탄소나노섬유에 탄소나노튜브를 성장시킬 수 있는 새로운 복합재료에 대한 기술개발 연구가 절실히 요구되는 시점이다.Therefore, it is a time when technology development research on a new composite material that can grow carbon nanotubes on carbon nanofibers is urgently required, breaking away from the existing composite materials of carbon nanotubes and carbon nanofibers.
본 발명은 상기한 문제점을 해소하기 위하여 발명된 것으로, 탄소나노섬유의 표면으로부터 탄소나노튜브가 성장될 수 있도록 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법 및 이에 의해 제조되는 탄소나노튜브-탄소나노섬유 복합체를 제공하는 것을 기술적 해결과제로 한다.The present invention was invented to solve the above problems, and a method for producing a carbon nanotube-carbon nanofiber composite that enables carbon nanotubes to grow from the surface of carbon nanofibers, and a carbon nanotube-carbon produced thereby It is a technical solution to provide a nanofiber composite.
상기의 기술적 과제를 해결하기 위하여 본 발명은, 알칼리금속 전구체를 용매에 용해시켜 알칼리금속 전구체용액을 제조하는 제1단계; 상기 알칼리금속 전구체용액에 탄소 함유 고분자를 용해시켜 방사용액을 제조하는 제2단계; 상기 방사용액을 전기방사하여 표면에 상기 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조하는 제3단계; 상기 탄소 함유 고분자 나노섬유를 열처리하여 표면에 상기 알칼리금속 전구체가 결합된 탄소나노섬유를 제조하는 제4단계; 및 상기 탄소나노섬유에 탄소원(carbon source)을 공급하면서 열처리하여 상기 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 상기 나노촉매에 의하여 상기 탄소원이 상기 탄소나노섬유의 표면에 결합되면서 탄소나노튜브로 결정화되어 성장하여, 표면에 탄소나노튜브가 결합된 탄소나노섬유를 제조하는 제5단계;를 포함하는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법을 제공한다.In order to solve the above technical problem, the present invention provides a first step of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution; a second step of preparing a spinning solution by dissolving a carbon-containing polymer in the alkali metal precursor solution; a third step of electrospinning the spinning solution to produce carbon-containing polymer nanofibers to which the alkali metal precursor is bonded to a surface; a fourth step of heat-treating the carbon-containing polymer nanofibers to prepare carbon nanofibers in which the alkali metal precursor is bonded to the surface; and heat treatment while supplying a carbon source to the carbon nanofibers so that the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bonded to the surface of the carbon nanofibers by the nanocatalyst as carbon nanotubes. It provides a method for producing a carbon nanotube-carbon nanofiber composite comprising; a fifth step of crystallizing and growing to produce carbon nanofibers having carbon nanotubes bonded to the surface.
본 발명에 있어서, 상기 알칼리금속 전구체는, 리튬전구체(Li precursor), 나트륨전구체(Na precursor), 칼륨전구체(K precursor) 및 이의 혼합으로 이루어진 군으로부터 선택되는 것을 특징으로 한다.In the present invention, the alkali metal precursor is characterized in that it is selected from the group consisting of a lithium precursor (Li precursor), a sodium precursor (Na precursor), a potassium precursor (K precursor), and mixtures thereof.
본 발명에 있어서, 상기 탄소 함유 고분자는, 폴리아크릴로니트릴(polyacrylonitrile, PAN), 폴리비닐아세테이트(polyvinyl acetate, PVA), 폴리비닐피롤리돈(polyvinyl pyrrolidone, PVP), 폴리카보네이트(polycarbonate, PC), 폴리비닐클로라이드(polyvinyl chloride, PVC), 셀룰로오스(cellulose), 셀룰로오스아세테이트(cellulose acetate) 및 이의 혼합으로 이루어진 군으로부터 선택되는 것을 특징으로 한다.In the present invention, the carbon-containing polymer is polyacrylonitrile (polyacrylonitrile, PAN), polyvinyl acetate (polyvinyl acetate, PVA), polyvinyl pyrrolidone (polyvinyl pyrrolidone, PVP), polycarbonate (polycarbonate, PC) , characterized in that it is selected from the group consisting of polyvinyl chloride (PVC), cellulose (cellulose), cellulose acetate (cellulose acetate), and mixtures thereof.
본 발명에 있어서, 상기 탄소원은, 액상, 기상 또는 고상 탄소원이고, 상기 액상 탄소원은 에탄올(C2H6O), 벤젠(C6H6), 자일렌(xylene), 톨루엔(C7H8) 및 이의 혼합으로 이루어진 군으로부터 선택되고, 상기 기상 탄소원은 메탄(CH4), 프로필렌(C3H6), 프로파인(C3H4), 프로판(C3H8), 부탄(C4H10), 부틸렌(C4H8), 부타디엔(C4H6), 에틸렌(C2H2) 및 이의 혼합으로 이루어진 군으로부터 선택되며, 상기 고상 탄소원은 캄퍼(C10H16O)인 것을 특징으로 한다.In the present invention, the carbon source is a liquid, gaseous or solid carbon source, and the liquid carbon source is ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ) ) and mixtures thereof, the gaseous carbon source is methane (CH 4 ), propylene (C 3 H 6 ), propine (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 ) H 10 ), butylene (C 4 H 8 ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ), and selected from the group consisting of mixtures thereof, the solid carbon source is camphor (C 10 H 16 O) characterized by being.
본 발명에 있어서, 상기 제3단계와 상기 제4단계의 사이에는, 상기 탄소 함유 고분자 나노섬유를 100 내지 300℃ 범위의 온도에서 예비 열처리를 하는 것을 특징으로 한다.In the present invention, between the third step and the fourth step, the carbon-containing polymer nanofiber is characterized in that the preliminary heat treatment at a temperature in the range of 100 to 300 ℃.
본 발명에 있어서, 상기 제4단계에서는, 비활성 가스 분위기 하에서 800 내지 1,200℃ 범위의 온도에서 열처리하여 상기 탄소 함유 고분자의 탄화가 이루어지는 것을 특징으로 한다.In the present invention, in the fourth step, it is characterized in that the carbon-containing polymer is carbonized by heat treatment at a temperature in the range of 800 to 1,200° C. under an inert gas atmosphere.
상기의 다른 기술적 과제를 해결하기 위하여 본 발명은, 상기 방법으로 제조되는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체를 제공한다.In order to solve the above other technical problems, the present invention provides a carbon nanotube-carbon nanofiber composite, characterized in that produced by the above method.
상기 과제의 해결 수단에 의한 본 발명의 탄소나노튜브-탄소나노섬유 복합체의 제조방법 및 이에 의해 제조되는 탄소나노튜브-탄소나노섬유 복합체는 다음과 같은 효과가 있다.The carbon nanotube-carbon nanofiber composite of the present invention by means of solving the above problems, and the carbon nanotube-carbon nanofiber composite prepared by the method have the following effects.
첫째, 철(Fe), 코발트(Co), 니켈(Ni)과 같은 8족, 9족, 10족의 비알칼리금속 즉, 전이금속 기반의 촉매를 사용하지 않고 리튬(Li), 칼륨(K) 특히 나트륨(Na)과 같은 알칼리금속 기반의 촉매를 사용하기 때문에, 나트륨과 같은 촉매 입자가 단순히 물에 용해되어 쉽게 제거 가능해 메탈-프리(metal-free) 탄소나노튜브-탄소나노섬유 복합체의 합성이 완료된 후 산처리와 같은 세정과정을 거치지 않아도 되므로 환경비용을 절감할 수 있는 효과가 있다.First, lithium (Li), potassium (K) without using a catalyst based on transition metals, that is, non-alkali metals of Groups 8, 9, and 10 such as iron (Fe), cobalt (Co), and nickel (Ni) In particular, since an alkali metal-based catalyst such as sodium (Na) is used, catalyst particles such as sodium are simply dissolved in water and can be easily removed, making the synthesis of metal-free carbon nanotube-carbon nanofiber composites easier. After completion, there is no need to go through a cleaning process such as acid treatment, which has the effect of reducing environmental costs.
둘째, 전기방사를 통해 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조하고, 이를 탄화시킨 후 탄소원을 공급하면서 열처리하는 과정만으로 탄소나노섬유의 표면으로부터 탄소나노튜브를 쉽게 성장시킬 수 있으므로, 탄소나노튜브-탄소나노섬유 복합체를 대량 생산할 수 있는 효과가 있다.Second, carbon nanotubes can be easily grown from the surface of carbon nanofibers only by manufacturing carbon-containing polymer nanofibers having an alkali metal precursor bonded to their surface through electrospinning, carbonizing them, and then heat-treating them while supplying a carbon source. , carbon nanotube-carbon nanofiber composites can be mass-produced.
셋째, 나노촉매를 통해 탄소나노섬유로부터 탄소나노튜브를 성장시켜 탄소나노섬유와 탄소나노튜브의 높은 결착력으로 탄소나노섬유와 탄소나노튜브가 분리되지 않으므로, 전지에 적용 시 수명을 향상시킬 수 있는 효과가 있다.Third, since carbon nanotubes are grown from carbon nanofibers through a nanocatalyst, and carbon nanofibers and carbon nanotubes are not separated due to the high binding force between carbon nanofibers and carbon nanotubes, the lifespan can be improved when applied to batteries there is
넷째, 본 발명을 통해 제조되는 탄소나노튜브-탄소나노섬유 복합체는 각종 장치의 방출원, VFD(Vacuum Fluorescent Display), 백색광원, FED(Field Emission Display), 리튬이온전지용 전극, 수소저장 연료전지, 나노 와이어, 가스센서, 의공학용 미세부품, 고기능성 복합체 등 다양한 에너지 응응(energy application) 분야에 폭넓게 이용될 수 있는 효과가 있다.Fourth, the carbon nanotube-carbon nanofiber composite produced through the present invention is an emission source of various devices, a vacuum fluorescent display (VFD), a white light source, a field emission display (FED), an electrode for a lithium ion battery, a hydrogen storage fuel cell, There is an effect that can be widely used in various energy application fields such as nanowires, gas sensors, micro-parts for biomedical engineering, and high-functional composites.
도 1은 종래 탄소나노튜브와 탄소나노섬유의 복합재료에 발생된 불량을 나타낸 TEM 사진.1 is a TEM photograph showing defects occurring in a conventional composite material of carbon nanotubes and carbon nanofibers.
도 2는 본 발명에 따른 탄소나노튜브-탄소나노섬유 복합체의 제조공정을 나타낸 순서도.Figure 2 is a flow chart showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention.
도 3은 본 발명에 따른 탄소나노튜브-탄소나노섬유 복합체의 제조공정을 나타낸 모식도.Figure 3 is a schematic diagram showing a manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention.
도 4는 본 발명의 알칼리금속 양이온이 배위된 크라운에테르의 구조.4 is a structure of the crown ether coordinated with an alkali metal cation of the present invention.
도 5는 본 발명에 따른 전기방사의 개념도.5 is a conceptual diagram of electrospinning according to the present invention.
도 6은 탄화 열처리로 사진.6 is a photograph of a carbonization heat treatment furnace.
도 7은 탄소나노섬유에 탄소나노튜브를 성장시키기 위한 열처리로 사진.7 is a photograph of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers.
도 8은 본 발명의 실시예 1에 따라 제조된 탄소나노튜브-탄소나노섬유 복합체의 SEM 사진.8 is a SEM photograph of the carbon nanotube-carbon nanofiber composite prepared according to Example 1 of the present invention.
도 9는 본 발명의 실시예 2에 따라 제조된 탄소나노튜브-탄소나노섬유 복합체의 SEM 사진.9 is a SEM photograph of the carbon nanotube-carbon nanofiber composite prepared according to Example 2 of the present invention.
도 10은 탄소나노섬유에 성장되는 탄소나노튜브의 길이를 나타낸 SEM 사진.10 is a SEM photograph showing the length of carbon nanotubes grown on carbon nanofibers.
도 11은 탄소나노섬유에 성장되는 탄소나노튜브의 밀도를 나타낸 SEM 사진.11 is a SEM photograph showing the density of carbon nanotubes grown on carbon nanofibers.
이하, 본 발명을 상세하게 설명하면 다음과 같다.Hereinafter, the present invention will be described in detail as follows.
도 2는 본 발명에 따른 탄소나노튜브-탄소나노섬유 복합체의 제조공정을 순서도로 나타낸 것이고, 도 3은 본 발명에 따른 탄소나노튜브-탄소나노섬유 복합체의 제조공정을 모식도로 나타낸 것으로, 이를 참고하면 본 발명의 탄소나노튜브-탄소나노섬유 복합체는 알칼리금속 전구체를 용매에 용해시켜 알칼리금속 전구체용액을 제조하는 제1단계(S10), 알칼리금속 전구체용액에 탄소 함유 고분자를 용해시켜 방사용액을 제조하는 제2단계(S20), 방사용액을 전기방사하여 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조하는 제3단계(S30), 탄소 함유 고분자 나노섬유를 열처리하여 표면에 알칼리금속 전구체가 결합된 탄소나노섬유를 제조하는 제4단계(S40) 및 탄소나노섬유에 탄소원(carbon source)을 공급하면서 열처리하여 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 나노촉매에 의하여 탄소원이 탄소나노섬유의 표면에 결합되면서 탄소나노튜브로 결정화되어 성장하여, 표면에 탄소나노튜브가 결합된 탄소나노섬유를 제조하는 제5단계(S50)를 통하여 제조되며, 각각의 단계에 대한 특징은 다음과 같다.2 is a flowchart showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention, and FIG. 3 is a schematic diagram showing the manufacturing process of the carbon nanotube-carbon nanofiber composite according to the present invention, see this When the carbon nanotube-carbon nanofiber composite of the present invention is a first step (S10) of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution, a carbon-containing polymer is dissolved in an alkali metal precursor solution to prepare a spinning solution A second step (S20) of electrospinning a spinning solution to produce a carbon-containing polymer nanofiber bonded to an alkali metal precursor on the surface (S30), heat treatment of the carbon-containing polymer nanofiber to an alkali metal precursor on the surface In the fourth step (S40) of manufacturing the bonded carbon nanofibers and heat treatment while supplying a carbon source to the carbon nanofibers, the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is carbon nanofiber by the nanocatalyst It is produced through a fifth step (S50) of crystallizing and growing into carbon nanotubes while being bonded to the surface of the fiber to produce carbon nanofibers having carbon nanotubes bonded to the surface, and the characteristics of each step are as follows. .
먼저, 알칼리금속 전구체를 용매에 용해시켜 알칼리금속 전구체용액을 제조한다(S10).First, an alkali metal precursor is dissolved in a solvent to prepare an alkali metal precursor solution (S10).
기존에는 탄소나노섬유에 탄소나노튜브 성장을 위해 철(Fe), 코발트(Co), 니켈(Ni)과 같은 8족, 9족, 10족의 비알칼리금속 즉, 전이금속 기반의 촉매가 주로 사용되었는데, 비알칼리금속촉매를 나노입자 형태로 만들어 탄소나노튜브의 합성 및 성장이 완료되면 다시 비알칼리금속촉매의 금속 상태로 잔존하는 나노입자들을 제거하기 위해 산처리 등 추가 공정이 필요하고, 산처리를 하려면 세정수도 필요하기 때문에 환경비용 증가에 따른 부담이 있어왔다.Conventionally, for the growth of carbon nanotubes on carbon nanofibers, non-alkali metals of Groups 8, 9, and 10 such as iron (Fe), cobalt (Co), and nickel (Ni), that is, transition metal-based catalysts are mainly used. When the synthesis and growth of carbon nanotubes is completed by making the non-alkali metal catalyst in the form of nanoparticles, an additional process such as acid treatment is required to remove the nanoparticles remaining in the metallic state of the non-alkali metal catalyst, and acid treatment In order to do this, washing water is required, so there has been a burden due to the increase in environmental costs.
이에 따라 본 단계에서는 수소를 제외한 1족 원소를 기반으로 한 알칼리금속 전구체를 용매에 용해시켜 알칼리금속 전구체용액을 제조함으로써, 이러한 알칼리금속 전구체용액의 알칼리금속은 제5단계에서 나노촉매로 활성화되어 탄소나노섬유의 표면으로부터 탄소나노튜브가 성장될 수 있도록 하고, 추후 산처리와 같은 별도의 과정을 거쳐 나노촉매를 제거하지 않고도 물에 쉽게 녹아 제거되므로 고순도의 탄소나노튜브-탄소나노섬유 복합체의 합성이 가능하다.Accordingly, in this step, an alkali metal precursor solution based on a Group 1 element other than hydrogen is dissolved in a solvent to prepare an alkali metal precursor solution. It allows the carbon nanotubes to grow from the surface of the nanofibers and is easily dissolved in water and removed without removing the nanocatalyst through a separate process such as acid treatment later, so that the synthesis of high-purity carbon nanotube-carbon nanofiber composites is possible. possible.
알칼리금속 전구체는 리튬전구체(Li precursor), 나트륨전구체(Na precursor), 칼륨전구체(K precursor) 및 이의 혼합으로 이루어진 군으로부터 선택된다. 즉 알칼리금속 전구체는 리튬(Li), 나트륨(Na) 및 칼륨(K)으로 이루어진 군에서 선택되는 1종 이상의 알칼리금속염(alkali metal salts), 알칼리금속 유기화합물(alkali metal organic compounds) 또는 알칼리금속 무기화합물(alkali metal inorganic compounds)로 구성된다 할 수 있다.The alkali metal precursor is selected from the group consisting of a lithium precursor (Li precursor), a sodium precursor (Na precursor), a potassium precursor (K precursor), and a mixture thereof. That is, the alkali metal precursor is one or more alkali metal salts selected from the group consisting of lithium (Li), sodium (Na) and potassium (K), alkali metal organic compounds, or alkali metal inorganic compounds. It can be said that it is composed of alkali metal inorganic compounds.
예를 들어, 리튬이 포함된 화합물인 리튬전구체의 경우에는 리튬 벤조에이트(Lithium benzoate), 염화리튬(Llithium chloride, LiCl) 및 이의 혼합으로 이루어진 군으로부터 선택되고, 나트륨이 포함된 화합물인 나트륨전구체의 경우에는 나트륨 벤조에이트(sodium benzoate), 염화나트륨(sodium chloride, NaOH), 중탄산 나트륨(sodium bicarbonate, NaHCO3) 및 이의 혼합으로 이루어진 군으로부터 선택되며, 칼륨이 포함된 화합물인 칼륨전구체의 경우에는 포타슘 벤조에이트(Potassium benzoate), 염화칼륨(Potassium chloride), 포타슘 하이드록사이드(Potassium hydroxide) 및 이의 혼합으로 이루어진 군으로부터 선택된다.For example, in the case of a lithium precursor, which is a compound containing lithium, it is selected from the group consisting of lithium benzoate, lithium chloride (LiCl), and mixtures thereof, and the sodium precursor is a compound containing sodium. In the case of sodium benzoate (sodium benzoate), sodium chloride (sodium chloride, NaOH), sodium bicarbonate (sodium bicarbonate, NaHCO 3 ) and mixtures thereof, it is selected from the group consisting of, and in the case of a potassium precursor, which is a compound containing potassium, potassium benzoate It is selected from the group consisting of ate (Potassium benzoate), potassium chloride (Potassium chloride), potassium hydroxide (Potassium hydroxide) and mixtures thereof.
용매는 극성용매 또는 비극성용매로 이루어지는데, 물, 디메틸포름아미드(dimethylformamide, DMF), 탄소수 1 내지 5의 저급 알코올 및 이의 혼합으로 이루어진 군으로부터 선택되는 극성용매이거나, 자일렌(xylene), 벤젠(benzene), 톨루엔(toluene) 및 이의 혼합으로 이루어진 군으로부터 선택되는 비극성용매를 선택하여 사용할 수 있다.The solvent consists of a polar solvent or a non-polar solvent, and is a polar solvent selected from the group consisting of water, dimethylformamide (DMF), lower alcohols having 1 to 5 carbon atoms, and mixtures thereof, or xylene, benzene ( A non-polar solvent selected from the group consisting of benzene), toluene, and mixtures thereof may be selected and used.
이처럼 용매에 알칼리금속 전구체가 혼합된 알칼리금속 전구체용액은 다음과 같은 두가지 방식으로 제조된다.As such, an alkali metal precursor solution in which an alkali metal precursor is mixed in a solvent is prepared in the following two ways.
첫번째로, 디메틸포름아미드와 같은 극성용매에 알칼리금속 전구체를 용해시켜 알칼리금속 전구체용액을 제조하는 방식이다.First, an alkali metal precursor solution is prepared by dissolving an alkali metal precursor in a polar solvent such as dimethylformamide.
이 경우, 알칼리금속 전구체의 사용량은 특별히 제한되지는 않으나, 용매 1ℓ 당 0.01mol 미만으로 혼합되면 제5단계의 열처리가 이루어질 때 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화 또는 기능화되지 못해 탄소나노섬유의 표면으로부터 탄소나노튜브가 성장될 수 있는 시점까지 시간이 많이 소요될 뿐만 아니라, 제5단계에서 공급되는 탄소원이 탄소나노튜브로 성장되지 못하기도 하는 경우가 생겨 에너지 애플리케이션(energy application) 분야에 적용하기에 한계가 있으며, 특히 알칼리금속 전구체가 너무 적은 양으로 첨가되면 반응속도를 높일 수 없기 때문에 생산효율 측면에서 바람직하지 못하다.In this case, the amount of the alkali metal precursor used is not particularly limited, but when mixed at less than 0.01 mol per 1 liter of solvent, the alkali metal precursor cannot be activated or functionalized with the alkali metal nano catalyst when the fifth step heat treatment is performed. Not only does it take a lot of time until the point at which carbon nanotubes can be grown from the surface, but there are also cases where the carbon source supplied in the fifth step cannot be grown into carbon nanotubes, so it is limited in application to energy application fields. In particular, when the alkali metal precursor is added in an excessively small amount, the reaction rate cannot be increased, which is not preferable in terms of production efficiency.
반면, 용매 1ℓ 당 알칼리금속 전구체가 0.05mol을 초과하면 제5단계에서 열처리되는 도중에 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화 또는 기능화된 후 나노촉매들이 오히려 탄소나노튜브에 일부 부착된 상태로 잔류하게 되어 탄소나노섬유에 성장된 탄소나노튜브의 순도가 저하된다.On the other hand, if the alkali metal precursor per 1 liter of solvent exceeds 0.05 mol, the alkali metal precursor is activated or functionalized with the alkali metal nanocatalyst during the heat treatment in the fifth step, and then the nanocatalysts remain partially attached to the carbon nanotubes. Thus, the purity of the carbon nanotubes grown on the carbon nanofibers is reduced.
이런 이유로, 알칼리금속 전구체는 용매 1ℓ 당 0.01 내지 0.05mol의 범위로 용해시키는 것이 바람직하며, 나노촉매로의 최적 활성을 고려하여 0.02mol이 가장 바람직하다.For this reason, it is preferable to dissolve the alkali metal precursor in the range of 0.01 to 0.05 mol per 1 liter of solvent, and 0.02 mol is most preferable in consideration of the optimal activity as a nanocatalyst.
두번째로, 크라운에테르(crown ether)의 첨가로 알칼리금속 전구체의 알칼리금속 양이온이 크라운에테르의 공동(cavity)에 배위되도록 하여 착물을 이룸으로써, 알칼리금속 양이온을 용매화하여 알칼리금속 전구체용액을 제조하는 방식이다.Second, by adding a crown ether, the alkali metal cation of the alkali metal precursor is coordinated to the cavity of the crown ether to form a complex, thereby solvating the alkali metal cation to prepare an alkali metal precursor solution. method.
크라운에테르(x-Crown ether-y; x는 고리에 있는 모든 원자수, y는 산소 원자수)는 에틸렌옥시(-CH2CH2O-) 단위가 반복되는 에틸렌옥사이드(ethylene oxide)의 올리고머(oligomer)인데, 알칼리금속 전구체용액 중의 알칼리금속 양이온을 크라운에테르의 중심에 있는 공동에 넣음에 따라 알칼리금속 양이온으로 안정된 구조를 형성함으로써, 알칼리금속 양이온이 용매화되면서 용해되도록 하여, 특히 비극성용매 중에 용질인 알칼리금속 전구체의 용해도를 높이게 된다. 즉 크라운에테르가 금속이온 즉, Li+, Na+, K+과 같은 알칼리금속 양이온과 안정된 착물을 만들기 때문에 벤젠, 자일렌, 톨루엔과 같이 탄화수소로 이루어진 비극성용매에 녹지 않는 알칼리금속 전구체를 잘 녹게 용매화할 수 있게 되는 것이다.Crown ether (x-Crown ether-y; x is the number of all atoms in the ring, y is the number of oxygen atoms) is an oligomer of ethylene oxide in which ethyleneoxy (-CH 2 CH 2 O-) units are repeated ( oligomer), which forms a stable structure with alkali metal cations as the alkali metal cations in the alkali metal precursor solution are put into the cavity at the center of the crown ether, so that the alkali metal cations are solvated and dissolved, especially in non-polar solvents. The solubility of the phosphorus alkali metal precursor is increased. In other words, since crown ether forms a stable complex with metal ions, that is, alkali metal cations such as Li + , Na + , K + It will be able to bloom.
알칼리금속 전구체가 크라운에테르를 통해 용매에 용해되면 투명색의 알칼리금속 전구체용액으로 전환되고, 최대한 많은 양의 알칼리금속 전구체를 용해시키기 위해서는 크라운에테르와의 비율을 조절하는 것이 좋으며(예컨대, 알칼리금속 전구체와 크라운에테르의 중량비는 1:0.1~100일 수도 있다.), 크라운에테르의 양 조절로 알칼리금속 전구체용액의 용해도 조절도 가능하다. 단, 알칼리금속 전구체와 크라운에테르가 혼합될 수 있는 양은 한정하지 않기로 한다.When the alkali metal precursor is dissolved in the solvent through the crown ether, it is converted into a transparent alkali metal precursor solution. The weight ratio of the crown ether may be 1:0.1-100.), it is also possible to control the solubility of the alkali metal precursor solution by adjusting the amount of the crown ether. However, the amount in which the alkali metal precursor and the crown ether can be mixed is not limited.
크라운에테르의 경우, 12-Crown-4, 15-Crown-5, 18-Crown-6 및 이의 혼합으로 이루어진 군으로부터 선택하여 사용할 수 있는데, 이는 본 발명의 알칼리금속 양이온이 배위된 크라운에테르의 구조를 나타낸 도 4를 통해 확인 가능하다. 도 4(a)는 Li+와 착물을 형성하는 12-Crown-4를 예시적으로 나타낸 것이고, 도 4(b)는 Na+와 착물을 형성하는 15-Crown-5를 예시적으로 나타낸 것이며, 도 4(c)는 K+과 착물을 형성하는 18-Crown-6을 예시적으로 나타낸 것이다. 도 4를 참조하면, 크라운에테르는 Crown을 구성하는 산소원자가 Crown 내의 공동에 알칼리금속 양이온을 배위하는데 도움을 주며, Crown 크기에 따라 안정된 착물이 형성되는 이온의 종류가 다름을 알 수 있다. 즉 Li+은 12-Crown-4와 가장 안정적인 착물을 형성시키고, Na+은 15-Crown-5과 가장 안정적인 착물을 형성시키며, K+은 18-Crown-6과 가장 안정적인 착물을 형성시키는 것을 통해 확인 가능하다.In the case of crown ether, it can be used by selecting from the group consisting of 12-Crown-4, 15-Crown-5, 18-Crown-6, and mixtures thereof. It can be confirmed through FIG. 4 shown. Figure 4 (a) is an illustrative example of 12-Crown-4 forming a complex with Li + , Figure 4 (b) is an illustrative example of 15-Crown-5 forming a complex with Na +, FIG. 4( c ) exemplarily shows 18-Crown-6 forming a complex with K + . 4, it can be seen that the crown ether helps the oxygen atoms constituting the crown to coordinate alkali metal cations to the cavity in the crown, and the types of ions that form a stable complex depend on the size of the crown. That is, Li + forms the most stable complex with 12-Crown-4, Na + forms the most stable complex with 15-Crown-5, and K + forms the most stable complex with 18-Crown-6. can be checked
특히 첫번째 방식에서 제시된 물이나 디메틸포름아미드와 같은 용매는 극성이어서 알칼리금속 전구체가 잘 녹으나, 극성용매와 다른 비극성용매(예를 들면, 자일렌) 중에는 알칼리금속 전구체가 녹지 않기 때문에 크라운에테르가 용질을 용매화시켜 용해도를 높이는데 중요한 역할을 하게 된다.In particular, the solvents such as water or dimethylformamide presented in the first method are polar, so alkali metal precursors are easily dissolved, but in polar solvents and other non-polar solvents (eg, xylene), the alkali metal precursor does not dissolve, so crown ether is the solute. It solvates and plays an important role in increasing solubility.
다음으로, 알칼리금속 전구체용액에 탄소 함유 고분자를 용해시켜 방사용액을 제조한다(S20).Next, a carbon-containing polymer is dissolved in an alkali metal precursor solution to prepare a spinning solution (S20).
알칼리금속 전구체용액 85 내지 99wt%에 탄소를 포함하는 고분자 1 내지 15wt%를 첨가해 교반하면서 용해시켜 전기방사가 이루어질 수 있는 방사용액을 제조한다.1 to 15 wt% of a polymer containing carbon is added to 85 to 99 wt% of the alkali metal precursor solution and dissolved while stirring to prepare a spinning solution capable of electrospinning.
특히 탄소 함유 고분자가 1wt% 미만이면 방사용액이 전기방사되더라도 균일한 형상의 탄소 함유 고분자 나노섬유를 만들어주기 어렵고, 15wt%를 초과하면 알칼리금속 전구체용액이 상대적으로 적게 함유되기 때문에 추후 제5단계에서 활성화되는 나노촉매의 양도 상대적으로 줄어들어 탄소나노섬유의 표면으로부터 성장될 수 있는 탄소나노튜브의 양도 줄어들게 된다. 다른 말로, 알칼리금속 전구체용액이 85wt% 미만이면 활성화되는 나노촉매의 양이 적어지기 때문에 성장시킬 수 있는 탄소나노튜브의 양 역시 적어지는 단점이 있으며, 알칼리금속 전구체용액이 99wt%를 초과하면 탄소나노섬유에 나노촉매가 형성될 수 있는 공간이 부족하여 탄소나노튜브의 성장이 안정적으로 이루어지지 못하는 단점이 있다. 탄소 함유 고분자 나노섬유로의 완전한 성형 후 탄소나노섬유에 탄소나노튜브를 안정적으로 성장시키기 위해서는 알칼리금속 전구체용액 내의 용매 휘발을 고려하여 탄소 함유 고분자가 9wt%로 포함되는 것이 가장 바람직하다.In particular, if the carbon-containing polymer is less than 1 wt%, even if the spinning solution is electrospun, it is difficult to make carbon-containing polymer nanofibers with a uniform shape, and if it exceeds 15 wt%, the alkali metal precursor solution is relatively small. The amount of the activated nanocatalyst is also relatively reduced, so that the amount of carbon nanotubes that can be grown from the surface of the carbon nanofibers is also reduced. In other words, if the alkali metal precursor solution is less than 85wt%, the amount of activated nanocatalyst is reduced, so the amount of carbon nanotubes that can be grown is also reduced. There is a disadvantage in that the growth of carbon nanotubes cannot be stably performed due to insufficient space in which the nanocatalyst can be formed in the fiber. In order to stably grow carbon nanotubes on carbon nanofibers after complete molding into carbon-containing polymer nanofibers, it is most preferable that the carbon-containing polymer be contained in an amount of 9wt% in consideration of solvent volatilization in the alkali metal precursor solution.
탄소 함유 고분자는 탄소나노섬유 전구체라 할 수 있는데, 폴리아크릴로니트릴(polyacrylonitrile, PAN), 폴리비닐아세테이트(polyvinyl acetate, PVA), 폴리비닐피롤리돈(polyvinyl pyrrolidone, PVP), 폴리카보네이트(polycarbonate, PC), 폴리비닐클로라이드(polyvinyl chloride, PVC), 셀룰로오스(cellulose), 셀룰로오스아세테이트(cellulose acetate) 및 이의 혼합으로 이루어진 군으로부터 선택될 수 있으며, 본 발명에서는 폴리아크릴로니트릴을 적용하기로 하였으나, 탄소나노섬유로 형성될 수 있는 탄소 함유 고분자라면 특별히 제한되지 않는다.Carbon-containing polymers can be called carbon nanofiber precursors, polyacrylonitrile (PAN), polyvinyl acetate (PVA), polyvinyl pyrrolidone (PVP), polycarbonate (polycarbonate, PC), polyvinyl chloride (PVC), cellulose, cellulose acetate, and mixtures thereof may be selected from the group consisting of, and in the present invention, polyacrylonitrile is applied, but carbon It is not particularly limited as long as it is a carbon-containing polymer that can be formed into nanofibers.
다음으로, 방사용액을 전기방사(electrospinning)하여 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조한다(S30).Next, by electrospinning the spinning solution (electrospinning) to prepare a carbon-containing polymer nanofiber bonded to the alkali metal precursor on the surface (S30).
본 단계는 방사용액을 파이버 형태의 탄소 함유 고분자 나노섬유를 제조하기 위한 것으로, 본 발명에 따른 전기방사의 개념도를 나타낸 도 5를 참조하면 전기방사를 하기 위해 우선 노즐에 (+) 또는 (-) 고전압 단자를 연결해주고, 전도체에 접지를 연결해준 상태에서 충분히 높은 전압을 인가해주게 되면 노즐과 전도체 사이에 전자기장이 형성되어 노즐 내부에 있는 방사용액이 영향을 받게 되면서 전자기력이 방사용액의 표면장력과 점도보다 크게 되면 테일러 콘(taylor cone)이 형성되고 그 끝에서 스트레칭되어 나노 크기의 복합섬유인 복합나노섬유가 만들어진다. 단, 본 발명에서 언급되는 '복합나노섬유'와 '나노 크기의 복합섬유'는 '표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유'를 의미한다.This step is for producing a carbon-containing polymer nanofiber in the form of a fiber with a spinning solution. Referring to FIG. 5 showing a conceptual diagram of electrospinning according to the present invention, in order to perform electrospinning, first (+) or (-) When a high voltage terminal is connected and a sufficiently high voltage is applied with the conductor connected to the ground, an electromagnetic field is formed between the nozzle and the conductor, and the spinning solution inside the nozzle is affected, and the electromagnetic force changes the surface tension and viscosity of the spinning solution. When it becomes larger, a taylor cone is formed and stretched at the tip to form composite nanofibers, which are nano-sized composite fibers. However, 'composite nanofibers' and 'nano-sized composite fibers' referred to in the present invention mean 'carbon-containing polymer nanofibers having an alkali metal precursor bonded to the surface'.
전기방사를 통해 나노 크기의 복합섬유 제작을 위하여 탄소 함유 고분자의 분자무게, 방사용액의 특성, 전압, 노즐과 전도체와의 거리, 탄소 함유 고분자의 유체량 및 농도, 매개변수, 노즐의 움직임, 전도체의 사이즈, 노즐의 크기 조건을 충족시키는 것이 바람직하며, 각각의 조건에 대하여 아래에서 상세히 설명해 보기로 한다.For the production of nano-sized composite fibers through electrospinning, the molecular weight of the carbon-containing polymer, the characteristics of the spinning solution, the voltage, the distance between the nozzle and the conductor, the amount and concentration of the carbon-containing polymer, the parameters, the movement of the nozzle, the conductor It is desirable to satisfy the size and nozzle size conditions of , and each condition will be described in detail below.
탄소 함유 고분자의 분자무게 조건은 다음과 같다. 즉 탄소를 포함하는 폴리머의 분자무게(Mw)가 45,000 미만이거나 1,000,000을 초과하면 복합나노섬유로의 형성이 균일하게 이루어지기 어려우므로, 45,000 내지 1,000,000 범위로 이루어지도록 하는 것이 바람직하다. The molecular weight conditions of the carbon-containing polymer are as follows. That is, if the molecular weight (M w ) of the polymer containing carbon is less than 45,000 or exceeds 1,000,000, it is difficult to form a composite nanofiber uniformly, so it is preferable to make it in the range of 45,000 to 1,000,000.
방사용액의 특성 조건은 다음과 같다. 방사용액의 점도와 관련하여, 1Pa·s 미만이면 점도가 너무 낮아 방사용액이 전기방사되는 과정에서 나노 크기의 복합섬유로 형성되기 전에 끊어짐으로써 복합나노섬유 형상이 아닌 droplet 형태로 만들어지고, 1,000Pa·s을 초과하면 점도가 너무 높아져서 노즐로부터 용출을 하기 위해서는 더 많은 전자기력이 필요하게 되고 그로 인해 과전류가 발생하여 실험 기자재가 타버리는 경우가 생기기 때문에, 1 내지 1,000Pa·s 범위의 점도를 갖는 것이 바람직하다. 방사용액의 전도도와 관련하여, 53㎲/cm를 초과하면 탄소나노섬유 형성에 적절하지 않아 방사용액은 53㎲/cm 이하의 전도도를 갖는 것이 바람직하다. 방사용액의 표면장력과 관련하여, 450dyn/cm를 초과하면 전자기력이 방사용액의 표면장력보다 작게 되어 테일러 콘 형성이 이루어지지 않아 복합나노섬유 형상이 이루어지기 어려운 단점이 있으므로, 방사용액의 표면장력은 450dyn/cm 이하로 이루어지는 것이 바람직하다.The characteristic conditions of the spinning solution are as follows. Regarding the viscosity of the spinning solution, if it is less than 1 Pa·s, the viscosity is too low and the spinning solution breaks before it is formed into nano-sized composite fibers in the process of electrospinning. If it exceeds s, the viscosity becomes too high and more electromagnetic force is required to elution from the nozzle, which causes overcurrent and burns the experimental equipment. desirable. With respect to the conductivity of the spinning solution, if it exceeds 53 μs/cm, it is not suitable for carbon nanofiber formation, so it is preferable that the spinning solution has a conductivity of 53 μs/cm or less. With respect to the surface tension of the spinning solution, if it exceeds 450 dyn/cm, the electromagnetic force becomes smaller than the surface tension of the spinning solution, and Taylor cone formation does not occur, making it difficult to form a composite nanofiber. It is preferably made of 450 dyn/cm or less.
전압 조건은 다음과 같다. 방사용액의 전기방사를 위해 30kV 이하의 전압을 인가해주게 되면 노즐과 전도체 사이에 전자기장이 형성되므로, 굳이 30kV를 초과하는 전압을 인가해줄 필요성은 없다.Voltage conditions are as follows. When a voltage of 30 kV or less is applied for electrospinning of the spinning solution, an electromagnetic field is formed between the nozzle and the conductor, so there is no need to apply a voltage exceeding 30 kV.
노즐과 전도체와의 거리 조건은 다음과 같다. 즉 방사용액이 수용된 노즐과 전도체와의 거리가 30cm 이하로 이루어지면 나노 크기의 복합섬유로 형성된다. 만약 노즐과 전도체와의 거리가 30cm를 초과하면 노즐 및 전도체 간 거리가 너무 멀어서 전자기력이 작아져 복합섬유의 나노 크기를 균일하게 만들어주기 힘들 뿐만 아니라, 나노섬유가 아닌 droplet 형태가 보일 수 있는 단점이 있다.The distance condition between the nozzle and the conductor is as follows. That is, when the distance between the nozzle in which the spinning solution is accommodated and the conductor is less than 30 cm, the nano-sized composite fiber is formed. If the distance between the nozzle and the conductor exceeds 30 cm, the distance between the nozzle and the conductor is too far and the electromagnetic force is small, making it difficult to make the nano-size of the composite fiber uniform, as well as the disadvantage that the form of droplets rather than nanofibers can be seen. there is.
탄소 함유 고분자의 유체량 및 농도 조건은 다음과 같다. 유체량의 경우 25㎖/min 이하이어야 방사용액이 테일러 콘으로 형성되면서 나노섬유로 스트레칭이 잘 되나, 25㎖/min를 초과하면 유체량이 너무 많아 스트레칭되는 양이 적어 균일하지 못한 나노섬유로 제조될 확률이 높아져 불량률 또한 높아질 수 있다. 농도의 경우 나노 크기의 복합섬유로 제조되기 위해 30wt%면 충분하다.The fluid amount and concentration conditions of the carbon-containing polymer are as follows. When the amount of fluid is 25ml/min or less, the spinning solution is formed into a Taylor cone so that the nanofibers can be stretched well. The higher the probability, the higher the defect rate. In the case of concentration, 30 wt% is sufficient to be manufactured into nano-sized composite fibers.
매개변수 조건은 다음과 같다. 매개변수는 온도, 습도, 공기흐름 등의 기본적인 환경적인 측면에 관한 것으로, 35℃ 이하의 온도, 60% 이하의 습도, 1 이하의 공기흐름 환경이라면 전기방사를 통해 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유로 제조 가능하다.The parameter conditions are as follows. The parameters relate to basic environmental aspects such as temperature, humidity, and airflow. In the case of a temperature of 35℃ or less, a humidity of 60% or less, and an airflow environment of 1 or less, the alkali metal precursor is bonded to the surface through electrospinning. It can be manufactured from carbon-containing polymer nanofibers.
노즐의 움직임, 전도체의 사이즈 조건은 다음과 같다. 우선 노즐의 움직임은 0.1mm/min 이하인 경우에만 전기방사를 통해 방사용액이 전도체로 안정적으로 스트레칭되고, 전도체의 사이즈는 10㎠ 이상만 되더라도 노즐로부터 전기방사되는 복합나노섬유가 전도체에 포집이 안정적으로 이루어질 수 있다. 다만, 전도체의 사이즈가 10㎠ 미만이면 면적이 너무 작아 복합나노섬유를 충분히 포집할 수 있는 공간을 확보하지 못하는 단점이 있다.The nozzle movement and conductor size conditions are as follows. First of all, the spinning solution is stably stretched to the conductor through electrospinning only when the movement of the nozzle is 0.1mm/min or less, and even if the size of the conductor is 10cm2 or more, the composite nanofibers electrospun from the nozzle are stably captured by the conductor. can be done However, if the size of the conductor is less than 10 cm 2 , the area is too small to secure a space to sufficiently collect the composite nanofibers.
노즐의 크기 조건은 다음과 같다. 노즐 크기가 0.01mm 미만이거나 1.7mm를 초과하면 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유로의 형성에 도움을 주지 못하므로, 노즐 크기는 0.01 내지 1.7mm 범위로 이루어지는 것이 바람직하다.The nozzle size conditions are as follows. If the nozzle size is less than 0.01 mm or exceeds 1.7 mm, it does not help the formation of carbon-containing polymer nanofibers bonded to the surface of the alkali metal precursor, so the nozzle size is preferably in the range of 0.01 to 1.7 mm.
다음으로, 탄소 함유 고분자 나노섬유를 열처리하여 표면에 알칼리금속 전구체가 결합된 탄소나노섬유를 제조한다(S40).Next, the carbon-containing polymer nanofibers are heat-treated to prepare carbon nanofibers having an alkali metal precursor bonded to the surface (S40).
본 단계에 앞서 탄화를 통해 탄소나노섬유를 제조하기 전, 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 대기 하에서 8 내지 12℃/min 승온 속도로 100 내지 300℃가 되도록 하여 20분 내지 1시간 동안 예비 열처리를 통해 탄소 함유 고분자를 안정화시킨다. 이때 100℃ 미만으로 예비 열처리되면 탄소 함유 고분자 나노섬유를 안정화시키기 어렵고, 300℃를 초과하여 예비 열처리가 이루어지면 온도가 필요 이상으로 높아 탄소 함유 고분자 나노섬유의 형상 또는 물성의 변질을 야기할 수 있다. 승온 속도의 경우 8 내지 12℃/min일 수 있으며, 10℃/min가 가장 바람직하다. 또한 20분 미만으로 예비 열처리가 이루어지면 온도 조건과 마찬가지로 탄소 함유 고분자 나노섬유의 탄소 함유 고분자를 안정화시키기 어려우며, 1시간을 초과하여 예비 열처리가 이루어지면 그 이하의 시간으로 수행된 경우와 비교하여 탁월한 효과가 없다. 특히 대기 중 산소 환경에서 예비 열처리를 해야 산소공급이 원활하여 빠른 속도로 탄소 함유 고분자 나노섬유로 형성시킬 수 있는 장점이 있다.Prior to this step, before preparing carbon nanofibers through carbonization, the carbon-containing polymer nanofibers having an alkali metal precursor bonded to the surface are heated to 100 to 300° C. at a temperature increase rate of 8 to 12° C./min in the atmosphere for 20 minutes to The carbon-containing polymer is stabilized through preliminary heat treatment for 1 hour. At this time, if the preliminary heat treatment is less than 100 ℃, it is difficult to stabilize the carbon-containing polymer nanofibers, and if the preliminary heat treatment is made above 300 ℃, the temperature is higher than necessary, which may cause deterioration of the shape or physical properties of the carbon-containing polymer nanofibers. . In the case of a temperature increase rate, it may be 8 to 12° C./min, and 10° C./min is most preferred. In addition, when the preliminary heat treatment is performed in less than 20 minutes, it is difficult to stabilize the carbon-containing polymer of the carbon-containing polymer nanofibers as in the temperature condition. There is no effect. In particular, it has the advantage of being able to rapidly form carbon-containing polymer nanofibers because oxygen supply is smooth only when preliminary heat treatment is performed in an oxygen environment in the atmosphere.
탄소 함유 고분자를 안정화시킨 탄소 함유 고분자 나노섬유의 형성 이후, 이어서 비활성 가스 분위기 하에서 3 내지 7℃/min 승온 속도로 800 내지 1,200℃가 되도록 하여 30분 내지 1시간 30분 동안 추가적인 열처리를 통해 탄화시킨 다음, 자연냉각과정을 거쳐 탄소나노섬유의 제조가 완료된다. 여기서의 탄화는 탄소 함유 고분자 나노섬유를 이루는 탄소 함유 고분자의 탄소/수소 비율을 증가시키는 열처리 공정을 의미하는 것으로, 탄소 함유 성분을 탄소로 전환시키는 공정을 의미한다.After the formation of carbon-containing polymer nanofibers in which the carbon-containing polymer is stabilized, it is then carbonized through additional heat treatment for 30 minutes to 1 hour and 30 minutes in an inert gas atmosphere at a temperature increase rate of 3 to 7° C./min to 800 to 1,200° C. Next, the production of carbon nanofibers is completed through a natural cooling process. Carbonization herein refers to a heat treatment process for increasing the carbon/hydrogen ratio of the carbon-containing polymer constituting the carbon-containing polymer nanofiber, and refers to a process for converting carbon-containing components into carbon.
탄화를 위한 열처리 온도와 관련하여, 800℃ 미만으로 열처리하면 불완전한 탄화로 탄소 함유 고분자의 탄화가 완료되기까지 많은 시간이 소요되어 완전한 탄화를 기대할 수 없기 때문에 탄소나노섬유의 표면 등이 손상된다. 이와 달리, 1,200℃를 초과하면 오히려 온도가 필요 이상으로 높아 탄소 함유 고분자가 탄소로 충분히 전환되지 않거나 과도한 열처리로 인해 탄소나노섬유의 물성 개선 정도가 감소될 뿐만 아니라, 너무 높은 온도로 인해 탄소나노섬유에 포함된 알칼리금속 전구체가 기화되어 없어져 추후 나노촉매 형성에 어려움이 생긴다. 완전 탄화를 위해서는 1,000℃로 열처리가 이루어지는 것이 가장 바람직하다.Regarding the heat treatment temperature for carbonization, if the heat treatment is less than 800° C., it takes a lot of time to complete carbonization of the carbon-containing polymer due to incomplete carbonization, so that complete carbonization cannot be expected, so the surface of carbon nanofibers are damaged. On the other hand, if the temperature exceeds 1,200° C., the temperature is rather high, so that the carbon-containing polymer is not sufficiently converted to carbon or the degree of improvement in the properties of carbon nanofibers is reduced due to excessive heat treatment. The alkali metal precursor contained in the vaporized and disappeared, resulting in difficulties in the formation of the nano-catalyst in the future. For complete carbonization, it is most preferable to heat treatment at 1,000°C.
탄화를 위한 승온 속도와 관련하여, 3 내지 7℃/min로써 앞서 탄소 함유 고분자 나노섬유를 안정화시키기 위한 예비 열처리를 할 때와 비교하여 승온 속도가 상대적으로 느린 이유는 탄화과정으로 가면서 온도가 높아지는 중에 탄소나노섬유로 형성되는데 문제가 없는지의 여부를 확인함과 동시에 탄소나노섬유의 물성 변질을 방지하기 위함이다. 안정적인 탄소나노섬유 제조를 위해 5℃/min로 수행되는 것이 가장 바람직하다.With respect to the temperature increase rate for carbonization, the reason why the temperature increase rate is relatively slow compared to when the preliminary heat treatment for stabilizing the carbon-containing polymer nanofibers is 3 to 7 °C/min is during the carbonization process while the temperature is increasing. This is to check whether there is any problem in the formation of carbon nanofibers and at the same time to prevent deterioration of the physical properties of carbon nanofibers. It is most preferably carried out at 5° C./min for stable carbon nanofiber production.
탄화를 위한 열처리 시간과 관련하여, 30분 미만으로 이루어지면 목적으로 하는 탄화 효과가 미미하고, 1시간 30분을 초과하면 너무 긴 시간으로 인해 공정상 비효율적인 측면이 부각된다. 공정상 효율 측면에서 가장 바람직하게는 60분 동안 열처리하여 탄화시키는 것이 좋다.Regarding the heat treatment time for carbonization, if it is made less than 30 minutes, the target carbonization effect is insignificant, and if it exceeds 1 hour and 30 minutes, the inefficient aspect in the process is highlighted due to too long time. In terms of process efficiency, most preferably, it is good to heat-treat for 60 minutes to carbonize it.
탄화과정에서 비활성 가스 분위기라 함은, 예를 들면 헬륨, 질소, 아르곤, 이산화탄소 등의 가스, 보다 구체적으로는 질소(N2) 가스를 이용할 수 있다. 즉 탄소 함유 고분자 나노섬유의 탄소 함유 고분자는 비활성 분위기 하에서의 열처리에 의해 탄화되어 탄소나노섬유로 전환될 수 있는 것이다.In the carbonization process, the inert gas atmosphere may be, for example, a gas such as helium, nitrogen, argon, or carbon dioxide, more specifically, a nitrogen (N 2 ) gas. That is, the carbon-containing polymer of the carbon-containing polymer nanofiber can be converted to carbon nanofiber by being carbonized by heat treatment in an inert atmosphere.
마지막으로, 탄소나노섬유에 탄소원(carbon source)을 공급하면서 열처리하여 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 나노촉매에 의하여 탄소원이 탄소나노섬유의 표면에 결합되면서 탄소나노튜브로 결정화되어 성장하여, 표면에 탄소나노튜브가 결합된 탄소나노섬유를 제조한다(S50).Finally, by heat treatment while supplying a carbon source to the carbon nanofibers, the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bonded to the surface of the carbon nanofiber by the nanocatalyst to crystallize and grow into carbon nanotubes. Thus, carbon nanofibers to which carbon nanotubes are bonded to the surface are prepared (S50).
우선 종래에는 탄소나노섬유에 탄소나노튜브의 성장을 위해 예컨대, 탄소나노섬유에 철(Fe)과 같은 비알칼리금속촉매가 코팅되어 이산화탄소와 기타 탄소 함유 가스를 통과시키면서 철 입자에 탄소원자가 용해되기 시작하여 결국 탄소나노섬유 주위에 탄소원자의 버티컬 튜브를 형성하는 과정으로 탄소나노튜브가 성장되는 방식이 주를 이루었다. 하지만 이런 경우, 철 입자가 탄소나노튜브 내에 잔존하게 되어 결국 철 입자 제거를 위한 산처리를 수 회 반복해야하는 단점이 있었다.First, in the prior art, for the growth of carbon nanotubes on carbon nanofibers, for example, carbon nanofibers are coated with a non-alkali metal catalyst such as iron (Fe), and carbon atoms start to dissolve in iron particles while passing carbon dioxide and other carbon-containing gases. As a result, the process of forming a vertical tube of carbon atoms around carbon nanofibers was mainly based on the method in which carbon nanotubes were grown. However, in this case, the iron particles remain in the carbon nanotubes, and eventually, there is a disadvantage that the acid treatment to remove the iron particles must be repeated several times.
이를 개선하고자, 본 단계에서는 쉽게 말해 알칼리금속 전구체의 알칼리금속이 나노촉매로 활성화되고, 이러한 나노촉매를 통해 탄소원이 탄소나노튜브로 결정화되면서 탄소나노섬유의 표면으로부터 성장될 수 있도록 한다.To improve this, in this step, the alkali metal of the alkali metal precursor is activated as a nanocatalyst, and the carbon source is crystallized into carbon nanotubes through this nanocatalyst so that it can be grown from the surface of the carbon nanofibers.
열처리 온도 조건과 관련하여, 700℃ 미만이면 알칼리금속 전구체의 알칼리금속들이 나노촉매로 활성화 또는 기능화되지 못하여 오히려 일부 성장된 탄소나노튜브에 불순물로 남아있게 되고, 800℃를 초과하면 오히려 과반응을 유도하여 나노촉매의 활성이 안정화되지 못하여 탄소나노튜브의 성장을 방해하게 된다.With respect to the heat treatment temperature condition, if it is less than 700 ° C, alkali metals of the alkali metal precursor cannot be activated or functionalized as a nano catalyst, and rather remain as impurities in some grown carbon nanotubes. As a result, the activity of the nanocatalyst is not stabilized, thereby hindering the growth of carbon nanotubes.
열처리 시간 조건과 관련하여, 15분 미만이면 나노촉매의 활성화를 유도하기에 부족한 시간이어서 탄소나노튜브가 성장될 수 있는 충분한 시간을 확보해 주지 못하며, 30분을 초과하면 성장되는 탄소나노튜브의 길이가 너무 길어져 최적 물성 달성에 어려움이 있을 뿐만 아니라 불필요한 부반응이 생성될 수 있어 30분 이내로 열처리하는 것이 바람직하다.Regarding the heat treatment time condition, if it is less than 15 minutes, it is insufficient time to induce the activation of the nanocatalyst, so it does not secure sufficient time for the carbon nanotubes to grow, and if it exceeds 30 minutes, the length of the grown carbon nanotubes It is preferable to heat treatment within 30 minutes because it becomes too long and it is difficult to achieve optimal physical properties and unnecessary side reactions may be generated.
나노촉매는 알칼리금속이긴 하지만 본 발명에서 적용되는 알칼리금속 전구체의 알칼리금속인 특히, 나트륨은 물에 녹기 때문에 별도의 산(acid)을 사용하여 제거할 필요가 없어 메탈-프리(metal-free) 탄소나노튜스-탄소나노섬유 복합체로 합성되는 것이 중요하다. 즉 나노촉매가 탄소나노튜브에 일부 잔존하게 되더라도 알칼리금속 양이온의 높은 반응성으로 인해 굳이 산처리가 아닌 일반 물에 용해시켜 제거가 가능한 효과가 있다.Although the nanocatalyst is an alkali metal, in particular, sodium, which is an alkali metal of the alkali metal precursor applied in the present invention, is soluble in water, so there is no need to remove it using a separate acid, so metal-free carbon It is important to synthesize the nanotube-carbon nanofiber composite. That is, even if a part of the nanocatalyst remains in the carbon nanotube, there is an effect that it can be removed by dissolving it in general water rather than an acid treatment due to the high reactivity of the alkali metal cation.
또한 나노촉매는 제5단계의 열처리되는 온도에 의해 간단히 기화 또는 증발되어 제거도 가능하기 때문에, 순수 탄소나노튜브만이 탄소나노섬유의 표면으로부터 성장이 이루어질 수 있도록 해준다. 이러한 나노촉매를 통해 탄소나노섬유로부터 탄소나노튜브를 성장시켜 탄소나노섬유와 탄소나노튜브의 높은 결착력이 생겨 탄소나노섬유와 탄소나노튜브가 분리되지 않기 때문에, 탄소나노섬유와 탄소나노튜브를 서로 결착시키기 위한 별도의 수단이 필요로 하지 않게 된다.In addition, since the nanocatalyst can be simply vaporized or evaporated and removed by the heat treatment temperature of the fifth step, only pure carbon nanotubes can be grown from the surface of the carbon nanofibers. By growing carbon nanotubes from carbon nanofibers through these nanocatalysts, high binding force between carbon nanofibers and carbon nanotubes is generated, and carbon nanofibers and carbon nanotubes are not separated, thereby binding carbon nanofibers and carbon nanotubes to each other. There is no need for a separate means to do this.
탄소나노섬유의 표면으로부터 탄소나노튜브를 성장 및 합성시킬 수 있는 탄소원으로는 액체 타입의 액상(液相) 탄소원, 기체 타입의 기상(氣相) 탄소원 및 고체 타입의 고상(固相) 탄소원 중에서 어느 하나 이상을 선택하여 사용한다. 액상(液相) 탄소원으로는 에탄올(C2H6O), 벤젠(C6H6), 자일렌(xylene), 톨루엔(C7H8) 및 이의 혼합으로 이루어진 군으로부터 선택된다. 기상(氣相) 탄소원으로는 메탄(CH4), 프로필렌(C3H6), 프로파인(C3H4), 프로판(C3H8), 부탄(C4H10), 부틸렌(C4H8), 부타디엔(C4H6), 에틸렌(C2H2) 및 이의 혼합으로 이루어진 군으로부터 선택된다. 고상(固相) 탄소원으로는 모노테르펜케톤의 하나인 캄퍼(C10H16O)를 사용할 수 있다.As a carbon source capable of growing and synthesizing carbon nanotubes from the surface of carbon nanofibers, any one of a liquid type carbon source, a gaseous gas phase carbon source, and a solid type carbon source Choose one or more to use. The liquid phase carbon source is selected from the group consisting of ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ), and mixtures thereof. Gas phase carbon sources include methane (CH4), propylene (C3H6), propane (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ), butylene (C 4 H 8 ) ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ) and mixtures thereof. As a solid carbon source, camphor (C 10 H 16 O), which is one of monoterpene ketones, may be used.
따라서 수소를 제외한 1족 원소, 특히 나트륨을 입자 형태의 촉매로 별도로 제조할 필요없이 탄소나노튜브의 성장을 도와주는 탄소원의 존재 하에 열처리를 하는 것만으로 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 탄소원이 나노촉매에 의해 탄소나노튜브로 결정화되면서 탄소나노섬유의 표면으로부터 성장이 될 수 있으며, 결국 탄소나노섬유의 표면에 탄소나노튜브가 결합된 탄소나노튜브-탄소나노섬유 복합체가 제조된다.Therefore, alkali metal precursors are activated as alkali metal nanocatalysts simply by heat treatment in the presence of a carbon source that helps the growth of carbon nanotubes without the need to separately prepare Group 1 elements other than hydrogen, especially sodium, as a catalyst in the form of particles, As the carbon source is crystallized into carbon nanotubes by the nanocatalyst, it can be grown from the surface of the carbon nanofibers, and eventually a carbon nanotube-carbon nanofiber composite in which the carbon nanotubes are bonded to the surface of the carbon nanofiber is manufactured.
이렇게 나노촉매에 의하여 탄소원이 탄소나노섬유로부터 탄소나노튜브로 성장됨과 동시에 나노촉매는 기화되어 제거될 수도 있으므로, 탄소나노섬유에 성장된 탄소나노튜브에 나노촉매가 부착 또는 결합된 상태로 붙어있지 않기 때문에 추가적인 열처리 또는 산처리와 같은 후처리 공정을 실시하여 나노촉매를 제거할 필요가 없게 되는 것이다. 탄소나노튜브에 나노촉매의 일부가 잔존하게 되더라도, 알칼리금속이온의 물에 대한 높은 반응성으로 인해 굳이 산처리가 아닌 일반 물(water)에 용해하여 제거하면 되기 때문에 공정상 장점이 유지된다.In this way, as the carbon source is grown from the carbon nanofiber to the carbon nanotube by the nanocatalyst, the nanocatalyst may be vaporized and removed, so that the nanocatalyst is not attached or attached to the carbon nanotube grown on the carbon nanofiber. Therefore, there is no need to remove the nano-catalyst by performing a post-treatment process such as additional heat treatment or acid treatment. Even if a part of the nanocatalyst remains in the carbon nanotube, the advantages of the process are maintained because the alkali metal ion needs to be removed by dissolving it in general water rather than acid treatment due to the high reactivity to water.
이하, 본 발명의 실시예를 더욱 상세하게 설명하면 다음과 같다. 단, 이하의 실시예는 본 발명의 이해를 돕기 위하여 예시하는 것일 뿐, 이에 의하여 본 발명의 범위가 한정되는 것은 아니다.Hereinafter, an embodiment of the present invention will be described in more detail as follows. However, the following examples are merely illustrative to aid the understanding of the present invention, and the scope of the present invention is not limited thereby.
<실시예 1> 탄소나노튜브-탄소나노섬유 복합체의 제조 <Example 1> Preparation of carbon nanotube-carbon nanofiber composite
sodium benzoate(Sigma Aldrich, BioXtra, > 99.5%)를 DMF(Sigma Aldrich, for molecular biology, > 99%) 용액에 0.02mol/L로 용해 시킨 후, PAN(Sigma Aldrich, Mw 150,000 Typical)을 9 wt% 비율로 재차 용해시켜 방사용액을 제조하였다.After dissolving sodium benzoate (Sigma Aldrich, BioXtra, > 99.5%) in DMF (Sigma Aldrich, for molecular biology, > 99%) solution at 0.02 mol/L, PAN (Sigma Aldrich, Mw 150,000 Typical) was dissolved in 9 wt% A spinning solution was prepared by dissolving again in the ratio.
0.01mm≤D≤1.7mm의 크기를 갖는 노즐의 움직임을 F≥0.1mm/min로 조절하고 전도체의 사이즈는 A≥10㎠로 하여 노즐과 전도체 간의 거리를 30cm 이하로 고정한 후, 유체량(Vf)이 25㎖/min 이하이고, 농도(C)가 30wt% 이하인 방사용액을 30kV 이하의 전압 인가로 전기방사하여 테일러 콘이 형성되면서 스트레칭된 탄소 함유 고분자 나노섬유를 제조하였다.Adjust the movement of the nozzle having a size of 0.01mm≤D≤1.7mm to F≥0.1mm/min and the size of the conductor to A≥10cm2, fix the distance between the nozzle and the conductor to 30cm or less, and then adjust the amount of fluid (V f ) is 25㎖/min or less, and the concentration (C) of 30wt% or less is electrospinning by applying a voltage of 30kV or less to form a Taylor cone to prepare stretched carbon-containing polymer nanofibers.
탄소 함유 고분자 나노섬유를 대기 하 10℃/min의 승온 속도로 200℃에서 40분간 열처리한 후, N2 분위기 하 5℃/min의 승온 속도로 1,000℃에서 60분간 열처리한 다음 자연 냉각하여 탄화된 탄소나노섬유를 제조하였다. 이러한 탄화과정은 도 6의 탄화 열처리로 사진에서 나타낸 바와 같은 열처리로를 이용하여 실시하였다.Carbon-containing polymer nanofibers were heat-treated at 200°C for 40 minutes at a temperature increase rate of 10°C/min in the atmosphere, then heat-treated at 1,000°C for 60 minutes at a temperature increase rate of 5°C/min in an N 2 atmosphere, and then naturally cooled to carbonize Carbon nanofibers were prepared. This carbonization process was carried out using a heat treatment furnace as shown in the photo of the carbonization heat treatment furnace of FIG. 6 .
이어서 탄소나노섬유에 탄소나노튜브를 성장시키기 위한 열처리로 사진을 나타낸 도 7에서와 같이 furnace 내부에 tube인 SUS pipe(직경 5cm, 길이 20cm)를 중앙에 위치시킨 후, SUS pipe 내부의 온도는 700℃로 유지시켰으며, 히터(heater)를 이용해 에탄올(ethanol)을 가열시키면서 생성되는 에탄올 증기를 N2 버블링을 통해 SUS pipe 내부로 15분간 공급하여 탄소나노섬유의 표면에 탄소나노튜브가 성장된 탄소나노튜브-탄소나노섬유 복합체를 제조하였다.Then, as shown in FIG. 7 showing a photo of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers, a SUS pipe (diameter 5cm, length 20cm), which is a tube, was placed in the center of the furnace, and the temperature inside the SUS pipe was 700 It was maintained at ℃, and the ethanol vapor generated while heating the ethanol using a heater was supplied to the inside of the SUS pipe through N 2 bubbling for 15 minutes so that carbon nanotubes were grown on the surface of the carbon nanofibers. A carbon nanotube-carbon nanofiber composite was prepared.
<실시예 2> 탄소나노튜브-탄소나노섬유 복합체의 제조 <Example 2> Preparation of carbon nanotube-carbon nanofiber composite
실시예 2에서는 알칼리금속 전구체로 실시예 1의 sodium benzoate와 다른 sodium bicarbonate를 이용하여 방사용액을 제조하였다. 즉 sodium bicarbonate(Sigma Aldrich, BioXtra, > 99.5%)를 DMF(Sigma Aldrich, for molecular biology, > 99%) 용액에 0.02mol/L로 용해 시킨 후, PAN(Sigma Aldrich, Mw 150,000 Typical)을 9 wt% 비율로 재차 용해시켜 방사용액을 제조하였다.In Example 2, a spinning solution was prepared using sodium benzoate and other sodium bicarbonate of Example 1 as alkali metal precursors. That is, after dissolving sodium bicarbonate (Sigma Aldrich, BioXtra, > 99.5%) in DMF (Sigma Aldrich, for molecular biology, > 99%) solution at 0.02 mol/L, PAN (Sigma Aldrich, Mw 150,000 Typical) was added with 9 wt % ratio was dissolved again to prepare a spinning solution.
0.01mm≤D≤1.7mm의 크기를 갖는 노즐의 움직임을 F≥0.1mm/min로 조절하고 전도체의 사이즈는 A≥10㎠로 하여 노즐과 전도체 간의 거리를 30cm 이하로 고정한 후, 유체량(Vf)이 25㎖/min 이하이고, 농도(C)가 30wt% 이하인 방사용액을 30kV 이하의 전압 인가로 전기방사하여 테일러 콘이 형성되면서 스트레칭된 탄소 함유 고분자 나노섬유를 제조하였다.Adjust the movement of the nozzle having a size of 0.01mm≤D≤1.7mm to F≥0.1mm/min and the size of the conductor to A≥10cm2, fix the distance between the nozzle and the conductor to 30cm or less, and then adjust the amount of fluid (V f ) is 25㎖/min or less, and the concentration (C) of 30wt% or less is electrospinning by applying a voltage of 30kV or less to form a Taylor cone to prepare stretched carbon-containing polymer nanofibers.
탄소 함유 고분자 나노섬유를 대기 하 10℃/min의 승온 속도로 200℃에서 40분간 열처리한 후, N2 분위기 하 5℃/min의 승온 속도로 1,000℃에서 60분간 열처리한 다음 자연 냉각하여 탄화된 탄소나노섬유를 제조하였다. 이러한 탄화과정은 실시예 1에 언급한 도 6의 탄화 열처리로 사진에서 나타낸 동일한 열처리로를 이용하여 실시하였다.Carbon-containing polymer nanofibers were heat-treated at 200°C for 40 minutes at a temperature increase rate of 10°C/min in the atmosphere, then heat-treated at 1,000°C for 60 minutes at a temperature increase rate of 5°C/min in an N 2 atmosphere, and then naturally cooled to carbonize Carbon nanofibers were prepared. This carbonization process was carried out using the same heat treatment furnace shown in the photo of the carbonization heat treatment furnace of FIG. 6 mentioned in Example 1.
이어서 탄소나노섬유에 탄소나노튜브를 성장시키기 위한 열처리로 사진을 나타낸 도 7에서와 같이 furnace 내부에 tube인 SUS pipe(직경 5cm, 길이 20cm)를 중앙에 위치시킨 후, SUS pipe 내부의 온도는 700℃로 유지시켰으며, 히터(heater)를 이용해 에탄올(ethanol)을 가열시키면서 생성되는 에탄올 증기를 N2 버블링을 통해 SUS pipe 내부로 15분간 공급하여 탄소나노섬유의 표면에 탄소나노튜브가 성장된 탄소나노튜브-탄소나노섬유 복합체를 제조하였다.Then, as shown in FIG. 7 showing a photo of a heat treatment furnace for growing carbon nanotubes on carbon nanofibers, a SUS pipe (diameter 5cm, length 20cm), which is a tube, was placed in the center of the furnace, and the temperature inside the SUS pipe was 700 It was maintained at ℃, and the ethanol vapor generated while heating the ethanol using a heater was supplied to the inside of the SUS pipe through N 2 bubbling for 15 minutes so that carbon nanotubes were grown on the surface of the carbon nanofibers. A carbon nanotube-carbon nanofiber composite was prepared.
도 8은 본 발명의 실시예 1에 따라 제조된 탄소나노튜브-탄소나노섬유 복합체의 SEM 사진이다. 도 8(a), 도 8(b) 및 도 8(c)에서는 탄소나노섬유에 탄소나노튜브가 결정화되어 성장된 모습의 확인이 가능하다. 도 9는 본 발명의 실시예 2에 따라 제조된 탄소나노튜브-탄소나노섬유 복합체의 SEM 사진으로, 도 9(a), 도 9(b) 및 도 9(c)에서는 탄소나노섬유에 탄소나노튜브가 결합되면서 성장된 모습의 확인이 가능하다.8 is an SEM photograph of the carbon nanotube-carbon nanofiber composite prepared according to Example 1 of the present invention. In FIGS. 8(a), 8(b) and 8(c), it is possible to confirm the crystallization and growth of carbon nanotubes on carbon nanofibers. 9 is an SEM photograph of a carbon nanotube-carbon nanofiber composite prepared according to Example 2 of the present invention. It is possible to confirm the growth of the tube as it is combined.
이러한 도 8과 도 9에 나타낸 SEM 사진을 살펴보면, 균일한 직경을 갖는 수백 나노미터 길이로 이루어진 다수 곱슬 형상의 탄소나노튜브가 탄소나노섬유의 표면에 매우 조밀하게 성장되어 계층적 네트워크 구조가 형성됨을 알 수 있으며, 이를 통해 탄소나노튜브가 탄소나노튜브-탄소나노섬유 복합체의 유연성 및 비표면적을 향상시킬 수 있음을 알 수 있다.Looking at the SEM photos shown in these FIGS. 8 and 9, it is confirmed that a number of curly-shaped carbon nanotubes having a uniform diameter and a length of several hundred nanometers are grown very densely on the surface of the carbon nanofibers to form a hierarchical network structure. It can be seen that, through this, it can be seen that the carbon nanotube can improve the flexibility and specific surface area of the carbon nanotube-carbon nanofiber composite.
도 10은 탄소나노섬유에 성장되는 탄소나노튜브의 길이를 나타낸 SEM 사진이다. 도 10(a)는 실시예 1에서의 모든 조건은 동일하게 설정하되, 탄소나노튜브 성장 시간만을 5분 미만으로 하여 열처리한 경우 제조되는 탄소나노튜브-탄소나노섬유 복합체를 SEM 사진으로 나타낸 것이고, 도 10(b)는 도 10(a)를 더 확대하여 SEM 사진으로 나타낸 것이며, 도 10(c)는 도 10(b)를 더 확대하여 SEM 사진으로 나타낸 것으로, 열처리 시간이 5분 미만인 경우 탄소나노섬유의 표면에 성장되는 탄소나노튜브의 길이가 현저히 짧아짐이 관찰된다. 이를 통해 탄소원 공급 하에 열처리 시간이 길어지면 탄소나노튜브의 성장됨에 따른 길이 또한 증가함을 알 수 있다.10 is an SEM photograph showing the length of carbon nanotubes grown on carbon nanofibers. 10 (a) is a carbon nanotube-carbon nanofiber composite prepared when all the conditions in Example 1 are set the same, but heat-treated with only the carbon nanotube growth time of less than 5 minutes as an SEM photograph, Figure 10 (b) is a further enlarged SEM photograph of Figure 10 (a), Figure 10 (c) is a further enlarged SEM photograph of Figure 10 (b), when the heat treatment time is less than 5 minutes carbon It is observed that the length of the carbon nanotube grown on the surface of the nanofiber is significantly shortened. Through this, it can be seen that the length of the carbon nanotubes increases as the heat treatment time increases under the carbon source supply.
도 11은 탄소나노섬유에 성장되는 탄소나노튜브의 밀도를 나타낸 SEM 사진이다. 도 11(a)는 실시예 1에서의 모든 조건은 동일하게 설정하되, DMF에 용해되는 알칼리금속 전구체인 sodium benzoate의 농도를 1/5로 줄인 경우 제조되는 탄소나노튜브-탄소나노섬유 복합체를 SEM 사진으로 나타낸 것이고, 도 11(b)는 도 11(a)를 더 확대하여 SEM 사진으로 나타낸 것이며, 도 11(c)는 도 11(b)를 더 확대하여 SEM 사진으로 나타낸 것으로, DMF에 용해되는 알칼리금속 전구체의 농도에 따라 탄소나노섬유의 표면으로부터 성장되는 탄소나노튜브의 밀도 제어가 가능함을 알 수 있다.11 is a SEM photograph showing the density of carbon nanotubes grown on carbon nanofibers. 11 (a) is a carbon nanotube-carbon nanofiber composite prepared when the concentration of sodium benzoate, which is an alkali metal precursor dissolved in DMF, is reduced to 1/5, except that all conditions in Example 1 are the same, SEM It is shown as a photograph, FIG. 11 (b) is an SEM photograph by further expanding FIG. 11 (a), and FIG. 11 (c) is an SEM photograph by further expanding FIG. It can be seen that it is possible to control the density of the carbon nanotubes grown from the surface of the carbon nanofibers according to the concentration of the alkali metal precursor.
이와 같이 본 발명은 탄소나노튜브-탄소나노섬유 복합체의 제조방법 및 이에 의해 제조되는 탄소나노튜브-탄소나노섬유 복합체에 관한 것으로, 알칼리금속 전구체용액에 탄소 함유 고분자를 용해시킨 방사용액을 전기방사하여 표면에 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조한 후, 탄소 함유 고분자 나노섬유를 열처리를 통해 탄화가 이루어진 탄소나노섬유를 제조한 다음, 탄소나노섬유에 탄소원을 공급하면서 열처리하여 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 나노촉매에 의해 탄소원이 탄소나노섬유의 표면에 결합되면서 탄소나노튜브로 결정화되어 성장될 수 있는데 특징이 있다.As such, the present invention relates to a method for producing a carbon nanotube-carbon nanofiber composite and a carbon nanotube-carbon nanofiber composite prepared thereby, by electrospinning a spinning solution in which a carbon-containing polymer is dissolved in an alkali metal precursor solution. After preparing carbon-containing polymer nanofibers bonded to alkali metal precursors on the surface, carbon nanofibers in which carbon-containing polymer nanofibers are carbonized through heat treatment are produced, and then heat-treated while supplying a carbon source to the carbon nanofibers to obtain alkali metal The precursor is activated with an alkali metal nanocatalyst, and a carbon source is bonded to the surface of the carbon nanofiber by the nanocatalyst, and can be crystallized and grown into carbon nanotubes.
이처럼 본 발명은 철(Fe), 코발트(Co), 니켈(Ni)과 같은 비알칼리금속 즉, 전이금속 기반의 촉매를 사용하지 않고 리튬(Li), 칼륨(K) 특히 나트륨(Na)과 같은 알칼리금속 기반의 촉매를 사용하므로, 나트륨과 같은 촉매 입자들이 물에 단순히 용해되어 쉽게 제거되므로 메탈-프리(metal-free) 탄소나노튜브-탄소나노섬유 복합체를 합성할 수 있다는 점에 큰 의미가 있다.As such, the present invention does not use a catalyst based on a non-alkali metal such as iron (Fe), cobalt (Co), or nickel (Ni), that is, a transition metal-based catalyst such as lithium (Li), potassium (K), especially sodium (Na). Since the alkali metal-based catalyst is used, catalyst particles such as sodium are simply dissolved in water and easily removed, so it is meaningful in that a metal-free carbon nanotube-carbon nanofiber composite can be synthesized. .
따라서 본 발명에 따르면, 촉매 입자 제거를 위해 산처리와 같은 세정과정을 하지 않아도 되므로 세정수가 불필요해 환경비용을 절감할 수 있을 뿐만 아니라, 탄소나노섬유 표면으로부터 탄소나노튜브를 용이하게 성장시킬 수 있으므로, 탄소나노튜브-탄소나노섬유 복합체를 대량 생산(mass production)할 수 있어 다양한 에너지 애플리케이션(energy application) 분야에 폭넓게 활용될 수 있을 것으로 기대된다.Therefore, according to the present invention, since there is no need for a cleaning process such as acid treatment to remove catalyst particles, washing water is unnecessary, thereby reducing environmental costs, and it is possible to easily grow carbon nanotubes from the surface of carbon nanofibers. , the carbon nanotube-carbon nanofiber composite can be mass-produced, so it is expected to be widely used in various energy application fields.
이상의 설명은 본 발명의 기술 사상을 예시적으로 설명한 것에 불과한 것으로, 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자라면 본 발명의 본질적인 특성에서 벗어나지 않는 범위에서 다양한 수정 및 변형이 가능할 것이다.The above description is merely illustrative of the technical idea of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains.
따라서 본 발명에 개시된 실시예는 본 발명의 기술 사상을 한정하기 위한 것이 아니라, 설명하기 위한 것이고, 이러한 실시예에 의하여 본 발명의 기술 사상의 범위가 한정되는 것도 아니다.Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to illustrate, and the scope of the technical spirit of the present invention is not limited by these embodiments.
본 발명의 보호 범위는 특허청구범위에 의하여 해석되어야 하며, 그와 동등한 범위 내에 있는 모든 기술사상은 본 발명의 권리범위에 포함되는 것으로 해석되어야 할 것이다.The protection scope of the present invention should be construed by the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (7)

  1. 알칼리금속 전구체를 용매에 용해시켜 알칼리금속 전구체용액을 제조하는 제1단계;A first step of dissolving an alkali metal precursor in a solvent to prepare an alkali metal precursor solution;
    상기 알칼리금속 전구체용액에 탄소 함유 고분자를 용해시켜 방사용액을 제조하는 제2단계;a second step of preparing a spinning solution by dissolving a carbon-containing polymer in the alkali metal precursor solution;
    상기 방사용액을 전기방사하여 표면에 상기 알칼리금속 전구체가 결합된 탄소 함유 고분자 나노섬유를 제조하는 제3단계;a third step of electrospinning the spinning solution to produce carbon-containing polymer nanofibers to which the alkali metal precursor is bonded to a surface;
    상기 탄소 함유 고분자 나노섬유를 열처리하여 표면에 상기 알칼리금속 전구체가 결합된 탄소나노섬유를 제조하는 제4단계; 및a fourth step of heat-treating the carbon-containing polymer nanofibers to prepare carbon nanofibers in which the alkali metal precursor is bonded to the surface; and
    상기 탄소나노섬유에 탄소원(carbon source)을 공급하면서 열처리하여 상기 알칼리금속 전구체가 알칼리금속 나노촉매로 활성화되고, 상기 나노촉매에 의하여 상기 탄소원이 상기 탄소나노섬유의 표면에 결합되면서 탄소나노튜브로 결정화되어 성장하여, 표면에 탄소나노튜브가 결합된 탄소나노섬유를 제조하는 제5단계;를 포함하는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.By heat treatment while supplying a carbon source to the carbon nanofibers, the alkali metal precursor is activated as an alkali metal nanocatalyst, and the carbon source is bonded to the surface of the carbon nanofiber by the nanocatalyst and crystallized into carbon nanotubes. A method of producing a carbon nanotube-carbon nanofiber composite comprising a; a fifth step of growing and producing carbon nanofibers having carbon nanotubes bonded to the surface.
  2. 제1항에 있어서,According to claim 1,
    상기 알칼리금속 전구체는,The alkali metal precursor is
    리튬전구체(Li precursor), 나트륨전구체(Na precursor), 칼륨전구체(K precursor) 및 이의 혼합으로 이루어진 군으로부터 선택되는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.A method for producing a carbon nanotube-carbon nanofiber composite, characterized in that it is selected from the group consisting of a lithium precursor (Li precursor), a sodium precursor (Na precursor), a potassium precursor (K precursor), and a mixture thereof.
  3. 제1항에 있어서,According to claim 1,
    상기 탄소 함유 고분자는,The carbon-containing polymer is
    폴리아크릴로니트릴(polyacrylonitrile, PAN), 폴리비닐아세테이트(polyvinyl acetate, PVA), 폴리비닐피롤리돈(polyvinyl pyrrolidone, PVP), 폴리카보네이트(polycarbonate, PC), 폴리비닐클로라이드(polyvinyl chloride, PVC), 셀룰로오스(cellulose), 셀룰로오스아세테이트(cellulose acetate) 및 이의 혼합으로 이루어진 군으로부터 선택되는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.Polyacrylonitrile (PAN), polyvinyl acetate (PVA), polyvinyl pyrrolidone (PVP), polycarbonate (PC), polyvinyl chloride (PVC), A method for producing a carbon nanotube-carbon nanofiber composite, characterized in that it is selected from the group consisting of cellulose, cellulose acetate, and mixtures thereof.
  4. 제1항에 있어서,According to claim 1,
    상기 탄소원은, 액상, 기상 또는 고상 탄소원이고,The carbon source is a liquid, gaseous or solid carbon source,
    상기 액상 탄소원은 에탄올(C2H6O), 벤젠(C6H6), 자일렌(xylene), 톨루엔(C7H8) 및 이의 혼합으로 이루어진 군으로부터 선택되고,The liquid carbon source is selected from the group consisting of ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ), and mixtures thereof,
    상기 기상 탄소원은 메탄(CH4), 프로필렌(C3H6), 프로파인(C3H4), 프로판(C3H8), 부탄(C4H10), 부틸렌(C4H8), 부타디엔(C4H6), 에틸렌(C2H2) 및 이의 혼합으로 이루어진 군으로부터 선택되며,The gaseous carbon source is methane (CH 4 ), propylene (C 3 H 6 ), propine (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ), butylene (C 4 H 8 ) ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ), and selected from the group consisting of mixtures thereof,
    상기 고상 탄소원은 캄퍼(C10H16O)인 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.The solid carbon source is camphor (C 10 H 16 O), characterized in that the carbon nanotube-carbon nanofiber composite manufacturing method.
  5. 제1항에 있어서,According to claim 1,
    상기 제3단계와 상기 제4단계의 사이에는,Between the third step and the fourth step,
    상기 탄소 함유 고분자 나노섬유를 100 내지 300℃ 범위의 온도에서 예비 열처리를 하는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.A method for producing a carbon nanotube-carbon nanofiber composite, characterized in that the carbon-containing polymer nanofiber is subjected to a preliminary heat treatment at a temperature in the range of 100 to 300°C.
  6. 제1항에 있어서,According to claim 1,
    상기 제4단계에서는,In the fourth step,
    비활성 가스 분위기 하에서 800 내지 1,200℃ 범위의 온도에서 열처리하여 상기 탄소 함유 고분자의 탄화가 이루어지는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체의 제조방법.A method for producing a carbon nanotube-carbon nanofiber composite, characterized in that the carbon-containing polymer is carbonized by heat treatment at a temperature in the range of 800 to 1,200° C. under an inert gas atmosphere.
  7. 제1항 내지 제6항 중 어느 한 항의 방법으로 제조되는 것을 특징으로 하는 탄소나노튜브-탄소나노섬유 복합체.A carbon nanotube-carbon nanofiber composite, characterized in that produced by the method of any one of claims 1 to 6.
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