Method and apparatus for synthesizing carbon nanotubes using ultrasonic evaporation

Abstract

Disclosed herein is an apparatus and method for synthesizing carbon nanotubes, including a fuel supply unit for supplying a large amount of liquid metal catalyst mixture using a syringe pump for quantitatively supplying a liquid metal catalyst mixture, mixed with hydrocarbon-based liquid carbon sources such as xylene, toluene, benzene and the like, and metal catalytic particles, such as iron, nickel, cobalt, molybdenum and the like, and a general liquid pump for supplying a liquid metal catalyst mixture depending on the amount thereof; an evaporation unit for evaporating and atomizing the liquid metal catalyst mixture supplied from the fuel supply unit into precursors having a uniform size on the nanometer scale; a carrier gas supply unit for transferring particles atomized in the evaporation unit to a reactor and transferring carrier gas, having an influence on the synthesis of carbon nanotubes, to the reactor; a horizontally oriented reaction unit for synthesizing carbon nanotubes in large quantities using the carrier gas supplied from the carrier gas supply unit and the precursors formed in the evaporation unit; a filtering unit comprising a filter for filtering residual particles among the atomized particles synthesized into carbon nanotubes in the horizontally oriented reaction unit and some of the carbon nanotubes synthesized in the vapor phase; and a vacuum generation unit comprising a vacuum pump configured to be connected with the filtering unit, decrease pressure in the reactor, and remove oxygen remaining in the reactor, or a continuous collection unit in the case where the apparatus includes a vertical type reaction unit.

1 . An apparatus for synthesizing carbon nanotubes using an ultrasonic evaporation method, comprising:
 a fuel supply unit for supplying a large amount of liquid metal catalyst mixture using a syringe pump for quantitatively supplying a liquid metal catalyst mixture mixed with hydrocarbon-based liquid carbon sources such as xylene, toluene, benzene and the like, and metal catalytic particles such as iron, nickel, cobalt, molybdenum and the like, and a general liquid pump for supplying a liquid metal catalyst mixture depending on the amount thereof;   an evaporation unit for evaporating and atomizing the liquid metal catalyst mixture, supplied from the fuel supply unit, into precursors having a uniform nanometer size;   a carrier gas supply unit for transferring particles atomized in the evaporation unit to a reactor and transferring carrier gas, influencing synthesis of carbon nanotubes, to the reactor;   a reaction unit, which is horizontally oriented, for synthesizing carbon nanotubes in large quantities using the carrier gas supplied from the carrier gas supply unit and the precursors formed in the evaporation unit;   a filtering unit comprising a filter for filtering residual particles among atomized particles synthesized into carbon nanotubes in the horizontally oriented reaction unit and a part of carbon nanotubes synthesized in a vapor phase; and   a vacuum generation unit comprising a vacuum pump configured to be connected with the filtering unit, decrease pressure in the reactor, and remove oxygen remaining in the reactor.   
     
     
         2 . An apparatus for synthesizing carbon nanotubes using an ultrasonic evaporation method, comprising:
 a fuel supply unit for supplying a large amount of liquid metal catalyst mixture using a syringe pump for quantitatively supplying a liquid metal catalyst mixture mixed with hydrocarbon-based liquid carbon sources such as xylene, toluene, benzene and the like, and metal catalytic particles such as iron, nickel, cobalt, molybdenum and the like, and a general liquid pump for supplying a liquid metal catalyst mixture depending on the amount thereof;   an evaporation unit for evaporating and atomizing the liquid metal catalyst mixture supplied from the fuel supply unit into precursors having a uniform nanometer size;   a carrier gas supply unit for transferring particles atomized in the evaporation unit to a reactor and transferring carrier gas, influencing synthesis of carbon nanotubes, to the reactor;   a reaction unit, which is vertically oriented, for continuously synthesizing carbon nanotubes using the carrier gas supplied from the carrier gas supply unit and the precursors formed in the evaporation unit;   a continuous collection unit for continuously collecting residual particles among atomized particles synthesized into carbon nanotubes in the vertically oriented reaction unit and carbon nanotubes synthesized mainly in vapor phase; and   a vacuum generation unit comprising a sample vessel connected with the continuous collection unit and a vacuum pump for decreasing pressure in the reactor and removing oxygen remaining in the reactor.   
     
     
         3 . The apparatus according to  claim 1  or  2 , wherein the evaporation unit comprises an ultrasonic vibration plate; and a ultrasonic evaporator control unit for controlling a time for operating the ultrasonic vibration plate such that, in a method of atomizing liquid droplets while instantaneously vibrating the ultrasonic vibration plate, the ultrasonic vibration plate is not operated when liquid droplets of the liquid metal catalyst mixture are not dropped thereon, and the ultrasonic vibration plate is operated when liquid droplets of the liquid metal catalyst mixture are dropped thereon, and for controlling intensity of operation of the ultrasonic vibration plate depending on an amount and kind of the liquid metal catalyst mixture. 
     
     
         4 . The apparatus according to  claim 1  or  2 , wherein the carrier gas supply unit comprises a flow control unit for controlling flow of carrier gas, and a mixing unit for uniformly mixing the carrier gas, controlled by the flow control unit, with other carrier gas; and is configured to transfer the mixed carrier gas to the evaporation unit. 
     
     
         5 . The apparatus according to  claim 1 , wherein the reactor comprises large area substrates. 
     
     
         6 . The apparatus according to  claim 2 , wherein the continuous collection unit comprises a screw; and a motor control unit configured such that the screw is operated by a motor, and an operation speed of the motor is controlled depending on a produced amount of the carbon nanotubes. 
     
     
         7 . The apparatus according to  claim 6 , wherein the continuous collection unit is connected with a sample vessel for finally collecting the carbon nanotubes discharged through the screw. 
     
     
         8 . The apparatus according to  claim 2 , wherein the reaction unit comprises a tube for a vertical type reactor; a heater for surrounding and heating the tube for a vertical type reactor; and a reactor temperature control unit for controlling a temperature of the heater. 
     
     
         9 . The apparatus according to  claim 8 , wherein the tube for a vertical type reactor can be used at a maximum temperature of 1200° C., is composed of a material other than quartz, and is configured to raise a temperature of the reactor to a maximum temperature of 1200° C. 
     
     
         10 . A method of synthesizing carbon nanotubes using an ultrasonic evaporation method, in which the carbon nanotubes, having high purity, controlled such that they have quantitatively known and uniform sizes, are synthesized on large area substrates in a horizontal orientation in large quantities, comprising steps of:
 providing an apparatus for synthesizing carbon nanotubes in large quantities using a ultrasonic control method of automatically controlling operation time and intensity and then quantitatively supplying a liquid metal catalyst mixture, which is a mixture of various liquid carbon sources and metal catalytic particles;   producing precursors having a uniform nanometer size, combined with metal catalytic particles, carbon atoms and hydrogen atoms, in large quantities by instantaneously evaporating and atomizing the supplied liquid metal catalyst mixture using an ultrasonic vibration method of automatically controlling operation time and intensity; and   transferring the atomized precursors having a uniform nanometer size with carrier gas, pyrolyzing them into carbon atoms, hydrogen atoms and metal catalytic particles in a high-temperature reactor, and then adsorbing and diffusing only the carbon atoms among the pyrolyzed particles using the metal catalytic particles, thereby forming the shape and structure of carbon nanotubes.   
     
     
         11 . A method of synthesizing carbon nanotubes using an ultrasonic evaporation method, in which the carbon nanotubes having high purity, controlled such that they have quantitatively known and uniform sizes, are continuously synthesized in a vertical state using a continuous collection method, comprising steps of:
 providing an apparatus for synthesizing carbon nanotubes in large quantities using an ultrasonic control method of automatically controlling operation time and intensity and then quantitatively supplying a liquid metal catalyst mixture, which is a mixture of various liquid carbon sources and metal catalytic particles;   continuously producing precursors having a uniform nanometer size, combined with metal catalytic particles, carbon atoms and hydrogen atoms, by instantaneously evaporating and atomizing the supplied liquid metal catalyst mixture using an ultrasonic vibration method of automatically controlling operation time and intensity; and   transferring the atomized precursors having a uniform nanometer size with carrier gas, pyrolyzing them into carbon atoms, hydrogen atoms and metal catalyst catalytic in a high-temperature reactor, and then adsorbing and diffusing only the carbon atoms among the pyrolyzed particles using the metal catalytic particles, thereby determining a shape and structure of carbon nanotubes.   
     
     
         12 . The method according to  claim 10  or  11 , wherein, in the step of pyrolysis, the concentration of the metal catalyst, determining the shape and structure of the carbon nanotubes, is controlled depending on the liquid metal catalyst mixture, in which the metal catalytic particle is mixed with liquid carbon sources to a concentration thereof of 0.1 mol %˜6.5 mol %. 
     
     
         13 . The method according to  claim 10  or  11 , wherein the liquid carbon sources are any one, or more than one, selected from various hydrocarbon sources such as xylene, toluene, benzene and the like. 
     
     
         14 . The method according to  claim 10  or  11 , wherein the metal catalyst particles are any one, or more than one, selected from various metal particles such as iron, nickel, cobalt, molybdenum and the like. 
     
     
         15 . The method according to  claim 10  or  11 , wherein, in the step of producing precursors by instantaneously evaporating and atomizing the liquid metal catalyst mixture using an ultrasonic vibration method, liquid droplets of the liquid metal catalyst mixture are dropped on the ultrasonic vibration plate in the evaporation unit using a syringe pump, but a time for operating the ultrasonic vibration plate is controlled such that the ultrasonic vibration plate is not operated when the liquid droplets of the liquid metal catalyst mixture are not dropped thereon and the ultrasonic vibration plate is operated when liquid droplets of the liquid metal catalyst mixture are dropped thereon, and intensity of operation of the ultrasonic vibration plate is controlled depending on an amount and kind of the liquid metal catalyst mixture, thereby evaporating and atomizing the liquid metal catalyst mixture. 
     
     
         16 . The method according to  claim 10  or  11 , wherein, as an apparatus for supplying the liquid metal catalyst mixture, a syringe pump is used, or a general quantitative liquid pump is used depending on an increase of an amount thereof. 
     
     
         17 . The method according to  claim 10  or  11 , wherein an ultrasonic evaporator for evaporating the liquid metal catalyst mixture is configured to easily an automatically control operation time using an ON/OFF timer depending on amount and kinds of the supplied liquid metal catalyst mixture, and to easily control operation intensity thereof by coordinating variation of the liquid metal catalyst mixture to variation of voltage supplied to the evaporator. 
     
     
         18 . The method according to  claim 10  or  11 , wherein the shape of the synthesized carbon nanotubes is controlled depending on conditions such as temperature, time, metal catalyst concentration, and the like. 
     
     
         19 . The method according to  claim 10 , wherein the carbon nanotubes are vertically synthesized on an entire surface (an entire exposed surface) of quartz, which can be used as a large area substrate, in large quantities. 
     
     
         20 . The method according to  claim 10 , wherein the carbon nanotubes are grown in a vapor phase state in a reactor, and are continuously synthesized.