Abstract:
Disclosed herein is a method for manufacturing metal/carbon nanotube nano-composite using electroplating, more particularly, to a method for manufacturing metal/carbon nanotube nano-composite comprising: adding carbon nanotubes and cationic surfactants in metal plating solution including metal or metal salt and performing electroplating in the cathode. 
     According to the present invention, the method for manufacturing metal/carbon nanotube nano-composite using electroplating comprises: immersing carbon nanotubes in acid solution and filtering the solution and carrying out heat treatment; adding the heat treated carbon nanotubes and cationic surfactants in metal plating solution including metal or metal salt and dispersing the carbon nanotubes; and providing a cathode and an anode in the metal plating solution including the carbon nanotubes and the cationic surfactant, to which current is applied and carrying out electroplating in order to obtain metal/carbon nanotube nano-composite(complex material).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates, generally, to methods for manufacturing metal/carbon nanotube Nano-composite using electroplating, more particularly, to a method for manufacturing metal/carbon nanotube Nano-composite comprising: adding carbon nanotubes and cationic surfactants in the metal plating solution and performing electroplating in the cathode to manufacture metal/carbon nanotube nano-composite. 
         [0003]    2. Description of the Related Art 
         [0004]    The carbon nanotube has excellent electrical conductivity, thermal conductivity and strength, thus is expected to show more excellent physical properties when combined with specific qualities of specific metals. Therefore, there have been a lot of developments of composites including carbon nanotubes. 
         [0005]    Especially, when it comes to forming nano-composite of metal and carbon nanotubes, researches are directed to improving mechanical properties and the nano-composite is mainly made in the form of bulk. The nano-composite in the above form is mainly manufactured via a powder method or a sintering process. 
         [0006]    Pure carbon nanotubes are formed at high temperature of 600˜1000° C. via chemical vapor deposition method deposition method and surface treatment prior to the deposition are important to control the growing direction and speed of the pure carbon nanotube. The carbon nanotube does not constitute densely packed structure to leave empty spaces between carbon nanotubes when it grows, leading to a big problem in replacing the existing metal thin film material. There have been attempts to fill the empty spaces between the carbon nanotubes with SiO 2  etc. to use as semiconductor interconnections. When these interconnections are connected to form some layers, there is no alternative as to a process for the next layer. 
         [0007]    There are no precedents of forming metal/carbon nanotube nano-composite in the type of thin film using electroplating until now due to the characteristics of the bar shape structure and no charges of the carbon nanotube. If metal and carbon nanotubes are simultaneously deposited at the same time by electroplating, densely packed structure unlike the growth of pure carbon nanotubes can be obtained and depositions at desired portions in a type of thin film are possible, also. Thus, all the metal thin films including the existing semiconductor metal interconnection can be replaced, improving their electrical, mechanical and thermal physical properties. Moreover, the present invention can be applied without changing the existing semiconductor interconnection process or the surface finishing process of electronic products, thus the present invention has good marketability and practicality. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide the method for manufacturing metal/carbon nanotube nano-composite where carbon nanotubes are distributed in a molecule level, comprising: adding carbon nanotubes and cationic surfactants which is adsorbed on the surface of the carbon nanotube in metal plating solution including metal or metal salt to constitute the plating solution; and completely separating and dispersing individual carbon nanotubes each other and carrying out electroplating. 
         [0009]    According to the present invention, a metal/carbon nanotube complex material can manufacture a complex material in a thin film using an electroplating. 
         [0010]    A method for manufacturing metal/carbon nanotube nano-composite (complex material) using electroplating, comprising: immersing carbon nanotubes in acid solution, filtering the solution and carrying out heat treatment; adding the heat treated carbon nanotubes and cationic surfactants in metal plating solution including metal or metal salt and dispersing the carbon nanotube; and providing a cathode and an anode in the metal plating solution including the carbon nanotube and the cationic surfactant, to which current is applied and carrying out electroplating in order to obtain metal/carbon nanotube nano-composite in the cathode. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  is a schematic view showing steps of purifying and cutting carbon nanotubes in acid solution. 
           [0013]      FIG. 2  is a schematic view showing a process for manufacturing the plating solution for electroplating. 
           [0014]      FIG. 3  is a schematic view showing a process for carrying out electroplating in the plating solution including carbon nanotubes and cationic surfactants to manufacture metal/carbon nanotube nano-composite. 
           [0015]      FIG. 4  is a SEM photograph of copper/carbon nanotube nano-composite formed using electroplating. 
           [0016]      FIG. 5  is an EDS component analyzing table of copper/carbon nanotube nano-composite formed using electroplating. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Hereinafter, the present invention now will be described in detail with reference to the accompanying drawings by steps. 
         [0018]      FIG. 1  is a schematic view showing a step for purifying and cutting carbon nanotubes in acid solution. 
         [0019]    Acid treatment of carbon nanotubes is carried out in acid solution in order to remove residues such as catalyst metals of carbon nanotubes and to cutting(sever) the carbon nanotube into the level of molecules via an oxidation. 
         [0020]    The acid solution may use at least one of sulfuric acid, nitric acid and hydrochloric acid. The embodiment described later uses acid solution with a component of sulfuric acid to nitric acid of 3:1 in volume ratio. 
         [0021]    After carbon nanotubes are immersed into the acid solution, the predetermined treatments may be further carried out in order to improve purifying and cutting the carbon nanotubes. As an instance of these treatments, at least one of sonication, laser treatment and a stirring by an agitato r in acid solution including carbon nanotubes may be performed. Carbon nanotubes are immersed in acid solution and one of the above methods is performed to remove catalysts of carbon nanotubes in use and residues present at the carbon nanotube and to cut the carbon nanotube with the length of μm into a carbon nanotube CNT with the length of nm sonication, laser treatment and stirring by a high speed agitator can be easily performed by those skilled in the art in order to improve purifying and cutting the carbon nanotube, therefore the detailed descriptions thereof will be omitted. 
         [0022]    After at least one of sonication, laser treatment and stirring by an agitator in acid solution including carbon nanotubes is performed, the acid solution is passed through a filter. And then Heat treatment is performed to the filtered carbon nanotube in order to remove residues (amorphous carbon etc.) 
         [0023]    Heat treatment is performed to the carbon nanotube passed through the filter so as to remove residues such as amorphouss carbon. According to the present invention, in an instance, Heat treatment is performed at 200˜500° C. for ½-2 hours. 
         [0024]    In  FIG. 1 , the numeral  10  refers to a carbon nanotube, and the numeral  12  refers to acid solution (H 2 SO 4 :HNO 3  to 3:1). 
         [0025]      FIG. 2  is a schematic view showing a process for manufacturing the plating solution for electroplating. The carbon nanotubes obtained in  FIG. 1  and surfactants with positive charges adsorbed on the surface of the carbon nanotube are added in metal plating solution including metal or metal salt to obtain the plating solution in  FIG. 2 . 
         [0026]    The cationic surfactant in the plating solution is adsorbed on the surface of a carbon nanotube to wrap and separate the carbon nanotubes each other. If at least one of sonication, laser agitation and mechanical agitation is performed to the plating solution, the separation and the uniform dispersion of the carbon nanotubes can occur in the solution. At this time, the mechanical agitation can disperse carbon nanotubes uniformly by stirring the plating solution with an agitator. 
         [0027]    The metal plating solution includes metal or metal salt. The metal as one component in the existing metal plating solution may use all metals which can be electroplated and the present invention may use at least one of metals such as copper, nickel, chrome, zinc, cadmium, tin, gold, silver and rhodium. In addition, the metal salt may use the salt including the metal. According to the present invention, at least one of metal salts selected from the group consisting of copper sulfate, copper hydroxide, copper pyrophosphate, copper borofluoride, nickel sulfate, nickel chloride and boric acid can be used as a metal salt. 
         [0028]    According to the present invention, copper plating solution can be used as metal plating solution. At this time, the copper plating solution has a composition of copper sulfate of 100˜300 g/l and sulfuric acid of 30˜100 g/l . The copper plating solution can be added by carbon nanotubes of 0.1˜10 g/l and cationic surfactant of 1.0×10 −5 ˜3.0×10 −6 M. 
         [0029]    However, the composition of the metal plating solution and the amount of carbon nanotubes and catonic surfactant added to the metal plating solution are easily selected by those skilled in the art in accordance with metal/carbon nanotube nano-composite and the detailed descriptions thereof will be omitted. 
         [0030]    According to the present invention, the metal plating solution can further include additives in order to improve characteristics of plating solution. Any additives which can improve the characteristics of the plating solution can be employed in the present invention. According to the present invention, brightener playing as a role in smoothing and brightening a plating surface can be used as an instance of these additives. 
         [0031]    The brightener which is currently distributed as products can be applied to a brightener used as an instance of additives to the metal plating solution in the present invention, and can be easily selected by those skilled in the art therefore, the detailed descriptions will be omitted. The currently distributed brighteners as products include CO-16A (Bosung Chemical Co., Kr.), CO-16B (Bosung Chemical Co., Kr.), N-160A (Bosung Chemical Co., Kr.) and N-160B (Bosung Chemical Co., Kr.), whichever can be used in the present invention. 
         [0032]    The major components added to the existing metal plating solution are carbon nanotubes and cationic surfactants. 
         [0033]    The carbon nanotube can use anything mentioned in the description with reference to  FIG. 1 . 
         [0034]    According to the present invention, the cationic surfactant is adsorbed on the surface of individual carbon nanotube and plays a role as wrapping and separating the carbon nanotubes each other. 
         [0035]    According to the present invention, all surfactants with positive charges can be used as a cationic surfactant for example, poly(diallyldimethylammonium chloride, PDMA), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), dodecyltrimethylammonium chloride (DTAC), Decylamine, Dodecylamine, Hexadecylamine, Triethylamine, Octylsulfate, sodium salt, Hexylamine and Octadecylamine. 
         [0036]    In  FIG. 2 , the numeral  14  refers to metal salts &amp; additives, the numeral  16  refers to cationic surfactants and the numeral  18  refers to sonication, respectively. 
         [0037]      FIG. 3  is a schematic view showing a process for carrying out electroplating in a plating solution including carbon nanotubes and cationic surfactants to manufacture metal/carbon nanotube nano-composite. 
         [0038]    A metal rod providing with metal cations is mounted at an anode and metal or substrate material to deposit metal/carbon nanotube nano-composite is mounted at a cathode in plating solution including carbon nanotubes and cationic surfactants. If the anode and the cathode are mounted and a proper current is applied, metal cations and carbon nanotubes covered with cationic surfactants with positive charges are moved and deposited to the cathode at the same time to form metal/carbon nanotube nano-composite in the type of thin film. 
         [0039]    Electroplating may be carried out by applying current so that the current density is 5˜100 mA/cm 2  at electroplating. 
         [0040]    The anode mounted at electroplating may use at least one selected from the group consisting of copper, nickel, chrome, zinc, cadmium, tin, gold, silver and rhodium. 
         [0041]    It would rather use the same metal with metal or metal solution of metal plating solution as the anode material for the following reason. If current is applied and metal of the plating solution at the cathode is started to deposite, the metal ions in the plating solution are consumed and the number of metal ions in the plating solution is decreased. As much anode metal ions consisting of the same metals as lost are dissolved in the solution to make up the deficit of the metal ions in the plating solution. 
         [0042]    The cathode to be mounted at electroplating can use metal or substrate material to which metal/carbon nanotube nano-composite is deposited. According to the present invention, a cathode can use one selected from the group consisting of copper, nickel, aluminum, a copper deposited substrate, a nickel deposited substrate and an aluminium deposited substrate. 
         [0043]    In  FIG. 3 , the numeral  20  refers to an anode, the numeral  22  refers to a cathode, the numeral  24  refers to the electroplating solution with metal cations, carbon nanotubes and cationic surfactants, the numeral  26  refers to metal/carbon nanotube nano-composite, the numeral  28  refers to metal cations and the numeral  30  refers to a carbon nanotube covered with cationic surfactants. 
         [0044]    A better understanding of the present invention may be obtained in light of the following examples which are set forth to illustrate, but are not to be construed to limit the present invention. 
       &gt;Embodiment&gt; 
       [0045]    Carbon nanotubes are added to acid solution including sulfuric acid and nitric acid in the volume ratio of 3:1 and sonication is carried out at a room temperature for 10 hours at 40 KHz to purify the carbon nanotubes and cut the same. After the sonication is performed, the acid solution is passed through a filter and Heat treatment is performed to the filtered carbon nanotubes at 350° C. for one hour to remove the residues like amorphous carbons. 
         [0046]    The carbon nanotubes from which the residues are removed via the heat treatment and cationic surfactants are added to plating solution to obtain plating solution with carbon nanotubes and cationic surfactants. The plating solution uses copper plating solution. The plating solution has the composition of copper sulfate of 250 g/l and a sulfuric acid of 75 g/l. 
         [0047]    The carbon nanotubes of 1 g/l and PDMA poly(diallyldimethylarnmonium chloride) of 1.25×10 −6  M as cationic surfactants are added in the copper plating solution. 
         [0048]    Copper plate as an anode is put in the plating solution with the carbon nanotubes and the cationic surfactants and a nickel-deposited silicon wafer as a cathode is mounted and then current is applied to form copper/carbon nanotube nano-composite in the form of thin film so that the current density is 20 mA/cm 2 . 
         [0049]      FIG. 4  is an SEM photograph of copper/carbon nanotube nano-composite obtained in the embodiment. As shown in the SEM photograph, the carbon nanotubes are uniformly dispersed in copper matrix. (Refer to arrows in  FIG. 4 ) 
         [0050]    If the carbon nanotubes are uniformly dispersed in the copper matrix, the amount of carbon nanotubes in the copper matrix depends on the current density at plating and the amount of cationic surfactants. 
         [0051]      FIG. 5  shows a component analyzing table of an energy dispersive spectroscopy (EDS) of the copper/carbon nanotube nano-composite shown in  FIG. 4 . From the component analysis, the content of carbons in the copper matrix is 13.93% by an atom fraction. We can assume that most of carbon contents are carbon nanotubes. 
         [0052]    At least one of the component of plating solution, a dispersion of carbon nanotubes and current density at electroplating is controlled to determine the content of carbon nanotubes in the metal base. 
         [0053]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
         [0054]    The metal/carbon nanotube nano-composite manufactured according to the present invention can obtain metal/carbon nanotube nano-composite in the type of thin film using electroplating, and can replace all metal thin film materials capable of electroplated including a semiconductor interconnection material like aluminum and copper, etc. 
         [0055]    The metal/carbon nanotube nano-composite manufactured according to the present invention, contrary to the growth of pure carbon nanotubes, grows to thin film with densely packed structure and can be used without changing the existing process method. 
         [0056]    As the metal/carbon nanotube nano-composite manufactured according to the present invention disperses carbon nanotubes uniformly into a metal matrix, the existing metal thin film is expected to improve the electric, mechanic and thermal physical characteristics.