Title of Invention: POROUS FILMS COMPRISING CARBON NANOSTRUCTURE-METAL COMPOSITE AND METHOD OF

MANUFACTURING THE SAME

Technical Field

[1 ] The present invention relates to porous films comprising carbon nanostructure-metal composite and a method of manufacturing the same, and more particularly, to porous films comprising carbon nanostructure-metal composite usable to manufacture a water treating membrane, a field emission display, a hydrogen storage device assembly, an electrode for a solar cell and a secondary battery, a supercapacitor, an electromagnetic wave shielding body, a high strength lightweight application product, or the like. Background Art

[2] Recently, a technology for manufacturing a membrane having high-purity separation capacity has been recognized as a very important field for various industries. The importance of the membrane has increased in a variety of fields such as the chemical, food, pharmaceutical, medical, biochemistry, and environmental industries. In particular, in the environmental industry, a demand for clean water including an interest in water shortage has increased. One of the methods for solving the above problem has largely focused on a technology for using the membrane.

[3] In particular, the water treating field uses as membranes a micro filtration (MF) membrane, an ultra filtration (UF) membrane, a nano filtration (NF) membrane, a reverse osmosis (RO) membrane, and an ion exchange membrane, which are used for industrial wastewater treatment, water treatment, sewage treatment, wastewater treatment, seawater desalination, or the like. The water treatment plant additionally uses the micro filtration membrane as well as the sewage treatment using a membrane bio reactor (MBR). The ultra filtration membrane is used to treat water by removing bacteria while the reverse osmosis membrane is used for seawater desalination facilities. The ion exchange membrane is mainly used for a dechlorination process.

[4] However, the most serious problem of the membrane is fouling. In particular,

biofouling is due to microorganisms that degrade the separation capacity, which have a negative effect on the lifespan of the membrane. Consequently, biofouling caused by the microorganisms may degrade the performance and lifespan of the membrane. Therefore, research of the membrane having various functions for solving the above- mentioned problems has continued.

[5]

Disclosure of Invention An object of the present invention is to provide a new type of porous films comprising carbon nanostructure-metal composite capable of increasing a flow rate.

Another object of the present invention is to provide porous films comprising carbon nanostructure-metal composite having a catalyst effect and a microorganism removing effect. Another object of the present invention is to provide composite porous films having controlled size pores according to a diameter size of the carbon nanostructure. Another object of the present invention is to provide porous films comprising carbon nanostructure-metal composite usable to manufacture a water treating membrane, a field emission display, a hydrogen storage device assembly, an electrode for a solar cell and a secondary battery, a supercapacitor, an electromagnetic wave shielding body, a high strength lightweight application product, or the like. Another object of the present invention is to provide porous films comprising carbon nanostructure-metal composite in which several nm to several hundred nm of metal particles are uniformly dispersed.

In one general aspect, porous films comprising carbon nanostructure-metal composite includes: a membrane support having micro or nano pores and carbon nanostructure-metal composite films formed on one side or both sides of the membrane support, wherein the surface of the porous films comprising carbon nanostructure- metal composite is subjected to a hydrophilic surface modifying treatment.

In another general aspect, a method of manufacturing the porous films comprising carbon nanostructure-metal composite includes: a) coating the carbon nanostructure- metal composite dispersed in a solvent on one surface or both surfaces of a membrane support; b) heat-treating the coated membrane support to fuse the carbon nanostructure-metal composite to the membrane support; and c) surface-modifying the membrane fused with the carbon nanostructure-metal composite and making it in a hydrophilic state.

The porous films comprising carbon nanostructure-metal composite according to the present invention can control the size of the pores of the composite porous films according to the size of the carbon nanostructure. The porous films comprising plasma treated carbon nanostructure-metal composite according to the present invention can be melted at a low temperature since the metal size of the carbon nanostructure-metal composite is several nm to several hundred nm. Therefore, the present invention can provide a new type of composite porous films manufactured by performing heat treatment at a low temperature in order to connect the metal with the carbon nanostructure in a network structure and fusing the metal to the membrane support, and the method of manufacturing the same. The present invention connects the carbon nanostructure-metal composite in a network structure by melting or sintering the metal even though the heat treatment is performed at a relatively low temperature, thereby making it possible to attach the carbon nano structure to the membrane support well. The manufactured composite porous films can effectively filtrate the microorganisms when they are used for the water treating membrane since the microorganisms are not filtered due to the size of pores of the composite porous films. Further, the present invention can maintain the flow rate even though the carbon nanostructure-metal composite is formed on the membrane support.

[11]

Brief Description of Drawings

[12] FIG. 1 is a photograph of carbon nanotube-silver composite manufactured in Manufacturing Example 1 and observed by a scanning electron microscope (SEM);

[13] FIG. 2 is a photograph of a filter fused with the carbon nanotube-silver composite at step b) of Example 1 and observed by a scanning electron microscope (SEM); and

[14] FIG. 3 is a diagram of comparing a flow rate of Example 1 with that of reference Example 1.

Best Mode for Carrying out the Invention

[15] Hereinafter, porous films comprising carbon nanostructure-metal composite

according to the present invention will be described in more detail.

[16] In an exemplary embodiment of the present invention, porous films comprising

carbon nanostructure-metal composite includes a membrane support having micro or nano pores and carbon nanostructure-metal composite films formed on one side or both sides of the membrane support, and having a hydrophilic modified surface.

[17] In this case, the hydrophilic modified surface is formed by surface modifying using plasma.

[18] Recently, plasma has becomes more frequently used in various industries. Generally, plasma implies a state in which a material is electrically neutral due to the coexistence of positive and negative charged particles that freely move. As a result, plasma is called a fourth state of a material. A state of a material may be largely classified into solid, liquid, gas, or plasma. When gas is in a high-temperature state, impact between gases is frequent. When impact energy is ionization energy, electrons in a gas atom come out. In this case, an atom is a cation, which becomes a plasma state, i.e., an ionization state that electrically separates gas into ions and electrons. This state is similar to an electrolyte solution state but is a gas state. An example of plasma viewable around us may include a fluorescent lamp, a neon sign, flare, lightning, aurora lights, etc. Since it is difficult to raise temperature to tens of thousands ¾C when gas is heated, plasma is generated by accelerating electrons and impacting them with gas atoms. Generally, when ionization energy is converted into voltage, it becomes about 10 to 20V, such that it can be easily changed into electric energy. [19] In the present invention, the carbon-nanostructure-metal composite is formed by combining or mixing the carbon nano-structure with a metal or a metal oxide.

[20] Generally, the carbon nanostructure may be classified into a carbon nano tube, a

carbon nano horn, a carbon nano fiber, or the like, according to a shape thereof, etc. In particular, the carbon nano tube can be applied to various fields, such as energy, environment, electronics, etc., due to excellent mechanical strength, thermal conductivity, electric conductivity, and chemical stability. In addition, the carbon nanos- tructure-metal composite is formed by inducing a functional group into the carbon nanotube and chemically combining the induced functional group with a metal (cobalt, copper, nickel, silver, etc.) by the reaction therebetween. The carbon nanostructure- metal composite has excellent characteristics for manufacturing structure mold such as, a field emission display, hydrogen storage device assembly, an electrode for a solar cell and a secondary battery, supercapacitor, electromagnetic wave shielding body, high strength lightweight application product, or the like, due to the metal components included therein. A method of manufacturing the material for the carbon nanostructure- metal composite is disclosed in US Patent 7,217,331, WO 2009/145393 Al, etc.

[21] Since the metal or the metal oxide of the carbon nanostructure-metal composite can be melted or sintered at a low temperature, the metal or the metal oxide is melted or sintered when the membrane coated with the carbon nanostructure-metal composite is heat-treated at a relatively low temperature, such that the carbon nanostructure-metal composites are connected in a network structure, thereby making it possible to manufacture nano porous films.

[22] The carbon nanostructure, metal, and metal oxide of the carbon nanostructure-metal composite has a size of several nm to several hundred nm. More specifically, the carbon nanostructure metal composite is composed of spherical metal particles or the metal oxide particles of 1 to 500 nm and the carbon nanostructure. Since the size of the metal is a nano unit, the metal has a lower melting point than that of a metal of a normal size. For this reason, the metal is melted and sintered even though it is heat- treated at a relatively low temperature, such that the carbon nanostructure-metal composite is connected in a network structure. As a result, the carbon nanostructure- metal composite can be combined with the membrane support well.

[23] In this case, the metal or the metal oxide may include at least one selected from a group consisting of Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Hf, Ir, Pt, Tl, Pb, or Bi.

[24] According to the present invention, it is possible to control the size of the pores of the porous films comprising carbon nanostructure-metal composite by the diameter size of the carbon nanostructure. The diameter of the carbon nanostructure is varied according to the type of carbon nanostructure, such that the size of the pores of the composite porous films can be controlled according to the type of carbon nanostructure. As a result, the controlled pore size of the porous films comprising carbon nanostructure-metal composite may be 0.1 to 500nm. The porous films comprising carbon nanostructure-metal composite according to the present invention can effectively filtrate microorganisms by controlling the size thereof.

[25] In the present invention, the carbon nanostructure-metal composite may be manufactured by mixing a dispersion of the carbon nanostructure dispersed in a reductive solvent with a metal precursor and heat-treating it. In this case, the dispersion may be further added with a stabilizer.

[26] In this case, the reductive solvent may be selected from polyhydric alcohol, glycol ethers, or a mixture thereof, wherein the polyhydric alcohol may be selected from a group consisting of glycols, glycerin, threitol, arabitol, glucose, mannitol, galactitol, and sorbitol according to the following chemical formula 1.

[27] [Chemical Formula 1]

[28] H-(OR') _n -OH

[29] (In Chemical Formula 1, R ¹ is selected from a linear or branched alkylene of C ₂ ~C] ₀ , and n is an integer of 1 to 100.)

[30] The glycol ethers may be selected from compounds of the following Chemical

Formula 2.

[31] [Chemical Formula 2]

[32] R ⁴ -(OR ² ) _m -OR ³

[33] (In Chemical Formula 2, R ² is selected from a linear or branched alkylene of C ₂ ~Ci ₀ ;

R ³ is a hydrogen atom, allyl, alkyl of Q -Qo, aryl of C ₅ ~C ₂₀ , or aralkyl group of C ₆ ~C ₃ () ; R ⁴ is selected from allyl, alkyl of C]~Ci ₀ , aryl of C ₅ ~Ci ₀ , aralkyl group of C ₆ ~C ₃₀ , or alkyl carbonyl group of C ₂ ~Ci ₀ , wherein the alkyl of alkyl carbonyl group may include a double bond in a carbon chain; m is an integer of 1 to 100).

[34] The glycol ethers may be selected from methyl glycol, methyl diglycol, methyl

triglycol, methyl polyglycol, ethyl glycol, ethyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, butyl polyglycol, hexyl glycol, hexyl diglycol, ethyl hexyl glycol, ethyl hexyl diglycol, allyl glycol, phenyl glycol, phenyl diglycol, benzil glycol, benzil diglycol, methyl propylene glycol, methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, propyl propylene diglycol, butyl propylene glycol, butyl propylene diglycol, phenyl propylene glycol, methyl propylene glycol acetate, and poly methyl glycol, but is not limited thereto.

[35] The glycols may be selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and hexylene glycol, more preferably, ethylene glycol, but is not limited thereto.

[36] The reductive solvent may preferably use a mixture of glycols and glycol ethers. In detail, the reductive solvent may more preferably use a mixture of glycols and methyl poly glycol.

[37] The metal precursor may be selected from silver nitrate, silver acetylacetonate, silver acetate, silver carbonate, silver chloride, aluminum hydroxide, aluminum chloride, aluminum acetylacetonate, aluminum acetate, aluminum nitrate, manganese carbonate, manganese chloride, manganese nitrate, manganese acetylacetonate, manganese acetate, zinc chloride, zinc nitrate, zinc acetate, zinc acetylacetonate, cobalt acetylacetonate, cobalt acetate, copper acetylacetonate, copper acetate, nickel acetylacetonate, nickel acetate, iron acetylacetonate, iron acetate, titanium acetate, titanium acetylacetonate, and hydrate thereof.

[38] The stabilizer may be selected from a surfactant, a water soluble polymer, amines, and a mixture thereof. A detailed example of the water soluble polymer may include polyvinyl pyrrolidone, the amines may be selected from primary amine, secondary amine, tertiary amine, aromatic amine, and a mixture thereof, more specifically, oleylamine.

[39] The carbon nanostructure may be selected from a single wall carbon nanotube, a double wall carbon nanotube, a multi wall carbon nanotube, a carbon nano horn, a carbon nano fiber, and a mixture thereof, more preferably, the single wall carbon nanotube, the double wall carbon nanotube, and the multi wall carbon nanotube. The size of the pore of the composite porous films according to the present invention may be controlled according to the diameter of the carbon nanostructure.

[40] Hereinafter, a method of manufacturing the porous films comprising a carbon nanostructure-metal composite according to the present invention will be described in more detail.

[41] An example of the method of manufacturing the porous films comprising a carbon nanostructure-metal composite includes: a) coating the carbon nanostructure-metal composite dispersed in a solvent on one surface or both surfaces of the membrane support; b) heat-treating the coated membrane support to fuse the carbon nanostructure-metal composite to the membrane support; and c) surface-modifying the membrane fused with the carbon nanostructure-metal composite and making it in a hy- drophilic state.

[42] At step c), the surface modification is performed during the plasma treatment. More specifically, the plasma treatment may be performed by a method using an inert gas as a discharge gas and in atmospheric pressure.

[43] In addition, the plasma treatment according to the present invention uses plasma selected from radio frequency (RF) plasma, corona discharge plasma, high frequency plasma, dielectric barrier discharge plasma, AC glow discharge plasma, DC discharge plasma, intermediate frequency plasma, and arc plasma, and may be performed by a method of treating plasma at a normal temperature.

[44] At step c), the plasma may be performed for 1 to 60 minutes under the conditions of normal temperature and atmospheric pressure.

[45] When the plasma is treated, the functional group is induced into the carbon nanostructure of the surface of the coated membrane to manufacture the structure of the hy- drophilic composite porous films. The plasma treatment may include an oxygen addition plasma treatment under a general vacuum or a normal pressure plasma treatment method, or a general corona treatment method, etc., but is not necessarily limited thereto.

[46] In more detail, when the coated membrane is subjected to the atmospheric pressure plasma treatment, inert gas and oxygen in the air becomes a free radical. The free radical attacks the surface of the membrane, such that hydroxyl group is induced into the surface of the membrane to form the hydrophilic surface. The hydrophilic surface has hydrophilic property with water to reduce permeation resistance on the surface of the membrane, thereby increasing the permeation flow rate.

[47] At step a), the membrane support may use at least one selected from a HEPA filter, an ULPA filter, a ceramic filter, a glass fiber filter, a glass powder sintering filter, a polymer nonwoven filter, a Teflon separator filter, a metal powder sintering filter, and a metal wire woven filter, but is not necessarily thereto.

[48] At step a), the size of the metal may be 1 to 500 nm and when the metal is silver, silver may be preferably included as 5 to 90 wt% for the carbon nanostructure-metal composite.

[49] At step a), the carbon nanostructure-metal composite may be manufactured by

mixing the carbon nanostructure dispersion dispersed in the reductive solvent with the metal precursor and heat-treating it. In addition, the carbon nanostructure-metal composite may be manufactured by further including the stabilizer in the dispersion, mixing it, mixing the metal precursor therewith, and heat-treating it.

[50] At step a), the coating may be performed by a method of filtering the carbon nanostructure-metal composite in the membrane support and compressing the carbon nanostructure-metal composite remaining in the membrane support. An example of the coating method may include a spin coating method, a dip coating method, a spray coating method, a bar coating method, and a screen printing method, a method of performing filtering and coating on the support, or the like, but is not necessarily limited thereto.

[51] At step a), the solvent may be selected from a group consisting of mixtures of water, alcohol, polyhydric alcohol, glycol ethers, and a mixture thereof. In detail, the alcohol may be selected from a group consisting of methyl alcohol, ethanol, propyl alcohol, butanol, pentanol, hexanol, and octyl alcohol, more preferably, propyl alcohol.

[52] At step a), the solvent may include a surfactant. The amount of surfactant may be

100 to 300 parts by weight for every 100 parts by weight of the carbon nanostructure- metal composite. In this case, the surfactant may be selected from non-ionic surfactant, cationic surfactant, anionic surfactant, and a mixture thereof. The surfactant can prevent the carbon nanostructure-metal composite from being tangled in the above- mentioned range and can effectively disperse it.

[53] In more detail, an example of the surfactant may include cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, sodium dodecyl sulfate, stearic acid, methyl glucoside, octyl glucoside, polyoxyethylene sorbitan monolaurate, poly- oxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, sorbitan monolaurate, ethylene glycol monolaurate, propylene glycol monolaurate, triglycerol monolaurate, and a mixture thereof, more preferably, cetyl trimethyl ammonium bromide or cetyl trimethyl ammonium chloride, but is not necessarily limited thereto.

[54] In the manufacturing method according to the present invention, the method of

dispersing the carbon nanostructure-metal composite in the solvent may use all of the known methods, but dispersing the carbon nanostructure-metal composite in the solvent by using ultrasonic treatment is more preferable since it simplifies the manufacturing process and has excellent dispersibility. The case in which the carbon nanostructure-metal composites are tangled with each other can be generally confirmed by a scanning electron microscope. The tangle of the carbon nanostructure-metal composites may hinder the carbon nanostructure-metal composite from being uniformly dispersed when being coated on the membrane support, such that it is preferable that the ultrasonic treatment is performed at the time of manufacturing the membrane comprising the carbon nanostructure-metal composite.

[55] Meanwhile, at step b), if the heat treatment may be performed in the range of temperature in which the membrane support is not melted, while considering the melting or sintering of metal, the temperature of the heat treatment is not limited thereto.

Preferably, the heat treatment may be in the range of 100 to 700 °C more preferably, 100 to 500 °C. When the metal of the carbon nanostructure-metal composite is silver, the heat treatment can be performed between 100 to 300 °C. The heat treatment is performed for 1 to 24 hours to melt or sinter the metal, thereby making it possible to form the network structure. The heat treatment is performed in a general low- temperature oven, by a method of passing a coated membrane support through a thermal roller, or in a high-temperature electric furnace, or the like, but is not limited thereto. [56] Due to the heat treatment in the temperature range, the carbon nanostructure-metal composites are connected to each other by melting or sintering a metal as well as the carbon nanostructure-metal composite may be fused to the membrane support without melting the membrane support.

[57] In more detail, a principle of combining the carbon nanostructure-metal composite to the membrane support is as follows. The carbon nanostructures do not have adhesion bonding therebetween. However, in the case of the carbon nanostructure-metal composite, it is combined with the metal and in the case where the metal particles are a nanosize, it may be fused at a low temperature. The carbon nanostructure-metal composites are connected to each other using the metal component by the heat treatment and it is fused to the membrane support, thereby making it possible to manufacture the porous films in which the carbon nanostructure-metal composite having a network structure is combined with the membrane support.

[58] When the metal is silver, the silver containing composite porous films may be used for the separator of antibacterial water treatment. 5 to 90 wt% of silver for the whole carbon nanostructure-metal composite may effectively show the antibiosis. In the carbon nanostructure-metal composite, if the content of silver is smaller than 5 wt%, it may be difficult to form the carbon nanostructure-metal composite in the network structure and if the content of silver exceeds 90 wt%, the liquid cannot smoothly flow when the porous films comprising the manufactured carbon nanostructure-metal composite are used as the separator.

Mode for the Invention

[59] Examples for explaining in detail the present invention will be described below, but the present invention is not limited to the following examples.

[60] The following examples show that the carbon nanotube-silver composite is manufactured, the porous films comprising the hydrophilic surface modified carbon nanotube-silver composite are manufactured therefrom, and an experiment showing the advantages of the hydrophilic surface modification is performed. However, this is not limited to the carbon nanotube-metal composite or the porous films comprising carbon nanotube-metal composite as well as does not decrease the inherent effects of the porous films comprising carbon nanotube-metal composite. This aspect recites contents described in Korean Patent Application No. 2009-0026356 already filed by the applicant.

[61] [Manufacturing Example 1] Manufacturing of Carbon Nanotube-Silver Composite [62] 0.3g of multi-wall CNT grade (diameter 10 nm) put in 500 ml of a round flask and 280 ml of ethylene glycol (EG) was put in the round flask reactor. It was agitated for 30 minutes by an agitator and the reactor was put in the ultrasonic washer to disperse the carbon nanotube in ethylene glycol for 3 hours by using an ultrasonic wave. In this case, the temperature of the reactor did not exceed 50°C. When the ultrasonic treatment is completed, the agitator was mounted again and a thermometer and a cooling condenser were connected thereto. 1.68g of poly vinlypyrrolidone (PVP)

(manufacturer: Fluka, average molecular weight (Mw): 40,000) and 5.6ml of oleylamine were introduced thereinto while agitating the reactor and 1.102g of silver nitrate (AgN0 ₃ ) was then introduced thereinto. The vacuum pump was connected to the reactor to remove air in the reactor, which substituted it into nitrogen. Nitrogen was continuously introduced into the reactor and flows to the outside through the inside of the reactor to prevent oxygen from being introduced thereinto. A mantle was mounted at the lower portion of the flask, the temperature in the reactor was increased to 200 °C for 40 minutes, and the reaction was performed in the reactor for 1 hour. When the reduction reaction was completed, the temperature of the reactor was slowly decreased to normal temperature for 3 hours. The synthesized carbon nanotube-silver composite was filtered by filter paper and washed with ethyl acetate and hexane several times, thereby obtaining the carbon nanotube-silver composite. The results of analyzing the carbon nanotube-silver composite by the scanning electron microscope (SEM) were shown in FIG. 1. It could be appreciated from FIG. 1 that the silver particles were a spherical shape and were uniformly dispersed at a predetermined size. In detail, the size of the silver particles was 5 to 40 nm and 30 to 70 wt% of silver particles were included in the whole composite.

[63] [Example 1] Manufacturing of Porous Films Comprising Carbon Nanotube-Silver Composite

[64] Step a) includes coating the carbon nanostructure-metal composite dispersed in the solvent on one surface or both surfaces of the membrane support.

[65] 0.45g of the carbon nanotube-silver composite manufactured in Manufacturing 1 was added to 100ml of ultra-pure water in 1000 ml of the round flask and 0.45g of anionic surfactant, i.e., sodium dodecy] sulfate was added thereto, which was in turn subjected to the ultrasonic dispersion for 60 minutes.

[66] 250 ml of dispersion of the carbon nanotube-silver composite was introduced into the cartridge mounted with a ceramic porous filter having a cylinder shape and was repeatedly coated on the surface of the ceramic porous filter by using a water pump four times in total. After the coating was completed, 250 ml of ethanol was injected into the cartridge and the washing was performed four times in total.

[67]

[68] Step b) includes heat-treating the coated membrane support to fuse the metal to the membrane support.

[69] The washed composite porous filter was subjected to heat treatment of 150 to 180 °C for 1 to 24 hours in the oven to fuse the silver of the carbon nanotube-silver composite to the filter. The filter surface fused with the carbon nanotube-silver composite photographed by the scanning electron microscope (SEM) was shown in FIG. 2. It could be appreciated from FIG. 2 that the silver particles were dispersed in the carbon nanotube.

[70]

[71 ] Step c) includes surface-modifying the membrane fused with the carbon nanos- tructure-metal composite and making it in a hydrophilic state.

[72] The present example treated plasma to modify the surface of the membrane fused with the carbon nanotube-silver composite. The apparatus used for the plasma treatment was the atmospheric pressure plasma reactor, which is the low-temperature flat apparatus generating plasma using an RF power supply of 13.56 MHz having low power of 30 to 500W, which is ATMOS developed by the PLASMART Co. The filter fused with the carbon nanotube-silver composite was hung from the sample holder and the rotating speed is then set to be rotated at a predetermined speed. In this case, the rotating speed was fixed to 0.5 cm/s. As the discharge gas for generating plasma, argon was used. The flow rate of argon was maintained at 5 literl i (LPM). The plasma treatment frequency was performed for 5 periods at normal pressure and normal temperature and the plasma power was fixed to RF power of 100W. A total of plasma treatment time was 10 minutes by 2 minutes per 1 period, thereby manufacturing the porous films comprising the carbon nanotube-silver composite.

[73] [Reference Example 1]

[74] Reference Example 1 was performed similar to Example 1 except for step c), i.e., the surface modification was not performed.

[75] [Experimental Example]

[76] After the porous films comprising carbon nanotube-silver composite manufactured by Example 1 was fixed to the cartridge, 250 ml of deionized water was introduced thereinto to measure the flow rate per pressure. In this case, the pressure was set to 1, 2, 3, 4, and 5 kgf/cm ² by using the pressure gauge connected to the compressor, such that the comparative experiment with the porous films comprising carbon nanotube- silver composite of Reference Example 1 , which is not surface-modified with plasma, was performed according to the pressure. The comparative experimental results were arranged in the following Table and shown in FIG. 3. In FIG. 3, no plasma treatment shown the results of Reference Example 1 and plasma treatment shown the results of Example 1. It can be appreciated that the flow rate is further increased by 50.4% in Example 1 than in Reference Example 1.

[77] [Table 1] Comparison of flow rate before and after plasma treatment [78]

Reference Example 1 Examaple 1

Improvement

Pressure Flow rate Pressure Flow rate

Rate (%)

( kqf/ cm ² ) ( L/min) (kqf/ cm ² ) (L/min)

1 0.460 1 0.622 35.4

2 0.780 2 1.199 53.7

3 1.157 3 1.812 56.5

4 1.538 4 2.417 57.1

5 1.932 5 2.885 49.3

Averaqe 50.4