KR20090037059A - Synthesis method of carbon nanotubes using carbon material obtained by heat treatment of cellulose fiber as support, carbon - carbon nanotube filter using thereof - Google Patents

Abstract

A synthesis method of carbide-carbon nanotubes using carbon obtained by heat treatment of cellulose fiber as a supporter is provided to grow carbon nanotubes showing excellent electric conductance, specific surface area and mechanical strength on carbides with high density. A synthesis method of carbide-carbon nanotubes using carbon obtained by heat treatment of cellulose fiber as a supporter comprises the following steps of: cleaning and drying cellulose fiber and inputting the cellulose fiber into a reactor to produce carbide in the presence of only hydrogen as ambient gas while controlling a temperature to a range of 500-1500°C; coating the produced carbide with nano-catalytic particles; inputting the prepared sample into a reaction furnace controlled within 500-700°C; and growing carbon nanotubes vertically with high density while supplying carbon sources.

Description

Synthesis method of carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fiber, carbon nanotube filter using carbide-carbon nanotube structure, carbide-carbon nanotube structure {Synthesis method of carbon nanotubes using carbon material obtained by heat treatment of cellulose fiber as support, carbon-carbon nanotube filter using Julia}

The present invention relates to a method for synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, and a carbon nanotube filter using a carbide-carbon nanotube structure and a carbide-carbon nanotube structure. In detail, the present invention relates to a carbide having a new structure by heat-treating cellulose fibers, which are forest resources, and synthesizing carbide-carbon nanotubes, which are materials of Nas, and various filters manufactured by the same.

Recently, research using forest resources has been actively conducted. In particular, attempts are being made to utilize forest resources as an advanced new material development technology fused with nanotechnology (NT), biotechnology (BT) and environmental technology (ET).

As the use of forest resources, the most prominent technology development and application field is the composite material technology using cellulose fiber, and many countries are pushing ahead to develop the technology for the development of environment-friendly high performance composite material. Recently, researches on producing nanoscale cellulose nanofibers and synthesizing composite materials using the same have been conducted mainly in developed countries. In addition to the composite materials described above, the technology using forest resources is a hybrid energy. Applications are also possible for materials, adsorbents, electrodes and batteries.

Research on the technology of manufacturing the conventional nano-scale cellulose nanofibers and synthesizing composite materials using the same is still in its infancy, even in developed countries, and there is almost no technical development in this field in Korea. .

Therefore, the trend of patent applications in related fields is not yet showing a marked increase. However, recent research trends in the United States and other European countries showed a slight increase since 2005, and technology development in related areas after 2010, when the demand for nano / bio technology and energy / environment technology is expected to increase rapidly. This is expected to show a sharp increase.

Therefore, preoccupying core technologies in the early stages of technology development is very important.

An object of the present invention for solving the above problems is a nano-bio filter, gas concentrator, gas sensor material, electrode material, hazardous material adsorbents such as VOC, carbide of a new structure that can be widely used as a catalyst support It provides a method for producing a carbide-carbon nanotube structure by synthesizing a high-performance carbon nanotube on the surface of the cellulose carbide produced for production from cellulose fiber, a natural forest resource, and a carbide-carbon nanotube structure manufactured therefrom. There is.

The present invention also provides a carbide-carbon nanotube filter using a carbide-carbon nanotube structure.

Specifically, the present invention relates to obtaining a carbide having a new structure that can be utilized even in a high temperature atmosphere, and directly growing a high-density carbon nanotube by using it as a support, while minimizing damage to the original structure of the cellulose fiber. To achieve the growth of uniform carbon nanotubes, it is possible to easily form uniformly the nanocatalyst particles without additional pattern work by controlling the concentration of metal catalyst particles and controlling the size of the particles. The present invention provides a method for synthesizing carbide-carbon nanotubes and uniformly forming carbide-carbon nanotubes by uniformly forming nanocatalyst particles capable of high density array.

It is another object of the present invention to provide a carbide-carbon nanotube filter combining a carbide-carbon nanotube structure and a microform or micro feed tube having various shapes.

The present invention to achieve the object as described above and to solve the conventional drawbacks in the method of directly synthesizing nano-sized carbon tube on the carbide obtained by heat treatment of cellulose fibers,

Washing and drying the cellulose fibers and placing them in a reactor, thereby producing a carbide by heat treatment using only hydrogen as an atmosphere gas while controlling the temperature of the reactor in the range of 500-1500 ° C .;

Thereafter, the nanocatalyst particles are coated on the produced carbide, and the prepared samples are placed in a high temperature reactor controlled at a temperature range of 500-700 ° C. to supply carbon sources, thereby directly growing carbon nanotubes in a vertical and high density. It is achieved by providing a method for synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers characterized by the synthetic method.

In another aspect, the present invention is a carbon nanotube structure, characterized in that the carbon nanotubes on the surface of the carbide carbonized cellulose fibers or the inner surface of the carbide microtubules, carbon nanotubes are grown in a vertical, high density structure It is accomplished by providing a carbide-carbon nanotube structure using carbon as a support through heat treatment of the wood fibers.

In addition, the present invention is a carbon nanotube filter,

The cellulose carbide-carbon nanotube structure; A micro foam containing the cellulose carbide-carbon nanotube structure; It is achieved by providing a carbon nanotube filter using a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, characterized in that the filter support frame for supporting the circumference of the micro foam.

In addition, the present invention is a carbon nanotube filter,

A cellulose carbide-carbon nanotube structure in which carbon nanotubes are carbonized to grow carbon nanotubes only on the inner surface of the carbide tubules; Carbon nanotube filter using a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, characterized by consisting of a cellulose carbide-carbon nanotube structure and a micro feed tube coupled to both ends in the longitudinal direction Is achieved by providing

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to carbides, which have been recently studied and utilized in various fields. The present invention provides an easy to obtain a unique carbon support with a new structure from cellulose fibers, which are biomaterials. Carbon nanotubes having excellent physical, chemical and mechanical properties such as mechanical strength can be grown on new carbides at high density.

The present invention can not only be used as a material for energy electrodes such as secondary batteries and fuel cells, but also combines the microstructure of the new carbide and the nanostructure of carbon nanotubes, and is a biofilter, nanoparticle filter, and gas concentrator. It can be used as a high performance filter product and gas sensor material.

In addition, the catalyst support has excellent properties, it is expected that it can be used as a reaction apparatus using the same, it is a useful invention that is expected to be utilized as an adsorbent of harmful substances such as VOC is an invention that is expected to be greatly used in the industry.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart for a method of obtaining a carbide from the heat treatment of the cellulose fibers according to the present invention, and synthesizing carbon nanotubes using the support,

Schematic methods include cellulose fiber preparation step, cellulose fiber cleaning step, cellulose fiber heat treatment step, dispersion of solution with metal catalyst and solution, solution coating step on carbides from cellulose fiber, drying step , The reduction of the carbide surface obtained from the cellulose fibers, the carbon nanotube synthesis step and the cooling step.

More specifically, cellulose fibers are prepared to produce carbides of new structure. Most fibers are less than 1 mm in size and can vary in shape.

The prepared cellulose fiber is sufficiently immersed in distilled water, washed clean, and dried sufficiently at room temperature.

The dried cellulose fibers are placed in a high temperature reactor and the vacuum pump is operated for 10 minutes to remove oxygen present in the reactor and material.

The reactor is then raised to the desired heat treatment temperature, where the temperature of the reactor is controlled according to experimental conditions from 500 ° C. to 1500 ° C. at most. The reason for the numerical limitation of such a temperature is that when the carbon is lower than the lower limit, there is a problem that the remaining blood may remain because it is not completely carbonized, and when it is higher than the upper limit, no better quality carbide is produced. This is shown in the Raman analysis results shown in FIG.

 From the start of temperature rise, the reactor is supplied with 100% hydrogen, and the amount of atmospheric gas (hydrogen) is not changed until the production temperature is reached, and the experiment is completed by cooling.

This completes the preparation of a new structure of carbide from cellulose fibers to synthesize carbon nanotubes.

The producing of the carbide may selectively produce cellulose carbide having carbon characteristics of a specific structure according to the selection of a specific temperature while hydrogen heat treatment in the range of 500-1500 ° C.

Metal catalysts used as a medium for synthesizing the carbon nanotubes are nickel, iron, cobalt, etc., and are coated in the form of a thin film on the surface of the carbide obtained from the heat treatment of cellulose. At this time, the coating of the catalyst can be selectively coated on the outer surface of the carbide and the inner surface of the carbide microtubule.

In the coating of the catalyst, a solution is prepared by dispersing a metal catalyst in an appropriate 0.01-0.1w% concentration in distilled water. The reason for the numerical limitation of such concentration is that the coating thickness may be coated differently than desired, if it is lower than the lower limit, it should be re-coated to the desired thickness through repeated coating operation, and if it is higher than the upper limit, it is locally coated. .

Once the catalyst solution is prepared, it can be selectively coated on the outer surface of the carbide and the inner surface of the carbide microtubules as described below.

Firstly, in order to coat the catalyst on the surface of the carbide,

Carbide obtained from the heat treatment of cellulose is added to the prepared catalyst solution so that the solution is sufficiently dispersed over the entire outer surface. Dispersion time is 30 minutes in the ultrasonic bath as shown in FIG. 30 minutes is almost all distributed.

The coating is carried out in an ultrasonic bath for about 10 minutes (which is almost completely dispersed in 10 minutes), followed by a drying step.

At this time, the carbide obtained from the heat treatment of cellulose was used in a structure containing dozens of microchannels with a diameter of about 5-10 μm.

Secondly, in order to coat the catalyst on the inner surface of the microtube of carbide,

A method different from the above is presented.

The reason is that the micro-tubules of carbides are in the form of micro-sized long tubes that, when submerged in the solution, do not absorb the solution well due to surface tension, and only a fraction of the contact can be made.

Therefore, the entire carbide is not immersed in the solution, but only one end is immersed and the remaining part is opened so that the solution can be drawn into the microtubule tube by capillary action.

After pulling up the solution once in the above process, the carbide is removed from the solution and dried while removing the remaining solution by applying a negative pressure (suction pressure) to the open carbide end.

This excess is repeated several times, finishing the catalyst coating on the inner surface of the microtube.

In the above cellulose fibers, various cellulose microfibers may be used, but a large number of platelets in the body tube may generate a large pressure gradient in the flow of the fluid, and sometimes may impede the flow of the fluid itself. It is advantageous to use plants with a lot of constitution).

In the present invention, henequen or setaria viridis is preferably used as the cellulose microfiber.

As described above, the carbide in which the solution is sufficiently dispersed on the surface is taken out of the container and dried.

Thereafter, to remove the oxygen component contained in the metal catalyst coated on the surface of the dried carbide it is reduced at a temperature of 500-700 ℃ (depending on the synthesis reaction temperature of carbon nanotubes). The reason for the limitation of the temperature is that the reduction process for the metal catalyst is performed to generate nano catalyst particles and increase the activity of the total catalyst layer in the thin film state, so when the temperature is higher than the upper limit temperature, the catalyst particles become too large and the lower limit value is reduced. If the temperature is lower than the nano catalyst particles are not produced well.

The reduction process is carried out for about 1 hour, and a gas in which nitrogen and hydrogen are mixed 1: 1 is used as the reducing gas.

In this step, nano-sized catalyst particles grow uniformly.

This completes all preparation for synthesizing carbon nanotubes.

As described above, the finished carbide is put in a high temperature reactor and the temperature is increased.

After that, the temperature of the reactor increases to 500-700 ℃ according to the synthesis conditions, and when it is stable, it supplies carbon sources such as acetylene and ethanol to synthesize carbon nanotubes by chemical vapor deposition, Stop supply and cool. The reason for the limitation of the temperature is that a lower amount than the lower limit may generate a large amount of impurities, such as an amorphous material. If the upper limit is higher than the carbon nanotubes, other types of graphite materials are more likely to be produced.

The following is a preferred embodiment of the present invention.

(Example 1)

2 shows an SEM image as an example of a new structure carbide 11 obtained through hydrogen heat treatment of cellulose fibers according to the present invention.

The cellulose fiber used in the experiment was henequen. Figures (a) and (b) show images of henequen raw materials. (a) is an image of the trunk of the fiber, (b) is an image of the cross section of the fiber. What is seen in the cross section of the raw material is the material that constitutes the water pipe and the body pipe, and appears to have a regularly dried structure. Figures (c) and (d) show the body and cross section of a henequen sample heat-treated in a hydrogen atmosphere. In the examples, the heat treatment temperature was 700 ° C., and hydrogen was supplied at 100 cc / min. The increase from room temperature to the heat treatment temperature rose as fast as 20 minutes, and maintained at 700 ℃ for 30 minutes. Hydrogen was cooled from the temperature rise point and supplied until the end of the experiment.

Experimental results showed that the shape of henequen raw material was not significantly impaired, carbonized, and most of the components were carbon, and calcium, sodium, magnesium, etc. contained in some raw materials were observed. (d) shows the cross section of the heat treated sample. It can be seen that the process was very clean compared to the raw material, and had a microtubule structure having a diameter of approximately 5-20 μm.

(Example 2)

Figure 3 is an embodiment of the synthesis of carbon nanotubes on a new carbide obtained through the hydrogen heat treatment of the cellulose fibers according to the present invention, shows an SEM image. Nickel was used as a nanocatalyst to synthesize carbon nanotubes. Nickel nanocatalyst was obtained using a solution in which nickel acetate was mixed with distilled water at 0.01w%. In order to form nanocatalyst particles for synthesizing carbon nanotubes, hydrogen and nitrogen were reduced at a temperature of 700 ° C. in a 1: 1 mixture for 1 hour. Since the temperature for the synthesis of carbon nanotubes was controlled to 700 ℃, ethanol was used as the carbon source. Ethanol was fed at 3 ml / h for 30 minutes.

Figure (a) shows an image of carbon nanotubes synthesized on a henequen sample heat-treated in a hydrogen atmosphere. It is confirmed that the synthesis is very uniform and high density. As shown in Figure (c), they do not grow vertically but appear to be somewhat curved. Figures (b) and (d) show carbon nanotubes grown on cross-sections of heat-treated henequen. It appeared to grow very uniformly, as in the body, and clearly shows the image of carbon nanotubes grown in the microtubule structure.

(Example 3)

Figure 4 is an embodiment of a new structure of the carbide obtained through the hydrogen heat treatment according to the temperature conditions of the cellulose fiber according to the present invention, shows the results of Raman analysis. The analysis showed that peak in the figure showing the strongest intensity in the vicinity of each of 1350cm ^-1 and 1580cm ^-1. The results at this location represent the D-line (Disordered line) and the G-line (Graphite line), respectively, which are commonly found in carbon-based materials. In general, it can be seen that the tendency of each peak changes little by little depending on the temperature conditions. At 500 ° C, it showed a similar tendency to amorphous carbon which is commonly found in charcoal, but as the temperature increases, it tends to change to the value of the carbon material observed in the graphitized carbon, although the peak of the D-line is large. .

(Example 4)

5 is a view showing the application of a carbide-carbon nanotube structure (1) synthesized with a carbon nanotube (12) to a carbide (11) of a new structure obtained through hydrogen heat treatment of cellulose fibers according to the present invention as a filter. Represents a conceptual diagram.

FIG. 5A shows the carbide-carbon nanotube structure 1 when the synthesized carbon nanotubes 12 are all synthesized on the outer surface of the cellulose fiber carbide.

The filter in such a structure may constitute a bulk filter as shown in Figs. (B) and (c), in which case the micro foam is used as a frame for the micro-sized carbide-carbon nanotube structure (1). Use the frame with (2). That is, as shown in the grid surface of the micro-foam tangled together like a nonwoven fabric or thread. The form of the frame is irrelevant. It also forms a filter support frame 21 that can be mounted to the system by supporting the foam form. The filter thus constructed can be densely packed with microstructures in which nano-sized carbon tubes are synthesized on carbides 11 produced from micro-sized cellulose fibers to form micro / nano pores. The system also synthesizes carbon nanotubes 12 on the carbides produced from nano cellulose fibers, filling tightly with nanostructures to form tiny nanopores. Therefore, filtering on both very small nanoparticles and biomaterials 22 is possible.

Figure (d) is a schematic diagram of the case where the synthesized carbon nanotubes 12 were grown only on the microtubule 13 of carbide. In this case, a single carbide-carbon nanotube structure (1) can be used directly as a micro filter with nanopores (3), which is directly connected to the microchannels as shown in the schematic diagram in Figure (e). It is possible. In the configuration diagram, the micro filter is connected to the micro transfer tube 24 to convert the nanoparticles and the biomaterial 22 into the filtering flow 23.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

1 is a flowchart illustrating a method for synthesizing carbon nanotubes using carbides obtained from heat treatment of cellulose fibers according to the present invention and using them as a support,

2 is an exemplary view of a carbide having a novel structure obtained through hydrogen heat treatment of cellulose fibers according to the present invention (SEM image),

Figure 3 is an embodiment of the synthesis of carbon nanotubes in a carbide of a new structure obtained through hydrogen heat treatment of cellulose fibers according to the present invention (SEM image),

Figure 4 is an embodiment of the new structure of the carbide obtained through the hydrogen heat treatment according to the temperature conditions of the cellulose fiber according to the present invention (Raman spectroscopy),

FIG. 5 is a conceptual view illustrating the application of a carbide-carbon nanotube structure synthesized with carbon nanotubes to a carbide having a new structure obtained through hydrogen heat treatment of cellulose fibers according to the present invention.

<Description of the symbols for the main parts of the drawings>

(1): carbide-carbon nanotube structure (2): micro foam

(3): micro filter (11): cellulose fiber carbide

(12): carbon nanotube (13): micro tubing

21: filter support frame 22: nanoparticles and biomaterials

(23): filtering flow (24): micro feed tube

Claims (13)

In the method of directly synthesizing nano-sized carbon tube on the carbide obtained by heat treatment of cellulose fiber, Washing and drying the cellulose fibers and placing them in a reactor, thereby producing a carbide by heat treatment using only hydrogen as an atmosphere gas while controlling the temperature of the reactor in the range of 500-1500 ° C .; Thereafter, the nanocatalyst particles are coated on the produced carbide, and the prepared samples are placed in a high temperature reactor controlled at a temperature range of 500-700 ° C. to supply carbon sources, thereby directly growing carbon nanotubes in a vertical and high density. A method of synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, characterized in that the synthesis method. The method of claim 1, The step of producing a new structure of carbide from cellulose fibers through heat treatment at a high temperature of the hydrogen atmosphere, Washing the cellulose fiber prepared in the distilled water solution with sufficient wetness and drying at room temperature; Placing cellulose fibers in a high temperature reactor and removing residual oxygen in the device with a vacuum pump, Synthesis of carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fiber, comprising the step of supplying 100% hydrogen while controlling the temperature of the reactor between 500-1500 ° C. Way. The method of claim 1, Synthesizing carbon nanotubes including the coating method of the nanocatalyst, Dispersing the metal catalyst ultrasonically in a distilled water solution; Coating a catalyst on the surface by putting a carbide obtained from cellulose fibers in a mixed solution in which the metal catalyst is dispersed; After the drying step, reducing the surface of the catalyst-coated carbide in a reducing atmosphere in which hydrogen and nitrogen are mixed 1: 1; In the reduction step, the reduction temperature is controlled between 500-700 ° C. according to the synthesis temperature of the carbon nanotubes, and includes uniformly forming nanocatalyst particles. Supplying a carbon source to the catalyst-coated carbide in a high temperature reactor controlled between 500-700 ° C. after the reduction step to synthesize carbon nanotubes by chemical vapor deposition. A method of synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment. The method of claim 1, Synthesizing carbon nanotubes including the coating method of the nanocatalyst, Dispersing the metal catalyst ultrasonically in a distilled water solution; Coating a catalyst using a capillary phenomenon on the inner surface of the microtubule of carbide obtained from cellulose fibers with a mixed solution of the metal catalyst dispersed therein; After the drying step, reducing the surface of the catalyst-coated carbide in a reducing atmosphere in which hydrogen and nitrogen are mixed 1: 1; The reduction temperature in the reduction step is controlled between 500-700 ° C. according to the synthesis temperature of the carbon nanotubes, and includes uniformly forming nanocatalyst particles. Supplying a carbon source to the catalyst-coated carbide in a high temperature reactor controlled between 500-700 ° C. after the reduction step to synthesize carbon nanotubes by chemical vapor deposition. A method of synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment. The method according to claim 3 or 4, The metal catalyst is a method of synthesizing a carbide-carbon nanotube structure using carbon as a support by heat treatment of cellulose fibers, characterized in that at least one selected from nickel, iron, cobalt. The method according to claim 3 or 4, The carbon source is a method for synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, characterized in that using ethanol or acetylene. The method of claim 1, The step of producing the carbide is a cellulose fiber, characterized in that the step of selectively producing cellulose carbide having a carbon characteristic of a specific structure according to the selection of a specific temperature while hydrogen heat treatment in the range of 500-1500 ℃ Method of synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of. The method of claim 1, The cellulose fiber is a method of synthesizing a carbide-carbon nanotube structure using carbon as a support through heat treatment of the cellulose fiber, characterized in that henequen or setaria viridis. In the carbon nanotube structure, The outer surface of the carbide or the microtubule inside of the carbide carbonized cellulose fiber prepared according to any one of claims 1, 2, 3, 4, 7, 8 A carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers, characterized in that the structure is grown in a vertical, high-density carbon nanotube directly on the surface. In the carbon nanotube filter, A cellulose carbide-carbon nanotube structure (1) prepared according to any one of the preceding claims 1, 2, 3, 7, and 8; A micro foam (2) containing the cellulose carbide-carbon nanotube structure (1); Carbon nanotube filter using a carbide-carbon nanotube structure using carbon as a support by heat treatment of cellulose fibers, characterized in that consisting of a filter support frame 21 for supporting the circumference of the micro foam (2). The method of claim 10, The cellulose fiber constituting the cellulose carbide-carbon nanotube structure 1 is a micro cellulose fiber having a micro diameter or a nano cellulose fiber having a nano diameter. Carbon nanotube filter using a carbide-carbon nanotube structure using carbon as a support through heat treatment. In the carbon nanotube filter, Cellulose carbide prepared by carbonizing the cellulose fibers according to any one of claims 1, 2, 4, 7, and 8 so that carbon nanotubes are grown only on the inner surface of the carbide tube. A carbon nanotube structure 1; Carbide-carbon nanotubes using carbon through heat treatment of cellulose fibers as a support, characterized by consisting of a cellulose carbide-carbon nanotube structure (1) and a micro feed tube (24) coupled to both ends in the longitudinal direction. Carbon nanotube filter using the structure. The method of claim 12, The plurality of tubules constituting the cellulose carbide-carbon nanotube structure each has a diameter of 5-20 micrometers, characterized in that the carbide-carbon nanotube structure using carbon as a support through heat treatment of cellulose fibers Carbon nanotube filter used.

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