KR101024169B1 - Chopped nanofiber, method of and apparatus for controlling the length of nanofiber and material using the chopped nanofiber - Google Patents

Abstract

The present invention is a nanofiber controlled the length of the nanofiber to control the length of the nanofiber to a desired level by using the mechanical impact energy generated in the process of rotating the nanofiber and the ball in the rotating body, the control method and device, the length It relates to a composite material using a controlled nanofiber.

Method for controlling the length of a nanofiber according to the present invention comprises the steps of charging a nanofiber, ball, crushing tank material in a milling device equipped with a cooling device and a gas control device; Mixing each of the additives at low speed; Cutting the length of the nanofiber using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed; And separating and recovering the length-controlled nanofibers using a sieve.

According to the length control method of the nanofiber of the present invention, by cutting the length of the nanofiber in a short time it is possible to prevent the occurrence of defects on the front surface of the nanofiber due to a long milling time.

Nanofibers, Carbon Nanotubes, Carbon Nanofibers, Synthesis, Chopped Nanofiber, Crushing Support Material

Description

Controlled length nanofibers, control method and device, composite material using controlled length nanofibers {Chopped nanofiber, method of and apparatus for controlling the length of nanofiber and material using the chopped nanofiber}

The present invention relates to a length-controlled nanofiber, a method and apparatus for controlling the same, and a composite material using a length-controlled nanofiber, in particular, mechanical impact energy generated in the process of mixing and rotating a nanofiber and a ball in a rotating body. It relates to a length-controlled nanofiber to control the length of the nanofibers to a desired level, the control method and device, a composite material using the length-controlled nanofiber.

Nanofiber is a graphite carbon material in which a single carbon atom is bonded to an adjacent carbon atom and has a hexagonal honeycomb structure. In the case of carbon nanotubes, the diameter is usually several to several tens of nanometers in length and tens of micrometers in length. It is a long cylindrical carbon material with a very large difference in diameter and length ratio of 10 to 10,000. Carbon nanofibers are 10 times larger in diameter than carbon nanotubes and are fibrous carbon materials with a full interior. Because of their long length and their entangled structure in the nanofiber synthesis step, it is difficult to disperse nanofibers in the liquid and solid phases, so attempts are made to keep them short while maintaining the properties of the nanofibers. have.

Prior art related to the control of the length of such nanofibers, "Method for treating carbon nanostructure using wet milling (Korean Patent Application No. 10-2003-0039657, 2003. 06. 19)", "Conductive inkjet ink using conductive polymer Manufacture (Korean Patent Application No. 10-2004-009153, 2004. 02. 11) "," Length control device of carbon nanotube using electrolytic action (Korean Patent Registration No. 10-0563251, 2006. 03. 15) " Etc.

The method for treating carbon nanostructures using wet milling (Korean Patent Application No. 10-2003-0039657, 2003. 06. 19) is a method of treating carbon nanostructures in a milling vessel with balls and acid solutions, oxidizing agents and / or surface treatment agents. Purification, surface treatment and / or length control are carried out by putting together and wet milling for a period of time. However, this method is mainly used for the purification and surface treatment of carbon nanotubes. The acid treatment and the impact energy of the ball act on the surface of the carbon nanotubes simultaneously, so that the carbon nanotubes are not only cut in the longitudinal direction but also in the width direction. Carbon nanotubes of non-uniform particle size are obtained, such as cracking / crushing. In addition, there is a problem in that functional CNT production through limiting the properties of the catalyst is limited because the catalyst is removed by the acid, the process cost is increased due to the attachment of unwanted functional groups, wet treatment. In particular, in wet milling, the entire surface of the carbon nanotubes reacts with an acid, and mechanical impact energy is applied thereto, so that there are many surface defects and difficulty in cutting to a specific length.

A device for controlling the length of carbon nanotubes using electrolysis (Korean Patent Application No. 10-0563251, 2006. 03. 15) is a method for controlling the length of carbon nanotubes using electrolytic reaction. The present invention relates to an apparatus for manufacturing carbon nanotubes having a desired length by cutting to a desired length, and controlling the energization time of the input speed and current of the carbon nanotubes. In this method, however, the carbon nanotubes are attached to the probe and moved in the longitudinal direction to contact the electrolyte solution, which is fixed by surface tension, while supplying power to the probe to selectively dissolve the site in contact with the electrolyte. There is a problem that it is complicated, expensive to manufacture and difficult to mass produce.

N. Pierard (Chemical Physics Letter, 335, 2001, 1-8, Production of short CNT with open tips by ball milling) reported how to cut the length of carbon nanotubes using dry ball milling. Specifically, the carbon nanotubes were charged to the planetary ball milling apparatus together with the balls, followed by dry ball milling for 120 hours to prepare carbon nanotubes having an average length of 0.9 μm. However, in this method, since the cooling device and the gas control device cannot be installed, there are disadvantages such as heat generation generated inside the milling device and the accompanying deterioration in productivity along with deterioration of the quality of the carbon nanotubes. Specifically, in this method, the concentration of energy by the ball is difficult, and as the milling up to 120 hours, the carbon nanotubes are unevenly cut due to the high heat (energy) generated by the collision between the ball and the ball and the wall. Oxidation phenomenon occurs due to an oxidizing atmosphere, and in particular, defects are generated on the front surface of the carbon nanotubes due to excessive contact by long time milling, and thus inherent characteristics of the carbon nanotubes are weakened. There is a limit to getting.

The present invention has been made to solve the conventional problems as described above, the object of the present invention is the non-uniform length of the nanofibers, which were the most problematic in the conventional wet milling and dry milling method, the complexity of the oxidation, heat generation, process To provide a composite material using a length-controlled nanofiber, a control method and apparatus thereof, and a length-controlled nanofiber to solve problems such as a long milling time.

In addition, another object of the present invention is based on a dry milling system equipped with a cooling device capable of releasing heat inside the milling apparatus and a gas control apparatus for controlling the gas atmosphere and pressure inside the milling apparatus. Due to the concentration of impact energy due to the use of a crushing tank material, the length of the nano-controlled nanometer can effectively cut the length of the carbon nanotubes in a short time of less than 1/100 of the time, and at the same time, obtain high quality homogeneous carbon nanotubes. It is to provide a composite material using a fiber, a method and device for controlling the same, and a nanofiber whose length is controlled.

In order to achieve the above object, the length control method of the nanofiber according to the present invention comprises the steps of charging the nanofiber, ball, crushing tank material in the milling device equipped with the cooling device and the gas control device; Mixing each of the additives at low speed; Cutting the length of the nanofiber using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed; And separating and recovering the length-controlled nanofiber using a sieve, wherein the crushing tank material is a ceramic material such as zirconia (ZrO 2), alumina (Al 2 O 3), silica (SiO 2) and tungsten (W). ), One or two or more of metal materials such as cemented carbide containing titanium (Ti).

In addition, in the nanofiber length control method according to the present invention, the nanofibers are characterized in that the tube or fiber having a diameter of 200nm or less including carbon nanotubes and carbon nanofibers.

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In addition, in the method for controlling the length of a nanofiber according to the present invention, the low-speed mixing step is mixed by rotating at a low speed of 150 rpm or less at 1 hour or less in an inert gas atmosphere.

In addition, in the nanofiber length control method according to the present invention, the high speed milling step may be roll milling, ball milling, attrition milling, planetary milling, It is characterized in that any one of the mechanical milling method selected from Jet Milling, Screw Mixing milling method.

In the method of controlling the length of a nanofiber according to the present invention, the high speed milling step controls the length of the nanofiber by rotating the milling apparatus at a high speed of 200 rpm to 500 rpm for 1 hour or less.

In the method for controlling the length of a nanofiber according to the present invention, the high speed milling step controls the length of the nanofiber to 1 to 3 μm by rotating the milling apparatus at a speed of 400 rpm for 10 minutes.

On the other hand, the length-controlled nanofiber according to the present invention comprises the steps of charging the nanofiber, ball, crushing tank material in the milling device equipped with the cooling device and the gas control device; Mixing each of the additives at low speed; Cutting the length of the nanofiber using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed; And separating and recovering the length-controlled nanofibers using a sieve.

On the other hand, the composite material using the nanofiber controlled length according to the present invention, the step of charging the nanofiber, ball, crushing tank material in the milling device equipped with the cooling device and the gas control device; Mixing each of the additives at low speed; Cutting the length of the nanofiber using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed; And separating and recovering the length-controlled nanofibers by using a sieve. Ultrasonic, roll milling, and ball milling of the length-controlled nanofibers in liquid and solid phases ), Jet milling, and screw mixing, which are prepared by dispersing by any one of dispersing methods.

On the other hand, the length control device of the nanofiber according to the present invention, the support of the milling device; A lower cooling device formed in a double wall structure surrounding the outer wall of the milling apparatus at a lower side of the support and having a refrigerant inlet and outlet; An upper cooling device formed in a double wall structure surrounding an outer shaft of a rotating shaft at an upper portion of the support part, and having a refrigerant inlet and outlet; The gas inlet and outlet valve and the flow rate control device is provided and includes a gas control device installed on the upper surface of the lower cooling device.

According to the length control method of the nanofiber of the present invention having the above configuration, by adding a crushing tank material in addition to the nanofiber, the ball to leave the nanofiber attached to the ball and the wall, and the impact energy applied to the nanofiber By concentrating on one point of the fiber, the length of the nanofiber can be cut in a short time, thereby preventing the occurrence of defects on the front of the nanofiber due to the long milling time.

In addition, according to the method for controlling the length of the nanofiber according to the present invention, by controlling the impact energy applied to the nanofiber using the crushing tank material, it is possible to manufacture a controlled nanofiber of uniform length in a short time, a simple process, It is easy to secure high productivity, low manufacturing cost and reproducibility, and mass production is possible.

In addition, according to the length control device of the nanofiber of the present invention, a continuous cooling device for releasing the heat generated between the ball and the ball, the ball and the wall surface in the milling process and the gas for preventing oxidation in the crushing process of the nanofiber Equipped with a gas control device to control the atmosphere and pressure, it is possible to effectively cool the heat generated inside the milling chamber and to prevent oxidation of nanofibers and catalysts, thus producing uniform and high-quality nanofibers. have.

In addition, the use of the controlled nanofiber length according to the present invention can improve the dispersibility in the liquid and solid materials compared to the conventional nanofiber, so that the composite material having excellent electrical and mechanical properties can be manufactured in industrial applications The field can be greatly expanded.

In addition, when manufacturing a composite material using a nano-controlled length of the present invention, the effect of improving the thermal conductivity and mechanical properties in addition to the improvement of electrical conductivity can be expected.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a length-controlled nanofiber, a control method and apparatus thereof, a composite material using a length-controlled nanofiber according to the present invention will be described in detail.

1 is a flowchart illustrating a process of a method for controlling a length of a nanofiber according to the present invention, and FIG. 2 is a conceptual diagram of an apparatus for controlling a length of a nanofiber according to the present invention.

1 and 2, the nanofiber length control method according to the present invention comprises the steps of charging the nanofibers, balls, crushing tank material in a milling device equipped with a cooling device and a gas control device, each additive Mixing at low speed, cutting the length of the nanofiber using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed, and controlling the length using the sieve Separation of fibers and balls and recovery of the nanofibers, and mixing the length-controlled nanofibers into various kinds of solid and liquid materials and then dispersed by various dispersion methods to implement electrical and mechanical properties.

The nanofibers employed in the charging step 111 may be a tube or fiber having a diameter of 200 nm or less, including carbon nanotubes and carbon nanofibers.

In addition, the balls for imparting mechanical impact energy in the milling process are metal and ceramic materials such as stainless and zirconia.

The crushing tank material prevents the nanofiber adhesion from the ball and the ball, the ball and the wall, and at the same time concentrates the impact energy to produce a uniform nanofiber in a short time, and it is a particulate zirconia (ZrO2), Al2O3), a ceramic material such as silica (SiO2) and one or more of metal materials such as cemented carbide containing tungsten (W), titanium (Ti) and the like may be targeted.

When the charging is completed, the mixture is rotated at a low speed of 150 rpm or less at 1 hour or less under a nitrogen gas-filled inert gas atmosphere in a milling apparatus equipped with a cooling device and an antioxidant, and then sufficiently mixed (113).

The mechanical milling method adopted in the high speed milling step 115 is roll milling, ball milling, attrition milling, planetary milling, jet milling. ), A mechanical milling method including at least one selected from milling methods using various energies such as screw mixing. In the present invention, the milling time of applying mechanical impact energy to control the length of the nanofibers may vary depending on the type of nanofibers. For example, it is preferable to increase the time in the case of carbon nanofibers rather than pure carbon nanotubes.

In the high-speed milling step 115, by using the mechanical impact energy of the ball-ball, ball-wall surface generated when the mixture is rotated to a milling device equipped with a cooling device in an inert atmosphere at a high speed of 200 rpm or more at less than 1 hour While controlling the length of the nanofiber is homogenized, preferably the length of the nanofiber is controlled to 5㎛ or less.

 The length-controlled nanofiber is subjected to separation and recovery using a sieve separated by particle size, preferably a sieve having a diameter of 3 mm, by applying physical energy such as a vibrating screen (117).

The recovered length-controlled nanofibers can be obtained by any one of dispersion methods such as ultrasonic and roll milling, ball milling, jet milling, screw mixing, and the like. By dispersing in the liquid and solid phase, a conductive material is produced. After mixing and dispersing the length-controlled nanofibers in the liquid resin, a liquid composite material is prepared using a dispersion method such as ultrasonic wave and 3 roll milling. Alternatively, the length-controlled nanofibers are mixed and dispersed in a solid metal, a polymer, and a ceramic, and then a solid composite material is manufactured by various molding processes. When the conductive material is manufactured using the controlled nanofiber length according to the present invention, as the dispersibility of the nanofiber is improved, thermal conductivity and mechanical properties are improved in addition to the electrical conductivity.

2 is a conceptual diagram of the length control device of the nanofiber according to the present invention, the length control device of the nanofiber according to the present invention is the attrition mill support 121, the lower cooling device 123, the upper cooling device 124, a gas control device 125, and a stainless ball 127, a crushing tank material 129, and a nanofiber 131 are loaded.

The lower cooling device 123 has a double structure surrounding the chamber wall of the milling device to allow the cooling water to flow continuously, and the cooling water also flows to the upper end of the rotating shaft by the upper cooling device 124 and the wall surface of the milling device. Cool the rotating shaft simultaneously. At this time, the refrigerant used may be a gas or a liquid substance.

The gas control device 125 is located above the attrition mill supporter 121 and is equipped with a valve and a flow control device in the inlet and the outlet, so that the gas atmosphere is inert, reduced, and oxidized at an appropriate pressure in the milling device. To be maintained.

At this time, the types of rotating bodies used are ball milling, jet milling, attrition milling and planetary milling. This can be

Hereinafter, a preferred embodiment of a composite material using a length-controlled nanofiber, a control method and apparatus thereof, and a length-controlled nanofiber according to the present invention will be described.

<Examples>

Effect of addition of crushing tank material and balls, influence of cooling device and gas supply device, milling time and rotation speed to control the length of carbon nanotubes through the length control method of nanofiber according to the present invention Changes in the properties and length of carbon nanotubes are shown in Table 1.

In the carbon nanotube properties of Table 1, the mark 'O' means that the surface of the carbon nanotubes is not uniform and is irregularly cut.

* Shredding material: O added, X not used

* Chiller: O Chiller operation, X not running

* Atmosphere: O nitrogen gas, X atmosphere

* Carbon nanotube properties: O uniform purity and surface, △ middle, X purity and surface defect

In the carbon nanotube length control method according to the present invention, first, a stainless steel ball 15kg, a crushing material of silica (Silica) 100g, and carbon nanotubes 100g in order to the Attrition Mill equipped with a cooling device and a gas control device Charge and mix at 150 rpm for 5 minutes in a nitrogen atmosphere. After fully charged contents are rotated at 400rpm for 10 ~ 60 minutes to control the length of carbon nanotubes to the desired level, carbon nanotubes and shredding materials of which length is finally controlled using a sieve having a diameter of 3mm Will be separated and recovered.

In the present embodiment, the effect of the crushing tank material was narrowed from 1 to 5 μm to 1 to 3 μm compared to before the addition, and the surface of the carbon nanotubes was similar to that before the crushing without tearing or defects. It was manifested. The crushing tank material prevents the carbon nanotubes from adhering to the ball and the wall and concentrates the impact energy applied to the carbon nanotubes to a point to complete the length control in a short time.

In the effect of the cooling apparatus according to the present embodiment, the carbon nanotubes and the catalyst were oxidized due to the heat generated during the milling process before the cooling apparatus was operated, and the purity of the carbon nanotubes was lowered and the surface was irregularly torn. It was found that this phenomenon does not occur when the cooling device is operated so that the length of the carbon nanotubes can be controlled without deterioration of quality.

In this embodiment, when the air in the milling chamber was replaced with nitrogen and kept in the nitrogen atmosphere during milling, it was possible to prevent oxidation of carbon nanotubes due to heat generated during the milling process. However, when the cooling device is not operated, the carbon nanotubes are partially oxidized while being exposed to the atmosphere during the recovery of the carbon nanotubes. Therefore, the cooling device and the gas atmosphere control device must be applied at the same time to effectively control the length of the carbon nanotubes. It could be confirmed.

In this embodiment, the milling time was changed to 10 minutes, 30 minutes, and 60 minutes while the rotation speed was fixed at 400 rpm, and the change in the length of the carbon nanotubes according to the influence of the energy applied to the carbon nanotubes was examined. If the time is longer than 30 minutes, the carbon nanotubes are excessively crushed to 500 nm or less, and serious defects are generated on the surfaces of the carbon nanotubes, thereby losing the inherent properties and characteristics of the carbon nanotubes. The particle size and characteristics of the carbon nanotubes obtained at the milling time of 30 minutes or more were similar to those of the conventional conductive carbon black. However, when the milling time is 10 minutes it was possible to obtain a clean carbon nanotube having a length of 1 ~ 3 ㎛.

In the effect of rotation speed, which is another method of applying energy, when the rotation speed was changed to the range of 200 to 500 rpm with the milling time fixed at 10 minutes, the carbon nanotubes were excessively below 500 nm due to excessive energy at 500 rpm. It was crushed very hardly and hardly crushed at 200 rpm. Although the crushing proceeded at 300 rpm, it could not be controlled to the desired level due to the lack of energy, while at 400 rpm, carbon nanotubes having a length of 1 to 3 ㎛ could be obtained.

In controlling the length of the carbon nanotubes, when the length control method of the nanofiber according to the present invention was applied, high-quality carbon nanotubes having a length of 1 to 3 µm were obtained, and for other lengths, according to the change of the corresponding conditions. It is confirmed in Table 1 that control is possible.

3 is a photograph taken using a transmission electron microscope (TEM) of the change in the length of the carbon nanotubes according to the milling time of Table 1, as shown in the milling time 30 minutes or more due to excessive energy It can be seen that the crushed to less than the size to be, in 10 minutes the length was cut to a length of 1 ~ 3㎛. That is, high-quality carbon nanotubes with a controlled length were obtained due to the cooling effect, the gas atmosphere effect, the addition of the crushing tank material, and the adjustment of the appropriate energy input amount by controlling the time and the rotation speed.

Figure 4 is a result of the Raman spectrum analysis (Raman Spectrum) to determine the crystallinity and defects of the length-controlled carbon nanotube step by step. In the case of excessively crushed carbon nanotubes milled for 30 minutes or more, the D peak value was increased, indicating that many defects occurred during the milling process. In the case of 10-minute milling having a length of 1 to 3 μm, the carbon before crushing Compared to the case of the nanotubes, the D peak value was increased, but the overall change in the value showed little defects due to crushing.

Figure 5 (a) is a conceptual diagram showing the dispersion state of the nanofiber when the conventional nanofibers are dispersed in liquid and solid materials to make a composite material, Figure 5 (b) is a nanofiber with a controlled length in accordance with the present invention Is a conceptual diagram showing the dispersion state of nanofibers when a composite material is prepared by dispersing in a liquid phase and a solid phase material. As shown in FIG. As it is in the tangled state as in this case, it is difficult to improve the conductivity, but the strength is weak, the carbon nanotube addition effect is lost. However, the controlled carbon nanotubes can be easily dispersed to achieve the desired electrical conductivity and mechanical properties.

1 is a flow chart of a method for controlling the length of a nanofiber according to the present invention.

2 is a schematic cross-sectional view of an apparatus for controlling the length of a nanofiber according to the present invention.

Figure 3 is a photograph showing the change in the length of the nanofiber according to the nanofiber milling time of the present invention.

Figure 4 is a graph of the Raman analysis of the length-controlled nanofiber of the present invention.

Figure 5 (a) is a conceptual diagram showing the dispersion state of the nanofiber when the composite material is made using a conventional nanofiber, Figure 5 (b) is a composite material using a length-controlled nanofiber according to the present invention Conceptual diagram showing the state of nanofiber dispersion when prepared.

DESCRIPTION OF THE REFERENCE NUMERALS

121: Attrition milling device 123: Cooling device

125: gas control device 127: stainless steel ball

129: crushing tank material 131: nanofiber

Claims (10)

Inserting nanofibers, balls, and crushing tank materials into a milling apparatus equipped with a cooling device and a gas control device (111); Mixing each of the additives at low speed (113) Cutting the length of the nanofiber by using impact energy at the ball and the ball, the ball and the wall while rotating the mixed contents at high speed (115); And Separating and recovering the length-controlled nanofibers using a sieve, The crushing tank material is one or two or more of a ceramic material such as zirconia (ZrO 2), alumina (Al 2 O 3), silica (SiO 2), and a metal material such as tungsten (W) and a cemented carbide containing titanium (Ti). Length control method of nanofibers. The method of claim 1, The nanofiber is a nanofiber length control method, characterized in that the tube or fiber of less than 200nm in diameter including carbon nanotubes and carbon nanofibers. delete The method of claim 1, Slow mixing step 113 is a method for controlling the length of the nanofiber, characterized in that the step of mixing by rotating at a low speed of 150 rpm or less in 1 hour or less in an inert gas atmosphere. The method of claim 1, The high speed milling step 115 is roll milling, ball milling, attrition milling, planetary milling, jet milling, screw mixing. Mixing) The length control method of the nanofiber, characterized in that any one of the mechanical milling method selected from the milling method. The method according to claim 1 or 5, The high speed milling step 115 is to control the length of the nanofiber, characterized in that for controlling the length of the nanofiber by rotating the milling device at a high speed of 200 rpm to 500 rpm for less than one hour. The method according to claim 1 or 5, The high speed milling step 115 is to rotate the milling device at a speed of 400 rpm for 10 minutes to control the length of the nanofiber to 1 ~ 3 ㎛ nanofiber length control method. delete delete delete

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