KR20130082364A - Manufacturing method for cathode module of x-ray generation apparatus using carbon nanotube - Google Patents

Abstract

PURPOSE: A manufacturing method of a cathode module for an x-ray generator unit, which uses carbon nano-tubes, is provided to mass-produce cathode modules by cutting a tube into small sized pieces. CONSTITUTION: A carbon nano-tube (20) is grown up on a substrate (10). A chemical vapor deposition (CVD) is used for the growth. A hardening solution (30) is coated on the carbon nano-tube and the substrate. The coating increases the connectivity between the substrate and the carbon nano-tube. The hardening solution is mixed with polystyrene and toluene.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing a cathode module of an X-ray generator using carbon nanotubes,

The present invention relates to a method of manufacturing a cathode module of an X-ray generator using carbon nanotubes, and more particularly, to a method of manufacturing a cathode module using a carbon nanotube (CNT) And more particularly, to a method of manufacturing a negative electrode module of an X-ray generator using carbon nanotubes.

The present invention can replace a conventional commercialized x-ray tube that uses a tungsten filament as a source of electrons for a hot cathode. Thus, the configuration and design of a carbon nanotube cathode electron source , And manufacturing.

The tungsten filament cathode used in the conventional X-ray generator emits x-rays by a thermoelectron generated through heating of the filament itself. However, since the scale is large, a relatively large production cost is incurred, and the space is limited, so there is a limit to the use by the users. In addition, thermoelectrons generated by filament heating are not constant in the direction of emission, resulting in a decrease in the radiation quality and a low generation efficiency of radiation generated in the target due to the low thermal density. The degree of vacuum is significantly lowered due to the outgas, and internal discharges are generated, which makes it impossible to use the material, and shortening the life of the target due to heat has been recognized as a technical problem. In addition, when the use of tungsten filament is prolonged, tungsten evaporates on the surface of the filament, thereby reducing the outer diameter of the filament. As a result, thermoelectron emission characteristics are changed. At this time, evaporated tungsten is deposited on the inner wall of the glass bulb, Lt; / RTI >

In order to solve this problem, a separate type radiation tube using a filament cathode has been manufactured and commercialized. However, since the light source is a filament, the X-ray quality is low due to many problems mentioned above. As described above, when a radiation source based on a thermoelectron emission through filament heating is used, its size is large and relatively large production costs are incurred, and there is a limit to the users to deal with a limited space. In addition, the recent development of laser-based radiation source technology and the use of gigantic radiation-based light source technology are difficult to apply to mechanical and semiconductor industries due to enormous installation cost, spatial and mobility constraints, and many commercial limitations And is used only for specific research fields such as science and medicine.

In order to solve the above problems, an X-ray generator using a carbon nanotube capable of replacing an X-ray tube using a tungsten filament as a cathode electron source has been proposed.

Many carbon nanotube-based cold cathode X-ray generators that use carbon nanotubes as a cathode and constitute a main electron source have registered or filed a number of patents both locally and externally.

The carbon nanotube electron source is more efficient than the existing cathode electron source, and it can instantly "on-off" the electron source, thereby suppressing the generation of residual x-rays in operation, preventing excessive x- It is possible to control the intensity and dose of X-rays and to drive the generation of electron beam in the form of a pulse, which can be used for fluoroscopy or fluoroscopy. However, the life span of the electron source, the robust durability and the repeatability are inferior to the tungsten electron source of the conventional hot cathode X-ray tube and have many advantages, but the commercialization is still limited.

The cold cathode X-ray tube based on the conventional carbon nanotube will be described by referring to a semiconductor substrate of a silicon (Si) material or a metal substrate of a stainless steel (SUS) material through "Chemical Vapor Deposition To grow carbon nanotubes on the substrate.

More specifically, a substrate such as silicon (Si) or stainless steel (SUS) is used as a substrate on which carbon nanotubes are grown, and the substrate is mounted on a vacuum chamber. Then, a buffer layer (Buffer) such as titanium nitride (TiN) Layer is deposited to a thickness of several nm and a catalyst metal such as Ni or Fe is deposited on the film to a thickness of several nm and then a gas such as ammonia (NH 4) or hydrogen (H 2) The surface of the substrate is etched to make the metal catalyst on the surface of the substrate generally have a size of several nm to several tens of nm of seed particles.

The size and density of the metal catalyst produced are controlled by the type of gas used and the time of the etching process. Through this method, various kinds of impurities and debris generated during the post-processing process are removed through a vacuum pump so that the catalyst coated on the surface of the substrate can have a desired size and density, When a gas containing carbon such as methane (C2H2) gas, which is a main raw material of carbon nanotubes, is introduced into a vacuum chamber, carbon nanotubes are vertically grown on a substrate based on catalyst particles formed on the substrate.

The thickness (or diameter) of the grown carbon nanotubes is closely related to the size of the metal catalyst formed on the substrate. The length of the grown carbon nanotubes is closely related to the process time of growing the carbon nanotubes by injecting gas .

The X-ray generator using the above-described prior art carbon nanotubes as a cold cathode electron emission source has a problem in that when the sharp voltage is applied to the grid to draw electrons because the adhesion strength of the carbon nanotubes to the substrate is not strong, Aging due to deterioration of the substrate caused by long-term use may result in weak bonding force with the substrate, which may cause detachment of the carbon nanotube electron emission source from the substrate.

In addition, when an X-ray tube using a carbon nanotube electron emission source is manufactured, the life of the carbon nanotube is remarkably deteriorated due to the collision with a carbon nanotube electron emission source caused by various ions and particles present in the tube There is a problem.

Since the carbon nanotube tip that emits electrons generally has a higher temperature than the surrounding temperature, the carbon nanotubes tend to be easily oxidized due to the oxygen present in the vacuum tube. There is a problem that the electron emitting ability of the carbon nanotubes is remarkably deteriorated.

The present invention is to solve the problems of the prior art as described above, the object is to manufacture a large sized specimen in a large chamber and then cut to a small size to enable mass production to the desired uniform standard The present invention provides a method for manufacturing a cathode module of an X-ray generator using carbon nanotubes.

It is another object of the present invention to provide a method of manufacturing a cathode module of an X-ray generator using a carbon nanotube that can improve the structure of a carbon nanotube cathode electron source and secure the stability and durability of the nanostructure material, .

Another object of the present invention is to provide a method of manufacturing a cathode module of an X-ray generator using carbon nanotubes, which can be commercialized by releasing a stable electron beam even when used for a long time.

However, the object of the present invention is not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to a feature of the invention for achieving the above object,

A first process of growing carbon nanotubes on a substrate through chemical vapor deposition (CVD);

A second step of coating the carbon nanotubes and the substrate so as to be immersed in a curing solution obtained by mixing polystyrene and toluene in order to increase the bonding force between the carbon nanotubes and the substrate after the first process, ; And

After the second process is progressed, the third step of opening the tip of the carbon nanotubes from the cured polymer (polymer); and a negative electrode module manufacturing method of the X-ray generator using a carbon nanotube comprising a; to provide.

At this time, according to an additional feature of the present invention, the first step of growing the carbon nanotubes comprises:

A first step of depositing a buffer layer on a substrate made of silicon (Si) or stainless steel (SUS) using a titanium nitride (TiN)

A second step of depositing a catalyst layer on the buffer layer deposited in the first step to a thickness of about several nm using iron (Fe), nickel (Ni), or gold (Au)

A third step of performing an appropriate time etching by using ammonia or hydrogen gas so as to have a desired catalyst size and density after the second step is performed;

After the third step, a carbon (C2H2) gas containing a carbon component is injected into the substrate in a state of several hundreds of degrees, and carbon nanotubes are grown on the substrate while maintaining the shape of a columnar structure. And the like.

According to another aspect of the present invention, there is provided a method for manufacturing a carbon nanotube,

A first step of rotating at a speed of 2000 to 4000 rpm to remove excess coating solution,

And a second step of exposing the carbon nanotube tip by removing the cured polymer at the upper end of the carbon nanotube through a plasma etching or laser etching method.

At this time, in the second step of exposing the carbon nanotube tip, the shape of the carbon nanotube tip can be processed into a pointed shape that can easily emit electrons.

According to another aspect of the present invention,

A first process of constructing a large-scale chemical vapor deposition (CVD) chamber, and inserting a large-scale substrate having a size of several m each in width and length;

A second step of growing carbon nanotubes on the substrate inserted into the CVD chamber through chemical vapor deposition (CVD) in the first step;

After the second process, a third step of coating the carbon nanotubes and the substrate so as to be immersed in a curing solution obtained by mixing polystyrene and toluene in order to increase the bonding force between the carbon nanotubes and the substrate ;

A fourth process of opening a tip of the carbon nanotubes from the cured polymer after the third process is performed; And

And a fifth step of cutting the substrate so that the unit cell has a width of several mm or less or a length of several tens of m or less after the fourth step,

The present invention provides a method for manufacturing a negative electrode module of an X-ray generator using carbon nanotubes, which is capable of mass-producing a desired uniform size carbon nanotube electron emission source.

The method of manufacturing the cathode module of the X-ray generator using the carbon nanotube according to the present invention can extend the service life due to stability and durability of the nanostructured material.

In addition, there is an effect that commercialization can be achieved by releasing a stable electron beam even when used for a long time.

In addition, it is possible to mass-produce the carbon nanotube electron emission source with a desired uniform size by manufacturing a large-sized chamber using a large-sized sample, and then cutting the small-sized chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a main process for manufacturing a cathode module of an X-ray generator using carbon nanotubes according to the present invention. FIG.
2 is a view showing a state in which a curing solution is coated to increase the adhesion between the substrate and the carbon nanotubes.
3 is a view for explaining a state in which electrons are generated from a carbon nanotube tip by an electric field E generated when a voltage "V" is applied to a grid electrode of a metal mesh type.
4 is a view for explaining a process of forming a carbon nanotube tip by processing a hardened polymer using a laser etching process equipment capable of precise position control of a laser beam.
5 is a diagram showing a system having an optical system capable of beam-shaping the shape of a laser beam.
FIG. 6 is a view comparing the typical shape of the carbon nanotube tip formed after removing the hardened polymer and the shape of the carbon nanotube tip formed after laser beam shaping.
FIG. 7 is a view for explaining a process for mass-producing a carbon nanotube electron emission source of uniform size.
8 is a view showing an embodiment of a cold cathode X-ray tube using a carbon nanotube electron emission source having an arbitrary unit cell size processed by a laser as a material.

Hereinafter, a preferred embodiment of a method of manufacturing a negative electrode module of an X-ray generator using carbon nanotubes according to the present invention will be described. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Referring to FIG. 1, main processes for manufacturing a cathode module of an X-ray generator using carbon nanotubes will be described.

First, the carbon nanotubes 20 are grown on the substrate 10 by chemical vapor deposition (CVD).

In detail, a buffer layer is deposited on the substrate 10 using a titanium nitride (TiN) as a thin film with a thickness of several nanometers.

Thereafter, a catalyst layer is deposited to a thickness of several nm on the deposited buffer layer using iron (Fe), nickel (Ni), or gold (Au).

Thereafter, gases such as ammonia and hydrogen are used to etch for an appropriate time so as to obtain a desired catalyst size and density.

Thereafter, the carbon nanotubes 20 are grown on the substrate while maintaining the shape of a columnar structure by injecting methane (C2H2) gas containing carbon components in a state of hundreds of substrates.

The carbon nanotubes 20 may be grown on a substrate 10 such as silicon (Si) or stainless steel (SUS) through chemical vapor deposition (CVD) as described above, A semiconductor substrate or various metal substrates capable of growing the carbon nanotubes 20 can be used. For example, molybdenum, tungsten, copper, titanium, zirconium, aluminum and the like can be used.

It is obvious that the length and the thickness (diameter) of the carbon nanotubes 20 grown on the substrate 10 are closely related to the type of gas and the etching time of the substrate 10, It is possible to grow the carbon nanotubes 20 having a desired thickness (for example, several nm to several tens nm) and a desired length (for example, several μm to several hundred μm) on the substrate 10.

The carbon nanotube 20 grown to a desired diameter and length by the above process is added to a curing solution 30 in which polystyrene and toluene are appropriately mixed to increase the bonding force with the substrate 10 The carbon nanotubes 20 and the substrate 10 are coated to be sufficiently immersed. At this time, the curing solution 30 sufficiently covers the carbon nanotubes 20 grown on the substrate 10 and the substrate 10 as well as the gap between the carbon nanotubes 20 so that no extra space is formed.

Thereafter, the resultant product is rotated at a speed of 2000 to 4000 rpm to remove excess coating solution, and then the vacuum pump is operated for an appropriate time while maintaining the temperature at about 50 캜 to 80 캜 to be coated with the curing solution 30 The carbon nanotubes 20 are removed.

At this time, as shown in FIG. 2, the curing solution 30 can strengthen the bonding force between the substrate 10 and the carbon nanotubes 20 by using silicon nitride (Si 3 N 4) The curing solution 30 filling the spaces between the tubes 20 is hardened to maintain the robust structure of the carbon nanotubes 20 and the carbon nanotubes 20 are prevented from colliding with various ions in the vacuum tubes It also serves to protect the durability and longevity.

After the above-described process, a process for opening a tip of the carbon nanotubes 20 from the cured polymer proceeds.

Since the cured polymer completely fills the carbon nanotubes 20, it is impossible to emit electrons even if an electric field is applied in order to emit electrons from the carbon nanotubes 20 in the present state. Accordingly, in order to emit electrons, the upper polymer surrounding the carbon nanotubes 20 should be removed to provide a conductive carbon nanotube tip.

The polymer removal on the top of the carbon nanotubes 20 can be removed by plasma etching or laser etching. Of course, according to the etching method used, the length of the carbon nanotube tip formed on the upper side of the hardened polymer can be controlled variously, and various types of tips can be provided according to parameters used in a specific process method.

The parameters include the type of laser (pulse or DC), energy, repetition rate, etc. used in the laser etching process.

FIG. 3 is a typical view of a carbon nanotube tip 20a obtained after removing the cured polymer 30a on the top of the carbon nanotube 20 by plasma or laser as described above.

3, since the carbon nanotubes 20 are conductive nanostructured materials, the metal nanotubes 20 are spaced apart from the carbon nanotube tips 20a by a distance of several tens to several hundreds of micrometers, An electric field (E = V / d) is generated between the distance d between the carbon nanotube tip 20a and the grid electrode 40 when the voltage V is applied to the grid electrode 40 made of So that electrons can be emitted from the carbon nanotube tip 20a.

The plasma etching process or the laser etching process is used not only to remove the cured polymer 30a and to form the carbon nanotube tip 20a, but also with the effect of annealing the formed carbon nanotube tip 20a. To provide excellent crystallinity of the carbon nanotube tips 20a, ultimately, the effect of enhancing electron emission can be achieved. In addition, the carbon nanotube tip can be processed in various structures depending on the intensity of the plasma or the intensity of the laser energy used and the pulse repetition rate in the case of the pulsed laser, that is, the electron emission efficiency is excellent.

FIG. 4 shows an embodiment of a laser etching process, in particular, of the above-mentioned method of etching the hardened polymer 30a, and FIG. 5 is a view And a process for forming a carbon nanotube tip by focusing a beam generated from the laser using an optical system.

The laser machining system 50 of FIGS. 4 and 5 can precisely control the position of the laser beam within a few micrometers when moving back and forth, right and left, and vertically and horizontally.

In addition, as shown in FIG. 5, the laser beam generated from the laser processing system 50 can be easily processed by the optical system 60 so that the laser beam can be arbitrarily used by the user.

As a result, the laser processing system 50 can be used to remove the cured polymer 30a located at the upper end of the carbon nanotube 20 to form the carbon nanotube tip 20a.

For example, as shown in FIG. 6, by properly controlling the intensity and shape of the laser beam, the shape of the carbon nanotube tip 20a formed after removing the upper portion of the cured polymer 30a is easily emitted (For example, a sharp-pointed tip).

The fact that a carbon nanotube tip made of a point-like shape with a pointed end, rather than the amount of electrons generated from a circular-shaped carbon nanotube tip, can emit more electrons if the electric field (E) It is a clear fact that anyone who has studied the theory of electromagnetism in physics can understand it.

The effect of the laser processing system 50 capable of precise control shown in FIGS. 4 and 5 is not satisfied merely with the advantage of forming the carbon nanotube tip 20a, Production.

Specifically, the method of forming the carbon nanotubes 20 on the substrate 10 through which electric current can pass through is the most common method of "CVD (Chemical Vapor Deposition)" and the "screen printing" method, the "spray" method There may be a variety of ways. CVD method is a well-known method, but the carbon nanotube manufacturing process is somewhat complicated and the carbon nanotube electron emission source to be manufactured is very sensitive to the CVD process conditions, so that the change of the fine process condition ultimately results in the electron emission source Thereby providing a carbon nanotube electron emission source having different shapes and characteristics. It is obvious that this will cause problems in reproducibility and durability of the electron emission source, which must have a certain specification and specification in commercialization, thereby causing a reduction in production efficiency.

Therefore, in the present invention, a large-scale CVD chamber and process conditions capable of forming carbon nanotubes are constructed, and a large-sized specimen (for example, a length of several meters in each of the width and height of the specimen) After the nanotubes are grown, the carbon nanotube tip 20a is formed through the processing shown in FIGS. 4, 5 and 6. Thereafter, when the specimen having the carbon nanotube grown thereon is cut into a small size used in the X-ray tube, the laser beam is focused using the optical system 60 to produce the carbon nanotube-based electron emission source. Lt; / RTI >

The laser machining system 50 can precisely control the position in the range of several micrometers when moving up and down, left and right, back and forth, as well as its operation and machining time is very short, so that the user can obtain uniform uniform carbon nanotube electron emission There can be a tremendous advantage in producing large quantities of circles. That is, considering that each individual carbon nanotube is a source that emits electrons, the size of an electron emission source made up of numerous carbon nanotubes is directly related to the generation of an electron beam generating X-rays, Is a very important factor for commercialization and the technology of the process which can provide a certain standard is a very important competitiveness and asset of the enterprise.

A specific example of a method of mass-producing a carbon nanotube electron emission source having a uniform size and size by utilizing a process equipment capable of precisely controlling the position of a laser beam described in FIGS. 4 and 5 emphasized above Is shown in Fig. As shown in FIG. 7, although the size of the substrate that can be inserted into the CVD chamber is several meters (m) in width and height, it is obvious that it is possible to use a size larger than several meters (m) The size of the unit cell-type carbon nanotube electron emission source is about several millimeters or less in each unit cell, but the laser processing error limit can be adjusted to several μm or less The size of the unit cell of the carbon nanotube-based electron emission source used as the cathode of the X-ray can be controlled to be several tens of μm or less in the lateral and vertical directions. It is a fact that it will depend entirely on the spec.

In Fig. 7, the unit cell can be processed into various shapes such as a square shape or a circular shape.

FIG. 8 shows an embodiment of a carbon nanotube electron emission source-based cold cathode X-ray tube, which is made by using unit cells of a carbon nanotube electron emission source of uniform size through the mass production process shown in FIG.

8, when a voltage V is applied to the grid electrode 40, an electric field is formed between the carbon nanotube tip 20a and the grid electrode 40 so that an electric field is generated between the carbon nanotube tip 20a and the grid electrode 40, It becomes possible to emit electrons from the light emitting layer 20a.

Reference numerals 60a and 60b may apply different voltages to respectively optimally focus the electron beam to an electrostatic electron beam focusing lens made of a cylindrical metal.

The electron beam emitted from the carbon nanotube tip 20a collides with the X-ray target 80 to generate X-rays.

10: substrate
20: Carbon nanotubes
20a: Carbon nanotube tips
30: Curing solution
30a: Cured polymer
40: grid electrode
50: Laser processing system
60: Optical system

Claims (5)

A first process of growing carbon nanotubes on a substrate through chemical vapor deposition (CVD);
A second step of coating the carbon nanotubes and the substrate so as to be immersed in a curing solution obtained by mixing polystyrene and toluene in order to increase the bonding force between the carbon nanotubes and the substrate after the first process, ; And
After the second process is performed, the third step of opening the tip of the carbon nanotubes from the cured polymer (polymer); the negative electrode portion of the X-ray generator using a carbon nanotubes comprising a Module manufacturing method.
The method of claim 1,
The first step of growing the carbon nanotubes comprises:
A first step of depositing a buffer layer on a substrate made of silicon (Si) or stainless steel (SUS) using a titanium nitride (TiN)
A second step of depositing a catalyst layer on the buffer layer deposited in the first step to a thickness of about several nm using iron (Fe), nickel (Ni), or gold (Au)
A third step of performing an appropriate time etching by using ammonia or hydrogen gas so as to have a desired catalyst size and density after the second step is performed;
After the third step, a carbon (C2H2) gas containing a carbon component is injected into the substrate in a state of several hundreds of degrees, and carbon nanotubes are grown on the substrate while maintaining the shape of a columnar structure. The method of claim 1, wherein the carbon nanotube is a carbon nanotube.
The method of claim 1,
The third process of opening the tip of the carbon nanotubes,
A first process of removing excess coating solution by rotating at a speed of 2000 to 4000 rpm;
Manufacturing a cathode module of an X-ray generator using a carbon nanotube comprising a second step of exposing the carbon nanotube tip by removing the cured polymer on the top of the carbon nanotube through a plasma etching or laser etching method Way.
The method of claim 3, wherein
In the second step of exposing the carbon nanotube tip,
Wherein the shape of the tip of the carbon nanotube tip is shaped into a pointed shape that can easily emit electrons.
A first process of constructing a large-scale chemical vapor deposition (CVD) chamber, and inserting a large-scale substrate having a size of several m each in width and length;
A second step of growing carbon nanotubes on the substrate inserted into the CVD chamber through chemical vapor deposition (CVD) in the first step;
After the second process, a third step of coating the carbon nanotubes and the substrate so as to be immersed in a curing solution obtained by mixing polystyrene and toluene in order to increase the bonding force between the carbon nanotubes and the substrate ;
A fourth process of opening a tip of the carbon nanotubes from the cured polymer after the third process is performed; And
And a fifth step of cutting the substrate so that the unit cell has a width of several mm or less or a length of several tens of m or less after the fourth step,
Wherein a carbon nanotube electron emission source having a desired uniform size can be produced in large quantities.

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