1. Field of the Invention
The present invention relates to a device and method for manufacturing carbon nanotube.
2. Related Art Statements
Up to now there have been developed various techniques for forming carbon nanotubes. However, in any of the techniques, it is very difficult to know the nature of the generated nanotubes and correct number of the nanotubes, so that until now there has not been developed a technique or device for forming nanotubes at desired locations with the desired number of nanotubes. For example, as conventional technologies of the nanotube generation, there have been developed various methods and devices for forming carbon nanotubes at high temperature (equal to or more than 1000 degrees centigrade). Moreover, there is a technique for generating nanotubes at low temperature (about 600 degrees centigrade) by Shigeo Maruyama who is one of the inventors of the present invention, et al. (Refer to Japanese documents: Maruyama Shigeo, “Growth of Nanotube by the cold CVD with Alcohol (experiment and simulation)”, Journal of Japanese Association for Crystal Growth cooperation (2002), Vol. 30, No. 4, pp. 32-41; Shigeo Maruyama, “Synthetic Technology of the Single Layer Carbon Nanotube with Alcohol”, Industrial material (2003), vol. 51, No. 1, pp. 38-41; and Shigeo Maruyama et al., “High Purity Generation at low temperature by Single Layer Carbon Nanotube with Low Temperature CCVD technique with Alcohol”, Journal of Japan Society of Mechanical Engineers (B part), (2003), vol. 69, No. 680, pp. 918-924.
It is an object of the present invention to provide a device and method for manufacturing carbon nanotube.
In order to solve the above-mentioned problems in the conventional devices and methods, there is provided a method for manufacturing carbon nanotube, the method comprises the steps of:
According to the present invention, it is possible to easily form carbon nanotubes at desired locations with desired number of nanotubes, because the nanotubes are manufactured while monitoring the forming of the nanotubes such that number and properties (for example, electric conductivity or length of a carbon nanotube) of the nanotubes generated and grown are correctly or precisely measured by the detecting means. For instance, it is assumed that one or more detecting means for detecting physical properties are provided in both or either a microstructure A and a microstructure B, at which one or more bridges of carbon nanotubes are built therebetween, desired number of the carbon nanotubes can be formed while monitoring the growth of the carbon nanotubes by stopping the generation and growth of the carbon nanotubes if when the number of the tubes, which have bridged between the microstructures A and B, reaches to a desired number based on the monitoring result. According to this invention, manufactured carbon nanotubes can be applied to various sensors, or various devices (e.g., a field effect transistor or optical crystal) which use nanotubes, because carbon nanotubes can be formed and grown at one or more desired locations with a desired number of tubes.
In an embodiment of the manufacturing method according to the present invention, the detecting means includes at least one, or combination, selected from the group consisting of a force sensor (e.g., minute vibrating cantilever type force sensor), an electrical resistance meter, optical lever method measurement instrument, and a Raman spectrometer.
According to the present embodiment, when a mechanical method using force sensor is employed, it is possible to measure mechanical properties regardless that the generated or formed carbon nanotubes are electrically conductive or semi-conductors. Meanwhile, when electric resistance is measured, it is possible to identify or figure out the number and characteristics of the carbon nanotubes such that how many semiconductor nanotubes are formed and that how many nanotubes having electrical conductivity are generated. Therefore, when changes in a plurality of physical properties are obtained using these various measurement devices, it is possible to manufacture desired nanotubes while correctly or precisely grasping the number and types/kinds (e.g., diameter of a tube, or electric conductivity, etc.) of the nanotubes.
In another embodiment of the manufacturing method according to the present invention, each of the plurality of microstructures includes at least one minute vibrating cantilever.
According to the present embodiment, it is possible to measure the lengths, properties, and the number of the formed carbon nanotubes with a high degree of accuracy, because the physical properties of the minute vibrating cantilever slightly varies depending on the minute stimulus arising from the nanotube generation (i.e., a nanotube bridge is finished up between the cantilevers/microstructures).
Meanwhile, silicone is preferable as a material to form a cantilever, but at 1000 degrees centigrade, in which normal nanotube forming method is performed, it is difficult to measure the mechanical characteristics of the silicone. However, when the above-described Low Temperature CCVD technique with alcohol by Maruyama is employed, nanotubes can be formed at low temperature such as approximately 600 degrees centigrade. This temperature, 600 degrees centigrade, is within the range (it is desirable to be equal or less than 700 degrees centigrade) of the elastic deformation of silicone. Therefore, if the Low Temperature CCVD technique is used, the minute changes in physical properties of the cantilever may sufficiently be measured. Hence, in this embodiment, when microstructures having cantilevers made of silicone are employed, it is preferable that the method includes a step of controlling temperature of a reaction region, at which the microstructures having cantilevers exist, to be within the range from approximately 600 to approximately 700 degrees centigrade.
In still another embodiment of the manufacturing method according to the present invention, the method further comprises providing vibration to the minute vibrating cantilever from without or from outside of the cantilever by using an electrostatic actuator or a piezoelectric actuator.
In yet another embodiment of the manufacturing method according to the present invention, there are a plurality of minute vibrating cantilevers, each having a different resonance frequency, the method further comprises adjusting a frequency of the provided vibration from without by the providing vibration step according to a desired resonance frequency of the minute vibrating cantilevers.
In yet another embodiment of the manufacturing method according to the present invention, there are an array of reaction regions, in other words reaction regions are accumulated on large scale to form the array, the method further comprises controlling at least one selected from the group consisting of heating of a reaction region, flow rate of reactant gas, and electric field for every reaction region.
According to the present embodiment, it is possible to manufacture only the desired number of the nanotubes having desired properties in a large quantity. For instance, when only certain reaction regions, at which microstructures exist where one or more nanotube bridges should be built therebetween, are heated according to this method, only the certain reaction regions are activated, and therefore this makes remaining reaction regions to not generate or form the carbon nanotubes in these remaining non-activated reaction regions. In addition, due to that electric filed is applied to spaces between certain microstructures at which one or more nanotubes bridges should be built therebetween, a direction of the growth of the nanotubes can be controlled.
In yet another embodiment of the manufacturing method according to the present invention, the heating of a reaction region done by a spot lamp, which locally heats by irradiating only a limited part of the reaction regions, or a heater having a resistance heating element.
In yet another embodiment of the manufacturing method according to the present invention, each of reaction regions included in the array is provided in each of micro flow channels which are provided in a substrate by MEMS (Micro electro mechanical systems) technology.
In yet another embodiment of the manufacturing method according to the present invention, each of the reaction regions is connected to a plurality of micro flow channels in a different direction, and the method further comprises controlling a flow direction of the reactant gas which passes through the reaction region by adjusting a flow of the reactant gas for every micro flow channel, and to generate and grow the at least one carbon nanotube.
According to this embodiment, it is possible to form and grow a nanotube in desired direction by flowing reactant gas in the desired direction through which a nanotube should be formed and grown, because the nanotube tends to grow according to (i.e., along with) the flow direction of a reactant gas.
In yet another embodiment of the manufacturing method according to the present invention, the method further comprises the steps of:
In yet another embodiment of the manufacturing method according to the present invention, the generation and growth of the at least one carbon nanotube is done in or under a non-oxidizing atmosphere (for example, by flowing an argon gas containing hydrogen through the reaction regions).
According to this embodiment, changes in physical properties such as optical or mechanical characteristics by the oxidation reaction of the minute structure can be avoided by preventing the microstructures from being oxidized, so that measurement error of the change in physical properties can be confined within a minimum range.
In an alternative embodiment, the method may further comprises calculating compensated values regarding mechanical properties from a temperature and an elapsed time by compensating the error of change in mechanical properties by oxidative reaction from heat and oxygen during nanotube forming (surfaces of the silicone will be converted into oxide silicone by heating).
By way of easy explanation the aspect of the present invention has been described as the methods, however it is understood that the present invention may be realized as devices corresponding to the methods.
For example, according to another aspect of the present invention, there is provided a device for manufacturing carbon nanotube, the device comprises:
In another embodiment of the manufacturing device according to the present invention, the device further comprises:
In still another embodiment of the manufacturing device according to the present invention, the detecting means includes at least one selected from the group consisting of a force sensor, an electrical resistance meter, measurement instrument using optical lever method, and a Raman spectrometer.
In yet another embodiment of the manufacturing device according to the present invention, each of the plurality of microstructures includes at least one minute vibrating cantilever, i.e., a cantilever which minutely vibrates.
In yet another embodiment of the manufacturing device according to the present invention, the device further comprises:
In yet another embodiment of the manufacturing device according to the present invention, there are a plurality of minute vibrating cantilevers, each having a different resonance frequency, the device further comprises a controlling means for controlling electrostatic actuator or a piezoelectric actuator to adjust a frequency of the provided vibration from without, or outside the cantilever, according to a desired resonance frequency of the minute vibrating cantilevers.
In yet another embodiment of the manufacturing device according to the present invention, the device further comprises a temperature control means for controlling temperature of a reaction region, at which the microstructures having cantilevers exist, to be within the range from about 600 to 700 degrees centigrade.
Several preferred embodiments of the present invention will be described with reference to the accompanying drawings.
The reactant gas feeding means 7 may feed or provide not only a reactant gas including alcohol vapor (source of carbon), which mainly consisting of carbon and hydrogen, as a raw material of nanotubes, but also an argon or hydrogen gas. Non-oxidizing atmosphere is used to prevent members of the reaction region, such as cantilevers or carbon nanotube, from alternation or degradation. When a reactant gas is fed into the vacuum chamber during heating the reaction region 3, one or more carbon nanotubes start to generate and grow from a front edge of one cantilever toward a front edge of other cantilever. When just a carbon nanotube is connected to the other cantilever, in other words a carbon nanotube bridge is finished up or built between the two cantilevers, a position, mechanical properties or optical properties of the both of either of the cantilever would changes. These changes in physical properties are measured using a force sensor using one or more cantilevers (members/elements other than cantilevers are not illustrated), or a measurement system for measuring minute change of position utilizing an optical lever method with an optical system having an argon laser, an optical filter and a split photodiode. The growth and generation of a carbon nanotube(s) can be controlled by stopping supply of the reactant gas, or by increasing the heat of the reaction region to prompt or activate the growth of the nanotubes.
In this embodiment an optical system for measuring the optical vibrations (optical lever) is employed. This optical system mainly includes a laser spot irradiation part 24 for irradiating a spot of laser light and a measuring part 26 using a split photodiode. Optionally, there is provided an optical filter and thus it can be distinguished between the heat ray from the spot lamp and the laser light from the laser spot irradiation part. The laser irradiation part 24 can be used as a light source for a Raman absorption measurement, but additional light source and measurement device for Raman absorption can be provided.
According to the number of carbon nanotubes to desire to measure or generate, a distance between the microstructures and a mechanical resonance frequency of each microstructure can be varied. It is preferable to set the sensitivity of a part to low when the part is a place to want to form a large amount of nanotubes, and it is preferable to set the sensitivity of a part to high when the part is a place to want to form or generate a small amount of nanotubes. It is sufficient that change in physical properties of either one side of the cantilevers, at which a nanotube bridge is formed therebetween, can be measured. A vibration measurement means can be provided in a cantilever, which is the other side of being bridged. A vibrating means for vibrating a cantilever(s) from without can be an electrostatic actuator or a piezoelectric actuator. A piezoelectric actuator 30 applies a voltage between the cantilever to desire to be vibrated and any member such as a substrate, and to actuate the cantilever by electrostatic force. This piezoelectric actuator can be located in the vacuum chamber or quartz tube. When a vibration field is provided from without or outside and a cantilever which resonates with vibrations by the vibration field can be measured, there is no need to dispose the actuator in the vacuum tube. For example, the vacuum chamber or quartz tube for reaction can be vibrated outside the chamber using various frequencies. Each microstructure has one or more electrodes (not shown in
Further, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, not to be used to interpret the scope of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Number | Date | Country | Kind |
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2004-15,962 | Jan 2004 | JP | national |