RU2365674C2 - Device of carbon nanotubes growth by method of ethanol pyrolysis - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to devices for carbon nanotubes production. Device contains reaction furnace with unit for supplying and introducing of ethanol vapours, holder of padding with padding, which has catalytic surface, and heating element. Inside of reaction furnace placed is reaction chamber, which contains separable part, joint with drive of axial movement. Unit of ethanol vapours supply contains evaporating cell with ethanol, joint with ethanol vapours input. Heating element is placed inside reaction chamber in padding zone. Device is supplied with generator of particle flow, placed in reaction chamber, and made in form of at least one conductive net, connected to source of alternating or/and source of continued voltage. At least one conductive net is made of catalytic material. Reaction chamber is made of quartz ceramics. In evaporating cell heater and ethanol temperature measuring instrument are placed. Inlet of ethanol vapours is made of conductive material, and is connected to source of alternating or/and source of continued voltage. Inlet of ethanol vapours is made in form of two pipes, which are coaxially placed one in the other with ability to move relative each other.

EFFECT: increasing nanotubes quality and device reliability.

6 cl, 1 dwg

Description

The device relates to the field of carbon nanomaterial production technology and can be used to grow carbon nanotube material, for example, for exclusive production, research purposes and training in the peculiarities of their growing processes.

A carbon nanotube growth device is known, including a reaction furnace with a gas supply module, in which a particle flow former, a substrate holder with a substrate having a catalytic surface, and a heating element are arranged. In this case, the gas supply module is located at an angle to the working surface of the substrate [1].

The disadvantage of this device is that the gas supply module is located at an angle to the working surface of the substrate, and this leads to an inhomogeneous distribution of the incident flow on the surface of the substrate and a decrease in the quality of nanotubes.

There is also known a device for the growth of carbon nanotubes by ethanol pyrolysis, including a reaction furnace with a feed module and ethanol vapor input, a substrate holder with a substrate having a catalytic surface, and a heating element [2].

This device is selected as a prototype of the proposed solution.

Its first drawback is the lack of a device for the precise supply of ethanol vapor, which leads to a decrease in the accuracy of process control and, accordingly, the quality of nanotubes.

The second disadvantage is that the integrality of the reaction chambers leads to a decrease in their resistance to shock and vibration loads, as well as temperature gradients. In addition, preventive cleaning is more difficult on such cameras. This reduces the reliability of the device, complicates its operation and also leads to a decrease in the quality of nanotubes.

The aim of the invention is the creation of a simple and safe device for the growth of carbon nanotubes for research and its use in the educational process.

The technical result of the invention is to improve the quality of nanotubes and increase the reliability of the device.

The technical result is achieved by the fact that in a carbon nanotube growth device by ethanol pyrolysis method, including a reaction furnace with a feed module and ethanol vapor input, a substrate holder with a substrate having a catalytic surface, and a heating element, a reaction chamber containing a detachable part is placed inside the reaction furnace coupled to the axial displacement drive, the ethanol vapor supply module comprises an ethanol vaporization cell coupled to the ethanol vapor input, and a heating element t is installed inside the reaction chamber in the region of the substrate, while the particle flow former installed in the reaction chamber is made in the form of at least one conductive grid connected to an alternating and / or constant voltage source, at least , one conductive mesh is made of catalytic material.

A variant is possible in which the reaction chamber is made of quartz ceramic.

It is also possible that a heater and an ethanol temperature meter are installed in the evaporation cell.

There is an option in which the input of ethanol vapor is made of a conductive material in the form of two tubes, coaxially arranged in one another with the possibility of moving relative to each other, and connected to an AC voltage source and (or) DC voltage source.

The drawing shows a layout diagram of a device for the growth of carbon nanotubes.

The carbon nanotube growth device (FIG. 1) contains a reaction furnace 1, inside which a reaction chamber 2 is made of quartz ceramic [3]. Chamber 2 consists of a cylinder 3 connected to a cover 4 mounted in a welded, for example, aluminum, housing 5. Elements 3, 4, and 5 represent a detachable part of the reaction chamber. The integral part of the reaction chamber consists of a work table 6 connected to the base 7. This connection can be carried out using elastic spring grippers (not shown), heat-resistant glue, etc. A viton seal 8 is installed between the housing 5 and the base 7. It should be noted that the gap A between the base 7 and the housing 5 must be larger than the gap B between the cylinder 3 and the table 6. The chamber 2 is connected via a channel 9 to a fore-vacuum pump 11 through a pipe 10. Between the pump 11 and the camera 2 has an electronic valve 12.

The first 13 and second 14 casings are mounted on the housing 5 in such a way that air chambers 15 and 16 are formed between them and the housing 5. The casings 13 and 14 are mounted on the housing 5 using spring hooks (not shown). The casing 13 is connected to the axial displacement actuator 17 (conventionally shown, the actuator 13 can be mechanically closed to the housing 5).

As the drive 17 can be used a stepper motor, pneumatic actuator, etc.

On the working table 6 is fixed a stage 18, made, for example, of titanium, quartz, etc., with a substrate 19 having a catalytic surface 20. Elements 6, 18 and 19 can be fastened with paws (not shown).

The catalytic surface 20 is made in the form of islands of nickel, iron, etc. [4, 5] with sizes of ~ 1 nm. As substrates, silicon, sapphire, polycor, etc. can be used.

Inside the chamber 2 in the area of the substrate 19, a heating element 21 is installed, made, for example, in the form of a nichrome spiral enclosed in a quartz screen (not shown).

The reaction furnace, and in particular the reaction chamber 2, is connected to an ethanol vapor supply module 22, comprising an evaporation cell 23 connected by a conduit 24 to an ethanol vapor input 25. The housing 5 can be connected to the inlet 25 by welding. Ethanol 26 is poured into the cell 23, and a needle leak 27 is installed between it and the inlet 25.

Inside the cell 23, a heater 28 and a temperature meter 29 can be installed. The heater 28 can be made in the form of a spiral of nichrome, and the meter 29 in the form of a thermocouple. Cell 23 has a filler hole (not shown) and is made of glass, quartz, and the like.

It should be noted that in cell 23 there may be no heater 28 and meter 29. In this case, cell 23 should be located so that direct supply of ethanol (its vapor) to chamber 2 is provided. For example, cell 23 can be located above input 25. Input 25 can be electrically conductive and consist of two tubes 30 and 31. In this case, tube 30 is vacuum-tightly fixed in housing 5, and tube 31 is mounted therein with the possibility of axial movement.

The axial movement of the tube 31 can be achieved by means of spring elements between it and the tube 30 (not shown).

In one embodiment, a window 32 is vacuum-tightly fastened at the inlet 25, and a translucent mirror 33, a laser 34, and a radiation receiver 35 are mounted along the device axis with the possibility of optical coupling with the substrate 19. A screen is usually used as a radiation receiver, but a spectrometer can also be used . In one embodiment, the elements 33, 34 and 35 are mounted on a bracket (not shown) with the possibility of shifting away from the reaction furnace for the unimpeded removal of its detachable part. An option of fixing the elements 33, 34 and 35 directly on the housing 5 (not shown). The cell 23 can also be mounted on a bracket (not shown), and the pipe 24 must have sufficient length and flexibility to remove the detachable part.

A conduit solenoid valve 36 is connected to the pipe 10 to allow air to enter the reaction chamber.

In the reaction chamber 2, a particle shaper 37 is installed (for example, in the form of grids [2]), a platinum-iridium thermocouple 38, and a pressure gauge 39 is connected to it.

Elements 11, 12, 17, 21, 25, 28, 29, 34, 36 and 38 can be connected to the control unit 40. Elements 25 and 37 can be connected to the block of constant and (or) alternating voltage 41. In this case, input 25 in most cases, ground.

Block 41 may be part of block 40 and be autonomous.

The control unit 40 can be made in the form of a microprocessor control system that provides the installation of carbon nanotube growth according to a predetermined program and controls the heating rate, the time mode of the process, raising and lowering the upper part of the device, turning the vacuum pump on and off. The microprocessor control system incorporates the following modules: KMP-70MT-50 controller; keyboard and display board DK - 50S; optothyristor module MOT-60. The control system is designed to store 100 individual programs. All programs are recorded in non-volatile memory. The display of the control system induces the program number, set and current temperature values, vacuum on / off temperature, process duration, duration of raising the upper part of the chamber, exposure time for cooling. The control system keyboard provides input of the process program, start and stop of the program, raising and lowering the upper part of the carbon nanotube growth chamber. For details, the control unit 40 see [7].

All mechanical and electrical leads from the reaction chamber 2 to the atmosphere are sealed with Viton seals or TorrSeal adhesives from Varian and UHU plus from GmbH & Co.

The particle flow generator 37 may consist of one or more grids connected to sources of alternating and (or) constant voltage. Its implementation is described in detail in the prototype. The difference lies in the use of catalytic materials such as Fe, Ni, Co, Pt, Pd.

The device operates as follows. Using the drive 17, raise the detachable part of the reaction chamber. When using the tubes 30 and 31, the desired position of the tube 31 and the flow former 37 are set relative to the stage 6, the substrate 19 with the catalytic surface 20 is mounted on the stage 6, then the detachable part is lowered, centering it at the end of lowering, due to the gap A. The pump 11 is turned on and adjust the residual pressure in chamber 2 from 1 to 20 kPa. After that, a short-term ~ 1 min washing of the chamber with 2 pairs of ethanol is carried out and its annealing for ~ 10 min using the heating element 21, as well as heating the substrate 19 to a value of 900 ° C.

Ethanol vapors are fed into chamber 2 using a needle leakage 22. The required amount of vapors is determined by the residual pressure in chamber 2 using pressure gauge 39. It can be in the range of 1-20 kPa.

Ethanol vapor can be supplied to chamber 2 due to its direct current from cell 23, as well as due to natural evaporation into the evacuated volume of chamber 2. The second variant of vapor supply is carried out by heating ethanol in cell 23 with heater 28 controlled by temperature meter 29.

Next, the nanotube growth process is carried out according to the program of the control unit 40, maintaining a certain temperature of the substrate 19 and the concentration of ethanol vapor.

The process of nanotube growth is controlled by also forming a field in the area of the substrate 19. Here various modes of using constant and variable fields can be used. (For details, see [2].) The difference from the prototype is the use of a catalyst as mesh materials. This leads to additional heating of the mixture, more uniform distribution over the surface of the substrate and preliminary catalytic decomposition of ethanol.

The growth control of nanotubes is as follows.

The value of the reflected signal changes depending on the thickness of the precipitate on the substrate. The magnitude of the reflected signal depends on the chirality of carbon nanotubes. For example, tubes with metal conductivity growing on a metal substrate practically do not change the magnitude of the reflected signal, but in the sediment their amount usually does not exceed 30%. In the general case, the amplitude, polarization, and frequency of reflected light change due to the spatial arrangement of nanotubes on the substrate, their structures (single-walled or multi-walled), chirality (metal or semiconductor). These patterns are usually determined empirically. The fine structure of the Raman excitation spectrum allows us to judge the diameter and length of carbon nanotubes. The growth device can be coupled through an optical window using a fiber optic cable to the Raman spectrum (for details, see [6]). Thus, the use of a laser and an analysis module allows one to control the growth of nanotubes and improve their quality.

After the end of the process, the leak pipe 27 is closed, the valve 12 is turned off, the pump 11 and the heating element 21 are turned off, the chamber 2 is cooled and the atmosphere is poured through the leak 36. After that, the detachable part of the reaction chamber 2 is lifted by the drive 17 and the substrate 19 with nanotubes is removed.

Using an evaporation cell with ethanol allows one to obtain high-quality nanotubes with relative safety and simplicity of the process.

The use of a reaction chamber with a detachable part increases its resistance to shock and vibration loads, as well as to temperature gradients. In addition, the operation and preventive cleaning of the chamber is simplified, which leads to an increase in the quality of nanotubes.

Placing a heating element in the substrate zone allows the same heater to conduct heating of the substrate and degassing of the reaction chamber, which also improves the quality of the nanotubes. The use of a particle flow former in the form of at least one conductive mesh made of catalytic material stimulates the growth of nanotubes.

The implementation of the reaction chamber of quartz ceramics provides "clean" conditions for the production of nanotubes. In addition, quartz ceramics is a good heat insulator, and this simplifies the operation of the device.

The installation of a heater and an ethanol temperature meter in the evaporation cell allows precise control of the supply of the gas-vapor mixture to the reaction chamber.

The introduction of a gas-vapor mixture from a conductive material and its connection to a source of alternating and (or) constant voltage expands the possibilities of electrophysical influence on the nanotube growth process.

The introduction of gas in the form of two tubes, coaxially arranged one in the other, regulates the process of supplying the gas mixture in the reaction zone, which is important for research purposes.

LITERATURE

1. Patent JP 2005187309, 07/14/2005.

2. Patent WO 2004065294, 08/05/2004.

3. Pivinsky Yu.E., Romashin A.G. Quartz ceramics. M .: Metallurgy, 1974

4. Bessonova A.V., Kolodiy P.P., Simunin M.M. "Growing carbon fibers on a sol - gel catalyst by pyrolysis from the ethanol gas phase" (report) // "Industry of nanosystems and materials." Conference proceedings. M .: MIET, 2005. - P.182.

5. Komarov I.A., Schlegel I.V., Simunin M.M. “Techniques for the production of carbon nanotubes by the catalytic pyrolysis of ethanol” (article) // Nanotechnology in Electronics: Proceedings // Ed. A.A. Gorbatsevich. - M.: MIET, 2007 .-- 168 p.: Ill. - S.88-92.

6. S. Maruyama, R. Kojima, Y. Miyauchi, S. Chiashi, M. Kohno. Lov-temperature synthesis of high - purity single - welled carbon nanotubes from alcohol. Chemical Physics Letters 2002, 360, p. 229-234.

7. www.spark_don.ru.

Claims (6)

1. A device for growing carbon nanotubes by ethanol pyrolysis, containing a reaction furnace with a feed module and ethanol vapor input, a substrate holder with a substrate having a catalytic surface, and a heating element, characterized in that a reaction chamber containing a detachable part is placed inside the reaction furnace, coupled to an axial displacement drive, the ethanol vapor supply module comprises an ethanol vapor cell coupled to the ethanol vapor input, and a heating element is installed inside the p the reaction chamber in the region of the substrate, the device comprising a particle flow former installed in the reaction chamber and made in the form of at least one conductive grid connected to an AC source and / or a constant voltage source, at least one conductive mesh is made of catalytic material. 2. The device according to claim 1, characterized in that the reaction chamber is made of quartz ceramic. 3. The device according to claim 1, characterized in that a heater and an ethanol temperature meter are installed in the evaporation cell. 4. The device according to claim 1, characterized in that the input of ethanol vapor is made of conductive material and is connected to an alternating voltage source and / or constant voltage source. 5. The device according to claim 1, characterized in that the input of ethanol vapor is made in the form of two tubes, coaxially arranged one in the other with the possibility of movement relative to each other. 6. The device according to claim 1, characterized in that the catalytic material is selected from the series: Pt, Pd.