CN114635121A - Platinum-assisted catalytic carbon nanotube growth method - Google Patents
Platinum-assisted catalytic carbon nanotube growth method Download PDFInfo
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- CN114635121A CN114635121A CN202210050762.7A CN202210050762A CN114635121A CN 114635121 A CN114635121 A CN 114635121A CN 202210050762 A CN202210050762 A CN 202210050762A CN 114635121 A CN114635121 A CN 114635121A
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/26—Deposition of carbon only
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- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
- C01B32/16—Preparation
- C01B32/162—Preparation characterised by catalysts
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- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
- C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/34—Sputtering
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/02—Pretreatment of the material to be coated
- C23C16/0272—Deposition of sub-layers, e.g. to promote the adhesion of the main coating
- C23C16/0281—Deposition of sub-layers, e.g. to promote the adhesion of the main coating of metallic sub-layers
Abstract
The invention discloses a platinum-assisted catalytic carbon nanotube growth method, which comprises the following steps: (1) pretreatment: cleaning and drying the surface of a metal substrate containing nickel or other catalytic metals; (2) sputtering a platinum layer on the surface of the pretreated alloy substrate, and finishing the sputtering; (3) and (3) placing the metal substrate processed in the step (2) in a CVD system for growing the carbon nano tube. The carbon nano tube prepared by the method has random orientation and good overall morphology, the random orientation and the good uniformity can reduce the generation of emission hot spots, and the phenomenon that the carbon tube is burnt or damaged due to overlarge joule heat in a local area caused by the edge effect under heavy current emission is avoided.
Description
Technical Field
The invention relates to the field of growth and preparation of carbon nanotubes, in particular to a platinum-assisted catalytic carbon nanotube growth method.
Background
Carbon Nanotubes (CNTs) have been used and studied in various fields due to their unique structural, chemical and physical properties. CNTs have the advantages of large length-diameter ratio, high conductivity, good thermal stability and the like, and show excellent field emission characteristics in the application of different types of vacuum electronic devices. However, many problems still remain in practical use, including emission uniformity and emission stability in a high-pressure environment. Improving the fabrication of CNT thin films and enhancing their emission properties is critical to facilitate device development. Among various carbon nanotube synthesis techniques, Chemical Vapor Deposition (CVD) is widely used due to its simplicity of processing, in situ growth on various substrates, and low cost. In most CVD syntheses, carbon nanotubes are grown from thin films of catalysts (e.g., iron, cobalt, and nickel) deposited on a substrate. For a field emission device, CNTs directly grown on a metal substrate containing a catalyst element exhibit significant advantages, and can effectively enhance adhesion between the CNTs and the substrate and reduce contact resistance, thereby improving field emission characteristics, for example, the chinese patent "method for directly growing a carbon nanotube field emission cathode on a metal substrate containing nickel" previously filed by the present inventors, the publication number of which is: CN104637758A, the applicant further studies and innovates to obtain the innovative scheme of the application.
Disclosure of Invention
The invention aims to overcome the defects and shortcomings of the prior art, and provides a platinum-assisted catalytic carbon nanotube growth method.
In order to achieve the purpose, the technical scheme of the invention is a platinum-assisted catalytic carbon nanotube growth method, which is characterized in that:
(1) pretreatment: carrying out anodic oxidation treatment on a metal substrate containing nickel, and then cleaning and drying the surface of the alloy substrate;
(2) sputtering a platinum layer on the surface of the pretreated metal substrate, and finishing the sputtering;
(3) and (3) placing the alloy substrate processed in the step (2) in a CVD system for growing the carbon nano tube.
The step (3) is further set as follows: vacuumizing the deposition chamber, introducing Ar or nitrogen gas as protective gas when the deposition chamber is heated to 500 ℃, introducing carbon source gas for growing the carbon nano tube when the temperature is raised to 600-800 ℃, wherein the carbon source gas is C2H2Or other hydrocarbon gas, closing the carbon source gas after the growth is finished, cooling to room temperature, and closing the Ar gas to obtain the finished product of the carbon nano tube.
The invention has the advantages that:
the inventor analyzes the prepared carbon tube by the characterization techniques of a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), a Raman scattering spectrum (Raman) and the like, and the result shows that the carbon nanotube prepared by the method has less impurities, good uniformity and good crystallinity. The inventor also carries out field emission test on the prepared excellent carbon tube, and the test is carried out in a high vacuum field emission test system by adopting a two-stage structure. The results of the open electric field, the threshold electric field, the I-V, F-N curve and the stability test of the carbon tube show that the carbon tube prepared by the method also has excellent field emission performance.
Please refer to the embodiments.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
FIG. 1 is SEM (a) and TEM (b) of Pt-assisted catalytic grown carbon nanotubes according to an embodiment of the present invention;
FIG. 2 is a Raman spectrum of a Pt-assisted catalytic grown carbon nanotube according to an embodiment of the present invention;
FIG. 3 is a graph of I-V and J-V curves for an emitter of a Pt-assisted catalytic grown carbon nanotube according to an embodiment of the present invention;
FIG. 4 is a graph illustrating the stability of an emitter with Pt-assisted catalytic growth of carbon nanotubes according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Preparation examples
Firstly, carrying out anodic oxidation treatment on a nickel-containing alloy sheet, then washing a substrate for multiple times by using alcohol and ultrapure water, and after completely washing the surface of the substrate, heating or blowing for drying. The treated substrate was placed in a sputtering chamber and a high purity platinum target was sputtered onto the surface of the alloy substrate. And placing the treated substrate in a sputtering chamber of a magnetron sputtering film plating machine, vacuumizing the sputtering chamber to about 2Pa in advance, introducing argon to increase the pressure to 9Pa, adjusting the power to about 40W, and sputtering a high-purity platinum target (with the purity of 99.99%) on the surface of the alloy substrate for 80-100 s.
After sputtering, the substrate is put in a CVD system for growth, a mechanical pump is used for evacuating the deposition chamber to about 4Pa, Ar or nitrogen gas is introduced as protective gas when the deposition chamber is heated to 500 ℃, and C is introduced when the temperature is raised to 600-800 DEG C2H2(or other hydrocarbon gas) growth gas, continuing for 10 minutes or a certain time to grow the carbon nano tube, and closing C after the growth is finished2H2And cooling the gas to room temperature, and then closing the Ar gas to take out the carbon nano tube.
The carbon nanotubes prepared by the method are multi-walled carbon nanotubes (MWNTs) and have good structural characteristics (as shown in figure 1). From the SEM image, it is obvious that the carbon tube grown by the platinum-assisted catalysis has random orientation and the overall morphology shows better uniformity. The random orientation and good uniformity can reduce the generation of emission hot spots, and avoid the carbon tube burning or damage caused by the overlarge joule heat in a local area due to the edge effect under the high-current emission. The diameter of the carbon tube grown by platinum-assisted catalysis is about 70-90 nm, the impurities such as amorphous carbon and the like attached to the outer wall are less, and the tube wall is smoother. The high resolution TEM image (fig. 2) of the pt-assisted catalytically grown carbon tubes shows that the pt-assisted grown carbon tubes are more straight and have a significant feature that few catalyst particles are not found in the tubes, indicating that the carbon nanotubes prepared by this method mainly follow the bottom growth mode and that few catalyst particles in the tubes also contribute to the improvement of electron transport and thermal conductivity.
Raman spectroscopy was performed on the platinum assisted growth carbon nanotubes as shown in figure 2. Located 1360cm-1Peak D of (2) and 1584cm-1Corresponds to the defect structure and vibration mode of the crystalline graphite, respectively. The ratio of the D peak to the G peak is often used to evaluate the crystallinity, I, of carbon nanotubesD/IGThe smaller, the better the crystallinity of the CNT proves. I of Pt-assisted catalytically grown carbon nanotubesD/IGCan reach below 0.56, which shows that the carbon tube prepared by the method has good crystallinity.
The test adopts a two-stage structure at 10-7Pa vacuum system, the area of CNT emission film is 12mm2The spacing between the cathode and anode was 300 microns and the results are shown in figure 3. In the three test cycles, the first cycle was offset from the second and third cycles due to desorption of the gas adsorption. The second and third tests then have good repeatability. The opening electric field of the cathode (corresponding to 0.01 mA/cm)2Current density) and threshold electric field (corresponding to 10 mA/cm)2Current density) of 2.0V/μm and 3.5V/μm, respectively, field enhancement factors are important parameters for measuring the field emission characteristics (β), according to the F-N equation:
where φ is the work function (4.8 eV for carbon nanotubes) and slope is the slope. The slope is taken from the slope of the F-N curve of the third test of fig. 3, and the field enhancement factor for the platinum assisted catalytic carbon nanotube cathode can be calculated to be 2486.
As shown in fig. 4, the field emission stability of the platinum-assisted catalytic growth carbon nanotube emitters was tested in a high vacuum system. The emitter emission current started at 3.0mA (25 mA/cm)2) The current fluctuated between 3.2mA and 4.8mA for the first 20 hours and then stabilized for 80 hoursAt 3.6 mA. The initial current increase of the platinum-assisted catalytic grown carbon nanotube emitter may be due to the stretching effect of the CNTs under the electrostatic action of the electric field, especially for long bent tubes, resulting in an increase of the field enhancement effect and a decrease of the CNT-anode distance. The high emission current may result in uniform melting of the CNT-catalyst-substrate interface, thereby improving the conductivity and mechanical strength of the interface. Such an effect is more pronounced for bottom-grown Pt-assisted CNTs, which can enhance the adhesion of CNTs to the substrate, helping to increase the initial current. After such a stretching period, the poorly adherent CNTs may be pulled off the substrate. Meanwhile, the emission hot spot may be burned off by over-current joule heating. Through such aging process, the emission reaches a fairly stable level with a fluctuation rate of less than 1%.
The CNT cathode prepared by the method has excellent field emission performance, obviously improved service life performance and advantages and potentials in field emission device application.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.
Claims (3)
1. A platinum-assisted catalytic carbon nanotube growth method is characterized by comprising the following steps:
(1) pretreatment: carrying out anodic oxidation treatment on a metal substrate containing nickel or other catalytic metals, and then cleaning and drying the surface of the metal substrate;
(2) sputtering a platinum layer on the surface of the pretreated metal substrate, and finishing sputtering;
(3) and (3) placing the metal substrate treated in the step (2) in a CVD system to grow the carbon nano tube.
2. The method of claim 1, wherein the method comprises the following steps: the step (3) is as follows: vacuumizing the deposition chamber, introducing Ar or nitrogen gas as protective gas when the deposition chamber is heated to 500 ℃, and introducing carbon source gas when the temperature is raised to 600-Growing carbon nanotube with carbon source gas C2H2Or other hydrocarbon gas, closing the carbon source gas after the growth is finished, cooling to room temperature, and closing the Ar gas to obtain the finished product of the carbon nano tube.
3. The method of claim 1, wherein the method comprises the following steps: in the step (2), the specific process for sputtering the platinum layer comprises the following steps: vacuumizing the sputtering coating system to the background working pressure, then introducing sputtering gas into the system, and sputtering for several seconds to several minutes to deposit a platinum metal film on the metal substrate under the condition of being higher than the background pressure.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030180461A1 (en) * | 2002-03-25 | 2003-09-25 | Industrial Technology Research Institute | Process of direct growth of carbon nanotubes on a substrate at low temperature |
| KR20070062711A (en) * | 2005-12-13 | 2007-06-18 | 삼성에스디아이 주식회사 | Method for growing carbon nanotubes and manufacturing method of field emission device therewith |
| US20070259128A1 (en) * | 2006-05-05 | 2007-11-08 | Farzad Parsapour | Method for controlled density growth of carbon nanotubes |
| CN104637758A (en) * | 2014-12-11 | 2015-05-20 | 温州大学 | Method for directly growing carbon nano tube field emission cathode on metal substrate containing nickel |
| CN104651899A (en) * | 2014-12-11 | 2015-05-27 | 温州大学 | Anodizing process of metal substrate for carbon nanotube growth |
| CN113380597A (en) * | 2021-05-05 | 2021-09-10 | 温州大学 | Carbon nanotube-based micro-focus field emission electron source and preparation method thereof |
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- 2022-01-17 CN CN202210050762.7A patent/CN114635121A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030180461A1 (en) * | 2002-03-25 | 2003-09-25 | Industrial Technology Research Institute | Process of direct growth of carbon nanotubes on a substrate at low temperature |
| KR20070062711A (en) * | 2005-12-13 | 2007-06-18 | 삼성에스디아이 주식회사 | Method for growing carbon nanotubes and manufacturing method of field emission device therewith |
| US20070259128A1 (en) * | 2006-05-05 | 2007-11-08 | Farzad Parsapour | Method for controlled density growth of carbon nanotubes |
| CN104637758A (en) * | 2014-12-11 | 2015-05-20 | 温州大学 | Method for directly growing carbon nano tube field emission cathode on metal substrate containing nickel |
| CN104651899A (en) * | 2014-12-11 | 2015-05-27 | 温州大学 | Anodizing process of metal substrate for carbon nanotube growth |
| CN113380597A (en) * | 2021-05-05 | 2021-09-10 | 温州大学 | Carbon nanotube-based micro-focus field emission electron source and preparation method thereof |
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