CN112978717A - Method for shortening carbon nano tube - Google Patents
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- CN112978717A CN112978717A CN201911287608.6A CN201911287608A CN112978717A CN 112978717 A CN112978717 A CN 112978717A CN 201911287608 A CN201911287608 A CN 201911287608A CN 112978717 A CN112978717 A CN 112978717A
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- C01B32/00—Carbon; Compounds thereof
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Abstract
The invention provides a carbon nanotube truncation method. The method comprises the following specific processes: firstly, heating the carbon nano tube in an oxygen atmosphere, and introducing defects on the tube wall of the carbon nano tube by using oxygen oxidation; then mixing the carbon nano tube with mixed acid (prepared by concentrated sulfuric acid and concentrated nitric acid) and carrying out ultrasonic treatment in water bath, wherein oxidizing species attack defects on the tube wall of the carbon nano tube so as to shorten the carbon nano tube; finally, the carbon nano tube is leached to be neutral and dried. The length distribution of the carbon nano tube after being shortened can be controlled by adjusting the temperature of the ultrasonic water bath and the time and the frequency of the ultrasonic treatment. The method has the characteristics of controllable length of the truncated carbon tube, suitability for multi-wall carbon nanotubes and single-wall carbon nanotubes, low equipment requirement, simple operation, high yield and the like.
Description
Technical Field
The invention relates to a controllable truncation method of a carbon nano tube, in particular to a method for truncating the carbon nano tube by chemical oxidation under a mild condition, belonging to the field of preparation of inorganic nano carbon materials.
Background
Since the discovery, carbon nanotubes have caused a hot trend in research in the scientific fields of physics, chemistry, materials, biology, etc. due to their unique structure and physicochemical properties on the nanometer scale. The quasi-one-dimensional nano-scale tubular cavity structure of the carbon nano-tube can be regarded as formed by winding single-layer or multi-layer graphene along a chiral vector. The carbon nano tube has unique and excellent mechanical, thermal, electromagnetic and adsorption properties, large specific surface area and high graphitization tube wall which is easy to be functionalized and modified. Therefore, the carbon nano tube has great application potential in the fields of nano composite materials, super capacitors, lithium ion batteries, hydrogen storage, catalysis and the like. Recently, the use of short carbon nanotubes (<1 μm) has attracted increasing research interest. In the field of biology, single-walled carbon nanotubes are used as imaging materials due to their photoluminescent properties in the infrared region, but short single-walled carbon nanotubes of appropriate length are required, while long carbon nanotubes are cytotoxic [ l.j.wilson, et.in. in. vivo biological of large nanotubes of ultra and long-length single-walled carbon nanotubes after and indoor administration to the small scale. acs Nano 2010,4,1481-1492 ]. In the field of mechanical engineering, single-walled carbon nanotubes are used as cantilevers for scanning probe microscopes, but the achievement of high resolution requires sufficiently short carbon nanotubes (50nm) [ J.Martinez, et al, Length control and sharing of atomic micro-carbon nanotubes fabricated by an electron beam, nanotechnology 2005,16,2493-2496 ]. In The field of catalysis, carbon nanotubes have unique domain-limiting effect, which can modulate The performance of catalyst, and The domain-limiting effect mainly includes The restriction effect of carbon nanotubes on The space of catalyst nanoparticles in a tube cavity, The modulation effect of The electron-deficient environment in The tube caused by The graphene coiled structure on The electronic structure of The catalyst nanoparticles, The selective enrichment effect of carbon nanotubes on reactant and product molecules, and The rapid diffusion of molecules such as water and methanol in The tube cavity [ x.l.panand x.h.bao, The effects of The defined entities carbon nanotubes on catalysis.acc.chem.res,2011,44, 553-. The wet chemical method is the most simple and feasible preparation method of the carbon nanotube confinement catalyst, and the huge length-diameter ratio of the carbon nanotube can not only hinder the diffusion of a precursor solution, but also influence the diffusion of reactants and products of the confinement catalytic reaction. Thus, uniform dispersion of the confined catalyst nanoparticles is more easily achieved with short carbon nanotubes (<1 μm) while also facilitating diffusion of reactant and product molecules [ X.L.Pan and X.H.Bao, Tailored cutting of carbon nanotubes and controlled dispersion of metal nanoparticles of the channels, J.Mater.chem.,2008,18, 5782-.
The carbon nano tube grown by the existing large-scale synthesis method is as long as several microns to dozens of microns, and the short carbon nano tube with the length of hundreds of nanometers is difficult to directly prepare, so the preparation of the short carbon nano tube mainly depends on the shortening of the grown carbon nano tube. At present, the truncated carbon nanotube is mainly prepared by means of chemical oxidation or mechanical ball milling. Concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) are mixed with multi-wall carbon nano-tubes for ultrasonic treatment [ R.E. Smalley, et al. Fullerene pipes, Science,1998,280,1253-]The multi-walled carbon nanotube can be cut to 100-300nm, and mixed with concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio 4:1) and stirred with the single-walled carbon nanotube [ R.E. Smalley, et al. controlledoxidative cutting of single-walled carbon nanotube no-tubes, J.AM. CHEM. SOC.,2005,127, 1541-1547-]The single-wall carbon nanotube can be truncated, but the simple liquid-phase oxidation method relies on oxidizing species to erode defects on the wall of the carbon nanotube to realize truncation, which results in great loss of the carbon nanotube (the yield of the carbon nanotube is only 46%), damages the complete tubular structure of the carbon nanotube, and introduces a great amount of functional groups on the wall of the tube. Using F2Oxidation of single-walled carbon nanotubes followed by high temperature treatment at 1000 ℃ to decompose the fluorinated region [ J.L. Margrave, et al.cutting single-wall carbon nanotube Nano-tube hf emission, Nano Lett.,2,2002]The gas phase oxidation method can shorten the carbon nano tube to be less than 60nm, but similar to the liquid phase oxidation, the carbon nano tube is shortened, and meanwhile, a large amount of loss of the carbon nano tube is caused, and the fluorination process has higher safety requirements on equipment and operation. Literature [ J.N.Wang, et., Cutting of multi-walled carbon nanotubes by solid-state reaction, J.Mater.chem.,2006,16, 4231-]Report and patent CN1807233A disclose the use of Ni deposited on multi-walled carbon nanotubes by solid phase oxidationThe O nanoparticles truncate the carbon nanotubes to below 200nm at high temperature with a carbon nanotube loss of about 20 wt%, as compared to the literature [ X.L.Pan, X.H.Bao, et al. Tailored cutting of carbon nanotubes and controlled dispersion of metal nanoparticles of the channels, J.Mater.chem.,2008,18, 5782-]The report and patent CN101638228A disclose a catalytic oxidation method for truncating carbon nanotubes to 100-500nm by using Ag or Fe nanoparticles deposited on the surface of multi-walled carbon nanotubes. These two methods cause less loss of carbon nanotubes than gas phase oxidation and liquid phase oxidation, but the operation process is relatively more complicated and introduction of metal impurities is unavoidable. A ball milling method is adopted [ F.Liu, et al.preparation of short carbon nanotubes by mechanical ball milling and the hydrogen adsorption catalyst. carbon,2003,41, 2527-2532; Z.Konya, et al.end morphology of ball milled carbon nanotubes, carbon,2004,42, 2001-2008; pierard, et al ball milling effect on the structure of single walled carbon nanotubes, 2004,42, 1691-]Or patent CN1696053A discloses that the ball milling method using high molecular polymer is simpler than the chemical oxidation method, but the ball milling method using mechanical force to cut the carbon nanotubes results in massive aggregation of the carbon nanotubes and collapse and closure of the tube opening, which is disadvantageous to the dispersion of the carbon nanotubes or the opening of the carbon nanotubes in practical application, and the addition of abrasive tends to introduce impurities. The result of the multiple carbon nanotube truncation methods is better than that of the truncation by a single method. Document [ L.D.Pfefferle, et al.controlled cutting of single-walled carbon nanotubes and low temperature connecting. carbon,201363,61-70]The reported adopted method is that firstly, the single-walled carbon nanotube is ball-milled to introduce defects on the tube wall, and then the oxidizing acid is used for attacking the defect position to shorten the carbon nanotube to 50-200nm, so that the loss of the carbon nanotube can be reduced to 12.2 wt%, the oxidizing acid treatment can also open the port closed by collapse of the carbon nanotube after ball milling, but impurities are introduced in the ball milling process, and the problem of aggregation of the carbon nanotube is still unavoidable.
The carbon nanotubes of different types, such as single-walled carbon nanotubes, double-walled carbon nanotubes and/or multi-walled carbon nanotubes, and the carbon nanotubes of the same type but grown by different process methods have great difference in many aspects, such as length distribution, tube wall defect quantity, impurity content, aggregation state and the like, and the carbon nanotube is simple, practicable, efficient and controllable, has the characteristics of controllable length of shortened carbon tubes, low equipment requirement, simplicity in operation, high yield and the like, and is simultaneously suitable for the multi-walled carbon nanotubes and the single-walled carbon nanotubes.
Disclosure of Invention
The technical problems solved by the invention are as follows: the method for shortening the carbon nano tube overcomes the defects of the prior art, utilizes oxygen to oxidize the carbon nano tube to introduce defects on the tube wall of the carbon nano tube, and then uses oxidizing acid to attack defect positions to further shorten the carbon nano tube, and has the characteristics of simplicity, practicability, high efficiency, controllability and universality.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a method for truncating carbon nanotubes, which is suitable for single-walled carbon nanotubes and multi-walled carbon nanotubes.
The method comprises the following specific steps:
(1) heating and oxidizing: introducing mixed gas (oxygen and inert gas configuration) into the carbon nano tube, and simultaneously carrying out temperature programming, firstly heating to the temperature of 150-;
(2) mixing mixed acid and circulating ultrasound: mixing the carbon nano tube obtained by the treatment in the step (1) with mixed acid (prepared by concentrated sulfuric acid and concentrated nitric acid), carrying out ultrasonic treatment for 1-12h in water bath at 25-60 ℃, taking out the uniform carbon nano tube acid solution on the upper layer after the ultrasonic treatment is finished, supplementing the mixed acid into the carbon nano tube precipitate which is not dispersed at the bottom, and continuing the ultrasonic treatment, thus circulating for 0-4 times;
(3) filtering the upper layer of uniform carbon nanotube acid solution, leaching the carbon nanotube to be neutral by pure water, and carrying out vacuum freeze sublimation drying for 50-120 h.
Based on the above technical solution, preferably, the carbon nanotube is a single-walled carbon nanotube, a double-walled carbon nanotube and/or a multi-walled carbon nanotube.
Based on the above technical scheme, preferably, in the step (1), the mixed gas is a mixed gas of an inert gas and oxygen, the inert gas is one or a mixture of nitrogen, helium, argon, krypton and xenon, and the content of oxygen in the mixed gas is 1% -100%, so that the oxidation condition is mild, the efficiency is high, defect sites can be uniformly generated on the wall of the carbon nanotube, and the truncated carbon nanotube is ensured to have a complete tubular structure.
Based on the technical scheme, the preferable dosage ratio of the carbon nano tube to the mixed acid is 1:0.5-1:10(mg/mL)
Based on the above technical scheme, preferably, in the step (2), the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid in the mixed acid is 1:1-10:1, preferably 1:3, and the mixed acid prepared in the ratio range has strong oxidizing property, so that the truncated carbon nanotube can be effectively obtained.
The step (1) can be omitted when the carbon nano tube with more defects on the original tube wall is treated, the carbon nano tube grown by some production processes has more defects on the tube wall, the defect position is introduced without reoxidation, and the carbon tube can be directly shortened by using oxidizing acid.
Advantageous effects
(1) The invention has wide applicable carbon nano tube range and can be used for shortening single-wall carbon nano tubes and multi-wall carbon nano tubes.
(2) The method utilizes oxygen to oxidize and introduce defects, and then uses oxidizing acid to truncate the carbon nano tube, compared with fluorine gas and chlorine gas, the truncation condition is mild, the equipment requirement is simple, and the process operation is safe and simple.
(3) The invention can control the length distribution of the truncated carbon nano tube by adjusting the temperature of the ultrasonic water bath and the time and the frequency of the ultrasonic treatment.
(4) The truncated carbon nanotube obtained by the invention has complete tube wall structure, the tube opening is opened, the aggregation is not easy, and the carbon nanotube can be easily dispersed in aqueous solution, thereby laying a material foundation for further application such as preparation of nano composite materials.
(5) The invention has high truncation efficiency, less loss of the carbon nano tube, yield of more than 80wt percent and capability of obtaining the macroscopic-scale (gram-scale) short carbon nano tube in a single experiment.
(6) The invention can remove residual transition metal impurities in the carbon nano tube for preparing the carbon nano tube, the metal impurities mostly exist in the form of carbon-coated metal nano particles and are difficult to remove by direct acid cleaning, while the oxygen oxidation process of the invention can remove a carbon layer outside the metal particles, the metal impurities are changed into metal ions in the acid treatment process and are removed in the leaching and filtering process, and new impurities can not be introduced in the invention.
Drawings
Fig. 1 is a transmission electron micrograph of the single-walled carbon nanotube oxidized using only oxygen in comparative example 1.
FIG. 2 is a transmission electron micrograph of the single-walled carbon nanotube ultrasonically treated for 6.5h in example 1.
FIG. 3 is a transmission electron micrograph of the single-walled carbon nanotube ultrasonically treated for 8h in example 1.
FIG. 4 is a transmission electron micrograph of the single-walled carbon nanotube ultrasonically treated for 7.5h in example 2.
FIG. 5 is a transmission electron micrograph of the single-walled carbon nanotubes ultrasonically treated for 9h in example 2.
FIG. 6 is a transmission electron micrograph and Raman characterization results of the multi-walled carbon nanotubes obtained in example 3 by performing cyclic ultrasound for 1,2, 3,4, and 5 times.
FIG. 7 is a transmission electron micrograph of multi-walled carbon nanotubes sonicated at 25 ℃ in example 4.
FIG. 8 is a transmission electron micrograph of the 45 ℃ sonicated multi-walled carbon nanotubes of example 4.
FIG. 9 is a transmission electron micrograph of the multi-walled carbon nanotubes sonicated at 55 ℃ in example 4.
Fig. 10 is a transmission electron micrograph of the ball-milled single-walled carbon nanotubes of comparative example 2 after sonication.
Detailed Description
To further illustrate the present invention, the following specific examples are set forth, but the scope of the claims of the present invention is not limited by these examples. Meanwhile, the embodiment only gives some conditions for achieving the purpose, but does not mean that the conditions must be met for achieving the purpose.
Comparative example 1
200mg of single-walled carbon nanotubes (SWCNTs) (with the inner diameter of 0.8-3nm) are filled into a quartz tube, oxygen-argon mixed gas with the oxygen volume fraction of 20% is introduced, the temperature is programmed to 225 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 18h, then the temperature is programmed to 325 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1.5h, and finally the temperature is programmed to 450 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1 h.
Fig. 1 is a low resolution transmission electron micrograph of single-walled carbon nanotubes oxidized using oxygen only. From the electron micrograph, it can be seen that the length of the single-walled carbon nanotube reaches several micrometers to several tens of micrometers, and a small amount of metal nanoparticles are also present therein.
Example 1
200mg of single-walled carbon nanotubes (SWCNTs) (with the inner diameter of 0.8-3nm) are filled into a quartz tube, oxygen-argon mixed gas with the oxygen volume fraction of 20% is introduced, the temperature is programmed to 225 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 18h, then the temperature is programmed to 325 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1.5h, and finally the temperature is programmed to 450 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1 h. 30mg of single-walled carbon nanotubes subjected to temperature programmed oxidation treatment are placed in a flask, 60mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1 in volume ratio) is added, and the flask is placed in an ultrasonic water bath at 50 ℃ for ultrasonic treatment for 6.5 hours. After the ultrasonic treatment, 45mL of the upper layer uniform carbon nanotube acid solution was taken out, 12mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1, volume ratio) was added to the remaining carbon nanotube acid solution at the bottom of the flask, and the ultrasonic treatment was continued in the water bath for 2 hours. And after the ultrasonic treatment is finished, 18mL of the upper-layer uniform carbon nanotube acid solution is taken out. And filtering the taken carbon nano tube acid solution, rinsing the carbon nano tube acid solution to be neutral by using pure water, and carrying out vacuum freeze sublimation drying for 120 h.
Fig. 2 and fig. 3 are low-resolution transmission electron micrographs of the single-walled carbon nanotube after 6.5h of ultrasound and 8h of ultrasound, respectively. It can be seen from the electron microscope photograph that the length of the carbon nanotube after the temperature programming oxidation and mixed acid ultrasound for 6.5h is distributed in the range of 1-2 microns, while the length of the carbon nanotube after the temperature programming oxidation and mixed acid ultrasound for 8h is reduced to 0.5-1.5 microns. It can be seen from the electron microscope photograph that the residual metal nanoparticles in the original sample disappeared after acid treatment, and no new impurities were introduced.
The mass of the single-walled carbon nanotube obtained after the treatment is weighed, and compared with the mass before the treatment, the yield of the single-walled carbon nanotube can reach 88%.
Example 2
200mg of single-walled carbon nanotubes (SWCNTs) (with the inner diameter of 0.8-3nm) are filled into a quartz tube, oxygen-argon mixed gas with the oxygen volume fraction of 20% is introduced, the temperature is programmed to 225 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 18h, then the temperature is programmed to 325 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1.5h, and finally the temperature is programmed to 450 ℃ at the temperature rise rate of 5 ℃/min and is maintained for 1 h. 30mg of single-walled carbon nanotubes subjected to temperature programmed oxidation treatment are placed in a flask, 60mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1 in volume ratio) is added, and the flask is placed in an ultrasonic water bath at 50 ℃ for ultrasonic treatment for 7.5 hours. After the ultrasonic treatment, 45mL of the upper layer uniform carbon nanotube acid solution was taken out, 12mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1, volume ratio) was added to the remaining carbon nanotube acid solution at the bottom of the flask, and the ultrasonic treatment was continued in the water bath for 1.5 h. And after the ultrasonic treatment is finished, 18mL of the upper-layer uniform carbon nanotube acid solution is taken out. And filtering the taken carbon nano tube acid solution, rinsing the carbon nano tube acid solution to be neutral by using pure water, and carrying out vacuum freeze sublimation drying for 120 h.
Fig. 4 and 5 are low-resolution transmission electron micrographs of the single-walled carbon nanotubes subjected to ultrasonic treatment for 7.5h and ultrasonic treatment for 9h respectively. From the electron microscope photograph, the length of the carbon nano tube after the temperature programming oxidation and the mixed acid ultrasound for 7.5h is distributed in the range of 0.5-1 micron, and the length of the carbon nano tube after the temperature programming oxidation and the mixed acid ultrasound for 9h is reduced to 0.1-1 micron.
The mass of the single-walled carbon nanotube obtained after the treatment was weighed, and the yield of the single-walled carbon nanotube was 81% as compared with the mass before the treatment.
Example 3
400mg of multi-walled carbon nanotubes (MWCNTs) are filled into a quartz tube, oxygen-argon mixed gas with the volume fraction of 20% of oxygen is introduced, the temperature is programmed to 225 ℃ at the heating rate of 5 ℃/min and is maintained for 18h, then the temperature is programmed to 325 ℃ at the heating rate of 5 ℃/min and is maintained for 1.5h, and finally the temperature is programmed to 450 ℃ at the heating rate of 5 ℃/min and is maintained for 1 h. Putting 60mg of multi-walled carbon nanotubes into a flask, adding 120ml of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1, volume ratio), putting the flask into an ultrasonic water bath at 40 ℃ for ultrasonic treatment for 5h, taking 50ml of the upper-layer carbon nanotube mixed acid solution, adding deionized water, and leaching to be neutral, wherein the sample is marked as CNT-1-soni 1. And (3) supplementing 50ml of mixed acid to the rest carbon tube mixed acid solution, continuing performing ultrasonic treatment in a water bath for 5 hours, then taking 50ml of the upper layer carbon tube mixed acid solution, adding deionized water to rinse the solution to be neutral, and marking the sample as CNT-1-soni 2. The above procedure was repeated to obtain samples CNT-1-soni3, CNT-1-soni4, and CNT-1-soni5 in this order.
FIG. 6 shows the electron micrographs of carbon tubes at various stages and the corresponding Raman characterization results. As can be seen from the electron micrograph of FIG. 6, the lengths of the obtained 5 samples CNT-1-soni1, CNT-1-soni2, CNT-1-soni3, CNT-1-soni4 and CNT-1-soni5 become shorter and shorter with the increase of the acid treatment time of the multi-wall carbon nanotube, the length of CNT-1-soni1 reaches several micrometers, and the lengths of CNT-1-soni2, CNT-1-soni3, CNT-1-soni4 and CNT-1-soni5 are sequentially reduced to the levels of 3 micrometers, 2 micrometers, 1 micrometer and 0.5 micrometer. From the Raman characterization results, it can be seen that the degree of graphitization of the carbon tube gradually decreases with the increase of the acid treatment time of the multi-walled carbon nanotube.
Example 4
400mg of multi-walled carbon nanotubes (MWCNTs) are filled into a quartz tube, oxygen-argon mixed gas with the volume fraction of 20% of oxygen is introduced, the temperature is programmed to 225 ℃ at the heating rate of 5 ℃/min and is maintained for 18h, then the temperature is programmed to 325 ℃ at the heating rate of 5 ℃/min and is maintained for 1.5h, and finally the temperature is programmed to 450 ℃ at the heating rate of 5 ℃/min and is maintained for 1 h. Putting three parts of 40mg multi-walled carbon nanotubes into three flasks respectively, adding 40ml of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1, volume ratio) into each flask, putting the three flasks into ultrasonic water baths at 25 ℃, 45 ℃ and 55 ℃ respectively, carrying out ultrasonic treatment for 5h, then taking 20ml of upper-layer carbon tube mixed acid solution respectively, adding deionized water to rinse the solution to be neutral, and marking samples as CNT-2-soni1-25, CNT-2-soni1-45 and CNT-2-soni1-55 respectively.
Fig. 7, 8 and 9 are the carbon tube electron micrographs obtained by 25, 45 and 55 ℃ ultrasonic water bath, respectively. From the electron microscope photograph, it can be seen that the lengths of the carbon tubes obtained by the ultrasonic water bath at 25, 45 and 55 ℃ are respectively more than 5 micrometers, 1-2 micrometers and less than 100 nanometers.
Comparative example 2
200mg of single-walled carbon nanotubes (SWCNTs) (inner diameter 0.8-3nm) were loaded and ball-milled for 6 h. 30mg of single-walled carbon nanotubes subjected to ball milling treatment are placed in a flask, 60mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1 in volume ratio) is added, and the flask is placed in an ultrasonic water bath at 50 ℃ for ultrasonic treatment for 6 hours. After the ultrasonic treatment, 45mL of the upper layer uniform carbon nanotube acid solution was taken out, 12mL of mixed acid (concentrated sulfuric acid: concentrated nitric acid: 3:1, volume ratio) was added to the remaining carbon nanotube acid solution at the bottom of the flask, and the ultrasonic treatment was continued in the water bath for 1.5 h. And after the ultrasonic treatment is finished, 18mL of the upper-layer uniform carbon nanotube acid solution is taken out. And filtering the taken carbon nano tube acid solution, rinsing the carbon nano tube acid solution to be neutral by using pure water, and carrying out vacuum freeze sublimation drying for 120 h.
FIG. 10 is a low resolution TEM image of the single-walled carbon nanotubes after ball milling and 6h of ultrasonication. The electron micrograph shows that the ball milling process causes a large amount of impurities to be introduced into the carbon nanotubes.
The above examples are provided only for the purpose of describing the present invention, and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications can be made without departing from the spirit and principles of the invention, and are intended to be within the scope of the invention.
Claims (8)
1. A method of truncating a carbon nanotube, comprising the steps of:
(1) under an oxidizing atmosphere, keeping the temperature of the carbon nano tube at the temperature of 150-250 ℃ for 1-24h, then heating to the temperature of 400-250 ℃ and keeping the temperature for 1-12h, and finally heating to the temperature of 500-400 ℃ and keeping the temperature for 0.5-6 h;
(2) mixing the carbon nano tube obtained by the treatment in the step (1) with mixed acid, carrying out ultrasonic treatment for 1-12h in water bath at 25-60 ℃, wherein after the ultrasonic treatment is finished, the upper layer is a carbon nano tube acid solution, and the lower layer is undispersed carbon nano tube precipitate;
(3) and filtering, washing and drying the carbon nano tube acid solution to obtain the truncated carbon nano tube.
2. The method according to claim 1, further comprising a step (4), wherein the step (4) is to add mixed acid to the undispersed carbon nanotube precipitate, perform ultrasonic treatment to obtain an upper carbon nanotube acid solution and a lower undispersed carbon nanotube precipitate, and circulate the step (4)0-4 times.
3. The method according to claim 1, wherein the mixed acid is a mixed acid of concentrated sulfuric acid and concentrated nitric acid; in the mixed acid, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 1:1-10: 1.
4. The method according to claim 1, wherein the washing in step (3) is rinsing with pure water to neutrality, and the drying is vacuum freeze sublimation drying for 50-120 h.
5. The method of claim 1, wherein: the carbon nano tube is a single-wall carbon nano tube or a multi-wall carbon nano tube.
6. The method of claim 1, wherein: in the step (1), the oxidizing atmosphere is a mixed gas of an inert gas and oxygen, the inert gas is one or a mixture of nitrogen, helium, argon, krypton and xenon, and the volume content of oxygen in the mixed gas is 1% -100%.
7. The method of claim 1, wherein the amount ratio of the carbon nanotubes to the mixed acid is 1:0.5 to 1:10 (mg/mL).
8. The method of claim 3, wherein: the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid is 1: 3.
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| CN115536005A (en) * | 2022-10-31 | 2022-12-30 | 山东大展纳米材料有限公司 | Carbon nano tube purification method |
| US20230270008A1 (en) * | 2022-01-25 | 2023-08-24 | National Cheng Kung University | Thermoelectric polymer film, manufacturing method thereof, power supply device and temperature control device |
| CN115536005B (en) * | 2022-10-31 | 2024-04-19 | 山东大展纳米材料有限公司 | Carbon nano tube purification method |
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