Short carbon nanotubes with open ends and methods for making the same

Abstract

The application discloses a short carbon nanotube with open ends and a preparation method thereof, and belongs to the technical field of short carbon nanotube preparation. The short carbon nanotube with open ends is prepared by taking waste plastics as raw materials, using nickel and molybdenum supported alumina as a catalyst, and optimizing a catalyst formula, raw material pretreatment and a thermal cracking process to precisely control the growth of the carbon nanotube. The method provided by the application is simple to operate, does not need complex equipment and high cost, the quality of the synthetic product is stable and uniform, the method is beneficial to large-scale production, and the method has great application potential in the fields of energy storage and nano electronic device manufacturing.

Description

Technical Field

[0001] This invention relates to a short carbon nanotube with an open end and its preparation method, belonging to the field of short carbon nanotube preparation technology. Background Technology

[0002] Carbon nanotubes, as nanomaterials with unique structures and excellent properties, can be viewed as seamlessly rolled graphene sheets. Based on the number of graphene layers, they are classified into single-walled and multi-walled carbon nanotubes. This special microstructure endows carbon nanotubes with many superior properties. In terms of mechanical properties, their tensile strength is extremely high, reaching tens of times that of steel, while their density is extremely low, making them ideal reinforcing materials for aerospace, high-end composite materials, and other fields. From an electrical perspective, carbon nanotubes exhibit excellent electrical conductivity, with some types even comparable to metals, making them highly promising for applications in electronic device manufacturing, such as the development of ultra-miniature transistors and high-performance wires. In terms of thermal properties, carbon nanotubes possess extremely high thermal conductivity, showing great promise in the field of thermal management materials.

[0003] However, carbon nanotubes face numerous challenges in practical applications. For example, long carbon nanotubes readily aggregate in solution systems, making uniform dispersion difficult and severely limiting their application in fields requiring high dispersibility, such as biomedicine and coatings. Short carbon nanotubes, on the other hand, provide a high density of active sites, making them widely applicable in biopharmaceuticals, catalysis, and energy storage methods. However, existing fabrication techniques produce carbon nanotubes with lengths in the micrometer range, making them unsuitable as anode materials for lithium-ion batteries. Furthermore, open-ended carbon nanotubes exhibit superior filling and field emission performance compared to closed-ended nanotubes. Therefore, developing a stable method for synthesizing short carbon nanotubes with open ends is crucial for expanding the application range of carbon nanotubes. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for synthesizing short and open carbon nanotubes. By optimizing the catalyst formulation, raw material pretreatment and thermal decomposition process, the growth of carbon nanotubes is precisely controlled to obtain short and open carbon nanotubes that meet the needs of various applications.

[0005] The technical solution of the present invention:

[0006] One objective of this invention is to provide a method for preparing short carbon nanotubes with open ends, the method comprising the following steps:

[0007] (1) Mix nickel nitrate powder, ammonium molybdate powder and aluminum nitrate powder evenly, add polyethylene glycol 200 to the mixed powder and stir until it becomes a slurry. After standing, place it in a muffle furnace for calcination treatment, cool it naturally to room temperature, grind it into powder, and obtain catalyst powder for later use.

[0008] (2) Grind the waste plastic into powder, add catalyst powder, mix evenly, place the mixed powder in plastic wrap and fix it into a small ball shape with a high-elasticity rubber band for later use.

[0009] (3) The small balls prepared in (2) are placed in a quartz tube and thermally decomposed in a nitrogen atmosphere until no gas is released. The tube is then cooled to room temperature to obtain short carbon nanotubes with open ends.

[0010] Further specified, (1) nickel nitrate powder, ammonium molybdate powder, and aluminum nitrate powder are mixed in a molar ratio of nickel, molybdenum, and aluminum of (1-5):0.21:1.

[0011] Further specifying, (1) the nickel nitrate powder, ammonium molybdate powder, and aluminum nitrate powder are mixed in a molar ratio of nickel, molybdenum, and aluminum of 3:0.21:1.

[0012] Further specifying, the mass-to-volume ratio of the mixed powder to polyethylene glycol 200 in (1) is 50g:5mL.

[0013] Further specifying, the settling time in (1) is 12h.

[0014] Further specified, in (1), the calcination temperature is 650℃ and the time is 1h.

[0015] Further specifying, (2) the waste plastic is one or more of PE, PP and PS mixed together.

[0016] Further specifying, in (2), the mass ratio of waste plastic powder to catalyst powder is (10~300):100.

[0017] Furthermore, in (2), the mass ratio of waste plastic powder to catalyst powder is 200:100.

[0018] Further specified, (3) the thermal decomposition temperature is 800℃ and the time is 5 to 40 min.

[0019] Further specifying, (3) the thermal decomposition temperature is 800℃ and the time is 5 to 15 minutes.

[0020] The second objective of this invention is to provide a short carbon nanotube with an open end, prepared by the above method.

[0021] A third objective of this invention is to provide an application of the aforementioned short carbon nanotubes with open ends, specifically for energy storage and the manufacture of nanoelectronic devices.

[0022] Beneficial effects of this invention:

[0023] This invention uses waste plastics as raw material and nickel- and molybdenum-supported alumina as catalyst. By optimizing the catalyst formulation, raw material pretreatment, and pyrolysis process, the growth of carbon nanotubes is precisely controlled to prepare short carbon nanotubes with open ends. Compared with existing technologies, it also has the following advantages:

[0024] (1) Using waste plastics as a carbon source can realize the recycling and reuse of waste plastics, which will greatly save energy and materials and alleviate social and ecological pressure.

[0025] (2) Using nickel and molybdenum supported alumina as a catalyst results in high catalytic activity, which can accelerate the reaction and precisely control the structure of carbon nanotubes. Moreover, the catalyst has good stability, and the raw materials are widely available and the cost is controllable, which is conducive to the large-scale industrial production of carbon nanotubes.

[0026] (3) The preparation process of the short carbon nanotubes with open ends provided by the present invention is simple, low in cost, and has good application prospects. Attached Figure Description

[0027] Figure 1 Raman contrast spectra of the carbon nanotubes prepared in Examples 1-5;

[0028] Figure 2 TEM images (at different magnifications) of the carbon nanotubes prepared in Example 3;

[0029] Figure 3 TEM image of the carbon nanotubes prepared in Example 10;

[0030] Figure 4 TEM image of the carbon nanotubes prepared in Example 12;

[0031] Figure 5 TEM image of the carbon nanotubes prepared in Example 15;

[0032] Figure 6 TEM image of the carbon nanotubes prepared in Example 16;

[0033] Figure 7 TEM image of the carbon nanotubes prepared in Example 17;

[0034] Figure 8 This is a TEM image of the carbon nanotubes prepared in Example 18. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0039] Example 1

[0040] Step 1: The recycled waste plastic is initially cleaned and sheared to obtain waste plastic pellets. The waste plastic is polyethylene (PE) plastic.

[0041] Step 2: Catalyst Preparation. Nickel nitrate, ammonium molybdate, and aluminum nitrate were selected as raw materials. First, they were ground into powder using a high-speed pulverizer. The appropriate mass of powder was accurately weighed and placed in a mortar according to a nickel:molybdenum:aluminum molar ratio of 1:0.21:1, and further ground and mixed evenly. Then, an appropriate amount of polyethylene glycol 200 was added (specifically, 10% of the mixed powder), and stirred until a slurry was formed. The mixture was allowed to stand for 12 hours, then placed in a muffle furnace and calcined at 650℃ for 1 hour. After calcination, it was removed, allowed to cool naturally to room temperature, ground again into powder, and collected for later use.

[0042] Step 3: Place the PE granules pretreated in Step 1 into a high-speed pulverizer and grind them into powder; weigh 100g of PE powder and 200g of catalyst powder into a mortar and grind them into a fine powder and mix them evenly; take 10g of the above mixed powder and place it in plastic wrap, and fix it into a small ball shape with a high-elasticity rubber band for later use.

[0043] Step 4: Place the prepared microspheres into a quartz tube and purge with nitrogen for 20 minutes to remove air. Simultaneously, heat the tube furnace to 800°C. After purging, place the quartz tube back into the furnace and, under continuous nitrogen protection, allow the mixture to undergo thermal decomposition at 800°C until no more gas is released. Remove the quartz tube and allow it to cool naturally to room temperature. The carbon-containing product is successfully obtained and placed in a resealable bag for weighing. The obtained product is named CNTs-1.

[0044] Example 2

[0045] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 2:0.21:1. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-2.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 3:0.21:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-3.

[0048] Example 4

[0049] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 4:0.21:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-4.

[0050] Example 5

[0051] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 5:0.21:1. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-5.

[0052] Example 6

[0053] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 3:0.07:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-6.

[0054] Example 7

[0055] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 3:0.14:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-7.

[0056] Example 8

[0057] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 3:0.28:1. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-8.

[0058] Example 9

[0059] The difference between this embodiment and embodiment 1 is that the molar ratio of nickel, molybdenum and aluminum in step 2 is 3:0.35:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-9.

[0060] Example 10

[0061] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:10g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-10.

[0062] Example 11

[0063] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:50g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-11.

[0064] Example 12

[0065] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:100g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-12.

[0066] Example 13

[0067] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:150g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-13.

[0068] Example 14

[0069] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:250g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-14.

[0070] Example 15

[0071] The difference between this embodiment and embodiment 3 is that the mass ratio of PE powder to catalyst powder in step 3 is 100g:300g. The remaining process steps and parameter settings are the same as in embodiment 1. A carbon-containing product is obtained, and the obtained product is named CNTs-15.

[0072] Example 16

[0073] The difference between this embodiment and embodiment 3 is that the waste plastic in step 1 is polypropylene (PP) plastic, while the remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained, which is named CNTs-16.

[0074] Example 17

[0075] The difference between this embodiment and embodiment 3 is that the waste plastic in step 1 is polystyrene (PS) plastic, while the remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained, which is named CNTs-17.

[0076] Example 18

[0077] The difference between this embodiment and embodiment 3 is that: in step 1, the waste plastic is made by mixing PE, PP and PS in a mass ratio of 1:1:1. The remaining process steps and parameter settings are the same as in embodiment 1, and a carbon-containing product is obtained. The obtained product is named CNTs-18.

[0078] Example of effect

[0079] (1) The yield of carbon nanotubes prepared in Examples 3 and 6-9 above was characterized, and the results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] As shown in Table 1 above, the yield of carbon nanotubes first increases and then decreases with the increase of the Mo content in the catalyst. Therefore, the highest yield is achieved when the catalyst ratio is 3:0.21:1, and this ratio has been determined.

[0083] (2) The carbon nanotubes prepared in Examples 1-5 were characterized using Raman spectroscopy, and the comparison spectra are shown below. Figure 1 As shown, all five groups of carbon nanotubes exhibit three distinct vibrational peaks, located at 1350 cm⁻¹. -1 1580cm -1 and 2700cm -1The peaks correspond to the D peak, G peak, and 2D peak. The D peak reflects the degree of disorder in the carbon nanotube structure, indicating defects in the carbon structure and the presence of carbon atoms. p2 The disorder of hybrid vibrations. The G peak reflects the degree of order in the carbon nanotube structure, corresponding to the E2g mode of hexagonal graphite in the graphite layer of the system. The 2D peak is the second-order Raman peak of two-phonon resonance, further reflecting the quality and purity of the carbon nanotubes. The peak intensity ratio of the G peak to the D peak (I G / I D The degree of graphitization of carbon nanotubes is directly proportional to I. G / I D The larger the ratio, the higher the degree of graphitization of the carbon nanotubes, the less amorphous carbon and the fewer structural defects. (See figure: Carbon nanotube I) G / I D The ratios are all relatively large, and with the increase of Ni content in the catalyst, I G / I D The ratios of the two peaks first increase and then decrease, and both peaks have sharp 2D peaks. Raman indicates that the carbon nanotubes prepared in Example 3 have a high degree of graphitization and fewer defects.

[0084] (3) The microstructure of the carbon nanotubes prepared in Examples 3, 10, 12 and Examples 15-18 was characterized, and the results are as follows: Figures 2-8 As shown. By Figure 2 As can be seen, the CNTs-3 prepared in Example 3 have a length of 100-400 nm. The magnified image of the end shows that it has an open structure and is relatively loosely distributed. Its morphology is that of carbon nanotubes with significant differences in length and uneven diameter. Figure 3-5 The results showed that the CNTs-10 prepared in Example 10 had a length range of 10–20 μm, exhibiting a relatively long tubular structure and an aggregated distribution; the CNTs-12 prepared in Example 12 had a length of 200–1000 nm; and the CNTs-15 prepared in Example 15 had a length of 200–1200 nm. Comparison revealed that the lengths of the carbon nanotubes prepared in Examples 12 and 15 were between those of Examples 10 and 3, indicating that with increasing catalyst content, the length of the carbon nanotubes first shortened and then lengthened, with the product obtained in Example 3 being the shortest and open at both ends. Figure 6-8 The results show that the CNTs-16 prepared in Example 16 have an uneven length distribution, with the main body ranging from 50 to 1000 nm, and contain a small number of ultralong carbon nanotubes; the CNTs-17 prepared in Example 17 have a length of 50 to 400 nm and exhibit an aggregated distribution; the CNTs-18 prepared in Example 18 have a similar morphology to CNTs-16, with a main body length of 100 to 800 nm, and also contain a small number of long tubular structures. Although different carbon sources were used in Examples 16 to 18, relatively short carbon nanotubes were prepared in all of them.

[0085] The above results demonstrate that the length and microstructure of carbon nanotubes can be effectively controlled by adjusting the ratio of catalyst to carbon source. The above description is merely a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing short carbon nanotubes with open ends, characterized in that, include: Step 1: Perform preliminary cleaning and shearing on the recycled waste plastic to obtain waste plastic granules, wherein the waste plastic is polyethylene plastic (PE). Step 2: Catalyst Preparation. Nickel nitrate, ammonium molybdate, and aluminum nitrate were selected as raw materials. First, they were ground into powder in a high-speed pulverizer. According to the molar ratio of nickel, molybdenum, and aluminum of 3:0.21:1, the corresponding mass of powder was accurately weighed and placed in a mortar for further grinding and mixing. Then, polyethylene glycol 200 was added, with the amount of polyethylene glycol 200 added being 10% of the mixed powder. The mixture was stirred until it formed a slurry. The mixture was allowed to stand for 12 hours and then placed in a muffle furnace and calcined at a high temperature of 650°C for 1 hour. After calcination, it was taken out, allowed to cool naturally to room temperature, ground into powder again, and collected for later use. Step 3: Place the PE granules pretreated in Step 1 into a high-speed pulverizer and grind them into powder; weigh 100g of PE powder and 200g of catalyst powder into a mortar and grind them into a fine powder and mix them evenly; take 10g of the mixed powder and place it in plastic wrap, and fix it into a small ball shape with a high-elasticity rubber band for later use. Step 4: Place the prepared small balls into a quartz tube, purge the air with nitrogen for 20 minutes, and while purging the air, heat the tube furnace to 800°C. After purging the air, place the quartz tube into the tube furnace and allow the mixture to undergo thermal decomposition at 800°C under continuous nitrogen protection until no more gas is released. Remove the quartz tube and allow it to cool naturally to room temperature to successfully obtain the carbon-containing product.

Images