A method and application for preparing nano-carbon spheres by Joule heating flash evaporation

Abstract

The present invention discloses a method and application for preparing nano-carbon spheres by Joule heat flash evaporation. For the first time, waste resin is used as a precursor, and nano-carbon spheres are prepared by Joule heat flash evaporation technology. Regular-shaped nano-carbon sphere particles are obtained, which have a small internal resistance, ideal electrochemical behavior and electrochemical reversibility, and are used for preparing supercapacitors. It can not only improve the preparation efficiency of new carbon materials, but also provide new ideas for the preparation of supercapacitor electrode materials.

Description

Technical Field:

[0001] The present invention relates to the technical field of nanomaterial preparation, and particularly relates to a method and application for preparing nanocarbon spheres by Joule heat flash evaporation. Background Art:

[0002] With the development of the new energy industry, a large number of new energy devices built in the early stage in our country will be decommissioned in large quantities, thus causing the problem of large-scale scrapping and recycling of decommissioned new energy devices, such as wind turbine blades, photovoltaic solar panels, power batteries, etc. The high-value green recycling of waste resin in the recycling of related devices has received extensive attention. Due to the irreversible chemical cross-linked structure and the insoluble and infusible characteristics of thermosetting resins such as epoxy resin, its recycling is difficult and requires high recycling technology. The pyrolysis method is one of the main methods for recycling such resins at present.

[0003] Tube furnace pyrolysis is one of the common methods for resin pyrolysis, and the resin can be pyrolyzed into pyrolysis gas, oil and coke at a temperature below one thousand degrees Celsius. Due to the limitation of the conventional tube furnace device, the pyrolysis process usually takes several hours or even dozens of hours, and the slow heating rate cannot provide energy for the cracked organic monomers in a very short time to prepare high-value recycled products other than pyrolysis gas and oil.

[0004] Nanocarbon spheres are a kind of carbon material with a hollow structure, and have excellent physical and chemical properties. They are usually prepared by methods such as chemical vapor deposition method, carbide reduction method, template method, etc. However, these preparation methods are complex, time-consuming, energy-consuming, and there are problems of secondary pollution. There is no report on the method of preparing nanocarbon spheres from waste resin by using Joule heat flash evaporation technology. Summary of the Invention:

[0005] The purpose of the present invention is to provide a method and application for preparing nanocarbon spheres by Joule heat flash evaporation.

[0006] The present invention is achieved by the following technical solutions:

[0007] A method for preparing nanocarbon spheres by Joule heat flash evaporation, comprising the following steps:

[0008] (1) After crushing, grinding and drying the waste resin, pass it through a 100-mesh sieve to obtain a powdery resin precursor;

[0009] (2) Load the powdery resin precursor obtained in step (1) into a graphite sample tube, place it in a Joule heating furnace, introduce argon as a protective gas, and under the conditions of a pulse voltage of 20 - 40 V, a pulse current of 180 - 500 A, and a heating chamber pressure of 0.4 - 0.6 MPa, heat the Joule heating furnace to 1000 - 3000 K within 4 - 10 s. After natural cooling, grind the obtained material into a powdery form so that the powder particles can pass through a 100-mesh sieve to obtain nanocarbon spheres.

[0010] The waste resin is any one of epoxy resin, polyethylene or polypropylene.

[0011] Preferably, in step (2), under the conditions that the pulse voltage is 30 - 40V, the pulse current is 250 - 400A, and the air pressure in the heating chamber is 0.45 - 0.55MPa, the Joule heating furnace is heated to 1200 - 2500K within 6 - 8s.

[0012] In the present invention, the Joule heat obtained by applying a pulse voltage enables the waste resin to quickly reach a high temperature and react. The reaction time scale is in seconds, and nanocarbon sphere particles with regular shapes are obtained, which have a small internal resistance, ideal electrochemical behavior and electrochemical reversibility. Therefore, the present invention also protects the application of the nanocarbon spheres obtained by the above method for preparing supercapacitors.

[0013] The present invention has the following advantages compared with the prior art:

[0014] 1. For the first time, waste resin is used as a precursor to prepare nanocarbon spheres by the Joule heat flash evaporation technique. Nanocarbon sphere particles with regular shapes are obtained, which have a small internal resistance, ideal electrochemical behavior and electrochemical reversibility, and are used for preparing supercapacitors. This can not only improve the preparation efficiency of new carbon materials, but also provide new ideas for the preparation of supercapacitor electrode materials.

[0015] 2. In the method for preparing nanocarbon spheres by the Joule heat flash evaporation technique, the precursor only contains the waste resin to be treated, and no additional conductive additives need to be added.

[0016] 3. Compared with the traditional synthesis methods of nanocarbon materials, the process of preparing nanocarbon spheres by the Joule heat flash evaporation technique is simple and easy to popularize. Description of the drawings:

[0017] Figure 1 It is a scanning electron microscope image of the 1500K nanocarbon spheres obtained in Example 1. It can be seen from the image that under the high-temperature treatment at 1500K, the material is uniform spherical particles and arranged in a chain-like manner, and the particle diameter is 80 - 300nm.

[0018] Figure 2 It is a transmission electron microscope image of the 1500K nanocarbon spheres obtained in Example 1. It can be seen from the image that the microstructure of the material is mainly a kind of hollow spherical particles, and the thickness of the spherical shell is about 70nm, indicating that the method effectively prepares nanocarbon spheres with a hollow structure.

[0019] Figure 3X-ray diffraction pattern of the 1500K nanocarbon spheres obtained in Example 1. As can be seen from the figure, strong characteristic peaks of graphite carbon crystals appear under the condition of 1500K, indicating that the nanocarbon spheres prepared based on the Joule flash evaporation technology have a stable graphite structure.

[0020] Figure 4 Raman spectrum of the 1500K nanocarbon spheres obtained in Example 1. After calculation, the ID / IG of the material is 0.69, indicating that the nanocarbon spheres prepared by this method have few defects and a complete graphite structure.

[0021] Figure 5 Galvanostatic charge / discharge curves (left), cyclic voltammograms (middle), and electrochemical impedance spectroscopy (right) of the 1500K nanocarbon spheres prepared in Example 1 after being fabricated into supercapacitors. The data shows that the nanocarbon spheres have electrochemical reversibility, ideal electrochemical behavior, and small internal resistance.

[0022] Figure 6 Scanning electron microscope image of the nanocarbon spheres obtained in Example 2.

[0023] Figure 7 Scanning electron microscope image of the nanocarbon spheres obtained in Example 3. Detailed implementation manners:

[0024] The following is a further description of the present invention, rather than a limitation to the present invention.

[0025] Example 1:

[0026] (1) After crushing, grinding, and drying the waste epoxy resin, it was passed through a 100-mesh sieve to obtain a powdery epoxy resin precursor.

[0027] (2) The powdery epoxy resin precursor was loaded into a graphite sample tube, placed in a Joule heating furnace, argon was introduced as a protective gas, and a cooling water circulation system was used as the cooling system. Under the conditions of a pulsed voltage of 40V, a pulsed current of 275A, and a heating chamber pressure of 0.5MPa, the Joule heating furnace was heated to 1500K within 7s. After natural cooling, the obtained material was ground into a powder so that the powder particles could pass through a 100-mesh sieve to obtain nanocarbon spheres, denoted as 1500K nanocarbon spheres. The elemental composition is shown in Table 1. The scanning electron microscope image is shown in Figure 1 , the transmission electron microscope image is shown in Figure 2 , the X-ray diffraction pattern is shown in Figure 3 , and its Raman spectrum is shown in Figure 4 .

[0028] Table 1 Elemental composition analysis of the epoxy resin precursor and 1500K nanocarbon spheres

[0029]

[0030] As can be seen from Table 1, after the reaction, the carbon content of the nanocarbon spheres at 1500 K is 93.94%, which is much higher than 65.76% of the resin precursor. The H / C value of the nanocarbon spheres decreases from 1.36 to 0.04 after the reaction, indicating that the degree of carbonization of the nanocarbon spheres is significantly improved and they have strong aromaticity.

[0031] From Figure 1 it can be seen that under the high-temperature treatment at 1500 K, the material is uniform spherical particles and arranged in a chain-like pattern, and the particle diameter is 80 - 300 nm.

[0032] From Figure 2 it can be seen that the microstructure of the material is mainly a kind of hollow spherical particles, and the thickness of the spherical shell is about 70 nm, indicating that the method effectively prepares nanocarbon spheres with a hollow structure.

[0033] From Figure 3 it can be seen that under the condition of 1500 K, a strong characteristic peak of graphite carbon crystal appears, indicating that the nanocarbon spheres prepared based on the Joule heat flash evaporation technology have a stable graphite structure.

[0034] Figure 4 is the Raman spectrum of the nanocarbon spheres at 1500 K. After calculation, the ID / IG of the material is 0.69, indicating that the nanocarbon spheres prepared by this method have few defects and a complete graphite structure.

[0035] 2 mg of the nanocarbon spheres at 1500 K were loaded on a stainless steel sheet and assembled into a supercapacitor. Figure 5 are the rapid charge-discharge curve, cyclic voltammetry curve and AC impedance spectrum measured after the nanocarbon spheres at 1500 K are prepared into a supercapacitor. It can be seen from the rapid charge-discharge curve that the material has electrochemical reversibility. It can be seen from the cyclic voltammetry curve that the material has relatively ideal electrochemical behavior. It can be seen from the AC impedance spectrum that the material has a small internal resistance.

[0036] Example 2:

[0037] (1) After the waste polyethylene resin was crushed, ground and dried, it was sieved through a 100-mesh sieve to obtain a powdery polyethylene precursor.

[0038] (2) The powdery polyethylene precursor was loaded into a graphite sample tube, placed in a Joule heating furnace, argon was introduced as a protective gas, and a cooling water circulation was used as a cooling system. Under the conditions of a pulse voltage of 40 V, a pulse current of 275 A, and a heating chamber pressure of 0.5 MPa, the Joule heating furnace was heated to 1500 K within 7 s. After natural cooling, the obtained material was ground into a powder so that the powder particles could pass through a 100-mesh sieve to obtain nanocarbon spheres. See the scanning electron microscope image in Figure 6 .

[0039] From Figure 6 It can be seen that after the polyethylene resin is treated at a high temperature of 1500K by the Joule heat flash evaporation technique, the obtained material is uniform spherical particles and arranged in a chain-like manner, with the particle diameter being 10 - 500nm.

[0040] Example 3:

[0041] (1) After the waste polypropylene resin is crushed, ground, and dried, it is sieved through a 100-mesh sieve to obtain a powdery polypropylene precursor.

[0042] (2) The powdery polypropylene precursor is loaded into a graphite sample tube, placed in a Joule heating furnace, argon is introduced as a protective gas, and a cooling water circulation is used as a cooling system. Under the conditions of a pulse voltage of 40V, a pulse current of 275A, and a heating chamber pressure of 0.5MPa, the Joule heating furnace is heated to 1500K within 7s. After natural cooling, the obtained material is ground into a powder so that the powder particles can pass through a 100-mesh sieve to obtain nano-carbon spheres. The scanning electron microscope image thereof is shown in Figure 7 .

[0043] From Figure 7 It can be seen that after the polypropylene resin is treated at a high temperature of 1500K by the Joule heat flash evaporation technique, the obtained material is uniform spherical particles and arranged in a chain-like manner, with the particle diameter being 300 - 600nm.

[0044] Comparative Example 1:

[0045] Referring to Example 1, the difference is that there is no Joule heat flash evaporation technique, and a pyrolysis method is adopted, including the following steps:

[0046] (1) After the waste epoxy resin is crushed, ground, and dried, it is sieved through a 100-mesh sieve to obtain a powdery epoxy resin precursor.

[0047] (2) The powdery epoxy resin precursor is loaded into a quartz boat, argon is introduced as a protective gas, and pyrolysis is carried out at 1000°C for 0.5h. After natural cooling, there is no solid-phase material residue in the quartz boat, and no carbon material can be formed.

Claims

1. A method for preparing nano-carbon spheres by Joule heat flash evaporation, characterized in that, It includes the following steps: (1) After crushing, grinding and drying the waste resin, it is sieved through a 100-mesh sieve to obtain a powdery resin precursor; (2) The powdery resin precursor obtained in step (1) is loaded into a graphite sample tube, placed in a Joule heating furnace, argon is introduced as a protective gas, and under the conditions of a pulsed voltage of 20 - 40 V, a pulsed current of 180 - 500 A, and a heating chamber pressure of 0.4 - 0.6 MPa, the Joule heating furnace is heated to 1000 - 3000 K within 4 - 10 s, and after natural cooling, the obtained material is ground into a powder so that the powder particles can pass through a 100-mesh sieve to obtain uniform nano-carbon spheres.

2. The method according to claim 1, wherein The waste resin is any one of epoxy resin, polyethylene or polypropylene.

3. The method according to claim 1, wherein In step (2), under the conditions of a pulsed voltage of 30 - 40 V, a pulsed current of 250 - 400 A, and a heating chamber pressure of 0.45 - 0.55 MPa, the Joule heating furnace is heated to 1200 - 2500 K within 6 - 8 s.

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