Micron-sized oversized carbon onion and preparation method thereof

Abstract

The invention discloses micron-sized oversized carbon onions and a preparation method thereof, and belongs to the technical field of carbon onion preparation. According to the preparation method, water-soluble saccharides, a gel monomer and a setting aid are taken as main raw materials, a gel structure is formed through coagulating bath setting and drying processes, and then high-temperature graphitization treatment is performed, so that efficient synthesis of large-size carbon onions is realized. Compared with a traditional method, the method has remarkable advantages in the aspects of environmental protection and synthesis efficiency, the size limitation is broken through, the successfully synthesized maximum carbon onion is ellipsoidal, the long axis of the ellipsoidal carbon onion reaches 21.94 microns, the short axis of the ellipsoidal carbon onion is 17.63 microns, the long axis of the ellipsoidal carbon onion is 399 times and 321 times of the size of the known maximum natural carbon onion respectively, the diameter of the ellipsoidal carbon onion is far greater than the maximum diameter (200 nm) of the artificially synthesized carbon onion, and the diameter of the ellipsoidal carbon onion is larger than that of the artificially synthesized carbon onion. And a wider prospect is provided for wide application of the carbon onion in the fields of supercapacitors, lithium batteries, catalyst carriers, gas adsorption and storage and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon onion preparation, and particularly relates to a micron-sized super-large carbon onion and a preparation method thereof. Background Art

[0002] Carbon onions have shown broad application prospects in many fields with their excellent electronic, optical, electromagnetic and tribological properties. Their high specific surface area, good conductivity and thermal stability make them ideal materials for technologies such as superlubricants, superconductors, ion batteries, supercapacitors, sensors, field emitters, catalyst carriers and gas adsorbents. Especially in the aerospace, energy, electronics, automotive, biomedicine, environmental remediation and chemical industries, carbon onions have attracted widespread attention due to their unique functionality.

[0003] However, the current preparation of carbon onions still faces many challenges. Although traditional synthesis methods, such as arc discharge, chemical vapor deposition (CVD) and electron beam irradiation, can obtain carbon onions, these technologies usually involve highly polluting chemical reagents or produce harmful gases, limiting their potential in green and sustainable development. At the same time, the carbon onions synthesized by existing methods are relatively small in size, mostly between tens of nanometers and hundreds of nanometers, which makes it difficult to fully exert their performance in large-scale applications, especially in situations requiring a large specific surface area or volume. Summary of the invention

[0004] The object of the present invention is to provide a micron-sized super-large carbon onion and a preparation method thereof. By using water-soluble sugars, gel monomers and shaping aids as main raw materials, forming a gel structure through a coagulation bath shaping and drying process, and then undergoing a high-temperature graphitization treatment, efficient synthesis of large-sized carbon onions is achieved. The preparation method provided by the present invention not only overcomes the limitations of traditional methods, but also has significant advantages in environmental protection and synthesis efficiency. The prepared micron-sized super-large carbon onions open up broad prospects for the application of carbon onions in supercapacitors, lithium batteries, catalyst carriers, gas adsorption and storage, sensors and other fields.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a method for preparing micron-sized super-large carbon onions, comprising the following steps:

[0007] Dissolving gel monomer, water-soluble sugar and cross-linking agent in water to obtain solution A; adding shaping aid, initiator and catalyst to the solution A to obtain precursor solution;

[0008] Prepare a solution identical to the solution A, add an ionic gelling agent, and obtain a coagulation bath;

[0009] The precursor solution is dripped into the coagulation bath using an injection device to form a spherical gel, and the spherical gel is fished out, dried, and graphitized to obtain the micron-sized super-large carbon onion.

[0010] Optionally, the gel monomer includes one or more of acrylamide, acrylic acid, methacrylic acid and N-isopropylacrylamide.

[0011] Optionally, the water-soluble sugar includes one or more of glucose, fructose, galactose, maltose, sucrose, lactose and oligofructose.

[0012] Optionally, the crosslinking agent includes one or more of N,N'-methylenebisacrylamide, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diacrylamide ethylenediamine, polyethylene glycol diacrylate, trimethylolpropane triacrylate and N,N'-ethylenebisacrylamide.

[0013] Preferably, the mass ratio of the gel monomer, the water-soluble sugar, the cross-linking agent and water in the solution A is 5-30:10-80:0.1-2:100.

[0014] Optionally, the shaping aid includes one or more of sodium alginate, sodium polyacrylate and sodium carboxymethyl cellulose.

[0015] Optionally, the initiator includes one or more of ammonium persulfate, azobisisobutyronitrile, potassium persulfate and hydrogen peroxide.

[0016] Optionally, the catalyst includes one or more of triethanolamine, sodium bisulfite and tetramethylethylenediamine.

[0017] Preferably, the shaping aid, initiator and catalyst are added in the form of aqueous solution, wherein the concentration of the shaping aid aqueous solution is 1-10wt.%, the concentration of the initiator aqueous solution is 0.5-20wt.%, and the concentration of the catalyst aqueous solution is 0.5-20wt.%.

[0018] Preferably, the mass ratio of the shaping aid to the water in the solution A is 0.5 to 5:100.

[0019] In the precursor solution, the amount of initiator and catalyst added is determined by the amount of gel monomer used, and can be added according to conventional amounts in the art.

[0020] Optionally, the ion gel aid includes one or more of calcium chloride, copper formate tetrahydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate and nickel nitrate hexahydrate.

[0021] Preferably, the ionic gelling agent accounts for 1-20% of the mass of the coagulation bath.

[0022] Preferably, the needle port diameter of the injection device is 30-200 μm.

[0023] Preferably, the drying temperature is 60 to 220° C. and the drying time is 2 to 6 hours.

[0024] Preferably, the graphitization is carried out under oxygen-free conditions, with the temperature being directly or gradually increased to 2000-3000° C., with a heating rate of 1-20° C., and the holding time of each gradient being 0.5-6 h.

[0025] The second technical solution of the present invention is to provide a micron-sized super-large carbon onion prepared according to the above-mentioned preparation method of the micron-sized super-large carbon onion.

[0026] The third technical solution of the present invention is to provide an application of the above-mentioned micron-sized super-large carbon onion in supercapacitors, lithium batteries, catalyst carriers or gas adsorption storage.

[0027] The beneficial technical effects of the present invention are as follows:

[0028] The present invention aims at the high pollution problem and the challenge of limited synthesis size in the preparation process of traditional carbon onions, and proposes an innovative preparation method for micron-sized super-large carbon onions. The method uses water-soluble sugars, gel monomers and shaping aids as the main raw materials, combines coagulation bath shaping and drying processes to form a gel structure, and realizes the efficient synthesis of large-sized carbon onions through high-temperature graphitization treatment. Compared with traditional methods, the present invention not only has significant advantages in environmental protection and synthesis efficiency, but also breaks through the size limit. The largest carbon onion successfully synthesized is ellipsoidal, with a major axis of 21.94μm and a minor axis of 17.63μm, which are 399 times and 321 times the size of the largest known natural carbon onion, respectively, far exceeding the maximum diameter of artificially synthesized carbon onions (200nm), which provides a broader prospect for the wide application of carbon onions in supercapacitors, lithium batteries, catalyst carriers and gas adsorption storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM images of the carbon onion prepared in Example 1, wherein (a) and (b) are at different magnifications.

[0030] Figure 2 This is a CT scan of the carbon onion prepared in Example 1.

[0031] Figure 3 This is a comparison chart of the diameters of the largest carbon onion prepared in Example 1 and the carbon onions reported in the literature.

[0032] Figure 4 This is a CT scan reconstruction of the carbon onion prepared in Example 2. DETAILED DESCRIPTION

[0033] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0034] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0035] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] (1) Preparation of precursor solution: First, 12 g of acrylic acid, 40 g of glucose and 0.3 g of ethylene glycol diacrylate were mixed and dissolved in 110 mL of deionized water, and stirred to form a uniform transparent solution. Then, 50 mL of 4% sodium alginate aqueous solution, 4 mL of 10% ammonium persulfate aqueous solution, and 4 mL of 10% tetramethylethylenediamine aqueous solution were added, and ultrasonic and stirred to form a uniform solution. The bubbles in the spinning solution were removed by a debubbler to obtain a precursor solution for standby use.

[0039] (2) Preparation of coagulation bath: 12 g of acrylic acid, 40 g of glucose, 0.3 g of ethylene glycol diacrylate, and 12 g of calcium chloride were mixed and dissolved in 110 mL of deionized water, and stirred to form a uniform transparent solution.

[0040] (3) Preparation of gel beads: Use a syringe to absorb an appropriate amount of precursor solution, and drop the precursor solution into the coagulation bath through a needle with a diameter of 30 μm to form transparent small spheres. When the target number of beads is reached, use a fishing net to fish them out, put them in a quartz boat, and keep them in an oven at 80°C and 200°C for 2 hours respectively to accelerate gelation and drying. The dried beads are wrapped with graphite paper and placed in a graphite box.

[0041] (4) Graphitization: Place the graphite box containing the sample into a graphitization furnace. In a vacuum atmosphere, heat the temperature directly to 1800°C at a heating rate of 8°C / min, then heat the temperature directly to 2800°C at a heating rate of 2°C / min, and keep the temperature for 3 hours. Cool the furnace to room temperature to obtain a sample containing carbon onion.

[0042] The TEM image of the carbon onion prepared in Example 1 is shown in Figure 1 , where (a) and (b) have different magnifications.

[0043] The CT scan of the carbon onion prepared in Example 1 is shown in Figure 2 .

[0044] Diameter comparison of the largest carbon onion prepared in Example 1 and the carbon onions reported in the literature.

[0045] Example 2

[0046] (1) Preparation of precursor solution: First, 42 g of acrylamide, 140 g of maltose and 2.3 g of polyethylene glycol diacrylate were mixed and dissolved in 385 mL of deionized water, and stirred to form a uniform transparent solution. Then, 175 mL of 6% sodium alginate aqueous solution, 14 mL of 10% hydrogen peroxide aqueous solution, and 14 mL of 10% sodium sulfite solution were added, and ultrasonic and stirred to form a uniform solution. The bubbles in the spinning solution were removed by a defoamer to obtain a precursor solution for standby use.

[0047] (2) Preparation of coagulation bath: 42 g of acrylamide, 140 g of maltose, 2.3 g of polyethylene glycol diacrylate, and 42 g of calcium chloride were mixed and dissolved in 385 mL of deionized water, and stirred to form a uniform transparent solution.

[0048] (3) Preparation of gel beads: Use a syringe to absorb an appropriate amount of precursor solution, and drop the precursor solution into the coagulation bath through a needle with a diameter of 30 μm to form transparent small spheres. When the target number of beads is reached, use a fishing net to fish them out, put them in a quartz boat, and keep them in an oven at 100°C and 220°C for 2 hours respectively to accelerate gelation and drying. The dried beads are wrapped with graphite paper and placed in a graphite box.

[0049] (4) Graphitization: Place the graphite box containing the sample into a graphitization furnace. In a vacuum atmosphere, heat the sample to 1400°C at a heating rate of 4°C / min and keep the temperature for 2 hours. Then heat the sample to 2800°C at a heating rate of 2°C / min and keep the temperature for 3 hours. The furnace is cooled to room temperature to obtain a sample containing carbon onion.

[0050] The CT scan reconstruction image of the carbon onion prepared in Example 2 is shown in Figure 2 .

[0051] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing micron-sized super-large carbon onions, characterized in that: The following steps are involved: Dissolving gel monomer, water-soluble sugar and cross-linking agent in water to obtain solution A; Adding a shaping aid, an initiator and a catalyst to the solution A to obtain a precursor solution; Prepare a solution identical to the solution A, add an ionic gelling agent, and obtain a coagulation bath; The precursor solution is dripped into the coagulation bath using an injection device to form a spherical gel, and the spherical gel is fished out, dried, and graphitized to obtain the micron-sized super-large carbon onion.

2. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The mass ratio of the gel monomer, the water-soluble sugar, the cross-linking agent and water in the solution A is 5-30:10-80:0.1-2:

100.

3. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The shaping aid, initiator and catalyst are added in the form of aqueous solution, wherein the concentration of the shaping aid aqueous solution is 1-10wt.%, the concentration of the initiator aqueous solution is 0.5-20wt.%, and the concentration of the catalyst aqueous solution is 0.5-20wt.%.

4. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The mass ratio of the shaping aid to the water in the solution A is 0.5 to 5:

100.

5. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The ionic gelling agent accounts for 1 to 20% of the mass of the coagulation bath.

6. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The diameter of the needle port of the injection device is 30-200 μm.

7. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The drying temperature is 60-220° C. and the drying time is 2-6 hours.

8. The method for preparing micron-sized super-large carbon onions according to claim 1, characterized in that: The graphitization is carried out under oxygen-free conditions, and the temperature is directly or gradually increased to 2000-3000° C., the heating rate is 1-20° C., and the insulation time of each gradient is 0.5-6 hours.

9. A micron-sized super-large carbon onion prepared according to the method for preparing micron-sized super-large carbon onion according to any one of claims 1 to 8.

10. Application of the micron-sized super-large carbon onion according to claim 9 in supercapacitors, lithium batteries, catalyst carriers or gas adsorption storage.

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