Micron-sized macrocarbon onions and methods for making the same

Abstract

The application discloses micron-level super-large carbon onions and a preparation method thereof, and belongs to the technical field of carbon onion preparation. The application uses water-soluble saccharides, gel monomers and shape fixing aids as main raw materials, forms a gel structure through a coagulation bath shaping and drying process, and then is subjected to high-temperature graphitization treatment, so that the efficient synthesis of large-size carbon onions is realized. Compared with the traditional method, the application has significant advantages in environmental protection and synthesis efficiency, and breaks through the size limit, successfully synthesizes the largest carbon onion in an ellipsoidal shape, with a long axis of 21.94 microns and a short axis of 17.63 microns, which are 399 times and 321 times of the size of the largest known natural carbon onion respectively, far exceeding the maximum diameter (200 nanometers) of the artificially synthesized carbon onion, and providing a more broad prospect for the wide application of the carbon onion in the fields of supercapacitors, lithium batteries, catalyst carriers and gas adsorption and storage.

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, with their excellent electronic, optical, electromagnetic, and tribological properties, hold broad application prospects across a wide range of fields. Their high surface area, excellent conductivity, and thermal stability make them ideal materials for applications such as superlubricants, superconductors, ion batteries, supercapacitors, sensors, field emitters, catalyst supports, and gas adsorbents. Their unique functionality has garnered significant attention in industries such as aerospace, energy, electronics, automotive, biomedicine, environmental remediation, and chemicals.

[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 produce carbon onions, these technologies usually involve highly polluting chemical reagents or produce harmful gases, limiting their potential for green and sustainable development. At the same time, the carbon onions synthesized by existing methods are relatively small, mostly ranging from tens to hundreds of nanometers, making it difficult to fully utilize their performance in large-scale applications, especially those requiring a large specific surface area or volume. Summary of the Invention

[0004] The present invention aims to provide a micron-sized, ultra-large carbon onion and a method for preparing the same. Using water-soluble sugars, gel monomers, and a shaping aid as the primary raw materials, the process forms a gel structure through a coagulation bath setting and drying process, followed by a high-temperature graphitization treatment, achieving efficient synthesis of large-sized carbon onions. The preparation method provided by the present invention not only overcomes the limitations of traditional methods but also offers significant advantages in environmental friendliness and synthesis efficiency. The resulting micron-sized, ultra-large carbon onions offer broad prospects for their application in supercapacitors, lithium batteries, catalyst supports, 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 a gel monomer, a water-soluble sugar, and a cross-linking agent in water to obtain a solution A; adding a shaping aid, an initiator, and a catalyst to the solution A to obtain a precursor solution;

[0008] Prepare a solution identical to 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 cross-linking 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 gelling agent 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 to 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 60-220° C. and the drying time is 2-6 hours.

[0024] Preferably, the graphitization is carried out under oxygen-free conditions, with the temperature being raised directly or gradually 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 addresses the challenges of high pollution and limited synthesis size in the preparation process of traditional carbon onions, and proposes an innovative method for preparing micron-sized super-large carbon onions. This 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 achieves 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), providing a broader prospect for the wide application of carbon onions in supercapacitors, lithium batteries, catalyst supports and gas adsorption storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM images of the carbon onion prepared in Example 1, where (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 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] Various exemplary embodiments of the present invention are now described in detail. 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, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

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

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can 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 homogeneous transparent solution. Then, 50 mL of a 4% sodium alginate aqueous solution, 4 mL of a 10% ammonium persulfate aqueous solution, and 4 mL of a 10% tetramethylethylenediamine aqueous solution were added. Ultrasonication and stirring were performed to form a homogeneous solution. The bubbles in the spinning solution were removed by a degassing machine to obtain a precursor solution for 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 balls. When the target number of balls is reached, use a fishing net to fish them out and place them in a quartz boat. Keep them in an oven at 80°C and 200°C for 2 hours respectively to accelerate gelation and drying. Wrap the dried balls with graphite paper and place them in a graphite box.

[0041] (4) Graphitization: Put the graphite box containing the sample into the graphitization furnace, directly heat to 1800℃ at a heating rate of 8℃ / min under the condition of vacuum atmosphere, then directly heat to 2800℃ at a heating rate of 2℃ / min, and keep for 3 hours, and the furnace is cooled to room temperature, to obtain a sample containing carbon onions.

[0042] The TEM image of the carbon onions prepared in Example 1 is shown in Figure 1 , wherein the magnification of (a) and (b) is different.

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

[0044] The comparison diagram of the diameter of the largest carbon onions 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 dissolved in 385 mL of deionized water 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 a uniform solution was obtained by ultrasonic stirring. The bubbles in the spinning solution were removed by a bubble removing machine to obtain the precursor solution for 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 dissolved in 385 mL of deionized water to form a uniform transparent solution.

[0048] (3) Preparation of gel beads: A suitable amount of precursor solution was taken by a syringe, and the precursor solution was dropped into the coagulation bath through a needle with a diameter of 30 μm to form transparent small round balls. When the number of small balls reached the target, they were fished out using a fishing net and placed in a quartz boat. The gel and drying were accelerated by keeping the temperature at 100℃ and 220℃ for 2 hours respectively. The dried small balls were wrapped with graphite paper and placed in a graphite box.

[0049] (4) Graphitization: Put the graphite box containing the sample into the graphitization furnace, directly heat to 1800℃ at a heating rate of 8℃ / min under the condition of vacuum atmosphere, then directly heat to 2800℃ at a heating rate of 2℃ / min, and keep for 3 hours, and the furnace is cooled to room temperature, to obtain a sample containing carbon onions.

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

[0051] The above described embodiments are only to illustrate the preferred modes of the present application, and are not intended to limit the scope of the present application. Any modification and improvement made by those skilled in the art to the technical solutions of the present application without departing from the design spirit of the present application shall fall within the protection scope of the present application.

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 solution A, add an ionic gelling agent, and obtain a coagulation bath; Using an injection device, dripping the precursor solution into the coagulation bath to form a spherical gel, scooping out the spherical gel, drying it, and graphitizing it to obtain the micron-sized super-large carbon onion; The gel monomer includes one or more of acrylamide, acrylic acid, methacrylic acid and N-isopropylacrylamide; The shaping aid comprises one or more of sodium alginate, sodium polyacrylate and sodium carboxymethyl cellulose; The ion gel assistant includes one or more of calcium chloride, copper formate tetrahydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate and nickel nitrate hexahydrate.

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 1-10 wt.%, the concentration of the initiator aqueous solution is 0.5-20 wt.%, and the concentration of the catalyst aqueous solution is 0.5-20 wt.%.

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 0.5-5:

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

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