Hollow / cavity carbon microsphere material and preparation method and application thereof

Abstract

The application provides a hollow / cavity carbon microsphere material and a preparation method and application thereof, and belongs to the technical field of carbon materials. The hollow / cavity microsphere precursor is obtained by mixing a polymer seed microsphere, a first dispersion solvent, a carbon double bond containing monomer and an initiator and performing a polymerization reaction; the hollow / cavity microsphere is obtained by mixing the hollow / cavity microsphere precursor and a second dispersion solvent and performing a hydrolysis reaction; and the hollow / cavity carbon microsphere material is obtained by sequentially performing a pre-oxidation reaction and carbonization treatment on the hollow / cavity microsphere. The polymer seed microsphere is used as a matrix, the prepared carbon microsphere is a carbon material derived from the polymer microsphere, has a controllable size and particle size distribution, and has the advantages of good conductivity, heat conduction and chemical inertness. The prepared hollow / cavity carbon microsphere material has good performance in the fields of wave absorption and supercapacitors.

Description

Technical Field

[0001] This invention relates to the field of carbon materials technology, and in particular to a hollow / cavity carbon microsphere material, its preparation method, and its application. Background Technology

[0002] Polymer microspheres are polymer materials or polymer composites with sizes distributed at the micrometer or nanometer scale. Microspheres exhibit a wide variety of morphologies, including not only the most common spherical shape but also porous, hollow, cavitary, and petal-shaped forms. This diversity of morphologies gives them more advantages than conventional materials, such as a larger specific surface area, controllable geometric dimensions, good biocompatibility, and stability. Furthermore, polymer microspheres can be modified by incorporating different functional groups, thereby further expanding their advantages.

[0003] Hollow / cavitary microspheres are a type of polymer microsphere, typically prepared using a template method. This involves first preparing a precursor and then removing the template with a solvent to obtain hollow or cavitary microspheres. However, microspheres prepared by this method exhibit inconsistent morphology and cannot be mass-produced, thus limiting their applications. Summary of the Invention

[0004] The purpose of this invention is to provide a hollow / cavity carbon microsphere material, its preparation method, and its application. The method can obtain carbon microspheres with uniform morphology and can be applied in the fields of microwave absorbing materials or supercapacitors.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing hollow / cavity carbon microsphere materials, comprising the following steps:

[0007] Polymer seed microspheres, a first dispersing solvent, a monomer containing carbon-carbon double bonds, and an initiator are mixed and polymerized to obtain a hollow / cavity microsphere precursor; the monomer of the polymer seed microspheres includes acrylonitrile;

[0008] The hollow / cavity microsphere precursor and the second dispersion solvent are mixed and subjected to a hydrolysis reaction to obtain hollow / cavity microspheres; the second dispersion solvent includes water.

[0009] The hollow / cavity microspheres were subjected to pre-oxidation and carbonization treatments in sequence to obtain hollow / cavity carbon microsphere materials.

[0010] The hollow / cavity carbon microsphere material exhibits a hollow or cavity structure.

[0011] Preferably, the carbon-carbon double bond-containing monomer includes one or more of styrene, divinylbenzene, methyl methacrylate, allyl methacrylate, acrylamide, glycidyl methacrylate, 4-acryloylmorpholine, itaconic acid, and maleic anhydride;

[0012] The first dispersion solvent includes at least one of ethanol, methanol, water, isopropanol, ethyl acetate, N,N-dimethylformamide, and acetonitrile; the second dispersion solvent further includes at least one of methanol, ethanol, isopropanol, acetonitrile, xylene, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane; the volume percentage of water in the second dispersion solvent is 80-100%.

[0013] The initiator includes azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride, or benzoyl peroxide.

[0014] Preferably, the mass ratio of the seed microspheres, the first dispersing solvent, the carbon-carbon double bond monomer, and the initiator is 8:200-400:2-16:0.3-2.

[0015] Preferably, the polymerization reaction is carried out at a temperature of 65–85°C for 3 hours.

[0016] Preferably, the mass ratio of the hollow / cavity microsphere precursor to the second dispersion solvent is 1–10:50–400; the hydrolysis reaction is carried out at a temperature of 180–260°C for 5–20 hours.

[0017] Preferably, the pre-oxidation reaction is carried out in an air atmosphere at a temperature of 250–300°C for 1–2 hours; the carbonization treatment is carried out in a nitrogen or argon atmosphere at a temperature of 700–1100°C for 1–3 hours.

[0018] Preferably, the particle size of the hollow / cavity microsphere precursor is 1.1–2.5 μm; the particle size of the hollow / cavity microspheres is 1.8–2.4 μm; and the particle size of the hollow / cavity carbon microsphere material is 0.6–1.7 μm.

[0019] The present invention provides hollow / cavity carbon microsphere materials prepared by the preparation method described in the above technical solution.

[0020] This invention provides the application of the hollow / cavity carbon microsphere material described in the above technical solution in the preparation of microwave absorbing materials.

[0021] This invention provides the application of the hollow / cavity carbon microsphere material described above as an electrode material in supercapacitors.

[0022] This invention uses polymer seed microspheres as a matrix, and coats their surface with polymer shells composed of different monomers through polymerization to give them different properties. Then, the resulting hollow / cavity microsphere precursor is hydrolyzed. By controlling the water ratio, hydrolysis temperature, and hydrolysis time during the hydrolysis process, hollow or cavity microspheres with uniform morphology and different degrees of hydrolysis can be obtained. Pre-oxidation during carbonization can prevent the product from collapsing during subsequent carbonization. By controlling different carbonization temperatures, carbon materials can have different degrees of carbonization, thereby controlling the degree of graphitization and lattice defects of the material, thus improving the electrochemical performance and microwave absorption performance of the material. The carbon microspheres prepared by this invention are carbon materials derived from polymer microspheres. The particle size of the polymer microspheres and the thickness of the coating layer are controllable, so the particle size shrinkage ratio after carbonization is relatively fixed. Thus, the prepared carbon microspheres have controllable size and particle size distribution, good electrical conductivity, thermal conductivity, and chemical inertness, etc., and can be used alone or as a precursor for composite applications with other materials.

[0023] The method of the present invention can prepare hollow microspheres or cavity microspheres separately, and can control the size of the cavity. The hollow / cavity carbon microsphere material formed by carbonizing the hollow / cavity microspheres can be applied in the fields of microwave absorbing materials or supercapacitors.

[0024] Furthermore, the method of this invention can obtain hollow or semi-hollow microspheres with different cavity diameters by controlling the hydrothermal time, hydrolysis solvent composition, and hydrothermal temperature; obtain hollow microspheres with different particle sizes by selecting core particles of different sizes; control the composition and wall thickness of hollow / spacious microspheres by controlling the composition and thickness of the shell; and adjust the morphology, elemental composition, and graphitization degree of the carbon material through the carbonization process, thereby changing the parameters of the carbon material and obtaining high-performance hollow / spacious carbon microsphere materials. The hollow / spacious carbon microsphere materials prepared by this invention exhibit good performance in both microwave absorption and supercapacitor applications. Attached Figure Description

[0025] Figure 1 SEM image of the hollow / cavity microsphere precursor obtained in Example 1;

[0026] Figure 2 Here is a SEM image of the hollow / cavity microspheres obtained in Example 1;

[0027] Figure 3 SEM image of the hollow / cavity carbon microsphere material obtained in Example 1;

[0028] Figure 4 TEM image of the hollow / cavity carbon microsphere material obtained in Example 1;

[0029] Figure 5 This is a nitrogen adsorption-desorption curve of the hollow / cavity carbon microsphere material obtained in Example 1;

[0030] Figure 6 This is a particle size distribution diagram of the hollow / cavity carbon microsphere material obtained in Example 1;

[0031] Figure 7 SEM image of the hollow / cavity microsphere precursor obtained in Example 2;

[0032] Figure 8 SEM image of the hollow / cavity microspheres obtained in Example 2;

[0033] Figure 9 SEM image of the hollow / cavity carbon microsphere material obtained in Example 2;

[0034] Figure 10 TEM image of the hollow / cavity carbon microsphere material obtained in Example 2;

[0035] Figure 11 This is a nitrogen adsorption-desorption curve of the hollow / cavity carbon microsphere material obtained in Example 2;

[0036] Figure 12 This is a particle size distribution diagram of the hollow / cavity carbon microsphere material obtained in Example 2;

[0037] Figure 13 SEM image of the hollow / cavity microsphere precursor obtained in Example 3;

[0038] Figure 14 SEM image of the hollow / cavity microspheres obtained in Example 3;

[0039] Figure 15 SEM image of the hollow / cavity carbon microsphere material obtained in Example 3;

[0040] Figure 16 TEM image of the hollow / cavity carbon microsphere material obtained in Example 3;

[0041] Figure 17 This is a nitrogen adsorption-desorption curve of the hollow / cavity carbon microsphere material obtained in Example 3;

[0042] Figure 18 This is a particle size distribution diagram of the hollow / cavity carbon microsphere material obtained in Example 3;

[0043] Figure 19 SEM image of the hollow / cavity microsphere precursor obtained in Example 4;

[0044] Figure 20 SEM image of the hollow / cavity microspheres obtained in Example 4;

[0045] Figure 21 SEM image of the hollow / cavity carbon microsphere material obtained in Example 4;

[0046] Figure 22 TEM image of the hollow / cavity carbon microsphere material obtained in Example 4;

[0047] Figure 23 This is a nitrogen adsorption-desorption curve of the hollow / cavity carbon microsphere material obtained in Example 4;

[0048] Figure 24 This is a particle size distribution diagram of the hollow / cavity carbon microsphere material obtained in Example 4;

[0049] Figure 25 The reflection loss diagram of the absorbing material prepared in Application Example 1 at different matching thicknesses;

[0050] Figure 26 The reflection loss diagram of the absorbing material prepared in Application Example 2 at different matching thicknesses;

[0051] Figure 27 The specific capacitance curves of the electrode material prepared in Application Example 3 at different current densities are shown.

[0052] Figure 28 The specific capacitance curves of the electrode material prepared in Application Example 4 at different current densities are shown. Detailed Implementation

[0053] This invention provides a method for preparing hollow / cavity carbon microsphere materials, comprising the following steps:

[0054] Polymer seed microspheres, a first dispersing solvent, a monomer containing carbon-carbon double bonds, and an initiator are mixed and polymerized to obtain a hollow / cavity microsphere precursor; the monomer of the polymer seed microspheres includes acrylonitrile;

[0055] The hollow / cavity microsphere precursor and the second dispersion solvent are mixed and subjected to a hydrolysis reaction to obtain hollow / cavity microspheres; the second dispersion solvent includes water.

[0056] The hollow / cavity microspheres were subjected to pre-oxidation and carbonization treatments in sequence to obtain hollow / cavity carbon microsphere materials.

[0057] The hollow / cavity carbon microsphere material exhibits a hollow or cavity structure.

[0058] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0059] This invention involves mixing polymer seed microspheres, a first dispersing solvent, a monomer containing carbon-carbon double bonds, and an initiator to carry out a polymerization reaction, thereby obtaining a hollow / cavity microsphere precursor.

[0060] In this invention, the monomers of the polymer seed microspheres preferably include acrylonitrile; the monomers of the seed microspheres preferably also include styrene and divinylbenzene; the mass ratio of acrylonitrile, styrene and divinylbenzene is preferably 1:0.088:0.03.

[0061] The polymer seed microspheres of this invention are preferably acrylonitrile self-polymerized microspheres or acrylonitrile-second monomer copolymerized polymer microspheres. When the polymer seed microspheres are acrylonitrile-second monomer copolymerized polymer microspheres, the mass percentage of acrylonitrile in the acrylonitrile-second monomer is preferably ≥80 wt%. In this invention, the second monomer preferably includes one or more of styrene (St), divinylbenzene (DVB), methyl methacrylate (MMA), allyl methacrylate (AMA), acrylamide (AM), glycidyl methacrylate (GMA), and 4-acryloylmorpholine (ACMO). When the second monomer is two or more of the above, this invention does not have a special limitation on the ratio of different types of second monomers, and can be adjusted according to actual needs. The polyacrylonitrile in the polymer seed microspheres used in this invention can be hydrolyzed under high temperature and high pressure. By utilizing this property to control the hydrothermal conditions, hollow or cavity microspheres with different degrees of hydrolysis can be obtained.

[0062] In this invention, the method for preparing the polymer seed microspheres preferably includes:

[0063] 128 parts acrylonitrile, 11.2 parts styrene, 4 parts divinylbenzene, 720 parts ethyl acetate, 80 parts N,N-dimethylformamide and 1 part initiator were mixed and reacted at 70°C for 3 hours. After filtration, washing and drying, polymer seed microspheres were obtained. The initiator preferably includes azobisisobutyronitrile.

[0064] In this invention, the first dispersing solvent preferably includes at least one of ethanol, methanol, water, isopropanol, ethyl acetate, N,N-dimethylformamide, and acetonitrile; when the first dispersing solvent is two or more of the above, this invention does not have a special limitation on the ratio of different types of first dispersing solvents, and any ratio is acceptable.

[0065] The preferred particle size of the polymer seed microspheres of the present invention is 1.7 to 2.0 μm. The particle size of the polymer seed microspheres can be controlled by appropriately increasing the amount of divinylbenzene to reduce the particle size of the product and by appropriately increasing the amount of styrene to increase the particle size of the product.

[0066] In this invention, the carbon-carbon double bond-containing monomer preferably includes one or more of styrene (St), divinylbenzene (DVB), methyl methacrylate (MMA), allyl methacrylate (AMA), acrylamide (AM), glycidyl methacrylate (GMA), 4-acryloylmorpholine (ACMO), itaconic acid, and maleic anhydride; when the carbon-carbon double bond-containing monomer is two or more of the above, this invention does not have a special limitation on the ratio of different types of carbon-carbon double bond-containing monomers, and can be adjusted according to actual needs.

[0067] The carbon-carbon double bond monomers described in this invention play a role in altering the morphology and composition of the coating layer product during the preparation of polymer microspheres. The bifunctional monomers (such as divinylbenzene) can act as crosslinkers, increasing the rigidity of the coating layer, while methacrylic acid monomers can increase the number of oxygen atoms in the product. By changing the type, amount, and number of coating layers used, the thickness of the coating layer and the properties of the resulting carbon microspheres can be altered.

[0068] In this invention, the initiator preferably includes azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutylamidine hydrochloride, or benzoyl peroxide. This invention utilizes the decomposition of the initiator to generate free radical active substances, thereby initiating the polymerization of monomers containing carbon-carbon double bonds.

[0069] In this invention, the preferred mass ratio of the seed microspheres, the first dispersing solvent, the carbon-carbon double bond-containing monomer, and the initiator is 8:200–400:2–16:0.3–2, more preferably 8:250–350:5–12:0.5–1, and even more preferably 8:250–300:6–8:0.6–0.8. This invention limits this ratio range to avoid the reaction failing due to insufficient monomer dosage, while also preventing product aggregation due to excessively high monomer concentration.

[0070] In this invention, the seed microspheres are preferably dispersed in a first dispersion solvent, and a monomer containing carbon-carbon double bonds and an initiator are added to carry out a polymerization reaction. The polymerization reaction temperature is preferably 65-85°C, more preferably 70-75°C, and the reaction time is preferably 3 hours. This invention controls the polymerization reaction temperature and the amount of initiator to avoid explosive polymerization. At the same time, within the range of the amounts of the monomer containing carbon-carbon double bonds and the initiator, the solvent amount is controlled to avoid the monomer concentration being too high, which would cause the reaction to be too fast and the product to agglomerate. Simultaneously, the monomer concentration is also controlled to avoid the reaction not initiating if it is too low.

[0071] During the polymerization reaction, carbon-carbon double bond monomers polymerize under the action of an initiator and coat the polymer seed microspheres. Divinylbenzene, as a crosslinking monomer, can act as a crosslinking agent. Styrene can increase the particle size of the product to a certain extent, thereby achieving controllable particle size. Styrene can make the particle size of carbon microspheres vary within the range of 0.9 to 2.5 μm, resulting in a wider particle size selectivity.

[0072] After the polymerization reaction is completed, the present invention preferably filters and washes the obtained product, and the resulting solid is the hollow / cavity microsphere precursor.

[0073] In this invention, preferably, after one polymerization reaction, a hollow / cavity microsphere precursor with a single coating layer is obtained by filtration and washing. Alternatively, multiple polymerization reactions can be carried out (the first dispersing solvent, carbon-carbon double bond monomer, and initiator are added again), and multiple coatings are achieved by filtration and washing to obtain a multilayer coated hollow / cavity microsphere precursor.

[0074] When multiple polymerization reactions are carried out, the total amount of the first dispersing solvent, carbon-carbon double bond monomer, and initiator used in each polymerization reaction can be within the mass ratio range of the seed microspheres, the first dispersing solvent, the carbon-carbon double bond monomer, and the initiator mentioned above.

[0075] In this invention, the particle size of the hollow / cavity microsphere precursor is 1.1 to 2.5 μm, more preferably 2 to 2.2 μm, and the surface exhibits particle accumulation or a thin layer.

[0076] After obtaining the hollow / cavity microsphere precursor, the present invention mixes the hollow / cavity microsphere precursor with a second dispersion solvent and performs a hydrolysis reaction to obtain hollow / cavity microspheres.

[0077] In this invention, the second dispersion solvent preferably further includes at least one of methanol, ethanol, isopropanol, acetonitrile, xylene, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane; the volume percentage of water in the second dispersion solvent is preferably 80-100%; when the second dispersion solvent is two or more of the above, this invention does not have a special limitation on the ratio of different types of second dispersion solvents, and any ratio is acceptable.

[0078] The second dispersing solvent of this invention includes water, and preferably also includes at least one of methanol, ethanol, isopropanol, acetonitrile, xylene, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane. When the second dispersing solvent is preferably pure water, it is preferable to add an acid or alkali to promote hydrolysis. The hydrolysis products of the resulting polyacrylonitrile will vary depending on the pH of the system. The acid is preferably sulfuric acid or nitric acid, and the alkali is preferably sodium hydroxide, potassium hydroxide, or sodium carbonate. This invention does not impose any special limitations on the amount or specific specifications of the acid or alkali; commercially available products well-known in the art can be used with adjusted dosages according to actual needs.

[0079] In this invention, the mass ratio of the hollow / cavity microsphere precursor to the second dispersion solvent is preferably 1-10:50-400, more preferably 5:300.

[0080] In this invention, the temperature of the hydrolysis reaction is preferably 180-260°C, more preferably 200-230°C; the time is preferably 5-20 h, more preferably 6 h; during the hydrolysis reaction, the polyacrylonitrile in the polyacrylonitrile seed microspheres undergoes hydrolysis, and the products of the hydrolysis reaction include polyacrylamide or ammonium polyacrylate; the coating layer formed by polymerization does not hydrolyze.

[0081] This invention controls the hydrothermal time and the amount of the second dispersion solvent to avoid hydrolysis being too slow or too fast.

[0082] In this invention, when the hydrothermal time and temperature are within a certain range, the water content is less than 50%, and the hydrolysis rate of the spheres will be greatly reduced. Therefore, the volume ratio of water in the second dispersion solvent used in the hydrolysis reaction in this invention is preferably 80-100%.

[0083] This invention controls the hydrothermal temperature and water content within a certain range, while simultaneously controlling the hydrothermal time to 5–20 hours. This avoids a lower degree of hydrolysis if the hydrothermal time is less than 2 hours, and also avoids complete hydrolysis if the hydrothermal time is more than 20 hours. By simultaneously controlling the hydrothermal time and temperature, this invention regulates the formation of hollow or cavity morphology of carbon microspheres (the higher the temperature and the longer the time, the more hollow structures are formed).

[0084] After the hydrolysis reaction is completed, the present invention preferably filters and washes the obtained product, then dries it to obtain hollow / cavity microspheres.

[0085] In this invention, the particle size of the hollow / cavity microspheres is preferably 1.8 to 2.4 μm, more preferably 2.0 to 2.2 μm.

[0086] After obtaining hollow / cavity microspheres, the present invention sequentially performs pre-oxidation reaction and carbonization treatment on the hollow / cavity microspheres to obtain hollow / cavity carbon microsphere materials.

[0087] In this invention, the pre-oxidation reaction is preferably carried out in an air atmosphere, the temperature of the pre-oxidation reaction is preferably 250-300°C, more preferably 260-280°C, and the time is preferably 1-2 hours, more preferably 2 hours; the pre-oxidation reaction is preferably carried out in a tube furnace, and the heating rate to the temperature of the pre-oxidation reaction is preferably 0.1-2°C / min, more preferably 0.5-1°C / min.

[0088] After the pre-oxidation reaction is completed, the present invention preferably allows the obtained product to be cooled to room temperature before carbonization treatment.

[0089] In this invention, the heating rate to the carbonization treatment temperature is preferably 1-8°C / min; the carbonization treatment is preferably carried out in a nitrogen or argon atmosphere, the carbonization treatment temperature is preferably 700-1100°C, more preferably 800-1000°C, and the holding time is preferably 1-3 hours, more preferably 2 hours.

[0090] This invention involves a pre-oxidation reaction in an air atmosphere to initially decompose products with low cross-linking degree and unstable structures, leaving behind a more stable structure, thereby improving the stability of carbon materials.

[0091] This invention limits the carbonization heating rate and carbonization reaction time to the above-mentioned range, avoiding temperatures below 600℃, which would result in a low degree of carbonization of the carbon material and reduce its electromagnetic wave absorption and capacitance performance; at the same time, it avoids carbonization reaction temperatures above 1100℃, which would result in an excessively high degree of graphitization of the carbon material, causing impedance mismatch in the material, which is not conducive to electromagnetic wave absorption and capacitance performance.

[0092] In this invention, the particle size of the hollow / cavity carbon microsphere material is preferably 0.6 to 1.7 μm, more preferably 1.3 to 1.5 μm.

[0093] The present invention provides hollow / cavity carbon microsphere materials prepared by the preparation method described in the above technical solution.

[0094] This invention provides the application of the hollow / cavity carbon microsphere material described in the above technical solution in the preparation of microwave absorbing materials.

[0095] In this invention, the preferred method for preparing the microwave absorbing material is as follows: hollow / cavity carbon microspheres are mixed with molten paraffin at a mass ratio of 1:10-12, and then pressed into a coaxial ring with an outer diameter of 7.00 mm and an inner diameter of 3.04 mm using a pressing machine. The microwave absorbing material prepared by this invention, with a matching thickness of 1.5-5.5 mm, exhibits a minimum reflection loss of 36.8-47.6 dB and an effective absorption bandwidth of 3.58-5.12 GHz in the frequency range of 2-18.00 GHz.

[0096] This invention provides the application of the hollow / cavity carbon microsphere material described above as an electrode material in supercapacitors.

[0097] In this invention, the preferred application of the hollow / cavitary carbon microsphere material as an electrode material in a supercapacitor is as follows: 5 mg of hollow / cavitary carbon microsphere material is used as the electrode material, pressed with nickel foam for 1 min under a pressure of 8–20 MPa to obtain the working electrode. This electrode is then activated by soaking in a 6 M KOH solution for 12 h. A mercury / mercuric chloride electrode is used as the reference electrode, and a platinum sheet is used as the counter electrode. A three-electrode system is employed for testing. The specific capacitance is calculated based on the charge-discharge current curve at 0.5 Ag. -1At current density, its specific capacitance is 157–377 F g. -1 .

[0098] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0099] This invention uses a vector network analyzer sold by Agilent Technologies under the trade name PNA Network Analyzer N5224A to test electromagnetic parameters under ambient temperature conditions. Based on the literature Luo Kong et al., entitled "Flexible CNTs / CNF-WPU aerogel for smart electromagnetic wave absorbing with tuning-effective absorption bandwidth", *Carbon*, 207, 2023, 13-22, the reflection loss diagram of the irregularly shaped carbon microsphere material was calculated using transmission line theory.

[0100] This invention uses an electrochemical workstation sold by Metrohm AG under the trade name Autolab to test specific capacitance performance (galvanostatic charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy) according to the test methods described in the literature Liu Ning et al, entitled “Litchi-like porous carbon nanospheres prep from crosslinked polymer precursors for supercapacitors and electromagnetic wave absorption”, Chemical Engineering Journal, 416, 2021, 128926.

[0101] Example 1

[0102] 128 parts acrylonitrile, 11.2 parts styrene, 4 parts divinylbenzene, 720 parts ethyl acetate, 80 parts N,N-dimethylformamide and 1 part initiator (azobisisobutyronitrile) were mixed and reacted in a three-necked flask at 70℃ for 3 h. After filtration, washing and drying, seed microspheres with a particle size of 1.7-2.0 μm were obtained.

[0103] Eight parts of seed microspheres (monomer mass ratio of acrylonitrile:styrene:divinylbenzene 1:0.088:0.03) were dispersed in 300 parts of ethanol, and five parts of divinylbenzene and 0.8 parts of azobisisobutyronitrile were added. The mixture was reacted at 75°C for 3 hours, filtered and washed to obtain a coated solid powder, which is the microsphere precursor.

[0104] Five parts of the microsphere precursor were dispersed in 280 parts of water and 20 parts of ethanol, reacted in a stirred tank at 230°C for 6 hours, filtered, washed, and dried to obtain microsphere powder.

[0105] The microsphere powder was heated to 300°C in a tube furnace at a heating rate of 1°C / min for 2 hours for pre-oxidation; then, under argon protection, the temperature was increased to 1000°C at a heating rate of 1.0°C / min for 2 hours for carbonization to obtain carbon microsphere material.

[0106] Example 2

[0107] Eight parts of seed microspheres prepared in Example 1 (monomer mass ratio of acrylonitrile:styrene:divinylbenzene 1:0.088:0.03) were dispersed in 300 parts of ethanol, and eight parts of divinylbenzene and 0.8 parts of azobisisobutyronitrile were added. The mixture was reacted at 75°C for 3 hours, filtered and washed to obtain a coated solid powder, which is the microsphere precursor.

[0108] Five parts of the microsphere precursor were dispersed in 280 parts of water and 20 parts of ethanol, reacted in a stirred tank at 230°C for 6 hours, filtered, washed, and dried to obtain microsphere powder.

[0109] The microsphere powder was heated to 300°C in a tube furnace at a heating rate of 1°C / min for 2 hours for pre-oxidation; then, under argon protection, the temperature was increased to 1000°C at a heating rate of 1.0°C / min for 2 hours for carbonization to obtain carbon microsphere material.

[0110] Example 3

[0111] Eight portions of seed microspheres prepared in Example 1 (monomer mass ratio of acrylonitrile:styrene:divinylbenzene 1:0.088:0.03) were dispersed in 300 portions of ethanol. Six portions of acrylamide and 0.6 portions of azobisisobutyronitrile were added, and the mixture was reacted at 75°C for 3 hours. The heating was then turned off, and the mixture was cooled for 3 hours. Six portions of divinylbenzene, 30 portions of ethanol, and 0.8 portions of azobisisobutyronitrile were added, and the mixture was reacted at 75°C for 3 hours. The mixture was then filtered and washed to obtain a two-layer coated solid powder, which is the microsphere precursor.

[0112] Five parts of the microsphere precursor were dispersed in 280 parts of water and 20 parts of ethanol, reacted in a stirred tank at 230°C for 6 hours, filtered, washed, and dried to obtain microsphere powder.

[0113] The microsphere powder was heated to 300°C in a tube furnace at a heating rate of 1°C / min for 2 hours for pre-oxidation; then, under argon protection, the temperature was increased to 800°C at a heating rate of 1.0°C / min for 2 hours for carbonization to obtain carbon microsphere material.

[0114] Example 4

[0115] Eight parts of seed microspheres prepared in Example 1 (monomer mass ratio of acrylonitrile:styrene:divinylbenzene 1:0.088:0.03) were dispersed in 300 parts of ethanol. Six parts of acrylamide and 0.6 parts of azobisisobutyronitrile were added, and the mixture was reacted at 75°C for 3 hours. The heating was then turned off, and the mixture was cooled for 3 hours. Eight parts of divinylbenzene, 30 parts of ethanol, and 0.8 parts of azobisisobutyronitrile were added, and the mixture was reacted at 75°C for 3 hours. The mixture was then filtered and washed to obtain a two-layer coated solid powder, which is the microsphere precursor.

[0116] Five parts of the microsphere precursor were dispersed in 280 parts of water and 20 parts of ethanol, reacted in a stirred tank at 230°C for 6 hours, filtered, washed, and dried to obtain microsphere powder.

[0117] The microsphere powder was heated to 300°C in a tube furnace at a heating rate of 1°C / min for 2 hours for pre-oxidation; then, under argon protection, the temperature was increased to 800°C at a heating rate of 1.0°C / min for 2 hours for carbonization to obtain carbon microsphere material.

[0118] Characterization

[0119] The microstructure of the different products prepared in Examples 1-4 was analyzed by scanning electron microscopy, the internal morphology was analyzed by transmission electron microscopy, and the specific surface area and pore size distribution of the samples were calculated by adsorption and specific surface area analyzer.

[0120] 1) Morphology diagram of the microsphere precursor obtained in Example 1 is shown below. Figure 1 ,Depend on Figure 1 It can be seen that the precursor product has a particle size of 2–2.2 μm and is approximately spherical.

[0121] The morphology of the microspheres obtained in Example 1 is shown in the figure below. Figure 2 As shown, the microspheres have wrinkled surfaces and a particle size of 1.6–1.8 μm.

[0122] The morphology of the carbon microsphere material obtained in Example 1 is shown in the figure below. Figures 3-4 As shown, Figure 3 As shown, some products exhibit a hollow, wrinkled internal morphology with a particle size of 1.3–1.5 μm. Figure 4 As shown, some products are hollow, and a small portion are cavitary.

[0123] The nitrogen adsorption-desorption curves and particle size distribution of the carbon microspheres obtained in Example 1 are shown below. Figures 5-6 As shown, the specific surface area of ​​the carbon microsphere material is 458 m². 2 ·g -1 It has an average pore size of 3.25 nm and mainly exists in the form of micropores.

[0124] 2) Morphology diagram of the microsphere precursor obtained in Example 2 is shown below. Figure 7 As shown, the product particle size is 2.2–2.4 μm, and the product is slightly aggregated.

[0125] The morphology of the microspheres obtained in Example 2 is shown in the figure below. Figure 8 As shown, the microspheres have a particle size of 2–2.2 μm.

[0126] The morphology of the carbon microsphere material obtained in Example 2 is shown in the figure below. Figures 9-10 As shown, Figure 9 As shown, some products exhibit a hollow internal morphology, surface damage, and a particle size of 1.3–1.5 μm. Figure 10 As shown, some products are hollow, and a small portion are cavitary.

[0127] The nitrogen adsorption-desorption curves and particle size distribution of the carbon microspheres obtained in Example 2 are shown below. Figures 11-12 As shown, the specific surface area of ​​the carbon microsphere material is 469 m². 2 ·g -1 The average pore size is 2.76 nm, and it mainly exists in the form of micropores.

[0128] 3) Morphology diagram of the microsphere precursor obtained in Example 3 is shown below. Figure 13 As shown, the product particle size is 2.2–2.4 μm, and the product is slightly aggregated.

[0129] The morphology of the microspheres obtained in Example 3 is shown in the figure below. Figure 14 As shown, the microspheres have a particle size of 2–2.2 μm and a cracked, porous surface.

[0130] The morphology of the carbon microsphere material obtained in Example 3 is shown in the figure below. Figures 15-16 As shown, Figure 15 As shown, some products exhibit a hollow internal morphology, a porous surface, and a particle size of 1.5–1.6 μm. Figure 16 As shown, some products are hollow, and a small portion are cavitary.

[0131] The nitrogen adsorption-desorption curves and particle size distribution of the carbon microspheres obtained in Example 3 are shown below. Figures 17-18 As shown, the specific surface area of ​​the carbon microsphere material is 888 m². 2 ·g -1 It has an average pore size of 3.77 nm and mainly exists in the form of micropores.

[0132] 4) Morphology diagram of the microsphere precursor obtained in Example 4 is shown below. Figure 19 As shown, the product particle size is 2.2–2.4 μm, the product is slightly aggregated, and there are many hemispherical products on the surface;

[0133] The morphology of the microspheres obtained in Example 4 is shown in the figure below. Figure 20 As shown, the microspheres have a particle size of 2–2.2 μm and have pores on their surface.

[0134] The morphology of the carbon microsphere material obtained in Example 4 is shown in the figure below. Figures 21-22 As shown, Figure 21 As shown, the surface has pores, and the particle size is 1.6–1.7 μm. Figure 22 As shown, some products are hollow, and a small portion are cavitary.

[0135] The nitrogen adsorption-desorption curves and particle size distribution of the carbon microspheres obtained in Example 4 are shown below. Figures 23-24 As shown, the specific surface area of ​​the carbon microsphere material is m. 2 ·g -1 The average pore size is 3.79 nm, and it mainly exists in the form of micropores.

[0136] Application Example 1

[0137] The carbon microsphere material prepared in Example 1 was mixed with paraffin at a mass ratio of 1:12 in a centrifuge tube. The water in the centrifuge tube was heated to 80°C using a product sold under the trade name Elma Select ultrasonic cleaner from Germany to completely melt the paraffin. The mixture was then poured into a mold, removed, and cooled. After the mold cooled to room temperature, it was pressed into a coaxial ring with an outer diameter of 7.0 mm and an inner diameter of 3.04 mm.

[0138] Application Example 2

[0139] The carbon microsphere material prepared in Example 2 was mixed with paraffin wax at a mass ratio of 1:10 in a centrifuge tube. The water in the centrifuge tube was heated to 80°C using a product sold under the trade name Elma Select ultrasonic cleaner from Germany to completely melt the paraffin wax. The mixture was then poured into a mold and removed to cool. After the mold cooled to room temperature, it was pressed into a coaxial ring with an outer diameter of 7.0 mm and an inner diameter of 3.04 mm.

[0140] Performance tests were conducted on the coaxial rings prepared for use cases 1 and 2: Electromagnetic parameters were tested at room temperature using a vector network analyzer sold by Agilent Technologies under the trade name PNA Network Analyzer N5224A. The reflection loss diagram of the irregularly shaped carbon microsphere material was calculated according to the method described in this specification, and the results are shown in [Figure 1]. Figures 25-26 .Depend on Figure 25 It can be seen that the optimal absorption performance of the carbon material in Application Example 1 is achieved under the conditions of a matching thickness of 2.5 mm and a frequency of 12.88 GHz, with a minimum reflection loss of -47.6 dB and an effective absorption bandwidth of 3.58 GHz; from Figure 26It can be seen that the best absorption performance of the carbon material in Application Example 2 is that, under the conditions of a matching thickness of 2 mm and a frequency of 14.8 GHz, the minimum reflection loss is -36.8 dB and the effective absorption bandwidth is 5.12 GHz.

[0141] Application Example 3

[0142] Using 5 mg of carbon microspheres prepared in Example 3 as the electrode material, a supercapacitor working electrode was fabricated by pressing it together with nickel foam at 10 MPa for 1 min. The electrode was then activated by immersion in 6 M KOH solution for 12 h. A three-electrode system was then used, with a mercury / mercuric chloride electrode as the reference electrode and a platinum sheet as the counter electrode, for testing in 6 M KOH electrolyte. The results are as follows: Figure 27 As shown. The specific capacitance was calculated using an electrochemical workstation sold by Metrohm AG under the trade name Autolab; the specific capacitance was calculated based on the GCD curve, and... Figure 27 It can be seen that at 0.5Ag -1 At current density, its specific capacitance is 377 F·g -1 .

[0143] Application Example 4

[0144] Using 5 mg of carbon microspheres prepared in Example 4 as the electrode material, a supercapacitor working electrode was fabricated by pressing it together with nickel foam at 10 MPa for 1 min. The electrode was then activated by immersion in 6 M KOH solution for 12 h. A three-electrode system was then used, with a mercury / mercuric chloride electrode as the reference electrode and a platinum sheet as the counter electrode, for testing in 6 M KOH electrolyte. The results are as follows: Figure 28 As shown. The specific capacitance was calculated using an electrochemical workstation sold by Metrohm AG under the trade name Autolab; the specific capacitance was calculated based on the GCD curve, and... Figure 28 It can be seen that at 0.5Ag -1 At current density, its specific capacitance is 229 F·g -1 .

[0145] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a hollow / cavity carbon microsphere material, characterized in that, The method comprises the following steps: mixing polymer seed microspheres, a first dispersion solvent, a carbon-carbon double bond-containing monomer, and an initiator to perform a polymerization reaction to obtain a hollow / cavity microsphere precursor; the monomer of the polymer seed microspheres comprises acrylonitrile; mixing the hollow / cavity microsphere precursor and a second dispersion solvent to perform a hydrolysis reaction to obtain a hollow / cavity microsphere; the second dispersion solvent comprises water; sequentially performing a pre-oxidation reaction and a carbonization treatment on the hollow / cavity microsphere to obtain a hollow / cavity carbon microsphere material; the hollow / cavity carbon microsphere material presents a hollow structure or a cavity structure; the carbon-carbon double bond-containing monomer comprises one or more of styrene, divinylbenzene, methyl methacrylate, allyl methacrylate, acrylamide, glycidyl methacrylate, 4-acryloylmorpholine, itaconic acid, and maleic anhydride; the first dispersion solvent comprises at least one of ethanol, methanol, water, isopropanol, ethyl acetate, N,N dimethylformamide, and acetonitrile; the second dispersion solvent further comprises at least one of methanol, ethanol, isopropanol, acetonitrile, dimethylbenzene, N,N-dimethylacetamide, dimethyl sulfoxide, and sulfolane; the volume ratio of water in the second dispersion solvent is 80-100%; the temperature of the hydrolysis reaction is 180-260°C, and the time is 5-20h.

2. The production method according to claim 1, characterized by, the initiator comprises azobisisobutyronitrile, azobisisoheptyl nitrile, azobisdimethylamidinum hydrochloride, or benzoyl peroxide.

3. The production method according to claim 1 or 2, characterized by, the mass ratio of the seed microspheres, the first dispersion solvent, the carbon-carbon double bond-containing monomer, and the initiator is 8:200-400:2-16:0.3-2.

4. The method of claim 1, wherein, the temperature of the polymerization reaction is 65-85°C, and the time is 3h.

5. The preparation method according to claim 1, characterized in that, the mass ratio of the hollow / cavity microsphere precursor and the second dispersion solvent is 1-10:50-400.

6. The production method according to claim 1 or 5, characterized by, the pre-oxidation reaction is performed in an air atmosphere, the temperature of the pre-oxidation reaction is 250-300°C, and the time is 1-2h; the carbonization treatment is performed in a nitrogen or argon atmosphere, the temperature of the carbonization treatment is 700-1100°C, and the holding time is 1-3h.

7. The preparation method according to claim 1, characterized in that, the particle size of the hollow / cavity microsphere precursor is 1.1-2.5μm; the particle size of the hollow / cavity microsphere is 1.8-2.4μm; and the particle size of the hollow / cavity carbon microsphere material is 0.6-1.7μm.

8. The hollow / cavity carbon microsphere material prepared by the preparation method in any one of claims 1-7.

9. The application of the hollow / cavity carbon microsphere material in claim 8 in the preparation of a wave-absorbing material.

10. The application of the hollow / cavity carbon microsphere material in claim 8 as an electrode material in a supercapacitor.

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