Lightweight carbon-based multiphase microspheres and a method for preparing the same

Abstract

The application discloses a light carbon-based composite microsphere and a preparation method thereof. The light carbon-based composite microsphere is prepared from cheap and easily-obtained raw materials, has the characteristics of low cost and simple preparation process, and has excellent high-temperature resistance. The technical scheme of the application is as follows: the premix ingredients are as follows in terms of weight percentage: 38-58 parts of carbon black powder, 32-52 parts of elemental silicon powder and 1-5 parts of an additive. The above raw materials are ball milled in a planetary ball mill to obtain a premix. A carboxymethyl cellulose solution with a concentration of 0.05-0.25 g / ml and accounting for 2-10% of the total weight of the premix is taken. 1-5% of polypropylene balls of the total weight of the premix are added into a spherical granulator and rotated. The carboxymethyl cellulose solution is sprayed until it is evenly covered on the surface of the polypropylene balls. The premix is added until uniform spherical precursors are formed. The obtained precursors are dried and solidified, and finally calcined in a carbon reduction atmosphere to obtain the light carbon-based composite microsphere.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refractory materials, and particularly relates to a light-weight carbon-based composite microsphere and a preparation method thereof. BACKGROUND

[0002] With the continuous pursuit of energy efficiency in the high-temperature industrial field, people have carried out in-depth research and development on refractory materials that can be directly applied to working lining materials. These materials have attracted widespread attention due to their high mechanical strength, excellent corrosion resistance and low thermal conductivity. The use of heat-insulating refractory materials in the vicinity of the high-temperature region not only meets the requirements, but also is expected to achieve more significant energy-saving effect. Therefore, under the premise of ensuring that the performance of the refractory material meets the standard, the introduction of light-weight aggregate becomes an effective strategy, which helps to reduce the bulk density of the lining refractory material, thereby improving the energy-saving efficiency of the thermal equipment.

[0003] As an important carbon source in carbon composite materials, the functionalization and light-weight development of carbon microspheres are inevitable trends. At present, the preparation methods of carbon microspheres are diversified, generally involving biomass, polymers and organic matter, and adopting hydrothermal method, ultrasonic spray pyrolysis method, emulsion polymerization and template method for comprehensive synthesis. However, in the synthesis process of polymers and organic matter, it is often difficult to avoid the use of organic solvents and harsh polymerization conditions.

[0004] Among them, "a hydrothermal method for preparing and applying heteroatom doped porous carbon microspheres" (CN117185278A) patent technology discloses a method for preparing atom doped porous carbon microspheres. Amino acid containing NH2 and sulfuric acid are used to prepare amino acid proton salt as raw material. The amino acid proton salt is directly hydrothermally self-polymerized at different temperatures to prepare carbon microspheres with a certain particle size. After washing and grinding with sodium bicarbonate, the porous carbon microspheres with different hierarchical pore structures are obtained by carbonization in an inert atmosphere at different temperatures. This method needs hydrothermal, salt washing, grinding and calcination processes, and the operation process is complex. At the same time, expensive chemical products such as amino acids are used in the reaction, and the cost is high. "Oxygen defect TiO2@Si@carbon microspheres and preparation method and application thereof" (CN117199299A) patent technology discloses a kind of TiO2@Si@carbon microspheres and preparation method thereof. Carbon microspheres, tetraethyl silicate and acid are chemically hydrolyzed to obtain SiO2@carbon microspheres; SiO2@carbon microspheres and reducing agent are chemically reduced to obtain Si@carbon microspheres; Si@carbon microspheres and organic titanium salt are chemically hydrolyzed and calcined to obtain TiO2@Si@carbon microspheres; TiO2@Si@carbon microspheres and reducing gas are chemically reduced to obtain oxygen defect TiO2@Si@carbon microspheres. This method needs to be chemically hydrolyzed with acid, and the operation process is complex. "Emulsification / oxidation synergistically prepared pitch-based carbon microspheres for high-rate potassium ion battery negative electrode" ([1] Liu Chang, Yao Junjun, Sun Ying, et al. Emulsification / oxidation synergistically prepared pitch-based carbon microspheres for high-rate potassium ion battery negative electrode [J]. Energy Storage Science and Technology, 2023, 12(05): 1444-1452.) Without the help of templates, with medium temperature coal tar pitch as raw material, under the assistance of surfactant and dispersion medium, combined with pre-oxidation and emulsification method, oxidized pitch microspheres are successfully prepared; This method needs to accurately control the reaction process, and the operation is complex. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a kind of lightweight carbon-based complex microspheres and a preparation method thereof;By ball milling premixing carbon black powder, elemental silicon powder and additives, polypropylene balls are used as spherical support, carboxymethyl cellulose solution is added, molding in a granulator, sieving, and then drying, heat treatment and other steps, low-temperature synthesis of lightweight carbon-based complex microspheres. The raw materials used are less, the process is relatively simple, the preparation cost is low, the preparation process is relatively simple, and the lightweight carbon-based complex microspheres prepared have superior performance.

[0006] The technical scheme adopted by the present application is: a light carbon-based composite microsphere and a preparation method thereof, wherein the premix ingredients are as follows in terms of weight fraction: 38-58 parts of carbon black powder, 32-52 parts of elemental silicon powder, and 1-5 parts of an additive; the above raw materials are ball milled in a planetary ball mill to obtain a premix; then, 2-10% of the total weight of the premix is taken, and a carboxymethyl cellulose solution with a concentration of 0.05-0.25 g / ml is obtained; then, 1-5% of the total weight of the premix is taken, and polypropylene balls are added to a spherical granulator for rotation; during the rotation, the carboxymethyl cellulose solution is sprayed to uniformly cover the surface of the polypropylene balls; then, the premix is added until a uniform spherical precursor is formed; the obtained precursor is dried and solidified, and finally calcined under a carbon reduction atmosphere to obtain the light carbon-based composite microsphere.

[0007] The purity of the carbon black powder is > 95%, and the particle size is ≤ 1 μm.

[0008] The purity of the elemental silicon powder is > 98%, and the particle size is ≤ 1 μm.

[0009] The additive is one or more of lanthanum nitrate, yttrium oxide, and iron nitrate, and the purity is > 99.9%.

[0010] The purity of the carboxymethyl cellulose is ≥ 90%.

[0011] The purity of the polypropylene balls is > 99%, and the particle size is 0.1-0.5 mm.

[0012] A preparation method of a light carbon-based composite microsphere, comprising the following steps:

[0013] Step one: 18-58 parts of carbon black powder, 32-52 parts of elemental silicon powder, and 1-5 parts of an additive are put into a ball mill for dry ball milling for 2-10 h at a speed of 400-800 r / min to obtain a premix;

[0014] Step two: balling, drying and solidification, and calcination treatment;

[0015] 2-10% of the total weight of the premix is taken, and a carboxymethyl cellulose solution with a concentration of 0.05-0.25 g / ml is obtained; then, 1-5% of the total weight of the premix is taken, and polypropylene balls are added to a spherical granulator for rotation at a speed of 60-120 r / min; during the rotation, the carboxymethyl cellulose solution is sprayed until the carboxymethyl cellulose solution uniformly covers the surface of the polypropylene balls; the premix is added until a uniform spherical precursor is formed; the obtained precursor is dried at 80-140 ℃ for 4-24 h, and finally calcined at 1300 ℃-1500 ℃ under a carbon reduction atmosphere for 1-5 h to obtain the light carbon-based microsphere.

[0016] The present application is applied to the preparation of hollow aggregate in the field of thermal insulation refractory materials.

[0017] The present application uses polypropylene balls as support, and controls the thickness of the formed Si2N2O-SiC balls by the concentration of carboxymethyl cellulose solution, with an average thickness of 0.5-2mm.

[0018] The concentration of the carboxymethyl cellulose solution in the present application is 0.05-0.2g / ml; the greater the concentration, the greater the viscosity. When the concentration of the carboxymethyl cellulose solution is 0.1g / ml, the average thickness of the formed Si2N2O-SiC balls is 1mm.

[0019] The additive in the present application is one or more of lanthanum nitrate, yttrium oxide, and iron nitrate;

[0020] The additive in the present application regulates the nucleation and development process of Si2N2O and SiC crystals on one hand, promotes the formation of liquid phase, and reduces the formation energy of Si2N2O and SiC nucleation according to the solid-liquid-gas growth mechanism; on the other hand, in the state of additive ions, the additive can change and induce the growth orientation of Si2N2O and SiC crystals, and further change the development morphology of the crystals.

[0021] The additive in the present application intensifies the secondary carbon conversion process of the polypropylene balls and carboxymethyl cellulose on the other hand, realizes the thickness control of the complex-phase carbon-based microspheres, and has outstanding technical advancement. Both the polypropylene balls and the carboxymethyl cellulose are carbon sources, and secondary carbon conversion occurs in the high-temperature process. In the reducing atmosphere, the additive promotes the release of CO gas phase from the carbon source and the SiO gas in the environment, and the reaction forms SiC whiskers. At the same time, under the action of the additive, there are 35% CO and 65% N2 in the environment under the carbon embedding condition. According to the thermodynamic reaction condition, when the CO partial pressure reaches a certain degree, N2 can react with the SiO gas in the environment to form Si2N2O. At the same time, CO and SiO gas in the sample also form SiC. The reactions are as follows:

[0022] Si(l)+O2(g)→SiO(g)

[0023] CO(g)+SiO(g)→SiC(s)

[0024] SiO(g)+N2(g)→Si2N2O(s)

[0025] SiO(g)+N2(g)→Si2N2O(s)

[0026] In step one, the carbon black, elemental silicon powder, and additive are put into a ball mill for dry ball milling, realizing the uniformity of the mixture and effectively reducing the particle size of the powder during the milling process. This not only helps to increase the specific surface area of the powder, but also reduces the activation energy of the particle surface to a certain extent.

[0027] The present application has the advantages that: the present application prepares the light carbon-based composite microspheres by mixing carbon black, elemental silicon powder and additives to prepare a premix, and then balling the premix, polypropylene balls and carboxymethyl cellulose solution. The carbon black, elemental silicon powder and additives are pre-milled to increase the specific surface area of the powder, reduce the particle surface activation energy and effectively reduce the nucleation temperature of Si2N2O and SiC crystals. The present application uses cheap and easily available raw materials, has the characteristics of low cost and simple preparation process, and the prepared light carbon-based composite microspheres have excellent high-temperature resistance. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 XRD pattern of the light carbon-based composite microspheres prepared in Example 1 after heat treatment at 1500℃;

[0029] Figure 2 The light carbon-based composite microspheres shown in Figure 1 The light carbon-based composite microspheres shown in DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in combination with specific examples. The light carbon-based composite microspheres and the preparation method thereof provided by the examples of the present application, wherein the purity of the carbon black powder is >95%, and the particle size is ≤1μm; the purity of the elemental silicon powder is >98%, and the particle size is ≤1μm; the purity of the additive is >99.9%, and the additive is one or more of lanthanum nitrate, yttrium oxide and iron nitrate; the purity of the carboxymethyl cellulose is ≥90%; and the purity of the polypropylene ball is >99%, and the particle size is 0.1-0.5mm.

[0031] Example 1

[0032] A preparation method of a light carbon-based composite microsphere, comprising the following steps:

[0033] Step one: 43 parts of carbon black powder, 52 parts of elemental silicon powder and 5 parts of lanthanum nitrate are put into a ball mill for dry milling for 2h at a speed of 400r / min to mill into fine powder to prepare a premix;

[0034] Step two: balling, drying, solidification and calcination treatment;

[0035] Take 2% of the total weight of the premix, and a carboxymethyl cellulose solution with a concentration of 0.1g / ml; then add 1% of the total weight of the premix of polypropylene balls into a spherical granulator and rotate at a speed of 60r / min, and spray the carboxymethyl cellulose solution during the rotation process until the carboxymethyl cellulose solution uniformly covers the surface of the polypropylene balls, then add the premix until uniform spherical precursors are formed, dry the obtained precursors at 80℃ for 4h, and finally calcine at 1500℃ under a carbon reduction atmosphere for 1h to obtain the light carbon-based microspheres.

[0036] Example 2:

[0037] Step one, put carbon black powder 58 parts, elemental silicon powder 41 parts, yttrium oxide 1 part into the ball mill dry ball milling 10h, speed 800r / min, grinding into fine powder to make premix;

[0038] Step two, balling, drying and curing and calcination treatment;

[0039] Take 10% of the total weight of the premix, the concentration of carboxymethyl cellulose solution is 0.05g / ml; Then add 5% of the total weight of the premix of polypropylene ball to the spherical granulator rotating, speed 120r / min, during the rotation, spray carboxymethyl cellulose solution, until the carboxymethyl cellulose solution evenly covers the surface of the polypropylene ball, add the premix until the formation of uniform spherical precursor, the resulting precursor is dried at 140℃ for 24h, finally in the carbon reduction atmosphere 1300℃ calcination 4h to obtain this light carbon-based microspheres.

[0040] Example 3:

[0041] Step one, put carbon black powder 48 parts, elemental silicon powder 49 parts, ferric nitrate 3 parts into the ball mill dry ball milling 7h, speed 600r / min, grinding into fine powder to make premix;

[0042] Step two, balling, drying and curing and calcination treatment;

[0043] Take 7% of the total weight of the premix, the concentration of carboxymethyl cellulose solution is 0.2g / ml; Then add 3% of the total weight of the premix of polypropylene ball to the spherical granulator rotating, speed 100r / min, during the rotation, spray carboxymethyl cellulose solution, until the carboxymethyl cellulose solution evenly covers the surface of the polypropylene ball, add the premix until the formation of uniform spherical precursor, the resulting precursor is dried at 100℃ for 18h, finally in the carbon reduction atmosphere 1400℃ calcination 3h to obtain this light carbon-based microspheres.

[0044] Example 4:

[0045] Step one, put carbon black powder 45 parts, elemental silicon powder 50 parts, additives are molar ratio of 1:1 of lanthanum nitrate and ferric nitrate, additives 5 parts into the ball mill dry ball milling 8h, speed 700r / min, grinding into fine powder to make premix;

[0046] Step two, balling, drying and curing and calcination treatment;

[0047] 8% of carboxymethyl cellulose solution with a concentration of 0.15 g / ml in total weight of the premix; 4% of polypropylene balls in total weight of the premix are added into a spherical granulator and rotated at a speed of 110 r / min, and the carboxymethyl cellulose solution is sprayed during the rotation until the carboxymethyl cellulose solution uniformly covers the surface of the polypropylene balls; the premix is added until uniform spherical precursors are formed; the obtained precursors are dried at 120℃ for 16 h, and finally calcined at 1350℃ for 2 h in a carbon reduction atmosphere to obtain the light carbon-based microspheres.

[0048] The preparation method has the following advantages: the raw materials are non-toxic, harmless and easy to obtain, so that the production cost is low; the preparation process only needs ball milling, granulation, drying and sintering processes, so that the process is simple.

[0049] The light carbon-based spheres prepared in Example 1 are subjected to XRD test, Figure 1 The X-ray diffraction pattern of the light carbon-based composite microspheres prepared in Example 1 after heat treatment at 1500℃; Figure 2 The X-ray diffraction pattern of the light carbon-based composite microspheres prepared in Example 1 after heat treatment at 1500℃; Figure 1 The SEM photo of the light carbon-based microspheres is shown in FIG. 1.

[0050] The part not described in detail in the present application is the prior art, and the above examples will help the relevant personnel in the field to further understand the present application, but do not limit the present application in any form. Within the scope of the present application defined by the appended claims, various changes in form or details or equivalents made by the present application are all within the protection scope of the present application.

Claims

1. A lightweight carbon-based multiphase microsphere, characterized by: The preparation method comprises the following steps: Step one, put 38-58 parts of carbon black powder, 32-52 parts of elemental silicon powder and 1-5 parts of additives into a ball mill for dry ball milling for 2-10 hours, the additives are one or more of lanthanum nitrate, yttrium oxide and iron nitrate with a purity of >99.9%; the rotation speed is 400-800 r / min, and the pre-mixture is prepared by milling into fine powder; Step two, balling, drying, solidification and calcination treatment; Take 2-10% of the total weight of the pre-mixture of carboxymethyl cellulose solution, and then add 1-5% of the total weight of the pre-mixture of polypropylene balls into a spherical granulator and rotate at a speed of 60-120 r / min, spray the carboxymethyl cellulose solution during the rotation process until the carboxymethyl cellulose solution uniformly covers the surface of the polypropylene balls, add the pre-mixture until uniform spherical precursors are formed, dry the obtained precursors at 80-140℃ for 4-24 hours, and finally calcine at 1300-1500℃ for 1-5 hours in a carbon reduction atmosphere containing nitrogen to obtain the lightweight carbon-based microspheres; the concentration of the carboxymethyl cellulose solution is used to control the thickness of the formed Si2N2O-SiC spherical, and the average thickness is 0.5-2 mm.

2. The lightweight carbon-based multiphase microspheres of claim 1, wherein: Preparation of hollow aggregate for thermal insulation refractory material field.

3. The lightweight carbon-based multiphase microspheres of claim 1, wherein: The purity of the carbon black powder is >95%, and the particle size is ≤1 μm.

4. The lightweight carbon-based multiphase microspheres of claim 1, wherein: The purity of the elemental silicon powder is >98%, and the particle size is ≤1 μm.

5. The lightweight carbon-based multiphase microspheres of claim 1, wherein: The concentration of the carboxymethyl cellulose solution is 0.05-0.25 g / ml.

6. The lightweight carbon-based multiphase microspheres of claim 1, wherein: When the concentration of the carboxymethyl cellulose solution is 0.1 g / ml, the average thickness of the formed Si2N2O-SiC spherical is 1 mm. When the concentration of the carboxymethyl cellulose solution is 0.1 g / ml, the average thickness of the formed Si2N2O-SiC spherical is 1 mm.

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