A multi-scale porous carbon-based microsphere and a preparation method thereof
Multi-scale porous carbon-based microspheres were prepared by ball milling and granulation processes. Walnut shell powder and metallic aluminum powder were used to form a carbon skeleton and ceramic phase, which solved the problem of decreased thermal shock resistance of traditional refractory materials. This enabled the preparation of low-cost, high-performance carbon-based microspheres, which are suitable for thermal insulation refractory materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LUO YANG SHI KE FENG YE JIN XIN CAI LIAO YOU XIAN GONG SI
- Filing Date
- 2024-05-29
- Publication Date
- 2026-06-09
AI Technical Summary
While increasing aggregate density can improve slag resistance, traditional refractory materials suffer from decreased thermal shock resistance. Furthermore, existing carbon microsphere preparation methods are complex and costly, making it difficult to achieve the functionalization and lightweighting of carbon-based materials.
Walnut shell powder, aluminum powder and additives were ball-milled and premixed, and then combined with polystyrene balls and silica sol solution. Multi-scale porous carbon-based microspheres were prepared by granulation, drying and calcination. Walnut shell powder was used to form carbon framework pores and Sialon-SiC composite ceramic phase, which improved the high-temperature performance and oxidation resistance of the material.
The prepared multi-scale porous carbon-based microspheres have excellent high-temperature resistance and oxidation resistance, are low in cost and simple to process, and are suitable as lightweight aggregates for heat insulation and refractory materials.
Smart Images
Figure CN118344152B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of refractory materials technology, specifically relating to a multi-scale porous carbon-based microsphere and its preparation method. Background Technology
[0002] Traditional refractory materials typically focus on increasing aggregate density, but this leads to a decrease in thermal shock resistance. Furthermore, the relatively simple matrix design makes it difficult to achieve close packing, thus affecting slag resistance. To address these issues, a method of "aggregate microporousization and matrix compaction" has been proposed, aiming to balance the slag resistance and thermal shock resistance of refractory materials, thereby improving the energy efficiency and lifespan of thermal equipment. As an important carbon source in carbon composites, the functionalization and lightweighting of carbon microspheres is an inevitable trend. Currently, the preparation of carbon microspheres mainly involves the conversion of biomass, polymers, and organic materials through synthetic methods such as hydrothermal methods, ultrasonic spray pyrolysis, emulsion polymerization, and template methods.
[0003] The patent technology "COF-derived functionalized porous carbon microsphere solid-phase extractant and its preparation method and application" (CN117185278A) discloses a method for preparing COF-derived functionalized porous carbon microsphere solid-phase extractant. The method involves taking bifunctional monomers with aldehyde and borate groups and polyamine functional monomers, adding them to a mixed solvent, ultrasonically dispersing, purging with nitrogen for protection, and maintaining the temperature at 120℃ for 12 hours to generate directional reversible covalent bonds. After cooling to room temperature, the solid is collected by filtration and then washed sequentially with dioxane, acetone, and n-hexane. The solid is then vacuum dried for 12 hours to obtain the covalent organic framework material COF. This method requires ultrasonic dispersion, nitrogen-protected heating, filtration, washing, and vacuum drying, making the operation complex. Furthermore, it uses expensive dioxane-based chemicals in the reaction, resulting in high costs.
[0004] The patent technology "A Hard Carbon Microsphere with Double Coating Layer, Its Preparation Method and Application" (CN117585664A) discloses a method for preparing hard carbon microspheres with double coating layers. The method involves placing a hard carbon source in a high-pressure reactor for a water bath reaction. After the reaction, the mixture is filtered, the precursor is collected, dehydrated, and then dispersed with an oxidant and a silane coupling agent in anhydrous toluene to obtain a monomolecularly coated precursor. This monomolecularly coated precursor is then placed in an environment containing conductive polymer monomer vapor for in-situ polymerization, resulting in an ordered polymer layer on the outer layer of the monomolecularly coated precursor. Finally, the mixture is sintered in an inert atmosphere to obtain hard carbon microspheres with double coating layers. This method requires heating in a reactor, filtration, dehydration, dispersion of the oxidant and silane coupling agent in toluene to obtain a monomolecularly coated precursor, polymerization in a polymer monomer vapor environment, and finally sintering in an inert atmosphere, making the process complex. "Preparation of Chitosan Mesoporous Carbon Materials and Study on Adsorption Performance of Tannins" (Wu Linyuan, Mu Linling, Chen Zhulin, et al. Preparation of Chitosan Mesoporous Carbon Materials and Study on Adsorption Performance of Tannins [J]. Chemical Research and Application, 2021, 33: 230-236) Nitrogen-doped mesoporous carbon spheres (NMCs) were prepared using chitosan as a new carbon and nitrogen source precursor and triblock amphiphilic copolymer (F127) as a soft template by spray drying and direct carbonization technology. This method requires precise control of the reaction process and has a complex operation process. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a multi-scale porous carbon-based microsphere and its preparation method. The method involves ball milling and premixing walnut shell powder, aluminum powder, and additives, then using polystyrene spheres as spherical supports, adding a silica sol solution, granulating the mixture in a granulator, sieving it, and subsequently drying and heat-treating to synthesize multi-scale porous carbon-based microspheres at low temperature. This invention uses fewer raw materials, has a relatively simple process, low preparation cost, and produces multi-scale porous carbon-based microspheres with superior performance.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a multi-scale porous carbon-based microsphere, wherein the premix composition by weight is: 38-58 parts walnut shell powder, 32-52 parts aluminum powder, and 1-5 parts additives; the amount of silica sol solution with a concentration of 0.05-0.25 g / ml added is 2-10% of the total weight of the premix, and the amount of polystyrene spheres added is 1-5% of the total weight of the premix.
[0007] The particle size of the walnut shell powder is ≤1μm.
[0008] The purity of the aluminum powder is >98%, and the particle size is ≤1μm.
[0009] The additive is one or more of nickel nitrate, lanthanum oxide, and ferric nitrate, with a purity > 99.9%.
[0010] The polystyrene spheres have a purity >99% and a particle size of 0.1-0.5 mm.
[0011] A method for preparing multi-scale porous carbon-based microspheres includes the following steps:
[0012] Step 1: Grind 38-58 parts of walnut shell powder, 32-52 parts of aluminum powder, and 1-5 parts of additives in a planetary ball mill for 2-10 hours at a speed of 400-800 r / min to obtain a premixed material.
[0013] Step 2: Pelletizing, drying, and calcination;
[0014] Take 2-10% of the total weight of the premix and prepare a silica sol solution with a concentration of 0.05-0.25 g / ml; add 1-5% of the total weight of the premix and place it into a spherical granulator for rotation, spraying the silica sol solution until it uniformly covers the surface of the polystyrene spheres, and add the premix until a uniform spherical precursor is formed; dry the obtained precursor at 100-115℃, and finally calcine it at 1000℃-1300℃ for 10-30 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere.
[0015] This invention is applied to the preparation of lightweight aggregates in the field of heat-insulating and refractory materials.
[0016] This invention uses walnut shell powder instead of other organic materials because walnut shell powder has a strong carbon structure. Under high temperature, the walnut shell powder carbonizes and transforms into a carbon structure. Under a nitrogen atmosphere, it undergoes partial micro-oxidation without complete burn-off. Simultaneously, the walnut shell powder acts as a carbon skeleton, forming a porous carbon skeleton pore structure. Furthermore, during the high-temperature process, the carbonized walnut shell powder can also react with trace amounts of oxygen in the environment to convert into CO, creating a certain CO partial pressure. According to the thermodynamic conditions of the Al-Si-ONC system, the partial pressures of N2 and CO in its environment can form Sialon-SiC. Therefore, a Sialon-SiC composite ceramic phase is generated in situ within the carbon skeleton pores formed by the walnut shell powder, filling some of the pores and thus creating pores of different sizes.
[0017] The Sialon-SiC composite ceramic phase can enhance the strength of carbon-based microspheres, thereby improving the high-temperature mechanical properties of carbon composite refractories. Furthermore, this ceramic phase, when coated on the carbon surface to form lightweight carbon microspheres, can improve the oxidation resistance of carbon.
[0018] This invention utilizes polystyrene spheres as a support, and the thickness of the formed Sialon-SiC composite ceramic phase can be controlled by adjusting the concentration of the silica sol solution, with an average thickness of 0.5-2 mm.
[0019] Silica sol solution acts as a binder, bonding Al powder and walnut shell powder together. Higher concentrations result in more bonded Al powder, allowing Sialon and other ceramic composite phases to transform into carbon-structured surfaces after walnut shell carbonization, thus controlling the surface thickness. Furthermore, the silica sol concentration also determines the SiO2 content, providing SiO gas to the environment and influencing the formation of SiC in pores or on the surface, thereby affecting the shell thickness.
[0020] The walnut shell powder has a particle size of ≤1μm, with some particles reaching the ultrafine powder level. The carbon skeleton pores formed by these ultrafine walnut shell powders are also ultrafine, which enables the Sialon-SiC composite ceramic phase to be generated in situ in the carbon skeleton pores and achieves the largest possible dense distribution, thus obtaining excellent high temperature resistance.
[0021] The particle size of metallic aluminum powder is ≤1μm. This particle size determines its reactivity. At high temperatures, it reacts with N2 gas in the environment to form ceramic phases such as aluminum nitride. Secondly, it can also react with CO to form plasmas such as AlO and Al2O. Thermodynamic regulation is beneficial for the formation of the Sialon phase.
[0022] In step one, walnut shell powder, aluminum powder and additives are put into a ball mill for dry ball milling, which achieves uniformity of the mixture and effectively reduces the particle size of the powder during the grinding 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.
[0023] The beneficial effects of this invention are as follows: This invention prepares a premix by grinding walnut shell powder, aluminum powder, and additives into fine powder, and then pelletizing the premix, polystyrene balls, and silica sol solution to prepare multi-scale porous microspheres; pre-ball milling of walnut shell powder, aluminum powder, and additives increases the specific surface area of the powder and reduces the surface activation energy of the particles; this invention uses inexpensive and readily available raw materials, and has the characteristics of low cost and simple preparation process, and the prepared multi-scale porous carbon microspheres have excellent high temperature resistance. Attached Figure Description
[0024] Figure 1 SEM images of multi-scale porous carbon microspheres. Detailed Implementation
[0025] The present invention will be further described in detail below with reference to specific embodiments. The present invention provides a lightweight carbon-based multiphase microsphere and its preparation method, wherein the walnut shell powder has a particle size ≤1μm; the aluminum powder has a purity >98% and a particle size ≤1μm; and the additive is one or more of nickel nitrate, lanthanum oxide, and ferric nitrate, with a purity >99.9%.
[0026] Example 1:
[0027] Step 1: Take 38 parts of walnut shell powder, 32 parts of aluminum powder, and 1 part of additive (nickel nitrate), and grind the above raw materials in a planetary ball mill for 2 hours at a speed of 400 r / min to obtain a fine powder and prepare a premix.
[0028] Step 2: Pelletizing, drying, and calcination;
[0029] Take 2% of the total weight of the premix and a silica sol solution with a concentration of 0.05 g / ml; then add 1% of the total weight of the premix and polystyrene spheres into a spherical granulator and rotate it, spraying the silica sol solution until it uniformly covers the surface of the polystyrene spheres, and add the premix until a uniform spherical precursor is formed; dry the obtained precursor at 100℃, and finally calcine it at 1000℃ for 10 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere; the thickness of the Sialon-SiC composite ceramic phase layer generated in situ in the carbon framework pores formed by walnut shell powder is 1.6-2 μm.
[0030] Example 2:
[0031] Step 1: Take 58 parts of walnut shell powder, 52 parts of aluminum powder, and 5 parts of additive (lanthanum oxide), and grind the above raw materials in a planetary ball mill for 10 hours at a speed of 800 r / min to obtain a fine powder and prepare a premix.
[0032] Step 2: Pelletizing, drying, and calcination;
[0033] Take 10% of the total weight of the premix and prepare a silica sol solution with a concentration of 0.25 g / ml; then add 5% of the total weight of the premix and prepare polystyrene spheres to a spherical granulator and rotate it. Spray the silica sol solution until it evenly covers the surface of the polystyrene spheres. Add the premix until a uniform spherical precursor is formed. Dry the obtained precursor at 115℃ and finally calcine it at 1300℃ for 30 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere. The thickness of the Sialon-SiC composite ceramic phase layer generated in situ in the carbon framework pores formed by walnut shell powder is 1.5-2 μm.
[0034] Example 3:
[0035] Step 1: Mix 48 parts of walnut shell powder, 42 parts of aluminum powder, and 3 parts of additives, wherein nickel nitrate, lanthanum oxide, and ferric nitrate are mixed in a ratio of 1:1:1. Grind the above raw materials in a planetary ball mill for 5 hours at a speed of 600 r / min to obtain a fine powder and prepare a premix.
[0036] Step 2: Pelletizing, drying, and calcination;
[0037] Take 5% of the total weight of the premix and prepare a silica sol solution with a concentration of 0.15 g / ml; add 3% of the total weight of the premix and prepare polystyrene spheres to a spherical granulator and rotate it. Spray the silica sol solution until it evenly covers the surface of the polystyrene spheres. Add the premix until a uniform spherical precursor is formed. Dry the obtained precursor at 110℃ and finally calcine it at 1200℃ for 20 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere. The thickness of the Sialon-SiC composite ceramic phase layer generated in situ in the carbon framework pores formed by walnut shell powder is 1-1.5 μm.
[0038] Example 4:
[0039] Step 1: Mix 40 parts of walnut shell powder, 45 parts of aluminum powder, and 2 parts of additives, wherein lanthanum oxide and ferric nitrate are mixed in a 1:1 ratio. Grind the above raw materials in a planetary ball mill for 7 hours at a speed of 500 r / min to obtain a fine powder and prepare a premix.
[0040] Step 2: Pelletizing, drying, and calcination;
[0041] Take 7% of the total weight of the premix and a silica sol solution with a concentration of 0.20 g / ml; then add 4% of the total weight of the premix and polystyrene spheres into a spherical granulator and rotate it, spraying the silica sol solution until it uniformly covers the surface of the polystyrene spheres, and add the premix until a uniform spherical precursor is formed; dry the obtained precursor at 105℃, and finally calcine it at 1100℃ for 15 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere; the thickness of the Sialon-SiC composite ceramic phase layer generated in situ in the carbon skeleton pores formed by walnut shell powder is 0.5-1 μm.
[0042] This preparation method has the following advantages: the raw materials are non-toxic, harmless, and readily available, thus requiring lower production costs; the preparation process only requires ball milling, granulation, drying, and calcination, making the process simple.
[0043] The parts of this invention not described in detail are prior art. The above embodiments will help those skilled in the art to further understand this invention, but do not limit this invention in any way. Various changes in form, detail, or equivalents made using this invention without departing from the scope of the appended claims are all within the protection scope of this invention.
Claims
1. A multi-scale porous carbon-based microsphere, characterized in that: The premix composition, by weight, is as follows: 38-58 parts walnut shell powder, 32-52 parts aluminum powder, and 1-5 parts additives; the additives are one or more of nickel nitrate, lanthanum oxide, and ferric nitrate, with a purity >99.9%; the amount of silica sol solution with a concentration of 0.05-0.25 g / ml added is 2-10% of the total weight of the premix, and the amount of polystyrene balls added is 1-5% of the total weight of the premix; the preparation method is as follows: Step 1, take 38-58 parts walnut shell powder, 32-52 parts aluminum powder, and 1-5 parts additives, and ball mill the above raw materials in a planetary ball mill for 2-10 hours at a speed of 400-800 r / min to obtain a fine powder to prepare the premix; Step 2: Pelletizing, drying, and calcination; Take 2-10% of the total weight of the premix and prepare a silica sol solution with a concentration of 0.05-0.25 g / ml; add 1-5% of the total weight of the premix and add polystyrene spheres to a spherical granulator for rotation, spraying the silica sol solution until it uniformly covers the surface of the polystyrene spheres, and add the premix until a uniform spherical precursor is formed; dry the obtained precursor at 100-115℃, and finally calcine it at 1000℃-1300℃ for 10-30 min under microwave nitriding conditions to obtain this multi-scale porous carbon-based microsphere; the obtained multi-scale porous carbon-based microspheres will form a Sialon-SiC composite ceramic phase in situ in the carbon skeleton pores formed by the walnut shell powder.
2. The multi-scale porous carbon-based microsphere according to claim 1, characterized in that: The particle size of walnut shell powder is ≤1μm.
3. The multi-scale porous carbon-based microsphere according to claim 1, characterized in that: The purity of the aluminum powder is >98%, and the particle size is ≤1μm.
4. The multi-scale porous carbon-based microsphere according to claim 1, characterized in that: The polystyrene spheres have a purity of >99% and a particle size of 0.1-0.5 mm.
5. The multi-scale porous carbon-based microsphere according to claim 1, characterized in that: The average thickness of the Sialon-SiC composite ceramic phase layer is 0.5-2 mm.