A method for preparing SiC ceramic powder by combining precursor conversion with microwave

Abstract

This invention belongs to the technical field of SiC material preparation and discloses a method for preparing SiC ceramic powder by combining precursor conversion with microwave heating. This method innovatively combines precursor conversion with microwave heating to synthesize silicon carbide powder. Using a SiOC system precursor as the raw material, the liquid precursor is thoroughly mixed with carbon powder through stirring. After curing and forming, a high-strength green body is obtained. During the pyrolysis process, the precursor green body undergoes ceramicization and is transformed into nanoscale SiOC series groups, which rapidly react with carbon powder under the action of microwaves to synthesize SiC ceramic powder.

Description

Technical Field

[0001] The present invention belongs to the technical field of SiC material preparation, and in particular relates to a method for preparing SiC ceramic powder by combining precursor conversion with microwaves. Background Art

[0002] Silicon carbide (SiC) has the characteristics of high modulus, high hardness, wear resistance, heat resistance, and excellent optical, electrical, mechanical, and magnetic properties. It is one of the semiconductor materials with great application prospects and is widely used in high-end fields such as aerospace, nuclear submarines, nanomaterials, and optical devices, with huge development potential.

[0003] Currently, common methods for preparing silicon carbide (SiC) include hot pressing, chemical vapor reaction, carbothermal reduction, sol-gel, isostatic pressing, and solvent thermal synthesis. While these diverse SiC synthesis methods are limited by high energy consumption, complex processes, high costs, poor quality, and the inability to mass produce them, the company noted.

[0004] CN108383530A discloses a precursor conversion process for preparing ZrB2-SiC ceramic composite powder, which describes the use of an inorganic salt solution and an organic carbon solution to prepare a boron silicon zirconium precursor solution, followed by heat treatment at high temperature to synthesize the ZrB2-SiC composite powder.

[0005] The present invention directly utilizes an organic silicon precursor with Si-C chains and carbon powder for compounding, utilizing the liquid and cross-linking curing properties of organic silicon for molding, and utilizing the microwave absorption properties of carbon for microwave heating to prepare high-purity silicon carbide powder. The present invention innovatively combines the precursor conversion method with microwave sintering. Due to the large amount of gas generated during the pyrolysis of the precursor, the microwave plasma effect is stimulated, causing the system temperature to rise rapidly, from 600°C to 1300°C within 15 minutes. Summary of the Invention

[0006] The present invention discloses a method for preparing SiC ceramic powder by combining precursor conversion with microwaves. The precursor conversion method is innovatively combined with microwave heating. With the help of a precursor of the SiOC system as a raw material, the liquid precursor can be fully mixed with carbon powder by stirring. After curing and molding, a high-strength green body can be obtained. During the pyrolysis process, the precursor green body will undergo ceramic transformation into a nano-scale Si-OC series group, which rapidly reacts with the carbon powder under the action of microwaves to synthesize SiC ceramic powder.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing SiC ceramic powder by combining precursor conversion with microwaves comprises the following steps:

[0009] Step 1, weighing polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi), pouring them into a container and mixing them to form a precursor mixture A;

[0010] Step 2: Weigh carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:4.6~6; add it to precursor mixture A, stir for 10 minutes to obtain mixture B, and add an appropriate amount of Pt-C catalyst in the middle to obtain mixture C;

[0011] Step 3: Pour the mixture C into a cylindrical mold, place it in a vacuum drying oven, and dry it at 80°C for 24 hours to obtain a sintered green body;

[0012] Step 4: Place the prepared green body into an alumina crucible, bury quartz sand and perform microwave sintering. Increase the input power every five minutes. After heating to 900-1300°C, keep warm for 10-60 minutes to finally obtain high-purity SiC ceramic powder.

[0013] Among them, polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in step 1 are of analytical grade and participate in the reaction as precursors.

[0014] Wherein, the mass ratio of polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in step 1 is 1:1.

[0015] The carbon powder in step 2 is of analytical grade, with a particle size of 1-50 μm; and the mass ratio of carbon to precursor mixture A is 1:4.6-6.

[0016] The carbon powder particle size is 1-50 μm. Too fine will make it difficult to couple with microwaves and heat the system. Therefore, the present invention selects a particle size of 1-50 μm, which can both heat the system and have sufficient activity to react with the nano-groups of the SiOC system to synthesize SiC powder.

[0017] The carbon powder in step 2 participates in the reaction as a carbon source, and may also be one or more of carbon black, graphite, and biochar.

[0018] Wherein, the catalyst in step 2 is one of a Pt noble metal catalyst, a Pt-C catalyst, a platinum-based alloy catalyst, a non-noble metal carbon-based catalyst, a PD-C or a RH-C catalyst.

[0019] The amount of catalyst added in step 3 is 0.5% to 2% of the mass of the precursor mixture A.

[0020] The sintering process in step 4 can also be carried out in a sintering atmosphere including one of nitrogen and argon.

[0021] In the present invention, SiOC ceramics are generated after the precursor is pyrolyzed, SiOC+C powder=SiC+CO, and SiC ceramic powder is finally obtained;

[0022] The present invention utilizes a SiOC precursor as raw material. The liquid precursor is thoroughly mixed with carbon powder through stirring, then solidified and formed to produce a high-strength green body. During the pyrolysis process, the precursor green body undergoes ceramicization and transforms into nanoscale Si-OC groups, which react rapidly with carbon powder under microwaves to form SiC ceramic powder.

[0023] The present invention innovatively combines the precursor conversion method with microwave sintering. Since a large amount of gas is generated during the precursor pyrolysis process, the microwave plasma effect is stimulated, causing the system temperature to rise rapidly, from 600°C to 1300°C within 15 minutes. This allows the nano-scale SiOC after pyrolysis to react rapidly with carbon powder to generate SiC powder with well-developed grains, high purity and large size.

[0024] The precursor conversion method is an advanced ceramic preparation method that uses polymer precursors as raw materials and converts them into ceramic materials through molding, curing, and pyrolysis. This method utilizes the excellent fluidity and curing properties of polymer liquids, combined with a variety of molding processes, to achieve the preparation of advanced ceramic materials. During the precursor synthesis process, the precursor composition, groups, and chemical bonds can be manipulated at the molecular level, thereby designing or controlling the composition and structure of ceramic materials at the nanoscale.

[0025] The preparation process of the present invention is simple, non-toxic and environmentally friendly, does not require external heat sources, has low energy consumption in the heating process, has low sintering temperature and short holding time, and the prepared SiC has high strength and excellent performance, can be mass-produced and is highly efficient.

[0026] Compared with existing technologies, the advantages of this technology are: the SiC samples prepared by this technology are low-cost, easy to control, have good finished product performance, fast heating speed, and high efficiency and energy saving. This technology can achieve an environmentally friendly, energy-saving and efficient production method.

[0027] This method synthesizes SiC based on precursor conversion and microwave heating technology. The SiC produced through precursor conversion combined with microwave sintering has excellent performance, low cost, and is suitable for large-scale production. Microwave heating technology offers advantages such as high efficiency, environmental protection, energy conservation, and rapid production, effectively resolving the long production cycle issues of traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the SEM image of the SiC sample prepared in Example 1. At this time, the carbon content is high, the coupled heat ratio is large, and the grains are finely developed.

[0029] Figure 2This is the SEM image of the SiC sample prepared in Example 3. At this time, the precursor content is increased, and the grains are well developed due to the effect of microwave plasma.

[0030] Figure 3 This is the temperature rise curve of the SiC sample prepared in Example 3. The plasma heat of the sample is obvious, and the temperature can be raised from 600°C to 1300°C in 15 minutes.

[0031] Figure 4 This is the SEM image of the SiC sample prepared in Example 4. As the amount of precursor increases, sintering becomes more obvious after heating at 1200°C. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0033] It should be noted that the reagents and materials used, unless otherwise specified, can be purchased on the market.

[0034] Example 1

[0035] Step 1: Weigh polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in a mass ratio of 1:1, pour them into a container and mix them to form a precursor mixture A;

[0036] Step 2: Weigh carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:4.6; add it to precursor mixture A, stir for 10 minutes to obtain mixture B, and add platinum-based alloy catalyst in the middle to obtain mixture C; the amount of platinum-based alloy catalyst added is 0.5% of the mass of precursor mixture A; the carbon powder particle size is 1 μm;

[0037] Step 3: Pour the mixture C into a cylindrical mold, place it in a vacuum drying oven, and dry it at 80°C for 24 hours to obtain a sintered green body;

[0038] Step 4: Place the prepared green body into an alumina crucible, bury quartz sand and perform microwave sintering. Increase the input power every five minutes. After heating to 900°C, keep the temperature for 10 minutes to finally obtain high-purity SiC ceramic powder.

[0039] Example 2

[0040] Step 1: Weigh polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in a mass ratio of 1:1, pour them into a container and mix them to form a precursor mixture A;

[0041] Step 2: Weigh carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:5.6; add it to precursor mixture A, stir for 10 minutes to obtain mixture B, and add Pt-C catalyst in the middle to obtain mixture C; the amount of Pt-C catalyst added is 1% of the mass of precursor mixture A; the carbon powder particle size is 50 μm;

[0042] Step 3: Pour the mixture C into a cylindrical mold, place it in a vacuum drying oven, and dry it at 80°C for 24 hours to obtain a sintered green body;

[0043] Step 4: Place the prepared green body into an alumina crucible, bury quartz sand and perform microwave sintering. Increase the input power every five minutes. After heating to 1100°C, keep the temperature for 60 minutes to finally obtain high-purity SiC ceramic powder.

[0044] Example 3

[0045] Step 1: Weigh polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in a mass ratio of 1:1, pour them into a container and mix them to form a precursor mixture A;

[0046] Step 2: Weigh carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:5.8; add it to precursor mixture A, stir for 10 minutes to obtain mixture B, and add RH-C catalyst in the middle to obtain mixture C; the amount of RH-C catalyst added is 2% of the mass of precursor mixture A; the carbon powder particle size is 30 μm;

[0047] Step 3: Pour the mixture C into a cylindrical mold, place it in a vacuum drying oven, and dry it at 80°C for 24 hours to obtain a sintered green body;

[0048] Step 4: Place the prepared green body into an alumina crucible, bury quartz sand and perform microwave sintering. Increase the input power every five minutes. After heating to 1300°C, keep the temperature for 40 minutes to finally obtain high-purity SiC ceramic powder.

[0049] Example 4

[0050] Step 1: Weigh polyhydrogenmethylsiloxane (PHMS) and tetramethyltetravinylcyclotetrasiloxane (D4Vi) in a mass ratio of 1:1, pour them into a container and mix them to form a precursor mixture A;

[0051] Step 2: Weigh carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:6; add it to precursor mixture A, stir for 10 minutes to obtain mixture B, and add Pt-C catalyst in the middle to obtain mixture C; the amount of Pt-C catalyst added is 2% of the mass of precursor mixture A; the carbon powder particle size is 50 μm;

[0052] Step 3: Pour the mixture C into a cylindrical mold, place it in a vacuum drying oven, and dry it at 80°C for 24 hours to obtain a sintered green body;

[0053] Step 4: Place the prepared green body into an alumina crucible, bury quartz sand and perform microwave sintering. Increase the input power every five minutes. After heating to 1200°C, keep the temperature for 45 minutes to finally obtain high-purity SiC ceramic powder.

[0054] Figure 4 This is the SEM image of the SiC sample prepared in Example 4. As the amount of precursor increases, sintering becomes more obvious after heating at 1200°C.

Claims

1. A method for preparing SiC ceramic powder by combining precursor conversion with microwaves, characterized in that: The method comprises the following steps: step 1, weighing polyhydrogen methylsiloxane and tetramethyltetravinylcyclotetrasiloxane, pouring them into a container and mixing them to form a precursor mixture A; step 2, weighing carbon powder; the mass ratio of carbon powder to precursor mixture A is 1:4.6-6; adding the carbon powder to the precursor mixture A, stirring for 10 minutes to obtain a mixture B, and adding an appropriate amount of catalyst during the process to obtain a mixture C; step 3, pouring the mixture C into a cylindrical mold, placing the mold in a vacuum drying oven, and drying at 80°C for 24 hours to obtain a sintered green body; step 4, placing the prepared green body into an alumina crucible, burying it with quartz sand and performing microwave sintering, increasing the input power every five minutes, heating to 900-1300°C, and then keeping the temperature for 10-60 minutes to finally obtain a high-purity SiC ceramic powder; during the pyrolysis process, the precursor green body undergoes ceramicization and is transformed into nano-scale Si-OC series groups.

2. The method for preparing SiC ceramic powder by precursor conversion combined with microwave according to claim 1, characterized in that: The mass ratio of polyhydrogen methylsiloxane to tetramethyl tetravinyl cyclotetrasiloxane in step 1 is 1:

1.

3. The method for preparing SiC ceramic powder by precursor conversion combined with microwave according to claim 1, characterized in that: The carbon powder in step 2 is of analytical grade, with a particle size of 1-50 μm; The mass ratio of carbon to precursor mixture A is 1:4.6~6.

4. The method for preparing SiC ceramic powder by precursor conversion combined with microwave according to claim 1, characterized in that: The catalyst in step 2 is one of a Pt noble metal catalyst, a Pt-C catalyst, a platinum-based alloy catalyst, a non-noble metal carbon-based catalyst, a PD-C or a RH-C catalyst.

5. The method for preparing SiC ceramic powder by precursor conversion combined with microwave according to claim 1, characterized in that: The amount of catalyst added is 0.5%~2% of the mass of the precursor mixture A.

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