Production system and production process of silicon carbide ceramic precursor

Abstract

The invention provides a production system and a production process of a precursor of silicon carbide ceramic. The production system comprises a high-pressure microjet device of a metal sodium suspension, a silane accurate metering device, a supergravity impact rotating flow reaction device and a post-treatment device. The high-pressure micro-jet device for the metal sodium suspension liquid comprises a metal sodium melting prefabricated metering tank, a pressurizing plunger pump, a micro-jet cavity, a cooler and a discharging pipe which are connected in sequence, the supergravity impact rotating flow reaction device comprises two electric diaphragm pumps, two nozzles which are coaxially, concentrically and oppositely arranged, and a rotating reactor; after being accurately metered by the high-pressure micro-jet device of the metal sodium suspension, the raw materials enter the supergravity impact rotating flow reactor to react to produce a polymer; and carrying out post-treatment procedures such as filtration, solvent removal and thermal crosslinking to obtain a precursor of the silicon carbide ceramic. According to the production system and the production process of the precursor of the silicon carbide ceramic, the precursor with excellent quality can be produced.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide ceramic precursor production technology, specifically relating to a silicon carbide ceramic precursor production system and production process.

[0002] A production system and process for manufacturing silicon carbide precursors (polymethylchlorosilane, PMS) using a series system of a high-pressure microjet device for sodium metal suspension, a precision metering system, and a supergravity impact rotating flow reactor. Background Technology

[0003] Silicon carbide ceramic matrix composites (CMC-SiC) share properties very similar to diamond—it is one of the lightest, hardest, and strongest ceramic materials, possessing excellent thermal conductivity, acid resistance, low thermal expansion, corrosion resistance, and wear resistance. Due to its superior performance, it is widely used in industries such as automotive, machinery, chemical, and defense, as well as in environmental protection, aerospace technology, information electronics, and energy.

[0004] The most advanced silicon carbide ceramic production technology currently employs the so-called precursor method: First, a polymer (precursor) for silicon carbide ceramics is prepared using chemical synthesis. Second, fibers are impregnated in the precursor solution, and then placed in a high-temperature electric furnace to remove the solvent at high temperature. Then, the polycarbosilane is cross-linked, cured, and pyrolyzed to obtain the ceramic matrix. By repeatedly repeating the impregnation and calcination process, the desired silicon carbide ceramic product can be obtained.

[0005] Current technology for producing silicon carbide ceramic precursors has the following drawbacks: 1. Current precursor production technology for silicon carbide ceramics involves heating solid sodium metal in a single solvent (n-hexane) until it melts, and then breaking the sodium metal into droplets using a stirrer. Because the particle size is not fine enough, the reaction product polymethylsilane is coated on the surface of large-particle sodium metal. The sodium metal cannot react with the fresh silane, and the reaction cannot proceed to completion. During the discharge process, the sodium metal is prone to ignition.

[0006] 2. Current precursor production technology for silicon carbide ceramics involves adding methylchlorosilane dropwise into a high-temperature sodium metal suspension system. The silane evaporates instantly into a gas and escapes from the reaction system, leading to inaccurate measurement and distorted proportions.

[0007] 3. Current precursor production technology for silicon carbide ceramics uses traditional batch reactors, which do not mix evenly enough, resulting in uneven particle size of metallic sodium and some sodium sand residue that may be carried into the product, posing a significant fire hazard.

[0008] 4. Current precursor production technology for silicon carbide ceramics uses a combination of natural sedimentation and centrifugal filtration to remove sodium chloride, a byproduct of the reaction. However, the filtration process is too time-consuming and cannot remove micron-sized sodium chloride. A small portion of sodium chloride will enter subsequent processes along with the target product, polymethylsilane, which will not only affect the processing of silicon carbide ceramics and cause strong acid corrosion, but also act as an impurity, directly damaging the quality of the product.

[0009] 5. Current precursor production technology for silicon carbide ceramics uses dimethyldichlorosilane as raw material, which has a high carbon-to-silicon ratio, resulting in insufficient hardness and strength of the product.

[0010] 6. Current precursor production technology for silicon carbide ceramics uses n-hexane as a solvent. The solubility of high molecular weight precursors is less than 30%, and they precipitate when the solvent temperature exceeds 90 degrees Celsius. The solution concentration is insufficient and cannot be well used for firing ceramics.

[0011] The aforementioned drawbacks result in low-quality silicon carbide ceramics produced from this precursor, excessive raw material consumption, high energy consumption, and high costs. Therefore, it is essential to improve the existing production systems and processes for silicon carbide ceramic precursors. Summary of the Invention

[0012] The purpose of this invention is to provide a production system and process for silicon carbide ceramic precursors. By improving the production equipment and process, silicon carbide ceramic precursors with low cost, excellent quality and good quality stability can be prepared.

[0013] A production system for silicon carbide ceramic precursors includes a high-pressure microjet device for forming a sodium metal suspension, a precise metering device for forming a silane liquid, a high-gravity impact rotating flow reactor for reacting the sodium metal suspension and the silane liquid, and a post-processing device for the silicon carbide ceramic precursors. The high-pressure microjet device is equipped with a pre-positioned sodium metal melting pre-metering tank. The high-pressure microjet device includes a circulating pump, a pressurized plunger pump, a microjet cavity, a cooler, and a discharge pipe. The sodium metal melting pre-metering tank includes an automatic feed hopper, a heater, and a multi-layer variable-speed stirrer. The sodium metal melting pre-metering tank forms a sodium metal suspension from sodium metal and a solvent. A high-pressure micro-jet device delivers a sodium metal suspension into a hypergravity impact-rotating flow reactor. The precise metering device is a silane liquid precise metering device, comprising a silane metering tank, a silane metering pump, a flow regulating valve, and a mass flow meter connected in sequence. The silane liquid enters the hypergravity impact-rotating flow reactor through the precise metering device. After the high-pressure sodium metal suspension and high-pressure silane liquid are injected into the hypergravity impact-rotating flow reactor, a reaction occurs to form a silicon carbide ceramic precursor. The silicon carbide ceramic precursor enters a post-processing device to form a finished silicon carbide ceramic precursor. The post-processing device includes a combined filtration device, a solvent removal vessel, and a thermal cross-linking vessel connected in sequence. As a preferred embodiment of the present invention, the supergravity impact rotating flow reaction device includes two electric diaphragm pumps, two coaxially and concentrically arranged nozzles, and a rotating reactor. The two electric three-pump head diaphragm pumps pressurize the sodium metal suspension or silane liquid respectively. Under high pressure, the sodium metal suspension and silane liquid enter the rotating reactor at high speed through the two coaxially and concentrically arranged nozzles. The sodium metal suspension and silane liquid raw materials fully contact each other in the rotating reactor and undergo a complete condensation reaction, followed by a polymerization reaction. The reaction product is a silicon carbide ceramic precursor with a molecular weight of 20,000-25,000.

[0014] As a preferred embodiment of the present invention, the combined filtration device includes a candle filter and a rotary filter connected in sequence, wherein the rotary filter is provided with a sintered metal filter element with a pore size of 0.1 micrometers.

[0015] A production process for a silicon carbide ceramic precursor production system includes the following steps: raw material metallic sodium and solvent are mixed in a metallic sodium melting pre-metering tank to form a metallic sodium suspension; the metallic sodium suspension is pre-treated by a high-pressure micro-jet device; the metallic sodium suspension reacts with silane in a high-gravity impact rotating flow reactor to form a silicon carbide ceramic precursor; the silicon carbide ceramic precursor is then processed through a combined filtration device, a solvent removal kettle, and a thermal cross-linking kettle in a post-processing unit to form the finished silicon carbide ceramic precursor.

[0016] As a preferred embodiment of the present invention, the silane liquid comprises the following four components: monomethyltrichlorosilane, trimethylchlorosilane, dimethyldichlorosilane, and monomethylchlorosilane, in a mass ratio of 12:18:60:10.

[0017] As a preferred embodiment of the present invention, the solvent removal vessel is used to remove the solvent from the reaction product. The solvent is composed of n-hexane, xylene, and toluene, and the mass ratio of n-hexane, xylene, and toluene is 30:30:40.

[0018] As a preferred embodiment of the present invention, the mass ratio of sodium metal to solvent in the sodium metal suspension is 1.1-1.5.

[0019] As a preferred embodiment of the present invention, when the sodium metal suspension and silane enter the supergravity impact rotating flow reactor, the mass ratio of sodium metal suspension to silane is 1033:2595.

[0020] As a preferred embodiment of the present invention, the reaction temperature of the supergravity impact rotating flow reactor is 115-135 degrees Celsius, the reaction pressure is 1.5-1.7 MPaG, and the reaction time is 5-10 hours.

[0021] As a preferred embodiment of the present invention, the temperature of the solvent removal vessel is controlled at 128-130 degrees Celsius, and the solvent removal is accelerated by vacuuming, with the residence time controlled at 3.5-4.0 hours.

[0022] As a preferred embodiment of the present invention, the function of the thermal crosslinking reactor is to provide a thermal crosslinking reaction site for the silicon carbide ceramic precursor. The temperature of the thermal crosslinking reactor is controlled at 350-380 degrees Celsius, the operating pressure is 15-17 MPaG, and the residence time is controlled at 13-15 hours.

[0023] A production system and process for silicon carbide ceramic precursors, and the silicon carbide ceramic precursors prepared therefrom.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The silicon carbide ceramic precursor production technology of the present invention has a particle size of sodium metal suspension that reaches the micron level and has a uniform particle size distribution, which can ensure that the sodium metal is completely reacted; it avoids the risk of sodium metal easily igniting during the processing and storage of precursors under current process conditions.

[0025] 2. The present invention uses a solvent combination (n-hexane + xylene + toluene) that can dissolve high molecular weight precursors, increasing the solubility by 72-74%. Moreover, the precursors will not precipitate when the solvent temperature exceeds 90 degrees Celsius, ensuring the fluidity of the precursors.

[0026] 3. The silicon carbide ceramic precursor production technology of the present invention can completely filter out the reaction byproduct sodium chloride, avoiding the mixing of sodium chloride into the precursor, which not only leads to corrosion and mechanical wear of processing equipment, but also affects the purity of the precursor; moreover, the filtration time is shortened from 15 days to 1 hour, significantly improving the filtration efficiency.

[0027] 4. The silicon carbide precursor production technology of the present invention can achieve a precursor molecular weight of about 20,000. Such a precursor can reduce material costs by 70% and energy consumption by 80% in subsequent silicon carbide ceramic processing. Moreover, the produced ceramic products have ultra-high hardness and ultra-high strength, which fully meet the technical requirements of aerospace components and high-end chips. Attached Figure Description

[0028] Appendix Figure 1 This is a production system diagram of the silicon carbide ceramic precursor of the present invention.

[0029] Appendix Figure 2 This is a schematic diagram of the high-pressure microjet device for the silicon carbide ceramic precursor of the present invention.

[0030] Appendix Figure 3 This is a schematic diagram of the precise silane metering device for the silicon carbide ceramic precursor of the present invention.

[0031] Appendix Figure 4 This is a schematic diagram of a supergravity impact rotating reactor for the silicon carbide ceramic precursor of the present invention.

[0032] Appendix Figure 5 This is a schematic diagram of a combined filter based on the silicon carbide ceramic precursor of the present invention.

[0033] Appendix Figure 6 This is a schematic diagram of the desolventizing vessel for the silicon carbide ceramic precursor of the present invention.

[0034] Appendix Figure 7 This is a schematic diagram of the thermal crosslinking reactor for the silicon carbide ceramic precursor of the present invention.

[0035] Appendix Figure 8 This is a production system diagram for Example 1.

[0036] Appendix Figure 9 This is a production system diagram for Example 2.

[0037] Appendix Figure 10 This is a production system diagram for Example 3.

[0038] In the diagram: 1. Pre-fabricated metering vessel for melting sodium metal; 2. Pressurized plunger pump; 3. Micro-jet cavity; 4. Cooler; 5. Discharge pipe; 6. Circulation pump; 7. Silane metering vessel; 8. Silane metering pump; 9. Flow regulating valve; 10. Mass flow meter; 11. High-pressure diaphragm pump; 12. Nozzle; 13. Reactor rotor; 14. Candle filter; 15. Rotary filter; 16. Solvent removal vessel; 17. Solvent cooler; 18. Thermal crosslinking vessel. Detailed Implementation

[0039] The following detailed description of the production system and process of the silicon carbide ceramic precursor of the present invention, in conjunction with preferred embodiments, is not intended to limit the present invention. Any equivalent substitutions made in the art based on the disclosure of the present invention shall fall within the protection scope of the present invention. The equipment and raw materials used in the following examples are all commercially available products. For example, the electric heater is manufactured by Wuxi Huaneng Electric Heating Equipment Co., Ltd., and the electric diaphragm pump is manufactured by Shanghai Xinguangming Pump Industry Manufacturing Co., Ltd.

[0040] As attached Figure 1 -Appendix Figure 10 As shown, A production system for silicon carbide ceramic precursors includes a high-pressure microjet device for sodium metal suspension, a precision metering device, a supergravity impact rotating flow reaction device, and a post-processing device, including a combined filtration device, a desolvation vessel, and a thermal crosslinking vessel connected in sequence.

[0041] The high-pressure micro-jet device for sodium metal includes a sodium metal melting pre-metering tank 1, a pressurized plunger pump 2, a micro-jet chamber 3, a cooler 4, and a discharge pipe 5, connected in sequence. The sodium metal melting pre-metering tank 1 is also equipped with a circulation pump 6. The process of sodium metal in the sodium metal melting pre-metering tank 1 is as follows: first, it is fed by an automatic feeding hopper, then weighed, and then the heater is started to melt the sodium metal. After the sodium metal is melted, the solvent is pumped in, and the multi-layer variable flow rate stirrer is started to allow the sodium metal to form fine liquids in the solvent suspension. After stirring to ensure proper mixing, the sodium suspension is circulated using the circulation pump 6. A portion of the suspension enters the pressurized plunger pump 2. The pressurized plunger pump 2 pressurizes the sodium suspension in the pre-fabricated sodium melting metering tank 1 and pumps the high-pressure liquid into the microjet cavity 3. The high-pressure liquid containing fine suspended sodium particles passes through the fine pore module of the dispersion unit at high speed in the microjet cavity 3, forming a completely uniform sodium suspension. Finally, the suspension leaves the high-pressure microjet device through the discharge pipe 5.

[0042] The sodium suspension enters the reaction system after passing through a high-pressure microjet device to carry out the reaction.

[0043] Using the high-pressure microfluidic device for sodium metal to prepare suspensions can produce particles with a size of 10-25 micrometers and a relative standard deviation (RSD) of less than 2%, which can significantly improve the quality of silicon carbide ceramic precursors.

[0044] The sodium particles in the suspension leaving the high-pressure microfluidic device have a diameter of less than 25 micrometers.

[0045] The production process of silicon carbide ceramic precursor is carried out through the aforementioned silicon carbide ceramic precursor production system. The raw material, metallic sodium, is dispersed through a high-pressure microjet device to obtain a qualified suspension, which then enters the reactor.

[0046] The high-pressure microjets for sodium metal are primarily used to prepare sodium metal suspensions in the 10-25 micrometer range. Sodium metal is first fed into an automatic feed hopper, weighed, and then heated to 125-130 degrees Celsius by the electric heater integrated into the sodium melting pre-metering tank 1. The pressure inside the tank is controlled at 0.5-0.8 MPaG to ensure complete melting of the sodium metal. After the sodium metal melts, a solvent is precisely prepared according to a mass ratio (n-hexane:xylene:toluene = 30:30:40). The prepared solvent is prepared according to the mass ratio of sodium metal to the combined solvent. For a formulation of 1.1-1.5, the combined solvent is pumped into the pre-fabricated metering tank 1 for melting sodium metal; the multi-layer variable flow rate stirrer inside the tank is started to uniformly disperse the sodium metal in the solvent, and the stirring speed is 120-125 RPM; the sodium metal forms fine droplets in the suspension, and this process of preparing the suspension by stirring takes 2 hours; after the time is up, the number of sodium metal droplets is measured with a laser counter, converted into the mass of the droplets, and then converted into the particle size, with 200-500 micrometers being considered acceptable. After obtaining qualified droplets, the sodium suspension in the pre-fabricated metering tank 1 is pressurized to 10.0 MPaG using a pressurized plunger pump 2, and the high-pressure liquid is pumped into the microjet chamber 3. In the microjet chamber 3, the high-pressure liquid flow containing fine sodium suspended particles enters the fine-pore module of the dispersion unit. At this time, the liquid pressure drops sharply, forming an ultrasonic flow velocity. The particles in the fluid collide, cavitation, and flow reduction, and the shear force splits the fine sodium droplets, forming a sodium suspension in a completely homogeneous state. The final particle size of the sodium is 10-25 micrometers, and the relative standard deviation (RSD) of the particle size is less than 2%. After exiting the fine-pore module, the suspension enters a cooler 4, which cools the high-temperature sodium suspension to 50-60 degrees Celsius. The sodium droplets become fine solid particles and are completely shaped, forming a stable fine powder sodium suspension. Then, through the discharge pipe 5, the cooled sodium suspension is transported to the reactor through a cold-insulating pipe.

[0047] The particle size of sodium droplets is measured using a laser spectrometer; a particle size of 0.5-1.0 mm indicates that the stirring is qualified.

[0048] After the stirring is qualified, the sodium metal suspension is circulated by the circulation pump 6. A part of the suspension will enter the pressurized plunger pump 2. The pressurized plunger pump 2 will increase the pump outlet pressure to 10.0-12.0 MPaG, so that the suspension has enough potential energy to enter the high-pressure micro-jet cavity 3.

[0049] Using the aforementioned high-pressure microfluidic technology, metallic sodium can form nanoscale uniformly dispersed solid microparticles in the solvent, which can react completely with silane without any residual metallic sodium entering the reaction product system, thus avoiding a high risk of fire.

[0050] Another raw material, a combination of methylchlorosilanes (trichlorosilane, trimethylchlorosilane, dimethyldichlorosilane and monomethylchlorosilane), is fed into the reactor with its flow rate controlled by a precise metering device. The precise metering device is a silane liquid precise metering device, which includes a silane metering tank 7, a silane metering pump 8, a flow regulating valve 9, and a mass flow meter 10 connected in sequence.

[0051] The precise metering device's main function is to control the feed rate of raw material silane. A combination of four silane raw materials, in a mass ratio of monomethyltrichlorosilane:trimethylchlorosilane:dimethyldichlorosilane:monomethylchlorosilane = 12:18:60:10, is pumped into silane metering tank 7. The temperature of silane metering tank 7 is maintained at 6-10 degrees Celsius to ensure it remains in a liquid state and does not decompose in a gaseous state. The agitator is then started for mixing, and after one hour, stirring is stopped. Silane metering pump 8 (precision gear pump) is then started, and silane enters the mass flow meter 10 through a pipeline. The reading from mass flow meter 10 is fed back to flow regulating valve 9 to control the valve opening, ensuring the final flow rate reaches the target value. This precise metering device controls the silane flow rate fluctuation within 0.1%, guaranteeing the accuracy and consistency of silane metering.

[0052] The supergravity impact rotating flow reactor refers to a reactor in which sodium metal suspension and silane liquid are pressurized by a high-pressure pump (a high-pressure diaphragm pump 11) and introduced at high speed into the rotating reactor through two coaxial, concentric, and opposite nozzles 12. The two reactants come into full contact, undergo a complete condensation reaction, and then complete the polymerization reaction. This special reactor design allows the reaction to proceed most thoroughly, and the molecular weight of the reaction product can reach 20,000-25,000.

[0053] The rotary reactor is a high-gravity impact rotating flow reactor. As mentioned earlier, the sodium suspension, after leaving the microjet device, is pressurized by a high-pressure diaphragm pump 11 and enters the reactor at a pressure of 2.0 MPa. Silane, after passing through a precise metering device, is also pressurized by the high-pressure diaphragm pump 11 and enters the reactor. The pressure entering the reactor is controlled at 2.0 MPa, and the mass ratio of the sodium metal suspension combination to the methylchlorosilane combination is controlled at 1033:2595. This ratio of sodium metal suspension and silane liquid is ejected at high speed from two nozzles 12, which are installed opposite each other and on the same axis. The two fluids collide violently, ensuring thorough contact between the two raw materials, resulting in a rapid reaction and generating a large amount of heat. Simultaneously, the reactor rotor 13 of the rotary reactor rotates at high speed (250-260 RPM), further accelerating the contact and reaction of the raw material molecules, allowing the reaction to reach its endpoint more quickly. The reaction temperature in the high-gravity impact rotary flow reactor is 115-135 degrees Celsius, the reaction pressure is 1.5-1.7 MPaG, the reaction time is 5-10 hours, and the temperature of the material at the reactor outlet is 125 ± 5℃.

[0054] The post-treatment system includes a combined filter unit, a desolventizing vessel 16, and a thermal crosslinking vessel connected in sequence.

[0055] The combined filtration system is a system that connects a candle filter 14 and a rotary filter 15 in sequence. The candle filter 14 is characterized by its large throughput, high precision, and convenient maintenance. The reaction product obtained after the reaction of metallic sodium and silane is a mixture system containing the main product polymethylsilane and the byproduct sodium chloride. This mixture system first enters the candle filter 14, filtering out most of the sodium chloride solid particles with a particle size of 10 micrometers to 1000 micrometers. This process is very rapid because the candle filter 14 has a large throughput. The product passes through the candle filter 14 in one go under the action of the transfer pump, and then enters the rotary filter 15. In the rotary filter 15, the pressure of the material is slightly increased to 0.5-0.6 MPaG, forcibly forcing the reaction product through the sintered metal filter element with a porosity of 0.1 micrometers. The extremely fine sodium chloride solid particles with a particle size of 0.2-10 micrometers are left in the product. The filtrate becomes a completely clean polymethylsilane solution and enters the desolventizing vessel 16.

[0056] The solvent removal vessel 16 is used to heat the polymer solution after it enters the vessel. For example, a hot oil circulation pipe is used to heat the vessel to about 128-130 degrees Celsius. The solvent removal is accelerated by vacuuming, and the residence time is controlled to be 3.5-4.0 hours. After the solvent is evaporated, it becomes a gas and enters the solvent cooler 17. The solvent gas is condensed into a liquid under the action of circulating cooling water, and then recovered and reserved as solvent for the next cycle.

[0057] The function of the thermal crosslinking reactor 18 is to transport the polymethylsilane after solvent removal to the thermal crosslinking reactor 18 by a mud pump, start the heater, for example, using a hot oil circulation pipe to heat the material to 350-380 degrees, the operating pressure is 15-17 MPaG, and the residence time is controlled to be 13-15 hours, so that the polymethylsilane undergoes a crosslinking reaction under the action of heat, the polymer structure becomes more compact, the molecular weight further increases to about 15,000-20,000, and becomes the final reaction product: silicon carbide ceramic precursor.

[0058] The present invention provides a silicon carbide ceramic precursor prepared by the above-mentioned production process, which can produce a silicon carbide ceramic precursor with low cost, excellent quality and good quality stability.

[0059] Currently, there are very few manufacturers producing silicon carbide precursors using existing technologies, and there are no unified national or industry standards for the products. We use the product quality inspection standards developed from our own pilot plant experiments to test the quality, and we compare them with samples from existing products (from a company whose factory is located in Bengbu, Anhui).

[0060] Test methods and standards: Molecular weight --- Number average absolute molecular weight method; Liquid density (g / cm3) --- GB / T4472-2011, Viscosity (mPa.S) --- GB / T 265; Silicon-to-carbon ratio of ceramic products (Si:C) --- Gb / t 16555; Ceramic yield (%), Chlorine content (wt%) --- GB / T 6324.

[0061] Comparative Example Five different batches of PMS-01 silicon carbide ceramic precursor, commercially available from a company in Bengbu City, Anhui Province, were purchased. These five batches were designated as Sample 1 to Sample 5, and performance tests were conducted on Samples 1 to 5. Seven parallel samples were tested for each sample, and the average value was taken as the test result, as shown in Appendix Table 1.

[0062] Appendix 1. Performance test results of the comparative example PMS-01 silicon carbide ceramic precursor

[0063] As shown in Appendix Table 1, the standard deviation S of the silicon carbide ceramic precursor PMS-01 in samples 1-5 is relatively large, with the standard deviation of molecular weight reaching 48.9. This indicates that the existing technology has poor quality consistency and cannot meet the market's requirements for the quality stability of precursors.

[0064] The production system in Example 1 is largely based on existing technologies, except that the sodium suspension pre-production utilizes the aforementioned high-pressure microjet device, and the process parameters have been improved, with better control of key parameters, resulting in higher quality.

[0065] The process flow diagram for this embodiment is attached. Figure 8 As shown, the production system includes: a high-pressure microjet device for sodium metal suspension, a silane metering tank, a silane metering pump, a batch reactor, a natural sedimentation method + centrifuge filtration, a desolvation tank, and a thermal crosslinking tank.

[0066] Sodium metal is heated and melted in a high-pressure microjet device, becoming a suspension. Under high pressure, it passes through a microjet fine-pore device and is transformed into extremely fine particles, which are then pumped into a conventional batch reactor. Silane is precisely metered through a metering system and enters the conventional reactor according to the ratio with sodium metal to carry out the reaction.

[0067] In this embodiment, the reactor is a conventional batch reactor used for precursor production in the prior art.

[0068] Based on the production system and process conditions of this embodiment, five batches were produced using the same production process and raw materials. Precursors for silicon carbide ceramics prepared from these five batches were sampled, and performance tests were performed on the five samples. Seven parallel samples were tested for each sample, and the average value was taken as the test result, as shown in Appendix Table 2.

[0069] Appendix Table 2 Performance test results of the silicon carbide ceramic precursor of Example 1

[0070] A comparison of the data in Appendix 2 and Appendix 1 shows that the standard deviation S of various indicators for the five precursor samples prepared in Example 1 is significantly smaller than that of the same indicators in Comparative Example 1. This indicates that the silicon carbide ceramic precursor product prepared in Example 1 has good quality consistency. Furthermore, the molecular weight of the product is significantly increased. The high-pressure microfluidic device using metallic sodium in this example greatly improves the contact area and contact time between metallic sodium and silane, enhancing the completeness of the reaction, thus resulting in a substantial increase in the final precursor molecular weight.

[0071] The production system in Example 2 is largely the novel production system described in this invention. Not only does it utilize the high-pressure microjet device for the pre-preparation of the sodium suspension, but it also replaces the conventional reactor with the hypergravity impact rotating flow reactor described in this invention. Furthermore, the process parameters have been improved, particularly the reaction temperature, pressure, and reaction time, all of which have been optimized.

[0072] The process flow diagram for this embodiment is attached. Figure 9 As shown. The production system includes: a high-pressure microjet device for sodium metal suspension, a silane metering tank, a silane metering pump, a high-gravity impact rotary reactor, natural sedimentation + centrifuge filtration, a desolvation vessel, and a thermal crosslinking vessel.

[0073] In this embodiment, the sodium pre-processing device is the high-pressure microjet device of the present invention. The sodium is heated and melted in this device to become a suspension. Under high pressure, it passes through the microjet fine hole device to become extremely fine particles, which are then pumped into the supergravity impact rotating flow reactor. Silane is precisely metered through a metering system and enters the supergravity impact rotating flow reactor according to the ratio with the sodium to carry out the reaction.

[0074] In this embodiment, the reactor is the supergravity impact rotating flow reactor of the present invention. The raw materials, metallic sodium and silane, are ejected from the nozzle under high pressure and collide with each other to form a wider contact and reaction interface, making the reaction more thorough. At the same time, the rotor of the reactor rotates at high speed, driving the entire material to collide and contact, so that the reaction develops towards a higher molecular weight.

[0075] Based on the production system and process conditions of this embodiment, five batches were produced using the same production process and raw materials. Precursors for silicon carbide ceramics prepared from these five batches were sampled, and performance tests were performed on the five samples. Seven parallel samples were tested for each sample, and the average value was taken as the test result, as shown in Appendix Table 3.

[0076] Appendix Table 3 Performance test results of the silicon carbide ceramic precursor in Example 2

[0077] A comparison of the data in Appendix 3 and Appendix 1 shows that the standard deviation S of various indicators of the five precursor samples prepared in Example 2 is significantly smaller than that of the same indicators in Comparative Example 1. This indicates that the silicon carbide ceramic precursor products prepared in Example 2 have good quality consistency. At the same time, it can be seen that the molecular weight of the product is greatly increased, reaching about 20,000. This indicates that the high-pressure microfluidic device and the supergravity impact rotating flow reactor used in this example greatly improve the contact area and contact time between sodium metal and silane, and improve the completion of the reaction. Therefore, the molecular weight of the final precursor is greatly increased.

[0078] Example 3's production system is entirely a novel production system described in this invention. The system includes: a high-pressure microjet device for sodium metal suspension, a silane metering tank, a silane metering pump, a high-gravity impact rotary reactor, a candle filter + rotary filter, a solvent removal vessel, and a thermal crosslinking vessel. The process flow diagram for this example is attached. Figure 10 As shown.

[0079] In this embodiment, the sodium pre-processing device is the high-pressure microjet device of the present invention. The sodium is heated and melted in this device to become a suspension. Under high pressure, it passes through the microjet fine hole device to become extremely fine particles, which are then pumped into the supergravity impact rotating flow reactor. Silane is precisely metered through a metering system and enters the supergravity impact rotating flow reactor according to the ratio with the sodium to carry out the reaction.

[0080] In this embodiment, the reactor is the supergravity impact rotating flow reactor of the present invention. Raw materials, metallic sodium and silane, are ejected from the nozzle under high pressure, colliding with each other to form a wider contact and reaction interface, allowing for a more complete reaction. Simultaneously, the reactor rotor rotates at high speed, driving the entire material to collide and contact, causing the reaction to progress towards higher molecular weights.

[0081] In this embodiment, the combined filter includes a candle filter and a rotary filter. The reaction product obtained after the reaction is a mixture system. It first enters the candle filter, where most of the sodium chloride solid particles with a particle size of 10 micrometers to 1000 micrometers are filtered out. This process is very rapid because the candle filter has a large throughput, and the product passes through the filter in one go under the action of the transfer pump. Then it enters the rotary filter, where the pressure is slightly increased to force the reaction product through a sintered metal filter element with a porosity of 0.1 micrometers. This leaves behind extremely fine sodium chloride solid particles with a particle size of 0.2 to 10 micrometers. The filtrate becomes a completely clean polymethylsilane solution, which enters the desolventizing vessel.

[0082] Based on the production system and production process conditions of this embodiment, five batches were produced using the same production process and raw materials. Precursors of silicon carbide ceramics prepared from the five batches were sampled, and performance tests were performed on the five samples. Seven parallel samples were tested for each sample, and the average value was taken as the test result, as shown in Appendix Table 4.

[0083] Appendix Table 4 Performance test results of the silicon carbide ceramic precursor in Example 3

[0084] A comparison of the data in Appendix 4 and Appendix 1 shows that the standard deviation S of various indicators of the five precursor samples prepared in Example 3 is significantly smaller than that of the same indicators in Comparative Example 1. This indicates that the silicon carbide ceramic precursor products prepared in Example 3 have good quality consistency. At the same time, it can be seen that the molecular weight of the product is greatly increased, reaching about 20,000. This indicates that the high-pressure microjets and high-gravity impact rotating flow reactors used in this example greatly improve the contact area and contact time between sodium metal and silane, and improve the completion of the reaction. Therefore, the molecular weight of the final precursor is greatly increased.

[0085] Most notably, the chlorine content in the reaction product was reduced by weight, decreasing from approximately 0.1% to approximately 0.005%. This indicates that the combination of candle filter and rotary filter has excellent filtration efficiency, and sodium chloride in the product was essentially removed, which fundamentally improved the quality of the product.

[0086] Stability test In Examples 1-3 and Comparative Example 1, one sample was taken and stored in an open container. The container was then exposed to the natural environment for one day, and the changes in the sample were observed to see if it absorbed moisture, smoked, or caught fire after being exposed to air for a certain period of time. The observation results are shown in Appendix Table 5.

[0087] Appendix 5: Performance test results of silicon carbide ceramic precursors in stability tests

[0088] As can be seen, the control sample successively experienced moisture absorption, smoke, and spontaneous combustion within 12 hours, which is extremely detrimental to the subsequent processing of the precursor. The precursor samples prepared by the production system and process of this invention did not experience smoke or spontaneous combustion, indicating that the quality is stable and reliable, which is beneficial to subsequent processing.

[0089] The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to this utility model are also within the scope of the present invention. Therefore, all equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A production system for silicon carbide ceramic precursors, characterized in that, It includes a high-pressure microjet device for forming a sodium metal suspension, a precise metering device for forming a silane liquid, a hypergravity impact rotating flow reaction device for reacting the sodium metal suspension with the silane liquid, and a post-processing device for silicon carbide ceramic precursors. The high-pressure microjet device is equipped with a pre-positioned sodium melting pre-metering tank. The high-pressure microjet device includes a circulation pump, a pressurized plunger pump, a microjet cavity, a cooler, and a discharge pipe. The sodium melting pre-metering tank includes an automatic feed hopper, a heater, and a multi-layer variable flow rate stirrer. The sodium melting pre-metering tank forms a sodium suspension from sodium and solvent. The high-pressure microjet device sends the sodium suspension into a high-gravity impact rotating flow reaction device. The precise metering device is a silane liquid precise metering device, which includes a silane metering tank, a silane metering pump, a flow regulating valve, and a mass flow meter connected in sequence. The silane liquid enters the hypergravity impact rotating flow reaction device through the precise metering device. After high-pressure sodium metal suspension and high-pressure silane liquid are injected into the supergravity impact rotating flow reactor, a reaction occurs to form a silicon carbide ceramic precursor. The silicon carbide ceramic precursor enters the post-processing device to form the finished silicon carbide ceramic precursor. The post-processing device includes a combined filtration device, a solvent removal kettle, and a thermal cross-linking kettle connected in sequence.

2. The silicon carbide ceramic precursor production system according to claim 1, characterized in that, The supergravity impact rotating flow reactor includes two electric diaphragm pumps, two coaxially and concentrically arranged nozzles, and a rotating reactor. The two electric three-pump head diaphragm pumps pressurize either a sodium suspension or a silane liquid. Under high pressure, the sodium suspension and silane liquid enter the rotating reactor at high speed through the two coaxially and concentrically arranged nozzles. The sodium suspension and silane liquid raw materials come into full contact in the rotating reactor and undergo a complete condensation reaction, followed by a polymerization reaction. The reaction product is a silicon carbide ceramic precursor with a molecular weight of 20,000-25,000.

3. The silicon carbide ceramic precursor production system according to claim 1, characterized in that, The combined filtration device includes a candle filter and a rotary filter connected in sequence, wherein the rotary filter is provided with a sintered metal filter element with a pore size of 0.1 micrometers.

4. The production process of the silicon carbide ceramic precursor production system according to any one of claims 1-3, characterized in that, Raw material sodium metal and solvent form a sodium metal suspension in a sodium metal melting pre-metering tank. The sodium metal suspension is pre-treated by a high-pressure micro-jet device. The sodium metal suspension reacts with silane in a high-gravity impact rotating flow reactor to form a silicon carbide ceramic precursor. The silicon carbide ceramic precursor is then processed by a combined filtration device, a solvent removal kettle, and a thermal crosslinking kettle to form the finished silicon carbide ceramic precursor.

5. The production process according to claim 4, characterized in that, The silane liquid comprises the following four components: monomethyltrichlorosilane, trimethylchlorosilane, dimethyldichlorosilane, and monomethylchlorosilane, in a mass ratio of 12:18:60:

10.

6. The production process according to claim 4, characterized in that, The solvent removal vessel is used to remove the solvent from the reaction products. The solvent is composed of hexane, xylene, and toluene in a mass ratio of 30:30:

40.

7. The production process according to claim 4, characterized in that, The mass ratio of sodium metal to solvent in the sodium metal suspension is 1.1-1.

5.

8. The production process according to claim 4, characterized in that, When the sodium metal suspension and silane enter the supergravity impact rotating flow reactor, the mass ratio of sodium metal suspension to silane is 1033:2595.

9. The production process according to claim 4, characterized in that, The reaction temperature of the supergravity impact rotating flow reactor is 115-135 degrees Celsius, the reaction pressure is 1.5-1.7 MPaG, and the reaction time is 5-10 hours.

10. The production process according to claim 4, characterized in that, The temperature of the solvent removal vessel is controlled at 128-130 degrees Celsius, and a vacuum method is used to accelerate solvent removal. The residence time is controlled at 3.5-4.0 hours.

11. The production process according to claim 4, characterized in that, The function of the thermal crosslinking reactor is to provide a thermal crosslinking reaction site for the silicon carbide ceramic precursor. The temperature of the thermal crosslinking reactor is controlled at 350-380 degrees Celsius, the operating pressure is 15-17 MPaG, and the residence time is controlled at 13-15 hours.

12. The silicon carbide ceramic precursor prepared by the production process according to any one of claims 4-11.

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