SiC powder synthesis system and method based on dynamic coupling

Abstract

According to the SiC powder synthesis system and method based on dynamic coupling, in the method, the temperature and pressure of silicon powder and graphite powder are precisely and dynamically regulated and controlled through a pressure-temperature dynamic coupling device in a high-temperature and high-pressure closed environment, and then the temperature and pressure are regulated and controlled in different reaction stages; the regulation and optimization of the formation rate and growth rate of the SiC crystal nucleus are realized, and the SiC powder with high crystal quality, purity of more than or equal to 99.9%, granularity of 1-5 microns and uniform distribution is obtained. According to the synthesis method provided by the invention, the synthesis time can be shortened to 4-5 hours, and the reaction temperature is reduced by 100-200 DEG C compared with that of an original normal-pressure synthesis method, so that the production efficiency is improved by 50% or above, and the energy consumption is reduced by 20-30%. The process parameters of the pressure-temperature dynamic coupling device can be accurately adjusted, and the pressure-temperature dynamic coupling device is suitable for preparing different SiC crystal form powder.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide material preparation technology, and relates to a SiC powder synthesis system and method based on dynamic coupling. Background Technology

[0002] SiC powder is a key starting material for the preparation of SiC crystals. Its purity, crystal phase structure and particle morphology directly affect the quality and efficiency of subsequent crystal growth.

[0003] Currently, SiC powder is typically prepared under normal pressure or low vacuum and high temperature conditions for more than 6 hours. However, at high temperatures, Si is prone to sublimation, leading to raw material loss; simultaneously, the diffusion rate of Si atoms is slow, making it difficult to form high-purity, high-crystallinity SiC powder. Therefore, existing methods for preparing SiC powder suffer from problems such as long reaction time, low crystallinity, and uneven composition. Summary of the Invention

[0004] The purpose of this invention is to provide a silicon carbide powder synthesis system and method based on dynamic coupling, so as to solve the problems of low crystallinity and uneven composition of SiC powder prepared by existing methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This application provides a method for synthesizing SiC powder based on dynamic coupling, the method comprising: After the silicon powder and graphite powder are mixed, they are placed in a pressure-resistant reactor and a vacuum is drawn. Argon gas is introduced into the pressure-resistant reactor. After the temperature core zone is controlled at 1750-1900℃ and the pressure at 1.2-1.5MPa by a pressure-temperature dynamic coupling device, the silicon powder and the graphite powder react for 0.5-1.5h to form initial crystal nuclei. After the core area temperature is controlled to 1600-1850℃ and the pressure to 0.8-1.0MPa by the pressure-temperature dynamic coupling device, the initial crystal nuclei grow for 1-3 hours. After depressurization, cooling, grinding and sieving, SiC powder is obtained.

[0006] In addition, this application also provides a SiC powder synthesis system based on dynamic coupling. The system includes: a pressure-resistant reactor, a pressure-temperature dynamic coupling device, and a vacuum pump; wherein, the pressure-temperature dynamic coupling device includes a pressure sensor located inside the pressure-resistant reactor and a partitioned heating module, a PCL programmable logic controller, an electric proportional valve, an electronic back pressure valve, and a gas cylinder, all located outside the pressure-resistant reactor. The pressure-resistant reactor is connected to the vacuum pump, the gas cylinder, the electric proportional valve, and the electronic back pressure valve, respectively; the zoned heating module is attached to the outside of the pressure-resistant reactor; The PCL programmable logic controller is electrically connected to the pressure sensor, the zoned heating module, the electric proportional valve, the electronic back pressure valve, the vacuum pump, and the gas cylinder, and the molecular sieve adsorption tower is located between the gas cylinder and the pressure-resistant reactor.

[0007] The present invention has the following beneficial effects: (1) In this application, silicon powder and graphite powder are subjected to high temperature and high pressure in a closed environment. By precisely and dynamically controlling the temperature and pressure at different reaction stages, the formation rate and growth rate of SiC crystal nuclei are controlled and optimized, so as to obtain SiC powder with high crystal quality, purity ≥99.9%, particle size of 1-5μm and uniform distribution.

[0008] (2) In this application, the high pressure environment can effectively improve the diffusion coefficient and collision frequency between gaseous reactants, significantly reduce the nucleation activation energy, improve mass transfer efficiency and suppress high temperature decomposition, shorten the synthesis time and optimize the crystal quality.

[0009] (3) In this application, high temperature can give silicon atoms and carbon atoms sufficient diffusion kinetic energy and reactivity, promote the reaction between the two, and enable silicon carbide to generate a large number of initial crystal nuclei in an explosive and uniform manner, thereby promoting the directional growth of SiC crystal form.

[0010] (4) In the synthesis method provided in this application, the synthesis time is shortened to 4-5h and the reaction temperature is reduced by 100-200℃ compared with the original atmospheric pressure synthesis method, which increases production efficiency by more than 50% and reduces energy consumption by 20-30%. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a SiC powder synthesis system based on dynamic coupling, provided in an embodiment of this application. Detailed Implementation

[0012] This application provides a SiC powder synthesis system based on dynamic coupling. The system includes a pressure-resistant reactor, a pressure-temperature dynamic coupling device, and a vacuum pump, as shown in the attached figure. Figure 1 As shown.

[0013] The pressure-resistant reactor is the main component for synthesizing SiC powder, possessing characteristics of high pressure and heat resistance. In this embodiment, the pressure-resistant reactor is a nickel-based alloy pressure-resistant reactor made of nickel-based high-temperature alloys such as Inconel 600 or Haynes 230, and the interior of the pressure-resistant reactor is coated with an Al2O3 ceramic coating to withstand a high temperature of 2000℃ and a pressure of 2.0MPa. More specifically, the working pressure of the pressure-resistant reactor in this embodiment is 0.8-1.8MPa, and the working temperature is 1600-1900℃. To ensure the pressure stability of SiC powder synthesis, the airtightness of the pressure-resistant reactor needs to be guaranteed. Based on this, the pressure-resistant reactor in this embodiment is equipped with a quick-opening flange and a metal C-ring sealing structure. Of course, existing sealing methods can also be used to achieve the airtightness of the pressure-resistant reactor.

[0014] The pressure-temperature dynamic coupling device is a component of the PCL programmable logic controller (PLC) that enables automatic dynamic coupling and adjustment of temperature and pressure according to the synthesis stage of SiC powder. In this embodiment, the pressure-temperature dynamic coupling device includes a pressure sensor located inside the pressure-resistant reactor, as well as zoned heating modules, a PCL programmable logic controller, an electric proportional valve, an electronic back pressure valve, and a gas cylinder, all located outside the pressure-resistant reactor.

[0015] A zoned heating module is attached to the outside of the pressure-resistant reactor to provide a heat source and achieve heating. In this embodiment, the zoned heating module is a high-purity isostatic graphite heating element, forming three independently temperature-controlled zones—upper, middle, and lower—along the outside of the pressure-resistant reactor. These zones correspond to the preheating zone, core zone, and gradient cooling zone inside the pressure-resistant reactor. This design establishes a stable longitudinal temperature field inside the pressure-resistant reactor, with the core zone having the highest temperature, followed by the gradient cooling zone, and the preheating zone having the lowest temperature. A total temperature difference of ≥350℃ is formed between the core zone and the gradient cooling zone, while the gradient cooling zone itself maintains a longitudinal cooling gradient of 50-100℃ / m. This temperature distribution pattern, characterized by a rapid initial drop followed by a slow decrease, effectively drives the chemical potential gradient of gaseous substances directionally transported from the core zone to the gradient cooling zone, thereby promoting the directional and preferential growth of SiC crystal nuclei.

[0016] The PCL (Programmable Logic Controller) is a component that enables dynamic temperature and pressure regulation in a pressure-temperature dynamic coupling device. It is electrically connected to the zone heating module, pressure sensor, vacuum pump, electric proportional valve, electronic back pressure valve, and gas cylinder. The PCL receives pressure values ​​detected by the pressure sensor, controls the temperature regulation of the zone heating module, and simultaneously controls the start and stop of the vacuum pump, electric proportional valve, electronic back pressure valve, and gas cylinder. In this embodiment, the pressure sensor has a detection accuracy of ±0.01 MPa.

[0017] Once the raw materials are placed inside the pressure reactor, the PCL programmable logic controller (PLC) activates the vacuum pump to create a vacuum inside the reactor, achieving a specific vacuum level. The PLC also controls the gas cylinder to begin filling the reactor with high-purity argon. Simultaneously, an electric proportional valve, an electronic back pressure valve, and a pressure sensor automatically control and monitor the pressure inside the reactor until the preset pressure is reached. Simultaneously, the PLC controls the zone heating module to heat the reactor in designated zones to achieve the preset temperatures.

[0018] In the embodiments of this application, the pressure-temperature dynamic coupling device can automatically and dynamically couple and adjust the temperature and pressure of the two stages of crystal nucleus formation and crystal nucleus growth according to the synthesis stage of SiC powder, so as to achieve rapid formation and optimized growth of SiC crystal nuclei under different temperatures and pressures.

[0019] Furthermore, the synthesis system provided in this application embodiment also includes a circulating fan and a molecular sieve adsorption tower, both of which are connected to a pressure-resistant reactor. The circulating fan is electrically connected to a PCL programmable logic controller. The circulating fan is used to drive inert gases such as argon to perform forced convection circulation to the pressure-resistant reactor, facilitating rapid cooling of the pressure-resistant reactor after depressurization. The molecular sieve adsorption tower is located between the gas cylinder and the pressure-resistant reactor, and is used to adsorb the high-purity argon gas in the gas cylinder before introducing the high-purity argon gas into the pressure-resistant reactor, preventing impurities in the high-purity argon gas from affecting the quality of the SiC powder.

[0020] Based on the above-described SiC powder synthesis system based on dynamic coupling, this application also provides a SiC powder synthesis method based on dynamic coupling, the method comprising: S01: After mixing silicon powder and graphite powder, place them in a pressure-resistant reactor and evacuate.

[0021] In an argon-protected glove box, silicon powder with a purity ≥99.9% and graphite powder with a purity ≥99.9% are mixed evenly at a molar ratio of 1:1 to 1:1.5 to form a mixed powder. The mixed powder is then loaded into a graphite crucible, which is placed inside the chamber of a pressure-resistant reactor, and the reactor is sealed. A PCL programmable logic controller (PLC) controls a vacuum pump to evacuate the pressure-resistant reactor until a predetermined vacuum level <5 × 10⁻⁶ is reached. -3 Pa.

[0022] S02: Argon gas is introduced into the pressure-resistant reactor. After the core area temperature is controlled to 1750-1900℃ and the pressure to 1.2-1.5MPa by the pressure-temperature dynamic coupling device, the silicon powder and the graphite powder react for 0.5-1.5h to form initial crystal nuclei.

[0023] Once the pressure-resistant reactor reaches the predetermined vacuum level, the PCL programmable logic controller in the pressure-temperature dynamic coupling device controls the gas cylinder and electric proportional valve to fill the reactor with high-purity argon gas (≥99.999%) to atmospheric pressure. Then, the vacuum pump is controlled again to evacuate the reactor, repeating this process 3-4 times to completely remove air from the reactor, ensuring the oxygen content is ≤1 ppm, thus completing air replacement. After air replacement is complete, high-purity argon gas (≥99.999%) is introduced until the pressure sensor detects a predetermined pressure of 1.2-1.5 MPa. Simultaneously, the PCL programmable logic controller controls the zoned heating module to heat the reactor, raising the temperature in the core area to 1750-1900℃, while maintaining a longitudinal cooling gradient of 50-100℃ / m within the gradient cooling zone.

[0024] When the temperature reaches 1750-1900℃ and the pressure reaches 1.2-1.5MPa, silicon powder and graphite powder react for 0.5-1.5 hours to form initial crystal nuclei. During this process, silicon powder and graphite powder instantly sublimate into a gaseous phase under high temperature and high pressure conditions. The high pressure environment of 1.2-1.5MPa can effectively increase the diffusion coefficient and collision frequency between gaseous reactants, significantly reduce the nucleation activation energy, thereby improving mass transfer efficiency and inhibiting high-temperature decomposition. At the same time, the high temperature of 1750-1900℃ can endow silicon and carbon atoms with sufficient diffusion kinetic energy and reactivity, promoting the reaction between them. This allows silicon carbide to generate a large number of initial crystal nuclei explosively and uniformly, providing abundant "seeds" for subsequent growth.

[0025] In the embodiments of this application, during the initial crystal nucleus formation process, the temperatures of the preheating zone, the core zone, and the gradient cooling zone are 1000-1300℃, 1750-1900℃, and 1100-1400℃, respectively.

[0026] S03: After the core area temperature is controlled to 1600-1750℃ and the pressure to 0.8-1.0MPa by the pressure-temperature dynamic coupling device, the initial crystal nuclei grow for 1-3 hours. After depressurization, cooling, grinding and sieving, SiC powder is obtained.

[0027] After the reaction between silicon powder and graphite powder reaches the set time, the PCL programmable logic controller in the pressure-temperature dynamic coupling device controls the electronic back pressure valve to reduce the pressure to 0.8-1.0 MPa. At the same time, it controls the temperature of the zone heating module to reduce the temperature of the core area of ​​the pressure-resistant reactor to 1600-1850℃. At this time, the temperatures of the preheating zone, the core zone, and the gradient cooling zone are 1200-1450℃, 1600-1850℃, and 800-1200℃, respectively.

[0028] When the temperature reaches 1600-1850℃ and the pressure reaches 0.8-1.0MPa, the initial crystal nuclei grow for 1-3 hours. During this process, the decrease in temperature reduces the diffusion rate of silicon and carbon atoms, making crystal growth controllable; simultaneously, the decrease in pressure inhibits new secondary nucleation, ensuring that the reactants are concentrated on supplying existing crystal nuclei, thus promoting crystal growth. Therefore, by cooling, depressurizing, and maintaining the reaction temperature, the Oswald ripening process of SiC crystals can be effectively promoted, allowing the crystals to grow fully in a milder and more controllable environment, thereby optimizing the crystal morphology, size uniformity, and crystal integrity of the final product.

[0029] In this embodiment, the automated control of temperature, pressure, and time is achieved by a pressure-temperature dynamic coupling device according to a pre-set three-dimensional process curve of "temperature-pressure-time" to precisely switch between rapid nucleation and controllable growth processes.

[0030] After the initial crystal nuclei have grown to the set time, a pressure sensor detects the pressure inside the pressure-resistant reactor and transmits the data to the PCL programmable logic controller (PLC). The PLC compares the pressure and time with the pre-set three-dimensional process curve of temperature-pressure-time. If the pressure and time match the curve, the PLC controls the electric proportional valve and electronic back pressure valve to gradually release pressure at a rate of 0.1-0.5 MPa / min. Once the pressure drops to atmospheric pressure, the PLC controls the circulation fan and gas cylinder to start, thereby reducing the temperature inside the pressure-resistant reactor to below 80°C under an argon flow. After natural cooling to room temperature, the lumpy product is ground and then classified using airflow classification or centrifugal classification techniques to obtain SiC powder with a median particle size of 1-5 μm.

[0031] In summary, this invention achieves decoupling and optimized control of the nucleation and growth process by setting up a three-segment temperature field consisting of a preheating zone, a core high-temperature zone, and a gradient cooling zone, and by precisely controlling the overall temperature difference between the core zone and the gradient cooling zone, as well as the cooling rate within the gradient cooling zone.

[0032] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0033] Example 1 This application provides a method for synthesizing SiC powder based on dynamic coupling, the method comprising: S101: In an argon-protected glove box, silicon powder with a purity ≥99.9% and graphite powder with a purity ≥99.9% are mixed evenly at a molar ratio of 1:1.05 to form a mixed powder. The mixed powder is then loaded into a graphite crucible, which is placed inside the chamber of a pressure-resistant reactor, and the reactor is sealed. A PCL programmable logic controller (PLC) controls a vacuum pump to evacuate the pressure-resistant reactor until a predetermined vacuum level of 5 × 10⁻⁶ is reached. -3 Pa.

[0034] S102: Once the pressure-resistant reactor reaches the predetermined vacuum level, the PCL programmable logic controller in the pressure-temperature dynamic coupling device controls the gas cylinder and electric proportional valve to fill the pressure-resistant reactor with high-purity argon gas (≥99.999%) up to atmospheric pressure. Then, the vacuum pump is controlled again to evacuate the pressure-resistant reactor. This process is repeated three times to completely remove the air from the pressure-resistant reactor, ensuring that the oxygen content inside the reactor is ≤1 ppm, thus completing the air replacement. After the air replacement is complete, high-purity argon gas (≥99.999%) is introduced into the pressure-resistant reactor until the pressure sensor detects a predetermined pressure of 1.5 MPa. Simultaneously, the PCL programmable logic controller controls the zoned heating module to heat the reactor, ensuring that the temperature inside the pressure-resistant reactor reaches 1500℃ within 2 hours. Maintaining the pressure at 1.5 MPa, the temperature is raised from 1500℃ to 1800℃ within 1 hour. At this time, a preheating zone, a core zone, and a gradient cooling zone of 1000℃, 1800℃, and 1200℃ are formed from top to bottom inside the pressure-resistant reactor. The silicon powder and graphite powder react at 1800℃ and 1.5 MPa for 1 hour to form initial crystal nuclei.

[0035] S103: After the initial reaction of silicon powder and graphite powder reaches the set time, the PCL programmable logic controller in the pressure-temperature dynamic coupling device controls the electronic back pressure valve to reduce the pressure to 1.0 MPa, and simultaneously controls the temperature of the zone heating module to decrease to 1600℃. At this time, the temperatures of the preheating zone, core zone, and gradient cooling zone are 1300℃, 1600℃, and 1000℃, respectively. The initial crystal nucleus grows for 2 hours at a temperature of 1600℃ and a pressure of 1.0 MPa. When the initial crystal nucleus grows to the set time, the pressure sensor detects the pressure inside the pressure-resistant reactor and transmits it to the PCL programmable logic controller. The PCL programmable logic controller compares the pressure and time with the pre-set three-dimensional process curve of "temperature-pressure-time". If the pressure and time match the three-dimensional process curve of "temperature-pressure-time", the PCL programmable logic controller controls the electric proportional valve and the electronic back pressure valve to gradually release pressure at a rate of 0.2 MPa / min. Once the pressure is reduced to atmospheric pressure, the PCL programmable logic controller starts the circulating fan and gas cylinders to reduce the temperature inside the pressure reactor to below 80°C within 3 hours under an argon flow. After natural cooling to room temperature, the blocky product is ground and passed through a 200-mesh sieve to obtain SiC powder.

[0036] Example 2 This application provides a method for synthesizing SiC powder based on dynamic coupling. The method is the same as in Example 1, except that the temperature in S102 is 1900℃.

[0037] Example 3 This application provides a method for synthesizing SiC powder based on dynamic coupling. The method is the same as in Example 1, except that the pressure in S102 is 1.2 MPa.

[0038] Example 4 This application provides a method for synthesizing SiC powder based on dynamic coupling. The method is the same as in Example 1, except that the temperature in S103 is 1750℃.

[0039] Example 5 This application provides a method for synthesizing SiC powder based on dynamic coupling. The method is the same as in Example 1, except that the pressure in S104 is 0.8 MPa.

[0040] Comparative Example 1 This application provides a comparative example of a method for synthesizing SiC powder based on dynamic coupling, the method comprising: D101: In an argon-protected glove box, silicon powder with a purity ≥99.9% and graphite powder with a purity ≥99.9% are mixed evenly at a molar ratio of 1:1.05 to form a mixed powder. The mixed powder is then placed into a graphite boat specifically designed for atmospheric pressure quartz tube furnaces, and the graphite boat is placed in the center of the reaction chamber of the atmospheric pressure quartz tube furnace. After sealing, high-purity argon gas is continuously introduced into the reaction chamber at a flow rate of 500 sccm for 30 minutes to purge air.

[0041] D102: Under atmospheric pressure and argon flow at a rate of 100 sccm, the temperature was increased to 2100℃ at a rate of 10℃ / min. After the temperature stabilized, it was calcined at this temperature for 8 hours to complete the synthesis and grain growth of SiC. After the reaction was completed, heating was stopped, and the mixture was allowed to cool naturally to room temperature under a continuous argon flow for 24-36 hours. The block product was then ground and passed through a 200-mesh sieve to obtain SiC powder.

[0042] The purity of the SiC powder prepared in Example 1 of this application was determined by detecting the content of each element using an inductively coupled plasma mass spectrometer, as shown in Table 1.

[0043] Table 1: Detection data of each element content As shown in Table 1, the purity of the SiC powder prepared in Example 1 is 99.992%.

[0044] Furthermore, comparing the synthesis time of SiC powder prepared in Example 1 of this application and Comparative Example 1, it can be seen that the synthesis time of Comparative Example 1 is 8 hours, while the synthesis time of Example 1 of this application is approximately 4-5 hours, which significantly shortens the synthesis time and reduces energy consumption. Therefore, the synthesis method provided by the embodiments of this application can improve the crystallinity and purity of the product while reducing energy consumption.

[0045] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for synthesizing SiC powder based on dynamic coupling, characterized in that, include: After the silicon powder and graphite powder are mixed, they are placed in a pressure-resistant reactor and a vacuum is drawn. Argon gas is introduced into the pressure-resistant reactor. After the temperature of the core area is controlled at 1750-1900℃ and the pressure at 1.2-1.5MPa by a pressure-temperature dynamic coupling device, the silicon powder and the graphite powder react for 0.5-1.5h to form initial crystal nuclei. After the core area temperature is controlled to 1600-1850℃ and the pressure to 0.8-1.0MPa by the pressure-temperature dynamic coupling device, the initial crystal nuclei grow for 1-3 hours. After depressurization, cooling, grinding and sieving, SiC powder is obtained.

2. The SiC powder synthesis method based on dynamic coupling according to claim 1, characterized in that, The pressure-resistant reactor includes a preheating zone, a core zone, and a gradient cooling zone from top to bottom, and the gradient cooling zone maintains a longitudinal cooling gradient of 50-100℃ / m.

3. The SiC powder synthesis method based on dynamic coupling according to claim 2, characterized in that, During the initial crystal nucleus formation process, the temperatures of the preheating zone, the core zone, and the gradient cooling zone are 1000-1300℃, 1750-1900℃, and 1100-1400℃, respectively.

4. The SiC powder synthesis method based on dynamic coupling according to claim 2, characterized in that, During the initial crystal nucleus growth process, the temperatures of the preheating zone, the core zone, and the gradient cooling zone are 1200-1450℃, 1600-1850℃, and 800-1200℃, respectively.

5. The SiC powder synthesis method based on dynamic coupling according to claim 2, characterized in that, The pressure relief rate is 0.1-0.5 MPa / min, and the sieve mesh size is 150-400 mesh.

6. The SiC powder synthesis method based on dynamic coupling according to claim 2, characterized in that, The vacuum level inside the pressure-resistant reactor is <5×10⁻⁶. -3 Pa.

7. A SiC powder synthesis system based on dynamic coupling, characterized in that, Implement the synthesis method according to any one of claims 1-6; The synthesis system includes: a pressure-resistant reactor, a pressure-temperature dynamic coupling device, and a vacuum pump; wherein, the pressure-temperature dynamic coupling device includes a pressure sensor located inside the pressure-resistant reactor, as well as a zoned heating module, a PCL programmable logic controller, an electric proportional valve, an electronic back pressure valve, and a gas cylinder, all located outside the pressure-resistant reactor; The pressure-resistant reactor is connected to the vacuum pump, the gas cylinder, the electric proportional valve, and the electronic back pressure valve, respectively; the zoned heating module is attached to the outside of the pressure-resistant reactor; The PCL programmable logic controller is electrically connected to the pressure sensor, the zone heating module, the electric proportional valve, the electronic back pressure valve, the vacuum pump, and the gas cylinder.

8. The SiC powder synthesis system based on dynamic coupling according to claim 7, characterized in that, The pressure-resistant reactor is a nickel-based alloy pressure-resistant reactor, and the interior of the pressure-resistant reactor is coated with an Al2O3 ceramic coating.

9. The SiC powder synthesis system based on dynamic coupling according to claim 7, characterized in that, The system also includes a circulating fan and a molecular sieve adsorption tower connected to the pressure-resistant reactor, respectively. The PCL programmable logic controller is electrically connected to the circulating fan, and the molecular sieve adsorption tower is located between the gas cylinder and the pressure-resistant reactor.

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