A method and apparatus for synthesizing liquid-phase silicon carbide powder

Abstract

This invention provides a liquid-phase silicon carbide powder synthesis method and apparatus, relating to the field of silicon carbide powder synthesis technology. The liquid-phase silicon carbide powder synthesis method involves controlling multiple graphite sheets arranged along an axial direction to extend into molten silicon, driving the graphite sheets and crucible to rotate, thereby forming a dense silicon carbide crystalline material. The rotation direction of the crucible is opposite to that of the graphite sheets, thus creating convection. This accelerates the penetration of molten silicon into the porous graphite sheets, allowing continuous molten silicon to penetrate into the graphite sheets, reducing the formation of pores and defects, and facilitating in-situ synthesis. Furthermore, a trace amount of carbon-silicon reaction also occurs on the inner surface of the crucible. The synthesized product is located in a high-temperature zone; under the influence of the temperature gradient, carbon atoms transfer to the low-temperature zone generated by convection on the graphite sheets, crystallizing on the graphite sheet surface to form large, high-density silicon carbide crystalline materials.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide powder synthesis technology, and more specifically, to a liquid-phase silicon carbide powder synthesis method and apparatus. Background Technology

[0002] Silicon carbide powder serves as a crucial bridge connecting basic raw materials with high-end applications. Its quality not only affects the mechanical, thermal, and electrical properties of the material but also determines the yield and reliability of semiconductor devices. Currently, high-purity, low-nitrogen, and uniformly sized micron-sized SiC powder is a core requirement for industry development.

[0003] The inventors discovered that some synthetic silicon carbide powders in related technologies have relatively small particle sizes. Powders with larger particle sizes tend to have lower densities. Summary of the Invention

[0004] The present invention aims to provide a liquid-phase silicon carbide powder synthesis method and apparatus, which can produce high-density, large-particle-size silicon carbide powder, specifically silicon carbide powder with a particle size greater than 2000 μm and a relatively high density.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a method for synthesizing liquid-phase silicon carbide powder, the method comprising:

[0007] The raw materials, including silicon, are filled into the crucible, and the crucible is placed in the furnace cavity.

[0008] Heat the crucible to melt the silicon material;

[0009] Multiple graphite sheets arranged along the axial direction are controlled to extend into the molten silicon and drive the multiple graphite sheets and the crucible to rotate, so as to form a dense silicon carbide crystal. The rotation axis of the crucible is coaxial with the rotation axis of the multiple graphite sheets, and the rotation direction of the crucible is opposite to the rotation direction of the graphite sheets.

[0010] In an optional implementation, the step of heating the crucible to melt the silicon material includes:

[0011] The furnace cavity is evacuated to bring it to a first preset pressure P1, and the crucible is heated to the impurity removal temperature T1 and held for a first preset time t1.

[0012] A rare gas is introduced into the furnace cavity, and the furnace cavity is brought to a second preset pressure P2;

[0013] Heat the crucible to the collapse temperature T2 and maintain it for the second preset time t2;

[0014] Air is drawn into the furnace cavity, and the furnace cavity is brought to the third preset pressure P3;

[0015] A rare gas is introduced into the furnace cavity, and the furnace cavity is brought to a fourth preset pressure P4;

[0016] Heat the crucible to the melting temperature T3;

[0017] Among them, T3 > T2 > T1, P4 > P3 > P1, and P2 > P3 > P1.

[0018] In an optional implementation, P1 is 10⁻⁴ to 10⁻³ Pa, T1 is 1000 to 1350 °C, and t1 is 9 to 11 h;

[0019] P2 is 20~80 kPa;

[0020] T2 is 1400~1600℃, t2 is 1.5~2.5h;

[0021] P3 is 1~5 Pa, P4 is 50~80 kPa, and T3 is 1600~1800℃.

[0022] In an optional embodiment, the step of controlling the insertion of a plurality of graphite sheets spaced apart along the axial direction into the molten silicon further includes:

[0023] After the steps of filling the furnace cavity with rare gas and bringing the furnace cavity to the fourth preset pressure P4, the graphite sheets are controlled to descend and the lower graphite sheets are made to have a preset gap with the raw material, and the graphite sheets are controlled to rotate at the first preset speed V1.

[0024] After the step of heating the crucible to the melting temperature T3, the method further includes controlling the crucible to rotate at a second preset speed V2 for a third preset time t3.

[0025] Multiple graphite sheets are controlled to continue descending, with the lower graphite sheet positioned above the upper surface of the raw material, and this continues for a fourth preset time t4.

[0026] In an optional implementation, the step of controlling a plurality of graphite sheets spaced apart along the axial direction to extend into the molten silicon includes:

[0027] Multiple graphite sheets are controlled to slowly rotate and sink downwards into the molten silicon. The crucible is controlled to rotate along the first direction at a third preset speed V3. Multiple graphite sheets are controlled to rotate along the second direction at a fourth preset speed V4. The crucible temperature is at the melting temperature T3 and is maintained for a fifth preset time t5.

[0028] The crucible is controlled to rotate along the second direction at a third preset speed V3, and multiple graphite sheets are controlled to rotate along the first direction at a fourth preset speed V4 for a sixth preset time t6. The first direction is opposite to the second direction in order to form a dense silicon carbide crystal.

[0029] In an optional embodiment, the method further includes the following steps before filling the furnace cavity with rare gas and bringing the furnace cavity to a fourth preset pressure P4:

[0030] Rare gas is repeatedly injected into the furnace cavity, and the furnace cavity is brought to a second preset pressure P2. Then, gas is extracted from the furnace cavity, and the furnace cavity is brought to a third preset pressure P3.

[0031] In an optional implementation, multiple graphite sheets are fitted onto a carbon rod.

[0032] In a second aspect, the present invention provides a liquid-phase silicon carbide powder synthesis apparatus, which generates dense silicon carbide powder by any of the liquid-phase silicon carbide powder synthesis methods described in the foregoing embodiments, comprising:

[0033] Furnace cavity;

[0034] A rotating device is installed inside the furnace cavity;

[0035] A crucible, which is mounted on a rotating device and can be rotated under the drive of the rotating device, is used to contain raw materials;

[0036] A rotary lifting device is installed in the furnace cavity. The rotary lifting device is connected to a connector that extends into the furnace cavity. The connector is connected to a carbon rod. Multiple graphite sheets are sleeved on the carbon rod. The rotary lifting device is used to drive the multiple graphite sheets to move in the height direction and can drive the multiple graphite sheets to rotate.

[0037] In an optional embodiment, the furnace cavity includes a first chamber, a second chamber, and a third chamber arranged sequentially along the height direction, wherein the height of the first chamber is higher than that of the second chamber, and the first chamber is connected to the second chamber;

[0038] A tilting plate valve is installed in the second chamber. The tilting plate valve can rotate in the second chamber to separate or connect the second chamber with the third chamber.

[0039] The second chamber also has a sealed chamber door for loading and unloading materials.

[0040] In an optional embodiment, the furnace cavity is also equipped with a ventilation system for filling the furnace cavity with gas and for evacuating the furnace cavity.

[0041] And / or, the rotary lifting device includes a rotary drive and a lifting member, the lifting member being connected to the rotary drive to drive the rotary drive to move in the height direction, and the rotary drive being connected to a connecting member.

[0042] The beneficial effects provided by the embodiments of the present invention include: The embodiments of the present invention provide a method and apparatus for synthesizing liquid-phase silicon carbide powder. The liquid-phase silicon carbide powder synthesis method synthesizes silicon carbide powder by controlling multiple graphite sheets arranged along the axial direction to extend into the molten silicon, and driving the multiple graphite sheets and crucible to rotate, thereby forming a dense silicon carbide crystal. The rotation direction of the crucible is opposite to the rotation direction of the graphite sheets, thereby forming convection, which can accelerate the penetration of molten silicon into the porous graphite sheets, allowing continuous molten silicon to penetrate into the graphite sheets, reducing the formation of pores and defects, and causing an in-situ synthesis reaction. Furthermore, a trace amount of carbon-silicon reaction also occurs on the inner surface of the crucible. The synthesized product is located in a high-temperature zone; under the action of the temperature gradient, carbon atoms transfer to the low-temperature zone generated by the convection of the graphite sheets, crystallizing on the surface of the graphite sheets to form large and dense silicon carbide crystals. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the steps of the liquid-phase silicon carbide powder synthesis method provided in this embodiment;

[0045] Figure 2 This is a flowchart of the steps before S4 in the liquid-phase silicon carbide powder synthesis method provided in this embodiment;

[0046] Figure 3 This is a flowchart of step S4 in the liquid-phase silicon carbide powder synthesis method provided in this embodiment;

[0047] Figure 4 This is a schematic diagram of the liquid-phase silicon carbide powder synthesis device provided in this embodiment;

[0048] Figure 5 This is a morphology diagram of the silicon carbide crystal material synthesized by the liquid-phase silicon carbide powder synthesis method provided in this embodiment and located on the connector.

[0049] Figure 6 This is a morphology diagram of the silicon carbide crystalline material synthesized by the liquid-phase silicon carbide powder synthesis method provided in this embodiment and located at the bottom of the connector.

[0050] Figure 7 for Figure 5 Raman plot of the obtained sample powder;

[0051] Figure 8 for Figure 6 Raman plot of the obtained sample powder;

[0052] Figure 9 This is a sample of silicon carbide powder obtained by crushing silicon carbide powder crystals synthesized by the liquid-phase silicon carbide powder synthesis method provided in this embodiment.

[0053] Figure 10 This is one of the dimension diagrams of one of the silicon carbide powders obtained after crushing;

[0054] Figure 11 This is the second schematic diagram showing the dimensions of one of the silicon carbide powders obtained after crushing.

[0055] Icons: 1-Liquid-phase silicon carbide powder synthesis device; 100-Furnace cavity; 110-First chamber; 120-Second chamber; 130-Third chamber; 140-Tilting plate valve; 150-Sealed chamber door; 200-Rotating lifting device; 210-Rotating drive component; 220-Lifting component; 230-Connecting component; 310-Carbon rod; 320-Graphite sheet; 400-Ventilation system; 500-Rotating device; 600-Crucible; 2-Raw material. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0058] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0059] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0060] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0061] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0062] In related technologies, most silicon carbide powder synthesis methods employ a high-temperature self-propagating process, where carbon powder and silicon powder are synthesized into silicon carbide powder at high temperatures. The resulting silicon carbide powder has a small particle size, for example, less than 2000 μm. Alternatively, the powder may have a large particle size but low density, for example, a particle size of 2000-5000 μm but a density of 1.0 g / cm³. 3 The amount of silicon carbide powder on the left and right sides restricts the growth of large-size, thick silicon carbide crystals.

[0063] To address the aforementioned problems, embodiments of the present invention provide a liquid-phase silicon carbide powder synthesis method, which can prepare silicon carbide powder with a particle size greater than 2000 μm and a high density, for example, greater than 1.5 g / cm³. 3 This method is used to grow large-particle, high-density silicon carbide powder, resulting in a dense silicon carbide powder that avoids the defects of small particle size and low density caused by high-temperature self-propagating silicon carbide powder synthesis. Please refer to [reference needed]. Figure 1 The present invention provides a method for synthesizing liquid-phase silicon carbide powder, comprising the following steps:

[0064] S1, fill the crucible 600 with raw material 2, which includes silicon material, and place the crucible 600 in the furnace cavity 100. Here, silicon material can be understood as silicon powder or silicon block.

[0065] It is understandable that the crucible 600 is placed in the furnace cavity 100 to reduce the interference of the external environment on the synthesis of silicon carbide crystals.

[0066] S2, Heat the crucible to 600 to melt the silicon material.

[0067] S4, control multiple graphite sheets 320 arranged along the axial direction to extend into the silicon liquid, and drive the multiple graphite sheets 320 and the crucible 600 to rotate, so as to form a dense silicon carbide crystal material. The rotation axis of the crucible 600 is coaxial with the rotation axis of the multiple graphite sheets 320, and the rotation direction of the crucible 600 is opposite to the rotation direction of the graphite sheets 320.

[0068] It should be noted that the graphite sheet 320 in this embodiment is made of porous graphite. The porous graphite sheet 320 provides a uniformly distributed carbon source, avoiding local carbon excess or deficiency.

[0069] Because the rotation direction of the graphite sheet 320 is opposite to that of the crucible 600, convection is formed. This accelerates the penetration of molten silicon into the porous graphite sheet 320 and also removes the heat generated by the reaction, preventing localized overheating. This convection allows continuous molten silicon to penetrate into the graphite sheet 320, reducing the formation of pores and defects, thus forming a high-density silicon carbide crystalline material. Furthermore, the counter-rotation enhances convection, resulting in a more uniform temperature and concentration field and reducing component segregation.

[0070] Furthermore, the porous graphite sheet 320 is infiltrated by the molten silicon, resulting in an in-situ synthesis reaction. Additionally, a trace amount of carbon-silicon reaction also occurs on the inner surface of the crucible 600. The synthesized material is located in a high-temperature zone, and under the influence of the temperature gradient, carbon atoms transfer to the low-temperature zone generated by convection in the graphite sheet 320, crystallizing on the surface of the graphite sheet 320 to form large, high-density silicon carbide crystals.

[0071] For forming large blocks of silicon carbide crystals, the particle size can be freely controlled according to the crushing method, which facilitates the formation of large silicon carbide powder.

[0072] Understandably, high-density crystalline materials mean that the internal crystal lattice of the particles is complete, with fewer pores and impurity inclusions. The dense structure is more stable, has stronger resistance to high-temperature decomposition, and is less likely to precipitate carbon during sublimation. The dense crystalline structure has good stability, thus effectively reducing the internal free carbon content and the tendency to decompose at high temperatures.

[0073] It should be noted that, in order to prevent the molten silicon from splashing out during the rotation of the crucible 600, the raw material 2 in the crucible 600 shall not exceed 2 / 3 of the volume of the crucible 600.

[0074] Please refer to Figure 2 In detail, in this embodiment, the step of heating the crucible 600 to melt the silicon powder includes:

[0075] S210, evacuate the furnace chamber 100 to bring it to a first preset pressure P1, then heat the crucible 600 to the impurity removal temperature T1 and maintain it for a first preset time t1. It should be noted that heating the crucible 600 to the impurity removal temperature T1 can be understood as allowing some impurities in the raw material 2 to vaporize and be discharged at this temperature, thereby improving the purity of the synthesized silicon carbide crystal. Maintaining this temperature for the first preset time t1 ensures thorough impurity removal.

[0076] S220, rare gas is introduced into furnace chamber 100 and furnace chamber 100 is brought to a second preset pressure P2.

[0077] S230, heat the crucible 600 to the collapse temperature T2 and maintain it for a second preset time t2. It should be noted that the collapse temperature can be understood as the temperature at which part of the silicon material in the crucible 600 begins to melt and the surface of the material collapses. In order to avoid the rapid rise in temperature and the splashing caused by the collapse of the material surface, it is necessary to maintain the collapse temperature T2 for the second preset time t2.

[0078] S240, then evacuate the furnace chamber 100 and bring the furnace chamber 100 to the third preset pressure P3. It can be understood that after injecting rare gas into the furnace chamber 100, the furnace chamber 100 is then evacuated to remove impurities, thereby ensuring the cleanliness of the synthesized silicon carbide crystals.

[0079] It also includes S250, which injects rare gas into the furnace chamber 100 and puts the furnace chamber 100 at a fourth preset pressure P4.

[0080] S260, heat the crucible 600 to the melting temperature T3. It should be noted that the melting temperature T3 can be understood as the temperature at which the silicon material completely melts into liquid silicon.

[0081] Understandably, in order to fully remove impurities from the furnace cavity 100, steps S220 and S240 can be performed multiple times before S250 to remove impurities from the furnace cavity 100. For example, this process can be repeated 2 to 5 times to fully remove impurities from the furnace cavity 100.

[0082] Understandably, to reduce silicon material loss due to silicon vaporization under low pressure, rare gas is injected into furnace chamber 100 before S260, and furnace chamber 100 is placed at a fourth preset pressure P4. Wherein, T3 > T2 > T1, P4 > P3 > P1, and P2 > P3 > P1.

[0083] In detail, P1 above is 10. -4 ~10 -3The rare gases are defined as follows: P1 = 1000~1350℃, t1 = 9~11h; P2 = 20~80kPa, T2 = 1400~1600℃, t2 = 1.5~2.5h; P3 = 1~5Pa; P4 = 50~80kPa. The rare gases mentioned above can be understood as helium or other types of rare gases.

[0084] For example, the step of heating the crucible 600 to melt the silicon powder includes:

[0085] Evacuate the furnace chamber 100 to bring it to a temperature of 10°C. -4 ~10 -3 Under the condition of Pa, the crucible is heated to the impurity removal temperature of 1000~1350℃ and maintained for the first preset time of 10h.

[0086] Helium gas is then injected into the furnace chamber 100 to bring the pressure inside the furnace chamber 100 to 20~80 kPa.

[0087] The crucible was then heated to 1400-1600℃ and held for 2 hours.

[0088] Then the helium gas is shut off and the furnace chamber 100 is evacuated to bring the pressure inside the furnace chamber 100 to 1~5 Pa.

[0089] To ensure the cleanliness of the furnace cavity 100 and to fully remove impurities from the furnace cavity 100, the air filling and evacuation steps can be repeated multiple times.

[0090] Helium gas is then injected into the furnace chamber 100 to bring the pressure inside the furnace chamber 100 to 50~80 kPa.

[0091] This causes the temperature of the crucible 600 to rise to 1600~1800℃, thereby completely melting the silicon material into liquid silicon.

[0092] In detail, in this embodiment, before the step of controlling the multiple graphite sheets 320 spaced apart along the axial direction to extend into the molten silicon, the following steps are included:

[0093] S310, control the multiple graphite sheets 320 to descend and make the lower graphite sheet 320 have a preset gap with the raw material 2, and control the multiple graphite sheets 320 to rotate at a first preset speed V1. It should be noted that S310 is after the above steps S250 and before S260.

[0094] This achieves the preheating of multiple graphite sheets 320. It is understandable that by driving multiple graphite sheets 320 to rotate at a first preset speed V1, it can be ensured that the preheating of each part of the graphite sheets 320 is relatively uniform, avoiding the risk of the graphite sheets 320 breaking due to thermal expansion and contraction when they directly enter the high-temperature silicon liquid from a low temperature state.

[0095] Following S260, S320 further includes controlling the crucible 600 to rotate at a second preset speed V2 for a third preset time t3. Understandably, at this time, the rotation direction of the crucible 600 is opposite to the rotation direction of the graphite sheet 320.

[0096] S330, then control the multiple graphite sheets 320 to continue to descend and position the lower graphite sheet 320 above the upper surface of the raw material 2, and continue for a fourth preset time t4. At this time, after the initial preheating of the graphite sheet 320 by S310 and S320, the graphite sheet 320 is lowered to continue preheating the graphite sheet 320, so that the temperature of the graphite sheet 320 rises slowly, avoiding the situation where the graphite sheet 320 is damaged due to rapid heating.

[0097] Where t4 can be 0.5~1.5h.

[0098] Please refer to Figure 3 After time t4, the graphite sheets 320 are preheated. Multiple graphite sheets 320 are then submerged in the molten silicon. Specifically, the steps for submerging multiple graphite sheets 320 spaced apart along the axial direction into the molten silicon include:

[0099] S410, control multiple graphite sheets 320 to slowly rotate and sink downwards into the molten silicon, control the crucible 600 to rotate along the first direction at a third preset speed V3, control multiple graphite sheets 320 to rotate along the second direction at a fourth preset speed V4, the temperature of the crucible 600 is at the melting temperature T3, and continues for a fifth preset time t5.

[0100] S420, control the crucible 600 to rotate along the second direction and at a third preset speed V3, control multiple graphite sheets 320 to rotate along the first direction and at a fourth preset speed V4, and continue for a sixth preset time t6. The first direction is opposite to the second direction, so as to form a dense silicon carbide crystal material.

[0101] For example, the first direction can be understood as clockwise, and the second direction can be understood as counterclockwise.

[0102] Understandably, after controlling the crucible 600 to rotate in the first direction and causing the multiple graphite sheets 320 to rotate in the second direction, and continuing for a fifth preset time t5, the crucible 600 and the multiple graphite sheets 320 are flipped so that the crucible 600 rotates in the second direction and the multiple graphite sheets 320 rotate in the first direction, and this continues for a sixth preset time t6.

[0103] In other words, after the crucible 600 and the multiple graphite sheets 320 have been continuously rotating in opposite directions for a certain period of time, the crucible 600 and the multiple graphite sheets 320 are controlled to rotate in opposite directions while still maintaining the crucible 600 and the multiple graphite sheets 320 rotating in opposite directions. This can ensure a more uniform formation of silicon carbide crystals and avoid the formation of deformed crystals.

[0104] In detail, to ensure the cleanliness of the formed large and dense silicon carbide crystals, multiple graphite sheets 320 are mounted on the carbon rod 310 to avoid introducing other impurities during the formation of large and dense silicon carbide crystals.

[0105] This invention also provides a liquid-phase silicon carbide powder synthesis apparatus 1, used to generate dense silicon carbide powder by the above-described liquid-phase silicon carbide powder synthesis method.

[0106] Please refer to Figure 4 The liquid-phase silicon carbide powder synthesis device 1 provided in this embodiment includes a furnace chamber 100, a rotating device 500, a crucible 600, and a rotating lifting device 200.

[0107] The rotating device 500 is located inside the furnace cavity 100. The crucible 600 is installed on the rotating device 500 and can rotate under the drive of the rotating device 500. The crucible 600 is used to hold the raw material 2. The rotating lifting device 200 is installed in the furnace cavity 100. The rotating lifting device 200 is connected to the connecting member 230 and the connecting member 230 extends into the furnace cavity 100. The connecting member 230 is connected to the carbon rod 310. Multiple graphite sheets 320 are sleeved on the carbon rod 310. The rotating lifting device 200 is used to drive the multiple graphite sheets 320 to move in the height direction and can also drive the multiple graphite sheets 320 to rotate.

[0108] Understandably, raw material 2 can be loaded into crucible 600, and the volume of raw material 2 can occupy 2 / 3 of the volume of crucible 600. Then, crucible 600 is placed into rotating device 500, and multiple graphite sheets 320 are connected in series through carbon rod 310. The carbon rod 310 is connected to connector 230, which can be made of molybdenum or tungsten. Connector 230 is connected to rotating lifting device 200.

[0109] In detail, in this embodiment, the furnace cavity 100 includes a first chamber 110, a second chamber 120 and a third chamber 130 arranged sequentially along the height direction. The height of the first chamber 110 is higher than that of the second chamber 120. The first chamber 110 is connected to the second chamber 120. A flip-plate valve 140 is provided in the second chamber 120. The flip-plate valve 140 can rotate in the second chamber 120 to separate or connect the second chamber 120 and the third chamber 130.

[0110] A sealed chamber door 150 is also provided outside the second chamber 120. The sealed chamber door 150 is used to open or close the second chamber 120, and then to take out or put in materials. The rotating device 500 is installed in the third chamber 130.

[0111] Understandably, the flip-plate valve 140 in the second chamber 120 can separate or open the connection between the third chamber 130 and the second chamber 120. The carbon rod 310 or the reaction-synthesized silicon carbide crystal material can be moved into the second chamber 120 by the rotating lifting device 200. This makes it easier for operators to take out large pieces of high-density silicon carbide crystal material or install graphite sheets 320 on the carbon rod 310 through the sealed chamber door 150.

[0112] Moreover, after the graphite sheet 320 is installed, the rotating lifting device 200 can move multiple graphite sheets 320 into the first chamber 110, and then control the rotating plate valve to open to connect the second chamber 120 and the third chamber 130, which can prevent the rotating plate valve from colliding with the graphite sheet 320 during the opening process.

[0113] In detail, the furnace cavity 100 is also equipped with a ventilation system 400, which is used to fill the furnace cavity 100 with air and to evacuate the furnace cavity 100. Optionally, the ventilation system 400 can be connected to the second chamber 120 or the first chamber 110.

[0114] Optionally, the rotary lifting device 200 includes a rotary drive 210 and a lifting member 220. The lifting member 220 is connected to the rotary drive 210 to drive the rotary drive 210 to move in the height direction. The rotary drive 210 is connected to the connecting member 230.

[0115] It should be noted that a heating element can be provided outside or inside the third chamber 130 to heat the crucible 600 inside the third chamber 130, thereby melting the raw material 2 inside the crucible 600.

[0116] The working principle of the liquid-phase silicon carbide powder synthesis device 1 provided in this embodiment is described below:

[0117] First, raw material 2 can be loaded into crucible 600, and the volume of raw material 2 can occupy 2 / 3 of the volume of crucible 600.

[0118] The crucible 600 is then placed into the rotating device 500, and multiple graphite sheets 320 are connected in series via carbon rods 310. The carbon rods 310 are then connected to the connector 230. The carbon rods 310 and the connector 230 can be connected within the second chamber 120 for easy installation by the operator. The connector 230 can be made of molybdenum or tungsten and is connected to the rotating drive 210.

[0119] The operator can raise multiple graphite sheets 320 into the first chamber 110 and open the flip valve 140 to connect the second chamber 120 and the third chamber 130, which can prevent the rotary valve from colliding with the graphite sheets 320 during the opening process.

[0120] Then, the ventilation system 400 evacuates the chamber to bring the furnace chamber 100 to a state of 10°C. -4 ~10 -3 Under the condition of Pa, the crucible is heated to the impurity removal temperature of 1000~1350℃ and maintained for the first preset time of 10h.

[0121] Helium gas is then injected into the furnace chamber 100 through the ventilation system 400 to bring the pressure inside the furnace chamber 100 to 20~80 kPa.

[0122] The crucible 600 is then heated to 1400~1600℃ using a heating element and maintained for 2 hours.

[0123] Then, the filling of the chamber with helium is stopped by the ventilation system 400, and the furnace chamber 100 is evacuated by the ventilation system 400 so that the pressure inside the furnace chamber 100 is 1~5pa.

[0124] In order to improve the cleanliness of the furnace cavity 100 and fully remove impurities from the furnace cavity 100, the gas filling and evacuation steps can be repeated multiple times.

[0125] Then, helium gas is injected into the furnace chamber 100 through the ventilation system 400 to make the pressure inside the furnace chamber 100 reach 50~80 kPa.

[0126] Then, the rotating lifting device 200 drives multiple graphite sheets 320 to move downwards, and positions the lowermost graphite sheet 320 at the connection between the second chamber 120 and the third chamber 130. The rotation speed of the multiple graphite sheets 320 is controlled at 10 r / min to ensure that the multiple graphite sheets 320 are preheated evenly.

[0127] The temperature of crucible 600 is then raised to 1600~1800℃, thereby completely melting the silicon material into liquid silicon. Crucible 600 is then rotated at a speed of 5r / min by rotating device 500, with the rotation direction of crucible 600 being opposite to that of graphite sheet 320, and this process is continued for 2 hours.

[0128] Then, the rotating lifting device 200 drives multiple graphite sheets 320 to continue to descend, and the multiple graphite sheets 320 are located in the third chamber 130. The graphite sheet 320 at the bottom of the multiple graphite sheets 320 has a gap with the upper surface of the raw material 2 in the crucible 600, and the graphite sheets 320 are further preheated for 1 hour.

[0129] Then, the rotating lifting device 200 drives multiple graphite sheets 320 to slowly rotate and sink downwards into the molten silicon. The crucible 600 is controlled to rotate clockwise at a speed of 1~5 r / min, and the multiple graphite sheets 320 are controlled to rotate counterclockwise at a speed of 1~10 r / min. The temperature of the crucible 600 is maintained at 1600~1800℃ for 15 hours. During this process, the amount of crystallization of the graphite sheets 320 is slow and controllable (due to the convection effect of the reverse rotation speed, the temperature at the graphite sheets 320 is relatively low, at which point two synthesis reactions occur: 1. The graphite sheets 320, made of porous graphite, are penetrated by the molten silicon, and an in-situ synthesis reaction occurs; 2. A trace amount of carbon-silicon reaction occurs on the inner surface of the crucible 600. The synthesized product is in a high-temperature zone. Under the action of the temperature gradient, carbon-silicon atoms transfer to the low-temperature zone generated by the convection of the graphite sheets 320, and crystallize on the surface of the graphite sheets 320 to form silicon carbide crystals).

[0130] The crucible 600 is then controlled to rotate counterclockwise at a speed of 1-5 r / min via the rotating device 500, while multiple graphite sheets 320 are controlled to rotate clockwise at a speed of 1-10 r / min for 15 hours. After the reaction is complete, a large block of high-density silicon carbide crystals is obtained. The silicon carbide crystals are then slowly lifted by the rotating lifting device 200 to detach them from the molten silicon. At this time, the connecting piece 230 rotates at a speed of 1-5 r / min to accelerate the cooling of the silicon carbide crystals. After cooling for 2-5 hours, the silicon carbide crystals are lifted into the first chamber 110 via the rotating lifting device 200.

[0131] Then, the flip valve 140 is controlled to flip and close the second chamber 120 and the third chamber 130, and then helium gas is injected into the second chamber 120 through the ventilation system 400 until the second chamber 120 reaches atmospheric pressure.

[0132] Then, the sealed chamber door 150 of the second chamber 120 is opened, and the rotating lifting device 200 is lowered to lower the silicon carbide crystal material, making it easier for the user to remove the silicon carbide crystal material. Since the obtained silicon carbide crystal material is large and dense, silicon carbide powder of the required particle size can be obtained by crushing the silicon carbide crystal material.

[0133] Then the graphite rod and multiple graphite sheets 320 can be reinstalled, and the above steps can be repeated to continue synthesizing silicon carbide crystals until the silicon liquid in the crucible 600 is completely consumed.

[0134] See also Figures 5-6 Therefore, it can be seen that the liquid-phase silicon carbide powder synthesis method provided in this embodiment can obtain large and high-density silicon carbide crystals, and combined with... Figures 7-8Raman plots show that the silicon carbide crystals obtained by the liquid-phase silicon carbide crystal synthesis method provided in this embodiment are 3C-SiC, which has fewer impurity peaks, a high signal-to-noise ratio, high crystallinity, a single crystal form, and high purity.

[0135] Please refer to Figures 9-11 The silicon carbide crystalline material synthesized by the liquid-phase silicon carbide powder synthesis method provided in this embodiment has a particle size significantly larger than 2000um after crushing. It should be noted that the particle size of the silicon carbide crystalline material can be freely controlled according to the crushing method to obtain large-particle-size silicon carbide powder, for example, the particle size can reach 10000-20000um.

[0136] In summary, the embodiments of the present invention provide a method and apparatus for synthesizing liquid-phase silicon carbide powder. The liquid-phase silicon carbide powder synthesis method involves controlling multiple graphite sheets 320 arranged along an axial direction to extend into the molten silicon and drive the multiple graphite sheets 320 and crucible 600 to rotate, thereby forming a dense silicon carbide crystal. The rotation axis of the crucible 600 is coaxial with the rotation axes of the multiple graphite sheets 320, and the rotation direction of the crucible 600 is opposite to the rotation direction of the graphite sheets 320, thus forming convection. This accelerates the penetration of molten silicon into the porous graphite sheets 320, allowing continuous molten silicon to penetrate into the graphite sheets 320, reducing the formation of pores and defects, and enabling an in-situ synthesis reaction. Furthermore, a small amount of carbon-silicon reaction will also occur on the inner surface of the crucible 600. The synthesized material is located in the high-temperature zone. Under the action of the temperature gradient, carbon atoms are transferred to the low-temperature zone generated by convection in the graphite sheet 320. Large and high-density silicon carbide crystals are formed on the surface of the graphite sheet 320. The particle size of the silicon carbide powder obtained by crushing can be freely controlled according to the crushing method.

[0137] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the synthesis of a liquid phase silicon carbide powder, characterized in that, The method comprises: filling raw material (2) in a crucible (600), the raw material (2) comprising silicon material, and placing the crucible (600) in a furnace chamber (100); heating the crucible (600) to melt the silicon material; controlling multiple graphite pieces (320) arranged along an axial direction to extend into the silicon liquid, the step of controlling the multiple graphite pieces (320) arranged along the axial direction to extend into the silicon liquid comprising: controlling the multiple graphite pieces (320) to rotate slowly and sink into the silicon liquid, controlling the crucible (600) to rotate along a first direction at a third preset speed V3, controlling the multiple graphite pieces (320) to rotate along a second direction at a fourth preset speed V4, the temperature of the crucible (600) being at a melting temperature T3, and lasting for a fifth preset time t5; controlling the crucible (600) to rotate along the second direction at the third preset speed V3, controlling the multiple graphite pieces (320) to rotate along the first direction at the fourth preset speed V4, and lasting for a sixth preset time t6, the first direction being opposite to the second direction, to form dense silicon carbide crystalline material, the rotation axis of the crucible (600) being coaxial with the rotation axis of the multiple graphite pieces (320), the graphite pieces (320) being made of porous graphite.

2. The liquid phase silicon carbide powder synthesis process of claim 1 wherein, The step of heating the crucible (600) to melt the silicon material comprises: vacuumizing the furnace chamber (100), so that the furnace chamber (100) is at a first preset pressure P1, heating the crucible (600) to a temperature T1 for removing impurities, and lasting for a first preset time t1; filling rare gas into the furnace chamber (100), so that the furnace chamber (100) is at a second preset pressure P2; heating the crucible (600) to a temperature T2 for collapsing material, and lasting for a second preset time t2; pumping gas out of the furnace chamber (100), so that the furnace chamber (100) is at a third preset pressure P3; filling rare gas into the furnace chamber (100), so that the furnace chamber (100) is at a fourth preset pressure P4; heating the crucible (600) to a melting temperature T3; wherein T3>T2>T1, P4>P3>P1, and P2>P3>P1.

3. The method according to claim 2, wherein: P1 is 10 -4 ~10 -3 pa, T1 is 1000-1350°C, and t1 is 9-11 h. P2 is 20-80 kPa; T2 is 1400-1600 ℃, and t2 is 1.5-2.5 h; P3 is 1-5 Pa, P4 is 50-80 kPa, and T3 is 1600-1800 ℃.

4. The method according to claim 2, wherein Before the step of controlling the multiple graphite pieces (320) arranged along an axial direction to extend into the silicon liquid, the method further comprises: after the step of filling rare gas into the furnace chamber (100), so that the furnace chamber (100) is at a fourth preset pressure P4, controlling the multiple graphite pieces (320) to descend and have a preset gap between the lower graphite pieces (320) and the raw material (2), and controlling the multiple graphite pieces (320) to rotate at a first preset speed V1. After the step of heating the crucible (600) to a melting temperature T3, the method further comprises controlling the crucible (600) to rotate at a second preset speed V2 for a third preset time t3. The method further comprises controlling the plurality of graphite sheets (320) to continue to descend and to have the lower graphite sheets (320) above the upper surface of the raw material (2) for a fourth preset time t4.

5. The method according to claim 2, wherein Before the step of filling the furnace chamber (100) with a rare gas and setting the furnace chamber (100) to a fourth preset pressure P4, the method further comprises: The method further comprises repeatedly performing the steps of filling the furnace chamber (100) with a rare gas and setting the furnace chamber (100) to a second preset pressure P2, and pumping the furnace chamber (100) and setting the furnace chamber (100) to a third preset pressure P3.

6. The method of claim 1, wherein: The plurality of graphite sheets (320) are sleeved on the carbon rods (310).

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