CN117486615B - Method for preparing SiC ceramic and composite material by vacuum microgravity suspension sintering - Google Patents

Method for preparing SiC ceramic and composite material by vacuum microgravity suspension sintering Download PDF

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CN117486615B
CN117486615B CN202311852118.2A CN202311852118A CN117486615B CN 117486615 B CN117486615 B CN 117486615B CN 202311852118 A CN202311852118 A CN 202311852118A CN 117486615 B CN117486615 B CN 117486615B
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ceramic
sintering
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殷杰
王力
魏玉全
陈晓
黄政仁
刘学健
陈忠明
姚秀敏
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Jiangsu Institute Of Advanced Inorganic Materials
Shanghai Institute of Ceramics of CAS
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Shanghai Institute of Ceramics of CAS
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Abstract

The invention belongs to the technical field of sintering and forming of ceramics, and particularly relates to a method for preparing SiC ceramics and composite materials by vacuum microgravity suspension sintering. The method adopts a pneumatic suspension mode to suspend the sample, and adopts high-power laser to heat the suspended sample to sinter the suspended sample. The method for preparing the SiC ceramic and the composite material by vacuum microgravity suspension sintering provided by the invention realizes densification of the SiC ceramic, and utilizes the high temperature rise and fall speed and the high sintering speed and cooling speed of the SiC ceramic, and the simulation of the microgravity environment can lighten the influence of the gravity effect, so that a series of SiC ceramics with uniform microcosmic appearance and small particle size and the SiC-containing ceramic composite material are prepared. Meanwhile, the method of the invention lays a good foundation for the on-orbit manufacture of SiC ceramics and composite materials pushed to space.

Description

Method for preparing SiC ceramic and composite material by vacuum microgravity suspension sintering
Technical Field
The invention belongs to the technical field of sintering and forming of ceramics, and particularly relates to a method for preparing SiC ceramics and composite materials by vacuum microgravity suspension sintering.
Background
SiC ceramics and SiC-containing ceramic composite materials are widely used in many severe environmental fields such as mechano-electronics, petrochemical industry, aerospace, and the like, because of their unique and excellent properties such as high temperature resistance, corrosion resistance, wear resistance, high strength, high hardness, high thermal conductivity, low thermal expansion, and the like. Specifically, the SiC ceramic device can be used as core components of space reflectors, micro-channel reactors, high-speed rail brake blocks and the like. Applications in these severe environments place high uniformity demands on SiC ceramics.
The general process of ceramic sintering is as follows: the ceramic green body is characterized in that solid particles are mutually bonded along with the rising of temperature and the prolonging of time, the grain size is large, the gaps (air holes) and grain boundaries are gradually reduced, the total volume is contracted through mass transfer, the density is increased, and finally the ceramic green body is formed into a hard polycrystalline sintered body with a certain microstructure.
Currently, the main sintering modes of SiC include pressureless sintering, hot press sintering, hot isostatic pressing sintering and reaction sintering. The hot press sintering process can only prepare SiC ceramic parts with simple shapes, and the quantity of products prepared by one hot press sintering process is small, so that the hot press sintering process is not beneficial to commercial production. Although the hot isostatic pressing process can obtain articles of complex shape, the greenbody must be encapsulated, so that it is difficult to realize industrial production. The component with complex shape can be prepared by the reaction sintering process, the sintering temperature is lower, but the high-temperature performance of the reaction sintering ceramic is poorer, and meanwhile, a large amount of residual silicon exists in a sample, so that the sample uniformity is poorer.
In addition, any material unit has a certain mass, and is influenced by the action of the earth's gravity on the earth's surface, so that the microscopic change behavior of the material in the sintering process is affected. In contrast, if the natural convection, which is the convection caused by the density difference, disappears in the microgravity environment, the stokes movement is greatly weakened, and the marangoni convection caused by the surface tension gradient is highlighted. The convective transport of heat and mass is inhibited in this environment, and diffusion process control during crystal growth is more pronounced. Different gravity environments have different uncertainty influences on the forming process of materials, but due to the limitation of the current scientific research platform capacity, in-situ on-orbit manufacturing experiments cannot be directly carried out in space.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a method for preparing SiC ceramic and composite materials by vacuum microgravity suspension sintering.
According to the method for preparing SiC ceramic and composite materials by vacuum microgravity suspension sintering, a sample is suspended in a pneumatic suspension mode, and a high-power laser is used for heating the suspended sample to sinter the suspended sample. On one hand, a pneumatic suspension mode is adopted to suspend the sample when heating, and microgravity conditions are simulated; on the other hand, the sample is kept rotating at a high speed during suspension, so that the sample is heated uniformly. The rapid temperature rise and fall process and microgravity suspension condition of the method lead the SiC ceramic to show different characteristics of more uniformity and finer grains on microcosmic scale. The rapid temperature rise and drop suppresses the growth of SiC grains, and microgravity conditions can prevent the SiC grains from being influenced by gravity, so that the gravity effects such as convection and diffusion are avoided, and the sintering of the sample is more complete due to longer heat preservation time.
The invention provides a method for preparing SiC ceramic by vacuum microgravity suspension sintering, which comprises the following steps:
step (1): ball milling and uniformly mixing the powder raw materials and the binder, and sieving to obtain powder for dry compression molding; the powder raw material is SiC powder;
Step (2): dry-pressing the powder for dry-pressing molding obtained in the step (1) to obtain a ceramic preform;
Step (3): performing debonding treatment on the ceramic preform obtained in the step (2) at 600-1200 ℃ to obtain a ceramic biscuit;
Step (4): suspending the ceramic biscuit obtained in the step (3) by using argon as a carrier gas flow, applying a laser beam to the suspended ceramic biscuit, and heating and sintering the ceramic biscuit to obtain the sintered SiC ceramic.
Preferably, the debonding treatment in step (3) is performed in vacuum or in a protective atmosphere, and the protective gas is one or more selected from argon and nitrogen.
Preferably, the SiC powder used in the step (1) is spray granulated SiC powder having a particle diameter of 20 to 200 μm and a density of 0.8 to 1g/cm 3.
Preferably, the binder used in the step (1) is one or more of epoxy resin, phenolic resin, PVA and PVB, and the mass ratio of the binder to the powder raw material is 2% -5%.
Preferably, the ball milling mixing conditions in step (1) are as follows: the ball milling rotating speed is 100-600 r/min, the ball milling time is 2-12 h, and the ball-material ratio is 1: 2-5; and (3) sieving the composite powder subjected to ball milling in the step (1) through a 50-300 mesh sieve.
Preferably, the dry press molding conditions in step (2) are: the pressure is 5-20 MPa, and the pressure is maintained for 2-10 minutes.
Preferably, the degree of debonding in step (3) is as follows: the temperature rising rate at 0-200 ℃ is 1-3 ℃/min; the temperature rising rate at 200-600 ℃ is 1 ℃/min; and when the temperature is higher than 600 ℃, the heating rate is 1-2 ℃/min, argon or nitrogen is filled into the mixture after the highest temperature is kept at 30 min ℃ for cooling to the room temperature.
Preferably, the laser source used in the sintering in the step (4) is a fiber laser.
Preferably, in the step (4), the sintering temperature is 1600-2200 ℃, the heating rate is 50-150 ℃/s, the cooling rate is 500-1500 ℃/s, and the heat preservation time is 0.5-20 minutes.
The invention provides a method for preparing a composite material containing SiC by vacuum microgravity suspension sintering, which is to replace the powder raw material in the method for preparing SiC ceramic with a mixture of SiC powder and additional powder, and sinter the mixture to prepare the composite material containing SiC.
Wherein the additional powder is selected from one or more of nano carbon black and carbon fiber.
Preferably, the additional powder is one or more of carbon nano-black with the diameter of 20-100 nm and carbon fiber with the length of 30-200 mu m and the diameter of 6-12 mu m.
Advantageous effects
The method for preparing the SiC ceramic and the composite material by vacuum microgravity suspension sintering provided by the invention realizes densification of the SiC ceramic, and utilizes the high temperature rise and fall speed and the high sintering speed and cooling speed of the SiC ceramic, and the simulation of the microgravity environment can lighten the influence of the gravity effect, so that a series of SiC ceramics with uniform microcosmic appearance and small particle size and the SiC-containing ceramic composite material are prepared.
In the invention, the laser is used for rapid heating, so that the temperature can be increased to the sintering temperature in a few seconds, and rapid sintering is realized; the ceramic is fine-crystallized by rapid temperature rise and reduction, and has higher strength; the sample can be sintered and formed under the simulated microgravity condition in a pneumatic suspension mode, so that the influence of gravity factors such as diffusion convection and the like in the sintering process is reduced; the pneumatic suspension mode can enable the sample to rotate at a high speed during sintering, so that the sample is heated uniformly.
The method of the invention also lays a good foundation for the on-orbit manufacture of SiC ceramics and composite materials pushed to space.
Drawings
FIG. 1 is a graphical representation of samples of example 1 at various sintering times.
FIG. 2 is an SEM image of the sample of examples 1-6, wherein (a) and (b) are SEM images of the sample of example 1; (e) and (f) are SEM images of the sample of example 2; (c) and (d) are SEM images of the sample of example 3; (g) and (h) are SEM images of the sample of example 4; (i) and (j) are SEM images of the sample of example 5; (k) and (l) are SEM images of the samples of example 6.
Fig. 3 is an SEM image of the sample of comparative example 1.
Fig. 4 is an SEM image of the sample of comparative example 2.
Fig. 5 is an SEM image of the sample of comparative example 3.
FIG. 6 is an EBSD map of the sample of example 1.
Detailed Description
The invention is further illustrated by the following specific examples, which are intended to illustrate the problem and to explain the invention, without limiting it.
The invention provides a method for preparing SiC ceramic and a composite material by vacuum microgravity suspension sintering, which comprises the following steps: and carrying out suspension sintering on the SiC biscuit and the composite biscuit containing SiC under vacuum or argon condition and simulated microgravity condition to obtain vacuum microgravity suspension sintered SiC ceramic and composite material.
Example 1: (100. Wt% SiC)
(1) Ball milling is carried out on 20g of SiC and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4 h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W per 5 seconds, preserving heat for 1 minute, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC composite material with the component of 100 wt% of SiC subjected to vacuum microgravity suspension sintering, wherein the density is 88.05%, and the average particle size is 0.71 mu m.
Example 2: (100. Wt% SiC)
(1) Ball milling is carried out on 20g of SiC and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4 h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W per 5 seconds, preserving heat for 5 minutes, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC composite material with the component of 100 wt% of SiC subjected to vacuum microgravity suspension sintering, wherein the density is 92.56%, and the average particle size is 0.45 mu m.
Example 3: (80. Wt% SiC, 20.Wt% nano carbon black)
(1) Ball milling is carried out on 16g of SiC, 4g of nano carbon black and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W per 5 seconds, preserving heat for 5 minutes, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC/C composite material with the components of 80 wt% of SiC and 20 wt% of nano carbon black subjected to vacuum microgravity suspension sintering, wherein the density is 91.40%, and the average particle size is 0.47 mu m.
Example 4: (50. Wt% SiC, 50.Wt% nano carbon black)
(1) Ball milling is carried out on 10g of SiC, 10g of nano carbon black and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W per 5 seconds, preserving heat for 5 minutes, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC/C composite material with the components of 50 weight percent of SiC and 50 weight percent of nano carbon black subjected to vacuum microgravity suspension sintering, wherein the density is 95.74 percent, and the average particle size is 0.32 mu m.
Example 5: (80. Wt% SiC, 20.Wt% carbon fiber)
(1) Ball milling is carried out on 16g of SiC, 4g of carbon fiber and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 50 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 1-3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 1-2 ℃/min at 600-900 ℃, argon is filled into the mixture after the highest temperature is kept at 30-min ℃ for cooling to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W every 5 seconds, preserving heat for 5 minutes, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC/C composite material with the components of 80 wt% of SiC and 20 wt% of carbon fiber subjected to vacuum microgravity suspension sintering, wherein the density is 93.75%, and the average particle size is 0.59 mu m.
Example 6: (50. Wt% SiC, 50.Wt% carbon fiber)
(1) Ball milling is carried out on 10g of SiC, 10g of carbon fiber and 0.4gPVB of powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out suspension sintering on the biscuit obtained in the step (3) under vacuum and microgravity conditions, increasing the laser power to a target temperature of 1900 ℃ at a speed of 2W every 5 seconds, preserving heat for 5 minutes, and cooling to room temperature at a speed of 1000 ℃/s to obtain the SiC/C composite material with the components of 50 weight percent of SiC and 50 weight percent of carbon fibers subjected to vacuum microgravity suspension sintering, wherein the density is 93.30 percent, and the average particle size is 0.51 mu m.
Comparative example 1: (liquid phase sintering)
(1) Ball milling is carried out on 92 wt% of SiC, 5 wt% of Al 2O3 and 3 wt% of Y 2O3 powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) preserving heat for more than 1 hour at the temperature of more than 1800 ℃ for the biscuit obtained in the step (3) to obtain the liquid phase sintered SiC ceramic, wherein the density is 98.80%, the liquid phase component is 21.24%, and the average grain diameter is 25.40 mu m.
Comparative example 2: (solid phase sintering)
(1) Ball milling is carried out on 95.8 wt% of SiC, 1.2 wt% of B 4 C and 3.wt% of C powder, the ball milling rotating speed is 300r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) preserving the temperature of the biscuit obtained in the step (3) for more than 1 hour at the temperature of more than 2100 ℃ to obtain the solid-phase sintered SiC ceramic, wherein the density is 95.55 percent, and the average grain diameter is 32.18 mu m.
Comparative example 3: (reaction sintering)
(1) Ball milling is carried out on 70 wt% of SiC and 30 wt% of C powder, the ball milling rotating speed is 300 r/min, the ball milling time is 4h, and the ball-to-material ratio is 1:2.5, uniformly mixing, and sieving with a 200-mesh sieve to obtain the SiC composite powder for dry compression molding.
(2) And (3) carrying out dry pressing molding on the SiC composite powder obtained in the step (1), wherein the pressure is 5MPa, and the pressure is maintained for 5 minutes to obtain the SiC ceramic preform.
(3) Debonding the press formed test specimen obtained in step (2): the temperature rising rate is 3 ℃/min at 0-200 ℃; the temperature rising rate at 200-600 ℃ is 1 ℃/min; the heating rate is 2 ℃/min at 600-900 ℃, argon is filled into the furnace after the highest temperature is kept at 30min ℃ and the furnace is cooled to the room temperature; obtaining the SiC ceramic biscuit.
(4) And (3) carrying out siliconizing treatment on the biscuit obtained in the step (3) under vacuum condition at 1550 ℃ to obtain the reaction-sintered SiC ceramic. The siliconizing system is 0-1200℃: heating rate is 10 ℃/min; 1200-1400℃: heating rate is 5 ℃/min; 1400-1550℃: heating at a speed of 3 ℃/min, and preserving heat at 1550 ℃ for 30 min; 1550-1200℃: the cooling rate is 2.5 ℃/min; argon is filled into the reactor and cooled to room temperature. Preserving heat for more than 0.5 hours at the temperature of more than 1550 ℃ to obtain the reaction sintering SiC ceramic with the density of 98.35 percent and the average grain diameter of 43.15 mu m.
In the invention, the porosity and the particle size of SiC ceramic and composite material samples are tested by SEM gray scale analysis by adopting imageJ software.
In the invention, the suspension sintering in the step (4) adopts a pneumatic suspension mode to suspend the sample, and the air flow makes the sample rotate at a high speed so as to homogenize the gravity applied to the sample in all directions, thereby simulating microgravity conditions approximately. In the invention, the sample is suspended by high air flow brought by a small amount of inflation, and the vacuum environment is kept by continuously vacuumizing, so that the sample is sintered in the vacuum environment.
Fig. 1 is a physical diagram of samples of example 1 at different sintering times, and it can be seen from fig. 1 that the temperature rising rate of the samples is fast, which is far higher than the temperature rising rate of sintering of other samples in a heating furnace. The samples of examples 2 to 6 were sintered in the same manner as in example 1, and therefore had extremely fast temperature rise rates.
FIG. 2 is an SEM image of examples 1-6, wherein (a) and (b) are SEM images of example 1; (e) and (f) are SEM images of example 2; (c) and (d) are SEM images of example 3; (g) and (h) are SEM images of example 4; (i) and (j) are SEM images of example 5; (k) and (l) are SEM images of example 6. As can be seen from FIG. 2, the sample components of examples 1 to 6 were uniform and had a small particle size, which was about 0.5. Mu.m.
Fig. 3 is an SEM image of comparative example 1, fig. 4 is an SEM image of comparative example 2, and fig. 5 is an SEM image of comparative example 3. As can be seen by comparing with the samples of examples, the samples of examples were significantly more uniform in microstructure than the comparative examples, and the grains of the samples of examples were also significantly finer than the comparative examples.
Fig. 6 is an EBSD plot of the sample of example 1, showing that no segregation of SiC occurs after sintering and that the sample composition has high uniformity.
The above embodiments are illustrative for the purpose of illustrating the technical concept and features of the present invention so that those skilled in the art can understand the content of the present invention and implement it accordingly, and thus do not limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims (7)

1. The method for preparing the SiC ceramic by vacuum microgravity suspension sintering is characterized by comprising the following steps of:
step (1): ball milling and uniformly mixing the powder raw materials and the binder, and sieving to obtain powder for dry compression molding; the powder raw material is SiC powder;
Step (2): dry-pressing the powder for dry-pressing molding obtained in the step (1) to obtain a ceramic preform;
Step (3): performing debonding treatment on the ceramic preform obtained in the step (2) at 600-1200 ℃ to obtain a ceramic biscuit;
Step (4): suspending the ceramic biscuit obtained in the step (3) by using argon as a carrier gas flow, rotating a sample at a high speed by the gas flow, and applying a laser beam to the suspended ceramic biscuit to heat and sinter the ceramic biscuit to obtain sintered SiC ceramic;
The degree of debonding in step (3) is as follows: the temperature rising rate at 0-200 ℃ is 1-3 ℃/min; the temperature rising rate at 200-600 ℃ is 1 ℃/min; heating rate is 1-2 ℃/min when the temperature is higher than 600 ℃, and argon or nitrogen is filled into the mixture after the highest temperature is kept at 30min ℃ for cooling to room temperature;
In the step (4), the sintering temperature is 1900-2200 ℃, the heating rate is 50-150 ℃/s, the cooling rate is 500-1500 ℃/s, and the heat preservation time is 0.5-20 minutes.
2. The method for preparing SiC ceramic by vacuum microgravity suspension sintering according to claim 1, wherein the method comprises the following steps: the SiC powder used in the step (1) has a particle diameter of 20 to 200 μm and a density of 0.8 to 1g/cm 3.
3. The method for preparing SiC ceramic by vacuum microgravity suspension sintering according to claim 1, wherein the method comprises the following steps: the binder used in the step (1) is one or more of epoxy resin, phenolic resin, PVA and PVB, and the mass ratio of the binder to the powder raw material is 2% -5%.
4. The method for preparing SiC ceramic by vacuum microgravity suspension sintering according to claim 1, wherein the method comprises the following steps: the ball milling mixing conditions in step (1) are as follows: the ball milling rotating speed is 100-600 r/min, the ball milling time is 2-12 h, and the ball-material ratio is 1: 2-5; and (3) sieving the composite powder subjected to ball milling in the step (1) through a 50-300 mesh sieve.
5. The method for preparing SiC ceramic by vacuum microgravity suspension sintering according to claim 1, wherein the method comprises the following steps: the dry press molding conditions in the step (2) are as follows: the pressure is 5-20 MPa, and the pressure is maintained for 2-10 minutes.
6. A method for preparing a composite material containing SiC by vacuum microgravity suspension sintering is characterized by comprising the following steps: replacing the powder raw material in the method for preparing the SiC ceramic by the vacuum microgravity suspension sintering according to any one of claims 1 to 5 with a mixture of SiC powder and additional powder, and sintering to prepare a composite material containing SiC; the additional powder is selected from one or more of nano carbon black and carbon fiber.
7. The method for preparing the SiC-containing composite material by vacuum microgravity suspension sintering according to claim 6, wherein the method comprises the following steps: the additional powder is one or more of nano carbon black with the diameter of 20-100 nm and carbon fiber with the length of 30-200 mu m and the diameter of 6-12 mu m.
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