High-precision photocurable silicon carbide ceramic slurry and preparation method thereof, method for preparing silicon carbide ceramic products

Abstract

The present invention relates to a high-precision photocurable printing silicon carbide ceramic slurry and a preparation method thereof, and a method for preparing a silicon carbide ceramic product. The SiC@SiO2 micro-nano composite powder is prepared by a controllable oxidation coating method, and the silicon carbide ceramic slurry is obtained by mixing the SiC@SiO2 micro-nano composite powder with a photosensitive resin, a carbon source resin, a prepolymer resin, a photoinitiator and a dispersant. The printed SiC@SiO2 ceramic green body is sintered by a two-step sintering method to obtain a silicon carbide ceramic. The minimum precision of the silicon carbide green body with a complex structure formed by the present invention is as high as 80 μm. Compared with the minimum precision of the photocurable silicon carbide structure reported in the background technology, this value is increased to 12.5 times. The two-step sintering method of the present invention not only eliminates or reduces the introduced SiO2 coating layer, but also ensures that the gaps of the fine and complex structure of silicon carbide are not significantly blocked.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic additive manufacturing, and relates to a high-precision photocurable silicon carbide ceramic slurry and a preparation method thereof, and a method for preparing silicon carbide ceramic products. Background Art

[0002] With the continuous expansion of the application scope of silicon carbide ceramic material components, the demand for complex structure silicon carbide ceramic composite products is becoming wider and wider.

[0003] As an effective way to prepare high-precision and specific complex structure components, 3D printing technology has opened up a new path for the preparation of high-performance ceramics. Among them, ceramic stereolithography technology has high forming accuracy and surface quality, and can form specific complex structures. However, this technology is greatly restricted by the printing material system, mainly concentrated on the preparation of bioceramics and structural ceramics. Due to the high ultraviolet light absorption rate, strong scattering effect, and large refractive index difference between silicon carbide powder and photosensitive resin, it is difficult to achieve photocuring forming and high-precision forming of silicon carbide ceramics.

[0004] Liquid-phase silicon infiltration reaction sintering of silicon carbide is a commonly used sintering method for preparing silicon carbide ceramics. However, for ceramic green bodies with complex structures, especially for ceramic green bodies with micron-level high-precision complex structures, there are problems such as free silicon blocking the gaps of complex structures in liquid-phase silicon infiltration, which is difficult to remove by post-treatment and destroys the original characteristics of the periodic structure. The gas-phase silicon infiltration reaction sintering process is a new process developed on the basis of the liquid-phase silicon infiltration reaction sintering process. Compared with the liquid-phase impregnation process, during the process of preparing composites by the gas-phase reaction process, the reaction rate decreases and the infiltration rate is higher, thus increasing the penetration depth of Si. Therefore, when the process conditions are appropriate, it can effectively solve the problems of sample cracking and post-silicon removal processing in liquid-phase sintering, and does not block the gaps of high-precision complex structures.

[0005] Chinese Patent CN 112723890 A discloses a photocurable ceramic slurry. This patent uses the method of coating a silicon carbide powder core with a silica shell to reduce the absorbance and refractive index of the silicon carbide powder. However, the solid content of the silicon carbide powder in the photocurable slurry is not high, which affects the mechanical properties of the silicon carbide sintered sample. Chinese Patent CN 114436658 A discloses a photocurable silicon carbide ceramic slurry. This patent also uses the method of coating the surface of silicon carbide powder with silica and increases the solid content of the silicon carbide powder in the photocurable slurry. However, since this patent does not achieve controllable coating of the silica shell on the surface of the silicon carbide powder, the structural accuracy of its photocurable printed green body is only 1000 μm, with low accuracy, which limits its wide application. Summary of the Invention

[0006] Technical Problems to be Solved

[0007] To avoid the deficiencies of the prior art, the present invention provides a high-precision photocurable printable silicon carbide ceramic slurry and its preparation method, as well as a method for preparing silicon carbide ceramic products, which solves the rapid manufacturing of 3D printing of high-precision complex-shaped silicon carbide ceramics. The minimum precision of the formed silicon carbide green body with a complex structure in the present invention is as high as 80 μm. Compared with the minimum precision of the photocurable silicon carbide structure reported in the background art, this value is increased to 12.5 times. The present invention also provides a two-step sintering method for silicon carbide ceramics, which not only eliminates or reduces the introduced SiO 2 coating layer, but also ensures that the gaps of the fine and complex structure of silicon carbide are not significantly blocked.

[0008] Technical Solution

[0009] A preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, characterized in that:

[0010] The SiC@SiO 2 micro-nano composite powder is prepared by a controllable oxidation coating method;

[0011] The SiC@SiO 2 micro-nano composite powder is mechanically stirred with a photosensitive resin, a carbon source resin and a prepolymer resin to obtain a pre-dispersed slurry;

[0012] Then, a photoinitiator and a dispersant are added and high-speed ball milling dispersion is carried out to obtain a high-precision photocurable printable silicon carbide ceramic slurry;

[0013] The preparation of the SiC@SiO 2 micro-nano composite powder by the controllable oxidation coating method is as follows: micron-sized silicon carbide powder is kept at 800 °C to 1000 °C for 10 min to 50 min to obtain SiC@SiO 2 with a micron-sized SiC core and a nano-sized SiO 2 shell; wherein; the thickness of the SiO 2 shell is greater than or equal to 5 nm and less than or equal to 15 nm;

[0014] After the preform is printed from the silicon carbide ceramic slurry, the particle size of the micron-sized SiC core is 0.1 μm to 26 μm, and the thickness of the nano-sized SiO 2 shell is 5 nm to 15 nm, realizing a high-precision photocurable printable silicon carbide ceramic preform.

[0015] The rotation speed of the mechanical stirring is 50 to 200 r / min, and the stirring time is 5 to 20 min.

[0016] The ball milling speed of the high-speed ball mill pre-dispersed slurry is 300-500 r / min, and the ball milling time is 10-14 h.

[0017] The micron-sized silicon carbide powder uses micron-sized SiC as the silicon carbide raw powder, and the particle size distribution is greater than or equal to 0.1 μm and less than or equal to 27 μm.

[0018] A high-precision photocurable printable silicon carbide ceramic slurry obtained by the preparation method, characterized in that: the SiC@SiO 2 The component ratio of the micro-nano composite powder, photosensitive resin, carbon source resin, prepolymer resin, photoinitiator and dispersant is in mass percentage: SiC@SiO 2 Micro-nano composite powder: 60-73%; photosensitive resin: 10%-20%; carbon source resin: 5%-25%; prepolymer resin: 5-10%; photoinitiator: 1-3%; dispersant: 1%-3%; the dispersant is a copolymer solution containing acidic groups; the carbon source resin is phenolic epoxy acrylate; the prepolymer is bisphenol A epoxy acrylate.

[0019] The photoinitiator includes one or more of 2,4,6(trimethylbenzoyl)diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0020] The photosensitive resin includes one or more of trimethylolpropane triacrylate and 1,6-hexanediol diacrylate.

[0021] A method for printing and preparing a silicon carbide ceramic product using the high-precision photocurable printable silicon carbide ceramic slurry, characterized by adopting a two-step sintering method, and the preparation steps are:

[0022] Using the high-precision photocurable silicon carbide ceramic slurry for photocurable printing and forming to obtain a SiC@SiO 2 Ceramic green body;

[0023] Subject the SiC@SiO 2 The ceramic green body is heated to carbonize the carbon source resin, and then kept at 1400°C-1450°C for 1 h-2 h to make SiO 2 React with carbon to form SiC to obtain a silicon carbide pre-sintered blank;

[0024] Finally, place the silicon carbide pre-sintered blank in a vapor phase silicon infiltration furnace for vapor phase reaction sintering to obtain silicon carbide ceramics.

[0025] The conditions for the heating-up process are as follows: heating up to 300 °C at a heating rate not higher than 2 °C / min, and holding for 30 min to 1 h; heating up to 380 °C at a heating rate not higher than 0.5 °C / min, and holding for 30 min to 1 h; heating up to 450 °C at a heating rate not higher than 0.2 °C / min, and holding for 30 min to 1 h; heating up to 600 °C at a heating rate not higher than 0.2 °C / min, and holding for 30 min to 1 h; heating up to 1000 °C at a heating rate not higher than 0.2 °C / min, and holding for 2 h to 4 h; heating up to 1400 °C - 1450 °C at a heating rate not higher than 2 °C / min, and holding for 2 h to 4 h.

[0026] The gas-phase reaction sintering of the silicon carbide pre-sintered blank in a gas-phase silicon infiltration furnace is as follows: when the reaction temperature is 1450 °C - 1700 °C, preferably 1650 °C, and the saturated vapor pressure of Si is 8 Pa - 197 Pa, preferably 59 Pa, a densified fine and complex structure silicon carbide ceramic is obtained.

[0027] Beneficial effects

[0028] A high-precision photocurable silicon carbide ceramic slurry, a preparation method thereof, and a method for preparing a silicon carbide ceramic article proposed by the present invention. The preparation method includes: by controlling the oxidation temperature and oxidation time, realizing the controllable coating of a nanoscale amorphous silica shell on a microscale crystalline silicon carbide core to obtain a SiC@SiO2 micro-nano composite powder with a core-shell structure; mechanically stirring and pre-dispersing the SiC@SiO 2 powder with a photosensitive resin, a carbon source resin, and a prepolymer resin, and then adding a dispersant and a photoinitiator for high-speed ball milling dispersion to obtain a high-precision photocurable silicon carbide ceramic slurry; using the above slurry to print a high-precision complex structure blank, first degreasing and carbonizing the blank, and then using a two-step sintering method. Among them, the first step is to reduce the coated SiO 2 shell to SiC by carbothermal reduction to ensure the high solid content and performance of the ceramic, and the second step is gas-phase silicon infiltration reaction sintering. By controlling the reaction temperature and the saturated vapor pressure of Si, it is ensured that the structural gaps are not significantly blocked, and a densified high-precision complex structure silicon carbide ceramic specimen is obtained; the carbon source resin after carbonization in the two-step sintering process provides a carbon source for both carbothermal reduction and gas-phase silicon infiltration, replacing the cumbersome steps of impregnation after removing the degreasing body phenolic resin in traditional liquid-phase silicon infiltration. The present invention realizes the printing and sintering of a high-precision complex structure silicon carbide specimen.

[0029] The beneficial effects of the present invention:

[0030] (1) By controlling the oxidation temperature and time, the present invention realizes the controllable coating of a micron-sized crystalline silicon carbide core with a nanoscale amorphous silica shell, obtaining a SiC@SiO micro-nano composite powder. On the one hand, it significantly improves the ultraviolet curing ability and forming ability of silicon carbide. On the other hand, it provides a necessary prerequisite for the printing of a slurry with a high-precision complex structure. In addition, the particle size distribution of the micron-sized SiC raw powder is 0.1 μm - 27 μm, which belongs to the fine powder in the micron scale and also provides a necessary condition for the printing of a slurry with a high-precision complex structure of silicon carbide. Finally, a high-precision photocurable silicon carbide ceramic slurry with a minimum precision of up to 80 μm for the 3D printing green body is obtained. 2 The micron-sized SiC raw powder has a particle size distribution of 0.1 μm - 27 μm, belonging to the fine powder in the micron scale, which also provides a necessary condition for the printing of a slurry with a high-precision complex structure of silicon carbide. Finally, a high-precision photocurable silicon carbide ceramic slurry with a minimum precision of up to 80 μm for the 3D printing green body is obtained.

[0031] (2) The present invention prints a complex structure green body by using a high-precision photocurable silicon carbide ceramic slurry, and after degreasing and carbonizing the green body, two-step sintering of silicon carbide ceramics is carried out, realizing the printing and sintering of a high-precision complex structure silicon carbide component. Among them, the first sintering method carbonizes the carbon source resin, controls the reaction temperature and time, reduces or removes the SiO coating, improves the silicon carbide solid content in the sample, and guarantees the mechanical properties of the silicon carbide ceramic green body after degreasing and sintering. The second sintering method is gas-phase silicon infiltration reaction sintering. By controlling the reaction temperature and the saturated vapor pressure of Si, it not only effectively solves the problems of sample cracking and post-silicon removal processing existing in liquid-phase sintering, but also ensures that the gaps of the high-precision complex structure are not blocked, obtaining a densified high-precision complex structure silicon carbide ceramic sample. Among them, the carbon source resin provides a carbon source for both carbothermal reduction and gas-phase silicon infiltration, replacing the cumbersome steps of impregnation after the phenolic resin of the degreased body in traditional liquid-phase silicon infiltration. 2 Coated SiO 2 shell, improving the silicon carbide solid content in the sample and guaranteeing the mechanical properties of the silicon carbide ceramic green body after degreasing and sintering. The second sintering method is gas-phase silicon infiltration reaction sintering. By controlling the reaction temperature and the saturated vapor pressure of Si, it not only effectively solves the problems of sample cracking and post-silicon removal processing existing in liquid-phase sintering, but also ensures that the gaps of the high-precision complex structure are not blocked, obtaining a densified high-precision complex structure silicon carbide ceramic sample. Among them, the carbon source resin provides a carbon source for both carbothermal reduction and gas-phase silicon infiltration, replacing the cumbersome steps of impregnation after the phenolic resin of the degreased body in traditional liquid-phase silicon infiltration. Description of the Drawings

[0032] Figure 1 : XRD patterns of SiC powder at different oxidation temperatures and the same holding time, and comparison diagrams of the mass ratio and atomic ratio of oxygen element;

[0033] are the XRD patterns of SiC powder in Examples 1, 4, and 5 at different oxidation temperatures and the same holding time, and comparison diagrams of the mass ratio and atomic ratio of oxygen element

[0034] Figure 2 : Microscopic state and comparison diagram of oxidation coating thickness of SiC powder coated with SiO 2 at different oxidation temperatures and holding times;

[0035] are the microscopic state and comparison diagram of oxidation coating thickness of SiC powder coated with SiO 2 at different oxidation temperatures and holding times in Examples 1 - 5

[0036] Figure 3 : It is the physical drawing and scanning drawing of the high-precision complex structure silicon carbide green body formed by photocuring in Example 1

[0037] Figure 4 : It is the physical drawing and scanning drawing of the silicon carbide ceramic with fine and complex structure in Example 10

[0038] Figure 5 : Flow chart of the method of the present invention Specific implementation manners

[0039] The present invention will be further described in combination with embodiments and drawings as follows:

[0040] The first aspect of the present invention provides a preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, and the preparation method includes the following steps:

[0041] Using micron-sized SiC as the silicon carbide raw powder, by controlling the oxidation temperature and oxidation time, realizing the controllable coating of the micron-sized crystalline silicon carbide core with a nano-sized amorphous silica shell layer, and obtaining the SiC@SiO 2 micro-nano composite powder;

[0042] Adding a photosensitive resin, a carbon source resin, and a prepolymer resin to the SiC@SiO 2 powder for mechanical stirring to obtain a pre-dispersed slurry; adding a dispersant and a photoinitiator to the pre-dispersed solution for high-speed ball milling dispersion to obtain the high-precision photocurable printable silicon carbide ceramic slurry.

[0043] Preferably, the particle size distribution of the micron-sized SiC raw powder is 0.1 μm to 27 μm.

[0044] Preferably, the thickness of the SiO 2 shell layer is 5 nm to 15 nm;

[0045] Preferably, the oxidation coating method is to heat the silicon carbide powder at a heating rate of 3 to 5 °C / min to 800 to 1000 °C and keep it warm for 10 to 50 min.

[0046] Preferably, the mechanical stirring rate of the pre-dispersed solution of the SiC@SiO 2 powder, the photosensitive resin, the carbon source resin, and the prepolymer resin is 50 to 200 r / min, and the time is 20 to 30 min.

[0047] Preferably, the photosensitive resin includes trimethylolpropane triacrylate and 1,6 - hexanediol diacrylate.

[0048] The photosensitive resin comprises trimethylolpropane triacrylate and 1,6 - hexanediol diacrylate in a mass ratio of 1:(0.5 - 2), preferably 1:1.

[0049] Preferably, the carbon source resin is phenolic epoxy acrylate.

[0050] The mass proportion of the carbon source resin is 5% - 25%, preferably 20%.

[0051] Preferably, the prepolymer is bisphenol A epoxy acrylate.

[0052] The mass ratio of the prepolymer to the photosensitive resin is 1:(1 - 4), preferably 1:1.2.

[0053] The high - speed ball - milling rate of the dispersant, photoinitiator and pre - dispersed slurry is 300 - 500 r / min, and the time is 10 - 14 h, preferably 12 h.

[0054] Preferably, the photoinitiator includes one or more of 2,4,6 - (trimethylbenzoyl) diphenylphosphine oxide, phenylbis(2,4,6 - trimethylbenzoyl) phosphine oxide.

[0055] The mass proportion of the photoinitiator is 1% - 3%, preferably 2%.

[0056] Preferably, the dispersant is a copolymer solution containing acidic groups.

[0057] The mass proportion of the dispersant is 1% - 3%, preferably 2%.

[0058] The second aspect of the present application provides a two - step sintering method for silicon carbide ceramics. The sintering method includes the following steps:

[0059] Perform photocuring molding on the photocurable silicon carbide ceramic slurry to obtain a SiC@SiO 2 green body.

[0060] The first - step sintering method of the two - step sintering method for silicon carbide ceramics is as follows: Program - heat the SiC@SiO 2 ceramic green body, carbonize the carbon source resin, and then keep it at 1400℃ - 1450℃ for 1 h - 2 h to make SiO 2 react with carbon to form SiC to obtain a pre - sintered silicon carbide blank.

[0061] The conditions for the programmed temperature rise are as follows: heating to 300 °C at a heating rate not higher than 2 °C / min, holding for 30 min to 1 h; heating to 380 °C at a heating rate not higher than 0.5 °C / min, holding for 30 min to 1 h; heating to 450 °C at a heating rate not higher than 0.2 °C / min, holding for 30 min to 1 h; heating to 600 °C at a heating rate not higher than 0.2 °C / min, holding for 30 min to 1 h; heating to 1000 °C at a heating rate not higher than 0.2 °C / min, holding for 2 h to 4 h; heating to 1400 °C to 1450 °C at a heating rate not higher than 2 °C / min, holding for 2 h to 4 h;

[0062] The second sintering method of the silicon carbide ceramic two-step sintering method described above is as follows: placing the silicon carbide pre-sintered blank in a vapor phase silicon infiltration furnace, when the reaction temperature is 1450 °C to 1700 °C, preferably 1650 °C, and the saturated vapor pressure of Si is 8 Pa to 197 Pa, preferably 59 Pa, to obtain a densified fine and complex structure silicon carbide ceramic.

[0063] Example 1:

[0064] A preparation method of a high-precision photocurable printing silicon carbide ceramic slurry includes the following steps:

[0065] (1) Placing SiC raw powder with a particle size distribution of 0.1 μm to 27 μm in a box furnace and heating to 800 °C at a heating rate of 3 °C / min and holding for 10 min to obtain amorphous SiO 2 SiC@SiO with a coating layer thickness of 5 nm 2 powder, as Figure 2 shown, and its corresponding XRD pattern and oxygen element content are as Figure 1 shown;

[0066] (2) Placing 6% trimethylolpropane triacrylate, 6% 1,6 - hexanediol diacrylate, 6% phenolic epoxy acrylate, 10% bisphenol A epoxy acrylate and the SiC@SiO 2 powder obtained in step (1) in a beaker and stirring at a mechanical stirring rate of 50 r / min for 20 min to obtain a pre-dispersed solution;

[0067] (3) Adding 1% 2,4,6(trimethylbenzoyl) diphenylphosphine oxide and 1% acidic group copolymer solution to the pre-dispersed solution obtained in step (2) and high-speed ball milling at a ball milling rate of 500 r / min for 10 h to obtain a high-precision photocurable printing silicon carbide ceramic slurry.

[0068] Example 2:

[0069] A preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, comprising the following steps:

[0070] (1) Place SiC raw powder with a particle size distribution of 0.1 μm to 27 μm in a box furnace and heat it at a heating rate of 3 °C / min to 800 °C and hold for 30 min to obtain amorphous SiO 2 SiC@SiO with a coating layer thickness of 10 nm 2 powder, as Figure 2 shown, and its corresponding XRD pattern and oxygen element content are as Figure 1 shown;

[0071] (2) Put 8% trimethylolpropane triacrylate, 8% 1,6 - hexanediol diacrylate, 8% phenolic epoxy acrylate, 5% bisphenol A epoxy acrylate and the SiC@SiO 2 powder obtained in step (1) into a beaker and stir at a mechanical stirring rate of 100 r / min for 30 min to obtain a pre-dispersed solution;

[0072] (3) Add 1% 2,4,6-(trimethylbenzoyl) diphenylphosphine oxide, 1% phenylbis(2,4,6 - trimethylbenzoyl) phosphine oxide and 2% acidic group copolymer solution to the pre-dispersed solution obtained in step (2), and perform high-speed ball milling at a ball milling rate of 300 r / min for 12 h to obtain a high-precision photocurable printable silicon carbide ceramic slurry.

[0073] Example 3:

[0074] A preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, comprising the following steps:

[0075] (1) Place SiC raw powder with a particle size distribution of 0.1 μm to 27 μm in a box furnace and heat it at a heating rate of 3 °C / min to 800 °C and hold for 50 min to obtain amorphous SiO 2 SiC@SiO with a coating layer thickness of 12 nm 2 powder, as Figure 2 shown;

[0076] (2) Put 10% 1,6 - hexanediol diacrylate, 25% phenolic epoxy acrylate and the SiC@SiO 2 powder obtained in step (1) into a beaker and stir at a mechanical stirring rate of 200 r / min for 30 min to obtain a pre-dispersed solution;

[0077] (3) Add the 2% phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 3% acidic group copolymer solution to the pre-dispersed solution obtained in step (2), and perform high-speed ball milling at a ball milling rate of 350 r / min for 14 h to obtain a high-precision photocurable printable silicon carbide ceramic slurry.

[0078] Example 4:

[0079] A preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, comprising the following steps:

[0080] (1) Place the SiC raw powder with a particle size distribution of 0.1 μm to 27 μm in a box furnace, heat it to 900°C at a heating rate of 4°C / min, and hold it for 10 min to obtain amorphous SiO 2 SiC@SiO with a coating layer thickness of 11 nm 2 powder, as Figure 2 shown;

[0081] (2) Put 9% trimethylolpropane triacrylate, 9% 1,6-hexanediol diacrylate, 5% phenolic epoxy acrylate and the SiC@SiO 2 powder obtained in step (1) into a beaker, and stir at a mechanical stirring rate of 150 r / min for 20 min to obtain a pre-dispersed solution;

[0082] (3) Add 2% 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide and 2% acidic group copolymer solution to the pre-dispersed solution obtained in step (2), and perform high-speed ball milling at a ball milling rate of 300 r / min for 14 h to obtain a high-precision photocurable printable silicon carbide ceramic slurry.

[0083] Example 5:

[0084] A preparation method of a high-precision photocurable printable silicon carbide ceramic slurry, comprising the following steps:

[0085] (1) Place the SiC raw powder with a particle size distribution of 0.1 μm to 27 μm in a box furnace, heat it to 1000°C at a heating rate of 5°C / min, and hold it for 10 min to obtain amorphous SiO 2 SiC@SiO with a coating layer thickness of 15 nm 2 powder, as Figure 2 shown, and its corresponding XRD pattern and oxygen element content are as Figure 1 shown;

[0086] (2) Put 10% 1,6-hexanediol diacrylate, 20% phenolic epoxy acrylate and the SiC@SiO 2The powder was placed in a beaker and stirred at a mechanical stirring rate of 200 r / min for 30 min to obtain a pre-dispersed solution;

[0087] (3)1% 2,4,6-(Trimethylbenzoyl) diphenylphosphine oxide and 3% acidic group copolymer solution were added to the pre-dispersed solution obtained in step (2), and high-precision photocurable printable silicon carbide ceramic slurry was obtained by high-speed ball milling at a ball milling rate of 350 r / min for 14 h.

[0088] Example 6:

[0089] A two-step sintering method for silicon carbide ceramics, comprising the following steps:

[0090] (1)The high-precision photocurable printable silicon carbide ceramic slurry of Example 1 was subjected to photocuring molding to obtain a SiC@SiO green body with a high-precision complex structure; 2 green body;

[0091] (2)The SiC@SiO ceramic green body obtained in step (1) was heated at a programmed rate: heated to 300 °C at a heating rate of 2 °C / min and held for 30 min; heated to 380 °C at a heating rate of 0.5 °C / min and held for 30 min; heated to 450 °C at a heating rate of 0.2 °C / min and held for 30 min; heated to 600 °C at a heating rate of 0.2 °C / min and held for 30 min; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 2 h; heated to 1400 °C at a heating rate of 2 °C / min and held for 2 h, so that SiO reacted with C to generate SiC by carbon reduction reaction to obtain a pre-sintered silicon carbide blank; 2 ceramic green body was heated at a programmed rate: heated to 300 °C at a heating rate of 2 °C / min and held for 30 min; heated to 380 °C at a heating rate of 0.5 °C / min and held for 30 min; heated to 450 °C at a heating rate of 0.2 °C / min and held for 30 min; heated to 600 °C at a heating rate of 0.2 °C / min and held for 30 min; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 2 h; heated to 1400 °C at a heating rate of 2 °C / min and held for 2 h, so that SiO 2 reacted with C to generate SiC by carbon reduction reaction to obtain a pre-sintered silicon carbide blank;

[0092] (3)The pre-sintered silicon carbide blank obtained in step (2) was placed in a vapor-phase silicon infiltration furnace, and at a Si saturation vapor pressure of 8 Pa and a temperature of 1450 °C, a densified fine and complex structure silicon carbide ceramic was obtained.

[0093] Example 7:

[0094] A two-step sintering method for silicon carbide ceramics, comprising the following steps:

[0095] (1)The high-precision photocurable printable silicon carbide ceramic slurry of Example 2 was subjected to photocuring molding to obtain a SiC@SiO green body with a high-precision complex structure; 2 green body;

[0096] (2)The SiC@SiO obtained in step (1) 2The ceramic green body is heated at a programmed rate: heated to 300 °C at a heating rate of 1 °C / min and held for 1 h; heated to 380 °C at a heating rate of 0.5 °C / min and held for 1 h; heated to 450 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 600 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 3 h; heated to 1450 °C at a heating rate of 2 °C / min and held for 3 h, so that SiO 2 reacts with C by carbothermal reduction to form SiC to obtain a pre-sintered SiC green body;

[0097] (3)The pre-sintered SiC green body obtained in step (2) is placed in a vapor-phase silicon infiltration furnace, and at a Si saturation vapor pressure of 59 Pa and a temperature of 1650 °C, a densified fine and complex structure SiC ceramic is obtained.

[0098] Example 8:

[0099] A two-step sintering method for SiC ceramics, comprising the following steps:

[0100] (1)The high-precision photocurable printable SiC ceramic slurry of Example 3 is photocured to form a SiC@SiO green body with a high-precision complex structure. 2 green body;

[0101] (2)The SiC@SiO ceramic green body obtained in step (1) is heated at a programmed rate: heated to 300 °C at a heating rate of 2 °C / min and held for 1 h; heated to 380 °C at a heating rate of 0.5 °C / min and held for 1 h; heated to 450 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 600 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 4 h; heated to 1450 °C at a heating rate of 2 °C / min and held for 4 h, so that SiO 2 reacts with C by carbothermal reduction to form SiC to obtain a pre-sintered SiC green body; 2 reacts with C by carbothermal reduction to form SiC to obtain a pre-sintered SiC green body;

[0102] (3)The pre-sintered SiC green body obtained in step (2) is placed in a vapor-phase silicon infiltration furnace, and at a Si saturation vapor pressure of 197 Pa and a temperature of 1700 °C, a densified fine and complex structure SiC ceramic is obtained.

[0103] Example 9:

[0104] A two-step sintering method for SiC ceramics, comprising the following steps:

[0105] (1) The high-precision photocurable silicon carbide ceramic slurry of Example 4 was subjected to photocuring forming to obtain a SiC@SiO green body with a high-precision complex structure; 2 green body;

[0106] (2) The SiC@SiO ceramic green body obtained in step (1) was heated with a programmed temperature rise: heated to 300 °C at a heating rate of 1 °C / min and held for 1 h; heated to 380 °C at a heating rate of 0.5 °C / min and held for 1 h; heated to 450 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 600 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 2 h; heated to 1400 °C at a heating rate of 2 °C / min and held for 2 h, so that SiO reacted with C to undergo a carbothermal reduction reaction to form SiC to obtain a silicon carbide pre-sintered body; 2 2

[0107] (3) The silicon carbide pre-sintered body obtained in step (2) was placed in a vapor-phase silicon infiltration furnace, and at a Si saturation vapor pressure of 59 Pa and a temperature of 1650 °C, a densified fine and complex structure silicon carbide ceramic was obtained.

[0108] Example 10:

[0109] A two-step sintering method for silicon carbide ceramics, comprising the following steps:

[0110] (1) The high-precision photocurable silicon carbide ceramic slurry of Example 5 was subjected to photocuring forming to obtain a SiC@SiO green body with a high-precision complex structure; 2 green body;

[0111] (2) The SiC@SiO ceramic green body obtained in step (1) was heated with a programmed temperature rise: heated to 300 °C at a heating rate of 1 °C / min and held for 1 h; heated to 380 °C at a heating rate of 0.5 °C / min and held for 1 h; heated to 450 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 600 °C at a heating rate of 0.2 °C / min and held for 1 h; heated to 1000 °C at a heating rate of 0.2 °C / min and held for 2 h; heated to 1450 °C at a heating rate of 2 °C / min and held for 3 h, so that SiO reacted with C to undergo a carbothermal reduction reaction to form SiC to obtain a silicon carbide pre-sintered body; 2 2

[0112] (3) The silicon carbide pre-sintered body obtained in step (2) was placed in a vapor-phase silicon infiltration furnace, and at a Si saturation vapor pressure of 59 Pa and a temperature of 1650 °C, a densified fine and complex structure silicon carbide ceramic was obtained. ​​​​

[0113] To highlight the beneficial effects of this application, the following comparative examples are set up.

[0114] Comparative Example 1:

[0115] A preparation method of a photocurable silicon carbide ceramic slurry:

[0116] Figure 3 It is a physical diagram and a scan diagram of a fine and complex structure formed by a high-precision photocurable printable silicon carbide ceramic slurry with a minimum precision of up to 80 μm obtained through Example 1.

[0117] The difference between this Comparative Example 1 and Example 1 is only that: SiC raw powder with a particle size distribution of 0.1 μm to 27 μm is used, and its surface is not subjected to SiO 2 Controlled oxidation coating, and the curing thickness of the obtained photocurable printed silicon carbide ceramic slurry is only 10 μm, and it cannot be formed into a high-precision complex structure green body.

[0118] Comparative Example 2:

[0119] A preparation method of a photocurable silicon carbide ceramic slurry:

[0120] The difference between this Comparative Example 2 and Example 2 is only that: SiC raw powder with a particle size distribution of 27 μm to 100 μm is used, and it cannot be formed into a complex structure green body with a precision less than 100 μm.

[0121] Comparative Example 3:

[0122] A sintering method of silicon carbide ceramics:

[0123] The difference between this Comparative Example 3 and Example 9 is only that: phenolic epoxy acrylate is not added to the slurry, and it cannot make SiO 2 React with C to generate SiC by carbon reduction reaction to obtain a silicon carbide pre-sintered green body, nor can it provide enough carbon source during the gas-phase silicon infiltration process, and the obtained silicon carbide ceramic is not dense either.

[0124] Comparative Example 4:

[0125] A sintering method of silicon carbide ceramics:

[0126] Figure 4 It is a physical diagram and a scan diagram of a fine and complex structure silicon carbide ceramic obtained through Example 10;

[0127] The difference between this Comparative Example 4 and Example 10 is only that: the sintering method selects a liquid-phase silicon infiltration furnace, and silicon blocks a large number of gaps in the fine and complex structures formed by photocuring, and a fine and complex structure silicon carbide ceramic cannot be obtained.

Claims

1. A method for preparing silicon carbide ceramic products by printing a high-precision photocurable silicon carbide ceramic slurry, characterized in that: Preparation of SiC@SiO micro-nano composite powder by controlled oxidation coating method 2 ​ The preparation of SiC@SiO by the controllable oxidation coating method is as follows: 2 The micro-nano composite powder is obtained by keeping the micron-sized silicon carbide powder at 800 °C to 1000 °C for 10 min to 50 min, resulting in a powder with a micron-sized SiC core and a nano-sized SiO 2 shell; among which; 2 ​ The SiO 2 shell thickness is greater than or equal to 5 nm and less than or equal to 15 nm; Disperse SiC@SiO 2 micro-nano composite powder, photosensitive resin, carbon source resin and prepolymer resin by mechanical stirring to obtain a pre-dispersed slurry; then add a photoinitiator and a dispersant and perform high-speed ball milling dispersion to obtain a high-precision photocurable printable silicon carbide ceramic slurry; The SiC@SiO 2 The component ratio of the micro-nano composite powder, photosensitive resin, carbon source resin, prepolymer resin, photoinitiator and dispersant is as follows by mass percentage: SiC@SiO 2 Micro-nano composite powder: 60 - 73%; photosensitive resin: 10% - 20%; carbon source resin: 5% - 25%; prepolymer resin: 5 - 10%; Photoinitiator: 1% - 3%; Dispersant: 1% - 3%; The total mass percentage of each component is 100%; The dispersant is a copolymer solution containing acidic groups; The carbon source resin is phenolic epoxy acrylate; The prepolymer is bisphenol A epoxy acrylate; The high-precision photocurable silicon carbide ceramic slurry is used to prepare silicon carbide ceramic products by a two-step sintering method, including: Using a high-precision photocurable silicon carbide ceramic slurry for photocuring printing and forming to obtain a SiC@SiO 2 ceramic green body; The SiC@SiO 2 ceramic green body is heated to carbonize the carbon source resin, and then held at 1400 °C to 1450 °C for 1 h to 2 h to make SiO 2 react with carbon to form SiC and obtain a pre-sintered silicon carbide body; Finally, the silicon carbide pre-sintered blank is placed in a vapor-phase silicon infiltration furnace for vapor-phase reaction sintering to obtain silicon carbide ceramics; The vapor-phase reaction sintering of the silicon carbide pre-sintered blank in the vapor-phase silicon infiltration furnace is as follows: when the reaction temperature is 1450°C - 1700°C, the saturated vapor pressure of Si is 8 Pa - 197 Pa, and a densified fine and complex structure silicon carbide ceramic is obtained; Among them, after the high-precision photocurable silicon carbide ceramic slurry is printed to obtain a ceramic green body, the particle size of the micron-sized SiC core is 0.1 μm to 26 μm, and the 2 thickness of the nano-scale SiO shell is 5 nm to 15 nm.

2. The method according to claim 1, characterized in that: The rotation speed of the mechanical stirring is 50 - 200 r / min, and the stirring time is 5 - 20 min.

3. The method according to claim 1, characterized in that: The ball milling speed of the high-speed ball milling pre-dispersed slurry is 300 - 500 r / min, and the ball milling time is 10 - 14 h.

4. The method according to claim 1, characterized in that: The micron-sized silicon carbide powder uses micron-sized SiC as the silicon carbide raw powder, and the particle size distribution is greater than or equal to 0.1 μm and less than or equal to 27 μm.

5. The method according to claim 1, characterized in that: The photoinitiator includes one or more of 2,4,6 (trimethylbenzoyl) diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide.

6. The method according to claim 1, characterized in that: The photosensitive resin includes one or more of trimethylolpropane triacrylate and 1,6-hexanediol diacrylate.

7. The method according to claim 1, characterized in that: The conditions of the heating process are: heating to 300°C at a heating rate not higher than 2°C / min, holding for 30 min - 1 h; heating to 380°C at a heating rate not higher than 0.5°C / min, holding for 30 min - 1 h; heating to 450°C at a heating rate not higher than 0.2°C / min, holding for 30 min - 1 h; heating to 600°C at a heating rate not higher than 0.2°C / min, holding for 30 min - 1 h; heating to 1000°C at a heating rate not higher than 0.2°C / min, holding for 2 h - 4 h; heating to 1400°C - 1450°C at a heating rate not higher than 2°C / min, holding for 2 h - 4 h.

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