A method for forming a ceramic green body based on microwave in-situ sintering and a product

Abstract

This invention belongs to the technical field of additive manufacturing and discloses a method and product for forming ceramic preforms based on microwave in-situ sintering. The method includes the following steps: preparing a microwave absorber and SiC powder; performing three-dimensional printing using the SiC powder; during the three-dimensional printing process, after printing and forming a slice layer, spraying the microwave absorber onto the surface of the slice layer; then microwaving the slice layer to perform in-situ heating and sintering, thereby forming each slice layer layer by layer to obtain the desired ceramic preform. This invention also discloses the product obtained by the above method. This invention solves the problems of organic binders easily clogging the ink path and corroding the printhead, and low preform strength. Furthermore, the in-situ sintering method eliminates the need for subsequent curing and degreasing heat treatment processes, simplifying the manufacturing process.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, and more specifically, relates to a method and product for forming ceramic preforms based on microwave in-situ sintering. Background Technology

[0002] Three-dimensional printing (3DP), also known as binder jetting technology, is a type of additive manufacturing technology. It primarily utilizes a nozzle to selectively jet liquid binder, bonding and depositing discrete powder layer by layer to form the desired part. It can be applied to the fabrication of complex parts made of ceramics, plastics, and metals. Compared to traditional processes, it offers numerous advantages, including faster forming speed, no need for molds, no influence from the geometric complexity of the part, and material recyclability. However, current 3D printing technology still has the following drawbacks or problems when forming ceramic parts:

[0003] 1. Organic binders easily clog and corrode printheads. Currently, the main binders are organic binders (such as polyvinyl alcohol, phenolic resin, and furan resin). Due to their long molecular chains, high content, and high viscosity, they can bind ceramic powder together, and their decomposition temperature is low, so they can be almost completely removed through subsequent heat treatment. However, precisely because of their long molecular chains, high viscosity, and easy precipitation upon heating, they easily clog the printhead and ink path during use, and are difficult to clean, resulting in low equipment stability and poor reliability, while also reducing the accuracy of printed parts and the lifespan of the printhead.

[0004] Second, the initial blank has low strength, requires numerous post-processing steps, and its performance is difficult to meet the required specifications. Ceramic 3D inkjet printing mainly uses organic binders to bond powder particles layer by layer, resulting in a ceramic blank with high porosity and low strength. After printing, it is difficult or impossible to remove it directly from the forming cavity; a series of cumbersome heat treatment processes, including overall heating and curing, degreasing, and sintering, are required. Each step necessitates strict control of process parameters such as temperature and time.

[0005] To address the above issues, some published patents have improved the binder formulation and post-treatment process to enhance the strength of the ceramic green body and meet usage requirements. For example, patents CN111875394A and CN110105073A respectively use water-based styrene-acrylic copolymer resin and hydroxyethyl acrylate and hydroxypropyl acrylate as the matrix, supplemented with phthalic acid ester wetting agent to reduce the surface tension of the binder, making it easier to penetrate and increasing the contact area with the ceramic powder, thereby improving the strength of the green body. However, its essence is still a high-molecular long-chain organic material, and there is still a possibility of nozzle clogging during use. Patent CN107098714A discloses a heat treatment process method for three-dimensional inkjet-printed silicon carbide ceramics, which first uses an organic binder to obtain a green body, followed by drying and degreasing. Chemical vapor deposition (CVD) followed by hot isostatic pressing (HIP) can produce dense parts with good high-temperature performance, but this method is more complex than traditional methods, and the subsequent HIP process limits the three-dimensional printing and forming of parts with complex hollow structures. Patent CN105562623A discloses a method for rapid forming of water glass sand, which uses a mixed solution of sodium water glass and polyvinyl alcohol as a binder to perform three-dimensional printing on the sand mold, and then uses microwave heating to cure each layer. However, it still uses an organic binder, which can damage the printhead and ink path. At the same time, it can only form a single material, and the sand mold strength requirement is low, which cannot meet the needs of ceramic parts.

[0006] In summary, 3D inkjet printing can quickly form ceramic blanks of various complex shapes, greatly reducing costs and shortening process time. However, existing technologies use organic binders for inkjet printing, which can easily clog ink paths and corrode printheads. Furthermore, the formed blanks have very low strength and require a series of post-processing steps to meet handling and usage requirements, making the process complex. Summary of the Invention

[0007] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method and product for forming ceramic preforms based on microwave in-situ sintering. Building upon existing three-dimensional inkjet printing technology, an inorganic microwave absorber is formulated to replace the traditional organic binder, adjusting the resistivity of silicon carbide ceramics and improving their dielectric properties to enable microwave absorption. This also solves the problems of organic binders clogging ink paths and corroding printheads, as well as low preform strength. Furthermore, the in-situ sintering process eliminates the need for subsequent curing and degreasing heat treatment, simplifying the manufacturing process.

[0008] To achieve the above objectives, according to the present invention, a method for forming a ceramic preform based on microwave in-situ sintering is provided, the method comprising the following steps:

[0009] Microwave absorber and SiC powder are prepared; the SiC powder is used for three-dimensional printing. In the three-dimensional printing process, after a slice layer is printed, the microwave absorber is sprayed on the surface of the slice layer, and then the slice layer is microwave heated to allow the slice layer to be sintered in situ. Each slice layer is formed layer by layer to obtain the desired ceramic blank.

[0010] More preferably, the microwave absorber is an inorganic microwave absorber with a viscosity of less than 2 mPa·s, a pH value of 6.9–7.1, and a surface tension of 20 mN / m–40 mN / m. More preferably, in the microwave heating, the microwave power is 200 W–800 W, the heating time for each layer is 0.5 s–6 s, and the heating temperature is 300 °C–800 °C.

[0011] More preferably, the microwave absorber is prepared according to the following method:

[0012] A water-soluble inorganic salt, a polymer modifier, and deionized water are mixed to form a mixed solution. The pH value of the mixed solution is measured, and then an organic acid is added to adjust the pH of the mixed solution to 6.9–7.1, thereby obtaining the desired microwave absorber.

[0013] More preferably, in the microwave absorber, the mass fraction of deionized water is 60wt% to 75wt%, the mass fraction of water-soluble inorganic salt is 25wt% to 40wt%, the mass fraction of polymer modifier is less than or equal to 2.5wt%, and the remainder is organic acid.

[0014] More preferably, the water-soluble inorganic salt is one or more chlorides, bromides, carbonates, sulfates, nitrates, phosphates, aluminates, and hydroxides containing one or more elements such as Al, Fe, Ni, and N.

[0015] More preferably, the polymeric modified material is one or more of polyethylene glycol, glycerol, furfuryl alcohol, starch, and cellulose.

[0016] More preferably, the organic acid is one or both of acetic acid and oxalic acid.

[0017] More preferably, the SiC powder is prepared by the following method:

[0018] α-SiC powders with particle sizes of 40-50 μm and 10-20 μm were selected and mixed at a volume fraction ratio of (50-80):(50-20), and then ball-milled and ground to obtain the desired SiC powder.

[0019] According to another aspect of the present invention, a ceramic preform product prepared by the forming method described above is provided.

[0020] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0021] 1. In this invention, a microwave absorber is sprayed onto the sliced ​​layer, and then microwave heating is used to bond the powders together to achieve layer-by-layer solidification and forming of the green body. This microwave absorber replaces the traditional binder, solving the problems of traditional organic binders easily corroding the printhead and clogging the ink path, reducing the possibility of printhead damage, improving the stability and reliability of the equipment, and greatly reducing costs. At the same time, the microwave absorber in the ceramic green body also greatly improves the dielectric properties of the ceramic powder.

[0022] 2. In this invention, a microwave absorber is used instead of a traditional binder. After the green body is cured, the interparticle bonding is better and the initial strength of the green body is greatly improved. This avoids subsequent curing and degreasing steps, simplifies the process, and saves costs. A microwave modifier is used to increase the dielectric properties of the ceramic powder, so that the powder can fully absorb microwaves, thereby achieving in-situ curing at a lower temperature. Then, the final sintering treatment can be carried out directly.

[0023] 3. This invention proposes selective spraying of microwave absorbers followed by in-situ sintering using microwave heating, which can then be sintered to obtain dense parts. Since the process does not require carburizing or siliconizing, it reduces the amount of residual carbon and silicon, improves the strength and SiC content of the parts, and the final parts have a very high solid content. This solves the problems of traditional organic binders producing a large amount of residual silicon or carbon after molding, with a silicon carbide content of only about 50%, which seriously affects the strength and use requirements of the parts.

[0024] 4. In this invention, the printhead of the 3D inkjet printing equipment is composed of tens of thousands of micron-sized micropores. If the viscosity of the modifier is too high, its fluidity will be reduced, making it difficult to spray normally from the printhead. Excessive acidity or alkalinity will corrode the printhead. This invention uses water-soluble inorganic salts as the main solute, maintaining the pH at neutral. Surface tension is related to wettability. If the surface tension is too high, the modifier and powder will have difficulty wetting each other and will not be able to exert their modifying effect. If the surface tension is too low, the modifier will have too strong wettability and will penetrate into the unprinted area, affecting the dimensional accuracy of the parts. The microwave heating power of 200-800W and 0.5s-6s ensure that the powder can be cured at a relatively low temperature. Household microwave equipment can meet the requirements, and the equipment requirements are not high. The configuration of the modifier mainly ensures that the content of modifying elements is sufficient to change the dielectric properties of SiC, which will also affect the microwave absorption efficiency of the blank and thus affect the mechanical properties of the blank. Using a ratio of large and small particles as raw materials, with small particles as fillers filling the gaps between large particles, can effectively improve the density of the blank and further improve the mechanical properties of the blank. Attached Figure Description

[0025] Figure 1This is a schematic diagram illustrating the principle of microblog solidification constructed according to a preferred embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a microwave in-situ sintering three-dimensional inkjet printing process device constructed according to a preferred embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the microwave in-situ sintering three-dimensional inkjet printing process constructed according to a preferred embodiment of the present invention.

[0028] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0029] 1-Printing nozzle, 2-Powder spreading roller, 3-Powder supply cylinder, 4-Forming cylinder, 5-Printed part, 6-Microwave heating oven. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] like Figure 1 As shown, this invention proposes a method for three-dimensional inkjet forming of silicon carbide ceramic preforms based on microwave in-situ sintering, specifically including the following steps:

[0032] S1 prepares an inorganic microwave absorber suitable for industrial nozzles by dissolving water-soluble inorganic salts and polymer modifiers in deionized water, mixing them thoroughly, measuring the pH value, and then adding organic acid to adjust the pH of the solution to 7-8 to obtain the microwave absorber.

[0033] Preferably, the microwave absorber comprises: 60wt%–75wt% deionized water, 25wt%–40wt% water-soluble inorganic salt, 0–2.5wt% polymeric modifier, and the remainder being organic acids. The water-soluble inorganic salt provides the microwave-absorbing modifier for the ceramic material, the polymeric modifier adjusts the viscosity and surface tension of the solution, and the organic acids adjust the pH of the solution. Deionized water serves as the solvent, and the inorganic salt improves the microwave absorption performance within this temperature range, effectively altering the dielectric properties of SiC to absorb microwaves for curing, while simultaneously ensuring that the modifier meets the viscosity and surface tension requirements.

[0034] Preferably, the water-soluble inorganic salt is one or more chlorides, bromides, carbonates, sulfates, nitrates, phosphates, aluminates, or hydroxides containing one or more elements such as Al, Fe, Ni, and N. Doping with Al, Fe, Ni, and N elements can adjust the resistivity of silicon carbide ceramics, thereby improving their dielectric properties and enabling them to absorb microwaves and undergo internal heating for sintering.

[0035] Preferably, the polymeric modified material is one or more of polyethylene glycol, glycerol, furfuryl alcohol, starch, and cellulose.

[0036] Preferably, the organic acid is one or both of acetic acid and oxalic acid.

[0037] Preferably, the final inorganic microwave absorber has a viscosity of less than 2 mPa·s, a pH value of 7–8, and a surface tension of 20 mN / m–40 mN / m. Preferably, the specific preparation method is as follows:

[0038] A. Weighing: Weigh the required water-soluble inorganic salts and polymer modifiers according to a certain composition using a balance;

[0039] B. Dissolving: Dissolve the weighed water-soluble inorganic salt and polymer modifier in water and stir until homogeneous;

[0040] C. Adjust the pH: Test the pH of the solution from the previous step with test paper, and use a dropper to titrate the organic acid to adjust the pH of the solution to between 7 and 8.

[0041] S2 prepares bimodal SiC powder by selecting commercial α-SiC powder with an average particle size of 10-100μm. After mixing powders of different particle sizes in a certain proportion, the powders are ball-milled and ground to obtain SiC powder for three-dimensional inkjet printing.

[0042] Preferably, bimodal mixed powder can increase the packing density, allowing the particles to bond over a larger area, thereby improving the strength of the printed and cured preform.

[0043] Preferably, the average particle size of the large particles is 50-70 μm, the average particle size of the small particles is 10-20 μm, and the powder of large and small particles is mixed in a volume fraction ratio of (50-80):(50-20).

[0044] Preferably, the powder is measured with a measuring cylinder, mixed with a certain amount of stainless steel balls, and then placed together in a ball mill. After a certain period of time, SiC spherical particles are obtained, which are then added to a grinding flask for further pulverization.

[0045] Preferably, the diameter of the stainless steel ball is 2mm to 6mm, the ball-to-material ratio is set to (3:1) to (10:1), the rotation speed is set to 100r / min to 250r / min, the time is set to 1h to 3h, and the grinding time is set to 10h to 24h.

[0046] Preferably, the ball milling is followed by air cooling for 10 minutes to avoid excessively high temperatures inside the tank.

[0047] Preferably, after ball milling and mixing, the bulk density of the powder is 50% to 70%, the flowability ratio is 1.35 to 1.6, and the silicon carbide ceramic powder has a bimodal particle size of 50 μm to 70 μm and 10 μm to 20 μm.

[0048] S3 begins printing and forming, such as Figure 2 As shown, the silicon carbide ceramic powder prepared above is loaded into the powder supply cylinder 3 of the 3D inkjet printing equipment. A layer of the powder is evenly spread on the forming table surface of the forming cylinder 4 using the powder spreading roller 2. The printing nozzle 1 selectively sprays the microwave absorber onto the surface of the powder layer according to the imported 3D part information. After each layer is completed, the microwave heating furnace 6 placed on both sides of the forming table surface is closed and sealed to microwave heat the forming table surface. The powder particles doped with modified elements absorb microwaves, and the particles inside the powder particles diffuse under the action of heat, thereby causing the particles to sinter and form in situ. At the same time, the powder between layers is also sintered and formed. Then the forming cylinder is lowered by the thickness of one layer, and the powder supply cylinder is raised by 1 to 1.5 times the thickness of the layer. The above process is repeated until the part is formed as a whole. After forming, it is finally cured by heating with microwave at 800W for 0.5 to 3 hours to obtain the desired ceramic blank.

[0049] Preferably, the powder layer thickness is 0.1mm to 0.5mm, the ink volume is 40% to 80%, the printhead scanning speed is 0.35m / s to 2.5m / s, and the powder spreading speed is 0.05m / s to 0.7m / s.

[0050] Preferably, the microwave power is 200W to 800W, the heating time for each layer is 0.5s to 6s, and the heating temperature is 300℃ to 800℃.

[0051] The flexural strength of the final ceramic blank can reach 10-20 MPa.

[0052] The main principle of microwave in-situ sintering is as follows: Microwaves are electromagnetic waves with wavelengths of 1m to 1mm. Silicon carbide ceramic materials have poor dielectric properties and are difficult to absorb microwaves, causing internal heating. By adding elements such as N, Fe, Ni, and Al, the resistivity of silicon carbide powder is controlled, giving it ideal microwave absorption properties, thus meeting the conditions for microwave sintering. During layer-by-layer deposition, the modified ceramic powder undergoes dielectric loss under the electromagnetic action of microwaves, resulting in overall heating from the inside out. This allows the internal particles to acquire sufficient energy to migrate at a lower temperature, thereby reaching the required sintering temperature, promoting adhesion between powder particles, and densifying the material. In this printing process, each layer of powder is sintered in-situ using microwaves after being sprayed with an inorganic microwave absorber. The adhesion between layers is more compact, resulting in a blank with a much higher strength than a blank with an organic binder. This directly meets the requirements for handling and has many advantages such as lower required sintering temperature, faster heating rate, shorter sintering time, and no pollution.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] This invention provides a method for three-dimensional inkjet forming of ceramic preforms based on microwave in-situ sintering, such as... Figure 3 As shown, the specific implementation steps are as follows:

[0055] Example 1

[0056] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0057] S1 prepares a microwave absorber by measuring 75 wt% deionized water, 25 wt% ferric nitrate powder, and 0.5 wt% glycerol.

[0058] Ferric nitrate powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0059] Add 0-0.5 wt% acetic acid to adjust the pH of the microwave absorbent;

[0060] The final solution binder has a viscosity of 1.3 mPa·s, a pH of 7.1, and a surface tension of 21 mN / m.

[0061] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0062] Measure the powder using a graduated cylinder, and mix 80 vol% of powder with an average particle size of 50 μm and 20 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 10:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 24 hours to obtain powder for 3D inkjet printing.

[0063] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.1mm. The powder spreading speed is set to 0.15m / s, the powder layer thickness is 0.1mm, the inkjet volume is 50%, the scanning speed is 0.5m / s, the microwave power is set to 300W, and the heating time is 1.5s. The powder is accumulated layer by layer, and finally microwave cured at 800W for 1h to obtain a high-strength preform with a bending strength of up to 10.15MPa.

[0064] Example 2

[0065] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0066] S1 prepares the microwave absorber by selecting 65wt% deionized water, measuring 33.5wt% aluminum chloride powder and 1wt% glycerol using a balance.

[0067] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0068] Add 0-0.5 wt% acetic acid to adjust the pH of the microwave absorbent;

[0069] The final solution binder has a viscosity of 1.65 mPa·s, a pH of 7.0, and a surface tension of 29 mN / m.

[0070] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0071] Measure the powder using a graduated cylinder, and mix 80 vol% of the powder with an average particle size of 50 μm and 20 vol% of the powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 7:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 20 hours to obtain powder for 3D inkjet printing.

[0072] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.15mm. The powder spreading speed is set to 0.15m / s, the powder layer thickness is 0.15mm, the inkjet volume is 60%, the scanning speed is 0.75m / s, the microwave power is set to 400W, and the heating time is 5s. The powder is accumulated layer by layer, and finally microwave cured at 800℃ for 1.5h to obtain a high-strength preform with a bending strength of up to 15.30MPa.

[0073] Example 3

[0074] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0075] S1 prepares the microwave absorber by selecting 60wt% deionized water, measuring 38.5wt% aluminum chloride powder and 1.4wt% furfuryl alcohol using a balance.

[0076] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0077] Add 0-0.1 wt% acetic acid to adjust the pH of the microwave absorbent;

[0078] The final solution binder has a viscosity of 1.83 mPa·s, a pH of 7.0, and a surface tension of 20 mN / m.

[0079] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0080] Measure the powder using a graduated cylinder, and mix 80 vol% of powder with an average particle size of 50 μm and 20 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 6:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 20 hours to obtain powder for 3D inkjet printing.

[0081] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.2mm. The powder spreading speed is set to 0.2m / s, the powder layer thickness is 0.2mm, the inkjet volume is 65%, the scanning speed is 0.80m / s, the microwave power is set to 600W, and the heating time is 4s. The powder is accumulated layer by layer and finally microwave cured at 800℃ for 0.5h to obtain a high-strength preform with a bending strength of up to 19.36MPa.

[0082] Example 4

[0083] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0084] S1 prepares the microwave absorber by selecting 65wt% deionized water, measuring 35wt% aluminum chloride powder and 1.5wt% furfuryl alcohol using a balance.

[0085] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0086] Add 0-0.1 wt% acetic acid to adjust the pH of the microwave absorbent;

[0087] The final solution binder has a viscosity of 1.83 mPa·s, a pH of 7.0, and a surface tension of 40 mN / m.

[0088] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0089] Measure the powder using a graduated cylinder, and mix 70 vol% of powder with an average particle size of 50 μm and 30 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 6:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 20 hours to obtain powder for 3D inkjet printing.

[0090] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.2mm. The powder spreading speed is set to 0.2m / s, the powder layer thickness is 0.2mm, the inkjet volume is 65%, the scanning speed is 0.80m / s, the microwave power is set to 300W, and the heating time is 1s. The process is carried out layer by layer, and finally microwave cured at 800℃ for 0.5h to obtain a high-strength preform with a bending strength of up to 13.21MPa.

[0091] Example 5

[0092] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0093] S1 prepares the microwave absorber by selecting 75wt% deionized water, weighing 40wt% aluminum chloride powder and 2wt% furfuryl alcohol using a balance.

[0094] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0095] Add 0-0.1 wt% acetic acid to adjust the pH of the microwave absorbent;

[0096] The final solution binder has a viscosity of 2 mPa·s, a pH of 6.9, and a surface tension of 26 mN / m.

[0097] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0098] Measure the powder using a graduated cylinder, and mix 50 vol% of powder with an average particle size of 50 μm and 50 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 6:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding bottle for 20 hours to obtain powder for 3D inkjet printing.

[0099] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.2mm. The powder spreading speed is set to 0.2m / s, the powder layer thickness is 0.2mm, the inkjet volume is 65%, the scanning speed is 0.80m / s, the microwave power is set to 300W, and the heating time is 0.5s. The powder is accumulated layer by layer, and finally microwave cured at 800℃ for 0.5h to obtain a high-strength preform with a bending strength of up to 11.15MPa.

[0100] Example 6

[0101] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0102] S1 prepares the microwave absorber by selecting 60wt% deionized water, measuring 25wt% aluminum chloride powder and 2.5wt% furfuryl alcohol using a balance.

[0103] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0104] Add 0-0.1 wt% acetic acid to adjust the pH of the microwave absorbent;

[0105] The final solution binder has a viscosity of 1.83 mPa·s, a pH of 7.0, and a surface tension of 26 mN / m.

[0106] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0107] Measure the powder using a graduated cylinder, and mix 80 vol% of powder with an average particle size of 50 μm and 20 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 6:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 20 hours to obtain powder for 3D inkjet printing.

[0108] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.2mm. The powder spreading speed is set to 0.2m / s, the powder layer thickness is 0.2mm, the inkjet volume is 65%, the scanning speed is 0.80m / s, the microwave power is set to 800W, and the heating time is 6s. The powder is accumulated layer by layer, and finally microwave cured at 800℃ for 0.5h to obtain a high-strength preform with a bending strength of up to 19.25MPa.

[0109] Example 7

[0110] A method for forming silicon carbide ceramics based on microwave sintering and three-dimensional inkjet printing includes the following steps:

[0111] S1 prepares the microwave absorber by selecting 65wt% deionized water, measuring 33.5wt% aluminum chloride powder and 1wt% furfuryl alcohol using a balance.

[0112] Aluminum chloride powder and glycerol were dissolved in deionized water and stirred until fully diffused. The viscosity of the solution was measured using a rotational spectroscopy meter, the surface tension of the solution was measured using a surface tension meter, and the acidity and alkalinity were measured using a pH meter.

[0113] Add 0-0.1 wt% acetic acid to adjust the pH of the microwave absorbent;

[0114] The final solution binder has a viscosity of 2 mPa·s, a pH of 7.0, and a surface tension of 26 mN / m.

[0115] S2 is configured with silicon carbide powder particles, using α-SiC powder with particle sizes of 50μm and 10μm.

[0116] Measure the powder using a graduated cylinder, and mix 80 vol% of powder with an average particle size of 50 μm and 20 vol% of powder with an average particle size of 10 μm. Add the mixture to a ball mill, using small balls and a low milling speed. Set the ball-to-powder mass ratio to 6:1 and mix at room temperature for 1 hour to obtain large spherical particles. Then, pulverize the powder in a grinding flask for 20 hours to obtain powder for 3D inkjet printing.

[0117] S3 printing preform: The prepared powder is spread on the forming table in layers with a thickness of 0.2mm. The powder spreading speed is set to 0.2m / s, the powder layer thickness is 0.2mm, the inkjet volume is 65%, the scanning speed is 0.80m / s, the microwave power is set to 200W, and the heating time is 1s. The powder is accumulated layer by layer and finally microwave cured at 800℃ for 0.5h to obtain a high-strength preform with a bending strength of up to 14.56MPa.

[0118] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for forming a silicon carbide ceramic green body based on microwave in-situ sintering, characterized in that, The method comprises the following steps: The method comprises the following steps: The method comprises the following steps: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method:

2. A method of forming a silicon carbide ceramic green body by microwave in-situ sintering according to claim 1, wherein The SiC powder is prepared by the following method: The SiC powder is prepared by the following method:

3. A method for forming a silicon carbide ceramic green body based on microwave in-situ sintering according to claim 1 or 2, characterized in that, The SiC powder is prepared by the following method:

4. A method of forming a silicon carbide ceramic green body by microwave in-situ sintering according to claim 1 or 2, wherein The SiC powder is prepared by the following method:

5. A silicon carbide ceramic green product obtainable by the forming process according to any one of claims 1 to 4, characterized in that The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The SiC powder is prepared by the following method: The 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