Ultrafine silicon carbide powder slurry and preparation method thereof

Abstract

The present invention belongs to the technical field of silicon carbide ceramic materials, and discloses an ultrafine silicon carbide powder slurry and a preparation method thereof. The preparation method comprises the following steps: removing impurities from the ultrafine silicon carbide powder and then mixing it with a modification aid, graphene and water; after ball milling, adding a photosensitive resin, a diluent, an initiator, a dispersant and a pH regulator and continuing ball milling to obtain an ultrafine silicon carbide powder slurry. The present invention effectively avoids the agglomeration of silicon carbide powder during the preparation process by sequentially removing impurities, modifying and ball milling the ultrafine silicon carbide powder; and the ultrafine silicon carbide powder slurry prepared by the present invention has low viscosity, high solid content and moderate yield stress, so that the ultrafine silicon carbide powder slurry prepared by the present invention can better maintain shape and dimensional stability during the printing process, effectively reducing deformation and cracking during the printing process, and is conducive to promoting the further application of silicon carbide ceramic materials.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide ceramic materials, and in particular to an ultrafine silicon carbide powder slurry and a preparation method thereof. Background Art

[0002] Silicon carbide ceramic materials are widely used in ceramic manufacturing, semiconductors, aerospace, new energy vehicles, photovoltaics, grinding and polishing, composite materials and coatings due to their excellent physical and chemical properties, such as high flexural strength, excellent oxidation resistance, good corrosion resistance, high wear resistance and low friction coefficient.

[0003] In order to meet the performance requirements and material structure requirements of the above-mentioned different fields, it is urgent to achieve efficient preparation of silicon carbide ceramic materials with complex structures. To this end, those skilled in the art have proposed to prepare corresponding silicon carbide slurries according to different requirements, and then use 3D printing technology to print the silicon carbide slurries in sequence according to a preset printing path to obtain the corresponding printed bodies. After light curing or heat curing, the required silicon carbide ceramic materials are formed. 3D printing has high flexibility and can realize the preparation of special complex structures with high precision and short production cycle, which is expected to achieve efficient preparation of silicon carbide ceramic materials.

[0004] The particle size of silicon carbide is one of the main factors affecting the performance of silicon carbide ceramic materials. Fine silicon carbide particles can better fill the pores between coarse particles, which is beneficial to improving the comprehensive properties of silicon carbide ceramic materials such as densification, mechanical properties and thermal conductivity. Therefore, the use of ultrafine silicon carbide powder to prepare silicon carbide ceramic materials is expected to further improve the comprehensive performance of silicon carbide ceramic materials. However, the fine particle size and large surface energy of ultrafine silicon carbide powder cause the prepared silicon carbide slurry to easily agglomerate during 3D printing, forming secondary ions, which in turn causes the printed silicon carbide ceramic material to have uneven component distribution, making it difficult to effectively exert the effectiveness of the ultrafine silicon carbide powder itself, and thus unable to effectively improve the comprehensive performance of silicon carbide ceramic materials.

[0005] To prevent silicon carbide slurry from agglomerating during the preparation process, those skilled in the art have proposed reducing the agglomeration of silicon carbide powder through surface modification. Although this method can improve the agglomeration of silicon carbide powder to a certain extent, it requires the use of a large amount of chemical reagents and produces a large amount of waste liquid, which is not in line with the concept of green synthesis. Moreover, the silicon carbide slurry prepared by this method is mainly suitable for gel casting, and the prepared silicon carbide slurry cannot effectively meet the process requirements of 3D printing preparation. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an ultrafine silicon carbide powder slurry and a preparation method thereof.

[0007] The ultrafine silicon carbide powder slurry and preparation method thereof of the present invention are achieved through the following technical solutions:

[0008] The present invention provides a method for preparing ultrafine silicon carbide powder slurry, comprising the following steps:

[0009] Step 1: Impurity removal of ultrafine silicon carbide powder:

[0010] 1.1) Disperse the impurity remover in water to obtain an impurity remover solution.

[0011] 1.2) The first ultrafine silicon carbide powder is dispersed in a decontamination liquid, and then ultrasonically treated, centrifuged, washed, and dried to obtain a first decontamination powder.

[0012] 1.3) The second ultrafine silicon carbide powder is dispersed in a portion of the impurity removal liquid, and then ultrasonically treated, centrifuged and washed, and then dried to obtain a second impurity-removed powder.

[0013] It should be noted that the present invention takes into account that the rheological properties of the final overall slurry will affect the performance of the ceramic material obtained by subsequent final printing. Therefore, in order to enable the final overall slurry to be used for 3D printing and to ensure the effect of the ceramic material obtained by the final printing, the present invention attempts to use a mixture of two silicon carbide powders of different particle sizes as ultrafine silicon carbide powder, so as to increase the repulsive force between particles through the size effect between the two silicon carbide powders of different particle sizes, thereby achieving the improvement of the dispersibility of the final overall slurry without adding too much alkali, thereby achieving the improvement of the rheological properties of the final overall slurry. However, the present invention takes into account that if the two silicon carbide powders of different particle sizes are directly subjected to impurity removal treatment together, they may agglomerate during the ultrasonic treatment process, or there may be insufficient impurity removal. In order to avoid the above situation, the present invention disperses the first ultrafine silicon carbide powder and the second ultrafine silicon carbide powder in the impurity removal liquid respectively, and then performs ultrasonic treatment, followed by centrifugal washing and drying to obtain the first impurity-removed powder and the second impurity-removed powder respectively.

[0014] In some more preferred embodiments of the present invention, the detergent used in the centrifugal washing is water, and the washing is performed at least three times to remove the impurity removal liquid on the surface of the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder.

[0015] In some more preferred embodiments of the present invention, the drying temperature is 50° C. to 70° C., and the drying time is 6 h to 12 h.

[0016] In some more preferred embodiments of the present invention, the ultrasonic power of the ultrasonic treatment is 80W to 120W, and the ultrasonic time is 0.5h to 1.5h, so that the ultrasound is performed under relatively mild conditions to improve the full contact between the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder and the impurity remover without affecting the structure of the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder itself.

[0017] In some more preferred embodiments of the present invention, the dispersion is carried out by stirring, that is, the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder is added to the impurity-removing liquid under stirring, and stirring is continued for 20 minutes to 40 minutes after the addition is completed to ensure that the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder is evenly dispersed in the impurity-removing liquid.

[0018] In some preferred embodiments of the present invention, the particle size of the first ultrafine silicon carbide powder used in the present invention is 0.8μm~1.2μm, and the particle size of the second ultrafine silicon carbide powder is 0.1μm~0.4μm, so as to ensure that the two silicon carbide powders with different particle sizes can increase the repulsive force between particles through the size effect between the two silicon carbide powders with different particle sizes, thereby achieving improvement in the dispersion of the final overall slurry.

[0019] The present invention also takes into account the possible presence of impurities on the surface of the first and second ultrafine silicon carbide powders, and the presence of impurities may cause the rheological properties of the final overall slurry to deteriorate. Therefore, the present invention first immerses the first and second ultrafine silicon carbide powders in a decontamination liquid, and then uses ultrasonic treatment to allow the decontamination liquid to fully contact the surface of the ultrafine silicon carbide powders, thereby removing impurities that may exist on the surfaces of the first and second ultrafine silicon carbide powders, thereby helping to reduce the viscosity of the slurry and thus improve the rheological properties of the slurry. In addition, the removal of impurity ions is conducive to subsequently improving the composite effect of the modifier on the surface of the ultrafine silicon carbide powder, thereby further improving the rheological properties of the slurry.

[0020] The present invention uses ammonium citrate as a benchmark and obtains an impurity remover by compounding ammonium carbonate and ammonium bicarbonate. That is, the present invention uses ammonium citrate, ammonium carbonate and ammonium bicarbonate together as impurity removers, wherein ammonium carbonate and ammonium bicarbonate are alkaline after being dissolved in water and can act as a weak base, which helps to dissolve impurities on the surface of ultrafine silicon carbide powder and enter the impurity removal liquid in the form of impurity ions. The impurity ions entering the impurity removal liquid can be complexed with ammonium citrate to form a stable complex soluble in water. For example, impurity ions such as iron ions and aluminum ions entering the impurity removal liquid can be complexed with ammonium citrate to form a stable complex soluble in water, thereby avoiding the situation where the dissolved impurity ions re-attach to the surface of the ultrafine silicon carbide powder, thereby effectively and efficiently achieving the removal of impurities on the surface of the ultrafine silicon carbide powder. In some preferred embodiments of the present invention, the amount of ammonium carbonate introduced is 80% to 100% of the mass of the ammonium citrate, and the amount of ammonium bicarbonate introduced is 80% to 100% of the mass of the ammonium citrate.

[0021] In some preferred embodiments of the present invention, the mass concentration of the impurity remover in the impurity removing liquid is 0.5% to 1.5%, so that the pH of the impurity removing liquid used in the present invention is relatively mild compared to strong acids and strong bases, and will not affect the surface active groups of the ultrafine silicon carbide powder during the treatment process, thereby not affecting the subsequent surface modification treatment of the ultrafine silicon carbide powder.

[0022] The present invention does not limit the specific usage ratio of the impurity-removing liquid to the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder, as long as the impurity-removing liquid can ensure that the first ultrafine silicon carbide powder or the second ultrafine silicon carbide powder is uniformly dispersed. In some more preferred embodiments of the present invention, the usage ratio of the impurity-removing liquid to the first ultrafine silicon carbide powder and the usage ratio of the impurity-removing liquid to the second ultrafine silicon carbide powder are both 100 mL:1.5 g to 2.5 g.

[0023] In some preferred embodiments of the present invention, the centrifugal speed during the centrifugal washing is 4000 r / min to 6000 r / min, and the centrifugal time is 3 min to 7 min.

[0024] Step 2, pre-modification treatment:

[0025] 2.1) Dispersing the modifying agent and graphene in water in sequence to obtain a modifying agent dispersion.

[0026] 2.2) The first impurity-removing powder and the second impurity-removing powder are sequentially dispersed in the modifier dispersion to form a mixed solution.

[0027] It should be noted that, in order to ensure that the modifying agent and graphene can be uniformly dispersed in water to form a modifier dispersion with uniform components, in some preferred embodiments of the present invention, the modifier dispersion is specifically obtained by the following steps: dispersing the modifying agent in water to obtain a modifying agent solution; using graphene as a modifier, dispersing it in the modifying agent solution to obtain a modifier dispersion.

[0028] It should be emphasized that in some preferred embodiments of the present invention, based on the first impurity-removing powder as 100%, the amount of the second impurity-removing powder added is 20% to 60% of the mass of the first impurity-removing powder, that is, the mass ratio of the first impurity-removing powder and the second impurity-removing powder added in the present invention is 100:20 to 60, so that the first impurity-removing powder and the second impurity-removing powder are mixed during the modification process of the present invention. Since the particle size of the second impurity-removing powder is finer than that of the first impurity-removing powder, the second impurity-removing powder can be filled in the gaps between the first impurity-removing powders during the dispersion process, thereby increasing the repulsive force between particles and thereby improving the dispersibility of the final overall slurry. Moreover, the addition of the second impurity-removing powder as a particle reinforcement can not only increase the solid content of the slurry, but also help to improve the density of the printed material, thereby improving the mechanical properties of the slurry such as strength and stiffness, thereby effectively improving the elastic modulus of the slurry to ensure that the ceramic material formed by the final overall slurry printing can maintain its required printed shape.

[0029] It should also be noted that the present invention uses graphene as a modifier, and forms a strong interface bond between the coated graphene layer and the surface of the first impurity-removing powder and the second impurity-removing powder through the coated graphene layer. This allows the final slurry to be printed into a ceramic material, and the resulting ceramic material can be deflected during crack propagation to improve fracture toughness. When the crack deflection encounters weak interface bonding, the fracture energy will be transmitted along the graphene surface, causing the graphene to be pulled out, thereby improving the fracture toughness of the material and improving the mechanical properties of the final ceramic material.

[0030] In order to achieve the above-mentioned effects, the present invention takes into account that graphene has a high specific surface area, which leads to the phenomenon of self-agglomeration of graphene. In order to avoid the self-agglomeration of graphene during the treatment process, the present invention first disperses the modification aid in water to form a modification aid solution, and then adds graphene, so that the graphene can be evenly dispersed in water under the dispersing action of the modification aid to form a modifier dispersion, so that the graphene can subsequently be evenly and fully contacted with the first impurity-removing powder and the second impurity-removing powder, so as to improve the subsequent modification efficiency and modification effect of the first impurity-removing powder and the second impurity-removing powder.

[0031] In some preferred embodiments of the present invention, the modification aid used in the present invention is SST-929 dispersant, which helps graphene to be uniformly dispersed in water. The SST-929 dispersant used in the present invention is purchased from Qingdao Hailan Chemical Technology Co., Ltd.

[0032] In some preferred embodiments of the present invention, in the modifier dispersion, the amount of the modifying agent added is 0.4% to 1% of the mass of the first impurity-removing powder, and the amount of the graphene added is 1% to 1.5% of the mass of the first impurity-removing powder, so that the modifying agent used in the present invention is not only used to achieve a high dispersion of graphene, but also can promote the dispersion of ultrafine powders, namely the first impurity-removing powder and the second impurity-removing powder, while avoiding the agglomeration of graphene, the first impurity-removing powder and the second impurity-removing powder, to obtain a mixed solution with low viscosity and high solid content. In some preferred embodiments of the present invention, the mass concentration of the modifying agent in the modifier dispersion is 0.4% to 1%.

[0033] In some preferred embodiments of the present invention, when dispersing the modifying agent, the present invention adopts room temperature ultrasonic treatment for dispersion, and the ultrasonic power of the room temperature ultrasonic treatment is 80W to 120W, and the ultrasonic time is 10min to 20min, so that the modifying agent is uniformly dispersed in water to form a modifying agent solution with uniform components.

[0034] In some preferred embodiments of the present invention, when dispersing graphene, the present invention adopts room temperature ultrasonic treatment for dispersion, and the ultrasonic power of the room temperature ultrasonic treatment is 80W to 120W, and the ultrasonic time is 20min to 40min, so that the graphene is uniformly dispersed in the modification auxiliary agent solution to form a modifier dispersion with uniform components.

[0035] In some preferred embodiments of the present invention, when dispersing the first impurity-removing powder and the second impurity-removing powder, the present invention adopts ultrasonic treatment for dispersion, and the temperature of the ultrasonic treatment is 25°C to 35°C, the ultrasonic power is 80W to 120W, and the ultrasonic time is 60min to 90min, so that the first impurity-removing powder and the second impurity-removing powder are uniformly dispersed in the modifier dispersion, and at the same time, it helps to wrap graphene on the surface of the first impurity-removing powder and the second impurity-removing powder to form a mixed solution with uniform components, so as to improve the effect and efficiency of subsequent modification treatment.

[0036] Step 3, modification treatment:

[0037] The mixed solution is ball-milled so that the graphene is tightly coated on the surfaces of the first impurity-removed powder and the second impurity-removed powder to form a mixed modified powder, thereby obtaining a precursor solution containing the mixed modified powder.

[0038] It should be noted that the present invention performs ball milling on the basis of the above-mentioned multiple ultrasonic treatments, so that the graphene is in closer contact with the surface of the first and second impurity-removing powders through ball milling, which is conducive to the formation of a strong interface bond between the graphene and the first and second impurity-removing powders at the interface under the mechanical force of ball milling, thereby improving the strength and toughness of the printed body formed by the final overall slurry printing. Moreover, after the surfaces of the first and second impurity-removing powders are coated with graphene, it is possible to give the surfaces of the first and second impurity-removing powders an electrostatic-steric hindrance effect, thereby further increasing the repulsive force between the particles, improving the dispersibility of the slurry, reducing the free activity space of the particles, and helping to improve the bonding force between the silicon carbide particles, thereby effectively improving the strength and toughness of the printed product. In addition, when the printed body formed by printing the final overall slurry of the present invention is cured to form the corresponding ceramic material by using a photocuring method, since the present invention introduces graphene on the surface of the first impurity-removing powder and the second impurity-removing powder, and the ultraviolet light absorption peak of graphene is at 230nm, the introduced graphene can also improve the slurry's effective absorption of ultraviolet light and improve the photocuring efficiency of the slurry.

[0039] The present invention takes into account that if the ball milling time is too short, it will lead to insufficient mixing, and if the ball milling time is too long, it will lead to the production of more small particles. The small particles produced are prone to aggregation, which in turn leads to excessive yield stress of the prepared precursor solution, which is not conducive to the subsequent printing of the final overall slurry. Therefore, in some preferred embodiments of the present invention, the ball milling time used is 1h to 2h. In some more preferred embodiments of the present invention, the ball milling speed is 200r / min to 400r / min, and the ball-to-material ratio is 1 to 3:1.

[0040] Step 4: ball milling and pulping:

[0041] The photosensitive resin, diluent, initiator, dispersant and pH regulator are sequentially dispersed in the precursor solution to obtain a mixed slurry; the mixed slurry is ball-milled to obtain the ultrafine silicon carbide powder slurry.

[0042] It should be noted that, in some preferred embodiments of the present invention, when the mixed slurry is ball-milled, the ball-to-material ratio of the ball-milling treatment is 1 to 3:1, the ball-milling speed is 150 r / min to 250 r / min, and the ball-milling time is 1.5 h to 2.5 h, so as to ensure that the components are fully in contact with each other. At the same time, it can avoid that the yield stress of the prepared ultrafine silicon carbide powder slurry is too large, so as to avoid the extrusion force of subsequent 3D printing being too high, and ensure that the ultrafine silicon carbide powder slurry of the present invention can be used for 3D printing.

[0043] In some preferred embodiments of the present invention, the total mass of the first modified powder and the second modified powder accounts for 50% to 60% of the total mass of the ultrafine silicon carbide powder slurry, that is, the total mass of the mixed modified powder accounts for 50% to 60% of the total mass of the ultrafine silicon carbide powder slurry.

[0044] In some preferred embodiments of the present invention, the photosensitive resin is one or more of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and polyethylene glycol diacrylate. In some more preferred embodiments of the present invention, the photosensitive resin accounts for 20% to 35% of the total mass of the ultrafine silicon carbide powder slurry.

[0045] In some preferred embodiments of the present invention, the diluent is one or more of trimethylolpropane triacrylate, pentaerythritol acrylate, and trimethylolpropane triacrylate. In some more preferred embodiments of the present invention, the diluent accounts for 0.1% to 0.5% of the total mass of the ultrafine silicon carbide powder slurry.

[0046] Considering the current widespread use of photocuring technology, the present invention utilizes a photoinitiator as the initiator to promote rapid curing of the ultrafine silicon carbide powder slurry under ultraviolet light. In some preferred embodiments, the photoinitiator employed is one or more of 2-hydroxy-2-methyl-1-phenylpropanone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. In some more preferred embodiments, the initiator comprises 0.5% to 2% of the total mass of the ultrafine silicon carbide powder slurry.

[0047] In some preferred embodiments of the present invention, the dispersant is PAA. PAA is an ionic dispersant that can be adsorbed on the particle surface to disperse the silicon carbide through a steric effect. Secondly, it can produce an electrostatic steric stabilization effect, thereby stably and evenly dispersing the silicon carbide in the slurry. In some more preferred embodiments of the present invention, the dispersant accounts for 0.3% to 1.7% of the total mass of the ultrafine silicon carbide powder slurry.

[0048] In some preferred embodiments of the present invention, the pH adjuster is used to adjust the pH value of the silicon carbide ceramic slurry to 8-9.

[0049] In some more preferred embodiments of the present invention, the pH adjuster is aqueous ammonia with a mass concentration of 30%.

[0050] The present invention also provides an ultrafine silicon carbide powder slurry prepared by the above preparation method.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention uses ammonium citrate as a basis, and obtains an impurity remover by compounding ammonium carbonate and ammonium bicarbonate. The first ultrafine silicon carbide powder and the second ultrafine silicon carbide powder are subjected to an impurity removal treatment to remove impurities that may exist on the surfaces of the first ultrafine silicon carbide powder and the second ultrafine silicon carbide powder, thereby facilitating the reduction of the viscosity of the slurry and thus improving the rheological properties of the slurry. The invention controls the amount of ammonium carbonate introduced to be 80% to 100% of the mass of ammonium citrate and the amount of ammonium bicarbonate introduced to be 80% to 100% of the mass of ammonium citrate, so that the ammonium carbonate and ammonium bicarbonate in the impurity remover are alkaline after being dissolved in water and can act as a weak base, thereby helping to dissolve impurities on the surface of ultrafine silicon carbide powder and enter the impurity removal liquid in the form of impurity ions. The impurity ions entering the impurity removal liquid can be complexed with the ammonium citrate to form a stable complex soluble in water. For example, impurity ions such as iron ions and aluminum ions entering the impurity removal liquid can be complexed with the ammonium citrate to form a stable complex soluble in water, thereby preventing the dissolved impurity ions from re-attaching to the surface of the ultrafine silicon carbide powder, thereby effectively and efficiently removing impurities on the surface of the ultrafine silicon carbide powder.

[0053] The present invention first disperses the modifying agent in water to form a modifying agent solution, and then adds graphene so that the graphene can be evenly dispersed in water under the dispersing effect of the modifying agent to form a modifying agent dispersion, so that the graphene can be uniformly and fully contacted with the first impurity-removing powder and the second impurity-removing powder in the future, so as to improve the subsequent modification efficiency and modification effect of the first impurity-removing powder and the second impurity-removing powder. Among them, the present invention uses graphene as a modifier, and forms a strong interface bond with the surface of the first impurity-removing powder and the second impurity-removing powder through the coated graphene layer, so that after the final slurry is prepared and printed into a ceramic material, the ceramic material formed can deflect and improve the fracture toughness during the crack propagation process. When the crack deflection encounters a weak interface bond, the fracture energy will be transmitted along the graphene surface, causing the graphene to be pulled out, improving the fracture toughness of the material, thereby achieving improvement of the mechanical properties of the final ceramic material. Moreover, the present invention mixes the first impurity-removing powder and the second impurity-removing powder during the modification process. Since the particle size of the second impurity-removing powder is finer than that of the first impurity-removing powder, the second impurity-removing powder can fill the gaps between the first impurity-removing powders during the dispersion process, thereby increasing the repulsive force between particles and thereby improving the dispersibility of the final overall slurry. Moreover, the addition of the second impurity-removing powder as a particle reinforcement can not only increase the solid content of the slurry, but also help to increase the density of the printed material, thereby improving the mechanical properties of the slurry, such as strength and stiffness, thereby effectively improving the elastic modulus of the slurry to ensure that the ceramic material formed by the final overall slurry printing can maintain its required printed shape.

[0054] The present invention ball-mills the obtained mixed solution so that the graphene is in closer contact with the surfaces of the first and second impurity-removing powders, which is beneficial for forming a strong interface bond between the graphene and the first and second impurity-removing powders at the interface under the mechanical force of ball milling, thereby improving the strength and toughness of the printed body formed by the final overall slurry printing. Moreover, after the surfaces of the first and second impurity-removing powders are coated with graphene, an electrostatic-steric hindrance effect can be imparted to the surfaces of the first and second impurity-removing powders, thereby further increasing the repulsive force between the particles, improving the dispersibility of the slurry, reducing the free activity space of the particles, and facilitating the improvement of the bonding force between the silicon carbide particles, thereby effectively improving the strength and toughness of the printed product. In addition, when the printed body formed by printing the final overall slurry of the present invention is cured to form the corresponding ceramic material by light curing, since the present invention introduces graphene on the surface of the first impurity-removed powder and the second impurity-removed powder, and the ultraviolet light absorption peak of graphene is at 230nm, the introduced graphene can also improve the slurry's effective absorption of ultraviolet light and improve the photocuring efficiency of the slurry. The present invention obtains the ultrafine silicon carbide powder slurry by directly adding a photosensitive resin, a diluent, an initiator, a dispersant, and a pH adjuster to the formed precursor solution and performing ball milling.

[0055] The present invention effectively avoids agglomeration of silicon carbide powder during the preparation process through impurity removal, pre-modification treatment, modification treatment, and ball milling. Furthermore, the preparation process avoids the use of strong acids, strong bases, and other reagents, thereby reducing washing water consumption and avoiding the generation of large amounts of waste liquid. Furthermore, compared to traditional modification treatments, the present invention eliminates a series of post-modification processes such as centrifugation, washing, and drying, simplifying the process flow and reducing the difficulty and cost of preparation.

[0056] The ultrafine silicon carbide powder slurry prepared by the preparation method of the present invention has a low viscosity, a high solid content, and a moderate yield stress, so that the ultrafine silicon carbide powder slurry prepared by the present invention can better maintain shape and dimensional stability during the printing process, effectively reducing deformation and cracking during the printing process, which is conducive to promoting the further application of silicon carbide ceramic materials. For example, by adding functional components that meet actual needs to the slurry, it can be achieved in the subsequent preparation of high-precision and high-performance silicon carbide ceramics, semiconductor materials, aerospace materials, new energy vehicle parts, photovoltaic materials, grinding and polishing materials, composite materials and coatings. It shows great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The test results of solid content and viscosity of Examples 1-2 and Comparative Examples 1-3 are shown.

[0058] Figure 2The test results of solid content and viscosity of Example 1, Examples 3-4 and Comparative Example 4 are shown.

[0059] Figure 3 The test results of solid content and viscosity of Example 1, Examples 5-6 and Comparative Examples 5-7 are shown.

[0060] Figure 4 The test results of solid content and viscosity of Example 1, Examples 7-8 and Comparative Examples 8-9 are shown.

[0061] Figure 5 These are the test results of solid content and viscosity of Example 1, Examples 9-10 and Comparative Example 10.

[0062] Figure 6 The test results of solid content and viscosity of Example 1, Examples 11-12 and Comparative Examples 11-12 are shown. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present invention are described clearly and completely below. It should be noted that in each of the following embodiments of the present invention, the particle size of the first ultrafine silicon carbide powder used is 0.8 μm to 1.2 μm, and the particle size of the second ultrafine silicon carbide powder is 0.1 μm to 0.4 μm; and the modified additive used is SST-929 dispersant purchased from Qingdao Hailan Chemical Technology Co., Ltd.

[0064] Example 1

[0065] This embodiment provides an ultrafine silicon carbide powder slurry, which is prepared by the following steps:

[0066] Step 1: Impurity removal of ultrafine silicon carbide powder:

[0067] 1.1) Preparation of impurity removal solution:

[0068] 1.1.1) Mix ammonium citrate, ammonium carbonate, and ammonium bicarbonate in a mass ratio of 1:1:1 to obtain an impurity remover.

[0069] 1.1.2) Disperse the impurity remover obtained in 1.1.1) above in deionized water and mix well to prepare an impurity remover solution with a mass concentration of 1%.

[0070] 1.2) Impurity removal of the first ultrafine silicon carbide powder:

[0071] 1.2.1) Add a corresponding amount of the first ultrafine silicon carbide powder to the impurity-removing solution prepared in 1.1.2) above at a ratio of 2 g:100 mL with stirring. Continue stirring for 30 minutes to obtain a first impurity-removing mixed solution.

[0072] 1.2.2) Ultrasonicate the first impurity removal mixture at 100 W for 1 h.

[0073] 1.2.3) Wash the product after sonication in 1.2.2) above by centrifugation three times with deionized water as the washing liquid, each time at 5000 rpm for 5 minutes.

[0074] 1.2.4) Place the product obtained by centrifugation and washing in 1.2.3) above in a vacuum drying oven at 60°C and dry for 9 hours to obtain a first impurity-removed powder.

[0075] 1.3) Impurity removal of the second ultrafine silicon carbide powder:

[0076] 1.3.1) Disperse the corresponding mass of the second ultrafine silicon carbide powder in the impurity-removing solution at a ratio of 2 g:100 mL. Add the corresponding mass of the first ultrafine silicon carbide powder to the impurity-removing solution prepared in 1.1.2) above while stirring. Continue stirring for 30 minutes after addition to obtain a second impurity-removing mixed solution.

[0077] 1.3.2) Ultrasonicate the second impurity-removing mixture at 100 W for 1 h.

[0078] 1.3.3) The product after sonication in 1.3.2) was washed by centrifugation three times with deionized water as the washing liquid, each time at 5000 rpm for 5 minutes.

[0079] 1.3.4) Place the product obtained by centrifugation and washing in 1.3.3) above in a vacuum drying oven at 60°C and dry for 9 hours to obtain a second impurity-removed powder.

[0080] Step 2, pre-modification treatment:

[0081] 2.1) In this example, SST-929 dispersant was used as a modification aid. It was added to deionized water and ultrasonically treated at room temperature at an ultrasonic power of 100 W for 15 minutes to prepare a modification aid solution with a mass concentration of 0.7%.

[0082] 2.2) Weigh the corresponding amounts of the modifying agent solution, graphene, the first impurity-removing powder, and the second impurity-removing powder in a mass ratio of 0.7:1.2:100:40, and set aside.

[0083] 2.3) The weighed graphene was added to the weighed modification agent solution, and ultrasonically treated at room temperature at an ultrasonic power of 100 W for 30 minutes to obtain a modification agent dispersion.

[0084] 2.4) The weighed first impurity-removing powder and the second impurity-removing powder were sequentially added to the modifier dispersion prepared in 2.3) above, and ultrasonically treated at 30° C. and 100 W of ultrasonic power for 75 minutes to obtain a mixed solution.

[0085] Step 3, modification treatment:

[0086] The mixed solution obtained in 2.4) above was subjected to ball milling treatment for 1.5 h at a ball milling speed of 300 r / min and a ball-to-material ratio of 2:1 to obtain a precursor solution containing a mixed modified powder.

[0087] Step 4: ball milling and pulping:

[0088] 4.1) Weigh the corresponding amounts of precursor solution containing mixed modified powder, photosensitive resin, diluent, initiator, and dispersant according to the following mass percentages:

[0089] Mix 55% modified powder, 30% photosensitive resin, 0.3% diluent, 1% initiator, 1% dispersant, and the rest is deionized water, totaling 100%.

[0090] In this embodiment, 1,6-hexanediol diacrylate is used as the photosensitive resin, trimethylolpropane triacrylate is used as the diluent, 2-hydroxy-2-methyl-1-phenylpropanone is used as the photoinitiator, and PAA is used as the dispersant.

[0091] 4.2) The weighed photosensitive resin, diluent, initiator, dispersant, and pH adjuster are sequentially dispersed in the weighed precursor solution, and then the pH adjuster is added to adjust the pH value of the silicon carbide ceramic slurry to 8 to obtain a mixed slurry.

[0092] In this embodiment, ammonia water with a mass concentration of 30% is used as the pH regulator.

[0093] 4.3) The mixed slurry obtained in 4.2) was ball milled for 2 h at a ball mill speed of 200 r / min and a ball-to-material ratio of 2:1 to obtain an ultrafine silicon carbide powder slurry.

[0094] In order to explore the effect of the ratio of the impurity remover on the overall performance of the ultrafine silicon carbide powder slurry, the present invention provides the following examples and comparative examples.

[0095] Example 2

[0096] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0097] In this embodiment, the impurity remover is prepared by mixing ammonium citrate, ammonium carbonate and ammonium bicarbonate in a mass ratio of 1:0.8:0.8.

[0098] Comparative Example 1

[0099] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0100] In this comparative example, the impurity remover was prepared by mixing ammonium citrate, ammonium carbonate and ammonium bicarbonate in a mass ratio of 1:0.5:0.5.

[0101] Comparative Example 2

[0102] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0103] In this comparative example, the impurity remover was prepared by mixing ammonium citrate, ammonium carbonate and ammonium bicarbonate in a mass ratio of 1:1.5:1.5.

[0104] Comparative Example 3

[0105] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0106] In this comparative example, the impurity remover is single ammonium bicarbonate.

[0107] In order to explore the influence of the process parameters of ultrasonic treatment on the ultrafine silicon carbide powder slurry during the impurity removal process, the present invention provides the following examples and comparative examples.

[0108] Example 3

[0109] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0110] In this embodiment, in step 1.2.2) and step 1.3.2), the process parameters of the ultrasonic treatment are: ultrasonic power of 80W, and ultrasonic time of 0.5h.

[0111] Example 4

[0112] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0113] In this embodiment, in step 1.2.2) and step 1.3.2), the process parameters of the ultrasonic treatment are: ultrasonic power of 120W, and ultrasonic time of 1.5h.

[0114] Comparative Example 4

[0115] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0116] In this comparative example, no ultrasonic treatment was performed, that is, the first impurity-removing mixed solution and the second impurity-removing mixed solution were directly centrifuged and washed.

[0117] In order to explore the effect of the relative ratio of the first impurity-removing powder and the second impurity-removing powder on the overall performance of the ultrafine silicon carbide powder slurry during the modification pretreatment process, the present invention provides the following examples and comparative examples.

[0118] Example 5

[0119] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0120] In step 2 of this embodiment, the mass ratio of the first impurity-removing powder to the second impurity-removing powder is 100:20.

[0121] Example 6

[0122] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0123] In step 2 of this embodiment, the mass ratio of the first impurity-removing powder to the second impurity-removing powder is 100:60.

[0124] Comparative Example 5

[0125] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0126] In step 2 of this comparative example, the mass ratio of the first impurity-removing powder to the second impurity-removing powder is 100:10.

[0127] Comparative Example 6

[0128] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0129] In step 2 of this comparative example, the mass ratio of the first impurity-removing powder to the second impurity-removing powder is 100:100.

[0130] Comparative Example 7

[0131] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0132] In step 2 of this comparative example, the second impurity-removing powder in Example 1 was replaced with the first impurity-removing powder of the same mass. That is, the second impurity-removing powder was not added in this comparative example.

[0133] In order to explore the effects of modification additives and graphene on the overall performance of ultrafine silicon carbide powder slurry, the present invention provides the following examples and comparative examples.

[0134] Example 7

[0135] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0136] In step 2 of this embodiment, the mass ratio of the modification aid in the modification aid solution to the graphene, the first impurity-removing powder, and the second impurity-removing powder is 0.4:1:100:40.

[0137] Example 8

[0138] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0139] In step 2 of this embodiment, the mass ratio of the modification aid in the modification aid solution to the graphene, the first impurity-removing powder, and the second impurity-removing powder is 1:1.5:100:40.

[0140] Comparative Example 8

[0141] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0142] In step 2 of this comparative example, no modification auxiliary solution is added, that is, the graphene, the first impurity-removing powder and the second impurity-removing powder are directly dispersed in deionized water.

[0143] Comparative Example 9

[0144] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0145] In step 2 of this comparative example, graphene is not added, that is, the first impurity-removing powder and the second impurity-removing powder are directly dispersed in the modification auxiliary agent solution.

[0146] In order to explore the influence of the process parameters of ball milling on the overall performance of ultrafine silicon carbide powder slurry during the modification process, the present invention provides the following examples and comparative examples.

[0147] Example 9

[0148] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0149] In step 3 of this embodiment, the ball milling speed is 200 r / min, the ball-to-material ratio is 1:1, and the ball milling time is 1 h.

[0150] Example 10

[0151] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0152] In step 3 of this embodiment, the ball milling speed is 400 r / min, the ball-to-material ratio is 3:1, and the ball milling time is 2 h.

[0153] Comparative Example 10

[0154] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0155] In this comparative example, the ball milling process in step 3 was not performed. That is, the mixed solution finally obtained in step 2 was directly used as a precursor solution for slurrying.

[0156] In order to explore the effect of the content of the mixed modified powder on the overall performance of the ultrafine silicon carbide powder slurry during the ball milling slurry process, the present invention provides the following examples and comparative examples.

[0157] Example 11

[0158] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0159] In this embodiment, the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator, and the dispersant were weighed in the following mass percentages:

[0160] Mix 60% modified powder, 20% photosensitive resin, 0.5% diluent, 2% initiator, 1.7% dispersant, and the rest is deionized water, totaling 100%.

[0161] Example 12

[0162] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0163] In this embodiment, the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator, and the dispersant were weighed in the following mass percentages:

[0164] Mix 50% modified powder, 35% photosensitive resin, 0.1% diluent, 0.5% initiator, 0.3% dispersant, and the rest is deionized water, totaling 100%.

[0165] Comparative Example 11

[0166] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0167] In this comparative example, according to the following mass percentage components, the corresponding masses of the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator and the dispersant were weighed:

[0168] Mix 40% modified powder, 45% photosensitive resin, 0.1% diluent, 0.5% initiator, 0.3% dispersant, and the rest is deionized water, totaling 100%.

[0169] Comparative Example 12

[0170] This comparative example provides an ultrafine silicon carbide powder slurry, and the difference between this example and Example 1 is only that:

[0171] In this comparative example, according to the following mass percentage components, the corresponding masses of the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator and the dispersant were weighed:

[0172] Mix 70% modified powder, 25% photosensitive resin, 0.1% diluent, 0.5% initiator, 0.3% dispersant, and the rest is deionized water, totaling 100%.

[0173] Example 13

[0174] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0175] In 1.1.2) of this embodiment, the mass concentration of the prepared impurity removal liquid is 0.5%.

[0176] In 1.2.1) of this embodiment, the ratio of the first ultrafine silicon carbide powder to the impurity removal liquid is 1.5 g:100 mL.

[0177] In 1.2.3) of this embodiment, centrifugation was performed at a speed of 4000 r / min for 3 min each time.

[0178] In 1.2.4) of this embodiment, the drying temperature is 50° C. and the drying time is 6 h.

[0179] In 1.3.1) of this embodiment, the ratio of the second ultrafine silicon carbide powder to the impurity removal liquid is 1.5 g:100 mL.

[0180] In 1.3.3) of this embodiment, centrifugation was performed at a speed of 4000 r / min for 3 min each time.

[0181] In 1.3.4) of this embodiment, the drying temperature is 50° C. and the drying time is 6 h.

[0182] In 2.1) of this embodiment, the mass concentration of the modification aid solution is 0.4%.

[0183] In 4.1) of this embodiment, the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator, and the dispersant were weighed in the following mass percentages:

[0184] Mix 50% modified powder, 35% photosensitive resin, 0.1% diluent, 0.5% initiator, 0.3% dispersant, and the rest is deionized water, totaling 100%.

[0185] In this embodiment, trimethylolpropane triacrylate is used as the photosensitive resin, pentaerythritol acrylate is used as the diluent, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide is used as the photoinitiator, and PAA is used as the dispersant.

[0186] In 4.2) of this embodiment, the pH value of the silicon carbide ceramic slurry is adjusted to 8.

[0187] In 4.3) of this embodiment, the mixed slurry obtained in 4.2) was ball milled for 1.5 h at a ball milling speed of 150 r / min and a ball-to-material ratio of 1:1.

[0188] Example 14

[0189] This embodiment provides an ultrafine silicon carbide powder slurry, and the difference between this embodiment and Example 1 is only that:

[0190] In 1.1.2) of this embodiment, the mass concentration of the prepared impurity removal liquid is 1.5%.

[0191] In 1.2.1) of this embodiment, the ratio of the first ultrafine silicon carbide powder to the impurity removal liquid is 2.5 g:100 mL.

[0192] In 1.2.3) of this embodiment, centrifugation was performed at a speed of 6000 r / min for 7 min each time.

[0193] In 1.2.4) of this embodiment, the drying temperature is 70° C. and the drying time is 12 h.

[0194] In 1.3.1) of this embodiment, the ratio of the second ultrafine silicon carbide powder to the impurity removal liquid is 2.5 g:100 mL.

[0195] In 1.3.3) of this embodiment, centrifugation was performed at a speed of 6000 r / min for 7 min each time.

[0196] In 1.3.4) of this embodiment, the drying temperature is 70° C. and the drying time is 12 h.

[0197] In 2.1) of this embodiment, the mass concentration of the modification aid solution is 1%.

[0198] In 4.1) of this embodiment, the precursor solution containing the mixed modified powder, the photosensitive resin, the diluent, the initiator, and the dispersant were weighed in the following mass percentages:

[0199] Mix 60% modified powder, 20% photosensitive resin, 0.5% diluent, 2% initiator, 1.7% dispersant, and the rest is deionized water, totaling 100%.

[0200] In this embodiment, polyethylene glycol diacrylate is used as the photosensitive resin, pentaerythritol acrylate is used as the diluent, a mixture of 2-hydroxy-2-methyl-1-phenylpropanone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide in an equal weight ratio is used as the photoinitiator, and PAA is used as the dispersant.

[0201] In 4.2) of this embodiment, the pH value of the silicon carbide ceramic slurry is adjusted to 9.

[0202] In 4.3) of this embodiment, the mixed slurry obtained in 4.2) was ball milled for 2.5 h at a ball mill speed of 250 r / min and a ball-to-material ratio of 3:1.

[0203] Experimental part

[0204] 1. Effect of the ratio of impurity remover on the performance of ultrafine silicon carbide powder slurry

[0205] It should be noted that the present invention uses the following method to test the dispersion stability of the ultrafine silicon carbide powder slurry of each embodiment or comparative example:

[0206] The ultrafine silicon carbide powder slurry of the embodiment or comparative example to be tested is placed in a 100 mL beaker, and then allowed to stand at room temperature for 24 hours. The state of the ultrafine silicon carbide powder slurry after standing is observed. When there is no sedimentation of the ultrafine silicon carbide powder slurry after standing, it is considered that the dispersion stability of the ultrafine silicon carbide powder slurry is excellent; when there is only a small amount of precipitation, it can be regarded as that the dispersion stability of the ultrafine silicon carbide powder slurry is excellent; when there is a large amount of sediment deposition or obvious stratification, it is considered that the dispersion stability of the ultrafine silicon carbide powder slurry is poor.

[0207] In the present invention, the dispersion stability test was performed on the ultrafine silicon carbide powder slurries of Examples 1 to 2 and Comparative Examples 1 to 3 according to the above method, and the test results are summarized as shown in Table 1.

[0208] Table 1 Stability test results of Examples 1 to 2 and Comparative Examples 1 to 3

[0209] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Subsidence phenomenon none none There is a little sediment at the bottom There is obvious sediment at the bottom There is a lot of sediment at the bottom

[0210] It can be seen from the test results in Table 1 that the ultrafine silicon carbide powder slurries of Examples 1 and 2 of the present invention have no sedimentation phenomenon and have excellent stability.

[0211] The present invention also takes the ultrafine silicon carbide powder slurry of Examples 1 to 2 and Comparative Examples 1 to 3 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 1 shown.

[0212] Depend on Figure 1 It can be seen from the test results that the ultrafine silicon carbide powder slurries of Example 1 and Example 2 can both reduce the viscosity of the ultrafine silicon carbide powder slurries to <10 Pa·s while ensuring a solid content of more than 60%, and both have excellent stability, a high solid content and a moderate viscosity.

[0213] From Table 1 and Figure 1 It can also be seen that when the content of ammonium carbonate and ammonium bicarbonate is too low, it is difficult to effectively remove impurities from the ultrafine silicon carbide powder, resulting in poor dispersion of the ultrafine silicon carbide powder. Although a higher solid content can be achieved, both will lead to increased viscosity of the ultrafine silicon carbide powder slurry and poor rheological properties.

[0214] Excessive amounts of ammonium carbonate and ammonium bicarbonate may result in excessive ionic components being provided to the slurry system, which in turn reduces the dispersion stability of the ultrafine silicon carbide powder. Although a higher solids content can be achieved, this will increase the viscosity of the ultrafine silicon carbide powder slurry and worsen its rheological properties.

[0215] When ammonium carbonate and ammonium citrate are not present, although the solid content of the slurry can be increased, it is impossible to effectively remove impurities on the surface of the ultrafine silicon carbide powder, and it is difficult to effectively improve the dispersibility of the ultrafine silicon carbide powder, resulting in low component stability of the overall slurry and a greatly increased viscosity.

[0216] Based on the above, the components of the impurity remover will affect the dispersion stability, solid content and rheological properties of the slurry. Therefore, the present invention preferably uses a mixture of ammonium citrate, ammonium carbonate and ammonium bicarbonate in a mass ratio of 1:0.8 to 1:0.8 to 1 as the impurity remover.

[0217] 2. Effect of ultrasonic treatment on the performance of ultrafine silicon carbide powder slurry during impurity removal

[0218] According to the above method, the present invention conducted a dispersion stability test on the ultrafine silicon carbide powder slurry of Example 1, Examples 3-4 and Comparative Example 4, and the test results are summarized as shown in Table 2.

[0219] Table 2 Stability test results of Example 1, Examples 3-4 and Comparative Example 4

[0220] Example 1 Example 3 Example 4 Comparative Example 4 Subsidence phenomenon none none none There is obvious sediment at the bottom

[0221] It can be seen from the test results in Table 2 that the ultrafine silicon carbide powder slurries of Examples 1, 3 and 4 of the present invention have no sedimentation phenomenon, indicating that the ultrafine silicon carbide powder slurries of Examples 1 and 3-4 have excellent stability.

[0222] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Examples 3-4 and Comparative Example 4 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 2 shown.

[0223] Depend on Figure 2 It can be seen from the test results that the ultrafine silicon carbide powder slurries of Examples 1, 3 and 4 can reduce the viscosity of the ultrafine silicon carbide powder slurries to <10Pa·s while ensuring a solid content of more than 60%. This shows that the ultrafine silicon carbide powder slurries prepared in Examples 1, 3 and 4 have excellent stability, a high solid content and a moderate viscosity.

[0224] By comparing the test results of Example 1 and Comparative Example 4, it can be seen that when ultrasonic treatment is not introduced, it is difficult to effectively remove impurities in the ultrafine silicon carbide powder by relying solely on immersion treatment. This shows that the process parameters of ultrasonic treatment during the impurity removal treatment will also affect the dispersion stability, solid content and rheological properties of the slurry. Therefore, the ultrasonic power of the ultrasonic treatment preferably used in the present invention is 80W to 120W, and the ultrasonic time is 0.5h to 1.5h.

[0225] 3. The influence of the relative ratio of the first impurity-removing powder and the second impurity-removing powder on the overall performance of ultrafine silicon carbide powder slurry

[0226] According to the above method, the present invention conducted a dispersion stability test on the ultrafine silicon carbide powder slurry of Example 1, Examples 5-6 and Comparative Examples 5-7, and the test results are summarized as shown in Table 3.

[0227] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Examples 5-6 and Comparative Examples 5-7 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 3 shown.

[0228] Table 3 Stability test results of Example 1, Examples 5-6 and Comparative Examples 5-7

[0229]

[0230] It can be seen from the test results in Table 3 that the ultrafine silicon carbide powder slurries of Example 1, Example 5 and Example 6 have no sedimentation phenomenon and all have excellent stability.

[0231] Depend on Figure 3 It can be seen from the test results that Example 1, Example 5 and Example 6 all have high solid content and moderate viscosity.

[0232] From Table 3 and Figure 3 It can also be seen that when the content of the second impurity-removing powder is too little or too much relative to the first impurity-removing powder, the dispersion stability of the ultrafine silicon carbide powder slurry will be reduced. This may be because when the size is not appropriate, the size effect between the two silicon carbide powders of different particle sizes cannot be effectively exerted, and the repulsive force between the particles cannot be effectively increased, making it difficult to improve the dispersibility of the slurry with less alkali addition, and it is also difficult to reduce the viscosity to <10Pa·s while ensuring a solid content of more than 60%. Therefore, the present invention preferably controls the mass ratio of the first impurity-removing powder to the second impurity-removing powder within the range of 100:20 to 60.

[0233] 4. Effects of Modification Additives and Graphene on the Performance of Ultrafine Silicon Carbide Powder Slurry

[0234] According to the above method, the present invention conducted dispersion stability tests on the ultrafine silicon carbide powder slurries of Example 1, Examples 7-8 and Comparative Examples 8-9, and the test results are summarized as shown in Table 4.

[0235] Table 4 Stability test results of Example 1, Examples 7-8 and Comparative Examples 8-9

[0236] Example 1 Example 7 Example 8 Comparative Example 8 Comparative Example 9 Subsidence phenomenon none none none There is obvious sediment deposition at the bottom There is obvious sediment deposition at the bottom

[0237] It can be seen from the test results in Table 4 that the ultrafine silicon carbide powder slurries of Examples 1, 7 and 8 have no sedimentation phenomenon, which indicates that the ultrafine silicon carbide powder slurries of Examples 1, 7 and 8 have excellent stability.

[0238] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Example 7, Example 8, Comparative Example 8 and Comparative Example 9 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 4 As shown. Figure 4 It can be seen from the test results that Example 1, Example 7 and Example 8 all have high solid content and moderate viscosity.

[0239] From Table 4 and Figure 4 It can also be seen that when no modifying agent or graphene is added, the first impurity-removing powder and the second impurity-removing powder cannot be effectively modified, which makes it difficult for the prepared ultrafine silicon carbide powder slurry to achieve improved slurry dispersibility under the premise of less alkali addition, and it is also difficult to reduce the viscosity to <10Pa·s while ensuring a solid content of more than 60%. Therefore, the present invention preferably controls the mass ratio of the modifying agent to graphene, the first impurity-removing powder and the second impurity-removing powder in the modifying agent solution within the range of 0.4~1:1~1.5:100:20~60.

[0240] 5. Effect of ball milling process parameters on the performance of ultrafine silicon carbide powder slurry during modification

[0241] According to the above method, the present invention conducted a dispersion stability test on the ultrafine silicon carbide powder slurry of Example 1, Examples 9-10 and Comparative Example 10, and the test results are summarized as shown in Table 5.

[0242] Table 5 Stability test results of Example 1, Examples 9-10 and Comparative Example 10

[0243] Example 1 Example 9 Example 10 Comparative Example 10 Subsidence phenomenon none none none There is obvious sediment deposition at the bottom

[0244] It can be seen from the test results in Table 5 that the ultrafine silicon carbide powder slurries of Examples 1, 9 and 10 have no sedimentation phenomenon, which indicates that the ultrafine silicon carbide powder slurries of Examples 1, 9 and 10 have excellent stability.

[0245] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Example 9, Example 10 and Comparative Example 10 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 5 As shown. Figure 5 It can be seen from the test results that the ultrafine silicon carbide powder slurries of Example 1, Example 9, and Example 10 all have a high solid content and a moderate viscosity.

[0246] From Table 5 and Figure 5 It can also be seen that when the ball milling treatment in step 3 is not performed, the first impurity-removing powder and the second impurity-removing powder cannot be effectively modified, which results in the difficulty in improving the dispersibility of the prepared ultrafine silicon carbide powder slurry under the premise of less alkali addition, and it is also difficult to reduce the viscosity to <10Pa·s while ensuring a solid content of more than 60%. Therefore, the ball milling time adopted in the ball milling treatment of the present invention is 1h~2h, the ball milling speed is 200r / min~400r / min, and the ball-to-material ratio is 1~3:1.

[0247] 6. Effect of the content of mixed modified powder on the performance of ultrafine silicon carbide powder slurry

[0248] According to the above method, the present invention conducted a dispersion stability test on the ultrafine silicon carbide powder slurry of Example 1, Examples 11-12 and Comparative Examples 11-12, and the test results are summarized as shown in Table 6.

[0249] Table 6 Stability test results of Example 1, Examples 11-12 and Comparative Examples 11-12

[0250]

[0251] It can be seen from the test results in Table 6 that the ultrafine silicon carbide powder slurries of Examples 1, 11 and 12 have no sedimentation phenomenon, which indicates that the ultrafine silicon carbide powder slurries of Examples 1, 11 and 12 have excellent stability.

[0252] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Example 11, Example 12, Comparative Example 11 and Comparative Example 12 as examples, and respectively measures the solid content and the shear rate of 400s -1 The apparent viscosity was tested and the test results were as follows Figure 6 As shown. Figure 6 It can be seen from the test results that Example 1, Example 11 and Example 12 all have high solid content and moderate viscosity.

[0253] From Table 6 and Figure 6 It can also be seen that when the amount of photosensitive resin, diluent, initiator and dispersant used is too much or too little, it is impossible to effectively achieve the viscosity reduction to <10Pa·s on the basis of ensuring a solid content of more than 60%. Therefore, the present invention preferably controls the amount of photosensitive resin added to be in the range of 20% to 35% of the total mass of the ultrafine silicon carbide powder slurry, the amount of diluent added to be in the range of 0.1% to 0.5% of the total mass of the ultrafine silicon carbide powder slurry, the amount of initiator added to be in the range of 0.5% to 2% of the total mass of the ultrafine silicon carbide powder slurry, and the amount of dispersant added to be in the range of 0.3% to 1.7% of the total mass of the ultrafine silicon carbide powder slurry.

[0254] The present invention also takes the ultrafine silicon carbide powder slurry of Example 1, Example 13 and Example 14 as an example, and takes 2g of the ultrafine silicon carbide powder slurry of Example 1, Example 13 and Example 14 respectively. It is placed on the printing platform of the 3D printing equipment and irradiated with ultraviolet light with a wavelength of 405nm. The results show that within 15s of irradiation, the ultrafine silicon carbide powder slurries of Example 1, Example 13 and Example 14 can all be cured, indicating that the ultrafine silicon carbide powder slurry prepared by the present invention can be used in a 3D printing preparation method using a photocuring method to achieve the preparation of the required silicon carbide ceramic material.

[0255] In addition, after curing the ultrafine silicon carbide powder slurry of the above-mentioned Examples 1, 13 and 14, the surfaces of the silicon carbide ceramic materials corresponding to Examples 1, 13 and 14 were observed and it was found that all three samples had a dense surface layer without cracking.

[0256] In summary, it can be seen that the excellent effect of the present invention is not obtained by adjusting a single factor, but is achieved through the organic synergistic effect of the above-mentioned main factors to jointly improve the comprehensive performance of the ultrafine silicon carbide powder slurry, so that the ultrafine silicon carbide powder slurry prepared by the present invention can have a high solid content on the basis of maintaining a viscosity of 10 Pa·s, and also has a moderate yield stress, so that the ultrafine silicon carbide powder slurry prepared by the present invention can better maintain shape and dimensional stability during the printing process, effectively reducing deformation and cracking during the printing process, and can obtain a dense silicon carbide ceramic material. The printed silicon carbide ceramic material also has excellent high temperature resistance and corrosion resistance, so that the ultrafine silicon carbide powder slurry prepared by the present invention can not only be used to prepare high-precision and high-performance silicon carbide ceramics, but also is expected to be used to prepare semiconductor materials, aerospace materials, new energy vehicle parts, photovoltaic materials, grinding and polishing materials, composite materials and coatings and other functional materials.

[0257] Obviously, the above embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine silicon carbide powder slurry, characterized in that: include: dispersing the impurity remover in water to obtain an impurity remover liquid; The impurity remover is prepared by compounding ammonium carbonate and ammonium bicarbonate with ammonium citrate as a base; wherein the amount of ammonium carbonate introduced is 80% to 100% of the mass of the ammonium citrate, and the amount of ammonium bicarbonate introduced is 80% to 100% of the mass of the ammonium citrate; Dispersing the first ultrafine silicon carbide powder in a portion of the impurity removal liquid, followed by ultrasonic treatment, centrifugal washing, and drying to obtain a first impurity-removed powder; the particle size of the first ultrafine silicon carbide powder is 0.8 μm to 1.2 μm; Dispersing the second ultrafine silicon carbide powder in a portion of the impurity removal liquid, followed by ultrasonic treatment, centrifugal washing, and drying to obtain a second impurity-removed powder; the particle size of the second ultrafine silicon carbide powder is 0.1 μm to 0.4 μm; dispersing the modification aid and graphene in water in sequence to obtain a modification agent dispersion; dispersing the first impurity-removed powder and the second impurity-removed powder in the modifier dispersion in sequence to form a mixed solution; ball-milling the mixed solution so that graphene is tightly coated on the surfaces of the first impurity-removed powder and the second impurity-removed powder to form a mixed modified powder, thereby obtaining a precursor solution containing the mixed modified powder; Taking the first impurity-removing powder as 100%, the amount of the second impurity-removing powder added is 20% to 60% of the mass of the first impurity-removing powder; In the modifier dispersion, the amount of the modifying agent added is 0.4% to 1% of the mass of the first impurity-removing powder, and the amount of the graphene added is 1% to 1.5% of the mass of the first impurity-removing powder; The photosensitive resin, diluent, initiator, dispersant and pH regulator are sequentially dispersed in the precursor solution to obtain a mixed slurry; the mixed slurry is ball-milled to obtain the ultrafine silicon carbide powder slurry.

2. The preparation method according to claim 1, wherein The modification aid is SST-929 dispersant.

3. The preparation method according to claim 1, wherein When the mixed solution is subjected to ball milling treatment, the ball milling time of the ball milling treatment is 1 h to 2 h.

4. The preparation method according to claim 1, wherein When the mixed solution is subjected to ball milling treatment, the ball milling speed is 200 r / min to 400 r / min, and the ball-to-material ratio is 1 to 3:

1.

5. The preparation method according to claim 1, wherein When the mixed slurry is ball-milled, the ball-to-material ratio of the ball-milling treatment is 1-3:1, the ball-milling speed is 150 r / min-250 r / min, and the ball-milling time is 1.5 h-2.5 h.

6. The preparation method according to claim 1, wherein The mass concentration of the impurity remover in the impurity removing liquid is 0.5% to 1.5%.

7. The preparation method according to claim 1, wherein The photosensitive resin is one or more of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and polyethylene glycol diacrylate; the photosensitive resin accounts for 20% to 35% of the total mass of the ultrafine silicon carbide powder slurry; The diluent is one or more of trimethylolpropane triacrylate, pentaerythritol acrylate and trimethylolpropane triacrylate; the diluent accounts for 0.1% to 0.5% of the total mass of the ultrafine silicon carbide powder slurry; The initiator is a photoinitiator; the initiator accounts for 0.5% to 2% of the total mass of the ultrafine silicon carbide powder slurry; The dispersant is PAA; the dispersant accounts for 0.3% to 1.7% of the total mass of the ultrafine silicon carbide powder slurry; The pH adjuster is used to adjust the pH value of the silicon carbide ceramic slurry to 8-9.

8. An ultrafine silicon carbide powder slurry prepared by the preparation method according to any one of claims 1 to 7.

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