A method for manufacturing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing

Abstract

The present invention relates to the field of ceramic 3D printing technology, and in particular to a method for manufacturing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing. The present invention mixes graphite, carbon black, silicon carbide and a surface modifier for modification, and the obtained surface modifier-coated composite ceramic powder and macromolecular binder system are subjected to internal mixing and internal mixing to obtain ceramic 3D printing feed; the ceramic 3D printing feed is sequentially subjected to 3D printing, degreasing, and reaction sintering to obtain complex-shaped silicon carbide ceramic special-shaped parts. The silicon carbide sintered body prepared by the present invention has a high density (2.9g / cm 3 It has high strength (350±32MPa), high purity (more than 99.5%, excluding free Si) and high precision (about 100-200μm), making it a very optimized solution for silicon carbide ceramic 3D printing.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic 3D printing, and in particular to a method for manufacturing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing. Background Art

[0002] 3D printing is an additive manufacturing technology that offers significant advantages over traditional, homogeneous manufacturing techniques. 3D printing eliminates the need for molds, significantly reducing mold-making costs and cycles. 3D printing is a net-size molding method that requires little or no post-processing compared to traditional methods. 3D printing is also an intelligent manufacturing method, enabling intelligent printing through computer modeling and slicing. This allows for the creation of details difficult to create with traditional methods, such as chip breakers, internal holes, and curved corners. 3D printing technology has advanced to the point where it can now print in multiple materials.

[0003] The most fundamental difference between specialty ceramic materials and metals and polymer materials in terms of processing is that ceramic materials are highly brittle and lack plasticity. Currently, specialty materials can only be molded using powder metallurgy: mixing ceramic powder with an organic binder to impart plasticity to the ceramic. The resulting suspension (which can be a liquid or a molten solid) is then poured into a mold for molding. The organic binder is then removed by degreasing, and the desired sample is obtained by sintering. This type of powder metallurgy method has a long process path and is prone to defects during the degreasing process. The cost and cycle time for post-processing are also high. While it is suitable for large-scale production of certain specialty ceramics, its advantages for small and medium-sized batches are significantly inferior to 3D printing. Specialty ceramic 3D printing primarily includes methods such as stereolithography (SLA, DLP), selective laser sintering (SLS), binder jetting (BJ), melt diffraction molding (FDM), and direct write 3D printing (DIW). FDM has become the most popular 3D printing method for special ceramics due to its simple equipment, simple printing logic and process, easy and precise printing control (printing in a very large space can be carried out with a robotic arm), low cost, and no selectivity for material properties (for example, photocuring is selective for the optical properties of powder materials).

[0004] However, the existing FDM usually uses small molecule binders (low molecular weight, low melting temperature, poor plasticity, poor strength, low precision, usually soluble in solvents, and obvious defects between printed samples), which cannot meet the needs of researchers and engineers for 3D printing. Typical samples manufactured by traditional FDM using small molecule binder systems are as follows: Figure 1 As shown in (a) in . Summary of the Invention

[0005] The purpose of the present invention is to provide a method for manufacturing complex silicon carbide special-shaped parts based on plastic FDM-3D printing of water extraction and degreasing. The complex-shaped silicon carbide ceramic special-shaped parts obtained by the method provided by the present invention have a high sintered body density (2.9g / cm 3 Above), higher sintered body strength (350±32MPa), higher sintered body purity (more than 99.5%, excluding free Si) and higher sintered body precision (about 100-200μm), and use environmentally friendly water solvent for degreasing. Through the optimization of the water extraction degreasing binder formula system, the degreasing rate is as high as more than 90% and the two-step hot degreasing stage can be skipped for direct sintering.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for manufacturing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing, comprising the following steps:

[0008] Graphite, carbon black, silicon carbide and a surface modifier are mixed and modified to obtain a composite ceramic powder coated with the surface modifier;

[0009] The composite ceramic powder coated with the surface modifier is mixed with a macromolecular binder and a water-soluble binder, and then crushed or granulated to obtain a ceramic 3D printing feed, wherein the macromolecular binder includes high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, and the water-soluble binder includes polyethylene glycol. The flexural strength of the high-strength engineering plastics is ≥50 MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50 MPa·m1. / 2 , the polyethylene glycol includes high molecular weight polyethylene glycol and low molecular weight polyethylene glycol; the weight average molecular weight of the low molecular weight polyethylene glycol is ≤1000, and the weight average molecular weight of the high molecular weight polyethylene glycol is >1000;

[0010] The ceramic 3D printing feed is sequentially subjected to plastic FDM-3D printing, water extraction degreasing, and reaction sintering to obtain complex-shaped silicon carbide ceramic special-shaped parts.

[0011] Preferably, the mass ratio of the graphite, carbon black and silicon carbide is (5-7):(1-2):100.

[0012] Preferably, the surface modifier includes a fatty acid surface modifier and / or a coupling agent surface modifier; the fatty acid surface modifier includes one or more of stearic acid, oleic acid and dodecyl stearic acid; the coupling agent surface modifier includes one or more of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent;

[0013] The ratio of the mass of the surface modifier to the total mass of the graphite, carbon black and silicon carbide is (0.5-3):100.

[0014] Preferably, the modification is carried out under ball milling conditions, and the ball milling method is wet high-energy ball milling;

[0015] The rotation speed of the ball mill is 500-700 rpm, the medium of the ball mill is alcohol, the ball-to-material mass ratio of the ball mill is 2-3:1, the time is 12-24 hours, and the grinding balls used are zirconium oxide microbeads.

[0016] Preferably, the ratio of the mass of the composite ceramic powder coated with the surface modifier to the total mass of the macromolecular binder and the water-soluble binder is (4.6-8):1; the mass ratio of the high-strength engineering plastic, high-toughness engineering plastic, polyethylene glycol and thermoplastic elastomer is (15-20):(15-20):(50-60):(5-10).

[0017] Preferably, the high molecular weight polyethylene glycol includes PEG2000 and / or PEG6000; the low molecular weight polyethylene glycol includes PEG500 and / or PEG800;

[0018] The mass ratio of the low molecular weight polyethylene glycol to the high molecular weight polyethylene glycol is 1 to 4:1.

[0019] Preferably, the banburying is carried out in an internal mixer at a temperature of 170 to 190° C. for 1 to 2 hours.

[0020] Preferably, the plastic FDM-3D printing is performed using a high-precision screw extrusion FDM printer;

[0021] The conditions for the plastic FDM-3D printing include: an extrusion pressure of 10 to 40 MPa, and the temperatures from the feed port to the nozzle of the screw extrusion FDM printer are 160° C., 170° C., 180° C., and 190° C., respectively.

[0022] Preferably, the water extraction degreasing temperature is 40-60° C. and the time is 72-120 h.

[0023] Preferably, the reaction sintering temperature is 2100-2250° C., the holding time is 3-7 hours, and the vacuum degree is ≤10Pa.

[0024] The present invention provides a method for preparing and manufacturing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing, comprising the following steps: mixing graphite, carbon black, silicon carbide and a surface modifier for modification to obtain a composite ceramic powder coated with the surface modifier; banburying the composite ceramic powder coated with the surface modifier with a macromolecular binder and a water-soluble binder, and then crushing or granulating to obtain a ceramic 3D printing feed, wherein the macromolecular binder includes high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, and the water-soluble binder includes polyethylene glycol, the high-strength engineering plastics have a flexural strength of ≥50 MPa, and the high-toughness engineering plastics have a fracture toughness of ≥50 MPa·m1 / 2 The polyethylene glycol includes high molecular weight polyethylene glycol and low molecular weight polyethylene glycol; the weight average molecular weight of the low molecular weight polyethylene glycol is ≤1000, and the weight average molecular weight of the high molecular weight polyethylene glycol is >1000; the ceramic 3D printing feed is sequentially subjected to plastic FDM-3D printing, water extraction degreasing, and reaction sintering to obtain complex-shaped silicon carbide ceramic special-shaped parts.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] The present invention adopts macromolecular binders, and uses high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers as skeleton binders. Engineering plastics have strong plasticity and high melting temperature (170-190°C). Under normal circumstances, they are insoluble in organic solvents. The injection blanks have extremely high precision (several microns) and high strength (tens to tens of MPa). The present invention adopts plastic FDM-3D printing (the injection molding nozzle is changed into a movable nozzle, which is developed into 3D printing, namely plastic FDM-3D printing). Compared with the traditional 3D printing method using small molecule binders, the present invention adopts injection molding formula for 3D printing, and adds macromolecular binders (skeleton binders, namely engineering plastics) to the components, giving the printed feed good plasticity, precision and strength. The method provided by the present invention has absolute advantages over traditional FDM. For example, the blank has high strength, high precision, high density, no obvious defects in the interlayer interface, and strong plasticity; and it can print larger parts (such as ceramic parts with a diameter of 1m), such as Figure 1 As shown in (b) in . Figure 1 (a) is a typical sample made by traditional FDM using a small molecule binder system. Figure 1 In (a), it can be seen that the sample is easy to break, the defects at the interface between the layers are very obvious, and the printed sample is only a simple shape. Figure 1 (b) is a typical sample prepared by the water extraction degreasing plastic FDM-3D printing provided by the present invention, Figure 1As shown in (b), this method can be used to prepare samples with more complex shapes, with unclear interfaces between layers and no obvious defects.

[0027] At the same time, the present invention uses the plastic FDM-3D printing method to prepare silicon carbide structural ceramic components. This method can be used to prepare silicon carbide reflectors for space satellites, silicon carbide foam ceramic filters for Fe filtration and flow limiting in the casting field, photovoltaic ceramic crystal boats, semiconductor ceramic crystal boats, etc. The above products have a high density (2.9g / cm 3 It has high strength (395±32MPa), high purity (more than 99%, excluding free Si) and high precision (about 100-200μm), making it a very optimized solution for silicon carbide ceramic 3D printing.

[0028] The method provided by the present invention mainly avoids the defects caused by water extraction degreasing by two means: (1) improving the performance of engineering plastics in macromolecular binders: high-strength and high-toughness engineering plastics are used for compounding, so that the printed blank has both good strength and good toughness, and such blanks have stronger resistance to defects during immersion in water; (2) improving the performance of water-soluble binders: compounding high- and low-molecular-weight polyethylene glycols can further solve the problem of defects. The principle is that during the water solvent degreasing process, the low-molecular-weight polyethylene glycol is first removed and enters the water, thus leaving a large number of pore channels in the blank. Then, the high-molecular-weight polyethylene glycol is removed along the channels left by the low-molecular-weight polyethylene glycol, which can effectively avoid the occurrence of defects. If the PEG compounding method is not adopted, defects are very likely to occur.

[0029] The present invention uses environmentally friendly, low-cost, and non-flammable water as a solvent for extraction and degreasing. After optimizing the binder formula for water extraction and degreasing (macromolecular binders include high-strength engineering plastics, high-toughness engineering plastics, and thermoplastic elastomers), the green body will still not show defects (bubbling and cracking, which are prone to defects in traditional water degreasing formulas if it exceeds 8 hours) after being immersed in water for about 3 to 5 days, and the degreasing rate exceeds 90%. Due to the extremely high degreasing rate, this method can omit the two-step thermal degreasing and directly perform sintering.

[0030] Furthermore, in the present invention, the surface modifier includes a fatty acid surface modifier and / or a coupling agent surface modifier; the fatty acid surface modifier includes one or more of stearic acid, oleic acid, and dodecyl stearic acid; and the coupling agent surface modifier includes one or more of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent. The fatty acid surface modifier can undergo an esterification reaction with the composite ceramic powder (graphite, carbon black, silicon carbide) and coat the surface of the powder, thereby achieving better wetting between the ceramic powder (graphite, carbon black, silicon carbide) and the macromolecular binder in the banburying step; the coupling agent surface modifier can undergo an ester exchange reaction with the ceramic powder (graphite, carbon black, silicon carbide) and coat the surface of the ceramic powder (graphite, carbon black, silicon carbide), thereby achieving better wetting between the ceramic powder and the macromolecular binder in the banburying step. In the present invention, the thickness of the surface modifier coating layer in the surface modifier-coated ceramic powder is preferably 0.5 to 4 nm.

[0031] Furthermore, in the present invention, the modification is performed under conditions of wet high-energy ball milling, wherein the ball milling method is wet high-energy ball milling; the rotation speed of the ball mill is 500-700 rpm. The present invention uses wet high-energy ball milling to achieve modification, and the ball milling is performed at a relatively high speed (500-700 rpm) in the ball mill. Under these conditions, the surface modifier can be adhered and coated on the powder.

[0032] In summary, the complex-shaped silicon carbide ceramic special-shaped parts obtained by the method provided by the present invention have a high sintered body density (2.9g / cm 3 More than), higher sintered body strength (350±32MPa), higher sintered body purity (more than 99%, excluding free Si) and higher sintered body precision (about 100-200μm). The use of environmentally friendly water extraction degreasing and optimizing the binder formula system (using high-strength and high-toughness engineering plastics for compounding; compounding through high and low molecular weight hydrophilic PEG) avoids the problem of defects caused by long-term degreasing. The sample will not have defects after being immersed in water solvent for about 72 to 120 hours. The degreasing rate is as high as more than 90%, and the two-step thermal degreasing stage can be skipped and sintering can be carried out directly. Typical complex-shaped large-sized silicon carbide ceramic parts prepared by this method are shown in Figure 2 . Figure 2 This is a typical complex-shaped silicon carbide ceramic special-shaped part produced by plastic FDM-3DP based on water extraction debinding. The sintering method is reaction sintering. Figure 2 (a) is a silicon carbide reflector for space use (the white inlay in the picture is the deposition of free Si during reactive sintering, which can be removed by sandblasting later). Figure 2 (b) in the figure is a silicon carbide wafer boat used in the photovoltaic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The following are pictures of typical samples prepared by different methods; Figure 1 (a) is a typical sample manufactured by traditional FDM using a small molecule binder system; Figure 1 (b) is a typical sample prepared by water extraction degreasing plastic FDM-3D printing;

[0034] Figure 2 This example uses plastic FDM-3DP based on water extraction and degreasing to prepare typical complex-shaped silicon carbide ceramic special-shaped parts, and the sintering method is reaction sintering. DETAILED DESCRIPTION

[0035] The present invention provides a method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing, comprising the following steps:

[0036] Graphite, carbon black, silicon carbide and a surface modifier are mixed and modified to obtain a composite ceramic powder coated with the surface modifier;

[0037] The composite ceramic powder coated with the surface modifier is mixed with a macromolecular binder and a water-soluble binder, and then crushed or granulated to obtain a ceramic 3D printing feed, wherein the macromolecular binder includes high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, and the water-soluble binder includes polyethylene glycol. The flexural strength of the high-strength engineering plastics is ≥50 MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50 MPa·m1. / 2 , the polyethylene glycol includes high molecular weight polyethylene glycol and low molecular weight polyethylene glycol; the weight average molecular weight of the low molecular weight polyethylene glycol is ≤1000, and the weight average molecular weight of the high molecular weight polyethylene glycol is >1000;

[0038] The ceramic 3D printing feed is sequentially subjected to plastic FDM-3D printing, water extraction degreasing, and reaction sintering to obtain complex-shaped silicon carbide ceramic special-shaped parts.

[0039] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0040] The present invention modifies a mixture of graphite, carbon black, silicon carbide, and a surface modifier to obtain a composite ceramic powder coated with a surface modifier. In the present invention, the purity of the silicon carbide is preferably ≥99.5%. The particle size of the silicon carbide is preferably submicron. The present invention does not have any special restrictions on the graphite and carbon black, and graphite and carbon black familiar to those skilled in the art can be used. In the present invention, the mass ratio of the graphite, carbon black, and silicon carbide is preferably (5-7): (1-2): 100, more preferably (6-6.5): (1.5-2): 100. The surface modifier preferably includes a fatty acid surface modifier and / or a coupling agent surface modifier. The fatty acid surface modifier preferably includes one or more of stearic acid, oleic acid, and dodecyl stearic acid; the coupling agent surface modifier preferably includes one or more of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent. In an embodiment of the present invention, the surface modifier is specifically oleic acid, a silane coupling agent, stearic acid, or a titanate coupling agent. The ratio of the mass of the surface modifier to the total mass of the graphite, carbon black, and silicon carbide is preferably (0.5-3):100, more preferably (1.5-3):100.

[0041] In the present invention, the modification is preferably performed under ball milling conditions, wherein the ball milling method is wet high-energy ball milling. The ball milling speed is preferably 500-700 rpm, the ball milling medium is preferably alcohol, the ball-to-material mass ratio is preferably 2-3:1, the ball milling time is preferably 12-24 hours, and the grinding balls used are zirconium oxide microbeads.

[0042] In an embodiment of the present invention, the ball milling speed is specifically 300 rpm, the medium is specifically alcohol with a volume concentration of 50-75%, the ball-to-material ratio can be 2-3:1, the time can be 12-24 hours, and the grinding balls used can be zirconia microspheres.

[0043] In the present invention, the thickness of the surface modifier coating layer in the surface modifier-coated ceramic powder is preferably 0.5 to 4 nm, more preferably 1.5 to 2.5 nm.

[0044] In the present invention, during the ball milling process, an esterification reaction or an ester exchange reaction occurs between the surface modifier and the ceramic powder. The role of the graphite / carbon black is to provide a carbon source during the reaction and sintering of silicon carbide, so that it can react with the free Si in the atmosphere to form silicon carbide. The role of the surface modifier as a coating layer is to increase the mass proportion of the composite ceramic powder in the subsequent ceramic 3D printing feed. The higher the mass proportion of the composite ceramic powder, the higher the density of the green body and the higher the density of the ceramic sintering. At the same time, the modification process can also enhance wettability, improve the uniformity of the mixture, and make the subsequent mixing process smoother. The above-mentioned modification process is different from the traditional injection molding process of introducing a surface modifier during the mixing stage. Its main advantage is that the surface modifier is introduced into the powder system before mixing, and the high-energy spherical graphite induces the surface modifier to form a coating on the surface of the ceramic powder. The surface modifier will be more regularly arranged on the powder particles, while when the surface modifier is introduced during the mixing process, the surface modifier is randomly and messily distributed and does not have the effect of pre-modification.

[0045] After obtaining the composite ceramic powder coated with the surface modifier, the present invention performs banburying on the composite ceramic powder coated with the surface modifier, a macromolecular binder and a water-soluble binder, and then crushes or granulates the composite ceramic powder to obtain a ceramic 3D printing feed, wherein the macromolecular binder includes high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, and the water-soluble binder includes polyethylene glycol. The flexural strength of the high-strength engineering plastics is ≥50 MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50 MPa·m1. / 2 The polyethylene glycol comprises a high molecular weight polyethylene glycol and a low molecular weight polyethylene glycol; the low molecular weight polyethylene glycol has a weight average molecular weight ≤ 1000, and the high molecular weight polyethylene glycol has a weight average molecular weight > 1000. In the present invention, the high-strength engineering plastic is preferably high-strength HDPE or high-strength PP. The high-toughness engineering plastic is preferably high-toughness HDPE or high-toughness LDPE.

[0046] In the present invention, the flexural strength of the high-strength engineering plastic is the flexural strength of a pure injection molded part of the engineering plastic. The high-molecular-weight polyethylene glycol preferably includes PEG2000 and / or PEG6000. The low-molecular-weight polyethylene glycol preferably includes PEG500 and / or PEG800. The mass ratio of the low-molecular-weight polyethylene glycol to the high-molecular-weight polyethylene glycol is preferably 1 to 4:1, specifically 3:1 or 4:1 in the embodiments. The thermoplastic elastomer preferably includes EVA and / or maleic anhydride-grafted POE.

[0047] In the present invention, the mass ratio of the high-strength engineering plastic, the high-toughness engineering plastic, polyethylene glycol (PEG) and the thermoplastic elastomer is preferably (15-20): (15-20): (50-60): (5-10), and more preferably (17-19): (17-19): (55-57): (6-8).

[0048] In the present invention, the ratio of the mass of the composite ceramic powder coated with the surface modifier to the total mass of the macromolecular binder and the water-soluble binder is preferably (4.6-8):1, more preferably (5-7.5):1, and specifically 5.2:1, 6.25:1, 7.4:1 or 6.29:1 in the embodiments.

[0049] In the present invention, the internal mixing is carried out in an internal mixer, the temperature of the internal mixing is preferably 170-190° C., and the time is preferably 1-2 hours.

[0050] In the present invention, the kneading process is preferably to preheat the ceramic internal mixer until the temperature of the cone reaches 170-190°C, first add 50wt% of the ceramic powder coated with the surface modifier, and then add all the macromolecular binder and water-soluble binder, until 50wt% of the ceramic powder coated with the surface modifier and the macromolecular binder and the water-soluble binder are completely melted together, and then add the remaining ceramic powder coated with the surface modifier.

[0051] After the banburying is completed, a banburying product is obtained. In the present invention, the banburying product is crushed or granulated. The present invention has no special limitation on the crushing or granulation process, and the process well known to those skilled in the art can be used.

[0052] In the present invention, the ceramic 3D printing feedstock comprises: the engineering plastics in the macromolecular binder (in this embodiment, high-strength engineering plastics and high-toughness engineering plastics) serving as a skeletal binder, providing sufficient plasticity and strength while also supporting the printed body; the small molecule binder (polyethylene glycol) in the water-soluble binder, along with the surface modifier, imparts fluidity to the ceramic feedstock and improves wettability and compatibility between the powder and the engineering plastics in the macromolecular binder. The present invention employs macromolecular binders to impart strong plasticity, strength, density, and printing accuracy to the ceramic printing material. This allows for the printing of various complex and irregular ceramic shapes.

[0053] After obtaining the ceramic 3D printing feed, the present invention sequentially subjects the ceramic 3D printing feed to plastic FDM-3D printing, water extraction degreasing, and reaction sintering to produce complex-shaped silicon carbide ceramic special-shaped parts. In the present invention, the plastic FDM-3D printing is preferably performed using a high-precision screw extrusion FDM printer. The plastic FDM-3D printing conditions preferably include: an extrusion pressure of 10 to 40 MPa, and temperatures from the feed inlet to the nozzle of the screw extrusion FDM printer of 160°C, 170°C, 180°C, and 190°C, respectively.

[0054] In the present invention, the temperature of the water extraction degreasing is preferably 40 to 60°C, more preferably 45 to 55°C, and the time is preferably 72 to 120 hours, more preferably 72 to 100 hours. The water extraction degreasing is preferably carried out under water bath conditions. In the present invention, the advantage of using the above degreasing process is that water extraction degreasing only uses water as a solvent for degreasing, which is almost cost-free compared to organic solvent degreasing; water degreasing is more environmentally friendly and safer (non-flammable) than organic solvent degreasing.

[0055] In the present invention, the temperature of the reaction sintering is preferably 2100-2250°C, the holding time is preferably 3-7h, more preferably 3-5h; the vacuum degree is preferably ≤10Pa, more preferably 2-9Pa. In an embodiment of the present invention, the reaction sintering process is specifically to cover the bottom layer of the vacuum sintering furnace with silicon powder. During the sintering process, Si will turn into gaseous Si, which will then react with the carbon in the degreased workpiece to form reaction-sintered SiC, so that the density of the reaction-sintered silicon carbide reaches 2.9g / cm 3 above.

[0056] In the present invention, the reaction sintering is to generate reaction-sintered SiC by initiating a reaction between free Si and the carbon source in SiC to fill the pores in the sintered body, thereby achieving densification.

[0057] The preparation method of the pan-semiconductor silicon carbide ceramic component provided by the present invention is described in detail below with reference to the examples, but they should not be understood as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] 62 g of graphite, 17 g of carbon black, 1000 g of silicon carbide (purity ≥99.5%), and 22 g of a surface modifier (specifically, oleic acid) were mixed and ball-milled using 50 vol% alcohol as a milling medium. The milling process used zirconium oxide balls at a rotation speed of 600 rpm for 15 h to obtain a ceramic powder coated with the surface modifier (the thickness of the surface modifier coating was 1.5 nm).

[0060] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, 550.5g of the ceramic powder coated with the surface modifier is first added, and then 211.73g of the binder system (high-strength HDPE, high-toughness HDPE, PEG and EVA in a mass ratio of 17:17:55:5, wherein PEG is compounded, specifically at a mass ratio of PEG500:PEG6000=3:1) is added until the ceramic powder coated with the surface modifier and the binder system are completely melted together, and then 550.5g of the ceramic powder coated with the surface modifier is added and crushed to obtain ceramic 3D printing feed;

[0061] A high-precision screw extrusion FDM printer was used for 3D printing (extrusion pressure was 20 MPa, and the temperatures from the feed port of the screw to the nozzle were 160°C, 170°C, 180°C and 190°C, respectively), followed by water solvent extraction degreasing (temperature was 50°C, time was 72h), and reaction sintering (temperature was 2170°C, time was 4h, and vacuum degree was 7Pa) to obtain multiple silicon carbide foam ceramic filters with complex shapes for casting.

[0062] Example 2

[0063] 130 g of graphite, 400 g of carbon black, 2000 g of silicon carbide (purity ≥99.5%), and 48.7 g of a surface modifier (specifically, a silane coupling agent) were mixed and ball-milled using 72 vol% alcohol as a milling medium. The milling process used zirconium oxide balls at a rotation speed of 700 rpm for 20 h to obtain a ceramic powder coated with the surface modifier (the thickness of the surface modifier coating was 3 nm).

[0064] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, 1289.35g of the ceramic powder coated with the surface modifier is first added, and then 412.592g of the binder system (high-strength PP, high-toughness HEPE, PEG, and EVA with a mass ratio of 18:19:57:8, wherein PEG is compounded, specifically with a mass ratio of PEG500:PEG2000=4:1) is added until the ceramic powder coated with the surface modifier and the binder system are completely melted together, and then 1289.35g of the ceramic powder coated with the surface modifier is added, and then granulation is directly performed to obtain ceramic 3D printing feed;

[0065] 3D printing was performed using a 3D printing screw extrusion printer (the extrusion pressure was 35 MPa, and the temperatures from the screw feed port to the nozzle were 160°C, 170°C, 180°C, and 190°C, respectively).

[0066] Subsequently, water solvent extraction degreasing (temperature of 48°C, time of 3 days) and reaction sintering (temperature of 2200°C, holding time of 5 hours, vacuum degree of 5 Pa) were carried out to obtain multiple small silicon carbide impellers.

[0067] Example 3

[0068] 256 g of graphite, 76 g of carbon black, 4000 g of silicon carbide (purity ≥99.5%), and 44 g of a surface modifier (specifically, stearic acid) were mixed and ball-milled using 72 vol% alcohol as a milling medium. The milling process used zirconium oxide balls at a rotation speed of 650 rpm for 19 h to obtain a surface modifier-coated ceramic powder (the thickness of the surface modifier coating was 2.3 nm).

[0069] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, 2386g of the ceramic powder coated with the surface modifier is first added, and then 644.22g of the binder system (high-strength HDPE, high-toughness LDPE, PEG and maleic anhydride grafted POE with a mass ratio of 16:18:58:6, wherein PEG is compounded, specifically with a mass ratio of PEG800:PEG2000=4:1) is added until the ceramic powder coated with the surface modifier and the binder system are completely melted together, and then 2386g of the ceramic powder coated with the surface modifier is added and crushed to obtain ceramic 3D printing feed;

[0070] 3D printing was carried out using a 3D printing screw extrusion printer (the extrusion pressure was 40 MPa, and the temperatures from the screw feed port to the nozzle were 160°C, 170°C, 180°C and 190°C, respectively), followed by aqueous solvent extraction degreasing (temperature 55°C, time 3.6 days) and reaction sintering (temperature 2180°C, time 4 hours, vacuum degree 7.5 Pa) to obtain a large-size silicon carbide reflector for space use.

[0071] Example 4

[0072] 350 g of graphite, 95 g of carbon black, 5000 g of silicon carbide (purity ≥99.5%), and 108.9 g of a surface modifier (specifically, a silane coupling agent) were mixed and ball-milled using 70 vol% alcohol as a milling medium. The milling process used zirconium oxide balls at a rotation speed of 700 rpm for 22 h to obtain a ceramic powder coated with the surface modifier (the thickness of the surface modifier coating was 1.9 nm).

[0073] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, 2776.95g of the ceramic powder coated with the surface modifier is first added, and then 833g of the binder system (high-strength HDPE, high-toughness LDPE, PEG and maleic anhydride grafted POE in a mass ratio of 20:20:53:7, wherein PEG is compounded, specifically at a mass ratio of PEG800:PEG6000=3:1) until the ceramic powder coated with the surface modifier and the binder system are completely melted, and then 2776.95g of the ceramic powder coated with the surface modifier is added, and granulation is performed to obtain ceramic 3D printing feed;

[0074] 3D printing was performed using a 3D printing screw extrusion printer (the extrusion pressure was 35 MPa, and the temperatures from the feed port of the screw to the nozzle were 160°C, 170°C, 180°C, and 190°C, respectively), followed by aqueous solvent extraction degreasing (temperature at 50°C, time for 4 days) and reaction sintering (temperature at 2200°C, time for 3.5 hours, vacuum degree of 6 Pa) to obtain a silicon carbide wafer boat for photovoltaics.

[0075] Test Case

[0076] Purity testing of the reaction-sintered photovoltaic wafer boat prepared using this method was performed by a third-party testing organization: Shanghai Microspectra Testing Technology Group Co., Ltd. GDMS was used to measure the content of various impurities, including metals, in the sample. Results showed that only the relative contents of Fe, Al, and B exceeded 100 ppm, with the relative content of Fe at 290 ppm, Al at 220 ppm, and B at 330 ppm. Conclusion: The impurity content of the sample was very low, sufficient for application in the photovoltaic industry.

[0077] Test item: Density test of reaction-sintered silicon carbide ceramic impeller (using a density meter based on the Archimedean drainage method). Test process: 12 small fragments of the silicon carbide impeller were randomly sampled for density testing. Test results: The density after testing was 2.956±0.45g / cm 3 ,The test performance meets the requirements of silicon carbide ceramic impeller under actual working conditions;

[0078] Test item: Strength test of the splines printed by this method. Test process: The bending strength of 12 splines was tested using a universal testing machine using three-point bending test. Test results: The strength test result was 395±32MPa, which meets the mechanical property requirements of silicon carbide as a structural ceramic.

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing, characterized in that: The following steps are involved: Graphite, carbon black, silicon carbide and a surface modifier are mixed and modified to obtain a composite ceramic powder coated with the surface modifier; The composite ceramic powder coated with the surface modifier is kneaded with a macromolecular binder and a water-soluble binder, and then crushed or granulated to obtain a ceramic 3D printing feed; the macromolecular binder includes high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, and the water-soluble binder includes polyethylene glycol. The flexural strength of the high-strength engineering plastics is ≥50 MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50 MPa·m1. / 2. The polyethylene glycol includes high molecular weight polyethylene glycol and low molecular weight polyethylene glycol; the high molecular weight polyethylene glycol includes PEG2000 and / or PEG6000; the low molecular weight polyethylene glycol includes PEG500 and / or PEG800; the mass ratio of the high-strength engineering plastic, the high-toughness engineering plastic, the polyethylene glycol and the thermoplastic elastomer is (15-20):(15-20):(50-60):(5-10); the mass ratio of the low molecular weight polyethylene glycol to the high molecular weight polyethylene glycol is 1-4:1; The ceramic 3D printing feed is sequentially subjected to plastic FDM-3D printing, water extraction degreasing, and reaction sintering to obtain complex-shaped silicon carbide ceramic special-shaped parts.

2. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The mass ratio of the graphite, carbon black and silicon carbide is (5-7): (1-2):

100.

3. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The surface modifier includes a fatty acid surface modifier and / or a coupling agent surface modifier; the fatty acid surface modifier includes one or more of stearic acid, oleic acid and dodecyl stearic acid; the coupling agent surface modifier includes one or more of a silane coupling agent, a titanate coupling agent and an aluminate coupling agent; The ratio of the mass of the surface modifier to the total mass of the graphite, carbon black and silicon carbide is (0.5-3):

100.

4. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The modification is carried out under ball milling conditions, and the ball milling method is wet high-energy ball milling; The rotation speed of the ball mill is 500-700 rpm, the medium of the ball mill is alcohol, the ball-to-material mass ratio of the ball mill is 2-3:1, the time is 12-24 hours, and the grinding balls used are zirconium oxide microbeads.

5. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The ratio of the mass of the composite ceramic powder coated with the surface modifier to the total mass of the macromolecular binder and the water-soluble binder is (4.6-8):

1.

6. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The internal mixing is carried out in an internal mixer at a temperature of 170 to 190° C. for 1 to 2 hours.

7. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The plastic FDM-3D printing is performed using a high-precision screw extrusion FDM printer; The conditions for the plastic FDM-3D printing include: an extrusion pressure of 10 to 40 MPa, and the temperatures from the feed port to the nozzle of the screw extrusion FDM printer are 160° C., 170° C., 180° C., and 190° C., respectively.

8. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The water extraction degreasing is carried out at a temperature of 40 to 60° C. and for a time of 72 to 120 hours.

9. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing according to claim 1, characterized in that: The reaction sintering temperature is 2100-2250° C., the heat preservation time is 3-7 hours, and the vacuum degree is ≤10Pa.

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