Method for manufacturing silicon carbide ceramic special-shaped part in complex shape through plastic FDM-3D printing based on water extraction degreasing

Abstract

The invention relates to the technical field of ceramic 3D printing, in particular to a method for manufacturing a silicon carbide ceramic special-shaped part in a complex shape through plastic FDM-3D printing based on water extraction degreasing. Graphite, carbon black, silicon carbide and a surface modifier are mixed for modification, obtained surface modifier coated composite ceramic powder and a macromolecular binder system are internally mixed through an internal mixer, and ceramic 3D printing feed is obtained; and the ceramic 3D printing feed is sequentially subjected to 3D printing, degreasing and reactive sintering, and the silicon carbide ceramic special-shaped part with the complex shape is obtained. The prepared silicon carbide sintered body has high density (2.9 g / cm < 3 > or above), high strength (350 + / -32 MPa), high purity (99.5% or above, excluding free Si) and high precision (about 100-200 microns), and is a very optimized scheme for silicon carbide ceramic 3D printing.

Description

Technical Field

[0001] The 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 technology is an additive manufacturing technology, which has obvious advantages over traditional equal-material manufacturing technology. 3D printing technology does not require mold opening, which greatly reduces the mold opening cost and eliminates the mold opening cycle; 3D printing is a net size molding method, which basically does not require post-processing or only requires a small amount of post-processing compared to traditional methods; 3D printing is an intelligent manufacturing method that can achieve intelligent printing through computer modeling and slicing, and can achieve printing details that are difficult to prepare with traditional methods, such as chip breakers, inner holes, corners, etc. 3D printing technology has developed to the point where it can also achieve multi-material printing.

[0003] The most essential difference between special ceramic materials and metals and polymer materials in terms of processing is that ceramic materials are very brittle and have no plasticity. At present, special materials can only be formed using the idea of ​​powder metallurgy. The ceramic powder is mixed with an organic binder to give the ceramic plasticity, and then the mixed suspension (which can be a liquid or a molten solid) is poured into a mold for molding. After that, the organic binder is removed by degreasing and then sintered to obtain the required sample. This type of powder metallurgy method has a long process route and is prone to defects during the degreasing process. At the same time, the cost and cycle of post-processing are not short. It is suitable for the occasion of mass production of a certain type of special ceramics, but the advantages of small and medium batches are obviously not as good as 3D printing. Special ceramic 3D printing mainly includes methods such as stereolithography (SLA, DLP), selective laser sintering (SLS), binder jetting (BJ), melt extrusion molding (FDM), and direct writing 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 control of printing (it can print in a very large space 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 by plastic FDM-3D printing based on 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 The product has high sintering performance (>350±32MPa), high sintering body strength (350±32MPa), high sintering body purity (more than 99.5%, excluding free Si) and high sintering body precision (about 100-200μm), and uses environmentally friendly water solvent for degreasing. By optimizing 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 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 kneaded 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 ≥50MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50MPa·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 internal mixing is carried out in an internal mixer, the temperature of the internal mixing is 170-190° C., and the time is 1-2 hours.

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

[0021] The conditions of 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 is carried out at a temperature of 40 to 60° C. and for a time of 72 to 120 hours.

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

[0024] The present invention provides a method for preparing and manufacturing a silicon carbide ceramic special-shaped part with a complex shape by plastic FDM-3D printing based on water extraction and degreasing, comprising the following steps: mixing and modifying graphite, carbon black, silicon carbide and a surface modifier 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 comprises high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, the water-soluble binder comprises polyethylene glycol, the flexural strength of the high-strength engineering plastics is ≥50MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50MPa·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 uses 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 point (170-190°C). Under normal circumstances, they are insoluble in organic solvents. The injection blank has extremely high precision (several microns) and high strength (tens to tens of MPa). The present invention uses 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 uses an 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 on the interface between the layers are very obvious, and only the sample with a simple shape is printed; Figure 1 (b) is a typical sample prepared by water extraction degreasing plastic FDM-3D printing provided by the present invention, Figure 1As can be seen from (b) in the figure, 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 filtering and limiting Fe 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), which is 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 at the same time, and the printed blank has both good strength and good toughness, and the anti-defect ability of such a blank becomes stronger during immersion in water; (2) improving the performance of water-soluble binders: the occurrence of defects can be further solved by compounding high- and low-molecular-weight polyethylene glycols. The principle is that during the degreasing process of water solvents, low-molecular-weight polyethylene glycol is first removed and enters the water, which leaves a large number of pore channels for the blank, and then high-molecular-weight polyethylene glycol is removed along the channels left by 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, 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 blank will not have defects (bubbling, cracking, traditional water degreasing formulas are generally prone to defects after more than 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, the method can omit the two-step thermal degreasing and directly carry out sintering.

[0030] Further, 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; 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 is coated on the surface of the powder, so that the ceramic powder (graphite, carbon black, silicon carbide) and the macromolecular binder in the banburying step can achieve better infiltration; the coupling agent surface modifier can undergo an ester exchange reaction with the ceramic powder (graphite, carbon black, silicon carbide), and is coated on the surface of the ceramic powder (graphite, carbon black, silicon carbide), and can also achieve better infiltration of 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 carried out under the condition of ball milling, the ball milling method is wet high-energy ball milling; the rotation speed of the ball milling is 500-700rpm. The present invention adopts the method of wet high-energy ball milling to achieve modification, and the ball milling is carried out at a faster speed (500-700rpm) in the ball mill. Only under such conditions can the surface modifier be attached 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 Above), 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 environmentally friendly water extraction degreasing is used to optimize the binder formula system (compounded with high-strength and high-toughness engineering plastics; compounded with high and low molecular weight hydrophilic PEG), which 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 can be seen. Figure 2 . Figure 2 Typical complex-shaped silicon carbide ceramic shaped parts are prepared by plastic FDM-3DP based on water extraction debinding, and the sintering method is reaction sintering; Figure 2 (a) is a silicon carbide reflector for space use (the picture has white inlays, which are the deposition of free Si during reaction 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 the physical 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 shows a typical complex-shaped silicon carbide ceramic special-shaped part prepared by plastic FDM-3DP based on water extraction and debinding, and the sintering method is reaction sintering. DETAILED DESCRIPTION

[0035] 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:

[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 kneaded 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 ≥50MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50MPa·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 mixes graphite, carbon black, silicon carbide and a surface modifier for modification 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, silane coupling agent, stearic acid or 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 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 preferably 500-700 rpm, the medium of the ball milling is preferably alcohol, the ball-to-material mass ratio of the ball milling is preferably 2-3:1, the 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, and 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 that introduces a surface modifier in the mixing stage. Its main advantage is that the surface modifier is introduced into the powder system before the banburying, and the surface modifier is induced by high-energy spherical graphite to form a coating layer on the surface of the ceramic powder. The surface modifier will be more regularly arranged on the powder particles, while the surface modifier introduced during the banburying process 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 of the composite ceramic powder coated with the surface modifier with a macromolecular binder and a water-soluble binder, and then obtains a ceramic 3D printing feed after crushing or granulation, wherein the macromolecular binder comprises high-strength engineering plastics, high-toughness engineering plastics and thermoplastic elastomers, the water-soluble binder comprises polyethylene glycol, the flexural strength of the high-strength engineering plastics is ≥50MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50MPa·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. 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 embodiment. 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 internal mixing 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 binders and water-soluble binders, 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, in the ceramic 3D printing feed: the engineering plastics in the macromolecular binder (in this embodiment, high-strength engineering plastics and high-toughness engineering plastics) are skeleton binders, which provide sufficient plasticity and strength, and support the printed blank; the small molecule binder (polyethylene glycol) and the surface modifier in the water-soluble binder together give the ceramic feed fluidity, and at the same time can improve the wettability and compatibility of the powder with the engineering plastics in the macromolecular binder. The present invention uses macromolecular binders to give ceramic printing materials strong plasticity, strength, density and printing accuracy. Various types of ceramic special-shaped parts of various complex shapes can be printed.

[0053] After obtaining the ceramic 3D printing feed, the present invention sequentially performs plastic FDM-3D printing, water extraction degreasing, and reaction sintering on the ceramic 3D printing feed to obtain 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 conditions for the plastic FDM-3D printing preferably include: an extrusion pressure of 10 to 40 MPa, and the temperature from the feed port to the nozzle of the screw extrusion FDM printer is 160°C, 170°C, 180°C, and 190°C, respectively.

[0054] In the present invention, the temperature of the water extraction degreasing is preferably 40-60°C, more preferably 45-55°C, and the time is preferably 72-120h, more preferably 72-100h. The water extraction degreasing is preferably carried out under the condition of a water bath. 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 safe (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, and during the sintering process, Si will become gaseous Si, and 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 role of the reaction sintering is to generate reaction-sintered SiC to fill the pores in the sintered body through the reaction between free Si and the carbon source in SiC, 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 in conjunction with the embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0058] Example 1

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

[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 with a mass ratio of 17:17:55:5, wherein PEG is compounded, specifically with 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, and then 550.5g of the ceramic powder coated with the surface modifier is added, and the mixture is crushed to obtain a ceramic 3D printing feed;

[0061] A high-precision screw extrusion FDM printer was used for 3D printing (the extrusion pressure was 20 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 water solvent extraction degreasing (temperature was 50°C, time was 72h), and reaction sintering (temperature was 2170°C, time was 4h, vacuum degree was 7Pa) to obtain multiple complex-shaped silicon carbide foam ceramic filters 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 with alcohol having a volume concentration of 72 vol% as a ball milling medium, the ball milling used was a zirconium oxide ball, the rotation speed was 700 rpm, and the time was 20 h to obtain a ceramic powder coated with a surface modifier (the thickness of the surface modifier coating layer 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 mutually melted, 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 extruder 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, insulation time of 5 hours, vacuum degree of 5 Pa) were carried out to obtain a plurality of 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 with alcohol having a volume concentration of 72 vol% as a ball milling medium, the ball milling used was a zirconium oxide ball, the rotation speed was 650 rpm, the time was 19 h, and a ceramic powder coated with a surface modifier was obtained (the thickness of the surface modifier coating layer was 2.3 nm);

[0069] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, first add 2386g of the ceramic powder coated with the surface modifier, and then add 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) until the ceramic powder coated with the surface modifier and the binder system are completely melted, and then add 2386g of the ceramic powder coated with the surface modifier, and crush it to obtain a ceramic 3D printing feed;

[0070] 3D printing was carried out using a 3D printing screw extruder printer (the extrusion pressure was 40MPa, and the temperatures from the screw feed port to the nozzle were 160℃, 170℃, 180℃ and 190℃ respectively), followed by aqueous solvent extraction degreasing (temperature was 55℃, time was 3.6 days), reaction sintering (temperature was 2180℃, time was 4h, vacuum degree was 7.5Pa), to obtain a large-sized 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 with alcohol having a volume concentration of 70 vol% as a ball milling medium, the ball milling used for the ball milling was a zirconium oxide ball, the rotation speed was 700 rpm, and the time was 22 h to obtain a ceramic powder coated with a surface modifier (the thickness of the surface modifier coating layer was 1.9 nm);

[0073] After preheating the ceramic mixer until the temperature of the cone reaches 180°C, first add 2776.95g of the ceramic powder coated with the surface modifier, and then add 833g of the binder system (high-strength HDPE, high-toughness LDPE, PEG and maleic anhydride grafted POE with a mass ratio of 20:20:53:7, wherein PEG is compounded, specifically with 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 add 2776.95g of the ceramic powder coated with the surface modifier, granulate, and obtain ceramic 3D printing feed;

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

[0075] Test Case

[0076] Test items: Purity test of the reaction sintered photovoltaic crystal boat prepared by this method (third-party testing agency: Shanghai Microspectra Testing Technology Group Co., Ltd.), test process: GDMS is used to test the content of various impurities such as metals in the sample; test results: only the relative content of Fe, Al, and B exceeds 100ppm, the relative content of Fe is 290ppm, the relative content of Al is 220ppm, and the relative content of B is 330ppm. Conclusion: The impurity content of the sample is very low, which can meet the application of the product in the photovoltaic industry;

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

[0078] Test items: The strength of the printed specimens was tested. Test process: The bending strength of 12 specimens was tested by three-point bending test using a universal testing machine. 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 principle of the present invention. These improvements and modifications should also be regarded as 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, 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 ≥50MPa, and the fracture toughness of the high-toughness engineering plastics is ≥50MPa·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.

2. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in 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 as claimed in 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 as claimed in 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 as claimed in claim 1, characterized in that: The mass ratio 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).

6. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in claim 1 or 5, characterized in that: 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 low molecular weight polyethylene glycol to the high molecular weight polyethylene glycol is 1 to 4:

1.

7. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in claim 1 or 5, 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.

8. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in claim 1, characterized in that: The plastic FDM-3D printing is performed using a high-precision screw extrusion FDM printer; The conditions of 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.

9. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in 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.

10. The method for preparing complex-shaped silicon carbide ceramic special-shaped parts by plastic FDM-3D printing based on water extraction and degreasing as claimed in 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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