Aluminum oxide ceramic based on powder extrusion printing molding and preparation method thereof

Abstract

The invention belongs to the technical field of additive manufacturing, and discloses aluminum oxide ceramic based on powder extrusion printing forming and a preparation method. Raw materials of the feed for preparing the aluminum oxide ceramic comprise aluminum oxide powder, an adhesive and an additive, and the adhesive comprises at least three of a semi-crystalline polymer, an amorphous polymer, microcrystalline wax and blend oil; the additive comprises at least one of a silane coupling agent, a passivating agent, an antioxidant and stearic acid. The semi-crystalline polymer and the amorphous polymer in a specific ratio are added into the binder of the feeding formula, so that the printed green body is not prone to deformation and collapse, and the accuracy of the printed green body structure is guaranteed; the binder and the additive in the feed are compounded for use, so that the storage time of the feed is prolonged; and the prepared aluminum oxide ceramic is good in physical compactness and high in mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, in particular to an alumina ceramic based on powder extrusion printing forming and a preparation method thereof. BACKGROUND

[0002] Alumina ceramic has a wide range of applications in industry due to its high hardness, high temperature resistance and chemical stability, and is widely used in electronic devices, mechanical parts, biomedical materials and other fields. The forming methods for alumina ceramic in the related art include dry pressing forming, isostatic pressing forming, slip casting forming, injection molding, tape casting and the like, but still have limitations, specifically, molds are needed and the cost is high, or the material performance obtained is insufficient, or the material surface finish is not enough and secondary processing is needed. Additive manufacturing technology has unique advantages in the forming of complex ceramic shapes, based on computer models, with materials being accumulated point by point, line by line or surface by surface into a certain shape of parts and components.

[0003] Powder extrusion printing (PEP) is a kind of additive manufacturing technology, which uses mixed particles of inorganic powder and organic binder as feedstock to be printed, debound and sintered to obtain ceramic. However, one of the main problems of PEP technology is the insufficient density of ceramic, which further affects the mechanical properties of ceramic. SUMMARY

[0004] The main purpose of the present application is to develop an alumina ceramic based on powder extrusion printing forming, which has high density after sintering, is not easy to crack, has long metamorphic time of feedstock, and is convenient for industrialized production and application.

[0005] To achieve the above purpose, the present application provides an alumina ceramic based on powder extrusion printing forming, characterized in that the feedstock for preparing the alumina ceramic comprises the following raw materials in volume fraction: alumina powder: 30% to 70%; binder: 24.9% to 57%; additive: 1.5% to 5.1%; wherein the binder comprises at least three of semi-crystalline polymer, amorphous polymer, microcrystalline wax and blended oil; and the additive comprises at least one of silane coupling agent, passivator, antioxidant and stearic acid.

[0006] In an embodiment, the semi-crystalline polymer in the binder comprises at least one of polyethylene and ethylene-vinyl acetate; wherein the content of vinyl acetate in the ethylene-vinyl acetate is less than 20%.

[0007] In an embodiment, the amorphous polymer in the binder comprises at least one of polystyrene and styrene-butadiene-styrene block copolymer.

[0008] In an embodiment, the additive, the passivation agent comprises at least one of passivation agent MDA-5 and passivation agent MD697.

[0009] In an embodiment, the adhesive, the volume fraction ratio of the semi-crystalline polymer and the amorphous polymer is (12.4~16.5):(1.5~5).

[0010] In an embodiment, the feedstock for preparing the alumina ceramic further comprises a modifier, the modifier comprises a maleic anhydride graft copolymer.

[0011] In an embodiment, the maleic anhydride graft copolymer comprises SEBS-g-MAH, the amount of SEBS-g-MAH is 4%~11% of the amount of alumina powder. In an embodiment, the maleic anhydride graft copolymer has a maleic anhydride grafting rate of 1%~2%.

[0012] The application further provides a preparation method of the alumina ceramic based on powder extrusion printing forming, comprising the following steps: S1, mixing alumina powder and additives according to the proportion, stirring, then adding adhesive according to the proportion, stirring, and densifying, granulating to prepare a feedstock; S2, placing the feedstock prepared in step S1 into a printing device, setting printing parameters and green body structure, and printing to prepare an alumina green body; S3, performing a debinding treatment on the alumina green body prepared in step S2, including solvent debinding treatment and high-temperature debinding treatment; S4, sintering the alumina green body after debinding treatment in step S3 to prepare an alumina ceramic.

[0013] In an embodiment, in step S1, the particle size of the alumina powder is 0.5μm~1μm; and / or, in step S1, the particle size of the feedstock is 4 mesh~12 mesh.

[0014] In an embodiment, in step S2, the extrusion temperature is 130℃~170℃, and the printing platform temperature is 90℃~120℃.

[0015] In an embodiment, in step S2, the nozzle size of the printing device is 0.1mm~0.8mm.

[0016] In an embodiment, in step S2, when printing, the single-layer layer thickness is 0.15mm~0.2mm, and the printing speed is 40mm / s~80mm / s.

[0017] In an embodiment, in the step S3, the solvent debinding treatment comprises: soaking the alumina green body in n-heptane or sodium citrate aqueous solution, and soaking at 40-70 DEG C for 12-48 hours.

[0018] In an embodiment, in the step S3, the high-temperature debinding treatment comprises: placing the alumina green body after the solvent debinding treatment in a muffle furnace, and heating from room temperature to 500-700 DEG C at a heating rate of 0.5-5 DEG C / min.

[0019] In an embodiment, in the step S4, the alumina green body after the debinding treatment is placed in a muffle furnace, sintering is performed in an air atmosphere, heating to 1400-1600 DEG C, and heat preservation treatment is performed for 0.5-2 hours.

[0020] The technical scheme in the present application is a preparation method of an alumina ceramic based on powder extrusion printing forming, by adding specific proportions of semi-crystalline polymers and amorphous polymers in the binder of the feed formula, the green body obtained by printing is not easy to deform and collapse, and the accuracy of the structure of the printed green body is ensured; the binder and additives in the feed are used in combination, which greatly prolongs the storage time of the feed, so that the feed can not deteriorate within a long period of time; the alumina ceramic prepared by the present application has good physical density and high mechanical strength, and the shrinkage rate of the prepared alumina ceramic is lower than that of the green body. In addition, compared with the traditional ceramic preparation process with complex structures such as porous structure, the method has the advantages of fast forming, controllable pore structure, high universality, uniform pore size and uniform distribution of the prepared porous structure alumina ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to the structures shown in the drawings without creative labor.

[0022] Figure 1 A physical picture of an alumina ceramic based on powder extrusion printing forming prepared by an embodiment of the present application; The implementation, functional characteristics and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0023] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work belong to the scope of protection of the present application.

[0024] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications will also change accordingly.

[0025] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the scope of protection claimed by the present application.

[0026] The technical problem solved by the present application is that the existing forming methods for alumina ceramics have limitations, including the need for a mold and high cost, or the performance of the prepared material is insufficient or does not meet the requirements, or the surface finish of the material is not enough and needs secondary processing, and many other problems.

[0027] In the related art, a method for preparing alumina ceramics by light-cured 3D printing is disclosed. Light-cured printing is a technology that uses a mixture of photosensitive resin and ceramic powder to solidify the resin by ultraviolet light irradiation, and then performs post-processing to prepare a ceramic part. During the light-cured printing process, the ceramic powder is prone to sedimentation, resulting in uneven ceramic material after sintering; and the problem of liquid accumulation during printing will also cause the sintered ceramic material to have poor density and poor mechanical strength.

[0028] The related art also discloses a method for preparing a porous alumina ceramic by fused deposition printing (FDM), wherein the FDM filament is prepared by using alumina as a raw material and being matched with a thermoplastic material, a dispersing agent, and a binder; the filament is placed into an FDM printing device to print a green body, and the green body is sequentially debound and sintered to obtain the alumina ceramic part. The filament preparation process in the FDM technology is complex and difficult to prepare, and the filament is prone to metamorphism, thereby resulting in excessively high production cost of the FDM technology.

[0029] The related art also discloses a binder jetting technology, wherein the binder is sprayed on a specific area of the pre-laid alumina powder, the powder is laid layer by layer and the binder is sprayed layer by layer through computer program control, and finally the excess powder is removed to obtain a blank, and the blank is sequentially debound and sintered to obtain the alumina ceramic part. Due to the limitations of the flowability, viscosity, and volatility of the binder in the preparation process, the binder cannot penetrate into the powder or cannot completely fill all the gaps in the solidification process, thereby resulting in the problem of low density.

[0030] The powder extrusion printing technology, as an additive manufacturing technology, can well solve the problem of the mold, and can easily print a product with complex structure, and the uniformity of the product and the smoothness of the surface of the product are also good, but the current deficiency is that the density of the ceramic obtained by sintering is not high enough and the mechanical property is low.

[0031] In order to solve the above technical problems, an alumina ceramic based on powder extrusion printing forming and a preparation method thereof are designed, which have high density after sintering, are not easy to crack, have long metamorphic time of the feedstock, and are convenient for industrialized production and application.

[0032] The application provides an alumina ceramic based on powder extrusion printing forming, characterized in that a feedstock for preparing the alumina ceramic comprises the following raw materials in volume fractions: alumina powder: 30%-70%; binder: 24.9%-57%; and additive: 1.5%-5.1%; wherein the binder comprises at least three of semi-crystalline polymer, amorphous polymer, microcrystalline wax and blended oil; and the additive comprises at least one of silane coupling agent, passivator, antioxidant and stearic acid.

[0033] It should be noted that the semi-crystalline polymer is a kind of polymer material with crystalline and amorphous regions, and by adding the semi-crystalline polymer into the binder, the crystalline region of the dispersed semi-crystalline polymer in the printed green body is quickly crystallized, so that the printed green body is quickly solidified and shrinkage and collapse are reduced, thereby improving the printing precision; the semi-crystalline polymer also has a high glass transition temperature, so that the printed green body can withstand a higher temperature in the debinding and sintering, and deformation and cracking caused by temperature change are reduced.

[0034] The amorphous polymer is a polymer with disordered molecular chains and amorphous shape. The amorphous polymer has high molecular chain activity and freedom. The melt of the amorphous polymer has low viscosity and good fluidity, can uniformly wet the surface of powder particles, has smaller shrinkage than the semi-crystalline polymer when cooled, and has little residue after decomposition in the debinding process. The crystalline region of the semi-crystalline polymer is easily decomposed incompletely, thereby affecting the sintering density. In addition, the disordered arrangement of the molecular chains of the amorphous polymer has good stress absorption, which can improve the impact resistance of the printed part.

[0035] Aluminum oxide is a high-performance ceramic material with high hardness, high temperature resistance, chemical inertness and high insulation. The melting point of aluminum oxide is higher than 2000℃, so a high sintering temperature is required. Correspondingly, the high sintering temperature also leads to a high shrinkage rate of the sintered aluminum oxide ceramic. The high hardness feature leads to a high filling rate of aluminum oxide powder in the feedstock, thereby ensuring the strength of the prepared aluminum oxide ceramic.

[0036] In an embodiment, the silane coupling agent is selected from KH-570.

[0037] It should be noted that the micron-sized aluminum oxide used in the present application has a high specific surface area and a large surface energy. Due to the high volume fraction, the aluminum oxide particles are easily agglomerated, thereby weakening the interfacial bonding between the aluminum oxide particles and the organic material. In the present application, the silane coupling agent and stearic acid are used in combination. During the mixing process, the trace amount of water in the powder reacts with the hydroxyl groups on the surface of the aluminum oxide through hydrolysis and condensation to form an organic coating layer, thereby increasing the compatibility with the polymer (such as polyolefin). In addition, the introduction of carboxyl groups enables the aluminum oxide surface to bond with stearic acid molecules. The hydrophobic segment can reduce the hydrogen bonding between the powders and increase the compatibility with small molecule alkanes (such as paraffin).

[0038] In an embodiment, the blending oil includes at least one of mineral oil, vegetable oil and synthetic ester oil; wherein the mineral oil includes at least one of saturated hydrocarbon oil and aromatic hydrocarbon oil.

[0039] In an embodiment, the semi-crystalline polymer includes at least one of polyethylene and ethylene-vinyl acetate; wherein the content of vinyl acetate in the ethylene-vinyl acetate is less than 20%.

[0040] It should be noted that polyethylene is a semi-crystalline polymer, and the mechanical properties and dimensional stability of the material can be optimized by adjusting the crystallinity. Polyethylene includes high-density polyethylene and low-density polyethylene, and the crystallinity of ethylene-vinyl acetate is determined by the content of vinyl acetate. When the content of vinyl acetate is less than 15%, the crystallinity is high, close to that of polyethylene, but it is more flexible and has better toughness than polyethylene. When the content of vinyl acetate is higher than 20%, the crystallinity of ethylene-vinyl acetate is significantly reduced, showing rubber-like elasticity. When the content of vinyl acetate is higher than 20%, there is almost no crystallinity, and it becomes a completely amorphous polymer, i.e. a non-crystalline polymer.

[0041] In an embodiment, the amorphous polymer includes at least one of polystyrene and styrene-butadiene-styrene block copolymer.

[0042] It should be noted that polystyrene is an amorphous polymer with a low melting temperature and good flowability in a molten state, which can fill the pores of complex powder structures and form dense interlayer bonding. However, the amorphous structure of polystyrene lacks the stress dispersion ability of the crystalline region, is prone to brittle fracture, and is prone to deformation at high temperatures. Styrene-butadiene-styrene block copolymer is an amorphous polymer, and its unique block structure gives it excellent flexibility and thermoplasticity. The hard segment styrene provides rigidity, strength and thermal stability, and the soft segment butadiene provides high elasticity, impact resistance and low temperature toughness. Compared with EVA, the butadiene soft segment in styrene-butadiene-styrene block copolymer provides higher elasticity. Compared with polystyrene, styrene-butadiene-styrene block copolymer has stronger impact resistance and is less prone to brittle fracture. Compared with polypropylene, the styrene segment of styrene-butadiene-styrene block copolymer is more compatible with more materials, and the bonding strength is more spectrum.

[0043] In an embodiment, the passivator includes at least one of passivator MDA-5 and passivator MD697.

[0044] It should be noted that passivator MDA-5, also known as N-salicyl amide phthalimide, is added to polyolefin polymer materials to chelate heavy metal ions such as copper, iron and manganese, thereby inhibiting the catalytic aging of heavy metal ions on the material and prolonging the deterioration time. Passivator MD-697 is an antioxidant with a dual structure of hindered phenol and oxamide. The hydrazine group in the metal passivator MD-697 can form a stable complex with metal ions through a lone pair of electrons, inhibit its catalytic activity, and block the oxidation reaction chain. By adding a passivator to the feedstock, the storage time of the feedstock can be extended, thereby facilitating large-scale production and storage of the feedstock in industrial production.

[0045] In an embodiment, the ratio of the volume fraction of the semi-crystalline polymer and the amorphous polymer in the adhesive is (12.4~16.5):(1.5~5).

[0046] It should be noted that alumina, as the main component of the ceramic obtained after printing, debinding and sintering of the feedstock, requires a high sintering temperature, and the shrinkage rate of the sintered alumina ceramic is also high; in addition, the high hardness and high filling rate of alumina lead to deformation or collapse of alumina during printing, so in order to improve the printing accuracy, rapid solidification and reduction of deformation are required after printing, so the semi-crystalline polymer and the amorphous polymer are compounded in a specific ratio in the adhesive, which can promote the rapid crystallization of the crystalline region of the dispersed semi-crystalline polymer in the green body after printing, so that the green body after printing can be rapidly solidified and the shrinkage and collapse can be reduced, thereby improving the printing accuracy; and the shrinkage rate is smaller when the green body after printing is cooled, the stress absorption is better, and the impact resistance of the printed part is better.

[0047] It should also be noted that after the semi-crystalline polymer and the amorphous polymer are compounded in a specific ratio and added to the raw material to prepare the feedstock by internal mixing, the crystalline region of the semi-crystalline polymer provides a physical barrier to slow down the penetration of oxygen and moisture, while the amorphous polymer has high fluidity, which can fill the voids and reduce internal defects of the material, both delaying aging and reducing the risk of crack propagation caused by stress concentration. And under the action of the passivator, the anti-aging ability and anti-deformation ability of the feedstock can be further improved.

[0048] In an embodiment, the feedstock for preparing the alumina ceramic further comprises a modifier, and the modifier comprises a maleic anhydride grafted copolymer.

[0049] In an embodiment, the maleic anhydride grafted copolymer comprises SEBS-g-MAH, and the amount of SEBS-g-MAH is 4%~11% of the amount of alumina powder.

[0050] In an embodiment, the maleic anhydride grafting rate of the maleic anhydride grafted copolymer is 1%~2%.

[0051] In a preferred embodiment, the feedstock for preparing the alumina ceramic further comprises a modifier, and the modifier comprises SEBS-g-MAH, and the amount of SEBS-g-MAH is 4%~11% of the amount of alumina powder, and the maleic anhydride grafting rate of the SEBS-g-MAH is 1.2%~1.6%.

[0052] It should be noted that the specific maleic anhydride grafting rate of the modifier SEBS-g-MAH is used to improve the interfacial bonding effect of the composite, and the anhydride group in SEBS-g-MAH can react with the surface of alumina in the mixing process to further modify. The thermal expansion coefficient and density of alumina and polyolefin macromolecular material or paraffin wax have great difference. In the cooling shrinkage process after printing, the shrinkage rates of the two do not match, resulting in internal stress at the interface, which is easy to produce cracks and continuously increase. The elastic block (ethylene / butylene) in SEBS-g-MAH can absorb the internal stress in the cooling process, prevent stress concentration from causing cracks, and even if cracks occur, the elastomer can delay crack growth through plastic deformation, thereby significantly improving the crack resistance of the product.

[0053] The application further provides a preparation method of the alumina ceramic based on powder extrusion 3D printing. S1, mixing alumina powder and additives according to the proportion, stirring, then adding a binder according to the proportion, stirring, mixing, and granulating to obtain a feedstock; S2, placing the feedstock prepared in step S1 into a printing device, setting printing parameters and green body structure, and printing to obtain an alumina green body; S3, performing a debinding treatment on the alumina green body prepared in step S2, including solvent debinding treatment and high-temperature debinding treatment; S4, sintering the alumina green body after the debinding treatment in step S3 to obtain an alumina ceramic.

[0054] It should be noted that the alumina ceramic prepared by adopting the powder extrusion 3D printing forming technology has high solid content and high mechanical strength, and the appearance of the part after debinding is complete, which can well maintain the complex shape of the 3D printing forming.

[0055] In an embodiment, in step S1, the particle size of the alumina powder is 0.5-1 mu m.

[0056] In an embodiment, in step S1, the particle size of the feedstock is 4-12 mesh.

[0057] In an embodiment, in step S2, the extrusion temperature is 130-170 DEG C, and the printing platform temperature is 90-120 DEG C.

[0058] In an embodiment, in step S2, the nozzle size of the printing device is 0.1-0.8 mm.

[0059] In an embodiment, in step S2, when printing, the single-layer layer thickness is 0.15-0.2 mm, and the printing speed is 40-80 mm / s.

[0060] In an embodiment, the solvent debinding treatment in step S3 comprises: soaking the green body of alumina in a liquid of n-heptane or a sodium citrate aqueous solution, and soaking for 12h-48h at 40℃-70℃.

[0061] It should be noted that the temperature of the solution during the solvent debinding process should be kept in the range of 40-70℃, and too low solution temperature will reduce the debinding rate, and too high solution temperature will cause high debinding rate, which will cause the green body of alumina to swell and other defects. The time of the green body of alumina in the solution is 12h-48h to ensure complete debinding, and too short time will cause incomplete debinding, and too long time will easily cause the green body to swell and break and other defects.

[0062] In an embodiment, the high-temperature debinding treatment in step S3 comprises: placing the green body of alumina after the solvent debinding treatment in a muffle furnace, and heating from room temperature to 500℃-700℃ at a heating rate of 0.5℃ / min-5℃ / min. It should be noted that too low heating rate during the high-temperature debinding treatment will cause the green body of alumina to easily collapse and other defects, and too high heating rate will easily cause the green body of alumina to be difficult to completely remove organic impurities. During the high-temperature debinding treatment, gradually heating and keeping the heating rate consistent before and after is beneficial to promote uniform decomposition of the organic impurities in the green body of alumina In an embodiment, in step S4, the green body of alumina after the debinding treatment is placed in a muffle furnace, sintered in an air atmosphere, heated to 1400℃-1600℃, and heat treated for 0.5h-2h. It should be noted that during the sintering of the alumina ceramic, the sintering temperature and the sintering time need to be reasonably controlled, and too low sintering temperature and too short sintering time cannot form sintering necks and cannot guarantee the density, and too high sintering temperature and too long sintering time will easily form coarse grains and deteriorate the performance.

[0063] The application is further described below through specific embodiments: The application does not make specific limitations on the source of raw materials, which are directly purchased on the market.

[0064] Embodiment 1 The particle size of the alumina powder in the feed in Embodiment 1 is 0.5μm-1μm.

[0065] The binder in the feed in Embodiment 1 comprises semi-crystalline polymers, amorphous polymers, microcrystalline wax and blended oil, wherein the semi-crystalline polymers comprise polyethylene and ethylene-vinyl acetate, and the amorphous polymers comprise styrene-butadiene-styrene block copolymer.

[0066] The additives in the feed in Embodiment 1 comprise silane coupling agent, passivation agent and stearic acid, wherein the silane coupling agent is KH-570, and the passivation agent is MD-697.

[0067] The feed used in Example 1 for preparing alumina ceramics includes the following raw materials by volume fraction: Alumina powder: 55.5 vol%; SEBS-g-MAH: 4.5 vol%; Microcrystalline wax: 17.2 vol%; Polyethylene: 10.4 vol%; Ethylene-vinyl acetate: 2 vol%; Styrene-butadiene-styrene block copolymer: 1.5 vol%; Blending oil: 6.5 vol%; Stearic acid: 1 vol%; Passivating agent MD-697: 0.8 vol%; KH-570 silane coupling agent: 0.6 vol%.

[0068] The grafting rate of maleic anhydride in SEBS-g-MAH is approximately 1.36%.

[0069] The preparation method of the alumina ceramic in Example 1 includes the following steps: S1. Mix alumina powder and additives according to the ratio, stir for 20 minutes, then add binder according to the ratio, stir for 30 minutes, knead and granulate to obtain feed with a particle size of 4 to 12 mesh. S2. Place the feed material obtained in step S1 into the printing equipment, set the printing parameters and green structure, and print to obtain an alumina green blank. The printing parameters specifically include: printing temperature of 160℃, nozzle size of 0.6mm, layer thickness of 0.15mm, printing speed of 60mm / s, and printing platform temperature of 100℃.

[0070] S3. The alumina green blank obtained in step S2 is subjected to degreasing treatment, including solvent degreasing treatment and high-temperature degreasing treatment. The solvent degreasing treatment process includes: immersing the alumina green blank in n-heptane liquid at 50°C for 24 hours; the high-temperature degreasing treatment process includes: placing the alumina green blank in a muffle furnace and heating it to 600°C at a heating rate of 0.5°C / min to complete the high-temperature degreasing treatment.

[0071] S4. The alumina green blank after high-temperature degreasing treatment in step S3 is placed in a muffle furnace and heated to 1600°C at a heating rate of 3°C / min, held for 2 hours, and sintered in air atmosphere to obtain alumina ceramic.

[0072] Example 2 The alumina powder in the feed in Example 2 has a particle size of 0.5 μm to 1 μm.

[0073] The binder in the feed in Example 2 includes a semi-crystalline polymer, an amorphous polymer, and a blending oil, wherein the semi-crystalline polymer includes polyethylene and ethylene-vinyl acetate, and the amorphous polymer includes polystyrene.

[0074] The additives in the feed in Example 2 include stearic acid and a passivating agent, the passivating agent being MD-697.

[0075] The feed used in Example 2 for preparing alumina ceramics includes the following raw materials by volume fraction: Alumina powder: 50 vol%; Polyethylene: 10 vol%; Ethylene-vinyl acetate: 6.5 vol%; Polystyrene: 5 vol%; Blended oil: 27 vol%; Stearic acid: 1 vol%; Passivating agent: 0.5%.

[0076] The preparation method of the alumina ceramic in Example 2 includes the following steps: S1. Mix alumina powder and additives according to the ratio, stir for 20 minutes, then add binder according to the ratio, stir for 30 minutes, knead and granulate to obtain feed with a particle size of 4 to 12 mesh. S2. Place the feed material obtained in step S1 into the printing equipment, set the printing parameters and green structure, and print to obtain an alumina green blank. The printing parameters specifically include: printing temperature of 150℃, nozzle size of 0.6mm, layer thickness of 0.2mm, printing speed of 60mm / s, and printing platform temperature of 95℃.

[0077] S3. The alumina green blank obtained in step S2 is subjected to degreasing treatment, including solvent degreasing treatment and high-temperature degreasing treatment. The solvent degreasing treatment process includes: immersing the alumina green blank in n-heptane liquid at 60°C for 12 hours; the high-temperature degreasing treatment process includes: placing the alumina green blank in a muffle furnace and heating it to 600°C at a heating rate of 3°C / min to complete the high-temperature degreasing treatment.

[0078] S4. The alumina green blank after high-temperature degreasing treatment in step S3 is placed in a muffle furnace and heated to 1400°C at a heating rate of 3°C / min, held for 0.5 hours, and sintered in air atmosphere to obtain alumina ceramic.

[0079] Example 3 The alumina powder in the feed in Example 3 has a particle size of 0.5 μm to 1 μm.

[0080] The binder in the feed in Example 3 includes a semi-crystalline polymer, microcrystalline wax, and blended oil, wherein the semi-crystalline polymer includes polyethylene.

[0081] The additives in the feed in Example 3 include a passivating agent and stearic acid, wherein the passivating agent is MDA-5.

[0082] The feed used in Example 3 for preparing alumina ceramics includes the following raw materials by volume fraction: Alumina powder: 40 vol%; microcrystalline wax: 26 vol%; polyethylene: 22 vol%; blended oil: 9 vol%; stearic acid: 1.5 vol%; passivating agent MDA-5: 1.5 vol%.

[0083] The preparation method of the alumina ceramic in Example 3 includes the following steps: S1. Mix alumina powder and additives according to the ratio, stir for 20 minutes, then add binder according to the ratio, stir for 30 minutes, knead and granulate to obtain feed with a particle size of 4 to 12 mesh. S2. Place the feed material obtained in step S1 into the printing equipment, set the printing parameters and green structure, and print to obtain an alumina green blank. The printing parameters specifically include: printing temperature of 130℃, nozzle size of 0.6mm, layer thickness of 0.2mm, printing speed of 80mm / s, and printing platform temperature of 90℃.

[0084] S3. The alumina green blank obtained in step S2 is subjected to degreasing treatment, including solvent degreasing treatment and high-temperature degreasing treatment. The solvent degreasing treatment process includes: immersing the alumina green blank in a saturated sodium citrate aqueous solution at 40°C for 36 hours; the high-temperature degreasing treatment process includes: placing the alumina green blank in a muffle furnace and heating it to 600°C at a heating rate of 0.5°C / min to complete the high-temperature degreasing treatment.

[0085] S4. The alumina green blank after high-temperature degreasing treatment in step S3 is placed in a muffle furnace and heated to 1400°C at a heating rate of 3°C / min, held for 0.5 hours, and sintered in air atmosphere to obtain alumina ceramic.

[0086] Example 4 The alumina powder in the feed in Example 4 has a particle size of 0.5 μm to 1 μm.

[0087] The binder in the feed in Example 4 includes an amorphous polymer, microcrystalline wax, and blending oil, wherein the amorphous polymer includes a styrene-butadiene-styrene block copolymer.

[0088] The additives in the feed in Example 4 include a silane coupling agent and stearic acid, wherein the silane coupling agent is KH-570.

[0089] The feed used in Example 4 for preparing alumina ceramics includes the following raw materials by volume fraction: Alumina powder: 70 vol%; Microcrystalline wax: 15 vol%; Styrene-butadiene-styrene block copolymer: 7.2 vol%; Blending oil: 2.7 vol%; Stearic acid: 4.2 vol%; KH-570 silane coupling agent: 0.9 vol%.

[0090] The preparation method of the alumina ceramic in Example 4 includes the following steps: S1. Mix alumina powder and additives according to the ratio, stir for 20 minutes, then add binder according to the ratio, stir for 30 minutes, knead and granulate to obtain feed with a particle size of 4 to 12 mesh. S2. Place the feed material obtained in step S1 into the printing equipment, set the printing parameters and green structure, and print to obtain an alumina green blank. The printing parameters specifically include: printing temperature of 180℃, nozzle size of 0.6mm, layer thickness of 0.15mm, printing speed of 40mm / s, and printing platform temperature of 120℃.

[0091] S3. The alumina green blank obtained in step S2 is subjected to degreasing treatment, including solvent degreasing treatment and high-temperature degreasing treatment. The solvent degreasing treatment process includes: immersing the alumina green blank in a saturated sodium citrate aqueous solution at 70°C for 48 hours; the high-temperature degreasing treatment process includes: placing the alumina green blank in a muffle furnace and heating it to 400°C at a heating rate of 0.5°C / min to complete the high-temperature degreasing treatment.

[0092] S4. The alumina green blank after high-temperature degreasing treatment in step S3 is placed in a muffle furnace and heated to 1600°C at a heating rate of 3°C / min, held for 2 hours, and sintered in air atmosphere to obtain alumina ceramic.

[0093] Performance testing: 1. The feed deterioration time in Examples 1 to 4 was measured respectively.

[0094] 2. The flexural strength and density of the alumina ceramics prepared in Examples 1 to 4 were measured respectively.

[0095] The measurement results are shown in Table 1.

[0096] Table 1

[0097] Analysis of Table 1 shows that comparing the feed degradation time of Examples 1 and 2 with that of Examples 3 and 4, it can be seen that the degradation time of the feed is significantly shortened when a passivating agent is added but no amorphous polymer is added, and the degradation time of the feed is further shortened when neither a passivating agent nor semi-crystalline polymer is added.

[0098] Analysis of Table 1 shows that when semi-crystalline polymers and amorphous polymers are compounded and used as the main components of the binder, the sintered alumina ceramics have higher flexural strength and density.

[0099] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An alumina ceramic based on powder extrusion printing, characterized in that, The feedstock used to prepare the alumina ceramic comprises the following raw materials by volume fraction: Alumina powder: 30%~70%; Adhesive: 24.9%~57%; Additives: 1.5%~5.1%; The adhesive comprises at least three of the following: semi-crystalline polymer, amorphous polymer, microcrystalline wax, and blended oil; the additive comprises at least one of silane coupling agent, passivating agent, antioxidant, and stearic acid.

2. The alumina ceramic based on powder extrusion printing as described in claim 1, characterized in that, In the adhesive, the semi-crystalline polymer includes at least one of polyethylene and ethylene-vinyl acetate; wherein the content of vinyl acetate in the ethylene-vinyl acetate is less than 20%. And / or, in the adhesive, the amorphous polymer includes at least one of polystyrene and styrene-butadiene-styrene block copolymer; And / or, in the additive, the passivating agent includes at least one of passivating agent MDA-5 and passivating agent MD697.

3. The alumina ceramic based on powder extrusion printing as described in claim 1, characterized in that, In the adhesive, the volume fraction ratio of the semi-crystalline polymer to the amorphous polymer is (12.4~16.5):(1.5~5).

4. The alumina ceramic based on powder extrusion printing as described in claim 1, characterized in that, The feedstock used to prepare the alumina ceramic also includes a modifier, which includes a maleic anhydride graft copolymer.

5. The alumina ceramic based on powder extrusion printing as described in claim 4, characterized in that, The maleic anhydride graft copolymer includes SEBS-g-MAH, and the amount of SEBS-g-MAH accounts for 4% to 11% of the amount of alumina powder. And / or, the maleic anhydride grafting rate of the maleic anhydride graft copolymer is 1% to 2%.

6. A method for preparing alumina ceramic based on powder extrusion printing as described in any one of claims 1 to 5, characterized in that, The method for preparing alumina ceramics based on powder extrusion printing includes the following steps: S1. Mix alumina powder and additives according to the formula, stir, then add binder according to the formula, stir, knead, granulate, and obtain feed. S2. Place the feed material obtained in step S1 into the printing device, set the printing parameters and green structure, print, and obtain alumina green billet; S3. The alumina green blank obtained in step S2 is subjected to degreasing treatment, including solvent degreasing treatment and high temperature degreasing treatment. S4. The alumina green blank after degreasing in step S3 is sintered to obtain alumina ceramic.

7. The method for preparing alumina ceramics based on powder extrusion printing as described in claim 6, characterized in that, In step S1, the particle size of the alumina powder is 0.5 μm to 1 μm; And / or, in step S1, the particle size of the feed is 4 mesh to 12 mesh.

8. The method for preparing alumina ceramics based on powder extrusion printing as described in claim 6, characterized in that, In step S2, the extrusion temperature is 130℃~170℃, and the printing platform temperature is 90℃~120℃. And / or, in step S2, the nozzle size of the printing device is 0.1mm~0.8mm; And / or, in step S2, when printing, the single-layer thickness is 0.15mm~0.2mm, and the printing speed is 40mm / s~80mm / s.

9. The method for preparing alumina ceramics based on powder extrusion printing as described in claim 6, characterized in that, In step S3, the solvent degreasing treatment includes: immersing the alumina green blank in an aqueous solution of n-heptane or sodium citrate at 40°C to 70°C for 12 to 48 hours. And / or, in step S3, the high-temperature degreasing treatment includes: placing the solvent-degreased alumina billet in a muffle furnace and heating it from room temperature to 500℃~700℃ at a heating rate of 0.5℃ / min~5℃ / min.

10. The method for preparing alumina ceramics based on powder extrusion printing as described in claim 6, characterized in that, In step S4, the degreased alumina green billet is placed in a muffle furnace and sintered in an air atmosphere, heated to 1400℃~1600℃ and held for 0.5h~2h.

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