A method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics

Abstract

A method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics, which relates to a method for forming whisker-toughened zirconia ceramics. The present invention is based on photocuring additive manufacturing technology and ultra-fast high-temperature sintering technology to achieve rapid additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics. The pre-dispersion, freeze-drying, and non-contact stirring steps included in the present invention can be combined to prepare a photocuring ceramic slurry with good dispersion of alumina whiskers and good printability without destroying the whiskers; the non-reactive diluent added to the resin formula of the present invention acts as a thermoplastic resin solvent and can be discharged at a lower temperature, thereby forming uniform pore channels in the matrix, which is beneficial to the subsequent discharge of pyrolysis gas of the resin and reduces the generation of defects; the added thermoplastic polyimide is resistant to high temperatures, can be retained until the sintering stage and improve the high-temperature toughness of the blank, preventing the semi-degreased blank from breaking during the ultra-fast high-temperature sintering process.

Description

Technical Field

[0001] The invention relates to a molding method of whisker toughened zirconia ceramics. Background Art

[0002] Partially stabilized zirconia polycrystalline ceramics with a tetragonal phase as the main component can overcome the inherent brittleness of ceramics to a certain extent due to the phase transformation toughening effect. At the same time, they also have good wear resistance, chemical stability, biocompatibility, etc., and have been widely used in various structural and functional devices.

[0003] However, the toughness of the zirconia ceramics currently used is still insufficient. Further improvement of fracture toughness depends on the synergistic effect of multiple toughening mechanisms. Adding second-phase whiskers is a powerful means to improve the toughness of ceramic materials. Thanks to whisker pullout and crack deflection, bifurcation, and bridging, the composite materials with added whiskers have significantly better mechanical properties than single-phase materials. Among various whiskers, alumina whiskers have similar strength and higher modulus, and have good matching with zirconia. As an oxide, they have the same high-temperature oxidation resistance as zirconia, making them a strong candidate as zirconia ceramic reinforcement.

[0004] CN108749040A discloses a zirconia toughened alumina ceramic-wear-resistant resin composite material and its preparation method. The use of wear-resistant resin improves the toughness of the material, but it cannot be applied to working conditions with more stringent strength and service temperature requirements. CN115010487A discloses a method for preparing whisker-toughened zirconia ceramics. Although it uses revolution and rotation stirring to avoid the breakage of whiskers during ball milling, it does not solve the problem of initial dispersion of whiskers, and the dry pressing molding method cannot prepare complex ceramic components. CN117383914A discloses a method for preparing nano-zirconia toughened nano-alumina ceramics. It uses injection molding to directly prepare nano-zirconia toughened nano-alumina ceramic parts with final shape and high dimensional accuracy. However, molds are still required and the degreasing and sintering steps require a lot of work hours. The final toughness of the zirconia particles toughening the alumina is also insufficient. Additive manufacturing technology based on a binder system can significantly reduce the preparation cycle and cost of complex ceramic components. However, the difficulty in introducing whiskers lies in the fact that whiskers are difficult to disperse evenly in the raw material system, whiskers make it difficult to densify ceramics, and traditional degreasing and sintering processes are too time-consuming. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a method for rapid additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics based on photocuring additive manufacturing technology and ultra-fast high-temperature sintering technology.

[0006] A method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics is specifically completed in the following steps:

[0007] 1. Preparation of slurry:

[0008] ① Add alumina whiskers and dispersant to water and stir ultrasonically for a period of time. After dispersion is completed, add part of stabilized zirconium oxide and dispersant and stir ultrasonically for a period of time to obtain a mixed powder slurry;

[0009] ②Putting the mixed powder slurry into a vacuum freezer for rapid vacuum freezing, and then performing vacuum freeze drying to obtain a mixed powder of alumina whiskers and partially stabilized zirconia;

[0010] ③ Weigh 40-45 parts by weight of a mixed powder of aluminum oxide whiskers and partially stabilized zirconium oxide and 55-60 parts of photosensitive resin, and stir them at high speed in a planetary degassing mixer for a period of time to obtain a light-cured ceramic slurry that can be used for printing;

[0011] 2. Green printing:

[0012] ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body.

[0013] ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body;

[0014] 3. Degreasing and sintering:

[0015] ①, thermally degreasing the green body after secondary curing to obtain a semi-degreased green body;

[0016] ②. Transfer the semi-degreased green body to an ultra-fast high-temperature sintering furnace and sinter it at a preset current for a preset time to obtain high-toughness alumina whisker-toughened zirconia ceramics.

[0017] The present invention has the following beneficial effects:

[0018] (1) The pre-dispersion, freeze-drying, and non-contact stirring steps included in the present invention can be combined to prepare a light-cured ceramic slurry with good dispersion of aluminum oxide whiskers and good printability without destroying the whiskers;

[0019] (2) The non-reactive diluent added to the resin formula of the present invention not only acts as a solvent for the thermoplastic resin, but also can be discharged at a lower temperature, thereby forming uniform pore channels in the matrix, which is beneficial to the subsequent discharge of pyrolysis gas of the resin and reduces the generation of defects;

[0020] (3) The thermoplastic polyimide added to the resin formula of the present invention is resistant to high temperatures and can be retained until the sintering stage and improve the high-temperature toughness of the green body, preventing the semi-degreased green body from breaking during the ultra-fast high-temperature sintering process;

[0021] (4) The present invention uses semi-degreased green compacts to directly perform ultra-fast high-temperature sintering, which can enable the degreasing and sintering of the latter half to be completed simultaneously, thereby improving manufacturing efficiency;

[0022] (5) The rapid temperature rise and fall and instantaneous ultra-high temperature characteristics of ultra-fast high-temperature sintering can reduce the occurrence of abnormally grown grains, achieve the densification of alumina whisker-toughened zirconia ceramics that is difficult to achieve with conventional pressureless sintering, and reduce the generation of monoclinic zirconia;

[0023] (6) Short-term high-temperature sintering can inhibit the transformation of whiskers into rods / round crystals based on diffusion, and maintain the dispersed distribution of whiskers in the matrix;

[0024] (7) Based on the above beneficial effects, the density of the high-toughness alumina whisker toughened zirconia ceramics prepared by the present invention reaches 96.2%, and the fracture toughness reaches 15.3 MPa·m 1 / 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a surface SEM image of the high-toughness alumina whisker toughened zirconia ceramic prepared in Example 1;

[0026] Figure 2 This is a surface SEM image of the alumina whisker toughened zirconia ceramic prepared in Comparative Example 1;

[0027] Figure 3 The figure is a comparison of XRD patterns of alumina whisker toughened zirconia ceramics prepared in Example 1 and Comparative Example 1;

[0028] Figure 4 This is a surface SEM image of the zirconia ceramic prepared in Comparative Example 2;

[0029] Figure 5 This is a surface SEM image of the zirconia ceramic prepared in Comparative Example 3;

[0030] Figure 6 This is a side SEM image of the alumina whisker toughened zirconia degreased blank prepared in Comparative Example 4;

[0031] Figure 7 This is a side SEM image of the alumina whisker toughened zirconia ceramic prepared in comparative example five. DETAILED DESCRIPTION

[0032] Specific embodiment 1: This embodiment provides a method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics, which is specifically completed in the following steps:

[0033] 1. Preparation of slurry:

[0034] ① Add alumina whiskers and dispersant to water and stir ultrasonically for a period of time. After dispersion is completed, add part of stabilized zirconium oxide and dispersant and stir ultrasonically for a period of time to obtain a mixed powder slurry;

[0035] ②Putting the mixed powder slurry into a vacuum freezer for rapid vacuum freezing, and then performing vacuum freeze drying to obtain a mixed powder of alumina whiskers and partially stabilized zirconia;

[0036] ③ Weigh 40-45 parts by weight of a mixed powder of aluminum oxide whiskers and partially stabilized zirconium oxide and 55-60 parts of photosensitive resin, and stir them at high speed in a planetary degassing mixer for a period of time to obtain a light-cured ceramic slurry that can be used for printing;

[0037] 2. Green printing:

[0038] ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body.

[0039] ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body;

[0040] 3. Degreasing and sintering:

[0041] ①, thermally degreasing the green body after secondary curing to obtain a semi-degreased green body;

[0042] ②. Transfer the semi-degreased green body to an ultra-fast high-temperature sintering furnace and sinter it at a preset current for a preset time to obtain high-toughness alumina whisker-toughened zirconia ceramics.

[0043] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the diameter of the aluminum oxide whisker described in step 1 ① is 300nm~500nm, and the length is 10μm~20μm; the partially stabilized zirconia described in step 1 ① is 3mol% yttria partially stabilized zirconia, D 50 =500nm~700nm; the mass ratio of the alumina whiskers to the partially stabilized zirconia in step 1① is 5:95; the solid content of the mixed powder slurry in step 1① is 10vol.%~20vol.%. The other steps are the same as those in the first embodiment.

[0044] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the dispersant in step 1 (1) is either polyethylene glycol 400 or polyethylene glycol 1000, or both; the amount of dispersant added each time is 1% to 2% of the mass of the powder added, and the ultrasonic stirring time is 30 to 60 minutes. The other steps are the same as those in specific embodiments 1 or 2.

[0045] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the vacuum rapid freezing described in step 1 (2) is performed at a temperature of -55°C for 20 to 40 minutes, and the vacuum freeze drying is performed at a temperature of -55°C, a vacuum degree of 1 Pa, and a time of 22 to 24 hours. The other steps are the same as specific embodiments 1 to 3.

[0046] Specific Embodiment 5: This embodiment differs from Specific Embodiments 1 to 4 in that the photosensitive resin described in step 1 (3) is composed of a monomer mixture, a dispersant, a non-reactive diluent, a thermoplastic resin, and a photoinitiator; the mass ratio of the monomer mixture, dispersant, non-reactive diluent, thermoplastic resin, and photoinitiator in the photosensitive resin is 60:(20-26):30:10:(1.2-1.3). The other steps are the same as Specific Embodiments 1 to 4.

[0047] Specific Embodiment 6: This embodiment differs from Specific Embodiments 1 to 5 in that the monomer mixture in step 1 (3) is a mixture of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and o-phenylphenoxyethyl acrylate, wherein the mass ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, and o-phenylphenoxyethyl acrylate is 30:10:20; the non-reactive diluent is polypropylene glycol 400; the thermoplastic resin is BASF Matrimid 5218 soluble polyimide; the dispersant is one or more of BYK-103, BYK-110, and BYK-111; and the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. Other steps are the same as Specific Embodiments 1 to 5.

[0048] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the high-speed stirring and mixing described in step 1 (3) is performed at a stirring speed of 1400 rpm to 2000 rpm and for a stirring time of 15 to 30 minutes. The other steps are the same as those of specific embodiments 1 to 6.

[0049] Specific embodiment 8: The difference between this embodiment and specific embodiments 1 to 7 is that the slice thickness in step 2 ① is 20 μm; the wavelength of the ultraviolet light in step 2 ② is 405 nm, and the exposure energy is 12.6 to 24.4 mW / cm2 The exposure time is 1 to 4 seconds. The resin monomer in step 2 (2) is hydroxyethyl acrylate, hydroxyethyl methacrylate, or 1,6-hexanediol diacrylate. The number of washes is 1 to 2. The other steps are the same as those in specific embodiments 1 to 7.

[0050] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the thermal debinding process described in step 3 (1) is as follows: the green body after secondary curing is placed in a debinding furnace, evacuated to below 10 Pa, and then 99.999% high-purity nitrogen is introduced to atmospheric pressure while maintaining a nitrogen flow rate of 50 mL / min. Heating is then initiated, heating at a rate of 1°C / min to 145°C and holding for 60 minutes, heating at a rate of 1°C / min to 265°C and holding for 60 minutes, heating at a rate of 1°C / min to 320°C and holding for 60 minutes, and cooling to room temperature at a rate of 1°C / min. The other steps are the same as those in specific embodiments 1 to 8.

[0051] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the sintering process described in step 3 ② is as follows: using carbon felt as a heating body, placing the semi-degreased green body in the carbon felt interlayer in an edge-to-edge contact manner, and starting sintering with argon as a protective atmosphere; the current is 20A to 30A, and the holding time is 60s to 120s; the high-toughness alumina whisker toughened zirconia ceramic described in step 3 ② can reach a density of 96.2% and a fracture toughness of 15.3MPa·m 1 / 2 The other steps are the same as those in Specific Embodiments 1 to 9.

[0052] The following examples are used to verify the beneficial effects of the present invention:

[0053] Example 1: A method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics, specifically completed by the following steps:

[0054] 1. Preparation of slurry:

[0055] ①, weighing 5 parts of aluminum oxide whiskers, 0.05 parts of polyethylene glycol 400, 95 parts of partially stabilized zirconium oxide, and 0.95 parts of polyethylene glycol 400 by weight; adding 5 parts of aluminum oxide whiskers and 0.05 parts of polyethylene glycol 400 to water and stirring ultrasonically for 30 minutes. After dispersion is completed, add 95 parts of partially stabilized zirconium oxide and 0.95 parts of polyethylene glycol 400 and stir ultrasonically for 30 minutes to obtain a mixed powder slurry;

[0056] The solid content of the mixed powder slurry described in step 1① is 15 vol.%;

[0057] The diameter of the aluminum oxide whiskers described in step 1① is 300nm to 500nm and the length is 10μm to 20μm;

[0058] The partially stabilized zirconium oxide described in step 1① is 3 mol% yttria partially stabilized zirconium oxide, D 50 =500nm~700nm;

[0059] ② Place the mixed powder slurry into a vacuum freezer and begin to vacuumize it and freeze it at -55°C for 30 minutes. Then, freeze-dry it at -55°C and a vacuum of 1 Pa for 24 hours to obtain a mixed powder of alumina whiskers and partially stabilized zirconia.

[0060] ③ Weigh 40 parts by weight of a mixed powder of aluminum oxide whiskers and partially stabilized zirconium oxide and 60 parts of photosensitive resin, and stir them at high speed in a planetary degassing mixer for a period of time to obtain a light-cured ceramic slurry that can be used for printing;

[0061] The photosensitive resin described in step 1 (3) is composed of a monomer mixture, a dispersant, a non-reactive diluent, a thermoplastic resin and a photoinitiator; the mass ratio of the monomer mixture, the dispersant, the non-reactive diluent, the thermoplastic resin and the photoinitiator in the photosensitive resin is 60:20:30:10:1.2;

[0062] The monomer mixture described in step 1 (3) is a mixture of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate, wherein the mass ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate is 30:10:20; the non-reactive diluent is polypropylene glycol 400; the thermoplastic resin is BASF Matrimid 5218 soluble polyimide; the dispersant is BYK-111; the photoinitiator is phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide;

[0063] The stirring speed of the high-speed stirring mixing described in step 1 (3) is 1400 r / min, and the stirring time is 30 min;

[0064] 2. Green printing:

[0065] ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body.

[0066] The slice thickness described in step 2① is 20 μm;

[0067] ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body;

[0068] The wavelength of the ultraviolet light in step 2 is 405nm, and the exposure energy is 12.6mW / cm 2 , exposure time is 3s;

[0069] The resin monomer described in step 2② is 1,6-hexanediol diacrylate, and the number of washings is 2 times;

[0070] 3. Degreasing and sintering:

[0071] ①, thermally degreasing the green body after secondary curing to obtain a semi-degreased green body;

[0072] The thermal debinding process described in step 3① is as follows: the green body after secondary curing is placed in a debinding furnace, evacuated to below 10Pa, and then 99.999% high-purity nitrogen is introduced to atmospheric pressure and maintained at a nitrogen flow rate of 50mL / min. Heating is started, heating to 145°C at 1°C / min and holding for 60min, heating to 265°C at 1°C / min and holding for 60min, heating to 320°C at 1°C / min and holding for 60min, and cooling to room temperature at 1°C / min;

[0073] ②. Transfer the semi-degreased green body to an ultra-fast high-temperature sintering furnace and sinter it at a preset current for a preset time to obtain high-toughness alumina whisker-toughened zirconia ceramics.

[0074] The sintering process described in step 3② is as follows: using carbon felt as a heating element, placing the semi-degreased green body in the carbon felt interlayer in an edge-to-edge manner, and starting sintering with argon as a protective atmosphere; the current is 26A, and the holding time is 90s;

[0075] The size of the high-toughness alumina whisker toughened zirconia ceramic described in step 3② is 2mm×4mm×20mm.

[0076] Figure 1 This is a surface SEM image of the high-toughness alumina whisker toughened zirconia ceramic prepared in Example 1;

[0077] from Figure 1 It can be seen that the high-toughness alumina whisker toughened zirconia ceramic prepared in Example 1 has a high degree of densification, and the alumina whiskers are evenly dispersed in the zirconia matrix; the density measured by the Archimedes method is 96.2%, and the fracture toughness measured by the single-edge notched beam method is 15.3 MPa·m 1 / 2 .

[0078] Comparative Example 1: A method for preparing alumina whisker-toughened zirconia ceramics is specifically completed by the following steps:

[0079] 1. Preparation of slurry:

[0080] ①, weighing 5 parts of aluminum oxide whiskers, 0.05 parts of polyethylene glycol 400, 95 parts of partially stabilized zirconium oxide, and 0.95 parts of polyethylene glycol 400 by weight; adding 5 parts of aluminum oxide whiskers and 0.05 parts of polyethylene glycol 400 to water and stirring ultrasonically for 30 minutes. After dispersion is completed, add 95 parts of partially stabilized zirconium oxide and 0.95 parts of polyethylene glycol 400 and stir ultrasonically for 30 minutes to obtain a mixed powder slurry;

[0081] The solid content of the mixed powder slurry described in step 1① is 15 vol.%;

[0082] The diameter of the aluminum oxide whiskers described in step 1① is 300nm to 500nm and the length is 10μm to 20μm; step 1

[0083] The partially stabilized zirconium oxide described in ① is 3 mol% yttria partially stabilized zirconium oxide,

[0084] D 50 =500nm~700nm;

[0085] ② Place the mixed powder slurry in an air oven at 70°C and dry for 12 hours to obtain a mixed powder;

[0086] ③ Weigh 40 parts by weight of a mixed powder of aluminum oxide whiskers and partially stabilized zirconium oxide and 60 parts of photosensitive resin, and stir them at high speed in a planetary degassing mixer for a period of time to obtain a light-cured ceramic slurry that can be used for printing;

[0087] The photosensitive resin described in step 1 (3) is composed of a monomer mixture, a dispersant, a non-reactive diluent, a thermoplastic resin and a photoinitiator; the mass ratio of the monomer mixture, the dispersant, the non-reactive diluent, the thermoplastic resin and the photoinitiator in the photosensitive resin is 60:20:30:10:1.2;

[0088] The monomer mixture described in step 1 (3) is a mixture of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate, wherein the mass ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate is 30:10:20; the non-reactive diluent is polypropylene glycol 400; the thermoplastic resin is BASF Matrimid 5218 soluble polyimide; the dispersant is BYK-111; the photoinitiator is phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide;

[0089] The stirring speed of the high-speed stirring mixing described in step 1 (3) is 1400 r / min, and the stirring time is 30 min;

[0090] 2. Green printing:

[0091] ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body.

[0092] The slice thickness described in step 2① is 20 μm;

[0093] ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body;

[0094] The wavelength of the ultraviolet light in step 2 is 405nm, and the exposure energy is 12.6mW / cm 2 , exposure time is 3s;

[0095] The resin monomer described in step 2② is 1,6-hexanediol diacrylate, and the number of washings is 2 times;

[0096] 3. Degreasing and sintering:

[0097] ①. Thermally degrease the green body after secondary curing to obtain a crack-free degreased body;

[0098] The thermal degreasing process described in step 3① is as follows: placing the secondary cured body in a degreasing furnace, evacuating it to below 10Pa, and then introducing 99.999% high-purity nitrogen to atmospheric pressure, and maintaining a nitrogen flow rate of 50mL / min, starting heating, heating to 145°C at 1°C / min and keeping warm for 60min, heating to 265°C at 1°C / min and keeping warm for 60min, heating to 320°C at 1°C / min and keeping warm for 60min, heating to 385°C at 1°C / min and keeping warm for 60min, heating to 450°C at 1°C / min and keeping warm for 60min, heating to 485°C at 1°C / min and keeping warm for 60min, heating to 525°C at 1°C / min and keeping warm for 60min, heating to 595°C at 1°C / min and keeping warm for 60min, cooling to room temperature at 1°C / min to obtain a crack-free degreased body;

[0099] ② Sintering the crack-free degreased body to obtain alumina whisker-toughened zirconia ceramics;

[0100] The sintering described in step 3② is divided into two stages: the first stage is pre-sintering: the crack-free degreased blank is placed in a sintering furnace, using a normal pressure air atmosphere and maintaining an air flow rate of 100 mL / min, and heating is started. It is heated to 600°C at 1°C / min, heated to 950°C at 5°C / min and kept warm for 120 minutes. The second stage is sintering: heated to 1500°C at 5°C / min and kept warm for 2 hours, and cooled to room temperature at 5°C / min to finally obtain alumina whisker toughened zirconia ceramics.

[0101] Figure 2 This is a surface SEM image of the alumina whisker toughened zirconia ceramic prepared in Comparative Example 1;

[0102] from Figure 2 It can be seen that some whiskers are agglomerated and there are a lot of pores in the agglomeration. It can also be seen that the whiskers are significantly coarsened due to long-term high-temperature sintering. The density measured by the Archimedes method is 92.1%, and the fracture toughness measured by the single-edge notched beam method is 9.1MPa·m 1 / 2 .

[0103] Figure 3 The figure is a comparison of XRD patterns of alumina whisker toughened zirconia ceramics prepared in Example 1 and Comparative Example 1;

[0104] from Figure 3 It can be seen that the alumina whisker-toughened zirconia ceramics prepared by the traditional pressureless sintering method contain a small amount of m-phase zirconia, while the samples prepared by ultra-rapid high-temperature sintering reduce the transformation of m-phase to t-phase during the cooling process due to the rapid cooling, which further improves the performance.

[0105] Comparative Example 2: This example differs from Example 1 in that, in step 1 (1), 0 parts of alumina whiskers and 100 parts of partially stabilized zirconia were weighed by weight; 0 parts of alumina whiskers and 100 parts of partially stabilized zirconia were added to water and ultrasonically stirred for 30 minutes to obtain a zirconia powder slurry; the final product was a zirconia ceramic. All other steps and parameters were the same as in Example 1.

[0106] Figure 4 This is a surface SEM image of the zirconia ceramic prepared in Comparative Example 2;

[0107] from Figure 4 It can be seen that the grain size is relatively uniform, the density measured by the Archimedes method is 98.9%, and the fracture toughness measured by the single-edge notched beam method is 11.2 MPa·m 1 / 2 .

[0108] Comparative Example 3: The process of preparing zirconia ceramics using traditional degreasing and sintering processes is completed in the following steps:

[0109] 1. Preparation of slurry:

[0110] ①, weighing 0 parts of alumina whiskers and 100 parts of partially stabilized zirconia by weight; adding 0 parts of alumina whiskers and 100 parts of partially stabilized zirconia to water and stirring ultrasonically for 30 minutes to obtain a zirconia powder slurry;

[0111] The solid content of the zirconium oxide powder slurry described in step 1① is 15 vol.%;

[0112] The partially stabilized zirconia described in step 1① is 3 mol% yttria partially stabilized zirconia.

[0113] D 50 =500nm~700nm;

[0114] ② Place the zirconium oxide powder slurry in an air oven at 70°C and dry for 12 hours to obtain powder;

[0115] ③ Weigh 40 parts by weight of dried partially stabilized zirconia powder and 60 parts of photosensitive resin, stir and mix them at high speed in a planetary deaerator for a period of time to obtain a photocurable ceramic slurry that can be used for printing;

[0116] The photosensitive resin described in step 1 (3) is composed of a monomer mixture, a dispersant, a non-reactive diluent, a thermoplastic resin and a photoinitiator; the mass ratio of the monomer mixture, the dispersant, the non-reactive diluent, the thermoplastic resin and the photoinitiator in the photosensitive resin is 60:20:30:10:1.2;

[0117] The monomer mixture described in step 1 (3) is a mixture of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate, wherein the mass ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate is 30:10:20; the non-reactive diluent is polypropylene glycol 400; the thermoplastic resin is BASF Matrimid 5218 soluble polyimide; the dispersant is BYK-111; the photoinitiator is phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide;

[0118] The stirring speed of the high-speed stirring mixing described in step 1 (3) is 1400 r / min, and the stirring time is 30 min;

[0119] 2. Green printing:

[0120] ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body.

[0121] The slice thickness described in step 2① is 20 μm;

[0122] ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body;

[0123] The wavelength of the ultraviolet light in step 2 is 405nm, and the exposure energy is 12.6mW / cm 2 , exposure time is 3s;

[0124] The resin monomer described in step 2② is 1,6-hexanediol diacrylate, and the number of washings is 2 times;

[0125] 3. Degreasing and sintering:

[0126] ①. Thermally degrease the green body after secondary curing to obtain a crack-free degreased body;

[0127] The thermal degreasing process described in step 3① is as follows: placing the secondary cured body in a degreasing furnace, evacuating it to below 10Pa, and then introducing 99.999% high-purity nitrogen to atmospheric pressure, and maintaining a nitrogen flow rate of 50mL / min, starting heating, heating to 145°C at 1°C / min and keeping warm for 60min, heating to 265°C at 1°C / min and keeping warm for 60min, heating to 320°C at 1°C / min and keeping warm for 60min, heating to 385°C at 1°C / min and keeping warm for 60min, heating to 450°C at 1°C / min and keeping warm for 60min, heating to 485°C at 1°C / min and keeping warm for 60min, heating to 525°C at 1°C / min and keeping warm for 60min, heating to 595°C at 1°C / min and keeping warm for 60min, cooling to room temperature at 1°C / min to obtain a crack-free degreased body;

[0128] ② Sintering the crack-free degreased body to obtain zirconia ceramics;

[0129] The sintering described in step 3② is divided into two stages: the first stage is pre-sintering: the crack-free degreased body is placed in a sintering furnace, using a normal pressure air atmosphere and maintaining an air flow rate of 100 mL / min, and heating is started. It is heated to 600°C at 1°C / min, heated to 950°C at 5°C / min and kept warm for 120 minutes. The second stage is sintering: heated to 1500°C at 5°C / min and kept warm for 2 hours, and cooled to room temperature at 5°C / min to finally obtain zirconia ceramics.

[0130] Figure 5 This is a surface SEM image of the zirconia ceramic prepared in Comparative Example 3;

[0131] from Figure 5 It can be seen that there are many abnormally grown grains.

[0132] Comparative Example 4: This example differs from Example 1 in that the non-reactive diluent is omitted and replaced with a mixed monomer of the same mass. Other steps and parameters are the same as those of Example 1.

[0133] Figure 6 This is a side SEM image of the alumina whisker toughened zirconia degreased blank prepared in Comparative Example 4;

[0134] from Figure 6 It can be seen that due to the lack of non-reactive diluent, more resin pyrolysis gas is discharged under the same debinding process, resulting in the generation of cracks.

[0135] Comparative Example 5: This embodiment differs from the first embodiment in that the thermoplastic polyimide is omitted and a monomer mixture of the same mass is used instead. The other steps and parameters are the same as those of the first embodiment.

[0136] Figure 7 This is a side SEM image of the alumina whisker toughened zirconia ceramic prepared in Comparative Example 5;

[0137] from Figure 7 It can be seen that due to the lack of thermoplastic polyimide, the toughness of the semi-degreased green body is insufficient, and delamination occurs during ultra-rapid high-temperature sintering.

Claims

1. A method for additive manufacturing of high-toughness alumina whisker-toughened zirconia ceramics, characterized in that The method is specifically completed according to the following steps:

1. Preparation of slurry: ① Add alumina whiskers and dispersant to water and stir ultrasonically for a period of time. After dispersion is completed, add part of stabilized zirconium oxide and dispersant and stir ultrasonically for a period of time to obtain a mixed powder slurry; ②Putting the mixed powder slurry into a vacuum freezer for rapid vacuum freezing, and then performing vacuum freeze drying to obtain a mixed powder of alumina whiskers and partially stabilized zirconia; ③ Weigh 40-45 parts by weight of a mixed powder of aluminum oxide whiskers and partially stabilized zirconium oxide and 55-60 parts of photosensitive resin, and stir them at high speed in a planetary degassing mixer for a period of time to obtain a light-cured ceramic slurry that can be used for printing; The photosensitive resin in step 1 (3) is composed of a monomer mixture, a dispersant, a non-reactive diluent, a thermoplastic resin and a photoinitiator; the non-reactive diluent is polypropylene glycol 400; and the thermoplastic resin is a soluble polyimide; 2. Green printing: ① First, create a model using CAD software and convert it into an STL file. Then, import the STL file into a 3D printing device and set the slice thickness. Then, use surface exposure projection to print the photocurable ceramic slurry to obtain a green body. ②, using a resin monomer to clean the green body, air-drying the green body and then performing secondary curing under ultraviolet light to obtain a secondary cured green body; 3. Degreasing and sintering: ①, thermally degreasing the green body after secondary curing to obtain a semi-degreased green body; ②. Transfer the semi-degreased green body to an ultra-fast high-temperature sintering furnace and sinter it at a preset current for a preset time to obtain high-toughness alumina whisker-toughened zirconia ceramics.

2. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The diameter of the aluminum oxide whiskers in step 1① is 300nm~500nm, and the length is 10μm~20μm; the partially stabilized zirconium oxide in step 1① is 3mol% yttria partially stabilized zirconium oxide, D 50 = 500nm ~ 700nm; the mass ratio of the alumina whiskers and the partially stabilized zirconia described in step 1 ① is 5:95; the solid content of the mixed powder slurry described in step 1 ① is 10vol.% ~ 20vol.%.

3. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The dispersant described in step 1① is one or both of polyethylene glycol 400 and polyethylene glycol 1000; the amount of dispersant added each time is 1%~2% of the mass of the powder added that time, and the ultrasonic stirring time is 30min~60min.

4. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The temperature of the vacuum rapid freezing described in step 1② is −55° C. and the time is 20 min to 40 min. The temperature of the vacuum freeze drying is −55° C., the vacuum degree is 1 Pa, and the time is 22 h to 24 h.

5. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The mass ratio of the monomer mixture, dispersant, non-reactive diluent, thermoplastic resin and photoinitiator in the photosensitive resin is 60:(20-26):30:10:(1.2-1.3).

6. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 5, characterized in that The monomer mixture described in step 1③ is a mixture of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate, wherein the mass ratio of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and o-phenylphenoxyethyl acrylate is 30:10:20; the dispersant is one or more of BYK-103, BYK-110, and BYK-111; the photoinitiator is phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide.

7. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The stirring speed of the high-speed stirring mixing described in step 1③ is 1400r / min~2000r / min, and the stirring time is 15min~30min.

8. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The slice thickness in step 2① is 20 μm; the wavelength of the ultraviolet light in step 2② is 405 nm, and the exposure energy is 12.6~24.4 mW / cm 2 , the exposure time is 1~4s; the resin monomer described in step 2② is hydroxyethyl acrylate, hydroxyethyl methacrylate or 1,6-hexanediol diacrylate; the number of cleanings is 1~2 times.

9. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The thermal degreasing process described in step 3① is as follows: the green body after secondary curing is placed in a degreasing furnace, evacuated to below 10Pa, and then 99.999% high-purity nitrogen is introduced to atmospheric pressure, and a nitrogen flow rate of 50mL / min is maintained. Heating is started, heated to 145°C at 1°C / min and kept warm for 60min, heated to 265°C at 1°C / min and kept warm for 60min, heated to 320°C at 1°C / min and kept warm for 60min, and cooled to room temperature at 1°C / min.

10. The additive manufacturing method of high-toughness alumina whisker toughened zirconia ceramics according to claim 1, characterized in that The sintering process described in step 3② is as follows: using carbon felt as a heating body, placing the semi-degreased green body in the carbon felt interlayer in an edge-to-edge contact manner, and starting sintering with argon as a protective atmosphere; the current is 20A~30A, and the holding time is 60s~120s; the high-toughness alumina whisker toughened zirconia ceramic described in step 3② can reach a density of 96.2% and a fracture toughness of 15.3MPa·m 1 / 2 .

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