3D printing zirconia ceramic with low shrinkage rate and preparation process thereof

Abstract

The application discloses a kind of low shrinkage 3D printing zirconia ceramic and its preparation process, select photosensitive polyimide, photosensitive polyimide has imine ring and photosensitive group on high molecular chain, with excellent photosensitivity, thermal stability, low volume shrinkage and other advantages, product system does not need to add photo initiator, can be directly completed curing under ultraviolet irradiation, avoid the volatilization or decomposition of photo initiator in workpiece during debinding, resulting in ceramic shrinkage, cracking and other problems;And optimize the ratio of dispersing agent and plasticizer in product system, reduce the viscosity of slurry, while increasing solid content, reduce shrinkage after sintering, and ensure the flowability of slurry and printing precision.In addition, combined with flash sintering process, inhibit grain growth coarsening, realize nanoscale dense structure, reduce internal defects, the zirconia ceramic prepared by the application is defect-free, dense structure, grain size is smaller, less than 1 μm, and has excellent fracture toughness and higher relative density.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing ceramic materials, and in particular to a 3D printing zirconia ceramic with low shrinkage and a preparation process thereof. Background Art

[0002] Zirconia ceramics are highly valued for their excellent mechanical properties, wear resistance, and biocompatibility, particularly in the medical, dental, and industrial fields. SLA (stereolithography) printing is an advanced additive manufacturing method widely used to create complex, high-precision three-dimensional objects. However, zirconia ceramics face shrinkage issues during the SLA printing process, which significantly impacts the dimensional accuracy and performance of the final product.

[0003] During the SLA printing process, the resin is cured by UV light. However, the cured resin undergoes significant shrinkage during the subsequent sintering process. This shrinkage is primarily due to two factors: first, the resin's volume decreases due to chemical reactions during the curing process; second, during the sintering process, additives such as photoinitiators evaporate or decompose, creating voids that are then filled with zirconium oxide particles, further causing the material to shrink. Controlling this shrinkage process is crucial to ensuring final product quality.

[0004] Patent publication number CN 113754430 B discloses a graded zirconia paste for 3D printing, its preparation method, and its application. By grading zirconia powder to produce a high-solids ceramic paste, structural parts produced from this paste have minimal shrinkage and are less susceptible to defects such as cracking and warping. However, the resin solution contains a photoinitiator, which volatilizes and decomposes during the debinding and sintering process, causing the ceramic to shrink and affecting the workpiece precision. Furthermore, the sintering process utilizes traditional methods, requiring high temperatures (1520-1500°C) and long times (120-150 minutes). This wastes resources and also leads to grain growth, increasing internal stress that is difficult to eliminate, resulting in more defects and cracks. Summary of the Invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a low-shrinkage 3D-printed zirconia ceramic and its preparation process. No photoinitiator and monomer are added to the product formula system, which significantly reduces the volume shrinkage and cracking risk of zirconia ceramics. In addition, the zirconia ceramic has a dense structure and a small grain size of less than 1μm. The fracture toughness and relative density are significantly improved, which significantly improves product performance and production efficiency. It is suitable for high-precision medical devices, industrial wear-resistant parts and other fields.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a low-shrinkage 3D-printed zirconia ceramic, which is obtained by SLA printing of a zirconia ceramic slurry to obtain a blank, and then subjecting the blank to a degreasing treatment and a flash sintering treatment;

[0008] The zirconia ceramic slurry comprises the following raw materials: a light-curable resin mixture and zirconia powder, wherein the mass ratio of the resin mixture to the zirconia powder is 1:(3-5);

[0009] The photocurable resin mixture is formed by mixing a photosensitive resin, a dispersant and a plasticizer in a mass ratio of (85-100): (2-5): 4;

[0010] The photosensitive resin is photosensitive polyimide, and the main chain of the photosensitive polyimide has an imide ring and an o-nitrobenzyl photosensitive group.

[0011] Using the above technical solution:

[0012] The present invention optimizes the product formula and adopts a photoinitiator-free formula. No photoinitiator is required to initiate the reaction in the slurry, and no monomer is required to dilute the oligomer. This can increase the solid content in the slurry and avoid large shrinkage or defects in the sample. The present invention creatively uses photosensitive polyimide, which has both imide rings and photosensitive groups on the polymer chain. When compounded with other components in the product system, it has excellent photosensitivity, thermal stability, and low volume shrinkage. No photoinitiator is required in the product system, and curing can be completed directly under ultraviolet irradiation. This avoids the volatilization or decomposition of the photoinitiator in the workpiece during degreasing, which can cause problems such as shrinkage and cracking of the ceramic and affect the precision of the workpiece. The ratio of dispersant to plasticizer in the product system is optimized to reduce the slurry viscosity (≤5.7 Pa·s), while increasing the solid content, reducing the shrinkage after sintering, and ensuring the slurry fluidity and printing accuracy. Furthermore, by combining it with a flash sintering process, the coarsening of grain growth is suppressed, achieving a nanoscale dense structure and reducing internal defects.

[0013] Furthermore, the photosensitive polyimide has a weight average molecular weight of 3,000 to 40,000 and a viscosity of 800 to 1,000 mPa.s.

[0014] Furthermore, the zirconia ceramic slurry is ground to a viscosity of ≤5.7 Pa.s.

[0015] Specifically, zirconium oxide powder, light-curable resin mixture and 5 mm grinding balls were added into an alumina ball mill at a mass ratio of (3-5):1:(14-16), and ball milled at a speed of 500 r / min until the shear rate reached 30 s -1 The slurry viscosity is ≤5.7Pa.S.

[0016] Due to the high solid content of the product system in this invention, the system viscosity is easily high. Excessive viscosity affects the slurry printing and leveling process, resulting in low sample printing accuracy. In this invention, by pre-ball milling the slurry, the slurry viscosity is controlled to ≤5.7Pa.s, resulting in high printing accuracy and good curing effect.

[0017] Furthermore, the dispersant is KOS110, ammonium polymethacrylate, BYK-103, BYK-111 or Solsperse™ AC7130.

[0018] The dispersant used in the present invention has an amphiphilic structure, which has a high affinity with ceramic particles and dispersion medium, can reduce the viscosity of the resin solution and improve the stability of the solution. The hydrophilic anchor group of the dispersant interacts with the hydrophilic surface of the ceramic particle surface. It avoids aggregation by adsorbing on the surface of the ceramic particles to generate repulsive force, while the hydrophobic chain extends toward the dispersion medium, forming a spatial barrier to stabilize the particles, making the spatial position of the ceramic powder in the dispersion medium more stable.

[0019] Furthermore, the plasticizer is polyethylene glycol (PEG), polypropylene glycol (PPG), diethyl phthalate (DEHP) or polyvinyl alcohol (PVA).

[0020] The plasticizer used in the present invention reduces the viscosity of the photocurable resin solution by embedding in the polymer to reduce the van der Waals force and friction between molecules, thereby reducing the viscosity of the resin solution; secondly, it can lower the glass transition temperature of the cured product, obtaining a green body with better flexibility; in addition, the plasticizer can also reduce the internal stress of the printed body, which helps to avoid the occurrence of defects such as cracks.

[0021] Furthermore, the specific parameters of the degreasing process are as follows: the degreasing process is divided into four stages, the first stage is heated to 110-130°C, and the holding time is 120-140min; the second stage is heated to 210-230°C, and the holding time is 120-140min; the third stage is heated to 390-410°C, and the holding time is 120-140min; the fourth stage is heated to 580-600°C, and the holding time is 120-140min; the heating rate below 400°C in the degreasing process is 0.15-0.25°C / min, and above 400°C is 0.08-0.12°C / min; the cooling rate is 1.1-1.3°C / min.

[0022] Furthermore, the specific parameters of the flash sintering process are as follows: the degreased sample is placed in a flash furnace, argon is introduced, the flash furnace is heated to 700-800°C, kept warm for 8-12 minutes, and then the flash furnace process is adjusted to an electric field strength of 240-260 V / cm and a current density of 28-32 mA / mm 2, hold for 12 to 18 seconds, with a cooling rate of 2 to 4°C / min, and the final sample is obtained after sintering.

[0023] Furthermore, the grain size of the 3D printed zirconia ceramic is less than 1 μm.

[0024] A second aspect of the present invention provides a process for preparing the above-mentioned low shrinkage 3D printed zirconia ceramic, comprising the following steps:

[0025] S1. Preparation of light-curable resin mixture:

[0026] Adding a photosensitive resin, a dispersant and a plasticizer in a specific formula into a container in sequence, stirring and mixing them evenly to prepare a light-curing resin mixture;

[0027] S2. Preparation of zirconia ceramic slurry:

[0028] The light-curable resin mixture and the zirconium oxide powder are ball-milled and dispersed to obtain a zirconium oxide ceramic slurry with a viscosity of ≤5.7 Pa.s;

[0029] S3, SLA printing blank:

[0030] Zirconia ceramic slurry was used for SLA printing to obtain the embryonic body;

[0031] S4, body degreasing treatment:

[0032] The embryo was degreased to obtain a degreased sample. The degreasing atmosphere was argon. The degreasing process was divided into four stages: the first stage was heating to 110-130°C and holding time was 120-140 min; the second stage was heating to 210-230°C and holding time was 120-140 min; the third stage was heating to 390-410°C and holding time was 120-140 min; the fourth stage was heating to 580-600°C and holding time was 120-140 min; the heating rate below 400°C in the degreasing process was 0.15-0.25°C / min, and above 400°C it was 0.08-0.12°C / min; the cooling rate was 1.1-1.3°C / min;

[0033] S5. Sintering treatment:

[0034] Place the degreased sample into the flash furnace, introduce argon, heat the flash furnace to 700-800℃, keep warm for 8-12 minutes, and then adjust the flash furnace process to an electric field strength of 240-260V / cm and a current density of 28-32mA / mm 2 , hold for 12 to 18 seconds, with a cooling rate of 2 to 4°C / min, and the final sample is obtained after sintering.

[0035] Furthermore, the zirconium oxide powder is 3YSZ, with a particle size of 100 to 500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention optimizes the product formula and adopts a photoinitiator-free formula. No photoinitiator is required to initiate the reaction in the slurry, and no monomer is required to dilute the oligomer. This can increase the solid content in the slurry and avoid large shrinkage or defects in the sample. The present invention creatively uses photosensitive polyimide. Photosensitive polyimide has both imide rings and photosensitive groups on the polymer chain. When compounded with other components in the product system, it has the advantages of excellent photosensitivity, thermal stability, and low volume shrinkage. No photoinitiator is required in the product system, and curing can be completed directly under ultraviolet irradiation. This avoids the volatilization or decomposition of the photoinitiator in the workpiece during degreasing, which causes shrinkage and cracking of the ceramic, affecting the precision of the workpiece. The ratio of dispersant to plasticizer in the product system is optimized to reduce the slurry viscosity (≤5.7 Pa·s), while increasing the solid content, reducing the shrinkage after sintering, and ensuring the slurry fluidity and printing accuracy. In addition, by combining the flash sintering process, the coarsening of grain growth is suppressed, a nano-scale dense structure is achieved, and internal defects are reduced. The zirconia ceramics prepared by the present invention are defect-free, have a dense structure, a small grain size of less than 1 μm, and have excellent fracture toughness and a high relative density. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Figure 1 This is a scanning electron microscope image of the zirconia ceramic sample prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Example 1

[0042] The preparation process of 3D printed zirconia ceramics with low shrinkage includes the following steps:

[0043] S1. Preparation of light-curable resin mixture:

[0044] A photosensitive resin, a dispersant and a plasticizer were sequentially added into a container in a mass ratio of 93:3:4, and the mixture was stirred and mixed uniformly to prepare a light-curing resin mixture.

[0045] The photosensitive resin is a photosensitive polyimide having an imide ring and an o-nitrobenzyl photosensitive group on its main chain, a weight average molecular weight of 3,000 to 40,000, and a viscosity of 800 to 1,000 mPa.s.

[0046] The dispersant is KOS110 and the plasticizer is polyvinyl alcohol (PVA).

[0047] S2. Preparation of zirconia ceramic slurry:

[0048] Zirconia powder, light-curable resin mixture and 5 mm grinding balls with a mass ratio of 4:1:15 were added to an alumina ball mill and ball milled at a speed of 500 r / min until the shear rate was 30 s -1 The slurry viscosity is 5.7 Pa.S.

[0049] The zirconium oxide powder is 3YSZ, with a particle size of 100-500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

[0050] S3, SLA printing blank:

[0051] The ceramic light-curing printer is an SLA ceramic printer, and the green body is prepared under the printing parameters of a light source wavelength of 355 nm, a laser power of 210 mW, a scanning speed of 6000 mm / s, and a printing layer thickness of 80 μm.

[0052] S4, body degreasing treatment:

[0053] The embryo was degreased to obtain a degreased sample. The degreasing atmosphere was argon. The degreasing process was divided into four stages: the first stage was heated to 120°C and kept warm for 130 minutes; the second stage was heated to 220°C and kept warm for 130 minutes; the third stage was heated to 400°C and kept warm for 130 minutes; the fourth stage was heated to 590°C and kept warm for 130 minutes; the heating rate below 400°C in the degreasing process was 0.2°C / min, and above 400°C it was 0.1°C / min; the cooling rate was 1.2°C / min.

[0054] S5. Sintering treatment:

[0055] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept at this temperature for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 250 V / cm and a current density of 30 mA / mm 2, hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0056] Figure 1 This is a scanning electron microscope image of the zirconia ceramic sample prepared in Example 1. It can be seen that the grain size of the zirconia ceramic prepared in Example 1 is relatively small, less than 1 μm.

[0057] Example 2

[0058] The preparation process of 3D printed zirconia ceramics with low shrinkage includes the following steps:

[0059] S1. Preparation of light-curable resin mixture:

[0060] A photosensitive resin, a dispersant and a plasticizer in a mass ratio of 90:3:4 were sequentially added into a container, and the mixture was stirred and mixed uniformly to prepare a light-curing resin mixture.

[0061] The photosensitive resin is a photosensitive polyimide having an imide ring and an o-nitrobenzyl photosensitive group on its main chain, a weight average molecular weight of 3,000 to 40,000, and a viscosity of 800 to 1,000 mPa.s.

[0062] The dispersant is KOS110 and the plasticizer is polyvinyl alcohol (PVA).

[0063] S2. Preparation of zirconia ceramic slurry:

[0064] Zirconia powder, light-curing resin mixture and 5 mm grinding balls with a mass ratio of 3:1:14 were added to an alumina ball mill and ball milled at a speed of 500 r / min until the shear rate was 30 s -1 The slurry viscosity is 5.7 Pa.S.

[0065] The zirconium oxide powder is 3YSZ, with a particle size of 100-500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

[0066] S3, SLA printing blank:

[0067] The ceramic light-curing printer is an SLA ceramic printer, and the green body is prepared under the printing parameters of a light source wavelength of 355 nm, a laser power of 210 mW, a scanning speed of 6000 mm / s, and a printing layer thickness of 80 μm.

[0068] S4, body degreasing treatment:

[0069] The embryo was degreased to obtain a degreased sample. The degreasing atmosphere was argon. The degreasing process was divided into four stages: the first stage was heated to 110°C and the holding time was 140 minutes; the second stage was heated to 210°C and the holding time was 140 minutes; the third stage was heated to 390°C and the holding time was 140 minutes; the fourth stage was heated to 580°C and the holding time was 140 minutes; the heating rate below 400°C in the degreasing process was 0.15°C / min, and above 400°C it was 0.08°C / min; the cooling rate was 1.1°C / min.

[0070] S5. Sintering treatment:

[0071] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept at this temperature for 10 minutes. The flash furnace process was then adjusted to an electric field strength of 240 V / cm and a current density of 30 mA / mm. 2 , hold for 12s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0072] Example 3

[0073] The preparation process of 3D printed zirconia ceramics with low shrinkage includes the following steps:

[0074] S1. Preparation of light-curable resin mixture:

[0075] Add photosensitive resin, dispersant and plasticizer in a mass ratio of 85:2:4 into a container in sequence, stir and mix evenly to prepare a light-curing resin mixture.

[0076] The photosensitive resin is a photosensitive polyimide having an imide ring and an o-nitrobenzyl photosensitive group on its main chain, a weight average molecular weight of 3,000 to 40,000, and a viscosity of 800 to 1,000 mPa.s.

[0077] The dispersant is KOS110 and the plasticizer is polyvinyl alcohol (PVA).

[0078] S2. Preparation of zirconia ceramic slurry:

[0079] Zirconia powder, light-curing resin mixture and 5 mm grinding balls with a mass ratio of 5:1:16 were added to an alumina ball mill and ball milled at a speed of 500 r / min until the shear rate was 30 s -1 The slurry viscosity is 5.7 Pa.S.

[0080] The zirconium oxide powder is 3YSZ, with a particle size of 100-500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

[0081] S3, SLA printing blank:

[0082] The ceramic light-curing printer is an SLA ceramic printer, and the green body is prepared under the printing parameters of a light source wavelength of 355 nm, a laser power of 210 mW, a scanning speed of 6000 mm / s, and a printing layer thickness of 80 μm.

[0083] S4, body degreasing treatment:

[0084] The embryo was degreased to obtain a degreased sample. The degreasing atmosphere was argon. The degreasing process was divided into four stages: the first stage was heated to 130°C and kept warm for 120 minutes; the second stage was heated to 230°C and kept warm for 120 minutes; the third stage was heated to 410°C and kept warm for 120 minutes; the fourth stage was heated to 600°C and kept warm for 120 minutes; the heating rate below 400°C in the degreasing process was 0.25°C / min, and above 400°C it was 0.12°C / min; the cooling rate was 1.3°C / min.

[0085] S5. Sintering treatment:

[0086] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 700°C and kept at this temperature for 12 minutes. The flash furnace process was then adjusted to an electric field strength of 240 V / cm and a current density of 28 mA / mm. 2 , hold for 18s, cool at a rate of 2℃ / min, and sinter to obtain the final sample.

[0087] Example 4

[0088] The preparation process of 3D printed zirconia ceramics with low shrinkage includes the following steps:

[0089] S1. Preparation of light-curable resin mixture:

[0090] A photosensitive resin, a dispersant and a plasticizer in a mass ratio of 100:5:4 were sequentially added into a container, and the mixture was stirred and mixed uniformly to prepare a light-curing resin mixture.

[0091] The photosensitive resin is a photosensitive polyimide having an imide ring and an o-nitrobenzyl photosensitive group on its main chain, a weight average molecular weight of 3,000 to 40,000, and a viscosity of 800 to 1,000 mPa.s.

[0092] The dispersant is KOS110 and the plasticizer is polyvinyl alcohol (PVA).

[0093] S2. Preparation of zirconia ceramic slurry:

[0094] Zirconia powder, light-curing resin mixture and 5 mm grinding balls with a mass ratio of 4:1:16 were added to an alumina ball mill and ball milled at a speed of 500 r / min until the shear rate was 30s. -1 The slurry viscosity is 5.7 Pa.S.

[0095] The zirconium oxide powder is 3YSZ, with a particle size of 100-500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

[0096] S3, SLA printing blank:

[0097] The ceramic light-curing printer is an SLA ceramic printer, and the green body is prepared under the printing parameters of a light source wavelength of 355 nm, a laser power of 210 mW, a scanning speed of 6000 mm / s, and a printing layer thickness of 80 μm.

[0098] S4, body degreasing treatment:

[0099] The embryo was degreased to obtain a degreased sample. The degreasing atmosphere was argon. The degreasing process was divided into four stages: the first stage was heated to 120°C and kept warm for 130 minutes; the second stage was heated to 220°C and kept warm for 130 minutes; the third stage was heated to 400°C and kept warm for 130 minutes; the fourth stage was heated to 590°C and kept warm for 130 minutes; the heating rate below 400°C in the degreasing process was 0.15°C / min, and above 400°C it was 0.08°C / min; the cooling rate was 1.2°C / min.

[0100] S5. Sintering treatment:

[0101] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 800°C and kept at this temperature for 8 minutes. Then the flash furnace process was adjusted to an electric field strength of 260 V / cm and a current density of 32 mA / mm 2 , hold for 12s, cool at a rate of 4℃ / min, and sinter to obtain the final sample.

[0102] Comparative Example 1

[0103] Comparative Example 1 is a comparative test example of Example 1. The difference between Comparative Example 1 and Example 1 is that:

[0104] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 80:3:4.

[0105] Comparative Example 2

[0106] Comparative Example 2 is a comparative test example of Example 1. The difference between Comparative Example 2 and Example 1 is that:

[0107] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 105:3:4.

[0108] Comparative Example 3

[0109] Comparative Example 3 is a comparative test example of Example 1. The difference between Comparative Example 3 and Example 1 is that:

[0110] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 93:1:4.

[0111] Comparative Example 4

[0112] Comparative Example 4 is a comparative test example of Example 1. The difference between Comparative Example 4 and Example 1 is that:

[0113] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 93:6:4.

[0114] Comparative Example 5

[0115] Comparative Example 5 is a comparative test example of Example 1. The difference between Comparative Example 5 and Example 1 is that:

[0116] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 93:6:3.

[0117] Comparative Example 6

[0118] Comparative Example 6 is a comparative test example of Example 1. The difference between Comparative Example 6 and Example 1 is that:

[0119] In this comparative example, the mass ratio of the photosensitive resin, the dispersant, and the plasticizer is 93:6:5.

[0120] Comparative Example 7

[0121] Comparative Example 7 is a comparative test example of Example 1. The difference between Comparative Example 7 and Example 1 is that:

[0122] The specific parameters of the degreasing process are the conventional processing process:

[0123] In the first stage, the temperature was increased from 25°C to 250°C at a rate of 1°C / min and the temperature was kept for 4 hours. In the second stage, the temperature was increased from 250°C to 550°C at a rate of 0.5°C / min and the temperature was kept for 2 hours. In the third stage, the temperature was increased from 550°C to 800°C at a rate of 2°C / min and the temperature was kept for 0.5 hours. In the fourth stage, the temperature was increased from 800°C to 1000°C at a rate of 4°C / min and the temperature was kept for 2 hours. Finally, the temperature was freely cooled to room temperature.

[0124] Comparative Example 8

[0125] Comparative Example 8 is a comparative test example of Example 1. The difference between Comparative Example 8 and Example 1 is that:

[0126] The specific parameters of the flash sintering process are:

[0127] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 650°C and kept warm for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 250 V / cm and a current density of 30 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0128] Comparative Example 9

[0129] Comparative Example 9 is a comparative test example of Example 1. The difference between Comparative Example 9 and Example 1 is that:

[0130] The specific parameters of the flash sintering process are:

[0131] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 850°C and kept warm for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 250 V / cm and a current density of 30 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0132] Comparative Example 10

[0133] Comparative Example 10 is a comparative test example of Example 1. The difference between Comparative Example 10 and Example 1 is that:

[0134] The specific parameters of the degreasing process are the conventional processing process:

[0135] The specific parameters of the flash sintering process are:

[0136] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept warm for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 200 V / cm and a current density of 30 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0137] Comparative Example 11

[0138] Comparative Example 11 is a comparative test example of Example 1. The difference between Comparative Example 11 and Example 1 is that:

[0139] The specific parameters of the degreasing process are the conventional processing process:

[0140] The specific parameters of the flash sintering process are:

[0141] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept warm for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 300 V / cm and a current density of 30 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0142] Comparative Example 12

[0143] Comparative Example 12 is a comparative test example of Example 1. The difference between Comparative Example 12 and Example 1 is that:

[0144] The specific parameters of the degreasing process are the conventional processing process:

[0145] The specific parameters of the flash sintering process are:

[0146] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept at this temperature for 10 minutes. The flash furnace process was then adjusted to an electric field strength of 250 V / cm and a current density of 20 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0147] Comparative Example 13

[0148] Comparative Example 13 is a comparative test example of Example 1. The difference between Comparative Example 13 and Example 1 is that:

[0149] The specific parameters of the degreasing process are the conventional processing process:

[0150] The specific parameters of the flash sintering process are:

[0151] The degreased sample was placed in a flash furnace, argon was introduced, and the flash furnace temperature was raised to 750°C and kept at this temperature for 10 minutes. Then the flash furnace process was adjusted to an electric field strength of 250 V / cm and a current density of 40 mA / mm 2 , hold for 15s, cool at a rate of 3℃ / min, and sinter to obtain the final sample.

[0152] The final zirconia ceramic samples prepared in Examples 1-4 and Comparative Examples 1-13 were subjected to performance tests. The performance test indicators included grain size, fracture toughness and relative density of the zirconia ceramic samples.

[0153] The grain size was obtained by scanning electron microscopy, and the fracture toughness and relative density of the zirconia ceramic samples were obtained by indentation and Archimedes methods, respectively.

[0154] The test results are shown in Table 1.

[0155] Table 1

[0156]

[0157] From the test results in Table 1, we can see that:

[0158] The photosensitive resin content in the product system of Comparative Example 1 was lower than the preferred range of photosensitive resin usage in the present invention, resulting in a slow curing speed, a low photocuring depth, low z-axis bonding strength, and easy cracking between layers. The photosensitive resin content in the product system of Comparative Example 2 was higher than the preferred range of photosensitive resin usage in the present invention, resulting in a faster curing speed, a larger curing width, and lower curing precision. Simultaneously, the slurry solids content was reduced, the printed body had a large volume shrinkage rate, and a low relative density.

[0159] In Comparative Example 3, the dispersant content was lower than the preferred dosage range of the present invention. The zirconium oxide powder was unevenly dispersed and easily agglomerated, resulting in a high slurry viscosity, which affected the printing process and resulted in low printing precision. In Comparative Example 4, the dispersant content was higher than the preferred dosage range of the present invention. The excess dispersant molecular chains could not be adsorbed on the particle surface and were easily entangled in the solution, resulting in excessive slurry viscosity, affecting the printing process and resulting in low printing precision.

[0160] In Comparative Example 5, the plasticizer content was below the preferred range of the present invention, resulting in an excessively high resin crosslink density, strong rigidity, and brittle samples. Furthermore, the photosensitive resin volatilized rapidly during degreasing, causing the samples to crack easily. In Comparative Example 6, the plasticizer content was above the preferred range of the present invention, reducing the crosslink density of the photosensitive resin, making the samples brittle and having low fracture toughness.

[0161] In Comparative Example 7, conventional degreasing treatment was adopted, and the heating rate was slow, resulting in abnormal grain growth.

[0162] In Comparative Example 8, the sintering temperature was too low, and the zirconia sintering process was incomplete, resulting in ineffective grain growth. The grains generally remained small, resulting in a large number of pores within the material, affecting its relative density. Because the grains were not fully bonded, the material's fracture toughness was low.

[0163] In Comparative Example 9, the sintering temperature is too high, resulting in excessive grain growth and the formation of larger grains. It also triggers phase change or sintering defects, which will affect the uniformity and performance of the material, increase the brittleness of the material, and reduce its fracture toughness.

[0164] During the flash firing process in Comparative Example 10, the electric field intensity was too low, the sintering process became slow, the density of the sample was low, and voids were generated.

[0165] During the flash firing process in Comparative Example 11, the electric field intensity was too high, resulting in excessive sintering of the zirconium oxide in a short period of time, causing grain growth and reducing the uniformity and fracture toughness of the material.

[0166] During the flash firing process in Comparative Example 12, the current density was too low, the density of the ceramic was insufficient, and the porosity was increased, resulting in a decrease in the fracture toughness and relative density of the material.

[0167] During the flash firing process in Comparative Example 13, the current density was too high, resulting in excessive sintering of the material in a short period of time, causing grain growth, and reducing the uniformity and fracture toughness of the material.

[0168] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A low shrinkage 3D printed zirconia ceramic, characterized in that: The embryo is obtained by SLA printing of zirconia ceramic slurry, and then the embryo is degreased and flash sintered. The zirconia ceramic slurry is composed of the following raw materials: a light-curable resin mixture and zirconia powder, wherein the mass ratio of the resin mixture to the zirconia powder is 1:(3-5); The photocurable resin mixture is formed by mixing a photosensitive resin, a dispersant and a plasticizer in a mass ratio of (85-100): (2-5): 4; The photosensitive resin is a photosensitive polyimide, and the main chain of the photosensitive polyimide has an imide ring and an o-nitrobenzyl photosensitive group; The specific parameters of the degreasing process are as follows: the degreasing process is divided into four stages: the first stage is heating to 110-130°C, and the holding time is 120-140 minutes; the second stage is heating to 210-230°C, and the holding time is 120-140 minutes; the third stage is heating to 390-410°C, and the holding time is 120-140 minutes; the fourth stage is heating to 580-600°C, and the holding time is 120-140 minutes; the heating rate below 400°C in the degreasing process is 0.15-0.25°C / min, and above 400°C is 0.08-0.12°C / min; the cooling rate is 1.1-1.3°C / min; The flash sintering process parameters are as follows: put the degreased sample into the flash furnace, introduce argon gas, heat the flash furnace to 700-800℃, keep warm for 8-12 minutes, and then adjust the flash furnace process to an electric field strength of 240-260V / cm and a current density of 28-32mA / mm 2 , hold for 12 to 18 seconds, with a cooling rate of 2 to 4°C / min, and the final sample is obtained after sintering.

2. The low shrinkage 3D printed zirconia ceramic according to claim 1, characterized in that: The weight average molecular weight of the photosensitive polyimide is 3000-40000, and the viscosity is 800-1000 mPa.s.

3. The low shrinkage 3D printed zirconia ceramic according to claim 2, characterized in that: The zirconia ceramic slurry is ground to a viscosity of ≤5.7 Pa.s.

4. The low shrinkage 3D printed zirconia ceramic according to claim 2 or 3, characterized in that: The dispersant is KOS110, ammonium polymethacrylate, BYK-103 or BYK-111.

5. The low shrinkage 3D printed zirconia ceramic according to claim 1, characterized in that: The plasticizer is polyethylene glycol, polypropylene glycol, diethyl phthalate or polyvinyl alcohol.

6. The low shrinkage 3D printed zirconia ceramic according to claim 1, characterized in that: The grain size of the 3D printed zirconia ceramic is less than 1 μm.

7. A process for preparing a low-shrinkage 3D-printed zirconia ceramic according to any one of claims 1 to 6, characterized in that: The steps include: S1. Preparation of light-curable resin mixture: Adding a photosensitive resin, a dispersant and a plasticizer in a specific formula into a container in sequence, stirring and mixing them evenly to prepare a light-curing resin mixture; S2. Preparation of zirconia ceramic slurry: The light-curable resin mixture and the zirconium oxide powder are ball-milled and dispersed to obtain a zirconium oxide ceramic slurry with a viscosity of ≤5.7 Pa.s; S3, SLA printing blank: Zirconia ceramic slurry was used for SLA printing to obtain the embryonic body; S4, body degreasing treatment: The embryo body is subjected to a degreasing treatment, and the degreasing process is divided into four stages. The first stage is to heat up to 110-130°C and keep warm for 120-140 minutes; the second stage is to heat up to 210-230°C and keep warm for 120-140 minutes; the third stage is to heat up to 390-410°C and keep warm for 120-140 minutes; the fourth stage is to heat up to 580-600°C and keep warm for 120-140 minutes; the heating rate below 400°C during the degreasing process is 0.15-0.25°C / min, and above 400°C it is 0.08-0.12°C / min; the cooling rate is 1.1-1.3°C / min; S5. Sintering treatment: Place the degreased sample into the flash furnace, introduce argon, heat the flash furnace to 700-800℃, keep warm for 8-12 minutes, and then adjust the flash furnace process to an electric field strength of 240-260V / cm and a current density of 28-32mA / mm 2 , hold for 12 to 18 seconds, with a cooling rate of 2 to 4°C / min, and the final sample is obtained after sintering.

8. The preparation process of 3D printed zirconia ceramics with low shrinkage according to claim 7, characterized in that: The zirconium oxide powder is 3YSZ, with a particle size of 100-500 nm, a D50 of 340 nm, and a specific surface area of ​​6.3 m 2 / g.

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