Al2O3 ceramic preparation and 3D printing method based on SiC whisker toughening

Abstract

The invention relates to a preparation method of toughened Al2O3 ceramic, in particular to a preparation method and a 3D printing method of Al2O3 ceramic based on SiC whisker toughening, and aims to solve the technical problem of agglomeration of SiC whiskers and Al2O3 particles in photosensitive slurry of existing toughened Al2O3 ceramic. The preparation method of the photosensitive resin comprises the following steps: uniformly mixing 1, 6-hexanediol diacrylate, trimethylolpropane triacrylate, a dispersing agent and a low-boiling-point solvent to obtain a resin mixed solution; the preparation method of the Al2O3 ceramic comprises the following steps: mixing a resin mixed solution, a photoinitiator, the modified Al2O3 particles and the modified SiC whiskers, stirring and dissolving to obtain photosensitive slurry; and after 3D printing is conducted through the photosensitive slurry, ceramization is conducted in a tubular furnace, and the ceramic part is obtained. And the finished product rate reaches 90-100%, the cost is low, and the method can be used in the field of Al2O3 ceramics.

Description

Technical Field

[0001] A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramics belongs to the technical field of 3D printing materials. Background Art

[0002] The high mechanical strength, good thermal stability and chemical stability of ceramic materials, as well as their excellent properties in optoelectronics, biology and other aspects, make them widely used in many fields such as metal cutting, aerospace, chemical industry and biomedicine. However, there are certain limitations in the processing cost and efficiency of conventional ceramic manufacturing technologies, and it is difficult for conventional processes to meet the forming preparation of high-precision complex structures. Compared with traditional forming processes, the obvious advantage of using additive manufacturing 3D printing technology to manufacture ceramic materials is that: since there is no need to use high-cost special molds, etc., additive manufacturing technology is more economical in small-batch production or individual customized ceramic parts. In addition, additive manufacturing technology has a higher degree of freedom in structure forming and is more suitable for the production and preparation of complex structure ceramic parts. Therefore, for the direct forming of small-batch complex ceramic parts, ceramic additive technology will have more advantages. Currently, 3D printing technologies applied to ceramic materials include direct writing forming technology (DIW), stereolithography technology (DLP / SLA), fused deposition modeling technology (FDM), selective laser sintering technology (SLS). Among them, compared with DIW, FDM, and SLS processes, the DLP process of stereolithography technology can manufacture dense ceramic parts with higher geometric complexity and excellent surface finish, and the stereolithography process uses cold processing to form, and after forming, it is made into a ceramic entity by heat treatment processes such as debinding and sintering, which can effectively avoid the internal thermal stress of the green body during the forming stage, so as to obtain low-defect ceramic parts.

[0003] At present, the method of toughening Al2O3 ceramics with SiC whiskers and performing stereolithography 3D printing will cause agglomeration of whiskers and ceramic powders in the stereolithography resin, affecting the mechanical properties of the sintered ceramics. Summary of the Invention

[0004] The present invention aims to solve the problem of agglomeration of SiC whiskers and Al2O3 ceramic powders in the stereolithography resin when toughening Al2O3 ceramics with existing SiC whiskers, and provides a new method for mixing SiC whiskers and Al2O3 ceramic powder in the stereolithography resin, a preparation method of photosensitive resin and a 3D printing method. The photosensitive resin for 3D printing toughened Al2O3 ceramics of the present invention has a simple preparation method and low cost, and the 3D printed Al2O3 ceramics are dense and have a high yield.

[0005] The preparation and 3D printing method of SiC whisker toughened Al2O3 ceramics of the present invention is carried out according to the following steps:

[0006] 1. Weigh 10 - 30 parts by weight of 1,6 - hexanediol diacrylate, 30 - 80 parts of trimethylolpropane triacrylate, 40 - 60 parts of solvent, and 1 - 10 parts of dispersant into a beaker and mix them evenly. Heat the mixture to 60 - 75 °C under the condition of a stirring speed of 400 - 600 r / min and keep it for 10 - 20 min to obtain a photocurable resin solution.

[0007] 2. After mechanically ball - milling and mixing the pretreated SiC whiskers and the surface - treated Al2O3 ceramic powder evenly, add them to the prepared photocurable resin and ball - mill for 12 h to obtain a toughened Al2O3 ceramic slurry for 3D printing.

[0008] 3. Weigh 100 parts by weight of the Al2O3 ceramic slurry, 1 - 4 parts of photoinitiator, and 0 - 0.01 part of inhibitor and stir until the powder is completely dissolved to obtain a photosensitive resin.

[0009] 4. Pour the photosensitive resin into the material tank of a 3D printer, ensure that the bottom layer of the material tank can be completely covered with a layer of resin after being scraped by a doctor blade, adjust the light exposure time to 1 - 10 s, the exposure intensity is 5 - 100 mw / cm 2 , the layer thickness of printing is 20 - 150 μm, and complete 3D printing layer by layer to obtain a green body.

[0010] 5. Rinse the green body with anhydrous ethanol to remove the uncured resin in the green body; then place the green body in the air at a temperature of 25 - 80 °C for 1 - 24 h to volatilize the remaining small molecules in the green body; then put the green body into a tubular furnace, and under an argon or nitrogen atmosphere, heat it to 1100 - 1700 °C at a heating rate of 0.5 - 5 °C / min and keep it for 0.5 - 2 h for ceramization, and cool it naturally to obtain an Al2O3 ceramic component.

[0011] Furthermore, in step 1, the solvent is a low - boiling - point solvent acetone. In the present invention, the low - boiling - point solvent acetone plays a key role in preventing whisker agglomeration. The polar acetone solvent eliminates the static charge on the surface of SiC whiskers and weakens the interaction between SiC whiskers.

[0012] Furthermore, the dispersants in step 1 are wetting dispersants BYK111 and BYK180.

[0013] Furthermore, the 1,6 - hexanediol diacrylate in step 1 is a bifunctional monomer. The curing speed of the bifunctional monomer is faster than that of the monofunctional monomer, and it is more likely to undergo cross - linking curing reaction, which can improve the mechanical properties of the formed resin; the trimethylolpropane triacrylate is a trifunctional monomer, and the trifunctional acrylate - based reactive diluent is more for improving the curing speed of the resin.

[0014] Further, in Step 1, 15-25 parts by weight of 1,6-hexanediol diacrylate, 40-60 parts by weight of trimethylolpropane triacrylate, 50-60 parts by weight of solvent, and 5-10 parts by weight of dispersant are weighed. Under these conditions, the toughened Al2O3 ceramic slurry synthesized exhibits better 3D printing forming stability and product yield, and the product yield reaches 100%.

[0015] Further, the pretreatment method of SiC whiskers in Step 2 is as follows: A 2.5 wt% dilute solution is prepared by mixing PEG-400 surfactant in ethanol, and then the SiCw whiskers are dispersed in the PEG-400 dilute solution, followed by ultrasonic vibration for 2 h and then drying.

[0016] Further, the surface treatment method of Al2O3 ceramic powder in Step 2 is as follows: 5 wt% of silane coupling agent KH550 of the Al2O3 powder is added to a 95 wt% ethanol solution prepared from deionized water and absolute ethanol, and ultrasonic dispersion is carried out for 10 min. The Al2O3 powder is slowly added, and magnetic stirring is carried out at a temperature of 70 °C for 1 h. Then, the obtained suspension is filtered by suction, washed 3 times with absolute ethanol, and the obtained powder is dried at 60 °C for 12 h.

[0017] Further, the amount of SiC whiskers added in Step 2 is 5 wt%, and the amount of Al2O3 ceramic powder is 50 wt%.

[0018] Further, during the 12-hour ball milling in Step 2, the low-boiling solvent acetone is volatilized completely, and a ceramic slurry with a solid content of 50% is obtained.

[0019] Further, the photoinitiator described in Step 3 is photoinitiator 819 or photoinitiator TPO. The photoinitiator is responsible for generating free radicals by breaking under ultraviolet irradiation to initiate free radical polymerization reactions.

[0020] Further, the inhibitor described in Step 3 is hydroquinone. The inhibitor is responsible for absorbing the free radicals that are not annihilated in time, preventing unwanted curing, and improving the forming accuracy.

[0021] The present invention improves the performance of the toughened Al2O3 ceramic for 3D printing from the following aspects.

[0022] (1) In the present invention, β-SiC whiskers with a diameter of 0.1-0.6 microns and a length of 10-50 microns are selected. The PEG-400 surfactant used in treating the SiC whiskers contains hydrophilic polyoxyethylene (-CH2CH2O-), which significantly reduces the surface tension of the solvent and is beneficial to the wetting of the solid surface. Moreover, the hydrophilic oxygen atoms in the PEG-400 molecular chain can also generate a strong van der Waals affinity for the hydroxyl groups (-OH) adsorbed on the surface of SiCw, forming a layer with a certain thickness on the whisker surface to prevent whisker agglomeration.

[0023] (2) For the Al2O3 ceramic powder, the method of first modifying and then adding is adopted. First, it is modified with the silane coupling agent KH550, and then the modified Al2O3 ceramic powder and the dispersant BYK111 are added into the photocurable resin together.

[0024] (3) The molecular weight of the Al2O3 ceramic slurry of the present invention is controllable, the viscosity is adjustable, and the synthesis process is simple. The prepared photosensitive resin is liquid and has high photosensitive activity, and can be directly applied to photocurable 3D printing without any auxiliary solvent; according to specific needs, the ceramic yield, viscosity, molecular weight, flexibility, mechanical properties and high temperature resistance of the resin can be easily adjusted.

[0025] A preparation and 3D printing method of Al2O3 ceramic toughened by SiC whiskers according to the present invention can be used in the field of Al2O3 ceramic preparation. Description of the Drawings

[0027] Figure 1 Showing the infrared spectra of alumina before and after modification;

[0028] Figure 2 Showing the scanning electron micrograph of alumina particles after modification;

[0029] Figure 3 Showing the rheological properties of alumina ceramic slurries with different solid phase contents;

[0030] Figure 4 Showing the influence of different dispersant contents on the viscosity of the slurry;

[0031] Figure 5 Showing the scanning electron micrograph of SiC whiskers after surface treatment with PEG400. Detailed Embodiments

[0032] The present invention will be specifically described below through examples. Unless otherwise stated, the raw materials used are commercially available.

[0033] Example 1: The preparation method of the photosensitive slurry of SiC whisker toughened Al2O3 ceramic for photocurable 3D printing in this example is carried out according to the following steps:

[0034] I. Mix 1,6 - hexanediol diacrylate, trimethylolpropane triacrylate, acetone, and BYK111 dispersant evenly according to the mass ratio of 20:80:50:13, heat to 60°C under the condition of a stirring speed of 600 r / min, and keep it for 10 min to obtain a photocurable resin mixture;

[0035] II. After mechanically ball-milling and mixing the pre-treated 5 wt% SiC whiskers and the surface-treated 50 wt% Al2O3 ceramic powder evenly, add them into the prepared photocurable resin and ball-mill for 12 h to obtain a toughened Al2O3 ceramic slurry for 3D printing.

[0036] The method for 3D printing Al2O3 ceramics using the above ceramic slurry is carried out according to the following steps:

[0037] I. Mix and stir the toughened Al2O3 ceramic slurry and the TPO photoinitiator according to a mass ratio of 100:4 until the powder is completely dissolved to obtain a photosensitive resin.

[0038] II. Pour the photosensitive resin into the material tank of the 3D printer, ensure that the bottom layer of the material tank can be completely covered with a layer of resin after the doctor blade passes, adjust the light exposure time to 4 s, and the exposure intensity is 70 mw / cm 2 , the printing layer thickness is 50 μm, and 3D printing is completed layer by layer to obtain a green body.

[0039] III. Rinse the green body with absolute ethanol to remove the uncured resin in the green body; then place the green body in the air at a temperature of 70 °C for 2 h to volatilize the residual small molecules in the green body; then put the green body into a tube furnace, and under an argon or nitrogen atmosphere, heat it to 1600 °C at a heating rate of 2 °C / min and hold for 2 h for ceramization, and cool it naturally to obtain a toughened Al2O3 ceramic component.

[0040] For the toughened Al2O3 ceramic component 3D printed in this example, the ceramic yield is 72.3%; the inside of the component is blocky and dense, and the finished product rate is 100%.

[0041] Example 2: The preparation method of the photosensitive slurry of SiC whisker toughened Al2O3 ceramics for photocuring 3D printing in this example is carried out according to the following steps:

[0042] I. Mix 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, acetone, and BYK111 dispersant evenly according to a mass ratio of 30:60:50:10, heat to 60 °C under the condition of a stirring speed of 600 r / min, and hold for 15 min to obtain a photocurable resin mixture.

[0043] II. After mechanically ball-milling and mixing the pre-treated 7 wt% SiC whiskers and the surface-treated 50 wt% Al2O3 ceramic powder evenly, add them into the prepared photocurable resin and ball-mill for 12 h to obtain a toughened Al2O3 ceramic slurry for 3D printing.

[0044] The method for 3D printing Al2O3 ceramics using the above ceramic slurry is carried out according to the following steps:

[0045] 1. Mix toughened Al2O3 ceramic slurry and TPO photoinitiator in a mass ratio of 100:4 and stir until the powder is completely dissolved to obtain photosensitive resin;

[0046] 2. Pour the photosensitive resin into the material tank of a 3D printer, ensure that the bottom layer of the material tank is completely covered with a layer of resin after the squeegee passes, adjust the light exposure time to 6 s, and the exposure intensity is 50 mw / cm 2 , the printing layer thickness is 30 μm, and complete 3D printing layer by layer to obtain a green body;

[0047] 3. Rinse the green body with absolute ethanol to remove the uncured resin in the green body; then place the green body in the air at 60 °C for 2 h to volatilize the residual small molecules in the green body; then put the green body into a tubular furnace, and under an argon or nitrogen atmosphere, heat it to 1700 °C at a heating rate of 2 °C / min and hold for 2 h for ceramization, and cool it naturally to obtain a toughened Al2O3 ceramic component.

[0048] For the toughened Al2O3 ceramic component prepared by 3D printing in this example, the ceramic yield is 65%; the inside of the component is blocky and dense, and the finished product rate is 90%.

[0049] Example 3: The preparation method of the photosensitive slurry of SiC whisker toughened Al2O3 ceramic for photocuring 3D printing in this example is carried out according to the following steps:

[0050] 1. Mix 1,6 - hexanediol diacrylate, trimethylolpropane triacrylate, acetone, and BYK111 dispersant evenly in a mass ratio of 30:60:50:10, heat to 60 °C under the condition of a stirring speed of 600 r / min, and hold for 15 min to obtain a photocuring resin mixture;

[0051] 2. After mechanically ball - milling and mixing the pretreated 5 wt% SiC whiskers and the surface - treated 50 wt% Al2O3 ceramic powder evenly, add them to the prepared photocuring resin and ball - mill for 12 h to obtain a toughened Al2O3 ceramic slurry for 3D printing.

[0052] The method for 3D printing Al2O3 ceramic using the above - mentioned ceramic slurry is carried out according to the following steps:

[0053] 1. Mix toughened Al2O3 ceramic slurry and TPO photoinitiator in a mass ratio of 100:4 and stir until the powder is completely dissolved to obtain photosensitive resin;

[0054] 2. Pour the photosensitive resin into the material tank of a 3D printer, ensure that the bottom layer of the material tank is completely covered with a layer of resin after the squeegee passes, adjust the light exposure time to 7 s, and the exposure intensity is 60 mw / cm 2 , the printing layer thickness is 60 μm, and complete 3D printing layer by layer to obtain a green body;

[0055] Thirdly, the green body is rinsed with absolute ethanol to remove the uncured resin in the green body; then the green body is placed in the air at a temperature of 60 °C for 2 h to volatilize the residual small molecules in the green body; then the green body is put into a tube furnace, and in an argon or nitrogen atmosphere, it is heated to 1500 °C at a heating rate of 5 °C / min and held for 2 h for ceramization, and then cooled naturally to obtain a toughened Al2O3 ceramic component.

[0056] For the toughened Al2O3 ceramic component printed by 3D printing in this example, the ceramic yield is 67%; the inside of the component is massive and dense, and the finished product rate is 95%.

Claims

1. A preparation and 3D printing method of Al2O3 ceramic toughened by SiC whiskers, characterized in that The method is carried out according to the following steps:

1. Weigh 10 - 30 parts by weight of 1,6 - hexanediol diacrylate, 30 - 80 parts by weight of trimethylolpropane triacrylate, 40 - 60 parts by weight of solvent, and 1 - 10 parts by weight of dispersant and add them to a beaker and mix evenly. Heat the mixture to 60 - 75 °C under the condition of a stirring speed of 400 - 600 r / min and keep it for 10 - 20 min to obtain a photocurable resin solution.

2. After mechanically ball - milling and mixing the pretreated SiC whiskers and surface - treated Al2O3 ceramic powder evenly, add them to the prepared photocurable resin and ball - mill for 12 h to obtain a toughened Al2O3 ceramic slurry for 3D printing.

3. Weigh 100 parts by weight of Al2O3 ceramic slurry, 1 - 4 parts by weight of photoinitiator, and 0 - 0.01 parts by weight of inhibitor and stir until the powder is completely dissolved to obtain a photosensitive resin. IV. Pour the photosensitive resin into the material tank of the 3D printer, ensure that the bottom layer of the material tank can be completely covered with a layer of resin after the squeegee passes, adjust the light exposure time to 1 - 10 s, and the exposure intensity is 5 - 100 mw / cm 2 , the layer thickness of printing is 20 - 150 μm, and 3D printing is completed layer by layer to obtain a green body; 5. Rinse the green body with anhydrous ethanol to remove the uncured resin in the green body. Then place the green body in the air at a temperature of 25 - 80 °C for 1 - 24 h to volatilize the residual small molecules in the green body. Then put the green body into a tubular furnace, and under an argon or nitrogen atmosphere, heat it to 1100 - 1700 °C at a heating rate of 0.5 - 5 °C / min and keep it for 0.5 - 2 h for ceramization, and then cool it naturally to obtain an Al2O3 ceramic component.

2. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramic according to claim 1, characterized in that, In step 1, the solvent is the low - boiling - point solvent acetone. In the present invention, the low - boiling - point solvent acetone plays a key role in preventing whisker agglomeration. The polar acetone solvent eliminates the static charge on the surface of SiC whiskers and weakens the interaction between SiC whiskers.

3. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramics according to claim 1 or 2, characterized in that, In step 1, weigh 15 - 25 parts by weight of 1,6 - hexanediol diacrylate, 40 - 60 parts by weight of trimethylolpropane triacrylate, 50 - 60 parts by weight of solvent, and 5 - 10 parts by weight of dispersant. Under this condition, the synthesized toughened Al2O3 ceramic slurry shows better 3D printing forming stability and yield, and the yield reaches 100%.

4. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramics according to claim 1 or 2, characterized in that, In step 1, 1,6 - hexanediol diacrylate is a bifunctional monomer. The curing speed of the bifunctional monomer is faster than that of the monofunctional monomer, and it is more likely to undergo cross - linking curing reaction, which can improve the mechanical properties of the molding resin. Trimethylolpropane triacrylate is a trifunctional monomer. The trifunctional acrylate - type reactive diluent is more about improving the curing speed of the resin.

5. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramics according to claim 1 or 2, characterized in that, The dispersant in step 1 is the wetting dispersant BYK111.

6. A preparation and 3D printing method of Al2O3 ceramic toughened by SiC whiskers according to claim 1 or 2, characterized in that, The pretreatment method of SiC whiskers in step 2 is: prepare a 2.5 wt% dilute solution by mixing PEG - 400 surfactant in ethanol, then disperse SiCw whiskers in the PEG - 400 dilute solution, and carry out ultrasonic vibration for 2 h and then dry.

7. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramic according to claim 1 or 2, characterized in that, The surface treatment method of Al2O3 ceramic powder in step 2 is: add 5 wt% of the silane coupling agent KH550 of Al2O3 powder to a 95 wt% ethanol solution prepared from deionized water and anhydrous ethanol, and carry out ultrasonic dispersion for 10 min. Slowly add the Al2O3 powder, magnetically stir at a temperature of 70 °C for 1 h, then filter the obtained suspension, wash it 3 times with anhydrous ethanol, and dry the obtained powder at 60 °C for 12 h.

8. A preparation and 3D printing method of SiC whisker toughened Al2O3 ceramic according to claim 1 or 2, characterized in that, The photoinitiator described in Step 1 is photoinitiator 819 or photoinitiator TPO. The photoinitiator is responsible for generating free radicals by breaking during ultraviolet irradiation to initiate the free radical polymerization reaction. The inhibitor is hydroquinone, which is responsible for absorbing the free radicals that are not annihilated in time to prevent unwanted curing and improve the forming accuracy.

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