A method for preparing a transparent ceramic based on laser sintering 3D printing MgAl2O4 powder

Abstract

The application belongs to the field of ceramics and relates to a preparation method of transparent ceramic profiles based on laser sintering 3D printing MgAl2O4 powder, which comprises the following steps: synthesizing MgAl2O4 powder; pickling the MgAl2O4 powder; repeatedly centrifuging and washing the MgAl2O4 powder; drying, calcining, grinding and sieving the obtained precipitate to obtain pretreated MgAl2O4 powder; heating polyurethane hot melt adhesive and soluble starch to fully dissolve them, then adding ammonium citrate and deionized water to mix them, and then adding the pretreated MgAl2O4 powder to mix them, and stirring and reacting at 50-70 DEG C; spray drying to obtain granulated MgAl2O4 powder; mixing the granulated MgAl2O4 powder, ethylenediamine, zinc stearate and ABS resin and placing them in a particle grinder to grind; adding N,N-dimethylformamide to continue grinding; spray drying to obtain modified granulated MgAl2O4 powder; and using the modified granulated MgAl2O4 powder as raw material to obtain transparent ceramic profiles through laser sintering 3D printing. The method improves the machining precision and yield of transparent ceramic profiles with high precision, special shapes and complex structures, and improves the comprehensive performance of the transparent ceramic profiles.

Description

Technical Field

[0001] This invention belongs to the field of transparent ceramic technology, and particularly relates to a method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder. Background Technology

[0002] Magnesium aluminum spinel (MgAl2O4) transparent ceramics not only possess high transmittance in the ultraviolet to mid-infrared band, but also theoretically exhibit excellent properties such as high strength, low density, corrosion resistance, and wear resistance. They hold broad application prospects in fields such as transparent armor, infrared windows, lenses, chemical reactors, and sensors. Due to their superior optical and mechanical properties, magnesium aluminum spinel transparent ceramics have become an ideal candidate material for infrared windows.

[0003] In existing technologies, solid-state reaction sintering combined with mold processing is commonly used to prepare MgAl2O4 transparent ceramic profiles. However, this method presents challenges for precision, irregularly shaped, and complex transparent ceramic profiles, including complex mold structures and molding processes. Direct drying of the ball-milled slurry during solid-state reaction sintering leads to severe agglomeration of nano- and micro-sized powders, resulting in irregular shapes, poor flowability, and high interparticle friction, all of which hinder subsequent transparent ceramic molding. This problem is exacerbated when preparing precision, irregularly shaped, and complex transparent ceramic profiles. The transparent ceramic profiles obtained by this method have high porosity, potentially causing inconsistent shrinkage and even cracking of the ceramic body during processing. Residual porosity, grain boundary impurities, and doping segregation in the transparent ceramics produced by this method result in low optical quality.

[0004] Laser sintering 3D printing is a method of additive manufacturing. This process uses a laser as an energy source, employing a laser beam to uniformly sinter powders of plastics, waxes, metals, or their composites onto a processing surface. A thin layer of powder is evenly spread on a worktable as raw material. Under computer control, the laser beam, through a scanner, scans layer by layer of two-dimensional data at a specific speed and energy density. After scanning, the powder at the corresponding locations sinters into solid layers of a certain thickness, while unscanned areas remain loose powder. After one layer is scanned, the next layer needs to be scanned. The worktable is lowered according to the layer thickness of the object, and a powder spreading roller spreads the powder again, allowing the scanning of a new layer to begin. This process is repeated until all layers are scanned. Excess powder is removed, and after post-processing, the product is obtained. Summary of the Invention

[0005] Technical issues:

[0006] A method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder is provided, so as to simultaneously achieve (1) improve the processing accuracy and yield of precision, irregular and complex transparent ceramic profile products; (2) improve the mechanical and optical properties of transparent ceramic profiles.

[0007] Technical concept:

[0008] Technical concept:

[0009] This invention first designs the following steps based on the requirements of laser sintering 3D printing technology for raw material powder: synthesis of MgAl2O4 powder, pretreatment of MgAl2O4 powder, preparation of granulated MgAl2O4 powder, and modification of granulated MgAl2O4 powder. In the pretreatment step, acid washing and water washing effectively reduce the content of harmful trace impurity ions such as K, Ca, and Na in the powder. Then, high-temperature calcination removes organic impurities introduced during acid washing, thereby purifying the MgAl2O4 powder. Without affecting the particle size, surface morphology, and agglomeration degree of the MgAl2O4 powder, the impurity content in the powder is reduced to <1 ppm, which is beneficial for the densification of transparent ceramics. The preparation of granulated MgAl2O4 powder involves forming a polymer adhesive (polyurethane hot melt adhesive) on the surface of the MgAl2O4 powder. The coating process produces granulated MgAl2O4 powder with uniform particle size, high sphericity, and good flowability, making it less prone to agglomeration. Eliminating the structural inhomogeneity caused by powder agglomeration facilitates densification at lower temperatures. Furthermore, through modification of the granulated MgAl2O4 powder, the resulting modified granulated MgAl2O4 powder can be directly laser-sintered for rapid prototyping, successfully producing precise, irregular, and complex transparent ceramic profiles. This further enhances the laser sintering 3D printing performance of the powder, and the resulting transparent ceramic profiles exhibit uniform structure, high density, low porosity, significantly reducing the likelihood of cracking and resulting in high strength. This invention utilizes 3D printing technology to precisely design and control the size, shape, and fine porous structure of ceramic materials (including pore size, size distribution, channel shape, and channel interconnection). It achieves a perfect combination of control over the structural-functional coordination of transparent ceramic profiles and control over the shape of complex profiles. Combining the moldless molding characteristics of laser sintering 3D printing, it overcomes the shortcomings of traditional mold forming processes, such as low precision, complex mold processes, and high mold design costs. The method is simple, low-cost, highly operable, and easy to industrialize.

[0010] Technical solution:

[0011] On the one hand, a method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder is provided, which includes the following steps:

[0012] (1) Synthesis of MgAl2O4 powder: MgSO4·7H2O and AlNH4(SO4)2·12H2O were fully dissolved in deionized water at a molar ratio of 1:2.5 to obtain an aqueous solution; the aqueous solution was calcined at high temperature. The calcination temperature program was as follows: first, the temperature was increased to 900-1500℃ at a heating rate of 3-6℃ / min, and then the temperature was kept at 900-1500℃ for 4-6 hours. After cooling, the powder was crushed and passed through a 200-mesh sieve to obtain MgAl2O4 powder.

[0013] (2) Pretreatment of MgAl2O4 powder: MgAl2O4 powder is mixed with acid solution for acid washing, wherein the mass ratio of MgAl2O4 powder to acid solution is 1:1. Deionized water is added for washing and repeated centrifugation and washing until the pH of the supernatant obtained by centrifugation is 6. The precipitate is dried, calcined, ground and sieved to control the particle size of the powder to be 0.2-5μm, thus obtaining pretreated MgAl2O4 powder.

[0014] (3) Preparation of granulated MgAl2O4 powder: First, heat and fully dissolve polyurethane hot melt adhesive and soluble starch and mix them. Then, add ammonium citrate and deionized water to dissolve and mix them. Then, add pretreated MgAl2O4 powder and mix it. Stir and react at 50-70℃ for 5-7 hours. The raw materials, by mass percentage, include: 0.25-2% polyurethane hot melt adhesive, 0.3-2% soluble starch, 0.2-2% ammonium citrate, 42%-54% pretreated MgAl2O4 powder and the balance deionized water. Then, spray dry to obtain granulated MgAl2O4 powder with a particle size in the range of 60-120μm.

[0015] (4) Modification of granulated MgAl2O4 powder: Granulated MgAl2O4 powder, ethylenediamine, zinc stearate and ABS resin (styrene-acrylonitrile-butadiene copolymer) are mixed and ground in a particle grinder. The grinding speed is set at 500-1200 rpm and the grinding time is 1-2.5 h. N,N-dimethylamide is added and grinding is continued at 500-1200 rpm for 3-5.5 h. Then, it is spray dried to obtain modified granulated MgAl2O4 powder with a particle size in the range of 70-140 μm. The raw materials, by mass percentage, include: 80-92% granulated MgAl2O4 powder, 0.3-1.2% ethylenediamine, 0.6-1.8% zinc stearate, 5-8% ABS resin and 3-9% N,N-dimethylamide.

[0016] (5) Processing and forming of transparent ceramic profiles: Using modified granulated MgAl2O4 powder as raw material, transparent ceramic profiles are obtained by laser sintering 3D printing. The laser beam scans the processing plane in a segmented scanning manner. The laser power is 50-70W, the scanning speed is 1200-1600mm / s, the scanning interval is 0.12-0.18mm, the layer thickness is 0.12-0.3mm, the preheating temperature is 70-80℃, and the processing temperature is 160-190℃.

[0017] In some embodiments, in step (1), MgSO4·7H2O and AlNH4(SO4)2·12H2O are fully dissolved in deionized water at a molar ratio of 1:2.5. Heating and stirring are used to promote dissolution. The heating temperature is 50-70°C and the stirring time is 1.5-2.5h.

[0018] In some embodiments, in step (2), the acid solution is an aqueous solution of nitric acid or hydrochloric acid, and the pickling time is 4 to 12 hours.

[0019] In some embodiments, in step (2), the temperature for drying the obtained precipitate is 60-80°C and the drying time is 30-45 h.

[0020] In some embodiments, in step (2), the calcination temperature is 750–900°C and the drying time is 40–60 h.

[0021] In some embodiments, in step (3), the mass ratio of polyurethane hot melt adhesive to soluble starch is 1:1.2.

[0022] In some embodiments, in steps (3) and (4), the parameters for spray drying are: inlet temperature of 80–100°C, outlet temperature of 85–95°C, and inlet flow rate of 180–240 m³ / h. 3 / h.

[0023] In some embodiments, in step (4), the mass ratio of granulated MgAl2O4 powder to ABS resin is 1:(0.03-0.2), and the mass ratio of ABS resin to ethylenediamine is 1:(0.06-0.1).

[0024] On the other hand, a transparent ceramic profile prepared by the aforementioned method is provided.

[0025] Beneficial effects:

[0026] 1. This invention first designs the following steps based on the requirements of laser sintering 3D printing technology for raw material powder: synthesis of MgAl2O4 powder, pretreatment of MgAl2O4 powder, preparation of granulated MgAl2O4 powder, and modification of granulated MgAl2O4 powder. In the pretreatment step, acid washing and water washing effectively reduce the content of harmful trace impurity ions such as K, Ca, and Na in the powder. Then, high-temperature calcination removes organic impurities introduced during acid washing, thereby purifying the MgAl2O4 powder. Without affecting the particle size, surface morphology, and agglomeration degree of the MgAl2O4 powder, the impurity content in the powder is reduced to <1 ppm, which is beneficial for the densification of transparent ceramics. The preparation of granulated MgAl2O4 powder forms a polymer adhesive (polyurethane hot melt adhesive) on its surface. The coating process produces granulated MgAl2O4 powder with uniform particle size, high sphericity, and good flowability, making it less prone to agglomeration. Eliminating the structural inhomogeneity caused by powder agglomeration facilitates densification at lower temperatures. Furthermore, through modification of the granulated MgAl2O4 powder, the resulting modified granulated MgAl2O4 powder can be directly laser-sintered for rapid prototyping, successfully producing precise, irregular, and complex transparent ceramic profiles. This further enhances the laser sintering 3D printing performance of the powder, and the resulting transparent ceramic profiles exhibit uniform structure, high density, low porosity, significantly reducing the likelihood of cracking and resulting in high strength.

[0027] 2. This invention utilizes 3D printing technology to precisely design and control the size, shape, and fine porous structure of ceramic materials (including pore size, size distribution, channel shape, and channel interconnection). It achieves a perfect combination of controlling the structure and function of transparent ceramic profiles and controlling the shape of complex profiles. Combining the advantages of laser sintering 3D printing's "mold-free" molding characteristics, it overcomes the shortcomings of traditional mold forming processes, such as low precision, complex mold processes, and high mold design costs. The method is simple, low-cost, highly operable, and easy to industrialize.

[0028] 3. The method of the present invention simultaneously achieves (1) improving the processing accuracy and yield of precision, irregular and complex transparent ceramic profile products; and (2) enhancing the mechanical and optical properties of transparent ceramic profiles. Detailed Implementation

[0029] In some embodiments, a method for preparing a transparent ceramic profile based on laser sintering 3D printing of MgAl2O4 powder is provided, which includes the following steps:

[0030] (1) Synthesis of MgAl2O4 powder: MgSO4·7H2O and AlNH4(SO4)2·12H2O were fully dissolved in deionized water at a molar ratio of 1:2.5 to obtain an aqueous solution; the aqueous solution was calcined at high temperature. The calcination temperature program was as follows: first, the temperature was increased to 900-1500℃ at a heating rate of 3-6℃ / min, and then the temperature was kept at 900-1500℃ for 4-6 hours. After cooling, the powder was crushed and passed through a 200-mesh sieve to obtain MgAl2O4 powder.

[0031] (2) Pretreatment of MgAl2O4 powder: MgAl2O4 powder is mixed with acid solution for acid washing, wherein the mass ratio of MgAl2O4 powder to acid solution is 1:1. Deionized water is added for washing and repeated centrifugation and washing until the pH of the supernatant obtained by centrifugation is 6. The precipitate is dried, calcined, ground and sieved to control the particle size of the powder to be 0.2-5μm, thus obtaining pretreated MgAl2O4 powder.

[0032] (3) Preparation of granulated MgAl2O4 powder: First, heat and fully dissolve polyurethane hot melt adhesive and soluble starch and mix them. Then, add ammonium citrate and deionized water to dissolve and mix them. Then, add pretreated MgAl2O4 powder and mix it. Stir and react at 50-70℃ for 5-7 hours. The raw materials, by mass percentage, include: 0.25-2% polyurethane hot melt adhesive, 0.3-2% soluble starch, 0.2-2% ammonium citrate, 42%-54% pretreated MgAl2O4 powder and the balance deionized water. Then, spray dry to obtain granulated MgAl2O4 powder with a particle size in the range of 60-120μm.

[0033] (4) Modification of granulated MgAl2O4 powder: Granulated MgAl2O4 powder, ethylenediamine, zinc stearate and ABS resin (styrene-acrylonitrile-butadiene copolymer) are mixed and ground in a particle grinder. The grinding speed is set at 500-1200 rpm and the grinding time is 1-2.5 h. N,N-dimethylamide is added and grinding is continued at 500-1200 rpm for 3-5.5 h. Then, it is spray dried to obtain modified granulated MgAl2O4 powder with a particle size in the range of 70-140 μm. The raw materials, by mass percentage, include: 80-92% granulated MgAl2O4 powder, 0.3-1.2% ethylenediamine, 0.6-1.8% zinc stearate, 5-8% ABS resin and 3-9% N,N-dimethylamide.

[0034] (5) Processing and forming of transparent ceramic profiles: Using modified granulated MgAl2O4 powder as raw material, transparent ceramic profiles are obtained by laser sintering 3D printing. The laser beam scans the processing plane in a segmented scanning manner. The laser power is 50-70W, the scanning speed is 1200-1600mm / s, the scanning interval is 0.12-0.18mm, the layer thickness is 0.12-0.3mm, the preheating temperature is 70-80℃, and the processing temperature is 160-190℃.

[0035] In some embodiments, in step (1), MgSO4·7H2O and AlNH4(SO4)2·12H2O are fully dissolved in deionized water at a molar ratio of 1:2.5. Heating and stirring are used to promote dissolution. The heating temperature is 50-70°C and the stirring time is 1.5-2.5h.

[0036] In some embodiments, in step (2), the acid solution is an aqueous solution of nitric acid or hydrochloric acid, and the pickling time is 4 to 12 hours.

[0037] In some embodiments, in step (2), the temperature for drying the obtained precipitate is 60-80°C and the drying time is 30-45 h.

[0038] In some embodiments, in step (2), the calcination temperature is 750–900°C and the drying time is 40–60 h.

[0039] In some embodiments, in step (3), the mass ratio of polyurethane hot melt adhesive to soluble starch is 1:1.2.

[0040] In some embodiments, in steps (3) and (4), the parameters for spray drying are: inlet temperature of 80–100°C, outlet temperature of 85–95°C, and inlet flow rate of 180–240 m³ / h. 3 / h.

[0041] In some embodiments, in step (4), the mass ratio of granulated MgAl2O4 powder to ABS resin is 1:(0.03-0.2), and the mass ratio of ABS resin to ethylenediamine is 1:(0.06-0.1).

[0042] In some embodiments, a transparent ceramic profile prepared by the aforementioned method is provided.

[0043] Example 1

[0044] A method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder includes the following steps:

[0045] (1) Synthesis of MgAl2O4 powder: MgSO4·7H2O and AlNH4(SO4)2·12H2O were dissolved in deionized water at a molar ratio of 1:2.5 at 55℃ (stirring time was 1.6h) to obtain an aqueous solution; the aqueous solution was placed in a high-purity corundum crucible and calcined at high temperature in a muffle furnace. The calcination temperature program was as follows: first, the temperature was increased to 1000℃ at a heating rate of 4℃ / min, and then the temperature was held at 1000℃ for 4h. After cooling, a fluffy white snow-like powder was obtained. The powder was crushed and passed through a 200-mesh sieve to obtain MgAl2O4 powder.

[0046] (2) Pretreatment of MgAl2O4 powder: MgAl2O4 powder and acid solution were stirred and mixed evenly, with the mass ratio of MgAl2O4 powder to acid solution being 1:1. The mixture was acid washed for 5 hours. Deionized water was added for washing and repeated centrifugation was performed until the pH of the supernatant obtained by centrifugation was 6. The precipitate was dried at 60°C for 32 hours and calcined at 760°C for 40 hours to remove organic impurities introduced during the acid washing process. The precipitate was then ground and sieved to control the particle size of the powder to be within 1 μm, thus obtaining pretreated MgAl2O4 powder.

[0047] (3) Preparation of granulated MgAl2O4 powder: First, heat and fully dissolve polyurethane hot melt adhesive and soluble starch and mix them. Then, add ammonium citrate and deionized water to dissolve and mix them. Then, add pretreated MgAl2O4 powder and mix it. Stir and react at 50-70℃ for 5 hours. The raw materials, by mass percentage, include: 0.4% polyurethane hot melt adhesive, 0.48% soluble starch, 0.4% ammonium citrate, 43% pretreated MgAl2O4 powder and the remainder deionized water. Then, spray dry the powder (spray drying parameters: inlet temperature 85℃, outlet temperature 86℃, inlet flow rate 180m³). 3 / h), to obtain granulated MgAl2O4 powder with a particle size (equivalent diameter of particle size measured by laser particle size analyzer) in the range of 60 to 120 μm;

[0048] (4) Modification of granulated MgAl2O4 powder: Granulated MgAl2O4 powder, ethylenediamine, zinc stearate and ABS resin (styrene-acrylonitrile-butadiene copolymer) were mixed and ground in a particle grinder at a speed of 500 rpm for 1 hour; N,N-dimethylamide was added and grinding was continued at a speed of 600 rpm for 3 hours; then spray drying was performed (spray drying parameters: inlet temperature 85℃, outlet temperature 85℃, inlet flow rate 180 m³ / min). 3 / h), to obtain modified granulated MgAl2O4 powder with a particle size in the range of 70 to 140 μm; wherein each raw material, by mass percentage, includes: 84% granulated MgAl2O4 powder, 0.4% ethylenediamine, 1.6% zinc stearate, 6% ABS resin and 8% N,N-dimethylamide;

[0049] (5) Processing and Forming of Transparent Ceramic Profiles: Using modified granulated MgAl2O4 powder as raw material, transparent ceramic profiles are obtained through laser sintering 3D printing. Specifically: A thin layer of MgAl2O4 powder is evenly spread on the worktable as raw material. Under computer control, the laser beam scans layer by layer according to the two-dimensional data of the layers at a certain speed and energy density. After the laser beam scans, the modified granulated MgAl2O4 powder at the corresponding position is sintered to form a solid layer with a certain thickness, while the unscanned areas remain loose powder. After this layer is scanned, the next layer needs to be scanned. First, the worktable is lowered according to the cross-sectional thickness of the object, i.e., the layer thickness, and the powder spreading roller spreads the powder again, and the scanning of the new layer can begin. This process is repeated until all layers are scanned. After removing excess powder and undergoing post-processing, the transparent ceramic profile product is obtained. The laser beam scans the processing plane in a segmented scanning manner, with a laser power of 55W, a scanning speed of 1250mm / s, a scanning interval of 0.14mm, a layer thickness of 0.16mm, a preheating temperature of 70℃, and a processing temperature of 175℃.

[0050] Example 2

[0051] A method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder includes the following steps:

[0052] (1) Synthesis of MgAl2O4 powder: MgSO4·7H2O and AlNH4(SO4)2·12H2O were dissolved in deionized water at a molar ratio of 1:2.5 at 70℃ (stirring time was 2.5h) to obtain an aqueous solution; the aqueous solution was placed in a high-purity corundum crucible and calcined at high temperature in a muffle furnace. The calcination temperature program was as follows: first, the temperature was increased to 1500℃ at a heating rate of 6℃ / min, and then the temperature was held at 1500℃ for 6h. After cooling, a fluffy white snow-like powder was obtained. The powder was crushed and passed through a 200-mesh sieve to obtain MgAl2O4 powder.

[0053] (2) Pretreatment of MgAl2O4 powder: MgAl2O4 powder and acid solution were stirred and mixed evenly, wherein the mass ratio of MgAl2O4 powder to acid solution was 1:1, and acid washing was performed for 12 hours; deionized water was added for washing and repeated centrifugation was performed until the pH of the supernatant obtained by centrifugation was 6; the precipitate was dried at 80℃ for 45 hours and calcined at 900℃ for 60 hours to remove organic impurities introduced during acid washing, and then ground and sieved to control the particle size of the powder to 5 μm to obtain pretreated MgAl2O4 powder;

[0054] (3) Preparation of granulated MgAl2O4 powder: First, heat and fully dissolve and mix polyurethane hot melt adhesive and soluble starch, then add ammonium citrate and deionized water to dissolve and mix, then add pretreated MgAl2O4 powder and mix, and stir and react at 70℃ for 7h; the raw materials, by mass percentage, include: 1.5% polyurethane hot melt adhesive, 1.8% soluble starch, 2% ammonium citrate, 54% pretreated MgAl2O4 powder and the remainder deionized water; then spray drying treatment (spray drying parameters: inlet temperature 100℃, outlet temperature 95℃, inlet flow rate 240m³ / h). 3 / h), to obtain granulated MgAl2O4 powder with a particle size (equivalent diameter of particle size measured by laser particle size analyzer) in the range of 60 to 120 μm;

[0055] (4) Modification of granulated MgAl2O4 powder: Granulated MgAl2O4 powder, ethylenediamine, zinc stearate and ABS resin (styrene-acrylonitrile-butadiene copolymer) were mixed and ground in a particle grinder at a speed of 1200 rpm for 2.5 h; N,N-dimethylamide was added and grinding was continued at 1200 rpm for 5.5 h; then spray drying was performed (spray drying parameters: inlet temperature 100℃, outlet temperature 95℃, inlet flow rate 240 m³ / min). 3 / h), to obtain modified granulated MgAl2O4 powder with a particle size in the range of 70 to 140 μm; wherein each raw material, by mass percentage, includes: 89.2% granulated MgAl2O4 powder, 0.5% ethylenediamine, 0.8% zinc stearate, 5% ABS resin and 4.5% N,N-dimethylamide;

[0056] (5) Processing and Forming of Transparent Ceramic Profiles: Using modified granulated MgAl2O4 powder as raw material, transparent ceramic profiles are obtained through laser sintering 3D printing. Specifically: A thin layer of MgAl2O4 powder is evenly spread on the worktable as raw material. Under computer control, the laser beam scans layer by layer according to the two-dimensional data of the layers at a certain speed and energy density. After the laser beam scans, the modified granulated MgAl2O4 powder at the corresponding position is sintered to form a solid layer with a certain thickness, while the unscanned areas remain loose powder. After this layer is scanned, the next layer needs to be scanned. First, the worktable is lowered according to the cross-sectional thickness of the object, i.e., the layer thickness, and the powder spreading roller spreads the powder again, and the scanning of the new layer can begin. This process is repeated until all layers are scanned. After removing excess powder and undergoing post-processing, the transparent ceramic profile product is obtained. The laser beam scans the processing plane in a segmented scanning manner, with a laser power of 70W, a scanning speed of 1600mm / s, a scanning interval of 0.18mm, a layer thickness of 0.3mm, a preheating temperature of 80℃, and a processing temperature of 190℃.

[0057] Example 3

[0058] Preliminary observations show that the granulated MgAl2O4 powders obtained in Examples 1 and 2 have uniform particle size, high sphericity, good flowability, and are not prone to agglomeration. Therefore, after modification, the granulated MgAl2O4 powders obtained in Examples 1 and 2 can be conveniently and quickly processed into precision, irregular, and complex transparent ceramic profiles through laser sintering 3D printing. The transparent ceramic profiles obtained in Examples 1 and 2 have a dense structure, low porosity, uniform texture, high strength, and high light transmittance, which can meet the application requirements of the products. Furthermore, extensive repeated experiments have confirmed that the preparation methods of Examples 1 and 2 have a high yield rate for producing precision, irregular, and complex transparent ceramic profiles.

[0059] Residual pores, grain boundary impurities, and doping segregation in transparent ceramics can affect their flexural yield strength, compressive yield strength, and elongation, thereby impacting their overall performance and applications in the optical field.

[0060] Flexural yield strength test Prepare a cubic transparent ceramic profile sample. Apply a load to the sample using a three-point bending tester to induce bending, and record the changes in force and deflection. Based on the relationship between bending strain and stress, the flexural yield strength of the ceramic material can be determined.

[0061] The flexural yield strength of the transparent ceramic profiles prepared in Examples 1 and 2 was tested. The test results showed that the flexural yield strengths of the transparent ceramic profiles prepared in Examples 1 and 2 were 609 MPa and 618 MPa, respectively, both not less than 600 MPa, confirming that the transparent ceramic profiles prepared by the method of the present invention have high flexural yield strength.

[0062] Compressive yield strength test Prepare a cubic transparent ceramic profile sample. Place the sample on a compression testing machine, apply gradually increasing compressive load, and record the changes in load and deformation. By plotting the stress-strain curve, the compressive yield strength of the ceramic material can be determined.

[0063] The compressive yield strength of the transparent ceramic profiles prepared in Examples 1 and 2 was tested. The test results showed that the compressive yield strengths of the transparent ceramic profiles prepared in Examples 1 and 2 were 704 MPa and 716 MPa, respectively, both not less than 700 MPa, confirming that the transparent ceramic profiles prepared by the method of the present invention have high compressive yield strength.

[0064] Elongation test Elongation testing was conducted using a universal testing machine. Before testing, the transparent ceramic profile sample was processed to standard dimensions. The sample was then clamped in the universal testing machine, and a gradually increasing tensile force was applied. The changes in load and elongation were recorded. The elongation was calculated from the measured data. The elongation was expressed as a percentage, and the calculation formula was: Elongation = (L2 - L0) / L0 × 100%, where L0 represents the initial gauge length (i.e., the initial length of the transparent ceramic profile sample), and L2 represents the gauge length at which the sample broke.

[0065] The elongation of the transparent ceramic profiles prepared in Examples 1 and 2 was tested. The test results showed that the elongation of the transparent ceramic profiles prepared in Examples 1 and 2 was 0.12 and 0.09, respectively, both within the range of 0.01 to 1%, confirming that the transparent ceramic profiles prepared by the method of the present invention have moderate elongation, which can meet the elongation requirements of electronic packaging.

[0066] In summary, the preparation method of the present invention can not only conveniently and successfully process transparent ceramic profiles of various precision, irregular and complex shapes with a high yield, but also produce transparent ceramic profiles with dense structure, uniform texture, low porosity, high light transmittance, high flexural yield strength, high compressive yield strength and moderate elongation, and excellent comprehensive mechanical properties, which is beneficial to extending the service life of transparent ceramic profiles and can meet the needs of electronic packaging.

Claims

1. A method for preparing transparent ceramic profiles based on laser sintering 3D printing of MgAl2O4 powder, characterized in that, Includes the following steps: (1) Synthesis of MgAl2O4 powder: MgSO4•7H2O and AlNH4(SO4)2•12H2O were fully dissolved in deionized water at a molar ratio of 1:2.

5. The solution was heated and stirred at a temperature of 50~70 ℃ for 1.5~2.5 h to obtain an aqueous solution. The aqueous solution was then calcined at high temperature. The calcination temperature program was as follows: the temperature was first increased to 900~1500 ℃ at a heating rate of 3~6 ℃ / min, and then kept at 900~1500 ℃ for 4~6 h. After cooling, the powder was crushed and passed through a 200-mesh sieve to obtain MgAl2O4 powder. (2) Pretreatment of MgAl2O4 powder: Mix MgAl2O4 powder with acid solution for acid washing, wherein the mass ratio of MgAl2O4 powder to acid solution is 1:

1. Add deionized water for washing and repeatedly centrifuge and wash until the pH of the supernatant obtained by centrifugation is 6. Dry the obtained precipitate, calcine, grind and sieve to control the particle size of the powder to be 0.2~5 μm, and obtain pretreated MgAl2O4 powder. (3) Preparation of granulated MgAl2O4 powder: First, heat and fully dissolve polyurethane hot melt adhesive and soluble starch and mix them. Then add ammonium citrate and deionized water to dissolve and mix them. Then add pretreated MgAl2O4 powder and mix them. Stir and react at 50~70 ℃ for 5~7 h. The raw materials, by mass percentage, include: 0.25~2% polyurethane hot melt adhesive, 0.3~2% soluble starch, 0.2~2% ammonium citrate, 42%~54% pretreated MgAl2O4 powder and the remainder deionized water. Then spray dry to obtain granulated MgAl2O4 powder with a particle size in the range of 60~120 µm. (4) Modification of granulated MgAl2O4 powder: Granulated MgAl2O4 powder, ethylenediamine, zinc stearate and styrene-acrylonitrile-butadiene copolymer were mixed and ground in a particle mill. The grinding speed was set at 500~1200 rpm and the grinding time was 1~2.5 h. N,N-dimethylamide was added and the grinding was continued at 500~1200 rpm for 3~5.5 h. Then, the powder was spray dried to obtain modified granulated MgAl2O4 powder with a particle size in the range of 70~140 µm. The raw materials, by mass percentage, included: 80~92% granulated MgAl2O4 powder, 0.3~1.2% ethylenediamine, 0.6~1.8% zinc stearate, 5~8% styrene-acrylonitrile-butadiene copolymer and 3~9% N,N-dimethylamide. (5) Processing and forming of transparent ceramic profiles: Using modified granulated MgAl2O4 powder as raw material, transparent ceramic profiles are obtained by laser sintering 3D printing. The laser beam scans the processing plane in a segmented scanning manner. The laser power is 50~70 W, the scanning speed is 1200~1600 mm / s, the scanning interval is 0.12~0.18 mm, the layer thickness is 0.12~0.3 mm, the preheating temperature is 70~80 ℃, and the processing temperature is 160~190 ℃. In steps (3) and (4), the parameters for spray drying are: inlet temperature 80~100 ℃, outlet temperature 85~95 ℃, and inlet flow rate 180~240 m³ / h. 3 / h.

2. The preparation method according to claim 1, characterized in that, In step (2), the acid solution is an aqueous solution of nitric acid or hydrochloric acid, and the acid washing treatment time is 4~12 h.

3. The preparation method according to claim 1, characterized in that, In step (2), the temperature for drying the obtained precipitate is 60~80 ℃ and the drying time is 30~45 h.

4. The preparation method according to claim 1, characterized in that, In step (2), the calcination temperature is 750~900℃ and the drying time is 40~60 h.

5. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of polyurethane hot melt adhesive to soluble starch is 1:1.

2.

6. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of granulated MgAl2O4 powder to styrene-acrylonitrile-butadiene copolymer is 1:(0.03~0.2), and the mass ratio of styrene-acrylonitrile-butadiene copolymer to ethylenediamine is 1:(0.06~0.1).

7. The transparent ceramic profile prepared by any one of claims 1 to 6.