A method for preparing finished products by 3D printing boron carbide ceramic slurry

Abstract

A method for preparing a finished product by 3D printing boron carbide ceramic slurry belongs to the field of ceramic material preparation. First, the boron carbide ceramic powder and the toughening agent are pre-ground and pre-mixed, and the sintered two phases of different particle sizes are crushed and mixed. After obtaining the dry powder mixture, additives are added, and finally water is added to obtain the slurry, and the viscosity is tested by a viscometer. By rewriting the slicing software and inputting the corresponding parameters, the qualified slurry is 3D directly written, and the variables such as the output, printing speed, printing outlet diameter, printing distance and thermal field temperature are controlled to control the single layer thickness of the lattice ceramic, the filling rate and other important parameters. The present invention controls the solid content of the ceramic slurry by controlling the ratio of external additives, and with the help of the external heating field, the ceramic obtains a clear and tough skeleton structure, and the toughening agent is added to improve the macroscopic properties of the ceramic. A finished product of direct writing 3D printing lattice boron carbide ceramic slurry with high solid content, low porosity and low single-layer collapse rate is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of ceramic material preparation, and in particular relates to a method for preparing a finished product of a high-solid content direct-writing 3D printing lattice boron carbide ceramic slurry. Background Art

[0002] 3D printing (3DP), a type of rapid prototyping technology, also known as additive manufacturing, is a technique that uses digital model files as a foundation and uses adhesive materials such as powdered metal or plastic to construct objects layer by layer. 3D printing is typically achieved using a digital material printer. It is often used to create models in fields such as mold making and industrial design, and has gradually been used for the direct manufacture of some products. Parts printed using this technology already exist. This technology has applications in jewelry, footwear, industrial design, architecture, engineering, and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, firearms, and other fields. 3D printing of ceramics was first proposed in the 1990s. To date, with the development of materials science and computer science, the mainstream 3D printing applied to ceramic materials is mainly concentrated in stereolithography (SLA), inkjet printing (IJP), three-dimensional printing technology (3DP), selective laser sintering (SLS) and direct writing (DIW). Among them, direct writing technology (DIW) has a simpler process and is more suitable for industrial production. It is often used in structural parts and decorative parts with low requirements for near-molding precision. This molding method is mainly affected by the rheological properties of the slurry, and the rheological properties of the slurry are often affected by the solid content and thermal field of the slurry.

[0003] As my country's military pursues higher combat capabilities and equipment lightweighting, high-performance B4C ceramics are widely used in the field of individual soldier protection due to their excellent high strength, high toughness, low density and corrosion resistance brought by their unique rhombus hexahedron structure. Summary of the Invention

[0004] With the further application of boron carbide ceramics, people have higher requirements for the shape of the ceramics themselves, especially boron carbide ceramics in the form of lattice have a higher specific surface area and can be used on a large scale in explosion-proof and bulletproof materials and neutron absorption materials. If boron carbide ceramics with a lattice porous structure are to be obtained through a direct writing 3D printing mode, the problem of low solid content of the ceramic slurry must be solved first. Adding a small amount of organic additives can make the lattice ceramics more dense during the pressureless sintering process. In response to the above problems, the present invention provides a method for preparing finished products by 3D printing boron carbide ceramic slurry. The technical solution of the present invention controls the solid content of the ceramic slurry by controlling the optimal ratio of external additives. The solid content determines the density of the slurry and also ultimately determines the microscopic morphology and performance of the B4C ceramics. At the same time, with the help of the effect of the external heating field, the ceramics obtain a clear and tough skeleton structure. Subsequently, according to the toughening requirements, toughening agents such as SiC whiskers and rare earth oxides can be added to the slurry to improve the macroscopic properties of the ceramics. The high solid content (boron carbide powder ratio) mentioned in the present invention can reach 89%, the porosity of the ceramic can be reduced to 5% after sintering, and the single-layer collapse rate can be controlled to be less than 1% (Y-axis comparison).

[0005] The design idea of ​​the present invention:

[0006] First, the boron carbide ceramic powder and the toughening agent are pre-ground and pre-mixed, and the sintered two phases of different particle sizes are crushed and mixed. After obtaining the dry powder mixture, the additives are added, and finally water is added to obtain the slurry, and the viscosity is tested by a rotational viscometer. By rewriting the slicing software and entering the corresponding parameters, the qualified slurry is 3D directly written, and the single-layer thickness, filling rate and other important parameters of the lattice ceramic are controlled by controlling variables such as the output, printing speed, printing outlet diameter, printing distance and thermal field temperature. Finally, the strength of the lattice green embryo can be increased by 20% (compared to 65% solid content), the hardness can reach up to 15GPa, and the fracture toughness can reach up to 2.5MPa.m 1 / 2 , which provides a better choice for the preparation of continuous phase composite materials.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a finished product by 3D printing boron carbide ceramic slurry, wherein the 3D printing boron carbide ceramic slurry is a high solid content direct writing 3D printing lattice boron carbide ceramic slurry, specifically comprising the following steps:

[0009] 1. Premixing of B4C powder and toughening phase: Boron carbide ceramics with a particle size of 0.5-1.0 μm and toughening phase are mixed in a mass ratio of 9:1-10:0.1 and ball milled. 6mm, 8mm and 10mm zirconium dioxide balls are used in a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 2.5:1-3.5:1. The powder loading amount is 1 / 3-1 / 2 of the barrel. The roller speed is 10-15r / min.

[0010] 2. Printing slurry preparation: Add additives in small batches to the mixture prepared in step 1. The additives include water reducer, binder and lubricant, and add pure water for mechanical stirring at a rate of 5-15r / min for 30-40h, so that the water reducer can fully combine with the functional groups on the surface of the powder and control the solid content of the ceramic slurry to be above 85%. Then use a rheometer to test, using a flat test rotor with a diameter of 30-35mm, a gap of 1-2mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0011] 3. Model import and slicing software settings: First, import the STL format file of the 3D drawing software into the slicing software Ultimaker Cure, with a print range of X: 90-180mm; Y: 90-180mm; Z: 10-50mm; the number of prints is 1; the nozzle size is selected as 1.2-1.5, the surface mode is selected, and the outer contour is set to smooth; the output diameter is 0.4-0.6mm, and the compensation value is 0.1mm; the single layer height is set to 0.3-0.5mm, the first layer height is 0.5-1mm, and the double line height is set to 1-2mm; there is no technical requirement for the thickness of the model's exterior wall; the cap thickness is set to 0.5-1mm; the printing temperature is set to 30-50℃; the printing speed is 0.7-5mm / s; the wall and top / bottom speed is 10-15mm / s.

[0012] 4. Pre-printing, actual printing, and post-processing: Edge loading time is 30 seconds to 1 minute, and any blockages in the feed barrel are removed. The total print height is 10 to 50 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying to dry any surface dust before use.

[0013] 5. Pressureless Sintering System Setup: Place the printed and dried raw material in a graphite mold, using 0.1-0.2mm graphite paper as a barrier layer on the top, bottom, left, and right sides. Lay down one to two layers of graphite paper on all sides. Sintering schedule: 0-500°C, ramp rate 5-10°C / min. After 500°C, adjust the temperature gradient based on the additives. Allow to cool in the furnace.

[0014] The above preparation method, wherein:

[0015] In the step 1, the toughening phase is selected from multi-walled carbon nanotubes (CNTs), rare earth oxides, SiC whiskers, and Al2O3; and the content of the toughening phase in the mixture of boron carbide ceramic and the toughening phase does not exceed 15%.

[0016] In the step 1, a three-bar double-layer horizontal dry ball mill is used for ball milling, and the ball barrel is made of a high molecular organic material such as polyurethane or nylon;

[0017] In step 2, the water reducer is a polycarboxylic acid water reducer, and the addition amount is controlled at 0.5% to 1.5%; the binder is a polyacrylic acid aqueous solution resin or an injection molding binder NE-119 (wax-based), and the addition amount is 0.01% to 0.05%; the lubricant is a stearic acid emulsion AP27, and the addition amount is controlled at 0.1% to 0.5%.

[0018] In step 3, a certain Z-axis compensation is performed, and the compensation amount is 0.3 to 0.5 mm;

[0019] In step 4, the printing height of the first layer during the actual printing process needs to be adjusted by 0.3 to 0.5 mm;

[0020] In step 4, the vacuum drying temperature is 60-80°C and the drying time is 36-48 hours;

[0021] The edge extrusion time in the present invention refers to the time when the front is not printed and the gas and solvent precipitate in the barrel are eliminated.

[0022] Beneficial effects and key points of the present invention:

[0023] The present invention uses high-solid content slurry direct writing to generate boron carbide ceramics in the form of a dot matrix. First, the high-solid content slurry has a profound impact on the micromorphology and macroscopic properties of the subsequent pressureless sintered boron carbide products. The control of the critical point of the rheological properties of the slurry gives the high-content ceramic slurry more added value. The porous array boron carbide, with its unique point-reinforced skeleton form, provides a new idea for the composite of metals such as steel / aluminum with it, and is expected to replace a single material (hot-pressed sintered boron carbide) for application in military industry and other fields. In addition, the boron carbide ceramic of this system can be applied in the field of nuclear radiation protection due to its high specific surface area and controllable porosity. Finally, this method abandons traditional hot pressing and sintering, is more green and energy-saving, and is suitable for industrial production.

[0024] As mentioned above, boron carbide slurries are relatively rare due to its high cost and poor slurry properties. Furthermore, 3D direct-write printing requires high rheological properties of the slurry, and the addition of different toughening agents significantly impacts the slurry's properties. This invention prepares boron carbide into a high-solids slurry and adds toughening agents and additives to improve the toughness, flexural strength, and other properties of the finished product. This provides an innovative solution for preparing boron carbide slurries suitable for 3D printing. DETAILED DESCRIPTION

[0025] Example 1

[0026] A method for preparing a finished product of a high solid content (89%) direct writing 3D printing lattice boron carbide / CNTs ceramic slurry comprises the following steps:

[0027] 1. Premixing of B4C powder and toughening phase: Use a three-bar double-layer horizontal dry ball mill for ball milling. Mix boron carbide ceramics with a particle size of 0.5μm and toughening phase multi-walled carbon nanotubes (CNTs) at a mass ratio of 9.7:0.3. The ball barrel is made of high molecular organic materials such as polyurethane or nylon. 6mm, 8mm and 10mm zirconium dioxide balls are used for grinding at a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 2.5:1. The powder loading amount is 1 / 3 of the barrel. The roller speed is 15r / min.

[0028] 2. Printing slurry preparation: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is controlled at 0.5%; the binder is polyacrylic acid aqueous solution, and the addition amount is 0.01%; the lubricant is stearic acid emulsion AP27, and the addition amount is 0.5%. Pure water is added for mechanical stirring at a rate of about 5r / min and a stirring time of 40h, so that the water reducer is fully combined with the functional groups on the surface of the powder, and the solid content of the ceramic slurry is controlled to be greater than 89%. The test was then carried out using a rheological tester, using a 35mm diameter flat test rotor, a gap of 1mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0029] 3. Model import and slicing software settings: First, import the STL file in 3D drawing software into the slicing software Ultimaker Cure. The print range is X: 180mm; Y: 180mm; Z: 50mm; the number of prints is 1; the nozzle size is selected as 1.5, the surface mode is selected, and the outer contour is set to smooth; the output diameter is 0.6mm, the compensation value is 0.1mm; a certain Z-axis compensation is performed, and the compensation amount is 0.5mm; the single layer height is set to 0.5mm, the first layer height is 1mm, and the double line height is set to 2mm; there is no technical requirement for the thickness of the model exterior wall; the cap thickness is set to 1mm, and encryption printing is not set; the print temperature is set to 50℃; the print speed is 0.7mm / s; the wall and top / bottom speed is 10mm / s.

[0030] 4. Pre-printing, actual printing, and post-processing: Allow 1 minute for edge loading, remove any blockages from the feed barrel, and a total print height of 50 mm. During actual printing, manually adjust the first layer's print height by 0.3-0.5 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying at 80°C for 48 hours. Blow dry any dust from the surface and set aside.

[0031] 5. Pressureless sintering setup: Place the printed and dried raw material in a graphite mold, using 0.1mm graphite paper as a barrier layer on the top, bottom, left, and right sides. Two layers of graphite paper are used, covering the entire mold. The sintering schedule is as follows: 0-500°C at a heating rate of 5°C / min; after 500°C, increase the temperature at a rate of 10°C / min, reaching 1950°C and holding for 30 minutes. Allow to cool in the furnace.

[0032] The final green strength of the lattice can be increased by 21.5% (compared with 65% solid content), the average hardness is 1.9GPa, and the average fracture toughness is 0.56MPa.m 1 / 2 The average hardness after sintering is 12GPa, and the average fracture toughness is 1.98MPa.m 1 / 2 .

[0033] Example 2

[0034] A method for preparing a finished product of a high solid content (85%) direct writing 3D printing lattice boron carbide / cerium oxide ceramic slurry comprises the following steps:

[0035] 1. Premixing of B4C powder and toughening phase: Use a three-bar double-layer horizontal dry ball mill for ball milling. Mix boron carbide ceramics with a particle size of 1.0μm and toughening phase cerium oxide at a mass ratio of 9.5:0.5. The ball barrel is made of high molecular organic materials such as polyurethane or nylon. 6mm, 8mm and 10mm zirconium dioxide balls are used for grinding at a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 3.5:1. The powder loading amount is 1 / 3 of the barrel. The roller speed is 15r / min.

[0036] 2. Preparation of printing slurry: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is controlled at 1.5%; the binder is NE-119 (wax system) for injection molding, and the addition amount is 0.05%; the lubricant is stearic acid emulsion AP27, and the addition amount is controlled at 0.5%. Pure water is added for mechanical stirring at a rate of about 15r / min and a stirring time of 30h, so that the water reducer is fully combined with the functional groups on the surface of the powder, and the solid content of the ceramic slurry is controlled to 85%. The test was then carried out using a rheological tester, using a 30mm diameter flat test rotor, a gap of 2mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0037] 3. Model import and slicing software settings: First, import the STL file in 3D drawing software into the slicing software Ultimaker Cure, with a print range of X: 90; Y: 90mm; Z: 50mm; set the number of prints to 1; select nozzle size 1.2, select surface mode, and set the outer contour to smooth; the output diameter is 0.4mm, the compensation value is 0.1mm; perform a certain Z-axis compensation of 0.5mm; set the single layer height to 0.5mm, the first layer height to 1mm, and the double line height to 2mm; there is no technical requirement for the thickness of the model's exterior wall; set the cap thickness to 1mm, and do not set encrypted printing; set the print temperature to 30℃; print speed to 1.6mm / s; and the wall and top / bottom speed to 15mm / s.

[0038] 4. Pre-printing, actual printing, and post-processing: The edge loading time is 30 seconds, and any blockages in the feed barrel are removed. The total print height is 50 mm. During actual printing, the first layer's print height requires manual adjustment of 0.3 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying at 60°C for 36 hours. Blow dry any dust from the surface and set aside.

[0039] 5. Pressureless Sintering Process Settings: Place the printed and dried raw material in a graphite mold, using 0.1mm graphite paper as insulation layers, with two layers of paper placed around the mold. The sintering process is as follows: 0-500°C, heating rate: 5°C / min; 500-900°C, heating rate: 10°C / min, holding at 900°C for 20 minutes; 900-1400°C, heating rate: 5°C / min, holding at 1400°C for 30 minutes; 1400-1900°C, heating rate: 10°C / min, holding at 1900°C for 30 minutes. Allow to cool in the furnace.

[0040] The final green strength of the lattice can be increased by 17.5% (compared with 65% solid content), the average hardness is 1.3GPa, and the average fracture toughness is 0.33MPa.m 1 / 2 The average hardness after sintering is 11Gpa, and the average fracture toughness is 1.52MPa.m 1 / 2 .

[0041] Example 3

[0042] A method for preparing a finished product of a high solid content (85%) direct writing 3D printing dot matrix boron carbide / lanthanum oxide ceramic slurry comprises the following steps:

[0043] 1. Premixing of B4C powder and toughening phase: Use a three-bar double-layer horizontal dry ball mill for ball milling. Mix boron carbide ceramics with a particle size of 1.0μm and toughening phase lanthanum oxide at a mass ratio of 9.5:0.5. The ball barrel is made of high molecular organic materials such as polyurethane or nylon. 6mm, 8mm and 10mm zirconium dioxide balls are used for grinding at a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 3.5:1. The powder loading amount is 1 / 3 of the barrel. The roller speed is 15r / min.

[0044] 2. Preparation of printing slurry: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is controlled at 1.5%; the binder is NE-119 (wax system) for injection molding, and the addition amount is 0.05%; the lubricant is stearic acid emulsion AP27, and the addition amount is controlled at 0.5%. Pure water is added for mechanical stirring at a rate of 15r / min and a stirring time of 30h, so that the water reducer is fully combined with the functional groups on the surface of the powder, and the solid content of the ceramic slurry is controlled to 85%. It is then tested with a rheological tester, using a 30mm diameter flat test rotor, a gap of 2mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0045] 3. Model import and slicing software settings: First, import the STL file in 3D drawing software into the slicing software Ultimaker Cure, with a print range of X: 90; Y: 90mm; Z: 50mm; set the number of prints to 1; select nozzle size 1.2, select surface mode, and set the outer contour to smooth; the output diameter is 0.4mm, the compensation value is 0.1mm; perform a certain Z-axis compensation of 0.5mm; set the single layer height to 0.5mm, the first layer height to 1mm, and the double line height to 2mm; there is no technical requirement for the thickness of the model's exterior wall; set the cap thickness to 1mm, and do not set encrypted printing; set the print temperature to 30℃; print speed to 1.6mm / s; and the wall and top / bottom speed to 15mm / s.

[0046] 4. Pre-printing, actual printing, and post-processing: The edge loading time is 30 seconds, and any blockages in the feed barrel are removed. The total print height is 50 mm. During actual printing, the first layer's print height requires manual adjustment of 0.3 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying at 60°C for 36 hours. Blow dry any dust from the surface and set aside.

[0047] 5. Pressureless Sintering Process Setup: Place the printed and dried raw material in a graphite mold, using 0.1mm graphite paper as insulation layers, with two layers of paper placed around the mold. The sintering process is as follows: 0-500°C, heating rate: 5°C / min; 500-900°C, heating rate: 10°C / min, hold at 900°C for 20 minutes; 900-1400°C, heating rate: 5°C / min, hold at 1400°C for 30 minutes; 1400-1900°C, heating rate: 10°C / min, hold at 1900°C for 30 minutes. Allow to cool in the furnace.

[0048] The final green strength of the lattice can be increased by 17.7% (compared with 65% solid content), the average hardness is 1.1GPa, and the average fracture toughness is 0.45MPa.m 1 / 2 The average hardness after sintering is 10.54Gpa, and the average fracture toughness is 1.22MPa.m 1 / 2 .

[0049] Example 4

[0050] A method for preparing a finished product of a high solid content (88%) direct writing 3D printing lattice boron carbide / SiC whisker ceramic slurry comprises the following steps:

[0051] 1. Premixing of B4C powder and toughening phase: Use a three-bar double-layer horizontal dry ball mill for ball milling. Mix boron carbide ceramics with a particle size of 0.5μm and toughening phase SiC whiskers at a mass ratio of 9.0:1.0. The ball barrel is made of high molecular organic materials such as polyurethane or nylon. 6mm, 8mm and 10mm zirconium dioxide balls are used for grinding at a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 2.5:1. The powder loading amount is 1 / 3 of the barrel. The roller speed is 11r / min.

[0052] 2. Printing slurry preparation: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is controlled at 1.5%; the binder is polyacrylic acid aqueous solution, and the addition amount is 0.01%; the lubricant is stearic acid emulsion AP27, and the addition amount is 0.5%. Pure water is added for mechanical stirring at a rate of about 5r / min and a stirring time of 40h, so that the water reducer is fully combined with the functional groups on the surface of the powder, and the solid content of the ceramic slurry is controlled to 88%. It is then tested with a rheological tester, using a 35mm diameter flat test rotor, a gap of 1mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0053] 3. Model import and slicing software settings: First, import the STL file in 3D drawing software into the slicing software Ultimaker Cure. The print range is X: 180mm; Y: 180mm; Z: 50mm; the number of prints is 1; the nozzle size is selected as 1.5, the surface mode is selected, and the outer contour is set to smooth; the output diameter is 0.6mm, the compensation value is 0.1mm; a certain Z-axis compensation is performed, and the compensation amount is 0.5mm; the single layer height is set to 0.5mm, the first layer height is 1mm, and the double line height is set to 2mm; there is no technical requirement for the thickness of the model exterior wall; the cap thickness is set to 1mm, and encryption printing is not set; the print temperature is set to 50℃; the print speed is 0.7mm / s; the wall and top / bottom speed is 10mm / s.

[0054] 4. Pre-printing, actual printing, and post-processing: Allow 1 minute for edge loading, remove any blockages from the feed barrel, and a total print height of 50 mm. During actual printing, manually adjust the first layer's print height by 0.3-0.5 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying at 80°C for 48 hours. Blow dry any dust from the surface and set aside.

[0055] 5. Pressureless sintering system setting: Place the printed and dried raw materials in a graphite mold, and use 0.1mm graphite paper as an isolation layer on the top, bottom, left and right sides, with 2 layers of graphite paper laid on the top and bottom sides. The sintering system is as follows: temperature 0-500℃, heating rate 5℃ / min; between 500-1600℃, heating rate 10℃ / min, 1600℃ holding temperature for 30 seconds. min Then, heat the sample to 2000°C at a rate of 10°C / min and hold for 30 minutes. Then cool the sample in the furnace.

[0056] The final green strength of the lattice can be increased by 27% (compared with 65% solid content), the average hardness is 2.0GPa, and the average fracture toughness is 0.36MPa.m 1 / 2 The average hardness after sintering is 13.1GPa, and the average fracture toughness is 1.78MPa.m 1 / 2 .

[0057] Example 5

[0058] A method for preparing a finished product of a high solid content (89%) direct writing 3D printing lattice boron carbide / Al2O3 ceramic slurry comprises the following steps:

[0059] 1. Premixing of B4C powder and toughening phase: Use a three-bar double-layer horizontal dry ball mill for ball milling. Mix boron carbide ceramics with a particle size of 0.5μm and toughening phase Al2O3 at a mass ratio of 9.0:1.0. The ball barrel is made of high molecular organic materials such as polyurethane or nylon. The grinding balls are 6mm, 8mm and 10mm zirconium dioxide balls at a mass ratio of 1:2:1. The ball-to-material ratio is controlled at 2.5:1. The powder loading amount is 1 / 3 of the barrel. The roller speed is 10r / min.

[0060] 2. Printing slurry preparation: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is controlled at 0.8%; the binder is polyacrylic acid aqueous solution, and the addition amount is 0.01%; the lubricant is stearic acid emulsion AP27, and the addition amount is 0.5%. Pure water is added for mechanical stirring at a rate of about 5r / min and a stirring time of 40h, so that the water reducer is fully combined with the functional groups on the surface of the powder, and the solid content of the ceramic slurry is controlled to be greater than 89%. The test was then carried out using a rheological tester, using a 35mm diameter flat test rotor, a gap of 1mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 The modulus test range is shear force from 1Pa to 1000Pa.

[0061] 3. Model import and slicing software settings: First, import the STL file in 3D drawing software into the slicing software Ultimaker Cure. The print range is X: 180mm; Y: 180mm; Z: 50mm; the number of prints is 1; the nozzle size is selected as 1.5, the surface mode is selected, and the outer contour is set to smooth; the output diameter is 0.6mm, the compensation value is 0.1mm; a certain Z-axis compensation is performed, and the compensation amount is 0.5mm; the single layer height is set to 0.5mm, the first layer height is 1mm, and the double line height is set to 2mm; there is no technical requirement for the thickness of the model exterior wall; the cap thickness is set to 1mm, and encryption printing is not set; the print temperature is set to 50℃; the print speed is 0.7mm / s; the wall and top / bottom speed is 10mm / s.

[0062] 4. Pre-printing, actual printing, and post-processing: Allow 1 minute for edge loading, remove any blockages from the feed barrel, and a total print height of 50 mm. During actual printing, manually adjust the first layer's print height by 0.3-0.5 mm. After printing, soak the feed barrel in pure water to prevent drying. Use vacuum drying at 80°C for 48 hours. Blow dry any dust from the surface and set aside.

[0063] 5. Pressureless sintering setup: Place the printed and dried raw material in a graphite mold, using two layers of 0.1mm graphite paper as insulation layers on the top, bottom, left, and right sides. The sintering schedule is as follows: 0-1100°C at a heating rate of 5°C / min; hold at 1100°C for 30 minutes; then increase the temperature to 1900°C at a rate of 10°C / min and hold for 30 minutes. Allow to cool in the furnace.

[0064] The final green strength of the lattice can be increased by 21.1% (compared with 65% solid content), the average hardness is 1.4GPa, and the average fracture toughness is 0.55MPa.m 1 / 2 The average hardness after sintering is 12.4GPa, and the average fracture toughness is 0.8MPa.m 1 / 2 .

Claims

1. A method for preparing a finished product by 3D printing boron carbide ceramic slurry, characterized in that: The 3D printing boron carbide ceramic slurry has a solid content of more than 85%, and is a direct writing 3D printing dot matrix boron carbide ceramic slurry. The method for preparing the finished product includes the following steps:

1. Premixing of B4C powder and toughening phase: Boron carbide ceramics with a particle size of 0.5-1.0 μm and toughening phase are mixed in a mass ratio of 9:1-10:0.1 and ball milled. 6mm, 8mm and 10mm zirconium dioxide balls are used. The ball-to-material ratio is controlled at 2.5:1-3.5:

1. The powder loading amount is 1 / 3-1 / 2 of the barrel. The roller speed is 10-15 r / min. The toughening phase is selected from multi-walled carbon nanotubes, rare earth oxides, SiC whiskers, and Al2O3.

2. Printing slurry preparation: Add additives in small batches to the mixture prepared in step 1. The additives include water reducers, binders and lubricants. The water reducer is polycarboxylic acid water reducer, and the addition amount is 0.5%~1.5%. The binder is polyacrylic acid aqueous solution resin or injection molding binder NE-119, and the addition amount is 0.01%~0.05%. The lubricant is stearic acid emulsion AP27, and the addition amount is 0.1%~0.5%. Pure water is added for mechanical stirring at a stirring rate of 5~15r / min and a stirring time of 30~40h, so that the water reducer is fully combined with the functional groups on the surface of the powder and the solid content of the ceramic slurry is controlled to be above 85%; then the rheological tester is used for testing, using a flat test rotor with a diameter of 30~35mm, a gap of 1~2mm, and a test temperature of room temperature; the test range of the viscosity test is a shear rate from 0.1s -1 Increase to 200s -1 , the modulus test range is shear stress from 1Pa to 1000Pa; 3. Model import and slicing software settings: First, import the STL file from the 3D drawing software into the slicing software Ultimaker Cure. Set the print range to 90-180mm (X), 90-180mm (Y), and 10-50mm (Z). Set the print quantity to 1. Select a nozzle size of 1.2-1.5, select surface mode, and set the outer contour to smooth. Set the output diameter to 0.4-0.6mm and the offset value to 0.1mm. Also set the single layer height to 0.3-0.5mm, the first layer height to 0.5-1mm, and the double line height to 1-2mm. Set the cap thickness to 0.5-1mm, the print temperature to 30-50°C, the print speed to 0.7-5mm / s, and the wall and top / bottom speed to 10-15mm / s.

4. Pre-printing, actual printing and post-processing: the edge material time is 30s~1min, the blockage of the feed barrel is discharged, and the total printing height is 10~50mm; vacuum drying is used to blow away the dust on the surface and then set aside; 5. Pressureless sintering system setting: Place the printed and dried raw materials in a graphite mold, and sinter with graphite paper as an isolation layer on the top, bottom, left and right sides. The sintering system is as follows: temperature 0~500℃, heating rate 5~10℃ / min, different temperature gradients need to be set after 500℃ depending on the additives; cool with the furnace.

2. The method for preparing a finished product by 3D printing boron carbide ceramic slurry according to claim 1, characterized in that: In the step 1, a three-bar double-layer horizontal dry ball mill is selected for ball milling, and the ball barrel is made of a high molecular organic material such as polyurethane or nylon; 6mm, 8mm and 10mm zirconium dioxide balls are added in a mass ratio of 1:2:

1.

3. The method for preparing a finished product by 3D printing boron carbide ceramic slurry according to claim 1, characterized in that: In step 3, a certain Z-axis compensation is performed, and the compensation amount is 0.3-0.5 mm.

4. The method for preparing a finished product by 3D printing boron carbide ceramic slurry according to claim 1, characterized in that: In step 4, the printing height of the first layer during the actual printing process needs to be adjusted by 0.3-0.5 mm.

5. The method for preparing a finished product by 3D printing boron carbide ceramic slurry according to claim 1, characterized in that: In step 4, the vacuum drying temperature is 60-80° C., and the drying time is 36-48 hours.