A SiBCN ceramic slurry for direct writing 3D printing and its preparation method and printing method

Abstract

A SiBCN ceramic slurry for direct-write 3D printing, its preparation method, and printing method, belonging to the field of ceramic additive manufacturing. The present invention aims to solve the problems of uneven selection and dispersion of SiBCN precursor fillers in existing direct-write printing. The slurry is prepared from solidified polyborosilazane (PBSZ) powder, an inorganic rheological additive, a rheological enhancer, and polyborosilazane (PBSZ) liquid. The preparation method includes the following steps: 1. solidifying the polyborosilazane (PBSZ); 2. ball milling; 3. weighing; and 4. preparing the slurry. The printing method includes the following steps: 1. printing a preform; 2. solidifying and sintering. The present invention is directed to SiBCN ceramic slurry for direct-write 3D printing, its preparation, and printing.

Description

Technical Field

[0001] The invention belongs to the field of ceramic additive manufacturing. Background Art

[0002] Real-time monitoring of internal pressure and temperature in aircraft turbine engines helps understand engine operating conditions and improve efficiency. SiBCN, a new type of multi-component silicon-based ceramic, exhibits significant application potential with enhanced thermal stability and superior mechanical properties. Its application in engine sensors could improve operational stability. Due to sensor application requirements, traditional preparation methods struggle to achieve complex SiBCN ceramic molding and optimized internal structure design. Combining SiBCN precursors with 3D printing technology, by manipulating the rheological properties of the slurry, allows for the molding of complex SiBCN ceramic structures, further expanding its application. However, the chemical sensitivity of the precursors poses a significant challenge in filler selection. The precursors are highly reactive and easily react with chemical additives. For SiBCN ceramics with high purity and high performance, strict control of the precursor's environmental factors during experimental processing is crucial. While inorganic fillers do not affect the precursor's properties, their chemical and physical properties differ from those of organic precursors, potentially preventing their proper dispersion. Therefore, filler selection is a challenging task and crucial for ensuring optimal final ceramic performance. Summary of the Invention

[0003] The present invention aims to solve the problems of uneven selection and dispersion of SiBCN precursor fillers in existing direct-write printing, and further provides a SiBCN ceramic slurry for direct-write 3D printing, a preparation method thereof, and a printing method.

[0004] A SiBCN ceramic slurry for direct-write 3D printing is prepared from 20% to 45% of cured polyborosilazane (PBSZ) powder, 3% to 6% of an inorganic rheological additive, 0% to 2% of a rheological enhancer, and the balance polyborosilazane (PBSZ) liquid in percentage by mass.

[0005] A method for preparing SiBCN ceramic slurry for direct-write 3D printing is carried out according to the following steps:

[0006] 1. Polyborosilazane PBSZ curing:

[0007] In a nitrogen atmosphere at a temperature of 200° C. to 500° C., the polyborosilazane PBSZ liquid is cured for 1 to 4 hours, and then cooled in the furnace to obtain a cured precursor;

[0008] 2. Ball mill crushing:

[0009] The solidified precursor is crushed by ball milling and sieved to obtain solidified polyborosilazane PBSZ powder;

[0010] 3. Weighing:

[0011] Weigh 20% to 45% of cured polyborosilazane PBSZ powder, 3% to 6% of inorganic rheological additive, 0% to 2% of rheological enhancer and the balance of polyborosilazane PBSZ liquid according to mass percentage;

[0012] 4. Slurry preparation:

[0013] The weighed solidified polyborosilazane PBSZ powder was added to the polyborosilazane PBSZ liquid and vacuum degassed, then an inorganic rheological additive was added and vacuum degassed, and finally a rheological enhancer was added and vacuum degassed to obtain SiBCN ceramic slurry for direct writing 3D printing.

[0014] A method for printing SiBCN ceramic slurry for direct-write 3D printing is carried out according to the following steps:

[0015] 1. Direct-write 3D printing SiBCN ceramic slurry is introduced into the printing syringe for degassing, and then printing is performed under the conditions of line spacing of 0.48mm to 0.54mm, printing layer thickness of 0.50mm to 0.60mm, pressure of 45Psi to 75Psi, printing speed of 5mm / min to 15mm / min, and printing nozzle size of 400μm to 800μm to obtain a printed blank;

[0016] 2. The printed blank is solidified and sintered to obtain a SiBCN ceramic structural part.

[0017] The beneficial effects of the present invention are:

[0018] The present invention uses solidified precursor powder as filler, which is homologous to the polyborosilazane (PBSZ) liquid and is used to adjust the viscosity of the slurry. While playing a supporting role, the two shrink synchronously during the sintering process, which can achieve better bonding and improve the density of the ceramic. The inorganic rheological additive can increase the network structure of the liquid molecules, prevent sedimentation, and improve the elasticity of the slurry. The use of a rheological enhancer can maximize the effectiveness of the rheological additive.

[0019] The slurry prepared in this way ensures the density and dispersion of ceramic materials, while also achieving high printing speeds and high material utilization, significantly reducing costs. The resulting ceramics achieve a flexural strength exceeding 90 MPa, a density exceeding 95%, and excellent formability, allowing for flexible fabrication of desired sizes and shapes, resulting in complex components. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are photos of the SiBCN ceramic structure printed in Example 1 before and after sintering, a is after curing and before sintering, b is after curing and sintering;

[0021] Figure 2 Rheological curves of SiBCN ceramic slurries for direct-write 3D printing prepared in Examples 1 and 2 and Comparative Experiments 1 and 2, (a) viscosity curve, (b) stress curve;

[0022] Figure 3 XRD patterns of SiBCN ceramic structures printed in Examples 1 and 2 and Comparative Experiments 1 and 2;

[0023] Figure 4 These are the fracture morphologies of SiBCN ceramic structural components printed in Examples 1 and 2 and Comparative Experiments 1 and 2, a) Comparative Experiment 1, b) Example 1, c) Example 2, d) Comparative Experiment 2. DETAILED DESCRIPTION

[0024] Specific embodiment 1: This embodiment is a SiBCN ceramic slurry for direct writing 3D printing, which is prepared by 20% to 45% of cured polyborosilazane PBSZ powder, 3% to 6% of inorganic rheological additive, 0% to 2% of rheological enhancer and the balance polyborosilazane PBSZ liquid.

[0025] The beneficial effects of this embodiment are:

[0026] This embodiment uses the solidified precursor powder as the filler, which is the same source as the polyborosilazane PBSZ liquid and is used to adjust the viscosity of the slurry. While playing a supporting role, the two shrink synchronously during the sintering process, which can achieve better bonding and improve the density of the ceramic; the inorganic rheological additive can increase the network structure of the liquid molecules, prevent sedimentation, and improve the elasticity of the slurry; and the use of a rheological enhancer can maximize the effectiveness of the rheological additive.

[0027] The slurry prepared in this way ensures the density and dispersion of ceramic materials, while also achieving high printing speeds and high material utilization, significantly reducing costs. The resulting ceramics achieve a flexural strength exceeding 90 MPa, a density exceeding 95%, and excellent formability, allowing for flexible fabrication of desired sizes and shapes, resulting in complex components.

[0028] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the inorganic rheological additive is one or a combination of nanoclay, fumed SiO2 and organically modified sheet silicate. Other aspects are the same as specific embodiment 1.

[0029] Specific embodiment 3: This embodiment differs from either specific embodiment 1 or 2 in that the SiBCN ceramic slurry for direct writing 3D printing is a gel-like fluid with shear-thinning properties. -1Under the conditions of , the viscosity is 1400Pa·s to 3000Pa·s. Other aspects are the same as those of the first or second embodiment.

[0030] Specific embodiment 4: This embodiment is a method for preparing SiBCN ceramic slurry for direct writing 3D printing, which is characterized by being carried out according to the following steps:

[0031] 1. Polyborosilazane PBSZ curing:

[0032] In a nitrogen atmosphere at a temperature of 200° C. to 500° C., the polyborosilazane PBSZ liquid is cured for 1 to 4 hours, and then cooled in the furnace to obtain a cured precursor;

[0033] 2. Ball mill crushing:

[0034] The solidified precursor is crushed by ball milling and sieved to obtain solidified polyborosilazane PBSZ powder;

[0035] 3. Weighing:

[0036] Weigh 20% to 45% of cured polyborosilazane PBSZ powder, 3% to 6% of inorganic rheological additive, 0% to 2% of rheological enhancer and the balance of polyborosilazane PBSZ liquid according to mass percentage;

[0037] 4. Slurry preparation:

[0038] The weighed solidified polyborosilazane PBSZ powder was added to the polyborosilazane PBSZ liquid and vacuum degassed, then an inorganic rheological additive was added and vacuum degassed, and finally a rheological enhancer was added and vacuum degassed to obtain SiBCN ceramic slurry for direct writing 3D printing.

[0039] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that the number average molecular weight of the polyborosilazane PBSZ liquid described in steps 1 and 3 is 600-800 and the viscosity is 8000 cp-20000 cp. Other aspects are the same as specific embodiment 4.

[0040] Specific embodiment 6: This embodiment differs from specific embodiment 4 or 5 in that in step 1, the polyborosilazane PBSZ liquid is heated to 200°C to 500°C at a heating rate of 1°C / min to 3°C / min under a nitrogen atmosphere. Other steps are the same as specific embodiment 4 or 5.

[0041] Specific embodiment 7: This embodiment differs from any one of specific embodiments 4 to 6 in that the ball milling in step 2 is performed for 2 to 6 hours at a ball milling speed of 200 to 300 r / min and a ball-to-material mass ratio of (10 to 20):1; and the particle size of the cured polyborosilazane (PBSZ) powder prepared in step 2 is 5 to 20 μm. Other aspects are the same as specific embodiments 4 to 6.

[0042] Specific embodiment eight: This embodiment differs from specific embodiments four to seven in that the vacuum degassing treatment described in step four is carried out according to the following steps: first, vacuum degassing for 60s to 120s at a vacuum degree of 90kPa to 102kPa and a rotation speed of 1500r / min to 2000r / min, then vacuum degassing for 100s to 200s at a vacuum degree of 50kPa to 70kPa and a rotation speed of 2000r / min to 2500r / min, and then vacuum degassing for 60s to 120s at a vacuum degree of 30kPa to 50kPa and a rotation speed of 1000r / min to 2000r / min. Other aspects are the same as specific embodiments four to seven.

[0043] Specific embodiment 9: This embodiment provides a method for printing SiBCN ceramic slurry for direct writing 3D printing, which is carried out according to the following steps:

[0044] 1. Direct-write 3D printing SiBCN ceramic slurry is introduced into the printing syringe for degassing, and then printing is performed under the conditions of line spacing of 0.48mm to 0.54mm, printing layer thickness of 0.50mm to 0.60mm, pressure of 45Psi to 75Psi, printing speed of 5mm / min to 15mm / min, and printing nozzle size of 400μm to 800μm to obtain a printed blank;

[0045] 2. The printed blank is solidified and sintered to obtain a SiBCN ceramic structural part.

[0046] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that: the degassing in step 1 is specifically carried out at a rotation speed of 2000-2500 r / min for 60-120 seconds; the curing in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 1-2°C / min to 120-160°C, followed by curing in a nitrogen atmosphere at a temperature of 120-160°C for 1-4 hours; the sintering in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 0.5-1.5°C / min to 900-1500°C, followed by sintering in a nitrogen atmosphere at a temperature of 900-1500°C for 1-4 hours. Other aspects are the same as specific embodiment 9.

[0047] The following examples are used to verify the beneficial effects of the present invention:

[0048] Example 1:

[0049] A method for preparing SiBCN ceramic slurry for direct-write 3D printing is carried out according to the following steps:

[0050] 1. Polyborosilazane PBSZ curing:

[0051] In a nitrogen atmosphere, the polyborosilazane PBSZ liquid was heated to 400°C at a heating rate of 1°C / min, and then the polyborosilazane PBSZ liquid was cured for 3 hours in a nitrogen atmosphere at 400°C, and then cooled in the furnace to obtain a cured precursor;

[0052] 2. Ball mill crushing:

[0053] The solidified precursor was ball-milled for 4 h at a ball-milling speed of 300 r / min and a ball-to-material mass ratio of 10:1, and then passed through a 100-mesh sieve to obtain solidified polyborosilazane PBSZ powder;

[0054] The particle size of the cured polyborosilazane PBSZ powder is 5 μm to 20 μm;

[0055] 3. Weighing:

[0056] Weigh 28% of the cured polyborosilazane PBSZ powder, 6% of the inorganic rheological additive and the balance of polyborosilazane PBSZ liquid according to mass percentage;

[0057] The inorganic rheological additive is fumed SiO2, which is purchased from Hubei Huifu Nanomaterials Co., Ltd.

[0058] 4. Slurry preparation:

[0059] The weighed solidified polyborosilazane PBSZ powder was added to the polyborosilazane PBSZ liquid and vacuum degassed. Then, an inorganic rheological additive was added and vacuum degassed. Finally, a rheological enhancer was added and vacuum degassed to obtain a SiBCN ceramic slurry for direct writing 3D printing, named 28% 400℃ + 6% SiO2.

[0060] The vacuum degassing treatment is carried out according to the following steps: first, vacuum degassing for 90 seconds at a vacuum degree of 100 kPa and a rotation speed of 2000 r / min, then vacuum degassing for 180 seconds at a vacuum degree of 50 kPa and a rotation speed of 2500 r / min, and then vacuum degassing for 90 seconds at a vacuum degree of 35 kPa and a rotation speed of 1500 r / min;

[0061] The SiBCN ceramic slurry for direct writing 3D printing is a gel-like fluid with shear thinning properties. -1 Under the conditions of , the viscosity is 1400Pa·s~1500Pa·s.

[0062] The polyborosilazane PBSZ liquid described in step 1 and step 3 has a number average molecular weight of 600 to 800 and a viscosity of 8000 cp to 20000 cp.

[0063] The printing method of the SiBCN ceramic slurry for direct writing 3D printing prepared above is carried out according to the following steps:

[0064] First, SiBCN ceramic slurry for direct-write 3D printing was introduced into the printing syringe for degassing. Printing was then performed under the following conditions: a line spacing of 0.54 mm, a print layer thickness of 0.56 mm, a pressure of 55 Psi, a print speed of 9 mm / min, and a print nozzle size of 600 μm to obtain a printed blank.

[0065] 2. The printed blank is solidified and sintered to obtain a SiBCN ceramic structural part.

[0066] The degassing described in step 1 is specifically carried out at a rotation speed of 2500r / min for 100s; the curing described in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 1°C / min to 150°C, and then in a nitrogen atmosphere and a temperature of 150°C, curing for 1h; the sintering described in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 0.5°C / min to 1000°C, and then in a nitrogen atmosphere and a temperature of 1000°C, sintering for 2h.

[0067] Example 2: This embodiment is different from the specific embodiment 1 in that: in the preparation method: in step 1, under a nitrogen atmosphere, the polyborosilazane PBSZ liquid is heated to 500°C at a heating rate of 1°C / min, and then the polyborosilazane PBSZ liquid is cured for 3 hours under the conditions of a nitrogen atmosphere and a temperature of 500°C; in step 3, 40% of the cured polyborosilazane PBSZ powder, 6% of the inorganic rheological additive and the balance of the polyborosilazane PBSZ liquid are weighed by mass percentage; the SiBCN ceramic slurry for direct writing 3D printing described in step 4 is a gel-like fluid with shear thinning properties, which is -1 Under the conditions of , the viscosity is 2300 Pa·s to 2500 Pa·s. The SiBCN ceramic slurry for direct-write 3D printing prepared in step 4 is named 40% 500°C + 6% SiO2. The printing method: pressure is 60 Psi, and the printing speed is 8 mm / min. Other steps are the same as those in Specific Embodiment 1.

[0068] Comparative Experiment 1: The difference between this embodiment and the specific embodiment 1 is that: in the preparation method: in step 1, under a nitrogen atmosphere, the polyborosilazane PBSZ liquid is heated to 160°C at a heating rate of 1°C / min, and then the polyborosilazane PBSZ liquid is cured for 3 hours under the conditions of a nitrogen atmosphere and a temperature of 160°C; in step 3, 40% of the cured polyborosilazane PBSZ powder, 6% of the inorganic rheological additive and the balance of the polyborosilazane PBSZ liquid are weighed by mass percentage; the SiBCN ceramic slurry for direct writing 3D printing described in step 4 is a gel-like fluid with shear thinning properties, which has a shear rate of 1s -1 Under the conditions of , the viscosity is 1400Pa·s to 1600Pa·s; the SiBCN ceramic slurry for direct writing 3D printing prepared in step 4 is named 40% 160℃ + 6% SiO2. Others are the same as the specific embodiment 1.

[0069] Comparative Experiment 2: The difference between this embodiment and the specific embodiment 1 is that: in the preparation method: in step 1, under a nitrogen atmosphere, the polyborosilazane PBSZ liquid is heated to 1000°C at a heating rate of 1°C / min, and then the polyborosilazane PBSZ liquid is cured for 3 hours under the conditions of a nitrogen atmosphere and a temperature of 1000°C; in step 3, 40% of the cured polyborosilazane PBSZ powder, 9% of the inorganic rheological additive and the balance of the polyborosilazane PBSZ liquid are weighed by mass percentage; the SiBCN ceramic slurry for direct writing 3D printing described in step 4 is a gel-like fluid with shear thinning properties, which has a shear rate of 1s -1 Under the conditions of , the viscosity is 2400 Pa·s to 2600 Pa·s. The SiBCN ceramic slurry for direct-write 3D printing prepared in step 4 is named 40% 1000°C + 9% SiO2. The printing method: pressure is 60 Psi, and the printing speed is 7 mm / min. Other steps are the same as those in Specific Embodiment 1.

[0070] Comparative Experiment 3: This embodiment differs from Specific Embodiment 1 in that: in the preparation method, in step 1, the polyborosilazane PBSZ liquid is heated to 160°C at a heating rate of 1°C / min under a nitrogen atmosphere, and then the polyborosilazane PBSZ liquid is cured under nitrogen at 160°C for 3 hours; in step 3, 45% of the cured polyborosilazane PBSZ powder and the remainder of the polyborosilazane PBSZ liquid are weighed by mass. Other methods are the same as Specific Embodiment 1.

[0071] The SiBCN ceramic slurry for direct writing 3D printing prepared in Example 3 is in a viscous gel state, and its rheology does not exhibit shear thinning behavior, indicating that the addition of inorganic rheological additives such as vapor-phase SiO2 is beneficial to improving the slurry formability.

[0072] Test and calculate based on the three-point test bending formula: Where L is the span (in mm), F is the failure strength (in MPa), h is the thickness (in mm), and b is the width (in mm). The printed sample for the performance test was a 6mm×4mm×35mm strip sample, with a straight fill pattern and a fill rate of 100%. The flexural strength of the SiBCN ceramic structure printed in Example 1 was 101.2MPa and the density was 1.67g / cm 3 The flexural strength of the SiBCN ceramic structure printed in Example 2 is 91.2 MPa and the density is 1.61 g / cm 3 , open porosity is 6.8%. Comparative Experiment 1: The bending strength of the SiBCN ceramic structure printed is 50.8MPa and the density is 1.69g / cm 3 , open porosity is 2.4%. Comparative Experiment 2: The strength of the SiBCN ceramic structure printed is 20.1MPa and the density is 1.58g / cm 3 , the open porosity is 20.1%.

[0073] Figure 1 Photos of the SiBCN ceramic structure printed in Example 1 before and after sintering. (a) shows the structure after curing and before sintering, and (b) shows the structure after curing and sintering. The images show that the slurry can be manipulated to form complex porous structures. The structure has a print size of 15×15 mm and a height of 5 mm, with a printing accuracy of ±10 μm. After sintering, the lateral shrinkage is 24.3%, and the longitudinal shrinkage is 18.8%.

[0074] Figure 2 Rheological curves of SiBCN ceramic slurries for direct-write 3D printing prepared in Examples 1 and 2 and Comparative Experiments 1 and 2, (a) viscosity curve, and (b) stress curve. As can be seen from the figures, in each embodiment, the Newtonian fluid can be converted into a non-Newtonian fluid by changing the additive ratio, which enhances the shear thinning behavior and apparent viscosity of the slurry, indirectly indicating that the slurry has print formability.

[0075] Figure 3 The XRD patterns of the SiBCN ceramic structures printed in Examples 1 to 2 and Comparative Experiments 1 to 2 are shown. As can be seen from the figure, the ceramics prepared in Examples 1 to 2 and Comparative Experiment 1 are amorphous, and the ceramic prepared in Comparative Experiment 2 has slight crystallization.

[0076] Figure 4The fracture morphologies of SiBCN ceramic structural parts printed for Examples 1 to 2 and Comparative Experiments 1 to 2 are as follows: a) Comparative Experiment 1, b) Example 1, c) Example 2, d) Comparative Experiment 2. Comparing the ceramic fractures, it can be clearly seen that the ceramic cross-sections prepared in Examples 1 to 2 and Comparative Experiment 1 are relatively dense, with no obvious pores. There are a large number of pores in the ceramic cross-section prepared in Comparative Experiment 2, which is also the main reason for the performance degradation. This is because the powder preparation temperature of Examples 1 to 2 and Comparative Experiment 1 is below the cracking temperature (900°C), and its property transformation is relatively low, with a high similarity to the properties of the organic precursor, which makes the powder dispersibility better. As the powder curing temperature increases, its cross-linking degree and properties gradually transform into inorganic structures, and the organic macromolecules gradually decompose. When the powder temperature is above the cracking temperature, such as in comparative experiment 2, the chemical property transformation caused by ceramicization increases the thermal expansion difference with the precursor, which makes the powder dispersibility worse, the slurry extrusion unstable, and the dispersion of the powder in the slurry reduced, resulting in sedimentation during printing, the introduction of a large amount of gas and defects, and the increase of porosity and the decrease of strength. In comparative experiment 1, although the density of the obtained ceramic is higher, its strength is lower than that of Example 1 and Example 2. This is because the preparation temperature of the filler powder in comparative experiment 1 is 160°C. Compared with Example 1 and Example 2, the cross-linking degree of its precursor is lower, and there are a large number of low molecular weight organic groups remaining. These organic groups can gradually fill the small pores during the sintering process, thereby forming a relatively dense microstructure; but low temperature curing may lead to an imperfect ceramic network structure and a lack of sufficient cross-linking density, resulting in a lower strength of the ceramic.

Claims

1. A SiBCN ceramic slurry for direct writing 3D printing, characterized in that The invention is prepared from 20% to 45% of solidified polyborosilazane PBSZ powder, 3% to 6% of inorganic rheological additive, 0% to 2% of rheological enhancer and the balance of polyborosilazane PBSZ liquid according to mass percentage. The above-mentioned method for preparing SiBCN ceramic slurry for direct writing 3D printing is carried out according to the following steps:

1. Polyborosilazane PBSZ curing: In a nitrogen atmosphere at a temperature of 200° C. to 500° C., the polyborosilazane PBSZ liquid is cured for 1 to 4 hours, and then cooled in the furnace to obtain a cured precursor; 2. Ball mill crushing: The solidified precursor is crushed by ball milling and sieved to obtain solidified polyborosilazane PBSZ powder; 3. Weighing: Weigh 20% to 45% of cured polyborosilazane PBSZ powder, 3% to 6% of inorganic rheological additive, 0% to 2% of rheological enhancer and the balance of polyborosilazane PBSZ liquid according to mass percentage; 4. Slurry preparation: The weighed solidified polyborosilazane PBSZ powder was added to the polyborosilazane PBSZ liquid and vacuum degassed, then an inorganic rheological additive was added and vacuum degassed, and finally a rheological enhancer was added and vacuum degassed to obtain SiBCN ceramic slurry for direct writing 3D printing.

2. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that The inorganic rheological additive is one or a combination of nanoclay, gas-phase SiO2 and organically modified sheet silicate.

3. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that The SiBCN ceramic slurry for direct writing 3D printing is a gel-like fluid with shear thinning properties. -1 Under the conditions of , the viscosity is 1400Pa·s~3000Pa·s.

4. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that The polyborosilazane PBSZ liquid described in step 1 and step 3 has a number average molecular weight of 600 to 800 and a viscosity of 8000 cp to 20000 cp.

5. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that In step 1, under a nitrogen atmosphere, the temperature of the polyborosilazane PBSZ liquid is raised to 200° C. to 500° C. at a heating rate of 1° C. / min to 3° C. / min.

6. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that The ball milling crushing described in step 2 is specifically carried out at a ball milling speed of 200r / min~300r / min and a ball-to-material mass ratio of (10~20):1 for 2h~6h; the particle size of the cured polyborosilazane PBSZ powder prepared in step 2 is 5μm~20μm.

7. The SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that The vacuum degassing treatment described in step 4 is carried out according to the following steps: first, under the conditions of a vacuum degree of 90kPa~102kPa and a rotation speed of 1500r / min~2000r / min, vacuum degassing for 60s~120s, then under the conditions of a vacuum degree of 50kPa~70kPa and a rotation speed of 2000r / min~2500r / min, vacuum degassing for 100s~200s, and then under the conditions of a vacuum degree of 30kPa~50kPa and a rotation speed of 1000r / min~2000r / min, vacuum degassing for 60s~120s.

8. A method for printing SiBCN ceramic slurry for direct writing 3D printing according to claim 1, characterized in that It is carried out in the following steps:

1. Direct-write 3D printing SiBCN ceramic slurry is introduced into the printing syringe for degassing, and then printing is performed under the conditions of line spacing of 0.48mm to 0.54mm, printing layer thickness of 0.50mm to 0.60mm, pressure of 45Psi to 75Psi, printing speed of 5mm / min to 15mm / min, and printing nozzle size of 400μm to 800μm to obtain a printed blank; 2. The printed blank is solidified and sintered to obtain a SiBCN ceramic structural part.

9. The method for printing SiBCN ceramic slurry for direct writing 3D printing according to claim 8, characterized in that The degassing described in step 1 is specifically carried out at a rotation speed of 2000r / min to 2500r / min for 60s to 120s; the curing described in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 1°C / min to 2°C / min to 120°C to 160°C, and then in a nitrogen atmosphere and at a temperature of 120°C to 160°C, curing for 1h to 4h; the sintering described in step 2 is specifically carried out in a nitrogen atmosphere at a heating rate of 0.5°C / min to 1.5°C / min to 900°C to 1500°C, and then in a nitrogen atmosphere and at a temperature of 900°C to 1500°C, sintering for 1h to 4h.

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