Method for preparing sibcn ceramic precursor by recycling by-product and product and application thereof

Abstract

The application discloses a preparation method of SiBCN ceramic precursor, a product and application thereof, and belongs to the technical field of ceramic materials. The preparation method comprises the following steps: taking chlorosilane, boron trichloride, optionally added or not added disilazane, and SiBCN ceramic precursor by-products as raw materials, and adopting a one-pot method to prepare SiBCN ceramic precursor, namely PBSZ, under the protection of an inert atmosphere and by heating reaction. The PBSZ by-products are recycled and used as raw materials to prepare the precursor, fundamentally solving the problem that the by-products generated in the process of preparing PBSZ by the one-pot method cannot be treated, reducing environmental pollution, effectively reducing production cost, and realizing the recyclable use of raw materials.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials, and relates to a SiBCN ceramic precursor, its preparation method and application, specifically to a method for preparing SiBCN ceramic precursor by recycling by-products, its products and applications. Background Technology

[0002] SiBCN ceramics possess excellent properties such as high temperature resistance, oxidation resistance, and high-temperature creep resistance, making them promising for applications and development in aerospace, weaponry, and other fields. The most common method for preparing SiBCN ceramics is the precursor pyrolysis conversion method. The most crucial step in this process is the preparation of the SiBCN ceramic precursor (i.e., polyborosilazane PBSZ). Currently, the most commonly used method is called the "one-pot method." The one-pot method for preparing the SiBCN ceramic precursor (PBSZ) has the advantages of being able to complete the process in a single reactor and having a simple reaction process. Numerous studies have been conducted both domestically and internationally on the one-pot method for PBSZ preparation.

[0003] Lee et al. (Journal of Non-Crystalline Solids, 2005, 351(37-39):2995-3005) used HSiCl3, BCl3 and hexamethyldisilazane (MM) N Using PBSZ as raw material, after treatment at 200℃, followed by cooling and vacuum distillation, further polycondensation was carried out to obtain a difficult-to-process, infusible, and insoluble solid PBSZ.

[0004] CN101274941B uses HSiCl3, BCl3 and heptamethyldisilazane as raw materials. After treatment at 150-500℃, it is further distilled under reduced pressure at a certain temperature to obtain fusible and soluble solid PBSZ.

[0005] Zhang et al. (Journal of Materials Science, 2011, 46(18): 5940-5947) used CH3(H)SiCl2, BCl3, C2H3CH3SiCl2 and MM N The raw material was treated at 200℃ and then further distilled under reduced pressure at a certain temperature to obtain liquid PBSZ.

[0006] The methods for preparing PBSZ mentioned above all include steps of atmospheric pressure and high temperature treatment and decompression polymerization to remove small molecule byproducts. However, they do not address the post-treatment of small molecule byproducts generated during the synthesis process. Furthermore, due to the removal of these byproducts, the final synthesis yield is not high, resulting in high production costs. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for preparing SiBCN ceramic precursor (PBSZ) using PBSZ byproducts. This invention can realize the reasonable recycling and reuse of PBSZ byproducts, reduce the production cost of PBSZ, and realize the recyclability of raw materials.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing a SiBCN ceramic precursor, the method comprising the following steps:

[0010] Using chlorosilane, boron trichloride, optional disilazane, and SiBCN ceramic precursor byproducts as raw materials, a one-pot method was adopted to prepare SiBCN ceramic precursor, namely PBSZ, by heating and reaction under an inert atmosphere.

[0011] According to the present invention, the method further includes a vacuum distillation step after the heating reaction, and then PBSZ is prepared.

[0012] According to the present invention, the SiBCN ceramic precursor byproduct, i.e., the PBSZ byproduct, is a byproduct formed in the vacuum distillation step of the preparation method. Unless otherwise specified, the byproduct is used only for the preparation of PBSZ with the same process and composition.

[0013] According to the present invention, the PBSZ byproduct can be separated and purified before the reaction, and the supernatant is used as the reaction raw material. Specifically, centrifugation is used for purification. More specifically, the centrifugation speed is 2000–20000 rpm, and the centrifugation time is 15–60 min. The centrifugation is carried out at room temperature.

[0014] According to the present invention, the PBSZ byproduct (or SiBCN ceramic precursor byproduct) comprises, by weight percentage, 10-50 wt.% disilazane, 1-10 wt.% borazane, and the balance being silazane oligomers. In this invention, the disilazane content in the byproduct can be confirmed by GC-MS.

[0015] According to the present invention, the molar ratio of disilazane to Cl in the raw materials is 1:0.5 to 1:1.8. Disilazane includes disilazane contained in the PBSZ byproduct and disilazane additionally added to the raw materials; Cl includes Cl contained in the raw material chlorosilane and boron trichloride. Specifically, the molar ratio is 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, or 1:1.8.

[0016] According to the present invention, the molecular formula of the disilazane is (R 1 R 2 2Si)2NH, where R 1 R 2 They may be the same or different, and are independent of each other, selected from one of the following groups: C 1-12 Alkyl; C 2-12 alkenyl; C 6-20 Aryl.

[0017] Preferably, R 1 R 2 They may be the same or different, and are independent of each other, selected from one of the following groups: C 1-6 Alkyl; C 2-6 alkenyl; C 6-14 Aryl.

[0018] Preferably, R 1 R 2 They may be the same or different, and are independent of each other, selected from one of the following groups: H, methyl, ethyl, vinyl, propyl, butyl, or phenyl.

[0019] For example, the disilazane is selected from hexamethyldisilazane or tetramethyldivinyldisilazane.

[0020] According to the present invention, the molar ratio of boron trichloride and chlorosilane is 10:1 to 1:10, preferably 5:1 to 1:5.

[0021] According to the present invention, the molar ratio of the SiBCN ceramic precursor byproduct to disilazane in the raw materials can be 1:0 to 1:10, for example, 1:0, 1:0.2 to 1:5, 1:0.5 to 1:3, or 1:0.8 to 1:2. Specifically, it can be 1:0, 1:0.2, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0022] According to the present invention, the molar ratio of the chlorosilane and the SiBCN ceramic precursor by-product in the raw materials is 1:0.1 to 1:3, preferably 1:0.5 to 1:2.5; exemplary ratios are 1:0.1, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.25, 1:1.5, 1:1.8, 1:2, 1:2.4, 1:2.5 or 1:3.

[0023] According to the present invention, the molecular formula of the chlorosilane is R 3 R 4 SiCl2, where R 3 R 4They may be the same or different, and are independent of each other, selected from one of the following groups: H, C 1-12 Alkyl, C 2-12 alkenyl, C 6-20 Aryl.

[0024] Specifically, R 3 R 4 They may be the same or different, and are independent of each other, selected from one of the following groups: H, C 1-8 alkyl, C 2-4 alkenyl, C 6-12 Aryl.

[0025] For example, the chlorosilane is selected from at least one of methylvinyldichlorosilane, methyldichlorosilane, dimethyldichlorosilane, and diphenyldichlorosilane.

[0026] According to the present invention, the reaction is carried out in an organic solvent. Specifically, the organic solvent may be an alkane, an aromatic or furan solvent, exemplarily tetrahydrofuran, n-hexane, toluene, etc.

[0027] According to the present invention, the amount of organic solvent added is 3 to 10 times the combined volume of chlorosilane and boron trichloride.

[0028] According to the present invention, the method comprises: mixing chlorosilane, boron trichloride and an organic solvent, then adding disilazane and PBSZ byproduct, heating and reacting under an inert atmosphere, and distilling under reduced pressure to prepare PBSZ.

[0029] According to the present invention, the temperature at which chlorosilane, boron trichloride, disilazane and PBSZ byproduct are added is -10°C to -30°C.

[0030] According to the present invention, the conditions for heating reaction and vacuum distillation are as follows: first, holding at 150–300°C for 2–24 hours, then cooling to 50–250°C for vacuum distillation for 0.5–3 hours. Preferably, the holding temperature is 150–250°C, more preferably, the holding time is 6–12 hours; exemplaryly, the holding temperatures are 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, and 250°C.

[0031] According to the present invention, the reaction heating rate is 0.5 to 10 °C / min, preferably 0.5 to 8 °C / min, more preferably 0.5 to 6 °C / min, most preferably 0.5 to 2 °C / min, and specifically, it can be 0.5 °C / min, 1 °C / min, 1.5 °C / min, or 2 °C / min.

[0032] According to the present invention, the temperature of vacuum distillation can be 50-250°C, preferably 100-220°C, more preferably 150-220°C, most preferably 180-220°C, and specifically, can be 100, 120, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or 220°C.

[0033] According to the present invention, the time for vacuum distillation can be 0.5 to 3 hours, preferably 1 to 2 hours, and specifically 1 hour, 1.5 hours, or 2 hours.

[0034] According to the present invention, the viscosity of the SiBCN ceramic precursor at 25°C is 5000–500000 cp. In this invention, the viscosity of the SiBCN ceramic precursor can be adjusted by the reaction time and reaction temperature.

[0035] According to the present invention, the yield of the SiBCN ceramic precursor is 70% or more.

[0036] According to the present invention, the preparation method of the SiBCN ceramic precursor specifically includes the following steps:

[0037] (1) The PBSZ byproduct (or SiBCN ceramic precursor byproduct) is centrifuged at room temperature, with the speed controlled at 2000-20000 rpm and the centrifugation time at 15-60 min. The supernatant is taken as the raw material for subsequent reaction, i.e. the purified PBSZ byproduct.

[0038] (2) The reactor equipped with a stirrer, peristaltic pump and distillation device is repeatedly evacuated and replaced with an inert atmosphere at least three times;

[0039] (3) Cool the reactor to -10 to -30°C, add an organic solvent to the reactor, and add boron trichloride gas (or boron trichloride solution) and chlorosilane to the reactor in proportion, dissolving them in the organic solvent;

[0040] (4) Mix the disilazane and the purified PBSZ byproduct evenly; add the mixed solution dropwise into the reactor, and keep the reactor temperature at -10 to -30°C during the dropwise addition process while stirring.

[0041] (5) After the addition is complete, slowly heat the reactor to 150-300℃ (preferably 150-250℃) and keep it at that temperature for 2-24 hours (preferably 6-12 hours);

[0042] (6) Reduce the temperature of the reactor to 50-250°C (preferably 100-220°C) and distill under reduced pressure for 0.5-3 hours (preferably 1-2 hours) to remove low molecular weight. After removing the low molecular weight, reduce the temperature of the reactor to room temperature under inert gas protection to obtain the SiBCN ceramic precursor, i.e., PBSZ. The removed low molecular weight can be collected and reused.

[0043] In step (4) of this invention, the dripping rate is not particularly limited, as long as the temperature of the reactor is maintained at -10 to -30°C.

[0044] The present invention also provides a SiBCN ceramic precursor prepared by the above-described method for preparing SiBCN ceramic precursor.

[0045] The present invention also provides a SiBCN ceramic, which is prepared by curing and pyrolysis of the above-mentioned SiBCN ceramic precursor.

[0046] The present invention also provides the application of the above-mentioned SiBCN ceramic precursor in ceramic matrix composites, ceramic fibers, ceramic coatings, ceramic bulk materials, etc.

[0047] Beneficial effects of the present invention

[0048] The PBSZ prepared by this invention is composed of elements such as Si, B, C, N, and H. By adjusting the proportions of the raw materials, it can be prepared into liquid or solid meltable polymers of different viscosities. The prepared PBSZ can be used to prepare ceramic matrix composites, ceramic fibers, ceramic coatings, and ceramic bulk materials.

[0049] PBSZ byproducts contain disilazane, silazane oligomers, trace amounts of organic solvents, and trace amounts of halosilanes. Due to their good compatibility and similar boiling points, effective and complete separation through distillation is impossible, making the recovery and reuse of disilazane difficult. Furthermore, the byproducts possess a certain degree of toxicity and environmental pollution, making direct discharge impossible and causing environmental impact. This invention reuses PBSZ byproducts as raw materials, fundamentally solving the problem of unmanageable byproducts generated during the "one-pot" PBSZ preparation process. This reduces environmental pollution, effectively lowers production costs, and achieves the recyclability of raw materials. Attached Figure Description

[0050] Figure 1 The PBSZ prepared in Example 1 1 H-NMR spectrum.

[0051] Figure 2 The PBSZ prepared in Example 1 29 Si-NMR spectrum.

[0052] Figure 3The PBSZ prepared in Example 1 11 B-NMR spectrum.

[0053] Figure 4 The infrared spectrum of PBSZ prepared in Example 1 is shown.

[0054] Figure 5 The thermogravimetric spectrum of PBSZ prepared in Example 1 is shown.

[0055] Figure 6 The image shows the GPC spectrum of PBSZ prepared in Example 1.

[0056] Figure 7 The thermogravimetric spectrum of PBSZ prepared in Example 1 after thermal curing is shown.

[0057] Figure 8 The image shows the XPS spectrum of PBSZ after thermosetting prepared in Example 1.

[0058] Figure 9 The thermogravimetric spectrum of PBSZ prepared in Example 5 is shown. Detailed Implementation

[0059] Terminology Definitions and Explanations

[0060] The term "halogen" refers to fluorine, chlorine, bromine, and iodine.

[0061] Term "C" 1-12 "Alkyl" should be understood to refer to straight-chain and branched alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms. 1-6 "Alkyl" means a straight-chain or branched alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, or their isomers.

[0062] Term "C" 2-12 "Alkenyl" should be understood to preferably represent a straight or branched monovalent hydrocarbon group containing one or more double bonds and having 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms, for example, having 2, 3, 4, 5 or 6 carbon atoms (i.e., C...). 2-6 alkenyl), having 2 or 3 carbon atoms (i.e., C24, C34, C4 ... 2-3Alkenyl). It should be understood that when the alkenyl group contains more than one double bond, the double bonds may be separable or conjugated. The alkenyl group is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, (E)-but-1-enyl, (Z)-but-1-enyl, pent-4-enyl, (E)-pent-3-enyl, (Z)-pent-3-enyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)- Pentyl-1-enyl, (Z)-pentyl-1-enyl, hex-5-enyl, (E)-hex-4-enyl, (Z)-hex-4-enyl, (E)-hex-3-enyl, (Z)-hex-3-enyl, (E)-hex-2-enyl, (Z)-hex-2-enyl, (E)-hex-1-enyl, (Z)-hex-1-enyl, isopropenyl, 2-methylprop-2-enyl, 1-methylprop-2-enyl 2-Methylprop-1-enyl, (E)-1-methylprop-1-enyl, (Z)-1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E)-2-methylbut-2-enyl, (Z)-2-methylbut-2-enyl, (E)-1-methylbut-2-enyl, (Z)-1-methyl But-2-enyl, (E)-3-methylbut-1-enyl, (Z)-3-methylbut-1-enyl, (E)-2-methylbut-1-enyl, (Z)-2-methylbut-1-enyl, (E)-1-methylbut-1-enyl, (Z)-1-methylbut-1-enyl, 1,1-dimethylprop-2-enyl, 1-ethylprop-1-enyl, 1-propylvinyl, 1-isopropylvinyl.

[0063] Term "C" 6-20 "Aryl" should be understood to preferably represent a monocyclic, bicyclic, or tricyclic hydrocarbon ring having 6 to 20 carbon atoms and possessing monovalent aromaticity or partial aromaticity, preferably "C". 6-14 Aryl. The term "C" 6-14 "Aryl" should be understood to preferably represent a monovalent aromatic or partially aromatic monocyclic, bicyclic, or tricyclic hydrocarbon ring ("C") having 6, 7, 8, 9, 10, 11, 12, 13, or 14 carbon atoms. 6-14 Aryl), particularly a ring with 6 carbon atoms (“C6 aryl”), such as phenyl; or biphenyl, or a ring with 9 carbon atoms (“C9 aryl”), such as indenyl or indenyl, or a ring with 10 carbon atoms (“C9 aryl”). 10 Aryl groups, such as tetrahydronaphthyl, dihydronaphthyl, or naphthyl, or rings with 13 carbon atoms (“C”). 13 Aryl groups, such as fluorene groups, or rings with 14 carbon atoms (“C”). 14 Aryl), for example, anthracene. When the C6-20 When the aryl group is substituted, it can be monosubstituted or polysubstituted. Furthermore, there are no restrictions on the substitution site; for example, it can be ortho, para, or meta substituted.

[0064] The inert atmosphere referred to in this invention is nitrogen or argon, and the entire reaction process is carried out under the protection of an inert atmosphere.

[0065] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0066] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0067] Example 1

[0068] A 250ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -20°C using a high-low temperature circulation device. 100ml of n-hexane was added to the reaction flask, and 0.1mol of boron trichloride gas was introduced while stirring. 0.1mol of methylvinyldichlorosilane and 0.1mol of methyldichlorosilane were then added, and the mixture was mechanically stirred at 400rpm for 30 minutes until homogeneous. Under nitrogen protection, 0.3mol of purified PBSZ byproducts (containing 50wt% disilazane, 5wt% borazane, and 45wt% silazane oligomers) and 0.3mol of hexamethyldisilazane were thoroughly mixed in a single-necked flask and slowly added dropwise using a peristaltic pump, with the dropping rate appropriately controlled to ensure the temperature inside the flask remained between -20°C and -10°C throughout the addition process.

[0069] After the addition was complete, the high and low temperature cycling device's cooling function was turned off. The system was slowly raised to room temperature while stirring, and stirring continued at room temperature for 2 hours. The high and low temperature cycling heating function was then turned on, and the system was heated to 250℃ (hexane solvent had already been distilled off) at a rate of 1℃ / min. This temperature was maintained for 6 hours, then reduced to 180℃ under reduced pressure to remove small molecule byproducts, and maintained for 1 hour. After the reduced pressure process, the system was cooled to room temperature to obtain liquid PBSZ, i.e., the SiBCN ceramic precursor. The yield of PBSZ was 78%, and its viscosity at 25℃ was 8337 cP. 1 H-NMR, 29 Si-NMR, 11 B-NMR and infrared spectra are as follows: Figures 1-4 As shown.

[0070] Figure 1 For the prepared PBSZ 1 The ¹H-NMR spectrum shows that the prepared PBSZ contains chemical bonds such as Si-H, Si-Me, NH, and Si-Vi (Vi being vinyl). 1 The absence of characteristic peaks for the solvent hexane in the H-NMR spectrum indicates that the solvent was distilled off during the reaction, and the final product PBSZ does not contain any solvent.

[0071] Figure 2 For the prepared PBSZ 29 The Si-NMR spectrum shows that the prepared PBSZ has a complex chemical structure, with chemical environments such as Si-N-Si, Si-NB, ViMeSiN2 (Vi is vinyl), MeHSiN2, and SiN3C.

[0072] Figure 3 For the prepared PBSZ 11 The B-NMR spectrum shows a relatively uniform peak, indicating that B elements in PBSZ exist in a BN3 environment.

[0073] Figure 4 The infrared spectrum of the prepared PBSZ is shown below. Figure 4 It can be seen that the prepared PBSZ contains chemical bonds such as NH, =CH, C-H3, Si-H, C=C, BN, and Si-N-Si.

[0074] Figure 5 The thermogravimetric curves of the prepared PBSZ are shown. The prepared liquid PBSZ was heated to 1000℃ at a rate of 10℃ / min under a nitrogen atmosphere, with a ceramic yield of 42.3%.

[0075] Figure 6 The image shows the GPC spectrum of the prepared PBSZ. Gel permeation chromatography analysis showed that the number-average molecular weight of the prepared PBSZ was 1056, the weight-average molecular weight was 1871, and the dispersion index was 1.77.

[0076] Figure 7 Thermogravimetric analysis (TGA) curves of the prepared PBSZ after thermal curing are shown. Under nitrogen protection, 0.5% (w / w) of dicumyl peroxide was added as a catalyst, and the mixture was cured at 170°C for 2 hours to obtain the PBSZ cured product. The weight loss during curing was less than 3%. Thermogravimetric analysis was performed on the PBSZ cured product. Under nitrogen atmosphere, the temperature was increased to 1000°C at a rate of 10°C / min, and the ceramic yield was 67.7% (the ceramic yield refers to the percentage of residual mass of the PBSZ cured product at 1000°C).

[0077] Figure 8The XPS spectrum of the prepared PBSZ after thermosetting shows that there are no binding energy characteristic peaks between 198 and 206, proving that the prepared PBSZ does not contain impurity chlorine.

[0078] Example 2

[0079] A 1000ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated three times to purge with argon, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -30℃ using a high-low temperature circulation device. 400ml of a hexane solution of BCl3 (with boron trichloride concentration of 1mol / L in hexane) and 0.8mol of dimethyldichlorosilane were added sequentially to the flask, and the mixture was mechanically stirred at 400rpm for 30 minutes until homogeneous. Under nitrogen protection, 2mol of PBSZ byproducts (50wt% disilazane, 5wt% borazane, and 45wt% silazane oligomers) and 0.4mol of hexamethyldisilazane were thoroughly mixed in a single-necked flask and slowly added dropwise using a peristaltic pump, with the dropping rate appropriately controlled to ensure the temperature inside the flask remained between -20℃ and -10℃ throughout the addition process.

[0080] After the addition was complete, the cooling function of the high-low temperature cycling device was turned off. The system was slowly raised to room temperature while stirring, and stirring continued at room temperature for 2 hours. The heating function of the high-low temperature cycling device was then turned on, and the system was raised to 220°C at a heating rate of 0.5°C / min (hexane solvent had already been distilled off). After holding at this temperature for 4 hours, the temperature was lowered to 100°C and reduced under reduced pressure to remove small molecule byproducts. This temperature was held for 30 minutes. After the reduced pressure was removed, the system was lowered to room temperature to obtain liquid PBSZ with a viscosity of 7536 cp and a yield of 73%.

[0081] Example 3

[0082] A 5000ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -20℃ using a high-low temperature circulation device. 2000ml of tetrahydrofuran solution of BCl3 (1mol / L boron trichloride in tetrahydrofuran) and 5mol of diphenyldichlorosilane were added sequentially to the flask, and the mixture was mechanically stirred at 400rpm for 30min until homogeneous. Under nitrogen protection, 16mol of PBSZ byproducts (50wt% disilazane, 5wt% borazane, and 45wt% silazane oligomers) were slowly added dropwise to the flask using a peristaltic pump, with the dropping rate appropriately controlled to ensure the temperature inside the flask remained between -20℃ and -10℃ throughout the addition process.

[0083] After the addition was complete, the cooling function of the high-low temperature cycling device was turned off. The system was slowly raised to room temperature while stirring, and stirring continued at room temperature for 2 hours. The heating function of the high-low temperature cycling device was turned on, and the system was raised to 250℃ at a heating rate of 1.5℃ / min (the tetrahydrofuran solvent had been distilled off). After holding at this temperature for 8 hours, the temperature was lowered to 150℃ and the pressure was reduced to remove small molecule byproducts. The temperature was held for 30 minutes. After the pressure reduction was completed, the system was lowered to room temperature to obtain solid PBSZ with a yield of 75%.

[0084] Example 4

[0085] A 250ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -15℃ using a high-low temperature circulation device. 100ml of a hexane solution of BCl3 (with a boron trichloride concentration of 1mol / L in hexane), 0.1mol of methyldichlorosilane, and 0.1mol of diphenyldichlorosilane were added to the reaction flask sequentially, and the mixture was mechanically stirred at 400rpm for 30min until homogeneous. Under nitrogen protection, 0.2 mol of PBSZ byproducts (50 wt% disilazane, 5 wt% borazane, and 45 wt% silazane oligomers) and 0.4 mol of tetramethyldivinyldisilazane were thoroughly mixed in a single-necked flask and slowly added dropwise to the flask using a peristaltic pump. The dropping rate was appropriately controlled to ensure that the temperature inside the flask was maintained between -20 and -10 °C during the dropping process.

[0086] After the addition was complete, the cooling function of the high-low temperature cycling device was turned off. The system was slowly raised to room temperature while being stirred, and stirring continued at room temperature for 2 hours. The heating function of the high-low temperature cycling device was then turned on, and the system was raised to 220°C at a heating rate of 1°C / min (the tetrahydrofuran solvent had already been distilled off). After holding at this temperature for 4 hours, the system was further heated under reduced pressure at 220°C to remove small molecule byproducts for 30 minutes. After the reduced pressure stage, the system was cooled to room temperature to obtain solid PBSZ with a yield of 73%.

[0087] Example 5

[0088] A 250ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -15℃ using a high-low temperature circulation device. 100ml of tetrahydrofuran solution of BCl3 (the concentration of boron trichloride in tetrahydrofuran was 1mol / L), 0.1mol of methyldichlorosilane, and 0.1mol of methylvinyldichlorosilane were added to the reaction flask sequentially. The mixture was mechanically stirred at 400rpm for 30min until homogeneous. Under nitrogen protection, 0.1 mol of PBSZ byproducts (50 wt% disilazane, 5 wt% borazane, and 45 wt% silazane oligomers) and 0.5 mol of tetramethyldivinyldisilazane were thoroughly mixed in a single-necked flask and slowly added dropwise to the flask using a peristaltic pump. The dropping rate was appropriately controlled to ensure that the temperature inside the flask was maintained between -20 and -10°C throughout the dropping process.

[0089] After the addition was complete, the cooling function of the high-low temperature cycling device was turned off. The system was slowly raised to room temperature while being stirred, and stirred at room temperature for 2 hours. The heating function of the high-low temperature cycling device was then turned on, and the system was raised to 200°C at a heating rate of 2°C / min (the tetrahydrofuran solvent had already been distilled off). After holding at this temperature for 4 hours, the system was further heated under reduced pressure at 200°C to remove small molecule byproducts, and held at this temperature for 2 hours. After the reduced pressure stage, the system was cooled to room temperature to obtain liquid PBSZ with a viscosity of 7892 cp and a yield of 76%.

[0090] Figure 9 The thermogravimetric spectrum (TGA) of the PBSZ prepared in Example 5 is shown. The prepared liquid PBSZ was heated to 1000°C at a rate of 10°C / min under a nitrogen atmosphere, with a ceramic yield of 54.5%.

[0091] Example 6

[0092] A 250ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction process was protected by nitrogen. The temperature inside the reaction flask was lowered to -15℃ using a high-low temperature circulation device. 100ml of tetrahydrofuran solution of BCl3 (1mol / L concentration of boron trichloride in tetrahydrofuran) and 0.2mol of methyldichlorosilane were added sequentially to the reaction flask, and the mixture was mechanically stirred at 400rpm for 30min until homogeneous. Under nitrogen protection, 0.4mol of PBSZ byproducts (50wt% disilazane, 5wt% borazane, and 45wt% silazane oligomers) and 0.2mol of tetramethyldisilazane were thoroughly mixed in a single-necked flask and slowly added dropwise using a peristaltic pump, with the dropping rate appropriately controlled to ensure the temperature inside the flask remained between -20℃ and -10℃ throughout the addition process.

[0093] After the addition was complete, the cooling function of the high-low temperature cycling device was turned off. The system was slowly raised to room temperature while stirring, and stirring continued at room temperature for 2 hours. The heating function of the high-low temperature cycling device was then turned on, and the system was raised to 250°C at a heating rate of 1°C / min (the tetrahydrofuran solvent had already been distilled off). After holding at this temperature for 4 hours, the temperature was lowered to 150°C and reduced under reduced pressure to remove small molecule byproducts. This was held for 2 hours. After the reduced pressure stage, the system was lowered to room temperature to obtain liquid PBSZ with a viscosity of 5674 cp and a yield of 71%.

[0094] Comparative Example 1

[0095] A 250ml four-necked round-bottom flask was dried and connected to a mechanical stirrer, a spherical condenser, a thermometer, a peristaltic pump, and a gas delivery device. The reaction apparatus was evacuated and purged with nitrogen three times, and the entire reaction was protected by nitrogen. The temperature inside the reaction flask was lowered to -20°C using a high-low temperature circulation device. 100ml of n-hexane was added to the flask, and 0.1mol of boron trichloride gas was introduced while stirring. 0.1mol of methylvinyldichlorosilane and 0.1mol of methyldichlorosilane were then added, and the mixture was mechanically stirred at 400rpm for 30 minutes until homogeneous. Under nitrogen protection, 0.6mol of hexamethyldisilazane was thoroughly mixed in a single-necked flask and slowly added dropwise using a peristaltic pump, with the dropping rate appropriately controlled to ensure the temperature inside the flask remained between -20°C and -10°C throughout the addition process.

[0096] After the addition was complete, the high and low temperature cycling device was turned off. The system was slowly raised to room temperature while being stirred, and stirring continued at room temperature for 2 hours. The high and low temperature cycling heating function was turned on, and the system was raised to 250℃ at a heating rate of 1℃ / min (hexane solvent had been distilled off), and held at this temperature for 6 hours. The temperature was then lowered to 180℃ to remove small molecule byproducts under reduced pressure, and held at this temperature for 1 hour. After the reduced pressure process was completed, the system was lowered to room temperature to obtain liquid PBSZ, i.e., SiBCN ceramic precursor. The yield of PBSZ was 56%, and the viscosity at 25℃ was 5674 cP.

[0097] The embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a SiBCN ceramic precursor, characterized in that, The method includes the following steps: Using chlorosilane, boron trichloride, optional disilazane, and SiBCN ceramic precursor byproducts as raw materials, a one-pot method was adopted to prepare SiBCN ceramic precursor, namely PBSZ, by heating and reaction under an inert atmosphere. The SiBCN ceramic precursor byproducts comprise, by weight percentage, 10-50 wt.% disilazane, 1-10 wt.% borazane, and the balance being silazane oligomers. In the raw materials, the molar ratio of the chlorosilane and the SiBCN ceramic precursor byproduct is 1:0.1 to 1:3; The heating reaction conditions are: keep at 150~300℃ for 2~24 hours.

2. The method according to claim 1, characterized in that, The method further includes a vacuum distillation step after the heating reaction, and then PBSZ is prepared.

3. The method according to claim 1, characterized in that, The molecular formula of the disilazane is (R 1 R 2 2Si)2NH, where R 1 R 2 They may be the same or different, and are independent of each other, selected from one of the following groups: C 1-12 Alkyl; C 2-12 alkenyl; C 6-20 Aryl.

4. The method according to claim 3, characterized in that, The disilazane is selected from hexamethyldisilazane or tetramethyldivinyldisilazane.

5. The method according to claim 1, characterized in that, In the raw materials, the molar ratio of boron trichloride to chlorosilane is 10:1 to 1:

10.

6. The method according to claim 1, characterized in that, In the raw materials, the molar ratio of the SiBCN ceramic precursor byproduct to disilazane is 1:0 to 1:

10.

7. The method according to claim 1, characterized in that, The molecular formula of the chlorosilane is R 3 R 4 SiCl2, where R 3 R 4 They may be the same or different, and are independent of each other, selected from one of the following groups: H, C 1-12 Alkyl, C 2-12 alkenyl, C 6-20 Aryl.

8. The method according to claim 7, characterized in that, The chlorosilane is selected from at least one of methylvinyldichlorosilane, methyldichlorosilane, dimethyldichlorosilane, and diphenyldichlorosilane.

9. The method according to claim 1, characterized in that, The method includes: mixing chlorosilane, boron trichloride and an organic solvent, then adding disilazane and SiBCN ceramic precursor byproducts, heating and reacting under an inert atmosphere, and distilling under reduced pressure to prepare PBSZ.

10. The method according to claim 9, characterized in that, The conditions for heating reaction and vacuum distillation are as follows: first, keep the temperature at 150~300℃ for 2~24 hours, then cool down to 50~250℃ and distill under vacuum for 0.5~3 hours.

11. A SiBCN ceramic precursor, characterized in that, The precursor is prepared by the method for preparing SiBCN ceramic precursor according to any one of claims 1-10.

12. The SiBCN ceramic precursor according to claim 11, characterized in that, The SiBCN ceramic precursor has a viscosity of 5000~500000cp at 25℃.

13. A SiBCN ceramic, characterized in that, The SiBCN ceramic is prepared by curing and pyrolysis of the SiBCN ceramic precursor as described in claim 11 or 12.

14. The application of the SiBCN ceramic precursor according to claim 11 or 12 in ceramic matrix composites, ceramic fibers, ceramic coatings, and ceramic bulk materials.

Images