Phenyl-regulated SiBCN high-temperature wave-absorbing ceramic as well as preparation method and application thereof
By introducing diphenyldichlorosilane into the SiBCN ceramic precursor to regulate the carbon content and structure, the problem of poor absorption performance of traditional ceramics in high-temperature environments is solved, high-temperature absorption performance regulation is achieved in different temperature ranges, and SiBCN ceramics suitable for different temperature domains are prepared.
Patent Information
- Application Number
- CN202510651025.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-20
- Publication Date
- 2025-07-22
AI Technical Summary
Traditional ceramic materials have poor wave absorption performance in high-temperature environments and insufficient dielectric performance controllability, making it difficult to meet the needs of different temperature regions.
By introducing diphenyl dichlorosilane into the SiBCN ceramic precursor, the carbon content and structure are regulated, and combined with appropriate pyrolysis temperature, phenyl-regulated SiBCN high-temperature wave absorbing ceramics are prepared to control dielectric properties and high-temperature wave absorbing performance.
SiBCN ceramics with excellent high-temperature absorbing performance in different temperature ranges were prepared to meet the needs of different temperature domains and provide new ideas for high-temperature absorbing materials.
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Figure CN120349189A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of absorbing materials, and in particular to a phenyl-regulated SiBCN high-temperature absorbing ceramic and a preparation method and application thereof. Background Art
[0002] Ceramic materials have excellent high-temperature stability and are ideal for preparing high-temperature absorbing materials. However, the poor controllability of dielectric properties of traditional ceramics limits their application. Polymer Derived Ceramics (PDCs) are expected to solve the problem of poor absorbing performance of traditional ceramic materials in high-temperature environments due to the flexible design of polymer molecules and strong controllability of dielectric properties.
[0003] The SiBCN ceramics prepared by the PDC route have the property of adjustable dielectric properties, which provides more ways to prepare high-performance high-temperature absorbing SiBCN ceramics. Studies have reported that higher carbon content and higher pyrolysis temperature in PBSZ will lead to the in-situ generation of more sp 2 Carbon can effectively improve the dielectric properties of SiBCN and further improve the microwave absorption performance of SiBCN ceramics. 2 Carbon can be protected by SiBCN ceramics, thereby improving the heat resistance of the material. However, how to effectively control the carbon content and structure in the ceramic precursor to improve the dielectric properties and high-temperature absorbing properties of SiBCN ceramics is one of the key issues that need to be solved in the field of absorbing materials. Summary of the invention
[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a phenyl-regulated SiBCN high-temperature absorbing ceramic and a preparation method and application thereof, so as to solve the problem of poor absorbing performance of traditional ceramic materials in high-temperature environments.
[0005] The technical solution of the present invention to solve the above technical problems is as follows:
[0006] The first object of the present invention is to provide a method for preparing SiBCN high temperature microwave absorbing ceramics regulated by phenyl groups, comprising the following steps:
[0007] (1) Synthesis of ceramic precursors
[0008] Firstly, dimethyldichlorosilane, diphenyldichlorosilane and hexamethyldisilazane are mixed for polymerization reaction, and then borane tetrahydrofuran complex is added for pre-crosslinking to obtain;
[0009] (2) Preparation of SiBCN high temperature microwave absorbing ceramics
[0010] First, the precursor obtained in step (1) is subjected to a cross-linking reaction, then ball-milled and sieved to form a green body, and finally high-temperature sintering is carried out to obtain it.
[0011] The beneficial effects of the present invention are as follows: Compared with other saturated alkanes, the carbon atoms in the benzene ring are sp 2 hybridized, and the benzene ring structure has a high carbon content. Therefore, increasing the phenyl structure in the precursor can effectively regulate the carbon content in the ceramic precursor, thereby adjusting the dielectric properties of the SiBCN ceramic. In the present invention, by adding diphenyldichlorosilane to the preparation of the SiBCN ceramic precursor, the phenyl group is successfully introduced, realizing the preparation of a high-temperature wave-absorbing ceramic material.
[0012] Furthermore, in step (1), the molar ratio of dimethyldichlorosilane, diphenyldichlorosilane, hexamethyldisilazane, and borane tetrahydrofuran complex is 1:(0.05 - 0.15):(10 - 20):(0.1 - 0.5).
[0013] The beneficial effects of adopting the above further technical solution are as follows: In the present invention, by adding diphenyldichlorosilane, the phenyl group is introduced into the SiBCN ceramic precursor. By regulating the content of diphenyldichlorosilane in the precursor, the C content and structure in the SiBCN ceramic can be effectively regulated, thereby regulating the dielectric properties of the SiBCN ceramic, realizing the preparation of SiBCN ceramics with high-temperature wave-absorbing properties that meet different temperature ranges, and providing a new idea for the preparation of high-temperature wave-absorbing SiBCN ceramics for use in different temperature ranges.
[0014] Furthermore, in step (1), dimethyldichlorosilane, diphenyldichlorosilane, and hexamethyldisilazane are mixed under the condition of an ice-water bath.
[0015] Furthermore, in step (1), the temperature of the polymerization reaction is 100 - 150 °C, and the time is 2 - 3 h.
[0016] Furthermore, in step (1), the borane tetrahydrofuran complex is added under the condition of an ice-water bath.
[0017] Furthermore, in step (1), the temperature of the pre-crosslinking is 120 - 180 °C, and the time is 20 - 40 min.
[0018] Furthermore, in step (2), the polymerization reaction conditions are as follows: under the atmosphere of a protective gas, the temperature is raised to 300 - 500 °C at a heating rate of 1 - 3 °C / min, and held for 3 - 5 h.
[0019] Further, the conditions for high-temperature sintering in step (2) are as follows: in an atmosphere of protective gas, first heat up to 1300-1400°C at a heating rate of 1-3°C / min, hold for 3-5 h, then cool down to 400-600°C at a cooling rate of 1-3°C / min, and finally cool naturally to room temperature.
[0020] The second object of the present invention is to provide a phenyl-regulated SiBCN high-temperature wave-absorbing ceramic prepared by the above preparation method.
[0021] The beneficial effects of the present invention are as follows: The SiBCN high-temperature wave-absorbing ceramic prepared by the present invention can meet the usage requirements in different temperature ranges by adjusting the ratio and sintering temperature, and has broad application prospects.
[0022] The third object of the present invention is to provide the application of the above phenyl-regulated SiBCN high-temperature wave-absorbing ceramic in wave-absorbing materials.
[0023] The present invention has the following beneficial effects:
[0024] In the present invention, diphenyldichlorosilane with a high carbon content monomer is added to the SiBCN ceramic precursor system, and phenyl is introduced into the molecular chain to prepare polysilazane PSZ. Further, borane tetrahydrofuran complex is introduced to prepare PBSZ ceramic precursor. By regulating the content of diphenyldichlorosilane and the pyrolysis temperature in the precursor, the C content and structure in the SiBCN ceramic are effectively regulated, the dielectric properties and high-temperature wave-absorbing properties of the SiBCN ceramic are realized, and the SiBCN ceramic with excellent high-temperature wave-absorbing properties in different temperature ranges is prepared, providing a new idea for preparing high-temperature wave-absorbing SiBCN ceramics for use in different temperature ranges. Description of the Drawings
[0025] Figure 1 FTIR spectra of PSZ and ceramic precursors PBSZ with different ratios in Test Example 1;
[0026] Figure 2 Thermogravimetric curves of ceramic precursors PBSZ with different ratios in Test Example 2;
[0027] Figure 3 Reflection coefficient curves of C1-C8 ceramics at room temperature in Test Example 3, where (a)-(h) are C1-C8 ceramic samples in sequence;
[0028] Figure 4 Reflection coefficients of C3-C6 ceramics in the range of 100°C to 800°C in Test Example 4, where (a)-(d) are C3-C6 ceramic samples in sequence;
[0029] Figure 5It is the TGA curves of C1-C8 ceramics in Ar and air atmospheres in Test Example 4. Detailed implementation mode
[0030] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained by purchasing in the market.
[0031] The raw materials used in the following examples:
[0032] Borane tetrahydrofuran complex solution (BTHF, 1.0 mol / L, Energy Chemical), Hexamethyldisilazane (HMDS, Energy Chemical, 99%), Dichlorodimethylsilane (DCDMS, Alfa Aesar, 98%), Diphenyldichlorosilane (DPDCS, Alfa Aesar, 96%). All chemical reagents were used directly after purchase without further purification.
[0033] Example 1:
[0034] A preparation method of phenyl-regulated SiBCN high-temperature wave-absorbing ceramics, comprising the following steps:
[0035] (1) Synthesis of ceramic precursor
[0036] The Schlenk technique was adopted throughout the process, and the whole process of the reaction was protected by argon atmosphere. Place a 500 mL reaction flask in an ice-water bath, add DCDMS (0.09 mol), DPDCS (0.0090 mol) and HMDS (0.1386 mol) to the reaction flask, then remove the ice-water bath, and then raise the reaction temperature to 120 °C. After maintaining for 2.5 h, polysilane (PSZ) was obtained. At this time, the PSZ was a colorless and transparent liquid with a certain viscosity. After it was cooled to room temperature, the reaction flask was placed in the ice-water bath again. After the temperature stabilized, BTHF (0.0297 mol) was slowly added into the reaction flask, and the temperature was slowly raised to 150 °C. After about 30 min, a white foamy solid was formed in the reaction flask, which was the pre-crosslinked PBSZ (ceramic precursor). In the SiBCN ceramic precursor prepared in this example, the molar ratio of DPDCS to DCDMS was 0.1:1, named PBSZ-0.1.
[0037] (2) Preparation of SiBCN ceramics
[0038] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for full ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1300°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C3) with a yield of 85.7%.
[0039] Embodiment 2:
[0040] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0041] (1) Synthesis of ceramic precursors
[0042] The whole process adopts Schlenk technology, and argon is used for atmosphere protection throughout the reaction. Place a 500mL reaction bottle in an ice-water bath, add DCDMS (0.09mol), DPDCS (0.0090mol) and HMDS (0.1386mol) to the reaction bottle, then remove the ice-water bath, then raise the reaction temperature to 120°C, and keep it for 2.5h to obtain polysilane (PSZ), at which time PSZ is a colorless, transparent liquid with a certain viscosity. After cooling to room temperature, place the reaction bottle in an ice-water bath again, and after the temperature stabilizes, slowly add BTHF (0.0297mol) to the reaction bottle, and slowly heat it to 150°C. After about 30min, a white foamy solid is generated in the reaction bottle, which is the pre-crosslinked PBSZ (ceramic precursor). The molar ratio of DPDCS to DCDMS in the SiBCN ceramic precursor prepared in this embodiment is 0.1:1, named PBSZ-0.1.
[0043] (2) Preparation of SiBCN ceramics
[0044] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for full ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1300°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C4) with a yield of 86.3%.
[0045] Embodiment 3:
[0046] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0047] (1) Synthesis of ceramic precursors
[0048] The whole process adopts Schlenk technology, and argon is used for atmosphere protection throughout the reaction. Place a 500mL reaction bottle in an ice-water bath, add DCDMS (0.09mol), DPDCS (0.0135mol) and HMDS (0.1449mol) to the reaction bottle, remove the ice-water bath, and then raise the reaction temperature to 120°C. After keeping for 2.5h, polysilane (PSZ) is obtained. At this time, PSZ is a colorless, transparent liquid with a certain viscosity. After cooling to room temperature, place the reaction bottle in an ice-water bath again. After the temperature stabilizes, slowly add BTHF (0.0297mol) to the reaction bottle, and slowly heat it to 150°C. After about 30min, a white foamy solid is generated in the reaction bottle, which is the pre-crosslinked PBSZ (ceramic precursor). The molar ratio of DPDCS to DCDMS in the SiBCN ceramic precursor prepared in this embodiment is 0.15:1, named PBSZ-0.15.
[0049] (2) Preparation of SiBCN ceramics
[0050] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for thorough ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1300°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C5) with a yield of 86.1%.
[0051] Embodiment 4:
[0052] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0053] (1) Synthesis of ceramic precursors
[0054] The whole process adopts Schlenk technology, and argon gas is used for atmosphere protection during the whole process of the reaction. Place a 500mL reaction bottle in an ice-water bath, add DCDMS (0.09mol), DPDCS (0.0135mol) and HMDS (0.1449mol) to the reaction bottle, then remove the ice-water bath, then raise the reaction temperature to 120°C, and keep it for 2.5h to obtain polysilane (PSZ), at which time PSZ is a colorless, transparent liquid with a certain viscosity. After cooling to room temperature, place the reaction bottle in an ice-water bath again, and after the temperature stabilizes, slowly add BTHF (0.0297mol) to the reaction bottle, and slowly heat it to 150°C. After about 30min, a white foamy solid is generated in the reaction bottle, which is a pre-crosslinked PBSZ (ceramic precursor). The molar ratio of DPDCS to DCDMS in the SiBCN ceramic precursor prepared in this embodiment is 0.1:15, named PBSZ-0.15.
[0055] (2) Preparation of SiBCN ceramics
[0056] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for thorough ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1400°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C6) with a yield of 86.3%.
[0057] Comparative Example 1:
[0058] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0059] (1) Synthesis of ceramic precursors
[0060] The whole process adopts Schlenk technology, and the whole process of reaction uses argon gas for atmosphere protection. 500mL reaction bottle is placed in an ice-water bath, and the ice-water bath is removed after adding DCDMS (0.09mol) and HMDS (0.1260mol) to the reaction bottle, and then the reaction temperature is warming up to 120 DEG C, and polysilane (PSZ) is obtained after keeping for 2.5h, and PSZ at this time is colorless and transparent and has a certain viscosity liquid. After it is cooled to room temperature, the reaction bottle is placed in an ice-water bath again, and after the temperature stabilizes, BTHF (0.0297mol) is slowly added to the reaction bottle, and it is slowly warmed to 150 DEG C, and a white foam solid is generated in the reaction bottle after about 30min, which is pre-crosslinked PBSZ (ceramic precursor). The present embodiment obtains SiBCN ceramic precursor without adding DPDCS, and is named as PBSZ-0.
[0061] (2) Preparation of SiBCN ceramics
[0062] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for thorough ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1300°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain a phenyl-regulated SiBCN high-temperature wave-absorbing ceramic (C1) with a yield of 81.5%.
[0063] Comparative Example 2:
[0064] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0065] (1) Synthesis of ceramic precursors
[0066] The whole process adopts Schlenk technology, and the whole process of reaction uses argon gas for atmosphere protection. 500mL reaction bottle is placed in an ice-water bath, and the ice-water bath is removed after adding DCDMS (0.09mol) and HMDS (0.1260mol) to the reaction bottle, and then the reaction temperature is warming up to 120 DEG C, and polysilane (PSZ) is obtained after keeping for 2.5h, and PSZ at this time is colorless and transparent and has a certain viscosity liquid. After it is cooled to room temperature, the reaction bottle is placed in an ice-water bath again, and after the temperature stabilizes, BTHF (0.0297mol) is slowly added to the reaction bottle, and it is slowly warmed to 150 DEG C, and a white foam solid is generated in the reaction bottle after about 30min, which is pre-crosslinked PBSZ (ceramic precursor). The present embodiment obtains SiBCN ceramic precursor without adding DPDCS, and is named as PBSZ-0.1.
[0067] (2) Preparation of SiBCN ceramics
[0068] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for full ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1400°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain a phenyl-regulated SiBCN high-temperature wave-absorbing ceramic (C2) with a yield of 81.1%.
[0069] Comparative Example 3:
[0070] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0071] (1) Synthesis of ceramic precursors
[0072] The whole process adopts Schlenk technology, and argon is used for atmosphere protection throughout the reaction. Place a 500mL reaction bottle in an ice-water bath, add DCDMS (0.09mol), DPDCS (0.0180mol) and HMDS (0.1512mol) to the reaction bottle, remove the ice-water bath, and then raise the reaction temperature to 120°C. After keeping for 2.5h, polysilane (PSZ) is obtained. At this time, PSZ is a colorless, transparent liquid with a certain viscosity. After cooling to room temperature, place the reaction bottle in an ice-water bath again. After the temperature stabilizes, slowly add BTHF (0.0297mol) to the reaction bottle, and slowly heat it to 150°C. After about 30min, a white foamy solid is generated in the reaction bottle, which is the pre-crosslinked PBSZ (ceramic precursor). The molar ratio of DPDCS to DCDMS in the SiBCN ceramic precursor prepared in this embodiment is 0.2:1, named PBSZ-0.2.
[0073] (2) Preparation of SiBCN ceramics
[0074] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for thorough ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1300°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C7) with a yield of 85.9%.
[0075] Comparative Example 4:
[0076] A method for preparing phenyl-regulated SiBCN high-temperature microwave-absorbing ceramics comprises the following steps:
[0077] (1) Synthesis of ceramic precursors
[0078] The whole process adopts Schlenk technology, and argon is used for atmosphere protection throughout the reaction. Place a 500mL reaction bottle in an ice-water bath, add DCDMS (0.09mol), DPDCS (0.0180mol) and HMDS (0.1512mol) to the reaction bottle, remove the ice-water bath, and then raise the reaction temperature to 120°C. After keeping for 2.5h, polysilane (PSZ) is obtained. At this time, PSZ is a colorless, transparent liquid with a certain viscosity. After cooling to room temperature, place the reaction bottle in an ice-water bath again. After the temperature stabilizes, slowly add BTHF (0.0297mol) to the reaction bottle, and slowly heat it to 150°C. After about 30min, a white foamy solid is generated in the reaction bottle, which is the pre-crosslinked PBSZ (ceramic precursor). The molar ratio of DPDCS to DCDMS in the SiBCN ceramic precursor prepared in this embodiment is 0.2:1, named PBSZ-0.2.
[0079] (2) Preparation of SiBCN ceramics
[0080] The PBSZ obtained in step (1) was quickly transferred to a ceramic crucible. Under the condition of continuous argon gas flow, the heating rate was designed to be 2°C / min. After heating to 400°C, it was maintained for h to allow the pre-crosslinked PBSZ to further crosslink. Then it was naturally cooled to room temperature to obtain a yellow thermally crosslinked block product. It was placed in a ball mill for full ball milling, and the ball-milled powder was sieved with a 100-mesh sieve. 1.2g of the sieved thermally crosslinked precursor powder was placed in a mold and pressed into a ceramic blank (32.65mm×14.24mm). The pressed ceramic blank was placed in a corundum crucible and placed in the middle of a tube furnace. Under an argon atmosphere, the temperature was first increased to 1400°C at a heating rate of 2°C / min and maintained for 4h, then cooled to 500°C at a rate of 1°C / min, and finally naturally cooled to room temperature to obtain phenyl-regulated SiBCN high-temperature wave-absorbing ceramics (C8) with a yield of 87.3%.
[0081] Test Example 1: FTIR Characterization
[0082] The PSZ prepared in Example 1, the PBSZ prepared in Example 1, Example 3, Comparative Example 1 and Comparative Example 3 were characterized by Fourier transform infrared spectroscopy. The experimental results are as follows: Figure 1 shown.
[0083] By comparing the curves of PSZ and PBSZ, the most obvious difference is that the wave number is 3150cm -1 The NH peak at 1340 cm -1 The stretching vibration peak of BN appeared at , and the source of NH bonds in PSZ and PBSZ is HMDS in the synthetic precursor raw materials. When BTHF is added, part of NH reacts with BTHF to form a boron nitrogen six-membered ring structure. When the reactants are cross-linked to form a solid, the reaction between NH in PSZ and BTHF becomes difficult. In the FTIR spectrum of PBSZ, the peak of NH weakened but did not completely disappear, indicating that some NH still remains inside PBSZ. By comparing the FTIR spectra of PBSZs with different ratios, no obvious changes occurred, indicating that the different dosages of DPDCS do not affect the molecular chain structure of PBSZ.
[0084] Test Example 2: Thermogravimetric Analysis
[0085] The PBSZ prepared in Example 1, Example 3, Comparative Example 1 and Comparative Example 3 were subjected to thermogravimetric analysis to analyze and test the thermal decomposition behavior of the polymer precursor. The experimental results are as follows: Figure 2 shown.
[0086] In the thermogravimetric TGA curve, when the temperature is below 200 °C, the mass of all PBSZ hardly changes. As the temperature increases, the residual mass of PBSZ rapidly decreases between 200 - 300 °C, and the rate of mass decrease slows down between 300 - 700 °C, converting from organic to inorganic. When the temperature exceeds 700 °C, the residual mass basically no longer changes, indicating that PBSZ has basically completed the inorganic transformation. During the entire TGA test process, as the test temperature increases, the thermogravimetric curves of PBSZ show the same downward trend. When the test temperature reaches 1400 °C, PBSZ all have a mass retention rate of approximately 60%. By observing the TGA curve, the ceramic yields of PBSZ-0, PBSZ-0.1, and PBSZ-0.15 are basically the same, while the ceramic yield of PBSZ-0.2 is slightly lower than that of other PBSZ.
[0087] Test Example 3: Room temperature wave absorption performance
[0088] The reflection coefficient curves of the SiBCN ceramics C1 - C8 prepared in Examples 1 - 4 and Comparative Examples 1 - 4 were measured in the X - band at room temperature, and the experimental results are as Figure 3 shown.
[0089] By observing Figure 3 the obtained reflection coefficient curves, it was found that due to the too low dielectric constants of C1 and C2, and the too high dielectric constants of C7 and C8, the reflection coefficients of the ceramics are all greater than - 10 dB, and the wave absorption performance of the ceramics is poor and not suitable as high - temperature wave absorption materials. Among the examples, C4 and C6 have relatively lower reflection coefficients and wider effective absorption bandwidths. When the matching thickness is 3.4 mm, the effective absorption bandwidth of C4 ceramic in the X - band is 3.8 GHz (8.2 - 12 GHz), and the minimum reflection coefficient is - 29.3 dB at a frequency of 9.7 GHz. When the matching thickness of C4 ceramic is 3.5 mm, the lowest reflection coefficient is obtained at 9.54 GHz, and the minimum reflection coefficient is - 30.1 dB, and the effective absorption bandwidth is 3 GHz (8.2 - 11.2 GHz). When the matching thickness is between 3.0 - 3.3 mm, the effective absorption bandwidth of C4 ceramic all exceeds 3 GHz, and the lowest reflection coefficients are all less than - 25 dB. Compared with C4 ceramic, C6 ceramic has further improved wave absorption performance. When the matching thickness is 2.9 mm, the effective absorption bandwidth of C6 ceramic covers the X - band, and the minimum reflection coefficient is - 47.2 dB at 9.9 GHz. When the matching thickness is in the range of 2.6 - 3.1 mm, the effective absorption bandwidth of C6 ceramic is all greater than 3 GHz, and the lowest reflection coefficients are all lower than the lowest reflection coefficient of C4 ceramic, and the lowest reflection coefficients are all less than - 30 dB, showing the best wave absorption performance at room temperature.
[0090] Test Example 4: High - temperature wave absorption performance
[0091] Take the SiBCN ceramics C3 - C6 prepared in Examples 1 - 4 as samples, and test their reflection coefficients in the range of 100°C to 800°C. The experimental results are as Figure 4 shown in Table 1.
[0092] Table 1 Effective absorption bandwidth and minimum reflection coefficient of C2 - C6 ceramics at 100 - 800°C
[0093]
[0094]
[0095] According to Figure 4 , it can be clearly observed that when the test temperature rises to 800°C, the wave - absorbing performance of C3 ceramics is significantly improved. When the matching thickness is 3.0 mm, the effective bandwidth is 3.5 GHz (8.9 GHz - 12.4 GHz), and the minimum reflection coefficient reaches - 20.2 dB at 10.6 GHz. C4 ceramics reach the lowest reflection coefficient of - 33.9 dB when the test temperature is 200°C and the matching thickness is 3.1 mm. C5 ceramics reach the lowest reflection coefficient of - 30.3 dB when the test temperature is 400°C, and the effective absorption bandwidth is 3.7 GHz (8.2 - 11.9 GHz). C6 ceramics have an effective absorption bandwidth covering the entire X - band with a minimum reflection coefficient of - 22.6 dB when the test temperature is 200°C and the matching thickness is 2.7 mm. At 100°C, 300°C, and 400°C, the effective absorption bandwidth exceeds 3.2 GHz, and the minimum reflection coefficient is - 25.8 dB. The above results show that the SiBCN ceramics prepared by the present invention can realize the preparation of high - temperature wave - absorbing materials for different working temperatures and different working requirements by adjusting the addition ratio of DPDCS and the temperature of high - temperature sintering, and have wide practical value.
[0096] Test Example 5: Heat - resistant performance
[0097] Take the SiBCN ceramics C1 - C8 prepared in Examples 1 - 4 and Comparative Examples 1 - 4, and conduct high - temperature thermogravimetric analysis in Ar and air environments respectively. The experimental results are as Figure 5 shown.
[0098] The results show that the TGA curves of C1-C8 basically coincide under Ar and air atmospheres, indicating that the ceramics prepared from precursors with different ratios have little effect on the heat resistance of the ceramics, and the C1-C8 ceramics all have good heat resistance. Under the Ar atmosphere, before 1300 °C, the mass of the ceramics did not decrease. When the temperature exceeded 1300 °C, the mass began to decrease slowly. At 1400 °C, the mass retention rate was about 98.8%. Under the air atmosphere, there was no phenomenon of mass increase in the TGA curve, proving that the ceramics have good antioxidant ability. Before 1300 °C, the mass did not decrease. After exceeding 1300 °C, the mass began to decrease slowly. At 1400 °C, the mass retention rate was about 98.1%, indicating that the C1-C8 ceramics can be stably used below 1300 °C.
[0099] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.
Claims
1. A preparation method of phenyl-regulated SiBCN high-temperature wave-absorbing ceramics, characterized in that, It includes the following steps: (1) Synthesis of ceramic precursor First, dimethyldichlorosilane, diphenyldichlorosilane and hexamethyldisilazane are mixed for a polymerization reaction, and then borane tetrahydrofuran complex is added for pre-crosslinking to obtain it; (2) Preparation of SiBCN high-temperature microwave-absorbing ceramic First, the precursor obtained in step (1) is subjected to a crosslinking reaction, then ball-milled and sieved to form a green body, and finally high-temperature sintered to obtain it.
2. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, characterized in that In step (1), the molar ratio of dimethyldichlorosilane, diphenyldichlorosilane, hexamethyldisilazane and borane tetrahydrofuran complex is 1:(0.05 - 0.15):(10 - 20):(0.1 - 0.5).
3. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, wherein In step (1), dimethyldichlorosilane, diphenyldichlorosilane and hexamethyldisilazane are mixed under the condition of an ice-water bath.
4. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, wherein, In step (1), the temperature of the polymerization reaction is 100 - 150 °C and the time is 2 - 3 h.
5. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, characterized in that, In step (1), borane tetrahydrofuran complex is added under the condition of an ice-water bath.
6. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, characterized in that In step (1), the temperature of the pre-crosslinking is 120 - 180 °C and the time is 20 - 40 min.
7. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, characterized in that, In step (2), the polymerization reaction conditions are: under the atmosphere of a protective gas, heating to 300 - 500 °C at a heating rate of 1 - 3 °C / min and holding for 3 - 5 h.
8. The preparation method of the phenyl-regulated SiBCN high-temperature wave-absorbing ceramic according to claim 1, characterized in that, In step (2), the high-temperature sintering conditions are: under the atmosphere of a protective gas, first heating to 1300 - 1400 °C at a heating rate of 1 - 3 °C / min and holding for 3 - 5 h, then cooling to 400 - 600 °C at a cooling rate of 1 - 3 °C / min, and finally naturally cooling to room temperature.
9. A phenyl-regulated SiBCN high-temperature wave-absorbing ceramic, characterized in that, It is obtained by using the preparation method described in any one of claims 1 - 8.
10. Application of the phenyl-regulated SiBCN high-temperature microwave-absorbing ceramic described in claim 9 in the field of microwave-absorbing materials.