Modified polysilazane and preparation method therefor, and silicon-carbon-nitrogen ceramic and preparation method therefor
Patent Information
- Application Number
- PCT/CN2026/085354
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-03-23
- Publication Date
- 2026-10-01
Smart Images
Figure CN2026085354_01102026_PF_FP_ABST
Abstract
Description
Modified polysilazane and its preparation method, silicon carbon nitrogen ceramics and their preparation method
[0001] This application claims priority to patent application No. 22025105273.8 filed on March 26, 2025, with the Patent Registry of the Intellectual Property Department of the Hong Kong Special Administrative Region Government, entitled “Modified polysilazane and preparation method thereof, silicon carbon nitride ceramic and preparation method thereof”, the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to the field of polymer and ceramic materials technology, and in particular to modified polysilazane and its preparation method, and silicon carbon nitrogen ceramics and their preparation method. Background Technology
[0003] Polysilazane compounds can be used as precursors to transform into silicon-carbon-nitrogen ceramics. In particular, the technical solution of using polyborosiazane as a precursor to transform into silicon-boron-carbon-nitrogen ceramics has several advantages over traditional sintered ceramics. On the one hand, compared with traditional powder-sintered silicon-boron-carbon-nitrogen ceramics, it has superior processing and forming performance and a lower preparation temperature. On the other hand, the resulting ceramics exhibit excellent thermal stability, mechanical stability, and chemical stability at high temperatures.
[0004] Precursor-converted silicon-boron-carbon-nitride ceramics have been developed for various applications in different fields, including high-temperature protection materials and electromagnetic wave absorbing materials in aerospace, and high-temperature resistant and functional materials in electrical engineering and nanoelectronics. The curing process of polyborosilicate preforms (mainly including thermosetting and photocuring) has a crucial impact on the morphology and properties of the final ceramic product. Thermosetting is not conducive to preparing ceramic products with complex morphologies, while photocuring has inherent advantages in this area.
[0005] Currently, there are two main methods for photocuring polyborosilicates. One method involves introducing unsaturated groups such as vinyl groups into the chemical structure of the polyborosilicate to achieve photoinitiated free radical polymerization of carbon-carbon double bonds. However, the number of carbon-carbon double bonds that can be introduced is limited, and these bonds are not very sensitive to ultraviolet light, resulting in a relatively slow photocuring rate. The other method involves physically mixing the polyborosilicate with ultraviolet-sensitive acrylate compounds to achieve a rapid photocuring reaction. However, this physical mixing inevitably leads to a decrease in ceramic yield. Other techniques for preparing silicon-carbon-nitrogen ceramics using polyborosilicates also suffer from the aforementioned problems of low curing rate and low ceramic yield. Summary of the Invention
[0006] The purpose of this application is to provide modified polysilazane and its preparation method, as well as silicon carbon nitrogen ceramics and their preparation method, in order to solve the problems of low curing rate and low ceramic yield when preparing silicon carbon nitrogen ceramics from polysilazane in the prior art.
[0007] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:
[0008] In a first aspect, this application provides a modified polysilazane, which includes a polysilazane backbone, isocyanate groups and photosensitive groups, wherein the carbon atoms of the isocyanate groups are bonded to at least a portion of the nitrogen atoms of the polysilazane backbone, and the photosensitive groups are bonded to the nitrogen atoms of the isocyanate groups.
[0009] This application modifies polysilazane by attaching carbon atoms of isocyanate groups to at least a portion of the nitrogen atoms of the polysilazane backbone and photosensitive groups to the nitrogen atoms of the isocyanate groups. This uses the isocyanate groups as a bridge between the polysilazane backbone and the photosensitive groups, resulting in higher UV sensitivity. Compared to existing technologies that directly introduce carbon-carbon double bonds into polysilazane or directly mix it with acrylic monomers to prepare precursors for silicon-carbon-nitrogen ceramics, this application's modified polysilazane significantly improves the efficiency of photocuring silicon-carbon-nitrogen ceramics. Furthermore, the type and number of photosensitive groups can be adjusted to regulate the yield of the photocured ceramics. Therefore, this application's modified polysilazane achieves dual optimization of efficiency and yield when used to prepare silicon-carbon-nitrogen ceramics.
[0010] Secondly, this application provides a method for preparing the modified polysilazane described above, comprising the following steps:
[0011] In an inert atmosphere, raw materials including polysilazane and isocyanate compounds containing photosensitive groups are subjected to an addition reaction, so that the isocyanate groups of the isocyanate compounds are grafted onto the nitrogen atoms of the main chain of polysilazane.
[0012] Because the isocyanate groups in isocyanate compounds have high chemical reactivity, the above preparation method allows the isocyanate groups to efficiently undergo addition reactions with the nitrogen-hydrogen bonds in polyborosilazanes, grafting the isocyanate groups onto the nitrogen atoms of the polysilazane backbone. This efficiently introduces photosensitive groups into the chemical structure of the polysilazane, yielding the modified polysilazane. Compared to existing methods that directly introduce carbon-carbon double bonds into polysilazanes or physically mix with acrylic monomers, this preparation method offers more controllable processes, and the modified polysilazanes prepared through chemical modification exhibit higher photocuring rates and yields for ceramic preparation.
[0013] Thirdly, this application provides a silicon-carbon-nitrogen ceramic obtained by curing a modified polysilazane comprising the above-described application or a modified polysilazane prepared by the above-described application method.
[0014] The silicon-carbon-nitrogen ceramic of this application is obtained by curing and pyrolyzing the modified polysilazane described above. During the pyrolysis process, the modified polysilazane is transformed into a ceramic material containing silicon, carbon, and nitrogen elements. Depending on the type of polysilazane used, it may also contain elements such as boron and aluminum. It can form a variety of phase domain structures in the ceramic material, and has strong high temperature resistance, oxidation resistance, and wave absorption properties, and can be used in a variety of different technical fields.
[0015] Fourthly, this application provides a method for preparing the silicon-carbon-nitrogen ceramic described in this application, comprising the following steps:
[0016] In an inert atmosphere, raw materials including modified polysilazane and photoinitiator are subjected to ultraviolet light curing treatment.
[0017] In the preparation method of this application, since the modified polysilazane contains photosensitive groups, these groups will crosslink and solidify under the action of a photoinitiator and ultraviolet light. Simultaneously, the main chain of the polysilazane will also undergo cleavage, and the silicon, nitrogen, carbon, and other elements in the polymer will recombine. Therefore, silicon-carbon-nitrogen ceramics can be obtained by curing the modified polysilazane and photoinitiator raw materials under ultraviolet light. This preparation method offers controllable processes, rapid and controllable ultraviolet curing rates, high ceramic yield, and the ability to prepare ceramic products with complex structures. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 is a schematic diagram of the chemical reactions involved in the preparation of modified polysilazane in Example A1 of this application;
[0020] Figure 2 is a Fourier transform infrared spectrum of the raw materials and the modified polysilazane obtained in Example A1 of this application;
[0021] Figure 3 shows the differential scanning calorimetry curves of the modified polysilazane of Example A1 with different amounts of photoinitiator and the polyborosilicate KH-PSNB-1 of Comparative Example A1 with 2 wt.% photoinitiator during the UV curing process of ceramic preparation.
[0022] Figure 4 shows the thermogravimetric curves of the modified polyborosilazane prepared in Example A1 of this application and the polyborosilazane in Comparative Example A1 during the preparation of ceramics by UV curing.
[0023] Figure 5 shows the thermogravimetric analysis (TGA) curves and differential thermal analysis (DTA) curves of the modified polyborosilicate prepared in Comparative Example A3. Detailed Implementation
[0024] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0025] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0026] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items.
[0027] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0028] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.
[0029] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.
[0030] The first aspect of this application provides a modified polysilazane, which includes a polysilazane backbone, isocyanate groups, and photosensitive groups. The carbon atoms of the isocyanate groups are bonded to at least a portion of the nitrogen atoms of the polysilazane backbone, and the photosensitive groups are bonded to the nitrogen atoms of the isocyanate groups.
[0031] The modified polysilazane of this application improves ultraviolet light sensitivity by combining carbon atoms of isocyanate groups with at least a portion of the nitrogen atoms of the polysilazane backbone and photosensitive groups with the nitrogen atoms of the isocyanate groups. This uses the isocyanate groups as a bridge between the polysilazane backbone and the photosensitive groups. Compared to existing technologies that directly introduce carbon-carbon double bonds into polysilazane or directly mix it with acrylic monomers to prepare precursors for silicon-carbon-nitrogen ceramics, the modified polysilazane of this application significantly improves the efficiency of photocuring for silicon-carbon-nitrogen ceramics. Furthermore, the type and number of photosensitive groups can be adjusted to regulate the yield of the photocured ceramics. Therefore, the modified polysilazane of this application achieves dual optimization of efficiency and yield when used to prepare silicon-carbon-nitrogen ceramics.
[0032] In some embodiments, the modified polysilazane comprises repeating units represented by the general chemical formula (I):
[0033] In general formula (I), it can be seen that the isocyanate group is bonded to the N atom of the polysilazane backbone.
[0034] In some embodiments, R3 is a photosensitive group, which includes at least one of acrylate groups and methacrylate groups; "includes" here means "contains," as in the exemplary example, the photosensitive group includes an acrylate group, but this does not mean that R3 is only an acrylate group; R3 can also be a group containing acrylate and alkyl segments. These photosensitive groups can be cross-linked and cured under ultraviolet light. By binding to the nitrogen atom of the isocyanate group and the carbon atom of the isocyanate group to the polysilazane backbone, the modified polysilazane has high ultraviolet light sensitivity, which can improve the curing efficiency and yield of silicon carbon nitride ceramics.
[0035] In some embodiments, a is 5 to 10; in exemplary embodiments, it may include, but is not limited to, any value of 5, 7, 8, 10 or any range between two values. The value of a represents the degree of polymerization of the silazane backbone. The larger the value of a, the higher the degree of polymerization, the larger the polymer scale, and the slower the subsequent curing rate, but the yield will be higher. Choosing a suitable value for the silazane backbone is beneficial to balance these properties.
[0036] In some embodiments, R1 and R2 may be the same or different, including at least one of alkyl, hydrogen, vinyl, and phenyl groups. In some embodiments, the polysilazane backbone includes at least one of polyborosilazane backbone, polyaluminosilicate backbone, and polyboroaluminosilicate backbone; polysilazane is a general term for silazane polymers, which, in addition to the polysilazane backbone, may also contain various doping elements to form abundant side chains, constituting polymers of various different forms. In the exemplary example, when the polysilazane is a polyborosilazane, it can be referred to as shown in the following formula (II):
[0037] Where R4 and R5 are the same or different, they include at least one of alkyl, hydrogen, vinyl, and phenyl groups. b is 5 to 10. Introducing these boron and aluminum elements can greatly improve the properties of ceramics prepared from modified polysilazane. Specifically, the introduction of boron can significantly reduce the molecular diffusion coefficients of silicon and nitrogen, increasing the crystallization temperature of the ceramic. Simultaneously, the BN bond can inhibit the crystallization of the ceramic and the decomposition of Si3N4, significantly improving the high-temperature resistance and density of the ceramic, and reducing surface porosity and grain size.
[0038] In some embodiments, the grafting rate of isocyanate groups onto the polysilazane backbone is 5%–20%. This grafting rate refers to the proportion of isocyanate groups to the total number of monomer units in the polysilazane backbone. The grafting rate of isocyanate groups will affect the content of photosensitive groups in the modified polysilazane, thereby affecting the ultraviolet light sensitivity of the modified polysilazane and the rate and yield of photocuring for ceramic preparation. This grafting rate of isocyanate groups is beneficial in ensuring the rate and yield of ceramic preparation from modified polysilazane.
[0039] In some embodiments, the modified polyborosilicate is a low-viscosity fluid to resin-type solid, readily soluble in various organic solvents, and can be used to prepare high-temperature resistant composite materials, ceramic precursors, high-performance protective coatings, high-temperature resistant adhesives, etc. It can be used to prepare ceramic or polymer products with complex structures through 3D printing, photolithography, and other methods according to actual needs.
[0040] The second aspect of this application provides a method for preparing the modified polysilazane described in the above application, comprising the following steps:
[0041] S10: In an inert atmosphere, raw materials including polysilazane and isocyanate compounds containing photosensitive groups are subjected to an addition reaction, so that the isocyanate groups of the isocyanate compounds are grafted onto the nitrogen atoms of the main chain of polysilazane.
[0042] Because the isocyanate groups in isocyanate compounds have high chemical reactivity, the above preparation method allows the isocyanate groups to efficiently undergo addition reactions with the nitrogen-hydrogen bonds in polysilazanes, grafting the isocyanate groups onto the nitrogen atoms of the polysilazane backbone. This efficiently introduces photosensitive groups into the chemical structure of the polysilazane, yielding the modified polysilazane described above. Compared to existing methods that directly introduce carbon-carbon double bonds into polysilazanes or physically mix them with acrylic monomers, this preparation method offers more controllable processes, and the modified polysilazanes prepared through chemical modification exhibit higher photocuring rates and yields for ceramic preparation.
[0043] In some embodiments, the polysilazane includes at least one of polyborosilazane, polyaluminasilazane, polyaluminasilazane, and polyboroaluminasilazane; wherein, the polyborosilazane may include at least one of perhydropolyborosilazane, hyperbranched polyborosilazane, and carborane-alkyl polyborosilazane; wherein, hyperbranched polyborosilazane has high solubility and good rheological properties, which is beneficial for the molding of complex ceramic structures, and its three-dimensional spherical topology helps to retain boron elements during the curing and preparation of ceramics. Perhydropolyborosilazane has a high ceramic yield and can effectively reduce the shrinkage rate during pyrolysis. Carborane-alkyl polyborosilazane has a high boron content, so the boron content of carborane-alkyl polyborosilazane can be widely controlled, and the rigid structure of carborane itself can significantly improve the ceramic yield of polyborosilazane. Polyaluminasilazane may include at least one of polyaluminasilazane and polyboroaluminasilazane. The silicon-aluminum carbon-nitrogen ceramics obtained by the pyrolysis of polyaluminasilazane have excellent high-temperature oxidation resistance. Compared to silicon-aluminum-carbon-nitrogen ceramics, silicon-boron-carbon-nitrogen-aluminum ceramics obtained by the pyrolysis of polyboron-aluminum-silazane exhibit higher thermal stability and anti-crystallization properties.
[0044] In some embodiments, the isocyanate compounds include at least one of ethyl 2-isocyanate acrylate and isocyanoethyl methacrylate. These isocyanate compounds not only contain isocyanate groups, which can be grafted onto polysilazanes via addition reactions, but also contain photosensitive groups, which facilitates the preparation of ceramics from the modified polysilazanes via photocuring.
[0045] In some embodiments, the mass ratio of polysilazane to isocyanate compound is (5–20):1; in exemplary examples, it may include, but is not limited to, any value or a range between any two of 5:1, 7:1, 8:1, 9:1, 10:1, and 20:1. These mass ratios of raw materials are conducive to the addition reaction and increase the yield of modified polysilazane. Simultaneously, the mass ratio of polysilazane to isocyanate compound also affects the content of photosensitive groups in the obtained modified polysilazane, thereby affecting the rate and yield when used for photocuring to prepare ceramics. By adjusting this mass ratio, the rate of subsequent photocuring to prepare ceramics can be controlled. Compared with the two prior art techniques, the preparation method of this application improves controllability, allowing for reasonable design during raw material preparation according to the requirements of the final application.
[0046] The inert atmosphere for the addition reaction can be nitrogen, helium, argon, etc. In some embodiments, the temperature of the addition reaction is 20–100°C, and the reaction time is 1–20 hours; these reaction temperatures and times are conducive to the progress of the addition reaction and to the full grafting of the isocyanate groups of the isocyanate compounds onto the N atoms of the polysilazane backbone.
[0047] In some embodiments, the addition reaction can be carried out in a solvent to improve the uniformity of the raw material dispersion. The reaction solvent can be an ultra-dry anhydrous solvent, which may include at least one of tetrahydrofuran, n-hexane, and xylene. Appropriate stirring can be performed during the addition reaction to facilitate a uniform and stable reaction. After the reaction is complete, the reaction solvent can be removed from the system at 20–80°C by means such as vacuum distillation to obtain the modified polysilazane.
[0048] A third aspect of this application provides a silicon-carbon-nitrogen ceramic, obtained by curing and pyrolyzing a modified polysilazane, including the polysilazane modified according to the embodiments of the above application or the modified polysilazane prepared by the preparation method of the embodiments of the above application.
[0049] The silicon-carbon-nitrogen ceramic of this application embodiment is obtained by curing and pyrolyzing the modified polysilazane described in the above embodiment. During the pyrolysis process, the modified polysilazane is transformed into a ceramic material containing silicon, carbon, and nitrogen elements. Depending on the type of polysilazane used, it may also contain elements such as boron and aluminum. It can form a variety of phase domain structures in the ceramic material, and has strong high temperature resistance, oxidation resistance, and wave absorption properties, and can be used in a variety of different technical fields.
[0050] In some embodiments, the silicon-carbon-nitrogen ceramic can be a silicon-boron-carbon-nitrogen ceramic containing BN or B4C domain structures, exhibiting high-temperature resistance exceeding 2000℃. Furthermore, it maintains good oxidation resistance at high temperatures and is not easily oxidized. It also contains self-generated silicon carbide, conforming to impedance matching structural design principles and facilitating electromagnetic wave absorption.
[0051] The fourth aspect of this application provides a method for preparing silicon-carbon-nitrogen ceramics according to the above-described embodiments, comprising the following steps:
[0052] S20: In an inert atmosphere, the raw materials, including modified polysilazane and photoinitiator, are subjected to ultraviolet light curing treatment.
[0053] In the preparation method of this application, since the modified polysilazane contains photosensitive groups, these groups will crosslink and solidify under the action of a photoinitiator and ultraviolet light. Simultaneously, the main chain of the polysilazane will also break down, and the silicon, nitrogen, carbon, and other elements in the polymer will recombine. Therefore, silicon-carbon-nitrogen ceramics can be obtained by curing the modified polysilazane and photoinitiator raw materials under ultraviolet light. This preparation method offers controllable processes, rapid and controllable ultraviolet curing rates, high ceramic yield, and the ability to prepare ceramic products with complex structures.
[0054] In some embodiments, the photoinitiator includes at least one of free radical photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone; these photoinitiators facilitate ultraviolet curing, making the ceramic preparation process rapid and controllable, and improving the ceramic yield.
[0055] In some embodiments, the mass ratio of modified polysilazane to photoinitiator is 100:(0.1 to 5). In exemplary examples, the ratio may include, but is not limited to, any or any two values of 100:0.1, 100:0.5, 100:1, 100:2, 100:5.
[0056] In some embodiments, the ultraviolet light wavelength used for ultraviolet curing is 365–405 nm; in some embodiments, the power of the ultraviolet lamp used for ultraviolet curing is 0.01–200 W, which covers the laser power for micro-nano printing and the ultraviolet light power for macroscopic bulk curing, adapting to different fabrication processes.
[0057] The following description is based on specific embodiments.
[0058] Example A1
[0059] This embodiment provides a modified polysilazane and its preparation method. The modified polysilazane is a modified polyborosilazane, in which isocyanate groups are grafted onto the N atoms of the polyborosilazane backbone, and acrylic acid groups are also bonded to the isocyanate groups.
[0060] Please refer to Figure 1. The preparation method includes the following steps S1 to S2:
[0061] Raw materials: The polyborosilazane is commercially available polyborosilazane KH-PSNB-1, the isocyanate compound containing the photosensitive group is ethyl 2-isocyanate (IEA), and the organic solvent is tetrahydrofuran (THF).
[0062] S1: Replace the air in the 100mL reaction flask equipped with a magnetic stirrer with nitrogen as an inert gas, add 30mL of tetrahydrofuran, 41.62g of polyborosilazane KH-PSNB-1 and 4.23g of ethyl 2-isocyanate (IEA) to the reaction flask, stir at 900 rpm, and react at 60°C for 4 hours;
[0063] S2: At room temperature, tetrahydrofuran is removed from the system by vacuum distillation to obtain modified polyborosilazane.
[0064] Example A2
[0065] This embodiment provides a modified polysilazane and its preparation method. The preparation method differs from that of Example A1 only in that the reaction solvent in step S1 is changed to 15 mL of tetrahydrofuran, and the reaction raw materials are changed to 16.8 g of polyborosilazane KH-PSNB-1 and 1.9 g of ethyl 2-isocyanate (IEA). All other aspects are the same.
[0066] Example A3
[0067] This embodiment provides a modified polysilazane and its preparation method. The preparation method differs from that of Example A1 only in that the reaction raw materials in step S1 are changed to 43.71g of polyborosilazane KH-PSNB-1 and 4.36g of isocyanate methacrylate (IEM). All other aspects are the same.
[0068] Example A4
[0069] This embodiment provides a modified polysilazane and its preparation method. The only difference between the preparation method and that of Example A1 is that in step S1, ethyl 2-isocyanate is replaced with the same mass of isocyanate methacrylate, and all other steps are the same.
[0070] Example A5
[0071] This embodiment provides a modified polysilazane and its preparation method. The only difference between the preparation method and that of Example A1 is that in step S1, ethyl 2-isocyanate is replaced with the same mass of isocyanate methacrylate, and all other steps are the same.
[0072] Example A6
[0073] This embodiment provides a modified polysilazane and its preparation method. The only difference between the preparation method and that of Example A1 is that in step S1, the polyborosilazane KH-PSNB-1 is replaced with the same mass of all-hydrogen polysilazane, and all other steps are the same.
[0074] Example A7
[0075] This embodiment provides a modified polysilazane and its preparation method. The only difference between the preparation method and that of Example A1 is that in step S1, the polyborosilazane KH-PSNB-1 is replaced with the same mass of carborane alkyl polysilazane, and all other steps are the same.
[0076] Example A8
[0077] This embodiment provides a modified polysilazane and its preparation method. The only difference between the preparation method and that of Example A1 is that in step S1, polyborosilazane KH-PSNB-1 is replaced with polyboroaluminosilicate of the same mass, while all other steps are the same.
[0078] Comparative Example A1
[0079] This comparative example provides polysilazane, namely polyborosilazane KH-PSNB-1 in Example 1, without any modification treatment.
[0080] Comparative Example A2
[0081] This comparative example provides modified polysilazane, which is a physical mixture. The raw materials are polyborosilazane KH-PSNB-1 from Example 1, and acrylic acid monomer.
[0082] At room temperature and in an inert atmosphere, 50.23 g of borosilicate and 5.11 g of acrylic monomer (mass ratio approximately 10:1) were mixed by magnetic stirring at a speed of 900 rpm for 4 hours to obtain physically mixed modified polysilazane.
[0083] Comparative Example A3
[0084] This comparative example provides modified polysilazane, which is a physical mixture. The only difference between this example and Comparative Example A2 is that it uses 50.23g of borosilicate and 10.2g of acrylic monomer (mass ratio of approximately 5:1). All other components are the same.
[0085] The differences between Examples A1 to A8 and Comparative Examples A1 to A3 are shown in Table 1.
[0086] Table 1
[0087] Examples of silicon-carbon-nitrogen ceramics:
[0088] The polysilazane and modified polysilazane provided in Examples A1 to A8 and Comparative Examples A1 to A3 above were used to prepare silicon-carbon-nitrogen ceramics according to the following method:
[0089] In an inert atmosphere, the samples provided in each case were mixed with phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator) at a mass ratio of 100:2, and cured under a 365nm, 100W ultraviolet lamp to obtain the corresponding silicon carbon nitride ceramics.
[0090] In this example, Example A1 modified polysilazane to prepare Example B1 silicon carbon nitrogen ceramic, Example A2 modified polysilazane to prepare Example B2 silicon carbon nitrogen ceramic, and so on, until Comparative Example A3 modified polysilazane to prepare Comparative Example B3 silicon carbon nitrogen ceramic.
[0091] Relevant performance tests and results analysis
[0092] 1. Fourier transform infrared test
[0093] The raw materials and products in Examples A1 to A8 and Comparative Examples A1 to A3 were tested by a Fourier transform infrared spectrometer to obtain Fourier transform infrared (FT-IR) spectra. The Fourier transform infrared spectra of KH-PSNB-1, IEA and modified polysilazane samples in Example A1 are shown in Figure 2.
[0094] As shown in Figure 2, the signal peak is 3381 cm⁻¹. -1 (NH); 3047cm -1 +3008cm -1 (CH=); 2957cm -1 +2883cm -1 (CH-); 2276cm -1 +1356cm -1 (-CNO); 2130cm -1 (Si-H); 1727cm -1 (C=O); 1639cm -1 (CC = C); 1593cm -1 (Si-C=C); 3320cm -1 +1690cm -1 +1537cm -1 +1464cm -1 (CO-NH); 1403cm -1 +1360cm -1 (BN); 1260cm -1 (Si-CH3)990cm -1(Si-N-Si). In the FTIR spectrum of the modified polysilazane in Example A1, the disappearance of the signal peak representing the -CNO group and the appearance of the signal peaks representing CC=C, C=O, and CO-NH groups indicate that the isocyanate compound underwent an addition reaction with the polysilazane, and the photosensitive group was successfully introduced into the chemical structure of the polyborosilicate, rather than a simple physical mixture.
[0095] 2 Differential Scan Calorimetry
[0096] Photo-DSC curves of silicon-carbon-nitrogen ceramics prepared by photocuring in each case were plotted using differential scanning calorimetry (DSC). Figure 3 shows the Photo-DSC curves of polyborosilazane KH-PSNB-1 (with 2 wt.% photoinitiator added) in Comparative Example A1 and modified polysilazane in Example A1 with different amounts of photoinitiator (0.5 wt.%, 1 wt.%, 2 wt.%) during the UV-curing process of ceramics. It can be seen that within a certain range, the more photoinitiator added, the higher the photocuring efficiency. In addition, KH-PSNB-1 polyborosilazane itself also contains vinyl groups (common knowledge in the industry). KH-PSNB-1 in Comparative Example A1 can be directly mixed with the photoinitiator for UV-curing pyrolysis to prepare ceramics. However, as can be seen from Figure 3, the photocuring efficiency of this method is extremely low. When 2 wt.% of photoinitiator is added, the modified polysilazane in Example A1 has a significantly higher photocuring efficiency than the unmodified polysilazane in Comparative Example A1.
[0097] 3. Thermogravimetric test
[0098] Figure 4 shows the thermogravimetric curves of polyborosilazane KH-PSNB-1 (UV irradiation for 60 minutes) in Comparative Example A1 and modified polyborosilazane (UV irradiation for 10 minutes) in Example A1 during UV curing for ceramic preparation. As can be seen in Figure 4, compared to unmodified polyborosilazane, introducing isocyanate compounds containing photosensitive groups into the chemical structure of polyborosilazane did not decrease the ceramic yield, but rather increased it.
[0099] Figure 5 shows the thermogravimetric analysis (TGA) curves and differential thermal analysis (DTA) curves of the modified polyborosilicate prepared in Comparative Example A3. The DTA curves show the curing and pyrolysis temperatures, and the TGA curves show that the ceramic yield is very low.
[0100] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A modified polysilazane characterized by: It includes a polysilazane backbone, an isocyanate group, and a photosensitive group, wherein the carbon atom of the isocyanate group is bonded to at least a portion of the nitrogen atom of the polysilazane backbone, and the photosensitive group is bonded to the nitrogen atom of the isocyanate group.
2. The modified polysilazane of claim 1, wherein: The modified polysilazane includes a repeating unit represented by the following general chemical structure (I): In general formula (I), R3 is the photosensitive group; a is 5 to 10; R1 and R2 may be the same or different, including at least one of alkyl, hydrogen atom, vinyl, and phenyl.
3. The modified polysilazane according to claim 1 or 2, characterized in that: The polysilazane backbone includes at least one of polyboron silazane backbone, polyaluminum silazane backbone, and polyboron aluminum silazane backbone. And / or, the grafting rate of the isocyanate group onto the polysilazane backbone is 5% to 20%; And / or, the photosensitive group includes at least one of acrylate group and methacrylate group.
4. A process for the preparation of a modified polysilazane according to any one of claims 1 to 3, characterized in that Includes the following steps: In an inert atmosphere, a raw material comprising polysilazane and an isocyanate compound containing the photosensitive group is subjected to an addition reaction, such that the isocyanate group of the isocyanate compound is grafted onto the nitrogen atom of the main chain of the polysilazane.
5. The method of claim 4, wherein: The mass ratio of the polysilazane to the isocyanate compound is (5-20):1; And / or, the polysilazane comprises at least one of perhydropolyborosilicate, hyperbranched polyborosilicate, carborane-alkyl polyborosilicate, polyaluminasilazane, and polyborosilicate; And / or, the isocyanate compound includes at least one of ethyl 2-isocyanate acrylate and ethyl isocyanate methacrylate.
6. The production method according to claim 4 or 5, characterized in that: The temperature of the addition reaction is 20–100°C; And / or, the addition reaction takes 1 to 20 hours; And / or, the reaction solvent for the addition reaction includes at least one of tetrahydrofuran, n-hexane, xylene, and toluene.
7. A silicon carbonitride ceramic, characterized by: It is obtained by curing and pyrolyzing the modified polysilazane according to any one of claims 1 to 3 or the modified polysilazane prepared by the preparation method according to any one of claims 4 to 6.
8. A method of making the silicon carbonitride ceramic of claim 7, wherein, Includes the following steps: The raw materials, including the modified polysilazane and the photoinitiator, are subjected to ultraviolet light curing in an inert atmosphere.
9. The method of claim 8, wherein: The photoinitiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone; And / or, the mass ratio of the modified polysilazane to the photoinitiator is 100:(0.1-5).
10. The production method according to claim 8 or 9, characterized in that: The ultraviolet light wavelength used in the ultraviolet curing process is 365–405 nm. And / or, the power of the ultraviolet lamp used in the ultraviolet curing treatment is 0.01 to 200W.