CN115651202A - Preparation method of modified polycarbosilane containing pyridine ring and wave-absorbing silicon carbide ceramic powder - Google Patents
Preparation method of modified polycarbosilane containing pyridine ring and wave-absorbing silicon carbide ceramic powder Download PDFInfo
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- 229920003257 polycarbosilane Polymers 0.000 title claims abstract description 65
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical group C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 title claims abstract description 40
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 33
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 239000000919 ceramic Substances 0.000 title claims description 43
- 239000000843 powder Substances 0.000 title claims description 23
- 239000000243 solution Substances 0.000 claims abstract description 29
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- 239000000376 reactant Substances 0.000 claims abstract description 18
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical compound C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000011259 mixed solution Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 14
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 claims abstract description 14
- XSDCTSITJJJDPY-UHFFFAOYSA-N chloro-ethenyl-dimethylsilane Chemical compound C[Si](C)(Cl)C=C XSDCTSITJJJDPY-UHFFFAOYSA-N 0.000 claims abstract description 11
- YLJJAVFOBDSYAN-UHFFFAOYSA-N dichloro-ethenyl-methylsilane Chemical compound C[Si](Cl)(Cl)C=C YLJJAVFOBDSYAN-UHFFFAOYSA-N 0.000 claims abstract description 11
- NNTOJPXOCKCMKR-UHFFFAOYSA-N boron;pyridine Chemical compound [B].C1=CC=NC=C1 NNTOJPXOCKCMKR-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 6
- 238000001816 cooling Methods 0.000 claims abstract description 4
- 238000005336 cracking Methods 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 16
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- 238000004132 cross linking Methods 0.000 claims description 12
- 239000000047 product Substances 0.000 claims description 11
- 239000002994 raw material Substances 0.000 claims description 9
- 239000006227 byproduct Substances 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 8
- 238000004821 distillation Methods 0.000 claims description 7
- 230000004048 modification Effects 0.000 claims description 7
- 238000012986 modification Methods 0.000 claims description 7
- UORVGPXVDQYIDP-UHFFFAOYSA-N borane Chemical compound B UORVGPXVDQYIDP-UHFFFAOYSA-N 0.000 claims description 6
- 239000012265 solid product Substances 0.000 claims description 5
- 238000000498 ball milling Methods 0.000 claims description 4
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 claims description 4
- 229910000085 borane Inorganic materials 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000000197 pyrolysis Methods 0.000 claims description 3
- 229910010293 ceramic material Inorganic materials 0.000 abstract description 9
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- 238000007254 oxidation reaction Methods 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000002349 favourable effect Effects 0.000 description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 6
- 229910052723 transition metal Inorganic materials 0.000 description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 5
- 239000006096 absorbing agent Substances 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
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- 150000003624 transition metals Chemical group 0.000 description 5
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 4
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- 239000013067 intermediate product Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- ZQOBAJVOKBJPEE-UHFFFAOYSA-N [B].[C].[N].[Si] Chemical compound [B].[C].[N].[Si] ZQOBAJVOKBJPEE-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 229910021426 porous silicon Inorganic materials 0.000 description 2
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- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 2
- 239000008096 xylene Substances 0.000 description 2
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
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- 238000006731 degradation reaction Methods 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- KTWOOEGAPBSYNW-UHFFFAOYSA-N ferrocene Chemical group [Fe+2].C=1C=C[CH-]C=1.C=1C=C[CH-]C=1 KTWOOEGAPBSYNW-UHFFFAOYSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- ZXSSXAUYKUTLBP-UHFFFAOYSA-N hexane;trichloroborane Chemical compound ClB(Cl)Cl.CCCCCC ZXSSXAUYKUTLBP-UHFFFAOYSA-N 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 229920001709 polysilazane Polymers 0.000 description 1
- -1 polysiloxane Polymers 0.000 description 1
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- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
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Abstract
The invention relates to modified polycarbosilane containing pyridine rings and a preparation method thereof, and the preparation method comprises the following steps: under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethylvinylchlorosilane in a certain proportion to obtain a mixed reactant; uniformly mixing polycarbosilane solution and hexamethyldisilazane to obtain a mixed solution; dripping the mixed solution into the mixed reactant in a cooling state, and reacting at room temperature under stirring for a first preset time after the mixed solution is dripped; and dropping borane pyridine into the mixed reactant after the room temperature reaction, and reacting at the first preset temperature for a second preset time to obtain the modified polycarbosilane containing the pyridine ring. The modified polycarbosilane containing pyridine rings and the preparation method thereof aim to solve the problem that the existing polymer-converted silicon carbide ceramic material has low wave-absorbing performance.
Description
Technical Field
The invention relates to the technical field of wave-absorbing materials, in particular to a preparation method of modified polycarbosilane containing pyridine rings and wave-absorbing silicon carbide ceramic powder.
Background
Because of its high temperature resistance, oxidation resistance, low density and semiconductor properties, siC materials are considered to be one of the best high temperature wave-absorbing materials, and have received much research attention. The SiC ceramics prepared conventionally can not be directly used as a wave absorbing agent generally, and doping modification is an important means for improving the wave absorbing performance and the high-temperature application performance of SiC materials. The precursor conversion method is an important method for preparing ceramics developed in recent years, and the silicon carbide ceramic material prepared by the method has a special micro-nano structure and has an important application prospect in the field of high-temperature wave-absorbing materials. In addition, the method also has the advantages of low preparation temperature, strong designability, multiple processing forms and the like.
In 2013, yan Xiaowei and the like utilize polycarbosilane precursors to prepare porous silicon carbide ceramics through pyrolysis, and research the electromagnetic wave absorption performance of the porous silicon carbide ceramics in the X wave band. They found that the appearance of SiC nanocrystals and free carbon nano-domains in the ceramic significantly improved the complex dielectric constant and dielectric loss tangent of the material. They also use polysilazane as raw material to crack, and a large amount of SiC nano-crystalline grains are separated out from the annealed amorphous SiBCN ceramic product, so that the dielectric constant, dielectric loss and conductivity of SiBCN are greatly improved. In 2017, they prepared polysiloxane containing ferrocene structure and pyrolyzed to obtain SiOC ceramic with minimum reflection loss RL when the annealing temperature was 1100 deg.C min Can reach-46 dB, and the effective absorption bandwidth in the X wave band reaches 3.5GHz. Recently, kong Jie et al designed and synthesized a silicon-boron-carbon-nitrogen precursor with a structure in which a large number of benzene rings were introduced, and studied the wave-absorbing properties of its cleavage products and the high-temperature stability under inert conditions. Later, they also designed and synthesized an iron-containing silicon boron carbon nitrogen precursor and found that the precursor converted ceramics had minimal reflection loss RL at a high temperature of 885 DEG C min Can reach-12.62 dB, and the effective absorption bandwidth can reach 3.2GHz. And the ceramic is in the air condition of 885 DEG CThe structure stability can be kept well under the inert condition of 1400 ℃.
The existing polymer-converted silicon carbide ceramic material is mainly characterized in that a wave absorbing agent is added or a transition metal and benzene ring structure and the like are introduced to improve the wave absorbing performance, wherein the addition of the transition metal has the following problems, on one hand, the transition metal element can catalyze the conversion of amorphous ceramic to a crystalline state at high temperature, and excessive high dielectric loss phases can be generated in the ceramic, so that the impedance matching imbalance is caused, and the wave absorbing performance of the material is reduced. In addition, the increase of the crystalline phase may also cause the decrease of the mechanical properties of the ceramic material, which is not favorable for the ceramic material to be used as a structural wave-absorbing material. And the introduction of a benzene ring structure may cause excessive carbon in a ceramic structure, and the material is easy to lose weight, reduce performance and the like due to oxidation in a high-temperature oxidation environment.
Therefore, the inventor provides a preparation method of modified polycarbosilane containing pyridine rings and wave-absorbing silicon carbide ceramic powder.
Disclosure of Invention
(1) Technical problem to be solved
The embodiment of the invention provides a preparation method of modified polycarbosilane containing pyridine rings and wave-absorbing silicon carbide ceramic powder, which solves the technical problem of low wave-absorbing performance of the existing polymer-converted silicon carbide ceramic material.
(2) Technical scheme
The invention provides a modified polycarbosilane containing pyridine rings, which is a solution containing a component A and a component B, wherein the component A has a structural formula as follows:
the component B is borane pyridine.
The invention also provides a preparation method of the modified polycarbosilane containing pyridine rings, which comprises the following steps:
under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethylvinylchlorosilane in a certain proportion to obtain a mixed reactant;
uniformly mixing polycarbosilane solution and hexamethyldisilazane to obtain a mixed solution;
dripping the mixed solution into the mixed reactant in a cooling state, and carrying out room temperature reaction under stirring for a first preset time after the mixed solution is dripped;
removing the solvent, unreacted raw materials and byproducts from the reacted solution by reduced pressure distillation to obtain a modified polycarbosilane solid product;
preparing the modified polycarbosilane into a solution, adding borane and pyridine, uniformly mixing, and ensuring that the mixture does not have the phenomenon of upper and lower layering, thereby preparing the modified polycarbosilane solution containing pyridine rings.
Furthermore, the molar ratio of the boron trichloride to the methyl vinyl dichlorosilane to the dimethyl vinyl chlorosilane is 1 (0.2-1) to 0.05-0.5.
Further, the concentration of the polycarbosilane solution is 30-60 wt%.
Further, the first preset time is 24-48 h.
Furthermore, the molar amount of the boron trichloride is 0.1-5% of the mass gram of the solid polycarbosilane.
Furthermore, the amount of the borane pyridine is 1-50% of the mass of the modified polycarbosilane.
Further, the molar amount of the hexamethyldisilazane is 2 to 4 times the molar amount of the mixed reactants.
The invention also provides a preparation method of the wave-absorbing silicon carbide ceramic powder containing the pyridine ring modified polycarbosilane, which comprises the following steps:
crosslinking the modified polycarbosilane containing the pyridine ring at 100-150 ℃, and then pre-cracking for 2-6 h at 380-420 ℃ to obtain a pre-cracked product;
and (3) ball-milling the pre-cracking product into powder, and then putting the powder into a high-temperature cracking furnace for cracking to obtain the wave-absorbing silicon carbide ceramic powder.
Further, the working temperature of the high-temperature cracking furnace is 1000-1600 ℃.
(3) Advantageous effects
In conclusion, the B (C) N structure is introduced into the polymer derived ceramic, so that the structure is beneficial to the improvement of the high-temperature wave-absorbing performance and the high-temperature environment performance of the ceramic material, transition metal or an additional wave-absorbing agent is not required to be introduced, a large number of benzene rings are not required to be introduced, and the stability of the structure of the ceramic material in a high-temperature oxidation environment is favorably kept.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic flow chart of a preparation method of a modified polycarbosilane containing pyridine ring provided by an embodiment of the invention;
FIG. 2 is a wave-absorbing effect diagram of a silicon carbide wave-absorbing coating prepared by pyrolysis conversion of polycarbosilane containing pyridine prepared in embodiment 1 of the invention.
In the figure:
a-wave absorbing effect curve chart of the silicon carbide wave absorbing coating prepared in the embodiment 1; b-wave-absorbing effect curve chart of the silicon carbide wave-absorbing coating prepared by the existing method.
Detailed Description
Embodiments of the present invention will be described in further detail with reference to the drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the invention and are not intended to limit the scope of the invention, i.e., the invention is not limited to the embodiments described, but covers any modifications, alterations, and improvements in the parts, components, and connections without departing from the spirit of the invention.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The embodiment of the invention provides modified polycarbosilane containing pyridine rings, which is a solution containing a component A and a component B, wherein the component A has a structural formula as follows:
the component B is borane pyridine.
In the embodiment, the B (C) N structure is introduced into the polymer derived ceramic, and the structure is beneficial to the improvement of the high-temperature wave-absorbing performance and the high-temperature environment performance of the ceramic material, and does not need to introduce transition metal or add a wave-absorbing agent.
Fig. 1 is a schematic flow chart of a preparation method of a polycarbosilane containing pyridine ring modification provided by an embodiment of the invention, and the method can comprise the following steps:
s101, under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethylvinylchlorosilane in a certain proportion to obtain a mixed reactant;
s102, uniformly mixing the polycarbosilane solution and hexamethyldisilazane to obtain a mixed solution;
s103, dropping the mixed solution into the mixed reactant in a cooling state, and reacting at room temperature under stirring for a first preset time after the mixed solution is dropped;
s104, distilling the reacted solution under reduced pressure to remove the solvent, unreacted raw materials and byproducts to obtain a modified polycarbosilane solid product;
s105, preparing the modified polycarbosilane into a solution, adding borane and pyridine, uniformly mixing, and ensuring that the mixture does not have an upper and lower layering phenomenon, thereby preparing the modified polycarbosilane solution containing pyridine rings.
In the above embodiment, it is not necessary to introduce a transition metal, add a wave absorber, or the like, and the problem of performance degradation caused by this can be avoided. The solid Polycarbosilane (PCS) is used as a base for modification, and the energy production advantage of the current solid polycarbosilane can be fully utilized. A large amount of benzene ring structures are not required to be introduced, so that the problem of reduction of the oxidation resistance caused by the benzene ring structures can be avoided. Compared with the wave-absorbing silicon carbide ceramic which is not modified, the prepared wave-absorbing silicon carbide ceramic has better wave-absorbing performance and stronger oxidation resistance, and can be used for preparing wave-absorbing silicon carbide ceramic powder, wave-absorbing silicon carbide composite ceramic and wave-absorbing silicon carbide composite materials. The used reaction raw materials are common commercialized chemical raw materials, and the unit price of the raw materials is low.
In step S103, the dropping speed should be controlled at the beginning of the reaction, and the mixed reactant is subjected to an ice-water bath, and a white and misty byproduct appears at the beginning of the reaction. Since the reaction is exothermic, the reaction can be overheated by the very high initial dropping speed, and the dropping speed can be increased when the white and vaporous by-product gradually disappears. After the mixed solution is dripped, the ice-water bath can be removed, and the room temperature reaction is carried out for a first preset time under the stirring condition.
In step S104, the solution after reaction is subjected to reduced pressure distillation to remove the solvent, unreacted raw materials and byproducts, and then a modified polycarbosilane solid product is obtained. The reduced pressure distillation is carried out at 120-150 ℃, the distillation temperature is too low, the target polymer has more by-products and unreacted raw materials, and the high distillation temperature can cause self-crosslinking and curing of the precursor polymer, thereby causing the precursor polymer to be unable to be separated.
As an alternative embodiment, the molar ratio of the boron trichloride to the methyl vinyl dichlorosilane to the dimethyl vinyl chlorosilane is 1 (0.2-1) to 0.05-0.5.
Specifically, unsaturated carbon can be introduced into the polymer by methyl vinyl dichlorosilane and dimethylvinyl chlorosilane, and graphite carbon or turbulent carbon and other structures can be generated after cracking, so that the wave-absorbing performance of the derived ceramic is improved. However, too much introduction of methyl vinyl dichlorosilane and dimethylvinylchlorosilane can also result in too high carbon content in the derived ceramic, reduce the high-temperature oxidation resistance of the derived ceramic, and is not favorable for the practical application of the wave-absorbing ceramic.
Preferably, the molar ratio of boron trichloride, methylvinyldichlorosilane and dimethylvinylchlorosilane is 1. The mixed reactants with optimal performance are prepared at the ratio.
As an alternative embodiment, the first preset time is 24-48 h. Among them, too short reaction time may result in insufficient reaction progress, while too long reaction time is disadvantageous in the efficiency of polymer production.
As an alternative embodiment, the solvent in the solid polycarbosilane solution can be a hydrocarbon solvent such as n-hexane, n-heptane, toluene, xylene, etc.; wherein, the hydrocarbon solvent can better dissolve the solid polycarbosilane on one hand and does not react with reactants such as boron trichloride and the like on the other hand.
As an alternative embodiment, the polycarbosilane concentration is from 30wt% to 60wt%. Wherein, too low concentration can reduce the preparation efficiency of the polymer, and too high concentration can cause too high solution viscosity to influence the reaction.
As an optional embodiment, the molar amount of the boron trichloride is 0.1-5% of the mass gram of the solid polycarbosilane. Wherein, too low molar consumption of boron trichloride can result in too few reaction sites and is not beneficial to the introduction of subsequent vinyl, and too high molar consumption of boron trichloride can result in too low content of silicon carbide serving as a cracking product and is not beneficial to the high-temperature oxidation resistance of the silicon carbide.
In an alternative embodiment, the solvent used for preparing the modified polycarbosilane solution may be a common hydrocarbon solvent such as n-hexane, n-heptane, toluene, xylene, or the like, or a common ether solvent such as diethyl ether, tetrahydrofuran, 2-methyl-tetrahydrofuran, or the like.
As an alternative embodiment, the amount of the borane pyridine is 1 to 50 percent of the mass of the modified polycarbosilane. The ratio is too low, the introduction amount of borane pyridine is too small, and the wave absorbing performance of the modified silicon carbide ceramic product is not favorably improved; too high a proportion may cause phase separation during cracking thereof and result in a decrease in oxidation resistance.
In an alternative embodiment, hexamethyldisilazane is used in a molar amount of 2 to 4 times the molar amount of the mixed reactants. Wherein, the reaction of B-Cl bond and Si-Cl bond is not fully carried out due to the low dosage; if the amount is too high, the preparation cost will be increased, which is not favorable for the economy of the technology.
As an alternative embodiment, the first preset time is 24-48 h. Among them, too short reaction time may result in insufficient reaction progress, while too long reaction time is disadvantageous in the efficiency of polymer production.
The embodiment of the invention also provides a preparation method of the wave-absorbing silicon carbide ceramic powder containing pyridine ring modified polycarbosilane, which comprises the following steps:
s201, crosslinking the modified polycarbosilane containing the pyridine ring at 100-150 ℃, and then pre-cracking for 2-6 h at 380-420 ℃ to obtain a pre-cracked product;
s202, ball-milling the pre-cracking product into powder, and putting the powder into a high-temperature cracking furnace for cracking to obtain the wave-absorbing silicon carbide ceramic powder.
In the above embodiment, the modified polycarbosilane component has a part of unsaturated vinyl bonds and an N-H bond structure, so that the borane-pyridine component can perform a boron-hydrogen addition reaction with vinyl groups and a dehydrogenation coupling reaction with N-H bonds at the temperature, thereby forming a polymer cross-linked network. The cross-linking temperature is too low or the cross-linking time is too short, which is not beneficial to the full cross-linking of the precursor, and the cross-linking reaction is too fast and the cross-linking is not sufficient due to too high cross-linking temperature, which is not beneficial to the improvement of the ceramic yield; and the too long cross-linking time is not favorable for the efficiency and the economy of the ceramic preparation of the technology.
The pre-cracking mainly comprises the step of fully removing a structure which has higher reaction activity and is easier to crack and remove and a low-boiling solvent component in a precursor, thereby obtaining an intermediate product which can be conveniently ball-milled into powder. The pre-cracking temperature is too low or the time is too short, so that more high-reaction activity structures and low-boiling solvent components are remained in the precursor, and the structural stability of the precursor in the ball milling process is not facilitated; the high pre-cracking temperature or the long pre-cracking time are not favorable for the efficiency and the economy of the ceramic preparation of the technology.
As an optional implementation mode, the working temperature of the high-temperature cracking furnace is 1000-1600 ℃. Wherein, the precursor is not fully cerammed when the cracking temperature is too low, thereby affecting the performance of the modified silicon carbide ceramic; too high cracking temperature makes the preparation conditions too harsh, which is not favorable for the economical efficiency of the wave-absorbing ceramic preparation.
Example 1
1) Under the protection of inert atmosphere, uniformly mixing 1000ml of boron trichloride n-hexane solution (1 mol/L), 70.5g of methyl vinyl dichlorosilane (0.5 mol) and 30.2g of dimethylvinylchlorosilane (0.25 mol) to obtain a mixed reactant; uniformly mixing 1000g of Polycarbosilane (PCS) 50wt% n-hexane solution and 600g of hexamethyldisilazane to obtain a mixed solution;
2) Dripping the solid polycarbosilane mixed solution into the mixed reactant, carrying out ice-water bath on the mixed reactant, and reacting for 24 hours at room temperature under the stirring condition after the mixed solution is dripped;
3) Carrying out reduced pressure distillation on the reacted solution at 150 ℃ to remove the solvent and byproducts, thus obtaining a modified polycarbosilane solid product; preparing a dimethylbenzene solution with the concentration of 50wt% of the product, then adding 50g of borane pyridine, uniformly mixing, and ensuring no layering to obtain a modified polycarbosilane solution containing pyridine rings.
4) Crosslinking the modified polycarbosilane solution containing pyridine rings for 4 hours at 150 ℃ in a tubular furnace, heating to 400 ℃ for pre-cracking for 4 hours to obtain a pre-cracking intermediate product, ball-grinding the pre-cracking intermediate product into powder, putting the powder into a high-temperature cracking furnace, and cracking at 1200 ℃ to obtain the wave-absorbing silicon carbide ceramic powder.
As shown in fig. 2, it can be known that the wave-absorbing property (curve a) of the wave-absorbing silicon carbide ceramic containing pyridine ring modified polycarbosilane prepared in this embodiment is much better than that of the conventional wave-absorbing silicon carbide ceramic (curve B).
It should be clear that the embodiments in this specification are described in a progressive manner, and the same or similar parts in the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the drawings. Also, a detailed description of known process techniques is omitted herein for the sake of brevity.
The above are merely examples of the present application and are not intended to limit the present application. Numerous modifications and variations could be made to the present disclosure by those skilled in the art without departing from the scope of the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. The modified polycarbosilane containing pyridine rings is characterized by being a solution containing a component A and a component B, wherein the component A has a structural formula as follows:
the component B is borane pyridine.
2. A preparation method of modified polycarbosilane containing pyridine rings is characterized by comprising the following steps:
under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethylvinylchlorosilane in a certain proportion to obtain a mixed reactant;
uniformly mixing polycarbosilane solution and hexamethyldisilazane to obtain a mixed solution;
dripping the mixed solution into the mixed reactant in a cooling state, and carrying out room temperature reaction under stirring for a first preset time after the mixed solution is dripped;
removing the solvent, unreacted raw materials and byproducts from the reacted solution by reduced pressure distillation to obtain a modified polycarbosilane solid product;
preparing the modified polycarbosilane into a solution, adding borane and pyridine, uniformly mixing, and ensuring that the mixture does not have the phenomenon of upper and lower layering, thereby preparing the modified polycarbosilane solution containing pyridine rings.
3. The method for preparing modified polycarbosilane containing pyridine ring according to claim 2, wherein the molar ratio of boron trichloride to methyl vinyl dichlorosilane to dimethyl vinyl chlorosilane is 1 (0.2-1) to (0.05-0.5).
4. The method for preparing polycarbosilane containing pyridine ring modifications according to claim 3, wherein the polycarbosilane solution has a concentration of 30-60 wt%.
5. The method for preparing the modified polycarbosilane containing pyridine ring according to claim 2, wherein the first predetermined time is 24-48 h.
6. The method for preparing modified polycarbosilane containing pyridine ring according to claim 2, wherein the molar amount of boron trichloride is 0.1-5% of the mass gram of solid polycarbosilane.
7. The method for preparing modified polycarbosilane containing pyridine ring according to claim 2, wherein the amount of the borane pyridine is 1-50% of the modified polycarbosilane.
8. The method of claim 2, wherein the hexamethyldisilazane is used in an amount of 2 to 4 times the molar amount of the mixed reactants.
9. The preparation method of the wave-absorbing silicon carbide ceramic powder containing the pyridine ring modified polycarbosilane according to claim 1 is characterized by comprising the following steps:
crosslinking the modified polycarbosilane containing the pyridine ring at 100-150 ℃, and then pre-cracking for 2-6 h at 380-420 ℃ to obtain a pre-cracked product;
and (3) ball-milling the pre-cracking product into powder, and then putting the powder into a high-temperature cracking furnace for cracking to obtain the wave-absorbing silicon carbide ceramic powder.
10. The method for preparing the wave-absorbing silicon carbide ceramic powder according to claim 9, wherein the working temperature of the pyrolysis furnace is 1000-1600 ℃.
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| JP2003002975A (en) * | 2001-06-25 | 2003-01-08 | Natl Space Development Agency Of Japan | Boron-containing organosilazane polymer, method for producing the same and ceramic obtained from the polymer |
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| CN114957675A (en) * | 2021-11-29 | 2022-08-30 | 中国航空制造技术研究院 | Boron modified polycarbosilane powder and preparation method thereof |
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