CN115651202B - Preparation method of pyridine ring-containing modified polycarbosilane and wave-absorbing silicon carbide ceramic powder - Google Patents
Preparation method of pyridine ring-containing modified polycarbosilane and wave-absorbing silicon carbide ceramic powder Download PDFInfo
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- 229920003257 polycarbosilane Polymers 0.000 title claims abstract description 65
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 36
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical group C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 33
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 239000000919 ceramic Substances 0.000 title claims description 42
- 239000000843 powder Substances 0.000 title claims description 23
- 239000000243 solution Substances 0.000 claims abstract description 28
- 239000000376 reactant Substances 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims abstract description 17
- 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
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 claims abstract description 14
- NNTOJPXOCKCMKR-UHFFFAOYSA-N boron;pyridine Chemical compound [B].C1=CC=NC=C1 NNTOJPXOCKCMKR-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 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
- 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 29
- 239000002904 solvent Substances 0.000 claims description 13
- 238000000034 method 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
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000004821 distillation Methods 0.000 claims description 6
- 239000012265 solid product Substances 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 229920000642 polymer Polymers 0.000 abstract description 12
- 229910010293 ceramic material Inorganic materials 0.000 abstract description 9
- 239000002243 precursor Substances 0.000 description 12
- 238000004132 cross linking Methods 0.000 description 9
- 230000003647 oxidation Effects 0.000 description 9
- 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
- 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
- 239000000463 material Substances 0.000 description 5
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 5
- 150000003624 transition metals Chemical class 0.000 description 5
- 239000011358 absorbing material Substances 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 239000004215 Carbon black (E152) Substances 0.000 description 3
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 239000005457 ice water Substances 0.000 description 3
- 239000013067 intermediate product Substances 0.000 description 3
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 3
- 239000008096 xylene Substances 0.000 description 3
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 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
- 230000001627 detrimental effect Effects 0.000 description 2
- 239000002159 nanocrystal Substances 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 229920002554 vinyl polymer Polymers 0.000 description 2
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 description 1
- ZQOBAJVOKBJPEE-UHFFFAOYSA-N [B].[C].[N].[Si] Chemical compound [B].[C].[N].[Si] ZQOBAJVOKBJPEE-UHFFFAOYSA-N 0.000 description 1
- 238000007259 addition reaction Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000002468 ceramisation Methods 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 230000007613 environmental effect Effects 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
- 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
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- -1 polysiloxanes Polymers 0.000 description 1
- 229910021426 porous silicon Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
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Abstract
The application relates to pyridine ring-containing modified polycarbosilane and a preparation method thereof, comprising the following steps: under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane according to a certain proportion to obtain a mixed reactant; uniformly mixing a 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 for a first preset time under the stirring condition after the mixed solution is dripped; and (3) dropwise adding borane pyridine into the mixed reactant after the room-temperature reaction, and reacting at a first preset temperature for a second preset time to obtain the pyridine ring-containing modified polycarbosilane. The pyridine ring-containing modified polycarbosilane and the preparation method thereof aim to solve the problem that the existing polymer converted silicon carbide type ceramic material has low wave absorbing performance.
Description
Technical Field
The application relates to the technical field of wave-absorbing materials, in particular to a preparation method of pyridine ring-containing modified polycarbosilane and wave-absorbing silicon carbide ceramic powder.
Background
SiC materials are considered to be one of the best high-temperature wave-absorbing materials because of their properties such as high temperature resistance, oxidation resistance, low density, and semiconductors. The conventional SiC ceramic cannot be directly used as a wave absorber, and doping modification is an important means for improving the wave absorbing performance and the high-temperature application performance of the SiC material. 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 important application prospect in the field of high-temperature wave-absorbing materials. In addition, the method has the advantages of low preparation temperature, strong designability, multiple processable forms and the like.
In 2013, yan Xiaowei et al prepared porous silicon carbide ceramics by pyrolysis of polycarbosilane precursors, and studied the electromagnetic wave absorption performance in the X-band. They found that the presence of SiC nanocrystals and free carbon nano domains in ceramics significantly improved the complex dielectric constant and dielectric loss tangent of the material. They also take polysilabozane as raw material to crack, and a large number of SiC nano crystal grains are separated out from the annealed amorphous SiBCN ceramic product, and the dielectric constant, dielectric loss and conductivity of SiBCN are greatly improved. In 2017, they prepared polysiloxanes containing ferrocene structure and pyrolyzed to SiOC ceramic, with minimum reflection loss RL at 1100 ℃ annealing temperature 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 large number of benzene rings introduced into the structure, and studied the wave-absorbing performance of the cleavage product and the high temperature stability under inert conditions. Then, they also designed and synthesized an Fe-containing SiBCN precursor, and found that the precursor converted ceramic had minimum reflection loss RL at a high temperature of 885 DEG C min Can reach-12.62 dB, and the effective absorption bandwidth reaches 3.2GHz. In addition, the ceramic can keep good structural stability under the air condition of 885 ℃ and the inert condition of 1400 ℃.
The existing polymer converted silicon carbide ceramic material mainly improves the wave absorbing performance by adding a wave absorbing agent or introducing a transition metal, a benzene ring structure and the like, wherein the addition of the transition metal has the following problems that on one hand, the transition metal element can catalyze the transition of amorphous ceramic to a crystalline state at high temperature, and excessive high dielectric loss phase can be generated in the ceramic, so that the unbalance of impedance matching is caused, and the wave absorbing performance of the material is reduced. In addition, the increase of the crystal phase may also cause the mechanical property of the ceramic material to be reduced, which is unfavorable for the ceramic material to be used as the structural wave-absorbing material. And the introduction of benzene ring structure may cause excessive carbon in ceramic structure, and the material weight loss, performance reduction and the like are easily caused by oxidation under high-temperature oxidation environment.
Therefore, the inventor provides a preparation method of pyridine ring-containing modified polycarbosilane and wave-absorbing silicon carbide ceramic powder.
Disclosure of Invention
(1) Technical problem to be solved
The embodiment of the application provides a preparation method of pyridine ring-containing modified polycarbosilane 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 proposal
The application provides pyridine ring-containing modified polycarbosilane which is a solution containing a component A and a component B, wherein the structural formula of the component A is as follows:
the component B is borane pyridine.
The application also provides a preparation method of the pyridine ring-containing modified polycarbosilane, which comprises the following steps:
under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane according to a certain proportion to obtain a mixed reactant;
uniformly mixing a 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 a stirring condition for a first preset time after the mixed solution is dripped;
removing solvent, unreacted raw materials and byproducts from the reacted solution through reduced pressure distillation to obtain a modified polycarbosilane solid product;
preparing the modified polycarbosilane into a solution, adding borane pyridine, uniformly mixing, and ensuring that the mixture does not generate vertical layering phenomenon, thereby preparing the pyridine ring-containing modified polycarbosilane solution.
Further, the molar ratio of the boron trichloride to the methylvinyldichlorosilane to the dimethylvinylchlorosilane is 1 (0.2-1): 0.05-0.5.
Further, the concentration of the polycarbosilane solution is 30-60 wt%.
Further, the first preset time is 24-48 hours.
Further, the molar dosage of the boron trichloride is 0.1-5% of the mass gram of the solid polycarbosilane.
Further, the dosage of the borane pyridine is 1-50% of the mass of the modified polycarbosilane.
Further, the molar amount of hexamethyldisilazane is 2 to 4 times the molar amount of the mixed reactant.
The application also provides a preparation method of the wave-absorbing silicon carbide ceramic powder containing pyridine ring modified polycarbosilane, which comprises the following steps:
the pyridine ring-containing modified polycarbosilane is firstly crosslinked at 100-150 ℃, and then is subjected to pre-cracking for 2-6 hours at 380-420 ℃ to obtain a pre-cracking product;
and (3) grinding 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 summary, the B (C) N structure is introduced into the polymer derived ceramic, so that the structure is beneficial to improving the high-temperature wave absorption performance and the high-temperature environment performance of the ceramic material, transition metal or an external wave absorber is not required to be introduced, a large amount of benzene rings are not required to be introduced, and the ceramic material is beneficial to keeping stable structure in the high-temperature oxidation environment.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort to a person of ordinary skill in the art.
FIG. 1 is a schematic flow chart of a preparation method of pyridine ring-containing modified polycarbosilane provided by the embodiment of the application;
FIG. 2 is a graph showing the wave-absorbing effect of a silicon carbide wave-absorbing coating prepared by cracking and converting pyridine-containing modified polycarbosilane prepared in example 1 of the present application.
In the figure:
a-a graph of the wave-absorbing effect of the silicon carbide wave-absorbing coating prepared in example 1; b-wave absorbing effect curve graph of the silicon carbide wave absorbing coating prepared by the prior method.
Detailed Description
Embodiments of the present application are described in further detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are provided to illustrate the principles of the application and are not intended to limit the scope of the application, i.e., the application is not limited to the embodiments described, but covers any modifications, substitutions and improvements in parts, components and connections without departing from the spirit of the application.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
The embodiment of the application provides pyridine ring-containing modified polycarbosilane which is a solution containing a component A and a component B, wherein the structural formula of the component A is as follows:
and the component B is borane pyridine.
In the above embodiments, the B (C) N structure is introduced into the polymer-derived ceramic, which facilitates the improvement of the high-temperature wave absorbing performance and the high-temperature environmental performance of the ceramic material without introducing a transition metal or adding a wave absorber.
Fig. 1 is a schematic flow chart of a preparation method of pyridine ring-containing modified polycarbosilane according to an embodiment of the present application, where the method may include the following steps:
s101, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane in a certain proportion under the protection of inert atmosphere to obtain a mixed reactant;
s102, uniformly mixing a polycarbosilane solution and hexamethyldisilazane to obtain a mixed solution;
s103, dripping the mixed solution into the mixed reactant in a cooling state, and reacting at room temperature for a first preset time under the stirring condition after the mixed solution is dripped;
s104, removing the solvent, unreacted raw materials and byproducts from the reacted solution through reduced pressure distillation to obtain a modified polycarbosilane solid product;
s105, preparing the modified polycarbosilane into a solution, adding borane pyridine, uniformly mixing, and ensuring that the mixture does not generate vertical layering phenomenon, thereby preparing the pyridine ring-containing modified polycarbosilane solution.
In the above embodiment, there is no need to introduce a transition metal or add a wave absorber or the like, and the problem of performance degradation caused thereby can be avoided. The modified solid Polycarbosilane (PCS) can fully utilize the productivity advantage of the current solid polycarbosilane. Without introducing a large amount of benzene ring structures, the problem of reduced oxidation resistance caused by the benzene ring structures can be avoided. Compared with unmodified wave-absorbing silicon carbide ceramic, 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 material. The reaction raw materials are common commercial chemical raw materials, and the unit price of the raw materials is low.
In step S103, the dripping speed should be controlled at the beginning of the reaction, and the mixed reactant is subjected to an ice-water bath, and white and vaporous byproducts appear at the beginning of the reaction. Because the reaction is exothermic, the reaction can be overheated when the dropping speed is too fast at the beginning, and the dropping speed can be improved when the white vaporific byproducts gradually disappear. 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 reacted solution is distilled under reduced pressure to remove the solvent, unreacted raw materials and byproducts, and then the modified polycarbosilane solid product is obtained. The reduced pressure distillation should be carried out at 120-150 ℃, the distillation temperature is too low, the target polymer has more byproducts and unreacted raw materials, and the precursor polymer can be crosslinked and solidified by itself due to the too high distillation temperature, so that the precursor polymer cannot be separated.
As an alternative embodiment, the molar ratio of boron trichloride, methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane is 1 (0.2-1): 0.05-0.5.
Specifically, the methylvinyldichlorosilane and the dimethylvinylchlorosilane can introduce unsaturated carbon into the polymer, and can generate graphite carbon or turbulent layer carbon and other structures after cracking, so that the wave absorbing performance of the derivative ceramic is improved. However, too much methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane are introduced, so that the carbon content in the derivative ceramic is too high, the high-temperature oxidation resistance of the derivative ceramic is reduced, and the actual application of the wave-absorbing ceramic is not facilitated.
Preferably, the molar ratio of boron trichloride to methyl vinyl dichlorosilane to dimethyl vinyl chlorosilane is 1:0.5:0.25. The mixed reactants prepared in this ratio have the best performance.
As an alternative embodiment, the first preset time is 24 h-48 h. Wherein, too short a reaction time may result in insufficient progress of the reaction, while too long a reaction time may be detrimental to the production efficiency of the polymer.
As an alternative embodiment, the solvent in the solid polycarbosilane solution may be a hydrocarbon solvent such as n-hexane, n-heptane, toluene, xylene, etc.; wherein, the hydrocarbon solvent can better dissolve 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 concentration of polycarbosilane is 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 affect the reaction.
As an alternative embodiment, the molar amount of boron trichloride is 0.1% to 5% of the mass gram of solid polycarbosilane. The molar consumption of the boron trichloride is too low, which can lead to too few reaction sites, is unfavorable for the subsequent introduction of vinyl, and the molar consumption of the boron trichloride is too high, which can lead to too low silicon carbide content of a cracking product and is unfavorable for the high-temperature oxidation resistance.
As an alternative embodiment, the solvent used for preparing the modified polycarbosilane solution may be a general hydrocarbon solvent such as n-hexane, n-heptane, toluene, xylene, or a general ether solvent such as diethyl ether, tetrahydrofuran, 2-methyl-tetrahydrofuran, or the like.
As an alternative embodiment, the amount of borane pyridine is 1-50% of the mass of the modified polycarbosilane. Wherein, the ratio is too low, the introduction amount of borane pyridine is too small, which is unfavorable for improving the wave absorbing performance of the modified silicon carbide ceramic product; too high a ratio may cause phase separation during the cracking thereof and result in a decrease in oxidation resistance.
As an alternative embodiment, the molar amount of hexamethyldisilazane is 2 to 4 times the molar amount of the mixed reactants. Wherein, the too low usage amount may lead to insufficient reaction of B-Cl bond and Si-Cl bond; if the dosage is too high, the preparation cost is increased, which is unfavorable for the economy of the technology.
As an alternative embodiment, the first preset time is 24 h-48 h. Wherein, too short a reaction time may result in insufficient progress of the reaction, while too long a reaction time may be detrimental to the production efficiency of the polymer.
The embodiment of the application also provides a preparation method of the wave-absorbing silicon carbide ceramic powder with pyridine ring-containing modified polycarbosilane, which comprises the following steps:
s201, firstly, crosslinking the pyridine ring-containing modified polycarbosilane at 100-150 ℃, and then, pre-cracking for 2-6 hours at 380-420 ℃ to obtain a pre-cracked product;
s202, grinding the pre-cracking product into powder, and then placing 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, due to having a partially vinyl unsaturated bond and an N-H bond structure, the borane pyridine component may undergo a boro-hydro addition reaction with vinyl groups at this temperature and a dehydrocoupling reaction with N-H bonds, thereby forming a polymer cross-linked network. Wherein, the too low crosslinking temperature or too short crosslinking time is unfavorable for the sufficient crosslinking of the precursor, too high crosslinking temperature can also cause too fast crosslinking reaction to cause insufficient crosslinking, which is unfavorable for the improvement of the ceramic yield; and the long crosslinking time is unfavorable for the efficiency and the economy of the technology for preparing ceramics.
The pre-cracking is mainly to fully remove the structure with higher reactivity and easier cracking removal in the precursor and the low-boiling solvent component, thereby obtaining an intermediate product which can be conveniently ball-milled into powder. The presplitting temperature is too low or the presplitting time is too short, so that more high-reactivity 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 presplitting temperature is too high or too long, which is unfavorable for the efficiency and economy of the technology for preparing ceramics.
As an alternative embodiment, the operating temperature of the pyrolysis furnace is 1000-1600 ℃. Wherein, too low a cracking temperature may result in insufficient ceramization of the precursor, thereby affecting the performance of the modified silicon carbide ceramic; too high cracking temperature makes the preparation conditions too severe, which is unfavorable for the economy of the preparation of the wave-absorbing ceramic.
Example 1
1) Under the protection of inert atmosphere, 1000ml of boron trichloride n-hexane solution (1 mol/L), 70.5g of methyl vinyl dichlorosilane (0.5 mol) and 30.2g of dimethyl vinyl chlorosilane (0.25 mol) are uniformly mixed to obtain a mixed reactant; uniformly mixing 1000g of Polycarbosilane (PCS) 50wt% normal hexane solution and 600g of hexamethyldisilazane to obtain a mixed solution;
2) Dropping the solid polycarbosilane mixed solution into the mixed reactant, wherein the mixed reactant is subjected to ice-water bath, and reacting for 24 hours at room temperature under the stirring condition after the mixed solution is added dropwise;
3) Distilling the reacted solution at 150 ℃ under reduced pressure to remove solvent and byproducts, thereby obtaining a modified polycarbosilane solid product; a50 wt% strength xylene solution of the product was prepared, followed by 50g of borane pyridine, mixed well and ensured that no delamination resulted in a pyridine ring containing modified polycarbosilane solution.
4) And (3) crosslinking the pyridine ring-containing modified polycarbosilane solution in a tubular furnace at 150 ℃ for 4 hours, then 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 seen that the wave-absorbing performance (curve a) of the silicon carbide ceramics containing pyridine ring modified polycarbosilane prepared in this example is much better than that of the conventional silicon carbide ceramics (curve B).
It should be understood that, in the present specification, each embodiment is described in an incremental manner, and the same or similar parts between the embodiments are all referred to each other, and each embodiment is mainly described in a different point from other embodiments. The application is not limited to the specific steps and structures described above and shown in the drawings. Also, a detailed description of known method techniques is omitted here for the sake of brevity.
The above is only an example of the present application and is not limited to the present application. Various modifications and alterations of this application will become apparent to those skilled in the art without departing from the scope of this application. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
Claims (9)
1. The preparation method of the pyridine ring-containing modified polycarbosilane is characterized by comprising the following steps of:
under the protection of inert atmosphere, uniformly mixing boron trichloride, methyl vinyl dichlorosilane and dimethyl vinyl chlorosilane according to a certain proportion to obtain a mixed reactant;
uniformly mixing a 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 a stirring condition for a first preset time after the mixed solution is dripped;
removing solvent, unreacted raw materials and byproducts from the reacted solution through reduced pressure distillation to obtain a modified polycarbosilane solid product;
preparing the modified polycarbosilane into a solution, adding borane pyridine, uniformly mixing, and ensuring that the mixture does not generate vertical layering phenomenon, thereby preparing the pyridine ring-containing modified polycarbosilane solution.
2. The method for producing a pyridine ring-containing modified polycarbosilane according to claim 1, wherein the molar ratio of boron trichloride to methylvinyldichlorosilane to dimethylvinylchlorosilane is 1 (0.2 to 1): 0.05 to 0.5.
3. The method for producing pyridine ring-containing modified polycarbosilane according to claim 2, wherein the concentration of the polycarbosilane solution is 30wt% to 60wt%.
4. The method for producing a pyridine ring-containing modified polycarbosilane according to claim 1, wherein the first preset time is 24 hours to 48 hours.
5. The method for preparing pyridine ring-containing modified polycarbosilane according to claim 1, wherein the molar amount of boron trichloride is 0.1% -5% of the mass gram of solid polycarbosilane.
6. The method for preparing pyridine ring-containing modified polycarbosilane according to claim 1, wherein the amount of the borane pyridine is 1% -50% of the mass of the modified polycarbosilane.
7. The method for producing a pyridine ring-containing modified polycarbosilane according to claim 1, wherein the molar amount of hexamethyldisilazane is 2 to 4 times the molar amount of the mixed reactant.
8. A method for producing a wave-absorbing silicon carbide ceramic powder having the pyridine ring-containing modified polycarbosilane according to any one of claims 1 to 7, comprising the steps of:
the pyridine ring-containing modified polycarbosilane is firstly crosslinked at 100-150 ℃, and then is subjected to pre-cracking for 2-6 hours at 380-420 ℃ to obtain a pre-cracking product;
and (3) grinding 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.
9. The method for preparing the wave-absorbing silicon carbide ceramic powder according to claim 8, wherein the working temperature of the high-temperature cracking 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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| 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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