Ti-containing Si-C-N ceramic precursor and synthesis method and application thereof
阅读说明：本技术 一种含Ti的Si-C-N陶瓷先驱体及其合成方法和应用 (Ti-containing Si-C-N ceramic precursor and synthesis method and application thereof ) 是由 蒋军军 朱建丰 薛珊燕 于 2020-12-11 设计创作，主要内容包括：本发明公开了一种含Ti的Si-C-N陶瓷先驱体及其合成方法和应用,将聚甲基硅烷先置于反应釜中,将反应釜升温至80～120℃,然后将含乙烯基聚硅氮烷(Vi-PSN)滴加进反应釜,第一次回流反应,冷却至室温后,再将TiCl_4滴加至反应釜内,第二次回流反应,即得含Ti的Si-C-N陶瓷先驱体。本发明的合成方法,先将Vi-PSN与PMS反应,将烯基基团及N元素带入到PMS的分子结构中,然后再利用TiCl_4中的Ti-Cl键与PMS中的Si-H反应,对PMS进行灭活处理,同时给先驱体引入Ti元素。所得Si-C-N陶瓷先驱体在空气中稳定；并且Ti元素的存在,能够提高陶瓷先驱体与基材之间的粘结性以及烧结陶瓷自身的致密度,从而在一定程度上提高复材的力学性能。(The invention discloses a Ti-containing Si-C-N ceramic precursor and a synthesis method and application thereof, which comprises the steps of firstly placing polymethylsilane in a reaction kettle, heating the reaction kettle to 80-120 ℃, then dropwise adding vinyl-containing polysilazane (Vi-PSN) into the reaction kettle, carrying out a first reflux reaction, cooling to room temperature, and then adding TiCl 4 Dropwise adding the mixture into a reaction kettle, and carrying out secondary reflux reaction to obtain the Ti-containing Si-C-N ceramic precursor. The synthesis method of the invention comprises the steps of firstly reacting Vi-PSN with PMS, bringing alkenyl group and N element into the molecular structure of PMS, and then utilizing TiCl 4 The Ti-Cl bond in the precursor reacts with Si-H in PMS to inactivate the PMS and introduce Ti element into the precursor. The obtained Si-C-N ceramic precursor is stable in the air; in addition, the existence of Ti can improve the cohesiveness between the ceramic precursor and the base material and the density of the sintered ceramic, thereby improving the mechanics of the composite material to a certain extentAnd (4) performance.)
1. A method for synthesizing a Ti-containing Si-C-N ceramic precursor is characterized by comprising the following steps: the method comprises the following steps:
placing polymethylsilane in a reaction kettle, heating the reaction kettle to 80-120 ℃, then dropwise adding vinyl-containing polysilazane into the reaction kettle, carrying out a first reflux reaction, cooling to room temperature, and then adding TiCl4Dropwise adding the mixture into a reaction kettle, and carrying out secondary reflux reaction to obtain the Ti-containing Si-C-N ceramic precursor.
2. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: and heating the reaction kettle to 80-90 ℃, then dropwise adding the vinyl-containing polysilazane into the reaction kettle, and carrying out a first reflux reaction.
3. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: the addition amount of the vinyl-containing polysilazane is 20 to 100 weight percent of the mass of the polymethylsilane.
4. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: the dripping speed of the vinyl-containing polysilazane is 60-80 mL/min.
5. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: the time of the first reflux reaction is 5-8 h.
6. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: the TiCl4The addition amount of (A) is 0.5 wt% -1 wt% of the mass of the polymethylsilane.
7. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein:the TiCl4The dropping speed of (a) is 20-30 mL/min.
8. The method for synthesizing a Ti-containing Si-C-N ceramic precursor as claimed in claim 1, wherein: the time of the second reflux reaction is 1-2 h.
9. A Ti-containing Si-C-N ceramic precursor prepared by the preparation method according to any one of claims 1 to 8.
10. Use of a Ti-containing Si-C-N ceramic precursor prepared by the preparation method according to any one of claims 1 to 8, wherein: the Si-C-N ceramic precursor containing Ti is applied to the preparation of ceramic matrix composites.
Technical Field
The invention belongs to the technical field of preparation of ceramic precursors, and particularly relates to a Ti-containing Si-C-N ceramic precursor as well as a synthesis method and application thereof.
Background
With the rapid development of modern science and technology, in various fields such as aviation, aerospace, energy, high-performance weaponry, high-temperature engineering and the like, a lightweight, high-specific modulus, high-temperature resistance, corrosion resistance, oxidation resistance and wear resistance ceramic material is urgently needed. The brittleness of the monomer ceramic material becomes a main factor limiting the application of the monomer ceramic material; therefore, the adoption of various methods such as phase change toughening, whisker or fiber reinforced toughening and the like to improve the brittleness of the ceramic material and the preparation of high-performance complex phase ceramic or ceramic matrix composite material becomes a continuous research subject for researchers in various countries for decades. In addition to brittleness, poor processability of ceramic materials makes them more complex and demanding manufacturing processes than organic polymer materials.
The precursor conversion method is a method and a process for converting organic materials into inorganic ceramic materials by using organic polymers as precursors, forming the precursors by utilizing the characteristics of solubility, meltability and the like, and then carrying out high-temperature thermal decomposition treatment. The method builds a bridge between two completely different materials, namely the organic high molecular polymer and the ceramic material, so that the two fields are not too numerous to be entered and are not related to each other, and the method is a new process for preparing the continuous fiber reinforced ceramic matrix composite material developed in recent years.
The ceramic precursor polymer is an organic matter containing inorganic elements and partial organic groups of target ceramic, can be rheologically formed and crosslinked, and can be subjected to cracking, structural rearrangement and other reactions through high-temperature treatment to form a ceramic material with a specific shape and a specific structure.
The silicon carbide ceramic precursor is mainly divided into two types, wherein polycarbosilane is solid, a large amount of solvent needs to be added, the ceramic yield is very low, and the polycarbosilane is naturally rich in carbon, so that the oxidation resistance of a converted ceramic product is insufficient, the mechanical property is insufficient, polymethyl silane is liquid, only a small amount of cross-linking agent needs to be added when the silicon carbide ceramic precursor is used, the ceramic yield is higher than that of the polycarbosilane, however, the silicon carbide ceramic precursor is unstable to air and easy to spontaneously combust due to the fact that the silicon carbide ceramic precursor has active silicon-hydrogen bonds, and meanwhile, a cracked product is rich in silicon, so that the application difficulty of the silicon carbide ceramic precursor is greatly improved.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a Ti-containing Si-C-N ceramic precursor with excellent characteristics of low activity, small viscosity, high ceramic yield and the like, and a synthesis method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a synthesis method of a Ti-containing Si-C-N ceramic precursor, which comprises the following steps: placing polymethyl silane in a reaction kettle, heating the reaction kettle to 80-120 ℃, then dropwise adding vinyl-containing polysilazane (Vi-PSN) into the reaction kettle, carrying out a first reflux reaction, cooling to room temperature, and then adding TiCl4Dropwise adding the mixture into a reaction kettle, and carrying out secondary reflux reaction to obtain the Ti-containing Si-C-N ceramic precursor.
The synthesis method comprises the steps of firstly carrying out a certain degree of reaction on Vi-PSN and PMS at 80-120 ℃, successfully bringing alkenyl groups and N elements into the molecular structure of PMS through the reaction of Si-H and vinyl, and then utilizing TiCl4The Ti-Cl bond in the precursor reacts with Si-H in PMS to inactivate the PMS and introduce Ti element into the precursor. The obtained Si-C-N ceramic precursor is stable in the air; and the existence of Ti element can improve the cohesiveness between the ceramic precursor and the base material and the density of the sintered ceramic, thereby improving the mechanical property of the composite material to a certain extent.
In the present invention, the reaction temperature of the polymethylsilane and the vinyl-containing polysilazane is controlled effectively, and if the temperature is too low, the polymethylsilane and the vinyl-containing polysilazane do not react sufficiently, and if the temperature is too high, the self-polymerization crosslinking reaction of the vinyl-containing polysilazane is caused, the viscosity of the product is increased, and even insoluble solids are generated, thereby affecting the yield of the ceramic.
The reaction provided by the invention is suitable for large-scale production, in the actual production process, the reaction system is firstly vacuumized to the vacuum degree of-0.08-0.09, the Polymethylsilane (PMS) is sucked into a reaction kettle, the vinyl-containing polysilazane (Vi-PSN) is sucked into a No. 1 elevated tank, and then TiCl is sucked into the reaction kettle4Sucking into No. 2 head tank, and introducing N2To form a gas blanketProtected reaction environment, said N2The purity was 99.999%.
In the invention, the Polymethylsilane (PMS) is produced and provided by Bo Wang carbon pottery Co., Ltd, the molecular weight is 800-1000, the viscosity is 200-300 cP, and the ceramic yield is 25-40%; it is unstable to air, dipped in absorbent cotton, and placed in an aerobic environment at 25 deg.C for 1min to spontaneously ignite.
According to the preferable scheme, the temperature of the reaction kettle is increased to 80-90 ℃, then the vinyl-containing polysilazane (Vi-PSN) is dripped into the reaction kettle, and the first reflux reaction is carried out.
In a preferred scheme, the addition amount of the vinyl-containing polysilazane (Vi-PSN) is 20 to 100 weight percent of the mass of the polymethylsilane.
The vinyl-containing polysilazane is controlled within the above range, and a ceramic precursor having a suitable viscosity can be obtained, and further, in the present invention, the cleavage product of the vinyl-containing polysilazane is rich in carbon and the polymethylsilane is rich in silicon, so that the cleavage product of the ceramic precursor can be controlled to be slightly rich in carbon and silicon by controlling the addition amount of the vinyl-containing polysilazane, and an ideal SiC/Si satisfying the stoichiometric ratio can be obtained3N4A complex phase ceramic.
More preferably, the amount of the vinyl-containing polysilazane (Vi-PSN) added is 40 to 50 wt% based on the mass of the polymethylsilane.
Controlling the vinyl-containing polysilazane within the preferred range can make the Ti-containing Si-C-N ceramic precursor cleavage product to satisfy the stoichiometric ratio of SiC/Si3N4A complex phase ceramic.
In the preferable scheme, the dropping speed of the vinyl-containing polysilazane (Vi-PSN) is 60-80 mL/min.
In the invention, the vinyl-containing polysilazane (Vi-PSN) is produced and provided by Bowang carbon-ceramic Co., Ltd, the molecular weight is 400-600, the viscosity is 50-100 cP, and the ceramic yield is 15-30%; oxidation reaction easily occurs in the air and becomes solid.
In the preferable scheme, the time of the first reflux reaction is 5-8 h.
In the present invention, the time of the first reflux reaction is the time of continuing the reaction after the completion of the dropwise addition of the vinyl group-containing polysilazane, and the first reflux reaction is carried out under stirring.
Preferred embodiment, the TiCl4The addition amount of (A) is 0.5 wt% -1 wt% of the mass of the polymethylsilane.
In the present invention, TiCl4The reaction with the polymethylsilane is a reversible reaction, and on one hand, the reaction with the Si-H bond can promote the rearrangement of the Si-Si bond.
TiCl4If TiCl is required to be effectively controlled4The addition amount is too small, the content of unreacted Si-H bonds is more, and the inactivation effect cannot be realized; TiCl (titanium dioxide)4Too large an amount of addition, too violent reaction, excessive crosslinking, increase in viscosity, and, in addition, TiCl4The addition of too large amount rather enhances the activity of the final product, which is equivalent to rendering the inactivation ineffective.
In addition, TiCl simultaneously4The dropping temperature and time also need to be controlled if TiCl4The rearrangement of Si-Si bonds can be promoted when the dropping temperature is too high or the reaction time is too long, so that the inactivation failure of the polymethylsilane is caused; and TiCl4The dropping temperature is too low or the reaction time is too short, the reaction is insufficient, and the product can not be completely inactivated.
In the present invention, TiCl4Purchased from Shanghai Michelin Biochemical technology, Ltd., purity of 99.0%, and was a colorless liquid.
Preferred embodiment, the TiCl4The dropping speed of (a) is 20-30 mL/min.
In the preferable scheme, the time of the second reflux reaction is 1-2 h.
In the present invention, the time of the second reflux reaction means TiCl4After the dropwise addition, the reaction was continued for a second reflux reaction with stirring.
The invention also provides a Ti-containing Si-C-N ceramic precursor prepared by the preparation method.
The viscosity of the Ti-containing Si-C-N ceramic precursor is 116-216 cp, the ceramic yield is 48-68%, and the optimal selection is 62-68%.
The invention also provides application of the Ti-containing Si-C-N ceramic precursor prepared by the preparation method, and the Ti-containing Si-C-N ceramic precursor is applied to preparation of a ceramic matrix composite.
Principles and advantages
Firstly, Vi-PSN and PMS are subjected to a certain degree of reaction at 80-120 ℃, and alkenyl groups and N elements are successfully brought into a molecular structure of PMS; due to the fact that the viscosity of Vi-PSN is low, the Vi-PSN can serve as a diluent to reduce the viscosity of PMS, and can be better applied to a PIP process; due to the existence of the alkenyl group, the modified vinyl acetate can well serve as a cross-linking agent in the subsequent ceramic heat treatment process, so that the cracked ceramic product has a compact structure, and the ceramic yield is greatly improved; the introduction of N element leads SiC/Si to be formed after sintering3N4The N element of the complex phase ceramic can well inhibit rapid growth of SiC grains at high temperature, so that the temperature resistance of the material is greatly improved. The invention utilizes a very small amount of TiCl4PMS is subjected to inactivation treatment due to TiCl4Is very active and one molecule of TiCl is used4Containing four Ti-Cl bonds, therefore, very small amounts of TiCl are employed at room temperature4A large amount of Si-H active groups in the PMS can be consumed, so that the stability of the PMS to air is greatly improved; and the existence of Ti element can improve the cohesiveness between the ceramic precursor and the base material and the density of the sintered ceramic, thereby improving the mechanical property of the composite material to a certain extent.
The Ti-containing Si-C-N ceramic precursor synthesized by the method has the excellent characteristics of low activity, small viscosity, high ceramic yield and the like, and is very suitable for being applied to the field of preparing ceramic matrix composites by precursor conversion (PIP).
Detailed Description
The present invention will be described in further detail with reference to examples.
The Polymethylsilane (PMS) used in the following examples and comparative examples of the present invention was supplied by the company bocheng carbon pottery, inc, of Hunan, and had a molecular weight of 1000 and a viscosity of 300 cP; it is unstable to air, dipped in absorbent cotton, and placed in an aerobic environment at 25 deg.C for 1min to spontaneously ignite.
The vinyl-containing polysilazane (Vi-PSN) used was supplied from Bowang carbon pottery Co., Ltd, Hunan, and had a molecular weight of 400 and a viscosity of 50 cP.
TiCl used4Purchased from Shanghai Michelin Biochemical technology, Ltd., purity of 99.0%, and was a colorless liquid.
Example 1
The synthesis method of the Ti-containing Si-C-N ceramic precursor comprises the following steps:
(1) vacuumizing the whole synthesis system to-0.09 MPa;
(2) sucking 60L of Polymethylsilane (PMS) into a reaction kettle;
(3) sucking 12L of vinyl-containing polysilazane (Vi-PSN) into a No. 1 head tank; sealing and storing nitrogen; the suction amount is 20 wt% of the mass of PMS;
(4) 300mL of TiCl4Sucking into No. 2 high-level tank; the amount added for synthesis is 0.5 wt% of the mass of PMS;
(5) n with the purity of 99.999 percent is introduced into the whole synthesis system2To form an inert environment;
(6) the reaction kettle is raised to 80 ℃;
(7) dropwise adding Vi-PSN in the No. 1 head tank to a reaction kettle at the speed of 60 mL/min;
(8) after the dropwise addition, the reaction kettle is refluxed and stirred at the temperature of 80 ℃ for reaction for 5 hours;
(9) after cooling to room temperature, TiCl in the No. 2 elevated tank4Dropwise adding the mixture into a reaction kettle at the speed of 20 mL/min;
(10) after the dropwise addition, the reaction kettle continuously performs reflux stirring reaction for 1 hour at room temperature;
the properties of the finished product obtained were as follows:
the characteristics are as follows: a reddish brown liquid;
air stability: dipping a little absorbent cotton in an aerobic environment at 25 ℃, and not spontaneously combusting or self-heating for about 24 hours;
viscosity: 185 cP;
the ceramic yield is as follows: 55 percent;
example 2
The synthesis method of the Ti-containing Si-C-N ceramic precursor comprises the following steps:
(1) vacuumizing the whole synthesis system to-0.09 MPa;
(2) sucking 40L of Polymethylsilane (PMS) into a reaction kettle;
(3) sucking 40L of vinyl-containing polysilazane (Vi-PSN) into a No. 1 head tank; sealing and storing nitrogen, wherein the amount added for synthesis accounts for 100 wt% of PMS;
(4) 200mL of TiCl4Sucking into No. 2 high-level tank; the amount added for synthesis accounts for 0.5 wt% of PMS;
(5) n with the purity of 99.999 percent is introduced into the whole synthesis system2To form an inert environment;
(6) the reaction kettle is raised to 120 ℃;
(7) dropwise adding Vi-PSN in the No. 1 head tank to a reaction kettle at the speed of 80 mL/min;
(8) after the dropwise addition, the reaction kettle is refluxed and stirred at 120 ℃ for reaction for 5 hours;
(9) after cooling to room temperature, TiCl in the No. 2 elevated tank4Dropwise adding the mixture into a reaction kettle at the speed of 20 mL/min;
(10) after the dropwise addition, the reaction kettle continuously performs reflux stirring reaction for 1 hour at room temperature;
the properties of the finished product obtained were as follows:
the characteristics are as follows: a reddish brown liquid;
air stability: dipping a little absorbent cotton in an aerobic environment at 25 ℃, and not spontaneously combusting or self-heating for about 24 hours;
viscosity: 116 cP;
the ceramic yield is as follows: 48 percent;
example 3
The synthesis method of the Ti-containing Si-C-N ceramic precursor comprises the following steps:
(1) vacuumizing the whole synthesis system to-0.09 MPa;
(2) sucking 60L of Polymethylsilane (PMS) into a reaction kettle;
(3) sucking 12L of vinyl-containing polysilazane (Vi-PSN) into a No. 1 head tank; sealing and storing nitrogen; the amount added for synthesis accounts for 20 wt% of PMS;
(4) 600mL of TiCl are added4Sucking into No. 2 high-level tank; the amount added for synthesis accounts for 1 wt% of PMS;
(5) n with the purity of 99.999 percent is introduced into the whole synthesis system2To form an inert environment;
(6) the reaction kettle is raised to 80 ℃;
(7) dropwise adding Vi-PSN in the No. 1 head tank to a reaction kettle at the speed of 60 mL/min;
(8) after the dropwise addition, the reaction kettle is refluxed and stirred at the temperature of 80 ℃ for reaction for 5 hours;
(9) after cooling to room temperature, TiCl in the No. 2 elevated tank4Dropwise adding the mixture into a reaction kettle at the speed of 20 mL/min;
(10) after the dropwise addition, the reaction kettle continuously performs reflux stirring reaction for 2 hours at room temperature;
the properties of the finished product obtained were as follows:
the characteristics are as follows: a reddish brown liquid;
air stability: dipping a little absorbent cotton, placing the absorbent cotton in an aerobic environment at 25 ℃, and not spontaneously combusting for about 24 hours;
viscosity: 216 cP;
the ceramic yield is as follows: 62 percent;
example 4
The synthesis method of the Ti-containing Si-C-N ceramic precursor comprises the following steps:
(1) vacuumizing the whole synthesis system to-0.09 MPa;
(2) sucking 50L of Polymethylsilane (PMS) into a reaction kettle;
(3) sucking 20L of vinyl-containing polysilazane (Vi-PSN) into a No. 1 head tank; sealing and storing nitrogen; the amount added for synthesis accounts for 40 wt% of PMS;
(4) 500mL of TiCl4Sucking into No. 2 high-level tank; the amount added for synthesis accounts for 1 wt% of PMS;
(5) n with the purity of 99.999 percent is introduced into the whole synthesis system2To form an inert environment;
(6) the reaction kettle is raised to 90 ℃;
(7) dropwise adding Vi-PSN in the No. 1 head tank to a reaction kettle at the speed of 60 mL/min;
(8) after the dropwise addition, the reaction kettle is refluxed and stirred at the temperature of 90 ℃ for reaction for 5 hours;
(9) after cooling to room temperature, TiCl in the No. 2 elevated tank4Dropwise adding the mixture into a reaction kettle at the speed of 20 mL/min;
(10) after the dropwise addition, the reaction kettle continuously performs reflux stirring reaction for 2 hours at room temperature;
the properties of the finished product obtained were as follows:
the characteristics are as follows: a reddish brown liquid;
air stability: dipping a little absorbent cotton, placing the absorbent cotton in an aerobic environment at 25 ℃, and not spontaneously combusting or generating heat for about 24 hours;
viscosity: 138 cP;
the ceramic yield is as follows: 68 percent.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the scope of the present invention.
Comparative example 1
The other conditions were the same as in example 4 except that the autoclave was raised to 150 ℃ and the product obtained was as follows:
the characteristics are as follows: a reddish brown viscous liquid;
air stability: dipping a little absorbent cotton in an aerobic environment at 25 ℃, wherein the absorbent cotton does not spontaneously combust for about 24 hours, but the absorbent cotton has the phenomena of blackening and heating;
viscosity: 2000 cP;
the ceramic yield is as follows: 40 percent.
Comparative example 2
The other conditions were the same as in example 4, except that TiCl was used4The amount of addition of (2%). The product performance data obtained are as follows:
the characteristics are as follows: a reddish brown viscous liquid;
air stability: dipping a little absorbent cotton in an aerobic environment at 25 ℃, and spontaneous combustion of the absorbent cotton after 1 h;
viscosity: 8000 cP;
the ceramic yield is as follows: and 55 percent.
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