CN114409906A

CN114409906A - Method for preparing polymetallic carbosilane by using liquid polycarbosilane and application

Info

Publication number: CN114409906A
Application number: CN202111607713.0A
Authority: CN
Inventors: 水洪涛; 张伟刚; 马奕成; 张�浩; 李新海; 程红梅
Original assignee: Ningbo Zhongxing New Materials Technology Co ltd
Current assignee: Ningbo Zhongxing New Materials Technology Co ltd
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-04-29

Abstract

The invention provides a method for preparing polymetallic carbosilane by using liquid polycarbosilane and application thereof, comprising the following steps: preparation of polymetallic carbosilane: putting liquid polycarbosilane and metallocene into a reaction kettle in proportion, heating to 300-500 ℃ under the protection of high-purity inert gas, carrying out heat preservation reaction, and cooling to room temperature after the reaction is finished; and (3) product fine treatment: dissolving the obtained solid product into an organic solvent, filtering to remove a small amount of precipitate in the solution to obtain a solution G, and removing the solvent in the solution G to obtain a product polymetallic carbosilane; after further heat treatment, the polymetallic carbosilane composite carbide is prepared. The method has the advantages of adjustable content of metal elements in the polymetallic carbosilane, simple reaction steps, mild and controllable reaction process, low preparation cost, suitability for industrial production and the like.

Description

Method for preparing polymetallic carbosilane by using liquid polycarbosilane and application

Technical Field

The invention relates to the technical field of organic chemistry, in particular to a method for preparing polymetallic carbosilane by using liquid polycarbosilane and application thereof.

Background

With the development of equipment towards faster, higher and farther directions, the high-temperature alloy material widely applied to the aerospace field in recent times cannot meet the design requirements of equipment of new-generation aircrafts and the like due to the limitation of the melting point of the high-temperature alloy material. The nickel-based alloys currently in use are approaching the limits of use and new materials capable of withstanding higher temperatures are needed for developing higher thrust-weight ratio aircraft and other equipment.

Advanced ceramic materials draw great attention to the material world due to excellent oxidation resistance, thermal shock resistance, corrosion resistance, high temperature resistance, high insulation and other properties, and are gradually applied to high and new technical fields such as aviation, aerospace, chemical engineering, metallurgy, electronics, machinery and the like. As an important member of advanced ceramics, silicon carbide (SiC) ceramics have excellent performances such as creep resistance, high-temperature mechanical property, corrosion resistance, oxidation resistance and the like, and have wide application prospects in high and new technical fields such as aviation, aerospace, national defense, nuclear industry and the like.

The manufacturing method of the silicon carbide ceramic matrix composite material mainly comprises a melt siliconizing method, a chemical vapor deposition method, an organic precursor conversion method and the like. Among them, the organic precursor conversion method has been developed rapidly due to its advantages of good operability, molecular design, fabrication of complex structural members, short fabrication period, low ceramization temperature, etc.

Polycarbosilanes (PCS) is the most commonly used Precursor raw material for preparing SiC ceramic materials by a Precursor conversion method, and the Precursor can be used for preparing Ceramic Matrix Composite (CMC) with a complex shape by a Precursor impregnation cracking technology (PIP) and can also be used for preparing high-performance SiC fibers by a melt spinning technology, so that the market potential of the Precursor is huge.

The most common technical scheme for industrial synthesis of PCS at present is the two-stage thermodynamic rearrangement method, also called "two-step method", invented in 1976 by japan scientist s.yajima, and the rearrangement method can be divided into a high-pressure high-temperature synthesis method and a normal-pressure high-temperature synthesis method. The normal pressure high temperature synthesis method comprises the following two steps: cracking at normal pressure (350-400 deg.C), and polymerizing at normal pressure (400-450 deg.C).

The normal-pressure high-temperature synthesis method is a PCS industrial synthesis method commonly used in China at present, and has the advantages of high equipment safety and low yield of polycarbosilane. According to statistics, the yield of the Polycarbosilane (PCS) synthesized at normal pressure and high temperature is about 35 percent according to the charge amount of the polydimethylsiloxane, and a byproduct Liquid Polycarbosilane (LPCS) of about 28 percent is generated at the same time. The LPCS is a colorless and transparent organic silicon material at normal temperature, has low ignition point and potential safety hazard, and has no clear industrial application direction at present. If the harmless treatment is carried out, mainly a combustion purification method or a chlorosilane method generated by hydrochloric acid reaction, the treatment cost is high.

Some studies have been made domestically on the recycling method of LPCS. One method is to mix LPCS with LPS according to a certain proportion and then put the mixture into a synthesis kettle for synthesis. Practice has shown that this method is limited to increasing the yield. Another approach is to add an initiator to the LPCS, such as: dibenzoyl peroxide (BPO), cyclohexene, ethylenediamine, and the like. These methods introduce elements such as oxygen, carbon, nitrogen, etc., which are not beneficial to the product. Therefore, there is a need for improvements over existing methods.

In recent years, the improvement of SiC ceramic materials by modifying precursors has been increasingly emphasized, wherein the introduction of specific elements by physical or chemical methods is one of the important routes for improving PCS performance. For example, elements such as Al, B, Zr, Ti, Hf and the like are introduced to improve the high temperature resistance and oxidation resistance of the prepared ceramic or fiber, and elements such as Fe, Ni and the like are introduced to enable the material to have wave-absorbing performance.

Zirconium carbide (ZrC) is a crystalline compound with very high melting point (melting point 3540 ℃) and hardness (mohs hardness of 9), good high-temperature oxidation resistance and very high chemical stability, and SiC-ZrC complex phase ceramics consisting of the zirconium carbide and SiC ceramics are considered to be ideal candidate materials applicable to extreme temperature environments.

Chinese patent with application number CN201310504827.1 discloses a machinable Si/C/Zr ceramic precursor and a preparation method thereof, belonging to the technical field of ceramic materials. Adding an organic solvent into zirconocene dichloride, and stirring at the temperature of 50-150 ℃ until the zirconocene dichloride is completely dissolved to obtain a solution; adding polycarbosilane into the solution, and stirring at the reaction temperature of 50-150 ℃; the reaction time is 1-100 h; and standing for 0.5-20 h after the reaction is finished, then splitting phases, taking the upper organic phase for rotary evaporation to obtain a product, curing the product, and sintering the cured product at high temperature to obtain the processable Si/C/Zr ceramic material.

Chinese patent with application number CN201110308637.3 discloses a preparation method of silicon carbide/zirconium carbide composite ceramic, relating to inorganic non-metallic material composite ceramic. Under the protection of inert atmosphere, dissolving zirconocene dichloride by using a solvent, and then adding liquid hyperbranched polycarbosilane to obtain a mixture A; and under the protection of inert atmosphere, distilling the mixture A under reduced pressure to remove the solvent to obtain a mixture B, and carrying out cracking reaction under the inert atmosphere to obtain the silicon carbide/zirconium carbide composite ceramic.

The main raw materials of the invention patent are respectively zirconocene dichloride/polycarbosilane (solid) and zirconocene dichloride/liquid hyperbranched polycarbosilane, and the prepared silicon carbide/metal carbide complex phase ceramic has single variety; the combination reaction process is carried out in an organic solvent system, and some unnecessary byproducts or residues are not generated in the synthesis process. Accordingly, there is a need for improvements in the prior art that overcome the deficiencies of the prior art.

Disclosure of Invention

The invention aims to provide a method for preparing poly-metallic carbosilane by using liquid poly-carbosilane and application thereof, which adopts zirconocene dichloride, titanocene dichloride or hafnocene dichloride as a bridging agent and utilizes Cl in metallocene^-Ion-capturing H of Si-H bond in LPCS small molecule⁺Hydrogen chloride gas is generated, so that LPCS small molecules are gradually polymerized to generateThe carbon silane/metal carbide composite carbide can be obtained after the polymetallic carbosilane finished product is further thermally treated, and the method has the advantages of adjustable content of metal elements in the polymetallic carbosilane, simple reaction steps, mild and controllable reaction process, low preparation cost, suitability for industrial production and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for preparing polymetallic carbosilane by using liquid polycarbosilane comprises the following steps:

1) preparation of polymetallic carbosilane: putting liquid polycarbosilane and metallocene into a reaction kettle in proportion, heating to 300-500 ℃ under the protection of high-purity inert gas, carrying out heat preservation reaction, and cooling to room temperature after the reaction is finished;

2) and (3) product fine treatment: dissolving the obtained solid product into an organic solvent, filtering to remove a small amount of precipitate in the solution to obtain a solution G, and removing the solvent in the solution G to obtain a product polymetallic carbosilane;

wherein, the organic solvent in the step 2) is a nonpolar solvent, and the structural formula of the liquid polycarbosilane is as follows:

the molecular chain is a nonlinear structure and is a space network structure with a complex structure, wherein m and n are integers equal to or more than 1;

wherein, the step 1) and the step 2) are both carried out under the anhydrous and anaerobic conditions.

According to the scheme, the preparation of the polymetallic carbosilane comprises the following steps: putting liquid polycarbosilane and metallocene into a high-pressure reaction kettle in proportion, introducing high-purity inert gas to replace air, then sealing the system, heating to the temperature of 300-.

According to the scheme, the preparation of the polymetallic carbosilane comprises the following steps: putting liquid polycarbosilane and metallocene into a high-temperature normal-pressure polymerization kettle in proportion, heating to 250 ℃ for heat preservation for 5-20h under the protection of high-purity inert gas according to a preset program, heating to 400 ℃ for heat preservation for 300-40 h, heating to 500 ℃ for heat preservation for 5-10h, discharging to a finished product tank after the reaction is finished, and cooling to room temperature.

According to the above scheme, the metallocene includes zirconocene dichloride, titanocene dichloride, hafnocene dichloride.

According to the scheme, the amount ratio of the liquid polycarbosilane to the metallocene substance is (2-20):1, and the mass of the organic solvent is 1-2 times of that of the solid product.

According to the above scheme, the non-polar solvent is toluene or xylene, and the inert gas is nitrogen or argon.

A method for preparing a complex phase ceramic material by using poly-metal carbosilane comprises the following steps: and (3) placing the polymetallic carbosilane in a heat treatment furnace, and carrying out high-temperature heat treatment at the temperature of over 1100 ℃ under the protection of high-purity inert gas to obtain the composite carbide of silicon carbide/metal carbide (SiC/MC) of the composite ceramic material.

According to the scheme, during the high-temperature heat treatment, the heating rate is 1-5 ℃/min, the heat treatment temperature is 1100-1800 ℃, and the heat preservation time is 1-5 h; the inert gas is nitrogen or argon.

The invention obtains the poly-metal carbonane by introducing zirconium (or titanium, hafnium) element into the LPCS through the reaction of the byproduct LPCS and metallocene at high temperature and high pressure or at high temperature and normal pressure, and the structural formula is as follows:

wherein M is Ti, Zr or Hf, and the mass content of M ions is more than 0 and less than or equal to 15 percent; l, m, n are integers equal to or greater than 1, Cp₁And Cp₂Each is a cyclopentadienyl or substituted cyclopentadienyl group.

The mass content of the metal elements in the polymetallic carbosilane is adjustable from 0-15%, the reaction steps are simple, the reaction process is mild and controllable, the preparation cost is low, and the method is suitable for industrial production.

Under different thermodynamic conditions, chloride ions in metallocene react with Si-H active groups in LPCS, and small molecules of LPCS which is liquid at normal temperature are linked by utilizing bridging of zirconocene (or titanium or hafnium) to generate the solid polymetallic carbosilane at normal temperature.

The invention has the beneficial effects that:

1) the invention provides a novel polymetallic carbosilane, wherein in the polymetallic carbosilane, metal elements and polycarbosilane exist in a chemical bond combination mode, and the content of the metal elements is adjustable;

2) the method for generating the poly-metal carbosilane by the chemical combination reaction of the metallocene and the LPCS is adopted, the used raw materials and the chemical combination process do not contain oxygen, the method can be carried out in a common high-pressure kettle or a normal-pressure polymerization kettle, the reaction condition is simple, and the preparation cost is low;

3) one of the main raw materials adopted by the invention is a byproduct LPCS in the domestic production of polycarbosilane by a high-temperature normal-pressure method, and an effective way for utilizing LPCS is provided;

4) the polymerization reaction of the invention has no solvent to participate in the reaction, so the process is mild and controllable, the product has no large amount of insoluble precipitates generated in the polymerization of a solvent system, the process repeatability is good, and the invention is more suitable for industrial production;

5) the polymetallic carbosilane provided by the invention can be pyrolyzed in an inert atmosphere above 1100 ℃ to be converted into high-purity SiC-MC complex phase ceramic (M ═ Ti, Zr or Hf), the ceramic transition temperature of the polymetallic carbosilane is lower, and the obtained complex phase ceramic is nano-scale dispersed SiC-MC complex phase ceramic, so that the polymetallic carbosilane provided by the invention can be used for preparing SiC-MC complex phase silicon carbide ceramic fibers and can also be used for preparing a matrix of a CMC material.

Drawings

FIG. 1 is an IR spectrum of a poly (zirconium carbosilane) prepared in example 1 of the present invention;

FIG. 2 is an IR spectrum of a poly (zirconium carbosilane) prepared in example 2 of the present invention;

FIG. 3 is an XRD spectrum of a composite carbide prepared in example 3 of the present invention;

FIG. 4 is a scanning electron microscope backscatter image of the composite carbide prepared according to example 3 of the present invention;

FIG. 5 is an XRD spectrum of a composite carbide prepared in example 4 of the present invention.

Detailed Description

The technical solution of the present invention is described below with reference to the accompanying drawings and examples.

Example 1, see figure 1:

the invention provides a method for preparing polymetallic carbosilane by using liquid polycarbosilane, which comprises the following steps:

1) preparation of polymetallic carbosilane: putting 5000g of LPCS and 750g of zirconocene dichloride into a 20L high-pressure reaction kettle, replacing air in the reaction kettle with high-purity nitrogen, closing an air outlet valve, heating to 430 ℃ according to a set heating program when the pressure of the nitrogen in the high-pressure kettle reaches 3MPa, preserving heat for 30h, and cooling to room temperature;

2) and (3) product fine treatment: dissolving the product obtained in the step 1) into xylene with the mass ratio of 2 times, filtering a small amount of precipitate to obtain a solution G1, and distilling off the solvent in the solution G1 to obtain 3571G of black brown solid A1, wherein the yield is as follows: 71 percent.

Upon detection, the softening point of product a1 was determined to be: at 215 ℃, the ceramic yield is: 63%, zirconium content: 8.75 percent; infrared spectroscopic analysis of the solid product A1 was carried out using KBr pellet, and the results are shown in FIG. 1. Wherein the wave number is 1452cm^-1、1080cm^-1An absorption peak corresponding to cyclopentadienyl in the zirconocene; wave number 1248cm^-1Corresponding to Si-CH₃Absorption peak of bond. The above analysis shows that zirconocene dichloride reacts with LPCS to produce PZCS.

Example 2, see figure 2:

1) preparation of polymetallic carbosilane: putting 200kg of LPCS and 20kg of zirconocene dichloride into a 500L polymerization reactor, replacing air in the reactor, a cracking column, a condenser, a storage tank and a pipeline with high-purity nitrogen, adjusting the flow of the high-purity nitrogen in the polymerization reactor to a fixed value, keeping the micro-positive pressure of the system, heating to 180 ℃ according to a set program, keeping the temperature for 20 hours, heating to 360 ℃ for 30 hours, heating to 480 ℃ for 5 hours, discharging to a finished product tank after the program is finished, and cooling to room temperature;

2) and (3) product fine treatment: dissolving the product obtained in the step 1) into xylene with the mass ratio of 2 times, filtering a small amount of precipitate to obtain a solution G2, and distilling off the solvent in the solution G2 to obtain 121.8kg of black brown solid A2, wherein the yield is as follows: 60.8 percent.

Upon detection, the softening point of product a2 was determined to be: at 208 ℃, the ceramic yield is: 55%, zirconium content: 6.19 percent; infrared spectroscopic analysis of the solid product A2 was carried out using KBr pellet, and the results are shown in FIG. 2. Wherein the wave number is 1452cm^-1、1080cm^-1An absorption peak corresponding to cyclopentadienyl in the zirconocene; wave number 1248cm^-1Corresponding to Si-CH₃Absorption peak of bond. The above analysis shows that zirconocene dichloride reacts with LPCS to produce PZCS.

Example 3, see fig. 3-4:

the invention provides a preparation method for preparing a complex phase ceramic material by using poly-metal carbosilane, which comprises the following steps: 14 g of the poly (zirconium-carbon-silane) A prepared in example 1 was heated in Ar atmosphere to 1500 ℃ at 3 ℃/min, and after 2 hours of heat preservation, the temperature was reduced at 10 ℃/min to obtain 2.84g of a gray black solid.

The measurement was performed by XRD, and the result showed that, as shown in fig. 3, diffraction peaks appeared at angles of 2 θ of 33.05 °, 38.35 °, 55.36 °, 66.01 °, which coincided with the characteristic peak of face centered cubic ZrC; diffraction peaks appear at 25.74 °, 60.03 °, 72.03 °, which coincide with characteristic peaks of face centered cubic SiC; the obtained solid is proved to be SiC-ZrC complex phase ceramic.

Because the atomic numbers of Si and Zr are greatly different, the back scattering electron imaging has obvious difference. The partial image with larger atomic number is brighter, and the partial image with smaller atomic number is darker. The distribution states of the two elements can be obviously distinguished through light and shade contrast. Thus, the resulting ceramic product was analyzed using back-scattered electron imaging techniques and the results are shown in FIG. 4. As can be seen from FIG. 4, the white spots (Zr) are uniformly dispersed in the gray matrix (Si) in nanometer scale, and the obtained SiC-ZrC is the complex phase ceramic uniformly distributed in nanometer scale.

Example 4, see figure 5:

the invention provides a preparation method for preparing a complex phase ceramic material by using poly-metal carbosilane, which comprises the following steps: about 4g of the poly (zirconium carbosilane) A2 prepared in example 2 was heated under Ar atmosphere to 1600 ℃ at 2 ℃/min, and after 1 hour of heat preservation, the temperature was reduced at 10 ℃/min to obtain 2.43g of a gray black solid.

The measurement was performed by XRD, and the result showed that, as shown in fig. 5, diffraction peaks appeared at angles of 2 θ of 33.05 °, 38.35 °, 55.36 °, 66.01 °, which coincided with the characteristic peak of face centered cubic ZrC; diffraction peaks appear at 25.74 °, 60.03 °, 72.03 °, which coincide with characteristic peaks of face centered cubic SiC; the obtained solid is proved to be SiC-ZrC complex phase ceramic.

The polymetallic carbosilane and the polycarbosilane have similar structures and can be mixed according to any proportion, so that the composite materials with different metal (zirconium, titanium and hafnium) contents can be designed, and the preparation method can be used for preparing the composite phase silicon carbide ceramic fiber with various metal (zirconium, titanium and hafnium) contents and also can be used for preparing the matrix material of the CMC material to prepare the SiC-ZrC ceramic matrix composite material.

The above embodiments are only used for illustrating but not limiting the technical solutions of the present invention, and although the above embodiments describe the present invention in detail, those skilled in the art should understand that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and any modifications and equivalents may fall within the scope of the claims.

Claims

1. A method for preparing polymetallic carbosilane by using liquid polycarbosilane is characterized by comprising the following steps:

2. The method for preparing the polycarbosilane using the liquid polycarbosilane as claimed in claim 1, wherein the preparation of the polymetallic carbosilane comprises the steps of: putting liquid polycarbosilane and metallocene into a high-pressure reaction kettle in proportion, introducing high-purity inert gas to replace air, then sealing the system, heating to the temperature of 300-.

3. The method for preparing the polycarbosilane using the liquid polycarbosilane as claimed in claim 1, wherein the preparation of the polymetallic carbosilane comprises the steps of: putting liquid polycarbosilane and metallocene into a high-temperature normal-pressure polymerization kettle in proportion, heating to 250 ℃ for heat preservation for 5-20h under the protection of high-purity inert gas according to a preset program, heating to 400 ℃ for heat preservation for 300-40 h, heating to 500 ℃ for heat preservation for 5-10h, discharging to a finished product tank after the reaction is finished, and cooling to room temperature.

4. The method of any one of claims 1-3, wherein the metallocene comprises zirconocene dichloride, titanocene dichloride, hafnocene dichloride.

5. The method for preparing polycarbosilane using liquid polycarbosilane as claimed in any one of claims 1-3, wherein the ratio of the amount of said liquid polycarbosilane to the amount of said metallocene is (2-20):1, and the mass of said organic solvent is 1-2 times the mass of said solid product.

6. The method of claim 1, wherein the nonpolar solvent is toluene or xylene and the inert gas is nitrogen or argon.

7. A method for preparing a complex phase ceramic material by using poly-metal carbosilane is characterized by comprising the following steps: and (3) placing the polymetallic carbosilane in a heat treatment furnace, and carrying out high-temperature heat treatment at the temperature of over 1100 ℃ under the protection of high-purity inert gas to obtain the composite carbide of silicon carbide/metal carbide of the composite ceramic material.

8. The method as claimed in claim 7, wherein the heating rate is 1-5 ℃/min, the heat treatment temperature is 1100-1800 ℃, and the holding time is 1-5 h; the inert gas is nitrogen or argon.