阅读说明：本技术 一种高韧性的c/超高温陶瓷复合材料及其制备方法 (High-toughness C/ultrahigh-temperature ceramic composite material and preparation method thereof ) 是由 杨良伟 朱申 刘伟 宋环君 张宝鹏 陈昊然 于新民 刘俊鹏 孙同臣 于 2021-08-06 设计创作，主要内容包括：本发明涉及一种高韧性的C/超高温陶瓷复合材料的制备方法,所述制备方法包括如下步骤：(1)提供碳/碳基体；(2)在真空条件下,将膨胀氮化硼与铪钽前驱体溶液进行超声混合,形成膨胀氮化硼改性的铪钽前驱体溶液；(3)以所述氮化硼改性的铪钽前驱体溶液作为反应物,通过浸渍裂解法与步骤(1)制得的碳/碳基体反应,形成膨胀氮化硼增韧的C/C复合材料；(4)重复步骤(3)至少一次,得到氮化硼增韧的C/超高温陶瓷基复合材料。本发明所用的制备方法进一步提高C/超高温陶瓷基复合材料的基体韧性,从而有效解决了C/超高温陶瓷基复合材料基体裂纹较多而导致力学性能较差的问题。(The invention relates to a preparation method of a high-toughness C/ultrahigh-temperature ceramic composite material, which comprises the following steps: (1) providing a carbon/carbon substrate; (2) ultrasonically mixing expanded boron nitride with the hafnium-tantalum precursor solution under a vacuum condition to form an expanded boron nitride modified hafnium-tantalum precursor solution; (3) taking the boron nitride modified hafnium-tantalum precursor solution as a reactant, and reacting the boron nitride modified hafnium-tantalum precursor solution with the carbon/carbon matrix prepared in the step (1) through a dipping pyrolysis method to form the expanded boron nitride toughened C/C composite material; (4) and (4) repeating the step (3) at least once to obtain the boron nitride toughened C/ultrahigh temperature ceramic matrix composite. The preparation method provided by the invention further improves the toughness of the matrix of the C/ultrahigh temperature ceramic matrix composite material, thereby effectively solving the problem of poor mechanical properties caused by more cracks of the matrix of the C/ultrahigh temperature ceramic matrix composite material.)

1. The preparation method of the high-toughness C/ultrahigh-temperature ceramic composite material is characterized by comprising the following steps of:

(1) providing a carbon/carbon substrate;

(2) ultrasonically mixing expanded boron nitride with the hafnium-tantalum precursor solution under a vacuum condition to form an expanded boron nitride modified hafnium-tantalum precursor solution;

(3) taking the boron nitride modified hafnium-tantalum precursor solution as a reactant, and reacting the boron nitride modified hafnium-tantalum precursor solution with the carbon/carbon matrix prepared in the step (1) through a dipping pyrolysis method to form the expanded boron nitride toughened C/C composite material;

(4) and (4) repeating the step (3) at least once to obtain the boron nitride toughened C/ultrahigh temperature ceramic matrix composite.

2. The production method according to claim 1, wherein the carbon/carbon matrix is a carbon fiber-reinforced carbon matrix composite produced from a carbon fiber preform by a chemical vapor deposition method or a dip pyrolysis method;

preferably, the carbon fiber reinforced carbon matrix composite has a density of 0.5 to 0.95g/cm³；

More preferably, the carbon fiber preform is knitted by needle punching or sewing.

3. The preparation method according to claim 1, wherein the expanded boron nitride is prepared by dispersing boron nitride powder in an alkaline solution and then performing a high-temperature high-pressure reaction;

preferably, the alkaline solution is a sodium hydroxide solution.

4. The preparation method according to claim 1, wherein in the step (2), the preparation method of the expanded boron nitride modified hafnium tantalum precursor solution is as follows:

(I) placing the expanded boron nitride in a round-bottom flask, adding a hafnium-tantalum precursor solution into a long-neck funnel, sealing the round-bottom flask and the long-neck funnel, and pumping vacuum;

(II) after the vacuum degrees in the round-bottom flask and the long-neck funnel reach 1-100Pa and are stable, dropwise adding the hafnium-tantalum precursor solution in the long-neck funnel into the round-bottom flask filled with the expanded boron nitride at the dropwise adding speed of 1-100mL/min, wherein the mass ratio of the expanded boron nitride to the hafnium-tantalum precursor solution is 1:10-1: 100;

(III) carrying out ultrasonic mixing on the round-bottom flask containing the expanded boron nitride and hafnium-tantalum precursor solution for 1-100min to obtain the expanded boron nitride modified hafnium-tantalum precursor solution.

5. The production method according to claim 1, wherein in the step (3), the impregnation pyrolysis method comprises the steps of:

(I) placing the carbon/carbon substrate in a modified hafnium-tantalum precursor solution for dipping;

(II) placing the C/SiC ceramic matrix composite material impregnated with the modified hafnium-tantalum precursor in a reaction furnace body, sealing, vacuumizing, introducing inert gas, and then sequentially carrying out a curing reaction and a cracking reaction;

(III) after the cracking reaction is finished, carrying out program control cooling at the cooling rate of 1-50 ℃/min, cooling to room temperature, stopping introducing inert gas, and recovering to atmospheric pressure;

(IV) repeating steps (I) to (III) at least once.

6. The preparation method according to claim 5, wherein the impregnation mode is vacuum pressure impregnation, and the impregnation time is 1-30 min;

the inert gas is argon or nitrogen, and the flow of the introduced inert gas is 1-1000 sccm.

7. The method of claim 5, wherein: in the step (4), the temperature of the curing reaction is 100-500 ℃, and the time of the curing reaction is 1-3 h.

8. The method according to claim 1, wherein in the step (4), the first pyrolysis reaction is carried out as follows: under the inert atmosphere, the temperature of the cured composite material is raised to 1500-2000 ℃ at the heating rate of 50-100 ℃/min, and the temperature is kept for 1-360 min; cooling to room temperature at a cooling rate of 50-100 ℃/min, closing the inert gas and recovering to atmospheric pressure to obtain the expanded boron nitride toughened C/ultrahigh temperature ceramic matrix composite;

preferably, the inert atmosphere is nitrogen or argon.

9. The method of claim 1, wherein in step (4), step (3) is repeated until the density of the produced composite material changes by less than 2% from the density of the produced composite material before the repetition.

10. A high-toughness C/ultrahigh-temperature ceramic composite material is characterized in that: the C/superhigh temperature ceramic composite material is prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of preparation of ultrahigh-temperature ceramic-based composite materials, in particular to a high-toughness C/ultrahigh-temperature ceramic composite material and a preparation method thereof.

Background

The aerospace craft needs to be tested in an extreme service environment, higher requirements are put on Ultra-High Temperature resistant materials, Ultra High Temperature Ceramics (UHTCs) represented by metal carbides and borides have extremely High melting points (more than 3000 ℃), and the aerospace craft becomes the most potential candidate material. However, the inherent brittleness of the ultra-high temperature ceramic leads to irreversible and destructive fracture, which causes extremely serious consequences. In recent years, in order to improve the toughness of ultra-high temperature ceramics, continuous carbon fibers may be used to reinforce the ultra-high temperature ceramics. The brittleness of the ultrahigh-temperature ceramic is greatly improved through the carbon fibers, the continuous carbon fiber reinforced ultrahigh-temperature ceramic can still keep the structural integrity in an extreme service environment, the formation of penetrating cracks is avoided, the normal work of the aerospace vehicle is ensured, and the aerospace vehicle shows excellent mechanical properties.

In the continuous carbon fiber reinforced ultrahigh-temperature ceramic matrix, ultrahigh-temperature ceramic with a certain size exists in the space between carbon fiber bundles, and the area still faces the problems of poor toughness, easy formation of cracks and the like, so that the long-time reusability of the continuous carbon fiber reinforced ultrahigh-temperature ceramic matrix composite is influenced. In order to further improve the mechanical property of the C/ultrahigh-temperature ceramic composite material, the problem of poor toughness of the ultrahigh-temperature ceramic matrix under the prior art is solved.

Therefore, in view of the above disadvantages, it is desirable to provide a high-toughness C/ultra-high temperature ceramic composite material and a method for preparing the same.

Disclosure of Invention

Technical problem to be solved

The invention aims to solve the technical problem of poor toughness of the ultrahigh-temperature ceramic matrix under the prior art.

(II) technical scheme

In order to solve the above technical problems, a first aspect of the present invention provides a method for preparing a high toughness C/ultra high temperature ceramic composite, the method comprising the steps of:

(1) providing a carbon/carbon substrate;

(2) ultrasonically mixing expanded boron nitride with the hafnium-tantalum precursor solution under a vacuum condition to form an expanded boron nitride modified hafnium-tantalum precursor solution;

(3) taking the expanded boron nitride modified hafnium-tantalum precursor solution as a reactant, and reacting the reactant with the carbon/carbon matrix prepared in the step (1) by using a dipping pyrolysis method to form an expanded boron nitride toughened C/C composite material;

(4) and (4) repeating the step (3) at least once to obtain the expanded boron nitride toughened C/ultrahigh temperature ceramic matrix composite.

The second aspect of the invention also provides a high-toughness C/ultrahigh-temperature ceramic composite material, which is prepared according to the preparation method of the first aspect of the invention.

(III) advantageous effects

The technical scheme of the invention has the following advantages:

(1) according to the invention, sodium hydroxide is used as a solvent, and the boron nitride powder is prepared into the expanded boron nitride under the conditions of high temperature and high pressure, so that the interlayer spacing is effectively enlarged;

(2) the method comprises the steps of fully soaking a hafnium-tantalum precursor solution into the expansion boron nitride layers under a vacuum condition, stripping the expansion boron nitride layers under the subsequent ultrasonic action, and realizing uniform dispersion of single-layer or few-layer boron nitride in the hafnium-tantalum precursor solution;

(3) according to the invention, a boron nitride modified hafnium-tantalum precursor impregnation curing cracking technology is introduced to prepare the ultrahigh-temperature ceramic matrix, so that the expanded boron nitride toughened C/ultrahigh-temperature ceramic matrix composite material is obtained, and the mechanical properties of the composite material are improved.

Drawings

The drawings of the present invention are provided for illustrative purposes only, and the scale and size in the drawings are not necessarily consistent with those of actual products.

FIG. 1 is an X-ray diffraction pattern (XRD pattern) of the high toughness C/UHT ceramic composite material of the present invention.

FIG. 2 is a curve of the bending performance of the high toughness C/UHT ceramic composite of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention provides a preparation method of a high-toughness C/ultrahigh-temperature ceramic composite material, which comprises the following steps:

(1) providing a carbon/carbon substrate;

(2) ultrasonically mixing expanded boron nitride with the hafnium-tantalum precursor solution under a vacuum condition to form an expanded boron nitride modified hafnium-tantalum precursor solution;

(3) taking the expanded boron nitride modified hafnium-tantalum precursor solution as a reactant, and reacting the reactant with the carbon/carbon matrix prepared in the step (1) by using a dipping pyrolysis method to form an expanded boron nitride toughened C/C composite material;

(4) and (4) repeating the step (3) at least once to obtain the expanded boron nitride toughened C/ultrahigh temperature ceramic matrix composite.

According to some preferred embodiments, the carbon/carbon matrix is a carbon fiber reinforced carbon matrix composite prepared by using a carbon fiber preform through other densification methods such as a chemical vapor deposition method or a dip pyrolysis method; preferably, the carbon fiber reinforced carbon matrix composite has a density of 0.5 to 0.95g/cm³(ii) a More preferably, the carbon fiber preform is knitted by needle punching or sewing. The limited density is 0.5-0.95g/cm³The method is used for adjusting the proportion of the ultrahigh-temperature ceramic matrix subsequently so as to investigate the change of mechanical properties.

According to some preferred embodiments, the expanded boron nitride is prepared by dispersing boron nitride powder in an alkaline solution, and then performing a high-temperature high-pressure reaction in a high-temperature high-pressure reaction kettle; boron nitride is a layered compound with a graphite-like structure, and the interlayer interaction force is weakened and the interlayer spacing is enlarged through the treatment process, so that the boron nitride is called as expanded boron nitride. Preferably, the alkaline solution is a sodium hydroxide solution.

According to some preferred embodiments, in the step (2), the method for preparing the expanded boron nitride modified hafnium tantalum precursor solution comprises:

(I) placing the expanded boron nitride in a round-bottom flask, adding a hafnium-tantalum precursor solution into a long-neck funnel, sealing the round-bottom flask and the long-neck funnel, and pumping vacuum;

(II) after the vacuum degrees in the round-bottom flask and the long-neck funnel reach 1-100Pa and the solutions are stable, dropwise adding the hafnium-tantalum precursor solution in the long-neck funnel into the round-bottom flask filled with the expanded boron nitride at the speed of 1-100mL/min, wherein the mass ratio of the expanded boron nitride to the hafnium-tantalum precursor solution is 1:10-1: 100;

(III) carrying out ultrasonic mixing on the round-bottom flask containing the expanded boron nitride and the hafnium tantalum precursor solution for 1-100min, and ensuring that the hafnium tantalum precursor solution can fully enter into the expanded boron nitride layer and be completely stripped, so that uniform dispersion of single-layer or few-layer boron nitride in the hafnium tantalum precursor solution is realized, and the expanded boron nitride modified hafnium tantalum precursor solution is obtained.

According to some preferred embodiments, in step (3), the impregnation cracking method comprises the steps of:

(I) placing the carbon/carbon substrate in a modified hafnium-tantalum precursor solution for dipping; the hafnium-tantalum precursor solution is obtained by dissolving a high molecular polymer mainly containing hafnium and tantalum metal elements in a solvent as a solute. The polymer can be converted into HfC-TaC ceramic through heat treatment processes such as curing and cracking. The polymer can be dispersed in a solvent such as xylene or ethylene glycol diethyl ether to form a polymer solution having a viscosity of 20-200 mPas.

(II) placing the C/SiC ceramic matrix composite material impregnated with the modified hafnium-tantalum precursor in a reaction furnace body, sealing, vacuumizing, enabling the expanded boron nitride modified hafnium-tantalum precursor solution to enter the C/C composite material in a vacuum pressure mode, introducing inert gas, and then sequentially carrying out a curing reaction and a cracking reaction;

(III) after the cracking reaction is finished, carrying out program control cooling at the cooling rate of 1-50 ℃/min, cooling to room temperature, stopping introducing inert gas, and recovering to atmospheric pressure;

(IV) repeating steps (I) to (III) at least once.

According to some preferred embodiments, the impregnation is by vacuum pressure impregnation; the dipping time is 1-30 min; the inert gas is argon or nitrogen; the flow rate of the introduced inert gas is 1-1000 sccm. The temperature of the curing reaction is 100-500 ℃, and the time of the curing reaction is 1-3 h.

According to some preferred embodiments, in step (4), the pyrolysis reaction is performed as follows: under the inert atmosphere, the temperature of the cured composite material is raised to 1500-2000 ℃ at the heating rate of 50-100 ℃/min, and the temperature is kept for 1-360 min; cooling to room temperature at a cooling rate of 50-100 ℃/min, closing the inert gas and recovering to atmospheric pressure to obtain the expanded boron nitride toughened C/ultrahigh temperature ceramic matrix composite; preferably, the inert atmosphere is nitrogen or argon.

According to some preferred embodiments, in step (4), step (3) is repeated until the density of the produced composite material changes by less than 2% from the density of the produced composite material before the present repetition.

The invention provides a high-toughness C/ultrahigh-temperature ceramic composite material, which is characterized in that: the C/ultrahigh-temperature ceramic composite material is prepared according to the preparation method of the first aspect of the invention. The boron nitride toughened C/ultrahigh temperature ceramic matrix composite material prepared by the method has the advantage of high toughness, and is shown by remarkably improving the mechanical property.

Example 1

(1) Providing a carbon/carbon matrix: providing a density of 0.5g/cm³The carbon/carbon matrix is prepared by performing carbon matrix deposition on the seam structure carbon fiber preform by adopting a chemical vapor deposition method.

(2) Expanding boron nitride modified hafnium tantalum precursor solution: dispersing boron nitride powder in a sodium hydroxide solution (the dosage ratio of the boron nitride powder to the sodium hydroxide is 1:10, and the concentration of the sodium hydroxide solution is 10g/mL), and placing the mixture in a high-temperature high-pressure reaction kettle for high-temperature high-pressure reaction to obtain the expanded boron nitride. And (3) putting 10.0g of the expanded boron nitride into a 250mL round-bottom flask, adding 100.0g of the hafnium-tantalum precursor solution into a long-neck funnel, wherein the mass ratio of the expanded boron nitride to the hafnium-tantalum precursor solution is 1:10, sealing the round-bottom flask and the long-neck funnel, and pumping vacuum by using a vacuum pump. And slowly dripping the hafnium-tantalum precursor solution in the long-neck funnel into the round-bottom flask filled with the expanded boron nitride after the vacuum in the device reaches 20Pa and is stable for 5min, wherein the dripping speed is 10 mL/min. And (3) placing the round-bottom flask in vacuum in an ultrasonic device, carrying out ultrasonic mixing for 10min, and collecting the expanded boron nitride modified hafnium-tantalum precursor solution obtained by the treatment.

(3) Preparing an ultrahigh-temperature ceramic matrix by dipping, curing and cracking: and (2) placing the carbon/carbon matrix in the step (1) into a container filled with the expanded boron nitride modified hafnium-tantalum precursor solution, carrying out vacuum pressure impregnation (the vacuum pressure is 100Pa and the pressure is 1MPa), then carrying out a curing reaction at 250 ℃ for 2 hours, then carrying out a pyrolysis reaction at 1800 ℃ and preserving heat for 2 hours.

(4) Repeating the step (3) for 7 times to finally prepare the product with the density of 3.12g/cm³The boron nitride toughened C/superhigh temperature ceramic matrix composite material.

(5) And (3) testing mechanical properties: the obtained boron nitride toughened C/ultrahigh temperature ceramic matrix composite is subjected to mechanical property test, and the fracture toughness is 27.8 MPa-m^1/2The bending strength was 386MPa (see FIGS. 1 and 2).

Example 2

(1) Providing a carbon/carbon matrix: providing a density of 0.5g/cm³The carbon/carbon matrix is prepared by performing carbon matrix deposition on the seam structure carbon fiber preform by adopting a chemical vapor deposition process.

(2) Boron nitride modified hafnium tantalum precursor solution: and dispersing the boron nitride powder in a sodium hydroxide solution, and placing the solution in a high-temperature high-pressure reaction kettle for reaction treatment to obtain the expanded boron nitride. And (3) putting 10.0g of the expanded boron nitride into a 250mL round-bottom flask, adding 500.0g of the hafnium-tantalum precursor solution into a long-neck funnel, wherein the mass ratio of the expanded boron nitride to the hafnium-tantalum precursor solution is 1: 50, sealing the round-bottom flask and the long-neck funnel, and pumping vacuum by using a vacuum pump. And slowly dripping the hafnium-tantalum precursor solution in the long-neck funnel into the round-bottom flask filled with the expanded boron nitride after the vacuum in the device reaches 10Pa and is stable for 5min, wherein the dripping speed is 20 mL/min. And (3) placing the round-bottom flask in vacuum in an ultrasonic device, carrying out ultrasonic mixing for 10min, and collecting the expanded boron nitride modified hafnium-tantalum precursor solution obtained by the treatment.

(3) Preparing an ultrahigh-temperature ceramic matrix by dipping, curing and cracking: the carbon/carbon matrix is placed in a container filled with the expanded boron nitride modified hafnium-tantalum precursor solution, vacuum pressure impregnation is carried out (the vacuum pressure is 100Pa and the pressure is 1MPa), then curing reaction is carried out for 2 hours at 250 ℃, then pyrolysis is carried out at 1800 ℃, and heat preservation is carried out for 2 hours.

(4) Repeating the step (3) for 7 times to finally prepare the product with the density of 3.09g/cm³Boron nitride toughened C/superhigh temperature ceramic base compositeA material.

(5) And (3) testing mechanical properties: the obtained boron nitride toughened C/ultrahigh temperature ceramic matrix composite is subjected to mechanical property test, and the fracture toughness is 24.6 MPa.m^1/2The flexural strength was 329 MPa.

Compared with the example 1, when the boron nitride modified hafnium tantalum precursor is prepared, the proportion of the expanded boron nitride to the hafnium tantalum precursor is adjusted, and the content of the boron nitride is reduced, so that the content of the boron nitride in the matrix of the C/ultrahigh temperature ceramic matrix composite is reduced, and the mechanical property of the composite is reduced.

Example 3

This example 3 is substantially the same as example 2 except that: the mass ratio of the expanded boron nitride to the hafnium-tantalum precursor is 1:100, and the dropping speed of the expanded boron nitride modified hafnium-tantalum precursor is 50 mL/min.

Example 4

This example 4 is substantially the same as example 1 except that: the density of the carbon/carbon matrix was 0.9g/cm³。

Example 5

This example 5 is substantially the same as example 2 except that: the density of the carbon/carbon matrix was 0.9g/cm³。

Example 6

This example 6 is substantially the same as example 3 except that: the density of the carbon/carbon matrix was 0.9g/cm³。

Example 7

(1) Providing a carbon/carbon matrix: providing a density of 0.9g/cm³The carbon/carbon matrix is prepared by performing carbon matrix deposition on the seam structure carbon fiber preform by adopting a chemical vapor deposition process.

(2) Boron nitride modified hafnium tantalum precursor solution: placing 10.0g of boron nitride into a 250mL round-bottom flask, adding 100.0g of hafnium-tantalum precursor solution into a long-neck funnel, wherein the mass ratio of the common boron nitride to the hafnium-tantalum precursor solution is 1:10, sealing the round-bottom flask and the long-neck funnel, and pumping vacuum by using a vacuum pump. And slowly dripping the hafnium-tantalum precursor solution in the long-neck funnel into the round-bottom flask filled with boron nitride after the vacuum in the device reaches 10Pa and is stable for 5min, wherein the dripping speed is 10 mL/min. And (3) placing the round-bottom flask in vacuum in an ultrasonic device, carrying out ultrasonic mixing for 10min, and collecting the expanded boron nitride modified hafnium-tantalum precursor solution obtained by the treatment.

(3) Preparing an ultrahigh-temperature ceramic matrix by dipping, curing and cracking: the carbon/carbon matrix is put into a container filled with a common boron nitride modified hafnium-tantalum precursor solution, vacuum pressure impregnation is carried out (the vacuum pressure is 100Pa and the pressure is 1MPa), then curing reaction is carried out for 2 hours at 250 ℃, then pyrolysis reaction is carried out at 1800 ℃, and heat preservation is carried out for 2 hours.

(4) Repeating the step (3) for 7 times to finally prepare the product with the density of 3.09g/cm³The boron nitride toughened C/superhigh temperature ceramic matrix composite material.

(5) And (3) testing mechanical properties: and (3) carrying out mechanical property test on the obtained common boron nitride toughened C/ultrahigh temperature ceramic matrix composite.

It can be seen that the C/ultra high temperature ceramic composite toughened with expanded boron nitride in example 3 has higher fracture toughness and flexural strength than the boron nitride toughened C/ultra high temperature ceramic composite in example 7, comparing example 3 with example 7.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.