HfC / HfB2 composite ceramic oxygen-free precursor as well as preparation method and application thereof

Abstract

The invention discloses an HfC / HfB2 composite ceramic precursor as well as a preparation method and application thereof. The precursor is prepared from a hafnium source and a boron source through a reaction, does not contain oxygen elements, and is converted into HfC / HfB2 multiphase ceramic through pyrolysis at the temperature of 1300-2000 DEG C in an argon atmosphere. The preparation method of the precursor comprises the following steps: carrying out amine exchange reaction on tetra-diethylamino hafnium and an amine compound, removing byproducts, adding amino borazine, and synthesizing under mild conditions to obtain the HfC / HfB2 composite ceramic precursor. The HfC / HfB2 composite ceramic precursor prepared by the method is suitable for being used as a dipping matrix raw material of an ultrahigh-temperature ceramic matrix composite material.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic precursor materials and relates to a HfC / HfB2 composite ceramic oxygen-free precursor and a preparation method and application thereof. Background Art

[0002] Hafnium-based ceramics such as HfC and HfB2 have excellent physical and chemical properties, such as ultra-high melting point, high hardness, wear resistance, good electrical and thermal conductivity, and chemical stability. They are important ultra-high temperature ceramic materials and can be used as thermal protection components for high-speed aircraft. Traditional synthesis methods for hafnium-based ceramics include solid-state elemental combustion, thermal reduction of oxide carbon and boron, and chemical vapor deposition. These methods generally require relatively harsh reaction conditions and have poor adaptability to molding and processing requirements. Compared with traditional methods, the ceramic precursor conversion method has the advantages of uniform and adjustable elemental composition, good precursor processing performance, and low conversion temperature, which has promoted the development of fields such as the preparation of ceramic-based composite materials by impregnation pyrolysis, and ceramic precursors are important raw materials for this method to be realized.

[0003] Existing hafnium-based ceramic precursors are mainly oxygen-containing systems, relying on oxygen-containing ligands to stabilize the metal center and meet the needs of composite material preparation in solution state. The main problem is that the residual oxygen content of the precursor pyrolysis product is high, and the high-temperature carbon thermal reduction process is easy to damage the composite fiber and adversely affect the performance of the final composite material. Therefore, the development of oxygen-free precursors has become the development direction of related material preparation and application. Limited by the high reactivity of the metal center and the type of oxygen-free ligands, there are few existing reports on HfC ceramic oxygen-free precursors, and the general synthesis method is complicated. HfB2 ceramics also require a suitable oxygen-free boron source, resulting in no reports of HfB2 ceramic oxygen-free precursors with processing performance. In order to develop fields such as ceramic-based composites, it is necessary to develop new hafnium-based ceramic oxygen-free precursors. Summary of the invention

[0004] In order to improve the above technical problems, the present invention provides a HfC / HfB2 composite ceramic precursor and a preparation method and use thereof.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] The present invention first provides a HfC / HfB2 composite ceramic precursor, which is the reaction product of a hafnium source and a boron source; wherein the hafnium source is selected from at least one substance with a chemical formula of Hf(NR2)4, NR2 is the same or different and independently selected from diethylamino, di-n-propylamino, diisopropylamino, diallylamino, di-n-butylamino, diisobutylamino, di-n-pentylamino, tetrahydropyrrolyl, hexahydropyridine; and the boron source is aminocycloborazine.

[0007] According to an embodiment of the present invention, the aminoborazine is an oligomeric mixture having similar structures and different molecular weights.

[0008] According to an embodiment of the present invention, the hafnium source is selected from hafnium tetradiethylamine, or an amine exchange reaction product of hafnium tetradiethylamine and an amine compound, and the amine compound is selected from at least one of di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole and hexahydropyridine. Preferably, the hafnium source is selected from the amine exchange reaction product of hafnium tetradiethylamine and an amine compound.

[0009] According to an embodiment of the present invention, in the amine exchange reaction, the molar ratio of the amine compound to hafnium tetradiethylamino is 0:1 to 4:1, exemplified by 1:1, 2:1, 3:1, and 4:1. The molar ratio of the amine compound to hafnium tetradiethylamino determines the substitution ratio of the amino groups in hafnium tetradiethylamino. When the molar ratio of the amine compound to hafnium tetradiethylamino is higher than the upper limit of 4:1, all the original four diethylamino groups are replaced.

[0010] According to an embodiment of the present invention, in the reaction of the hafnium source and the boron source, the feeding mass ratio of the boron source to the tetrakisdiethylamino hafnium in the hafnium source is 0.05:1 to 0.20:1. Aminoborazine is an oligomeric mixture with similar structures and different molecular weights, which is used as an oxygen-free boron source. If the feeding amount of aminoborazine is too small (less than 0.05:1), the HfB2 content in the pyrolysis ceramic product is extremely low. If the feeding amount of aminoborazine is too large (higher than 0.20:1), the stability of the ceramic precursor is poor, and it is easy to gel and cannot be used.

[0011] The present invention also provides a method for preparing the HfC / HfB2 composite ceramic precursor, comprising: mixing a hafnium source and a boron source to react to obtain the HfC / HfB2 composite ceramic precursor.

[0012] According to an embodiment of the present invention, the hafnium source is selected from hafnium tetradiethylamide, or is prepared by an amine exchange reaction between hafnium tetradiethylamide and an amine compound. Preferably, the hafnium source is prepared by an amine exchange reaction between hafnium tetradiethylamide and an amine compound.

[0013] According to an embodiment of the present invention, the amine compound is at least one of di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole and hexahydropyridine.

[0014] According to an embodiment of the present invention, the preparation method further comprises subjecting the product after the amine exchange reaction to vacuum distillation and then mixing it with a boron source for reaction. The amine compound undergoes an amine exchange reaction with tetradiethylamino hafnium, and the byproduct is low-boiling diethylamine. After the low-boiling byproduct is removed by vacuum distillation, the hafnium source is obtained, and then mixed with a boron source for reaction.

[0015] According to an embodiment of the present invention, the molar ratio of the amine compound to hafnium tetradiethylamino is 0:1 to 4:1, exemplified by 1:1, 2:1, 3:1, and 4:1. The molar ratio of the amine compound to hafnium tetradiethylamino determines the substitution ratio of the amino groups in hafnium tetradiethylamino. When the molar ratio of the amine compound to hafnium tetradiethylamino is higher than the upper limit of 4:1, all the original four diethylamino groups are replaced.

[0016] According to an embodiment of the present invention, the mass ratio of the boron source to hafnium tetradiethylamino is 0.05:1 to 0.20:1. Aminoborazine is a oligomeric mixture with similar structures and different molecular weights, which is used as an oxygen-free boron source. If the amount of aminoborazine added is too little (less than 0.05:1), the HfB2 content in the pyrolysis ceramic product is extremely low. If the amount of aminoborazine added is too much (higher than 0.20:1), the ceramic precursor has poor stability and is prone to gelation and cannot be used.

[0017] According to an embodiment of the present invention, the preparation method is carried out in an inert gas atmosphere, such as a nitrogen or argon atmosphere. Since both the reaction raw materials and products are air sensitive, an inert gas atmosphere is required for protection to prevent other side reactions.

[0018] According to an embodiment of the present invention, the amine exchange reaction and the mixing reaction temperature are the same or different, and are independently 0 to 40°C, specifically 20°C to 30°C.

[0019] According to an embodiment of the present invention, the amine exchange reaction and the mixing reaction time are the same or different, and are independently 4 to 24 hours, specifically 12 to 18 hours.

[0020] The present invention also provides the use of the HfC / HfB2 composite ceramic precursor as an impregnation matrix for preparing ceramic-based composite materials and carbon / carbon composite materials.

[0021] The present invention also provides a ceramic-based composite material, which is prepared by impregnation pyrolysis using the above-mentioned HfC / HfB2 multiphase ceramic precursor as an impregnation matrix.

[0022] The present invention also provides a carbon / carbon composite material, which is prepared by impregnation pyrolysis using the above-mentioned HfC / HfB2 multiphase ceramic precursor as an impregnation matrix.

[0023] The present invention also provides a HfC / HfB2 composite ceramic, which is a thermal decomposition reaction product of the HfC / HfB2 composite ceramic precursor as described above.

[0024] According to an embodiment of the present invention, the pyrolysis reaction is to pyrolyze the HfC / HfB2 composite ceramic precursor at 1300-2000°C for 1-12 hours, such as 1400-1600°C for 1-5 hours under an inert gas such as argon atmosphere.

[0025] The present invention also provides a method for preparing the HfC / HfB2 composite ceramic as described above, comprising: subjecting the HfC / HfB2 composite ceramic precursor as described above to a pyrolysis reaction.

[0026] According to an embodiment of the present invention, the pyrolysis reaction is to pyrolyze the HfC / HfB2 composite ceramic precursor at 1300-2000°C for 1-12 hours, such as 1400-1600°C for 1-5 hours under an inert gas such as argon atmosphere.

[0027] The present invention also provides the use of the HfC / HfB2 multiphase ceramics and / or ceramic-based composites and / or carbon / carbon composites described above in the preparation of materials in the aerospace field, for example, in the preparation of thermal protection components for high-speed aircraft.

[0028] Compared with the prior art, the present invention has the following characteristics:

[0029] (1) The synthetic raw materials hafnium source and boron source of the present invention do not contain oxygen, so the prepared HfC / HfB2 composite ceramic precursor does not contain oxygen in composition, which is beneficial to reduce the residual oxygen content of the pyrolysis product. The obtained HfC / HfB2 composite ceramic precursor is in liquid state and is suitable for the processing technology of various ceramic-based composite materials.

[0030] (2) The preparation method of the HfC / HfB2 composite ceramic precursor of the present invention has mild conditions and good universality, and the element ratio can be adjusted, which is conducive to large-scale preparation and meets different application requirements, and provides key raw materials for the manufacture of ultra-high temperature ceramic-based composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the nuclear magnetic hydrogen spectrum of the HfC / HfB2 composite ceramic precursor prepared in Example 1 of the present invention.

[0032] Figure 2 This is the XRD diagram of the thermal decomposition product of the HfC / HfB2 composite ceramic precursor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods are conventional methods unless otherwise specified, and the raw materials can be obtained from public commercial channels unless otherwise specified. Hafnium tetrakisdiethylamino is prepared according to the method in the literature (J. Chem. Soc. (A) 1968, 1940), and amino borazine is purchased from Shandong Industrial Ceramics Research and Design Institute Co., Ltd.

[0034] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0035] Example 1

[0036] The preparation method of HfC / HfB2 composite ceramics comprises the following steps:

[0037] (1) A 100 mL three-necked flask was repeatedly evacuated and filled with argon to replace the air, 7.48 g (16.0 mmol) of hafnium tetradiethylamino was added, and then 3.12 g (32.1 mmol) of diallylamine was added. The reaction was stirred at 20°C for 18 hours. After that, the reactants were distilled under reduced pressure to remove low-boiling substances, and then 0.82 g of aminoborazine was added. The reaction was stirred at 20°C for 18 hours to obtain a liquid HfC / HfB2 composite ceramic precursor. Its H NMR spectrum is as follows Figure 1 shown.

[0038] (2) The HfC / HfB2 composite ceramic precursor prepared in step (1) was pyrolyzed at 1600° C. in an argon atmosphere for 2 hours to obtain a black ceramic product with a ceramic yield of 43.8% and an oxygen content of 1.1%. XRD analysis showed that the product was a HfC / HfB2 composite ceramic, and its XRD spectrum was as follows: Figure 2 shown.

[0039] Example 2

[0040] The preparation method of HfC / HfB2 composite ceramics comprises the following steps:

[0041] (1) A 100 mL three-necked flask was evacuated several times and filled with argon to replace the air. 12.89 g (27.6 mmol) of hafnium tetradiethylamino was added, and then 2.79 g (27.6 mmol) of di-n-propylamine was added. The mixture was stirred at 20°C for 12 hours. The reactants were then distilled under reduced pressure to remove low-boiling substances. 2.32 g of aminoborazine was added, and the mixture was stirred at 20°C for 12 hours to obtain a liquid HfC / HfB2 composite ceramic precursor.

[0042] (2) The HfC / HfB2 composite ceramic precursor prepared in step (1) was pyrolyzed at 1500°C in an argon atmosphere for 2 hours to obtain a black ceramic product with a ceramic yield of 32.5% and an oxygen content of 1.8%. XRD analysis showed that the product was a HfC / HfB2 composite ceramic.

[0043] Example 3

[0044] The preparation method of HfC / HfB2 composite ceramics comprises the following steps:

[0045] (1) A 100 mL three-necked flask was evacuated several times and filled with argon to replace the air. 6.67 g (14.3 mmol) of tetrakisdiethylamino hafnium was added, and then 3.05 g (42.9 mmol) of tetrahydropyrrole was added. The mixture was stirred at 30°C for 18 hours. The reactants were then distilled under reduced pressure to remove low-boiling substances. 0.40 g of aminoborazine was added, and the mixture was stirred at 30°C for 4 hours to obtain a liquid HfC / HfB2 composite ceramic precursor.

[0046] (2) The HfC / HfB2 composite ceramic precursor prepared in step (1) was pyrolyzed at 1600°C in an argon atmosphere for 2 hours to obtain a black ceramic product with a ceramic yield of 49.6% and an oxygen content of 1.0%. XRD analysis showed that the product was a HfC / HfB2 composite ceramic.

[0047] Comparative Example 1

[0048] The preparation method of HfC ceramics comprises the following steps:

[0049] (1) A 100 mL three-necked flask was evacuated several times and filled with argon to replace the air, 4.35 g (9.3 mmol) of hafnium tetrakisdiethylamino was added, and then 1.81 g (18.6 mmol) of diallylamine was added. The mixture was stirred at 20° C. for 18 hours, and then the reactants were distilled under reduced pressure to remove low-boiling substances without adding aminoborazine to obtain a liquid HfC ceramic precursor.

[0050] (2) The HfC ceramic precursor prepared in step (1) was pyrolyzed in an argon atmosphere at 1600° C. for 2 hours to obtain a black ceramic product with a ceramic yield of 42.6% and an oxygen content of 1.4%. XRD analysis showed that the product was HfC ceramic without any HfB2 ceramic component.

[0051] Comparative Example 2

[0052] A 100 mL three-necked flask was evacuated several times and filled with argon to replace the air, 6.67 g (14.3 mmol) of tetrakisdiethylamino hafnium was added, and then 3.05 g (42.9 mmol) of tetrahydropyrrole was added. The reaction was stirred at 30°C for 18 hours, and then the reactants were distilled under reduced pressure to remove low-boiling substances. 3.30 g of aminocycloborazine was added, and the reaction was stirred at 30°C for 4 hours to obtain a nearly solid product, which could not be used as an impregnation precursor.

[0053] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A HfC / HfB2 composite ceramic precursor, characterized in that: It is the reaction product of a hafnium source and a boron source; wherein the hafnium source is selected from at least one substance with the chemical formula Hf(NR2)4, NR2 are the same or different and independently selected from diethylamino, di-n-propylamino, diisopropylamino, diallylamino, di-n-butylamino, diisobutylamino, di-n-pentylamino, tetrahydropyrrolyl, hexahydropyridyl; and the boron source is aminoborazine.

2. The HfC / HfB2 composite ceramic precursor according to claim 1, characterized in that: The aminoborazine is an oligomeric mixture having similar structures and different molecular weights; Preferably, the hafnium source is selected from hafnium tetradiethylamino, or an amine exchange reaction product of hafnium tetradiethylamino and an amine compound, and the amine compound is selected from at least one of di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole and hexahydropyridine; Preferably, in the amine exchange reaction, the molar ratio of the amine compound to hafnium tetrakis diethylamino is 0:1 to 4:1; Preferably, in the reaction of the hafnium source and the boron source, the feed mass ratio of the boron source to the hafnium tetrakis diethylamino in the hafnium source is 0.05:1 to 0.20:

1.

3. The method for preparing the HfC / HfB2 composite ceramic precursor according to claim 1 or 2, characterized in that: The preparation method comprises: mixing a hafnium source and a boron source for reaction to obtain the HfC / HfB2 composite ceramic precursor.

4. The preparation method according to claim 3, characterized in that: The hafnium source is selected from hafnium tetradiethylamino, or is prepared by an amine exchange reaction between hafnium tetradiethylamino and an amine compound; Preferably, the hafnium source is prepared by an amine exchange reaction between hafnium tetradiethylamino and an amine compound; the amine compound is at least one of di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole, and hexahydropyridine; Preferably, the molar ratio of the amine compound to hafnium tetrakis diethylamino is 0:1 to 4:1; Preferably, the mass ratio of the boron source to hafnium tetrakis diethylamino is 0.05:1 to 0.20:

1.

5. Use of the HfC / HfB2 composite ceramic precursor according to claim 1 or 2 as an impregnation matrix to prepare ceramic matrix composite materials and carbon / carbon composite materials.

6. A ceramic matrix composite material, characterized in that: The HfC / HfB2 composite ceramic precursor according to claim 1 or 2 is used as an impregnation matrix and is prepared by impregnation pyrolysis.

7. A carbon / carbon composite material, characterized in that: The HfC / HfB2 composite ceramic precursor according to claim 1 or 2 is used as an impregnation matrix and is prepared by impregnation pyrolysis.

8. A HfC / HfB2 composite ceramic, characterized in that: It is the thermal decomposition reaction product of the HfC / HfB2 composite ceramic precursor as described in claim 1 or 2.

9. The method for preparing the HfC / HfB2 composite ceramic according to claim 8, characterized in that: include: The HfC / HfB2 composite ceramic precursor according to claim 1 is subjected to a pyrolysis reaction.

10. Use of the HfC / HfB2 composite ceramics according to claim 8 and / or the ceramic-based composite materials according to claim 6 and / or the carbon / carbon composite materials according to claim 7 in the preparation of materials in the aerospace field.

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