HfC / hfb2 composite ceramic oxygen-free precursor, and preparation method and use thereof

Abstract

The application discloses an HfC / HfB2 composite ceramic precursor, a preparation method and application thereof. The precursor is prepared by reacting a hafnium source and a boron source, does not contain oxygen, and is converted into HfC / HfB2 composite ceramic by pyrolysis at 1300-2000 DEG C under an argon atmosphere. The preparation method comprises the following steps: carrying out amine exchange reaction on tetra-diethylamino hafnium and an amine compound, adding aminoborazene after removing by-products, and synthesizing the HfC / HfB2 composite ceramic precursor under mild conditions. The prepared HfC / HfB2 composite ceramic precursor is suitable for being used as an impregnation matrix raw material of an ultra-high temperature ceramic matrix composite.

Description

Technical Field

[0001] This invention belongs to the field of ceramic precursor material technology, and relates to an oxygen-free HfC / HfB2 multiphase ceramic precursor, its preparation method and uses. Background Technology

[0002] Hafnium-based ceramics, such as HfC and HfB2, possess excellent physical and chemical properties, including 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, oxide carbon-boron thermal reduction, and chemical vapor deposition. These methods generally require harsh reaction conditions and have poor adaptability to molding and processing requirements. Compared to traditional methods, ceramic precursor conversion methods offer advantages such as uniform and tunable elemental composition, good precursor processing performance, and lower conversion temperatures. This has promoted the development of fields such as impregnation pyrolysis for preparing ceramic matrix composites, and ceramic precursors are crucial raw materials for this method.

[0003] Existing hafnium-based ceramic precursors are mainly oxygen-based systems, relying on oxygen-containing ligands to stabilize the metal center and meeting the needs of composite material preparation in solution state. The main problem is the high residual oxygen content in the precursor pyrolysis products, which easily damages the composite fiber during high-temperature carbothermic reduction treatment, adversely affecting the performance of the final composite material. Therefore, developing oxygen-free precursors has become a development direction for related material preparation and application. Limited by the high reactivity of the metal center and the variety of oxygen-free ligands, there are few existing reports on oxygen-free precursors for HfC ceramics, and their synthesis methods are generally complex. Furthermore, HfB2 ceramics require a suitable oxygen-free boron source, resulting in the lack of reports on oxygen-free precursors for HfB2 ceramics with processability. For the development of fields such as ceramic matrix composites, it is necessary to develop novel oxygen-free precursors for hafnium-based ceramics. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an HfC / HfB2 multiphase ceramic precursor, its preparation method, and its applications.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] This invention first provides an HfC / HfB2 multiphase 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 of the substances with the chemical formula Hf(NR2)4, and NR2 is selected from diethylamino, di-n-propylamino, diisopropylamino, diallylamino, di-n-butylamino, diisobutylamino, di-n-pentanamino, tetrahydropyrrolyl, and hexahydropyridyl; the boron source is an aminocycloborane.

[0007] According to an embodiment of the present invention, the aminocycloborane is an oligomer mixture having a similar structure but different molecular weights.

[0008] According to an embodiment of the present invention, the hafnium source is selected from tetradiethylaminohafnium, or the product of an amine exchange reaction between tetradiethylaminohafnium and an amine compound, wherein 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 product of an amine exchange reaction between tetradiethylaminohafnium 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 tetradiethylaminohafnium is 0:1 to 4:1, with exemplary ratios of 1:1, 2:1, 3:1, and 4:1. The molar ratio of the amine compound to tetradiethylaminohafnium determines the substitution ratio of the amino groups in tetradiethylaminohafnium. When the molar ratio of the amine compound to tetradiethylaminohafnium is higher than the upper limit of 4:1, all four original diethylamino groups are substituted.

[0010] According to an embodiment of the present invention, in the reaction of the hafnium source and the boron source, the mass ratio of the boron source to the tetraethylaminohafnium in the hafnium source is 0.05:1 to 0.20:1. Aminocycloborazine is an oligomer mixture with similar structures but different molecular weights, used as an oxygen-free boron source. If the amount of aminocycloborazine added is too small (below 0.05:1), the HfB2 content in the pyrolysis ceramic product is extremely low. If the amount of aminocycloborazine added is too large (above 0.20:1), the stability of the ceramic precursor is poor, and it is prone to gelation and cannot be used.

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

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

[0013] According to an embodiment of the present invention, the amine compound is at least one selected from 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 includes subjecting the product after the amine exchange reaction to vacuum distillation and then mixing it with a boron source for further reaction. The amine compound undergoes an amine exchange reaction with tetradiethylaminohafnium, producing a low-boiling-point diethylamine as a byproduct. After removing the low-boiling-point byproduct by vacuum distillation, a hafnium source is obtained, which is then mixed with a boron source for further reaction.

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

[0016] According to an embodiment of the present invention, the mass ratio of the boron source to tetraethylaminohafnium is 0.05:1 to 0.20:1. Aminocycloborazines are oligomer mixtures with similar structures but different molecular weights, used as oxygen-free boron sources. If too little aminocycloborazine is added (below 0.05:1), the HfB2 content in the pyrolysis ceramic product is extremely low; if too much aminocycloborazine is added (above 0.20:1), the stability of the ceramic precursor is poor, and it 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 reactants 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 mixed reaction are at the same or different temperatures, and are independent of each other from 0 to 40°C, specifically from 20°C to 30°C.

[0019] According to an embodiment of the present invention, the amine exchange reaction and the mixed reaction may have the same or different time, and are independent of each other for 4 to 24 hours, specifically 12 to 18 hours.

[0020] The present invention also provides the use of the HfC / HfB2 multiphase ceramic precursor as described above as an impregnation matrix for preparing ceramic matrix composites and carbon / carbon composites.

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

[0023] The present invention also provides an HfC / HfB2 multiphase ceramic, which is the pyrolysis reaction product of the HfC / HfB2 multiphase ceramic precursor as described above.

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

[0025] The present invention also provides a method for preparing the HfC / HfB2 multiphase ceramic as described above, comprising: subjecting the HfC / HfB2 multiphase 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 multiphase ceramic precursor at 1300-2000°C for 1-12 hours under an inert gas atmosphere such as argon, for example, at 1400-1600°C for 1-5 hours.

[0027] The present invention also provides the use of the HfC / HfB2 multiphase ceramics and / or ceramic matrix composites and / or carbon / carbon composites as described above in the preparation of materials for the aerospace field, such as 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 hafnium source and boron source of the present invention do not contain oxygen elements, so that the prepared HfC / HfB2 composite ceramic precursor does not contain oxygen elements in composition, which is beneficial to reduce the residual oxygen content of pyrolysis products. In addition, the obtained HfC / HfB2 composite ceramic precursor is liquid, which is suitable for the processing technology of various ceramic matrix 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 controlled, which is conducive to mass production and meeting different application requirements, and provides key raw materials for the manufacture of ultra-high temperature ceramic matrix composite materials. Attached Figure Description

[0031] Figure 1 This is the 1H NMR spectrum of the HfC / HfB2 multiphase ceramic precursor prepared in Example 1 of this invention.

[0032] Figure 2 This is the XRD pattern of the pyrolysis product of the HfC / HfB2 multiphase ceramic precursor prepared in Example 1 of this invention. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are all available from commercially available sources. Tetraethylaminohafnium was prepared according to the method in the literature (J. Chem. Soc. (A) 1968, 1940), and aminocycloborane was purchased from Shandong Industrial Ceramics Research and Design Institute Co., Ltd.

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

[0035] Example 1

[0036] The preparation method of HfC / HfB2 multiphase ceramics includes the following steps:

[0037] (1) A 100 mL three-necked flask was repeatedly evacuated and purged with argon to replace the air. 7.48 g (16.0 mmol) of tetraethylaminohafnium was added, followed by 3.12 g (32.1 mmol) of diallylamine. The mixture was stirred at 20 °C for 18 hours. Afterward, the reactants were distilled under reduced pressure to remove low-boiling-point substances. Then, 0.82 g of aminocycloborane was added, and the mixture was stirred at 20 °C for 18 hours to obtain a liquid HfC / HfB2 multiphase ceramic precursor. Its 1H NMR spectrum is shown below. Figure 1 As shown.

[0038] (2) The HfC / HfB2 multiphase ceramic precursor prepared in step (1) was pyrolyzed at 1600℃ for 2 hours in an argon atmosphere 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 an HfC / HfB2 multiphase ceramic, and its XRD pattern is shown in the figure. Figure 2 As shown.

[0039] Example 2

[0040] The preparation method of HfC / HfB2 multiphase ceramics includes the following steps:

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

[0042] (2) The HfC / HfB2 composite ceramic precursor prepared in step (1) was placed in an argon atmosphere and pyrolyzed at 1500℃ 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 HfC / HfB2 composite ceramic.

[0043] Example 3

[0044] The preparation method of HfC / HfB2 multiphase ceramics includes the following steps:

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

[0046] (2) The HfC / HfB2 composite ceramic precursor prepared in step (1) was placed in an argon atmosphere and pyrolyzed at 1600℃ 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 HfC / HfB2 composite ceramic.

[0047] Comparative Example 1

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

[0049] (1) A 100mL three-necked flask was evacuated multiple times and filled with argon to replace the air. 4.35g (9.3mmol) of tetradiethylaminohafnium was added, followed by 1.81g (18.6mmol) of diallylamine. The mixture was stirred at 20°C for 18 hours. After that, the reactants were distilled under reduced pressure to remove low-boiling-point substances. No aminocycloborane was added to obtain liquid HfC ceramic precursor.

[0050] (2) The HfC ceramic precursor prepared in step (1) was placed in an argon atmosphere and pyrolyzed at 1600℃ 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 and there was no HfB2 ceramic component.

[0051] Comparative Example 2

[0052] A 100 mL three-necked flask was repeatedly evacuated and purged with argon to replace the air. 6.67 g (14.3 mmol) of tetradiethylaminohafnium was added, followed by 3.05 g (42.9 mmol) of tetrahydropyrrole. The mixture was stirred at 30 °C for 18 hours. After that, the reactants were distilled under reduced pressure to remove low-boiling-point substances. Then, 3.30 g of aminocycloborane was added, and the mixture was stirred at 30 °C for 4 hours to obtain a near-solid product that could not be used as an impregnation precursor.

[0053] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A HfC / HfB2 multiphase ceramic precursor, characterized in that, It is a reaction product of hafnium source and boron source; The hafnium source is selected from tetradiethylaminohafnium, or the product of the amine exchange reaction between tetradiethylaminohafnium and an amine compound; The boron source is an aminocycloborane; The mass ratio of the boron source to the tetraethylaminohafnium in the hafnium source is 0.05:1 to 0.20:

1.

2. The HfC / HfB2 multiphase ceramic precursor according to claim 1, characterized in that, 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; In the amine exchange reaction, the molar ratio of amine compounds to tetraethylaminohafnium is 0:1 to 4:

1.

3. The method for preparing the HfC / HfB2 multiphase ceramic precursor according to claim 1 or 2, characterized in that, The preparation method includes: mixing and reacting a hafnium source and a boron source to obtain the HfC / HfB2 multiphase ceramic precursor; The mass ratio of the boron source to the tetraethylaminohafnium in the hafnium source is 0.05:1 to 0.20:

1.

4. The preparation method according to claim 3, characterized in that, The hafnium source is selected from tetradiethylaminohafnium, or prepared by a amine exchange reaction between tetradiethylaminohafnium and an amine compound.

5. The preparation method according to claim 4, characterized in that, The hafnium source is prepared by a amine exchange reaction of tetraethylaminohafnium with an amine compound; the amine compound is at least one selected from di-n-propylamine, diisopropylamine, diallylamine, di-n-butylamine, diisobutylamine, di-n-pentylamine, tetrahydropyrrole, and hexahydropyridine. The molar ratio of the amine compound to tetraethylaminohafnium is 0:1 to 4:

1.

6. The use of the HfC / HfB2 multiphase ceramic precursor as described in claim 1 or 2 as an impregnation matrix for preparing ceramic matrix composites and carbon / carbon composites.

7. A ceramic matrix composite material, characterized in that, It is prepared by impregnation pyrolysis using the HfC / HfB2 multiphase ceramic precursor as described in claim 1 or 2 as the impregnation matrix.

8. A carbon / carbon composite material, characterized in that, It is prepared by impregnation pyrolysis using the HfC / HfB2 multiphase ceramic precursor as described in claim 1 or 2 as the impregnation matrix.

9. An HfC / HfB2 multiphase ceramic, characterized in that, It is the pyrolysis reaction product of the HfC / HfB2 multiphase ceramic precursor as described in claim 1 or 2.

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

11. Use of the HfC / HfB2 multiphase ceramic of claim 9 and / or the ceramic matrix composite of claim 7 and / or the carbon / carbon composite of claim 8 in the preparation of materials for the aerospace field.

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