A low-cost, easily sinterable ZrC-SiC multiphase ceramic precursor, the multiphase ceramic, and its preparation method

Abstract

This invention discloses a low-cost, easily sinterable ZrC / SiC multiphase ceramic precursor, the multiphase ceramic, and its preparation method. Using a low-cost difunctional siloxane as the silicon source and a zirconium alkoxide as the zirconium source, the copolymerization rate of the two components is controlled by a dual-ligand mechanism, achieving the copolymerization reaction of Zr-O and Si-O components. This yields a ZrC-Si multiphase ceramic precursor with Zr, Si, C, and O uniformly distributed at the nanoscale. Significant sintering occurs after pressureless pyrolysis at 1600℃ for 2 hours, transforming it into a multiphase ceramic with a cross-dispersed ZrC and SiC structure. The choice of siloxane as the silicon source significantly reduces the preparation cost of the multiphase ceramic precursor, thus showing broad application prospects in the field of ultra-high temperature ceramic matrix composites.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature ceramic materials. Specifically, it relates to a low-cost, easily sinterable ZrC-SiC multiphase ceramic precursor, multiphase ceramic, and preparation method. Background Technology

[0002] ZrC ceramics possess advantages such as high melting point, high hardness, high chemical stability, and good mechanical properties, making them widely used in wear-resistant and high-temperature-resistant components. However, the oxidation resistance of ZrC ceramics alone is insufficient, necessitating the introduction of a SiC second phase to improve its oxidation resistance. Currently, among the methods for preparing ZrC-SiC multiphase ceramics, the precursor conversion method is suitable for preparing ceramic matrix composites due to the processability of the precursor, and it has attracted widespread attention from researchers due to the elemental distribution in ceramic matrix composites prepared by the precursor conversion method.

[0003] Currently, the main methods for preparing ZrC-SiC multiphase ceramic precursors use high-cost polycarbosilane (PCS) as the silicon source and zirconium-containing polymers as the zirconium source. The resulting ZrC / SiC multiphase ceramics, obtained by pyrolyzing the precursor, exhibit a dispersed distribution of ZrC and SiC phases, which mutually inhibit crystallization. Consequently, the resulting ceramics are mostly nanopowder structures. However, the particle size of the multiphase ceramic particles obtained from pyrolysis at 1600℃ is generally no higher than 200nm. Therefore, even under pressureless conditions, the powder remains difficult to sinter at 2000℃. This leads to the low mechanical properties and insufficient erosion resistance of C / ZrC-SiC ceramic matrix composites prepared from existing ZrC-SiC multiphase ceramic precursors.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a low-cost, easily sinterable ZrC-SiC multiphase ceramic precursor and its preparation method. This invention uses a low-cost difunctional siloxane as the silicon source and a zirconium alkoxide as the zirconium source. By controlling the copolymerization rate of the two through dual ligands, the copolymerization reaction of Zr-O and Si-O components is achieved, thereby obtaining a ZrC-SiC multiphase ceramic precursor containing Zr, Si, C, and O. This precursor readily forms Zr during the pyrolysis process. x Si y O m The intermediate phase acts as an aid to sintering, thus sintering can occur under pressureless conditions through pyrolysis at 1600℃. The ZrC-SiC multiphase ceramic precursor prepared by this invention can significantly reduce the preparation cost of multiphase ceramic precursors and improve the mechanical properties of ZrC-SiC multiphase ceramics.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing a ZrC-SiC multiphase ceramic precursor, comprising using siloxane as a silicon source and zirconium alkoxide as a zirconium source, and under the action of ligand 1 and ligand 2, undergoing a copolymerization reaction (the copolymerization reaction rate of the two is controlled by the two ligands to achieve the copolymerization reaction of Zr-O and Si-O components) to prepare the ZrC-SiC multiphase ceramic precursor.

[0008] In the ZrC-SiC multiphase ceramic precursor of the present invention, Zr, Si, C, O and other elements are uniformly distributed at the nanoscale.

[0009] According to an embodiment of the present invention, the preparation method of the ZrC-SiC multiphase ceramic precursor includes: dissolving zirconium alkoxide, siloxane monomer, ligand 1, and ligand 2 in a first solvent, adding a second solvent to carry out a co-hydrolysis reaction, then heating and refluxing to carry out a copolymerization reaction, followed by vacuum distillation to obtain a zirconium-silicon copolymer, and finally adding a carbon source to the system and mixing to obtain the ZrC-SiC multiphase ceramic precursor.

[0010] According to an embodiment of the present invention, the siloxane monomer is a difunctional siloxane. For example, the difunctional siloxane is at least one selected from dimethyldimethoxysilane, methylvinyldimethoxysilane, diphenyldimethoxysilane, and methylphenyldimethoxysilane.

[0011] In this invention, the hydrolysis polymerization product of difunctional siloxanes is a linear polymer, which helps to improve the stability of multiphase ceramic precursors. However, if trifunctional or tetrafunctional siloxanes are selected, they are prone to forming cross-linked structures. When copolymerized with multifunctional zirconium sources, it is even more difficult to obtain liquid precursors with good storage stability. Monofunctional siloxanes can only be attached to side chains or end groups, so they are easily lost during the cracking process to form a single ZrC ceramic precursor. Therefore, the oxidation resistance of the obtained ceramic precursor is insufficient, so they are not considered.

[0012] According to an embodiment of the present invention, the zircon alkoxide is at least one selected from zirconium ethoxide, zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide.

[0013] According to an embodiment of the present invention, the ligand 1 is one of acetylacetone and ethyl acetate.

[0014] According to an embodiment of the present invention, the ligand 2 is one of acetic acid, citric acid and salicylic acid.

[0015] According to an embodiment of the present invention, the first solvent is at least one selected from n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol methyl ether, and ethylene glycol ethyl ether.

[0016] According to an embodiment of the present invention, the second solvent is a mixture of water and the first solvent. Preferably, the mass ratio of water to the first solvent in the mixture is 1:2 to 6, exemplarily 1:2, 1:3, 1:4, 1:5, or 1:6.

[0017] According to an embodiment of the present invention, the temperature of the co-hydrolysis reaction is 50-80°C, exemplarily 50°C, 60°C, 70°C, and 80°C.

[0018] According to an embodiment of the present invention, the reflux temperature is 85-100°C, exemplarily 85°C, 90°C, 95°C, or 100°C; the reflux time is 1-4 hours, exemplarily 1 hour, 2 hours, 3 hours, or 4 hours.

[0019] According to an embodiment of the present invention, the temperature of the vacuum distillation is 85-100°C, exemplarily 85°C, 90°C, 95°C, or 100°C; the time of the vacuum distillation is 0.5-4 hours, exemplarily 0.5 hours, 1 hour, 2 hours, 3 hours, or 4 hours.

[0020] According to an embodiment of the present invention, the carbon source is allylphenolic resin.

[0021] According to an embodiment of the present invention, the molar ratio of the zirconium alkoxide to the siloxane monomer and ligand 1 is 1:0.125-0.5:0.5-1.5, and exemplary ratios are 1:0.125:0.5, 1:0.35:1, 1:0.5:1.5, 1:0.4:1, 1:0.125:1.5, and 1:0.125:1.5.

[0022] According to an embodiment of the present invention, the molar ratio of the siloxane monomer to the ligand 2 is 1:0.1 to 0.5, and exemplary ratios are 1:0.1, 1:0.2, 1:0.3, 1:0.4, and 1:0.5.

[0023] According to an embodiment of the present invention, before hydrolysis, the molar ratio of the zirconium alkoxide to the first solvent is 1:0.5 to 10, with exemplary values ​​of 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, and 1:10.

[0024] According to an embodiment of the present invention, the molar ratio of the sum of the moles of the zirconium alkoxide and the siloxane monomer to water is 1:1 to 2, with exemplary ratios of 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, and 1:2.0.

[0025] According to an embodiment of the present invention, the mass ratio of zirconium element to carbon source in the zirconium alkoxide is 1:0.5 to 0.8, with exemplary ratios being 1:0.5, 1:0.6, 1:0.7, and 1:0.8.

[0026] The present invention also provides a ZrC-SiC multiphase ceramic precursor prepared by the above method.

[0027] According to an embodiment of the present invention, the ZrC-SiC multiphase ceramic precursor includes elements such as Zr, Si, C, and O. Preferably, the elements Zr, Si, C, and O are uniformly distributed at the nanoscale.

[0028] According to an embodiment of the present invention, the viscosity of the ZrC-SiC multiphase ceramic precursor is 15–100 mPa·s.

[0029] According to an embodiment of the present invention, the viscosity change rate of the ZrC-SiC multiphase ceramic precursor stored for 6 months is no more than 10%.

[0030] The present invention also provides a ZrC-SiC multiphase ceramic, which is prepared by pyrolyzing the above-mentioned ZrC-SiC multiphase ceramic precursor under vacuum or inert atmosphere protection at normal pressure.

[0031] According to an embodiment of the present invention, the ZrC-SiC multiphase ceramic comprises elements such as Zr, Si, C, and O. Preferably, the elements Zr, Si, C, and O are uniformly distributed at the nanoscale.

[0032] According to an embodiment of the present invention, in the ZrC-SiC multiphase ceramic, the Zr content is 70-85 wt%, for example 72.3 wt%, 79.0 wt%, and 84.3 wt%; and the Si content is 1-15 wt%, for example 3.2 wt%, 5.6 wt%, and 10.8 wt%.

[0033] According to an embodiment of the present invention, the inert atmosphere may be argon, helium, or a mixture thereof.

[0034] The present invention also provides a method for preparing ZrC-SiC multiphase ceramics, comprising curing and pyrolyzing the above-mentioned ZrC-SiC multiphase ceramic precursor to obtain the multiphase ceramics.

[0035] According to an embodiment of the present invention, the pyrolysis temperature is not higher than 1600℃, preferably 1400~1600℃, and exemplary values ​​are 1400℃, 1500℃, and 1600℃; the pyrolysis time is 0.5~5h, and exemplary values ​​are 0.5h, 1h, 2h, 3h, 4h, and 5h.

[0036] According to an embodiment of the invention, the pyrolysis is carried out in a vacuum environment or under an inert atmosphere. Preferably, the inert atmosphere is selected from argon, helium, or a mixture of both.

[0037] Preferably, the curing atmosphere is air, the curing temperature is 100-300℃, for example 100℃, 150℃, 200℃, 250℃, 300℃; and the curing time is 2-24h, for example 2h, 5h, 8h, 12h, 24h.

[0038] The ZrC-SiC multiphase ceramic precursor of the present invention was heated from room temperature to 1600°C and held for 2 hours under an inert atmosphere and without pressure. The resulting ZrC and SiC crystal phases were uniformly distributed, and there were obvious sintering pyrolysis products between the particles.

[0039] The beneficial effects of this invention:

[0040] (1) The present invention uses siloxane as silicon source, which is inexpensive (the price is less than RMB 100 per kilogram), which is significantly lower than the polycarbosilane used in the preparation of existing multiphase ceramic precursors (the price is more than RMB 3,000 per kilogram). Therefore, the present invention selects siloxane as silicon source, which can significantly reduce the preparation cost of multiphase ceramic precursor.

[0041] (2) When using siloxane as a precursor for SiC ceramics, this invention achieves the copolymerization reaction of zirconium source and silicon source by controlling the type of ligand and the ratio of each raw material in the copolymerization reaction system, thereby reducing the proportion of free SiO2 in the cracking process and overcoming the problem that the existing use of siloxane as a precursor for SiC ceramics generally results in low cracking conversion efficiency and uncontrollable process, leading to low ceramic yield of SiC components.

[0042] (3) This invention uses low-cost difunctional siloxanes as silicon sources and controls the types and proportions of ligands in the copolymerization reaction system to achieve the copolymerization reaction of Zr-O and Si-O components. Furthermore, during the cracking process, Zr-O and Si-O readily form Zr. x Si y O m The intermediate phase can promote the sintering process of ZrC-SiC composite ceramic particles. Therefore, under pressureless conditions, the pyrolysis product of the ZrC-SiC composite ceramic precursor can be obtained by pyrolysis at 1600℃ for 2 hours, thus providing a new technical approach for improving the mechanical properties of ultra-high temperature ceramic matrix composites. Attached Figure Description

[0043] Figure 1 This is a SEM image of the product obtained from the multiphase ceramic precursor in Example 1 after pressureless pyrolysis at 1600℃ for 2 hours.

[0044] Figure 2 The image shows the XRD pattern of the product obtained by pressureless pyrolysis of the multiphase ceramic precursor at 1600℃ for 2 hours in Example 1.

[0045] Figure 3 This is a SEM image of the product obtained by pressureless pyrolysis at 1600℃ from the multiphase ceramic precursor prepared from polycarbosilane in Comparative Example 1. Detailed Implementation

[0046] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0047] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0048] Example 1

[0049] In this embodiment, the following method is used to prepare low-cost, easily sinterable ZrC / SiC composite ceramic precursor and ZrC-SiC composite ceramic:

[0050] (1) 1 mol zirconium propoxide, 0.125 mol methyl vinyl dimethoxysilane, 0.5 mol acetylacetone and 0.025 mol citric acid were added to 0.5 mol n-propanol, heated to 70°C, and a mixed solvent of 30.38 g water and 121.5 g n-propanol was added with stirring. Then the mixture was heated to 95°C and refluxed for 2 hours. The mixture was then distilled under reduced pressure at 90°C for half an hour to obtain zirconium-silicon copolymer. 45.62 g allylphenol aldehyde was added to the system and stirred evenly to obtain ZrC-SiC multiphase ceramic precursor ZS-1 with a viscosity of 80 mPa·s.

[0051] (2) The ZS-1 precursor was cured in an oven at 250°C for 2 hours, and then placed in an argon atmosphere and heated to 1600°C for pyrolysis. The temperature was maintained for 2 hours to obtain ZrC / SiC composite ceramic. Inductively coupled plasma emission spectroscopy showed that the Zr content in the ceramic was 84.3 wt% and the Si content was 3.2 wt%.

[0052] Figure 1 The image shows the SEM image of the product obtained by pressureless pyrolysis at 1600℃ for 2 hours from the multiphase ceramic precursor in Example 1. The results in the image show that the average particle size of the pyrolysis product is 300nm to 400nm, and there is obvious sintering phenomenon between the particles.

[0053] Figure 2The image shows the XRD pattern of the product obtained by pressureless pyrolysis at 1600℃ for 2 hours from the multiphase ceramic precursor in Example 1. The diffraction peaks of ZrC and SiC can be clearly seen in the image.

[0054] Example 2

[0055] In this embodiment, the following method is used to prepare low-cost, easily sinterable ZrC-SiC composite ceramic precursor and ZrC-SiC composite ceramic:

[0056] (1) 1 mol zirconium propoxide, 0.35 mol dimethyldimethoxysilane, 1 mol acetylacetone and 0.08 mol acetic acid were added to 1 mol ethylene glycol ethyl ether. The mixture was heated to 80 °C and 48.6 g water and 97.2 g ethylene glycol ethyl ether were added dropwise with stirring. The mixture was then heated to 100 °C and refluxed for 2 hours. The mixture was then distilled under reduced pressure at 80 °C for 1 hour to obtain zirconium-silicon copolymer. 72.9 g allylphenol was added to the system to obtain ZrC-SiC multiphase ceramic precursor ZS-1. The precursor viscosity was 50 mPa·s.

[0057] (2) The ZS-1 precursor was cured in an oven at 250°C for 2 hours, and then placed in argon gas and heated to 1600°C for pyrolysis. The temperature was maintained for 2 hours to obtain ZrC / SiC composite ceramics with Zr content of 79.0 wt% and Si content of 5.6 wt%.

[0058] Example 3

[0059] In this embodiment, the following method is used to prepare low-cost, easily sinterable ZrC-SiC composite ceramic precursor and ZrC-SiC composite ceramic:

[0060] (1) 1 mol zirconium propoxide, 0.5 mol diphenyldimethoxysilane, 1.5 mol acetylacetone and 0.25 mol salicylic acid were added to 10 mol ethylene glycol methyl ether. The mixture was heated to 50 °C and 54 g water and 162 g ethylene glycol methyl ether were added dropwise with stirring. The mixture was then heated to 90 °C and refluxed for 3 hours. The mixture was then distilled under reduced pressure at 90 °C for 40 min to obtain zirconium-silicon copolymer. 54.7 g allylphenol aldehyde was added to the system to obtain ZrC-SiC multiphase ceramic precursor ZS-1. The precursor viscosity was 60 mPa·s.

[0061] (2) The ZS-1 precursor was cured in an oven at 250°C for 2 hours, and then placed in argon gas and heated to 1600°C for pyrolysis. The temperature was maintained for 2 hours to obtain ZrC / SiC composite ceramics with Zr content of 72.3wt% and Si content of 10.8wt%.

[0062] Comparative Example 1

[0063] The preparation methods of ZrC / SiC multiphase precursor and ZrC-SiC multiphase ceramic using polycarbosilane as silicon source in this comparative example are as follows.

[0064] (1) Add 1 mol zirconium propoxide, 0.5 mol acetylacetone and 0.025 mol citric acid to 0.5 mol n-propanol, heat to 70℃, add 30.38 g water and 121.5 g n-propanol mixed solvent dropwise while stirring, then heat to 95℃ and reflux for 2 hours, distill under reduced pressure at 90℃ for half an hour to obtain zirconium precursor, add 45.62 g allylphenol aldehyde and 0.125 mol polycarbosilane to the system to obtain ZrC-SiC multiphase ceramic precursor.

[0065] (2) The ZrC-SiC composite ceramic precursor was cured in an oven at 250°C for 2 hours, and then placed in an argon atmosphere and heated to 1600°C for pyrolysis. The temperature was maintained for 2 hours to obtain ZrC / SiC composite ceramic.

[0066] The SEM image of the product obtained by pressureless pyrolysis at 1600℃ from the multiphase ceramic precursor prepared from polycarbosilane in this comparative example is shown below. Figure 3 As shown, the SEM characterization results of the pyrolysis products indicate that the average particle size of the products obtained in this comparative example is between 100 nm and 200 nm, and the particles are relatively loose and no obvious sintering has occurred.

[0067] Comparative Example 2

[0068] Compared with Example 2, the only difference is that: in this comparative example, tetrafunctional tetraethyl orthosilicate was used as the silicon source to prepare ZrC / SiC composite precursor and ZrC-SiC composite ceramic, and the preparation method was the same as in Example 2.

[0069] Experimental results showed that the system gelled during vacuum distillation, and liquid zirconium-silicon copolymer was not obtained.

[0070] Comparative Example 3

[0071] Compared with Example 2, the only difference is that: in this comparative example, ZrC / SiC composite precursor and ZrC-SiC composite ceramic were prepared using trifunctional methyltrimethoxysilane as the silicon source, and the preparation method was the same as in Example 2.

[0072] The experimental results showed that the viscosity of the ZrC / SiC multiphase precursor prepared in this comparative example was 300 mPa·s at room temperature, and a white precipitate appeared after being stored at room temperature for 2 days.

[0073] Comparative Example 4

[0074] Compared with Example 2, the only difference is that this comparative example uses monofunctional trimethylmethoxysilane as the silicon source to prepare ZrC / SiC multiphase precursors and ZrC-SiC multiphase ceramics, and the preparation method is the same as in Example 2. The viscosity is 10 mPa·s.

[0075] Experimental results showed that curing the obtained ZrC / SiC composite precursor in an oven at 250℃ for 2 hours, then heating it to 1600℃ in argon gas for pyrolysis and holding it at that temperature for 2 hours yielded ZrC / SiC composite ceramics with a Zr content of 67.2 wt% and a Si content of only 0.2 wt%.

[0076] 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 method for preparing a ZrC-SiC multiphase ceramic precursor, characterized in that, The ZrC-SiC multiphase ceramic precursor was prepared by copolymerization using siloxane as the silicon source and zirconium alkoxide as the zirconium source, under the action of ligand 1 and ligand 2.

2. The preparation method according to claim 1, characterized in that, The method for preparing the ZrC-SiC multiphase ceramic precursor includes: dissolving zirconium alkoxide, siloxane monomer, ligand 1, and ligand 2 in a first solvent, adding a second solvent for co-hydrolysis reaction, then heating and refluxing for copolymerization reaction, followed by vacuum distillation to obtain zirconium-silicon copolymer, and finally adding a carbon source to the system and mixing to obtain the ZrC-SiC multiphase ceramic precursor.

3. The preparation method according to claim 1 or 2, characterized in that, The siloxane monomer is a difunctional siloxane. For example, the difunctional siloxane is at least one selected from dimethyldimethoxysilane, methylvinyldimethoxysilane, diphenyldimethoxysilane, and methylphenyldimethoxysilane. Preferably, the zirconium alkoxide is at least one selected from zirconium ethoxide, zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide. Preferably, the ligand 1 is one of acetylacetone and ethyl acetate. Preferably, the ligand 2 is one of acetic acid, citric acid, and salicylic acid. Preferably, the first solvent is at least one selected from n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol methyl ether, and ethylene glycol ethyl ether. Preferably, the second solvent is a mixture of water and the first solvent. Preferably, the mass ratio of water to the first solvent in the mixture is 1:2 to 6.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperature of the co-hydrolysis reaction is 50–80°C. Preferably, the reflux temperature is 85–100°C; and the reflux time is 1–4 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, The carbon source is allylphenolic resin. Preferably, the molar ratio of the zirconium alkoxide to the siloxane monomer and ligand 1 is 1:0.125-0.5:0.5-1.

5. Preferably, the molar ratio of the siloxane monomer to ligand 2 is 1:0.1 to 0.

5. Preferably, before hydrolysis, the molar ratio of the zirconium alkoxide to the first solvent is 1:0.5 to 10. Preferably, the molar ratio of the sum of the moles of the zirconium alkoxide and the siloxane monomer to water is 1:1 to 2. Preferably, the mass ratio of zirconium to carbon source in the zirconium alkoxide is 1:0.5 to 0.

8.

6. The ZrC-SiC multiphase ceramic precursor prepared by the preparation method according to any one of claims 1-5.

7. The ZrC-SiC multiphase ceramic precursor as described in claim 6, characterized in that, The ZrC-SiC multiphase ceramic precursor includes elements such as Zr, Si, C, and O. Preferably, the elements Zr, Si, C, and O are uniformly distributed at the nanoscale. Preferably, the viscosity of the ZrC-SiC multiphase ceramic precursor is 15–100 mPa·s. Preferably, the viscosity change rate of the ZrC-SiC multiphase ceramic precursor after 6 months of storage is no more than 10%.

8. A ZrC-SiC multiphase ceramic, characterized in that, The multiphase ceramic is prepared by pyrolyzing the ZrC-SiC multiphase ceramic precursor described in claim 6 under vacuum or inert atmosphere protection at normal pressure.

9. The method for preparing ZrC-SiC multiphase ceramics according to claim 8, characterized in that, The preparation method includes curing and pyrolyzing the ZrC-SiC multiphase ceramic precursor according to claim 6 to obtain the multiphase ceramic.

10. The preparation method according to claim 9, characterized in that, The pyrolysis temperature is not higher than 1600℃, preferably 1400~1600℃; the pyrolysis time is 0.5~5h. Preferably, the curing atmosphere is air, the curing temperature is 100–300°C, and the curing time is 2–24 hours.

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