Preparation method of oxide eutectic ceramic with uniform and refined nanometer eutectic structure

Abstract

The invention discloses a preparation method of oxide eutectic ceramic with a uniform and refined nanometer eutectic structure, and belongs to the technical field of ceramic. The preparation method comprises the following steps: (1) preparing an oxide eutectic ceramic preform: taking Al2O3, RE2O3 and ZrO2 ceramic powder as initial raw materials, weighing and uniformly mixing according to the eutectic ratio, pressing into a ceramic blank, and sintering at high temperature; (2) solidifying to prepare the oxide eutectic amorphous ceramic: scanning and melting the oxide eutectic amorphous ceramic by using a high-energy laser beam, and solidifying to form an amorphous ceramic sample; and (3) uniform crystallization of the amorphous ceramic: carrying out heat treatment on the amorphous ceramic sample obtained in the step (2) for uniform crystallization to obtain the uniformly refined oxide eutectic ceramic sample with the nanometer eutectic structure. The eutectic ceramic prepared by the method has no coarse primary phase, dendrite and cellular structure, is uniform and fine in tissue, can reach the nanoscale, and has the characteristics of tissue refinement and uniformity.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology, specifically to a method for preparing uniformly refined nano-eutectic structure oxide eutectic ceramics. Background Technology

[0002] Oxide eutectic ceramics, as a type of composite ceramic material formed spontaneously through the eutectic solidification process, occupy a core position in the field of high-temperature structural materials due to their unique "in-situ self-generated phase synergy" mechanism. Their core advantage stems from the thermodynamic compatibility and microstructural synergy of different oxide phases in the eutectic system: during the eutectic reaction, each component spontaneously forms a continuously distributed phase structure according to stoichiometric ratios, with no impurity contamination at the interface and high bonding strength. Simultaneously, it combines the high-temperature resistance of a single oxide with the toughening advantages of a composite system, exhibiting excellent high-temperature flexural strength and resistance to high-temperature oxidation corrosion, making it an ideal candidate material for extreme environments such as hot-end components of aerospace engines.

[0003] Oxide eutectic ceramics prepared using laser melting and solidification technology possess excellent comprehensive properties and hold significant application potential in the aerospace field. With the development of aerospace technology, increasingly stringent requirements are being placed on the performance of high-temperature structural materials. Refining the microstructure size is a key method for optimizing material performance. However, when refining the microstructure size of oxide eutectic ceramics to the micro-nano scale using existing solidification preparation techniques, significant microstructure inhomogeneity can easily occur. For example, the combined effects of thermodynamic equilibrium disruption, kinetic imbalance, and limitations imposed by the material's inherent physical properties during solidification lead to the formation of coarse primary phases and dendrites, while also introducing numerous large-angle grain boundaries. These defects, such as coarse primary phases, dendrites, and cellular structures, result in microstructure inhomogeneity, discrete mechanical properties, and deterioration of high-temperature stability in oxide eutectic ceramics. In industries requiring long-term exposure to ultra-high temperatures, high pressures, alternating loads, or corrosive environments, these defects can directly cause component failure, safety accidents, or substandard performance, such as in the aerospace, advanced manufacturing, and extreme environment equipment fields.

[0004] How to achieve the homogenization and synergistic control of the solidification structure of oxide eutectic ceramics has become a key and urgent bottleneck problem in this field. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this invention provides a method for preparing a uniformly refined nano-eutectic structure oxide eutectic ceramic. This method causes the amorphous sample to undergo uniform crystallization, thereby obtaining an oxide eutectic ceramic sample with a uniformly refined microstructure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic, the innovation of which lies in that: the eutectic ceramic structure is composed of a nano-scale homogeneous and refined eutectic structure, and the preparation method includes the following steps: (1) Weigh, mix, dry, and sieve Al2O3, RE2O3, and ZrO2 ceramic powders and press them into ceramic blanks. Then, the ceramic blanks are sintered at high temperature to densify them and obtain oxide eutectic ceramic preforms. (2) The oxide eutectic ceramic preform is scanned and melted using a high-energy laser beam and then solidified to form an amorphous ceramic sample; (3) The amorphous ceramic sample obtained in step (2) is heat-treated to obtain a uniform and refined nano-eutectic structure oxide eutectic ceramic sample.

[0007] Preferably, in step (1), the RE2O3 is a rare earth oxide, wherein RE is a rare earth element, including Sc, Y and lanthanides.

[0008] Preferably, in step (1), the composite ceramic powder pressed into a ceramic blank can be combined and mixed evenly in any of the following ways: (1) It includes Al2O3 and RE2O3, and the molar percentages of Al2O3 and RE2O3 are 82% and 18%, respectively; (2) Includes Al2O3 and RE2O3, and the molar percentages of Al2O3 and RE2O3 are 77% and 23%, respectively; (3) It includes Al2O3, RE2O3 and ZrO2, and the molar percentages of Al2O3, RE2O3 and ZrO2 are 65%, 16% and 19%, respectively; (4) Includes Al2O3, RE2O3 and ZrO2, and the molar percentages of Al2O3, RE2O3 and ZrO2 are 58%, 19% and 23%, respectively.

[0009] Preferably, in step (1), the mixing method is ball milling, and the ball milling conditions are: wet ball milling with anhydrous ethanol as the medium, ball milling speed is 500-800 r / min, and ball milling time is 5h-10h.

[0010] Preferably, the drying conditions in step (1) are: drying at a temperature of 100-150℃ for 10-15 hours; and the sieving conditions are: passing through a 150-mesh sieve.

[0011] Preferably, in step (1), the high-temperature sintering temperature is 1550-1620℃, and the temperature is maintained for 5-10 hours after sintering.

[0012] Preferably, in step (2), after evacuating and introducing high-purity argon gas as a protective gas, scanning is performed. The laser power for scanning the melting is 50W-200W, and the scanning rate is 500mm / s-1500mm / s.

[0013] Preferably, in step (3), the heat treatment temperature is 1300-1400℃, the holding time is 10-20h, and the heating rate and cooling rate are both 2-5℃ / min.

[0014] This invention provides a method for preparing uniform and refined nano-eutectic structure oxide eutectic ceramics, which has the following beneficial effects: (1) In the preparation of eutectic ceramics, the present invention first prepares an amorphous ceramic sample and then obtains a eutectic ceramic sample through heat treatment. This is a solid-solid phase transformation (the oxide eutectic ceramic prepared by one-step method is a liquid-solid phase transformation). Solid-solid phase transformation is completed by short-range diffusion of atoms and ions. The diffusion uniformity is high, which can realize the uniform distribution of each component phase and improve the stability of the structure. Therefore, the obtained eutectic ceramics are free of coarse primary phases, dendrites, and cellular structures.

[0015] (2) In the crystallization process of the eutectic oxide eutectic ceramic prepared by the present invention, each eutectic phase grows in a thermodynamic equilibrium ratio, which can form a stable microstructure with the lowest interfacial energy. This not only prevents the unconstrained growth of a single phase to achieve grain and phase domain refinement, but also eliminates defects such as uneven microstructure and local phase segregation through multi-phase synergistic growth, and finally obtains a refined and uniform eutectic microstructure. Attached Figure Description

[0016] Figure 1 The XRD pattern of the amorphous ceramic prepared in Example 1 of this invention.

[0017] Figure 2 The image shows the XRD pattern of the eutectic ceramic prepared in Example 1 of this invention.

[0018] Figure 3 This is a SEM image of the overall microstructure of the eutectic ceramic prepared in Example 1 of the present invention.

[0019] Figure 4 This is a SEM image of the local microstructure of the eutectic ceramic prepared in Example 1 of the present invention.

[0020] Figure 5 This is a SEM image of the overall microstructure of the eutectic ceramic prepared in Comparative Example 1 of this invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the content described.

[0022] In the following embodiments of the present invention, the composite ceramic powder comprises Al2O3, RE2O3, and ZrO2, and the composite ceramic powder can be combined and mixed uniformly in any of the following ways: (1) It comprises Al2O3 and RE2O3, with the molar percentages of Al2O3 and RE2O3 being 82% and 18%, respectively, and is prepared by the method of the present invention to obtain Al2O3 / RE3Al5O 12 Binary eutectic amorphous layered composite ceramics; (2) The Al2O3 / RE2O3 binary eutectic amorphous layered composite ceramic is prepared by the method of the present invention, comprising Al2O3 and RE2O3, wherein the molar percentages of Al2O3 and RE2O3 are 77% and 23% respectively. (3) It comprises Al2O3, RE2O3 and ZrO2, and the molar percentages of Al2O3, RE2O3 and ZrO2 are 65%, 16% and 19%, respectively. Al2O3 / RE3Al5O is prepared by the method of the present invention. 12 / ZrO2 ternary eutectic amorphous layered composite ceramic; (4) The Al2O3 / RE2O3 / ZrO2 ternary eutectic amorphous layered composite ceramic is prepared by the method of the present invention, comprising Al2O3, RE2O3 and ZrO2, wherein the molar percentages of Al2O3, RE2O3 and ZrO2 are 58%, 19% and 23%, respectively.

[0023] Among them, RE3Al5O 12 RE2O3 is a phase formed by the reaction of Al2O3 and RE2O3. RE2O3 is a rare earth oxide, where RE represents rare earth elements, including Sc, Y, and lanthanides.

[0024] Example 1 (1) Using commercially available Al2O3, Gd2O3, and ZrO2 with a particle size range of 1-5 μm as initial raw material powders, the corresponding ceramic powders were weighed according to the eutectic molar ratio Al2O3:Gd2O3:ZrO2=58:19:23. The composite ceramic powder was placed in a nylon ball mill jar and ball milled in a planetary ball mill at a speed of 500 r / min for 5 h to ensure thorough mixing. The uniformly mixed composite ceramic powder was placed in a drying oven and dried at a drying temperature of 100℃ for 10 h to remove the anhydrous ethanol added during the ball milling process. The dried composite ceramic powder was ground and passed through a 150-mesh sieve. 1.5 g of the sieved composite ceramic powder was weighed and placed in a stainless steel pressing mold with a diameter of 15 mm. The mold was pressurized at a pressure of 20 MPa and held for 5 min to obtain a composite ceramic green body. The ceramic blank was placed in a muffle furnace and calcined at 1620℃ for 5 hours to obtain a eutectic ceramic preform with a density of 98%.

[0025] (2) Place the eutectic ceramic preform obtained in step (1) on the worktable of the laser powder bed melting equipment, close the equipment door, evacuate, and introduce high-purity argon as a protective gas. Turn on the laser and let the high-energy laser beam melt the eutectic ceramic preform at an ultra-fast scanning speed of 500 mm / s with a laser power of 300 W. After solidification, an amorphous ceramic sample is formed.

[0026] (3) The amorphous ceramic sample obtained in step (2) is placed in a tube heat treatment furnace and heated to 1300℃ at a heating rate of 2℃ / min and held for 10h. Then it is cooled to room temperature at a cooling rate of 2℃ / min to obtain a uniformly refined nano-eutectic structure Al2O3 / GdAlO3 / ZrO2 eutectic ceramic sample.

[0027] XRD analysis was performed on the amorphous ceramic sample prepared in this embodiment, and the results are as follows: Figure 1 As shown; XRD analysis was performed on the homogeneous and refined nano-eutectic structure oxide eutectic ceramic sample prepared in this embodiment, and the results are as follows. Figure 2 As shown; the overall microstructure of the prepared homogeneous and refined nano-eutectic oxide eutectic ceramic sample was observed by scanning electron microscopy, and the results are as follows. Figure 3 As shown; the local microstructure of the prepared homogeneous and refined nano-eutectic oxide eutectic ceramic sample was observed by scanning electron microscopy, and the results are as follows. Figure 4 As shown.

[0028] Depend on Figure 1 It can be seen that the XRD diffraction peaks are broadened "bun peaks", which is a typical characteristic of amorphous materials, proving that the ultrafast laser scanning melting and solidification scheme in this invention has achieved the preparation of amorphous ceramic samples.

[0029] Depend on Figure 2 It can be seen that the amorphous ceramics crystallized after heat treatment and formed three eutectic phases: Al2O3, GdAlO3, and ZrO2.

[0030] Depend on Figure 3 It can be seen that the oxide eutectic ceramic prepared by the present invention has a very uniform structure, without the formation of primary phase, dendrites, cellular structures, or other structures.

[0031] Depend on Figure 4 It can be seen that the oxide eutectic ceramic microstructure prepared by this invention is the same as that prepared by traditional directional solidification and other techniques, exhibiting a typical eutectic structure and a very fine microstructure. The eutectic spacing was measured to be 270 nm, proving that this invention successfully prepared a nano-eutectic structure Al2O3 / GdAlO3 / ZrO2 eutectic ceramic sample with a uniform and fine microstructure.

[0032] Example 2 The difference between this embodiment and Embodiment 1 is that: The composite ceramic powder in step (1) is made from commercially available Al2O3 and Gd2O3 with a particle size range of 1-5μm as initial raw material powders. The corresponding ceramic powders are weighed according to the eutectic molar ratio of Al2O3:Gd2O3=77:23. The powders are then ball-milled in a planetary ball mill at a speed of 800r / min for 10h to ensure thorough mixing. The uniformly mixed composite ceramic powder is then placed in a drying oven and dried at a drying temperature of 150℃ for 15h. The high-temperature sintering temperature of the ceramic body is 1550℃, and the holding time is 10h.

[0033] In step (2), the laser power of the laser beam used for scanning and melting is 50W and the scanning speed is 1500mm / s.

[0034] In step (3), the temperature is uniformly raised to 1400℃ at a heating rate of 5℃ / min and held for 20h. Then, the temperature is lowered to room temperature at a cooling rate of 5℃ / min to obtain a uniformly refined nano-eutectic structure Al2O3 / GdAlO3 eutectic ceramic sample.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that: The composite ceramic powder in step (1) is made from commercially available Al2O3, Y2O3 and ZrO2 with a particle size range of 1-5μm as initial raw material powders. The corresponding ceramic powders are weighed according to the eutectic molar ratio of Al2O3:Y2O3:ZrO2=65:16:19. The powders are then ball-milled in a planetary ball mill at a speed of 600r / min for 8 hours to ensure thorough mixing. The uniformly mixed composite ceramic powder is then placed in a drying oven and dried at a drying temperature of 125℃ for 12 hours. The ceramic body is then sintered at a high temperature of 1600℃ for 8 hours.

[0036] In step (2), the laser power of the laser beam used for scanning and melting is 100W and the scanning speed is 700mm / s.

[0037] In step (3), the temperature is uniformly increased to 1350℃ at a heating rate of 3℃ / min and held for 15h, then cooled to room temperature at a cooling rate of 3℃ / min to obtain a uniformly refined nano-eutectic structure Al2O3 / Y3Al5O 12 / ZrO2 eutectic ceramic sample.

[0038] Example 4 The difference between this embodiment and Embodiment 1 is that: The composite ceramic powder in step (1) is made from commercially available Al2O3 and Y2O3 with a particle size range of 1-5μm as initial raw material powders. The corresponding ceramic powders are weighed according to the eutectic molar ratio of Al2O3:Y2O3=82:18. The powders are then ball-milled in a planetary ball mill at a speed of 600r / min for 8 hours to ensure thorough mixing. The uniformly mixed composite ceramic powder is then placed in a drying oven and dried at a drying temperature of 125℃ for 12 hours. The high-temperature sintering temperature of the ceramic body is 1600℃, and the holding time is 8 hours.

[0039] In step (2), the laser power of the laser beam used for scanning and melting is 150W and the scanning speed is 1000mm / s.

[0040] In step (3), the temperature is uniformly increased to 1350℃ at a heating rate of 3℃ / min and held for 15h, then cooled to room temperature at a cooling rate of 3℃ / min to obtain a uniformly refined nano-eutectic structure Al2O3 / Y3Al5O 12 Eutectic ceramic sample.

[0041] The eutectic ceramic structures prepared in Examples 2-4 have similar characteristics to those in Example 1, lacking coarse primary phases, dendrites, and cellular structures. The eutectic ceramic microstructure is uniform and fine, reaching the nanoscale, exhibiting both microstructure refinement and uniformity.

[0042] Comparative Example 1 This example demonstrates the preparation of Al2O3-Gd2O3-ZrO2 ternary ceramics using existing high-speed directional solidification techniques. The specific process is as follows: Step 1: Preparation of the Al2O3-Gd2O3-ZrO2 ternary system eutectic component powder. Al2O3 powder, Gd2O3 powder, and ZrO2 powder were selected. They were mixed according to the ratio of Al2O3:Gd2O3:ZrO2 = 58:19:23 (molar percentage). 100g of the obtained mixed powder was weighed, and 20ml of polyvinyl alcohol solution and 80ml of anhydrous ethanol were added to the weighed mixed powder. The mixture was thoroughly mixed using a ball mill at 500r / min for 5h. The mixed powder was then placed in a drying oven and dried at 100℃ for 10h to obtain a dry and uniformly mixed Al2O3-Gd2O3-ZrO2 eutectic component powder. The added polyvinyl alcohol solution was obtained by dissolving 5g of polyvinyl alcohol in 100ml of purified water by heating.

[0043] Step 2: Preparation of the preform. Weigh 1.5g of the Al2O3-Gd2O3-ZrO2 eutectic powder obtained in Step 1, place it in a stainless steel mold, apply a uniaxial pressure of 20MPa to the powder using a press, and hold the pressure at 20MPa for 5 minutes to obtain a sample. Place the obtained sample in a sintering furnace and sinter at 1620℃ for 5 hours to obtain the Al2O3-Gd2O3-ZrO2 sintered body.

[0044] Step 3: Preform Melting. Fix the preform obtained in Step 2 in the laser levitation zone melting device, ensuring the upper end of the preform is fixed while the lower end is unconstrained. Open the vacuum pump to reduce the vacuum level in the vacuum chamber to [a value missing]. Pa; Fill the vacuum chamber with nitrogen to atmospheric pressure. Set the laser spot size to 6 mm, start the laser, adjust the laser to align with the bottom of the sample, set the laser power to 300 W initially, increase the laser power to 300 W at a rate of 50 W / 10 s and hold for 5 s; repeat this process until the power reaches 600 W and is held, causing the preform to melt, obtaining a ceramic melt of the Al2O3-Gd2O3-ZrO2 ternary system.

[0045] Step 4: Preparation of alumina-based ternary nano-eutectic ceramics. Open the pulling mechanism of the laser levitation melting device and set the pulling speed to 100 μm / s. When the volume of the Al2O3-Gd2O3-ZrO2 ternary ceramic melt increases to a point where the surface tension is less than gravity, the resulting Al2O3-Gd2O3-ZrO2 ternary ceramic melt falls into the liquid gallium indium tin alloy located in the laser levitation melting device for quenching, yielding an Al2O3-Gd2O3-ZrO2 ternary ceramic sample.

[0046] The overall microstructure of the eutectic ceramic sample prepared in Comparative Example 1 is shown in the scanning electron microscope image. Figure 5 As shown, Comparative Example 1 uses the same material system as Example 1, consisting of... Figure 5 It can be seen that the eutectic ceramic sample obtained in Comparative Example 1 exhibits obvious non-uniform structure and other phenomena.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a homogenized and refined nano-eutectic structure oxide eutectic ceramic, characterized in that: The eutectic ceramic microstructure is composed of a nanoscale homogeneous and refined eutectic structure, and the preparation method includes the following steps: (1) Weigh, mix, dry, and sieve Al2O3, RE2O3, and ZrO2 ceramic powders and press them into ceramic blanks. Then, the ceramic blanks are sintered at high temperature to densify them and obtain oxide eutectic ceramic preforms. (2) The oxide eutectic ceramic preform is scanned and melted using a high-energy laser beam and then solidified to form an amorphous ceramic sample; (3) The amorphous ceramic sample obtained in step (2) is heat-treated to obtain a uniform and refined nano-eutectic structure oxide eutectic ceramic sample.

2. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (1), RE2O3 is a rare earth oxide, wherein RE is a rare earth element, including Sc, Y and lanthanides.

3. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (1), the composite ceramic powder pressed into a ceramic blank can be combined and mixed evenly in any of the following ways: (1) It includes Al2O3 and RE2O3, and the molar percentages of Al2O3 and RE2O3 are 82% and 18%, respectively; (2) Includes Al2O3 and RE2O3, and the molar percentages of Al2O3 and RE2O3 are 77% and 23%, respectively; (3) It includes Al2O3, RE2O3 and ZrO2, and the molar percentages of Al2O3, RE2O3 and ZrO2 are 65%, 16% and 19%, respectively; (4) Includes Al2O3, RE2O3 and ZrO2, and the molar percentages of Al2O3, RE2O3 and ZrO2 are 58%, 19% and 23%, respectively.

4. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (1), the mixing method is ball milling, and the ball milling conditions are: wet ball milling with anhydrous ethanol as the medium, ball milling speed is 500-800 r / min, and ball milling time is 5h-10h.

5. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 4, characterized in that: The drying conditions in step (1) are: drying at 100-150℃ for 10-15 hours; the sieving conditions are: passing through a 150-mesh sieve.

6. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (1), the high-temperature sintering temperature is 1550-1620℃, and the temperature is maintained for 5-10 hours after sintering.

7. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (2), after evacuating and introducing high-purity argon as a protective gas, scanning is performed. The laser power for scanning the melting is 50W-200W, and the scanning rate is 500mm / s-1500mm / s.

8. The method for preparing a homogeneous and refined nano-eutectic structure oxide eutectic ceramic according to claim 1, characterized in that: In step (3), the heat treatment temperature is 1300-1400℃, the holding time is 10-20h, and the heating rate and cooling rate are both 2-5℃ / min.

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