Method for preparing oxide eutectic ceramics by using ultrafast high temperature furnace

Abstract

The application discloses a method for preparing oxide eutectic ceramics by using an ultrafast high-temperature furnace. Raw material powders are proportioned according to eutectic composition, and then are sequentially subjected to ball milling, drying, sieving and compression molding; the green body is placed in a thin-wall graphite crucible and is put into a heating carbon felt element sandwich hole; the temperature is rapidly increased to a set temperature by using ultrafast heating, and the temperature is kept for a very short time, and then the oxide eutectic ceramics are obtained after cooling. The oxide eutectic ceramics are rapidly formed by using ultrafast heating and Joule heat radiation heating at a furnace temperature far below the eutectic temperature, and the microstructure of the eutectic ceramics can be controlled by adjusting the temperature parameters. The eutectic structure obtained is fine in size and excellent in mechanical properties; and the problems of long time consumption, high cost and complex block material preparation process in the existing oxide eutectic ceramic preparation method are solved.

Description

Technical Field

[0001] This invention relates to the field of ceramic material preparation technology, specifically a method for preparing oxide eutectic ceramics in an ultrafast high-temperature furnace. Background Technology

[0002] Oxide eutectic ceramics are ceramics with a three-dimensionally interwoven, fine-grained eutectic structure formed in situ during melt solidification through eutectic reactions. They possess excellent mechanical properties, high-temperature structural stability, oxidation and corrosion resistance, and creep resistance, making them ideal high-temperature structural materials for long-term stable operation in oxygen-rich environments above 1400℃. For example, alumina-based oxide eutectic ceramics (such as Al2O3 / YAG and Al2O3 / GAP systems) have become candidate materials for hot-end components of aero-engines and nuclear energy systems due to their high-temperature strength, oxidation resistance, and excellent creep resistance. The performance of oxide eutectic ceramics is highly dependent on the directional control of their microstructure; therefore, optimizing their preparation process is crucial for the engineering of this material.

[0003] Currently, the commonly used preparation technologies for oxide eutectic ceramics mainly include directional solidification technology, powder sintering technology, and additive manufacturing technology.

[0004] Directional solidification is the preferred technique for achieving high-performance eutectic structures. It involves controlling the directional crystallization of the melt to form lamellar or fibrous regular structures. Methods include the Bridgman method, micro-pulling, boundary epitaxial growth, laser zone melting, electron beam zone melting, optical levitation zone melting, and laser levitation zone melting. The Bridgman method uses an iridium or molybdenum crucible in an inert atmosphere (Ar) to complete a melting-solidification process exceeding 1800°C, with temperature gradient control achieved using a moving furnace. Laser levitation zone melting (LFZ) utilizes a high-energy CO2 laser beam to locally melt the sample, achieving crucible-free growth through a rotating traction mechanism. The micro-pulling method, using a high-frequency induction furnace and capillary mold, can prepare single-crystal fibers with diameters less than 5 mm. These methods based on directional solidification technology can effectively control the texture direction and characteristic dimensions of the solidified structure, thereby improving the mechanical properties of the material in specific directions and obtaining directional structures with high flexural strength and high fracture toughness. However, directional solidification usually requires operation at temperatures above 1820℃~2000℃, which presents limitations such as complex equipment, equipment limitations due to high temperatures, difficulty in preparing complex eutectic ceramic components, and high costs.

[0005] The preparation of oxide eutectic ceramics using powder sintering technology has been widely reported. For example, Yao et al. successfully prepared Al2O3 / YAG binary eutectic ceramic blocks using directional solidification and hot pressing sintering techniques; Yu et al. prepared Al2O3 / 3YSZ binary eutectic ceramic blocks using combustion synthesis-gas phase atomization combined with vacuum hot pressing sintering. However, traditional powder sintering methods all require powders with eutectic structures as raw materials, meaning that the sintering process itself does not form a eutectic structure, only powder sintering and grain growth occur, resulting in densification. The above two-step method for preparing oxide eutectic ceramics relies on obtaining eutectic structure powders through a preliminary method, increasing costs. Furthermore, the large number of grain boundaries generated during the sintering process of the eutectic powder weakens its thermodynamic properties, resulting in significantly lower mechanical properties compared to the directional solidification method.

[0006] In recent years, studies have employed flash sintering technology to prepare oxide eutectic ceramics. This method eliminates the need for a pre-treatment step of eutectic structure powder, requiring only one step to obtain the oxide eutectic ceramic. For example, Sun et al. used flash sintering to prepare Al2O3-GdAlO3-ZrO2 ternary oxide eutectic ceramics. Flash sintering involves applying a high voltage to the material, generating a Joule heating effect through the flow of current within the material, causing a decrease in resistivity and a rapid increase in temperature when the material reaches its flash point, resulting in localized melting and solidification to form a eutectic. Flash sintering can achieve densification within seconds, significantly shortening the sintering time. It requires materials with good electrical conductivity and high-temperature conductivity. However, because flash sintering utilizes the rapid densification of materials at their flash point, the uncontrollable flashing (i.e., internal current) during flash sintering leads to random and localized microstructure distribution within the material. Therefore, the eutectic microstructure formed by flash sintering often exhibits uneven distribution, with the eutectic structure only partially forming at the channels, while the remaining areas retain the characteristics of sintered ceramics. This localized formation of oxide eutectic ceramics limits its practical application. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a method for preparing oxide eutectic ceramics using an ultrafast high-temperature furnace, which has advantages such as simple process, low preparation temperature, extremely short preparation time, and one-step in-situ generation of eutectic microstructure.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0009] A method for preparing oxide eutectic ceramics in an ultrafast high-temperature furnace, the ultrafast high-temperature furnace including a Joule heating device, the Joule heating device including a carbon felt element for Joule heating, the carbon felt element having a sandwiched hole for placing a crucible, the carbon felt element serving as both the heating element and the crucible support. During operation, a ceramic green body is placed inside the crucible, which is placed within the sandwiched hole of the carbon felt element; through the Joule heating device, the Joule heat generated by the electrically energized carbon felt element forms a high-temperature field, which is used to subject the ceramic green body in the crucible to pure radiative heating, causing it to rapidly heat up and undergo a eutectic reaction to form a eutectic structure, thus obtaining the oxide eutectic ceramic. More specifically, the method includes the following steps:

[0010] Step 1: Weigh any two or three ceramic powders from alumina, zirconium oxide, yttrium oxide, magnesium oxide, gadolinium oxide, erbium oxide, lanthanum oxide, and calcium oxide, and mix them according to the eutectic composition ratio.

[0011] Step 2: The weighed ceramic powder is ball-milled, dried, sieved, and pressed into ceramic green bodies.

[0012] Step 3: Place the ceramic green body in a thin-walled graphite crucible and then place it into the interlayer hole of the carbon felt element, and evacuate to below 5 Pa.

[0013] Step 4: Rapidly heat to the set temperature, hold at that temperature for a very short time, and then rapidly cool to room temperature to obtain an oxide eutectic ceramic. The set temperature is determined based on the eutectic temperature of the ceramic powder composition system from Step 1, and is 300-550 °C lower than the eutectic temperature.

[0014] Furthermore, the specific method for ball milling in step 2 is as follows: the weighed ceramic powder is added to deionized water and mixed in a planetary ball mill. The rotation speed of the ball mill is 200~300 r / min, and the ball milling time is 12~24 h. Thorough ball milling promotes uniform mixing of powder particles.

[0015] Furthermore, in step 2, the drying temperature is 70~90 ℃ and the time is 12~24 h.

[0016] Furthermore, the specific method for sieving in step 2 is as follows: the dried ceramic agglomerate is placed in an agate mortar and ground into powder, and the powder is sieved through a 200-400 mesh metal sieve. After sieving, the powder particles are uniform in size, ensuring consistent heating during the heating process.

[0017] Furthermore, the specific method for pressing and molding in step 2 is as follows: the sieved powder is pressed and molded using a molding method to achieve a green body relative density of over 50%. A higher green body density results in fewer bubbles being generated during the ultra-fast heating and melting process, less venting of the melt, and a shorter holding time required to achieve uniformity. Furthermore, the molding pressure is 280-320 MPa, and the holding time is 200-300 s.

[0018] Furthermore, in step 4, the temperature is increased at a rate of 5-20 ℃ / s, held for 30-120 s, and the rapid cooling rate is 2-50 ℃ / s.

[0019] This invention employs an ultrafast high-temperature furnace for the preparation of oxide eutectic ceramics. Ultrafast high-temperature furnaces can typically reach temperatures exceeding 2000℃. Especially when equipped with a Joule heating device, rapid heating is achieved. Conventional sintering furnaces primarily use resistance heating, resulting in low heating and cooling rates, typically <50℃ / min, requiring tens of hours or even longer to complete a single sintering process, leading to enormous energy consumption. In contrast, this invention utilizes ultrafast high-temperature furnace sintering technology, employing a Joule heating device within the furnace body. Heating is achieved through the heat generated when an electric current passes through a conductor, utilizing the Joule heating of an energized carbon felt element to create a high-temperature field, thus achieving rapid heating. In this invention, the ultrafast high-temperature furnace does not use ceramic powder or green ceramic bodies as self-heating components; instead, it uses carbon felt as the heating element and crucible support. The Joule heat generated by the conduction of current within the carbon felt element provides pure radiative heating to the ceramic green ceramic body within the crucible. Heating via current-controlled carbon felt elements results in extremely rapid temperature rise and excellent controllability. Simultaneously, the heating carbon felt elements provide pure radiative heating to the ceramic green body material they support. This heating method ensures uniform heating, resulting in a highly homogeneous eutectic structure formed by the powder constituting the ceramic green body.

[0020] In this invention, the morphology of the oxide eutectic ceramic is controlled through a one-step process in an ultrafast high-temperature furnace. This control is achieved by adjusting temperature parameters, particularly by regulating the cooling rate. This is because the morphology of the eutectic structure (i.e., the size, shape, and distribution of the eutectic phase grains) is extremely sensitive to the cooling rate. In this invention, a higher cooling rate results in a finer structure, with the obtained oxide eutectic ceramic primarily exhibiting rod-like or plate-like shapes with a uniform and regular distribution. Conversely, a lower cooling rate results in a coarser structure, primarily exhibiting pictographic or irregular distribution.

[0021] In addition, the present invention also provides an oxide eutectic ceramic prepared by the above preparation method, wherein the oxide eutectic ceramic is a eutectic ceramic composed of two or three solid phases formed by a eutectic reaction of a component system consisting of any two or three of alumina, zirconium oxide, yttrium oxide, magnesium oxide, gadolinium oxide, erbium oxide, lanthanum oxide, and calcium oxide.

[0022] Furthermore, the proportion of each solid phase in the oxide eutectic ceramic is the eutectic composition ratio of the composition system composed of each solid phase. For example, the prepared oxide eutectic ceramic is an Al2O3-8YSZ binary eutectic ceramic, which is composed of two solid phases: Al2O3 phase and c-ZrO2 phase in YSZ. The molar ratio of the Al2O3 phase and the YSZ phase satisfies Al2O3:8YSZ = 62.5:37.5. This ratio is the eutectic composition ratio of the composition system of Al2O3-8YSZ binary eutectic ceramic, which consists of alumina and 8 mol% yttrium oxide-stabilized zirconium oxide, in the phase diagram.

[0023] Furthermore, in the oxide eutectic ceramic, the solid phases are intertwined and interwoven, and the phase interfaces between the solid phases replace the grain boundaries prepared by sintering. That is, the oxide eutectic ceramic has only phase boundaries and no grain boundaries inside; and each solid phase constituting the oxide eutectic ceramic is a eutectic solid phase, and there are no other impurity phases except for each eutectic solid phase.

[0024] The present invention achieves the following beneficial effects:

[0025] 1. The present invention uses an ultrafast high-temperature furnace to prepare oxide eutectic ceramics. The process is simple, the preparation cycle is extremely short, and the cost is low. There is no need for a pre-process to prepare eutectic ceramic powder as a sintering raw material.

[0026] 2. The oxide eutectic ceramic prepared by the ultrafast high-temperature furnace of this invention exhibits a uniform eutectic structure and has superior thermodynamic properties.

[0027] 3. This invention employs an ultrafast high-temperature furnace, which rapidly forms an oxide ceramic eutectic structure at a furnace temperature far below the eutectic temperature through Joule thermal radiation heating, resulting in low power consumption. Furthermore, the microstructure and morphology of the eutectic ceramic can be controlled by adjusting the cooling rate, yielding a eutectic structure with fine dimensions and excellent mechanical properties. Attached Figure Description

[0028] Figure 1 The XRD pattern is shown for the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1.

[0029] Figure 2 The image shows a SEM image of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1, with a cooling rate of 5 °C / s.

[0030] Figure 3 This is a high-magnification SEM image of the Al2O3-8YSZ (alumina-8mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1.

[0031] Figure 4The EDS diagram of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1 is shown, corresponding to... Figure 3 The element distribution diagram.

[0032] Figure 5 The image shows a SEM image of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 4, with a cooling rate of 20 °C / s. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The method for preparing oxide eutectic ceramics in an ultrafast high-temperature furnace of the present invention uses a green body formed by pressing a mixed ceramic powder of multiple oxides as the sintering raw material. In the ultrafast high-temperature furnace, Joule heating generated by conducting current through a carbon felt element in the furnace body is used to radiate heat the ceramic green body in the crucible. The high-temperature field radiation formed by the current-controlled carbon felt element rapidly heats the ceramic green body, which is then held at a temperature 300-450°C below the eutectic temperature for an extremely short time, and then rapidly cooled and solidified to form a eutectic, thus achieving the one-step acquisition of oxide eutectic ceramics.

[0034] Example 1

[0035] The preparation method of Al2O3-8YSZ binary eutectic ceramics includes the following steps:

[0036] Step 1: According to the eutectic composition of the composition system consisting of alumina and 8 mol% yttrium-stabilized zirconium oxide in the phase diagram, that is, the molar ratio of the two is Al2O3:8YSZ = 62.5:37.5. Weigh 20 g of Al2O3 and 8YSZ ceramic powders respectively.

[0037] Step 2: Add 200 mL of deionized water to the weighed ceramic powder and mix it in a planetary ball mill at a speed of 300 r / min for 24 h. After thorough ball milling and mixing, a slurry is formed.

[0038] Step 3: The obtained slurry is dried to form ceramic agglomerates at a temperature of 80 ℃ for 24 hours.

[0039] Step 4: Place the dried ceramic agglomerate into an agate mortar and grind it into powder. Sieve the powder through a 300-mesh metal sieve to obtain a mixed ceramic powder with uniform particle size.

[0040] Step 5: The sieved mixed ceramic powder is pressed into shape using a molding method: the powder is weighed and pressed into round green bodies with a diameter of 10 mm; in this embodiment, about 0.3 g of the mixed ceramic powder from step 4 is weighed for each round body; the pressure is 300 MPa and the holding time is 300 s, and the relative density of the green body is 66%.

[0041] Step 6: Place the green blank in a thin-walled graphite crucible and put it into the jacket hole of the heating carbon felt element, and evacuate to below 5 Pa.

[0042] Step 7: Rapidly heat to the set temperature of 1500 ℃ at a heating rate of 10 ℃ / s, hold at that temperature for 60 s, and cool to room temperature at a cooling rate of 5 ℃ / s to prepare Al2O3-8YSZ eutectic ceramic. The eutectic point temperature of this composition system in the phase diagram is 1940 ℃. In this embodiment, the furnace temperature is set at 1500 ℃. At this set temperature, Al2O3-8YSZ eutectic ceramic can be prepared in one step.

[0043] Example 2

[0044] The preparation method of Al2O3-MgO binary eutectic ceramics includes the following steps:

[0045] Step 1: Weigh the powder according to the molar ratio Al2O3:MgO = 36:64, totaling 20 g;

[0046] Step 2: Add 200 mL of deionized water to the weighed powder and mix in a planetary ball mill at a speed of 300 r / min for 24 h.

[0047] Step 3: Dry the obtained slurry at 80 ℃ for 24 h;

[0048] Step 4: Place the dried ceramic agglomerate into an agate mortar and grind it into powder. Sieve the powder through a 300-mesh metal sieve to obtain a uniformly mixed ceramic powder.

[0049] Step 5: The sieved uniform powder is pressed into shape using a molding method. The powder is weighed and pressed into discs with a diameter of 10 mm. Each disc weighs about 0.3 g of powder. The pressure is 320 MPa, and the holding time is 300 s. The relative density of the green body is 66%.

[0050] Step 6: Place the green blank in a thin-walled graphite crucible and put it into the jacket hole of the heating carbon felt element, and evacuate to below 5 Pa;

[0051] Step 7: The eutectic point temperature of Al2O3-MgO binary eutectic ceramic is 2050℃. In this embodiment, the temperature is increased to 1500℃ at a heating rate of 20℃ / s, held for 30s, and then cooled to room temperature at a cooling rate of 2℃ / s.

[0052] Example 3

[0053] The preparation method of Al2O3-Gd2O3 binary eutectic ceramics includes the following steps:

[0054] Step 1: Weigh the powder according to the molar ratio Al2O3:Gd2O3 = 33:77, totaling 20 g;

[0055] Step 2: Add 200 mL of deionized water to the weighed powder and mix in a planetary ball mill at a speed of 300 r / min for 12 h.

[0056] Step 3: Dry the obtained slurry at 70 ℃ for 24 h;

[0057] Step 4: Place the dried ceramic agglomerate into an agate mortar and grind it into powder. Sieve the powder through a 200-mesh metal sieve to obtain a uniformly mixed ceramic powder.

[0058] Step 5: The sieved uniform powder is pressed into shape using a molding method. The powder is weighed and pressed into discs with a diameter of 10 mm. Each disc weighs about 0.3 g of powder. The pressure is 320 MPa, the holding pressure is 300 s, and the relative density of the green body is 50%.

[0059] Step 6: Place the green blank in a thin-walled graphite crucible and put it into the jacket hole of the heating carbon felt element, and evacuate to below 5 Pa;

[0060] Step 7: The binary eutectic point temperature of Al2O3-Gd2O3 binary eutectic ceramic in the phase diagram is 1742℃; heat to 1400℃ at a heating rate of 5℃ / s, hold for 120 s, and cool to room temperature at a cooling rate of 50℃ / s.

[0061] Example 4

[0062] The preparation method of Al2O3-8YSZ binary eutectic ceramics, in this embodiment, uses a different cooling rate in the eutectic reaction, but is otherwise the same as in Example 1. Specifically, it includes the following steps:

[0063] Step 1: According to the eutectic composition of the composition system consisting of alumina and 8 mol% yttrium-stabilized zirconium oxide in the phase diagram, that is, the molar ratio of the two is Al2O3:8YSZ = 62.5:37.5. Weigh 20 g of Al2O3 and 8YSZ ceramic powders respectively.

[0064] Step 2: Add 200 mL of deionized water to the weighed ceramic powder and mix it in a planetary ball mill at a speed of 300 r / min for 24 h. After thorough ball milling and mixing, a slurry is formed.

[0065] Step 3: The obtained slurry is dried to form ceramic agglomerates at a temperature of 80 ℃ for 24 hours.

[0066] Step 4: Place the dried ceramic agglomerate into an agate mortar and grind it into powder. Sieve the powder through a 300-mesh metal sieve to obtain a mixed ceramic powder with uniform particle size.

[0067] Step 5: The sieved mixed ceramic powder is pressed into shape using a molding method: the powder is weighed and pressed into round green bodies with a diameter of 10 mm; in this embodiment, about 0.3 g of the mixed ceramic powder from step 4 is weighed for each round body; the pressure is 320 MPa and the holding time is 200 s, and the relative density of the green body is 66%.

[0068] Step 6: Place the green blank in a thin-walled graphite crucible and put it into the jacket hole of the heating carbon felt element, and evacuate to below 5 Pa.

[0069] Step 7: Rapidly heat to the set temperature of 1500 ℃ at a heating rate of 10 ℃ / s, hold for 60 s, and cool to room temperature at a cooling rate of 20 ℃ / s to prepare Al2O3-8YSZ eutectic ceramic.

[0070] Example 5

[0071] The preparation method of Al2O3-MgAl2O4-ZrO2 ternary eutectic ceramics includes the following steps:

[0072] Step 1: Weigh the powder according to the molar ratio Al2O3:MgO:ZrO2 = 42.1:17.4:40.5, totaling 20 g;

[0073] Step 2: Add 200 mL of deionized water to the weighed powder and mix in a planetary ball mill at a speed of 200 r / min for 24 h.

[0074] Step 3: Dry the obtained slurry at 90 ℃ for 12 h;

[0075] Step 4: Place the dried ceramic agglomerate into an agate mortar and grind it into powder. Sieve the powder through a 400-mesh metal sieve to obtain a uniformly mixed ceramic powder.

[0076] Step 5: The sieved uniform powder is pressed into shape using a molding method. The powder is weighed and pressed into discs with a diameter of 10 mm. Each disc weighs about 0.3 g of powder. The pressure is 280 MPa, and the holding time is 300 s. The relative density of the green body is 50%.

[0077] Step 6: Place the green blank in a thin-walled graphite crucible and put it into the jacket hole of the heating carbon felt element, and evacuate to below 5 Pa;

[0078] Step 7: The ternary eutectic point temperature of Al2O3-MgAl2O4-ZrO2 ternary eutectic ceramic in the phase diagram is 1830℃; heat to 1500℃ at a heating rate of 5℃ / s, hold for 120 s, and cool to room temperature at a cooling rate of 10℃ / s.

[0079] The crystal structure, composition, and microstructure of the oxide eutectic ceramics prepared in the above embodiments were analyzed. Details are as follows.

[0080] (1) XRD Analysis: The oxide eutectic ceramics prepared in the above embodiments were subjected to phase analysis using XRD patterns. The XRD patterns showed that the oxide eutectic ceramics prepared in each embodiment were all composed of eutectic solid phases formed by eutectic points determined by their composition systems. Apart from the eutectic solid phases, no other impurity phases were present. For example, Figure 1 The image shows the XRD pattern of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1. As can be seen from the image, the prepared oxide eutectic ceramic is pure, consisting only of two phases: Al2O3 and c-ZrO2. Both Al2O3 and c-ZrO2 are eutectic solid phases of Al2O3-8YSZ, without any other reactive or impurity phases. "c-ZrO2" refers to cubic zirconium oxide, a type of YSZ phase, generally a zirconium oxide phase stabilized by a high Y2O3 content. In this example, the 8 mol% yttrium-stabilized zirconium oxide forms the c-ZrO2 phase within the YSZ phase.

[0081] (2) SEM microstructure analysis: The oxide eutectic ceramics prepared in the above embodiments were analyzed by SEM images. The SEM morphology analysis showed that the oxide eutectic ceramics prepared in each embodiment all exhibited a uniform eutectic structure. There were only phase interfaces of each eutectic solid phase and no grain boundaries in the eutectic ceramics. Moreover, the microstructure also changed with the cooling rate. That is, the microstructure morphology of the eutectic ceramics can be controlled relatively precisely by controlling the cooling rate. For example: Figure 2 and Figure 3 The image shows the SEM image of the Al2O3-8YSZ (alumina-8mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1 at a cooling rate of 5 °C / s. Figure 5This is a SEM image of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 4 at a cooling rate of 20 °C / s. The only difference between Examples 1 and 4 in the formation of the Al2O3-8YSZ eutectic ceramic was the changing cooling rate during the eutectic reaction. The microstructure of both examples confirms that the microstructure of the eutectic ceramic can be controlled by adjusting the cooling rate, resulting in a eutectic structure with fine dimensions. Figure 3 The SEM backscattered image clearly shows that the prepared Al2O3-8YSZ has a typical pictographic morphology eutectic structure, with two phases intertwined; from Figure 5 The SEM backscattered image clearly shows that the higher cooling rate results in the formation of a more uniform rod-shaped and lamellar eutectic structure. The phase interface between the two phases replaces the grain boundary prepared by sintering, that is, there are only phase boundaries and no grain boundaries in this eutectic ceramic.

[0082] (3) Compositional Analysis: Elemental analysis of the oxide eutectic ceramics prepared in the above embodiments was performed using EDS diagrams. The results showed that the constituent elements in the eutectic ceramics matched those of their respective eutectic solid phases, and that the constituent elements were uniformly distributed. For example, Figure 4 The EDS diagram of the Al2O3-8YSZ (alumina-8 mol% yttrium-stabilized zirconium oxide) eutectic ceramic prepared in Example 1 is shown below, corresponding to... Figure 3 The elemental distribution diagram of the SEM image shows that the elemental distributions of the two phases are complementary, further confirming that the Al2O3-8YSZ binary eutectic ceramic structure was rapidly formed in Example 1 at a furnace temperature below the eutectic temperature of 440°C.

Claims

1. A method of preparing an oxide eutectic ceramic by an ultrafast high-temperature furnace, characterized by, The ultrafast high-temperature furnace comprises a Joule heating device, wherein the Joule heating device comprises a carbon felt element for Joule heating, and the carbon felt element is provided with a sandwich hole for placing a crucible; The method comprises the following steps: Step 1, weighing any two or three ceramic powders selected from the group consisting of alumina, zirconia, yttria, magnesia, gadolinia, erbium oxide, lanthanum oxide and calcium oxide, and mixing the powders according to the eutectic composition ratio; Step 2, sequentially ball-milling, drying, sieving and pressing the weighed ceramic powders to form a ceramic green body; Step 3, placing the ceramic green body in a thin-wall graphite crucible and placing the thin-wall graphite crucible in the sandwich hole of the carbon felt element, and then vacuumizing to below 5 Pa; Step 4, generating Joule heat by electrifying the carbon felt element to form a high-temperature field through the Joule heating device, and then rapidly heating the ceramic green body to a set temperature, and then rapidly cooling the ceramic green body to room temperature after keeping the ceramic green body at the set temperature for a certain time, so that a eutectic structure is formed through a eutectic reaction during the heating and cooling process, and the oxide eutectic ceramic is prepared. The set temperature in step 4 is determined according to the eutectic temperature of the component system composed of the ceramic powders in step 1, and the set temperature is 300-550 ℃ lower than the eutectic temperature.

2. A method of preparing oxide eutectic ceramics by an ultrafast high-temperature furnace according to claim 1, characterized in that, In step 2, the ball-milling is performed by mixing the weighed ceramic powders with deionized water in a planetary ball mill, the rotation speed of the ball mill is 200-300 r / min, and the ball-milling time is 12-24 h.

3. A method of preparing oxide eutectic ceramics by an ultrafast high-temperature furnace according to claim 1, characterized in that, In step 2, the drying is performed at a temperature of 70-90 ℃ for 12-24 h.

4. The method of claim 1, wherein the super-fast high-temperature furnace is characterized by, In step 2, the sieving is performed by grinding the dried ceramic agglomerates into powder in an agate mortar, and then sieving the powder through a 200-400 mesh metal sieve.

5. The method of claim 1, wherein the ultrafast high-temperature furnace is characterized by, In step 2, the pressing is performed by pressing the sieved powder into a green body through die pressing, so that the relative density of the green body is above 50%; the die pressing pressure is 280-320 MPa, and the pressure holding time is 200-300 s.

6. The method of claim 1, wherein the ultrafast high-temperature furnace is characterized by, In step 4, the rapid heating rate is 5-20 ℃ / s, the holding time is 30-120 s, and the rapid cooling rate is 2-50 ℃ / s.

7. The oxide eutectic ceramic produced according to the method of any one of claims 1-6, characterized by: The oxide eutectic ceramic is composed of a component system composed of any two or three of alumina, zirconia, yttria, magnesia, gadolinia, erbium oxide, lanthanum oxide and calcium oxide, and the oxide eutectic ceramic is formed through a eutectic reaction of two or three solid phases.

8. The oxide eutectic ceramic of claim 7, wherein: The proportion of each solid phase in the oxide eutectic ceramic is the eutectic composition ratio of the component system.

9. The oxide eutectic ceramic of claim 7, wherein: In the oxide eutectic ceramic, each solid phase is interlaced with each other, and the phase interface between each solid phase replaces the grain boundary prepared through sintering, that is, the oxide eutectic ceramic has only phase boundaries but no grain boundaries; and each solid phase constituting the oxide eutectic ceramic is a eutectic solid phase, and no other impurity phase exists except the eutectic solid phase.

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