Composite ceramic and preparation method and application thereof

Abstract

The application provides a composite ceramic and a preparation method and application thereof. The composite ceramic of the application comprises a SiBCN matrix and a doped phase, and the doped phase comprises Ti3AlC2. By incorporating the second phase Ti3AlC2, a composite ceramic material with the SiBCN as the matrix is prepared, the material greatly improves the cyclic stability of the resistivity of the single-phase PDC-SiBCN in an extreme environment while retaining the original high-temperature sensing performance, and a high-cyclic-stability composite ceramic material which can be used in an air environment up to 1200 DEG C at a temperature rising rate of 100 DEG C / min for a long time cycle service is obtained, and the material has an application prospect as an extreme environment high-temperature sensor. The application further provides a preparation method and application of the composite ceramic.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a composite ceramic, its preparation method, and its application. Background Technology

[0002] As the core power source of aircraft, the aero-engine involves the mixing of fuel and gases in the combustion chamber during operation, resulting in a violent combustion reaction. Therefore, the engine interior is an extreme environment characterized by high temperature, high pressure, and oxidation / corrosion. Under these extreme conditions, it is desirable to monitor the engine's operating status, control the combustion process, and determine the lifespan of critical components, ultimately making aero-engines more reliable and intelligent. However, currently available temperature sensors all have various limitations when operating in such extreme environments, with most being constrained by limitations in high-temperature stability and resistance to oxidation and corrosion. Current temperature sensors mainly include silicon-based semiconductors, silicon carbide-based sensors, and traditional metal-based sensors. However, silicon-based semiconductors suffer from excessive leakage current due to doping and impurity diffusion, rendering them inoperable at high temperatures and limiting their use to below 350°C. Silicon carbide sensors generally do not exceed 600°C. Traditional metal-based sensors are severely oxidized and corroded at high temperatures, rendering them unusable. Therefore, developing temperature sensor materials with high-temperature stability and good oxidation resistance to meet extreme service conditions is a crucial and practically significant task.

[0003] Polymer precursor-derived silicon boron carbon nitride ceramics (PDC-SiBCN) exhibit excellent high-temperature stability and some resistance to oxidation and corrosion. They maintain a stable structure above 1000℃, and also possess good thermoelectric resistance characteristics, exhibiting semiconductor conductivity at high temperatures, with resistivity changing across multiple orders of magnitude with increasing temperature. This makes them a potential high-temperature sensor material for use in extreme environments. However, current research only demonstrates high-temperature sensing performance of PDC-SiBCN under low-rate heating conditions. In air environments below 800℃, resistivity shows some stability in heating and cooling cycles at a rate of 10℃ / min for up to 10 cycles, but still shows a significant upward trend.

[0004] Therefore, it is still necessary to develop a new sensing material that can withstand extreme environments such as high temperature, high pressure, and oxidation corrosion. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a composite ceramic that is resistant to high temperature, high pressure, and oxidation corrosion, and has promising applications as a high-temperature sensor in extreme environments.

[0006] The present invention also provides a method for preparing composite ceramics.

[0007] The present invention also provides a high-temperature temperature sensor.

[0008] A first aspect of the present invention provides a composite ceramic comprising a SiBCN matrix and a doped phase, wherein the doped phase comprises Ti3AlC2.

[0009] One of the technical solutions of the present invention concerning composite ceramics has at least the following beneficial effects:

[0010] Based on current research, this invention conducted a preliminary experiment on PDC-SiBCN under air atmosphere, performing 50 cycles within a high cycling temperature range of 500℃ to 1200℃ and a wide cycling range, at a heating rate of 100℃ / min. It was found that in the extreme high-temperature environment of rapid heating and cooling, the resistivity of PDC-SiBCN showed a significant increase and fluctuation with increasing cycle count, and the upward drift trend did not slow down with increasing cycle count. This is because oxidation and volatilization of free carbon occur near the surface of the material, leading to a mismatch in the thermal expansion coefficients of the surface oxide film and the substrate, resulting in cracks. This causes the oxidation degree of the material to continue to deepen with increasing service time. Therefore, PDC-SiBCN still has certain service defects as a high-temperature sensor material in extreme environments. This defect mainly focuses on the increase in resistivity due to insufficient oxidation resistance.

[0011] Given that PDC-SiBCN ceramics exhibit resistivity increases in extreme environments with rapid heating and cooling cycles, thus affecting their cyclic stability as high-temperature sensors, this invention prepares a composite ceramic material based on SiBCN by incorporating a second phase, Ti3AlC2. This material retains the original high-temperature sensing performance while significantly improving the cyclic stability of resistivity in single-phase PDC-SiBCN under extreme environments. The result is a high-cycle-stability composite ceramic material that can operate for extended periods in air environments up to 1200°C with a heating rate of 100°C / min, demonstrating promising application prospects as a high-temperature sensor in extreme environments.

[0012] According to some embodiments of the present invention, the content of Ti3AlC2 in the composite ceramic is 5wt% to 50wt%.

[0013] A second aspect of the present invention provides a method for preparing composite ceramics, comprising the following steps:

[0014] S1: The polymer precursor polyborosilicate is heated to crosslink and cure it;

[0015] S2: The doped phase is mixed with the product of step S1, ball-milled, and then pressed into shape to obtain a green body;

[0016] S3: The green body is pyrolyzed under a protective atmosphere to obtain the composite ceramic.

[0017] One technical solution of the present invention relating to the preparation method of composite ceramics has at least the following beneficial effects:

[0018] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0019] The preparation method of this invention involves first heating the polymer precursor polyborosilicate to crosslink and solidify it, then mixing the dopant phase with the product from step S1, ball milling, and pressing to obtain a green body. If the polymer precursor and dopant phase are directly mixed before solidification, two problems arise. First, due to the large molecular weight and high viscosity of the polymer precursor, the dopant phase powder is difficult to disperse uniformly within it, easily leading to the preparation of a heterogeneous material with numerous internal defects, affecting the ceramic's performance. Second, the polymer precursor releases a large amount of small-molecule gas during the initial crosslinking and solidification process. Directly mixing this into the precursor with the dopant phase will hinder the gas release during solidification. Furthermore, during the liquid-to-solid transition, the powder may cause internal stress in the solidified green body. Simultaneously, during the subsequent high-temperature pyrolysis and inorganication process, the material shrinks. The stress accumulated due to the pre-mixed dopant phase can cause internal defects such as cracks, severely affecting the material's structure and electrical properties.

[0020] Therefore, this invention first cross-links and solidifies the liquid polymer precursor polyborosilicate by heating, and then mixes it with the dopant phase, ensuring that the prepared material is a homogeneous material. During the subsequent pressing and high-temperature treatment of the green body, because the liquid polymer precursor polyborosilicate has already cross-linked and released a large amount of gas, and there is no significant stress accumulation that might occur during the mixing of liquid and solid phases, the prepared ceramic has higher density and fewer structural defects.

[0021] Based on preliminary research on single-phase materials, this invention specifically focuses on optimizing the temperature resistance cycling stability in extreme environments to prepare composite ceramic materials with applicable scenarios, which greatly improves the high-temperature sensing performance of the materials.

[0022] According to some embodiments of the present invention, in step S1, the heating temperature is 100°C to 140°C.

[0023] According to some embodiments of the present invention, in step S1, the heating temperature is approximately 120°C.

[0024] According to some embodiments of the present invention, the heating time is 0.5h to 4h.

[0025] According to some embodiments of the present invention, the heating time is approximately 0.5 hours.

[0026] Heating can be carried out in a vacuum oven.

[0027] The polymer precursor, polyborosilicate, is a thermosetting resin that undergoes self-crosslinking upon heating. A catalyst can be added to further lower the crosslinking temperature. This invention employs a heat-curing method.

[0028] According to some embodiments of the present invention, step S1 further includes pulverizing the cross-linked and cured polymer precursor polyborosilicate.

[0029] After pulverization, a pale yellow transparent solid is obtained. The solidified pale yellow transparent block is crushed and placed in a ball mill jar (preferably a silicon nitride ball mill jar and silicon nitride balls) for 6 to 12 hours for further pulverization and refinement.

[0030] The mass ratio of balls to powder is 5:1. One cycle of ball milling consists of 0.5 hours of forward rotation, 1 minute of intermittent rotation, and 0.5 hours of reverse rotation. The cycle is repeated 12 times, which is 12 hours. The ball milling speed is 300 rpm to 400 rpm. After ball milling, white PSNB powder is obtained.

[0031] According to some embodiments of the present invention, in step S2, the mass ratio of the doped phase Ti3AlC2 to the product of step S1 is 1:1 to 19, corresponding to a mass fraction of Ti3AlC2 of 5wt% to 50wt%.

[0032] According to some embodiments of the present invention, in step S2, the rotational speed of the ball mill is 350 rpm to 450 rpm.

[0033] According to some embodiments of the present invention, in step S2, the ball milling time is 10h to 15h.

[0034] According to some embodiments of the present invention, in step S2, the ball milling method may be: the mass ratio of balls to powder is 5:1, and one cycle of the ball milling program is 0.5h forward rotation, 1min interval, and 0.5h reverse rotation, and the cycle is repeated 12 times, i.e., 12h.

[0035] After ball milling, the resulting powder has a particle size range of 1 micrometer to 50 micrometers.

[0036] According to some embodiments of the present invention, in step S2, the pressing and molding method includes: placing the ball-milled mixed powder in a mold for cold pressing to obtain a preliminary blank, and subjecting the preliminary blank to cold isostatic pressing to obtain a blank body.

[0037] According to some embodiments of the present invention, in step S2, the pressing method may be: placing the uniformly mixed powder in a mold with a diameter of 13 mm, and uniaxially cold pressing under a pressure of 7 MPa for 2 min (holding pressure for 30 s in each direction) to obtain a cylindrical blank.

[0038] The cylindrical blank has a diameter of 13mm and a thickness of 3mm.

[0039] According to some embodiments of the present invention, cold isostatic pressing of the initial blank refers to placing the vacuum-sealed blank in a hydraulic cylinder and subjecting it to cold isostatic pressing at 200 MPa to obtain a dense blank.

[0040] Vacuum sealing is used to prevent oil from being forced into the sample during cold isostatic pressing (cold isostatic pressing refers to placing the sample in an oil cylinder and applying pressure, where the pressure is the same in all directions, hence the term isostatic pressing).

[0041] Uniaxial cold pressing is used to form the blank first. Since only longitudinal pressure is applied, the powder distribution in the horizontal direction is not dense and uniform enough. Therefore, isostatic pressing can further make the sample more dense and uniform.

[0042] According to some embodiments of the present invention, in step S3, the pyrolysis method includes: heating the billet to 1400°C at a heating rate of 3°C / min to 5°C / min, holding it at that temperature, cooling it to 800°C / min at a cooling rate of 5°C / min, and then cooling it in the furnace.

[0043] According to some embodiments of the present invention, the heat preservation time is 3h to 5h.

[0044] According to some embodiments of the present invention, the heat preservation time can be about 4 hours.

[0045] Pyrolysis can be carried out in a tube furnace under a high-purity argon atmosphere.

[0046] During pyrolysis, the polymer precursor undergoes carbon-carbon double bond breaking and dehydrogenation coupling of highly polar chemical bonds such as NH, deepening the cross-linking and forming a three-dimensional network structure through interatomic bonding, thus binding the powder particles together. Subsequently, the hydrocarbon groups and other structures undergo cleavage and rearrangement, and the precursor is further dehydrogenated and inorganicated. After 1000℃, H almost completely disappears, forming an amorphous ceramic matrix. At high temperatures, Ti3AlC2 decomposes and reacts with the amorphous matrix to generate crystalline components such as TiC and TiB2.

[0047] A third aspect of the present invention provides a high-temperature temperature sensor, which is prepared from the composite ceramic of the present invention or the ceramic obtained by the method of the present invention.

[0048] One of the technical solutions for the high-temperature sensor of the present invention has at least the following beneficial effects:

[0049] The high-temperature sensor of the present invention, by using the composite ceramic of the present invention, possesses all the beneficial effects of composite ceramics, specifically:

[0050] Ti3AlC2, as one of the doping phases, can improve the oxidation resistance of composite ceramics. This helps to slow down the oxidation rate of the material in high-temperature environments, reduce the formation of oxide layers, and thus improve the resistivity stability of the material.

[0051] The structural and compositional design of composite ceramics enables them to better maintain the stability of their structural and electrical properties under high-temperature environments. The addition of Ti3AlC2 improves the high-temperature oxidation resistance of composite ceramics, reduces crack formation in the oxide film, and thus enhances the material's thermal stability. Due to the introduction of Ti3AlC2, the resistivity cycling stability of composite ceramics in extreme environments with rapid high-temperature heating and cooling is improved. A more protective oxide film can form on the surface, preventing further reaction between the matrix and the oxidizing medium, significantly enhancing the material's oxidation resistance. This means that the material's resistivity is more stable and its performance is more reliable during long-term high-temperature cycling, making it suitable for long-term operation of high-temperature sensors.

[0052] The matrix of the composite ceramic is SiBCN, a ceramic material that performs well at high temperatures. Therefore, by incorporating Ti3AlC2, the composite ceramic can improve its stability while retaining its original high-temperature sensing performance, making it suitable for high-temperature sensor applications.

[0053] Due to its improved resistivity stability and oxidation resistance, this composite ceramic material is more suitable for long-term high-temperature cycling in extreme environments, such as high-temperature air, enabling it to operate reliably under extreme conditions.

[0054] High temperature sensor, "high temperature" refers to 500℃~1200℃. Attached Figure Description

[0055] Figure 1 The results are X-ray powder diffraction test results of the ceramics prepared in Example 1 and Comparative Example 1.

[0056] Figure 2 This is the cyclic resistivity-time curve of the composite ceramic prepared in Example 1.

[0057] Figure 3 This is the resistivity-temperature relationship of the composite ceramic prepared in Example 1 after different cycles.

[0058] Figure 4This is the cyclic resistivity-time curve of the composite ceramic prepared in Example 2.

[0059] Figure 5 This is the resistivity-temperature relationship of the composite ceramic prepared in Example 2 after different cycles.

[0060] Figure 6 This is the cyclic resistivity-time curve of the single-phase ceramic prepared in Comparative Example 1.

[0061] Figure 7 This is the resistivity-temperature relationship of the single-phase ceramic prepared in Comparative Example 1 after different cycles.

[0062] Figure 8 This is the cyclic resistivity-time curve of the composite ceramic prepared in Comparative Example 2.

[0063] Figure 9 This is the resistivity-temperature relationship of the composite ceramic prepared in Comparative Example 2 after different cycles. Detailed Implementation

[0064] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0065] In some embodiments of the present invention, a composite ceramic is provided, comprising a SiBCN matrix and a doped phase, wherein the doped phase comprises Ti3AlC2.

[0066] It is understandable that PDC-SiBCN ceramics suffer from resistivity increases in extreme environments with rapid temperature increases and decreases, which affects their cyclic stability as high-temperature sensors. This invention prepares a composite ceramic material based on SiBCN by incorporating a second phase, Ti3AlC2. This material retains the original high-temperature sensing performance while significantly improving the cyclic stability of resistivity of single-phase PDC-SiBCN in extreme environments. The result is a high-cycle-stability composite ceramic material that can operate for extended periods in air environments up to 1200°C with a heating rate of 100°C / min, showing promise as a high-temperature sensor for extreme environments.

[0067] In some embodiments of the present invention, the content of Ti3AlC2 in the composite ceramic is 5wt% to 50wt%.

[0068] In other embodiments of the present invention, a method for preparing composite ceramics is provided, comprising the following steps:

[0069] S1: The polymer precursor polyborosilicate is heated to crosslink and cure it;

[0070] S2: The doped phase is mixed with the product of step S1, ball-milled, and then pressed into shape to obtain a green body;

[0071] S3: The green body is pyrolyzed under a protective atmosphere to obtain composite ceramics.

[0072] It is understood that the preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0073] It should be noted that the preparation method of this invention involves first heating the polymer precursor polyborosilicate to crosslink and solidify it, then mixing the dopant phase with the product from step S1, ball milling, and pressing to obtain a green body. If the polymer precursor and dopant phase are directly mixed before solidification, two problems arise. First, due to the large molecular weight and high viscosity of the polymer precursor, the dopant phase powder is difficult to disperse uniformly within it, easily leading to the preparation of a heterogeneous material. This heterogeneous material has many internal defects, affecting the ceramic's performance. Second, the polymer precursor releases a large amount of small-molecule gas during the initial crosslinking and solidification process. Directly mixing this into the precursor with the dopant phase will cause the released gas to be hindered by the powder. Furthermore, during the liquid-to-solid transition, the powder may cause internal stress in the solidified green body. Simultaneously, during the subsequent high-temperature pyrolysis and inorganication process, the material shrinks. The stress accumulated due to the pre-mixed dopant phase can cause internal defects such as cracks, severely affecting the material's structure and electrical properties.

[0074] Therefore, this invention first cross-links and solidifies the liquid polymer precursor polyborosilicate by heating, and then mixes it with the dopant phase, ensuring that the prepared material is a homogeneous material. During the subsequent pressing and high-temperature treatment of the green body, because the liquid polymer precursor polyborosilicate has already cross-linked and released a large amount of gas, and there is no significant stress accumulation that might occur during the mixing of liquid and solid phases, the prepared ceramic has higher density and fewer structural defects.

[0075] Based on preliminary research on single-phase materials, this invention specifically focuses on optimizing the temperature resistance cycling stability in extreme environments to prepare composite ceramic materials with applicable scenarios, which greatly improves the high-temperature sensing performance of the materials.

[0076] In some embodiments of the present invention, in step S1, the heating temperature is 100°C to 140°C.

[0077] In some embodiments of the present invention, in step S1, the heating temperature is about 120°C.

[0078] In some embodiments of the present invention, the heating time is 0.5h to 4h.

[0079] In some embodiments of the present invention, the heating time is approximately 0.5 hours.

[0080] Heating can be carried out in a vacuum oven.

[0081] The polymer precursor, polyborosilicate, is a thermosetting resin that undergoes self-crosslinking upon heating. A catalyst can be added to further lower the crosslinking temperature. This invention employs a heat-curing method.

[0082] In some embodiments of the present invention, step S1 further includes pulverizing the cross-linked and cured polymer precursor polyborosilicate.

[0083] After pulverization, a pale yellow transparent solid is obtained. The solidified pale yellow transparent block is crushed and placed in a ball mill jar (preferably a silicon nitride ball mill jar and silicon nitride balls) for 6 to 12 hours for further pulverization and refinement.

[0084] The mass ratio of balls to powder is 5:1. One cycle of ball milling consists of 0.5 hours of forward rotation, 1 minute of intermittent rotation, and 0.5 hours of reverse rotation. The cycle is repeated 12 times, which is 12 hours. The ball milling speed is 300 rpm to 400 rpm. After ball milling, white PSNB powder is obtained.

[0085] In some embodiments of the present invention, in step S2, the mass ratio of the doped phase Ti3AlC2 to the product of step S1 is 1:1 to 19, corresponding to a mass fraction of Ti3AlC2 of 5wt% to 50wt%.

[0086] In some embodiments of the present invention, in step S2, the rotational speed of the ball mill is 350 rpm to 450 rpm.

[0087] In some embodiments of the present invention, in step S2, the ball milling time is 10h to 15h.

[0088] In some embodiments of the present invention, in step S2, the ball milling method may be: the mass ratio of balls to powder is 5:1, and one cycle of the ball milling program is 0.5h forward rotation, 1min interval, and 0.5h reverse rotation, and the cycle is repeated 12 times, i.e., 12h.

[0089] After ball milling, the resulting powder has a particle size range of 1 micrometer to 50 micrometers.

[0090] In some embodiments of the present invention, step S2, the pressing method includes: placing the ball-milled mixed powder in a mold for cold pressing to obtain a preliminary blank, and performing cold isostatic pressing on the preliminary blank to obtain a blank body.

[0091] In some embodiments of the present invention, in step S2, the pressing method may be: placing the uniformly mixed powder in a mold with a diameter of 13 mm, and uniaxially cold pressing under a pressure of 7 MPa for 2 min (holding pressure for 30 s in each direction) to obtain a cylindrical blank.

[0092] The cylindrical blank has a diameter of 13mm and a thickness of 3mm.

[0093] In some embodiments of the present invention, cold isostatic pressing of the initial blank refers to placing the vacuum-sealed blank in an oil cylinder and subjecting it to cold isostatic pressing at 200 MPa to obtain a dense blank.

[0094] Vacuum sealing is used to prevent oil from being forced into the sample during cold isostatic pressing (cold isostatic pressing refers to placing the sample in an oil cylinder and applying pressure, where the pressure is the same in all directions, hence the term isostatic pressing).

[0095] Uniaxial cold pressing is used to form the blank first. Since only longitudinal pressure is applied, the powder distribution in the horizontal direction is not dense and uniform enough. Therefore, isostatic pressing can further make the sample more dense and uniform.

[0096] In some embodiments of the present invention, in step S3, the pyrolysis method includes: heating the billet to 1400°C at a heating rate of 3°C / min to 5°C / min, holding it at that temperature, cooling it to 800°C / min at a cooling rate of 5°C / min, and then cooling it in the furnace.

[0097] In some embodiments of the present invention, the heat preservation time is 3h to 5h.

[0098] In some embodiments of the present invention, the heat preservation time can be about 4 hours.

[0099] Pyrolysis can be carried out in a tube furnace under a high-purity argon atmosphere.

[0100] During pyrolysis, the polymer precursor undergoes carbon-carbon double bond breaking and dehydrogenation coupling of highly polar chemical bonds such as NH, deepening the cross-linking and forming a three-dimensional network structure through interatomic bonding, thus binding the powder particles together. Subsequently, the hydrocarbon groups and other structures undergo cleavage and rearrangement, and the precursor is further dehydrogenated and inorganicated. After 1000℃, H almost completely disappears, forming an amorphous ceramic matrix. At high temperatures, Ti3AlC2 decomposes and reacts with the amorphous matrix to generate crystalline components such as TiC and TiB2.

[0101] In some other embodiments of the present invention, a high-temperature temperature sensor is provided, which is prepared from the composite ceramic of the present invention or the ceramic obtained by the method of the present invention.

[0102] It is understood that the high-temperature sensor of the present invention, due to the use of the composite ceramic of the present invention, possesses all the beneficial effects of composite ceramics, specifically:

[0103] Ti3AlC2, as one of the doping phases, can improve the oxidation resistance of composite ceramics. This helps to slow down the oxidation rate of the material in high-temperature environments, reduce the formation of oxide layers, and thus improve the resistivity stability of the material.

[0104] The structural and compositional design of composite ceramics allows them to better maintain the stability of their structure and electrical properties at high temperatures. The addition of Ti3AlC2 improves the high-temperature oxidation resistance of composite ceramics, reduces crack formation in the oxide film, and thus enhances the material's thermal stability. Due to the introduction of Ti3AlC2, the resistivity cycling stability of composite ceramics in extreme environments with rapid temperature rise and fall is improved. A more protective oxide film can form on the surface, preventing further reaction between the matrix and the oxidizing medium, significantly improving the material's oxidation resistance. This means that the material's resistivity is more stable and its performance is more reliable during long-term high-temperature cycling, making it suitable for long-term operation of high-temperature sensors. The matrix of the composite ceramic is SiBCN, a ceramic material that performs well at high temperatures. Therefore, by incorporating Ti3AlC2, the composite ceramic can retain its original high-temperature sensing performance while improving stability, making it suitable for high-temperature sensor applications.

[0105] Due to its improved resistivity stability and oxidation resistance, this composite ceramic material is more suitable for long-term high-temperature cycling in extreme environments, such as high-temperature air, enabling it to operate reliably under extreme conditions.

[0106] It should be noted that for high-temperature sensors, "high temperature" refers to 500℃~1200℃.

[0107] The technical solution of the present invention will be better understood below with reference to specific embodiments.

[0108] It should be noted that all reagents used in the examples were obtained from commercially available sources.

[0109] The commercially available liquid polymer precursor, polyborosilicate PSNB-1, was purchased from the Institute of Chemistry, Chinese Academy of Sciences.

[0110] Example 1

[0111] A composite ceramic comprising a SiBCN matrix and a doped phase, wherein the doped phase is Ti3AlC2.

[0112] The content of Ti3AlC2 in the composite ceramic is 10 wt%.

[0113] The preparation method specifically includes the following steps:

[0114] S1: The polymer precursor polyborosilazane PSNB-1 is heated to crosslink and cure it;

[0115] S2: The doped phase is mixed with the product of step S1, ball-milled, and then pressed into shape to obtain a green body;

[0116] S3: The green body is pyrolyzed under a protective atmosphere of argon to obtain black composite ceramic.

[0117] In step S1:

[0118] The heating temperature is 120℃, and the heating time is 0.5h.

[0119] The cross-linked and cured polymer precursor, polyborosilicate, was pulverized.

[0120] In step S2:

[0121] The ball mill rotates at 400 rpm for 12 hours, with a ball-to-material ratio of 5:1. One cycle of the ball milling program consists of 0.5 hours of forward rotation, 1 minute of pause, and 0.5 hours of reverse rotation, with 12 cycles totaling 12 hours.

[0122] The pressing and molding method is as follows: the ball-milled mixed powder is placed in a mold and cold-pressed to obtain a preliminary blank, which is then subjected to cold isostatic pressing to obtain a billet. The billet has a diameter of 13mm and a thickness of 3mm.

[0123] In step S3:

[0124] The pyrolysis method is as follows: the billet is heated to 1400℃ at a heating rate of 3℃ / min, held at that temperature for 4 hours, and then cooled to 800℃ / min at a cooling rate of 5℃ / min, and then cooled in the furnace.

[0125] Example 2

[0126] A composite ceramic differs from Example 1 in that the content of Ti3AlC2 in the composite ceramic is 20wt%.

[0127] Comparative Example 1

[0128] A ceramic, which differs from Example 1 in that Ti3AlC2 is not added to the ceramic.

[0129] Comparative Example 2

[0130] A composite ceramic differs from Example 1 in that the content of Ti3AlC2 in the composite ceramic is 4.76 wt%.

[0131] Material characterization and performance testing

[0132] The ceramics prepared in Example 1 and Comparative Example 1 were characterized by X-ray powder diffraction, and the results are as follows: Figure 1 As shown.

[0133] from Figure 1 Characteristic peaks of TiC and TiB2 were observed, indicating that Ti3AlC2 was successfully incorporated into the composite ceramic of Example 1, but it mainly exists in the composite ceramic in the form of crystalline TiC and TiB2, rather than single-phase Ti3AlC2. Both TiC and TiB2 are ultra-high temperature ceramics, which can effectively improve the high-temperature stability of materials. This preparation method allows this ultra-high temperature ceramic phase to be generated in situ at a relatively low sintering temperature.

[0134] The resistivity-time relationship of the composite ceramic prepared in Example 1 was tested in air at a heating rate of 100 °C / min for 10-50 cycles at 500-1200 °C. The results are as follows: Figure 2 As shown, the resistivity of the composite ceramic is very stable over time and remains essentially unchanged during cycling, with no significant change in resistivity at the boundary temperature.

[0135] The resistivity-temperature relationship of the composite ceramic prepared in Example 1 was tested at different cycles (10-50) in air at a heating rate of 100 °C / min at 500-1200 °C. The results are as follows: Figure 3 As shown, the temperature-resistance curves for 10-50 cycles basically overlap, the resistivity at different temperature points with different number of cycles does not change significantly, and the curves are very stable.

[0136] Figure 2 and Figure 3 The test results show that the composite ceramic prepared by this invention has a significant improvement on the cycle stability of single-phase ceramics and has the potential to be used as a high-temperature sensor material in extreme environments.

[0137] The resistivity-time relationship of the composite ceramic prepared in Example 2 was tested in air at a heating rate of 100 °C / min for 10-50 cycles at 500-1200 °C. The results are as follows: Figure 4 As shown, the resistivity of the composite ceramic is very stable over time and remains essentially unchanged during cycling, with no significant change in resistivity at the boundary temperature.

[0138] The resistivity-temperature relationship of the composite ceramic prepared in Example 2 was tested at different cycles (10-50) in air at a heating rate of 100 °C / min at 500-1200 °C. The results are as follows: Figure 5 As shown, the temperature-resistance curves for 10-50 cycles basically overlap, the resistivity at different temperature points with different number of cycles does not change significantly, and the curves are very stable.

[0139] Figure 4 and Figure 5 The test results show that the composite ceramic prepared by this invention has a significant improvement on the cycle stability of single-phase ceramics and has the potential to be used as a high-temperature sensor material in extreme environments.

[0140] The resistivity-time relationship of the single-phase ceramic prepared in Comparative Example 1 was tested in air at a heating rate of 100 °C / min for 10-50 cycles at 500-1200 °C. The results are as follows: Figure 6 As shown in the figure, the resistivity of single-phase ceramics increases significantly with time, and fluctuates considerably at the two boundary temperatures of heating and cooling.

[0141] The resistivity-temperature relationship of the single-phase ceramic prepared in Comparative Example 1 was tested at different cycles (10-50) in air at a heating rate of 100 °C / min at 500-1200 °C. The results are as follows: Figure 7 As shown, during the rapid temperature rise and fall of single-phase ceramics in the 500-1200℃ range, the resistivity shows a significant upward trend at each temperature point, and the temperature-resistance curve is not stable and fluctuates significantly.

[0142] Figure 6 and Figure 7 The test results show that single-phase ceramics have poor cyclic stability as temperature sensors in extreme environments, which greatly limits their application prospects.

[0143] The resistivity-time relationship of the composite ceramic prepared in Comparative Example 2 was tested in air at a heating rate of 100℃ / min for 10-50 cycles at 500-1200℃. The results are as follows: Figure 8 As shown, when the content of Ti3AlC2 in the composite ceramic is less than 5 wt%, the addition of the second phase Ti3AlC2 actually exacerbates the fluctuation of resistivity during cycling. The presumed reason is that with a low content of the second phase, a uniform and dense oxide film cannot form on the surface when the material is oxidized during service. Previous studies have found that the oxide film generated by the matrix itself develops cracks and pores during high-temperature rapid heating and cooling cycles, leading to a deepening of oxidation with increasing service time, gradually penetrating into the sample interior, thus resulting in poor resistivity cycling stability. Furthermore, while Ti3AlC2 can act as a sintering aid, insufficient content after mixing with the polymer precursor may reduce the material's density, and increased porosity makes the material more susceptible to oxidation. The decrease in density is due to the second phase affecting the chemical bonding during the inorganication of the precursor, but its content is insufficient to compensate for the defects caused by hindered atomic bonding during sintering.

[0144] The resistivity-temperature relationship of the composite ceramic prepared in Comparative Example 2 was tested at different cycles (10-50) in air at a heating rate of 100 °C / min at 500-1200 °C. The results are as follows: Figure 9 As shown, the resistivity shows a significant upward trend with increasing cycle count in the 500-700℃ and 1000-1200℃ ranges. Although the cycle stability is somewhat improved in the 700-1000℃ range, the overall temperature-resistance curve is still not stable enough, especially with significant fluctuations near the boundary temperature, which is not conducive to its use as a temperature sensing material for long-term service.

[0145] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A composite ceramic, characterized in that, The composite ceramic comprises a SiBCN matrix and a doped phase, wherein the doped phase includes Ti3AlC2, and the content of Ti3AlC2 in the composite ceramic is 5wt%~50wt%. The composite ceramic is prepared by the following method: S1: The polymer precursor polyborosilicate is heated at 100℃~140℃ for 0.5h~4h to crosslink and solidify it, and the crosslinked and solidified polymer precursor polyborosilicate is pulverized. S2: The doped phase is mixed with the product of step S1, ball-milled, and then pressed into shape to obtain a green body; S3: The green body is pyrolyzed under a protective atmosphere to obtain the composite ceramic.

2. The composite ceramic according to claim 1, characterized in that, In step S2, the ball mill rotation speed is 350 rpm to 450 rpm; and / or, the ball milling time is 10 h to 15 h.

3. The composite ceramic according to claim 1, characterized in that, In step S2, the pressing and molding method includes: placing the ball-milled mixed powder into a mold for cold pressing to obtain a preliminary blank, and then performing cold isostatic pressing on the preliminary blank to obtain a blank body.

4. The composite ceramic according to claim 1, characterized in that, In step S3, the pyrolysis method includes: heating the billet to 1400°C at a heating rate of 3°C / min to 5°C / min, holding it at that temperature, cooling it to 800°C / min at a cooling rate of 5°C / min, and then cooling it in the furnace.

5. The composite ceramic according to claim 4, characterized in that, The heat preservation time is 3 to 5 hours.

6. A high-temperature temperature sensor, characterized in that, The high-temperature sensor is prepared from the composite ceramic according to any one of claims 1 to 5.

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