A SiBCN ceramic sensor suitable for high-temperature and oxygen-rich environments and its fabrication method

Abstract

This invention provides a SiBCN ceramic sensor suitable for high-temperature aerobic environments and its preparation method, belonging to the field of sensor technology. The SiBCN ceramic sensor for high-temperature aerobic environments is a SiBCN ceramic sensor with a coating on the surface of the sensing element; the coating comprises SiBCN, ZrO2, SiO2, and BN. The SiBCN ceramic sensor provided by this invention exhibits excellent high-temperature oxidation resistance, a wide temperature measurement range (room temperature to 1200℃), and good oxygen corrosion resistance. It can be applied to temperature measurement in aerobic environments up to 1200℃, solving the problem that existing SiBCN sensors have operating temperatures below 1000℃ and cannot meet the requirements for use in high-temperature aerobic environments.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a SiBCN ceramic sensor suitable for high-temperature oxygen-containing environments and its preparation method. Background Technology

[0002] During operation, aero-engines are subjected to multiple extreme environments, including high temperature, high pressure, high corrosion, and intense vibration. Under such harsh conditions, real-time monitoring of the temperature of internal engine components becomes crucial, as it directly affects the engine's performance stability and lifespan. Currently widely used thermocouple technology is prone to aging and data drift at high temperatures, and its thermal stability is not ideal, making it unsuitable for the complex internal environment of engines. Precursor-converted SiBCN ceramics, with their superior high-temperature stability, excellent oxidation and corrosion resistance, maintain structural integrity even in extreme high-temperature environments. Furthermore, SiBCN ceramics possess excellent high-temperature semiconductor properties and significant piezoresistive effects, opening up broad prospects for their application in the field of high-temperature sensors.

[0003] However, in practical applications, the operating temperature range of SiBCN ceramics as temperature sensors is mainly concentrated below 1000℃, and even in most applications below 850℃. This is primarily due to the chemical stability issues of SiBCN ceramics at high temperatures. Despite its excellent oxidation resistance, under extreme high-temperature conditions, the ceramic will still react with oxygen, leading to the gradual consumption of amorphous Si and free carbon in the material. Their reduction directly affects the electrical conductivity of the ceramic. This change not only affects the accuracy of temperature monitoring by the sensor, but in severe cases, may even cause sensor failure. Summary of the Invention

[0004] To address one or more technical problems existing in the prior art, this invention provides a SiBCN ceramic sensor suitable for high-temperature aerobic environments and its preparation method. The SiBCN ceramic sensor provided by this invention has excellent high-temperature oxidation resistance, a wide temperature measurement range (room temperature to 1200℃), and good oxygen corrosion resistance. It can be applied to temperature measurement in aerobic environments up to 1200℃, solving the problem that the operating temperature of existing SiBCN sensors is below 1000℃, which cannot meet the requirements for use in high-temperature aerobic environments.

[0005] In a first aspect, the present invention provides a SiBCN ceramic sensor suitable for high-temperature aerobic environments, wherein the SiBCN ceramic sensor suitable for high-temperature aerobic environments is a SiBCN ceramic sensor with a coating on the surface of the sensing element.

[0006] The coating comprises SiBCN, ZrO2, SiO2 and BN.

[0007] Preferably, the coating is made from a coating slurry comprising polyborosilazane, ZrO2, SiO2, BN and a dispersant.

[0008] Preferably, in the coating slurry, polyborosilazane accounts for 40-80 wt%; the ZrO2 content is 5-20 wt% of the polyborosilazane.

[0009] The SiO2 content is 5-20 wt% of the polyborosilicate;

[0010] The BN content is 5–20 wt% of the polyborosilazane; and / or

[0011] The content of the dispersant is 30-50% of the total mass of polyborosilazane, ZrO2, SiO2 and BN.

[0012] Preferably, the thickness of the coating is 10–30 μm.

[0013] The present invention provides, in a second aspect, a method for fabricating the SiBCN ceramic sensor described in the first aspect, suitable for high-temperature aerobic environments, the method comprising:

[0014] S1. Polyborosilicate is first cured, and the cured polyborosilicate powder and polyborosilicate are mixed evenly. The mixed powder is hot-pressed to obtain a sensitive element blank, and an electrode is composited on the sensitive element blank. After first pyrolysis, a SiBCN ceramic sensor is obtained.

[0015] S2. Mix polyborosilazane, ZrO2, SiO2, BN and dispersant to obtain a coating slurry;

[0016] S3. The coating slurry is sprayed onto the surface of the sensitive element of the SiBCN ceramic sensor, and after a second curing and a second pyrolysis, a coating is formed on the surface of the sensitive element to obtain the SiBCN ceramic sensor suitable for high temperature and oxygen environment.

[0017] Preferably, in step S1, the amount of polyborosilazane used is 10-15% of the mass of the cured polyborosilazane powder.

[0018] Preferably, the first curing process involves heating to 300-350°C at a heating rate of 0.5-1.5°C / min and holding at that temperature for 2-4 hours.

[0019] The hot pressing is performed at 60–100°C and 250–350 MPa, with a holding temperature and pressure for 30–180 minutes; and / or

[0020] The first pyrolysis is carried out under a protective atmosphere, with the temperature increased to 1100-1300℃ at a heating rate of 1-3℃ / min, and held at that temperature for 2-6 hours.

[0021] Preferably, the sensitive element blank is cylindrical, and more preferably, the diameter of the cylinder is 5 mm and the height of the cylinder is 3-10 mm; and / or

[0022] The electrode is a platinum wire electrode, preferably with a diameter of 0.2 to 0.45 mm.

[0023] Preferably, the number of spraying operations is 2 to 5.

[0024] Preferably, the second curing process involves heating to 250–350°C at a heating rate of 0.5–1.5°C / min and holding at that temperature for 2–4 hours.

[0025] The second pyrolysis involves heating to 800–1000°C at a rate not exceeding 1°C / min and holding at that temperature for 2–6 hours.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The SiBCN ceramic sensor provided by this invention, suitable for high-temperature and oxygen-rich environments, has a surface coating containing SiBCN, ZrO2, SiO2, and BN. This coating uses SiBCN as the substrate, exhibiting excellent oxidation resistance and being identical to the sensing element material, thus providing good thermal matching. ZrO2, SiO2, and BN particles are used as inert fillers, which not only prevent cracking during pyrolysis shrinkage but also possess excellent high-temperature oxidation resistance, good thermal conductivity, and resistance to thermal shock. Furthermore, the inert fillers themselves are non-conductive, making the coating's resistance significantly higher than that of the sensing element. Therefore, even if the electrode passes through both the coating and the sensing element simultaneously, the measured resistance remains the same as that of the sensing element, ensuring its functionality. This coating can react with oxygen in a high-temperature, oxygen-rich environment to form a dense oxide layer, effectively preventing oxygen from further diffusing into the ceramic and thus preventing oxidation. It can establish a barrier between the sensing element and the high-temperature, oxygen-rich environment, preventing oxygen from penetrating the sensing element, reducing the impact of the oxygen-rich environment on the sensing performance of the sensing element, playing an anti-oxidation protection role, ensuring the high-temperature oxidation resistance and stability of the sensor, and improving the reliability and service life of the sensor.

[0028] The SiBCN ceramic sensor provided by this invention exhibits excellent high-temperature oxidation resistance, a wide temperature range (room temperature to 1200℃), and good resistance to oxygen corrosion. It can be applied to temperature measurement in oxygen-enriched environments up to 1200℃, solving the problem that existing SiBCN sensors, whose operating temperature is below 1000℃, cannot meet the requirements for use in high-temperature oxygen-enriched environments. It is the first SiBCN sensor capable of effective measurement in oxygen-enriched environments up to 1200℃, providing strong technical support for the application of SiBCN ceramics in the field of high-temperature sensing. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The images show physical models of SiBCN ceramic sensors suitable for high-temperature and oxygen-rich environments, as provided in Embodiment 1 and Comparative Example 1 of the present invention.

[0031] Figure 2 A flowchart illustrating the fabrication process of a SiBCN ceramic sensor suitable for high-temperature and oxygen-rich environments, provided by this invention.

[0032] Figure 3 This is a SEM image of the coating in a SiBCN ceramic sensor suitable for high-temperature and oxygen-rich environments, provided in Embodiment 1 of the present invention.

[0033] Figure 4 This is a cross-sectional view of the coating in a SiBCN ceramic sensor suitable for high-temperature and oxygen-rich environments, provided in Embodiment 1 of the present invention.

[0034] Figure 5 SEM image (top) and elemental analysis (bottom) of the sensitive element cross section in the SiBCN ceramic sensor suitable for high temperature and oxygen environment provided in Embodiment 1 of the present invention;

[0035] Figure 6 The image shows a comparison of the temperature resistance curves (left) and a magnified view (right) of the SiBCN ceramic sensor provided in Comparative Example 1 of this invention under high temperature oxygen-free and oxygen-enriched environments.

[0036] Figure 7 Comparison of temperature resistance curves and enlarged view (internal) of SiBCN ceramic sensor suitable for high temperature and oxygen environment provided in Embodiment 1 of the present invention under high temperature and oxygen-free environment.

[0037] Figure 8 The temperature resistance curves (room temperature ~ 1200℃) of the SiBCN ceramic sensor suitable for high temperature and oxygen environment provided in Embodiments 1 and 2 of the present invention.

[0038] Figure 9 The temperature resistance curve (room temperature ~ 1200℃) of the SiBCN ceramic sensor provided in Comparative Example 4 of this invention is shown.

[0039] Figure 10 This is a macroscopic morphology diagram of the SiBCN ceramic sensor provided in Comparative Example 5 of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] In a first aspect, the present invention provides a SiBCN ceramic sensor suitable for high-temperature aerobic environments, wherein the SiBCN ceramic sensor suitable for high-temperature aerobic environments is a SiBCN ceramic sensor with a coating on the surface of the sensing element.

[0042] The coating comprises SiBCN, ZrO2, SiO2 and BN.

[0043] In this invention, the coating uses SiBCN as the matrix and ZrO2, SiO2 and BN as fillers.

[0044] The SiBCN ceramic sensor provided by this invention, suitable for high-temperature and oxygen-rich environments, has a surface coating containing SiBCN, ZrO2, SiO2, and BN. This coating uses SiBCN as the substrate, exhibiting excellent oxidation resistance and being identical to the sensing element material, thus providing good thermal matching. ZrO2, SiO2, and BN particles are used as inert fillers, which not only prevent cracking during pyrolysis shrinkage but also possess excellent high-temperature oxidation resistance, good thermal conductivity, and resistance to thermal shock. Furthermore, the inert fillers themselves are non-conductive, making the coating's resistance significantly higher than that of the sensing element. Therefore, even if the electrode passes through both the coating and the sensing element simultaneously, the measured resistance remains the same as that of the sensing element, ensuring its functionality. This coating can react with oxygen in a high-temperature, oxygen-rich environment to form a dense oxide layer, effectively preventing oxygen from further diffusing into the ceramic and thus preventing oxidation. It can establish a barrier between the sensing element and the high-temperature, oxygen-rich environment, preventing oxygen from penetrating the sensing element, reducing the impact of the oxygen-rich environment on the sensing performance of the sensing element, playing an anti-oxidation protection role, ensuring the high-temperature oxidation resistance and stability of the sensor, and improving the reliability and service life of the sensor.

[0045] The SiBCN ceramic sensor provided by this invention exhibits excellent high-temperature oxidation resistance, a wide temperature range (room temperature to 1200℃), and good resistance to oxygen corrosion. It can be applied to temperature measurement in oxygen-enriched environments up to 1200℃, solving the problem that existing SiBCN sensors, whose operating temperature is below 1000℃, cannot meet the requirements for use in high-temperature oxygen-enriched environments. It is the first SiBCN sensor capable of effective measurement in oxygen-enriched environments up to 1200℃, providing strong technical support for the application of SiBCN ceramics in the field of high-temperature sensing.

[0046] According to some preferred embodiments, the coating is made from a coating slurry comprising polyborosilazane, ZrO2, SiO2, BN and a dispersant.

[0047] According to some preferred embodiments, the coating slurry contains 40 to 80 wt% polyborosilazane (for example, it can be 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt% or 80 wt%).

[0048] According to some preferred embodiments, the ZrO2 content is 5 to 20 wt% of the polyborosilicate (e.g., 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%), preferably 10 to 20 wt%.

[0049] According to some preferred embodiments, the SiO2 content is 5 to 20 wt% of the polyborosilazane (e.g., 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%), preferably 5 to 15 wt%.

[0050] According to some preferred embodiments, the BN content is 5 to 20 wt% of the polyborosilazane (e.g., 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%), preferably 5 to 15 wt%.

[0051] According to some preferred embodiments, the content of the dispersant is 30-50% of the total mass of polyborosilazane, ZrO2, SiO2 and BN (e.g., it can be 30%, 35%, 38%, 40%, 42%, 45%, 48% or 50%).

[0052] According to some preferred embodiments, the thickness of the coating is 10 to 30 μm (for example, it can be 10 μm, 15 μm, 20 μm, 25 μm or 30 μm).

[0053] The present invention provides, in a second aspect, a method for fabricating the SiBCN ceramic sensor described in the first aspect, suitable for high-temperature aerobic environments, the method comprising:

[0054] S1. Polyborosilicate is first cured, and the cured polyborosilicate powder and polyborosilicate are mixed evenly. The mixed powder is hot-pressed to obtain a sensitive element blank, and an electrode is composited on the sensitive element blank. After first pyrolysis, a SiBCN ceramic sensor is obtained.

[0055] S2. Mix polyborosilazane, ZrO2, SiO2, BN and dispersant to obtain a coating slurry;

[0056] S3. The coating slurry is sprayed onto the surface of the sensitive element of the SiBCN ceramic sensor, and after a second curing and a second pyrolysis, a coating is formed on the surface of the sensitive element to obtain the SiBCN ceramic sensor suitable for high temperature and oxygen environment.

[0057] This invention first involves mixing cured polyborosilazane powder and polyborosilazane, then hot-pressing and forming a composite electrode. Following a first pyrolysis, a SiBCN ceramic sensor is prepared. Next, a coating slurry containing polyborosilazane, ZrO2, SiO2, BN, and a dispersant is sprayed onto the surface of the sensing element of the SiBCN ceramic sensor. After a second curing and pyrolysis, a coating is formed on the surface of the sensing element, resulting in a SiBCN ceramic sensor suitable for high-temperature, oxygen-enriched environments. The method for preparing a SiBCN ceramic sensor suitable for high-temperature, oxygen-enriched environments provided by this invention is simple, efficient, and low-cost. The resulting SiBCN ceramic sensor is small in size, has a wide temperature range (room temperature to 1200℃), and is resistant to oxygen corrosion, making it suitable for high-temperature, oxygen-enriched environments. Furthermore, the use of spraying technology provides a simple, low-cost method for preparing SiBCN coatings on complex component surfaces over large areas, allowing for adjustable coating thickness and high-quality preparation.

[0058] The present invention uses ball milling to mix the cured polyborosilicate powder and polyborosilicate, and uses a planetary ball mill to pulverize the mixture, wherein the ball-to-material ratio is 10:1 and the ball milling time is 6 hours.

[0059] According to some preferred embodiments, in step S1, the amount of polyborosilazane is 10-15% of the mass of the cured polyborosilazane powder (for example, it can be 10%, 11%, 12%, 13%, 14% or 15%).

[0060] According to some preferred embodiments, the first curing is performed by raising the temperature to 300-350°C (e.g., 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1.0°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min or 1.5°C / min) at a heating rate of 0.5-1.5°C / min (e.g., 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1.0°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min or 1.5°C / min) and holding it at that temperature for 2-4 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours).

[0061] The hot pressing is performed at 60–100°C (e.g., 60°C, 70°C, 80°C, 90°C, or 100°C) and 250–350 MPa (e.g., 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, 310 MPa, 320 MPa, 330 MPa, 340 MPa, or 350 MPa) for 30–180 min (e.g., 30 min, 50 min, 60 min, 80 min, 100 min, 120 min, 150 min, 160 min, or 180 min); and / or

[0062] The first pyrolysis is carried out under a protective atmosphere, with the temperature increased to 1100-1300℃ (e.g., 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃) at a heating rate of 1-3℃ / min (e.g., 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ or 3℃ / min) and held at that temperature for 2-6 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours).

[0063] According to some preferred embodiments, the sensitive element blank is cylindrical, preferably with a diameter of 5 mm and a height of 3–10 mm; and / or

[0064] The electrode is a platinum wire electrode, preferably with a diameter of 0.2 to 0.45 mm.

[0065] According to some specific implementation methods, the preparation method of SiBCN ceramic sensor includes the following steps: (1) Pour polyborosilicate (PSNB, liquid) into a polytetrafluoroethylene mold, and then transfer it to a vacuum curing oven for curing to obtain cured polyborosilicate. The curing procedure is as follows: heat to 300-350°C at a heating rate of 0.5-1.5°C / min and keep warm for 2-4 hours; then use a planetary ball mill to pulverize the solid, wherein the ball-to-material ratio is 10:1, the ball milling time is 6 hours, and the solid is passed through a 200-mesh sieve to obtain cured polyborosilicate powder; mix the cured polyborosilicate powder with polyborosilicate and mix evenly in a mortar to obtain mixed powder, wherein the amount of polyborosilicate is 10-15% of the mass of the cured polyborosilicate powder;

[0066] (2) Take 0.05-0.15g of mixed powder and pour it into a stainless steel mold with a diameter of 5mm. Use a hot press to hot press the powder to obtain a cylindrical blank with a height of 3-10m. The hot pressing temperature is 60-100℃, the pressure is 250-350Mpa, and the pressing time is 30-180min.

[0067] (3) Two small holes are drilled on the surface of the cylindrical blank by micromachining, and platinum wire electrodes are inserted. The hole diameter is 0.25-0.5 mm, the hole depth is 2-4 mm, the distance between the two holes is 2-3 mm, and the diameter of the platinum wire is 0.2-0.45 mm. Then, the blank is pyrolyzed in a high-temperature tube furnace to obtain an integrated SiBCN ceramic temperature sensor. The pyrolysis is carried out by heating the blank to 1100-1300℃ at a heating rate of 1-3℃ / min under a protective atmosphere and holding it at that temperature for 2-6 hours. The protective atmosphere is argon atmosphere.

[0068] According to some preferred embodiments, the number of spraying applications is 2 to 5. By controlling the number of spraying applications within this range, the present invention can obtain a coating with excellent antioxidant and high-temperature resistance properties. The inventors have found that if the number of spraying applications is too few, the thickness of the sprayed slurry is too small, which cannot guarantee complete coverage of the sensitive elements, resulting in poor protective effect; if the number of spraying applications is too many, the thickness of the sprayed slurry is too large, and the high-temperature pyrolysis process will cause the coating to crack.

[0069] According to some preferred embodiments, the curing is carried out at a heating rate of 0.5 to 1.5°C / min (e.g., 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1.0°C / min, 1.1°C / min, 1.2°C / min, 1.3°C / min, 1.4°C / min, or 1.5°C / min) to a temperature of 250 to 350°C (e.g., 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, or 350°C), and held at that temperature for 2 to 4 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours).

[0070] According to some preferred embodiments, the second pyrolysis involves heating to 800–1000°C (e.g., 800°C, 850°C, 900°C, 950°C, or 1000°C) at a heating rate not exceeding 1°C / min, and holding at that temperature for 2–6 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours). The heating rate during the pyrolysis process of this invention should not be too fast; if the heating rate is too fast, uneven heating of the coating during pyrolysis can easily lead to cracking.

[0071] According to some specific implementation methods, the preparation method of the coating on the surface of the sensitive element of SiBCN ceramic sensor includes the following steps: (1) Mix polyborosilazane (PSNB), ZrO2 powder, SiO2 powder and BN powder, stir evenly, then add dispersant (xylene), use electromagnetic stirring to mix evenly, stir for 2 to 6 hours to obtain coating slurry, and finally transfer to a spray bottle for later use; wherein, the content of polyborosilazane in the coating slurry is 40 to 80 wt%, the content of ZrO2 is 5 to 20 wt% of polyborosilazane, the content of SiO2 is 5 to 20 wt% of polyborosilazane, the content of BN is 5 to 20 wt% of polyborosilazane, and the powder particle size is 20 nm to 1 μm; the content of xylene is 30% to 50% of the total mass of polyborosilazane, ZrO2, SiO2 and BN. (2) Before spraying, the sensor element is ultrasonically cleaned with deionized water and then dried in an oven. The prepared coating slurry is then evenly sprayed onto the surface of the element and left to stand for a period of time until the xylene completely evaporates. The ultrasonic cleaning time is 15-60 min, the drying temperature is 80-150℃, the drying time is 1-4 h, the number of sprayings is 2-5, and the standing time is 15-60 min. (3) The element coated with the coating slurry is transferred to a vacuum curing oven for curing. The curing process is to raise the temperature to 250-350℃ at a heating rate of 0.5-1.5℃ / min and hold it for 2-4 h. Then, pyrolysis is carried out in a tubular furnace under a flowing argon atmosphere. The pyrolysis process is to raise the temperature to 800-1000℃ at a heating rate of ≤1℃ / min and hold it for 2-6 h to form a coating on the surface of the SiBCN ceramic sensor element.

[0072] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0073] The testing methods for the performance data of the cubic silicon carbide crystals obtained by the embodiments and comparative examples of this invention are as follows:

[0074] Example 1

[0075] S1. Pour polyborosilazane (PSNB) into a polytetrafluoroethylene mold, then transfer it to a vacuum curing oven for curing at 350℃ for 2 hours to obtain a light yellow solid; use a planetary ball mill to pulverize the solid at a ball-to-material ratio of ~10:1 for 6 hours, and pass it through a 200-mesh sieve to obtain solid powder; mix the solid powder and PSNB evenly in a mortar to obtain a mixed powder, wherein the amount of PSNB is 12wt% of the solid powder. 0.1g of the mixed powder was poured into a stainless steel mold with a diameter of 5mm, and the powder was hot-pressed into a small cylinder with a height of 6mm using a hot press. The hot pressing pressure was 350Mpa, the hot pressing time was 60min, and the hot pressing temperature was 100℃. Two small holes were drilled on the surface of the cylinder using micromachining, and platinum wire electrodes were inserted. The diameter of the holes was 0.25mm, the depth of the holes was 2mm, the distance between the two holes was 2mm, and the diameter of the platinum wire was 0.2mm. Then, the mixture was pyrolyzed in a high-temperature tube furnace under a flowing argon atmosphere at a temperature of 1200℃ for 4h at a heating rate of 2℃ / min to obtain the SiBCN ceramic sensor.

[0076] S2. Mix PSNB, ZrO2 powder, SiO2 powder and BN powder evenly by mechanical stirring to obtain a mixture. Then add xylene and stir electromagnetically for 4 hours to obtain a coating slurry. Transfer the slurry to a spray bottle for later use. The content of ZrO2 powder is 10wt% of PSNB, the content of SiO2 powder is 5wt% of PSNB, the content of BN powder is 5wt% of PSNB, the particle size of all powders is 100nm, and the amount of xylene is 40% of the mass of the mixture.

[0077] S3. The sensing element in the SiBCN ceramic sensor is ultrasonically cleaned with deionized water for 30 min, then transferred to an oven and baked at 120℃ for 2 h. Then, the coating slurry is evenly sprayed onto the surface of the sensing element using a spray bottle and left to stand for 30 min. The spraying is repeated twice. The coated sensing element is then transferred to a vacuum curing oven for curing (300℃, 2 h). Finally, it is pyrolyzed in a tube furnace at a temperature of 1000℃ for 4 h with a heating rate of 1℃ / min to obtain a SiBCN ceramic sensor suitable for high-temperature oxygen-containing environments.

[0078] The SiBCN ceramic sensor prepared in this embodiment is suitable for high-temperature and oxygen-rich environments, such as... Figure 1 As shown. A surface morphology image of the coating on the surface of the sensitive element of the SiBCN ceramic sensor prepared in this embodiment, suitable for use in high-temperature oxygen-rich environments. Figure 3 As can be seen, the coating is relatively dense and without obvious cracks, indicating that the prepared coating is of good quality. A cross-sectional view of the coating on the surface of the SiBCN ceramic sensor sensing element prepared in this embodiment, suitable for use in high-temperature and oxygen-rich environments, is shown. Figure 4 The coating is clearly visible, with a thickness of approximately 11.7 μm, and it bonds well to the ceramic substrate without any obvious cracks. Figure 5 As can be seen, the elements in the coating are uniformly dispersed, and the Zr element is only dispersed in the coating, which once again proves that the aforementioned cross-sectional structure is the prepared coating, indicating that the coating preparation was successful.

[0079] Example 2

[0080] The process is basically the same as in Example 1, except that in step S2, the content of ZrO2 powder is 20wt% of PSNB, the content of SiO2 powder is 15wt% of PSNB, the content of BN powder is 15wt% of PSNB, the amount of xylene is 60% of the mass of the mixture, and the number of spraying times is 4.

[0081] Comparative Example 1

[0082] It is basically the same as Example 1, except that the surface of the sensitive element of the SiBCN ceramic sensor is not coated.

[0083] The SiBCN ceramic sensor prepared in this comparative example exhibits vibrational changes in resistance under high-temperature and oxygen-containing environments, leading to the failure of its temperature resistance characteristics and thus rendering the sensor unable to function properly.

[0084] The SiBCN ceramic sensor prepared in this comparative example is suitable for high-temperature and oxygen-rich environments, such as... Figure 1 As shown.

[0085] The SiBCN ceramic sensors provided in Example 1 and Comparative Example 1 were placed in tube furnaces and subjected to temperature resistance tests under air and argon atmospheres, respectively. Figure 6 As shown in the figure (the horizontal axis represents time, and the vertical axes represent resistance (left) and temperature (right), respectively), the resistance change curve of the uncoated SiBCN ceramic sensor in Comparative Example 1 exhibits high stability and smoothness in an oxygen-free environment. A good one-to-one correspondence exists between the resistance value and temperature, which fully demonstrates the excellent temperature measurement potential of SiBCN ceramics in an oxygen-free environment. However, in an oxygen-containing environment, the resistance value becomes unstable and fluctuates significantly at high temperatures. This reflects that the stability of the uncoated SiBCN ceramic sensor in a high-temperature oxygen-containing environment is significantly affected by oxidation.

[0086] like Figure 7 As shown in the figure (the horizontal axis represents temperature and the vertical axis represents resistance), the temperature-resistance curves of the coated SiBCN ceramic sensor in Example 1 showed good repeatability in high-temperature oxygen-free and oxygen-containing environments. This fully demonstrates that the coating plays an effective role in anti-oxidation and significantly improves the stability of the sensor in high-temperature oxygen-containing environments.

[0087] like Figure 8 As shown in the figure (the horizontal axis represents temperature, and the vertical axis represents resistance), the coated SiBCN ceramic sensors in Examples 1 and 2 exhibited stable temperature-resistance characteristics over a wide temperature range from room temperature to 1200°C. This result fully demonstrates that the coated SiBCN ceramic sensor of the present invention is not only suitable for high-temperature oxygen-free environments, but also capable of achieving accurate temperature measurement in high-temperature oxygen-containing environments.

[0088] In summary, the coated SiBCN ceramic sensor prepared by this invention exhibits excellent stability and measurement accuracy in high-temperature and oxygen-containing environments, providing a feasible and effective solution for temperature measurement in high-temperature environments.

[0089] Comparative Example 2

[0090] The process is basically the same as in Example 1, except that in the preparation of the coating slurry, ZrO2 powder, SiO2 powder and BN powder are replaced with TiB2 powder.

[0091] The resistance of the coating prepared in this comparative example is lower than that of the sensitive element of the SiBCN ceramic sensor, resulting in the measured resistance being the coating resistance, which causes the SiBCN ceramic sensor to fail.

[0092] Comparative Example 3

[0093] It is basically the same as Example 1, except that the number of spraying times is 6.

[0094] The thickness of the sprayed slurry in this comparative example was too thick, and the coating cracked after pyrolysis, failing to protect the sensitive elements.

[0095] Comparative Example 4

[0096] It is basically the same as Example 1, except that only BN powder is added during the preparation of the coating slurry, and ZrO2 powder and SiO2 powder are not added.

[0097] like Figure 9 As shown in the figure (the horizontal axis represents time, and the vertical axes represent resistance (left) and temperature (right) respectively), the SiBCN ceramic sensor prepared in this comparative example exhibits a sawtooth-shaped temperature resistance curve at high temperatures with large fluctuations, indicating that the coating does not provide anti-oxidation protection.

[0098] Comparative Example 5

[0099] The process is basically the same as in Example 1, except that only SiO2 powder and BN powder are added during the preparation of the coating slurry, and ZrO2 powder is not added.

[0100] like Figure 10As shown, the coating prepared in this comparative example has poor quality and is not evenly dispersed on the surface of the sensitive element.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A SiBCN ceramic sensor suitable for high-temperature, oxygen-rich environments, characterized in that, The SiBCN ceramic sensor suitable for high-temperature and oxygen-rich environments is a SiBCN ceramic sensor with a coating on the surface of the sensing element. The coating comprises SiBCN, ZrO2, SiO2, and BN; the coating is prepared from a coating slurry comprising polyborosilicate, ZrO2, SiO2, BN, and a dispersant; in the coating slurry, polyborosilicate accounts for 40-80 wt%; the content of ZrO2 is 5-20 wt% of polyborosilicate; the content of SiO2 is 5-20 wt% of polyborosilicate; the content of BN is 5-20 wt% of polyborosilicate; and the content of the dispersant is 30-50% of the total mass of polyborosilicate, ZrO2, SiO2, and BN.

2. The SiBCN ceramic sensor suitable for high-temperature aerobic environments according to claim 1, characterized in that, The thickness of the coating is 10~30 μm.

3. A method for preparing a SiBCN ceramic sensor suitable for high-temperature aerobic environments as described in any one of claims 1-2, characterized in that, The preparation method includes: S1. Polyborosilicate is first cured, and the cured polyborosilicate powder and polyborosilicate are mixed evenly. The mixed powder is hot-pressed to obtain a sensitive element blank, and an electrode is composited on the sensitive element blank. After first pyrolysis, a SiBCN ceramic sensor is obtained. S2. Mix polyborosilazane, ZrO2, SiO2, BN and dispersant to obtain a coating slurry; S3. The coating slurry is sprayed onto the surface of the sensitive element of the SiBCN ceramic sensor, and after a second curing and a second pyrolysis, a coating is formed on the surface of the sensitive element to obtain the SiBCN ceramic sensor suitable for high temperature and oxygen environment.

4. The preparation method according to claim 3, characterized in that, In step S1, the amount of polyborosilazane used is 10-15% of the mass of the cured polyborosilazane powder.

5. The preparation method according to claim 3, characterized in that, The first curing process involves heating the temperature to 300-350°C at a rate of 0.5-1.5°C / min and holding it at that temperature for 2-4 hours. The hot pressing is performed at 60~100℃ and 250~350MPa pressure, with a holding temperature and pressure for 30~180min; and / or The first pyrolysis is carried out under a protective atmosphere, with the temperature increased to 1100-1300℃ at a heating rate of 1-3℃ / min, and held at that temperature for 2-6 hours.

6. The preparation method according to claim 3, characterized in that, The sensitive element blank is cylindrical, with a diameter of 5 mm and a height of 3-10 mm; and / or The electrode is a platinum wire electrode with a diameter of 0.2~0.45mm.

7. The preparation method according to claim 3, characterized in that, The number of spraying operations is 2 to 5.

8. The preparation method according to claim 3, characterized in that, The second curing process involves heating to 250-350°C at a rate of 0.5-1.5°C / min and holding at that temperature for 2-4 hours; and / or The second pyrolysis involves heating to 800~1000℃ at a heating rate of no more than 1℃ / min and holding at that temperature for 2~6 hours.

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