Precursor ceramic high-temperature sensing material with in-situ antioxidant coating and preparation method thereof

Abstract

The present invention belongs to the technical field of sensor materials, and discloses a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating and a preparation method thereof, including a raw material layer, and a transition layer and an antioxidant coating are successively arranged on the outer side of the raw material layer; the preparation method is as follows: the raw material layer is obtained by the molding and pyrolysis of a polymer precursor; the transition layer is obtained by the temperature gradient constructed by a laser; the antioxidant coating is obtained by an in-situ carbothermal reduction reaction under the action of laser surface heating; the present invention constructs a surface gradient temperature field based on the surface heating effect of the laser, and combines the carbothermal reduction reaction of the precursor ceramic at high temperature to consume the surface free carbon, so as to realize the in-situ preparation of a high-temperature resistant and high-resistance antioxidant coating. The gradient temperature field constructed by the laser can not only realize the in-situ preparation of the antioxidant coating, but also ensure the gradient transition of the components, and can effectively relieve the thermal stress caused by the mismatch of the thermal expansion coefficients.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor materials, and particularly to a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating and a preparation method thereof. Background Art

[0002] Accurately quantifying the energy transfer process of aerodynamic heating is the basis for the design of the thermal protection system of a new generation of high Mach number near-space vehicles, and is also a key technology for further optimizing the structural efficiency of near-space vehicles and improving flight performance. Among them, the measurement of temperature and heat flux during high-speed flight has always been the focus of attention in the field of near-space vehicles. However, the harsh flight environment poses severe challenges to the direct measurement of parameters such as temperature and heat flux in the thermal protection system.

[0003] At present, the testing of parameters such as surface temperature and heat flux of the thermal protection system of near-space vehicles is mainly achieved through thermocouples. Its disadvantages are high cost, large volume, insufficient testing accuracy and stability, poor compatibility with thermal protection materials, and difficult assembly. The development of microelectromechanical systems (MEMS) provides the possibility of embedding micro sensors in the thermal protection system. However, the testing capabilities of existing MEMS sensors generally do not exceed 500°C.

[0004] The precursor-derived ceramic (PDC) technology is a method for preparing inorganic ceramics by high-temperature pyrolysis of organic polymers. Due to its excellent formability, high-temperature stability, oxidation / corrosion resistance, and high-temperature semiconductor properties, it has become one of the most promising material systems for solving the temperature sensing problem in harsh high-temperature environments in the future. Research shows that the precursor-derived SiCNO ceramic still has good semiconductor properties at 1300°C, which is much higher than any known material at present. Under an inert atmosphere, the highest operating temperature of the known PDC temperature sensor reaches 1800°C; but under aerobic conditions, the highest operating temperature is only 800°C, and the oxidation of the PDC sensitive material will significantly increase its resistance, thereby affecting the accuracy of the temperature sensor. Summary of the Invention

[0005] The present invention aims to provide a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating and a preparation method thereof. Based on the surface heating effect of a laser, a surface gradient temperature field is constructed, and the surface free carbon is consumed by the carbothermal reduction reaction of the precursor ceramic at high temperature to realize the in-situ preparation of a high-temperature resistant and high-resistance antioxidant coating. The gradient temperature field constructed by the laser can not only realize the in-situ preparation of the antioxidant coating, but also ensure the gradient transition of the composition, which can effectively relieve the thermal stress caused by the mismatch of thermal expansion coefficients.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Precursor ceramic high-temperature sensing material with in-situ antioxidant coating, including a raw material layer, and a transition layer and an antioxidant coating are sequentially provided on the outer side of the raw material layer.

[0008] Further, the raw material layer is a precursor conversion silicon-based ceramic that can undergo a carbothermal reduction reaction at high temperature.

[0009] Further, the precursor conversion silicon-based ceramic is one of SiCN, SiOC, SiBCN, and SiBOC.

[0010] Further, the thickness of the raw material layer is 0.1 mm to 3 mm, the thickness of the transition layer is 1 μm to 50 μm, and the thickness of the antioxidant coating is 1 μm to 100 μm.

[0011] The preparation method of the above-mentioned precursor ceramic high-temperature sensing material with in-situ antioxidant coating is as follows: the raw material layer is obtained by the molding and pyrolysis of a polymer precursor; the transition layer is obtained by the temperature gradient constructed by laser; the antioxidant coating is obtained by the in-situ carbothermal reduction reaction under the action of laser surface heating.

[0012] The preparation method of the above-mentioned precursor ceramic high-temperature sensing material with in-situ antioxidant coating, the specific steps are as follows:

[0013] S1. Preparation of raw materials: Select a precursor ceramic with excellent formability for molding, and after molding, heat it to 1000 °C to 1600 °C in a vacuum or inert environment and keep it warm for 4 h, then cool it to room temperature to obtain the required raw materials for the high-temperature sensor, and then carry out pretreatment;

[0014] S2. Preparation of the transition layer: In an inert gas environment, irradiate the surface of the raw material with continuous or pulsed laser. The surface heating effect of the laser realizes the construction of a continuous temperature gradient. The material reacts to different degrees with the change of temperature. The continuous temperature gradient causes a continuous gradient of surface composition, and the transition layer is prepared;

[0015] S3. Preparation of the antioxidant coating: In an inert gas environment, irradiate the surface of the raw material with continuous or pulsed laser. The surface heating effect of the laser makes the surface temperature of the material the highest. The occurrence of the carbothermal reduction reaction consumes the free carbon in the material. After repeated impregnation and laser heating, a dense antioxidant coating is prepared.

[0016] Further, in S1, the molding method is one of powder molding, liquid molding, and photocuring molding.

[0017] Further, in S1, the pretreatment includes the following processes: grinding the raw material layer with metallographic sandpapers of 200 mesh, 500 mesh, and 1000 mesh respectively, then ultrasonically cleaning with acetone for 5 min to 15 min and ultrasonically cleaning with alcohol for 5 min to 15 min, and drying at 100 °C to 150 °C for 20 min to 60 min.

[0018] Further, in S2, when preparing the transition layer, a continuous laser beam is used for laser irradiation of the raw material, and the laser power is 40 W to 200 W; a pulsed laser beam is used for laser irradiation of the raw material, and the laser power is 0.01 W to 10 W; thus, a temperature gradient is constructed to obtain the transition layer.

[0019] Further, in S3, when preparing the antioxidant coating, a continuous laser beam is used for laser irradiation of the raw material, and the laser power is 40 W to 200 W; a pulsed laser beam is used for laser irradiation of the raw material, and the laser power is 0.01 W to 10 W; thus, an in-situ reaction occurs in the raw material to obtain the antioxidant coating.

[0020] The beneficial effects of the technical solution are as follows:

[0021] 1. The present invention provides a precursor ceramic high-temperature sensing material containing an in-situ antioxidant coating and a preparation method thereof. Through the continuous temperature gradient generated by laser irradiation, a continuous composition gradient of the antioxidant coating is achieved. The obtained antioxidant coating has excellent high-temperature stability and high-resistance characteristics, and the continuous gradient transition layer can effectively relieve the thermal stress caused by the mismatch of thermal expansion coefficients, which can greatly expand the use temperature of the precursor ceramic high-temperature sensing material under high-temperature aerobic conditions;

[0022] 2. The preparation process of the precursor ceramic high-temperature sensing material containing an in-situ antioxidant coating provided by the present invention is simple, applicable to all precursor ceramics that can undergo carbothermal reduction reactions, and the prepared material has good stability and is easy to be widely promoted and applied. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of a precursor ceramic high-temperature sensing material containing an in-situ antioxidant coating according to the present invention;

[0024] Figure 2 is a schematic diagram of the preparation process of a precursor ceramic high-temperature sensing material containing an in-situ antioxidant coating according to the present invention;

[0025] The names of the corresponding marks in the drawings are as follows:

[0026] Raw material layer 1, transition layer 2, antioxidant coating 3, high-temperature electrode 4, vacuum environment 5, laser irradiation source 6. Detailed Embodiments

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments:

[0028] As Figure 1 shown, a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating includes a raw material layer 1, and a transition layer 2 and an antioxidant coating 3 are sequentially arranged on the outer side of the raw material layer 1; the raw material layer 1 is ceramic SiCN with a thickness of 0.1 mm to 3 mm; the thickness of the transition layer 2 is 0.5 μm to 2 μm; the thickness of the antioxidant coating 3 is 2 μm to 3 μm.

[0029] As Figure 2 shown, a preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating, the raw material layer 1 is prepared by the molding and pyrolysis of a polymer; the transition layer 2 is prepared by the temperature gradient constructed by a laser; the antioxidant coating 3 is obtained by an in-situ reaction under the action of a laser.

[0030] The specific steps are as follows:

[0031] S1. Preparation and pretreatment of the raw material layer 1: The precursor ceramic SiCN is heated to 1200 °C to 1600 °C in a vacuum environment 5 and kept warm for 4 h, then cooled to room temperature, and then ground into powder and pressed into tablets, and the raw material layer 1 is obtained by repeated impregnation and pyrolysis, and then pretreatment is carried out; among them, the pretreatment includes the following processes: the raw material layer 1 is ground with metallographic sandpapers with mesh numbers of 2000#, 3000#, and 5000# for 0.5 h to 2 h respectively, and then ultrasonically cleaned with acetone for 5 min to 15 min, ultrasonically cleaned with alcohol for 5 min to 15 min, and ultrasonically cleaned with water for 5 min to 15 min, and dried at 100 °C to 150 °C for 20 min to 60 min;

[0032] S2. Preparation of the transition layer 2: The raw material is irradiated by a laser irradiation source 6 in an inert gas environment, and the transition layer 2 is prepared by the temperature gradient constructed by the laser; among them, the conditions for laser irradiation of the raw material are: a continuous laser beam is used, and the laser power is 40 W to 200 W;

[0033] S3. Preparation of the antioxidant coating 3: The surface of the raw material is irradiated by continuous or pulsed laser in an inert gas environment, and the surface heating effect of the laser makes the surface temperature of the material the highest, and the free carbon in the material is consumed by the occurrence of the carbothermal reduction reaction. After repeated impregnation and laser heating, a dense antioxidant coating 3 is obtained; among them, the conditions for laser irradiation of the raw material are: a continuous laser beam is used, and the laser power is 40 W to 200 W.

[0034] The above are only embodiments of the present invention, and common general technical solutions or characteristics in the solutions are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A precursor ceramic high-temperature sensing material with an in-situ antioxidant coating, characterized in that, it includes a raw material layer, and a transition layer and an antioxidant coating are sequentially arranged on the outer side of the raw material layer; wherein, the raw material layer is a precursor conversion silicon-based ceramic that undergoes a carbothermal reduction reaction at high temperature, and the precursor conversion silicon-based ceramic is one of SiCN, SiOC, SiBCN, and SiBOC; The preparation method of the transition layer is: continuously or pulse laser irradiates the surface of the raw material, and the surface heating effect of the laser realizes the construction of a continuous temperature gradient. The material reacts to varying degrees with the change of temperature, and the continuous temperature gradient causes a continuous gradient of surface composition to obtain the transition layer; The preparation method of the antioxidant coating is: continuously or pulse laser irradiates the surface of the raw material, and the surface heating effect of the laser makes the surface temperature of the material the highest. The occurrence of the carbothermal reduction reaction consumes the free carbon in the material, and the antioxidant coating is obtained after repeated impregnation and laser heating.

2. A precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 1, characterized in that, the thickness of the raw material layer is 0.1 mm to 3 mm, the thickness of the transition layer is 1 μm to 50 μm, and the thickness of the antioxidant coating is 1 μm to 100 μm.

3. A preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 2, characterized in that, the specific steps are: S1. Preparation of raw materials: Select a precursor ceramic with excellent formability for forming, and after forming, heat it to 1000 °C to 1600 °C in a vacuum or inert environment and keep it warm for 4 h, then cool it to room temperature to obtain the raw materials required for the high-temperature sensor, and then perform pretreatment; S2. Preparation of the transition layer: Continuously or pulse laser irradiates the surface of the raw material in an inert gas environment, and the surface heating effect of the laser realizes the construction of a continuous temperature gradient. The material reacts to varying degrees with the change of temperature, and the continuous temperature gradient causes a continuous gradient of surface composition to prepare the transition layer; S3. Preparation of the antioxidant coating: Continuously or pulse laser irradiates the surface of the raw material in an inert gas environment, and the surface heating effect of the laser makes the surface temperature of the material the highest. The occurrence of the carbothermal reduction reaction consumes the free carbon in the material, and after repeated impregnation and laser heating, a dense antioxidant coating is prepared.

4. A preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 3, in S1, the forming method is one of powder forming and liquid forming.

5. A preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 3, in S1, the pretreatment includes the following process: Grind the raw material layer with metallographic sandpapers with mesh numbers of 200#, 500#, and 1000# respectively, then ultrasonically clean it with acetone for 5 min to 15 min and ultrasonically clean it with alcohol for 5 min to 15 min, and dry it at 100 °C to 150 °C for 20 min to 60 min.

6. The preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 3. In S2, when preparing the transition layer, a continuous laser beam is used for laser irradiation of the raw material, and the laser power is 40 W to 200 W; a pulsed laser beam is used for laser irradiation of the raw material, and the laser power is 0.01 W to 10 W; thus, a temperature gradient is constructed to obtain the transition layer.

7. The preparation method of a precursor ceramic high-temperature sensing material with an in-situ antioxidant coating according to claim 3. In S3, when preparing the antioxidant coating, a continuous laser beam is used for laser irradiation of the raw material, and the laser power is 40 W to 200 W; a pulsed laser beam is used for laser irradiation of the raw material, and the laser power is 0.01 W to 10 W; thus, an in-situ reaction occurs in the raw material to obtain the antioxidant coating.

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