An insulating layer for a C / SiC composite material substrate thin film sensor and a preparation method thereof

Abstract

The present invention belongs to the field of thin film sensor design and production technology, specifically an insulating layer for a C / SiC composite material substrate thin film sensor and a preparation method thereof. It utilizes the characteristic that similar chemical bonds can form bond transitions: a SiO2 thin film layer is used as a filling layer, and a Si3N4 thin film layer is used as a buffer layer. After being sequentially arranged on a C / SiC composite material substrate, the three have the same Si element and similar chemical bonds exist, so that bond transitions can be formed at their respective interfaces, and the entire insulating layer has good adhesion. The barrier layer adopts an Al2O3 thin film layer, and the insulating layer is prepared with Al2O3 as the main component material and is arranged on the barrier layer. Similarly, the insulating layer material and Al2O3 have similar chemical compositions, forming chemical bonds at the interface, thereby improving the adhesion between the insulating layer and the Al2O3 barrier layer. This achieves the improvement of the stability and reliability of the thin film sensor in harsh environments of high temperature and high pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film sensor design and production, and particularly relates to an insulating layer for a C / SiC composite material substrate thin film sensor and a preparation method thereof. Background Art

[0002] New-generation aircraft engines are continuously developing towards high thrust-to-weight ratios, high maneuverability, and long lifespans. As a result, internal operating temperatures within aircraft engines are rising, and the operating temperatures of high-temperature components such as turbine blades and shafts are approaching the limits of high-temperature alloys. To ensure safe and reliable operation of hot-end components in high-temperature environments, a growing number of aircraft engine hot-end components are being manufactured using high-temperature resistant materials, such as carbon fiber-reinforced silicon carbide ceramic-based composites (C / SiC), silicon carbide fiber-reinforced silicon carbide composites (SiC / SiC), and high-temperature ceramics. C / SiC composites, with their high hardness, low density, oxidation resistance, excellent thermal shock resistance, and high operating temperature, are widely used in the manufacture of hot-end components in the aerospace industry. Due to the large temperature gradients present on the surfaces of these hot-end components, they are subject to complex strain loads during rapid temperature increases, making them susceptible to ablation or fracture, severely impacting aircraft performance and safety. Therefore, the development of stable and reliable temperature and strain measurement sensors suitable for the harsh operating environments of aerospace, such as high temperature, high pressure, and strong vibration, is of great significance.

[0003] Using vacuum coating technologies such as magnetron sputtering or electron beam evaporation, sensitive thin films are deposited directly on the surface of the component being measured, forming temperature and strain sensors. This approach does not damage the component's mechanical structure and does not require adhesives, thus avoiding the errors and limitations associated with high-temperature testing. Thin-film sensors are only micrometers thick, minimally disturbing the airflow field on the component surface and adding minimal mass. These characteristics enable thin-film sensors to achieve faster response, higher accuracy, and greater reliability, making them suitable for use in harsh environments such as high temperatures.

[0004] To ensure proper operation of thin-film sensors, good electrical insulation must be maintained between the sensor and the substrate. However, C / SiC composites have numerous surface defects, such as millimeter- and micron-scale depressions or penetrating holes. Directly depositing insulating films on these surfaces can easily lead to film discontinuities, ultimately resulting in sensor performance degradation or even failure.

[0005] A Chinese patent document with authorization publication number CN109778131B discloses a method for preparing a thin-film thermocouple on the surface of a C / SiC composite material. This invention patent prepares a Ni-Cr-ZrO2 composite transition layer on the surface of the C / SiC composite material by electroplating, and then prepares a SiO2 insulating film, a NiCr thermode, a NiSi thermode, and a SiO2 protective film on the surface by DC pulsed magnetron sputtering. Although this method can provide a continuous and smooth attachment surface for the thin-film thermocouple, the composite transition layer and SiO2 insulating film still have shortcomings: the Ni-Cr-ZrO2 composite transition layer prepared by electroplating cannot fill the holes on the surface of the C / SiC composite material, and the film still has discontinuities. In addition, SiO2 has poor thermal shock resistance and cracks when the temperature changes drastically, causing the insulating layer to fail. Summary of the Invention

[0006] In response to the above-mentioned deficiencies in the prior art, the present invention proposes an insulating layer for a C / SiC composite material substrate thin film sensor and a preparation method thereof. Through this preparation method, a continuous insulating layer thin film can be deposited on the surface of the C / SiC composite material, effectively improving the stability and reliability of the thin film sensor in harsh environments of high temperature and high pressure.

[0007] The technical solution adopted in the present invention is as follows:

[0008] An insulating layer for a C / SiC composite material substrate thin film sensor, wherein the insulating layer is prepared on a C / SiC composite material substrate and comprises a filling layer, a buffer layer, a barrier layer, and an insulating layer arranged in sequence from bottom to top; the filling layer is a SiO2 thin film layer, the buffer layer is a Si3N4 thin film layer, the barrier layer is an Al2O3 thin film layer, and the insulating layer is prepared with Al2O3 as the main material.

[0009] Furthermore, the SiO2 thin film layer is prepared by a sol-gel method.

[0010] Furthermore, the Al2O3 thin film layer is prepared by using PEALD deposition technology.

[0011] Furthermore, the insulating layer is preferably a YSZ / Al2O3 thin film layer.

[0012] Furthermore, the thickness of the SiO2 thin film layer is 20-500 nm, the thickness of the Si3N4 thin film layer is 2-6 μm, the thickness of the Al2O3 thin film layer is 100-200 nm, and the thickness of the insulating layer is 1-4 μm.

[0013] A C / SiC composite material substrate thin film sensor insulating layer, the preparation method of which comprises the following steps:

[0014] Step 1: Treat the surface of the C / SiC composite material substrate to make it clean and dry;

[0015] Step 2: preparing a SiO2 thin film on the C / SiC composite material substrate treated in step 1 by a sol-gel method;

[0016] Step 3: Using PECVD deposition technology or magnetron sputtering technology to prepare a Si3N4 thin film layer on the upper surface of the SiO2 thin film layer;

[0017] Step 4: Prepare an Al2O3 thin film layer on the Si3N4 thin film layer using PEALD deposition technology;

[0018] Step 5: Prepare an insulating layer on the Al2O3 thin film layer using magnetron sputtering technology or electron beam evaporation technology.

[0019] Furthermore, the detailed process of step 1 is as follows:

[0020] The C / SiC composite material was ultrasonically cleaned in acetone, ethanol and deionized water for 10 min in sequence and then dried in a clean room.

[0021] Furthermore, the detailed process of step 2 is as follows:

[0022] The C / SiC composite material substrate is immersed in silica sol with a particle size of 10 to 100 nm, and is pulled at a speed of 10 to 90 mm / min, and repeated 5 to 20 times to obtain a SiO2 film layer with a thickness of 20 to 500 nm.

[0023] Furthermore, the detailed process of step 3 is as follows:

[0024] The PECVD equipment was evacuated to below 0.02 torr, and then 5-10% SiH4 / Ar and N2 were introduced, wherein the SiH4 / Ar gas flow rate was 100-200 sccm and the N2 gas flow rate was 20-80 sccm; during the preparation, the PECVD equipment power was 50-100 W; or the magnetron sputtering equipment was evacuated to 8.0×10 -4 Below Pa, N2 and Ar are used as reaction gases, with a gas flow ratio of N2:Ar = 1:2 to 1:7, a gas pressure of 0.4p to 1.2pa, and a sputtering power of 150W to 300W. A Si3N4 thin film layer with a thickness of 2 to 6μm is obtained.

[0025] Furthermore, the detailed process of step 4 is as follows:

[0026] The PEALD equipment was evacuated to below 0.15 torr, the reaction chamber temperature was set to 100-200°C, trimethylaluminum (TMA) and water vapor (H2O) were introduced as reaction gases, and an Al2O3 film of 100-200 nm was generated by reaction with the assistance of plasma.

[0027] Furthermore, the detailed process of step 5 is as follows:

[0028] 5.1. Pump the sputtering chamber to a vacuum degree of 8×10 -4 Pa below, using a YZr target embedded with Al flakes as the sputtering target, a mixed gas of O2 and Ar as the sputtering gas, the flow ratio of O2 and Ar is 1:9 to 2:8, and the gas pressure is 0.4 to 1.2 Pa, and a reactive sputtering method is used to deposit the YSZ / Al2O3 thin film layer;

[0029] 5.2. Place the structure obtained in step 5.1 under vacuum with a degree of less than 8.0×10 -4 Annealing treatment is carried out in a vacuum annealing furnace of Pa, the annealing temperature is 600-1000℃, the annealing holding time is 2-5h, and the thickness of the prepared YSZ / Al2O3 insulating layer is 1-4μm;

[0030] Furthermore, in step 5.1, a YZr target with a purity of ≥99wt% and an Al2O3 target with a purity of ≥99% can be alternately deposited to deposit a YSZ / Al2O3 thin film layer by reactive sputtering; or an Al2O3-YSZ evaporation material with a YSZ content of 6 to 10wt.% can be used to deposit a YSZ / Al2O3 layer by electron beam evaporation.

[0031] The present invention provides a C / SiC composite substrate thin film sensor insulating layer, which utilizes the characteristic that similar chemical bonds can form bond transitions: a SiO2 film layer is used as a filling layer and a Si3N4 film layer is used as a buffer layer. After being sequentially arranged on a C / SiC composite substrate, the three have the same Si element and have similar chemical bonds, so that bond transitions can be formed at their respective interfaces, so that the entire insulating layer has good adhesion. The barrier layer adopts an Al2O3 film layer, and the insulating layer is selected to be prepared with Al2O3 as the main component material and is arranged on top of the barrier layer. The insulating layer material and the Al2O3 chemical composition are similar, forming chemical bonds at the interface, improving the adhesion between the insulating layer and the Al2O3 barrier layer. On this basis, the Al2O3 film layer is prepared on the Si3N4 film layer using PEALD deposition technology. Since the Al2O3 film layer prepared by the PEALD deposition technology has the characteristics of good coverage, density, and thin thickness, it is arranged by the dense Al2O3 film layer, which can effectively block the expansion of microcracks generated in the buffer layer and the insulating layer when the temperature changes drastically. At the same time, the thickness of the Al2O3 film layer is controlled within the range of 100-200nm to limit the growth of aluminum oxide grains, making the Al2O3 film layer microcrystalline. This effectively blocks the connection between the high-angle grain boundaries generated after the buffer layer and the insulating layer crystallize, thereby improving the high-temperature insulation performance of the insulating layer.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The SiO2 thin film layer of the present invention is produced by the sol-gel method, which uses the fluidity of the sol to penetrate into the substrate, effectively filling the millimeter and micron-scale depressions or penetrating holes on the surface of the C / SiC composite material, reducing the surface roughness, and laying the foundation for the continuity of subsequent film layers.

[0034] 2) The Si3N4 thin film layer of the present invention has good thermal shock resistance and high-temperature stability, and can maintain high mechanical strength when the temperature changes drastically.

[0035] 3) The present invention adopts PEALD technology to deposit Al2O3 thin film layer, which prevents the micro cracks generated inside the buffer layer and the insulating layer film and the connection of large-angle grain boundaries under high temperature and drastic temperature changes, thereby preventing the problem of a sharp decline in insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of the insulating layer of a thin film sensor based on a C / SiC composite material substrate provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0038] Example

[0039] like Figure 1 As shown, this embodiment provides an insulating layer of a thin film sensor based on a C / SiC composite material substrate. The insulating layer is prepared on a C / SiC composite material substrate and includes a filling layer, a buffer layer, a barrier layer, and an insulating layer arranged in sequence from bottom to top; the filling layer is a SiO2 thin film layer, the buffer layer is a Si3N4 thin film layer, the barrier layer is an Al2O3 thin film layer, and the insulating layer is YSZ / Al2O3.

[0040] The method for preparing the insulating layer of the thin film sensor based on the C / SiC composite material substrate of the present invention comprises the following steps:

[0041] Step 1. Surface treatment of the C / SiC composite substrate: Surface treatment of the C / SiC composite substrate: ultrasonically clean the substrate sample in acetone, ethanol, and deionized water for 10 minutes each to remove organic pollutants and dust particles on the substrate surface, and then blow dry with a nitrogen gun to dry out residual moisture; keep it clean and dry.

[0042] Step 2: Immerse the C / SiC composite material substrate treated in step 1 in silica sol and pull it at a speed of 20 mm / min. After each pulling, place it in an oven at 200°C for drying. Repeat this 5 times to obtain a 150 nm thick SiO2 film.

[0043] Step 3: Place the composite substrate obtained in step 2 into the PECVD reaction chamber, and deposit a 4 μm thick Si3N4 thin film layer on the SiO2 film. The deposition conditions are: set the corresponding gas source and flow rate to 5% SiH4 / Ar:N2=120:40sccm, the RF power to 60W, and the deposition time to 70min.

[0044] Step 4: Place the composite substrate obtained in step 3 into the PEALD reaction chamber and deposit a 100 nm thick Al2O3 film on the SiO2 film layer. The deposition conditions are: the equipment vacuum degree is 0.15 torr, the reaction temperature is 150°C, TMA and H2O are introduced in sequence, and the reaction is repeated for 1000 cycles.

[0045] Step 5: Preparation of YSZ / Al2O3 film: Place the composite substrate obtained in step 4 in a vacuum chamber with a backside vacuum of 8×10 - 4Pa vacuum chamber, with a YSZ target with an Al sheet attached as the target, a mixture of O2 and Ar as the sputtering gas, the flow ratio of O2 to Ar is 1:24, the sputtering pressure is 0.4Pa, and a YSZ / Al2O3 film with a thickness of about 2μm is deposited by reactive sputtering method; then it is placed in a vacuum chamber with a vacuum degree of 8.0×10 -4 Annealing was performed in a vacuum annealing furnace at 800°C for 2 hours to obtain a 2μm thick YSZ / Al2O3 thin film layer, thereby obtaining a C / SiC composite material substrate thin film sensor insulation layer structure.

[0046] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An insulating layer for a C / SiC composite material substrate thin film sensor, characterized in that: The invention comprises a filling layer, a buffer layer, a barrier layer and an insulating layer which are sequentially arranged on a C / SiC composite material substrate from bottom to top; the filling layer is a SiO2 thin film layer, the buffer layer is a Si3N4 thin film layer; the barrier layer is an Al2O3 thin film layer with a thickness of 100 to 200 nm, which is prepared by PEALD deposition technology; and the insulating layer is prepared with Al2O3 as the main material.

2. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 1, characterized in that: The SiO2 thin film layer is prepared by a sol-gel method.

3. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 1, characterized in that: The insulating layer prepared with Al2O3 as the main material is a YSZ / Al2O3 thin film layer.

4. The insulating layer for a C / SiC composite material substrate thin film sensor according to any one of claims 1 to 3, characterized in that: The thickness of the SiO2 film layer is 20-500 nm, the thickness of the Si3N4 film layer is 2-6 μm, and the thickness of the insulating layer prepared with Al2O3 as the main material is 1-4 μm.

5. A C / SiC composite material substrate thin film sensor insulating layer, the preparation method of which comprises the following steps: Step 1: Treat the surface of the C / SiC composite material substrate to make it clean and dry; Step 2: preparing a SiO2 thin film on the C / SiC composite material substrate treated in step 1 by a sol-gel method; Step 3: Using PECVD deposition technology or magnetron sputtering technology to prepare a Si3N4 thin film layer on the upper surface of the SiO2 thin film layer; Step 4: Prepare an Al2O3 thin film layer on the Si3N4 thin film layer using PEALD deposition technology, specifically: evacuate the PEALD equipment to below 0.15 torr, set the reaction chamber temperature to 100-200°C, introduce trimethylaluminum (TMA) and water vapor (H2O) as reaction gases, and react to form an Al2O3 thin film with the assistance of plasma; Step 5: Using magnetron sputtering technology or electron beam evaporation technology, prepare an insulating layer on the Al2O3 thin film layer; the specific operation is as follows: 5.

1. Pump the sputtering chamber to a vacuum degree of 8×10 -4 Pa below, using a YZr target embedded with Al flakes as the sputtering target, a mixed gas of O2 and Ar as the sputtering gas, the flow ratio of O2 and Ar is 1:9 to 2:8, and the gas pressure is 0.4 to 1.2 Pa, and a reactive sputtering method is used to deposit the YSZ / Al2O3 thin film layer; 5.

2. Place the structure obtained in step 5.1 under vacuum with a degree of less than 8.0×10 -4 The YSZ / Al2O3 insulating layer is prepared by annealing in a vacuum annealing furnace at a temperature of 600-1000°C and an annealing holding time of 2-5h.

6. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 5, characterized in that: The detailed process of step 1 is as follows: The C / SiC composite material was ultrasonically cleaned in acetone, ethanol and deionized water for 10 min in sequence and then dried in a clean room.

7. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 5, characterized in that: The detailed process of step 2 is as follows: The C / SiC composite material substrate is immersed in silica sol with a particle size of 10 to 100 nm, and is pulled at a speed of 10 to 90 mm / min, and repeated 5 to 20 times to obtain a SiO2 thin film layer.

8. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 5, characterized in that: The detailed process of step 3 is as follows: The PECVD equipment was evacuated to below 0.02 torr, and then 5-10% SiH4 / Ar and N2 were introduced, wherein the SiH4 / Ar gas flow rate was 100-200 sccm and the N2 gas flow rate was 20-80 sccm; during the preparation, the PECVD equipment power was 50-100 W; or the magnetron sputtering equipment was evacuated to 8.0×10 -4 Below Pa, N2 and Ar are used as reaction gases, the gas flow ratio is N2:Ar=1:2~1:7, the gas pressure is 0.4~1.2Pa, and the sputtering power is 150W~300W; a Si3N4 thin film layer with a thickness of 2~6μm is obtained.

9. The insulating layer for a C / SiC composite material substrate thin film sensor according to claim 5, characterized in that: In step 5.1, a YZr target with a purity of ≥99wt% and an Al2O3 target with a purity of ≥99% may be alternately deposited to deposit a YSZ / Al2O3 thin film layer by reactive sputtering; or an Al2O3-YSZ evaporation material with a YSZ content of 6-10wt.% may be used to deposit a YSZ / Al2O3 layer by electron beam evaporation.

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