CN115493730A - High-temperature ceramic film strain gauge and preparation method thereof - Google Patents

Abstract

The invention provides a high-temperature ceramic thin-film strain gauge and a preparation method thereof, comprising the following steps: S1, cleaning the high-temperature insulating substrate; S2, using polysilazane as a precursor ceramic solution, directly writing the sensitive layer and the high-temperature insulating substrate on the high-temperature insulating substrate The pattern of the electrode, the pattern of the electrode is located at the end of the pattern of the sensitive layer; then heat crosslinking and high temperature cracking to prepare the sensitive layer and the electrode; S3, use silver paste soldering points to fix the platinum lead on the electrode. The gauge coefficient of the high temperature ceramic film strain gauge is large.

Description

A kind of high-temperature ceramic film strain gauge and preparation method thereof

technical field

The invention relates to a high-temperature ceramic film strain gauge and a preparation method thereof, belonging to the technical field of strain gauge preparation.

Background technique

In modern civil aeroengines, compressor blades work in a high-temperature, high-pressure, and high-rotation working environment for a long time, and are prone to fatigue, wear, deformation and other adverse phenomena. Therefore, the design and material selection of the compressor has become a crucial link in the design and manufacture of the engine. In order to determine the structure of the compressor blade and evaluate the performance of new blade materials, it is necessary to monitor the mechanical behavior of the blade in real time.

At present, thin-film strain gauges are mainly used to test the mechanical behavior of blades. Thin film strain gauges are mainly of the foil type. However, since metals have no band gap and the change in resistance is mainly provided by Poisson's ratio, their resistivity changes only slightly under applied strain, which results in a strain gauge with a small gauge factor, often less than 2 , it is difficult to meet the needs of practical applications.

Contents of the invention

The invention provides a high-temperature ceramic film strain gauge and a preparation method thereof, which can effectively solve the above problems.

The present invention is achieved like this:

A method for preparing a high-temperature ceramic film strain gauge, comprising the following steps:

S1, cleaning the high temperature insulating substrate;

S2, using polysilazane as a precursor ceramic solution, directly write the pattern of the sensitive layer and the electrode on the high-temperature insulating substrate, and the pattern of the electrode is located at the end of the pattern of the sensitive layer; then heat cross-linking and high-temperature cracking, Preparation of sensitive layers and electrodes;

S3, the platinum lead is fixedly connected to the electrode with silver paste soldering point.

As a further improvement, the cleaning is ultrasonic cleaning with absolute ethanol, acetone or deionized water.

As a further improvement, the heat crosslinking is to keep the high-temperature insulating substrate with the pattern of the sensitive layer and the electrode in a nitrogen atmosphere at 150-250° C. for 5-60 minutes.

As a further improvement, the high-temperature cracking is to keep the high-temperature insulating substrate with patterns of the sensitive layer and electrodes in a nitrogen atmosphere at 500-1400° C. for 1-20 hours.

As a further improvement, the step S3 is to connect the platinum lead wires to the electrodes, coat the solder joints with silver paste, and keep warm at 400-600° C. for 0.5-4 hours.

As a further improvement, the thickness of the sensitive layer is 1-3 μm.

As a further improvement, the electrode has a thickness of 1-2 μm.

A high-temperature ceramic film strain gauge, comprising a high-temperature insulating substrate, a sensitive layer, electrodes, silver paste solder joints, and platinum leads; the sensitive layer and electrodes are directly written on the high-temperature insulating layer with polysilazane as a precursor ceramic solution It is formed by heating, cross-linking and pyrolysis at a high temperature after being placed on the substrate, the electrode is located at the end of the sensitive layer, the platinum lead is connected to the electrode, and the silver paste solder spot is welded between the platinum lead and the electrode of the connection.

As a further improvement, the thickness of the sensitive layer is 1-3 μm.

As a further improvement, the electrode has a thickness of 1-2 μm.

The beneficial effects of the present invention are: the present invention uses polysilazane as a precursor ceramic solution, writes directly on the high-temperature insulating substrate, and then heats cross-linking and high-temperature cracking to form a sensitive layer, which has excellent strain characteristics, and its The gauge coefficient reaches more than 40, which is much larger than that of metal strain gauges.

The invention adopts the combination of the precursor ceramic solution and the direct writing technology, which can realize the adjustable film thickness and line width of the sensitive layer written directly, high production efficiency, simple preparation method and high reliability.

The SiCN strain-sensitive layer prepared by using polysilazane as a precursor ceramic solution in the present invention has good oxidation resistance. If the SiCN strain-sensitive layer is covered with an alumina/silicon oxide protective layer, it can work normally below 1000°C.

The surface quality of the sensitive layer prepared by the invention is good.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is a schematic structural diagram of a high temperature ceramic thin film strain gauge provided in Example 1 of the present invention.

Fig. 2 is a flow chart of the preparation of the high-temperature ceramic film strain gauge provided by Example 1 of the present invention.

Fig. 3 is a surface electron microscope image of the sensitive layer of the high-temperature ceramic film strain gauge provided in Example 1 of the present invention.

Fig. 4 is an electron microscopic view of a cut section of the sensitive layer of the high temperature ceramic thin film strain gauge provided in Example 1 of the present invention.

FIG. 5 is a test platform for strain characteristics provided by Embodiment 1 of the present invention.

FIG. 6 is a schematic diagram of testing the strain characteristics provided by Example 1 of the present invention.

Fig. 7 is a static test diagram of the strain characteristics of the high temperature ceramic film strain gauge provided in Example 1 of the present invention.

Fig. 8 is a repeatability test chart of the strain characteristics of the high temperature ceramic thin film strain gauge provided in Example 1 of the present invention.

Fig. 9 is a dynamic test diagram of the strain characteristics of the high temperature ceramic thin film strain gauge provided in Example 1 of the present invention.

Reference signs: high-temperature insulating substrate 1 , sensitive layer 2 , electrode 3 , silver paste solder joint 4 , and platinum lead 5 .

detailed description

In order to make the purpose, 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 in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is some embodiments of the present invention, but not all of them. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

An embodiment of the present invention provides a method for preparing a high-temperature ceramic thin-film strain gauge, comprising the following steps:

S1, select a high-temperature insulating substrate with an application temperature of 300-1700° C., such as an alumina insulating substrate, and clean the high-temperature insulating substrate; the cleaning is ultrasonic cleaning with absolute ethanol, acetone or deionized water.

S2, using polysilazane as a precursor ceramic solution, directly write the pattern of the sensitive layer and the electrode on the high-temperature insulating substrate, and the pattern of the electrode is located at the end of the pattern of the sensitive layer; then heat cross-linking and high-temperature cracking, Preparation of sensitive layer and electrodes. The polysilazane is cross-linked and solidified by heating, and cracked at high temperature to form SiCN inorganic ceramics. The inorganic ceramics are mainly composed of free carbon (conducting phase) and SiCN amorphous phase (insulating phase). When a small deformation occurs at the sensitive layer of the strain gauge, the distance between free carbon as the conductive phase will change, resulting in strain The resistance of the grid varies greatly, so that the strain gauge has a large gauge factor.

Preferably, the heating cross-linking is to keep the high-temperature insulating substrate with the patterns of the sensitive layer and the electrodes in a nitrogen atmosphere at 150-250° C. for 5-60 minutes. The high-temperature pyrolysis is to keep the high-temperature insulating substrate with patterns of the sensitive layer and electrodes in a nitrogen atmosphere at 500-1400° C. for 1-20 hours, and a more preferred temperature is 1100° C.

S3, using silver paste solder joints to fix the platinum lead wires on the electrodes, specifically connect the platinum lead wires to the electrodes, coat the silver paste solder joints at the joints, and keep warm at 400-600° C. for 0.5-4 hours.

In this embodiment, the thickness and pattern of the sensitive layer and the electrodes can be adjusted as required. Preferably, the thickness of the sensitive layer is 1-3 μm, and the thickness of the electrodes is 1-2 μm, so that the gauge coefficient of the strain gauge is greater than 40.

The embodiment of the present invention also provides a high-temperature ceramic film strain gauge, including a high-temperature insulating substrate, a sensitive layer, electrodes, silver paste solder joints, and platinum leads; It is written on the high-temperature insulating substrate and then heated and cross-linked and cracked at high temperature. The electrode is located at the end of the sensitive layer, the platinum lead is connected to the electrode, and the silver paste solder spot is welded to the The connection of the platinum leads to the electrodes.

As a further improvement, the thickness of the sensitive layer is 1-3 μm.

As a further improvement, the electrode has a thickness of 1-2 μm.

Embodiment 1 Preparation of High Temperature Ceramic Thin Film Strain Gauge

Step 1: ultrasonically clean the alumina high-temperature insulating substrate 1 with absolute ethanol, acetone, and deionized water.

Step 2: Use Weissenberg direct writing equipment to directly write the polysilazane (PSN2) precursor ceramic solution on the high-temperature insulating substrate 1 to complete the pattern preparation of the sensitive layer and electrodes.

The motor speed of the Weissenburg direct writing equipment is 200r/min, the distance between the liquid outlet needle tip and the high-temperature insulating substrate is 2μm, and the moving speed of the high-temperature insulating substrate is 5mm/s.

Step 3: Place the high-temperature insulating substrate 1 completed in step 2 on a heating platform, heat it to 180° C. in a nitrogen atmosphere, and keep it warm for 10 minutes.

Step 4: Place the high-temperature insulating substrate 1 completed in step 3 in a tube furnace, and keep it warm at 1100° C. for 4 hours in a nitrogen atmosphere to complete the preparation of the sensitive layer 2 and the electrode 3 .

Step 5: On the electrode 3 of the high-temperature insulating substrate 1 completed in step 4, silver paste solder joints 4 are coated and fixed with platinum leads 5 .

Step 6: Place the high-temperature insulating substrate 1 completed in step 5 in a tube furnace, heat it at 500° C. for 0.5 hours, sinter the silver paste into shape, and complete the preparation of silver paste solder joints 4 and platinum leads 5 .

The schematic diagram of the structure of the prepared high-temperature ceramic thin film strain gauge is shown in Figure 1, and its preparation process is shown in Figure 2.

The electron microscope image of the sensitive layer surface of the high-temperature ceramic film strain gauge is shown in Figure 3, and the electron microscope image of its section cut is shown in Figure 4. It can be seen from Figure 3 that the surface morphology of the sensitive layer is very good, without defects such as cracks, holes, and cracks. It can be seen from Figure 4 that the inside of the sensitive layer is also very dense and has no defects such as holes.

The strain characteristics of the high-temperature ceramic film strain gauge are measured by the deflection method, and the measurement method is shown in Figure 4-5.

The static test is to clamp one end of the strain gauge, and then use a stepping motor to press the other end, the base of the strain gauge is equivalent to a cantilever beam, and then use the data acquisition instrument to collect the resistance of the strain gauge, and give the cantilever beam (base ) The deflection applied to the free end is different, and the strain on the strain gauge on the corresponding substrate is also different. After the strain gauge is strained, the resistance (R) will change, and then it will be repeated 5 times, and then unloaded symmetrically in reverse until it recovers initial state. The magnitude of the applied strain can be calculated by formula (2); the gauge factor (G.F) can be obtained by formula (1). The test results are shown in Figure 7. From the static test results, it can be found that the resistance of the strain gauge changes with the strain, and there will be an obvious step phenomenon. Through the calculation formula of the gauge factor, it can be obtained that the gauge factor of the strain gauge is between 56 and 64, which is much larger than that of the metal strain gauge. And after being strained, the resistance of the strain gauge can maintain stability after a corresponding sudden change.

G.F＝(ΔR/R)/ε..........(1)

l: the length of the cantilever beam

x: distance from the center of the strain gauge to the free end

y: the distance the free end falls

h: thickness of the cantilever beam

The repeatability test is the same test environment as the static test. Several loading/unloading cycles are measured, and the relationship between the resistance change rate and the strain is drawn according to the test data. The coincidence of different curves represents the repeatability of the strain gauge; the slope represents the strain The gage factor of the gauge is shown in Figure 8. The results show that the resistance change rate under the same strain is basically the same, and the strain-resistance change rate curves after multiple tests basically coincide, indicating good repeatability. It can be observed from the strain-resistance change rate curve that the strain characteristic of the strain gauge is nonlinear.

The dynamic test is the same test environment, except that the time period of loading and unloading is shortened, and the strain is unloaded immediately after the strain is applied in one direction, so that the dynamic test figure 9 is obtained. The results show that the maximum and minimum resistances of the strain gauges are basically on the same horizontal line in each dynamic test under the same strain, which shows that the dynamic response of the strain gauges is good.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The preparation method of the high-temperature ceramic film strain gauge is characterized by comprising the following steps of:

s1, cleaning a high-temperature insulating substrate;

s2, directly writing patterns of a sensitive layer and an electrode on a high-temperature insulating substrate by taking polysilazane as a precursor ceramic solution, wherein the pattern of the electrode is positioned at the tail end of the pattern of the sensitive layer; then heating for crosslinking and pyrolysis to prepare a sensitive layer and an electrode;

and S3, fixedly connecting the platinum lead on the electrode by using a silver paste welding point.

2. The method for manufacturing the high-temperature ceramic thin film strain gauge according to claim 1, wherein the cleaning is ultrasonic cleaning with absolute ethyl alcohol, acetone or deionized water.

3. The method for manufacturing a high-temperature ceramic thin film strain gauge according to claim 1, wherein the heating crosslinking is performed by keeping the high-temperature insulating substrate with the patterns of the sensitive layer and the electrodes at 150-250 ℃ for 5-60 min in a nitrogen atmosphere.

4. The method for manufacturing a high-temperature ceramic thin film strain gauge according to claim 1, wherein the pyrolysis is performed by keeping the high-temperature insulating substrate with the patterns of the sensitive layer and the electrode at 500-1400 ℃ for 1-20 h in a nitrogen atmosphere.

5. The method for preparing the high-temperature ceramic thin film strain gauge according to claim 1, wherein the step S3 is to connect a platinum lead wire to an electrode, coat a silver paste welding spot on the connection position, and keep the temperature at 400-600 ℃ for 0.5-4 h.

6. The method for manufacturing a high temperature ceramic thin film strain gauge according to claim 1, wherein the thickness of the sensitive layer is 1 to 3 μm.

7. The method of manufacturing a high temperature ceramic thin film strain gauge according to claim 1, wherein the thickness of the electrode is 1 to 2 μm.

8. A high-temperature ceramic film strain gauge is characterized by comprising a high-temperature insulating substrate, a sensitive layer, an electrode, a silver paste welding spot and a platinum lead; the sensitive layer and the electrode are formed by directly writing a ceramic solution with polysilazane as a precursor on the high-temperature insulating substrate, then performing thermal crosslinking and pyrolysis, the electrode is positioned at the tail end of the sensitive layer, the platinum lead is connected with the electrode, and the silver paste welding spot is welded at the joint of the platinum lead and the electrode.

9. The high temperature ceramic thin film strain gauge of claim 8, wherein the thickness of the sensitive layer is 1-3 μm.

10. The high temperature ceramic thin film strain gauge of claim 8, wherein the thickness of the electrode is 1-2 μm.

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