Method for testing micro-area elastic modulus of silicon carbide ceramic matrix composite material

Abstract

The present application relates to a kind of silicon carbide ceramic matrix composite micro area elastic modulus testing method, comprising: (1) the polishing surface topography of silicon carbide ceramic matrix composite sample is scanned by starting AFM contact mode, and the high-resolution topography image of sample is obtained, then force / curve mode is started to AFM, and force / curve determination is carried out to silicon carbide ceramic matrix composite sample;(2) according to the micro area structure characteristics and elastic deformation mechanism of silicon carbide ceramic matrix composite sample, establish probe / test surface mathematical contact model, and the deflection-displacement curve is fitted by Image Analysis software calculation unit, and the elastic deformation process force-displacement curve of micro area structure is obtained;The micro area structure includes fiber, base phase body and interface phase;(3) the curve slope of the elastic deformation process force-displacement curve of micro area structure is calculated to obtain elastic modulus.

Description

Technical Field

[0001] This invention relates to a method for testing the elastic modulus of micro-regions in ceramic matrix composites, specifically a method for testing the elastic modulus of micro-regions (fibers, interfaces, and matrix) in silicon carbide ceramic matrix composites using atomic force microscopy (AFM). Background Technology

[0002] Ceramic matrix composites possess outstanding high-temperature mechanical properties and corrosion resistance, making them highly promising for applications in aerospace hot-end structures. These composites consist of fibers, a matrix, and an interfacial phase. This structural composite effect endows the material with non-brittle fracture characteristics distinct from single-phase ceramics, thus ensuring high damage tolerance and long service life. Elastic modulus is a crucial indicator for evaluating the mechanical properties of ceramic matrix composites, primarily obtained through tensile, bending, shear, and compression tests. However, the elastic modulus obtained through conventional mechanical testing methods is a comprehensive reflection of the mechanical properties of each structural unit (fiber, matrix, and interfacial phase), failing to reflect the influence of individual micro-region structures on the material's performance.

[0003] Therefore, in order to further optimize material properties, it is necessary to measure the mechanical properties of the microscale structure of the material and compare them with the macroscopic properties to guide the material structure design. Atomic force microscopy (AFM) is an effective method for measuring the mechanical properties of materials at the microscale. The principle is to obtain the deflection-displacement spectrum curve by preloading the microscale surface of the material with a rigid probe (Si or diamond material) at the nanoscale, and then calculate the elastic modulus of the microscale region of the material according to a certain probe / material contact model and mathematical fitting method. AFM technology has been widely used in the fields of biology and nanomaterials. For example, Hansen et al. used AFM technology to measure the elastic modulus of microbial cell membranes and found that the surface nanostructure has an important influence on the elastic modulus of cell membranes (Hansen JC, et al. Effect of surface nanoscale topography on elastic modulus of individual osteoblastic cells as determined by atomic force microscopy. J Bioomech. 2007; 40(13):2865-2871.). Chen Ailian et al. used AFM technology to study the effect of SiO2 layer thickness on the elastic modulus of polystyrene-silica (PS-SiO2) hybrid particles. They found that when the SiO2 layer thickness increased from 11 nm to 16 nm, the elastic modulus of the hybrid particles increased from 4.4 ± 0.5 GPa to 10.2 ± 1.1 GPa (Chen Ailian, et al. Effect of shell thickness on compressive elastic modulus of core-shell structured PS-SiO2 hybrid particles. Journal of Composite Materials, 2015; 32(4):1125-1131.). Compared with biological and nanomaterials, ceramic matrix composites are composed of toughening phase, matrix and interface phase, exhibiting a more complex multi-dimensional structure at the micro / nano scale, which brings certain difficulties to the testing of micro-region elastic modulus. Summary of the Invention

[0004] To address the limitations of conventional mechanical testing methods in measuring the micro-region elastic modulus of silicon carbide ceramic matrix composites, this invention provides a method for testing the micro-region elastic modulus. Specifically, high-resolution AFM technology is used to accurately obtain the deflection-displacement curves of the micro-region structure (fibers, interface phases, and matrix) of the silicon carbide ceramic matrix composite, a suitable mathematical contact model of the probe / test surface is established, and the model is analyzed and fitted using Image Analysis software to finally calculate the micro-region elastic modulus.

[0005] This invention provides a method for testing the residual elastic modulus of a micro-region in a silicon carbide ceramic matrix composite material, comprising:

[0006] (1) Start the AFM contact working mode to scan the polished surface morphology of the silicon carbide ceramic matrix composite sample to obtain a high-resolution morphology image of the sample, and then start the AFM force / curve working mode to perform force / curve measurement on the silicon carbide ceramic matrix composite sample; the silicon carbide ceramic matrix composite includes: fiber as the reinforcing phase, silicon carbide ceramic as the matrix phase, and an interface phase (PyC layer and / or BN layer) deposited between the reinforcing phase and the matrix phase.

[0007] (2) Based on the micro-regional structural characteristics and elastic deformation mechanism of the silicon carbide ceramic matrix composite sample, a mathematical contact model of the probe / test surface is established. The deflection-displacement curve is fitted by the ImageAnalysis software calculation unit to obtain the force-displacement curve of the elastic deformation process of the micro-regional structure. The micro-regional structure includes fibers, matrix phase and interface phase.

[0008] (3) The elastic modulus is calculated based on the slope of the force-displacement curve during the elastic deformation process of the micro-region structure.

[0009] In the preliminary research, this invention discovered that the core challenge in applying AFM to measure the micro-region mechanical properties of silicon carbide ceramic matrix composites lies in establishing a mathematical contact model between the micro-region structure and the probe, which is both simplified for computational purposes and objectively valid. To address this, the inventors considered the multi-component composite micro-region structural characteristics of silicon carbide ceramic matrix composites, using AFM probes to perform measurements and obtain deflection-displacement curves. A reasonable probe / material contact mathematical model was established, ultimately yielding the force-displacement curves of the elastic deformation process in the material's micro-regions, thereby obtaining the elastic modulus. Finally, based on the high-resolution microscale detection advantages of AFM and the multi-scale multi-component structural properties of ceramic matrix composites, applying AFM to the testing of the micro-region mechanical properties of ceramic matrix composites will greatly facilitate the design, evaluation, and control of material microstructures.

[0010] Preferably, the silicon carbide ceramic matrix composite sample has a size ≤10mm and a thickness ≤2mm.

[0011] Preferably, the method for preparing the silicon carbide ceramic matrix composite material sample is as follows: the silicon carbide ceramic matrix composite material is cut into square thin slices using a machining device, and the cut square thin slices are ultrasonically cleaned, dried, and polished.

[0012] The ultrasonic cleaning agent is at least one of ethanol, acetone or deionized water, the ultrasonic treatment frequency is 1 to 1000 kHz, and the ultrasonic cleaning time is 5 to 30 minutes; the drying temperature is 80 to 130°C, and the time is 1 to 24 hours.

[0013] Preferably, the polishing includes: first, placing the ultrasonically cleaned and dried square sheet sample into a mounting machine, adding mounting material to prepare a mounting sample, wherein the mounting material is resin; second, polishing the obtained mounting sample on a polishing machine; further removing surface scratches with diamond polishing fluid; and finally placing the polished mounting sample into a carbon tube furnace for pyrolysis to remove the mounting material; preferably, the pyrolysis temperature is 600-900℃, the time is 30-60 minutes, the pyrolysis atmosphere is argon, and the flow rate is 5-15 L / min.

[0014] Preferably, the probe used in the AFM is made of single-crystal silicon, silicon nitride, or diamond; the elastic modulus of the probe tip is ≥100 GPa, and the tip radius of curvature is 5–20 nm.

[0015] Preferably, to ensure the accuracy and validity of the test data, the number of test points for each micro-region structure is ≥5; preferably, the probe elastic coefficient is calibrated by a thermal modulation program before each test to eliminate test errors.

[0016] Preferably, establishing a mathematical contact model of the probe / test surface includes:

[0017] Assuming that only uniaxial compressive deformation occurs on the sample surface, the relationship between the load F applied by the probe and the deformation Δh of the silicon carbide ceramic matrix composite sample is as follows: R0 is the radius of the contact surface between the probe and the silicon carbide ceramic matrix composite sample, and K is the coupling elastic modulus between the probe and the silicon carbide ceramic matrix composite, which can be defined as follows:

[0018]

[0019] Where r is the probe tip radius, ω is the surface deformation deflection of the silicon carbide ceramic matrix composite sample, k and ν are the probe elastic modulus and Poisson's ratio, respectively, and according to the DMT contact model, Δh is expressed as:

[0020]

[0021] Substituting equations (2)-(4) into equation (1), we obtain the mathematical contact model of the probe / test surface, as follows:

[0022]

[0023] Preferably, the force-displacement curve of the elastic deformation process of the micro-region structure is obtained by fitting the deflection-displacement curve using Image Analysis software calculation unit.

[0024] Preferably, the elastic modulus is calculated based on the slope of the force-displacement curve during the elastic deformation process of the micro-region structure.

[0025] Beneficial effects:

[0026] This invention leverages the high-resolution microscale testing and analysis capabilities of AFM (Advanced Mechanical Function) to develop a method for testing the elastic modulus of micro-regions in ceramic matrix composites by establishing a suitable mathematical contact model. Compared to conventional mechanical testing methods that can only obtain the macroscopic elastic modulus of materials, the testing technique provided by this invention can accurately obtain the elastic modulus of the micro-region structure of ceramic matrix composites. This will provide a new perspective on the correspondence between the mechanical properties of the micro-region structure and the macroscopic performance of materials, greatly promoting the scientific guidance for the design and control of material microstructures. Attached Figure Description

[0027] Figure 1 A mathematical contact model for the composite micro-region structure of AFM probe and silicon carbide ceramic substrate;

[0028] Figure 2 Two-dimensional AFM images and AFM force curves of silicon carbide ceramic-based composite micro-region structures;

[0029] Figure 3 The elastic modulus of the silicon carbide ceramic matrix composite interface phase. Detailed Implementation

[0030] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0031] This disclosure discloses a method for testing the elastic modulus of micro-regions (fibers, interfaces, and matrix) of silicon carbide ceramic matrix composites using atomic force microscopy (AFM). Specifically, the method includes: processing the material to be tested into a block of a certain shape, polishing the test surface, and placing it into an AFM test chamber; performing probe scanning on the micro-region of the material to be tested to obtain a deflection-displacement curve, and analyzing and fitting the curve using ImageAnalysis software to calculate the elastic modulus of the micro-region.

[0032] The following exemplifies a method for testing the microregion elastic modulus of silicon carbide ceramic matrix composites.

[0033] Preparation of silicon carbide ceramic matrix composite samples:

[0034] The silicon carbide ceramic matrix composite material was cut into square samples using a machining device. The sample side length was ≤10mm and the thickness was ≤2mm.

[0035] Place the sample in a beaker containing an appropriate amount of cleaning agent (such as ethanol, acetone, or deionized water), clean it in an ultrasonic cleaner, and then remove the sample and place it in an oven to dry.

[0036] The dried sample is placed in an automatic mounting machine for mounting preparation, and the prepared mounting sample is then polished on a polishing machine.

[0037] The polished inlay sample was placed in a carbon tube furnace for pyrolysis to remove the inlay material and obtain a silicon carbide ceramic matrix composite sample.

[0038] AFM test:

[0039] The silicon carbide ceramic matrix composite sample is placed in the high-resolution AFM test chamber. First, the contact working mode is activated to scan the morphology of the polished surface of the sample, and a high-resolution morphology image of the silicon carbide ceramic matrix composite sample is obtained.

[0040] Several test points are selected from the same structural micro-region (one of fiber, matrix, and interface phase) on the morphology image. The force / curve working mode is started to perform force / curve measurement on the sample. Before each measurement, the probe elastic coefficient needs to be calibrated by the thermal modulation program to eliminate test errors.

[0041] Force / curve measurements were then performed on the other two structural microregions in turn, and finally the data were summarized according to the microregion structure.

[0042] Data Analysis:

[0043] Import the measured force / curve data into ImageAnalysis software to obtain the deflection-displacement curve.

[0044] Based on the micro-regional structural characteristics and elastic deformation mechanism of the material, a mathematical contact model of the probe / test surface is established.

[0045] Based on the established mathematical contact model, the deflection-displacement curve was fitted by the calculation unit of Image Analysis software to obtain the force-displacement curve of the elastic deformation process of the micro-region structure.

[0046] The elastic modulus is calculated based on the slope of the force-displacement curve.

[0047] Typically, the elastic modulus of silicon carbide composite materials is measured using mechanical property tests (tensile, bending, shear, etc.). However, these mechanical methods are insufficient to obtain the elastic modulus of the material's microstructure. In contrast, the measurement technique provided by this invention can obtain the elastic modulus of different microscales within the material, better reflecting the complex multi-dimensional and multi-scale structural characteristics of the material itself. Therefore, the testing method proposed in this invention has significant guiding value in the design, control, and evaluation of material microstructures. Since silicon carbide ceramic matrix composites are multiphase composites, with each phase having a micrometer-scale microstructure and significant differences in physical properties, it is difficult to obtain the micro-region elastic modulus using conventional methods. Secondly, data analysis differs. Due to the large modulus of the material itself, the elastic deformation of the probe itself needs to be considered, and the deformation of the probe must be deducted when calculating the elastic displacement of the material. Because the AFM probe is at the micrometer scale, significant bending (deflection) occurs during testing, and the probe contact surface undergoes significant elastic deformation. Therefore, the calculation of elastic displacement is more complex, requiring the establishment of a more complex mathematical calculation model. This patent uses a DMT model for processing, allowing the mechanical probe to directly acquire force parameters.

[0048] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0049] Example 1

[0050] The preparation of silicon carbide ceramic matrix composites includes: the material preparation can be any one of chemical vapor deposition, melt infiltration or precursor impregnation pyrolysis.

[0051] Sample preparation:

[0052] (1) Use an inner circle cutter to cut the silicon carbide ceramic matrix composite material into square samples with a side length of 8mm and a thickness of 2mm.

[0053] (2) Place the sample in a beaker containing an appropriate amount of acetone, and clean it in an ultrasonic cleaner (1-1000KHz) for 5 minutes. Then take out the sample and put it in an oven to dry at 120℃ for 30 minutes.

[0054] (3) Place the dried sample into an automatic mounting machine, add an appropriate amount of resin mounting material to prepare the mounting sample, place the prepared mounting sample on a polishing machine for polishing, and remove surface scratches with 3μm and 1μm diamond polishing liquid in sequence.

[0055] (4) The embedded sample was placed in a carbon tube furnace for pyrolysis to remove the embedded material and obtain a polished sample. The pyrolysis temperature was 600℃, the time was 30min, the pyrolysis atmosphere was argon, and the flow rate was 5L / min.

[0056] AFM test

[0057] (1) Place the sample into the high-resolution AFM test chamber, first activate the contact working mode to scan the morphology of the polished surface of the sample, and obtain a high-resolution morphology image of the sample. Figure 2 The scanning range is 10μm×10μm, and the scanning speed is 0.8Hz.

[0058] (2) Six test points were selected from the interface phase (BN) micro-region on the morphology image. The force / curve working mode was started to perform force / curve measurement on the sample. Before each measurement, the probe elastic coefficient was calibrated by the thermal modulation program to eliminate test error. The probe material used in this test was single crystal silicon with an elastic modulus of about 160 GPa, a Poisson's ratio of 0.27, and a tip curvature radius of about 10 nm.

[0059] Data Analysis:

[0060] (1) Import the measured force / curve data into ImageAnalysis software to obtain the deflection-displacement curve. Figure 2 );

[0061] (2) Based on the characteristics of the interface phase structure, the elastic deformation mechanism and the mathematical contact model of the probe / test surface, as shown in Equation (5), by substituting k = 160 GPa, ν = 0.27 and r = 10 nm, the deflection-displacement curve can be transformed into a force-displacement curve.

[0062] (3) The force-displacement curve was fitted using the Image Analysis software calculation unit FCProcessor2. The elastic modulus was calculated based on the curve slope. The data from each group were summarized, and the average value was obtained to get the final value of the interfacial phase elastic modulus. Figure 3 ).

[0063] It should be noted that the above-listed examples are merely specific embodiments of the present invention, and their content does not fully represent the scope of the present invention. It should be understood that all modifications directly or indirectly derived by those skilled in the art from the disclosure of the present invention, provided they do not depart from its scope and essence, are considered to be within the protection scope of the present invention.

Claims

1. A method for testing the residual elastic modulus of a micro-region in a silicon carbide ceramic matrix composite material, characterized in that, include: (1) Start the AFM contact working mode to scan the polished surface morphology of the silicon carbide ceramic matrix composite sample to obtain a high-resolution morphology image of the sample, and then start the AFM force / curve working mode to perform force / curve measurement on the silicon carbide ceramic matrix composite sample. The silicon carbide ceramic matrix composite material comprises: fiber as the reinforcing phase, silicon carbide ceramic as the matrix phase, and an interface phase deposited between the reinforcing phase and the matrix phase; (2) Based on the micro-region structure characteristics and elastic deformation mechanism of the silicon carbide ceramic matrix composite sample, a mathematical contact model of the probe / test surface is established. The deflection-displacement curve is fitted by the Image Analysis software calculation unit to obtain the force-displacement curve of the elastic deformation process of the micro-region structure. The micro-region structure includes fibers, matrix phase and interface phase. (3) Calculate the elastic modulus based on the slope of the force-displacement curve during the elastic deformation process of the micro-region structure; Establishing a mathematical contact model for the probe / test surface includes: Assuming that only uniaxial compressive deformation occurs on the sample surface, the relationship between the load F applied by the probe and the deformation Δh of the silicon carbide ceramic matrix composite sample is as follows: (1); R0 is the radius of the contact surface between the probe and the silicon carbide ceramic matrix composite sample, and K is the coupling elastic modulus between the probe and the silicon carbide ceramic matrix composite, which can be defined as follows: （2）； (3); where r is the probe tip radius, ω is the surface deformation deflection of the silicon carbide ceramic matrix composite sample, k and ν are the probe elastic modulus and Poisson's ratio, respectively. According to the DMT contact model, Δh is expressed as: （4）； Substituting equations (2)-(4) into equation (1), we obtain the mathematical contact model of the probe / test surface, as follows: （5）。 2. The test method according to claim 1, characterized in that, The dimensions of the silicon carbide ceramic matrix composite material sample are ≤10mm and the thickness is ≤2mm.

3. The test method according to claim 2, characterized in that, The preparation method of the silicon carbide ceramic matrix composite material sample is as follows: the silicon carbide ceramic matrix composite material is cut into square thin slices using a machining device, and the cut square thin slices are ultrasonically cleaned, dried and polished. The ultrasonic cleaning agent is at least one of ethanol, acetone or deionized water, the ultrasonic treatment frequency is 1 to 1000 kHz, and the ultrasonic cleaning time is 5 to 30 minutes; the drying temperature is 80 to 130°C, and the time is 1 to 24 hours.

4. The test method according to claim 3, characterized in that, The polishing process includes: first, placing the ultrasonically cleaned and dried square sheet sample into a mounting machine, adding mounting material to prepare a mounting sample, wherein the mounting material is resin; second, polishing the obtained mounting sample on a polishing machine; further removing surface scratches with diamond polishing fluid; and finally, placing the polished mounting sample into a carbon tube furnace for pyrolysis to remove the mounting material; the pyrolysis temperature is 600–900°C, the time is 30–60 minutes, the pyrolysis atmosphere is argon, and the flow rate is 5–15 L / min.

5. The test method according to claim 1, characterized in that, The probe used in the AFM is made of single-crystal silicon, silicon nitride, or diamond; the elastic modulus of the probe tip is ≥100 GPa, and the tip curvature radius is 5–20 nm.

6. The test method according to claim 1, characterized in that, To ensure the accuracy and validity of the test data, the number of test points for each micro-region structure is ≥5; the probe elastic coefficient is calibrated by thermal modulation before each test to eliminate test errors.

7. The test method according to claim 1, characterized in that, The force-displacement curve of the elastic deformation process of the micro-region structure was obtained by fitting the deflection-displacement curve using Image Analysis software calculation unit.

8. The test method according to any one of claims 1-7, characterized in that, The elastic modulus is calculated based on the slope of the force-displacement curve during the elastic deformation process of the micro-region structure.

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