Density testing method for ceramic-based composite material

Abstract

The invention discloses a density testing method for a ceramic-based composite material, relates to the technical field of ceramic-based composite material testing, and can solve the problem of density testing of a ceramic-based composite material with a low-toughness characteristic. The density testing method of the ceramic-based composite material comprises the following steps: S1, obtaining a plurality of ceramic-based composite material standard samples with known densities and different sizes, testing specific surface area data of the standard samples, and drawing a corresponding standard curve between the specific surface area and the density of the standard samples; s2, obtaining a to-be-tested sample made of the ceramic-based composite material, and testing specific surface area data of the to-be-tested sample; s3, acquiring density data of the to-be-detected sample according to the specific surface area data of the to-be-detected sample and the standard curve.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic matrix composite material production, and particularly relates to a method for testing the density of ceramic matrix composites. Background Art

[0002] Ceramic matrix composites have been widely used in aerospace, energy, automotive, and high-temperature industrial equipment due to their excellent high-temperature strength, oxidation resistance, low density, and corrosion resistance.

[0003] However, different from traditional metal materials, ceramic matrix composites have high brittleness and complex microstructural characteristics, which pose challenges for density testing. Especially in the application of ceramic matrix composite bolts, due to their structural complexity, surface precision requirements, and possible porosity, traditional density measurement methods may not be fully applicable. Density, as an important physical parameter of materials, can reflect the compactness, preparation quality, and internal structural state of materials, and is of great significance for evaluating the performance of ceramic matrix composite bolts.

[0004] Existing density measurement methods, such as the Archimedes method, geometric measurement method, and gas displacement method, although perform well in dense materials, face certain limitations in porous ceramic matrix composites, such as difficulty in excluding the influence of internal micropores or cracks. Especially in the case of complex bolt shapes, it becomes particularly difficult to accurately measure the volume. In addition, the low toughness characteristics of ceramic matrix composites pose higher requirements for operations during the testing process, and it is necessary to ensure the integrity of the samples.

[0005] Therefore, it is necessary to develop a density testing method for ceramic matrix composite bolts that is applicable to complex shapes, porous structures, and high-precision requirements to solve the above problems. Summary of the Invention

[0006] The purpose of this application is to provide a method for testing the density of ceramic matrix composites, and solve the problem of density testing for ceramic matrix composites with low toughness characteristics.

[0007] To solve the above technical problems, the present invention adopts the following solutions:

[0008] This application provides a method for testing the density of ceramic matrix composites, including the following steps:

[0009] S1. Obtain multiple standard samples of ceramic matrix composites with known densities and different sizes, test the specific surface area data of the standard samples, and draw a corresponding standard curve between the specific surface area and density of the standard samples;

[0010] S2. Obtain a test sample made of ceramic matrix composites, and test the specific surface area data of the test sample;

[0011] S3. Obtain the density data of the sample to be measured based on the specific surface area data of the sample to be measured and the standard curve.

[0012] Optionally, in S1 and S2, the specific surface area data of the standard sample and the sample to be measured are obtained according to the following steps:

[0013] Sa. Obtain the specific surface area curves of the standard sample and the sample to be measured;

[0014] Sb. Obtain the specific surface area data of the standard sample and the sample to be measured based on the specific surface area curves of the standard sample and the sample to be measured in Sa.

[0015] Optionally, in step Sa, to plot the specific surface area curve, multiple sets of abscissa x and ordinate y need to be obtained, and each set of abscissa x and ordinate y is calculated by the following formula:

[0016]

[0017] In the formula, v represents the volume of the adsorbed gas;

[0018] P represents the actual pressure value;

[0019] P 0 represents the initial saturated vapor pressure value.

[0020] Optionally, to obtain multiple sets of abscissa x and ordinate y, needs to be transformed;

[0021] The transformation range of

[0022] is: 0.05 - 0.3. Optionally, when performing the

[0023] transformation, it is incremented or decremented at least 4 times within the range of 0.05 - 0.3, and the value of each transformation is the same.

[0024]

[0025] In the formula: v c represents the sample chamber volume;

[0026] P C0 represents the initial saturated vapor pressure value of the sample chamber;

[0027] P C1 represents the pressure value of the sample chamber after sample adsorption;

[0028] Pa represents the standard atmospheric pressure value.

[0029] Optionally, in step Sb, the specific surface area data needs to be calculated through a two-step formula;

[0030] The first-step formula:

[0031]

[0032] In the formula, v m represents the monolayer adsorption capacity;

[0033] k represents the slope of the specific surface area curve;

[0034] b represents the vertical intercept of the specific surface area curve;

[0035] The second-step formula:

[0036] As = v m *N*S

[0037] In the formula, N represents Avogadro's constant: 6.02x10²³;

[0038] S represents the cross-sectional area of a single adsorbed molecule.

[0039] Optionally, the adsorbed molecule is nitrogen, and the cross-sectional area of S is: 0.162 nm 2 .

[0040] Optionally, in S1, the standard curve is plotted according to the following formula;

[0041]

[0042] In the formula: AS represents the specific surface area;

[0043] A V represents the total surface area per unit volume;

[0044] ρ represents the density;

[0045] When plotting the standard curve, use As as the X-axis and Av as the Y-axis for plotting.

[0046] Advantages of the present invention:

[0047] First, the test method disclosed in this application is highly efficient and can complete the density test of the sample to be tested in a relatively short time.

[0048] Second, the test method disclosed in this application is non-destructive. The entire density test process does not require cutting or damaging the ceramic matrix composite bolt, and is suitable for measurement in the actual part state.

[0049] Third, the test method disclosed in this application has strong adaptability and can effectively measure the density of ceramic matrix composite bolts with complex pore structures.

[0050] IV. The test method disclosed in this application is based on the combination of the BET method and the standard curve, with relatively small density measurement errors for ceramic matrix composites, and the measurement results have high accuracy. Description of the Drawings

[0051] Figure 1 It is a schematic flow chart of the sample test method in the embodiment of this application.

[0052] Figure 2 It is a standard curve graph of the standard sample in the embodiment of this application.

[0053] Figure 3 It is a BET curve graph of the sample to be measured in the embodiment of this application. Detailed Embodiments

[0054] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0055] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "longitudinal", "lateral", "horizontal", "inner", "outer", "front", "rear", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0056] In the description of the present invention, it should also be noted that unless otherwise clearly defined and limited, the terms "set", "provided with", "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] The present invention will be described in detail below by referring to the drawings and in conjunction with the embodiments.

[0058] As Figures 1 to 3 shown, this application provides a density test method for ceramic matrix composites, including the following steps:

[0059] S1. Obtain multiple ceramic matrix composite standard samples with known densities and different sizes, test the specific surface area data of the standard samples, and draw the corresponding standard curve between the specific surface area and density of the standard samples;

[0060] S2. Obtain a sample to be tested made of ceramic matrix composite, and test the specific surface area data of the sample to be tested;

[0061] S3. According to the specific surface area data of the sample to be tested and the standard curve, obtain the density data of the sample to be tested.

[0062] In this embodiment, by first drawing the standard curve of the ceramic matrix composite standard sample and then testing the specific surface area data of the sample to be tested, the accurate density data of the sample to be tested can be obtained quickly and non-destructively, thereby providing a reliable basis for the performance evaluation and structure optimization of the ceramic matrix composite.

[0063] Specifically, in this embodiment, in S1 and S2, the specific surface area data of the standard sample and the sample to be tested are obtained according to the following steps:

[0064] Sa. Obtain the specific surface area curves of the standard sample and the sample to be tested;

[0065] Sb. According to the specific surface area curves of the standard sample and the sample to be tested in Sa, obtain the specific surface area data of the standard sample and the sample to be tested.

[0066] Optionally, in step Sa, to draw the specific surface area curve, multiple sets of abscissa x and ordinate y need to be obtained, and each set of abscissa x and ordinate y is calculated by the following formula:

[0067]

[0068] In the formula, v represents the volume of the adsorbed gas;

[0069] P represents the actual pressure value;

[0070] P 0 represents the initial saturated vapor pressure value.

[0071] Optionally, to obtain multiple sets of abscissa x and ordinate y, needs to be transformed;

[0072] The transformation range of is: 0.05 - 0.3.

[0073] In this embodiment, Starting from 0.05 for the transformation, a total of 5 transformations are made to obtain multiple abscissas of the specific surface area curve. Subsequently, according to the transformed values, the y coordinates are calculated, and multiple sets of abscissa x and ordinate y can be obtained. In this embodiment, including the initial value 0.05, a total of 6 sets of abscissa x and ordinate y can be obtained, as shown in the following table:

[0074]

[0075] The BET curve of the sample to be measured drawn according to the above table is as Figure 3 shown.

[0076] In some embodiments, when performing the transformation, the transformation can be increased or decreased at least 4 times within the range of 0.05 - 0.3, and the value of each transformation is the same.

[0077] Specifically, in this embodiment, when obtaining the x - coordinate and y - coordinate, the v value needs to be calculated according to the following formula:

[0078]

[0079] In the formula: v c represents the volume of the sample chamber;

[0080] P C0 represents the initial saturated vapor pressure value of the sample chamber;

[0081] P C1 represents the pressure value of the sample chamber after sample adsorption;

[0082] Pa represents the standard atmospheric pressure value.

[0083] In this embodiment, the volume of the sample chamber: 100 ml;

[0084] Pco: 5 Kpa;

[0085] Pa: 101.325 Kpa;

[0086] Pc1: 4.8 Kpa;

[0087] Substituting into the following formula can obtain the v value

[0088]

[0089] In this embodiment, the volume v of the sample chamber c needs to be measured in advance, and P C0 and P C1 need to be read according to the pressure gauge connected to the sample chamber.

[0090] Specifically, in this embodiment, in step Sb, the specific surface area data needs to be calculated through a two - step formula;

[0091] The first - step formula:

[0092]

[0093] In the formula, v m represents the monolayer adsorption capacity;

[0094] k represents the slope of the specific surface area curve;

[0095] b represents the vertical intercept of the specific surface area curve;

[0096] The formula for the second step:

[0097] As = v m *N*S

[0098] In the formula, N represents Avogadro's constant: 6.02 x 10^23;

[0099] S represents the cross-sectional area of a single adsorbed molecule.

[0100] In this embodiment, multiple sets of values of k, b, and v m are as follows:

[0101] k 0.76 0.73 0.62 0.66 0.81 b 2.86 3.56 2.94 3.25 3.16 Vm 0.276 0.233 0.281 0.256 0.252

[0102] Substituting into the formula can obtain the As value as follows:

[0103] As 2.692 2.272 2.740 2.497 2.458

[0104] Specifically, in this embodiment, the adsorbed molecule is nitrogen, and the cross-sectional area of S is: 0.162 nm². Technicians can also replace it with other adsorbed molecules, which will not be elaborated here.

[0105] Specifically, in this embodiment, in S1, the standard curve is plotted according to the following formula;

[0106]

[0107] In the formula: AS represents the specific surface area;

[0108] A V represents the total surface area per unit volume;

[0109] ρ represents the density;

[0110] When plotting the standard curve, use As as the X-axis and Av as the Y-axis for plotting.

[0111] The known As values and densities are shown in the following table:

[0112] As 5.46 5.49 5.53 5.59 5.64 ρ 3.2527 3.2514 3.2441 3.2254 3.2128

[0113] The relative Av values can be calculated according to the formula.

[0114] Av 17.76 17.85 17.94 18.03 18.12

[0115] The A of the standard sample VThe value needs to be calculated based on the As value and the known density. The As values and A of multiple standard samples in this embodiment are as follows: V As shown in the following table:

[0116] As 5.46 5.49 5.53 5.59 5.64 Av 17.76 17.85 17.94 18.03 18.12

[0117] Plot the corresponding multiple groups of As values and A in the table V values to draw a standard curve and perform smoothing processing, then the curve graphs of multiple standard samples can be obtained. The obtained standard curve graphs are as follows: Figure 2 shown.

[0118] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. A density testing method for ceramic-based composites, characterized in that: The following steps are involved: S1. Obtain multiple ceramic-based composite standard samples with known density and different sizes, test the specific surface area data of the standard samples, and draw a standard curve corresponding to the specific surface area and density of the standard samples; S2. Obtain a sample to be tested made of a ceramic-based composite material, and test the specific surface area data of the sample to be tested; S3. Obtain density data of the sample to be tested according to the specific surface area data of the sample to be tested and the standard curve.

2. The density testing method of a ceramic-based composite material according to claim 1, characterized in that: In S1 and S2, the specific surface area data of the test standard sample and the sample to be tested are obtained according to the following steps: Sa, obtain the specific surface area curves of the standard sample and the sample to be tested; Sb. According to the specific surface area curves of the standard sample and the sample to be tested in Sa, obtain the specific surface area data of the standard sample and the sample to be tested.

3. The density testing method of a ceramic-based composite material according to claim 2, characterized in that: In step Sa, drawing the specific surface area curve requires obtaining multiple sets of abscissas x and ordinates y, and each set of abscissas x and ordinates y is calculated by the following formula: Where v represents the volume of adsorbed gas; P represents the actual pressure value; P0 represents the initial saturated vapor pressure value.

4. The density testing method of a ceramic-based composite material according to claim 3, characterized in that: To obtain multiple sets of horizontal coordinates x and vertical coordinates y, you need to Make a transformation; The transformation range is: 0.05-0.

3.

5. The density testing method of a ceramic-based composite material according to claim 4, characterized in that: In progress When transforming, the value is increased or decreased within the range of 0.05-0.3 for at least 4 times, and the value of each transformation is the same.

6. The density testing method of a ceramic-based composite material according to claim 3, characterized in that: When you get the x- and y-coordinates, you need to calculate the v value according to the following formula: Where: v c represents the volume of the sample chamber; P C0 Indicates the initial saturated vapor pressure value of the sample chamber; P C1 Indicates the pressure value of the sample chamber after sample adsorption; Pa represents standard atmospheric pressure.

7. The density testing method of a ceramic-based composite material according to claim 2, characterized in that: In step Sb, the specific surface area data needs to be calculated using a two-step formula; The first step formula: In the formula, v m represents the monolayer adsorption amount; k represents the slope of the specific surface area curve; b represents the longitudinal intercept of the specific surface area curve; The second step formula: As=v m *N*S Where N is Avogadro's constant: 6.02 x 1023; S represents the cross-sectional area of ​​a single adsorbed molecule.

8. The density testing method of a ceramic-based composite material according to claim 7, characterized in that: The adsorbed molecule is nitrogen, and the cross-sectional area of ​​S is: 0.162nm 2 .

9. The density testing method of a ceramic-based composite material according to claim 1, characterized in that: In S1, the standard curve was drawn according to the following formula; Where: AS represents specific surface area; A V It expresses the total surface area per unit volume; ρ represents density; When drawing the standard curve, As is used as the X-axis and Av is used as the Y-axis.

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