A method for testing the coefficient of thermal expansion of powdered materials

Abstract

This application discloses a method for testing the coefficient of thermal expansion of powdered materials, relating to the field of powder testing technology. The method includes: placing aluminum foil at the bottom of an alumina crucible without the powdered sample to be tested, forming a first test assembly; testing the first expansion data of the first test assembly within a target temperature range; after completing the first expansion data test, removing the aluminum foil from the alumina crucible; placing the powdered sample to be tested into the alumina crucible after removing the aluminum foil, and then covering the powdered sample with the aluminum foil to form a second test assembly; testing the second expansion data of the second test assembly within a target temperature range; and calculating the coefficient of thermal expansion of the powdered sample based on the first and second expansion data. This application can accurately test the coefficient of thermal expansion of powdered materials in a loose state.

Description

Technical Field

[0001] This application relates to the field of powder testing technology, and in particular to a method for testing the coefficient of thermal expansion of powdered materials. Background Technology

[0002] Currently, when testing the coefficient of thermal expansion of powdered materials, the powder is usually pressed into shape and sintered to obtain a dense, isotropic (or known anisotropic) solid sample, which is then measured using a standard thermomechanical analyzer according to the testing standards for solid materials.

[0003] However, this testing method actually measures the thermal expansion properties of dense solids, not the expansion behavior of the powder itself. Furthermore, factors such as pressure and sintering regime during the preparation process can affect the microstructure of the final sample, thus impacting the accuracy of the test results. In powder transportation, storage, filling, or certain non-sintering molding processes, it is often necessary to directly understand the thermal expansion behavior of the powder in a loose state, a requirement that current testing methods struggle to meet. Summary of the Invention

[0004] The main objective of this application is to provide a method for testing the coefficient of thermal expansion of powdered materials, which aims to accurately test the coefficient of thermal expansion of powdered materials in a loose state.

[0005] This application provides a method for testing the coefficient of thermal expansion of powdered materials, the method comprising:

[0006] Aluminum foil is placed at the bottom of an alumina crucible that does not contain the powdered sample to be tested, forming the first test assembly; Test the first expansion data of the first test assembly within the target temperature range; After the first expansion data test is completed, the aluminum foil is removed from the alumina crucible; The powder sample to be tested is placed in an alumina crucible after the aluminum foil has been removed, and after being placed, the aluminum foil is covered on the powder sample to be tested to form a second test assembly. Test the second expansion data of the second test assembly within the target temperature range; The expansion coefficient of the powder sample to be tested is calculated based on the first expansion data and the second expansion data.

[0007] In one embodiment, the step of testing the first expansion data of the first test assembly within a target temperature range includes: The first displacement value of the first test assembly at each temperature in the target temperature range is obtained by a test probe; The first expansion data is generated by associating each first displacement value with the temperature corresponding to each first displacement value.

[0008] In one embodiment, prior to the step of obtaining the first displacement value of the first test assembly at each temperature within the target temperature range using a test probe, the method further includes: The first test assembly is placed at the test station, and the test probe is controlled to contact the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load. After the test probe is controlled to contact the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load, the first displacement change of the test probe within a preset time period is monitored. If the first displacement change is less than a preset change threshold, then the step of obtaining the first displacement value of the first test assembly at each temperature in the target temperature range through the test probe is performed.

[0009] In one embodiment, the step of testing the second expansion data of the second test assembly within the target temperature range includes: The second displacement value of the second test assembly at each temperature within the target temperature range is obtained by using a test probe; The second expansion data is generated by associating each second displacement value with the temperature corresponding to each second displacement value.

[0010] In one embodiment, prior to the step of obtaining the second displacement value of the second test assembly at each temperature within the target temperature range using a test probe, the method further includes: The second test assembly is placed at the test station, and the test probe is controlled to contact the upper surface of the aluminum foil in the second test assembly in the vertical direction with a preset contact load. After the test probe is controlled to contact the upper surface of the aluminum foil in the second test assembly in a vertical direction with a preset contact load, the second displacement change of the test probe within a preset time period is monitored. If the second displacement change is less than a preset change threshold, then the step of obtaining the second displacement value of the second test assembly at each temperature in the target temperature range through the test probe is executed.

[0011] In one embodiment, the step of placing the powdered sample to be tested into an alumina crucible after removing the aluminum foil, and then covering the powdered sample with the aluminum foil to form a second test assembly, includes: The powdered sample to be tested is placed at a preset height position in the alumina crucible after the aluminum foil has been removed; The alumina crucible containing the powdered sample to be tested was subjected to vibration. After vibration treatment, the aluminum foil is covered on the powder sample to be tested to form the second test assembly.

[0012] In one embodiment, the step of calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data includes: Subtract the second inflation data from the first inflation data to obtain the net inflation data; The net expansion data is linearly fitted to obtain the expansion coefficient of the powder sample to be tested.

[0013] In one embodiment, after calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data, the method further includes: Obtain the bulk density of the powdered sample to be tested and the inner diameter of the alumina crucible; Based on the expansion coefficient, the target temperature range, the loose density, and the inner diameter, the theoretical height change of the powder sample to be tested within the target temperature range is calculated. Based on the net expansion data, determine the actual height change of the powder sample to be tested; Determine whether the absolute difference between the actual height change and the theoretical height change is less than a preset deviation threshold. If not, output an error message indicating an abnormal test result.

[0014] In one embodiment, prior to the step of testing the first expansion data of the first test assembly within the target temperature range, the method further includes: Inert protective gas is continuously introduced into the test chamber containing the first test assembly until the test of the first expansion data is completed. Prior to the step of testing the second expansion data of the second test assembly within the target temperature range, the method further includes: An inert protective gas is continuously introduced into the test chamber containing the second test assembly until the second expansion data test is completed.

[0015] In one embodiment, before the step of calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data, the method further includes: Smoothing filtering is applied to the first and second inflated data. The expansion coefficient of the powder sample to be tested is calculated based on the first and second expansion data after smoothing and filtering.

[0016] This application provides a method for testing the coefficient of thermal expansion of powdered materials, comprising: placing aluminum foil at the bottom of an alumina crucible without containing the powdered sample to be tested, forming a first test assembly; testing the first expansion data of the first test assembly within a target temperature range; after completing the test of the first expansion data, removing the aluminum foil from the alumina crucible; placing the powdered sample to be tested into the alumina crucible after removing the aluminum foil, and after placing the sample, covering the powdered sample with the aluminum foil, forming a second test assembly; testing the second expansion data of the second test assembly within a target temperature range; and calculating the coefficient of thermal expansion of the powdered sample to be tested based on the first and second expansion data.

[0017] Therefore, the technical solution provided in this application involves constructing and testing a first test assembly containing only bottom aluminum foil within the same alumina crucible, and a second test assembly containing loose powder covered with the same aluminum foil. The expansion data from the two sets of tests are then differentially calculated. This not only deducts the thermal expansion contribution of the testing system itself (such as the alumina crucible and aluminum foil), but also ensures that the powdered sample is only lightly covered by the aluminum foil during the test, without the need for compaction. This maximizes the preservation of its natural loose state and avoids the influence of molding operations on the internal structure and expansion characteristics of the sample. Therefore, this application can accurately test the expansion coefficient of powdered materials in a loose state. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic flowchart illustrating the method for testing the coefficient of thermal expansion of powdered materials provided in the first embodiment of this application; Figure 2 This is a schematic diagram of the structure of the first test assembly provided in the first embodiment of this application; Figure 3 This is a schematic diagram of the structure of the second test assembly provided in the first embodiment of this application; Figure 4 A schematic flowchart illustrating the method for testing the coefficient of thermal expansion of powdered materials provided in the second embodiment of this application; Figure 5This is a schematic flowchart of the method for testing the coefficient of thermal expansion of powdered materials provided in the fourth embodiment of this application.

[0021] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0023] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0024] Currently, when testing the coefficient of thermal expansion of powdered materials, the powder is usually pressed into shape and sintered to obtain a dense, isotropic (or known anisotropic) solid sample, which is then measured using a standard thermomechanical analyzer according to the testing standards for solid materials.

[0025] However, this testing method actually measures the thermal expansion properties of dense solids, not the expansion behavior of the powder itself. Furthermore, factors such as pressure and sintering regime during the preparation process can affect the microstructure of the final sample, thus impacting the accuracy of the test results. In powder transportation, storage, filling, or certain non-sintering molding processes, it is often necessary to directly understand the thermal expansion behavior of the powder in a loose state, a requirement that current testing methods struggle to meet.

[0026] Based on this, this application provides a method for testing the coefficient of thermal expansion of powdered materials, comprising: placing aluminum foil at the bottom of an alumina crucible without containing the powdered sample to be tested, forming a first test assembly; testing the first expansion data of the first test assembly within a target temperature range; after completing the test of the first expansion data, removing the aluminum foil from the alumina crucible; placing the powdered sample to be tested into the alumina crucible after removing the aluminum foil, and after placing the sample, covering the powdered sample with the aluminum foil, forming a second test assembly; testing the second expansion data of the second test assembly within a target temperature range; and calculating the coefficient of thermal expansion of the powdered sample to be tested based on the first expansion data and the second expansion data.

[0027] Therefore, the technical solution provided in this application involves constructing and testing a first test assembly containing only bottom aluminum foil within the same alumina crucible, and a second test assembly containing loose powder covered with the same aluminum foil. The expansion data from the two sets of tests are then differentially calculated. This not only deducts the thermal expansion contribution of the testing system itself (such as the alumina crucible and aluminum foil), but also ensures that the powdered sample is only lightly covered by the aluminum foil during the test, without the need for compaction. This maximizes the preservation of its natural loose state and avoids the influence of molding operations on the internal structure and expansion characteristics of the sample. Therefore, this application can accurately test the expansion coefficient of powdered materials in a loose state.

[0028] This application proposes a method for testing the coefficient of thermal expansion of powdered materials according to a first embodiment. Please refer to [link / reference needed]. Figure 1 The method for testing the coefficient of thermal expansion of powdered materials may include steps S10 to S60: Step S10: Place aluminum foil at the bottom of the alumina crucible that does not contain the powdered sample to be tested, to form the first test assembly; It should be noted that aluminum foil refers to a thin sheet material made of pure aluminum or aluminum alloy, which has good ductility, thermal conductivity, and corrosion resistance. In this embodiment, the aluminum foil is used as an isolation layer and a reference layer to assist in measuring the expansion behavior of the powdered material. The alumina crucible is a container made of alumina ceramic, which has excellent high-temperature resistance and chemical stability. In this embodiment, the alumina crucible is used to hold the powdered sample to be tested and serves as a support structure during the testing process. The powdered sample to be tested refers to the powdered material whose coefficient of expansion needs to be measured. After placing the aluminum foil at the bottom of the alumina crucible before it contains the powdered sample, a structure can be formed as follows: Figure 2 The first test assembly shown.

[0029] The inner diameter of the alumina crucible can be 5.50 mm and the height can be 4.00 mm; the outer diameter of the aluminum foil can be 5.00 mm and the thickness can be 0.1 mm.

[0030] Step S20: Test the first expansion data of the first test assembly within the target temperature range; It should be noted that the target temperature range refers to the temperature interval set when conducting the coefficient of thermal expansion test, for example, -50℃ to 200℃. The first expansion data refers to the displacement data of the first test assembly as a function of temperature within the target temperature range, which reflects the combined expansion behavior of the alumina crucible and aluminum foil during the heating process.

[0031] When testing the first expansion data of the first test assembly within the target temperature range, the first displacement value of the first test assembly at each temperature within the target temperature range can be obtained through the test probe; the first displacement value is correlated with the temperature corresponding to the first displacement value to generate the first expansion data.

[0032] The test probe is a sensor used to accurately measure the dimensional changes of an object at different temperatures. It is typically rod-shaped or columnar, with one end connected to a displacement sensor and the other end in contact with the sample surface. To obtain the first displacement value of the first test assembly at various temperatures within the target temperature range using the test probe, the first test assembly can be placed on the test stage of a thermomechanical analyzer equipped with a high-precision quartz probe. The furnace of the thermomechanical analyzer can then heat the assembly at a set heating rate (e.g., 5°C / min). The test probe continuously monitors the vertical displacement of the first test assembly due to thermal expansion, recording this displacement as the first displacement value. Simultaneously, thermocouples measure the temperature inside the furnace in real time. The control system of the thermomechanical analyzer synchronously records the first displacement value and the corresponding temperature at a set interval (e.g., every 1 degree Celsius or every 1 second).

[0033] It is understood that this embodiment utilizes a test probe to accurately acquire the first displacement value of the first test assembly at various temperatures within the target temperature range, and correlates it with the corresponding temperature to systematically and accurately generate the first expansion data. This method avoids errors that may arise from traditional visual inspection or rough measurement, significantly improving the accuracy and reliability of the first expansion data. This provides high-quality reference data for subsequently subtracting the first expansion data from the second expansion data to obtain the pure expansion information of the powder sample under test, thereby ensuring the accuracy of the final calculated expansion coefficient of the powder sample under test and effectively solving the problem of inaccurate data acquisition affecting the final test results.

[0034] Furthermore, in one feasible implementation, before the step of obtaining the first displacement value of the first test assembly at various temperatures within the target temperature range using a test probe, the method for testing the coefficient of thermal expansion of powdered materials may further include steps S201-S203: Step S201: Place the first test assembly at the test station and control the test probe to contact the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load. Step S202: After the test probe contacts the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load, monitor the first displacement change of the test probe within a preset time period. Step S203: If the first displacement change is less than a preset change threshold, then the step of obtaining the first displacement value of the first test assembly at each temperature in the target temperature range through the test probe is executed.

[0035] The test station refers to a specific area or device used for measuring the coefficient of thermal expansion. It typically includes a sample stage to stably support the sample and ensure accurate contact between the test probe and the sample. This test station is usually located within the measurement chamber of the thermomechanical analyzer, providing a stable temperature environment and precise displacement measurement conditions. Vertical contact means the probe's axis is perpendicular to the sample surface, ensuring the displacement measurement direction aligns with the sample's expansion direction. The preset contact load is a pre-set force value applied when the probe contacts the sample. Its purpose is to ensure a stable and consistent physical contact between the probe and the sample, avoiding sample deformation due to excessive contact force or poor contact due to insufficient force. The preset contact load can be a default value, such as 0.01N, or it can be flexibly set by the user according to actual conditions; this embodiment does not impose specific limitations on this. The preset duration is a time period set after the probe contacts the sample to evaluate contact stability. It can be a default duration or flexibly set by the user according to actual conditions; this embodiment does not impose specific limitations on this. The first displacement change refers to the total range or fluctuation of the displacement reading after the test probe contacts the upper surface of the aluminum foil in the first test assembly under a preset contact load within a preset time period. The preset change threshold is a pre-set maximum allowable displacement change used to judge contact stability. It can be a default value or can be flexibly set by the user according to the actual situation. This embodiment does not specifically limit it.

[0036] This embodiment limits the determination of the initial contact stability between the test probe and the sample before obtaining the first displacement value of the first test assembly at each temperature within the target temperature range using the test probe. This effectively avoids initial displacement measurement errors caused by unstable contact between the probe and the sample, ensuring high accuracy and reliability of the first displacement value obtained subsequently within the target temperature range. This allows the first expansion data to more accurately reflect the expansion characteristics of the first test assembly itself, thus providing a more solid and accurate foundation for subsequent calculation of the net expansion data and final expansion coefficient of the powder sample under test, significantly improving the accuracy of the expansion coefficient test of powder materials.

[0037] Step S30: After completing the test of the first expansion data, remove the aluminum foil from the alumina crucible; Step S40: The powder sample to be tested is placed in the alumina crucible after the aluminum foil has been removed, and after placement, the aluminum foil is covered on the powder sample to be tested to form the second test assembly. It should be noted that after placing the powdered sample to be tested into the alumina crucible after removing the aluminum foil, and then covering the powdered sample with the aluminum foil, a structure can be formed as follows: Figure 3 The second test assembly is shown.

[0038] When placing the powdered sample to be tested into an alumina crucible after removing the aluminum foil, and then covering the powdered sample with the aluminum foil to form a second test assembly, the powdered sample to be tested can be placed at a preset height position in the alumina crucible after removing the aluminum foil; the alumina crucible containing the powdered sample to be tested is vibrated; after the vibration is completed, the aluminum foil is covered on the powdered sample to be tested to form the second test assembly.

[0039] The preset height position can be a default value, such as two-thirds of the height of the alumina crucible, or it can be flexibly set by the user according to the actual situation. This embodiment does not make specific limitations on this.

[0040] Understandably, placing the powdered sample at a preset height in the alumina crucible after removing the aluminum foil ensures consistency in the initial filling volume and height of the powder sample for each test. This provides a standardized starting condition for subsequent expansion measurements, thereby improving the repeatability and accuracy of the measurements. Vibrating the alumina crucible containing the powdered sample aims to achieve a more uniform and denser packing of the powder within the crucible, eliminating voids and irregularities. This ensures that the sample more accurately reflects its inherent material properties during thermal expansion, reducing measurement errors caused by inconsistent sample packing. After vibration, covering the powdered sample with aluminum foil ensures a flat surface and provides a stable contact surface for the subsequent test probe, preventing direct contact with irregular powder surfaces that could lead to measurement instability or probe embedding in the powder. Simultaneously, the aluminum foil also helps prevent powder from splashing or being affected by airflow during heating, further improving the accuracy and reliability of the test.

[0041] Step S50: Test the second expansion data of the second test assembly within the target temperature range; It should be noted that the second expansion data refers to the displacement data of the second test assembly as the temperature changes within the target temperature range. It reflects the comprehensive expansion behavior of the alumina crucible, aluminum foil, and the powdered sample to be tested during the heating process.

[0042] When testing the second expansion data of the second test assembly within the target temperature range, the second displacement value of the second test assembly at each temperature within the target temperature range can be obtained through the test probe; the second displacement value is correlated with the temperature corresponding to the second displacement value to generate the second expansion data.

[0043] In the process of obtaining the second displacement value of the second test assembly at various temperatures within the target temperature range using the test probe, the second test assembly can first be placed on the test stage of a thermomechanical analyzer equipped with a high-precision quartz probe. Then, the furnace of the thermomechanical analyzer can be heated at a set heating rate (e.g., 5°C / min). The test probe will continuously monitor the vertical displacement of the second test assembly due to thermal expansion, which will be used as the second displacement value. At the same time, the thermocouple will measure the temperature inside the furnace in real time. The control system of the thermomechanical analyzer will synchronously record the second displacement value and the corresponding temperature at a set period (e.g., every 1 degree Celsius or every 1 second).

[0044] It is understood that this embodiment, by using a test probe to accurately obtain the second displacement value of the second test assembly at various temperatures within the target temperature range and correlating it with the corresponding temperature, can systematically and accurately generate second expansion data, providing high-quality and highly reliable raw data for subsequent expansion coefficient calculation. This ensures the accuracy of the final calculated expansion coefficient of the powder sample and effectively solves the problem of inaccurate data acquisition affecting the final test results.

[0045] Furthermore, in one feasible implementation, before the step of obtaining the second displacement value of the second test assembly at various temperatures within the target temperature range using a test probe, the method for testing the coefficient of thermal expansion of powdered materials may further include steps S501 to S503: Step S501: Place the second test assembly at the test station and control the test probe to contact the upper surface of the aluminum foil in the second test assembly in the vertical direction with a preset contact load. Step S502: After the test probe contacts the upper surface of the aluminum foil in the second test assembly in the vertical direction with a preset contact load, monitor the second displacement change of the test probe within a preset time period. Step S503: If the second displacement change is less than a preset change threshold, then the step of obtaining the second displacement value of the second test assembly at each temperature in the target temperature range through the test probe is executed.

[0046] The second displacement change refers to the total range or fluctuation of the displacement reading after the test probe contacts the upper surface of the aluminum foil in the second test assembly within a preset time period and at a preset contact load.

[0047] This embodiment limits the determination of the initial contact stability between the test probe and the sample before obtaining the second displacement value of the second test assembly at various temperatures within the target temperature range using the test probe. This effectively avoids initial displacement measurement errors caused by unstable contact between the probe and the sample, ensuring high accuracy and reliability of the second displacement value obtained subsequently within the target temperature range. This allows the second expansion data to more accurately reflect the expansion characteristics of the second test assembly itself, thus providing a more solid and accurate foundation for subsequent calculation of the net expansion data and final expansion coefficient of the powder sample under test, significantly improving the accuracy of the expansion coefficient test of powder materials.

[0048] Step S60: Calculate the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data.

[0049] It should be noted that the coefficient of thermal expansion refers to the degree to which the dimensions (length, area, or volume) of a material change when the temperature changes.

[0050] When calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data, the second expansion data can be subtracted from the first expansion data to obtain the net expansion data; the net expansion data is then subjected to linear fitting to obtain the expansion coefficient of the powder sample to be tested.

[0051] The net expansion data is obtained by subtracting the first expansion data from the second expansion data. Essentially, this means subtracting the first expansion data (which only includes the expansion of the aluminum foil and alumina crucible) from the second expansion data (which includes the total expansion of the powdered sample, aluminum foil, and alumina crucible). This yields net expansion data representing only the expansion of the powdered sample itself. After linear fitting of the net expansion data, a straight line can be obtained, and the slope of this line is the expansion coefficient of the powdered sample.

[0052] When subtracting the second expansion data from the first expansion data, a point-by-point subtraction method can be used. That is, for each temperature point within the target temperature range, the displacement value in the second expansion data corresponding to that temperature point is subtracted from the displacement value in the first expansion data to obtain the net displacement value corresponding to that temperature point, thus forming the net expansion data.

[0053] Based on the above, the technical solution provided in this embodiment involves constructing and testing a first test assembly containing only bottom aluminum foil and a second test assembly containing loose powder covered with the same aluminum foil within the same alumina crucible. The expansion data from the two sets of tests are then differentially calculated. This not only eliminates the contribution of thermal expansion from the testing system itself (such as the alumina crucible and aluminum foil), but also ensures that the powdered sample is only lightly covered by the aluminum foil during the test, without the need for compaction. This maximizes the preservation of its natural loose state and avoids the impact of molding operations on the sample's internal structure and expansion characteristics. Therefore, this embodiment can accurately test the expansion coefficient of powdered materials in a loose state.

[0054] Based on the first embodiment described above, a second embodiment of the method for testing the coefficient of thermal expansion of powdered materials according to this application is proposed. For the second embodiment, please refer to... Figure 4 After step S60, the method for testing the coefficient of thermal expansion of powdered materials may further include steps S601 to S605: Step S601: Obtain the bulk density of the powder sample to be tested and the inner diameter of the alumina crucible; It should be noted that loose density refers to the density of powder in its natural packed state, reflecting the degree of compactness of the powder packing. It can be obtained by calculating the mass of a known volume of loose powder, or by measuring it using a tap density meter; this embodiment does not specifically limit this method. The inner diameter of the alumina crucible, i.e., the internal diameter of the alumina crucible, can be directly measured using a high-precision vernier caliper or micrometer, or it can be measured non-contactly using optical measuring equipment; this embodiment does not specifically limit this method either.

[0055] Step S602: Based on the coefficient of expansion, target temperature range, loose density, and inner diameter, calculate the theoretical height change of the powder sample to be tested within the target temperature range. When calculating the theoretical height change of the powder sample under test within the target temperature range based on the coefficient of thermal expansion, target temperature range, loose density, and inner diameter, the equivalent height of the powder sample under test at the initial temperature can be estimated based on the loose density of the powder sample under test and the inner diameter of the alumina crucible. Then, the theoretical height change can be calculated using the thermal expansion formula by combining the coefficient of thermal expansion and the target temperature range.

[0056] Step S603: Determine the actual height change of the powder sample to be tested based on the net expansion data; It should be noted that the net expansion data has excluded the expansion effects of the alumina crucible and aluminum foil, and directly reflects the total displacement change of the powder sample under test within the target temperature range. Therefore, the net expansion data can be directly used as the actual height change of the powder sample under test.

[0057] Step S604: Determine whether the absolute difference between the actual height change and the theoretical height change is less than a preset deviation threshold. It should be noted that the preset deviation threshold is used as the basis for determining whether the difference between the actual height change and the theoretical height change is large. It can be a default value or it can be flexibly set by the user according to the actual situation. This embodiment does not make specific limitations on this.

[0058] Step S605: If not, output an error message indicating an abnormal test result.

[0059] It should be noted that abnormal test results can be output in various forms, such as popping up a warning window on the display interface, flashing an indicator light, or generating an abnormal report. This embodiment does not impose any specific limitations on this.

[0060] This embodiment effectively improves the reliability of the expansion coefficient test results for powdered materials by introducing a result verification mechanism. After calculating the expansion coefficient of the powdered sample to be tested based on the first and second expansion data, this embodiment first obtains the loose density of the powdered sample and the inner diameter of the alumina crucible. Then, based on the determined expansion coefficient, target temperature range, loose density, and inner diameter, the theoretical height change of the powdered sample to be tested within the target temperature range is calculated. This theoretical height change represents the amount of expansion that the powdered sample should undergo under ideal conditions according to the inherent properties of the material. Next, the actual height change of the powdered sample to be tested is determined using the net expansion data. Then, it is judged whether the absolute difference between the actual height change and the theoretical height change is less than a preset deviation threshold. If not, it indicates that the difference between the actual height change and the theoretical height change is large, and the test result is abnormal. The system will immediately output an abnormal test result alert message, thereby promptly warning the operator and avoiding the use of inaccurate data for subsequent analysis or decision-making.

[0061] Based on the first and / or second embodiments described above, a third embodiment of the method for testing the coefficient of thermal expansion of powdered materials according to this application is proposed. In the third embodiment, before the step of testing the first expansion data of the first test assembly within the target temperature range, the method for testing the coefficient of thermal expansion of powdered materials may further include: Inert protective gas is continuously introduced into the test chamber containing the first test assembly until the first expansion data test is completed; Prior to the step of testing the second expansion data of the second test assembly within the target temperature range, the method for testing the coefficient of thermal expansion of powdered materials also includes: An inert protective gas is continuously introduced into the test chamber containing the second test assembly until the second expansion data test is completed.

[0062] It should be noted that continuously introducing inert protective gas into the test chamber containing the first test assembly until the first expansion data test is completed is a step designed to provide an inert environment for the first test assembly during the first expansion data test, preventing it from reacting with reactive gases (such as oxygen and water vapor) at high temperatures, thereby ensuring the accuracy and stability of the test data. Similarly, continuously introducing inert protective gas into the test chamber containing the second test assembly until the second expansion data test is completed is also a step designed to provide inert protection for the second test assembly during the second expansion data test, preventing it from reacting with reactive gases at high temperatures, thereby ensuring the accuracy and stability of the test data.

[0063] During the introduction of inert protective gas, the flow rate of the gas can be precisely controlled by a gas flow controller to ensure a stable flow into the test chamber. An exhaust port is installed at the outlet of the test chamber to maintain positive pressure and prevent external air from entering. Alternatively, a circulation purification system can be used to extract the gas from the test chamber, purify it, and then return it to the test chamber, while simultaneously replenishing a small amount of fresh inert gas to maintain the purity of the inert atmosphere within the test chamber.

[0064] This embodiment establishes a controlled inert atmosphere environment by continuously introducing an inert protective gas into the test chamber containing the test assemblies during the expansion data testing of the first and second test assemblies. This ensures that, throughout the target temperature range, neither the first test assembly containing only aluminum foil and an alumina crucible, nor the second test assembly containing the powdered sample, aluminum foil, and an alumina crucible, will undergo adverse chemical reactions with the reactive gas in the test chamber. This effectively avoids changes in quality, structure, or surface properties caused by reactions such as sample oxidation, decomposition, or hydrolysis, improving the accuracy and reliability of the test results.

[0065] Based on the first, second, and / or third embodiments described above, a fourth embodiment of the method for testing the coefficient of thermal expansion of powdered materials according to this application is proposed. In this fourth embodiment, please refer to... Figure 5 Before step S60, the method for testing the coefficient of thermal expansion of powdered materials may further include steps S01 to S02: Step S01: Perform smoothing filtering on the first and second dilated data; Step S02: Calculate the expansion coefficient of the powder sample to be tested based on the first and second expansion data after smoothing and filtering.

[0066] It should be noted that smoothing filtering is applied to the first and second dilated data to eliminate random noise and spikes in the data, making the data curve smoother and thus improving data quality and the accuracy of subsequent calculations. This smoothing filtering can be implemented in various ways. For example, moving average filtering can be used, replacing the current data point by calculating the average of data within a certain window surrounding it; median filtering can be used, replacing the data point with the median of its neighborhood; or wavelet transform filtering can be used, removing high-frequency noise components through wavelet decomposition and reconstruction.

[0067] This embodiment, by limiting the process to include smoothing and filtering after obtaining the first and second expansion data, effectively removes random noise and measurement errors from the original data. This ensures that the smoothed and filtered data more accurately reflects the true expansion behavior of the powder sample at different temperatures. Subsequently, using the smoothed and filtered data, the expansion coefficient of the powder sample can be accurately determined.

[0068] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0069] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0070] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent scope of this application.

Claims

1. A method for testing the coefficient of thermal expansion of powdered materials, characterized in that, The method includes: Aluminum foil is placed at the bottom of an alumina crucible that does not contain the powdered sample to be tested, forming the first test assembly; Test the first expansion data of the first test assembly within the target temperature range; After the first expansion data test is completed, the aluminum foil is removed from the alumina crucible; The powder sample to be tested is placed in an alumina crucible after the aluminum foil has been removed, and after being placed, the aluminum foil is covered on the powder sample to be tested to form a second test assembly. Test the second expansion data of the second test assembly within the target temperature range; The expansion coefficient of the powder sample to be tested is calculated based on the first expansion data and the second expansion data.

2. The method as described in claim 1, characterized in that, The step of testing the first expansion data of the first test assembly within the target temperature range includes: The first displacement value of the first test assembly at each temperature in the target temperature range is obtained by a test probe; The first expansion data is generated by associating each first displacement value with the temperature corresponding to each first displacement value.

3. The method as described in claim 2, characterized in that, Before the step of obtaining the first displacement value of the first test assembly at each temperature within the target temperature range using a test probe, the method further includes: The first test assembly is placed at the test station, and the test probe is controlled to contact the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load. After the test probe is controlled to contact the upper surface of the aluminum foil in the first test assembly in the vertical direction with a preset contact load, the first displacement change of the test probe within a preset time period is monitored. If the first displacement change is less than a preset change threshold, then the step of obtaining the first displacement value of the first test assembly at each temperature in the target temperature range through the test probe is performed.

4. The method as described in claim 2, characterized in that, The step of testing the second expansion data of the second test assembly within the target temperature range includes: The second displacement value of the second test assembly at each temperature within the target temperature range is obtained by using a test probe; The second expansion data is generated by associating each second displacement value with the temperature corresponding to each second displacement value.

5. The method as described in claim 4, characterized in that, Before the step of obtaining the second displacement value of the second test assembly at each temperature within the target temperature range using a test probe, the method further includes: The second test assembly is placed at the test station, and the test probe is controlled to contact the upper surface of the aluminum foil in the second test assembly in the vertical direction with a preset contact load. After the test probe is controlled to contact the upper surface of the aluminum foil in the second test assembly in a vertical direction with a preset contact load, the second displacement change of the test probe within a preset time period is monitored. If the second displacement change is less than a preset change threshold, then the step of obtaining the second displacement value of the second test assembly at each temperature in the target temperature range through the test probe is executed.

6. The method as described in claim 1, characterized in that, The step of placing the powdered sample to be tested into an alumina crucible after removing the aluminum foil, and then covering the powdered sample with the aluminum foil to form the second test assembly, includes: The powdered sample to be tested is placed at a preset height position in the alumina crucible after the aluminum foil has been removed; The alumina crucible containing the powdered sample to be tested was subjected to vibration. After vibration treatment, the aluminum foil is covered on the powder sample to be tested to form the second test assembly.

7. The method as described in claim 1, characterized in that, The step of calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data includes: Subtract the second inflation data from the first inflation data to obtain the net inflation data; The net expansion data is linearly fitted to obtain the expansion coefficient of the powder sample to be tested.

8. The method as described in claim 7, characterized in that, After calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data, the method further includes: Obtain the bulk density of the powdered sample to be tested and the inner diameter of the alumina crucible; Based on the expansion coefficient, the target temperature range, the loose density, and the inner diameter, the theoretical height change of the powder sample to be tested within the target temperature range is calculated. Based on the net expansion data, determine the actual height change of the powder sample to be tested; Determine whether the absolute difference between the actual height change and the theoretical height change is less than a preset deviation threshold. If not, output an error message indicating an abnormal test result.

9. The method according to any one of claims 1 to 8, characterized in that, Before the step of testing the first expansion data of the first test assembly within the target temperature range, the method further includes: Inert protective gas is continuously introduced into the test chamber containing the first test assembly until the test of the first expansion data is completed. Prior to the step of testing the second expansion data of the second test assembly within the target temperature range, the method further includes: An inert protective gas is continuously introduced into the test chamber containing the second test assembly until the second expansion data test is completed.

10. The method according to any one of claims 1 to 8, characterized in that, Before the step of calculating the expansion coefficient of the powder sample to be tested based on the first expansion data and the second expansion data, the method further includes: Smoothing filtering is applied to the first and second inflated data. The expansion coefficient of the powder sample to be tested is calculated based on the first and second expansion data after smoothing and filtering.

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