A test method for assessing the pressure resistance of granular materials

Abstract

This invention relates to the field of materials technology, specifically to a test method for evaluating the pressure resistance of particulate materials. The method includes: S1, taking an initial particulate material n equal parts to obtain n portions of particulate material to be tested, and applying test pressures F1, F2, ..., Fn to the n portions of the particulate material to be tested respectively. n‑1 and test pressure F n The following steps are performed: S1) Depressurize each initial granular material and plot n compression stress-compression displacement curves; S2) Calculate the elastic recovery work, total work, and elastic recovery work percentage for each compression stress-compression displacement curve; S3) calibrate the curves using the calculated elastic recovery percentage as the ordinate and the test pressure as the abscissa, and calculate the pressure corresponding to the zero slope of the curve, which is the maximum withstand pressure of the initial granular material. This invention provides a simple, accurate, and efficient method for the rapid screening of fumed silicon-carbon materials with good pressure resistance.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and more specifically, to a test method for evaluating the compressive strength of particulate materials. Background Technology

[0002] Petroleum, as a strategic resource, can be fractionated to obtain many products, gasoline being one of them. Currently, automobiles primarily use fossil fuels such as gasoline for power. The non-renewable nature, pollution, and unstable supply of petroleum have spurred the vigorous development of new energy vehicles, whose main power source is lithium-ion batteries. The range stability of new energy vehicles largely depends on the energy density of lithium batteries. To improve energy density, it is necessary to increase the specific capacity and voltage of the positive and negative electrode materials of lithium-ion batteries. Regarding negative electrode materials, silicon anode materials are a promising category, possessing a high theoretical specific capacity (3579 mAh / g at room temperature), a suitable charge-discharge platform, and abundant crustal element resources. Silicon anode materials are divided into two main categories: silicon-carbon and silicon suboxide. Silicon-carbon includes nano-silicon-carbon, micron-silicon-carbon, and fumed silicon-carbon, while silicon suboxide includes conventional silicon suboxide and pre-lithium / magnesium silicon suboxide. In recent years, fumed silicon-carbon has gained favor and attention from various material and battery manufacturers due to its excellent cycle stability, but some problems still hinder its large-scale application. One of the problems is the pressure resistance of fumed silicon-carbon materials and the testing method for pressure resistance. If the material breaks during the rolling of the electrode after the material is coated, it will affect the performance of the subsequent battery. Therefore, it is important to develop a testing method to evaluate the pressure resistance of fumed silicon-carbon materials. Summary of the Invention

[0003] In view of this, the present invention aims to provide a test method for evaluating the pressure resistance of particulate materials, so as to detect the pressure resistance and pressure resistance of fumed silicon-carbon materials, and reduce the impact of material breakage during electrode rolling after material slurry coating on the performance of subsequent batteries.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows:

[0005] This invention provides a test method for evaluating the compressive strength of particulate materials, the test method comprising the following steps:

[0006] S1. Take n equal parts of the initial particulate material to obtain n portions of particulate material to be tested, and apply test pressures F1, F2, ..., F to the n portions of the particulate material to be tested respectively. n-1 and test pressure F n The pressure was then released, and each sample of the test particle material was plotted with the compressive stress as the ordinate and the compressive displacement as the abscissa to obtain n compressive stress-compression displacement curves of the initial particle material.

[0007] S2. Calculate the elastic recovery work, total work, and elastic recovery work percentage for each of the compression stress-compression displacement curves, where the elastic recovery work percentage is the ratio of the elastic recovery work to the total work.

[0008] S3. Using the elastic recovery percentage calculated from each of the compression stress-compression displacement curves as the vertical axis and the test pressure as the horizontal axis, calibrate and plot the curves. Calculate the pressure corresponding to the zero slope in the curve, which is the maximum withstand pressure of the initial particulate material.

[0009] Optionally, the initial particulate material includes fumed silicon-carbon material and / or porous silicon-carbon material.

[0010] Optionally, the mass of each particulate material to be tested is 0.5 to 3 g.

[0011] Optionally, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The numbers increase sequentially in an arithmetic progression.

[0012] Optionally, the test pressure F1 is 500–4000 N; the arithmetic sequence F1, F2, …, F… n-1 and F n The tolerance ranges from 500 to 4000 N.

[0013] Optionally, in step S1, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The pressurization initiation control method is displacement control; wherein, the displacement control speed of the pressurization is 5-15 mm / min; the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The final control method for pressurization is force control; the control forces for pressurization are F1, F2, ..., F... n-1 and F n .

[0014] Optionally, in step S1, the initial control method for depressurization is displacement control; the displacement control speed for depressurization is 20-40 mm / min; the final control method for depressurization is force control, and the control force for depressurization is 10-40 N.

[0015] Optionally, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F nThe pressurization process includes a first pressure holding process, the duration of which is 15 to 45 seconds; the depressurization process includes a second pressure holding process, the duration of which is 5 to 20 seconds.

[0016] Optionally, the elastic recovery work is calculated by calculating the area under the curve during the decompression stage of the compressive stress-compression displacement curve.

[0017] Optionally, the total work is calculated by calculating the area under the curve during the pressurization phase of the compressive stress-compressive displacement curve.

[0018] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0019] This invention involves plotting compressive stress-compression displacement curves on the initial particulate material; calculating the elastic recovery work, total work, and percentage of elastic recovery work for each curve; and calibrating the curve using the calculated percentage of elastic recovery work as the ordinate and the test pressure as the abscissa. By calculating the pressure corresponding to a zero slope on the curve, the maximum withstand pressure of the initial particulate material is obtained. This testing method directly assesses the pressure resistance of negative electrode powder materials using compressive stress-compression displacement curves. It is simple to operate, provides accurate test results, and facilitates the rapid screening of particulate materials with good pressure resistance.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0022] Figure 1 The figure shown is a curve of compressive stress-compressive displacement of the fumed silicon-carbon material A used in Example 1 under a pressure of 10000N.

[0023] Figure 2 The figure shown is a graph showing the relationship between the elastic recovery ratio and pressure of the fumed silicon-carbon material A used in Example 1.

[0024] Figure 3 The image shows the particle size distribution of the fumed silicon-carbon material A used in Example 1 before and after compression.

[0025] Figure 4 The figure shown is a graph showing the relationship between the elastic recovery ratio and pressure of the gaseous silicon-carbon material B used in Example 2.

[0026] Figure 5 The image shows the particle size distribution of the fumed silicon-carbon material B used in Example 2 before and after compression.

[0027] Figure 6 The figure shown is a graph showing the relationship between the elastic recovery ratio and pressure of the gaseous silicon-carbon material C used in Example 3.

[0028] Figure 7 The figure shown is a particle size distribution diagram of the gaseous silicon-carbon material C used in Example 3 before and after compression. Detailed Implementation

[0029] This invention discloses a test method for evaluating the compressive strength of particulate materials. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0030] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0031] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0034] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0035] Currently, the mainstream silicon anode materials, or those awaiting large-scale production, are mainly fumed silicon-carbon materials. Their preparation process primarily includes carbon substrate preparation, silicon vapor deposition, and carbon layer coating. Whether biomass or resin-based, carbon substrates are currently prone to cracking during electrode rolling due to their inherent low structural strength. The more broken silicon anode particles there are, the more likely subsequent battery performance will suffer, such as a decrease in initial capacity and deterioration in high-temperature storage performance.

[0036] To test the pressure resistance and withstand capability of fumed silicon-carbon materials, and to reduce the impact of material breakage during electrode rolling after slurry coating on the performance of subsequent batteries, the present invention adopts the following technical solution:

[0037] This invention provides a test method for evaluating the compressive strength of particulate materials, the test method comprising the following steps:

[0038] S1. Take n equal parts of the initial particulate material to obtain n portions of particulate material to be tested, and apply test pressures F1, F2, ..., F to the n portions of the particulate material to be tested respectively. n-1 and test pressure F n The pressure was then released, and each sample of the test particle material was plotted with the compressive stress as the ordinate and the compressive displacement as the abscissa to obtain n compressive stress-compression displacement curves of the initial particle material.

[0039] S2. Calculate the elastic recovery work, total work, and elastic recovery work percentage for each of the compression stress-compression displacement curves, where the elastic recovery work percentage is the ratio of the elastic recovery work to the total work.

[0040] S3. Using the elastic recovery percentage calculated from each of the compression stress-compression displacement curves as the vertical axis and the test pressure as the horizontal axis, calibrate and plot the curves. Calculate the pressure corresponding to the zero slope in the curve, which is the maximum withstand pressure of the initial particulate material.

[0041] In the description of this invention, the term "compressive stress" is the value obtained by dividing the compressive load applied to the specimen during a compression test by the original cross-sectional area of ​​the specimen. The unit is MPa. In the art, compressive stress is used to determine material properties such as compressive strength, compressive failure stress, compressive yield stress, and compressive stress at constant strain, in the form of constant compression tests or compression fracture tests.

[0042] In the description of this invention, the term "compressive displacement" refers to the deformation displacement that occurs when an object is subjected to an external force.

[0043] The compressive stress-compression displacement curve of this invention can be obtained by measuring a powder compaction density meter. Specifically, the powder compaction density meter includes a first sensor and a second sensor. The first sensor is used to monitor pressure, and the second sensor is used to monitor displacement. The pressure and displacement are in one-to-one correspondence. After the test, the instrument will provide a compressive stress-compression displacement curve.

[0044] This invention involves plotting compressive stress-compression displacement curves on the initial particulate material; calculating the elastic recovery work, total work, and percentage of elastic recovery work for each curve; and calibrating the curve using the calculated percentage of elastic recovery work as the ordinate and the test pressure as the abscissa. By calculating the pressure corresponding to a zero slope on the curve, the maximum withstand pressure of the initial particulate material is obtained. This testing method directly assesses the pressure resistance of negative electrode powder materials using compressive stress-compression displacement curves. It is simple to operate, provides accurate test results, and facilitates the rapid screening of particulate materials with good pressure resistance.

[0045] For example, the initial particulate material may include fumed silicon carbide material and / or porous silicon carbide material.

[0046] According to the present invention, if the mass of each portion of the test particle material is too large, it may lead to uneven stress distribution; if the mass of each portion of the test particle material is too small, it may lead to insignificant displacement. To accurately determine the compressive stress-compression displacement curve of the initial particle material, the mass of each portion of the test particle material can be 0.5–3 g. Exemplarily, the mass of each portion of the test particle material can be any value selected from 0.5 g, 0.8 g, 1 g, 1.2 g, 1.4 g, 1.6 g, 1.8 g, 2.0 g, 2.2 g, 2.4 g, 2.6 g, 2.8 g, and 3.0 g, or any value within the range formed by any pair of the above values.

[0047] In this invention, to facilitate the plotting of the compressive stress-compression displacement curve, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n Preferably, they form an arithmetic sequence, for example, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The numbers increase sequentially in an arithmetic progression.

[0048] According to the present invention, both excessively small and excessively large test pressures F1 are detrimental to finding the critical breakage point where particles undergo irreversible deformation under pressure. The test pressure F1 in this invention can be 500–4000 N. Exemplarily, the test pressure F1 can be any value selected from 500 N, 1000 N, 1500 N, 2000 N, 2500 N, 3000 N, 3500 N, and 4000 N, or any value within the range formed by any two of the above values.

[0049] According to this invention, it is necessary to calculate the ratio of elastic recovery work to total work based on the pressure-displacement curve, and then fit it to a scatter plot of each maximum pressure. If the tolerance range is too small, overfitting may occur, making it difficult to find the critical point; if the tolerance range is too large, the fit will be insufficient, and the error at the critical point will be amplified. The arithmetic sequence F1, F2, ..., F... described in this invention... n-1 and F n The tolerance can range from 500 to 4000N. For example, the arithmetic sequence F1, F2, ..., F... n-1 and F n The tolerance can be any value among 500N, 1000N, 1500N, 2000N, 2500N, 3000N, 3500N and 4000N, or any value within the range formed by any two of the above values.

[0050] In one embodiment of the present invention, in step S1, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The initial control method for pressurization can be displacement control; in this invention, displacement control is used as the initial control method for pressurization to facilitate the plotting of stress-displacement curves. Considering time cost and the accuracy of time sampling points, the displacement control speed for pressurization can be 5–15 mm / min; exemplarily, the displacement control speed for pressurization can be any value among 5 mm / min, 7 mm / min, 9 mm / min, 11 mm / min, 13 mm / min, and 15 mm / min, or any value within the range formed by any two of the above values.

[0051] In one embodiment of the present invention, in step S1, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The final control method for pressurization can be force control; in this invention, force control is used as the final control method for pressurization to facilitate subsequent scatter plotting of elastic recovery work ratio and test pressure. The control forces for pressurization are F1, F2, ..., F... n-1 and F n .

[0052] In one embodiment of the present invention, in step S1, the initial control method for depressurization can be consistent with the pressurization process, for example, it can be displacement control. Considering time cost and the accuracy of time sampling, the displacement control speed for depressurization can be 20 to 40 mm / min; for example, the displacement control speed for depressurization can be any value among 20 mm / min, 25 mm / min, 30 mm / min, 35 mm / min, and 40 mm / min, or any value within the range formed by any two of the above values.

[0053] In one embodiment of the present invention, in step S1, the final control method for depressurization is preferably to ensure that the test particle material is not subjected to force (i.e., is not crushed as much as possible). For example, the final control method for depressurization can be force control. The depressurization control force can be 10-40N. If the depressurization control force is too small, the precision of the instrument may not be achieved; if the depressurization control force is too large, the test particle material may still be under pressure, failing to achieve the final detection purpose. For example, the depressurization control force can be any value among 10N, 15N, 20N, 25N, 30N, 35N, and 40N, or any value within the range of any two of the above values.

[0054] For example, the pressurization control process in this invention can be as follows: the mold for hydraulically filling powder material includes a force sensor and a displacement sensor; the pressurization program is edited and run; the magnitude of the applied force and the amount of displacement are monitored by the force sensor and the displacement sensor to obtain a series of data points.

[0055] In the description of this invention, the term "initial control method" refers to the control method used at the start of the test in the test scheme of the material tensile testing machine.

[0056] In the description of this invention, the term "final control method" refers to the control method for how the test steps in a material tensile test are terminated.

[0057] According to the present invention, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F nThe pressurization process includes a first pressure holding process, which allows the test particle material to be fully stressed. In this invention, the duration of the first pressure holding process is 15–45 seconds. If the duration is too short, the test particle material may not be able to withstand sufficient stress; if the duration is too long, unnecessary time costs will be incurred. The depressurization process includes a second pressure holding process, the duration of which is 5–20 seconds. For example, the duration of the first pressure holding process can be 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, etc., and the duration of the second pressure holding process can be 5 seconds, 8 seconds, 10 seconds, 12 seconds, 14 seconds, 16 seconds, 18 seconds, 20 seconds, etc.

[0058] In one embodiment of the present invention, the calculation of the elastic recovery work includes calculating the area under the curve during the decompression stage of the compressive stress-compression displacement curve.

[0059] In one embodiment of the present invention, the total work is calculated by calculating the area under the curve during the pressurization phase of the compressive stress-compressive displacement curve.

[0060] As an example, the integral area under the curve involved in this invention can be obtained by performing area integration on the curve using Origin software.

[0061] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available. Specifically, fumed silicon carbide material A was purchased from Changzhou Silicon Source, fumed silicon carbide material B was purchased from Jiangxi Yijin, and fumed silicon carbide material C was purchased from Lanxi Zhide.

[0062] Example 1

[0063] (1) Test: Take 10 equal portions of fumed silicon-carbon material A, each 1g, and apply pressures of 2000N, 4000N, 6000N, 8000N, 10000N, 12000N, 14000N, 16000N, 18000N, and 20000N respectively. The pressure application displacement control speed is 10mm / min. After pressure application, maintain the pressure for 30s, then depressurize. The depressurization program controls the force at 20N and the depressurization displacement control speed at 30mm / min. After depressurization, maintain the pressure for 10s. Ten compressive stress-compression displacement curves are obtained. Figure 1 The figure shows the compressive stress-compression displacement curves under 10000N pressure (and the compressive stress-compression displacement curves under 2000N, 4000N, 6000N, 8000N, 12000N, 14000N, 16000N, 18000N, and 20000N pressures). Figure 1 The curves in the text are similar in shape, and will not be listed one by one here.

[0064] (2) Calculation: The obtained curves are integrally processed using Origin software. The area under the curve during the decompression phase of each curve is recorded as the elastic recovery work (where the decompression phase is the pressure drop curve in the compressive stress-compressive displacement curve, such as...). Figure 1 As shown, the curve for the decompression stage corresponds to the initial x-coordinate of 1 mm and the final x-coordinate of 1.6 mm. The area under the curve for the pressurization stage is recorded as the total work (where the pressurization stage is the curve representing the pressure rise in the compressive stress-compressive displacement curve, such as...). Figure 1 As shown, the curves for the pressurization stage correspond to the initial x-coordinate of 0 mm and the final x-coordinate of 1.6 mm. These curves represent the compressive stress-compression displacement curves for 2000 N, 4000 N, 6000 N, 8000 N, 10000 N, 12000 N, 14000 N, 16000 N, 18000 N, and 20000 N. The calculated W... 弹1 W 总1 W 弹2 W 总2 ,…,W 弹9 W 总9 W 弹10 W 总10 (that is, each pressure corresponds to one W) 弹n and W 总n ), using W for each group 弹 Divide by W 总 Obtain eta1, eta2,..., eta9, eta 10 Plot a scatter plot of the pressure against the corresponding pressure, and then fit the curve to obtain the pressure value with a slope of 0, which is the maximum pressure F that the gaseous silicon-carbon material A can withstand. x ,like Figure 2 As shown, its size is 7200N.

[0065] (3) Result Verification: To verify the accuracy of this method, the particle size distribution of fumed silicon-carbon material A powder before, after 6000N, and after 8000N compression was tested. The results are as follows: Figure 3 As shown in the figure, the particle size of the gaseous silicon carbide material A before and after 6000N compression is not significantly different. However, after 8000N compression, the particle size of the gaseous silicon carbide material A decreases significantly, indicating that the material has been crushed. This means that the critical crushing force range of gaseous silicon carbide material A is between 6000N and 8000N, which is consistent with the previously calculated F. x The size is consistent with 7200N.

[0066] Example 2

[0067] (1) Test: Take 10 equal parts of fumed silicon carbide material B, each part is 1g, and apply pressure of 2000N, 4000N, 6000N, 8000N, 10000N, 12000N, 14000N, 16000N, 18000N and 20000N respectively. The pressure displacement control speed is 10mm / min. After pressure is applied, the pressure is held for 30s, and then the pressure is released. The pressure release program control force is 20N, the pressure release displacement control speed is 30mm / min, and the pressure is held for 10s after release. 10 compression stress-compression displacement curves are obtained.

[0068] (2) Calculation: The obtained curves were integrated using Origin software. The area under the curve during the decompression phase of each curve was recorded as the elastic recovery work, and the area under the curve during the pressurization phase was recorded as the total work. The compressive stress-compression displacement curves corresponding to 2000N, 4000N, 6000N, 8000N, 10000N, 12000N, 14000N, 16000N, 18000N, and 20000N were used to calculate W. 弹1 W 总1 W 弹2 W 总2 ,…,W 弹9 W 总9 W 弹10 W 总10 (that is, each pressure corresponds to one W) 弹n and W 总n Dividing the W_bullets of each group by the total W_total yields η1, η2, ..., η9, η_total. 10 Plot a scatter plot of the pressure against the corresponding pressure, and then fit the curve to obtain the pressure value with a slope of 0, which is the maximum pressure F that the gaseous silicon-carbon material B can withstand. x ,like Figure 4 As shown, its size is 9000N.

[0069] (3) Result Verification: To verify the accuracy of this method, the particle size distribution of fumed silicon-carbon material B powder before, after 8000N, and after 10000N compression was tested. The results are as follows: Figure 5 As shown in the figure, the particle size of the gaseous silicon carbide material B before and after 8000N compression is not significantly different. However, after 10000N compression, the particle size of the gaseous silicon carbide material B decreases significantly, indicating that the material has been crushed. This means the critical crushing force range for gaseous silicon carbide material is between 8000N and 10000N, consistent with the previously calculated F. x The size is consistent with 9000N.

[0070] Example 3

[0071] (1) Test: Take 10 equal parts of fumed silicon carbide material C, each part is 1g, and apply pressure of 2000N, 4000N, 6000N, 8000N, 10000N, 12000N, 14000N, 16000N, 18000N and 20000N respectively. The pressure displacement control speed is 10mm / min. After pressure is applied, the pressure is held for 30s, and then the pressure is released. The pressure release program control force is 20N, the pressure release displacement control speed is 30mm / min, and the pressure is held for 10s after release. 10 compression stress-compression displacement curves are obtained.

[0072] (2) Calculation: The obtained curves were integrated using Origin software. The area under the curve during the decompression phase of each curve was recorded as the elastic recovery work, and the area under the curve during the pressurization phase was recorded as the total work. The compressive stress-compression displacement curves corresponding to 2000N, 4000N, 6000N, 8000N, 10000N, 12000N, 14000N, 16000N, 18000N, and 20000N were used to calculate W. 弹1 W 总1 W 弹2 W 总2 ,…,W 弹9 W 总9 W 弹10 W 总10 (that is, each pressure corresponds to one W) 弹n and W 总n ), using W for each group 弹 Divide by W 总 Obtain eta1, eta2,..., eta9, eta 10 Plot a scatter plot of the pressure against the corresponding pressure, and then fit the curve to obtain the pressure value with a slope of 0, which is the maximum pressure F that the gaseous silicon-carbon material C can withstand. x ,like Figure 6 As shown, its size is 11500N.

[0073] (3) Result Verification: To verify the accuracy of this method, particle size distribution tests were performed on fumed silicon carbide C powder before, after 10000N, and after 12000N compression. The results are as follows: Figure 7 As shown in the figure, the particle size of the gaseous silicon carbide material C before and after 10000N compression is not significantly different. However, the particle size of the gaseous silicon carbide material C after 11500N compression shows a significant decrease, indicating that the material has been crushed. This means the critical crushing force range of the gaseous silicon carbide material C is between 10000N and 12000N, which is consistent with the previously calculated F. x The size is consistent with 11500N.

[0074] The verification results of Examples 1-3 show that the present invention plots compressive stress-compression displacement curves on the initial granular material; calculates the elastic recovery work, total work, and elastic recovery work percentage for each compressive stress-compression displacement curve; and calibrates and plots the curves using the calculated elastic recovery percentage as the ordinate and the test pressure as the abscissa. By calculating the pressure corresponding to a slope of zero on the curve, the maximum withstand pressure of the initial granular material is obtained. This maximum withstand pressure is consistent with the critical crushing force range obtained through particle size distribution testing. Therefore, the test method for evaluating the compressive strength of granular materials in this invention has good accuracy and is beneficial for the rapid screening of granular materials with good compressive strength.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A test method for evaluating the compressive strength of particulate materials, characterized in that, The testing method includes the following steps: S1. Take n equal parts of the initial particulate material to obtain n portions of particulate material to be tested, and apply test pressures F1, F2, ..., F to the n portions of the particulate material to be tested respectively. n-1 and test pressure F n The pressure was then released, and each sample of the test particle material was plotted with the compressive stress as the ordinate and the compressive displacement as the abscissa to obtain n compressive stress-compression displacement curves of the initial particle material. S2. Calculate the elastic recovery work, total work, and elastic recovery work percentage for each of the compression stress-compression displacement curves, where the elastic recovery work percentage is the ratio of the elastic recovery work to the total work. S3. Using the elastic recovery percentage calculated from each of the compression stress-compression displacement curves as the vertical axis and the test pressure as the horizontal axis, calibrate and plot the curves. Calculate the pressure corresponding to the zero slope in the curve, which is the maximum withstand pressure of the initial particulate material.

2. The test method according to claim 1, characterized in that, The initial particulate material includes fumed silicon-carbon material and / or porous silicon-carbon material.

3. The test method according to claim 1, characterized in that, The mass of each sample of the particulate material to be tested is 0.5–3 g.

4. The test method according to claim 1, characterized in that, The test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The numbers increase sequentially in an arithmetic progression.

5. The test method according to claim 4, characterized in that, The test pressure F1 is 500–4000 N; The arithmetic sequence F1, F2, ..., F n-1 and F n The tolerance ranges from 500 to 4000 N.

6. The test method according to claim 1, characterized in that, In step S1, the test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The pressurization is initiated by displacement control; wherein the displacement control speed for pressurization is 5–15 mm / min. The test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The final control method for pressurization is force control; the control forces for pressurization are F1, F2, ..., F... n-1 and F n .

7. The test method according to claim 1, characterized in that, In step S1, the initial control method for depressurization is displacement control; the displacement control speed for depressurization is 20-40 mm / min. The final control method for depressurization is force control, and the control force for depressurization is 10-40N.

8. The test method according to claim 1, characterized in that, The test pressure F1, the test pressure F2, ..., the test pressure F n-1 and the test pressure F n The pressurization process includes a first pressure holding process, the duration of which is 15 to 45 seconds. The depressurization process includes a second pressure holding process, which lasts for 5 to 20 seconds.

9. The test method according to claim 1, characterized in that, The calculation method for the elastic recovery work includes calculating the area under the curve during the decompression stage of the compressive stress-compression displacement curve.

10. The test method according to claim 1, characterized in that, The calculation of the total work includes calculating the area under the curve during the compression stage of the compressive stress-compression displacement curve.

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