Method for measuring particle size of metal powder by using scanning electron microscope

Abstract

The invention discloses a method for measuring the particle size of metal powder by using a scanning electron microscope, which comprises the following steps: step 1, sample treatment: adhering a small conductive adhesive tape on a sample table, sprinkling metal powder on the adhered conductive adhesive tape, and purging to obtain the conductive adhesive tape adhered with the metal powder; step 2, parameter setting: setting acceleration voltage, working distance, diaphragm, image contrast, brightness, magnification times and scanning speed of a scanning electron microscope to observe the conductive adhesive tape adhered with the metal powder obtained in the step 1 to obtain an electronic image of metal powder particles; and processing and calculating the electronic image of the metal powder particles by using software to obtain the average particle size of the metal powder particles. According to the method disclosed by the invention, a solvent is not needed to disperse the sample, pollution of the solvent to the sample is effectively avoided, and the result is more accurate than that of directly measuring the particle size by using length software.

Description

Technical Field

[0001] The present invention relates to the technical field of material analysis and testing, and in particular to a method for measuring the particle size of metal powder using a scanning electron microscope. Background Art

[0002] Scanning electron microscopy (SEM) is an important electron microscopy technique widely used in fields such as materials science, biology, and physics. It forms an image by scanning the surface of a sample with a focused electron beam and detecting the reflected or emitted secondary electrons and backscattered electrons.

[0003] Scanning electron microscopy allows for intuitive observation of sample morphology and measurement of particle size. Traditional methods for measuring powder particle size using electron microscopy typically require dispersing the sample using dispersants, ultrasound, and other methods. This requires dozens or even hundreds of calculations, which is computationally intensive, tedious, and prone to errors.

[0004] Existing methods for measuring metal powder particle size suffer from sample contamination due to the use of solvents to disperse the sample. There are also problems such as cumbersome calculations and human errors. The present invention provides a method for measuring metal powder particle size using a scanning electron microscope. This method simplifies sample preparation and can derive the average particle size without tedious calculations. This method is more accurate than directly measuring the particle size using length software. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for measuring the particle size of metal powder using a scanning electron microscope. The method is simple to operate and highly practical.

[0006] According to one aspect of the present invention, a method for measuring the particle size of metal powder using a scanning electron microscope is provided, the method comprising at least the following steps: Step 1, sample preparation: stick a small strip of conductive tape on the sample stage of the scanning electron microscope, sprinkle the metal powder to be tested on the conductive tape, and blow it to obtain the conductive tape with the metal powder to be tested; Step 2, parameter setting: setting the acceleration voltage, working distance, aperture, image contrast, brightness, magnification, and scanning speed of the scanning electron microscope, observing the conductive tape with the metal powder to be tested obtained in step 1, and obtaining a secondary electron image of the metal powder particles; Step 3, software processing: using image processing software to process the secondary electron image of the metal powder particles obtained in step 2, adjusting the threshold in the software interface to extract the metal powder particles to obtain a black and white binary image; Step 4: Manual processing, correcting and improving the black and white binary image obtained in step 3, and calculating the white area S and the total number of metal powder particles N in the black and white binary image; Step 5: Calculate the average particle size of the metal powder particles using Formula I after multi-field measurement based on the white area S and the total number N of metal powder particles in the black and white binary image obtained in Step 4;

[0007] Formula I.

[0008] Optionally, the image processing described in step 4 is specifically to check and improve the black and white binary image obtained in step 3. Due to the unclear image quality and the limitations of the algorithm, the image after computer segmentation is inevitably over-segmented or unsegmented, and it is necessary to correct it, including manually filling the unsegmented interface, manually restoring the over-segmentation, and deleting the incomplete particles at the edge of the field of view or in the lower layer that are blocked.

[0009] Optionally, the conductive tape in step 1 is a conductive tape specially used for scanning electron microscopes; and the metal powder to be tested is selected from one of iron powder and aluminum powder.

[0010] Optionally, the purging in step 1 is to use an ear bulb to blow away loosely adhered metal powder to prevent the powder from flying during vacuuming and contaminating the sample chamber.

[0011] Optionally, in step 2, the acceleration voltage of the scanning electron microscope is 10-25 kV.

[0012] Optionally, the working distance in step 2 is 10-15 mm.

[0013] Optionally, in step 2, the aperture is 30 to 60 microns.

[0014] Optionally, the magnification in step 2 is 500 to 8000 times.

[0015] Optionally, in step 2, the scanning speed is 15 to 25 s / frame.

[0016] Optionally, the image processing software in step 3 is Image J software.

[0017] Optionally, the threshold T of the image processing software in step 3 is 0-255.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for measuring the particle size of metal powder using a scanning electron microscope. The sample preparation is simple and does not require operations such as solution dispersion. The sample can be directly prepared using carbon conductive tape and the image can be processed with software to calculate the average particle size. The result is more accurate than directly measuring the particle size using length software. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a secondary electron image of the aluminum powder particles obtained in Example 1 of the present invention; Figure 2 The secondary electron image of the aluminum powder particles obtained in Example 1 of the present invention is converted into a black and white binary image after being processed by software; Figure 3 This is the manually processed image obtained in Example 1 of the present invention; Figure 4 This is a secondary electron image of the iron powder particles obtained in Example 2 of the present invention; Figure 5 The secondary electron image of the iron powder particles obtained in Example 2 of the present invention is converted into a black and white binary image after being processed by software; Figure 6 This is the manually processed image obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to specific examples, but the present invention is not limited thereto in any way.

[0021] In Examples 1 and 2 of the present invention, the particle sizes of aluminum powder and iron powder were detected using a ZEISS EVO25 scanning electron microscope; The conductive tape used in Examples 1 and 2 of the present invention was purchased from Oxford Instruments Technology (Shanghai) Co., Ltd., and the aluminum powder and iron powder were homemade in the laboratory.

[0022] Example 1 Step 1, sample preparation: stick a small piece of conductive tape (specially for SEM) on the SEM sample stage, sprinkle a little aluminum powder to be tested on the conductive tape, use an ear bulb to blow off the loose aluminum powder to get the conductive tape with the aluminum powder to be tested.

[0023] Step 2, parameter setting: Set the acceleration voltage of the scanning electron microscope to 10kV, the working distance to 13mm, and the aperture to 30μm. Adjust the image contrast and brightness to observe the conductive tape with the aluminum powder to be tested obtained in step 1 so that the edges of the observed aluminum powder particles are clear. Set the magnification to 2000 times so that the observed aluminum powder particles are of appropriate size and have clear edges. At the same time, set the scanning speed to 25 seconds / frame to obtain the secondary electron image of the aluminum powder particles (such as Figure 1 shown).

[0024] Step 3, software processing: Use image J software to process the secondary electron image of the aluminum powder particles obtained in step 2, and adjust the threshold T to 35 in the image J interface to extract the aluminum powder particles (such as Figure 2 As shown in the figure, the pixels with grayscale values ​​≥ 35 are set to 1 (white), and the pixels with grayscale values ​​< 35 are set to 0 (black), resulting in a black and white binary image.

[0025] Step 4: Manual processing: check and improve the black and white binary image obtained in step 3, manually fill the unsegmented interface, manually restore the over-segmented image, and delete the incomplete particles at the edge of the field of view or in the lower layer (such as Figure 3 As shown in the figure), the area of ​​the white region in the black and white binary image is calculated to be 5563.1µm 2 , the total number of aluminum powder particles is 67.

[0026] Step 5: Calculate the average particle size of the aluminum powder particles in the field of view as 10.28 µm using the white area and the total number of aluminum powder particles in the black and white binary image obtained in Step 4 using the formula shown in Formula I.

[0027] Formula I.

[0028] Example 2 Step 1, sample preparation: stick a small piece of conductive tape (specially for scanning electron microscope) on the sample stage of the scanning electron microscope, sprinkle a little iron powder to be tested on the conductive tape, use an ear bulb to blow off the loose iron powder to be tested, and get the conductive tape with the iron powder to be tested.

[0029] Step 2, parameter setting: Set the acceleration voltage of the scanning electron microscope to 15kV, the working distance to 10mm, and the aperture to 30μm. Adjust the image contrast and brightness to observe the conductive tape with the iron powder to be tested obtained in step 1 so that the observed iron powder particles have clear edges. Set the magnification to 2000 times so that the observed iron powder particles are of appropriate size and have clear edges. At the same time, set the scanning speed to 25 seconds / frame to obtain the secondary electron image of the iron powder particles (such as Figure 4 shown).

[0030] Step 3, software processing: Use image J software to process the secondary electron image of the iron powder particles obtained in step 2, and adjust the threshold T to 90 in the image J interface to extract the aluminum powder particles (such as Figure 5 As shown in the figure, the pixels with grayscale values ​​≥ 90 are set to 1 (white), and the pixels with grayscale values ​​< 90 are set to 0 (black), resulting in a black and white binary image.

[0031] Step 4: Manual processing: check and improve the black and white binary image obtained in step 3, manually fill the unsegmented interface, manually restore the over-segmented image, and delete the incomplete particles at the edge of the field of view or in the lower layer (such as Figure 6 As shown in the figure), calculate the white area and the total number of iron powder particles in the black and white binary image.

[0032] Step 5: Calculate the area of ​​the white region in the black and white binary image obtained in step 4 and the total number of iron powder particles (the formula is the same as in Example 1) to obtain an average particle size of 9.87 µm in the field of view.

[0033] Comparative Example 0.5 g of aluminum powder was ultrasonically dispersed in 100 mL of ethanol to obtain a dispersion containing the aluminum powder to be tested. The dispersion was dried and placed on a scanning electron microscope sample stage. The acceleration voltage of the scanning electron microscope was set to 10 kV, the working distance was 13 mm, and the aperture was 30 μm. The image contrast and brightness were adjusted, the magnification was 2000 times, and the scanning speed was 25 seconds / frame. The secondary electron image of the aluminum powder particles was obtained, and the particle size of each aluminum powder particle was measured in turn using the length measurement software provided by the scanning electron microscope. The average particle size of the aluminum powder was calculated to be 10.67 μm. The results show that the technical solution adopted in Example 1 of the present invention can obtain a measured particle size with higher accuracy and more statistical significance by the area method without using a solvent for dissolution.

[0034] The above descriptions are merely several embodiments of the present invention and do not constitute any form of limitation to the present invention. Although the present invention is disclosed as above in terms of preferred embodiments, they are not intended to limit the present invention. Any technician familiar with the present profession who, without departing from the scope of the technical solution of the present invention, makes slight changes or modifications using the technical contents disclosed above are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for measuring the particle size of metal powder using a scanning electron microscope, characterized in that: The method comprises at least the following steps: Step 1, sample preparation: stick a small strip of conductive tape on the sample stage of the scanning electron microscope, sprinkle the metal powder to be tested on the conductive tape, and blow it to obtain the conductive tape with the metal powder to be tested; Step 2, parameter setting: setting the acceleration voltage, working distance, aperture, image contrast, brightness, magnification, and scanning speed of the scanning electron microscope, observing the conductive tape with the metal powder to be tested obtained in step 1, and obtaining a secondary electron image of the metal powder particles; Step 3, software processing: using image processing software to process the secondary electron image of the metal powder particles obtained in step 2, adjusting the threshold in the software interface to extract the metal powder particles to obtain a black and white binary image; Step 4: Manual processing, correcting and improving the black and white binary image obtained in step 3, and calculating the white area S and the total number of metal powder particles N in the black and white binary image; Step 5: Calculate the average particle size of the metal powder particles using the formula (I) after multi-field measurement based on the white area S and the total number of metal powder particles N obtained in step 4; Formula I.

2. The method according to claim 1, characterized in that The conductive tape is a special conductive tape for scanning electron microscope; The metal powder to be tested is selected from iron powder and aluminum powder.

3. The method according to claim 1, characterized in that The accelerating voltage of the scanning electron microscope in step 2 is 10~25kV.

4. The method according to claim 1, wherein The working distance in step 2 is 10~15mm.

5. The method according to claim 1, wherein In step 2, the aperture is 30 to 60 microns.

6. The method according to claim 1, characterized in that The magnification in step 2 is 500~8000 times.

7. The method according to claim 1, wherein In step 2, the scanning speed is 15-25 s / frame.

8. The method according to claim 1, characterized in that The image processing software in step 3 is Image J software.

9. The method according to claim 1, characterized in that The threshold T of the image processing software in step 3 is 0~255.

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