Preparation Method and Device for Scanning Electron Microscope Sample of Metal or Ceramic Powder

Abstract

The present invention provides a method and device for preparing a scanning electron microscope sample of metal or ceramic powder, which relates to the technical field of material detection. The method for preparing a scanning electron microscope sample of metal or ceramic powder provided by the present invention comprises the following steps: suspending and melting a metal embedding material, allowing the molten metal embedding material to fall into the powder material to be detected, and embedding the powder material to be detected to obtain a scanning electron microscope sample of metal or ceramic powder. The present invention can realize the preparation of a scanning electron microscope sample of metal or ceramic powder with firm embedding in a short time, and significantly improve the analysis and characterization quality of the scanning electron microscope sample of the powder material.

Description

Technical Field

[0001] The present invention relates to the technical field of material detection, and particularly relates to a method and device for preparing a scanning electron microscope sample of metal or ceramic powder. Background Art

[0002] A scanning electron microscope (SEM) is a precision instrument that uses a focused high-energy electron beam to scan the surface of a sample and obtains the surface topography of the sample by collecting and analyzing various signals generated by the interaction between the electron beam and the sample. It has a large magnification, a large depth of field, and can, in combination with other equipment, collect information such as the elemental composition and crystallographic characteristics of materials, playing an important role in the field of material research and can be used for the characterization of the structure and morphology of various materials such as ceramics, metals, and polymers.

[0003] Powder materials are one of the difficulties in the preparation of scanning electron microscope samples. Due to the small size and light weight of powder materials, when observing samples using a scanning electron microscope, methods such as adhesion with conductive tape, cold embedding, or hot embedding are often used for fixation. However, the small particles fixed by adhesion are very likely to float during the test, resulting in contamination of the high-vacuum chamber of the scanning electron microscope. Cold embedding usually uses resin materials for coating, and the poor conductivity of the resin will lead to a reduction in imaging effect, making it difficult to clearly characterize the material at high magnification. Hot embedding requires the application of pressure while heating, and some materials sensitive to temperature and stress are easily damaged. Electron backscatter diffraction (EBSD) is a technique assembled on a scanning electron microscope for analyzing the crystal micro-region orientation and crystal structure. This technique requires accurate collection of signals generated by surface atoms of the sample, so the quality requirements for the sample are very high. Electrolytic polishing is a technique for polishing the metal surface using the principle of anodic dissolution. It has simple operation, short time consumption, and low cost, and is the first choice for EBSD sample preparation, but this technique has very high requirements for the conductivity of the sample. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for preparing a scanning electron microscope sample of metal or ceramic powder. The present invention can achieve the preparation of a firmly embedded scanning electron microscope sample of metal or ceramic powder in a short time, and significantly improve the analysis and characterization quality of the scanning electron microscope sample of powder materials.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a scanning electron microscope sample of metal or ceramic powder, comprising the following steps:

[0007] Suspend the metal inlay material for melting, and let the molten metal inlay material fall into the powder material to be detected, so as to inlay the powder material to be detected and obtain a scanning electron microscope sample of metal or ceramic powder; the powder material to be detected is one or more of metal powder and ceramic powder.

[0008] Preferably, the diameter of the powder material to be detected is in the range of micrometers to millimeters.

[0009] Preferably, the melting point of the metal inlay material is lower than that of the powder material to be detected, and the molten metal inlay material does not react with the powder material to be detected.

[0010] Preferably, the temperature of the suspension melting is 50 - 300K overheated after the metal inlay material melts.

[0011] Preferably, the metal inlay material includes a metal element or an alloy.

[0012] Preferably, the preparation of the scanning electron microscope sample of metal or ceramic powder is carried out in a protective atmosphere.

[0013] The present invention provides a device for preparing a scanning electron microscope sample of metal or ceramic powder, which includes a cavity 1, a suspension melting system and a cavity mold 3; the suspension melting system includes an induction coil 2, a feeding rod 9 and a power supply; the induction coil 2 and the cavity mold 3 are arranged inside the cavity 1; the cavity mold 3 is arranged below the induction coil 2;

[0014] The end of the feeding rod 9 is arranged at the center of the induction coil 2.

[0015] Preferably, it further includes a vacuum pump 6 and a protective atmosphere gas source 7 connected to the cavity 1.

[0016] Preferably, the induction coil 2 is wound by a copper pipe with circulating cooling water inside.

[0017] Preferably, the distance between the opening of the cavity mold 3 and the bottom of the induction coil 2 is 5 - 50 cm.

[0018] The present invention provides a method for preparing a scanning electron microscope sample of metal or ceramic powder, comprising the following steps: suspending and melting a metal embedding material, allowing the molten metal embedding material to fall into the powder material to be detected, and embedding the powder material to be detected to obtain a scanning electron microscope sample of metal or ceramic powder; the powder material to be detected is one or more of metal powder and ceramic powder. The metal embedding material adopted in the present invention has good conductivity, enabling the powder material to be detected to still have a good analysis effect at high magnification in the electron microscope. At the same time, the powder material that is itself conductive does not require processes such as gold spraying. The metal embedding material is solidified with the powder material to be detected after being suspended and melted under the conditions of no container and no pollution, thus effectively avoiding the pollution of the powder material to be detected during the electron microscope sample preparation process. And the stirring effect of the electromagnetic force makes the melting of the metal embedding material more uniform, further improving the embedding quality of the powder material. In the present invention, the powder material to be detected is in full contact with the metal embedding material, so it can be used for the preparation of EBSD samples with higher requirements, reducing the cost and sample preparation cycle compared with ion polishing and vibratory polishing; at the same time, the firm embedding of the powder material effectively reduces the sample loss during the processing process.

[0019] In the present invention, after the molten metal embedding material falls into the powder material to be detected, it quickly solidifies and cools to room temperature within a few minutes, achieving the preparation of a scanning electron microscope sample of powder material with high efficiency and low cost. The results of the examples show that the preparation of the scanning electron microscope sample can be completed within 10 minutes by using the method of the present invention. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the preparation device for the scanning electron microscope sample of metal or ceramic powder of the present invention; Figure 1 In [the figure], 1 is a cavity; 2 is an induction coil; 3 is a cavity mold; 4 is the powder material to be detected; 5 is the metal embedding material; 6 is a vacuum pump; 7 is a protective atmosphere gas source; 8 is a temperature measuring device; 9 is a feeding rod;

[0021] Figure 2 It is an SEM image of the scanning electron microscope sample prepared in Example 1 of the present invention;

[0022] Figure 3 It is the EBSD test result of the scanning electron microscope sample prepared in Example 2 of the present invention. Detailed Embodiments

[0023] The present invention provides a method for preparing a scanning electron microscope sample of metal or ceramic powder, comprising the following steps:

[0024] Suspending and melting a metal embedding material, allowing the molten metal embedding material to fall into the powder material to be detected, and embedding the powder material to be detected to obtain a scanning electron microscope sample of metal or ceramic powder; the powder material to be detected is one or more of metal powder and ceramic powder.

[0025] The present invention suspends and melts the metal embedding material. The present invention selects a suitable metal embedding material according to the physical and chemical properties of the powder material to be detected. In the present invention, the melting point of the metal embedding material is preferably lower than that of the powder material to be detected, and the molten metal embedding material does not react with the powder material to be detected. In the present invention, the metal embedding material preferably includes elemental metals or alloys, and specifically preferably includes Sn, Al, Cu, Ni, Fe, FeTi or Ni3Al. In the present invention, the shape of the metal embedding material preferably includes spherical, near-spherical, square or cylindrical. In the present invention, the size of the metal embedding material is preferably 1-6 cm.

[0026] In the present invention, the temperature of the suspension melting is preferably 50-300 K above the melting point of the metal embedding material after melting, and more preferably 100-150 K above the melting point. After heating the metal embedding material to the melting point and overheating it by 50-300 K in the present invention, the metal embedding material can still remain in a molten state after falling into the mold, so as to wrap the powder material to be detected. If the overheating is too small, it will cause the metal embedding material to solidify too quickly after falling into the mold, and the powder material cannot be well embedded.

[0027] In the present invention, the obtained molten metal embedding material after suspension melting falls into the powder material to be detected to embed the powder material to be detected, and a scanning electron microscope sample of metal or ceramic powder is obtained. In the present invention, preferably after obtaining the molten metal embedding material, the suspension melting system is closed, and the molten metal embedding material directly falls into the powder material to be detected under the action of gravity to embed the powder material to be detected. In the present invention, the mutual infiltration of the molten metal embedding material and the powder material to be detected can make the embedding of the powder material to be detected more firm.

[0028] In the present invention, the powder material to be detected is placed directly below the metal embedding material.

[0029] In the present invention, the powder material to be detected is one or more of metal powders and ceramic powders; the diameter of the powder material to be detected is preferably in the micron to millimeter range, and specifically preferably 800 μm, 500 μm or 2 mm.

[0030] In the present invention, the powder material to be detected is specifically preferably Monel K-500 alloy powder, Ni 64 Cu 28 Al4Mo4 alloy powder or Al2O3 ceramic powder.

[0031] In the present invention, the preparation of the scanning electron microscope sample of metal or ceramic powder is preferably carried out in a protective atmosphere. In the present invention, the protective atmosphere is preferably an argon atmosphere or a helium atmosphere.

[0032] Preferably, after the inlaying, the obtained ingot is cooled to room temperature, and then polished or electro-polished to obtain a scanning electron microscope sample of metal or ceramic powder.

[0033] The present invention provides a device for preparing a scanning electron microscope sample of metal or ceramic powder, which comprises a cavity 1, a suspension melting system and a cavity mold 3; the suspension melting system comprises an induction coil 2, a feeding rod 9 and a power supply; the induction coil 2 and the cavity mold 3 are arranged inside the cavity 1; the cavity mold 3 is arranged below the induction coil 2;

[0034] The end of the feeding rod 9 is arranged at the center of the induction coil 2.

[0035] The preparation device provided by the present invention comprises a cavity 1. In the present invention, the cavity 1 is preferably cylindrical; the material of the cavity 1 is preferably demagnetized stainless steel. In the present invention, the cavity 1 is used to isolate oxygen and prevent the metal inlay from being rapidly oxidized after heating and being difficult to stably suspend and melt.

[0036] The preparation device provided by the present invention comprises a suspension melting system. In the present invention, the suspension melting system comprises an induction coil 2, a feeding rod 9 and a power supply. In the present invention, the metal inlay is placed at the end of the feeding rod 9. In the present invention, the end of the feeding rod 9 is arranged at the center of the induction coil 2. In the present invention, the material of the feeding rod 9 is preferably ceramic. In the present invention, the feeding rod 9 is used to place the metal inlay at the position where the suspension force of the induction coil 2 is the largest, and its movement in the cavity 1 can be manually controlled outside the cavity 1.

[0037] As an embodiment of the present invention, the induction coil 2 is wound by a copper pipe with circulating cooling water inside. In the present invention, the induction coil 2 can suspend and melt the metal inlay.

[0038] In the present invention, the power supply is connected to the induction coil 2. As an embodiment of the present invention, the power supply is a high-frequency power supply. The present invention uses the suspension melting system to stably suspend the metal inlay at the center of the induction coil 2. Preferably, the feeding rod 9 is removed after the metal inlay is stably suspended.

[0039] The preparation device provided by the present invention comprises a cavity mold 3. In the present invention, the induction coil 2 and the cavity mold 3 are arranged inside the cavity 1; the cavity mold 3 is arranged below the induction coil 2. As an embodiment of the present invention, the cavity mold 3 is arranged directly below the induction coil 2. In the present invention, the distance between the opening of the cavity mold 3 and the bottom of the induction coil 2 is preferably 5 - 50 cm, more preferably 15 cm.

[0040] As an embodiment of the present invention, the cavity mold 3 includes a body and a cavity provided in the body. In the present invention, the cavity is preferably cylindrical. In the present invention, the cavity mold 3 is used to place the powder material to be detected and catch the molten metal inlay. The present invention preferably spreads the powder material to be detected evenly on the bottom of the cavity of the cavity mold 3.

[0041] In the present invention, the material of the cavity mold 3 preferably includes oxygen-free copper, stainless steel, alumina ceramic or graphite. In the present invention, the cavity mold 3 does not react with the metal inlay. In the present invention, the cavity mold 3 is preferably in a regular shape, specifically preferably cylindrical or square, and preferably composed of two identical halves combined; the bottom is preferably provided with exhaust holes. As an embodiment of the present invention, the cavity mold 3 is placed directly below the metal inlay.

[0042] As an embodiment of the present invention, the preparation device further includes a vacuum pump 6 and a protective atmosphere gas source 7 connected to the cavity 1. As an embodiment of the present invention, the vacuum pump 6 is connected to the cavity 1 through a pipeline. The present invention can use the vacuum pump 6 to evacuate the cavity 1 to 5×10 1 ~1×10 -1 Pa. As an embodiment of the present invention, the protective atmosphere gas source 7 is connected to the cavity 1 through a pipeline. The present invention can use the protective atmosphere gas source 7 to backfill the cavity 1 with a protective gas to 1×10 4 ~1×10 5 Pa. In the present invention, the protective gas is preferably argon or helium.

[0043] The present invention uses the vacuum pump 6 and the protective atmosphere gas source 7 to evacuate the cavity 1 and then backfill it with a protective gas to provide a protective atmosphere.

[0044] As an embodiment of the present invention, the preparation device further includes a temperature measuring device 8. In the present invention, the temperature measuring device 8 is preferably an infrared thermometer. As an embodiment of the present invention, the temperature measuring device 8 is placed above the cavity 1 for monitoring the temperature of the metal inlay.

[0045] In the present invention, the electromagnetic levitation melting technology is a technology for heating and melting a sample under containerless conditions. The sample is levitated by the Lorentz force within an induction coil with an externally applied high-frequency current, and is heated and melted under the action of a high-frequency magnetic field. During the levitation melting process, the sample is always under the action of electromagnetic force and does not contact the container. Therefore, the sample will not be secondarily contaminated and is melted evenly under the action of magnetic stirring. Aiming at the problems of existing powder material scanning electron microscope samples being prone to contaminating the cavity, having a long preparation cycle, and high cost for preparing high-quality EBSD samples, the present invention uses the method of electromagnetic levitation containerless melting of metal inlay materials followed by drop casting to inlay powder materials. The metal inlay material with good conductivity can significantly improve the signal intensity generated by the electron microscope sample, realizing high-resolution and high-magnification observation and characterization of the structure and morphology of powder materials.

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] The preparation device used in the embodiment is as Figure 1 shown, including a cavity 1, a levitation melting system, a cavity mold 3, a vacuum pump 6, a protective atmosphere gas source 7, and a temperature measuring device 8; the cavity 1 is cylindrical and made of demagnetized stainless steel; the levitation melting system includes an induction coil 2, a feeding rod 9, and a high-frequency power supply; the induction coil 2 is wound by a copper tube with circulating cooling water inside; the feeding rod 9 is made of ceramic and is used to place the metal inlay material at the position with the maximum levitation force of the induction coil 2, and its movement inside the cavity 1 can be manually controlled outside the cavity 1; the cavity mold 3 is placed directly below the metal inlay material, and the distance between the opening of the cavity mold 3 and the bottom of the induction coil 2 is 15 cm; the vacuum pump 6 and the protective atmosphere gas source 7 are respectively connected to the cavity 1 through pipelines; the temperature measuring device 8 is an infrared thermometer and is placed above the cavity 1.

[0048] Example 1

[0049] This embodiment provides a method for preparing a scanning electron microscope sample of a micron-sized alloy powder material, which is used to prepare a scanning electron microscope sample of Monel K-500 alloy powder. The steps are as follows:

[0050] (1) Loading the sample: Select an oxygen-free copper mold with an inner diameter of 1.5 cm, a depth of 3 cm, an outer diameter of 5 cm, and a height of 5 cm as the cavity mold 3, lay the Monel K-500 alloy powder with a diameter of 800 μm at the bottom of the oxygen-free copper mold, and place a spherical pure Al inlay material with a diameter of 2 cm at the position with the maximum levitation force of the induction coil 2 through the sample feeding rod;

[0051] (2) Prepare the experimental atmosphere: Turn on the vacuum pump 6 to pump the cavity 1 to 1×10 -1 Pa, and then fill the cavity 1 with high-purity helium gas to 1×10 5 Pa. The time for this process is 8 minutes;

[0052] (3) Levitation melting: Start the high-frequency power supply, monitor the temperature of the pure Al inlay through the infrared thermometer, adjust the power of the high-frequency power supply to heat the pure Al inlay to 150 K above melting, and move the feeding rod 9 away after it stably levitates;

[0053] (4) Casting and sample preparation: Immediately turn off the high-frequency power supply. The pure Al inlay falls into the oxygen-free copper mold and solidifies. The Monel K-500 alloy powder is inlaid to obtain a cylindrical ingot; The total time for levitation melting and casting and sample preparation is 2 minutes;

[0054] (5) Grinding and polishing: Take out the cylindrical ingot in the mold, grind it step by step with 600-3000 mesh sandpaper and then polish it with diamond grinding paste to obtain a scanning electron microscope sample;

[0055] (6) Metallographic etching: Use FeCl3 hydrochloric acid solution (10 g FeCl3 + 30 mL hydrochloric acid solution with a concentration of 1 mol / L + 120 mL H2O) to etch the scanning electron microscope sample for a clearer observation of the microstructure of the material.

[0056] Figure 2 This is the SEM image of the scanning electron microscope sample prepared in Example 1 of the present invention. It can be Figure 2 clearly observed that the clear dendritic morphology inside during the solidification process of the alloy particles.

[0057] Example 2

[0058] This example provides a method for preparing an EBSD sample of a micron-scale alloy powder material, used to prepare a Ni 64 Cu 28 Al4Mo4 alloy powder sample, and the steps are as follows:

[0059] (1) Loading the sample: Select an oxygen-free copper mold with an inner diameter of 1 cm, a depth of 2 cm, an outer diameter of 5 cm, and a height of 5 cm as the cavity mold 3, and lay the Ni 64 Cu 28 Al4Mo4 alloy powder with a diameter of 500 μm at the bottom of the oxygen-free copper mold, and place the pure Cu inlay with a diameter of 2 cm at the place with the maximum levitation force of the induction coil 2 through the sample feeding rod;

[0060] (2) Prepare the experimental atmosphere: Turn on the vacuum pump 6 to pump the cavity 1 to 1×10 -1 Pa, and then fill the cavity 1 with high-purity helium gas to 1×10 5Pa, and the time for this process is 8 min.

[0061] (3) Levitation melting: Start the high-frequency power supply, observe the temperature of the pure Cu inlay through an infrared thermometer, adjust the power of the high-frequency power supply to heat the pure Cu inlay until it melts and then superheats by 100 K. After it stably levitates, move the feeding rod 9 away.

[0062] (4) Casting sample preparation: Immediately turn off the high-frequency power supply. The pure Cu inlay falls into the oxygen-free copper mold and solidifies. Embed the Ni 64 Cu 28 Al4Mo4 alloy powder to obtain a cylindrical ingot. The total time for levitation melting and casting sample preparation is 2 min.

[0063] (5) Electrolytic polishing: Take out the cylindrical ingot in the mold, polish it step by step with 600 - 2000 mesh sandpaper and then perform electrolytic polishing with a perchloric acid-alcohol solution (100 mL perchloric acid + 400 mL alcohol) to obtain a scanning electron microscope sample.

[0064] Figure 3 This is the EBSD test result of the scanning electron microscope sample prepared in Example 2 of the present invention. From Figure 3 it can be seen the crystal orientations of different grains and the large-angle grain boundaries inside the alloy powder particles.

[0065] Example 3

[0066] This example provides a preparation method for millimeter-scale ceramic powder materials for preparing a scanning electron microscope sample of Al2O3 ceramic powder. The steps are as follows:

[0067] (1) Loading samples: Select a cylindrical alumina ceramic mold with an inner diameter of 2 cm, a depth of 4 cm, an outer diameter of 6 cm, and a height of 6 cm as the cavity mold 3. Lay the Al2O3 ceramic powder with a diameter of 2 mm at the bottom of the mold, and place the pure Ni inlay with a diameter of 2 cm at the position with the maximum levitation force of the induction coil 2 through the sample feeding rod.

[0068] (2) Preparing the experimental atmosphere: Turn on the vacuum pump 6 to pump the cavity 1 to 1×10 -1 Pa, and then fill the cavity 1 with high-purity argon gas to 0.5×10 5 Pa. The time for this process is 8 min;

[0069] (3) Levitation melting: Start the high-frequency power supply, observe the temperature of the pure Ni inlay through an infrared thermometer, adjust the power of the high-frequency power supply to heat the pure Ni inlay until it melts and then superheats by 100 K. After it stably levitates, move the feeding rod 9 away.

[0070] (4) Casting sample preparation: Immediately turn off the high-frequency power supply. After the pure Ni embedding material falls into the mold and solidifies, the Al2O3 ceramic powder is embedded to obtain a cylindrical ingot. The total time for suspension melting and casting sample preparation is 2 minutes.

[0071] (5) Grinding and polishing: Take out the cylindrical ingot in the mold. After mechanical grinding and polishing, a scanning electron microscope sample is obtained. Use a scanning electron microscope to observe the scanning electron microscope sample of the ceramic powder to obtain the shape, size, and defect distribution characteristics of the powder material.

[0072] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a scanning electron microscope sample of metal or ceramic powder, comprising the following steps: Suspend and melt the metal embedding material, and let the molten metal embedding material fall into the powder material to be detected, so as to embed the powder material to be detected and obtain a scanning electron microscope sample of metal or ceramic powder; the powder material to be detected is one or several of metal powder and ceramic powder; The melting point of the metal embedding material is lower than that of the powder material to be detected, and the molten metal embedding material does not react with the powder material to be detected; The temperature of the suspension melting is 50 - 300K overheated after the metal embedding material melts; The preparation of the scanning electron microscope sample of metal or ceramic powder is carried out in a protective atmosphere.

2. The preparation method according to claim 1, characterized in that, The diameter of the powder material to be detected is in the range of micrometers to millimeters.

3. The preparation method according to claim 1, characterized in that, The metal embedding material includes a metal element or an alloy.

4. A device for preparing a scanning electron microscope sample of metal or ceramic powder, comprising a cavity (1), a suspension melting system and a cavity mold (3); the suspension melting system includes an induction coil (2), a feeding rod (9) and a power source; the induction coil (2) and the cavity mold (3) are arranged inside the cavity (1); the cavity mold (3) is arranged below the induction coil (2); The end of the feeding rod (9) is arranged at the center of the induction coil (2).

5. The preparation device according to claim 4, wherein, It further includes a vacuum pump (6) and a protective atmosphere gas source (7) connected to the cavity (1).

6. The preparation device according to claim 4, characterized in that, The induction coil (2) is wound by a copper pipe with circulating cooling water inside.

7. The preparation device according to claim 4, characterized in that, The distance between the opening of the cavity mold (3) and the bottom of the induction coil (2) is 5 - 50 cm.

Images