Preparation method and test method of micro-nano powder material profile sample

Abstract

The invention provides a preparation method and a test method of a micro-nano powder material profile sample. The method comprises the following steps: mixing a to-be-tested micro-nano-scale powder material with glass powder, heating to melt the glass powder and keep micro-nano-scale powder particles unchanged, then cooling and curing, and polishing to form a particle profile of the micro-nano-scale powder. According to the preparation method, only the glass powder is used as the curing agent, the curing time is short, the preparation cost is low, the efficiency is high, the Mohs hardness of a cured sample is high, the polished section is fine, clear and flat, and observation of internal element distribution and structural morphology of the to-be-measured micro-nano particles is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of material testing, and in particular to a method for preparing and testing a cross-section sample of a micro-nano powder material. Background Art

[0002] The internal element distribution and structural morphology of materials play an important role in the performance evaluation of materials. The materials include macroscopic materials and microscopic materials. Microscopic materials include micron- or nano-scale powder materials. For example, the positive and negative electrode materials of lithium-ion batteries are usually micron- or nano-scale powder particles. The internal element distribution and structural morphology of the particle materials play an important role in the performance evaluation of the positive and negative electrode materials of lithium-ion batteries.

[0003] In order to observe the internal element distribution and structural morphology of micron- or nano-scale powder materials, a common method is to mix the micron- or nano-scale powder with a liquid organic polymer resin, and then grind out the cross-section of the powder material for observation after curing. The shortcomings of this method are: (1) the sample preparation cycle is too long, the curing time is generally more than 24 hours, generally 24 hours to 100 hours, and the sample preparation efficiency is low; (2) a curing reagent is required, and there are many types of curing reagents, usually 2-3 types are required, such as adhesives, curing agents, etc., which increases the preparation cost; (3) when the hardness of the sample is moderate after curing, it is beneficial to improve the mechanical properties, which is beneficial to grinding and protecting the sample cross-section. After the resin is cured, the Mohs hardness is about 1-2, and the hardness is relatively low and needs to be improved. Summary of the invention

[0004] In view of the above technical status, the present invention provides a method for preparing a cross-section sample of a micro-nano powder material, which is simple and easy to operate, and the cross-section of the micro-nano powder material is complete, clear and flat, which is conducive to the observation of the internal element distribution and structural morphology of the micro-nano powder material.

[0005] The technical solution provided by the present invention is: a method for preparing a cross-section sample of a micro-nano powder material, comprising the following steps: mixing the micro-nano powder material to be tested with glass powder to obtain a mixed powder; the melting point of the glass powder is lower than the melting point of the micro-nano powder material;

[0006] The mixed powder is heated to melt the glass powder therein while the micro-nano powder particles remain unchanged, that is, the melting point of the glass powder is ≤ the heating temperature ≤ the melting point of the micro-nano powder material, and then cooled and solidified to obtain a solidified sample;

[0007] The solidified sample is polished to reveal the particle profile of the micro-nano powder.

[0008] The micro-nano powder material is not limited, including oxide powders, such as titanium oxide, aluminum oxide, iron oxide, etc., and also for example, lithium ion battery positive and negative electrode materials LiNi1-x-yCo x Mn y O2, 0≤x≤1, 0≤y≤1 (referred to as NCM positive electrode material).

[0009] The glass powder is an inorganic amorphous hard particle powder. The glass powder can be mixed with raw materials containing SiO2 and then subjected to solid phase reaction to form a glass homogeneous body with disordered structure. The chemical composition of the glass powder is usually converted into oxides, that is, including SiO2 and other oxides, and the other oxides are not limited to one or more of B2O3, ZnO, Na2O, BaO, and PbO.

[0010] The source of the glass powder is not limited, including commercially available glass powder.

[0011] Preferably, the particle size of the glass powder is 1 μm-20 μm. Preferably, the D50 of the micro-nano powder material is about 10 μm-20 μm.

[0012] Preferably, the glass powder has a Mohs hardness of 5-8.

[0013] In the mixed powder, the mass ratio of the micro-nano powder material to the glass powder is preferably 1:12-1:30, and more preferably 1:15-1:25.

[0014] Preferably, the melting point of the glass powder is less than the heating temperature and less than the melting point of the micro-nano powder material. More preferably, the heating temperature is greater than the melting point of the glass powder + 100°C.

[0015] Preferably, the heating time of the mixed powder is 10 min, more preferably.

[0016] Preferably, the cooling and curing time is less than 1 hour, more preferably 20 minutes to 50 minutes, for example 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, etc.

[0017] The polishing method is not limited, such as polishing with sandpaper.

[0018] Preferably, the mixed powder is heated to melt and then placed in a mold, and after cooling and solidification, it is taken out of the mold for grinding.

[0019] Preferably, the grinding is followed by a polishing treatment. Further preferably, the polished sample is ultrasonically cleaned in anhydrous ethanol.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention uses inorganic glass powder as a curing agent, which is mixed with the micro-nano powder material to be tested and then heated. The glass powder is melted by controlling the heating temperature while the state of the micro-nano powder particles remains unchanged, and then cured. On the one hand, the curing time can be less than or equal to 1 hour, the curing time is short, and the sample preparation efficiency is high. On the other hand, since only one reagent, glass powder, is needed, the sample preparation cost is greatly reduced and the sample preparation efficiency is improved.

[0022] (2) Compared with the resins currently used, the inorganic glass powder used in the present invention has a higher Mohs hardness, so the Mohs hardness of the cured sample is higher, which can be greater than 4, for example, in the range of 5-7, and has strong mechanical processability. The polished cross-section is more delicate, clear, and smooth, which is conducive to the observation of the internal element distribution and structural morphology of the micro-nano powder particles to be tested, for example, by electron microscopy.

[0023] (3) In the present invention, the melting point of the inorganic glass powder can be adjusted according to its composition and content, so the appropriate inorganic glass powder and heating temperature can be selected according to the melting point of the micro-nano powder material to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an appearance diagram of a mixed powder and a solid sample in which the mass ratio of micro-nano powder material to glass powder is 1:10 in Example 1 of the present invention.

[0025] Figure 2 This is an appearance diagram of a mixed powder and a solid sample in Example 1 of the present invention, in which the mass ratio of micro-nano powder material to glass powder is 1:20.

[0026] Figure 3 This is an appearance diagram of a mixed powder and a solid sample in which the mass ratio of micro-nano powder material to glass powder is 1:50 in Example 1 of the present invention.

[0027] Figure 4 This is an appearance diagram of a mixed powder of micro-nano powder material and glass powder and a solid sample when the heating temperature is 300° C. in Example 2 of the present invention.

[0028] Figure 5 This is an appearance diagram of a mixed powder of micro-nano powder material and glass powder and a solid sample when the heating temperature is 400° C. in Example 2 of the present invention.

[0029] Figure 6 This is an appearance diagram of a mixed powder of micro-nano powder material and glass powder and a solid sample when the heating temperature is 450° C. in Example 2 of the present invention.

[0030] Figure 7This is an appearance diagram of a mixed powder of micro-nano powder material and glass powder and a solid sample when the heating temperature is 500° C. in Example 2 of the present invention.

[0031] Figure 8 This is a morphology of the solidified sample of the micro-nano powder material and glass powder prepared at a heating temperature of 450° C. in Example 2 of the present invention after being processed under an electron microscope. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention, and non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0033] The words “include”, “including” and the like used in the present invention should be interpreted as including rather than being exclusive or exhaustive; that is, the meaning is “including but not limited to”.

[0034] Embodiment 1:

[0035] In this embodiment, the micro-nano powder material is a lithium-ion battery positive electrode material LiNi1-x-yCo x Mn y O2, 0≤x≤1, 0≤y≤1 (referred to as NCM positive electrode material), its D50 is in the range of 10μm-20μm, and the melting point is 800℃.

[0036] The cross-section sample preparation method of the micro-nano powder material is as follows:

[0037] (1) Use commercially available glass powder, the main components of which are SiO2, B2O2, and PbO, and the mass percentage of SiO2 is greater than 15%, the mass percentage of B2O2 is less than 20%, and the mass percentage of PbO is greater than 60%. The glass powder has a melting point of 300°C, a D50 particle size of 15 μm, and a Mohs hardness of 6.3.

[0038] The micro-nano powder material and the glass powder are uniformly mixed to obtain a mixed powder, wherein the mass ratios of the micro-nano powder material to the glass powder are 1:10, 1:20, and 1:50, respectively.

[0039] (2) The mixed powder is heated at 450°C for 20 min, the glass powder in the mixed powder is melted and the micro-nano powder material remains in a granular state, thereby obtaining a blend. The blend is placed in a circular mold and cooled for 30 min to solidify, and then the mold is removed to obtain a solid sample.

[0040] (3) Grind the solid sample with sandpaper to expose the micro-nano powder material and then polish it. After polishing, put it in anhydrous ethanol for ultrasonic cleaning.

[0041] The appearance of the mixed powder in step (1) and the solid sample in step (2) are as follows: Figure 1-3 .

[0042] When the mass ratio of micro-nano powder material to glass powder is 1:10, Figure 1 As shown, the cured sample is brittle and easy to lose powder, which is not conducive to mechanical processing;

[0043] When the mass ratio of micro-nano powder material to glass powder is 1:50, Figure 3 As shown, the solidified sample is harder and the difficulty of exposing the cross section of the micro-nano powder material by mechanical processing is increased due to the small content of the micro-nano powder material.

[0044] In contrast, when the mass ratio of micro-nano powder material to glass powder is 1:20, Figure 2 As shown, the hardness of the cured sample is moderate, and the content of micro-nano powder material is moderate, which is conducive to mechanical processing to expose the cross-section of the micro-nano powder material.

[0045] Embodiment 2:

[0046] In this embodiment, the micro-nano powder material is the same as the micro-nano powder material in Embodiment 1.

[0047] The cross-section sample preparation method of the micro-nano powder material is as follows:

[0048] (1) The commercially available glass powder in Example 1 is used.

[0049] The micro-nano powder material and the glass powder are uniformly mixed to obtain a mixed powder, wherein the mass ratio of the micro-nano powder material to the glass powder is 1:20.

[0050] (2) heating the mixed powder at 300°C, 400°C, 450°C, and 500°C for 10 min, respectively, until the glass powder in the mixed powder melts and the micro-nano powder material remains in a granular state, thereby obtaining a blend. The blend is placed in a circular mold and cooled for 30 min to solidify, and then the mold is removed to obtain a solid sample.

[0051] (3) Grind the solid sample with sandpaper to expose the micro-nano powder material and then polish it. After polishing, put it in anhydrous ethanol for ultrasonic cleaning.

[0052] The appearance of the mixed powder in step (1) and the solid sample in step (2) are as follows: Figure 4-7 .

[0053] When the heating temperature is 300℃, Figure 4 As shown in Figure 2, the surface of the solidified sample is rough, the glass powder is not completely melted, and the sample cannot be stably solidified; when the heating temperature is 400℃, Figure 5 As shown in Figure 2, the surface of the cured sample tends to be smooth; when the heating temperature is 450°C, Figure 6 As shown in the figure, after solidification, the sample surface is brighter, tighter, and the sample block has good integrity, which is more suitable for subsequent grinding and polishing. The reason may be that 300°C is the starting melting point of the glass powder, and the glass powder in the mixed powder is not completely melted; similarly, when the heating temperature is 400°C, the glass powder in the mixed powder is still not completely melted, resulting in a loose connection between the sample powder and the glass powder; when the temperature reaches 450°C, the glass powder in the mixed powder is completely melted and the bonding performance is increased, making the sample tight and complete after cooling; when the temperature reaches 500°C, the glass powder in the mixed powder is completely melted, and the fluidity is enhanced, resulting in the separation of the micro-nano powder particles and the glass powder melt, and the bonding performance between the micro-nano powder particles is reduced, as shown in the figure. Figure 7 As shown, the shrinkage phenomenon increases during cooling and causes cracking of the cured sample.

[0054] When the heating temperature is 450°C, the morphology of the cured sample after step (4) is shown in the electron microscope. Figure 8 shown. Figure 8 The three pictures in the figure are gradually enlarged from left to right. It can be seen that in the mixed sample of micro-nano powder material and glass powder, the cross-section of the micro-nano particles is clear, smooth, delicate and complete, which is conducive to the study and testing of the internal element distribution and structural morphology of the micro-nano particles.

[0055] The above-described embodiments provide a detailed description of the technical solutions of the present invention. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a cross-section sample of a micro-nano powder material, characterized in that: The steps include: Mixing the micro-nano powder material to be tested with glass powder to obtain a mixed powder; the melting point of the glass powder is lower than the melting point of the micro-nano powder material; The mixed powder is heated to melt the glass powder therein while the micro-nano powder particles remain unchanged, that is, the melting point of the glass powder is ≤ the heating temperature ≤ the melting point of the micro-nano powder material, and then cooled and solidified to obtain a solidified sample; The solidified sample is polished to reveal the particle profile of the micro-nano powder.

2. The preparation method according to claim 1, characterized in that: The micro-nano powder material includes oxide powder; Preferably, the oxide powder is one or more of titanium oxide, aluminum oxide, and iron oxide; Preferably, the oxide powder is a lithium-ion battery positive and negative electrode material LiNi1-x-yCo x Mn y O2, 0≤x≤1, 0≤y≤1.

3. The preparation method according to claim 1, characterized in that: The glass powder includes SiO2 and other oxides, and the other oxides include one or more of B2O3, ZnO, Na2O, BaO, and PbO.

4. The preparation method according to claim 1, characterized in that: The particle size of the glass powder is 1 μm-20 μm; Preferably, the D50 of the micro-nano powder material is about 10 μm-20 μm; Preferably, the glass powder has a Mohs hardness of 5-8.

5. The preparation method according to claim 1, characterized in that: In the mixed powder, the mass ratio of the micro-nano powder material to the glass powder is 1:12-1:30, preferably 1:15-1:

25.

6. The preparation method according to claim 1, characterized in that: The melting point of the glass powder is less than the heating temperature and less than the melting point of the micro-nano powder material; Preferably, the heating temperature is greater than the melting point of the glass powder + 100°C; Preferably, the heating time of the mixed powder is 10 min-30 min.

7. The preparation method according to claim 1, characterized in that: The cooling and curing time is less than 1 hour, preferably 20 minutes to 50 minutes, for example 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes.

8. The preparation method according to claim 1, characterized in that: Preferably, the mixed powder is heated to melt and then placed in a mold, and after cooling and solidification, it is taken out of the mold for grinding.

9. The preparation method according to claim 1, characterized in that: Polishing is performed after grinding; Preferably, the polished sample is placed in anhydrous ethanol for ultrasonic cleaning.

10. A profile testing method for micro-nano granular materials, characterized by: A cross-sectional sample of a micro-nano-scale particle material is prepared by the preparation method described in any one of claims 1 to 9, and then the cross-sectional sample is observed using an electron microscope.

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