A sample preparation method for electron microscope detection of hard film layer on metal surface

Abstract

The invention relates to the fields of sample preparation and electron microscope detection, and particularly to a sample preparation method for electron microscope detection of a hard film layer on a metal surface. The method comprises the following steps: wrapping a metal prefabricated sample with metal foil, hot-mounting the metal prefabricated sample with resin inlay powder, making the soft metal foil fit tightly between the two samples, and then grinding and polishing the sample to obtain an electron microscope detection sample. The method ensures that the extremely surface layer has good electrical conductivity, the surface boundary is obvious when multiple samples are prepared, the hard film is completely prepared and easy to analyze and observe with an electron microscope, solves the problem of poor electrical conductivity of the extremely surface layer when multiple samples are prepared when hard films on metal surfaces are prepared, solves the problem of unclear interface caused by excessive hot-mounting extrusion on the most surface, and solves the problem of incomplete hard film preparation. The method is simple and quick, has high sample preparation efficiency, and is low in cost. In particular, the method is well applied in the preparation of multi-layer insulating films of electrical steel that are hard and brittle and have thin film layers and substrates.

Description

Technical Field

[0001] The invention relates to the fields of sample preparation and electron microscope detection, and in particular to a sample preparation method for electron microscope detection of a hard film layer on a metal surface. Background Art

[0002] In order to increase the wear resistance, corrosion resistance or insulation of metal surfaces such as aluminum alloys and steel, an inorganic hard film layer (the hardness of the film layer is greater than the hardness of the substrate) is prepared on the metal surface to achieve its special functions and uses. In addition, a hard and brittle oxide film is produced during the hot processing and manufacturing process of steel production. These hard films have different thicknesses and phase structures under different process conditions. They need to be characterized by microscopic analysis electron microscope equipment such as scanning electron microscope (SEM) or electron probe for morphology and composition, and then the production process is optimized based on the detection and analysis results.

[0003] However, due to the significant difference in hardness between the hard film and the base metal, it is difficult to prepare a complete hard film. In addition, when the hard film is thin, it is also necessary to ensure good conductivity of the very surface layer of the film to facilitate surface morphology and composition analysis under an electron microscope. Conventional surface film sample preparation methods are direct hot or cold mounting through resin, or hot mounting with conductive mounting powder. Although these sample preparation methods can also produce a complete hard film layer, when preparing multiple samples, when the gaps between the sample hard film are too tight, the interface between the hard film's surface cannot be distinguished, and the hard films are squeezed and easily damaged. Or when the gaps are too large, the organic mounting material filling causes electrons to accumulate near the organic material when observing the same position under an electron microscope for a long time or at high magnification. The organic material is bombarded by the electrons and heats up and melts, making it impossible to observe or detect the very surface film layer properly. Summary of the Invention

[0004] The present invention aims to provide a sample preparation method for electron microscopic detection of a hard film layer on a metal surface. Based on the above problems, the sample preparation method is improved. By ensuring good conductivity of the extreme surface layer, clear surface boundaries when preparing multiple samples, and complete preparation of the hard film to facilitate electron microscopic analysis and observation, the invention solves the problems of poor conductivity of the extreme surface layer when preparing multiple samples of hard films on metal surfaces, unclear interfaces caused by excessive hot mounting and extrusion on the outermost surface, and incomplete preparation of the hard film. The method is simple, fast, has high sample preparation efficiency, and is low in cost. It has been particularly well applied in the preparation of multi-layer insulating films on electrical steel that are hard and brittle and have relatively thin film layers and substrates.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a sample for electron microscopy inspection of a hard film layer on a metal surface comprises the following steps: firstly, wrapping a conductive metal foil on the surface of a metal prefabricated sample; then, using resin inlay powder to hot-mount the sample so that the conductive metal foil is laminated between the samples to obtain an electron microscopy prefabricated sample;

[0007] The metal prefabricated sample comprises metal and a hard film on the surface thereof.

[0008] As a further solution of the present invention: the metal prefabricated sample is processed by wire cutting.

[0009] As a further solution of the present invention: the metal prefabricated sample is ultrasonically cleaned with alcohol after online cutting.

[0010] As a further solution of the present invention, the hard film cross section of the obtained metal prefabricated sample has no burrs or stress, and the size of the metal prefabricated sample can meet the requirements of hot mounting and observation using an electron microscope.

[0011] As a further embodiment of the present invention: the conductive metal foil is a combination of one or more of copper foil, aluminum foil, zinc foil, nickel foil, tin foil, lead foil, cobalt foil, titanium foil, indium foil, molybdenum foil, zirconium foil, niobium foil, tantalum foil, silver foil, and gold foil.

[0012] As a further solution of the present invention: the thickness of the conductive metal foil is 10-100 μm.

[0013] As a further solution of the present invention: the electron microscope prefabricated sample is subjected to coarse grinding, fine grinding, coarse polishing and fine polishing to obtain an electron microscope detection sample.

[0014] As a further solution of the present invention: firstly perform rough grinding and fine grinding, then perform rough polishing and fine polishing, and the total polishing time is 10-60 minutes.

[0015] As a further solution of the present invention: electron microscopy shows that the surface of the sample is obviously separated, the conductivity is good, there is no gap, and the integrity of the hard film is good.

[0016] Beneficial effects of the present invention:

[0017] (1) The present invention uses metal foil to wrap the metal prefabricated sample, uses resin inlay powder to hot-inlay the metal prefabricated sample, makes the soft aluminum foil fit tightly between the two samples, and then grinds and polishes to obtain an electron microscope test sample, thereby ensuring that the extremely surface layer has good conductivity, the surface boundary is obvious when multiple samples are prepared, and the hard film is prepared completely and easy to analyze and observe by an electron microscope. This solves the problem of poor conductivity of the extremely surface layer when multiple samples are prepared of the hard film on the metal surface, and solves the problem of unclear interface caused by excessive hot-inlay extrusion on the surface and incomplete preparation of the hard film. The method is simple and fast, has high sample preparation efficiency, and is low in cost. It is particularly well applied in the preparation of multi-layer insulating films of electrical steel that are hard and brittle and have thin film layers and substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1This is a sample preparation flow chart for electron microscopy detection samples of the present invention;

[0020] Figure 2 This is the effect diagram of the metal hard film layer after hot inlay under the existing technology;

[0021] Figure 3 This is a diagram showing the effect of the metal prefabricated sample after hot mounting of the present invention;

[0022] Figure 4 This is the effect diagram of electron microscope detection after hot mounting of samples under existing technology;

[0023] Figure 5 It is a rendering of the electron microscope detection effect of the electron microscope detection sample of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] See also Figure 1-Figure 5 As shown, the present invention discloses a sample preparation method for electron microscope detection of a hard film layer on a metal surface;

[0026] Figure 1 The present invention discloses a sample preparation process of one specific embodiment: wire cutting → alcohol ultrasonic cleaning → aluminum foil wrapping → hot mounting → rough grinding → fine grinding → rough polishing → fine polishing;

[0027] As a preferred embodiment of the present invention, a conductive metal foil is first wrapped on the surface of a metal prefabricated sample, and then the sample is hot-mounted using resin mounting powder so that the conductive metal foil is attached between the samples to obtain an electron microscope prefabricated sample;

[0028] The metal prefabricated sample comprises metal and a hard film on the surface thereof.

[0029] In order to enhance the wear resistance, corrosion resistance or insulation of metals used in metal prefabricated samples, such as aluminum alloys and steel, a covering film layer that can improve the wear resistance, corrosion resistance or insulation is often covered on its surface, that is, a hard film. Therefore, the hardness of the hard film is higher than the hardness of the metal. As two substances with different hardness, the thickness of the metal matrix and the hard film is also different, and the material properties are also different, which inevitably leads to different internal stresses. When the hard film is bonded to the surface of the metal matrix, cracks may appear in the hard film, making the preparation It is difficult to form a complete hard film. In addition, when the hard film is thin, it is also necessary to ensure good conductivity of the very surface of the film to facilitate surface morphology analysis and composition analysis under an electron microscope. Furthermore, when preparing multiple samples, when the gaps in the sample hard film are too tight, the interface between the outermost surfaces of the hard film cannot be distinguished, and the hard films are squeezed and easily damaged. Or when the gaps are too large, the organic mosaic material is filled, resulting in electrons gathering near the organic material when observing the same position under an electron microscope for a long time or at high magnification. The organic material is bombarded by the electrons, heats up and melts, and the very surface film layer cannot be observed or detected normally.

[0030] Therefore, in the technical solution of the present invention, when preparing multiple samples, the present invention uses conductive metal foil to wrap a metal prefabricated sample, and then uses the wrapped metal prefabricated sample to hot-mount another metal sample using resin mounting powder. The pressure generated by the hot mounting tightly connects the hard film and the metal foil together. At the same time, due to the good conductivity of the metal foil, it can also facilitate the transmission of the electron beam during electron microscopy, thereby avoiding the conventional use of organic mounting materials that melts and expands under the electron beam, resulting in unclear morphology and state of the hard film under electron microscopy.

[0031] As a preferred embodiment of the present invention, in the actual sample preparation process, two non-analyzed metal prefabricated samples need to be embedded together on both sides of the wrapped electron microscope prefabricated sample to ensure the detection of the hard film on the outermost surface of the electron microscope prefabricated sample;

[0032] As a preferred embodiment of the present invention, the metal prefabricated sample is processed using wire cutting. A significant advantage of wire cutting is that the cut product requires virtually no deburring. After wire cutting, the metal prefabricated sample is ultrasonically cleaned with alcohol. This combination of alcohol and ultrasonic cleaning effectively removes oil contamination from the metal prefabricated sample during wire cutting.

[0033] The hard film cross section of the obtained electron microscope prefabricated sample has no burrs or stress, and the size of the electron microscope prefabricated sample can meet the requirements of hot mounting and observation using an electron microscope.

[0034] In a preferred embodiment of the present invention, the conductive metal foil is a combination of one or more of copper foil, aluminum foil, zinc foil, nickel foil, tin foil, lead foil, cobalt foil, titanium foil, indium foil, molybdenum foil, zirconium foil, niobium foil, tantalum foil, silver foil, and gold foil. In the technical solution of the present invention, after wrapping the metal prefabricated sample with a conductive metal foil such as aluminum foil, the soft properties of the aluminum foil material complement the harder hard film, thereby improving the sample preparation effect.

[0035] As a preferred embodiment of the present invention, the conductive metal foil has a thickness of 10-100 μm.

[0036] As a preferred embodiment of the present invention, an electron microscope prefabricated sample is subjected to rough grinding, fine grinding, rough polishing, and fine polishing to obtain an electron microscope detection sample. During the grinding and polishing process of a conventional hot-mounted metal hard film, the sample part and the mounting material part cannot be ground synchronously, resulting in an inability to obtain a flat observation surface. As is common knowledge in the field, the grinding rate depends on the hardness of the material. The inconsistent grinding caused by the hardness difference often produces rounded corners at the edge of the sample, which in turn makes it impossible to focus in the same focal plane and distorted observation. Under normal circumstances, the edge of the sample is also a very important observation area, which affects the observation effect.

[0037] As a preferred embodiment of the present invention, when selecting a conductive metal foil to wrap a metal prefabricated sample, the present invention preferably uses a metal foil with a hardness close to that of the metal substrate, and then ensures that the grinding effects of the metal substrate and the metal foil are similar during the grinding and polishing process, thereby ensuring the consistency of the overall observation during electron microscopy inspection, improving the observation effect, ensuring good surface conductivity, obvious surface boundaries when preparing multiple samples, and complete preparation of the hard film for easy electron microscopy analysis and observation.

[0038] As a preferred embodiment of the present invention, rough grinding and fine grinding are first performed, and then rough polishing and fine polishing are performed, and the total polishing time is 10-60 minutes.

[0039] Electron microscopy showed that the surface of the sample was clearly separated, the conductivity was good, there was no gap, and the integrity of the hard film was good.

[0040] like Figure 2-5 As shown, the improvement effect of the sample preparation for electron microscopy detection after the technical solution of the present invention using aluminum foil is implemented is:

[0041] (1) Separability between the two sample surfaces and integrity of the hard film:

[0042] The sample preparation effect before the improvement of the sample preparation method is shown in Figure 2 , the improved sample preparation effect is shown in Figure 3 After the improvement of the present invention, the two electron microscope prefabricated hard films are completely separated, the prepared hard films are complete, and the hard films do not fall off.

[0043] (2) Conductivity of the polar surface between the two sample surfaces:

[0044] The sample preparation effect before the improvement of the sample preparation method is shown in Figure 4 , the improved sample preparation effect is shown in Figure 5 Before the improvement, the resin in the gap melted and bulged during high-magnification photography or energy spectrum component analysis, making it impossible to observe or detect the surface film layer normally; however, after the improvement of the present invention, this problem does not exist in the electron microscope detection sample obtained, and the boundary between the hard film and the metal foil is clear.

[0045] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A sample preparation method for electron microscopy detection of a hard film layer on a metal surface, characterized in that: The method comprises the following steps: firstly, wrapping a conductive metal foil on the surface of a metal prefabricated sample, and then using resin inlay powder to hot-mount the sample so that the conductive metal foil is attached between the samples to obtain an electron microscope prefabricated sample; The metal prefabricated sample comprises metal and a hard film on the surface thereof.

2. The method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to claim 1, characterized in that: Metal prefabricated samples are processed by wire cutting.

3. The method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to claim 2, characterized in that: The metal prefabricated samples were ultrasonically cleaned with alcohol after online cutting.

4. The method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to any one of claims 1 to 3, characterized in that: The hard film cross section of the obtained electron microscope prefabricated sample has no burrs or stress, and the size of the electron microscope prefabricated sample can meet the requirements of hot mounting and observation using an electron microscope.

5. The method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to claim 1, characterized in that: The conductive metal foil is a combination of one or more of copper foil, aluminum foil, zinc foil, nickel foil, tin foil, lead foil, cobalt foil, titanium foil, indium foil, molybdenum foil, zirconium foil, niobium foil, tantalum foil, silver foil, and gold foil.

6. The method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to claim 5, characterized in that: The conductive metal foil has a thickness of 10-100 μm.

7. A method for preparing a sample for electron microscopic detection of a hard film layer on a metal surface according to any one of claims 1 to 3, 5 and 6, characterized in that: The electron microscope prefabricated sample is subjected to rough grinding, fine grinding, rough polishing and fine polishing to obtain an electron microscope detection sample.

8. The method for preparing samples for electron microscopic detection of a hard film layer on a metal surface according to claim 7, characterized in that: First, it undergoes rough grinding and fine grinding, then rough polishing and fine polishing. The total polishing time is 10-60 minutes.

9. A sample preparation method for electron microscopic detection of a hard film layer on a metal surface according to claim 8, wherein the surface of the sample detected by electron microscopy is clearly separated without any gaps.

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