A method for preparing a sample of continuous casting protective slag by FIB

Abstract

The application provides a FIB sample preparation method for a continuous casting protective slag sample, and relates to the field of metallurgical auxiliary materials for steelmaking; the method comprises the following steps: configuring a solidified liquid containing the continuous casting protective slag and carbon powder; shaping the solidified liquid into a shaped sample; cutting the shaped sample to obtain a sample slice; fixing the sample slice on a scanning electron microscope general T-shaped table through glue, and making the surface edges of the sample test surface and the sample tested surface conduct electricity with the test surface of the T-shaped table through conductive glue; putting the T-shaped table with the fixed sample slice into a high-vacuum carbon spraying device to spray carbon; and putting the T-shaped table with the sample slice after the carbon spraying into a FIB sample preparation device, finding a characteristic area through an accessory energy spectrometer of the device, and preparing a FIB sample; the application solves the problem that the sample preparation area is uncontrollable when a sample preparation device is used to prepare a sample of a non-conductive and uneven sample through a specific solidified liquid formula for sample shaping and a multi-layer conductive design.

Description

Technical Field

[0001] This invention relates to the field of metallurgical auxiliary materials technology for steelmaking, specifically to a method for preparing FIB samples of continuous casting protective slag. Background Technology

[0002] Continuous casting flux plays a crucial role in the smooth casting of molten steel. It not only serves as insulation, preventing oxygen from the air from entering the molten steel and affecting its quality, but also absorbs and dissolves inclusions floating from the molten steel to the slag interface to purify the steel. Furthermore, it acts as a lubricant to reduce casting resistance, thus preventing the solidified shell from adhering to the mold wall, and as a filler to fill the air gap between the billet shell and the mold, improving heat transfer in the mold. Therefore, strict requirements are placed on the composition of the continuous casting flux and the proportions of its different components.

[0003] When testing the components and proportions of protective slag, chemical analysis methods such as spectroscopy and manual operation can test the chemical elements present in the protective slag, as well as the mass or atomic percentage of the corresponding chemical elements, and can also convert them in the form of oxides. However, chemical analysis methods cannot obtain the actual existence mode of the components in the protective slag, such as which phases the protective slag is composed of and the interaction mode between different phases. XRD can analyze the phase composition of the protective slag, but it cannot directly obtain the actual existence mode of different phases.

[0004] Focused ion beam (FIB) technology can be used to prepare transmission electron microscopy (TEM) samples of mold flux, obtaining TEM images of the flux and enabling direct analysis of the actual existence of different phases within the flux. However, due to the poor conductivity of mold flux, severe charge accumulation occurs during FIB preparation, leading to image drift and distortion in characteristic areas, making it impossible to precisely locate and process these areas. Furthermore, continuous casting mold flux samples are high-hardness powders with irregular particle shapes, making it difficult to find planes on the micrometer scale for sampling during FIB preparation. This results in uncontrollable thinning of the sample during subsequent thinning processes.

[0005] Existing FIB sample preparation methods are all designed for conductive powders or particles, and there are no relevant solutions for continuous casting protective slag. Summary of the Invention

[0006] The purpose of this invention is to provide a FIB sample preparation method for continuous casting protective slag samples. By combining a solidification liquid containing continuous casting protective slag, a sample forming fixture, and the FIB sample preparation method, the invention solves the existing technical problems and enables in-situ transmission electron microscopy analysis of characteristic regions of continuous casting protective slag.

[0007] To achieve the above objectives, the present invention proposes the following technical solution: a method for preparing FIB samples of continuous casting protective slag, comprising the following steps:

[0008] 1) Prepare a curing solution containing continuous casting protective slag and carbon powder;

[0009] 2) The curing liquid is used to form a sample with a height of not less than 20mm and a size of 10mm×10mm in the sample forming fixture;

[0010] 3) Cut the shaped sample to obtain a sample sheet with a thickness not exceeding 2 mm;

[0011] 4) Fix the cut sample slices onto the universal T-shaped stage of the scanning electron microscope with glue, and use conductive glue to make the edges of the sample test surface and the sample tested surface electrically connected to the test surface of the T-shaped stage respectively.

[0012] 5) Place the T-shaped stage with the sample sheet fixed in it into a high-vacuum carbon spraying device for carbon spraying;

[0013] 6) Place the T-shaped stage with the sample sheet fixed after carbon spraying into the FIB sample preparation equipment, find the characteristic region through the energy dispersive spectrometer attached to the equipment and perform FIB sample preparation, and finally obtain a transmission electron microscope sample with specific characteristic regions and controllable preparation region.

[0014] Furthermore, in step 1), the mass ratio of continuous casting protective slag to carbon powder in the curing liquid is 1:1~2;

[0015] Furthermore, the curing liquid in step 1) also includes epoxy resin and curing agent, wherein the volume ratio of curing agent, epoxy resin and toner is 1:5:1~2.

[0016] Furthermore, in step 3), the cut surface of the sample sheet is parallel to its opposite surface, and any cut surface of the sample sheet can be used as a test surface for detection.

[0017] Furthermore, the purity of the toner is not less than 99.9%, and the particle size does not exceed 2000 mesh.

[0018] Furthermore, in step 6), during the FIB sample preparation process, the environmental parameters for the sample to be transparent in the electronic image are 50% brightness and 20% contrast.

[0019] Furthermore, in step 5), the thickness of the carbon sprayed onto the T-shaped stage on which the sample sheet is fixed does not exceed 50 nm.

[0020] Furthermore, the parameters of the carbon injection process are controlled as follows:

[0021] The distance between the surface of the sample sheet on the T-shaped stage and the carbon rod on the high-vacuum carbon spraying equipment is D, where D > 20 mm; when the high-vacuum carbon spraying equipment is working, the carbon spraying vacuum is better than 1 × 10⁻⁶ mm. -3 mbar.

[0022] Furthermore, the sample forming fixture in step 2) includes a support platform, a concave shaping fixture, a convex shaping fixture, and a fastening mechanism;

[0023] The support platform is placed on the platform, with its upper surface horizontal and a T-shaped protrusion at its center; the upper surface of the T-shaped protrusion is parallel to the upper surface of the support platform, and the upper surface of the T-shaped protrusion has a size of 10mm × 10mm.

[0024] The concave shaping fixture and the convex shaping fixture are respectively disposed on opposite sides of the T-shaped protrusion; the bottom of the concave shaping fixture near the convex shaping fixture is provided with a first groove, and the bottom of the convex shaping fixture is provided with a second groove corresponding to the first groove; the side of the concave shaping fixture near the convex shaping fixture is provided with a first molding chamber from its upper end surface to the top of the first groove, the first molding chamber is vertically arranged and its opening faces the convex shaping fixture; the side of the convex shaping fixture opposite to the concave shaping fixture is provided with a second molding chamber, the second molding chamber is vertically arranged and its opening faces the first molding chamber;

[0025] The concave shaping fixture is provided with a pair of grooves that are recessed into the interior of the concave shaping fixture on both sides along the extension direction of the first forming chamber. The convex shaping fixture is provided with a pair of protrusions that extend in the direction of the concave shaping fixture at positions corresponding to the grooves, and the protrusions are adapted to the grooves.

[0026] When the protrusion is fitted into the slot, the first and second grooves are fitted onto the outer periphery of the T-shaped protrusion. The first molding chamber, the second molding chamber, and the upper surface of the T-shaped protrusion fit together tightly to form a molding cavity with a cross-sectional dimension of 10mm×10mm and an open top. The height of the molding cavity is not less than 20mm, and the curing liquid is used to form and shape the sample within the molding cavity. The fastening mechanism is used to fasten the concave shaping fixture and the convex shaping fixture.

[0027] Furthermore, a triangular protrusion is provided at the bottom of the inner side of the first molding chamber, the triangular protrusion extends toward the second molding chamber, and the shape of the triangular protrusion in the first molding chamber is the same as the shape of the transverse cross section of the first molding chamber.

[0028] When the concave shaping fixture and the convex shaping fixture are assembled on the support platform, the triangular protrusion is located directly above the upper end face of the T-shaped protrusion, and when the curing liquid is cured into a shaped sample in the molding cavity, the shaped sample forms a triangular groove at the position of the triangular protrusion.

[0029] As can be seen from the above technical solutions, the technical solutions of the present invention have achieved the following beneficial effects:

[0030] This invention overcomes the shortcomings of existing technologies in preparing transmission electron microscopy (TEM) samples of non-conductive continuous casting mold flux using fibrillation (FIB) due to poor conductivity, which makes it impossible to locate feature regions, and the uncontrollable sample preparation area caused by uneven sample surfaces. It provides a FIB sample preparation method for continuous casting mold flux samples, specifically including the following steps: 1) preparing a curing solution containing continuous casting mold flux and carbon powder; 2) molding the curing solution into a shaped sample; 3) cutting the shaped sample to obtain sample slices; 4) fixing the sample slices to a universal T-shaped stage for scanning electron microscopy using adhesive, and using conductive adhesive to ensure electrical conductivity between the sample test surface, the edge of the sample being tested, and the test surface of the T-shaped stage; 5) placing the T-shaped stage with the sample slices fixed in it into a high-vacuum carbon spraying device for carbon spraying; 6) placing the T-shaped stage with the carbon-sprayed sample slices fixed in it into an FIB sample preparation device, locating feature regions using an energy dispersive spectrometer (EDS) accessory, and performing FIB sample preparation.

[0031] This invention addresses the drawback of uneven sample surfaces leading to uncontrollable sample preparation by using a curing solution containing continuous casting flux and carbon powder to solidify and shape the sample, followed by cutting the sample into thin slices. Furthermore, it solves the problem of poor conductivity in continuous casting flux, which prevents the localization of characteristic regions in FIB (fiber optic electrophoresis) samples, by employing three methods to increase conductivity: using the curing solution containing carbon powder, coating with conductive adhesive to achieve electrical conductivity, and carbon spraying onto the sample surface. The sample preparation method proposed in this invention is simple and easy to operate, applicable to the preparation of various poorly conductive powder FIB samples, has a wide range of applications, and high sample preparation efficiency.

[0032] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0033] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0034] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0035] Figure 1 This is a flowchart of the FIB sample preparation process for continuous casting protective slag of the present invention;

[0036] Figure 2 This is an exploded view of the sample forming fixture of the present invention;

[0037] Figure 3 This is a schematic diagram of the sample forming fixture clamping according to the present invention;

[0038] Figure 4 Electron micrograph of a sample prepared directly by FIB without any treatment of the continuous casting protective slag;

[0039] Figure 5 An electron microscope image showing the uncontrollable phenomenon in the processing area caused by the unevenness of the sample thin section surface;

[0040] Figure 6 This is an electron microscope image of the FIB sample preparation of the characteristic region obtained by the method of the present invention.

[0041] The specific meanings of each mark in the diagram are as follows:

[0042] 1- Supporting platform, 1-2- Second cuboid, 1-3- First cuboid; 2- Shaped sample; 3- Concave shaping fixture, 3-1- Slot, 3-2- First threaded hole, 3-3- Triangular protrusion, 3-4- First groove; 4- Convex shaping fixture, 4-1- Protrusion, 4-2- Through hole, 4-3- Second threaded hole; 5- Bolt; 6- First protective layer; 7- Second protective layer; 8- Third protective layer. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0044] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0045] The method for preparing transmission electron microscopy (TEM) samples based on fibrillation-injection (FIB) requires that the sample has good conductivity and that the test surfaces are parallel to each other. This ensures a controllable observation area and uniform thickness in the prepared TEM sample. If the test surfaces are not parallel, the height difference between the surfaces during FIB preparation can lead to uncontrollable thinning of the sample during the thinning process. Furthermore, poor sample conductivity can cause severe charge accumulation when locating marker features, resulting in image drift and distortion in the feature area, making it impossible to locate and process the feature area, or leading to incorrect positioning and processing. This invention aims to improve the conductivity and thickness uniformity of the sample, solving the above-mentioned sample preparation problems, and proposes a FIB sample preparation method for continuous casting protective slag samples.

[0046] Specifically, such as Figure 1 As shown, the FIB sample preparation method for continuous casting protective slag samples disclosed in this invention includes the following steps: S1, preparing a curing liquid containing continuous casting protective slag and carbon powder; S2, forming a shaped sample with a height of not less than 20 mm and a size of 10 mm × 10 mm in a sample forming fixture using the curing liquid; S3, cutting the shaped sample to obtain sample slices with a thickness of not more than 2 mm, wherein the cut surface of the sample slice is parallel to its opposite surface, and any cut surface of the sample slice can be used as a test surface for detection; S4, cutting the sample slices... The sample sheet is then fixed to a universal T-shaped stage for scanning electron microscopes using adhesive. Conductive adhesive is used to ensure electrical conductivity between the sample test surface and the edge of the sample being tested surface and the test surface of the T-shaped stage. S5, the T-shaped stage with the sample sheet fixed is placed in a high-vacuum carbon spraying device for carbon spraying. The carbon spraying thickness does not exceed 50 nm. The carbon spraying process parameters are controlled as follows: the distance between the surface of the sample sheet on the T-shaped stage and the carbon rod on the high-vacuum carbon spraying device is D, where D > 20 mm; the high-vacuum carbon spraying device operates with a carbon spraying vacuum better than 1 × 10⁻⁶.-3 mbar; S6, the T-shaped stage with the sample sheet fixed after carbon spraying is placed into the FIB sample preparation equipment. The characteristic region is found by the energy dispersive spectroscopy instrument in the equipment accessory and FIB sample preparation is performed. Finally, a transmission electron microscope sample with specific characteristic regions and controllable preparation region is obtained.

[0047] In step 1), the curing liquid also includes epoxy resin and curing agent. The mass ratio of continuous casting protective slag to carbon powder in the curing liquid is 1:1~2, and the volume ratio of curing agent, epoxy resin and carbon powder is 1:5:1~2. The purity of carbon powder is not less than 99.9%, and the particle size does not exceed 2000 mesh.

[0048] The following detailed description, in conjunction with the specific embodiments shown in the accompanying drawings, further illustrates the FIB sample preparation method for continuous casting protective slag samples disclosed in this invention.

[0049] Example 1

[0050] 1. Grind carbon rods with a purity ≥99.9% using an agate mortar and pestle, then sieve through a 2000-mesh sieve to obtain carbon powder. Weigh 1g of continuous casting protective slag and place it in a beaker, then add 1g of carbon powder to the beaker and mix well. 1g of carbon powder has a volume of 1.2mL. Add 6mL of epoxy resin and stir evenly. Finally, add 1.2mL of curing agent and stir evenly to obtain a cured liquid. In practice, EpoFix type epoxy resin and EpoFix curing agent are used in combination.

[0051] 2. Pour the prepared curing liquid into the molding cavity of the assembled sample molding fixture and mold it. After the curing liquid solidifies, take out the molded sample 2.

[0052] 3. Clamp the long side of the rectangular prism sample 2 with a precision cutting machine, cut a sample sheet with a thickness of 2mm along the long side, and use the cut surface of the rectangular prism sample sheet as the test surface.

[0053] 4. Fix the cut sample slices onto the universal T-stage of the scanning electron microscope with 502 glue. Apply silver conductive adhesive evenly to the sample test surface and the T-stage test surface to make the sample test surface and the T-stage test surface electrically connected. Then apply silver conductive adhesive evenly to the edge of the surface to be tested to make the surface edge and the test surface electrically connected.

[0054] 5. Place the sample containing the T-shaped stage into the high-vacuum carbide spraying equipment for carbide spraying. The distance between the sample surface and the carbon rod on the carbide spraying equipment should be 25 mm, and the carbide spraying vacuum should be 9 × 10⁻⁶ mm. -4 With mbar, carbon spraying time of 1.5s, and current of 70A, the thickness of the carbon film sprayed under these parameters is about 20-30nm.

[0055] 6. Place the T-shaped stage with the sample sheet fixed after carbon spraying into the FIB sample preparation equipment. Locate the characteristic region using the energy dispersive spectroscopy (EDS) instrument attached to the equipment, and perform FIB sample preparation. The FIB sample preparation steps are as follows:

[0056] 1) Deposit a carbon protective layer with a thickness of 0.3µm, a length of 15µm, and a width of 2µm in the region of interest, followed by a Pt protective layer with a thickness of 1.8µm, a length of 15µm, and a width of 2µm on top of the carbon protective layer; 2) Create downward-facing recesses on both sides of the long side to a depth of 5µm, then perform L-shaped cuts on the bottom and test surface, and remove the sample using a robotic arm, welding it onto a semi-copper mesh; 3) Perform sample thinning sequentially, with the following settings: sample stage 54°±1°, ion gun 30kV, 700pA; 54°±1°, ion gun 30kV, 300pA; 54°±1°, ion gun 30kV, 100pA until the sample is in the electron image: accelerated. 4) Perform sample thinning sequentially: sample stage 54°±1°, ion gun 30kV, 50pA; 54°±1°, ion gun 30kV, 20pA; 54°±1°, ion gun 30kV, 10pA until the sample is transparent in the electron image: accelerating voltage 5kV, current 2nA, brightness 50%, contrast 20%; 5) Perform two thinning operations: sample stage 54°±4°, ion gun 5kV, current 40pA, to finally obtain a transmission electron microscope sample with controllable specific feature areas and preparation areas. The sample effect is as follows: Figure 6 As shown.

[0057] Example 2

[0058] 1) Grind carbon rods with a purity ≥ 99.9% using an agate mortar and sieve them through a 2000-mesh sieve to obtain carbon powder; 2) Weigh 1g of continuous casting protective slag and put it into a beaker, then add 2g of carbon powder to the beaker and mix well. 1g of carbon powder has a volume of 1.2mL. Add 6mL of epoxy resin and stir evenly. Finally, add 1.2mL of curing agent and stir evenly to obtain a cured liquid.

[0059] 2. Pour the prepared curing liquid into the molding cavity of the assembled sample molding fixture and mold it. After the curing liquid solidifies, take out the molded sample 2.

[0060] 3. Clamp the long side of the rectangular prism-shaped sample 2 with a precision cutting machine, and cut a sample slice with a thickness of 1mm along the long side. The cut surface of the long sample slice is used as the test surface.

[0061] 4. Fix the cut sample onto the universal T-stage of the scanning electron microscope with 502 glue. Apply silver conductive adhesive evenly to the test surface of the sample and the test surface of the T-stage to make the test surface of the sample and the test surface of the T-stage electrically conductive. Then apply silver conductive adhesive evenly to the edge of the surface to be tested to make the edge of the surface and the test surface electrically conductive.

[0062] 5. Place the sample containing the T-shaped stage into the high-vacuum carbide spraying equipment for carbide spraying. The distance between the sample surface and the carbon rod of the carbide spraying equipment should be 25mm, and the carbide spraying vacuum should be 9×10. -4 With mbar, carbon spraying time of 1.5s, and current of 70A, the thickness of the carbon film sprayed under these parameters is about 20-30nm.

[0063] 6. Place the carbon-sprayed sample into the FIB sample preparation equipment. Locate the characteristic region using the energy dispersive spectroscopy (EDS) instrument attached to the equipment and perform FIB sample preparation. The FIB sample preparation steps are as follows:

[0064] 1) Deposit a carbon protective layer with a thickness of 0.3µm, a length of 15µm, and a width of 2µm in the region of interest, and then deposit a Pt protective layer with a thickness of 1.8µm, a length of 15µm, and a width of 2µm on the carbon protective layer; 2) Make downward recesses on both sides of the long side to a depth of 5µm, then make L-shaped cuts on the bottom and test surface, and remove the sample by a robotic arm and weld it to a semi-copper mesh; 3) Perform sample thinning sequentially, with the sample stage at 54°±1° and the ion gun at 30kV and 700pA; 54°±1° and the ion gun at 30kV and 300pA; 54°±1° and the ion gun at 30kV and 100pA until the sample is in the electron image: 4) Perform sample thinning sequentially: sample stage 54°±1°, ion gun 30kV, 50pA; 54°±1°, ion gun 30kV, 20pA; 54°±1°, ion gun 30kV, 10pA until the sample is transparent in the electron image: accelerating voltage 5kV, current 2nA, brightness 50%, contrast 20%; 5) Sample stage 54°±4°, ion gun 5kV, current 40pA, perform two thinning operations to finally obtain a transmission electron microscope sample with controllable specific feature areas and preparation areas.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 1 is that the sample preparation process of Comparative Example 1 only includes step 6, that is, the continuous casting protective slag is not treated before FIB sample preparation. The sample preparation results are as follows: Figure 4 and Figure 5 As shown.

[0067] It is known that during FIB sample preparation, a protective layer such as C or Pt needs to be sprayed onto the feature locations to prevent damage to the feature areas during subsequent processing; however, if Figure 4As shown, when the continuous casting flux is directly prepared without treatment, due to its poor conductivity, when a protective layer is sprayed three times consecutively at the same location in the characteristic area (referred to as the first protective layer 6, the second protective layer 7, and the third protective layer 8), the protective layer is not in the preset position after each spraying, making subsequent processing impossible, i.e., the characteristic area cannot be located. Furthermore, the surface of the directly prepared continuous casting flux is uneven, such as... Figure 5 The phenomenon of uncontrollable thinning area during sample thinning is shown, which is caused by the uneven thickness of the continuous casting protective slag and the non-parallelism between the test surface and the opposing surface. (Combined with...) Figure 6 The continuous casting protective slag is solidified into a regular sample using a curing liquid. This ensures that the test surfaces of the sample are manually parallel to each other during testing, preventing uncontrollable thinning of the sample during thinning. In addition, a three-step method to increase the conductivity of the sample prevents charge accumulation when searching for marked feature locations during sample preparation. This also prevents drift and distortion of the feature area image in the field of view, effectively enabling the positioning and processing of the feature area.

[0068] Figure 6 The sample preparation effect diagram shown indicates that the FIB sample preparation method disclosed in this invention effectively solves the problems of poor conductivity and uneven particle surface of the protective slag. As a result, it is possible to prepare transmission electron microscopy samples of characteristic regions of continuous casting protective slag through FIB, thereby achieving the goal of in-situ transmission electron microscopy analysis of characteristic regions of continuous casting protective slag.

[0069] The sample forming fixture used in the above embodiments of the present invention is mainly for producing a formed sample 2 that matches the size of the FIB equipment. Therefore, any forming mold that can obtain this size can be used in this solution.

[0070] As an optional implementation, this embodiment of the invention provides a sample forming fixture, the structure of which is as follows: Figure 2 and Figure 3 As shown, the sample forming fixture includes a support platform 1, a concave shaping fixture 3, a convex shaping fixture 4, and a fastening mechanism; wherein, the support platform 1 is placed on a platform, its upper end face is horizontal and a T-shaped protrusion is provided at the center position, the upper end face of the T-shaped protrusion is parallel to the upper end face of the support platform, and the upper end face of the T-shaped protrusion has a size of 10mm×10mm; Figure 2 In the middle, the T-shaped protrusion is composed of a first cuboid 1-3 and a second cuboid 1-2 stacked vertically and coaxially. The bottom area of ​​the first cuboid 1-3 located above is larger than the bottom area of ​​the second cuboid 1-2 located below.

[0071] Further integration Figure 2As shown, a concave shaping fixture 3 and a convex shaping fixture 4 are respectively disposed on opposite sides of the T-shaped protrusion; a first groove 3-4 is provided at the bottom of the side of the concave shaping fixture 3 near the convex shaping fixture 4, and a second groove is provided at the bottom of the convex shaping fixture 4 at a position corresponding to the first groove 3-4; a first molding chamber is provided on the side of the concave shaping fixture 3 near the convex shaping fixture 4 from its upper end surface to the top of the first groove 3-4, the first molding chamber is vertically arranged, and its opening faces the convex shaping fixture 4; a second molding chamber is provided on the side of the convex shaping fixture 4 opposite to the concave shaping fixture 3, the second molding chamber is vertically arranged, and its opening faces the first molding chamber;

[0072] The concave shaping fixture 3 is provided with a pair of grooves 3-1 recessed into the interior of the concave shaping fixture 3 on both sides along the extension direction of the first forming chamber. The convex shaping fixture 4 is provided with a pair of protrusions 4-1 extending in the direction of the concave shaping fixture 3 at positions corresponding to the grooves 3-1, and the protrusions 4-1 are adapted to the grooves 3-1.

[0073] When the protrusion 4-1 is fitted into the slot 3-1, the first groove 3-4 and the second groove are fitted onto the outer periphery of the T-shaped protrusion. The first molding chamber, the second molding chamber, and the upper surface of the T-shaped protrusion are tightly fitted together to form a molding cavity with a cross-sectional dimension of 10mm×10mm and an open top. The height of the molding cavity is not less than 20mm, and the curing liquid is used to form and shape the sample 2 in the molding cavity. The fastening mechanism is used to fasten the concave shaping fixture 3 and the convex shaping fixture 4 until the curing liquid is cured.

[0074] Optionally, the fastening mechanism includes a plurality of first threaded holes 3-2 provided on the concave shaping fixture 3, a plurality of through holes 4-2 provided on the convex shaping fixture 4, and a plurality of bolts 5. The positions of the through holes 4-2 correspond one-to-one with the positions of the first threaded holes 3-2. When the upper surfaces of the first forming chamber, the second forming chamber, and the T-shaped protrusion are tightly fitted together, the plurality of bolts 5 are sequentially fastened from one end of the through holes 4-2 into the corresponding first threaded holes 3-2 until the concave shaping fixture 3 and the convex shaping fixture 4 are completely fitted together, with the effect as follows: Figure 3 As shown. To prevent the bolts 5 from being lost, a number of second threaded holes 4-3 are also provided on the convex shaping fixture. When the bolts 5 are removed from the first threaded holes 3-2, they are stored in the second threaded holes 4-3.

[0075] To facilitate the separation of the shaped sample 2 from the upper surface of the first cuboid 3, a triangular protrusion 3-3 with the same transverse cross-sectional shape as the first molding chamber is designed at the bottom of the first molding chamber. This triangular protrusion 3-3 extends towards the second molding chamber. When the concave molding fixture 3 and the convex molding fixture 4 are aligned on the support platform 1, the triangular protrusion 3-3 is located directly above the upper surface of the first cuboid 3. When the curing liquid solidifies into the shaped sample 2 in the molding cavity, a triangular groove is formed at the location of the triangular protrusion 3-3 in the shaped sample 2. When the shaped sample 2 is removed, the bolt 5 is turned slowly until the concave molding fixture 3 and the convex molding fixture 4 are separated. The concave molding fixture 3 and the convex molding fixture 4 are then removed. A flathead screwdriver is inserted into the triangular groove above the interface between the shaped sample 2 and the first cuboid 1-3, and the handle of the flathead screwdriver is gently tapped with a small hammer to remove the shaped sample 2. In specific implementation, the triangular protrusions 3-3 used to form triangular grooves on the molded sample 2 can also be arranged at the bottom inside the second molding chamber, or they can be arranged at the bottom inside the first molding chamber and the second molding chamber respectively.

[0076] This invention solves the problems of poor conductivity making it impossible to locate feature areas and uneven surface leading to uncontrollable sample preparation areas when preparing transmission electron microscopy (TEM) samples from continuous casting protective slag using FIB through a specific curing liquid formulation, combined with sample forming fixtures and sample preparation process. The method is not only simple and easy to operate, but also applicable to the preparation of TEM samples from various powders with poor conductivity via FIB, and has high sample preparation efficiency.

[0077] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for preparing FIB samples of continuous casting protective slag, characterized in that, Includes the following steps: 1) Prepare a curing solution containing continuous casting protective slag and carbon powder. The mass ratio of continuous casting protective slag and carbon powder in the curing solution is 1:1~2. The curing solution also includes epoxy resin and curing agent. The volume ratio of curing agent, epoxy resin and carbon powder is 1:5:1~2. 2) The curing liquid is used to form a sample with a height of not less than 20mm and a size of 10mm×10mm in the sample forming fixture; 3) Cut the shaped sample to obtain a sample sheet with a thickness not exceeding 2 mm. The cut surface of the sample sheet is parallel to its opposite surface, and any cut surface of the sample sheet can be used as a test surface for detection. 4) Fix the cut sample slices onto the universal T-shaped stage of the scanning electron microscope with glue, and use conductive glue to make the test surface and the edge of the sample test surface electrically connected to the test surface of the T-shaped stage respectively. 5) Place the T-shaped stage with the sample sheet fixed in it into a high-vacuum carbon spraying device for carbon spraying. The purity of the carbon powder shall not be less than 99.9% and the particle size shall not exceed 2000 mesh. In step 5), the thickness of the carbon sprayed onto the T-shaped stage on which the sample sheet is fixed shall not exceed 50 nm. 6) Place the T-shaped stage with the sample sheet fixed after carbon spraying into the FIB sample preparation equipment, find the characteristic area through the energy dispersive spectrometer attached to the equipment and perform FIB sample preparation, and finally obtain a transmission electron microscope sample with specific characteristic area and controllable preparation area. In step 6), during the FIB sample preparation process, the environmental parameters for the sample's transparency in the electronic image are 50% brightness and 20% contrast. The sample forming fixture in step 2) includes a support platform, a concave shaping fixture, a convex shaping fixture, and a fastening mechanism; The support platform is placed on the platform, with its upper surface horizontal and a T-shaped protrusion at its center; the upper surface of the T-shaped protrusion is parallel to the upper surface of the support platform, and the upper surface of the T-shaped protrusion has a size of 10mm × 10mm. The concave shaping fixture and the convex shaping fixture are respectively disposed on opposite sides of the T-shaped protrusion; the bottom of the concave shaping fixture near the convex shaping fixture is provided with a first groove, and the bottom of the convex shaping fixture is provided with a second groove corresponding to the first groove; the side of the concave shaping fixture near the convex shaping fixture is provided with a first molding chamber from its upper end surface to the top of the first groove, the first molding chamber is vertically arranged and its opening faces the convex shaping fixture; the side of the convex shaping fixture opposite to the concave shaping fixture is provided with a second molding chamber, the second molding chamber is vertically arranged and its opening faces the first molding chamber; The concave shaping fixture is provided with a pair of grooves that are recessed into the interior of the concave shaping fixture on both sides along the extension direction of the first forming chamber. The convex shaping fixture is provided with a pair of protrusions that extend in the direction of the concave shaping fixture at positions corresponding to the grooves, and the protrusions are adapted to the grooves. When the protrusion is fitted into the slot, the first and second grooves are fitted onto the outer periphery of the T-shaped protrusion. The first molding chamber, the second molding chamber, and the upper surface of the T-shaped protrusion fit together tightly to form a molding cavity with a cross-sectional dimension of 10mm×10mm and an open top. The height of the molding cavity is not less than 20mm, and the curing liquid forms and shapes the sample within the molding cavity. The fastening mechanism is used to fasten the concave shaping fixture and the convex shaping fixture; A triangular protrusion is provided at the bottom of the inner side of the first molding chamber. The triangular protrusion extends toward the second molding chamber, and the shape of the triangular protrusion in the first molding chamber is the same as the shape of the transverse cross section of the first molding chamber. When the concave shaping fixture and the convex shaping fixture are assembled on the support platform, the triangular protrusion is located directly above the upper end face of the T-shaped protrusion, and when the curing liquid is cured into a shaped sample in the molding cavity, the shaped sample forms a triangular groove at the position of the triangular protrusion.

2. The FIB sample preparation method for continuous casting protective slag samples according to claim 1, characterized in that, The parameters for the carbon injection process are controlled as follows: The distance between the surface of the sample sheet on the T-shaped stage and the carbon rod on the high-vacuum carbon spraying equipment is D, where D > 20 mm; when the high-vacuum carbon spraying equipment is working, the carbon spraying vacuum is better than 1 × 10⁻⁶ mm. -3 mbar.

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