Method for realizing multi-scale characterization of quasi-in-situ heating transmission electron microscope through oxidation control

Abstract

The invention relates to a method for realizing multi-scale characterization of a quasi-in-situ heating transmission electron microscope through oxidation control, and belongs to the technical field of multi-scale characterization of nonferrous metals and transmission electron microscopes. The method is suitable for all non-ferrous metal materials. The preparation process comprises the following steps: preparing and screening a transmission electron microscope sample, sealing a tube, removing oxygen, taking out the sample after cooling, and carrying out characterization testing. According to the method, the oxidation degree of the sample in the heating process is reduced until TEM characterization is not affected, and the position marks return to the same position for characterization in different heating stages, so that continuous change of the same position is fed back by results. According to the method, a special in-situ sample rod does not need to be used, the quasi-in-situ effect can be achieved by using a 3 mm disc sample, the method is generally suitable for various electron microscopes and various characterization methods, and characterization of atomic resolution can be achieved.

Description

Technical Field

[0001] This invention relates to a method for achieving quasi-in-situ heated transmission electron microscopy (TEM) multi-scale characterization through oxidation control, and more particularly to a method for achieving quasi-in-situ heated TEM multi-scale characterization of non-ferrous metals through oxidation control, belonging to the technical field of non-ferrous metals and TEM multi-scale characterization. Background Technology

[0002] As materials science research deepens, researchers urgently need to investigate the mechanisms of material action, structural changes, and factors influencing their properties. However, traditional ex-situ methods can only test the state before and after a reaction, failing to provide dynamic testing during the process and thus unable to meet the current demand for more in-depth research on process changes. In contrast, in-situ heating characterization techniques can track and observe phase changes in single nanoparticles in real time under heating conditions, offering dynamism, real-time monitoring, and intuitive visualization. For temperature-induced phase transitions, in-situ heating characterization techniques overcome the limitations of traditional ex-situ methods, providing more intuitive evidence for elucidating phase transition mechanisms.

[0003] For a long time, in-situ heated TEM observation has been inseparable from a heating sample rod. According to the heating principle, it can be mainly divided into two categories: molten pool heating and microelectromechanical systems (MEMS) chip heating. Each of these two methods has its advantages and disadvantages. Molten pool heating can be compatible with various types of transmission samples, but the heating temperature control is poor, the temperature difference fluctuates greatly, and the sample observation area drifts significantly. It is often accompanied by deformation caused by thermal expansion, making it difficult to achieve high-resolution transmission electron microscopy characterization.

[0004] Currently, widely used chip heating rods offer good temperature and drift control, enabling in-situ observation at atomic resolution using HAADF-STEM. However, chip heating rods can only use focused ion beam (FIB) sample preparation, which has the following three drawbacks.

[0005] First, ion implantation during FIB cutting is unavoidable. Although a low-energy ion beam is used to clean the sample surface and remove the highly implanted layer after sample cutting, some early phase structures in light alloys are fragile, and prolonged high-energy electron beam irradiation will damage the structure. Since the ion beam has even higher energy, the damage to the fragile phase structure during sample cutting is unavoidable.

[0006] Secondly, Pt deposition is unavoidable, which is detrimental to TEM imaging. Cut FIB samples need to be fixed onto a heated chip using Pt deposition. When Pt is deposited from the vapor phase to the solid phase, in addition to deposition at the fixed point, trace amounts also deposit in a surrounding area. Pt has an atomic number of 78, which is high. During STEM imaging with a transmission electron microscope, this can easily obscure the sample signal, making it difficult to detect some early phases that already have low contrast.

[0007] Third, the FIB sample size is extremely small. Due to the size effect, the diffusion situation deviates from that of the bulk material, and it is questionable whether it can reflect the true situation of phase transformation in the bulk material.

[0008] To avoid the adverse effects of FIB (fiber osmosis) and to continuously track changes in the same region or the same nano-precipitated phase at different stages of heating, this study proposes a quasi-in-situ heating method suitable for transmission electron microscopy (TEM) characterization. This method does not require a special sample holder, can use a 3mm disk sample, is universally applicable to various electron microscopes and characterization methods, and can achieve atomic resolution characterization. Furthermore, compared to FIB samples, the results provided by the 3mm disk sample more closely approximate the true condition of bulk materials. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies, avoid the adverse effects of FIB (fiber osmosis), and simultaneously achieve continuous tracking of changes in the same region or the same nano-precipitated phase at different stages of heating. This invention proposes a quasi-in-situ heating method suitable for transmission electron microscopy (TEM) characterization. This method does not require a special in-situ sample holder, can use 3 mm disk samples, is universally applicable to various electron microscopes and characterization methods, and can achieve atomic resolution characterization.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] TEM sample preparation employed two methods: electrolytic double-jet thinning and ion thinning.

[0012] In practical applications, samples are mechanically thinned to a thickness of 30-80 μm and then punched into 3 mm diameter disks using a DERVEE1700-3A disk punching machine. The disks are then thinned into TJE samples using a Struers TenuPol-5 dual-jet electrolytic thinning instrument in a methanol electrolyte containing 33 vol% nitric acid. Ion-thinned samples are prepared using a Gatan 695 PIPS II ion thinning instrument. The thinning process involves using an ion beam with 6 keV energy and a 6° incident angle to thin the sample to perforation, followed by a slight enlargement of the pores using 3 keV at 3°, and finally finishing and enlarging the observable thin area using 2 keV at 2° and 1 keV at 2°.

[0013] BF, HRTEM, HAADF-STEM images and energy-dispersive X-ray spectroscopy (EDX) were acquired using a Thermo Fisher Talos F200x transmission electron microscope operating at 200 kV. Atomic resolution HAADF-STEM and high-magnification EDX spectra were acquired using a Thermal Fisher Spectra 300 transmission electron microscope operating at 300 kV.

[0014] This invention is applicable to all non-ferrous metals.

[0015] This invention discloses a method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization through oxidation control, comprising the following steps:

[0016] The first step is to prepare TEM samples.

[0017] Choose either electrolytic dual-spray thinning or ion thinning sample preparation as needed;

[0018] The second step is to screen TEM samples.

[0019] The samples were screened using a transmission electron microscope to identify regions of interest, and the location of these regions and the precipitated particles of interest were recorded and numbered.

[0020] The third step is to seal the tube.

[0021] The selected sample is placed in a clean and dry ceramic crucible. The opening of the ceramic crucible is sealed with ceramic crucible sealing material. The sealed ceramic crucible with the sample is placed into a container filled with protective gas. Then, a support is set at the opening of the ceramic crucible, and an oxygen absorber carrier is placed on the other end of the support. Oxygen absorber is placed on the oxygen absorber carrier. Finally, the container is sealed to obtain a ready-to-use sealed tube.

[0022] Step 4, removing oxygen

[0023] Place the spare sealing tube in a heating device for heating and deoxidation; the deoxidizing agent is heated to 100-200% of the sample's melting point, but the sample does not dissolve.

[0024] Step 5, vacuum heating

[0025] The deoxidized spare sealing tube is placed in a vacuum heating device and subjected to vacuum heating treatment at a set temperature.

[0026] Step 6: Cool and remove the sample.

[0027] After stopping heating and cooling to below 100°C, immerse the sealed tube in water for further cooling; to ensure complete cooling, a cooling time of more than 8 hours is recommended. After cooling, wipe the surface dry, crush the oxygen absorber end with pliers, remove the sample, and vacuum preserve it.

[0028] Step 7, Characterization Test. Perform TEM characterization on the sample again, locate the areas to be observed and the precipitated particles based on the positions recorded in Step 2, and capture the necessary image data.

[0029] Step 8: Repeat steps 3 through 7 to obtain continuous changes in the same location and the same particle at different stages of heating at the nanoscale.

[0030] In step one of this invention, the metal sample to be observed is mechanically thinned and punched into a disc with a diameter of 3 mm using a disc punching machine. Electrolytically thinned samples and ion-thinned samples are prepared using a dual-jet electrolytic thinning instrument and an ion thinning instrument.

[0031] In step two of this invention, the position recording is selected from at least one of the following two methods. Position recording method one: First, the entire appearance of the sample pores needs to be observed under low magnification (50x-1000x) in a transmission electron microscope to find suitable pore edges. Images of the area to be observed are then taken, and the area is magnified sequentially and images are taken. Typically, images are recorded at approximately Ax, Bx, Cx, and Dx magnification. Then, in bright field mode, the precipitated phase particles to be studied are located at approximately Ex and Fx magnification, and images are taken. Since the precipitated phase particles may dissolve or precipitate during heating, their position can be marked by the relative positions of a group of precipitated phases, or by selecting unchanging surrounding markers. The distance from the precipitated phase particles to be studied and the reference object to the pores is recorded as the basis for the next determination. Among them, the value of A is 2000~4000; the value of B is 5000~7000; the value of C is 15000~25000; the value of D is 55000~65000; the value of E is 75000~85000; and the value of F is 115000~125000.

[0032] Method 2 for recording location: The entire pore structure of the sample can be observed at low magnification (50x-1000x) using a transmission electron microscope (TEM). Find the appropriate pore edge and photograph the area to be observed. Gradually magnify the area and photograph it, typically recording at approximately Ax, Bx, Cx, and Dx magnification. Then, in bright-field mode, locate the precipitate particles to be studied at approximately Ex and Fx magnification and photograph them. Next, magnify the area near the precipitate particles to high resolution mode (approximately Gx) and focus the electron beam until the sample is burned through. Small pores in the sample may heal on their own if they are too small. Therefore, the process needs to be repeated several times to enlarge the burned-through pores. Then, the magnification is reduced to approximately H times, and the distance from the precipitated phase particles to the pores is recorded. The values ​​for A are 2000–4000; B is 5000–7000; C is 15000–25000; D is 55000–65000; E is 75000–85000; F is 115000–125000; G is 480000–550000; and H is 380000–420000. Accurate position recording is crucial in this invention. Failure to record accurate positions will directly lead to the failure of in-situ characterization.

[0033] As a further preferred method, the location recording method is as follows: First, the entire appearance of the sample pores needs to be observed under low magnification (50x-1000x) in a transmission electron microscope to find the appropriate pore edge and take pictures of the area to be observed. The area to be observed is magnified and pictures are taken in sequence. Usually, the magnification is recorded at about 3000x, 6000x, 20000x, and 60000x respectively. Then, in bright field mode, the precipitate particles to be studied are found at about 80000x and 120000x and pictures are taken. Since the precipitate particles may dissolve or precipitate during heating, their location can be marked by the relative positions of a group of precipitates, or by selecting unchanging markers in the surrounding area. The distance from the precipitate particles to be studied and the reference object to the pores is recorded as the basis for the next judgment.

[0034] Method 2 for recording location: The entire pore of the sample can be observed at low magnification (50x-1000x) in a transmission electron microscope. Find the appropriate edge of the pore, take pictures of the area to be observed, and then magnify the area to be observed and take pictures in sequence. Usually, the magnification is recorded at about 3000x, 6000x, 20000x, and 60000x respectively. Then, in bright field mode, find the precipitate particles to be studied at about 80000x and 120000x and take pictures. Then, magnify the area near the precipitate particles to be studied to high resolution mode (about 520000x) and focus the electron beam until the sample is burned through. If the small hole on the sample is too small, it will heal itself. Therefore, it is necessary to repeat the operation several times to enlarge the burned hole. Then reduce the magnification to about 400000x and record the distance from the precipitate particles to be studied to the pore.

[0035] As a preferred option, the container used in the third step includes a glass tube.

[0036] As a preferred embodiment, in the third step, the sealing material used for the ceramic crucible is selected from at least one of ceramic fiber, aluminum foil wire, high-purity quartz fiber, a matching ceramic lid, and graphite fiber. In this invention, the ceramic crucible sealing material blocks the crucible opening to prevent the sample from falling out.

[0037] In this invention, all materials inside the container must be clean, able to withstand high temperatures, and non-volatile.

[0038] As a preferred option, in the third step, the oxygen absorber carrier is selected from one of the following: quartz plate, stainless steel plate, alumina ceramic, and zirconia ceramic.

[0039] As a preferred embodiment, in the third step, the oxygen absorber is selected from at least one of sponge titanium, magnesium, calcium, and zirconium aluminum getters. More preferably, it is selected from at least one of sponge titanium and calcium.

[0040] As a preferred option, in the third step, the material used to seal the container includes one of the following: quartz plug, oxygen-free copper gasket, aluminum gasket, and graphite plug.

[0041] As a preferred option, in the fourth step, during heating for deoxygenation, the sample is positioned below the oxygen absorber. In practical applications, using a sealed tube with a hydrogen flame for oxygen removal is effective.

[0042] As a preferred option, the deoxygenation time in the fourth step is 5-10 minutes.

[0043] After sealing, deoxygenation, and vacuum heating, the present invention achieves excellent surface oxidation control, with the amorphous layer thickness increasing by only about 1.28 nm. When using Ti oxygen absorber, there is no deposition or oxidation that would lead to unclear field of view. Furthermore, the bright field (BF) images, high resolution transmission electron microscopy (HRTEM) images, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images before and after heating are all clear.

[0044] The most prominent substantive features and significant advancements of this invention are mainly reflected in:

[0045] (1) This invention reduces the degree of oxidation of the sample during the heating process to the point that it does not affect TEM characterization, and returns to the same position for characterization at different stages of heating by position marking, thereby achieving continuous change of the same position in the result feedback.

[0046] (2) This invention verifies a feasible quasi-in-situ heating TEM observation method: the disk TEM sample is vacuum sealed in a quartz tube and heated in a muffle furnace, and the controllability of sample oxidation during heating is verified.

[0047] (3) The heating process of this invention can be stopped at any time, and the sample can be removed for observation. By marking the target observation area at different magnifications, the same area can be locked in multiple TEM observations, thereby replacing the heating function of the in-situ sample rod and completing high-resolution TEM imaging.

[0048] (4) The present invention is simple to operate and does not require the use of special sample rods. It can use 3 mm disk samples, is widely applicable to various electron microscopes and various characterization methods, and can achieve atomic resolution characterization.

[0049] (5) The present invention replaces the heating function of the in-situ sample rod with vacuum sealing heating, which has a very obvious cost advantage. Attached Figure Description

[0050] Appendix Figure 1 Flowchart of the sealing heating method and how to achieve near-in-situ effect;

[0051] Appendix Figure 2 Schematic diagram of the internal layout of a quartz tube;

[0052] Appendix Figure 3 A schematic diagram showing the relative positions of the precipitated phases.

[0053] Appendix Figure 4 Schematic diagram of the marking position for electron beam focusing and hole burning.

[0054] Appendix Figure 5 Changes in the thickness of the amorphous layer before and after sample heating;

[0055] Appendix Figure 6 Bright-field images, HRTEM images, and HAADF-STEM images before and after heating;

[0056] Appendix Figure 7 STEM-EDX elemental surface distribution analysis of the sample when Mg is used as the oxygen absorber;

[0057] Appendix Figure 8 STEM-EDX elemental surface distribution analysis of samples when Ti is used as the oxygen absorber;

[0058] Appendix Figure 9 In-situ heated TEM image of circumferential suture sample: (a) is a bright field TEM image; (b) is an HRTEM image when the wire is connected; (c) is an HRTEM image after the wire is pulled out. All three images were taken using an in-situ heated sample rod.

[0059] Appendix Figure 10 Drift and curling of ordinary TEM samples during heating: (a), (b), and (c) show the changes in the samples during the process of heating followed by cooling; (d), (e), and (f) show the changes in the part indicated by the arrow in (a) during cooling.

[0060] From the appendix Figure 1 It can be seen that the tube sealing and heating method and the process of achieving quasi-in-situ effect mainly include the preparation and screening of TEM samples, vacuum heating in a muffle furnace after deoxygenation of the tube, and taking out the sample for characterization and testing after cooling. By repeatedly performing TEM observation and vacuum heating, data are collected to form continuous changes at the same location, and finally quasi-in-situ effect is achieved.

[0061] From the appendix Figure 2 As can be seen, the process involves sealing the tube. The selected sample is placed in a small ceramic crucible, and then vacuum-sealed with a titanium sponge block within a clean quartz glass tube using a vacuum sealer. The titanium sponge block serves as the oxygen absorber, and aluminum foil is used to block the crucible opening to prevent the sample from falling out. All internal materials must be clean, heat-resistant, and non-volatile.

[0062] From the appendix Figure 3 It can be seen that the relative positions of the precipitated phases are used to mark their locations. First, the overall appearance of the sample pores needs to be observed under low magnification in a transmission electron microscope (e.g., ...). Figure 3 a) Locate a suitable edge of the hole and take a picture of the area to be observed (e.g., ...). Figure 3b), zoom in on the area to be observed and take pictures (e.g., ... Figure 3 (c, 3d, 3e) Since the precipitated phase particles may dissolve or precipitate during heating, their position markings can be based on the relative positions of a group of precipitated phases (e.g., ...). Figure 3 Particles 22, 25, and 29 in d and 3e are recorded, and the distance from the precipitated phase particles to be studied and the reference to the pores is recorded as the basis for the next judgment.

[0063] From the appendix Figure 4 As can be seen, the marking positions of the holes are burned off by electron beam focusing. First, it is necessary to observe the overall appearance of the sample holes at low magnification in a transmission electron microscope (such as...). Figure 4 a) Locate a suitable edge of the hole and take a picture of the area to be observed (e.g., ...). Figure 4 b), zoom in on the area to be observed and take pictures (e.g., ... Figure 4 (c, 4d, 4e), then magnify to high resolution mode near the precipitate particles to be studied and focus the electron beam until the sample is burned through, the burned-through pores are as follows: Figure 4 As shown in e, record the distance from the precipitated phase particles to the pores to be studied.

[0064] From the appendix Figure 5 It can be seen that the oxidation control effect on the sample surface after vacuum heating is good, and the thickness of the amorphous layer on the surface increases by only about 1.28 nm.

[0065] From the appendix Figure 6 It can be seen that the bright-field image, HRTEM image, and HAADF-STEM image of the sample before and after vacuum heating are all clear.

[0066] From the appendix Figure 7 It can be seen that when the oxygen absorber is Mg, heating during oxygen removal can easily cause it to volatilize and then deposit on the sample surface, obstructing the field of view. At the same time, Mg is highly reactive and easily combines with oxygen to oxidize after depositing on the sample surface, further obstructing the field of view and making the image even less clear.

[0067] From the appendix Figure 8 It can be seen that when the oxygen absorber is Ti, there will be no deposition or oxidation that would cause the field of view to be unclear.

[0068] From the appendix Figure 9 It can be seen that when the Gatan in-situ heating rod is used to heat the 3 mm disc electrolytic double-jet sample, the image is unclear due to the vibration of the sample rod connection line to the heating device. The resolution is restored only after the line is disconnected.

[0069] From the appendix Figure 10It can be seen that, because the Gatan in-situ heating rod fixes the 3 mm disc electrolytic double-jet sample by fixing the entire outer ring of the sample, the sample is fixed all around. When heated, the sample volume expansion cannot extend outward, but instead extends towards the central double-jet hole, resulting in severe deformation and curling of the observation area at the double-jet hole. Detailed Implementation

[0070] This invention proposes a quasi-in-situ heating method suitable for transmission electron microscopy (TEM) characterization of non-ferrous metals. This method eliminates the need for a special in-situ sample holder, allows the use of 3 mm disc samples, is universally applicable to various electron microscopes and characterization methods, and enables atomic resolution characterization.

[0071] The present invention also provides a corresponding preparation method:

[0072] (1) Preparation of TEM samples. Electrolytic double-jet thinning or ion thinning can be selected as needed for sample preparation.

[0073] (2) Screening TEM Samples. Samples are screened using a transmission electron microscope (TEM) to identify regions of interest. The location of these regions and the precipitates of interest are recorded and numbered. Location recording requires taking images of the target observation area at different magnifications. There are two main methods to facilitate finding the same location later. First, the entire pore of the sample needs to be observed at low magnification (50x-1000x) in the TEM to find suitable pore edges and take images of the area to be observed. The area to be observed is then magnified and images are taken sequentially, typically at approximately 3000x, 6000x, 20000x, and 60000x. Then, in bright field mode, the precipitates to be studied are found at approximately 80000x and 120000x, and images are taken. Since the precipitates may dissolve or precipitate during heating, their location can be marked by the relative positions of a group of precipitates, or by selecting unchanging markers in the surrounding area. The distance from the precipitates to be studied and the reference object to the pore is recorded as the basis for subsequent determination. Alternatively, the entire pore structure of the sample can be observed at low magnification (50x-1000x) in a transmission electron microscope. A suitable pore edge can be located, and images of the area to be observed can be taken. The area to be observed can be magnified sequentially, and images can be taken at approximately 3000x, 6000x, 20000x, and 60000x. Then, in bright field mode, the precipitate particles to be studied can be located at approximately 80000x and 120000x, and images can be taken. Next, near the precipitate particles to be studied, the magnification can be increased to high resolution mode (approximately 520000x) and the electron beam focused until the sample is burned through. If the small pores on the sample are too small, they will heal themselves, so the process needs to be repeated several times to enlarge the burned-through pores. Then, the magnification can be reduced to approximately 400000x, and the distance from the precipitate particles to the pores can be recorded.

[0074] (3) Sealing. Place the selected sample in a small ceramic crucible and use a vacuum sealer to vacuum seal it and the titanium sponge block in a clean quartz glass tube. The titanium sponge block is used as the oxygen absorber, and aluminum foil is used to block the crucible opening to prevent the sample from falling out. All internal materials must be clean, heat-resistant, and non-volatile.

[0075] (4) Oxygen removal. Clamp the quartz tube horizontally with a test tube clamp, so that the sample end is lower and the oxygen absorber end is higher. Use a flame with a heating temperature of 600℃-1600℃, which is higher than the vacuum heating temperature of the sample, to sweep and heat the oxygen absorber for 5-10 minutes. In this study, the hydrogen flame with a sealed tube was used to remove oxygen effectively.

[0076] (5) Vacuum heating. The quartz tube is heated, and the required heating equipment and temperature can be selected to achieve vacuum heating of the TEM sample.

[0077] (6) Cooling and removing the sample. After the quartz tube has stopped heating and cooled to below 100°C, immerse the entire tube in water to cool. To ensure complete cooling, it is recommended that the cooling time exceed 8 hours. After cooling, wipe the surface dry, crush the oxygen absorber end with pliers, remove the sample, and vacuum preserve it.

[0078] (7) Characterization test. Perform TEM characterization on the sample again, locate the area to be observed and the precipitated particles according to the location recorded in step 2, and take the required image data.

[0079] (8) Repeat steps (3) to (7) to obtain the continuous change results of the same position and the same particle at the nanoscale at different stages of heating, thus achieving the effect of quasi-in-situ.

[0080] Example

[0081] A quasi-in-situ heating method suitable for transmission electron microscopy characterization of non-ferrous metals is specifically carried out according to the following steps:

[0082] I. According to the mass percentage of each element in the alloy as Si: 0.44%, Mg: 0.66%, with the balance being industrial Al and unavoidable impurities, weigh out the industrial Al for smelting, high-purity Mg particles, and high-purity aluminum-silicon master alloy respectively; the industrial Al contains 0.11% iron, the purity of the high-purity Mg particles is 99.9%, and the high-purity aluminum-silicon master alloy is 99.9 wt.% AlSi25;

[0083] 2. Add the industrial Al, high-purity Mg particles and high-purity aluminum-silicon master alloy weighed in step 1 to the melting furnace and melt them at 740°C. After they are completely melted, stir to obtain the melt.

[0084] 3. Add the melt prepared in step 2 to hexachlorohexane for refining and slag removal. After holding at the temperature for 20 minutes, add magnesium particles wrapped in aluminum foil and stir thoroughly. After the temperature drops to 700℃, cast the ingot.

[0085] 4. Homogenize the ingot from step 3 at 530℃ for 12 h, hold it at 450℃ for 2 h and hot roll it to 6 mm, then cold roll it into a 1 mm thick plate, then solution heat treat it at 550℃ for 30 min, water quench it, and immediately age it at 180℃ for 15 h.

[0086] 5. After mechanical thinning and aging, the alloy from step four is reduced to a thickness of 30-80 μm, and then punched into a 3 mm diameter disk using a DERVEE1700-3A disk punching machine. Using a Struers TenuPol-5 dual-jet electrolytic thinning instrument, the disk is thinned into a TJE sample in a methanol electrolyte containing 33 vol% nitric acid. An ion-thinned sample is prepared using a Gatan 695 PIPS II ion thinning instrument. The thinning process involves using an ion beam with 6 keV energy and a 6° incident angle to thin the sample to perforation, then slightly enlarging the hole with 3 keV at 3°, and finally finishing and enlarging the observable thin area with 2 keV at 2° and 1 keV at 2°.

[0087] VI. The TEM samples obtained in step five are screened under a transmission electron microscope to identify regions of interest. The location of these regions and the precipitated particles of interest are recorded and numbered. There are two main methods for recording the locations; the first method is shown in the attached figure. Figure 3 As shown, the positions of the precipitated phases are marked by their relative positions. First, the overall appearance of the sample pores needs to be observed under low magnification in a transmission electron microscope (e.g., Figure 3 a) Locate a suitable edge of the hole and take a picture of the area to be observed (e.g., ...). Figure 3 b), zoom in on the area to be observed and take pictures (e.g., ... Figure 3 (c, 3d, 3e) Since the precipitated phase particles may dissolve or precipitate during heating, their position markings can be based on the relative positions of a group of precipitated phases (e.g., ...). Figure 3 Particles 22, 25, and 29 in d and 3e are recorded, and the distance from the precipitated phase particles to be studied and the reference to the pores is recorded as the basis for the next judgment.

[0088] The second method is as follows Figure 4 As shown, the hole markings are created by electron beam focusing. First, the overall appearance of the sample holes needs to be observed under low magnification in a transmission electron microscope (such as...). Figure 4 a) Locate a suitable edge of the hole and take a picture of the area to be observed (e.g., ...). Figure 4 b), zoom in on the area to be observed and take pictures (e.g., ... Figure 4(c, 4d, 4e), then magnify to high resolution mode near the precipitate particles to be studied and focus the electron beam until the sample is burned through, the burned-through pores are as follows: Figure 4 As shown in e, record the distance from the precipitated phase particles to the pores to be studied;

[0089] 7. Seal the TEM samples selected in step 6. Place the selected samples in a small ceramic crucible and use a Partulab MRVS-1002 vacuum sealer to vacuum seal them with a titanium sponge block in a clean quartz glass tube. The titanium sponge block is used as the oxygen absorber, and aluminum foil is used to block the crucible opening to prevent the samples from falling out.

[0090] 8. Remove oxygen from the sample in the quartz glass tube from step 7. Hold the quartz tube horizontally with the test tube clamp so that the sample end is lower and the oxygen absorber end is higher. Use a flame with a heating temperature of 600℃-1600℃, which is higher than the vacuum heating temperature of the sample, to sweep and heat the oxygen absorber for 5-10 minutes.

[0091] 9. Heat the quartz tube from step 8 using a muffle furnace to achieve vacuum heating of the TEM sample (temperature 180-550℃).

[0092] 10. After cooling the heated quartz tube from step nine to below 100°C, immerse the complete quartz tube in water to cool it further.

[0093] 11. Perform TEM characterization on the sample from step 10 again. Locate the area to be observed and the precipitated particles based on the location recorded in step 6, and capture the required image data. Repeat steps 6 to 11 to obtain continuous changes of the same nanoscale particles at the same location during different heating stages, achieving a quasi-in-situ effect.

[0094] Testing showed that the surface oxidation control in this embodiment was excellent, with the amorphous layer thickness increasing by only about 1.28 nm. Figure 5 Furthermore, the bright-field images, HRTEM images, and HAADF-STEM images before and after heating are all clear, such as... Figure 6 Oxygen absorbers like Mg have a lower boiling point than Ti. Heating during oxygen removal can cause them to volatilize and deposit on the sample surface, obstructing the field of view. Furthermore, Mg is more reactive than Ti, readily combining with oxygen after deposition and further obstructing the field of view, resulting in even less clear images. Figure 7 Using a Ti oxygen absorber will prevent the formation of deposits and oxidation that could obscure the field of vision, such as... Figure 8 .

[0095] Comparative Example

[0096] The method for in-situ heating using the Gatan in-situ heating rod is as follows:

[0097] I. Based on the following element mass percentages: Si: 0.44%, Mg: 0.66%, with the balance being industrial Al and unavoidable impurities, weigh out industrial Al for smelting, high-purity Mg particles, and high-purity aluminum-silicon master alloy; wherein the industrial Al contains 0.11% iron, the high-purity Mg particles have a purity of 99.9%, and the high-purity aluminum-silicon master alloy is 99.9 wt.% AlSi25;

[0098] 2. Add the industrial Al, high-purity Mg particles and high-purity aluminum-silicon master alloy weighed in step 1 to the melting furnace and melt them at 740°C. After they are completely melted, stir to obtain the melt.

[0099] 3. Add the melt prepared in step 2 to hexachlorohexane for refining and slag removal. After holding at the temperature for 20 minutes, add magnesium particles wrapped in aluminum foil and stir thoroughly. After the temperature drops to 700℃, cast the ingot.

[0100] 4. Homogenize the ingot from step 3 at 530℃ for 12 h, hold it at 450℃ for 2 h and hot roll it to 6 mm, then cold roll it into a 1 mm thick plate, then solution heat treat it at 550℃ for 30 min, water quench it, and immediately age it at 180℃ for 15 h.

[0101] 5. After mechanical thinning and aging, the alloy from step four is reduced to a thickness of 30-80 μm, and then punched into a 3 mm diameter disk using a DERVEE1700-3A disk punching machine. Using a Struers TenuPol-5 dual-jet electrolytic thinning instrument, the disk is thinned into a TJE sample in a methanol electrolyte containing 33 vol% nitric acid. An ion-thinned sample is prepared using a Gatan 695 PIPS II ion thinning instrument. The thinning process involves using an ion beam with 6 keV energy and a 6° incident angle to thin the sample to perforation, then slightly enlarging the hole with 3 keV at 3°, and finally finishing and enlarging the observable thin area with 2 keV at 2° and 1 keV at 2°.

[0102] 6. The TEM sample obtained in step 5 is heated in situ under a transmission electron microscope to observe the changes in the sample and the precipitated phase.

[0103] Testing revealed the following results for the comparative sample, obtained by heating the disc electrolytic double-spray sample using a Gatan in-situ heating rod: Figure 9 When connecting the heating device, vibration of the sample rod connection wire caused unclear images, such as... Figure 9 (b) Resolution is restored only after disconnecting the cable, such as Figure 9 (c) Because the Gatan in-situ heating rod fixes the sample by fixing the entire outer ring of the sample, the sample is fixed all around. During heating, the sample volume expansion cannot extend outwards, but instead extends towards the central dual-jet nozzle, resulting in severe deformation and curling of the observation area at the dual-jet nozzle. Figure 10 .

[0104] Therefore, this invention verifies a feasible quasi-in-situ heated TEM observation method: by vacuum-sealing a disc-shaped TEM sample inside a quartz tube and heating it in a muffle furnace, the controllability of sample oxidation during heating is verified. Furthermore, the heating process can be stopped at any time, and the sample can be removed for observation. By marking the target observation area at different magnifications, the same area can be locked in multiple TEM observations, thus replacing the heating function of the in-situ sample rod and achieving high-resolution TEM imaging, thereby achieving a quasi-in-situ effect.

Claims

1. A method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization through oxidation control, characterized in that, Includes the following steps: The first step is to prepare TEM samples. Choose either electrolytic dual-spray thinning or ion thinning sample preparation as needed; The second step is to screen TEM samples. The samples were screened using a transmission electron microscope to identify regions of interest, and the location of these regions and the precipitated particles of interest were recorded and numbered. The third step is to seal the tube. The selected sample is placed in a clean and dry ceramic crucible. The opening of the ceramic crucible is sealed with ceramic crucible sealing material. The sealed ceramic crucible with the sample is placed into a container filled with protective gas. Then, a support is set at the opening of the ceramic crucible, and an oxygen absorber carrier is placed on the other end of the support. Oxygen absorber is placed on the oxygen absorber carrier. Finally, the container is sealed to obtain a ready-to-use sealed tube. Step 4, removing oxygen Place the spare sealing tube in a heating device for heating and deoxidation; the deoxidizing agent is heated to 100-200% of the sample's melting point, but the sample does not dissolve; Step 5: Vacuum heating The deoxidized spare sealing tube is placed in a vacuum heating device and subjected to vacuum heating treatment at a set temperature. Step 6: Cool and remove the sample. After stopping heating and cooling to below 100°C, immerse the sealed tube in water to cool. After cooling, wipe the surface dry, crush the oxygen absorber end with pliers, remove the sample, and preserve it under vacuum. Step 7, Characterization Testing The sample was characterized again by TEM. Based on the location recorded in the second step, the area to be observed and the precipitated particles were located, and the required image data was captured. Step 8: Repeat steps 3 through 7 to obtain continuous changes in the same nanoscale position and the same particle at different stages of heating.

2. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: Location records are selected from at least one of the following two methods; Location recording method 1: First, observe the entire pore of the sample under low magnification in a transmission electron microscope, find the appropriate pore edge, and take pictures of the area to be observed. Then, magnify the area to be observed in sequence and take pictures. Usually, the magnification is recorded at A, B, C, and D magnification respectively. Then, in bright field mode, find the precipitate particles to be studied at E and F magnification and take pictures. Since the precipitate particles may dissolve or precipitate during heating, their position can be marked by the relative positions of a group of precipitates, or by selecting unchanging markers in the surrounding area. Record the distance from the precipitate particles to be studied and the reference object to the pore as the basis for the next judgment. In transmission electron microscopy, the low magnification is 50-1000x; where A is 2000-4000; B is 5000-7000; C is 15000-25000; D is 55000-65000; E is 75000-85000; and F is 115000-125000. Method 2 for recording location: Observe the overall appearance of the sample pores under low magnification in a transmission electron microscope (TEM) to find suitable pore edges and take pictures of the area to be observed. Gradually magnify the area to be observed and take pictures, typically recording at Ax, Bx, Cx, and Dx magnification. Then, in bright field mode, locate the precipitate particles to be studied at Ex and Fx magnification and take pictures. Next, magnify to Gx in high-resolution mode near the precipitate particles and focus the electron beam until the sample is burned through. If the pores on the sample are too small, they will heal themselves, so the process needs to be repeated several times until the sample is burned through. The pores are enlarged, then the magnification is reduced to H, and the distance from the precipitated phase particles to the pores is recorded. In the transmission electron microscope (TEM), the low magnification is 50-1000x, where A is 2000-4000; B is 5000-7000; C is 15000-25000; D is 55000-65000; E is 75000-85000; F is 115000-125000; G is 480000-550000; and H is 380000-420000.

3. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the containers used include glass tubes.

4. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the sealing material for the ceramic crucible is selected from at least one of ceramic fiber, aluminum foil wire, high-purity quartz fiber, matching ceramic lid, and graphite fiber.

5. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the oxygen absorber carrier is selected from one of the following: quartz plate, stainless steel plate, alumina ceramic, and zirconium oxide ceramic.

6. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the oxygen absorber is selected from at least one of sponge titanium, magnesium, calcium, and zirconium aluminum getters.

7. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the oxygen absorber is at least one of sponge titanium and calcium.

8. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the materials used to seal the container include one of the following: quartz stopper, oxygen-free copper gasket, aluminum gasket, and graphite stopper.

9. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the oxygen absorber is used. In the fourth step, during heating and deoxygenation, the sample is located below the oxygen absorber.

10. The method for achieving quasi-in-situ heated transmission electron microscopy multi-scale characterization by oxidation control according to claim 1, characterized in that: In the third step, the oxygen absorber is used in the fourth step, and the deoxygenation time is 5-10 minutes.

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