Method for preparing optical sheets, method for analyzing powdered samples, and applications

Abstract

A method for preparing a light slice of a powdered sample, a method for analyzing a powdered sample, and an application, the method for preparing a light slice of a powdered sample comprising: sequentially adhering sample particles of a powdered sample to a substrate; placing a mold on the substrate and positioning the sample particles in the mold; pouring a uniform gel formed by a curing agent and a resin into the mold to embed the sample particles in the uniform gel; sequentially performing preliminary curing, demolding, and complete curing on the uniform gel to obtain a demolded cured gel, the demolded cured gel having a sample side with the powdered sample; and sequentially polishing and grinding the demolded cured gel to expose an area of the powdered sample on the sample side that is observed in an observation direction that is approximately equal to one-half of a sample area observed in the observation direction and to smooth the sample side to obtain a light slice.

Description

Technical Field

[0001] This invention relates to the field of detection science and technology, and in particular to methods for preparing optical sheets, analytical methods for powdered samples, and their applications. Background Technology

[0002] The Chang'e 5 lunar exploration mission, part of the third phase of China's lunar exploration program, collected two types of lunar samples: drilled samples and shoveled samples. After returning to Earth, the samples needed to be prepared and distributed before analysis and testing. The main purpose of preparing the samples into smooth sheets (i.e., flat plates) was to ensure maximum sample exposure, a smooth surface, and minimize sample loss during the grinding process. The prepared smooth plates could be reused multiple times, maximizing sample utilization.

[0003] In related technologies, a foreign research institution established the Lunar Sample Laboratory Facility in 1979 to preserve Apollo samples and future lunar samples. Since most of the samples obtained during the Apollo missions were rock fragments, they were cut into different rock slices and then used to prepare slides. However, lunar regolith samples (powder samples) have not been reported as slides; most powder samples were processed by the applicants themselves or prepared into different analytical samples. Most of the samples published in related lunar sample laboratories are raw samples; the preparation of analytical samples must be performed by laboratory professionals to ensure that the samples are suitable for different laboratory tests.

[0004] Thin section samples are widely used in geological research. The rock section preparation method (SY / T5913—2004) and the rock thin section preparation method (DZ / T 0275.2—2015, Technical Specification for Rock and Mineral Identification, Part 2) published in 2015 provide detailed regulations for thin section sample preparation. However, compared to lunar samples, the amount of samples obtained by lunar missions is very small, and they are mostly lunar regolith and fine rock fragments. Simply using geological sample preparation methods would result in significant sample loss, affecting subsequent research on lunar samples.

[0005] The Chang'e 5 mission, the third phase of China's lunar exploration program, established a lunar sample laboratory to conduct work on the storage, separation, processing, and preparation of lunar samples. Based on the characteristics of lunar samples and combined with methods for preparing geological samples, a smooth sheet preparation method was proposed. Extensive experience has been accumulated in the preparation process, ensuring minimal loss of lunar sample smooth sheets during preparation. This method is suitable for powder samples and fine rock fragments. After grinding, the smooth sheets have a flat surface, making them compatible with most analytical testing equipment. Furthermore, preparing lunar samples as smooth sheets significantly reduces the special requirements for the storage environment, ensuring that lunar samples are less affected by the Earth's external environment and avoiding oxidation and contamination. Currently, the lunar sample laboratory has prepared hundreds of smooth sheets. Some of these sheets, after basic characteristic description and analysis, have been released to the public for analysis, testing, and research by different laboratories, yielding corresponding research results.

[0006] The powder sheet preparation method is an important method in the future lunar sample processing and analysis process. It is one of the foundations for the safe preparation, storage and analysis of lunar samples in the laboratory. It is essential to develop a method and operation procedure for preparing powdered lunar samples into light sheets. Summary of the Invention

[0007] In view of this, the main objective of the present invention is to provide a method for preparing optical sheets, an analytical method for powdered samples, and their applications, thereby enabling the preparation of optical sheets from rare, powdered samples. According to an embodiment of the present invention, as one aspect of the present invention, a method for preparing optical sheets from powdered samples is provided, comprising:

[0008] The sample particles of the powdered sample are sequentially adhered to the substrate;

[0009] Place the mold on the substrate and position the sample particles inside the mold;

[0010] A uniform colloid formed by curing agent and resin is poured into the mold so that the sample is embedded in the uniform colloid;

[0011] The uniform colloid is subjected to preliminary curing, demolding, and complete curing in sequence to obtain a demolded cured colloid. The side of the demolded cured colloid containing the powder sample is the sample side.

[0012] The cured colloid after demolding is successively ground and polished so that the area of ​​the powder sample exposed on the sample surface observed in the observation direction is approximately equal to half of the sample area observed in the observation direction, and the sample surface is smoothed to obtain a light sheet; wherein, the direction in which the sample surface is viewed directly is the observation direction.

[0013] According to an embodiment of the present invention, sanding the cured colloid after demolding includes:

[0014] The cured colloid is polished manually, including:

[0015] Manually sand the back side with 200-grit sandpaper until the air bubbles in the cured colloid after demolding disappear; the side of the cured colloid opposite the sample surface after demolding is the back side.

[0016] The back surface is manually sanded using 2000-grit sandpaper until it is smooth and shiny and parallel to the sample surface.

[0017] The sample surface was manually polished using 2000-grit sandpaper until the area of ​​the powder sample exposed in the observation direction was approximately equal to half the area of ​​the sample observed in the observation direction.

[0018] The sample surface was manually polished using 3000-grit sandpaper until the exposed powder sample surface became reflective, so as to reduce the scratches on the exposed powder sample surface.

[0019] The sample surface was manually polished using 5000-grit sandpaper until the scratches on the exposed powder sample surface became finer.

[0020] According to an embodiment of the present invention, sanding the cured colloid after demolding includes:

[0021] The cured colloid is polished using an automated method, including:

[0022] The sample surface is automatically polished using an automatic polishing machine equipped with 2400-grit sandpaper until the area of ​​the powder sample exposed on the sample surface as observed in the observation direction is approximately equal to half of the area of ​​the sample as observed in the observation direction.

[0023] The sample surface was automatically polished using an automatic polishing machine equipped with 4000-grit sandpaper until the scratches on the exposed powder sample surface became finer.

[0024] According to an embodiment of the present invention, sequentially attaching sample particles of a powdered sample to a substrate includes:

[0025] The sample particles of the powdered sample are sequentially adhered to the substrate using an adhesive, ensuring that there are no air bubbles between the adhesive and the substrate.

[0026] According to an embodiment of the present invention, before casting the uniform colloid formed by the curing agent and resin into the mold, the method for preparing the light film further includes:

[0027] The homogeneous colloid formed by the curing agent and resin is subjected to degassing treatment to remove air bubbles from the homogeneous colloid.

[0028] According to an embodiment of the present invention, degassing treatment of the homogeneous colloid formed by the curing agent and resin includes:

[0029] Nitrogen gas is introduced into the homogeneous colloid formed by the curing agent and resin under vacuum conditions to remove air bubbles from the homogeneous colloid.

[0030] According to an embodiment of the present invention, the initial curing of the uniform colloid includes:

[0031] Under vacuum conditions, nitrogen gas is introduced into the homogeneous colloid to initially solidify the homogeneous colloid and to initially expel air bubbles from the homogeneous colloid.

[0032] According to an embodiment of the present invention, the particle diameter of the powder sample is 0.5-1 mm; the substrate is a glass substrate.

[0033] According to embodiments of the present invention, an analytical method for powdered samples is also provided, comprising:

[0034] The optical sheet was prepared using the powder sample preparation method described above.

[0035] The powder sample in the optical sheet was analyzed.

[0036] According to embodiments of the present invention, an application of the analytical method described above in the analysis of powdered samples from the moon is also provided. The method for preparing optical sheets from powdered samples according to embodiments of the present invention can produce optical sheets from powdered particles. In this embodiment, sample particles of the powdered sample are sequentially adhered to a substrate. After preparing a cured colloid with the powdered sample on one side, air bubbles in the cured colloid after demolding are removed by grinding and polishing. The area of ​​the powdered sample exposed on the sample surface observed in the observation direction is approximately equal to half the area of ​​the sample observed in the observation direction, and the sample surface is smoothed to obtain the prepared optical sheet. This method has low sample loss and is suitable for preparing optical sheets from rare, fine rock fragments, for example, for preparing optical sheets from powdered samples collected from the moon. Attached Figure Description

[0037] Figure 1 A flowchart of a method for preparing a powdered sample optical sheet according to an embodiment of the present invention is shown;

[0038] Figure 2 The optical sheet prepared by the optical sheet preparation method of the powder sample provided in the present invention is shown. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0040] Figure 1 A flowchart of a method for preparing a light sheet from a powder sample according to an embodiment of the present invention is shown.

[0041] like Figure 1 As shown, the method for preparing the optical sheet of the powder sample includes operations S1-S4.

[0042] In operation S1, sample particles of the powdered sample are sequentially adhered to the substrate.

[0043] In operation S2, the mold is placed on the substrate and the sample particles are positioned inside the mold.

[0044] In operation S3, a uniform colloid formed by curing agent and resin is poured into the mold so that the sample is embedded in the uniform colloid.

[0045] In operation S4, the uniform colloid is sequentially subjected to preliminary curing, demolding, and complete curing to obtain a demolded cured colloid. The side of the demolded cured colloid containing the powdery sample is the sample side.

[0046] In operation S5, the cured colloid after demolding is successively ground and polished so that the area of ​​the powder sample exposed on the sample surface observed in the observation direction is approximately equal to half of the sample area observed in the observation direction, and the sample surface is made smooth; wherein, the direction of looking directly at the sample surface is the observation direction.

[0047] Light slides are commonly used in laboratories primarily for research on rock and mineral composition, crystal identification, component analysis, and description of structural and textural features. Therefore, light slides are suitable for testing and analysis using polarizing microscopes, reflecting microscopes, electron microscopes, electron probes, and other similar instruments.

[0048] According to the embodiment of the present invention, the method for preparing optical sheets from powdered samples can be used to produce optical sheets from powdered particles. In this embodiment, the sample particles of the powdered sample are sequentially adhered to a substrate. After preparing a cured colloid with the powdered sample on one side, air bubbles in the cured colloid after demolding are removed by grinding and polishing. The area of ​​the powdered sample exposed on the sample surface observed in the observation direction is approximately equal to half of the area of ​​the sample observed in the observation direction, and the sample surface is smoothed to obtain the prepared optical sheet. This method has low sample loss and is suitable for preparing optical sheets from rare, fine rock fragments, such as those from powdered samples collected from the moon.

[0049] The optical sheet preparation method provided by the present invention can be applied to the preparation of optical sheets for powder and rock fragment samples involved in the laboratory analysis of lunar return samples, in order to constrain and standardize the process.

[0050] According to an embodiment of the present invention, before sequentially attaching the sample particles of the powdered sample to the substrate, the method further includes: randomly sampling and weighing the original powdered sample (particle size less than 1 mm) to obtain the powdered sample to be prepared into a sheet. The original powder can be powder with location information (e.g., sampled from the Chang'e 5 lunar probe) or powder without location information. The original powdered sample can also be obtained by arbitrarily splitting rock cuttings. The obtained powdered sample to be prepared into a sheet is stored in the atmosphere.

[0051] Before preparing the optical section, the necessary tools must be prepared, including but not limited to sample containers, sample vials, sample spoons, tweezers, steel needles, and scribing knives. The tools should generally be made of stainless steel, quartz glass, or Teflon, such as 306 stainless steel. All tools should be cleaned with ultrapure water and dried before preparing the optical section. To ensure that powdered samples are not confused, sample numbering must be checked. The weight of the powdered samples should also be confirmed.

[0052] According to an embodiment of the present invention, operation S1 includes: using an adhesive to sequentially adhere sample particles of the powdered sample to the substrate, ensuring that there are no air bubbles between the adhesive and the substrate. More specifically, it includes the following steps: preparing a substrate (e.g., a glass plate) and an adhesive (e.g., 3M double-sided tape); taking a length of approximately 5 cm of double-sided tape and attaching it to the center of the glass plate; pressing the double-sided tape flat, ensuring no wrinkles or air bubbles appear; placing a mold (with the bottom removed) at the center of the double-sided tape, and using a fine marker to draw the circular outline of the inner wall of the mold on the back of the glass plate, then removing the mold. The radius of this large circle is approximately 25 mm (approximately equivalent to 1 inch); sequentially attaching the selected sample particles, carefully placing them within the appropriate position of the circular outline of the double-sided tape. The sample attachment position should be concentrated within a center diameter of 12-15 mm as much as possible.

[0053] According to an embodiment of the present invention, before operation S3, the method further includes: forming a homogeneous colloid using a curing agent and a resin; and performing a degassing treatment on the homogeneous colloid formed by the curing agent and the resin to remove air bubbles from the homogeneous colloid. These will be described in detail below.

[0054] The process of forming a homogeneous colloid using a curing agent and resin includes the following steps:

[0055] First, prepare the glue dispensing equipment and tools. Turn on the power to the balance and level it. Prepare epoxy resin, curing agent, disposable glue cups, and stirring rods.

[0056] Next, the operator puts on a mask and gloves, turns on the balance, places the glue container on the balance, and presses the "tare" button to zero the balance. Slowly pour at least 10g of epoxy resin into the glue container (10g of epoxy resin can prepare approximately two 1-inch diameter films).

[0057] Then, calculate the amount of curing agent needed based on the mass ratio of curing agent to epoxy resin. Note: There are two types of resins to choose from: 1) a mass ratio of curing agent to epoxy resin (23:100 for BOC); 2) a mass ratio of curing agent to epoxy resin (45:100 for BOC).

[0058] Finally, press the "tare" button on the balance to zero, and pour the calculated amount of hardener into the container. After the epoxy resin and hardener are placed in the container, use a stirring rod to slowly and continuously stir in the same direction for about 5-8 minutes until a uniform colloid without any stringy particles is obtained. The stirring rod should not be removed from the colloid during the stirring process. In winter, when the temperature is low, the colloid stirring process can be carried out under the heating of an electric heater, but the temperature should not be too high, approximately 50℃. The entire stirring process takes about 3 minutes.

[0059] The homogeneous colloid formed by the curing agent and resin is degassed to remove air bubbles. This process includes the following steps:

[0060] Place the homogeneous colloid, after mixing, into a positive pressure permeabilizer or vacuum drying oven, tighten the lid, rotate the valve to the Closed position, and purge with nitrogen gas at approximately 2 bar (green range on the instrument). The vacuum condition is approximately below 1000 Pa. The entire degassing time should not exceed 8 minutes; within this time range, the epoxy resin will not cure. Then, slowly rotate the valve to the Open position to purge the nitrogen and purge with air. Once the pressure inside and outside the positive pressure permeabilizer or vacuum drying oven has balanced, remove the container containing the colloid.

[0061] According to an embodiment of the present invention, in operation S4, the preliminary curing of the uniform colloid includes: under vacuum conditions, filling the uniform colloid with nitrogen gas to allow it to initially cure and to initially expel air bubbles from the uniform colloid. Specifically, the upper half of the glue-holding cup is cut off with scissors, and the uniform colloid in the cup is slowly injected into the glue-dispensing mold to a height of about 5-8 mm. Epoxy resin curing: The glue-dispensing mold is placed in a positive pressure permeabilizer, the lid is tightened, the valve is rotated to the Closed position, and nitrogen gas at a pressure of about 2 bar (green range on the instrument) is introduced; nitrogen gas is replenished every half hour for the first two hours; under these conditions, curing is carried out for more than 8 hours.

[0062] According to an embodiment of the present invention, demolding in operation S4 includes: rotating the permeabilizer valve to the open position to release nitrogen gas, and removing the mold after the internal and external pressures are balanced. Rotating the injection mold to remove the pre-cured adhesive (polished sheet blank) from the injection mold. Another method is to: lift the double-sided tape on the glass plate to the blank position, hold the glass plate against a corner or hard object, and forcefully embed a cutting tool into the bottom of the polished sheet blank to separate it from the glass plate. Remove the double-sided tape from the bottom of the polished sheet blank and remove any remaining tape. Avoid contact between your hands and the blade during the operation to prevent injury.

[0063] According to an embodiment of the present invention, complete curing in operation S4 includes: drying and curing the blank at 60 degrees Celsius for no less than three days to achieve complete curing. Step S4 achieves the distribution of sample particles of the powdered sample on the sample surface, avoiding sample loss caused by traditional cutting and grinding processes.

[0064] According to an embodiment of the present invention, operation S5 specifically includes S51-S52.

[0065] In operation S51, the cured colloid after demolding is sanded to obtain a sanded cured colloid. Sanding the cured colloid after demolding can be done manually or automatically. These will be explained in detail below.

[0066] The cured colloid after demolding is sanded manually (including a1)-h1).

[0067] a1) Manually sand the back side using 200-grit sandpaper until air bubbles in the cured colloid after demolding disappear; the side of the cured colloid opposite the sample surface after demolding is the back side. For example, lay the 200-grit sandpaper flat on the sanding table, turn on the water pipe, and control the water flow to continuously rinse the sandpaper surface during the sanding process. Hold the blank and sand the back side in a figure-eight motion until air bubbles disappear and the back surface is smooth. Apply even pressure during sanding, keeping the sample surface and back side parallel. Manual sanding before the sample initially emerges allows for better exposure of the sample while ensuring the sample is not over-sanded.

[0068] b1) Manually sand the back side using 2000-grit sandpaper until it is smooth and shiny, and parallel to the sample surface. For example, remove the 200-grit sandpaper and rinse the sanding table; lay the 2000-grit sandpaper flat on the sanding table, turn on the water pipe, and control the water flow to continuously rinse the sandpaper surface during the sanding process. Hold the blank and sand the back side of the blank in a figure-eight motion until it is smooth and shiny. Apply even pressure during sanding, keeping the sample surface and back side of the blank parallel.

[0069] c1) Manually polish the sample surface using 2000-grit sandpaper until the area of ​​the powder sample exposed in the observation direction is approximately half the area of ​​the sample observed in the observation direction. For example, hold the blank sheet and polish the sample surface in a figure-eight motion. Apply even pressure during polishing, keeping the front and back of the blank sheet parallel. Polish for approximately 2 minutes, then observe the powder sample surface using a dual-purpose microscope (reflective light conditions) to check for exposure and surface scratches. Repeat the polishing steps until the area of ​​the powder sample exposed in the observation direction is approximately half the area of ​​the sample observed in the observation direction. Note: If the sample particles are small (<0.5mm), this step can be skipped, and proceed directly to the next polishing step.

[0070] d1) Manually polish the sample surface using 3000-grit sandpaper until the exposed powder sample surface shows reflection, thus reducing the scratches on the exposed powder sample surface. For example, hold the blank and polish the sample surface in a figure-eight motion; the polishing process requires even force, with light downward pressure from the hand, keeping the sample surface and back parallel; polish for about 3 minutes, then check the surface reflection and scratches of the sample surface with the naked eye and a dual-purpose microscope (reflection conditions); repeat the polishing steps until the sample particle (e.g., mineral particle) surface shows slight reflection when observed with the naked eye, and the deep scratches on the surface of individual sample particles are significantly reduced under the dual-purpose microscope.

[0071] e1) Manually polish the sample surface using 5000-grit sandpaper until the scratches on the exposed powder sample surface become finer. For example, hold the blank sheet and polish the sample in a figure-eight motion; apply even pressure during polishing, keep the front and back of the blank sheet parallel; polish for about 5 minutes, then use a dual-purpose microscope to examine the scratches on the exposed sample particles; repeat the polishing steps until the deep scratches on the exposed sample particles surface under the dual-purpose microscope have basically disappeared.

[0072] The cured colloid is polished using an automated method, including a2)-c2).

[0073] a2) Manually sand the back side using 200-grit sandpaper until air bubbles in the cured colloid after demolding disappear. The side of the cured colloid opposite the sample surface is the back side. For example, lay the 200-grit sandpaper flat on the sanding table, turn on the water pipe, and control the water flow to continuously rinse the sandpaper surface during the sanding process. Hold the blank and sand the back side of the blank in a figure-eight motion until air bubbles disappear and the surface is smooth. Apply even pressure during sanding and keep the front and back sides of the blank parallel.

[0074] (b2) Use an automatic polishing machine equipped with 2400-grit sandpaper to automatically polish the sample surface until the area of ​​powder sample exposed on the sample surface observed in the observation direction is approximately equal to half of the sample area observed in the observation direction. For example, clean the polishing disc and clamp by fitting the clamp onto the polishing machine; flatten the 2400-grit sandpaper on the iron disc and place it on the polishing disc; set the polishing parameters—time 30 seconds, rotation speed 130, water supply selected as tap water (the middle button is for manual water supply control, the last option is for rotating the polishing disc separately for cleaning). Select the same direction for the polishing disc and clamp (for a smoother finish, reverse rotation is faster), single-point rotation of the sample clamp (the lower option, the upper option is for center force), and set the polishing pressure to 10 or 15 N (select N, do not select LBS).

[0075] c2) Use an automatic polishing machine equipped with 4000-grit sandpaper to automatically polish the sample surface until the scratches on the exposed powder sample surface become finer. For example, clean the polishing disc and clamps by placing the clamps on the polishing machine; smoothly attach the 4000-grit sandpaper to the iron disc and place it on the polishing disc; set the polishing parameters—time 30 seconds, speed 130, water supply selected as tap water (the middle button is for manual water supply control, the last option is for rotating the polishing disc separately for cleaning). Select the same direction for the polishing disc and clamp rotation (for a smoother finish, reverse rotation is faster), single-point rotation of the sample clamp (the lower option, the upper option is for center force), and set the polishing pressure to 10 or 15 N (select N, do not select LBS).

[0076] In operation S52, the cured colloid after grinding is polished to obtain a smooth sheet. Polishing the cured colloid to obtain a smooth sheet includes: polishing the cured colloid using an automatic polishing method and polishing it using a manual polishing method. These will be explained in detail below.

[0077] The process of polishing the cured colloid after grinding to obtain a smooth sheet using an automatic polishing method includes a3)-h3).

[0078] a3), Prepare polishing cloth and polishing liquid. Each type of polishing cloth corresponds to a specific polishing liquid (3 microns, 1 micron, and 0.05 microns).

[0079] b3), polish using 3-micron polishing fluid (approximately 3 minutes). Clean the grinding disc and fixture, and place the fixture onto the polishing machine; smoothly attach the 3-micron polishing cloth to the iron disc and place it on the grinding disc of the polishing machine; set the polishing parameters—time 3 minutes, speed 130. Turn off the water supply during the polishing process. Select the same direction for the grinding disc and fixture (for smoother polishing, reverse rotation is faster), rotate the sample fixture to a single point (the lower option, the upper option is the center force), and set the polishing pressure to 10 or 15 N (select N, do not select LBS).

[0080] c3) Use a dual-purpose microscope to check whether most of the surface scratches on the exposed sample have disappeared and whether the exposed sample has obvious graininess; if the requirements are not met, continue polishing.

[0081] d3), polishing with micron-sized polishing solution (approximately 4 minutes): Clean the grinding disc and fixture, and place the fixture onto the polishing machine; smoothly attach the 3-micron polishing cloth to the iron disc and place it on the grinding disc of the polishing machine; set the polishing parameters—time 3 minutes, rotation speed 130. Turn off the water supply during the polishing process. Select the same direction for the grinding disc and fixture (for smoother polishing, reverse rotation is faster), rotate the sample fixture to a single point (the lower option, the upper option is the center force), and set the polishing pressure to 10 or 15 N (select N, do not select LBS).

[0082] e3) Use a dual-purpose microscope to check whether the surface scratches of the exposed sample have basically disappeared and whether the exposed sample has obvious graininess; if the requirements are not met, continue polishing.

[0083] f3), Polishing with 0.05 micron polishing slurry (approximately 3 minutes): Clean the grinding disc and fixture, and place the fixture onto the polishing machine; smoothly attach the 3 micron polishing cloth to the iron disc and place it on the grinding disc of the polishing machine; set the polishing parameters—time 2 minutes, speed 130. Turn off the water supply during the polishing process. Select the same direction for the grinding disc and fixture (for smoother polishing, reverse rotation is faster), single-point rotation of the sample fixture (lower option, upper option is center force), and set the polishing pressure to 10 or 15 N (select N, do not select LBS).

[0084] g3), use a dual-purpose microscope to check whether the scratches on the resin surface have basically disappeared; if the requirements are not met, continue polishing.

[0085] h3), after polishing is complete, apply water for the last 20 seconds to clean the polishing cloth and grinding disc.

[0086] The process of polishing the cured colloid after grinding to obtain a smooth sheet using manual polishing includes a4)-f4).

[0087] a4) Prepare a polishing pad, polishing cloth, polishing compound (6L mesh, 1L mesh and 0.25L mesh), spray bottle and lint-free cloth.

[0088] b4) Attach the polishing cloth to the polishing pad; fill the spray bottle with anhydrous alcohol.

[0089] c4), 6L mesh polishing: Apply a small amount of 6L mesh polishing paste to the polishing cloth. The operator, wearing latex gloves, presses the blank down slightly and polishes in a circular motion in the same direction (if the polishing cloth is dry and the friction is low, polishing paste can be added as needed); after polishing for about 20 minutes, wipe the blank clean with anhydrous alcohol and a lint-free cloth; use a dual-purpose microscope to check whether most of the scratches on the sample surface have disappeared and whether the exposed sample initially shows a grainy texture; if the requirements are not met, continue polishing, checking every 5 minutes until the requirements are met.

[0090] d4), 1L mesh polishing: Squeeze a small amount of 1L mesh polishing paste onto the polishing cloth, and follow the same steps as 6L mesh polishing; after polishing for about 20 minutes, wipe the blank clean with anhydrous alcohol and a lint-free cloth; use a dual-purpose microscope to check whether the scratches on the sample surface have basically disappeared and whether the exposed sample has obvious graininess; if the requirements are not met, continue polishing, checking every 5 minutes until the requirements are met.

[0091] e4), 0.25L mesh polishing: Squeeze a small amount of 0.25L mesh polishing paste onto the polishing cloth. The specific operation steps are the same as for 6L mesh polishing. After polishing for 20-30 minutes, wipe the blank clean with anhydrous alcohol and a lint-free cloth. Use a dual-purpose microscope to check whether the scratches on the resin surface have basically disappeared. If the requirements are not met, continue polishing and check every 5 minutes until the requirements are met to obtain a polished sheet.

[0092] f4) After cleaning the surface of the optical film with tap water and dish soap, clean the surface of the optical film with ultrapure water and anhydrous alcohol in turn; finally, dry the cleaned optical film at 50℃ for 2-3 days.

[0093] According to embodiments of the present invention, an analytical method for powdered samples is also provided, comprising:

[0094] A light section is prepared using the powder sample preparation method described above; the powder sample in the light section is then analyzed. According to an embodiment of the present invention, the overall thickness of the finished light section is approximately 7.5 ± 0.2 mm. This size is suitable for most analytical testing equipment such as electron microscopes, polarizing microscopes, electron probes, and ion probes. If the light section is thicker, a slow-speed cutter can be used to cut it to a suitable size. The speed parameter of the slow-speed cutter is usually set to level 6-7, approximately equivalent to 200 rpm; excessive speed can easily cause the light section to be cut off-center and damage the cutting saw blade. When the light section is cut halfway, the direction of the light section is adjusted, and cutting is performed from another direction. After the light section is prepared, it must be numbered immediately to avoid confusion. The quality of the light section directly affects subsequent identification and analytical research and must be strictly controlled. The exposed sample surface needs to be polished, requiring the sample surface to be smooth as a mirror, the relative protrusions of sample particles (including hard and soft minerals) should not be too obvious, and there should be no small pits, fine cracks, or scratches.

[0095] According to an embodiment of the present invention, an application of the analytical method described above in the analysis of powdered samples from the moon is also provided.

[0096] Lunar samples, due to their rarity, uniqueness, and small particle size (most powder particles are on the order of tens of micrometers, and rock fragments are mostly on the order of millimeters), require different light-sheet preparation methods compared to traditional terrestrial samples. The light-sheet preparation method provided in this invention has been validated in experiments preparing light-sheets of lunar powder samples, meeting scientific rigor and rationality. This method improves the utilization efficiency of lunar powder samples in terrestrial laboratories. Furthermore, preparing powder and fine particles into corresponding light-sheets ensures relatively low sample usage and loss, uniform exposure, and increases the number of times samples can be reused, maximizing sample utilization. In addition, the light-sheet preparation method provided in this invention can also be applied to the preparation of light-sheets for other laboratory powder or fine-particle samples, and is also applicable to similar samples obtained from extraterrestrial sources such as asteroids and Mars.

[0097] The optical sheet preparation method provided by the present invention can be applied to the preparation of optical sheets for powder and rock fragment samples involved in the laboratory analysis of lunar return samples, in order to constrain and standardize the process.

[0098] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a light film from a powder sample, comprising: Sample particles of a powdery sample collected from the moon are sequentially adhered to a substrate. The diameter of the powdery sample particles is 0.5-1 mm. Place the mold on the substrate and position the sample particles inside the mold; A uniform colloid formed by curing agent and resin is poured into the mold so that the sample is embedded in the uniform colloid; The uniform colloid is subjected to preliminary curing, demolding, and complete curing in sequence to obtain a demolded cured colloid. The side of the demolded cured colloid containing the powder sample is the sample side. The cured colloid after demolding is successively ground and polished so that the area of ​​the powder sample exposed on the sample surface observed in the observation direction is approximately equal to half of the sample area observed in the observation direction, and the sample surface is made smooth to obtain a light sheet; wherein, the direction in which the sample surface is viewed directly is the observation direction; The initial solidification of the uniform colloid includes: Under vacuum conditions, nitrogen gas is introduced into the homogeneous colloid to allow it to initially solidify and for air bubbles to initially escape from the homogeneous colloid.

2. The method for preparing an optical sheet according to claim 1, wherein, The polishing of the cured colloid after demolding includes: The cured colloid is polished manually, including: Manually sand the back side with 200-grit sandpaper until the air bubbles in the cured colloid after demolding disappear; the side of the cured colloid opposite the sample surface after demolding is the back side. The back surface is manually sanded using 2000-grit sandpaper until it is smooth and shiny and parallel to the sample surface. The sample surface was manually polished using 2000-grit sandpaper until the area of ​​the powder sample exposed in the observation direction was approximately equal to half the area of ​​the sample observed in the observation direction. The sample surface was manually polished using 3000-grit sandpaper until the exposed powder sample surface became reflective, so as to reduce the scratches on the exposed powder sample surface. The sample surface was manually polished using 5000-grit sandpaper until the scratches on the exposed powder sample surface became finer.

3. The method for preparing an optical sheet according to claim 1, wherein, The polishing of the cured colloid after demolding includes: The cured colloid is polished using an automated method, including: The sample surface is automatically polished using an automatic polishing machine equipped with 2400-grit sandpaper until the area of ​​the powder sample exposed on the sample surface as observed in the observation direction is approximately equal to half of the area of ​​the sample as observed in the observation direction. The sample surface was automatically polished using an automatic polishing machine equipped with 4000-grit sandpaper until the scratches on the exposed powder sample surface became finer.

4. The method for preparing an optical sheet according to claim 1, wherein, The process of sequentially attaching sample particles from a powdered sample to a substrate includes: The sample particles of the powdered sample are sequentially adhered to the substrate using an adhesive, ensuring that there are no air bubbles between the adhesive and the substrate.

5. The method for preparing a light film according to claim 1, further comprising, before casting the uniform colloid formed by the curing agent and resin into the mold, the method for preparing a light film further comprises: The homogeneous colloid formed by the curing agent and resin is subjected to degassing treatment to remove air bubbles from the homogeneous colloid.

6. The method for preparing an optical sheet according to claim 5, wherein, Degassing treatment of the homogeneous colloid formed by the curing agent and resin includes: Nitrogen gas is introduced into the homogeneous colloid formed by the curing agent and resin under vacuum conditions to remove air bubbles from the homogeneous colloid.

7. The method for preparing an optical sheet according to claim 1, wherein, The initial curing of the homogeneous colloid includes: Under vacuum conditions, nitrogen gas is introduced into the homogeneous colloid to allow it to initially solidify and for air bubbles to initially escape from the homogeneous colloid.

8. The method for preparing an optical sheet according to claim 1, wherein, The substrate is a glass substrate.

9. An analytical method for powdered samples, comprising: A light sheet was prepared according to the method for preparing powdered samples according to any one of claims 1-8; The powder sample in the optical sheet was analyzed.

10. An application of the analytical method of claim 9 in the analysis of powdered lunar samples.

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