Simulated lunar soil capable of maintaining surface chemical activity and preparation method of simulated lunar soil

Abstract

The invention discloses simulated lunar soil capable of maintaining surface chemical activity and a preparation method of the simulated lunar soil. The method comprises the following steps: (1) selecting and collecting natural volcanic rock and single mineral samples; (2) obtaining a clean particle sample; (3) analyzing chemical components and phase composition of various particle samples, and preparing a particle mixture required for simulating lunar soil according to an analysis result; (4) drying the particle mixture under a vacuum condition, keeping a vacuum sealing state after drying, transferring into an environment filled with high-purity inert gas, loading into a ball milling tank, and keeping sealing; and (5) loading the sealed ball milling tank on a ball mill for ball milling until all particles are finely ground, returning to a high-purity inert gas environment after the grinding is finished, taking out and storing in a closed container, and preventing the surfaces of the particles from being affected with damp. The surface chemical reaction activity and the charge effect of the simulated lunar soil can be kept to the maximum extent, and the device can be used for simulating the lunar environment on the ground and researching the harm of lunar dust to the health of equipment and astronauts.

Description

Technical Field

[0001] The present invention relates to a method for preparing simulated lunar soil, and particularly to a simulated lunar soil that maintains surface chemical activity and a method for preparing the same. Background Art

[0002] With the development of the aerospace industry, the research on lunar soil has become increasingly in-depth. However, due to the extreme preciousness and limited quantity of real lunar soil, it is difficult to meet the needs of various engineering experiments and scientific research. Simulated lunar soil can be used to study the geological, physical, chemical and other properties of the moon, helping scientists better understand the lunar surface environment.

[0003] Although the existing methods for preparing simulated lunar soil are highly similar to real lunar soil in terms of mineral composition, chemical composition, particle size and mechanical parameters, they neglect the protection of the surface chemical active sites of lunar soil. In particular, the processing and preparation processes of these simulated lunar soils are often directly carried out in the Earth's atmospheric environment with relatively high humidity, and even include processes such as wet grinding, which causes the chemical active sites (including ≡Si•, ≡SiO• and ≡SiOO•) on the fractured surface of fresh minerals to react with water molecules, resulting in the loss of surface chemical reaction activity and charge effect of the simulated lunar soil particles. These distorted simulated lunar soils are seriously inconsistent with the physical and chemical properties of the mineral dust generated by impacts under the high-vacuum drying conditions on the lunar surface layer, and cannot meet the needs of lunar environment ground simulation engineering construction, lunar exploration engineering equipment design and research on astronaut health protection.

[0004] Therefore, it is of great significance to develop a method for preparing simulated lunar soil that can maintain surface chemical activity.

[0005] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure. Therefore, it may include information that does not belong to the scope of the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] The object of the present invention is to provide a simulated lunar soil that maintains surface chemical activity and a method for preparing the same, which solves the problem that the existing methods will cause the loss of surface chemical reaction activity and charge effect of the simulated lunar soil particles, and can maintain the real surface chemical reaction activity and charge effect to the greatest extent, and can be used for lunar environment ground simulation construction and research on protecting equipment and astronauts from the harm of lunar dust.

[0007] To achieve the above object, the present invention provides a method for preparing a simulated lunar soil that maintains surface chemical activity, and the method comprises the following steps: (1) Select and collect natural volcanic rocks and single mineral samples; (2) Clean, crush and screen the natural volcanic rock and single mineral samples to obtain clean particulate samples; (3) Analyze the chemical composition and phase composition of various particle samples. According to the analysis results, prepare the particle mixture required for the simulated lunar soil according to the weight ratio; (4) Dry the particle mixture under vacuum conditions at 50~1000 °C (the temperature depends on the sample situation. Samples with a higher hydroxyl water content are selected at a higher temperature, and samples with a lower hydroxyl water content can be dried at a lower temperature) to remove the adsorbed water molecules and structural hydroxyls on the particle surface. After drying, keep the vacuum-sealed state, transfer it to an environment filled with high-purity inert gas, load it into a ball mill jar and keep it sealed. The ball mill jar is filled with high-purity inert gas or evacuated to vacuum; among them, in the high-purity inert gas environment, the volume concentration of the inert gas ≥99.99%, the volume concentration of water molecules ≤25 ppm, and the volume concentration of oxygen ≤25 ppm. This condition can avoid the loss of the reaction activity of the simulated lunar soil caused by the interaction between environmental water molecules and the active sites on the mineral surface; (5) Load the sealed ball mill jar on the ball mill for ball milling until the particle size of all materials is less than 75 μm. After the ball milling is completed, return it to the high-purity inert gas environment, take it out and store it in a sealed container, and avoid moisture on the particle surface before use.

[0008] Preferably, in step (1), the natural volcanic rock includes: basalt and volcanic cinder; the single mineral sample includes: any one or more of olivine, pyroxene, plagioclase, and ilmenite.

[0009] Preferably, in step (3), the basalt, volcanic cinder, and single mineral are all formed by the cooling of magma, and the matching dosage of various raw materials is determined according to the chemical composition and mineral composition ratio of the target lunar soil.

[0010] Preferably, in step (2), the crushing and screening obtain particles with a particle size of 180~1700 µm for ball milling.

[0011] Preferably, in step (4), the drying time is more than 0.5 hours.

[0012] Preferably, in step (4), prepare a ball mill jar with a sealing device and keep the pressure stable at 1×10 -1 ~ 1×10 2 Pa for more than 3 hours.

[0013] Preferably, in step (4), the inner lining material of the ball mill jar is selected from any one of zirconia, agate, and corundum as the hard inert material to reduce the pollution of the sample.

[0014] Preferably, in step (4), the inert gas is selected from any one or more of nitrogen, argon, and helium.

[0015] Preferably, in step (5), for the ball milling, the ball milling speed ranges from 100 to 800 revolutions per minute, and the ball milling time is 0.5 hours or more.

[0016] The second object of the present invention is to provide the simulated lunar soil that maintains surface chemical activity obtained by the described preparation method.

[0017] The simulated lunar soil that maintains surface chemical activity and its preparation method in the present invention solve the problem that the existing methods will cause the simulated lunar soil particles to lose surface chemical reaction activity and charge effect, and have the following advantages: (1) The raw materials are mainly natural volcanic rocks and single minerals, which are characterized by wide sources and easy availability; (2) The method for removing the moisture of the raw materials is mainly the vacuum high-temperature drying process, which is simple to operate and highly reliable; (3) Detection is carried out by using the active oxygen yield and surface charge analysis, and the surface reaction activity of the simulated lunar soil prepared by this method can be effectively confirmed. Therefore, the method of grinding rock mineral particles under dry inert gas or vacuum conditions to prepare the simulated lunar soil is close to the real lunar soil and lunar dust formation process, and can effectively maintain the surface reaction activity and charge effect of the minerals, thereby providing a simulated lunar soil with highly faithful physical and chemical properties for the lunar environment ground simulation construction project and the development of protection technologies. Description of the Drawings

[0018] Figure 1 is the flow chart of the simulated lunar soil preparation method provided by the present invention.

[0019] Figure 2 is the photo of the basalt and volcanic slag hand specimens used in the present invention.

[0020] Figure 3 is the XRD pattern of the basalt and volcanic slag used in the present invention.

[0021] Figure 4 is the particle size distribution diagram of the pseudo lunar soil prepared by the present invention.

[0022] Figure 5 is the XRD pattern of the simulated lunar soil prepared by the present invention.

[0023] Figure 6 is the microscopic morphology diagram of the simulated lunar soil prepared by the present invention.

[0024] Figure 7 is the types of surface-bound radicals generated by the simulated lunar soil prepared by the present invention. Detailed Embodiments

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be noted that for those not specified in the embodiments, the operations are carried out under conventional conditions or conditions recommended by the manufacturer. For the instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase. For the raw materials and reagents not specified in terms of the manufacturer, they are all commercially available products or can be prepared by known methods.

[0027] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0028] The features mentioned in the present invention can be combined arbitrarily as long as there is no contradiction in the combination of these features. All possible combinations should be considered as being within the scope described in this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equivalent or similar features.

[0029] Based on a large number of scientific experiments and in combination with the basic situation of natural volcanic rock samples, the present invention continuously improves the process flow to obtain the method for preparing simulated lunar soil of the present invention. The simulated lunar soil obtained by the method of the present invention can maintain the true surface chemical reaction activity and charging effect to the greatest extent, and can be used for the construction of lunar environment ground simulation and the research on protecting equipment and astronauts from the harm of lunar dust.

[0030] The following provides a detailed description of a method for preparing simulated lunar soil with surface chemical activity provided by the present invention through examples and experimental examples.

[0031] Example 1 A method for preparing simulated lunar soil with surface chemical activity, taking the Chang'e-5 lunar soil sample as a reference example (including but not limited to Chang'e-5), see Figure 1 , the method comprises the following steps: (1) Select and collect natural volcanic rock and single mineral samples; In this step, natural volcanic rock samples are collected from Quaternary volcanic rocks, which have characteristics of low weathering degree and high glass content, including basalt, scoria, etc. These volcanic rocks are extremely similar in composition to lunar soil. Among them, basalt contains the same minerals as lunar soil, and scoria contains a large amount of glassy substances, which can be used as raw materials for lunar soil simulation samples. The present invention mainly uses the basalt and scoria of Dayizi Volcano in Huinan County, Jilin Province. This volcano belongs to the Longgang Volcanic Group, and the volcanic age belongs to the middle and late Pleistocene (0.23 ± 0.02 Ma), meeting the requirements for simulating young lunar volcanic activities.

[0032] The single mineral samples include: olivine, pyroxene, plagioclase, ilmenite, etc.

[0033] (2) Clean, crush, and screen to obtain clean granular samples; Clean the collected basalt, scoria, and single mineral samples, and then preliminarily crush the samples. Use mechanical crushing to make the particle size in the range of 180 - 1700 µm, avoiding mixing in samples with too small particle size for subsequent processing. The hand specimens of basalt and scoria are shown in Figure 2 .

[0034] (3) Analyze the chemical composition and phase composition of various granular samples. According to the analysis results, prepare the granular mixture required for specific simulated lunar soil according to the weight ratio; Weigh a small amount of basalt, scoria, and single mineral samples and grind them to obtain powder samples with a particle size less than 75 µm. Conduct XRD analysis on them. The results are as shown in Figure 3 . The basalt and scoria samples mainly contain minerals such as plagioclase, pyroxene, and olivine, and the scoria contains a large amount of glassy substances. Conduct XRF analysis on the powder to obtain the chemical composition of the basalt, scoria, and single mineral samples. According to the mineral composition and chemical composition of the lunar soil of Chang'e-5, proportion the basalt, scoria, and mineral composition by weight to obtain the granular mixture. In the present invention, the total amount of the granular mixture is 50 g, including 29 g of basalt, 14 g of scoria, 5 g of augite, and 2 g of ilmenite.

[0035] (4) Dry the granular mixture under high-temperature vacuum conditions, and after completion, keep it in a vacuum-sealed state, transfer it to an environment filled with high-purity inert gas, and load it into a ball mill jar and keep it sealed; Put the prepared granular mixture into a vacuum drying oven at a temperature of 250 °C for a drying time of more than 5 hours. Take out the dried sample and put it into an environment of high-purity inert gas provided by a glove box filled with high-purity dry inert gas. The specific conditions are that the volume concentration of nitrogen ≥ 99.99%, the volume concentration of water molecules ≤ 25 ppm, and the volume concentration of oxygen ≤ 25 ppm. Prepare a ball mill jar with a sealing device and keep it in a medium vacuum state (1×10 -1~ 1×10 2 Pa) Maintain a stable pressure for more than 3 hours to prevent the leakage of the earth's atmosphere during the ball milling process.

[0036] (5) Load the sealed ball milling tank onto the ball mill for high-speed ball milling until the particle size of all materials is less than 75 μm. After the ball milling is completed, return to the high-purity inert gas environment, take out and store in a sealed container; Put the dried mixed sample into a zirconia-lined ball milling tank, fill the tank with high-purity inert gas or evacuate it to vacuum, and keep it sealed during the ball milling process; the ball milling speed is in the range of 100 - 800 revolutions per minute, and the ball milling time is more than 0.5 hours; after the ball milling is completed, return to the glove box, take out the powder sample in the high-purity inert gas environment, and obtain simulated lunar soil with a particle size less than 75 µm; seal the obtained simulated lunar soil sample and store it for a long time under the condition of being filled with dry high-purity inert gas.

[0037] Example 2 Analysis of the simulated lunar soil prepared in Example 1 1. Particle size analysis Use a laser particle size analyzer to analyze the particle size of the simulated lunar soil. The particle size distribution is within the range of real lunar soil, and the median particle size D 50 is 16.64 µm, and the particle size distribution is as Figure 4 shown.

[0038] 2. Specific surface area analysis Use a specific surface area analyzer to analyze the simulated lunar soil. Its specific surface area is about 3.2 m 2 / g.

[0039] 3. Phase, chemical composition and morphology analysis Conduct phase, chemical composition and morphology analysis on the obtained simulated lunar soil. Through XRD analysis of the simulated lunar soil, as Figure 5 shown, the main mineral components of the simulated lunar soil are pyroxene, olivine, plagioclase, etc. Conduct X-ray fluorescence analysis on the simulated lunar soil, and its chemical composition is shown in Table 1. It can be seen from Table 1 that the contents of SiO2, Al2O3, Na2O, and K2O in the simulated lunar soil are higher than those of the Chang'e-5 lunar soil, and the contents of TiO2, FeO, and CaO are significantly lower than those of the Chang'e-5 lunar soil. This is related to the fact that Fe in the earth's basalt mainly exists in the form of Fe2O3. However, considering the Apollo returned lunar samples, the Chang'e mission returned lunar samples and other simulated lunar soils comprehensively, the chemical composition contents are within the range, and this simulated lunar soil belongs to low-titanium lunar soil. Use a scanning electron microscope to observe the morphology of the simulated lunar soil, and it is found that some fine-grained lunar soil shows an aggregated situation, and due to the ball milling effect, the particles have sharp edges, as Figure 6 shown.

[0040] Table 1 Chemical composition analysis of simulated lunar soil (wt%)

[0041] 4. Surface Chemical Activity Analysis Perform surface chemical activity analysis on the simulated lunar soil, mainly including the analysis of the types of surface-bound free radicals, reactive oxygen species, and surface charge.

[0042] 1) Analysis of the Types of Surface-Bound Free Radicals Use electron paramagnetic resonance (EPR) to test the surface-bound free radicals of the simulated lunar soil. The results show that the main free radicals on the surface of the simulated lunar soil are peroxyl radicals (≡SiOO•) and E' centers (≡Si•), as Figure 7 shown.

[0043] 2) Analysis of Reactive Oxygen Species Analyze the reactive oxygen species (Equations 1 - 4) generated by the reaction of the simulated lunar soil with water, including the test of the cumulative concentration of hydroxyl radicals and the test of the hydrogen peroxide concentration. Compare and analyze the reactive oxygen species concentration of the simulated lunar soil (CLRS-1 / 2) prepared by the wet grinding process in the Institute of Geochemistry, Chinese Academy of Sciences, and analyze the surface-bound free radical site density.

[0044] The analysis of reactive oxygen species adopts the test methods of the cumulative concentration of hydroxyl radicals and the hydrogen peroxide concentration, as follows: ≡SiO• + H2O → ≡SiOH + •OH (Equation 1) 2•OH → H2O2 (Equation 2) ≡SiOO• + H2O → ≡SiOH + HO2• (Equation 3) 2HO2• → H2O2 + O2 (Equation 4) (1) Test of the Cumulative Concentration of Hydroxyl Radicals - Taking the Benzoic Acid Method as an Example Determine •OH by measuring the concentration of the oxidation product of benzoic acid (BA) - p -hydroxybenzoic acid, p -HBA). The experiment is carried out in an environment of 25 ± 2 °C, using a 20 mL brown vial, and accompanied by magnetic stirring. The sample is mixed with a solution containing a •OH scavenger (BA, 10 mM), and after stirring for 10 min, the sample is filtered and sampled. 1.00 mL of the filtrate is quickly mixed with 1.00 mL of methanol (chromatographic grade) to quench secondary •OH, thereby preventing further oxidation of BA. Use high-performance liquid chromatography (ultraviolet detection wavelength 255 nm, C18 chromatographic column (4.6 mm × 250 mm)) to measure p-HBA concentration. The mobile phase was a mixture of aqueous solution containing 0.1% trifluoroacetic acid and acetonitrile (65:35, v:v), and the flow rate was 1 mL·min -1 . The injection volume was 20 μL, the column temperature was 30 °C, and the UV detection wavelength was 255 nm. p -The retention time of -HBA was 3.2 ± 0.2 min, optimized p -The detection limit of -HBA was 0.01 μM, corresponding to 0.059 μM •OH.

[0045] (2) Hydrogen peroxide concentration test - taking the LCV method as an example The concentration of H2O2 was determined using colorless crystal violet (LCV). Peroxidase (HRP, type Ⅲ, >300 units·g -1 ) catalyzes hydrogen peroxide, and the •OH generated can oxidize LCV. The oxidation product of LCV is crystal violet cation (CV + ), and the maximum absorbance is at 590 nm. Take 1.7 mL of the filtrate sample, and add reagents to the filtrate in the following order to a total volume of 2 mL: 200 µL of KH2PO4 buffer (pH = 4.2), 50 µL of a solution of 41 mM LCV (dissolved in dilute hydrochloric acid), and 50 µL of a solution containing 0.5 mg·mL -1 HRP. After shaking well, store in the dark at room temperature (25 ± 2 °C) for 30 min, and perform the test until the absorbance is stable.

[0046] The analysis results of reactive oxygen species in simulated lunar soil are shown in Table 2. According to the production of reactive oxygen species, the density of surface-bound radical sites of the samples prepared in Example 1 of the present invention (GIG-CE5-1) and the simulated lunar soil prepared by the wet grinding method (CLRS-1 / 2) were analyzed, and the relevant data are listed in Table 2.

[0047] Table 2 Estimation results of the density of surface-bound radical sites of simulated lunar soil based on ROS production

[0048] 5. Surface charge analysis To analyze the surface charge of the simulated lunar soil, the dust pattern method, the electrostatic probe method, or the optical measurement method based on the Pockels effect can be used for testing. In the present invention, the electrostatic probe method was selected for testing. The results showed that the surface charge density of the simulated lunar soil prepared by the method of the present invention reached 0.1~0.3 nC / mm 2 . For the samples prepared by the wet grinding method, the broken bonds on the surface of mineral particles will contact a large amount of water during wet grinding, and the surface charge of the particles will disappear after reacting with water, so the surface charge cannot be detected.

[0049] As can be seen from the above test results, the simulated lunar soil prepared by the present invention can maintain the true surface chemical reaction activity and charging effect to the greatest extent, and can be used for the construction of lunar environment ground simulation and the research on protecting equipment and astronauts' health from the harm of lunar dust.

[0050] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be regarded as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions of the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A preparation method of simulated lunar soil for maintaining surface chemical activity, characterized in that, The method comprises the following steps: (1) Select and collect natural volcanic rocks and single mineral samples; (2) Clean, crush and screen the natural volcanic rocks and single mineral samples to obtain clean particulate samples; (3) Analyze the chemical compositions and phase compositions of various particulate samples, and prepare a particulate mixture required for simulating lunar soil according to the analysis results by weight ratio; (4) Dry the particulate mixture under vacuum conditions at 50-1000 °C to remove adsorbed water molecules and structural hydroxyl groups on the particle surface. After completion, maintain the vacuum-sealed state, transfer it to an environment filled with high-purity inert gas, load it into a ball milling jar and keep it sealed. The ball milling jar is filled with high-purity inert gas or evacuated to vacuum; wherein, in the high-purity inert gas environment, the volume concentration of the inert gas ≥ 99.99%, the volume concentration of water molecules ≤ 25 ppm, and the volume concentration of oxygen ≤ 25 ppm; (5) Load the sealed ball milling jar onto a ball mill for ball milling until the particle size of all materials is less than 75 μm. After the ball milling is completed, return it to the high-purity inert gas environment, take it out and store it in a closed container.

2. The preparation method according to claim 1, characterized in that, In step (1), the natural volcanic rocks include: basalt and volcanic cinder; the single mineral samples include: any one or more of olivine, pyroxene, plagioclase and ilmenite.

3. The preparation method according to claim 2, characterized in that, In step (3), the basalt, volcanic cinder and single mineral are all formed by magma cooling, and the matching dosage of various raw materials is determined according to the chemical composition and mineral composition ratio of the target lunar soil.

4. The preparation method according to claim 1, wherein In step (2), for the crushing and screening, particles with a particle size in the range of 180-1700 µm are obtained.

5. The preparation method according to claim 1, characterized in that In step (4), the drying time is more than 0.5 hours.

6. The preparation method according to claim 1, characterized in that, In step (4), a ball milling tank with a sealing device is prepared and the pressure is kept stable for more than 3 hours under a medium vacuum of 1×10 -1 ~ 1×10 2 Pa.

7. The preparation method according to claim 1, characterized in that, In step (4), the inner lining material of the ball milling jar is selected from any one of zirconia, agate and corundum as the hard inert material.

8. The preparation method according to claim 1, wherein, In step (4), the inert gas is selected from any one or more of nitrogen, argon and helium.

9. The preparation method according to claim 1, characterized in that In step (5), for the ball milling, the ball milling speed is in the range of 100-800 revolutions per minute, and the ball milling time is more than 0.5 hours.

10. A simulated lunar soil with surface chemical activity maintained obtained by the preparation method according to any one of claims 1-8.

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