CN113355472B

CN113355472B - Preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust

Info

Publication number: CN113355472B
Application number: CN202110487783.0A
Authority: CN
Inventors: 彭艳华; 李雄耀; 曾小家; 唐红; 莫冰
Original assignee: Nanning Institute Of Technology; Guilin University of Technology; Institute of Geochemistry of CAS
Current assignee: Nanning Institute Of Technology; Guilin University of Technology; Institute of Geochemistry of CAS
Priority date: 2021-04-30
Filing date: 2021-04-30
Publication date: 2022-05-31
Anticipated expiration: 2041-04-30
Also published as: CN113355472A

Abstract

The invention provides a preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust, which comprises the following steps: (1) loading the simulated lunar soil CLRS-2 and graphite flakes into a crucible, and controlling the mass ratio of the simulated lunar soil CLRS-2 to the graphite flakes to be (26-27): 1; (2) placing the crucible in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace, and introducing argon; (3) heating the high-temperature atmosphere furnace to 1550-1600 ℃, and preserving heat for 3.5-4 h at the temperature; (4) and after the heat preservation is finished, immediately putting the reaction product in the crucible into water for quenching treatment to obtain the simulated lunar soil/lunar dust containing nano-submicron elementary iron. The components of the product prepared by the method are close to those of real lunar soil/lunar dust, the particle size of simple substance iron in the product is not more than 300nm, and is also close to that of the simple substance iron in the real lunar soil/lunar dust.

Description

Preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust

Technical Field

The invention belongs to the field of celestial body simulation materials, and relates to a preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust.

Background

Through research on lunar samples returned from Apollo, the vitreous is one of main substance components forming lunar soil, and particularly for lunar dust (the lunar dust refers to a part with the particle size of less than 20 micrometers in the lunar soil), the content of the cementitious glass reaches to 80 vol%. The cementitious glass contains a unique component, namely metallic iron simple substances, and the metallic iron simple substances have important influence on the physical and chemical properties of the lunar soil/lunar dust. Researches show that the adhesiveness, floatability, biotoxicity and the like of the lunar dust are closely related to the simple substance iron component. With the development of a new round of lunar exploration engineering, people urgently need to solve the practical problems of adhesion, abrasion, shielding, blockage and the like of lunar dust on space suits and spacecrafts. In view of the rarity of lunar soil samples, detailed research on the influence of metallic iron monomers in lunar soil/lunar dust on the physicochemical properties of lunar soil/lunar dust, particularly engineering test research, mainly depends on a large number of earth simulation samples to be carried out, and therefore, the batch preparation of lunar soil/lunar dust simulation samples meeting the requirements is particularly important.

The elemental metallic iron in lunar soil mainly has two occurrence states, one is wrapped in a cementitious glass phase, and the other is in an amorphous layer on the surface of mineral particles. The iron elementary substance in the amorphous layer on the surface of the mineral particles is mainly considered to be formed by evaporation deposition and sputtering deposition at present, the particle size of the metal iron elementary substance is distributed between several nanometers and dozens of nanometers, and the average particle size is only about 3 nm; the metallic iron simple substance in the cementitious glass phase is mainly formed by high-temperature melting reduction when meteorites or micro meteorites impact the surface of the moon, and researches show that the particle size of the metallic iron simple substance in the cementitious glass is distributed between dozens of nanometers and 2 micrometers, and the average particle size is about 100 nm. In view of the limitation of the preparation process of submicron elementary iron, the conventional simulated lunar soil/lunar dust samples at home and abroad are only the CLDS-i simulated lunar dust samples developed by the geochemistry research institute of Chinese academy of sciences, which are low in yield and cannot meet the engineering requirements. The addition of nano-metallic iron was attempted in a simulated lunar dust JSC-1A sample developed in the United states, but it was later confirmed that the added component was actually titanomagnetite (Ti-magnetite).

At present, two methods for preparing submicron-grade elementary iron are mainly used: physical methods and chemical methods. The physical method is mainly a vapor deposition method, which is characterized in that an iron target is gasified by methods such as laser heating evaporation, electron beam irradiation, sputtering and the like, and then nano iron particles are deposited on the surfaces of mineral particles such as plagioclase feldspar, pyroxene, olivine and the like due to rapid cooling. The chemical method mainly comprises a thermal decomposition method and a thermal reduction method, wherein the thermal decomposition method is to heat iron-containing minerals such as ilmenite and the like under a high-temperature condition to decompose the minerals to obtain iron simple substances, the product components of the method are greatly different from cementitious glass components in natural lunar soil, and the particle size of the generated metal iron simple substances is larger and is between 100 and 1000 nm. The thermal reduction method generally adopts reducing gases such as hydrogen or carbon monoxide to reduce basalt, glass and iron-containing minerals (plagioclase, pyroxene, olivine, ilmenite and the like) to prepare the iron simple substance, but the hydrogen and the carbon monoxide are easy to explode in the high-temperature experimental process, so that the potential safety hazard is large, and the particle size of the metal iron simple substance obtained by the method is also large and is between 100 and 2000 nm.

In order to obtain a metallic iron simple substance with a small particle size, research is carried out by preparing sol carriers with different pore sizes, then soaking ferric nitrate in the sol carriers, allowing iron ions to enter the pore sizes of the sol, drying the sol soaked with ferric nitrate in the air, and then calcining the sol at 550 ℃ for 60-80 hours to obtain the silica gel containing the nano hematite. Grinding the silica gel into powder, introducing hydrogen at 850 ℃, heating for 4 hours, and reducing to obtain a metallic iron simple substance of 10-60 nm. Although the grain size of the nano-iron obtained by the method is very small, the experimental process is very complicated, the conditions are not easy to control, and the vitreous component of the obtained product is mainly single silicon dioxide, which has larger difference with the actual lunar soil component.

The preparation method for simulating nano-submicron metallic iron elementary substance in lunar soil/lunar dust expected by technical personnel in the field firstly meets the requirement that the product components are as close as possible to real lunar soil/lunar dust, simultaneously has simple process and safe production process, does not introduce impurities, can realize batch production to meet engineering requirements, and secondly, the particle size of the prepared elementary substance iron is as close as possible to the particle size of the elementary substance metallic iron in the real lunar soil/lunar dust, but the existing method has some problems more or less and cannot meet the requirements at the same time.

Disclosure of Invention

Aiming at the defects of complex process, low efficiency, large danger coefficient, easy impurity mixing, large particle size of the simple substance iron or large difference between the product component and the actual lunar soil/lunar dust and the like of the existing method for preparing the simple substance iron in the simulated lunar soil/lunar dust, the invention provides the method for preparing the nano-submicron grade simple substance iron in the simulated lunar soil/lunar dust, so as to obtain the simulated lunar soil/lunar dust which contains the metal simple substance iron with smaller particle size and has the component very close to the lunar soil/lunar dust, simultaneously avoid introducing impurities in the preparation process, simplify the preparation process, improve the production efficiency and the safety of the production process, and better meet the requirements of engineering tests.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method for simulating nano-submicron elementary iron in lunar soil/lunar dust comprises the following steps:

(1) placing simulated lunar soil CLRS-2 and graphite flakes into a crucible, wherein the mass ratio of the simulated lunar soil CLRS-2 to the graphite flakes is (26-27): 1;

(2) placing the crucible filled with the simulated lunar soil CLRS-2 and the graphite sheets in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace to remove air, and then introducing argon into the high-temperature atmosphere furnace;

(3) heating a high-temperature atmosphere furnace to 1550-1600 ℃, and preserving heat for 3.5-4 hours under the temperature condition, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a completely molten state to react with the graphite flake;

(4) and (3) immediately putting the reaction product in the crucible into water for quenching treatment after the heat preservation in the step (3) is finished, and obtaining the simulated lunar soil/lunar dust containing nano-submicron level elementary iron.

In the step (3) of the preparation method for simulating nano-submicron-level elemental iron in lunar soil/lunar dust, when a high-temperature atmosphere furnace is heated, the heating rate is as high as possible, and because the thermodynamic is relatively poorer and the reduction speed of the elemental iron is slower than the crystallization speed under the low-temperature condition, the particle size of the elemental iron is easy to increase. Generally, the temperature rise rate is limited by the equipment of the high temperature atmosphere furnace, but it is preferable to heat the high temperature atmosphere furnace to 1550 to 1600 ℃ at a temperature rise rate of at least 10 ℃/min.

In the preparation method of the nano-submicron elementary iron in the simulated lunar soil/lunar dust, the crucible is made of materials which can meet the requirements of high temperature resistance (at least 1600 ℃), acid and alkali resistance, difficult decomposition and no impurity introduction, and for example, the crucible can be feasible and comprises a platinum crucible, an alumina crucible and the like.

In the step (2) of the preparation method for the nano-submicron-level elemental iron in the simulated lunar soil/lunar dust, the high-temperature atmosphere furnace is vacuumized to fully remove air in a cavity of the high-temperature atmosphere furnace, and argon is introduced into the high-temperature atmosphere furnace to ensure that the crucible and materials in the crucible are in an argon protective atmosphere so as to prevent the materials in the crucible from being oxidized by air in the processes of temperature rise and heat preservation.

In the preparation method of the nano-submicron elementary iron in the simulated lunar soil/lunar dust, the particle size of the elementary iron in the simulated lunar soil/lunar dust containing the nano-submicron elementary iron prepared in the step (4) is not more than 300nm, and the elementary iron is alpha-Fe.

In the step (4) of the preparation method of the nano-submicron elementary iron in the simulated lunar soil/lunar dust, the reaction product in the crucible is immediately placed in water for quenching treatment, which means that the reaction product is placed in water with room temperature for rapid cooling.

The phase morphology and the component characteristics of the simulated lunar soil prepared by the method are tested by using a Scanning Electron Microscope (SEM) and energy spectrum analysis (EDS), the elementary metal iron with the particle size not more than 300nm is primarily confirmed to be distributed in the simulated lunar soil prepared by the method, and the high resolution image of the transmission electron microscope and the selective area electron diffraction image further confirm that the simulated lunar soil prepared by the method has the advantages of high resolution, and high resolutionThe metal iron simple substance particles in the simulated lunar soil have the same interplanar spacing with the crystal planes of alpha-Fe

And the included angle of a crystal face, further confirming that the iron simple substance in the simulated lunar soil prepared by the method is alpha-Fe, and verifying through an in-situ XRD analysis technology that after the simulated lunar soil CLRS-2 is reduced by graphite flakes, no graphite flake residue is found except that alpha-Fe is newly generated in the simulated lunar soil CLRS-2, and no other new phase is generated, which shows that impurities cannot be introduced when the method is used for preparing the simulated lunar soil containing nano-submicron level simple substance iron.

Compared with the prior art, the technical scheme provided by the invention has the following beneficial technical effects:

1. the invention provides a preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust, which comprises the steps of heating simulated lunar soil CLRS-2 and graphite flakes according to a specific proportion at 1550-1600 ℃ under an argon protective atmosphere, preserving heat for 3.5-4 hours under the temperature condition, and after the heat preservation is finished, putting the obtained reaction product into water for quenching treatment to obtain the simulated lunar soil/lunar dust containing the nano-submicron elementary iron. Compared with the physical method, the method has the advantages of simpler process and higher production efficiency, and compared with the existing thermal reduction method, the method has the advantage of higher safety because reducing gases such as hydrogen, carbon monoxide and the like are not needed.

2. Experiments prove that the simulated lunar soil prepared by the method contains simple substance alpha-Fe with the particle size not more than 300nm, the particle size of the simple substance alpha-Fe is closer to that of the simple substance alpha-Fe particles in real lunar soil/lunar dust, and the particle size is distributed in the particle size range (dozens of nanometers to 2 micrometers) of the simple substance iron in the natural lunar soil vitreous substance. Meanwhile, the product prepared by the method has no carbon residue, and the chemical components of the product are very close to those of real lunar soil/lunar dust because the product is prepared by taking the high-titanium basalt simulated lunar soil as a raw material. The invention solves the problems that the preparation process of the existing physical method is easy to cause product pollution, the particle size of the simple substance iron prepared by the existing thermal decomposition method and the thermal reduction method is overlarge, and the invention also solves the problem that the product components obtained by the existing thermal decomposition method and the method for preparing the simple substance iron based on the sol carrier have larger difference with the actual lunar soil components.

Drawings

Fig. 1 is a back-Scattered (SEM) picture of the product prepared in example 1.

Fig. 2 is an EDS analysis picture of elemental iron in the product prepared in example 1.

Fig. 3 is a high angle annular dark field image (HAADF) image of elemental iron in the product prepared in example 1.

FIG. 4 is a partial high resolution transmission electron microscope image of elemental iron in the product prepared in example 1.

FIG. 5 is a selected area electron diffraction analysis (SAED) image of elemental iron in the product prepared in example 1.

Figure 6 is an XRD in situ analysis image of the product prepared in example 1.

Fig. 7 is a back-Scattered (SEM) image of the product prepared in comparative example 1.

Fig. 8 is an EDS test picture of the product prepared in comparative example 1.

FIG. 9 is a graph comparing the product prepared in comparative example 2 with the starting materials and the mixture before heating.

Fig. 10 is an XRD test picture of the product prepared in comparative example 2.

Fig. 11 is an EDS test picture of the product prepared in comparative example 2.

Fig. 12 is a back-Scattered (SEM) image of the product prepared in comparative example 3.

Fig. 13 is an XRD test picture of the product prepared in comparative example 3.

Fig. 14 is a back-Scattered (SEM) image of the product prepared in comparative example 4.

Fig. 15 is a back-Scattered (SEM) image of the product prepared in comparative example 5.

Fig. 16 is a back-Scattered (SEM) image of the product prepared in comparative example 6.

Detailed Description

The preparation method of nano-submicron elementary iron in simulated lunar soil/lunar dust according to the invention is further illustrated by the following examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and those skilled in the art can make some insubstantial modifications and adjustments to the present invention based on the above disclosure and still fall within the scope of the present invention.

In the following examples and comparative examples, the lunar soil simulation CLRS-2 is high-titanium basalt simulated lunar soil developed by Chinese academy of sciences, is a national standard sample, has components very close to those of the lunar soil simulation lunar soil, and can be purchased from the market.

Example 1

In this embodiment, a method for preparing nano-submicron elementary iron in lunar soil is provided, which includes the following steps:

(1) 38.9g of lunar soil simulant CLRS-2 was charged into an alumina crucible, and then 1.46g of graphite flakes were inserted into the alumina crucible.

(2) Placing an alumina crucible filled with simulated lunar soil CLRS-2 and graphite sheets in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace to fully remove air in a cavity of the high-temperature atmosphere furnace, and then introducing high-purity argon into the high-temperature atmosphere furnace to ensure that materials in the crucible are in an argon protective atmosphere in the reaction process and prevent a formed reduction product from being oxidized by air.

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1600 ℃ at a heating rate of 10 ℃/min, and preserving heat for 4 hours at 1600 ℃, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a complete molten state to react with the graphite flake.

(4) And (3) immediately taking out the alumina crucible after the heat preservation in the step (3), pouring the reaction product into water at room temperature for quenching treatment, and cooling the sample to obtain the simulated lunar soil containing nano-submicron level simple substance iron.

Obtaining a vitreous sample after quenching and cooling in the step (4), grinding the sample into a polished section, analyzing the polished section by using a Scanning Electron Microscope (SEM) and an energy spectrum (EDS), wherein FIG. 1 is a back scattering picture of the polished section, and a large number of round bright small particles (as indicated by arrows in FIG. 1) are distributed in the vitreous material⁰Fe particles) in the figure, the particle size distribution of the small particles is on the nano-submicron scale. Fig. 2 is an energy spectrum analysis picture of the metal particles in the polished section, from which it can be seen that the small particles are very rich in iron, and it is preliminarily confirmed that the small particles are elementary metal iron, and the energy spectrum contains a small amount of elements such as Si and P, possibly due to too small particle size, the beam spot is formed by hitting the surrounding substances. In order to further confirm the properties of the metallic iron in the sample, a Focused Ion Beam (FIB) in-situ ultrathin section of the optical sheet was performed, and a lattice structure image of a High Resolution Transmission Electron Microscope (HRTEM) and a Selected Area Electron Diffraction (SAED) analysis were performed, with the results shown in fig. 3 to 5. As can be seen from FIG. 3, the particle size of the elementary metal iron particles is about 280nm, and FIGS. 4 to 5 show that the elementary metal iron particles in the sample have the same interplanar spacing with the crystal planes of alpha-Fe

And the included angle of the crystal plane, further confirming that the metal particles in the sample are alpha-Fe simple substances. Fig. 6 is an XRD in-situ analysis image of the sample prepared in this example, which also confirms that the metal particles in the sample are elemental α -Fe.

Comparative example 1

In this comparative example, a simulated lunar soil was prepared by following the procedure of example 1, replacing the graphite flakes of example 1 with an equal amount of carbon black powder, as follows:

(1) 38.9g of lunar soil simulation CLRS-2 and 1.46g of carbon black powder are mixed and then put into an alumina crucible.

(2) Placing an alumina crucible filled with simulated lunar soil CLRS-2 and carbon black in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace to fully remove air in a cavity of the high-temperature atmosphere furnace, and then introducing high-purity argon into the high-temperature atmosphere furnace to ensure that a sample is in an argon protective atmosphere in the reaction process and prevent a reduction product from being oxidized by air.

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1600 ℃ at the heating rate of 10 ℃/min, and preserving heat at 1600 ℃ for 4h, wherein the lunar soil CLRS-2 is simulated to be in a completely molten state to react with carbon black in the heat preservation process.

(4) And (4) immediately taking out the alumina crucible after the heat preservation in the step (3), pouring the reaction product into water with the room temperature for quenching treatment, and cooling the sample to obtain a vitreous product.

The glassy product obtained after quenching and cooling in the step (4) is ground into a polished sheet, and the particle size of the metallic elementary substance iron in the polished sheet is observed by using SEM, and as shown in figure 7, the particle size of the elementary substance iron in the glassy product prepared by the comparative example is as high as about 2.8 μm. The optical sheet was analyzed by EDS, and the result is shown in fig. 8, in which a C peak appeared, indicating that carbon remained in the vitreous product prepared by this comparative example.

Comparative example 2

In the comparative example, the simulated lunar soil is prepared by changing the mass ratio of the CLRS-2 to the carbon black in the comparative example 1 and adjusting the temperature and time of the reduction reaction, and the steps are as follows:

(1) 10.6g of lunar soil simulated CLRS-2 and 2g of carbon black powder (the mass ratio of the lunar soil simulated CLRS-2 to the carbon black powder is 5.3:1) are mixed and then are put into an alumina crucible.

(2) Placing an alumina crucible filled with simulated lunar soil CLRS-2 and carbon black in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace to fully remove air in a cavity of the high-temperature atmosphere furnace, and then introducing high-purity argon into the high-temperature atmosphere furnace to ensure that materials in the crucible are in an argon protective atmosphere in the reaction process and prevent a formed reduction product from being oxidized by air.

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1050 ℃ at a heating rate of 10 ℃/min, preserving heat at 1050 ℃ for 1.3h, and simulating that lunar soil CLRS-2 is not melted in the heat preservation process and is always in a powder state.

(4) And (4) immediately taking out the alumina crucible after the heat preservation in the step (3) is finished, placing the alumina crucible in an air atmosphere, and cooling to room temperature to obtain a powdery product.

A comparison of the product prepared in this comparative example with the starting material and the mixture before heating is shown in FIG. 9, and it can be seen that the product prepared in this comparative example was black in color, indicating that a large amount of carbon black powder remained in the product in powder form. The powder product prepared in this comparative example was subjected to XRD powder diffraction test, and the result is shown in fig. 10, in which α -Fe peaks appear and the phase composition of the product is mainly α -Fe, plagioclase feldspar, pyroxene and olivine, indicating that α -Fe is generated in the process, and XRD cannot detect carbon in the product because carbon in the carbon black powder is amorphous. Further EDS analysis of the composition of the product prepared in this comparative example resulted in the peak C appearing in fig. 11, indicating that a large amount of carbon remained in the powdery product prepared in this comparative example.

Comparative example 3

In this comparative example, simulated lunar soil was prepared by the procedure of example 1 while changing the temperature at which the reduction reaction was performed in example 1, and the procedure was as follows:

(2) Placing an alumina crucible filled with simulated lunar soil CLRS-2 and graphite sheets in a high-temperature atmosphere furnace, vacuumizing the high-temperature atmosphere furnace to fully remove air in a cavity of the high-temperature atmosphere furnace, and then introducing high-purity argon into the high-temperature atmosphere furnace to ensure that materials in the crucible are in an argon protective atmosphere in the reaction process and prevent a formed reaction product from being oxidized by air.

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1150 ℃ at the heating rate of 10 ℃/min, preserving heat for 4 hours at 1150 ℃, wherein in the heat preservation process, the simulated lunar soil CLRS-2 is not melted (the complete melting temperature of the simulated lunar soil CLRS-2 is about 1200 ℃) and is in a powder state to react with the graphite flake all the time.

The product prepared in this comparative example was in the form of powder with graphite flakes remaining therein, and the product was observed by SEM, as shown in fig. 12, from which it was understood that the mineral particles in the product were intact in crystal form, no melting occurred, and no metallic elemental iron particles were found. In order to further confirm the phase composition of the product, the product was subjected to XRD powder diffraction analysis, and as a result, as shown in fig. 13, no α -Fe peak was found, which also confirmed that elemental iron was not formed under the conditions of the present comparative example.

Comparative example 4

In this comparative example, simulated lunar soil was prepared by the procedure of example 1 while changing the temperature at which the reduction reaction was performed in example 1, as follows:

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1400 ℃ at the heating rate of 10 ℃/min, and preserving heat at 1400 ℃ for 4 hours, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a completely molten state to react with the graphite sheets.

As shown in fig. 14, when the glassy product obtained by quenching and cooling in this comparative example was polished into a polished sheet and observed with an SEM, the product contained metallic iron particles, but the size of the metallic iron particles was greatly different, and the maximum particle size of the metallic iron particles reached about 5 μm.

Comparative example 5

In this comparative example, simulated lunar soil was prepared according to the procedure of example 1, varying the time for the reduction reaction in example 1, as follows:

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1600 ℃ at a heating rate of 10 ℃/min, and preserving heat at 1600 ℃ for 3 hours, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a completely molten state to react with the graphite flake.

As shown in fig. 15, when the glassy product obtained by quenching and cooling the comparative example was polished into a polished sheet and the sample was observed by SEM, the product contained metallic iron particles, but the size of the metallic iron particles was greatly different from each other, and the maximum particle size of the metallic iron particles reached about 7.5 μm.

Comparative example 6

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1600 ℃ at the heating rate of 10 ℃/min, and preserving heat at 1600 ℃ for 4.5 hours, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a complete molten state to react with the graphite flake.

As shown in fig. 16, when the glassy product obtained by quenching and cooling the comparative example was polished into a polished sheet and the sample was observed by SEM, the product contained metallic iron particles, but the size of the metallic iron particles was greatly different from each other, and the maximum particle size of the metallic iron particles reached about 8.3 μm.

It can be known by combining the example 1 and the comparative example 1 that under the same raw material proportion and reduction reaction conditions, the graphite sheet is used as the reducing agent in the example 1, the particle size of the simple substance iron in the prepared simulated lunar soil is not more than 300nm, the carbon black powder is used as the reducing agent in the comparative example 1, the particle size of the simple substance iron in the prepared simulated lunar soil is as high as 2.6 μm, the particle size difference between the simple substance iron and the simple substance iron is very obvious, meanwhile, unreacted carbon black powder is remained in the prepared simulated lunar soil by using the carbon black powder as the reducing agent, and carbon residue does not occur when the graphite sheet is used as the reducing agent, which shows that the selection of the reducing agent not only has a remarkable influence on the particle size of the simple substance iron, but also has an influence on the impurity residue problem of the product. Since both use carbon as a reducing agent, this technical effect is unexpected to those skilled in the art from the viewpoint of the principle of producing elemental iron by a reduction reaction. Meanwhile, in combination with the comparative example 2, the problem of residual carbon black powder still cannot be avoided after the material ratio of the lunar soil CLRS-2 to the carbon black and the temperature and time conditions of the reduction reaction are changed.

Combining example 1 and comparative examples 3 to 4, it is known that when the temperature of the reduction reaction is lower than the melting temperature of the simulated lunar soil CLRS-2, even though the graphite flake is used as a reducing agent, no elemental iron is detected in the prepared simulated lunar soil, and graphite remains, and when the temperature of the reduction reaction is higher than the melting temperature of the simulated lunar soil CLRS-2 but lower than the temperature range defined by the present invention, although the lunar soil CLRS-2 reacts with the graphite flake in a molten state to form metallic iron particles, the size of the metallic iron particles is greatly different, and the maximum particle size of the metallic iron particles reaches several micrometers. The graphite flake is taken as a reducing agent, and on the basis of proper raw material proportion, the simulated lunar soil containing simple substance iron and with the scale of the simple substance iron being nano-submicron grade can be prepared only when the temperature of reduction reaction is properly controlled.

Combining example 1 and comparative examples 4-6, it can be seen that when graphite flakes are used as a reducing agent, nano-submicron nano-iron particles with the particle size not more than 300nm can be formed in the simulated lunar soil only when the temperature and time of the reduction reaction are properly controlled on the basis of proper raw material proportioning.

Example 2

In this embodiment, a method for preparing nano-submicron elementary iron in lunar soil simulation is provided, which includes the following steps:

(3) And opening a heating switch of the high-temperature atmosphere furnace, heating the high-temperature atmosphere furnace to 1600 ℃ at the heating rate of 10 ℃/min, and preserving heat at 1550 ℃ for 3.5h, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a complete molten state to react with the graphite flake.

Claims

1. A preparation method for simulating nano-submicron elementary iron in lunar soil/lunar dust is characterized by comprising the following steps:

(1) loading simulated lunar soil CLRS-2 and graphite flakes into a crucible, wherein the mass ratio of the simulated lunar soil CLRS-2 to the graphite flakes is (26-27): 1;

(3) heating the high-temperature atmosphere furnace to 1550-1600 ℃ at a heating rate of at least 10 ℃/min, and preserving heat for 3.5-4 hours at the temperature, wherein in the heat preservation process, the lunar soil CLRS-2 is simulated to be in a completely molten state to react with the graphite flake;

2. The method for preparing nano-submicron elementary iron in simulated lunar soil/lunar dust according to claim 1, characterized in that the crucible is a platinum crucible or an alumina crucible.

3. The method for preparing nano-submicron elementary iron in simulated lunar soil/lunar dust according to claim 1 or 2, characterized in that, in the simulated lunar soil/lunar dust containing nano-submicron elementary iron prepared in step (4), the particle size of the elementary iron is not more than 300nm, and the elementary iron isα-Fe。