Fe-containing lunar soil sintered blocks and their low-temperature carbothermic reduction preparation method

Abstract

This invention provides a method for preparing Fe-containing lunar soil sintered blocks and its low-temperature carbothermal reduction process with improved resource utilization in high-altitude locations. The method uses lunar soil powder and graphite powder as raw materials, and prepares Fe-containing lunar soil sintered blocks through low-temperature carbothermal reduction technology. Compared to existing carbothermal reduction processes for producing Fe from lunar soil, this process, because the reduction temperature does not reach the sintering temperature, can directly carry out the reduction process within the green body. The Fe product can be generated in situ inside the green body, and the gas produced by the reaction can escape along the pores of the green body, avoiding the difficulty in escaping the gas produced by reduction and the resulting bubbling phenomena caused by the increased density of the green body at high temperatures. After sufficient low-temperature reduction, the elemental Fe in the green body can play a role in promoting sintering and strengthening during subsequent heating sintering and service processes, greatly improving the efficiency of in-situ resource utilization, reducing energy consumption, and simplifying the operation steps.

Description

Technical Field

[0001] This invention relates to the field of extraterrestrial materials metallurgy, specifically to a Fe-containing lunar soil sintered block and its low-temperature carbothermal reduction preparation method. Background Technology

[0002] With the announcement of my country's new round of lunar exploration plans, the next key focus of my country's Chang'e lunar exploration program is "exploration, research, and construction." For the construction of a lunar base, transporting the necessary materials from Earth is highly impractical due to economic and practical reasons. Future lunar exploration missions will largely depend on in-situ resource utilization (ISRU). Lunar regolith, as a raw material for base construction, will play a crucial role in future lunar missions. Research indicates that lunar regolith contains an average of approximately 10% iron oxides by mass, and iron oxides are the most easily reduced substances in lunar regolith, possessing high utilization value and providing the possibility of in-situ resource utilization of metals in the lunar environment.

[0003] Lunar regolith pressing and sintering technology is one of the best techniques for preparing building structural materials with high-altitude resource utilization in the lunar environment, offering advantages such as simple operation and high preparation efficiency. However, irregular lunar regolith particles have poor thermal conductivity, requiring high heat during sintering, resulting in low sintering efficiency, and the sintered material exhibits the brittleness typical of ceramic materials. Fe can serve as a sintering activator, possessing higher diffusion and heat transfer capabilities compared to lunar regolith. Furthermore, Fe exhibits good plasticity and toughness; if the sintered material contains a certain amount of Fe, it can promote sintering and strengthen the lunar regolith matrix.

[0004] Studies have found that lunar regolith contains small amounts of elemental Fe due to solar wind ion bombardment, cosmic ray radiation, and micrometeorite impacts. This Fe exists primarily as nano-Fe within small amounts of glass, making it difficult to utilize directly. To fully utilize Fe while maintaining high resource utilization rates, the reduction of iron-containing substances in lunar regolith needs to be considered. Currently, techniques for preparing elemental Fe from lunar regolith include electrolysis, hydrogen reduction, carbothermal reduction, and thermal decomposition. Electrolysis requires complex equipment, pyrolysis requires temperatures above 2000℃ and consumes a lot of energy, and hydrogen reduction requires hydrogen that is difficult to obtain on the moon and is complex to prepare. Carbothermal reduction is considered the most promising technique for preparing elemental Fe due to its high economic efficiency, simple operation, and relatively low energy consumption. Current research simulates the carbothermal reduction of lunar regolith to obtain elemental Fe at temperatures between 1500 and 1700℃. At this temperature range, the lunar regolith is in a molten state, and the elemental Fe obtained under this reduction process is in the form of fine particles embedded in a glassy matrix formed by the molten cooling process. Similar to the Fe-containing glassy material originally present in lunar soil, the Fe-containing lunar soil glassy material obtained after high-temperature carbothermic reduction requires multiple complex processing steps before it can be utilized. Therefore, the product obtained from carbothermic reduction at this temperature range is not suitable for direct use or for the construction of efficient lunar soil bases, and has disadvantages such as high energy consumption, complex operation, low utilization efficiency, and long processing time. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the main objective of this invention is to provide a method for preparing Fe-containing lunar soil sintered blocks and its low-temperature carbothermal reduction process with improved high-altitude resource utilization. This method uses lunar soil powder and graphite powder as raw materials, and prepares Fe-containing lunar soil sintered blocks through low-temperature carbothermal reduction technology. Compared to existing carbothermal reduction processes for producing Fe from lunar soil, since the reduction temperature does not reach the sintering temperature, the reduction process can be carried out directly in the green body. The Fe product can be generated in situ inside the green body, and the gas produced by the reaction can escape along the pores of the green body, avoiding the difficulty in venting the gas produced by reduction and the resulting bubbling phenomena caused by the increased density of the green body at high temperatures. After sufficient low-temperature reduction, the elemental Fe in the green body can play a role in promoting sintering and strengthening during subsequent heating sintering and service processes, greatly improving the efficiency of in-situ resource utilization, reducing energy consumption, and simplifying the operation steps.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing Fe-containing soil sintered blocks by low-temperature carbothermal reduction.

[0007] The method for preparing Fe-containing lunar soil sintered blocks by low-temperature carbothermal reduction includes the following steps:

[0008] Weigh out lunar soil powder and graphite powder, and mix them to obtain a mixed powder;

[0009] The mixed powder is vacuum sintered and then cooled in a furnace to obtain the Fe-containing soil sintered block; wherein, the vacuum sintering process includes first carrying out a reduction reaction at a reduction temperature, and then raising the temperature to the sintering temperature and holding it at that temperature.

[0010] Furthermore, the reduction temperature is 800–980°C, and the reaction time is 2–10 h.

[0011] Furthermore, the first heating rate when heating to the reduction temperature is 2 to 10 °C / min.

[0012] Furthermore, the sintering temperature is 1030–1100℃, and the holding time is 60–240 min;

[0013] Preferably, the vacuum degree of the vacuum sintering is 2×10⁻⁶. -3 ~8×10 -3 Pa.

[0014] Furthermore, the second heating rate when the temperature is increased from the reduction temperature to the sintering temperature is 1 to 5 °C / min;

[0015] Preferably, the second heating rate is less than the first heating rate.

[0016] Furthermore, the lunar soil powder comprises the following components by mass percentage:

[0017] SiO2 43.51~51.67%, Al2O3 12.07~31.61%, Fe x O y 5.08–22.51%, CaO 6.79–15.70%, MgO 0.35–9.40%, TiO2 0.54–19.29%, Na2O 0.41–4.92%, balance being impurities;

[0018] Preferably, the particle size of the lunar soil powder is ≤270μm.

[0019] Furthermore, in the mixed powder, the mass percentage of graphite powder is 0.1% to 3% wt.%.

[0020] Preferably, the particle size of the graphite powder is ≤106μm.

[0021] Furthermore, a mixer is used to perform the mixing operation, the mixer speed is 120-250 r / min, and the mixing time is 4-15 h;

[0022] Preferably, the ratio of grinding balls to the mixed powder in the mixing operation is 1:1 to 5:1.

[0023] Furthermore, before the vacuum sintering, the mixed powder is pressed and compacted at a pressure of 1-10 MPa for a holding time of 30-90 s.

[0024] To achieve the above objectives, a second aspect of the present invention provides a Fe-containing soil sintered block.

[0025] Fe-containing soil sintered blocks were prepared using the preparation method provided in the first aspect of this invention.

[0026] This invention uses lunar soil powder and graphite powder as raw materials. After pressing and full reduction at low temperature, the mixture is directly sintered at higher temperatures to obtain sintered lunar soil blocks containing Fe-reinforced phases. Compared with existing technologies, this invention has the following advantages:

[0027] (1) The low-temperature carbothermic reduction-sintering process proposed in this invention prepares Fe-containing lunar soil blanks by low-temperature reduction below 1000℃ and then directly heats up and sintersperses them to obtain Fe-containing lunar soil sintered blocks that can be used as base building materials. That is, the reduction of Fe and the preparation of Fe-containing lunar soil sintered blocks are completed in one step. Compared with the traditional lunar soil reduction process for producing Fe, it has the characteristics of high efficiency and low energy consumption.

[0028] Meanwhile, compared with the traditional process of adding Fe and pressing and sintering to prepare Fe-containing lunar soil sintered blocks, the preparation process proposed in this invention can obtain a higher mass fraction of Fe elemental under the same amount of added Fe, that is, under the condition of high plateau resource utilization, lunar soil sintered blocks with high Fe content can be prepared.

[0029] (2) The low-temperature carbothermic reduction-sintering process proposed in this invention uses a carbothermic reduction temperature lower than the sintering temperature of lunar regolith. Therefore, at the low-temperature carbothermic reduction temperature, the powder in the green body is still mainly mechanically interlocked, without forming a sintering neck, and no sintering process occurs. Thus, during the low-temperature carbothermic reduction process, the CO2 gas generated simultaneously with Fe can escape through numerous interconnected pores in the green body, as shown in the reaction equation below. This reduces the expansion caused by excessive internal gas pressure, thereby maintaining the shape of the green body during the reduction process and ultimately obtaining a lunar regolith sintered block with a certain degree of dimensional regularity. In contrast, a high-temperature carbothermic reduction reaction is carried out in the temperature range of 1500–1700℃. During the reduction process, the lunar regolith is in a molten state. After cooling, a glassy body is obtained, containing pores caused by insufficient gas expulsion, which reduces the mechanical strength of the sintered block. Compared to the high-temperature carbothermic reduction method, the part prepared by this invention has better dimensional accuracy and shape retention. Furthermore, due to the reduction of internal pores caused by the escape of internal gas, its mechanical strength is significantly higher than that of the glassy body obtained by high-temperature carbothermic reduction.

[0030] The reaction equation for the carbothermic reduction reaction is:

[0031] FeO + C → Fe + CO↑ (1)

[0032]

[0033] Overall reaction: FeO + C → Fe + CO2↑ (3)

[0034] (3) In the process proposed in this invention, the elemental Fe produced in the lunar soil matrix during the low-temperature carbothermic reduction stage, as the core Fe particles, continues to grow through reaction, diffusion and migration during the further heating process. In addition, Fe acts as a sintering aid, which can effectively absorb and conduct heat, promoting the sintering process. At the same time, the presence of elemental Fe in the sintered block also provides a strengthening effect during service.

[0035] (4) In terms of application technology: Compared with commonly used lunar building material preparation technologies such as lunar soil additive manufacturing technology, lunar soil bonding technology and lunar soil hydration or geopolymer concrete technology, the pressing-reduction-sintering technology selected in this invention has the advantages of simple equipment, easy operation and high preparation efficiency. It can easily achieve efficient automated production in the lunar environment, greatly reducing manpower and time costs. Attached Figure Description

[0036] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:

[0037] Figure 1 The XRD pattern of Fe-containing lunar soil powder prepared by low-temperature carbothermal reduction method in the embodiments provided by the present invention;

[0038] Figure 2 This is a schematic diagram of the Fe-containing lunar soil sintered block prepared by the low-temperature carbothermal reduction method in Example 1 of the present invention;

[0039] Figure 3 This is a schematic diagram of the Fe-containing lunar soil sintered block prepared by the low-temperature carbothermal reduction method in Example 4 of the present invention. Detailed Implementation

[0040] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0041] In this invention, simulated lunar soil is used to replace real lunar soil in the lunar environment. The simulated lunar soil, also known as the lunar soil powder in this invention, has the following chemical composition by mass percentage: SiO2 43.51–51.67%, Al2O3 12.07–31.61%, Fe... x O y 5.08–22.51%, CaO 6.79–15.70%, MgO 0.35–9.40%, TiO2 0.54–19.29%, Na2O 0.41–4.92%, with the balance being unavoidable impurities.

[0042] The first aspect of this invention provides a method for preparing Fe-containing lunar soil sintered blocks by low-temperature carbothermal reduction under high-altitude resource utilization conditions, comprising the following steps:

[0043] S1: The lunar soil powder and graphite powder are sieved through a sieve to obtain lunar soil powder and graphite powder with a certain particle size distribution.

[0044] In an embodiment of the present invention, the particle size of the lunar soil powder is ≤270μm.

[0045] In embodiments of the present invention, the particle size of the graphite powder is ≤106μm.

[0046] S2: Weigh the sieved lunar soil powder and graphite powder obtained in step S1 according to the mass ratio. At the same time, weigh zirconia balls according to a certain ball-to-material ratio. Put all the weighed powder and zirconia balls into a mixing tank, then seal the mixing tank and put it into a mixer to mix at a certain speed for a certain period of time. After the mixing is completed, separate the mixed powder from the zirconia balls to obtain mixed powder.

[0047] In embodiments of the present invention, the mass percentage of graphite powder in the mixed powder is 0.1-3% wt.%.

[0048] In an embodiment of the present invention, a mixer is used for mixing, with a speed of 120-250 r / min and a mixing time of 4-15 h.

[0049] In an embodiment of the present invention, the ratio of grinding balls to mixed powder in the mixing operation is 1:1 to 5:1.

[0050] In embodiments of the present invention, the diameter of the grinding ball includes at least one of 6 mm and 3 mm.

[0051] The grinding balls can be zirconia balls.

[0052] S3: Spread the mixed powder obtained in step S2 into the graphite sintering boat, and compact it after vibration to increase the contact area between the powders. After fully compacting, cover the graphite sintering boat with the lid.

[0053] In an embodiment of the present invention, a compaction pressure of 1 to 10 MPa is applied during the compaction process, and the holding time is 30 to 90 seconds.

[0054] In an embodiment of the present invention, the material of the burning boat includes graphite, wherein the graphite material can act as a reducing agent to undergo a reduction reaction with the lunar soil in contact, thereby improving the reduction efficiency.

[0055] It is worth mentioning that the material is not limited to graphite-fired boats; it only needs to meet the requirements of high temperature resistance (≥1100℃), acid and alkali resistance, non-decomposition, and no introduction of impurities.

[0056] S4: Place the graphite boat containing the compacted mixed powder obtained in step S3 into a vacuum sintering furnace, raise the temperature to the reduction temperature using the first heating rate, hold it at the reduction temperature for a certain time to carry out a full reduction reaction, continue to raise the temperature using the second heating rate to the sintering temperature and hold it at the temperature, and then cool it with the furnace to obtain Fe-containing soil sintered blocks.

[0057] In an embodiment of the present invention, the reduction temperature is 800–980°C, the reaction time is 2–10 h, and the first heating rate when heating to the reduction temperature is 2–10°C / min, which can be understood as the heating rate below the reduction temperature being in the range of 2–10°C / min.

[0058] In an embodiment of the present invention, the sintering temperature is 1030–1100°C and the holding time is 60–240 min; the second heating rate when the temperature is increased from the reduction temperature to the sintering temperature is 1–5°C / min, which can be understood as the heating rate when the temperature is higher than the reduction temperature being in the range of 1–5°C / min.

[0059] In this invention, the second heating rate is less than the first heating rate, that is, the heating rate below the reduction temperature is greater than the heating rate above the reduction temperature. This is because the green body has not undergone reduction reaction and sintering below the reduction temperature. At this stage, the heating rate has no significant impact on the performance of the sintered part. Therefore, a higher heating rate can be used to reduce the time required for the sintering process and improve the preparation efficiency. Above the reduction temperature, a lower heating rate is used, which allows the gaseous products generated by the reduction reaction and the gas generated by the vaporization of low-melting-point components in the soil to be slowly discharged, avoiding expansion and deformation inside the green body due to obstruction of gas discharge. At the same time, a slow heating rate can make the green body heat evenly, reducing the generation of internal stress and defects.

[0060] In an embodiment of the present invention, the vacuum degree of vacuum sintering is 2 × 10⁻⁶. -3 ~8×10 -3 Within the Pa range.

[0061] The second aspect of the present invention provides a Fe-containing lunar soil sintered block, which is prepared by the low-temperature carbothermal reduction method of the first aspect of the present invention.

[0062] The following detailed description of the Fe-containing lunar soil sintered blocks and their low-temperature carbothermal reduction preparation method in this invention will be provided through specific embodiments.

[0063] Example 1:

[0064] Simulated lunar soil was used, with the main chemical components being 48.12% SiO2, 18.23% Al2O3, and 10.04% Fe. x O y 10.70% CaO, 8.45% MgO, 1.75% TiO2, 1.60% Na2O, balance being unavoidable impurities.

[0065] The simulated lunar soil and graphite powder were sieved to obtain a particle size range of 48–75 μm, and the graphite powder particle size was ≤25 μm. The raw material powder was weighed and added to a mixing tank at a ratio of 1.2 wt.% graphite powder. At the same time, zirconia balls with an equal mass of 6 mm and 3 mm diameter were added. The mixer was started and mixed at a speed of 180 r / min for 10 h. After the mixing was completed, the mixed powder and zirconia balls were removed from the tank and separated.

[0066] The mixed powder was placed in a graphite sintering boat with dimensions of 50mm×30mm×20mm and compacted thoroughly with a pressing pressure of 1MPa for 90s.

[0067] A graphite sintering boat containing the mixed powder was placed in a vacuum sintering furnace with a vacuum degree of 6 × 10⁻⁶. -3 Pa, the specific operating parameters for carbothermal reduction are: heating at a rate of 5℃ / min to the reduction temperature of 900℃, and holding at the reduction temperature for 6 hours;

[0068] After the reduction process was completed, the temperature was immediately increased to 1050℃ at a heating rate of 2℃ / min and held for 2 hours. After sintering, the sample was cooled to room temperature with the furnace, and Fe-containing soil sintered blocks were finally obtained.

[0069] According to the measurement and calculation, the average density of the sintered sample prepared in Example 1 was 80.52±4.03%, and the average compressive strength of the sample was 93.31±4.67MPa after compression test.

[0070] Example 2:

[0071] Simulated lunar soil was used, with the main chemical components being 43.64% SiO2, 22.07% Al2O3, and 9.05% Fe.x O y 6.89% CaO, 7.68% MgO, 4.29% TiO2, 2.26% Na2O, with the balance being unavoidable impurities.

[0072] The simulated lunar soil and graphite powder were sieved to obtain a particle size range of 23–48 μm and a graphite powder particle size of 10 μm. The raw material powder was weighed and added to a mixing tank at a ratio of 1 wt.% of graphite powder. At the same time, zirconia balls with an equal mass of 6 mm and 3 mm in diameter were added. The mixer was started and mixed at a speed of 150 r / min for 15 h. After the mixing was completed, the mixed powder and zirconia balls were removed from the tank and separated.

[0073] The mixed powder was placed in a graphite sintering boat with dimensions of 50mm×30mm×20mm and compacted thoroughly with a pressure of 3MPa for 60s.

[0074] A graphite sintering boat containing the mixed powder was placed in a vacuum sintering furnace with a vacuum degree of 5 × 10⁻⁶. -3 The specific operating parameters for carbothermal reduction are as follows: the temperature is increased to the reduction temperature of 930℃ at a heating rate of 8℃ / min, and held at the reduction temperature for 8 hours; after the reduction process is completed, the temperature is immediately increased to the sintering temperature of 1040℃ at a heating rate of 5℃ / min, and held for 1.5 hours. After sintering, the sample is cooled to room temperature with the furnace, and finally Fe-containing soil sintered blocks are obtained.

[0075] According to measurements and calculations, the average density of the sintered sample prepared in Example 2 was 82.31±4.12%, and the average compressive strength of the sample was 96.54±4.83 MPa after compression testing.

[0076] Example 3:

[0077] Simulated lunar soil was used, with the main chemical components being 43.86% SiO2, 17.68% Al2O3, and 12.0% Fe. x O y 7.13% CaO, 3.68% MgO, 12.32% TiO2, 2.12% Na2O, balance being unavoidable impurities.

[0078] The simulated lunar soil and graphite powder were sieved to obtain a particle size of ≤23μm and a graphite powder particle size of 5μm. The raw material powder was weighed and added to a mixing tank at a ratio of 3wt.% graphite powder. At the same time, zirconia balls with a diameter of 6mm and a diameter of 3mm were added at a ball-to-material ratio of 5:1. The mixer was started and mixed at a speed of 200r / min for 15h. After the mixing was completed, the mixed powder and zirconia balls were removed from the tank and separated.

[0079] The mixed powder was placed in a graphite sintering boat with dimensions of 50mm×30mm×20mm and compacted thoroughly with a pressure of 5MPa for 40s.

[0080] After compaction, the graphite boat is placed in a vacuum sintering furnace with a vacuum degree of 8×10⁻⁶. -3 The specific operating parameters for Pa, carbothermic reduction are as follows: the temperature is increased to the reduction temperature of 950℃ at a heating rate of 5℃ / min, and held at the reduction temperature for 9h; after the reduction process is completed, the temperature is immediately increased to the sintering temperature of 1080℃ at a heating rate of 2℃ / min, and held for 4h. After sintering, the sample is cooled to room temperature with the furnace, and finally Fe-containing soil sintered blocks are obtained.

[0081] According to measurements and calculations, the average density of the sintered sample prepared in Example 3 was 80.31±4.02%, and the average compressive strength of the sample was 88.63±4.43 MPa after compression testing.

[0082] Example 4:

[0083] Simulated lunar soil was used, with the main chemical components being 48.40% SiO2, 19.06% Al2O3, and 13.26% Fe. x O y 15.04% CaO, 0.39% MgO, 0.68% TiO2, 2.47% Na2O, balance being unavoidable impurities.

[0084] The simulated lunar soil and graphite powder were sieved to obtain a particle size of ≤23μm for the lunar soil and 5μm for the graphite powder. The raw material powder was weighed and added to a mixing tank at a mass ratio of 0.6wt.% for graphite powder. At the same time, zirconia balls with a diameter of 6mm and a diameter of 3mm were added at a ball-to-material ratio of 3:1. The mixer was started and mixed at a speed of 180r / min for 10h. After the mixing was completed, the mixed powder and zirconia balls were removed from the tank and separated.

[0085] The mixed powder was placed in a graphite sintering boat with dimensions of 120mm×60mm×30mm and compacted thoroughly with a pressure of 5MPa for 30s.

[0086] After compaction, the graphite boat is placed in a vacuum sintering furnace with a vacuum degree of 3×10⁻⁶. -3 The specific operating parameters for carbothermal reduction are as follows: the temperature is increased to the reduction temperature of 920℃ at a heating rate of 4℃ / min, and held at the reduction temperature for 6 hours; after the reduction process is completed, the temperature is immediately increased to the sintering temperature of 1030℃ at a heating rate of 3℃ / min, and held for 2.5 hours. After sintering, the sample is cooled to room temperature with the furnace, and finally Fe-containing soil sintered blocks are obtained.

[0087] According to measurements and calculations, the average density of the sintered sample prepared in Example 4 was 75.24±3.76%, and the average compressive strength of the sample was 69.21±3.46 MPa after compression testing.

[0088] The following performance comparison experiment will be conducted between the Fe-containing sintered blocks prepared in Examples 1-3 and the blocks prepared in Comparative Examples 1-3.

[0089] Comparative Example 1:

[0090] Using simulated lunar soil and graphite powder with the same particle size range and type as in Example 1 as raw materials, sintered blocks were prepared with the same addition amount as in Example 1. The only difference was the reduction and sintering process: in Example 1, a reduction temperature of 900°C and a sintering temperature of 1050°C were used, while in Comparative Example 1, the reduction temperature and sintering temperature were the same, both at 1070°C. After cooling in the furnace, a large number of bubbles appeared on the surface of the sample in Comparative Example 1.

[0091] According to the measurements and calculations, the average density of the sintered sample prepared in Comparative Example 1 was 62.54±3.13%, and the average compressive strength of the sample was 43.23±2.16 MPa after compression testing.

[0092] Comparative Example 2:

[0093] Using simulated lunar soil and graphite powder with the same particle size range and type as in Example 2 as raw materials, sintered blocks were prepared with the same addition amount as in Example 2. The only difference was the reduction and sintering process: in Example 2, a reduction temperature of 930°C and a sintering temperature of 1040°C were used, while in Comparative Example 2, the reduction temperature and sintering temperature were the same, both at 1100°C. After cooling in the furnace, a large number of bubbles appeared on the surface of the sample in Comparative Example 2.

[0094] According to the measurements and calculations, the average density of the sintered sample prepared in Comparative Example 2 was 60.87±3.04%, and the average compressive strength of the sample was 41.56±2.08 MPa after compression testing.

[0095] Comparative Example 3:

[0096] Using simulated lunar soil and graphite powder with the same particle size range and type as in Example 3 as raw materials, sintered blocks were prepared with the same addition amount as in Example 3. The only difference was the reduction and sintering temperatures: in Example 3, a reduction temperature of 950°C and a sintering temperature of 1080°C were used, while in Comparative Example 3, the reduction temperature was set at 1600°C. After the reduction was completed, the sample in Comparative Example 3 was cooled with the furnace. The sample became a glassy body with many bubbles and microcracks on the surface and a large number of spherical bubbles inside.

[0097] According to the measurements and calculations, the average density of the sintered sample prepared in Comparative Example 3 was 55.28±2.76%, and the average compressive strength of the sample was 32.16±1.61 MPa after compression testing.

[0098] Combination Figures 1-3 Comparative analysis shows that the Fe-containing lunar soil blocks prepared by high-temperature carbothermal reduction in the comparative example have lower dimensional accuracy, shape regularity, and mechanical strength; while the sintered parts prepared by the process of low-temperature carbothermal reduction followed by direct sintering of Fe-containing lunar soil blocks proposed in this invention have good dimensional accuracy, shape regularity, and high mechanical strength.

[0099] The descriptions using terms such as "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0100] The technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0101] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of producing Fe-containing lunar soil sintered blocks by low-temperature carbothermal reduction, characterized by, The method comprises the following steps: The simulated lunar soil powder and graphite powder are weighed and mixed to obtain a mixed powder, wherein the mass percentage of the graphite powder in the mixed powder is 0.6-3 wt%; the simulated lunar soil powder comprises the following components in percentage by mass: SiO243.51-51.67%, Al2O312.07-31.61%, Fe x O y 5.08-22.51%, CaO 6.79-15.70%, MgO 0.35-9.40%, TiO20.54-19.29%, Na2O 0.41-4.92%, and the balance is impurities; The mixed powder is subjected to compaction and compaction pressure of 1-10 MPa and pressure holding time of 30-90 s, and then the mixed powder after compaction is subjected to vacuum sintering and then furnace cooling to obtain the Fe-containing lunar soil sintered block; the vacuum sintering process comprises first performing a reduction reaction at a reduction temperature of 800-980 ℃ for 2-10 h, and then heating to a sintering temperature of 1030-1100 ℃ and holding for 60-240 min.

2. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks according to claim 1, wherein, The first heating rate when heating to the reduction temperature is 2-10 ℃ / min.

3. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 1, wherein, The vacuum sintering has a vacuum degree of 2x10 -3 8x10 -3 Pa.

4. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 1, wherein, The second heating rate when heating from the reduction temperature to the sintering temperature is 1-5 ℃ / min.

5. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 1, wherein, The particle size of the simulated lunar soil powder is ≤270 μm.

6. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 1, wherein, The particle size of the graphite powder is ≤106 μm.

7. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 1, wherein, The mixing operation is performed by using a mixer, the rotation speed of the mixer is 120-250 r / min, and the mixing time is 4-15 h.

8. The method of cryogenic carbothermic reduction to produce Fe-containing lunar soil sintered blocks of claim 7, wherein, The ball-to-powder ratio of the grinding ball to the mixed powder in the mixing operation is 1:1-5:

1.

9. An Fe-containing lunar soil sintered block prepared by the low-temperature carbonthermal reduction method according to any one of claims 1-8.

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