Millimeter wave vacuum lunar soil sintering device and control method

Abstract

This invention relates to the field of extraterrestrial in-situ resource utilization technology, and particularly to a millimeter-wave vacuum lunar soil sintering apparatus and control method. The apparatus includes a vacuum chamber module, a sample support platform, a millimeter-wave feed module, and a densification monitoring module. The vacuum chamber module has a viewing window. The sample support platform is located inside the vacuum chamber, and its support portion is made of a transparent material. The output end of the millimeter-wave feed module faces the sample support platform. The densification monitoring module is located outside the vacuum chamber, and its acquisition end obtains the sample height change through the viewing window and the support portion. By real-time acquisition of temperature distribution, reflected power, and sample height change, the control module dynamically adjusts the millimeter-wave output power and sample spatial position, and determines the sintering endpoint based on the height change rate. This invention achieves synchronous monitoring and closed-loop control of the temperature field and densification state during vacuum millimeter-wave sintering, significantly improving the uniformity of lunar soil sintering and the consistency of product density.

Description

Technical Field

[0001] This invention relates to the field of extraterrestrial in-situ resource utilization technology, and in particular to a millimeter-wave vacuum lunar soil sintering device and control method. Background Technology

[0002] Lunar regolith is the most widely distributed solid resource on the lunar surface that can be directly utilized on-site. Transforming lunar regolith into building materials or functional components through sintering technology is an important approach for future lunar base construction and in-situ resource utilization. Currently, the main methods for sintering and shaping lunar regolith include conventional microwave heating.

[0003] While conventional microwave heating can achieve a certain volumetric heating effect, its long wavelength easily leads to complex electromagnetic field distributions within the sintering cavity, generating standing wave hotspots and resulting in uneven temperature field distribution. Furthermore, unstable reflected power affects the controllability and repeatability of the sintering process. Simultaneously, lunar soil transforms from a loose powder to a dense structure during sintering, undergoing significant changes in its physical state and accompanied by marked volume shrinkage. This densification behavior is closely related to the material's mechanical properties and porosity. However, existing microwave sintering equipment mostly employs open-loop control strategies with preset power and time. Even those devices that incorporate temperature feedback rely solely on thermocouples or infrared thermometry to obtain temperature information, failing to provide real-time information on the material's internal densification state. Operators struggle to determine whether the sintering process is complete, easily leading to under-sintering or over-sintering, which affects the mechanical properties and dimensional accuracy of the finished product. Summary of the Invention

[0004] The purpose of this invention is to provide a millimeter-wave vacuum lunar soil sintering device and control method to address the shortcomings of the aforementioned background technology.

[0005] To achieve the above objectives, the present invention provides a millimeter-wave vacuum lunar soil sintering apparatus, comprising: A vacuum chamber module, wherein the vacuum chamber module is provided with a viewing window; A sample carrying platform is disposed within the vacuum chamber module. The sample carrying platform is provided with a movable supporting part, which is a transparent geometric structure. A millimeter-wave feed module, wherein the output end of the millimeter-wave feed module extends into the vacuum cavity and faces the sample support platform; A densification monitoring module is disposed outside the vacuum chamber module, with its acquisition end facing the sample inside the support unit through a viewing window and the support unit.

[0006] Preferably, the vacuum chamber module includes a vacuum chamber, inside which a first cavity is provided, the first cavity being connected to a vacuum pump via a pipeline, and a valve being provided on the pipeline; a resonant cavity is provided inside the first cavity, and a second cavity is provided inside the resonant cavity; the end of the viewing window is respectively sealed and connected to the vacuum chamber and the resonant cavity.

[0007] Preferably, the sample carrying platform includes a two-degree-of-freedom slide, which is disposed in the second cavity, and the sliding part of the two-degree-of-freedom slide is connected to the bottom of the carrying part.

[0008] Preferably, the millimeter-wave feed module includes a millimeter-wave source, which is disposed outside the vacuum cavity module. The output end of the millimeter-wave source is connected to one end of a waveguide, and the other end of the waveguide extends into the first cavity and is connected to a cone horn. The cone section of the cone horn extends into the second cavity.

[0009] Preferably, the densification monitoring module includes a laser rangefinder, which is located outside the vacuum cavity module, and its acquisition end obtains the height change of the sample in real time through the viewing window and the support part.

[0010] Preferably, it also includes a temperature monitoring module and a reflection power detection module. The temperature monitoring module is located outside the vacuum cavity module, and its acquisition end monitors the temperature of the sample through a viewing window. The reflection power detection module is located inside the waveguide and is used to acquire the incident power and reflected power of the millimeter wave in real time.

[0011] Preferably, the system further includes a control module, which is electrically connected to the temperature monitoring module, the reflection power detection module, the sample support platform, the millimeter-wave feed module, and the densification monitoring module, respectively.

[0012] This invention also provides a millimeter-wave vacuum lunar soil sintering control method, implemented using the above-mentioned device, comprising the following steps: Place the lunar soil sample inside the support section and evacuate the vacuum chamber module to the preset vacuum level. The millimeter-wave feed module was activated to heat the lunar soil sample; During the heating process, the temperature distribution on the surface of the lunar soil sample, the reflected power in the millimeter wave transmission path, and the height change of the lunar soil sample were collected in real time. The control module dynamically adjusts the millimeter-wave output power and the spatial position of the lunar soil sample relative to the pyramidal horn based on the collected temperature distribution, reflected power, and height changes. When the surface temperature of the lunar soil sample is within the target sintering temperature range and maintained for a preset time, the real-time apparent sintering density estimated based on the height change reaches the target value, and the height shrinkage rate change rate is lower than the preset threshold, sintering is determined to be complete, and heating is stopped.

[0013] Preferably, the dynamic adjustment includes: When the temperature difference on the sample surface exceeds a preset threshold, the position of the sample in the horizontal and / or vertical directions is adjusted to change the position of the sample relative to the cone-shaped horn radiation field, thereby adjusting the energy absorption distribution in different regions of the sample. When the reflected power rises to a preset threshold, reduce the output power or adjust the distance between the sample and the cone-shaped horn. When the rate of change of sample height exceeds the set range, the output power is reduced to control the rate of change.

[0014] Preferably, the height shrinkage rate is obtained based on the height change. Obtained from formula 1, (1) in, The initial average height; This is the current average height; Under the conditions that the sample mass remains approximately constant, the supporting part constrains the lateral dimensions of the sample, and the sample cross-sectional area remains approximately constant, the height shrinkage rate is obtained based on the height change, and the real-time sintering density is estimated. Real-time sintering density It is obtained from calculation formula 2, (2) in, The initial density; When the real-time sintering density reaches the target value and the rate of change of the height shrinkage is lower than the threshold, the control module determines that sintering is complete.

[0015] The above-described solution of the present invention has the following beneficial effects: This invention effectively disperses energy distribution through real-time temperature monitoring and dynamic adjustment of sample position, avoiding the problems of standing wave hotspots and unstable reflected power caused by conventional long-wavelength microwaves, and improving the uniformity of the sintering temperature field.

[0016] This invention utilizes a transparent support and an external laser rangefinder to continuously monitor the height change of the sample in a non-contact manner and calculate the shrinkage rate and sintering density online, thus overcoming the shortcomings of existing technologies that rely solely on temperature and cannot determine the densification process of the material.

[0017] The control module in this invention coordinates the millimeter wave power and sample position based on temperature distribution, reflection power and height change rate, and uses the stabilization of height change as the criterion for sintering completion, thereby avoiding under-sintering or over-sintering and improving the consistency of product quality.

[0018] Other beneficial effects of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the sample height according to the present invention; [Explanation of Labels in the Attached Image] 1. Millimeter wave source; 2. Directional coupler and power detection unit; 3. Waveguide; 4. Conical horn; 5. Resonant cavity; 6. Sample; 7. Support unit; 8. Two-degree-of-freedom slide stage; 9. Infrared thermal imager; 10. Laser rangefinder; 11. Viewing window; 12. Vacuum pump; 13. Sealing flange; 14. Vacuum valve; 15. Vacuum chamber; 16. Control module. Detailed Implementation

[0020] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] like Figure 1 As shown, an embodiment of the present invention provides a millimeter-wave vacuum lunar soil sintering device, including a vacuum chamber module, a sample support platform, a millimeter-wave feed module, and a densification monitoring module. The vacuum chamber module is used to simulate a vacuum environment. The sample support platform is disposed in the vacuum chamber and is used to place and move the sample 6. The output end of the millimeter-wave feed module is located inside the vacuum chamber module and is used to heat the sample 6 on the sample support platform. The densification monitoring module is used to acquire the height change of the sample 6 in real time.

[0024] The vacuum chamber module includes a vacuum chamber 15 and a resonant cavity 5 disposed within the vacuum chamber 15. Specifically, the vacuum chamber 15 is made of metal and forms a metal shielding structure. The interior of the vacuum chamber 15 forms a first cavity, which is provided with a first observation window, a vacuum interface, and a first millimeter-wave feed inlet. The resonant cavity 5 is disposed within the first cavity and is used to confine the electromagnetic field and improve energy coupling efficiency. The interior of the resonant cavity 5 forms a second cavity for placing and heating the sample 6. The second cavity is provided with a second observation window and a second millimeter-wave feed inlet. The viewing window 11 is made of sapphire glass, and its ends are sealed to the vacuum chamber 15 and the resonant cavity 5 through the first observation window and the second observation window, respectively, to ensure vacuum sealing and unobstructed optical path.

[0025] Furthermore, the first cavity is also equipped with a vacuum gauge for real-time monitoring of the vacuum level. The vacuum interface is connected to one end of the pipeline, and the other end of the pipeline is connected to a vacuum pump 12. A vacuum valve 14 is installed on the pipeline.

[0026] The sample carrying platform includes a two-degree-of-freedom slide 8, the bottom of which is fixed to the bottom of the second cavity. It includes an X-axis sliding system and a Z-axis sliding system disposed on the X-axis sliding system. The sliding part of the Z-axis sliding system is connected to the bottom of the carrying part 7. The carrying part 7 is a regular geometric structure made of a low dielectric loss and transparent material to facilitate the acquisition of height changes and density calculation. The carrying part 7 can move along the horizontal X direction and the vertical Z direction on the two-degree-of-freedom slide 8.

[0027] Furthermore, the area at the connection between the sliding part and the bearing part 7 is much smaller than the bottom area of ​​the bearing part 7, so as to reduce heat conduction loss.

[0028] The millimeter-wave feed module includes a millimeter-wave source 1, which is installed on the outside of the vacuum chamber 15. The output end of the millimeter-wave source 1 is connected to a waveguide 3 via a flange. The waveguide 3 passes through a first millimeter-wave feed inlet into the first cavity, and then connects to the feed section of a pyramidal horn 4. The pyramidal section of the pyramidal horn 4 passes through a second millimeter-wave feed inlet into the second cavity, with the horn opening facing downwards towards the support portion 7. The sample 6 on the support portion 7 is located within the radiation heating range of the pyramidal horn 4. During the sintering process, the sample 6 remains entirely within the radiation heating range of the millimeter waves.

[0029] Furthermore, the waveguide 3 is connected to the first millimeter-wave feed inlet via a sealing flange 13 to ensure the formation of a vacuum environment. The waveguide 3 is equipped with a reflection power detection module, which includes a directional coupler and a power detection unit 2, for monitoring incident power and reflection power.

[0030] The densification monitoring module includes a laser rangefinder 10, which is installed on the outside of the vacuum chamber 15. The laser beam emitted from the acquisition end of the laser rangefinder 10 is projected onto the sample 6 through the viewing window 11 and the support part 7. During the sintering process, the laser rangefinder 10 continuously measures the sample 6.

[0031] Furthermore, it also includes a temperature monitoring module, which is located on the outside of the vacuum chamber 15. It includes an infrared thermal imager 9, whose acquisition end is aligned with the viewing window 11. The field of view of the infrared thermal imager 9 covers the upper surface of the sample 6, and can acquire the surface temperature distribution of the sample 6 in real time.

[0032] Furthermore, it also includes a control module 16, which is electrically connected to the power control interface of the millimeter wave source 1, the driver of the dual-degree-of-freedom slide stage 8, the infrared thermal imager 9, the laser rangefinder 10, the directional coupler and power detection unit 2, the vacuum gauge, the controller of the vacuum pump 12, etc., to dynamically adjust the millimeter wave power and the position of the sample 6 to achieve closed-loop control.

[0033] Embodiments of the present invention also provide a method for controlling millimeter-wave vacuum lunar soil sintering, comprising the following steps: Preparation stage: Take an appropriate amount of sample 6 and place it into the bearing part 7, and smooth the upper surface with a scraper. Close the vacuum chamber 15 and start the vacuum pump 12 to evacuate to the preset low pressure value. The control module 16 records the height of multiple points on the initial upper surface measured by the laser rangefinder 10, and calculates the initial height. H 0.

[0034] Preheating stage: The control module 16 sets the millimeter wave source 1 to a low initial power, adjusts the distance between the horn and the upper surface of the sample 6 to an initial value, and after heating for a period of time, the infrared thermal imager 9 monitors that the surface temperature of the sample 6 rises to about several hundred degrees Celsius, and the temperature difference is controlled within a small range.

[0035] Sintering Stage: Control module 16 gradually increases the power to the required sintering level according to the predetermined heating rate. Real-time measurement is performed during this period. Temperature distribution: When the surface temperature difference of sample 6 exceeds the preset threshold, the control module 16 adjusts the two-degree-of-freedom slide 8 to move sample 6 in the horizontal and / or vertical directions, thereby changing the position of sample 6 relative to the radiation field of the pyramidal horn 4, thereby adjusting the energy absorption distribution of different regions of sample 6, so that the temperature difference gradually falls back to the allowable range.

[0036] Reflected power: When the ratio of reflected power to incident power exceeds the set upper limit, the output power is appropriately reduced and the distance is finely adjusted to reduce the ratio to an acceptable range.

[0037] Height variation: The laser rangefinder 10 measured the average height of sample 6 at a certain moment. H t The temperature begins to decrease slowly. When the temperature reaches the target sintering range and the rate of change of the height shrinkage exceeds the rapid densification criterion, the control module 16 reduces the millimeter-wave output power according to a preset strategy and maintains the temperature for a period of time.

[0038] Endpoint determination: As the heat preservation process continued, the height shrinkage rate of sample 6 gradually increased, and the rate of change of shrinkage rate decreased to below the stable threshold. Control module 16 calculated the real-time sintering density based on the law of conservation of mass. When the sintering density reaches the target value and the height change is minimal over a continuous period of time, the sintering is considered complete, and the millimeter wave source 1 is turned off.

[0039] Cooling: After natural cooling to room temperature, the sintered sample was taken out and its mechanical properties and microstructure were tested. The resulting product has high density and compressive strength.

[0040] Real-time sintering density calculated based on mass conservation. Theoretical basis: Since sample 6 is housed within the support portion 7, which has a regular geometric structure, the support portion 7 constrains the lateral boundaries of sample 6. Therefore, the cross-sectional area of ​​sample 6 can be approximated as constant during sintering. V This can be obtained from Formula 3: (3) in, The cross-sectional area of ​​the sample; This represents the sample height.

[0041] Under vacuum conditions and without additives, sample 6 showed no significant oxidation or volatilization loss, and its mass can be approximated as unchanged. According to density calculation formula 4: (4) The following relationship can be obtained between density and height: (5) in, The initial density; This represents the density at a specific moment during the sintering process. H 0 represents the initial height of sample 6, such as... Figure 2 As shown, H 0= Z 2- Z 1; H t The height at a certain moment during the sintering process, such as Figure 2 As shown, H t = Z 3- Z 1.

[0042] From this, the real-time sintering density can be determined: (2) in, High shrinkage rate; It can be obtained from Formula 1. (1) in, The initial average height, This represents the current average altitude.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A millimeter-wave vacuum lunar soil sintering device, characterized in that, include: A vacuum chamber module, wherein the vacuum chamber module is provided with a viewing window; A sample carrying platform is disposed within the vacuum chamber module. The sample carrying platform is provided with a movable supporting part, which is a transparent geometric structure. A millimeter-wave feed module, wherein the output end of the millimeter-wave feed module extends into the vacuum cavity and faces the sample support platform; A densification monitoring module is disposed outside the vacuum cavity module. The acquisition end of the densification monitoring module is directed through the viewing window and the support portion toward the sample inside the support portion to acquire the change in the height of the sample in real time.

2. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 1, characterized in that, The vacuum chamber module includes a vacuum chamber, inside which a first cavity is provided. The first cavity is connected to a vacuum pump via a pipeline, and a valve is provided on the pipeline. A resonant cavity is provided inside the first cavity, and a second cavity is provided inside the resonant cavity. The end of the viewing window is sealed to the vacuum chamber and the resonant cavity respectively.

3. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 2, characterized in that, The sample carrying platform includes a two-degree-of-freedom slide, which is disposed in the second cavity, and the sliding part of the two-degree-of-freedom slide is connected to the bottom of the carrying part.

4. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 2, characterized in that, The millimeter-wave feed module includes a millimeter-wave source, which is located outside the vacuum cavity module. The output end of the millimeter-wave source is connected to one end of a waveguide, and the other end of the waveguide extends into the first cavity and is connected to a cone horn. The cone section of the cone horn extends into the second cavity.

5. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 1, characterized in that, The densification monitoring module includes a laser rangefinder, which is located outside the vacuum cavity module. The laser rangefinder's acquisition end obtains the sample's height change in real time through the viewing window and the support unit.

6. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 1, characterized in that, It also includes a temperature monitoring module and a reflection power detection module. The temperature monitoring module is located outside the vacuum cavity module, and its acquisition end monitors the temperature of the sample through a viewing window. The reflection power detection module is located inside the waveguide and is used to acquire the incident power and reflected power of the millimeter wave in real time.

7. The millimeter-wave vacuum lunar soil sintering apparatus according to claim 6, characterized in that, It also includes a control module, which is electrically connected to the temperature monitoring module, the reflection power detection module, the sample carrying platform, the millimeter wave feed module, and the densification monitoring module.

8. A millimeter-wave vacuum lunar soil sintering control method, employing the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: Place the lunar soil sample inside the support section and evacuate the vacuum chamber module to the preset vacuum level. The millimeter-wave feed module was activated to heat the lunar soil sample; During the heating process, the temperature distribution on the surface of the lunar soil sample, the reflected power in the millimeter wave transmission path, and the height change of the lunar soil sample were collected in real time. The control module dynamically adjusts the millimeter-wave output power and the spatial position of the lunar soil sample relative to the pyramidal horn based on the collected temperature distribution, reflected power, and height changes. When the surface temperature of the lunar soil sample is within the target sintering temperature range and maintained for a preset time, the real-time apparent sintering density estimated based on the height change reaches the target value, and the height shrinkage rate change rate is lower than the preset threshold, sintering is determined to be complete, and heating is stopped.

9. The control method according to claim 8, characterized in that, The dynamic adjustment includes: When the temperature difference on the sample surface exceeds a preset threshold, the position of the sample in the horizontal and / or vertical directions is adjusted to change the position of the sample relative to the cone-shaped horn radiation field, thereby adjusting the energy absorption distribution in different regions of the sample. When the reflected power rises to a preset threshold, reduce the output power or adjust the distance between the sample and the cone-shaped horn. When the rate of change of sample height exceeds the set range, the output power is reduced to control the rate of change.

10. The control method according to claim 8, characterized in that, Height shrinkage rate obtained from the height change Obtained from formula 1, （1） in, This represents the initial average height. This is the current average height; Under the conditions that the sample mass remains approximately constant, the supporting part constrains the lateral dimensions of the sample, and the sample cross-sectional area remains approximately constant, the height shrinkage rate is obtained based on the height change, and the real-time sintering density is estimated. Real-time sintering density It is obtained from calculation formula 2, （2） in, The initial density; When the real-time density reaches the target value and the rate of change of the height shrinkage is lower than the threshold, the control module determines that sintering is complete.

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