Liquid encapsulation method and apparatus for the preparation of magnesium-based thermoelectric materials

Abstract

The application discloses a liquid sealing method and device for magnesium-based thermoelectric material preparation, relates to the technical field of thermoelectric material preparation, and aims to solve the problems of high-temperature magnesium element volatilization, easy introduction of impurity pollution, easy adhesion and damage of the sealing structure, high preparation cost and insufficient operation safety in the magnesium-based thermoelectric material preparation process. The device comprises an inner and outer sealing crucible body, an automatic cover opening support, a top frame and a base, the inner and outer sealing crucible body adopts a double-layer crucible structure, the outer crucible body is matched with the outer crucible end cover through an annular groove and an annular convex strip, high-temperature liquid sealing is realized through cooperation with a sealing agent, the automatic cover opening support is fixedly connected with the outer crucible end cover, and the automatic separation of the end cover and the crucible body is realized through cooperation with a liftable base structure. The application can effectively isolate the sample from the sealing agent, inhibit high-temperature magnesium element volatilization, realize automatic cover opening without damage, and improve the material preparation purity and performance stability.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric material preparation, and specifically to a liquid sealing method and apparatus for preparing magnesium-based thermoelectric materials. Background Technology

[0002] Currently, the widely used technology for preparing magnesium-based thermoelectric materials is the combination of mechanical alloying and hot-pressing sintering. This method requires first alloying the raw materials through long-term high-energy ball milling, followed by sintering to obtain bulk materials. However, this method suffers from drawbacks such as long preparation cycle, low production efficiency, large raw material loss, and low yield per batch. Furthermore, the ball milling process easily introduces impurities, making it difficult to achieve large-scale industrial applications and failing to meet the needs of the industrialization and promotion of magnesium-based thermoelectric materials. High-temperature melting-annealing is a conventional technique for preparing metal-based thermoelectric materials. Compared to mechanical alloying, this method has advantages such as a shorter process flow, higher synthesis efficiency, and better product uniformity, making it a core technological direction for achieving low-cost, large-scale preparation of magnesium-based thermoelectric materials. However, in the practical application of magnesium-based thermoelectric materials, this process faces many technical challenges that urgently need to be addressed.

[0003] Firstly, there are issues with interfacial reactions and contamination. Existing melting processes typically involve vacuum sealing of quartz tubes before melting synthesis. However, magnesium is chemically highly reactive, and in the high-temperature molten state, the magnesium melt readily reacts with the quartz matrix, introducing impurities such as silicon and oxygen into the prepared sample. This not only contaminates the sample and deteriorates the intrinsic electrical transport properties of the material, but also significantly reduces the thermoelectric figure of merit. Even using quartz tubes with carbon-coated inner walls cannot completely isolate the magnesium melt from the quartz matrix, making it difficult to completely avoid interfacial reactions. Furthermore, quartz tubes are susceptible to magnesium corrosion and thermal stress concentration at high temperatures, which can lead to cracking and pose serious safety hazards, compromising the stability and operational safety of the preparation process.

[0004] Secondly, there is the issue of high-temperature volatilization of magnesium. Magnesium has a high saturated vapor pressure at the synthesis temperature, and it undergoes violent volatilization during high-temperature melting. This causes the stoichiometry of the melt to deviate significantly from the design value, resulting in a large number of magnesium vacancy defects. This leads to an imbalance in the charge carrier concentration of the material, making it impossible to achieve precise control over the thermoelectric properties of the material. The performance consistency between batches of samples is poor, making it difficult to stably obtain high-performance magnesium-based thermoelectric materials. To solve the interfacial reaction problem of quartz tubes, some existing technologies use high-purity tantalum tubes as sealing containers. Although tantalum tubes have excellent high-temperature resistance and chemical stability, which can effectively avoid reactions with magnesium melt, tantalum is a rare and precious metal with extremely high raw material procurement costs. Moreover, it is a disposable consumable in the preparation process, and the post-processing procedures after use are cumbersome. This not only significantly increases the material preparation cost but also makes it unsuitable for routine laboratory research and large-scale batch preparation.

[0005] Furthermore, existing melting processes, regardless of whether borosilicate glass or boron oxide systems are used as sealants in the sealed crucible structure, share common technical challenges: on the one hand, the sealant easily comes into direct contact with the prepared sample, leading to mutual diffusion and chemical reactions, causing sample contamination and performance degradation; on the other hand, after cooling and solidification, the sealant forms a strong adhesion to the crucible body and end caps. Opening the crucible after sintering requires mechanical force through knocking and prying, easily causing sample breakage and crucible damage, further increasing preparation costs and hindering automation. In summary, existing magnesium-based thermoelectric material preparation technologies cannot simultaneously achieve material purity, magnesium volatilization suppression, operational safety, preparation cost control, and automation levels, severely restricting the research and development and industrial application of high-performance magnesium-based thermoelectric materials. Therefore, those skilled in the art propose a liquid sealing method and apparatus for the preparation of magnesium-based thermoelectric materials that can effectively solve the above problems. Summary of the Invention

[0006] In view of the deficiencies mentioned above in the background technology, a technical solution is provided for a liquid sealing method and apparatus for the preparation of magnesium-based thermoelectric materials.

[0007] A liquid sealing device for the preparation of magnesium-based thermoelectric materials includes inner and outer sealing crucible bodies, an automatic opening bracket fixed around the outer and inner sealing crucible bodies, a top frame disposed above the inner and outer sealing crucible bodies, and a base disposed below the inner and outer sealing crucible bodies.

[0008] The inner and outer sealed crucible body includes an outer crucible body and an inner crucible body placed inside the outer crucible body. The upper port of the inner crucible body is covered with an inner crucible end cap, and the top port of the outer crucible body is covered with an outer crucible end cap. The upper end face of the outer crucible body is provided with a ring-shaped groove, and the lower end face of the outer crucible end cap is provided with a ring-shaped protrusion coupled to the inside of the ring-shaped groove.

[0009] The automatic lid opening bracket includes an upper ring fixed to the outer ring of the outer crucible end cap by multiple high-temperature alloy screws, multiple support bars fixed to the lower end face of the upper ring, and a lower ring fixed to the bottom of the support bars. Explosion-proof steel wire mesh is embedded and fixed in the space between the support bars.

[0010] The top frame includes a support located directly above the inner and outer sealed crucible bodies, and an upper high-temperature resistant pad fixed at the bottom of the support and in contact with the top surface of the outer crucible end cap, wherein the support and the upper high-temperature resistant pad are an integral structure.

[0011] The base includes a platform located directly below the inner and outer sealed crucible bodies, a lifting device fixed in the center of the platform, and a lower high-temperature resistant pad fixed on the telescopic shaft of the lifting device. The top of the lower high-temperature resistant pad is in contact with the bottom surface of the outer crucible body.

[0012] In the above technical solution, preferably: the outer crucible body, inner crucible body, inner crucible end cap, outer crucible end cap, annular protrusion and automatic opening bracket are made of high temperature resistant material, and the outer crucible body and inner crucible body are selected from graphite crucibles, alumina crucibles, boron nitride crucibles, zirconium oxide crucibles, platinum crucibles or cemented carbide crucibles.

[0013] In the above technical solution, preferably, the annular protrusion and the annular groove are circular or square rings, and their vertical cross-sectional shape is elliptical, semi-circular, triangular or trapezoidal.

[0014] In the above technical solution, preferably, the gap between the annular protrusion and the annular groove is filled with a sealant, and the sealant is selected from at least one of boron oxide, borosilicate glass or halide salt.

[0015] In the above technical solution, preferably, the contact seal between the outer crucible cover and the outer crucible body relies on the annular protrusion being inserted into the annular groove.

[0016] In the above technical solution, preferably: the inner and outer sealed crucible body is adapted to a furnace body, and the furnace body is selected from crucible furnace, muffle furnace, pit furnace, tube furnace, vacuum hot pressing sintering furnace, induction heating furnace, rapid hot pressing sintering furnace, hot isostatic pressing furnace (HIP) or spark plasma sintering system (SPS).

[0017] In the above technical solution, preferably, multiple threaded blind holes are provided in a ring array around the outer ring of the outer crucible end cap and the upper ring, and the threaded blind holes can be optical blind holes.

[0018] In the above technical solution, preferably, the top surface of the lower high-temperature resistant pad is provided with a groove that couples with the bottom end face of the outer crucible body.

[0019] In the above technical solution, preferably: the base has a cavity inside, the inner diameter of the lower ring at the bottom of the automatic opening bracket is larger than the outer diameter of the lifting device, and the outer diameter of the lower ring is larger than the inner diameter of the base below.

[0020] A liquid sealing method for the preparation of magnesium-based thermoelectric materials includes the following steps:

[0021] S1: After placing the reactants into the inner crucible, place the inner crucible into the outer crucible.

[0022] S2: Fill the gap between the annular convex strip and the annular groove with sealant;

[0023] S3: Control the lifting device to rise so that its bearing surface is higher than the platform to form a height difference, and then place the outer crucible containing the inner crucible on the lower high-temperature pad;

[0024] S4: Fix the automatic lid opening bracket to the outer crucible end cap to form a combination;

[0025] S5: Control the lifting device to continue rising until the upper surface of the outer crucible end cap contacts and presses against the bottom surface of the upper high-temperature resistant pad, the sealant melts under heat to form a seal, and sintering is carried out;

[0026] S6: Start the heating program. The sealant melts under heat, forming a sealed cavity in the crucible for sample synthesis.

[0027] S7: After the sintering process is completed, during the cooling process, when the temperature drops above the solidification point of the sealant, the lifting device is controlled to descend to the lower limit. During this process, the top of the upper ring is embedded in the crucible cover and cannot be separated in the fixed position. The lower ring descends with the lifting device until the bottom of the lower ring contacts the top of the platform. The lifting device then stops descending, realizing the automatic separation between the outer crucible end cap and the outer crucible body.

[0028] In the above technical solution, preferably: the trigger condition for controlling the descent of the lifting device in S7 is that the crucible temperature monitored in real time reaches above the melting point of the sealant.

[0029] As can be seen from the above technical solution, the liquid sealing method and apparatus for the preparation of magnesium-based thermoelectric materials provided by the present invention have the following beneficial effects compared with the prior art:

[0030] This technical solution utilizes a double-layered crucible structure to completely physically isolate the reactants from the sealant, fundamentally preventing cross-diffusion and chemical reactions between the sample, sealant, and crucible material. This avoids the introduction of impurities and ensures the purity and performance stability of the magnesium-based thermoelectric materials. Through the coupling of annular protrusions and annular grooves, a stable and reliable liquid sealing barrier is formed during heating using the molten sealant. This effectively suppresses the vigorous volatilization of magnesium at high temperatures, preventing deviations in the stoichiometric ratio from the design value and improving the controllability and batch consistency of the material's thermoelectric performance. Combined with an automatic lid-opening bracket and a lifting base structure, automatic and non-destructive separation of the crucible end cap and crucible body can be achieved while the sealant is molten. This avoids component damage and sample breakage caused by sealant solidification and adhesion, improving sample recovery rate, enabling crucible reuse, and reducing overall preparation costs. The device is directly adaptable to various conventional sintering furnaces without requiring equipment modification, simplifying the preparation process and improving automation, operational safety, and stability. It is suitable for the large-scale preparation of magnesium-based thermoelectric materials. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments of the present invention or the prior art will be briefly introduced and explained below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall structure of the liquid sealing device;

[0033] Figure 2 This is an exploded view of the internally and externally sealed crucible body;

[0034] Figure 3 This is a schematic diagram of an automatic lid-opening bracket;

[0035] Figure 4 This is a schematic diagram of the top frame;

[0036] Figure 5 This is a schematic diagram of the base.

[0037] Appendix Figure 1 - Appendix Figure 5 The correspondence between the components is as follows:

[0038] 1. Inner and outer sealed crucible bodies; 1-1. Outer crucible body; 1-2. Inner crucible body; 1-3. Inner crucible end cap; 1-4. Threaded blind hole; 1-5. Outer crucible end cap; 1-6. Annular convex strip; 1-7. Annular groove; 2. Automatic lid opening bracket; 2-1. Lower ring; 2-2. Support bar; 2-3. Upper ring; 2-4. High-temperature alloy screw; 2-5. Explosion-proof steel wire mesh; 3. Top frame; 3-1. Bracket; 3-2. Upper high-temperature resistant pad; 4. Base; 4-1. Platform; 4-2. Lifting device; 4-3. Lower high-temperature resistant pad. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In order to provide a clearer explanation and description of the technical solutions and implementation methods of the present invention, the following describes specific embodiments that implement the preferred technical solutions of the present invention.

[0040] The liquid sealing device for preparing magnesium-based thermoelectric materials disclosed in this embodiment includes inner and outer sealing crucible bodies 1, an automatic lid-opening bracket 2 fixed around the outer and inner sealing crucible bodies 1, a top frame 3 disposed above the inner and outer sealing crucible bodies 1, and a base 4 disposed below the inner and outer sealing crucible bodies 1; the inner and outer sealing crucible bodies 1 include an outer crucible body 1-1, an inner crucible body 1-2 placed inside the outer crucible body 1-1, an inner crucible end cap 1-3 covering the upper port of the inner crucible body 1-2, an outer crucible end cap 1-5 covering the top port of the outer crucible body 1-1, and the upper end of the outer crucible body 1-1... The inner surface of the outer crucible end cap 1-5 has a ring-shaped groove 1-7. The lower end face of the outer crucible end cap 1-5 has a ring-shaped protrusion 1-6 coupled to the inner surface of the ring-shaped groove 1-7. The outer ring of the outer crucible end cap 1-5 has four threaded blind holes 1-4 arranged in a ring array around its outer perimeter. The automatic opening bracket 2 includes an upper ring 2-3 fixed to the outer ring of the outer crucible end cap 1-5 by four screws 2-4, four support bars 2-2 fixed to the lower end face of the upper ring 2-3, and a lower ring 2-1 fixed to the bottom of the support bars 2-2. Explosion-proof steel wire mesh 2-5 is embedded and fixed in the space between the support bars 2-2. The outer ring 2-3 has four threaded blind holes 1-4 arranged in a ring around its outer perimeter, corresponding to the outer crucible end cap 1-5; the top frame 3 includes a support 3-1 located directly above the inner and outer sealed crucible bodies 1, and an upper high-temperature resistant pad 3-2 fixed to the bottom of the support 3-1 in contact with the top surface of the outer crucible end cap 1-5; the base 4 includes a platform 4-1 located directly below the inner and outer sealed crucible bodies 1, a lifting device 4-2 fixed in the center of the platform 4-1, and a lower high-temperature resistant pad 4-3 fixed on the telescopic shaft of the lifting device 4-2, the top of the lower high-temperature resistant pad 4-3 being flush with the outer crucible body 1. The bottom surface of the -1 is in contact with the top surface of the high-temperature resistant pad 4-3, which has a groove coupling with the bottom end face of the outer crucible body 1-1. The interior of the platform 4-1 has a chamber. The inner diameter of the lower ring 2-1 at the bottom of the automatic opening bracket 2 is larger than the outer diameter of the lifting device 4-2, and the outer diameter of the lower ring 2-1 is larger than the inner diameter of the platform 4-1 below. The vertical cross-sectional shape of the annular protrusion 1-6 and the annular groove 1-7 is elliptical, semi-circular, triangular, or trapezoidal, etc. The gap between the annular protrusion 1-6 and the annular groove 1-7 is filled with sealant. The inner and outer sealed crucible bodies 1 are adapted to the corresponding furnace bodies. In actual use, the top frame 3 is assembled with the fixed frame part of the furnace body, and the base 4 is assembled with the fixed platform part of the furnace body, so that the entire device and the furnace body form a compatible fitting structure. The corresponding magnesium-based thermoelectric material preparation sealing sintering and automatic opening operation can be completed in the furnace body chamber. The adapted furnace body can correspond to different sintering equipment types and meet different preparation process requirements.

[0041] The liquid sealing method for preparing magnesium-based thermoelectric materials corresponding to this embodiment is applicable to the aforementioned liquid sealing device for preparing magnesium-based thermoelectric materials. This method includes the following steps.

[0042] Step S1: After placing the reactants inside the inner crucible 1-2, cover the upper end of the inner crucible 1-2 with the end cap 1-3. Then, place the inner crucible 1-2 inside the outer crucible 1-1, positioning the inner crucible 1-2 at the center of the outer crucible 1-1. A corresponding gap is left between the outer wall of the inner crucible 1-2 and the inner wall of the outer crucible 1-1 to avoid direct contact and mutual interference. Simultaneously, the closing of the end cap 1-3 ensures the reactants are contained within the enclosed space of the inner crucible 1-2. The inner crucible forms a physical barrier with the subsequent sealant, preventing contact or interaction between the reactants and the sealant, reducing the introduction of impurities during the preparation process, and preventing the volatilization of reactants from affecting the sealing structure. After the inner crucible end cap 1-3 is closed, it can further prevent the reactants from volatilizing into the internal space of the outer crucible body 1-1 at high temperatures, reducing the loss of volatile components. At the same time, it prevents the volatilized materials from contacting the outer crucible body 1-1, the outer crucible end cap 1-5, and the sealant, further reducing the possibility of impurity introduction and maintaining the performance stability of the prepared materials.

[0043] Step S2: Fill the gap between the annular protrusion 1-6 and the annular groove 1-7 with sealant. The sealant fills the interior of the annular groove 1-7, corresponding to the position directly below the annular protrusion 1-6 on the lower end face of the outer crucible end cap 1-5. This allows the annular protrusion 1-6 to extend into the annular groove 1-7 and make full contact with the sealant when the outer crucible end cap 1-5 is subsequently closed with the outer crucible body 1-1, providing a basis for subsequent liquid sealing. The amount of sealant filled corresponds to the internal space of the annular groove 1-7, ensuring full contact between the annular protrusion 1-6 and the sealant when it extends into the annular groove 1-7. After heating and melting, the sealant can completely fill all gaps between the annular protrusion 1-6 and the annular groove 1-7. A seamless liquid sealing ring is formed, achieving complete sealing of the internal cavity of the outer crucible body 1-1. The elliptical, semi-circular, triangular, or trapezoidal vertical cross-section structures of the annular protrusion 1-6 and the annular groove 1-7 allow the molten sealant to be evenly filled in the gap between the annular groove 1-7 and the annular protrusion 1-6 during subsequent pressurization and heating, forming a continuous sealing structure. At the same time, it can reduce the mechanical resistance between the structures during the subsequent separation process, facilitating the separation of the outer crucible end cap 1-5 from the outer crucible body 1-1. The arc-shaped contact surface can reduce the viscous resistance between the structures, making the separation process of the outer crucible end cap 1-5 from the outer crucible body 1-1 smoother and avoiding component damage caused by structural adhesion.

[0044] Step S3: Control the lifting device 4-2 to rise to a certain height, so that the bearing surface of the lower high-temperature resistant pad 4-3 fixed on the telescopic shaft of the lifting device 4-2 forms a height difference with the upper surface of the platform 4-1. Then, place the outer crucible body 1-1 containing the inner crucible body 1-2 on the lower high-temperature resistant pad 4-3, so that the bottom end face of the outer crucible body 1-1 is coupled and positioned with the groove on the top surface of the lower high-temperature resistant pad 4-3. This can limit the horizontal movement of the outer crucible body 1-1, ensuring that the outer crucible body 1-1 remains stationary during the lifting process. The movement is kept vertical to avoid horizontal displacement that could cause misalignment between the outer crucible body 1-1 and the inner crucible body 1-2, and the outer crucible end cap 1-5. This ensures stability during device operation. At the same time, the inner diameter of the chamber inside the platform 4-1 is the same as that of the lower ring 2-1, which allows the telescopic shaft of the lifting device 4-2 to move without obstruction during lifting. It also ensures that when the lower ring 2-1 contacts the platform 4-1, the contact area is uniform and the force is stable, preventing excessive local stress that could cause component deformation.

[0045] Step S4: Align the upper ring 2-3 of the automatic lid-opening bracket 2 with the outer crucible end cap 1-5, ensuring a one-to-one correspondence between the threaded blind holes 1-4 on the upper ring 2-3 and the threaded blind holes 1-4 on the outer crucible end cap 1-5. Then, secure the upper ring 2-3 and the outer crucible end cap 1-5 with four screws 2-4, forming a rigid assembly between the automatic lid-opening bracket 2 and the outer crucible end cap 1-5. This assembly prevents relative displacement in both the vertical and horizontal directions, ensuring stable force transmission during subsequent lid opening. The four support bars 2-2 of the automatic lid-opening bracket 2 are evenly distributed circumferentially along the upper ring 2-3. The force transmitted by the support bar 2-2 is evenly distributed between the upper ring 2-3 and the lower ring 2-1, which avoids uneven force distribution during the subsequent opening process, resulting in tilting or jamming of the outer crucible end cap 1-5. This improves the smoothness and reliability of the automatic opening process. The explosion-proof steel wire mesh 2-5 embedded between the support bars 2-2 forms a continuous protective structure, covering the outer area of ​​the automatic opening bracket 2. In the event of abnormal chamber pressure during the preparation process, it can effectively prevent component breakage and material splashing, avoiding damage to the internal structure of the furnace body, and improving the safety protection level of the operation process.

[0046] Step S5: Control the lifting device 4-2 to continue rising, driving the lower high-temperature resistant pad 4-3 and the outer crucible body 1-1 placed on the lower high-temperature resistant pad 4-3 to rise synchronously until the upper surface of the outer crucible end cap 1-5 contacts and presses against the bottom surface of the upper high-temperature resistant pad 3-2. At this time, the annular protrusion 1-6 on the lower end face of the outer crucible end cap 1-5 fully extends into the annular groove 1-7 on the upper end face of the outer crucible body 1-1, compressing the sealant in the annular groove 1-7. After the outer crucible end cap 1-5 contacts and presses against the upper high-temperature resistant pad 3-2, the entire inner and outer sealed crucible body 1 can be positioned between the upper high-temperature resistant pad 3-2 and the lower high-temperature resistant pad 4-3, forming a stable The clamping structure allows for heating of the inner and outer sealed crucible bodies 1 during sintering via the upper high-temperature resistant pad 3-2 and the lower high-temperature resistant pad 4-3, meeting the temperature requirements of the sintering process. Simultaneously, the environmental atmosphere within the furnace cavity can be adjusted according to process requirements to further prevent oxidation of the reactants and improve the purity of the prepared materials. During subsequent sintering heating, the sealant melts upon heating to form a liquid sealing structure, sealing the gap between the outer crucible body 1-1 and the outer crucible end cap 1-5, thus forming a sealed chamber inside the outer crucible body 1-1. This effectively suppresses the escape of volatile components from the reactants during the preparation process and maintains the chemical stability of the reactants.

[0047] Step S6: Then, start the sintering program of magnesium-based thermoelectric material, heat the reaction system to the reaction temperature, and then hold it at the temperature for 30-60 min to melt and synthesize the sample, and complete the sintering preparation in the furnace chamber;

[0048] Step S7: After the sintering process is completed, during the cooling process, when the crucible temperature monitored in real time reaches above the melting point of the sealant, the lifting device 4-2 is controlled to descend to the lower limit. During this process, the lifting device 4-2 drives the lower high-temperature pad 4-3 and the outer crucible body 1-1 to descend synchronously. When the bottom of the lower ring 2-1 at the bottom of the automatic opening bracket 2 contacts the top of the platform 4-1, the combination of the automatic opening bracket 2 and the outer crucible end cap 1-5 stops descending, while the lifting device 4-2 continues to drive the outer crucible body 1-1 to descend, causing a relative displacement between the outer crucible body 1-1 and the outer crucible end cap 1-5. At this time, the sealant in the molten state cannot prevent the generation of this relative displacement, realizing the automatic separation between the outer crucible end cap 1-5 and the outer crucible body 1-1.

[0049] During the cooling process, when the crucible temperature is above the melting point of the sealant, the sealant is still in a molten or viscous flow state. Separating the outer crucible end cap 1-5 from the outer crucible body 1-1 at this time avoids adhesion caused by the sealant's cooling and solidification, significantly reducing the force required for separation. It also prevents damage to components caused by the adhesive force of the solidified sealant on the structure. The descent of the lifting device 4-2 can be controlled by a program to maintain a stable descent speed, preventing material shaking and spillage within the inner crucible body 1-2 due to excessive descent speed. This ensures a smooth and controllable separation process between the outer crucible body 1-1 and the outer crucible end cap 1-5. The automatic separation process is entirely completed within the furnace chamber, eliminating the need for manual operation and avoiding the risk of operator contact with high-temperature components. After separation, the cooling program continues until the furnace chamber and the entire device reach room temperature. Then, the furnace chamber can be opened, and the automatically opened parts can be removed sequentially. The assembly of the cover bracket 2 and the outer crucible end cap 1-5, the outer crucible body 1-1, and the inner crucible body 1-2 are then removed from the outer crucible body 1-1 to complete the preparation of magnesium-based thermoelectric materials. After separation, the device components can be easily disassembled after cooling to room temperature without the need for external force such as knocking or prying, and the prepared magnesium-based thermoelectric materials can be completely removed. At the same time, each component of the device can be reused after simple cleaning, reducing the overall cost of the preparation process. The entire preparation process, from material loading, sealing and sintering to automatic opening, cooling and sample unloading, can be completed continuously through program control, improving the automation level and batch repeatability of the preparation process. In addition, the device does not require electrical or mechanical modifications to the furnace body; the corresponding functions can be achieved simply through the structure of the device itself. It can be adapted to various types of sintering equipment and has a wide range of applications, and can be used for the preparation of various volatile and highly reactive metal-based functional materials.

[0050] This invention is not limited to the preferred embodiments described above. Anyone should understand that structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention. Finally, it should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effects and objectives of this application, should still fall within the scope of the technical content disclosed in this application.

Claims

1. A liquid sealing device for the preparation of magnesium-based thermoelectric materials, characterized in that: It includes an inner and outer sealed crucible body (1), an automatic lid opening bracket (2) fixed around the inner and outer sealed crucible body (1), a top frame (3) set above the inner and outer sealed crucible body (1), and a base (4) set below the inner and outer sealed crucible body (1). The inner and outer sealed crucible body (1) includes an outer crucible body (1-1) and an inner crucible body (1-2) placed inside the outer crucible body (1-1). The upper port of the inner crucible body (1-2) is covered with an inner crucible end cap (1-3), and the top port of the outer crucible body (1-1) is covered with an outer crucible end cap (1-5). The upper end face of the outer crucible body (1-1) is provided with a ring-shaped groove (1-7), and the lower end face of the outer crucible end cap (1-5) is provided with a ring-shaped protrusion (1-6) coupled to the inside of the ring-shaped groove (1-7). A temperature measuring hole is left at the outer center wall of the outer crucible body (1-1). The automatic lid opening bracket (2) includes an upper ring (2-3) fixed to the outer ring of the outer crucible end cap (1-5) by multiple high-temperature alloy screws (2-4), multiple support bars (2-2) fixed to the lower end face of the upper ring (2-3), and a lower ring (2-1) fixed to the bottom of the support bars (2-2). Explosion-proof steel wire mesh (2-5) is embedded and fixed in the space between the support bars (2-2). The top frame (3) includes a support (3-1) located directly above the inner and outer sealed crucible bodies (1), and an upper high-temperature resistant pad (3-2) fixed at the bottom of the support (3-1) in contact with the top surface of the outer crucible end cap (1-5). The base (4) includes a platform (4-1) located directly below the inner and outer sealed crucible bodies (1), a lifting device (4-2) fixed in the center of the platform (4-1), and a lower high-temperature resistant pad (4-3) fixed on the telescopic shaft of the lifting device (4-2). The top of the lower high-temperature resistant pad (4-3) is in contact with the bottom surface of the outer crucible body (1-1).

2. The liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The outer crucible body (1-1), inner crucible body (1-2), inner crucible end cap (1-3), outer crucible end cap (1-5), annular protrusion (1-6), annular groove (1-7), and automatic lid opening bracket (2) are made of high-temperature resistant materials. The outer crucible body (1-1) and inner crucible body (1-2) are graphite crucibles, alumina crucibles, boron nitride crucibles, zirconium oxide crucibles, platinum crucibles, or hard alloy crucibles.

3. The liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The annular protrusion (1-6) and the annular groove (1-7) are circular or square rings, and their vertical cross-sections are elliptical, semi-circular, triangular or trapezoidal.

4. A liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The gap between the annular protrusion (1-6) and the annular groove (1-7) is filled with a sealant selected from at least one of boron oxide, borosilicate glass, or halide salt.

5. A liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The inner and outer sealed crucible body (1) is adapted to be equipped with a furnace body, wherein the furnace body is selected from crucible furnace, muffle furnace, pit furnace, tube furnace, vacuum hot pressing sintering furnace, induction heating furnace, rapid hot pressing sintering furnace, hot isostatic pressing furnace (HIP) or spark plasma sintering system (SPS).

6. A liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: Multiple threaded blind holes (1-4) are provided around the outer ring of the outer crucible end cap (1-5) and the upper ring (2-3).

7. A liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The top surface of the lower high-temperature resistant pad (4-3) is provided with a groove that couples with the bottom end face of the outer crucible body (1-1).

8. A liquid sealing device for the preparation of magnesium-based thermoelectric materials according to claim 1, characterized in that: The base (4-1) has a cavity inside. The inner diameter of the lower ring (2-1) at the bottom of the automatic cover opening bracket (2) is larger than the outer diameter of the lifting device (4-2), and the outer diameter of the lower ring (2-1) is larger than the inner diameter of the base (4-1) below.

9. A liquid sealing method for the preparation of magnesium-based thermoelectric materials, characterized in that: The method is applicable to a liquid sealing device for the preparation of magnesium-based thermoelectric materials according to any one of claims 1-8, and the method comprises the following steps: S1: After placing the reactants into the inner crucible body (1-2), place the inner crucible body (1-2) into the outer crucible body (1-1); S2: Fill the gap between the annular convex strip (1-6) and the annular groove (1-7) with sealant; S3: Control the lifting device (4-2) to rise so that its bearing surface is higher than the platform (4-1) to form a height difference, and then place the outer crucible body (1-1) containing the inner crucible body (1-2) on the lower high-temperature pad (4-3); S4: Fix the automatic lid opening bracket (2) to the outer crucible end cap (1-5) to form a combination; S5: Control the lifting device (4-2) to continue rising until the upper surface of the outer crucible end cap (1-5) contacts and presses against the bottom surface of the upper high-temperature resistant pad (3-2); S6: Start the heating program. The sealant melts under heat, forming a sealed cavity in the crucible for sample synthesis. S7: After the sintering process is completed, during the cooling process, when the temperature drops above the solidification point of the sealant, the lifting device (4-2) is controlled to descend to the lower limit. During this process, the lower ring (2-1) descends with the lifting device (4-2) until the bottom of the lower ring (2-1) contacts the top of the platform (4-1). The lifting device (4-2) then stops descending, realizing the automatic separation between the outer crucible end cap (1-5) and the outer crucible body (1-1).

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