Multi-layer efficient heat preservation microwave cavity suitable for vacuum environment

Abstract

The invention discloses a multi-layer efficient heat preservation microwave cavity suitable for a vacuum environment. The multi-layer efficient heat preservation microwave cavity comprises a shell, and the shell comprises a reflecting shell and at least one heat insulation shell which are sequentially sleeved together at intervals from inside to outside; the inner layer of the heat insulation shell is made of a heat reflection material, and the outer layer of the heat insulation shell is made of a thermal insulation material; a heat insulation table is arranged at the bottom in the reflecting shell; a crucible is arranged on the heat insulation table; the crucible is made of a microwave transparent material which is resistant to high temperature, uniform in heat conduction and not prone to reacting with a to-be-sintered material, the top of the crucible is open, and heating pieces are distributed outside the crucible; the heating sheet is used for generating heat under microwave excitation; a microwave generator is arranged outside the shell, the output end of the microwave generator is connected with a microwave conduction pipe, and the microwave conduction pipe extends into the shell and points to the interior of the crucible. The cavity is good in heat preservation, microwave energy is fully utilized, a temperature field is evenly distributed, temperature can be rapidly increased, and the sintering energy efficiency and the sintering efficiency are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of microwave sintering, and in particular relates to a multi-layer high-efficiency heat-insulating microwave cavity suitable for a vacuum environment. Background Art

[0002] Microwave sintering utilizes the unique microwave wavelengths coupled with the fundamental microstructure of a material to generate heat. Dielectric losses in the material heat the entire material to the sintering temperature, achieving densification. Microwave sintering technology offers rapid and uniform heating, high energy efficiency, selective heating, the absence of a protective atmosphere, and a wide range of applications. Consequently, it has a wide range of applications, including but not limited to the preparation of high-performance ceramics, nanomaterials, metal-based powder metallurgy materials, and microwave self-propagating high-temperature synthesis materials.

[0003] Vacuum microwave sintering has many advantages: First, vacuum microwave sintering can avoid the influence of air on the sintered material, and the coupled induction heating form can make the green body temperature more uniform and efficient, thereby improving the uniformity and density of the product; second, since heat transfer in a vacuum can only be carried out through radiation, it can effectively reduce heat loss and improve energy utilization.

[0004] In the vacuum environment of the lunar surface, vacuum microwave sintering has the advantages of fast heating speed, large sintering depth, overall sintering molding and high energy utilization compared with other sintering methods. Therefore, it is considered to be a lunar soil processing and molding technology with great potential: on the one hand, the lunar soil layer covering the lunar surface cannot be directly used for lunar engineering construction. Through vacuum microwave sintering technology, the lunar soil can be solidified into structural materials that can be used for lunar base construction; on the other hand, vacuum microwave sintering technology can be used for large-scale in-situ molding of lunar soil on the lunar surface, such as road hardening, launch site / landing site construction, and other large-scale rapid solidification that does not require high precision.

[0005] The temperature of vacuum microwave sintering is relatively high, usually reaching above 1000°C. Although the vacuum environment blocks heat convection, the large temperature difference between the inside and outside of the sintering furnace cavity will still cause a large amount of heat loss through thermal radiation and heat conduction. Especially in the sintering process of lunar construction materials, efficient energy utilization is particularly important, which places higher requirements on the thermal insulation of the sintering furnace cavity.

[0006] Current vacuum microwave equipment is typically equipped with insulation devices designed primarily for auxiliary heating, with insulation taking a secondary role. While these devices offer certain advantages in sintering, they suffer from significant energy loss. For example, patent CN215413159U describes a vacuum microwave sintering furnace that uses a heating liner to absorb microwave energy and transfer heat to the material as a secondary heating source. However, since the microwave energy is first absorbed by the heating liner and then transferred to the sintered material, significant energy loss occurs. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment, which has good heat preservation, fully utilizes microwave energy, has uniform temperature field distribution, can heat up quickly, and significantly improves sintering energy efficiency and sintering efficiency.

[0008] The technical solution adopted in the present invention is: A multi-layer, high-efficiency, thermally insulating microwave cavity suitable for a vacuum environment comprises a sealed shell, the shell comprising a reflective shell and at least one thermal insulation shell which are sequentially spaced and nested from the inside to the outside; the reflective shell is made of microwave reflecting material for reflecting microwaves inward; the inner layer of the thermal insulation shell is made of heat reflecting material and the outer layer is made of thermal insulation material for insulating the interior of the reflective shell; an insulation platform is provided at the bottom of the reflective shell, and a crucible is provided on the insulation platform; the insulation platform is used to support the crucible and reduce heat conduction from the crucible to the reflective shell; the crucible is used to hold material to be sintered and is made of microwave transparent material that is resistant to high temperatures, can conduct heat evenly, and is not easy to react with the material to be sintered, the top of the crucible is open, and heating plates are distributed on the outside; the heating plates are used to generate heat under microwave excitation; a microwave generator is provided outside the shell, the output end of the microwave generator is connected to a microwave conduction tube, the microwave conduction tube extends into the shell and points into the crucible; the microwave generator is used to generate microwaves, and the microwave conduction tube is used to efficiently conduct microwaves.

[0009] Preferably, the microwave reflecting material used in the reflective shell is selected from smooth molybdenum, smooth tungsten and carbon fiber reinforced composite materials, with a thickness of 1-3 mm; the heat reflecting material used in the inner layer of the thermal insulation shell is selected from aluminum-based ceramic reinforced reflective coating, graphite reflective coating, aluminum oxide coating, titanium oxide coating and zirconium oxide coating, with a thickness of 0.2-0.5 mm; the thermal insulation material used in the outer layer of the thermal insulation shell is aluminum oxide fiber cotton, with a thickness of 30-50 mm; the interval between the reflective shell and the thermal insulation shell, and between adjacent thermal insulation shells is 10-30 mm.

[0010] Preferably, the reflective shell and the heat-insulating shell, and adjacent heat-insulating shells are connected in an interval-fitting manner through distributed screws and nuts. The screws pass through the shell, and the nuts are fitted on the screws and clamped on both sides of the reflective shell and the heat-insulating shell.

[0011] Preferably, the lower part of the crucible is thickened to form a base, and the upper part is a circle of thin-walled tubes, and the heating plates are evenly distributed and attached to the outer wall of the thin-walled tubes.

[0012] Preferably, the heating plate is detachably inserted into a groove connecting the outer wall of the thin-walled tube and the top surface of the base.

[0013] Preferably, the contact area between the heating plate and the outer wall of the thin-walled tube does not exceed 1 / 2 of the area of ​​the outer wall of the thin-walled tube.

[0014] Preferably, the shell is a split structure, the bottom surface of the shell is separated from the other surfaces, and the other surfaces of the shell are connected as a whole and can be covered on the bottom surface of the shell.

[0015] Preferably, the shell is in the shape of a vertical cylinder, the crucible is in the shape of a vertical cylinder and is located in the center of the shell, the microwave generator and the microwave conduction tube are installed on the top of the shell, and the microwave conduction tube points downward to the center of the crucible.

[0016] Preferably, the four sides of the heat insulating platform are supported on the inner bottom surface of the reflective shell, and the lower middle part is separated from the inner bottom surface of the reflective shell by a cavity. The crucible is arranged on the heat insulating platform and is located in the corresponding area of ​​the cavity.

[0017] Preferably, the microwave generator can precisely control the output power and frequency to precisely regulate the heating process.

[0018] The beneficial effects of the present invention are: The shell has a reflective shell and at least one heat-insulating shell. The reflective shell can reflect microwaves inward to prevent microwave leakage and ensure that microwave energy is efficiently utilized in the reflective shell. The inner layer of the heat-insulating shell can reflect most of the thermal radiation energy into the reflective shell. The outer layer of the heat-insulating shell can provide additional heat-insulating protection, thereby ensuring that the temperature in the reflective shell is stable. The reflective shell combined with the heat-insulating shell can effectively maintain the required high-temperature environment; the top of the crucible is open, and the material to be sintered can directly receive the microwaves conducted by the microwave conduction tube. The crucible is made of microwave transparent material that can conduct heat evenly. On the one hand, it does not affect the reflected microwaves passing through and acting on the material to be sintered. On the other hand, on the sintering material, the heating plate generates heat under microwave excitation, and the crucible can evenly conduct the heat generated by the heating plate to the material to be sintered, that is, the material to be sintered is affected by both the directly received microwaves and the reflected microwaves, as well as the heat conduction of the crucible. The heat insulation table can reduce the heat conduction from the crucible to the reflective shell, and the outer shell can provide heat insulation protection. Compared with the secondary heat transfer method, microwave energy acts on the material to be sintered almost directly and indirectly, making full use of microwave energy, and the temperature field is evenly distributed. Under multiple actions, the temperature can rise rapidly, which significantly improves the sintering energy efficiency and sintering efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 This is a cross-sectional view of the multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment in the present invention, in a closed state.

[0021] Figure 2 This is a cross-sectional view of the multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment in the present invention, in the open state.

[0022] Figure 3 It is a cross-sectional view of the shell in the present invention.

[0023] Figure 4 It is a disassembled diagram of the crucible and the heating plate in the present invention.

[0024] In the figure: 1-microwave generator; 2-microwave conduction tube; 3-reflection shell; 31-microwave reflective material; 4-thermal insulation shell; 41-heat reflective material; 42-thermal insulation material; 5-spacer; 6-screw; 7-thermal insulation platform; 8-crucible; 81-base; 82-thin-walled cylinder; 9-heating plate; 10-nut; a-groove. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0028] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0029] Example 1 This embodiment discloses a multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment, such as Figure 1 and Figure 2As shown, it includes a shell, an insulating platform 7, a crucible 8, a heating plate 9, a microwave generator 1 and a microwave conduction tube 2; wherein: the shell is a closed structure that can be opened and closed, and the shell includes a reflective shell 3 and a heat-insulating shell 4. A reflective shell 3 and at least one heat-insulating shell 4 are sequentially spaced together from the inside to the outside. The reflective shell 3 uses a microwave reflective material 31, the inner layer of the heat-insulating shell 4 uses a heat-reflecting material 41, and the outer layer uses a heat-insulating material 42. The reflective shell 3 is used to reflect microwaves inwardly, and the heat-insulating shell 4 is used to keep the interior of the reflective shell 3 warm. Figures 1 to 3 ; Insulation platform 7 is provided at the bottom of the reflective shell 3, the insulation platform 7 is used to support the crucible 8 and reduce the heat conduction from the crucible 8 to the reflective shell 3, see Figure 1 and Figure 2 Crucible 8 is provided on the heat-insulating platform 7, crucible 8 is used to hold the material to be sintered, crucible 8 is made of high temperature resistant, uniform heat conduction, not easy to react with the material to be sintered microwave transparent material, the top of the crucible 8 is open, see Figure 1 、 Figure 2 and Figure 4 The heating plate 9 is distributed outside the crucible 8, and the heating plate 9 is used to generate heat under microwave excitation. Figure 1 、 Figure 2 and Figure 4 ; The microwave generator 1 is provided outside the housing, and the microwave generator 1 is used to generate microwaves, see Figure 1 and Figure 2 ; The microwave conduction tube 2 is connected to the output end of the microwave generator 1, the microwave conduction tube 2 extends into the shell and points to the crucible 8, the microwave conduction tube 2 is used to efficiently conduct microwaves, see Figure 1 and Figure 2 .

[0030] In the above scheme: the shell has a reflective shell 3 and at least one thermal insulation shell 4. The reflective shell 3 can reflect microwaves inward to prevent microwave leakage and ensure that the microwave energy is efficiently utilized in the reflective shell 3. The inner layer of the thermal insulation shell 4 can reflect most of the thermal radiation energy into the reflective shell 3. The outer layer of the thermal insulation shell 4 can provide additional thermal insulation protection, thereby ensuring that the temperature in the reflective shell 3 is stable. The reflective shell 3 combined with the thermal insulation shell 4 can effectively maintain the required high temperature environment. The top of the crucible 8 is open, and the material to be sintered can directly receive the microwaves conducted by the microwave conduction tube 2. The crucible 8 is made of microwave transparent material that can conduct heat evenly. On the one hand, it does not affect the reflected microwaves passing through and acting on the material to be sintered. On the other hand, the heating plate 9 generates heat under microwave excitation, and the crucible 8 can evenly conduct the heat generated by the heating plate 9 to the material to be sintered. That is, the material to be sintered is affected by both the directly received microwaves and the reflected microwaves, as well as the heat conduction of the crucible 8. The heat insulation platform 7 can reduce the heat conduction from the crucible 8 to the reflective shell 3, and the shell can provide heat insulation protection. Compared with the secondary heat transfer method, the microwave energy acts on the material to be sintered almost directly and indirectly, making full use of the microwave energy, the temperature field is evenly distributed, and the temperature can rise rapidly under multiple actions, which significantly improves the sintering energy efficiency and sintering efficiency.

[0031] like Figures 1 to 3 As shown, in this embodiment, two heat-insulating shells 4 are used. The specific number of heat-insulating shells 4 is set according to actual needs, and two heat-insulating shells 4 are sufficient to meet the heat-insulating effect of this embodiment.

[0032] like Figures 1 to 3 As shown, in this embodiment, preferably, the reflective shell 3 and the insulating shell 4, as well as adjacent insulating shells 4, are connected in a spaced, nested manner via distributed screws 6 and nuts 10. The screws 6 pass through the shells, and the nuts 10 fit over the screws 6 and clamp onto both sides of the reflective shell 3 and the insulating shell 4. This arrangement not only securely mounts the reflective shell 3 and the insulating shell 4 together, but also allows for adjustable spacing. The screws 6 and nuts 10 can be made of zirconium oxide, silicon nitride, or aluminum oxide ceramics.

[0033] like Figure 1 、 Figure 2 and Figure 4As shown, in this embodiment, preferably: the lower part of the crucible 8 is thickened to form a base 81, and the upper part is a circle of thin-walled tubes 82. The heating plates 9 are evenly distributed and attached to the outer wall of the thin-walled tube 82. The thickened base 81 can play a role in heat storage, which can not only conduct heat to the bottom of the sintered material, but also prevent heat from radiating downward. The thin-walled tube 82 can minimize the obstruction to the reflected microwaves, so that the reflected microwaves can act more on the sintered material. The uniform distribution of the heating plates 9 can achieve uniform heating. The heating plates 9 can be detachably inserted into the groove a connecting the outer wall of the thin-walled tube 82 and the top surface of the base 81, which is convenient for loading and unloading. The contact area between the heating plate 9 and the outer wall of the thin-walled tube 82 does not exceed 1 / 2 of the area of ​​the outer wall of the thin-walled tube 82, ensuring sufficient passage area for the reflected microwaves. The crucible 8 can be made of alumina, and the heating plates 9 can be made of silicon carbide.

[0034] like Figure 1 、 Figure 2 and Figure 4 As shown, in this embodiment, preferably: the shell is in a vertical cylindrical shape as a whole, the crucible 8 is in a vertical cylindrical shape as a whole and is located in the center of the shell, the microwave generator 1 and the microwave conduction tube 2 are installed on the top of the shell, and the microwave conduction tube 2 points downward to the center of the crucible 8. This arrangement can make the reflected microwaves more concentrated on the material to be sintered in the center of the crucible 8.

[0035] like Figure 1 and Figure 2 As shown, in this embodiment, preferably: the four sides of the heat insulating platform 7 are supported on the inner bottom surface of the reflective shell 3, and the lower middle portion is separated from the inner bottom surface of the reflective shell 3 by a cavity. The crucible 8 is arranged on the heat insulating platform 7 and is located in the corresponding area of ​​the cavity. This arrangement can further reduce heat conduction from the crucible 8 to the reflective shell 3. The heat insulating platform 7 can be made of mullite.

[0036] like Figure 2 As shown, in this embodiment, preferably: the shell is a split structure, the bottom surface of the shell is separated from the other surfaces, and the other surfaces of the shell are connected as a whole and can be covered on the bottom surface of the shell. This structure can smoothly place the material to be sintered, has a simple structure, and does not require a hatch and door for placing the material to be sintered on the shell.

[0037] In this embodiment, preferably, the microwave generator 1 can accurately control the output power and frequency so as to precisely regulate the heating process. The microwave conduction tube 2 can be a high temperature resistant hollow metal tube.

[0038] Example 2 This embodiment discloses the materials of the reflective shell 3 and the heat-insulating shell 4 in the first embodiment.

[0039] In this embodiment, the microwave reflecting material 31 used in the reflective shell 3 is selected from polished molybdenum, polished tungsten and carbon fiber reinforced composite materials, with a thickness of 1-3 mm; the heat reflecting material 41 used in the inner layer of the insulating shell 4 is selected from aluminum-based ceramic reinforced reflective coating, graphite reflective coating, aluminum oxide coating, titanium oxide coating and zirconium oxide coating, with a thickness of 0.2-0.5 mm; the thermal insulation material 42 used in the outer layer of the insulating shell 4 is aluminum oxide fiber cotton, with a thickness of 30-50 mm; the spacing layer 5 between the reflective shell 3 and the insulating shell 4 and between adjacent insulating shells 4 has a thickness of 10-30 mm.

[0040] Table 1 Material selection and thickness of heat reflective materials, microwave reflective materials, thermal insulation materials, and spacer layers

[0041] The materials and thicknesses of the heat reflecting material 41 , microwave reflecting material 31 , thermal insulation material 42 , and vacuum layer 5 may be selected according to the wave absorbing capability of the material to be sintered and the sintering temperature, as shown in the following table.

[0042] Table 2 Materials and thickness of each layer from inside to outside of the shell (select 1)

[0043] Table 3 Materials and thickness of each layer from inside to outside of the shell (select 2)

[0044] Tables 2 and 3 above provide two options. The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A multi-layer, high-efficiency, heat-insulating microwave cavity suitable for vacuum environments, characterized by: The invention comprises a sealed shell, which comprises a reflecting shell and at least one heat-insulating shell which are sequentially spaced from the inside to the outside; the reflecting shell is made of microwave reflecting material for reflecting microwaves inward; the inner layer of the heat-insulating shell is made of heat-reflecting material and the outer layer is made of heat-insulating material for keeping the interior of the reflecting shell warm; an insulation platform is provided at the bottom of the reflecting shell, and a crucible is provided on the insulation platform; the insulation platform is used to support the crucible and reduce heat conduction from the crucible to the reflecting shell; the crucible is used to hold the material to be sintered, and is made of microwave transparent material that is resistant to high temperature, can conduct heat evenly, and is not easy to react with the material to be sintered. The top of the crucible is open, and heating plates are distributed on the outside; the heating plates are used to generate heat under microwave excitation; a microwave generator is provided outside the shell, and the output end of the microwave generator is connected to a microwave conduction tube, which extends into the shell and points into the crucible; the microwave generator is used to generate microwaves, and the microwave conduction tube is used to efficiently conduct microwaves.

2. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The microwave reflecting material used in the reflective shell is selected from smooth molybdenum, smooth tungsten and carbon fiber reinforced composite materials, with a thickness of 1-3mm; the heat reflecting material used in the inner layer of the thermal insulation shell is selected from aluminum-based ceramic reinforced reflective coating, graphite reflective coating, aluminum oxide coating, titanium oxide coating and zirconium oxide coating, with a thickness of 0.2-0.5mm; the thermal insulation material used in the outer layer of the thermal insulation shell is aluminum oxide fiber cotton, with a thickness of 30-50mm; the interval between the reflective shell and the thermal insulation shell, and between adjacent thermal insulation shells is 10-30mm.

3. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The reflective shell and the heat-insulating shell, and the adjacent heat-insulating shells are connected in an interval arrangement by distributed screws and nuts. The screws pass through the shells, and the nuts fit on the screws and are clamped on both sides of the reflective shell and the heat-insulating shell.

4. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The lower part of the crucible is thickened to form a base, and the upper part is a circle of thin-walled tubes. The heating plates are evenly distributed and attached to the outer wall of the thin-walled tubes.

5. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 4, characterized in that: The heating plate is detachably inserted into a groove connecting the outer wall of the thin-walled cylinder and the top surface of the base.

6. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 4, characterized in that: The contact area between the heating plate and the outer wall of the thin-walled tube does not exceed 1 / 2 of the area of ​​the outer wall of the thin-walled tube.

7. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The shell is a split structure, the bottom surface of the shell is separated from other surfaces, and the other surfaces of the shell are connected as a whole and can be covered on the bottom surface of the shell.

8. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The shell is in the shape of a vertical cylinder as a whole, the crucible is in the shape of a vertical cylinder as a whole and is located in the center of the shell, the microwave generator and the microwave conduction tube are installed on the top of the shell, and the microwave conduction tube points downward to the center of the crucible.

9. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The four sides of the heat insulation platform are supported on the inner bottom surface of the reflective shell, and the lower middle part is separated from the inner bottom surface of the reflective shell by a cavity. The crucible is arranged on the heat insulation platform and is located in the corresponding area of ​​the cavity.

10. The multi-layer high-efficiency heat-insulating microwave cavity suitable for vacuum environment according to claim 1, characterized in that: The microwave generator can precisely control the output power and frequency to precisely regulate the heating process.

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