An integrated preparation method for multi-gradient vacuum ceramic insulation devices

Abstract

The present invention relates to the technical field of ceramic insulation device preparation, and more specifically to an integrated preparation method for a multi-gradient vacuum ceramic insulation device, comprising the following steps: (1) multi-gradient 3D model design; (2) printing slurry preparation; (3) photocuring printing of a multi-gradient connector structure; (4) degreasing the multi-gradient connector structure; and (5) sintering the multi-gradient connector structure, ultimately achieving integrated molding of the multi-gradient vacuum ceramic device. This preparation method not only improves production efficiency and reduces costs, but also ensures high surface dielectric strength and good operational reliability of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic insulation device preparation, and in particular to an integrated preparation method of a multi-gradient vacuum ceramic insulation device. Background Art

[0002] Ceramic insulators, due to their low outgassing, excellent temperature resistance, high insulation resistance, and superior chemical corrosion resistance, are widely used in cutting-edge scientific devices such as pulsed power weapons, semiconductor manufacturing equipment, and high-end CT medical devices, providing potential isolation, mechanical support, and vacuum sealing. Typically, when using ceramic insulators, their surfaces are often metallized to facilitate connection with metal materials such as copper or stainless steel to form an electrical vacuum device. Furthermore, a vacuum device often contains multiple potential conductors to achieve different functional partitions, so it is often necessary to achieve a good connection between multiple ceramic components and the metal to form a multi-grade connection.

[0003] In order to effectively and tightly combine the ceramic insulating body and the metal material and improve its surface dielectric strength and long-term operating reliability, the existing technology can generally be divided into two aspects: achieving reliable mechanical connection between ceramic and metal and effectively improving the surface dielectric strength of the device after connection.

[0004] In terms of ceramic-metal mechanical connection, the most commonly used methods currently include vacuum brazing technology, solid-phase diffusion technology and transient liquid-phase connection technology, which achieve the purpose of reliable connection through the mutual penetration of ceramics and metals at the ionic level.

[0005] Vacuum brazing: This method utilizes materials with relatively low melting points as brazing filler metals. The filler metal is heated in a vacuum environment, causing it to liquefy and wet the ceramic and metal surfaces, thus achieving a joint. This method typically requires high temperatures, precise temperature control, and vacuum equipment. The complexity and high cost of this technique make precise connections difficult to achieve, resulting in relatively low electrical strength in the welded joints. Electric field stress can lead to breakdown or insulation failure, particularly if gases or impurities introduced during the welding process compromise the insulation properties of the joint, further reducing the electrical strength.

[0006] Solid-phase diffusion welding: This method utilizes a chemical reaction between ceramic and metal to achieve a bond, eliminating the need for additional brazing filler metal. By introducing an active element, the oxide film between the ceramic and metal is broken, allowing direct contact and forming a bond. This method often requires more process control but avoids the challenges of brazing filler metal selection and cost. However, the use of active elements to achieve the bond can lead to uneven chemical composition distribution, which can create localized weaknesses in the bond area and reduce electrical strength. This unevenness can also lead to electric field stress concentrations, increasing the risk of electrical breakdown.

[0007] Transient liquid phase joining technology: This method achieves a connection by heating the joining materials to a liquid state in a very short time and then rapidly cooling them. This method typically requires very high heating and cooling rates to ensure a secure connection without excessive thermal stress. The high temperature and rapid cooling process can lead to uneven internal stress distribution in the weld area, which can affect the electrical strength of the joint. High temperatures can also cause thermal stress and thermal deformation, further reducing electrical strength. Furthermore, the high operational difficulty and demanding equipment requirements can lead to unstable weld quality, thereby reducing electrical strength.

[0008] In terms of improving the surface electrical strength of the device after connection, the existing technology usually hinders electron multiplication or charge accumulation through surface treatment processes after the device is prepared, such as surface ion implantation, surface chromium oxide (Cr2O3) coating and ceramic microstructure (such as micro grain size, etc.) optimization.

[0009] Surface ion implantation: This involves implanting ions into the surface of a ceramic using methods such as carburizing or nitriding, forming a very thin doped layer. This alters the surface's electrical properties, such as its electron trapping properties. This method can increase the insulating material's conductivity, reduce the secondary electron emission coefficient, and suppress secondary electron avalanche multiplication.

[0010] Surface Cr2O3 coating: Compared with aluminum oxide (Al2O3), the secondary electron emission coefficient of Cr2O3 material is low. A thin layer of Cr2O3 coating can be formed on the surface of the device by brushing, which also plays a role in suppressing the avalanche multiplication of secondary electrons.

[0011] Ceramic microstructure optimization: By changing the microstructure of the ceramic surface, such as adjusting the roughness and defect density, the electrical and mechanical properties of the ceramic can be improved, secondary electron avalanche multiplication can be suppressed, and its application effect in high vacuum and strong electric field systems can be enhanced.

[0012] Surface treatment methods such as surface ion implantation, Cr2O3 coating, and ceramic microstructure optimization significantly increase the number of process steps and production costs. Furthermore, the surface coating carries the risk of detachment, and the higher surface conductivity significantly increases leakage current, leading to increased device energy consumption and reduced lifespan. Furthermore, all of these methods are performed after the metal and ceramic components are fabricated, making the manufacturing process complex and costly.

[0013] In summary, on the one hand, the traditional ceramic-metal connection method requires that after the ceramic material is prepared, vacuum brazing and other processes are performed to weld it to the metal material to form an integrated structure. The process steps are complex and often produce local stress defects, resulting in cold welding and affecting the sealing of the device. On the other hand, the current ceramic-metal connection process often only focuses on the mechanical properties of the connector, while ignoring the comprehensive design considerations of electrical and mechanical properties. As a result, the connected devices often suffer from surface discharge accidents, reducing the reliability of the equipment operation and limiting the development of miniaturization and high voltage. The surface flashover voltage threshold can be effectively improved through device surface treatment, but the complex process steps often reduce production efficiency, and the coating method can only suppress the secondary electron multiplication in the flashover development stage, and cannot improve the field-induced electron emission in the initial stage of surface flashover, resulting in limited effect on the flashover voltage improvement, and there is also a risk of shedding during long-term operation.

[0014] In view of the defects and shortcomings in the above-mentioned existing research, the creators of the present invention have carried out innovations in the design of ceramic insulation 3D printing models, preparation of printing slurry, photocuring printing of multi-gradient connector structures, degreasing of multi-gradient connector structures, and sintering of multi-gradient connector structures after a long period of research and practice, and finally obtained the content of the present invention. Summary of the Invention

[0015] The purpose of the present invention is to solve the problems of complicated preparation steps and weak electrical resistance of traditional ceramic-metal connecting devices, and to provide an integrated preparation method for multi-gradient vacuum ceramic insulating devices.

[0016] In order to achieve the above object, the present invention discloses an integrated preparation method of a multi-gradient vacuum ceramic insulation device, comprising the following steps:

[0017] An integrated preparation method for a multi-gradient vacuum ceramic insulation device, characterized by comprising the following steps:

[0018] S1, Multi-gradient 3D model design: Multi-gradient design of the structural layer of the vacuum ceramic insulation device is carried out, and a combination of three structures, namely metal, Cr2O3 / Al2O3 composite ceramic, and pure Al2O3 ceramic, is constructed. By simulating the flashover process, the material properties and geometric dimensions of the three structures are optimized to obtain a multi-gradient 3D model;

[0019] S2, printing slurry preparation: prepare metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry respectively, according to the material property results obtained by S1 optimization, determine the proportion of each slurry component based on the experimental data, select the filler particle size distribution and filler content, and obtain the printing slurry;

[0020] S3, multi-gradient connector structured light-curing printing: Based on an inverted multi-material printing device, the printing slurry obtained in step S2 is poured into the corresponding material tank. By rotating and switching the three material tanks, ultraviolet light is used for selective curing. Based on the geometric size results optimized in step S1, the printing order and the geometric shape of the printed model are set. The Z axis is raised to make room for the next stage of printing. After multiple cycles, the rapid prototyping of the multi-gradient connector structure embryo is completed;

[0021] S4, multi-gradient connector structure light curing debinding: After the blank is printed, the formed part is placed in the debinding furnace, the temperature curve is set, and the blank is debinded;

[0022] S5, light-curing sintering of the multi-gradient connector structure: placing the debinding formed part obtained in step S4 into a sintering furnace, setting a temperature curve, and completing the preparation of the multi-gradient vacuum ceramic insulation device.

[0023] In step S1, the electric field distribution at the triple junction and the evolution law of the secondary electron multiplication process are obtained by finite element numerical calculation according to the functional distribution of the device, and the relative dielectric constant ε of the optimized Cr2O3 / Al2O3 composite ceramic is obtained. r , secondary electron emission coefficient δ and length h of Cr2O3 / Al2O3 composite ceramics.

[0024] The specific preparation process of the metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry in step S2 is as follows: metal or ceramic powder is added to a planetary vacuum mixer, and acrylate monomer, UV photoinitiator and dispersant are added in sequence, and stirred at room temperature to obtain metal slurry, Al2O3 ceramic slurry or Cr2O3 / Al2O3 mixed slurry.

[0025] The metal powder is one of the high-melting-point metals such as spherical oxygen-free copper, stainless steel alloy, titanium alloy, tantalum, etc. with a particle size of 1 to 3 μm; the ceramic powder is Al2O3 powder or Cr2O3 powder, and the Al2O3 powder is a combination of two spherical particles with a particle size of 2 to 3 μm and a particle size of 0.6 to 1 μm; the Cr2O3 powder is an ellipsoidal particle with a particle size of 2 to 4 μm.

[0026] The mass ratio of the two spherical particles of the Al2O3 powder with a particle size of 2 to 3 μm and a particle size of 0.6 to 1 μm is 100:1, and the volume ratio of the two types of particles of Cr2O3 and Al2O3 in the Cr2O3 / Al2O3 mixed slurry is 1:11 to 1:5.

[0027] In step S2, the volume percentages of the metal powder and other components in the metal slurry are 60% and 40%, respectively. The other components include an acrylate monomer, a UV photoinitiator, and a dispersant. The mass percentages of the acrylate monomer, the UV photoinitiator, and the dispersant are 97%, 2%, and 1%, respectively.

[0028] The volume percentages of Al2O3 powder and other components in the Al2O3 ceramic slurry are 60% and 40%, respectively. The other components include acrylate monomer, UV photoinitiator, and dispersant. The mass percentages of acrylate monomer, UV photoinitiator, and dispersant are 97%, 2%, and 1%, respectively.

[0029] The volume percentages of Al2O3 powder and other components in the Cr2O3 / Al2O3 ceramic slurry are 60% and 40%, and the mass percentages of other components including acrylate monomer, UV photoinitiator and dispersant are 97%, 2% and 1% respectively.

[0030] The exposure energy of the UV light machine for the metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry in step S3 is 90-120 mW·cm -2 , 20~30mW·cm -2 and 60-80 mW·cm -2 The exposure time of a single layer is 1s or 2s, and the step length of the Z-axis stepping is 0.05mm or 0.025mm.

[0031] In step S4, the debinding temperature curve is increased from room temperature to 500° C. at a rate of 1° C. / min, and is kept at 200° C. and 400° C. for 1 hour respectively. The debinding atmosphere is vacuum or nitrogen atmosphere protection.

[0032] In step S5 , the sintering curve is increased from room temperature to 800° C. at a rate of 5° C. / min, and then rapidly increased to the maximum temperature.

[0033] The sintering process in step S5 is one of microwave plasma sintering, arc plasma sintering, and tube furnace sintering, and the sintering atmosphere is argon inert gas protection.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. Simplified manufacturing process: Through material-structure integrated molding, multiple different functional components of vacuum ceramic insulation devices are directly integrated and printed, avoiding the tedious process of processing and assembling ceramic insulation devices and metal components in traditional manufacturing methods. This method greatly simplifies the manufacturing process, reduces manufacturing steps, and thus improves manufacturing efficiency;

[0036] 2. Improved surface electrical resistance: By constructing a gradient structure, the present invention successfully improves the surface electrical resistance of vacuum ceramic insulation devices. During the optimization process, special attention was paid to the electric field distribution and secondary electron multiplication process at the connection point during flashover. By adding a Cr2O3 / Al2O3 composite ceramic layer, the electric field distribution and secondary electron multiplication were regulated, effectively improving the electric field distribution at the triple junction and suppressing surface secondary electron multiplication, thereby significantly improving the surface electrical resistance of the insulator and making its operation more stable and reliable.

[0037] 3. Improved manufacturing precision: By optimizing the composition and proportion of ceramic slurry, we can effectively ensure the slurry has good processing properties such as viscosity, sedimentation, and curing characteristics, avoiding material switching failures and cross-contamination during the printing process. Further controlling key parameters such as layer thickness, printing speed, and UV light source power during the printing process can significantly improve the manufacturing precision of complex parts and obtain complex and fine structures that cannot be achieved by traditional insulating ceramic forming processes;

[0038] 4. Reduce costs: Integrated molding can reduce the number of parts and assembly steps, reducing manufacturing costs. In addition, since ceramic insulation components and metal connection parts can be manufactured simultaneously during the integrated molding process, production time is also reduced, reducing time costs.

[0039] 5. Enhanced Design Flexibility: Multi-material 3D printing technology allows for the free design of device shapes and structures during the manufacturing process, enabling the creation of complex shapes and structures that are impossible with traditional manufacturing methods, providing greater flexibility in the design of vacuum insulation devices. Furthermore, multi-material 3D printing technology can also combine and match multiple materials, further diversifying device designs and creating more room for innovation in the appearance, functionality, and performance of vacuum equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 An integrated preparation process for multi-gradient vacuum ceramic insulation devices;

[0041] Figure 2 It is a schematic diagram of the sleeve-type ceramic insulation structure;

[0042] Figure 3 Schematic diagram for constructing a sleeve-type ceramic insulation multi-gradient model;

[0043] Figure 4 Schematic diagram of field-induced electron emission and secondary electron multiplication during vacuum flashover;

[0044] Figure 5 Schematic diagram of the multi-gradient light-curing 3D printing process; DETAILED DESCRIPTION

[0045] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0046] Example 1

[0047] An integrated preparation method for a multi-gradient vacuum ceramic insulation device, the main steps of which are as follows Figure 1 As shown, it includes multi-gradient 3D model design, printing slurry preparation, multi-gradient connector structure photocuring printing, multi-gradient connector structure degreasing, and multi-gradient connector structure sintering. Taking the key vacuum ceramic components in low-light night vision devices as an example, Figure 2 As shown, it has a total length of 11.5mm and contains three potential conductors, which are isolated by alumina ceramic insulation. Conventional manufacturing methods involve multiple steps, such as alumina fabrication and metal bonding. This process is cumbersome and the device's electrical strength is limited. To achieve integrated molding and effectively improve the device's electrical strength, a multi-gradient structure was formed using photo-curing 3D printing.

[0048] First, in the multi-gradient 3D model design step, by studying the changes in the relative dielectric constant and the number of secondary electron multiplication at the ceramic-metal interface, the electric field distribution and secondary electron multiplication process of the device are reconstructed using mature commercial finite element simulation methods to obtain optimized material properties and geometric structures. Specifically, Figure 3 As shown, a Cr2O3 / Al2O3 composite ceramic layer is set at the junction of metal and Al2O3 ceramic. The material properties of the composite ceramic layer, including the relative dielectric constant ε r , secondary electron emission coefficient δ and geometric structure, including the thickness h of the composite ceramic layer. The specific determination method is as follows:

[0049] The optimized material range is obtained by numerical calculation. Specifically, in COMSOL simulation software, according to Figure 2 The actual geometric length shown is used to construct the electric field simulation model of the multi-gradient structure ceramic device. The thickness of the Al2O3 ceramic is d and the relative dielectric constant is ε r1 Obtain the metal-ceramic-vacuum medium triple junction E at each position before optimization max1 . Then, to reduce E max1 As the target, a Cr2O3 / Al2O3 composite ceramic layer is inserted between the metal and Al2O3 ceramic layers, such as Figure 3 As shown, the thickness of the intercalation layer is h, and the relative dielectric constant of the material of the intercalation layer is ε r2 According to the geometric relationship and material properties, the selection of each parameter should meet the following constraints:

[0050]

[0051] Where: εrmax In order to obtain the maximum dielectric constant of the material that can be obtained by doping Cr2O3 into Al2O3 while ensuring the processing performance in subsequent experiments. After the insulation configuration is determined, the simulation software is used to recalculate the h and ε of different intercalation layers. r2 The maximum electric field E at the triple junction under the value max2 , the optimization objective f is

[0052] f=E max2 / E max1 (2)

[0053] Using the parameter sweep of the electric field simulation in the software, the optimization direction is to reduce the optimization objective function, and the parameters h and ε are adjusted within the constraints. r2 Perform permutations and combinations to obtain the optimized material relative dielectric constant ε r and the thickness of the composite ceramic layer h. ε r Once determined, the content of Cr2O3 doped in the composite ceramic layer is also determined, thereby determining the optimized secondary electron emission coefficient δ of the composite ceramic.

[0054] The beneficial effects of the above settings are as follows: Figure 4 As shown, due to the relative dielectric constant ε of Al2O3 / Cr2O3 composite ceramics r , is larger than that of pure Al2O3 ceramics, and the gradient structure formed can effectively reduce the number of initial electrons caused by field electron emission at the triple junction; further, since the secondary electron emission coefficient δ of Al2O3 / Cr2O3 composite ceramics is smaller than that of pure Al2O3 ceramics, it can effectively reduce the secondary electron emission caused by the initial electrons, thereby comprehensively improving the surface discharge voltage threshold of the device from two perspectives.

[0055] Example 1

[0056] Formula optimization of metal slurry, Al2O3 ceramic slurry, and Cr2O3 / Al2O3 composite ceramic slurry:

[0057] In the printing slurry preparation step, the higher the metal / ceramic content in the slurry, the lower the probability of defects such as cracks during printing and subsequent sintering. However, an excessively high content of particle fillers will cause the slurry viscosity to increase sharply. Especially in the process of preparing multi-gradient structures, the mismatch in the processing properties of multiple materials will cause interlayer contamination and affect the forming accuracy. Conversely, when the filler content is too low, the filler will settle to the bottom of the trough, also degrading the processing performance. For the non-Newtonian fluid formed by the filler / resin composite, the slurry viscosity can be expressed by the Maron-Pierce formula as:

[0058]

[0059] Where: η is the viscosity of the composite slurry, the unit is mPa·s, η0 is the viscosity of the pure resin, φ f is the mass or volume fraction of the filler, ranging from 0 to φ max ,φ max is the maximum filler content in the Maron-Pierce model, which is related to the filler's shape, particle size and other properties. The sedimentation rate of the filler can be expressed by the Stokes equation:

[0060]

[0061] Where: ρ f and ρ are the densities of the filler and the resin matrix, respectively, d is the particle size of the filler, g is the acceleration of gravity, and η is the viscosity of the composite slurry. Combining equations (1) and (2), it can be seen that the mathematical relationship between the filler sedimentation rate and the filler satisfies:

[0062]

[0063] According to formula (5), the filler sedimentation rate can be controlled by regulating the particle size and content of the filler. According to formula (5), the present invention optimizes and screens the material components and filler categories of the three slurries used, and tests and characterizes the processing properties of the slurries such as curing and rheology. The obtained data are listed in Tables 1 to 3. It should be noted that in order to ensure the quality of the formed parts and avoid cracking of the parts, it has become a consensus to increase the filler content as much as possible. Compared with other irregularly shaped fillers, the use of spherical fillers can significantly increase the solidification thickness and reduce the initial viscosity at the same filling amount, so that the slurry has good processing properties. Therefore, in the present invention, the filler shape is spherical or quasi-spherical. By regulating its particle size and filling amount as well as the components of the slurry, the processing properties of the slurry under different formulas and the control of surface defects of the formed parts are explored.

[0064] Table 1 Metal slurry formulation optimization

[0065]

[0066] Table 2 Al2O3 ceramic slurry formula optimization

[0067]

[0068]

[0069] Tables 1 and 2 show that when the filler content is 60%, the composite slurry achieves a moderate cured thickness, a low sedimentation rate, and no cracking in the formed parts. To ensure a consistent total solids content throughout the composite slurry, the total filler volume fraction was maintained at 60 vol% in the optimized Cr2O3 / Al2O3 composite ceramic slurry formulation shown in Table 3.

[0070] Table 3 Optimization of Cr2O3 / Al2O3 composite ceramic slurry formula

[0071]

[0072] It should be noted that the " / " in Tables 1 to 3 indicates that the material system cannot be formed. Based on the experimental data in Tables 1 to 3, the preferred formulation system has low initial viscosity, slow sedimentation rate, and defect-free parts after forming. The final preferred material composition is shown in Table 4.

[0073] Table 4 Optimized composition ratios of the three slurries

[0074]

[0075]

[0076] It should be noted that the ratios of fillers and other components in Table 4 are based on volume fraction to ensure consistent filling ratios for fillers of varying densities, thereby ensuring essentially identical rheological properties for the three slurries. The other components, including acrylate monomer, UV photoinitiator, and dispersant, are calculated by mass fraction. After determining the proportions of each component in the slurry, the metal or ceramic powder was added to a planetary vacuum mixer, followed by the acrylate monomer, UV photoinitiator, and dispersant. The mixture was stirred at 1000 rpm for 3 minutes at room temperature to obtain a photocurable composite slurry with well-dispersed fillers.

[0077] Example 2

[0078] Optimization of Cr2O3 content in Cr2O3 / Al2O3 mixed slurry:

[0079] Table 5 shows the relative dielectric constant and secondary electron emission coefficient of the composite ceramics at different Cr2O3 / Al2O3 volume ratios. The optimal volume ratio of Cr2O3 to Al2O3 in the Cr2O3 / Al2O3 slurry is found to be between 1:11 and 1:5. When the Cr2O3 content in the composite ceramic is below this ratio, the secondary electron coefficient and relative dielectric constant of the material approach those of pure Al2O3 ceramics, failing to achieve the desired electric field improvement and secondary electron multiplication suppression effects. When the Cr2O3 content in the composite ceramic is above this ratio, the Cr2O3 significantly absorbs ultraviolet light, resulting in a reduced cured thickness and degraded processing performance. Furthermore, the excessive doping creates more crystal structural defects, making microcracks and other defects more likely to form within the sintered component. The relative dielectric constant is the value obtained at power frequency using broadband dielectric spectroscopy, and the secondary electron emission coefficient is the peak value in the secondary electron emission curve obtained using a secondary electron meter.

[0080] Table 5 Effect of Cr2O3 content in Cr2O3 / Al2O3 mixed slurry on the electrical properties of composite ceramics

[0081] <![CDATA[Volume ratio of Cr2O3 / Al2O3]]> 0 1：15 1：11 1：9 1：7 1：5 1：4 Relative dielectric constant 8.56 8.73 10.47 11.3 11.82 12.06 10.87 Secondary electron emission coefficient 8.34 8.21 6.36 5.64 3.44 3.19 6.53

[0082] In the multi-gradient connector structure light curing printing step, in order to achieve integrated molding, multi-gradient 3D printing technology is adopted, using an inverted light curing 3D printing platform. Pour the three slurries into the corresponding material tanks, such as Figure 5 As shown, three troughs are rotated and switched, and UV light is used for selective curing. Based on the resulting geometric dimensions of the multi-gradient 3D model design, the printing order and model geometry are set. The Z-axis is raised to clear space for the next printing stage. After multiple cycles, the multi-gradient connector structure embryo is rapidly formed. This integrated forming process not only simplifies the manufacturing process but also improves manufacturing precision and efficiency. Furthermore, multi-gradient 3D printing technology enables the integrated rapid manufacturing of complex shapes and structures, providing greater design freedom for vacuum ceramic insulation devices.

[0083] Example 3

[0084] Optimization of UV light exposure energy:

[0085] In the specific printing process, first determine the single-layer exposure power and exposure time based on the curing characteristics of the three slurries. Specifically, irradiate the slurry under a fixed light energy E and measure its cured thickness C. d , according to formula (6) to fit:

[0086]

[0087] According to the solidification thickness data under fixed energy in Tables 1 to 3, the transmission depth coefficient D is obtained by fitting. p and critical exposure energy E c Then, according to the step length of the printer's Z-axis stepping, 0.05mm or 0.025mm can be selected. The exposure energy of the UV light machine for metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry is determined to be 90-120mW·cm -2 , 20~30mW·cm -2 and 60-80 mW·cm -2 The exposure time for a single layer is 1s (when the step size is 0.025mm) or 2s (when the step size is 0.05mm).

[0088] Example 4

[0089] Debinding and sintering process:

[0090] During the debinding step, to prevent oxidation of the metal material, the entire process must be performed under vacuum or nitrogen to remove organic matter from the ceramic while maintaining the integrity and stability of the metal. The debinding temperature curve is increased from room temperature to 500°C at a rate of 1°C / min, with 1 hour each at 200°C and 400°C. This slow heating rate effectively prevents cracking of the green blank, while the holding period fully removes moisture and organic matter from the green blank.

[0091] During the sintering step, the sintering atmosphere is protected by an inert gas such as argon, and the sintering curve is increased from room temperature to 800°C at a rate of 5°C / min to preheat the metal and ceramic connection parts. The temperature is then raised to the maximum temperature at a rate of 10°C / min to fuse the metal and ceramic connection parts together. And its density is improved. After sintering is completed, the furnace is naturally cooled to room temperature, and the sintered multi-gradient ceramic insulation device is taken out. The sintering process used is one of microwave plasma sintering, arc plasma sintering, and tubular furnace sintering. The maximum temperature set is related to the metal material. The maximum sintering temperatures set for various high-melting-point metals are shown in Table 6.

[0092] Table 6 Maximum sintering temperature settings for various metal materials

[0093] Metal material oxygen-free copper stainless steel alloys titanium alloy Tantalum Maximum sintering temperature 1450 1510 1650 1700

[0094] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. An integrated preparation method for a multi-gradient vacuum ceramic insulation device, characterized in that: The following steps are involved: S1, Multi-gradient 3D model design: Multi-gradient design of the structural layer of the vacuum ceramic insulation device is carried out, and a combination of three structures, namely metal, Cr2O3 / Al2O3 composite ceramic, and pure Al2O3 ceramic, is constructed. By simulating the flashover process, the material properties and geometric dimensions of the three structures are optimized to obtain a multi-gradient 3D model; S2, printing slurry preparation: prepare metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry respectively, according to the material property results obtained by S1 optimization, determine the proportion of each slurry component based on the experimental data, select the filler particle size distribution and filler content, and obtain the printing slurry; S3, multi-gradient connector structured light-curing printing: Based on an inverted multi-material printing device, the printing slurry obtained in step S2 is poured into the corresponding material tank. By rotating and switching the three material tanks, ultraviolet light is used for selective curing. Based on the geometric size results optimized in step S1, the printing order and the geometric shape of the printed model are set, and the Z axis is raised to make room for the next stage of printing. After multiple cycles, the rapid prototyping of the multi-gradient connector structure blank is completed; S4, multi-gradient connector structure light curing debinding: After the blank is printed, the formed part is placed in the debinding furnace, the temperature curve is set, and the blank is debinded; S5, light-curing sintering of the multi-gradient connector structure: placing the debinding formed part obtained in step S4 into a sintering furnace, setting a temperature curve, and completing the preparation of the multi-gradient vacuum ceramic insulation device; The specific preparation process of the metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry in step S2 is as follows: adding metal powder or ceramic powder to a planetary vacuum mixer, adding acrylate monomer, UV photoinitiator and dispersant in sequence, and stirring at room temperature to obtain metal slurry, Al2O3 ceramic slurry or Cr2O3 / Al2O3 mixed slurry; The metal powder is one of spherical oxygen-free copper, stainless steel alloy, titanium alloy, and tantalum with a particle size of 1 to 3 μm; the ceramic powder is Al2O3 powder or Cr2O3 powder, wherein the Al2O3 powder is a combination of two spherical particles with a particle size of 2 to 3 μm and a particle size of 0.6 to 1 μm; the Cr2O3 powder is an ellipsoidal particle with a particle size of 2 to 4 μm; The mass ratio of the two spherical particles of the Al2O3 powder with a particle size of 2 to 3 μm and the particle size of 0.6 to 1 μm is 100:1, and the volume ratio of the two types of particles of Cr2O3 and Al2O3 in the Cr2O3 / Al2O3 mixed slurry is 1:11 to 1:5; In step S2, the volume percentages of the metal powder and other components in the metal slurry are 60% and 40%, and the other components are acrylate monomer, UV photoinitiator, and dispersant, and the mass percentages of acrylate monomer, UV photoinitiator, and dispersant are 97%, 2%, and 1%, respectively; The volume percentages of Al2O3 powder and other components in the Al2O3 ceramic slurry are 60% and 40%, respectively. The other components are acrylate monomer, UV photoinitiator, and dispersant. The mass percentages of acrylate monomer, UV photoinitiator, and dispersant are 97%, 2%, and 1%, respectively. The volume percentages of Cr2O3 powder, Al2O3 powder and other components in the Cr2O3 / Al2O3 ceramic slurry are 60% and 40%, respectively. The other components are acrylate monomer, UV photoinitiator and dispersant, and the mass percentages of acrylate monomer, UV photoinitiator and dispersant are 97%, 2% and 1% respectively.

2. The integrated preparation method of a multi-gradient vacuum ceramic insulation device according to claim 1, characterized in that: The exposure energy of the UV light machine for the metal slurry, Al2O3 ceramic slurry and Cr2O3 / Al2O3 mixed slurry in step S3 is 90-120 mW·cm -2 , 20~30mW·cm -2 and 60-80 mW·cm -2 The exposure time of a single layer is 1s or 2s, and the step length of the Z-axis stepping is 0.05mm or 0.025mm.

3. The integrated preparation method of a multi-gradient vacuum ceramic insulation device according to claim 1, characterized in that: In step S4, the debinding temperature curve is increased from room temperature to 500° C. at a rate of 1° C. / min, and is kept at 200° C. and 400° C. for 1 hour respectively. The debinding atmosphere is vacuum or nitrogen atmosphere protection.

4. The integrated preparation method of a multi-gradient vacuum ceramic insulation device according to claim 1, characterized in that: In step S5 , the sintering curve is increased from room temperature to 800° C. at a rate of 5° C. / min, and then rapidly increased to the maximum temperature.

5. The integrated preparation method of a multi-gradient vacuum ceramic insulation device according to claim 1, characterized in that: The sintering process in step S5 is one of microwave plasma sintering, arc plasma sintering, and tube furnace sintering, and the sintering atmosphere is argon inert gas protection.

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