Multiphase ceramic material with high density and excellent electromagnetic shielding performance and low-temperature sintering preparation method thereof
By combining low-temperature sintering technology with oxide additives, the problem of high-temperature sintering of ultra-high temperature ceramic materials has been solved, realizing multiphase ceramic materials with high density and excellent electromagnetic shielding performance, reducing energy consumption and cost, and expanding their application range.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-12
AI Technical Summary
Existing ultra-high temperature ceramic materials require ultra-high temperature sintering above 2000°C during preparation, resulting in high energy consumption and high cost. Furthermore, they are difficult to combine with carbon fibers, which limits their application in lightweight and high-strength electromagnetic shielding materials.
Multiphase ceramic materials are prepared at relatively low temperatures (around 1300℃) by using hot pressing sintering or spark plasma sintering technology combined with oxide additives (such as MgO, SiO2, Al2O3). By introducing oxide additives, the densification temperature of ultra-high temperature ceramics is reduced, and high density and excellent electromagnetic shielding performance are achieved at low temperatures.
It significantly reduces the energy consumption and cost of material preparation, achieves high density and excellent electromagnetic shielding performance, broadens its application in aerospace, electronic communications and other fields, and provides the possibility of composite with carbon fiber reinforcement.
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Figure CN122010574A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electromagnetic shielding and protection materials, specifically to a multiphase ceramic material with high density and excellent electromagnetic shielding performance, and its low-temperature sintering preparation method. Background Technology
[0002] With the rapid development of electronic information technology, electromagnetic pollution and electromagnetic interference problems are becoming increasingly serious, making the development of high-performance electromagnetic shielding materials a research hotspot. Among them, ceramic matrix composites, especially ultra-high temperature ceramics represented by transition metal borides (such as TiB2, ZrB2, HfB2) and carbides (such as HfC, TiC), are considered to be a promising new generation of high-temperature, corrosion-resistant electromagnetic shielding materials due to their high melting point, high hardness, good chemical stability, and excellent electromagnetic wave absorption and shielding effectiveness in the mid-to-high frequency band.
[0003] However, such materials face a key technological bottleneck in practical applications: extremely high sintering densification temperatures. Borides and carbides have strong covalent bonds and low self-diffusion coefficients, typically requiring ultra-high temperatures above 2000°C (e.g., 2100°C) and / or external pressure (such as hot pressing or spark plasma sintering) to achieve densification. Such high sintering temperatures lead to several serious problems. First, the ultra-high sintering temperature means enormous energy consumption and high production costs, limiting large-scale production and application. Second, it restricts research on carbon fiber reinforced ceramic matrix composites. Carbon fibers undergo severe graphitization, grain growth, and mechanical property degradation at temperatures exceeding 1500°C, and may even ablate in oxidizing atmospheres. Therefore, it is difficult to achieve the combination of boride / carbide ceramics with lightweight, high-strength carbon fiber composites using traditional ultra-high temperature sintering processes, and it is also impossible to prepare integrated components that combine excellent electromagnetic shielding performance with lightweight structural load-bearing characteristics.
[0004] To overcome the aforementioned sintering challenges, the research community has attempted to introduce various sintering aids to improve sintering kinetics. Common additives include: ① carbides (such as SiC, B4C), which can promote mass migration by forming liquid phases or solid solutions; ② layered compounds (such as hexagonal boron nitride hBN), which may assist densification through interfacial slip or by providing diffusion channels; ③ silicides (such as MoSi2) and certain transition metal carbides (such as WC, VC). These additives can not only effectively reduce sintering temperature and promote densification, but also often refine grains, optimize microstructure, and thus improve the overall thermophysical and mechanical properties of the material. In recent years, another type of material, refractory metal oxides (such as Al2O3, Y2O3, ZrO2, etc.), has also begun to be explored as potential second phases or sintering aids in ultra-high temperature ceramic systems due to their high melting point, excellent thermal stability and chemical inertness, as well as their mature application background in extreme environments (such as aerospace thermal protection systems). The aim is to improve processability and potentially bring new dimensions of regulation to electrical properties or interface characteristics.
[0005] In summary, the core contradiction in current technological development lies in the conflict between the intrinsic properties of materials (excellent electromagnetic shielding potential) and the stringent preparation conditions (ultra-high temperature sintering) required to achieve these properties. Therefore, developing a boride / carbide / nitride preparation method that can significantly reduce the densification sintering temperature of ultra-high temperature ceramics (e.g., from >2000°C to the mid-temperature range of 1200°C and below) without sacrificing the final material properties (high density, uniform microstructure, and excellent electromagnetic shielding performance) has significant scientific and engineering implications. This will not only substantially reduce energy consumption and costs, and broaden its application range in high-tech fields (such as aerospace, high-end electronic communications, and precision instrument protection), but more importantly, it paves the way for successful and effective composites with carbon fiber reinforcements, thus opening a new chapter in the design and manufacture of next-generation lightweight, high-strength, multifunctional integrated electromagnetic shielding composite materials. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a multiphase ceramic material with high density and excellent electromagnetic shielding performance, along with its low-temperature sintering preparation method. Using ultra-high temperature ceramics such as borides / carbides / nitrides (e.g., ZrB2, ZrC, ZrN) as electromagnetic function modifiers and various oxides (e.g., Al2O3, MgO, SiO2) as the matrix, the multiphase ceramic is prepared at a relatively low temperature using hot pressing sintering or spark plasma sintering (SPS) technology. When the oxide content exceeds 40 vol%, the sintering temperature of the ultra-high temperature ceramic can be reduced to approximately 1300℃, achieving good electromagnetic shielding performance while maintaining low-temperature densification. This process not only significantly reduces the cost and energy consumption of material preparation but also preserves or even enhances the electromagnetic shielding performance of ultra-high temperature ceramics, showing broad application prospects in high-temperature thermal protection materials and carbon fiber reinforced ceramic matrix composites.
[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a method for preparing a multiphase ceramic material with high density and excellent electromagnetic shielding performance, comprising the following steps: (1) Mix ultra-high temperature ceramic powder and oxide powder in a predetermined ratio to obtain a mixed powder; (2) The mixed powder is placed in a mold and sintered using a pressure sintering process, wherein the target sintering temperature is 800-1500℃, and a preset pressure of 10-200MPa is applied at the same time. The mixture is held at the target sintering temperature for 5-60 minutes to obtain a densified multiphase ceramic material.
[0008] As a preferred embodiment of the present invention, the ultra-high temperature ceramic includes at least one of boride MB2, carbide MC, and nitride MN, wherein M is one or more of Zr, Hf, Nb, and Ta.
[0009] As a preferred embodiment of the present invention, the oxide includes one or more of MgO, SiO2, and Al2O3.
[0010] As a preferred embodiment of the present invention, the volume fraction of the ultra-high temperature ceramic powder in the mixed powder is 20-100%, and the volume fraction of the oxide powder in the mixed powder is 0-80%.
[0011] As a preferred technical solution of the present invention, in step (1), the mixing is carried out by wet ball milling for a time of 6 to 20 hours, and the ball milling media include ZrO2 grinding balls and anhydrous ethanol; after mixing, the slurry is dried by rotary evaporation, and then crushed and sieved to obtain the mixed powder.
[0012] As a preferred technical solution of the present invention, in step (2), the pressure sintering process is hot pressing sintering or spark plasma sintering.
[0013] As a preferred technical solution of the present invention, when using spark plasma sintering, the heating program is as follows: heating from room temperature to 400°C at a first rate, and then heating to the target sintering temperature at a rate of 20 to 100°C / min; wherein when the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to the preset pressure and maintained.
[0014] As a preferred technical solution of the present invention, when hot pressing sintering is used, the heating program is as follows: the temperature is increased from room temperature to the target sintering temperature at a rate of 5 to 30°C / min; wherein when the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to the preset pressure and maintained.
[0015] Secondly, the present invention provides a multiphase ceramic material prepared by the method described above, wherein the relative density of the multiphase ceramic material is ≥95% and the average shielding effectiveness in the X-band is ≥30dB.
[0016] Thirdly, the present invention provides an application of the aforementioned multiphase ceramic material in electromagnetic shielding, high-temperature thermal protection, or lightweight structural-functional integrated composite material components.
[0017] Compared with the prior art, the specific beneficial effects of the present invention are summarized as follows: 1. This invention significantly reduces the densification sintering temperature (>2000℃) of traditional ultra-high temperature ceramics (such as ZrB2, HfC, ZrN, etc.) by introducing oxides (such as MgO, SiO2, Al2O3), with a temperature reduction of over 800℃. This substantial reduction in sintering temperature significantly decreases energy consumption and equipment wear, thus helping to lower production costs. It also solves the key technical challenge of densifying ultra-high temperature ceramics due to their strong covalent bonds and low diffusion coefficient, making it possible to composite them with heat-sensitive reinforcements such as carbon fibers.
[0018] 2. This invention can still obtain highly dense multiphase ceramics with a relative density of ≥95% under low-temperature sintering conditions. The material exhibits an average shielding effectiveness of ≥30dB in the X-band (8.2~12.4GHz), and in some embodiments, it can reach more than 40dB, possessing both good absorption and reflection shielding mechanisms.
[0019] 3. This invention supports two mainstream pressure sintering processes: hot pressing (HP) and spark plasma sintering (SPS), and provides corresponding heating and pressurization procedures. The process parameters are clear and have good repeatability. The mixing method of wet ball milling combined with rotary evaporation drying ensures powder uniformity and process stability.
[0020] 4. The ultra-high temperature ceramics of this invention can be selected from various systems such as borides, carbides, and nitrides, and the metallic elements (Zr, Hf, Nb, Ta, etc.) can be used individually or in combination. The types and proportions of oxides can be adjusted within a certain range to achieve synergistic control of the material's electromagnetic properties, mechanical properties, and sintering behavior. The raw materials used are mostly common ceramic powders with wide availability, and no harmful additives are used in the process, making it environmentally friendly.
[0021] 5. The low-temperature sintering process of this invention provides a feasibility for the composite of ultra-high temperature ceramics and reinforcing materials such as carbon fibers, and is expected to be used to prepare lightweight, high-strength, high-temperature resistant, and electromagnetically shielding integrated structural-functional components. It has clear application prospects in aerospace thermal protection, high-end electronic equipment shielding, and precision instrument protection. Attached Figure Description
[0022] Figure 1 This is a SEM-EDS image of the multiphase ceramic material prepared in Example 1 of the present invention.
[0023] Figure 2 The electromagnetic shielding performance of the multiphase ceramic material prepared in Example 2 of this invention.
[0024] Figure 3 The image shows the XRD pattern of the multiphase ceramic material prepared in Example 3 of this invention.
[0025] Figure 4 The electromagnetic shielding performance of the multiphase ceramic material prepared in Example 4 of this invention. Detailed Implementation
[0026] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, these should not be construed as limiting the present invention and are merely examples.
[0027] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.
[0028] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available chemical raw materials that are known in the market.
[0029] This invention provides a method for preparing multiphase ceramic materials with high density and excellent electromagnetic shielding properties by low-temperature sintering, comprising the following steps: Step 1: Load raw material powders A and B into a mixing tank (A is various ultra-high temperature ceramics, such as boride (MB2) / carbide (MC) / nitride (MN), M is one or a combination of Zr, Hf, Nb, and Ta, and B is MgO, SiO2, Al2O3, or a combination thereof). The volume fractions of raw material powders A and B are A: 100%-20% and B: 0-80%, respectively. Use ZrO2 grinding balls and anhydrous ethanol as the ball milling media, and ball mill for 6-20 hours to mix them evenly. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and sieved to obtain a uniform mixed powder.
[0030] Step 2: The powder obtained in Step 1 is loaded into a graphite mold and sintered using a hot-press sintering or spark plasma sintering furnace. The spark plasma sintering temperature program is set as follows: the sample is heated from room temperature to 400°C within 5 minutes, then increased to the target sintering temperature at a rate of (20-100)°C / min. When the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to a preset pressure value of (10-200) MPa within 1 minute and maintained until sintering is complete. After holding at the target sintering temperature for (5-60) minutes, the pressure is gradually released, and cooling is performed in an argon atmosphere. The hot-press sintering temperature program is as follows: the temperature is increased from room temperature to the target sintering temperature at a rate of (5-30)°C / min. When the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to (10-200) MPa and maintained until sintering is complete. After holding at the target sintering temperature for 5-60 minutes, gradually depressurize and cool with the furnace.
[0031] Step 3: The sample is initially ground using a surface grinder to remove residual graphite paper from the surface. Then, the sample is processed into test strips of the target size using wire electrical discharge machining. After that, the processed surface is finely ground and polished to characterize the microstructure, phase composition, etc.
[0032] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.
[0033] Example 1 Weigh commercially available raw materials according to the specified ratio: ZrB2 powder and MgO powder (MgO volume fraction 42.5%). Use ZrO2 grinding balls and anhydrous ethanol as the ball milling media and ball mill for 8 hours to mix them evenly. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0034] The powder obtained above was placed into a graphite mold with an inner diameter of 40 mm and sintered using a spark plasma sintering furnace. The heating program was set as follows: the sample was heated from room temperature to 400°C within 5 minutes, and then increased from 400°C to 1300°C at a rate of 100°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure (approximately 16 MPa) to 60 MPa within 1 minute and maintained at this pressure until the sintering was completed. After holding at 1300°C for 20 minutes, the pressure was gradually released, and the sample was cooled in an argon atmosphere. The resulting sample was processed into test strips of the target size, and then the surface was finely ground and polished for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 96.81%, and the microstructure and elemental distribution are as follows. Figure 1 As shown, at room temperature, the material's total shielding effectiveness in the X-band (8.2–12.4 GHz) ranges from 30 to 51 dB, with an average shielding effectiveness of 40 dB, an average absorption shielding effectiveness of 25 dB, and an average reflection shielding effectiveness of 15 dB.
[0035] Example 2 Weigh commercially available raw materials according to the specified ratio: ZrB2 powder and MgO powder (MgO volume fraction 48.7%). Use ZrO2 grinding balls and anhydrous ethanol as the ball milling media and ball mill for 10 hours to mix them evenly. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0036] The powder obtained above was placed into a graphite mold with an inner diameter of 30 mm and sintered using a spark plasma sintering furnace. The heating program was set as follows: the sample was heated from room temperature to 400°C within 5 minutes, and then increased from 400°C to 1200°C at a rate of 80°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure of 13 MPa to 70 MPa within 1 minute and maintained at this pressure until the sintering was completed. After holding at 1200°C for 10 minutes, the pressure was gradually released and cooled in an argon atmosphere. The obtained sample was processed into test strips of the target size, and then the surface was finely ground and polished for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 97.23%, and the measured electromagnetic shielding performance was as follows. Figure 2 As shown, at room temperature, the material's total shielding effectiveness (SET) in the X-band (8.2–12.4 GHz) ranges from 30 to 47 dB, with an average shielding effectiveness of 38 dB, an average absorbed shielding effectiveness (SEA) of 25 dB, and an average reflected shielding effectiveness (SER) of 13 dB.
[0037] Example 3 Weigh commercially available raw materials according to the specified ratio: ZrB2 powder and MgO powder (MgO volume fraction 56.45%). Use ZrO2 grinding balls and anhydrous ethanol as the ball milling media and ball mill for 12 hours to mix them evenly. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0038] The powder obtained above was loaded into a graphite mold and placed in a hot-press sintering furnace. Sintering was carried out under an argon protective atmosphere, with the temperature program set to increase from room temperature to 1300°C at a rate of 15°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure (approximately 10 MPa) to 40 MPa over 2 minutes and maintained at this pressure until the end of sintering. After holding at 1300°C for 30 minutes, the pressure was gradually released, and the sample was cooled with the furnace. After processing, fine grinding, and polishing, the relative density of the sample was measured to be 95.42% using the water displacement method. The XRD pattern of the sample is shown below. Figure 3 As shown, at room temperature, the material's total shielding effectiveness in the X-band (8.2–12.4 GHz) ranges from 38 to 49 dB, with an average shielding effectiveness of 42 dB, an average absorption shielding effectiveness of 26 dB, and an average reflection shielding effectiveness of 16 dB.
[0039] Example 4 Weigh commercially available raw materials according to the specified ratio: ZrB2 powder and Al2O3 powder (Al2O3 volume fraction approximately 42.1%). Use ZrO2 grinding balls and anhydrous ethanol as the ball milling media and ball mill for 8 hours to mix them evenly. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0040] The powder obtained above was loaded into a graphite mold and placed in a hot-press sintering furnace. The heating program was set to increase the temperature from room temperature to 1250°C at a rate of 10°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure (approximately 10 MPa) to 30 MPa within 2 minutes and maintained at this pressure until the end of sintering. After holding at 1250°C for 40 minutes, the pressure was gradually released, and the sample was cooled with the furnace. The resulting sample was processed into test strips of the target size, followed by surface grinding and polishing for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 97.22%, and the electromagnetic shielding performance was as follows: Figure 4 As shown, at room temperature, the material has a total shielding effectiveness of 30-35 dB in the X-band (8.2–12.4 GHz), an average shielding effectiveness of 33 dB, an average absorption shielding effectiveness of 16 dB, and an average reflection shielding effectiveness of 17 dB.
[0041] Example 5 Weigh commercially available raw materials according to the specified ratio: (Hf,Ta)B2 powder and SiO2 powder (SiO2 volume fraction approximately 60.7%). Use ZrO2 grinding balls and anhydrous ethanol as the medium, and ball mill for 12 hours to ensure uniform mixing. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0042] The powder obtained above was loaded into a graphite mold and placed in a hot-press sintering furnace. The heating program was set to increase the temperature from room temperature to 1200°C at a rate of 10°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure (approximately 10 MPa) to 35 MPa within 2 minutes and maintained at this pressure until the end of sintering. After holding at 1200°C for 30 minutes, the pressure was gradually released, and the sample was cooled with the furnace. The obtained sample was processed into test strips of the target size, followed by surface grinding and polishing for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 98.77%. At room temperature, the material exhibited a total shielding effectiveness of 30-48 dB in the X-band (8.2–12.4 GHz), an average shielding effectiveness of 40 dB, an average absorption shielding effectiveness of 29 dB, and an average reflection shielding effectiveness of 11 dB.
[0043] Example 6 Weigh commercially available raw materials according to the specified ratio: ZrN powder and MgO powder (MgO volume fraction approximately 44.2%). Use ZrO2 grinding balls and anhydrous ethanol as the medium, and ball mill for 10 hours to ensure uniform mixing. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0044] The powder obtained above was placed into a graphite mold with an inner diameter of 30 mm and sintered using a spark plasma sintering furnace. The heating program was set as follows: the sample was heated from room temperature to 400°C within 5 minutes, and then increased from 400°C to 1150°C at a rate of 100°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure of 13 MPa to 80 MPa within 2 minutes and maintained at this pressure until the sintering was completed. After holding at 1150°C for 15 minutes, the pressure was gradually released and cooled in an argon atmosphere. The obtained sample was processed into test strips of the target size, and then the surface was finely ground and polished for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 97.02%. At room temperature, the material has a total shielding effectiveness in the X-band (8.2–12.4 GHz) ranging from 25 to 40 dB, with an average shielding effectiveness of 43 dB, an average absorption shielding effectiveness of 32 dB, and an average reflection shielding effectiveness of 11 dB.
[0045] Example 7 Weigh the commercially available raw materials according to the specified ratio: pentagonal high-entropy boride (Zr) 0.2 Ti 0.2 Nb 0.2 Ta 0.2 Hf 0.2 B2 powder and MgO powder (MgO volume fraction approximately 49.58%) were ball-milled for 15 hours using ZrO2 grinding balls and anhydrous ethanol as the medium to ensure uniform mixing. The resulting slurry was dried by rotary evaporation, and the dried material was then crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0046] The powder obtained above was placed into a graphite mold with an inner diameter of 50 mm and sintered using a spark plasma sintering furnace. The heating program was set as follows: the sample was heated from room temperature to 400°C within 5 minutes, and then increased from 400°C to 1300°C at a rate of 80°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure of 13 MPa to 65 MPa within 1 minute and maintained at this pressure until the sintering was completed. After holding at 1300°C for 20 minutes, the pressure was gradually released and cooled in an argon atmosphere. The obtained sample was processed into test strips of the target size, and then the surface was finely ground and polished for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 99.20%. At room temperature, the material has a total shielding effectiveness of 35-45 dB in the X-band (8.2–12.4 GHz), an average shielding effectiveness of 40 dB, an average absorption shielding effectiveness of 26 dB, and an average reflection shielding effectiveness of 14 dB.
[0047] Example 8 Weigh commercially available raw materials according to the specified ratio: TiC powder and Al2O3 powder (Al2O3 volume fraction approximately 57.0%). Use ZrO2 grinding balls and anhydrous ethanol as the medium, and ball mill for 12 hours to ensure uniform mixing. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0048] The powder obtained above was loaded into a graphite mold and placed in a hot-press sintering furnace. The heating program was set to increase the temperature from room temperature to 1250°C at a rate of 10°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure (approximately 10 MPa) to 30 MPa within 2 minutes and maintained at this pressure until the end of sintering. After holding at 1250°C for 60 minutes, the pressure was gradually released, and the sample was cooled with the furnace. The obtained sample was processed into test strips of the target size, followed by surface grinding and polishing for subsequent characterization tests. The relative density of the sample, measured by the water displacement method, was 98.60%. At room temperature, the material exhibited a total shielding effectiveness of 32-40 dB in the X-band (8.2–12.4 GHz), an average shielding effectiveness of 35 dB, an average absorption shielding effectiveness of 19 dB, and an average reflection shielding effectiveness of 16 dB.
[0049] Example 9 Weigh commercially available raw materials according to the specified ratio: ZrN powder and MgO powder (MgO volume fraction approximately 64.2%). Use ZrO2 grinding balls and anhydrous ethanol as the medium, and ball mill for 12 hours to ensure uniform mixing. The resulting slurry is dried by rotary evaporation, and then the dried material is crushed and passed through a 200-mesh sieve to obtain a uniform mixed powder.
[0050] The powder obtained above was placed into a graphite mold with an inner diameter of 30 mm and sintered using a spark plasma sintering furnace. The heating program was set as follows: the sample was heated from room temperature to 400°C within 5 minutes, and then increased from 400°C to 1300°C at a rate of 100°C / min. When the temperature reached 600°C, the pressure was gradually increased from the initial contact pressure of 13 MPa to 60 MPa within 1 minute and maintained at this pressure until the sintering was completed. After holding at 1300°C for 10 minutes, the pressure was gradually released and cooled in an argon atmosphere. The obtained sample was processed into test strips of the target size, and then the surface was finely ground and polished for subsequent testing and characterization. The relative density of the sample, measured by the water displacement method, was 95.82%. At room temperature, the material has a total shielding effectiveness in the X-band (8.2–12.4 GHz) ranging from 26 to 43 dB, with an average shielding effectiveness of 36 dB, an average absorption shielding effectiveness of 23 dB, and an average reflection shielding effectiveness of 13 dB.
[0051] It should be noted that the above embodiments are merely preferred examples of the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications, substitutions, or variations can be made to the technical solutions of the present invention without departing from the core concept of the present invention, and none of these require creative effort.
[0052] Therefore, any modifications, equivalent substitutions, and improvements made based on the inventive concept should fall within the scope of protection defined by the claims of this invention. In other words, any technical solution that can be readily obtained by a person skilled in the art through conventional logical analysis, reasoning, or a limited number of experiments based on the technical solution disclosed in this invention should be considered within the scope of protection defined by the claims of this invention.
Claims
1. A method for preparing multiphase ceramics with high density and excellent electromagnetic shielding properties by low-temperature sintering, characterized in that, Includes the following steps: (1) Mix ultra-high temperature ceramic powder and oxide powder in a predetermined ratio to obtain a mixed powder; (2) The mixed powder is placed in a mold and sintered using a pressure sintering process, wherein the target sintering temperature is 800-1500℃, and a preset pressure of 10-200MPa is applied at the same time. The mixture is held at the target sintering temperature for 5-60 minutes to obtain a densified multiphase ceramic material.
2. The method according to claim 1, characterized in that: The ultra-high temperature ceramic includes at least one of boride MB2, carbide MC, and nitride MN, wherein M is one or more of Zr, Hf, Nb, and Ta.
3. The method according to claim 1 or 2, characterized in that: The oxide includes one or more of MgO, SiO2, and Al2O3.
4. The method according to claim 1, characterized in that: The volume fraction of the ultra-high temperature ceramic powder in the mixed powder is 20-100%, and the volume fraction of the oxide powder in the mixed powder is 0-80%.
5. The method according to claim 1, characterized in that: In step (1), the mixing is carried out by wet ball milling for 6 to 20 hours. The ball milling media include ZrO2 grinding balls and anhydrous ethanol. After mixing, the slurry is dried by rotary evaporation and then crushed and sieved to obtain the mixed powder.
6. The method according to claim 1, characterized in that: In step (2), the pressure sintering process is hot pressing sintering or spark plasma sintering.
7. The method according to claim 6, characterized in that: When using spark plasma sintering, the heating program is as follows: heat from room temperature to 400°C at a first rate, and then heat to the target sintering temperature at a rate of 20-100°C / min; when the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to the preset pressure and maintained.
8. The method according to claim 6, characterized in that: When hot pressing sintering is used, the heating program is as follows: the temperature is increased from room temperature to the target sintering temperature at a rate of 5 to 30°C / min; when the temperature reaches 600°C, the pressure is gradually increased from the initial contact pressure to the preset pressure and maintained.
9. A multiphase ceramic material with high density and excellent electromagnetic shielding performance, characterized in that: The composite ceramic material prepared by the method according to any one of claims 1 to 8 has a relative density ≥95% and an average shielding effectiveness ≥30dB in the X-band.
10. The application of the multiphase ceramic material of claim 9 in electromagnetic shielding, high-temperature thermal protection, or lightweight structural-functional integrated composite material components.